Method for manufacturing rubbery latex

Abstract

To provide a method for producing rubbery latex with excellent polymerization stability. [Solution] A method for producing rubbery latex, comprising step 1 of emulsion polymerization of a monomer mixture (I) containing at least one diene monomer or a monomer mixture (II) containing at least one alkyl (meth)acrylate monomer in the presence of a salt of a fatty acid mixture containing a salt of carboxylic acid (A), a salt of carboxylic acid (B), and a salt of carboxylic acid (C), wherein the total mass of carboxylic acid (A) / total mass of carboxylic acid (B) / total mass of carboxylic acid (C) is 5-40 / 35-55 / 20-40.

Description

Technical Field

[0001] The present invention relates to a method for producing a rubbery latex and an emulsifier for emulsion polymerization used in the method for producing the rubbery latex.

Background Art

[0002] Acrylonitrile-butadiene-styrene (ABS) resin and acrylonitrile-styrene-acrylic ester (ASA) resin are excellent in various physical properties such as mechanical strength, molding processability, and surface gloss, and are used in a wide range of fields such as automotive parts and electrical equipment parts. ABS resin and ASA resin are usually produced by emulsion polymerization of a monomer mixture containing at least a part of the monomers constituting these resins to produce a rubbery latex, and further by grafting the rubbery latex by emulsion polymerization.

[0003] The properties of ABS resin and ASA resin are related to the size of rubber particles (i.e., dispersed substances) in the rubbery latex. When the average particle size of the rubber is large, the ABS resin prepared from the latex has excellent impact resistance, while when it is small, the resin has excellent gloss. Also, the gloss is preferably uniform in particle size. In other words, it is preferable that the particle size distribution is narrow. ABS resin and ASA resin produced from a rubbery latex containing coarse particles have poor gloss. Thus, the particle size and particle size distribution of rubber particles in the rubbery latex are extremely important factors that influence the performance of ABS resin and ASA resin. Also, the grafting rate of ABS resin and ASA resin greatly affects the impact resistance and gloss of ABS resin and ASA resin. Therefore, in order to prepare high-performance ABS resin and ASA resin, high-precision particle size control during the preparation of the rubbery latex and control of the grafting rate during the preparation of the ABS resin latex and ASA resin latex are required.

[0004] In the production of ABS resin latex and ASA resin latex, which are used to manufacture ABS resin and ASA resin, respectively, that have a well-balanced performance in terms of impact strength, flow properties, gloss, etc., rubbery latex with an average particle size of 150 to 500 nm of its dispersed phase is often used as a raw material. Rubbery latex is manufactured by emulsion polymerization, and the average particle size of its dispersed phase is usually less than 150 nm. Therefore, instead of using the rubbery latex as is in the production of ABS resin latex and ASA resin latex, rubbery latex manufactured by emulsion polymerization is usually subjected to a treatment to increase the particle size of its dispersed phase, and this prepared rubbery latex is then used in graft copolymerization. One method for increasing the particle size of the dispersed phase of rubbery latex involves adding an acidic substance such as sulfuric acid or acetic acid to the rubbery latex to lower its pH and cause the dispersed phase (rubber) particles to adhere to each other. However, this method has problems such as difficulty in adjusting the processing conditions for emulsion polymerization and the processing conditions for increasing the particle size of the dispersed phase, which reduces the stability of the rubbery latex and generates aggregates and coarse particles.

[0005] Furthermore, there are the following problems. Specifically, in the process of preparing graft copolymer latex (e.g., ABS resin latex and ASA resin latex) by graft copolymerizing aromatic vinyl monomers and vinyl monomers having cyano groups into rubbery latex using emulsion polymerization, if the amount of emulsifier is small, a large amount of aggregates and coarse particles are generated. On the other hand, if the amount of emulsifier is large, ABS resin latex and ASA resin latex with a small amount of aggregates and coarse particles are prepared. However, in this case, it is difficult to increase the grafting rate, and the ABS resin produced from the ABS resin latex prepared in this way, and the ASA resin produced from the ASA resin latex, have low physical properties such as impact resistance, gloss, and heat resistance.

[0006] On the other hand, emulsifiers conventionally used to produce rubbery latex and graft copolymer latex include alkali metal salts of higher fatty acids such as semi-hardened beef tallow fatty acids, alkali metal salts of resin acids, and sulfonates such as sodium dodecylbenzenesulfonate. Of these emulsifiers, alkali metal salts of higher fatty acids are commonly used as emulsifiers in both the preparation of rubbery latex by emulsion polymerization and the preparation of graft copolymer latex by emulsion polymerization, because the copolymer produced can be easily extracted from the latex produced using these emulsifiers.

[0007] Alkali metal salts of higher fatty acids are produced from natural oils and fats. For example, potassium salts of partially hydrogenated tallow fatty acids (semi-hardened tallow fatty acids) derived from beef tallow are widely used as emulsifiers for the preparation of rubbery latex and graft copolymer latex. However, the composition of higher fatty acids in conventional higher fatty acid salt-based emulsifiers is determined based on the fatty acid composition of the raw material oils and fats, and is not appropriately set. In fact, conventional higher fatty acid salt-based emulsifiers each have their own advantages and disadvantages, and therefore have not always been satisfactory in the production of rubbery latex and graft copolymer latex.

[0008] Therefore, Patent Document 1 aims to develop a method for producing latex with low content of aggregates and coarse particles, which is useful for producing graft copolymers such as ABS resin that have excellent physical properties such as impact resistance, gloss, and heat resistance. The method involves (I) polymerizing at least one diene monomer with a monomer other than a diene monomer that can be copolymerized with the diene monomer by emulsion polymerization to prepare a (co)polymer, and then processing the (co)polymer with an aromatic vinyl monomer and a vinyl monomer having a cyano group. A method for producing a graft copolymer latex is disclosed, comprising step (II) of copolymerizing a graft copolymer with a graft copolymer and / or a (meth)acrylate monomer by emulsion polymerization, wherein step (I) and / or step (II) are carried out in the presence of a fatty acid salt mixture consisting of palmitate, stearate, and octadecenoate, where the weight ratio of the acid is palmitate / stearate / octadecenoate = 45~70 / 5~20 / 15~30. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Patent Application Publication No. 9-110943 [Overview of the project] [Problems that the invention aims to solve]

[0010] However, the preparation of fatty acid salt mixtures such as semi-hardened palm stearin oil and semi-hardened beef tallow used in the method described in Patent Document 1 requires special equipment for semi-hardening, and there is a need for an emulsifier for emulsion polymerization that can be prepared by a simple method. Furthermore, there is a need for an emulsifier for emulsion polymerization that can solve problems such as the formation of aggregates when the particle size of the dispersed phase in rubbery latex is increased by the addition of acid. Moreover, when the fatty acid salt mixture used in the method described in Patent Document 1 has a high content of octadecenoic acid (oleic acid), there is a need for further improvement of the emulsifier for emulsion polymerization to avoid problems such as a deterioration in the recovery rate in the acid precipitation process when extracting the prepared rubbery latex. [Means for solving the problem]

[0011] In light of the current situation, the present inventors diligently conducted research with the aim of developing a method for producing rubbery latex that is useful for manufacturing graft copolymers such as ABS resin and ASA resin with excellent properties, and that exhibits excellent polymerization stability, acid aggregation stability, and acid precipitation properties. As a result of their investigation, the inventors found that the above objective can be achieved by using a mixture of higher fatty acid salts of a specific chemical composition as an emulsifier for emulsion polymerization in the manufacturing process of rubbery latex made of (co)polymers such as rubber, and in the manufacturing process of graft copolymer latex. In other words, the present invention relates to the following [1] to [3]. [1] A method for producing rubbery latex, comprising step 1 of emulsion polymerization of a monomer mixture (I) containing at least one diene monomer or a monomer mixture (II) containing at least one alkyl (meth)acrylate monomer, in the presence of a fatty acid salt mixture containing a salt of carboxylic acid (A), a salt of carboxylate (B), and a salt of carboxylic acid (C) as shown below, The total mass of fatty acids (A1) and (A2) / the total mass of (B1) and (B2) / the total mass of (C1) and (C2) shown below is 5-40 / 35-55 / 20-40. The carboxylic acid (A) consists of one or more saturated fatty acids selected from those having 12 carbon atoms (A1) and saturated fatty acids having 14 carbon atoms (A2). Carboxylic acid (B) consists of one or more selected from saturated fatty acids (B1) having 16 carbon atoms and unsaturated fatty acids (B2) having one double bond with 16 carbon atoms. The carboxylic acid (C) consists of one or more selected from saturated fatty acids (C1) with 18 carbon atoms and unsaturated fatty acids (C2) with one double bond with 18 carbon atoms. A method for manufacturing rubbery latex. A method for producing a graft copolymer comprising step 3 of emulsion polymerization of a rubbery latex produced by the manufacturing method described in [1], an aromatic vinyl monomer, and a monomer mixture (III) containing one or more selected from vinyl monomers having a cyano group and (meth)acrylate monomers, The emulsion polymerization is carried out in the presence of a fatty acid salt mixture containing the following carboxylic acid (A) salt, carboxylic acid (B) salt, and carboxylic acid (C) salt. The total mass of fatty acids (A1) and (A2) / the total mass of (B1) and (B2) / the total mass of (C1) and (C2) shown below is 5-40 / 35-55 / 20-40. The carboxylic acid (A) consists of one or more saturated fatty acids selected from those having 12 carbon atoms (A1) and saturated fatty acids having 14 carbon atoms (A2). Carboxylic acid (B) consists of one or more selected from saturated fatty acids (B1) having 16 carbon atoms and unsaturated fatty acids (B2) having one double bond with 16 carbon atoms. The carboxylic acid (C) consists of one or more selected from saturated fatty acids (C1) with 18 carbon atoms and unsaturated fatty acids (C2) with one double bond with 18 carbon atoms. A method for producing graft copolymers. [3] An emulsifier for emulsion polymerization comprising a salt of carboxylic acid (A), a salt of carboxylic acid (B), and a salt of carboxylic acid (C) as shown below, The total mass of the following fatty acids (A1) and (A2) / the total mass of (B1) and (B2) / the total mass of (C1) and (C2) is 5-40 / 35-55 / 20-40. The carboxylic acid (A) consists of one or more saturated fatty acids selected from those having 12 carbon atoms (A1) and saturated fatty acids having 14 carbon atoms (A2). Carboxylic acid (B) consists of one or more selected from saturated fatty acids (B1) having 16 carbon atoms and unsaturated fatty acids (B2) having one double bond with 16 carbon atoms. The carboxylic acid (C) is an emulsifier for emulsion polymerization, comprising one or more selected from saturated fatty acids (C1) having 18 carbon atoms and unsaturated fatty acids (C2) having one double bond with 18 carbon atoms. [Effects of the Invention]

[0012] According to the present invention, a method for producing a rubbery latex with excellent polymerization stability, acid aggregation stability, and acid precipitation properties, as well as an emulsifier for emulsion polymerization used in the production method, can be provided. [Modes for carrying out the invention]

[0013] [Method for manufacturing rubbery latex] The present invention provides a method for producing rubbery latex, comprising step 1 of emulsion polymerization of a monomer mixture (I) containing at least one diene monomer or a monomer mixture (II) containing at least one alkyl (meth)acrylate monomer, in the presence of a salt of a fatty acid mixture containing a salt of carboxylic acid (A), a salt of carboxylic acid (B), and a salt of carboxylic acid (C). Carboxylic acid (A) consists of one or more selected from saturated fatty acids having 12 carbon atoms (A1) and saturated fatty acids having 14 carbon atoms (A2); carboxylic acid (B) consists of one or more selected from saturated fatty acids having 16 carbon atoms (B1) and unsaturated fatty acids having one double bond with 16 carbon atoms (B2); and carboxylic acid (C) consists of one or more selected from saturated fatty acids having 18 carbon atoms (C1) and unsaturated fatty acids having one double bond with 18 carbon atoms (C2). Furthermore, the ratio of the total mass of saturated fatty acids with 12 carbon atoms (A1) and 14 carbon atoms (A2) / the total mass of saturated fatty acids with 16 carbon atoms (B1) and unsaturated fatty acids with one double bond (B2) / the total mass of saturated fatty acids with 18 carbon atoms (C1) and unsaturated fatty acids with one double bond (C2) is 5-40 / 35-55 / 20-40.

[0014] The present invention provides a method for producing rubbery latex that exhibits excellent polymerization stability, acid aggregation stability, and acid precipitation properties. While the detailed reasons are not entirely clear, they are thought to be as follows. In the method for producing a rubber latex of the present invention, the salt of the fatty acid mixture used as an emulsifier for emulsion polymerization contains one or more selected from salts of a saturated fatty acid (B1) having 16 carbon atoms and salts of an unsaturated fatty acid (B2) having 1 double bond and 16 carbon atoms, and one or more selected from salts of a saturated fatty acid (C1) having 18 carbon atoms and salts of an unsaturated fatty acid (C2) having 1 double bond and 18 carbon atoms. Therefore, in step 2 of increasing the particle size of the dispersed substance in the rubber latex prepared in step ①, the generation of aggregates can be suppressed. The reason for this is considered to be that the salts of the saturated fatty acid (B1) having 16 carbon atoms, the salts of the unsaturated fatty acid (B2) having 1 double bond and 16 carbon atoms, the salts of the saturated fatty acid (C1) having 18 carbon atoms, and the salts of the unsaturated fatty acid (C2) having 1 double bond and 18 carbon atoms are converted into hydrophobic fatty acids under acidic conditions, and by modifying the particle surface of the dispersed substance, the generation of aggregates can be suppressed. In addition, since the salt of the fatty acid mixture contains one or more selected from salts of a saturated fatty acid (A1) having 12 carbon atoms and salts of a saturated fatty acid (A2) having 14 carbon atoms, the recovery rate in the acid precipitation step when removing the resin from the rubber latex prepared in step ① can be improved. The reason for this is considered to be that the saturated fatty acid (A1) having 12 carbon atoms and the saturated fatty acid (A2) having 14 carbon atoms generated by the addition of an acid have high crystallinity.

[0015] (Definition) In the present invention, the description of "N1 to N2" indicates a range including N1 and N2, and is synonymous with "N1 or more and N2 or less" unless otherwise specified. In the present invention, the term "rubber latex" refers to a latex composed of a copolymer containing at least a structural unit derived from a diene monomer or at least a structural unit derived from a (meth)acrylic acid alkyl ester monomer. In the present invention, "acid aggregation stability" refers to the stability when an acid is added to a rubber latex to increase the particle size of the dispersed substance. In the present invention, "acid precipitation property" refers to the recovery rate in the acid precipitation step when removing the prepared rubber latex. It should be noted that in the translation of the content of , there is an unclear "step ①" in the original text. It is recommended to check and correct the relevant content in the original text to ensure the accuracy of the translation.In the present invention, the fatty acid is a monovalent fatty acid unless otherwise specified, and includes all isomers. In the present invention, “(meth)acrylic acid” means acrylic acid or methacrylic acid, and “(meth)acrylate” means acrylate or methacrylate.

[0016] ≪Step 1≫ In the method for producing the rubbery latex of the present invention, Step 1 is a step of emulsion-polymerizing a monomer mixture (I) containing at least one diene monomer or a monomer mixture (II) containing at least one (meth)acrylic acid alkyl ester monomer in the presence of a salt of a fatty acid mixture containing a salt of carboxylic acid (A), a salt of carboxylic acid (B), and a salt of carboxylic acid (C).

[0017] <Salt of fatty acid mixture> In Step 1, a salt of a fatty acid mixture is used as an emulsifier for emulsion polymerization. The salt of the fatty acid mixture contains a salt of carboxylic acid (A), a salt of carboxylic acid (B), and a salt of carboxylic acid (C).

[0018] The content of each fatty acid in the salt of the fatty acid mixture of the present invention can be measured, for example, by subjecting a mixture of methylated fatty acids to gas chromatography, gas chromatography-mass spectrometry, etc. Methylation of the fatty acid can be carried out by adding an acid to the salt of the fatty acid mixture to obtain a fatty acid mixture, extracting this with an organic solvent, and then treating it with a methylating agent. Examples of the methylating agent include diazomethane, (trimethylsilyl)diazomethane, etc.

[0019] 〔Carboxylic acid (A)〕 The carboxylic acid (A) consists of one or more saturated fatty acids selected from a 12-carbon saturated fatty acid (A1) (hereinafter sometimes simply referred to as "(A1)") and a 14-carbon saturated fatty acid (A2) (hereinafter sometimes simply referred to as "(A2)"), and the mass ratio (A1 / A2) of the 12-carbon saturated fatty acid (A1) to the 14-carbon saturated fatty acid (A2) is preferably 60 / 40 or less, more preferably 50 / 50 or less, even more preferably 30 / 70 or less, even more preferably 15 / 85 or less, and even more preferably 0 / 100, from the viewpoint of improving the polymerization stability and acid aggregation stability of the method for producing rubbery latex.

[0020] (Saturated fatty acid with 12 carbon atoms (A1)) The saturated fatty acid (A1) having 12 carbon atoms may be either a straight-chain saturated fatty acid with 12 carbon atoms or a branched-chain saturated fatty acid with 12 carbon atoms. The saturated fatty acid (A1) having 12 carbon atoms is preferably a saturated fatty acid having 12 carbon atoms with a carboxyl group at the end of the carbon chain, and more preferably lauric acid, a straight-chain saturated fatty acid having 12 carbon atoms with a carboxyl group at the end, from the viewpoint of improving the polymerization stability of the rubbery latex manufacturing method and the acid precipitation properties after the rubbery latex is manufactured.

[0021] (Saturated fatty acid with 14 carbon atoms (A2)) The saturated fatty acid (A2) with 14 carbon atoms may be either a straight-chain saturated fatty acid with 14 carbon atoms or a branched-chain saturated fatty acid with 14 carbon atoms. The saturated fatty acid (A2) having 14 carbon atoms is preferably a saturated fatty acid having 14 carbon atoms with a carboxyl group at the end of the carbon chain, and more preferably myristic acid, a straight-chain saturated fatty acid having 14 carbon atoms with a carboxyl group at the end, from the viewpoint of improving the polymerization stability and acid aggregation stability of the rubbery latex manufacturing method and the acid precipitation properties after the rubbery latex is manufactured.

[0022] The salts of the carboxylic acid (A), namely the salt of a 12-carbon saturated fatty acid (A1) and the salt of a 14-carbon saturated fatty acid (A2), are at least one selected from the group consisting of potassium salts, sodium salts, lithium salts, ammonium salts, and lower amine salts. Examples of lower amine salts of a saturated fatty acid having 12 carbon atoms (A1) and a saturated fatty acid having 14 carbon atoms (A2) include salts of a saturated fatty acid having 12 carbon atoms (A1) and a saturated fatty acid having 14 carbon atoms (A2) that preferably have a countercation derived from an amine having 9 or fewer carbon atoms, more preferably 2 to 9 carbon atoms. Examples of such lower amines include triethylamine, monoethanolamine, diethanolamine, and N,N-diisopropylethylamine.

[0023] [Carboxylic acid (B)] The carboxylic acid (B) consists of one or more selected from a saturated fatty acid (B1) having 16 carbon atoms (hereinafter sometimes simply referred to as "(B1)") and an unsaturated fatty acid (B2) having one double bond with 16 carbon atoms (hereinafter sometimes simply referred to as "(B2)"). From the viewpoint of improving the acid precipitation properties after the production of rubbery latex, the mass ratio (B1 / B2) of the saturated fatty acid (B1) having 16 carbon atoms (B1) to the unsaturated fatty acid (B2) having one double bond with 16 carbon atoms is preferably 90 / 10 or higher, more preferably 95 / 5 or higher, even more preferably 98 / 2 or higher, and even more preferably 100 / 0.

[0024] (Saturated fatty acid with 16 carbon atoms (B1)) The saturated fatty acid (B1) having 16 carbon atoms may be either a straight-chain saturated fatty acid with 16 carbon atoms or a branched-chain saturated fatty acid with 16 carbon atoms. From the viewpoint of improving the polymerization stability of the rubbery latex manufacturing method, the saturated fatty acid (B1) having 16 carbon atoms is preferably a saturated fatty acid having 16 carbon atoms with a carboxyl group at the end of the carbon chain, and more preferably palmitic acid, which is a straight-chain saturated fatty acid having 16 carbon atoms with a carboxyl group at the end.

[0025] (An unsaturated fatty acid (B2) containing one double bond with 16 carbon atoms) The unsaturated fatty acid (B2) having one double bond with 16 carbon atoms may be either a straight-chain unsaturated fatty acid having one double bond with 16 carbon atoms, or a branched-chain unsaturated fatty acid having one double bond with 16 carbon atoms. The unsaturated fatty acid (B2) having one double bond with 16 carbon atoms is preferably an unsaturated fatty acid having one double bond with 16 carbon atoms and a carboxyl group at the end of the carbon chain, and more preferably an unsaturated fatty acid having one straight-chain double bond with 16 carbon atoms and a carboxyl group at the end.

[0026] Examples of salts of carboxylic acid (B) that constitute a salt of a saturated fatty acid (B1) having 16 carbon atoms and a salt of an unsaturated fatty acid (B2) having one double bond with 16 carbon atoms include salts having the same countercation as the salt of the saturated fatty acid (A1) having 12 carbon atoms and the salt of the saturated fatty acid (A2) having 14 carbon atoms mentioned above.

[0027] [Carboxylic acid (C)] The carboxylic acid (C) consists of one or more selected from a saturated fatty acid (C1) having 18 carbon atoms (hereinafter sometimes simply referred to as "(C1)") and an unsaturated fatty acid (C2) having one double bond with 18 carbon atoms (hereinafter sometimes simply referred to as "(C2)"). From the viewpoint of improving the acid precipitation properties after the production of rubbery latex, the mass ratio (C1 / C2) of the saturated fatty acid (C1) having 18 carbon atoms (C1) to the unsaturated fatty acid (C2) having one double bond with 18 carbon atoms is preferably 75 / 25 or more, more preferably 80 / 20 or more, even more preferably 82 / 18 or more, and preferably 98 / 2 or less, more preferably 95 / 5 or less, and even more preferably 90 / 10 or less.

[0028] (Saturated fatty acid with 18 carbon atoms (C1)) The saturated fatty acid (C1) with 18 carbon atoms may be either a straight-chain saturated fatty acid with 18 carbon atoms or a branched-chain saturated fatty acid with 18 carbon atoms. From the viewpoint of improving the polymerization stability of the rubbery latex manufacturing method, the 18-carbon saturated fatty acid (C1) is preferably a 18-carbon saturated fatty acid having a carboxyl group at the end of the carbon chain, and more preferably stearic acid, which is a straight-chain 18-carbon saturated fatty acid having a carboxyl group at the end.

[0029] (An unsaturated fatty acid (C2) having one double bond with 18 carbon atoms) An unsaturated fatty acid (C2) having one double bond with 18 carbon atoms may be either a straight-chain unsaturated fatty acid having one double bond with 18 carbon atoms, or a branched-chain unsaturated fatty acid having one double bond with 18 carbon atoms. From the viewpoint of improving the polymerization stability of the method for producing rubbery latex, the unsaturated fatty acid (C2) having one carbon-18 double bond is preferably an unsaturated fatty acid having one carbon-18 double bond with a carboxyl group at the end of the carbon chain, and from the viewpoint of economic efficiency, it is more preferably an unsaturated fatty acid having one straight-chain carbon-18 double bond with a carboxyl group at the end of the carbon chain.

[0030] Examples of salts of carboxylic acid (C) that constitute a salt of a saturated fatty acid (C1) having 18 carbon atoms and a salt of an unsaturated fatty acid (C2) having one double bond with 18 carbon atoms include salts having the same countercation as the salt of the saturated fatty acid (A1) having 12 carbon atoms and the salt of the saturated fatty acid (A2) having 14 carbon atoms mentioned above.

[0031] In a fatty acid mixture, the mass of carboxylic acid (A1) and carboxylic acid (A2) relative to 100 parts by mass of the total mass of carboxylic acid (A1), carboxylic acid (A2), carboxylic acid (B1), carboxylic acid (B2), carboxylic acid (C1), and carboxylic acid (C2) constituting it is 5 parts by mass or more, preferably 8 parts by mass or more, more preferably 10 parts by mass or more, from the viewpoint of improving the acid aggregation stability in the production of rubbery latex and improving the acid precipitation after the production of rubbery latex, and from the viewpoint of improving the polymerization stability of the rubbery latex production method, it is 40 parts by mass or less, preferably 35 parts by mass or less, more preferably 30 parts by mass or less. In a fatty acid mixture, the mass of carboxylic acid (B1) and carboxylic acid (B2) relative to 100 parts by mass of the total mass of carboxylic acid (A1), carboxylic acid (A2), carboxylic acid (B1), carboxylic acid (B2), carboxylic acid (C1), and carboxylic acid (C2) constituting it is 35 parts by mass or more, preferably 37 parts by mass or more, more preferably 39 parts by mass or more, from the viewpoint of improving the acid aggregation stability of the rubbery latex production method, and 55 parts by mass or less, preferably 53 parts by mass or less, more preferably 51 parts by mass or less, from the viewpoint of improving the acid precipitation after production of the rubbery latex. In a fatty acid mixture, the masses of carboxylic acid (C1) and carboxylic acid (C2) relative to 100 parts by mass of the total mass of carboxylic acid (A1), carboxylic acid (A2), carboxylic acid (B1), carboxylic acid (B2), carboxylic acid (C1), and carboxylic acid (C2) constituting it are 20 parts by mass or more, preferably 25 parts by mass or more, more preferably 30 parts by mass or more, from the viewpoint of improving the acid aggregation stability of the rubber latex production method and improving the acid precipitation properties after production of the rubber latex, and 40 parts by mass or less, preferably 38 parts by mass or less, more preferably 36 parts by mass or less, from the viewpoint of improving the acid precipitation properties after production of the rubber latex.

[0032] The fatty acid mixture may contain salts of carboxylic acids other than salts of carboxylic acid (A), salts of carboxylic acid (B), and salts of carboxylic acid (C). Examples of such carboxylic acids include unsaturated fatty acids having one double bond with 12 carbon atoms, unsaturated fatty acids having one double bond with 14 carbon atoms, unsaturated fatty acids having two or more double bonds with 16 carbon atoms, unsaturated fatty acids having two or more double bonds with 18 carbon atoms, and fatty acids with 20 or more carbon atoms.

[0033] The total content of unsaturated fatty acids having one C16 double bond (B2) and unsaturated fatty acids having one C18 double bond (C2) in the fatty acid mixture is preferably 10% by mass or less, more preferably 8.0% by mass or less, and even more preferably 6.0% by mass or less, from the viewpoint of improving acid precipitation after the production of rubbery latex, and from the viewpoint of availability and economic efficiency, it is preferably more than 0% by mass, more preferably 0.50% by mass or more, and even more preferably 1.0% by mass or more.

[0034] The total content of carboxylic acid (A), carboxylic acid (B), and carboxylic acid (C) in the fatty acid mixture is preferably 90.0% by mass or more, more preferably 93.0% by mass or more, and even more preferably 95.0% by mass or more, from the viewpoint of improving polymerization stability and reaction efficiency of the rubbery latex production method, and preferably 100% by mass or less, more preferably 99.5% by mass or less, and even more preferably 99.0% by mass or less, from the viewpoint of availability and economic efficiency.

[0035] (Method for producing salts of fatty acid mixtures) Salts of fatty acid mixtures may be prepared by mixing salts of carboxylic acid (A), salts of carboxylic acid (B), salts of carboxylic acid (C), and salts of other carboxylic acids. Alternatively, a fatty acid mixture may be prepared by mixing carboxylic acid (A1), carboxylic acid (A2), carboxylic acid (B1), carboxylic acid (B2), carboxylic acid (C1), and carboxylic acid (C2), as well as other carboxylic acids, and then mixing it with a potassium compound, a sodium compound, a lithium compound, ammonia, and a lower amine. Examples of potassium compounds, sodium compounds, and lithium compounds include potassium hydroxide, sodium hydroxide, and lithium hydroxide, respectively. From the viewpoint of productivity, it is preferable to add the above fatty acid mixture to an aqueous solution of the potassium compound, sodium compound, lithium compound, ammonia, and lower amine.

[0036] <Monomer mixture> In step 1, a monomer mixture (I) containing at least one diene monomer or a monomer mixture (II) containing at least one alkyl (meth)acrylate monomer is used as the monomer mixture.

[0037] [Monomer mixture (I)] The monomer mixture (I) contains at least one diene monomer. Examples of diene monomers include butadiene, isoprene, chloroprene, etc., with butadiene being preferred. The monomer mixture (I) may contain monomers other than diene monomers. Examples of monomers other than diene monomers include aromatic vinyl monomers such as styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, and p-methylstyrene, and vinyl monomers having a cyano group such as methacrylonitrile and acrylonitrile. The monomer mixture (I) may also contain the alkyl (meth)acrylate monomers shown below.

[0038] From the viewpoint of obtaining a resin with excellent impact resistance, the content of diene monomers in monomer mixture (I) is preferably 60.0% by mass or more, more preferably 70.0% by mass or more, even more preferably 80.0% by mass or more, and preferably 100% by mass or less.

[0039] [Monomer mixture (II)] The monomer mixture (II) contains at least one alkyl (meth)acrylate monomer. Examples of alkyl (meth)acrylate monomers include methyl (meth)acrylate and butyl (meth)acrylate, and butyl acrylate is preferred from the viewpoint of availability and obtaining a resin with excellent impact resistance and weather resistance. From the viewpoint of efficiently obtaining graft polymers from the resulting rubbery latex, the monomer mixture (II) preferably contains alkenyl (meth)acrylate monomers such as allyl (meth)acrylate in addition to alkyl (meth)acrylate monomers. The monomer mixture (II) may contain monomers other than alkyl (meth)acrylate monomers and alkenyl (meth)acrylate monomers. Examples of monomers other than alkyl (meth)acrylate monomers and alkenyl (meth)acrylate monomers include aromatic vinyl monomers such as styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, and p-methylstyrene, and vinyl monomers having a cyano group such as methacrylonitrile and acrylonitrile. The monomer mixture (II) may also contain the above-mentioned diene monomers.

[0040] From the viewpoint of obtaining a resin with excellent impact resistance, the content of alkyl (meth)acrylate monomers in monomer mixture (II) is preferably 60.0% by mass or more, more preferably 70.0% by mass or more, even more preferably 80.0% by mass or more, and preferably 99.6% by mass or less, more preferably 99.0% by mass or less, and even more preferably 98.5% by mass or less.

[0041] In step 1, the amount of the fatty acid mixture salt used as an emulsifier for emulsion polymerization is preferably 0.1 parts by mass or more, more preferably 1.0 part by mass or more, even more preferably 2.0 parts by mass or more, and even more preferably 2.5 parts by mass or more, per 100 parts by mass of monomer mixture (I) or monomer mixture (II), from the viewpoint of polymerization stability of the method for producing rubbery latex, and from the viewpoint of economic efficiency, preferably 5.0 parts by mass or less, more preferably 4.0 parts by mass or less, and even more preferably 3.5 parts by mass or less.

[0042] (Radical polymerization initiator) As the radical polymerization initiator used in the emulsion polymerization of Step 1, any of those commonly used in emulsion polymerization can be used. Examples of radical polymerization initiators include water-soluble persulfates such as sodium persulfate, potassium persulfate, and ammonium persulfate; organic peroxides such as hydrogen peroxide, t-butyl hydroperoxide, benzoyl peroxide, and cumene hydroperoxide; and azo-based initiators such as azobis-diisobutyronitrile and 2,2-azobis(2-amidinopropane) dihydrochloride. From the viewpoint of polymerization reactivity, workability, and economy, water-soluble persulfates and organic peroxides are preferred, and one or more selected from sodium persulfate, potassium persulfate, ammonium persulfate, and t-butyl hydroperoxide are more preferred. Furthermore, as polymerization initiators, redox-type initiators combining a peroxide compound with a water-soluble reducing agent such as sodium sulfite, rongalit, or ascorbic acid can also be used.

[0043] In step 1, the amount of radical polymerization initiator used is preferably 0.05 parts by mass or more, more preferably 0.10 parts by mass or more, and even more preferably 0.15 parts by mass or more, per 100 parts by mass of monomer mixture (I) or monomer mixture (II), from the viewpoint of manufacturing efficiency, and preferably 2.00 parts by mass or less, more preferably 1.00 part by mass or less, and even more preferably 0.50 parts by mass or less, from the viewpoint of economic efficiency.

[0044] In step 1, the amount of monomer mixture (I) or monomer mixture (II) added is preferably 10% by mass or more, more preferably 15% by mass or more, and even more preferably 20% by mass or more, relative to the total mass of monomer mixture (I) or monomer mixture (II) and dispersion medium, from the viewpoint of manufacturing efficiency and economics, and preferably 60% by mass or less, more preferably 55% by mass or less, and even more preferably 50% by mass or less, from the viewpoint of polymerization stability of the method for producing rubbery latex.

[0045] In step 1, the dispersion medium is an aqueous medium, preferably water. Here, "aqueous" means that water makes up the largest proportion in the medium. As the water in the aqueous medium, ion-exchanged water or distilled water is preferably used. The aqueous medium may further contain an organic solvent. Examples of such organic solvents include aliphatic alcohols having 1 to 4 carbon atoms, such as methanol, ethanol, and 2-propanol; ketones having 3 to 8 carbon atoms, such as acetone and methyl ethyl ketone; and water-soluble organic solvents such as ethers, such as diethyl ether and tetrahydrofuran. From an environmental standpoint, the water content in the aqueous medium is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 90% by mass or more, even more preferably 95% by mass or more, and even more preferably 100% by mass.

[0046] In step 1, there are no particular restrictions on the emulsion polymerization conditions, but the polymerization temperature is adjusted by the decomposition temperature of the polymerization initiator. From the viewpoint of manufacturing efficiency, a temperature of 20°C to 80°C is preferred. Similarly, from the same viewpoint, the polymerization time is preferably 2 hours to 36 hours. In step 1, emulsion polymerization may be stopped by cooling the reaction system, or by adding a pH adjuster and a polymerization inhibitor.

[0047] In step 1, polymerization auxiliary materials such as chain transfer agents, dispersants, oxygen scavengers, chelating agents, particle size modifiers, surfactants, molecular weight modifiers, inorganic salts, and pH adjusters may be used as needed. The type and amount of these materials used are not particularly limited.

[0048] The average particle size of the resin particles used as the dispersed phase in the rubbery latex produced in step 1 is preferably 50 nm or more, more preferably 60 nm or more, and even more preferably 70 nm or more, from the viewpoint of obtaining a resin with excellent impact resistance, and preferably 150 nm or less, more preferably 120 nm or less, and even more preferably 110 nm or less, from the viewpoint of polymerization stability of the rubbery latex production method. Furthermore, the resin particles used as the dispersed phase in the rubbery latex are polymer particles of monomer mixture (I) or monomer mixture (II).

[0049] ≪Process 2≫ The present invention's method for producing rubbery latex may also include, in addition to step 1, step 2, which increases the particle size of the dispersed phase in the rubbery latex produced in step 1. From a productivity standpoint, step 2 may use the rubbery latex obtained in step 1 as is, or, from the viewpoint of facilitating particle size control of the dispersed phase, the dispersed phase may be filtered from the rubbery latex obtained in step 1 before proceeding.

[0050] In step 2, the resin particles as a dispersed phase are fused together by adding an acid component or salt, or by mechanical force, thereby increasing the particle size of the dispersed phase. In particular, step 2 is preferably carried out by adding an acid component. When an acid component is used in step 2, the acid component is preferably an inorganic acid such as hydrochloric acid or sulfuric acid, and an organic acid such as acetic acid, and more preferably acetic acid. The pH of the rubbery latex after the addition of the acid component is preferably 5.5 or less, more preferably 5.0 or less, and even more preferably 4.5 or less, from the viewpoint of increasing the particle size of the dispersed phase after agglomeration, and from the viewpoint of the stability of the dispersed phase after acid agglomeration, it is preferably 2.5 or higher, more preferably 3.0 or higher, and even more preferably 3.5 or higher. When salt is used in step 2, the salt is preferably a sodium salt, potassium salt, or calcium salt, and more preferably a sodium salt, from the viewpoint of increasing the particle size of the dispersed phase after agglomeration. The amount of salt added to the rubbery latex is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 3 parts by mass or more, per 100 parts by mass of polymer of monomer mixture (I) or monomer mixture (II), from the viewpoint of the stability of the dispersed phase after acid agglomeration, and from the viewpoint of economy, preferably 10 parts by mass or less, more preferably 9 parts by mass or less, and even more preferably 8 parts by mass or less. When mechanical force is applied in step 2, the mechanical force can be applied to the rubbery latex using, for example, an ultrasonic homogenizer or a high-pressure homogenizer, and from the viewpoint of productivity, a high-pressure homogenizer is preferred.

[0051] The temperature at which step 2 is performed is preferably 20°C to 50°C, from the viewpoint of keeping the average particle size of the dispersed particles in the rubbery latex within the desired range.

[0052] The average particle size of the dispersed phase in the rubbery latex obtained in step 2 is preferably greater than 130 nm, more preferably 140 nm or more, and even more preferably 150 nm or more, from the viewpoint of obtaining a resin with excellent impact resistance, and preferably 500 nm or less, more preferably 400 nm or less, and even more preferably 350 nm or less, from the viewpoint of the stability of graft polymerization in step 3.

[0053] [Graft copolymer] ≪Step 3≫ The present invention provides a method for producing a graft copolymer, comprising step 3 of emulsion polymerization of a monomer mixture (III) containing a rubbery latex produced by the above production method and an aromatic vinyl monomer, and one or more selected from vinyl monomers having a cyano group and (meth)acrylate monomers, in the presence of a salt of a fatty acid mixture.

[0054] [Monomer mixture (III)] Monomer mixture (III) comprises an aromatic vinyl monomer and one or more selected from vinyl monomers having a cyano group and (meth)acrylate monomers. Examples of aromatic vinyl monomers and vinyl monomers having cyano groups include the aromatic vinyl monomers and vinyl monomers having cyano groups shown in monomer mixture (I) and monomer mixture (II) above. Examples of (meth)acrylate monomers include methyl (meth)acrylate.

[0055] In step 1, if monomer mixture (I) containing at least one diene monomer is used, monomer mixture (III) preferably contains an aromatic vinyl monomer and a vinyl monomer or (meth)acrylate monomer having a cyano group. Furthermore, if a monomer mixture (II) containing at least one alkyl acrylate monomer is used in step 1, it is preferable that monomer mixture (III) contains an aromatic vinyl monomer and a vinyl monomer having a cyano group.

[0056] <Salts of fatty acid mixtures> The fatty acid mixture salt used as an emulsifier for emulsion polymerization in step 3 is the same as the fatty acid mixture salt used in step 1, and the preferred range is also the same. If step 3 is performed in a one-pot process starting from step 1, it is not necessary to add a new salt of the fatty acid mixture in step 3, but it may be added if necessary. If the method for producing rubbery latex includes step 2 above, and an acidic component is added in step 2, the salt of the fatty acid mixture used in step 1 may be regenerated and used by adding a basic component.

[0057] (Radical polymerization initiator) The radical polymerization initiator used in the emulsion polymerization of step 3 is the same as the radical polymerization initiator used in step 1, and the amount of radical polymerization initiator used per monomer mixture (III) is the same as the amount of radical polymerization initiator used per 100 parts by mass of monomer mixture (I) or monomer mixture (II) shown in step 1.

[0058] In step 3, the amount of monomer mixture (III) blended with 100 parts by mass of dispersed phase in the rubbery latex obtained above is preferably 35% by mass or more, more preferably 40% by mass or more, and even more preferably 45% by mass or more, from the viewpoint of obtaining a resin with excellent impact resistance, and preferably 65% ​​by mass or less, more preferably 60% by mass or less, and even more preferably 55% by mass or less, from the viewpoint of economic efficiency.

[0059] In step 3, the amount of monomer mixture (III) added is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 25% by mass or more, relative to the total mass of the rubbery latex, monomer mixture (III), and dispersion medium, from the viewpoint of economic efficiency, and preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 35% by mass or less, from the viewpoint of improving the polymerization stability of the rubbery latex production method. In step 3, the dispersion medium is an aqueous medium, preferably water, and the preferred aqueous medium and the water content in the aqueous medium are the same as in step 1.

[0060] In step 3, there are no particular restrictions on the emulsion polymerization conditions, but preferably they are the same as those in step 1. In step 3, emulsion polymerization may be stopped by cooling the reaction system, or by adding a pH adjuster and a polymerization inhibitor.

[0061] The graft copolymer can be recovered from the graft copolymer latex obtained by emulsion polymerization in step 3 using known methods. For example, the graft copolymer can be precipitated by adding an acid component such as hydrochloric acid or sulfuric acid, or a salt such as magnesium chloride, magnesium sulfate, or calcium chloride, and then recovered by filtration or other means.

[0062] (Compound) The graft copolymer obtained above may be mixed with other resins to form a compound having a sea-island structure in which the graft copolymer is contained as domains and the other resin as a matrix. As for other resins, copolymerization of monomers used as monomer mixture (III) is preferred from the viewpoint of compatibility with graft copolymers. That is, for example, when monomer mixture (III) containing an aromatic vinyl monomer and a (meth)acrylate monomer is used, the other resin may be a copolymer of the aromatic vinyl monomer and the (meth)acrylate monomer, and when monomer mixture (III) containing an aromatic vinyl monomer and a vinyl monomer having a cyano group is used, the other resin may be a copolymer of the aromatic vinyl monomer and the vinyl monomer having a cyano group.

[0063] The mixing of the graft copolymer with other resins is preferably carried out using, for example, a twin-screw extruder. There are no particular restrictions on the mixing temperature, but from the viewpoint of improving the miscibility with other resins, it is preferable that it be between 200°C and 300°C.

[0064] [Emulsifier for emulsion polymerization] The emulsifier for emulsion polymerization of the present invention comprises a salt of carboxylic acid (A), a salt of carboxylic acid (B), and a salt of carboxylic acid (C). Carboxylic acid (A) consists of one or more selected from saturated fatty acids having 12 carbon atoms (A1) and saturated fatty acids having 14 carbon atoms (A2); carboxylic acid (B) consists of one or more selected from saturated fatty acids having 16 carbon atoms (B1) and unsaturated fatty acids having one double bond with 16 carbon atoms (B2); and carboxylic acid (C) consists of one or more selected from saturated fatty acids having 18 carbon atoms (C1) and unsaturated fatty acids having one double bond with 18 carbon atoms (C2). Furthermore, the ratio of the total mass of saturated fatty acids with 12 carbon atoms (A1) and 14 carbon atoms (A2) / the total mass of saturated fatty acids with 16 carbon atoms (B1) and unsaturated fatty acids with one double bond (B2) / the total mass of saturated fatty acids with 18 carbon atoms (C1) and unsaturated fatty acids with one double bond (C2) is 5-40 / 35-55 / 20-40.

[0065] Examples of emulsifiers for emulsion polymerization include those similar to the salts of the fatty acid mixture used in step 1 above, and the preferred range is also the same.

[0066] The emulsifier for emulsion polymerization of the present invention can be used for emulsion polymerization of polymerizable monomers, and preferably for emulsion polymerization of monomer mixtures containing at least one of monomer mixture (I), monomer mixture (II), and monomer mixture (III).

[0067] With respect to the embodiments described above, the present invention further discloses a method for producing a rubbery latex, a method for producing a graft copolymer using the rubbery latex, and an emulsifier for emulsion polymerization used in the method for producing the rubbery latex. <1> A method for producing rubbery latex, comprising step 1 of emulsion polymerization of a monomer mixture (I) containing at least one diene monomer or a monomer mixture (II) containing at least one alkyl (meth)acrylate monomer, in the presence of a salt of a fatty acid mixture containing a salt of carboxylic acid (A), a salt of carboxylic acid (B), and a salt of carboxylic acid (C) as shown below, The total mass of fatty acids (A1) and (A2) / the total mass of (B1) and (B2) / the total mass of (C1) and (C2) shown below is 5-40 / 35-55 / 20-40. The carboxylic acid (A) consists of one or more saturated fatty acids selected from those having 12 carbon atoms (A1) and saturated fatty acids having 14 carbon atoms (A2). Carboxylic acid (B) consists of one or more selected from saturated fatty acids (B1) having 16 carbon atoms and unsaturated fatty acids (B2) having one double bond with 16 carbon atoms. The carboxylic acid (C) consists of one or more selected from saturated fatty acids (C1) with 18 carbon atoms and unsaturated fatty acids (C2) with one double bond with 18 carbon atoms. A method for manufacturing rubbery latex. <2> The mass ratio (A1 / A2) of the saturated fatty acid having 12 carbon atoms (A1) to the saturated fatty acid having 14 carbon atoms (A2) is 0 / 100 to 60 / 40, preferably 0 / 100 to 50 / 50, more preferably 0 / 100 to 30 / 70, even more preferably 0 / 100 to 15 / 85, and even more preferably 0 / 100. <1> A method for producing the rubbery latex described above. <3> The mass ratio (B1 / B2) of the saturated fatty acid having 16 carbon atoms (B1) and the unsaturated fatty acid having one double bond with 16 carbon atoms (B2) is 90 / 10 to 100 / 0, preferably 95 / 5 to 100 / 0, more preferably 98 / 2 to 100 / 0, and even more preferably 100 / 0. <1> or <2> A method for producing the rubbery latex described above. <4> The mass ratio (C1 / C2) of the saturated fatty acid having 18 carbon atoms (C1) and the unsaturated fatty acid having one double bond with 18 carbon atoms (C2) is 75 / 25 to 98 / 2, preferably 80 / 20 to 95 / 5, and more preferably 82 / 18 to 90 / 10. <1> ~ <3> A method for producing rubbery latex as described in any of the following. <5> In the fatty acid mixture, the mass of carboxylic acid (A1) and carboxylic acid (A2) relative to 100 parts by mass of the total mass of carboxylic acid (A1), carboxylic acid (A2), carboxylic acid (B1), carboxylic acid (B2), carboxylic acid (C1), and carboxylic acid (C2) constituting it is 5 parts by mass or more, preferably 8 parts by mass or more, more preferably 10 parts by mass or more, and 40 parts by mass or less, preferably 35 parts by mass or less, more preferably 30 parts by mass or less. <1> ~ <4> A method for producing rubbery latex as described in any of the following. <6> In the fatty acid mixture, the mass of carboxylic acid (B1) and carboxylic acid (B2) is 35 parts by mass or more, preferably 37 parts by mass or more, more preferably 39 parts by mass or more, and 55 parts by mass or less, preferably 53 parts by mass or less, more preferably 51 parts by mass or less, with respect to 100 parts by mass of the total mass of carboxylic acid (A1), carboxylic acid (A2), carboxylic acid (B1), carboxylic acid (B2), carboxylic acid (C1), and carboxylic acid (C2) constituting it. <1> ~ <5> A method for producing rubbery latex as described in any of the following. <7> In the fatty acid mixture, the mass of carboxylic acid (C1) and carboxylic acid (C2) relative to 100 parts by mass of the total mass of carboxylic acid (A1), carboxylic acid (A2), carboxylic acid (B1), carboxylic acid (B2), carboxylic acid (C1), and carboxylic acid (C2) constituting it is 20 parts by mass or more, preferably 25 parts by mass or more, more preferably 30 parts by mass or more, and 40 parts by mass or less, preferably 38 parts by mass or less, more preferably 36 parts by mass or less. <1> ~ <6> A method for producing rubbery latex as described in any of the following. <8> In the fatty acid mixture, the total content of the unsaturated fatty acid (B2) having one double bond with 16 carbon atoms and the unsaturated fatty acid (C2) having one double bond with 18 carbon atoms is 10.0% by mass or less, preferably 0.5% by mass or more and 8.0% by mass or less, and more preferably 1.0% by mass or more and 6.0% by mass or less. <1> ~ <7> A method for producing rubbery latex as described in any of the following. <9> The total content of carboxylic acid (A), carboxylic acid (B), and carboxylic acid (C) in the fatty acid mixture is 90.0% by mass or more and 100% by mass or less, preferably 93% by mass or more and 99.5% by mass or less, and more preferably 95.0% by mass or more and 99.0% by mass or less. <1> ~ <8> A method for producing rubbery latex as described in any of the following. <10> The salt is at least one selected from the group consisting of potassium salts, sodium salts, lithium salts, ammonium salts, and lower amine salts. <1> ~ <9> A method for producing rubbery latex as described in any of the following. <11> The amount of the fatty acid mixture salt per 100 parts by mass of the monomer mixture (I) or the monomer mixture (II) is 0.1 parts by mass or more and 5.0 parts by mass or less, preferably 1.0 parts by mass or more and 4.0 parts by mass or less, more preferably 2.0 parts by mass or more and 3.5 parts by mass or less, and even more preferably 2.5 parts by mass or more and 3.5 parts by mass or less. <1> ~ <10> A method for producing rubbery latex as described in any of the following. <12> The process includes step 2, which increases the particle size of the dispersed phase in the rubbery latex produced in step 1. <1> ~ <11> A method for producing rubbery latex as described in any of the following. <13> Step 2 is carried out by adding an acid component. <12> A method for producing the rubbery latex described above. <14> The pH of the rubbery latex after the addition of the acid component is preferably 5.5 or less, more preferably 5.0 or less, even more preferably 4.5 or less, and preferably 2.5 or higher, more preferably 3.0 or higher, and even more preferably 3.5 or higher. <13> A method for producing the rubbery latex described above. <15> <1> ~ <14> A method for producing a graft copolymer comprising step 3 of emulsion polymerization of a rubbery latex produced by any of the methods described above, and a monomer mixture (III) containing an aromatic vinyl monomer and one or more selected from vinyl monomers having a cyano group and (meth)acrylate monomers, The emulsion polymerization is carried out in the presence of a salt of a fatty acid mixture containing a salt of carboxylic acid (A), a salt of carboxylic acid (B), and a salt of carboxylic acid (C) as shown below. The total mass of fatty acids (A1) and (A2) / the total mass of (B1) and (B2) / the total mass of (C1) and (C2) shown below is 5-40 / 35-55 / 20-40. The carboxylic acid (A) consists of one or more saturated fatty acids selected from those having 12 carbon atoms (A1) and saturated fatty acids having 14 carbon atoms (A2). Carboxylic acid (B) consists of one or more selected from saturated fatty acids (B1) having 16 carbon atoms and unsaturated fatty acids (B2) having one double bond with 16 carbon atoms. A method for producing a graft copolymer, wherein the carboxylic acid (C) is selected from one or more saturated fatty acids (C1) having 18 carbon atoms and unsaturated fatty acids (C2) having one double bond with 18 carbon atoms. <16> <1> ~ <14> The amount of monomer mixture (III) blended with 100 parts by mass of dispersed phase in rubbery latex produced by any of the manufacturing methods described herein is preferably 35% by mass or more, more preferably 40% by mass or more, even more preferably 45% by mass or more, and preferably 65% ​​by mass or less, more preferably 60% by mass or less, and even more preferably 55% by mass or less. <15> A method for producing the graft copolymer described above. <17> An emulsifier for emulsion polymerization comprising a salt of carboxylic acid (A), a salt of carboxylic acid (B), and a salt of carboxylic acid (C) as shown below, The total mass of the following fatty acids (A1) and (A2) / the total mass of (B1) and (B2) / the total mass of (C1) and (C2) is 5-40 / 35-55 / 20-40. The carboxylic acid (A) consists of one or more saturated fatty acids selected from those having 12 carbon atoms (A1) and saturated fatty acids having 14 carbon atoms (A2). Carboxylic acid (B) consists of one or more selected from saturated fatty acids (B1) having 16 carbon atoms and unsaturated fatty acids (B2) having one double bond with 16 carbon atoms. The carboxylic acid (C) is an emulsifier for emulsion polymerization, comprising one or more selected from saturated fatty acids (C1) having 18 carbon atoms and unsaturated fatty acids (C2) having one double bond with 18 carbon atoms. [Examples]

[0068] The present invention will be specifically described below with reference to examples, but the present invention is not limited in any way by these examples.

[0069] [Average particle size of particles in rubbery latex] Using a particle size and molecular weight measurement system (manufactured by Otsuka Electronics Co., Ltd., product name: ELSZ-1000ZS), the average particle size of particles in rubbery latex was measured after diluting the rubbery latex 30,000 times. The measurement and analysis method used was the cumulant average particle size obtained by accumulating 70 measurements.

[0070] [Solid content concentration of rubbery latex] Using a vacuum low-temperature dryer "VO-320" (manufactured by Advantec Toyo Co., Ltd.), 2g of the sample (mass before drying) was dried under reduced pressure at 105°C for 2 hours at 25kPa, and the dried mass was measured. The concentration of the active ingredient and the solid content concentration were calculated according to the following formula. Concentration of active ingredient and solid content (mass%) = Dry mass / Mass before drying × 100

[0071] [Production of salts from fatty acid mixtures] Manufacturing Example 1 (Production of Salt 1 of Fatty Acid Mixture) In a 1L four-necked flask equipped with a stirrer and a raw material inlet, 446.50g of deionized water and 39.43g of 48% potassium hydroxide solution (manufactured by Kanto Chemical Co., Ltd.) were charged. Then, a fatty acid mixture consisting of 14.26g of Lunac MY-98 (manufactured by Kao Corporation), 43.75g of Lunac P-95 (manufactured by Kao Corporation), 24.06g of Lunac S-90V (manufactured by Kao Corporation), and 5.43g of Lunac OV (manufactured by Kao Corporation) was added. The mixture was heated to 75°C and stirred for 2 hours to obtain salt 1 of the fatty acid mixture with a solid content of 17.5% by mass. The content of each fatty acid in the fatty acid mixture is shown in Table 1.

[0072] Manufacturing Example 2 (Production of Salt 2 of Fatty Acid Mixture) In a 1L four-necked flask equipped with a stirrer and a raw material inlet, 446.75g of deionized water and 39.65g of 48% potassium hydroxide solution (manufactured by Kanto Chemical Co., Ltd.) were charged. Then, a fatty acid mixture consisting of 6.04g of Lunac L-98 (manufactured by Kao Corporation), 6.04g of Lunac MY-98 (manufactured by Kao Corporation), 43.75g of Lunac P-95 (manufactured by Kao Corporation), 26.25g of Lunac S-90V (manufactured by Kao Corporation), and 5.43g of Lunac OV (manufactured by Kao Corporation) was added. The mixture was heated to 75°C and stirred for 2 hours to obtain Salt 2 of the fatty acid mixture with a solid content of 17.5% by mass. The content of each fatty acid in the fatty acid mixture is shown in Table 1.

[0073] Manufacturing Example 3 (Production of Salt 3 of Fatty Acid Mixture) In a 1L four-necked flask equipped with a stirrer and a raw material inlet, 447.64g of deionized water and 40.74g of 48% potassium hydroxide solution (manufactured by Kanto Chemical Co., Ltd.) were charged. Then, a fatty acid mixture consisting of 11.46g of Lunac L-98 (manufactured by Kao Corporation), 11.55g of Lunac MY-98 (manufactured by Kao Corporation), 35.00g of Lunac P-95 (manufactured by Kao Corporation), 24.06g of Lunac S-90V (manufactured by Kao Corporation), and 5.43g of Lunac OV (manufactured by Kao Corporation) was added. The mixture was heated to 75°C and stirred for 2 hours to obtain salt 3 of the fatty acid mixture with a solid content of 17.5% by mass. The content of each fatty acid in the fatty acid mixture is shown in Table 1.

[0074] Comparative manufacturing example 1 (Production of fatty acid mixture salt C1) In a 1L four-necked flask equipped with a stirrer and a raw material inlet, 330.60g of deionized water and 27.60g of 48% potassium hydroxide solution (manufactured by Kanto Chemical Co., Ltd.) were charged. Then, 65.00g of DFA-T45 (manufactured by Miyoshi Oil & Fat Co., Ltd.) was added as a fatty acid mixture, the mixture was heated to 75°C, and stirred for 2 hours to obtain salt C1 of the fatty acid mixture with a solid content of 17.5% by mass. The content of each fatty acid in the fatty acid mixture is shown in Table 1.

[0075] Comparative manufacturing example 2 (Production of fatty acid mixture salt C2) In a 1L four-necked flask equipped with a stirrer and a raw material inlet, 445.87g of deionized water and 38.64g of 48% potassium hydroxide solution (manufactured by Kanto Chemical Co., Ltd.) were charged. Then, a fatty acid mixture consisting of 0.53g of Lunac L-98 (manufactured by Kao Corporation), 1.49g of Lunac MY-98 (manufactured by Kao Corporation), 52.94g of Lunac P-95 (manufactured by Kao Corporation), 11.81g of Lunac S-90V (manufactured by Kao Corporation), and 20.74g of oleic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) was added. The mixture was heated to 75°C and stirred for 2 hours to obtain salt C2 of the fatty acid mixture with a solid content of 17.5% by mass. The content of each fatty acid in the fatty acid mixture is shown in Table 1.

[0076] Comparative manufacturing example 3 (Production of fatty acid mixture salt C3) In a 500 mL four-necked flask equipped with a stirrer and a raw material inlet, 170.53 g of deionized water and 14.37 g of 48% potassium hydroxide solution (manufactured by Kanto Chemical Co., Ltd.) were charged. Then, a fatty acid mixture consisting of 33.50 g of purified stearic acid 450V (manufactured by Kao Corporation) was added, the mixture was heated to 75°C, and stirred for 2 hours to obtain salt C3 of the fatty acid mixture with a solid content of 17.5% by mass. The content of each fatty acid in the fatty acid mixture is shown in Table 1.

[0077] Comparative manufacturing example 4 (Production of fatty acid mixture salt C4) In a 1L four-necked flask equipped with a stirrer and a raw material inlet, 448.61g of deionized water and 41.81g of 48% potassium hydroxide solution (manufactured by Kanto Chemical Co., Ltd.) were charged. Then, a fatty acid mixture consisting of 16.45g of Lunac L-98 (manufactured by Kao Corporation), 17.50g of Lunac MY-98 (manufactured by Kao Corporation), 26.25g of Lunac P-95 (manufactured by Kao Corporation), 21.88g of Lunac S-90V (manufactured by Kao Corporation), and 5.43g of Lunac OV (manufactured by Kao Corporation) was added. The mixture was heated to 75°C and stirred for 2 hours to obtain salt C4 of the fatty acid mixture with a solid content of 17.5% by mass. The content of each fatty acid in the fatty acid mixture is shown in Table 1.

[0078] [Table 1]

[0079] [Manufacturing of rubbery latex] Example 1 (Manufacturing of rubbery latex 1) (Process 1) In a 1L four-necked flask equipped with a stirrer and a raw material inlet, 270.76g of deionized water, 0.21g of potassium persulfate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as a polymerization initiator, and 5.14g of fatty acid mixture salt 1 (0.90g as active ingredient) were mixed to obtain an aqueous solution with a pH of 11.0. 7.5g of butyl acrylate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added to the obtained aqueous solution, nitrogen purging was performed, and the temperature was raised to 80°C for 30 minutes to carry out emulsion polymerization. Subsequently, a mixed aqueous solution of fatty acid mixture salt 1 (3.75g as active ingredient), 0.09g of potassium persulfate, and 57.21g of deionized water, along with 142.5g of butyl acrylate, was added dropwise over 2 hours. After the dropwise addition was complete, the mixture was aged for another hour at 80°C. This was cooled to 30°C and filtered through a 200-mesh wire mesh to remove coarse particles, yielding a rubbery latex (solid content concentration 30.5% by mass) in which resin particles with an average particle size of 78 nm were dispersed.

[0080] (Process 2) 25 g of the rubbery latex produced in step 1 above was placed in a screw vial and stirred with a magnetic stirrer at 600 rpm. A 5% by mass aqueous acetic acid solution was gradually added dropwise to lower the pH to 4.5, and then a 10% by mass aqueous acetic acid solution was added dropwise to obtain a polymer emulsion solution with a pH of 4.0. After standing for 5 hours, aggregates were removed by filtration through a 200-mesh wire mesh to obtain rubbery latex 1 with an average particle size 2 of the dispersed phase growing to 216 nm.

[0081] Examples 2 and 3, and Comparative Examples 1-4 (Production of rubber latex 2 and 3, and rubber latex C1-C4) In Example 1, rubbery latex 2 and 3, and rubbery latex C1 to C4 were obtained in the same manner, except that salt 1 of the fatty acid mixture was the fatty acid mixture shown in Table 2. The average particle size 1 of the resin particles in the rubbery latex produced in step 1, the average particle size 2 of the resin particles in rubbery latex 2 and 3, and rubbery latex C1 to C4, produced in step 2, and the solid content concentration are shown in Table 2.

[0082] 〔evaluation〕 Polymerization stability, acid aggregation stability, and acid precipitation properties in the examples and comparative examples were evaluated by the following methods. The evaluation results are shown in Table 2.

[0083] (Polymerization stability) In step 1, the coarse particles removed by filtration through a 200-mesh wire mesh were washed with water and then dried under reduced pressure at 105°C for 2 hours. The dried coarse particles were weighed, and the ratio of coarse particles to the mass of butyl acrylate used as a raw material was used as an indicator for evaluating polymerization stability. The ratio of coarse particles to the mass of butyl acrylate used as a raw material is shown in Table 2. A lower ratio of coarse particles indicates better emulsion polymerization stability.

[0084] (Acid aggregation stability) In step 2, the aggregates removed by filtration through a 200-mesh wire mesh were washed with water and then dried under reduced pressure at 105°C for 2 hours. The dried coarse particles were weighed, and the ratio of aggregates to the mass of dispersed phase in the rubbery latex produced in step 1 was used as an indicator for evaluating acid agglomeration stability. A lower ratio of aggregates indicates better acid agglomeration stability.

[0085] (acid precipitation) A 1% hydrochloric acid aqueous solution was prepared by mixing 8.63 g of 1 mol / L hydrochloric acid aqueous solution (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) with 22.82 g of deionized water. The rubbery latex obtained in step 1 was added to this solution and shaken for 1 hour to precipitate the resin. The resin was washed with a large amount of deionized water and then dried at 80°C for 16 hours. The resin was weighed, and the recovery rate of the resin relative to the mass of the dispersed phase in the rubbery latex was used as an indicator for evaluating the acid precipitation property. A higher resin recovery rate indicates better acid precipitation property.

[0086] [Table 2]

[0087] Table 2 shows that the polymerization stability of the rubber latex manufacturing method in the example is comparable to that of the rubber latex manufacturing method in the comparative example. Furthermore, the average particle size 1 of the rubber latex in the example is also comparable to that of the rubber latex manufacturing method in the comparative example. Therefore, it can be concluded that the manufacturing method of the present invention exhibits comparable stability in emulsion polymerization compared to conventional rubber latex manufacturing methods. On the other hand, the acid agglomeration stability of the rubber latex production method of the example was superior to that of the rubber latex production method of Comparative Example 3, which used fatty acid mixture salt C3 with a high content of carboxylic acid (C) salt, and the acid agglomeration stability of the rubber latex production method of Comparative Example 4, which used fatty acid mixture salt C4 with a low content of carboxylic acid (B) salt. Furthermore, the acid precipitation properties of the rubber latex production method of the example were superior to those of the rubber latex production methods of Comparative Examples 1 to 3, which used fatty acid mixture salts C1 to C3 with a low content of carboxylic acid (A) salt.

Claims

1. A method for producing rubbery latex, comprising step 1 of emulsion polymerization of a monomer mixture (I) containing at least one diene monomer or a monomer mixture (II) containing at least one alkyl (meth)acrylate monomer, in the presence of a salt of a fatty acid mixture containing a salt of carboxylic acid (A), a salt of carboxylic acid (B), and a salt of carboxylic acid (C) as shown below, The total mass of fatty acids (A1) and (A2) / total mass of (B1) and (B2) / total mass of (C1) and (C2) shown below is 5-40 / 35-55 / 20-40. The carboxylic acid (A) consists of one or more saturated fatty acids selected from those having 12 carbon atoms (A1) and saturated fatty acids having 14 carbon atoms (A2). Carboxylic acid (B) consists of one or more selected from saturated fatty acids (B1) having 16 carbon atoms and unsaturated fatty acids (B2) having one double bond with 16 carbon atoms. The carboxylic acid (C) consists of one or more selected from saturated fatty acids (C1) having 18 carbon atoms and unsaturated fatty acids (C2) having one double bond with 18 carbon atoms. A method for manufacturing rubbery latex.

2. A method for producing a rubbery latex according to claim 1, wherein the mass ratio (A1 / A2) of the saturated fatty acid having 12 carbon atoms (A1) to the saturated fatty acid having 14 carbon atoms (A2) is 0 / 100 to 60 / 40.

3. A method for producing a rubbery latex according to claim 1, wherein the mass ratio (B1 / B2) of the saturated fatty acid having 16 carbon atoms (B1) and the unsaturated fatty acid having one double bond with 16 carbon atoms (B2) is 90 / 10 to 100 / 0.

4. A method for producing a rubbery latex according to claim 1, wherein the mass ratio (C1 / C2) of the saturated fatty acid having 18 carbon atoms (C1) and the unsaturated fatty acid having one double bond with 18 carbon atoms (C2) is 75 / 25 to 98 / 2.

5. The method for producing a rubbery latex according to claim 1, wherein the total content of the unsaturated fatty acid (B2) having one double bond with 16 carbon atoms and the unsaturated fatty acid (C2) having one double bond with 18 carbon atoms in the fatty acid mixture is 10% by mass or less.

6. A method for producing a rubbery latex according to claim 1, wherein the total content of carboxylic acid (A), carboxylic acid (B), and carboxylic acid (C) in the fatty acid mixture is 90% by mass or more and 100% by mass or less.

7. The method for producing a rubbery latex according to claim 1, wherein the salt is at least one selected from the group consisting of potassium salts, sodium salts, lithium salts, ammonium salts, and lower amine salts.

8. The method for producing a rubbery latex according to claim 1, wherein the amount of the salt of the fatty acid mixture per 100 parts by mass of the monomer mixture (I) or the monomer mixture (II) is 0.1 parts by mass or more and 5.0 parts by mass or less.

9. A method for producing rubbery latex according to claim 1, comprising a step 2 for increasing the particle size of the dispersed phase in the rubbery latex produced in step 1.

10. A method for producing a graft copolymer comprising step 3 of emulsion polymerization of a rubbery latex produced by the manufacturing method described in any one of claims 1 to 9, and a monomer mixture (III) containing an aromatic vinyl monomer and one or more selected from vinyl monomers having a cyano group and (meth)acrylate monomers, The emulsion polymerization described above is carried out in the presence of a salt of a fatty acid mixture containing a salt of carboxylic acid (A), a salt of carboxylic acid (B), and a salt of carboxylic acid (C) as shown below. The total mass of fatty acids (A1) and (A2) / total mass of (B1) and (B2) / total mass of (C1) and (C2) shown below is 5-40 / 35-55 / 20-40. The carboxylic acid (A) consists of one or more saturated fatty acids selected from those having 12 carbon atoms (A1) and saturated fatty acids having 14 carbon atoms (A2). Carboxylic acid (B) consists of one or more selected from saturated fatty acids (B1) having 16 carbon atoms and unsaturated fatty acids (B2) having one double bond with 16 carbon atoms. A method for producing a graft copolymer, wherein the carboxylic acid (C) is selected from one or more saturated fatty acids (C1) having 18 carbon atoms and unsaturated fatty acids (C2) having one double bond with 18 carbon atoms.

11. An emulsifier for emulsion polymerization comprising a salt of carboxylic acid (A), a salt of carboxylic acid (B), and a salt of carboxylic acid (C) as shown below, The total mass of the following fatty acids (A1) and (A2) / the total mass of (B1) and (B2) / the total mass of (C1) and (C2) is 5-40 / 35-55 / 20-40. The carboxylic acid (A) consists of one or more saturated fatty acids selected from those having 12 carbon atoms (A1) and saturated fatty acids having 14 carbon atoms (A2). Carboxylic acid (B) consists of one or more selected from saturated fatty acids (B1) having 16 carbon atoms and unsaturated fatty acids (B2) having one double bond with 16 carbon atoms. The carboxylic acid (C) is an emulsifier for emulsion polymerization, comprising one or more selected from saturated fatty acids (C1) having 18 carbon atoms and unsaturated fatty acids (C2) having one double bond with 18 carbon atoms.

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