Solution, dispersant, method for producing vinyl compound polymer, and method for producing solution

Abstract

Provided are a solution, a method for producing such a solution, and the like, the solution being highly stable regardless of the alcohol content and excellent in the performance as a dispersant for suspension polymerization. The solution includes a vinyl alcohol-based polymer (A) having a saponification degree of 30-80 mol% and a polymerization degree of 100-700, a compound (B), and an alcohol (C). The compound (B) is represented by formula (1). In formula (1), X is an oxygen atom or the like. Y is a group having a carbon number of 1-10. Z is one type selected from the group consisting of carboxyl groups, sulfo groups, phosphate groups, salts thereof, and anions thereof. R 1 is an acyl group or a hydrocarbon group.

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 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) for emulsion polymerization and suspension polymerization, and a binder for inorganic materials.

[0003] PVA is sometimes stored, distributed, sold, used, etc., in the form of a solution. Generally, the solubility of PVA in water, etc., varies depending on the degree of saponification, degree of polymerization, modified species introduced, etc. When storing or using PVA as a solution, a highly concentrated, low-viscosity, and highly stable solution is required, particularly in terms of productivity and handleability. Here, in the prior art, it is known that even PVA that is insoluble in water alone can become soluble in water when combined 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] As described above, the use of a specific surfactant can increase the solubility of PVA and improve the stability of the resulting solution. However, due to the influence of the surfactant, 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, even without using a surfactant. However, solutions containing solvents with a high alcohol content may be subject to restrictions on their handling due to waste liquid treatment, environmental impact, etc.

[0006] An object of the present invention is to provide a solution that 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 that has 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 containing 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 bonding 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], in which the content of the vinyl alcohol polymer (A) is 15% by 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 one of [1] to [4], in which the content of the alcohol (C) is 5% by mass or more and 80% by mass or less; [6] A solution of any one of [1] to [5], in which the content of alcohol (C) is less than 20 mass%; [7] A solution of any one 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 dispersant 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 bonding 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 dispersant described in [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 multiple batches: [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 bonding 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 vinyl ester units 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 vinyl ester units 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 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% by mass or more is introduced into a polymerization reaction system of the 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% by mass or more is diluted and introduced into a polymerization reaction system of the vinyl compound; This is achieved by providing either: [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a solution that 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, the present invention can provide a dispersant that has 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 INVENTION

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

[0010] <Solution> A 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), wherein 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). By adjusting the composition ratio, the solution can be made to have a high PVA (A) concentration, low viscosity, and high stability. Such a solution is particularly suitable in terms of productivity and ease of handling. The content of alcohol (C) in the solution is not limited. 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 handleability in waste liquid treatment, etc. Furthermore, 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. Furthermore, polymer particles obtained by suspension polymerization using the solution as a dispersant also have good plasticizer absorption.

[0012] Although the reason why the solution exhibits the above-mentioned effects is unclear, the following reasons are presumed. It is presumed that the compound (B) has a specific structure, which allows it to function as a good surfactant, maintaining a good dispersion state of PVA (A) in the solution and thereby enhancing the stability of the solution. Furthermore, the inclusion of alcohol (C) in the solution enhances the solution stability. It is also presumed that the acid dissociation constant of compound (B) falls within an appropriate range due to the specific structure of compound (B), which contributes to the above-mentioned effects. That is, for example, in a near-neutral environment, compound (B) can interact with PVA (A) to enhance the dispersion stability of PVA (A). On the other hand, in a suspension polymerization system, which is typically a weakly acidic environment, compound (B) separates from PVA (A), which reduces the influence of compound (B) on PVA (A), and therefore functions satisfactorily as a dispersant for suspension polymerization.

[0013] Thus, the solution can be suitably used as a dispersant by adding it to a suspension polymerization system during suspension polymerization. Furthermore, since the solution is a liquid, when used as a dispersant for suspension polymerization, it is not necessary to dissolve the vinyl alcohol polymer, and therefore 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 usually has low solubility in water, and even if a solution is obtained, the solution has low stability and is prone to gelation, precipitation, etc. The solution according to one embodiment of the present invention contains compound (B) and alcohol (C), and therefore has high solution stability despite containing such 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 thereby 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 degree of polymerization of PVA (A) is 100, and may be 130, 160, 190, or 210. A degree of polymerization equal to or greater than the lower limit enhances protective colloid properties, enabling the production of polymer particles with smaller particle sizes when used as a dispersant for suspension polymerization. On the other hand, the upper limit of the degree of polymerization is 700, and may be 600, 500, 400, or 300. A degree of polymerization equal to or less than the upper limit enhances surface activity, enabling the production of polymer particles with smaller particle sizes when used as a dispersant for suspension polymerization, enhancing the plasticizer absorption capacity of the resulting polymer particles. Furthermore, a degree of polymerization equal to or less than the upper limit tends to result in a lower viscosity solution. The degree of polymerization of PVA (A) refers to the viscosity-average degree of polymerization 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 provide these 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 hydroxy groups such as ethylene glycol vinyl ether, 1,3-propanediol vinyl ether, and 1,4-butanediol vinyl ether. Examples of the hydroxyl group-containing vinyl ether include vinyl ethers, allyl acetate, allyl ethers such as propyl allyl ether, butyl allyl ether, and 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, and 3-methyl-3-buten-1-ol, and monomers having a silyl group such as vinyltrimethoxysilane, vinylmethyldimethoxysilane, vinyldimethylmethoxysilane, vinyltriethoxysilane, vinylmethyldiethoxysilane, vinyldimethylethoxysilane, 3-(meth)acrylamidopropyltrimethoxysilane, and 3-(meth)acrylamidopropyltriethoxysilane. Among these, α-olefins, acrylic acid, methacrylic acid, acrylic acid esters, and methacrylic acid esters are preferred. In one embodiment of the present invention, it is preferable that the PVA (A) does not have a polyoxyethylene side chain, and in another embodiment, it is preferable 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, while the proportion of the other structural units may be, for example, 0.1 mol % or more, or 1 mol % or more.

[0020] PVA (A) that has not been graft-copolymerized can be preferably used. However, PVA (A) may be modified with one or more graft-copolymerizable monomers. 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 graft-copolymerizable monomers include unsaturated carboxylic acids or derivatives thereof; unsaturated sulfonic acids or derivatives thereof; and α-olefins having 2 to 30 carbon atoms. The proportion of structural units derived from graft-copolymerizable monomers in PVA (A) is preferably 5 mol % or less based on the total structural units in PVA (A).

[0021] The block character of the vinyl ester unit in PVA (A) (hereinafter simply referred to as "block character") may be, for example, 0.3 or more and 0.8 or less, 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 within the above range, the performance as a dispersant for suspension polymerization is improved due to, for example, good 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 solution stability is great.

[0022] The block character of PVA is a numerical value that represents the distribution of residual esters (usually alkoxycarbonyl groups) and hydroxy groups generated by saponification of the esters, and takes a value between 0 and 2. 0 indicates that the residual esters or hydroxy groups are distributed in a completely block-like manner. As the value increases, the alternation increases, with 1 indicating that the residual esters and hydroxy groups are present completely randomly and 2 indicating that the residual esters and hydroxy 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 of 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 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 saponification conditions such as catalyst and solvent. For example, when saponification is performed using an alkaline 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 block character of over 0.6 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%, 35%, or 40% by mass. By setting the content of PVA (A) to the above lower limit or more, a highly concentrated PVA solution can be obtained, allowing for efficient distribution, storage, and the like. Furthermore, by setting the content of PVA (A) to the above lower limit or more, the stability of the solution tends to be further improved. The upper limit of the content of PVA (A) may be 70% by mass, or may be 60%, 50%, or 40% by mass. By setting the content of PVA (A) to the above upper limit or less, it is possible to reduce the viscosity of the solution, etc.

[0026] (Method for producing PVA(A)) PVA (A) can be produced, for example, by polymerizing a vinyl ester monomer 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. Of these, vinyl acetate is preferred.

[0028] 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, with methanol being even more preferred. When carrying out the polymerization reaction by bulk polymerization or solution polymerization, either a batch system or a continuous system can be used.

[0029] Examples of polymerization initiators used in the polymerization reaction include known polymerization initiators such as azo initiators such as 2,2'-azobisisobutyronitrile, 2,2'-azobis(2,4-dimethylvaleronitrile), and 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), and organic peroxide initiators such as benzoyl peroxide, n-propyl peroxycarbonate, cumyl peroxyneodecanoate, and t-butyl peroxyneodecanoate. 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 present during the polymerization of vinyl ester monomers. Examples of chain transfer agents 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 also function as a modifier. Depending on the type of chain transfer agent, a specific group (e.g., a carboxyl group) may be introduced at the end of the PVA (A). Using a PVA (A) having a carboxyl group at its end tends to improve the plasticizer absorption of polymer particles obtained by suspension polymerization. When the PVA (A) has a carboxyl group at its end, the carboxyl group may exist in the form of a salt or an anion.

[0032] The resulting vinyl ester polymer can be saponified, for example, by treating the vinyl ester polymer in an alcohol solution with an alkali or acid catalyst. The saponification reaction of the vinyl ester polymer can be carried out by conventional alcoholysis or hydrolysis using an alkali catalyst such as sodium hydroxide, potassium hydroxide, or sodium methoxide, or an acid catalyst such as p-toluenesulfonic acid. Examples of solvents used in the saponification reaction include alcohols such as methanol and ethanol; esters such as methyl acetate and ethyl acetate; ketones such as acetone and methyl ethyl ketone; and aromatic hydrocarbons such as benzene and toluene. These solvents can be used alone or in combination. Among these, it is preferable to use methanol or a mixed solution of methanol and methyl acetate as the solvent and carry out the saponification reaction in the presence of sodium hydroxide as an alkali catalyst, as this 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 bonding to Y. * is a bond.

[0037] It is presumed that when compound (B) has a group containing an electron-withdrawing atom such as an oxygen atom or a nitrogen atom as X, the uniformity of the solution and separability from PVA (A) are improved, 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, even more preferably a hydrogen atom or a methyl group, and even 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 still more 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 also bond with 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 groups 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 Y 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 preferred, and a methylene group (-CH2-) is even more preferred. 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, which contains an electron-withdrawing atom such as an oxygen atom or a nitrogen atom, is located in the vicinity of Z, which can further improve the uniformity of the solution and the separability from PVA (A).

[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. When the solution is, for example, an aqueous solution, Z is preferably 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 phosphate group (H2PO4-), compound (B) may be a phosphate ester or a sulfonate 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 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 can be added to the N-long-chain acyl amino acid.

[0042] R 1 The number of carbon atoms is, for example, 7 to 24, preferably 8 to 21, more preferably 10 to 14, and even more preferably 11 to 13.

[0043] R 1 is preferably an acyl group. 1 is an acyl group, R 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 is also preferably 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 is more preferably 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 salts, acylamino acid salts, acyl lactates, acyltaurine salts, alkylsulfosuccinates, acyl hydrolyzed collagen salts, and acylisethionates, more preferably at least one selected from the group consisting of acyl lactates and acylamino acid salts, and even more preferably an acylamino acid salt. The acylamino acid salt is more preferably an N-acylamino acid salt.

[0048] The N-acylamino acid salt is preferably a salt of an N-acylamino acid (also referred to as an "N-long-chain acylamino acid") in which an acyl group derived from a saturated or unsaturated fatty acid having 8 to 21 carbon atoms has been introduced into the amino group of the amino acid. The amino acid residue of the N-acylamino acid salt may be any of various amino acids, such as α-amino acid, β-amino acid, γ-amino acid, or ω-amino acid. The amino group may be in the N-methyl or N-ethyl form. Furthermore, the optical isomer, i.e., the D-form, L-form, or racemic form, is not important. 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, dienecholic acid, ferric Examples of suitable 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. Of these, sarcosine is preferred.

[0049] The acyl group in the acyl lactate salt and the 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, nonenoic acid, decenoic acid, dipentylheptanoic 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, and butylheptylnonanoic acid; octenoic acid, nonenoic acid, and decenoic acid. Straight-chain monoenoic acids such as carboxylic acid, caproleic acid, undecylenic acid, linderic acid, cinnamic acid, lauroleic acid, tridecenoic acid, tsuzuic acid, myristoleic acid, pentadecenoic acid, hexedecenoic 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 suitable fatty acids include di- and 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, aleprolic acid, areprestic acid, aleprilic acid, alepuric acid, hydnocarpic acid, schormuglic acid, golric acid, α-cyclopentylic acid, α-cyclohexylic acid, and α-cyclopentylethyl acid. The preferred fatty acids are straight-chain fatty acids. Saturated fatty acids are preferred, with straight-chain saturated fatty acids being more preferred, and lauric acid being particularly preferred.

[0050] The acyl group in the acyl lactate salt and the 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 8 to 21 carbon atoms. Examples of such acyl groups include acyl groups derived from coconut oil fatty acids, palm oil fatty acids, linseed oil fatty acids, sunflower oil fatty acids, soybean oil fatty acids, sesame oil fatty acids, castor oil fatty acids, olive oil fatty acids, camellia oil fatty acids, 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 thereof include cocoyl methyl alanine TEA, cocoyl methyl alanine potassium, lauroyl methyl alanine sodium, lauroyl methyl alanine TEA, lauroyl methyl alanine potassium, sodium cocoyl glycine, cocoyl glycine TEA, potassium cocoyl glycine, sodium lauroyl glycine, lauroyl glycine TEA, potassium lauroyl glycine, sodium myristoyl sarcosine, myristoyl sarcosine TEA, potassium myristoyl sarcosine, sodium lauroyl methyl-β-alanine, lauroyl methyl-β-alanine TEA, lauroyl methyl-β-alanine potassium, cocoyl methyl-β-alanine sodium, cocoyl methyl-β-alanine TEA, and cocoyl methyl-β-alanine potassium. 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 lactiate, TEA cocoyl lactiate, potassium cocoyl lactiate, sodium lauroyl lactiate, TEA lauroyl lactiate, potassium lauroyl lactiate, sodium stearoyl lactiate, TEA stearoyl lactiate, potassium stearoyl lactiate, sodium isostearoyl lactiate, TEA isostearoyl lactiate, potassium isostearoyl lactiate, and the like.

[0053] 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 or more and 6.0 or less. 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 compound (B) is an acid or a salt thereof within the above pKa range, the solubility of PVA (A) in a solution containing PVA (A) and compound (B) is superior, and the separability from PVA (A) in the solution under weakly acidic conditions (for example, in a suspension polymerization system) is superior.

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

[0055] The lower limit of the content of 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 setting the content of compound (B) to the above lower limit or more, it is possible to further increase the stability of the solution. The upper limit of the content of compound (B) is preferably 10% by mass, more preferably 4% by mass, and even more preferably 2% by mass. By setting the content of compound (B) to the above upper limit or less, the effect of compound (B) during suspension polymerization is further reduced, and 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. From the viewpoints of the solubility of the PVA (A), compatibility with water, and viscosity of the solution, the alcohol (C) is preferably an alcohol having 1 to 4 carbon atoms. The number of carbon atoms in the alcohol (C) is more preferably 1 to 3, and even more preferably 2. In one embodiment, the alcohol (C) is preferably a linear alcohol. The alcohol (C) is preferably a monohydric alcohol, or preferably a primary alcohol, with ethanol being particularly preferred.

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

[0058] The lower limit of the content of 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 setting the content of alcohol (C) to the above lower limit or above, it is possible to further increase the stability of the solution. The upper limit of the content of alcohol (C) is preferably 80% by mass, more preferably 50% by mass. In some cases, the content of alcohol (C) is more preferably less than 20% by mass or 15% by mass or below. Setting the content of alcohol (C) to the above upper limit or below the above upper limit makes it possible to facilitate waste liquid treatment, reduce environmental impact, 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 easy to handle 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 other components such as 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. Furthermore, 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. Having a viscosity of the solution equal to or less than the upper limit makes it possible to improve handleability. The lower limit of the viscosity may be 1 mPa·s, or may be 10 mPa·s, 100 mPa·s, 500 mPa·s, or 1,000 mPa·s. The viscosity of the solution is measured using a Brookfield viscometer (spindle LV-03 to LV-04) at 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 enhanced. The pH of the solution is preferably 5.0 or higher, more preferably 6.0 or higher. The pH of the solution is preferably 9.0 or lower, more preferably 8.0 or lower, and may be 7.5 or lower, or 7.0 or lower.

[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 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 the components. However, it is preferable to produce the solution by the following method.

[0066] That is, a method for producing a solution according to one embodiment of the present invention comprises 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 times, and may be, for example, two to 20 times, or three to 12 times. In the production method, the liquid containing compound (B) and alcohol (C) may further contain water, etc. The specific and preferred forms of each component, such as PVA (A), compound (B), and alcohol (C), used in the production method 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.

[0069] <Dispersant> A 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 enhance the dispersibility of monomers during suspension polymerization and to control the plasticizer absorption of the resulting polymer particles. Specific and preferred forms of the PVA (A), compound (B), and optional alcohol (C), which will be described later, contained in the dispersant (1) are the same as those of the components contained in the solution according to one embodiment of the present invention.

[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 even more preferably 70%, 90%, 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 volatile content in the dispersant (1) is, for example, 80% by mass, and may be 60% or 40% by mass. Volatile components that may be contained in the dispersant (1) include alcohol (C), water, etc.

[0071] The dispersant (1) may be, for example, a solid (e.g., powdery) dispersant consisting only of PVA (A) and compound (B). The solid dispersant dissolves well in a solvent containing alcohol. The solid dispersant (1) may be used by dissolving it in a solvent not containing alcohol (e.g., water). When used as a dispersant in suspension polymerization, the concentration of PVA (A) in the polymerization system is usually not high, for example, 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) in addition to the PVA (A) and the compound (B), or may contain water. That is, the solution according to one embodiment of the present invention described above 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 an 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 with a small average particle size and few coarse particles. Furthermore, the polymer particles obtained by suspension polymerization using the dispersant (1) also have good plasticizer absorption.

[0074] The lower limit of the content of compound (B) relative to 100 parts by mass of 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. When the content of compound (B) is equal to or greater than the above lower limit, the solubility of PVA (A) can be increased, etc. The upper limit of the content of compound (B) relative to 100 parts by mass of 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. When the content of compound (B) is equal to or less than the above upper limit, the effect of compound (B) during suspension polymerization is reduced, and the performance as a dispersant is further improved.

[0075] Another embodiment of the dispersant (2) of the present invention is a solution containing PVA (A) having a saponification degree 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, at a concentration of 15 mass% or more. The dispersant (2) is an additive used to enhance the dispersibility of monomers during suspension polymerization. The dispersant (2) is suitable for use in the polymerization of vinyl compounds. The dispersant (2) is suitable as a dispersant for the suspension polymerization of vinyl compounds, and can efficiently produce polymer particles with a small average particle size and few coarse particles. Furthermore, the polymer particles obtained by suspension polymerization using the dispersant (2) also have good plasticizer absorption.

[0076] The specific and preferred forms 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 acid (compound (B')) selected from the group consisting of acids, salts thereof, and anions thereof, 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. Examples of such compounds (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 hydrocarbon group in the compound (B') preferably has 8 to 21 carbon atoms, more preferably 10 to 14 carbon atoms, and even more preferably 11 to 13 carbon atoms. The hydrocarbon group in the compound (B') is preferably an aliphatic hydrocarbon group, and more preferably an alkyl group. A suitable embodiment of the compound (B') is 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] It is preferable that the dispersant (2) further contains an alcohol (C). Specific and preferred forms 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. Specific and preferred forms of the dispersant (2) include the specific and preferred forms 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 comprises a step of polymerizing a vinyl compound in the presence of a dispersant according to one embodiment of the present invention. The production method may be a method for polymerizing a vinyl compound. The production method is similar to conventionally known methods for producing a vinyl compound polymer, except that the dispersant according to one embodiment of the present invention is used as the dispersant.

[0080] In this production method, a vinyl compound is usually suspension polymerized in an aqueous medium. As the aqueous medium, 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 to be added when carrying out suspension polymerization of a vinyl compound is not particularly limited, but may be preferably 1 ppm or more and 50,000 ppm or less, more preferably 10 ppm or more and 20,000 ppm or less, and even more preferably 10,000 ppm or less, 5,000 ppm or less, or 1,000 ppm or less, based on the mass of the 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 commonly used when suspension polymerizing vinyl compounds in aqueous media. Specific examples include water-soluble cellulose ethers such as methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, and hydroxypropylmethyl 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 copolymers; and water-soluble emulsifiers such as polyoxyethylene sorbitan monolaurate, polyoxyethylene glycerin oleate, and sodium laurate.

[0083] The polymerization initiator used in this production method can be one that has been conventionally used in the polymerization of vinyl compounds. Specifically, the same polymerization initiators as those exemplified for the polymerization of vinyl ester monomers 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 needed. Examples of additives include polymerization regulators such as aldehydes, halogenated hydrocarbons, and mercaptans; and polymerization inhibitors such as phenol compounds, sulfur compounds, and N-oxide compounds. pH adjusters, scale inhibitors, and crosslinking agents can also be added. Multiple additives may be used in combination.

[0085] Examples of vinyl compounds that can be suspension polymerized in this 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; and vinyl ethers. Among these vinyl compounds, vinyl halides are preferred, and vinyl chloride is more preferred. This production method is particularly suitable as a method for suspension polymerizing vinyl chloride alone or as a method for suspension polymerizing vinyl chloride and a monomer copolymerizable 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; and vinyl ethers. 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 thought to function particularly well as a dispersant for suspension polymerization.

[0086] In the suspension polymerization of a vinyl compound in this production method, 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 are also no limitations on the charging order or ratio of the vinyl compound, polymerization initiator, dispersant, aqueous medium, and other additives.

[0087] According to this production method, vinyl compound polymer particles can be efficiently obtained without increasing the average particle size and with few coarse particles, and the vinyl compound polymer particles obtained by this production method also have good plasticizer absorption.

[0088] Another embodiment of the present invention provides a method for producing a vinyl compound polymer, comprising: 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, wherein a solution having a PVA (A) concentration of 15 mass % or more is prepared in the preparation step. 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 a 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 a polymerization reaction system of the vinyl compound in the polymerization step. In addition, 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. [Example]

[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 3-L reactor equipped with a stirrer, reflux condenser, nitrogen inlet, additive inlet, and initiator inlet was charged with 300 parts by mass of vinyl acetate and 1,200 parts by mass of methanol. The temperature was raised to 60°C, and the system was then purged with nitrogen by nitrogen bubbling for 30 minutes. Polymerization was initiated by adding 4.8 parts by mass of 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile) (AIBN). The polymerization temperature was maintained at 60°C during the polymerization, and after 4 hours, the polymerization was terminated by cooling when the conversion reached 50%. Unreacted vinyl acetate was then removed under reduced pressure to obtain a methanol solution of polyvinyl acetate (PVAc). A 40% by mass PVAc solution was saponified by adding a 10% by mass NaOH methanol solution to the solution 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 and 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 this purified PVAc was saponified with an alkali molar ratio of 0.2, followed by Soxhlet extraction with methanol for three days and subsequent drying to obtain a purified PVA. The degree of polymerization (viscosity-average degree of polymerization) of the resulting PVA was measured in accordance with JIS K6726:1994. The block character of the vinyl ester unit of the PVA obtained in each manufacturing example was measured at a temperature of 70°C and 18,000 cumulative times using a sample in which PVA was dissolved in a heavy water / heavy methanol mixed solvent. 13C-NMR measurements were performed, and the peak integrals were determined by analyzing three peaks associated with two-unit chain structures (dyads) that appear in the methylene region. These three peaks correspond to the methylene carbon 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; the methylene carbon between the carbon atom of the main chain bonded to the residual ester and the carbon atom of the main chain adjacent to that carbon atom and bonded to the residual ester; and the methylene carbon between the carbon atom of the main chain bonded to the hydroxyl group and the carbon atom of the main chain adjacent to that carbon atom and bonded to the hydroxyl group. Specific measurement and calculation methods are described in Poval (Polymer Publishing Association, 1984, pp. 246-249) and Macromolecules, 10, 532 (1977), and measurements and calculations were performed in accordance with these descriptions.

[0092] [Production Examples 2 to 3] (Production of PVA-2 to 3) PVA-2 to PVA-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 PVA-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 3-L reactor equipped with a stirrer, reflux condenser, nitrogen inlet, additive inlet, and initiator inlet was charged with 1,050 parts by weight of vinyl acetate and 450 parts by weight of methanol. The temperature was raised to 60°C, and the system was then purged with nitrogen by bubbling with nitrogen for 30 minutes. A 50% by weight solution of 3-mercaptopropionic acid (hereinafter referred to as 3-MPA) in methanol was prepared as a chain transfer agent, and nitrogen was purged by bubbling with nitrogen gas. The temperature inside the reactor was adjusted to 60°C, and 1.0 part by weight of 3-MPA was added. Then, 1.2 parts by weight of 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile) was added to initiate polymerization. The polymerization temperature was maintained at 60°C during the polymerization, and a 50% by weight methanol solution of 3-MPA was continuously added at 5 mL / hr to achieve a total concentration of 11.5 parts by weight of 3-MPA in the system. After 4 hours, when the conversion reached 40%, the system was cooled to terminate the polymerization. Next, unreacted vinyl acetate was removed under reduced pressure to obtain a methanol solution of modified polyvinyl acetate (modified PVAc). To the modified PVAc solution adjusted to a concentration of 40% by mass, a NaOH methanol solution (10% by mass concentration) was added so that the alkali molar ratio (moles of NaOH / moles of vinyl ester units in modified PVAc) was 0.0243, followed by saponification. The water content of the solution during saponification was adjusted to 1% by mass. Through these operations, a vinyl alcohol polymer (PVA-5) was obtained as PVA (A), with a degree of polymerization of 140, a degree of saponification of 33.0 mol%, and a block character of 0.525, and having a terminal carboxyl group salt. The presence or absence of a carboxyl group salt at the end of the 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. The results confirmed the presence of a carboxyl group salt (COONa group) 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] A solution of Example 1 was obtained by adding 40 parts by mass of PVA-1 in six divided portions to a liquid containing 1 part by mass of sodium lauroyl sarcosine (Nalauroyl sarcosine) as compound (B), 8 parts by mass of ethanol as alcohol (C), and 51 parts by mass of water. The viscosity of the resulting 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 30, Comparative Examples 1 to 5, Reference Example 1] Solutions of Examples 2 to 30, Comparative Examples 1 to 5, and Reference Example 1 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) The solutions obtained in Examples 1 to 30, Comparative Examples 1 to 5, and Reference Example 1 were left to stand at 40°C for 7 days, and then their viscosity was measured in the same manner as above. Based on the viscosity before and after standing, the stability of the solutions was evaluated according to the following criteria. In this evaluation, solutions with a rating of A or B were judged to have 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 over 1%). C: No fluidity and gelation.

[0099] Additionally, suspension polymerization of vinyl chloride was carried out by the following method using separately prepared solutions of Examples 1 to 30, Comparative Examples 3 and 5, and Reference Example 1 as dispersants. Note that the solutions of Comparative Examples 1, 2, and 4 were not used in suspension polymerization because they were less stable. The resulting vinyl chloride polymer particles were then evaluated for average particle size, amount of coarse particles, and plasticizer absorption as described below. The evaluation results are shown in Table 2.

[0100] (Suspension polymerization of vinyl chloride) From each solution of the Examples and Comparative Examples, an amount of the solution was sampled so that the solid content of the solution would be 400 ppm relative to the vinyl chloride content described below. The sampled solution was diluted with deionized water to obtain a first aqueous dispersant solution. 100 parts by mass of the first aqueous dispersant solution was charged into a 5 L autoclave. Similarly, from an aqueous PVA solution prepared by dissolving commercially available PVA ("Kuraray Poval 48-80" manufactured by Kuraray), an amount of the PVA aqueous solution was sampled so that the solid content of the PVA aqueous solution would be 800 ppm relative to the vinyl chloride content. The sampled PVA aqueous solution was diluted with deionized water to obtain a second aqueous dispersant solution. 100 parts by mass of the second aqueous dispersant solution was charged into the autoclave. Next, deionized water was added to the autoclave so that the total amount of deionized water was 1,300 parts by mass. Next, the autoclave was charged with 0.65 parts by mass of a 70% by mass toluene solution of cumyl peroxyneodecanoate and 1.05 parts by mass of a 70% by mass toluene solution of t-butyl peroxyneodecanoate. 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 was charged into the autoclave, and the contents were heated to 57°C to initiate polymerization with stirring. The pressure inside the autoclave at the start of polymerization was 0.83 MPa. 3.5 hours after the start of polymerization, the polymerization was terminated when the pressure inside the autoclave reached 0.70 MPa, and unreacted vinyl chloride was removed. The polymerized slurry was then removed 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 determine the average particle diameter (d p50 (median diameter) was calculated. In this evaluation, an average particle diameter of 220 μm or less was determined to be not large. In Comparative Examples 3 and 5, the obtained vinyl chloride polymer particles were blocked, and although the average particle diameter was not determined by the above method, the average particle diameter was clearly large.

[0102] (2) Amount of coarse particles in vinyl chloride polymer particles The content of the obtained vinyl chloride polymer particles 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 was 10 mass % or less, it was determined that there were few coarse particles. In Comparative Examples 3 and 5, the obtained vinyl chloride polymer particles were blocked. In other words, in Comparative Examples 3 and 5, substantially all of the particles were coarse particles.

[0103] (3) Plasticizer absorption of vinyl chloride polymer particles (CPA) A 5 mL syringe containing 0.02 g of absorbent cotton was weighed (referred to as X (g)), and 0.5 g of vinyl chloride polymer particles was placed in it, followed by weighing (referred to as Y (g)). 1 g of dioctyl phthalate (DOP) was added and allowed to stand for 15 minutes. The mixture was then centrifuged at 3,000 rpm for 40 minutes to remove any unabsorbed DOP, and the mass after removal was measured (referred to as Z (g)). The plasticizer absorbency (%) of the vinyl chloride polymer particles was calculated using the following formula. Higher plasticizer absorbency indicates easier processing and less likelihood of appearance defects, such as bumps, occurring during processing into a sheet. In this evaluation, a plasticizer absorbency of 25% or higher was considered to be good. Comparative Examples 3 and 5 were not evaluated. Plasticizer absorption (%) = 100 × [{(ZX) / (YX)}-1]

[0104] [Table 1]

[0105] [Table 2]

[0106] As shown in Table 2, each of the solutions of Examples 1 to 30 was highly stable. Furthermore, when suspension polymerization was carried out using each of the solutions of Examples 1 to 30 as a dispersant, vinyl chloride polymer particles with good plasticizer absorption and without an increase in average particle size and with few coarse particles were obtained. Each of the solutions of Examples 1 to 30 was confirmed to be useful as a dispersant for suspension polymerization.

[0107] On the other hand, in Comparative Examples 1 to 5, a highly stable solution containing PVA (A) was not obtained, or the vinyl chloride polymer particles obtained had a large average particle size and contained many coarse particles.

[0108] 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 4, the solution not containing compound (B) was less stable. In contrast, when compound (B) was contained as in each of the solutions of Examples 1 to 30, a highly stable solution was obtained regardless of the content of alcohol (C). Furthermore, a comparison between Example 9 and Reference Example 1 confirmed that the viscosity of a solution was reduced by including 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 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) having 1 to 4 carbon atoms, wherein the compound (B) is a compound represented by the following formula (1): 【Chemistry 1】 (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 hydrocarbon group having 1 to 10 carbon atoms in which some or all of the hydrogen atoms may be substituted with a carboxy group, a salt thereof, or an anion thereof. Z is one selected from the group consisting of a carboxy group, a sulfo group, a salt thereof, and an anion thereof. R １ is an acyl group represented by the following formula (4): 【Chemistry 2】 【Transformation 3】 (In formula (2) and formula (3), R ２ , R ３ and R ４ are each independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. * is a bond. 【Chemistry 4】 (In formula (4), R 5 is a saturated or unsaturated hydrocarbon group having 7 to 20 carbon atoms or a group derived from coconut oil. * represents a bond.)

2. The solution according to claim 1, wherein 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. The solution according to claim 1 or 2, wherein the content of the vinyl alcohol polymer (A) is 15% by mass or more.

4. The solution according to claim 1 or 2, wherein the content of the compound (B) is 0.5% by mass or more and 10% by mass or less.

5. The solution according to claim 1 or 2, wherein the content of the alcohol (C) is 5% by mass or more and 80% by mass or less.

6. 3. The solution according to claim 1, wherein the content of the alcohol (C) is less than 20% by mass.

7. The solution according to claim 1 or 2, wherein 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.

8. The present invention relates to a method for producing 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): A dispersant further comprising (C) an alcohol having 1 to 4 carbon atoms, or used together with (C) an alcohol having 1 to 4 carbon atoms. 【Transformation 5】 (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 hydrocarbon group having 1 to 10 carbon atoms in which some or all of the hydrogen atoms may be substituted with a carboxy group, a salt thereof, or an anion thereof. Z is one selected from the group consisting of a carboxy group, a sulfo group, a salt thereof, and an anion thereof. R １ is an acyl group represented by the following formula (4): 【Transformation 6】 【Transformation 7】 (In formula (2) and formula (3), R ２ , R ３ and R ４ are each independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. * is a bond. 【Transformation 8】 (In formula (4), R 5 is a saturated or unsaturated hydrocarbon group having 7 to 20 carbon atoms or a group derived from coconut oil. * represents a bond.)

9. 9. The dispersant of claim 8, which is in solid form.

10. A method for producing a vinyl compound polymer, comprising a step of polymerizing a vinyl compound in the presence of the dispersant according to claim 8 or 9.

11. A method for producing a solution, comprising a step of adding, in multiple batches, 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) having 1 to 4 carbon atoms: 【Chemistry 9】 (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 hydrocarbon group having 1 to 10 carbon atoms in which some or all of the hydrogen atoms may be substituted with a carboxy group, a salt thereof, or an anion thereof. Z is one selected from the group consisting of a carboxy group, a sulfo group, a salt thereof, and an anion thereof. R １ is an acyl group represented by the following formula (4): 【Chemistry 10】 【Chemistry 11】 (In formula (2) and formula (3), R ２ , R ３ and R ４ are each independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. * is a bond. 【Chemistry 12】 (In formula (4), R 5 is a saturated or unsaturated hydrocarbon group having 7 to 20 carbon atoms or a group derived from coconut oil. * represents a bond.)

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