JPS62241905A - Novel production process for methacrylic polymer - Google Patents

Abstract

PURPOSE:To obtain a methacrylic polymer remarkably low in the contents of impurities and by-products such as oligomers and excellent in optical properties, by radical-polymerizing methyl methacrylate or its mixture with other alkyl (meth)acrylates in the presence of a specified monohydric alcohol as a solvent. CONSTITUTION:Methyl methacrylate alone or a monomer mixture comprising 50wt% or above methyl methacrylate and 50wt% or below alkyl (meth)acrylate (other than methyl methacrylate) is polymerized in an solvent slurry by using a radical polymerization initiator in the presence of 80-30pts.wt., per 20-70pts. wt. monomer component, aliphatic monohydric alcohol having 1-5 carbon atoms and a solubility parameter (delta) of 10.5-14.5(cal/cm<2>)<1/2> as a solvent. As said aliphatic monohydric alcohol, methyl alcohol or ethyl alcohol is particularly desirable.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a new method for producing methacrylic polymers [Prior Art] Conventionally, suspension polymerization has been generally used as a method for producing methacrylic polymers, especially molding materials. Although this method uses water as a medium and has excellent effects such as easy removal of polymerization heat, it uses a water-soluble polymer and an inorganic salt as a suspension stabilizer, so it is difficult to incorporate these into the polymer. There is a problem with deterioration of optical properties or waste water treatment due to residual suspension stabilizer. In recent years, for these reasons, the continuous bulk polymerization method has attracted attention as a method for producing methacrylic polymers, and various methods have been proposed, such as Japanese Patent Publication No. 52-32665, Japanese Patent Publication No. 42035-1982, and Japanese Patent Publication No. 132002-1982. and has also been put into practical use. These continuous bulk polymerization methods do not contain any additives other than monomers, so at first glance it seems that very pure polymers can be obtained, but as the polymerization rate increases, the viscosity of the system increases rapidly. The polymerization method for methacrylic monomers is a high-temperature reaction at around 150°C, which results in a large amount of by-products such as oligomers, and in order to increase the monomer recycling yield, it is necessary to add oligomers, etc. to the polymer. The contamination of by-products such as these oligomers cannot be avoided, and the contamination of by-products such as these oligomers causes coloring and deteriorates optical properties.

[Problem that the invention seeks to solve]

In view of the above-mentioned drawbacks of the conventional methods, an object of the present invention is to provide a new method for producing a methacrylic polymer with extremely low levels of by-products such as impurities and oligomers and excellent optical properties.

[Means for solving problems]

The purpose 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 radical polymerization initiator. Monomer component 2
0 to 70 parts by weight, the solvent has 1 to 5 carbon atoms and has a solubility parameter δ of 10.5 to 14.5 (
This is achieved by a novel method for producing a methacrylic polymer by a solvent slurry polymerization method, which is characterized in that the polymerization is carried out in the presence of 80 to 30 parts by weight of an aliphatic monohydric alcohol having an aliphatic monohydric alcohol of cal/cm') h.

The monomer component used in the method of the present invention is methyl methacrylate alone or 50% by weight of methyl methacrylate.
It is a monomer mixture consisting of up to 50% by weight of the above and alkyl acrylate or alkyl methacrylate (excluding methyl methacrylate). Examples include methyl acrylate, ethyl acrylate, n-propyl acrylate, and n-butyl acrylate.

In addition, alkyl methacrylates other than methyl methacrylate consist of monomers selected from furkyl methacrylate monomers in which the alkyl group has 2 to 8 carbon atoms, such as ethyl methacrylate, n-propyl methacrylate, and n-butyl methacrylate-F. , butyl methacrylate, cyclohexyl methacrylate, and the like. These comonomers with methyl methacrylate may be used in combination of two or more. (Hereinafter, methyl methacrylate homopolymers and copolymers consisting of the above monomer components are referred to as methacrylic polymers.) The aliphatic monohydric alcohol in the present invention is a homogeneous mixture with the monomers used, Since the solubility of the methacrylic polymer produced is moderately low, the temperature and stirring power of the polymerization system can be controlled to maintain the polymerization system in a uniformly mixed system or a two-phase system in which the polymer continuously precipitates. In the present invention, aliphatic 1
By using the alcohol, it is possible to reduce the viscosity of the polymer mixture, suppress the gel effect that accompanies an increase in the polymerization rate, and enhance the system with a high polymer content. By controlling the polymerization system to maintain a homogeneous mixing system, it is possible to prevent the polymer from adhering to the walls of the polymerization tank or the stirring blades, regardless of the high polymerization rate. The polymer can be easily precipitated and separated by lowering the temperature of the system.

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

The precipitate of the methacrylic polymer obtained using the aliphatic monohydric alcohol in the present invention is gel-like but not sticky.
Separation from the solvent consisting of alcohol and unreacted monomers is very easy, and at the same time, low molecular weight substances such as oligomers generated during the polymerization reaction and by-products from the radical polymerization initiator are contained in the separated solvent. This is a polymer with extremely low content of these by-products.

In order to satisfy these above-mentioned characteristics, in the present invention, the monomer component is used in an amount of 20 to 70 parts by weight, the solvent has a carbon number of 1 to 5, and has a solubility parameter (hereinafter referred to as δ).

Polymer-Handbook, 5econde
dition, ^Wiloy 1nter 5cien
Quoted from ce publication. ) is 10.5
~14. 5 (cal/am3) aliphatic 1
Succeeded to use 80 to 30 parts by weight of alcohol.
be done.

The aliphatic monohydric alcohol used in the present invention has 1 to 5 carbon atoms, and if the carbon number is 6 or more, the boiling point is 150°C or higher, so the solvent contained in the polymer after separation and precipitation cannot be completely removed. Difficult and undesirable.

In addition, the δ of the methacrylic polymer is 9.5 (cal/cm
3) δ of aliphatic monohydric alcohol is around 10.5 to 14. S (cal/qm', more preferably 10.9 to 14.5 (cal/cm3), and when δ is less than 10.5 (cut/cm3), the compatibility with the methacrylic polymer increases and the polymerization rate decreases. As the temperature increases, the viscosity of the system increases and stirring becomes impossible, and even if the temperature of the polymerization system or the temperature of the solvent slurry taken out is lowered, a large amount of methacrylic polymer is contained in the solvent, resulting in a decrease in yield. Examples of the aliphatic monohydric alcohol in the present invention include methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, and n-7 methyl alcohol. , ethyl alcohol is preferred.

Further, in the present invention, the aliphatic monohydric alcohol is used in a ratio of 80 to 30 parts by weight, more preferably 70 to 50 parts by weight, relative to 20 to 70 parts by weight, more preferably 30 to 50 parts by weight, of the monomer component. If the monomer component is less than 20% by weight, the yield per hour will be very low and the energy cost will be high. On the other hand, if it exceeds 70% by weight, the viscosity of the polymerization system increases and polymer precipitates may adhere to stirring blades, etc., 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 those with a 10-hour half-life temperature of 100°C or less are preferred, such as inbutyl peroxide, diisopropyl peroxycabonate, etc. , No-2-ethylhexyl peroxydicarbonate, tert-butyl peroxyneodeca 7ate, tert-butyl peroxy bivalate, 3,5.5-)dimethylhexanoyl peroxide, lauroyl peroxide, acetyl peroxide oxide, benzoyl peroxide, tert-butyl peroxyisobutyrate, 1,1-bis(tert-peroxy) -3,3,
5-) Organic peroxides such as dimethylcyclohexane, tert-butylperoxyisopropyl carbonate, or 2,2'-7zobis(4-methoxy-2,4-
dimethylvaleronitrile), 2,2'azobis(2,4
-dimethylvaleronitrile), (1-7dynylethyl)
-7 zodiphenylmethane, 2,2'-7 zobisisobutyronitrile, dimethyl-2,2'-7 zobisisobutyrate, 2,2'-azobis(2-methylbutyronitrile), 1 Examples include azo compounds such as 1'-azobis(1-cyclohexanecarbonitrile).

As the chain transfer agent, thi-butyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan, isooctyl thioglycolate, etc., which are used in ordinary radical polymerization, can be used.

〔Effect of the invention〕

The methacrylic polymer obtained by the new production method of the present invention has very little contamination by impurities and by-products such as oligomers that could not be easily removed by conventional production methods, and has excellent optical properties. It is something.

〔Example〕

The monomers, polymerization initiators, and chain transfer agents used in the examples are represented by the following abbreviations. Abbreviations are in parentheses.

Methyl methacrylate (MMA), ethyl methacrylate (EMA), methyl acrylate (MA),
Ethyl 7-acrylate (EA), n-butyl acrylate
) (BA).

Tertiary butyl peroxyneodecanoate (BPN)
D), lauroyl peroxide (LPO), benzoyl peroxide (BPO), 2゜2'-7zobisisobutyronitrile (AIBN), 1,1'-azobis(1-cyclohexane carbonitrile) (ACCN)
) t-Butyl mercaptan, t-butyl mercaptan (n-〇-M), n-dodecyl mercaptan (n-DM).

Further, the b value in the examples is a value measured with a Hunter colorimeter and represents the degree of yellowness.

Example 1.

The right 1715 ρ polymerization tank is heavy - this L is 95% by weight of methacrylate, 5% by weight of methyl acrylate.
2.9 g of tert-butylperoxyneodecanoe as a polymerization initiator, 2.2 g of n-octyl mercaptan as a chain transfer agent, and δ of 14.5 (cal/cra”). After adding and mixing 2160 g of methyl alcohol, the inside of the polymerization tank was sufficiently replaced with nitrogen, stirring speed was 2 Orpm, and polymerization temperature was 60°C.
After 6 hours of reaction, the temperature of the thread was cooled to 10°C, and after 30 minutes, the obtained polymer and solvent were separated, and the polymer was heated to 40°C.
``Methacrylic polymer 119 dried under C1 vacuum for 48 hours.
Obtained 0g. 8w of methacrylic polymer is 10.3X10
, 4Rw/Mm is 1.95, and Mll+ is 1000
The following oligomer content was very low at 64 ppm. Furthermore, the total light transmittance, haze, and b value of a 3 mm plate obtained by press-molding a methacrylic polymer after heating it at 250°C for 10 minutes were 92.3, 0.2, and 0.1, respectively.
6, showing good optical properties and no coloration was observed.

Table 1 shows the results of Examples 2 to 6, Comparative Examples 1 to 2, and the same methods as Example 1.

The test was carried out under the same conditions as in Example 1 except for the conditions listed in Table 1.

Example 7 Using a 52 polymerization tank equipped with a stirrer that allows continuous addition and removal, polymerization was started using 30 parts by weight of a monomer component consisting of 90% by weight of methyl methacrylate and 1% by weight of ethyl acrylate. 0.12 parts by weight of lauroyl peroxide as a starting material, n-octyl mercaptan O as a chain transfer agent, parts by weight of OS and δ of 12.7 (c
A mixture of these raw materials was prepared in a nitrogen atmosphere by adding 70 parts by weight of ethyl alcohol (al/am co)h, and the temperature was controlled at 20°C, in a polymerization tank which was sufficiently purged with nitrogen at a rate of 0.71/HR per hour. The polymerization temperature was maintained at 75° C. and the stirring speed at 30 rpm. 5.5 hours after the start of preparation, the operation was switched to continuous operation, and the continuous supply amount of the above raw material mixture was reduced to 0.5 hours per hour.
It was operated continuously for 10 hours at 91/HR. The polymer content in the continuously taken out solvent slurry was 25.5% by weight, and this solvent slurry was cooled to 10°C, and the polymer obtained after precipitation separation was dried at 40°C under vacuum for 48 hours. 1880 g of methacrylic polymer was obtained. The weight of the obtained methacrylic polymer is 13.2X104.8/1.9
8, and the oligomer content with Mll of 1000 or less was 821) p. In addition, this methacrylic polymer is
3I obtained by press molding after heating at 50"C for 10 minutes
The total light transmittance, haze, and b value of the III plate were 92.2%, 0.3%, and 0.19, respectively, indicating good optical properties and no coloration was observed.

Procedural amendment (voluntary) May 28, 1986

Claims (1)

[Claims] Methyl methacrylate alone or 50% by weight or more of methyl methacrylate and alkyl acrylate or alkyl methacrylate (excluding methyl methacrylate) 50% by weight
When polymerizing a monomer mixture consisting of % by weight or less in the presence of a radical polymerization initiator, the solvent has a carbon number of 1 to 5 and a solubility parameter (δ) for 20 to 70 parts by weight of the monomer components. is 10.5 to 14.5 (cal/cm^
3) Aliphatic monohydric alcohol that is ^1^/^2 80-3
A novel method for producing a methacrylic polymer by a solvent slurry polymerization method, characterized in that the polymerization is carried out in the presence of 0 parts by weight.