JPS60226516A - Preparation of copolymer - Google Patents

Abstract

PURPOSE:To obtain a copolymer having a low molecular weight in high yield by smooth reaction, by radically copolymerizing an aromatic vinyl compound with maleic anhydride in the presence of a vinyl chloride-vinyl acetate copolymer (partially hydrolyzed copolymer) as a dispersing agent. CONSTITUTION:An aromatic vinyl compound, preferably styrene is copolymerized with maleic anhydride in the presence of a radical polymerization initiator and a vinyl chloride-vinyl acetate copolymer or a partially hydrolyzed copolymer thereof, preferably having 10-20wt% vinyl acetate content and 5,000-200,000 mol.wt. as a dispersing agent in a solvent capable of dissolving the monomers but not dissolving the resultant copolymer, preferably toluene to give the aimed copolymer having <=10,000 weight-average molecular weight. The amount of the dispersing agent to be used is preferably 0.2-5wt% based on the total amount of the monomers.

Description

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

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 thus obtained are high molecular weight alternating copolymers, containing pour point depressants, coal, dyes,
It is widely used as a solid dispersant for pigments, adhesives, and paper sizing agents. 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 the performance may deteriorate depending on the application, so copolymers with a molecular weight of 10.000 or less are used as products. desired.

Furthermore, in the above precipitation polymerization, when the copolymer is precipitated from the solvent, the wall portion in the reaction vessel, the stirrer portion,
This method has disadvantages in that a uniform dispersion cannot be obtained because precipitates adhere to and solidify in the coil portion, or block-like agglomerates are formed, and the yield of the copolymer is also significantly reduced.

For this purpose, the use of various dispersants has been considered, but
At present, there are very few products with sufficiently satisfactory performance.
However, it is difficult to obtain products with a certain low molecular weight.

The method of the present invention overcomes the above drawbacks by using a specific copolymer 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. Provided is a method for producing a copolymer of an aromatic vinyl compound and maleic anhydride having a molecular weight of io, ooo or less, which uses a vinyl chloride-vinyl acetate copolymer or a partial hydrolyzate thereof as an agent. It is.

Aromatic vinyl compounds used in the present invention include styrene, α-methylstyrene, paramethylstyrene, etc.
; Among them, styrene is the 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 a poor solvent for the copolymer, but aromatic solvents such as tilbenzene, cumene, and paracymene are used because the particles of the copolymer produced are large. The ratio of the total amount of monomers to the solvent is 1:9 to 3:1 by weight, preferably 1:4 to 1: azo compound such as tyronitrile, benzoyl peroxide, methyl ethyl ketone peroxide, cumene hydroperoxide, tert-butyl peroxide. -Organic peroxides such as 2-ethylhexanoate are used.

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. Suitable dispersants include vinyl chloride-vinyl acetate copolymers or partial hydrolysates thereof. The composition and molecular weight of the above copolymer are not particularly limited, but preferably have a vinyl acetate content of 5 to 95% by weight and a molecular weight of 500 to 500,000%, particularly preferably a vinyl acetate content of 10 to 20% by weight. Section, molecular weight 5.
000 to 200,000. Vinyl chloride-vinyl acetate copolymer can be easily synthesized by known methods,
Moreover, it is commercially available and can be easily obtained.

The amount of the dispersant used is 0.1 to 50% by weight, preferably 0.2 to 5% by weight based on the total amount of monomers.

If this amount is less than 01 weight ratio, there is no effect of preventing the adhesion of sediment, and if it exceeds 50 weight ratio, it is economically disadvantageous, and
The quality of the resulting product was impaired, and the dispersed particles were too fine to pass through.

The monopolymerization temperature is about 80 to 200°C, preferably about 90 to 200°C.
Desirably, the temperature is 140°C and remains constant during the polymerization time.

A sufficient polymerization time of 5 hours, including the time for gradually adding the monomer to the reaction vessel, is sufficient. Furthermore, although stirring speed is generally thought to affect 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 in a polymerization temperature chamber 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. In the method of the present invention, a specific dispersant is dissolved in a solvent in advance and polymerization is carried out, so that a uniform dispersion state is maintained from the beginning to the end of the reaction, and the dispersion is produced by cooling after the reaction is completed. There is no adhesion of the copolymer at all, and it is easy to take out the copolymer from the reaction vessel.
Since the copolymer also has good liquid removal properties, the amount of heat required in the drying process can be reduced, and at the same time, the size of the drying equipment can 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 is obtained, so that the molecular weight is 10. A copolymer of an aromatic vinyl compound having a molecular weight of '000 or less and maleic anhydride can be produced in 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 A 1 t flask equipped with a stirrer, a thermometer, a steam condenser, a nitrogen inlet tube, and a dropping tank was equipped with 354 y of toluene, 64 y of maleic anhydride, and ESLEK CL [vinyl chloride-acetic acid manufactured by Tanezu Kagaku Kogyo ■] as a dispersant. Trade name of vinyl copolymer (
Molecular weight approximately 40,000: vinyl acetate content 13% by weight) + s, o
7 was taken, and the temperature was raised to the boiling point (approximately 11 otr) while stirring.

Next, add toluene 1265F to a 300g drip tank.

Take styrene 56y1 benzoyl peroxide 3y,
It was added dropwise into the above flask over a period of 2 hours. After the dropwise addition was completed, the same temperature was maintained for 3 hours. During this time, the produced copolymer precipitated to become 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 by filtration, and was vacuum dried to obtain a solid content of 118.5y.

The vacuum-dried solid content was confirmed to be a copolymer of styrene and maleic anhydride by measurement using an infrared spectrophotometer and a nuclear magnetic resonance absorption needle. The molecular weight was 6,500.

Example 2 In Example 1, Eslec CH (trade name of vinyl chloride-vinyl acetate copolymer manufactured by Tanemizu Kagaku Kogyo ■) (molecular weight approximately 90,000: Contains vinyl acetate -3J13% by weight) was used as the dispersant instead of Eslec CL. )) The procedure of Example 1 was followed except that 4.8F was used. Stirring of the reaction solution was extremely smooth, and filtration of the reaction product was also easy. The yield of solid matter obtained by vacuum drying is l]9. oy, and its molecular weight is 7
There were 11 in 300.

Example 3 Example 1 except that Eslec A (trade name of a partial hydrolyzate of hinyl chloride-vinyl acetate copolymer manufactured by Tanemizu Kagaku Kogyo ■) 42y was used instead of Eslec CL as a dispersant. It was carried out according to 1. Stirring of the reaction solution was extremely smooth, and filtration of the reaction product was also easy. The yield of solid matter obtained by vacuum drying was 119. '5.
F, and its molecular weight was 5,800.

Comparative Example 1 Example 1 was carried out except that no dispersant was used. 10 minutes after the start of dropping, the reaction product was observed to adhere to the container wall, and as the dropping progressed, it became more noticeable. When about half of the liquid in the dripping tank was dropped, the reaction product was attached to the entire surface of the container wall and the stirring. The reaction was stopped because the impeller was covered and stirring became impossible.

Comparative Example 2 The same procedure as in Example 1 was carried out, except that 6°C vinyl acetate polymer having a molecular weight of about 40,000 was used instead of S-LEC CL as a dispersant.

20 minutes after the start of dropping, the reaction product was observed to adhere to the container wall, and as the dropping progressed, this became more noticeable. Near the end of dropping, the reaction product was so attached that it was difficult to continue the reaction, so the reaction was stopped.

Patent applicant: NOF Corporation

Claims (1)

[Claims] When copolymerizing an aromatic vinyl compound and maleic anhydride using a radical polymerization initiator in a solvent in which these monomers dissolve but the resulting copolymer only slightly dissolves, vinyl chloride is used as a dispersant. - A method for producing a copolymer of an aromatic vinyl compound and maleic anhydride having a weight average molecular weight of 10.000 or less, which comprises using a vinyl acetate copolymer or a partial hydrolyzate thereof.