Fiber sizing agent, fiber material, molding compound and molded part

Abstract

Fiber sizing agents, including: a vinyl ester resin (A) with an alkoxypolyoxyalkylene structure and a urethane bond; an epoxy compound (B); and an aqueous medium.

Description

Technical area

[0001] The present invention relates to a fiber sizing agent suitable for bonding fibers together, as well as to a fiber material, a molding compound and a molded part. State of the art

[0002] Fiber-reinforced plastics containing a matrix resin, such as an epoxy resin or a vinyl ester resin (epoxy acrylate), and a glass fiber, a carbon fiber or the like, are used in automobile parts, aircraft parts and the like, which must have high strength and excellent durability.

[0003] In many cases, the glass fiber or carbon fiber used in fiber-reinforced plastics is typically a fiber material containing several thousand to several tens of thousands of fibers bonded together by a fiber sizing agent. One purpose of using such a material is to achieve high strength.

[0004] A well-known example of a fiber sizing agent is one containing an aliphatic epoxy compound and a compound containing a terminal unsaturated group and a polar group in one molecule (see, for example, PTL 1). Unfortunately, problems arose in that the fiber sizing agent lacked sufficient bonding ability for carbon fibers, and molded parts produced from a molding compound using carbon fibers treated with the fiber sizing agent lacked sufficient strength. Citation listPatent literature

[0005] PTL 1: Japanese unexamined patent application JP 2015 - 7 300 A Summary of the inventionTechnical problem

[0006] An object of the present invention is to provide a fiber sizing agent that exhibits excellent fiber bonding ability and enables the production of a molded article having various excellent physical properties. Examples of the physical properties include flexural strength, compressive strength, and interlaminar shear strength. Another object of the present invention is to provide a fiber material, a molding compound, and a molded article produced therefrom. Solution to the Problem

[0007] The present inventors conducted studies to achieve the above-described objectives and discovered that the objectives can be achieved with a fiber sizing agent containing a vinyl ester resin, an epoxy compound, and an aqueous medium, wherein the vinyl ester resin has a specific structure. Accordingly, the present invention has been completed.

[0008] In particular, the present invention relates to a fiber sizing agent containing a vinyl ester resin (A), an epoxy compound (B), and an aqueous medium. The vinyl ester resin (A) has an alkoxypolyoxyalkylene structure and a urethane bond. Advantageous effects of the invention

[0009] The fiber sizing agent of the present invention can be used to produce a fiber material that can impart excellent strength to a molded part, and the fiber sizing agent has excellent fiber bonding ability. Therefore, the fiber sizing agent is suitable for use as a sizing agent for glass fibers, carbon fibers, and the like. Description of Embodiments

[0010] A fiber sizing agent of the present invention contains a vinyl ester resin (A), an epoxy compound (B), and an aqueous medium. The vinyl ester resin (A) has an alkoxypolyoxyalkylene structure and a urethane bond.

[0011] The vinyl ester resin (A) is described. The vinyl ester resin (A) has an alkoxypolyoxyalkylene structure, and the alkoxypolyoxyalkylene structure is a structure in which one end of the polyoxyalkylene chain is capped with an alkoxy group.

[0012] Examples of the polyoxyalkylene chain include polyoxyethylene chains, polyoxypropylene chains and polyoxybutylene chains, and also include those in which two or more of the above-mentioned chains are arranged in a block or random manner.

[0013] Examples of the alkoxy group capping one end of the polyoxyalkylene chain include methoxy groups, ethoxy groups, propoxy groups, and butoxy groups.

[0014] The alkoxypolyoxyalkylene structure may be one containing oxyethylene unit structures in the structure in an amount of more than or equal to 35 mass%. This is preferred because in such a case, water dispersibility is further improved.

[0015] In addition, the alkoxypolyoxyalkylene structure may be one having a number-average molecular weight of 300 to 7000. This is preferred because, in such a case, water dispersibility is further improved.

[0016] The alkoxypolyoxyalkylene structure may be present in an amount of 3 to 60 mass% in the vinyl ester resin (A). This is preferred because water dispersibility is further improved in such a case. More preferably, the alkoxypolyoxyalkylene structure may be present in an amount ranging from 10 to 55 mass%.

[0017] The vinyl ester resin (A) contains a (meth)acryloyl group at one of its ends. The (meth)acryloyl equivalent weight of the vinyl ester resin (A) may be in the range of 500 to 3000 g / eq. This is preferred because in such a case, the bonding ability is improved and a molded article with higher strength can be obtained. More preferably, the (meth)acryloyl equivalent weight may be in the range of 800 to 200 g / eq.

[0018] In the present invention, “(meth)acryloyl” refers to one or both of “acryloyl” and “methacryloyl”; “(meth)acrylic acid” refers to one or both of “acrylic acid” and “methacrylic acid”; “(meth)acrylate” refers to one or both of “acrylate” and “methacrylate”; and “acid (anhydride)” refers to one or both of “acid” and “acid anhydride”.

[0019] Furthermore, the vinyl ester resin (A) may have a structure derived from a bisphenol A epoxy resin. This is preferred because in such a case, the bonding ability is improved and a molded article with higher strength can be obtained.

[0020] The vinyl ester resin (A) can be obtained, for example, by reacting a urethane resin (a1) having an alkoxypolyoxyalkylene structure and an epoxy group with (meth)acrylic acid and / or (meth)acrylic anhydride (a2).

[0021] Preferably, the reaction between the epoxy group of the urethane resin (a1) and the (meth)acrylic acid and / or the (meth)acrylic anhydride (a2) is carried out at a temperature of 60 to 140°C using an esterification catalyst. Furthermore, a polymerization inhibitor and / or the like may be used.

[0022] The urethane resin (a1) has an epoxy group, and the epoxy equivalent weight of the urethane resin (a1) may be in the range of 250 to 2000 g / eq. This is preferred because in such a case, the bonding ability is improved and a molded part with higher strength can be obtained.

[0023] The urethane resin (a1) can be prepared, for example, by reacting a compound (a1-1), a polyisocyanate (a1-2), and a polyoxyalkylene monoalkyl ether (a1-3), wherein the compound (a1-1) has an epoxy group and a hydroxy group, in the absence of a solvent or in the presence of an organic solvent according to a method known in the art; if necessary, a polyol (a1-4) other than the compound (a1-1) and a chain extender (a1-5) can be reacted together. In particular, it is preferable that the reaction be carried out at a reaction temperature of 50 to 120°C for 1 to 15 hours to ensure safety.

[0024] The compound (a1-1) having an epoxy group and a hydroxy group may be, for example, a hydroxy group-containing epoxy resin.

[0025] Examples of the epoxy resin include bisphenol A epoxy resins, bisphenol F epoxy resins, phenol novolak epoxy resins, ethylphenol novolak epoxy resins, butylphenol novolak epoxy resins, octylphenol novolak epoxy resins, cresol novolak epoxy resins, such as ortho-cresol novolak epoxy resins, resorcinol novolak epoxy resins, bisphenol A novolak epoxy resins, bisphenol F novolak epoxy resins, bisphenol AD ​​novolak epoxy resins, and bisphenol S novolak epoxy resins. The epoxy resin can be a phenol novolak epoxy resin, a cresol novolak epoxy resin, or a bisphenol A epoxy resin. This is preferred because in such a case, the bonding ability is improved and a molded part with higher strength can be obtained. More preferably, the epoxy resin can be a bisphenol A epoxy resin. Note that these epoxy resins can be used alone or in a combination of two or more.

[0026] Preferably, the compound (a1-1) can be a hydroxyl group-containing phenol novolak epoxy resin, a hydroxyl group-containing cresol novolak epoxy resin, or a hydroxyl group-containing bisphenol A epoxy resin. Among them, a hydroxyl group-containing bisphenol A epoxy resin is preferred because this resin improves bonding ability and can produce a molded part with higher strength.

[0027] Preferably, the compound (a1-1) may be a compound having an epoxy equivalent weight of 150 to 2000 g / eq., more preferably a compound having an epoxy equivalent weight of 150 to 900 g / eq., and even more preferably a compound having an epoxy equivalent weight of 150 to 500 g / eq.

[0028] The hydroxy groups of compound (a1-1) may be present in an amount ranging from 5 to 150 mol%, based on the total number of moles of the epoxy groups of the urethane resin (A). This is preferred because, in such a case, the bonding ability is improved and a molded article with higher strength can be obtained. More preferably, the hydroxy groups may be present in an amount ranging from 5 to 130 mol%, and even more preferably in an amount ranging from 5 to 120 mol%.

[0029] Examples of the polyisocyanate (a1-2) include aromatic polyisocyanates such as 1,3- and 1,4-phenylene diisocyanate, 1-methyl-2,4-phenylene diisocyanate (2,4-TDI), 1-methyl-2,6-phenylene diisocyanate (2,6-TDI), 1-methyl-2,5-phenylene diisocyanate, 1-methyl-2,6-phenylene diisocyanate, 1-methyl-3,5-phenylene diisocyanate, 1-ethyl-2,4-phenylene diisocyanate, 1-isopropyl-2,4-phenylene diisocyanate, 1,3-dimethyl-2,4-phenylene diisocyanate, 1,3-dimethyl-4,6-phenylene diisocyanate, 1,4-dimethyl-2,5-phenylene diisocyanate, diethylbenzene diisocyanate, diisopropylbenzene diisocyanate, 1-methyl-3,5-diethylbenzene diisocyanate, 3-methyl-1,5-diethylbenzene-2,4-diisocyanate, 1,3,5-triethylbenzene-2,4-diisocyanate, naphthalene-1,4-diisocyanate, naphthalene-1,5-diisocyanate, 1-methyl-naphthalene-1,5-diisocyanate, naphthalene-2,6-diisocyanate, Naphthalene-2,7-diisocyanate, 1,1-dinaphthyl-2,2'-diisocyanate, biphenyl-2,4'-diisocyanate, biphenyl-4,4'-diisocyanate, 3-3'-dimethyl-biphenyl-4,4'-diisocyanate, diphenylmethane-4,4'-diisocyanate, diphenylmethane-2,2'-diisocyanate and diphenylmethane-2,4-diisocyanate; aliphatic polyisocyanates such as tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate (HDI), dodecamethylene diisocyanate, trimethylhexamethylene diisocyanate and lysine diisocyanate; alicyclic polyisocyanates such as 1,3-cyclopentylene diisocyanate, 1,3-cyclohexylene diisocyanate, 1,4-cyclohexylene diisocyanate, 1,3-di(isocyanatomethyl)cyclohexane, 1,4-di(isocyanatomethyl)cyclohexane, isophorone diisocyanate (IPDI), 4,4'-dicyclohexylmethane diisocyanate, 2,4'-dicyclohexylmethane diisocyanate, 2,2'-dicyclohexylmethane diisocyanate and 3,3'-dimethyl-4,4'-dicyclohexylmethane diisocyanate; and trimers of any of the aforementioned polyisocyanates.

[0030] The polyoxyalkylene monoalkyl ether (a1-3) is one represented by the following general formula (1).

[0031] In the formula, R 1 an alkylene group, R 2 is an alkylene group, and n is an integer greater than or equal to 1.

[0032] As for the polyoxyalkylene monoalkyl ether (a1-3), R 1 in the general formula (1) may be a methyl group, an ethyl group, a propyl group, or a butyl group. This is preferred because in such a case, the storage stability is further improved. More preferably, R 1 be a methyl group.

[0033] Furthermore, R 2 in the general formula (1) may be an ethylene group or a propylene group. This is preferred because in such a case, the storage stability and fiber binding capacity are further improved. More preferably, R 2 be an ethylene group.

[0034] Furthermore, n in general formula (1) can be an integer from 5 to 150. This is preferable because in such a case, the storage stability, fiber bonding ability, and strength of a resulting molded article are further improved. More preferably, n can be an integer from 5 to 100.

[0035] Furthermore, the polyoxyalkylene monoalkyl ether (a1-3) may be one having a hydroxyl number in the range of 10 to 200. This is preferred because in such a case, storage stability is further improved. More preferably, the hydroxyl number is in the range of 15 to 200.

[0036] The polyoxyalkylene monoalkyl ether (a1-3) can be a polyoxyethylene monoalkyl ether. This is particularly preferred because in such a case, storage stability and fiber bonding capacity are further improved. The polyoxyalkylene monoalkyl ether (a1-3) can particularly preferably be a polyoxyethylene monomethyl ether.

[0037] Examples of the polyol (a1-4) include polyether polyols, polycarbonate polyols, polyester polyols, ethylene glycol, 1,2-propanediol, 1,3-butanediol, 1,4-butanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, diethylene glycol, dipropylene glycol, glycerin, trimethylolpropane, acrylic polyols in which hydroxy groups are introduced into an acrylic copolymer, polybutadiene polyols which are copolymers of butadiene and have hydroxy groups in a molecule, hydrogenated polybutadiene polyols and partially saponified products of an ethylene-vinyl acetate copolymer.

[0038] Examples of the polyether polyols include polyols obtained by addition polymerization of an alkylene oxide with one or more compounds having two or more active hydrogen atoms used as initiators.

[0039] Other examples of polycarbonate polyols include polyols obtained by reacting a carbonic acid ester with a polyol; and polyols obtained by reacting phosgene with bisphenol A or the like.

[0040] Furthermore, examples of the polyester polyols include polyester polyols obtained by subjecting a low-molecular-weight polyol and a polycarboxylic acid to an esterification reaction; polyesters obtained by subjecting a cyclic ester compound such as ε-caprolactone or γ-butyrolactone to a ring-opening polymerization reaction; and copolymerized polyesters containing either of these substances.

[0041] The polyether polyols, the polycarbonate polyols and the aliphatic polyester polyols may preferably be those having a number average molecular weight of 300 to 4000 and more preferably those having a number average molecular weight of 500 to 2000.

[0042] The chain extender (a1-5) can be, for example, a polyamine or another compound with active hydrogen atoms.

[0043] Examples of the polyamine include diamines such as ethylenediamine, 1,2-propanediamine, 1,6-hexamethylenediamine, piperazine, 2,5-dimethylpiperazine, isophoronediamine, 4,4'-dicyclohexylmethanediamine, 3,3'-dimethyl-4,4'-dicyclohexylmethanediamine, and 1,4-cyclohexanediamine; N-hydroxymethylaminoethylamine, N-hydroxyethylaminoethylamine, N-hydroxypropylaminopropylamine, N-ethylaminoethylamine, N-methylaminopropylamine; diethylenetriamine, dipropylenetriamine, triethylenetetramine; hydrazine, N,N'-dimethylhydrazine, 1,6-hexamethylenebishydrazine; succinic dihydrazide, adipic dihydrazide, glutaric dihydrazide, sebacic dihydrazide, isophthalic dihydrazide; β-Semicarbazide propionic acid hydrazide, 3-semicarbazide propylcarbazate and semicarbazide 3-semicarbazide methyl-3,5,5-trimethylcyclohexane.

[0044] Examples of the various compounds containing active hydrogen include glycol compounds such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, hexamethylene glycol, sucrose, methylene glycol, glycerin, and sorbitol; phenolic compounds such as bisphenol A, 4,4'-dihydroxydiphenyl, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxydiphenyl sulfone, hydrogenated bisphenol A, and hydroquinone; and water.

[0045] Preferably, the chain extender (a1-5) can be used, for example, in a range in which an equivalent ratio between the amino groups of a polyamine and excess isocyanate groups is less than or equal to 1.9 (equivalence ratio), and more preferably in a range in which the equivalent ratio is 0.3 to 1.0 (equivalence ratio).

[0046] The urethanization reaction can be carried out in the absence of a catalyst or in the presence of a known catalyst. Examples include tin compounds such as tin octoate, dibutyltin dilaurate, dibutyltin dimaleate, dibutyltin diphthalate, dibutyltin dimethoxide, dibutyltin diacetyl acetate, and dibutyltin diversate; titanate compounds such as tetrabutyl titanate, tetraisopropyl titanate, and triethanolamine titanate; tertiary amine compounds; and quaternary ammonium salts.

[0047] With regard to the epoxy compound (B), examples thereof include glycidyl ethers of phenols, examples of which are bisphenol-type epoxy resins such as bisphenol A epoxy resins, bisphenol F epoxy resins, bisphenol-fluorene epoxy resins, and biscresol-fluorene epoxy resins; novolak-type epoxy resins such as phenol-novolak epoxy resins and cresol-novolak epoxy resins; oxazolidone-modified epoxy resins and brominated epoxy resins of any of the above resins; glycidyl ethers of polyhydric alcohols such as dipropylene glycol diglycidyl ether, trimethylolpropane triglycidyl ether, diglycidyl ethers of alkylene oxide adducts of bisphenol A, and diglycidyl ethers of hydrogenated bisphenol A; cycloaliphatic epoxy resins, such as 3,4-epoxy-6-methylcyclohexylmethyl-3,4-epoxy-6-methylcyclohexanecarboxylate and 1-epoxyethyl-3,4-epoxycyclohexane; glycidyl esters, such as diglycidyl phthalate, diglycidyl tetrahydrophthalate, diglycidyl-p-hydroxybenzoic acid and glycidyl dimer; glycidylamines,such as tetraglycidyldiaminodiphenylmethane, tetraglycidyl-m-xylenediamine, triglycidyl-p-aminophenol, and N,N-diglycidylaniline; and heterocyclic epoxy resins such as 1,3-diglycidyl-5,5-dimethylhydantoin and triglycidyl isocyanurate. One or more modified products of one of these epoxy compounds can be used. Such products can be obtained by a variety of modification methods. Examples of such products include epoxy compounds having an alkoxypolyoxyalkylene structure and epoxy compounds having an alkoxypolyoxyalkylene structure and a urethane bond. Among such products, aromatic epoxy compounds containing an aromatic ring are preferred. This is because aromatic epoxy compounds can be easily coemulsified with the vinyl ester resin (A), have a higher affinity (compatibility) with a molding compound, and improve the handleability of a molding compound.Improve the flowability of a molding compound during molding and the strength of a molded part. It should be noted that these epoxy compounds can be used alone or in a combination of two or more.

[0048] The mass ratio (A:B) between the vinyl ester resin (A) and the epoxy compound (B) can be in a range of 95:5 to 40:60. This is preferred because in such a case, the strength of a resulting molded article is further increased. More preferably, the mass ratio (A:B) can be in a range of 90:10 to 60:40.

[0049] The aqueous medium may be water, a water-miscible organic solvent, or a mixture thereof. Examples of the water-miscible organic solvent include alcohol compounds such as methanol, ethanol, and isopropanol; ketone compounds such as acetone and methyl ethyl ketone; polyalkylene glycol compounds such as ethylene glycol, diethylene glycol, and propylene glycol; alkyl ether compounds of polyalkylene glycol; and lactam compounds such as N-methyl-2-pyrrolidone. In the present invention, water alone, a mixture of water and a water-miscible organic solvent, or a water-miscible organic solvent alone may be used. From the viewpoint of safety and environmental compatibility, it is preferable to use water alone or a mixture of water and a water-miscible organic solvent. It is particularly preferable to use only water.

[0050] The fiber sizing agent of the present invention comprises the vinyl ester resin (A), the epoxy compound (B), and the aqueous medium. Preferably, the fiber sizing agent is an aqueous dispersion in which the vinyl ester resin (A) and the epoxy compound (B) are dispersed in the aqueous medium.

[0051] The fiber sizing agent of the present invention can be obtained, for example, by mixing and stirring a mixed solution of the vinyl ester resin (A) and the epoxy compound (B) with an emulsifier, then mixing with the aqueous medium and optionally removing an organic solvent.

[0052] Examples of the emulsifier include polyoxyalkylene alkyl ethers, polyoxyalkylene phenyl ethers, polyoxyalkylene alkylphenyl ethers, polyoxyalkylene benzylphenyl ethers, polyoxyalkylene styrylphenyl ethers, polyoxyalkylene cumylphenyl ethers, polyoxyalkylene naphthylphenyl ethers, polyoxyalkylene fatty acid esters, polyoxyethylene-polyoxypropylene block copolymers, and polyethylene glycol. Among them, polyoxyalkylene alkyl ethers, polyoxyalkylene styrylphenyl ethers, and polyoxyethylene-polyoxypropylene block copolymers are preferred because with each of them, the strength of a resulting molded article is further increased; polyoxyalkylene alkyl ethers and polyoxyalkylene styrylphenyl ethers are more preferred. These emulsifiers can be used alone or in a combination of two or more.

[0053] Examples of the polyoxyalkylene alkyl ethers include polyoxyethylene alkyl ethers such as polyoxyethylene hexyl ether, polyoxyethylene octyl ether, polyoxyethylene nonyl ether, polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, and polyoxyethylene icosyl ether; and alkyl ethers of a polyoxyethylene-polyoxypropylene copolymer such as hexyl ether of a polyoxyethylene-polyoxypropylene copolymer, octyl ether of a polyoxyethylene-polyoxypropylene copolymer, nonyl ether of a polyoxyethylene-polyoxypropylene copolymer, lauryl ether of a polyoxyethylene-polyoxypropylene copolymer, stearyl ether of a polyoxyethylene-polyoxypropylene copolymer, and eicosyl ether of a polyoxyethylene-polyoxypropylene copolymer. Among these, ethers having an alkyl group having 8 to 18 carbon atoms, ie, polyoxyethylene octyl ether, polyoxyethylene nonyl ether, polyoxyethylene lauryl ether, polyoxyethylene stearyl ether and the like are particularly preferred because with each of them an emulsifying property is improved.These polyoxyalkylene alkyl ethers can be used alone or in a combination of two or more.

[0054] Examples of polyoxyalkylene styrylphenyl ethers include polyoxyethylene styrylphenyl ethers with 1 to 3 mol of styrene added, such as polyoxyethylene monostyrylphenyl ether, polyoxyethylene distyrylphenyl ether, and polyoxyethylene tristyrylphenyl ether, and styrylphenyl ethers of a polyoxyethylene-polyoxypropylene copolymer with 1 to 3 mol of styrene added. Polyoxyethylene styrylphenyl ethers with 1 to 3 mol of styrene added are preferred because an emulsifying property is enhanced with each of them. These polyoxyalkylene styryl ethers can be used alone or in a combination of two or more.

[0055] The polyoxyethylene-polyoxypropylene block copolymers may be those having an average molecular weight in the range of 1,000 to 30,000. This is preferred because, in such a case, the emulsifying property is improved. More preferably, the polyoxyethylene-polyoxypropylene copolymer may be one having an average molecular weight in the range of 5,000 to 20,000. Further, a content of the polyoxyethylene may preferably be in a range of 40 to 90 mass%, and more preferably in a range of 50 to 80 mass%.

[0056] In the fiber sizing agent of the present invention, the mass fraction of the aqueous medium may be in a range of 10 to 98 mass%. This is preferred because in such a case, storage stability and runnability are further improved. More preferably, the mass fraction may be in a range of 20 to 90 mass%.

[0057] In the fiber sizing agent of the present invention, the mass fraction of the solid may be in a range of 2 to 80 mass%. This is preferred because in such a case, storage stability and runnability are further improved. More preferably, the mass fraction may be in a range of 10 to 70 mass%.

[0058] Furthermore, the fiber sizing agent of the present invention can be used, if necessary, in combination with one or more additives such as a silane coupling agent, a curing catalyst, a lubricant, a filler, a thixotropic agent, a tackifier, a wax, a heat stabilizer, a light stabilizer, a fluorescent brightener, and a foaming agent, and / or in combination with one or more of the following: a pH adjuster, a leveling agent, an anti-gelling agent, a dispersion stabilizer, an antioxidant, a radical scavenger, a heat-resistant agent, an inorganic filler, an organic filler, a plasticizer, a reinforcing agent, a catalyst, an antimicrobial agent, an antifungal agent, a corrosion inhibitor, a thermoplastic resin, a thermosetting resin, a pigment, a dye, a conductive agent,an antistatic agent, a moisture permeability-improving agent, a water-repellent agent, an oil-repellent agent, a hollow foam, a water-containing compound, a flame retardant, a water-absorbing agent, a moisture-absorbing agent, a deodorant, a foam-stabilizing agent, a defoaming agent, an antibacterial agent, a preservative, an algae inhibitor, a pigment dispersant, an antiblocking agent, and a hydrolysis inhibitor.

[0059] Particularly in cases where the fiber sizing agent of the present invention is used as a sizing agent for glass fibers, it is preferable that a silane coupling agent is used in combination to further increase the adhesive strength of the sizing agent with respect to the glass fibers.

[0060] Examples of the silane coupling agent include γ-(2-aminoethyl)aminopropyltrimethoxysilane, γ-(2-hydroxyethyl)aminopropyltrimethoxysilane, γ-(2-aminoethyl)aminopropyltriethoxysilane, γ-(2-hydroxyethyl)aminopropyltriethoxysilane, γ-(2-aminoethyl)aminopropylmethyldimethoxysilane, aminopropylmethyldimethoxysilane, γ-(2-aminoethyl)aminopropylmethyldiethoxysilane, γ-(2-hydroxyethyl)aminopropylmethyldimethoxysilane, γ-(2-hydroxyethyl)aminopropylmethyldiethoxysilane, γ-(N,N-di-2-hydroxyethyl)aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-aminopropylmethyldimethoxysilane, γ-aminopropylmethyldiethoxysilane, γ-(N-phenyl)aminopropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane and γ-mercaptophenyltrimethoxysilane.

[0061] Preferably, the silane coupling agent may be used in an amount ranging from 1 to 30 parts by mass per 100 parts by mass of the total resin components of the fiber sizing agent.

[0062] Furthermore, the fiber sizing agent of the present invention can be used in combination with, for example, an emulsion, a latex, a water-soluble resin, and / or the like. The emulsion may be a vinyl acetate-based emulsion, an ethylene-vinyl acetate-based emulsion, an acrylic-based emulsion, an epoxy-based emulsion, a urethane-based emulsion, a polyester-based emulsion, a polyamide-based emulsion, or the like. The latex may be a styrene-butadiene-based latex, an acrylonitrile-butadiene-based latex, an acrylobutadiene-based latex, or the like. The water-soluble resin may be polyvinyl acetate, cellulose, or the like.

[0063] The fiber sizing agent of the present invention can be used for bonding and / or surface treatment of fibers to prevent, for example, fiber breakage, wear, and the like of glass fibers, carbon fibers, and the like.

[0064] Examples of fiber materials that can be treated with the fiber sizing agent of the present invention include glass fibers, carbon fibers, silicon carbide fibers, cellulose fibers, hemp fibers, cotton fibers, nylon fibers, polyester fibers, acrylic fibers, polyurethane fibers, polyimide fibers, and polyamide fibers made of an aramid material such as Kevlar or Nomex. Among these, glass fibers and carbon fibers are preferred because these fibers have high strength.

[0065] Examples of glass fibers that can be treated with the fiber sizing agent include fibers made of materials such as alkali-containing glass, low-alkali glass, or alkali-free glass. In particular, alkali-free glass (E-glass), which exhibits low susceptibility to aging degradation and stable mechanical properties, is preferred.

[0066] In addition, the carbon fibers that can be treated with the fiber sizing agent generally include carbon fibers such as polyacrylonitrile-based fibers and pitch-based fibers. In particular, the carbon fibers can be polyacrylonitrile-based carbon fibers; this is preferred in view of providing excellent strength.

[0067] Furthermore, the carbon fibers may have a single fiber diameter of 0.5 to 20 µm. This is preferred for even higher strength and the like. More preferred are carbon fibers with a single fiber diameter of 2 to 15 µm.

[0068] Examples of carbon fibers include those produced by a twisting process, those produced by a combination process, those produced by a spinning process, and those produced by a nonwoven process. Furthermore, the carbon fibers may be in any of the following forms: filaments, yarn, roving, spun yarn, short spun yarn, felt, needle-punched fabric, cloth, roving fabric, milled fiber, and the like.

[0069] A method for forming a bundle of glass fibers or carbon fibers using the fiber sizing agent of the present invention to form a coating on a surface of the glass fiber bundle or the carbon fiber bundle may be, for example, as follows: The fiber sizing agent is uniformly applied to the surface of the fibers using a known method, examples of which include a kiss coating method, a rolling method, a dipping method, a spraying method, and a brushing method. In cases where the fiber sizing agent contains an aqueous medium and / or an organic solvent as a solvent, it is preferable that heat drying be performed after application using a heated roller, a hot air stream, a hot plate, or the like.

[0070] A coating amount of the coating formed on the surface of the fibers is preferably 0.1 to 5 mass%, and more preferably 0.3 to 1.5 mass%, based on a total mass of the fiber bundle which is in the form of a bundle and surface-treated.

[0071] A fiber material of the present invention produced by the above-described method, which is in the form of a bundle and is surface-treated, can be used in combination with a matrix resin and the like described below to form a molding material for producing a molded article having high strength.

[0072] In cases where a molded article or the like is formed by using the fiber material of the present invention in combination with a matrix resin, the adhesion at the interface between the fiber and the matrix resin is significantly improved. Therefore, the fiber material can increase the strength of a molded article.

[0073] Examples of the matrix resin that can be used in a molding composition of the present invention include thermosetting resins and thermoplastic resins. Examples of thermosetting resins include phenolic resins, polyimide resins, bismaleimide resins, unsaturated polyester resins, epoxy resins, vinyl ester resins, and vinyl urethane resins. Examples of thermoplastic resins include saturated polyester resins such as polyethylene terephthalate and polybutylene terephthalate, polypropylene, polystyrene, polycarbonate, polyphenylene sulfide, polyphenylene oxide, polyamide resins such as 6-nylon and 6,6-nylon, acrylonitrile-styrene copolymers, acrylonitrile-butadiene-styrene copolymers, polyacetal, polyetherimide, and polyetheretherketone.

[0074] The matrix resin can be a thermosetting resin. This is preferred because a thermosetting resin can produce a molded part with higher strength. More preferably, the matrix resin can be a vinyl ester resin or an unsaturated polyester resin.

[0075] The molding compound of the present invention comprises the fiber material and the matrix resin, and optionally contains a polymerizable monomer and / or the like. A molded part with higher strength can be obtained, for example, by a variety of molding methods, such as hand lay-up methods, spray-on methods, FRP lining methods, resin transfer molding (RTM) methods, resin injection molding (RI) methods, vacuum-assisted resin transfer molding (VARTM) methods, infusion molding methods, compression molding methods, autoclave molding methods, filament winding methods, and pultrusion molding methods. For molding, a material in the form of a prepreg or a sheet molding compound (SMC), for example, can be used.

[0076] The prepreg can be produced, for example, by applying the matrix resin to a release paper, placing the surface-treated fiber material on the coated surface, and, if necessary, pressing and impregnating it with a roller or similar.

[0077] In the production of the prepreg, an epoxy resin, a vinyl ester resin, or similar is preferably used as the matrix resin. The epoxy resin can be a bisphenol A epoxy resin, a glycidylamine epoxy resin such as tetraglycidylaminodiphenylmethane, a novolac-type epoxy resin, or similar.

[0078] Furthermore, the film molding compound can be produced, for example, by sufficiently impregnating the surface-treated fiber material with a mixture of the matrix resin and a polymerizable unsaturated monomer, such as styrene, and then processing it, for example, into a film. In the production of the film molding compound, an unsaturated polyester resin, a vinyl ester resin, or the like is preferably used as the matrix resin.

[0079] Curing of the molding compound can be achieved, for example, by initiating radical polymerization through heating or light irradiation under high or normal pressure. In this case, a known thermal curing agent or photocuring agent can also be used.

[0080] Further examples of the molding compound include those obtained, for example, by kneading a thermoplastic resin and the surface-treated fiber material together under heat. Such molding compounds can be subjected to post-processing, such as injection molding or similar.

[0081] Furthermore, the prepreg containing a thermoplastic resin can be produced, for example, by layering the surface-treated fiber material and then impregnating the thermoplastic resin that has been melted into the fiber material.

[0082] For example, one or more prepregs containing a thermoplastic resin can be stacked and then subjected to secondary processing, which may include heating and molding under high or normal pressure.

[0083] The molded parts produced with the molding compound have a high strength and can therefore be used in, for example, automobile parts, aircraft parts, windmill parts, industrial parts, etc. Examples

[0084] The present invention will now be described in more detail with reference to Examples. Note that the average molecular weight of the resins was measured under the GPC measurement conditions described below. [GPC measurement conditions] Instrument: High-performance GPC instrument (HLC-8220GPC, manufactured by Tosoh Corporation) Columns: The following columns, manufactured by Tosoh Corporation, were connected in series and used. TSKgel G5000 (7.8mm ID×30cm)×1 TSKgel G4000 (7.8mm ID×30cm)×1 TSKgel G3000 (7.8mm ID×30cm)×1 TSKgel G2000 (7.8mm ID×30cm)×1 Detector: RI (Differential Refractometer) Column temperature: 40°C Eluent: Tetrahydrofuran (THF) Flow rate: 1.0 mL / min Injection volume: 100µL (a tetrahydrofuran solution with a sample concentration of 4 mg / mL) Standard: A standard curve was prepared using the following monodisperse polystyrene. (Monodisperse polystyrene) TSKgel standard polystyrene A-500, manufactured by Tosoh Corporation TSKgel standard polystyrene A-1000, manufactured by Tosoh Corporation TSKgel standard polystyrene A-2500, manufactured by Tosoh Corporation TSKgel standard polystyrene A-5000, manufactured by Tosoh Corporation TSKgel Standard Polystyrene F-1, manufactured by Tosoh Corporation TSKgel Standard Polystyrene F-2, manufactured by Tosoh Corporation TSKgel standard polystyrene F-4, manufactured by Tosoh Corporation TSKgel standard polystyrene F-10, manufactured by Tosoh Corporation TSKgel standard polystyrene F-20, manufactured by Tosoh Corporation TSKgel standard polystyrene F-40, manufactured by Tosoh Corporation TSKgel standard polystyrene F-80, manufactured by Tosoh Corporation TSKgel standard polystyrene F-128, manufactured by Tosoh Corporation TSKgel standard polystyrene F-288, manufactured by Tosoh Corporation TSKgel standard polystyrene F-550, manufactured by Tosoh Corporation (Synthesis Example 1: Synthesis of the epoxy compound (B-1))

[0085] 124 parts by mass of polyethylene glycol (moles of added ethylene oxide: 12), 45 parts by mass of polyoxyethylene monomethyl ether (moles of added ethylene oxide: 12), and 179 parts by mass of methyl ethyl ketone were placed in a four-necked flask equipped with a thermometer, a stirrer, a reflux condenser, and a dropping funnel, and dissolution was performed. Subsequently, 100 parts by mass of diphenylmethane diisocyanate (Millionate MT, manufactured by Tosoh Corporation) was added and allowed to react at 80°C for 2 hours. Thereafter, 150 parts by mass of a bisphenol A epoxy resin (Epiclon 1050, manufactured by DIC Corporation, epoxy equivalent weight: 477 g / eq.) containing hydroxy groups was added, and further reaction was allowed to proceed.The disappearance of the isocyanate groups in the reaction solution was confirmed by an infrared absorption spectrum, and accordingly, a solution (solid content: 70%, and an epoxy equivalent weight: 1360 g / eq) of an aromatic epoxy compound having a methoxypolyoxyethylene structure and an epoxy group was obtained. The epoxy compound had a weight-average molecular weight of 12,000. To the solution, 40 parts by mass of a nonionic emulsifier (polyoxyethylene (70 mol) styrenated (5 mol) cumylphenol (mass ratio: 90:10) was added, and the contents were thoroughly stirred. Thereafter, 1360 parts by mass of ion-exchanged water was added dropwise over 30 minutes, and the contents were mixed with stirring for another 15 minutes. The aqueous dispersion was concentrated by distillation under reduced pressure, and accordingly, an aqueous dispersion (solid content: 30%) of an epoxy compound (B-1) was obtained. (Synthesis Example 2: Synthesis of Vinyl Ester Resin (X))

[0086] 620 parts by mass of a phenol novolak epoxy resin (Epiclone N-740-80M, manufactured by DIC Corporation, an epoxy equivalent weight of solids: 180 g / eq., and active ingredients: 80%), 205 parts by mass of acrylic acid, 1 part by mass of t-butylhydroquinone, and 10 parts by mass of 2-methylimidazole were placed in a four-necked flask equipped with a thermometer, a stirrer, a reflux condenser, and a dropping funnel, and stirred thoroughly at 40°C to dissolve. The solution was then heated to a temperature of 75 to 80°C under a gas stream in which nitrogen and air were mixed in a 1:1 ratio. The reaction was allowed to proceed at a temperature of 75 to 80°C for 10 hours to achieve an acid value of 1 or less (mg KOH / g). The reaction was then stopped and accordingly a vinyl ester resin (X) was obtained. (Example 1: Preparation and evaluation of the fiber sizing agent (1))

[0087] 124 parts by mass of polyoxyethylene monoethyl ether (Uniox M-550, manufactured by NOF Corporation, hydroxyl value: 100), 99 parts by mass of a bisphenol A epoxy resin (Epiclon 1050, manufactured by DIC Corporation, epoxy equivalent weight: 477 g / eq.), and 65 parts by mass of methyl ethyl ketone were placed in a four-necked flask equipped with a thermometer, a stirrer, a reflux condenser, and a dropping funnel, and stirred thoroughly at 40°C to dissolve. Thereafter, 38 parts by mass of tolylene diisocyanate were added at 40°C and allowed to react at a temperature of 60 to 65°C for 6 hours. The disappearance of the 2260 cm peak characteristic of NCO -1was confirmed by an infrared absorption spectrum. Subsequently, the solution was cooled to 40°C, and then 15 parts by mass of acrylic acid, 1 part by mass of t-butylhydroquinone, and 3 parts by mass of 2-methylimidazole were added. The contents were then heated to a temperature of 75 to 80°C under a gas stream in which nitrogen and air were mixed in a 1:1 ratio. The reaction was allowed to proceed for 10 hours at a temperature of 75 to 80°C so that an acid value of 1 or less (mg KOH / g) was achieved. The reaction was then stopped, and accordingly, a solution of a vinyl ester resin (A-1) was obtained. The vinyl ester resin (A-1) had a weight-average molecular weight of 13,000.

[0088] Thereafter, the solution was cooled to 40°C, and then 465 mass parts of an aqueous dispersion of the epoxy compound (B-1) obtained in Synthesis Example 1 and 27 mass parts of polyoxyethylene distyrenated phenyl ether (Emulgen A-500, manufactured by Kao Corporation) were added. The contents were then thoroughly stirred. Thereafter, 1000 mass parts of ion-exchanged water were added dropwise over 30 minutes, and the contents were mixed with stirring for a further 15 minutes. The aqueous dispersion was concentrated by distillation under reduced pressure, and accordingly, a fiber sizing agent (1) was obtained, which was an aqueous dispersion with a nonvolatile content of 30 mass%. [Manufacturing the carbon fiber bundle]

[0089] Unsized polyacrylonitrile-based carbon fibers (single fiber diameter: 7 µm, strand strength: 4400 MPa, elastic modulus: 235 GPa, number of single fibers: 6000) were assembled and immersed in an aliquot of the fiber sizing agent (1) diluted with ion-exchanged water to a non-volatile content of 5 mass%. The resulting mass was rolled with a roller to adjust the coating amount of the active agent to 1 mass%. The resulting mass was then heat-treated at 150°C for 30 minutes. Accordingly, a carbon fiber bundle (1) surface-treated with the fiber sizing agent (1) was obtained. [Evaluation of fiber binding capacity]

[0090] On a TM-200 abrasion tester (manufactured by Daiei Kagaku Seiki Mfg. Co., Ltd.), the carbon fiber bundle (1) was rubbed 1000 times against three stainless steel pins with a mirror-chrome finish arranged in a zigzag configuration at a tension of 50 g (reciprocating speed: 300 times / minute). The degree of wear of the carbon fiber bundle (1) was visually assessed according to the following criteria. A: No wear was observed, it was as before rubbing. B: Wear was observed in some fibers, but the degree of wear was not significant for practical application. C: Wear and fiber breakage were observed in some areas. D: Wear and individual fiber breaks were observed in numerous areas. [Manufacturing of carbon fiber fabric]

[0091] Made of a carbon fiber fabric (sized (surface-treated) carbon fiber fabric based on polyacrylonitrile, textile weight: 200 g / m 2 A fabric measuring approximately 300 mm × 300 mm was cut from a carbon fiber (single fiber diameter: 7 µm, strand strength: 4400 MPa, and elastic modulus: 235 GPa). At room temperature, the fabric was immersed in acetone, which had a mass of approximately 30 parts by mass per part by mass of the fabric, and allowed to stand for 12 hours. After immersion, the fabric was dried in a dryer at 80°C for 2 hours to remove the resin component and the like adhering to the surface of the carbon fiber. Thus, an unsized (unsurface-treated) carbon fiber fabric was obtained.

[0092] The carbon fiber fabric was impregnated with an aliquot of the fiber sizing agent (1) diluted with ion-exchanged water to have a non-volatile content of 5 mass%, such that the coating amount of the solids became 1 mass%. The resultant was dried in a dryer at 150°C for 30 minutes, and a carbon fiber fabric (1) was obtained. [Production of the molded part]

[0093] A mixture was prepared by mixing 0.5 mass parts of cobalt naphthenate (6 mass%) and 1.0 mass parts of methyl ethyl ketone peroxide (Permek N, manufactured by NOF Corporation) with 100 mass parts of a vinyl ester resin solution (Exdhoma 9102-01NP, manufactured by DIC Material Inc.). The mixture was applied to a release-treated glass plate measuring 350 mm × 350 mm, and the carbon fiber fabric (1) obtained as above was placed thereon. Accordingly, a laminate was prepared by hand lay-up (8 layers). The laminate was then cured at room temperature (25°C) for 12 hours and then further cured at 60°C for 3 hours. Accordingly, a carbon fiber reinforced plastic molded part (1) (carbon fiber content: 50 vol%) was obtained. [Evaluation of the flexural strength of molded parts]

[0094] A measurement according to JIS K 7181 was performed on the molded part (1) obtained as described above. The test specimen used had dimensions of 15 mm × 100 mm × 2 mm (width × length × thickness). [Evaluation of compressive strength of molded part]

[0095] A measurement according to JIS K 7074 was performed on the molded part (1) obtained as described above. The dumbbell specimen used had dimensions of 13 mm × 77 mm × 2 mm (width × length × thickness). [Evaluation of the interlaminar shear strength of molded parts]

[0096] A measurement according to JIS K 7078 was performed on the molded part (1) obtained as described above. The test specimen used had dimensions of 10 mm × 15 mm × 2 mm width × length × thickness. (Example 2: Preparation and evaluation of the fiber sizing agent (2))

[0097] 81 parts by mass of polyethylene glycol (moles of added ethylene oxide: 12), 30 parts by mass of polyoxyethylene monoethyl ether (Uniox M-550, manufactured by NOF Corporation, hydroxyl value: 100), and 64 parts by mass of methyl ethyl ketone were placed in a four-necked flask equipped with a thermometer, a stirrer, a reflux condenser, and a dropping funnel, and stirred thoroughly at 40°C to dissolve. Then, 47 parts by mass of tolylene diisocyanate were added at 40°C and allowed to react at 75°C for 2 hours. Then, 97 parts by mass of a bisphenol A epoxy resin (Epiclon 1050, manufactured by DIC Corporation, epoxy equivalent weight: 477 g / eq.) were allowed to react at a temperature of 60 to 65°C for 6 hours. The disappearance of the characteristic peak of NCO at 2260 cm -1was confirmed by an infrared absorption spectrum. Subsequently, the solution was cooled to 40°C, and then 15 parts by mass of acrylic acid, 1 part by mass of t-butylhydroquinone, and 3 parts by mass of 2-methylimidazole were added. The contents were then heated to a temperature of 75 to 80°C under a gas stream in which nitrogen and air were mixed in a 1:1 ratio. The reaction was allowed to proceed for 10 hours at a temperature of 75 to 80°C so that an acid value of 1 or less (mg KOH / g) was achieved. The reaction was then stopped, and accordingly, a solution of a vinyl ester resin (A-2) was obtained. The vinyl ester resin (A-2) had a weight-average molecular weight of 13800.

[0098] Thereafter, the solution was cooled to 40°C, and then 180 parts by mass of an aqueous dispersion of the epoxy compound (B-1) obtained in Synthesis Example 1 and 27 parts by mass of polyoxyethylene distyrenated phenyl ether (Emulgen A-500, manufactured by Kao Corporation) were added. The contents were then thoroughly stirred. Thereafter, 950 parts by mass of ion-exchanged water were added dropwise over 30 minutes, and the contents were mixed with stirring for a further 15 minutes. The aqueous dispersion was concentrated by distillation under reduced pressure, and accordingly, a fiber sizing agent (2) was obtained, which was an aqueous dispersion having a nonvolatile content of 30 mass%. (Example 3: Production and evaluation of the fiber sizing agent (3))

[0099] 85 parts by mass of polyoxyethylene monoethyl ether (Uniox M-550, manufactured by NOF Corporation, hydroxyl number: 100), 69 parts by mass of a bisphenol A epoxy resin (Epiclon 1050, manufactured by DIC Corporation, epoxy equivalent weight: 477 g / eq.), and 50 parts by mass of methyl ethyl ketone were placed in a four-necked flask equipped with a thermometer, a stirrer, a reflux condenser, and a dropping funnel, and stirred thoroughly at 40°C to dissolve. Thereafter, 29 parts by mass of tolylene diisocyanate were added at 40°C and allowed to react at a temperature of 60 to 65°C for 6 hours. The disappearance of the 2260 cm peak characteristic of NCO -1was confirmed by an infrared absorption spectrum. Subsequently, the solution was cooled to 40°C, and then 10 parts by mass of acrylic acid, 1 part by mass of t-butylhydroquinone, and 2 parts by mass of 2-methylimidazole were added. The contents were then heated to a temperature of 75 to 80°C under a gas stream in which nitrogen and air were mixed in a 1:1 ratio. The reaction was allowed to proceed for 10 hours at a temperature of 75 to 80°C so that an acid value of 1 or less (mg KOH / g) was achieved. The reaction was then stopped, and accordingly, a solution of a vinyl ester resin (A-3) was obtained. The vinyl ester resin (A-3) had a weight-average molecular weight of 13,000.

[0100] The solution was then cooled to 40°C. Then, 24 parts by mass of a phenol novolak epoxy resin (Epiclon N-740-80M, manufactured by DIC Corporation), used as epoxy compounds (B-2), and 115 parts by mass of a bisphenol A vinyl ester resin (Unidic V-5500, manufactured by DIC Corporation, active ingredients: 99% or more) were added. Furthermore, 20 parts by mass of polyoxyethylene distyrenated phenyl ether (Emulgen A-500, manufactured by Kao Corporation) were added. The contents were then thoroughly stirred. Afterward, 860 parts by mass of ion-exchanged water were added dropwise over 30 minutes, and the contents were mixed with stirring for another 15 minutes. The aqueous dispersion was concentrated by distillation under reduced pressure, and accordingly, a fiber sizing agent (3) was obtained, which was an aqueous dispersion having a non-volatile content of 30 mass%. (Example 4: Preparation and evaluation of the fiber sizing agent (4))

[0101] 92 parts by mass of polyoxyethylene monoethyl ether (Uniox M-550, manufactured by NOF Corporation, hydroxyl number: 100), 74 parts by mass of a bisphenol A epoxy resin (Epiclon 1050, manufactured by DIC Corporation, epoxy equivalent weight: 477 g / eq.), and 50 parts by mass of methyl ethyl ketone were placed in a four-necked flask equipped with a thermometer, a stirrer, a reflux condenser, and a dropping funnel, and stirred thoroughly at 40°C to dissolve. Thereafter, 30 parts by mass of tolylene diisocyanate were added at 40°C and allowed to react at a temperature of 60 to 65°C for 6 hours. The disappearance of the 2260 cm peak characteristic of NCO -1was confirmed by an infrared absorption spectrum. Subsequently, the solution was cooled to 40°C, and then 11 parts by mass of acrylic acid, 1 part by mass of t-butylhydroquinone, and 2 parts by mass of 2-methylimidazole were added. The contents were then heated to a temperature of 75 to 80°C under a gas stream in which nitrogen and air were mixed in a 1:1 ratio. The reaction was allowed to proceed for 10 hours at a temperature of 75 to 80°C so that an acid value of 1 or less (mg KOH / g) was achieved. The reaction was then stopped, and accordingly, a solution of a vinyl ester resin (A-4) was obtained. The vinyl ester resin (A-4) had a weight-average molecular weight of 13,000.

[0102] The solution was then cooled to 40°C. Then, 21 parts by mass of a bisphenol A epoxy resin (Epiclon 850, manufactured by DIC Corporation) used as epoxy compounds (B-3) and 148 parts by mass of the vinyl ester resin (X) obtained in Synthesis Example 2 were added. Furthermore, 21 parts by mass of polyoxyethylene distyrenated phenyl ether (Emulgen A-500, manufactured by Kao Corporation) were added. The contents were then thoroughly stirred. Thereafter, 920 parts by mass of ion-exchanged water were added dropwise over 30 minutes, and the contents were mixed with stirring for a further 15 minutes. The aqueous dispersion was concentrated by distillation under reduced pressure, and accordingly, a fiber sizing agent (4), which was an aqueous dispersion having a non-volatile content of 30 mass%, was obtained. (Example 5: Preparation and evaluation of the fiber sizing agent (5))

[0103] 124 parts by mass of polyoxyethylene monoethyl ether (Uniox M-550, manufactured by NOF Corporation, hydroxyl number: 100), 99 parts by mass of a bisphenol A epoxy resin (Epiclon 1050, manufactured by DIC Corporation, epoxy equivalent weight: 477 g / eq.), and 65 parts by mass of methyl ethyl ketone were placed in a four-necked flask equipped with a thermometer, a stirrer, a reflux condenser, and a dropping funnel, and stirred thoroughly at 40°C to dissolve. Thereafter, 38 parts by mass of 1,6-hexamethylene diisocyanate were added at 40°C and allowed to react at a temperature of 60 to 65°C for 6 hours. The disappearance of the 2260 cm peak characteristic of NCO -1was confirmed by an infrared absorption spectrum. Subsequently, the solution was cooled to 40°C, and then 15 parts by mass of acrylic acid, 1 part by mass of t-butylhydroquinone, and 3 parts by mass of 2-methylimidazole were added. The contents were then heated to a temperature of 75 to 80°C under a gas stream in which nitrogen and air were mixed in a 1:1 ratio. The reaction was allowed to proceed for 10 hours at a temperature of 75 to 80°C so that an acid value of 1 or less (mg KOH / g) was achieved. The reaction was then stopped, and accordingly, a solution of a vinyl ester resin (A-5) was obtained. The vinyl ester resin (A-5) had a weight-average molecular weight of 14800.

[0104] Thereafter, the solution was cooled to 40°C, and then 460 mass parts of an aqueous dispersion of the epoxy compound (B-1) obtained in Synthesis Example 1 and 27 mass parts of polyoxyethylene distyrenated phenyl ether (Emulgen A-500, manufactured by Kao Corporation) were added. The contents were then thoroughly stirred. Thereafter, 1000 mass parts of ion-exchanged water were added dropwise over 30 minutes, and the contents were mixed with stirring for a further 15 minutes. The aqueous dispersion was concentrated by distillation under reduced pressure, and accordingly, a fiber sizing agent (5) was obtained, which was an aqueous dispersion with a nonvolatile content of 30 mass%. (Example 6: Preparation and evaluation of the fiber sizing agent (6))

[0105] 124 parts by mass of polyoxyethylene monoethyl ether (Uniox M-550, manufactured by NOF Corporation, hydroxyl number: 100), 99 parts by mass of a bisphenol A epoxy resin (Epiclon 1050, manufactured by DIC Corporation, epoxy equivalent weight: 477 g / eq.), and 70 parts by mass of methyl ethyl ketone were placed in a four-necked flask equipped with a thermometer, a stirrer, a reflux condenser, and a dropping funnel, and stirred thoroughly at 40°C to dissolve. Then, 50 parts by mass of trimethylhexamethylene diisocyanate were added at 40°C and allowed to react at a temperature of 60 to 65°C for 6 hours. The disappearance of the 2260 cm peak characteristic of NCO -1was confirmed by an infrared absorption spectrum. Subsequently, the solution was cooled to 40°C, and then 15 parts by mass of acrylic acid, 1 part by mass of t-butylhydroquinone, and 3 parts by mass of 2-methylimidazole were added. The contents were then heated to a temperature of 75 to 80°C under a gas stream in which nitrogen and air were mixed in a 1:1 ratio. The reaction was allowed to proceed for 10 hours at a temperature of 75 to 80°C so that an acid value of 1 or less (mg KOH / g) was achieved. The reaction was then stopped, and accordingly, a solution of a vinyl ester resin (A-6) was obtained. The vinyl ester resin (A-6) had a weight-average molecular weight of 14,500.

[0106] Thereafter, the solution was cooled to 40°C, and then 480 mass parts of an aqueous dispersion of the epoxy compound (B-1) obtained in Synthesis Example 1 and 29 mass parts of polyoxyethylene distyrenated phenyl ether (Emulgen A-500, manufactured by Kao Corporation) were added. The contents were then thoroughly stirred. Thereafter, 1000 mass parts of ion-exchanged water were added dropwise over 30 minutes, and the contents were mixed with stirring for a further 15 minutes. The aqueous dispersion was concentrated by distillation under reduced pressure, and accordingly, a fiber sizing agent (6) was obtained, which was an aqueous dispersion having a nonvolatile content of 30 mass%. (Example 7: Preparation and evaluation of the fiber sizing agent (7))

[0107] 124 parts by mass of polyoxyethylene monoethyl ether (Uniox M-550, manufactured by NOF Corporation, hydroxyl number: 100), 99 parts by mass of a bisphenol A epoxy resin (Epiclon 1050, manufactured by DIC Corporation, epoxy equivalent weight: 477 g / eq.), and 70 parts by mass of methyl ethyl ketone were placed in a four-necked flask equipped with a thermometer, a stirrer, a reflux condenser, and a dropping funnel, and stirred thoroughly at 40°C to dissolve. Then, 50 parts by mass of isophorone diisocyanate were added at 40°C and allowed to react at a temperature of 60 to 65°C for 6 hours. The disappearance of the 2260 cm peak characteristic of NCO -1was confirmed by an infrared absorption spectrum. Subsequently, the solution was cooled to 40°C, and then 15 parts by mass of acrylic acid, 1 part by mass of t-butylhydroquinone, and 3 parts by mass of 2-methylimidazole were added. The contents were then heated to a temperature of 75 to 80°C under a gas stream in which nitrogen and air were mixed in a 1:1 ratio. The reaction was allowed to proceed for 10 hours at a temperature of 75 to 80°C so that an acid value of 1 or less (mg KOH / g) was achieved. The reaction was then stopped, and accordingly, a solution of a vinyl ester resin (A-7) was obtained. The vinyl ester resin (A-7) had a weight-average molecular weight of 14,000.

[0108] Thereafter, the solution was cooled to 40°C, and then 480 mass parts of an aqueous dispersion of the epoxy compound (B-1) obtained in Synthesis Example 1 and 29 mass parts of polyoxyethylene distyrenated phenyl ether (Emulgen A-500, manufactured by Kao Corporation) were added. The contents were then thoroughly stirred. Thereafter, 1000 mass parts of ion-exchanged water were added dropwise over 30 minutes, and the contents were mixed with stirring for a further 15 minutes. The aqueous dispersion was concentrated by distillation under reduced pressure, and accordingly, a fiber sizing agent (7) was obtained, which was an aqueous dispersion having a nonvolatile content of 30 mass%.

[0109] Carbon fiber bundles (2) to (7) and molded parts (2) to (7) were prepared in a similar manner to Example 1, except that the fiber sizing agent (1) used in Example 1 was replaced with the fiber sizing agents (2) to (7). Evaluations were then conducted. (Comparative Example 1: Preparation of a fiber sizing agent (R1))

[0110] 149 mass parts of glycerol dimethacrylate hexamethylene diisocyanate (UA101H, manufactured by Kyoeisha Chemical Co., Ltd, number of terminal unsaturated groups: 4), 16.5 mass parts of a nonionic emulsifier (polyoxyethylene (70 mol) styrenated (5 mol) cumylphenol (mass ratio: 90:10)), and 142 mass parts of methyl ethyl ketone were added to a four-necked flask equipped with a thermometer, a stirrer, a reflux condenser, and a dropping funnel, and dissolution was carried out uniformly at 50°C. Subsequently, the contents were transferred to an emulsion vessel, and then 166 parts by weight of polyglycerol polyglycidyl ether (Denacol EX-521, manufactured by Nagase ChemteX Corporation, an epoxy equivalent weight: 183 g / eq., and the number of epoxy groups: 3 or greater) was added and uniformly dispersed with stirring.Subsequently, 3000 parts by mass of ion-exchanged water were added over 10 minutes while forcibly stirring the contents with a homomixer, and the contents were forcibly emulsified. The aqueous dispersion was then concentrated by distillation under reduced pressure, yielding a fiber sizing agent (R1), which was an aqueous dispersion with a nonvolatile content of 15% by mass.

[0111] A carbon fiber bundle (R1) and a molded part (R1) were prepared in a similar manner to Example 1, except that the fiber sizing agent (1) used in Example 1 was replaced with the fiber sizing agent (R1). Evaluations were then conducted.

[0112] The results of the evaluations of Examples 1 to 7 and Comparative Example 1 are shown in Tables 1 and 2. [Table 1] Table 1 Example 1 Example 2 Example 3 Example 4 Fiber sizing agents (1) (2) (3) (4) Vinyl ester resin (A) A-1 A-2 A-3 A-4 Epoxy compound (B) B-1 B-1 B-2 B-3 Mass ratio (A:B) 67:33 83:17 90:10 90:10 Reviews Fiber binding capacity A A A A Flexural strength of the molded part (MPa) 890 860 940 980 Compressive strength of the molded part (MPa) 320 300 355 360 Interlaminar shear strength of the molded part (MPa) 74 72 79 78 [Table 2] Table 2 Example 5 Example 6 Example 7 Comparison example 1 Fiber sizing agents (5) (6) (7) (R1) Vinyl ester resin (A) A-5 A-6 A-7 Epoxy compound (B) B-1 B-1 B-1 Mass ratio (A:B) 67:33 67:33 67:33 Reviews Fiber binding capacity A A A C Flexural strength of the molded part (MPa) 870 850 880 700 Compressive strength of the molded part (MPa) 315 305 310 205 Interlaminar shear strength of the molded part (MPa) 73 72 70 57

[0113] It was confirmed that the fiber sizing agent of Examples 1 to 7, which are fiber sizing agents of the present invention, has excellent fiber bonding ability and the molded articles produced therewith have excellent strength.

[0114] In contrast, Comparative Example 1 is an example in which the fiber sizing agent used includes an aliphatic epoxy compound and a compound containing a terminal unsaturated group and a polar group in one molecule, and it was confirmed that the fiber bonding ability of the fiber sizing agent was insufficient and the strengths of the molded article produced therewith were also insufficient.

Claims

[1] Fiber sizing agent comprising: a vinyl ester resin (A) having an alkoxypolyoxyalkylene structure and a urethane bond; an epoxy compound (B); and an aqueous medium. [2] The fiber sizing agent according to claim 1, wherein the vinyl ester resin (A) has a structure derived from a bisphenol A epoxy resin. [3] Fiber sizing agent according to claim 1 or 2, wherein the epoxy compound (B) is an aromatic epoxy resin. [4] Fiber material comprising the fiber sizing agent according to any one of claims 1 to 3. [5] A molding composition comprising the fiber material according to claim 4 and a thermosetting resin. [6] A molded article comprising a cured product of the molding composition according to claim 5.