Surfactant composition for emulsion polymerization

Abstract

The present invention pertains to: [1] a surfactant composition for emulsion polymerization comprising a compound (A) represented by formula (1), an inorganic salt, and water, wherein the content of the inorganic salt is 0.05-5 parts by mass with respect to 100 parts by mass of the compound (A) in the surfactant composition for emulsion polymerization; [2] a method for producing a polymer emulsion, the method comprising emulsion-polymerizing a radically polymerizable monomer (C) in the presence of the surfactant composition for emulsion polymerization; and [3] a polymer emulsion comprising the surfactant composition for emulsion polymerization and a resin. [In formula (1), R1 represents a C14-C24 alkyl group, A1 represents a C2-C4 alkylene group, m represents the average addition molar number of A1O and is 4-20, and M represents a cation or a hydrogen atom.]

Description

Surfactant composition for emulsion polymerization

[0001] The present invention relates to a surfactant composition for emulsion polymerization, a polymer emulsion containing the surfactant composition for emulsion polymerization, and a method for producing the polymer emulsion.

[0002] Conventionally, polymer emulsions obtained by emulsion polymerization of vinyl monomers such as acrylic esters and styrene have been widely used as they are in fields such as paints, adhesives, paper processing, and textile processing. Anionic surfactants such as alkyl sulfates and polyoxyethylene alkyl ether sulfates, and nonionic surfactants such as polyoxyethylene alkyl ethers, have been used as emulsifiers in emulsion polymerization. In paints, adhesives, and the like containing polymer emulsions using these surfactants, a coating film is formed by drying the polymer emulsion, but the emulsifier remains in the coating film, which is known to cause a decrease in water resistance, adhesion, weather resistance, heat resistance, and the like.

[0003] For example, polymer emulsions obtained by emulsion polymerization of (meth)acrylic acid esters are used in water-based paints, but if the coating film has poor water resistance, it cannot be used for applications requiring water resistance, such as building exterior walls and bathroom walls. Similarly, if the coating film of a water-based adhesive has poor water resistance, the adhesive strength will be reduced, making it impossible to use as an adhesive. Therefore, various surfactants for emulsion polymerization and methods for producing polymer emulsions have been proposed, in which an emulsifier suitable for the intended use of the resulting polymer emulsion is used during the production of the polymer emulsion.

[0004] For example, Japanese Patent Application Laid-Open No. 2018-95752 (Patent Document 1) describes a method for producing a polymer emulsion for a waterproof coating film, in which a radically polymerizable monomer is emulsion-polymerized in the presence of a polyoxyethylene alkyl ether sulfate ester having a specific structure or a salt thereof.

[0005] The present invention relates to a surfactant composition for emulsion polymerization containing a compound (A) represented by the following formula (1), an inorganic salt, and water, wherein the content of the inorganic salt in the surfactant composition for emulsion polymerization is 0.05 parts by mass or more and 5 parts by mass or less per 100 parts by mass of the compound (A): [In formula (1), R １ represents an alkyl group having 14 to 24 carbon atoms; A １ represents an alkylene group having 2 to 4 carbon atoms, and m represents A １ represents the average number of moles of O added, and is 4 to 20, and M represents a cation or a hydrogen atom.

[0006] From the viewpoint of reducing transportation costs and obtaining excellent handleability, there is a need for the development of a surfactant for emulsion polymerization that contains a high concentration of surfactant and has excellent fluidity, and a surfactant for emulsion polymerization that is suitable for polymer emulsions for waterproof coatings. The present invention provides a surfactant for emulsion polymerization that contains a high concentration of surfactant and has excellent fluidity, a polymer emulsion containing the surfactant composition for emulsion polymerization, and a method for producing the polymer emulsion.

[0007] The present inventors have discovered that an emulsion polymerization surfactant containing a polyoxyalkylene alkyl ether sulfate or a salt thereof having a specific structure, an inorganic salt, and water has excellent fluidity despite containing a high concentration of the polyoxyalkylene alkyl ether sulfate or a salt thereof, and that the surfactant has excellent handleability during the production of a polymer emulsion using the emulsion polymerization surfactant, and that a coating film of the polymer emulsion has excellent water resistance.

[0008] That is, the present invention provides the following [1] to [6]: [1] A surfactant composition for emulsion polymerization containing a compound (A) represented by the following formula (1), an inorganic salt, and water, wherein the content of the inorganic salt in the surfactant composition for emulsion polymerization is 0.05 parts by mass or more and 5 parts by mass or less per 100 parts by mass of the compound (A): [In formula (1), R １ represents an alkyl group having 14 to 24 carbon atoms; A １represents an alkylene group having 2 to 4 carbon atoms, and m represents A １ and M represents the average number of moles of O added, and is 4 to 20, and M represents a cation or a hydrogen atom.] [2] The inorganic salt is one or more selected from sodium chloride, potassium chloride, ammonium chloride, sodium sulfate, potassium sulfate, ammonium sulfate, disodium hydrogen phosphate, dipotassium hydrogen phosphate, and diammonium hydrogen phosphate. [3] The surfactant composition for emulsion polymerization according to [1] or [2], wherein the total content of compound (A) and the inorganic salt in the surfactant composition for emulsion polymerization is 10 to 40 mass%. [4] The surfactant composition for emulsion polymerization according to any one of [1] to [3], further comprising compound (B) represented by the following formula (2), in which the amount of compound (B) is 10 parts by mass or less per 100 parts by mass of compound (A): [In formula (2), R ２ represents an alkyl group having 14 to 24 carbon atoms; A ２ represents an alkylene group having 2 to 4 carbon atoms, and n is A ２

[0016]

[0017] The surfactant composition for emulsion polymerization according to any one of [1] to [4], wherein R represents the average number of moles of O added, and is 4 or more and 20 or less.] [5] A method for producing a polymer emulsion, comprising emulsion polymerizing a radically polymerizable monomer (C) in the presence of the surfactant composition for emulsion polymerization according to any one of [1] to [4]. [6] A polymer emulsion containing the surfactant composition for emulsion polymerization according to any one of [1] to [4], and a resin.

[0009] [Surfactant Composition for Emulsion Polymerization] The surfactant composition for emulsion polymerization of the present invention (hereinafter, may be simply referred to as "composition") contains compound (A) represented by formula (1), an inorganic salt, and water, and the content of the inorganic salt is 0.05 parts by mass or more and 5 parts by mass or less per 100 parts by mass of compound (A).

[0010] [In formula (1), R １ represents an alkyl group having 14 to 24 carbon atoms; A １ represents an alkylene group having 2 to 4 carbon atoms, and m represents A １ represents the average number of moles of O added, and is 4 to 20, and M represents a cation or a hydrogen atom.

[0011] The surfactant composition for emulsion polymerization of the present invention contains a high concentration of compound (A) represented by formula (1) (hereinafter, sometimes simply referred to as "compound (A)"), yet has excellent fluidity. Coatings produced using polymer emulsions produced using the surfactant composition for emulsion polymerization of the present invention (hereinafter, sometimes referred to as "polymer coatings") have excellent water resistance. The reason for this is unclear, but is thought to be as follows. Polyoxyalkylene alkyl ether sulfates or salts thereof have a high crystallinity, which makes them prone to precipitation in surfactant compositions. It is believed that by adjusting the average number of polyoxyalkylene-derived molar additions within a specific range, compound (A)'s crystallinity can be controlled, thereby suppressing precipitation in surfactant compositions. However, the inventors have discovered a problem with compositions containing compound (A) at high concentrations: when the concentration of compound (A) exceeds a certain level, compound (A) assumes a liquid crystal structure, resulting in a loss of fluidity. The addition of an inorganic salt to this composition prevents the compound (A) from arranging regularly, thereby maintaining the fluidity of the compound (A). Furthermore, by adjusting the amount of inorganic salt relative to the compound (A) to an appropriate range, it is believed that a surfactant composition for emulsion polymerization with excellent fluidity can be obtained, despite containing a high concentration of the compound (A) represented by formula (1). Furthermore, when emulsion polymerizing a radically polymerizable monomer (C) in the presence of the compound (A), the compound (A) has high surface activity, making it possible to reduce the particle size of the resin particles in the polymer emulsion. It is believed that the coating film prepared using this polymer emulsion becomes a dense film with excellent water resistance. Furthermore, since the Krafft point of the compound (A) is relatively high, it is difficult to move within the coating film and does not bleed to the coating film surface even when left for a long period of time. Therefore, even when placed in an environment exposed to water, it is difficult to draw water into the coating film, which is believed to result in excellent water resistance of the coating film.

[0012] <Compound (A)> Compound (A) is a polyoxyalkylene alkyl ether sulfate or a salt thereof represented by the following formula (1): Note that compound (A) may contain one or more compounds selected from polyoxyalkylene alkyl ether sulfates and salts of polyoxyalkylene alkyl ether sulfates represented by formula (1).

[0013]

[0014] In formula (1), R １ represents an alkyl group having 14 to 24 carbon atoms; A １ represents an alkylene group having 2 to 4 carbon atoms, and m represents A １ O represents the average number of moles of alkylene oxide added, which is 4 or more and 20 or less, and M represents a cation or a hydrogen atom.

[0015] R in formula (1) １ The alkyl group represented by the formula (I) may be linear or branched, but is preferably linear from the viewpoint of improving the water resistance of the polymer coating film of the compound (A) in the composition. The number of carbon atoms in the alkyl group is preferably 15 or more, more preferably 16 or more, and preferably 20 or less, more preferably 18 or less, from the viewpoint of increasing the concentration of the compound (A) in the composition and improving the water resistance of the polymer coating film. That is, the number of carbon atoms in the alkyl group is preferably 15 or more and 20 or less, more preferably 16 or more and 18 or less. R １ Specific examples of the alkyl group include a myristyryl group, a pentadecyl group, a palmityl group, a margaryl group, an isostearyl group, a 2-heptylundecyl group, a stearyl group, an arachidyl group, a behenyl group, and a lignoceryl group. From the viewpoint of improving the water resistance of the polymer coating film of compound (A) in the composition, one or more selected from a myristyryl group, a palmityl group, a stearyl group, and an arachidyl group are preferred, and a stearyl group is more preferred.

[0016] A in formula (1) １ The alkylene group may be a straight chain or a branched chain. １Specific examples of the alkylene group include an ethylene group, a propylene group, a trimethylene group, a butylene group, and a tetramethylene group. From the viewpoint of improving the handleability during production of the polymer emulsion and improving the water resistance of the polymer coating film of the compound (A) in the composition, one or more selected from an ethylene group and a propylene group are preferred, and an ethylene group is more preferred.

[0017] In formula (1), m is A １ From the viewpoint of increasing the concentration of compound (A) in the composition and improving the water resistance of the polymer coating film, m is 4 or more, preferably 6 or more, more preferably 9 or more, even more preferably 10 or more, still more preferably 11 or more, and 20 or less, preferably 18 or less, more preferably 16 or less. That is, m is 4 or more and 20 or less, preferably 6 or more and 18 or less, more preferably 9 or more and 16 or less, even more preferably 10 or more and 16 or less, still more preferably 11 or more and 16 or less. The average number of moles added, m, can be measured, for example, by the method described in the Examples.

[0018] In formula (1), M represents a cation or a hydrogen atom. When M is a cation, the compound represented by formula (1) becomes a polyoxyalkylene alkyl ether sulfate. In this case, the compound represented by formula (1) is strictly represented by the following formula (1-1):

[0019]

[0020] R in formula (1-1) １ and m is R in formula (1). １ , A １ The meanings and preferred ranges of M are the same as those of m. ＋ indicates a cation.

[0021] Examples of the cation M include alkali metal ions such as lithium ion, sodium ion, and potassium ion, ammonium ion, and alkanolammonium ion such as triethanolammonium ion. Among these, from the viewpoint of reducing the particle size of the resin particles in the polymer emulsion and improving the water resistance of the polymer coating film, M is preferably at least one selected from alkali metal ions and alkanolammonium ions, more preferably an alkali metal ion, and even more preferably a sodium ion (Na ＋ ) and potassium ions (K ＋ ), and even more preferably sodium ion (Na ＋ )

[0022] When M in formula (1) is a hydrogen atom, the compound represented by formula (1) is a polyoxyalkylene alkyl ether sulfate.

[0023] From the viewpoint of improving the water resistance of the polymer coating film, the Krafft point of compound (A) is preferably 0° C. or higher, more preferably 5° C. or higher, and even more preferably 10° C. or higher. From the viewpoint of workability in producing the polymer emulsion, it is preferably 100° C. or lower, more preferably 90° C. or lower, even more preferably 80° C. or lower, still more preferably 60° C. or lower, still more preferably 50° C. or lower, and even more preferably 40° C. or lower. That is, the Krafft point of compound (A) is preferably 0° C. or higher and 100° C. or lower, more preferably 0° C. or higher and 90° C. or lower, even more preferably 5° C. or higher and 80° C. or lower, still more preferably 5° C. or higher and 60° C. or lower, still more preferably 10° C. or higher and 50° C. or lower, and even more preferably 10° C. or higher and 40° C. When two or more types of compound (A) are used, it is preferable to set the Krafft point in the above range as a weighted average weighted by the contents (% by mass) of multiple compounds having different Krafft points.

[0024] <Compound (B)> The surfactant composition for emulsion polymerization of the present invention may further contain a compound (B) represented by the following formula (2). Compound (B) is a polyoxyalkylene alkyl ether represented by the following formula (2). The composition may contain one type or two or more types of compound (B).

[0025]

[0026] In formula (2), R ２ represents an alkyl group having 14 to 24 carbon atoms; A ２ represents an alkylene group having 2 to 4 carbon atoms, and n is A ２ The average number of moles of alkylene oxide added is 4 or more and 20 or less. ２ Suitable examples of R in formula (1) １ is the same as A ２ Suitable examples of the formula (1) include A １ The preferred examples of n are the same as those of m in formula (1).

[0027] When the surfactant composition for emulsion polymerization of the present invention contains compound (B), its content is preferably 10 parts by mass or less, more preferably 9 parts by mass or less, even more preferably 8 parts by mass or less, and even more preferably 5 parts by mass or less, and preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, even more preferably 1 part by mass or more, and even more preferably 1.5 parts by mass or more, relative to 100 parts by mass of compound (A). That is, when the surfactant composition for emulsion polymerization of the present invention contains compound (B), its content is preferably 0.01 parts by mass or more and 10 parts by mass or less, more preferably 0.1 parts by mass or more and 9 parts by mass or less, even more preferably 1 part by mass or more and 8 parts by mass or less, and even more preferably 1.5 parts by mass or more and 5 parts by mass or less, relative to 100 parts by mass of compound (A). When the content of compound (B) is within this range, the concentration of compound (A) in the composition can be increased, the emulsification ability of radically polymerizable monomer (C) during the production of polymer emulsion can be improved, the particle size of the resulting resin particles can be reduced, and the stability of the resin particles in the polymer emulsion can be improved.

[0028] <Inorganic Salt> The inorganic salt is a chloride, sulfate, or phosphate of an alkali metal ion, alkaline earth ion, or ammonium ion. The composition may contain one or more inorganic salts. From the viewpoint of increasing the concentration of compound (A) in the composition and improving the water resistance of the polymer coating film, the inorganic salt is preferably a chloride, sulfate, or phosphate of an alkali metal ion or ammonium ion, more preferably sodium chloride, potassium chloride, ammonium chloride, sodium sulfate, potassium sulfate, ammonium sulfate, disodium hydrogen phosphate, dipotassium hydrogen phosphate, or diammonium hydrogen phosphate, and even more preferably sodium sulfate.

[0029] The content of the inorganic salt in the surfactant composition for emulsion polymerization of the present invention is 0.05 parts by mass or more and 5 parts by mass or less relative to 100 parts by mass of the compound (A). From the viewpoint of increasing the concentration of the compound (A) in the composition to improve the handleability during the production of the polymer emulsion and to improve the water resistance of the polymer coating film, it is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, even more preferably 0.5 parts by mass or more, and from the same viewpoint, it is preferably 4.7 parts by mass or less, more preferably 4.5 parts by mass or less, even more preferably 3 parts by mass or less. That is, the content of the inorganic salt in the surfactant composition for emulsion polymerization is 0.05 parts by mass or more and 5 parts by mass or less, preferably 0.1 parts by mass or more and 4.7 parts by mass or less, more preferably 0.2 parts by mass or more and 4.5 parts by mass or less, even more preferably 0.2 parts by mass or more and 3 parts by mass or less, and even more preferably 0.5 parts by mass or more and 3 parts by mass or less relative to 100 parts by mass of the compound (A).

[0030] The total content of compound (A) and inorganic salt in the surfactant composition for emulsion polymerization of the present invention is preferably 10% by mass or more, more preferably 13% by mass or more, even more preferably 15% by mass or more, and preferably 40% by mass or less, more preferably 30% by mass or less, even more preferably 25% by mass or less.That is, the total content of compound (A) and inorganic salt in the surfactant composition for emulsion polymerization is preferably 10% by mass or more and 40% by mass or less, more preferably 13% by mass or more and 30% by mass or less, even more preferably 15% by mass or more and 25% by mass or less.If the total content of compound (A) and inorganic salt is within this range, the concentration of compound (A) in the composition can be further increased, the handling property during the production of polymer emulsion can be further improved, and the water resistance of polymer coating film can be further improved.

[0031] <Water> Tap water, distilled water, ion-exchanged water, etc. can be used as the water, and distilled water and ion-exchanged water are preferred. The surfactant composition for emulsion polymerization of the present invention may contain an organic solvent such as an alcohol such as methanol, ethanol, or 1,2-propanediol; a ketone such as acetone or methyl ethyl ketone; an alkylnitrile such as acetonitrile; or an ether such as diethyl ether or tetrahydrofuran. When the composition contains an organic solvent, the content thereof is preferably 0.2% by mass or less, more preferably 0.15% by mass or less, and even more preferably 0.1% by mass or less.

[0032] [Method for producing surfactant composition for emulsion polymerization] <Method for producing compound (A)> Compound (A) represented by formula (1) can be obtained by sulfate esterification of polyoxyalkylene alkyl ether (compound (B)) represented by formula (2) with a sulfating agent, and neutralizing it with a basic substance as needed. As a method for producing compound (A) represented by formula (1), for example, the production method described in JP 2018-95752 A can be referenced.

[0033] <Method for producing surfactant composition for emulsion polymerization> A surfactant composition for emulsion polymerization can be obtained by mixing the compound (A) obtained by the above method with an inorganic salt and water. The inorganic salt may be the inorganic salt produced during the production of compound (A) and used as is with compound (A), or the desired inorganic salt may be mixed after desalting compound (A). When the surfactant composition for emulsion polymerization contains compound (B), the compound (B) remaining unreacted during the production of compound (A) may be used as is with compound (A), or the desired compound (B) may be mixed after isolating compound (A).

[0034] The surfactant composition for emulsion polymerization of the present invention contains a high concentration of surfactant and has excellent fluidity, making it possible to reduce transportation costs and storage costs. Furthermore, when producing a polymer emulsion by emulsion polymerization or when using the surfactant composition for emulsification as described below to produce a resin emulsion, the surfactant composition for emulsion polymerization of the present invention exhibits excellent handleability, such as simplifying the labor required for preparation.

[0035] [Method for Producing Polymer Emulsion] The method for producing a polymer emulsion of the present invention is a method for emulsion polymerization of a radically polymerizable monomer (C) (hereinafter also simply referred to as "monomer (C)") in the presence of the surfactant composition for emulsion polymerization. In other words, the method for producing a polymer emulsion of the present invention is the use of a surfactant composition containing a compound (A) represented by formula (1), an inorganic salt, and water, and optionally a compound (B) represented by formula (2), in the emulsion polymerization of the radically polymerizable monomer (C). The surfactant composition for emulsion polymerization contains compound (A) at a high concentration and has excellent fluidity, which can simplify the preparation work during polymer emulsion production and improve handleability. Furthermore, since the content of inorganic salt is low, the coating film obtained from the polymer emulsion obtained by the method for producing a polymer emulsion of the present invention can exhibit high water resistance.

[0036] <Radically Polymerizable Monomer (C)> Preferred examples of the radically polymerizable monomer (C) include one or more selected from aromatic vinyl monomers such as styrene, α-methylstyrene, and chlorostyrene; (meth)acrylic acid; (meth)acrylic acid esters having an alkyl group preferably having from 1 to 22 carbon atoms, more preferably from 1 to 12, and even more preferably from 1 to 8 carbon atoms, such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate; vinyl halides such as vinyl chloride and vinyl bromide, and vinylidene halides such as vinylidene chloride; vinyl esters such as vinyl acetate and vinyl propionate; (meth)acrylonitrile; and conjugated dienes such as butadiene and isoprene. These monomers (C) may be homopolymerized or copolymerized in combination of two or more types. Hereinafter, (meth)acrylic acid means one or two selected from methacrylic acid and acrylic acid, (meth)acrylic acid ester means one or two selected from methacrylic acid ester and acrylic acid ester, and (meth)acrylonitrile means one or two selected from methacrylonitrile and acrylonitrile. Among these, the radically polymerizable monomer (C) to be emulsion-polymerized in the method for producing a polymer emulsion of the present invention is more preferably one or more selected from styrene, α-methylstyrene, (meth)acrylic acid, methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, vinyl chloride, vinylidene chloride, vinyl acetate, and (meth)acrylonitrile, even more preferably one or more selected from styrene, (meth)acrylic acid, methyl (meth)acrylate, butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate, and even more preferably one or more selected from (meth)acrylic acid, methyl (meth)acrylate, and butyl (meth)acrylate.

[0037] <Other emulsifiers> In the method for producing a polymer emulsion of the present invention, other emulsifiers than the compound (A) and compound (B) contained in the surfactant composition for emulsion polymerization can be used in combination, as long as the effects of the present invention are not impaired. Examples of other emulsifiers include nonionic surfactants such as alcohol ethoxylates, alkyl polyglycosides, and alkanolamides; anionic surfactants such as alkyl sulfates, alkyl ether sulfates other than compound (A), fatty acid soaps, alkyl ether carboxylates, alkyl phenyl sulfonates, and internal olefin sulfonates, as well as water-soluble protective colloids. In the method for producing a polymer emulsion of the present invention, the content of other emulsifiers than the compound (A) and compound (B) is preferably 15% by mass or less, more preferably 5% by mass or less, even more preferably 1% by mass or less, even more preferably 0.1% by mass or less, and even more preferably substantially 0% by mass, relative to the surfactant composition for emulsion polymerization of the present invention.

[0038] Any radical polymerization initiator used in conventional emulsion polymerization can be used for emulsion polymerization. Examples of radical polymerization initiators include persulfates such as potassium persulfate and ammonium persulfate; inorganic peroxides such as hydrogen peroxide; organic peroxides such as t-butyl hydroperoxide, benzoyl peroxide, cumene hydroperoxide, and paramenthane peroxide; and azo compounds such as azobisdiisobutyronitrile and 2,2-azobis(2-amidinopropane) dihydrochloride. From the viewpoints of polymerization reactivity, workability, and economy, persulfates are preferred. Furthermore, redox-based initiators in which a peroxide compound is combined with a reducing agent such as sodium sulfite, Rongalite, or ascorbic acid can also be used as the polymerization initiator. Furthermore, sodium hydrogen sulfite, ferrous ammonium sulfate, and the like can also be used as a polymerization promoter.

[0039] In the method for producing a polymer emulsion of the present invention, emulsion polymerization is carried out in water. Examples of the water used include tap water, distilled water, and ion-exchanged water, with distilled water and ion-exchanged water being preferred. The water may contain an organic solvent. Examples of the organic solvent include the same organic solvents that may be contained in the surfactant composition for emulsion polymerization.

[0040] (Amount of each component) In the method for producing a polymer emulsion of the present invention, the amount of radically polymerizable monomer (C) used is preferably 30% by mass or more, more preferably 40% by mass or more, and preferably 70% by mass or less, more preferably 60% by mass or less, based on the total system, from the viewpoints of reducing the average particle size of resin particles in the polymer emulsion, polymerization stability, and water resistance of the polymer coating film. That is, in the method for producing a polymer emulsion of the present invention, the amount of radically polymerizable monomer (C) used is preferably 30% by mass or more and 70% by mass or less, more preferably 40% by mass or more and 60% by mass or less, based on the total system. In the method for producing a polymer emulsion of the present invention, the amount of surfactant composition for emulsion polymerization used is such that, based on 100 parts by mass of monomer (C), the amount of compound (A) is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, even more preferably 0.5 parts by mass or more, and preferably 10 parts by mass or less, more preferably 5 parts by mass or less, even more preferably 3 parts by mass or less. That is, in the method for producing a polymer emulsion, the amount of the surfactant composition for emulsion polymerization used is an amount such that the amount of compound (A) is preferably 0.05 parts by mass or more and 0 parts by mass or less, more preferably 0.1 parts by mass or more and 5 parts by mass or less, and even more preferably 0.5 parts by mass or more and 3 parts by mass or less, relative to 100 parts by mass of the monomer (C).

[0041] (Emulsion Polymerization Conditions) When adding monomer (C) in emulsion polymerization, any of methods such as the monomer dropping method, the monomer bulk charging method, and the pre-emulsion method can be used. However, from the viewpoint of polymerization stability, the so-called pre-emulsion method is preferred, in which a pre-emulsion is prepared by emulsifying monomer (C) with the surfactant composition for emulsion polymerization of the present invention in a temperature environment at least 10°C lower than the 10-hour half-life temperature of the radical polymerization initiator, and this pre-emulsion is then added to a reaction system maintained at the radical polymerization temperature for emulsion polymerization. The pre-emulsion dropping time is preferably 1 hour to 8 hours, and the aging time is preferably 1 hour to 5 hours. The polymerization temperature is adjusted based on the 10-hour half-life temperature of the polymerization initiator, and is preferably 50°C to 90°C, and particularly preferably 70°C to 85°C in the case of persulfates.

[0042] [Polymer emulsion] The polymer emulsion of the present invention is obtained by the above-mentioned method for producing a polymer emulsion. That is, the polymer emulsion of the present invention contains the above-mentioned surfactant composition for emulsion polymerization and a resin that is a polymer of a radically polymerizable monomer (C). The polymer emulsion of the present invention is preferably used for producing a coating film, more preferably for producing a waterproof coating film.

[0043] In this specification, the term "coating film" refers to a film obtained by applying a polymer emulsion to a substrate, followed by curing and drying as necessary, and the term "water-resistant coating film" refers to a coating film that is water-resistant. Furthermore, "water-resistant" does not refer to a coating film that is simply evaluated based on the presence or absence of swelling or peeling when immersed in water, but rather refers to a coating film that is immersed in warm water at 40°C for 7 days and then dried at room temperature, as described in the Examples, and the haze value of the coating film is measured, and the haze value is preferably 55% or less, more preferably 40% or less, even more preferably 30% or less, still more preferably 20% or less, still more preferably 15% or less, still more preferably 10% or less, and still more preferably 5% or less.

[0044] The average particle size of the resin particles in the polymer emulsion of the present invention is preferably 300 nm or less, more preferably 250 nm or less, even more preferably 200 nm or less, and even more preferably 180 nm or less from the viewpoint of water resistance of the polymer coating film, and is preferably 30 nm or more, more preferably 50 nm or more, and even more preferably 80 nm or more from the viewpoint of polymerization stability. That is, the average particle size of the resin particles in the polymer emulsion is preferably 30 nm or more and 250 nm or less, more preferably 50 nm or more and 200 nm or less, and even more preferably 80 nm or more. The average particle size of the resin particles in the polymer emulsion can be measured by the method described in the Examples. Furthermore, from the viewpoint of workability, the viscosity of the polymer emulsion is preferably 10 mPa·s or more, more preferably 25 mPa·s or more, even more preferably 50 mPa·s or more, and preferably 50,000 mPa·s or less, more preferably 10,000 mPa·s or less, and even more preferably 5,000 mPa·s or less. That is, the viscosity of the polymer emulsion is preferably 10 mPa s or more and 50,000 mPa s or less, more preferably 25 mPa s or more and 10,000 mPa s or less, and even more preferably 50 mPa s or more and 5,000 mPa s or less. The viscosity of the polymer emulsion can be measured by a commonly used measurement method such as a rotational viscometer method using a Brookfield viscometer.

[0045] [Method for Producing Polymer Coating Film] The method for producing a coating film using the polymer emulsion of the present invention includes the steps of applying the polymer emulsion to a substrate and drying it.

[0046] There are no particular limitations on the substrate used, and examples thereof include substrates made of glass, metal (aluminum, stainless steel, etc.), ceramics (insulators, tiles, etc.), heat-resistant polymer materials, etc. There are no particular limitations on the method for applying the polymer emulsion to the substrate, and conventionally known coating devices can be used, such as roll coaters such as comma coaters, blade coaters, and gravure coaters, slot die coaters, lip coaters, and curtain coaters.

[0047] The polymer emulsion is applied to a substrate and dried, and the drying may be natural drying or heat drying. Heating in the drying process can shorten the drying time and improve the hardness of the coating film formed. When drying is performed by heat drying, the heating temperature is preferably 50°C or higher, more preferably 90°C or higher, and preferably 200°C or lower, more preferably 150°C or lower, from the viewpoints of productivity and coating film uniformity. That is, the heating temperature is preferably 50°C or higher and 200°C or lower, more preferably 90°C or higher and 150°C or lower. When drying is performed by heat drying, the heating time is preferably 10 seconds or higher, more preferably 30 seconds or higher, more preferably 1 minute or higher, and preferably 1 hour or lower, more preferably 30 minutes or lower, from the viewpoints of productivity and coating film uniformity. That is, the heating time is preferably 10 seconds or higher and 1 hour or lower, more preferably 30 seconds or higher and 30 minutes or lower, more preferably 1 minute or higher and 30 minutes or lower. The thickness of the coating film varies depending on the application, etc., but from the viewpoints of productivity and water resistance of the coating film, it is preferably 100 μm or less, more preferably 50 μm or less, and even more preferably 30 μm or less, and from the viewpoint of increasing hardness, it is preferably 1 μm or more, more preferably 2 μm or more. That is, the thickness of the coating film is preferably 1 μm or more and 100 μm or less, more preferably 2 μm or more and 50 μm or less, and even more preferably 2 μm or more and 30 μm or less.

[0048] [Paint Composition] Because the coating film produced using the polymer emulsion of the present invention has excellent water resistance, the polymer emulsion can be used as a paint composition. The paint composition can further contain a pigment and, if necessary, a thickener, a tackifier, a viscosity control agent, an antifoaming agent, an antioxidant, an ultraviolet absorber, a film-forming aid, etc. Examples of pigments include extender pigments such as talc, kaolin, calcium carbonate, and barium sulfate; colored pigments such as red iron oxide, carbon black, ultramarine, and yellow iron oxide; inorganic pigments such as white pigments such as titanium dioxide and zinc oxide, and pearl pigments such as mica titanium and bismuth oxychloride; dyes as organic synthetic dyes, and organic pigments. These pigments can be used alone or in combination of two or more.

[0049] The content of the polymer emulsion in the coating composition can be adjusted as appropriate, and from the viewpoint of the water resistance of the coating film, is preferably 2% by mass or more, more preferably 4% by mass or more, and even more preferably 5% by mass or more, calculated as solids, relative to the total solids in the coating composition.

[0050] When a paint composition contains a pigment, the content of the pigment in the paint composition, in terms of solids weight (PWC), relative to the total solids content in the paint composition, is preferably 5% by mass or more, more preferably 20% by mass or more, even more preferably 30% by mass or more, and preferably 95% by mass or less, more preferably 80% by mass or less, and even more preferably 70% by mass or less, from the viewpoint of water resistance of the paint film. That is, the content of the pigment in the paint composition, in terms of solids weight (PWC), relative to the total solids content in the paint composition, is preferably 5% by mass or more and 95% by mass or less, more preferably 20% by mass or more and 80% by mass or less, and even more preferably 30% by mass or more and 70% by mass or less. PWC is calculated using the following formula: PWC = (pigment solids content in paint composition ÷ total solids content in paint composition) × 100

[0051] When the polymer emulsion of the present invention is used as a coating composition, it may be applied so that the dry film thickness is about 1 to 500 μm, preferably about 10 to 300 μm, and then air-dried or heat-dried to obtain a coating film with excellent water resistance.

[0052] The polymer emulsion of the present invention can also be used for adhesive applications. In this case, a polymer (resin) having a low glass transition temperature (Tg) is produced using 2-ethylhexyl acrylate, butyl acrylate, or the like during the production of the polymer emulsion. The resulting polymer emulsion is then blended with a thickener, a tackifier, or the like, as needed, and applied to a substrate such as paper or film. The resulting mixture is then dried with hot air to form a polymer coating film having a thickness of approximately 10 to 40 μm, thereby producing an adhesive product with excellent water resistance and adhesive performance. The coating film produced using the polymer emulsion of the present invention has excellent water resistance and can be preferably used in paints, particularly in the fields of water-based paints and adhesives, and its applications are expected to expand even further.

[0053] [Surfactant Composition for Emulsification] The surfactant composition for emulsion polymerization of the present invention can also be used for emulsifying resins. That is, the surfactant composition for emulsion polymerization of the present invention is also a surfactant composition for emulsification. Resins that can be emulsified by the surfactant composition for emulsification are not particularly limited, but include resins obtained from the radically polymerizable monomer (C) described above; synthetic resins such as aliphatic petroleum resins and aromatic petroleum resins; and natural resins such as rosin and terpene resins. A resin emulsion prepared using the surfactant composition for emulsification contains a compound (A) represented by formula (1), an inorganic salt, water, and a resin, and optionally a compound (B) represented by formula (2). When the emulsion contains one or more resins selected from rosin and terpene resins, the emulsion can be used as a tackifier. This tackifier has excellent water resistance, similar to that of a coating film produced using the polymer emulsion of the present invention, and therefore can suppress a decrease in adhesion.

[0054] According to the present invention, it is possible to provide a surfactant for emulsion polymerization that contains a high concentration of a surfactant and has excellent fluidity, a polymer emulsion that contains the surfactant composition for emulsion polymerization, and a method for producing the polymer emulsion.

[0055] Synthesis Example 1 (Synthesis of Compound A1) An ethylene oxide adduct of stearyl alcohol (average number of moles of ethylene oxide added: 11.0) was placed in a thin-film sulfonation reactor having an external jacket, and a sulfuric acid esterification reaction was carried out using sulfur trioxide gas under the condition that hot water at 50°C was passed through the external jacket of the reactor. ３ The molar ratio of the ethylene oxide adduct of stearyl alcohol to the reactant was set to 1.05. The reactant was added to an alkaline aqueous solution prepared with sodium hydroxide and neutralized at 50°C for 1 hour while stirring. After completely distilling off water from the aqueous solution by freeze-drying, the solution was dissolved in ethanol heated to 50°C. Sodium sulfate precipitated during dissolution was removed by filtration, and the filtrate was dried to obtain sodium polyoxyethylene stearyl ether sulfate (C １８ H ３７ O-(CH ２ CH ２ O) １１ -SO３ A mixture 1 of Na (compound A1) and unreacted ethylene oxide adduct of stearyl alcohol (compound B1) (compound A1 / compound B1=97 parts by mass / 3 parts by mass) was obtained.

[0056] The amount of compound B1 in mixture 1 was quantified by the following method. A calibration curve for the ethylene oxide adduct of stearyl alcohol was prepared using high performance liquid chromatography (manufactured by Tosoh Corporation, product name: HPLC8220, detector: RI-8022) and an eluent (MeOH:ultrapure water=95:5) at 40°C. Thereafter, mixture 1 was measured under the same conditions, and the amount of compound B1 in mixture 1 was quantified from the calibration curve.

[0057] Synthesis Example 2 (Synthesis of Compound A2) An ethylene oxide adduct of stearyl alcohol (average number of moles of ethylene oxide added: 13.0) was distilled under reduced pressure at 250°C and 133.3 Pa to remove unreacted alcohol, and a sulfuric acid esterification reaction was carried out with sulfamic acid (molar ratio of sulfamic acid / ethylene oxide adduct of stearyl alcohol: 1.02) at a reaction temperature of 110°C. The reaction product was neutralized with a 48% by mass aqueous solution of sodium hydroxide, and then heated to 80°C under a nitrogen flow to remove ammonia. Water was completely removed from the aqueous solution by freeze-drying, and the solution was then dissolved in ethanol heated to 50°C. Sodium sulfate precipitated during dissolution was removed by filtration, and the filtrate was dried to obtain sodium polyoxyethylene stearyl ether sulfate (C １８ H ３７ O-(CH ２ CH ２ O) １３ -SO ３ A mixture 2 (compound A2 / compound B2=98 parts by mass / 2 parts by mass) of Na (compound A2) and unreacted ethylene oxide adduct of stearyl alcohol (compound B2) was obtained.

[0058] Synthesis Example 3 (Synthesis of Compound A3) Mixture 3 was synthesized in the same manner as in Synthesis Example 1, except that an ethylene oxide adduct of stearyl alcohol having an average number of moles of ethylene oxide added of 9 was used. Mixture 3 was synthesized using sodium polyoxyethylene stearyl ether sulfate (C １８ H ３７ O-(CH ２CH ２ O) ９ -SO ３ The compound A3 / compound B3 was a mixture of unreacted ethylene oxide adduct of stearyl alcohol (compound A3 / compound B3=96 parts by mass / 4 parts by mass) and the corresponding unreacted ethylene oxide adduct of stearyl alcohol (compound B3).

[0059] <Calculation of average number of moles of ethylene oxide added m> The hydroxyl value of the ethylene oxide adduct of stearyl alcohol, which is the starting material, was determined by the method described in "JIS K 0070-1992 7.1 Neutralization titration method," and the average number of moles of ethylene oxide added to the stearyl alcohol, which is the starting material, was calculated by the following formula. The results are shown in Table 1. The average number of moles of ethylene oxide added m of Compounds A1 to A3 is considered to be the same as the average number of moles of ethylene oxide added to the ethylene oxide adduct of stearyl alcohol, which is the starting material. Average number of moles added m = ((1 ÷ ((OHV ÷ M ａ ) ÷ 1000)) - M ｂ ))÷M ｃ OHV: Hydroxyl value of ethylene oxide adduct of stearyl alcohol (mgKOH / g) M ａ : Molecular weight of potassium hydroxide (56.1) M ｂ M: molecular weight of stearyl alcohol ｃ The acid value used to calculate the OHV (hydroxyl value) was determined by the method described in "JIS K 0070-1992 3.1 Neutralization titration method."

[0060] <Kraft Point of Mixtures> The Krafft points of Mixtures 1 to 3 were measured by the following method. The results are shown in Table 1. Using a high-sensitivity differential scanning calorimeter (manufactured by Hitachi High-Tech Science Corporation, product name: DSC7000X), Mixtures 1 to 3, each prepared as a 10% aqueous solution, were placed in a 70 μL pan and heated from −20° C. to 1° C. at a rate of 1° C. / min, and then heated to 60° C. at a rate of 0.1° C. / min. The Krafft points were determined as the temperature at the maximum peak of the temperature difference excluding the melting point of water as a function of the heating time, as detected by a differential thermal electrode. The Krafft points of Mixtures 1 to 3 shown in the table can be considered to be the Krafft points of Compounds A1 to A3.

[0061]

[0062] Example 1 (Surfactant Composition 1 for Emulsion Polymerization) 16.00 parts of Mixture 1 (containing 15.52 parts of Compound A1 and 0.48 parts of Compound B1), 0.09 parts of sodium sulfate (anhydrous, reagent, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), and 83.91 parts of ion-exchanged water were placed in a screw vial and stirred with a magnetic stirrer for 6 hours while heating to 50°C to obtain Surfactant Composition 1 for emulsion polymerization. Composition 1 was stored at 20°C for 3 days, and the fluidity and appearance after storage were evaluated visually. Note that when the screw vial was tilted 90°, a composition that flowed was rated as "fluidity present," and a composition that did not flow was rated as "fluidity absent." Furthermore, a composition that was visually transparent was rated as "transparent," and a composition that was cloudy was rated as "cloudy." The results are shown in Table 2.

[0063] Examples 2 to 6 and Comparative Examples 1 to 3 (Surfactant compositions 2 to 6 for emulsion polymerization and surfactant compositions 11 to 13) Surfactant compositions 2 to 6 for emulsion polymerization and surfactant compositions 11 to 13 were obtained in the same manner as in Example 1, except that mixture 1 was changed to the mixture shown in Table 2 and the amounts of the mixture, sodium sulfate, disodium hydrogen phosphate (anhydrous, reagent, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), and ion-exchanged water were changed to the amounts shown in Table 2. These were evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0064]

[0065] As can be seen from Table 2, surfactant compositions 1 to 6 for emulsion polymerization of the present invention had excellent fluidity, and despite containing a high concentration of compound (A) represented by formula (1), they were transparent and free from precipitation of compound (A). On the other hand, surfactant compositions 11 and 13 of Comparative Examples 1 and 3, which did not contain an inorganic salt, had no fluidity. Furthermore, surfactant composition 12 of Comparative Example 2, which contained 5 parts by mass or more of an inorganic salt per 100 parts by mass of compound (A), was turbid.

[0066] Example 7 (Polymer Emulsion 1) Emulsion polymerization was carried out by the following method using surfactant composition for emulsion polymerization 1 obtained in Example 1. In a 1 L four-neck flask equipped with a stirrer and a raw material inlet, 87.2 g of ion-exchanged water, 0.36 g of potassium persulfate (10-hour half-life temperature 69°C) as a polymerization initiator, and 27.97 g of surfactant composition for emulsion polymerization 1 were mixed, and while stirring at 500 r / min, a monomer mixture of 110.8 g of butyl acrylate, 110.8 g of methyl methacrylate, and 3.4 g of acrylic acid was added dropwise at room temperature over about 5 minutes, and the mixture was stirred for 30 minutes to obtain an emulsion. Next, 157.8 g of ion-exchanged water, 0.09 g of potassium persulfate as a polymerization initiator, 5.59 g of surfactant composition 1 for emulsion polymerization, and 17.1 g (corresponding to 5% by mass) of the above emulsion dropping solution were charged into a 1 L separable flask equipped with a stirrer, a reflux condenser, and a raw material inlet, and the mixture was heated to 80 ° C. and subjected to first-stage polymerization for 30 minutes. Thereafter, the remaining emulsion dropping solution was added dropwise over 3 hours, and after completion of the addition, the mixture was further aged at 80 ° C. for 1 hour. This was cooled to 30 ° C. to obtain polymer emulsion 1.

[0067] <Performance Evaluation> Using Polymer Emulsion 1, the average particle size of resin particles in the polymer emulsion and the water resistance of the polymer coating film were evaluated. The results are shown in Table 3. (1) Average Particle Size of Resin Particles in Polymer Emulsion Using a particle size / molecular weight measurement system (manufactured by Otsuka Electronics Co., Ltd., product name: ELSZ-1000ZS), the polymer emulsion neutralized with 25% by mass of aqueous ammonia was diluted 30,000 times to measure the average particle size of the resin particles. The measurement and analysis method employed was the cumulant average particle size obtained by integrating measurements 70 times. (2) Water Resistance of Polymer Coating Film To the polymer emulsion neutralized with 25% by mass of aqueous ammonia, 5 parts by mass of 2-(2-butoxyethoxy)ethanol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added as a film-forming aid per 100 parts by mass of the solids in the polymer emulsion, mixed, and allowed to stand overnight. The obtained polymer emulsion was applied to a transparent acrylic plate using a Baker-type film applicator No. The acrylic plate was coated to a dry film thickness of 50 μm using a 510 (0-50 mil) film (manufactured by Yasuda Seiki Seisakusho Co., Ltd.) and dried at room temperature for one day. After immersing the acrylic plate in water at 40°C for seven days, the haze value of the polymer coating film was measured using a haze / transmittance meter (manufactured by Murakami Color Research Laboratory Co., Ltd., product name: HM-150). The smaller the haze value, the better the water resistance, and a haze value of 20% or less is considered to be particularly good.

[0068] Example 8 and Comparative Examples 4 and 5 (Polymer Emulsions 2, 11, and 12) Polymer emulsions 2, 11, and 12 were obtained in the same manner as in Example 7, except that surfactant composition 1 for emulsion polymerization was changed to the surfactant composition for emulsion polymerization or surfactant composition shown in Table 3. In Comparative Example 4, compound A1 formed liquid crystal in surfactant composition 11, and the surfactant composition could not be used unless it was heated to 60°C during reaction charging. These were evaluated in the same manner as in Example 7. The results are shown in Table 3.

[0069]

[0070] As can be seen from Table 3, the average particle size of the resin particles in Polymer Emulsions 1 and 2 was equivalent to that of Polymer Emulsion 11 produced using Surfactant Composition 11 of the prior art, and the water resistance of the coating films produced therefrom was also equivalent. On the other hand, as shown above, the addition of the surfactant composition for emulsion polymerization was easy in the production of Polymer Emulsions 1 and 2, whereas the addition of the surfactant composition was not easy in the production of Polymer Emulsion 11. Furthermore, Polymer Emulsion 12 produced using Surfactant Composition 12, in which the content of inorganic salt was more than 5 parts by mass per 100 parts by mass of Compound (A), had poor water resistance.

[0071] Surfactant composition a for emulsion polymerization in Table 4, which was produced in the same manner as in Example 1 except that mixture 1 was changed to mixture 3 and the amounts of mixture 3, sodium sulfate, and ion-exchanged water were changed to those shown in Table 4, is considered to have fluidity and appearance equivalent to surfactant composition 1 for emulsion polymerization, and is considered to be suitable as a surfactant for emulsion polymerization. Furthermore, the handleability when producing a polymer emulsion in the same manner as in Example 7 except that surfactant composition 1 for emulsion polymerization was changed to surfactant composition a for emulsion polymerization, and the average particle size of the resin particles in the resulting polymer emulsion are considered to be equivalent to those of Example 7.

[0072]

Claims

1. A surfactant composition for emulsion polymerization, comprising a compound (A) represented by the following formula (1), an inorganic salt, and water, wherein the content of the inorganic salt in the surfactant composition for emulsion polymerization is 0.05 parts by mass or more and 5 parts by mass or less per 100 parts by mass of the compound (A): [In formula (1), R １ represents an alkyl group having 14 to 24 carbon atoms; A １ represents an alkylene group having 2 to 4 carbon atoms; m represents A １ represents the average number of moles of O added, which is 4 to 20, and M represents a cation or a hydrogen atom.

2. The surfactant composition for emulsion polymerization according to claim 1, wherein the inorganic salt is one or more selected from the group consisting of sodium chloride, potassium chloride, ammonium chloride, sodium sulfate, potassium sulfate, ammonium sulfate, disodium hydrogen phosphate, dipotassium hydrogen phosphate, and diammonium hydrogen phosphate.

3. A surfactant composition for emulsion polymerization according to claim 1 or 2, wherein the total content of said compound (A) and said inorganic salt in said surfactant composition for emulsion polymerization is 10% by mass or more and 40% by mass or less.

4. The surfactant composition for emulsion polymerization according to any one of claims 1 to 3, further comprising a compound (B) represented by the following formula (2), the compound (B) being contained in an amount of 10 parts by mass or less per 100 parts by mass of the compound (A): [In formula (2), R ２ represents an alkyl group having 14 to 24 carbon atoms; A ２ represents an alkylene group having 2 to 4 carbon atoms; n is A ２ The average number of moles of O added is 4 or more and 20 or less.

5. A method for producing a polymer emulsion, which comprises emulsion polymerizing a radically polymerizable monomer (C) in the presence of the surfactant composition for emulsion polymerization according to any one of claims 1 to 4.

6. A polymer emulsion comprising the surfactant composition for emulsion polymerization according to any one of claims 1 to 4 and a resin.

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