WO2010113568A1

WO2010113568A1 - Dispersion stabilizer for suspension polymerization

Info

Publication number: WO2010113568A1
Application number: PCT/JP2010/052787
Authority: WO
Inventors: 悠太田岡; 真輔新居; 昌人仲前
Original assignee: 株式会社クラレ
Priority date: 2009-04-01
Filing date: 2010-02-23
Publication date: 2010-10-07
Also published as: JP5632830B2; JPWO2010113568A1; TW201036995A

Abstract

Disclosed is a dispersion stabilizer for suspension polymerization, which comprises: a vinyl alcohol polymer (A) that has a saponification degree of 60 mol% or more and a viscosity average polymerization degree of 200 or more; and a polyoxyalkylene-modified vinyl alcohol polymer (B) that contains a polyoxyalkylene group represented by general formula (I) in a side chain thereof and has a viscosity average polymerization degree of 200 to 1000, a saponification degree of less than 60 mol%, and an amount of modified polyoxyalkylene groups of 0.1 to 10 mol%. When suspension polymerization is carried out using the dispersion stabilizer for suspension polymerization, it becomes possible to produce polymer particles containing little coarse particles formed therein and having uniform particle diameters. It is also possible to reduce blocking or the adhesion of scales. (In the formula, R1 represents a hydrogen atom or a methyl group: R2 represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms; and each of m and n represents the number of repeated oxyalkylene units, wherein m and n meet a requirement represented by the following formulae: 1 ≤ m ≤ 10 and 3 ≤ n ≤ 20.)

Description

Dispersion stabilizer for suspension polymerization

The present invention relates to a dispersion stabilizer for suspension polymerization. In particular, it relates to a dispersion stabilizer for suspension polymerization of vinyl compounds.

Conventionally, it is known to use partially saponified vinyl alcohol polymers as dispersion stabilizers for suspension polymerization of vinyl compounds (particularly vinyl chloride).
Dispersion stabilizers for suspension polymerization of vinyl compounds include [1] high plasticizer absorbability even when used in small amounts, and easy processing, [2] removal of monomer components such as residual vinyl compounds. There are demands for performance that are easy, [3] few coarse particles, and [4] particles that are as uniform in particle size as possible and that can prevent scale adhesion.

In response to these requirements, a method of using a dispersion stabilizing aid in combination has been proposed. For example, a method has been proposed in which a vinyl alcohol resin having a low polymerization degree, a low saponification degree, and an oxyalkylene group is used as a dispersion stabilizing aid in a dispersion stabilizer for suspension polymerization of vinyl compounds. (Patent Documents 1 to 7). However, it cannot be said that the dispersion stabilizing aids described in Patent Documents 1 to 7 always have satisfactory performance with respect to the above-mentioned requirements [1] to [4].

Japanese Patent Laid-Open No. 9-100301 Japanese Patent Laid-Open No. 10-147604 Japanese Patent Laid-Open No. 10-147605 Japanese Patent Laid-Open No. 10-259213 JP-A-11-217413 Japanese Patent Laid-Open No. 2001-040019 Japanese Patent Laid-Open No. 2002-069105

The present invention provides a dispersion stabilizer for suspension polymerization that satisfies the above-mentioned required performances [1] to [4] and is excellent in polymerization stability when suspension polymerization of vinyl compounds such as vinyl chloride is carried out. The purpose is to do.

As a result of intensive studies, the present inventors have found that a vinyl alcohol polymer (A) having a saponification degree of 60 mol% or more and a viscosity average polymerization degree of 200 or more, and a polyoxy compound represented by the following general formula (I) A vinyl alcohol polymer containing an alkylene group in a side chain, the viscosity average polymerization degree of the vinyl alcohol polymer is 200 to 1000, the saponification degree is less than 60 mol%, and the polyoxyalkylene group modification amount is It has been found that a dispersion stabilizer for suspension polymerization containing 0.1 to 10 mol% of a polyoxyalkylene-modified vinyl alcohol polymer (B) solves the above-mentioned problems. It came to be completed.

In the formula, R1 represents a hydrogen atom or a methyl group, and R2 represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. m and n represent the number of repeating units of each oxyalkylene unit, and 1 ≦ m ≦ 10 and 3 ≦ n ≦ 20. Here, a unit represented by the number m of repeating units is referred to as unit 1, and a unit represented by the number of repeating units n is referred to as unit 2. The arrangement of the unit 1 and the unit 2 may be random or block.

It is also preferred that the weight ratio (A) / (B) of the vinyl alcohol polymer (A) to the polyoxyalkylene-modified vinyl alcohol polymer (B) is 99/1 to 5/95.

When suspension polymerization of a vinyl compound is performed using the dispersion stabilizer for suspension polymerization according to the present invention, since the polymerization stability is high, formation of coarse particles is small, and particles having a uniform particle diameter are obtained. Further, blocking and scale adhesion due to unstable polymerization are reduced.

The saponification degree of the vinyl alcohol polymer (A) (hereinafter, the vinyl alcohol polymer may be abbreviated as PVA) used in the present invention is 60 mol% or more, preferably 65 to 95 mol%. More preferably, it is 70 to 90 mol%. When the degree of saponification is less than 60 mol%, the water solubility of PVA is lowered and the handleability is deteriorated. The saponification degree of PVA is a value that can be measured according to JIS-K6726.

The viscosity average polymerization degree of PVA (A) is 200 or more, preferably 500 or more, more preferably 550 to 8000, and further preferably 600 to 3500. When the viscosity average polymerization degree of the PVA polymer is less than 200, the polymerization stability when the vinyl compound is subjected to suspension polymerization is lowered.

The viscosity average degree of polymerization (P) of PVA (A) is measured according to JIS-K6726. That is, after re-saponifying and purifying the PVA, it is obtained by the following equation from the intrinsic viscosity [η] measured in water at 30 ° C.
P = ([η] × 10 ³ /8.29) ^{(1 / 0.62)}
The viscosity average degree of polymerization may be simply referred to as the degree of polymerization.

In the dispersion stabilizer for suspension polymerization of the present invention, PVA (A) may be used alone, or two or more types having different characteristics may be used in combination.

The polyoxyalkylene-modified vinyl alcohol copolymer (B) used in the present invention (hereinafter, the polyoxyalkylene-modified vinyl alcohol copolymer may be abbreviated as POA-modified PVA) is represented by the above general formula (I). Is contained in the side chain.

POA-modified PVA (B) needs to have a polyoxyalkylene (POA) group modification amount of 0.1 to 10 mol%. When the POA group modification amount exceeds 10 mol%, the proportion of hydrophobic groups contained in one molecule of POA modified PVA (B) increases, and the water solubility of the PVA may decrease. The POA group modification amount is preferably 5 mol% or less, and particularly preferably 2 mol% or less. On the other hand, when the POA group modification amount is less than 0.1 mol%, the water solubility of the POA modified PVA (B) is excellent, but the number of POA groups contained in the PVA is small, and the physical properties based on the POA modification are low. It may not develop.

The POA group modification amount is represented by the mole fraction of the POA group with respect to the main chain methylene group of PVA. The POA group modification amount of the POA-modified PVA (A) is, for example, a POA-modified polyvinyl ester that is a precursor of the PVA. As a specific example, a POA-modified polyvinyl acetate (hereinafter, polyvinyl acetate is abbreviated as PVAc). In some cases). Specifically, after re-precipitation purification of POA-modified PVAc with n-hexane / acetone three or more times, it is dried under reduced pressure at 50 ° C. for 2 days to prepare POA-modified PVAc for analysis. The PVAc is dissolved in CDCl ₃ and measured at room temperature using 500 MHz proton NMR (JEOL GX-500). POA group modification from the peak α (4.7 to 5.2 ppm) derived from the main chain methine of vinyl ester and the peak β (0.8 to 1.0 ppm) derived from the terminal methyl group of unit 2 using the following formula Calculate the amount.
POA group modification amount (mol%) = {(number of protons of β / 3n) / (number of protons of α + (number of protons of β / 3n))} × 100
n represents the number of repeating units of unit 2.

POA-modified PVA (B) has a polymerization degree of 200 to 1,000. When the degree of polymerization exceeds 1000, it is difficult to remove the monomer component from the vinyl polymer particles obtained by suspension polymerization of the vinyl compound, or the plasticizer absorbability is lowered, which is not preferable. When the degree of polymerization is less than 200, the physical properties of PVA as a polymer are not expressed, which is not preferable. The degree of polymerization of POA-modified PVA (B) is measured by the same method as the method for measuring the degree of polymerization of PVA (A) described above.

The saponification degree of the POA-modified PVA (B) is less than 60 mol% from the viewpoint of water solubility and water dispersibility, preferably 58 mol% or less, more preferably 55 mol% or less, and even more preferably 52 mol% or less. is there. Although there is no restriction | limiting in particular about the minimum of a saponification degree, From a viewpoint on manufacture of a partially saponified PVA-type polymer, 10 mol% or more is preferable and 20 mol% or more is more preferable. The saponification degree of POA-modified PVA (B) is a value that can be measured according to JIS-K6726.

The number m of repeating units of the unit 1 of the POA group represented by the general formula (I) needs to satisfy 1 ≦ m ≦ 10. When m is in such a range, since the polymerization stability is high, formation of coarse particles is small, and particles having a uniform particle diameter can be obtained. m is preferably 1.5 or more. m is preferably 5 or less, and more preferably 3 or less. The number of repeating units n of unit 2 (polyoxybutylene) needs to satisfy 3 ≦ n ≦ 20. When n is less than 3, the interaction between POA groups does not appear, and the viscosity of the POA-modified PVA aqueous solution may be low. n is preferably 5 or more, and particularly preferably 8 or more. When n exceeds 20, the hydrophobicity of the POA group increases, and the water solubility of the POA-modified PVA (B) may decrease. n is preferably 18 or less, and more preferably 15 or less.

In the present invention, POA-modified PVA (B) can be produced by copolymerizing an unsaturated monomer having a POA group represented by the general formula (I) and a vinyl ester monomer in an alcohol solvent or without. A method of saponifying the obtained POA-modified vinyl ester copolymer with a solvent is preferred. The temperature employed when copolymerizing the unsaturated monomer having a POA group and the vinyl ester monomer is preferably 0 to 200 ° C, more preferably 30 to 140 ° C. A copolymerization temperature lower than 0 ° C. is not preferable because a sufficient polymerization rate cannot be obtained. Moreover, when the temperature which superposes | polymerizes is higher than 200 degreeC, since it becomes difficult to obtain POA modified PVA (B) which has the target POA group modification amount, it is unpreferable. As a method for controlling the temperature employed in the copolymerization to 0 to 200 ° C., for example, by controlling the polymerization rate, the heat generated by the polymerization is balanced with the heat released from the surface of the reactor. Examples thereof include a method and a method of controlling by an external jacket using an appropriate heating medium, but the latter method is preferable from the viewpoint of safety.

The polymerization method used for copolymerizing an unsaturated monomer having a POA group and a vinyl ester monomer may be any of batch polymerization, semi-batch polymerization, continuous polymerization, and semi-continuous polymerization. As the polymerization method, any known method such as a bulk polymerization method, a solution polymerization method, a suspension polymerization method, or an emulsion polymerization method can be used. Among them, a bulk polymerization method or a solution polymerization method in which polymerization is performed without a solvent or an alcohol solvent is suitably employed, and an emulsion polymerization method is employed for the purpose of producing a copolymer having a high degree of polymerization. As the alcohol solvent, methyl alcohol, ethyl alcohol, propyl alcohol, and the like can be used, but are not limited thereto. These solvents can be used in combination of two or more.

As the initiator used for copolymerization, conventionally known azo initiators, peroxide initiators, redox initiators and the like are appropriately selected according to the polymerization method. Examples of the azo initiator include 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (4-methoxy-2,4- Dimethyl valeronitrile), etc., and peroxide initiators include perisopropyl compounds such as diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, diethoxyethyl peroxydicarbonate; t-butyl Perester compounds such as peroxyneodecanate, α-cumylperoxyneodecanate, t-butylperoxydecanate; acetylcyclohexylsulfonyl peroxide; 2,4,4-trimethylpentyl-2-peroxyphenoxyacetate, etc. Is mentioned. Furthermore, the initiator can be combined with potassium persulfate, ammonium persulfate, hydrogen peroxide, or the like to form an initiator. Examples of the redox initiator include a combination of the above-described peroxide and a reducing agent such as sodium hydrogen sulfite, sodium hydrogen carbonate, tartaric acid, L-ascorbic acid, or longalite.

In addition, when copolymerization of an unsaturated monomer having a POA group and a vinyl ester monomer is performed at a high temperature, coloring of PVA due to decomposition of the vinyl ester monomer may be observed. Therefore, in that case, for the purpose of preventing coloring, an antioxidant such as tartaric acid may be added to the polymerization system in an amount of 1 to 100 ppm (based on the vinyl ester monomer).

As vinyl ester monomers, vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl versatate, vinyl caproate, vinyl caprylate, vinyl laurate, vinyl palmitate, Examples include vinyl stearate, vinyl oleate, and vinyl benzoate. Among them, vinyl acetate is most preferable.

When the unsaturated monomer having a POA group and the vinyl ester monomer are copolymerized, other monomers may be copolymerized within a range not impairing the gist of the present invention. Examples of monomers that can be used include α-olefins such as ethylene, propylene, n-butene, and isobutylene; acrylic acid and salts thereof; methyl acrylate, ethyl acrylate, n-propyl acrylate, and I-propyl acrylate. Acrylates such as n-butyl acrylate, I-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, octadecyl acrylate; methacrylic acid and its salts; methyl methacrylate, methacryl Methacrylic acid such as ethyl acetate, n-propyl methacrylate, I-propyl methacrylate, n-butyl methacrylate, I-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate, octadecyl methacrylate Beauty treatment Acrylamide; N-methylacrylamide, N-ethylacrylamide, N, N-dimethylacrylamide, diacetoneacrylamide, acrylamidepropanesulfonic acid and its salt, acrylamidopropyldimethylamine and its salt or quaternary salt thereof, N-methylolacrylamide And acrylamide derivatives such as methacrylamide; N-methyl methacrylamide, N-ethyl methacrylamide, methacrylamide propanesulfonic acid and salts thereof, methacrylamide propyldimethylamine and salts thereof or quaternary salts thereof, N-methylol methacryl Methacrylamide derivatives such as amides and derivatives thereof; methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, I-propyl vinyl Vinyl ethers such as nyl ether, n-butyl vinyl ether, I-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether and stearyl vinyl ether; nitriles such as acrylonitrile and methacrylonitrile; vinyl halides such as vinyl chloride and vinyl fluoride; Vinylidene halides such as vinylidene chloride and vinylidene fluoride; allyl compounds such as allyl acetate and allyl chloride; unsaturated dicarboxylic acids such as maleic acid, itaconic acid and fumaric acid, and salts or esters thereof; vinyltrimethoxysilane, etc. Vinylsilyl compounds; isopropenyl acetate and the like.

The PVA (A) and POA-modified PVA (B) used in the present invention may have an ionic functional group at the terminal. Examples of these ionic functional groups include a carboxyl group and a sulfonic acid group, and among them, a carboxyl group is preferable. These ionic groups include salts thereof, and alkali metal salts are preferred from the viewpoint that PVA (A) and POA-modified PVA (B) are preferably water-dispersible. As a method for introducing an ionic functional group into the terminal part of PVA (A) and POA-modified PVA (B), the presence of a thiol compound such as thiol acetic acid, mercaptopropionic acid, 3-mercapto-1-propanesulfonic acid sodium salt Below, a method of polymerizing a vinyl ester monomer such as vinyl acetate and saponifying the resulting polymer can be used.

Further, in the copolymerization of an unsaturated monomer having a POA group and a vinyl ester monomer, for the purpose of adjusting the degree of polymerization of the obtained copolymer, the scope of the present invention is not impaired. Copolymerization may be carried out in the presence of a chain transfer agent. Examples of chain transfer agents include aldehydes such as acetaldehyde and propionaldehyde; ketones such as acetone and methyl ethyl ketone; mercaptans such as 2-hydroxyethanethiol; and halogenated hydrocarbons such as trichloroethylene and perchloroethylene. Of these, aldehydes and ketones are preferably used. The addition amount of the chain transfer agent is determined according to the chain transfer constant of the chain transfer agent to be added and the degree of polymerization of the target vinyl ester polymer, but is generally 0.1% relative to the vinyl ester monomer. ~ 10% by weight is desirable.

For the saponification reaction of POA-modified PVAc obtained by copolymerizing an unsaturated monomer having a POA group and a vinyl ester monomer, conventionally known sodium hydroxide, potassium hydroxide, sodium methoxide, etc. An alcoholysis or hydrolysis reaction using a basic catalyst or an acidic catalyst such as p-toluenesulfonic acid can be applied. Examples of the solvent that can be used in this reaction include alcohols such as methanol and ethanol; esters such as methyl acetate and ethyl acetate; ketones such as acetone and methyl ethyl ketone; aromatic hydrocarbons such as benzene and toluene; These can be used alone or in combination of two or more. Among them, it is convenient and preferable to perform the saponification reaction using methanol or a methanol / methyl acetate mixed solution as a solvent and sodium hydroxide as a catalyst.

Examples of the unsaturated monomer having a POA group represented by the general formula (I) include unsaturated monomers represented by the following general formula (II).

R1 is a hydrogen atom or a methyl group, R2 is a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, and R3 is a hydrogen atom or —COOM. Here, M represents a hydrogen atom, an alkali metal or an ammonium group. R4 is a hydrogen atom, a methyl group or —CH ₂ —COOM, where M is as defined above. X is —O—, —CH ₂ —O—, —CO—, —CO—O— or —CO—NR 5 —. Here, R5 represents a hydrogen atom or a saturated alkyl group having 1 to 4 carbon atoms. m and n represent the number of repeating units of each oxyalkylene unit, and 1 ≦ m ≦ 10 and 3 ≦ n ≦ 20.

As R2 of the unsaturated monomer represented by the general formula (II), a hydrogen atom, a methyl group or a butyl group is preferable, and a hydrogen atom or a methyl group is more preferable. Furthermore, it is particularly preferable that R1 of the unsaturated monomer represented by the general formula (II) is hydrogen, R2 is a hydrogen atom or a methyl group, and R3 is a hydrogen atom.

For example, when R1 in the general formula (II) is a hydrogen atom, R2 is a hydrogen atom, and R3 is a hydrogen atom, the unsaturated monomer represented by the general formula (II) is specifically polyoxyethylene polyoxybutylene. Monoacrylate, polyoxyethylene polyoxybutylene monomethacrylate, polyoxyethylene polyoxybutylene monoacrylic amide, polyoxyethylene polyoxybutylene monomethacrylamide, polyoxyethylene polyoxybutylene monoallyl ether, polyoxyethylene polyoxybutylene Examples include monomethallyl ether and polyoxyethylene polyoxybutylene monovinyl ether. Among them, polyoxyethylene polyoxybutylene monoacrylic acid amide, polyoxyethylene polyoxybutylene monomethacrylic acid amide, polyoxyethylene polyoxybutylene monovinyl ether are preferably used, polyoxyethylene polyoxybutylene monomethacrylic acid amide, Polyoxyethylene polyoxybutylene monovinyl ether is particularly preferably used.

In the case where R2 in the general formula (II) is an alkyl group having 1 to 8 carbon atoms, specifically as the unsaturated monomer represented by the general formula (II), R1 in the general formula (II) is a hydrogen atom, An example in which is a hydrogen atom and R3 is a hydrogen atom is one in which the terminal OH group of the unsaturated monomer exemplified above is substituted with an alkoxy group having 1 to 8 carbon atoms. Of these, unsaturated monomers in which the OH group at the terminal of polyoxyethylene polyoxybutylene monomethacrylamide or polyoxyethylene polyoxybutylene monovinyl ether is substituted with a methoxy group are preferably used. An unsaturated monomer in which the OH group at the terminal of butylene monomethacrylamide is substituted with a methoxy group is particularly preferably used.

The weight ratio (A) / (B) of PVA (A) to POA-modified PVA (B) in the dispersion stabilizer for suspension polymerization of the present invention is not particularly limited, but may be 99/1 to 5/95. preferable. When the weight ratio (A) / (B) is larger than 99/1, the plasticizer absorbability of the vinyl polymer obtained by suspension polymerization of the vinyl compound may be deteriorated or the particle size distribution may be widened. There is. The weight ratio (A) / (B) is preferably 97/3 or less, and more preferably 95/5 or less. When the weight ratio (A) / (B) is smaller than 5/95, the polymerization stability may be lowered when the vinyl compound is subjected to suspension polymerization. The weight ratio (A) / (B) is preferably 10/90 or more, and more preferably 15/85 or more.

The dispersion stabilizer for suspension polymerization of the present invention is particularly suitably used for suspension polymerization of vinyl compounds. Examples of 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; Examples include styrene, acrylonitrile, vinylidene chloride, vinyl ether and the like. Among these, the dispersion stabilizer for suspension polymerization of the present invention is particularly preferably used in suspension polymerization of vinyl chloride alone or together with a monomer capable of copolymerizing with vinyl chloride and vinyl chloride. Used. Monomers that can be copolymerized with vinyl chloride include vinyl esters such as vinyl acetate and vinyl propionate; (meth) acrylic 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.

For suspension polymerization of vinyl compounds, oil-soluble or water-soluble polymerization initiators conventionally used for polymerization of vinyl chloride monomers and the like can be used. Examples of the oil-soluble polymerization initiator include percarbonate compounds such as diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, diethoxyethyl peroxydicarbonate; t-butyl peroxyneodecanate, t -Perester compounds such as butyl peroxypivalate, t-hexyl peroxypivalate, α-cumyl peroxyneodecanate; acetylcyclohexylsulfonyl peroxide, 2,4,4-trimethylpentyl-2-peroxyphenoxyacetate Peroxides such as 3,5,5-trimethylhexanoyl peroxide and lauroyl peroxide; azo compounds such as azobis-2,4-dimethylvaleronitrile and azobis (4-2,4-dimethylvaleronitrile) Raising It is. Examples of the water-soluble polymerization initiator include potassium persulfate, ammonium persulfate, hydrogen peroxide, cumene hydroperoxide, and the like. These oil-soluble or water-soluble polymerization initiators can be used alone or in combination of two or more.

In suspension polymerization of vinyl compounds, other various additives can be added to the polymerization reaction system as necessary. Examples of the additive include polymerization regulators such as aldehydes, halogenated hydrocarbons and mercaptans, and polymerization inhibitors such as phenol compounds, sulfur compounds and N-oxide compounds. Moreover, a pH adjuster, a crosslinking agent, etc. can also be added arbitrarily.

In suspension polymerization of a vinyl compound, the polymerization temperature is not particularly limited, and can be adjusted to a high temperature exceeding 90 ° C. as well as a low temperature of about 20 ° C. In order to increase the heat removal efficiency of the polymerization reaction system, it is also one of preferred embodiments to use a polymerization vessel with a reflux condenser.

The dispersion stabilizer for suspension polymerization of the present invention is blended with additives such as preservatives, antifungal agents, antiblocking agents, antifoaming agents and the like that are usually used in suspension polymerization and emulsion polymerization, if necessary. be able to.

Although the dispersion stabilizer for suspension polymerization of the present invention may be used alone, methylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose which are usually used for suspension polymerization of vinyl compounds in an aqueous medium are used. Water-soluble cellulose ethers such as; water-soluble polymers such as gelatin; oil-soluble emulsifiers such as sorbitan monolaurate, sorbitan trioleate, glycerin tristearate, ethylene oxide propylene oxide block copolymers; polyoxyethylene sorbitan monolaurate, poly A water-soluble emulsifier such as oxyethylene glycerol oleate or sodium laurate may be used in combination. The amount added is not particularly limited, but is preferably 0.01 to 1.0 part by weight per 100 parts by weight of the vinyl compound.

Hereinafter, the present invention will be described in more detail with reference to examples. In the following examples and comparative examples, parts and% indicate parts by weight and% by weight, respectively, unless otherwise specified.

Example 1
(Production of POA-modified PVA (B))
Into a 3 L reactor equipped with a stirrer, reflux condenser, nitrogen inlet tube, comonomer dropping port and initiator addition port, 550 g of vinyl acetate, 450 g of methanol, 3.3 g of POA group-containing monomer (monomer A) were added. The system was purged with nitrogen for 30 minutes while charging and nitrogen bubbling. Also, a comonomer solution having a concentration of 20% was prepared by dissolving POA group-containing monomer (monomer A) in methanol as a delay solution, and nitrogen substitution was performed by bubbling nitrogen gas. The temperature of the reactor was increased, and when the internal temperature reached 60 ° C., 0.25 g of 2,2′-azobisisobutyronitrile (AIBN) was added to initiate polymerization. While the delay solution was added dropwise so that the monomer composition (ratio of vinyl acetate and monomer A) in the polymerization solution was constant, polymerization was performed at 60 ° C. for 3 hours and then cooled to stop the polymerization. The total amount of comonomer solution added until the polymerization was stopped was 40 ml. The solid content concentration when the polymerization was stopped was 24.4%. Subsequently, unreacted vinyl acetate monomer was removed while adding methanol occasionally at 30 ° C. under reduced pressure to obtain a methanol solution (concentration 35%) of POA-modified PVAc. Furthermore, 2.0 g of alkaline solution (10% methanol solution of sodium hydroxide) was added to 453.4 g of POA-modified PVAc methanol solution prepared by adding methanol to this (100.0 g of POA-modified PVAc in solution). Saponification was carried out (POA modified PVAc concentration in the saponified solution 20%, molar ratio of sodium hydroxide to vinyl acetate units in POA modified PVAc 0.003). A gel-like substance was formed in about 45 minutes after the addition of the alkaline solution. This was pulverized with a pulverizer and allowed to stand at 40 ° C. for 1 hour to proceed with saponification, and then 500 g of methyl acetate was added to leave the remaining alkali. Neutralized. After confirming that the neutralization was completed using a phenolphthalein indicator, a white solid was obtained by filtration, 2000 g of methanol was added thereto, and the mixture was allowed to stand and washed at room temperature for 3 hours. After the above washing operation was repeated three times, the white solid obtained by centrifugal drainage was left in a dryer at 65 ° C. for 2 days to obtain POA-modified PVA (B). The polymerization degree was 960, the saponification degree was 50 mol%, and the POA group modification amount was 0.4 mol%.

(Suspension polymerization of vinyl chloride)
A PVA polymer (A) having a polymerization degree of 850 and a saponification degree of 72 mol% is 800 ppm based on the vinyl chloride monomer, and the POA-modified PVA (B) obtained above is 400 ppm based on the vinyl chloride monomer. Each was dissolved in deionized water to prepare a dispersion stabilizer. The dispersion stabilizer thus obtained was charged into a glass-lined autoclave in which the scale adhesion inhibitor NOXOL WSW (CIRS) was applied to a solid content of 0.3 g / m ² . Next, 0.04 part of a 70% toluene solution of diisopropyl peroxydicarbonate was charged into a glass-lined autoclave, deaerated until the pressure in the autoclave reached 0.0067 MPa, and after removing oxygen, 30 parts of vinyl chloride was added. The content in the autoclave was charged to 63 ° C. and polymerization was started with stirring. The pressure in the autoclave at the start of polymerization was 10.2 MPa. When the pressure in the autoclave became 0.5 MPa after 5 hours from the start of the polymerization, the polymerization was stopped and unreacted vinyl chloride was removed. Time drying was performed to obtain vinyl chloride polymer particles.

(Evaluation of vinyl chloride polymer particles)
For the vinyl chloride polymer particles, the average particle size, particle size distribution, and scale adhesion were measured according to the following methods. The evaluation results are shown in Table 1.
(1) Average particle size of vinyl chloride polymer particles Using a Tyler mesh standard wire mesh, the particle size distribution was measured by dry sieve analysis to determine the average particle size.
(2) Particle Size Distribution of Vinyl Chloride Polymer Particles The content of JIS standard sieve 42 mesh on was expressed in weight%.
A: Less than 0.5% B: 0.5% or more and less than 1% C: 1% or more The content of JIS standard sieve 80 mesh-on was expressed in weight%.
A: Less than 5% B: 5% or more and less than 10% C: 10% or more The smaller the number, the smaller the coarse particles, the sharper the particle size distribution, and the better the polymerization stability.
(3) Scale adhesion (fish eye)
100 parts of vinyl chloride polymer particles, 50 parts of dioctyl phthalate (DOP), 5 parts of tribasic lead sulfate and 1 part of lead stearate are roll-kneaded for 7 minutes at 150 ° C., and a sheet having a thickness of 0.1 mm, 1400 mm × 1400 mm Were prepared and the number of fish eyes was measured. It converted into the number of fish eyes per 1000 cm < ² >, and evaluated on the following references | standards.
A: 0-3, very few B: 4-10, few C: 11 or more, many

Examples 2 to 16
Except for changes in saponification conditions such as the amount of vinyl acetate and methanol charged, polymerization conditions such as the type and amount of POA comonomer used during polymerization, the concentration of PVAc during saponification, and the molar ratio of sodium hydroxide to vinyl acetate units Using POA-modified PVA (B) synthesized in the same manner as in Example 1, suspension polymerization of vinyl chloride was performed in the same manner as in Example 1 to obtain vinyl chloride polymer particles. Table 2 shows the structure of the comonomer used, and Table 1 shows the evaluation results of the obtained POA-modified PVA (B) and vinyl chloride polymer particles.

Comparative Example 1
The suspension polymerization of vinyl chloride was carried out in the same manner as in Example 1 except that the POA-modified PVA (B) was not used and the PVA (A) powder was used as it was as a dispersion stabilizer. In this case, vinyl chloride polymer particles could not be obtained because vinyl chloride was blocked and could not be polymerized.

Comparative Example 2
The vinyl chloride polymer was subjected to suspension polymerization of vinyl chloride in the same manner as in Example 1 except that the POA-modified PVA (B) was synthesized and used with a POA group modification amount of 0.005 mol%. Particles were obtained. The evaluation results are shown in Table 1. Uniform polymer particles could not be obtained due to the presence of coarse particles, and the amount of scale adhered was large and stable polymerization could not be performed.

Comparative Example 3
A vinyl chloride polymer particle was obtained by carrying out suspension polymerization of vinyl chloride in the same manner as in Example 1, except that a POA-modified PVA (B) having a polymerization degree of 150 was synthesized and used. The evaluation results are shown in Table 1. Uniform polymer particles could not be obtained due to the presence of coarse particles, and the amount of scale adhered was large and stable polymerization could not be performed.

Comparative Example 4
Except that a POA-modified PVA (B) having a polymerization degree of 1500 was synthesized and used, suspension polymerization of vinyl chloride was performed in the same manner as in Example 1 to obtain vinyl chloride polymer particles. The evaluation results are shown in Table 1. Uniform polymer particles could not be obtained due to the presence of coarse particles, and the amount of scale adhered was large and stable polymerization could not be performed.

Comparative Example 5
Suspension polymerization of vinyl chloride was carried out in the same manner as in Example 1 except that PVA (A) was not used and only POA-modified PVA (B) was used in an amount corresponding to 400 ppm with respect to the vinyl chloride monomer. It was. In this case, vinyl chloride polymer particles could not be obtained because vinyl chloride was blocked and could not be polymerized.

Comparative Examples 6 and 7
As the POA-modified PVA (B), suspension polymerization of vinyl chloride was carried out in the same manner as in Example 1 except that the types of POA comonomer shown in Table 2 were used to obtain vinyl chloride polymer particles. The evaluation results are shown in Table 1. Uniform polymer particles could not be obtained due to the presence of coarse particles, and the amount of scale adhered was large and stable polymerization could not be performed.

As shown in the examples, when the dispersion stabilizer for suspension polymerization of the vinyl compound of the present invention is used, since the polymerization stability is high, the formation of coarse particles is small, and particles having a uniform particle size are obtained. can get. Further, blocking and scale adhesion due to unstable polymerization are reduced. Thus, the industrial evaluation of the dispersion stabilizer for suspension polymerization of the present invention is extremely high.

Claims

A vinyl alcohol polymer (A) having a saponification degree of 60 mol% or more and a viscosity average polymerization degree of 200 or more, and a vinyl alcohol type polymer containing a polyoxyalkylene group represented by the following general formula (I) in the side chain A polyoxyalkylene polymer having a viscosity average polymerization degree of 200 to 1000, a saponification degree of less than 60 mol%, and a polyoxyalkylene group-modified amount group of 0.1 to 10 mol%. A dispersion stabilizer for suspension polymerization comprising an alkylene-modified vinyl alcohol polymer (B).

(Wherein R1 represents a hydrogen atom or a methyl group, R2 represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, m and n represent the number of repeating units of each oxyalkylene unit, 1 ≦ m ≦ 10, (3 ≦ n ≦ 20)
The suspension according to claim 1, wherein the weight ratio (A) / (B) of the vinyl alcohol polymer (A) to the polyoxyalkylene-modified vinyl alcohol polymer (B) is 99/1 to 5/95. Dispersion stabilizer for polymerization.