JPWO2020050106A1 - Method for Producing Dispersion Aid for Suspension Polymerization and Vinyl Resin - Google Patents

Abstract

It is a dispersion aid for suspension polymerization with excellent handleability, and when the dispersion aid for suspension polymerization is used for suspension polymerization of a vinyl compound, the formation of coarse particles is small and the absorbability of the plasticizer is high. Provided is a dispersion aid for suspension polymerization that can obtain high vinyl resin particles. A dispersion aid for suspension polymerization of a vinyl compound containing a vinyl ester polymer having an acid value (KOH mg / g) of 5 or more and less than 100.

Description

The present invention relates to a dispersion aid for suspension polymerization, particularly a vinyl compound, particularly a dispersion aid for suspension polymerization suitable for suspension polymerization of vinyl chloride.

Industrially, the production of vinyl-based polymers such as vinyl chloride-based resins is carried out by a suspension polymerization method in which a vinyl-based compound is dispersed in a water-soluble medium in the presence of a dispersant and polymerization is carried out using an oil-soluble catalyst. Widely implemented. In general, factors that control the quality of the resin include the polymerization rate, the water-monomer ratio, the polymerization temperature, the amount and preparation time of the polymerization initiator, the type of the polymerization tank, the stirring speed or the type and amount of the dispersant, and the like. However, it is said that the effect of the dispersant is large among these.

The performance required for the dispersant for suspension polymerization of vinyl compounds is as follows: (1) The suspension polymerization stability is remarkably excellent even when a small amount is used, and the particle size distribution of the obtained vinyl polymer particles is made as sharp as possible. (2) Increase the absorption rate of the plasticizer into the polymer particles to facilitate the processability of the polymer, and facilitate the removal of monomers such as vinyl chloride remaining in the polymer particles. In addition, in order to prevent the formation of fish eyes and the like in the molded product, it has a function of making it porous, (3) has a function of forming polymer particles having a large bulk specific gravity, and (4) has good handleability. And so on.

The level of demand for these performances (1) to (4) is increasing day by day. In particular, regarding the removability of the monomer component described in (2) above, the regulation of the amount of residual monomer is at a very high level from the viewpoint of the environment. Further, when it is difficult to remove the vinyl chloride monomer remaining in the particles in the drying step after the completion of the polyvinyl chloride polymerization, it is necessary to dry for a long time or under high temperature conditions in order to remove the residual monomer, but at the same time, the polyvinyl chloride is dried. There is also concern about deterioration of vinyl resin. Regarding the handleability described in (4) above, the use of an organic solvent such as methanol has not been preferred in recent years due to environmental problems, and the dispersant for suspension polymerization can be used in the form of an aqueous liquid. There is a request for.

As the dispersant for suspension polymerization, a main dispersant of a polyvinyl alcohol-based resin (hereinafter, may be abbreviated as PVA) is mainly used. Among them, PVA having a saponification degree of 65 to 99 mol% is used as a main dispersant, and PVA having a saponification degree of less than 65 mol% is often used as a dispersion aid. The main dispersant is mainly used with the expectation of the performances of (1) and (3), and the dispersion aid is mainly used with the expectation of the performance of (2). Further, the performance of (4) is required for all the dispersants used.

As such a dispersion aid, a polyvinyl alcohol-based polymer having an ionic group at one end and a saponification degree of 10 to 85 mol% (Patent Document 1) or a polymer composed of vinyl acetate and an unsaturated carboxylic acid is saponified. Polyvinyl alcohol-based polymer (Patent Document 2), a vinyl alcohol-based polymer having a saponification degree of 35 mol% or more and 65 mol% or less and an aliphatic hydrocarbon group having 6 or more and 12 or less carbon atoms at the terminal (Patent Document 3). ) Etc. have been proposed.

Japanese Unexamined Patent Publication No. 10-168128 Japanese Unexamined Patent Publication No. 2013-203994 International Publication No. 2015/019614

However, in response to the performance requirements of (1) to (4) that have increased in recent years, dispersion aids of vinyl compounds that sufficiently satisfy these required performances, including the dispersion aids using PVA described in Patent Documents 1 to 3, are assisted. It is hard to say that the agent exists. Further, since the conventional dispersion aid is produced by polymerizing a vinyl ester-based monomer to obtain a vinyl ester-based polymer and then performing a saponification reaction with an alkali or the like, the solvent used in the saponification reaction is contained in the product. There are drawbacks that there is a concern that it will remain and that the process will be long and costly.

Therefore, the present invention is a dispersion aid for suspension polymerization having excellent handleability, and when the dispersion aid for suspension polymerization is used for suspension polymerization of a vinyl-based compound, the formation of coarse particles is small. One of the problems is to provide a dispersion aid for suspension polymerization capable of obtaining vinyl-based resin particles having high absorbability of a plasticizer. Furthermore, one of the other problems of the present invention is to provide a method for producing a vinyl resin using such a dispersion aid for suspension polymerization.

As a result of intensive research to solve the above problems, the present inventors have dispersed vinyl ester polymers having an acid value (KOH mg / g) of 5 or more and less than 100 for suspension polymerization of vinyl compounds. We have found that it is effective to use it as an auxiliary agent.

Therefore, in one aspect, the present invention is a dispersion aid for suspension polymerization containing a vinyl ester polymer having an acid value (KOH mg / g) of 5 or more and less than 100.

In one embodiment of the dispersion aid for suspension polymerization according to the present invention, the vinyl ester-based polymer is a vinyl acetate-based polymer.

In another embodiment of the dispersion aid for suspension polymerization according to the present invention, the vinyl ester polymer has a viscosity average degree of polymerization of 100 to 1000.

In still another embodiment of the dispersion aid for suspension polymerization according to the present invention, the degree of saponification of the vinyl ester polymer is 5 mol% or less.

In still another embodiment of the dispersion aid for suspension polymerization according to the present invention, the vinyl ester-based polymer is contained in an amount of 60% by mass or more.

In still another embodiment of the dispersion aid for suspension polymerization according to the present invention, the acid value (KOH mg / g) of the vinyl ester polymer is 10 or more and less than 40.

In another aspect of the present invention, the dispersion aid for suspension polymerization according to the present invention is used to obtain a vinyl-based compound monomer or a mixture of a vinyl-based compound monomer and a monomer copolymerizable therewith. Is a method for producing a vinyl-based resin, which comprises dispersing the material in water and carrying out suspension polymerization.

The present invention is a dispersion aid for suspension polymerization having excellent handleability, and when the dispersion aid for suspension polymerization is used for suspension polymerization of a vinyl-based compound, formation of coarse particles is small and a plasticizer. A dispersion aid for suspension polymerization capable of producing vinyl-based resin particles having high absorbency can be obtained.

Hereinafter, embodiments for carrying out the present invention will be described in detail. The present invention is not limited to the embodiments described below.

The vinyl ester-based polymer contained in the dispersion aid for suspension polymerization according to the embodiment of the present invention has an acid value (KOH mg / g) of 5 or more and less than 100 from the viewpoint of water solubility and performance. is important. If the acid value is less than 5 mg / g, the water solubility becomes insufficient, which is a practical problem in terms of handling. Therefore, the acid value needs to be 5 mg / g or more, preferably 7 mg / g or more, and more preferably 10 mg / g or more. Further, when the acid value is 100 mg / g or more, the dispersion system becomes unstable and coarse particles of the obtained vinyl-based resin particles are generated, which causes a practical problem. Therefore, the acid value needs to be less than 100 mg / g, preferably less than 90 mg / g, more preferably less than 80 mg / g, even more preferably less than 70 mg / g, 60 mg. It is even more preferably less than / g, even more preferably less than 50 mg / g, more preferably less than 40 mg / g, and even more preferably less than 30 mg / g.

The acid value is measured according to JIS K0070: 1992. That is, it is obtained from the amount of potassium hydroxide required for neutralizing the vinyl ester polymer.

The vinyl ester-based polymer contained in the dispersion aid for suspension polymerization according to the embodiment of the present invention has a saponification degree of preferably 5 mol% or less, more preferably 2 mol% or less, still more preferably. Is less than 1 mol%. The saponification degree can also be set to 0 mol%. Reducing the degree of saponification is economically advantageous because the saponification process can be omitted or shortened, and it is also advantageous for increasing the acid value.

The saponification degree of the vinyl ester polymer is measured by a method according to JIS-K6726: 1994. That is, it is obtained from back titration using N / 10 sulfuric acid specified in JIS-K8951: 2006 and N / 10 sodium hydroxide solution specified in JIS-K8576: 2019.

The method for producing the vinyl ester-based polymer contained in the dispersion aid for suspension polymerization according to the embodiment of the present invention is not particularly limited, but an unsaturated carboxylic acid coexists when the vinyl ester-based monomer is radically polymerized. The method of polymerization underneath is convenient.

Examples of the unsaturated carboxylic acid used in the present invention include, but are not limited to, crotonic acid, isocrotonic acid, itaconic acid, maleic acid, fumaric acid, and (meth) acrylic acid. One type of unsaturated carboxylic acid may be used, or two or more types may be used in combination. The use of crotonic acid is most preferable because of its reactivity ratio with vinyl ester and ease of handling.

Vinyl ester-based monomers include, but are not limited to, vinyl acetate, vinyl formate, vinyl propionate, vinyl valerate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pivalate, and versa. Examples include vinyl tickate. One type of vinyl ester-based monomer may be used, or two or more types may be used in combination. The use of vinyl acetate is most preferable in terms of availability, handling, and economy.

The viscosity average degree of polymerization of the vinyl ester polymer contained in the dispersion aid for suspension polymerization is preferably 100 or more from the viewpoint of dispersion stability and production efficiency when suspend polymerization of the vinyl compound. When the viscosity average degree of polymerization is less than 100, the dispersion system tends to be unstable when the vinyl compound is suspension-polymerized, and the particle size of the obtained vinyl resin tends to be coarsened. In addition, since the softening temperature of the dispersion aid for suspension polymerization is lowered, it becomes easy to block in the drying step, which makes production difficult. Therefore, the viscosity average degree of polymerization is preferably 100 or more, more preferably 150 or more, and even more preferably 200 or more. In addition, the viscosity average degree of polymerization of the vinyl ester polymer contained in the dispersion aid for suspension polymerization is obtained when the vinyl ester compound is suspended and polymerized to prevent the aqueous solution from becoming too viscous and difficult to handle. In order to increase the porosity of the particles to be obtained and enhance the plasticizer absorbability, the content is preferably 1000 or less, more preferably 800 or less, and even more preferably 600 or less.

The viscosity average degree of polymerization is measured according to JIS K6725: 1977. That is, the vinyl ester-based polymer contained in the dispersion aid for suspension polymerization is determined from the ultimate viscosity [η] measured in acetone at 30 ° C.

The polymerization method of the vinyl ester-based polymer contained in the dispersion aid for suspension polymerization according to the embodiment of the present invention is not particularly limited, and the polymerization method includes batch polymerization, semi-batch polymerization, continuous polymerization, and semi-continuous polymerization. It may be any of. The monomers may be charged all at once, may be charged separately, or may be added continuously or intermittently. Further, known polymerization methods such as solution, emulsification, suspension, and bulk polymerization are arbitrarily used, but the method in which no solvent remains after polymerization and the polymer is obtained in particles does not leave a solvent in the product and is easy to dry. From the point of view, it is preferable, and the suspension polymerization method is preferable.

At this time, other monomers may be further copolymerized as long as the effects of the present invention are not impaired. Specific examples of other monomers include olefins such as ethylene and propylene, maleic acid dialkyl esters, fumaric acid dialkyl esters, and alkyl vinyl ethers.

The polymerization initiator for radical polymerization of vinyl ester-based monomers is not particularly limited, but is azobisisobutyronitrile, azobis-2,4-dimethylvaleronitrile, and azobis (4-methoxy-2, 4-Dimethylvaleronitrile), azobisdimethylvaleronitrile, azo compounds such as azobismethoxyvaleronitrile, acetyl peroxide, benzoyl peroxide, lauroyl peroxide, acetylcyclohexylsulfonyl peroxide, 2,4,4-trimethylpentyl- Peroxides such as 2-peroxyphenoxyacetate, percarbonate compounds such as diisopropylperoxydicarbonate, di-2-ethylhexyl peroxydicarbonate, diethoxyethylperoxydicarbonate, α-cumylperoxyneodecanoate , T-Butylperoxyneodecanoate and other perester compounds can be used alone or in combination of two or more.

Further, when the copolymerization is carried out at a high temperature, aldehydes due to oxidative decomposition of the vinyl ester-based monomer are generated to form a condensate, which may cause coloring or the like. In that case, for the purpose of preventing coloration, an antioxidant such as citric acid may be added to the polymerization system by about 1 ppm or more and 100 ppm or less (relative to the total mass of the vinyl ester-based monomer).

The dispersion aid for suspension polymerization according to one embodiment of the present invention contains 60% by mass of a vinyl ester polymer having an acid value (KOH mg / g) of 5 or more and less than 100 from the viewpoint of exhibiting desired performance. It is preferably contained in an amount of% or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more. Further, the dispersion aid for suspension polymerization of the present invention may contain various additives as long as the gist of the present invention is not impaired. Examples of the additive include polymerization regulators such as aldehydes, halogenated hydrocarbons and mercaptans; polymerization inhibitors such as phenol compounds, sulfur compounds and N-oxide compounds; pH regulators; cross-linking agents; preservatives. ; Antifungal agent, antiblocking agent; antifoaming agent and the like.

The dispersion aid for suspension polymerization according to one embodiment of the present invention can be particularly preferably used for suspension polymerization of vinyl compounds. Vinyl-based compounds include vinyl halides such as vinyl chloride; vinyl esters such as vinyl acetate and vinyl propionate; acrylic acids, methacrylic acids, esters and salts thereof; maleic acid, fumaric acid, esters and anhydrides thereof; Examples thereof include styrene, acrylonitrile, vinylidene chloride, vinyl ether and the like. Among these, the dispersion aid for suspension polymerization of the present invention is particularly preferably used for suspension polymerization of vinyl chloride alone or with a monomer capable of copolymerizing vinyl chloride with vinyl chloride. Used. Monomers that can be copolymerized with vinyl chloride include vinyl esters such as vinyl acetate and vinyl propionate; (meth) acrylate esters such as methyl (meth) acrylate and ethyl (meth) acrylate; ethylene, Α-olefins such as propylene; unsaturated dicarboxylic acids such as maleic anhydride and itaconic acid; acrylonitrile, styrene, vinylidene chloride, vinyl ether and the like can be mentioned.

The dispersion aid for suspension polymerization according to one embodiment of the present invention is suitable for producing a vinyl chloride resin for soft in terms of producing vinyl chloride resin particles having excellent plasticizer absorbability, but has a demonomerizing property. It can also be applied to the production of hard vinyl chloride resin because it has an excellent particle size distribution.

The dispersion aid for suspension polymerization according to one embodiment of the present invention can be used alone, but can also be used in combination with other stabilizers such as cellulosic derivatives and surfactants.

Since the dispersion aid for suspension polymerization according to one embodiment of the present invention has a large amount of plasticizer absorbed, by using this, the resin particles are porous and the fish eyes are few, and the physical characteristics are very excellent. Vinyl chloride resin is always available. Hereinafter, the method for polymerizing a vinyl compound will be specifically described with reference to examples, but the method is not limited thereto.

In the case of producing resin particles of a vinyl-based compound such as vinyl chloride resin particles, in one embodiment, 0.01 mass by mass of the above-mentioned dispersion aid for suspension polymerization is added to 100 parts by mass of the vinyl-based compound monomer. Parts to 0.3 parts by mass, preferably 0.02 parts by mass to 0.10 parts by mass are added. The ratio of the vinyl compound to water can be a mass ratio of vinyl compound: water = 1: 0.9 to 1: 3, preferably vinyl compound: water = 1: 1 to 1: 1. It is 5.

The polymerization initiator may be one conventionally used for the polymerization of vinyl compounds, which includes percarbonates such as diisopropyl peroxy dicarbonate, di-2-ethylhexyl peroxy dicarbonate, and diethoxyethyl peroxy dicarbonate. Compounds, perester compounds such as t-butylperoxyneodecanoate, α-cumylperoxyneodecanoate, acetylcyclohexylsulfonyl peroxide, 2,4,4-trimethylpentyl-2-peroxyphenoxyacetate and the like. Peroxide, azo compounds such as azobis-2,4-dimethylvaleronitrile and azobis (4-methoxy-2,4-dimethylvaleronitrile), and potassium persulfate, ammonium persulfate, hydrogen peroxide and the like alone or in combination. Can be used.

Further, it is also optional to add a polymerization regulator, a chain transfer agent, a gelation improver, an antistatic agent, a PH regulator and the like, which are appropriately used for the polymerization of vinyl compounds.

In carrying out the polymerization of the vinyl compound, the charging ratio of each component, the polymerization temperature and the like may be determined according to the conditions conventionally adopted in the suspension polymerization of the vinyl compound, and there is no particular reason for limitation.

Hereinafter, the present invention will be described in more detail with reference to examples.
Unless otherwise specified, "parts" and "%" mean "parts by mass" and "% by mass".

(Example 1)
<Manufacturing of dispersion aid for suspension polymerization> 97 parts of vinyl acetate, 180 parts of water, 0.3 part of polyvinyl alcohol (W-20N manufactured by Denka Co., Ltd.) as a dispersant, normal butylaldehyde (nBA) 1 as a chain transfer agent. .6 parts, 3 parts of crotonic acid and 0.9 parts of azobisisobutyronitrile were placed in a polymerization can, heated to polymerize at 60 ° C., and polymerized for 7 hours. The polymerization rate at the end of polymerization was measured by the method shown below. Then, unpolymerized vinyl acetate was removed by a conventional method, and the obtained vinyl ester-based polymer was flow-dried at 40 ° C. to obtain a dispersion aid A for suspension polymerization. In this example, no additive is added, and the vinyl ester-based polymer itself constitutes the dispersion aid A for suspension polymerization. The obtained dispersion aid A for suspension polymerization was evaluated for viscosity average degree of polymerization, saponification degree, acid value and water solubility by the methods shown below, and the evaluation results are shown in Table 1.

[Polymerization rate]
The polymerization rate was determined by a gravimetric method after sampling a small amount of vinyl ester monomer and vinyl ester-based polymer particles in a state of being uniformly dispersed in water, and drying the sampled solution at 150 ° C. for 30 minutes.

[Viscosity average degree of polymerization]
According to JIS K6725: 1977, the obtained dispersion aid A for suspension polymerization was determined from the ultimate viscosity [η] measured in acetone at 30 ° C.

[Saponification degree]
The degree of saponification of the obtained dispersion aid A for suspension polymerization was determined according to JIS-K6726: 1994.

[Acid value]
It was determined from the amount of potassium hydroxide required for neutralization of the obtained dispersion aid A for suspension polymerization in accordance with JIS K0070: 1992.

[Water soluble]
After adding 10 parts of the dispersion aid A for suspension polymerization to 90 parts of water, sodium carbonate was added so that the pH became 7.5-8.5, and the mixture was stirred at room temperature for 4 hours. The presence or absence was visually confirmed and evaluated according to the following criteria.
◯: It is a uniform solution or dispersion, and no precipitation has occurred.
X: Precipitation has occurred.

<Suspension Polymerization of Vinyl Chloride> 14 kg of water at 30 ° C. under stirring in a 30 L stainless steel autoclave equipped with a stirrer, and polyvinyl alcohol with a saponification degree of 80 mol% as the main dispersant (W-20N manufactured by Denka Co., Ltd.) ) 12 g, 2 g of the dispersion aid A for suspension polymerization obtained above, 4.6 g of t-butylperoxyneodecanoate as a polymerization initiator, and 1 g of α-cumylperoxyneodecanoate. is. After degassing the autoclave in vacuum, 10 kg of vinyl chloride monomer was added, and the mixture was polymerized at 57 ° C. for 4 hours.

<Evaluation of Vinyl Chloride Resin> The obtained vinyl chloride resin was evaluated for average particle size, particle size distribution, plasticizer absorption amount, and bulk specific gravity by the methods shown below, and the evaluation results are shown in Table 1.

[Average particle size, particle size distribution]
Sieves of 60 mesh (opening 250 μm), 80 mesh (opening 180 μm), 100 mesh (opening 150 μm), 150 mesh (opening 106 μm), 200 mesh (opening 75 μm) in accordance with JIS Z8815: 1994. The vinyl chloride resin obtained using the above is separated, and the particle size (D50) having a cumulative frequency of 50% is the average particle size, the particle size (D80) having a cumulative frequency of 80% and the particle size (D20) having a cumulative frequency of 20%. The difference between the two was used as the particle size distribution.

[Amount of plasticizer absorbed]
Measured according to ISO 4608: 1998 (E).

[Umbrella density]
Measured according to JIS K6720-2: 1999.

(Examples 2 to 3)
Dispersion aids B and C for suspension polymerization were obtained in the same manner as in Example 1 except that the amount of normal butyraldehyde added and the amount of crotonic acid added were changed to the conditions shown in Table 1. Next, suspension polymerization of vinyl chloride was carried out under the same conditions as in Example 1 except that the obtained dispersion aids B and C for suspension polymerization were used. Table 1 shows the evaluation results of the dispersion aids B and C for suspension polymerization and the vinyl chloride resin obtained by using them.

(Example 4)
97 parts of vinyl acetate, 180 parts of water, 0.3 part of polyvinyl alcohol (W-20N manufactured by Denka Co., Ltd.) as a dispersant, 1.4 parts of normal butyraldehyde (nBA) as a chain transfer agent, and azobisisobutyronitrile. 0.9 parts were charged into a polymerization can and heated to 60 ° C., and then polymerized while continuously adding itaconic acid for 6 hours so that the total addition amount was 1.0 part, and further polymerized for 1 hour. Table 1 shows the polymerization rate at the end of polymerization. Next, unpolymerized vinyl acetate was removed by a conventional method, and the obtained vinyl ester-based polymer was flow-dried at 40 ° C. to obtain a dispersion aid D for suspension polymerization. In this example, no additive is added, and the vinyl ester polymer itself constitutes the dispersion aid D for suspension polymerization. The obtained dispersion aid D for suspension polymerization was evaluated for viscosity average degree of polymerization, saponification degree, acid value and water solubility by the same method as in Example 1, and the evaluation results are shown in Table 1.

(Comparative Example 1)
Suspension polymerization of vinyl chloride was carried out under the same conditions as in Example 1 except that the dispersion aid for suspension polymerization was not used. The evaluation results of the vinyl chloride resin are shown in Table 1.

(Comparative Example 2)
A dispersion aid E for suspension polymerization was obtained in the same manner as in Example 1 except that the amount of crotonic acid added was changed to the conditions shown in Table 1. The obtained dispersion aid E for suspension polymerization did not show water solubility. Next, suspension polymerization of vinyl chloride was carried out under the same conditions as in Example 1 except that the obtained dispersion aid E for suspension polymerization was used. Table 1 shows the evaluation results of the dispersion aid E for suspension polymerization and the vinyl chloride resin obtained by using the dispersion aid E.

(Comparative Example 3)
A dispersion aid F for suspension polymerization was obtained in the same manner as in Example 1 except that the amount of normal butyraldehyde added and the amount of crotonic acid added were changed to the conditions shown in Table 1. The obtained dispersion aid F for suspension polymerization showed water solubility. Next, suspension polymerization of vinyl chloride was carried out under the same conditions as in Example 1 except that the obtained dispersion aid F for suspension polymerization was used, but vinyl chloride was blocked in the autoclave and the vinyl chloride particles were separated. I couldn't get it. Table 1 shows the evaluation results of the dispersion aid F for suspension polymerization.

(Comparative Example 4)
100 parts of vinyl acetate, 150 parts of methanol (solvent and chain transfer agent), and 0.03 part of azobisisobutyronitrile (as a 1% methanol solution) were placed in a polymerization can and placed at 60 ° C. in a nitrogen atmosphere. Polymerization was carried out for 8 hours. Table 1 shows the polymerization rate at the end of polymerization. Then, unpolymerized vinyl acetate was removed by a conventional method, and the solvent of the vinyl ester-based polymer was removed by drying to obtain a dispersion aid G for suspension polymerization. In this comparative example, no additive is added, and the vinyl ester-based polymer itself constitutes the dispersion aid G for suspension polymerization. The obtained dispersion aid G for suspension polymerization did not show water solubility. Next, suspension polymerization of vinyl chloride was carried out under the same conditions as in Example 1 except that the obtained dispersion aid G for suspension polymerization was used. Table 1 shows the evaluation results of the dispersion aid G for suspension polymerization and the vinyl chloride resin obtained by using the dispersion aid G.

(Comparative Example 5)
100 parts of vinyl acetate, 22.5 parts of methanol (solvent and chain transfer agent), 0.23 parts of 3-MPA (3-mercaptopropionic acid) of chain transfer agent, and azobisisobutyronitrile (1% methanol solution) As a result, 0.03 part was charged into a polymerization can and replaced with a nitrogen atmosphere. From the time when the mixture was heated to 60 ° C., 1.81 parts of a 10% methanol solution of mercaptopropionic acid was continuously added in 6 hours so as to be completely contained, and polymerization was carried out for 6 hours. Table 1 shows the polymerization rate at the end of polymerization. Then, unpolymerized vinyl acetate was removed by a conventional method, and the solvent of the vinyl ester-based polymer was removed by drying to obtain a modified vinyl ester-based polymer. The obtained modified vinyl ester polymer was dissolved in methanol to obtain a methanol solution having a polymer concentration of 35% in methanol. This was saponified with sodium hydroxide at 35 ° C. for 90 minutes. The amount of sodium hydroxide used was 7 mmol equivalent with respect to 1 mol of vinyl acetate unit of the obtained modified vinyl ester polymer. The dispersion aid H for suspension polymerization was obtained by filtration and drying. In this comparative example, no additive is added, and the vinyl ester-based polymer itself constitutes the dispersion aid H for suspension polymerization. The obtained dispersion aid H for suspension polymerization had a saponification degree of 43 mol% as measured in accordance with JIS K6726: 1994. Suspension polymerization of vinyl chloride was carried out under the same conditions as in Example 1 except that the obtained dispersion aid H for suspension polymerization was used. Table 1 shows the evaluation results of the dispersion aid H for suspension polymerization and the vinyl chloride resin obtained by using the dispersion aid H.

From the results shown in Table 1, the dispersion aid for suspension polymerization of the present invention is water-soluble and therefore has excellent handleability, and the vinyl resin obtained by suspension polymerization using this is absorbent with a plasticizer. It can be seen that the value is high and the formation of coarse particles is small. In Comparative Example 5, the reason why the acid value was low but water-soluble was that the hydroxyl group was introduced by saponification.

Claims (7)

A dispersion aid for suspension polymerization of a vinyl compound containing a vinyl ester polymer having an acid value (KOH mg / g) of 5 or more and less than 100. A dispersion aid for suspension polymerization of a vinyl compound in which the vinyl ester polymer is a vinyl acetate polymer. The dispersion aid for suspension polymerization according to claim 1 or 2, wherein the vinyl ester-based polymer has a viscosity average degree of polymerization of 100 to 1000. The dispersion aid for suspension polymerization according to any one of claims 1 to 3, wherein the degree of saponification of the vinyl ester polymer is 5 mol% or less. The dispersion aid for suspension polymerization according to any one of claims 1 to 4, which contains 60% by mass or more of the vinyl ester-based polymer. The dispersion aid for suspension polymerization according to any one of claims 1 to 4, wherein the acid value (KOH mg / g) of the vinyl ester polymer is 10 or more and less than 40. Using the dispersion aid for suspension polymerization according to any one of claims 1 to 6, a vinyl compound monomer or a mixture of a vinyl compound monomer and a monomer copolymerizable therewith. A method for producing a vinyl-based resin, which comprises dispersing the mixture in water and performing suspension polymerization.