Aqueous polymer dispersion and method for stably producing the same

Abstract

To provide a water-soluble polymer dispersion which exhibits suppressed thickening during polymerization by dispersion polymerization in a saline solution under coexistence of a polymer dispersant, and a method for stably producing the water-soluble polymer dispersion.SOLUTION: In a saline solution according to the present invention, a specific monomer mixture aqueous solution is subjected to dispersion polymerization under stirring in a saline solution under coexistence of a polymer dispersant containing a primary amino group as a constitutional unit, thereby producing a water-soluble polymer dispersion with suppressed thickening during production. The addition ratio of the polymer dispersant containing a primary amino group as a constitutional unit is preferably in the range of 1 to 30 mass% relative to the total monomer amount.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an aqueous solution of a water-soluble polymer dispersion and a method for producing the same by a dispersion polymerization method in an aqueous salt solution in the presence of a polymer dispersant.

Background Art

[0002] Regarding the stable production technology of a dispersion composed of an ionic water-soluble polymer produced by coexisting an ionic polymer dispersant in an aqueous salt solution, various studies have been made, for example, as in Patent Document 1. In Patent Document 2, when producing a dispersion composed of an anionic or cationic water-soluble polymer, a method of coexisting a polyhydric alcohol such as ethylene glycol, propylene glycol, glycerin or polyethylene glycol is used. In Patent Document 3, a copolymer containing an alkali metal acrylate or an alkali metal 2-acrylamido-2-methylpropanesulfonate as an ionic polymer dispersant to be coexisted is disclosed. However, there have been problems that the aqueous polymer dispersion thickens during production and cannot be stably produced, and for this reason, the polymerization concentration cannot be increased. Therefore, various methods of using an additive for suppressing thickening during dispersion polymerization have been disclosed. Patent Document 4 discloses a thickening inhibitor composed of a cyclic compound having a sulfone group or a salt thereof. Patent Document 5 discloses that thickening is suppressed by using a graft copolymer having a polyoxyethylene chain soluble in the aqueous salt solution as a dispersant. Although these have certain effects, there are cases where thickening cannot be suppressed depending on the composition of the aqueous polymer dispersion and stable production cannot be achieved, or cases where the polymerization concentration can only be achieved at a low concentration. Therefore, a method for suppressing thickening during polymerization and stably producing a dispersion polymerization liquid is desired.

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

[0004] An object of the present invention is to provide a water-soluble polymer dispersion which is inhibited from thickening during polymerization by dispersion polymerization in a salt solution in the presence of a polymer dispersant, and a method for producing the same. [Means for solving the problem]

[0005] As a result of intensive research conducted to solve the above problems, it has been found that a water-soluble polymer dispersion in which thickening during polymerization is suppressed can be obtained by dispersion polymerizing a monomer or a monomer mixture essentially containing a specific monomer in a salt solution in the presence of a polymer dispersant containing a primary amino group as a constituent unit. Effect of the Invention

[0006] The water-soluble polymer dispersion of the present invention is a water-soluble polymer dispersion in which thickening during polymerization is suppressed, and a method for producing the same, which allows for stable production, enables an increase in polymerization concentration, and reduces restrictions on polymerization equipment such as a stirrer used during production. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] The water-soluble polymer dispersion in the present invention is a water-soluble polymer dispersion obtained by dispersing and polymerizing, under stirring, an aqueous solution of a monomer or monomer mixture essentially containing a monomer represented by the following general formula (1) in a salt solution in the presence of a polymer dispersant containing a primary amino group as a constituent unit in the salt solution: JPEG2025079401000001.jpg2460 General formula (1) R 1 is hydrogen or a methyl group, R 2 , R 3 is an alkyl or alkoxy group having 1 to 3 carbon atoms, R4 is an alkyl group or an aryl group having 7 to 20 carbon atoms; A is oxygen or NH; B is an alkylene group or an alkoxylene group having 2 to 4 carbon atoms; X 1 - represents an anion.

[0008] The cationic monomer represented by the general formula (1) used in producing the water-soluble polymer dispersion of the present invention includes halogenated aryl compounds such as dimethylaminoethyl (meth)acrylate or dimethylaminopropylacrylamide benzyl chloride, and quaternized products of alkyl halides having 7 to 20 carbon atoms. These cationic vinyl monomers can be used alone or in combination of two or more. Specific examples include (meth)acryloyloxyethyl dimethylbenzyl ammonium chloride, (meth)acryloyloxy-2-hydroxypropyl benzyl dimethyl ammonium chloride, (meth)acryloylaminopropyl dimethyl benzyl ammonium chloride, etc. The cationic monomer represented by the general formula (1) can be used in the range of 1 to 100 mol %. 1 to 50 mol % is preferable, and 1 to 30 mol % is more preferable. This is because when the molar % ratio of the cationic monomer represented by the general formula (1) is low, the viscosity increases during polymerization, and the viscosity increase suppression effect of the polymer dispersant of the present invention is more effectively exerted.

[0009] The cationic monomer represented by the general formula (1) used in producing the water-soluble polymer dispersion of the present invention can be copolymerized with a cationic monomer represented by the following general formula (2) and used. JPEG2025079401000002.jpg2160 General formula (2) R 5 is hydrogen or a methyl group, R 6 , R 7 is an alkyl or alkoxy group having 1 to 3 carbon atoms, R 8 represents an alkyl group or an alkoxy group having 1 to 3 carbon atoms, A represents oxygen or NH, and B represents an alkylene group or an alkoxylene group having 2 to 4 carbon atoms; X 2- Each represents an anion.

[0010] Examples of the cationic monomer represented by the general formula (2) include dimethylaminoethyl (meth)acrylate and alkyl halides such as methyl chloride. These cationic monomers can be used alone or in combination of two or more. Specific examples include quaternary compounds of dimethylaminoethyl (meth)acrylate or dimethylaminopropylacrylamide with halides of lower alkyl groups such as methyl chloride and ethyl chloride. For example, (meth)acryloyloxyethyltrimethylammonium chloride, (meth)acryloyloxy-2-hydroxypropyltrimethylammonium chloride, (meth)acryloylaminopropyltrimethylammonium chloride, and the like.

[0011] The cationic monomer represented by the general formula (1) and the nonionic monomer can be copolymerized and used. Examples of the nonionic monomer used in that case include (meth)acrylamide, N,N-dimethylacrylamide, acrylonitrile, 2-hydroxyethyl (meth)acrylate, diacetoneacrylamide, N-vinylpyrrolidone, N-vinylformamide, N-vinylacetamide, acryloylmorpholine, and the like. These may be used in combination of two or more. Also, the cationic monomer represented by the general formula (1), the cationic monomer represented by the general formula (2), and the nonionic monomer may be copolymerized.

[0012] The water-soluble polymer dispersion in the present invention may be amphoteric in terms of ionic property. In that case, an anionic monomer represented by the following general formula (3) is used during production. TIFF2025079401000003.tif2968 General formula (3) R 9 is hydrogen, a methyl group or a carboxymethyl group, and Q is SO 3 , C 6 H 4 SO 3 , CONHC(CH 3 ) 2 CH2 SO 3 , C 6 H 4 COO or COO, R 10 is hydrogen or COOY 2 , Y 1 Or Y 2 represents a hydrogen atom or a cation.

[0013] Examples of the anionic monomer represented by the general formula (3) include vinylsulfonic acid, vinylbenzenesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, methacrylic acid, acrylic acid, itaconic acid, maleic acid, fumaric acid, and p-carboxystyrene acid. Two or more of these may be used in combination. In addition, an anionic monomer represented by the general formula (3) and a nonionic monomer may be used, or an anionic monomer represented by the general formula (3) and a cationic monomer represented by the general formula (2) and a nonionic monomer may be used.

[0014] The polymer dispersant containing a primary amino group as a constituent unit in the present invention is at least one selected from a primary amino group-containing polymer obtained by polymerizing a monomer mixture essentially containing a cationic monomer represented by a specific structural formula, a polyvinylamine-based polymer, and a polyamidine-based polymer.

[0015] The primary amino group-containing polymer in the present invention is a primary amino group-containing polymer obtained by polymerizing a monomer mixture essentially containing a cationic monomer represented by the following general formula (4). Examples of the cationic monomer represented by general formula (4) include salts of organic acids or inorganic acids such as 2-aminoethyl acrylate, 2-aminoethyl methacrylate, 3-aminopropyl acrylate, and 3-aminopropyl methacrylate. These monomers can usually only exist in the form of inorganic or organic acid salts, and examples of such salts include sulfates, hydrochlorides, phosphates, oxalates, methanesulfonates, paratoluenesulfonates, naphthalenesulfonates, methylphosphonic acid, and phenylphosphonic acid salts. Of these, sulfates, hydrochlorides, methanesulfonates, and paratoluenesulfonates are preferred. Particularly preferred are 2-aminoethyl acrylate hydrochloride, 2-aminoethyl methacrylate hydrochloride, 2-aminoethyl acrylate sulfate, 2-aminoethyl methacrylate sulfate, 2-aminoethyl acrylate methanesulfonate, 2-aminoethyl methacrylate methanesulfonate, 2-aminoethyl acrylate paratoluenesulfonate, and 2-aminoethyl methacrylate paratoluenesulfonate. JPEG2025079401000004.jpg2691 General formula (4) R 1 is a hydrogen atom or a methyl group, A is an oxygen atom or NH, B is an alkylene group or an alkoxylene group having 2 to 3 carbon atoms, and X - represents an anion.

[0016] The cationic monomer represented by the general formula (4) may be polymerized alone or may be copolymerized with other monomers. For example, nonionic monomers such as (meth)acrylamide, N,N-dimethylacrylamide, vinyl acetate, acrylonitrile, methyl acrylate, (meth)acrylate 2-hydroxyethyl, diacetone acrylamide, N-vinylpyrrolidone, N-vinylformamide, and N-vinylacetamide may be mentioned, and it is also possible to copolymerize with one or more of the nonionic monomers. The most preferred nonionic monomer is acrylamide. It is also possible to copolymerize with anionic monomers and monomers containing tertiary amino groups or quaternary ammonium groups, but it is preferable to limit the amount of these to 20 mol% or less.

[0017] The molar percentage of the primary amino group-containing monomer represented by general formula (4) in the primary amino group-containing polymer is preferably 80 to 100 mol %, more preferably 85 to 100 mol %, in order to maximize the effect as a polymer dispersant.

[0018] The primary amino group-containing polymer can be obtained by any of the known methods such as aqueous solution polymerization, emulsion polymerization, dispersion polymerization, suspension polymerization, etc. (JP Patent Publication No. 8310 / 1963, etc.). The aqueous solution polymerization will be explained below. The polymer is obtained by polymerizing a monomer component having a cationic monomer as an essential component. The polymerization can be obtained by adding a monomer mixture, water, a radical polymerization initiator, and optionally a surfactant to a specified reaction vessel, and stirring and heating the mixture in an inert gas atmosphere such as nitrogen gas.

[0019] As a polymerization mechanism, polymers can be produced by general radical polymerization using a radical polymerization initiator. That is, as the initiator, any of azo-based, redox-based, and peroxide-based initiators can be used for polymerization. Examples of oil-soluble azo-based initiators include 2,2'-azobisisobutyronitrile, 1,1'-azobis(cyclohexanecarbonitrile), 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis(2-methylpropionate), etc., which are dissolved and added in a water-miscible solvent. Examples of water-soluble azo-based initiators include 2,2'-azobis(amidinopropane) dihydrochloride, 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride, 4,4'-azobis(4-cyanovaleric acid), etc. Also, examples of redox-based initiators include combinations of ammonium or potassium peroxydisulfate with sodium sulfite, sodium bisulfite, trimethylamine, tetramethylethylenediamine, etc. Furthermore, examples of peroxide-based initiators include ammonium peroxydisulfate, hydrogen peroxide, benzoyl peroxide, lauroyl peroxide, octanoyl peroxide, succinic peroxide, t-butylperoxy 2-ethylhexanoate, etc. Among these, particularly preferred initiators are water-soluble azo-based initiators such as 2,2'-azobis(amidinopropane) dihydrochloride, 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride, etc.

[0020] The polymer dispersant containing a primary amino group as a constituent unit in the present invention does not exhibit its effect unless it has a certain level of aqueous solution viscosity (0.5 mass% aqueous solution viscosity) measured by a rotational viscometer at 25°C when completely dissolved to a polymer concentration of 0.5 mass%, and if it is too high, the viscosity of the dispersion becomes high, which is not preferable. The 0.5 mass% aqueous solution viscosity is preferably in the range of 3 mPa·s or more and 70 mPa·s or less, and more preferably 5 mPa·s or more and 50 mPa·s or less. The addition rate of the polymer dispersant is 1 to 30 mass% and preferably 2 to 20 mass% based on the total amount of monomer. If it is less than 1 mass%, the thickening suppression effect cannot be obtained, and if it is added in excess of 30 mass%, the viscosity of the dispersion increases and no further effect can be obtained, which is disadvantageous in terms of cost. In the present invention, the viscosity properties are values ​​measured using a Brookfield viscometer with a No. 1 rotor at 60 rpm. For viscosity values ​​of 100 mPa s or more, a No. 2 rotor is used, and for viscosity values ​​of 10 mPa s or less, a low viscosity adapter is used. A Brookfield viscometer such as Toki Sangyo's TVB-10M is used.

[0021] The polyvinylamine polymer can be synthesized by hydrolysis of N-vinyl carboxylic acid amide polymer with acid or alkali. Hydrolysis with alkali is preferred. The acid used is preferably a strong inorganic acid, such as hydrochloric acid, nitric acid, or p-toluenesulfonic acid. The alkali is preferably a caustic alkali, such as sodium hydroxide or potassium hydroxide. Examples of N-vinyl carboxylic acid monomers include N-vinylformamide and N-vinylacetamide. The molar percentage (amination degree) of cationic groups in the molecule after hydrolysis is 5 to 100 mol%, preferably 10 to 100 mol%, and most preferably 20 to 100 mol%. The nonionic structural unit is an unhydrolyzed carboxylic acid amide group, and its molar percentage is 0 to 95 mol%, preferably 0 to 90 mol%, and most preferably 0 to 80 mol%. Also included are copolymers of vinylamine units with one or more monomers selected from the group consisting of cationic monomers, anionic monomers and nonionic monomers used in producing the water-soluble polymer dispersion of the present invention. When the polymer is completely dissolved to a polymer concentration of 0.5% by mass, the aqueous solution viscosity measured with a rotational viscometer at 25°C is in the range of 1 mPa s to 50 mPa s, and preferably 2 mPa s to 30 mPa s.

[0022] The polyamidine polymer can be synthesized by hydrolysis of a copolymer of N-vinyl carboxylic acid amide and (meth)acrylonitrile with an acid. Examples of N-vinyl carboxylic acid as a monomer include N-vinyl formamide and N-vinyl acetamide. The acid used is preferably an inorganic or organic strong acid, such as hydrochloric acid, nitric acid, or p-toluenesulfonic acid. Acrylonitrile is the most common vinyl nitrile to be copolymerized. The molar percentage of amidine groups in the molecule after hydrolysis is 5 to 100 mol%, preferably 10 to 100 mol%, and most preferably 20 to 100 mol%. The nonionic structural unit is an unhydrolyzed carboxylic acid amide group and an unreacted nitrile group, and the molar percentage is 0 to 95 mol%, preferably 0 to 90 mol%, and most preferably 0 to 80 mol%. When the polymer is completely dissolved to a polymer concentration of 0.2% by mass, the aqueous solution viscosity measured with a rotational viscometer at 25°C is in the range of 5 mPa·s to 100 mPa·s, and preferably 10 mPa·s to 80 mPa·s.

[0023] The dispersion polymerization in salt water in the present invention can be produced by a conventional method disclosed in JP-A-62-15251, JP-A-62-20511, JP-A-2007-16086, etc. In a salt water solution, a polymer dispersant containing a primary amino group as a constituent unit is made to coexist in the salt water solution, and a monomer or monomer mixture aqueous solution containing a monomer represented by general formula (1) as an essential component is dispersion polymerized. The water-soluble polymer obtained by essentially containing a monomer represented by general formula (1) is difficult to dissolve in a salt water solution due to the presence of a hydrophobic group such as a benzyl group in general formula (1), and is suitable for dispersion polymerization. When dispersion polymerization is performed, a polymerization retarding substance is added in an amount of 0.5 to 5 mol % based on the total monomers, which has an effect of suppressing thickening, and can be produced by adding it appropriately. Examples of the polymerization retarding substance include itaconic acid, maleic acid, and phthalic acid. Furthermore, the coexistence of a polyhydric alcohol such as glycerin or polyethylene glycol is preferable since it may facilitate smooth precipitation of polymer particles during polymerization.

[0024] The inorganic salts used in the polymerization include salts of alkali metal ions such as sodium and potassium, alkaline earth metals such as calcium and magnesium, and ammonium ions with halide ions, sulfate ions, nitrate ions, phosphate ions, etc., and preferably salts with polyvalent anions. The monomers are dissolved in an aqueous solution of such an inorganic salt, and a polymer dispersant is further added to adjust the pH to 2 to 5. After nitrogen replacement, the polymerization is started with a polymerization initiator.

[0025] When the water-soluble polymer dispersion of the present invention is polymerized, as the polymerization proceeds in the salt solution, the concentration of the polymer produced exceeds the solubility, and the precipitation of polymer particles begins. However, before that, the viscosity of the polymer itself (polymerization system) also increases due to the dissolved polymer, and the dissolved polymer and precipitated particles coexist. After this, the proportion of precipitated polymer increases, and the viscosity of the polymer gradually decreases, resulting in a phase change to a dispersed state. At this time, it is considered that the phase change from the thickened state before the phase change to the dispersed state is smoothly transitioned by the polymer dispersant containing a primary amino group, allowing stable production. In particular, it is preferable to use a primary amino group-containing polymer obtained by polymerizing a monomer mixture essentially containing a cationic monomer represented by general formula (4) as the polymer dispersant.

[0026] The polymerization concentration is 10% by mass to 35% by mass as the monomer concentration, and preferably 15% by mass to 30% by mass. This is because, although a higher monomer concentration is more economically advantageous in terms of transportation costs, if the monomer concentration exceeds 35% by mass, the viscosity increases significantly during production, making it difficult to obtain a dispersion. As a method for supplying the monomer, the monomer may be charged all at once at the start of polymerization, or may be charged in appropriate portions.

[0027] The polymerization conditions are usually appropriately determined depending on the monomers and copolymerization mol% used, and the temperature is in the range of 0 to 100°C. A radical polymerization initiator is used to start the polymerization. These initiators may be either oil-soluble or water-soluble, and polymerization can be carried out using any of azo, peroxide, and redox initiators. Examples of oil-soluble azo initiators include 2,2'-azobisisobutyronitrile, 1,1'-azobis(cyclohexanecarbonitrile), 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis(2-methylpropionate), and 4,4-azobis(4-methoxy-2,4 dimethyl)valeronitrile, which are dissolved in a water-miscible solvent and added.

[0028] Examples of water-soluble azo initiators include 2,2'-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride, 2,2'-azobis[2-(2-amidinopropane)]dihydrochloride, 4,4'-azobis(4-cyanovaleric acid), etc. Examples of redox initiators include combinations of ammonium peroxodisulfate with sodium sulfite, sodium hydrogensulfite, trimethylamine, tetramethylethylenediamine, etc. Examples of peroxides include ammonium or potassium peroxodisulfate, hydrogen peroxide, benzoyl peroxide, lauroyl peroxide, octanoyl peroxide, succinic peroxide, t-butylperoxy 2-ethylhexanoate, etc. Among these initiators, the most preferred are the water-soluble azo initiators 2,2'-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride and 2,2'-azobis[2-(2-amidinopropane)]dihydrochloride. The amount of the azo initiator added at the start of polymerization is 30 to 500 ppm, preferably 50 to 200 ppm, per monomer. However, since a single addition results in a low polymerization rate, it is preferable to add it in several portions.

[0029] Also, when copolymerizing with a redox initiator, if polymerization is started under conditions of 40°C or higher, it is difficult to control the polymerization, and a sudden temperature rise or clumping of the polymerization liquid occurs, making it difficult to obtain a stable dispersion with a high degree of polymerization; therefore, 15 to 35°C is preferred. The addition rate of this initiator is 5 to 100 ppm, preferably 10 to 50 ppm per monomer at the start of polymerization. However, since the polymerization rate is low when added once, it is preferred to add it several times. The number of additions is 2 to 5 times, preferably 2 to 3 times.

[0030] A structural modifier, i.e., a crosslinkable monomer that structurally modifies the polymer, may be used during polymerization. When a crosslinkable monomer is used, it is present in a range of 0.1 to 200 ppm by mass relative to the total amount of monomers. Examples of crosslinkable monomers include N,N'-methylenebis(meth)acrylamide, triallylamine, and ethylene glycol dimethacrylate.

[0031] The water-soluble polymer dispersion of the present invention can be used as an agent to be added when flocculating and treating raw sludge, excess sludge, flocculated sludge, digested sludge or a mixture of these sludges from urban sewage, sewage, general industrial wastewater, or when flocculating and dehydrating them using a decanter, belt press, filter press, screw press dehydrator or the like; an oil separating agent used in an oil refining process or an oil separation process and treatment of oil-containing industrial wastewater; a papermaking agent such as a drainage improver, a retention improver or a valuable material recovery agent in a papermaking process; and in order to function for these applications, the 0.5 mass% salt solution viscosity, which is an indicator of the molecular weight of the water-soluble polymer dispersion of the present invention, i.e., the aqueous solution viscosity in a 4 mass% sodium chloride aqueous solution at 0.5 mass% of the water-soluble polymer constituting the dispersion, measured at 25°C, is preferably in the range of 5 to 150 mPa s. EXAMPLES

[0032] The water-soluble polymer dispersion of the present invention and the method for producing the same will be specifically described below, but the present invention is not limited to the following examples.

[0033] (Example 1) 127.8 g of deionized water, 13.5 g of 10 mass% poly(2-aminoethyl methacrylate) hydrochloride, and 44.6 g of ammonium sulfate were added to a 0.5 L separable flask equipped with an anchor blade stirrer, a cooling tube, and a nitrogen inlet tube. The temperature was raised to 36 °C with stirring and dissolved uniformly. Next, 63.3 g of 50 mass% acrylamide, 16.7 g of 80 mass% acryloyloxyethyl dimethylbenzyl ammonium chloride, and 2.25 g of glycerin were added to form a uniform solution, which was immersed in a 36 °C water bath to stabilize the temperature. Next, under a nitrogen atmosphere, a 1 mass% aqueous solution of 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride was added as a polymerization initiator at 50 ppm per monomer, and polymerization was carried out at 36 °C for 5 hours with stirring. Thereafter, 100 ppm of the above polymerization initiator was added and polymerization was carried out for 17 hours. After completion of the reaction, 31.9 g of ammonium sulfate was added to the obtained dispersion, and stirring was carried out until no undissolved ammonium sulfate remained to obtain an aqueous polymer dispersion. The molar composition ratio of this aqueous polymer was acrylamide / acryloyloxyethyl dimethylbenzyl ammonium chloride = 90 / 10 mol%. The viscosity of this dispersion was 48 mPa·s, and the viscosity when the aqueous polymer dispersion was dissolved in a 4 mass% aqueous sodium chloride solution at a concentration of 0.5 mass% was 47 mPa·s. This is shown in Table 1 as Example 1.

[0034] (Example 2) 135.8g of demineralized water, 30.0g of 10% by mass poly 2-aminoethyl methacrylate hydrochloride, 41.0g of ammonium sulfate, and 4.6g of ammonium chloride were added to a 0.5L separable flask equipped with an anchor blade stirrer, a cooling tube, and a nitrogen inlet tube, and the mixture was heated to 36°C under stirring to dissolve uniformly. Next, 8.2g of 50% by mass acrylamide, 48.8g of 80% by mass acryloyloxyethyl dimethylbenzylammonium chloride, and 21.0g of 80% by mass acryloyloxyethyl trimethylammonium chloride were added to make a uniform solution, which was then immersed in a 36°C water bath to stabilize the temperature. Next, under a nitrogen atmosphere, a 1% by mass aqueous solution of 2,2'-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride was added as a polymerization initiator at 150ppm per monomer, and polymerization was carried out at 36°C for 22 hours under stirring. After the reaction was completed, 10.5 g of ammonium sulfate was added to the resulting dispersion and stirred until no ammonium sulfate remained dissolved, to obtain a water-soluble polymer dispersion. The molar composition ratio of this water-soluble polymer was acrylamide / acryloyloxyethyldimethylbenzylammonium chloride / acryloyloxyethyltrimethylammonium chloride = 20 / 50 / 30 mol%. The viscosity of this dispersion was 148 mPa·s, and the viscosity when the water-soluble polymer dispersion was dissolved in a 4 mass% sodium chloride aqueous solution to a concentration of 0.5 mass% was 20 mPa·s. This is shown in Table 1 as Example 2.

[0035] (Example 3) 153.3g of demineralized water, 13.5g of 10% by mass poly 2-aminoethyl methacrylate hydrochloride, and 53.4g of ammonium sulfate were added to a 0.5L separable flask equipped with an anchor blade stirrer, a cooling tube, and a nitrogen inlet tube, and the mixture was heated to 36°C under stirring to dissolve uniformly. Next, 29.3g of 50% by mass acrylamide, 20.2g of 80% by mass acryloyloxyethyl dimethylbenzylammonium chloride, 12.7g of 80% by mass acryloyloxyethyl trimethylammonium chloride, 5.1g of 80% acrylic acid, and 2.25g of glycerin were added to obtain a uniform solution, which was then immersed in a 36°C water bath to stabilize the temperature. Next, in a nitrogen atmosphere, a 1% by mass aqueous solution of 2,2'-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride was added as a polymerization initiator at 100ppm per monomer, and polymerization was carried out at 36°C for 6 hours under stirring. Then, 200 ppm of the polymerization initiator was added and polymerization was carried out for 16 hours. After the reaction was completed, 10.3 g of sodium sulfate was added to the obtained dispersion and stirred until there was no residual sodium sulfate left, to obtain a water-soluble polymer dispersion. The molar composition ratio of this water-soluble polymer was acrylamide / acryloyloxyethyl dimethylbenzyl ammonium chloride / acryloyloxyethyl trimethyl ammonium chloride / acrylic acid = 55 / 16 / 14 / 15 mol %. The viscosity of this dispersion was 35 mPa·s, and the viscosity when the water-soluble polymer dispersion was dissolved in a 4 mass % sodium chloride aqueous solution to a concentration of 0.5 mass % was 39 mPa·s. This is shown in Table 1 as Example 3.

[0036] (Example 4) 131.6g of demineralized water, 9.6g of 14% by mass polyvinylamine, and 44.6g of ammonium sulfate were added to a 0.5L separable flask equipped with an anchor blade stirrer, a cooling tube, and a nitrogen inlet tube, and the mixture was heated to 36°C under stirring to dissolve uniformly. Next, 63.3g of 50% by mass acrylamide, 16.7g of 80% by mass acryloyloxyethyl dimethylbenzyl ammonium chloride, and 2.25g of glycerin were added to obtain a uniform solution, which was then immersed in a 36°C water bath to stabilize the temperature. Next, under a nitrogen atmosphere, a 1% by mass aqueous solution of 2,2'-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride was added as a polymerization initiator at 50 ppm per monomer, and polymerization was carried out at 36°C for 5 hours under stirring. After that, 100 ppm of the above polymerization initiator was added, and polymerization was carried out for 17 hours. After the reaction was completed, 31.9 g of ammonium sulfate was added to the resulting dispersion and stirred until no ammonium sulfate remained dissolved, yielding a water-soluble polymer dispersion. The molar composition of this water-soluble polymer was acrylamide / acryloyloxyethyldimethylbenzylammonium chloride = 90 / 10 mol%. The viscosity of this dispersion was 16 mPa·s, and when the water-soluble polymer dispersion was dissolved in a 4 mass% sodium chloride aqueous solution to a concentration of 0.5 mass%, the viscosity was 8 mPa·s. This is shown in Table 1 as Example 4.

[0037] (Example 5) 114.3g of demineralized water, 27.0g of 5% by mass acrylamide / 2-aminoethyl methacrylate hydrochloride (5 / 95 mol%) copolymer, and 44.6g of ammonium sulfate were added to a 0.5L separable flask equipped with an anchor blade stirrer, a cooling tube, and a nitrogen inlet tube, and the mixture was heated to 36°C under stirring to dissolve uniformly. Next, 63.3g of 50% by mass acrylamide, 16.7g of 80% by mass acryloyloxyethyl dimethylbenzyl ammonium chloride, and 2.25g of glycerin were added to obtain a uniform solution, which was then immersed in a 36°C water bath to stabilize the temperature. Next, under a nitrogen atmosphere, a 1% by mass aqueous solution of 2,2'-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride was added as a polymerization initiator at 50 ppm per monomer, and polymerization was carried out at 36°C for 5 hours under stirring. After that, 100 ppm of the above polymerization initiator was added, and polymerization was carried out for 17 hours. After the reaction was completed, 31.9 g of ammonium sulfate was added to the resulting dispersion and stirred until no ammonium sulfate remained dissolved, yielding a water-soluble polymer dispersion. The molar composition ratio of this water-soluble polymer was acrylamide / acryloyloxyethyldimethylbenzylammonium chloride = 90 / 10 mol%. The viscosity of this dispersion was 39 mPa·s, and when the water-soluble polymer dispersion was dissolved in a 4 mass% sodium chloride aqueous solution to a concentration of 0.5 mass%, the viscosity was 52 mPa·s. This is shown in Table 1 as Example 5.

[0038] (Comparative Example 1) 134.5g of demineralized water, 6.8g of 20% by mass polyacryloyloxyethyl trimethylammonium chloride, and 44.6g of ammonium sulfate were added to a 0.5L separable flask equipped with an anchor blade stirrer, a cooling tube, and a nitrogen inlet tube, and the mixture was heated to 36°C under stirring to dissolve uniformly. Next, 63.3g of 50% by mass acrylamide, 16.7g of 80% by mass acryloyloxyethyl dimethylbenzylammonium chloride, and 2.25g of glycerin were added to obtain a uniform solution, which was then immersed in a 36°C water bath to stabilize the temperature. Next, under a nitrogen atmosphere, a 1% by mass aqueous solution of 2,2'-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride was added as a polymerization initiator at 50 ppm per monomer, and polymerization was carried out at 36°C for 5 hours under stirring. Then, 100 ppm of the above polymerization initiator was added, and polymerization was carried out for 17 hours. The viscosity of the reaction solution increased during the reaction. After the reaction was completed, 31.9 g of ammonium sulfate was added to the resulting dispersion and stirred until no ammonium sulfate remained dissolved, yielding a water-soluble polymer dispersion. The molar composition ratio of this water-soluble polymer was acrylamide / acryloyloxyethyldimethylbenzylammonium chloride = 90 / 10 mol%. The viscosity of this dispersion was 110 mPa·s, and when the water-soluble polymer dispersion was dissolved in a 4 mass% sodium chloride aqueous solution to a concentration of 0.5 mass%, the viscosity was 55 mPa·s. This is shown in Table 1 as Comparative Example 1.

[0039] (Comparative Example 2) 134.5g of demineralized water, 6.8g of 20% by mass polydimethylaminoethyl methacrylate hydrochloride, and 44.6g of ammonium sulfate were added to a 0.5L separable flask equipped with an anchor blade stirrer, a cooling tube, and a nitrogen inlet tube, and the mixture was heated to 36°C under stirring to dissolve uniformly. Next, 63.3g of 50% by mass acrylamide, 16.7g of 80% by mass acryloyloxyethyl dimethylbenzyl ammonium chloride, and 2.25g of glycerin were added to obtain a uniform solution, which was then immersed in a 36°C water bath to stabilize the temperature. Next, under a nitrogen atmosphere, a 1% by mass aqueous solution of 2,2'-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride was added as a polymerization initiator at 50 ppm per monomer, and polymerization was carried out at 36°C for 5 hours under stirring. Then, 100 ppm of the above polymerization initiator was added, and polymerization was carried out for 17 hours. The viscosity of the reaction solution increased during the reaction. After the reaction was completed, 31.9 g of ammonium sulfate was added to the resulting dispersion and stirred until no ammonium sulfate remained dissolved, yielding a water-soluble polymer dispersion. The molar composition ratio of this water-soluble polymer was acrylamide / acryloyloxyethyldimethylbenzylammonium chloride = 90 / 10 mol%. The viscosity of this dispersion was 44 mPa·s, and when the water-soluble polymer dispersion was dissolved in a 4 mass% sodium chloride aqueous solution to a concentration of 0.5 mass%, the viscosity was 64 mPa·s. This is shown in Table 1 as Comparative Example 2.

[0040] (Table 1) TIFF2025079401000005.tif4293 Monomer; AAM: Acrylamide DMBZ: Acryloyloxyethyl dimethylbenzyl ammonium chloride DMQ: Acryloyloxyethyl trimethylammonium chloride AAC: Acrylic acid Polymeric dispersants; p-AMC: Poly(2-aminoethyl methacrylate) hydrochloride, 0.5% by weight aqueous solution viscosity 37 mPa s PVAm: Polyvinylamine (degree of amination 30 mol%), viscosity of 0.5 mass% aqueous solution 6 mPa s p-AAM / AMC: Acrylamide / 2-aminoethyl methacrylate hydrochloride (5 / 95 mol%) copolymer, 0.5 mass% aqueous solution viscosity 20 mPa s p-DMQ: Polyacryloyloxyethyltrimethylammonium chloride, 0.5% by weight aqueous solution viscosity 10 mPa s p-DAM: Polydimethylaminoethyl methacrylate hydrochloride, 0.5% by weight aqueous solution viscosity 43 mPa s Polymer dispersant addition rate (mass%); relative to monomer Polymerization salts: (a): ammonium sulfate, (b): ammonium chloride Monomer concentration: mass ratio of monomer to water-soluble polymer dispersion Inorganic salt concentration: mass ratio of inorganic salt to water-soluble polymer dispersion Appearance during the reaction: ◯: The polymerization reaction liquid surface is flat, ×: The polymerization reaction liquid has thickened and is rising up in the agitator Dispersion viscosity: Viscosity of a water-soluble polymer dispersion measured at 25°C. Viscosity of 0.5% by mass salt water solution: Viscosity measured at 25°C when the polymer is dissolved in 4% by mass sodium chloride water to a polymer concentration of 0.5% by mass.

[0041] In Examples 1 to 5 of the water-soluble polymer dispersions using poly(2-aminoethyl methacrylate hydrochloride) or polyvinylamine, which are polymer dispersants containing a primary amino group as a constituent unit, thickening during the reaction could be suppressed. On the other hand, in Comparative Examples 1 and 2, using polyacryloyloxyethyltrimethylammonium chloride or poly(dimethylaminoethyl methacrylate hydrochloride), which contain a quaternary ammonium group or a tertiary amino group, as the polymer dispersant, thickening during the reaction could not be suppressed. It was confirmed that a stable water-soluble polymer dispersion in which thickening during production is suppressed can be obtained by dispersing a monomer or monomer mixture aqueous solution essentially containing a monomer represented by general formula (1) in a salt solution in the presence of a polymer dispersant containing a primary amino group as a constituent unit, and dispersing the resulting solution under stirring.

Claims

1. A water-soluble polymer dispersion obtained by dispersing and polymerizing an aqueous solution of a monomer or a monomer mixture essentially containing a monomer represented by the following general formula (1) in a salt solution while stirring the aqueous solution of the salt solution in the presence of a polymer dispersant containing a primary amino group as a constituent unit: General formula (1) R １ is hydrogen or a methyl group, R ２ , R ３ is an alkyl or alkoxy group having 1 to 3 carbon atoms, R ４ is an alkyl group or an aryl group having 7 to 20 carbon atoms; A is oxygen or NH; B is an alkylene group or an alkoxylene group having 2 to 4 carbon atoms; X is １ － represents an anion.

2. The water-soluble polymer dispersion according to claim 1, characterized in that the polymer dispersant containing a primary amino group as a constituent unit is at least one selected from a primary amino group-containing polymer obtained by polymerizing a monomer mixture essentially containing a cationic monomer represented by the following general formula (4), a polyvinylamine-based polymer, and a polyamidine-based polymer: General formula (4) R １ is a hydrogen atom or a methyl group, A is an oxygen atom or NH, B is an alkylene group or an alkoxylene group having 2 to 3 carbon atoms, X － represents an anion.

3. 3. The water-soluble polymer dispersion according to claim 1, wherein the content of the polymer dispersant containing a primary amino group as a constituent unit is 1 to 30% by mass based on the total amount of monomers.

4. A method for producing a water-soluble polymer dispersion, comprising dispersing an aqueous solution of a monomer or a monomer mixture essentially containing a monomer represented by the following general formula (1) in a salt solution, in the presence of a polymer dispersant containing a primary amino group as a constituent unit in the salt solution, and carrying out dispersion polymerization under stirring. General formula (1) R １ is hydrogen or a methyl group, R ２ , R ３ is an alkyl or alkoxy group having 1 to 3 carbon atoms, R ４ is an alkyl group or an aryl group having 7 to 20 carbon atoms; A is oxygen or NH; B is an alkylene group or an alkoxylene group having 2 to 4 carbon atoms; X is １ － represents an anion.

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