JPH0485303A - Dispersing aid and dispersion stabilizer for suspension polymerization of vinyl compound - Google Patents

Abstract

PURPOSE:To obtain the title dispersing aid useful for obtaining a dispersion stabilizer which can give a suspension polymer which is porous and has a high plasticizer absorption rate and from which the residual vinyl chloride compound can be easily removed by selecting a dispersing aid comprising a specified polyvinyl ester polymer. CONSTITUTION:A dispersing aid comprising a polyvinyl ester polymer (e.g. PVAc) having a degree of saponification of below 50mol% and an average degree of polymerization of 4000 or above is selected.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Industrial Application The present invention relates to a dispersion aid and a dispersion stabilizer for suspension polymerization of vinyl compounds, particularly vinyl chloride.

B. Conventional technology When producing vinyl chloride resin industrially, suspension polymerization is widely used, in which vinyl chloride monomers are dispersed in an aqueous medium in the presence of a dispersion stabilizer and polymerized using an oil-soluble catalyst. <It has been implemented. In general, factors governing the quality of the resin include the polymerization rate, water-monomer ratio, polymerization temperature, type and amount of catalyst, type of polymerization tank, stirring speed, and type and amount of dispersion stabilizer, among others. It is known that the type of dispersion stabilizer has a very large effect.

The performance required of a dispersion stabilizer for suspension polymerization of vinyl chloride monomers is (i) to exhibit high dispersion power even when used in small amounts, and to sharpen the particle size distribution of the resulting vinyl chloride polymer particles as much as possible; (11) In order to increase the absorption rate of the plasticizer and facilitate processability, and to facilitate the removal of vinyl chloride monomer remaining in the polymer particles, as well as fish eyes in the molded product, etc. (iii) It has the function of making each polymer particle as uniform as possible and porous in order to prevent the formation of pores, and (iii) It has the function of creating polymer particles with a large filling specific gravity.

Conventionally, cellulose derivatives such as methyl cellulose and carboxymethyl cellulose, partially saponified polyvinyl alcohol, and the like have been used alone or in combination as dispersion stabilizers for suspension polymerization of vinyl compounds.

Conventional dispersion stabilizers, which C1 aims to solve, have drawbacks such as low ability to make vinyl chloride polymer particles porous, slow plasticizer absorption rate, and difficulty in removing residual vinyl chloride monomer. The object of the present invention is to provide a dispersion aid and a dispersion stabilizer free from such drawbacks.

In view of the current situation, the present inventors investigated better dispersion aids and dispersion stabilizers for suspension polymerization, and found that
A dispersion aid (A) consisting of a polyvinyl ester (hereinafter sometimes abbreviated as PVAc) polymer having a saponification degree of less than 50 mol% and an average degree of polymerization of 4000 or more and a dispersion stabilizer using the same were discovered, and the present invention I've reached the point where I can complete this.

In the present invention, PVAC used as a dispersion aid (A)
The average degree of polymerization of the system polymer is 4000 or more, preferably 70
00 or more, and the degree of saponification is less than 50 mol%, preferably 15 mol% or more and less than 50 mol%, more preferably 2
It is 5 to 45 mol%.

Polyvinyl ester, which is the raw material for the P,VAc-based polymer of the present invention, can be polymerized using commonly known methods such as bulk polymerization,
Any method such as solution polymerization, suspension polymerization, or emulsion polymerization may be employed, but solution polymerization and emulsion polymerization are preferred from an industrial perspective. Furthermore, the polymerization process can be produced using any of the batch, semi-batch, and continuous methods.

When the PVAC polymer of the present invention is a partially saponified product, the PVAC polymer can be obtained by saponifying polyvinyl ester. Specifically, generally known methods such as alkali saponification and acid saponification can be employed, but industrially, NaOH, CH, ONa
methanol decomposition catalyzed by The saponification temperature is not particularly limited, but from the viewpoint of preventing discoloration of the resulting PVAC polymer, it is preferably carried out at 20 to 60°C.

The amount of NaOH or CHsOHa used as a catalyst is usually 0.2 mol or less per 1 mol of vinyl ester units, which is preferable from the viewpoint of preventing coloring of the PVA c-based polymer and keeping the amount of sodium acetate low.

The degree of polymerization of the PVAC polymer of the present invention was determined by the following formula from the intrinsic viscosity in an acetone solution at 30°C after completely saponifying the PVAC polymer and acetylating it to polyvinyl acetate. It is expressed as a viscosity average degree of polymerization.

Moreover, the degree of saponification means the degree of saponification of the vinyl ester component, and when other components are copolymerized, those components are not included. The degree of saponification can be analyzed by conventionally known chemical analysis methods, nuclear magnetic resonance analysis methods, and the like.

There is no particular restriction on the content of the dispersion aid (A) of the present invention when the dispersion aid (A) of the present invention and another dispersant (8) are used together, but it is preferably 5 to 70% by weight. Further, 5 to 50% by weight is preferable.

Ratio of the dispersion aid (A) of the present invention to other dispersants (B) (
When the ratio of (A)/(B) is less than 5/95, the effect of addition is small, and when the ratio of (A)/(B) is more than 70/30, polymerization stability may be adversely affected.

Other dispersants (B) to be used in combination with the dispersion aid (B) of the present invention are usually not particularly limited as long as they are dispersants for suspension polymerization of vinyl compounds; Particularly preferred are polyvinyl alcohol polymers having a mol% and a degree of polymerization of 500 or more.

It is also possible to use conventionally known cellulose derivatives.

When using the dispersion stabilizer made of the PVAC polymer of the present invention to carry out suspension polymerization of a mixture of vinyl chloride alone or a monomer copolymerizable with vinyl chloride, it is usually dispersed in an aqueous medium. A stabilizer is added, and a vinyl chloride monomer or a mixture of a monomer copolymerizable with the vinyl chloride monomer is dispersed in the presence of an oil-soluble catalyst. The dispersion stabilizer can be added to the aqueous medium as a powder or as an aqueous solution.

The dispersion stabilizer of the present invention is o, oos to 1% by weight, preferably 0.01 to 0.5% by weight, based on the vinyl chloride monomer or a mixture of vinyl chloride monomers and monomers copolymerizable with the vinyl chloride monomer.
% by weight used.

The catalyst used in suspension polymerization may be any oil-soluble catalyst, such as benzoyl peroxide,
lauroyl peroxide, diisopropyl peroxydicarbonate, 2.2゛-azoisobutyronitrile,
2.2°-Azobis-2,4-dimethylvaleronitrile or a mixture thereof is used.

The polymerization temperature is selected from a range of about 30 to 70°C.

A conventionally known dispersion stabilizer can also be appropriately used as an auxiliary agent during polymerization.

As the monomer copolymerizable with vinyl chloride, vinylidene halide, vinyl ether, vinyl acetate, acrylic acid, methacrylic acid and their esters, maleic acid and its anhydride, itaconic acid, styrene, etc. are used.

Although the above description has mainly focused on the polymerization of vinyl chloride, the dispersion stabilizer of the present invention is not necessarily limited to the suspension polymerization of vinyl chloride, but can also be used for the suspension polymerization of vinyl compounds such as styrene and methacrylate. It will be done.

Although the present invention has been described in detail above, particularly preferred embodiments of the present invention are as follows.

The dispersion aid according to claim 1, wherein the polyvinyl ester polymer (a) has a saponification degree of 15 mol% or more and less than 50 mol%.

(b) Polyvinyl ester polymer saponification degree 25-4
5 mol % and an average degree of polymerization of 7000 or more, the dispersion aid according to embodiment item (a).

The present invention will be explained in more detail with reference to Examples below, but the dispersion aid and dispersion stabilizer of the present invention are not limited to these Examples.

In the following examples, "parts" indicate "parts by weight."

Examples 1 to 8 and Comparative Examples 1 to 3 Suspension polymerization of vinyl chloride was carried out by the following method using the dispersion stabilizers shown in Table 1.

40 parts deionized water in a glass-lined autoclave;
0.75 parts of a 2% by weight aqueous solution of the dispersion stabilizer shown in Table 1 and 0.009 parts of a 50% by weight toluene solution of diisopropyl peroxydicarbonate were charged, and the inside of the autoclave was degassed to 50 ta m H,g. After removing oxygen, 30 parts of vinyl chloride monomer was charged, and the temperature was raised to 57° C. while stirring to carry out polymerization.

At the start of polymerization, the pressure inside the autoclave was 8.5 kg/c.
+a'G, but 4.5 kg/7 hours after the start of polymerization.
At this point, the polymerization was stopped, unreacted vinyl chloride monomer was purged, and the contents were taken out and dehydrated and dried.

The polymerization yield of vinyl chloride resin is 85%, and the average degree of polymerization is 1.
It was 050.

Table 1 shows the physical properties and usage amount of the dispersion stabilizer and the performance of the obtained vinyl chloride resin.

Margin below (1) Particle size distribution: Measured with a dry sieve using a wire mesh based on Tyler mesh.

(2) Filling specific gravity: JIS K6721-195
9.

(3) Using a planetary mixer connected to a plasticizer absorber niblastograph, put 100 parts of vinyl chloride resin and 50 parts of dioctyl phthalate into a container kept at 80°C, and mix the mixture every hour while stirring. Record the torque and display the kneading time at the point at which the crosstalk torque decreased.

(4) Residual vinyl chloride monomer: A certain amount of vinyl chloride resin was dissolved in tetrahydrofuran, and the vinyl chloride monomer content in the vinyl chloride resin was determined by gas chromatography.

P, B(1)'IJN As is clear from the above examples, the dispersion stabilizer consisting of the dispersion aid of the present invention makes the vinyl chloride polymer particles more porous than the conventional polyvinyl alcohol polymer. It exhibits excellent performance such as very high capacity, high plasticizer absorption rate, and easy removal of residual vinyl chloride, and also has a large particle size and smooth distribution, making it easy to handle during handling. It is a suspension polymer with excellent performance such as less scattering of powder and good penetration into molding machines, etc., and is excellent as a dispersion stabilizer for suspension polymerization.

Patent applicant RiRashi Co., Ltd.

Claims (4)

[Claims] (1) Saponification degree of less than 50 mol% and average polymerization degree of 400
A dispersion aid for suspension polymerization of a vinyl compound consisting of 0 or more polyvinyl ester polymers. (2) The dispersion aid according to claim 1, wherein the vinyl compound is vinyl chloride. (3) A dispersion stabilizer for suspension polymerization of vinyl compounds, containing 5 to 70% by weight of the dispersion aid according to claim 1 or 2. (4) 30 to 95% by weight of polyvinyl alcohol polymer with a saponification degree of 60 to 90 mol% and a polymerization degree of 500 or more
The dispersion stabilizer according to claim 3, which contains the dispersion stabilizer according to claim 3.