JP7467320B2 - Signal lens and lens cover - Google Patents

Description

The present invention relates to a lens and a lens cover for a traffic light.

Due to their high transparency, methacrylic resins, such as polymethyl methacrylate (PMMA), have traditionally been widely used in fields such as optical materials, vehicle parts, building materials, lenses, household goods, office equipment, industrial equipment, and lighting equipment. In particular, in the field of optical components such as light guides, such as light guide plates and thick lenses, methacrylic resins are widely used due to the ease of molding, a feature of thermoplastic resins, and their outstanding transparency among thermoplastic resins.

On the other hand, traffic light lenses and lens covers have become thinner in recent years, with the distance between the LED light source and the lens becoming closer. At the same time, the amount of internal heat generated is increasing due to the higher brightness and light emission of the internal LEDs. This has created a need for transparent heat-resistant resins that have the heat resistance to withstand such conditions and a certain level of impact resistance to withstand outdoor use.

In view of the above, polycarbonate resins are sometimes used as materials for traffic light lenses and lens covers from the standpoint of heat resistance and impact resistance. However, polycarbonate resins, particularly when used for outdoor applications, are inferior in weather resistance to methacrylic resins, and therefore require the incorporation of a larger amount of ultraviolet absorbent. If there is insufficient ultraviolet absorbent, the resins will yellow and will no longer function as optical components.

For this reason, the weather resistance of polycarbonate-based resins has been improved by blending ultraviolet absorbents, but blending ultraviolet absorbents tends to reduce light transmittance, which poses the problem that it is not possible to meet the demands for long optical path designs and improved brightness mentioned above.
Furthermore, the surface of a polycarbonate molded product is easily scratched, and if the product is installed outdoors and exposed to flying debris and sand caused by wind and rain, the surface will be scratched, reducing visibility.
Furthermore, polycarbonate has a high birefringence, which reduces visibility.

In addition, for applications that do not require high transparency, i.e., high long-path transmittance, such as vehicle components, it is known to use a methacrylic copolymer resin containing a methacrylic acid monomer unit and a monomer unit having a cyclic structure (see, for example, Patent Document 1).
However, the methacrylic copolymer resin disclosed in Patent Document 1 has a problem in that it does not have sufficient moldability and is not suitable for producing fine or thin optical members such as lenses.
Furthermore, a technique for improving long-path transmittance by using a resin containing a methacrylic acid ester monomer, a maleimide monomer, and a styrene monomer has been disclosed (see, for example, Patent Document 2).
According to the technology of Patent Document 2, the long light path transmittance is significantly improved, but from the viewpoint of long-term hue stability and improvement of whiteness over a long light path, there is a problem that further improvement is required.

JP 2014-024361 A JP 2016-210963 A

As mentioned above, traffic light lenses and lens covers require resin materials that provide a good balance of heat resistance, weather resistance, optical properties, color, and moldability. The previously proposed resin materials mentioned above are still insufficient, and higher levels of properties are required.

The present invention aims to provide a traffic light lens and lens cover that contain a methacrylic resin composition that has excellent releasability, scratch resistance, heat resistance, weather resistance, optical properties, hue, and moldability.

The present inventors have conducted extensive research to solve the above-mentioned problems of the conventional technology, and as a result have completed the present invention.
That is, the present invention is as follows.

・・・（１）
（式（１）中、Ｒは、水素原子、炭素数が１～１２の脂肪族炭化水素基又は炭素数が１～１２の芳香族炭化水素基を表す。Ｒの脂肪族炭化水素基及び芳香族炭化水素基は、それぞれ炭素原子上に硫黄原子、窒素原子、酸素原子、リン原子を有していてもよい。また、Ｒ’は、炭素数１～１２の脂肪族炭化水素基又は炭素数６～１８の芳香族炭化水素基を表す。Ｒ’の脂肪族炭化水素基及び芳香族炭化水素基は、それぞれ炭素原子上に硫黄原子、窒素原子、酸素原子、リン原子を有していてもよい。）
〔２〕
下記式（Ｉ）で表される、射出成形の成形温度を２８０℃、サイクル時間を４５秒として作製した厚さ３ｍｍ×幅２０ｍｍ×長さ２２０ｍｍの試験片についてＪＩＳ Ｋ ７１０５に準拠して測定した２２０ｍｍ長光路ＹＩ値（２２０ｍｍ長光路ＹＩ値（４５秒））に対する、射出成形の成形温度を２８０℃、サイクル時間を２７０秒として作製した試験片についてＪＩＳ Ｋ ７１０５に準拠して測定した２２０ｍｍ長光路ＹＩ値（２２０ｍｍ長光路ＹＩ値（２７０秒））の変化度（ΔＹＩ）が、２０以下であるメタクリル系樹脂組成物を含み、前記メタクリル樹脂組成物が、脂肪酸化合物、シリコーン、ポリエーテル、及びケイ酸塩化合物からなる群から選ばれる少なくとも一種の化合物を含有し、
前記メタクリル系樹脂組成物が、主鎖に環構造を有する構造単位（Ｂ）を含むメタクリル系樹脂：１００質量部と、下記一般式（１）で表わされる化合物（Ｄ）：０．００１～０．２質量部と、を含有し、
前記メタクリル系樹脂組成物における前記主鎖に環構造を有する構造単位（Ｂ）の含有量の前記メタクリル系樹脂組成物における前記（Ｄ）成分の含有量に対する割合（（Ｂ）／（Ｄ））が２５以上１０００以下であることを特徴とする、信号機用レンズ。
ΔＹＩ＝｛２２０ｍｍ長光路ＹＩ値（２７０秒）－２２０ｍｍ長光路ＹＩ値（４５秒）｝／２２０ｍｍ長光路ＹＩ値（４５秒）・・・（Ｉ）

・・・（１）
（式（１）中、Ｒは、水素原子、炭素数が１～１２の脂肪族炭化水素基又は炭素数が１～１２の芳香族炭化水素基を表す。Ｒの脂肪族炭化水素基及び芳香族炭化水素基は、それぞれ炭素原子上に硫黄原子、窒素原子、酸素原子、リン原子を有していてもよい。また、Ｒ’は、炭素数１～１２の脂肪族炭化水素基又は炭素数６～１８の芳香族炭化水素基を表す。Ｒ’の脂肪族炭化水素基及び芳香族炭化水素基は、それぞれ炭素原子上に硫黄原子、窒素原子、酸素原子、リン原子を有していてもよい。）
〔２〕
下記式（Ｉ）で表される、射出成形の成形温度を２８０℃、サイクル時間を４５秒として作製した厚さ３ｍｍ×幅２０ｍｍ×長さ２２０ｍｍの試験片についてＪＩＳ Ｋ ７１０５に準拠して測定した２２０ｍｍ長光路ＹＩ値（２２０ｍｍ長光路ＹＩ値（４５秒））に対する、射出成形の成形温度を２８０℃、サイクル時間を２７０秒として作製した試験片についてＪＩＳ Ｋ ７１０５に準拠して測定した２２０ｍｍ長光路ＹＩ値（２２０ｍｍ長光路ＹＩ値（２７０秒））の変化度（ΔＹＩ）が、２０以下であるメタクリル系樹脂組成物を含み、前記メタクリル樹脂組成物が、脂肪酸化合物、シリコーン、ポリエーテル、及びケイ酸塩化合物からなる群から選ばれる少なくとも一種の化合物を含有し、
前記メタクリル系樹脂組成物が、主鎖に環構造を有する構造単位（Ｂ）を含むメタクリル系樹脂：１００質量部と、下記一般式（１）で表わされる化合物（Ｄ）：０．００１～０．２質量部と、を含有し、
前記メタクリル系樹脂組成物における前記主鎖に環構造を有する構造単位（Ｂ）の含有量の前記メタクリル系樹脂組成物における前記（Ｄ）成分の含有量に対する割合（（Ｂ）／（Ｄ））が２５以上１０００以下であることを特徴とする、信号機用レンズカバー。
ΔＹＩ＝｛２２０ｍｍ長光路ＹＩ値（２７０秒）－２２０ｍｍ長光路ＹＩ値（４５秒）｝／２２０ｍｍ長光路ＹＩ値（４５秒）・・・（Ｉ）

・・・（１）
（式（１）中、Ｒは、水素原子、炭素数が１～１２の脂肪族炭化水素基又は炭素数が１～１２の芳香族炭化水素基を表す。Ｒの脂肪族炭化水素基及び芳香族炭化水素基は、それぞれ炭素原子上に硫黄原子、窒素原子、酸素原子、リン原子を有していてもよい。また、Ｒ’は、炭素数１～１２の脂肪族炭化水素基又は炭素数６～１８の芳香族炭化水素基を表す。Ｒ’の脂肪族炭化水素基及び芳香族炭化水素基は、それぞれ炭素原子上に硫黄原子、窒素原子、酸素原子、リン原子を有していてもよい。）
〔４〕
３ｍｍ厚の試験片を用いてＪＩＳ Ｋ７３５０－４の手法を用いて２０４０時間曝露試験を行った前後におけるＪＩＳ Ｚ８７３０に従って測定した色差ΔＥ＊が３以下である、〔１〕に記載の信号機用レンズ及びレンズカバー、〔２〕に記載の信号機用レンズ、又は〔３〕に記載の信号機用レンズカバー。
〔５〕
前記メタクリル系樹脂組成物のゲルパーミエーションクロマトグラフィー（ＧＰＣ）で測定した重量平均分子量が６．５万～３０万である、〔１〕もしくは〔４〕に記載の信号機用レンズ及びレンズカバー、〔２〕もしくは〔４〕に記載の信号機用レンズ、又は〔３〕もしくは〔４〕に記載の信号機用レンズカバー。
〔６〕
前記メタクリル系樹脂が、メタクリル酸エステル単量体単位（Ａ）：５０～９７質量％と、主鎖に環構造を有する構造単位（Ｂ）：３～３０質量％と、メタクリル酸エステル単量体と共重合可能なその他のビニル系単量体単位（Ｃ）：０～２０質量％とを含む、〔１〕、〔４〕、もしくは〔５〕に記載の信号機用レンズ及びレンズカバー、〔２〕、〔４〕、もしくは〔５〕に記載の信号機用レンズ、又は〔３〕、〔４〕、もしくは〔５〕に記載の信号機用レンズカバー。
〔７〕
前記主鎖に環構造を有する構造単位（Ｂ）が、マレイミド系構造単位（Ｂ－１）、グルタル酸無水物系構造単位（Ｂ－２）、グルタルイミド系構造単位（Ｂ－３）、ラクトン環構造単位（Ｂ－４）、及び酸無水物構造単位（Ｂ－５）からなる群より選ばれる少なくとも一種の構造単位を含む、〔１〕、〔４〕～〔６〕のいずれかに記載の信号機用レンズ及びレンズカバー、〔２〕、〔４〕～〔６〕のいずれかに記載の信号機用レンズ、又は〔３〕～〔６〕のいずれかに記載の信号機用レンズカバー。
〔８〕
厚みが０．０３～１０ｍｍである、〔１〕、〔４〕～〔７〕のいずれかに記載の信号機用レンズ及びレンズカバー、〔２〕、〔４〕～〔７〕のいずれかに記載の信号機用レンズ、又は〔３〕～〔７〕のいずれかに記載の信号機用レンズカバー。
〔９〕
前記脂肪酸化合物、シリコーン、ポリエーテル、及びケイ酸塩化合物からなる群から選ばれる少なくとも一種の化合物の含有量が、前記メタクリル系樹脂１００質量部に対し、０．０５～６質量部である、〔１〕、〔４〕～〔８〕のいずれかに記載の信号機用レンズ及びレンズカバー、〔２〕、〔４〕～〔８〕のいずれかに記載の信号機用レンズ、又は〔３〕～〔８〕のいずれかに記載の信号機用レンズカバー。
〔１０〕
前記メタクリル樹脂組成物を金型磨き番手８０００番の金型を用いて厚み２ｍｍの平板として射出成形したときに、ＪＩＳ Ｋ７３６１－１に準拠して測定した前記平板の全光線透過率が８５％以上であり、ＪＩＳ Ｋ７１３６に準拠して測定した前記平板のヘイズが５以下である、〔１〕、〔４〕～〔９〕のいずれかに記載の信号機用レンズ及びレンズカバー、〔２〕、〔４〕～〔９〕のいずれかに記載の信号機用レンズ、又は〔３〕～〔９〕のいずれかに記載の信号機用レンズカバー。 [1]
The present invention relates to a methacrylic resin composition having a change rate (ΔYI) of 20 or less in a 220 mm long optical path YI value (220 mm long optical path YI value (45 seconds)) measured in accordance with JIS K7105 on a test piece prepared at an injection molding temperature of 280° C. and a cycle time of 270 seconds, relative to a 220 mm long optical path YI value (220 mm long optical path YI value (270 seconds)) measured in accordance with JIS K7105 on a test piece prepared at an injection molding temperature of 280° C. and a cycle time of 270 seconds, the change rate being represented by the following formula (I) :
The methacrylic resin composition contains 100 parts by mass of a methacrylic resin including a structural unit (B) having a ring structure in its main chain, and 0.001 to 0.2 parts by mass of a compound (D) represented by the following general formula (1),
a ratio ((B)/(D)) of a content of a structural unit (B) having a ring structure in the main chain in the methacrylic resin composition to a content of the component (D) in the methacrylic resin composition is 25 or more and 1,000 or less .
ΔYI={220 mm long optical path YI value (270 seconds)−220 mm long optical path YI value (45 seconds)}/220 mm long optical path YI value (45 seconds) (I)

... (1)
(In formula (1), R represents a hydrogen atom, an aliphatic hydrocarbon group having 1 to 12 carbon atoms, or an aromatic hydrocarbon group having 1 to 12 carbon atoms. The aliphatic hydrocarbon group and aromatic hydrocarbon group of R may each have a sulfur atom, a nitrogen atom, an oxygen atom, or a phosphorus atom on a carbon atom. Furthermore, R' represents an aliphatic hydrocarbon group having 1 to 12 carbon atoms, or an aromatic hydrocarbon group having 6 to 18 carbon atoms. The aliphatic hydrocarbon group and aromatic hydrocarbon group of R' may each have a sulfur atom, a nitrogen atom, an oxygen atom, or a phosphorus atom on a carbon atom.)
[2]
The present invention includes a methacrylic resin composition having a change rate (ΔYI) of 20 or less in a 220 mm long optical path YI value (220 mm long optical path YI value (45 seconds)) measured in accordance with JIS K 7105 for a test piece prepared at an injection molding temperature of 280° C. and a cycle time of 270 seconds, relative to a 220 mm long optical path YI value (220 mm long optical path YI value (270 seconds)) measured in accordance with JIS K 7105 for a test piece prepared at an injection molding temperature of 280° C. and a cycle time of 270 seconds, the change rate being represented by the following formula (I):
The methacrylic resin composition contains 100 parts by mass of a methacrylic resin including a structural unit (B) having a ring structure in its main chain, and 0.001 to 0.2 parts by mass of a compound (D) represented by the following general formula (1),
a ratio ((B)/(D)) of a content of a structural unit (B) having a ring structure in the main chain in the methacrylic resin composition to a content of the component (D) in the methacrylic resin composition is 25 or more and 1,000 or less.
ΔYI={220 mm long optical path YI value (270 seconds)−220 mm long optical path YI value (45 seconds)}/220 mm long optical path YI value (45 seconds) (I)

... (1)
(In formula (1), R represents a hydrogen atom, an aliphatic hydrocarbon group having 1 to 12 carbon atoms, or an aromatic hydrocarbon group having 1 to 12 carbon atoms. The aliphatic hydrocarbon group and aromatic hydrocarbon group of R may each have a sulfur atom, a nitrogen atom, an oxygen atom, or a phosphorus atom on a carbon atom. Furthermore, R' represents an aliphatic hydrocarbon group having 1 to 12 carbon atoms, or an aromatic hydrocarbon group having 6 to 18 carbon atoms. The aliphatic hydrocarbon group and aromatic hydrocarbon group of R' may each have a sulfur atom, a nitrogen atom, an oxygen atom, or a phosphorus atom on a carbon atom.)
[2]
The present invention includes a methacrylic resin composition having a change rate (ΔYI) of 20 or less in a 220 mm long optical path YI value (220 mm long optical path YI value (45 seconds)) measured in accordance with JIS K 7105 for a test piece prepared at an injection molding temperature of 280° C. and a cycle time of 270 seconds, relative to a 220 mm long optical path YI value (220 mm long optical path YI value (270 seconds)) measured in accordance with JIS K 7105 for a test piece prepared at an injection molding temperature of 280° C. and a cycle time of 270 seconds, the change rate being represented by the following formula (I):
The methacrylic resin composition contains 100 parts by mass of a methacrylic resin including a structural unit (B) having a ring structure in its main chain, and 0.001 to 0.2 parts by mass of a compound (D) represented by the following general formula (1),
A traffic light lens cover, characterized in that a ratio ((B)/(D)) of a content of a structural unit (B) having a ring structure in the main chain in the methacrylic resin composition to a content of the component (D) in the methacrylic resin composition is 25 or more and 1,000 or less.
ΔYI={220 mm long optical path YI value (270 seconds)−220 mm long optical path YI value (45 seconds)}/220 mm long optical path YI value (45 seconds) (I)

... (1)
(In formula (1), R represents a hydrogen atom, an aliphatic hydrocarbon group having 1 to 12 carbon atoms, or an aromatic hydrocarbon group having 1 to 12 carbon atoms. The aliphatic hydrocarbon group and aromatic hydrocarbon group of R may each have a sulfur atom, a nitrogen atom, an oxygen atom, or a phosphorus atom on a carbon atom. Furthermore, R' represents an aliphatic hydrocarbon group having 1 to 12 carbon atoms, or an aromatic hydrocarbon group having 6 to 18 carbon atoms. The aliphatic hydrocarbon group and aromatic hydrocarbon group of R' may each have a sulfur atom, a nitrogen atom, an oxygen atom, or a phosphorus atom on a carbon atom.)
[ 4 ]
The traffic light lens and lens cover described in [1], the traffic light lens described in [2], or the traffic light lens cover described in [3], have a color difference ΔE* of 3 or less as measured in accordance with JIS Z8730 before and after a 2040-hour exposure test using a 3 mm thick test piece using the method of JIS K7350-4.
[ 5]
The traffic light lens and lens cover according to [1] or [4], the traffic light lens according to [2] or [4], or the traffic light lens cover according to [3] or [4], wherein the methacrylic resin composition has a weight average molecular weight of 65,000 to 300,000 as measured by gel permeation chromatography (GPC) .
[6]
The methacrylic resin contains 50 to 97 mass% of methacrylic acid ester monomer units (A), 3 to 30 mass% of structural units (B) having a ring structure in the main chain, and 0 to 20 mass% of other vinyl monomer units (C) copolymerizable with the methacrylic acid ester monomer. The traffic light lens and lens cover according to [1], [4], or [5] , the traffic light lens according to [2], [4], or [5], or the traffic light lens cover according to [3], [4], or [5] .
[7]
The traffic light lens and lens cover according to any one of [1] and [4] to [6], the traffic light lens according to any one of [2] and [4] to [6], or the traffic light lens cover according to any one of [3] to [6], wherein the structural unit (B) having a ring structure in the main chain contains at least one structural unit selected from the group consisting of a maleimide-based structural unit (B-1), a glutaric anhydride-based structural unit (B-2), a glutarimide-based structural unit (B-3), a lactone ring structural unit (B-4), and an acid anhydride structural unit (B-5) .
[8]
The traffic light lens and lens cover according to any one of [1], [4] to [7] , the traffic light lens according to any one of [2], [4] to [7], or the traffic light lens cover according to any one of [3] to [7], each having a thickness of 0.03 to 10 mm .
[9]
The content of at least one compound selected from the group consisting of fatty acid compounds, silicones, polyethers, and silicate compounds is 0.05 to 6 parts by mass relative to 100 parts by mass of the methacrylic resin. The traffic light lens and lens cover according to any one of [1] , [4] to [8] , the traffic light lens according to any one of [2], [4] to [8], or the traffic light lens cover according to any one of [3] to [8] .
[10]
When the methacrylic resin composition is injection molded into a flat plate having a thickness of 2 mm using a mold having a polishing number of 8000, the flat plate has a total light transmittance of 85% or more as measured in accordance with JIS K7361-1 and a haze of 5 or less as measured in accordance with JIS K7136. The traffic light lens and lens cover according to any one of [1] , [4] to [9] , the traffic light lens according to any one of [2], [4] to [9], or the traffic light lens cover according to any one of [3] to [9] .

The present invention provides a traffic light lens and a lens cover that contain a methacrylic resin composition that has excellent releasability, scratch resistance, heat resistance, weather resistance, optical properties, hue, and moldability.

Below, a form for carrying out the present invention (hereinafter referred to as the "present embodiment") will be described in detail, but the present invention is not limited to the following description and can be carried out in various modified forms within the scope of its gist.
In the following description, a structural unit constituting the polymer constituting the methacrylic resin contained in the methacrylic resin composition used in the present embodiment will be referred to as a "monomer unit" and/or a "structural unit" containing a plurality of the "monomer units".
Furthermore, the constituent material of such a "monomer unit" may be referred to simply as "monomer" without the "unit" part.

(Methacrylic resin composition)
The methacrylic resin composition used in the present embodiment has a change rate (ΔYI) of 20 or less between a 220 mm long optical path YI value (220 mm long optical path YI value (45 seconds)) measured in accordance with JIS K7105 on a test piece prepared at an injection molding temperature of 280° C. and a cycle time of 45 seconds, and a 220 mm long optical path YI value (220 mm long optical path YI value (270 seconds)) measured in accordance with JIS K7105 on a test piece prepared at an injection molding temperature of 280° C. and a cycle time of 270 seconds.
ΔYI={220 mm long optical path YI value (270 seconds)−220 mm long optical path YI value (45 seconds)}/220 mm long optical path YI value (45 seconds) (I)

The methacrylic resin composition of the present embodiment may contain at least one compound selected from the group consisting of a methacrylic resin, a fatty acid compound, a silicone, a polyether, and a silicate compound, compound (D), other components, and the like.
The methacrylic resin composition of the present embodiment preferably contains 80% by mass or more of the methacrylic resin relative to 100% by mass of the methacrylic resin composition, more preferably 85% by mass or more, even more preferably 90% by mass or more, and even more preferably 94% by mass or more. By setting the content of the methacrylic resin to the above-mentioned preferred amount, it is possible to improve the releasability, scratch resistance, heat resistance, weather resistance, optical properties, hue, and moldability required for the traffic light lens and lens cover.

(Methacrylic resin)
The methacrylic resin used in the methacrylic resin composition used in the present embodiment is not particularly limited in its composition, but may contain 50 to 97 mass% of methacrylic acid ester monomer units (A), 3 to 30 mass% of structural units (B) having a ring structure in the main chain, and 0 to 20 mass% of other vinyl monomer units (C) copolymerizable with the methacrylic acid ester monomer.

<Methacrylic acid ester monomer unit (A)>
As the methacrylic acid ester monomer unit (A) (hereinafter, sometimes referred to as monomer unit (A)) constituting the methacrylic resin, a monomer unit represented by the following general formula (A) is suitably used.

In the general formula (A), R ¹ represents a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, and the alkyl group may be substituted with a hydroxyl group. R ¹ is preferably a methyl group.
^R2 is a group having 1 to 12 carbon atoms, preferably a hydrocarbon group having 1 to 12 carbon atoms, which may be substituted with a hydroxyl group. ^R2 is preferably a group having 1 to 8 carbon atoms.

The monomer constituting the methacrylic acid ester monomer unit (A) shown in the above general formula (A) is not particularly limited, but it is preferable to use a methacrylic acid ester monomer shown in the following general formula (B).

In the general formula (ii), R ¹ represents a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, and the alkyl group may be substituted with a hydroxyl group. R ¹ is preferably a methyl group.
^R2 is a group having 1 to 12 carbon atoms, preferably a hydrocarbon group having 1 to 12 carbon atoms, which may be substituted with a hydroxyl group. ^R2 is preferably a group having 1 to 8 carbon atoms.

Examples of methacrylic acid ester monomers include, but are not limited to, butyl methacrylate, ethyl methacrylate, methyl methacrylate, propyl methacrylate, isopropyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, 2-ethylhexyl methacrylate, t-butylcyclohexyl methacrylate, benzyl methacrylate, and 2,2,2-trifluoroethyl methacrylate.
From the viewpoints of heat resistance, ease of handling, and optical properties, the methacrylic acid ester monomer is preferably methyl methacrylate, ethyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, or benzyl methacrylate, and from the viewpoint of availability, etc., methyl methacrylate is preferred.
The methacrylic acid ester monomer may be used alone or in combination of two or more kinds.

The methacrylic acid ester monomer unit (A) of the methacrylic resin must be contained in the methacrylic resin in an amount of 50% by mass or more and 97% by mass or less in order to provide sufficient heat resistance and good hue to the methacrylic resin composition used in this embodiment and the traffic light lens and lens cover of this embodiment by the structural unit (B) having a ring structure in the main chain described later. The content is preferably 55% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, even more preferably 80% by mass or more, and even more preferably 90% by mass or more.
Furthermore, when it is necessary to impart particularly high heat resistance, the content of the methacrylic acid ester monomer unit (A) in the methacrylic resin is preferably 96 mass % or less, and more preferably 95 mass % or less.

<Structural Unit (B) Having a Ring Structure in the Main Chain>
The structural unit (B) having a ring structure in the main chain constituting the methacrylic resin (hereinafter, may be referred to as a (B) structural unit) preferably contains at least one structural unit selected from the group consisting of a maleimide structural unit (B-1), a glutaric anhydride structural unit (B-2), a glutarimide structural unit (B-3), a lactone ring structural unit (B-4), and an anhydride oxide (B-5) from the viewpoint of heat resistance.
The structural unit (B) having a ring structure in the main chain may be used alone or in combination of two or more kinds.

[Maleimide structural unit (B-1)]
As the maleimide structural unit (B-1) constituting the methacrylic resin, a structural unit represented by the following general formula (III) is preferably used.

In the general formula (c), R ¹ represents any one selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, and an aryl group having 6 to 12 carbon atoms, and the alkyl group, alkoxy group, cycloalkyl group, and aryl group may have a substituent on a carbon atom.

Examples of monomers for forming the maleimide structural unit (B-1) include, but are not limited to, maleimide; N-alkyl group-substituted maleimides such as N-methylmaleimide, N-ethylmaleimide, and N-cyclohexylmaleimide; and N-aryl group-substituted maleimides such as N-phenylmaleimide, N-methylphenylmaleimide, N-ethylphenylmaleimide, N-butylphenylmaleimide, N-dimethylphenylmaleimide, N-hydroxyphenylmaleimide, N-methoxyphenylmaleimide, N-(o-chlorophenyl)maleimide, N-(m-chlorophenyl)maleimide, and N-(p-chlorophenyl)maleimide.
From the viewpoints of heat resistance and moist heat resistance, preferred examples of the monomer for forming the maleimide structural unit (B-1) include N-cyclohexylmaleimide, N-phenylmaleimide, N-methylphenylmaleimide, N-(o-chlorophenyl)maleimide, N-(m-chlorophenyl)maleimide, and N-(p-chlorophenyl)maleimide. From the viewpoints of availability and heat resistance, more preferred examples include N-cyclohexylmaleimide and N-phenylmaleimide, and even more preferred examples include N-phenylmaleimide.
The maleimide structural unit (B-1) may be used alone or in combination of two or more kinds.

[Glutaric anhydride structural unit (B-2)]
The glutaric anhydride structural unit (B-2) constituting the methacrylic resin may be formed after polymerization of the methacrylic resin.
As the structural unit (B-2), a structural unit represented by the following general formula (IV) is preferably used.

In the general formula (IV), R ¹ and R ² each independently represent a hydrogen atom or a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, and the alkyl group may be substituted with a hydroxyl group.
The glutaric anhydride structural unit (B-2) may be used alone or in combination of two or more kinds.

The method for forming the glutaric anhydride structural unit (B-2) is not particularly limited, but an example of such a method is to copolymerize a monomer having a structure represented by the following general formula (e) with a monomer constituting the above-mentioned methacrylic acid ester monomer unit (A), and then cyclize the monomer by heat treatment in the presence or absence of a catalyst.

In the general formula (e), R ¹ represents a hydrogen atom or a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, and the alkyl group may be substituted with a hydroxyl group.
^R2 represents a hydrogen atom or a t-butyl group.
Furthermore, as long as the effects of the present invention can be exhibited, the monomer having the structure represented by the general formula (e) may remain unreacted in the methacrylic resin.

[Glutarimide structural unit (B-3)]
The glutarimide structural unit (B-3) constituting the methacrylic resin may be formed after the resin polymerization.
As the (B-3) structural unit, a structural unit represented by the following general formula (f) is preferably used.

In the general formula (f), R ¹ and R ² each independently represent a hydrogen atom or a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, and the alkyl group may be substituted with a hydroxyl group.
Furthermore, ^R3 represents any one selected from the group consisting of a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, and a substituted or unsubstituted aryl group having 6 to 18 carbon atoms.
Particularly preferably, R ¹ , R ² and R ³ are all methyl groups.
The glutarimide structural unit (B-3) may be used alone or in combination of two or more kinds.

The content of the glutarimide structural unit (B-3) is not particularly limited and can be appropriately determined taking into consideration heat resistance, moldability, optical properties, and the like.
The content of the glutarimide structural unit (B-3) is preferably 1 to 50 mass %, more preferably 3 to 30 mass %, and even more preferably 3 to 20 mass %, based on 100 mass % of the methacrylic resin.
The content of the glutarimide structural unit (B-3) can be calculated, for example, by the method described in paragraphs [0136] to [0137] of WO 2015/098096.

The acid value of the resin containing the glutarimide structural unit (B-3) is preferably 0.50 mmol/g or less, more preferably 0.45 mmol/g or less, in consideration of the balance of the physical properties, moldability, color tone, etc. of the resin.
The acid value can be calculated, for example, by the titration method described in JP-A-2005-23272.

The glutarimide structural unit (B-3) can be obtained by a known method, such as a method of copolymerizing a methacrylic acid ester and/or methacrylic acid, followed by reacting ammonia or an amine with urea or unsubstituted urea at high temperature, a method of reacting a methyl methacrylate-methacrylic acid-styrene copolymer or a methyl methacrylate-styrene copolymer with ammonia or an amine, or a method of reacting polymethacrylic anhydride with ammonia or an amine.
Specifically, there may be mentioned the method described in US Pat. No. 4,246,374 to R.M. Kopchik.
The glutarimide structural unit (B-3) can also be formed by imidizing an acid anhydride such as maleic anhydride, a half ester of the acid anhydride with a linear or branched alcohol having 1 to 20 carbon atoms, or an α,β-ethylenically unsaturated carboxylic acid.

Furthermore, another preferred method for forming the glutarimide structural unit (B-3) includes a method in which a (meth)acrylic acid ester and, if necessary, an aromatic vinyl monomer or other vinyl monomers are polymerized, followed by an imidization reaction to obtain a resin containing the glutarimide structural unit (B-3).
In the imidization reaction step, an imidization agent may be used, and a ring-closing promoter may be added as necessary.
The imidizing agent may be ammonia or a primary amine, such as methylamine, ethylamine, n-propylamine, or cyclohexylamine.
The method for carrying out the imidization reaction is not particularly limited, and a conventionally known method can be used, for example, a method using an extruder, a horizontal twin-screw reaction apparatus, or a batch reaction tank. The extruder is not particularly limited, and a single-screw extruder, a twin-screw extruder, or a multi-screw extruder can be preferably used. More preferably, a tandem-type reactive extruder having two twin-screw extruders arranged in series can be used.

In addition, in producing the methacrylic resin containing the glutarimide structural unit (B-3), an esterification step of treating with an esterifying agent can be included in addition to the imidization reaction step.
By including the esterification step, carboxyl groups contained in the methacrylic resin that are by-produced during the imidization step can be converted into ester groups, and the acid value of the resin can be adjusted to a desired range.
The esterification agent is not particularly limited as long as it can exhibit the effects of the present invention, but preferably dimethyl carbonate or trimethyl acetate can be used. The amount of the esterification agent used is not particularly limited, but is preferably 0 to 12 parts by mass per 100 parts by mass of the methacrylic resin.
In addition to the esterifying agent, an aliphatic tertiary amine such as trimethylamine, triethylamine, or tributylamine can be used in combination as a catalyst.

[Lactone ring structural unit (B-4)]
The lactone ring structural unit (B-4) constituting the methacrylic resin may be formed after polymerization of the methacrylic resin.
As the structural unit (B-4), a structural unit represented by the following general formula (G) is preferably used.

In the general formula (G), R ¹ , R ² , and R ³ each independently represent a hydrogen atom or an organic group having 1 to 20 carbon atoms. The organic group may contain an oxygen atom.
The lactone ring structural unit (B-4) may be used alone or in combination of two or more kinds.

The method for producing a polymer containing a lactone ring structural unit (B-4) is not particularly limited, but may be, for example, a method in which a monomer having a hydroxyl group in the side chain, specifically a monomer having a structure represented by the following general formula (H) (e.g., 2-(hydroxymethyl)methyl acrylate) is copolymerized with a monomer having an ester group, such as the above-mentioned methacrylic acid ester monomer (A), and the resulting copolymer is then heat-treated in the presence/absence of a specific catalyst to introduce a lactone ring structure into the polymer.

In the general formula (h), R ¹ represents a hydrogen atom or a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, and the alkyl group may be substituted with a hydroxyl group.
^R2 represents a group having 1 to 12 carbon atoms, preferably a hydrocarbon group having 1 to 12 carbon atoms, which may be substituted with a hydroxyl group.
Particularly preferably, R ¹ is a hydrogen atom and R ² is a methyl group.
Furthermore, as long as the effects of the present invention can be exhibited, the monomer having the structure represented by the general formula (h) may remain unreacted in the methacrylic resin.

[Acid anhydride structural unit (B-5)]
The acid anhydride structural unit (B-5) constituting the methacrylic resin can be suitably formed, for example, by using an acid anhydride such as maleic anhydride, a half ester of the acid anhydride with a linear or branched alcohol having 1 to 20 carbon atoms, or an α,β-ethylenically unsaturated carboxylic acid.

The structural unit (B) having a ring structure in the main chain contained in the above-mentioned methacrylic resin preferably contains at least one structural unit selected from the group consisting of a maleimide-based structural unit (B-1) and a glutarimide-based structural unit (B-3), from the viewpoints of thermal stability and moldability, and more preferably contains a maleimide-based structural unit (B-1).
Among the maleimide structural units (B-1), in consideration of availability, N-cyclohexylmaleimide structural units and/or N-aryl-substituted maleimide structural units are preferred, and in terms of the hue of the molded product, N-cyclohexylmaleimide structural units are more preferred.

The content of the structural unit (B) having a ring structure in the main chain in the methacrylic resin is 3% by mass or more, preferably 4% by mass or more, and more preferably 5% by mass or more, from the viewpoint of imparting heat resistance and thermal stability to the methacrylic resin composition used in the present embodiment.
From the viewpoint of maintaining a good balance between the strength and fluidity required for a molded body, the content of the structural unit (B) having a ring structure in the main chain in the methacrylic resin is 30% by mass or less, preferably 25% by mass or less, more preferably 20% by mass or less, even more preferably 14% by mass or less, and still more preferably 10% by mass or less.

In particular, when a maleimide-based structural unit (B-1) is used as the structural unit (B) having a ring structure in the main chain, the content of the maleimide-based structural unit (B-1) is preferably less than 50% by mass, more preferably less than 40% by mass, even more preferably less than 35% by mass, even more preferably 1 to 30% by mass, and even more preferably 2 to 20% by mass, when the total amount of the methacrylic acid ester monomer unit (A) and the structural unit (B) having a ring structure in the main chain is taken as 100% by mass, from the viewpoint of heat resistance and thermal stability.

<Other vinyl monomer units (C) copolymerizable with methacrylic acid ester monomer>
In the methacrylic resin, from the viewpoint of obtaining a resin superior in weather resistance, fluidity, chemical resistance, thermal stability, etc., and imparting other properties, it is preferable to copolymerize other vinyl monomer units.
For example, acrylic acid ester monomer units (C-1) and vinyl cyanide monomer units (C-2) can be mentioned.

[Acrylic acid ester monomer unit (C-1)]
The monomer used to form the acrylic acid ester monomer unit (C-1) constituting the methacrylic resin is not particularly limited, but is preferably an acrylic acid ester monomer represented by the following general formula (i):

In the general formula (i), R ¹ represents a hydrogen atom or an alkoxy group having 1 to 12 carbon atoms, and R ² represents an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group having 1 to 18 carbon atoms, or an aryl group having 1 to 18 carbon atoms.

As a monomer for forming the acrylic acid ester monomer unit (C-1), from the viewpoint of enhancing weather resistance, heat resistance, fluidity, and thermal stability in the methacrylic resin used in the present embodiment, preferred are methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, sec-butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, phenyl acrylate, and the like, more preferred are methyl acrylate, ethyl acrylate, and n-butyl acrylate, and from the viewpoint of easy availability, methyl acrylate and ethyl acrylate are even more preferred.
The acrylic acid ester monomer unit (C-1) may be used alone or in combination of two or more kinds.
When the acrylic acid ester monomer unit (C-1) is used, its content is preferably 5% by mass or less, and more preferably 3% by mass or less, based on 100% by mass of the total amount of the monomer unit (A) and the structural unit (B), from the viewpoints of heat resistance and thermal stability.

[Cyanide vinyl monomer unit (C-2)]
In the methacrylic resin, the monomer unit (C) is preferably a vinyl cyanide monomer unit (C-2) from the viewpoints of easy availability and of obtaining a resin having even more excellent chemical resistance.
The monomer used to form the vinyl cyanide monomer unit (C-2) constituting the methacrylic resin includes, but is not limited to, acrylonitrile, methacrylonitrile, vinylidene cyanide, and the like. Among them, acrylonitrile is preferred from the viewpoints of availability and chemical resistance.
The vinyl cyanide monomer unit (C-2) may be used alone or in combination of two or more kinds.
When the vinyl cyanide monomer unit (C-2) is used, its content is preferably 15% by mass or less, more preferably 12% by mass or less, and even more preferably 10% by mass or less, based on 100% by mass of the total amount of the monomer unit (A) and the structural unit (B), from the viewpoint of maintaining solvent resistance and heat resistance.

[Monomer unit (C-3) other than (C-1) and (C-2)]
Examples of monomers used to form the monomer unit (C-3) other than (C-1) and (C-2) constituting the methacrylic resin include, but are not limited to, amides such as styrene, acrylamide, and methacrylamide; ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, and tetraethylene glycol di(meth)acrylate, in which both terminal hydroxyl groups of ethylene glycol or its oligomers are esterified with acrylic acid or methacrylic acid; neopentyl glycol di(meth)acrylate, di(meth)acrylate, and other esters of two alcohol hydroxyl groups with acrylic acid or methacrylic acid; trimethylolpropane, pentaerythritol, and other polyhydric alcohol derivatives esterified with acrylic acid or methacrylic acid; and polyfunctional monomers such as divinylbenzene.

Among the monomers used to form the above-mentioned (C) monomer unit, at least one selected from the group consisting of methyl acrylate, ethyl acrylate, and acrylonitrile is preferred from the viewpoint of availability. Also, from the viewpoint of maintaining transmittance and hue in a long optical path of 100 mm or more, (C) methyl acrylate is preferred.

The content of the other vinyl monomer unit (C) copolymerizable with the methacrylic acid ester monomer is 0 to 20 mass%, preferably 0 to 18 mass%, and more preferably 0 to 15 mass%, based on 100 mass% of the methacrylic resin, from the viewpoint of enhancing the effect of imparting heat resistance by the structural unit (B).
In particular, when a styrene monomer unit is used as the monomer unit (C), the content of the styrene monomer unit is preferably 0 to 6 mass% or less, more preferably 0 to 5 mass% or less, and even more preferably 0 to 3 mass% or less, based on 100 mass% of the methacrylic resin, from the viewpoint of improving weather resistance.
In particular, when a crosslinkable polyfunctional (meth)acrylate having a plurality of reactive double bonds is used as the (C) monomer unit, the content of the (C) monomer unit is preferably 0.5 mass% or less, more preferably 0.3 mass% or less, and even more preferably 0.2 mass% or less, from the viewpoint of flowability.

(Compound (D))
The compound (D) that can be contained in the methacrylic resin composition of the present embodiment is represented by the following general formula (1) or (2).

・・・（１）

... (1)

Here, R represents a hydrogen atom, an aliphatic hydrocarbon group having 1 to 12 carbon atoms, or an aromatic hydrocarbon group having 1 to 12 carbon atoms. The aliphatic hydrocarbon group and aromatic hydrocarbon group of R may each have a sulfur atom, a nitrogen atom, an oxygen atom, or a phosphorus atom on a carbon atom.
Furthermore, R' represents an aliphatic hydrocarbon group having 1 to 12 carbon atoms or an aromatic hydrocarbon group having 6 to 18 carbon atoms. The aliphatic hydrocarbon group and aromatic hydrocarbon group of R' may each have a sulfur atom, a nitrogen atom, an oxygen atom or a phosphorus atom on a carbon atom.

・・・（２）

... (2)

Here, R, R', and R" each independently represent a hydrogen atom, an aliphatic hydrocarbon group having 1 to 12 carbon atoms, or an aromatic hydrocarbon group having 1 to 12 carbon atoms. The aliphatic hydrocarbon group and aromatic hydrocarbon group of R, R', and R" may each have a sulfur atom, a nitrogen atom, an oxygen atom, or a phosphorus atom on a carbon atom. R' and R" may also bond to each other to form a ring.

From the viewpoint of suppressing the degree of change in the YI value during long-term residence, it is preferable that the (D) compound has a succinimide skeleton of the above formula (1), and it is more preferable that the (D) compound has a 3-hydroxysuccinimide skeleton in which R in the above formula (1) is a hydrogen atom.

From the viewpoint of minimizing the degree of change in the YI value during molding when repeatedly exposed to high temperatures for a long period of time, the content of the compound (D) is preferably 0.001 part by mass or more, more preferably 0.005 part by mass or more, even more preferably 0.01 part by mass or more, still more preferably 0.015 part by mass or more, still more preferably 0.02 part by mass or more, and particularly preferably 0.03 part by mass or more, relative to 100 parts by mass of the methacrylic resin.
Furthermore, from the viewpoint of maintaining high transmittance over a long optical path and high whiteness, the content is preferably 0.2 parts by mass or less, more preferably 0.15% by mass or less, even more preferably 0.12% by mass or less, even more preferably 0.11% by mass or less, and even more preferably 0.1% by mass or less.
By containing a certain amount of the compound (D), thermal decomposition of the methacrylic resin when placed in a high-temperature environment is suppressed, and the effects of reducing yellowing over a long optical path and improving transmittance stability can be obtained.

In this embodiment, the mass ratio of the compound (D) to the structural unit (B) having a ring structure in the main chain in the methacrylic resin composition is in the range of 25≦(B)/(D)≦1000 from the viewpoints of obtaining the effects of stability of YI during continuous molding, reduction of yellowing in a long optical path, and improvement of transmittance stability, and reduction of silver streaks and the like during molding processing.
From the viewpoint of reducing the yellowing degree dependency of the methacrylic resin composition on the thickness from 3 mm to 220 mm, that is, the change in the YI value between each thickness when the YI value is measured on a molded piece having a predetermined thickness between 3 mm and 220 mm, the (B)/(D) is preferably 800 or less, more preferably 700 or less, even more preferably 600 or less, and even more preferably 500 or less. From the viewpoint of the heat resistance of the methacrylic resin composition, the (B)/(D) is preferably 30 or more, more preferably 45 or more, and even more preferably 50 or more.

The characteristics of methacrylic resins are described below.

<Weight average molecular weight, molecular weight distribution>
The weight average molecular weight (Mw) of the methacrylic resin of this embodiment is 65,000 to 300,000 from the viewpoint of obtaining a methacrylic resin having even more excellent mechanical strength, solvent resistance, and fluidity.
By setting the weight average molecular weight of the methacrylic resin within the above range, the methacrylic resin and the methacrylic resin composition used in the present embodiment will have excellent mechanical strength, such as Charpy impact strength, and flowability.
From the viewpoint of maintaining mechanical strength, the weight average molecular weight is preferably 65,000 or more, more preferably 70,000 or more, even more preferably 80,000 or more, and still more preferably 100,000 or more.
In addition, from the viewpoints of ensuring flowability during molding, reducing distortion during molding, and imparting long optical path transmittance, the weight average molecular weight is preferably 250,000 or less, more preferably 200,000 or less, even more preferably 150,000 or less, still more preferably 130,000 or less, and even more preferably 120,000 or less.
From the viewpoint of the balance between fluidity, mechanical strength, and solvent resistance, the molecular weight distribution (weight average molecular weight (Mw)/number average molecular weight (Mn)) of the methacrylic resin is preferably 1.5 to 5. It is more preferably 1.5 to 4.5, even more preferably 1.6 to 4, even more preferably 1.6 to 3, and still more preferably 1.6 to 2.3.
The weight average molecular weight (Mw) and number average molecular weight (Mn) can be measured by gel permeation chromatography (GPC). In detail, a calibration curve is prepared from the elution time and the weight average molecular weight using a standard methacrylic resin that is available as a reagent and has a known monodisperse weight average molecular weight, number average molecular weight, and peak molecular weight, and an analytical gel column that elutes high molecular weight components first. Next, the weight average molecular weight and number average molecular weight of the methacrylic resin sample to be measured can be obtained from the obtained calibration curve.
Specifically, it can be measured by the method described in the Examples below.

(Methacrylic resin manufacturing method)
The method for producing the methacrylic resin is not particularly limited as long as the above-mentioned methacrylic resin can be obtained.

The methacrylic resin can be produced by bulk polymerization, solution polymerization, suspension polymerization, precipitation polymerization, or emulsion polymerization using the methacrylic acid ester monomer units (A), the structural units (B) having a ring structure in the main chain, and, if necessary, each monomer for forming the other vinyl monomer units (C) copolymerizable with the above-mentioned methacrylic acid ester monomer.
Preferably, bulk polymerization, solution polymerization, and suspension polymerization are used, more preferably solution polymerization and suspension polymerization, and further preferably suspension polymerization is used.
The methacrylic resin may be produced in a continuous manner or in a batch manner.
In the method for producing the methacrylic resin, it is preferable to polymerize the monomers by radical polymerization.

In the polymerization reaction of the methacrylic resin, a polymerization initiator may be used.
The polymerization initiator may be any one that decomposes at the polymerization temperature to generate active radicals, but it is necessary to achieve the required polymerization conversion within the range of the residence time, and a polymerization initiator having a half-life of 0.6 to 60 minutes, preferably 1 to 30 minutes, at the polymerization temperature is selected. However, even with respect to a polymerization initiator having a half-life of more than 60 minutes at the polymerization temperature, it can be used as a polymerization initiator that generates an amount of active radicals suitable for this embodiment by adding a predetermined amount all at once or over a period of about 10 minutes. In that case, in order to achieve the required polymerization conversion, a polymerization initiator having a half-life of 60 to 1800 minutes, preferably 260 to 900 minutes, at the polymerization temperature is selected.
A polymerization initiator to be suitably used can be appropriately selected in consideration of the polymerization temperature and polymerization time. For example, initiators described in "Organic Peroxides" data 13th Edition, published by Nippon Oil & Fats Co., Ltd., technical data published by Atochem Yoshitomi Co., Ltd., and "Azo Polymerization Initiators" published by Wako Pure Chemical Industries, Ltd. can be suitably used. The half-life can be easily determined from various constants described therein.

In the case of radical polymerization, the polymerization initiator is not limited to the following, but examples thereof include di-t-butyl peroxide, lauroyl peroxide, stearyl peroxide, benzoyl peroxide, t-butyl peroxy neodecane, t-butyl peroxy pivalate, dilauroyl peroxide, dicumyl peroxide, t-butylperoxy-2-ethylhexanoate, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(t-butylperoxy)cyclohexane (e.g., Perhexa (registered trademark) C), acetyl peroxide, capryl peroxide, etc. Side, 2,4-dichlorobenzoyl peroxide, isobutyl peroxide, acetylcyclohexylsulfonyl peroxide, t-butyl peroxybiparate, t-butylperoxy-2-ethylhexanoate, iso-propyl peroxydicarbonate, iso-butyl peroxydicarbonate, sec-butyl peroxydicarbonate, n-butyl peroxydicarbonate, 2-ethylhexyl peroxydicarbonate, bis(4-t-butylcyclohexyl)peroxydicarbonate, t-amylperoxy-2-ethylhexanoate, 1,1,3,3-tetramethylbutylperoxyethylhexanoate peroxyisopropyl monocarbonate, 1,1,2-trimethylpropylperoxy-2-ethylhexanoate, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane (e.g., Perhexa (registered trademark) 25B), t-butylperoxyisopropyl monocarbonate, t-amylperoxyisopropyl monocarbonate, 1,1,3,3-tetramethylbutylperoxyisopropyl monocarbonate, 1,1,2-trimethylpropylperoxyisopropyl monocarbonate, 1,1,3,3-tetramethylbutylperoxyisononatoate, 1,1,2-trimethylpropylperoxy-isononatoate, t-butylperoxybenzoate, and the like. Examples of common radical polymerization initiators include organic peroxides such as azobisisobutyronitrile, azobisisovaleronitrile, azobisdimethylvaleronitrile, azobiscyclohexanenitrile, 1,1-azobis(1-cyclohexanecarbonitrile), 2,2'-azobis-4-methoxy-2,4-azobisisobutyronitrile, 2,2'-azobis-2,4-dimethylvaleronitrile, 2,2'-azobis-2-methylbutyronitrile, 1,1'-azobis(1-acetoxy-1-phenylethane), dimethyl-2,2'-azobisisobutyrate, and 4,4'-azobis-4-cyanovaleric acid.

The above-mentioned radical polymerization initiators may be used as redox initiators in combination with an appropriate reducing agent.
These polymerization initiators may be used alone or in combination of two or more.

The polymerization initiator may be added in an amount necessary to obtain a desired polymerization rate in a polymerization reactor.
In a polymerization reaction, the degree of polymerization can be increased by increasing the amount of polymerization initiator supplied. However, using a large amount of polymerization initiator tends to decrease the overall molecular weight and increases the amount of heat generated during polymerization, which may result in a decrease in polymerization stability due to overheating.
From the viewpoint of facilitating obtaining a desired molecular weight and ensuring polymerization stability, the polymerization initiator is used in an amount of preferably 0 to 1 part by mass, more preferably 0.001 to 0.8 parts by mass, and even more preferably 0.01 to 0.5 parts by mass, relative to 100 parts by mass of the total amount of all monomers used.
The amount of the polymerization initiator to be added can be appropriately selected taking into consideration the temperature at which the polymerization is carried out and the half-life of the initiator.

In the polymerization reaction of the methacrylic resin, a chain transfer agent, an iniferter, or the like can be optionally used as a molecular weight regulator.
In the process for producing the methacrylic resin, the molecular weight of the polymer produced can be controlled within a range that does not impair the object of the present invention.
Examples of the chain transfer agent and the iniferter include, but are not limited to, alkyl mercaptans, dimethylacetamide, dimethylformamide, triethylamine, and other chain transfer agents; dithiocarbamates, triphenylmethylazobenzene, tetraphenylethane derivatives, and other iniferters; and the molecular weight can be controlled by using these chain transfer agents and iniferters. Furthermore, the molecular weight can be controlled by adjusting the amount of these chain transfer agents and iniferters added.

When these chain transfer agents or iniferters are used, alkyl mercaptans are preferably used from the viewpoint of handleability and stability. Examples of such alkyl mercaptans include, but are not limited to, n-butyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, n-tetradecyl mercaptan, n-octadecyl mercaptan, 2-ethylhexyl thioglycolate, ethylene glycol dithioglycolate, trimethylolpropane tris(thioglycolate), pentaerythritol tetrakis(thioglycolate), and the like.
These molecular weight modifiers can be added as appropriate depending on the required molecular weight, but are generally used in an amount of 0.001 to 3 parts by mass per 100 parts by mass of the total amount of all monomers used.

Other methods for controlling the molecular weight include changing the polymerization method, adjusting the amount of the polymerization initiator, and changing the polymerization temperature.
These molecular weight control methods may be used alone or in combination of two or more kinds.

In the methacrylic resin, a chain transfer agent (molecular weight regulator) may be used to adjust the molecular weight and to improve the thermal stability of the polymer. There are no limitations on the type and method of use of the chain transfer agent used, so long as it can exert the effects of the present invention.

<Production method by suspension polymerization method>
When the methacrylic resin is produced by suspension polymerization such as organic suspension polymerization or inorganic suspension polymerization, a particulate methacrylic resin is produced through a polymerization process, a washing process, a dehydration process, and a drying process using a stirring device described later.
Usually, an aqueous suspension polymerization method using water as a medium is preferably used.

[Polymerization process]
In the polymerization step, a predetermined stirring device is used, and the raw material monomers, a suspending agent, and, if necessary, a polymerization initiator and additives are appropriately supplied to the stirring device to carry out polymerization, thereby obtaining a slurry of a methacrylic resin.
Examples of the stirring device used in the polymerization step for obtaining a methacrylic resin by suspension polymerization include known stirring devices such as a stirring device having a stirring blade such as an inclined paddle blade, a flat paddle blade, a propeller blade, an anchor blade, a Pfaudler blade (swept back blade), a turbine blade, a Blue Margin blade, a Max Blend blade, a Full Zone blade, a ribbon blade, a Super Mix blade, an Intermig blade, a special blade, or an axial flow blade inside, a stirring device having a shovel blade inside, a stirring device having a chopper blade inside, and a stirring device having a rotating disk such as a disk type, a notched disk type, or a screw type inside.
The stirring speed during polymerization depends on the type of stirring device used, the stirring efficiency of the stirring blades, the volume of the polymerization tank, and the like, but is preferably about 1 to 500 rpm in consideration of the ability to obtain an appropriate particle size, the ability to reduce the content of components having a particle size of less than 0.15 mm, polymerization stability, and the like.

The temperature when adding the raw material mixture of the methacrylic resin may be within a range in which the effects of the present invention can be exhibited, and is preferably 0°C or higher and the boiling point of the raw material used or lower. If the temperature is high, the raw materials tend to volatilize during addition, which changes the composition of the copolymer constituting the resulting methacrylic resin, and if the temperature is low and lower than 0°C, it takes time to increase the temperature after adding the raw materials, so it is preferable to add the raw material mixture at a certain temperature. Specifically, the temperature is preferably 0°C or higher and 85°C or lower, more preferably 10°C or higher and 85°C or lower, even more preferably 30°C or higher and 85°C or lower, even more preferably 50°C or higher and 80°C or lower, and even more preferably 60°C or higher and 80°C or lower.
In consideration of productivity and the amount of aggregates produced, the temperature in the suspension polymerization step is preferably 40° C. or higher and 90° C. or lower, more preferably 50° C. or higher and 85° C. or lower, even more preferably 60° C. or higher and 85° C. or lower, and even more preferably 65° C. or higher and 83° C. or lower.

The polymerization time in suspension polymerization is preferably 20 minutes or more and 240 minutes or less from the viewpoint of effectively suppressing heat generation during polymerization and reducing the generation of aggregates and residual monomers, which will be described later. More preferably, it is 30 minutes or more and 210 minutes or less, even more preferably 45 minutes or more and 180 minutes or less, even more preferably 60 minutes or more and 180 minutes or less, and even more preferably 90 minutes or more and 150 minutes or less.

From the viewpoint of reducing the amount of residual monomers, it is preferable to raise the temperature to a temperature higher than the polymerization temperature after the polymerization step and maintain the temperature for a certain period of time.
The temperature at which the mixture is maintained is preferably higher than the polymerization temperature because the degree of polymerization can be increased. When the temperature is higher, the temperature is preferably increased by 5° C. or more from the polymerization temperature.
When the temperature is increased, it is preferably equal to or lower than the glass transition temperature of the resulting methacrylic resin in order to prevent aggregation of the resulting polymer.
Specifically, it is 120°C or less, preferably 100°C or less, more preferably 80°C or more and 100°C or less, even more preferably 85°C or more and 100°C or less, still more preferably 88°C or more and 100°C or less, and still more preferably 90°C or more and 100°C or less.
By carrying out the polymerization at the above-mentioned polymerization temperature and holding time, it is possible to produce polymer particles having a small angle of repose after the drying step described below.
Taking into consideration the effect of reducing residual monomers, the time for which the temperature is maintained after the temperature is raised is preferably from 15 minutes to 360 minutes, more preferably from 30 minutes to 240 minutes, even more preferably from 30 minutes to 180 minutes, still more preferably from 30 minutes to 150 minutes, and still more preferably from 30 minutes to 120 minutes.

In order to reduce the amount of residual monomers, an organic solvent may be used during polymerization within a range that does not affect polymerization stability. Suitable organic solvents are those that can dissolve the resulting resin, and aromatic hydrocarbon solvents such as xylene, toluene, and ethylbenzene are suitable.
When used, the amount used is preferably 15 parts by mass or less, more preferably 10 parts by mass or less, even more preferably 8 parts by mass or less, and even more preferably 6 parts by mass or less, based on 100 parts by mass of the total amount of monomers used.

[Cleaning process]
The methacrylic resin slurry obtained through the above-mentioned polymerization step is preferably subjected to an operation such as acid washing, water washing or alkali washing in order to remove the suspending agent.
The number of times these washing operations are carried out may be selected optimally from the viewpoints of work efficiency and efficiency of removing the suspending agent, and may be carried out once or multiple times.
The temperature for washing may be selected optimally in consideration of the efficiency of removing the suspending agent, the degree of coloration of the resulting copolymer, etc., and is preferably 20 to 100° C., more preferably 30 to 95° C., and even more preferably 40 to 95° C.
The washing time per washing is preferably 10 to 180 minutes, more preferably 20 to 150 minutes, from the viewpoints of washing efficiency, effect of reducing the angle of repose, and ease of process.

The pH of the washing solution used during washing may be within a range that allows removal of the suspending agent, and is preferably 1 to 12.
The pH when acid washing is carried out is preferably from 1 to 5, more preferably from 1.2 to 4, from the viewpoints of the efficiency of removing the suspending agent and the color tone of the resulting copolymer.
The acid used in this case is not particularly limited as long as it is capable of removing the suspending agent, and any conventionally known inorganic acid or organic acid can be used.
Suitable acids include inorganic acids such as hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, and boric acid, each of which may be used in the form of a diluted solution diluted with water, etc. Suitable organic acids include those having a carboxyl group, a sulfo group, a hydroxyl group, a thiol group, and an enol group.
Considering the effect of removing the suspending agent and the color tone of the resulting resin, nitric acid, sulfuric acid, and organic acids having a carboxyl group are more preferable.

After the acid washing, it is preferred to further carry out washing with water or washing with an alkali from the viewpoints of the color tone of the resulting polymer and reducing the angle of repose.
When alkaline cleaning is performed, the pH of the alkaline solution is preferably 7.1 to 12, more preferably 7.5 to 11, and even more preferably 7.5 to 10.5. The alkaline component used in alkaline cleaning is preferably a tetraalkylammonium hydroxide, an alkali metal hydroxide, an alkaline earth metal hydroxide, or the like. More preferably, it is an alkali metal hydroxide or an alkaline earth metal hydroxide, even more preferably, it is lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, cesium hydroxide, magnesium hydroxide, calcium hydroxide, or barium hydroxide, even more preferably, it is lithium hydroxide, sodium hydroxide, potassium hydroxide, magnesium hydroxide, or calcium hydroxide, and even more preferably, it is sodium hydroxide or potassium hydroxide. These alkaline components can be used by diluting with water or the like to adjust the pH.

[Dehydration process]
As a method for dehydrating the obtained polymer slurry of the methacrylic resin and separating the polymer particles, a conventionally known method can be applied.
For example, there may be mentioned a dehydration method using a centrifuge which utilizes centrifugal force to spin off water, and a method in which water is removed by suction on a porous belt or a filter membrane to separate polymer particles.

[Drying process]
The polymer of the methacrylic resin in a water-containing state obtained through the above-mentioned dehydration step can be dried by a known method and recovered.
Examples of the drying method include hot air drying, which involves blowing hot air into a tank from a hot air blower, blow heater, or the like; vacuum drying, which involves drying by reducing the pressure inside the system and then heating it as necessary; barrel drying, which involves rotating the obtained polymer in a container to remove moisture; and spin drying, which involves drying using centrifugal force.
These methods may be used alone or in combination.
The water content of the resulting methacrylic resin is preferably 0.01% by mass to 1% by mass, more preferably 0.05% by mass to 1% by mass, even more preferably 0.1% by mass to 1% by mass, and still more preferably 0.27% by mass to 1% by mass, taking into consideration the handleability, color tone, and the like of the resulting methacrylic resin.
The water content of the resulting resin can be measured by the Karl Fischer method.

When the methacrylic resin is produced by the above-mentioned suspension polymerization method, the resulting methacrylic resin is usually substantially spherical, but aggregates may be formed in some cases.
The term "agglomerates" refers to residues remaining on a 1.68 mm mesh sieve when the obtained polymer is passed through the sieve.
If the aggregates remain in the methacrylic resin, the color tone of the resulting methacrylic resin tends to be deteriorated. From this viewpoint, the amount of aggregates in the methacrylic resin is preferably 1.2% by mass or less, and more preferably 1.0% by mass or less.
The content of agglomerates can be determined by passing the mixture through a 1.68 mm mesh sieve, drying the material remaining on the sieve in a drying oven at 80°C for 12 hours, measuring its weight, and dividing the resulting mass by the total amount of the raw materials to calculate the amount of agglomerates generated (mass %).

The average particle size of the methacrylic resin obtained by using the above-mentioned suspension polymerization method is preferably 0.1 mm or more, taking into consideration workability during molding and extrusion, and is more preferably 0.1 mm or more and 1 mm or less, even more preferably 0.1 mm or more and 0.5 mm or less, and even more preferably 0.1 mm or more and 0.4 mm or less, taking into consideration the color tone of the molded piece obtained by molding.
The average particle size can be measured, for example, by using sieves (Tokyo Screen JTS-200-45-44 (mesh size 500 μm), 34 (mesh size 425 μm), 35 (mesh size 355 μm), 36 (mesh size 300 μm), 37 (mesh size 250 μm), 38 (mesh size 150 μm), 61 (receiving pan)) based on JIS-Z8801, sieving is performed for 10 minutes at a vibration force of MAX using a sieving tester TSK B-1, measuring the mass of particles remaining on each sieve, and determining the particle size when the mass becomes 50%.

<Production method by solution polymerization method>
Hereinafter, as a suitable method for producing a methacrylic resin, for example, the solution polymerization method described in JP 2017-125185 can be mentioned.

The methacrylic resin composition used in this embodiment contains at least one compound selected from the group consisting of fatty acid compounds, silicones, polyethers, and silicate compounds. This compound makes the surface of molded articles exposed to outdoor wind, rain, and dust, such as traffic light covers and lenses, less susceptible to scratches, and also improves the releasability of molded articles with precise optical designs, such as traffic light covers and lenses.

<Fatty Acid Compounds>
Examples of the fatty acid compound include, but are not limited to, higher fatty acids such as stearic acid, behenic acid, zinc stearate, calcium stearate, magnesium stearate, and metal salts thereof, higher fatty acid amides such as ethylene bisstearamide, fatty acid esters, fatty acid amides, and fatty acid metal salts.

The fatty acid ester is not particularly limited, and any of the conventionally known fatty acid esters can be used.
Examples of fatty acid esters that can be used include ester compounds of fatty acids having 12 to 32 carbon atoms, such as lauric acid, palmitic acid, heptadecanoic acid, stearic acid, oleic acid, arachic acid, and behenic acid, with monohydric aliphatic alcohols, such as palmityl alcohol, stearyl alcohol, and behenyl alcohol, and polyhydric aliphatic alcohols, such as glycerin, pentaerythritol, dipentaerythritol, and sorbitan; and complex ester compounds of fatty acids, polybasic organic acids, and monohydric aliphatic alcohols or polyhydric aliphatic alcohols.
Examples of such fatty acid esters include cetyl palmitate, butyl stearate, stearyl stearate, stearyl citrate, glycerin monocaprylate, glycerin monocaprate, glycerin monolaurate, glycerin monopalmitate, glycerin dipalmitate, glycerin monostearate, glycerin distearate, glycerin tristearate, glycerin monooleate, glycerin dioleate, glycerin trioleate, glycerin monolinoleate, glycerin monobehenate, glycerin mono 12-hydroxystearate, glycerin di 12-hydroxystearate, glycerin tri 12-hydroxystearate, glycerin diacetomonostearate, glycerin citric acid fatty acid ester, pentaerythritol adipic acid stearate, partially saponified montanic acid ester, pentaerythritol tetrastearate, dipentaerythritol hexastearate, and sorbitan tristearate.
These fatty acid esters may be used alone or in combination of two or more.
Examples of commercially available products include, but are not limited to, the Rikemal series, Poem series, Rikestar series, and Rikemaster series manufactured by Riken Vitamin Co., Ltd., and the Excel series, Leo D'or series, Exepar series, and Coconard series manufactured by Kao Corporation, and more specific examples include Rikemal S-100, Rikemal H-100, Poem V-100, Rikemal B-100, Rikemal HC-100, Rikemal S-200, Poem B-200, Rikestar EW-200, Rikestar EW-400, Excel S-95, and Leo D'or MS-50.

The fatty acid amide is also not particularly limited, and any of the conventionally known fatty acid amides can be used.
Examples of fatty acid amides include saturated fatty acid amides such as lauric acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, and hydroxystearic acid amide; unsaturated fatty acid amides such as oleic acid amide, erucic acid amide, and ricinoleic acid amide; substituted amides such as N-stearyl stearic acid amide, N-oleyl oleic acid amide, N-stearyl oleic acid amide, N-oleyl stearic acid amide, N-stearyl erucic acid amide, and N-oleyl palmitic acid amide; methylol amides such as methylol stearic acid amide and methylol behenic acid amide; methylene bisstearic acid amide, ethylene biscapric acid amide, ethylene bislauric acid amide, and ethylene bisstearic acid amide (ethylene bis saturated fatty acid bisamides such as ethylene bisstearylamide, ethylene bisisostearic acid amide, ethylene bishydroxystearic acid amide, ethylene bisbehenic acid amide, hexamethylene bisstearic acid amide, hexamethylene bisbehenic acid amide, hexamethylene bishydroxystearic acid amide, N,N'-distearyl adipamide, and N,N'-distearyl sebacic acid amide; unsaturated fatty acid bisamides such as ethylene bisoleic acid amide, hexamethylene bisoleic acid amide, N,N'-dioleyl adipamide, and N,N'-dioleyl sebacic acid amide; and aromatic bisamides such as m-xylylene bisstearic acid amide and N,N'-distearyl isophthalic acid amide.
These fatty acid amides may be used alone or in combination of two or more.
Examples of commercially available products include, but are not limited to, the Diamid series (manufactured by Nippon Kasei Chemical Industry Co., Ltd.), the Amide series (manufactured by Nippon Kasei Chemical Industry Co., Ltd.), the Nikka Amide series (manufactured by Nippon Kasei Chemical Industry Co., Ltd.), the Methylol Amide series, the Bis Amide series, the Slipax series (manufactured by Nippon Kasei Chemical Industry Co., Ltd.), the Kaowax series (manufactured by Kao Corporation), the Fatty Acid Amide series (manufactured by Kao Corporation), and ethylene bis stearic acid amides (manufactured by Dainichi Chemical Industry Co., Ltd.).

The fatty acid metal salt refers to a metal salt of a higher fatty acid, and includes, but is not limited to, for example, lithium stearate, magnesium stearate, calcium stearate, calcium laurate, calcium ricinoleate, strontium stearate, barium stearate, barium laurate, barium ricinoleate, zinc stearate, zinc laurate, zinc ricinoleate, zinc 2-ethylhexoate, lead stearate, dibasic lead stearate, lead naphthenate, calcium 12-hydroxystearate, lithium 12-hydroxystearate, and the like. Among these, calcium stearate, magnesium stearate, and zinc stearate are particularly preferred because the resulting methacrylic resin composition has excellent processability and extremely excellent transparency.
These fatty acid metal salts may be used alone or in combination of two or more.
Examples of commercially available products include the SZ series, SC series, SM series, and SA series manufactured by Sakai Chemical Industry Co., Ltd.

The fatty acid compounds may be used alone or in combination of two or more.
The fatty acid compound to be used is preferably one having a decomposition onset temperature of 200° C. or higher. The decomposition onset temperature can be measured based on the 1% weight loss temperature by TGA.

If the content of the fatty acid compound is excessive, problems such as bleed-out during processing and poor extrusion due to screw slippage may occur, so the content is preferably 1 part by mass or less, more preferably 0.5 parts by mass or less, even more preferably 0.4 parts by mass or less, and even more preferably 0.3 parts by mass or less, relative to 100 parts by mass of the methacrylic resin. In addition, in order to improve scratch resistance and releasability, the content of the fatty acid compound is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, and even more preferably 0.2 parts by mass or more.
When added in an amount within the above range, the decrease in transparency and bleed-out caused by the addition of fatty acid compounds are suppressed, and the scratch resistance and mold releasability of the molded body are improved, resulting in a lens or lens cover with good physical properties for use in a traffic light.

<Silicone>
The silicone contains a polymer having a polyorganosiloxane as a main chain. Among the polymers having a polyorganosiloxane as a main chain, at least one selected from organic modified silicone and dimethyl silicone oil is preferable because the molded body has good scratch resistance.
As the organic modified silicone, polyester modified silicone is preferred because it has excellent compatibility with methacrylic resins, can ensure the transparency of the molded product, and has excellent scratch resistance. Polyester modified silicone refers to a compound in which a saturated polyester group is added to the side chain of polydimethylsiloxane (PDMS).
The content of silicone is preferably 0.1 parts by mass or more to improve scratch resistance and 6 parts by mass or less to improve transparency of the molded product, more preferably 0.2 parts by mass or more and 5 parts by mass or less, and even more preferably 0.3 parts by mass or more and 4 parts by mass or less, relative to 100 parts by mass of the methacrylic resin.
The silicones may be used alone or in combination of two or more.

<Polyether>
Examples of polyethers include polyethylene glycol, polypropylene glycol, and polytetramethylene glycol.
In order to improve scratch resistance over a long period of time, the molecular weight of the polyether is preferably 2,000 or more, and from the viewpoint of maintaining the transparency of the methacrylic resin composition, it is preferably 30,000 or less. The molecular weight of the polyether is more preferably 3,000 to 25,000, and even more preferably 4,000 to 22,000.
The content of the polyether is preferably 0.5 parts by mass or more to improve scratch resistance, and is preferably 8 parts by mass or less to suppress molding defects and prevent slipping, more preferably 1 part by mass or more and 6 parts by mass or less, and even more preferably 2 parts by mass or more and 5 parts by mass or less, relative to 100 parts by mass of the methacrylic resin.
The polyethers may be used alone or in combination of two or more kinds.

<Silicate Compound>
The silicate compound is, for example, a salt of a silicate ion, such as an orthosilicate ion, a pyrosilicate ion, or a hexafluorosilicate ion, with a metal species, such as sodium, magnesium, lithium, calcium, iron, manganese, aluminum, zinc, or potassium.
The silicate compound used in this embodiment is preferably modified by an organic modifier to improve dispersibility and transparency when added to a methacrylic resin composition. The organic modifier is preferably 10 parts by mass or more per 100 parts by mass of the silicate compound. In this range, dispersibility and transparency can be improved when added to a methacrylic resin composition. In addition, the organic modifier is preferably 70 parts by mass or less per 100 parts by mass of the silicate compound. By setting the organic modifier to 70 parts by mass or less, silver during molding due to volatilization of the organic modifier can be suppressed. The organic modifier is more preferably 20 parts by mass or more and 60 parts by mass or less, and even more preferably 30 parts by mass or more and 50 parts by mass or less.
The content of the silicate compound is preferably 0.05 parts by mass or more relative to 100 parts by mass of the methacrylic resin in order to improve scratch resistance, and is preferably 1 part by mass or less in order to improve the transparency of the methacrylic resin composition. The content of the silicate compound is more preferably 0.1 parts by mass or more and 0.8 parts by mass or less, and even more preferably 0.15 parts by mass or more and 0.5 parts by mass or less, relative to 100 parts by mass of the methacrylic resin.
The silicate compounds may be used alone or in combination of two or more.

(Other ingredients)
<Other resins>
The methacrylic resin composition of the present embodiment may contain other known resins in combination, as long as the resins can exhibit the properties required for the methacrylic resin composition of the present embodiment.
Examples of other resins include thermoplastic resins. Examples of the thermoplastic resins include, but are not limited to, rubber polymers such as acrylic rubber, polyethylene resins, polypropylene resins, polystyrene resins, syndiotactic polystyrene resins, polycarbonate resins, ABS resins, acrylic resins, AS resins, BAAS resins, MBS resins, AAS resins, biodegradable resins, polycarbonate-ABS resin alloys, polyalkylene arylate resins (polybutylene terephthalate, polyethylene terephthalate, polypropylene terephthalate, polytrimethylene terephthalate, polyethylene naphthalate, etc.), polyamide resins, polyphenylene ether resins, polyphenylene sulfide resins, phenol resins, and the like.
In particular, AS resin and BAAS resin are preferred from the viewpoint of improving flowability, acrylic rubber polymer, ABS resin and MBS resin are preferred from the viewpoint of improving impact resistance, and polyester resin is preferred from the viewpoint of improving chemical resistance.
Polycarbonate-based resins are preferred when it is necessary to impart heat resistance, impact resistance, or adjust optical properties, while acrylic-based resins have good compatibility with the above-mentioned methacrylic-based resins and are preferred when it is necessary to adjust properties such as fluidity and impact resistance while maintaining transparency.
The above-mentioned various thermoplastic resins may be used alone or in combination of two or more kinds.

In the methacrylic resin composition used in the present embodiment, when the above-mentioned methacrylic resin and the other resin are combined, it is sufficient that the effects of the present invention can be exhibited. However, taking into consideration the effect of imparting characteristics, the blending ratio of the other resin, when a general-purpose acrylic resin is blended as the other resin, is preferably 95% by mass or less, more preferably 85% by mass or less, even more preferably 80% by mass or less, and even more preferably 75% by mass or less, relative to 100% by mass of the total amount of the above-mentioned methacrylic resin and the other resin.
Furthermore, when a resin other than an acrylic resin is blended as the other resin, the amount is preferably 50% by mass or less, more preferably 45% by mass or less, even more preferably 40% by mass or less, still more preferably 30% by mass or less, and even more preferably 20% by mass or less, relative to 100% by mass of the total amount of the above-mentioned methacrylic resin and other resin.
In addition, taking into consideration the effect of imparting characteristics when other resins are blended, the lower limit of the blending amount when other resins are blended is preferably 0.1 mass % or more, more preferably 1 mass % or more, even more preferably 2 mass % or more, still more preferably 3 mass % or more, and still more preferably 5 mass % or more.
The type and content of the other resin can be appropriately selected depending on the effect expected when used in combination with the other resin.

<Additives>
In the methacrylic resin composition used in the present embodiment, additives may be optionally blended. The additives are not particularly limited as long as they can exert the effects of the present invention, and may be appropriately selected depending on the purpose.
Examples of additives include, but are not limited to, various stabilizers such as ultraviolet absorbers, heat stabilizers, and light stabilizers; plasticizers (paraffin-based process oils, naphthene-based process oils, aromatic process oils, paraffin, and mineral oils); flame retardants (e.g., phosphorus-based, halogen-based, silica-based, and silicone-based additives such as organic phosphorus compounds, red phosphorus, and inorganic phosphates); flame retardant assistants (e.g., antimony oxides, metal oxides, and metal hydroxides); curing agents (diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, Amines such as diethylaminopropylamine, 3,9-bis(3-aminopropyl)-2,4,8,10-tetraoxaspiro[5,5]undecane, menthenediamine, isophoronediamine, N-aminoethylpiperazine, m-xylenediamine, m-phenylenediamine, diaminophenylmethane, diaminodiphenylsulfone, dicyandiamide, and adipic acid dihydrazide; phenolic resins such as phenol novolac resin and cresol novolac resin; polymercaptans such as liquid polymercaptan and polysulfide; phthalic anhydride; tetrahydric (b) Phthalic anhydride, hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, methylnadic anhydride, pyromellitic anhydride, methylcyclohexenetetracarboxylic anhydride, dodecylsuccinic anhydride, trimellitic anhydride, chlorendic anhydride, benzophenonetetracarboxylic anhydride, ethylene glycol bis(anhydrotrimate), and other acid anhydrides; curing accelerators (2-methylimidazole, 2-ethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-undecyl imidazoles such as midazole, 2-heptadecylimidazole, 2-phenyl-4-methylimidazole, etc.; organic phosphines such as triphenylphosphine, tributylphosphine, etc.; tertiary amines such as benzyldimethylamine, 2-dimethylaminomethyl)phenol, 2,4,6-tris(diaminomethyl)phenol, tetramethylhexanediamine, etc.; boron salts such as triphenylphosphine tetraphenylborate, tetraphenylphosphonium tetraphenylborate, triethylamine tetraphenylborate, etc.; 1,4-benzoquinone, 1,4- quinoid compounds such as naphthoquinone, 2,3-dimethyl-1,4-benzoquinone, 2,6-dimethylbenzoquinone, and 2,3-dimethoxy-1,4-benzoquinone); antistatic agents (for example, polyamide elastomers, quaternary ammonium salts, pyridine derivatives, aliphatic sulfonates, aromatic sulfonates, aromatic sulfonate copolymers, sulfates, polyhydric alcohol partial esters, alkyldiethanolamines, alkyldiethanolamides, polyalkylene glycol derivatives, betaines, and imidazoline derivatives); conductivity imparting agents; stress relaxation agents; crystallization Accelerators; hydrolysis inhibitors; compatibilizers; nucleating agents; reinforcing agents such as fillers; impact agents; flow control agents; dyes (nitroso dyes, nitro dyes, azo dyes, stilbene azo dyes, ketoimine dyes, triphenylmethane dyes, xanthene dyes, acridine dyes, quinoline dyes, methine/polymethine dyes, thiazole dyes, indamine/indophenol dyes, azine dyes, oxazine dyes, thiazine dyes, sulfur dyes, aminoketone/oxyketone dyes, anthraquinone dyes, indigoid dyes, phthalocyanine dyes, and other dyes); sensitizers; colorants (titanium oxide, carbon black, etc.) Inorganic pigments such as chromium, titanium yellow, iron oxide pigments, ultramarine, cobalt blue, chromium oxide, spinel green, lead chromate pigments, and cadmium pigments; azo pigments such as azo lake pigments, benzimidazolone pigments, diarylide pigments, and condensed azo pigments; phthalocyanine pigments such as phthalicyanine blue and phthalocyanine green; organic pigments such as isoindolinone pigments, quinophthalone pigments, quinacridone pigments, perylene pigments, anthraquinone pigments, perinone pigments, and condensed polycyclic pigments such as dioxazine violet; aluminum flake metallic pigments; Examples of suitable pigments include spherical aluminum pigments used to improve the color of the product, mica powder for pearlescent metallic pigments, and other metallic pigments obtained by coating inorganic polyhedral particles such as glass with metal plating or sputtering; thickeners; anti-settling agents; anti-sagging agents; fillers (fibrous reinforcing agents such as glass fiber and carbon fiber, as well as glass beads, calcium carbonate, talc, clay, etc.); defoamers (silicone-based defoamers, surfactants, and organic defoamers such as polyethers and higher alcohols); coupling agents; light-diffusing fine particles; rust inhibitors; antibacterial and anti-fungal agents; antifouling agents; and conductive polymers.

<<Light stabilizers>>
A light stabilizer may be added to the methacrylic resin composition used in this embodiment in order to improve weather resistance.
As the light stabilizer, a hindered amine light stabilizer (HALS) can be suitably added.
Examples of light stabilizers that can be suitably used include, but are not limited to, bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate, bis(1-octyloxy-2,2,6,6-tetramethyl-4-piperidyl)sebacate, bis(1,2,2,6,6-pentamethyl-4-piperidinyl)sebacate, 2-(3,5-di-tert-butyl-4-hydroxybenzyl)-2-n-butylmalonate bis(1,2,2,6,6-pentamethyl-4-piperidyl), tetra kis(1,2,2,6,6-pentamethyl-4-piperidyl)1,2,3,4-butanetetracarboxylate, 1,2,2,6,6-pentamethyl-4-piperidyl/tridecyl-1,2,3,4-butanetetracarboxylate, {1,2,2,6,6-pentamethyl-4-piperidyl/β,β,β',β'-tetramethyl-3,9-[2,4,8,10-tetraoxaspiro(5,5)undecane]diethyl}-1,2,3,4butanetetracarboxylate, and the like.
Also, dimethyl succinate-1-(2-hydroxyethyl)-4-hydroxy-2,2,6,6-tetramethylpiperidine polycondensate, N,N'-bis(3-aminopropyl)ethylenediamine-2,4-bis[N-butyl-N-(1,2,2,6,6-pentamethyl-4-piperidyl)amino]-6-chloro-1,3,5-triazine condensate, poly[[6-[(1,1,3,3-tetramethylbutyl)amino]-1,3,5-triazine-2,4-diyl][(2,2,6,6-tetramethyl-4-piperidinyl)imino]], poly[{6-(1,1,3-trimethylpentyl)amino-1,3,5-triazine-2,4-diyl}{(N-methyl-2,2,6,6-tetramethyl-piperidyl) imino}octamethylene{(N-methyl-2,2,6,6-tetramethyl-piperidyl) imino}], poly[(6-morpholino-S-triazine-2,4-di)[1,2,2,6,6-pentamethyl-4-piperidyl]imino]-hexamethylene[(1,2,2,6,6-pentamethyl-4-piperidyl)imino]], poly[{6-(1,1,3,3-tetramethylbutyl) amino-1,3,5-triazine-2,4-diyl}{(2,2,6,6-tetramethyl-piperidyl) imino}hexamethylene{(2,2,6,6-tetramethyl-piperidyl) imino}], bis(1,2,2,6,6-pentamethyl-4-piperidyl)[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]butylmalonate, mixture of bis(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate and methyl 1,2,2,6,6-pentamethyl-4-piperidylsebacate, bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate, N,N'-bis(2,2,6,6-tetramethyl-4-piperidyl dibutylamine 1,3,5-triazine and N,N'-bis(2,2,6,6-tetramethyl-4-piperidyl-1,6-hexamethylenediamine and N-(2,2,6,6-tetramethyl-4-piperidyl)butylamine polycondensate, poly[{6-(1,1,3,3-tetramethylbutyl)amino-1,3,5-triazine-2,4-diyl}{2,2,6,6-tetramethyl-4-piperidyl)imino}hexamethylene {(2,2,6,6-tetramethyl-4-piperidyl)imino}], tetrakis(1,2,2,6,6-pentamethyl-4-piperidyl)butane-1,2,3,4-tetracarboxylate, tetrakis(2,2,6,6-tetramethyl-4-piperidyl)butane-1,2,3,4-tetracarboxylate, 1,2,2,6,6-pentamethyl-4-piperidiol and β,β,β',β'-tetramethyl-2,4,8,10-tetraoxaspiro[5.5]undecane-3 ,9-diethanol, a reaction product of 2,2,6,6-tetramethyl-4-piperidiol and β,β,β',β'-tetramethyl-2,4,8,10-tetraoxaspiro[5.5]undecane-3,9-diethanol, bis(1-undecanoxy-2,2,6,6-tetramethylpiperidin-4-yl)carbonate, 1,2,2,6,6-pentamethyl-4-piperidyl methacrylate, and 2,2,6,6-tetramethyl-4-piperidyl methacrylate.
Among these, from the viewpoint of the thermal stability of the light stabilizer, bis(1,2,2,6,6-pentamethyl-4-piperidyl)[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]butylmalonate, a polycondensate of dibutylamine 1,3,5-triazine, N,N'-bis(2,2,6,6-tetramethyl-4-piperidyl-1,6-hexamethylenediamine, and N-(2,2,6,6-tetramethyl-4-piperidyl)butylamine, and poly[{6-(1,1,3,3-tetramethylbutyl)amino-1,3,5-triazine-2 ,4-diyl}{2,2,6,6-tetramethyl-4-piperidyl)imino}hexamethylene{(2,2,6,6-tetramethyl-4-piperidyl)imino}], a reaction product of 1,2,2,6,6-pentamethyl-4-piperidiol and β,β,β',β'-tetramethyl-2,4,8,10-tetraoxaspiro[5.5]undecane-3,9-diethanol, and 2,2,6,6-tetramethyl-4-piperidiol and β,β,β',β'-tetramethyl-2,4,8,10-tetraoxaspiro[5.5]undecane-3,9-diethanol are preferably used.

<<Heat stabilizer>>
Examples of the heat stabilizer include, but are not limited to, (a) hindered phenol-based antioxidants, (b-1) phosphorus-based antioxidants, and (b-2) sulfur-based antioxidants.
The methacrylic resin composition used in the present embodiment is suitable for various applications such as melt extrusion, injection molding, film molding, etc. The heat history during processing varies depending on the processing method, but ranges from about several tens of seconds in an extruder to several tens of minutes to several hours in the molding processing of thick-walled products and sheet molding.
When subjected to a long-term heat history, it is necessary to increase the amount of heat stabilizer added in order to obtain the desired heat stability. From the viewpoint of suppressing bleed-out of the heat stabilizer and preventing the film from sticking to the roll during film formation, it is preferable to use a combination of multiple types of heat stabilizers, for example, it is preferable to use a combination of at least one selected from (b-1) a phosphorus-based antioxidant and (b-2) a sulfur-based antioxidant and (a) a hindered phenol-based antioxidant.
These antioxidants may be used alone or in combination of two or more.

As the heat stabilizer, from the viewpoint of having even better thermal stability in air, a binary system using (a) a hindered phenol-based antioxidant and (b-2) a sulfur-based antioxidant, or a binary system using (a) a hindered phenol-based antioxidant and (b-1) a phosphorus-based antioxidant is preferred, and from the viewpoint of having particularly excellent thermal stability in air over the short and long term, a ternary system using three types of antioxidants, namely (a) a hindered phenol-based antioxidant, (b-1) a phosphorus-based antioxidant, and (b-2) a sulfur-based antioxidant, is more preferred.

Examples of the heat stabilizer include, but are not limited to, pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], thiodiethylene bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 3,3',3'',5,5',5''-Hexa-tert-butyl-a,a',a''-(mesitylene-2,4,6-triyl)tri-p-cresol, 4,6-bis(octylthiomethyl)-o-cresol, 4,6-bis(dodecylthiomethyl)-o-cresol, ethylene bis(oxyethylene) bis[3-(5-tert-butyl-4-hydroxy-m-tolyl)propionate], hexamethylene bis[3-(3,5 -di-tert-butyl-4-hydroxyphenyl)propionate], 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 1,3,5-tris[(4-tert-butyl-3-hydroxy-2,6-xylin)methyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 2,6- Examples of the acrylate ester include di-tert-butyl-4-(4,6-bis(octylthio)-1,3,5-triazin-2-ylamine)phenol, 2-[1-(2-hydroxy-3,5-di-tert-pentylphenyl)ethyl]-4,6-di-tert-pentylphenyl acrylate, and 2-tert-butyl-4-methyl-6-(2-hydroxy-3-tert-butyl-5-methylbenzyl)phenyl acrylate.
Particularly preferred are pentaerythritol terakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, and 2-[1-(2-hydroxy-3,5-di-tert-pentylphenyl)ethyl]-4,6-di-tert-pentylphenyl acrylate.

In addition, as the (a) hindered phenol-based antioxidant as the heat stabilizer, a commercially available phenol-based antioxidant may be used. Examples of such commercially available phenol-based antioxidants include, but are not limited to, Irganox 1010 (Irganox 1010: pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], manufactured by BASF), Irganox 1076 (Irganox 1076: octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, manufactured by BASF), Irganox 1330 (Irganox 1330: octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, manufactured by BASF), and Irganox 1330 (Irganox 1330: octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, manufactured by BASF). 1330: 3,3',3'',5,5',5''-hexa-t-butyl-a,a',a''-(mesitylene-2,4,6-triyl)tri-p-cresol, manufactured by BASF Corporation), Irganox 3114 (Irganox 3114: 1,3,5-tris(3,5-di-t-butyl-4-hydroxybenzyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, manufactured by BASF Corporation), Irganox 3125 (Irganox 3125, manufactured by BASF), Adeka STAB AO-60 (pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], manufactured by ADEKA), Adeka STAB AO-80 (3,9-bis{2-[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]-1,1-dimethylethyl}-2,4,8,10-tetraoxaspiro[5.5]undecane, manufactured by ADEKA), Sumilizer BHT (Sumilizer BHT, manufactured by Sumitomo Chemical), Cyanox 1790 (Cyanox 1790, manufactured by Cytec), Sumilizer GA-80 (Sumilizer GA-80, manufactured by Sumitomo Chemical), Sumilizer GS (Sumilizer Examples of the acrylate copolymer include GS (2-[1-(2-hydroxy-3,5-di-tert-pentylphenyl)ethyl]-4,6-di-tert-pentylphenyl acrylate, manufactured by Sumitomo Chemical), Sumilizer GM (2-tert-butyl-4-methyl-6-(2-hydroxy-3-tert-butyl-5-methylbenzyl)phenyl acrylate, manufactured by Sumitomo Chemical), and Vitamin E (manufactured by Eisai).
Among these commercially available hindered phenol-based antioxidants, Irganox 1010, Adeka STAB AO-60, Adeka STAB AO-80, Irganox 1076, Sumilizer GS, and the like are preferred from the viewpoint of the effect of imparting thermal stability to the resin.
These may be used alone or in combination of two or more.

In addition, examples of the phosphorus-based antioxidant (b-1) as the heat stabilizer include, but are not limited to, tris(2,4-di-t-butylphenyl)phosphite, bis(2,4-bis(1,1-dimethylethyl)-6-methylphenyl)ethyl ester phosphorous acid, tetrakis(2,4-di-t-butylphenyl)(1,1-biphenyl)-4,4'-diylbisphosphonite, bis(2,4-di-t-butylphenyl)pentaerythritol diphosphite, bis(2,6-di-t-butyl-4-methylphenyl) bis(2,4-dicumylphenyl)pentaerythritol diphosphite, bis(2,4-dicumylphenyl)pentaerythritol diphosphite, tetrakis(2,4-t-butylphenyl)(1,1-biphenyl)-4,4'-diylbisphosphonite, di-t-butyl-m-cresyl-phosphonite, 4-[3-[(2,4,8,10-tetra-tert-butyldibenzo[d,f][1,3,2]dioxaphosphepin)-6-yloxy]propyl]-2-methyl-6-tert-butylphenol, etc.

Furthermore, a commercially available phosphorus-based antioxidant may be used as the phosphorus-based antioxidant. Examples of such commercially available phosphorus-based antioxidants include, but are not limited to, Irgafos 168 (Irgafos 168: tris(2,4-di-t-butylphenyl)phosphite, manufactured by BASF), Irgafos 12 (Irgafos 12: tris[2-[[2,4,8,10-tetra-t-butyldibenzo[d,f][1,3,2]dioxaphosphen-6-yl]oxy]ethyl]amine, manufactured by BASF), Irgafos 38 (Irgafos 38: bis(2,4-bis(1,1-dimethylethyl)-6-methylphenyl)ethyl ester phosphorous acid, manufactured by BASF), Adeka STAB 329K (ADK STAB-329K, manufactured by ADEKA), and Adeka STAB PEP-36 (ADK STAB-329K, manufactured by ADEKA). Adeka STAB PEP-36, manufactured by ADEKA), Adeka STAB PEP-36A (ADK STAB PEP-36A, manufactured by ADEKA), Adeka STAB PEP-8 (ADK STAB PEP-8, manufactured by ADEKA), Adeka STAB HP-10 (ADK STAB HP-10, manufactured by ADEKA), Adeka STAB 2112 (ADK STAB 2112, manufactured by ADEKA), Adeka STAB 1178 (ADKA STAB 1178, manufactured by ADEKA), Adeka STAB 1500 (ADK STAB 1500, manufactured by ADEKA), Sandstab P-EPQ (manufactured by Clariant), Weston 618 (Weston 618, manufactured by GE), Weston 619G (Weston 619G, manufactured by GE), Ultranox 626, manufactured by GE, Sumilizer GP (4-[3-[(2,4,8,10-tetra-tert-butyldibenzo[d,f][1,3,2]dioxaphosphepin)-6-yloxy]propyl]-2-methyl-6-tert-butylphenol, manufactured by Sumitomo Chemical), and HCA (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, manufactured by Sanko Co., Ltd.).
Among these commercially available phosphorus-based antioxidants, from the viewpoint of the effect of imparting thermal stability to the resin and the effect of using them in combination with various types of antioxidants, Irgafos 168, ADK STAB PEP-36, ADK STAB PEP-36A, ADK STAB HP-10, and ADK STAB 1178 are preferred, and ADK STAB PEP-36A and ADK STAB PEP-36 are particularly preferred.
These phosphorus-based antioxidants may be used alone or in combination of two or more kinds.

In addition, the (b-2) sulfur-based antioxidant as the heat stabilizer is, but is not limited to, for example, 2,4-bis(dodecylthiomethyl)-6-methylphenol (Irganox 1726, manufactured by BASF Corporation), Irganox 1520L, manufactured by BASF Corporation), 2,2-bis{[3-(dodecylthio)-1-oxoporopoxy]methyl}propane-1,3-diylbis[3-dodecylthio]methyl}propane-1,3-diylbis[3-dodecylthio]methyl] ... 2,2-bis{[3-(dodecylthio)-1-oxopropoxy]methyl}propane-1,3-diylbis[3-dodecylthio]propionate] (Adekastab AO-412S, manufactured by ADEKA Corporation), 2,2-bis{[3-(dodecylthio)-1-oxopropoxy]methyl}propane-1,3-diylbis[3-dodecylthio]propionate] (ChemiNox PLS, manufactured by Chemipro Chemical Co., Ltd.), and di(tridecyl) 3,3′-thiodipropionate (AO-503, manufactured by ADEKA Corporation).
Among these commercially available sulfur antioxidants, Adeka STAB AO-412S and Cheminox PLS are preferred from the viewpoints of the effect of imparting thermal stability to the resin, the effect of using them in combination with various types of antioxidants, and ease of handling.
These sulfur-based antioxidants may be used alone or in combination of two or more kinds.

The content of the heat stabilizer may be any amount that provides the effect of improving heat stability. If the content is excessive, problems such as bleeding out during processing may occur. Therefore, the content is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, even more preferably 1 part by mass or less, still more preferably 0.8 parts by mass or less, still more preferably 0.01 to 0.8 parts by mass, and particularly preferably 0.01 to 0.5 parts by mass, relative to 100 parts by mass of the methacrylic resin.
In addition, from the viewpoint of suppressing the thermal decomposition of the methacrylic resin, suppressing the deterioration of the color tone of the obtained molded body, and suppressing the volatilization of the heat stabilizer to suppress the occurrence of silver streaks during molding processing, it is preferable to contain 0.01 to 2 parts by mass (preferably 0.02 to 1 part by mass) of (a) hindered phenol-based antioxidant and 0.01 to 2 parts by mass (preferably 0.01 to 1 part by mass) of (b-1) phosphorus-based antioxidant and (b-2) sulfur-based antioxidant in total relative to 100 parts by mass of the methacrylic resin. Also, from the same viewpoint, it is preferable to contain 0.01 to 2 parts by mass (preferably 0.02 to 1 part by mass) of (a) hindered phenol-based antioxidant and 0.01 to 2 parts by mass (preferably 0.01 to 1 part by mass) of (b-1) phosphorus-based antioxidant and/or (b-2) sulfur-based antioxidant in total relative to 100 parts by mass of the methacrylic resin.

<<Ultraviolet absorbing agent>>
Examples of the ultraviolet absorber include, but are not limited to, benzotriazole-based compounds, benzotriazine-based compounds, benzoate-based compounds, benzophenone-based compounds, oxybenzophenone-based compounds, phenol-based compounds, oxazole-based compounds, malonic acid ester-based compounds, cyanoacrylate-based compounds, lactone-based compounds, salicylic acid ester-based compounds, and benzoxazinone-based compounds.

Benzotriazole compounds include, but are not limited to, 2,2'-methylenebis[4-(1,1,3,3-tetramethylbutyl)-6-(2H-benzotriazol-2-yl)phenol], 2-(3,5-di-tert-butyl-2-hydroxyphenyl)-5-chlorobenzotriazole, 2-(2H-benzotriazol-2-yl)-p-cresol, 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol, 2-benzotriazol-2-yl-4,6-di-tert-butylphenol, 2-[5-chloro(2H)-benzotriazol-2-yl]-4-methyl-6-t-butylphenol, 2-(2H-benzotriazol-2-yl)-4,6-di-t-butylphenol, 2-(2H-benzotriazol-2-yl)-4,6-di-t-butylphenol, 2-(2H-benzotriazol-2-yl)-4,6-di-t-butylphenol, 2-(2H-benzotriazol-2-yl)-4-methyl-6-(3,4,5,6-tetrahydrophthalimidylmethyl)phenol, methyl 3-(3-(2H-benzotriazol-2-yl)-5-t-butyl-4-hydroxyphenyl)propionate/polyethylene glycol 300 reaction product, 2-(2H-benzotriazol-2-yl)-6-(linear and side chain dodecyl)-4-methylphenol, 2-(5-methyl-2-hydroxyphenyl)benzotriazole, 2-[2-hydroxy-3,5-bis(α,α-dimethylbenzyl)phenyl]-2H-benzotriazole, 3-(2H-benzotriazol-2-yl)-5-(1,1-dimethylethyl)-4-hydroxy-C7-9 side chain and linear alkyl esters.

Benzotriazine compounds include, but are not limited to, 2-mono(hydroxyphenyl)-1,3,5-triazine compounds, 2,4-bis(hydroxyphenyl)-1,3,5-triazine compounds, and 2,4,6-tris(hydroxyphenyl)-1,3,5-triazine compounds. Specific examples include 2,4-diphenyl-6-(2-hydroxy-4-methoxyphenyl)-1,3,5-triazine, 2,4-diphenyl-6-(2-hydroxy-4-ethoxyphenyl)-1,3,5-triazine, and 2,4-diphenyl-(2-hydroxy-4-propoxyphenyl)-1,3 ,5-triazine, 2,4-diphenyl-(2-hydroxy-4-butoxyphenyl)-1,3,5-triazine, 2,4-diphenyl-6-(2-hydroxy-4-butoxyphenyl)-1,3,5-triazine, 2,4-diphenyl-6-(2-hydroxy-4-hexyloxyphenyl)-1,3,5-triazine, 2,4-diphenyl-6-(2-hydroxy-4-octyloxyphenyl)-1,3,5-triazine, 2,4-diphenyl-6-(2-hydroxy-4-dodecyloxyphenyl)-1,3,5-triazine, 2,4-diphenyl-6-(2-hydroxy-4-benzyloxyphenyl)-1,3,5-triazine nyl)-1,3,5-triazine, 2,4-diphenyl-6-(2-hydroxy-4-butoxyethoxy)-1,3,5-triazine, 2,4-bis(2-hydroxy-4-butoxyphenyl)-6-(2,4-dibutoxyphenyl)-1,3-5-triazine, 2,4,6-tris(2-hydroxy-4-methoxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-4-ethoxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-4-propoxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-4-butoxyphenyl )-1,3,5-triazine, 2,4,6-tris(2-hydroxy-4-butoxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-4-hexyloxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-4-octyloxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-4-dodecyloxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-4-benzyloxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-4-ethoxyethoxyphenyl)-1,3, 5-triazine, 2,4,6-tris(2-hydroxy-4-butoxyethoxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-4-propoxyethoxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-4-methoxycarbonylpropyloxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-4-ethoxycarbonylethyloxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-4-(1-(2-ethoxyhexyloxy)-1-oxopropan-2-yloxy)phenyl)-1, 3,5-triazine, 2,4,6-tris(2-hydroxy-3-methyl-4-methoxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-3-methyl-4-ethoxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-3-methyl-4-propoxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-3-methyl-4-butoxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-3-methyl-4-butoxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-3-methyl-4-butoxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-3-methyl-4-butoxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-3-methyl-4-hexyloxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-3-methyl-4-octyloxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-3-methyl-4-dodecyloxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-3-methyl-4-benzyloxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-3-methyl-4-ethoxyethoxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-3-methyl-4-butoxyethoxyphenyl) -1,3,5-triazine, 2,4,6-tris(2-hydroxy-3-methyl-4-propoxyethoxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-3-methyl-4-methoxycarbonylpropyloxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-3-methyl-4-ethoxycarbonylethyloxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-3-methyl-4-(1-(2-ethoxyhexyloxy)-1-oxopropan-2-yloxy)phenyl)-1,3,5-triazine, etc.

Among these, ultraviolet absorbers having a 2,4-bis(2,4-dimethylphenyl)-6-[2-hydroxy-4-(3-alkyloxy-2-hydroxypropyloxy)-5-α-cumylphenyl]-s-triazine skeleton (where "alkyloxy" refers to a long-chain alkyloxy group such as octyloxy, nonyloxy, or decyloxy) are preferred because they are highly compatible with amorphous thermoplastic resins, particularly acrylic resins, and have excellent absorption properties.

As the ultraviolet absorber, benzotriazole-based compounds and benzotriazine-based compounds are particularly preferred from the viewpoints of compatibility with the resin and volatility upon heating.
These ultraviolet absorbents may be used alone or in combination of two or more kinds.

The melting point (Tm) of the ultraviolet absorber is preferably 80° C. or higher, more preferably 100° C. or higher, even more preferably 130° C. or higher, and even more preferably 160° C. or higher.
The ultraviolet absorber preferably exhibits a mass reduction rate of 50% or less, more preferably 30% or less, even more preferably 15% or less, even more preferably 10% or less, and even more preferably 5% or less, when heated from 23° C. to 260° C. at a rate of 20° C./min.

The amount of the ultraviolet absorber to be blended may be an amount that does not impair heat resistance, moist heat resistance, thermal stability, and moldability, and that exerts the effects of the present invention, but if too much is added, problems such as bleeding out during processing may occur, so the amount is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, even more preferably 2.5 parts by mass or less, even more preferably 2 parts by mass or less, and even more preferably 1.8 parts by mass or less, per 100 parts by mass of methacrylic resin, and from the viewpoint of exerting the effects of the blending, it is preferably 0.01 parts by mass or more.

(Characteristics of methacrylic resin composition)
The characteristics of the methacrylic resin composition are described below.

<Weight average molecular weight, molecular weight distribution>
The weight average molecular weight (Mw) of the methacrylic resin composition used in this embodiment is 65,000 to 300,000 from the viewpoint of obtaining a methacrylic resin composition having even more excellent mechanical strength, solvent resistance, and fluidity.
By setting the weight average molecular weight of the methacrylic resin composition within the above range, the methacrylic resin composition becomes excellent in mechanical strength such as Charpy impact strength and in fluidity.
From the viewpoint of maintaining mechanical strength, the weight average molecular weight is preferably 65,000 or more, more preferably 70,000 or more, even more preferably 80,000 or more, and still more preferably 100,000 or more.
In addition, from the viewpoints of ensuring flowability during molding, reducing distortion during molding, and imparting long optical path transmittance, the weight average molecular weight is preferably 250,000 or less, more preferably 200,000 or less, even more preferably 150,000 or less, still more preferably 130,000 or less, and even more preferably 120,000 or less.
From the viewpoint of the balance between fluidity, mechanical strength, and solvent resistance, the molecular weight distribution (weight average molecular weight (Mw)/number average molecular weight (Mn)) of the methacrylic resin composition is preferably 1.5 to 5. It is more preferably 1.5 to 4.5, even more preferably 1.6 to 4, even more preferably 1.6 to 3, and still more preferably 1.6 to 2.5.
The weight average molecular weight (Mw) and number average molecular weight (Mn) of the methacrylic resin composition can be measured by gel permeation chromatography (GPC). In detail, a calibration curve is prepared from the elution time and the weight average molecular weight using a standard methacrylic resin that is available as a reagent and has a known monodisperse weight average molecular weight, number average molecular weight, and peak molecular weight, and an analytical gel column that elutes high molecular weight components first. Next, the weight average molecular weight and number average molecular weight of the sample of the methacrylic resin composition to be measured can be obtained from the obtained calibration curve.
Specifically, it can be measured by the method described in the Examples below.

<Heat resistance>
As an index of heat resistance, the VICAT softening temperature can be used.
From the viewpoint of heat resistance during actual use, the Vicat softening temperature of the methacrylic resin composition used in this embodiment is preferably 113° C. or higher, and more preferably 115° C. or higher. The higher the heat resistance, the more stable the dimensions of the molded body are when the molded body is exposed to the heat of a built-in high-brightness LED light source or high-output LED light source, and the more likely it is that the molded body can be used as a traffic light lens or lens cover that achieves the designed luminous flux.
The Vicat softening temperature can be measured in accordance with ISO306 B50, specifically, by the method described in the examples below.

<Transparency>
As an index of transparency, total light transmittance and haze can be used.
The total light transmittance of the methacrylic resin composition used in the present embodiment may be optimized as appropriate depending on the application, but when used in an application requiring transparency, from the viewpoint of visibility, the total light transmittance at a thickness of 2 mm measured in accordance with JIS K7361-1 is preferably 85% or more, more preferably 90% or more, even more preferably 91% or more, and even more preferably 92% or more.
From the viewpoint of visibility, the haze at a thickness of 2 mm measured in accordance with JIS K7136 is preferably 5 or less, more preferably 4 or less, even more preferably 3 or less, and even more preferably 2 or less.
Combining high total light transmittance and low haze results in good transparency, ensuring visibility of traffic lights when used as traffic light lenses and lens covers.
The total light transmittance and haze are values measured using a flat plate having a thickness of 2 mm obtained by injection molding the methacrylic resin composition using a mold having a polishing number of 8000. Specifically, the total light transmittance and haze can be measured by the method described in the examples described later.

<Change in YI value during retention>
When a resin composition is subjected to a heat history treatment such as molding, it may be exposed to high temperatures for a long time due to troubleshooting, etc. In such a case, the heat history may cause the composition to turn yellow.
According to the methacrylic resin composition of the present embodiment, the degree of change (ΔYI) between the YI when subjected to a short-term thermal history and the YI when subjected to a long-term thermal history can be suppressed.
For example, when the methacrylic resin composition of this embodiment is used to prepare a test piece having a thickness of 3 mm, a width of 20 mm, and a length of 220 mm, using an injection molding machine (EC-100SX, manufactured by Toshiba Machine Co., Ltd.) under conditions of a molding temperature of 280° C. and a mold temperature of 60° C., and the injection molding cycle time (injection time+cooling time) is set to a normal cycle of (c) 45 seconds and an estimated retention time in the molding machine of (d) 270 seconds, the YI value can be estimated by measuring the 220 mm long optical path YI value of five test pieces each of the test pieces obtained at the cycle time (c) and the test pieces obtained at the cycle time (d) using the test pieces from the 11th shot to the 15th shot after molding has stabilized.
The average value of the YI values of the five test pieces in (c) and the average value of the YI values of the five test pieces in (d) are determined, and the degree of change in the YI value is calculated by the following formula, which can be used as an index of evaluation.
Degree of change in YI value=[average YI value of (d)−average YI value of (c)]/average YI value of (c) The degree of change (ΔYI) in the above YI (220 mm) must be 20 or less, preferably 18 or less, more preferably 15 or less, even more preferably 13 or less, and still more preferably 10 or less.
The means for achieving the above-mentioned degree of change (ΔYI) include making the content of the styrene monomer unit equal to or less than a predetermined amount, incorporating a small amount of a compound (D) represented by general formula (1) or (2) described later, making the ratio of the content of the (D) component to the content of the structural unit (B) having a ring structure in the main chain within a specific range, making Mw equal to or greater than a predetermined level, and the like, and these may be used alone or in combination.
The YI value can be measured using a color difference meter (manufactured by Tokyo Denshoku Industries Co., Ltd., TC-8600A, light source: C light source, 2° visual field) in accordance with JIS K7105, and specifically, can be measured by the method described in the examples described later.

<Appearance>
The appearance of the methacrylic resin composition of the present embodiment can be evaluated based on, for example, the presence or absence of bubbles, streaks, silver streaks, and the like.
In the methacrylic resin composition of the present embodiment, the methacrylic resin composition is dried at 80° C. for 24 hours, and then 50 test pieces are molded using an injection molding machine and a measuring mold. Of these, the number of test pieces on which silver streaks are observed on the surface is preferably 10 or less, more preferably 5 or less, and even more preferably 2 or less.
The presence or absence of silver streaks in the methacrylic resin composition can be evaluated by the method described in the Examples below. Good appearance leads to good productivity of traffic light lenses and lens covers.

<Weather resistance>
The weather resistance of the methacrylic resin composition of the present embodiment can be evaluated by measuring the color difference (ΔE*) of a sample before and after an exposure test.
For example, the methacrylic resin composition of this embodiment is molded using an injection molding machine (EC-100SX, manufactured by Toshiba Machine Co., Ltd.) under conditions of a resin temperature of 280° C. and a mold temperature of 70° C. to prepare a long optical path test piece having a thickness of 3 mm, a width of 20 mm, and a length of 220 mm. Using this 3 mm-thick test piece, an exposure test is performed for a total exposure time of 2040 hours using the method of JIS K7350-4, and the color difference (ΔE*) before and after the exposure test can be measured using a color difference meter in accordance with JIS Z8730.
In the methacrylic resin composition of the present embodiment, the color difference (ΔE*) in the above evaluation is preferably less than 3, more preferably less than 2.5, and even more preferably 2 or less.
When ΔE* is within the above-mentioned preferred range, the heat-resistant traffic light lens and lens cover can maintain a stable color tone even when used for a long period of time, and the appearance of the color of the traffic light can be made uniform over a long period of time.
The means for achieving the above-mentioned change in color difference (ΔE*) include making the content of the styrene monomer unit equal to or less than a predetermined amount, incorporating a small amount of the compound (D) represented by the general formula (1) or (2) described later, making the ratio of the content of the (D) component to the content of the structural unit (B) having a ring structure in the main chain within a specific range, making Mw equal to or more than a predetermined level, and the like, and these may be used alone or in combination.
The color difference (ΔE*) can be specifically measured by the method described in the examples below.

In particular, from the viewpoints of heat resistance, suppression of silver smearing during molding, and hue, the amount of the remaining component (A), i.e., the methacrylic acid ester monomer, in the methacrylic resin composition is preferably 1 mass % or less, more preferably 0.7 mass % or less, even more preferably 0.5 mass % or less, still more preferably 0.3 mass % or less, and still more preferably 0.2 mass % or less.
In particular, the content of the monomer component derived from the (B) component remaining in the methacrylic resin composition is preferably 0.5% by mass or less, more preferably 0.3% by mass or less, even more preferably 0.2% by mass or less, even more preferably 0.15% by mass or less, and even more preferably 0.1% by mass or less, when the methacrylic resin composition is taken as 100% by mass, from the viewpoint of improving the yellowness and transmittance of the molded piece. It is also preferable to keep the amount of remaining monomer low, but if the amount of remaining monomer is reduced as much as possible, the process may become complicated, and productivity may be affected. In consideration of the hue and productivity, the content of the remaining (B) component is preferably 0.001% by mass or more, more preferably 0.005% by mass or more, even more preferably 0.011% by mass or more, and even more preferably 0.02% by mass or more.
The content of the residual monomer can be evaluated by the method described in the Examples below.

(Methacrylic resin composition manufacturing method)
The methacrylic resin composition of the present embodiment can be produced by melt-kneading the above-mentioned methacrylic resin, the compound (D) represented by the general formula (1) or (2), and, as necessary, other resins, additives, and the like.
Examples of the method for producing the methacrylic resin composition include a method of kneading using a kneading machine such as an extruder, a heating roll, a kneader, a roller mixer, a Banbury mixer, etc. Among these, kneading using an extruder is preferred from the viewpoint of productivity.
The kneading temperature may be determined according to the preferred processing temperatures of the polymer constituting the methacrylic resin and the other resins to be mixed, and is generally in the range of 140 to 300°C, preferably 180 to 280°C.
It is also preferable to provide the extruder with a vent port in order to reduce volatile content.

(Molded body)
The molded article used as the traffic light lens and lens cover of this embodiment may contain 80 mass % or more, preferably 90 mass % or more, and more preferably 95 mass % or more of the above-mentioned methacrylic resin composition of this embodiment, and may be made of the above-mentioned methacrylic resin composition of this embodiment (including 100 mass %).

The shape of the molded body of this embodiment may be determined appropriately depending on the purpose and application as a traffic light lens and lens cover.

Hereinafter, the present embodiment will be described with reference to specific examples , reference examples , and comparative examples, but the present embodiment is not limited to the examples described below.

〔material〕
The raw materials used in the Examples , Reference Examples and Comparative Examples described later are shown below.

The traffic lights to which the traffic light lens and lens cover of this embodiment can be applied are not particularly limited, but may be traffic lights that include an LED light source, and in particular, traffic lights in which the distance between the LED light source and the lens is short, and traffic lights that include high-brightness or high-luminance LEDs are preferred.

The present embodiment will be described below with specific examples and comparative examples, but the present embodiment is not limited to the examples described below.

〔material〕
The raw materials used in the examples and comparative examples described later are shown below.

(Monomers that make up methacrylic resins)
<(A) Methacrylic acid ester monomer>
<<(A-1)>>
Methyl methacrylate (MMA): manufactured by Asahi Kasei Corporation (containing 2.5 ppm of 2,4-dimethyl-6-tert-butylphenol manufactured by Chugai Trading Co., Ltd. as a polymerization inhibitor)

<(B) Monomer for forming a structural unit having a ring structure in the main chain>
<<(B-1-1) Maleimide-based structural unit>>
N-phenylmaleimide (N-PMI): manufactured by Nippon Shokubai Co., Ltd. <<(B-1-2) Maleimide structural unit>>
N-Cyclohexylmaleimide (N-CMI): Synthesized by the following production method.
Maleic anhydride and ortho-xylene in an amount six times the unit mass of maleic anhydride were charged into a flask equipped with a thermometer, a Dean-Stark tube, a dropping funnel, and a stirrer, and the mixture was heated to 55° C. and stirred to prepare a homogeneous ortho-xylene solution of maleic anhydride.
Next, a solution containing cyclohexylamine in an amount equivalent to maleic anhydride in terms of molar ratio and ortho-xylene in an equal mass was added dropwise to the maleic anhydride solution at 55° C. over a period of 30 minutes with stirring to synthesize a slurry of N-cyclohexylmaleamic acid in ortho-xylene.
Next, the slurry was added with the same mass of orthophosphoric acid as cyclohexylamine as an acid catalyst, and 200 ppm of copper dibutyldithiocarbamate relative to N-cyclohexylmaleamic acid as a polymerization inhibitor, and heated to 140°C under stirring, and reacted for 8 hours while distilling water generated by the reaction out of the reaction system using a Dean-Stark tube. After the reaction was completed, the acid catalyst layer separated into the lower layer from the reaction solution at 140°C was separated and removed. Next, the reaction solution was washed twice with 3% by mass sulfuric acid water and twice with ion-exchanged water, and ortho-xylene was removed from the organic layer under reduced pressure of 10 mmHg. The mixture was then purified by distillation at an internal temperature of 130 to 150°C under reduced pressure of 5 mmHg to obtain a white raw material mainly composed of N-cyclohexylmaleimide.
<<(B-3) Glutarimide Structural Unit>>
Methyl methacrylate (MMA): the above-mentioned <<(A-1)>>.
Methacrylic acid (MA): manufactured by Tokyo Chemical Industry Co., Ltd.

<(C) Vinyl-based monomer>
<<(C-1)>>
Styrene (St): manufactured by Asahi Kasei Corporation <<(C-2)>>
Methacrylic acid (MA): manufactured by Tokyo Chemical Industry Co., Ltd. <<(C-3)>>
- Methyl acrylate: Tokyo Chemical Industry Co., Ltd.

<Compound (D)>
<<(D-1)>>
N-cyclohexyl-2-hydroxysuccinimide: needle-like crystals of the component (D-1) were obtained by repeatedly recrystallizing and purifying the initial fraction obtained during the distillation process obtained during the production of the component (B-2).

<Fatty Acid Compounds, Silicones, Polyethers, and Silicate Compounds>
<<(E-1)>>
BA: Dainichi Chemical Industry Co., Ltd. (Ethylene bis stearic acid amide)
<<(E-2)>>
・Kalcol 8098: Kao Corporation (stearyl alcohol)
<<(E-3)>>
Tegomer H-Si6441P: manufactured by Evonik (polyester modified silicone)
<<(E-4)>>
Tegomer H-Si6444P: manufactured by Evonik (polyester modified silicone)
<<(E-5)>>
SOLID-HT: manufactured by TenasiTech (a silicate compound modified with an organic modifier)
<<(E-6)>>
SOLID-TT: manufactured by TenasiTech (70 parts by mass of silicate compound modified with 30 parts by mass of organic modifier)
<<(E-7)>>
Nofalloy KA-200: NOF Corporation (polyether with a molecular weight of approximately 4,000)

(I. Measurement of weight average molecular weight of methacrylic resin and methacrylic resin composition)
The weight average molecular weight (Mw) of the methacrylic resins produced in the Production Examples described below and the methacrylic resins in the methacrylic resin compositions produced in the Examples and Reference Examples were measured using the following apparatus and conditions.
Measurement device: gel permeation chromatography (HLC-8320GPC) manufactured by Tosoh Corporation
·Measurement condition:
Column: One TSKguard column Super H-H, two TSKgel Super HM-M, and one TSKgel Super H2500 were connected in series. In this column, high molecular weight molecules elute early and low molecular weight molecules elute late.
Developing solvent: tetrahydrofuran, flow rate: 0.6 mL/min, and 0.1 g/L of 2,6-di-t-butyl-4-methylphenol (BHT) was added as an internal standard.
Detector: RI (differential refractive index) detector Detection sensitivity: 3.0 mV/min Column temperature: 40° C.
Sample: 0.02 g of methacrylic resin in 20 mL of tetrahydrofuran Injection volume: 10 μL
Standard sample for calibration curve: The following ten types of polymethyl methacrylate (PMMA Calibration Kit MM-10, manufactured by Polymer Laboratories) having known monodisperse weight peak molecular weights and different molecular weights were used.
Weight peak molecular weight (Mp)
Standard sample 1 1,916,000
Standard sample 2 625,500
Standard sample 3 298,900
Standard sample 4 138,600
Standard sample 5 60,150
Standard sample 6 27,600
Standard sample 7 10,290
Standard sample 8 5,000
Standard sample 9 2,810
Standard sample 10 850
Under the above conditions, the RI detection intensity versus the elution time of the methacrylic resin was measured.
The weight average molecular weight (Mw) of the methacrylic resin and the methacrylic resin composition was determined based on the area in the GPC elution curve and the calibration curve of the third order approximation. The results are shown in Table 1.

(others)
n-Octylmercaptan (NOM): manufactured by Arkema Co., Ltd., used as a chain transfer agent.
Perhexa C-75 (EB): manufactured by NOF Corporation, purity 75% (containing 25% ethylbenzene), used as a polymerization initiator.
t-Butylperoxy-2-ethylhexanoate: manufactured by NOF Corporation, used as a polymerization initiator.
- Calcium phosphate (CaP): manufactured by Nippon Chemical Industry Co., Ltd., used as a suspending agent.
Calcium carbonate: manufactured by Shiraishi Kogyo Co., Ltd., used as a suspending agent.
Sodium lauryl sulfate: manufactured by Wako Pure Chemical Industries, Ltd., used as a suspension aid.

<Additives>
<<a-1>>
・ Adeka STAB 2112: manufactured by ADEKA CORPORATION <<a-2>>
・ Adeka STAB AO-80: manufactured by ADEKA CORPORATION <<a-3>>
- Tinuvin P: manufactured by BASF

<III-1. Heat resistance: Measurement of VICAT softening temperature>
Using 4 mm thick test pieces molded from the resin pellets obtained in the Examples , Reference Examples , and Comparative Examples described later, the VICAT softening temperature (°C) was measured in accordance with ISO 306 B50 and used as an index for evaluating heat resistance.

<III-2. Transparency (Optical Properties): Measurement of Total Light Transmittance>
Using the resin pellets obtained in the Examples , Reference Examples, and Comparative Examples described later, 3 mm thick test pieces were molded by injection molding, and the total light transmittance was measured in accordance with JIS K7361-1. The total light transmittance is preferably 90% or more, which is equivalent to that of a general commercially available acrylic resin (PMMA).

<III-3. Degree of change in YI value (ΔYI)>
The methacrylic resins and resin compositions obtained in the Examples , Reference Examples , and Comparative Examples described below were subjected to an injection molding machine (EC-100SX, manufactured by Toshiba Machine Co., Ltd.) at a molding temperature of 280°C and a mold temperature of 60°C to prepare test pieces having a thickness of 3 mm, a width of 20 mm, and a length of 220 mm.
The injection molding cycle time (injection time plus cooling time) was (c) 45 seconds or (d) 270 seconds.
After the molding had stabilized, the test pieces obtained from the 11th to 15th shots were used to measure the 220 mm long optical path YI values of five test pieces each obtained at cycle times (c) and (d).
Then, the average value of the YI values of the five test pieces of (c) and the average value of the YI values of the five test pieces of (d) were obtained, and the degree of change in the YI value (ΔYI) in the 220 mm long optical path was calculated from [average value of the YI values of (d)−average value of the YI values of (c)]/average value of the YI value of (c).
The YI value was measured using a color difference meter (manufactured by Tokyo Denshoku Co., Ltd., TC-8600A, light source: 10-C) in accordance with JIS K7105.
<Long-term retention evaluation>
The change in the YI value was evaluated as follows: 10 or less: "A", 10 or more and 13 or less: "O", 20 or less: "Δ", and more than 20: "X".

(III. Physical Property Measurements)
The evaluation methods for the methacrylic resin and the methacrylic resin composition will be described below.

<III-4. Presence or absence of Silver Streaks>
The methacrylic resin compositions obtained in the Examples , Reference Examples , and Comparative Examples described later were dried at 80°C for 24 hours, and then evaluated for the presence or absence of silver streaks using the injection molding machine and measurement mold described below under the molding conditions described below.
Specifically, the resin was injected into the center of the mold surface under the following conditions, and 40 seconds after the end of injection, the spiral molded product was removed and evaluated for the occurrence of silver streaks. After switching the resin, 20 shots were discarded, and the evaluation was carried out using 50 pieces from the 21st to 70th shots.
・Injection molding machine: EC-100SX (Toshiba Machine Co., Ltd.)
Measurement mold: A mold with a groove 2 mm deep and 12.7 mm wide carved into the surface in an Archimedes spiral shape from the center of the surface. Molding conditions: Resin temperature: 290°C
Mold temperature: 70°C
Maximum injection pressure: 75MPa
Injection time: 20 sec
Evaluation of the presence or absence of silver streaks: ◎: out of 50 samples, 2 or less samples had silver streaks. ○: out of 50 samples, 5 or less samples had silver streaks. △: out of 50 samples, 10 or less samples had silver streaks. ×: out of 50 samples, more than 10 samples had silver streaks.

<III-5. Evaluation of releasability>
The methacrylic resin compositions obtained in the Examples , Reference Examples , and Comparative Examples described later were dried at 80° C. for 24 hours, and then the releasability was evaluated using the injection molding machine and measurement mold described below under the molding conditions described below. Specifically, after switching the resin, 15 shots were discarded, and the evaluation was performed using 30 pieces from the 16th shot to the 45th shot.
・Injection molding machine: EC-100SX (Toshiba Machine Co., Ltd.)
Measurement mold: Long optical path test piece mold with thickness 3 mm x width 20 mm x length 220 mm Molding conditions Resin temperature: 280°C
Mold temperature: 70°C
Mold release evaluation: ◎: out of 30 samples, 1 or less samples showed release failure. ○: out of 30 samples, 3 or less samples showed release failure. △: out of 30 samples, 7 or less samples showed release failure. ×: out of 30 samples, more than 10 samples showed release failure.

<III-3. Degree of change in YI value (ΔYI)
The methacrylic resins and resin compositions obtained in the examples and comparative examples described below were molded using an injection molding machine (EC-100SX, manufactured by Toshiba Machine Co., Ltd.) at a molding temperature of 280°C and a mold temperature of 60°C to produce test pieces having a thickness of 3 mm, a width of 20 mm, and a length of 220 mm.
The injection molding cycle time (injection time plus cooling time) was (c) 45 seconds or (d) 270 seconds.
After the molding had stabilized, the test pieces obtained from the 11th to 15th shots were used to measure the 220 mm long optical path YI values of five test pieces each obtained at cycle times (c) and (d).
Then, the average value of the YI values of the five test pieces of (c) and the average value of the YI values of the five test pieces of (d) were obtained, and the degree of change in the YI value (ΔYI) in the 220 mm long optical path was calculated from [average value of the YI values of (d)−average value of the YI values of (c)]/average value of the YI value of (c).
The YI value was measured using a color difference meter (manufactured by Tokyo Denshoku Co., Ltd., TC-8600A, light source: C light source, viewing angle: 2 degrees) in accordance with JIS K7105.
<Long-term retention evaluation results>
The change in the YI value of 10 or less was evaluated as "◎" (particularly excellent), that of more than 10 and not more than 15 was evaluated as "◯" (good), that of 20 or less was evaluated as "△" (no problem in practical use), and that of more than 20 was evaluated as "×" (poor).

<III-4. Presence or absence of Silver Streaks>
The methacrylic resin compositions obtained in the examples and comparative examples described below were dried at 80°C for 24 hours, and then evaluated for the presence or absence of silver streaks using the injection molding machine and measurement mold described below under the molding conditions described below.
Specifically, the resin was injected into the center of the mold surface under the following conditions, and 40 seconds after the end of injection, the spiral molded product was removed and evaluated for the occurrence of silver streaks. After switching the resin, 20 shots were discarded, and the evaluation was carried out using 50 pieces from the 21st to 70th shots.
・Injection molding machine: EC-100SX (Toshiba Machine Co., Ltd.)
Measurement mold: A mold with a groove 2 mm deep and 12.7 mm wide carved into the surface in an Archimedes spiral shape from the center of the surface. Molding conditions: Resin temperature: 290°C
Mold temperature: 70°C
Maximum injection pressure: 75MPa
Injection time: 20 sec
Evaluation of the presence or absence of silver streaks: ◎: out of 50 samples, 2 or less samples had silver streaks. ○: out of 50 samples, 5 or less samples had silver streaks. △: out of 50 samples, 10 or less samples had silver streaks. ×: out of 50 samples, more than 10 samples had silver streaks.

<III-5. Evaluation of releasability>
The methacrylic resin compositions obtained in the examples and comparative examples described later were dried at 80°C for 24 hours, and then the releasability was evaluated using the injection molding machine and measurement mold described below under the molding conditions described below. Specifically, after switching the resin, 15 shots were discarded, and the evaluation was performed using 30 pieces from the 16th shot to the 45th shot.
・Injection molding machine: EC-100SX (Toshiba Machine Co., Ltd.)
Measurement mold: Long optical path test piece mold with thickness 3 mm x width 20 mm x length 220 mm Molding conditions Resin temperature: 280°C
Mold temperature: 70°C
Mold release evaluation: ◎: out of 30 samples, 1 or less samples showed release failure. ○: out of 30 samples, 3 or less samples showed release failure. △: out of 30 samples, 7 or less samples showed release failure. ×: out of 30 samples, more than 10 samples showed release failure.

<III-6. Evaluation of Weather Resistance (Weather Resistance) and Measurement of Weather Resistance (Color Difference (ΔE*))>
As an index for evaluating weather resistance, the color difference (ΔE*) of the sample before and after the exposure test was measured.
The 3 mm thick test piece molded in (III-5) above was used to carry out an exposure test according to the method of JIS K7350-4. The exposure conditions were: black panel temperature setting of 63±3°C, water spray time setting of (18±0.5) minutes, spray stop time setting of (102±0.5) minutes, and total exposure time of 2040 hours.
The sample piece was set so that the 20 mm x 220 mm surface of the 3 mm thick test piece described above was the exposed surface.
After the exposure, the test pieces were washed with water and the object color was measured.
The color difference was measured using a ΔE* value. The measurement was performed on the exposed surface of the flat evaluation sample using a color difference meter in accordance with JIS Z8730. Specifically, the color difference ΔE* of the transmitted light from the exposed surface in the thickness direction was measured.
<Weather resistance evaluation>
In the above evaluation, ΔE* of 2 or less was evaluated as "◎" (particularly excellent), ΔE* of more than 2 and less than 2.5 was evaluated as "○" (good), ΔE* of 2.5 or more and less than 3 was evaluated as "△" (no problem in practical use), ΔE* of 3 or more and less than 3.5 was evaluated as "×" (bad), and ΔE* of 3.5 or more was evaluated as "XX" (inferior).

<III-7. Evaluation of scratch resistance>
The resin composition pellets obtained in the examples and comparative examples described below were injection molded in a mold having a polishing number of 8000 to obtain a flat plate sample having a thickness of 2 mm. Using this flat plate sample, an evaluation of scratch resistance was carried out, assuming that sand and dust were blown onto the traffic light cover.
The flat sample and a reference white slide glass No. 001 manufactured by Matsunami Glass Co., Ltd. were placed vertically on the ground so as not to move. 22 g of sand (Quarzsand F36 manufactured by Quarzwerke GmbH), 512 g of water, and a stirrer were placed in a spray gun with a nozzle diameter of 1.3 mm, and Quarzsand F36 was sprayed toward the front of the flat sample and the reference glass so that both were hit in the same way, under the conditions of an injection pressure of 0.3 MPa, a flow rate of 0.25 L/min, and a distance of 19 cm from the nozzle to the flat sample and the reference glass, while stirring at a speed of 1000 rpm with a magnetic stirrer.
The haze before and after the test was measured in accordance with JIS K7136 using NDH7000 manufactured by Nippon Denshoku Industries Co., Ltd., and the amount of change was calculated to evaluate the scratch resistance. The haze was measured at the center of the test area hit by Quarzsand F36. The test was terminated when the haze of the reference glass reached 3. If the haze of the reference glass did not reach 3 in one test, sand and water were charged into the spray gun under the same conditions again, and the test was repeated until the haze of the reference glass reached 3. The amount of change in haze was calculated according to the following formula.
(Change in haze) = (haze after test) - (haze before test)
The scratch resistance was evaluated as follows: a change in haze of 7.2 or less was "○" (exceptionally excellent); a change in haze of more than 7.2 to 8.0 or less was "△" (no problem in practical use); and a change in haze of more than 8.0 was "×" (poor).

The following describes an example of how to manufacture methacrylic resin.

[Production Example 1]
Into a vessel equipped with a stirrer equipped with four inclined paddle blades were added 2 kg of water, 65 g of tribasic calcium phosphate, 39 g of calcium carbonate, and 0.39 g of sodium lauryl sulfate to obtain a mixed liquid (a).
Next, 26 kg of water was charged into a 60 L reactor equipped with a stirrer equipped with three sweepback blades, and the temperature was raised to 75° C., and the mixed liquid (a) was charged, followed by 22 kg of a monomer mixed liquid prepared in advance by mixing 95 parts by mass of methyl methacrylate (A), 5 parts by mass of cyclohexylmaleimide (B-2), 0.295 parts by mass of the chain transfer agent n-octyl mercaptan, and 0.25 parts by mass of the polymerization initiator t-butylperoxy-2-ethylhexanoate.

The suspension polymerization was carried out while maintaining the temperature at about 75° C., and an exothermic peak was observed about 120 minutes after the raw material mixture was added. After that, the temperature was raised to 97° C. at a rate of 1° C./min, and the mixture was aged for 120 minutes, at which point the polymerization reaction was essentially completed.
Next, the mixture was cooled to 50° C., and 20% by mass sulfuric acid was added to dissolve the suspending agent.
Next, the polymerization reaction solution was sieved through a 1.68 mm mesh sieve to remove aggregates, and then the water was filtered off. The resulting slurry was dehydrated to obtain a bead-shaped polymer. The resulting bead-shaped polymer was washed with water, dehydrated in the same manner as above, and further washed with ion-exchanged water and dehydrated repeatedly to obtain polymer particles. The average particle size was 0.29 mm.
The obtained polymer particles were subjected to a devolatilization treatment at 200 rpm and 12 kg/hour in terms of resin amount, using a 3-vent φ37 mm extruder with the cylinder temperature close to the die set to 270°C, the kneading section cylinder temperature set to 260°C, and 230°C from the resin introduction section to the kneading section, while adding purified water in an amount of 4% by mass of the resin amount between the resin introduction section and the kneading section, to obtain resin pellets.
The weight-average molecular weight of the obtained resin pellets was 100,000, and the resin composition determined by NMR was: MMA unit: 95% by mass, CMI unit: 5% by mass.

[Production Example 2]
Into a vessel equipped with a stirrer equipped with four inclined paddle blades were added 2 kg of water, 65 g of tribasic calcium phosphate, 39 g of calcium carbonate, and 0.39 g of sodium lauryl sulfate to obtain a mixed liquid (a).
Next, 26 kg of water was charged into a 60 L reactor equipped with a stirrer equipped with three sweepback blades, and the temperature was raised to 75° C., and the mixed liquid (a) was charged, followed by charging 90 parts by mass of methyl methacrylate (A), 5 parts by mass of cyclohexylmaleimide (B-2), 5 parts by mass of styrene, 0.24 parts by mass of the chain transfer agent n-octyl mercaptan, 0.20 parts by mass of the polymerization initiator t-butylperoxy-2-ethylhexanoate, and 22 kg of a premixed monomer mixed liquid.
Suspension polymerization was carried out while maintaining the temperature at about 75° C., and an exothermic peak was observed about 120 minutes after the raw material mixture was charged.
Thereafter, the temperature was raised to 93° C. at a rate of 1° C./min, and the mixture was aged for 120 minutes to essentially complete the polymerization reaction.
Next, the mixture was cooled to 50° C., and 20% by mass sulfuric acid was added to dissolve the suspending agent.
Next, the polymerization reaction solution was passed through a 1.68 mm mesh sieve to remove aggregates, and then the water was filtered off. The resulting slurry was dehydrated to obtain a bead-like polymer. The resulting bead-like polymer was washed with water and then dehydrated in the same manner as above, and further washed with ion-exchanged water and dehydrated repeatedly to obtain polymer particles.
The obtained polymer particles were subjected to a devolatilization treatment at 200 rpm and 12 kg/hour in terms of resin amount, using a 3-vent φ37 mm extruder with the cylinder temperature close to the die set to 270°C, the kneading section cylinder temperature set to 260°C, and 230°C from the resin introduction section to the kneading section, while adding purified water in an amount of 4% by mass of the resin amount between the resin introduction section and the kneading section, to obtain resin pellets.
The weight average molecular weight of the obtained resin pellets was 110,000, and the resin composition determined by NMR was as follows: MMA units: 90% by mass, CMI units: 5% by mass, and St units: 5% by mass.

[Production Example 3]
Into a vessel equipped with a stirrer equipped with four inclined paddle blades were added 2 kg of water, 65 g of tribasic calcium phosphate, 39 g of calcium carbonate, and 0.39 g of sodium lauryl sulfate to obtain a mixed liquid (a).
Next, 26 kg of water was charged into a 60 L reactor equipped with a stirrer equipped with three sweepback blades, and the temperature was raised to 75° C., and the mixed liquid (a) was charged, followed by charging 89 parts by mass of methyl methacrylate (A), 11 parts by mass of cyclohexylmaleimide (B-2), 5 parts by mass of meta-xylene, 0.208 parts by mass of the chain transfer agent n-octyl mercaptan, 0.25 parts by mass of the polymerization initiator t-butylperoxy-2-ethylhexanoate, and 22 kg of a premixed monomer mixed liquid.
The suspension polymerization was carried out while maintaining the temperature at about 75° C., and an exothermic peak was observed about 120 minutes after the raw material mixture was charged.
Thereafter, the temperature was raised to 93° C. at a rate of 1° C./min, and the mixture was aged for 120 minutes to essentially complete the polymerization reaction.
Next, the mixture was cooled to 50° C., and 20% by mass sulfuric acid was added to dissolve the suspending agent.
Next, the polymerization reaction solution was sieved through a 1.68 mm mesh sieve to remove aggregates, and then the water was filtered off. The resulting slurry was dehydrated to obtain a bead-like polymer. The resulting bead-like polymer was washed with water, dehydrated in the same manner as above, and further washed with ion-exchanged water and dehydrated repeatedly to obtain polymer particles. The average particle size was 0.29 mm.
The obtained polymer particles were subjected to a devolatilization treatment at 200 rpm and 12 kg/hour in terms of resin amount, using a 3-vent φ37 mm extruder with the cylinder temperature close to the die set to 270°C, the kneading section cylinder temperature set to 260°C, and 230°C from the resin introduction section to the kneading section, while adding purified water in an amount of 4% by mass of the resin amount between the resin introduction section and the kneading section, to obtain resin pellets.
The weight-average molecular weight of the obtained resin pellets was 130,000, and the resin composition determined by NMR was: MMA unit: 90% by mass, CMI unit: 10% by mass.

[Production Example 4]
A 1.25 ^m3 reaction vessel equipped with a stirring device equipped with a paddle blade, a temperature sensor, a cooling tube, and a nitrogen inlet tube was charged with 470 kg of methyl methacrylate (MMA), 39 kg of N-phenylmaleimide (B-1), 41 kg of N-cyclohexylmaleimide (B-2), 450.0 kg of meta-xylene, and n-octyl mercaptan in an amount of 1200 ppm by mass relative to 100 parts by mass of the total amount of all monomers, and dissolved to prepare a raw material solution. The temperature was raised to 125°C while stirring and passing nitrogen through the solution.
Separately, an initiator feed solution was prepared by mixing 0.23 kg of Perhexa C-75 and 1.82 kg of meta-xylene.
When the raw material solution reached 127° C., feeding (addition) of the initiator feed liquid (polymerization initiator mixed liquid) was started according to the profiles (1) to (6).
(1) 0.0 to 0.5 hours: feed rate of 1.00 kg/hour (2) 0.5 to 1.0 hours: feed rate of 0.50 kg/hour (3) 1.0 to 2.0 hours: feed rate of 0.41 kg/hour (4) 2.0 to 3.0 hours: feed rate of 0.36 kg/hour (5) 3.0 to 4.0 hours: feed rate of 0.14 kg/hour (6) 4.0 to 7.0 hours: feed rate of 0.13 kg/hour After the initiator was fed over a total of 7 hours (B time = 7 hours), the reaction was continued for another 2 hours, and the polymerization reaction was carried out for 8 hours from the start of the addition of the initiator.
During the polymerization reaction, the internal temperature was controlled at 127±2° C. The polymerization conversion of the obtained polymerization liquid was measured, and the results were as follows: MMA unit: 94.1% by mass, PMI unit: 95.5% by mass, and CMI unit: 93.2% by mass. Overall, the polymerization conversion was 93%.
This polymer solution was fed to a concentration device consisting of a tubular heat exchanger and a vaporization tank, both of which had been preheated to 170° C., to increase the concentration of the polymer contained in the solution to 70% by mass.
The obtained polymerization solution was supplied to a thin-film evaporator having a heat transfer area of 0.2 ^m2 , and devolatilization was carried out at an internal temperature of 275°C, a supply rate of 25 L/h, a rotation speed of 300 rpm, and a vacuum degree of 25 Torr. The polymer after devolatilization was pressurized with a gear pump and extruded from a strand die, cooled with water, and cut into resin pellets.
The weight-average molecular weight of the obtained resin pellets was 120,000, and the resin composition determined by NMR was as follows: MMA units: 86% by mass, PMI units: 7% by mass, and CMI units: 7% by mass.

Examples , Reference Examples and Comparative Examples of methacrylic resin compositions are described below.

[Production Example 6]
A 200 L reactor equipped with a paddle-equipped stirring device, a temperature sensor, a cooling tube, and a nitrogen inlet tube was charged with 69.1 kg of methyl methacrylate (MMA), 5.32 kg of styrene (St), 9.57 kg of methacrylic acid (MAA), 56.0 kg of meta-xylene, and 0.105 kg of n-octyl mercaptan to prepare a raw material solution. The temperature was raised to 117° C. while stirring and passing nitrogen through the solution.
Separately, an initiator feed liquid A was prepared by mixing 0.029 kg of Perhexa 25B and 0.10 kg of meta-xylene, and an initiator feed liquid B was prepared by mixing 0.0098 kg of Perhexa 25B and 0.10 kg of meta-xylene.
When the temperature of the raw material solution reached 117° C., initiator feed liquid A was fed at a feed rate of 0.774 kg/hour for 10 minutes, and the reaction was allowed to proceed for 2 hours. Thereafter, initiator feed liquid B was fed at a feed rate of 0.110 kg/hour for 10 minutes, and the reaction was continued for another 10 hours, and the polymerization reaction was carried out for a total of 12 hours and 20 minutes, and the reaction was completed.
The resulting polymerized liquid was fed into a high-temperature vacuum chamber set at 280° C., where unreacted materials and the solvent were removed to produce a 6-membered cyclic acid anhydride.
Compositional analysis of the produced copolymer by NMR showed that it contained 78% by mass of MMA units, 7% by mass of St units, 3% by mass of MAA units, and 12% by mass of 6-membered cyclic acid anhydride units.
0.5 kg of the copolymer pellets thus obtained was charged into an autoclave with an internal volume of 5 L, and then 3.0 kg of N,N-dimethylformamide was added and dissolved by stirring. 28% ammonia water containing 2 equivalents of ammonia relative to the unit amount of the 6-membered cyclic acid anhydride was charged, and the mixture was reacted at 150° C. for 2 hours.
The reaction liquid was extracted and poured into n-hexane to precipitate a polymer, which was then further treated in a 10 torr volatilization furnace at 250° C. for 2 hours.
The copolymer finally obtained was pale yellow and transparent, and its composition was as follows: MMA unit: 78% by mass, St unit: 7% by mass, MAA unit: 3% by mass, glutarimide structural unit: 12% by mass, as determined by elemental analysis of nitrogen content, NMR, and IR. The weight-average molecular weight of the copolymer was 130,000.
The above procedure was repeated to prepare the polymers required for evaluation.

[Examples 2 to 9, Reference Example 10], [Comparative Examples 1 to 3]
Methacrylic resin compositions were produced in the same manner as in Example 1 except that the conditions shown in Table 1 were used, and evaluations were carried out.
The evaluation results are shown in Table 1.

Below, we will describe examples and comparative examples of methacrylic resin compositions.

As shown in Table 1, when the weight average molecular weight of the methacrylic resin is within a predetermined range, the (D) component is within a predetermined range, and the mass ratio (B)/(D) is within a predetermined range, it has been found that the heat-resistant traffic light lens and lens cover have sufficient optical properties and are excellent in heat resistance, thermal stability, appearance, weather resistance, and moldability. In Reference Example 10, although the heat resistance is sufficient for practical use , it is lower than that of the Examples, and the light source output as a traffic light lens and lens cover may be limited.

Comparative Example 5
LC1500 was used as the polycarbonate resin.
The evaluation results are shown in Table 1.

As shown in Table 1, when the weight average molecular weight of the methacrylic resin is within a specified range, the (D) component is within a specified range, the mass ratio (B)/(D) is within a specified range, and the methacrylic resin composition contains at least one of a fatty acid compound, a polyether, a silicone, and a silicate compound, it has sufficient optical properties for use as a traffic light lens and lens cover, and is excellent in balance of scratch resistance, heat resistance, thermal stability, appearance, weather resistance, and moldability. In Example 10, the heat resistance is sufficient for practical use, but is lower than that of the other examples, and there is a possibility that the light source output as a traffic light lens and lens cover may be limited.

The methacrylic resin composition of the present invention and molded articles containing the same have industrial applicability as traffic light lenses and lens covers.

Claims (10)

The present invention includes a methacrylic resin composition having a change rate (ΔYI) of 20 or less in a 220 mm long optical path YI value (220 mm long optical path YI value (45 seconds)) measured in accordance with JIS K 7105 for a test piece prepared at an injection molding temperature of 280° C. and a cycle time of 270 seconds, relative to a 220 mm long optical path YI value (220 mm long optical path YI value (270 seconds)) measured in accordance with JIS K 7105 for a test piece prepared at an injection molding temperature of 280° C. and a cycle time of 270 seconds, the change rate being represented by the following formula (I) :
The methacrylic resin composition contains 100 parts by mass of a methacrylic resin including a structural unit (B) having a ring structure in its main chain, and 0.001 to 0.2 parts by mass of a compound (D) represented by the following general formula (1),
a ratio ((B)/(D)) of a content of a structural unit (B) having a ring structure in the main chain in the methacrylic resin composition to a content of the component (D) in the methacrylic resin composition is 25 or more and 1,000 or less .
ΔYI={220 mm long optical path YI value (270 seconds)−220 mm long optical path YI value (45 seconds)}/220 mm long optical path YI value (45 seconds) (I)

... (1)
(In formula (1), R represents a hydrogen atom, an aliphatic hydrocarbon group having 1 to 12 carbon atoms, or an aromatic hydrocarbon group having 1 to 12 carbon atoms. The aliphatic hydrocarbon group and aromatic hydrocarbon group of R may each have a sulfur atom, a nitrogen atom, an oxygen atom, or a phosphorus atom on a carbon atom. Furthermore, R' represents an aliphatic hydrocarbon group having 1 to 12 carbon atoms, or an aromatic hydrocarbon group having 6 to 18 carbon atoms. The aliphatic hydrocarbon group and aromatic hydrocarbon group of R' may each have a sulfur atom, a nitrogen atom, an oxygen atom, or a phosphorus atom on a carbon atom.) The present invention includes a methacrylic resin composition having a change rate (ΔYI) of 20 or less in a 220 mm long optical path YI value (220 mm long optical path YI value (45 seconds)) measured in accordance with JIS K 7105 for a test piece prepared at an injection molding temperature of 280° C. and a cycle time of 270 seconds relative to a 220 mm long optical path YI value (220 mm long optical path YI value (270 seconds)) measured in accordance with JIS K 7105 for a test piece prepared at an injection molding temperature of 280° C. and a cycle time of 270 seconds, the change rate being represented by the following formula (I):
The methacrylic resin composition contains 100 parts by mass of a methacrylic resin including a structural unit (B) having a ring structure in its main chain, and 0.001 to 0.2 parts by mass of a compound (D) represented by the following general formula (1),
a ratio ((B)/(D)) of a content of a structural unit (B) having a ring structure in the main chain in the methacrylic resin composition to a content of the component (D) in the methacrylic resin composition is 25 or more and 1,000 or less.
ΔYI={220 mm long optical path YI value (270 seconds)−220 mm long optical path YI value (45 seconds)}/220 mm long optical path YI value (45 seconds) (I)

... (1)
(In formula (1), R represents a hydrogen atom, an aliphatic hydrocarbon group having 1 to 12 carbon atoms, or an aromatic hydrocarbon group having 1 to 12 carbon atoms. The aliphatic hydrocarbon group and aromatic hydrocarbon group of R may each have a sulfur atom, a nitrogen atom, an oxygen atom, or a phosphorus atom on a carbon atom. Furthermore, R' represents an aliphatic hydrocarbon group having 1 to 12 carbon atoms, or an aromatic hydrocarbon group having 6 to 18 carbon atoms. The aliphatic hydrocarbon group and aromatic hydrocarbon group of R' may each have a sulfur atom, a nitrogen atom, an oxygen atom, or a phosphorus atom on a carbon atom.) The present invention includes a methacrylic resin composition having a change rate (ΔYI) of 20 or less in a 220 mm long optical path YI value (220 mm long optical path YI value (45 seconds)) measured in accordance with JIS K 7105 for a test piece prepared at an injection molding temperature of 280° C. and a cycle time of 270 seconds, relative to a 220 mm long optical path YI value (220 mm long optical path YI value (270 seconds)) measured in accordance with JIS K 7105 for a test piece prepared at an injection molding temperature of 280° C. and a cycle time of 270 seconds, the change rate being represented by the following formula (I):
The methacrylic resin composition contains 100 parts by mass of a methacrylic resin including a structural unit (B) having a ring structure in its main chain, and 0.001 to 0.2 parts by mass of a compound (D) represented by the following general formula (1),
A traffic light lens cover, characterized in that a ratio ((B)/(D)) of a content of a structural unit (B) having a ring structure in the main chain in the methacrylic resin composition to a content of the component (D) in the methacrylic resin composition is 25 or more and 1,000 or less.
ΔYI={220 mm long optical path YI value (270 seconds)−220 mm long optical path YI value (45 seconds)}/220 mm long optical path YI value (45 seconds) (I)

... (1)
(In formula (1), R represents a hydrogen atom, an aliphatic hydrocarbon group having 1 to 12 carbon atoms, or an aromatic hydrocarbon group having 1 to 12 carbon atoms. The aliphatic hydrocarbon group and aromatic hydrocarbon group of R may each have a sulfur atom, a nitrogen atom, an oxygen atom, or a phosphorus atom on a carbon atom. Furthermore, R' represents an aliphatic hydrocarbon group having 1 to 12 carbon atoms, or an aromatic hydrocarbon group having 6 to 18 carbon atoms. The aliphatic hydrocarbon group and aromatic hydrocarbon group of R' may each have a sulfur atom, a nitrogen atom, an oxygen atom, or a phosphorus atom on a carbon atom.) The traffic light lens and lens cover according to claim 1, the traffic light lens according to claim 2, or the traffic light lens cover according to claim 3, wherein the color difference ΔE* measured according to JIS Z8730 before and after a 2040-hour exposure test using a 3 mm thick test piece using the method of JIS K7350-4 is 3 or less . The methacrylic resin composition has a weight average molecular weight of 65,000 to 300,000 as measured by gel permeation chromatography (GPC). The traffic light lens and lens cover according to claim 1 or 4 , the traffic light lens according to claim 2 or 4, or the traffic light lens cover according to claim 3 or 4 . The methacrylic resin contains 50 to 97 mass% of methacrylic acid ester monomer units (A), 3 to 30 mass% of structural units (B) having a ring structure in the main chain, and 0 to 20 mass% of other vinyl monomer units (C) copolymerizable with the methacrylic acid ester monomer. The traffic light lens and lens cover according to claim 1, 4, or 5 , the traffic light lens according to claim 2, 4, or 5, or the traffic light lens cover according to claim 3, 4, or 5 . The traffic light lens and lens cover according to any one of claims 1 and 4 to 6, wherein the structural unit (B) having a ring structure in the main chain includes at least one structural unit selected from the group consisting of a maleimide-based structural unit (B-1), a glutaric anhydride-based structural unit (B-2), a glutarimide-based structural unit (B-3), a lactone ring structural unit (B-4), and an acid anhydride structural unit (B-5). The traffic light lens and lens cover according to any one of claims 2 and 4 to 6, or the traffic light lens cover according to any one of claims 3 to 6 . The traffic light lens and lens cover according to any one of claims 1 and 4 to 7 , the traffic light lens according to any one of claims 2 and 4 to 7, or the traffic light lens cover according to any one of claims 3 to 7, each having a thickness of 0.03 to 10 mm . The traffic light lens and lens cover according to any one of claims 1 and 4 to 8, the traffic light lens according to any one of claims 2 and 4 to 8, or the traffic light lens cover according to any one of claims 3 to 8, wherein the content of at least one compound selected from the group consisting of fatty acid compounds, silicones, polyethers, and silicate compounds is 0.05 to 6 parts by mass relative to 100 parts by mass of the methacrylic resin . The traffic light lens and lens cover according to any one of claims 1 and 4 to 9, the traffic light lens according to any one of claims 2 and 4 to 9, or the traffic light lens cover according to any one of claims 3 to 9, wherein, when the methacrylic resin composition is injection molded into a flat plate having a thickness of 2 mm using a mold having a polishing number of 8000 , the flat plate has a total light transmittance of 85% or more as measured in accordance with JIS K7361-1, and a haze of 5 or less as measured in accordance with JIS K7136 .