JP2020169255A - Method for producing sulfonic acid group-containing copolymer - Google Patents

Abstract

To provide a method for producing a sulfonic acid group-containing copolymer that shows improved dispersion in composite stains compared with polymers prepared by the conventional production methods.SOLUTION: A method for producing a sulfonic acid group-containing copolymer, includes the step of polymerizing a monomer composition containing a sulfonic acid group-containing monomer (A), an ether linkage-containing monomer (B), and a carboxyl group-containing monomer (C). In the sulfonic acid group-containing monomer (A), the content of bisulfite is 18000 ppm or less.SELECTED DRAWING: None

Description

The present invention relates to a method for producing a sulfonic acid group-containing copolymer. More specifically, the present invention relates to a method for producing a sulfonic acid group-containing copolymer useful as a raw material for detergent additives and the like.

Conventionally, detergents used for clothing and the like are blended with detergent builders (detergent aids) such as zeolite, carboxymethyl cellulose, and polyethylene glycol for the purpose of improving the cleaning effect of the detergent. Further, in addition to the above-mentioned various detergent builders, in recent years, a polymer has been blended into the detergent composition as a detergent builder.
Regarding such a polymer, for example, Patent Document 1 describes a carboxyl group-containing polymer, and the carboxyl group-containing polymer is represented by a predetermined structure derived from the ether bond-containing monomer (A). The structural unit (a), the structural unit (b) derived from the sulfonic acid group-containing polymer (B), and the structural unit (c) derived from the acrylate-based polymer (C) are essentially contained. The carboxyl group-containing polymer contains 0.5% by mass or more of the structural unit (a) and 9% by mass with respect to 100% by mass of the total amount of structural units derived from all the monomers forming the carboxyl group-containing polymer. % Or less, structural unit (b) is 0.5% by mass or more and 25% by mass or less, and structural unit (c) is 55% by mass or more and 99% by mass or less, and the weight average molecular weight is 30,000 to 60, A carboxyl group-containing polymer is disclosed, which is characterized by being 000.

Further, Patent Document 2 contains an ether bond-containing compound represented by a predetermined structure, and contains 0 to 20% by mass of a predetermined diol compound and 1 to 20% by mass of a compound having two predetermined carbon-carbon double bonds. %, A composition containing 0 to 1% by mass of a predetermined epoxy compound, and a silica-scale dispersibility for a copolymer produced by using such a composition and acrylic acid are disclosed.

Japanese Patent No. 6275131 Japanese Unexamined Patent Publication No. 2014-62176

As described above, conventionally, sulfonic acid group-containing copolymers used for detergent applications have been developed. For example, Patent Document 1 reports the ability to prevent recontamination using carbon black. However, as various detergents are becoming more sophisticated and compact, it is required that the cleaning performance of polymers used for detergents be further improved as compared with conventional polymers, and in particular, hydrophilic substances such as mud. There has been a demand for a technique for improving dispersibility in complex stains in which hydrophobic substances such as sebum and soot are combined in a complex manner.

The present invention has been made in view of the above situation, and provides a method for producing a sulfonic acid group-containing copolymer, which is superior in dispersibility to complex stains as compared with the polymer obtained by the conventional production method. The purpose.

The present inventor has studied various methods for producing a sulfonic acid group-containing copolymer, and obtained the results by setting the content of bisulfite in the sulfonic acid group-containing monomer used for polymerization to a specific amount or less. We have found that the dispersibility of the above-mentioned copolymer with respect to complex stains is improved, and have arrived at the idea that the above-mentioned problems can be solved brilliantly, and have reached the present invention.

That is, the present invention is a method for producing a sulfonic acid group-containing copolymer, wherein the production method is a sulfonic acid group-containing monomer (A), an ether bond-containing monomer (B), and a carboxyl group. A sulfonic acid group-containing compound in which the content of hydrogen sulfite in the sulfonic acid group-containing monomer (A) is 18,000 ppm or less, which comprises a step of polymerizing a monomer composition containing the containing monomer (C). This is a method for producing a polymer.

The sulfonic acid group-containing monomer (A) has the following formula (1);

(In the formula, R ¹ represents a hydrogen atom or a methyl group. R ² represents CH ₂ , CH ₂ CH ₂ or a direct bond.) By the reaction of the epoxy compound represented by the hydrogen sulfite. It is preferably obtained.

The sulfonic acid group-containing monomer (A) has the following formula (2);

(In the formula, R ¹ represents a hydrogen atom or a methyl group. R ² represents CH ₂ , CH ₂ CH ₂ or a direct bond. R ³ , R ⁴ represents a hydroxyl group or -SO ₃ Z. , Z represents a hydrogen atom, a metal atom, an ammonium group or an organic amine group. However, one of R ³ and R ⁴ represents -SO ₃ Z, and the other represents a hydroxyl group). It is preferably a structure.

The ether bond-containing monomer (B) has the following formula (3);

(In the formula, R ⁵ represents a hydrogen atom or a methyl group. R ⁶ represents CH ₂ group, CH ₂ CH ₂ group or a direct bond. X is a hydroxyl group, a group represented by the following formula (4). , Or a group represented by the following formula (5). Y represents a hydroxyl group, a group represented by the following formula (4), or a group represented by the following formula (5), except that X. , Y represents a hydroxyl group, and the other represents a group represented by the following formula (4) or a group represented by the following formula (5).)

(Wherein, ^{R 7} are the same or different, .n representing an alkylene group having 2 to 4 carbon atoms, oxyalkylene groups ^{(-O-R 7} - an average molar number of addition), 0-5 R ⁸ , R ⁹ , and R ¹⁰ are the same or different, and preferably have a structure represented by an alkyl group having 1 to 4 carbon atoms.

The method for producing a sulfonic acid group-containing copolymer of the present invention has the above-mentioned structure, and the obtained sulfonic acid group-containing copolymer has a higher dispersibility in complex stains than the polymer obtained by the conventional production method. Since it is excellent, it can be suitably used as a raw material such as a detergent additive.

Hereinafter, preferred embodiments of the present invention will be specifically described, but the present invention is not limited to the following description, and can be appropriately modified and applied without changing the gist of the present invention. A form in which two or three or more of the individual preferred forms of the present invention described below are combined also falls under the preferred form of the present invention.

The method for producing a sulfonic acid group-containing copolymer of the present invention simply comprises a sulfonic acid group-containing monomer (A), an ether bond-containing monomer (B), and a carboxyl group-containing monomer (C). The content of the hydrogen sulfite in the sulfonic acid group-containing monomer (A) includes a step of polymerizing the polymer composition, and is 18,000 ppm or less. Since bisulfite acts as a chain transfer agent in the polymerization step, by setting the content of bisulfite in the monomer component to a specific amount or less, unexpected chain transfer reactions can be sufficiently suppressed. It is possible to sufficiently suppress the formation of a copolymer having a small molecular weight and the amount of impurities derived from bisulfite. Thereby, the dispersibility of the obtained copolymer with respect to the composite stain can be improved.
The content of hydrogen sulfite in the sulfonic acid group-containing monomer (A) is preferably 15,000 ppm or less, more preferably 13,000 ppm or less, and further preferably 11,000 ppm or less.
The lower limit of the content of hydrogen sulfite in the sulfonic acid group-containing monomer (A) is not particularly limited, but is usually 10 ppm or more, and may be 100 ppm or more or 1000 ppm or more. ..
The content of hydrogen sulfite in the sulfonic acid group-containing monomer (A) can be measured by the method described in Examples.

The method for producing the sulfonic acid group-containing copolymer is not particularly limited as long as it includes a step of polymerizing the above-mentioned monomer composition, but the above-mentioned polymerization step has a hydrogen sulfite content of 18,000 ppm or less. It preferably includes a step of mixing the sulfonic acid group-containing monomer (A), the ether bond-containing monomer (B), and the carboxyl group-containing monomer (C).

The hydrogen sulfite is not particularly limited, and examples thereof include alkali metal salts of hydrogen bisulfite such as sodium hydrogen sulfite and potassium hydrogen sulfite; salts of hydrogen sulfite with ammonium or organic amines, and the like. Examples of the organic amine include alkanolamines such as monoethanolamine, diethanolamine and triethanolamine; triethylamine and the like.
The hydrogen sulfite is preferably sodium bisulfite or potassium bisulfite.

The content ratio of the sulfonic acid group-containing monomer (A) in the monomer composition in the above polymerization step is preferably 1 to 30 mol% with respect to 100 mol% of all the monomers. When the copolymer thus obtained is used as a detergent builder or the like, the interaction between the copolymer and the stain component becomes good, so that the stain component particles interacting with the polymer are dispersed. It is possible to exert the ability to prevent recontamination. The content ratio of the sulfonic acid group-containing monomer (A) is more preferably 2 to 25 mol%, further preferably 3 to 20 mol%, still more preferably 4 to 15 mol%, and particularly preferably. It is 5 to 10 mol%.

The content ratio of the ether bond-containing monomer (B) in the monomer composition in the above polymerization step is preferably 0.1 to 10 mol% with respect to 100 mol% of all the monomers. When the copolymer thus obtained is used as a detergent builder or the like, the interaction between the copolymer and the stain component becomes good, so that the stain component particles interacting with the polymer are dispersed. It is possible to exert the ability to prevent recontamination. In addition, a remarkable effect of improving compatibility with a surfactant can be obtained. The content ratio of the ether bond-containing monomer (B) is more preferably 0.5 to 8 mol%, further preferably 1 to 6 mol%, still more preferably 1.5 to 5 mol%. Particularly preferably, it is 2 to 4 mol%.

The content ratio of the carboxyl group-containing monomer (C) in the monomer composition in the above polymerization step is preferably 60 to 99 mol% with respect to 100 mol% of all the monomers. When the copolymer thus obtained is used as a detergent builder or the like, the interaction between the copolymer and the stain component becomes good, so that the stain component particles interacting with the polymer are dispersed. It is possible to exert the ability to prevent recontamination. The content ratio of the carboxyl group-containing monomer (C) is more preferably 70 to 98 mol%, further preferably 75 to 97 mol%, still more preferably 80 to 96 mol%, and particularly preferably 85. ~ 95 mol%.

The monomer composition in the above polymerization step includes a sulfonic acid group-containing monomer (A), an ether bond-containing monomer (B), and other monomers other than the carboxyl group-containing monomer (C). (E) may be included. The content ratio of the other monomer (E) in the monomer composition is preferably 0 to 10 mol% with respect to 100 mol% of all the monomers. It is more preferably 0 to 5 mol%, further preferably 0 to 3 mol%, and most preferably 0 mol%.

<Sulfonic acid group-containing monomer (A)>
The sulfonic acid group-containing monomer (A) is not particularly limited as long as it has a sulfonic acid (salt) group and an ethylenically unsaturated hydrocarbon group, and is, for example, 3- (meth) allyloxy-2-hydroxy. Propane sulfonic acid, 2- (meth) allyloxyethylene sulfonic acid, 2-acrylamide-2-methylpropane sulfonic acid, p-styrene sulfonic acid, α-methyl-p-styrene sulfonic acid, vinyl sulfonic acid, vinyl sulfamic acid, (Meta) allyl sulfonic acid, isoprene sulfonic acid, 4- (allyloxy) benzene sulfonic acid, 1-methyl-2-propen-1-sulfonic acid, 1,1-dimethyl-2-propen-1-sulfonic acid, 3- Buten-1-sulfonic acid, 1-buten-3-sulfonic acid, 2-acrylamide-1-methylpropanesulfonic acid, 2-acrylamidepropanesulfonic acid, 2-acrylamide-n-butanesulfonic acid, 2-acrylamide-2- Examples thereof include unsaturated sulfonic acids such as phenylpropanesulfonic acid and 2-((meth) acryloyloxy) ethanesulfonic acid, and salts thereof.

The sulfonic acid group-containing monomer (A) has the following formula (2);

(In the formula, R ¹ represents a hydrogen atom or a methyl group. R ² represents CH ₂ , CH ₂ CH ₂ or a direct bond. R ³ , R ⁴ represents a hydroxyl group or -SO ₃ Z. , Z represents a hydrogen atom, a metal atom, an ammonium group or an organic amine group. However, one of R ³ and R ⁴ represents -SO ₃ Z, and the other represents a hydroxyl group). It is preferably a structure.
In the above equation (2), when R ² is a direct bond, H ₂ C = C (R ¹ ) −R ² −O− in the equation (2) is H ₂ C = C (R ¹ ) −. It means that it is represented by O-.
In the above formula (2), R ¹ is preferably a hydrogen atom. R ² is preferably CH ₂ groups.

The above Z represents a hydrogen atom, a metal atom, an ammonium group or an organic amine group, and when Z is a metal atom, an ammonium group or an organic amine group, -SO ₃ Z is a metal salt, an ammonium salt or an organic amine of a sulfonic acid. Represents salt.
Examples of the metal atom in Z include alkali metal atoms such as lithium, sodium and potassium; alkaline earth metal atoms such as magnesium and calcium; aluminum and iron.
Examples of the organic amine group include alkanolamines such as monoethanolamine, diethanolamine and triethanolamine; alkylamines such as monoethylamine, diethylamine and triethylamine; and polyamines such as ethylenediamine and triethylenediamine.
Z is preferably a hydrogen atom, an alkali metal atom, or an ammonium group, more preferably a hydrogen atom, sodium, or potassium, and even more preferably a hydrogen atom or sodium.

The sulfonic acid group-containing monomer (A) is more preferably 3- (meth) allyloxy-2-hydroxypropanesulfonic acid and a salt thereof, and particularly preferably 3-allyloxy-2-hydroxypropanesulfonic acid and its salt. It is a sodium salt.

The method for preparing the sulfonic acid group-containing monomer (A) is not particularly limited, and the sulfonic acid group-containing monomer (A) can be prepared by any suitable method. Further, a commercially available product may be used, but the following formula (1);

(In the formula, R ¹ represents a hydrogen atom or a methyl group. R ² represents CH ₂ , CH ₂ CH ₂ or a direct bond.) By the reaction of the epoxy compound represented by the hydrogen sulfite. It is preferably obtained.
A preferred embodiment of ^R 1, ^{R 2} in the formula (1) are the same as the preferred embodiment of ^R 1, ^{R 2} in the formula (2).

Specific examples of the epoxy compound represented by the above formula (1) include (meth) allyl glycidyl ether, glycidyl vinyl ether, and glycidyl isopropenyl ether. It is preferably (meth) allyl glycidyl ether or glycidyl vinyl ether, more preferably (meth) allyl glycidyl ether, and most preferably allyl glycidyl ether.

The amount of bisulfite used in the reaction between the epoxy compound represented by the above formula (1) and the hydrogen sulfite is 0.8 to 1.5 mol with respect to 1 mol of the epoxy compound represented by the formula (1). Is preferable. This allows the sulfonation reaction to proceed sufficiently. It is more preferably 0.85 to 1.3 mol, still more preferably 0.9 to 1.1 mol.
When the sulfonic acid group-containing monomer (A) is produced by the above method, it is preferable to use a predetermined amount of hydrogen sulfite from the viewpoint of sufficiently advancing sulfonate. In such a case, the obtained sulfonic acid The hydrogen sulfite tends to remain in the group-containing monomer (A). For example, if the hydrogen sulfite in the obtained sulfonic acid group-containing monomer (A) is 1000 to 18,000 ppm, the sulfonic acid It is obtained when the sulfonate rate of the group-containing monomer (A) is sufficiently high and the sulfonic acid group-containing monomer (A) is used for producing a sulfonic acid group-containing copolymer. The copolymer has excellent dispersibility in complex stains.

The method for obtaining the sulfonic acid group-containing monomer (A) having a hydrogen sulfite content of 18,000 ppm or less is not particularly limited, and a sulfonic acid group-containing monomer (A) having a low hydrogen sulfite content is commercially available. Select a product, adjust the amount of bisulfite used in the reaction between the epoxy compound represented by the above formula (1) and bisulfite, purify the sulfonic acid group-containing monomer (A), etc. For example, the content of bisulfite may be reduced.
The method for purifying the sulfonic acid group-containing monomer (A) is not particularly limited, and examples thereof include a method for crystallization.

<Ether bond-containing monomer (B)>
The ether bond-containing monomer (B) is not particularly limited as long as it has an ether bond and an ethylenically unsaturated hydrocarbon group and does not have a sulfonic acid (salt) group, but the following formula (3) ;

(In the formula, R ⁵ represents a hydrogen atom or a methyl group. R ⁶ represents CH ₂ group, CH ₂ CH ₂ group or a direct bond. X is a hydroxyl group, a group represented by the following formula (4). , Or a group represented by the following formula (5). Y represents a hydroxyl group, a group represented by the following formula (4), or a group represented by the following formula (5), except that X. , Y represents a hydroxyl group, and the other represents a group represented by the following formula (4) or a group represented by the following formula (5).)

(Wherein, ^{R 7} are the same or different, .n representing an alkylene group having 2 to 4 carbon atoms, oxyalkylene groups ^{(-O-R 7} - an average molar number of addition), 0-5 R ⁸ , R ⁹ , and R ¹⁰ are the same or different, and preferably have a structure represented by an alkyl group having 1 to 4 carbon atoms.
In the above formula (3), H ₂ C = C (R ⁵ ) -R ^6- is a metallic group when R ⁵ is a methyl group and R ⁶ is a CH ₂ group; R ⁵ is a methyl group and R ⁶ is a CH. for ₂ CH ₂ group isoprenyl group; ^{R 5} is a methyl group, an isopropenyl group if ^{R 6} is a direct bond; ^{R 5} is a hydrogen atom, if ^{R 6} is a CH ₂ group allyl group; the ^{R 5} hydrogen When the atom, R ⁶ is CH ₂ CH ₂ groups, it represents a butenyl group; when R ⁵ is a hydrogen atom and R ⁶ is a direct bond, it represents a vinyl group.
^{_{H 2 C = C (R 5}} ) -R 6 - The, isoprenyl group, a methallyl group, an allyl group, a vinyl group is preferable. From the viewpoint of enhancing the polymerizable property, an isoprenyl group, a metalyl group and an allyl group are more preferable, and an isoprenyl group and a metalyl group are further preferable.

X and Y in the above formula (3) represent a hydroxyl group, a group represented by the above formula (4), or a group represented by the above formula (5), and either one of X and Y represents a hydroxyl group. The other represents the group represented by the formula (4) or the group represented by the formula (5).

R ⁷ in the above formulas (4) and (5) represents the same or different alkylene group having 2 to 4 carbon atoms. Examples of the alkylene group having 2 to 4 carbon atoms include an ethylene group, a propylene group and a butylene group. Further, from the viewpoint of improving the polymerizable property of the ether bond-containing monomer (A), an alkylene group having 2 to 3 carbon atoms such as an ethylene group and a propylene group is preferable. As the alkylene group, one kind or two or more kinds can be used.
N in the formula (4), (5), the oxyalkylene group ^{(-O-R 7} -) is the average mole number of added, represents a number of 0 to 5. From the viewpoint of mud stain detergency, n is preferably 0 to 4, more preferably 0 to 3, further preferably 0 to 2, particularly preferably 0 to 1, and most preferably 0.

R ⁸ , R ⁹ , and R ¹⁰ in the above formulas (4) and (5) represent alkyl groups having 1 to 4 carbon atoms, which are the same or different from each other. Examples of the alkyl group having 1 to 4 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a t-butyl group and the like. The hydrogen atom of the alkyl group having 1 to 4 carbon atoms may be substituted with a substituent. Examples of the substituent include an amino group, a hydroxyl group and the like. Among the alkyl groups having 1 to 4 carbon atoms, a methyl group, an ethyl group and a butyl group are preferable, and a butyl group is more preferable, from the viewpoint of improving the recontamination prevention ability of the obtained polymer.

Further, R ⁹ and R ¹⁰ in the above formula (5) may be combined with each other to form a cyclic structure. In this case, the cyclic structure formed by the nitrogen atom, R ⁹ and R ¹⁰ is a 3- to 7-membered ring, that is, the total number of carbon atoms of R ⁹ and R ¹⁰ is 2 to 6 in that the cyclic structure is stable. It is preferable to have.

As a combination of X and Y, X is a hydroxyl group, Y is a group represented by the above formula (4); X is a hydroxyl group, Y is a group represented by the above formula (5); X is the above formula (4). The group represented by, Y is a hydroxyl group; X is a group represented by the above formula (5), and Y is a hydroxyl group. From the viewpoint of improving the ability to prevent recontamination, X is preferably a hydroxyl group and Y is a group represented by the above formula (4); X is a hydroxyl group and Y is a group represented by the above formula (5), more preferably. X is a hydroxyl group and Y is a group represented by the above formula (4).

The method for preparing the ether bond-containing monomer (B) is not particularly limited, and the ether bond-containing monomer (B) can be prepared by any suitable method. As such a preparation method, for example, the epoxy ring of a compound having a carbon-carbon double bond and an epoxy ring has an alkyl group having 1 to 4 carbon atoms and a hydroxyl group and / or the hydroxyl group and / or the hydroxyl group of the compound having an amino group. Alternatively, a method of producing by reacting an amino group or the like can be mentioned as a simple method. Examples of the compound having a carbon-carbon double bond and an epoxy ring include (meth) allyl glycidyl ether and glycidyl vinyl ether. Examples of the compound having an alkyl group having 1 to 4 carbon atoms and a hydroxyl group and / or an amino group include methanol, ethanol, isopropanol, n-butanol, din-isopropylamine, and din-butylamine. The above reaction may be carried out without a catalyst, but may be carried out in the presence of an acidic catalyst such as boron trifluoride or a basic catalyst such as sodium hydroxide or potassium hydroxide.

<Carboxylic group-containing monomer (C)>
The carboxyl group-containing monomer (C) is not particularly limited as long as it has a carboxyl group or a salt group thereof and an ethylenically unsaturated hydrocarbon group, but is not particularly limited as long as it has an unsaturated monocarboxylic acid-based monomer or an unsaturated hydrocarbon group. Saturated dicarboxylic acid-based monomers and the like are suitable, and examples of the unsaturated monocarboxylic acid-based monomer include (meth) acrylic acid, crotonic acid, tigric acid, 3-methylcrotonic acid, and 2-methyl-2. -Pentenoic acid, itaconic acid and the like; these monovalent metal salts, divalent metal salts, ammonium salts and organic amine salts are preferable.

Examples of the unsaturated dicarboxylic acid-based monomer include maleic acid, itaconic acid, mesaconic acid, citraconic acid, fumaric acid and the like, monovalent metal salts, divalent metal salts, ammonium salts and organic amine salts thereof. , Their anhydrides, or half esters are preferred.
As the carboxyl group-containing monomer (C), (meth) acrylic acid (salt) and maleic acid (salt) are preferable, (meth) acrylic acid (salt) is more preferable, and acrylic acid (salt) is particularly preferable. Salt).
The salt of the carboxyl group-containing monomer (C) is not particularly limited, and examples thereof include the metal salt, ammonium salt, and organic amine salt described for Z in the above formula (2). Alkali metal salts such as sodium and potassium are preferable.

As described above, the monomer composition in the polymerization step includes the sulfonic acid group-containing monomer (A), the ether bond-containing monomer (B), and other than the carboxyl group-containing monomer (C). The monomer (E) may be contained, and as the other monomer (E), specifically, a monomer obtained by adding an alkylene oxide to an unsaturated alcohol such as (meth) allyl alcohol or isoprenol. , Polyalkylene glycol chain-containing monomer such as (meth) acrylic acid ester of alkoxyalkylene glycol; vinyl aromatic monomer having heterocyclic aromatic hydrocarbon group such as vinylpyridine and vinylimidazole; dimethylaminoethyl Dialkylaminoalkyl (meth) acrylates such as acrylates, dimethylaminoethyl methacrylates and dimethylaminopropyl acrylates, dialkylaminoalkyl (meth) acrylamides such as dimethylaminoethylacrylamide, dimethylaminoethylmethacrylate and dimethylaminopropylacrylamide, diallylamine and diallyldimethyl Amino group-containing monomers such as allylamine such as diallylalkylamine such as amine and quaternized products thereof; N-vinylpyrrolidone, N-vinylformamide, N-vinylacetamide, N-vinyl-N-methylformamide, N- N-vinyl monomers such as vinyl-N-methylacetamide and N-vinyloxazolidone; amide-based monomers such as (meth) acrylamide, N, N-dimethylacrylamide and N-isopropylacrylamide; (meth) allyl alcohols, Hydroxyl group-containing monomer such as isoprenol; (meth) acrylic acid alkyl ester-based monomer such as butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, dodecyl (meth) acrylate; 2-hydroxyethyl (meth) acrylate , 2-Hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 2-hydroxyhexyl (meth) acrylate and other (meth) hydroxyalkyl acrylate monomers; Vinyl aryl monomers such as styrene, inden and vinylaniline; examples thereof include isobutylene and vinyl acetate.
The quaternized product is obtained by reacting the amino group-containing monomer with a quaternizing agent usually used. Examples of the quaternizing agent include alkyl halides and dialkyl sulfuric acids.

The polymerization method in the above polymerization step is not particularly limited, and a commonly used polymerization method or a modified method thereof can be adopted. Examples of the polymerization method include a radical polymerization method, and specifically, an oil-in-water emulsion polymerization method, a water-in-oil emulsion polymerization method, a suspension polymerization method, a dispersion polymerization method, a precipitation polymerization method, and a solution polymerization method. , Aqueous solution polymerization method, massive polymerization method and the like can be adopted. Among the above-exemplified polymerization methods, it is preferable to adopt the solution polymerization method because it is highly safe and the production cost (polymerization cost) can be reduced.

In the above solution polymerization method, the monomer component is polymerized in a solvent.
As the solvent, it is possible to use only an organic solvent, but it is preferable to include water. It is more preferable to use 50% by mass or more of water, more preferably 80% by mass or more of water, and particularly preferably 100% by mass of water with respect to 100% by mass of the total amount of the solvent used. Examples of the organic solvent that can be used alone or in combination with water include lower alcohols such as ethanol and isopropanol; amides such as N, N-dimethylformamide; ethers such as diethyl ether and dioxane; glycols, glycerin and polyethylene glycol. Aqueous organic solvents such as class; etc. are preferably mentioned.
As the solvent, only one kind may be used, or two or more kinds may be used in combination.

The amount of the solvent used is preferably 40 to 300 parts by mass, more preferably 40 parts by mass, based on 100 parts by mass of the total amount of all the monomers (monomers (A), (B), (C), (E)). Is 45 to 200 parts by mass, more preferably 50 to 150 parts by mass. When the amount of the solvent used is 40 parts by mass or more with respect to 100 parts by mass of the total amount of all the monomers, it is possible to sufficiently suppress that the molecular weight of the obtained polymer becomes too high. On the other hand, if the amount of the solvent used is 300 parts by mass or less with respect to 100 parts by mass of the total amount of all the monomers, it is possible to sufficiently suppress the concentration of the obtained polymer from becoming low, and the solvent removal step is omitted. You can also do it.
A part or all of the solvent may be charged in the reaction vessel at the initial stage of polymerization, but a part of the solvent may be added (dropped) into the reaction system during the polymerization reaction, or a monomer. In the form in which the components, the polymerization initiator and the like are dissolved in a solvent in advance, they may be added (dropped) into the reaction system together with these components during the polymerization reaction.

The reaction form of the solution polymerization method is not particularly limited, and the reaction can be carried out in a form usually used. Typically, for example, the above-mentioned single amount is contained in a solvent prepared in advance in the reaction system. Examples thereof include a form in which a polymerization initiator (hereinafter, also referred to as “initiator”) is dropped onto the body to carry out a reaction. In such a reaction form, the concentration of each of the dropped solutions is not particularly limited, and any appropriate concentration can be adopted.
Examples of the form in which the monomer and the initiator are dropped into the solvent prepared in advance in the reaction system to carry out the reaction include monomer (A), monomer (B), and a single amount. The body (C), the monomer (E) if necessary, the initiator component, and other additives as needed are each dissolved in a solvent, or are being polymerized as they are without being dissolved in the solvent. There is a form in which polymerization is carried out by appropriately adding (dropping) the solvent into the reaction system. Further, in the reaction form, a part or all of the total amount of the monomer (A) used can be added (initially charged) to the reaction system in advance before the start of polymerization.

<Polymerization initiator>
As the polymerization initiator used in the above production method, a commonly used one can be used. Specifically, hydrogen peroxide; persulfates such as sodium persulfate, potassium persulfate, ammonium persulfate; 2,2'-azobis (2-amidinopropane) hydrochloride, 4,4'-azobis-4-cyanovalerin Azo compounds such as acids, azobisisobutyronitrile, 2,2'-azobis (4-methoxy-2,4-dimethylvaleronitrile); benzoyl peroxide, lauroyl peroxide, peracetic acid, di-t-butyl Organic peroxides such as peroxide and cumenehydroperoxide are preferable. Of these polymerization initiators, hydrogen peroxide, persulfate, and 2,2'-azobis (2-amidinopropane) hydrochloride are preferable, and persulfate and 2,2'-azobis (2-amidinopropane) hydrochloric acid are preferable. Salt is more preferred. These polymerization initiators may be used alone or in combination of two or more.

<Chain transfer agent>
In the above production method, it is preferable to use a chain transfer agent as a molecular weight adjusting agent for the polymer. When a chain transfer agent is used, it is possible to prevent the produced polymer from becoming unnecessarily high in molecular weight, and to efficiently produce a low molecular weight copolymer.
In the above production method, it is preferable to use a compound capable of generating hydrogen sulfite and / or hydrogen sulfite as the chain transfer agent. In that case, it is more preferable to use a polymerization initiator in addition to the hydrogen sulfite and the compound capable of generating hydrogen sulfite. Further, heavy metal ions may be used in combination as the reaction accelerator.
Further, when a compound capable of generating a hydrogen sulfite and / or a hydrogen sulfite is used as the chain transfer agent, a polymer having a sulfonic acid (salt) group at at least one of the terminals of the main chain can be obtained.

Examples of the compound capable of generating the above-mentioned hydrogen sulfite include pyrosulfite (salt), dithionous acid (salt), sulfite (salt) and the like, and pyrosulfite (salt) is preferable.
As the salt, a salt with a metal atom, ammonium or an organic amine is suitable. Specific examples of the metal atom and the organic amine are as described above.
Among the compounds capable of generating hydrogen sulfite and hydrogen sulfite, hydrogen sulfite is preferable.
As the hydrogen sulfite, for example, sodium hydrogen sulfite, potassium hydrogen sulfite, ammonium hydrogen sulfite and the like are preferably mentioned, and sodium hydrogen sulfite is more preferable.
Examples of the compound capable of generating the hydrogen sulfite include sodium pyrosulfite, potassium pyrosulfite; sodium dithionite, potassium dithionite; sodium sulfite, potassium sulfite, ammonium sulfite; and the like, and sodium pyrosulfite is preferable. Is more preferable.
The above-mentioned hydrogen sulfite and the compound capable of generating hydrogen sulfite may be used alone or in combination of two or more.

Further, as the chain transfer agent, in addition to the above-mentioned hydrogen sulfite and a compound capable of generating hydrogen sulfite, the following compounds can also be used. Examples of the chain transfer agent include thiol-based chain transfer agents such as mercaptoethanol, thioglycolic acid, 2-mercaptopropionic acid, 3-mercaptopropionic acid, octyl 3-mercaptopropionate, 2-mercaptoethanesulfonic acid, and n-dodecyl mercaptan. Agents; halides such as carbon tetrachloride, methylene chloride, bromoform, bromotrichloroethane; secondary alcohols such as isopropanol and glycerin; phosphite, hypophosphorous acid and salts thereof (sodium hypophosphate, hypophosphorous acid) Lower oxides such as potassium) and salts thereof; and the like. The chain transfer agent may be used alone or in combination of two or more.

The combination of the chain transfer agent, the polymerization initiator and the reaction accelerator is not particularly limited, and can be appropriately selected from the above examples. Further, only one of the polymerization initiator and the reaction accelerator may be used. The combinations of the chain transfer agent / polymerization initiator / reaction accelerator are described in this order, for example, sodium bisulfite / hydrogen peroxide / none, sodium bisulfite / sodium persulfite / none, sodium bisulfite / none. / Fe (ion), sodium bisulfite / hydrogen peroxide / Fe (ion), sodium bisulfite / sodium persulfite / Fe (ion), sodium bisulfite / sodium persulfite, hydrogen peroxide / none, etc. are preferable. More preferably, sodium bisulfite / sodium persulfite / none, sodium bisulfite / sodium persulfite / Fe (ion), and even more preferably sodium bisulfite / sodium persulfite / Fe (ion). In the above, "none" means that the component is not used.

<Amount of polymerization initiator, etc.>
The total amount of the polymerization initiator used is not particularly limited as long as it can initiate copolymerization of the monomers, but all the monomer components (monomers (A), (B), (C) and ( E)) is preferably 15 g or less with respect to 1 mol of the total amount. More preferably, it is 1 to 12 g.
When hydrogen peroxide is used as the polymerization initiator, the amount of hydrogen peroxide added is preferably 1.0 to 10.0 g, preferably 2.0 to 10.0 g, based on 1 mol of the total amount of all monomer components. More preferably, it is ~ 8.0 g. When the amount of hydrogen peroxide added is less than 1.0 g, the weight average molecular weight of the obtained polymer tends to be high. On the other hand, if the addition amount exceeds 10.0 g, the effect corresponding to the increase in the addition amount cannot be obtained, and further, there is a possibility of adverse effects such as an increase in the amount of residual hydrogen peroxide.

When persulfate is used as the polymerization initiator, the amount of persulfate added is preferably 1.0 to 5.0 g, preferably 2.0 to 5.0 g, based on 1 mol of the total amount of all monomer components. It is more preferably ~ 4.0 g. When the amount of persulfate added is less than 1.0 g, the molecular weight of the obtained polymer tends to be high. On the other hand, if the amount added exceeds 5.0 g, it becomes difficult to obtain an effect commensurate with the increase in the amount added, and there is a risk of adverse effects such as a decrease in the purity of the obtained polymer.
When hydrogen peroxide and persulfate are used in combination as the polymerization initiator, the mass ratio of persulfate to hydrogen peroxide is preferably 0.1 to 5.0, preferably 0.2 to 2.0. Is more preferable. When the mass ratio of persulfate is less than 0.1, the weight average molecular weight of the obtained copolymer tends to be high. On the other hand, when the mass ratio of persulfate exceeds 5.0, the effect of reducing the molecular weight due to the addition of persulfate cannot be obtained to match the increase in the amount of persulfate added, and the persulfate is wasted in the polymerization reaction system. May be consumed.

The amount of the chain transfer agent added is not limited as long as the amounts of the monomers (A), (B), (C) and (E) polymerize well, but the amounts of the monomers (A), (B), and It is preferably 0.5 to 20 g, more preferably 1 to 15 g, based on 1 mol of the total amount of all the monomer components composed of (C) and (E). If it is less than 0.5 g, the molecular weight may not be controlled. On the other hand, if it exceeds 20 g, a large amount of impurities may be generated and the pure polymer content may decrease. In particular, when hydrogen sulfite is used, if the amount added exceeds 20 g, excess hydrogen sulfite may be decomposed in the reaction system to generate sulfur dioxide gas, which is economically disadvantageous. There is a risk.
It is assumed that the amount of the chain transfer agent added does not include the hydrogen sulfite contained in the monomer (A).

As the combination of the initiator and the chain transfer agent, it is preferable to use one or more persulfate and hydrogen sulfite, respectively.
In this case, the mixing ratio of the persulfate and the hydrogen sulfite is not particularly limited, but it is preferable to use 0.5 to 5 parts by mass of the hydrogen sulfite with respect to 1 part by mass of the persulfate. The lower limit of the amount of hydrogen sulfite is more preferably 1 part by mass with respect to 1 part by mass of persulfate, and even more preferably 2 parts by mass. The upper limit of the amount of hydrogen sulfite is more preferably 4 parts by mass, still more preferably 3 parts by mass with respect to 1 part by mass of persulfate. If the amount of bisulfite is less than 0.5 parts by mass with respect to 1 part by mass of persulfate, the total amount of initiator required for lowering the molecular weight may increase, and if it exceeds 5 parts by mass, Side reactions may increase, which may increase impurities.

The total amount of the chain transfer agent, initiator and reaction accelerator used is based on 1 mol of the total amount of all the monomer components composed of the monomers (A), (B), (C) and (E). It is preferably 2 to 20 g. Within such a range, the sulfonic acid group-containing copolymer of the present invention can be efficiently produced, and the molecular weight distribution of the polymer can be desired. It is more preferably 3 to 18 g, still more preferably 4 to 15 g.

<Polymerization conditions>
In the above production method, the polymerization temperature is appropriately determined depending on the polymerization method, solvent, polymerization initiator and the like used, but is preferably 25 to 200 ° C. It is more preferably 50 to 150 ° C, still more preferably 60 to 120 ° C, and particularly preferably 80 to 110 ° C. If the polymerization temperature is lower than 25 ° C., the weight average molecular weight of the obtained polymer may become too high, or the amount of impurities produced may increase.
It is not necessary to keep the polymerization temperature substantially constant in the polymerization reaction. For example, the polymerization is started from room temperature, the temperature is raised to a set temperature at an appropriate temperature rise time or rate, and then the set temperature is set. It may be retained, or the temperature may be fluctuated (increased or lowered) with time during the polymerization reaction depending on the dropping method of the monomer component, the initiator and the like. The polymerization temperature refers to the temperature of the reaction solution of the polymerization reaction. Further, as the method for measuring the polymerization temperature and the means for controlling the polymerization temperature, any appropriate method or means can be adopted. For example, the measurement may be performed using a commonly used device.

The pressure at the time of polymerization in the above production method is not particularly limited, and any appropriate pressure can be adopted. For example, it may be under normal pressure (atmospheric pressure), reduced pressure, or pressurized. Further, the atmosphere in the reaction system may be the air atmosphere as it is, or may be an inert gas atmosphere. When the atmosphere in the reaction system is an inert gas atmosphere, for example, the reaction system can be replaced with an inert gas such as nitrogen before the start of polymerization. As a result, the atmospheric gas (for example, oxygen gas, etc.) in the reaction system dissolves in the liquid phase and acts as a polymerization inhibitor.

In the above production method, the solid content concentration in the reaction solution (polymer solution) at the time when the total amount of the monomer, the polymerization initiator and the chain transfer agent is dropped is preferably 35% by mass or more. .. If it is less than 35% by mass, the productivity of the obtained polymer may not be significantly improved. It is more preferably 40 to 70% by mass, still more preferably 45 to 65% by mass. As described above, when the solid content concentration at the end of the dropping is 35% by mass or more, the polymerization can be carried out in one step in the high concentration reaction solution. Therefore, the polymer can be efficiently obtained. For example, the concentration step can be omitted, the productivity of the polymer can be significantly improved, and the increase in production cost can be suppressed.
The solid content concentration can be calculated by taking out a part of the reaction solution at the end of the dropping and determining the non-volatile content after treating the reaction solution with a hot air dryer at 130 ° C. for 1 hour.

In the above production method, after the addition of all the raw materials used is completed, an aging step may be provided for the purpose of increasing the polymerization rate of the monomer. The aging time is preferably 1 to 120 minutes, more preferably 5 to 60 minutes, still more preferably 10 to 30 minutes. If the aging time is less than 1 minute, the monomer component may remain due to insufficient aging, and impurities caused by the residual monomer may cause performance deterioration and the like. If the aging time exceeds 120 minutes, the polymer solution may be colored.

In the above production method, the polymerization time is not particularly limited, but is preferably 30 to 420 minutes, more preferably 45 to 390 minutes, still more preferably 60 to 360 minutes, and particularly preferably 90 to 300 minutes. Minutes. In the present invention, the "polymerization time" refers to the time during which the monomer is added, that is, the time from the start to the end of the addition of the monomer, unless otherwise specified.

<Sulfonic acid group-containing copolymer-containing composition>
As described above, the production method of the present invention can reduce the amount of impurities derived from hydrogen sulfite in the obtained copolymer. Examples of impurities derived from hydrogen sulfite include sulfites and sulfates. The salt in the above-mentioned sulfite and sulfate is not particularly limited, and examples thereof include the same salt as in hydrogen sulfite.
The present invention contains a sulfonic acid group-containing copolymer obtained by the production method of the present invention, and contains a sulfonic acid group-containing copolymer having a total content of sulfites and / or sulfates of 1000 to 30,000 ppm. It is also a composition. Such a sulfonic acid group-containing copolymer-containing composition is excellent in dispersibility in complex stains.
The total content of sulfites and / or sulfates is preferably 3000 to 20000 ppm, more preferably 5000 to 16000 ppm.
The content of sulfites and sulfates in the sulfonic acid group-containing copolymer-containing composition can be measured by the method described in Examples.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples. Unless otherwise specified, "part" means "part by mass" and "%" means "% by mass".

<Measurement conditions for weight average molecular weight and number average molecular weight (GPC)>
Equipment: HLC-8320GPC manufactured by Tosoh Corporation
Column: TSKgek PW _XL , TSKgelGMPW _XL manufactured by Tosoh Corporation Column temperature: 40 ° C
Flow velocity: 1 ml / min
Calibration curve: Polyacrylic acid standard manufactured by Sowa Chemical Co., Ltd.
Eluent: (60.84 mM aqueous sodium carbonate solution + 60.84 mM aqueous sodium hydrogen carbonate solution) / acetonitrile = 83.74 / 16.26 (mass ratio).

<Measurement of content of hydrogen sulfite in sulfonic acid group-containing monomer (A)>
The following operations (1) to (8) were carried out, and the concentration of hydrogen sulfite in the sulfonic acid group-containing monomer (A) was measured based on the following formulas (I) to (III).
(1) Weigh 3 g of the sulfonic acid group-containing monomer (A) and 15 g of 0.1% hydrogen peroxide solution into a 50 ml screw tube, and stir with a magnetic stirrer.
(2) Weigh 1 g of potassium iodide into a 100 ml beaker, add 70 g of pure water, and stir with a magnetic stirrer.
(3) Add 15 ml of 18N sulfuric acid to the beaker of (2) with a whole pipette under stirring.
(4) Add the solution of (1) to the beaker of (3) under stirring until the color turns brown, and stir for 2 minutes.
(5) Add 1 ml of a 1% starch aqueous solution to the beaker of (4) with a whole pipette under stirring, and confirm that the solution turns dark brown.
(6) Immediately after confirming the discoloration of (5), titrate with a 0.1 M sodium thiosulfate aqueous solution under stirring, and the end point is where the color disappears.
(7) Separately, in the steps (1) to (6) above, the sample excluding the step (4) is measured.
(8) Separately, in the steps (1) to (6) above, in the step (4), measure a sample in which 2.5 g of 0.1% hydrogen peroxide solution is added instead of the solution of (1). ..
-Sulfonic acid group-containing monomer (A) weighing value: A (g)
-0.1% hydrogen peroxide solution weighing value: B (g)
-Amount of solution of (1) added dropwise in step (4): C (g)
-Sodium thiosulfate titration: D (ml)
-0.1 M sodium thiosulfate aqueous solution added in step (7): D ₀ (g)
-Weighed value of 0.1% hydrogen peroxide solution dropped in the step (8): B ₁ (g)
-0.1 M sodium thiosulfate aqueous solution added dropwise in step (8): D ₁ (g)
Hydrogen peroxide concentration E (%) charged into the measuring solution = (B × ((D ₁ − D ₀ ) × 0.17 / B ₁ ) / 100) / (A + B) × 100 (I)
Actual hydrogen peroxide concentration in the measuring solution F (%) = (DD ₀ ) × 0.17 / C (II)
Bisulfite concentration (ppm) in the sulfonic acid group-containing monomer (A) = ((C × (EF) / 100/34 × 104) × A / (C × A / (A + B))) / A x 1000000 (III)

<Measurement of sulfite and sulfate content in polymer>
Equipment: IC-2010 manufactured by Tosoh Corporation
Column: Showa Denko Shodex IC SI-904E (4.0 mm x 250 mm), Shodex IC SI-90G
Column temperature: 25 ° C
Flow velocity: 1.2 ml / min
Eluent: (1.05 mM sodium carbonate aqueous solution + 4.21 mM sodium hydrogen carbonate aqueous solution / acetone = 95/5 (mass ratio)

<Evaluation of dispersibility of composite stains (carbon black-clay)>
(1) 2.94 g of calcium chloride dihydrate was placed in a 500 mL beaker, and pure water was added to make 500 g, and hard water was prepared.
(2) 10 g of a 0.1% solid content aqueous solution of each evaluation sample was prepared in a 20 mL screw tube.
(3) 7.51 g of glycine, 1.18 g of ethanol, and 7.00 g of 48% NaOH were put in a 1 L beaker, and pure water was added to make 1000 g, and a glycine buffer solution having a pH of 10.5 was prepared.
(4) Next, a 30 mL test tube having an inner diameter of 16 mm was prepared for the number of evaluation samples, and each of them had 0.03 g of carbon black, 0.30 g of JIS 11 type clay, 1.50 g of hard water of (1), and an aqueous sample solution of (2). 50 g and 27.0 g of the glycine buffer solution of (3) were added and capped with septum. In this way, a suspended aqueous solution containing 1000 ppm of carbon black, 10000 ppm of clay, and 50 ppm of sample solid content was prepared in each test tube.
(5) After slowly reversing each test tube 60 times, the cap was removed and the test tube was allowed to stand in a horizontal and stable place for 1 hour. After 1 hour, 5 mL of the supernatant was collected using a whole pipette.
(6) The absorbance of the supernatant at 380 nm was measured using an ultraviolet-visible spectrophotometer UV-1800 manufactured by Shimadzu Corporation. This absorbance was used as the dispersibility. The larger the absorbance value, the higher the dispersibility.

<Synthesis example 1>
244.0 parts of deionized water and 114.9 parts of 48% sodium hydroxide aqueous solution were charged into a SUS reaction vessel equipped with a thermometer, a stirrer, a nitrogen inflow pipe and a cooling trap at the nitrogen outlet, while introducing nitrogen. , 820.5 parts of a 35% aqueous sodium hydrogen sulfite solution (hereinafter, also referred to as “35% SBS”) was added. The liquid temperature was raised to 63 ° C., and 320.6 parts of allyl glycidyl ether was added dropwise over 225 minutes. After completion of dropping the allyl glycidyl ether, the reaction was completed by maintaining the temperature of the reaction solution at 63 ° C. for 30 minutes to obtain a sulfonic acid group-containing monomer (1).

<Synthesis example 2>
A sulfonic acid group-containing monomer (2) was obtained in the same manner as in Synthesis Example 1 except that the amount of the 35% aqueous sodium hydrogen sulfite solution was 850.0 parts.

<Synthesis example 3>
A sulfonic acid group-containing monomer (3) was obtained in the same manner as in Synthesis Example 1 except that the amount of the 35% aqueous sodium hydrogen sulfite solution was 875.0 parts.

<Synthesis example 4>
370.0 g of n-butyl alcohol and 4.27 g of pelletized sodium hydroxide were placed in a glass four-necked flask with a capacity of 500 mL equipped with a reflux condenser and a stirrer (paddle blade), and the temperature was raised to 60 ° C. with stirring. The temperature was raised. Next, 57.0 g of allyl glycidyl ether was added over 30 minutes, and then the reaction was carried out for 5 hours. The solution was transferred to a 1000 ml eggplant flask and desolvated with a rotary evaporator. To this, 200.0 g of a 20 mass% sodium chloride aqueous solution was added, the aqueous solution was transferred to a 500 ml separatory funnel, shaken well, and then allowed to stand until the layers were separated, and the lower layer was removed. The remaining upper layer was transferred to a 300 ml eggplant flask and desolvated with a rotary evaporator. The precipitated salt was removed by filtration to obtain an ether bond-containing monomer (1).

<Example 1>
A glass separable flask with a capacity of 2000 mL equipped with a reflux condenser and a stirrer (paddle blade) is charged with 181.27 g of pure water and 0.0593 g of molle salt, and the temperature is raised to 85 ° C. while stirring to carry out the polymerization reaction. It was a system. Next, 327.6 g of an 80% aqueous acrylic acid solution (hereinafter, also referred to as "80% AA") and the sulfonic acid group obtained in Synthesis Example 1 were contained in a polymerization reaction system maintained at 85 ° C. under stirring. 136.7 g of a 40% aqueous solution of the monomer (1) (hereinafter, also referred to as “40% sulfonic acid group-containing monomer (1)”), the ether bond-containing monomer (1) obtained in Synthesis Example 4. ) 16.4 g, 88.0 g of a 15% aqueous sodium persulfate solution (hereinafter, also referred to as “15% NaPS”), and 14.1 g of 35% SBS were added dropwise from separate nozzles. The dropping time of each solution was 180 minutes for 80% AA, 120 minutes for the 40% sulfonic acid group-containing monomer (1), 150 minutes for the ether bond-containing monomer (1), and 15% NaPS. Was 210 minutes and 35% SBS was 175 minutes. In addition, the dropping rate of each solution was constant, and each solution was dropped continuously.
After the completion of dropping 80% AA, the reaction solution was kept at 85 ° C. (aged) for another 30 minutes to complete the polymerization. After completion of the polymerization, while stirring and allowing the polymerization reaction solution to cool, 163.09 g of a 48% sodium hydroxide aqueous solution was gradually added dropwise to neutralize the polymerization reaction solution.

<Example 2 and Comparative Example 1>
A sulfonic acid group-containing copolymer was synthesized in the same manner as in Example 1 except that the sulfonic acid group-containing monomer having the SBS content shown in Table 1 was used.

With respect to the sulfonic acid group-containing copolymers obtained in Examples 1 and 2 and Comparative Example 1, the weight average molecular weight, the number average molecular weight, the sodium sulfite and sodium sulfate contents, and the dispersion performance of the composite stain were measured, and the results were obtained. Is shown in Table 1.

Claims (4)

A method for producing a sulfonic acid group-containing copolymer.
The production method includes a step of polymerizing a monomer composition containing a sulfonic acid group-containing monomer (A), an ether bond-containing monomer (B), and a carboxyl group-containing monomer (C). ,
A method for producing a sulfonic acid group-containing copolymer, wherein the content of bisulfite in the sulfonic acid group-containing monomer (A) is 18,000 ppm or less. The sulfonic acid group-containing monomer (A) has the following formula (1);

(In the formula, R ¹ represents a hydrogen atom or a methyl group. R ² represents a CH ₂ group, a CH ₂ CH ₂ group or a direct bond.) By the reaction of the epoxy compound represented by the hydrogen sulfite. The method for producing a sulfonic acid group-containing copolymer according to claim 1, wherein the product is obtained. The sulfonic acid group-containing monomer (A) has the following formula (2);

(In the formula, R ¹ represents a hydrogen atom or a methyl group. R ² represents CH ₂ , CH ₂ CH ₂ or a direct bond. R ³ , R ⁴ represents a hydroxyl group or -SO ₃ Z. , Z represents a hydrogen atom, a metal atom, an ammonium group or an organic amine group. However, one of R ³ and R ⁴ represents -SO ₃ Z, and the other represents a hydroxyl group). The method for producing a sulfonic acid group-containing copolymer according to claim 1 or 2, which is characterized by having a structure. The ether bond-containing monomer (B) has the following formula (3);

(In the formula, R ⁵ represents a hydrogen atom or a methyl group. R ⁶ represents CH ₂ group, CH ₂ CH ₂ group or a direct bond. X is a hydroxyl group, a group represented by the following formula (4). , Or a group represented by the following formula (5). Y represents a hydroxyl group, a group represented by the following formula (4), or a group represented by the following formula (5), except that X. , Y represents a hydroxyl group, and the other represents a group represented by the following formula (4) or a group represented by the following formula (5).)

(Wherein, ^{R 7} are the same or different, .n representing an alkylene group having 2 to 4 carbon atoms, oxyalkylene groups ^{(-O-R 7} - an average molar number of addition), 0-5 R ⁸ , R ⁹ and R ¹⁰ represent the same or different alkyl groups having 1 to 4 carbon atoms), according to claims 1 to 3. The method for producing a sulfonic acid group-containing copolymer according to any one.