Polyvinyl alcohol resin, film roll, and polyvinyl acetal resin

Abstract

Provided is a polyvinyl alcohol resin with which it is possible to produce a film having a high capacitance retention rate at high temperatures and excellent strength and flexibility. The present invention relates to a polyvinyl alcohol resin which satisfies the following formulae (1) and (2), where A is the dielectric constant at 25 DEG C when the polyvinyl alcohol resin is measured at 1 kHz, and B is the dielectric constant at 125 DEG C when the polyvinyl alcohol resin is measured at 1 kHz. A > = 3.0 (1) 1.0 > = B / A > = 0.6 (2).

Description

Technical Field

[0001] The present invention relates to polyvinyl alcohol resins. Background Art

[0002] Polyvinyl alcohol resin is obtained by saponifying a polymer obtained by polymerizing a vinyl ester monomer. Polyvinyl alcohol resin has been used in various applications such as a polymerization suspension agent for vinyl chloride resin, a dielectric sheet for a film capacitor, a polarizing film, a water-soluble film, and an adhesive.

[0003] On the other hand, as a resin for dielectric sheets for film capacitors, in addition to polyvinyl alcohol resin, biaxially oriented polypropylene (OPP) has been mainly studied. However, the dielectric constant of the OPP film is low, and there is a problem that the size of the capacitor becomes larger in order to ensure the electrostatic capacitance of the capacitor. In addition, the OPP film has a low heat resistance temperature and a change in the dielectric constant at high temperatures, especially in automotive applications such as electric vehicles that require high temperature resistance. In addition, since the OPP film is obtained by stretching, there is a limit to making the thickness thinner.

[0004] From the above viewpoint, the use of polyvinyl alcohol resin soluble in an aqueous solvent to produce a film for a film capacitor has also been studied. As the polyvinyl alcohol resin, for example, amide-modified polyvinyl alcohol resin is disclosed in Patent Document 1. In addition, modified polyvinyl alcohol resin containing acrylamide monomer units is disclosed in Patent Document 2.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2019-065059

[0008] Patent Document 2: International Publication No. 2015 / 098978 Summary of the invention

[0009] Problems to be solved by the invention

[0010] However, conventional polyvinyl alcohol resins have problems with the capacitance of the resulting film capacitors and the capacitance retention in a high temperature environment. Therefore, there is a demand for a material for a dielectric resin sheet that can be formed into a film using an aqueous solvent and can provide a high-performance electronic component.

[0011] An object of the present invention is to provide a polyvinyl alcohol resin capable of producing a film having a high capacitance retention rate at high temperature and excellent strength and flexibility.

[0012] Means for solving problems

[0013] The present disclosure (1) relates to a polyvinyl alcohol resin that satisfies the following equations (1) and (2) when the dielectric constant of the polyvinyl alcohol resin at 25° C. measured at 1 kHz is represented by A and the dielectric constant of the polyvinyl alcohol resin at 125° C. measured at 1 kHz is represented by B.

[0014] A ≥ 3.0 (1)

[0015] 1.0≥B / A≥0.6 (2)

[0016] The present disclosure (2) relates to the polyvinyl alcohol resin of the present disclosure (1), wherein the solubility parameter is 12 or more.

[0017] The present disclosure (3) relates to the polyvinyl alcohol resin of the present disclosure (1) or (2), which has at least one functional group selected from the group consisting of a carboxylic acid group, a sulfonic acid group, a pyrrolidone ring group, an amide group and an amino group in a side chain.

[0018] The present disclosure (4) relates to a film roll comprising the polyvinyl alcohol resin according to any one of the present disclosures (1) to (3).

[0019] The present disclosure (5) relates to a polyvinyl acetal resin, which is an acetalized product of the polyvinyl alcohol resin according to any one of the present disclosures (1) to (3).

[0020] Hereinafter, the present invention will be described in detail.

[0021] The inventors conducted intensive research and found that by making a polyvinyl alcohol resin in which the dielectric constant at 25°C and the dielectric constant at 125°C measured at 1 kHz satisfy a specified relationship, it is possible to produce a film with little change in performance even at high temperatures, thereby completing the present invention.

[0022] The polyvinyl alcohol resin satisfies the following formulae (1) and (2) when the dielectric constant at 25° C. measured at 1 kHz is defined as A and the dielectric constant at 125° C. measured at 1 kHz is defined as B.

[0023] A ≥ 3.0 (1)

[0024] 1.0≥B / A≥0.6 (2)

[0025] By using a polyvinyl alcohol resin, a film can be produced using an aqueous solvent, and by satisfying the above relationship, a film with little change in performance even at high temperatures can be produced. Thus, a particularly high-performance film capacitor can be produced.

[0026] The above-mentioned A is preferably 3.5 or more, more preferably 4.0 or more. The upper limit is not particularly limited, but is preferably 5.0 or less.

[0027] The above B is preferably 3.0 or more, more preferably 3.3 or more, and further preferably 3.5 or more. The upper limit is not particularly limited, but is preferably 4.5 or less.

[0028] In addition, the above-mentioned B / A is preferably 0.7 or more, and more preferably 0.8 or more.

[0029] The dielectric constant can be determined by measuring a polyvinyl alcohol resin film prepared to have a thickness of 0.05 mm using an LCR meter.

[0030] The above A and B / A can be adjusted by the ratio of each structural unit of the polyvinyl alcohol resin, the blockiness (Japanese: ブロック property) and other structures, the conditions when the polyvinyl alcohol resin is produced, etc. More specifically, in the production process of polyvinyl ester, a series of continuous tank reactors can be used to adjust the temperature in each reaction tank, the average residence time, and the stirring state in each reaction tank.

[0031] The solubility parameter of the polyvinyl alcohol resin is preferably 12 or more.

[0032] When the solubility parameter is 12 or more, the solubility in water can be improved.

[0033] The solubility parameter is more preferably 12.3 or more, further preferably 12.6 or more, and is preferably 15 or less, more preferably 14 or less, and further preferably 13.5 or less.

[0034] The above solubility parameter is a value measured by the Fedors method.

[0035] The above solubility parameter can be adjusted by the type and amount of modification of the modification group.

[0036] The amount of residual acetyl groups in the polyvinyl alcohol resin is preferably 0.01 mol% or more, more preferably 0.1 mol% or more, further preferably 0.5 mol% or more, further preferably 1.0 mol% or more, preferably 30.0 mol% or less, more preferably 20.0 mol% or less, further preferably 10.0 mol% or less, further preferably 5.0 mol% or less. That is, the amount of residual acetyl groups is preferably 0.01 to 30.0 mol%, more preferably 0.1 to 20.0 mol%, further preferably 0.5 to 10.0 mol%, further preferably 1.0 to 5.0 mol%.

[0037] The residual acetyl group content refers to the ratio of the structural unit having an acetyl group represented by the following formula (3) to all the structural units constituting the polyvinyl alcohol resin.

[0038] The amount of residual acetyl groups can be determined, for example, by1 The measurement is performed by H-NMR, and as a measuring instrument, for example, AVANCE400 (manufactured by Bruker Biospin) can be used.

[0039] [Chemical formula 1]

[0040]

[0041] The amount of hydroxyl groups in the polyvinyl alcohol resin is preferably 70.0 mol% or more, more preferably 85.0 mol% or more, and even more preferably 90.0 mol% or more, and preferably 99.5 mol% or less, more preferably 99.0 mol% or less, and even more preferably 98.5 mol% or less. That is, the amount of hydroxyl groups is preferably 70.0 to 99.5 mol%, more preferably 85.0 to 99.0 mol%, and even more preferably 90.0 to 98.5 mol%.

[0042] The hydroxyl group amount refers to the ratio of the structural unit having a hydroxyl group represented by the following formula (4) to all the structural units constituting the polyvinyl alcohol resin.

[0043] The above-mentioned hydroxyl group amount can be measured by the same method as the above-mentioned residual acetyl group amount.

[0044] [Chemical formula 2]

[0045]

[0046] The saponification degree of the polyvinyl alcohol resin is preferably 80.0 mol% or more, more preferably 85.0 mol% or more, further preferably 87.0 mol% or more, and particularly preferably 90.0 mol% or more. In addition, the saponification degree is preferably 99.9 mol% or less, more preferably 99.0 mol% or less, further preferably 98.0 mol% or less, and particularly preferably 97.0 mol% or less. That is, the saponification degree is preferably 80.0 to 99.9 mol%, more preferably 85.0 to 99.0 mol%, further preferably 87.0 to 98.0 mol%, and particularly preferably 90.0 to 97.0 mol%.

[0047] The saponification degree refers to the ratio of the amount of the hydroxyl groups in the polyvinyl alcohol resin to the total amount of the residual acetyl groups and the amount of the hydroxyl groups.

[0048] The saponification degree can be measured by a method in accordance with JIS K6726-1994.

[0049] The polyvinyl alcohol resin preferably has at least one functional group selected from the group consisting of a carboxylic acid group, a sulfonic acid group, a pyrrolidone ring group, an amide group and an amino group in a side chain. The carboxylic acid group and the sulfonic acid group may be derivatives thereof such as salts.

[0050] With the above structure, it is possible to obtain a polyvinyl alcohol resin having a smaller change in dielectric constant at high temperature.

[0051] Examples of the structural unit having the functional group include structural units having a carboxylic acid group represented by the following formulas (5-1) to (5-4), structural units having a sulfonic acid group represented by the following formula (6), structural units having a pyrrolidone ring group represented by the following formula (7), structural units having an amide group represented by the following formula (8), and structural units having an amino group represented by the following formula (9).

[0052] Among them, from the perspective of being able to reduce the change in dielectric constant, preferred are a structural unit having a carboxylic acid group represented by the following formula (5-1), a structural unit having a salt having a sulfonic acid group represented by the following formula (6), a structural unit having a pyrrolidone ring group represented by the following formula (7), and a structural unit having an amino group represented by the following formula (9). More preferred are structural units having a sulfonic acid group represented by the following formula (6), and even more preferred are structural units having a salt having a sulfonic acid group represented by the following formula (6-1).

[0053] [Chemical formula 3]

[0054]

[0055] In formula (5-1), R 1 and R 2 Each independently represents an alkylene group having 0 to 10 carbon atoms, and X 1 and X 2 Each independently represents a hydrogen atom, a metal atom or an alkyl group having 1 to 3 carbon atoms.

[0056] In the above formula (5-1), R 1 and R 2 The number of carbon atoms of the alkylene group represented is preferably 0 or more, preferably 5 or less, and more preferably 3 or less.

[0057] Examples of the alkylene group having 0 to 10 carbon atoms include straight-chain alkylene groups such as a single bond, methylene, ethylene, trimethylene, tetramethylene, pentamethylene, hexamethylene, octamethylene, and decamethylene, branched-chain alkylene groups such as methylmethylene, methylethylene, 1-methylpentylene, and 1,4-dimethylbutylene, and cyclic alkylene groups such as cyclopropylene, cyclobutylene, and cyclohexylene. Among these, straight-chain alkylene groups such as a single bond, methylene, ethylene, n-propylene, and n-butylene are preferred, and single bonds, methylene, and ethylene are more preferred.

[0058] The above R 1 and R 2They may be the same or different, but are preferably different. In addition, at least one of them is preferably a single bond, and one is more preferably a single bond and the other is a methyl group.

[0059] In the above formula (5-1), in X 1 and X 2 When at least any one of is a metal atom, examples of the metal atom include a sodium atom, a lithium atom, and a potassium atom. Among them, a sodium atom is preferred.

[0060] In the above formula (5-1), X 1 and X 2 Examples of the alkyl group having 1 to 3 carbon atoms include methyl, ethyl, and propyl. Among them, methyl is preferred.

[0061] The above X 1 and X 2 They may be the same or different, but are preferably the same. In addition, they are preferably a hydrogen atom or a methyl group, and more preferably a hydrogen atom.

[0062] In the above formula (5-2), R 3 represents an alkylene group having 0 to 12 carbon atoms, X 3 represents a hydrogen atom, a metal atom or an alkyl group having 1 to 3 carbon atoms, R 4 , R 5 and R 6 Each independently represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms.

[0063] In the above formula (5-2), R 3 The alkylene group represented by may be the same as R in the above formula (5-1) 1 and R 2 Among the alkylene groups described above, a single bond, a methylene group, an ethylene group, a trimethylene group, a tetramethylene group, or the like are preferred, a single bond, a methylene group, an ethylene group are more preferred, and a single bond is further preferred.

[0064] In the above formula (5-2), in X 3 When it is a metal atom, examples of the metal atom include those which are the same as X in the above formula (5-1). 1 and X 2 The metal atoms are the same as those exemplified above, and among them, a sodium atom is preferred.

[0065] In the above formula (5-2), in X 3 In the case of an alkyl group having 1 to 3 carbon atoms, examples of the alkyl group include the following: 1 and X 2 The alkyl groups are the same as those exemplified, and among them, a methyl group is preferred.

[0066] In the above formula (5-2), R 4 , R 5 and R 6 They may be the same or different, but are more preferably the same. 4 , R 5 and R 6 Preferred is a hydrogen atom.

[0067] Examples of the alkyl group having 1 to 10 carbon atoms include straight-chain alkyl groups such as methyl, ethyl, propyl, n-butyl, n-pentyl, n-heptyl, n-octyl, n-nonyl, and n-decyl, branched-chain alkyl groups such as isopropyl, isobutyl, sec-butyl, tert-butyl, isopentyl, 2,2-dimethylpropyl, 1,1,3,3-tetramethylbutyl, and 2-ethylhexyl, and cycloalkyl groups such as cyclopropyl, cyclopropylmethyl, cyclobutyl, cyclopentyl, and cyclohexyl. Among them, straight-chain alkyl groups such as methyl, ethyl, propyl, and n-butyl are preferred, and methyl and ethyl are more preferred.

[0068] In the above formula (5-3), R 7 and R 8 Each independently represents an alkylene group having 0 to 10 carbon atoms, and X 4 and X 5 Each independently represents a hydrogen atom, a metal atom or an alkyl group having 1 to 3 carbon atoms, and R 9 and R 10 Each independently represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms.

[0069] In the above formula (5-3), R 7 and R 8 The alkylene group represented by may be the same as R in the above formula (5-1) 1 and R 2 Among the alkylene groups described above, a single bond, a methylene group, an ethylene group, a trimethylene group, a tetramethylene group, or the like are preferred, a single bond, a methylene group, an ethylene group are more preferred, and a single bond is further preferred.

[0070] In the above formula (5-3), in X 4 and X 5 When at least one of the above is a metal atom, examples of the above metal atom include 1 and X 2 The metal atoms are the same as those exemplified above, and among them, a sodium atom is preferred.

[0071] In the above formula (5-3), in X 4 and X 5 When at least one of the above is an alkyl group having 1 to 3 carbon atoms, examples of the above alkyl group include the same group as X in the above formula (5-1): 1 and X2 The alkyl groups are the same as those exemplified, and among them, a methyl group is preferred.

[0072] In the above formula (5-3), R 9 and R 10 The alkyl group represented by may be the same as R in the above formula (5-2) 4 , R 5 and R 6 The alkyl groups are the same as those exemplified.

[0073] In the above formula (5-4), R 11 represents an alkylene group having 1 to 12 carbon atoms, X 6 , X 7 represents a hydrogen atom, a metal atom or an alkyl group having 1 to 3 carbon atoms, R 12 , R 13 and R 14 Each independently represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms.

[0074] In the above formula (5-4), R 11 The alkylene group represented by may be the same as R in the above formula (5-1) 1 and R 2 Among the alkylene groups described above, a single bond, a methylene group, an ethylene group, a trimethylene group, a tetramethylene group, or the like are preferred, a single bond, a methylene group, an ethylene group are more preferred, and a single bond is further preferred.

[0075] In the above formula (5-4), in X 6 , X 7 When X is a metal atom, examples of the metal atom include those having the same structure as X in the above formula (1-1). 1 and X 2 The metal atoms are the same as those exemplified above, and among them, a sodium atom is preferred.

[0076] In the above formula (5-4), in X 6 , X 7 In the case of an alkyl group having 1 to 3 carbon atoms, examples of the alkyl group include the following: 1 and X 2 The alkyl groups are the same as those exemplified, and among them, a methyl group is preferred.

[0077] In the above formula (5-4), R 12 , R 13 and R 14 The alkyl group represented by may be the same as R in the above formula (5-2) 4 and R 5 The alkyl groups are the same as those exemplified.

[0078] [Chemical formula 4]

[0079]

[0080] In the above formula (6), R 15 and R 16 each independently represents an alkylene group having 0 to 4 carbon atoms, an amide group (-CONH-), an ester group (-COO-) or an ether group (-O-), and X 8 It represents a hydrogen atom, a metal atom or an alkyl group having 1 to 3 carbon atoms.

[0081] Examples of the alkylene group having 0 to 4 carbon atoms include straight-chain alkylene groups such as a single bond, methylene, ethylene, trimethylene, and tetramethylene, and branched alkylene groups such as propylene (1-methylethylene, 2-methylethylene), butylene (1-ethylethylene, 2-ethylethylene), 1,2-dimethylethylene, 2,2-dimethylethylene, 1-methyltrimethylene, 2-methyltrimethylene, and 3-methyltrimethylene. Among them, 2,2-dimethylethylene is preferred.

[0082] In the above formula (6), X 8 , which is the same as X in the above formula (5-1) 1 and X 2 The same as those exemplified above, among them, a sodium atom is preferred.

[0083] As the structural unit having a sulfonic acid group, a structural unit having a salt of a sulfonic acid group represented by the following formula (6-1) is preferred.

[0084] [Chemical formula 5]

[0085]

[0086] In the above formula (6-1), R 17 It represents an alkylene group having 1 to 4 carbon atoms.

[0087] Examples of the alkylene group having 1 to 4 carbon atoms include the group consisting of: 15 and R 16 The alkylene groups are the same as those exemplified above, and among them, 2,2-dimethylethylene is preferred.

[0088] [Chemical formula 6]

[0089]

[0090] [Chemical formula 7]

[0091]

[0092] In the above formula (8), R 18It represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms.

[0093] In the above formula (8), R 18 The alkyl group represented by may be the same as R in the above formula (5-2) 4 , R 5 and R 6 The alkyl groups are the same as those exemplified.

[0094] [Chemical formula 8]

[0095]

[0096] In the above formula (9), R 19 It represents an alkylene group having 0 to 10 carbon atoms.

[0097] In the above formula (9), R 19 The alkylene group represented by can be exemplified by the same group as R in the above formula (5-1): 1 and R 2 The alkylene groups are the same as those exemplified above. Among them, a single bond is preferred.

[0098] The content of the structural unit having the functional group in the polyvinyl alcohol resin (hereinafter also referred to as the modified group amount) is preferably 0.01 mol% or more, more preferably 0.05 mol% or more, further preferably 1.0 mol% or more, further preferably 2.0 mol% or more, preferably 11.0 mol% or less, more preferably 10.0 mol% or less, further preferably 8.0 mol% or less, further preferably 5.0 mol% or less. That is, the modified group amount is preferably 0.01 to 11.0 mol%, more preferably 0.05 to 10.0 mol%, further preferably 1.0 to 8.0 mol%, further preferably 2.0 to 5.0 mol%.

[0099] The amount of the modified groups can be measured by the same method as the amount of the residual acetyl groups.

[0100] The viscosity average polymerization degree of the polyvinyl alcohol resin is preferably 300 or more, more preferably 500 or more, further preferably 600 or more, further preferably 700 or more, for example 800 or more, and is preferably 3500 or less, more preferably 3000 or less, further preferably 2500 or less, further preferably 2000 or less, for example 1800 or less. That is, the viscosity average polymerization degree is preferably 300 to 3500, more preferably 500 to 3000, further preferably 600 to 2500, further preferably 700 to 2000, and particularly preferably 800 to 1800.

[0101] The viscosity average degree of polymerization can be determined by measuring the viscosity of a 4 wt % concentration aqueous solution by a method in accordance with JIS K6726-1994.

[0102] Examples of a method for producing the polyvinyl alcohol resin include a method of obtaining a vinyl ester copolymer by copolymerizing a vinyl ester and other unsaturated monomers, and then adding a saponification catalyst to saponify, that is, hydrolyze, the vinyl ester copolymer.

[0103] In particular, as a polymerization method for obtaining a vinyl ester copolymer, a series of continuous tank reactors is used, and the temperature in each tank, the average residence time, and the stirring state in each reaction tank are adjusted, thereby producing a polyvinyl alcohol resin having the above-mentioned specified characteristics. In addition, in particular, in each reaction tank, by setting the ratio of the vortex volume generated at the gas-liquid interface during stirring to the weight of the reaction liquid in each reaction tank to a specified range, setting the ratio of the distance from the liquid surface to the stirring blade in each reaction tank to the liquid surface height to a specified range, setting the ratio of the stirring blade diameter to the reaction container diameter to a specified range, etc., the polyvinyl alcohol resin having the above-mentioned specified characteristics can be produced.

[0104] The vinyl ester is not particularly limited, and examples thereof include vinyl formate, vinyl acetate, vinyl propionate, vinyl pivalate, and the like. Among them, vinyl acetate is preferred.

[0105] As the above-mentioned other unsaturated monomers, monomers having carbon-carbon double bonds such as vinyl groups as monomers other than vinyl esters can be mentioned. For example, monocarboxylic acids having free radical polymerizable unsaturated double bonds, unsaturated acids such as dicarboxylic acids having free radical polymerizable unsaturated double bonds, derivatives such as salts or esters thereof, olefins, (meth)acrylamides, N-vinylamides, vinyl ethers, nitriles, halogenated vinyls, allyl compounds, vinyl silyl compounds, sulfonic acid group-containing compounds, amino group-containing compounds, etc. Among them, unsaturated acids, salts or esters thereof are preferred.

[0106] Examples of the monocarboxylic acid having a radical polymerizable unsaturated double bond include acrylic acid, crotonic acid, methacrylic acid, and oleic acid.

[0107] Examples of the dicarboxylic acid having a radical polymerizable unsaturated double bond include methylenemalonic acid, itaconic acid, 2-methyleneglutaric acid, 2-methyleneadipic acid, and 2-methylenesebacic acid.

[0108] Examples of the olefins include ethylene, propylene, 1-butene, and isobutylene.

[0109] Examples of the (meth)acrylamides include acrylamide, n-methacrylamide, N-ethylacrylamide, and N,N-dimethylacrylamide.

[0110] Examples of the N-vinylamides include N-vinylformamide and N-vinylpyrrolidone.

[0111] Examples of the vinyl ethers include methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, and n-butyl vinyl ether.

[0112] Examples of the nitriles include (meth)acrylonitrile and the like.

[0113] Examples of the vinyl halides include vinyl chloride and vinylidene chloride.

[0114] Examples of the allyl compound include allyl acetate and allyl chloride.

[0115] Examples of the vinylsilyl compound include vinyltrimethoxysilane and the like.

[0116] Examples of the sulfonic acid group-containing compound include (meth)acrylamide alkanesulfonic acids and salts thereof such as (meth)acrylamide propanesulfonic acid and 2-acrylamide-2-methylpropanesulfonic acid, and olefinsulfonic acids and salts thereof such as vinylsulfonic acid, allylsulfonic acid and methallylsulfonic acid.

[0117] Examples of the amino group-containing compound include vinylamine, allylamine, polyoxyethylene allylamine, polyoxypropylene allylamine, polyoxyethylene vinylamine, and polyoxypropylene vinylamine.

[0118] Among them, monomers having free radical polymerizable unsaturated double bonds and having functional groups such as carboxylic acid groups, sulfonic acid groups, salts of sulfonic acid groups, pyrrolidone ring groups, amide groups, and amino groups are preferably used. Specifically, dicarboxylic acids having free radical polymerizable unsaturated double bonds such as itaconic acid, monocarboxylic acids having free radical polymerizable unsaturated double bonds such as acrylic acid, and derivatives such as salts or esters thereof, sulfonic acid group-containing compounds such as (meth)acrylamide alkanesulfonic acid and salts thereof, N-vinylamides such as N-vinylformamide and N-vinylpyrrolidone, and amino group-containing compounds such as vinylamine and allylamine are preferably used.

[0119] Examples of the polymerization catalyst used in the polymerization include 2-ethylhexyl peroxydicarbonate (Trigonox EHP manufactured by Tianjin McEIT Co., Ltd.), 2,2'-azobisisobutyronitrile (AIBN), tert-butyl peroxyneodecanoate, bis(4-tert-butylcyclohexyl) peroxydicarbonate, di-n-propyl peroxydicarbonate, di-n-butyl peroxydicarbonate, dicetyl peroxydicarbonate, and di-sec-butyl peroxydicarbonate. The above-mentioned polymerization catalysts may be used alone or in combination of two or more.

[0120] Examples of commercially available products of the polymerization catalyst include KAYACARBON EH-C70 and Trigonox EHP-70 (both manufactured by Akzo Chemicals Co., Ltd.).

[0121] As the polymerization method, a method using a series of continuous tank reactors is preferred. The number of continuous tanks is not particularly limited as long as it is 2 or more.

[0122] Hereinafter, a method using a series continuous tank type reactor in which two tanks are connected in series will be described.

[0123] In the above polymerization method, vinyl ester, other unsaturated monomers, polymerization initiator, and solvent are continuously supplied to the first tank. The method for supplying vinyl ester, other unsaturated monomers, and polymerization initiator is not particularly limited, and examples thereof include: a method of preparing a vinyl ester solution, other unsaturated monomer solution, and polymerization initiator solution separately and supplying them; a method of preparing a monomer solution containing vinyl ester and other unsaturated monomers, and a polymerization initiator solution and supplying them, etc.

[0124] When the supply amount of the vinyl ester supplied to the first tank is 100 parts by weight, the supply amount of the other unsaturated monomer supplied to the first tank is preferably 0.001 to 5 parts by weight, and more preferably 0.01 to 3 parts by weight.

[0125] The amount of the polymerization initiator supplied to the first tank is preferably 0.001 to 1 part by weight, more preferably 0.01 to 0.5 part by weight, based on 100 parts by weight of the monomers such as vinyl ester and other unsaturated monomers supplied to the first tank.

[0126] When the amount of the monomers such as vinyl ester and other unsaturated monomers supplied to the first tank is 100 parts by weight, the amount of the solvent supplied to the first tank is preferably 5 to 80 parts by weight, more preferably 10 to 40 parts by weight.

[0127] The average residence time MRT1 of the component supplied to the first tank in the first tank is preferably 2 to 20 hours, more preferably 5 to 15 hours. It should be noted that the above average residence time indicates the degree to which the component supplied to each reaction tank is retained in each reaction tank, and can be adjusted based on the volume of the reaction solution in the reaction tank and the volume flow rate of the component supplied to each tank. For example, when the volume of the reaction solution in the first tank is 180L and the volume flow rate of the component supplied to the first tank is 5ml / second, the average residence time is 10 hours.

[0128] The temperature T1 of the first tank is preferably 50 to 150°C, more preferably 70 to 120°C.

[0129] In the first tank, the reaction solution is preferably polymerized while being stirred. As stirring conditions, when the vortex volume is V1 (L) and the weight of the reaction solution is M1 (kg), it is preferable to set the stirring condition such that V1 / M1 is 0.009 to 0.143 (L / kg), and more preferably 0.01 to 0.1 (L / kg).

[0130] If V1 / M1 is 0.009 (L / kg) or more, the volatilized monomers return to the liquid phase and circulate, thereby improving the reactivity. If it is 0.143 (L / kg) or less, the monomers introduced into the liquid phase are less likely to be released into the gas phase, thereby enabling a uniform reaction.

[0131] It should be noted that the above-mentioned vortex volume refers to the volume of the vortex generated at the gas-liquid interface during stirring. The above-mentioned vortex volume can be calculated, for example, using the thermal fluid powder analysis software "R-FLOW" (manufactured by R-flow). Specifically, it can be calculated based on the distance between the center of the stirring blade and the interface between the gas phase and the liquid phase during stirring. It should be noted that during stirring, pressure is generated in the liquid by the stirring blade serving as a stirring power, the liquid phase becomes a positive pressure, and the gas phase becomes a negative pressure. Therefore, the interface between the gas phase and the liquid phase can be confirmed as the boundary portion between the positive pressure and the negative pressure.

[0132] It should be noted that in the first tank, the rotation speed of the stirring blade during stirring is preferably 10 to 500 rpm, more preferably 50 to 250 rpm, and the capacity of the first tank is preferably 0.01 to 100 m 3 , more preferably 0.05 to 50 m 3 .

[0133] In addition, in the first tank, when the distance from the liquid surface to the stirring blade is set to D1 (m) and the liquid surface height is set to H1 (m), D1 / H1 is preferably adjusted to 0.3 to 0.9 (m / m), and more preferably adjusted to 0.35 to 0.8 (m / m). It should be noted that the above-mentioned liquid surface height refers to the distance from the bottom of the reaction tank to the reaction liquid surface when the reaction liquid in the reaction tank is not stirred. In addition, the distance from the above-mentioned liquid surface to the stirring blade refers to the distance from the liquid surface to the uppermost part of the stirring blade.

[0134] In the first tank, when the stirring blade diameter is BD1 (m) and the inner diameter of the reaction tank is VD1 (m), BD1 / VD1 is preferably 0.1 to 0.5 (m / m), more preferably 0.15 to 0.35 (m / m).

[0135] By adopting the above stirring conditions, the reaction can be carried out uniformly.

[0136] In the above polymerization method, the polymerization solution (1) is continuously taken out from the first tank so that the amount of the reaction solution in the first tank is constant and is continuously supplied to the second tank. In addition to the polymerization solution (1), vinyl ester, other unsaturated monomers, polymerization initiator, etc. may be continuously supplied.

[0137] When the amount of the vinyl ester supplied to the first tank is 100 parts by weight, the amount of the vinyl ester supplied to the second tank is preferably 0 to 50 parts by weight, more preferably 5 to 30 parts by weight.

[0138] When the supply amount of the unsaturated monomer to the first tank is 100 parts by weight, the supply amount of the unsaturated monomer to the second tank is preferably 50 to 200 parts by weight, and more preferably 75 to 150 parts by weight.

[0139] When the amount of the polymerization initiator supplied to the first tank is 100 parts by weight, the amount of the polymerization initiator supplied to the second tank is preferably 50 to 150 parts by weight, and more preferably 80 to 120 parts by weight.

[0140] When the amount of the solvent supplied to the first tank is 100 parts by weight, the amount of the solvent supplied to the second tank is preferably 50 to 150 parts by weight, and more preferably 80 to 120 parts by weight.

[0141] When the amount of the vinyl ester supplied to the first tank and the second tank is 100 parts by weight, the amount of the unsaturated monomer supplied to the first tank and the second tank is preferably 1 to 50 parts by weight, more preferably 10 to 30 parts by weight.

[0142] When the amount of the monomers such as vinyl ester and other unsaturated monomers supplied to the first tank and the second tank is 100 parts by weight, the amount of the polymerization initiator supplied to the first tank and the second tank is preferably 0.001 to 1 part by weight, more preferably 0.01 to 0.5 part by weight.

[0143] When the amount of the monomers such as vinyl ester and other unsaturated monomers supplied to the first tank and the second tank is 100 parts by weight, the amount of the solvent supplied to the first tank and the second tank is preferably 5 to 60 parts by weight, more preferably 10 to 40 parts by weight.

[0144] The average residence time MRT2 of the component supplied to the second tank in the second tank is preferably 1.5 to 8 hours, more preferably 2.5 to 7.5 hours.

[0145] The ratio of the average residence time MRT2 in the second tank to the average residence time MRT1 in the first tank (MRT2 / MRT1) is preferably 0.3 to 0.9, and more preferably 0.35 to 0.7.

[0146] The temperature T2 of the second tank is preferably 60 to 100°C, more preferably 70 to 90°C.

[0147] The ratio (T2 / T1) of the temperature T2 of the second tank to the temperature T1 of the first tank is preferably 0.6 to 1.5, and more preferably 0.9 to 1.2.

[0148] In the second tank, the reaction solution is preferably polymerized while being stirred. As stirring conditions, when the vortex volume is V2 (L) and the weight of the reaction solution is M2 (kg), it is preferable to set the stirring condition such that V2 / M2 is 0.04 to 0.18 (L / kg), and more preferably 0.06 to 0.15 (L / kg).

[0149] If V2 / M2 is 0.04 (L / kg) or more, the volatilized unsaturated monomers return to the liquid phase and circulate, thereby improving the reactivity. If it is 0.18 (L / kg) or less, the monomers introduced into the liquid phase are difficult to be released into the gas phase, so the unsaturated monomers can react while being locally present.

[0150] It should be noted that in the second tank, the rotation speed of the stirring blade during stirring is preferably 10 to 500 rpm, more preferably 100 to 400 rpm, and the capacity of the second tank is preferably 0.01 to 100 m 3 , more preferably 1 to 50 m 3 .

[0151] In the second tank, when the distance from the liquid surface to the stirring blade is D2 (m) and the liquid surface height is H2 (m), D2 / H2 is preferably adjusted to 0.3 to 0.9 (m / m), more preferably 0.35 to 0.6 (m / m).

[0152] In the second tank, when the stirring blade diameter is BD2 (m) and the inner diameter of the reaction tank is VD2 (m), BD2 / VD2 is preferably 0.1 to 0.5 (m / m), more preferably 0.2 to 0.4 (m / m).

[0153] By adopting the above stirring conditions, the unsaturated monomer is localized, and the change in properties due to the modifying group can be further enhanced.

[0154] Regarding the stirring conditions in the first tank and the second tank (vortex volume / weight of reaction solution), the ratio of V2 / M2 to V1 / M1 ([V2 / M2] / [V1 / M1]) is preferably 0.9 to 1.5, more preferably 1.0 to 1.2.

[0155] In addition, regarding (distance from the liquid surface to the stirring blade / liquid surface height), the ratio of D2 / H2 to D1 / H1 ([D2 / H2] / [D1 / H1]) is preferably 0.9 to 1.5, and more preferably 1.0 to 1.2.

[0156] In addition, regarding (stirring blade diameter / inner diameter of reaction vessel), the ratio of BD2 / VD2 to BD1 / VD1 ([BD2 / VD2] / [BD1 / VD1]) is preferably 0.9 to 1.5, and more preferably 1.0 to 1.2.

[0157] In the above-mentioned polymerization method, the polymerization solution (2) is continuously taken out from the second tank so that the amount of the reaction solution in the second tank becomes constant. In this way, a vinyl ester copolymer can be obtained.

[0158] Furthermore, a polyvinyl alcohol resin having predetermined physical properties can be obtained by adding a saponification catalyst to the obtained vinyl ester and performing saponification.

[0159] In particular, by using a vinyl ester copolymer obtained by a method satisfying the reaction conditions in the first tank and the second tank, a polyvinyl alcohol resin having predetermined physical properties can be obtained.

[0160] Examples of the saponification catalyst used in the saponification include alkaline catalysts such as sodium hydroxide, potassium hydroxide, sodium alkoxide, and sodium carbonate, and acidic catalysts such as sulfuric acid, phosphoric acid, and hydrochloric acid. Among them, alkaline catalysts are preferred, and sodium hydroxide is particularly preferred, from the perspective of accelerating the saponification rate and improving productivity.

[0161] The amount of the saponification catalyst added is preferably 1.4 to 30 parts by weight, more preferably 2 to 25 parts by weight, based on 100 parts by weight of the vinyl ester copolymer.

[0162] The amount of the saponification catalyst added is preferably 0.01 to 0.8, more preferably 0.03 to 0.6, in terms of the caustic molar ratio (molar ratio of CMR, alkali, and acetyl group on PVAc) relative to the vinyl ester copolymer.

[0163] The method of adding the saponification catalyst is not particularly limited, and the catalyst may be added all at once at the beginning of the saponification reaction, or a portion may be added at the beginning of the saponification reaction and the remainder may be added during the polymerization reaction.

[0164] The reaction temperature during the saponification is preferably 15 to 80°C, more preferably 20 to 60°C.

[0165] The reaction time during the saponification is preferably 0.4 to 5 hours, more preferably 0.5 to 4 hours.

[0166] In addition, the remaining saponification catalyst may be neutralized as required by the saponification degree. Examples of the neutralizing agent used include organic acids such as acetic acid and lactic acid.

[0167] The polyvinyl alcohol resin obtained by the above method has a dielectric constant A at 25° C. measured at 1 kHz and a dielectric constant B at 125° C. measured at 1 kHz that satisfy a predetermined relationship.

[0168] It is believed that by adopting the above method, a polyvinyl alcohol resin with high polarity can be obtained, and by using such a polyvinyl alcohol resin, a film with little change in performance even at high temperature can be produced. In addition, it is believed that the polyvinyl alcohol resin having a specific modified group has less change in dielectric constant at high temperature, and it is believed that by adopting the above method, the modified group is blocked (Japanese: ブロック) to become a polyvinyl alcohol resin with extremely high polarity.

[0169] The polyvinyl alcohol resin is soluble in an aqueous solvent, so an aqueous solvent can be used to make a film roll. Therefore, there is no need to use an organic solvent that has a large environmental impact. In addition, the polyvinyl alcohol resin has little change in dielectric constant even at high temperatures, and can be suitably used as a material for a film for a film capacitor.

[0170] The polyvinyl alcohol resin of the present invention has excellent solubility. For example, it can be formed into a film roll by film formation, and thus can be used as a material for film capacitors and a packaging material for storing various substances such as pesticides, drugs, dyes, detergents, fertilizers, cosmetics, and sanitary products. In addition, it can be used for applications such as a viscosity modifier for aqueous solutions, a gas barrier coating agent, a suspending agent, an emulsifier, a polarizing plate, a water-soluble film, and a dispersant.

[0171] A film roll containing the polyvinyl alcohol resin is also one of the present invention.

[0172] Furthermore, the polyvinyl alcohol resin can be acetalized by reacting an aldehyde to obtain a polyvinyl acetal resin.

[0173] The present invention also includes a polyvinyl acetal resin which is an acetalized product of the polyvinyl alcohol resin.

[0174] Effects of the Invention

[0175] According to the present invention, there can be provided a polyvinyl alcohol resin capable of producing a film having a high capacitance retention rate at high temperature and excellent strength and flexibility. DETAILED DESCRIPTION

[0176] Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

[0177] (Example 1)

[0178] (Production of polyvinyl acetate)

[0179] A series continuous tank reactor was used in which a glass-lined reaction vessel (first tank) having an internal volume of 300 L and a glass-lined reaction vessel (second tank) having an internal volume of 300 L were connected in series via a metering pump.

[0180] A methanol solution of vinyl acetate and vinylamine (monomer solution (1)) is prepared. Separately, a methanol solution of 2,2'-azobisisobutyronitrile (initiator solution (1)) is prepared.

[0181] The monomer solution (1) and the initiator solution (1) were adjusted to 2 parts by weight of vinylamine, 0.01 parts by weight of polymerization initiator, and 30 parts by weight of solvent per 100 parts by weight of vinyl acetate by separate supply lines using metering pumps, and were continuously supplied to the first tank. While maintaining the internal temperature at 80°C, the polymerization was carried out for an average residence time of 10 hours while stirring such that the ratio (V1 / M1) of the vortex volume V1 (L) generated at the gas-liquid interface by stirring to the weight M1 (kg) of the reaction solution (monomer solution (1) and initiator solution (1)) in the first tank was 0.07 (L / kg), and the polymerization solution (1) was continuously taken out from the first tank so that the amount of the reaction solution in the first tank was fixed at 180 kg and supplied to the second tank. The height of the stirring blade was adjusted such that the ratio (D1 / H1) of the distance D1 from the liquid surface to the stirring blade to the liquid surface height H1 was 0.5 (m / m). In addition, the ratio of the stirring blade diameter BD1 to the reaction container diameter VD1 (BD1 / VD1) was 0.3 (m / m).

[0182] In addition to the polymerization solution (1) from the first tank, a methanol solution of vinyl acetate and vinylamine (monomer solution (2)) and a methanol solution of 2,2'-azobisisobutyronitrile (initiator solution (2)) were adjusted so that the amount of vinyl acetate supplied to the second tank was 30 parts by weight, 20 parts by weight of vinylamine, 0.01 parts by weight of the polymerization initiator, and 50 parts by weight of the solvent, relative to 100 parts by weight of the vinyl acetate supplied to the first tank, and were continuously supplied to the second tank. While maintaining the internal temperature at 80°C, the mixture was stirred so that the ratio (V2 / M2) of the vortex volume V2 (L) generated at the gas-liquid interface by stirring to the weight M2 (kg) of the reaction solution (polymerization solution (1), monomer solution (2) and initiator solution (2)) in the second tank was 0.07 (L / kg), and polymerization was carried out with an average residence time of 5 hours, and the polymerization solution (2) was continuously taken out from the second tank so that the amount of the reaction solution in the second tank was fixed at 150 kg. It should be noted that the height of the stirring blade was adjusted so that the ratio of the distance D2 from the liquid surface to the stirring blade to the liquid surface height H2 (D2 / H2) was 0.6 (m / m). In addition, the ratio of the stirring blade diameter BD2 to the reaction container diameter VD2 (BD2 / VD2) was 0.4 (m / m).

[0183] Methanol vapor was introduced into the polymerization solution (2) taken out from the second tank to remove unreacted monomers, thereby obtaining a methanol solution of polyvinyl acetate (PVAc-1).

[0184] (Production of polyvinyl alcohol resin)

[0185] Methanol was added to the obtained PVAc-1 so that its concentration became 35 wt % to prepare a PVAc solution, and sodium hydroxide as a saponification catalyst was added to the PVAc solution so that the caustic molar ratio (CMR, the molar ratio of the alkali to the acetyl group on the PVAc) became 0.02, and saponification was performed by maintaining at 40° C. for 3 hours. The solidified polymer was pulverized in a pulverizer, washed with methanol, and then dried in an oven to obtain a polyvinyl alcohol resin (1) having a structural unit having an amino group represented by the following formula (9-1).

[0186] [Chemical formula 9]

[0187]

[0188] (Example 2)

[0189] In the first tank, the amount of vinyl amine was adjusted to 20 parts by weight, the amount of polymerization initiator was adjusted to 0.005 parts by weight, and the amount of solvent was adjusted to 15 parts by weight, relative to 100 parts by weight of vinyl acetate supplied to the first tank. In the second tank, the amount of vinyl acetate supplied to the second tank was adjusted to 30 parts by weight, the amount of vinyl amine was adjusted to 40 parts by weight, the amount of polymerization initiator was adjusted to 0.01 parts by weight, and the amount of solvent was adjusted to 50 parts by weight, relative to 100 parts by weight of vinyl acetate supplied to the first tank. In addition, the temperature, V1 / M1, D1 / H1, BD1 / VD1, and the average residence time in the first tank, the temperature, V2 / M2, D2 / H2, BD2 / VD2, and the average residence time in the second tank were changed as shown in Table 1, and a polyvinyl alcohol resin (2) was obtained in the same manner as in Example 1.

[0190] (Example 3)

[0191] Sodium 2-acrylamido-2-methylpropanesulfonate (AMPS) was used instead of vinylamine. In the first tank, the amount of AMPS was adjusted to 3 parts by weight relative to 100 parts by weight of vinyl acetate. Except for the above, the same operation as in Example 1 was carried out to obtain a polyvinyl alcohol resin (3) having a structural unit having a sulfonic acid group represented by the following formula (6-1-1).

[0192] [Chemical formula 10]

[0193]

[0194] (Example 4)

[0195] N-vinyl pyrrolidone was used instead of vinylamine. In the first tank, the amount of N-vinyl pyrrolidone was adjusted to 3 parts by weight relative to 100 parts by weight of vinyl acetate. Except for the above, the same operation as in Example 1 was carried out to obtain a polyvinyl alcohol resin (4) having a structural unit having a pyrrolidone ring group represented by the following formula (7).

[0196] [Chemical formula 11]

[0197]

[0198] (Example 5)

[0199] Itaconic acid was used instead of ethyleneamine. In the first tank, itaconic acid was adjusted to 3 parts by weight relative to 100 parts by weight of vinyl acetate. In addition, the temperature, V1 / M1, D1 / H1, BD1 / VD1, average residence time in the first tank, the temperature, V2 / M2, D2 / H2, BD2 / VD2, average residence time in the second tank, the amount of saponification catalyst added, and the saponification reaction time were changed as shown in Table 1. The same operation as in Example 1 was performed to obtain a polyvinyl alcohol resin (5) having a structural unit having a carboxyl group represented by the following formula (5-1-1).

[0200] [Chemical formula 12]

[0201]

[0202] (Example 6)

[0203] Polyvinyl acetate (PVAc-6) was produced in the same manner as in Example 1, except that itaconic acid was used instead of ethyleneamine, and the temperature, V1 / M1, D1 / H1, BD1 / VD1, and average residence time in the first tank, and the temperature, V2 / M2, D2 / H2, BD2 / VD2, and average residence time in the second tank were as shown in Table 1.

[0204] In addition, polyvinyl acetate (PVAc-7) was produced in the same manner as in Example 1, except that ethyleneamine was not added and the temperature, V1 / M1, D1 / H1, BD1 / VD1, and average residence time in the first tank, and the temperature, V2 / M2, D2 / H2, BD2 / VD2, and average residence time in the second tank were as shown in Table 1.

[0205] In (Preparation of Polyvinyl Alcohol Resin), a polyvinyl alcohol resin (6) was obtained in the same manner as in Example 1 except that a PVAc solution was prepared so that the weight ratio of PVAc-6 to PVAc-7 was 50:50.

[0206] (Examples 7 to 35, Comparative Examples 1 to 26)

[0207] A polyvinyl alcohol resin was produced in the same manner as in Example 1, except that the type of other unsaturated monomers, the temperature in the first tank, V1 / M1, D1 / H1, BD1 / VD1, the average residence time, the temperature in the second tank, V2 / M2, D2 / H2, BD2 / VD2, the average residence time, the amount of saponification catalyst added, and the saponification reaction time were changed as shown in Tables 1 to 4.

[0208] (evaluate)

[0209] The polyvinyl alcohol resins obtained in Examples and Comparative Examples were evaluated as follows. The results are shown in Tables 5 to 10.

[0210] (1) Hydroxyl group content, residual acetyl group content, and modified group content

[0211] The obtained polyvinyl alcohol resin was dissolved in heavy water so as to have a concentration of 1 wt %. 1 The amount of hydroxyl groups, the amount of residual acetyl groups, and the amount of modified groups were measured by H-NMR.

[0212] (2) Viscosity average degree of polymerization

[0213] A 4 wt % aqueous solution of the obtained polyvinyl alcohol resin was prepared, and the viscosity average polymerization degree was measured by a method in accordance with JIS K6726-1994.

[0214] (3) Dielectric constant

[0215] Add polyvinyl alcohol resin to water above 95°C to make it 10% by weight, stir for more than 2 hours to dissolve, cool to 25°C, and degas fully. After applying the obtained polyvinyl alcohol resin solution with a gap thickness of 1mm, dry it in a Gill oven at 90°C for more than 5 hours to prepare a film roll for film capacitors with a thickness of 0.05mm containing polyvinyl alcohol resin. A 40mm square film was cut out from the obtained film roll, and a platinum electrode with a diameter of 20mm and a thickness of 0.1μm was formed on both sides by sputtering to prepare a sample. For the obtained sample, the dielectric constant A was measured at 25°C and 1kHz using an LCR tester (E4980AL manufactured by Keysight). In addition, the dielectric constant B was measured at 125°C and 1kHz in the same manner, and B / A was calculated.

[0216] (4) Solubility parameter

[0217] The solubility parameters were calculated by the Fedors method.

[0218] (5) Electrostatic capacitance and electrostatic capacitance maintenance rate

[0219] In the same manner as the evaluation of the dielectric constant, a film of 40 mm square size was cut out, and a sample with platinum electrodes of 20 mm in diameter and 0.1 μm in thickness formed on both sides was prepared by sputtering, and the electrostatic capacitance was measured by the following method. A 4-terminal probe 9140 was installed on the LCR Hitester 3522-50 manufactured by Hioki Electric Co., Ltd. The two terminals (leads) of the film capacitor element were clamped with the 4-terminal probe 9140, and an AC voltage of 0.1 V and 1 kHz was applied through the built-in power supply of the LCR Hitester 3522-50. When the displayed value stabilized, the electrostatic capacitance value was read. It should be noted that the measurement conditions other than those described here are based on "4.2.2 Electrostatic Capacitance" of JIS C5101-16:2009.

[0220] Similarly, the capacitance at 125° C. was measured and then divided by the capacitance at 25° C. to determine the capacitance retention rate.

[0221] (6) Breaking strength and elongation at break

[0222] Films with a width of 20 mm and a length of 100 mm were cut out from the film roll for film capacitors obtained in "(3) Dielectric constant" to prepare samples. The obtained samples were subjected to a tensile test using a Tensilon tensile tester (Autograph AGS-X 500N manufactured by Shimadzu Corporation) at 25°C and a tensile speed of 510 mm / s to measure the breaking strength (MPa) and breaking elongation (%).

[0223] (7) Insulation breakdown voltage

[0224] A film of 100 mm square was cut from the film roll for film capacitor obtained in "(3) Dielectric constant" to prepare a sample. The dielectric breakdown voltage of the obtained sample was measured in silicone oil at 25°C. The measuring device used was a dielectric breakdown voltage measuring device (TOJ-200, an oil test electrode device manufactured by Tama Denso Co., Ltd.), and the electrodes used were a cylindrical upper electrode with a diameter of 6.425 mm and a cylindrical lower electrode with a diameter of 75 mm. The dielectric breakdown voltage (kV / mm) was measured at a voltage increase rate of 50 V / sec.

[0225] (8) Cracks in the winding body

[0226] A polyvinyl alcohol film was prepared in the same manner as in "(3) Dielectric constant", and was wound around a 3-inch core for 1 m, then unwound again. The number of cracks at this time was visually confirmed and evaluated based on the following criteria.

[0227] 1: No cracks were observed in the film.

[0228] 2: 1 to 5 cracks were observed on the film at the winding core.

[0229] 3: 10 to 50 cracks were observed in the entire film.

[0230] 4: 51 or more cracks were confirmed in the entire film.

[0231] [Table 1]

[0232]

[0233] [Table 2]

[0234]

[0235] [Table 3]

[0236]

[0237] [Table 4]

[0238]

[0239] [Table 5]

[0240]

[0241] [Table 6]

[0242]

[0243] [Table 7]

[0244]

[0245] [Table 8]

[0246]

[0247] [Table 9]

[0248]

[0249] [Table 10]

[0250]

[0251] Industrial Applicability

[0252] According to the present invention, there can be provided a polyvinyl alcohol resin capable of producing a film having a high capacitance retention rate at high temperature and excellent strength and flexibility.

Claims

1. A polyvinyl alcohol resin, wherein when a dielectric constant of the polyvinyl alcohol resin at 25° C. measured at 1 kHz is defined as A, and when a dielectric constant of the polyvinyl alcohol resin at 125° C. measured at 1 kHz is defined as B, the following equations (1) and (2) are satisfied: A ≥ 3.0 (1) 1.0≥B / A≥0.6 (2). 2 . The polyvinyl alcohol resin according to claim 1 , which has a solubility parameter of 12 or more. 3 . The polyvinyl alcohol resin according to claim 1 , which has at least one functional group selected from the group consisting of a carboxylic acid group, a sulfonic acid group, a pyrrolidone ring group, an amide group and an amino group in a side chain. A film roll comprising the polyvinyl alcohol resin according to any one of claims 1 to 3. 5 . A polyvinyl acetal resin, which is an acetalized product of the polyvinyl alcohol resin according to claim 1 .

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