JPH02145604A - Dispersion stabilizer for suspension polymerization of vinyl-based compound - Google Patents

Abstract

PURPOSE:To obtain the title stabilizer providing polymer particles having uniform and sharp particle diameter distribution and high packing specific gravity, comprising PVA prepared by saponifying a polyvinyl ester in a specific solvent in the presence of an organic sulfonic acid catalyst and water. CONSTITUTION:First, a polyvinyl ester (preferably polyvinyl acetate) is saponified in a solvent comprising a cyclic polyoxyalkylene compound (preferably 1, 4-dioxane) shown by the formula (R<1> and R2 are alkylene which is replaceable with lower alkyl and contains 2-4C main chain; m and n are 0-6 and m+n>=2) in the presence of an organic sulfonic acid (e.g., benzenesulfonic acid) as a catalyst and water. Then the prepared PVA having 65-95mol% degree of saponification is used as a dispersion stabilizer for suspension polymerization of vinyl- based compound. The PVA has preferably 700-2,500 polymerization degree.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Industrial Field of Application The present invention relates to a dispersion stabilizer used in suspension polymerization of vinyl compounds in an aqueous medium, and particularly to a dispersion stabilizer used for suspension polymerization of vinyl compounds or other monomers that can be copolymerized with vinyl chloride. The present invention relates to a dispersion stabilizer used when suspension polymerizing a monomer mixture (hereinafter collectively referred to as vinyl chloride monomer) in an aqueous medium.

B. Prior art When producing vinyl chloride resins 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 melting medium. <
It has been implemented. In general, factors that control the quality of the resin include the polymerization rate, water-motsumer 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 (1) a function that shows high dispersion power even when used in a small amount and sharpens the particle size distribution of the resulting vinyl chloride polymer particles as much as possible; (11) In order to increase the absorption rate of plasticizer and facilitate processability, and to facilitate the removal of vinyl chloride monomer remaining in polymer particles, it is also necessary to reduce the amount of fish in molded products. G11) It has the function of making each polymer particle as uniform and porous as possible in order to prevent the formation of eyes, etc., and G11) It has the function of creating polymer particles with a high filling specific gravity.

Conventionally, dispersion stabilizers for suspension polymerization of vinyl compounds have been obtained by saponifying cellulose-conducting conductors such as methyl cellulose and hydroxypropyl methyl cellulose, or polyvinyl esters using an alkali catalyst (hereinafter abbreviated as alkali saponification). polyvinyl alcohol (
(hereinafter abbreviated as PvA), or saponification using an acid catalyst in an alcoholic solvent (hereinafter abbreviated as acid saponification)
It is known that PVA etc. obtained by the above methods can be used alone or in combination.

However, these have disadvantages in that the particle size distribution of the vinyl chloride polymer particles is broad and the packed specific gravity tends to decrease. Especially in recent years, in order to improve the operating rate of polymerization tanks,
It is required to add vinyl chloride polymer to water at a temperature close to the polymerization temperature, for example, 40°C or higher. The reality is that particles cannot be obtained.

C Problems to be Solved by the Invention The present inventors have overcome these drawbacks and solved the above-mentioned (1) to (ii).
As a result of intensive research to develop a dispersion stabilizer that simultaneously satisfies the required performance (i), we were surprised to find that.

- Formula % Formula % (1) (R1 and R2 represent a fullkylene group having 2 to 4 carbon atoms in the main chain, which may be substituted with a lower alkyl group, and m and n are 0 or an integer of 1 to 6. PVA obtained by saponifying polyvinyl ester in the presence of water using an organic sulfonic acid as a catalyst in a reaction system using a cyclic polyoxyalkylene compound represented by m+n22) as a solvent, and having a saponification degree of 65 to PV of 95 molti
When A is used as a dispersion stabilizer, the resulting vinyl chloride polymer particles have almost the same particle size distribution with good reproducibility, have a sharp particle size distribution, each particle is porous, and have excellent uniformity. , and the filling specific gravity is also large, etc. (1) ~
The present invention has been completed by devising a method that satisfies all of the performance requirements (iii).

D Means for Solving the Problems The dispersion stabilizer of the present invention has the general formula (R1 and R2 represent an alkylene group having 2 to 4 carbon atoms in the main chain which may be substituted with a lower alkyl group, 0m and n is 0 or an integer from 1 to 6 and m+n≧2) In a reaction system using a cyclic polyoxyalkylene compound as a solvent, polyvinyl ester is saponified using an organic sulfonic acid as a catalyst in the presence of water. It is obtained by

F! is a specific example of the cyclic polyoxyalkylene compound represented by the general formula (1) used as a solvent during acid saponification. %
1.4-dioxane% 2-methyl-1,4-dioxane, 2-ethyl-1,4-dioxane, 2゜5-dimethyl-1,4-dioxane, 2-methyl-3-n-propyl-1, 4-dioxane, 2.3.5.6-tetramethyl-1,4-dioxane, 2,2,5.5-tetramethyl-1,4-dioxane, 1,4-dioxepane, 6
-Methyl-1,4-dioxepane, 1,5-dioxocane, 3,7-dimethyl-1,5-dioxocane, 1,6
-thioxecane, 1,4.7-) rioxacyclononane, 1,4.7.10-tetraoxacyclododecane,
Examples include 1,4,7,10.13-pentaoxacyclopentadecane, 1,4,7,10,13.16-hexaoxacyclooctadecane, among others 1
,4-dioxane is particularly preferred.

As acid catalysts, benzenesulfonic acid, p-toluenesulfonic acid, α- or β-naphthalenesulfonic acid, 3,4-dimethylbenzenesulfonic acid, 2-methyl-5-1-propylbenzenesulfonic acid, 1,5-naphthalene Disulfonic acid, 1,6-naphthalenedisulfonic acid [,2,7-naphthalenedisulfonic acid.

Examples include organic sulfonic acids such as methanesulfonic acid, ethanesulfonic acid% n-butanesulfonic acid, n-octanesulfonic acid wn-y'cansulfonic acid, 1-octanesulfonic acid% 1.2-ethanedisulfonic acid.

Examples of the vinyl ester include vinyl formate, vinyl acetate, vinyl butyrate, vinyl pivalate, vinyl versatate, and vinyl acetate is preferred from an industrial standpoint.

The dispersion stabilizer of the present invention can be obtained by saponifying the vinyl ester polymer in the solvent of the cyclic polyoxyalkylene compound represented by the general formula (1) using the acid catalyst in the presence of water. However, the degree of saponification of PVA is preferably 65 to 95 mol, more preferably 70 to 85 mol. If the degree of saponification is outside this range, stable polymerization cannot be carried out.

Further, the degree of polymerization of PVA is preferably 500 to 3000,
More preferably, a range of 700 to 2,500 provides the best performance.

The dispersion stabilizer of the present invention can be used alone, but one or more nonionic surfactants and/or anionic surfactants can be used as dispersion aids during polymerization, and in addition, conventionally known alkali saponification It is also possible to use PVA and a small amount of partially saponified PVA with a saponification degree of 55 molar or less.

The dispersion stabilizer of the present invention is generally used as an aqueous solution or aqueous dispersion, and the amount of dispersion stabilizer used is 0.01 to 1% by weight, preferably 0.02 to 0.5% by weight based on the vinyl chloride monomer. % used The vinyl chloride monomer mentioned above is vinyl chloride monomer alone or vinylidene halide which can be copolymerized with vinyl chloride monomer.

Vinyl ether, vinyl acetate, acrylic acid, methacrylic acid and their esters, maleic acid and its anhydride, itaconic acid, styrene, etc. are used.

Further, 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.

E Function and Effects of the Invention The dispersion stabilizer of the present invention is specially designed to be obtained by acid saponifying polyvinyl ester in a reaction using a cyclic polyoxyalkylene compound represented by formula (1) as a solvent. The dispersion stabilizer of the present invention is PVA% obtained by a conventionally known alkali saponification method or PVA% obtained by acid saponification in an alcoholic solvent.
Compared to the case where PVC is used as a dispersion stabilizer, vinyl chloride polymer particles with a sharper particle size distribution, each particle being porous and more uniform, and with a larger packed specific gravity can be obtained. There is a big advantage.

Furthermore, in the suspension polymerization of vinyl chloride compounds among vinyl compounds, usually vinyl chloride 7th polymer is added to an aqueous dispersion stabilizer solution at room temperature, and after dispersing it, the temperature is raised to the polymerization temperature and polymerization is carried out. However, in the case of the dispersion stabilizer of the present invention, when the vinyl chloride monomer is added to the dispersion stabilizer aqueous solution at room temperature, and at 40°C at a temperature close to the polymerization temperature,
This method has extremely high industrial value, as very good results can be obtained even when the monomer is introduced into an aqueous dispersion stabilizer solution at a temperature of 0.degree. C. or higher.

The above explanation has mainly been about vinyl chloride monomers, but the dispersion stabilizer of the present invention can also be used in addition to vinyl chloride monomers.
Styrenic monomers (meth)acrylic acid ester monomers can also be used in the same manner.

The present invention will be explained in more detail with reference to Examples below, but the dispersion stabilizer of the present invention is not limited to these Examples. In the examples, 1 part indicates part by weight.

Implementation @1-5 As an example of the method for producing PVA by acid saponification, 1.4
A synthesis example using an acid hydrolysis method using para-toluenesulfonic acid as a catalyst in a -dioxane solvent is shown below.

(Synthesis example) Polyvinyl acetate (polymerization degree 2200. Hereinafter referred to as P V Ac) was placed in a simple glass reaction apparatus equipped with a thermometer, an electromagnetic stirrer, a heating device, a sample inlet, a sample outlet, and a pressure gauge. Abbreviation) B□y (0.93 mol in terms of ester residue in pVAc) and 1.4-dioxane 18
After charging 01 and sufficiently replacing the 1 reaction system with nitrogen gas,
The temperature was raised until the internal temperature reached 80°C, and PVAc was dissolved under stirring. After dissolving PVAc, in an atmosphere of dissolved ions, transfer p-)luenesulfone e-1 hydrate 14F (
A solution of 0,074 mol) dissolved in 502 (2,78 mol) water was added all at once, and the internal temperature was raised to 100°C while it was left standing.
(gauge pressure 0.7 Ky/crs) o
After confirming that the internal temperature is constant at 100℃, turn the engine to 350 rpm.
Stirring was started at a stirring speed of , and the saponification reaction was carried out. The reaction solution was a colorless, transparent, viscous, homogeneous solution. Reaction start 20
After a few minutes, precipitation of PVA was observed in the reaction system, but the i
Stirring was continued for 50 minutes to carry out the reaction. Thereafter, stirring was stopped, and after cooling the reaction mixture, the precipitated PVA was separated and recovered from the reaction mixture. The recovered PVA was white and no coloration was observed.

The produced PVA was cut into small pieces, washed with 1,4-dioxane, and dried under reduced pressure in a water bath at 40°C. As a result of measuring the degree of saponification of the dried PVA using a titration method, the degree of saponification was 75 mol.

The solution portion after completion of the reaction was colorless and transparent, and analysis using gas chromatography confirmed that cyacetic acid was quantitatively produced.

PVA of Examples 1 to 5 in Table 1 was prepared in the same manner as in the synthesis example.
was synthesized.

(1) Suspension polymerization of vinyl chloride: 4 quarts of deionized water in a 204 glass lined autoclave
0 parts (the water temperature is shown in Table 1), a dispersion stabilizer (the type and amount of dispersion stabilizer used are shown in Table 1), and 50% by weight of diisopropyl peroxydicarbonate) toluene solution 0.028 53 mH inside the autoclave.
After removing oxygen by degassing until f, a total of 30 parts of vinyl chloride monomer at room temperature was charged, and a blue margin type stirring blade 6 was added.
Polymerization was carried out by raising the temperature to 57° C. while stirring at 20 rpm.

At the start of polymerization, the pressure inside the autoclave was 8.5 V4/
dG, but 6.5 Kt/10 hours after the start of polymerization.
Since crAG was formed, the polymerization was stopped at this point, unreacted vinyl chloride salt was purged, and the contents were taken out and dehydrated and dried.

(2) Performance evaluation results of vinyl chloride resin: Table 2 shows the performance of the obtained vinyl chloride resin.

The polymerization yield of vinyl chloride resin is 92%, and the average degree of polymerization is 1.
It was 100.

Comparative Examples 1 to 5 Comparative Examples 1 to 5 were carried out in the same manner as Examples 1 to 5 except that the dispersion stabilizers shown in Table 1 were used instead of the dispersion stabilizers in Examples 1 to 5. The results are shown in Table-2.

/ / / / / / (1) Particle size distribution: Measured by dry high analysis using a wire mesh based on Tyler mesh.

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

(3) Uniformity of particle porosity: 100 parts% vinyl chloride resin
A mixture of 50 parts of DOP, 1 part of dibutyltin maleate, 1 part of cetyl alcohol, 0.25 parts of titanium white, and 0.1 part of carbon black was kneaded with a roll at 150°C for a predetermined time to form a sheet with a wall thickness of 0.2 fl. The number of fish eyes contained in the 100oA sheet was counted by transmitting light through the sheet. This shows that the shorter the fish eyes disappear, the better the uniformity of the particle porosity7.

(4) Using a planetary mixer connected to a plasticizer-absorbing niblastograph, put 100 parts of vinyl chloride resin and 50 parts of dioctyl phthalate into a container kept at 80°C, and add it every hour while stirring. Record the kneading torque and display the crosstalk time at the point where the crosstalk torque decreased.

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.

Patent applicant: RiRashi Co., Ltd.

Claims (4)

[Claims] (1) General formula ▲ Numerical formulas, chemical formulas, tables, etc. ▼... (1) (R^1 and R^2 have 2 to 4 carbon atoms in the main chain, which may be substituted with a lower alkyl group. represents an alkylene group,
m and n are 0 or integers of 1 to 6, and m+n≧2) In a reaction system using a cyclic polyoxyalkylene compound as a solvent, polyvinyl ester is saponified using an organic sulfonic acid as a catalyst in the presence of water. Polyvinyl alcohol obtained by
A dispersion stabilizer for suspension polymerization of a vinyl compound, characterized in that the content is 95 mol %. (2) The dispersion stabilizer according to claim (1), wherein the solvent represented by general formula (1) is 1,4-dioxane, and the polyvinyl ester is polyvinyl acetate. (3) Polymerization degree of polyvinyl alcohol is 500 to 300
The dispersion stabilizer according to claim 1, wherein the dispersion stabilizer has a molecular weight of 0. (4) Claim (1) in which the vinyl compound is vinyl chloride.
The dispersion stabilizer described in.