TW202019976A - Dispersing auxiliary agent for suspension polymerization and method for producing vinyl resin - Google Patents

Abstract

Provided is a dispersing auxiliary agent for suspension polymerization having excellent handling properties in which, when the dispersing auxiliary agent for suspension polymerization is used for the suspension polymerization of a vinyl compound, coarse particles are less formed and vinyl resin particles having high plasticizer absorbability can be obtained. This dispersing auxiliary agent for the suspension polymerization of a vinyl compound, contains a vinyl ester polymer having an acid value (KOH mg/g) of 5-100 (exclusive of 100).

Description

Dispersing aid for suspension polymerization and method for producing vinyl resin

The present invention relates to a dispersion aid for suspension polymerization, in particular to a dispersion aid for suspension polymerization suitable for suspension polymerization of vinyl compounds, especially vinyl chloride.

Regarding the production of vinyl polymers such as vinyl chloride resins, a suspension polymerization method is widely carried out industrially. This suspension polymerization method is to disperse a vinyl compound in the presence of a dispersant in a water-soluble medium and use an oil-soluble catalyst Perform polymerization. The main factors that generally determine the quality of the resin include polymerization rate, water-to-monomer ratio, polymerization temperature, amount or feed period of polymerization initiator, type of polymerization tank, stirring speed, or type and amount of dispersant And so on, the main factor can also be said that the influence of the dispersant is great.

Examples of the performance required for the dispersant for suspension polymerization of vinyl compounds include: (1) Use in a small amount and the suspension polymerization stability is remarkably excellent, and the particle size distribution of the obtained vinyl polymer particles can be as narrow as possible Function; (2) increase the absorption rate of the plasticizer towards the polymer particles to make the processability of the polymer easy, make the removal of monomers such as vinyl chloride remaining in the polymer particles easy, and in order to prevent The formation of fish eyes has the effect of adjusting to porosity; (3) the function of forming polymer particles with a large volume ratio; (4) the operability is good.

The level of requirements for these properties (1) to (4) is increasing day by day. In particular, in terms of the removability of the monomer components described in (2) above, from the environmental point of view, the limit of the amount of residual monomers becomes a very high level. In addition, when it is difficult to remove the vinyl chloride monomer remaining in the particles in the drying step after the polymerization of polyvinyl chloride, in order to remove the residual monomer, a long time or high temperature drying is required, but at the same time, there is also concern about polyvinyl chloride The resin deteriorated. In addition, regarding the operability described in the above (4), in terms of environmental issues, in recent years, it has been reluctant to use organic solvents such as methanol, but it is desired that the dispersant for suspension polymerization can be used in the form of an aqueous liquid.

As the dispersant for suspension polymerization, a main dispersant of a polyvinyl alcohol-based resin (hereinafter sometimes simply referred to as PVA) may be used. Among them, PVA with a saponification degree of 65 mol% to 99 mol% can be used as the main dispersant. In addition, PVA with a saponification degree of less than 65 mol% is often used as a dispersion aid. The main dispersant is mainly used in anticipation of the performance of (1) or (3), and the dispersion aid is used in anticipation of the performance of (2). In addition, the performance of (4) is required for all dispersants used.

As the dispersing aid, a polyvinyl alcohol-based polymer (Patent Document 1) having an ionic group at one terminal and a saponification degree of 10 mol% to 85 mol% is proposed. Saponified polyvinyl alcohol-based polymer (Patent Document 2), or a saponification degree of 35 mol% or more to 65 mol% or less and a fat having a carbon number of 6 or more and 12 or less at the terminal A vinyl alcohol polymer of a hydrocarbon group (Patent Document 3) and the like. [Prior Technical Literature] [Patent Literature]

Patent Document 1: Japanese Patent Laid-Open No. 10-168128. Patent Document 2: Japanese Patent Laid-Open No. 2013-203994. Patent Document 3: International Publication No. 2015/019614.

(Problems to be solved by the invention)

However, it is difficult to say that there are ethylenes that fully satisfy the required performances including the dispersing aids using the PVA described in Patent Literatures 1 to 3, including the requirement performances (1) to (4) that have soared in recent years. It is a compound dispersion aid. In addition, conventional dispersion aids are produced by polymerizing vinyl ester-based monomers to obtain vinyl ester-based polymers, and then subjected to saponification reaction with an alkali or the like. Therefore, they have the following disadvantages: they worry that the solvent used during the saponification reaction may remain in the product , Or the steps are long and costly.

Therefore, an object of the present invention is to provide a dispersion aid for suspension polymerization, which is excellent in handleability, and when the dispersion aid for suspension polymerization is used in the suspension polymerization of a vinyl compound It is possible to obtain vinyl resin particles with little formation of coarse particles and high plasticizer absorption. Furthermore, another object of the present invention is to provide a method for producing an ethylene-based resin using such a dispersion aid for suspension polymerization. (Means to solve the problem)

In order to solve the above-mentioned problems, the present inventors have repeatedly studied intensively and found that it is effective to use a vinyl ester polymer having an acid value (KOH mg/g) of 5 or more and less than 100 as a dispersion aid for suspension polymerization of a vinyl compound. .

Therefore, in one aspect, the present invention is a dispersion aid for suspension polymerization, which contains 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 of the present invention, the vinyl ester polymer is a vinyl acetate polymer.

In another embodiment of the dispersion aid for suspension polymerization of the present invention, the viscosity average polymerization degree of the vinyl ester polymer is 100 to 1,000.

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

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

Another aspect of the present invention is a method for producing an ethylene-based resin, comprising: using the dispersion aid for suspension polymerization of the present invention to make the vinyl compound monomer, or the vinyl compound monomer and the vinyl compound monomer The monomer mixture of bulk copolymerization is dispersed in water for suspension polymerization. (Effect of invention)

The present invention can obtain a dispersion aid for suspension polymerization, which is excellent in handleability, and when the dispersion aid for suspension polymerization is used in suspension polymerization of an ethylene-based compound, coarse particles can be produced The vinyl resin particles with little formation and high plasticizer absorption.

Hereinafter, embodiments of the present invention will be described in detail. Furthermore, the present invention is not limited to the embodiments described below.

The vinyl ester polymer contained in the dispersion aid for suspension polymerization according to an embodiment of the present invention is important from the viewpoint of water solubility and performance in that the acid value (KOH mg/g) is 5 or more and less than 100. When 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 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 becomes 100 mg/g or more, the dispersion system becomes unstable, and coarse particles of the obtained vinyl resin particles are generated, which is a problem in practical use. Therefore, the acid value must 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, still more preferably less than 60 mg/g, and even more preferably Less than 50mg/g, particularly preferably less than 40mg/g, particularly preferably less than 30mg/g.

The acid value is measured in accordance with JIS (Japanese Industrial Standard) K0070:1992. That is, it is determined from the amount of potassium hydroxide required to neutralize the vinyl ester polymer.

The saponification degree of the vinyl ester-based polymer contained in the dispersion aid for suspension polymerization according to an embodiment of the present invention is preferably 5 mol% or less, more preferably 2 mol% or less, and still more preferably 1 mol% the following. The saponification degree can also be set to 0 mol%. Reducing the degree of saponification means that the steps of saponification can be omitted or shortened, so it is economically advantageous and is also beneficial for increasing the acid value.

The saponification degree of the vinyl ester-based 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 production method of the vinyl ester-based polymer contained in the dispersion aid for suspension polymerization according to an embodiment of the present invention is not particularly limited, but it is convenient when the vinyl ester-based monomer is radically polymerized, The method of polymerization in the presence of acid.

Examples of the unsaturated carboxylic acid used in the present invention include butenoic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, (meth)acrylic acid, and the like, but are not limited thereto. One type of unsaturated carboxylic acid may be used, or two or more types may be used in combination. In terms of reactivity ratio with vinyl ester or ease of operation, it is best to use crotonic acid.

The vinyl ester monomer is not limited, and examples thereof include vinyl acetate, vinyl formate, vinyl propionate, vinyl valerate, vinyl caprate, vinyl laurate, vinyl stearate, and benzoic acid. Vinyl ester, trimethyl vinyl acetate, and tertiary vinyl carbonate. One type of vinyl ester monomer may be used, or two or more types may be used in combination. In terms of ease of acquisition, operation, and economy, it is best to use vinyl acetate.

The viscosity average polymerization degree of the vinyl ester polymer contained in the dispersion aid for suspension polymerization is preferably 100 or more from the viewpoint of dispersion stability or production efficiency when the vinyl compound is subjected to suspension polymerization. When the average viscosity polymerization degree is less than 100, the dispersion system tends to become unstable when the ethylene-based compound is subjected to suspension polymerization, and the particle size of the resulting ethylene-based resin is likely to be coarsened. In addition, the softening temperature of the dispersion aid for suspension polymerization becomes low, so that it tends to agglomerate during the drying step, and manufacturing becomes difficult. Therefore, the average viscosity degree of polymerization is preferably 100 or more, more preferably 150 or more, and still more preferably 200 or more. In addition, with regard to the average viscosity degree of polymerization of the vinyl ester polymer contained in the dispersion aid for suspension polymerization, in order to prevent the viscosity of the aqueous solution from becoming high, the treatment becomes difficult or the porosity of the particles obtained when the vinyl compound is subjected to suspension polymerization ( porosity) to improve the absorbency of the plasticizer, preferably 1000 or less, more preferably 800 or less, and even more preferably 600 or less.

The average polymerization degree of viscosity is measured in accordance with JIS K6725:1977. That is, it is determined from the limit 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 an embodiment of the present invention is not particularly limited, and the polymerization method may be batch polymerization, semi-batch polymerization, continuous polymerization, and semi-continuous polymerization. Any of them. The monomers can be fed at once, or in batches, or can be added continuously or intermittently. In addition, any known polymerization method such as solution, emulsification, suspension, and bulk polymerization can be used arbitrarily. In terms of no solvent remaining in the product and easy drying, a method of obtaining a polymer from particles without leaving a solvent after polymerization More suitable, preferably suspension polymerization.

At this time, other monomers may be further copolymerized as long as the range of the present invention is not impaired. Specific examples of other monomers include olefins such as ethylene and propylene; dialkyl maleates; dialkyl fumarates; alkyl vinyl ethers, and the like.

The polymerization initiator when the vinyl ester monomer is subjected to radical polymerization is not particularly limited, and the following compounds may be used alone or in combination of two or more: azobisisobutyronitrile, azobis-2, Azo compounds such as 4-dimethylvaleronitrile, azobis (4-methoxy-2,4-dimethylvaleronitrile), azobisdimethylvaleronitrile, azobismethoxyvaleronitrile ; Peroxide, benzoyl peroxide, lauryl peroxide, ethoxycyclohexylsulfonyl peroxide, 2-peroxyphenoxyacetic acid-2,4,4-trimethylpentyl peroxide, etc. Substances; peroxycarbonate compounds such as diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, diethoxyethyl peroxydicarbonate; neodecanoic acid-α-isopropyl peroxide Peroxyester compounds such as phenyl ester and neobutyl decanoate.

In addition, when copolymerization is performed at a high temperature, aldehydes caused by the oxidative decomposition of vinyl ester-based monomers may be seen to form a condensate and cause coloring. In this case, in order to prevent coloring, a citric acid-like antioxidant may be added to the polymerization system to the extent of 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 an embodiment of the present invention preferably contains a vinyl ester system having an acid value (KOH mg/g) of 60% by mass or more and 5 or more and less than 100 from the viewpoint of exhibiting desired performance. The polymer preferably contains 80% by mass or more, and more preferably contains 90% by mass or more. In addition, the dispersion aid for suspension polymerization of the present invention may contain various additives within a range not detracting from the gist of the present invention. Examples of the additives include polymerization regulators such as aldehydes, halogenated hydrocarbons, and thiols; polymerization inhibitors such as phenol compounds, sulfur compounds, and N-peroxide compounds; pH adjusters; crosslinking agents; preservatives ; Antifungal agent, anti-blocking agent; antifoaming agent, etc.

The dispersion aid for suspension polymerization according to an embodiment of the present invention can be particularly suitably used for suspension polymerization of vinyl compounds. Examples of the vinyl compounds include halogenated ethylene such as vinyl chloride; vinyl esters such as vinyl acetate and vinyl propionate; acrylic acid, methacrylic acid, esters and salts of these; maleic acid, fumaric acid, and the like Ester and anhydride; styrene, acrylonitrile, vinylidene chloride, vinyl ether, etc. Among these, the dispersion aid for suspension polymerization of the present invention is particularly suitable for the suspension polymerization of vinyl chloride alone or the suspension polymerization of vinyl chloride and a monomer copolymerizable with vinyl chloride. Examples of monomers copolymerizable with vinyl chloride include vinyl esters such as vinyl acetate and vinyl propionate; (meth)acrylates 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, etc.

The dispersion aid for suspension polymerization according to an embodiment of the present invention is suitable for the production of vinyl chloride resins for soft plastics in terms of producing vinyl chloride resin particles with excellent plasticizer absorption, but in terms of demonomerization and particle size distribution In terms of excellence, it can also be used in the manufacture of rigid vinyl chloride resins.

The dispersion aid for suspension polymerization according to an 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 dispersion aid for suspension polymerization according to one embodiment of the present invention has a large amount of plasticizer absorption, by using the dispersion aid for suspension polymerization, the resin particles are always porous and have very good physical properties such as few fish eyes. Vinyl chloride resin. Hereinafter, examples of the polymerization method of the ethylene-based compound will be specifically described, but not limited to these.

In the case of producing resin particles of vinyl compounds such as vinyl chloride resin particles, in one embodiment, 0.01 to 0.3 parts by mass, preferably 0.02 parts by mass to 100 parts by mass of the vinyl compound monomer is added 0.10 parts by mass of the above-mentioned dispersion aid for suspension polymerization. In addition, the ratio of the vinyl compound to water can be set as the mass ratio of the vinyl compound: water = 1: 0.9 to 1: 3, preferably the vinyl compound: water = 1:1 to 1: 1.5.

The polymerization initiator may also be a polymerization initiator previously used for the polymerization of ethylene-based compounds. With regard to the polymerization initiator, the following compounds may be used alone or in combination: diisopropyl peroxide dicarbonate, di peroxide Percarbonate compounds such as di-2-ethylhexyl carbonate, diethoxyethyl peroxydicarbonate; tertiary butyl peroxyneodecanoate, α-cumyl peroxyneodecanoate, etc. Oxygen acid ester compounds; peroxides such as ethoxycyclohexylsulfonyl peroxide, 2-peroxyphenoxyacetic acid-2,4,4-trimethylpentyl ester; azobis-2,4-dimethyl Azo compounds such as valeronitrile, azobis (4-methoxy-2,4-dimethylvaleronitrile); and further potassium persulfate, ammonium persulfate, hydrogen peroxide, etc.

Furthermore, a polymerization adjuster, a chain transfer agent, a gelation improver, an antistatic agent, a pH adjuster, etc. suitable for the polymerization of ethylene-based compounds are optionally added.

The feed rate of each component, polymerization temperature, etc. at the time of carrying out the polymerization of the ethylene-based compound may be set according to the conditions previously used for the suspension polymerization of the ethylene-based compound, and there is no reason for particular limitation. [Example]

Hereinafter, the present invention will be described in more detail with examples. In addition, unless otherwise specified, "parts" and "%" mean "mass parts" and "mass %", respectively.

(Example 1) <Manufacture 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 dispersant, and n-butyl chain transfer agent 1.6 parts of aldehyde (nBA), 3 parts of crotonic acid and 0.9 parts of azobisisobutyronitrile were fed to a polymerization tank, heated and polymerized at 60°C, and polymerized for 7 hours. The polymerization rate at the end of polymerization was measured by the method shown below. Subsequently, the unpolymerized vinyl acetate was removed by an ordinary method, and the obtained vinyl ester polymer was flow-dried at 40° C. to obtain a dispersion aid A for suspension polymerization. In this embodiment, no additives are added, and the vinyl ester polymer itself constitutes the dispersion aid A for suspension polymerization. The obtained dispersion aid A for suspension polymerization was evaluated for the average viscosity degree of polymerization, saponification degree, acid value and water solubility by the method shown below. Table 1 shows the evaluation results.

[Polymerization rate] The polymerization rate is obtained by sampling a small amount in a state where the vinyl ester monomer and vinyl ester polymer particles are uniformly dispersed in water, and the sampled solution is dried at 150°C for 30 minutes and determined by gravimetry.

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

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

[Acid Value] According to JIS K0070:1992, it was determined from the amount of potassium hydroxide required to neutralize the obtained dispersion aid A for suspension polymerization.

[Water Soluble] After adding 10 parts of dispersing aid A for suspension polymerization to 90 parts of water, sodium carbonate was added in such a way that the pH became 7.5 to 8.5 and after stirring at room temperature for 4 hours, the stirring was stopped, and the presence or absence of precipitation was visually confirmed according to Evaluation is based on the following criteria. ○: It became a uniform solution or dispersion, and no precipitation occurred. ×: Precipitation occurred.

<Suspension polymerization of vinyl chloride> In a 30-liter stainless steel autoclave equipped with a stirrer, feed 14 kg of water at 30° C. under stirring, as the main dispersant, a polyvinyl alcohol with a saponification degree of 80 mole% (electrochemical (W-20N manufactured by Denka) Co., Ltd. 12g, 2g of the dispersion aid A for suspension polymerization obtained above, 4.6g of tertiary butyl neodecanoate as a polymerization initiator, and neodecanoic acid peroxide -α-Cumene ester 1g. After degassing the autoclave under vacuum, 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 the average particle diameter, particle size distribution, plasticizer absorption and volume specific gravity by the method shown below. Table 1 shows the evaluation results.

[Average particle size, particle size distribution] According to JIS Z8815:1994, the resulting vinyl chloride resin was separated using a sieve of 60 mesh (aperture 250 μm), 80 mesh (aperture 180 μm), 100 mesh (aperture 150 μm), 150 mesh (aperture 106 μm), 200 mesh (aperture 75 μm) For the granules, the particle diameter (D50) with a cumulative frequency of 50% is defined as the average particle diameter, and the difference between the particle diameter (D80) with a cumulative frequency of 80% and the particle diameter (D20) with a cumulative frequency of 20% is defined as the particle size distribution.

[Plasticizer absorption] The measurement was performed according to ISO (International Organization for Standardization) 4608:1998(E).

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

[Table 1]

(Example 2 to Example 3) A dispersion aid for suspension polymerization B and a dispersion aid for suspension polymerization C were obtained in the same manner as in Example 1, except that the addition amount of n-butyraldehyde and the addition amount of crotonic acid were changed to the conditions described in Table 1. Next, the suspension polymerization of vinyl chloride was carried out under the same conditions as in Example 1, except that the obtained dispersion aid B for suspension polymerization and dispersion aid C for suspension polymerization were used. Table 1 shows the evaluation results of the vinyl chloride resin obtained by using the dispersion aid B for suspension polymerization, the dispersion aid C for suspension polymerization, and the dispersion aid B for suspension polymerization and the dispersion aid C for suspension polymerization.

(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 dispersant, 1.4 parts of n-butyraldehyde (nBA) of chain transfer agent and azobis 0.9 parts of isobutyronitrile was fed to a polymerization tank, and after heating to 60°C, polymerization was carried out while itaconic acid was continuously added for 6 hours so that the total addition amount became 1.0 part, and polymerization was further carried out for 1 hour. Table 1 shows the polymerization rate at the end of polymerization. Subsequently, the unpolymerized vinyl acetate was removed by a conventional method, and the obtained vinyl ester polymer was flow-dried at 40° C. to obtain a dispersion aid D for suspension polymerization. In this embodiment, no additives are added, and the vinyl ester polymer itself constitutes the dispersion aid D for suspension polymerization. For the obtained dispersion aid D for suspension polymerization, the average viscosity degree of polymerization, the degree of saponification, the acid value, and the water solubility were evaluated in the same manner as in Example 1. Table 1 shows the evaluation results.

(Comparative example 1) The 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. Table 1 shows the evaluation results of 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 addition amount of crotonic acid was changed to the conditions described in Table 1. The resulting dispersion aid E for suspension polymerization did not show water solubility. Next, the 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 for suspension polymerization.

(Comparative example 3) A dispersion aid F for suspension polymerization was obtained in the same manner as in Example 1, except that the addition amount of n-butyraldehyde and the addition amount of crotonic acid were changed to the conditions described in Table 1. The resulting dispersion aid F for suspension polymerization showed water solubility. Next, the 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 agglomerated in an autoclave, and vinyl chloride particles could not be obtained. 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 parts of azobisisobutyronitrile (in the form of a 1% methanol solution) were fed to the polymerization tank, which was carried out at 60°C under a nitrogen atmosphere 8 Hourly polymerization. Table 1 shows the polymerization rate at the end of polymerization. Then, the unpolymerized vinyl acetate was removed by a conventional method, and the solvent of the vinyl ester polymer was removed by drying to obtain a dispersion aid G for suspension polymerization. In this comparative example, no additives are added, and the vinyl ester polymer itself constitutes the dispersion aid G for suspension polymerization. The resulting dispersion aid G for suspension polymerization does not show water solubility. Next, the 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 for suspension polymerization.

(Comparative example 5) Mix 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 the chain transfer agent and azobisisobutyronitrile (in the form of 1% methanol solution) 0.03 parts were fed to the polymerization tank and replaced with nitrogen atmosphere. From the time of heating to 60° C., while continuously adding 1.81 parts of a 10% mercaptopropionic acid methanol solution so as to complete the addition in 6 hours, polymerization was carried out for 6 hours. Table 1 shows the polymerization rate at the end of polymerization. Subsequently, the 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 obtained modified vinyl ester polymer was dissolved in methanol to obtain a methanol solution with a concentration of 35% of the polymer in methanol. This modified vinyl ester polymer was saponified with sodium hydroxide at 35°C for 90 minutes. The amount of sodium hydroxide used was 7 millimolar equivalents relative to 1 mole of vinyl acetate units of the resulting modified vinyl ester polymer. The dispersion aid H for suspension polymerization is obtained by filtration and drying. In this comparative example, no additives are added, and the vinyl ester polymer itself constitutes the dispersion aid H for suspension polymerization. The resulting dispersion aid H for suspension polymerization was 43 mol% measured according to JIS K6726:1994. The 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 for suspension polymerization.

From the results shown in Table 1, it is known that the dispersion aid for suspension polymerization of the present invention is water-soluble and therefore has excellent operability, and the ethylene-based resin plasticizer obtained by suspension polymerization using the dispersion aid for suspension polymerization has high absorbency And less formation of coarse particles. In addition, the reason why Comparative Example 5 is water-soluble despite the low acid value is that saponification is carried out and hydroxyl groups are introduced.

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Claims (7)

A dispersing aid for suspension polymerization of vinyl compounds, which contains vinyl ester polymers having an acid value (KOH mg/g) of 5 or more and less than 100. The dispersion aid for suspension polymerization according to claim 1, wherein the vinyl ester polymer is a vinyl acetate polymer. The dispersion aid for suspension polymerization as described in claim 1 or 2, wherein the viscosity average polymerization degree of the vinyl ester-based polymer is 100 to 1,000. The dispersion aid for suspension polymerization according to claim 1 or 2, wherein the saponification degree of the vinyl ester-based polymer is 5 mol% or less. The dispersion aid for suspension polymerization as described in claim 1 or 2 contains 60% by mass or more of the aforementioned vinyl ester polymer. The dispersion aid for suspension polymerization according to claim 1 or 2, wherein the acid value (KOH mg/g) of the vinyl ester-based polymer is 10 or more and less than 40. A method for producing an ethylene-based resin, comprising: using the dispersion aid for suspension polymerization as described in any one of claims 1 to 6, to make the ethylene-based compound monomer, or the ethylene-based compound monomer and the aforementioned ethylene compound The mixture of monomers copolymerized by compound monomers is dispersed in water for suspension polymerization.