JP7337075B2 - Dispersing aid for suspension polymerization and method for producing vinyl resin - Google Patents

Description

TECHNICAL FIELD The present invention relates to a dispersing aid for suspension polymerization, particularly a dispersing aid for suspension polymerization suitable for suspension polymerization of vinyl compounds, particularly vinyl chloride.

For the production of vinyl polymers such as vinyl chloride resins, the industrial suspension polymerization method involves dispersing a vinyl compound in the presence of a dispersant in a water-soluble medium and polymerizing it using an oil-soluble catalyst. Widely implemented. In general, the factors governing the quality of the resin include polymerization rate, water-monomer ratio, polymerization temperature, amount and charging time of polymerization initiator, type of polymerization tank, stirring speed or type and amount of dispersant. However, it is said that the influence of the dispersant is particularly large.

The properties required for a dispersant for suspension polymerization of a vinyl compound are as follows: (1) Remarkably excellent suspension polymerization stability when used in a small amount, and the particle size distribution of the resulting vinyl polymer particles to be 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; (3) it functions to form polymer particles having a large bulk specific gravity; (4) it is easy to handle; etc.

Demand levels for these performances (1) to (4) are increasing day by day. In particular, regarding the removability of the monomer components described in (2) above, the regulation of the amount of residual monomers is at a very high level from the environmental point of view. In addition, if it is difficult to remove the vinyl chloride monomer remaining in the particles in the drying process after polyvinyl chloride polymerization, drying for a long time or under high temperature conditions is required to remove the residual monomer. There is also concern about deterioration of the vinyl resin. Regarding the handleability described in (4) above, the use of organic solvents such as methanol is not preferred in recent years due to environmental concerns, and the dispersant for suspension polymerization can be used in the form of an aqueous liquid. I have a request for

As such a suspension polymerization dispersant, a main dispersant of polyvinyl alcohol resin (hereinafter sometimes abbreviated as PVA) is mainly used. Among them, PVA with a degree of saponification of 65 to 99 mol% is used as a main dispersant, and PVA with a degree of saponification of less than 65 mol% is often used as a dispersing aid. The main dispersant is used mainly expecting the performance of (1) or (3), and the dispersing aid is used expecting the performance of (2). Moreover, the performance of (4) is required for all dispersants used.

Such dispersing aids include a polyvinyl alcohol-based polymer having a saponification degree of 10 to 85 mol% having an ionic group at one end (Patent Document 1) or a polymer composed of vinyl acetate and unsaturated carboxylic acid. A polyvinyl alcohol polymer (Patent Document 2), a vinyl alcohol 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 end (Patent Document 3 ) have been proposed.

JP-A-10-168128 JP 2013-203994 A WO2015/019614

However, with respect to the performance requirements (1) to (4) that have increased in recent years, dispersing aids for vinyl compounds that fully satisfy these performance requirements, including dispersion aids using PVA described in Patent Documents 1 to 3, have been developed. It is difficult to say that the agent exists. In addition, conventional dispersing aids are produced by polymerizing vinyl ester monomers to obtain a vinyl ester polymer, and then performing a saponification reaction with an alkali or the like. There are disadvantages that there is a concern that it will remain, and that the process is long and costly.

Accordingly, the present invention provides a dispersing aid for suspension polymerization which is excellent in handleability, and when the dispersing aid for suspension polymerization is used for suspension polymerization of a vinyl compound, formation of coarse particles is small, An object of the present invention is to provide a dispersing aid for suspension polymerization, which enables vinyl-based resin particles having high plasticizer absorbability to be obtained. Another object 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 studies to solve the above problems, the present inventors have found that a vinyl ester polymer having an acid value (KOH mg/g) of 5 or more and less than 100 is used as a dispersion for suspension polymerization of a vinyl compound. It has been found to be effective to use it as an auxiliary agent.

Accordingly, one aspect of 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 polymer is a vinyl acetate 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 1,000.

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 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 vinyl ester polymer has an acid value (KOH mg/g) of 10 or more and less than 40.

In another aspect of the present invention, a vinyl compound monomer or a mixture of a vinyl compound monomer and a monomer copolymerizable therewith using the dispersion aid for suspension polymerization according to the present invention is dispersed in water to carry out suspension polymerization.

The present invention provides a dispersion aid for suspension polymerization that is excellent in handleability, and when the dispersion aid for suspension polymerization is used in the suspension polymerization of a vinyl compound, the formation of coarse particles is small, and the plasticizer It is possible to obtain a dispersing aid for suspension polymerization with which vinyl-based resin particles having high absorbability can be produced.

EMBODIMENT OF THE INVENTION Hereinafter, the form for implementing this invention is demonstrated in detail. In addition, this invention is not limited to embodiment described below.

The vinyl ester polymer contained in the dispersion aid for suspension polymerization according to one 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 poses a practical problem in terms of handling. Therefore, the acid value must be 5 mg/g or more, preferably 7 mg/g or more, and more preferably 10 mg/g or more. In addition, when the acid value is 100 mg/g or more, the dispersion system becomes unstable, resulting in the formation of coarse particles in the resulting vinyl resin particles, which poses practical problems. Therefore, the acid number should 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, and 60 mg/g. /g, even more preferably less than 50 mg/g, more preferably less than 40 mg/g, more preferably less than 30 mg/g.

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

The vinyl ester polymer contained in the dispersion aid for suspension polymerization according to one embodiment of the present invention preferably has a degree of saponification of 5 mol% or less, more preferably 2 mol% or less, and still more preferably. is 1 mol % or less. The degree of saponification can also be 0 mol %. Reducing the degree of saponification is economically advantageous because the saponification step can be omitted or shortened, and 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 determined by 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 polymer contained in the dispersion aid for suspension polymerization according to one embodiment of the present invention is not particularly limited. It is convenient to polymerize under

Examples of unsaturated carboxylic acids used in the present invention include crotonic acid, isocrotonic acid, itaconic acid, maleic acid, fumaric acid, and (meth)acrylic acid, but are not limited thereto. 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 preferred because of its reactivity ratio with the vinyl ester and ease of handling.

Vinyl ester 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. Vinyl tic acid and the like can be mentioned. One kind of vinyl ester monomer may be used, or two or more kinds may be used in combination. The use of vinyl acetate is most preferred from the standpoint of availability, handling, and economics.

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 during suspension polymerization of the vinyl compound. If the viscosity-average degree of polymerization is less than 100, the dispersion system tends to be unstable when the vinyl compound is subjected to suspension polymerization, and the resulting vinyl resin tends to have a coarse particle size. In addition, since the softening temperature of the dispersion aid for suspension polymerization is low, it tends to block during the drying process, making production difficult. Therefore, the viscosity average degree of polymerization is preferably 100 or more, even 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 important for preventing the aqueous solution from becoming difficult to handle due to an increase in viscosity, and for preventing the vinyl compound from being difficult to handle when the suspension polymerization is carried out. It is preferably 1000 or less, more preferably 800 or less, and even more preferably 600 or less, in order to increase the porosity of the particles to be formed and the plasticizer absorbability.

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

The polymerization method of the vinyl ester polymer contained in the dispersion aid for suspension polymerization according to one embodiment of the present invention is not particularly limited, and the polymerization method may be batch polymerization, semi-batch polymerization, continuous polymerization, or semi-continuous polymerization. Either The monomers may be charged all at once, may be charged in portions, or may be added continuously or intermittently. In addition, known polymerization methods such as solution, emulsion, suspension, bulk polymerization, etc. can be arbitrarily used, but a method in which no solvent remains after polymerization and the polymer is obtained in the form of particles leaves no solvent in the product and is easy to dry. point, and the suspension polymerization method is preferred.

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, dialkyl maleates, dialkyl fumarate, and alkyl vinyl ethers.

Polymerization initiators for radical polymerization of vinyl ester monomers are not particularly limited, but azobisisobutyronitrile, azobis-2,4-dimethylvaleronitrile, azobis(4-methoxy-2, 4-dimethylvaleronitrile), azo compounds such as azobisdimethylvaleronitrile, azobismethoxyvaleronitrile, acetyl peroxide, benzoyl peroxide, lauroyl peroxide, acetylcyclohexylsulfonyl peroxide, 2,4,4-trimethylpentyl- Peroxides such as 2-peroxyphenoxyacetate, peroxydicarbonate compounds such as diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, diethoxyethyl peroxydicarbonate, α-cumyl peroxyneodecanoate , t-butyl peroxyneodecanoate 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, aldehyde is generated due to oxidative decomposition of the vinyl ester monomer to form a condensate, which may cause coloration or the like. In that case, an antioxidant such as citric acid may be added to the polymerization system in an amount of 1 ppm or more and 100 ppm or less (with respect to the total mass of vinyl ester monomers) for the purpose of preventing coloration.

From the viewpoint of exhibiting desired performance, the dispersion aid for suspension polymerization according to one embodiment of the present invention contains 60 masses of a vinyl ester polymer having an acid value (KOH mg/g) of 5 or more and less than 100. % or more, more preferably 80 mass % or more, and even more preferably 90 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 such additives include polymerization modifiers such as aldehydes, halogenated hydrocarbons and mercaptans; polymerization inhibitors such as phenol compounds, sulfur compounds and N-oxide compounds; pH adjusters; cross-linking agents; antifungal agents, antiblocking agents; antifoaming agents and the like.

The dispersion aid for suspension polymerization according to one embodiment of the present invention can be suitably used particularly for suspension polymerization of vinyl compounds. Vinyl compounds include vinyl halides such as vinyl chloride; vinyl esters such as vinyl acetate and vinyl propionate; acrylic acid, methacrylic acid, esters and salts thereof; maleic acid, fumaric acid, esters and anhydrides thereof; Styrene, acrylonitrile, vinylidene chloride, vinyl ether and the like. Among these, the dispersing aid for suspension polymerization of the present invention is particularly suitable for suspension polymerization of vinyl chloride alone or vinyl chloride together with a monomer capable of copolymerizing with vinyl chloride. Used. Examples of 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.

The dispersion aid for suspension polymerization according to one embodiment of the present invention is suitable for the production of vinyl chloride resin for soft materials in terms of producing vinyl chloride resin particles having excellent plasticizer absorbability. Due to its excellent particle size distribution, it can also be applied to the production of rigid vinyl chloride resins.

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 cellulose derivatives and surfactants.

Since the dispersing aid for suspension polymerization according to one embodiment of the present invention has a large amount of plasticizer absorption, by using this, the resin particles are porous and the physical properties such as few fish eyes are very excellent. A vinyl chloride resin is always obtained. Hereinafter, the polymerization method of the vinyl compound will be specifically described with examples, but the method is not limited to these.

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

The polymerization initiator may be one conventionally used for the polymerization of vinyl compounds, including peroxydicarbonate such as diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, diethoxyethyl peroxydicarbonate. compounds, perester compounds such as t-butyl peroxyneodecanoate and α-cumyl peroxyneodecanoate, acetylcyclohexylsulfonyl peroxide, 2,4,4-trimethylpentyl-2-peroxyphenoxyacetate Peroxides, azo compounds such as azobis-2,4-dimethylvaleronitrile and azobis(4-methoxy-2,4-dimethylvaleronitrile), potassium persulfate, ammonium persulfate, hydrogen peroxide, etc. alone or in combination can be used

Furthermore, it is optional to add a polymerization modifier, a chain transfer agent, a gelation modifier, an antistatic agent, a pH adjuster, etc., which are appropriately used in the polymerization of the vinyl compound.

The charging ratio of each component, the polymerization temperature, etc. in carrying out the polymerization of the vinyl compound may be determined according to the conditions conventionally employed 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.
"Parts" and "%" mean "parts by mass" and "% by mass" unless otherwise specified.

(Example 1)
<Production of dispersion aid for suspension polymerization> 97 parts of vinyl acetate, 180 parts of water, 0.3 parts of polyvinyl alcohol (W-20N manufactured by Denka Co., Ltd.) as a dispersant, 1 part of normal butyraldehyde (nBA) as a chain transfer agent .6 parts of crotonic acid, 3 parts of crotonic acid and 0.9 parts of azobisisobutyronitrile were placed in a polymerization vessel, 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. Next, unpolymerized vinyl acetate was removed by a conventional method, and the resulting vinyl ester polymer was fluidized and dried at 40°C to obtain a dispersion aid A for suspension polymerization. In this example, no additive was added, and the vinyl ester polymer itself constitutes the dispersion aid A for suspension polymerization. The viscosity-average polymerization degree, saponification degree, acid value, and water solubility of the obtained dispersion aid A for suspension polymerization were evaluated by the methods described below. Table 1 shows the evaluation results.

[Polymerization rate]
The rate of polymerization was determined by a gravimetric method by taking a small amount of sample while the vinyl ester monomer and vinyl ester polymer particles were uniformly dispersed in water, drying the sampled solution at 150° C. for 30 minutes.

[Viscosity average degree of polymerization]
Based on JIS K6725:1977, the intrinsic viscosity [η] of the obtained dispersing aid A for suspension polymerization was 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]
Based on JIS K0070:1992, it was determined from the amount of potassium hydroxide necessary for neutralizing the obtained dispersing aid A for suspension polymerization.

[Water soluble]
After adding 10 parts of dispersion aid A for suspension polymerization to 90 parts of water, sodium carbonate was added so that the pH was 7.5 to 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.
◯: Uniform solution or dispersion, no precipitation.
x: Precipitation occurs.

<Suspension polymerization of vinyl chloride> In a stainless steel autoclave with a capacity of 30 L equipped with a stirrer, 14 kg of water at 30 ° C. was stirred, polyvinyl alcohol (W-20N manufactured by Denka Co., Ltd.) with a saponification degree of 80 mol% was added as a main dispersant. ), 2 g of the dispersion aid A for suspension polymerization obtained above, 4.6 g of t-butyl peroxyneodecanoate as a polymerization initiator, and 1 g of α-cumyl peroxyneodecanoate. is. After evacuating the autoclave, 10 kg of vinyl chloride monomer was added and 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 and bulk specific gravity by the following methods.

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

[Plasticizer absorption]
Measured according to ISO 4608:1998(E).

[Bulk specific gravity]
Measured according to JIS K6720-2:1999.

(Examples 2-3)
Dispersing aids B and C for suspension polymerization were obtained in the same manner as in Example 1, except that the amount of normal butyraldehyde 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 resins obtained using these.

(Example 4)
97 parts of vinyl acetate, 180 parts of water, 0.3 parts 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 After 0.9 part was charged in a polymerization vessel and heated to 60° C., itaconic acid was continuously added for 6 hours so that the total amount of itaconic acid added was 1.0 part, and the polymerization was further continued for 1 hour. Table 1 shows the polymerization rate at the end of the polymerization. Next, unpolymerized vinyl acetate was removed by a conventional method, and the resulting vinyl ester polymer was fluidized and dried at 40°C to obtain a dispersion aid D for suspension polymerization. In this example, no additive was added, and the vinyl ester polymer itself constitutes the dispersion aid D for suspension polymerization. The viscosity-average degree of polymerization, saponification degree, acid value and water solubility of the obtained dispersion aid D for suspension polymerization were evaluated in the same manner 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 no dispersion aid for suspension polymerization was used. Table 1 shows the evaluation results of the vinyl chloride resin.

(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 exhibit 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 using the same.

(Comparative Example 3)
A dispersing aid F for suspension polymerization was obtained in the same manner as in Example 1 except that the amount of normal butyraldehyde and the amount of crotonic acid added were changed to the conditions shown in Table 1. The obtained dispersion aid F for suspension polymerization exhibited 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 for suspension polymerization F was used. I didn't get it. Table 1 shows the evaluation results of 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 parts of azobisisobutyronitrile (as a 1% methanol solution) were placed in a polymerization vessel and heated at 60°C under a nitrogen atmosphere. Polymerization was carried out for 8 hours. Table 1 shows the polymerization rate at the end of the polymerization. Next, unpolymerized vinyl acetate was removed by a conventional method, and the solvent for the vinyl ester polymer was removed by drying to obtain dispersion aid G for suspension polymerization. In this comparative example, no additive was added, and the vinyl ester polymer itself constitutes the dispersion aid G for suspension polymerization. The obtained dispersion aid G for suspension polymerization did not exhibit 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 using the same.

(Comparative Example 5)
100 parts of vinyl acetate, 22.5 parts of methanol (solvent and chain transfer agent), 0.23 parts of chain transfer agent 3-MPA (3-mercaptopropionic acid) and azobisisobutyronitrile (1% methanol solution 0.03 part as a solution) was charged into a polymerization vessel and replaced with a nitrogen atmosphere. When the temperature reached 60° C. by heating, 1.81 parts of a 10% mercaptopropionic acid methanol solution was constantly added continuously for 6 hours to carry out polymerization for 6 hours. Table 1 shows the polymerization rate at the end of the polymerization. Next, unpolymerized vinyl acetate was removed by a conventional method, and the solvent of the vinyl ester polymer was removed by drying to obtain a modified vinyl ester polymer. The resulting 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 millimol equivalents per 1 mol of vinyl acetate units in the modified vinyl ester polymer obtained. A dispersion aid H for suspension polymerization was obtained by filtration and drying. In this comparative example, no additive was added, and the vinyl ester polymer itself constitutes the dispersion aid H for suspension polymerization. The resulting suspension polymerization dispersing aid H had a saponification degree of 43 mol % measured according to 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 dispersing aid H for suspension polymerization and the vinyl chloride resin obtained using the same.

From the results shown in Table 1, the dispersion aid for suspension polymerization of the present invention is water-soluble and therefore excellent in handleability. is high and the formation of coarse particles is small. The reason why Comparative Example 5 was water-soluble in spite of its low acid value was that hydroxyl groups were introduced through saponification.

Claims (6)

A dispersing 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 and a viscosity average degree of polymerization of 100 to 570 . A dispersing aid for suspension polymerization of a vinyl-based compound, wherein the vinyl ester-based polymer is a vinyl acetate-based polymer. 3. The dispersing aid for suspension polymerization according to claim 1, wherein the vinyl ester polymer has a degree of saponification of 5 mol % or less. 4. The dispersing aid for suspension polymerization according to any one of claims 1 to 3 , containing 60% by mass or more of the vinyl ester polymer. The dispersing aid for suspension polymerization according to any one of claims 1 to 4, wherein the vinyl ester polymer has an acid value (KOH mg/g) of 10 or more and less than 40. Using the dispersion aid for suspension polymerization according to any one of claims 1 to 5 , a vinyl compound monomer, or a mixture of a vinyl compound monomer and a monomer copolymerizable therewith A method for producing a vinyl resin, comprising dispersing in water and performing suspension polymerization.