JPH0556365B2 - - Google Patents

Description

Detailed Description of the Invention The present invention is directed to the production of a copolymer of an aromatic vinyl compound and maleic anhydride, particularly a copolymer of styrene and maleic anhydride having a weight average molecular weight (hereinafter referred to as molecular weight) of 10,000 or less. Regarding suitable methods.

Aromatic vinyl compounds and maleic anhydride are inert to these monomers, and can be radically polymerized with peroxides or azo compounds in a solvent that dissolves the monomers but not the copolymer. Precipitation polymerization can be carried out using an initiator. Generally, the copolymers obtained in this way are high molecular weight alternating copolymers, and are widely used as pour point depressants, solid dispersants for coal, dyes, pigments, etc., adhesives, and paper sizing agents. There is. However, if the molecular weight of the above copolymer is high, the viscosity of the solution will be high, making it difficult to handle, and depending on the application, the performance will deteriorate, so copolymers with a molecular weight of 10,000 or less are desired as products. There is.

Furthermore, when the copolymer precipitates from the solvent in the above-mentioned precipitation polymerization, the precipitate may adhere to and harden on the wall, stirrer, coil, etc. in the reaction vessel, or form block-like solids. This method has disadvantages in that a uniform dispersion cannot be obtained and the yield of the copolymer is significantly reduced.

For this purpose, the use of various dispersants has been considered, but at present there are almost no dispersants with sufficiently satisfactory performance, and furthermore, it is difficult to obtain a product with a specified low molecular weight.

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

That is, the present invention provides dispersion when copolymerizing an aromatic vinyl compound and maleic anhydride using a radical polymerization initiator in a solvent that dissolves these monomers but does not dissolve the resulting copolymer. The present invention provides a method for producing a copolymer of an aromatic vinyl compound with a molecular weight of 10,000 or less and maleic anhydride, which is characterized by using polyvinyl butyral resin as an agent.

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

The solvent used in the present invention is not particularly limited, and it is inert and has excellent solubility for the reacting monomers (namely, aromatic vinyl compound and maleic anhydride), and the resulting copolymer Any solvent may be used as long as it is inert and poor solvent for the copolymer, but a solvent that makes the particles of the produced copolymer large and relatively uniform is particularly preferred. Suitable solvents include aromatic solvents such as benzene, toluene, xylene, ethylbenzene, cumene, paracymene, and the like. The ratio of the total amount of monomers to the solvent is from 1:9 to 3:1 by weight, preferably 1:
The ratio ranges from 4 to 1:1.

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

As the dispersant used in the present invention, since this reaction is a reaction between a nonpolar monomer and a polar monomer, the dispersant also has a nonpolar part and a polar part in the molecule, It is preferable to use one that is also soluble in a solvent. The polyvinyl butyral resin used in the present invention as a suitable dispersant is a polyvinyl alcohol derivative represented by the following general formula, It is obtained by reacting polyvinyl alcohol obtained by saponifying polyvinyl acetate with butyraldehyde. In this case, l, m, and n are arbitrary, but those having a molecular weight of about 5,000 to 300,000 are generally commercially available or can be obtained by synthesis, and any of them can be preferably used in the present invention.

The amount of dispersant used is 0.1 based on the total amount of monomers.
~50% by weight, preferably 0.2-5% by weight.
If this amount is less than 0.1% by weight, there is no effect of preventing the adhesion of precipitates, and if it exceeds 50% by weight, it is not only economically disadvantageous, but also may impair the quality of the resulting product, or cause the dispersed particles to become too fine, leading to overuse. becomes difficult.

Polymerization temperature is about 80-200℃, preferably about 90-140℃
℃, which is preferably constant during the polymerization time. Furthermore, 5 hours is sufficient for the polymerization time, including the time for gradually adding the monomer to the reaction vessel.

Further, although it is generally thought that the stirring speed affects the dispersion effect, this effect is small in the method of the present invention, and stirring to the extent that the reaction solution is moved is sufficient.

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

A mixture of the same solvent, aromatic vinyl compound, and radical polymerization initiator as described above is added dropwise into the mixture to maintain the polymerization temperature. After the reaction is completed, the mixture is cooled, and the produced copolymer is separated and dried to obtain the copolymer targeted by the present invention.

In the method of the present invention, a specific dispersant is dissolved in a solvent before polymerization, so a uniform dispersion state is maintained from the beginning to the end of the reaction, and there is no adhesion of the copolymer inside the reaction vessel. Therefore, the copolymer can be easily taken out from the reaction vessel, and the copolymer has good liquid removal properties, so the amount of heat required in the drying process is small, and the drying equipment can also be made smaller.

According to the method of the present invention, by using a specific dispersant, the polymerization reaction proceeds smoothly and a thick uniform dispersion liquid can be obtained. can be produced with good yield.

EXAMPLES The present invention will be specifically explained below using Examples and Comparative Examples, but the present invention is not limited thereto. Molecular weight was measured by gel permeation chromatography.

Example 1 Toluene 354 was placed in one flask equipped with a stirrer, a thermometer, a steam condenser, a nitrogen inlet tube and a dropping tank.
g, maleic anhydride 64 g, Eslec BL-1 (Sekisui Chemical Co., Ltd. butyral resin: butyral group 63
%mol%) was taken and the temperature was raised to the boiling point (approximately 110°C) while stirring. Next, 126g of toluene,
56 g of styrene and 3.0 g of benzoyl peroxide were mixed at room temperature, placed in a 300 ml dropping tank, and added dropwise to the flask at the boiling point for 2.0 hours. After the dropwise addition was completed, the same temperature was maintained for 3.0 hours. During this time, the produced polymer precipitated to become a milky white slurry, and the reaction solution was stirred very smoothly. Further, the resulting polymer was very easily filtered after cooling, and it was vacuum-dried to obtain 119.8 g of dry polymer.
This polymer was confirmed to be a styrene-maleic anhydride copolymer by infrared absorption spectrum and nuclear magnetic resonance absorption spectrum. Moreover, its molecular weight was 6900.

Example 2 The same procedure as in Example 1 was carried out, except that 4.8 g of Eslec BM-S (butyral resin manufactured by Sekisui Chemical Co., Ltd., containing 70 mol % or more of butyral groups) was used instead of Eslec BL-1. Stirring of the system during polymerization was extremely smooth, and the resulting polymer was extremely easy to filter. The yield of dry polymer is
The weight was 119.5g, and its molecular weight was 5300.

Comparative Example 1 The procedure of Example 1 was followed except that no dispersant was used. 10 minutes after the start of dripping, adhesion of the produced polymer to the container wall was observed, and as the dripping proceeded, it became more noticeable. When about half of the liquid in the dripping tank had been reduced to drops, the precipitated polymer covered the entire surface of the container wall and the stirring blade. The reaction was stopped because it became impossible to stir.

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

20 minutes after the start of dropping, adhesion of the produced polymer to the container wall was observed, which became more noticeable as the dropping progressed, and near the end of dropping, the precipitated polymer was so attached that it was difficult to continue the reaction, so the reaction was stopped.

Claims (1)

[Claims] 1 When copolymerizing an aromatic vinyl compound and maleic anhydride using a radical polymerization initiator in a solvent that dissolves these monomers but does not dissolve the resulting copolymer, polyvinyl butyral is used as a dispersant. 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, the method comprising using a resin.