Emulsion for reinforced fiber binder for FRP

Abstract

To provide an emulsion for reinforced fiber binder for FRP excellent in long-term storage stability and capable of obtaining a reinforced-fiber preform excellent in moldability.SOLUTION: An emulsion for a reinforced fiber binder for FRP, contains orthophthalic acid-based unsaturated polyester (A), bisphenol A-type epoxy (meth)acrylate (B), glycerin (C), and water, where a content of glycerin (C) is 2 to 10 pts.mass, with respect to a total of 100 pts.mass of orthophthalic acid-based unsaturated polyester (A) and bisphenol A-type epoxy (meth)acrylate (B).SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an emulsion for use as a binder for reinforcing fibers in FRP. [Background technology]

[0002] FRP (Fiber Reinforced Plastics) is used in a variety of molded products, including water tank panels, bathtubs, septic tanks, chairs, and helmets. Preform-matched die molding is one of the molding methods used to produce FRP products. In the preform-matched die molding method, a preform mat is obtained by preforming reinforcing fibers such as glass roving with a binder resin, and the preform mat is then set in a mold, charged with a thermosetting resin, and the mold is heated and pressurized to mold the FRP. As the thermosetting resin, radically polymerizable unsaturated polyester resin, epoxy (meth)acrylate resin, or the like is used, which is economical and has a fast molding cycle. The preform-matched die molding method is characterized by the fact that the preform mat follows the shape of the mold and has high compatibility with thermosetting resin, resulting in a high-strength FRP molded product with excellent appearance, but the selection of the preform mat is important. An example of a preform mat is one in which cut glass roving is sprayed with binder resin onto a preform screen of the mold shape and then heated and hardened. The binder resin used here is preferably an emulsion emulsified with water, due to its adhesion to glass and drying properties. In addition, it is preferable to select the thermosetting resin used in mold molding as the resin, in terms of compatibility with the thermosetting resin.

[0003] The following are examples of emulsions of thermosetting resins, which are used as reinforcing fiber binders for FRP: For example, Patent Document 1 discloses an epoxy (meth)acrylate resin emulsion composition for glass fiber binders used in FRP, which contains a prescribed amount of an epoxy (meth)acrylate resin, a high boiling point polymerizable monomer, a nonionic emulsifier, an anionic emulsifier, a curing agent, and water as a glass fiber binder that does not contain a low boiling point polymerizable monomer or a flammable solvent. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 05-271366 Summary of the Invention [Problem to be solved by the invention]

[0005] The reinforced fiber preform mat used in the preform matched die molding method must be flexible because it must conform to the shape of the mold to obtain a molded product with the desired shape and appearance. Although plasticizers such as phthalates are mixed into the binder resin to impart flexibility, there are safety issues with these, so there is a demand for binder resins and reinforced fiber preform mats that are flexible and have good moldability without using plasticizers. As described above, the binder resin is preferably used in the form of an emulsion in which the resin is emulsified in water, because of its adhesiveness to glass and drying property. However, since thermosetting resins are hydrophobic, there is a problem that the resin and water separate during long-term storage, and therefore an emulsion-type binder resin with excellent storage stability is required. Therefore, an object of the present invention is to provide an emulsion for a reinforcing fiber binder for FRP, which can give a reinforcing fiber preform having excellent long-term storage stability and excellent moldability. [Means for solving the problem]

[0006] The present inventors have found that the above problems can be solved by adding an orthophthalic acid-based unsaturated polyester, a bisphenol A-type epoxy (meth)acrylate, a specific amount of glycerin, and water to an emulsion for a reinforcing fiber binder. That is, the present invention relates to the following. [1] An emulsion for FRP reinforcing fiber binders, comprising an orthophthalic acid-based unsaturated polyester (A), a bisphenol A type epoxy (meth)acrylate (B), glycerin (C) and water, in which the content of glycerin (C) is 2 to 10 parts by mass per 100 parts by mass of the total of the content of the orthophthalic acid-based unsaturated polyester (A) and the content of the bisphenol A type epoxy (meth)acrylate (B). [2] The emulsion for FRP reinforcing fiber binder according to the above [1], wherein the mass ratio [(A) / (B)] of the orthophthalic acid-based unsaturated polyester (A) to the bisphenol A-type epoxy (meth)acrylate (B) is 50 / 50 to 97 / 3. [3] The emulsion for FRP reinforcing fiber binders according to the above [1] or [2], wherein the bisphenol A type epoxy (meth)acrylate (B) has a number average molecular weight of 500 to 1,500. [4] The emulsion for FRP reinforcing fiber binder according to any one of the above [1] to [3], wherein the mass ratio [(A) / (B)] of the orthophthalic acid-based unsaturated polyester (A) to the bisphenol A-type epoxy (meth)acrylate (B) is 70 / 30 to 96 / 4. [5] The emulsion for FRP reinforcing fiber binders according to any one of the above [1] to [4], further comprising a polymerizable monomer, the content of the polymerizable monomer being 10 to 40 parts by mass per 100 parts by mass of the total of the content of the orthophthalic acid-based unsaturated polyester (A) and the content of the bisphenol A-type epoxy (meth)acrylate (B). [6] The emulsion for FRP reinforcing fiber binders according to any one of the above [1] to [5], further comprising an emulsifier, the content of the emulsifier being 2 to 20 parts by mass per 100 parts by mass of the total content of the orthophthalic acid-based unsaturated polyester (A) and the bisphenol A-type epoxy (meth)acrylate (B). [7] A reinforcing fiber preform obtained by applying the emulsion for a reinforcing fiber binder for FRP according to any one of the above [1] to [6] onto reinforcing fibers and thermally curing the same. Effect of the Invention

[0007] According to the present invention, there is provided an emulsion for a reinforcing fiber binder for FRP, which can obtain a reinforcing fiber preform having excellent long-term storage stability and excellent moldability. Therefore, the emulsion is useful as a material for obtaining a molded product made of FRP, and is particularly useful as a material used in a preform-matched die molding method. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] [Emulsion for FRP reinforcing fiber binder] The emulsion for FRP reinforcing fiber binder of the present invention contains an orthophthalic acid-based unsaturated polyester (A), a bisphenol A-type epoxy (meth)acrylate (B), glycerin (C) and water, in which the content of glycerin (C) is 2 to 10 parts by mass per 100 parts by mass of the total content of the orthophthalic acid-based unsaturated polyester (A) and the bisphenol A-type epoxy (meth)acrylate (B). Here, "(meth)acrylate" means "methacrylate" and "acrylate". The emulsion for FRP reinforcing fiber binder of the present invention has excellent long-term storage stability and can give reinforcing fiber preforms with excellent moldability, and therefore the emulsion is useful as a material for obtaining FRP molded products, and is particularly useful as a material used in the preform matched die molding method. The reason why the emulsion for FRP reinforcing fiber binder of the present invention is able to exhibit the above-mentioned excellent effects is not clear, but is thought to be as follows. The emulsion for FRP reinforcing fiber binder of the present invention contains an orthophthalic acid-based unsaturated polyester and a bisphenol A-type epoxy (meth)acrylate. By selecting an orthophthalic acid-based unsaturated polyester, it is generally possible to impart moderate flexibility to the preform even if there is a reaction between molecules, and it is believed that the affinity with the thermosetting resin is high. By using an epoxy (meth)acrylate in combination with this, it is possible to increase the strength and hold the reinforcing fibers, thereby improving the moldability. Furthermore, it is believed that an appropriate amount of glycerin acts as a hydrophilic and safe plasticizer for the resin, thereby imparting further flexibility to the resin in the emulsion. This is believed to improve the moldability of the preform using the emulsion of the present invention. In addition, since it has a hydroxyl group, it also functions as an emulsion stabilizer, which is believed to contribute to improving storage stability.

[0009] The emulsion for FRP reinforcing fiber binder of the present invention contains, as resin components, an orthophthalic acid-based unsaturated polyester (A) (hereinafter also simply referred to as unsaturated polyester (A)) and a bisphenol A-type epoxy(meth)acrylate (B) (hereinafter also simply referred to as epoxy(meth)acrylate (B)). The mass ratio [(A) / (B)] of the unsaturated polyester (A) and the epoxy (meth)acrylate (B) contained in the emulsion for FRP reinforcing fiber binder of the present invention is preferably 40 / 60 to 97 / 3, more preferably 50 / 50 to 97 / 3, even more preferably 70 / 30 to 97 / 3, even more preferably 70 / 30 to 96 / 4, even more preferably 80 / 20 to 96 / 4, and even more preferably 80 / 20 to 95 / 5. By setting the mass ratio within the above range, it is possible to improve long-term storage stability. Furthermore, it is possible to impart flexibility to the preform, and to improve the moldability of the preform.

[0010] The total content of the unsaturated polyester (A) and the epoxy (meth)acrylate (B) contained in the emulsion for FRP reinforcing fiber binder of the present invention is preferably 20 to 60 mass %, more preferably 30 to 50 mass %, and even more preferably 35 to 45 mass %, based on the total amount of the emulsion for FRP reinforcing fiber binder.

[0011] The emulsion for FRP reinforcing fiber binder of the present invention may contain a resin component other than the unsaturated polyester (A) and the epoxy (meth)acrylate (B) within a range that does not impair the effects of the present invention. Examples of such a resin component include a urethane acrylate resin.

[0012] <Orthophthalic acid unsaturated polyester (A)> The orthophthalic acid-based unsaturated polyester (A) is not particularly limited as long as it is a polyester having a structure derived from orthophthalic acid and an unsaturated bond, but it preferably contains a constituent unit derived from a saturated dicarboxylic acid, a constituent unit derived from an unsaturated dicarboxylic acid, and a constituent unit derived from a diol, and more preferably consists essentially of a constituent unit derived from a saturated dicarboxylic acid, a constituent unit derived from an unsaturated dicarboxylic acid, and a constituent unit derived from a diol. The constituent units derived from saturated dicarboxylic acids include constituent units derived from orthophthalic acid.

[0013] The saturated dicarboxylic acid that gives the constituent units derived from the saturated dicarboxylic acid includes at least orthophthalic acid (phthalic anhydride). Since phthalic anhydride is an anhydride of orthophthalic acid, it is possible to obtain the constituent units derived from orthophthalic acid regardless of whether either is used as a raw material. The ratio (mol) of the orthophthalic acid-derived constituent units in the saturated dicarboxylic acid-derived constituent units is preferably 50 to 100 mol%, more preferably 60 to 100 mol%, even more preferably 80 to 100 mol%, and even more preferably 90 to 100 mol%, calculated based on the number of carboxy groups, and the saturated dicarboxylic acid-derived constituent units may be composed only of orthophthalic acid-derived constituent units. By including the orthophthalic acid-derived constituent units in the unsaturated polyester (A) in this way, it is possible to improve the long-term storage stability and the moldability of the preform.

[0014] The saturated dicarboxylic acid that gives a constituent unit derived from a saturated dicarboxylic acid other than orthophthalic acid (phthalic anhydride) is preferably at least one selected from the group consisting of an aromatic dicarboxylic acid, an alicyclic dicarboxylic acid, and an aliphatic dicarboxylic acid, and more preferably an aromatic dicarboxylic acid. Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, and 4,4'-biphenyldicarboxylic acid, and from the viewpoint of the balance between the availability of raw materials and the performance of the resulting unsaturated polyester, at least one selected from the group consisting of terephthalic acid and isophthalic acid is preferred. The aromatic dicarboxylic acid may be an anhydride. Examples of the alicyclic dicarboxylic acid include 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, and endomethylenetetrahydrophthalic anhydride. Examples of the aliphatic dicarboxylic acid include succinic acid, adipic acid, sebacic acid, azelaic acid, succinic acid substituted with an alkyl group having 16 to 18 carbon atoms, and dimer acid. The saturated dicarboxylic acids may be used alone or in combination of two or more kinds.

[0015] Examples of unsaturated dicarboxylic acids that provide structural units derived from unsaturated dicarboxylic acids include maleic acid, maleic anhydride, fumaric acid, itaconic acid, itaconic anhydride, citraconic acid, citraconic anhydride, etc., and are preferably at least one selected from the group consisting of maleic acid, maleic anhydride, and fumaric acid, more preferably at least one selected from the group consisting of maleic acid and maleic anhydride, and even more preferably maleic anhydride. The unsaturated dicarboxylic acids may be used alone or in combination of two or more kinds.

[0016] Examples of diols that provide diol-derived structural units include aliphatic diols, alicyclic diols, etherified diphenols, polyalkylene glycols, and the like, with aliphatic diols being preferred. Aliphatic diols include ethylene glycol, propylene glycol (1,2-propanediol), 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,4-butenediol, 2-methyl-1,3-propanediol, 1,5-pentanediol, neopentyl glycol, 2-ethyl-2-methylpropane-1,3-diol, 2-butyl -2-Ethylpropane-1,3-diol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 2-ethyl-1,3-hexanediol, 2,4-dimethyl-1,5-pentanediol, 2,2,4-trimethyl-1,3-pentanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 3-hydroxy-2,2-dimethylpropyl-3-hydroxypropyl Examples of the glycol esters include 2,2-dimethylpropanoate, diethylene glycol, triethylene glycol, and dipropylene glycol. Of these, at least one selected from the group consisting of ethylene glycol, 1,2-propanediol (propylene glycol), diethylene glycol, dipropylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, and 1,8-octanediol is preferred, at least one selected from the group consisting of ethylene glycol, 1,2-propanediol (propylene glycol), diethylene glycol, dipropylene glycol, and neopentyl glycol is more preferred, and at least one selected from the group consisting of 1,2-propanediol (propylene glycol) and diethylene glycol is even more preferred. The aliphatic diols may be used alone or in combination of two or more, and it is preferable to use two or more of them in combination.

[0017] Examples of the alicyclic diol include 1,4-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, hydrogenated bisphenol A, and hydrogenated bisphenol F. Examples of the etherified diphenol include bisphenol A ethylene oxide adduct and bisphenol A propylene oxide adduct. Examples of the polyalkylene glycol include polyethylene glycol, polyalkylene glycol, and polytetramethylene glycol. The diols may be used alone or in combination of two or more kinds.

[0018] The unsaturated polyester resin (A) may contain other structural units in addition to the structural units described above. Examples of components that provide other structural units include monocarboxylic acids, trivalent or higher polycarboxylic acids, monoalcohols, trivalent or higher polyhydric alcohols, and hydroxycarboxylic acids. As the carboxylic acid component (saturated dicarboxylic acid, unsaturated dicarboxylic acid, monocarboxylic acid, trivalent or higher polycarboxylic acid, hydroxycarboxylic acid), lower alkyl esters and anhydrides thereof may be used.

[0019] The molar ratio of the total of the carboxy groups of the carboxylic acid components (saturated dicarboxylic acids, unsaturated dicarboxylic acids, monocarboxylic acids, tri- or higher carboxylic acid polycarboxylic acids, hydroxycarboxylic acids) to the total of the hydroxyl groups of the alcohol components (diols, monoalcohols, tri- or higher carboxylic acid polyhydric alcohols, hydroxycarboxylic acids) [carboxy groups / hydroxyl groups] is preferably 0.9 / 1.1 to 1.1 / 0.9, and more preferably 0.95 / 1.05 to 1.05 / 0.95. The ratio (mol) of the constituent units derived from unsaturated dicarboxylic acids in the constituent units derived from the carboxylic acid components (saturated dicarboxylic acids, unsaturated dicarboxylic acids, monocarboxylic acids, trivalent or higher polycarboxylic acids, and hydroxycarboxylic acids) is preferably 30 to 60 mol %, more preferably 30 to 55 mol %, even more preferably 35 to 50 mol %, and still more preferably 35 to 45 mol %, calculated in terms of the number of carboxy groups. The ratio (mol) of the constitutional units derived from a diol in the constitutional units derived from the alcohol component (diol, monoalcohol, trihydric or higher polyhydric alcohol, hydroxycarboxylic acid) is preferably 50 to 100 mol%, more preferably 60 to 100 mol%, even more preferably 80 to 100 mol%, and still more preferably 90 to 100 mol%, calculated in terms of the number of hydroxyl groups, and the constitutional units derived from the alcohol component may be composed only of constitutional units derived from a diol.

[0020] The method for producing the unsaturated polyester resin (A) is not particularly limited, but it can be obtained by reacting the carboxylic acid component and the alcohol component described above. In this case, an esterification catalyst may be used. The esterification catalyst may be at least one metal compound selected from antimony, germanium, titanium, tin, zinc, aluminum, and manganese. The amount of the esterification catalyst added is preferably 0.01 to 1.5 mol% based on the saturated carboxylic acid component. In order to suppress the reaction of unsaturated bonds, a polymerization inhibitor may be added as necessary. Examples of the polymerization inhibitor include polyhydric phenol-based polymerization inhibitors such as hydroquinone, toluhydroquinone, trimethylhydroquinone, and tertiary butylcatechol, and quinone-based polymerization inhibitors such as parabenzoquinone and toluquinone. The amount of the polymerization inhibitor added is preferably 0.002 to 1.0 part by mass, and more preferably 0.005 to 0.3 part by mass, based on 100 parts by mass of the total amount of the carboxylic acid component and the alcohol component. The reaction temperature is preferably 150 to 280°C, and more preferably 160 to 250°C. The end point of the reaction can be judged based on the acid value of the reaction mixture, the amount of condensation water (alcohol when a lower alkyl ester is used as the raw material) generated, the viscosity of the resulting polyester, and the like.

[0021] <Bisphenol A type epoxy (meth)acrylate (B)> The bisphenol A type epoxy (meth)acrylate (B) is a polymer obtained by addition reaction of an epoxy resin containing a bisphenol A type epoxy resin with an unsaturated basic acid.

[0022] The epoxy resin includes at least a bisphenol A type epoxy resin. The ratio (mass) of the bisphenol A type epoxy resin in the epoxy resin is preferably 50 to 100 mass%, more preferably 60 to 100 mass%, even more preferably 80 to 100 mass%, and still more preferably 90 to 100 mass%, based on the total amount of the epoxy resin, and the epoxy resin may be composed only of a bisphenol A type epoxy resin. By including a bisphenol A type epoxy resin in the epoxy resin constituting the bisphenol A type epoxy (meth)acrylate (B) in this way, it is possible to improve the long-term storage stability and the moldability of the preform.

[0023] The epoxy resin other than the bisphenol A type epoxy resin is not particularly limited as long as it is an epoxy compound having at least two epoxy groups in one molecule, but is preferably at least one selected from the group consisting of bisphenol F type epoxy resin, novolac type epoxy resin, brominated epoxy resin, nitrogen-containing type epoxy resin, peracetic acid oxidized type epoxy resin, and glycol type epoxy resin, more preferably at least one selected from the group consisting of bisphenol F type epoxy resin, novolac type epoxy resin, and brominated epoxy resin, and even more preferably at least one selected from the group consisting of bisphenol F type epoxy resin and novolac type epoxy resin.

[0024] More specifically, the epoxy resin may be a glycidyl ether synthesized by reacting epichlorohydrin or methylepichlorohydrin with bisphenol A, bisphenol F or brominated bisphenol A; a polyglycidyl ether obtained by reacting a polynuclear phenol resin, such as phenol novolac or brominated novolac, with epichlorohydrin or methylepichlorohydrin; or a glycidyl ether obtained by reacting an ethylene oxide or propylene oxide adduct of bisphenol A or bisphenol F or hydrogenated bisphenol A with epichlorohydrin or methylepichlorohydrin.

[0025] The epoxy resin may contain, as an optional component, a diphenol compound such as bisphenol A, bisphenol F, bisphenol AF, bisphenol S, bisphenol fluorene, 1,5-naphthalenediol, or 1,4-naphthalenediol, or a dicarboxylic acid compound such as fumaric acid, adipic acid, isophthalic acid, terephthalic acid, or 2,6-naphthalenedicarboxylic acid. Specifically, the component is preferably bisphenol A, bisphenol F, fumaric acid, or adipic acid, and more preferably bisphenol A. By containing at least one selected from the group consisting of these diphenol compounds and dicarboxylic acid compounds as a component, the molecular weight of the epoxy resin can be increased, and the strength of the obtained molded product can be improved and durability can be imparted. The epoxy resins may be used alone or in combination of two or more kinds.

[0026] The unsaturated basic acid is not particularly limited, but is preferably at least one selected from the group consisting of acrylic acid, methacrylic acid, crotonic acid, cinnamic acid, sorbic acid, hydroxymethyl methacrylate maleate, hydroxyethyl acrylate maleate, hydroxypropyl methacrylate maleate, hydroxypropyl acrylate maleate, and dicyclopentadiene acrylate maleate, and more preferably at least one selected from the group consisting of acrylic acid and methacrylic acid. These may be used alone or in combination of two or more.

[0027] The method for producing the epoxy (meth)acrylate (B) is not particularly limited, but a method in which an epoxy resin is subjected to an addition reaction with an unsaturated basic acid is preferred, and the following methods are more preferred.

[0028] First, the epoxy resin and the unsaturated basic acid are mixed, and it is preferable to add a polymerization inhibitor and an esterification catalyst. The amount of the unsaturated basic acid used is preferably 0.9 to 1.2 chemical equivalents, more preferably 1.0 to 1.1 chemical equivalents, of the carboxyl group of the unsaturated basic acid relative to 1 chemical equivalent of the epoxy group of the epoxy resin. By using the unsaturated basic acid in the above range, the storage stability after the reaction becomes good, and the stability of the emulsion becomes good.

[0029] The polymerization inhibitor is not particularly limited, but examples thereof include phenols, organic and inorganic copper salts, amidines, hydrazine salts, quaternary ammonium salts, amines, nitro compounds, oximes, sulfur, and amine hydrochlorides, with phenols being preferred. The phenol is preferably at least one selected from the group consisting of monomethyl ether hydroquinone, toluhydroquinone, hydroquinone, and tertiary butyl hydroquinone, and more preferably at least one selected from the group consisting of monomethyl ether hydroquinone and toluhydroquinone. The amount of the polymerization inhibitor used is preferably 0.001 to 0.1 mass%, more preferably 0.01 to 0.07 mass%, even more preferably 0.01 to 0.06 mass%, and still more preferably 0.01 to 0.05 mass%, based on the total amount of the epoxy resin and the unsaturated basic acid.

[0030] The esterification catalyst is preferably at least one selected from the group consisting of a compound containing tertiary nitrogen, a phosphorus compound, an amine salt and an antimony compound, and more preferably a compound containing tertiary nitrogen. Examples of compounds containing tertiary nitrogen include triethylamine, pyridine derivatives, and imidazole derivatives, and imidazole derivatives are preferred. Among the imidazole derivatives, 2-methylimidazole is more preferred. Examples of the phosphorus compound include trimethylphosphine and triphenylphosphine. Examples of the amine salt include tetramethylammonium chloride and benzyltriethylamine chloride. Examples of the antimony compound include triphenylantimony and trimethylantimony. The amount of the esterification catalyst used is preferably 0.005 to 0.7 mass%, more preferably 0.01 to 0.6 mass%, even more preferably 0.05 to 0.5 mass%, and still more preferably 0.08 to 0.5 mass%, based on the total amount of the epoxy resin and the unsaturated basic acid.

[0031] The reaction temperature is preferably 100 to 160°C, more preferably 110 to 150°C, and further preferably 115 to 130°C. By the above method, the bisphenol A type epoxy (meth)acrylate (B) can be efficiently obtained.

[0032] The number average molecular weight of the epoxy (meth)acrylate (B) is preferably 400 to 2000, more preferably 500 to 1500, even more preferably 500 to 1000, and even more preferably 500 to 800. When the number average molecular weight of the epoxy (meth)acrylate (B) is within the above range, the long-term storage stability can be particularly improved, and the compatibility with the thermosetting resin used to obtain the molded product is also excellent. The number average molecular weight is a polystyrene-equivalent molecular weight measured by the GPC method. Specifically, GPC (gel permeation chromatography) measurement is performed under the following conditions, and the value can be calculated by relative comparison with a standard substance. Equipment: Shodex GPC101 Column: Shodex GPC KF-802, KF-803, KF-804, KF-805 Standard substances: styrene monomer and Shodex STANDARD SL-105, SM-105 (molecular weight range 104-662000) Temperature: 40℃ Free liquid: THF (tetrahydrofuran) Flow rate: 1.0mL / min Detector: RI (differential refractometer) Sample concentration: 1% by mass Injection volume: 200μL

[0033] <Glycerin (C)> The emulsion for FRP reinforcing fiber binder of the present invention contains glycerin (C), and the content of the glycerin (C) is 2 to 10 parts by mass per 100 parts by mass of the total content of the orthophthalic acid-based unsaturated polyester (A) and the bisphenol A-type epoxy (meth)acrylate (B). As mentioned above, although the reason is unclear, it is believed that the glycerin in the above content acts as a hydrophilic and safe plasticizer for the resin, thereby imparting flexibility to the resin in the emulsion and also functioning as an emulsion stabilizer. The content of glycerin (C) is 2 to 10 parts by mass, preferably 2 to 9 parts by mass, more preferably 2 to 8 parts by mass, even more preferably 2 to 6 parts by mass, and still more preferably 3 to 6 parts by mass, relative to 100 parts by mass of the total content of the orthophthalic acid-based unsaturated polyester (A) and the bisphenol A-type epoxy (meth)acrylate (B). By having the content of glycerin (C) within the above range, it is possible to improve the long-term storage stability and the moldability of the preform.

[0034] <Water> The emulsion for a reinforcing fiber binder for FRP of the present invention contains water. The water content is preferably 50 to 400 parts by mass, more preferably 80 to 300 parts by mass, even more preferably 80 to 200 parts by mass, and even more preferably 100 to 150 parts by mass, relative to 100 parts by mass of the total content of the orthophthalic acid-based unsaturated polyester (A) and the bisphenol A-type epoxy (meth)acrylate (B). By keeping the water content within the above range, it is possible to particularly improve long-term storage stability.

[0035] <Polymerizable monomer> The emulsion for FRP reinforcing fiber binder of the present invention preferably contains a polymerizable monomer as an optional component. The polymerizable monomer functions as a diluent and a solvent for the resin before curing, and as a crosslinked portion after curing, it can improve the strength and hardness of the resulting molded product. The polymerizable monomer is preferably at least one selected from the group consisting of a styrene-based monomer, a (meth)acrylic acid-based monomer, and a vinyl acetate-based monomer, more preferably at least one selected from the group consisting of a styrene-based monomer and a (meth)acrylic acid-based monomer, and even more preferably a styrene-based monomer. The styrene-based monomer is preferably at least one selected from the group consisting of styrene, vinyltoluene, and α-methylstyrene, and more preferably styrene. Examples of (meth)acrylic acid monomers include methyl methacrylate, methacrylic acid, acrylic acid, benzyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, glycidyl (meth)acrylate, hydroxypropyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, and norbornyl (meth)acrylate. Examples of the acrylate include acrylate, dicyclopentenyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, acrylic (meth)acrylate, 2-(meth)acryloyloxyethyl succinate, 2-(meth)acryloyloxyethyl maleate, 2-(meth)acryloyloxyethyl phthalate, 2-(meth)acryloyloxyethyl hexahydrophthalate, pentamethylpiperidyl (meth)acrylate, tetramethylpiperidyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, and diethylaminoethyl (meth)acrylate. The content of the polymerizable monomer is preferably 5 to 40 parts by mass, more preferably 10 to 40 parts by mass, even more preferably 20 to 30 parts by mass, and still more preferably 23 to 29 parts by mass, relative to 100 parts by mass of the total content of the orthophthalic acid-based unsaturated polyester (A) and the bisphenol A-type epoxy (meth)acrylate (B).

[0036] <Emulsifier> The emulsion for FRP reinforcing fiber binder of the present invention preferably contains an emulsifier as an optional component. The emulsifier is preferably a surfactant, more preferably at least one selected from the group consisting of nonionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants, still more preferably at least one selected from the group consisting of nonionic surfactants and anionic surfactants, and even more preferably a nonionic surfactant. In addition to the nonionic surfactant, an anionic surfactant is also used, and it is even more preferable to use the nonionic surfactant and the anionic surfactant in combination. Examples of the nonionic surfactant include polyoxyethylene alkyl ether, fatty acid sorbitan ester, alkyl polyglucoside, fatty acid diethanolamide, alkyl monoglyceryl ether, and the like. Examples of the anionic surfactant include sodium fatty acid, monoalkyl sulfate, alkyl polyoxyethylene sulfate, alkylbenzene sulfonate, monoalkyl phosphate, and the like. The content of the emulsifier is preferably 1 to 20 parts by mass, more preferably 2 to 20 parts by mass, still more preferably 5 to 15 parts by mass, and even more preferably 7 to 12 parts by mass with respect to a total of 100 parts by mass of the contents of the orthophthalic acid-based unsaturated polyester (A) and the bisphenol A type epoxy (meth) acrylate (B).

[0037] <Other components> The emulsion for the reinforcing fiber binder for FRP of the present invention may contain, as other components, a curing accelerator such as an organometallic compound or an amine compound, an air dryer such as waxes, a polymerization inhibitor, a chain transfer agent, a release agent, an antifoaming agent, a wetting regulator, a low shrinkage agent, a filler, a colorant, an organic solvent other than glycerin, etc., as long as the effects of the present invention are not impaired.

[0038] <Method for producing the emulsion for the reinforcing fiber binder for FRP> The method for producing the emulsion for FRP reinforcing fiber binder of the present invention is not particularly limited as long as it contains the orthophthalic acid-based unsaturated polyester (A), the bisphenol A-type epoxy (meth)acrylate (B), a predetermined amount of glycerin (C), and water, as described above. However, it is preferable to produce the emulsion by the method described below.

[0039] First, the orthophthalic acid-based unsaturated polyester (A), the bisphenol A-type epoxy (meth)acrylate (B), and glycerin (C) are mixed together to form a uniform solution or dispersion. It is preferable to add the polymerizable monomer at this stage, since the polymerizable monomer acts as a diluent during mixing, making it possible to obtain a more uniform solution. Also, a part of the polymerizable monomer may be mixed in advance with the orthophthalic acid-based unsaturated polyester (A) to form an unsaturated polyester solution. Furthermore, a part of the polymerizable monomer may be mixed in advance with the bisphenol A type epoxy(meth)acrylate (B) to form an epoxy(meth)acrylate solution. When an emulsifier is used, depending on the type of emulsifier, it may be added to water or to the above-mentioned solution or dispersion, but it is preferable to add it to the above-mentioned solution or dispersion and dissolve it.

[0040] Next, the above solution or dispersion is mixed with water to obtain an emulsion. Although there is no particular limitation on the method of mixing the above-mentioned solution with water, it is preferable to emulsify by gradually adding water to the above-mentioned solution. Since the resulting emulsion is a water-in-oil emulsion, it is preferable to carry out phase inversion emulsification. When mixing and emulsifying, a more stable emulsion can be obtained by using a dispersing / emulsifying machine such as a disperser, homomixer, or ultrasonic disperser.

[0041] [Reinforced fiber preform] The reinforcing fiber preform of the present invention is a reinforcing fiber preform obtained by applying the emulsion for reinforcing fiber binders for FRP onto reinforcing fibers and thermally curing the same. Therefore, the method for producing a reinforcing fiber preform of the present invention includes a step of applying the emulsion for a reinforcing fiber binder for FRP onto reinforcing fibers and thermally curing the emulsion.

[0042] The emulsion for FRP reinforcing fiber binder is applied onto reinforcing fibers, but in order to efficiently react the resin contained in the emulsion and use it as a binder for the reinforcing fibers, it is preferable to add a curing agent to the emulsion before application.

[0043] The curing agent used here is preferably a peroxide. The peroxides are not particularly limited, but are preferably at least one selected from the group consisting of ketone peroxides, diacyl peroxides, peroxy esters, hydroperoxides, peroxycarbonates, peroxyketals, and peroxy esters, and more preferably ketone peroxides. Examples of the ketone peroxide include methyl ethyl ketone peroxide and acetoacetate peroxide. Examples of the diacyl peroxide include t-butylperoxy-2-ethylhexanoate and benzoyl peroxide. Examples of the peroxy ester include t-butylperoxybenzoate and t-butylperoxy-2-ethylhexanoate. Examples of the hydroperoxide include cumene hydroperoxide. Examples of the peroxycarbonate include bis-(4-t-butylcyclohexyl)peroxycarbonate. Examples of the peroxyketal include 1,1-di-t-butylperoxy-3,3,5-trimethylcyclohexanone and 1,1-di-t-butylperoxycyclohexanone. Examples of the peroxy ester include t-butylperoxybenzoate and t-butylperoxy-2-ethylhexanoate. The amount of the curing agent added is preferably 1 to 10 mass %, more preferably 2 to 8 mass %, even more preferably 3 to 7 mass %, and still more preferably 3 to 6 mass %, based on the total amount of the orthophthalic acid-based unsaturated polyester (A) and the bisphenol A-type epoxy (meth)acrylate (B) contained in the emulsion for FRP reinforcing fiber binder.

[0044] In addition, the emulsion may be diluted with an aqueous solvent to adjust the applicability and viscosity when applied to the reinforcing fibers. There is no limitation on the aqueous solvent used, but water is preferred. The amount of water used for dilution can be appropriately adjusted depending on the viscosity of the emulsion, the time required for application, the size of the molded product, the amount of reinforcing fibers, etc. The amount of water used for dilution is preferably 1 to 10 times (mass), more preferably 2 to 8 times (mass), and even more preferably 2 to 6 times (mass) the total amount of the emulsion for FRP reinforcing fiber binder.

[0045] The reinforcing fibers are preferably applied onto the reinforcing fibers by scattering the reinforcing fibers onto a screen having the same shape as the mold for the molded product and simultaneously scattering the emulsion for FRP reinforcing fiber binder. The amount of the emulsion for FRP reinforcing fiber binder used is not particularly limited and may be appropriately adjusted depending on the shape of the target preform, the type of reinforcing fiber, etc., but is preferably 50 to 500 parts by mass, more preferably 80 to 300 parts by mass, and even more preferably 100 to 200 parts by mass, relative to 100 parts by mass of reinforcing fiber. When the amount of the emulsion for FRP reinforcing fiber binder used is within the above range, the reinforcing fiber can be firmly fixed to the shape of the preform, the preform has excellent moldability, and the obtained molded product has excellent appearance and strength. The amount of the diluted emulsion diluted with an aqueous solvent is not particularly limited and may be appropriately adjusted, but is preferably 100 to 1000 parts by mass, more preferably 200 to 700 parts by mass, and even more preferably 300 to 500 parts by mass, relative to 100 parts by mass of the reinforcing fibers. When the amount of the diluted emulsion is within the above range, it can be uniformly sprayed on the reinforcing fibers, so that the reinforcing fibers can be firmly fixed to the shape of the preform, and the preform has excellent moldability, and the appearance and strength of the obtained molded product are also excellent.

[0046] The reinforcing fibers are preferably glass fibers. The reinforcing fiber is preferably in the form of roving, and the roving is preferably cut and scattered on the screen. The reinforcing fiber may be used alone or in combination of two or more types having different numbers or properties. The reinforcing fibers scattered on the screen preferably have a length of 10 to 50 mm, and reinforcing fibers of different lengths may be used in combination. The amount of reinforcing fibers used is preferably 20 to 50% by mass, and more preferably 25 to 40% by mass, based on the final molded article obtained.

[0047] The conditions for heat curing may be adjusted appropriately depending on the type of curing agent used, but the curing temperature is preferably 80 to 200°C, and more preferably 100 to 180°C. In this manner, a mat-like reinforcing fiber preform having approximately the same shape as one surface of the molded article can be obtained.

[0048] <Production of molded products> A molded article can be produced by a production method including the steps of placing the reinforcing fiber preform in a mold, filling it with a thermosetting resin, and performing heat and pressure molding.

[0049] The thermosetting resin used in this method is not particularly limited, but it is preferable to use either unsaturated polyester or epoxy (meth)acrylate. These have a similar structure to the resin used as the raw material for the reinforced fiber preform, so they are highly compatible, have a unified appearance, and can produce molded products with excellent strength. It is preferable to add a hardener to thermosetting resin before filling a mold, in order to efficiently obtain a molded product by heating and pressurizing. In addition, other optional components can be added depending on the performance and appearance required for the molded article. Examples of other optional components include fillers, colorants, flame retardants, weather resistance agents, etc. A preferred filler is at least one selected from the group consisting of silica, aluminum hydroxide, and calcium carbonate, with calcium carbonate being more preferred.

[0050] The reinforcing fiber preform is placed in a mold. Since the reinforcing fibers in the reinforcing fiber preform are fixed with a binder obtained by using the emulsion for reinforcing fiber binder for FRP, the shape of the reinforcing fiber mat matches the mold, and the reinforcing fibers can be present throughout the entire molded product, resulting in a molded product with excellent appearance. Next, the reinforcing fiber preform is filled with a thermosetting resin and molded under heat and pressure. Since the reinforcing fibers in the reinforcing fiber preform are fixed with a binder obtained using the emulsion for reinforcing fiber binders for FRP, the reinforcing fibers are not scattered by pressure and a molded product with excellent strength can be obtained. The molded product obtained in the above manner has excellent appearance and strength, and can be made into molded products of various shapes such as water tank panels, bathtubs, septic tanks, chairs, helmets, etc., and can be suitably used for various applications. EXAMPLES

[0051] The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples. Measurements and evaluations in the examples were carried out by the following methods.

[0052] <Number average molecular weight of epoxy (meth)acrylate (B)> GPC (gel permeation chromatography) measurements were performed under the following conditions, and the values ​​were calculated by relative comparison with standard substances. Equipment: Shodex GPC101 (Showa Denko Co., Ltd.) Column: Shodex GPC KF-802, KF-803, KF-804, KF-805 (Showa Denko K.K.) Standard substances: styrene monomer and Shodex STANDARD SL-105, SM-105 (manufactured by Showa Denko K.K.) (molecular weight range 104 to 662,000) Temperature: 40℃ Free liquid: THF (tetrahydrofuran) Flow rate: 1.0mL / min Detector: RI (differential refractometer) Sample concentration: 1% by mass Injection volume: 200μL

[0053] <Acid value> Measurements were taken in accordance with JIS K 6901:2021.

[0054] <Storage stability test> 180 g of the emulsion for FRP reinforcing fiber binder obtained in the examples and comparative examples was placed in a glass bottle with a volume of 200 mL, sealed and left to stand at room temperature (25°C), and the presence or absence of separation of water was visually observed every day. The results were evaluated according to the following criteria. The slower the separation of water, the better the storage stability. Furthermore, those that do not separate water even after long-term storage have even better long-term storage stability. (Evaluation Criteria) ◎: Water did not separate even after 30 days or more ○: Water separated within 7 to 30 days △: Water separated within 1 to 7 days ×: Water separated in less than one day

[0055] <Reinforced fiber preform moldability test> The moldability was evaluated by the followability of the reinforced fiber preform obtained by the method described below to the mold when it was set in a mini bathtub mold having the same shape as the screen, and by the appearance of the FRP molded product obtained by the method described below. The results were evaluated according to the following criteria. The more the reinforced fiber preform conforms to the shape of the mold, the better the moldability. Note that when the reinforced fiber preform conforms to the shape of the mold, the appearance of the FRP molded product is excellent. (Evaluation criteria) ○: It completely conformed to the shape of the mold. There was no problem with the appearance of the FRP molded product. △: There were parts that did not conform to the shape of the mold, but there was no problem with the appearance of the FRP molded product, and no creases were observed. ×: There were parts that did not conform to the shape of the mold, and creases were observed in the appearance of the FRP molded product.

[0056] <FRP molding test (FRP flexural strength, glass content)> Test pieces were cut out from the bottom of the FRP molded product (mini bathtub) obtained by the method described below, and a flexural test was conducted in accordance with JIS K 7171. After the flexural test, the resin content of the test pieces was fired in a combustion furnace at 590 °C, and calcium carbonate was separated with dilute hydrochloric acid to calculate the glass content (mass%) of the test pieces. The higher the numerical value of the flexural strength obtained in the flexural test, the better the strength of the molded product. The more the glass content, the more the glass fibers of the preform are maintained in the mold during molding, which is preferable. It is considered that when the glass content is low, the glass fibers of the preform dissipate outside the mold due to the pressure during molding.

[0057] [Manufacture of orthophthalic acid-based unsaturated polyester (A)] Production Example 1 A flask equipped with a stirrer, a packed tower, a thermometer, and a gas inlet tube was charged with 408 g (2.8 mol) of phthalic anhydride, 212 g (2.2 mol) of maleic anhydride, 255 g (3.4 mol) of 1,2-propylene glycol, and 213 g (2.0 mol) of diethylene glycol, and the mixture was heated under a nitrogen stream with stirring, and reacted while removing condensed water from the system at a tower top temperature of 100° C., and the liquid temperature was raised to 215° C. over 4 hours. Next, the packed tower was replaced with a cooling tube, and the mixture was reacted at 215° C. for another 4 hours while removing condensed water from the system, to obtain an orthophthalic acid-based unsaturated polyester (A-1) with an acid value of 15 mgKOH / g.

[0058] [Production of bisphenol A type epoxy (meth)acrylate (B)] Manufacturing Example 2 In a flask equipped with a stirrer, a cooling tube, a thermometer and a gas inlet tube, 678g (3.6eq.) of bisphenol A type epoxy resin with an epoxy equivalent of 189g / eq., 317g (3.7eq.) of methacrylic acid with a carboxy group equivalent of 86g / eq., 4.0g of 2-methylimidazole and 2.0g of monomethyl ether hydroquinone were charged, and the mixture was reacted at 120°C for 4 hours with stirring while blowing in air, to obtain bisphenol A type epoxy methacrylate (B-1) with an acid value of 9mgKOH / g and a number average molecular weight of 550.

[0059] Production Example 3 In a flask equipped with a stirrer, a cooling tube, a thermometer and a gas inlet tube, 660g (3.5eq.) of bisphenol A type epoxy resin with an epoxy equivalent of 188g / eq., 219g (1.9eq.) of bisphenol A, and 0.4g of triethylamine were charged, and the mixture was reacted at 150°C for 1 hour while blowing in air and stirring to obtain bisphenol A type epoxy resin with an epoxy equivalent of 550g / eq. (1.6eq.). The mixture was then cooled to 100°C, and 119g (1.7eq.) of acrylic acid with a carboxyl group equivalent of 72g / eq., 2.0g of 2-methylimidazole, and 0.4g of toluhydroquinone were added, and the mixture was reacted at 120°C for 5 hours while stirring to obtain bisphenol A type epoxy acrylate (B-2) with an acid value of 5mgKOH / g and a number average molecular weight of 1244.

[0060] [Production of emulsion for FRP reinforcing fiber binder] Example 1 Orthophthalic acid-based unsaturated polyester (A-1) obtained in Production Example 1, bisphenol A-type epoxy methacrylate (B-1) obtained in Production Example 2, and glycerin were mixed in the mass ratio shown in Table 1, and stirred to form a homogeneous liquid. Next, styrene, emulsifier A ("Noigen EA-207D", nonionic surfactant, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) and emulsifier C ("DKS NL-30", nonionic surfactant, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) were added in the mass ratio shown in Table 1, and stirred to form a homogeneous liquid. Next, water was gradually added using a Monodisper disperser to emulsify, and water was finally added in the mass ratio shown in Table 1 to obtain an emulsion for FRP reinforcing fiber binder. The evaluation results of the obtained emulsion are shown in Table 1.

[0061] Examples 2 to 5 and Comparative Examples 1 to 3 An emulsion for FRP reinforcing fiber binder was obtained in the same manner as in Example 1, except that the types and amounts of raw materials in Example 1 were changed to those shown in Table 1. The evaluation results of the obtained emulsion are shown in Table 1. The emulsifiers, which are raw materials, shown in Table 1 are as follows. Emulsifier A ("Noigen EA-207D", non-ionic surfactant, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) Emulsifier B ("Hitenol NF-13", anionic surfactant, POE alkyl ether sulfate, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) Emulsifier C ("DKS NL-30", non-ionic surfactant, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) Emulsifier D ("Neogen S-20F", anionic surfactant, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)

[0062] [Manufacturing of reinforced fiber preforms] The emulsion for FRP reinforcing fiber binder obtained in the examples and comparative examples was diluted with twice the amount (mass) of water, and 5 parts by mass (based on the total mass of the orthophthalic acid-based unsaturated polyester (A) and the bisphenol A-type epoxy (meth)acrylate (B) being 100 parts by mass) of organic peroxide "Permec N" (manufactured by NOF Corporation) was added to prepare a binder emulsion for preform production. Next, roving "RS240F562" (glass fiber, manufactured by Nitto Boseki Co., Ltd.) was cut to a length of 25 mm, and while being spread on a mini bathtub-shaped screen for testing, the binder emulsion was sprayed onto it, and the binder emulsion was heated for 5 minutes in a hot air dryer at 150 ° C. to volatilize the moisture and form a reinforcing fiber preform. The amount of the binder emulsion used was about 300 to 500 parts by mass per 100 parts by mass of roving, as a result of spraying the emulsion so as to sufficiently cover the roving.

[0063] [Manufacturing of FRP molded products] The obtained reinforcing fiber preform was set in a mini bathtub mold having the same shape as the screen. Next, 0.5 parts by mass of organic peroxide "Niper FF" (NOF Corporation) was dissolved in 100 parts by mass of epoxy acrylate resin "Neopor 8250H" (Japan U-Pica Co., Ltd.), and 50 parts by mass of calcium carbonate was added to prepare a compound. The obtained compound was placed on the preform set in the mold, and the mixture was heated at 150°C and compressed at 10 kgf / cm. 2 The mixture was pressed at 400° C. for 5 minutes to form a mini bathtub for testing as an FRP molded product. The evaluation results of the obtained reinforcing fiber preforms and molded articles are shown in Table 1. In Comparative Example 3, the preform did not come together and glass fibers were significantly scattered, so that an FRP molded product was not obtained and the FRP bending strength and glass content could not be evaluated.

[0064] [Table 1]

[0065] From Table 1, it can be seen that the emulsions for FRP reinforcing fiber binders of the examples are stable and do not separate even when stored for a long period of time. In addition, the obtained preforms can follow the shape of the mold, and there is no occurrence of creases or loss of glass fiber, so it can be seen that the moldability is good. The obtained molded products have excellent strength. The emulsions for FRP reinforcing fiber binders of the present invention are useful as materials for obtaining molded products made of FRP, and are particularly useful as materials used in the preform-matched die molding method.

Claims

1. An emulsion for FRP reinforcing fiber binders, comprising an orthophthalic acid-based unsaturated polyester (A), a bisphenol A type epoxy (meth)acrylate (B), glycerin (C) and water, wherein the content of the glycerin (C) is 2 to 10 parts by mass per 100 parts by mass of the total content of the orthophthalic acid-based unsaturated polyester (A) and the bisphenol A type epoxy (meth)acrylate (B).

2. 2. The emulsion for FRP reinforcing fiber binders according to claim 1, wherein the mass ratio [(A) / (B)] of the orthophthalic acid-based unsaturated polyester (A) to the bisphenol A-type epoxy (meth)acrylate (B) is 50 / 50 to 97 / 3.

3. 2. The emulsion for FRP reinforcing fiber binders according to claim 1, wherein the bisphenol A type epoxy (meth)acrylate (B) has a number average molecular weight of 500 to 1,500.

4. 2. The emulsion for FRP reinforcing fiber binders according to claim 1, wherein the mass ratio [(A) / (B)] of the orthophthalic acid-based unsaturated polyester (A) to the bisphenol A-type epoxy (meth)acrylate (B) is 70 / 30 to 96 / 4.

5. 2. The emulsion for FRP reinforcing fiber binders according to claim 1, further comprising a polymerizable monomer, the content of the polymerizable monomer being 10 to 40 parts by mass per 100 parts by mass of the total of the content of the orthophthalic acid-based unsaturated polyester (A) and the content of the bisphenol A-type epoxy (meth)acrylate (B).

6. The emulsion for FRP reinforcing fiber binders according to claim 1, further comprising an emulsifier, the content of the emulsifier being 2 to 20 parts by mass per 100 parts by mass of the total content of the orthophthalic acid-based unsaturated polyester (A) and the bisphenol A-type epoxy (meth)acrylate (B).

7. A reinforcing fiber preform obtained by applying the emulsion for a reinforcing fiber binder for FRP according to any one of claims 1 to 6 onto reinforcing fibers and thermally curing the same.

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