Sizing agent for inorganic fibers and inorganic fibers

Abstract

The present invention aims to improve the bundling of inorganic fibers to which a sizing agent for inorganic fibers is attached, and to shorten the time for curing treatment when producing a fiber-reinforced resin composite. The sizing agent for inorganic fibers contains a resin (A) containing a vinyl ester resin and an ionic polyester resin, and the mass ratio of the vinyl ester resin to the ionic polyester resin is greater than 1.

Description

TECHNICAL FIELD

[0001] The present application relates to a sizing agent for inorganic fibers and an inorganic fiber. BACKGROUND

[0002] Generally, as a material containing inorganic fibers such as carbon fibers and a matrix resin such as a thermosetting resin as a base material, a fiber-reinforced resin composite material is known, which is widely used in various fields such as building materials, transportation equipment, and the like. In order to improve the interfacial adhesion of inorganic fibers and a matrix resin, a treatment of attaching a sizing agent to inorganic fibers is performed.

[0003] In the past, for example, a sizing agent for reinforcing fibers disclosed in Patent Literature 1 is known as a sizing agent for inorganic fibers. The sizing agent for inorganic fibers of Patent Literature 1 necessarily contains a compound containing an exothermic functional group, and a thermoplastic resin. The weight proportion of the compound containing an exothermic functional group in the entire non-volatile component of the sizing agent for inorganic fibers is 5 to 50 weight%, and the weight proportion of the thermoplastic resin is 50 to 95 weight%. As the compound containing an exothermic functional group, a vinyl ester compound can be exemplified, and as the thermoplastic resin, a copolymer polyester-based resin can be exemplified.

[0004] PRIOR ART DOCUMENTS

[0005] PATENT LITERATURE

[0006] Patent Literature 1: Japanese Patent Application Laid-Open No. 2011-21281 SUMMARY

[0007] PROBLEMS TO BE SOLVED BY THE INVENTION

[0008] In addition, in the existing sizing agent for inorganic fibers, it is required to further improve the bunching property of inorganic fibers to which the sizing agent for inorganic fibers is attached. In addition, it is required to shorten the time of the curing treatment when inorganic fibers to which the sizing agent for inorganic fibers is attached are molded together with a matrix resin and a fiber-reinforced resin composite material is produced by performing the curing treatment.

[0009] MEANS FOR SOLVING THE PROBLEMS

[0010] The sizing agent for inorganic fibers for solving the above problems is characterized by containing a resin (A) containing a vinyl ester resin and an ionic polyester resin, the mass ratio of the vinyl ester resin with respect to the ionic polyester resin being greater than 1.

[0011] In the above sizing agent for inorganic fibers, it is preferable that the vinyl ester resin have at least one selected from a bisphenol A skeleton and a bisphenol F skeleton.

[0012] In the above sizing agent for inorganic fibers, the resin (A) preferably further contains at least one selected from a non-ionic polyester resin and an epoxy resin.

[0013] In the sizing agent for inorganic fibers, the nonionic polyester resin preferably has at least one selected from a bisphenol A skeleton and a bisphenol F skeleton.

[0014] In the sizing agent for inorganic fibers, the nonionic polyester resin preferably has an aliphatic unsaturated bond.

[0015] In the sizing agent for inorganic fibers, the epoxy resin preferably has an epoxy group of 2 or more functions.

[0016] In the sizing agent for inorganic fibers, the epoxy resin preferably has at least one selected from a bisphenol A skeleton and a bisphenol F skeleton.

[0017] In the sizing agent for inorganic fibers, the resin (A) can further include a nonionic polyester resin and an epoxy resin, in which case, when the total content ratio of the vinyl ester resin, the ionic polyester resin, the nonionic polyester resin, and the epoxy resin is set to 100 parts by mass, the sizing agent for inorganic fibers preferably contains the vinyl ester resin in a ratio of 20 parts by mass or more and 70 parts by mass or less, the ionic polyester resin in a ratio of 2 parts by mass or more and 50 parts by mass or less, the nonionic polyester resin in a ratio of 5 parts by mass or more and 50 parts by mass or less, and the epoxy resin in a ratio of 5 parts by mass or more and 50 parts by mass or less.

[0018] The sizing agent for inorganic fibers preferably further contains a surfactant.

[0019] In the sizing agent for inorganic fibers, the surfactant preferably has an aromatic hydrocarbon group.

[0020] In the sizing agent for inorganic fibers, when the content ratio of the resin (A) is set to 100 parts by mass, the sizing agent for inorganic fibers preferably contains the surfactant in a ratio of 10 parts by mass or more and 50 parts by mass or less.

[0021] The inorganic fiber for solving the above problem is characterized in that the inorganic fiber has the above-described sizing agent for inorganic fibers attached thereto.

[0022] Effects of the Invention

[0023] According to the present application, the bundling property of the inorganic fiber having the sizing agent for inorganic fibers attached thereto can be improved. In addition, the time of the curing process when producing a fiber-reinforced resin composite can be shortened. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is a schematic view of a composite interface property evaluation device used for the adhesion evaluation in the example column. DETAILED DESCRIPTION

[0025] <1st Embodiment>

[0026] A first embodiment in which the inorganic fiber of the present application is embodied with a sizing agent (hereinafter also referred to as a sizing agent) will be described.

[0027] The sizing agent of the present embodiment contains a resin (A) containing a vinyl ester resin and an ionic polyester resin, and the mass ratio of the vinyl ester resin with respect to the ionic polyester resin is greater than 1.

[0028] By containing the ionic polyester resin in the sizing agent, the bundling property of the inorganic fiber to which the sizing agent is attached can be improved. In addition, by making the mass ratio of the vinyl ester resin with respect to the ionic polyester resin greater than 1, when the inorganic fiber to which the sizing agent is attached is subjected to a curing treatment with a matrix resin to produce a fiber-reinforced resin composite (hereinafter also referred to as a composite), the curing treatment can be performed in a shorter time.

[0029] The mass ratio of the vinyl ester resin with respect to the ionic polyester resin is preferably 1.2 or greater. In addition, the above mass ratio is preferably 20 or less.

[0030] (Vinyl ester resin)

[0031] The vinyl ester resin is a resin having a vinyl ester compound having a highly reactive double bond such as a vinyl group, an acrylate group, a methacrylate group, etc. at the end of the main chain. The vinyl ester resin can be any one of an aromatic resin, an aliphatic resin.

[0032] As specific examples of the vinyl ester compound, for example, (meth)allyl alkyl ester, alkoxy polyalkylene glycol (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, 2-hydroxyalkyl (meth)acrylate, dialkylaminoethyl (meth)acrylate, glycidyl (meth)acrylate, 2-methacryloyloxyethyl 2-hydroxypropyl phthalate, polyalkylene glycol di(meth)acrylate, alkane diol di(meth)acrylate, glycerol di(meth)acrylate, 2-hydroxy-3-methacryloyloxypropyl (meth)acrylate, dimethylol tricyclodecane di(meth)acrylate, bisphenol A (meth)acrylate, alkylene oxide-addition bisphenol A (meth)acrylate, bisphenol A diglycidyl ether (meth)acrylate-addition product, alkylene oxide-addition bisphenol A diglycidyl ether (meth)acrylate-addition product, trimethylolpropane tri(meth)acrylate, glycidyl (meth)acrylate, phenoxyalkyl (meth)acrylate, phenoxy polyalkylene glycol (meth)acrylate, 2-hydroxy-3-phenoxypropanol (meth)acrylate, polyalkylene glycol nonylphenyl ether (meth)acrylate, 2-(meth)acryloyloxyethyl succinate, 2-(meth)acryloyloxyethyl phthalate, 2-(meth)acryloyloxyethyl-2-hydroxyethyl phthalate, neopentyl glycol (meth)acrylate benzoate, alkylene oxide-addition trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, pentaerythritol tri(meth)acrylate hexamethylene diisocyanate urethane prepolymer, and the like can be given. These vinyl ester compounds can be used singly or in combination of two or more.

[0033] The vinyl ester resin preferably has at least one selected from the group consisting of a bisphenol A skeleton and a bisphenol F skeleton. If having at least one selected from the group consisting of a bisphenol A skeleton and a bisphenol F skeleton, the matrix resin is easily impregnated with respect to the bundle of inorganic fibers to which a sizing agent is attached. The case where the matrix resin is easily impregnated is also referred to as an improvement in impregnability hereinafter.

[0034] (Ionic polyester resin)

[0035] The ionic polyester resin is a polyester resin having an ionic bond within a molecule.

[0036] As the ionic bond within the molecule, there can be given a case where a functional group such as a carboxyl group, a sulfonic acid group, or the like is present in the polyester resin and an alkali metal, an amine, an ammonium, a phosphonium, or the like is ionically bonded to the functional group.

[0037] As the polyester resin, there can be given a linear polyester composed of a diol and a dibasic acid, a lactone ring-opening polymer, and a polyhydroxycarboxylic acid, and the like.

[0038] As the diol, an alcohol having 2 or more and 30 or less carbon atoms can be given. As specific examples of the diol, for example, ethylene glycol, propylene glycol, butylene glycol, neopentyl glycol, and an aliphatic alkane diol obtained by adding 2 or more and 4 or less alkylene oxides to these diols, an alkylene oxide adduct of a primary alkylamine such as methylamine, ethylamine, propylamine, octylamine, dodecylamine, and the like, an alkylene oxide adduct of a diphenol such as bisphenol A, bisphenol F, bisphenol S, and cresol, and the like containing an aromatic ring, and the like can be given.

[0039] The above diol can be used alone or two or more can be used in combination.

[0040] As the diacid, a dicarboxylic acid having 2 or more and 24 or less carbon atoms can be given. As specific examples of the diacid, for example, saturated aliphatic dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, adipic acid, and sebacic acid, unsaturated aliphatic dicarboxylic acids such as maleic acid and fumaric acid, aromatic dicarboxylic acids such as phthalic acid, terephthalic acid, and isophthalic acid, dicarboxylic acid anhydrides such as maleic anhydride and phthalic anhydride, and the like can be given.

[0041] The above diacid can be used alone or two or more can be used in combination.

[0042] As the lactone ring-opening polymer, a substance obtained by ring-opening polymerization of a lactone such as a monolactone having 3 or more and 12 or less carbon atoms using a catalyst such as a metal oxide and an organometallic compound, and the like can be given. As specific examples of the lactone, β-propiolactone, γ-butyrolactone, δ-valerolactone, ε-caprolactone, and the like can be given.

[0043] As specific examples of the polyhydroxycarboxylic acid, a substance obtained by dehydration condensation of a hydroxycarboxylic acid such as glycolic acid and lactic acid can be given.

[0044] In the sizing agent, the resin (A) preferably further contains at least one selected from the group consisting of a non-ionic polyester resin and an epoxy resin. The resin (A) more preferably contains both the non-ionic polyester resin and the epoxy resin.

[0045] By causing the resin (A) to contain the non-ionic polyester resin, the fiber separation property of the inorganic fiber to which the sizing agent is attached can be improved. In addition, by causing the resin (A) to contain the epoxy resin, the adhesion of the inorganic fiber to which the sizing agent is attached to the matrix resin can be improved.

[0046] (non-ionic polyester resin)

[0047] The non-ionic polyester resin is a polyester resin that does not have an ionic bond in the molecule. That is, it is a polyester resin in which a functional group such as a carboxyl group and a sulfonic acid group is not present in the resin. The non-ionic polyester resin can use the same polyester resin as the above-mentioned ionic polyester resin except that the above-mentioned functional group is not present.

[0048] The acid value of the nonionic polyester resin is preferably 2.5 or less. In addition, from the viewpoint of common manufacturing techniques, a substance that can include a trace amount of carboxylic acid can be included.

[0049] The nonionic polyester resin preferably has at least one selected from a bisphenol A skeleton and a bisphenol F skeleton.

[0050] The nonionic polyester resin preferably has an aliphatic unsaturated bond. By having the nonionic polyester resin have an aliphatic unsaturated bond, it is possible to perform the curing treatment in a shorter time.

[0051] (Epoxy Resin)

[0052] As the epoxy resin, either a mono-epoxy resin having one epoxy group in the molecule or a polyfunctional epoxy resin having two or more epoxy groups can be used. The polyfunctional epoxy resin can also be referred to as an epoxy resin having two or more functional epoxy groups.

[0053] If the epoxy resin is a polyfunctional epoxy resin, it is possible to improve the impregnation of the base resin with respect to the bundle of inorganic fibers to which the sizing agent is attached.

[0054] As specific examples of the epoxy resin, for example, bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol S type epoxy resins, phenol novolac type epoxy resins, cresol novolac type epoxy resins, alkylphenol novolac type epoxy resins, biphenyl type epoxy resins, dicyclopentadiene type epoxy resins, naphthalene type epoxy resins, resorcinol diglycidyl ether, polypropylene glycol diglycidyl ether, trimethylolpropane polyglycidyl ether, pentaerythritol polyglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, polyethylene glycol diglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, alkyl glycidyl ether, polyoxyalkylene-added alkyl glycidyl ether, phenyl glycidyl ether, polyoxyalkylene-added phenyl glycidyl ether, tri-glycidyl amine, tetra-glycidyl amine, and the like, amine type epoxy resins, and the like can be given.

[0055] The epoxy resin preferably has at least one selected from a bisphenol A skeleton and a bisphenol F skeleton.

[0056] The proportions of the vinyl ester resin, the ionic polyester resin, the nonionic polyester resin, and the epoxy resin in the sizing agent are not particularly limited.

[0057] When the total content ratio of the vinyl ester resin, the ionic polyester resin, the non-ionic polyester resin, and the epoxy resin is set to 100 parts by mass, the sizing agent preferably contains 20 parts by mass or more and 70 parts by mass or less of the vinyl ester resin. In addition, the sizing agent preferably contains the ionic polyester resin in a ratio of 2 parts by mass or more and 50 parts by mass or less, the non-ionic polyester resin in a ratio of 5 parts by mass or more and 50 parts by mass or less, and the epoxy resin in a ratio of 5 parts by mass or more and 50 parts by mass or less.

[0058] The sizing agent preferably further contains a surfactant. By containing the surfactant, the impregnability of the base resin can be improved.

[0059] (Surfactant)

[0060] As the surfactant, for example, nonionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants can be given. These surfactants can be used alone or in combination of two or more.

[0061] (Nonionic Surfactant)

[0062] As specific examples of the nonionic surfactant, for example, the following can be given: (1) compounds obtained by adding an alkylene oxide having 2 to 4 carbon atoms to an organic acid, an organic alcohol, an organic amine, and / or an organic amide, such as polyoxyethylene dilaurylate, polyoxyethylene oleate, polyoxyethylene dioleate, polyoxyethylene octyl ether, polyoxyethylene lauryl ether, polyoxyethylene lauryl ether methyl ether, polyoxyethylene polyoxypropylene lauryl ether, polyoxypropylene lauryl ether methyl ether, polyoxyethylene oleyl ether, polyoxybutylene oleyl ether, polyoxyethylene polyoxypropylene nonyl ether, polyoxypropylene nonyl ether, polyoxyethylene polyoxypropylene octyl ether, an ethylene oxide adduct of 2-hexylhexanol, polyoxyethylene 2-ethyl-1-hexyl ether, polyoxyethylene isononyl ether, polyoxyethylene dodecyl ether, a compound obtained by adding an ethylene oxide to a secondary dodecyl alcohol, polyoxyethylene tridecyl ether, polyoxyalkylene myristyl ether, polyoxyethylene lauryl amino ether, polyoxyethylene lauryl amido ether, ether-type nonionic surfactants such as polyoxyalkylene tristyryl phenyl ether, and the like; (2) polyoxyalkylene sorbitan trioleate, polyoxyalkylene coconut oil, polyoxyalkylene castor oil, polyoxyalkylene hydrogenated castor oil, polyoxyalkylene hydrogenated castor oil trioctanoate, polyoxyalkylene hydrogenated castor oil maleate, stearate, or oleate, polyoxyalkylene polyol fatty acid ester-type nonionic surfactants; (3) alkyl amide-type nonionic surfactants such as stearic acid diethanolamide, diethanolamine monolauryl amide, and the like; (4) polyoxyalkylene fatty amide-type nonionic surfactants such as polyoxyethylene diethanolamine monooleyl amide, polyoxyethylene lauryl amine, polyoxyethylene tallow amine, and the like; and the like.

[0063] (anionic surfactant)

[0064] As the anionic surfactant, a known substance can be appropriately used. As specific examples of the anionic surfactant, for example, the following can be given: (1) phosphate ester salts of fatty alcohol such as lauryl phosphate ester salt, cetyl phosphate ester salt, octyl phosphate ester salt, oleyl phosphate ester salt, and stearyl phosphate ester salt; (2) phosphate ester salts of a substance in which at least one alkylene oxide selected from ethylene oxide and propylene oxide is added to a fatty alcohol, such as polyoxyethylene lauryl ether phosphate ester salt, polyoxyethylene oleyl ether phosphate ester salt, and polyoxyethylene stearyl ether phosphate ester salt; (3) fatty or aromatic sulfonic acid salts such as lauryl sulfonate, myristyl sulfonate, cetyl sulfonate, oleyl sulfonate, stearyl sulfonate, tetradecyl sulfonate, dodecylbenzenesulfonate, and secondary alkyl sulfonate (C13-15); (4) sulfates of fatty alcohol such as lauryl sulfate, oleyl sulfate, and stearyl sulfate; (5) sulfates of a substance in which at least one alkylene oxide selected from ethylene oxide and propylene oxide is added to a fatty alcohol, such as polyoxyethylene lauryl ether sulfate, polyoxyalkylene (polyoxyethylene, polyoxypropylene) lauryl ether sulfate, and polyoxyethylene oleyl ether sulfate; (6) sulfates of fatty acid such as ricin oil fatty acid sulfate, sesame oil fatty acid sulfate, tall oil fatty acid sulfate, soybean oil fatty acid sulfate, rapeseed oil fatty acid sulfate, palm oil fatty acid sulfate, lard fatty acid sulfate, tallow fatty acid sulfate, and whale oil fatty acid sulfate; (7) sulfates of oil and fat such as ricin oil sulfate, sesame oil sulfate, tall oil sulfate, soybean oil sulfate, rapeseed oil sulfate, palm oil sulfate, lard sulfate, tallow sulfate, and whale oil sulfate; (8) salts of fatty acid such as lauryl acid salt, oleyl acid salt, and stearyl acid salt; (9) sulfosuccinate salts of fatty alcohol such as dioctyl sulfosuccinate; and the like. As the counter ion of the anionic surfactant, for example, an alkali metal salt such as potassium salt and sodium salt, an ammonium salt, an alkanolamine salt such as triethanolamine, and the like can be given.

[0065] (cationic surfactant)

[0066] As the cationic surfactant, a known substance can be appropriately used. As specific examples of the cationic surfactant, for example, the following can be given: lauryl trimethylammonium chloride, cetyl trimethylammonium chloride, stearyl trimethylammonium chloride, behenyl trimethylammonium chloride, didodecyldimethylammonium chloride, 1,2-dimethylimidazole, triethanolamine, and the like.

[0067] (amphoteric surfactant)

[0068] As the amphoteric surfactant, a publicly known substance can be appropriately used. As specific examples of the amphoteric surfactant, for example, betaine type amphoteric surfactants and the like can be given.

[0069] The surfactant preferably has an aromatic hydrocarbon group. By having an aromatic hydrocarbon group, the impregnability of the base resin can be further improved.

[0070] The content ratio of the surfactant in the sizing agent is not particularly limited.

[0071] When the content ratio of the resin (A) containing the vinyl ester resin and the ionic polyester resin is set to 100 parts by mass, the sizing agent preferably contains the surfactant in a ratio of 10 parts by mass or more and 50 parts by mass or less, and more preferably contains the surfactant in a ratio of 15 parts by mass or more and 45 parts by mass or less.

[0072] <2nd Embodiment>

[0073] Next, a 2nd embodiment in which the inorganic fiber of the present application is embodied will be described. In the 2nd embodiment, the same configuration as the 1st embodiment is applied except for the following description. That is, in the following description of the 2nd embodiment, the description of the same configuration as the 1st embodiment is omitted.

[0074] The inorganic fiber of the present embodiment has the sizing agent of the 1st embodiment attached to the surface. The manufacturing method of the inorganic fiber includes a step of attaching the sizing agent of the 1st embodiment to the inorganic fiber. The attachment amount (excluding the solvent) is not particularly limited, and the inorganic fiber is preferably attached in a manner of 0.01 mass% or more and 10 mass% or less as the sizing agent. By limiting the value in this range, the effect of further improving the bundling property and the like of the inorganic fiber can be obtained.

[0075] (Inorganic fiber)

[0076] The kind of the inorganic fiber applied in the present embodiment is not particularly limited, and for example, glass fibers, carbon fibers, ceramic fibers, metal fibers, mineral fibers, rock fibers, slag fibers, and the like can be given. Among these, from the aspect that the effect of the present application can be more effectively exhibited, glass fibers and carbon fibers are preferred. As the kind of the carbon fiber, for example, PAN-based carbon fibers obtained by using acrylic fibers as a raw material, pitch-based carbon fibers obtained by using pitch as a raw material, recycled carbon fibers, polyester fibers, carbon fibers obtained by using polyethylene resin, phenol resin, cellulose resin, lignin resin, and the like as a raw material can be given.

[0077] The sizing agent of the first embodiment can be applied to inorganic fibers using a method commonly used in industry. For example, roll impregnation, roll contact, spraying, papermaking, and the like can be given. The inorganic fibers to which the sizing agent has been applied can be dried using a known method.

[0078] <Third Embodiment>

[0079] Next, a third embodiment in which the composite material of the present application is embodied will be described. In the third embodiment, the same configuration as in the first embodiment and the second embodiment is applied, except for the following description. That is, in the following description of the third embodiment, the same configuration as in the first embodiment or the second embodiment will not be described.

[0080] The inorganic fibers to which the sizing agent has been applied by the second embodiment are impregnated into a matrix resin as a base material, thereby obtaining a composite material. In the production of the composite material, the form of the inorganic fibers is not particularly limited, and for example, long fiber form, short fiber form, nonwoven fabric form, and the like can be used.

[0081] (Matrix Resin)

[0082] The matrix resin is appropriately selected from known resins according to the purpose, use, and the like of the composite material. Specific examples of the matrix resin include, for example, epoxy resins, vinyl ester resins, polyamide resins, polyolefin resins, polyurethane resins, polycarbonate resins, polyester resins, PEEK resins, fluororesins, phenoxy resins, phenol resins, BMI resins, polyimide resins, polyimide resin precursors, polyether sulfone resins, and the like. Among these, a thermosetting resin is preferably used from the viewpoint of more effectively exhibiting adhesive properties.

[0083] According to the sizing agent and the inorganic fibers of the present embodiment, the following effects and advantages can be obtained.

[0084] (1) The sizing agent contains a vinyl ester resin and an ionic polyester resin, and the mass ratio of the vinyl ester resin to the ionic polyester resin is greater than 1.

[0085] By containing the ionic polyester resin in the sizing agent, the bundling property of the inorganic fibers to which the sizing agent has been applied can be improved. In addition, by making the mass ratio of the vinyl ester resin to the ionic polyester resin greater than 1, the curing process can be performed in a shorter time when the composite material is produced.

[0086] (2) The vinyl ester resin has at least one selected from a bisphenol A skeleton and a bisphenol F skeleton. Thus, the impregnation property of the matrix resin can be improved.

[0087] (3) By including a nonionic polyester resin in the sizing agent, the opening property of the inorganic fiber to which the sizing agent is attached can be improved. In addition, by including an epoxy resin in the sizing agent, the adhesion of the inorganic fiber to which the sizing agent is attached to the matrix resin can be improved.

[0088] (4) The nonionic polyester resin has an aliphatic unsaturated bond. Therefore, the curing treatment can be performed in a shorter time when the composite material is produced.

[0089] (5) The sizing agent contains a surfactant. Therefore, the impregnation property of the matrix resin can be improved.

[0090] (6) The surfactant has an aromatic hydrocarbon group. Therefore, the impregnation property of the matrix resin can be further improved.

[0091] <Modification Example>

[0092] The above embodiment can be implemented as follows. The above embodiment and the following modification example can be implemented in combination with each other within a range in which they are not technically contradictory.

[0093] • In the sizing agent of the present embodiment, components generally used in the sizing agent, such as a stabilizing agent for maintaining the quality of the sizing agent, a charge control agent, an antistatic agent, a linking agent, an antioxidant, an ultraviolet absorber, a defoaming agent (a silicone-based compound), a smoothing agent, water, an organic solvent, and the like, can be further mixed within a range in which the effects of the present application are not hindered.

[0094] Examples

[0095] The following examples and the like are presented in order to more specifically explain the configuration and effects of the present application, but the present application is not limited by these examples. Note that in the following explanation of the examples and comparative examples, the parts refer to mass parts.

[0096] Test Group 1 (Preparation of Sizing Agent)

[0097] (Example 1)

[0098] The sizing agent of Example 1 was obtained by mixing the raw materials, a vinyl ester resin, an ionic polyester resin, a nonionic polyester resin, an epoxy resin, and a surfactant, in the proportions shown in Table 1.

[0099] (Examples 2 to 15, Comparative Examples 1 to 4)

[0100] The sizing agents of Examples 2 to 15 and Comparative Examples 1 to 4 were obtained by mixing the components in the proportions shown in Table 1.

[0101] The kinds and contents of the vinyl ester resin, the kinds and contents of the ionic polyester resin, the kinds and contents of the nonionic polyester resin, the kinds and contents of the surfactant, and the mass ratio of the vinyl ester resin to the ionic polyester resin are shown in the "Vinyl ester resin" column, the "Ionic polyester resin" column, the "Nonionic polyester resin" column, the "Surfactant" column, and the "Mass ratio (vinyl ester resin / ionic polyester resin)" column of Table 1, respectively.

[0102] [Table 1]

[0103]

[0104] In Table 1, the mass ratio of the vinyl ester resin to the ionic polyester resin can be calculated from the mixing ratio of the two components. Alternatively, it can be determined by extracting the sizing agent adhering to the inorganic fiber with a solvent such as acetone, and then combining proton nuclear magnetic resonance (also referred to as H-NMR) and an analysis method based on fluorescent X-rays or the like.

[0105] The detailed contents of the resins (A) described in Table 1 are shown in Table 2. The kinds and structures of the vinyl ester resin, the ionic polyester resin, the nonionic polyester resin, and the epoxy resin are shown in the "Kinds" column and the "Structure" column, respectively.

[0106] [Table 2]

[0107]

[0108] In Table 2, the epoxy resins EP-1 to EP-4 (jER828 (registered trademark), jER1001 (registered trademark), jER1002 (registered trademark), jER1004 (registered trademark)) are manufactured by Mitsubishi Chemical Corporation, and have 2-functional epoxy groups. EP-5 (Denacol (registered trademark) EX-421) is manufactured by Nagase chemtex Corporation, and has a multi-functional epoxy group.

[0109] Newpol (registered trademark) BPE-20, Newpol (registered trademark) BPE-40, and Newpol (registered trademark) BPE-100 are polyester resins manufactured by Sanyo Chemical Industries, Inc.

[0110] The epoxy resins EP-1 to EP-4, the vinyl ester resins VE-1 to VE-4, and the nonionic polyester resins PE-1 to PE-3 have a bisphenol A skeleton.

[0111] The nonionic polyester resins PE-1 and PE-2 have an aliphatic unsaturated bond.

[0112] The details of the surfactants described in Table 1 are shown in Table 3. The structure of the surfactants is shown in the "Structure" column. Whether or not the surfactants have an aromatic hydrocarbon group is shown in the "Presence or absence of aromatic hydrocarbon group" column.

[0113] [Table 3]

[0114]

[0115] Test Group 2 (Sizing of Inorganic Fibers, Production of Composites)

[0116] The sizing agent of each example prepared in Test Group 1 was diluted with water to produce an aqueous solution having a solid content of 2%, and was placed in a treatment bath. Unsized carbon fibers (tensile strength 3500 MPa, tensile elastic modulus 2.3 x 10 5 MPa, 12000 Filament) obtained from polyacrylonitrile-based fibers were continuously immersed in the above treatment bath, and the pressing conditions of the rollers were adjusted so that the amount of sizing agent (excluding solvent) adhered was fixed at 2% with respect to the carbon fibers, and the sizing agent was adhered. Similarly, the sizing agent was adhered to the glass fibers as well.

[0117] The fiber bundle of the carbon fibers or glass fibers to which the sizing agent was adhered was opened while being conveyed with rollers. The opened fiber bundle was passed through a resin tank of a vinyl ester resin as a matrix resin, and was impregnated with the vinyl ester resin. As the vinyl ester resin, Ripoxy (registered trademark) R-804B manufactured by Showa Denko K.K. (using a methyl ethyl ketone peroxide curing agent manufactured by Showa Denko K.K.) was used. After the impregnation of the vinyl ester resin, it was passed through a curing mold of 1 m in length set to 140°C, and was subjected to draw forming, and a composite material was produced. Note that by the draw forming, the sizing agent was cured together with the matrix resin.

[0118] Test Group 3 (Evaluation)

[0119] The adhesion, opening, bundling, curing, and impregnation of the inorganic fibers to which the sizing agent of Examples 1 to 15 and Comparative Examples 1 to 4 was adhered were evaluated. The procedure of each test is shown below. In addition, the results of the evaluation based on each test are shown in the "adhesion", "opening", "bundling", "curing", and "impregnation" columns of Table 1.

[0120] (Adhesion)

[0121] The adhesion was evaluated by the stress determined using a commercially available composite material interface property evaluation device using a droplet method. Figure 1 A schematic diagram of the composite material interface property evaluation device 10 is shown in FIG. 1.

[0122] In test group 2, one carbon fiber 12 was taken out from a fiber bundle of carbon fibers to which a sizing agent was attached, and the carbon fiber 12 was fixed to a plate-shaped, square frame-shaped holder 11 at both ends thereof in a state of being stretched using an adhesive 14.

[0123] Next, a base resin mixed in a ratio of 100 / 3 (mass ratio) of an epoxy resin (epoxy equivalent 190, manufactured by Mitsubishi Chemical Corporation, trade name jER828) / BF3 monoethylamine salt (Stella Chemifa Corporation, trade name boron trifluoride monoethylamine) was attached to the carbon fiber 12 to form a resin drop 13 having a diameter of approximately 70 μm, and was fixed by heating for 90 minutes in an air atmosphere at 160°C.

[0124] In addition, a vinyl ester resin (manufactured by Showa Denko, trade name: Ripoxy (registered trademark) R-804B (using a methyl ethyl ketone peroxide curing agent manufactured by Showa Denko)) was attached to the carbon fiber 12 to form a resin drop 13 having a diameter of approximately 70 μm, and was fixed by heating for 20 minutes in an air atmosphere at 160°C, separately from the evaluation using the above-described epoxy resin.

[0125] In a device main body not shown, two plate-shaped blades 17, 18 whose vertical cross sections of one side surface are shaped in a slender manner were installed in a state in which the tip end portions 17a and 18a thereof face each other.

[0126] The carbon fiber 12 on which the resin drop 13 was fixed was gripped with the tip end portions 17a, 18a of the two blades 17, 18, and the holder 11 was installed to the base plate 16 fixed to the device main body in this state. The load cell 15 was connected to the base plate 16, and the stress applied to the base plate 16 was measured. When the holder 11 was moved in the fiber axial direction at a speed of 5 mm / minute, the resin drop 13 was peeled from the carbon fiber 12 using the tip end portions 17a, 18a of the blades 17, 18, and the maximum stress F generated at this time was measured using the load cell 15.

[0127] Using the measured value, the interfacial shear strength τ was calculated according to the calculation formula of Number 1 below. The same operation was performed 20 times, and the average value of the interfacial shear strengths obtained was calculated.

[0128] The reference value of the maximum stress of the epoxy resin was set to 60 MPa, and the reference value of the maximum stress of the vinyl ester resin was set to 40 MPa, and the adhesiveness was evaluated according to the increase rate of the average value with respect to these reference values according to the following reference. The same test was also performed using glass fibers. The results of the evaluation are shown in the "adhesiveness" column of Table 1.

[0129] [Number 1]

[0130] τ = FπDL

[0131] The calculation formula of the number 1,

[0132] F represents the maximum stress (N) generated when the carbon fiber 12 peels the resin droplet 13,

[0133] D represents the diameter (m) of the carbon fiber 12,

[0134] L represents the diameter (m) of the pulling direction of the resin droplet 13.

[0135] Evaluation criteria of adhesiveness

[0136] ◎ (Good): The increase rate of both the epoxy resin and the vinyl ester resin is 5% or more in either of the carbon fiber and the glass fiber

[0137] O (Pass): The increase rate of either of the epoxy resin and the vinyl ester resin is 5% or more in either of the carbon fiber and the glass fiber

[0138] X (Fail): The increase rate of both the epoxy resin and the vinyl ester resin is less than 5% in either of the carbon fiber and the glass fiber

[0139] (Opening property)

[0140] In the test group 2, for the carbon fiber and the glass fiber which are opened while being conveyed by a roller, the state after opening is visually observed. The evaluation is made in accordance with the following criteria.

[0141] Evaluation criteria of opening property

[0142] ◎ (Good): There is no gap between the fiber bundles after opening, and the opening is uniform.

[0143] O (Pass): A part of the gap is observed between the fiber bundles after opening, but there is no problem in practical use, and the opening is substantially uniform.

[0144] X (Fail): There are many gaps between the fiber bundles after opening, and it is a level which becomes a problem in practical use.

[0145] (Bunching property)

[0146] In the test group 2, for the carbon fiber and the glass fiber which are opened while being conveyed by a roller, the roller after passing the carbon fiber and the glass fiber is visually observed. The evaluation is made in accordance with the following criteria.

[0147] Evaluation criteria of bunching property

[0148] ◎ (Good): There is almost no fiber observed to be wound around the roller.

[0149] O (Pass): Slightly observed the fiber wound on the roll, but the level of not hindering the operation.

[0150] X (Fail): Much fiber wound on the roll, the level of causing an obstacle to the operation.

[0151] (Curing property)

[0152] The vinyl ester resin was impregnated into the carbon fiber to which the sizing agent was attached, and the curing property of the composite material when being drawn in a length of 1 m using a mold for curing set to 140°C was evaluated while changing the passing time. Similarly, the test was also performed for the glass fiber, and the evaluation was performed in accordance with the following criteria. Note that, regarding the evaluation of the curing property, when the surface of the composite material was pressed with a finger, in the case where it was in a state of not having elasticity and not being recessed, it was judged to have sufficient curing property.

[0153] • Evaluation criteria of the curing property

[0154] O (Pass): The mold for curing was passed in 5 minutes, and sufficient curing property was exhibited.

[0155] O (Pass): The mold for curing was passed in 6 minutes, and sufficient curing property was exhibited.

[0156] X (Fail): The mold for curing was passed in 6 minutes, and sufficient curing property was not exhibited.

[0157] (Impregnation property)

[0158] In Test Group 2, for the fiber bundle of the carbon fiber to which the sizing agent was attached and the glass fiber in a thread-like shape, a satin chrome-plated pin having a diameter of 1 cm was used as an opening rod, and opening was performed at a width of 1 cm. 0.06 g of a vinyl ester resin (manufactured by Showa Denko, trade name: Ripoxy (registered trademark) R-804B) as a matrix resin was dropped on the carbon fiber bundle and the glass fiber bundle in an atmosphere of 25°C, and the maximum diameter of the dropped vinyl ester resin after 60 seconds was measured.

[0159] The matrix resin was changed to an epoxy resin (epoxy equivalent 190, trade name jER828 (registered trademark) manufactured by Mitsubishi Chemical), and the maximum diameter of the dropped epoxy resin after 60 seconds was measured in the same manner as described above. Based on the measurement results, the impregnation property of the matrix resin was evaluated in accordance with the following criteria.

[0160] • Evaluation criteria of the impregnation property

[0161] O (Pass): The maximum diameter of each of the epoxy resin and the vinyl ester resin was 5.5 mm or more

[0162] O (Pass): The maximum diameter of either one of the epoxy resin and the vinyl ester resin is 5.5 mm or more

[0163] X (Fail): The maximum diameter of each of the epoxy resin and the vinyl ester resin is less than 5.5 mm

[0164] According to the results of Table 1, with the present application, the bundling of inorganic fibers to which a sizing agent for inorganic fibers has been attached can be improved. In addition, the time for curing treatment when producing a fiber-reinforced resin composite can be shortened.

[0165] Explanation of Reference Signs

[0166] 10... Composite material interface property evaluation device

[0167] 11... Holder

[0168] 12... Carbon fiber

[0169] 13... Resin drop

[0170] 14... Adhesive

[0171] 15... Force transducer

[0172] 16... Substrate

[0173] 17, 18... Blade

Claims

1. A sizing agent for inorganic fibers, characterized in that, The sizing agent for this inorganic fiber contains resin (A) comprising vinyl ester resin and ionic polyester resin. The mass ratio of the vinyl ester resin to the ionic polyester resin is greater than 1 and less than 20. The vinyl ester resin is either an aromatic vinyl ester resin or an aliphatic vinyl ester resin, wherein the aromatic vinyl ester resin has at least one selected from bisphenol A backbone and bisphenol F backbone. The ionic polyester resin has carboxyl or sulfonic acid groups that are ionicly bonded to alkali metals, amines, ammonium, or phosphorus.

2. The sizing agent for inorganic fibers according to claim 1, wherein, The resin (A) further comprises at least one selected from nonionic polyester resins and epoxy resins.

3. The sizing agent for inorganic fibers according to claim 2, wherein, The nonionic polyester resin has at least one selected from bisphenol A backbone and bisphenol F backbone.

4. The sizing agent for inorganic fibers according to claim 2, wherein, The nonionic polyester resin has aliphatic unsaturated bonds.

5. The sizing agent for inorganic fibers according to claim 2, wherein, The epoxy resin has two or more functional epoxy groups.

6. The sizing agent for inorganic fibers according to claim 2, wherein, The epoxy resin has at least one selected from bisphenol A backbone and bisphenol F backbone.

7. The sizing agent for inorganic fibers according to claim 1, wherein, The resin (A) further comprises a nonionic polyester resin and an epoxy resin. When the total content of the vinyl ester resin, the ionic polyester resin, the nonionic polyester resin, and the epoxy resin is set to 100 parts by mass, The resin contains 20 parts by weight or more and 70 parts by weight of the vinyl ester resin, 2 parts by weight or more and 50 parts by weight of the ionic polyester resin, 5 parts by weight or more and 50 parts by weight of the nonionic polyester resin, and 5 parts by weight or more and 50 parts by weight of the epoxy resin.

8. The sizing agent for inorganic fibers according to any one of claims 1 to 7, wherein, The inorganic fiber is further sized with a surfactant.

9. The sizing agent for inorganic fibers according to claim 8, wherein, The surfactant has an aromatic hydrocarbon group.

10. The sizing agent for inorganic fibers according to claim 8, wherein, When the content of the resin (A) is set to 100 parts by mass, It contains the surfactant in a proportion of 10 parts by weight or more and 50 parts by weight or less.

11. An inorganic fiber, characterized in that, It is coated with any one of the inorganic fiber sizing agents according to claims 1 to 10.

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