Modified vinyl alcohol polymer, method for producing modified vinyl alcohol polymer, particles, aqueous solution, coating solution, coated product, molded article, release paper, dispersant, method for producing vinyl polymer, and mixture

Abstract

This modified vinyl alcohol-based polymer has a structural unit represented by formula (1) and has at most 1,000 ppm of a water-insoluble component. In formula (1), X, Y, and Z are each independently a C1-C20 alkyl group, a C2-C20 alkenyl group, a phenyl group, a benzyl group, a vinylphenyl group, a C1-C20 halogenated alkyl group, a halogenated phenyl group, a C1-C20 aminoalkyl group, a C1-C20 mercaptoalkyl group, a C2-C20 ureidoalkyl group, a C2-C8 isocyanate alkyl group, a C3-C20 group including an epoxy group, a C3-C20 group including an acrylamide group, a C4-C20 group including a methacrylamide group, an acetoxy group, or a group represented by -(CH2)n-O-R1 (R1 represents a C1-C20 alkyl group or the like, and n represents an integer of 0-6).

Description

Technical Field

[0001] The present disclosure relates to a modified vinyl alcohol-based polymer, a method for producing a modified vinyl alcohol-based polymer, polymer particles, an aqueous solution, a coating liquid, a coated article, a molded article, a release paper, a dispersant, a method for producing a vinyl-based polymer, and a mixture.

Background Art

[0002] Vinyl alcohol-based polymers (hereinafter, vinyl alcohol-based polymers may be abbreviated as "PVA") are water-soluble and are used in various applications such as synthetic fiber raw materials, film raw materials, emulsifying and dispersing agents, and adhesives.

[0003] PVA is usually obtained by saponifying a vinyl ester-based polymer obtained by polymerizing a vinyl ester-based monomer. It is known that a modified PVA having a special function can be obtained by saponifying a modified vinyl ester-based polymer obtained by copolymerizing a vinyl ester-based monomer and a monomer having various functional groups.

[0004] On the other hand, various techniques of "post-modification" have been reported in which a reactant having various functional groups is reacted with PVA after saponification, and the functional group derived from the reactant is introduced into PVA. For example, the use of dicarboxylic acid as a modifier (Patent Document 1), etc., post-modification is utilized as a useful technique for producing modified PVA.

[0005] In addition, an anti-fogging composition (Patent Document 2), a resin composition (Patent Document 3), a fiber treatment agent (Patent Document 4), etc. obtained by mixing PVA or its derivative and a silane coupling agent have been reported.

[0006] Also, Patent Document 5 discloses a method for obtaining a modified PVA by reacting PVA and a specific silane coupling agent.

[0007] However, Documents 1 to 5 do not disclose a modified PVA that has a polymer structure in which a silane coupling agent is introduced into PVA and yet is more excellent in handleability and applicable to multiple uses. For example, when a modified PVA with low water solubility is used in a coating liquid, a dispersant for suspension polymerization, etc., it may take time to dissolve sufficiently, or undissolved components may have an unfavorable impact. Further, in Patent Document 5, the reaction between PVA and a specific silane coupling agent is carried out in an aqueous solution, and the modified PVA is obtained in the form of a solution. Such a solution-form modified PVA is expected to be improved in terms of handleability, storage stability, transportability, etc. Further, when the solution-form modified PVA is made into particles by drying or the like, a crosslinking reaction proceeds during the drying process, and the water solubility tends to decrease.

[0008] Further, PVA is used as a paper strength enhancer, a dispersant for fluorescent whitening pigments, and a binder for inorganic substances (calcium carbonate, clay, silica, etc.) in the paper field. Since PVA has excellent film-forming properties, by coating it on paper, barrier properties against gases, etc. and oil resistance can be imparted.

[0009] Paper coated with PVA may be used as barrier paper, and a representative example of barrier paper is release paper base paper. Release paper base paper is usually manufactured by coating PVA on the surface of a cellulose substrate. Then, a release paper is obtained by forming a release layer (silicone layer) on the surface of this release paper base paper. In release paper, PVA serves as a stopper for suppressing penetration into expensive silicone or platinum substrates. These days, there is a demand for release paper base paper that can promote the curing of silicone in the release layer and enhance the adhesion between the PVA layer and the silicone layer in addition to such stopper properties.

[0010] Patent Document 6 describes a release paper base paper coated with PVA having a silyl group that satisfies specific conditions. Further, Patent Document 7 describes PVA in which a double bond is introduced into the side chain by an acetalization reaction. However, Documents 6 and 7 do not disclose a coating liquid that is excellent in silicone curability and adhesion to a substrate.

[0011] Furthermore, PVA is widely used as a dispersant, for example, as a dispersion stabilizer for suspension polymerization and emulsion polymerization of vinyl compounds. It is particularly useful as a dispersion stabilizer when using suspension polymerization of vinyl chloride.

[0012] The resulting polyvinyl chloride resin (hereinafter sometimes abbreviated as "PVC resin") has excellent chemical resistance and electrical insulation properties, as well as excellent processability, and can be made both hard and soft, making it widely used as a molding material for various applications. PVC resin is generally manufactured on an industrial scale by suspension polymerization, in which vinyl chloride monomer is polymerized in an aqueous medium in the presence of a dispersion stabilizer using an oil-soluble polymerization initiator.

[0013] PVA is widely used as a dispersion stabilizer in the polymerization of vinyl chloride, and it has been proposed to use PVA having an ethylenic double bond to improve the stability during polymerization of vinyl chloride (polymerization stability) (Patent Document 8). However, the above-mentioned document 8 does not disclose a dispersant containing modified PVA having a specific structure derived from a silane coupling agent. [Prior art documents] [Patent Documents]

[0014] [Patent Document 1] International Publication No. 2007 / 119735 [Patent Document 2] Japanese Patent Application Publication No. 48-47939 [Patent Document 3] Japanese Patent Publication No. 2002-275338 [Patent Document 4] Japanese Patent Application Publication No. 6-16738 [Patent Document 5] Japanese Patent Application Publication No. 3-119002 [Patent Document 6] Japanese Patent Publication No. 2005-194672 [Patent Document 7] Special Publication No. 2013-531136 [Patent Document 8] International Publication No. 2019 / 181915 [Overview of the project] [Problems that the invention aims to solve]

[0015] The present disclosure aims to provide a modified vinyl alcohol polymer having a polymer structure incorporating a silane coupling agent, which is easy to handle and useful for various applications; a method for producing the modified vinyl alcohol polymer; particles of the modified vinyl alcohol polymer; and an aqueous solution of the modified vinyl alcohol polymer. Furthermore, this disclosure also aims to provide a coating liquid capable of forming a coating layer with excellent silicone curability and adhesion to a substrate, a coated product obtained by applying the coating liquid to a substrate, a molded product, and a release paper. Furthermore, this disclosure also aims to provide a dispersant, a method for producing vinyl polymers, and a mixture that, when used in the manufacturing process of vinyl polymers, can reduce the average particle size, the amount of coarse particles, and the amount of fisheyes in the resulting vinyl polymer. [Means for solving the problem]

[0016] The present invention encompasses the following forms of disclosure. [1] A modified vinyl alcohol polymer having a structural unit represented by the following formula (1), and having a water-insoluble content of 1000 ppm or less; [ka] [In formula (1), X, Y, and Z are each independently a C1-C20 alkyl group, a C2-C20 alkenyl group, a phenyl group, a benzyl group, a vinylphenyl group, a C1-C20 halogenated alkyl group, a halogenated phenyl group, a C1-C20 aminoalkyl group, a C1-C20 mercaptoalkyl group, a C2-C20 ureidoalkyl group, a C2-C8 isocyanate alkyl group, a C3-C20 group containing an epoxy group, a C3-C20 group containing an acrylamide group, a C4-C20 group containing a methacrylamide group, an acetoxy group, or -(CH2) n -OR 1 (R 1 The group is represented by , where n represents a hydrogen atom, alkali metal atom, alkaline earth metal atom, alkyl group having 1 to 20 carbon atoms, alkenyl group having 2 to 20 carbon atoms, acryloyl group, methacryloyl group, or glycidyl group, and n is an integer from 0 to 6. [2] A modified vinyl alcohol polymer of [1], wherein the content of the structural unit represented by formula (1) above is 0.01 mol% or more and less than 5 mol%; [3] A modified vinyl alcohol polymer of [1] or [2], wherein the content of the structural unit represented by formula (1) above is 90 mol% or more relative to all structural units containing silicon atoms; [4] A method for producing a modified vinyl alcohol polymer, comprising the step of impregnating a solid vinyl alcohol polymer with a silane coupling agent; [5] A method for producing the modified vinyl alcohol polymer according to [4], wherein vinyl alcohol polymer particles are impregnated by spraying them with a solution containing the silane coupling agent in the impregnation step; [6] A method for producing the modified vinyl alcohol polymer of [4] or [5], wherein the silane coupling agent has a structure represented by the following formula (2); [ka] [In formula (2), R is an alkyl group having 1 to 8 carbon atoms, an acetyl group, or -(CH2) m -OR 2 (R 2represents an alkyl group having 1 to 20 carbon atoms, and m represents an integer of 1 to 6.). X, Y, and Z are each independently an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, a phenyl group, a benzyl group, a vinylphenyl group, a halogenated alkyl group having 1 to 20 carbon atoms, a halogenated phenyl group, an aminoalkyl group having 1 to 20 carbon atoms, a mercaptoalkyl group having 1 to 20 carbon atoms, a ureidoalkyl group having 2 to 20 carbon atoms, an isocyanatealkyl group having 2 to 8 carbon atoms, a group having 3 to 20 carbon atoms containing an epoxy group, a group having 3 to 20 carbon atoms containing an acrylamide group, a group having 4 to 20 carbon atoms containing a methacrylamide group, an acetoxy group or -(CH2) n -O-R 1 (R 1 represents an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an acryloyl group, a methacryloyl group or a glycidyl group, and n represents an integer of 0 to 6.). It is a group represented by] [7] A method for producing the modified vinyl alcohol polymer according to [4], [5] or [6], further comprising a step of heat-treating the vinyl alcohol polymer impregnated with the above silane coupling agent obtained in the above impregnating step; [8] Particles containing the modified vinyl alcohol polymer according to [1], [2] or [3]; [9] The particles according to [8], wherein the dispersion degree A of silicon atoms is 0.2 or more and less than 1;

[10] An aqueous solution containing the modified vinyl alcohol polymer according to [1], [2] or [3];

[11] A coating liquid containing a modified vinyl alcohol polymer having a structural unit represented by the following formula (1); [Chemical formula] [In formula (1), X, Y, and Z are each independently a C1-C20 alkyl group, a C2-C20 alkenyl group, a phenyl group, a benzyl group, a vinylphenyl group, a C1-C20 halogenated alkyl group, a halogenated phenyl group, a C1-C20 aminoalkyl group, a C1-C20 mercaptoalkyl group, a C2-C20 ureidoalkyl group, a C2-C8 isocyanate alkyl group, a C3-C20 group containing an epoxy group, a C3-C20 group containing an acrylamide group, a C4-C20 group containing a methacrylamide group, an acetoxy group, or -(CH2) n -OR 1 (R 1 The group is represented by , where n represents a hydrogen atom, alkali metal atom, alkaline earth metal atom, alkyl group having 1 to 20 carbon atoms, alkenyl group having 2 to 20 carbon atoms, acryloyl group, methacryloyl group, or glycidyl group, and n is an integer from 0 to 6.

[12] The coating solution of

[11] , wherein the content of the structural unit represented by formula (1) in the modified vinyl alcohol polymer is 0.01 mol% or more and less than 5 mol%;

[13] A coating solution of

[11] or

[12] , wherein the content of the structural unit represented by formula (1) is 90 mol% or more relative to all structural units containing silicon atoms in the modified vinyl alcohol polymer;

[14] A coating solution of the above modified vinyl alcohol polymer having a viscosity-average degree of polymerization of 500 to 5000 and a degree of saponification of 70 mol% to 99.9 mol%;

[15] A coating solution of any of

[11] to

[14] , wherein the insoluble portion of the modified vinyl alcohol polymer in the coating solution is 1000 ppm or less; A coated product obtained by applying any of the coating liquids

[16]

[11] ~

[15] to a substrate;

[17] A molded article comprising a layer containing a modified vinyl alcohol polymer having a structural unit represented by the following formula (1'); [ka] [In formula (1'), X, Y, and Z are each independently a C1-C20 alkyl group, a C2-C20 alkenyl group, a phenyl group, a benzyl group, a vinylphenyl group, a C1-C20 halogenated alkyl group, a halogenated phenyl group, a C1-C20 aminoalkyl group, a C1-C20 mercaptoalkyl group, a C2-C20 ureidoalkyl group, a C2-C8 isocyanate alkyl group, a C3-C20 group containing an epoxy group, a C3-C20 group containing an acrylamide group, a C4-C20 group containing a methacrylamide group, an acetoxy group, or -(CH2) n -OR 1 (R 1 The group is represented by , where n represents a hydrogen atom, alkali metal atom, alkaline earth metal atom, C1-C20 alkyl group, C2-C20 alkenyl group, acryloyl group, methacryloyl group, glycidyl group, or bond, and n is an integer from 0 to 6.

[18] Release paper comprising a base material, a silicone sealing layer and a release layer, wherein the silicone sealing layer contains a modified vinyl alcohol polymer having a structural unit represented by the following formula (1'); [ka] [In formula (1'), X, Y, and Z are each independently a C1-C20 alkyl group, a C2-C20 alkenyl group, a phenyl group, a benzyl group, a vinylphenyl group, a C1-C20 halogenated alkyl group, a halogenated phenyl group, a C1-C20 aminoalkyl group, a C1-C20 mercaptoalkyl group, a C2-C20 ureidoalkyl group, a C2-C8 isocyanate alkyl group, a C3-C20 group containing an epoxy group, a C3-C20 group containing an acrylamide group, a C4-C20 group containing a methacrylamide group, an acetoxy group, or -(CH2) n -OR 1 (R 1 The group is represented by , where n represents a hydrogen atom, alkali metal atom, alkaline earth metal atom, C1-C20 alkyl group, C2-C20 alkenyl group, acryloyl group, methacryloyl group, glycidyl group, or bond, and n is an integer from 0 to 6.

[19] Release paper of the above release layer comprising addition-type silicone and platinum, wherein the content of platinum is 0.001 to 0.05 parts by mass per 100 parts by mass of the addition-type silicone

[18] ;

[20] A dispersant comprising a modified vinyl alcohol polymer having a structural unit represented by the following formula (1); [ka] [In formula (1), X, Y, and Z are each independently a C1-C20 alkyl group, a C2-C20 alkenyl group, a phenyl group, a benzyl group, a vinylphenyl group, a C1-C20 halogenated alkyl group, a halogenated phenyl group, a C1-C20 aminoalkyl group, a C1-C20 mercaptoalkyl group, a C2-C20 ureidoalkyl group, a C2-C8 isocyanate alkyl group, a C3-C20 group containing an epoxy group, a C3-C20 group containing an acrylamide group, a C4-C20 group containing a methacrylamide group, an acetoxy group, or -(CH2) n -OR 1 (R 1 The group is represented by , where n represents a hydrogen atom, alkali metal atom, alkaline earth metal atom, alkyl group having 1 to 20 carbon atoms, alkenyl group having 2 to 20 carbon atoms, acryloyl group, methacryloyl group, or glycidyl group, and n is an integer from 0 to 6.

[21] The dispersant of

[20] , wherein the content of the structural unit represented by formula (1) in the modified vinyl alcohol polymer is 0.01 mol% or more and less than 5 mol%;

[22] A dispersant according to

[20] or

[21] , wherein the content of the structural unit represented by formula (1) is 90 mol% or more relative to all structural units containing silicon atoms in the modified vinyl alcohol polymer;

[23] A dispersant of the above modified vinyl alcohol polymer having a viscosity-average degree of polymerization of 500 to 1500 and a degree of saponification of 60 mol% to 90 mol%;

[24] A dispersant from any of

[20] to

[23] , wherein the water-insoluble content of the modified vinyl alcohol polymer is 1000 ppm or less;

[25] A dispersant of any of

[20] to

[24] for suspension polymerization; A method for producing a vinyl polymer, comprising the step of suspend polymerization of a vinyl compound in the presence of any of the dispersants

[26] ,

[20] , to

[25] ;

[27] A mixture comprising a vinyl compound and any of the dispersants

[20] to

[25] . [Effects of the Invention]

[0017] According to this disclosure, it is possible to provide a modified vinyl alcohol polymer having a polymer structure incorporating a silane coupling agent, which is easy to handle and useful for various applications, a method for producing the modified vinyl alcohol polymer, particles of the modified vinyl alcohol polymer, and an aqueous solution of the modified vinyl alcohol polymer. Furthermore, this disclosure provides a coating liquid capable of forming a coating layer with excellent silicone curability and adhesion to a substrate, a coated product obtained by coating a substrate with the coating liquid, a molded product, and a release paper. Furthermore, according to this disclosure, a dispersant, a method for producing vinyl polymers, and a mixture can be provided that, when used in the manufacturing process of vinyl polymers, can reduce the average particle size of the resulting vinyl polymer, reduce the amount of coarse particles, and reduce fisheyes. [Modes for carrying out the invention]

[0018] <Modified vinyl alcohol polymer (modified PVA)> The modified PVA of this disclosure has structural units represented by the following formula (1), and has a water-insoluble content of 1000 ppm or less.

[0019] [ka]

[0020] In formula (1), X, Y, and Z are each independently a C1-C20 alkyl group, a C2-C20 alkenyl group, a phenyl group, a benzyl group, a vinylphenyl group, a C1-C20 halogenated alkyl group, a halogenated phenyl group, a C1-C20 aminoalkyl group, a C1-C20 mercaptoalkyl group, a C2-C20 ureidoalkyl group, a C2-C8 isocyanate alkyl group, a C3-C20 group containing an epoxy group, a C3-C20 group containing an acrylamide group, a C4-C20 group containing a methacrylamide group, an acetoxy group, or -(CH2) n -OR 1 (R 1 The group is represented by (where n represents a hydrogen atom, alkali metal atom, alkaline earth metal atom, alkyl group having 1 to 20 carbon atoms, alkenyl group having 2 to 20 carbon atoms, acryloyl group, methacryloyl group, or glycidyl group, and n represents an integer from 0 to 6).

[0021] The modified PVA of this disclosure has a polymer structure incorporating a silane coupling agent, yet exhibits excellent water solubility with low water insoluble content, resulting in excellent handling and usefulness for various applications. Specifically, the modified PVA of this disclosure dissolves easily when used in aqueous solution form, such as in coating solutions and dispersants for suspension polymerization, and leaves little undissolved residue, making it easy to handle. Due to its excellent water solubility, the modified PVA of this disclosure is particularly useful for various applications where it is dissolved in water, such as in coating solutions and dispersants for suspension polymerization. Furthermore, because the modified PVA has such excellent water solubility, it can be stored and transported in granular (powder) form and easily used by dissolving it in water, thus offering excellent handling.

[0022] X, Y, Z, or R 1 Examples of alkyl groups having 1 to 20 carbon atoms represented by include methyl, ethyl, propyl, butyl, isobutyl, hexyl, and lauryl groups. The number of carbon atoms in these alkyl groups is preferably 1 to 6, and more preferably 1 to 3.

[0023] X, Y, Z, or R 1Examples of alkenyl groups having 2 to 20 carbon atoms, represented by , include vinyl groups, allyl groups, hexenyl groups, and oleyl groups. The number of carbon atoms in these alkenyl groups is preferably 2 to 6, and more preferably 2 to 3. Among the alkenyl groups, vinyl groups are particularly preferred.

[0024] The vinylphenyl group represented by X, Y, or Z is the group represented by CH2=CH-C6H4-.

[0025] Examples of halogens in the C1-C20 halogenated alkyl group and halogenated phenyl group represented by X, Y, or Z include chlorine, bromine, and fluorine. The number of carbon atoms in the halogenated alkyl group is preferably 1-6, and more preferably 1-3.

[0026] The aminoalkyl group with 1 to 20 carbon atoms, represented by X, Y, or Z, is generally NR2-C. na H 2na -(where R is independently a hydrogen atom or a hydrocarbon group having 1 to 6 carbon atoms, and na is an integer from 1 to 20) is a group. The number of carbon atoms in this aminoalkyl group is preferably 1 to 10, and more preferably 1 to 6.

[0027] Mercaptoalkyl groups with 1 to 20 carbon atoms, represented by X, Y, or Z, are generally HS-C nb H 2nb This is a group represented by -(nb is an integer from 1 to 20). The number of carbon atoms in this mercaptoalkyl group is preferably 1 to 6. The mercaptopropyl group is particularly preferred as the mercaptoalkyl group.

[0028] A ureidoalkyl group with 2 to 20 carbon atoms, represented by X, Y, or Z, is generally NH2CONH-C. nc H 2nc This group is represented by -(nc is an integer from 1 to 19). The number of carbon atoms in this ureidoalkyl group is preferably 2 to 6.

[0029] Isocyanate alkyl groups having 2 to 8 carbon atoms, represented by X, Y, or Z, are generally OCN-Cnd H 2nd This group is represented by -(nd being an integer from 1 to 7). The number of carbon atoms in this isocyanate alkyl group is preferably 2 to 6.

[0030] A group having 3 to 20 carbon atoms and containing an epoxy group represented by X, Y, or Z refers to a group having 3 to 20 carbon atoms and containing a three-membered ring cyclic ether structure. Examples of such groups include epoxy groups, glycidyl groups, glycidoxymethyl groups, 3-glycidoxypropyl groups, and 2-(3,4-epoxycyclohexyl)ethyl groups. The number of carbon atoms in this epoxy group is preferably 3 to 12.

[0031] Examples of groups with 3 to 20 carbon atoms containing an acrylamide group represented by X, Y, or Z include the acrylamide group, acrylamidemethyl group, 3-acrylamidopropyl group, N-(2-acrylamidoethyl)-aminopropyl group, and (3-acrylamidopropyl)-oxypropyl group. The number of carbon atoms in this acrylamide group is preferably 3 to 12.

[0032] Examples of groups with 4 to 20 carbon atoms containing a methacrylamide group represented by X, Y, or Z include methacrylamide group, methacrylamidemethyl group, 3-methacrylamidopropyl group, N-(2-methacrylamidoethyl)-aminopropyl group, and (3-methacrylamidopropyl)-oxypropyl group. The number of carbon atoms in the group containing the methacrylamide group is preferably 4 to 12.

[0033] -(CH2) n -OR 1 The group represented is preferably a (meth)acryloxyalkyl group, and preferably a methacryloxypropyl group.

[0034] R 1 Preferred alkali metal atoms represented by are lithium atoms, sodium atoms, potassium atoms, rubidium atoms, cesium atoms, or francium atoms.

[0035] R1 The alkaline earth metal represented by is preferably a magnesium atom, a calcium atom, a strontium atom, or a barium atom.

[0036] At least one of X, Y, and Z is an alkenyl group having 2 to 20 carbon atoms, a mercaptoalkyl group having 1 to 20 carbon atoms, or -(CH2) n -OR 1 It is preferable that the group is represented by .

[0037] X, Y, and Z are C1-C20 alkyl groups, C2-C20 alkenyl groups, phenyl groups, benzyl groups, vinylphenyl groups, C1-C20 halogenated alkyl groups, halogenated phenyl groups, C1-C20 aminoalkyl groups, C1-C20 mercaptoalkyl groups, C2-C20 ureidoalkyl groups, C2-C8 isocyanate alkyl groups, C3-C20 groups containing acrylamide groups, C4-C20 groups containing methacrylamide groups, acetoxy groups, or -(CH2) n -OR 1 A group represented by may be preferred, and may be an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, a phenyl group, a benzyl group, or -(CH2) n -OR 1 A group represented by may be more preferred, such as an alkenyl group having 2 to 20 carbon atoms or -(CH2) n -OR 1 A base represented by may be even more preferable. n may be an integer between 0 and 4, or an integer between 0 and 2.

[0038] The modified PVA in this disclosure has a water-insoluble content of 1000 ppm or less. The upper limit of this water-insoluble content is preferably 500 ppm, more preferably 200 ppm, and even more preferably 100 ppm, 70 ppm, 50 ppm, or 10 ppm. Because the modified PVA has a low water-insoluble content, it is easy to handle and can exhibit excellent effects when used in coating liquids, dispersants, etc. The lower limit of this water-insoluble content may be 0 ppm or 1 ppm. The water-insoluble content in this disclosure is the mass ratio of components that remain undissolved after adding modified PVA to water to a concentration of 5% by mass and stirring at 90°C for 60 minutes, and is specifically measured by the following method.

[0039] Specifically, a 500 mL flask equipped with a stirrer and reflux condenser is prepared in a water bath set to 20°C. 285 g of distilled water is added to the flask, and stirring is started at 300 rpm. 15 g of modified PVA is weighed and gradually added to the flask. After adding the entire amount (15 g) of modified PVA, the modified PVA is dissolved by raising the water bath temperature to 90°C over 30 minutes to obtain a modified PVA solution. After the water bath temperature reaches 90°C, dissolution is continued for another 60 minutes while stirring at 300 rpm. Subsequently, the modified PVA solution is used to filter out any remaining insoluble solids of modified PVA (hereinafter sometimes referred to as "insoluble solids" or "insoluble particles") through a metal filter with a mesh size of 63 μm. Next, the filter is washed with 90°C hot water to remove any modified PVA solution adhering to the filter, leaving only the insoluble solids on the filter. The filter is then dried in a 120°C heating dryer for 1 hour. The mass of the filter after drying is compared with the mass of the filter before use for filtration to calculate the mass of the insoluble solids. The ratio of the mass of the insoluble solids to the mass of the modified PVA initially added to the water (15g) is defined as the water-insoluble portion.

[0040] The modified PVA of this disclosure is a polymer having vinyl alcohol units as its main structural units. The lower limit of the ratio of vinyl alcohol units to total structural units in the modified PVA is preferably 30 mol%, more preferably 50 mol%, even more preferably 65 mol%, and may be even more preferably 70 mol%, 80 mol%, 85 mol%, 90 mol%, or 95 mol%. On the other hand, the upper limit of the ratio of vinyl alcohol units is preferably 99.9 mol%, more preferably 99 mol%, and may be even more preferably 98 mol%, 95 mol%, 90 mol%, 85 mol%, or 80 mol%.

[0041] The modified PVA of this disclosure is obtained, for example, by reacting PVA with a silane coupling agent represented by formula (2), described later, in the presence of an acid catalyst (post-modification), where the -OR group of the silane coupling agent reacts with the -OH group of the PVA.

[0042] The lower limit of the modification amount of silane coupling agent-derived functional groups in modified PVA is preferably 0.01 mol%, more preferably 0.1 mol%, and even more preferably 0.2 mol%. When the modification amount of silane coupling agent-derived functional groups is above the above lower limit, the effects of the silane coupling agent-derived functional groups in modified PVA are more easily expressed. On the other hand, the upper limit of the modification amount of silane coupling agent-derived functional groups is preferably 5 mol%, more preferably 3 mol%, and even more preferably 1 mol%. When the modification amount of silane coupling agent-derived functional groups is below the above upper limit, the water solubility of the modified PVA tends to be better.

[0043] In this disclosure, the amount of modification refers to the ratio of the total number of moles of functional groups derived from the silane coupling agent introduced by post-modification to the total number of moles of structural units in the modified PVA, and may be referred to as the "amount of modification of silane coupling agent-derived functional groups" or simply the "amount of modification." In this specification, a structure represented by -CR'2-CR'2- is considered to be one structural unit. Each of the above R' is independently a hydrogen atom or any substituent, and two R' contained in the same or different structural units may be bonded together. For example, the structural unit represented by formula (1) above is considered to consist of one structural unit. On the other hand, vinyl alcohol units, residual vinyl ester units, structural units derived from other monomers, etc., are each considered to consist of one structural unit. In other words, a structural unit is a structure corresponding to a monomer having a carbon-carbon double bond that was used in polymerization.

[0044] The degree of modification of the functional group derived from the silane coupling agent is the same as that of modified PVA. 1 This can be determined by 1H-NMR measurement. For example, in the case of modified PVA obtained using PVA, which is a saponified polyvinyl acetate, and trimethoxyvinylsilane, the modified PVA is dissolved in DMSO-d6 and NMR is performed at 400 MHz. 1 Measurements are performed using 1H-NMR. The peaks originating from the hydrogen atoms in the hydroxyl group of the vinyl alcohol unit and the hydrogen atoms attached to the carbon atom to which the acetoxy group of the vinyl acetate unit is bonded are attributed to 4.2–5.2 ppm (integral value α). The peaks originating from the three hydrogen atoms in the vinyl group of trimethoxyvinylsilane are attributed to approximately 5.8–6.2 ppm (integral value β). From these integral values, the amount of modification of the functional group derived from the silane coupling agent is calculated using the following formula. Degree of modification of functional groups derived from silane coupling agent (mol%) = {β / (3α+β)} × 100 When using other silane coupling agents, the amount of modification can be similarly determined based on the peaks originating from the unreacted groups in the silane coupling agent.

[0045] The lower limit of the content of the structural unit represented by formula (1) in the modified PVA of this disclosure is preferably 0.01 mol%, more preferably 0.1 mol%, and even more preferably 0.2 mol%. When the content of the structural unit represented by formula (1) is above the lower limit, the effect of introducing the silane coupling agent into the modified PVA is more easily exhibited. On the other hand, the content of the structural unit represented by formula (1) is preferably less than 5 mol%. The upper limit of the content of the structural unit represented by formula (1) is more preferably 3 mol%, more preferably 2 mol%, and even more preferably 1 mol%. When the content of the structural unit represented by formula (1) is below or equal to the upper limit, the water solubility and handling properties of the modified PVA are better, and the performance when used in coating liquids and dispersants for suspension polymerization tends to be better. The content of the structural unit represented by formula (1) is similar to the amount of modification in the modified PVA. 1 This can be determined by 1H-NMR measurement. For example, in the modified PVA obtained in each of the examples described later, it is presumed that the amount of modification and the content of the structural unit represented by formula (1) above are substantially equal.

[0046] In the modified PVA of this disclosure, the lower limit of the content of the structural unit represented by formula (1) relative to all structural units containing silicon atoms is preferably 90 mol%, more preferably 99 mol%, and the content may be substantially 100 mol%. For example, when a silane coupling agent having an epoxy group and PVA are reacted in solution under a predetermined catalyst, the epoxy group and the hydroxyl group of PVA react. In such cases, structural units containing silicon atoms that are different from the structural unit represented by formula (1) are formed, and the desired effect may not be fully achieved. In contrast, by setting the content of the structural unit represented by formula (1) relative to all structural units containing silicon atoms to be above the lower limit, excellent water solubility is achieved, and the product becomes more suitable as a coating liquid, dispersant, etc.

[0047] In modified PVA, the lower limit of the block character of residual vinyl ester units is preferably 0.30, and more preferably 0.40. On the other hand, the upper limit of the block character is preferably 1, and more preferably 0.8. Having the block character within the above range facilitates the production of modified PVA.

[0048] The block character mentioned above is a numerical value representing the distribution of residual ester groups and hydroxyl groups produced by the saponification of ester groups, and takes a value between 0 and 2. A value of 0 indicates that residual ester groups or hydroxyl groups are distributed in a completely block-like manner, and as the value increases, the alternation increases, with 1 indicating that residual ester groups and hydroxyl groups are present in a completely random manner, and 2 indicating that residual ester groups and hydroxyl groups are present in a completely alternating manner. The residual ester group mentioned above refers to the ester group (-OC(=O)-Q (where Q represents a hydrocarbon group other than the CH2=CH-OC(=O) portion contained in the vinyl ester monomer)) contained in the vinyl ester monomer unit in the modified PVA obtained after saponification treatment. If the modified PVA contains structural units other than vinyl ester monomer units and / or vinyl alcohol units, the block character is calculated for all consecutive sites of vinyl ester monomer units and / or vinyl alcohol units in the modified PVA.

[0049] The lower limit of the degree of saponification of the modified PVA is preferably 30 mol%, more preferably 65 mol%, and may be even more preferably 70 mol%, 80 mol%, or 90 mol%. On the other hand, the upper limit of the degree of saponification of the modified PVA is preferably 99.9 mol%, more preferably 99 mol%, and may be even more preferably 98 mol%, 93 mol%, 90 mol%, or 85 mol%. By setting the degree of saponification of the modified PVA within the above range, a modified PVA with superior water solubility can be obtained. The degree of saponification of the modified PVA and the raw material PVA described later is measured by the method described in JIS-K6726-1994.

[0050] The lower limit of the viscosity-average degree of polymerization (hereinafter also simply referred to as "degree of polymerization") of modified PVA is preferably 100, more preferably 300, and may be even more preferably 500, 600, 650, 700, or 1000. On the other hand, the upper limit is preferably 5000, more preferably 4000, and may be even more preferably 3000, 2000, 1500, 1000, or 800. The viscosity-average degree of polymerization is measured by the method described in JIS-K6726-1994.

[0051] The modified PVA of this disclosure can be used in a variety of applications. Examples are given below, but the applications of the modified PVA of this disclosure are not limited to these. (1) Uses of vinyl chloride dispersant: Dispersion stabilizer and dispersion aid for suspension polymerization of vinyl chloride and vinylidene chloride. (2) Coating agent applications: sizing agent, textile processing agent, leather finishing agent, paint, antifogging agent, metal corrosion inhibitor, zinc plating polish, antistatic agent (3) Adhesives and binders: Adhesives, adhesives, re-moistened adhesives, various binders, and additives for cement and mortar. (4) Dispersion stabilizer applications: Dispersion stabilizer for organic and inorganic pigments in paints and adhesives, dispersion stabilizer for emulsion polymerization of various vinyl compounds, post-emulsifier for bitumen, etc. (5) Paper processing applications: paper strength enhancers, oil and solvent resistance enhancers, smoothness enhancers, surface gloss enhancers, sealants, barrier agents, lightfastness enhancers, water resistance enhancers, dye and color developer dispersants, adhesive strength enhancers, binders (6) Agricultural uses: pesticide binders, pesticide spreading agents, agricultural coatings, soil conditioners, erosion inhibitors, pesticide dispersants (7) Medical and cosmetic applications: Granulation binders, coating agents, emulsifiers, patches, binders, film formulation bases, film-forming agents (8) Viscosity modifiers: Uses: Thickening agents, rheology modifiers (9) Uses of flocculants: Flocculants for suspended and dissolved substances in water, metal flocculants (10) Film applications: Water-soluble films, polarizing films, barrier films, films for packaging textile products, seed protection sheets, vegetation sheets, seed tapes, moisture-absorbing films (11) Applications of molded products: Fibers, pipes, tubes, leak-proof membranes, water-soluble fibers for chemical lace, sponges (12) Applications of resin raw materials: Raw materials for polyvinyl butyral, photosensitive resin raw materials, graft polymer raw materials, various gel raw materials (13) Post-reaction applications: Post-reaction applications with low molecular weight organic compounds, high molecular weight organic compounds, and inorganic compounds. In particular, as will be described later, dispersants and coating liquids for paper processing are preferred applications for the modified PVA of this disclosure. Film applications are also preferred, and film applications for unit packaging are more preferred.

[0052] <Particle> One embodiment of the modified PVA of this disclosure is particles (modified PVA particles). The particles of this disclosure are particles containing modified PVA. These particles have excellent water solubility and handling properties and are useful for various applications. For example, coating liquids can be efficiently obtained using these particles. These particles can also be effectively used as a dispersant. These particles may consist substantially of modified PVA alone. The content of modified PVA in these particles may be, for example, 90% by mass or more, 99% by mass or more, or 100% by mass.

[0053] The average particle size (dp50) of the particles in this disclosure is preferably 100 μm or more and 5 mm or less, more preferably 200 μm or more and 3 mm or less, and even more preferably 300 μm or more and 1 mm or less. When the average particle size is within the above range, handling properties tend to be improved. The average particle size (dp50) is calculated by measuring the particle size distribution using a JIS standard sieve and the dry sieving method described in JIS-Z8815-1994, and plotting the results on the Rosin-Rammler distribution formula.

[0054] The dispersion degree A of silicon atoms in the particles is preferably 0.2 or more and less than 1. The dispersion degree A of silicon atoms in the particles is the ratio of silicon atom content in the center of the particle to silicon atom content on the particle surface in the modified PVA in particle state, and serves as an indicator of the degree of dispersion of functional groups derived from the silane coupling agent in the polymer of modified PVA. Specifically, the dispersion degree A is measured by the following method.

[0055] First, ten particles with a diameter of 100 μm or more that are close to spherical are selected. These particles are divided into two halves so as to maximize their cross-sectional area. The center of the inscribed circle of the cross-section is defined as the particle center, and the point of contact between the inscribed circle and the particle surface is defined as the particle surface. The silicon atom content is then measured using an energy-dispersive X-ray spectrometer (EDS). For each particle, the dispersion A is calculated based on the following formula, and the average value of the ten particles is adopted. Dispersion A = Silicon atom content in the particle center (mol%) / Silicon atom content on the particle surface (mol%)

[0056] The lower limit of the degree of dispersion A is preferably 0.2, more preferably 0.5, even more preferably 0.7, even more preferably 0.8, and even more preferably 0.9. Furthermore, the degree of dispersion A may be less than 1, and the upper limit may be 0.99. Having the degree of dispersion A within the above range results in better dispersion of the functional groups derived from the silane coupling agent within the polymer or particles of the modified PVA, thereby improving the water solubility and handling properties of the modified PVA. Additionally, the high water solubility resulting from the above-mentioned degree of dispersion A makes it suitable for use in coating solutions, dispersants, etc., enhancing its performance as a coating solution, dispersant, etc.

[0057] <Aqueous solution> The aqueous solution of this disclosure contains the modified PVA of this disclosure. The aqueous solution of this disclosure has a low amount of insoluble modified PVA and can be suitably used as a coating liquid, etc. That is, the coating liquid, etc. described later is one embodiment of the aqueous solution. The aqueous solution can be obtained by dissolving modified PVA in water by a conventionally known method.

[0058] The aqueous solution of this disclosure may contain no silane coupling agent, or may further contain a silane coupling agent, and it is preferable that the ratio of silicon atoms contained in the modified PVA to the total content of silicon atoms contained in the modified PVA and the silane coupling agent is 50 mol% or more. More preferably, the lower limit of the silicon atom content is 70 mol%, 90 mol%, or 95 mol%. When the content of the silane coupling agent in the aqueous solution is low in this way, the storage stability and reaction uniformity of the aqueous solution tend to be improved.

[0059] The aqueous solution may contain substantially only modified PVA as the solute. The content of modified PVA relative to the total solute in the aqueous solution is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 90% by mass or more, and even more preferably 95% by mass or more. The concentration of modified PVA in the aqueous solution is set appropriately depending on the application, etc., but may be, for example, 0.1% by mass or more and 30% by mass or less, or 1% by mass or more and 25% by mass or less. The aqueous solution may further contain solvents other than water.

[0060] <Method for manufacturing modified PVA> Modified PVA can be produced, for example, by saponifying a vinyl ester polymer obtained by polymerizing vinyl ester monomers to obtain PVA, and then reacting the PVA with a silane coupling agent.

[0061] Examples of the vinyl ester monomers mentioned above include vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pivalate, and vinyl versatate. Among these, vinyl acetate is preferred.

[0062] Known methods for polymerizing vinyl ester monomers include, for example, bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization. Of these methods, bulk polymerization carried out without a solvent and solution polymerization carried out using a solvent such as an alcohol are preferred, and in terms of enhancing the effects of this disclosure, solution polymerization carried out in the presence of a lower alcohol is more preferred. As the lower alcohol, alcohols having 3 or fewer carbon atoms are preferred, methanol, ethanol, n-propanol and isopropanol are more preferred, and methanol is even more preferred. When carrying out the polymerization reaction by bulk polymerization or solution polymerization, either batch or continuous reaction methods can be employed.

[0063] Examples of initiators used in polymerization reactions include azo-based initiators such as 2,2'-azobisisobutyronitrile, 2,2'-azobis(2,4-dimethylvaleronitrile), and 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile); and known initiators such as organic peroxide-based initiators such as benzoyl peroxide and n-propyl peroxycarbonate. There are no particular restrictions on the polymerization temperature when carrying out the polymerization reaction, but a range of 5°C to 200°C is appropriate.

[0064] When polymerizing vinyl ester monomers, copolymerizable monomers can be further copolymerized, to the extent that the spirit of this disclosure is not impaired. The copolymerizable monomers may also be silane coupling agents. Such monomers include α-olefins such as ethylene, propylene, 1-butene, isobutene, and 1-hexene; acrylamide derivatives such as N-methylacrylamide and N-ethylacrylamide; methacrylamide derivatives such as N-methylmethacrylamide and N-ethylmethacrylamide; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, and n-butyl vinyl ether; hydroxyl group-containing vinyl ethers such as ethylene glycol vinyl ether, 1,3-propanediol vinyl ether, and 1,4-butanediol vinyl ether; allyl acetate; propyl allyl ether, and butyl allyl ether. Examples include allyl ethers such as hexylallyl ether; monomers having an oxyalkylene group; isopropenyl acetate; hydroxyl group-containing α-olefins such as 3-buten-1-ol, 4-penten-1-ol, 5-hexen-1-ol, 7-octen-1-ol, 9-decen-1-ol, and 3-methyl-3-buten-1-ol; and monomers having a silyl group such as vinyltrimethoxysilane, vinylmethyldimethoxysilane, vinyldimethylmethoxysilane, vinyltriethoxysilane, vinylmethyldiethoxysilane, vinyldimethylethoxysilane, 3-(meth)acrylamidopropyltrimethoxysilane, and 3-(meth)acrylamidopropyltriethoxysilane. The upper limit of the amount of these monomers used varies depending on the purpose and application, but 20 mol% and more preferably 10 mol% relative to the total monomers are preferred.

[0065] In the saponification reaction of the vinyl ester polymer obtained in the polymerization step described above, an alkaline catalyst or an acid catalyst may be used. For example, an alcohol decomposition or hydrolysis reaction using a conventionally known basic catalyst such as sodium hydroxide, potassium hydroxide, or sodium methoxide can be applied. 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. These can be used individually or in combination of two or more. Among these, it is convenient and preferable to use methanol or a mixed solution of methanol and methyl acetate as the solvent and carry out the saponification reaction in the presence of sodium hydroxide, which is a basic catalyst. PVA can be obtained by this method.

[0066] The viscosity of a 4% by mass aqueous solution of PVA before reaction with the silane coupling agent (hereinafter sometimes referred to as "raw material PVA") is preferably 1 mPa·s to 200 mPa·s, more preferably 2 mPa·s to 100 mPa·s, and even more preferably 3 mPa·s to 50 mPa·s, from the viewpoint of further suppressing excessive crosslinking of the resulting modified PVA.

[0067] The lower limit of the saponification degree of the raw material PVA is preferably 30 mol%, more preferably 60 mol%, even more preferably 65 mol%, and in some cases 70 mol%, 80 mol%, or 90 mol% are even more preferable. On the other hand, the upper limit of the saponification degree of the raw material PVA is preferably 99.9 mol%, more preferably 99 mol%, and in some cases 98 mol%, 93 mol%, 90 mol%, or 85 mol% are even more preferable. By setting the saponification degree of the raw material PVA within the above range, it is expected that the reaction with the silane coupling agent will proceed more efficiently.

[0068] The lower limit of the degree of polymerization of the raw material PVA is preferably 100, more preferably 300, and may be even more preferably 500, 600, 650, 700, or 1000. On the other hand, the upper limit is preferably 5000, more preferably 4000, and may be even more preferably 3000, 2000, 1500, 1000, or 800.

[0069] For example, modified PVA can be obtained by reacting (post-modifying) the above-mentioned raw material PVA with a silane coupling agent.

[0070] It is preferable to use a compound represented by the following formula (2) as the silane coupling agent.

[0071] [ka]

[0072] In formula (2), R is an alkyl group having 1 to 8 carbon atoms, an acetyl group, or -(CH2) m -OR 2 (R 2 X represents an alkyl group having 1 to 20 carbon atoms, and m represents an integer from 1 to 6. X, Y, and Z are each independently an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, a phenyl group, a benzyl group, a vinylphenyl group, a halogenated alkyl group having 1 to 20 carbon atoms, a halogenated phenyl group, an aminoalkyl group having 1 to 20 carbon atoms, a mercaptoalkyl group having 1 to 20 carbon atoms, a ureidoalkyl group having 2 to 20 carbon atoms, an isocyanate alkyl group having 2 to 8 carbon atoms, a group having 3 to 20 carbon atoms containing an epoxy group, a group having 3 to 20 carbon atoms containing an acrylamide group, a group having 4 to 20 carbon atoms containing a methacrylamide group, an acetoxy group, or -(CH2) n -OR 1 (R 1 The group is represented by (where n is an integer from 0 to 6, and n is an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an acryloyl group, a methacryloyl group, or a glycidyl group).

[0073] In formula (2), R is preferably an alkyl group having 1 to 8 carbon atoms, and more preferably an alkyl group having 1 to 3 carbon atoms. Specific and preferred forms of X, Y, and Z in formula (2) can be given by examples of specific and preferred forms of X, Y, and Z in formula (1).

[0074] Examples of compounds represented by formula (2) include vinyltrimethoxysilane, vinylmethyldimethoxysilane, vinyldimethylmethoxysilane, vinyltriethoxysilane, vinylmethyldiethoxysilane, vinyldimethylethoxysilane, allyltrimethoxysilane, allylmethyldimethoxysilane, allyldimethylmethoxysilane, allyltriethoxysilane, allylmethyldiethoxysilane, allyldimethylethoxysilane, vinyltris(β-methoxyethoxy)silane, vinylisobutyldimethoxysilane, vinylethyldimethoxysilane Lan, vinylmethoxydibutoxysilane, vinyldimethoxybutoxysilane, vinyltributoxysilane, vinylmethoxydihexyloxysilane, vinyldimethoxyhexyloxysilane, vinyltrihexyloxysilane, vinylmethoxydioctyloxysilane, vinyldimethoxyoctyloxysilane, vinyltrioctyloxysilane, vinylmethoxydilauryloxysilane, vinyldimethoxylauryloxysilane, vinylmethoxydioleyloxysilane, vinyldimethoxyoleyloxysilane, 3-(meth)acrylamide-propyltrimeth Xysilane, 3-(meth)acrylamide-propyltriethoxysilane, 3-(meth)acrylamide-propyltri(β-methoxyethoxy)silane, 2-(meth)acrylamide-ethyltrimethoxysilane, 1-(meth)acrylamide-methyltrimethoxysilane, 2-(meth)acrylamide-2-methylpropyltrimethoxysilane, 2-(meth)acrylamide-isopropyltrimethoxysilane, N-(2-(meth)acrylamide-ethyl)-aminopropyltrimethoxysilane, (3-(meth)acrylamide-propyl N-(meth)acrylamide-propyltriacetoxysilane, 3-(meth)acrylamide-propyltriacetoxysilane, 2-(meth)acrylamide-ethyltriacetoxysilane, 4-(meth)acrylamide-butyltriacetoxysilane, 3-(meth)acrylamide-propyltripropionyloxysilane, 2-(meth)acrylamide-2-methylpropyltriacetoxysilane, N-(2-(meth)acrylamide-ethyl)-aminopropyltriacetoxysilane, 3-(meth)acrylamide-propylisobutyldimethoxysilane,2-(meth)acrylamide-ethyldimethylmethoxysilane, 3-(meth)acrylamide-propylmethyldiacetoxysilane, 2-(meth)acrylamide-2-methylpropylhydrogendimethoxysilane, 3-(N-methyl-(meth)acrylamide)-propyltrimethoxysilane, 2-(N-ethyl-(meth)acrylamide)-ethyltriacetoxysilane, p-styryltrimethoxysilane (silane coupling agent having a vinylphenyl group), 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3- Examples include glycidoxypropyltriethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, 3-ureidopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, 3-isocyanatetopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, and 3-mercaptopropyltrimethoxysilane. Among these, vinyltrimethoxysilane is preferred because it is easily manufactured industrially and readily available at low cost.

[0075] For example, a condensation reaction can occur between the OR group of the silane coupling agent represented by formula (2) and the OH group of PVA to form a structural unit represented by formula (1), thereby obtaining modified PVA.

[0076] The lower limit of the amount of silane coupling agent to be added is preferably 0.1 parts by mass, more preferably 0.5 parts by mass, and still more preferably 1 part by mass, per 100 parts by mass of PVA. On the other hand, the upper limit of the amount of silane coupling agent to be added is preferably 20 parts by mass, more preferably 15 parts by mass, and still more preferably 10 parts by mass, per 100 parts by mass of PVA. By adding silane coupling agent within the above range, the water solubility and handling properties of the resulting modified PVA can be further improved.

[0077] There are no particular restrictions on the method of reacting PVA with a silane coupling agent, but for example, the desired reaction can be carried out by mixing powdered or particulate PVA with a solution containing a silane coupling agent using a ribbon blender, Henschel mixer, V-blender, rotary kiln, planetary mixer, high-speed mixer, Henschel mixer, turbulator, Redigge mixer, etc.

[0078] Another embodiment of the present disclosure is a method for producing modified PVA, which includes the step of impregnating solid PVA with a silane coupling agent.

[0079] Furthermore, one embodiment of this disclosure is a manufacturing method in which, in the impregnation step, a solution containing a silane coupling agent is sprayed onto PVA to impregnate (penetrate) it.

[0080] In the impregnation process described above, it is preferable to use a solvent that ensures the silane coupling agent is uniformly dispersed in the PVA. Specifically, it is preferable to add a solvent (solution) containing the silane coupling agent to the PVA particles and react the mixture consisting of PVA and the silane coupling agent. There is no limit to the amount of solvent added, but 10 to 50 parts by mass per 100 parts by mass of PVA is preferred. By adding solvent within this range, the silane coupling agent penetrates the PVA particles more uniformly, and consequently, the reaction between the silane coupling agent and PVA proceeds more uniformly, resulting in a tendency for the resulting modified PVA to have higher water solubility and easier handling.

[0081] The average particle size (dp50) of the PVA particles used in the impregnation process described above is preferably 100 μm to 5 mm, more preferably 200 μm to 3 mm, and even more preferably 300 μm to 1 mm. Using PVA particles of this size allows the silane coupling agent to penetrate more uniformly into the PVA particles, which tends to improve the water solubility and handling properties of the resulting modified PVA.

[0082] Furthermore, it is preferable to use an acidic catalyst in the impregnation process described above. Possible acidic catalysts include inorganic acids such as sulfuric acid, hydrochloric acid, and phosphoric acid, and organic acids such as acetic acid and p-toluenesulfonic acid. However, since using a highly acidic catalyst may cause the saponification reaction of PVA to proceed, it is preferable to use an acidic catalyst with an acid dissociation constant pKa of 4 to 6. Among these, acetic acid is preferred.

[0083] As the solvent that can be used in the impregnation step described above, polar solvents with high affinity for PVA are preferred. For example, various solvents such as alcohols like methanol, ethanol, and isopropanol; ketones like acetone, ethyl methyl ketone, and diethyl ketone; esters like methyl acetate and ethyl acetate; dimethyl sulfoxide; and N,N-dimethylformamide can be used. Among these, methanol and methyl acetate are preferred.

[0084] Furthermore, one embodiment of the method for producing modified PVA according to this disclosure further includes a step of heat-treating the PVA impregnated with the silane coupling agent obtained in the impregnation step. This heat treatment ensures that the reaction between the silane coupling agent and PVA occurs sufficiently. When heat treatment is performed on PVA impregnated with the silane coupling agent, drying occurs, which promotes the dehydration condensation reaction between the OR groups of the silane coupling agent and the OH groups of PVA, resulting in sufficient formation of the structural unit represented by formula (1) above. However, if heat treatment is performed on a solution containing the silane coupling agent and PVA, the dehydration condensation reaction does not proceed sufficiently, and it is considered that the formation of the structural unit represented by formula (1) above hardly occurs.

[0085] The means of the heat treatment described above are not particularly limited, but for example, the heat treatment may be carried out using a dryer, and it is preferable to carry out the heat treatment using a hot air dryer. The impregnation process and the heat treatment process may also be carried out simultaneously, for example, the heat treatment may be carried out while mixing powdered or particulate PVA and a solution containing a silane coupling agent using a ribbon blender, Henschel mixer, V-blender, rotary kiln, planetary mixer, high-speed mixer, Henschel mixer, turbulator, Redigge mixer, etc.

[0086] In the step of heat-treating the PVA and silane coupling agent described above, the lower limit of the heat treatment temperature (reaction temperature) is preferably 20°C, more preferably 40°C, even more preferably 60°C, even more preferably 75°C, and particularly preferably 80°C. On the other hand, the upper limit of the heat treatment temperature is preferably 120°C, more preferably 110°C, and even more preferably 100°C. By setting the heat treatment temperature within the above range, the reaction proceeds more smoothly, and the water solubility and handling properties of the resulting modified PVA can be further improved.

[0087] In the heat treatment process described above, the heat treatment time can be set appropriately according to the heat treatment temperature, but it is preferably 1 hour or more and 18 hours or less, and more preferably 3 hours or more and less than 12 hours. Furthermore, it is preferable to react at a heat treatment temperature of 70°C or more and 90°C or less for 3 hours or more and less than 12 hours.

[0088] The above manufacturing method allows the silane coupling agent to penetrate the solid PVA, causing it to swell. By allowing the reaction between PVA and the silane coupling agent to proceed in this state, the uneven distribution of functional groups derived from the silane coupling agent in the modified PVA is suppressed, resulting in modified PVA particles with a higher degree of dispersion A. Furthermore, such modified PVA has a lower water-insoluble content, superior water solubility and handling properties, making it easier to apply to a wider range of uses. For example, when used in coating solutions, dispersants, etc., it can exhibit excellent performance as a coating solution or dispersant.

[0089] <Coating liquid> The coating liquid of this disclosure contains modified PVA having a structural unit represented by formula (1) above. The coating liquid of this disclosure is preferably a coating liquid for paper substrates or film substrates, and may also be a coating liquid used when manufacturing release paper or release film. The coating liquid can form a coating layer with excellent silicone curability and adhesion to the substrate. Furthermore, the coating layer formed from the coating liquid also has sufficient sealing properties. The specific form and preferred form of the modified PVA used in the coating liquid is the same as that of the modified PVA of this disclosure described above, except that it is not essential that the water-insoluble content be 1000 ppm or less. However, it is preferable that the water-insoluble content of the modified PVA used in the coating liquid be within the above range.

[0090] The viscosity-average degree of polymerization of the modified PVA used in the coating liquid of this disclosure is not particularly limited, but its lower limit is preferably 500, more preferably 600, and even more preferably 650. When the lower limit of the viscosity-average degree of polymerization of the modified PVA is within the above range, the air permeability resistance of the coating layer made of the coating liquid containing the modified PVA tends to increase, and the sealing properties tend to improve. Furthermore, the upper limit of the viscosity-average degree of polymerization is preferably 5000, more preferably 4000, even more preferably 3000, and even more preferably 2000. When the upper limit of the viscosity-average degree of polymerization of the modified PVA is within the above range, the productivity of the modified PVA can be further increased. In addition, it is preferable that the viscosity-average degree of polymerization of the modified PVA is between 500 and 5000.

[0091] The lower limit of the degree of saponification of the modified PVA used in the coating liquid of this disclosure is preferably 70 mol%, more preferably 80 mol%, and even more preferably 90 mol%. On the other hand, the upper limit of the degree of saponification of the modified PVA is preferably 99.9 mol%. By setting the degree of saponification of the modified PVA within the above range, it is possible to obtain a modified PVA with excellent water solubility and water resistance of the film after coating and drying, resulting in superior performance as a coating liquid.

[0092] The upper limit of the insoluble portion of modified PVA in the coating solution is preferably 1000 ppm, more preferably 500 ppm, even more preferably 200 ppm, even more preferably 100 ppm, particularly preferably 70 ppm, even more preferably 50 ppm, and in some cases even more preferably 10 ppm. The lower limit of the insoluble portion of modified PVA in the coating solution is preferably 0 ppm, and may be 1 ppm. In this disclosure, the insoluble portion of modified PVA in the coating solution refers to the mass ratio of modified PVA-derived components that remain undissolved in the coating solution, and is specifically measured by the following method.

[0093] The coating solution is passed through a metal filter with a mesh size of 63 μm, and the filter is then washed with 90°C hot water to obtain solid modified PVA that remains insoluble in the coating solution. The ratio of the mass of the insoluble solid modified PVA to the mass of modified PVA contained in the coating solution before filtration is calculated, and this is defined as the insoluble portion of modified PVA in the coating solution.

[0094] The lower limit of the modified PVA concentration in the coating solution is preferably 2% by mass, and may be more preferably 5% by mass. The upper limit of the modified PVA concentration in the coating solution is preferably 30% by mass, and may be more preferably 25% by mass. When the concentration of modified PVA in the coating solution is within the above range, the coating efficiency is further improved and the high-speed coating performance is superior.

[0095] The coating solution of this disclosure may contain no silane coupling agent, or may further contain a silane coupling agent, and it is preferable that the ratio of silicon atoms contained in the modified PVA to the total content of silicon atoms contained in the modified PVA and the silane coupling agent is 50 mol% or more. More preferably, the lower limit of the silicon atom content is 70 mol%, 90 mol%, or 95 mol%. When the silane coupling agent content in the coating solution is low in this way, the storage stability and reaction uniformity of the coating solution tend to improve.

[0096] The coating solution of this disclosure is preferably an aqueous solution containing modified PVA. In this case, the aqueous solution may contain a small amount of organic solvent, or a small amount of water-insoluble organic or inorganic particles. The concentration of modified PVA in the aqueous solution is preferably 1% by mass or more and 30% by mass or less.

[0097] The method for producing the coating solution described herein is not particularly limited. For example, the coating solution can be obtained by dissolving modified PVA particles in water.

[0098] The above coating solution may contain other components besides the vinyl alcohol polymers of this disclosure, to the extent that the effects of this disclosure are not impaired. Other components include aqueous dispersible resins such as SBR latex, NBR latex, vinyl acetate emulsion, ethylene / vinyl acetate copolymer emulsion, (meth)acrylic ester emulsion, and vinyl chloride emulsion; raw starch obtained from wheat, corn, rice, potato, sweet potato, tapioca, sago palm, etc.; raw starch decomposition products such as oxidized starch and dextrin; starch derivatives such as etherified starch, esterified starch, and cationized starch; cellulose derivatives such as methylcellulose, hydroxyethylcellulose, and carboxymethylcellulose (CMC); monosaccharides such as glucose, fructose, isomerized sugar, and xylose; maltose and lactose Examples include disaccharides such as sucrose, trehalose, palatinose, reduced maltose, reduced palatinose, and reduced lactose; oligosaccharides such as corn syrup, isomaltoligosaccharides, fructooligosaccharides, lactose oligosaccharides, soybean oligosaccharides, xylooligosaccharides, coupling sugars, and cyclodextrin compounds; polysaccharides such as pullulan, pectin, agar, konjac mannan, polydextrose, and xanthan gum; and albumin, gelatin, casein, acacia gum, polyamide resin, melamine resin, poly(meth)acrylamide, polyvinylpyrrolidone, sodium poly(meth)acrylate, anionic modified PVA, sodium alginate, and water-soluble polyesters. The content of these components in the above coating liquid is usually 10% by mass or less.

[0099] The above coating solution may contain pigments to the extent that the effects of this disclosure are not impaired. Examples of pigments include inorganic pigments (such as clay, kaolin, aluminum hydroxide, calcium carbonate, and talc) and organic pigments (such as plastic pigments) that are generally used in the field of coated paper manufacturing. Preferably, the content of these pigment components in the above coating solution is 50% by mass or less.

[0100] <Coated materials> A preferred embodiment of the present disclosure is a coated product obtained by coating the surface of a substrate with the above-mentioned coating liquid. Paper substrates and film substrates are preferred as the substrate. The method for manufacturing the coated product is not particularly limited, and may include, for example, a step of coating the substrate with the coating liquid and a step of drying the substrate after coating.

[0101] As the paper substrate, known papers or synthetic papers obtained by papermaking from chemical pulps such as hardwood kraft pulp and softwood kraft pulp, or mechanical pulps such as GP (wood pulp), RGP (refiner gland pulp), and TMP (thermomechanical pulp) can be used. In addition, as the paper substrate, fine paper, medium paper, alkaline paper, glassine paper, semi-glassine paper, or paperboard and white paperboard used for corrugated cardboard, building materials, white cardboard, chipboard, etc., can also be used. The paper substrate may contain organic and inorganic pigments, as well as papermaking aids such as paper strength enhancers, sizing agents, and yield enhancers. Furthermore, the paper substrate may be subjected to various surface treatments.

[0102] The film substrate is preferably made of a thermoplastic resin. Examples of thermoplastic resins include polyolefins, polyesters, and polyamides.

[0103] Coating equipment includes 2-roll size presses, gate roll size presses, metering size presses, air knife coaters, bar coaters, roll coaters, and blade coaters. The coating speed is preferably 100 to 2,000 m / min. More preferably, the coating speed is 300 m / min or higher, and sometimes even more preferably 1,800 m / min or lower. A coating speed within this range allows for higher production efficiency and easier uniform coating. The coating amount can be arbitrarily selected according to the properties of the paper, but is generally 0.05 to 10 g / m² per side of the paper. 2 The degree is suitable.

[0104] Drying after coating can be performed by methods such as hot air, infrared radiation, heated cylinders, or a combination thereof. The barrier properties of the dried coated material can be further improved by humidity control and calendering. Desirable humidity control conditions are those that result in a paper moisture content of 5 to 20% by mass. For calendering conditions, a roll temperature of room temperature to 200°C and a roll linear pressure of 20 to 350 kg / cm are preferred.

[0105] The lower limit of the air permeability resistance of the coating is preferably 400 seconds, more preferably 2,000 seconds, even more preferably 5,000 seconds, even more preferably 7,000 seconds, and sometimes particularly preferably 10,000 seconds. The upper limit of the air permeability resistance of the coating is not particularly limited, but may be 20,000 seconds.

[0106] Examples of coated materials include release paper base paper, barrier paper, oil-resistant paper, packaging paper, cardboard, polyethylene-based release film, polypropylene-based release film, polyester-based release film, etc. Among these, release paper base paper, in which a coating liquid is applied to the surface of a paper substrate, is a preferred embodiment of this disclosure. A release layer may be formed on the surface of the release paper base paper. When forming the release layer, solvent-based silicones and non-solvent-based (emulsion-based, oligomer-based) silicones are preferably used. Since solvent-based silicones contain solvents (such as toluene), it is preferable that the release paper base paper of this disclosure has barrier properties against solvents. Furthermore, when using non-solvent-based silicones, water resistance may be required, so it is preferable that the release paper base paper of this disclosure has water resistance. In this disclosure, release paper having the release paper base paper and a release layer formed on the surface of the release paper base paper is also a preferred embodiment.

[0107] <Molded body> One embodiment of the present disclosure is a molded article comprising a layer containing modified PVA having structural units represented by the following formula (1').

[0108] [ka]

[0109] In formula (1'), X, Y, and Z are each independently a C1-C20 alkyl group, a C2-C20 alkenyl group, a phenyl group, a benzyl group, a vinylphenyl group, a C1-C20 halogenated alkyl group, a halogenated phenyl group, a C1-C20 aminoalkyl group, a C1-C20 mercaptoalkyl group, a C2-C20 ureidoalkyl group, a C2-C8 isocyanate alkyl group, a C3-C20 group containing an epoxy group, a C3-C20 group containing an acrylamide group, a C4-C20 group containing a methacrylamide group, an acetoxy group, or -(CH2) n -OR 1 (R 1The group is represented by (where n represents a hydrogen atom, alkali metal atom, alkaline earth metal atom, alkyl group having 1 to 20 carbon atoms, alkenyl group having 2 to 20 carbon atoms, acryloyl group, methacryloyl group, glycidyl group, or bond, and n is an integer from 0 to 6).

[0110] The specific form and preferred form of the structural unit represented by formula (1') are R 1 Except for the fact that it may include cases where it is a bonding agent, i.e., it may form a cross-linked structure, the specific form and preferred form of the structural unit represented by formula (1) described above are the same as the specific form and preferred form of the structural unit represented by formula (1) described above. Furthermore, the specific form and preferred form of the modified PVA contained in the molded article are the same as the specific form and preferred form of the modified PVA used in the coating liquid, etc. of this disclosure, except that it may form the cross-linked structure described above.

[0111] The molded body is not particularly limited and may be, for example, a three-dimensional object or a sheet. The material constituting the molded body is not particularly limited and may include, for example, metal, ceramics, glass, resin, concrete, etc. The metal may be, for example, iron, steel, aluminum, stainless steel, gold, silver, copper, etc. The molded body may also be the above-mentioned base material, and paper base material and film base material are preferred as the base material.

[0112] The layer containing modified PVA in the molded article may be a coating film formed by applying the above-mentioned coating liquid to the target molded article.

[0113] The content of modified PVA in the layer containing modified PVA may be, for example, 50% to 100% by mass, or 70% to 99.9% by mass. The layer containing modified PVA may further contain other components besides modified PVA. Examples of other components include the various components that may be contained in the coating liquid described above.

[0114] <Release paper> One embodiment of the present disclosure is a release liner. The release liner comprises a substrate, a silicone sealant layer, and a release layer, wherein the silicone sealant layer contains modified PVA having a structural unit represented by formula (1'). Preferably, the release liner is laminated in the order of the substrate, the silicone sealant layer, and the release layer. The release liner of the present disclosure is one form of the molded article of the present disclosure. That is, the silicone sealant layer of the release liner of the present disclosure corresponds to the layer containing modified PVA in the molded article described above.

[0115] The release layer preferably contains addition-curing silicone and platinum, and preferably the platinum content is 0.001 to 0.05 parts by mass per 100 parts by mass of addition-curing silicone. This can further improve the curability of the addition-curing silicone in the release layer. Furthermore, since the curing speed of the addition-curing silicone can be accelerated, it is expected that the time required for the silicone curing process can be shortened, or the amount of platinum used can be reduced, thereby reducing manufacturing costs.

[0116] Examples of substrates for release paper include those mentioned above, with paper substrates and film substrates being preferred. In this disclosure, even if the release paper comprising a substrate, a silicone sealing layer, and a release layer consists solely of a film substrate, it may still be referred to as "release paper."

[0117] <Dispersant> The dispersant of this disclosure comprises modified PVA having a structural unit represented by formula (1) above. The vinyl polymer produced using this dispersant has a small average particle size, a low amount of coarse particles, and few fish eyes. The specific form and preferred form of the modified PVA used in this dispersant are the same as those of the modified PVA of this disclosure described above, except that it is not essential that the water-insoluble content be 1000 ppm or less. However, it is preferable that the water-insoluble content of the modified PVA used in this dispersant is within the range described above.

[0118] The content of modified PVA in the dispersant of this disclosure is preferably 50% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and even more preferably 95% by mass or more. Alternatively, the content of modified PVA in the dispersant may be 100% by mass, i.e., the dispersant may consist substantially of modified PVA alone.

[0119] The dispersant of this disclosure is preferably a dispersant for suspension polymerization, and may be a dispersant used when performing suspension polymerization of vinyl compounds.

[0120] The dispersant may be in particulate form, or it may be dissolved in water. That is, one embodiment of the present disclosure is an aqueous solution containing a dispersant and water.

[0121] The degree of polymerization of the modified PVA used in the dispersant of this disclosure is not particularly limited. Its lower limit may be, for example, 300, but 500 is preferred, 600 is more preferred, and 650 is even more preferred. The upper limit of the degree of polymerization may be, for example, 3000, but 1500 is preferred, 1000 is more preferred, and 800 is even more preferred. Furthermore, the viscosity-average degree of polymerization of the modified PVA is preferably 500 or more and 1500 or less. Because the degree of polymerization of the modified PVA is within the above range, when the dispersant containing the modified PVA is used as a dispersion stabilizer for suspension polymerization of vinyl compounds, the resulting vinyl polymer has a low proportion of coarse particles, and when the resulting vinyl polymer is made into a sheet, fisheyes are reduced.

[0122] The lower limit of the degree of saponification of the modified PVA used in the dispersant of this disclosure is preferably 30 mol%, more preferably 60 mol%, and may even be 80 mol%. On the other hand, the upper limit of the degree of saponification of the modified PVA is preferably 99.9 mol%, more preferably 99 mol%, even more preferably 98 mol%, even more preferably 93 mol%, particularly preferably 90 mol%, and may even be 85 mol%. Setting the degree of saponification of the modified PVA within the above range increases its water solubility and improves its performance as a dispersant for suspension polymerization. For example, the degree of saponification of the modified PVA is preferably 60 mol% or more and 90 mol% or less. By setting the degree of saponification of the modified PVA within the above range, the surfactant performance is further optimized, and when the modified PVA is used as a dispersant, vinyl polymer particles with smaller particle sizes can be produced. In addition, by keeping the degree of saponification below the upper limit, the plasticizer absorption of vinyl polymer particles obtained using modified PVA as a dispersant is further improved.

[0123] The dispersant of this disclosure may contain various additives, as long as they do not impair the spirit of the present invention. Examples of such additives include polymerization regulators such as aldehydes, halogenated hydrocarbons, and mercaptans; polymerization inhibitors such as phenol compounds, sulfur compounds, and N-oxide compounds; pH adjusters; crosslinking agents; preservatives; fungicides; antiblocking agents; defoaming agents; and compatibilizers. The content of various additives in the dispersant is preferably 10% by mass or less, and more preferably 5% by mass or less, relative to the total amount of the dispersant.

[0124] <Method for producing vinyl polymers> One embodiment of the present disclosure is a method for producing a vinyl polymer, comprising the step of suspension polymerization of a vinyl compound in the presence of the above-mentioned dispersant. In such a production method, the resulting vinyl polymer may be in particulate form.

[0125] Methods for introducing the dispersant into the polymerization tank include, for example, (i) introducing it as an aqueous solution, and (ii) introducing it in powder form. From the viewpoint of uniformity within the polymerization tank, method (i) is preferred.

[0126] In the suspension polymerization of vinyl compounds, the amount (concentration) of dispersant used may be 1500 ppm or less, 1000 ppm or less, or 800 ppm or less relative to the vinyl compound. The amount (concentration) of dispersant used may be 100 ppm or more, 300 ppm or more, or 500 ppm or more relative to the vinyl compound. Here, ppm refers to mass ppm.

[0127] Examples of vinyl compounds include vinyl halides such as vinyl chloride; vinyl esters such as vinyl acetate and vinyl propionate; (meth)acrylic acid, their esters and salts; maleic acid, fumaric acid, their esters and anhydrides; styrene, acrylonitrile, vinylidene chloride, vinyl ethers, etc. Among these, it is preferable to use vinyl chloride alone or in combination with monomers that can copolymerize with vinyl chloride. Examples of monomers that can copolymerize with vinyl chloride include vinyl esters such as vinyl acetate and vinyl propionate; (meth)acrylic acid esters such as methyl (meth)acrylate and ethyl (meth)acrylate; α-olefins such as ethylene and propylene; unsaturated dicarboxylic acids such as maleic anhydride and itaconic acid; acrylonitrile, styrene, vinylidene chloride, vinyl ethers, etc.

[0128] For the suspension polymerization of vinyl compounds, oil-soluble or water-soluble polymerization initiators, which have been conventionally used for the polymerization of vinyl compounds (e.g., vinyl chloride), can be used. Examples of oil-soluble polymerization initiators include percarbonate compounds such as diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, and diethoxyethyl peroxydicarbonate; perester compounds such as t-butyl peroxyneodecanoate, t-butyl peroxypivalate, t-hexyl peroxypivalate, and cumyl peroxyneodecanoate; peroxides such as acetylcyclohexylsulfonyl peroxide, 2,4,4-trimethylpentyl-2-peroxyphenoxyacetate, 3,5,5-trimethylhexanoyl peroxide, and lauroyl peroxide; and azo compounds such as 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(isobutyronitrile), and 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile). Examples of water-soluble polymerization initiators include potassium persulfate, ammonium persulfate, hydrogen peroxide, and cumene hydroperoxide. These polymerization initiators can be used individually or in combination of two or more.

[0129] In the suspension polymerization of vinyl compounds, there are no particular restrictions on the polymerization temperature; it can be as low as around 20°C or as high as over 90°C, with a preference of around 40-70°C. Furthermore, a polymerizer equipped with a reflux condenser may be used to improve the heat removal efficiency of the polymerization reaction system.

[0130] The dispersant may be used alone in the suspension polymerization of vinyl compounds, but to the extent that it does not impair the spirit of the present invention, water-soluble cellulose ethers such as methylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, hydroxyethylmethylcellulose (HEMC), and hydroxypropylmethylcellulose (HPMC); water-soluble polymers such as modified (e.g., modified by ionic groups such as carboxylic acids and sulfonic acids) or unmodified polyvinyl alcohol and gelatin other than the above-mentioned modified PVA; oil-soluble emulsifiers such as sorbitan monolaurate, sorbitan triolate, glycerin tristearate, and ethylene oxide propylene oxide block copolymer; and water-soluble emulsifiers such as polyoxyethylene sorbitan monolaurate, polyoxyethylene glycerin oleate, and sodium laurate may be used in combination.

[0131] Examples of polyvinyl alcohols other than the modified PVA mentioned above include polyvinyl alcohol (S) with a degree of saponification of less than 65 mol% and a viscosity-average degree of polymerization of 50 to 750, and polyvinyl alcohol (T) with a degree of saponification of 65 mol% or more and 99.5 mol% or less and a viscosity-average degree of polymerization of 800 to 3500. These degrees of saponification and viscosity-average degree of polymerization can be measured in the same manner as the modified PVA mentioned above. For polyvinyl alcohol (S), polyvinyl alcohol with a degree of saponification of 30 to 60 mol% and a viscosity-average degree of polymerization of 180 to 650 is preferred. For polyvinyl alcohol (T), polyvinyl alcohol with a degree of saponification of 80 mol% or more and 99.5 mol% or less and a viscosity-average degree of polymerization of 1000 to 3200 is preferred. Furthermore, polyvinyl alcohol (S) and polyvinyl alcohol (T) may be unmodified, or they may be modified by introducing ionic groups such as carboxylic acids or sulfonic acids to impart self-emulsifying properties. The mass ratio of polyvinyl alcohol (S) used in combination with modified PVA (modified PVA / polyvinyl alcohol (S)) is not particularly limited, but 95 / 5 to 20 / 80 is preferred, and 90 / 10 to 30 / 70 may be more preferred. The mass ratio of polyvinyl alcohol (T) used in combination with modified PVA (modified PVA / polyvinyl alcohol (T)) is not particularly limited, but 95 / 5 to 20 / 80 is preferred, and 90 / 10 to 30 / 70 may be more preferred. Modified PVA and polyvinyl alcohol (S) and / or polyvinyl alcohol (T) may be charged together at the beginning of suspension polymerization, or they may be charged in portions during suspension polymerization.

[0132] The resulting vinyl polymer can be used for various molded product applications by appropriately blending it with plasticizers, etc.

[0133] <Mixture> One embodiment of the present disclosure is a mixture comprising a vinyl compound and a dispersant. The mixture may further contain water. The mixture may be, for example, a reaction solution comprising the vinyl compound, dispersant, and water before suspension polymerization in the above method for producing a vinyl polymer, or it may be the reaction solution after suspension polymerization. Another embodiment of the present disclosure is a mixture comprising a vinyl polymer and a dispersant. The mixture may further contain water. The mixture may be, for example, a reaction solution after suspension polymerization in the above method for producing a vinyl polymer.

[0134] The present invention includes embodiments that combine the above configurations in various ways, within the scope of the technical idea of ​​this disclosure, as long as they achieve the effects of the present invention. [Examples]

[0135] The present disclosure will be further described below using examples. In the following, "parts" and "%" refer to mass unless otherwise specified.

[0136] [Degree of saponification of PVA] The degree of saponification (mol%) of PVA (raw PVA or modified PVA) was determined by the method described in JIS-K6726-1994.

[0137] [Viscosity of 4% by mass aqueous solution of raw material PVA] A 300 mL flask equipped with a stirrer and reflux condenser was prepared in a water bath at room temperature. 192 g of distilled water was added, and stirring was started at 300 rpm. 8 g of PVA was weighed and gradually added to the flask. After adding the entire amount of PVA (8 g), the water bath temperature was immediately raised to 95°C over approximately 30 minutes. After the flask temperature reached 90°C, dissolution was continued for another 2 hours while stirring at 300 rpm. Then, the water bath temperature was reduced to room temperature, and the flask was cooled slowly while stirring. The resulting aqueous solution was transferred to a 100 mL sample tube, and the viscosity was measured at 20°C at a rotation speed of 60 rpm using a Type B viscometer BLII (manufactured by Toki Sangyo Co., Ltd.).

[0138] [Viscosity average degree of polymerization] The viscosity-average degree of polymerization of the raw material PVA or modified PVA was measured in accordance with JIS-K6726-1994.

[0139] [Amount of modification of silane coupling agent-derived functional groups in modified PVA (content of structural units represented by formula (1) above)] The degree of modification of functional groups derived from silane coupling agents in modified PVA (content of structural units represented by formula (1) above: mol%) is as described above. 1 The results were obtained using a method based on 1H-NMR.

[0140] [Dispersion degree A of silicon atoms in modified PVA particles] The dispersion degree A of silicon atoms in modified PVA particles was determined by selecting 10 particles with a diameter of 100 μm or more that were close to spherical, dividing these particles in half to maximize their cross-sectional area, defining the particle center as the center of the inscribed circle of the cross-section, and defining the particle surface as the point of contact between the inscribed circle and the particle surface, and measuring the silicon atom content using an energy-dispersive X-ray analyzer (EDS) as described below, and calculating the dispersion degree A based on the following formula. Dispersion A = Silicon atom content in the particle center (mol%) / Silicon atom content on the particle surface (mol%) A single modified PVA particle was embedded in thermosetting epoxy resin, and then cut in a frozen state using a cryo-ultramicrotome UC7 / FC7 (Leica Microsystems Inc.) to expose the particle cross-section, which was used as the observation sample. To correct the charge of the observation sample, platinum deposition to a thickness of approximately 2 nm was performed using a Hitachi High-Tech MC1000. Next, a scanning electron microscope (SEM) SU-70 (Hitachi High-Tech Inc.) was used to capture cross-sectional images of the PVA resin, and elemental analysis was performed on the particle edges and center using an energy-dispersive X-ray spectrometer (EDS, Oxford Instruments X-Max50). Image observation and elemental analysis were performed under ultra-high vacuum. EDS analysis was performed on secondary electron images obtained at an observation magnification of 2500x, an acceleration voltage of 15kV, and a working distance of 15mm, and the elemental composition was obtained from the resulting spectrum. The average value of 10 measured samples was used as the silicon atom content.

[0141] [Water-insoluble content of modified PVA] A 500 mL flask equipped with a stirrer and reflux condenser was prepared in a water bath set to 20°C. 285 g of distilled water was added to the flask, and stirring was started at 300 rpm. 15 g of modified PVA particles were weighed and gradually added to the flask. After adding the entire amount (15 g) of modified PVA particles, the modified PVA particles were dissolved by raising the water bath temperature to 90°C over 30 minutes to obtain a modified PVA solution. After the water bath temperature reached 90°C, dissolution was continued for another 60 minutes while stirring at 300 rpm. Subsequently, the modified PVA solution was used to filter out any remaining undissolved modified PVA particles (undissolved particles) through a metal filter with a mesh size of 63 μm. The filter was then thoroughly washed with 90°C hot water to remove any remaining modified PVA solution, leaving only the undissolved particles on the filter. The filter was then dried in a 120°C heating dryer for 1 hour. The mass of the filter after drying was compared with the mass of the filter before use for filtration to calculate the mass of insoluble particles. The ratio of the mass of insoluble particles to the mass of modified PVA initially added to water (15g) was defined as the water-insoluble content (ppm).

[0142] [Example 1] A methanol solution of vinyltrimethoxysilane was prepared by adding 3.0 parts vinyltrimethoxysilane as a silane coupling agent, 0.13 parts acetic acid as a catalyst, and 7.0 parts methanol as a solvent to a 100 mL beaker. Next, 100 parts of PVA particles with a 4% by mass aqueous solution viscosity of 5 mPa·s and a degree of saponification of 88 mol% were placed in a 1 L wide-mouthed round-bottom flask, and the above methanol solution of vinyltrimethoxysilane was spray-impregnated into the flask to obtain a mixture of vinyltrimethoxysilane and PVA. The round-bottom flask was stored (heat-treated) in a hot-air dryer at 80°C for 4 hours to obtain particulate modified PVA(1) in which vinyltrimethoxysilane had reacted. The obtained modified PVA(1) had a degree of saponification of 88 mol%, a modification amount of 0.4 mol%, a dispersion degree A of 0.98, and a water-insoluble content of less than 10 ppm, indicating excellent water solubility. Since the obtained modified PVA(1) is particulate and has excellent water solubility, it can be judged to have excellent handling properties.

[0143] [Examples 2-9, Comparative Examples 1-2] Modified PVA (2) to (11) were produced in the same manner as in Example 1, except that the type of raw material PVA used, the type and amount of solvent used, the type and amount of silane coupling agent used, the type and amount of catalyst used, and the manufacturing conditions (heat treatment conditions) were changed as shown in Table 1. The results of evaluating the dispersion A, degree of saponification, amount of modification, and water-insoluble content of each obtained modified PVA are shown in Table 2.

[0144] [Table 1]

[0145] [Table 2]

[0146] As shown in Table 2, the modified PVA (1) to (9) of the examples had excellent water solubility, with a water-insoluble content of 1000 ppm or less. Such modified PVA possesses excellent water solubility while retaining functional groups derived from the silane coupling agent, making it easy to handle and applicable to many uses. On the other hand, modified PVA (10), obtained by reacting PVA with a silane coupling agent under alkaline conditions as in Comparative Example 1, had poor water solubility, with a water-insoluble content exceeding 1000 ppm, possibly due to excessive crosslinking of the silane coupling agent. Such modified PVA is difficult to handle and difficult to apply to multiple uses. Furthermore, when hexane was used as the solvent in the impregnation process as in Comparative Example 2, the PVA did not swell and the silane coupling agent did not penetrate the PVA well, resulting in a low dispersion A of the particles of the obtained modified PVA (11) and a high water-insoluble content. Modified PVA (11) also had poor water solubility and handling properties.

[0147] [Example 10] In a 100 ml beaker, 4.8 parts of vinyltrimethoxysilane (silane coupling agent) and 0.13 parts of acetic acid were added to 11.2 parts of methyl acetate to prepare a methyl acetate solution of vinyltrimethoxysilane. Next, 100 parts of PVA (raw material PVA) with a viscosity-average degree of polymerization of 1000, a 4% by mass aqueous solution viscosity of 10 mPa·s, and a degree of saponification of 94 mol% were added to a 1 L wide-mouthed round-bottom flask, where the above solution was spray-impregnated to obtain a mixture of vinyltrimethoxysilane and PVA. The round-bottom flask was stored (heat-treated) in a hot air dryer at 80°C for 4 hours to obtain modified PVA(12) resulting from the reaction of raw material PVA and vinyltrimethoxysilane. The obtained modified PVA(12) had a viscosity-average degree of polymerization of 1000, a degree of saponification of 94 mol%, a modification amount of vinyltrimethoxysilane of 0.55 mol%, a dispersion degree A of 0.87, and a water-insoluble content of 60 ppm.

[0148] [Examples 11-17, Comparative Example 3] Modified PVA(13) to (19) and PVA(X) were manufactured in the same manner as in Example 10, except that the type of raw material PVA, the type and amount of solvent used, the type and amount of silane coupling agent used, the type and amount of catalyst used, and the manufacturing conditions (heat treatment conditions) were changed as shown in Table 3, and their physical properties were evaluated. The results are shown in Table 4.

[0149] [Preparation of release paper base] Release paper bases were prepared and evaluated using the modified PVA(12)-(19) and PVA(X) obtained in Examples 10-17 and Comparative Example 3 by the following method. A 6% by mass aqueous solution of modified PVA was prepared and used as the coating solution. This coating solution was applied to glassine paper with an air permeability resistance of 100 seconds using a wire bar, with a dry weight of approximately 2.0 g / m². 2 The paper was coated in the manner described above. After coating, it was dried at 100°C for 5 minutes to obtain coated paper. The obtained coated paper was then calculated in a supercalender at 70°C and 400 kg / cm². 2 A release paper base was obtained by processing it twice. A coating layer derived from the above coating liquid, i.e., a silicone sealing layer, was formed on this release paper base.

[0150] [Evaluation of air permeability resistance of release paper base material] The air permeability resistance of the release paper base was measured using a Wang Ken type air permeability tester in accordance with JIS-P8117-2009, and this air permeability resistance was used as an indicator of the silicone sealing performance in the release paper base. Higher air permeability resistance tends to correlate with better silicone sealing performance. The results are shown in Table 4.

[0151] [Evaluation of silicone curing properties] A solution was prepared by mixing LTC1056L, manufactured by Toray Dow Corning, as the addition-type silicone, and SRX212 as the platinum catalyst, so that the mass ratio of the addition-type silicone to the platinum was 100 / 0.007. The obtained solution was then coated onto the silicone sealing layer of the obtained release paper base paper with a solid content of 2.0 g / m². 2 The material was coated using a blade coater in this manner. This formed a silicone layer on the release paper base. Then, the material was heat-treated at 110°C, and the time it took for the silicone to harden was measured. Here, the time it took for the silicone to harden is defined as the time (in seconds) required when the silicone layer was rubbed hard with a finger 10 times at predetermined time intervals until the silicone layer could no longer be peeled off. The results are shown in Table 4.

[0152] [Evaluation of adhesion of the release layer] A solution was prepared by mixing LTC1056L, manufactured by Toray Dow Corning, as the addition-type silicone, with SRX212 as the platinum catalyst, so that the ratio of addition-type silicone to platinum was 100 / 0.009. The obtained solution was then coated onto the silicone sealing layer on the prepared release paper base paper with a solid content of 2.0 g / m². 2 The release paper was coated using a blade coater and heat-treated at 110°C for 90 seconds to obtain a release layer (silicone layer) formed on the release paper base. The obtained release paper was evaluated using the following indicators. The results are shown in Table 4. A + Under conditions of 40°C and 90% RH, the sample was left for one week, and then the release layer was rubbed vigorously with a finger. As a result, the release layer did not peel off. Under the same conditions, the sample was left for another week, and then the release layer was rubbed vigorously with a finger. As a result, the release layer did not peel off. A: Under conditions of 40°C and 90% RH, the material was left for one week, and then the release layer was rubbed vigorously with a finger. As a result, the release layer did not peel off. However, under the same conditions, after leaving it for another week, the release layer was rubbed vigorously with a finger, and then the release layer peeled off. B: After being left for one week under conditions of 40°C and 90% RH, the peeling layer was rubbed vigorously with a finger. As a result, the peeling layer was removed. After being left for one week under conditions of 40°C and 90% RH, the peeling layer was gently rubbed with a finger. As a result, the peeling layer was removed.

[0153] [Table 3]

[0154] [Table 4]

[0155] As shown in Table 4, Examples 10-17 exhibited excellent silicone curability and adhesion, while Comparative Example 3 showed inferior silicone curability and adhesion. Examples 13 and 14 also had high air permeability resistance (sealing properties).

[0156] [Example 18] In a 100 mL beaker, 4.0 parts of vinyltrimethoxysilane (silane coupling agent) and 0.11 parts of acetic acid were added to 9.3 parts of methyl acetate to prepare a methyl acetate solution of vinyltrimethoxysilane. Next, 100 parts of PVA (raw material PVA) with a viscosity-average degree of polymerization of 750, a 4% by mass aqueous solution viscosity of 8 mPa·s, and a degree of saponification of 72 mol% were added to a 1 L wide-mouthed round-bottom flask, where the above solution was spray-impregnated to obtain a mixture of vinyltrimethoxysilane and PVA. The round-bottom flask was stored (heat-treated) in a hot air dryer at 80°C for 4 hours to obtain modified PVA(20) resulting from the reaction of raw material PVA and vinyltrimethoxysilane. The obtained modified PVA(20) had a viscosity-average degree of polymerization of 750, a degree of saponification of 72 mol%, a modification amount of vinyltrimethoxysilane of 0.5 mol%, a dispersion A of 0.98, and a water-insoluble content of less than 10 ppm.

[0157] [Examples 19-24, Comparative Example 4] Modified PVA(21) to (26) and PVA(Y) were produced in the same manner as in Example 18, except that the type of raw material PVA, the type and amount of solvent used, the type and amount of silane coupling agent used, the type and amount of catalyst used, and the manufacturing conditions (heat treatment conditions) were changed as shown in Table 5, and their physical properties were evaluated. The results are shown in Table 6.

[0158] [Evaluation of vinyl polymers] Modified PVA(20)-(26) obtained in Examples 18-24 and PVA(Y) obtained in Comparative Example 4 were used as dispersants for suspension polymerization, and polyvinyl chloride particles, which are vinyl polymers, were obtained by the following method.

[0159] 1390 g of aqueous solution containing 0.94 g of each suspension polymerization dispersant (1000 ppm relative to vinyl chloride monomer) was placed in a 5 L autoclave. Next, 1.5 g of a 70% toluene solution of diisopropyl peroxydicarbonate was placed in the autoclave. The autoclave was degassed to remove oxygen until the pressure inside the autoclave reached 0.0067 MPa. Then, 940 g of vinyl chloride was placed in the autoclave, and the contents of the autoclave were heated to 57°C. Suspension polymerization was started under stirring. The pressure inside the autoclave at the start of polymerization was 0.83 MPa. After 4 hours from the start of suspension polymerization, when the pressure inside the autoclave reached 0.65 MPa, the polymerization was stopped and unreacted vinyl chloride was removed. The polymerization slurry was then removed and dried overnight at 65°C to obtain vinyl chloride polymer particles.

[0160] The average particle size (MGS), amount of coarse particles, and fisheye were evaluated for the obtained vinyl chloride polymer particles (vinyl polymer particles) using the method described below. The results are shown in Table 6. [Evaluation Method] (1) Average particle diameter (μm) The particle size distribution was measured using a JIS standard sieve and the dry sieving method described in JIS-Z8815-1994. The results were plotted on the Rosin-Rammler distribution formula to calculate the average particle size (dp50). (2) Coarse particle content (%) The content (mass %) of polyvinyl chloride polymer particles that did not pass through a sieve with a mesh size of 355 μm (equivalent to 42 mesh in JIS standard sieve mesh equivalent) was evaluated according to the following evaluation criteria. The above content represents the cumulative content on the sieve (%). The sieve mesh size was in accordance with the nominal mesh size W of JIS-Z8801-1-2006. A + : Less than 0.5% by mass A: 0.5% by mass or more and less than 1.0% by mass B: 1.0% by mass or more and less than 2.5% by mass C: 2.5% by mass or more (3) Fish eye (piece) 100 parts of polyvinyl chloride polymer particles, 50 parts of dioctyl phthalate, 5 parts of tribasic lead sulfate, and 1 part of lead stearate were roll-kneaded at 150°C for 7 minutes to produce five sheets measuring 0.1 mm thick and 1400 mm x 1400 mm. The number of fish eyes was visually measured. 2 The number of fisheyes per sheet was converted to an average and evaluated according to the following criteria. A lower number of fisheyes indicates fewer defects on the sheet. A + :0~5 pieces A:6~10 pieces B: 11~49 pieces C: 50 or more

[0161] [Table 5]

[0162] [Table 6]

[0163] As shown in Table 6, when the modified PVA(20) to(26) of Examples 18 to 24 were used as dispersants, the resulting vinyl polymer particles had a small average particle size, and a high-quality vinyl chloride polymer resin with fewer coarse particles and fewer fisheyes was obtained. [Industrial applicability]

[0164] The modified PVA disclosed herein has functional groups derived from silane coupling agents, yet exhibits excellent water solubility and high handling ease. Therefore, the modified PVA disclosed herein can be used in a variety of applications, such as dispersants, coatings, adhesives, and binders, and has very high industrial value.

Claims

1. It has a structural unit represented by the following formula (1), The water-insoluble content is 1000 ppm or less. A modified vinyl alcohol polymer in which the content of the structural unit represented by the above formula (1) relative to all structural units containing silicon atoms is 90 mol% or more. 【Chemistry 1】 [In formula (1), X, Y, and Z are each independently a C1-C20 alkyl group, a C2-C20 alkenyl group, a phenyl group, a benzyl group, a vinylphenyl group, a C1-C20 halogenated alkyl group, a halogenated phenyl group, a C1-C20 aminoalkyl group, a C1-C20 mercaptoalkyl group, a C2-C20 ureidoalkyl group, a C2-C8 isocyanate alkyl group, a C3-C20 group containing an epoxy group, a C3-C20 group containing an acrylamide group, a C4-C20 group containing a methacrylamide group, an acetoxy group, or -(CH ２ ) ｎ -O-R １ (R １ The group is represented by , where n represents a hydrogen atom, alkali metal atom, alkaline earth metal atom, C1-C20 alkyl group, C2-C20 alkenyl group, or glycidyl group, and n is an integer from 0 to 6.

2. The modified vinyl alcohol polymer according to claim 1, wherein the content of the structural unit represented by the above formula (1) is 0.01 mol% or more and less than 5 mol%.

3. A method for producing a modified vinyl alcohol polymer, comprising the step of impregnating a solid vinyl alcohol polymer with a silane coupling agent.

4. A method for producing a modified vinyl alcohol polymer according to claim 3, wherein in the impregnation step described above, vinyl alcohol polymer particles are impregnated by spraying them with a solution containing the silane coupling agent.

5. A method for producing a modified vinyl alcohol polymer according to claim 3 or 4, wherein the silane coupling agent has a structure represented by the following formula (2). 【Chemistry 2】 In formula (2), R is an alkyl group having 1 to 8 carbon atoms, an acetyl group or -(CH ２ ), ｍ -O-R ２ where R ２ represents an alkyl group having 1 to 20 carbon atoms, and m represents an integer of 1 to 6). X, Y and Z are each independently an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, a phenyl group, a benzyl group, a vinylphenyl group, a halogenated alkyl group having 1 to 20 carbon atoms, a halogenated phenyl group, an aminoalkyl group having 1 to 20 carbon atoms, a mercaptoalkyl group having 1 to 20 carbon atoms, a ureidoalkyl group having 2 to 20 carbon atoms, an isocyanatealkyl group having 2 to 8 carbon atoms, a group having 3 to 20 carbon atoms containing an epoxy group, a group having 3 to 20 carbon atoms containing an acrylamide group, a group having 4 to 20 carbon atoms containing a methacrylamide group, an acetoxy group or -(CH ２ ), ｎ -O-R １ where R １ represents an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an acryloyl group, a methacryloyl group or a glycidyl group, and n represents an integer of 0 to 6).].

6. A method for producing a modified vinyl alcohol polymer according to claim 3, 4, or 5, further comprising the step of heat-treating the vinyl alcohol polymer impregnated with the silane coupling agent obtained in the impregnation step described above.

7. Particles containing the modified vinyl alcohol polymer described in claim 1 or 2.

8. The particle according to claim 7, wherein the dispersion degree A of silicon atoms is 0.2 or more and less than 1.

9. An aqueous solution containing the modified vinyl alcohol polymer described in claim 1 or 2.

10. It contains a modified vinyl alcohol polymer having a structural unit represented by the following formula (1), A coating solution in which the insoluble portion of the above-mentioned modified vinyl alcohol polymer is 1000 ppm or less, and the content of the structural unit represented by formula (1) relative to all structural units containing silicon atoms in the above-mentioned modified vinyl alcohol polymer is 90 mol% or more. 【Transformation 3】 [In formula (1), X, Y, and Z are each independently a C1-C20 alkyl group, a C2-C20 alkenyl group, a phenyl group, a benzyl group, a vinylphenyl group, a C1-C20 halogenated alkyl group, a halogenated phenyl group, a C1-C20 aminoalkyl group, a C1-C20 mercaptoalkyl group, a C2-C20 ureidoalkyl group, a C2-C8 isocyanate alkyl group, a C3-C20 group containing an epoxy group, a C3-C20 group containing an acrylamide group, a C4-C20 group containing a methacrylamide group, an acetoxy group, or -(CH ２ ) ｎ -O-R １ (R １ The group is represented by , where n represents a hydrogen atom, alkali metal atom, alkaline earth metal atom, C1-C20 alkyl group, C2-C20 alkenyl group, or glycidyl group, and n is an integer from 0 to 6.

11. The coating solution according to claim 10, wherein the content of the structural unit represented by formula (1) in the modified vinyl alcohol polymer is 0.01 mol% or more and less than 5 mol%.

12. The coating liquid according to claim 10 or 11, wherein the viscosity-average degree of polymerization of the modified vinyl alcohol polymer is 500 or more and 5000 or less, and the degree of saponification is 70 mol% or more and 99.9 mol% or less.

13. A coated article obtained by applying the coating liquid according to any one of claims 10 to 12 to a substrate.

14. The system comprises a base material, a silicone sealing layer, and a release layer. The above silicone sealing layer contains a modified vinyl alcohol polymer having a structural unit represented by the following formula (1'), Release paper having a content of 90 mol% or more of the structural unit represented by the above formula (1') relative to all structural units containing silicon atoms. 【Chemistry 4】 [In formula (1'), X, Y, and Z are each independently a C1-C20 alkyl group, a C2-C20 alkenyl group, a phenyl group, a benzyl group, a vinylphenyl group, a C1-C20 halogenated alkyl group, a halogenated phenyl group, a C1-C20 aminoalkyl group, a C1-C20 mercaptoalkyl group, a C2-C20 ureidoalkyl group, a C2-C8 isocyanatealkyl group, a C3-C20 group containing an epoxy group, a C3-C20 group containing an acrylamide group, a C4-C20 group containing a methacrylamide group, an acetoxy group, or -(CH ２ ) ｎ -O-R １ (R １ The group is represented by (where n represents a hydrogen atom, alkali metal atom, alkaline earth metal atom, C1-C20 alkyl group, C2-C20 alkenyl group, acryloyl group, methacryloyl group, glycidyl group, or bond, and n is an integer from 0 to 6).

15. The release paper according to claim 14, wherein the release layer contains addition-type silicone and platinum, and the content of platinum relative to 100 parts by mass of the addition-type silicone is 0.001 to 0.05 parts by mass.

16. The modified vinyl alcohol polymer having a structural unit represented by the following formula (1) comprises A dispersant wherein the content of the structural unit represented by formula (1) above is 90 mol% or more relative to all structural units containing silicon atoms in the above-mentioned modified vinyl alcohol polymer. 【Transformation 5】 [In formula (1), X, Y, and Z are each independently a C1-C20 alkyl group, a C2-C20 alkenyl group, a phenyl group, a benzyl group, a vinylphenyl group, a C1-C20 halogenated alkyl group, a halogenated phenyl group, a C1-C20 aminoalkyl group, a C1-C20 mercaptoalkyl group, a C2-C20 ureidoalkyl group, a C2-C8 isocyanate alkyl group, a C3-C20 group containing an epoxy group, a C3-C20 group containing an acrylamide group, a C4-C20 group containing a methacrylamide group, an acetoxy group, or -(CH ２ ) ｎ -O-R １ (R １ The group is represented by , where n represents a hydrogen atom, alkali metal atom, alkaline earth metal atom, C1-C20 alkyl group, C2-C20 alkenyl group, acryloyl group, methacryloyl group, or glycidyl group, and n is an integer from 0 to 6.

17. The dispersant according to claim 16, wherein the content of the structural unit represented by formula (1) in the modified vinyl alcohol polymer is 0.01 mol% or more and less than 5 mol%.

18. The dispersant according to claim 16 or 17, wherein the viscosity-average degree of polymerization of the modified vinyl alcohol polymer is 500 or more and 1500 or less, and the degree of saponification is 60 mol% or more and 90 mol% or less.

19. The dispersant according to any one of claims 16 to 18, wherein the water-insoluble portion of the modified vinyl alcohol polymer is 1000 ppm or less.

20. A dispersant according to any one of claims 16 to 19, for use in suspension polymerization.

21. A method for producing a vinyl polymer, comprising the step of suspend polymerization of a vinyl compound in the presence of a dispersant according to any one of claims 16 to 20.

22. A mixture comprising a vinyl compound and a dispersant according to any one of claims 16 to 20.

Images