JP7333777B2 - POLYVINYL ALCOHOL COMPOSITION, USES THEREOF, AND METHOD FOR PRODUCING VINYL RESIN - Google Patents

Description

The present invention relates to a composition (D) containing modified polyvinyl alcohol (A) and unsaturated monocarboxylic acid or salt thereof (B). The present invention also relates to a dispersion stabilizer for suspension polymerization of a vinyl compound containing the composition (D) and a method for producing a vinyl resin.

Polyvinyl alcohol (hereinafter sometimes abbreviated as "PVA") has been used in various products such as dispersion stabilizers for suspension polymerization of vinyl compounds, coating agents, adhesives, polarizing films, water-soluble films, pharmaceuticals, and cosmetics. used for purposes. It is also known that the presence of reactive groups such as double bonds in PVA improves various performances or produces special effects.

Since the double bonds are highly reactive, there is a risk that the double bonds will react and gel when PVA is stored for a long period of time. Therefore, when PVA stored for a long period of time is used, various performances are deteriorated.

Applications requiring storage stability of PVA include dispersion stabilizers for suspension polymerization of vinyl compounds. It is believed that the use of PVA having a double bond as a dispersion stabilizer for suspension polymerization of a vinyl compound stabilizes the polymerization reaction of the vinyl compound (Patent Documents 1 and 2).

Patent Document 1 discloses a suspension polymerization containing a polyvinyl alcohol polymer having a double bond in a side chain obtained by acetalizing a polyvinyl alcohol polymer with a monoaldehyde having an olefinically unsaturated double bond. Dispersion stabilizers are described.

Patent Document 2 discloses a dispersion stabilizer comprising a polyvinyl alcohol polymer having a double bond in its side chain, which is obtained by esterifying a polyvinyl alcohol polymer with a carboxylic acid having an unsaturated double bond or a salt thereof. Are listed.

However, when suspension polymerization of a vinyl compound is carried out using these dispersion stabilizers, a satisfactory effect in terms of polymerization stability has not been obtained. Also, the storage stability of the dispersion stabilizer was not sufficient. In this specification, the polymerization stability means that droplets made of a vinyl compound have good dispersibility during suspension polymerization. means to be obtained.

WO2015/182567 WO2007/119735

The present invention has been made to solve the above problems, and provides a composition containing a modified polyvinyl alcohol that exhibits excellent performance as a dispersion stabilizer for suspension polymerization of a vinyl compound even after a long period of time has passed since its production. intended to Further, when a vinyl compound is subjected to suspension polymerization, the present invention provides a dispersion stabilizer for suspension polymerization that exhibits high polymerization stability, has a small average particle size, produces little coarse particles, has high plasticizer absorption, and has a high plasticizer absorbability. An object of the present invention is to provide a vinyl-based resin in which eyes are suppressed.

The subject is a composition (D) containing a modified polyvinyl alcohol (A) and an unsaturated monocarboxylic acid or a salt thereof (B);
A composition (D) containing a modified polyvinyl alcohol (A) and an unsaturated monocarboxylic acid or a salt thereof (B); the modified polyvinyl alcohol (A) has a viscosity average degree of polymerization of 100 or more and 600 or less, The degree of saponification is 33 mol% or more and 60 mol% or less, has 0.01 mol% or more and 1.50 mol% or less of an acryloyl group or a methacryloyl group in a side chain, and an unsaturated monocarboxylic acid or a salt thereof (B) is , acrylic acid, methacrylic acid, at least one selected from the group consisting of sodium acrylate and sodium methacrylate, and the modified polyvinyl alcohol (A) in the composition (D) / unsaturated monocarboxylic acid or salt thereof (B ) in a mass ratio of 82/18 to 99.9/0.1.

A composition (D) in which the modified polyvinyl alcohol (A) has a methacryloyl group in the side chain is also a preferred embodiment of the present invention.

A composition (D) in which the unsaturated monocarboxylic acid or its salt (B) is methacrylic acid or sodium methacrylate is also a preferred embodiment of the present invention.

A compound having a conjugated double bond and having two or more hydroxyl groups bonded to the carbon atoms constituting the conjugated double bond, or a salt thereof or an oxide thereof (C1); alkoxyphenol (C2); and cyclic nitro A composition (D) further comprising at least one compound (C) selected from the group consisting of a xyl radical (C3); is also a preferred embodiment of the present invention.

A dispersion stabilizer for suspension polymerization of a vinyl compound containing the composition (D) is also a preferred embodiment of the present invention.

A method for producing a vinyl-based resin, which comprises the step of carrying out suspension polymerization of a vinyl compound in the presence of the composition (D), is also a preferred embodiment of the present invention.

A method for producing a vinyl resin in combination with polyvinyl alcohol (F) having a viscosity average degree of polymerization of 1500 or more and 3500 or less and a degree of saponification of 78 mol% or more and less than 92 mol% is also a preferred embodiment of the present invention.

When the dispersion stabilizer for suspension polymerization containing the composition (D) of the present invention is used, even when stored for a long period of time after production, very high polymerization stability is exhibited during suspension polymerization of a vinyl compound, and the average particle diameter It is possible to provide a vinyl-based resin having a small particle size, little generation of coarse particles, high plasticizer absorbability, and suppressed fish eyes.

(Composition (D))
The composition (D) of the present invention has a viscosity-average degree of polymerization and a degree of saponification within specific ranges, and has a modified polyvinyl alcohol (A) (hereinafter referred to as "modified PVA (A)") having an acryloyl group or a methacryloyl group in its side chain. It is characterized by containing a specific amount of unsaturated monocarboxylic acid or its salt (B).

The mass ratio of modified PVA (A)/unsaturated monocarboxylic acid or salt thereof (B) in composition (D) is 82/18 to 99.9/0.1. As is clear from the comparison between Examples and Comparative Examples to be described later, when the mass ratio is less than 82/18, when the composition (D) is used as a dispersion stabilizer for suspension polymerization of a vinyl compound, plasticization does not occur. Low drug absorption and many fish eyes. Therefore, it is important that the mass ratio is between 82/18 and 99.9/0.1. The mass ratio is preferably 90/10 to 99.8/0.2, more preferably 92/8 to 99.7/0.3.

(Method for producing composition (D))
The composition (D) in the present invention comprises a modified PVA (A) and at least one unsaturated monocarboxylic acid or salt thereof selected from the group consisting of acrylic acid, methacrylic acid, sodium acrylate and sodium methacrylate ( B). The method for producing the composition (D) is not particularly limited, and (i) in the presence of an unsaturated monocarboxylic acid or its salt (B), polyvinyl alcohol (E) and an unsaturated carboxylic acid or its ester as an esterifying agent. (ii) a method of reacting polyvinyl alcohol (E) with an unsaturated carboxylic acid or a derivative thereof as an esterifying agent, and then adding an unsaturated monocarboxylic acid or a salt thereof (B); mentioned. When the polyvinyl alcohol (E) and the esterifying agent are reacted, it is preferable to heat them in order to promote the reaction. The heating temperature is preferably 80 to 180°C. The heating time is appropriately set in relation to the heating temperature, but is usually 10 minutes to 24 hours. Here, polyvinyl alcohol (E) is PVA having no double bond in the side chain (hereinafter sometimes referred to as "PVA (E)").

As a method for reacting PVA (E) with an unsaturated carboxylic acid or a derivative thereof as an esterifying agent, a mixed powder is obtained by mixing PVA (E) and an unsaturated carboxylic acid or a derivative thereof, and A method of heating the mixed powder obtained is preferred. Thus, by conducting the reaction in a solid state in the presence of an unsaturated carboxylic acid or a derivative thereof as an esterifying agent, the esterification reaction can proceed while suppressing the progress of undesired cross-linking reaction. By this reaction method, modified PVA (A) can be obtained, and a powder of composition (D) can be obtained in combination with unsaturated monocarboxylic acid or salt thereof (B).

In the above reaction method, the content of the esterifying agent in the mixed powder before heating is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, relative to 100 parts by mass of PVA (E). 0.5 parts by mass or more is particularly preferred. On the other hand, the content of the esterification agent in the mixed powder before heating is preferably 40 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 10 parts by mass or less with respect to 100 parts by mass of PVA (E). , 7 parts by mass or less is particularly preferred.

Although the form of the composition (D) is not particularly limited, it is preferably powder from the viewpoint of dissolution rate in the solvent. The particle size of the powder at this time is usually 50 to 2000 μm. The particle size of the powder is the average particle size determined by the method of JIS-K6726 (1994).

(Modified PVA (A))
Modified PVA (A) is synthesized by reacting PVA (E) with an esterification agent. It can be produced by a conventionally known method such as a method and a dispersion polymerization method. Preferred polymerization methods from an industrial point of view are solution polymerization, emulsion polymerization and dispersion polymerization. In the polymerization operation, any of a batch method, a semi-batch method and a continuous method can be employed.

Vinyl ester monomers used for polymerization include, for example, vinyl acetate, vinyl formate, vinyl propionate, vinyl caprylate, and vinyl versatate. Among these, vinyl acetate is preferred from an industrial point of view.

When the vinyl ester monomer is polymerized, the vinyl ester monomer may be copolymerized with another monomer as long as the gist of the present invention is not impaired. Examples of usable monomers include α-olefins such as ethylene, propylene, n-butene and isobutylene; acrylic acid and its salts, methyl acrylate, ethyl acrylate, n-propyl acrylate, i-acrylate, Acrylate esters such as propyl, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate and octadecyl acrylate; methacrylic acid and its salts; 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 and octadecyl methacrylate Acid esters; acrylamide, N-methylacrylamide, N-ethylacrylamide, N,N-dimethylacrylamide, diacetoneacrylamide, acrylamidopropanesulfonic acid and its salts, acrylamidopropyldimethylamine and its salts or quaternary salts thereof, N- Acrylamide derivatives such as methylolacrylamide and derivatives thereof; methacrylamide derivatives such as methylol methacrylamide and its derivatives; methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, n-butyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether, stearyl vinyl ether 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; acids, unsaturated dicarboxylic acids such as itaconic acid and fumaric acid, and salts or esters thereof; vinylsilyl compounds such as vinyltrimethoxysilane; isopropenyl acetate; The copolymerization amount of such other monomers is usually 10 mol % or less.

In addition, when the vinyl ester monomer is polymerized, a chain transfer agent may coexist for the purpose of adjusting the degree of polymerization of the resulting polyvinyl ester. Examples of chain transfer agents include aldehydes such as acetaldehyde, propionaldehyde, butyraldehyde and benzaldehyde; ketones such as acetone, methyl ethyl ketone, hexanone and cyclohexanone; mercaptans such as 2-hydroxyethanethiol and dodecylmercaptan; trichlorethylene and perchlorethylene. Among them, aldehydes and ketones are preferably used. The amount of the chain transfer agent to be added is determined according to the chain transfer constant of the chain transfer agent to be added and the desired degree of polymerization of the polyvinyl ester, but is generally 0.1 to 10 masses relative to the vinyl ester monomer. % is desirable.

For the saponification reaction of polyvinyl ester, an alcoholysis or hydrolysis reaction using a conventionally known basic catalyst such as sodium hydroxide, potassium hydroxide or sodium methoxide or an acidic catalyst such as p-toluenesulfonic acid is carried out. Applicable. Solvents 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; and aromatic hydrocarbons such as benzene and toluene. can be used alone or in combination of two or more. Among them, it is convenient and preferable to use methanol or a mixed solution of methanol and methyl acetate as a solvent and perform the saponification reaction in the presence of sodium hydroxide as a basic catalyst.

It is important that the modified PVA (A) has 0.01 mol % or more and 1.50 mol % or less of acryloyl groups or methacryloyl groups in side chains. The amount of modification with an acryloyl group or methacryloyl group (hereinafter sometimes abbreviated as "introduced modified group amount") can be determined from the content of double bonds in the acryloyl group or methacryloyl group. The double bond means a carbon-carbon double bond. When a vinyl compound is subjected to suspension polymerization using a dispersion stabilizer for suspension polymerization containing modified PVA (A) having an amount of introduced modified groups of less than 0.01 mol %, the polymerization stability decreases and many coarse particles are formed. or a vinyl resin with many fish eyes can be obtained. The amount of modified groups to be introduced is preferably 0.03 mol % or more. On the other hand, if the amount of the introduced modified group exceeds 1.50 mol %, the production is difficult, gelation is likely to occur, and the performance deteriorates when left for a long period of time after production. Furthermore, when the composition (D) is used as a dispersion stabilizer for suspension polymerization of a vinyl compound, the resulting vinyl resin has low plasticizer absorbability and many fish eyes. The amount of modified groups introduced is preferably 1.3 mol % or less, more preferably 1 mol % or less.

It is important that the double bond in the side chain of the modified PVA (A) is an acryloyl group or a methacryloyl group, with a methacryloyl group being particularly preferred. Other functional groups having a double bond lower the performance when used as a dispersion stabilizer for suspension polymerization of a vinyl compound.

The amount of modified groups introduced into the modified PVA (A), that is, the content of double bonds can be measured by a known method. Specifically, measurement by ¹ H-NMR is convenient. When measuring the amount of modified groups introduced into the modified PVA (A), a method of measuring after washing with a solution in which the modified PVA (A) does not dissolve can be mentioned. % solution, the modified PVA (A) solution is dropped into a solvent in which the modified PVA (A) does not dissolve, and the modified PVA (A) is precipitated and washed by reprecipitation, which is simple and preferable.

Examples of unsaturated carboxylic acids or derivatives thereof used for esterification of PVA (E) include acrylic acid or its salts, methacrylic acid or its salts, methacrylic anhydride, acrylic anhydride, acrylic acid alkyl esters, and methacrylic acid alkyl esters. mentioned. The unsaturated carboxylic acid or derivative thereof can be used alone or in combination of two or more.

Among these, the unsaturated carboxylic acid or derivative thereof is preferably acrylic anhydride or methacrylic anhydride from the viewpoint of various application performance when modified PVA (A) is used, and methacrylic anhydride from the viewpoint of availability. is more preferred.

The modified PVA (A) has a viscosity average degree of polymerization of 100 or more. From the viewpoint of productivity, it is preferably 120 or more. When used as a dispersion stabilizer for suspension polymerization of a vinyl compound, the modified PVA (A) preferably has a viscosity-average degree of polymerization of 150 or more. On the other hand, the modified PVA (A) has a viscosity average degree of polymerization of 600 or less, preferably 580 or less. When used as a dispersion stabilizer for suspension polymerization of a vinyl compound, the modified PVA (A) has a viscosity-average degree of polymerization of 550 or less, more preferably 500 or less. The viscosity average degree of polymerization is a value obtained by measuring according to JIS-K6726 (1994). Specifically, when the saponification degree is less than 99.5 mol%, the intrinsic viscosity [η] (liter/ g) was used to determine the viscosity-average degree of polymerization (P) according to the following formula.
P=([η]×10 ⁴ /8.29) ^(1/0.62)

The degree of saponification of the modified PVA (A) is 33 mol% or more. When the degree of saponification is less than 33 mol %, when used as a dispersant for suspension polymerization of a vinyl compound, the plasticizer absorption of the obtained vinyl resin is low and fish eyes are increased. On the other hand, the degree of saponification of modified PVA (A) is 60 mol % or less. When the modified PVA (A) having a degree of saponification exceeding 60 mol % is used as a dispersant for suspension polymerization of a vinyl compound, the obtained vinyl resin has low plasticizer absorbability and many fish eyes. When used as a dispersion stabilizer for suspension polymerization of a vinyl compound, the lower limit of the degree of saponification of the modified PVA (A) is preferably 35 mol% or more, and the upper limit is preferably 57 mol% or less, more preferably 54 mol% or less. . The degree of saponification is a value obtained by measuring according to JIS-K6726 (1994).

(Unsaturated monocarboxylic acid or salt thereof (B))
The composition (D) of the present invention may contain at least one unsaturated monocarboxylic acid selected from the group consisting of acrylic acid, methacrylic acid, sodium acrylate and sodium methacrylate or a salt thereof (B). is important. Other unsaturated monocarboxylic acids or salts thereof deteriorate various performances of the composition (D) during long-term storage. In particular, when the composition (D) is used as a dispersion stabilizer for suspension polymerization of a vinyl compound, the resulting vinyl resin has a large particle size, a wide particle size distribution, low plasticizer absorption, and no fish eyes. become more. The unsaturated monocarboxylic acid or its salt (B) is preferably methacrylic acid or sodium methacrylate.

(Compound (C))
The composition (D) of the present invention is a compound having a conjugated double bond and two or more hydroxyl groups bonded to carbon atoms constituting the conjugated double bond, or a salt thereof or an oxide thereof (C1) alkoxyphenol (C2); and cyclic nitroxyl radical (C3); at least one compound (C) selected from the group consisting of preferably further included.

A compound having a conjugated double bond and having two or more hydroxyl groups bonded to the carbon atoms constituting the conjugated double bond, or a salt thereof or an oxide thereof (C1), the conjugated double bond defined herein Bonding includes conjugation through carbon-carbon double bonds, conjugation through carbon-heteroatom double bonds, and conjugation through aromatic compounds. Compounds having a conjugated double bond and having two or more hydroxyl groups bonded to carbon atoms constituting the conjugated double bond, or salts thereof or oxides thereof (C1) include catechol and t-butyl. Hydroquinone, 2,6-di-t-butylhydroquinone, pyrogallol, 1,3,5-trihydroxybenzene, hexahydroxybenzene; gallic acid or salts thereof; methyl gallate, ethyl gallate, propyl gallate, octyl gallate , gallic acid alkyl esters such as dodecyl gallate; catechins such as epicatechin, epigallocatechin and epigallocatechin-3-gallate; ascorbic acid or salts thereof; benzoquinone; dehydroascorbic acid and the like. Among them, compounds having two or more hydroxyl groups bonded to carbon atoms forming a conjugated double bond are preferred, and compounds having two or more phenolic hydroxyl groups are more preferred.

The alkoxyphenol (C2) in the present invention refers to a compound in which at least one hydrogen atom on the benzene ring is substituted with an alkoxy group and at least one hydrogen atom is substituted with a hydroxyl group. Other hydrogen atoms may be substituted with alkyl groups such as methyl groups and ethyl groups, and halogen groups, and the number and bonding positions thereof are not limited. The number of carbon atoms in the alkoxy group is usually 10 or less, preferably 8 or less, more preferably 6 or less, still more preferably 4 or less, and particularly preferably 2 or less. The carbon chain of the alkoxy group may be linear or branched, but linear is preferred from the standpoint of availability. Examples of alkoxy groups include methoxy, ethoxy, propoxy, and butoxy groups, with methoxy groups being preferred.

The alkoxyphenol (C2) used in the present invention is preferably a compound in which one hydrogen atom on the benzene ring is substituted with an alkoxy group and one hydrogen atom is substituted with a hydroxyl group. At this time, the bonding position of the alkoxy group is not particularly limited, but from the viewpoint of availability, the ortho-position or para-position is preferable, and the para-position is more preferable.

Alkoxyphenol (C2) preferably used in the present invention includes methoxyphenol, ethoxyphenol, propoxyphenol and butoxyphenol. Among them, methoxyphenol is preferable from the point of availability.

The cyclic nitroxyl radical (C3) in the present invention has a heterocyclic ring formed from carbon atoms and heteroatoms, and the nitrogen atom of the nitroxyl radical (=NO) forms part of the ring. A compound that Examples of the heteroatom constituting the ring include nitrogen atom, oxygen atom, phosphorus atom, sulfur atom and the like. The number of atoms forming the ring is usually 5 or 6. A substituent such as an alkyl group, a hydroxyl group, a carboxyl group, a sulfo group, or a halogen group may be bonded to the atoms forming the ring. The number of substituents and the bonding positions of the substituents are not particularly limited, and a plurality of substituents may be bonded to the same or different atoms. From the standpoint of availability, the cyclic nitroxyl radical is preferably 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) or a derivative thereof. As the TEMPO derivative, 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl is preferably used.

From the viewpoint of availability, the compound (C) has a conjugated double bond and has two or more hydroxyl groups bonded to the carbon atoms constituting the conjugated double bond, or a salt thereof or an oxide thereof ( C1); or preferably alkoxyphenol (C2), a compound having a conjugated double bond and having two or more hydroxyl groups bonded to the carbon atoms constituting the conjugated double bond, or a salt thereof or an oxide thereof ( C1) is more preferred.

(Application)
The composition (D) of the present invention is used for various purposes. Examples are given below, but are not limited to these.
(1) Dispersant Applications: Dispersion stabilizer for organic and inorganic pigments such as paints and adhesives, dispersion stabilizer for suspension polymerization of various vinyl compounds such as vinyl chloride, vinylidene chloride, styrene, (meth)acrylate, and vinyl acetate and dispersion aid (2) Coating agent Applications: paper coating agents, sizing agents, fiber processing agents, leather finishing agents, paints, anti-fogging agents, metal corrosion inhibitors, brighteners for galvanizing, antistatic agents (3) Adhesive applications: Adhesives, pressure sensitive adhesives, rewetting adhesives, various binders, additives for cement and mortar (4) Emulsifier applications: Emulsifiers for emulsion polymerization, post-emulsifiers such as bitumen (5) Flocculant applications: Suspension in water Flocculant for substances and dissolved substances, metal flocculant (6) Paper processing applications: paper strength enhancer, oil and solvent resistance agent, smoothness improver, surface gloss improver, filling agent, barrier agent, light resistance Imparting agent, water resistance agent, dye/developer dispersant, adhesion improver, binder Dispersant for agricultural chemicals (8) Medical/cosmetics Applications: granulating binders, coating agents, emulsifiers, patches, binders, film formulation bases, film-forming agents (9) Viscosity modifiers Applications: Thickeners, rheology modifiers (10) Film applications: Water-soluble films, polarizing films, barrier films, textile product packaging films, seed curing sheets, vegetation sheets, seed tapes, hygroscopic films (11) Molded product applications: Fibers, pipes, tubes, leakage prevention Membrane, water-soluble fiber for chemical lace, sponge (12) Gel use: medical gel, industrial gel (13) Post-reaction use: low-molecular-weight organic compound, high-molecular-weight organic compound, post-reaction use with inorganic compound Among them, the present invention The composition (D) of is suitably used for (1) dispersant use, as will be described later.

(Dispersion stabilizer for suspension polymerization of vinyl compound)
Among others, the composition (D) of the present invention is preferably used as a dispersion stabilizer for suspension polymerization of a vinyl compound containing the composition (D). When the composition (D) of the present invention is used as a dispersion stabilizer in suspension polymerization of a vinyl compound, it exhibits high performance even when stored for a long period of time, stabilizes the polymerization reaction, and reduces the formation of coarse particles. In addition, it is possible to obtain a vinyl-based resin with high plasticizer absorbability and few fish eyes.

The dispersion stabilizer for suspension polymerization may contain various additives as long as the gist of the present invention is not impaired. Examples of the above additives include polymerization modifiers such as aldehydes, halogenated hydrocarbons, and mercaptans; polymerization inhibitors such as phenol compounds, sulfur compounds, and N-oxide compounds; pH adjusters; cross-linking agents; antifungal agents; antiblocking agents; antifoaming agents; compatibilizers and the like. The content of various additives in the dispersion stabilizer for suspension polymerization is preferably 10% by mass or less, more preferably 5% by mass or less, relative to the total amount of the composition (D).

(Method for producing vinyl resin)
A preferred embodiment of the present invention is a method for producing a vinyl resin, comprising suspension polymerization of a vinyl compound in the presence of the composition (D) of the present invention. In a preferred embodiment of the present invention, polyvinyl alcohol having a viscosity average degree of polymerization of 1500 or more and 3500 or less and a saponification degree of 78 mol% or more and less than 92 mol% in the presence of the composition (D) of the present invention (F) is used in combination to produce a vinyl resin by suspension polymerization of a vinyl compound. Polyvinyl alcohol (F) having a degree of polymerization and a degree of saponification within the above ranges is preferable in terms of high polymerization stability. The method for producing polyvinyl alcohol (F) can be appropriately adjusted according to the method for producing PVA (E). The amount of polyvinyl alcohol (F) used is preferably 10 to 1000% by mass based on the total amount of composition (D).

Vinyl compounds used in the method for producing a vinyl resin of the present invention 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, their esters and anhydrides; styrene, acrylonitrile, vinylidene chloride, vinyl ethers, and the like. Among them, vinyl chloride alone or combined use of vinyl chloride and a monomer that can be copolymerized with vinyl chloride is preferable. Examples of monomers that can be copolymerized 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; α-olefins; unsaturated dicarboxylic acids such as maleic anhydride and itaconic acid; acrylonitrile; styrene; vinylidene chloride;

For suspension polymerization of a vinyl compound, an oil-soluble or water-soluble polymerization initiator conventionally used for vinyl chloride polymerization can be used. Examples of oil-soluble polymerization initiators include peroxydicarbonate 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; azo compounds such as azobis-2,4-dimethylvaleronitrile and azobis(4-2,4-dimethylvaleronitrile); be done. Examples of water-soluble polymerization initiators include potassium persulfate, ammonium persulfate, hydrogen peroxide, and cumene hydroperoxide. These 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 may be about 20°C or higher than 90°C. A polymerization vessel with a reflux condenser can also be used in order to increase the heat removal efficiency of the polymerization reaction system.

In suspension polymerization of a vinyl compound, in addition to the composition (D), a water-soluble polymer such as methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose, etc., which are usually used in the suspension polymerization of a vinyl compound in an aqueous medium. Cellulose ethers; water-soluble polymers such as gelatin; oil-soluble emulsifiers such as sorbitan monolaurate, sorbitan trioleate, glycerin tristearate, ethylene oxide propylene oxide block copolymer; polyoxyethylene sorbitan monolaurate, polyoxyethylene glycerin oleate, laurin A water-soluble emulsifier such as sodium sulfate may be used in combination. Although there is no particular limitation on the amount of addition, it is preferably 0.01 parts by mass or more and 1.0 parts by mass or less per 100 parts by mass of the vinyl compound.

EXAMPLES The present invention will be described in more detail below with reference to examples. In the following examples and comparative examples, "parts" and "%" indicate parts by mass and % by mass, respectively, unless otherwise specified.

[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 saponification degree is less than 99.5 mol%, the intrinsic viscosity [η] (liter/ g) was used to determine the viscosity-average degree of polymerization (P) according to the following formula. The degree of saponification of the modified PVA (A) is a value measured for the modified PVA (A) isolated by reprecipitation purification of the obtained powder of the composition (D).
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 reprecipitation purification of the obtained powder of the composition (D).

[Introduced Modified Group Amount of Modified PVA (A)]
A 10% methyl acetate solution of composition (D) was prepared. 5 g of this solution was dropped into 500 g of water to precipitate modified PVA (A), which was collected and dried. For the isolated modified PVA (A), the amount of double bonds introduced into the modified PVA (A) was measured using ¹ H-NMR to determine the amount of modified groups introduced. The amount of double bonds is the number of moles of double bonds with respect to all monomer units in the modified PVA (A).

Production of composition 1 4.6 parts of methacrylic anhydride as an esterifying agent, 0.3 parts of t-butyl hydroquinone as a compound (C), and PVA (E) having a viscosity average polymerization degree of 250 and a saponification degree of 45 mol% A mixed powder was obtained by adding to 100 parts. After heat-treating the obtained mixed powder at a temperature of 120° C. for 6 hours, 1.5 parts of methacrylic acid is added as an unsaturated monocarboxylic acid or a salt thereof (B), thereby modifying a methacryloyl group introduced. A powdery composition 1 containing PVA (A), unsaturated monocarboxylic acid or its salt (B) and compound (C) was obtained. The amount of unsaturated monocarboxylic acid or salt thereof (B) used is the amount per 100 parts of modified PVA (A). In the above modified PVA (A), a double bond peak was confirmed at around 6.0 to 6.5 ppm, and the amount of modified groups introduced was 0.23 mol % relative to all monomer units. The modified PVA (A) had a viscosity average degree of polymerization of 250 and a degree of saponification of 45 mol %. The mass ratio of modified PVA (A)/unsaturated monocarboxylic acid or salt thereof (B) in composition 1 was 98.5/1.5.

Production of compositions 2 to 13 PVA (E), esterifying agent, compound (C), unsaturated monocarboxylic acid or salt thereof (B), each type and amount, heat treatment conditions as shown in Tables 1 and 2 Compositions 2-13 were prepared in the same manner as composition 1 except for the changes. Conditions and results are shown in Tables 1 and 2.

Example 1
As a suspension polymerization test of a vinyl compound, Composition 1 left at 50° C. for 6 months after production was dissolved in methanol as a dispersion stabilizer for suspension polymerization, and 10 parts of the solution were placed in an autoclave. The concentration of Composition 1 in the methanol solution was 500 ppm with respect to the charged amount of vinyl chloride. Next, 100 parts of PVA having a viscosity average degree of polymerization of 2000 and a degree of saponification of 80 mol % dissolved in deionized water was charged as PVA to be used in combination. The concentration of PVA used in combination was 800 ppm with respect to the charged amount of vinyl chloride. Additional deionized water was then charged to bring the total deionized water to 1200 parts. Next, 0.65 parts of a 70% toluene solution of cumyl peroxyneododecanoate and 1.05 parts of a 70% toluene solution of t-butyl peroxyneododecanoate were charged into the autoclave, and the pressure inside the autoclave was 0.2 MPa. Nitrogen was introduced as follows. Thereafter, the operation of purging with nitrogen was performed a total of 5 times, and after the inside of the autoclave was sufficiently replaced with nitrogen to remove oxygen, 940 parts of vinyl chloride was charged. The content in the autoclave was heated to 57° C. and suspension polymerization of vinyl chloride was initiated under stirring. The pressure inside the autoclave at the start of polymerization was 0.80 MPa. After about 3.5 hours from the start of the polymerization, the polymerization was stopped when the pressure inside the autoclave reached 0.70 MPa. and dried for 16 hours to obtain vinyl chloride polymer particles.

(Evaluation of vinyl chloride polymer particles)
The obtained vinyl chloride polymer particles were evaluated for (1) average particle size, (2) particle size distribution, (3) plasticizer absorption and (4) fish eyes according to the following methods. Table 2 shows the evaluation results.

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

(2) Particle size distribution The content of 42-mesh JIS standard sieve is shown 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 mass %.
A: Less than 5% B: 5% or more and less than 10% C: 10% or more

For both the content of 42 meshes and the content of 60 meshes, the smaller the value, the fewer the coarse particles, the sharper the particle size distribution, and the better the polymerization stability. Among the above particle size distributions, A and B are usable levels.

(3) Absorption of plasticizer A 5 mL syringe filled with 0.02 g of absorbent cotton is weighed (A (g)), and 0.5 g of vinyl chloride polymer particles are put therein and weighed (B (g)). , 1 g of dioctyl phthalate (DOP) was added thereto, allowed to stand for 15 minutes, centrifuged at 3000 rpm for 40 minutes, and weighed (C(g)). Then, the plasticizer absorbency (%) was obtained from the following formula. The higher the plasticizer absorbency, the easier the processing, and the less likely defects such as pimples that occur in appearance during processing into sheets.
Plasticizer absorbency (%) = 100 x [{(C-A) / (B-A)}-1]

(4) Fish eye 100 parts of the obtained vinyl chloride polymer particles, 50 parts of DOP (dioctyl phthalate), 5 parts of tribasic lead sulfate and 1 part of zinc stearate were rolled at 150°C for 7 minutes to obtain a particle size of 0.1 mm. A thick sheet was prepared and the number of fish eyes per 1000 cm ² was measured.

Examples 2-5
A vinyl compound suspension polymerization test was carried out using Compositions 2 to 5 thus obtained. Suspension polymerization of vinyl chloride was carried out in the same manner as in Example 1, except that the composition (D) used as the dispersion stabilizer for suspension polymerization was changed as shown in Table 2. Table 2 shows the conditions and the evaluation results of the obtained vinyl chloride polymer particles.

Comparative example 1
The obtained composition 6 was used for suspension polymerization of a vinyl compound in the same manner as in Example 1. Composition 6 did not contain an unsaturated monocarboxylic acid or its salt (B), had a large vinyl chloride polymer particle size, a wide particle size distribution, low plasticizer absorption, and many fish eyes. Table 2 shows the conditions and results.

Comparative example 2
The obtained composition 7 was used for suspension polymerization of a vinyl compound in the same manner as in Example 1. Since the unsaturated monocarboxylic acid or its salt (B) contained in composition 7 is oleic acid, the vinyl chloride polymer particles have a large particle diameter, a wide particle size distribution, a low plasticizer absorption, and a fish-eye structure. There were many Table 2 shows the conditions and results.

Comparative example 3
The resulting composition 8 was used for suspension polymerization of a vinyl compound in the same manner as in Example 1. Since the degree of saponification of the modified PVA (A) in composition 8 was too high, plasticizer absorption was low and fish eyes were numerous. Table 2 shows the conditions and results.

Comparative example 4
The obtained composition 9 was used for suspension polymerization of a vinyl compound in the same manner as in Example 1. The degree of polymerization of the modified PVA (A) in composition 9 was high and the degree of saponification was too low, resulting in low plasticizer absorption and many fish eyes. Table 2 shows the conditions and results.

Comparative example 5
The resulting composition 10 was used for suspension polymerization of a vinyl compound in the same manner as in Example 1. Since the composition 10 did not contain the modified PVA (A), the vinyl chloride polymer particles had a large particle size, a wide particle size distribution, low plasticizer absorption, and many fish eyes. Table 2 shows the conditions and results.

Comparative example 6
The resulting composition 11 was used for suspension polymerization of a vinyl compound in the same manner as in Example 1. Since the side chain of the modified PVA (A) contained in composition 11 was a maleinyl group, the vinyl chloride polymer particles had a large particle size, a wide particle size distribution, low plasticizer absorption, and many fish eyes. Table 2 shows the conditions and results.

Comparative example 7
The obtained composition 12 was used for suspension polymerization of a vinyl compound in the same manner as in Example 1. Since composition 12 contained too much unsaturated monocarboxylic acid or salt thereof (B), the particle size distribution was wide, the plasticizer absorption was low, and fish eyes were numerous. Table 2 shows the conditions and results.

Comparative example 8
The resulting composition 13 was used for suspension polymerization of a vinyl compound in the same manner as in Example 1, except that the type of PVA used in combination was changed. Since the modified amount of the modified PVA (A) contained in composition 13 was too large, the result was low plasticizer absorbability and many fish eyes. Table 2 shows the conditions and results.

As shown in the examples, the composition (D) of the present invention, when used as a dispersion stabilizer for suspension polymerization of a vinyl compound, exhibits excellent polymerization stability even after a long period of time has passed since its production. It is possible to provide a vinyl-based resin having a small average particle size, less generation of coarse particles, high plasticizer absorption, and suppressed fish eyes. Therefore, the industrial utility of the present invention is extremely high.

Claims (6)

A dispersion stabilizer for suspension polymerization of a vinyl compound containing a composition (D) containing a modified polyvinyl alcohol (A) and an unsaturated monocarboxylic acid or a salt thereof (B);
Modified polyvinyl alcohol (A) has a viscosity average degree of polymerization of 100 or more and 600 or less, a saponification degree of 33 mol% or more and 60 mol% or less, and an acryloyl group or methacryloyl group in a side chain of 0.01 mol% or more. .50 mol% or less,
The unsaturated monocarboxylic acid or its salt (B) is at least one selected from the group consisting of acrylic acid, methacrylic acid, sodium acrylate and sodium methacrylate,
A composition (D) characterized in that the mass ratio of modified polyvinyl alcohol (A)/unsaturated monocarboxylic acid or salt thereof (B) in composition (D) is 82/18 to 99.9/0.1 ) for suspension polymerization of a vinyl compound containing . A dispersion stabilizer for suspension polymerization of a vinyl compound containing the composition (D) according to claim 1, wherein the modified polyvinyl alcohol (A) has a methacryloyl group in its side chain. 3. A dispersion stabilizer for suspension polymerization of a vinyl compound containing the composition (D) according to claim 1 or 2, wherein the unsaturated monocarboxylic acid or its salt (B) is methacrylic acid or sodium methacrylate. A compound having a conjugated double bond and having two or more hydroxyl groups bonded to the carbon atoms constituting the conjugated double bond, or a salt thereof or an oxide thereof (C1); alkoxyphenol (C2); and cyclic nitro xyl radical (C3); a suspension of a vinyl compound containing the composition (D) according to any one of claims 1 to 3, further comprising at least one compound (C) selected from the group consisting of: Dispersion stabilizer for polymerization . A method for producing a vinyl resin, comprising the step of carrying out suspension polymerization of a vinyl compound in the presence of a composition (D) containing a modified polyvinyl alcohol (A) and an unsaturated monocarboxylic acid or a salt thereof (B). there;
Modified polyvinyl alcohol (A) has a viscosity average degree of polymerization of 100 or more and 600 or less, a saponification degree of 33 mol% or more and 60 mol% or less, and an acryloyl group or methacryloyl group in a side chain of 0.01 mol% or more. .50 mol% or less,
The unsaturated monocarboxylic acid or its salt (B) is at least one selected from the group consisting of acrylic acid, methacrylic acid, sodium acrylate and sodium methacrylate,
A composition (D) characterized in that the mass ratio of modified polyvinyl alcohol (A)/unsaturated monocarboxylic acid or salt thereof (B) in composition (D) is 82/18 to 99.9/0.1 ), a method for producing a vinyl-based resin, comprising the step of carrying out suspension polymerization of a vinyl compound. The method for producing a vinyl resin according to claim 5 , wherein polyvinyl alcohol (F) having a viscosity average degree of polymerization of 1500 or more and 3500 or less and a degree of saponification of 78 mol% or more and less than 92 mol% is used in combination.