Fiber sizing agents and their uses

Abstract

The present invention provides a fiber scrubbing agent that can produce fiber strands with excellent fluff suppression even after long-term storage of the fiber scrubbing agent. [Solution] A fiber sizing agent containing a thermosetting resin (A) and a nonionic surfactant (B), satisfying at least one of the following conditions 1 and 2. Condition 1: The non-volatile content concentration is 50 to 100% by weight, and the light transmittance at 25°C with a path length of 10 mm and a wavelength of 660 nm is 10% or more. Condition 2: The agent contains a solvent (D) represented by the following formula (1), and the weight of water contained in the sizing agent is 0 to 8000 relative to the total weight of solvent (D) contained in the sizing agent. However, if the weight of water contained in the sizing agent is 600 to 8000 relative to the total weight of solvent (D) contained in the sizing agent, the solvent (D) contains a compound other than m = 1 in the following formula (1). TIFF2026143664000012.tif22119 (In formula (1), R is a hydrocarbon group or H, and AO is an oxyalkylene group.)

Description

Technical Field

[0001] The present invention relates to a sizing agent for fibers and use thereof. Specifically, the present invention relates to a sizing agent for fibers, a fiber strand using the same, and a fiber-reinforced composite material. Background Art

[0002] Fiber-reinforced composite materials, which are obtained by reinforcing plastic materials (called matrix resins) with various synthetic fibers, are widely used in automotive applications, aerospace applications, sports and leisure applications, general industrial applications and the like. Examples of fibers used in these composite materials include various inorganic fibers such as carbon fiber, glass fiber and ceramic fiber, and various organic fibers such as aramid fiber, polyamide fiber and polyethylene fiber. These various fibers are usually produced in a filament form, then processed into a sheet-shaped intermediate material called unidirectional prepreg by a hot melt method, a drum winding method or the like, processed by a filament winding method, or optionally processed into a woven fabric or chopped fiber form, and thus are used after going through various higher-order processing steps.

[0003] Epoxy resins are widely used as matrix resins for fiber-reinforced composite materials. In addition to epoxy resins, unsaturated polyester resins, vinyl ester resins, acrylic resins and the like are used as radical polymerization-based matrix resins. In order to improve the mechanical strength of a fiber-reinforced composite material, the wettability and adhesion between the matrix resin and the fibers are important, and sizing agents that improve the wettability and adhesion of fibers to the above-mentioned epoxy resins and radical polymerization-based matrix resins have been proposed (for example, Patent Documents 1 and 2). Prior Art Documents Patent Documents

[0004] Patent Document 1 Japanese Unexamined Patent Publication No. 53-52796 Patent Document 2 Japanese Patent Publication No. 06-173170 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, while the sizing agents described in Patent Documents 1 and 2 improve adhesion between the matrix resin and reinforcing fibers, they result in reduced sizing and handling properties due to fuzzing. An investigation into the cause revealed that the amount of fuzzing increases, especially when using fiber sizing agents that have been stored for a long period of time. Therefore, the object of the present invention is to provide a fiber scrubbing agent that can produce fiber strands with excellent fluff suppression even when the fiber scrubbing agent has been stored for a long period of time. [Means for solving the problem]

[0006] As a result of diligent research to solve the above problems, the inventors of the present invention have found that a fiber sizing agent containing a thermosetting resin (A) and a nonionic surfactant (B), and satisfying at least one selected from specific condition 1 and specific condition 2, can solve the above problems. In other words, the present invention includes the following embodiments.

[0007] <1> A fiber sizing agent containing a thermosetting resin (A) and a nonionic surfactant (B), and satisfying at least one of the following conditions 1 and 2. Condition 1: Non-volatile content concentration is 50% to 100% by weight, and the light transmittance at 25°C with a path length of 10 mm and a wavelength of 660 nm is 10% or more. Condition 2: The sizing agent contains a solvent (D) represented by the following general formula (1), and the weight of water contained in the sizing agent is 0 or more and 8000 or less relative to 100 units of the total weight of solvent (D) contained in the sizing agent. However, if the weight of water contained in the sizing agent is 600 or more and 8000 or less relative to 100 units of the total weight of solvent (D) contained in the sizing agent, then the solvent (D) contains a compound other than m = 1 in the following general formula (1). [ka] (In formula (1), R is a hydrocarbon group having 1 to 7 carbon atoms or a hydrogen atom, AO is an oxyalkylene group, m is an integer from 0 to 3, when m is 0, R is a hydrocarbon group having 3 to 7 carbon atoms, and when m is 2 or greater, the AOs within the molecule may be the same or different.) <2> The complex viscosity at 25°C is 0.1 Pa·s to 10 Pa·s. <1> A fiber sizing agent as described above. <3> The solvent (C) contains at least one selected from water and hydrophilic solvents. <1> ~ <2> A fiber scrubbing agent as described in any of the following. <4> The thermosetting resin (A) includes at least one selected from epoxy resin, vinyl ester resin, unsaturated polyester resin, and acrylic resin. <1> ~ <3> A fiber scrubbing agent as described in any of the following. <5> The proportion of nonionic surfactant (B) in the nonvolatile components of the aforementioned fiber sizing agent is 10 to 70% by weight. <1> ~ <4> A fiber scrubbing agent as described in any of the following. <6> The thermosetting resin (A) contains an epoxy resin, and the epoxy equivalent of the fiber sizing agent is 250 to 8000 g / mol. <1> ~ <5> A fiber scrubbing agent as described in any of the following. <7> The hydroxyl value of the aforementioned fiber scrubbing agent is 10 to 150 mg KOH / g. <1> ~ <6> A fiber scrubbing agent as described in any of the following. <8> For carbon fiber, <1> ~ <7> A fiber scrubbing agent as described in any of the following. <9> <1> ~ <8> A diluted solution of a fiber sizing agent, comprising a fiber sizing agent as described in any of the above, wherein the non-volatile content concentration is 0.5% by weight or more and less than 50% by weight. <10> <1> ~ <8> A diluted solution of a fiber sizing agent as described in any of the following, <1> ~ <8> A method for producing fiber strands, comprising the step of applying at least one selected from the fiber sizing agents described in any of the above to raw fibers. <11> <1> ~ <8> A diluted solution of a fiber sizing agent as described in any of the following, <1> ~ <8> A fiber strand obtained by applying at least one selected from the fiber sizing agents described in any of the above to a raw fiber. <12> Matrix resin and <11> A fiber-reinforced composite material comprising the fiber strands described above. [Effects of the Invention]

[0008] The fiber sizing agent and diluted fiber sizing agent of the present invention enable the production of fiber strands with excellent fluff suppression even after long-term storage of the fiber sizing agent. Since the fiber strands produced by the fiber strand production method of the present invention exhibit excellent fluff suppression, a fiber-reinforced composite material with excellent physical properties can be obtained. [Modes for carrying out the invention]

[0009] The components of the fiber sizing agent of the present invention (hereinafter sometimes simply referred to as the sizing agent) will be described in detail below. [Thermosetting resin (A)] The fiber scrubber of the present invention comprises a thermosetting resin (A). The thermosetting resin (A) is not particularly limited, but it is preferable to include at least one selected from epoxy resin, vinyl ester resin, unsaturated polyester resin, and acrylic resin, in terms of improving adhesion between the fibers and the matrix resin, and in terms of easily satisfying the complex viscosity of the sizing agent between 0.1 Pa·s and 10 Pa·s. It is more preferable to include at least one selected from epoxy resin and vinyl ester resin, and even more preferable to include epoxy resin. One or more thermosetting resins (A) may be used in combination.

[0010] An epoxy resin is a compound having one or more reactive epoxy groups in the molecular structure, and a compound having two or more epoxy groups is preferred from the viewpoint of adhesion between fibers and a matrix resin. Representative epoxy resins having one or more epoxy groups include glycidyl ether types obtained from epichlorohydrin and active hydrogen compounds, and other examples include glycidyl ester types, glycidyl amine types, and alicyclic types. One type of epoxy resin may be used alone, or two or more types may be used in combination. Examples of epoxy resins include bisphenol-type epoxy resins, bisphenol novolak-type epoxy resins, amine-type epoxy resins, phenol novolak-type epoxy resins, cresol novolak-type epoxy resins, resorcinol-type epoxy resins, phenol aralkyl-type epoxy resins, naphthol aralkyl-type epoxy resins, dicyclopentadiene-type epoxy resins, epoxy resins having a biphenyl skeleton, isocyanate-modified epoxy resins, tetraphenylethane-type epoxy resins, and triphenylmethane-type epoxy resins.

[0011] Here, the bisphenol-type epoxy resin is obtained by glycidylating two phenolic hydroxyl groups of a bisphenol compound, and examples include bisphenol A type, bisphenol F type, bisphenol AD type, bisphenol S type, as well as halogen, alkyl substituted products, acid modified products, hydrogenated products of these bisphenols. In addition, not only monomers but also high molecular weight compounds having a plurality of repeating units can be suitably used.

[0012] Examples of amine-type epoxy resins include tetraglycidyl diaminodiphenylmethane, triglycidyl aminophenol, triglycidyl aminocresol, tetraglycidyl xylylenediamine, as well as halogen, alkynol substituted products, and hydrogenated products thereof.

[0013] An aromatic epoxy resin having an aromatic ring in the molecular structure is preferred as the epoxy resin, from the viewpoint of improving the adhesion between fibers and the matrix resin, and from the viewpoint that the complex viscosity of the sizing agent easily satisfies 0.1 Pa·s to 10 Pa·s. Among these aromatic epoxy resins, it is preferable to include at least one selected from bisphenol-type epoxy resin, bisphenol novolac-type epoxy resin, and dicyclopentadiene-type epoxy resin in terms of improving adhesion, more preferable to include at least one selected from bisphenol-type epoxy resin and dicyclopentadiene-type epoxy resin, and even more preferable to include bisphenol-type epoxy resin.

[0014] The epoxy equivalent of epoxy resin (A) is preferably 100 to 2500 g / mol, as this provides excellent fluff suppression even when the sizing agent is stored for a long period of time. The upper limit of the epoxy equivalent is more preferably 2000 g / mol, and even more preferably 1000 g / mol. On the other hand, the lower limit of the epoxy equivalent is more preferably 150 g / mol, and even more preferably 200 g / mol. In this invention, epoxy equivalent refers to the value in accordance with JIS-K-7236.

[0015] The weight-average molecular weight of epoxy resin (A) is preferably 100 to 10000, from the viewpoint of heat resistance and the ease with which the complex viscosity of the sizing agent satisfies 0.1 Pa·s to 10 Pa·s. The upper limit of the average molecular weight is more preferably 5000, and even more preferably 2000. On the other hand, the lower limit of the average molecular weight is more preferably 200, and even more preferably 300.

[0016] The method for producing the epoxy resin described above is not particularly limited, and known methods can be used. Furthermore, the epoxy resin described above is generally commercially available, and these commercially available epoxy resins can be used in the fiber sizing agent of the present invention.

[0017] The vinyl ester resin is not particularly limited, and any known resin may be appropriately selected and used. It is a compound having at least one selected from a vinyl ester group, an acrylate group, and a methacrylate group. One or more vinyl ester resins may be used. The vinyl ester group is represented by the group "CH2=CHOCO-", the acrylate group is represented by the group "CH2=CHCOO-", and the methacrylate group is represented by the group "CH2=CCH3COO-".

[0018] Examples of vinyl ester resins include alkyl (meth)acrylic acid esters, alkoxy polyalkylene glycol (meth)acrylic acid esters, benzyl (meth)acrylic acid esters, phenoxyethyl (meth)acrylate, 2-hydroxyalkyl (meth)acrylic acid esters, dialkylaminoethyl (meth)acrylic acid esters, glycidyl (meth)acrylate, 2-methacryloyloxyethyl 2-hydroxypropyl phthalate, polyalkylene glycol di(meth)acrylate, alkanediol di(meth)acrylate, glycerin di(meth)acrylate, 2-hydroxy-3-acryloyloxypropyl (meth)acrylate, dimethylol-tricyclodecane di(meth)acrylate, bisphenol A (meth)acrylic acid ester, alkylene oxide-added bisphenol A (meth)acrylic acid ester, bisphenol A diglycidyl ether (meth)acrylic acid adduct, and alkylene oxide-added bisphenol A diglycidyl ether (meth)acrylic acid Examples of adducts include trimethylolpropane tri(meth)acrylate, glycidyl(meth)acrylate, phenoxyalkyl(meth)acrylate, phenoxypolyalkylene glycol(meth)acrylate, 2-hydroxy-3 phenoxypropanol(meth)acrylate, polyalkylene glycol nonylphenyl ether(meth)acrylate, 2-(meth)acryloyloxyethyl succinic acid, 2-(meth)acryloyloxyethyl phthalic acid, 2-(meth)acryloyloxyethyl-2-hydroxyethyl phthalic acid, neopentyl glycol(meth)acrylate benzoate, alkylene oxide-added trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and pentaerythritol tri(meth)acrylate hexamethylene diisocyanate urethane prepolymer.

[0019] Among these, vinyl ester resins are preferably those having at least one selected from oxyalkylene groups and aryl groups, and more preferably those containing aryl groups, in order to have excellent adhesion to the matrix resin and to easily satisfy a complex viscosity of 0.1 Pa·s to 10 Pa·s for the sizing agent. Specifically, it is preferable to include at least one selected from 2-methacryloyloxyethyl 2-hydroxypropyl phthalate, polyalkylene glycol di(meth)acrylate, 2-(meth)acryloyloxyethyl phthalic acid, 2-(meth)acryloyloxyethyl-2-hydroxyethyl phthalic acid, neopentyl glycol (meth)acrylic acid benzoate, bisphenol A (meth)acrylic acid ester, alkylene oxide-added bisphenol A (meth)acrylic acid ester, bisphenol A diglycidyl ether (meth)acrylic acid adduct, and alkylene oxide-added bisphenol A diglycidyl ether (meth)acrylic acid adduct, and polyalkylene glycol di(meth) It is more preferable to include at least one selected from acrylate, bisphenol A (meth)acrylic acid ester, alkylene oxide-added bisphenol A (meth)acrylic acid ester, bisphenol A diglycidyl ether (meth)acrylic acid adduct, and alkylene oxide-added bisphenol A diglycidyl ether (meth)acrylic acid adduct, and even more preferable to include at least one selected from bisphenol A (meth)acrylic acid ester, alkylene oxide-added bisphenol A (meth)acrylic acid ester, bisphenol A diglycidyl ether (meth)acrylic acid adduct, and alkylene oxide-added bisphenol A diglycidyl ether (meth)acrylic acid adduct.

[0020] The unsaturated polyester resin is not particularly limited as long as it is a polyester resin having a carbon-carbon double bond and is not a vinyl ester resin. For example, an unsaturated polyester obtained by reacting an acid component containing an α,β-unsaturated dicarboxylic acid with an alcohol can be used. Examples of α,β-unsaturated dicarboxylic acids include maleic acid, fumaric acid, itaconic acid, and derivatives thereof such as acid anhydrides, and two or more of these may be used in combination. Furthermore, as needed, saturated dicarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, tetrahydrophthalic acid, adipic acid, sebacic acid, and derivatives thereof such as acid anhydrides may be used in combination with α,β-unsaturated dicarboxylic acids as acid components other than α,β-unsaturated dicarboxylic acids. Examples of alcohols include aliphatic glycols such as ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,2-propanediol, 1,2-butanediol, 1,3-butanediol, and 1,4-butanediol, alicyclic diols such as cyclopentanediol and cyclohexanediol, aromatic diols such as hydrogenated bisphenol A, bisphenol A propylene oxide (1 to 100 mol) adduct, and xylene glycol, and polyhydric alcohols such as trimethylolpropane and pentaerythritol. Two or more of these may be used in combination.

[0021] Among unsaturated polyester resins, aromatic unsaturated polyester resins are preferred because they exhibit excellent adhesion to the matrix resin and the complex viscosity of the sizing agent easily satisfies 0.1 Pa·s to 10 Pa·s. Among aromatic unsaturated polyester resins, condensates of fumaric acid or maleic acid and bisphenol A ethylene oxide (hereinafter abbreviated as EO) adduct, condensates of fumaric acid or maleic acid and bisphenol A propylene oxide (hereinafter abbreviated as PO) adduct, and condensates of fumaric acid or maleic acid and bisphenol A EO and PO adducts (the adducting of EO and PO may be random or blocky) are more preferred.

[0022] The weight-average molecular weight of the unsaturated polyester resin is preferably between 1,000 and 12,000, from the viewpoint of heat resistance and the ease with which the complex viscosity of the sizing agent satisfies 0.1 Pa·s to 10 Pa·s. The upper limit of the weight-average molecular weight is more preferably 8,000, and even more preferably 7,000. On the other hand, the lower limit of the weight-average molecular weight is more preferably 1,500, and even more preferably 2,000. Also, for example, 1,500 to 8,000 is more preferable, and even more preferably 2,000 to 7,000. The acid value is preferably 5 mg KOH / g or less. The weight-average molecular weight in this invention was calculated from the peaks measured with a differential refractive index detector after injecting a sample at a concentration of 3 mg / cc into separation columns KF-402HQ and KF-403HQ manufactured by Showa Denko K.K., using a high-speed gel permeation chromatography apparatus HLC-8220GPC manufactured by Tosoh Corporation.

[0023] Acrylic resins are compounds obtained by polymerizing polymerizable monomers containing monomers with vinyl groups. Examples of acrylic resins include thermosetting acrylic resins. Thermosetting acrylic resins are acrylic copolymers having functional groups in their side chains. These functional groups are mostly inactive at room temperature but exhibit self-reactivity or co-reactivity upon heating. Examples of these functional groups include carboxyl groups, amino groups, methylol groups, hydroxyl groups, and epoxy groups. Monomers having a vinyl group may also contain monomers having functional groups other than a vinyl group. Examples of monomers having functional groups other than a vinyl group include acrylic acid, methacrylic acid, maleic anhydride, acrylamide, N-methylolacrylamide, 2-hydroxyalkyl acrylate, 2-hydroxyalkyl methacrylate, glycidyl acrylate, and glycidyl methacrylate.

[0024] [Nonionic surfactant (B)] The fiber scrubber of the present invention contains a nonionic surfactant (B). The nonionic surfactant (B) is not particularly limited, and any known surfactant can be appropriately selected and used. One or more nonionic surfactants (B) may be used in combination.

[0025] Nonionic surfactants (B) are organic compounds having hydrophilic and hydrophobic groups. Examples of hydrophilic groups include polyoxyethylene groups and polyoxyethylene / polyoxypropylene random copolymer groups. Examples of hydrophobic groups include alkyl groups, alkenyl groups, aryl groups, alkylaryl groups, polycyclic aryl groups, and polypropylene oxide groups. Examples of nonionic surfactants (B) include alkylene oxide-added nonionic surfactants (structures in which alkylene oxides such as ethylene oxide and propylene oxide (two or more can be used in combination) are added to higher alcohols, higher fatty acids, monoalkylphenols, dialkylphenols, trialkylphenols, monostylenide, distylenide, tristylenide, monobenzylphenol, dibenzylphenol, tripenzylphenol, bisphenol, sorbitan, sorbitan esters, castor oil, hydrogenated castor oil, etc.), structures in which higher fatty acids, etc. are added to polyalkylene glycols, and ethylene oxide / propylene oxide copolymers.

[0026] Examples of alkyl or alkenyl groups constituting the hydrophobic group include methyl, ethyl, propyl, butyl, hexyl, 2-ethylhexyl, decyl, lauryl, isodecyl, tridecyl, cetyl, stearyl, oleyl, and behenyl groups, and they may be primary, secondary, or tertiary groups, and may have a linear or branched structure.

[0027] Examples of alkylaryl groups that constitute the hydrophobic group include tolyl group, xylyl group, cumyl group, octylphenyl group, 2-ethylhexylphenyl group, nonylphenyl group, decylphenyl group, and methylnaphthyl group, and there are no limitations on the position or number of alkyl groups.

[0028] Examples of polycyclic aryl groups that constitute the hydrophobic group include styrylphenyl, styrylmethylphenyl, styrylnonylphenyl, alkylstyrylphenyl, distyrylphenyl, distyrylmethylphenyl, tristyrylphenyl, benzylphenyl, dibenzylphenyl, alkyldiphenyl, diphenyl, cumylphenyl, naphthyl, and bisphenol groups, and there are no limitations on the position or number of substituents.

[0029] Examples of the above-mentioned higher fatty acids include capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, montanic acid, oleic acid, linoleic acid, linolenic acid, eleostearic acid, ricinoleic acid, erucic acid, coconut oil fatty acids, palm oil fatty acids, palm kernel oil fatty acids, beef tallow fatty acids, castor oil fatty acids, and rapeseed oil fatty acids.

[0030] The nonionic surfactant (B) is preferably selected from polyoxyalkylene monostylenide phenyl ether, polyoxyalkylene distylenide phenyl ether, polyoxyalkylene torstylenide phenyl ether, and nonionic surfactants having polyoxyalkylene groups at multiple terminals, as this makes it easier to satisfy the range of the present invention in terms of light transmittance, and is even more preferably selected from nonionic surfactants having polyoxyalkylene groups at multiple terminals. Examples of nonionic surfactants having polyoxyalkylene groups at multiple terminals include sorbitan, sorbitan esters, castor oil, hydrogenated castor oil with added alkylene oxide, and polypropylene glycol with added ethylene oxide (so-called Pluronic® type surfactants).

[0031] The nonionic surfactant (B) preferably contains at least one selected from polyoxyalkylene monostylenide phenyl ether, polyoxyalkylene distylenide phenyl ether, polyoxyalkylene torstylenide phenyl ether, polyoxyalkylene hydrogenated castor oil, and a structure in which ethylene oxide is added to polypropylene glycol, from the viewpoint of the light transmittance easily satisfying the range of the present invention and the stability of the dilution of the sizing agent; more preferably contains at least one selected from polyoxyethylene monostylenide phenyl ether, polyoxyethylene distylenide phenyl ether, polyoxyethylene tristylenide phenyl ether, and a structure in which ethylene oxide is added to polypropylene glycol; and even more preferably contains a structure in which ethylene oxide is added to polypropylene glycol.

[0032] The weight-average molecular weight of the nonionic surfactant (B) is preferably 200 to 18000, given that its light transmittance easily satisfies the range of the present invention, and the complex viscosity of the sizing agent easily satisfies 0.1 Pa·s to 10 Pa·s. The upper limit of the average molecular weight is more preferably 10000, and even more preferably 5000. On the other hand, the lower limit of the average molecular weight is more preferably 500, and even more preferably 1000. Also, for example, 500 to 10000 is more preferable, and 1000 to 5000 is even more preferable. The weight-average molecular weight of the nonionic surfactant (B) refers to the value calculated by the method described above.

[0033] [Solvent (C)] The fiber sizing agent of the present invention is preferable in that it contains a solvent (C) selected from water and hydrophilic solvents, as this allows the light transmittance to easily satisfy the range of the present invention, the complex viscosity of the sizing agent to easily satisfy 0.1 Pa·s to 10 Pa·s, the stability of the diluted solution, and the excellent fluff suppression even when the sizing agent is stored for a long period of time. Examples of solvent (C) include water, alcohol-based solvents, glycol-based solvents, ether-based solvents, polyhydric alcohol-based solvents of trivalent or higher, and ketone-based solvents. In the present invention, hydrophilicity of a hydrophilic solvent means that the solubility of water in the solvent is 5.0 (g / 100g) or higher.

[0034] As an alcoholic solvent, alcohols having hydrocarbon groups with 1 to 8 carbon atoms and no ether linkages are preferred. Specifically, examples include methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butanol, and isobutanol. Preferred glycol solvents are alcohols having hydrocarbon groups with 2 to 8 carbon atoms and two hydroxyl groups in the molecule. Specifically, examples include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, tripropylene glycol, and polyethylene glycol.

[0035] As a polyhydric alcohol solvent with a valency of 3 or higher, a trihydric alcohol or higher that does not have an ether bond with 3 to 8 carbon atoms is preferred, and specific examples include glycerin and pentaerythritol.

[0036] As ketone solvents, ketones having 3 to 6 carbon atoms are preferred, such as acetone and methyl ethyl ketone.

[0037] Preferred ether solvents include ethers having 4 to 8 carbon atoms and one or fewer hydroxyl groups, specifically dioxane, tetrahydrofuran, ethylene glycol monoethyl ether, ethylene glycol diethyl ether, ethylene glycol monobutyl ether (butyl glycol), ethylene glycol dibutyl ether, ethylene glycol monoisopropyl ether (isopropyl glycol), diethylene glycol monobutyl ether (butyl diglycol), triethylene glycol monomethyl ether, propylene glycol monomethyl ether, and dipropylene glycol monoethyl ether.

[0038] The solvent (C) preferably contains at least one selected from alcohol-based solvents, glycol-based solvents, and ether-based solvents, in terms of its light transmittance easily satisfying the range of the present invention, its complex viscosity of the stimulant easily satisfying 0.1 Pa·s to 10 Pa·s, and its stability as a stimulant diluent. It is more preferably contains at least one selected from ethers having ether bonds with 4 to 8 carbon atoms and one or fewer hydroxyl groups, and is particularly preferably contains at least one selected from butyl glycol, butyl diglycol, and isopropyl glycol. The solvent (C) may contain one or more types.

[0039] [Solvent (D)] The fiber sizing agent of the present invention is preferable in that it contains a solvent (D) represented by the following general formula (1) in that its light transmittance easily satisfies the range of the present invention, its complex viscosity easily satisfies 0.1 Pa·s to 10 Pa·s, its dilution is stable, and it exhibits excellent fluff suppression even when the sizing agent is stored for a long period of time.

[0040] [ka] (In formula (1), R is a hydrocarbon group having 1 to 7 carbon atoms or a hydrogen atom, AO is an oxyalkylene group, m is an integer from 0 to 3, when m is 0, R is a hydrocarbon group having 3 to 7 carbon atoms, and when m is 2 or greater, the AOs within the molecule may be the same or different.)

[0041] The number of carbon atoms in R is preferably 1 to 6, in terms of light transmittance easily satisfying the range of the present invention, stability of the diluent, and excellent fluff suppression even when the sizing agent is stored for a long period of time. The upper limit of the number of carbon atoms is more preferably 5, and even more preferably 4. On the other hand, the lower limit of the number of carbon atoms is more preferably 2, and even more preferably 3. Also, for example, 2 to 5 is more preferably, and even more preferably 3 to 4. While there are no particular limitations on R, examples include alkyl groups and aryl groups. Alkyl groups are preferred in terms of light transmittance easily satisfying the scope of the present invention, stability of the diluent, and excellent fluff suppression even when the scrubbing agent is stored for a long period of time. Methyl groups, isopropyl groups, and n-butyl groups are more preferred, isopropyl groups and n-butyl groups are even more preferred, and n-butyl groups are particularly preferred.

[0042] In terms of AO, an oxyethylene group and / or an oxyethyleneoxypropylene group are preferred, and an oxyethylene group is more preferred, in terms of light transmittance easily satisfying the range of the present invention, stability of the diluent, and excellent fluff suppression even when the sizing agent is stored for a long period of time. m is preferably 1 to 3, more preferably 2 to 3, and even more preferably 2, in terms of light transmittance easily satisfying the range of the present invention, stability of the diluent, and excellent fluff suppression even when the sizing agent is stored for a long period of time.

[0043] The solvent (D) is not particularly limited as long as it satisfies general formula (1), but examples include (poly)ethylene glycol monoalkyl ether, (poly)ethylene glycol monophenyl ether, (poly)propylene glycol monoalkyl ether, (poly)propylene glycol monophenyl ether, (poly)ethylene glycol, (poly)propylene glycol, isopropyl alcohol, benzyl alcohol, etc. (poly)ethylene glycol monoalkyl ether is preferred in terms of its light transmittance easily satisfying the range of the present invention, the stability of the diluent, and its excellent fluff suppression even when the sizing agent is stored for a long period of time. Methyl glycol, butyl glycol and isopropyl glycol are more preferred, butyl glycol and isopropyl glycol are even more preferred, and isopropyl glycol is particularly preferred.

[0044] The solvent (D) is one in which the solubility of water in the solvent is 5.0 (g / 100g) or higher, and is represented by general formula (1). While there are no particular limitations on the solvent (CD), examples include ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, propylene glycol monomethyl ether, dipropylene glycol monoethyl ether, ethylene glycol, propylene glycol, and isopropyl alcohol. (Poly)ethylene glycol monoalkyl ether is preferred in terms of its light transmittance easily satisfying the range of the present invention, the stability of the diluent, and its excellent fluff suppression even when the scrubbing agent is stored for a long period of time. Isopropyl glycol, butyl glycol, and butyl diglycol are more preferred, isopropyl glycol and butyl diglycol are even more preferred, and butyl diglycol is particularly preferred. If the fiber sizing agent of the present invention contains solvent (CD), the sizing agent shall contain solvent (C) and solvent (D).

[0045] [Other ingredients] The fiber sizing agent of the present invention may contain other components such as other surfactants, smoothing agents, antioxidants, and preservatives, to the extent that they do not impair the effects of the present invention, in order to maintain the performance of the sizing agent and improve its ability to adhere to fibers.

[0046] Other surfactants include anionic surfactants other than nonionic surfactants (B), cationic surfactants, and amphoteric surfactants.

[0047] Examples of anionic surfactants include organic carboxylic acids (salts), sulfate salts of higher alcohols and higher alcohol ethers, organic sulfonates, and phosphate salts of higher alcohols and higher alcohol ethers. Preferably, sulfate salts of higher alcohols and higher alcohol ethers, or phosphate salts of higher alcohols and higher alcohol ethers are used.

[0048] Anionic surfactants include, specifically, alkyl sulfates, alkylaryl sulfates, polycyclic aryl sulfates, polyoxyalkylene alkyl ether sulfates, polyoxyalkylene alkylaryl ether sulfates (such as polyoxyalkylene nonylphenyl ether sulfate), polyoxyalkylene polycyclic aryl sulfates (such as polyoxyalkylene toristyrylphenyl ether sulfate, polyoxyalkylene distyrylphenyl ether sulfate, polyoxyalkylene styrylphenyl ether sulfate, polyoxyalkylene styrylmethylphenyl ether sulfate, polyoxyalkylene distyrylmethylphenyl ether sulfate, polyoxyalkylene toristyrylmethylphenyl ether sulfate, polyoxyalkylene benzylphenyl ether sulfate, polyoxyalkylene dibenzylphenyl ether sulfate, polyoxyalkylene cumylphenyl ether sulfate, polyoxyalkylene cumylphenyl ether sulfate, polyoxyalkylene Alkylene naphthyl ether sulfate salts, etc., polyoxyalkylene alkyl polyhydric alcohol ether sulfate salts, alkyl sulfonate salts, α-olefin sulfonate salts, alkylaryl sulfonate salts, alkylaryl disulfonate salts (alkyl diphenyl disulfonate salts, etc.), bis(polyoxyalkylene styrylphenyl ether) succinate ester sulfonate salts, alkyl sulfosuccinate salts, alkyl phosphate salts, alkylaryl phosphate salts, polyoxyalkylene alkyl ether phosphate salts, poly Oxyalkylene alkylaryl ether phosphate salts, polycyclic aryl ether phosphate salts, polyoxyalkylene polycyclic aryl ether phosphate salts, polyoxyalkylene alkyl polyhydric alcohol ether phosphate salts, aromatic sulfonates (alkylnaphthalene sulfonates, naphthalene sulfonates, etc.), aromatic sulfonic acid formalin condensate salts (alkylnaphthalene sulfonic acid formalin condensate salts, naphthalene sulfonic acid formalin condensate salts, creosote oil sulfonate-based formalin condensates, etc.), melamine sulfonate condensates,Examples include bisphenol sulfonate condensates, alkyl carboxylate salts, polyoxyalkylene alkyl ether carboxylate salts, polycarboxylate salts, belladonna oil, and lignin sulfonates.

[0049] When the above-mentioned anionic surfactant is a salt, it may be an alkali metal salt, alkaline earth metal salt, ammonium salt, organic amine salt, quaternary ammonium salt, etc. Examples of alkali metals include sodium, potassium, and lithium. Examples of alkaline earth metals include magnesium, calcium, and barium. Examples of organic amines include alkylamines (trimethylamine, triethylamine, monomethylamine, dimethylamine, etc.) and alkanolamines (monoethanolamine, diethanolamine, triethanolamine, monoisopropanolamine, diisopropanolamine, triisopropanolamine, dimethylethanolamine, diethylethanolamine, etc.). Examples of quaternary ammonium compounds include tetramethylammonium, tetraethylammonium, tetramethanolammonium, and tetraethanolammonium. These anionic surfactants may be used individually or in combination of two or more types. Preferably, the light transmittance is such that it easily satisfies the scope of the present invention, and therefore, ammonium salts, organic amine salts, and quaternary ammonium salts are used.

[0050] Examples of cationic surfactants include quaternary ammonium salt type cationic surfactants (such as lauryltrimethylammonium chloride and oleylmethylethylammonium ethosulfate) and amine salt type cationic surfactants (such as polyoxyethylene laurylamine lactate).

[0051] Examples of amphoteric surfactants include amino acid-type amphoteric surfactants (such as sodium laurylaminopropionate) and betaine-type amphoteric surfactants (such as stearyldimethylbetaine and lauryldihydroxyethylbetaine).

[0052] The fiber scrubbing agent of the present invention may contain a smoothing agent to further improve fluff suppression even after long-term storage. Examples of smoothing agents include esters of higher fatty acids and higher alcohols, natural oils and fats (such as coconut oil, beef tallow, olive oil, and rapeseed oil), liquid paraffin, and wax. Examples of higher fatty acids are as described above. Examples of alkyl groups of higher alcohols are as described above as alkyl groups constituting a hydrophobic group. Examples of waxes include polyethylene, polypropylene, oxidized polyethylene, oxidized polypropylene, modified polyethylene, modified polypropylene, paraffin wax, candelilla wax, carnauba wax, rice wax, and beeswax. The amount of the smoothing agent is preferably 0.1 to 20% by weight, and more preferably 1 to 10% by weight, relative to the non-volatile content of the fiber sizing agent.

[0053] Among smoothing agents, those containing fatty acids and / or alcohols, and their esterified products, are preferable because they exhibit excellent fluff suppression even when the sizing agent is stored for a long period of time. Examples include oleyl oleate, candelilla wax, and carnauba wax.

[0054] [Fiber sizing agent] The fiber scrubbing agent of the present invention contains a thermosetting resin (A) and a nonionic surfactant (B), and satisfies at least one of the conditions 1 and 2 described below, thereby enabling the production of fiber strands with excellent fluff suppression even when the fiber scrubbing agent has been stored for a long period of time. The reason why fiber strands with excellent fluff suppression can be produced even with fiber scrubbing agents that have been stored for a long period of time is thought to be that (i) the non-volatile content concentration and light transmittance are within a specific range and / or (ii) a specific solvent (D) is included within a specific range, which suppresses the separation of components contained in the scrubbing agent and inhibits the reaction of the thermosetting resin during long-term storage.

[0055] The fiber scrubbing agent of the present invention is preferable in that, when the non-volatile content concentration is 50% to 100% by weight, it can produce fiber strands with excellent fluff suppression even when the fiber scrubbing agent has been stored for a long period of time. The lower limit of the non-volatile content concentration is preferably (1) 60% by weight, (2) 70% by weight, (3) 75% by weight, (4) 80% by weight, (5) 85% by weight, and (6) 90% by weight (the higher the number in parentheses, the more preferable it is). On the other hand, the upper limit of the non-volatile content concentration is preferably (1) 99.999% by weight, (2) 99.99% by weight, (3) 99.9% by weight, (4) 99% by weight, and (5) 98% by weight (the higher the number in parentheses, the more preferable it is). In this invention, the non-volatile content concentration is determined by the method described in the examples.

[0056] The fiber scrubbing agent of the present invention is preferable in that it can produce fiber strands with excellent fluff suppression even after long-term storage, provided that it has a light transmittance of 10% or more at 25°C with an optical path length of 10 mm and a wavelength of 660 nm. The upper limit of the transmittance is preferably 100%, more preferably 99%, even more preferably 98%, and particularly preferably 97%. On the other hand, the lower limit of the transmittance is more preferably 15%, even more preferably 20%, particularly preferably 25%, and most preferably 30%. Also, for example, 15 to 100% is preferred, and 20 to 99% is more preferred. The method for measuring the optical transmittance at 25°C with a path length of 10 mm and a wavelength of 660 nm in this invention is as described in the examples.

[0057] The fiber sizing agent of the present invention preferably has a complex viscosity of 0.1 Pa·s to 10 Pa·s at 25°C, in terms of sizing properties and the stability of the sizing agent dilution. The upper limit of the complex viscosity is more preferably 8 Pa·s, even more preferably 6 Pa·s, and particularly preferably 5 Pa·s. On the other hand, the lower limit of the permeability is more preferably 0.2 Pa·s, even more preferably 0.4 Pa·s, and particularly preferably 0.5 Pa·s. Also, for example, 0.2 to 8 Pa·s is more preferable, and 0.5 to 5 Pa·s is even more preferable. The method for measuring complex viscosity at 25°C in this invention is as described in the examples.

[0058] The proportion of thermosetting resin (A) in the nonvolatile content of the fiber sizing agent of the present invention is preferably 5 to 90% by weight, from the viewpoint of sizing properties, fiber-opening properties, and the ease with which the complex viscosity of the sizing agent satisfies 0.1 Pa·s to 10 Pa·s. The upper limit of this proportion is more preferably 85% by weight, even more preferably 80% by weight, and particularly preferably 75% by weight. On the other hand, the lower limit of this proportion is more preferably 25% by weight, even more preferably 30% by weight, and particularly preferably 35% by weight. Also, for example, 25 to 80% by weight is more preferably, and 30 to 75% by weight is even more preferably.

[0059] When the fiber sizing agent of the present invention contains an epoxy resin, the proportion of epoxy resin in the non-volatile content is preferably 5 to 90% by weight, in terms of adhesion and the ease with which the complex viscosity of the sizing agent satisfies 0.1 Pa·s to 10 Pa·s. The upper limit of this proportion is more preferably 85% by weight, even more preferably 80% by weight, and particularly preferably 75% by weight. On the other hand, the lower limit of this proportion is more preferably 10% by weight, even more preferably 15% by weight, and particularly preferably 20% by weight. Also, for example, 10 to 80% by weight is more preferable, and 20 to 75% by weight is even more preferable.

[0060] The proportion of nonionic surfactant (B) in the nonvolatile content of the fiber sizing agent of the present invention is preferably 10 to 70% by weight, in terms of the light transmittance easily satisfying the range of the present invention, the complex viscosity of the sizing agent easily satisfying 0.1 Pa·s to 10 Pa·s, and the stability of the sizing agent dilution. The upper limit of this proportion is more preferably 65% ​​by weight, even more preferably 60% by weight, and particularly preferably 55% by weight. On the other hand, the lower limit of this proportion is more preferably 15% by weight, even more preferably 20% by weight, and particularly preferably 25% by weight. Also, for example, 15 to 65% by weight is more preferably, and 20 to 60% by weight is even more preferably.

[0061] When the fiber sizing agent of the present invention contains a nonionic surfactant having polyoxyethylene groups at multiple terminals, the proportion of the nonionic surfactant having polyoxyethylene groups at multiple terminals in the nonvolatile content is preferably 5 to 70% by weight, in order to easily adjust the light transmittance to the range of the present invention. The upper limit of this proportion is more preferably 65% ​​by weight, even more preferably 60% by weight, and particularly preferably 55% by weight. On the other hand, the lower limit of this proportion is more preferably 10% by weight, even more preferably 15% by weight, and particularly preferably 20% by weight. Also, for example, 10 to 65% by weight is more preferably, and 15 to 60% by weight is even more preferably.

[0062] The proportion of solvent (C) in the fiber sizing agent of the present invention is preferably 0 to 50% by weight, in terms of ease of adjusting the light transmittance to the range of the present invention, ease of adjusting the complex viscosity to 0.1 Pa·s to 10 Pa·s, and stability of the diluent. The upper limit of this proportion is more preferably 40% by weight, even more preferably 30% by weight, and particularly preferably 25% by weight. On the other hand, the lower limit of this proportion is more preferably 0.01% by weight, even more preferably 0.1% by weight, and particularly preferably 1% by weight. Also, for example, 0.01 to 40% by weight is more preferably, and 0.1 to 30% by weight is even more preferably. Note that the proportion of solvent (C) includes solvent (CD).

[0063] When the fiber sizing agent of the present invention contains at least one selected from alcohol-based solvents, glycol-based solvents, and ether-based solvents, the total proportion of alcohol-based solvents, glycol-based solvents, and ether-based solvents in the fiber sizing agent is preferably 0.1 to 50% by weight, in terms of ease of satisfying the range of light transmittance of the present invention, ease of satisfying the complex viscosity of the sizing agent of 0.1 Pa·s to 10 Pa·s, and stability of the sizing agent dilution. The upper limit of this proportion is more preferably 40% by weight, even more preferably 30% by weight, and particularly preferably 25% by weight. On the other hand, the lower limit of this proportion is more preferably 0.01% by weight, even more preferably 0.1% by weight, and particularly preferably 1% by weight. Also, for example, 0.01 to 40% by weight is more preferable, and 0.1 to 30% by weight is even more preferable. Note that the total proportion of alcohol-based solvents, glycol-based solvents, and ether-based solvents includes the solvent (CD).

[0064] The proportion of water in the fiber sizing agent of the present invention is preferably 0 to 50% by weight, in terms of the stability of the sizing agent during long-term storage. The upper limit of this proportion is more preferably 40% by weight, even more preferably 30% by weight, and particularly preferably 25% by weight. On the other hand, the lower limit of this proportion is more preferably 0.01% by weight, even more preferably 0.1% by weight, and particularly preferably 1% by weight. Also, for example, 0.01 to 40% by weight is more preferable, and 0.1 to 30% by weight is even more preferable.

[0065] The proportion of solvent (D) in the fiber sizing agent of the present invention is preferably 0 to 50% by weight, in terms of ease of adjusting the light transmittance to the range of the present invention, ease of adjusting the complex viscosity to 0.1 Pa·s to 10 Pa·s, and stability of the diluent. The upper limit of this proportion is more preferably 40% by weight, even more preferably 30% by weight, and particularly preferably 25% by weight. On the other hand, the lower limit of this proportion is more preferably 0.01% by weight, even more preferably 0.1% by weight, and particularly preferably 1% by weight. Also, for example, 0.01 to 40% by weight is more preferably, and 0.1 to 30% by weight is even more preferably. Note that the proportion of solvent (D) includes solvent (CD).

[0066] The proportion of solvent (CD) in the fiber sizing agent of the present invention is preferably 0 to 50% by weight, in terms of ease of adjusting the light transmittance to the range of the present invention, ease of adjusting the complex viscosity to 0.1 Pa·s to 10 Pa·s, and stability of the diluent. The upper limit of this proportion is preferably (1) 40% by weight, (2) 30% by weight, (3) 25% by weight, (4) 20% by weight, and (5) 15% by weight, in that order (the larger the number in parentheses, the more preferable). On the other hand, the lower limit of this proportion is preferably (1) 0.01% by weight, (2) 0.1% by weight, (3) 1% by weight, (4) 1.5% by weight, and (5) 2% by weight, in that order (the larger the number in parentheses, the more preferable). Furthermore, for example, 0.01 to 40% by weight is more preferable, and 0.1 to 30% by weight is even more preferable.

[0067] The fiber sizing agent of the present invention contains a solvent (D), optionally contains water as an optional component, and is preferable in that the weight of water contained in the sizing agent is 0 to 8000 relative to the total weight of solvent (D) contained in the sizing agent, in that it is possible to produce fiber strands with excellent fluff suppression even when the fiber sizing agent is stored for a long period of time, and the light transmittance is more likely to satisfy the range of the present invention. The upper limit of the weight is more preferably 6000, even more preferably 4000, and particularly preferably 1000. On the other hand, the lower limit of the weight is more preferably 0.01, even more preferably 0.1, and particularly preferably 1. Also, for example, 0.01 to 6000 is more preferable, and 0.1 to 4000 is even more preferable.

[0068] When the weight of water contained in the sizing agent is 600 to 8000 per 100 units of the total weight of solvent (D) contained in the sizing agent, it is preferable that solvent (D) contains a compound other than m = 1 in general formula (1) because it is possible to produce fiber strands with excellent fluff suppression even in fiber sizing agents that have been stored for a long period of time, and the light transmittance is more likely to satisfy the range of the present invention. When the weight is 600 to 8000, it is thought that when solvent (D) contains a compound other than m = 1 in general formula (1), the affinity with thermosetting resin or nonionic surfactant and water is improved, making it easier to suppress the separation of components contained in the sizing agent and thus easier to suppress the reaction of thermosetting resin during long-term storage. When the weight is 0.01 to 8000, it is more preferable that solvent (D) contains a compound other than m = 1 in general formula (1), and when the weight is 0.1 to 8000, it is even more preferable that solvent (D) contains a compound other than m = 1 in general formula (1). Furthermore, solvent (D) is more preferably a compound in which m in general formula (1) is 2 to 3, and even more preferably a compound in which R has 3 to 4 carbon atoms and m is 2 to 3. Any combination of preferred ranges for the weight of water contained in the sizing agent relative to 100 units of the total weight of solvent (D) and preferred compounds to be included in solvent (D) can be applied.

[0069] In the fiber sizing agent of the present invention, the ratio of nonionic surfactant (B) to thermosetting resin (A) per 100 parts by weight is preferably 10 to 800 parts by weight, given that the light transmittance easily satisfies the range of the present invention and the complex viscosity of the sizing agent easily satisfies 0.1 Pa·s to 10 Pa·s. The lower limit of this ratio is more preferably 30 parts by weight, even more preferably 50 parts by weight, and particularly preferably 70 parts by weight. On the other hand, the upper limit of this ratio is more preferably 780 parts by weight, even more preferably 760 parts by weight, and particularly preferably 740 parts by weight. Also, for example, 30 to 780 parts by weight is more preferably, and 50 to 760 parts by weight is even more preferably.

[0070] When the thermosetting resin (A) contains an epoxy resin, the epoxy equivalent of the fiber sizing agent of the present invention is preferably 250 to 8000 g / mol, in that it exhibits excellent fluff suppression even when the sizing agent is stored for a long period of time. The upper limit of the epoxy equivalent is more preferably 7500 g / mol, even more preferably 7000 g / mol, and particularly preferably 6000 g / mol. On the other hand, the lower limit of the epoxy equivalent is more preferably 300 g / mol, even more preferably 350 g / mol, and particularly preferably 400 g / mol. Also, for example, 300 to 7500 g / mol is more preferably, and 350 to 7000 g / mol is even more preferably. In this invention, epoxy equivalent refers to that which conforms to JIS-K-7236.

[0071] The hydroxyl value of the fiber sizing agent of the present invention is preferably 10 to 150 mgKOH / g, as this allows the light transmittance to easily satisfy the range of the present invention. The upper limit of the hydroxyl value is more preferably 120 mgKOH / g, even more preferably 100 mgKOH / g, and particularly preferably 80 mgKOH / g. On the other hand, the lower limit of the hydroxyl value is more preferably 20 mgKOH / g, even more preferably 30 mgKOH / g, and particularly preferably 40 mgKOH / g. For example, 20 to 120 mgKOH / g is more preferably, and 30 to 100 mgKOH / g is even more preferably. Note that the hydroxyl value in the present invention refers to the value in accordance with JIS-K-0070.

[0072] There are no particular limitations on the method for producing the fiber sizing agent of the present invention, and known methods can be employed. For example, a method in which each component constituting the sizing agent is heated above its softening point while being mixed, and then water or a solvent is added as needed and stirred until a homogeneous solution is obtained; a method in which each component constituting the sizing agent is added to water under stirring to obtain an aqueous solution, emulsion or aqueous dispersion; a method in which each component constituting the sizing agent is produced as an aqueous solution, emulsion or aqueous dispersion; a method in which each component constituting the sizing agent is added to water containing a surfactant under stirring to emulsify or disperse; a method in which each component constituting the sizing agent is mixed with an emulsion dispersion that has been previously emulsified and dispersed; a method in which each component constituting the sizing agent is mixed, the resulting mixture is heated above its softening point, and then phase inversion emulsification is performed by gradually adding water while applying mechanical shear force using a homogenizer, homomixer, ball mill, etc.; a method in which the emulsion dispersion is mixed with an emulsified and dispersed emulsion in an oiling bath to which the sizing agent is applied.

[0073] The pH of the fiber sizing agent of the present invention is preferably 2 to 12, and more preferably 4 to 10, in terms of formulation stability. The pH can be measured using a pH meter at a constant temperature of 25°C after diluting 100 times with pure water.

[0074] [Diluted fiber sizing agent] The fiber sizing agent diluent of the present invention contains the fiber sizing agent and has a non-volatile content concentration of 0.5% by weight or more and less than 50% by weight. The fiber sizing agent diluent can be, for example, one in which the fiber sizing agent is dissolved or dispersed in at least one selected from water and an organic solvent. There are no particular limitations on the method for dissolving or dispersing the fiber sizing agent, and known methods can be employed. The average particle size of the fiber sizing agent diluent of the present invention is not particularly limited, but from the viewpoint of diluent stability, it is preferably 10 μm or less, more preferably 0.01 to 1 μm, and even more preferably 0.01 to 0.5 μm. In this invention, the average particle size refers to the arithmetic mean calculated from the particle size distribution measured by a laser diffraction / scattering particle size distribution analyzer (Horiba LA-920).

[0075] [Fiber strands and methods for manufacturing fiber strands] The fiber strand of the present invention is obtained by applying the fiber sizing agent of the present invention or a diluted solution of the fiber sizing agent of the present invention to a raw fiber strand, and is a fiber for reinforcing a thermosetting resin or a thermoplastic matrix resin.

[0076] The present invention provides a method for producing fiber strands, which includes the step of applying the aforementioned fiber sizing agent or diluted fiber sizing agent solution to raw fiber strands. Preferably, the present invention provides a method for producing fiber strands, which includes the step of drying the fibers to which the fiber sizing agent or diluted fiber sizing agent solution has been applied. There are no particular limitations on the method for obtaining the attached material by applying a fiber sizing agent or a diluted solution of the fiber sizing agent to the raw fiber strands, but any method that applies the fiber sizing agent to the raw fiber strands, such as the kiss roller method, roller immersion method, spray method, or other known methods, is acceptable. Among these methods, the roller immersion method is preferred because it allows for uniform application of the fiber sizing agent to the raw fiber strands. There are no particular limitations on the drying method of the resulting deposit; for example, it can be heat-dried using a heating roller, hot air, or hot plate. There are no particular limitations on the drying temperature; for example, it can be 100 to 250°C.

[0077] Furthermore, when applying the fiber sizing agent of the present invention to the raw fiber strands, all components of the fiber sizing agent may be mixed together and then applied, or the components may be applied separately in two or more stages. Furthermore, thermosetting resins such as epoxy resins, vinyl ester resins, and phenolic resins, and / or thermoplastic resins other than the polymer components of the present invention, such as polyolefin resins, nylon resins, polycarbonate resins, polyester resins, polyacetal resins, ABS resins, phenoxy resins, polymethyl methacrylate resins, polyphenylene sulfide resins, polyetherimide resins, and polyetherketone resins, may be attached to the raw material synthetic fiber strands, to the extent that they do not impair the effects of the present invention.

[0078] The fiber strands of the present invention are used as reinforcing fibers in composite materials having various thermosetting resins or various thermoplastic resins as the matrix resin, and may be used in a continuous fiber state or in a state cut to a predetermined length.

[0079] The amount of non-volatile components of the fiber sizing agent or diluted fiber sizing agent adhering to the raw fiber strands can be appropriately selected, and should be the amount necessary for the fiber strands to have the desired function, but the amount of adhering is preferably 0.1 to 20% by weight relative to the raw fiber strands. For fiber strands in a continuous fiber state, the amount of adhering is more preferably 0.1 to 10% by weight, and even more preferably 0.5 to 5% by weight, relative to the raw fiber strands. Furthermore, for strands cut to a predetermined length, it is more preferably 0.5 to 20% by weight, and even more preferably 1 to 10% by weight.

[0080] Examples of fibers that can be used as (raw material) fiber strands to which the fiber sizing agent of the present invention can be applied include various inorganic fibers such as carbon fibers, glass fibers, and ceramic fibers, and various organic fibers such as aramid fibers, polyethylene fibers, polyethylene terephthalate fibers, polybutylene terephthalate fibers, polyethylene naphthalate fibers, polyarylate fibers, polyacetal fibers, PBO fibers, polyphenylene sulfide fibers, and polyketone fibers. From the viewpoint of the physical properties of the resulting fiber-reinforced composite material, at least one selected from carbon fibers, aramid fibers, polyethylene fibers, polyethylene terephthalate fibers, polybutylene terephthalate fibers, polyethylene naphthalate fibers, polyarylate fibers, polyacetal fibers, PBO fibers, polyphenylene sulfide fibers, and polyketone fibers is preferred. More preferably, carbon fibers are used. The fiber strand of the present invention is a fiber bundle formed by bundling together 3,000 to 100,000 single filaments (single threads) selected from the group consisting of these fibers. From the viewpoint of bundleability, the number of strands is preferably 10,000 or more, and more preferably 20,000 or more. The synthetic fiber strand of the present invention may undergo a fiber opening process to widen the strand width. Methods of fiber opening include, for example, rubbing against a metal surface. The temperature during the fiber opening process is, for example, 20 to 100°C.

[0081] [Fiber-reinforced composite materials] The fiber-reinforced composite material of the present invention comprises a matrix resin and the aforementioned fiber strands. Since the fiber strands are treated with the fiber sizing agent of the present invention, fuzzing is suppressed, resulting in a high-quality fiber-reinforced composite material. Here, the matrix resin can be any known type, but examples include a matrix resin containing thermosetting resins or thermoplastic resins, and may contain one or more types. There are no particular restrictions on thermosetting resins, and examples include epoxy resins, phenolic resins, unsaturated polyester resins, vinyl ester resins, cyanate ester resins, and polyimide resins. There are no particular restrictions on thermoplastic resins, and examples include polyolefin resins, polyamide resins, polycarbonate resins, polyester resins, polyacetal resins, ABS resins, phenoxy resins, polymethyl methacrylate resins, polyphenylene sulfide resins, polyetherimide resins, and polyetherketone resins. Among these, thermosetting resins are preferred because they provide a higher adhesion-improving effect with the fiber sizing agent of the present invention, and epoxy resins and vinyl ester resins are even more preferred.

[0082] These matrix resins may be partially or entirely modified for purposes such as further improving adhesion to the fiber strands. There are no particular limitations on the manufacturing method of fiber-reinforced composite materials, and known methods such as compound injection molding using chopped fibers or long fiber pellets, press molding using UD sheets or woven sheets, and filament winding molding can be employed. There are no particular limitations on the fiber strand content in the fiber-reinforced composite material; it can be appropriately selected depending on the type and form of the fiber, the type of thermoplastic matrix resin, etc. However, 5 to 70% by weight is preferred, and 20 to 60% by weight is more preferred, relative to the resulting fiber-reinforced composite material. [Examples]

[0083] The present invention will be specifically described below with reference to examples, but is not limited to the examples described herein. In the following examples, percentages (%) and parts refer to "weight percent" and "parts by weight" respectively, unless otherwise specified. Each characteristic value was measured based on the method described below.

[0084] <Manufacturing of fiber sizing agents, diluted fiber sizing agents, and fiber strands> A fiber sizing agent was prepared by mixing and stirring the materials to achieve the compositions shown in the Examples and Comparative Examples in Tables 1 to 8 below. Furthermore, the obtained fiber sizing agent was diluted with water to prepare a diluted fiber sizing agent solution with a non-volatile content of 3% by weight. Next, untreated carbon fiber strands (fineness 800 tex, filament count 12,000) were immersed and impregnated with a prepared diluted sizing agent solution at a target OPU of 1% by weight using the Dip Nip method. Afterward, they were hot-air dried at 105°C for 15 minutes to obtain sizing agent-treated carbon fiber strands (OPU 1% by weight). The resulting sizing agent-treated carbon fiber strands were evaluated for their bundling properties, adhesion, and abrasion resistance using the methods described below. The results are shown in Tables 1-8.

[0085] <Measurement of non-volatile content concentration and preparation of non-volatile content> 2.0 to 3.0 g of the sizing agent was spread flat in an aluminum cup with a diameter of 6 cm, and heated and dried in a dryer set to 105°C. The weight was measured every hour, and the residue when the difference in the weight of nonvolatile matter before and after one hour of drying was 0.10% or less was defined as the nonvolatile matter, and the nonvolatile matter concentration was calculated using the following formula. A = (W2 - W3) / (W1 - W3) × 100 A: Non-volatile content concentration (weight %) W1: Total weight of the sizing agent and aluminum cup before drying (g) W2: Total weight of the sizing agent and aluminum cup after drying (g) W3: Weight of the aluminum cup (g)

[0086] <Light transmittance> The focusing agent was used as the sample, and the sample was transferred to a 12.5 mm square polystyrene cell with a path length of 10 mm. The light transmittance at a wavelength of 660 nm was measured using an ultraviolet-visible-near-infrared spectrophotometer (JASCO V-750) with pure water as the reference.

[0087] <Complex viscosity> The stimulant was used as the sample, and its complex viscosity was measured using a rheometer (HAAKE MARS 40, ThermoFisher SCIENTIFIC) under the following conditions. Complex viscosity: Sample temperature 25°C, frequency 1Hz, strain 0.1, cap 0.5mm, plate diameter 25mm

[0088] <Convergence> The sizing agent-treated carbon fiber strands obtained in the examples and comparative examples were visually evaluated to see if they unraveled when 10 pieces of 5 mm length were cut with a utility knife. The following evaluation criteria were used, with ◎, ○, and △ being considered pass / fail. ◎: Two or fewer strands loosen ○: 3-4 strands loosen △: 5 to 7 strands loosen ×: 8 or more strands loosen

[0089] <Adhesiveness> Adhesion was evaluated using the microdroplet method with the HM410 composite material interface property evaluation device (manufactured by Toei Sangyo Co., Ltd.). Carbon fiber filaments were extracted from the carbon fiber strands obtained in the examples and comparative examples and set in a sample holder. A drop of matrix resin was formed on the carbon fiber filament, and the drop was cured using the method described below to obtain a sample for measurement. The sample for measurement was set in the apparatus, the drop was clamped between the apparatus blades, and the carbon fiber filament was moved on the apparatus at a speed of 0.06 mm / min. The maximum pull-out load F when pulling the drop from the carbon fiber filament was measured. The interfacial shear strength τ was calculated using the following formula, and the adhesion between the carbon fiber filament and each matrix resin was evaluated. The following epoxy resins were used as the matrix resins. The curing method for the matrix resins is shown below. Interfacial shear strength τ (unit: MPa) = F / πdl (F: Maximum pull-out load, d: Carbon fiber filament diameter, l: Particle diameter in the pull-out direction of the drop) <Method for curing matrix resin drops> Epoxy resin was used for the matrix resin drops. Epoxy resin: A matrix resin drop was prepared by mixing 100 parts by weight of epoxy resin jER828 (manufactured by Mitsubishi Chemical Corporation) and 3 parts by weight of DICY (manufactured by Mitsubishi Chemical Corporation). The drop was heated at 80°C for 1 hour and then at 150°C for 3 hours to cure. <Evaluation of Adhesion> Adhesion was judged according to the following evaluation criteria, with ◎, ○, and △ being considered passing grades. ◎: Interfacial shear strength of 50 MPa or higher ○: Interfacial shear strength is 45 MPa or more and less than 50 MPa △: Interfacial shear strength is between 40 MPa and 45 MPa ×: Interfacial shear strength is less than 40 MPa

[0090] <Evaluation of fluff suppression> The sizing agent-treated carbon fiber strands obtained in the examples and comparative examples were used as evaluation samples. Using a TM-200 friction bonding force tester (manufactured by Daiei Kagaku Seiki Seisakusho Co., Ltd.), the strands were rubbed 1000 times with a tension of 50g through three mirror-finish chrome-plated stainless steel needles arranged in a zigzag pattern (reciprocating motion speed of 300 times / min). The condition of the fuzziness of the carbon fiber strands was visually judged according to the following criteria, with ◎, ○, and △ being considered acceptable. The sizing agents used in the samples were either those immediately after manufacture or those stored at 40°C for 3 months after manufacture. The fluff suppression performance was compared to that of a fiber sizing agent that had been stored for a long period, with the case using the sizing agent stored at 40°C for 3 months after manufacture being used. ◎: No fluffing was observed, just as before abrasion. ○: Although a few stray hairs were visible, it was at a level that did not pose any practical problems. △: There was a lot of pilling, and some thread breakage was also observed. ×: A significant amount of fuzzing and single-thread breakage were observed.

[0091] The components used in the examples and comparative examples are as follows: [Thermosetting resin (A)] (A1): jER(registered trademark) 828 (manufactured by Mitsubishi Chemical Corporation) Bisphenol A type epoxy resin (epoxy equivalent: 184~194 g / mol) (A2): Epotote (registered trademark) YD-011 (Nippon Steel Chemical & Material Co., Ltd.) Bisphenol A type epoxy resin (Epoxy equivalent: 440~510 g / mol) (A3): Lipoxy(registered trademark) VR-60 (manufactured by Showa Denko Corporation), vinyl ester resin (A4): Unsaturated polyester resin shown below (A4) (A5): Light Acrylate (registered trademark) BP-4EAL (manufactured by Kyoeisha), vinyl ester resin (A6): Denacol® EX411 (manufactured by Nagase ChemteX Corporation), epoxy resin (A7): Styrene-maleic anhydride copolymer, acrylic resin

[0092] [Surfactants (B)] (B1): POE isodecyl ether (EO10 mol) (B2): Sorbitan monooleate (B3): Pluronic® P-103 (manufactured by ADEKA Corporation) POEO polyether (B4): Pluronic® L-44 (manufactured by ADEKA Corporation) POEO polyether (B5): POE styrene-modified phenyl ether (EO 60 mol) (B6): POE styrene-modified phenyl ether (EO9 mol) (B7): POE hydrogenated castor oil ether (EO 20 mol) (B8): POE hydrogenated castor oil ether (EO 150 mol) POEO stands for polyoxypropylene polyoxyethylene.

[0093] [Solvent (C) and Solvent (D)] (CD1): Butylcarbitol (a compound in which R is a butyl group, AO is an oxyethylene group, and m is 2 in general formula (1)) (CD2): Butyl glycol (a compound in which R is a butyl group, AO is an oxyethylene group, and m is 1 in general formula (1)) (CD3): Isopropyl alcohol (a compound in which R is an isopropyl group and m is 0 in general formula (1)) (CD4): Isopropyl glycol (a compound in which R is an isopropyl group, AO is an oxyethylene group, and m is 1 in general formula (1)) (CD5): Ethylene glycol (a compound in which R is a hydrogen atom, AO is an oxyethylene group, and m is 1 in general formula (1)) (C6): Glycerin (C7): Water (CD8): Propylene glycol monomethyl ether (a compound in which R is a methyl group, AO is an oxypropylene group, and m is 1 in general formula (1)) (CD9): Triethylene glycol monomethyl ether (a compound in which R is a methyl group, AO is an oxyethylene group, and m is 3 in general formula (1)) (D10): Phenyl glycol (a compound in which R is a phenyl group, AO is an oxyethylene group, and m is 1 in general formula (1)) (D11): Benzyl alcohol (a compound in which R is a benzyl group and m is 0 in general formula (1)) (C12): Ethanol

[0094] [Other ingredients (E)] (E1): Toluene

[0095] [Synthesis of unsaturated polyester (A4)] The reactor was purged with nitrogen gas, and 88 parts of maleic anhydride and 404 parts of a 4-mol ethylene oxide adduct of bisphenol A were charged. The reaction was carried out at 140°C for 5 hours, and water was removed by distillation to obtain an unsaturated polyester (A4) with an acid value of 2.5. The weight-average molecular weight Mw was 3550.

[0096] [Table 1]

[0097] [Table 2]

[0098] [Table 3]

[0099] [Table 4]

[0100] [Table 5]

[0101] [Table 6]

[0102] [Table 7]

[0103] [Table 8]

[0104] As can be seen from Tables 1 to 8, the fiber scrubbers of Examples 1 to 51 contain a thermosetting resin (A) and a nonionic surfactant (B), and satisfy at least one of the conditions 1 and 2 above, so that fiber strands with excellent fluff suppression can be produced even when the fiber scrubbers are stored for a long period of time. On the other hand, when the thermosetting resin (A) is not included (Comparative Examples 1-4), when the nonionic surfactant (B) is not included (Comparative Examples 5-8, 15), or when conditions 1 and 2 are not met (9-14, 16-26), the sizing agent is unstable and cannot be evaluated, making it unsuitable for use as a sizing agent (Comparative Examples 5-8), or the problem of excellent fluff suppression even in fiber sizing agents that have been stored for a long period of time has not been solved (Comparative Examples 1-4, 9-26). [Industrial applicability]

[0105] Fiber strands and the like treated with the fiber sizing agent of the present invention exhibit excellent fuzz suppression even after long-term storage of the fiber sizing agent, making them suitable for use in the manufacture of fiber-reinforced composite materials. Fiber-reinforced composite materials, in which a matrix resin is reinforced with reinforcing fibers, are used in automotive, aerospace, sports and leisure, and general industrial applications. Examples of reinforcing fibers include various inorganic fibers such as carbon fibers, glass fibers, and ceramic fibers, and various organic fibers such as aramid fibers, polyamide fibers, and polyethylene fibers.

Claims

1. A fiber sizing agent containing a thermosetting resin (A) and a nonionic surfactant (B), and satisfying at least one selected from the following conditions 1 and 2. Condition 1: Non-volatile content concentration is 50% to 100% by weight, and the light transmittance at 25°C with a path length of 10 mm and a wavelength of 660 nm is 10% or more. Condition 2: The sizing agent contains a solvent (D) represented by the following general formula (1), and optionally contains water, wherein the weight of water contained in the sizing agent is 0 or more and 8000 or less relative to the total weight of solvent (D) contained in the sizing agent. However, if the weight of water contained in the sizing agent is 600 or more and 8000 or less relative to the total weight of solvent (D) contained in the sizing agent, then the solvent (D) contains a compound other than m = 1 in the following general formula (1). 【Chemistry 1】 (In formula (1), R is a hydrocarbon group having 1 to 7 carbon atoms or a hydrogen atom, AO is an oxyalkylene group, m is an integer from 0 to 3, when m is 0, R is a hydrocarbon group having 3 to 7 carbon atoms, and when m is 2 or more, the AO groups in the molecule may be the same or different.)

2. The fiber sizing agent according to claim 1, wherein the complex viscosity at 25°C is 0.1 Pa·s to 10 Pa·s.

3. The fiber sizing agent according to claim 1 or 2, comprising a solvent (C) selected from water and hydrophilic solvents.

4. The fiber sizing agent according to any one of claims 1 to 3, wherein the thermosetting resin (A) comprises at least one selected from epoxy resin, vinyl ester resin, unsaturated polyester resin, and acrylic resin.

5. The fiber sizing agent according to any one of claims 1 to 4, wherein the proportion of nonionic surfactant (B) in the nonvolatile components of the fiber sizing agent is 10 to 70% by weight.

6. The fiber sizing agent according to any one of claims 1 to 5, wherein the thermosetting resin (A) contains an epoxy resin, and the epoxy equivalent of the fiber sizing agent is 250 to 8000 g / mol.

7. The fiber sizing agent according to any one of claims 1 to 6, wherein the hydroxyl value of the fiber sizing agent is 10 to 150 mg KOH / g.

8. A fiber sizing agent according to any one of claims 1 to 7, for use with carbon fibers.

9. A diluted solution of a fiber sizing agent, comprising the fiber sizing agent described in any one of claims 1 to 8, wherein the non-volatile content concentration is 0.5% by weight or more and less than 50% by weight.

10. A method for producing fiber strands, comprising the step of applying to raw fiber a diluted solution of a fiber sizing agent according to any one of claims 1 to 8, and at least one selected from the fiber sizing agents according to any one of claims 1 to 8.

11. A fiber strand obtained by applying a diluted solution of a fiber sizing agent according to any one of claims 1 to 8, and at least one selected from the fiber sizing agents according to any one of claims 1 to 8, to a raw fiber.

12. A fiber-reinforced composite material comprising a matrix resin and the fiber strands described in claim 11.

Images