JPWO2019244967A1 - Method for producing vinyl polymer - Google Patents

Abstract

A method for producing a vinyl polymer in which a vinyl compound is suspended and polymerized in the presence of a dispersion stabilizer. The dispersion stabilizer contains modified PVA (A), PVA (B) and PVA (C), and the modified PVA is contained. (A) has a double bond in the side chain of 0.05 mol% or more and less than 0.5 mol%, the saponification degree of the modified PVA (A) is 68 mol% or more and less than 77 mol%, and the viscosity average polymerization. The degree is 500 or more and less than 1500, the degree of saponification of PVA (B) is 30 mol% or more and less than 60 mol%, the degree of polymerization average polymerization is 150 or more and less than 600, and the degree of saponification of PVA (C) is 77 mol. % Or more and less than 90 mol%, and a viscosity average degree of polymerization of 1700 or more and less than 3000. According to the production method of the present invention, the polymerization reaction is stable and the formation of coarse particles is reduced. Further, the fish eye of the molded product made of the vinyl polymer can be suppressed, and the plasticizer absorbability and the bulk specific density of the vinyl polymer can be improved.

Description

The present invention relates to a method for producing a vinyl-based polymer in which a vinyl compound is suspended and polymerized in the presence of a dispersion stabilizer containing polyvinyl alcohol.

Polyvinyl alcohol (hereinafter, may be abbreviated as "PVA") has conventionally been used for adhesives, paper coating agents, polarizing films, water-soluble films, pharmaceuticals, cosmetic composition, vinyl compounds (for example, vinyl chloride). It is used in various products such as dispersion stabilizers for suspension polymerization. It is known that the presence of a reactive group such as a double bond in PVA improves various performances or obtains a special effect.

PVA is widely used as a dispersion stabilizer used for suspension polymerization of vinyl compounds (Patent Documents 1 to 5). Improvements in polymerization stability, plasticizer absorbency, and bulk specific density are required, but it cannot be said that all of them are sufficiently satisfactory with the current technology. In particular, the relationship between plasticizer absorbability and bulk specific density is basically a trade-off relationship, so it is difficult to improve both. Therefore, it has been difficult to obtain a vinyl-based polymer having excellent plasticizer absorbency and a high bulk specific density.

It has been proposed to use heat-treated PVA in the polymerization reaction for the purpose of improving the stability (polymerization stability) of vinyl chloride during polymerization (Patent Documents 1 to 3). However, when suspension polymerization of vinyl chloride was carried out using these PVAs as dispersion stabilizers, satisfactory effects were not always obtained in terms of polymerization stability, plasticizer absorbability, and bulk specific density.

Patent Document 4 describes a dispersion for suspension polymerization, which is obtained by acetalizing polyvinyl alcohol with a monoaldehyde having an olefin-based unsaturated double bond and contains polyvinyl alcohol having a double bond in the side chain. Stabilizers are listed. When the polymerization reaction was carried out using the dispersion stabilizer for suspension polymerization described in Patent Document 4, it was difficult to say that the polymerization stability, the plasticizer absorbability of the obtained vinyl polymer, and the bulk specific density were sufficient.

Further, since an acid is used in producing the polyvinyl alcohol described in Patent Document 4, there is also a problem that expensive equipment resistant to the acid is required. Furthermore, the monoaldehyde having a double bond used in the production of the polyvinyl alcohol is expensive, unstable in the air, some are designated as toxic substances, have a pungent odor and are difficult to handle, and supply raw materials. It had problems such as poor sex.

Patent Document 5 describes a dispersion stabilizer made of polyvinyl alcohol having a double bond in the side chain, which is obtained by esterifying polyvinyl alcohol with a carboxylic acid having an unsaturated double bond or a salt thereof. It is said that the polyvinyl alcohol used in this dispersion stabilizer can be obtained by a simple method using an inexpensive carboxylic acid.

However, when suspension polymerization of a vinyl compound is carried out using this dispersion stabilizer made of polyvinyl alcohol, a large number of fish eyes are generated in the obtained molded product made of a vinyl polymer, and polymerization stability and plasticizer absorbability are also generated. There was also a problem with the bulk specific weight.

Japanese Unexamined Patent Publication No. 51-45189 Japanese Unexamined Patent Publication No. 10-67806 Japanese Unexamined Patent Publication No. 2004-250695 International Publication 2015/182567 International Publication No. 2007/11973

The present invention has been made to solve the above problems, and when suspend-polymerizing a vinyl compound, it is possible to have excellent polymerization stability and improve the plasticizer absorbability and bulk specific gravity of the obtained vinyl polymer. It is an object of the present invention to provide a method for producing a vinyl-based polymer, which can suppress fish eyes of a molded product made of the vinyl-based polymer.

The above problem is a method for producing a vinyl-based polymer in which a vinyl compound is suspended and polymerized in the presence of a dispersion stabilizer, wherein the dispersion stabilizer is modified polyvinyl alcohol (A), polyvinyl alcohol (B) and polyvinyl alcohol (). C) is contained, and the modified polyvinyl alcohol (A) has 0.05 mol of a double bond in the side chain derived from at least one selected from the group consisting of itaconic acid and its derivatives, and methacrylic acid and its derivatives. % Or more and less than 0.5 mol%, the saponification degree of the modified polyvinyl alcohol (A) is 68 mol% or more and less than 77 mol%, the viscosity average degree of polymerization is 500 or more and less than 1500, and the degree of polyvinyl alcohol (B) is The degree of saponification is 30 mol% or more and less than 60 mol%, the degree of viscosity average polymerization is 150 or more and less than 600, the degree of saxification of polyvinyl alcohol (C) is 77 mol% or more and less than 90 mol%, and the degree of viscosity average polymerization is The content of the modified polyvinyl alcohol (A) is 10 to 45 parts by mass with respect to 100 parts by mass of the total of the modified polyvinyl alcohol (A), the polyvinyl alcohol (B) and the polyvinyl alcohol (C). It is solved by providing a production method in which the content of polyvinyl alcohol (B) is 1 to 45 parts by mass and the content of polyvinyl alcohol (C) is 10 to 89 parts by mass.

At this time, the dispersion stabilizer further contains 0.001 part by mass or more and less than 5 parts by mass of the compound (D) with respect to 100 parts by mass of the modified polyvinyl alcohol (A), and the compound (D) contains a phenolic hydroxyl group. It is preferably a compound having two or more, or a salt thereof or an oxide thereof.

Further, it is preferable that the modified polyvinyl alcohol (A) has a double bond derived from itaconic acid in the side chain.

According to the production method of the present invention, the polymerization reaction is stable and the formation of coarse particles is reduced. Further, the fish eye of the molded product made of the vinyl polymer can be suppressed, and the plasticizer absorbability and the bulk specific density of the vinyl polymer can be improved.

The present invention relates to a method for producing a vinyl polymer in which a vinyl compound is suspended and polymerized in the presence of a dispersion stabilizer. As a result of diligent studies to solve the above problems, the present inventor has made modified polyvinyl alcohol (A) (hereinafter abbreviated as "modified PVA (A)"), polyvinyl alcohol (B) (hereinafter, "PVA (B)". ) ”) And polyvinyl alcohol (C) (hereinafter abbreviated as“ PVA (C) ”) have been used to complete a method for producing a vinyl polymer.

In the production method of the present invention, it is important to use a dispersion stabilizer containing a specific amount of modified PVA (A), PVA (B) and PVA (C) at the same time. According to the production method of the present invention, the stability of the vinyl compound during polymerization is improved, and a vinyl-based polymer having a small average particle size and a small number of coarse particles can be obtained. In addition, the fish eye of the obtained molded product is also suppressed. Moreover, surprisingly, the vinyl-based polymer obtained by the production method of the present invention was excellent in plasticizer absorbency and also had a high bulk specific density.

(Denatured PVA (A))
The modified PVA (A) used in the present invention has a double bond in the side chain derived from at least one selected from the group consisting of itaconic acid and its derivatives, and methacrylic acid and its derivatives.

The method for producing the modified PVA (A) used in the present invention is not particularly limited, but a suitable production method is polyvinyl alcohol (E) (E) in the presence of the above-mentioned specific carboxylic acid (itaconic acid or methacrylic acid) and a derivative thereof. Hereinafter, it may be abbreviated as “PVA (E)”), which is a method of heating and reacting. At this time, the specific carboxylic acid and its derivative can be used alone or in combination of two or more. The reaction temperature and reaction time are not particularly limited. The reaction temperature is preferably 30 to 200 ° C. The reaction time is usually 10 minutes to 24 hours. Here, PVA (E) is PVA having no double bond in the side chain.

In the present invention, examples of the itaconic acid derivative include itaconic acid alkyl ester and itaconic anhydride. Examples of the methacrylic acid derivative include methacrylic acid alkyl ester and methacrylic anhydride. These carboxylic acids and their derivatives may be salts.

Among the above-mentioned specific carboxylic acids (itaconic acid or methacrylic acid) and derivatives thereof, itaconic acid is preferable from the viewpoint of reactivity with PVA (E) and performance when used as a dispersion stabilizer. That is, it is preferable that the modified PVA (A) in the present invention has a double bond derived from itaconic acid in the side chain.

The above-mentioned PVA (E) can be produced by adopting a conventionally known polymerization method such as a bulk polymerization method, a solution polymerization method, a suspension polymerization method, an emulsion polymerization method, and a dispersion polymerization method for vinyl ester-based monomers. From an industrial point of view, preferred polymerization methods are a solution polymerization method, an emulsion polymerization method and a dispersion polymerization method. In the polymerization operation, any of a batch method, a semi-batch method and a continuous method can be adopted.

Examples of the vinyl ester-based monomer used for the polymerization include vinyl acetate, vinyl formate, vinyl propionate, vinyl caprylate, vinyl versaticate, and the like, and vinyl acetate is particularly preferable from an industrial point of view.

When polymerizing the vinyl ester-based monomer, the vinyl ester-based monomer may be copolymerized with another monomer as long as the gist of the present invention is not impaired. Examples of the monomers that can be used include α-olefins such as ethylene, propylene, n-butyl and isobutylene; acrylic acid and salts thereof, methyl acrylate, ethyl acrylate, n-propyl acrylate, and i-acrylate. Acrylic acid esters such as propyl, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, octadecyl acrylate; methacrylic acid and salts thereof; methyl methacrylate, Methacrylates such as 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. Acid esters; acrylamide, N-methylacrylamide, N-ethylacrylamide, N, N-dimethylacrylamide, diacetoneacrylamide, acrylamidepropanesulfonic acid and its salts, acrylamidepropyldimethylamine and its salts or its quaternary salts, N- Acrylamide derivatives such as methylolacrylamide and derivatives thereof; methacrylamide, N-methylmethacrylate, N-ethylmethacrylate, methacrylamide propanesulfonic acid and its salts, methacrylamidepropyldimethylamine and its salts or quaternary salts thereof, N- Methylamide derivatives such as methylolmethacrylate and derivatives thereof; such as methylvinyl ether, ethylvinyl ether, n-propylvinyl ether, i-propylvinyl ether, n-butylvinyl ether, i-butylvinyl ether, t-butylvinyl ether, dodecylvinyl ether, stearylvinyl ether and the like Vinyl ethers; 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; malein Examples thereof include unsaturated dicarboxylic acids such as acid, itaconic acid and fumaric acid and salts thereof or esters thereof; vinylsilyl compounds such as vinyltrimethoxysilane; isopropenyl acetate and the like. The copolymerization amount of such other monomers is usually 10 mol% or less.

Further, in the polymerization of the vinyl ester-based monomer, a chain transfer agent may coexist for the purpose of adjusting the degree of polymerization of the obtained polyvinyl ester. Chain transfer agents include aldehydes such as acetaldehyde, propionaldehyde, butylaldehyde and benzaldehyde; ketones such as acetone, methyl ethyl ketone, hexanone and cyclohexanone; mercaptans such as 2-hydroxyethanethiol and dodecyl mercaptan; trichloroethylene and perchloroethylene. Examples thereof include halogenated hydrocarbons such as, and among them, aldehydes and ketones are preferably used. The amount of the chain transfer agent added is determined according to the chain transfer constant of the chain transfer agent to be added and the degree of polymerization of the target polyvinyl ester, but is generally 0.1 to 10 mass by mass with respect to the vinyl ester-based monomer. % Is desirable.

The saponification reaction of the polyvinyl ester includes an alcohol-added decomposition or hydrolysis reaction using a conventionally known basic catalyst such as sodium hydroxide, potassium hydroxide, or sodium methoxydo, or an acidic catalyst such as p-toluenesulfonic acid. Applicable. Examples of the solvent used in the saponification 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, and the like. Can be used alone or in combination of two or more. Above all, it is convenient and preferable to carry out the saponification reaction in the presence of sodium hydroxide, which is a basic catalyst, using methanol or a mixed solution of methanol and methyl acetate as a solvent.

In the present invention, the modified PVA (A) has a double bond derived from at least one selected from the group consisting of itaconic acid and its derivatives, and methacrylic acid and its derivatives in the side chain of 0.05 mol% or more. It is important to have less than .5 mol%. The double bond means a carbon-carbon double bond.

When a vinyl compound is suspension-polymerized using a dispersion stabilizer containing modified PVA (A) having a double bond amount of less than 0.05 mol%, the polymerization stability is lowered and a large number of coarse particles are formed. There are problems that a large number of fish eyes are generated in a molded product made of a based polymer and that the bulk specific gravity of the vinyl polymer is low. The amount of the double bond is preferably 0.08 mol% or more, more preferably 0.10 mol% or more, and further preferably 0.12 mol% or more.

On the other hand, when a vinyl compound is suspended and polymerized using a dispersion stabilizer containing a modified PVA (A) having a double bond amount of 0.5 mol% or more, a large number of fish eyes are present in the molded product made of a vinyl polymer. As it is generated, the plasticizer absorbability of the vinyl polymer becomes low. The amount of the double bond is preferably less than 0.45 mol%, more preferably less than 0.40 mol%, still more preferably less than 0.35 mol%.

The amount of the double bond can be measured by a known method. Specifically, ¹ H-NMR measurement is convenient. When measuring the amount of the double bond, it is preferable to remove the unreacted carboxylic acid or its derivative in advance and purify it.

The purification method is not particularly limited, and examples thereof include a method of washing with a solution in which the modified PVA (A) is not dissolved and an unreacted carboxylic acid or a derivative thereof can be dissolved. After the modified PVA (A) is once made into an aqueous solution having a concentration of about 1 to 20% by mass, the aqueous solution is dropped into a solution in which the modified PVA (A) is not dissolved and the unreacted carboxylic acid or its derivative can be dissolved. , The reprecipitation method of purifying by precipitating the modified PVA (A) is convenient and preferable.

The saponification degree of the modified PVA (A) is 68 mol% or more and less than 77 mol%. When the degree of saponification is less than 68 mol%, there are problems that the water solubility is lowered and the handleability is lowered, the polymerization is unstable and the number of coarse particles is increased. The saponification degree of the modified PVA (A) is preferably 70 mol% or more. On the other hand, when the saponification degree of the modified PVA (A) is 77 mol% or more, many coarse particles are formed, a large number of fish eyes are generated in the molded product made of the vinyl polymer, and the plasticizer absorption of the vinyl polymer is performed. The problem of low sex arises. The degree of saponification of the modified PVA (A) is preferably less than 75 mol%. The saponification degree is a value obtained by measuring according to JIS-K6726 (the saponification degree described below is also the same measuring method).

The viscosity average degree of polymerization (sometimes simply referred to as "degree of polymerization") of the modified PVA (A) is 500 or more and less than 1500. When the degree of polymerization is less than 500, the polymerization stability is lowered and many coarse particles are formed, a large number of fish eyes are generated in the molded product made of the vinyl polymer, and the bulk specific gravity of the vinyl polymer is low. Occurs. The degree of polymerization of the modified PVA (A) is preferably 600 or more. On the other hand, when the degree of polymerization is 1500 or more, there are problems that many coarse particles are formed, a large number of fish eyes are generated in a molded product made of a vinyl polymer, and the plasticizer absorbability and bulk specific density of the vinyl polymer are low. Occurs. The degree of polymerization of the modified PVA (A) is preferably less than 1000, more preferably less than 900. When the degree of saponification is less than 99.5 mol%, PVA saponified to a degree of saponification of 99.5 mol% or more is subjected to the ultimate viscosity [η] (liter / g) measured at 30 ° C. in water. The viscosity average degree of polymerization (P) was determined by the following formula.
P = ([η] × 10 ⁴ / 8.29) ^{(1 / 0.62)}

(PVA (B))
The PVA (B) in the present invention is a PVA having no double bond in the side chain, and the production method is the same as that of the PVA (E).

The saponification degree of PVA (B) is 30 mol% or more and less than 60 mol%. When the saponification degree is less than 30 mol%, the polymerization stability when used as a dispersion stabilizer for a vinyl compound is lowered. The degree of saponification is preferably 35 mol% or more. On the other hand, when the saponification degree of PVA (B) is 60 mol% or more, there are problems that a large number of fish eyes are generated in the molded product made of the vinyl polymer and the plasticizer absorbability of the vinyl polymer is low. .. The degree of saponification is preferably less than 57 mol%, more preferably less than 54 mol%.

The viscosity average degree of polymerization of PVA (B) is 150 or more and less than 600. When the degree of polymerization is less than 150, the polymerization stability when used as a dispersion stabilizer for a vinyl compound is lowered, a large number of coarse particles are formed, and a large number of fish eyes are generated in a molded product made of a vinyl polymer. The problem that the bulk specific gravity of the vinyl polymer is low occurs. The degree of polymerization is preferably 200 or more. On the other hand, when the degree of polymerization is 600 or more, there is a possibility that a large number of fish eyes are generated in the molded product made of the vinyl polymer, and the plasticizer absorbability of the vinyl polymer is low. The degree of polymerization is preferably less than 550.

(PVA (C))
The PVA (C) in the present invention is a PVA having no double bond in the side chain, and the production method is the same as that of the PVA (E).

The saponification degree of PVA (C) is 77 mol% or more and less than 90 mol%. When the degree of saponification is less than 77 mol%, problems such as a decrease in polymerization stability when used as a dispersion stabilizer for a vinyl compound and a low bulk specific gravity of a vinyl polymer occur. The degree of saponification is preferably 78 mol% or more. On the other hand, when the saponification degree of PVA (C) is 90 mol% or more, there are problems that a large number of fish eyes are generated in the molded product made of the vinyl polymer and the plasticizer absorbability of the vinyl polymer is low. .. The degree of saponification is preferably less than 85 mol%.

The viscosity average degree of polymerization of PVA (C) is 1700 or more and less than 3000. When the degree of polymerization is less than 1700, the polymerization stability when used as a dispersion stabilizer for a vinyl compound is lowered, a large number of coarse particles are formed, and the bulk specific gravity of the vinyl polymer is low. The degree of polymerization is preferably 1800 or more. On the other hand, when the degree of polymerization is 3000 or more, there are problems that a large number of fish eyes are generated in the molded product made of the vinyl polymer and that the plasticizer absorbability of the vinyl polymer is low. The degree of polymerization is preferably less than 2700.

(Compound (D))
The dispersion stabilizer used in the production method of the present invention preferably further contains compound (D). At this time, the compound (D) is preferably a compound having two or more phenolic hydroxyl groups, a salt thereof, or an oxide thereof. Specific examples of the compound having two or more phenolic hydroxyl groups include benzenediol such as hydroquinone, catechol, resorcinol, t-butylhydroquinone and dit-butylhydroquinone, benzenetriol such as pyrogallol, fluoroglucinol and hydroxyquinone, and hexahydroxy. Phenolic carboxylic acids such as benzene and gallic acid; phenol carboxylic acid esters such as gallic acid alkyl esters; catechins such as epicatechin, epigallocatekin and epigallocatekin-3-gallate may also be mentioned. Examples of the gallate alkyl ester include methyl gallate, ethyl gallate, propyl gallate, octyl gallate, and dodecyl gallate. These salts or oxides can be used as well.

Of these, benzenediol, gallic acid, and alkyl gallate are preferable, benzenediol or alkyl gallate are more preferable, benzenediol is even more preferable, and t-butylhydroquinone is particularly preferable.

(Dispersion stabilizer)
In the dispersion stabilizer of the present invention, it is important that the content of the modified PVA (A) is 10 to 45 parts by mass with respect to a total of 100 parts by mass of the modified PVA (A), PVA (B) and PVA (C). is there.

When the content of the modified PVA (A) is less than 10 parts by mass, the polymerization stability is lowered in the suspension polymerization of the vinyl compound, and a large number of coarse particles are formed. There arises a problem that a large number of vinyl polymers are generated and the bulk specific gravity of the vinyl polymer is low. The content of the modified PVA (A) is preferably 20 parts by mass or more. On the other hand, when the content of the modified PVA (A) exceeds 45 parts by mass, there are problems that a large number of fish eyes are generated in the molded product made of the vinyl polymer and the plasticizer absorbability of the vinyl polymer is low. To do. The content of the modified PVA (A) is preferably 43 parts by mass or less.

In the present invention, it is also important that the content of PVA (B) is 1 to 45 parts by mass with respect to a total of 100 parts by mass of the modified PVA (A), PVA (B) and PVA (C).

When the content of PVA (B) is less than 1 part by mass, a large number of fish eyes are generated in the molded product made of the vinyl polymer, and the plasticizer absorbability of the vinyl polymer is low. The content of PVA (B) is preferably 5 parts by mass or more. On the other hand, when the content of PVA (B) exceeds 45 parts by mass, the polymerization stability is lowered in the suspension polymerization of the vinyl compound, and a large number of coarse particles are formed. There arises a problem that a large number of vinyl polymers are generated and the bulk specific gravity of the vinyl polymer is low. The content of PVA (B) is preferably 40 parts by mass or less.

In the present invention, it is important that the content of PVA (C) is 10 to 89 parts by mass with respect to a total of 100 parts by mass of the modified PVA (A), PVA (B) and PVA (C).

When the content of PVA (C) is less than 10 parts by mass, the polymerization stability is lowered and many coarse particles are formed. A large number of fish eyes are generated in a molded product made of a vinyl polymer. Is it a vinyl polymer? The problem of low specific gravity occurs. The content of PVA (C) is preferably 15 parts by mass or more. When the content of PVA (C) exceeds 89 parts by mass, there are problems that a large number of fish eyes are generated in the molded product made of the vinyl polymer and the bulk specific density of the vinyl polymer is low. The content of PVA (C) is preferably 75 parts by mass or less.

In the present invention, it is preferable that the dispersion stabilizer further contains 0.001 part by mass or more and less than 5 parts by mass of the compound (D) with respect to 100 parts by mass of the modified PVA (A). When the content of the compound (D) is less than 0.001 part by mass, a fish eye tends to occur in a molded product made of a vinyl polymer. The content of compound (D) is more preferably 0.01 parts by mass or more. On the other hand, when the content of the compound (D) is 5 parts by mass or more, the fish eye is formed in a molded product made of a vinyl polymer in which the polymerization stability is lowered and a large number of coarse particles are formed in the suspension polymerization of the vinyl compound. It tends to occur easily. The content of compound (D) is more preferably less than 3 parts by mass.

(Manufacturing method of vinyl polymer)
The present invention is a method for producing a vinyl-based polymer in which a vinyl compound is suspended and polymerized in the presence of a dispersion stabilizer. Then, the dispersion stabilizer simultaneously contains a specific amount of modified PVA (A), PVA (B) and PVA (C). By using the dispersion stabilizer, a vinyl polymer having a small average particle size and a small number of coarse particles can be obtained. In addition, the fish eye of a molded product made of a vinyl-based polymer is suppressed, and a vinyl-based polymer can also be obtained. Further, it is possible to obtain a vinyl-based polymer having excellent plasticizer absorbability and a high bulk specific density.

At this time, the total content of the modified PVA (A), PVA (B) and PVA (C) is preferably 0.01 to 1 part by mass with respect to 100 parts by mass of the vinyl compound. When the total content of the modified PVA (A), PVA (B) and PVA (C) is less than 0.01 parts by mass, the polymerization stability is low and vinyl-based polymer particles tend not to be obtained. The total content of the modified PVA (A), PVA (B) and PVA (C) is more preferably 0.02 parts by mass or more with respect to 100 parts by mass of the vinyl compound. On the other hand, when the total content of the modified PVA (A), PVA (B) and PVA (C) exceeds 1 part by mass, the economic efficiency tends to deteriorate. The total content of the modified PVA (A), PVA (B) and PVA (C) is preferably 0.5 parts by mass or less with respect to 100 parts by mass of the vinyl compound.

The dispersion stabilizer may contain various additives as long as the gist of the present invention is not impaired. Examples of the additive include polymerization inhibitors such as aldehydes, halogenated hydrocarbons, and mercaptans; polymerization inhibitors such as phenol compounds, sulfur compounds, and N-oxide compounds; pH adjusters; cross-linking agents; preservatives. ; Antifungal agents, antiblocking agents, antifoaming agents, compatibilizers and the like can be mentioned. The content of various additives in the dispersion stabilizer is preferably 10% by mass or less, more preferably 5% by mass or less, based on the amount of the dispersion stabilizer.

The method for charging the dispersion stabilizer into the polymerization tank is not particularly limited. Examples of the charging method include the following methods (i) to (iv).
Method (i): A method in which modified PVA (A), PVA (B) and PVA (C) are mixed in a powder state and then made into an aqueous solution and charged into a polymerization tank. Method (ii): Modified PVA (A), PVA (B) And PVA (C) are prepared as separate aqueous solutions, and then the aqueous solution obtained by mixing them is charged into a polymerization tank. Method (iii): Modified PVA (A), PVA (B) and PVA (C). Method (iv): Modified PVA (A), PVA (B) and PVA (C) in a powder state. Method of charging as it is From the viewpoint of uniformity in the polymerization tank, any of the above methods (i), (ii) and (iii) is preferable.

Further, as described above, in the present invention, it is preferable that the dispersion stabilizer further contains the compound (D). In this case, the method of charging the dispersion stabilizer into the polymerization tank is not particularly limited, but the method described below is preferable. First, it is preferable to react PVA (E) with the above-mentioned specific carboxylic acid or a derivative thereof in the presence of compound (D) to obtain a composition containing modified PVA (A). In this composition, the PVA (E) before the reaction reacts with the above-mentioned specific carboxylic acid or a derivative thereof to become a modified PVA (A), and the compound (D) remains as it is. Then, a method in which the composition, PVA (B) and PVA (C) are charged into the polymerization tank as a dispersion stabilizer is preferable. The preparation method at this time is not particularly limited, and examples thereof include the above methods (i) to (iv).

Examples of the vinyl compound used in the production method of the present invention include vinyl halides such as vinyl chloride; vinyl esters such as vinyl acetate and vinyl propionate; acrylic acids, methacrylic acids, esters and salts thereof; maleic acid, fumaric acid, and the like. Examples thereof include these esters and anhydrides; styrene; acrylonitrile; vinylidene chloride; vinyl ether and the like. Among them, the dispersion stabilizer of the present invention is particularly preferably used for suspension polymerization of vinyl chloride alone or with a monomer copolymerizable with vinyl chloride and vinyl chloride. Examples of the monomer copolymerizable with vinyl chloride include vinyl esters such as vinyl acetate and vinyl propionate; (meth) acrylate esters such as methyl (meth) acrylate and ethyl (meth) acrylate; ethylene and propylene. Examples thereof include α-olefin; unsaturated dicarboxylic acids such as maleic anhydride and itaconic acid; acrylonitrile; styrene; vinylidene chloride; vinyl ether and the like.

For suspension polymerization of the vinyl compound, an oil-soluble or water-soluble polymerization initiator conventionally used for polymerization of vinyl chloride can be used. Examples of the oil-soluble polymerization initiator include percarbonate compounds such as diisopropylperoxydicarbonate, di-2-ethylhexyl peroxydicarbonate, and diethoxyethylperoxydicarbonate; t-butylperoxyneodecanate, t. Perester compounds such as −butylperoxypivalate, t-hexylperoxypivalate, α-cumylperoxyneodecanate; acetylcyclohexylsulfonyl peroxide, 2,4,4-trimethylpentyl-2-peroxyphenoxyacetate , 3,5,5-trimethylhexanoyl peroxide, lauroyl peroxide and other peroxides; azo compounds such as azobis-2,4-dimethylvaleronitrile and azobis (4-2,4-dimethylvaleronitrile) Can be mentioned. 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, the polymerization temperature is not particularly limited, and it can be adjusted not only to a low temperature of about 20 ° C. but also to a high temperature of more than 90 ° C. Further, in order to increase the heat removal efficiency of the polymerization reaction system, a polymer with a reflux capacitor can also be used.

In addition to the above dispersion stabilizers for suspension polymerization of vinyl compounds, water-soluble celluloses such as methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, and hydroxypropyl methyl cellulose, which are usually used for suspension polymerization of vinyl compounds in an aqueous medium. Ether; water-soluble polymer such as gelatin; oil-soluble emulsifier such as sorbitan monolaurate, sorbitan triolate, glycerin tristearate, ethylene oxide propylene oxide block copolymer; polyoxyethylene sorbitan monolaurate, polyoxyethylene glycerin oleate, lauric acid A water-soluble emulsifier such as sodium may be used in combination. The amount to be added is not particularly limited, but is preferably 0.01 part by mass or more and 1.0 part by mass or less per 100 parts by mass of the vinyl compound.

The vinyl-based polymer obtained by the production method of the present invention can be used for various molded articles by appropriately blending a plasticizer or the like.

Hereinafter, the present invention will be described in more detail with reference to Examples. In the following Examples and Comparative Examples, unless otherwise specified, "parts" and "%" indicate parts by mass and% by mass, respectively.

[Viscosity average degree of polymerization of PVA]
The viscosity average degree of polymerization of PVA was measured according to JIS-K6726 (1994). Specifically, when the degree of saponification is less than 99.5 mol%, the ultimate viscosity [η] (liter / liter /) measured at 30 ° C. in water for PVA saponified to a degree of saponification of 99.5 mol% or more. The viscosity average degree of polymerization (P) was determined by the following formula using g).
P = ([η] × 10 ⁴ / 8.29) ^{(1 / 0.62)}

[Saponification degree of PVA]
The degree of saponification of PVA was determined by the method described in JIS-K6726 (1994). The degree of saponification of the modified PVA (A) is a value measured for the modified PVA (A) isolated by reprecipitating the powder composed of the obtained composition (C).

[Amount of double bonds introduced into modified PVA (A)]
A 10% aqueous solution of modified PVA (A) was prepared. 5 g of this aqueous solution was added dropwise to a solution of 500 g of methyl acetate / water = 95/5 to precipitate modified PVA (A), which was recovered and dried. For the isolated modified PVA (A), ¹ H-NMR was used to measure the amount of double bonds introduced into the modified PVA (A). The amount of the double bond is the amount of the double bond of the modified PVA (A) with respect to all the monomer units.

Production Example 1 (Production of PVA (A1))
A solution prepared by dissolving 6.5 parts of itaconic acid in 120 parts of methanol was prepared, and 100 parts of PVA having a viscosity average degree of polymerization of 700 and a saponification degree of 72 mol% as PVA (E) and t-butylhydroquinone as compound (D) were prepared therein. 0.1 part was added and methanol was removed under reduced pressure. Then, heat treatment was carried out at a temperature of 110 ° C. for 7 hours to obtain PVA (A1) having an itaconic acid-derived double bond in the side chain. Table 1 shows the production conditions of PVA (A1).

In the above PVA (A1), the peak of the double bond introduced at around 5.6 to 6.0 ppm was confirmed, and the amount of the double bond was 0.23 mol%. The viscosity average degree of polymerization of PVA (A1) was 700, and the saponification degree was 72 mol%. The production results of PVA (A1) are shown in Table 2.

Production Examples 2 to 12 (Production of PVA (A2 to A12))
PVA (A2 to A12) was produced in the same manner as PVA (A1) except that the heat treatment conditions such as the type and amount of raw materials used, the heat treatment temperature, and the heat treatment time were changed. The manufacturing conditions are shown in Table 1, and the manufacturing results are shown in Table 2.

Example 1
100 parts of the filtrate obtained by dissolving PVA (A1) in deionized water and filtering with a nylon mesh having a 200 mesh opening was charged into an autoclave as a dispersion stabilizer. The amount of PVA (A1) used in the filtrate was 0.04 parts by mass (400 ppm) with respect to 100 parts by mass of the amount of vinyl chloride charged. Next, as PVA (B), PVA having a viscosity average degree of polymerization of 250 and a saponification degree of 40 mol% was dissolved in a solution of deionized water / methanol = 1/1 at a concentration of 40% and charged into an autoclave as a dispersion stabilizer. .. The amount of PVA (B) charged was 0.02 parts by mass (200 ppm) with respect to 100 parts by mass of vinyl chloride charged. Next, as PVA (C), a filtrate obtained by dissolving PVA (C) having a viscosity average degree of polymerization of 2000 and a saponification degree of 80 mol% in deionized water and filtering with a nylon mesh having a 200 mesh opening was used as a dispersion stabilizer. I put 100 copies in the autoclave. The amount of PVA (C) charged was 0.04 parts by mass (400 ppm) with respect to 100 parts by mass of vinyl chloride charged. Next, deionized water was added and charged so that the total amount of deionized water was 1200 parts.

Next, 0.65 parts of a 70% toluene solution of cumylperoxyneodecanoate and 1.05 parts of a 70% toluene solution of t-butylperoxyneododecaneate were charged into the autoclave, and the pressure was 0.2 MPa in the autoclave. Nitrogen was introduced as described above. After that, the operation of purging nitrogen was performed a total of 5 times, and after sufficiently replacing nitrogen in the autoclave to remove oxygen, 940 parts of vinyl chloride was charged. The content in the autoclave was heated to 57 ° C. and polymerization of vinyl chloride was started under stirring. The pressure in the autoclave at the start of polymerization was 0.80 MPa. Approximately 3.5 hours after the start of the polymerization, the polymerization was stopped when the pressure in the autoclave reached 0.70 MPa, unreacted vinyl chloride was removed, and then the polymerization reaction product was taken out and 65 ° C. The mixture was dried for 16 hours to obtain a vinyl resin (vinyl chloride polymer particles). Then, the particles obtained by the method shown below were evaluated. The evaluation results are shown in Table 3.

(Evaluation of vinyl chloride polymer particles)
The obtained vinyl chloride polymer particles were evaluated for (1) average particle size, (2) particle size distribution, (3) bulk specific gravity, (4) plasticizer absorbency and (5) fisheye according to the following methods. .. The evaluation results are shown in Table 3.

(1) Average particle size Using a wire mesh based on Tyler mesh, the particle size distribution was measured by the dry sieving method described in JIS-Z8815 (1994). From the results, the average particle size was calculated using the Rosin-Rammler plot.

(2) Particle size distribution The content of JIS standard sieve 42 mesh-on was displayed in% by mass.
A: Less than 0.5% B: 0.5% or more and less than 1% C: 1% or more

The content of JIS standard sieve 60 mesh-on was displayed in% by mass.
A: Less than 5% B: 5% or more and less than 10% C: 10% or more

The smaller the value of both the 42 mesh-on content and the 60 mesh-on content, the smaller the coarse particles and the sharper the particle size distribution, indicating that the polymerization stability is excellent.

(3) Bulk specific gravity Measured according to JIS-K6720-2 (1999).

(4) Plasticizer absorption Measure the mass (Ag) of a 5 mL syringe filled with 0.02 g of degreased cotton, put 0.5 g of vinyl chloride polymer particles into it, measure the mass (Bg), and dioctyl there. After adding 1 g of phthalate (DOP) and allowing it to stand for 15 minutes, it was centrifuged at 3000 rpm for 40 minutes to measure the mass (Cg). Then, the plasticizer absorbability (%) was calculated from the following formula. The higher the plasticizer absorbency, the easier it is to process and the less likely it is that defects such as bumps will occur during processing into a sheet.
Plasticizer absorbency (%) = 100 × [{(CA) / (BA)} -1]

(5) Fisheye 100 parts of the obtained vinyl chloride polymer particles, 50 parts of DOP, 5 parts of lead tribasic sulfate and 1 part of zinc stearate are rolled and kneaded at 150 ° C. for 7 minutes to prepare a 0.1 mm thick sheet. The number of fish eyes per 1000 cm ^{2 was measured.}

Examples 2-12
Suspension polymerization of vinyl chloride in the same manner as in Example 1 except that the types and amounts of modified PVA (A), PVA (B) and PVA (C) used as dispersion stabilizers were changed as shown in Table 2. Was done. The conditions and results are shown in Tables 2 and 3.

Comparative Example 1
As shown in Table 2, suspension polymerization of vinyl chloride was carried out in the same manner as in Example 1 except that PVA (A8) was used as the modified PVA (A). The results are shown in Table 3. Since the degree of polymerization of PVA (A8) was too low, the polymerization was unstable, the average particle size of the obtained vinyl chloride polymer particles was large, the proportion of coarse particles was large, the bulk specific density was low, and the fish eyes were also large. It was.

Comparative Example 2
As shown in Table 2, suspension polymerization of vinyl chloride was carried out in the same manner as in Example 1 except that PVA (A9) was used as the modified PVA (A). The results are shown in Table 3. Since the degree of polymerization of PVA (A9) was too high, the bulk specific density and the plasticizer absorbency were low, and the number of fish eyes increased.

Comparative Example 3
As shown in Table 2, suspension polymerization of vinyl chloride was carried out in the same manner as in Example 1 except that PVA (A10) was used as the modified PVA (A). The results are shown in Table 3. Since the degree of saponification of PVA (A10) was too high, the average particle size of the obtained vinyl chloride polymer particles was large, the plasticizer absorption was low, and the number of fish eyes increased.

Comparative Example 4
As shown in Table 2, suspension polymerization of vinyl chloride was carried out in the same manner as in Example 1 except that PVA (A11) was used as the modified PVA (A). The results are shown in Table 3. Polymerization is unstable because the side chain of PVC (A11) does not have a double bond derived from at least one selected from the group consisting of itaconic acid and its derivatives, and methacrylic acid and its derivatives. The average particle size of the obtained vinyl chloride polymer particles was large, the proportion of coarse particles was large, the bulk specific gravity was low, and the number of fish eyes was large.

Comparative Example 5
As shown in Table 2, suspension polymerization of vinyl chloride was carried out in the same manner as in Example 1 except that PVA (A12) was used as the modified PVA (A). The results are shown in Table 3. Since the amount of double bonds that PVA (A12) has in the side chain is too large, the plasticizer absorption is low and the fish eyes are also increased.

Comparative Example 6
As shown in Table 2, suspension polymerization of vinyl chloride was carried out in the same manner as in Example 1 except that the modified PVA (A) was not used. The results are shown in Table 3. Since the modified PVA (A) was not used, the polymerization was unstable, the average particle size of the obtained vinyl chloride polymer particles was large, the proportion of coarse particles was large, the bulk specific density was low, and the number of fish eyes was large. ..

Comparative Example 7
As shown in Table 2, suspension polymerization of vinyl chloride was carried out in the same manner as in Example 1 except that PVA (B) was not used. The results are shown in Table 3. Since PVA (B) was not used, the plasticizer absorption was low and the number of fish eyes increased.

Comparative Example 8
As shown in Table 2, suspension polymerization of vinyl chloride was carried out in the same manner as in Example 1 except that the amounts of modified PVA (A), PVA (B) and PVA (C) used were changed. The results are shown in Table 3. Since the amount of PVA (B) used is large and the amount of PVA (C) used is small, the polymerization is unstable, the average particle size of the obtained vinyl chloride polymer particles is large, and the proportion of coarse particles is large. The bulk specific weight was low, and the number of fish eyes increased.

Comparative Example 9
As shown in Table 2, suspension polymerization of vinyl chloride was carried out in the same manner as in Example 1 except that the amounts of modified PVA (A), PVA (B) and PVA (C) used were changed. The results are shown in Table 3. Due to the large amount of PVA (A) used, the plasticizer absorption was low and the number of fish eyes increased.

Comparative Example 10
As shown in Table 2, suspension polymerization of vinyl chloride was carried out in the same manner as in Example 1 except that PVA (B) having a high degree of saponification was used. The results are shown in Table 3. Since the degree of saponification of PVA (B) was too high, the plasticizer absorption was low and the number of fish eyes increased.

Comparative Example 11
As shown in Table 2, suspension polymerization of vinyl chloride was carried out in the same manner as in Example 1 except that PVA (C) having a high degree of saponification was used. The results are shown in Table 3. Since the degree of saponification of PVA (C) was too high, the plasticizer absorption was low and the number of fish eyes increased.

Comparative Example 12
As shown in Table 2, suspension polymerization of vinyl chloride was carried out in the same manner as in Example 1 except that PVA (C) having a low degree of polymerization was used. The results are shown in Table 3. Since the degree of polymerization of PVA (C) is too low, the polymerization is unstable, the average particle size of the obtained vinyl chloride polymer particles is large, the proportion of coarse particles is large, the bulk specific gravity is low, and the fish eyes are also large. It was.

Comparative Example 13
As shown in Table 2, suspension polymerization of vinyl chloride was carried out in the same manner as in Example 1 except that PVA (B) having a low degree of polymerization was used. The results are shown in Table 3. Since the degree of polymerization of PVA (B) is too low, the polymerization is unstable, the average particle size of the obtained vinyl chloride polymer particles is large, the proportion of coarse particles is large, the bulk specific gravity is low, and the fish eyes are also large. It was.

Comparative Example 14
As shown in Table 2, suspension polymerization of vinyl chloride was carried out in the same manner as in Example 1 except that PVA (B) and PVA (C) were not used and the amount of modified PVA (A) used was changed. went. The results are shown in Table 3. Since PVA (B) and PVA (C) were not used, the plasticizer absorption was low and the number of fish eyes was increased.

As shown in Examples, modified PVA (A), PVA (B) and PVA (as dispersion stabilizers) are used as dispersion stabilizers when suspend-polymerizing a vinyl compound such as vinyl chloride to produce a vinyl-based polymer. Polymerization stability is improved by using C) in a specific ratio. As a result, it is possible to provide a vinyl-based polymer that produces less coarse particles and less fish eyes in the molded product, and can achieve both plasticizer absorbability and bulk specific density. Therefore, the industrial usefulness of the present invention is extremely high.

Claims (3)

A method for producing a vinyl polymer in which a vinyl compound is suspended and polymerized in the presence of a dispersion stabilizer;
The dispersion stabilizer contains modified polyvinyl alcohol (A), polyvinyl alcohol (B) and polyvinyl alcohol (C).
The modified polyvinyl alcohol (A) has a double bond derived from at least one selected from the group consisting of itaconic acid and its derivatives, and methacrylic acid and its derivatives in a side chain of 0.05 mol% or more and 0.5 mol. Have less than%
The degree of saponification of the modified polyvinyl alcohol (A) is 68 mol% or more and less than 77 mol%, and the viscosity average degree of polymerization is 500 or more and less than 1500.
The saponification degree of polyvinyl alcohol (B) is 30 mol% or more and less than 60 mol%, and the viscosity average degree of polymerization is 150 or more and less than 600.
The saponification degree of polyvinyl alcohol (C) is 77 mol% or more and less than 90 mol%, the viscosity average degree of polymerization is 1700 or more and less than 3000, and the modified polyvinyl alcohol (A), polyvinyl alcohol (B) and polyvinyl alcohol (C). ), The content of the modified polyvinyl alcohol (A) is 10 to 45 parts by mass, the content of the polyvinyl alcohol (B) is 1 to 45 parts by mass, and the content of the polyvinyl alcohol (C) is 100 parts by mass. A manufacturing method in which the amount is 10 to 89 parts by mass. The dispersion stabilizer further contains 0.001 parts by mass or more and less than 5 parts by mass of the compound (D) with respect to 100 parts by mass of the modified polyvinyl alcohol (A).
The production method according to claim 1, wherein the compound (D) is a compound having two or more phenolic hydroxyl groups, or a salt thereof or an oxide thereof. The production method according to claim 1 or 2, wherein the modified polyvinyl alcohol (A) has a double bond derived from itaconic acid in the side chain.