JP5674325B2 - Molded product obtained using methacrylic resin composition - Google Patents

Description

  The present invention relates to a methacrylic resin composition having improved moldability and a method for producing the same.

Methacrylic resin is characterized by having higher light transmittance, weather resistance, and rigidity than other plastic transparent resins as a transparent resin, and is used for vehicle parts, lighting equipment, building materials, signboards, nameplates, paintings, and display devices. It is used in a wide range of applications such as windows. In particular, a methacrylic resin molded product is often used for a transparent member of a rear lamp of a vehicle.
However, in recent years, there is an increasing demand for improving the fluidity of materials in vehicle applications, such as thinning for weight reduction accompanying improvement in fuel efficiency and enlargement for realizing a novel design. Conventionally, improving fluidity of a material sacrifices strength, heat resistance, secondary workability, and the like.
Thinning of the transparent member of a vehicle lamp is also being studied, and a demand for improved fluidity of the material is desired. As a method for improving the fluidity, there is a method of lowering the molecular weight, but there is a problem that the resin twists the yarn when the hot plate is welded to the housing member, resulting in poor appearance.
Patent document 1 is mentioned as a method of making the fluidity | liquidity at the time of injection molding and the physical property of the obtained molded article compatible. Patent Document 1 discloses a resin that improves fluidity and solvent resistance at the time of injection molding. However, sufficient examination has not been made on stringing properties at the time of hot plate welding, and fluidity and heat at the time of injection molding are not disclosed. The stringing property at the time of sheet welding was not satisfied at the same time.

WO2007-060891 pamphlet

  An object of the present invention is to provide a methacrylic resin composition excellent in physical properties such as moldability and secondary processability, and a method for producing the same.

As a result of intensive studies to solve the above problems, the present inventors can solve both molding processability and secondary processability if the viscosity of the resin measured under specific conditions is within a certain numerical range. The present invention has been found and the present invention has been made.
That is, the present invention and embodiments are described below.
[1] The methacrylic resin is the following polymer (1) and polymer (2) , and the methacrylic resin composition has a weight average molecular weight of 5000 to 50000 as measured by gel permeation chromatography, and is based on the entire methacrylic resin composition. A methacrylic resin composition comprising a polymer (1) having a weight average molecular weight of 90,000 to 350,000 and a polymer (2) having a weight average molecular weight of 90,000 to 350,000 and 90 to 65% by weight based on the whole methacrylic resin composition. And at least one selected from methyl methacrylate monomer units 80 to 99 wt%, alkyl methacrylate having 2 to 18 carbon atoms, and alkyl acrylate having 1 to 18 carbon atoms. comprises 1 to 20 wt% vinyl monomer units of the species, the resin temperature 240 ° C. with a rheometer, conditions of angular 4 rad / s In the measured viscosity is not more 4900Pa · s or more, the resin temperature of 240 ° C., viscosity at the conditions of angular velocity 100 rad / s is not more than 1450Pa · s, Teflon heated to 245 ° C. (R) worked into an aluminum plate A molded body obtained by using a methacrylic resin composition characterized by having a long yarn generation rate of 20% or less when a test piece is pressed and released after 20 seconds and a resin yarn of 5 mm or more is generated. A molded body obtained by welding the molded body to a hot plate.
[2] Spiral length under the following measurement conditions is 26 cm or more, and a molded body obtained by using the methacrylic resin composition according to the above [1] and another molded body are hot plate welded Molded body.
・ Injection molding machine: Toshiba Machine IS-100EN
・ Measurement mold: A mold with a groove of 2mm depth and 10mm width dug into the Archimedes spiral shape from the center on the mold surface
・ Resin temperature: 250 ℃
-Mold temperature: 55 ° C
・ Injection pressure: 98 MPa,
・ Injection time: 10 sec
・ Cooling time: 10 seconds ・ Measurement method: After 40 shot molding, 10 samples for spiral length measurement are sampled, and the average value of the length of the spiral part of 2 mm is set as the spiral length.

  The methacrylic resin composition of the present invention is excellent in both fluidity during injection molding and stringiness during hot plate welding.

It is explanatory drawing regarding the GPC area of the methacryl resin in this invention. The vertical axis of the graph indicates RI (differential refraction) detection intensity (mV), the horizontal axis of the graph indicates the elution time (min.) At the bottom, and the cumulative area area (%) with respect to the entire GPC area area. It is the figure which showed an example of the accumulation area area. It is the schematic which shows the position of 0-2% of accumulation area areas, and 98-100% of accumulation area areas on a GPC elution curve measurement graph.

The present invention is described in detail below.
According to the study by the present inventors, the stringing rate at the time of hot plate welding of the methacrylic resin composition molded body is correlated with the viscosity at a resin temperature of 240 ° C. and an angular velocity of 4 rad / s using a rheometer. I found it. The specific reason is as follows.
That is, the temperature at which stringing occurs is considered to be related to the melt viscosity at the resin temperature when the molded body is welded. The setting temperature of the hot plate in a general molding line is 250 ° C, but in the actual line, the surface temperature of the hot plate is lowered by several degrees, and when the resin is pressed against the hot plate, the resin temperature near the hot plate Is considered to be a few degrees lower. Therefore, the effect of the present invention may not be obtained even with a resin having an appropriate resin viscosity at 250 ° C. Therefore, the inventors set the temperature at which the viscosity of the resin is measured to 240 ° C. Furthermore, in order to accurately evaluate the degree of stringing at the time of molding, it is necessary to look at the stringing state at a temperature that reflects the actual surface temperature of the resin, but the appropriate temperature is found to be 245 ° C. It was.

Therefore, the methacrylic resin composition of the present invention, the resin Temperature 240 ° C. using a rheometer, that the viscosity of the condition of the angular velocity 4 rad / s to the methacrylic Le resins composition which exhibits more than 4900Pa · s, which will be described later It has been found that the stringiness at the time of hot plate welding at 245 ° C. can be suppressed to 20% or less. Preferably it is 5000 Pa · s or more, more preferably 5100 Pa · s or more. Moreover, in order to ensure the fluidity | liquidity at the time of injection molding, 20000 Pa * s or less is preferable. More preferably, it is 18000 Pa.s or less, More preferably, it is 15000 Pa.s or less.

The fluidity at the time of injection molding of the methacrylic resin composition in the present invention correlates with the viscosity when measured using a rheometer under the conditions of a resin temperature of 240 ° C. and an angular velocity of 100 rad / s. With respect to the molding fluidity of the methacrylic resin composition in the present invention, the viscosity at a resin temperature of 240 ° C. and an angular velocity of 100 rad / s is set to 1450 Pa · s or less using a rheometer. With satisfying this condition methacrylic Le resins composition, evaluated by the spiral length, Ru can achieve more fluidity 26cm. Preferably it is 1400 Pa.s or less, More preferably, it is 1370 Pa.s or less. In order to keep the mechanical strength in a preferable state, the viscosity is preferably 500 Pa · s or more. More preferably, it is 600 Pa · s or more, and more preferably 700 Pa · s or more.
In addition, the viscosity measured by the present invention is measured with a rheometer (product name: ARES-G2 manufactured by TA Instruments). As a measuring jig, a cone having a diameter of 25 mm and an angle of 1 degree was used. The cradle has a flat disk shape with a diameter of 25 mm.

In the measurement, a methacrylic resin composition as a sample is previously formed into a resin disk having a diameter of 25 mm and a thickness of 1.2 to 1.5 mm by press molding. After heating the measurement part of the rheometer to 250 ° C., a resin disk was set between the cradle and the cone, and the cone was pushed until the distance from the top of the cone to the cradle reached 0.05 mm. Then, measurement was started after removing the protruding resin. The viscosity was measured from the torque applied to the jig at an angular velocity of 100 rad / s and 4 rad / s.
In order to adjust the viscosity within this range, the composition of the low molecular weight polymer (1) and the high molecular weight polymer (2) (ratio and molecular weight, weight of other vinyl monomers copolymerizable with methyl methacrylate) %). For example, by increasing the difference in molecular weight between the low molecular weight polymer (1) and the high molecular weight polymer (2), the viscosity at an angular velocity of 100 rad / s tends to increase and the viscosity at 4 rad / s tends to decrease. .

The methacrylic resin composition is preferably composed of methyl methacrylate and other vinyl monomers copolymerizable with methyl methacrylate. The content of methyl methacrylate contained in the methacrylic Le resins composition is preferably 80～99Wt% relative methacrylic resin. 99 wt% or less is preferable from the viewpoint of the thermal decomposability of the resin. If it is this range, generation | occurrence | production of the bubble which the foaming of the monomer produced by decomposition | disassembly of the resin called silver at the time of shaping | molding will be suppressed. Moreover, 80 wt% or more is preferable from the viewpoint of heat resistance. More preferably, it is 85-98.8 wt%, More preferably, it is 90-98.7 wt%. Most preferably, it is 95-98.5 wt%. By setting it as such a preferable range, distortion can be suppressed even when the molded product is subjected to an environmental test.

Other vinyl monomers copolymerizable with methyl methacrylate affect fluidity and heat resistance. Examples of other vinyl monomers copolymerizable with methyl methacrylate include the following.
Alkyl methacrylate having 2 to 18 carbon atoms in alkyl group, alkyl acrylate having 1 to 18 carbon atoms in alkyl group; α, β-unsaturated acid such as acrylic acid and methacrylic acid, maleic acid, fumaric acid, itacon Unsaturated group-containing divalent carboxylic acids such as acids and their alkyl esters; styrene, α-methylstyrene, aromatic vinyl compounds such as styrene having a substituent on the benzene ring; vinyl cyanide compounds such as acrylonitrile and methacrylonitrile ;
Maleic anhydride, maleimide, N-substituted maleimide and the like;
Ethylene glycol such as ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, etc. Esterified; Esterified hydroxyl group of two alcohols such as neopentyl glycol di (meth) acrylate and di (meth) acrylate with acrylic acid or methacrylic acid; Polyhydric alcohol such as trimethylolpropane and pentaerythritol Derivatives esterified with acrylic acid or methacrylic acid; polyfunctional monomers such as divinylbenzene, and the like. These can be used alone or in combination of two or more.
Among these, methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, sec-butyl acrylate, 2-ethylhexyl acrylate, and the like are preferable from the viewpoints of light resistance, heat resistance, and fluidity. Used. Among them, methyl acrylate, ethyl acrylate, and n-butyl acrylate are particularly preferable, and methyl acrylate is most preferable because it is easily available.

The content of other vinyl monomer units copolymerizable with methyl methacrylate is preferably 1 to 20 wt% with respect to the methacrylic resin composition . From the viewpoint of the thermal decomposability of the resin, 1 wt% or more is preferable, and from the viewpoint of heat resistance, 20 wt% or less is preferable. More preferably, it is 1.2-15 wt%, More preferably, it is 1.3-10 wt%. Most preferred is 1.5 to 5 wt%.
The methacrylic resin composition preferably has a weight average molecular weight of 80,000 to 230000 as measured by gel permeation chromatography (GPC). 80,000 or more is preferable from the viewpoint of mechanical strength, and 230000 or less is preferable from the viewpoint of fluidity. In this case, the molding process becomes easy. More preferably, it is 85000-210000, More preferably, it is 90000-200000. Most preferably, it is 95000-190000.
Moreover, since the methacrylic resin composition component having a weight average molecular weight of 500 or less tends to cause a foam-like appearance defect called silver at the time of molding, it is preferably as small as possible.

The weight average molecular weight is measured by gel permeation chromatography (GPC).
A calibration curve is prepared in advance from the elution time and the weight average molecular weight using a monodispersed standard methacrylic resin having a known weight average molecular weight and available as a reagent, and an analytical gel column that elutes a high molecular weight component in advance. The molecular weight of each sample can be obtained from the obtained calibration curve.
The peak weight average molecular weight (Mp) refers to the weight average molecular weight showing a peak in the GPC elution curve. When there are a plurality of peaks in the GPC elution curve, the peak is indicated by the weight-average molecular weight having the largest abundance.

The weight average molecular weight component of 1/5 or less of Mp present in the methacrylic resin composition is related to the mechanical strength of the resin and the distortion of the molded product, and has the plasticizing effect due to the presence of this component. When the amount of this component is in the range of 7 to 30% with respect to the methacrylic resin composition component, the resin is plasticized to improve moldability. Further, since the injection pressure at the time of molding can be suppressed, the residual strain is reduced, and the effect of suppressing distortion of the molded product after molding is obtained, which is preferable. More preferably, it is 8 to 25%, and further preferably 8 to 20%.
In addition, it is preferable that the other vinyl monomer copolymerizable with methyl methacrylate has a larger composition ratio in the high molecular weight component of the obtained methacrylic resin than the composition ratio in the low molecular weight component. This is because the fluidity can be further improved while maintaining the low occurrence rate of cracks and distortion of molded products and mechanical strength under heat resistance and environmental tests. High molecular weight component and the low molecular weight component of methacrylic Le resins compositions may be determined by the area dimension in the GPC elution curve.

Here, the area area in the GPC elution curve indicates the hatched portion shown in FIG. The specific method is as follows.
First, point A and point B where the baseline automatically drawn by the measuring instrument and the GPC elution curve intersect with the GPC elution curve obtained from the elution time obtained by GPC measurement and the detected intensity by RI (differential refraction detector). Determine. Point A is a point where the GPC elution curve at the beginning of the elution time and the baseline intersect. Point B is a position where, as a general rule, the weight average molecular weight is 500 or more and the baseline and the GPC elution curve intersect. If the weight average molecular weight does not intersect within the range of 500 or more, the value of RI detection intensity at the elution time when the weight average molecular weight is 500 is defined as point B. A hatched portion surrounded by the GPC elution curve between the points A and B and the line segment AB is an area in the GPC elution curve. This area is the area of the GPC elution curve.
In order to determine the area, a column eluted first from the high molecular weight component is used, so that the high molecular weight component is observed at the beginning of the elution time and the low molecular weight component is observed at the end of the elution time.

The cumulative area area (%) of the area area in the GPC elution curve is point 0 shown in FIG. 1 being 0%, which is the standard for the cumulative area area (%), toward the end of the elution time, and detection corresponding to each elution time. The view is that the intensity accumulates and an area area in the GPC elution curve is formed. A specific example of the accumulated area area is shown in FIG.
In FIG. 2, a point on the baseline at a certain elution time is a point X, and a point on the GPC elution curve is a point Y. The ratio of the area surrounded by the curve AY, the line segment AX, and the line segment XY to the area area in the GPC elution curve is the value of the accumulated area area (%) at a certain elution time.
Let Mh (wt%) be the average composition ratio of other vinyl monomer units copolymerizable with methyl methacrylate in the methacrylic resin having a weight average molecular weight component in the cumulative area of 0 to 2%.

On the other hand, the average composition ratio of other vinyl monomer units that can be copolymerized with methyl methacrylate in a methacrylic resin having a cumulative area of 98 to 100%, that is, a low molecular weight is defined as Ml (wt%).
FIG. 3 shows a schematic diagram of positions on the measurement graph of the accumulated area area of 0 to 2% and 98 to 100%.
The values of Mh and Ml can be obtained by fractionating several times or several tens of times according to the column size based on the elution time obtained from GPC. The composition of the collected sample may be analyzed by a known pyrolysis gas chromatography method.
It is preferable that the relationship of the following formula [1] is established between Mh (wt%) and Ml (wt%).
(Mh−0.8) ≧ Ml ≧ 0 (1)

This indicates that the high molecular weight component has an average composition of 0.8 wt% or more of other vinyl monomer units copolymerizable with methyl methacrylate than the low molecular weight component. The low molecular weight component indicates that other vinyl monomers do not necessarily have to be copolymerized. The difference between Mh (wt%) and Ml (wt%) is preferably 0.8 wt% or more for the effect of improving fluidity. More preferably, it is 1.0 wt%, and more preferably, the following formula [2] is satisfied.
(Mh-2) ≧ Ml ≧ 0 [2]

In other words, by increasing the average composition of other vinyl monomer units copolymerizable with methyl methacrylate of the methacrylic resin in the high molecular weight component by 2 wt% or more than the average composition of the low molecular weight component, heat resistance and environmental test This is preferable because a drastic improvement in fluidity can be obtained while maintaining a low incidence of cracks and distortion of molded products and mechanical strength. However, in applications where heat resistance is required, the average composition of other vinyl monomer units copolymerizable with total methyl methacrylate may be 2 wt% or less. In that case, it is preferable to satisfy the expression [3].
This is because a methacrylic resin having a good balance between heat resistance, fluidity and mechanical strength can be obtained.
1.2 ≧ (Mh−0.8) ≧ Ml ≧ 0 [3]

That is, it is preferable to set Mh (wt%) to 2 wt% or less and to maintain the difference between Mh (wt%) and Ml (wt%) to 0.8 wt% or more. By setting it within this range, the fluidity improvement effect can be obtained while maintaining the low occurrence rate of cracks and distortion of molded products and mechanical strength in heat resistance and environmental tests.
The methacrylic resin composition of the present invention is excellent in heat resistance, and can achieve a Vicat softening temperature of 95 ° C. or higher according to the B50 method defined in JIS-K7206. More preferably, it is 100 degreeC or more, More preferably, it is 103 degreeC or more. Most preferably, it is 106 ° C. or higher. In order to adjust to this range, other vinyl monomer units copolymerizable with methyl methacrylate may be adjusted to 20 wt% or less with respect to the entire methacrylic resin composition.

There is no particular limitation on the method for producing methacrylic resins assembly formed product, and specific examples thereof include the following methods.
1. A polymer (A) is produced in advance, and the polymer (A) is mixed with a raw material composition mixture of a polymer (B) having a molecular weight different from that of the polymer (A), and the mixture is polymerized to produce. Method.
2. A method of producing a polymer (A) by adding and polymerizing a raw material composition mixture of a polymer (B) having a molecular weight different from that of the polymer (A).
3. A method in which a polymer (B) having a molecular weight different from that of the polymer (A) and the polymer (A) is separately produced in advance and blended.

These methods relate to a method of producing using two components having different molecular weight components, but for methods 1 and 2, polymers (C), polymers (D), etc. having different molecular weight compositions are the same. You may manufacture by a procedure. As for method 3, polymers (C) and polymers (D) having different molecular weight compositions may be further blended and melt-kneaded with an extruder, polymer mixer, static mixer or the like.
Preferably, the polymer (A) is produced, and the polymer (B) is produced in a state where the polymer (A) is present in the raw material composition mixture of the polymer (B). This is because it is easy to control the compositions of the polymer (A) and the polymer (B), the temperature rise due to the heat generated during polymerization is suppressed, and the viscosity in the system can be obtained stably. In this case, the raw material composition mixture of the polymer (B) may be in a state where the polymerization is partially started when (A) is added.
Either the polymer (A) or the polymer (B) may have a high molecular weight, and either one may have a low molecular weight. The compositions of the polymer (A) and the polymer (B) are preferably different.
For example, if the content of other vinyl monomers copolymerizable with methyl methacrylate is 1 to 20 wt% with respect to the methacrylic resin composition , the content of the polymer (A) and the polymer (B) Are preferably different.

Here, a method for producing a polymer (1) having a low molecular weight as the polymer (A) and producing a polymer (2) having a high molecular weight as the polymer (B) will be described.
First, 0-100 wt% of a monomer composed of 0-100 wt% of methyl methacrylate monomer and at least one other vinyl monomer copolymerizable with methyl methacrylate, The first stage so as to obtain a polymer (1) comprising 80 to 100 wt% of a monomer and 0 to 20 wt% of a monomer composed of at least one other vinyl monomer copolymerizable with methyl methacrylate. Prepare the raw materials. A more preferable ratio of the polymer (1) is 90 to 100 wt% of a methyl methacrylate monomer and 0 to 10 wt% of a monomer composed of at least one other vinyl monomer copolymerizable with methyl methacrylate. %, Most preferably 95 to 100 wt% of methyl methacrylate monomer and 0 to 5 wt% of monomer composed of at least one other vinyl monomer copolymerizable with methyl methacrylate.

Moreover, it is preferable to manufacture so that the molecular weight of a polymer (1) may become the weight average weight average amount measured by the gel permeation chromatography from 5000 to 50000. A weight average molecular weight of 5,000 or more is preferred because the solvent resistance of the resulting molded product of the resin composition can be maintained. Since the fluidity | liquidity of the obtained resin composition increases more that a weight average molecular weight is 50000 or less, it is preferable. More preferably, it is 10000-45000, More preferably, it is 13000-40000. The optimum range is 15000-35000.
In addition, it is preferable to mix | blend a raw material so that the ratio of a polymer (1) may be 10-35 wt%. In order to enhance the effect of improving the fluidity of the obtained resin composition, the content is preferably 10 wt% or more, and preferably 35 wt% or less from the viewpoint of the mechanical strength of the resin composition. More preferably, it is 15-33 wt%, More preferably, it is 20-30 wt%.

After producing the polymer (1), the polymer (2) is produced. At this time, a method for producing the polymer (2) in the presence of the polymer (1) is preferred. Furthermore, the time of the polymer (2) is preferably made longer than the polymerization time of the polymer (1).
The raw materials are adjusted so as to be 0.5 to 31 wt% of a monomer composed of 69 to 99.5 wt% of methyl methacrylate monomer and at least one other vinyl monomer copolymerizable with methyl methacrylate. It is preferable to charge. More preferably, it is composed of 80 to 99.5 wt% of methyl methacrylate monomer and 0.5 to 20 wt% of monomer composed of at least one other vinyl monomer copolymerizable with methyl methacrylate. The raw material of the second stage is charged so that the coalescence (2) is obtained. A more preferable ratio of the polymer (2) is a monomer 0 composed of 85 to 99.5 wt% of methyl methacrylate monomer and at least one other vinyl monomer copolymerizable with methyl methacrylate. 0.5-15 wt%, most preferably 90 to 99.5 wt% of methyl methacrylate monomer and at least one other vinyl monomer copolymerizable with methyl methacrylate. 5 to 10 wt%.

Moreover, it is preferable to manufacture so that the molecular weight of a polymer (2) may become 90000-350,000 of the weight average weight measured by the gel permeation chromatography. Since the mechanical strength of the obtained resin composition improves, 90000 or more is preferable. 350,000 or less is preferable from the viewpoint of improving fluidity. More preferably, it is 95000 to 310000, More preferably, it is 100,000 to 270000. Most preferably, it is 105000-250,000.
The ratio of the polymer (2) to the polymer (2) is preferably 90 to 65 wt%. In order to obtain the effect of improving the fluidity of the obtained resin composition, 90 wt% or less is preferable. Moreover, 65 wt% or more is preferable from the point of the mechanical strength of a resin composition. More preferably, it is 85-67 wt%, More preferably, it is 80-70 wt%.

Further, the composition ratio Mal (wt%) of other vinyl monomer units copolymerizable with methyl methacrylate of the polymer (1) in the present invention and the other copolymerizable with methyl methacrylate of the polymer (2). It is preferable to manufacture so that the relationship of Formula [4] may be satisfied in the composition ratio Mah (wt%) of the vinyl monomer unit.
(Mah−0.8) ≧ Mal ≧ 0 ... [4]
The composition ratios Mal and Mah show values almost the same as the composition ratios used in the respective preparations, and can be determined by measuring the polymer (1) and the polymer (2) by pyrolysis gas chromatography. Is possible.
The difference between Mah (wt%) and Mal (wt%) is preferably 0.8 wt% or more from the viewpoint of fluidity.

If the polymer (1) having a high molecular weight contains a larger amount of other vinyl monomers copolymerizable with methyl methacrylate, the fluidity can be improved while maintaining heat resistance and mechanical strength. preferable.
When the relationship of the formula [5] is established, it is more preferable because the fluidity is dramatically improved while maintaining the low heat generation and the low occurrence rate of cracks and distortion of the molded product and the mechanical strength in the environmental test.
(Mah-2) ≧ Mal ≧ 0 ... [5]

However, in applications requiring heat resistance, the average composition amount of other vinyl monomer units copolymerizable with methyl methacrylate in the entire methacrylic resin composition may be 2 wt% or less.
In that case, by satisfying the formula [6], a methacrylic resin composition having a good balance between heat resistance, fluidity and mechanical strength can be obtained.
1.2 ≧ (Mah−0.8) ≧ Mal ≧ 0 [6]
In other words, the heat resistance, the low incidence of cracks and distortion of molded products in the environmental test, and the difference between the Mah (wt%) and the Mal (wt%) should be 0.8 wt% or more It is preferable for improving the fluidity while maintaining the strength.
Since the flow characteristics are improved, it is preferable to reduce the ratio of the other vinyl monomer copolymerizable with the methyl methacrylate of the polymer (1) rather than the polymer (2), and it may not be used.

Among these methods, preferred examples of production methods are shown below from the viewpoints of productivity and physical property stability.
That is, the polymerization time of the polymer (1), that is, the time (Tl) until the exothermic peak temperature is reached due to the polymerization exotherm after the addition of the monomer in the first stage polymerization, and the polymerization time of the polymer (2), In relation to the time (Th) required to reach the exothermic peak temperature due to the polymerization exotherm after the addition of the monomer in the second and subsequent stages, the following relational expression [7] needs to be established.
Th / Tl ≧ 1 [7]
From the viewpoint of productivity, Th / Tl ≧ 1 is preferable. On the other hand, if Th is too long, there is a high possibility that the polymer (2) will not reach the target molecular weight, and there is a concern that the physical properties will decrease due to a decrease in molecular weight, so 5 ≧ Th / Tl is preferable. More preferably, 4 ≧ Th / Tl ≧ 1, and further preferably 3 ≧ Th / Tl ≧ 1.
By satisfying the formula [7], the polymerization is stabilized and the methacrylic resin composition of the present invention can be obtained effectively. In order to adjust the time required to reach the exothermic peak temperatures in the first stage and the second stage as shown in Formula [7], a polymerization initiator used for the production of the polymer (1) and the polymer (2) The amount may be adjusted as appropriate.
The polymerization temperature may be produced by appropriately selecting the optimum polymerization temperature according to the polymerization method, but is preferably 50 ° C to 180 ° C.

<Production example by suspension polymerization>
Hereinafter, as an example, the production method in the suspension polymerization method will be described in detail.
The polymerization temperature in the present invention is preferably 60 ° C. or higher and 100 ° C. or lower in order to reduce productivity and the amount of aggregates produced. More preferably, it is 65 degreeC or more and 95 degrees C or less, More preferably, it is 70 degreeC or more and 90 degrees C or less, Most preferably, it is 75 degreeC or more and 85 degrees C or less.
The polymerization temperatures of the polymer (1) and the polymer (2) may be the same or different. When the relationship of the above formula (1) is established in the suspension polymerization method, the amount of aggregates can be reduced, and the difference in the weight average molecular weight between the particle diameters of the obtained polymer fine particles can be reduced. From the viewpoint of obtaining a polymer, production stability tends to be improved.
More preferably, in order to suppress the formation of aggregates to a smaller amount, it is preferable that 5 ≧ Th / Tl ≧ 1 holds for the formula [7], more preferably 4 ≧ Th / Tl ≧ 1, and particularly preferably 3 ≧ Th / Tl ≧ 1.

The time (Tl) from the addition of the raw material mixture of the polymer (1) to the arrival of the exothermic peak temperature due to the polymerization exotherm to the arrival of the exothermic peak temperature due to the polymerization exotherm is within the range where the effect of the present invention can be exhibited. Although what is necessary is just 20 minutes or more and 240 minutes or less. More preferably, they are 30 minutes or more and 210 minutes or less, More preferably, they are 40 minutes or more and 180 minutes or less, Most preferably, they are 50 minutes or more and 150 minutes or less.
The raw material mixture of the polymer (2) may be added immediately after an exothermic peak due to the polymerization of the polymer (1) is observed, or may be added after holding for a certain time. When it is necessary to increase the degree of polymerization of the raw material mixture of the polymer (1), after the exothermic peak due to the polymer (1) is observed, the raw material mixture of the polymer (2) is held for a certain period of time. Is preferably introduced.

The holding time is not particularly defined, but is preferably 0 minutes or more and 180 minutes or less, more preferably 10 minutes or more and 150 minutes or less, still more preferably 20 minutes or more and 120 minutes or less, and most preferably 30 minutes or more and 90 minutes or less. .
Since the temperature at the time of holding | maintenance can raise a polymerization degree, it is preferable that it is the same temperature as the polymerization temperature of a polymer (1), or a temperature higher than the polymerization temperature of a polymer (1). When setting it to higher temperature, it is preferable to heat up 5 degreeC or more from polymerization temperature. More preferably, it is 7 degreeC or more, More preferably, it is 10 degreeC or more. Moreover, when raising temperature, it is preferable that it is 100 degrees C or less from a viewpoint of preventing aggregation of the polymer obtained. Specifically, it is preferably 80 ° C. or higher and 100 ° C. or lower, more preferably 85 ° C. or higher and 99 ° C. or lower, still more preferably 87 ° C. or higher and 99 ° C. or lower, and most preferably 90 ° C. or higher and 99 ° C. or lower.

The temperature (Th) from the addition of the raw material mixture of the polymer (2) to the time when the exothermic peak temperature due to the polymerization exotherm is observed may be within a range in which the effect of the present invention can be exhibited. The following is preferred. More preferably, it is 40 minutes or more and 210 minutes or less, More preferably, it is 50 minutes or more and 180 minutes or less, Most preferably, it is 60 minutes or more and 150 minutes or less.
After the exotherm peak temperature by the heat generated by the polymerization raw material mixture was added the polymer (2) was observed, since it is possible to suppress the residual monomer content in methacryloxypropyl Le resins resulting composition, the polymer It is preferable to raise the temperature by 5 ° C. or more than the polymerization temperature of (2). More preferably, it is 7 degreeC or more, More preferably, it is 10 degreeC or more. Moreover, when raising temperature, it is preferable that it is 100 degrees C or less from a viewpoint of preventing aggregation of the polymer obtained. Specifically, it is 85 ° C. or higher and 100 ° C. or lower, more preferably 87 ° C. or higher and 99 ° C. or lower, more preferably 90 ° C. or higher and 99 ° C. or lower.
The holding time after raising the temperature is not particularly defined as long as the effect of the present application can be exhibited, but it is preferable to hold the temperature for a certain period of time. Specifically, it is 10 minutes to 180 minutes, preferably 15 minutes to 150 minutes, more preferably 20 minutes to 120 minutes, and most preferably 30 minutes to 90 minutes.

As a polymerization initiator for producing a methacrylic resin composition, when using free radical polymerization, the following general radical polymerization initiator can be used.
Di-t-butyl peroxide, lauroyl peroxide, dilauroyl peroxide, t-butylperoxy 2-ethylhexanoate, 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane Peroxide systems such as 1,1-bis (t-butylperoxy) cyclohexane; azo systems such as azobisisobutyronitrile, azobisisovaleronitrile, 1,1-azobis (1-cyclohexanecarbonitrile); Etc. These may be used alone or in combination of two or more. Moreover, you may implement as a redox type | system | group initiator combining these radical initiators and a suitable reducing agent. These initiators are generally used in the range of 0.001 to 1 wt% with respect to the monomer mixture.

In the case of producing a methacrylic resin composition by a radical polymerization method, a commonly used chain transfer agent can be used to adjust the molecular weight of the polymer (A) and the polymer (B).
Examples of the chain transfer agent include n-butyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan, 2-ethylhexyl thioglycolate, ethylene glycol dithioglycolate, trimethylolpropane tris (thioglycolate), pentaerythritol tetrakis (thioglycolate). Etc.) are preferably used. The chain transfer agent used for the polymer (A) and the polymer (B) may be the same or different.
The amount of the chain transfer agent of the polymer (A) and the polymer (B) can be determined depending on the desired molecular weight, but generally used in the range of 0.001 to 1 wt% with respect to the monomer mixture. It is done.

You may use the following additive for a methacryl resin composition as needed.
Heat stabilizers such as dyes, pigments, hindered phenols and phosphates;
UV absorbers such as benzotriazole, 2-hydroxybenzophenone, and salicylic acid phenyl ester; plasticizers such as phthalate, fatty acid ester, trimellitic acid ester, phosphate ester, and polyester; higher fatty acids, Release agents such as higher fatty acid esters and mono-, di- or triglycerides of higher fatty acids; lubricants such as higher fatty acid esters and polyolefins;
Antistatic agents such as polyether-based, polyetherester-based, polyetheresteramide-based, alkylsulfonate, alkylbenzenesulfonate; flame retardants such as phosphorus, phosphorus / chlorine, phosphorus / bromine;
Acrylic rubber obtained by multistage polymerization as a reinforcing agent;
Examples thereof include organic and organic inorganic light diffusing agents such as methyl methacrylate / styrene polymer beads and organic siloxane beads; inorganic light diffusing agents such as barium sulfate, titanium oxide, calcium carbonate, and talc.

The methacrylic resin composition in the present invention may be used alone, or a plurality of methacrylic resin compositions of the present invention having different compositions may be combined, or may be used by mixing with existing methacrylic resins or other resins. In the case of mixing with other resins, they may be blended and mixed by heating and melting, or may be blended by heating and mixing after plural types of pellets extruded by heating and melting and mixing are blended. The additives mentioned above may be blended and mixed at this time.

Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.
<Raw material>
The raw materials used are as follows.
・ Methyl methacrylate: manufactured by Asahi Kasei Chemicals (2.5 ppm of 2,4-dimethyl-6-tert-butylphenol) is added as a polymerization inhibitor. thing)
-Methyl acrylate: manufactured by Mitsubishi Chemical (14-ppm phenol-made by Kawaguchi Chemical Industry is added as a polymerization inhibitor)
-N-octylmercaptan: manufactured by Arkema- 2-ethylhexyl thioglycolate: manufactured by Arkema Lauroyl peroxide: manufactured by Nippon Oil & Fats Industrial use, used as suspending agent Calcium carbonate: manufactured by Shiraishi Kogyo Co., Ltd., used as suspending agent, sodium lauryl sulfate: manufactured by Wako Pure Chemical Industries, Ltd., used as suspending aid [measurement method]

<Measurement of resin composition and molecular weight>
1. Composition analysis of methacrylic resin composition The composition analysis of the methacrylic resin composition was performed by pyrolysis gas chromatography and mass spectrometry.
Pyrolysis device: PY-2020D made by FRONTIER LAB
Column: DB-1 (length 30 m, inner diameter 0.25 mm, liquid phase thickness 0.25 μm)
Column temperature program: After holding at 40 ° C. for 5 minutes, the temperature is raised to 320 ° C. at a rate of 50 ° C./min, and 320 ° C. is held for 4.4 minutes
Pyrolysis furnace temperature: 550 ° C
Column inlet temperature: 320 ° C
Gas chromatography: Agilent GC6890
Carrier: pure nitrogen, flow rate 1.0 ml / min
Injection method: Split method (split ratio 1/200)
Detector: JEOL mass spectrometer Automass Sun
Detection method: Electron impact ionization method (ion source temperature: 240 ° C., interface temperature: 320 ° C.)
Sample: 10 μl of 10 g chloroform solution of 0.1 g methacrylic resin composition

A sample was collected in a platinum sample cup for a thermal decomposition apparatus, vacuum-dried at 150 ° C. for 2 hours, and then the sample cup was placed in a thermal decomposition furnace, and composition analysis of the sample was performed under the above conditions. The composition ratio of the methacrylic resin composition was determined based on the peak area on total ion chromatography (TIC) of methyl methacrylate and methyl acrylate and the calibration curve of the following standard sample.
Preparation of standard sample for calibration curve: The ratio of methyl methacrylate and methyl acrylate is (methyl methacrylate / methyl acrylate) = (100% / 0%), (98% / 2%), (94% / 6% ) And (90% / 10%) (80% / 20%) were added to 50 g of each of the five solutions in total, 0.25% lauroyl peroxide and 0.25% n-octyl mercaptan.
Each of these mixed solutions was put into a 100 cc glass ampule bottle, and the air was replaced with nitrogen and sealed.
The glass ampoule bottle was placed in an 80 ° C. water bath for 3 hours and then in an oven at 150 ° C. for 2 hours.
After cooling to room temperature, the glass was crushed and the methacrylic resin inside was taken out and subjected to composition analysis.
A graph of (methyl acrylate area value) / (methyl methacrylate area value + methyl acrylate area value) and methyl acrylate charge ratio obtained by measurement of a standard sample for a calibration curve is used as a calibration curve. It was.

2. Apparatus for measuring and measuring weight-average molecular weight of methacrylic resin composition: Gel Permeation Chromatography (LC-908) manufactured by Nippon Analytical Industry
Column: 1 JAIGEL-4H and 2 JAIGEL-2H, in series connection This column elutes high molecular weight early, and low molecular weight elutes slowly.
Detector: RI (differential refraction) detector Detection sensitivity: 2.4 μV / sec
Sample: Chloroform 15 ml solution of 0.450 g methacrylic resin composition Injection amount: 3 ml
Developing solvent: chloroform, flow rate 3.3 ml / min
Under the above conditions, the RI detection intensity with respect to the elution time of the methacrylic resin composition was measured.
The average molecular weight of the methacrylic resin composition was determined based on the area area in the GPC elution curve and the calibration curve.
The following 10 methacrylic resins (manufactured by EasiCal PM-1 Polymer Laboratories) having different molecular weights and known monodispersed weight average molecular weights were used as standard samples for calibration curves.

Weight average molecular weight
Standard sample 1 1,900,000
Standard sample 2 790,000
Standard sample 3 281,700
Standard sample 4 144,000
Standard sample 5 59,800
Standard sample 6 28,900
Standard sample 7 13,300
Standard sample 8 5,720
Standard sample 9 1,936
Standard sample 10 1,020

When the polymer (1) and the polymer (2) are mixed, the GPC elution curve of the polymer (1) alone is measured in advance to determine the weight average molecular weight, and the polymer (1) is present. GPC elution in which the polymer (1) and the polymer (2) are mixed by multiplying the GPC elution curve of the polymer (1) by the ratio (the charge ratio used in this application) By drawing from the curve, a GPC elution curve of the polymer (2) alone is obtained. From this, the weight average molecular weight of the polymer (2) was determined.
Further, the peak weight average molecular weight (Mp) in the GPC elution curve is determined from the GPC elution curve and the calibration curve.

The content of a weight average molecular weight component of 1/5 or less of Mp is determined as follows.
First, the area area in the GPC elution curve of the methacrylic resin composition is determined.
The area area in the GPC elution curve indicates the hatched portion shown in FIG. The specific method is as follows. First, the GPC elution curve obtained from the GPC elution curve obtained from the GPC measurement and the detection intensity by RI (differential refraction detector) is crossed with the GPC elution curve by subtracting the automatically drawn baseline obtained by the measuring instrument. Define A and point B. Point A is a point where the GPC elution curve at the beginning of the elution time and the baseline intersect. Point B is a position where, as a general rule, the weight average molecular weight is 500 or more and the base line and the elution curve intersect. If they do not intersect, point B is the value of the RI detection intensity at the elution time when the weight average molecular weight is 500. The hatched portion surrounded by the GPC elution curve and the base line between points A and B is the area in the GPC elution curve. This area is the area of the GPC elution curve. In order to determine the area, a column in which the high molecular weight component is eluted first is used, so the high molecular weight component is observed at the beginning of the elution time (point A side), and the low molecular weight component at the end of the elution time (point B side). Is observed.
The area area in the GPC elution curve is divided by the elution time corresponding to the weight average molecular weight of 1/5 of Mp, and the area area in the GPC elution curve corresponding to the weight average molecular weight component of 1/5 or less of Mp is obtained. From the ratio of the area and the area area in the GPC elution curve, the ratio of the weight average molecular weight of 1/5 or less of Mp was determined.

3. Measurement of composition ratio of vinyl copolymer copolymerizable with methyl methacrylate in high molecular weight and low molecular weight components of methacrylic resin composition
In this measurement, a composition analysis of a molecular weight component having a cumulative area area of 0 to 2% and a molecular weight component of 98 to 100% is performed. The cumulative area area (%) of the area area in the GPC elution curve is point 0 shown in FIG. 1 being 0%, which is the standard for the cumulative area area (%), toward the end of the elution time, and detection corresponding to each elution time. The view is that the intensity accumulates and an area area in the GPC elution curve is formed.

A specific example of the accumulated area area is shown in FIG. In FIG. 2, a point on the baseline at a certain elution time is a point X, and a point on the GPC elution curve is a point Y. The ratio of the area surrounded by the curve AY, the line segment AX, and the line segment XY to the area area in the GPC elution curve is the value of the accumulated area area (%) at a certain elution time.
A molecular weight component having a cumulative area of 0 to 2% and a molecular weight component being 98 to 100% were separated from the column based on the corresponding elution time, and the composition analysis was performed. Measurement and fractionation of each component are as follows. The same apparatus and conditions were used.
Perform the fractionation twice, and 10 μl of the fractionated sample is 1. The sample was collected in a platinum sample cup for a pyrolysis apparatus of the pyrolysis gas chromatography analysis and mass spectrometry method used in the above, and dried in a vacuum dryer at 100 ° C. for 40 minutes. 1. The composition of the methacrylic resin composition corresponding to the accumulated area area fractionated under the same conditions as above was determined.

<Measurement of practical properties>
1. Viscosity measurement with a rheometer The viscosity of the resin is measured with a rheometer: ARES-G2 (manufactured by TA Instruments). The measuring jig used was a cone. As the shape of the cone, a cone having a diameter of 25 mm and an angle of 1 degree was used. The cradle has a flat disk shape with a diameter of 25 mm.
In the measurement, a methacrylic resin composition serving as a viscosity measurement sample was previously formed into a resin disk having a diameter of 25 mm and a thickness of 1.2 to 1.5 mm by press molding. Before heating the cone and cradle, which are the measuring part of the rheometer, to 250 ° C, set the resin disc between the cradle and the cone until the distance from the top of the cone to the cradle reaches 0.05 mm. Pressed the cone. Start measurement after removing the protruding resin. The viscosity was measured from the torque applied to the jig at an angular velocity of 100 rad / s and 4 rad / s.

2. Measurement of stringiness Twenty sheets of resin obtained in Examples and Comparative Examples formed into a width of 20 mm, a length of 75 mm, and a thickness of 2 mm were prepared and used as test pieces.
The hot plate was heated to a surface temperature of 245 ° C. using a hot plate welder (manufactured by Takagi Seiko). As the hot plate, a metal plate having a Teflon (registered trademark) processed surface was used. The 20 mm × 2 mm surface of the test piece is pressed against the hot plate at a speed of 1 mm / s, pressed to 0.7 ± 0.2 mm from the contacted position, contacted for 20 seconds, and then the test piece at a speed of 20 ± 10 mm / s. When the was released, the long yarn generation rate was calculated from the number of test pieces in which a resin yarn of 5 mm or more was generated, and was defined as the stringiness.

3. Measurement of spiral length This is a test for determining the relative fluidity based on the distance that resin flows through a spiral cavity with a constant cross-sectional area.
Injection molding machine: Toshiba Machine IS-100EN
Mold for measurement: A mold in which a groove having a depth of 2 mm and a width of 10 mm is dug into the Archimedes spiral shape from the center on the mold surface.
Resin temperature: 250 ° C
Mold temperature: 55 ° C
Injection pressure: 98 MPa
Injection time: 10 sec
Cooling time: 10 seconds Resin was injected into the center of the mold surface under the above conditions.
After 40 shot molding, 10 spiral length measurement molded products were sampled, and the average value of the length of the spiral portion of 2 mm was defined as the spiral length.

4). Measurement of Vicat Softening Temperature The heat resistance of the methacrylic resin composition was evaluated by the Vicat softening temperature measured by the B50 method defined in JIS-K7206.

<Manufacturing method>
The method for producing the resin is shown below. The blending amounts are shown in Table 1, and the charged composition of the monomer and the ratio of the polymers, and the measurement results of the weight average molecular weight of each polymer are shown in Table 2.

[Examples 1 to 5, Comparative Examples 1 and 2]
Into a 60 L SUS reactor, the raw materials of the polymer (1) were added in the amounts shown in Table 1 and mixed with stirring. Suspension polymerization was performed at a reaction temperature of 80 ° C., and after confirmation of the polymerization peak, 60 minutes. While maintaining at 80 ° C., a polymer (1) was obtained. This polymer (1) was sampled and the polymerization average molecular weight was measured by GPC. Thereafter, the raw material of the polymer (2) was put into the polymerization system containing the polymer (1) into the blending amount reactor shown in Table 1, and then suspension polymerization was carried out at 80 ° C. After confirming the polymerization peak, 92 ° C. The mixture was heated at a rate of about 1 ° C./min and then aged for 60 minutes to substantially complete the polymerization reaction. Next, in order to cool to 50 ° C. or lower and dissolve the suspending agent, 20 wt% sulfuric acid was added, washed and dehydrated and dried to obtain methacrylic resin composition beads. The polymerization average molecular weight of the methacrylic resin composition beads was measured by GPC, and based on the GPC elution curve of the polymer (1), the ratio of the polymer (1) was multiplied to obtain the methacrylic resin composition beads. From the GPC elution curve, the GPC portion of the polymer (1) was removed, and the weight average molecular weight of the polymer (2) was determined.

[Comparative Examples 3 to 5]
Into a 60 L SUS reactor, the raw materials for the polymer (1) were added in the amounts shown in Table 1 and mixed by stirring. Suspension polymerization was performed at a reaction temperature of 80 ° C., and after confirmation of the polymerization peak, 92 ° C. The mixture was heated at a rate of about 1 ° C./min and then aged for 60 minutes to substantially complete the polymerization reaction. Next, in order to cool to 50 ° C. or lower and dissolve the suspending agent, 20 wt% sulfuric acid was added, washed and dehydrated and dried to obtain methacrylic resin beads: polymer (1). This polymer (1) was sampled and the polymerization average molecular weight was measured by GPC.
<Evaluation results>
Table 3 shows the results of practical property evaluation.

[Examples 1 to 5]
The required characteristics of the resin, which is particularly demanding as molding conditions for vehicle lamps, are 20% or less in stringing property, 26 cm or more in spiral length, and more preferable conditions are Vicat softening temperature of 106 ° C or more. Although evaluated, Examples 1-5 were excellent in both stringing property and spiral length.
Further, Examples 1, 3, and 4 were excellent in Vicat softening temperature. When Example 2 and Example 5 were compared, the stringing property and heat resistance were equivalent, but Example 2 was superior in spiral length.

[Comparative Examples 1-5]
In Comparative Examples 1 and 3, the spiral length was good, but the stringiness was poor. In Comparative Examples 2, 4 and 5, the stringing property was good, but the spiral length was short.

  The methacrylic resin composition of the present invention is suitable for obtaining a molded product by injection molding or the like, and can be particularly suitably used in the field of performing hot plate welding processing such as a vehicle lamp.

1. GPC elution curve (a curve connecting RI detection intensity at each elution time)
2. Base line

Claims (2)

The methacrylic resin is the following polymer (1) and polymer (2) , and the methacrylic resin composition has a weight average molecular weight of 5,000 to 50,000 as measured by gel permeation chromatography, and is 10 to 10 for the entire methacrylic resin composition. A methacrylic resin composition comprising 35% by mass of a polymer (1) and a polymer (2) having a weight average molecular weight of 90,000 to 350,000 and 90 to 65% by mass relative to the entire methacrylic resin composition. At least one vinyl selected from methyl methacrylate monomer units of 80 to 99 wt%, alkyl methacrylate having 2 to 18 carbon atoms, and alkyl acrylate having 1 to 18 carbon atoms. It comprises monomer units 1 to 20 wt%, the resin temperature 240 ° C. with a rheometer, measurement under conditions of angular 4 rad / s A is the viscosity of 4900Pa · s or more, the resin temperature of 240 ° C., viscosity at the conditions of angular velocity 100 rad / s is not more than 1450Pa · s, is pressed against a Teflon machined aluminum plate heated to 245 ° C. A molded body obtained by using a methacrylic resin composition and other moldings, characterized in that when a test piece is released after 20 seconds, a long yarn generation rate in which a resin yarn of 5 mm or more is generated is 20% or less. A molded body with a hot plate welded to the body. 2. A molded body obtained by welding a molded body obtained by using the methacrylic resin composition according to claim 1 and another molded body, wherein the spiral length under the following measurement conditions is 26 cm or more. .
・ Injection molding machine: Toshiba Machine IS-100EN
・ Measurement mold: A mold with a groove of 2mm depth and 10mm width dug into the Archimedes spiral shape from the center on the mold surface
・ Resin temperature: 250 ℃
-Mold temperature: 55 ° C
・ Injection pressure: 98 MPa,
・ Injection time: 10 sec
・ Cooling time: 10 seconds ・ Measurement method: After 40 shot molding, 10 samples for spiral length measurement are sampled, and the average value of the length of the spiral part of 2 mm is set as the spiral length.

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