JPH0737482B2 - Method for producing methacrylic polymer - Google Patents

Description

TECHNICAL FIELD The present invention relates to a novel method for producing a methacrylic polymer.

[Conventional technology]

Conventionally, a suspension polymerization method is generally used as a method for producing a methacrylic polymer, particularly a molding material, but this method has excellent effects such as easy removal of heat of polymerization using water as a medium, Since the water-soluble polymer and the inorganic salt are used as the suspension stabilizer, there is a problem of deterioration of optical properties or wastewater treatment due to the presence of the suspension stabilizer in the polymer. In recent years, for these reasons, the continuous bulk polymerization method has been attracting attention also in the method for producing a methacrylic polymer, and JP-B-52-32665, JP-B-54-42035, and JP-A-58-1320.
Various methods such as No. 02 have been proposed and put into practical use.
These continuous bulk polymerization methods seem to give a seemingly very pure polymer because they contain no additives other than monomers, but the viscosity of the system rapidly increases with an increase in the polymerization rate. As a method of polymerizing methacrylic monomers at around 150 ° C, it is a reaction in the high temperature range, and byproducts such as oligomers increase, and in order to increase the recycling yield of monomers, oligomers to be polymerized However, there is a drawback that the inclusion of by-products such as these oligomers causes coloration and deteriorates the optical properties.

[Problems to be solved by the invention]

In view of the above-mentioned drawbacks of the conventional method, it is an object of the present invention to provide a novel method for producing a methacrylic polymer which has extremely few by-products such as impurities and oligomers and is excellent in optical properties.

[Means for solving problems]

An object of the present invention is to polymerize methyl methacrylate alone or a monomer mixture consisting of 50% by weight or more of methyl methacrylate and 50% by weight or less of alkyl acrylate or alkyl methacrylate (excluding methyl methacrylate) in the presence of a solvent and a radical polymerization initiator, In producing a polymer having a weight average molecular weight of 6.5 × 10 ^{4 to} 15.5 × 10 ⁴ and a weight average molecular weight / number average molecular weight of 1.82 to 2.03, the number of carbon atoms as a solvent is 20 to 70 parts by weight as a solvent. 4-8
And the solubility parameter (δ) is 6.5 to 8.5 (cal / cm
³ ) Methacrylic polymer by solvent-slurry polymerization characterized by polymerizing using 80 to 30 parts by weight of ^1/2 aliphatic hydrocarbon, separating the polymer from the solvent and further drying the polymer. It is achieved by the manufacturing method of.

The monomer component used in the method of the present invention is methyl methacrylate alone or a monomer mixture of 50% by weight or more of methyl methacrylate and 50% by weight or less of alkyl acrylate or alkyl methacrylate (excluding methyl methacrylate). Is composed of an alkyl acrylate monomer having an alkyl group having 1 to 8 carbon atoms, such as methyl acrylate, ethyl acrylate, n-propyl acrylate,
Examples thereof include n-butyl acrylate. The alkyl methacrylate excluding methyl methacrylate is composed of an alkyl methacrylate monomer having an alkyl group having 2 to 8 carbon atoms, such as ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, t-butyl. Examples thereof include methacrylate and cyclohexyl methacrylate. These copolymerized monomers with methyl methacrylate may be used in a combination of two or more kinds. (Hereinafter, the methyl methacrylate homopolymers and copolymers composed of the above-mentioned monomer components are referred to as methacrylic polymers.) The aliphatic hydrocarbon in the present invention forms a homogeneous mixed system with the monomers to be used, Since its solubility in methacrylic polymer is moderately low, it is possible to maintain the polymerization system in a homogeneous mixed system or a two-phase system in which the polymer continuously precipitates by controlling the temperature and stirring force of the polymerization system. In addition to having the feature that the use of the aliphatic hydrocarbon in the present invention can reduce the viscosity of the polymer mixture, suppress the gel effect accompanying the increase in the polymerization rate, and increase the system to a high polymerization rate.

By maintaining and controlling the polymerization system to be a uniform mixing system, it becomes possible to prevent the polymer from adhering to the wall surface of the polymerization tank or the stirring blade despite the high polymerization rate. By lowering the temperature of the system, the polymer can be easily separated by precipitation.

Further, the polymerization method of the present invention can be carried out by batch polymerization method and continuous polymerization method.

The precipitate of the methacrylic polymer obtained by using the aliphatic hydrocarbon in the present invention is in the form of powder, and the separation from the solvent consisting of the aliphatic hydrocarbon and the unreacted monomer is very easy and at the same time. The low molecular weight substances such as oligomers produced during the polymerization reaction and the by-products from the radical polymerization initiator are contained in the separated solvent, so that the content of these by-products is extremely low.

In order to satisfy the above characteristics, in the present invention, 20 to 70 parts by weight of the monomer component is used and the solvent has 4 to 4 carbon atoms.
8 and solubility parameter (hereinafter referred to as δ. Polymer
r−Handbook, second edition, A Wiley interscience pu
Quoted from blication. ) Is 6.5 to 8.5 (cal / cm ³ ) ^1/2 and is achieved by using 80 to 30 parts by weight of an aliphatic hydrocarbon.

The number of carbon atoms of the aliphatic hydrocarbon in the present invention is 4 to 8, and 3
In the following, the boiling point is extremely low, and at a temperature carried out using a normal radical polymerization initiator, the pressure of the polymerization system becomes very high, and a special pressure resistant polymerization tank or the like is required, which not only increases the cost but is not preferable, When the methacrylic polymer is precipitated and separated, gasification is rapid even at around 0 ° C., and by-products such as oligomers remain contained in the polymer. When the number of carbon atoms is 9 or more, the boiling point becomes 150 ° C. or more, so that the solvent contained in the polymer after separation and precipitation is not completely removed, which is not preferable. Since the δ of the methacrylic polymer is around 9.5 (cal / cm ³ ) ^1/2 , the δ of the aliphatic hydrocarbon is 6.5 to 8.5 (cal / cm ³ ) ^1/2 , more preferably 6.
8 to 8.2 (cal / cm ³ ) ^1/2 and δ is 6.5 (cal / cm ³ ) ^1/2
If it is less than the above, the polymer is apt to precipitate in the polymerization system, and the degree of polymerization required for using the methacrylic polymer as a molding material cannot be reached. When δ exceeds 8.5 (cal / cm ³ ) ^1/2 , the compatibility with the methacrylic polymer increases, the viscosity of the system increases with the increase of the polymerization rate, and stirring becomes impossible. Even if the temperature of the solvent slurry taken out is lowered, there is a drawback that the methacrylic polymer is contained in the solvent in a large amount and the yield is lowered. As the aliphatic hydrocarbon in the present invention, n-butane, n-pentane, 2-methylbutane, n-hexane,
Examples thereof include 2-methylpentane, 2.3-dimethylbutane, n-heptane, 2-methylhexane and n-octane, and n-pentane, n-hexane and n-heptane are particularly preferable.

In the present invention, more preferably 20 to 70 parts by weight of the monomer component
The aliphatic hydrocarbon is used in an amount of 80 to 30 parts by weight, preferably 70 to 50 parts by weight, based on 30 to 50 parts by weight. If the amount of the monomer component is less than 20% by weight, the yield per hour is very low and the energy cost is high. On the other hand, if it exceeds 70% by weight, the viscosity of the polymerization system increases, and the polymer precipitate adheres to the stirring blade and the like, which is not preferable.

The polymerization temperature in the present invention is 50 to 120 ° C, and the radical polymerization initiator is not particularly limited, but the 10-hour half-life temperature is
Those having a temperature of 100 ° C. or less are preferable, and isobutyl peroxide, diisopropyl peroxydicarbonate, di-2
-Ethylhexyl peroxydicarbonate, tert-butyl peroxy neodecanoate, tert-butyl peroxypivalate, 3,5,5-trimethylhexanoyl peroxide, lauroyl peroxide, acetyl peroxide, benzoyl peroxide, tert-sia Organic peroxides such as rubutyl peroxyisobutyrate, 1,1-bis (tertiaryperoxy) -3,3,5-trimethylcyclohexane, tert-butyl peroxyisopropyl carbonate, or 2,2'-azobis ( 4-methoxy-2,4-dimethylvaleronitrile),
2,2'-azobis (2,4-dimethylvaleronitrile),
(1-phenylethyl) azodiphenylmethane, 2,2 '
-Azobisisobutyronitrile, dimethyl-2,2'-azobisisobutyrate, 2,2'azobis (2-methylbutyronitrile), 1,1'-azobis (1-cyclohexanecarbonitrile), etc. Compounds.

As the chain transfer agent, o-butyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan, isooctyl thioglycolate and the like which are commonly used in radical polymerization can be used.

According to the method of the present invention, the polymerization average molecular weight (hereinafter sometimes abbreviated as w) is 6.5 × 10 ^{4 to} 15.5 × 10 ⁴ , and the weight average molecular weight / number average molecular weight (hereinafter abbreviated as w / n). It is possible to produce a methacrylic polymer of 1.82 to 2.03.

〔The invention's effect〕

The methacrylic polymer obtained by the novel production method of the present invention has very few impurities such as by-products such as oligomers, which could not be easily removed by the conventional production method, and has excellent optical properties. It is a thing.

〔Example〕

 The present invention will be specifically described below with reference to examples.

The monomers, polymerization initiators and chain transfer agents used in the examples are represented by the following abbreviations. () Is an abbreviation.

Methyl methacrylate (MMA), ethyl methacrylate (EMA), methyl acrylate (MA), ethyl acrylate (EA), n-butyl acrylate (BA).

Tert-butyl peroxyneodecanoate (BP-N
D), lauroyl peroxide (LPO), benzoyl peroxide (BPO), 2,2'-azobis (4-methoxy-2,4'-dimethylvaleronitrile) (AMVN), 2,2'-
Azobisisobutyronitrile (AIBN). t-Butyl mercaptan (t-BM), n-octyl mercaptan (n-
OM), n-dodecyl mercaptan (n-DM).

The b value in Examples and the like is a value measured by a Hunter colorimetric color difference meter and represents yellowness.

Example 1 A 5 polymerization vessel having a stirrer was used, in which 1440 g of a monomer component consisting of 95% by weight of methyl methacrylate and 5% by weight of methyl acrylate, 2.9 g of tert-butyl peroxy neodecanoate as a polymerization initiator, As a chain transfer agent, N-octyl mercaptan 2.9 g and δ 7.3 (cal / c
After 2160 g of n-hexane (m ³ ) ^1/2 was added and mixed, the inside of the polymerization tank was sufficiently replaced with nitrogen, and the mixture was reacted at a stirring speed of 20 rpm and a polymerization temperature of 65 ° C. for 6 hours. After the reaction, the temperature of the system was cooled to 10 ° C, and after 30 minutes, the obtained polymer and solvent were separated, and the polymer was dried at 40 ° C under vacuum for 48 hours to obtain 1226 g of a methacrylic polymer. The w of the obtained methacrylic polymer was 14.5 × 10 ⁴ , w / n
Is 2.03, w has an oligomer content of 1000 or less is 76
It was very low as ppm. In addition, this methacrylic polymer
The total light transmittance, haze, and b value of a 3 mm plate obtained by heating at 50 ° C for 10 minutes and press-molding were 92.4% and 0.2, respectively.
% And 0.12, showing good optical properties and no coloring was observed.

Examples 2-5, Comparative Examples 1-2 The results of carrying out by the same method as in Example 1 are shown in Table 1.

The conditions were the same as in Example 1 except for the conditions shown in Table 1.

Example 6 Five polymerization tanks having a stirrer capable of continuous addition and removal were used, and 30 parts by weight of a monomer component consisting of 90% by weight of methyl methacrylate and 10% by weight of ethyl acrylate was used as a polymerization initiator. Lauroyl peroxide 0.12
Parts by weight, n-octyl mercaptan as a chain transfer agent 0.
05 parts by weight and 70 parts by weight of cyclohexane with a δ of 8.2 (cal / cm ³ ) ^1/2 were added and blended in a choking atmosphere and the temperature was adjusted to 20 ° C. Was charged in a polymerization tank sufficiently replaced with, the polymerization temperature was maintained at 80 ° C., and the stirring speed was maintained at 30 rpm. Switch to continuous operation 5 hours after the start of charging, and continuously supply the above raw material mixture at 1 / H / hour.
It was set to R and continuously operated for 10 hours. The polymer content in the solvent slurry continuously taken out was 26.7% by weight, and the solvent slurry was cooled to 10 ° C.
After drying under vacuum at 40 ° C. for 48 hours, 2150 g of a methacrylic polymer was obtained. The w of this methacrylic polymer is 11.2 × 10 ⁴ , w /
The n was 2.01 and the oligomer content with w of 1000 or less was 58 ppm. Also, this methacrylic polymer at 250 ℃
The total light transmittance, haze, and b value of the 3 mm plate obtained by heating for 10 minutes and press molding were 92.2%, 0.3%, and 0.14, respectively, showing good optical properties, and no coloring was observed.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koji Arakawa 4-7 Kyowa-cho, Nakajo-machi, Kitakanbara-gun, Niigata Prefecture Nakawa Plant, Kyowa Gas Chemical Industry Co., Ltd. (56) Reference JP-A-48-17888 A) JP-A-50-55628 (JP, A)

Claims (1)

[Claims] 1. A monomer mixture consisting of methyl methacrylate alone or 50% by weight or more of methyl methacrylate and 50% by weight or less of alkyl acrylate or alkyl methacrylate (excluding methyl methacrylate) is polymerized in the presence of a solvent and a radical polymerization initiator, In producing a polymer having a weight average molecular weight of 6.5 × 10 ^{4 to} 15.5 × 10 ⁴ and a weight average molecular weight / number average molecular weight of 1.82 to 2.03, the number of carbon atoms as a solvent is 20 to 70 parts by weight as a solvent. 4 to 8 and the solubility parameter (δ) is 6.5 to 8.5 (cal / c
A methacrylic polymer by a solvent slurry polymerization method, which comprises polymerizing using 80 to 30 parts by weight of an aliphatic hydrocarbon of m ³ ) ^1/2 , separating the polymer from the solvent, and further drying the polymer. Manufacturing method of coalescence.