Water-in-oil emulsion polymer

Abstract

To provide a water-in-oil emulsion that relates to a water-in-oil emulsion polymer used as a paper-making yield improving agent and a filtration aid, a coagulation processing agent and a sludge dewatering agent for industrial waste water and drainage and night soil sludge, and can improve storage stability by suppressing product separation and condensation and foreign matter compared with a conventional water-in-oil emulsion.SOLUTION: It is possible for a water-in-oil emulsion polymer to improve the storage stability, the water-in-oil emulsion polymer obtained by adjusting the charge on the surface of emulsion particles through the addition of ionic surfactants during the production of water-in-oil emulsion polymers, thereby promoting the repulsion between particles, and thus solve the aforementioned problem.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a water-in-oil emulsion polymer that can be used for applications such as a retention aid or drainage aid in papermaking, a flocculating agent or sludge dehydration agent for treating industrial wastewater or sewage sludge, and more specifically to a water-in-oil emulsion polymer that has good water solubility, dispersion stability, and storage stability and produces a low product viscosity. [Background technology]

[0002] Recent advances in chemical technology have led to significant developments in polymer technology used in industrial applications. Polymer products in various forms are used in a variety of fields, including daily necessities, building materials, and process chemicals used in manufacturing processes. Demand for liquid products is increasing due to their ease of handling, and in some fields, liquid products are replacing conventional solid products. Among liquid product technologies, two-phase products such as latex, emulsions, and dispersions have low viscosity and are easy to handle because the polymer is present in the dispersed phase, and they can also be highly concentrated, which can reduce transportation costs. Among the industries that use polymers, for example, retention aids or drainage aids for papermaking, and flocculating or sludge dewatering agents for industrial wastewater or sewage sludge treatment, high molecular weights of around 10 million are often essential for their functionality. From the standpoint of ease of handling, water-in-oil emulsions are a very effective product form, but on the other hand, the drawbacks of high polymerization include difficulty in dissolving, increased product viscosity, and reduced storage stability due to factors such as product separation and the generation of condensation. To solve these problems, an invention has been proposed in which a polymer dispersant and a low molecular weight ionic surfactant are used as a dispersant (Patent Document 1), and an invention in which the particle size is reduced by using an emulsifier (Patent Document 2). Also, an invention in which an anionic surfactant is present during the production of a water-absorbent resin (Patent Document 3) is an invention aimed at improving products by controlling particle size, although it is in a different industrial field. However, Patent Document 1 requires labor to prepare the dispersant, and even in the case of emulsification using the emulsifier of Patent Document 2, there are problems such as the size of the emulsion particles easily changing depending on the type of emulsifier and the monomer concentration, and when the machine shear is increased to miniaturize the emulsion particles, the viscosity of the product increases and handling becomes significantly worse. Patent Document 3 states that a uniform particle size is preferable for improving storage stability, and that the water-absorbent resin system does not necessarily apply to liquid products. As such, there are several inventions that aim to solve the problems of difficulty in dissolving water-in-oil emulsions, increased product viscosity, and poor storage stability, but each has its own issues, and there is a particular need for improved storage stability that can suppress product separation and the occurrence of condensation.

[0003] [Patent Document 1] Japanese Patent Application Publication No. 3-28202 [Patent Document 2] Japanese Patent Application Publication No. 6-157668 [Patent Document 3] Japanese Patent Application Publication No. 6-93008 Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention relates to a water-in-oil emulsion polymer that can be used as a retention aid and drainage aid in papermaking, and as a flocculating agent and sludge dehydration agent for treating industrial wastewater and sewage sludge. An object of the present invention is to provide a water-in-oil emulsion polymer that can suppress product separation and the occurrence of condensation foreign matter and has improved storage stability compared to conventional water-in-oil emulsions. [Means for solving the problem]

[0005] The present inventors have conducted extensive research to solve the problems of the prior art, and as a result have found that by adding an ionic surfactant during the production of a water-in-oil emulsion polymer, the charge on the surface of the emulsified particles can be adjusted and the repulsion between the particles can be promoted, thereby improving the storage stability of the resulting water-in-oil emulsion polymer and solving the above-mentioned problems. [Effects of the Invention]

[0006] The water-in-oil emulsion polymer of the present invention has a controlled surface charge at the particle interface, and the repulsion between particles results in excellent dispersion stability, suppressing the generation of foreign matter during production and improving separation of the oil phase and polymer during storage stability. In addition, the addition of an ionic surfactant improves solubility, allowing for a reduction in the amount of phase inversion agent required for dissolving the water-in-oil emulsion. The reduction in the amount of phase inversion agent also prevents the generation of film-like foreign matter when condensed water is mixed in. The improved separation stability and condensation stability allow for maximum effectiveness when used in industrial applications such as papermaking retention aids or drainage aids, flocculation treatment agents or sludge dewatering agents for industrial wastewater or sewage sludge treatment. DETAILED DESCRIPTION OF THE INVENTION

[0007] The water-in-oil emulsion polymer of the present invention comprises, as constituent units, 1 to 99 mol % of a cationic vinyl monomer represented by the following general formula (1) and / or 1 to 99 mol % of an anionic vinyl monomer represented by the following general formula (2), and 1 to 99 mol % of a nonionic monomer. When producing a cationic polymer, a cationic vinyl monomer represented by the general formula (1) and a nonionic monomer are used. When producing an anionic polymer, an anionic vinyl monomer represented by the general formula (2) and a nonionic monomer are used. When producing an amphoteric polymer, a cationic vinyl monomer represented by the general formula (1), an anionic vinyl monomer represented by the general formula (2), and a nonionic monomer are used. JPEG2025145809000001.jpg2771 General formula (1) R1 is hydrogen or a methyl group, R2 and R3 are alkyl or alkoxy groups having 1 to 3 carbon atoms, R4 is hydrogen, alkyl or alkoxy groups having 1 to 3 carbon atoms, alkyl or aryl groups having 7 to 20 carbon atoms, A is oxygen or NH, B is an alkylene group having 2 to 4 carbon atoms, X1 - represents an anion, respectively. TIFF2025145809000002.tif2771 General formula (2) R5 is hydrogen, methyl group or carboxymethyl group, R6 is hydrogen or carboxyl group, Q is SO3 - , CH2SO3 - , C6H4SO3 - , CONHC(CH3)2CH2SO3 - Or COO - Y2, Y1 or Y2 each represents hydrogen or a cation.

[0008] Examples of the quaternary amino group-containing cationic monomer of the cationic monomer represented by general formula (1) include (meth)acryloyloxyethyl trimethylammonium chloride, (meth)acryloyloxyethyl dimethylbenzylammonium chloride, (meth)acryloylaminopropyl trimethylammonium chloride, (meth)acryloylaminopropyl dimethylbenzylammonium chloride, etc. Examples of the tertiary amino group-containing cationic monomer include dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylate, dimethylaminopropyl (meth)acrylamide, diethylaminopropyl (meth)acrylamide, etc. Two or more of these may be used in combination. Examples of the anionic vinyl monomer represented by general formula (2) include (meth)acrylic acid, acrylamido-2-methylpropanesulfonic acid, methacrylic acid, itaconic acid, and salts thereof. Two or more of these may be used in combination.

[0009] Examples of nonionic monomers used in the present invention include (meth)acrylamide, N,N'-dimethylacrylamide, acrylonitrile, 2-hydroxyethyl (meth)acrylate, diacetone acrylamide, N-vinylpyrrolidone, N-vinylformamide, N-vinylacetamide, and acryloylmorpholine. Among these, (meth)acrylamide is preferred. Two or more of these may be used in combination.

[0010] Examples of ionic surfactants used in the present invention include cationic surfactants containing an alkyl group having 8 to 18 carbon atoms, such as dodecyltrimethylammonium chloride, coconut alkyltrimethylammonium chloride, hexadecyltrimethylammonium chloride, tetradecyldimethylbenzylammonium chloride, and coconut alkyldimethylbenzylammonium chloride; and anionic surfactants such as sodium alkyl sulfates having 8 to 18 carbon atoms, such as sodium lauryl sulfate and sodium polyoxyethylene alkyl sulfate, and sodium 2-ethylhexyl sulfate. Two or more of these surfactants may be combined as long as they have the same charge. To achieve optimal effects, the addition rate of the ionic surfactant is preferably in the range of 0.1 to 5.0% by mass relative to the monomer.

[0011] The polymer of the present invention can be produced by water-in-oil emulsion polymerization. Specifically, an aqueous phase containing a monomer mixture selected from cationic and / or anionic monomers and nonionic monomers is mixed with an oily substance consisting of at least a water-immiscible hydrocarbon and at least one nonionic surfactant having an HLB value in an amount effective to form a water-in-oil emulsion, and the mixture is vigorously stirred to form a water-in-oil emulsion, followed by polymerization. The ionic surfactant is added to the aqueous phase containing the monomer mixture. It may also be added during or after polymerization. Addition to the aqueous phase containing the monomer mixture is preferred. Alternatively, the monomer mixture may be added in portions, continuously or intermittently, and polymerization may be carried out.

[0012] Examples of hydrocarbon oily substances used as dispersion media include paraffins, naphthenes, mineral oils such as kerosene, light oil, and medium-weight oil, hydrocarbon synthetic oils having substantially the same ranges of boiling point, viscosity, and other properties as these, and mixtures thereof. The content is in the range of 20 to 50% by mass, preferably 20 to 35% by mass, based on the total amount of the water-in-oil emulsion.

[0013] The emulsification is carried out using a high HLB surfactant with an HLB of 8 to 15 as at least one nonionic surfactant having an effective amount for forming a water-in-oil emulsion. Surfactants other than those with a high HLB may also be used in combination. Examples of surfactants include nonionic surfactants, such as sorbitan monooleate, sorbitan monostearate, sorbitan monopalmitate, polyoxyethylene sorbitan trioleate, and polyoxyethylene nonylphenyl ether. Two or more of these may also be used in combination. The addition rate of these surfactants is 0.5 to 10% by mass, preferably 1 to 5% by mass, based on the total amount of the water-in-oil emulsion.

[0014] The concentration of the monomer during polymerization is in the range of 15 to 50% by mass, and the polymerization concentration and temperature are set appropriately depending on the monomer composition and the selection of initiator. From the viewpoint of achieving a high concentration product, the concentration during polymerization is preferably 30 to 50% by mass, and more preferably 30 to 45% by mass. The polymerization temperature is in the range of 20 to 80°C, preferably 20 to 60°C. A radical polymerization initiator is used to initiate polymerization. These initiators may be either oil-soluble or water-soluble, and polymerization can be carried out using any of the azo, redox, and peroxide types. Examples of oil-soluble azo initiators include 2,2'-azobisisobutyronitrile, dimethyl-2,2'-azobisisobutyrate, 1,1'-azobis(cyclohexane-1-carbonitrile), 2,2'-azobis(2-methylbutyronitrile), dimethyl-2,2'-azobis(2-methylpropionate), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), and the like.

[0015] Examples of water-soluble azo initiators include 2,2'-azobis(amidinopropane) dihydrochloride, 2,2'-azobis[2-(5-methyl-imidazolin-2-yl)propane] dihydrochloride, and 4,4'-azobis(4-cyanovaleric acid). Examples of redox initiators include combinations of ammonium peroxodisulfate with sodium sulfite, sodium hydrogensulfite, trimethylamine, tetramethylethylenediamine, and the like. Examples of peroxide initiators include ammonium or potassium peroxodisulfate, hydrogen peroxide, benzoyl peroxide, lauroyl peroxide, octanoyl peroxide, succinic peroxide, t-butylperoxy-2-ethylhexanoate, and t-butyl hydroperoxide.

[0016] When a crosslinkable monomer is used as a structural modifier during or after polymerization in producing the water-in-oil emulsion polymer of the present invention, the three-dimensional structure of the polymer changes compared to when no crosslinkable monomer is added. The structural change changes the function of the polymer as a papermaking retention aid, drainage aid, flocculating agent for industrial wastewater and sewage sludge treatment, and sludge dewatering agent, making it possible to impart different properties to the polymer despite having the same composition. When used, the crosslinkable monomer is preferably present in a range of 0.0001 to 0.1% by mass relative to the total amount of monomers. Examples of crosslinkable monomers include N,N'-methylenebis(meth)acrylamide, triallylamine, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, polyethylene glycol di(meth)acrylate, N-vinyl(meth)acrylamide, N-methylallylacrylamide, glycidyl acrylate, polyethylene glycol diglycidyl ether, acrolein, glyoxal, and vinyltrimethoxysilane, with N,N'-methylenebis(meth)acrylamide being preferred.

[0017] It is also effective to use isopropyl alcohol in an amount of 0.1 to 5% by mass relative to the monomer as a chain transfer agent for controlling the degree of polymerization, or to use a formate in an amount of 0.01 to 0.5% by mass relative to the monomer or a hypophosphite in an amount of 0.1 to 5% by mass relative to the monomer. Succinic acid, acetic acid, citric acid, adipic acid, sulfamic acid, or salts thereof may be added to adjust the pH during or after polymerization and prevent deterioration of the polymer.

[0018] After polymerization, a hydrophilic surfactant called a phase inversion agent is added as needed to make the oil-coated emulsion particles more compatible with water and to facilitate the dissolution of the water-soluble polymers inside, and the emulsion is then diluted with water for use in various applications. Examples of hydrophilic surfactants include cationic surfactants and nonionic surfactants with an HLB of 9 to 15, such as polyoxyethylene polyoxypropylene alkyl ethers and polyoxyethylene alcohol ethers.

[0019] In the present invention, the ionic surfactant is added to adjust the surface charge of the emulsified particles, and the nonionic surfactant is added to form a stable W / O type emulsion. Generally, ionic surfactants are used in suspension polymerization and emulsion polymerization of hydrophobic monomers because they stabilize O / W type dispersion systems, but they are rarely used in emulsion polymerization of water-soluble monomers. In the present invention, it is presumed that the W / O type dispersion system is stabilized with a large amount of nonionic surfactant added, and therefore the ionic surfactant also orients to the W / O type.

[0020] To achieve water-in-oil emulsion polymerization, it is necessary to form a stable W / O emulsion. The ratio of the amount of ionic surfactant to nonionic surfactant added is important; if the ratio exceeds the optimum value, the water-in-oil emulsion will change to an oil-in-water emulsion, making it impossible to achieve the desired water-in-oil emulsion polymerization. The optimum amount of ionic surfactant added is 50% by mass or less, preferably 25% by mass or less, of the nonionic surfactant.

[0021] The function of the ionic surfactant in this invention is to adjust the surface charge of the emulsified particles. One of the causes of foreign matter in water-in-oil emulsion products is thought to be coalescence due to insufficient electrostatic repulsion between particles. We speculate that the addition of an ionic surfactant strengthens the surface charge of the emulsion due to the charge of the ionic surfactant located at the particle interface, thereby preventing the association between the emulsified particles. The zeta potential of the particle surface of a water-in-oil emulsion is one indicator of the repulsion between particles. However, since zeta electron measurement of a water-in-oil emulsion is performed in a low-dielectric-constant solvent, a special device is generally required. In the present invention, an inexpensive and simple method is used to measure the sedimentation amount of polymer particles by centrifugation, which is used as an indicator of the degree of repulsion of particle surface charges.

[0022] The separation stability of the water-in-oil emulsion polymer of the present invention is measured as follows: 40.00 g of the water-in-oil emulsion polymer is placed in a centrifuge test tube (inner diameter 32 mm, height 100 mm, round bottom, plastic) and centrifuged at 4,000 rpm for 10 minutes. The test tube is turned upside down, and the liquid portion is removed after 2 minutes. The mass of the remaining polymer at the bottom of the test tube is measured, and the separation stability is calculated according to the following formula. Separation stability (mass%) = bottom residue after centrifugation (g) / 40.00 (g) × 100

[0023] Adding an appropriate amount of phase inversion agent promotes polymer dissolution, but adding too much can result in dissolution occurring before dispersion of the polymer particles during dissolution of the water-in-oil emulsion particles, resulting in coalescence and integration of the polymers. In such cases, despite sufficient electrical conductivity, the effectiveness as a papermaking retention aid, drainage aid, flocculation treatment agent for industrial wastewater and sewage sludge treatment, and sludge dehydration agent is reduced. The addition of the ionic surfactant of the present invention improves the solubility of the water-in-oil emulsion, thereby reducing the amount of phase inversion agent required for dissolution. Water-soluble liquid products, such as water-in-oil emulsions, can dissolve in high concentrations only on the surface of the product due to the inclusion of condensed water on the top of the container during storage or transportation after production, resulting in the inclusion of condensed water at the top of the container due to temperature differences between day and night. This condensed water often forms a film-like or strong gel-like substance, which can clog transport pumps. Reducing the amount of phase inversion agent reduces the formation of film-like contaminants when condensed water is mixed in. The amount of phase inversion agent that can be reduced by adding an ionic surfactant is 20 to 30% of the amount when no ionic surfactant is added.

[0024] The particle size of the water-in-oil emulsion in the present invention is measured by dynamic light scattering. Dynamic light scattering measurement is performed as follows using an ELS-Z (zeta potential / particle size measurement system) manufactured by Otsuka Electronics Co., Ltd. A 0.01% by mass diluted emulsion solution is prepared and placed in a plastic deposit cell (material: methacrylate) with an optical path length of 10 mm. Measurement is performed under the following conditions: temperature 25°C, solvent: mineral spirits containing 4% by mass of sorbitan fatty acid ester (HLB = 4.0 to 5.0), refractive index 1.438, and analysis is performed using the cumulant method. [Example]

[0025] The water-in-oil emulsion polymer of the present invention will be specifically explained below, but the present invention is not limited to the following examples.

[0026] Example 1 A reaction vessel equipped with a stirrer and temperature control device was charged with 251.5 g of isoparaffin (boiling point 190°C to 230°C), 14.0 g of sorbitan monooleate (HLB 4.3), and 4.5 g of polyoxyethylene sorbitan trioleate (HLB 11.0) and dissolved. Separately, 421.1 g of a 50% by weight aqueous solution of acrylamide (AAM), 114.4 g of an 80% by weight aqueous solution of acrylic acid (AAC), 0.33 g of sodium formate (0.1% by weight relative to monomer), 1.0 g of sodium lauryl sulfate (0.33% by weight relative to monomer), and 76.11 g of ion-exchanged water were mixed and completely dissolved. Then, while cooling the surroundings, 105.9 g of a 48% by weight aqueous solution of sodium hydroxide was added, and the pH was adjusted to 8.4. The oil and aqueous solution were then mixed and emulsified using a homogenizer at 7,000 rpm for 30 seconds. The monomer composition at this time was AAM / AAC = 70 / 30 (mol %). The temperature of the resulting emulsion was kept at 45-50°C. The monomer solution was purged with nitrogen for 30 minutes, and then 0.132 g (0.04 mass% relative to the monomer) of 2,2'-azobis(isobutyrate)dimethyl (V-601, Fujifilm Wako Pure Chemical Industries, Ltd.) was added to initiate the polymerization reaction. The reaction temperature was 48±2°C for 4 hours, and then the temperature was raised to 70°C and the reaction was continued for 1 hour to complete the polymerization. 11.2 g (1.12 mass% relative to the liquid) of polyoxyethylene polyoxypropylene alkyl ether with an HLB of 11.7 was added to the resulting water-in-oil emulsion as a phase inversion agent, and the emulsion was mixed to obtain a total of 1 kg of water-in-oil emulsion. This emulsion is designated Example 1, and its composition and physical properties are shown in Table 1.

[0027] Example 2 A reaction vessel equipped with a stirrer and temperature control device was charged with 283.0 g of isoparaffin (boiling point 190°C to 230°C), 12.0 g of sorbitan monooleate (HLB 4.3), and 5.0 g of polyoxyethylene sorbitan trioleate (HLB 11.0) and dissolved. Separately, 33.6 g of a 50% by weight aqueous solution of acrylamide (AAM), 229.0 g of an 80% by weight aqueous solution of acryloyloxyethyltrimethylammonium chloride (DMQ), 7.0 g of citric acid, 0.38 g of sodium formate (0.19% by weight relative to monomer), 6.0 g of 50% by weight coconut alkyl dimethyl benzyl ammonium chloride (1.5% by weight relative to monomer), and 416.02 g of ion-exchanged water were added, mixed, and completely dissolved. The oil and aqueous solution were then mixed and emulsified using a homogenizer at 7,000 rpm for 30 seconds. The monomer composition at this time was AAM / DMQ = 20 / 80 (mol%). The temperature of the resulting emulsion was maintained at 45-50°C. After 30 minutes of nitrogen substitution, 0.06 g (0.020 wt% relative to the monomer) of 2,2'-azobis(isobutyrate) dimethyl (V-601, Fujifilm Wako Pure Chemical Industries, Ltd.) was added to initiate the polymerization reaction. The polymerization was carried out at a reaction temperature of 48±2°C for 4 hours, then heated to 70°C and reacted for 1 hour to complete the polymerization. 8.0 g (0.8 wt% relative to the liquid) of polyoxyethylene polyoxypropylene alkyl ether with an HLB of 11.7 was added to the resulting water-in-oil emulsion as a phase inversion agent, and mixed to obtain a total of 1 kg of water-in-oil emulsion. This emulsion is designated Example 2, and its composition and physical properties are shown in Table 1.

[0028] Example 3 A reaction vessel equipped with a stirrer and a temperature controller was charged with 243.0 g of isoparaffin having a boiling point of 190°C to 230°C, and 12.0 g of sorbitan monooleate (HLB 4.3) and 5.0 g of polyoxyethylene sorbitan trioleate (HLB 11.0) were dissolved in the resulting solution. Separately, 145.4 g of a 50% by weight aqueous solution of acrylamide (abbreviated as AAM), 371.6 g of an 80% by weight aqueous solution of acryloyloxyethyltrimethylammonium chloride (abbreviated as DMQ), 7.0 g of citric acid, 0.51 g of sodium formate (0.14% by weight relative to the monomer), 0.005 g of methylenebisacrylamide (0.013% by weight relative to the monomer), 6.0 g of 50% by weight coconut alkyl dimethyl benzyl ammonium chloride (0.81% by weight relative to the monomer), and 201.08 g of ion-exchanged water were added, mixed, and completely dissolved. The oil and aqueous solution were then mixed and emulsified using a homogenizer at 7,000 rpm for 30 seconds. The monomer composition at this time was AAM / DMQ = 40 / 60 (mol %). The temperature of the resulting emulsion was maintained at 45-50°C. After 30 minutes of nitrogen substitution, 0.093 g (0.025 wt % relative to the monomer) of 2,2'-azobis(isobutyrate)dimethyl (V-601, Fujifilm Wako Pure Chemical Industries, Ltd.) was added to initiate the polymerization reaction. The reaction temperature was maintained at 48±2°C for 4 hours, and the temperature was then raised to 70°C for 1 hour to complete the polymerization. 8.0 g (0.8 wt % relative to the liquid) of polyoxyethylene polyoxypropylene alkyl ether with an HLB of 11.7 was added to the resulting water-in-oil emulsion as a phase inversion agent, and the emulsion was mixed to obtain a total of 1 kg of water-in-oil emulsion. This emulsion is designated Example 3, and its composition and physical properties are shown in Table 1.

[0029] Example 4 In a reaction vessel equipped with a stirrer and a temperature controller, 10.5 g of sorbitan monooleate (HLB 4.3) and 4.5 g of polyoxyethylene sorbitan trioleate (HLB 11.0) were added and dissolved in 265.0 g of isoparaffin having a boiling point of 190°C to 230°C. Separately, 411.6 g of a 50% by weight aqueous solution of acrylamide (AAM), 214.2 g of an 80% by weight aqueous solution of acryloyloxyethyl trimethylammonium chloride (DMQ), 10.4 g of an 80% by weight aqueous solution of methacryloyloxyethyl trimethylammonium chloride (DMC), 18.1 g of an 80% by weight aqueous solution of acrylic acid (AAC), 0.052 g of sodium hypophosphite (0.013% by weight relative to monomer), 6.0 g of 50% by weight coconut alkyl dimethyl benzyl ammonium chloride (0.75% by weight relative to monomer), and 51.61 g of ion-exchanged water were collected, mixed, and completely dissolved. The oil and aqueous solution were then mixed and emulsified using a homogenizer at 7000 rpm for 30 seconds. The monomer composition at this time was AAM / DMQ / DMC / AAC = 72 / 22 / 1 / 5 (mol%). The resulting emulsion was maintained at a monomer solution temperature of 25-30°C and purged with nitrogen for 30 minutes. Then, 0.08 g (0.02% by mass of monomer) of 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile) (V-70, Fujifilm Wako Pure Chemical Industries, Ltd.) was added to initiate the polymerization reaction. The polymerization was carried out at a reaction temperature of 27±2°C for 4 hours, then heated to 60°C and continued for 1 hour to complete the polymerization. 8.0 g (0.8% by mass of liquid) of polyoxyethylene polyoxypropylene alkyl ether with an HLB of 11.7 was added to the resulting water-in-oil emulsion as a phase inversion agent, and mixed to obtain a total of 1 kg of water-in-oil emulsion. This emulsion is designated Example 4, and its composition and physical properties are shown in Table 1.

[0030] Example 5 A reaction vessel equipped with a stirrer and temperature control device was charged with 263 g of isoparaffin having a boiling point of 190°C to 230°C, and 12 g of sorbitan monooleate (HLB 4.3) and 5.0 g of polyoxyethylene sorbitan trioleate (HLB 11.0) were dissolved. Separately, 59.6 g of dimethylaminoethyl methacrylate (abbreviated as DAM), 593.4 g of a 50% by weight aqueous solution of acrylamide (abbreviated as AAM), 17.1 g of an 80% by weight aqueous solution of acrylic acid (abbreviated as AAC), 24.3 g of anhydrous citric acid, 0.74 g of sodium hypophosphite (0.2% by weight relative to monomer), 0.007 g of methylenebisacrylamide (0.002% by weight relative to monomer), 6.0 g of 50% by weight coconut alkyl dimethyl benzyl ammonium chloride (0.81% by weight relative to monomer), and 6.83 g of ion-exchanged water were added, mixed, and completely dissolved. The oil and aqueous solution were then mixed and emulsified using a homogenizer at 5000 rpm for 15 minutes. The monomer composition at this time was DAM / AAC / AAM = 8 / 4 / 88 (mol%). The temperature of the resulting emulsion was maintained at 25-30°C. After 30 minutes of nitrogen substitution, 0.074 g (0.02 wt% relative to the monomer) of 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile) (V-70, Fujifilm Wako Pure Chemical Industries, Ltd.) was added to initiate the polymerization reaction. The polymerization was continued for 24 hours at a reaction temperature of 27±2°C to complete the reaction. After polymerization, 12.0 g (1.2 wt% relative to the liquid) of polyoxyethylene polyoxypropylene alkyl ether with an HLB of 11.7 was added to the resulting water-in-oil emulsion as a phase inversion agent, and the resulting emulsion was mixed to obtain a total of 1 kg of water-in-oil emulsion. This is Example 5, and its composition and physical properties are shown in Table 1.

[0031] Example 6 A reaction vessel equipped with a stirrer and a temperature controller was charged with 263 g of isoparaffin having a boiling point of 190°C to 230°C, and 12 g of sorbitan monooleate (HLB 4.3) and 5.0 g of polyoxyethylene sorbitan trioleate (HLB 11.0) were dissolved in the resulting solution. Separately, 59.6 g of dimethylaminoethyl methacrylate (abbreviated as DAM), 593.4 g of a 50% by weight aqueous solution of acrylamide (abbreviated as AAM), 17.1 g of an 80% by weight aqueous solution of acrylic acid (abbreviated as AAC), 24.3 g of anhydrous citric acid, 0.74 g of sodium hypophosphite (0.2% by weight relative to the monomer), 0.007 g of methylenebisacrylamide (0.002% by weight relative to the monomer), 10.0 g of 30% by weight dodecyltrimethylammonium chloride (0.81% by weight relative to the monomer), and 2.82 g of ion-exchanged water were added, mixed, and completely dissolved. The oil and aqueous solution were then mixed and emulsified using a homogenizer at 5000 rpm for 15 minutes. The monomer composition at this time was DAM / AAC / AAM = 8 / 4 / 88 (mol%). The temperature of the resulting emulsion was maintained at 25-30°C. After 30 minutes of nitrogen substitution, 0.074 g (0.02 wt% relative to the monomer) of 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile) (V-70, Fujifilm Wako Pure Chemical Industries, Ltd.) was added to initiate the polymerization reaction. The polymerization was continued for 24 hours at a reaction temperature of 27±2°C to complete the reaction. After polymerization, 12.0 g (1.2 wt% relative to the liquid) of polyoxyethylene polyoxypropylene alkyl ether with an HLB of 11.7 was added to the resulting water-in-oil emulsion as a phase inversion agent, and the resulting emulsion was mixed to obtain a total of 1 kg of water-in-oil emulsion. This is Example 6, and its composition and physical properties are shown in Table 1.

[0032] Example 7 A reaction vessel equipped with a stirrer and a temperature controller was charged with 263 g of isoparaffin having a boiling point of 190°C to 230°C, and dissolved therein were 12 g of sorbitan monooleate (HLB 4.3) and 5.0 g of polyoxyethylene sorbitan trioleate (HLB 11.0). Separately, 59.6 g of dimethylaminoethyl methacrylate (hereinafter abbreviated as DAM), 593.4 g of a 50% by weight aqueous solution of acrylamide (abbreviated as AAM), 17.1 g of an 80% by weight aqueous solution of acrylic acid (abbreviated as AAC), 24.3 g of anhydrous citric acid, 0.74 g of sodium hypophosphite (0.2% by weight relative to monomer), 0.007 g of methylenebisacrylamide (0.002% by weight relative to monomer), 3.57 g of 28% by weight hexadecyltrimethylammonium chloride (0.27% by weight relative to monomer), and 9.25 g of ion-exchanged water, mixed, and completely dissolved. The oil and aqueous solution were then mixed and emulsified using a homogenizer at 5000 rpm for 15 minutes. The monomer composition at this time was DAM / AAC / AAM = 8 / 4 / 88 (mol%). The temperature of the resulting emulsion was maintained at 25-30°C. After 30 minutes of nitrogen substitution, 0.074 g (0.02 wt% relative to the monomer) of 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile) (V-70, Fujifilm Wako Pure Chemical Industries, Ltd.) was added to initiate the polymerization reaction. The polymerization was continued for 24 hours at a reaction temperature of 27±2°C to complete the reaction. After polymerization, 12.0 g (1.2 wt% relative to the liquid) of polyoxyethylene polyoxypropylene alkyl ether with an HLB of 11.7 was added to the resulting water-in-oil emulsion as a phase inversion agent, and the resulting emulsion was mixed to obtain a total of 1 kg of water-in-oil emulsion. This is Example 7, and its composition and physical properties are shown in Table 1.

[0033] Example 8 A reaction vessel equipped with a stirrer and temperature control device was charged with 263 g of isoparaffin (boiling point 190°C to 230°C) and dissolved in 12 g of sorbitan monooleate (HLB 4.3) and 5.0 g of polyoxyethylene sorbitan trioleate (HLB 11.0). Separately, 59.6 g of dimethylaminoethyl methacrylate (abbreviated as DAM), 593.4 g of a 50% by weight aqueous solution of acrylamide (abbreviated as AAM), 17.1 g of an 80% by weight aqueous solution of acrylic acid (abbreviated as AAC), 24.3 g of anhydrous citric acid, 0.74 g of sodium hypophosphite (0.2% by weight relative to monomer), 0.007 g of methylenebisacrylamide (0.002% by weight relative to monomer), and 6.83 g of ion-exchanged water were added, mixed, and completely dissolved. The oil and aqueous solution were then mixed and emulsified using a homogenizer at 5,000 rpm for 15 minutes. The monomer composition at this time was DAM / AAC / AAM = 8 / 4 / 88 (mol%). The temperature of the resulting emulsion was maintained at 25-30°C. After purging with nitrogen for 30 minutes, 0.074 g (0.02 wt% of monomer) of 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile) (V-70, Fujifilm Wako Pure Chemical Industries, Ltd.) was added to initiate the polymerization reaction. The polymerization was continued for 24 hours at a reaction temperature of 27±2°C to complete the reaction. After polymerization, 6.0 g (0.81 wt% of monomer) of 50 wt% alkyldimethylbenzylammonium chloride was added to the resulting water-in-oil emulsion and stirred until homogeneous. 12.0 g (1.2 wt% of liquid) of polyoxyethylene polyoxypropylene alkyl ether with an HLB of 11.7 was added as a phase inversion agent, yielding a total of 1 kg of water-in-oil emulsion. This is Example 8, and its composition and physical properties are shown in Table 1.

[0034] (Comparative Example 1) A reactor equipped with a stirrer and temperature control device was charged with 251.5 g of isoparaffin (boiling point 190°C to 230°C), 14.0 g of sorbitan monooleate (HLB 4.3), and 4.5 g of polyoxyethylene sorbitan trioleate (HLB 11.0), and dissolved. Separately, 421.1 g of a 50% by weight aqueous solution of acrylamide (AAM), 114.4 g of an 80% by weight aqueous solution of acrylic acid (AAC), 0.33 g of sodium formate (0.1% by weight relative to the monomer), and 74.31 g of ion-exchanged water were mixed and completely dissolved. Then, while cooling the surroundings, 105.9 g of a 48% by weight aqueous solution of sodium hydroxide was added, and the pH was adjusted to 8.4. The oil and aqueous solution were then mixed and emulsified using a homogenizer at 7000 rpm for 30 seconds. The monomer composition at this time was AAM / AAC = 70 / 30 (mol%). The temperature of the resulting emulsion was maintained at 25-30°C. The monomer solution was purged with nitrogen for 30 minutes, and then 0.132 g (0.04% by mass relative to the monomer) of 2,2'-azobis(isobutyrate)dimethyl (V-601, Fujifilm Wako Pure Chemical Industries, Ltd.) was added to initiate the polymerization reaction. The polymerization was carried out at a reaction temperature of 48±2°C for 4 hours, then the temperature was raised to 70°C and the reaction was continued for 1 hour to complete the polymerization. 14.0 g (1.4% by mass relative to the liquid) of polyoxyethylene polyoxypropylene alkyl ether with an HLB of 11.7 was added to the resulting water-in-oil emulsion as a phase inversion agent, and mixed to obtain a total of 1 kg of water-in-oil emulsion. This emulsion is designated Comparative Example 1, and its composition and physical properties are shown in Table 1.

[0035] (Comparative Example 2) A reaction vessel equipped with a stirrer and temperature control device was charged with 283.0 g of isoparaffin (boiling point 190°C to 230°C) and dissolved with 12.0 g of sorbitan monooleate (HLB 4.3) and 5.0 g of polyoxyethylene sorbitan trioleate (HLB 11.0). Separately, 33.6 g of a 50% by weight aqueous solution of acrylamide (AAM), 229.0 g of an 80% by weight aqueous solution of acryloyloxyethyl trimethylammonium chloride (DMQ), 7.0 g of citric acid, 0.38 g of sodium formate (0.19% by weight relative to monomer), and 420.02 g of ion-exchanged water were mixed and completely dissolved. The oil and aqueous solution were then mixed and emulsified using a homogenizer at 7000 rpm for 30 seconds. The monomer composition at this time was AAM / DMQ = 20 / 80 (mol %). The temperature of the resulting emulsion was maintained at 45-50°C. The monomer solution was purged with nitrogen for 30 minutes, and then 0.06 g (0.020% by mass of monomer) of 2,2'-azobis(isobutyrate)dimethyl (V-601, Fujifilm Wako Pure Chemical Industries, Ltd.) was added to initiate the polymerization reaction. The polymerization was carried out at a reaction temperature of 48±2°C for 4 hours, after which the temperature was raised to 70°C and the reaction was continued for 1 hour to complete the polymerization. The resulting water-in-oil emulsion was mixed with 10.0 g (1.0% by mass of the liquid) of polyoxyethylene polyoxypropylene alkyl ether with an HLB of 11.7 as a phase inversion agent, yielding a total of 1 kg of water-in-oil emulsion. This emulsion is designated Comparative Example 2, and its composition and physical properties are shown in Table 1.

[0036] (Comparative Example 3) A reaction vessel equipped with a stirrer and temperature control device was charged with 243.0 g of isoparaffin (boiling point 190°C to 230°C), 12.0 g of sorbitan monooleate (HLB 4.3), and 5.0 g of polyoxyethylene sorbitan trioleate (HLB 11.0) and dissolved. Separately, 145.4 g of a 50% by weight aqueous solution of acrylamide (AAM), 371.6 g of an 80% by weight aqueous solution of acryloyloxyethyl trimethylammonium chloride (DMQ), 7.0 g of citric acid, 0.51 g of sodium formate (0.14% by weight relative to the monomer), 0.005 g of methylenebisacrylamide (0.013% by weight relative to the monomer), and 205.08 g of ion-exchanged water were added, mixed, and completely dissolved. The oil and aqueous solution were then mixed and emulsified using a homogenizer at 7,000 rpm for 30 seconds. The monomer composition at this time was AAM / DMQ = 40 / 60 (mol%). The temperature of the resulting emulsion was maintained at 45-50°C. The temperature of the monomer solution was then purged with nitrogen for 30 minutes. Then, 0.093 g (0.025% by mass of monomer) of 2,2'-azobis(isobutyrate) dimethyl (V-601, Fujifilm Wako Pure Chemical Industries, Ltd.) was added to initiate the polymerization reaction. The polymerization was carried out at a reaction temperature of 48±2°C for 4 hours, after which the temperature was raised to 70°C and the reaction was continued for 1 hour to complete the polymerization. 10.0 g (1.0% by mass of the liquid) of polyoxyethylene polyoxypropylene alkyl ether with an HLB of 11.7 was added to the resulting water-in-oil emulsion as a phase inversion agent, and the emulsion was mixed to obtain a total of 1 kg of water-in-oil emulsion. This emulsion is designated Comparative Example 3. The composition and physical properties are shown in Table 1.

[0037] Comparative Example 4 A reaction vessel equipped with a stirrer and a temperature controller was charged with 265.0 g of isoparaffin having a boiling point of 190°C to 230°C, and 10.5 g of sorbitan monooleate (HLB 4.3) and 4.5 g of polyoxyethylene sorbitan trioleate (HLB 11.0) were dissolved. Separately, 411.6 g of a 50% by weight aqueous solution of acrylamide (abbreviated as AAM), 214.2 g of an 80% by weight aqueous solution of acryloyloxyethyl trimethylammonium chloride (abbreviated as DMQ), 10.4 g of an 80% by weight aqueous solution of methacryloyloxyethyl trimethylammonium chloride (abbreviated as DMC), 18.1 g of an 80% by weight aqueous solution of acrylic acid (abbreviated as AAC), 0.052 g of sodium hypophosphite (0.013% by weight relative to the monomer), and 55.61 g of ion-exchanged water were added, mixed, and completely dissolved. The oil and aqueous solution were then mixed and emulsified using a homogenizer at 7000 rpm for 30 seconds. The monomer composition at this time was AAM / DMQ / DMC / AAC = 72 / 22 / 1 / 5 (mol%). The temperature of the resulting emulsion was kept at 25-30°C, and the monomer solution was purged with nitrogen for 30 minutes. Then, 0.08 g (0.02% by mass of monomer) of 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile) (V-70, Fujifilm Wako Pure Chemical Industries, Ltd.) was added to initiate the polymerization reaction. The reaction temperature was kept at 27±2°C for 4 hours, and then the temperature was raised to 60°C and the reaction was continued for 1 hour to complete the polymerization. To the resulting water-in-oil emulsion, 10.0 g (1.0 mass % relative to the liquid) of polyoxyethylene polyoxypropylene alkyl ether with an HLB of 11.7 was added as a phase inversion agent and mixed to obtain a total of 1 kg of water-in-oil emulsion. This is Comparative Example 4, and its composition and physical properties are shown in Table 1.

[0038] (Comparative Example 5) A reaction vessel equipped with a stirrer and temperature control device was charged with 263 g of isoparaffin (boiling point 190°C to 230°C) and dissolved with 12 g of sorbitan monooleate (HLB 4.3) and 5.0 g of polyoxyethylene sorbitan trioleate (HLB 11.0). Separately, 59.6 g of dimethylaminoethyl methacrylate (hereinafter abbreviated as DAM), 593.4 g of a 50% by weight aqueous solution of acrylamide (abbreviated as AAM), 17.1 g of an 80% by weight aqueous solution of acrylic acid (abbreviated as AAC), 24.3 g of anhydrous citric acid, 0.74 g of sodium hypophosphite (0.2% by weight relative to monomer), 0.007 g of methylenebisacrylamide (0.002% by weight relative to monomer), and 9.82 g of ion-exchanged water were added, mixed, and completely dissolved. The oil and aqueous solution were then mixed and emulsified using a homogenizer at 5,000 rpm for 15 minutes. The monomer composition at this time was DAM / AAC / AAM = 8 / 4 / 88 (mol%). The temperature of the resulting emulsion was maintained at 25-30°C. The monomer solution was purged with nitrogen for 30 minutes, and then 0.074 g (0.02% by mass of monomer) of 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile) (V-70, Fujifilm Wako Pure Chemical Industries, Ltd.) was added to initiate the polymerization reaction. The polymerization was continued for 24 hours at a reaction temperature of 27±2°C to complete the reaction. After polymerization, 15.0 g (1.5% by mass of liquid) of polyoxyethylene polyoxypropylene alkyl ether with an HLB of 11.7 was added to the resulting water-in-oil emulsion as a phase inversion agent, and the resulting emulsion was mixed to obtain a total of 1 kg of water-in-oil emulsion. This emulsion is designated Comparative Example 5, and its composition and physical properties are shown in Table 1.

[0039] (Table 1) TIFF2025145809000003.tif6794 Monomer; DMQ: Acryloyloxyethyltrimethylammonium chloride DMC: methacryloyloxyethyltrimethylammonium chloride DAM: dimethylaminoethyl methacrylate; AAC: acrylic acid, AAM: acrylamide Ionic surfactants: A: sodium lauryl sulfate, B: coconut alkyl dimethyl benzyl ammonium chloride, C: dodecyl trimethyl ammonium chloride, D: hexadecyl trimethyl ammonium chloride, addition rate (mass%): relative to monomer Product viscosity: The viscosity of the product measured at 25°C. Intrinsic viscosity: The intrinsic viscosity of a water-soluble polymer measured at 25°C in a 1N saline solution. Degrees. Particle size: Measured by dynamic light scattering using an Otsuka Electronics ELS-Z (zeta potential / particle size measurement system).

[0040] (Test Examples 1-1 to 1-8, Separation Stability Test) A separation stability test was conducted on water-in-oil emulsions. First, 40 g of the water-in-oil emulsion polymer of Example 1 in Table 1 was weighed into a centrifuge test tube (inner diameter 32 mm, height 100 mm, round bottom, plastic), and centrifuged at 4,000 rpm for 10 minutes. The test tube was inverted upside down, and the liquid portion was removed for 2 minutes. The mass of the polymer remaining at the bottom of the test tube was measured, and the separation stability was calculated using the following formula. This was designated as Experimental Test Example 1-1, and the results are shown in Table 2. Similar tests were conducted using the water-in-oil emulsion polymers of Examples 2 to 8 in Table 1, designated as Experimental Test Examples 1-2 to 1-8. These results are shown in Table 2. Separation stability (mass%) = bottom residue after centrifugation (g) / 40.00 (g) × 100

[0041] (Comparative Test Examples 1-1 to 1-5, Separation Stability Test) The same test was carried out in the same procedure as in Experimental Test Example 1-1 using the water-in-oil emulsion polymer of the comparative example in Table 1. The results are shown in Table 2.

[0042] (Test Examples 2-1 to 2-8, Condensation Stability Test) A condensation stability test was conducted on water-in-oil emulsions. 3.00 g of the water-in-oil emulsion polymer of Example 1 in Table 1 was spread on a plastic petri dish (90 x 15 mm), and 3.00 g of tap water was sprayed on using a spray bottle. The dish was left to stand overnight at 25°C and 2°C. The next day, the surface of the water-in-oil emulsion was scratched with a spatula, and the product properties were observed. The results were rated on a 5-point scale depending on the condition. This was designated as Experimental Test Example 2-1, and the results are shown in Table 2. Similar tests were conducted using the water-in-oil emulsion polymers of Examples 2 to 8 in Table 1, designated Experimental Test Examples 2-2 to 2-8. The results are shown in Table 2.

[0043] (Comparative Test Examples 2-1 to 2-5, Condensation Stability Test) The same test was carried out in the same procedure as in Experimental Test Example 2-1 using the water-in-oil emulsion polymer of the comparative example in Table 1. The results are shown in Table 2.

[0044] (Table 2) TIFF2025145809000004.tif9089 Condensation stability; 1: Non-film-forming, 2: Non-film-forming, flexible lumps present, 3: Non-film-forming, elastic lumps present, 4: Film-forming, weak film, 5: Film-forming, strong film

[0045] The water-in-oil emulsion polymer of the present invention was confirmed to have a high separation stability, with a smaller value than that of a comparative example having the same monomer composition. It also showed excellent condensation stability, revealing that local swelling of the polymer is unlikely to occur when condensation occurs. Such water-in-oil emulsion polymers with excellent separation stability and condensation stability are highly valuable industrially for applications such as retention aids or drainage aids for papermaking, flocculation treatment agents or sludge dewatering agents for industrial wastewater or sewage sludge treatment, etc.

Claims

1. A water-in-oil emulsion polymer obtained by emulsion polymerization using a nonionic surfactant in such a manner that an aqueous monomer mixture solution containing 1 to 99 mol % of a cationic vinyl monomer represented by the following general formula (1) and / or 1 to 99 mol % of an anionic vinyl monomer represented by the following general formula (2), 1 to 99 mol % of a nonionic monomer, and an ionic surfactant serves as a dispersed phase, and a water-immiscible hydrocarbon serves as a continuous phase. 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 represents hydrogen, an alkyl or alkoxy group having 1 to 3 carbon atoms, an alkyl or aryl group having 7 to 20 carbon atoms, A represents oxygen or NH, B represents an alkylene group having 2 to 4 carbon atoms, X １ － represents an anion, respectively. General formula (2) R ５ is hydrogen, a methyl group or a carboxymethyl group, R ６ is hydrogen or a carboxyl group, and Q is SO ３ － , C.H. ２ SO ３ － , C ６ H ４ SO ３ － , CONHC (CH ３ ) ２ CH ２ SO ３ － Or COO － Y ２ , Y １ Or Y ２ represents a hydrogen atom or a cation, respectively.

2. 2. The water-in-oil emulsion polymer according to claim 1, wherein the content of the ionic surfactant is 0.1 to 5.0% by mass based on the total amount of the monomers.

3. 3. The water-in-oil emulsion polymer according to claim 1, wherein the ionic surfactant is either a cationic surfactant or an anionic surfactant.

4. 3. The water-in-oil emulsion polymer according to claim 1, wherein the ionic surfactant is one or more selected from the group consisting of cationic surfactants containing an alkyl group having 8 to 18 carbon atoms, and anionic surfactants such as sodium lauryl sulfate, sodium alkyl sulfate having 8 to 18 carbon atoms, and sodium 2-ethylhexyl sulfate.

5. 3. The water-in-oil emulsion polymer according to claim 1, wherein the content of the ionic surfactant is 50% by mass or less relative to the content of the nonionic surfactant.

6. A papermaking retention aid or drainage aid comprising the water-in-oil emulsion polymer of claim 1 or 2.

7. A flocculating treatment agent or sludge dewatering agent comprising the water-in-oil emulsion polymer according to claim 1 or 2.

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