Dispersant, and method for producing vinyl compound polymer

Abstract

To provide dispersants and the like that deliver excellent performance as dispersants for suspension polymerization.SOLUTION: A dispersant comprises a solution containing a vinyl alcohol polymer (A) at a concentration of 15 mass% or more, with a saponification degree of 30 mol% or more to 80 mol% or less, a polymerization degree of 100 or more to 700 or less, and a block character of the vinyl ester unit of 0.6 or less. The solution contains at least one selected from the group consisting of acids with an acid dissociation constant (pKa) of 0 or more and 6.0 or less in water, their salts, and their anions.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a solution, a dispersant, a method for producing a vinyl compound polymer, and a method for producing a solution. [Background technology]

[0002] Vinyl alcohol polymers (hereinafter, also referred to as "PVA") are known as water-soluble synthetic polymers. PVA is used in a variety of applications, including as a raw material for films and fibers, an additive for paper and fiber processing, an adhesive, a dispersant (also called a dispersion stabilizer, etc.) for emulsion polymerization and suspension polymerization, and a binder for inorganic materials.

[0003] PVA may be stored, distributed, sold, used, etc., in the form of a solution. In general, the solubility of PVA in water, etc. varies depending on the degree of saponification, the degree of polymerization, the modified species introduced, etc. When storing or using PVA as a solution, it is required that the solution be highly concentrated, low viscous, and highly stable, particularly in terms of productivity and ease of handling. Here, in the prior art, it is known that even PVA that is insoluble in water alone can become soluble in water by combining it with a specific surfactant (see Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 53-133252 Summary of the Invention [Problem to be solved by the invention]

[0005] By using a specific surfactant, it is possible to increase the solubility of PVA and increase the stability of the resulting solution as described above. However, since the surfactant is influential, it has not been possible to obtain a solution that is both stable and has excellent properties as a dispersant for suspension polymerization. On the other hand, according to the findings of the inventors, it is possible to prepare a PVA solution that is highly stable and has good performance as a dispersant for suspension polymerization by using a solvent with a high alcohol content without using a surfactant. However, the handling form of a solution containing a solvent with a high alcohol content may be limited due to waste liquid treatment, environmental impact, etc.

[0006] An object of the present invention is to provide a solution which is highly stable regardless of the alcohol content and has excellent performance as a dispersant for suspension polymerization, and a method for producing such a solution. Another object of the present invention is to provide a dispersant having excellent performance as a dispersant for suspension polymerization, and a method for producing a vinyl compound polymer using such a dispersant. [Means for solving the problem]

[0007] The above objectives are: [1] A solution comprising a vinyl alcohol polymer (A) having a degree of saponification of 30 mol % or more and 80 mol % or less and a degree of polymerization of 100 or more and 700 or less, a compound (B) and an alcohol (C), wherein the compound (B) is a compound represented by the following formula (1): [ka] (In formula (1), X is an oxygen atom, a group represented by the following formula (2), or a group represented by the following formula (3). Y is a group having 1 to 10 carbon atoms. Z is one selected from the group consisting of a carboxy group, a sulfo group, a phosphate group, salts thereof, and anions thereof. R 1 is an acyl group or a hydrocarbon group. [ka] [ka] (In formula (2) and formula (3), R 2 , R 3 and R 4 are each independently a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or a bond bonded to Y. * is a bond.) [2] A solution of [1], in which the block character of the vinyl ester unit in the vinyl alcohol polymer (A) is 0.4 or more and 0.6 or less; [3] A solution of [1] or [2] having a content of the vinyl alcohol polymer (A) of 15 mass% or more; [4] A solution of any one of [1] to [3], in which the content of compound (B) is 0.5% by mass or more and 10% by mass or less; [5] A solution of any of [1] to [4], in which the content of alcohol (C) is 5% by mass or more and 80% by mass or less; [6] A solution of any of [1] to [5], wherein the alcohol (C) content is less than 20 mass%; [7] A solution of any of [1] to [6], in which the content of compound (B) is 0.5% by mass or more and 4% by mass or less, and the content of alcohol (C) is 5% by mass or more and 15% by mass or less; [8] A dispersing agent comprising: a vinyl alcohol polymer (A) having a degree of saponification of 30 mol % or more and 80 mol % or less and a degree of polymerization of 100 or more and 700 or less; and a compound (B), wherein the compound (B) is a compound represented by the following formula (1): [ka] (In formula (1), X is an oxygen atom, a group represented by the following formula (2), or a group represented by the following formula (3). Y is a group having 1 to 10 carbon atoms. Z is one selected from the group consisting of a carboxy group, a sulfo group, a phosphate group, salts thereof, and anions thereof. R 1 is an acyl group or a hydrocarbon group. [ka] [ka] (In formula (2) and formula (3), R 2 , R 3 and R 4 are each independently a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or a bond bonded to Y. * is a bond.) [9] A method for producing a vinyl compound polymer, comprising a step of polymerizing a vinyl compound in the presence of the dispersing agent according to [8];

[10] A method for producing a solution, comprising a step of adding a vinyl alcohol polymer (A) having a degree of saponification of 30 mol % or more and 80 mol % or less and a degree of polymerization of 100 or more and 700 or less to a liquid containing a compound (B) represented by the following formula (1) and an alcohol (C) in a plurality of portions: [ka] (In formula (1), X is an oxygen atom, a group represented by the following formula (2), or a group represented by the following formula (3). Y is a group having 1 to 10 carbon atoms. Z is one selected from the group consisting of a carboxy group, a sulfo group, a phosphate group, salts thereof, and anions thereof. R 1 is an acyl group or a hydrocarbon group. [ka] [ka] (In formula (2) and formula (3), R 2 , R 3 and R 4 are each independently a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or a bond bonded to Y. * is a bond.)

[11] A dispersant which is a solution containing a vinyl alcohol polymer (A) having a degree of saponification of 30 mol % or more and 80 mol % or less, a degree of polymerization of 100 or more and 700 or less, and a block character of a vinyl ester unit of 0.6 or less, at a concentration of 15 mass % or more;

[12] The dispersant according to

[11] , wherein the solution contains at least one selected from the group consisting of an acid having an acid dissociation constant (pKa) in water of 0 to 6.0, a salt thereof, and an anion thereof;

[13] A dispersant according to

[11] or

[12] , used in the polymerization of vinyl compounds;

[14] A method for producing a vinyl compound polymer, comprising: a preparation step of preparing a vinyl alcohol polymer (A) having a degree of saponification of 30 mol% or more and 80 mol% or less, a degree of polymerization of 100 or more and 700 or less, and a block character of a vinyl ester unit of 0.6 or less; and a polymerization step of polymerizing a vinyl compound in the presence of the vinyl alcohol polymer (A) to obtain vinyl compound polymer particles having an average particle size of 220 μm or less, wherein in the preparation step, a solution having a concentration of the vinyl alcohol polymer (A) of 15 mass% or more is prepared;

[15] The method for producing a vinyl compound polymer according to

[14] , wherein the solution in the preparation step contains at least one acid selected from the group consisting of an acid having an acid dissociation constant (pKa) in water of 0 to 6.0, a salt thereof, and an anion thereof;

[16] The method for producing a vinyl compound polymer according to

[14] or

[15] , wherein in the polymerization step, a solution having a concentration of the vinyl alcohol polymer (A) of 15 mass% or more is introduced into a polymerization reaction system of a vinyl compound;

[17] The method for producing a vinyl compound polymer according to

[14] or

[15] , wherein in the polymerization step, a solution having a concentration of the vinyl alcohol polymer (A) of 15 mass% or more is diluted and introduced into a polymerization reaction system of a vinyl compound; This is achieved by providing either Effect of the Invention

[0008] According to the present invention, it is possible to provide a solution which is highly stable regardless of the alcohol content and has excellent performance as a dispersant for suspension polymerization, and a method for producing such a solution. Furthermore, according to the present invention, it is possible to provide a dispersant having excellent performance as a dispersant for suspension polymerization, and a method for producing a vinyl compound polymer using such a dispersant. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] In this specification, a numerical range described using "to" means that the numerical range includes the numerical values ​​before and after "to" as the lower limit and upper limit.

[0010] <Solution> The solution according to one embodiment of the present invention contains a vinyl alcohol polymer (A) (hereinafter also referred to as "PVA (A)") having a degree of saponification of 30 mol % or more and 80 mol % or less and a degree of polymerization of 100 or more and 700 or less, a compound (B), and an alcohol (C), in which the compound (B) is a compound represented by the formula (1) described below.

[0011] The solution is highly stable regardless of the content of alcohol (C). The solution can be made to have a high concentration of PVA (A), low viscosity, and high stability by adjusting the composition ratio. Such a solution is particularly suitable in terms of productivity and handling. The content of alcohol (C) in the solution is not limited, and for example, by increasing the content of alcohol (C), a solution with particularly low viscosity can be prepared. On the other hand, by decreasing the content of alcohol (C), it is possible to improve the handling in waste liquid treatment, etc. In addition, the solution has excellent performance as a dispersant for suspension polymerization. Specifically, by using the solution as a dispersant in suspension polymerization, polymer particles with a small average particle size and few coarse particles can be efficiently obtained. In addition, the polymer particles obtained by suspension polymerization using the solution as a dispersant also have good plasticizer absorption.

[0012] The reason why the solution has the above-mentioned effect is not clear, but the following reasons are presumed. It is presumed that the compound (B) has a specific structure, and functions as a good surfactant, and the good dispersion state of PVA (A) in the solution is maintained, thereby increasing the stability of the solution. Furthermore, the solution contains alcohol (C), which increases the stability of the solution. It is also presumed that the acid dissociation constant of compound (B) is in an appropriate range due to the compound (B) having a specific structure, which affects the above-mentioned effect. That is, for example, in an environment close to neutral, compound (B) can increase the dispersion stability of PVA (A) by interacting with PVA (A). On the other hand, in the suspension polymerization system, which is usually in a weak acidic environment, compound (B) separates from PVA (A), and PVA (A) becomes less susceptible to the influence of compound (B), and it is considered that compound (B) functions sufficiently as a dispersant for suspension polymerization.

[0013] In this way, the solution can be suitably used as a dispersant by adding it to a suspension polymerization system when suspension polymerization is performed. In addition, since the solution is a liquid, when it is used as a dispersant for suspension polymerization, it is not necessary to dissolve the vinyl alcohol polymer, and it has advantages such as excellent handleability.

[0014] The solution may further contain other components in addition to the PVA (A), the compound (B) and the alcohol (C). Each component of the solution will be described in detail below.

[0015] (PVA(A)) PVA (A) is a polymer having a vinyl alcohol unit as a structural unit. PVA (A) is usually obtained by saponifying a vinyl ester polymer. PVA (A) is a PVA having a degree of saponification of 30 mol% or more and 80 mol% or less and a degree of polymerization of 100 or more and 700 or less. PVA (A) having such a degree of saponification and polymerization is usually low in solubility in water, and even if a solution is obtained, the stability is low and gelation, precipitation, etc. are likely to occur. In the solution according to one embodiment of the present invention, since it contains a compound (B) and an alcohol (C), the stability of the solution is high despite the inclusion of such a PVA (A).

[0016] The lower limit of the saponification degree of PVA (A) is 30 mol%, and may be 32 mol% or 34 mol%. The upper limit of the saponification degree of PVA (A) is 80 mol%, and may be 70 mol%, 60 mol%, 50 mol%, 45 mol%, or 40 mol%. When the saponification degree of PVA (A) is within the above range, the surface activity is optimized, and the performance as a dispersant for suspension polymerization can be improved. The saponification degree is a value measured by the method described in JIS K6726:1994.

[0017] The lower limit of the polymerization degree of PVA (A) is 100, and may be 130, 160, 190, or 210. When the polymerization degree is equal to or higher than the lower limit, the protective colloid property is enhanced, and when used as a dispersant for suspension polymerization, polymer particles having a smaller particle size can be produced. On the other hand, the upper limit of the polymerization degree is 700, and may be 600, 500, 400, or 300. When the polymerization degree is equal to or lower than the upper limit, the surface activity is enhanced, and when used as a dispersant for suspension polymerization, the plasticizer absorption ability of the obtained polymer particles is enhanced, and polymer particles having a smaller particle size can be produced. In addition, when the polymerization degree is equal to or lower than the upper limit, the viscosity of the solution tends to be low. The polymerization degree of PVA (A) means the viscosity average polymerization degree measured in accordance with JIS K6726:1994.

[0018] PVA (A) may have structural units other than vinyl alcohol units and vinyl ester units (hereinafter also referred to as "residual vinyl ester units"). Examples of monomers that give the other structural units include α-olefins such as ethylene, propylene, 1-butene, isobutene, 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 and N-ethylacrylamide; methacrylamide derivatives such as N-methylmethacrylamide and N-ethylmethacrylamide; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, and n-butyl vinyl ether; and hydroxyl groups such as ethylene glycol vinyl ether, 1,3-propanediol vinyl ether, and 1,4-butanediol vinyl ether. Containing vinyl ether; allyl acetate; allyl ether such as propyl allyl ether, butyl allyl ether, hexyl allyl ether; monomers having an oxyalkylene group; isopropenyl acetate; hydroxyl group-containing α-olefins such as 3-buten-1-ol, 4-penten-1-ol, 5-hexen-1-ol, 7-octen-1-ol, 9-decen-1-ol, 3-methyl-3-buten-1-ol; monomers having a silyl group such as vinyl trimethoxysilane, vinyl methyl dimethoxysilane, vinyl dimethyl methoxysilane, vinyl triethoxysilane, vinyl methyl diethoxysilane, vinyl dimethyl ethoxysilane, 3-(meth)acrylamidopropyl trimethoxysilane, 3-(meth)acrylamidopropyl triethoxysilane, etc. Among these, α-olefins, acrylic acid, methacrylic acid, acrylic acid esters, or methacrylic acid esters are preferred. In one embodiment of the present invention, it is preferred that the PVA (A) does not have a polyoxyethylene side chain, and in another embodiment, it is preferred that the PVA (A) does not contain a structural unit derived from a monomer having an oxyalkylene group.

[0019] The proportion of the other structural units in the total structural units in PVA (A) may be preferably 20 mol% or less, more preferably 15 mol% or less, 10 mol% or less, 5 mol% or less, or 1 mol% or less. On the other hand, the proportion of the other structural units may be, for example, 0.1 mol% or more, or 1 mol% or more.

[0020] As the PVA (A), one that has not been graft-copolymerized can be preferably used. However, the PVA (A) may be modified with one or more graft-copolymerizable monomers. The graft copolymerization can be carried out on at least one of a vinyl ester polymer and a PVA obtained by saponifying the vinyl ester polymer. Examples of the graft-copolymerizable monomer include unsaturated carboxylic acid or a derivative thereof; unsaturated sulfonic acid or a derivative thereof; and α-olefins having 2 to 30 carbon atoms. The ratio of the structural unit derived from the graft-copolymerizable monomer in the PVA (A) is preferably 5 mol % or less based on the total structural units in the PVA (A).

[0021] The block character of the vinyl ester unit in PVA(A) (hereinafter, also simply referred to as "block character") may be, for example, 0.3 or more and 0.8 or less, but preferably 0.4 or more and 0.6 or less. The lower limit of the block character may be 0.42 or 0.45. The upper limit of the block character may be 0.58, 0.55, or 0.53. When the block character is in the above range, the performance as a dispersant for suspension polymerization is improved due to good expression of the surface activity. Specifically, for example, polymer particles with better plasticizer absorption can be produced. On the other hand, when the block character is in the above-mentioned relatively low range, the water solubility and solution stability of PVA(A) usually tend to be low. Therefore, when the present invention is applied to PVA(A) having such a block character, the technical significance of improving the stability of the solution is great.

[0022] The block character of PVA is a numerical value that represents the distribution of residual esters (usually alkoxycarbonyl groups) and hydroxyl groups resulting from saponification of the esters, and takes a value between 0 and 2. 0 indicates that the residual esters or hydroxyl groups are distributed completely in blocks. As the value increases, the alternation increases, with 1 indicating that the residual esters and hydroxyl groups are present completely randomly, and 2 indicating that the residual esters and hydroxyl groups are present completely alternately. The above-mentioned residual esters refer to esters (-OC(=O)-Q (Q represents a hydrocarbon group other than the CH2=CH-OC(=O) moiety contained in the vinyl ester monomer)) contained in the vinyl ester units in the PVA obtained through saponification treatment. In other words, the block character is a numerical value that represents the distribution of vinyl ester units and vinyl alcohol units. The block character is 13 It can be determined by C-NMR measurement. When the PVA contains repeating units other than vinyl ester units and / or vinyl alcohol units, the block character is calculated for all the sites in the PVA where vinyl ester units and / or vinyl alcohol units are continuous.

[0023] The block character can be adjusted by the type of vinyl ester monomer, the presence or absence of a chain transfer agent, and the saponification conditions such as catalyst and solvent. For example, when saponification is performed using an alkali catalyst, PVA with a relatively high block character of 0.6 or less tends to be obtained. On the other hand, when saponification is performed using an acid catalyst, PVA with a relatively high randomness of 0.6 or more tends to be obtained.

[0024] The solution may contain one or more types of PVA (A).

[0025] The lower limit of the content of PVA (A) in the solution is preferably 15% by mass, more preferably 20% by mass, even more preferably 25% by mass, and even more preferably 30% by mass, 35% by mass, or 40% by mass. By making the content of PVA (A) equal to or more than the above lower limit, a high-concentration PVA solution can be obtained, which allows for efficient distribution, storage, and the like. In addition, by making the content of PVA (A) equal to or more than the above lower limit, the stability of the solution tends to be further improved. The upper limit of the content of PVA (A) may be 70% by mass, 60% by mass, 50% by mass, or 40% by mass. By making the content of PVA (A) equal to or less than the above upper limit, the viscosity of the solution can be reduced, and the like.

[0026] (Production method of PVA(A)) PVA (A) can be prepared, for example, by polymerizing vinyl ester monomers to obtain a vinyl ester polymer and saponifying the obtained vinyl ester polymer.

[0027] Examples of vinyl ester monomers include vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pivalate, vinyl versatate, etc. Among these, vinyl acetate is preferred.

[0028] Examples of methods for polymerizing vinyl ester monomers include known methods such as bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization. Among these methods, bulk polymerization carried out without a solvent or solution polymerization carried out using a solvent such as alcohol is preferred, and solution polymerization carried out in the presence of a lower alcohol is more preferred. As the lower alcohol, an alcohol having 3 or less carbon atoms is preferred, and methanol, ethanol, n-propanol or isopropanol is more preferred, and methanol is even more preferred. When carrying out a polymerization reaction by the bulk polymerization method or the solution polymerization method, either a batch method or a continuous method can be adopted as the reaction method.

[0029] Examples of the polymerization initiator used in the polymerization reaction include known polymerization initiators such as azo initiators such as 2,2'-azobisisobutyronitrile, 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), etc., and organic peroxide initiators such as benzoyl peroxide, n-propyl peroxycarbonate, cumyl peroxy neodecanoate, t-butyl peroxy neodecanoate, etc. The polymerization temperature when carrying out the polymerization reaction is not particularly limited, but is preferably in the range of 5°C to 200°C.

[0030] When polymerizing the vinyl ester monomer, other copolymerizable monomers can be further copolymerized. Examples of the other monomers include those mentioned above as monomers that provide other structural units.

[0031] A specific chain transfer agent may be allowed to coexist during the polymerization of vinyl ester monomers. Examples of the chain transfer agent include aldehydes such as acetaldehyde, propionaldehyde, and butylaldehyde; ketones such as acetone and methyl ethyl ketone; mercaptans such as 2-hydroxyethanethiol and 3-mercaptopropionic acid; thiocarboxylic acids such as thioacetic acid; and halogenated hydrocarbons such as trichloroethylene and perchloroethylene. The chain transfer agent may function as a modifier. Depending on the type of chain transfer agent, a specific group (e.g., a carboxyl group, etc.) may be introduced to the end of the PVA (A). When the PVA (A) having a carboxyl group at the end is used, the plasticizer absorption of the polymer particles obtained by suspension polymerization tends to be better. When the PVA (A) has a carboxyl group at its end, the carboxyl group may be present in the form of a salt or an anion.

[0032] The saponification of the obtained vinyl ester polymer can be carried out, for example, by treating the vinyl ester polymer in an alcohol solution using an alkali catalyst or an acid catalyst. For the saponification reaction of the vinyl ester polymer, a conventionally known alcoholysis or hydrolysis reaction using an alkali catalyst such as sodium hydroxide, potassium hydroxide, or sodium methoxide, or an acid catalyst such as p-toluenesulfonic acid, can be applied. Examples of the solvent used in the saponification reaction include alcohols such as methanol and ethanol; esters such as methyl acetate and ethyl acetate; ketones such as acetone and methyl ethyl ketone; and aromatic hydrocarbons such as benzene and toluene. These can be used alone or in combination of two or more. Among these, it is preferable to use methanol or a mixed solution of methanol and methyl acetate as a solvent and carry out the saponification reaction in the presence of sodium hydroxide as an alkali catalyst, as it is simple and convenient.

[0033] The saponification can be carried out using a belt reactor, a kneader reactor, a column reactor, etc. The PVA (A) obtained through the saponification may be subjected to a washing treatment and a drying treatment.

[0034] (Compound (B)) The compound (B) is a compound represented by the following formula (1). [ka]

[0035] In formula (1), X is an oxygen atom, a group represented by the following formula (2), or a group represented by the following formula (3). Y is a group having 1 to 10 carbon atoms. Z is one selected from the group consisting of a carboxy group, a sulfo group, a phosphate group, salts thereof, and anions thereof. R 1 is an acyl group or a hydrocarbon group. [ka] [ka]

[0036] In formula (2) and formula (3), R 2 , R 3 and R 4 are each independently a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or a bond bonded to Y. * is a bond.

[0037] It is presumed that the compound (B) having, as X, a group containing an electron-withdrawing atom such as an oxygen atom or a nitrogen atom improves the uniformity of the solution and the separability from the PVA (A), thereby achieving the above-mentioned effects of the present invention.

[0038] X is preferably a group represented by the above formula (2) or a group represented by the above formula (3), and more preferably a group represented by the above formula (2). When X is a group represented by the above formula (2), R 2 is preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, more preferably a hydrogen atom, a methyl group or an ethyl group, still more preferably a hydrogen atom or a methyl group, and still more preferably a methyl group. When X is a group represented by the above formula (3), R 3 and R 4 are each independently preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, more preferably a hydrogen atom, a methyl group or an ethyl group, and further preferably a hydrogen atom or a methyl group. X is preferably a secondary amine, a tertiary amine or a quaternary amine, and more preferably a secondary amine or a tertiary amine.

[0039] Y is a group having 1 to 10 carbon atoms, preferably a group having 1 to 8 carbon atoms, and more preferably a group having 1 to 5 carbon atoms. Y may contain an atom other than carbon. The atom other than carbon contained in Y is preferably at least one selected from the group consisting of oxygen, nitrogen, and hydrogen, and more preferably hydrogen. Y may be bonded to X to form a ring structure. In this case, when X is a group represented by the above formula (2), R 2 is a bond bonded to Y, and when X is a group represented by the above formula (3), R 3 and R 4At least one of the above is a bond bonded to Y. In one embodiment, it is preferred that Y does not bond to X to form a ring structure. In one embodiment, Y may be a hydrocarbon group. Some or all of the hydrogen atoms of this hydrocarbon group may be substituted with other atoms or groups, or may be unsubstituted, but it is preferred that the hydrocarbon group is unsubstituted or substituted with a carboxy group, a salt thereof, or an anion thereof. Y is preferably a hydrocarbon group having 1 to 5 carbon atoms, and is preferably a linear alkanediyl group having 1 to 5 carbon atoms (-(CH2) n -:n is an integer of 1 to 5.) is more preferable, and a methylene group (-CH2-) is even more preferable. Y is also preferably an alkanediyl group having 1 to 3 carbon atoms. The hydrogen atoms of these alkanediyl groups may be substituted with a carboxy group, a salt thereof, or an anion thereof. When Y is a relatively small group, X containing an oxygen atom or a nitrogen atom, which is an electron-withdrawing atom, is positioned in the vicinity of Z, and the uniformity of the solution and separability from PVA (A) can be further improved.

[0040] Z is preferably a salt of a carboxy group, a salt of a sulfo group, or a salt of a phosphate group. In one embodiment, Z is also preferably a carboxy group, a salt of a carboxy group, or an anion of a carboxy group, and more preferably a salt of a carboxy group. In addition, when the solution is, for example, an aqueous solution, Z is an anion of a carboxy group (-COO - ), sulfo group anion (-SO3 - ) or the anion of the phosphate group (-HPO4 - Or -PO4 2- When Z is a sulfo group (SO3H-) or a phosphoric acid group (H2PO4-), compound (B) may be a phosphoric acid ester or a sulfonic acid ester.

[0041] When Z is a salt of a carboxy group, a salt of a sulfo group, or a salt of a phosphate group, the type of the salt is not particularly limited. Examples of salts include alkali metal salts such as sodium, potassium, and lithium, alkaline earth metal salts such as calcium and magnesium, aluminum salts, zinc salts, ammonium salts, organic amine salts such as monoethanolamine, diethanolamine, triethanolamine, and triisopropanolamine, and basic salts such as arginine and lysine. Among these, alkali metal salts are preferred, and sodium salts are more preferred. Compound (B) in the form of a salt can be obtained, for example, by adding an alkaline compound or an aqueous solution thereof to compound (B) which is a carboxylic acid, sulfonic acid, or phosphoric acid. For example, to convert the N-long-chain acyl amino acid described below into a salt, an alkaline compound or an aqueous solution thereof may be added to the N-long-chain acyl amino acid.

[0042] R 1 has, for example, 7 to 24 carbon atoms, preferably 8 to 21, more preferably 10 to 14, and further preferably 11 to 13.

[0043] R 1 R is preferably an acyl group. 1 When R is an acyl group, 1 is preferably a group represented by the following formula (4). [ka] In formula (4), R 5 is a saturated or unsaturated hydrocarbon group having 7 to 20 carbon atoms. * is a bond.

[0044] R 5 The number of carbon atoms in R is preferably 9 to 13, and more preferably 10 to 12. 5 R is preferably a linear saturated or unsaturated hydrocarbon group, and more preferably a linear saturated hydrocarbon group. 5 It is also preferred that R is a saturated hydrocarbon group. 5 is preferably derived from coconut oil.

[0045] R 1 When R is a hydrocarbon group, the hydrocarbon group is preferably a saturated or unsaturated hydrocarbon group having 7 to 21 carbon atoms, more preferably a linear saturated or unsaturated hydrocarbon group having 7 to 21 carbon atoms, and even more preferably a linear saturated hydrocarbon group having 7 to 21 carbon atoms. 1 is preferably an n-octyl group, an n-decyl group, a lauryl group or an n-tetradecyl group.

[0046] In one embodiment, compound (B) is a compound represented by formula (1), wherein X is a group represented by formula (2) above, and R 1 In one embodiment, X is a group represented by the above formula (2), Y is a hydrocarbon group having 1 to 5 carbon atoms, Z is a salt of a carboxy group, and R 1 is a group represented by formula (4), and R 2 is an alkyl group having 1 to 3 carbon atoms, and R 5 It is more preferable that the alkyl group is a linear saturated hydrocarbon group having 9 to 13 carbon atoms.

[0047] In one embodiment, compound (B) is preferably at least one selected from the group consisting of phosphate salt, acylamino acid salt, acyl lactate, acyltaurine salt, alkylsulfosuccinate, acyl hydrolyzed collagen salt and acylisethionate, more preferably at least one selected from the group consisting of acyl lactate and acylamino acid salt, and even more preferably acylamino acid salt.As acylamino acid salt, N-acylamino acid salt is more preferable.

[0048] The N-acylamino acid salt is preferably a salt of an N-acylamino acid (also called "N-long chain acylamino acid") in which an acyl group derived from a saturated or unsaturated fatty acid having 8 to 21 carbon atoms is introduced into the amino group of the amino acid. The amino acid residue of the N-acylamino acid salt may be various amino acids such as α-amino acid, β-amino acid, γ-amino acid, or ω-amino acid. The amino group may be an N-methyl or N-ethyl form. In addition, it does not matter whether the optical isomer is a D-form, an L-form, or a racemic form. Examples of the amino acid residue of the N-acylamino acid salt include glutamic acid, aspartic acid, glycine, sarcosine, alanine, leucine, isoleucine, serine, threonine, cysteine, cystine, methionine, lysine, arginine, phenylalanine, tyrosine, histidine, tryptophan, proline, oxyproline, β-aminopropionic acid, γ-aminobutyric acid, anthranilic acid, m-aminobenzoic acid, p-aminobenzoic acid, lanthionine, β-methyllanthionine, cystathionine, dienocholic acid, ferric acid, and the like. Examples of such amino acids include sarcosine, aminomalonic acid, β-oxyaspartic acid, α-amino-α-methylsuccinic acid, β-oxyglutamic acid, γ-oxyglutamic acid, γ-methylglutamic acid, γ-methyleneglutamic acid, γ-methyl-γ-oxyglutamic acid, α-aminoadipic acid, α,α'-diaminoadipic acid, β,β'-diaminoadipic acid, α-amino-γ-oxyadipic acid, α-aminopimelic acid, α-amino-γ-oxypimelic acid, β-aminopimelic acid, α-aminosuberic acid, and α-aminosebacic acid. Among these, sarcosine is preferred.

[0049] The acyl group in the acyl lactate and acyl amino acid salt is preferably derived from a saturated or unsaturated fatty acid having 8 to 21 carbon atoms. The fatty acid may be linear, branched or cyclic. Examples of the fatty acid include linear saturated fatty acids such as caprylic acid, pelargonic acid, capric acid, undecanoic acid, lauric acid, tridecanoic acid, myristic acid, pentadecanoic acid, palmitic acid, margaric acid, stearic acid, nonadecanoic acid and arachic acid;2-Butyl-5-methylpentanoic acid, 2-isobutyl-5-methylpentanoic acid, dimethyloctanoic acid, dimethylnonanoic acid, 2-butyl-5-methylhexanoic acid, methylundecanoic acid, dimethyldecanoic acid, 2-ethyl-3-methylnonanoic acid, 2,2-dimethyl-4-ethyloctanoic acid, methyldocosanoic acid, 2-propyl-3-methylnonanoic acid, methyltridecanoic acid, dimethyldodecanoic acid, 2-butyl-3-methylnonanoic acid, methyltetradecanoic acid, ethyltridecanoic acid, propyldodecanoic acid, butylundecanoic acid, pentyldecanoic acid, hexylnonanoic acid , 2-(3-methylbutyl)-3-methylnonanoic acid, 2-(2-methylbutyl)-3-methylnonanoic acid, butylethylnonanoic acid, methylpentadecanoic acid, ethyltetradecanoic acid, propyltridecanoic acid, butyldodecanoic acid, pentylundecanoic acid, hexyldecanoic acid, heptylnonanoic acid, dimethyltetradecanoic acid, butylpentylheptanoic acid, trimethyltridecanoic acid, methylhexadecanoic acid, ethylpentadecanoic acid, propyltetradecanoic acid, butyltridecanoic acid, pentyldodecanoic acid, hexylundecanoic acid, heptyldecanoic acid, methylheptylnonanoic acid Branched saturated fatty acids such as octenoic acid, dipentanoic acid, methylheptadecanoic acid, ethylhexadecanoic acid, ethylhexadecanoic acid, propylpentadecanoic acid, butyltetradecanoic acid, pentyltridecanoic acid, hexyldodecanoic acid, heptylundecanoic acid, octyldecanoic acid, dimethylhexadecanoic acid, methyloctylnonanoic acid, methyloctadecanoic acid, ethylheptadecanoic acid, dimethylheptadecanoic acid, methyloctyldecanoic acid, methylnonadecanoic acid, methylnonadecanoic acid, dimethyloctadecanoic acid, butylheptylnonanoic acid, etc., octenoic acid, nonenoic acid, decene acid, etc. linear monoenoic acids such as carboxylic acid, caproleic acid, undecylenic acid, Linderic acid, tallow acid, lauroleic acid, tridecenoic acid, tsuzuic acid, myristoleic acid, pentadecenoic acid, hexede-cenoic acid, palmitoleic acid, heptadecenoic acid, octadecenoic acid, oleic acid, nonadecenoic acid, and gondoic acid; branched monoenoic acids such as methylheptenoic acid, methylnonenoic acid, methylundecenoic acid, dimethyldecenoic acid, methyldodecenoic acid, methyltridecenoic acid, dimethyldodecenoic acid, dimethyltridecenoic acid, methyloctadecenoic acid, dimethylheptadecenoic acid, and ethyloctadecenoic acid;Examples of the fatty acids include di- or trienoic acids such as linoleic acid, linoelaidic acid, eleostearic acid, linolenic acid, linoleneelaidic acid, pseudoeleostearic acid, parinaric acid, and arachidonic acid; acetylenic acids such as octynoic acid, nonynoic acid, decynoic acid, undecynoic acid, dodecynoic acid, tridecynoic acid, tetradecynoic acid, pentadecynoic acid, heptadecynoic acid, octadecynoic acid, nonadecynoic acid, and dimethyloctadecynoic acid; and cyclic acids such as methyleneoctadecenoic acid, methyleneoctadecanoic acid, aleprol acid, areprestinic acid, aleprilic acid, alepuric acid, hydnocarpic acid, shormooglic acid, gorlic acid, α-cyclopentyl acid, α-cyclohexyl acid, and α-cyclopentylethyl acid. The fatty acid is preferably a straight-chain fatty acid. The fatty acid is preferably a saturated fatty acid, more preferably a straight-chain saturated fatty acid, and particularly preferably lauric acid.

[0050] The acyl group in the acyl lactate and acyl amino acid salt may be an acyl group derived from a fatty acid obtained from natural fats and oils, and is preferably an acyl group derived from a mixed fatty acid containing 80% by mass or more of saturated or unsaturated fatty acids having carbon numbers of 8 to 21. Examples of such acyl groups include acyl groups derived from coconut oil fatty acid, palm oil fatty acid, linseed oil fatty acid, sunflower oil fatty acid, soybean oil fatty acid, sesame oil fatty acid, castor oil fatty acid, olive oil fatty acid, camellia oil fatty acid, etc.

[0051] When compound (B) is an acyl amino acid salt, preferred acyl amino acid salts include sodium cocoyl glutamate, TEA cocoyl glutamate, potassium cocoyl glutamate, sodium lauroyl glutamate, TEA lauroyl glutamate, potassium lauroyl glutamate, sodium cocoyl sarcosine, TEA cocoyl sarcosine, potassium cocoyl sarcosine, sodium lauroyl sarcosine, TEA lauroyl sarcosine, potassium lauroyl sarcosine, sodium cocoyl aspartate, TEA cocoyl aspartate, potassium cocoyl aspartate, sodium lauroyl aspartate, TEA lauroyl aspartate, potassium lauroyl aspartate, sodium cocoyl methylalanine, Examples of such compounds include cocoyl methylalanine TEA, cocoyl methylalanine potassium, sodium lauroyl methylalanine, TEA lauroyl methylalanine, potassium lauroyl methylalanine, sodium cocoyl glycine, TEA cocoyl glycine, potassium cocoyl glycine, sodium lauroyl glycine, TEA lauroyl glycine, potassium lauroyl glycine, sodium myristoyl sarcosine, TEA myristoyl sarcosine, potassium myristoyl sarcosine, sodium lauroyl methyl-β-alanine, TEA lauroyl methyl-β-alanine, potassium lauroyl methyl-β-alanine, sodium cocoyl methyl-β-alanine, TEA cocoyl methyl-β-alanine, potassium cocoyl methyl-β-alanine, etc. Among these, lauroyl sarcosine salt is more preferred, and sodium lauroyl sarcosine is even more preferred.

[0052] When compound (B) is an acyl lactate, preferred acyl lactate include sodium cocoyl lactate, TEA cocoyl lactate, potassium cocoyl lactate, sodium lauroyl lactate, TEA lauroyl lactate, potassium lauroyl lactate, sodium stearoyl lactate, TEA stearoyl lactate, potassium stearoyl lactate, sodium isostearoyl lactate, TEA isostearoyl lactate, potassium isostearoyl lactate, and the like.

[0053] The compound (B) is preferably at least one selected from the group consisting of acids, their salts, and their anions, each having an acid dissociation constant (pKa) in water of 0 to 6.0. The lower limit of pKa is more preferably 1.0, and even more preferably 1.5. The upper limit of pKa is more preferably 5.5, and even more preferably 5.0. When the compound (B) is an acid or a salt thereof in the above pKa range, the solubility of PVA (A) in a solution containing PVA (A) and the compound (B) is excellent, and the separability from PVA (A) in the solution under weak acidic conditions (for example, in a suspension polymerization system) is excellent.

[0054] The solution may contain one or more compounds (B).

[0055] The lower limit of the content of the compound (B) in the solution may be, for example, 0.1% by mass, but is preferably 0.5% by mass, more preferably 0.7% by mass, and even more preferably 0.8% by mass or 0.9% by mass. By making the content of the compound (B) equal to or greater than the above lower limit, the stability of the solution can be further improved. The upper limit of the content of the compound (B) is preferably 10% by mass, more preferably 4% by mass, and even more preferably 2% by mass. By making the content of the compound (B) equal to or less than the above upper limit, the effect of the compound (B) during suspension polymerization is further reduced, and the performance as a dispersant for suspension polymerization is further improved.

[0056] (Alcohol (C)) Examples of the alcohol (C) include monohydric alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-methyl-1-propanol, 2-butanol, and 2-methyl-2-propanol, and polyhydric alcohols such as ethylene glycol and glycerin. The alcohol (C) is preferably an alcohol having 1 to 4 carbon atoms in terms of the solubility of the PVA (A), compatibility with water, and viscosity of the solution. The number of carbon atoms of the alcohol (C) is more preferably 1 to 3, and further preferably 2. In one embodiment, the alcohol (C) is preferably a linear alcohol. The alcohol (C) is preferably a monohydric alcohol, and is preferably a primary alcohol, and is particularly preferably ethanol.

[0057] The solution may contain one or more alcohols (C).

[0058] The lower limit of the content of the alcohol (C) in the solution may be, for example, 1% by mass, but is preferably 3% by mass, more preferably 5% by mass, even more preferably 6% by mass, and even more preferably 7% by mass. By making the content of the alcohol (C) equal to or greater than the above lower limit, it is possible to further increase the stability of the solution. The upper limit of the content of the alcohol (C) is preferably 80% by mass, more preferably 50% by mass. In some cases, the content of the alcohol (C) is less than 20% by mass or even more preferably 15% by mass or less. By making the content of the alcohol (C) equal to or less than the above upper limit, it is possible to facilitate waste liquid treatment, reduce the impact on the environment, and improve handleability.

[0059] In the solution, it is more preferable that the content of the compound (B) is 0.5% by mass or more and 4% by mass or less, and the content of the alcohol (C) is 5% by mass or more and 15% by mass or less. In such a case, the solution has excellent properties as a dispersant in suspension polymerization, and is also excellent in handleability in waste liquid treatment, etc.

[0060] (Other ingredients, etc.) The solution may contain, for example, water as a component other than PVA (A), compound (B) and alcohol (C). The solution may be an aqueous solution. The lower limit of the water content in the solution may be, for example, 0.1% by mass, or may be 1%, 10%, 20%, 30%, 40% or 50% by mass. The upper limit of the water content in the solution may be, for example, 90% by mass, or may be 80%, 70% or 60% by mass.

[0061] The solution may further contain, as other components, solids other than PVA (A) and compound (B), organic solvents other than alcohol, etc. Examples of solids other than PVA (A) and compound (B) include resins other than PVA (A), surfactants other than compound (B), plasticizers, and compounds used during production. However, the lower limit of the total content of PVA (A), compound (B), alcohol (C), and water in the solution is preferably 90% by mass, more preferably 99% by mass, and even more preferably 99.9% by mass. The upper limit of the total content of PVA (A), compound (B), alcohol (C), and water in the solution may be 100% by mass. In addition, the lower limit of the total content of PVA (A) and compound (B) in the solid content of the solution is preferably 90% by mass, more preferably 99% by mass, and even more preferably 99.9% by mass. The upper limit of the total content of PVA (A) and compound (B) in the solid content of the solution may be 100% by mass.

[0062] The upper limit of the viscosity of the solution is preferably 30,000 mPa·s, more preferably 20,000 mPa·s, even more preferably 10,000 mPa·s, even more preferably 5,000 mPa·s, and particularly preferably 3,000 mPa·s. When the viscosity of the solution is equal to or less than the upper limit, the ease of handling can be improved. The lower limit of the viscosity may be 1 mPa·s, 10 mPa·s, 100 mPa·s, 500 mPa·s, or 1,000 mPa·s. The viscosity of the solution is measured using a B-type viscometer (spindle LV-03 to LV-04) under conditions of a rotor rotation speed of 60 rpm and a temperature of 20°C.

[0063] The solution is preferably neutral or alkaline, more preferably neutral or weakly alkaline. In such a case, the stability of the solution is further increased. The pH of the solution is preferably 5.0 or more, more preferably 6.0 or more. The pH of the solution is preferably 9.0 or less, more preferably 8.0 or less, and may be 7.5 or less or 7.0 or less.

[0064] The solution can be suitably used as a dispersant for suspension polymerization. The solution may be used for purposes other than as a dispersant for suspension polymerization. The solution may be used as a dispersant for emulsion polymerization, or may be used for purposes other than as a dispersant. Examples of uses other than as a dispersant include uses similar to those of conventional PVA.

[0065] <Solution manufacturing method> The method for producing the solution according to one embodiment of the present invention is not particularly limited, and for example, the solution can be produced by mixing each component. However, the solution is preferably produced by the following method.

[0066] That is, the method for producing a solution according to one embodiment of the present invention includes a step of adding PVA (A) in multiple batches to a liquid containing a compound (B) and an alcohol (C).

[0067] According to this production method, the solution according to one embodiment of the present invention can be efficiently produced. That is, PVA (A), which has low solubility in water, etc., can be efficiently dissolved to obtain a solution that is highly stable and has excellent performance as a dispersant for suspension polymerization.

[0068] The number of times PVA (A) is added is not particularly limited as long as it is two or more, and may be, for example, two or more to 20 or less, or three or more to 12 or less. In the production method, the liquid containing compound (B) and alcohol (C) may further contain water or the like. The specific form and preferred form of each component such as PVA (A), compound (B) and alcohol (C) used in the production method are the same as the specific form and preferred form of these components contained in the solution according to one embodiment of the present invention described above.

[0069] <Dispersant> The dispersant (1) according to one embodiment of the present invention contains PVA (A) and a compound (B). The dispersant (1) is an additive used to increase the dispersibility of monomers during suspension polymerization and to control the plasticizer absorption of the resulting polymer particles. The specific and preferred forms of the PVA (A), compound (B) and optional alcohol (C) contained in the dispersant (1) are the same as the specific and preferred forms of these components contained in the solution according to one embodiment of the present invention described above.

[0070] The lower limit of the total content of PVA (A) and compound (B) in the non-volatile content of the dispersant (1) is preferably 30% by mass, more preferably 50% by mass, and may be even more preferably 70% by mass, 90% by mass, or 99% by mass. The upper limit of the total content of PVA (A) and compound (B) in the non-volatile content of the dispersant (1) may be 100% by mass. Non-volatile components other than PVA (A) and compound (B) that may be contained in the dispersant (1) include resins other than PVA (A), surfactants other than compound (B), plasticizers, and various compounds used during production. The upper limit of the content of volatile components in the dispersant (1) is, for example, 80% by mass, and may be 60% by mass or 40% by mass. Examples of volatile components that may be contained in the dispersant (1) include alcohol (C), water, and the like.

[0071] The dispersant (1) may be, for example, a solid (such as a powder) dispersant consisting of only PVA (A) and compound (B). The solid dispersant dissolves well in a solvent containing alcohol. The solid dispersant (1) may be dissolved in a solvent not containing alcohol (such as water) before use. When used as a dispersant in suspension polymerization, the concentration of PVA (A) in the polymerization system is usually not high, for example, not exceeding 1% by mass, and therefore it is sufficiently soluble in a solvent not containing alcohol.

[0072] The dispersant (1) may be in the form of a solution. The dispersant (1) may contain an alcohol (C) or water in addition to the PVA (A) and the compound (B). That is, the solution according to one embodiment of the present invention is one embodiment of the dispersant of the present invention when used as a dispersant. A dispersant in the form of a solution and having a relatively high concentration can also be used after dilution. The dispersant (1) in the form of a solution containing alcohol is highly stable.

[0073] The dispersant (1) has excellent performance as a dispersant for suspension polymerization. The dispersant (1) is suitable as a dispersant for suspension polymerization of vinyl compounds, and can efficiently produce polymer particles having a small average particle size and a small amount of coarse particles. In addition, the polymer particles obtained by suspension polymerization using the dispersant (1) have good plasticizer absorption.

[0074] The lower limit of the content of the compound (B) relative to 100 parts by mass of the PVA (A) in the dispersant (1) is preferably 0.5 parts by mass, more preferably 1 part by mass, and even more preferably 2 parts by mass. By having the content of the compound (B) be equal to or greater than the lower limit, the solubility of the PVA (A) can be increased. The upper limit of the content of the compound (B) relative to 100 parts by mass of the PVA (A) in the dispersant (1) is preferably 20 parts by mass, more preferably 12 parts by mass, and even more preferably 10 parts by mass. By having the content of the compound (B) be equal to or less than the upper limit, the effect of the compound (B) during suspension polymerization is reduced, and the performance as a dispersant is further improved.

[0075] Dispersant (2) according to another embodiment of the present invention is a solution containing PVA (A) having a degree of saponification of 30 mol% or more and 80 mol% or less, a degree of polymerization of 100 or more and 700 or less, and a block character of vinyl ester units of 0.6 or less, at a concentration of 15 mass% or more. The dispersant (2) is an additive used for increasing the dispersibility of monomers during suspension polymerization. The dispersant (2) can be suitably used for the polymerization of vinyl compounds. The dispersant (2) is suitable as a dispersant for suspension polymerization of vinyl compounds, and can efficiently obtain polymer particles having a small average particle size and a small number of coarse particles. In addition, the polymer particles obtained by suspension polymerization using the dispersant (2) also have good plasticizer absorption.

[0076] The specific form and preferred form of the PVA (A) contained in the dispersant (2) are the same as those described above for the PVA (A) contained in the solution according to one embodiment of the present invention. The lower limit of the concentration of the PVA (A) in the dispersant (2) is preferably 20% by mass, more preferably 25% by mass, even more preferably 30% by mass, and in some cases even more preferably 35% by mass or 40% by mass. The upper limit of the concentration of the PVA (A) may be 70% by mass, 60% by mass, 50% by mass, or 40% by mass.

[0077] The dispersant (2) preferably contains at least one selected from the group consisting of acids, their salts, and their anions having an acid dissociation constant (pKa) in water of 0 to 6.0 (compound (B')). The lower limit of pKa is more preferably 1.0, and even more preferably 1.5. The upper limit of pKa is more preferably 5.5, and even more preferably 5.0. Examples of such compound (B') include compounds having a carboxy group or a salt thereof. The compound (B') preferably has a hydrocarbon group having 7 to 24 carbon atoms and a carboxy group or a salt thereof. The number of carbon atoms in the hydrocarbon group of the compound (B') is preferably 8 to 21, more preferably 10 to 14, and even more preferably 11 to 13. The hydrocarbon group of the compound (B') is preferably an aliphatic hydrocarbon group, and more preferably an alkyl group. A suitable embodiment of the compound (B') includes the compound (B) contained in the solution according to one embodiment of the present invention. In another embodiment of the present invention, the dispersant (2) preferably contains the compound (B).

[0078] The dispersant (2) preferably further contains an alcohol (C). The specific form and preferred form of the alcohol (C) that may be contained in the dispersant (2) are the same as those described above for the alcohol (C) contained in the solution according to one embodiment of the present invention. In addition, the specific form and preferred form of the dispersant (2) include the specific form and preferred form of the solution or dispersant (1) according to one embodiment of the present invention described above.

[0079] <Method of producing vinyl compound polymer> A method for producing a vinyl compound polymer according to one embodiment of the present invention includes a step of polymerizing a vinyl compound in the presence of a dispersant according to one embodiment of the present invention. The method for producing may be a method for polymerizing a vinyl compound. The method for producing a vinyl compound polymer is similar to a conventionally known method for producing a vinyl compound polymer, except that the dispersant according to one embodiment of the present invention is used as a dispersant.

[0080] In this production method, a vinyl compound is usually suspension polymerized 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 be used. A dispersant is added to this aqueous medium. A polymerization initiator and a vinyl compound are further added to the aqueous medium, and suspension polymerization is carried out under stirring.

[0081] The amount of the dispersant according to one embodiment of the present invention added when carrying out suspension polymerization of a vinyl compound is not particularly limited, but is preferably 1 ppm or more and 50,000 ppm or less, more preferably 10 ppm or more and 20,000 ppm or less, and in some cases is even more preferably 10,000 ppm or less, 5,000 ppm or less, or 1,000 ppm or less, based on the mass standard of solid content relative to the vinyl compound.

[0082] The dispersant according to one embodiment of the present invention may be used alone or in combination with other dispersants. Examples of other dispersants include various dispersants that are usually used when a vinyl compound is suspension polymerized in an aqueous medium. Specifically, examples of the dispersant include water-soluble cellulose ethers such as methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, and hydroxypropyl methyl cellulose; water-soluble polymers such as PVA other than PVA(A) and gelatin; oil-soluble emulsifiers such as sorbitan monolaurate, sorbitan trioleate, glycerin tristearate, and ethylene oxide-propylene oxide block copolymer; and water-soluble emulsifiers such as polyoxyethylene sorbitan monolaurate, polyoxyethylene glycerin oleate, and sodium laurate.

[0083] The polymerization initiator used in the production method can be one that has been conventionally used in the polymerization of vinyl compounds, and specifically, the same polymerization initiators as those exemplified in the polymerization of the vinyl ester monomers described above can be used. In one embodiment, the polymerization initiator is preferably an organic peroxide initiator. The organic peroxide initiator may be a compound having a percarboxylic acid structure (-C(=O)-OO-).

[0084] In this production method, various other additives can be added to the polymerization system as necessary. Examples of additives include polymerization regulators such as aldehydes, halogenated hydrocarbons, and mercaptans; polymerization inhibitors such as phenol compounds, sulfur compounds, and N-oxide compounds. In addition, pH adjusters, scale inhibitors, crosslinkers, and the like can also be added. A plurality of additives may be used in combination.

[0085] Examples of vinyl compounds that can be suspension polymerized in the production method include vinyl halides such as vinyl chloride; vinyl esters such as vinyl acetate and vinyl propionate; acrylic acid, methacrylic acid, esters and salts thereof; maleic acid, fumaric acid, esters and anhydrides thereof; styrene; acrylonitrile; vinylidene chloride; vinyl ethers, etc. Among these vinyl compounds, vinyl halides are preferred, and vinyl chloride is more preferred. The production method is particularly suitable as a method of suspension polymerizing vinyl chloride alone, or a method of suspension polymerizing vinyl chloride and a monomer that can be copolymerized with vinyl chloride together. Examples of monomers that can be copolymerized with vinyl chloride include vinyl esters such as vinyl acetate and vinyl propionate; (meth)acrylic acid esters such as methyl (meth)acrylate and ethyl (meth)acrylate; α-olefins such as ethylene and propylene; unsaturated dicarboxylic acids such as maleic anhydride and itaconic acid; acrylonitrile; styrene; vinylidene chloride; vinyl ethers, etc. In addition, when a vinyl compound containing a halogen, such as vinyl halide or vinylidene chloride, is used as the vinyl compound, hydrogen halide is generated as the polymerization proceeds, and the polymerization system tends to become weakly acidic. When the polymerization system becomes weakly acidic, as described above, compound (B) separates from PVA (A), and PVA (A) is not affected by compound (B) and is considered to function particularly well as a dispersant for suspension polymerization.

[0086] In the present production method, when a vinyl compound is suspension polymerized, the charging ratio of each component, polymerization temperature, polymerization time, etc. can be the same as those employed in conventional suspension polymerization of vinyl compounds. There is no limitation on the charging order or ratio of the vinyl compound, polymerization initiator, dispersant, aqueous medium, and other additives.

[0087] According to the production method, it is possible to efficiently obtain vinyl compound polymer particles having a small amount of coarse particles without increasing the average particle size. Moreover, the vinyl compound polymer particles obtained by the production method have good plasticizer absorption.

[0088] A method for producing a vinyl compound polymer according to another embodiment of the present invention includes a preparation step of preparing PVA (A) having a degree of saponification of 30 mol% to 80 mol%, a degree of polymerization of 100 to 700, and a block character of vinyl ester units of 0.6 or less, and a polymerization step of polymerizing a vinyl compound in the presence of PVA (A) to obtain vinyl compound polymer particles having an average particle size of 220 μm or less, and the preparation step is a method for preparing a solution having a PVA (A) concentration of 15 mass% or more. Specific and preferred forms of the solution prepared by this production method are the same as those of the dispersant (2) according to one embodiment of the present invention described above.

[0089] In the method for producing a vinyl compound polymer according to one embodiment of the present invention, a solution of PVA (A) (dispersant (2)) may be introduced into the polymerization reaction system of the vinyl compound in the polymerization step. Also, in the production method, the solution of PVA (A) (dispersant (2)) may be diluted and introduced into the polymerization reaction system of the vinyl compound in the polymerization step. EXAMPLES

[0090] The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples in any way.

[0091] [Production Example 1] (Production of PVA-1) A 3L reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen inlet, an additive inlet, and an initiator inlet was charged with 300 parts by mass of vinyl acetate and 1,200 parts by mass of methanol, and the temperature was raised to 60°C, after which the system was substituted with nitrogen by nitrogen bubbling for 30 minutes. 4.8 parts by mass of 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile) (AIBN) was added to initiate polymerization. The polymerization temperature was maintained at 60°C during polymerization, and after 4 hours, when the polymerization rate reached 50%, the polymerization was stopped by cooling. Next, unreacted vinyl acetate was removed under reduced pressure to obtain a methanol solution of polyvinyl acetate (PVAc). A PVAc solution adjusted to 40% by mass was saponified by adding a NaOH methanol solution (10% by mass concentration) so that the alkali molar ratio (moles of NaOH / moles of vinyl ester units in PVAc) was 0.0025. The water content of the solution during saponification was adjusted to 1% by mass. By the above operations, a vinyl alcohol polymer (PVA-1) having a degree of polymerization (viscosity average degree of polymerization) of 250, a degree of saponification of 43.1 mol % and a block character of 0.499 was obtained as PVA (A). The degree of polymerization of the PVA obtained in each production example was measured as follows. The previously obtained methanol solution of PVAc from which unreacted vinyl acetate had been removed before the saponification reaction was poured into n-hexane to precipitate PVAc. The recovered PVAc was dissolved in acetone for reprecipitation purification three times, and then dried under reduced pressure at 60°C to obtain a purified PVAc. The methanol solution of the purified PVAc was saponified with an alkali molar ratio of 0.2, followed by Soxhlet extraction with methanol for three days and then drying to obtain a purified PVA. The degree of polymerization (viscosity average degree of polymerization) of the obtained PVA was measured in accordance with JIS K6726:1994. In addition, the block character of the vinyl ester unit of PVA obtained in each manufacturing example was measured at a measurement temperature of 70°C and an accumulated number of 18,000 times for a sample in which PVA was dissolved in a heavy water / heavy methanol mixed solvent. 13C-NMR measurement was performed, and the peak integral value was obtained by analyzing three peaks related to the two-unit chain structure (dyad) that appears in the methylene region. The above three peaks correspond to a methylene carbon sandwiched between the carbon atom of the main chain bonded to the residual ester (-OC(=O)-Q (Q has the same meaning as above)) and the carbon atom of the main chain bonded to the hydroxyl group; a methylene carbon sandwiched between the carbon atom of the main chain bonded to the residual ester and the carbon atom of the main chain bonded to the residual ester adjacent to the carbon atom; and a methylene carbon sandwiched between the carbon atom of the main chain bonded to the hydroxyl group and the carbon atom of the main chain bonded to the hydroxyl group adjacent to the carbon atom. Specific measurement and calculation methods are described in Poval (Polymer Publishing Association, published in 1984, pp. 246-249) and Macromolecules, 10, 532 (1977), and measurements and calculations were performed according to these descriptions.

[0092] [Production Examples 2 to 3] (Production of PVA-2 to 3) PVA-2 to 3 were produced as PVA (A) in the same manner as in Production Example 1, except that the molar ratio of sodium hydroxide to vinyl acetate units (alkali molar ratio) during saponification was changed as shown in Table 1. The physical properties of PVA-2 to 3 are shown in Table 2.

[0093] [Production Example 4] (Production of PVA-4) PVA-4 was produced as PVA (A) in the same manner as in Production Example 1, except that paratoluenesulfonic acid was used instead of NaOH in the saponification step and the molar ratio (moles of paratoluenesulfonic acid / moles of vinyl ester units in PVAc) was changed to 0.0210. The physical properties of PVA-4 are shown in Table 2.

[0094] [Production Example 5] (Production of PVA-5) A 3L reaction vessel equipped with a stirrer, reflux condenser, nitrogen inlet, additive inlet and initiator inlet was charged with 1,050 parts by mass of vinyl acetate and 450 parts by mass of methanol, and the temperature was raised to 60°C, after which the system was substituted with nitrogen by nitrogen bubbling for 30 minutes. A 50% by mass solution of 3-mercaptopropionic acid (hereinafter referred to as 3-MPA) dissolved in methanol as a chain transfer agent was prepared, and nitrogen was substituted by bubbling with nitrogen gas. The temperature inside the reaction vessel was adjusted to 60°C, 1.0 part by mass of 3-MPA was added, and then 1.2 parts by mass of 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile) was added to start polymerization. The polymerization temperature was maintained at 60°C during polymerization, and a 50% by mass methanol solution of 3-MPA was continuously added at 5mL / hr so ​​that the amount of 3-MPA in the entire system was 11.5 parts by mass. After 4 hours, when the polymerization rate reached 40%, the polymerization was stopped by cooling. Next, unreacted vinyl acetate was removed under reduced pressure to obtain a methanol solution of modified polyvinyl acetate (modified PVAc). A NaOH methanol solution (10% by mass concentration) was added to the modified PVAc solution adjusted to 40% by mass so that the alkali molar ratio (moles of NaOH / moles of vinyl ester units in modified PVAc) was 0.0243, and saponification was performed. The water content of the solution during saponification was adjusted to 1% by mass. By the above operations, a vinyl alcohol polymer (PVA-5) was obtained as PVA (A), which has a degree of polymerization of 140, a degree of saponification of 33.0 mol%, a block character of 0.525, and a salt of a carboxy group at the end. The presence or absence of a carboxyl group salt at the end of PVA-5 was confirmed as follows. The PVA whose degree of polymerization had been measured was dissolved in heavy water and subjected to nuclear magnetic resonance analysis. As a result, it was confirmed that a carboxyl group salt (COONa group) was present at one end of the molecule.

[0095] [Production Examples 6 to 11] (Production of PVA-6 to 11) PVA-6 to PVA-11 were produced as PVA (A) in the same manner as in Production Example 5, except that the amounts of vinyl acetate and methanol used during polymerization, the type and amount of chain transfer agent used, the amount of AIBN used, and the alkali molar ratio during saponification were changed as shown in Table 1. The physical properties of PVA-6 to PVA-11 are shown in Table 2.

[0096] [Example 1] The solution of Example 1 was obtained by adding 40 parts by mass of PVA-1 in six portions to a liquid containing 1 part by mass of sodium lauroyl sarcosine (Na lauroyl sarcosine) as compound (B), 8 parts by mass of ethanol as alcohol (C), and 51 parts by mass of water. The viscosity of the obtained solution was measured and found to be 3,110 mPa s. The viscosity of the solution was measured using a B-type viscometer BLII (spindle LV-04) manufactured by Toki Sangyo Co., Ltd. at a rotor speed of 60 rpm and a temperature of 20°C.

[0097] [Examples 2 to 29, Comparative Example 1, Reference Examples 1 and 2] Solutions of Examples 2 to 29, Comparative Example 1, and Reference Examples 1 and 2 were obtained in the same manner as in Example 1, except that the types and amounts of PVA (A), compound (B), and alcohol (C), and the amount of water were changed as shown in Table 2. Viscosity measurements were performed on each of the obtained solutions. The results are shown in Table 2.

[0098] [evaluation] (Solution stability) Each of the solutions obtained in Examples 1 to 29, Comparative Example 1, and Reference Examples 1 and 2 was left to stand at 40°C for 7 days, and then the viscosity was measured in the same manner as above. Based on the viscosity before and after standing, the stability of the solution was evaluated according to the following criteria. In this evaluation, A or B was judged to be high stability. The evaluation results are shown in Table 2. A: There was no change in viscosity (viscosity increase rate less than 1%). B: The liquid had fluidity but had become viscous (viscosity increase rate of more than 1%). C: No fluidity and gelation occurred.

[0099] Furthermore, using the solutions of Examples 1 to 29 and Reference Examples 1 and 2 prepared separately as dispersants, suspension polymerization of vinyl chloride was carried out by the following method. Note that the solution of Comparative Example 1 was not subjected to suspension polymerization using this solution because of its low stability. Next, the average particle size, amount of coarse particles, and plasticizer absorption of the obtained vinyl chloride polymer particles were evaluated in the following manner. The evaluation results are shown in Table 2.

[0100] (Suspension Polymerization of Vinyl Chloride) From each solution of the examples, an amount was collected so that the solid content of the solution was 400 ppm relative to the vinyl chloride described below. The collected solution was diluted with deionized water to obtain a first dispersant aqueous solution. 100 parts by mass of the first dispersant aqueous solution was charged into an autoclave with a capacity of 5 L. Similarly, from a PVA aqueous solution in which a commercially available PVA ("Kuraray Poval 48-80" manufactured by Kuraray) was dissolved, an amount was collected so that the solid content of the PVA aqueous solution was 800 ppm relative to the vinyl chloride. The collected PVA aqueous solution was diluted with deionized water to obtain a second dispersant aqueous solution. 100 parts by mass of the second dispersant aqueous solution was charged into the autoclave. Next, deionized water was added to the autoclave so that the total amount of deionized water was 1300 parts by mass. Next, 0.65 parts by mass of a 70% by mass toluene solution of cumyl peroxy neodecanoate and 1.05 parts by mass of a 70% by mass toluene solution of t-butyl peroxy neodecanoate were charged into the autoclave. The autoclave was degassed to remove oxygen until the pressure inside the autoclave reached 0.0067 MPa. Then, 800 parts by mass of vinyl chloride were charged into the autoclave, and the contents inside the autoclave were heated to 57°C to initiate polymerization under stirring. The pressure inside the autoclave at the start of polymerization was 0.83 MPa. After 3.5 hours had passed since the start of polymerization, the polymerization was stopped when the pressure inside the autoclave reached 0.70 MPa, and unreacted vinyl chloride was removed. Then, the polymerization slurry was taken out and dried at 65°C for 17 hours to obtain vinyl chloride polymer particles.

[0101] (1) Average particle size of vinyl chloride polymer particles The particle size distribution of the obtained vinyl chloride polymer particles was measured by dry sieve analysis using a wire mesh with a Tyler mesh standard. The results were plotted using the Rosin-Rammler distribution equation to obtain the average particle diameter (d p50 In this evaluation, when the average particle size was 220 μm or less, the average particle size was determined to be not large.

[0102] (2) Amount of coarse particles in vinyl chloride polymer particles The content of the vinyl chloride polymer particles obtained that did not pass through a sieve with 250 μm openings (60 mesh in terms of JIS standard sieve mesh) was calculated in mass %. The smaller the value, the fewer the coarse particles, indicating that the dispersant used has excellent polymerization stability. In this evaluation, when the amount of coarse particles is 10 mass % or less, it is determined that there are few coarse particles.

[0103] (3) Plasticizer absorption of vinyl chloride polymer particles (CPA) The mass of a 5mL syringe filled with 0.02g of absorbent cotton was measured (referred to as X(g)), and 0.5g of vinyl chloride polymer particles was added thereto and the mass was measured (referred to as Y(g)). 1g of dioctyl phthalate (DOP) was added thereto and left to stand for 15 minutes. After that, the mixture was centrifuged at 3000 rpm for 40 minutes to remove unabsorbed DOP, and the mass after removal was measured (referred to as Z(g)). The plasticizer absorption (%) of the vinyl chloride polymer particles was calculated using the following formula. The higher the plasticizer absorption, the easier it is to process and the less likely it is to cause defects in the appearance, such as bumps, when processing into a sheet. In this evaluation, a plasticizer absorption of 25% or more was determined to be good. Plasticizer Absorption (%) = 100 x [{(ZX) / (YX)}-1]

[0104] [Table 1]

[0105] [Table 2]

[0106] As shown in Table 2, each of the solutions of Examples 1 to 29 was highly stable. In addition, when suspension polymerization was carried out using each of the solutions of Examples 1 to 29 as a dispersant, vinyl chloride polymer particles having good plasticizer absorption properties and without increasing the average particle size and with few coarse particles were obtained. Each of the solutions of Examples 1 to 29 was confirmed to be useful as a dispersant for suspension polymerization.

[0107] On the other hand, in Comparative Example 1, a highly stable solution containing PVA (A) was not obtained.

[0108] In addition, when the content of alcohol (C) was increased as in Reference Example 1, even a solution not containing compound (B) was highly stable and could be used as a dispersant for suspension polymerization. However, when the content of alcohol (C) was low as in Comparative Example 1, a solution not containing compound (B) had low stability. In contrast, when compound (B) was contained as in each of the solutions of Examples 1 to 29, a highly stable solution was obtained regardless of the content of alcohol (C). In addition, a comparison between Example 9 and Reference Example 1 confirmed that the viscosity of the solution was reduced by containing compound (B). [Industrial Applicability]

[0109] The solution of the present invention can be suitably used as a dispersant for suspension polymerization.

Claims

1. a solution containing a vinyl alcohol polymer (A) having a degree of saponification of 30 mol % or more and 80 mol % or less, a degree of polymerization of 100 or more and 700 or less, and a block character of a vinyl ester unit of 0.6 or less, and having a concentration of 15 mass % or more; The solution contains at least one selected from the group consisting of an acid having an acid dissociation constant (pKa) in water of 0 or more and 6.0 or less, a salt thereof, and an anion thereof.

2. The dispersant according to claim 1 , which is used in the polymerization of vinyl compounds.

3. A preparation step of preparing a vinyl alcohol polymer (A) having a degree of saponification of 30 mol % or more and 80 mol % or less, a degree of polymerization of 100 or more and 700 or less, and a block character of a vinyl ester unit of 0.6 or less; A polymerization step for polymerizing a vinyl compound in the presence of a vinyl alcohol polymer (A) to obtain vinyl compound polymer particles having an average particle size of 220 μm or less. Equipped with In the preparation step, a solution having a concentration of the vinyl alcohol polymer (A) of 15% by mass or more is prepared, A method for producing a vinyl compound polymer, wherein the solution in the preparation step contains at least one acid selected from the group consisting of an acid having an acid dissociation constant (pKa) in water of 0 to 6.0, a salt thereof, and an anion thereof.

4. The method for producing a vinyl compound polymer according to claim 3, wherein in the polymerization step, a solution having a concentration of the vinyl alcohol polymer (A) of 15% by mass or more is introduced into a polymerization reaction system of the vinyl compound.

5. 5. The method for producing a vinyl compound polymer according to claim 3, wherein in the polymerization step, a solution having a concentration of the vinyl alcohol polymer (A) of 15% by mass or more is diluted and introduced into a polymerization reaction system of the vinyl compound.

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