Composition, dispersant for suspension polymerization, and method for producing vinyl polymer

Abstract

Provided are a composition containing a vinyl alcohol polymer and an amphiphilic substance, a dispersant for suspension polymerization containing the composition, and a method for producing a vinyl polymer, the composition being capable of obtaining polymer particles having a small average particle diameter, few coarse particles, and good plasticizer absorbability even when suspension polymerization is performed at high temperatures. The present invention is a composition containing a vinyl alcohol polymer (A) having a carbonyl group and a degree of saponification of 60 mol% or more, and an amphiphilic substance (B) containing at least one substance selected from the group consisting of a surfactant and a vinyl alcohol polymer having a degree of saponification of less than 60 mol%.

Description

Technical Field

[0001] The present invention relates to a composition, a dispersant for suspension polymerization and a method for producing a vinyl polymer. Background Art

[0002] Polyvinyl alcohol (PVA) is known as a water-soluble synthetic polymer. PVA is used in various applications such as raw materials for films and fibers, additives for paper processing and fiber processing, adhesives, dispersants (also known as dispersion stabilizers, etc.) and dispersing aids for emulsion polymerization and suspension polymerization, and binders for inorganic substances.

[0003] In order to improve the performance of PVA, various modified PVAs have been put into practical use or are being developed. For example, Patent Document 1 describes the following vinyl alcohol polymer, which is characterized in that it has a carbonyl group, a formyl group, and an alkenyl group in the same or different molecules, and describes that the vinyl alcohol polymer can be used as a dispersant for suspension polymerization.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: International Publication No. 2022 / 071345 Summary of the invention

[0007] Problems to be solved by the invention

[0008] In suspension polymerization, when PVA is used as a dispersant, an operation called hot charging is sometimes performed in which an aqueous solution of PVA is added to a polymerization system solution prepared at a high temperature of 60°C or above. When hot charging is performed using a conventional aqueous solution containing a dispersant, aggregation of PVA sometimes occurs, and as a result, coarse polymer particles are sometimes obtained. In addition, even in the absence of hot charging, in conventional suspension polymerizations in which PVA is used as a dispersant, there is a tendency for the function of PVA as a dispersant to decrease under high temperature conditions of 60°C or above. The above-mentioned Patent Document 1 does not disclose a dispersant that can obtain polymer particles with a small average particle size, few coarse particles, and good plasticizer absorption even when suspension polymerization is performed under high temperature conditions.

[0009] The object of the present invention is to provide a composition comprising a vinyl alcohol polymer and an amphiphilic substance, a dispersant for suspension polymerization comprising the composition, and a method for producing a vinyl alcohol polymer, wherein the composition can produce polymer particles having a small average particle size, a small amount of coarse particles, and good plasticizer absorption even when suspension polymerization is carried out at a high temperature.

[0010] Means used to solve problems

[0011] The above object is achieved by providing any one of the following technical solutions.

[0012] [1] A composition comprising a vinyl alcohol polymer (A) and an amphiphilic substance (B), wherein the vinyl alcohol polymer (A) is a vinyl alcohol polymer having a carbonyl group and a saponification degree of 60 mol % or more, and the amphiphilic substance (B) comprises at least one selected from a surfactant and a vinyl alcohol polymer having a saponification degree of less than 60 mol %;

[0013] [2] The composition according to [1], wherein the vinyl alcohol polymer (A) further has a formyl group and an alkenyl group;

[0014] [3] The composition according to [1] or [2], wherein the vinyl alcohol polymer (A) has a structure containing the carbonyl group and represented by the following formula (1);

[0015] [Chemistry 1]

[0016]

[0017] In formula (1), m is an integer of 1 to 11.

[0018] [4] The composition according to any one of [1] to [3], wherein the vinyl alcohol polymer (A) has a group containing the carbonyl group and represented by the following formula (2) at the end of the polymer chain;

[0019] [Chemistry 2]

[0020]

[0021] In formula (2), R 1 It is an alkenyl group or an alkyl group.

[0022] [5] The composition according to [4], wherein R in the above formula (2) 1 is an alkenyl group having a methylene group at the terminal of the carbonyl side;

[0023] [6] The composition according to any one of [1] to [5], wherein the vinyl alcohol polymer (A) has a tertiary carbon atom;

[0024] [7] The composition according to any one of [1] to [6], wherein the vinyl alcohol polymer (A) has a structural unit derived from an aliphatic unsaturated aldehyde;

[0025] [8] The composition according to [7], wherein the aliphatic unsaturated aldehyde has 3 to 14 carbon atoms;

[0026] [9] The composition according to [7] or [8], wherein the aliphatic unsaturated aldehyde has a carbon-carbon double bond at the terminal end;

[0027]

[10] The composition according to any one of [1] to [9], wherein the amphiphilic substance (B) comprises at least one surfactant selected from anionic surfactants and nonionic surfactants;

[0028]

[11] The composition according to

[10] , wherein the amphiphilic substance (B) comprises at least one selected from acylamino acid salts and acyltaurates as the anionic surfactant;

[0029]

[12] The composition according to any one of [1] to

[11] , wherein the amphiphilic substance (B) comprises an anion-modified vinyl alcohol polymer having a saponification degree of less than 60 mol % as the vinyl alcohol polymer having a saponification degree of less than 60 mol %;

[0030]

[13] The composition according to

[12] , wherein the amphiphilic substance (B) comprises a carboxylic acid-modified vinyl alcohol polymer having a saponification degree of less than 60 mol % as the anion-modified vinyl alcohol polymer having a saponification degree of less than 60 mol %;

[0031]

[14] The composition according to any one of [1] to

[13] , wherein the content of the amphiphilic substance (B) is 0.001% by mass or more and 30% by mass or less relative to the vinyl alcohol polymer (A);

[0032]

[15] A dispersant for suspension polymerization, comprising the composition of any one of [1] to

[14] ;

[0033]

[16] A method for producing a vinyl polymer, comprising: a step of polymerizing a vinyl compound in the presence of a vinyl alcohol polymer (A) and an amphiphilic substance (B), wherein the vinyl alcohol polymer (A) is a vinyl alcohol polymer having a carbonyl group and a saponification degree of 60 mol % or more, and the amphiphilic substance (B) comprises at least one selected from a surfactant and a vinyl alcohol polymer having a saponification degree of less than 60 mol %.

[0034] Effects of the Invention

[0035] According to the present invention, there can be provided a composition comprising a vinyl alcohol polymer and an amphiphilic substance, a dispersant for suspension polymerization comprising the composition, and a method for producing a vinyl polymer, wherein the composition can obtain polymer particles having a small average particle size, a small number of coarse particles, and good plasticizer absorption even when suspension polymerization is performed at a high temperature. DETAILED DESCRIPTION

[0036] <Composition>

[0037] The composition of the present invention comprises a vinyl alcohol polymer (A) and an amphiphilic substance (B), wherein the vinyl alcohol polymer (A) is a vinyl alcohol polymer having a carbonyl group and a saponification degree of 60 mol% or more, and the amphiphilic substance (B) comprises at least one selected from a surfactant and a vinyl alcohol polymer having a saponification degree of less than 60 mol%.

[0038] (Vinyl alcohol polymer (A))

[0039] The vinyl alcohol polymer (A) (hereinafter also referred to as "PVA(A)") is a vinyl alcohol polymer having a carbonyl group and a saponification degree of 60 mol% or more. PVA(A) may contain PVA molecules that do not have a carbonyl group. In other words, PVA(A) is a PVA (an aggregate of PVA molecules) having a saponification degree of 60 mol% or more as measured by the method described later, wherein at least a portion of the PVA molecules have a carbonyl group. PVA(A) preferably also has a formyl group and an alkenyl group. PVA(A) may contain PVA molecules that do not have one or more of the carbonyl group, formyl group and alkenyl group. PVA(A) may have a carbonyl group, formyl group and alkenyl group in the same or different molecules. When PVA(A) has a carbonyl group, formyl group and alkenyl group in the same or different molecules, in PVA(A), all of the carbonyl group, formyl group and alkenyl group may not be contained in one molecule. That is, PVA(A) may be, for example, a mixture of PVA(a) having two groups among carbonyl, formyl and alkenyl and PVA(b) having the remaining one group. In this case, both PVA(a) and PVA(b) may have one or more groups among carbonyl, formyl and alkenyl. PVA(A) may be a mixture of three or more PVAs. It should be noted that the form of PVA having all the groups among carbonyl, formyl and alkenyl in one molecule and the form of a mixture containing multiple PVAs and the mixture having carbonyl, formyl and alkenyl have substantially the same properties. In addition, it is usually very difficult to distinguish these two forms by analysis.

[0040] PVA (A) is a polymer having a vinyl alcohol unit as a structural unit. PVA (A) can be obtained by, for example, polymerizing vinyl esters in the presence of an aliphatic unsaturated aldehyde, and saponifying the resulting vinyl ester polymer. The lower limit of the saponification degree of PVA (A) is 60 mol%, preferably 65 mol%, and more preferably 70 mol%. On the other hand, the upper limit of the above-mentioned saponification degree can be 100 mol%, preferably 95 mol%, more preferably 90 mol%, further preferably 85 mol%, and further preferably 80 mol%. By making the saponification degree of PVA (A) the above range, the surface activity performance is optimized, and thus, for example, each performance (polymer particles with small average particle size and few coarse particles, good plasticizer absorbency, etc.) when used as a dispersant for suspension polymerization is improved. The saponification degree is a value measured by the method described in JIS K6726:1994.

[0041] The carbonyl group (-C(=O)-) contained in PVA(A) is a divalent group in which a carbon atom is bonded together with two connecting bonds. PVA(A) preferably has a structure including a carbonyl group and represented by the following formula (1).

[0042] [Chemistry 3]

[0043]

[0044] In formula (1), m is an integer of 1 to 11. m is preferably an integer of 2 to 9 in some cases, and is preferably an integer of 3 to 7.

[0045] In addition, in this specification, the numerical range described using "to" means that the numerical values ​​described before and after "to" are included as the lower limit and the upper limit.

[0046] The content of carbonyl groups in PVA (A) relative to the total content of vinyl alcohol units and vinyl ester units is preferably 0.01 mol% or more and 5 mol% or less, more preferably 0.03 mol% or more and 3 mol% or less, further preferably 0.05 mol% or more and 2 mol% or less, further preferably 0.1 mol% or more and 1 mol% or less, and particularly preferably 0.15 mol% or more and 0.3 mol% or less. When the content of carbonyl groups in PVA (A) is within the above range, various properties such as when used as a dispersant for suspension polymerization are improved. The content of the above carbonyl groups is set to a value obtained by the method described in the embodiments described later.

[0047] When PVA(A) has a formyl group, the formyl group is a monovalent group represented by -C(=O)H.

[0048] As the content of the formyl group in PVA (A) relative to the total content of vinyl alcohol units and vinyl ester units, it is preferably 0.01 mol% or more and 5 mol% or less, more preferably 0.03 mol% or more and 3 mol% or less, further preferably 0.05 mol% or more and 2 mol% or less, and further preferably 0.1 mol% or more and 1 mol% or less. The upper limit of the content of the above-mentioned formyl group can be 0.5 mol% or 0.3 mol%. When the content of the formyl group in PVA (A) is the above-mentioned range, various properties when used as a dispersant for suspension polymerization, etc. are improved. The content of the above-mentioned formyl group is set to the value obtained by the method described in the embodiments described later.

[0049] When PVA (A) has an alkenyl group, the alkenyl group is a monovalent group obtained by removing any one hydrogen atom from an olefin. The number of carbon atoms in the alkenyl group is preferably 2 to 13, more preferably 3 to 12, further preferably 4 to 11, and further preferably 5 to 9. The alkenyl group may be straight-chain or branched, but is preferably straight-chain. The alkenyl group is preferably located at the end of the polymer chain.

[0050] When PVA (A) has an alkenyl group, the alkenyl group preferably has a carbon-carbon double bond at the terminal (front end). That is, PVA (A) preferably has a vinyl group at the terminal (front end). The alkenyl group possessed by PVA (A) is more preferably a group represented by the following formula (5).

[0051] [Chemistry 4]

[0052]

[0053] In formula (5), n is an integer of 1 to 11. n is preferably an integer of 2 to 9, and more preferably an integer of 3 to 7.

[0054] As the content of alkenyl in PVA (A) relative to the total content of vinyl alcohol unit and vinyl ester unit, it is sometimes preferably 0.01 mol% or more and 5 mol% or less, more preferably 0.03 mol% or more and 3 mol% or less, further preferably 0.05 mol% or more and 1 mol% or less, and further preferably 0.1 mol% or more and 0.5 mol% or less. The upper limit of the content of the alkenyl can be 0.3 mol%. When the content of the alkenyl in PVA (A) is the above range, various properties such as when used as a dispersant for suspension polymerization are improved. The content of the alkenyl is set to the value obtained by the method described in the embodiments described later. The range of the suitable content of the vinyl in PVA (A) relative to the total content of vinyl alcohol unit and vinyl ester unit is the same as the range of the suitable content of the alkenyl.

[0055] PVA (A) preferably has a group represented by the following formula (2) at the terminal of the polymer chain.

[0056] [Chemistry 5]

[0057]

[0058] In formula (2), R 1 It is an alkenyl group or an alkyl group.

[0059] R in formula (2) 1 In the case of an alkenyl group, the number of carbon atoms of the alkenyl group is preferably 2 to 13, more preferably 3 to 12, further preferably 4 to 11, and further preferably 5 to 9. The alkenyl group may be straight-chain or branched, but is preferably straight-chain. The alkenyl group is preferably a group having a methylene group at the end of the carbonyl side (a group represented by R-CH2- (R is an alkenyl group)), more preferably a group having a carbon-carbon double bond at the end (front end), and further preferably a group represented by the above formula (5). Among the groups represented by formula (2), R 1 Alkenyl groups are generally formed when an aliphatic unsaturated aldehyde acts as a chain transfer agent.

[0060] PVA (A) may have a carbon-carbon double bond in addition to the alkenyl group, and particularly preferably has -CO-(CH=CH) p - (p is an integer of 1 to 5). This structure is introduced, for example, by heat-treating PVA obtained by polymerizing and saponifying vinyl ester in the presence of an aliphatic unsaturated aldehyde.

[0061] R in formula (2) 1 When it is an alkyl group, the alkyl group is -C s H (2s+1) Here, s is preferably an integer of 1 to 12.

[0062] PVA (A) contains R in formula (2) 1 When it is an alkyl group, R in the formula (2) in PVA (A) 1 The content of the alkyl group relative to the total content of the vinyl alcohol unit and the vinyl ester unit is preferably 0.01 mol% to 5 mol%, more preferably 0.03 mol% to 3 mol%, further preferably 0.05 mol% to 2 mol%, and even more preferably 0.1 mol% to 1 mol%. 1 When the content of the alkyl group is within the above range, various properties when used as a dispersant for suspension polymerization, for example, are improved. 1 The content of the alkyl group is a value determined by the method described in Examples below.

[0063] Among the groups represented by the above formula (2), R 1 The alkyl group is introduced to the terminal of the polymer chain when, for example, vinyl ester is polymerized in the presence of an aliphatic saturated aldehyde and the aliphatic saturated aldehyde acts as a chain transfer agent. The aliphatic saturated aldehyde is preferably acetaldehyde.

[0064] When PVA (A) has a group represented by the above formula (2) at the end of the polymer chain, the PVA (A) may include R in the formula (2): 1 The group is an alkenyl group and R in the formula (2) 1 These two are alkyl groups.

[0065] PVA (A) preferably has a terminal group derived from an aliphatic unsaturated aldehyde or a structural unit derived from an aliphatic unsaturated aldehyde. The aliphatic unsaturated aldehyde may preferably have 3 to 14 carbon atoms, more preferably 4 to 12, and even more preferably 6 to 10 carbon atoms.

[0066] The above-mentioned aliphatic unsaturated aldehyde preferably has a carbon-carbon double bond, and more preferably has a carbon-carbon double bond at the end (front end). That is, the above-mentioned aliphatic unsaturated aldehyde preferably contains a vinyl group. As the above-mentioned aliphatic unsaturated aldehyde having a carbon-carbon double bond, it is preferably an aliphatic unsaturated aldehyde containing an alkenyl group having a methylene group at the end of the carbonyl side, that is, an aliphatic unsaturated aldehyde represented by a group represented by R-CH2- (R is an alkenyl group). In other words, the above-mentioned aliphatic unsaturated aldehyde is preferably an aliphatic unsaturated aldehyde other than α, β-unsaturated aldehyde. By using an aliphatic unsaturated aldehyde having a structure as described above, the reactivity during polymerization is improved, and PVA with a sufficient amount of functional groups (carbonyl groups, etc.) introduced is effectively obtained.

[0067] The aliphatic unsaturated aldehyde is particularly preferably a compound represented by the following formula (6).

[0068] [Chemistry 6]

[0069]

[0070] In formula (6), p is an integer of 1 to 11. p is preferably an integer of 2 to 9, and more preferably an integer of 3 to 7.

[0071] Examples of the aliphatic unsaturated aldehydes include 2-propenal, 3-butenal, 4-pentenal, 5-hexenal, 3-methyl-5-hexanal, 6-heptenal, 6-octenal, 7-octenal, 7-methyl-7-octenal, 3,7-dimethyl-7-octenal, 8-nonenal, 9-decenal, 10-undecenal, and 11-dodecenal.

[0072] As the terminal group derived from an aliphatic unsaturated aldehyde which PVA (A) preferably has, among the groups represented by the following formula (2), R 1 A group which is an alkenyl group.

[0073] [Chemistry 7]

[0074]

[0075] In this case, the specific form and suitable form of the group (terminal group) represented by the above formula (2) are as described above. 1 As described above, when vinyl ester is polymerized in the presence of an aliphatic unsaturated aldehyde, the alkenyl group is introduced to the terminal of the polymer chain when the aliphatic unsaturated aldehyde acts as a chain transfer agent.

[0076] Examples of the structural unit derived from an aliphatic unsaturated aldehyde that PVA (A) preferably has include a structural unit represented by the following formula (3) or (4).

[0077] [Chemistry 8]

[0078]

[0079] In formulas (3) and (4), R 2 ~R 7 Each is independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. q is an integer of 1 to 11. r is an integer of 1 to 11.

[0080] R in formula (3) 2 ~R 4 It is preferably a hydrogen atom. q is also preferably an integer of 2 to 9 in some cases, and more preferably an integer of 3 to 7. The structural unit represented by formula (3) is usually formed when an aliphatic unsaturated aldehyde is used as a monomer, and is introduced into the polymer chain.

[0081] R in formula (4) 5 ~R 7 Preferably, it is a hydrogen atom. r is also preferably an integer of 2 to 9, more preferably an integer of 3 to 7. The structural unit represented by formula (4) is usually formed when the formyl group in the structural unit represented by formula (3) is further used as a chain transfer agent.

[0082] PVA (A) preferably has a tertiary carbon atom (a carbon atom directly bonded to three carbon atoms). In addition, PVA (A) preferably has a structural unit containing a tertiary carbon atom. In this case, that is, when PVA (A) has a branched structure, various properties when used as a dispersant for suspension polymerization, etc. are improved. PVA (A) has, for example, a structural unit represented by the above formula (3) or (4) and R 2~R 7 When it is a hydrogen atom, PVA(A) has a tertiary carbon atom.

[0083] PVA (A) may have other structural units in addition to the structural units derived from vinyl esters (vinyl alcohol units and vinyl ester units) and the structural units derived from aliphatic unsaturated aldehydes. Examples of monomers providing the above-mentioned other structural units include α-olefins such as ethylene, propylene, 1-butene, isobutylene, and 1-hexene; acrylic acid, methacrylic acid; acrylic acid esters such as methyl acrylate and ethyl acrylate; methacrylic acid esters such as methyl methacrylate and ethyl methacrylate; acrylamide derivatives such as N-methylacrylamide, N-ethylacrylamide, and 2-acrylamide-2-methylpropanesulfonic acid; methacrylamide derivatives such as N-methylmethacrylamide and N-ethylmethacrylamide; maleic acid; maleic acid esters such as monomethyl maleate and dimethyl maleate; fumaric acid; fumaric acid esters such as monomethyl fumarate and dimethyl fumarate; itaconic acid; 3,4-diacetoxy-1-butene; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, and n-butyl vinyl ether; Ethylene glycol vinyl ether, 1,3-propylene glycol vinyl ether, 1,4-butanediol vinyl ether and other vinyl ethers containing hydroxyl groups; allyl acetate; allyl ethers such as propyl allyl ether, butyl allyl ether, hexyl allyl ether and other allyl ethers; monomers having oxyalkylene groups; isopropenyl acetate; α-olefins containing hydroxyl groups such as 3-butene-1-ol, 4-pentene-1-ol, 5-hexene-1-ol, 7-octen-1-ol, 9-decen-1-ol, 3-methyl-3-butene-1-ol and other olefins; monomers having silyl groups such as vinyltrimethoxysilane, vinylmethyldimethoxysilane, vinyldimethylmethoxysilane, vinyltriethoxysilane, vinylmethyldiethoxysilane, vinyldimethylethoxysilane, 3-(meth)acrylamidepropyltrimethoxysilane, 3-(meth)acrylamidepropyltriethoxysilane and the like.

[0084] The ratio of the above-mentioned other structural units in all structural units in PVA (A) is preferably 20 mol% or less, more preferably 10 mol% or less, and even more preferably 5 mol% or 1 mol%. On the other hand, the ratio of the above-mentioned other structural units may be, for example, 0.1 mol% or more, or 1 mol% or more.

[0085] The lower limit of the viscosity average degree of polymerization of PVA (A) may be, for example, 100, and may be preferably 200, more preferably 300, further preferably 400, and further preferably 500. When the viscosity average degree of polymerization is equal to or greater than the above lower limit, the protective colloid property is improved, and for example, various properties when used as a dispersant for suspension polymerization are improved. On the other hand, the upper limit of the viscosity average degree of polymerization is preferably 2,000, more preferably 1,500, further preferably 1,000, and further preferably 800. When the viscosity average degree of polymerization is equal to or less than the above upper limit, the surface active property is improved, and for example, various properties when used as a dispersant for suspension polymerization are improved. The viscosity average degree of polymerization is a value measured in accordance with JIS K6726: 1994. That is, it can be obtained by the following formula based on the intrinsic viscosity [η] (unit: liter / g), which is measured in water at 30° C. after PVA is re-saponified to a saponification degree of 99.5 mol % or more and purified.

[0086] Viscosity average degree of polymerization = ([η] × 10 4 / 8.29) (1 / 0.62)

[0087] PVA (A) can be produced by a production method comprising, for example, the steps of polymerizing a vinyl ester in the presence of an aliphatic unsaturated aldehyde and / or an aliphatic saturated aldehyde (step A); and saponifying the obtained vinyl ester polymer (step B).

[0088] In step A, vinyl ester is polymerized in the presence of aliphatic unsaturated aldehydes and / or aliphatic saturated aldehydes to obtain a vinyl ester polymer. As methods for polymerizing vinyl esters, known methods such as bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization can be cited. Among these methods, bulk polymerization under solvent-free conditions and solution polymerization using solvents such as alcohols are preferred. As the above-mentioned alcohol, alcohols with a carbon number of 3 or less are preferred, methanol, ethanol, n-propanol and isopropanol are more preferred, and methanol is further preferred. When the polymerization reaction is carried out by these methods, the reaction mode may also be any of intermittent and continuous. There is no particular limitation on the polymerization temperature when the polymerization reaction is carried out, and a range of 5°C or more and 200°C or less is appropriate.

[0089] Examples of the vinyl ester include vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pivalate, and vinyl versatate. Among them, vinyl acetate is preferred.

[0090] Examples of the polymerization initiator used in the polymerization reaction include azo initiators such as 2,2'-azobisisobutyronitrile, 2,2'-azobis(2,4-dimethylvaleronitrile), and 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile); and known polymerization initiators such as organic peroxide initiators such as benzoyl peroxide, n-propyl peroxycarbonate, and diisopropyl peroxydicarbonate. The amount of the polymerization initiator used is preferably 0.01 to 5% by mass relative to the vinyl ester used.

[0091] Specific examples and suitable examples of aliphatic unsaturated aldehydes are as described above. As aliphatic saturated aldehydes, acetaldehyde, propionaldehyde, butyraldehyde, 1-pentanal, 1-hexanal, 1-octanal, 1-nonanal, 1-decanal, etc. can be listed, preferably acetaldehyde. Aliphatic unsaturated aldehydes and aliphatic saturated aldehydes can be used in one or more kinds. As the amount of aliphatic unsaturated aldehydes and aliphatic saturated aldehydes, for example, it is preferably 0.1 to 10% by mass relative to vinyl ester. During the polymerization of vinyl ester, other chain transfer agents other than aliphatic unsaturated aldehydes and aliphatic saturated aldehydes can coexist. As other chain transfer agents, ketones such as acetone and methyl ethyl ketone; mercaptans such as 2-hydroxyethanethiol and 3-mercaptopropionic acid; thiocarboxylic acids such as thioacetic acid; halogenated hydrocarbons such as trichloroethylene and perchloroethylene, etc.

[0092] When the vinyl ester is polymerized, a copolymerizable monomer may be further copolymerized within a range that does not impair the gist of the present invention. Examples of the copolymerizable monomer include the monomers described above as monomers that provide other structural units.

[0093] In step B, the vinyl ester polymer obtained in step A is saponified using an alkali catalyst or an acid catalyst, for example, in an alcohol solution to obtain PVA. The saponification reaction of the vinyl ester polymer can be applied to an alcohol decomposition or hydrolysis reaction using an alkaline catalyst such as sodium hydroxide, potassium hydroxide, sodium methoxide, or an acidic catalyst such as p-toluenesulfonic acid. As the solvent used in the saponification reaction, alcohols such as methanol and ethanol; esters such as methyl acetate and ethyl acetate; ketones such as acetone and methyl ethyl ketone; aromatic hydrocarbons such as benzene and toluene, etc. can be listed. They can be used alone or in combination of two or more. Among these, it is simple to use methanol or a mixed solution of methanol and methyl acetate as a solvent and to carry out the saponification reaction in the presence of sodium hydroxide as an alkaline catalyst, so it is preferred. Saponification can be carried out using a belt reactor, a kneader reactor, a tower reactor, etc.

[0094] A resin solid material containing PVA is obtained by going through step B. In this production method, as steps after step B, there may be further steps of: washing the resin solid material containing PVA; drying the resin solid material containing PVA; heat treating the resin solid material containing PVA, etc.

[0095] (Amphiphilic substance (B))

[0096] The amphiphilic substance (B) contained in the composition of the present invention comprises at least one selected from a surfactant and a vinyl alcohol polymer having a saponification degree of less than 60 mol%. Here, the amphiphilic substance refers to a substance (polymer, compound, etc.) having a hydrophilic group and a hydrophobic group in the same molecule. The amphiphilic substance (B) is preferably at least one selected from a surfactant and a vinyl alcohol polymer having a saponification degree of less than 60 mol%.

[0097] As described above, in suspension polymerization, when PVA is used as a dispersant for suspension polymerization, an operation called hot charging is sometimes performed in which an aqueous solution of PVA is put into a polymerization system solution prepared at a high temperature of 60°C or above. When hot charging is performed using an aqueous solution containing a dispersant for suspension polymerization in the past, aggregation of PVA sometimes occurs, and as a result, coarse polymer particles are sometimes obtained. The mechanism of aggregation of PVA is still unclear, but it can be inferred that if an aqueous solution containing PVA that is affinity with water molecules by means of electrostatic interaction and hydrogen bonds is instantly mixed with a high temperature and polarity different from that of the PVA aqueous solution, the affinity loses equilibrium and aggregation of PVA occurs. In addition, in the previous suspension polymerization using PVA as a dispersant, under high temperature conditions above 60°C, there is a tendency for the function of PVA as a dispersant to decrease, and a dispersant that is stable under high temperature conditions above 60°C is sought. The present inventors have found that by combining PVA (A) with an amphiphilic substance (B), the aggregation of PVA (A) can be suppressed when the aqueous solution of PVA (A) is hot-charged, and even when suspension polymerization is carried out at a high temperature of 60°C or higher, polymer particles with a small average particle size, few coarse particles, and good plasticizer absorption can be obtained. The mechanism for obtaining such an effect is still uncertain, but it can be inferred that the amphiphilic substance (B) suppresses the rapid loss of affinity between substances and stabilizes the colloidal particles, resulting in the suppression of the aggregation of PVA (A).

[0098] As the content of the amphiphilic substance (B) in the composition of the present invention, relative to PVA (A) (100% by mass), it is preferably 0.001% by mass or more and 30% by mass or less, more preferably 0.01% by mass or more and 20% by mass or less, further preferably 0.1% by mass or more and 10% by mass or less, and further preferably 1.0% by mass or more and 5.0% by mass or less. In addition, when the amphiphilic substance (B) includes a plurality of compounds, the total content of the compounds is preferably within the above range. By making the content of the amphiphilic substance (B) within the above range, the effect of suppressing the aggregation of the molecules of PVA (A) themselves is improved, and the stability of the suspension polymerization is more excellent.

[0099] As the surfactant, an anionic surfactant and a nonionic surfactant are preferred, and an anionic surfactant is more preferred. The surfactant may be used alone or in combination of two or more.

[0100] As anionic surfactants, for example, alkyl sulfates, alkyl sulfonates, alkylbenzene sulfonates, polyoxyalkylene alkyl ether sulfates (alkyl ether sulfates), polyoxyalkylene alkyl ether carboxylates (alkyl ether acetates), α-olefin sulfonates, phosphates, acylamino acid salts, acyl taurates, acyl lactylates, soaps (higher fatty acids), alkyl sulfosuccinates, acyl hydrolyzed collagen salts and acyl hydroxyethanesulfonates, etc., preferably acylamino acid salts and acyl taurates, more preferably acylamino acid salts. Anionic surfactants are preferably metal salts, more preferably alkali metal salts, and further preferably sodium salts. As acylamino acid salts, sodium lauroyl sarcosinate, sodium lauroyl methylalanine, sodium cocoyl glutamate, potassium cocoyl glycinate, etc., are listed, preferably sodium lauroyl sarcosinate. As acyl taurates, sodium lauroyl taurate, etc., can be listed. Anionic surfactants can be used only one, or two or more can be used in combination.

[0101] Examples of the nonionic surfactant include polyoxyethylene lauryl ether, oleyl ether, octylphenyl ether, nonylphenyl ether, polyoxyethylene monostearate, palmitate, and oleate, etc. The nonionic surfactant may be used alone or in combination of two or more.

[0102] The vinyl alcohol polymer having a saponification degree of less than 60 mol% is preferably a vinyl alcohol polymer having a saponification degree of 40 mol% or less. The lower limit of the saponification degree of the vinyl alcohol polymer having a saponification degree of less than 60 mol% is preferably 10 mol%, more preferably 20 mol%, and further preferably 30 mol%.

[0103] The vinyl alcohol polymer having a saponification degree of less than 60 mol% is preferably an anion-modified vinyl alcohol polymer. Examples of anion-modified vinyl alcohol polymers include carboxylic acid-modified vinyl alcohol polymers and phosphonic acid-modified vinyl alcohol polymers, and more preferably carboxylic acid-modified vinyl alcohol polymers. The carboxyl group of the carboxylic acid-modified vinyl alcohol polymer may be in a salt state.

[0104] The viscosity average degree of polymerization of the vinyl alcohol polymer having a saponification degree of less than 60 mol% is, for example, preferably 50 or more and 500 or less, and more preferably 100 or more and 300 or less. By setting the viscosity average degree of polymerization of the vinyl alcohol polymer having a saponification degree of less than 60 mol% within the above range, various properties when the composition of the present invention is used as a dispersant for suspension polymerization are improved.

[0105] In the amphiphilic substance (B), the mass ratio of the hydrophobic group to the hydrophilic group (hydrophobic group:hydrophilic group) is preferably 4:1 or more and 1:4 or less.

[0106] The composition of the present invention may also include other components except PVA (A) and amphiphilic substance (B). As other components, solvents such as water, alcohol, resins except PVA (A) and amphiphilic substance (B), surfactants, additives such as plasticizers, and various compounds used in manufacturing can be listed. The composition of the present invention can be in the form of solutions such as aqueous solutions, or in the form of powders. As the lower limit of the total amount of PVA (A) and amphiphilic substance (B) in the non-volatile component in the composition of the present invention, it is sometimes preferably 30% by mass, more preferably 50% by mass, and further preferably 70% by mass, 90% by mass or 99% by mass. The upper limit of the total amount of PVA (A) and amphiphilic substance (B) in the non-volatile component in the composition of the present invention can be 100% by mass. Non-volatile component refers to the component except solvent.

[0107] The composition of the present invention can be used for various purposes such as raw materials for films and fibers, additives for paper processing and fiber processing, adhesives, dispersants for emulsion polymerization and suspension polymerization, binders for inorganic substances, etc., which are the same as the conventionally known PVA. Among these, as described in detail later, it can be particularly suitably used as a dispersant for suspension polymerization such as vinyl compounds.

[0108] <Dispersant for suspension polymerization>

[0109] The dispersant for suspension polymerization of the present invention (hereinafter also referred to as "dispersant") comprises the composition of the present invention described above. Dispersant refers to an additive used in order to improve the dispersibility of monomers, control the particle size of the obtained polymer particles, etc. during suspension polymerization. The lower limit of the total amount of PVA (A) and amphiphilic substances (B) in the non-volatile component of the dispersant of the present invention is sometimes preferably 30% by mass, more preferably 50% by mass, and further preferably 70% by mass, 90% by mass or 99% by mass. The upper limit of the total amount of PVA (A) and amphiphilic substances (B) in the non-volatile component of the dispersant of the present invention can be 100% by mass. The non-volatile components other than PVA (A) and amphiphilic substances (B) that can be included in the dispersant of the present invention can include additives such as resins, surfactants, plasticizers, and various compounds used in the manufacture, etc., other than PVA (A) and amphiphilic substances (B). In one embodiment of the present invention, the content of the volatile components in the dispersant can be less than 20% by mass, can be less than 15% by mass, and can be less than 10% by mass. As volatile components that may be contained in the dispersant of the present invention, alcohol, water, etc. may be cited. That is, the dispersant of the present invention may be substantially composed of PVA (A) and an amphiphilic substance (B). The shape of the dispersant of the present invention is not particularly limited, and may be a powder. The dispersant of the present invention may be a solution such as an aqueous solution. When the dispersant of the present invention is a solution, the content of the volatile components in the dispersant may be, for example, 50% by mass or more and 99.9% by mass.

[0110] One embodiment of the dispersant of the present invention may be a dispersant for suspension polymerization, which is formed by combining PVA (A) and an amphiphilic substance (B). A method for manufacturing a dispersant having a step of mixing PVA (A) with an amphiphilic substance (B), and a dispersant obtained by mixing PVA (A) with an amphiphilic substance (B) are also embodiments of the present invention. The dispersants of these embodiments may further include other components in addition to PVA (A) and the amphiphilic substance (B).

[0111] The dispersant of the present invention is suitable as a dispersant for suspension polymerization of vinyl compounds. By using the dispersant of the present invention, the polymerization stability under high temperature conditions is improved, and polymer particles with a small average particle size and few coarse particles can be effectively obtained. In addition, the polymer particles obtained by suspension polymerization using the dispersant of the present invention also have good plasticizer absorption.

[0112] <Method for producing vinyl polymer>

[0113] The method for producing a vinyl polymer of the present invention comprises a step of polymerizing a vinyl compound in the presence of PVA (A) and an amphiphilic substance (B). The method is the same as a known method for producing a vinyl polymer except that PVA (A) and an amphiphilic substance (B) are used as dispersants.

[0114] In the method for producing the vinyl polymer of the present invention, the vinyl compound is usually subjected to suspension polymerization in an aqueous medium. As the aqueous medium, in addition to pure water, an aqueous solution containing various additives or an aqueous medium containing other organic solvents can also be used. The method for producing the vinyl polymer of the present invention can include a step of adding PVA (A) and an amphiphilic substance (B) to the aqueous medium.

[0115] When suspension polymerization of a vinyl compound is carried out, the amount of PVA (A) added is not particularly limited, but is sometimes preferably 100 ppm or more and 50,000 ppm or less, more preferably 200 ppm or more and 20,000 ppm or less, further preferably 10,000 ppm or less, 5,000 ppm or less, or 2,000 ppm or less, based on mass, relative to the vinyl compound.

[0116] When performing suspension polymerization of vinyl compounds, the amount of the amphiphilic substance (B) added is not particularly limited. For example, according to the preferred amount of PVA (A), the amount of the amphiphilic substance (B) added is preferably 0.001% by mass or more and 30% by mass or less, more preferably 0.01% by mass or more and 20% by mass or less, further preferably 0.1% by mass or more and 10% by mass or less, and further preferably 1.0% by mass or more and 5.0% by mass or less. By making the content of the amphiphilic substance (B) within the above range, the effect of suppressing the aggregation of the molecules of PVA (A) itself is improved, and the stability of the suspension polymerization is more excellent.

[0117] In the suspension polymerization system of the vinyl compound, PVA (A) and the amphiphilic substance (B) may be mixed in advance and supplied, or PVA (A) and the amphiphilic substance (B) may be supplied separately.

[0118] PVA (A) and the amphiphilic substance (B) can be processed in the form of powders, for example, or can be mixed with a medium such as water and processed in the form of a solution. That is, when PVA (A) and the amphiphilic substance (B) are mixed, for example, a powdery substance obtained by mixing powdery PVA (A) and powdery amphiphilic substance (B) can be prepared, and a solution obtained by mixing a solution of PVA (A) with a solution of amphiphilic substance (B) can be prepared, a solution obtained by adding a powdery amphiphilic substance (B) to a solution of PVA (A) can be prepared, and these powdery substances and solutions can be put into a polymerization tank, etc. The powder or solution of PVA (A) and the powder or solution of the amphiphilic substance (B) can be separately put into a polymerization tank, etc.

[0119] PVA (A) and the amphiphilic substance (B) may be the dispersant of the present invention. The dispersant of the present invention may be used alone or in combination with other dispersants.

[0120] As the polymerization initiator used in the method for producing the vinyl polymer of the present invention, polymerization initiators conventionally used for polymerization of vinyl compounds can be used. Specifically, polymerization initiators similar to those exemplified in the polymerization of the above-mentioned vinyl ester monomers can be used.

[0121] In the manufacture method of the vinyl polymer of the present invention, other various additives can be added to the polymerization system as required. As additives, polymerization regulators such as aldehydes, halogenated hydrocarbons, mercaptans, polymerization inhibitors such as phenol compounds, sulfur compounds, N-oxide compounds, etc. can be listed. In addition, pH adjusting agents, antioxidants, crosslinking agents, etc. can also be added. It is also possible to use a variety of the above-mentioned additives in combination.

[0122] As the vinyl compounds that can be subjected to suspension polymerization in the method for producing the vinyl polymer of the present invention, there can be listed halogenated vinyls such as vinyl chloride; vinyl esters such as vinyl acetate and vinyl propionate; acrylic acid, methacrylic acid, their esters and salts; maleic acid, fumaric acid, their esters and anhydrides; styrene; acrylonitrile; vinylidene chloride; vinyl ether, etc. Among these vinyl compounds, vinyl chloride is preferred. The method for producing the vinyl polymer of the present invention is particularly suitable for suspension polymerization of vinyl chloride alone or suspension polymerization of vinyl chloride together with a monomer copolymerizable with vinyl chloride. As the monomer copolymerizable with vinyl chloride, there can be listed vinyl esters such as vinyl acetate and vinyl propionate; (meth)acrylates 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 ether, etc.

[0123] In the method for producing vinyl polymers of the present invention, when the vinyl compound is subjected to suspension polymerization, the charging ratio of each component, the polymerization temperature, the polymerization time, etc. can be set to the same conditions as those used in the suspension polymerization of vinyl compounds such as vinyl chloride in the past. It should be noted that the method for producing vinyl polymers of the present invention can also be suitably applied to suspension polymerization at a high temperature of more than 60°C (for example, more than 60°C and less than 80°C), and the polymerization temperature can be lower than 60°C. The polymerization temperature can be, for example, more than 30°C and less than 80°C, more than 40°C and less than 75°C, or more than 50°C and less than 70°C. In addition, there is no limitation on the charging order and ratio of vinyl compounds, polymerization initiators, dispersants, aqueous media and other additives.

[0124] According to the method for producing a vinyl polymer of the present invention, even when the polymerization temperature is high, vinyl polymer particles having high stability during polymerization, a small average particle size and few coarse particles can be effectively obtained. In addition, the vinyl polymer particles obtained by the method for producing the present invention also have good plasticizer absorption.

[0125] Example

[0126] The present invention will be specifically described by the following examples, but the present invention is not limited to these examples at all. It should be noted that the following are the respective measurement methods used in the following examples and comparative examples.

[0127] [Viscosity average degree of polymerization of PVA]

[0128] The viscosity average polymerization degree of PVA was measured in accordance with JIS K6726: 1994. Specifically, when the saponification degree of PVA is less than 99.5 mol%, the viscosity average polymerization degree is determined by the following formula using the intrinsic viscosity [η] (liter / g) obtained by measuring the saponification degree of PVA in water at 30°C until the saponification degree reaches 99.5 mol% or more.

[0129] Viscosity average degree of polymerization = ([η] × 10 4 / 8.29) (1 / 0.62)

[0130] [Saponification degree of PVA]

[0131] The saponification degree of PVA was determined by the method described in JIS K6726:1994.

[0132] [Carbonyl content of PVA]

[0133] conduct 1H-NMR measurement, calculate the content of carbonyl group of PVA. The sample was subjected to Soxhlet cleaning for 10 hours using methyl acetate and vacuum dried at 40 ° C for 16 hours to remove impurities and then provided for measurement. Using a sample prepared in the form of 1 mass % DMSO-d6 solution (adding 0.03 mass % tetramethylsilane as internal standard), it was measured at 400 MHz (80 ° C, cumulative 256 times). Among the methines in the main chain of PVA, CH connected to the OH group has a peak at 3.8 to 4.0 ppm (integral value [M]), and CH connected to the OAc group has a peak at 4.2 to 4.6 ppm (integral value [N]). In addition, the methyl group adjacent to the carbonyl group belongs to 2.08 to 2.22 ppm (integral value [O]), and the methylene group adjacent to the methine group connected to the OH group or OAc group and adjacent to the formyl group or carbonyl group belongs to 2.3 to 2.5 ppm (integral value [P]). Furthermore, the peak of protons constituting the formyl group appears at 9.5 to 10.0 ppm (integral value [Q]). The carbonyl group content of PVA is calculated by the following formula based on the structural units (vinyl alcohol units and vinyl ester units) derived from the vinyl alcohol monomer.

[0134] Carbonyl content (mol%) = {([O] / 3+[P] / 2-[Q]) / ([M]+[N])]×100

[0135] [Alkenyl content of PVA]

[0136] conduct 1 H-NMR measurement, calculate the content of alkenyl (vinyl) in PVA. The sample was subjected to Soxhlet cleaning with methyl acetate for 10 hours and vacuum dried at 40°C for 16 hours to remove impurities before being measured. A sample prepared in the form of a 1% by mass DMSO-d6 solution (0.03% by mass of tetramethylsilane was added as an internal standard) was measured at 400MHz (80°C, cumulative 256 times). Among the methyl groups in the main chain of PVA, the CH connected to the OH group has a peak at 3.8 to 4.0ppm (integral value [M]), and the CH connected to the OAc group has a peak at 4.2 to 4.6ppm (integral value [N]). In addition, the peak of the proton derived from the alkenyl (vinyl) group belongs to 5.7 to 6.0ppm (integral value [R]). The content of the alkenyl group of PVA is calculated relative to the value of the structural unit (vinyl alcohol unit and vinyl ester unit) derived from the vinyl alcohol monomer, and is obtained using the following formula.

[0137] Alkenyl content (mol%) = {[R] / ([M]+[N])}×100

[0138] [Formyl content of PVA]

[0139] conduct1 H-NMR measurement, calculate the content of formyl group in PVA. The sample was subjected to Soxhlet cleaning with methyl acetate for 10 hours and vacuum dried at 40°C for 16 hours to remove impurities before being measured. A sample prepared in the form of a 1% by mass DMSO-d6 solution (with 0.03% by mass tetramethylsilane added as an internal standard) was measured at 400 MHz (80°C, cumulative 256 times). Among the methyl groups in the main chain of PVA, the CH connected to the OH group has a peak at 3.8 to 4.0 ppm (integral value [M]), and the CH connected to the OAc group has a peak at 4.2 to 4.6 ppm (integral value [N]). The peak derived from the proton of the formyl group belongs to 9.5 to 10.0 ppm (integral value [Q]). The content of formyl group in PVA is calculated by the following formula relative to the value of the structural unit (vinyl alcohol unit and vinyl ester unit) derived from the vinyl alcohol monomer.

[0140] Formyl content (mol%) = {[Q] / ([M]+[N])}×100

[0141] [R in the formula (2) of PVA 1 The content of alkyl groups]

[0142] conduct 1 H-NMR measurement, calculation of R in formula (2) in PVA 1 The content of the group is an alkyl group. The sample was subjected to Soxhlet cleaning with methyl acetate for 10 hours and vacuum dried at 40°C for 16 hours to remove impurities before being measured. The sample was prepared in the form of a 1% by mass DMSO-d6 solution (with 0.03% by mass tetramethylsilane added as an internal standard) and measured at 400 MHz (80°C, cumulative 256 times). Among the methyl groups in the main chain of PVA, the CH connected to the OH group has a peak at 3.8 to 4.0 ppm (integral value [M]), and the CH connected to the OAc group has a peak at 4.2 to 4.6 ppm (integral value [N]). The peak of the proton of the methyl group of the alkyl group derived from formula (2) belongs to 2.08 to 2.22 ppm (integral value [T]) or 0.7 to 1.0 ppm (integral value [S]). The content of the alkyl group is calculated relative to the value of the structural unit (vinyl alcohol unit and vinyl ester unit) derived from the vinyl alcohol monomer using the following formula. The content of the alkyl group is equivalent to R in the formula (2) in PVA. 1 The content of the alkyl group.

[0143] Alkyl content (mol%) = {([T] / 3+[S] / 3) / ([M]+[N])}×100

[0144] ·Manufacturing of PVA(A)

[0145] [Manufacturing Example 1] (Manufacturing of PVA-1)

[0146] 1600 parts by mass of vinyl acetate, 17.5 parts by mass of 7-octenal and 15 parts by mass of acetaldehyde were added to a reactor equipped with a stirrer, a reflux condenser, a nitrogen inlet pipe and a polymerization initiator addition port, and the system was purged with nitrogen for 30 minutes while bubbling with nitrogen. The temperature of the reactor was started, and 1.5 parts by mass of 2,2'-azobisisobutyronitrile (AIBN) was added when the internal temperature reached 60°C to start polymerization. After polymerization at 60°C for 3 hours, the polymerization was stopped by cooling. The solid content concentration at the time of polymerization termination was 43.6% by mass and the polymerization rate was 45%. Then, methanol was added from time to time at 30°C under reduced pressure while removing the unreacted monomers to obtain a methanol solution of a vinyl ester polymer (concentration of 38.2% by mass). Next, 1.78 parts by mass of a 10% by mass methanol solution of sodium hydroxide, 0.88 parts by mass of ion exchange water, and 10 parts by mass of methyl acetate were added to 58.0 parts by mass of a methanol solution of a vinyl ester polymer prepared by further adding methanol to the methanol solution (34 parts by mass of the above polymer in the solution), and saponification was performed at 40°C (the above polymer concentration in the saponification solution was 30% by mass, the water content of the saponification solution was 1% by mass, and the molar ratio of sodium hydroxide to vinyl acetate units in the above polymer was 0.0128). About 15 minutes after the addition of the methanol solution of sodium hydroxide, a gel-like substance was generated, so it was crushed with a grinder and further left at 40°C for 1 hour to perform saponification. Thereafter, 160 parts by mass of methyl acetate and 40 parts by mass of methanol were added, and the mixture was left at 40°C for washing for 30 minutes. After repeating this washing operation twice, the liquid was removed, and the white solid thus obtained was vacuum dried at 40°C for 16 hours to obtain PVA-1 as PVA (A). Table 3 shows the physical properties of PVA-1.

[0147] [Manufacturing Examples 2 to 4] (Manufacturing of PVA-2 to 4)

[0148] PVA-2 to PVA-4 were prepared as PVA (A) by the same method as in Preparation Example 1 except that the type and amount of aldehyde used in polymerization, the amount of AIBN used, and the molar ratio of sodium hydroxide to vinyl acetate unit (NaOH molar ratio) in saponification were changed as shown in Table 1. The physical properties of PVA-2 to PVA-4 are shown in Table 3.

[0149] ·Production of amphiphilic substances (B) (PVA-5, 6)

[0150] [Production Example 5] (PVA-5)

[0151] 1120 parts by mass of vinyl acetate and 480 parts by mass of methanol were added to a 3L reaction tank equipped with a stirrer, a nitrogen inlet, an additive inlet, and an initiator addition port. After the temperature was raised to 60°C, the system was purged with nitrogen by bubbling with nitrogen for 30 minutes. A 50% solution of 3-mercaptopropionic acid (hereinafter referred to as 3-MPA) as a chain transfer agent dissolved in methanol was prepared, and nitrogen was purged by bubbling with nitrogen. The internal temperature of the above-mentioned reaction tank was adjusted to 60°C, and after adding 0.5 parts by mass of 3-MPA, 1.2 parts by mass of 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile) was added to start polymerization. During the polymerization, the polymerization temperature was maintained at 60°C, and a 50% methanol solution of 3-MPA was continuously added at 4 mL / hr in such a manner that 3-MPA became 5 parts by mass in the entire system. After 4 hours, when the polymerization rate reached 40%, the polymerization was stopped by cooling. Then, unreacted vinyl acetate is removed under reduced pressure to obtain a methanol solution of modified polyvinyl acetate (modified PVAc). In a manner where the alkali molar ratio (the number of moles of NaOH / the number of moles of vinyl ester units in modified PVAc) is 0.0042, a NaOH methanol solution (10% concentration) is added to the modified PVAc solution in which the concentration of the modified PVAc is adjusted to 27% by mass to carry out saponification. The water content of the saponified solution is adjusted to 1% by mass. By the above operation, as an amphiphilic substance (B), a polyvinyl alcohol polymer PVA-5 having a viscosity-average polymerization degree of 140, a saponification degree of 40 mol%, and a carboxyl group as an ionic group at the end is obtained. It should be noted that the determination of the polymerization degree of PVA-5 and the confirmation of the presence or absence of a carboxyl group at the end are carried out as follows. The modified PVAc methanol solution obtained previously after removing the unreacted vinyl acetate and before the saponification reaction was put into n-hexane three times to precipitate the modified PVAc, and the recovered modified PVAc was dissolved in acetone and purified by reprecipitation, and then dried under reduced pressure at 60°C to obtain a refined modified PVAc. The methanol solution of the refined modified PVAc was saponified at an alkali molar ratio of 0.2, and then Soxhlet extraction was performed with methanol for 3 days, followed by drying to obtain a refined modified PVA. The viscosity-average degree of polymerization of the modified PVA was measured according to JIS K6726:1994 as a conventional method, and it was 140. The modified PVA was dissolved in heavy water, and when nuclear magnetic resonance analysis was performed, it was confirmed that a carboxyl group (COONa group) existed at a single end in the molecule.

[0152] [Manufacturing Example 6] (Manufacturing of PVA-6)

[0153] A polyvinyl alcohol polymer PVA-6 having a viscosity average degree of polymerization of 200 and a saponification degree of 50 mol % was produced as an amphiphilic substance (B) by the same method as in Production Example 5, except that no chain transfer agent was used during polymerization, and the amounts of vinyl acetate, methanol and AIBN, the polymerization rate, the concentration of the vinyl ester polymer (modified PVAc) during saponification, and the molar ratio of sodium hydroxide to vinyl acetate units (NaOH molar ratio) were changed as shown in Table 2.

[0154] [Example 1]

[0155] A 4 mass % aqueous solution of PVA-1 and a 30 mass % aqueous solution of sodium lauroyl sarcosinate (manufactured by Kawaken Fine Chemicals, "SOYPON (registered trademark) SLP") as an amphiphilic substance (B) were mixed at a mass ratio of 750:1 under the condition of 25° C. to obtain an aqueous solution of a composition having a content of 1 mass % of sodium lauroyl sarcosinate relative to PVA-1 (100 mass %).

[0156] [Examples 2 to 10, Comparative Examples 1 to 3]

[0157] Except that the type of PVA (A) used and the type and amount of the amphiphilic substance (B) were changed as shown in Table 3, the same method as in Example 1 was used to obtain compositions (aqueous solutions) of Examples 2 to 10 and Comparative Examples 1 to 3.

[0158] [evaluate]

[0159] Each composition obtained in Examples 1 to 10 and Comparative Examples 1 to 3 was used as a dispersant for suspension polymerization, and suspension polymerization of vinyl chloride was carried out by the following method. Next, the average particle size, amount of coarse particles, and plasticizer absorption of the obtained vinyl chloride polymer particles were evaluated. The evaluation results are shown in Table 3.

[0160] (Suspension Polymerization of Vinyl Chloride)

[0161] From each composition (aqueous solution) obtained by the examples and comparative examples, the solid content of the composition is taken in an amount of 1000 ppm relative to the vinyl chloride described later, and deionized water is added to the solution taken to dilute it to obtain a dispersant aqueous solution. Next, 100 parts by mass of the dispersant aqueous solution is put into an autoclave with a capacity of 5L. Next, deionized water is added in a manner that the total amount of deionized water becomes 1300 parts by mass. Next, 1.07 parts by mass of a 70% toluene solution of di(2-ethylhexyl) peroxydicarbonate is put into the autoclave. Degas until the pressure in the autoclave reaches 0.0067MPa to remove oxygen. Thereafter, 800 parts by mass of vinyl chloride are put in, the contents in the autoclave are heated to 65°C, and polymerization is started under stirring. The pressure in the autoclave at the start of polymerization is 1.02MPa. After 2.5 hours from the start of polymerization, the polymerization is stopped at the moment when the pressure in the autoclave reaches 0.70MPa, and unreacted vinyl chloride is removed. Thereafter, the polymerization slurry was taken out and dried at 65° C. for 17 hours to obtain vinyl chloride polymer particles.

[0162] (1) Average particle size of vinyl chloride polymer particles

[0163] The obtained vinyl chloride polymer particles were subjected to dry sieve analysis to measure the particle size distribution using a metal mesh based on a Taylor sieve. The results were plotted on a Rosin-Rammler distribution to calculate the average particle size (d p50 ; median particle size).

[0164] (2) Amount of coarse particles of vinyl chloride polymer particles

[0165] The content of the obtained vinyl chloride polymer particles that did not pass through a 250 μm sieve (60 mesh in JIS standard sieve conversion) was determined in mass %. A smaller value means fewer coarse particles and better polymerization stability of the dispersant used.

[0166] (3) Plasticizer absorption of vinyl chloride polymer particles (CPA)

[0167] Measure the mass of a 5mL syringe containing 0.02g of cotton wool (denoted as X(g)), add 0.5g of vinyl chloride polymer particles into it and measure the mass (denoted as Y(g)). Add 1g of dioctyl phthalate (DOP) into it and let it stand for 15 minutes. Thereafter, centrifuge at 3000rpm for 40 minutes to remove the unabsorbed DOP, and measure the mass after removal (denoted as Z(g)). In addition, the plasticizer absorption (%) of the vinyl chloride polymer particles is calculated according to the following calculation formula. The higher the plasticizer absorption, the easier it is to process, mainly because it is less likely to produce defects in appearance such as particles when processed into sheets. In this evaluation, when the plasticizer absorption is 20.3% or more, the plasticizer absorption is judged to be good.

[0168] Plasticizer absorption (%) = 100 × [{(ZX) / (YX)}-1]

[0169]

[0170]

[0171]

[0172] As shown in Table 3, when the compositions of Examples 1 to 10 were used as dispersants for suspension polymerization, even when suspension polymerization was carried out under high temperature conditions such as 65° C., vinyl chloride polymer particles having a small average particle size, few coarse particles, and good plasticizer absorption were obtained. It was confirmed that each composition of Examples 1 to 10 was useful as a dispersant for suspension polymerization.

[0173] On the other hand, in Comparative Examples 1 to 3, the vinyl chloride polymer particles obtained by suspension polymerization under high temperature conditions had a large average particle size and many coarse particles, and also showed low plasticizer absorption.

[0174] Industrial Applicability

[0175] The composition of the present invention can be used as a dispersant or the like in suspension polymerization of a vinyl compound.

Claims

1. A composition comprising a vinyl alcohol polymer (A) and an amphiphilic substance (B), The vinyl alcohol polymer (A) is a vinyl alcohol polymer having a carbonyl group and having a saponification degree of 60 mol% or more. The amphiphilic substance (B) contains at least one selected from the group consisting of a surfactant and a vinyl alcohol polymer having a saponification degree of less than 60 mol %.

2. The composition according to claim 1, wherein The vinyl alcohol polymer (A) further has a formyl group and an alkenyl group.

3. The composition according to claim 1, wherein The vinyl alcohol polymer (A) has a structure including the carbonyl group and represented by the following formula (1). [Chemistry 1] In formula (1), m is an integer of 1 to 11.

4. The composition according to claim 1, wherein The vinyl alcohol polymer (A) has a group containing the carbonyl group and represented by the following formula (2) at the terminal of the polymer chain, [Chemistry 2] In formula (2), R 1 It is an alkenyl group or an alkyl group.

5. The composition according to claim 4, wherein In the formula (2), R 1 It is an alkenyl group having a methylene group at the terminal of the carbonyl side.

6. The composition according to claim 1, wherein The vinyl alcohol polymer (A) has tertiary carbon atoms.

7. The composition according to claim 1, wherein The vinyl alcohol polymer (A) has a structural unit derived from an aliphatic unsaturated aldehyde.

8. The composition according to claim 7, wherein The aliphatic unsaturated aldehyde has 3 to 14 carbon atoms.

9. The composition according to claim 7, wherein The aliphatic unsaturated aldehyde has a carbon-carbon double bond at the terminal end.

10. The composition according to any one of claims 1 to 9, wherein The amphiphilic substance (B) contains at least one selected from anionic surfactants and nonionic surfactants as the surfactant.

11. The composition according to claim 10, wherein The amphiphilic substance (B) contains at least one selected from acylamino acid salts and acyltaurates as the anionic surfactant.

12. The composition according to any one of claims 1 to 9, wherein The amphiphilic substance (B) includes an anion-modified vinyl alcohol polymer having a saponification degree of less than 60 mol % as the vinyl alcohol polymer having a saponification degree of less than 60 mol %.

13. The composition according to claim 12, wherein The amphiphilic substance (B) includes a carboxylic acid-modified vinyl alcohol polymer having a saponification degree of less than 60 mol % as the anion-modified vinyl alcohol polymer having a saponification degree of less than 60 mol %.

14. The composition according to any one of claims 1 to 9, wherein The content of the amphiphilic substance (B) is 0.001% by mass or more and 30% by mass or less based on the vinyl alcohol polymer (A).

15. A dispersant for suspension polymerization, comprising the composition according to any one of claims 1 to 9.

16. A method for producing a vinyl polymer, comprising: a step of polymerizing a vinyl compound in the presence of a vinyl alcohol polymer (A) and an amphiphilic substance (B); The vinyl alcohol polymer (A) is a vinyl alcohol polymer having a carbonyl group and having a saponification degree of 60 mol% or more. The amphiphilic substance (B) contains at least one selected from the group consisting of a surfactant and a vinyl alcohol polymer having a saponification degree of less than 60 mol %.

Images