JPH0686492B2 - Novel 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 has been 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, while suspension method Since a water-soluble polymer and an inorganic salt are used as the stabilizer, there is a problem of deterioration of optical properties or wastewater treatment due to the presence of these suspension stabilizers in the polymer. In recent years, the continuous bulk polymerization method has been attracting attention also in the production method of methacrylic polymers for these reasons, and various methods such as JP-B-52-32665, JP-B-54-42035, and JP-A-58-132002 are proposed. Has been put to 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 a high temperature range, and byproducts such as oligomers increase, and in order to increase the recycling yield of monomers, oligomers etc. However, there is a drawback that the inclusion of by-products such as these oligomers causes coloring 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]

The purpose of the present invention is to polymerize 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) in the presence of a radical polymerization initiator and a chain transfer agent. In doing
1 to 20 carbon atoms as a solvent for 20 to 70 parts by weight of monomer components
˜5 and the solubility parameter δ is 10.5-14.5 (cal /
A solvent characterized by polymerizing in the presence of 80 to 30 parts by weight of an aliphatic monohydric alcohol (cm ³ ) ^1/2 , solid-liquid phase separation of the polymer and solvent system, and then separating and removing the solvent system. It is achieved by a novel method for producing a methacrylic polymer by a slurry polymerization method.

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 copolymerizable monomers with methyl methacrylate may be used in a combination of two or more. (Hereinafter, the methyl methacrylate homopolymers and copolymers comprising the above monomer components are referred to as methacrylic polymers.) The aliphatic monohydric alcohol in the present invention forms a homogeneous mixed system with the monomers to be used, Since the solubility of the methacrylic polymer formed 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 of being possible, the aliphatic 1 according to the present invention
The use of the polyhydric alcohol can reduce the viscosity of the polymer mixture, suppress the gel effect associated with the increase in the polymerization rate, and increase the system to a high polymerization rate. By controlling the polymerization system to be maintained in a uniform mixing system, it becomes possible to prevent the polymer from adhering to the wall of the polymerization tank or the stirring blade regardless of the high polymerization rate. By lowering the temperature of the system, the polymer can be easily separated by precipitation.

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 monohydric alcohol according to the present invention is in the form of gel but does not have tackiness,
Separation from the solvent consisting of alcohol and unreacted monomer is very efficient and easy, and at the same time, low molecular weight products such as oligomers produced during the polymerization reaction and by-products from radical polymerization initiators are Can be concentrated,
By performing solid-liquid separation from the precipitate of the methacrylic polymer, it becomes possible to remove these impurities efficiently. As a result, a polymer having a very low content of unreacted monomers and by-products can be obtained.

In order to satisfy the above characteristics, 20 to 70 parts by weight of the monomer component is used in the present invention, and the solvent has 1 carbon atoms.
And a solubility parameter (hereinafter referred to as δ. Poly.
mer−Handbook, secondedition, A Wiloy interscience p
Quoted from ublication. ) Is 10.5-14.5 (cal / cm ³ ) ^1/2 and is achieved by using 80-30 parts by weight of an aliphatic monohydric alcohol.

The aliphatic monohydric alcohol according to the present invention has 1 to 5 carbon atoms, and when the carbon number is 6 or more, the boiling point becomes 150 ° C. or more. Therefore, the solvent contained in the polymer after separation and precipitation is completely removed. It is difficult and not preferable. The methacrylic polymer has a δ of 9.
Since it is around 5 (cal / cm ³ ) ^1/2 , the δ of the aliphatic monohydric alcohol is 10.5 to 14.5 (cal / cm ³ ) ^1/2 , more preferably
10.9 to 14.5 (cal / cm ³ ) ^1/2 and δ is 10.5 (cal / c
If it is less than m 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, and the temperature of the polymerization system or the temperature of the solvent slurry taken out is increased. Even if the amount is lowered, there is a drawback that a large amount of methacrylic polymer is contained in the solvent and the yield is lowered. Aliphatic 1 in the present invention
Examples of the polyhydric alcohol include methyl alcohol, ethyl alcohol, n-propyl alcohol, isoprobe alcohol, n-butyl alcohol, isobutyl alcohol,
Examples thereof include n-amyl alcohol, and methyl alcohol and ethyl alcohol are particularly preferable.

In the present invention, the monomer component is 20 to 70 parts by weight, more preferably 30 to 50 parts by weight, and the aliphatic monohydric alcohol is 80 to 30 parts by weight.
It is used in a proportion of preferably 70 to 50 parts by weight, more preferably 70 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, penzoyl peroxide, tert-sia Organic peroxides such as ributylperoxyisobutyrate, 1,1-bis (tertiaryperoxy) -3,3,5-trimethylcyclohexane, tertiarybutylperoxyisopropyl 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. Azo compounds may be mentioned.

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

〔The invention's effect〕

The methacrylic polymer obtained by the novel production method of the present invention is excellent in optical properties with very little inclusion of impurities, by-products such as oligomers, which cannot be easily removed by the conventional production method. 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 oxyperoxy neodecanoate (BPN
D), lauroyl peroxide (LPO), benzoyl peroxide (BPO), 2.2'-azobisisobutyronitrile (AIBN), 1.1'-azobis (1-cyclohexanecarbonitrile) (ACCN) 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 l polymerization tank having a stirrer was used, and 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, N as a chain transfer agent
-Octyl mercaptan 2.2g and δ 14.5 (cal / c
2160 g of methyl alcohol which is m ³ ) ^1/2 is added and mixed,
After sufficiently replacing the inside of the polymerization tank with nitrogen, the stirring speed is 20 rpm and the polymerization temperature is 6
The reaction was carried out at 0 ° C for 6 hours. After the reaction, the temperature of the system was cooled to 10 ° C, and after 30 minutes, the polymer and the solvent obtained were separated, and the polymer was cooled to 40 ° C.
After drying at ℃ for 48 hours under vacuum, 1190 g of a methacrylic polymer was obtained. Methacrylic polymer w is 10.3 × 10 ⁴ w / n is 1.9
5, and the oligomer content with w of 1000 or less was 64 ppm, which was extremely low. Also, the methacrylic polymer was
The total light transmittance, haze and b value of the 3 mm plate obtained by press molding after heating for 1 minute were 92.3, 0.2 and 0.16, respectively.
It showed good optical properties and no coloring was observed.

Examples 2 to 6, Comparative Examples 1 and 2, and Table 1 shows the results obtained by the same method as in Example 1.

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

Example 7. A 5 l polymerization tank having a stirrer capable of continuous addition and withdrawal was used, and 30 parts by weight of a monomer component composed 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 ethyl alcohol with δ of 12.7 (cal / cm ³ ) ^1/2 are added and mixed under a nitrogen atmosphere at 20 ° C.
The raw material mixture whose temperature has been adjusted to 0.7 l / hr is charged into a polymerization tank sufficiently replaced with nitrogen at a rate of 0.7 l / HR, and the polymerization temperature is 75 ° C.
The stirring speed was kept at 30 rpm. Switch to continuous operation 5.5 hours after the start of charging, and continuously supply the above raw material mixture at 0.9 l / h
/ HR and continuous operation for 10 hours. The polymer content in the solvent slurry continuously taken out was 25.5% by weight, the solvent slurry was cooled to 10 ° C, and the polymer obtained after precipitation separation was dried at 40 ° C under vacuum for 48 hours. Methacrylic polymer 1880
got g. The w of the obtained methacrylic polymer is 13.2 × 1.
0 ^4, w / n is 1.98, and w is 1000 or less oligomer content was found to be 82 ppm. Further, this methacrylic polymer was heated at 250 ° C. for 10 minutes and then press-molded to obtain a 3 mm plate having a total light transmittance, haze and b value of 92.2% and 0.
3% and 0.19, showing good optical properties, and no coloring was observed.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Koji Arakawa 4-7 Kyowa-machi, Nakajo-machi, Kitakanbara-gun, Niigata Prefecture Kyowa Gas Chemicals Co., Ltd. Nakajo Plant (56) Reference JP-A-57-2309 (JP, A) JP-A-55-86806 (JP, A) JP-B-50-34071 (JP, B1)

Claims (1)

[Claims] 1. Polymerization of 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) in the presence of a radical polymerization initiator and a chain transfer agent. In doing
1 to 20 carbon atoms as a solvent for 20 to 70 parts by weight of monomer components
~ 5 and the solubility parameter (δ) is 10.5-14.5
Characterized by polymerizing in the presence of 80 to 30 parts by weight of an aliphatic monohydric alcohol (cal / cm ³ ) ^1/2 , solid-liquid phase separation of the polymer and solvent system, and then separating and removing the solvent system. Novel method for producing methacrylic polymer by solvent slurry polymerization method.