JP5465615B2 - Dispersion stabilizer for suspension polymerization - Google Patents

Description

  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 a partially saponified vinyl alcohol polymer as a dispersion stabilizer in suspension polymerization of vinyl compounds such as vinyl chloride.
The dispersion stabilizer for suspension polymerization of vinyl compounds includes [1] a plasticizer with high absorbency even when used in a small amount and easy processing, and [2] removal of monomer components such as remaining vinyl compounds. There are demands for necessary performance such as being easy, [3] having few coarse particles, [4] being able to obtain particles having a uniform particle size as much as possible, and preventing scale adhesion.

  In response to these requirements, for example, a method has been proposed in which a vinyl alcohol resin having a low polymerization degree and a low saponification degree is used in combination as a dispersion stabilizing aid for a dispersion stabilizer for suspension polymerization of a vinyl compound.

  In Patent Document 1 (Japanese Patent Laid-Open No. 4-154810), a polyvinyl ester polymer having an amino group, an ammonium group, a carboxyl group or a sulfonic acid group in the side chain and having a saponification degree of 70 mol% or less is used as a dispersoid. Dispersion aids for suspension polymerization of vinyl compounds comprising aqueous dispersions are disclosed.

  In Patent Document 2 (JP-A-10-259213), for example, a partially saponified vinyl ester resin aqueous solution containing an oxyalkylene group is highly useful as a dispersion aid for suspension polymerization of vinyl compounds. Have been described.

  Patent Document 3 (WO91 / 15518) discloses a polyvinyl ester polymer having an ionic group at the terminal or a polyvinyl alcohol polymer having a saponification degree of 90 mol% or less obtained by saponifying the polyvinyl ester polymer. Suspension polymerization method of vinyl compound is disclosed using as a dispersant.

  Patent Document 4 (JP-A-10-168128) discloses a polyvinyl alcohol polymer having an ionic group at one end and a saponification degree of 10 to 85 mol% and a polymerization degree of 50 to 3000. It is described that it is useful for suspension polymerization of compounds.

  Patent Document 5 (Japanese Patent Application Laid-Open No. 10-152508) has a pH of 4.0 to 7.0 in the case of an aqueous dispersion, contains 10 mol% or less of ionic groups in the side chain or terminal, Dispersion aids for suspension polymerization of vinyl compounds comprising a vinyl ester polymer having a degree of conversion of 60 mol% or less are disclosed.

  In Patent Document 6 (Japanese Patent Laid-Open No. 9-183805), 0.01 to 0.3 mol% of a sulfonic acid group (A) and 0.05 to 1.0 of a carboxyl group (B) are present at the side chain or terminal. It is made of a polyvinyl ester polymer having a molar ratio of (A) and (B) of 0.01 ≦ (A) / (B) ≦ 0.5 and a saponification degree of 60 mol% or less. Dispersing aids for suspension polymerization of vinyl compounds are disclosed.

  Patent Document 7 (JP-A-8-259609) discloses a modified polyvinyl alcohol (A) having an ethylene unit content of 1 to 24 mol% and a saponification degree of more than 80 mol%, and a saponification degree of 60 to 95 mol% and For suspension polymerization of a vinyl compound obtained by mixing a polyvinyl alcohol polymer (B) having a polymerization degree of 600 or more in a weight ratio of (A) component / (B) component of 1/9 to 8/2. Dispersion stabilizers are disclosed.

  However, even when the dispersion stabilizing aid for suspension polymerization described in Patent Documents 1 to 7 is used, a considerable amount must be added in order to satisfy the required performances of [1] to [4] described above. There was a problem of not becoming.

JP-A-4-154810 JP 10-259213 A WO91 / 15518 JP-A-10-168128 JP-A-10-152508 JP-A-9-183805 JP-A-8-259609

  In the suspension polymerization of vinyl compounds such as vinyl chloride, the present invention satisfies the above-mentioned required performances [1] to [4], and has excellent polymerization stability even if the addition amount is small. It aims at providing the dispersion stabilizer for superposition | polymerization.

  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 group represented by the following general formula (I): A vinyl alcohol polymer having a terminal and a vinyl alcohol polymer (B) having a viscosity average polymerization degree of 200 to 1000 and a saponification degree of less than 60 mol%. The present inventors have found that a dispersion stabilizer for suspension polymerization of a series compound solves the above-mentioned problems, and has completed the present invention.

（式中、Ｒは水素原子またはＯＭ基を表し、Ｍは、水素原子、アルカリ金属原子、１／２アルカリ土類金属原子、またはアンモニウム基を表す。）

(In the formula, R represents a hydrogen atom or an OM group, and M represents a hydrogen atom, an alkali metal atom, a ½ alkaline earth metal atom, or an ammonium group.)

  At this time, the weight ratio (A) / (B) between the vinyl alcohol polymer (A) and the vinyl alcohol polymer (B) is preferably 99/1 to 5/95.

  The present invention also includes a method for producing a vinyl polymer in which a vinyl compound is subjected to suspension polymerization in the presence of the dispersion stabilizer for suspension polymerization. At this time, it is preferable that the usage-amount of the vinyl alcohol-type polymer (B) with respect to 100 weight part of vinyl-type compounds is 0.002-0.05 weight part.

  When suspension polymerization of a vinyl compound is performed using the dispersion stabilizer for suspension polymerization of the present invention, the above-mentioned required performances [1] to [4] are satisfied, and even if the addition amount is small. An effect of excellent polymerization stability can be achieved.

  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 70-90 mol%. When the degree of saponification is less than 60 mol%, the water solubility of PVA is lowered and the handleability is deteriorated. In addition, the saponification degree of PVA is a value obtained by measuring according to JIS-K6726.

  Moreover, the viscosity average polymerization degree of PVA (A) is 200 or more, Preferably it is 500 or more, More preferably, it is 550-8000, More preferably, it is 600-3500. When the viscosity average degree of polymerization of PVA 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.

  PVA (B) used in the present invention has a group represented by the above general formula (I) at the terminal.

Examples of the alkali metal atom represented by M include a sodium atom and a potassium atom. Examples of the ½ alkaline earth metal atom represented by M include a ½ magnesium atom and a ½ calcium atom. When M is a ½ alkaline earth metal atom, the remaining ½ alkaline earth metal atom (that is, the remaining bond of the divalent alkaline earth metal atom) is oxygen in the general formula (I). atom, an oxygen atom in the following general formula (II), may be combined with P (H ₂ O ₂₎ or the like.

（ただし、Ｍは水素原子、アルカリ金属、１／２アルカリ土類金属原子、またはアンモニウム基を表す。）

(However, M represents a hydrogen atom, an alkali metal, a 1/2 alkaline earth metal atom, or an ammonium group.)

  PVA (B) may contain a group represented by the general formula (II) in the main chain.

  The degree of polymerization of PVA (B) is 200-1000. 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. In addition, the polymerization degree of PVA (B) is measured by the method similar to the measuring method of the polymerization degree of PVA (A) demonstrated above.

  The degree of saponification of 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. 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 degree of saponification of PVA (B) is a value that can be measured according to JIS-K6726.

  The production method of PVA (B) is not particularly limited as long as the obtained PVA has a group represented by the general formula (I) at the end, but for example, vinyl ester monomers are present in the presence of a compound containing phosphorus. It can be produced by a method comprising a step of radical polymerization under the step and a step of saponifying the obtained polymer.

  Examples of vinyl ester monomers include 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, vinyl benzoate, etc. Among them, vinyl acetate is most preferable.

  Compounds containing phosphorus include hypophosphorous acid such as hypophosphorous acid, sodium hypophosphite, potassium hypophosphite, calcium hypophosphite, magnesium hypophosphite, ammonium hypophosphite and hydrates thereof. Examples of the compound include sodium hypophosphite or a hydrate thereof, which is the most inexpensive industrially.

  There is no restriction | limiting in particular in the usage-amount of the compound containing phosphorus, What is necessary is just to set suitably according to the quantity of group represented by general formula (I) to introduce | transduce into PVA (B). As for the usage-amount of the compound containing phosphorus, 0.001-30 weight part is preferable with respect to 100 weight part of vinyl ester monomers.

  The polymerization of the vinyl ester monomer can be performed in a solvent such as an alcohol solvent or without a solvent.

  As a polymerization method used for the polymerization of the vinyl ester monomer, any of batch polymerization, semi-batch polymerization, continuous polymerization, and semi-continuous polymerization may be used. 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, methanol, ethanol, n-propanol or the like can be used, but is 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. As the azo initiator, 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (4-methoxy-2,4- Dimethyl valeronitrile) and the like, and peroxide initiators include perisopropyl compounds such as diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate and diethoxyethyl peroxydicarbonate; t-butyl Perester compounds such as peroxyneodecanate, α-cumylperoxyneodecanate, and 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. Moreover, as a redox-type initiator, what combined said peroxide and reducing agents, such as sodium hydrogen sulfite, sodium hydrogencarbonate, tartaric acid, L-ascorbic acid, Rongalite, is mentioned. In addition, when the polymerization of the vinyl ester monomer is performed at a high temperature, coloring of PVA due to the decomposition of the vinyl ester monomer may be seen. It is safe to add an antioxidant such as tartaric acid to the polymerization system in an amount of 1 to 100 ppm (relative to the vinyl ester monomer).

  0-200 degreeC is preferable and the temperature employ | adopted when superposing | polymerizing a vinyl ester-type monomer has more preferable 30-140 degreeC. When the polymerization temperature is lower than 0 ° C., a sufficient polymerization rate cannot be obtained, which is not preferable. Moreover, when the temperature which performs superposition | polymerization is higher than 200 degreeC, since it becomes difficult to obtain the target PVA, it is unpreferable. As a method for controlling the temperature employed in the polymerization to 0 to 200 ° C., for example, a method of balancing the heat generated by the polymerization and the heat radiation from the surface of the reactor by controlling the polymerization rate. In addition, a method of controlling by an external jacket using an appropriate heating medium can be mentioned, but the latter method is preferable from the viewpoint of safety.

  When the vinyl ester monomer is polymerized, it may be copolymerized with other monomers as long as the gist of the present invention is not impaired. Examples of monomers copolymerizable with vinyl ester monomers include α-olefins such as ethylene, propylene, n-butene, and isobutylene; acrylic acid and its salts; methyl acrylate, ethyl acrylate, and acrylic acid n. Acrylic esters such as -propyl, i-propyl acrylate, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, octadecyl acrylate; methacrylic acid and Salts thereof: methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, i-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate , Octadecyl methacrylate, etc. Methacrylic acid esters; acrylamide; N-methylacrylamide, N-ethylacrylamide, N, N-dimethylacrylamide, diacetoneacrylamide, acrylamidepropanesulfonic acid and its salt, acrylamidopropyldimethylamine and its salt or quaternary salt thereof, N Acrylamide derivatives such as methylolacrylamide and its derivatives; methacrylamide; N-methylmethacrylamide, N-ethylmethacrylamide, methacrylamidepropanesulfonic acid and salts thereof, methacrylamidepropyldimethylamine and salts thereof or quaternary salts thereof, N -Methacrylamide derivatives such as methylol methacrylamide and derivatives thereof; methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether , Vinyl ethers such as i-propyl vinyl 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; halogens such as vinyl chloride and vinyl fluoride Vinyl halides; 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; Vinylsilyl compounds such as methoxysilane; polyoxyethylene (meth) acrylate, polyoxypropylene (meth) acrylate, polyoxyethylene (meth) acrylic acid amide, polyoxypropylene (meth) Crylic acid amide, polyoxyethylene (1- (meth) acrylamide-1,1-dimethylpropyl) ester, polyoxyethylene (meth) allyl ether, polyoxypropylene (meth) allyl ether, polyoxyethylene vinyl ether, polyoxypropylene And oxyalkylene group-containing monomers such as vinyl ether; isopropenyl acetate and the like.

  In the polymerization of the vinyl ester monomer, the polymerization may be carried out in the presence of a chain transfer agent within the range not impairing the gist of the present invention for the purpose of adjusting the degree of polymerization of the obtained PVA. . Chain transfer agents include aldehydes such as acetaldehyde and propionaldehyde; ketones such as acetone and methyl ethyl ketone; mercaptans such as 2-hydroxyethanethiol, n-dodecanethiol and 3-mercaptopropionic acid; tetrachloromethane, bromo Halides such as trichloromethane, trichlorethylene, and perchloroethylene are exemplified.

  By polymerization of a vinyl ester monomer in the presence of a phosphorus-containing compound, a vinyl ester (co) polymer incorporating a phosphorus-containing compound at the terminal is obtained.

  For the saponification reaction of vinyl ester polymers, alcoholysis or hydrolysis using a conventional basic catalyst such as sodium hydroxide, potassium hydroxide or sodium methoxide or an acidic catalyst such as p-toluenesulfonic acid. Reaction 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.

  According to the above method, the PVA having the group represented by the general formula (I) at the terminal and the group represented by the general formula (I) at the terminal and represented by the general formula (II) PVA having groups in the main chain can be obtained as a mixture.

  In PVA (B), the modification amount of the group represented by the general formula (I) is preferably 0.01 to 0.9 mol%. If it is less than 0.01 mol%, the standing stability of the aqueous dispersion of the dispersion aid may be deteriorated. If it exceeds 0.9 mol%, the hydrophilicity is strong, and the dispersion stabilizer is protected during suspension polymerization. Colloidal properties may be reduced.

  The weight ratio (A) / (B) of PVA (A) to PVA (B) in the dispersion stabilizer for suspension polymerization of the present invention is not particularly limited, but is preferably 99/1 to 5/95. 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 more preferably 97/3 or less, and further 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 more preferably 10/90 or more, and further preferably 15/85 or more.

  The dispersion stabilizer for suspension polymerization of the present invention is 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, Examples include α-olefins such as propylene; unsaturated dicarboxylic acids such as maleic anhydride and itaconic acid; acrylonitrile, styrene, vinylidene chloride, and vinyl ether.

  In the suspension polymerization of the vinyl compound, the amount of the dispersion stabilizer for suspension polymerization of the present invention is not particularly limited, but the amount of PVA (B) used is 0.002 to 0 with respect to 100 parts by weight of the vinyl compound. It is preferably 0.05 parts by weight, more preferably 0.003 to 0.04 parts by weight, and even more preferably 0.005 to 0.02 parts by weight. When the amount of PVA (B) used is less than 0.002 parts by weight, 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. When the amount of PVA (B) used is more than 0.05 parts by weight, the polymerization stability may be lowered when the vinyl compound is subjected to suspension polymerization.

  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, and 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; 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (4-methoxy-2) , 4-Dimethylvalero Azo compounds such tolyl) and the like. 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 the suspension polymerization of the vinyl compound, other various additives can be added to the polymerization reaction system as necessary. Examples of the additives 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 the suspension polymerization of the 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.

  In the dispersion stabilizer for suspension polymerization of the present invention, additives such as preservatives, antifungal agents, antiblocking agents, antifoaming agents and the like that are usually used in suspension polymerization can be blended as necessary. .

  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 polymers such as water-soluble cellulose ether and gelatin; oil-soluble emulsifiers such as sorbitan monolaurate, sorbitan trioleate, glycerin tristearate and ethylene oxide propylene oxide block copolymer; polyoxyethylene sorbitan monolaurate, polyoxy A water-soluble emulsifier such as ethylene glycerol oleate or sodium laurate may be used in combination. Although there is no restriction | limiting in particular about the addition amount, 0.01-1.0 weight part is preferable per 100 weight part of vinyl-type compounds.

  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.

Production Example 1
(Production of PVA (B-1))
A reactor was charged with 300 g of methanol and 2.0 g of sodium phosphinate monohydrate to prepare a methanol solution of sodium phosphinate monohydrate. Next, 1200 g of vinyl acetate was charged into the reactor, and the inside of the reactor was purged with nitrogen by bubbling nitrogen gas. The temperature of the reactor was increased, and when the internal temperature reached 60 ° C., 0.3 g of 2,2′-azobisisobutyronitrile was added to the reactor to initiate polymerization. The polymerization temperature was maintained at 60 ° C. during the polymerization. After 4 hours, when the polymerization rate reached 50%, the polymerization was stopped by cooling. Next, unreacted vinyl acetate was removed under reduced pressure to obtain a methanol solution of polyvinyl acetate (PVAc). The PVAc solution adjusted to 40% was saponified by adding a NaOH methanol solution (10% concentration) so that the alkali molar ratio (number of moles of NaOH / number of moles of vinyl acetate units in PVAc) was 0.003. After adding the alkaline solution, a gel-like material was formed in about 45 minutes. This was pulverized with a pulverizer and allowed to stand at 40 ° C. for 1 hour to proceed with saponification. The alkali was neutralized. After confirming the completion of neutralization using a phenolphthalein indicator, a white solid was obtained by filtration, 4000 g of methanol was added thereto, and the mixture was left to wash 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 PVA (B-1). This polymer had a viscosity average polymerization degree of 760 and a saponification degree of 50 mol%.

The modification amount of the group represented by the general formula (I) of the obtained PVA (B-1) was determined by ¹ H-NMR as follows. The obtained PVA (B-1) was purified by Soxhlet extraction with methanol for 48 hours, then dissolved in d ₆ -DMSO, and analyzed using ¹ H-NMR (JEOL GX-500) of 500 MHz, The peak derived from the proton attached to the phosphorus of the group represented by the formula (I) and the area α of the peak (1.1 to 1.9 ppm) derived from the main chain methylene of PVA (7.5 to 7.7 ppm) The amount of modification of the group represented by the general formula (I) was calculated from the area β of 6.3 to 6.6 ppm) using the following formula. In PVA (B-1), the modification amount of the group represented by the general formula (I) was 0.18 mol%.

Modification amount of group represented by general formula (I) (mol%) = {((peak area β)) / ((peak area α / 2) + ((peak area β)))} × 100

Production Examples 2-8
Except for changing the saponification conditions such as the amount of vinyl acetate, methanol and sodium phosphinate monohydrate, and the molar ratio of sodium hydroxide to vinyl acetate units at the time of saponification, PVA (B -2) to PVA (B-8) were obtained.

Example 1
(Suspension polymerization of vinyl chloride)
PVA (A) having a polymerization degree of 850 and a saponification degree of 72 mol% was 800 ppm with respect to the vinyl chloride monomer, and PVA (B-1) obtained above was deionized with 200 ppm with respect to the vinyl chloride monomer. Dispersion stabilizer was prepared by dissolving in water. 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)
With respect to the vinyl chloride polymer particles, the particle size distribution, plasticizer absorbability, residual monomer amount, and scale adhesion amount were measured according to the following methods. The evaluation results are shown in Table 1.

(1) 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 is indicated by 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.

(2) Plasticizer Absorption Amount (%) of dioctyl phthalate (DOP) absorption at 23 ° C. was measured according to the method described in ASTM-D3367-75.

(3) Residual vinyl chloride monomer amount 1 g of vinyl chloride polymer particles was dissolved in 25 g of tetrahydrofuran, and the content of vinyl chloride monomer remaining in the vinyl chloride resin was determined by gas chromatography.
A: Less than 5 ppm B: 5 ppm or more and less than 10 ppm C: 10 ppm or more

(4) 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 at 150 ° C. for 7 minutes, 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 2-6
Vinyl chloride suspension polymerization was performed in the same manner as in Example 1 except that PVA (B-2) to PVA (B-6) were used instead of PVA (B-1). Got. Table 1 shows the evaluation results of the PVA (B) used and the obtained vinyl chloride polymer particles.

Examples 7 and 8
Except having changed the usage-amount of PVA (B-1), suspension polymerization of vinyl chloride was performed like Example 1 and the vinyl chloride polymer particle was obtained. Table 1 shows the evaluation results of the PVA (B) used and the obtained vinyl chloride polymer particles.

Comparative Example 1
A suspension polymerization of vinyl chloride was attempted in the same manner as in Example 1 except that PVA (B-1) was not used and the PVA (A) powder was used as it was as a dispersion stabilizer. The polymerization could not be carried out and vinyl chloride polymer particles could not be obtained.

Comparative Examples 2 and 3
Vinyl chloride suspension polymerization was performed in the same manner as in Example 1 except that PVA (B-7) or PVA (B-8) was used instead of PVA (B-1). Got. Table 1 shows the evaluation results of the PVA (B) used and the obtained vinyl chloride polymer particles. The obtained vinyl chloride polymer particles contained coarse particles, so that uniform polymer particles could not be obtained, and the amount of scale adhered was large and stable polymerization could not be performed.

Comparative Example 4
A suspension polymerization of vinyl chloride was attempted in the same manner as in Example 1 except that PVA (A) was not used and only PVA (B-1) was used in an amount corresponding to 200 ppm with respect to the vinyl chloride monomer. However, vinyl chloride was blocked and polymerization could not be performed, and vinyl chloride polymer particles could not be obtained.

Comparative Example 5
Instead of PVA (B-1), a single-terminal carboxylic acid-modified PVA (C-1) having a polymerization degree of 760 and a saponification degree of 50 mol% was used in an amount corresponding to 50 ppm with respect to the vinyl chloride monomer. In the same manner as in Example 1, suspension polymerization of vinyl chloride was performed to obtain vinyl chloride polymer particles. The evaluation results are shown in Table 1. The obtained vinyl chloride polymer particles contained coarse particles, uniform polymer particles were not obtained, and plasticizer absorbability was insufficient. Moreover, the amount of residual monomers was also large. Furthermore, the amount of scale adhered was large and stable polymerization could not be performed.

Claims (4)

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 polymer having a group represented by the following general formula (I) at the terminal; A dispersion stabilizer for suspension polymerization of a vinyl compound containing a vinyl alcohol polymer (B) having a viscosity average polymerization degree of the vinyl alcohol polymer of 200 to 1000 and a saponification degree of less than 60 mol%.

(In the formula, R represents a hydrogen atom or an OM group, and M represents a hydrogen atom, an alkali metal atom, a ½ alkaline earth metal atom, or an ammonium group.)   The suspension of a vinyl compound according to claim 1, wherein the weight ratio (A) / (B) of the vinyl alcohol polymer (A) to the vinyl alcohol polymer (B) is 99/1 to 5/95. Dispersion stabilizer for polymerization.   A method for producing a vinyl polymer, comprising subjecting a vinyl compound to suspension polymerization in the presence of the dispersion stabilizer for suspension polymerization according to claim 1.   The manufacturing method of the vinyl polymer of Claim 3 whose usage-amount of the vinyl alcohol polymer (B) with respect to 100 weight part of vinyl compounds is 0.002-0.05 weight part.