JPH0610217B2 - Method for producing copolymer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a copolymer of an aromatic vinyl compound and maleic anhydride, particularly a weight average molecular weight (hereinafter referred to as molecular weight) 10
000 or less and a method suitable for producing a copolymer of styrene and maleic anhydride.

Aromatic vinyl compounds and maleic anhydride are radically polymerized in peroxides or azo compounds in a solvent that is inert to these monomers and that dissolves the monomers but not the copolymer. Precipitation polymerization can be performed using an initiator. Generally the copolymers thus obtained are high molecular weight alternating copolymers, pour point depressants, coal, dyes,
It is widely used for solid dispersants such as pigments, adhesives, and paper sizing agents. However, when the molecular weight of the above copolymer is high, the viscosity of the solution becomes high, the handling becomes difficult, and the performance deteriorates depending on the application. Therefore, a copolymer having a molecular weight of 10,000 or less is desired as a product. .

Furthermore, when the copolymer is precipitated from the solvent in the above precipitation polymerization, the wall surface part in the reaction vessel, the stirrer part,
There is a drawback that a precipitate is adhered and solidified on the coil part or a block-like solidification occurs and a uniform dispersion cannot be obtained, and the yield of the copolymer is remarkably reduced.

For this reason, the use of various dispersants has been considered,
At present, there are almost no satisfactory performances, and it is difficult to obtain a product having a predetermined low molecular weight.

The method of the present invention eliminates the above-mentioned drawbacks by using a specific copolymer as a dispersant.

That is, the present invention, when the aromatic vinyl compound and maleic anhydride are copolymerized with a radical polymerization initiator in a solvent in which these monomers dissolve but the resulting copolymer does not dissolve, a dispersion is obtained. Provided is a method for producing a copolymer of an aromatic vinyl compound having a molecular weight of 10,000 or less and maleic anhydride, which comprises using a vinyl chloride-vinyl acetate copolymer or a partial hydrolyzate thereof as an agent. .

Examples of the aromatic vinyl compound used in the present invention include styrene, α-methylstyrene, and paramethylstyrene, and among them, styrene is most preferable.

The solvent used in the present invention is not particularly limited, and is a copolymer which is inactive and has excellent solubility with respect to reacting monomers (that is, aromatic vinyl compounds and maleic anhydride). Any solvent may be used as long as it is a poor solvent which is inactive with respect to, but a solvent in which the particles of the produced copolymer are large and relatively uniform is particularly preferable.
Suitable solvents include aromatic solvents such as benzene, toluene, xylene, ethylbenzene, cumene, paracimene. The total monomer to solvent ratio by weight is in the range of 1: 9 to 3: 1, preferably 1: 4 to 1: 1.

Examples of the radical polymerization initiator include azo compounds such as azobisisobutyronitrile, benzoyl peroxide, methyl ethyl ketone peroxide, cumene hydroperoxide, and organic peroxides such as tertiary butyl peroxy-2-ethyl hexanoate.

As the dispersant used in the present invention, since the present reaction is a reaction between a non-polar monomer and a polar monomer, the dispersant also has a non-polar part and a polar part in the molecule, It is also preferable that it be soluble in a solvent. Suitable dispersants include vinyl chloride-vinyl acetate copolymers or partial hydrolysates thereof. The composition and molecular weight of the above-mentioned copolymer are not particularly limited, but those having a vinyl acetate content of 5 to 95% by weight and a molecular weight of 500 to 500,000 are preferable, and a vinyl acetate content of 10 to 20% by weight and a molecular weight are particularly preferable. Fifty
It is the thing of 00-200000. The vinyl chloride-vinyl acetate copolymer can be easily synthesized by a known method and can be easily obtained since it is commercially available.

The amount of the dispersant used is 0.1 to 50 with respect to the total amount of the monomers.
% By weight, preferably 0.2 to 5% by weight. If this amount is less than 0.1% by weight, there is no effect of preventing deposits from adhering to the precipitate.
If it exceeds 0% by weight, it is economically disadvantageous, the quality of the obtained product is impaired, and the dispersed particles become too fine, which makes it difficult to pass.

The polymerization temperature is about 80 to 200 ° C, preferably about 90 to 14 ° C.
It is desirable to be constant at 0 ° C. during the polymerization time. Also,
A polymerization time of 5 hours is sufficient, including the time for gradually adding the monomer to the reaction vessel.

In addition, it is generally considered that the stirring speed affects the dispersion effect, but in the method of the present invention, the effect is small, and the stirring may be such that the reaction solution is moved.

In carrying out the present invention, first, a solvent in which a dispersant is dissolved and maleic anhydride are taken in a reaction vessel and heated to a polymerization temperature while stirring.

The same solvent, aromatic vinyl compound and radical polymerization initiator mixture as described above is added dropwise thereto to maintain the polymerization temperature. After the completion of the reaction, the reaction mixture is cooled, the produced copolymer is separated, and then dried to obtain the copolymer of the present invention.

In the method of the present invention, a specific dispersant is dissolved in a solvent in advance to carry out polymerization, so that a uniform dispersion state is maintained from the beginning to the end of the reaction, and the adhesion of the copolymer in the reaction vessel is completely eliminated. In addition, the copolymer can be easily taken out of the reaction vessel and the liquid can be removed easily from the reaction vessel. Therefore, the heat amount required in the drying step can be small and the drying device can be downsized.

According to the method of the present invention, by using a specific dispersant, the polymerization reaction proceeds smoothly to obtain a concentrated uniform dispersion liquid. Therefore, a copolymer of an aromatic vinyl compound having a molecular weight of 10,000 or less and maleic anhydride is used. Can be produced in good yield.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited thereto. The molecular weight was measured by the gel permeation chromatography method.

Example 1. To a flask equipped with a stirrer, a thermometer, a steam condenser, a nitrogen introducing tube and a dropping tank, 354 g of toluene, 64 g of maleic anhydride, and S-LEC CL as a dispersant (vinyl chloride manufactured by Sekisui Chemical Co., Ltd.) -Trade name of vinyl acetate copolymer (molecular weight: about 40,000: vinyl acetate content 13% by weight)] 6.
0 g was taken and the temperature was raised to the boiling point (about 110 ° C.) while stirring.

Next, 126 g of toluene, 56 g of styrene and 3 g of benzoyl peroxide were placed in a 300 ml dropping tank and added dropwise to the above flask over 2 hours. After the completion of dropping, the temperature was maintained for 3 hours. During this period, the produced copolymer was precipitated and turned into a milky white slurry, and the stirring state of the reaction solution was extremely smooth. After cooling, the reaction product could be easily taken out and dried under vacuum to obtain 118.5 g of solid content. The vacuum-dried solid content was confirmed to be a copolymer of styrene and maleic anhydride by measurement with an infrared spectrophotometer and a nuclear magnetic resonance absorption spectrometer. The molecular weight was 6500.

Example 2 In Example 1, the dispersant was replaced with S-REC CL by S-REC CH [vinyl chloride manufactured by Sekisui Chemical Co., Ltd.
A trade name of vinyl acetate copolymer (molecular weight: about 90,000: vinyl acetate content 13% by weight)] was used in the same manner as in Example 1 except that 4.8 g was used. The stirring of the reaction solution was extremely smooth, and the amount of the reaction product was easy. The solid content obtained by vacuum drying was 119.0 g, and the molecular weight was 7
It was 300.

Example 3. In Example 1, instead of S-REC CL as a dispersant, S-REC A [(trade name of partial hydrolyzate of vinyl chloride-vinyl acetate copolymer manufactured by Sekisui Chemical Co., Ltd.)
It carried out according to Example 1 except that 4.2 g was used. The stirring of the reaction solution was extremely smooth, and the amount of the reaction product was easy. The yield of solids obtained by vacuum drying is 11
It was 9.5 g and its molecular weight was 5,800.

Comparative Example 1. Example 1 was repeated except that no dispersant was used. Adhesion of the reaction product was observed on the container wall 10 minutes after the start of the dropping, and it became remarkable with the progress of the dropping, and when about half of the liquid in the dropping tank was dropped, the reaction product was on the entire surface of the container wall and the stirring blade. The reaction was stopped because it became impossible to stir.

Comparative Example 2. The procedure of Example 1 was repeated except that 6.0 g of a vinyl acetate polymer having a molecular weight of about 40,000 was used as the dispersant instead of S-REC CL.

Twenty minutes after the start of the dropping, the reaction product adhered to the container wall, which became remarkable as the dropping proceeded, and the reaction product was markedly adhered near the end of the dropping, and the reaction was stopped because the reaction could not be continued.

Claims (1)

[Claims] 1. A dispersant for copolymerizing an aromatic vinyl compound and maleic anhydride with a radical polymerization initiator in a solvent in which these monomers dissolve but the resulting copolymer does not. A method for producing a copolymer of an aromatic vinyl compound having a weight average molecular weight of 10,000 or less and maleic anhydride, which comprises using a vinyl chloride-vinyl acetate copolymer or a partial hydrolyzate thereof.