WO2010113570A1

WO2010113570A1 - Method for producing vinyl-based resin

Info

Publication number: WO2010113570A1
Application number: PCT/JP2010/052789
Authority: WO
Inventors: 悠太田岡; 真輔新居; 仲前　昌人
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: TW201036994A; JP5548678B2; JPWO2010113570A1

Abstract

A vinyl-based resin which has an excellent defoaming effect on dry foam generated during polymerization and causes little scale deposition can be obtained by adding a polyoxyalkylene-modified vinyl alcohol-based polymer (A) which is a vinyl alcohol-based polymer containing a polyoxyalkylene group represented by formula (I) in a side chain and has an amount of modification with the polyoxyalkylene group of 0.01 to 10 mol% in an amount of 0.001 to 5 parts by weight with respect to 100 parts by weight of a vinyl-based compound at the time point of achieving a polymerization conversion of 10% or more when performing suspension polymerization of the vinyl-based compound in the presence of a dispersion stabilizer for use in suspension polymerization using a polymerization bath with a reflux condenser. In formula (I), 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 m and n represent the number of oxyalkylene repeating units, respectively, and satisfy formulae: 1 ≤ m ≤ 10 and 3 ≤ n ≤ 20.

Description

Method for producing vinyl resin

The present invention relates to a method for producing a vinyl resin by suspension polymerization of a vinyl compound using a polymerization tank with a reflux condenser having excellent productivity. More specifically, the present invention relates to a method for producing a vinyl resin in which the obtained vinyl chloride polymer particles are uniform and have excellent antifoaming properties against dry foam generated in the middle to late stage of polymerization in a polymerization tank.

Recently, in the production of vinyl-based resins such as polyvinyl chloride, it has been required to shorten the time required for one batch of polymerization in order to improve productivity, and in order to increase the removal rate of polymerization reaction heat. There have been proposed a method using a polymerization tank with a flux capacitor and a method (hot charge method) for charging a preheated aqueous medium in order to shorten the temperature raising time. However, when a polymerization tank with a reflux condenser is used, the pressure in the vicinity of the reflux condenser decreases as the vinyl compound (monomer) gas condenses, so wet and dry foam become intense. There was a problem. The wet foam is a foam mainly composed of water mainly derived from polyvinyl alcohol. On the other hand, dry foam is foaming mainly composed of polyvinyl chloride (PVC) or vinyl chloride monomer (VCM), and occurs mainly in the middle to late stage of polymerization. The generated dry foam floats over the surface of the liquid layer of the charged mixture. Since this foam does not disappear easily even with stirring, it is subjected to polymerization in the form of foam. For this reason, (1) the scale adheres to the interface portion between the gas phase portion and the liquid phase portion where the bubbles adhere, resulting in a decrease in productivity. (2) The temperature of the polymerization tank cannot be controlled due to the scale adhesion. (3) Foam polymer is generated, resulting in a decrease in yield, (4) Fish eye is generated, resulting in a decrease in product quality, (5) Mixing of irregularly shaped particles derived from the foam polymer However, there is a problem that uniform particles cannot be obtained. These tend to increase with an increase in the size of the reflux condenser. When no reflux condenser is used, dry foam does not occur, but there is a problem that the polymerization time is long and productivity is low.

As countermeasures against these problems, Patent Document 1 (Japanese Patent Laid-Open No. 2-180908) discloses that when the removal amount of the polymerization reaction heat in the reflux condenser is 10% or less of the total polymerization reaction amount, silicone such as dimethylpolysiloxane, A method of adding low saponification degree polyvinyl alcohol or the like is disclosed.

Patent Document 2 (Japanese Patent Application Laid-Open No. 3-212409) discloses a degree of saponification with respect to 100 parts by weight of vinyl chloride monomer when the amount of polymerization reaction heat removed by the reflux condenser does not exceed 10% of the total polymerization reaction heat. A method of adding 0.002 to 0.007 parts by weight of a water-insoluble partially saponified polyvinyl alcohol having 20 to 50 mol% and a polymerization degree of 200 to 400 and 0.001 to 0.01 parts by weight of an antifoaming agent such as dimethylpolysiloxane Is disclosed.

Patent Document 3 (Japanese Patent Laid-Open No. 55-137105) discloses that ion-modified polyvinyl alcohol having a saponification degree of 60 to 80% is added before the start of polymerization.

In Patent Document 4 (Japanese Patent Laid-Open No. 7-179507), water-soluble polyvinyl alcohol having a saponification degree of 70 to 85 mol% and a polymerization degree of 700 to 3000 is added at the time of polymerization conversion of 5 to 50%, and polymerization is performed. Is disclosed in a temperature range of 58-70 ° C.

Patent Document 5 (Japanese Patent Application Laid-Open No. 7-53607) discloses that water-soluble polyvinyl alcohol having a saponification degree of 70 to 85 mol% and a polymerization degree of 700 to 3000 is continuously or A method of sequential addition is disclosed.

Patent Document 6 (Japanese Patent Application Laid-Open No. 7-18007) discloses a method of adding water-soluble polyvinyl alcohol having a saponification degree of 75 to 85 mol% and a polymerization degree of 1500 to 2700 at a polymerization conversion rate of 30 to 60%. Has been.

Patent Document 7 (Japanese Patent Laid-Open No. 8-73512) discloses a method of adding partially saponified polyvinyl alcohol having a saponification degree of 20 to 55 mol% and an average polymerization degree of 150 to 600 between a polymerization rate conversion of 20 to 60%. Is disclosed.

Patent Document 8 (Japanese Patent Laid-Open No. 10-1503) discloses a method of adding a vinyl alcohol polymer having a saponification degree of 85 mol% or less at a polymerization conversion rate of 30 to 90%.

In Patent Document 9 (Japanese Patent Application Laid-Open No. 11-116630), a vinyl alcohol polymer having a saponification degree of 85 mol% or less is added continuously or divided into two or more times at a polymerization conversion rate of 30 to 90%. A method is disclosed.

In Patent Document 10 (Japanese Patent Laid-Open No. 2001-122910), when the polymerization conversion rate is 30% or more, the saponification degree is 65 mol% or more, the polymerization degree is 700 or more, and 0.0300 ≦ (3-Y ) /X≧0.0330 is disclosed as a method of adding a polyvinyl alcohol resin. (X: degree of saponification, Y: iodine coloration)

Patent Document 11 (Japanese Patent Laid-Open No. 2001-233904) discloses that the dielectric constant is 32 c. g. s. e. s. u. A side chain obtained by saponifying a vinyl acetate polymer in the presence of the following solvent, having a saponification degree of 70 mol% or less and satisfying η−0.00005Y ² + 0.0085Y ≦ 0.80 A method of adding a polyvinyl alcohol polymer having an ionic group at the terminal and further containing an oxyalkylene group is disclosed. (Y: degree of saponification, η: block character)

Patent Document 12 (Japanese Patent Laid-Open No. 59-155408) discloses a method for producing a modified PVA characterized by saponifying a copolymer of an unsaturated monomer containing an oxyalkylene group and vinyl acetate. It is disclosed. Examples of the oxyalkylene group in the unsaturated monomer used for the production of the modified PVA include polyoxyethylene groups, polyoxypropylene groups, polyoxybutylene groups having about 1 to 50 repeating units.

However, the methods described in Patent Documents 1 and 2 have a problem in that dry foam generation is severe and the bulk specific gravity of the vinyl chloride resin tends to decrease. Further, the methods described in Patent Documents 3, 4, 5, 6, and 7 have a problem that the polymerization time is long and productivity is low because no reflux condenser is used. Furthermore, in the methods described in Patent Documents 8, 9, 10, and 11, a polymerization tank with a reflux condenser is used, and the productivity is high. It is not satisfactory, and problems such as adhesion of scale remain, and further improvement is desired. Patent Document 12 discloses a method for producing a modified PVA containing an oxyalkylene group, but there is no description or suggestion about suppression of dry foam.

Japanese Patent Laid-Open No. 2-180908 JP-A-3-212409 JP-A-55-137105 Japanese Unexamined Patent Publication No. 7-179507 JP-A-7-53607 JP 7-18007 A JP-A-8-73512 Japanese Patent Laid-Open No. 10-1503 Japanese Patent Laid-Open No. 11-116630 JP 2001-122910 A JP 2001-233904 A JP 59-155408 A

In the present invention, in the suspension polymerization of a vinyl compound using a polymerization tank equipped with a reflux condenser, the resulting vinyl polymer particles are uniform and have a defoaming property against dry foam generated from the middle to the later stage of the polymerization. It aims at providing the manufacturing method of the outstanding vinyl resin.

As a result of intensive studies to solve the above problems, the present inventors perform suspension polymerization of vinyl compounds in the presence of a dispersion stabilizer for suspension polymerization using a polymerization tank equipped with a reflux condenser. In this case, when the polymerization conversion rate is 10% or more, a vinyl alcohol polymer containing a polyoxyalkylene group represented by the following general formula (I) in the side chain with respect to 100 parts by weight of the vinyl compound, It has been found that the above problem can be solved by adding 0.001 to 5 parts by weight of a polyoxyalkylene-modified vinyl alcohol polymer (A) having a polyoxyalkylene group modification amount of 0.01 to 10 mol%. The present invention has been 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.

According to the method for producing a vinyl resin of the present invention, since it is excellent in antifoaming property against dry foam occurring in the middle to late stage of polymerization, the productivity of vinyl resin can be increased. In addition, since vinyl polymer particles having a uniform particle diameter can be obtained, a high-quality vinyl resin can be provided.

The present invention will be described in detail below. In the present invention, the reflux condenser is used for efficiently removing the heat of polymerization reaction generated by suspension polymerization of a vinyl compound. The gas of the unreacted vinyl compound (monomer) generated from the suspension in the polymerization tank is liquefied by the reflux condenser and returned to the polymerization tank, whereby the polymerization heat is removed. The temperature of the cooling water in the reflux condenser is usually about 10 to 50 ° C. Usually, the temperature control of the polymerization tank is performed in combination with the temperature control by the jacket or coil of the polymerization tank in addition to the heat removal by the reflux condenser. The removal amount of the polymerization reaction heat in the reflux condenser is not particularly limited, but is preferably 10 to 80%, more preferably 20 to 60% of the total polymerization reaction heat amount.

The suspension polymerization of the vinyl compound is performed in the presence of a dispersion stabilizer for suspension polymerization. The dispersion stabilizer for suspension polymerization is not particularly limited, and examples thereof include cellulose derivatives such as methylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, carboxymethylcellulose, water-soluble polymers such as gelatin, polyvinyl alcohol, and polyvinylpyrrolidone. Among them, polyvinyl alcohol having a saponification degree of 60 to 95 mol%, preferably 68 to 93 mol%, and a polymerization degree of 200 to 3,500, preferably 500 to 2500 is suitably used.

In the present invention, the amount of the dispersion stabilizer for suspension polymerization is preferably 0.01 to 5 parts by weight, more preferably 0.02 to 2 parts by weight, more preferably 0.02 to 2 parts by weight based on 100 parts by weight of the vinyl compound. 1 part by weight is more preferred. When the amount is less than 0.01 part by weight, the polymerization stability may decrease when suspension polymerization of the vinyl compound. When the amount exceeds 5 parts by weight, the waste liquid after suspension polymerization becomes cloudy. Chemical oxygen demand (COD) may be high.

In the present invention, when a vinyl compound is subjected to suspension polymerization in the presence of a dispersion stabilizer for suspension polymerization using a polymerization tank equipped with a reflux condenser, when the polymerization conversion rate is 10% or more, the above general A vinyl alcohol polymer containing a polyoxyalkylene group represented by the formula (I) in the side chain (hereinafter, the vinyl alcohol polymer may be abbreviated as PVA), and the polyoxyalkylene group modification amount is 0. A polyoxyalkylene-modified vinyl alcohol polymer (A) (hereinafter, the polyoxyalkylene-modified vinyl alcohol polymer may be abbreviated as POA-modified PVA) in an amount of 0.01 to 10 mol% is added.

POA-modified PVA (A) needs to have a polyoxyalkylene (POA) group modification amount of 0.01 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 (A) increases, and the water solubility of the PVA may decrease. On the other hand, when the POA group modification amount is less than 0.01 mol%, the water solubility of the POA modified PVA (A) 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 obtained from, for example, the proton NMR of the POA modified polyvinyl ester which is the precursor of the PVA, for example, POA modified polyvinyl acetate (POA modified PVAc). Can do. 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). From the peak α (4.7 to 5.2 ppm) derived from the main chain methine of the vinyl ester and the peak β (0.8 to 1.0 ppm) derived from the terminal methyl group of the oxybutylene unit (unit 2) of the POA group The POA group modification amount is calculated using the following formula.
POA group modification amount (mol%) = {(number of protons of β / 3n) / (number of protons of α + (number of protons of β / 3n))} × 100
n is the number of oxybutylene units (unit 2)

The viscosity average degree of polymerization (P) of the POA-modified 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 degree of polymerization of POA-modified PVA (A) is preferably 200 or more, more preferably 200 to 3000, and still more preferably 300 to 2500. If the degree of polymerization is less than 200, the effect of suppressing dry foam is insufficient, and on the contrary, the wet foam may become intense. If it exceeds 3000, the plasticizer absorbability of the resulting vinyl resin may be reduced.

In the present invention, POA-modified PVA (A) may be used alone, or two or more kinds having different characteristics may be mixed and used.

The degree of saponification of POA-modified PVA (A) is preferably 50 to 99 mol%, more preferably 60 to 98 mol%, still more preferably 65 to 95 mol%. If the degree of saponification is less than 50 mol%, the effect of suppressing dry foam may not be obtained, and foaming may occur. If it exceeds 99%, the plasticizer absorbability of the resulting vinyl resin may be reduced.

The number of repeating units m of the unit 1 of the POA group represented by the general formula (I) must be 1 ≦ m ≦ 10, preferably 1 ≦ m ≦ 5, more preferably 1 ≦ m ≦ 3, and 1 ≦ m. ≦ 2 is particularly preferred. The number of repeating units n of unit 2 (polyoxybutylene) must be 3 ≦ n ≦ 20, preferably 5 ≦ n ≦ 18, and particularly preferably 8 ≦ n ≦ 15. 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. When n is more than 20, the hydrophobicity of the POA group becomes high, and POA-modified PVA ( The water solubility of A) may decrease.

In order to produce POA-modified PVA (A) in the present invention, copolymerization of an unsaturated monomer having a POA group represented by the general formula (I) and a vinyl ester monomer is carried out 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 (A) 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, 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) for the purpose of preventing coloring.

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 Acrylamide derivatives such as methacrylamide; N-methyl methacrylamide, N-ethyl methacrylamide, methacrylamide propane sulfonic 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 POA-modified PVA (A) 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 POA-modified PVA (A) is preferably water-dispersible. As a method for introducing an ionic functional group into the terminal part of the POA-modified PVA (A), vinyl acetate is used in the presence of a thiol compound such as thiolacetic acid, mercaptopropionic acid, 3-mercapto-1-propanesulfonic acid sodium salt. For example, a method of polymerizing a vinyl ester monomer such as 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 —, wherein R 5 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.

When 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, R2 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.

In suspension polymerization of vinyl compounds, the POA-modified PVA (A) is added at a time when the polymerization conversion of the vinyl compound is 10% or more, preferably 15% to 90%, and more preferably 18% to 87%. More preferably, 20% to 85% is particularly preferable. In addition, when foaming due to dry foam occurs immediately before the internal pressure of the polymerization tank starts to decrease or immediately after the internal pressure of the polymerization tank starts to decrease, it is also preferable to add at this point. Although there is no restriction | limiting in particular in the addition method of POA modified PVA (A), The method of adding with forms, such as aqueous solution, aqueous dispersion, organic solvent solutions, such as methanol, and a methanol-water mixed solution, is mentioned. The concentration of the POA-modified PVA (A) solution is usually 0.01 to 30% by weight. The temperature of the solution of the POA-modified PVA (A) is not particularly limited, and may be one raised to room temperature or the polymerization temperature. The addition amount of the POA-modified PVA (A) is 0.001 to 5 parts by weight, preferably 0.001 to 0.5 parts by weight, based on 100 parts by weight of the vinyl compound to be subjected to suspension polymerization. More preferred is 0.01 to 0.1 parts by weight. When the addition amount of POA-modified PVA (A) is less than 0.001 part by weight, the effect of suppressing dry foam is not sufficient, and when the addition amount of POA-modified PVA (A) exceeds 5 parts by weight, the resulting chloride This is not preferable in that the bulk specific gravity of the vinyl resin becomes too high.

Examples of vinyl compounds used for suspension polymerization 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, and the like. Esters and anhydrides; styrene, acrylonitrile, vinylidene chloride, vinyl ether and the like. Of these, vinyl chloride is particularly preferred. The suspension polymerization of vinyl chloride may be homopolymerization or copolymerization. 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.

As the polymerization initiator that can be used for suspension polymerization of vinyl compounds, any oil-soluble catalyst or water-soluble catalyst conventionally used for polymerization of vinyl chloride monomers and the like can be used. Examples of the oil-soluble catalyst include percarbonate compounds such as diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, diethoxyethyl peroxydicarbonate; t-butyl peroxyneodecanate, t-butyl percarbonate. Perester compounds such as oxypivalate, t-hexylperoxypivalate, α-cumylperoxyneodecanate; acetylcyclohexylsulfonyl peroxide, 2,4,4-trimethylpentyl-2-peroxyphenoxyacetate, 3, Examples thereof include peroxides such as 5,5-trimethylhexanoyl peroxide and lauroyl peroxide; azo compounds such as azobis-2,4-dimethylvaleronitrile and azobis (4-2,4-dimethylvaleronitrile). Examples of the water-soluble catalyst include potassium persulfate, ammonium persulfate, hydrogen peroxide, cumene hydroperoxide, and the like. These oil-soluble catalysts or water-soluble catalysts 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. Further, it is optional to add a pH adjusting agent, a crosslinking agent, etc., and a plurality of the above additives may be used in combination.

In suspension polymerization of a vinyl compound, a partially saponified vinyl alcohol polymer having a saponification degree of 60 mol% or less may be used as a dispersion stabilizing aid. The addition amount is preferably 0.1 to 120 parts by weight, more preferably 0.5 to 110 parts by weight, and particularly preferably 1 to 100 parts by weight with respect to 100 parts by weight of the dispersion stabilizer for suspension polymerization. As the partially saponified vinyl alcohol polymer used as a dispersion stabilizing aid, in addition to the unmodified partially saponified vinyl alcohol polymer, 10 mol% of an ionic group such as a carboxyl group or an oxyalkylene group is added to the side chain or terminal. Examples thereof include partially saponified vinyl alcohol polymers.

In the present invention, in suspension polymerization of vinyl compounds, oil-soluble emulsifiers such as sorbitan monolaurate, sorbitan trioleate, glycerin tristearate, ethylene oxide propylene oxide block copolymer, polyoxyethylene sorbitan monolaurate, polyoxy Water-soluble emulsifiers such as ethylene glycerol oleate and sodium laurate may be used. 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.

Evaluation of vinyl chloride polymer particles and dry foam generation state was performed as follows.
(Evaluation of vinyl chloride polymer particles)
For the vinyl chloride polymer particles, the particle size distribution and the amount of scale adhesion were measured according to the following methods.
(1) Particle size distribution The content of JIS standard sieve 42 mesh on and 200 mesh pass was expressed in weight%. It shows that the smaller the content, the smaller the coarse particles or fine powder, and the more uniform particles are obtained.
A: Less than 0.5% B: 0.5% or more and less than 1% C: 1% or more (2) Bulk specific gravity Measured according to JIS K6721.

(Evaluation of dry foam condition)
The state of dry foam generation in the polymerization tank was evaluated by the following method.
(1) Foaming After the polymerization, before purging the unreacted vinyl chloride monomer, the foaming state in the polymerization tank was observed from the observation window on the side of the autoclave. The evaluation criteria are as follows.
A: Almost no foaming.
B: There is foaming.
C: Foaming is remarkable.
(2) Scale adhesion amount It evaluated by visually observing the adhesion state of the scale in the inner wall of a polymerization tank after taking out a polymer slurry from a polymerization tank. The evaluation criteria are as follows.
A: Almost no adhesion of scale.
B: There is scale adhesion.
C: Scale adhesion is remarkable.

Example 1
(Production of POA-modified PVA (A))
Into a 3 L reactor equipped with a stirrer, reflux condenser, nitrogen inlet tube, comonomer dropping port and initiator addition port, 400 g of vinyl acetate, 600 g of methanol, and 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 75 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, 2.7 g of an alkaline solution (sodium hydroxide in 10% methanol) 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 of saponified solution 20%, molar ratio of sodium hydroxide to vinyl acetate unit in POA modified PVAc 0.0055). A gel-like material was formed in about 20 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 (A). POA-modified PVA (A) had a polymerization degree of 520, a saponification degree of 70 mol%, and a POA modification amount of 0.4 mol%.

(Suspension polymerization of vinyl chloride)
PVA having a polymerization degree of 2000 and a saponification degree of 80 mol% was dissolved in 0.1 part of deionized water (90 L) to prepare a dispersion stabilizer, and charged into a 200 L capacity polymerization tank with a reflux condenser. Next, 0.1 part of t-butylperoxyneopeptanoate was added, and after degassing until the pressure in the polymerization tank reached 0.0067 MPa to remove oxygen, 100 parts of vinyl chloride was added and stirred. The temperature was raised to 63 ° C. by passing hot water through the jacket, and polymerization was started. The pressure in the polymerization tank at the start of the polymerization was 1.02 MPa. Subsequently, the polymerization was continued, and when the polymerization conversion rate reached 70%, 10 L of the aqueous solution of POA-modified PVA (A) synthesized above (0.02 parts as PVA (A)) was added. When the pressure in the polymerization tank reached 0.5 MPa, the polymerization was stopped, the unreacted monomer was recovered, the polymer slurry was taken out, and dried at 65 ° C. overnight to obtain vinyl chloride polymer particles. . Table 1 shows the evaluation results of the resulting vinyl chloride polymer particles and the state of occurrence of dry foam.

Examples 2-14
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 Vinyl chloride was prepared in the same manner as in Example 1 except that POA-modified PVA (A) synthesized in the same manner as in Example 1 was used and POA-modified PVA (A) was added at the time of polymerization conversion shown in Table 1. Was subjected to suspension polymerization 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 (A) and vinyl chloride polymer particles.

Comparative Example 1
Except that the POA-modified PVA (A) was not added, vinyl chloride suspension polymerization was carried out in the same manner as in Example 1 to obtain vinyl chloride polymer particles. The evaluation results are shown in Table 1. There were many coarse particles, uniform polymer particles could not be obtained, many bubbles were generated after polymerization, and there was much scale adhesion on the inner wall of the polymerization tank.

Comparative Example 2
Instead of POA-modified PVA (A), suspension polymerization of vinyl chloride was carried out in the same manner as in Example 1 except that a POA-modified amount of 0.005 mol% was synthesized and used. Combined particles were obtained. The evaluation results are shown in Table 1. There were coarse particles, uniform polymer particles could not be obtained, foaming after polymerization occurred, and scale adhered to the inner wall of the polymerization tank.

Comparative Example 3
Instead of POA-modified PVA (A), suspension polymerization of vinyl chloride was carried out in the same manner as in Example 1 except that a POA-modified amount of 11 mol% was synthesized and used. Vinyl chloride polymer particles could not be obtained because the block could not be polymerized.

Comparative Example 4
The vinyl chloride polymer was subjected to suspension polymerization of vinyl chloride in the same manner as in Example 1 except that POA-modified PVA (A) synthesized in the same manner as in Example 1 was added when the polymerization conversion was 5%. Particles were obtained. The evaluation results are shown in Table 1. Uniform polymer particles were not obtained due to the presence of coarse particles, and there were many bubbles after the polymerization, and the scale adhered to the inner wall surface of the polymerization tank.

Comparative Examples 5 and 6
As the POA-modified PVA (A), 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. There were coarse particles, uniform polymer particles could not be obtained, foaming after polymerization occurred, and scale adhered to the inner wall of the polymerization tank.

As shown in the examples, when a vinyl resin is produced by the production method of the present invention, it is excellent in antifoaming property against dry foam generated in the middle to late stage of polymerization. In addition, since vinyl polymer particles having a uniform particle diameter can be obtained, a high quality vinyl resin can be provided, and its industrial evaluation is extremely high.

Claims

In the suspension polymerization of a vinyl compound in the presence of a dispersion stabilizer for suspension polymerization, using a polymerization tank with a reflux condenser, the vinyl compound is 100 wt. Is a vinyl alcohol polymer containing a polyoxyalkylene group represented by the following general formula (I) in the side chain with a polyoxyalkylene group modification amount of 0.01 to 10 mol%. A method for producing a vinyl resin, comprising adding 0.001 to 5 parts by weight of an alkylene-modified vinyl alcohol polymer (A).

(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)