Sizing agent for carbon fiber, carbon fiber, and method for producing carbon fiber

Abstract

To provide a sizing agent for a carbon fiber having high adhesiveness and wettability to a matrix resin.SOLUTION: The ink composition comprises (A) at least one selected from the group consisting of vinyl ester resins, polyolefin resins and polyurethane resins and (B) a surface active agent containing an acetylene-based surface active agent (B1).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a sizing agent for carbon fibers, carbon fibers, and a method for producing carbon fibers. [Background technology]

[0002] Sizing agents are chemicals applied to inorganic fibers such as carbon fibers, and are used for purposes such as reducing fiber damage and increasing fiber bundling. For example, International Publication No. 2016 / 208306 (Patent Document 1) discloses a sizing agent for reinforcing fibers that contains at least one selected from a compound obtained by reacting a titanium compound with a compound having an active hydrogen group, and a titanium compound and a compound having an active hydrogen group. The sizing agent in Patent Document 1 is characterized by excellent heat resistance and high viscosity at high temperatures. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2016 / 208306 Summary of the Invention [Problem to be solved by the invention]

[0004] However, inorganic fibers treated with the sizing agent of Patent Document 1 sometimes had insufficient adhesiveness and wettability to the resin that forms the matrix of the fiber-reinforced resin, leaving room for improvement in terms of improving the strength of the fiber-reinforced resin.

[0005] Therefore, there is a need to develop a sizing agent for carbon fibers that has high adhesiveness and wettability to the matrix resin. [Means for solving the problem]

[0006] The sizing agent for carbon fiber according to the present invention is characterized by containing a resin (A) containing at least one selected from the group consisting of a vinyl ester resin, a polyolefin resin, and a polyurethane resin, and a surfactant (B) containing an acetylene-based surfactant (B1).

[0007] The carbon fiber according to the present invention is characterized in that the above-mentioned sizing agent for carbon fiber is attached thereto.

[0008] Furthermore, the method for producing carbon fibers according to the present invention is characterized by comprising a step of adhering to carbon fibers a sizing agent for carbon fiber, the sizing agent containing: resin (A) including at least one selected from the group consisting of vinyl ester resins, polyolefin resins, and polyurethane resins; and surfactant (B) including an acetylene-based surfactant (B1).

[0009] In one aspect of the sizing agent for carbon fiber according to the present invention, the content of the resin (A) is preferably 10 parts by mass or more and 97 parts by mass or less, where the total content of the resin (A) and the surfactant (B) is 100 parts by mass.

[0010] Further features and advantages of the present invention will become more apparent from the following description of illustrative and non-limiting embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0011] The following describes embodiments of the sizing agent for inorganic fibers and its use, inorganic fibers, and a method for producing carbon fibers according to the present invention. Hereinafter, an example will be described in which the sizing agent for inorganic fibers according to the present invention (hereinafter simply referred to as "sizing agent") is applied to a sizing treatment of carbon fibers (an example of inorganic fibers).

[0012] [Configuration of sizing agent] The sizing agent according to this embodiment contains a resin (A) and a surfactant (B). The sizing agent preferably further contains a nonionic polyester resin (D).

[0013] (resin) Resin (A) contains at least one resin selected from the group consisting of epoxy resins, vinyl ester resins, polyolefin resins, polyurethane resins, and acrylic resins. Resin (A) may be used in the production of the sizing agent as a solid, or in a liquid form provided together with a solvent such as water. Resin (A) preferably contains at least one resin selected from the group consisting of epoxy resins and vinyl ester resins, as this improves the wettability of the sizing agent. Resin (A) may be a single resin or a mixture of multiple resins.

[0014] Examples of epoxy resins include commercially available products such as bisphenol A-based epoxy resins such as jER (registered trademark) 828 and jER (registered trademark) 1001 (both manufactured by Mitsubishi Chemical Corporation), and diglycerol polyglycidyl ether-based epoxy resins such as Denacol (registered trademark) EX-421, but are not limited to these. Note that all of these example epoxy resins are available in solid form.

[0015] Examples of vinyl ester resins include, but are not limited to, reaction compounds of bisphenol A epoxy resins such as jER (registered trademark) 828 with methacrylic acid (bisphenol A diglycidyl ether methacrylic acid adducts), alkylene oxide-added bisphenol A acrylic acid adducts, and 2-acryloyloxyethyl-2-hydroxyethyl-phthalic acid. Note that these vinyl ester resins are all available in solid form.

[0016] Typical polyolefin resins include, but are not limited to, polyethylene and polypropylene. The polyolefin resin may be a modified polyolefin having a portion derived from a monomer other than an olefin-based monomer. Examples of commercially available polyolefin resins include, but are not limited to, MGP-1650 (manufactured by Maruyoshi Chemical Co., Ltd.) and Hi-Tec (trademark) P-9018 (manufactured by Toho Chemical Industry Co., Ltd.). The polyolefin resins in these examples are all aqueous dispersions of modified polypropylene.

[0017] Examples of polyurethane resins include, but are not limited to, commercially available products such as Superflex (registered trademark) 650 (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.), trade name: Adeka Bontitor (registered trademark) HUX-564 (manufactured by ADEKA Corporation), and MELUSI (registered trademark) 6900 (manufactured by Toyo Polymer Co., Ltd.) Polyurethane resins may be water-based or solvent-based, and may be self-emulsifying or forced-emulsifying.

[0018] Examples of acrylic resins include, but are not limited to, a 23% aqueous solution of a copolymer of maleic anhydride and n-butyl methacrylate (mass ratio 60 / 40) neutralized with ammonia, and a 30% aqueous solution of a copolymer of acrylic acid and 2-hydroxyethylacrylamide (mass ratio 15 / 85) neutralized with sodium.

[0019] The content of resin (A) is preferably 10 to 97 parts by mass, where the total content of resin (A) and surfactant (B) is 100 parts by mass. The content of resin (A) is specified as the content of resin solids. Therefore, when resin (A) is used in the production of a sizing agent in the form of an aqueous dispersion, the weight of the dispersion medium, emulsifier, and the like contained in the liquid is not included in the content of resin (A). When resin (A) is a mixture, the total content of resin solids of each component constituting the mixture is referred to as the content of resin (A).

[0020] (surfactant) The surfactant (B) contains an acetylene-based surfactant (B1). Preferably, the surfactant (B) further contains an aromatic surfactant (B2). However, the surfactant (B) may contain other surfactants besides the acetylene-based surfactant (B1) and the aromatic surfactant (B2).

[0021] The content of surfactant (B) is preferably 0.1 to 70 parts by mass, where the total content of resin (A) and surfactant (B) is 100 parts by mass. When surfactant (B) is a mixture, the total content of each component constituting the mixture is referred to as the content of surfactant (B).

[0022] The acetylene surfactant (B1) is a surfactant containing an acetylene skeleton (carbon-carbon triple bond) in the molecule. The acetylene surfactant (B1) may be, for example, at least one selected from the group consisting of acetylene alcohol (B1a), acetylene diol (B1b), alkylene oxide adduct of acetylene alcohol (B1c), and alkylene oxide adduct of acetylene diol (B1d), but is not limited thereto. The acetylene surfactant (B1) may be one type of acetylene surfactant or a mixture of multiple types of acetylene surfactants.

[0023] The acetylene alcohol (B1a) is a compound having one or more acetylene skeletons (carbon-carbon triple bonds) and one hydroxy group in the molecule, and is represented by, for example, formula (1). [ka]

[0024] In formula (1), R 1 and R 2 is a substituted or unsubstituted alkyl group having 1 to 8 carbon atoms. 1 and R 2The number of carbon atoms in the alkyl group is preferably from 1 to 7, more preferably from 1 to 6, and even more preferably from 1 to 4. The alkyl group may be either a straight chain or a branched chain.

[0025] The alkyl group having 1 to 8 carbon atoms may be selected from the group consisting of, for example, a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a t-butyl group, a sec-butyl group, an n-pentyl group, a 3-methylbutyl group, a 2,2-dimethylpropyl group, a 1-methylbutyl group, a 1-ethylpropyl group, a 1,1-dimethylpropyl group, an n-hexyl group, a 4-methylpentyl group, a 3-methylpentyl group, a 2-methylpentyl group, a 1-methylpentyl group, a 2-ethylbutyl group, a 1-ethylbutyl group, a 2,3-dimethylbutyl group, a 1,3-dimethylbutyl group, a 1,2-dimethylbutyl group, a 1-ethyl-2-methylpropyl group, an n-heptyl group, and an n-octyl group.

[0026] R 1 and R 2 R may be the same alkyl group or may be different alkyl groups. 1 and R 2 and R are preferably different alkyl groups, more preferably one is a linear alkyl group and the other is a branched alkyl group, and even more preferably the alkyl group with a smaller carbon number is a linear alkyl group and the alkyl group with a larger carbon number is a branched alkyl group. 1 is selected from the group consisting of methyl, ethyl, and propyl groups; R 2 is particularly preferably an isopropyl group or an isobutyl group, and R 1 is a methyl group and R 2 It is especially preferred that is an isobutyl group.

[0027] The acetylene diol (B1b) is a compound having one or more acetylene skeletons (carbon-carbon triple bonds) and two hydroxy groups in the molecule, and is represented by, for example, formula (2). [ka]

[0028] In equation (2), R 3 , R 4 , R 5 , and R 6 is a substituted or unsubstituted alkyl group having 1 to 8 carbon atoms. Examples of alkyl groups having 1 to 8 carbon atoms are as described above. 3 , R 4 , R 5 , and R 6 The number of carbon atoms in the alkyl group is preferably from 1 to 7, more preferably from 1 to 6, and even more preferably from 1 to 4. The alkyl group may be either a straight chain or a branched chain.

[0029] R 3 , R 4 , R 5 , and R 6 may be the same alkyl group partially or entirely, or may be different alkyl groups. 3 and R 5 and are preferably identical, and R 4 and R 6 It is also preferred that R 3 and R 5 and R 4 and R 6 It is more preferable that each set of is identical.

[0030] R 3 and R 4 and R are preferably different alkyl groups, more preferably one is a linear alkyl group and the other is a branched alkyl group, and even more preferably the alkyl group with a smaller carbon number is a linear alkyl group and the alkyl group with a larger carbon number is a branched alkyl group. 3 is selected from the group consisting of methyl, ethyl, and propyl groups; R 4 is particularly preferably an isopropyl group or an isobutyl group, and R 3 is a methyl group and R4 It is especially preferred that is an isobutyl group.

[0031] R 5 and R 6 and R are preferably different alkyl groups, more preferably one is a linear alkyl group and the other is a branched alkyl group, and even more preferably the alkyl group with a smaller carbon number is a linear alkyl group and the alkyl group with a larger carbon number is a branched alkyl group. 5 is selected from the group consisting of methyl, ethyl, and propyl groups; R 6 is particularly preferably an isopropyl group or an isobutyl group, and R 5 is a methyl group and R 6 It is especially preferred that is an isobutyl group.

[0032] The alkylene oxide adduct (B1c) of acetylene alcohol is a compound in which an alkylene oxide is added to the hydroxy group of the above acetylene alcohol (B1a), and is represented by, for example, formula (3). [ka]

[0033] R in Equation (3) 1 and R 2 is R in Equation (1). 1 and R 2 Similar to R 7 is a substituted or unsubstituted alkylene group having 1 to 8 carbon atoms. The alkylene group may be linear or branched. i is an integer of 1 to 10. i is preferably an integer of 1 to 8, more preferably an integer of 1 to 5, even more preferably an integer of 1 to 4, particularly preferably an integer of 1 to 3, and even more preferably an integer of 1 to 2.

[0034] Examples of the alkylene group having 1 to 8 carbon atoms include -CH2- having one carbon atom, -CH2CH2- having two carbon atoms, -CH2CH2CH2-, -CH2CH(CH3)-, -CH(CH3)CH2-, and -C(CH3)2- having three carbon atoms, -CH2CH2CH2CH2-, -CH2CH2CH(CH3)-, -CH2CH(CH3)CH2-, -CH(CH3)CH2CH2-, -CH(CH3)CH(CH3)-, -CH2C(CH3)2-, -C(CH3)2CH2-, -CH2CH(C2H5)-, and -CH(C2H5)CH2- having four carbon atoms. , -CH2CH2CH2CH2CH2-, -CH2CH2CH2CH(CH3)-, -CH2CH2CH(CH3)CH2-, -CH2CH(CH3)CH2CH2-, -CH(CH3)CH2CH2CH2-, -CH2CH(CH3)CH(CH3)-, -CH(CH3)CH2CH(CH3)-, -CH(CH3)CH2CH(CH3)CH2-, -CH2CH2CH(C2H5)-, -CH2CH(C2H5)CH2-, and -CH(C2H5)CH2CH2-, which have 5 carbon atoms; -CH2CH2CH2CH2CH2CH2-, -CH2CH2CH2CH(CH3)-, -CH2CH(CH3)CH2CH2-, -CH2C H2CH2CH2CH(CH3)-, -CH2CH2CH2CH(CH3)CH2-, -CH2CH2CH(CH3)CH2CH2-, -CH2CH(CH3)CH2CH2CH2-, -CH(CH3)CH2CH2CH2CH2-, -CH2CH2CH2CH(C2H5 )-, -CH2CH2CH(C2H5)CH2-, -CH2CH(C2H5)CH2CH2-, and -CH(C2H5)CH2CH2CH2-, -CH2CH2CH2CH2CH2CH2CH2-, -CH2CH2CH2CH2CH2CH(CH3)-, -CH 2CH2CH2CH2CH(CH3)CH2-, -CH2CH2CH2CH(CH3)CH2CH2-, -CH2CH2CH(CH3)CH2CH2CH2-, -CH2CH(CH3)CH2CH2CH2CH2-, -CH(CH3)CH2CH2CH2CH2CH2-, -CH2CH2CH2CH2CH(C2H5)-, -CH2CH2CH2CH(C2H5)CH2-, -CH2CH2CH(C2H5)CH2CH2-, -CH2CH(C2H5)CH2CH2CH2-, and -CH(C2H5)CH2CH2CH2CH2-, and-CH2CH2CH2CH2CH2CH2CH2CH2-, -CH2CH2CH2CH2CH2CH2CH(CH3)-, -CH2CH2CH2CH2CH2CH(CH3)CH2-, -CH2CH2CH2CH with 8 carbon atoms 2CH(CH3)CH2CH2-, -CH2CH2CH2CH(CH3)CH2CH2CH2-, -CH2CH2CH(CH3)CH2CH2CH2CH2-, -CH2CH(CH3)CH2CH2CH2CH2CH2-, It may be selected from the group consisting of -CH(CH3)CH2CH2CH2CH2CH2CH2-, -CH2CH2CH2CH2CH2CH2CH(C2H5)-, -CH2CH2CH2CH2CH2CH(C2H5)CH2-, -CH2CH2CH2CH2CH(C2H5)CH2CH2-, -CH2CH2CH(C2H5)CH2CH2CH2-, -CH2CH2CH(C2H5)CH2CH2CH2CH2-, and -CH(C2H5)CH2CH2CH2CH2CH2-.

[0035] R 7 is preferably an alkylene group having 2 or 3 carbon atoms, and more preferably an alkylene group having 2 carbon atoms. That is, R 7 is preferably -CH2CH2- (ethylene group) or -CH2CH2CH2- (propylene group), more preferably -CH2CH2- (ethylene group).

[0036] The alkylene oxide adduct (B1d) of acetylene diol is a compound in which an alkylene oxide is added to one or both of the two hydroxy groups of the above acetylene diol (B1b), and is represented by, for example, formula (4). [ka]

[0037] R in Equation (4) 3 , R 4 , R 5 , and R 6 is R in Equation (2) 3 , R 4 , R 5 , and R 6 Similar to R8 and R 9 R is a substituted or unsubstituted alkylene group having 1 to 8 carbon atoms. Examples of alkylene groups having 1 to 8 carbon atoms are as described above. 8 and R 9 and may be the same alkylene group or different alkylene groups.

[0038] j is an integer of 1 or more and 10 or less. j is preferably an integer of 1 or more and 8 or less, more preferably an integer of 1 or more and 5 or less, even more preferably an integer of 1 or more and 4 or less, particularly preferably an integer of 1 or more and 3 or less, and even more preferably an integer of 1 or more and 2 or less.

[0039] k is an integer of 0 or more and 10 or less. k is preferably an integer of 0 or more and 8 or less, more preferably an integer of 0 or more and 5 or less, even more preferably an integer of 0 or more and 4 or less, particularly preferably an integer of 0 or more and 3 or less, and even more preferably an integer of 1 or more and 2 or less.

[0040] j and k may be the same or different. The sum of j and k is preferably 1 or more and 10 or less, more preferably 1 or more and 9 or less, even more preferably 1 or more and 7 or less, particularly preferably 1 or more and 5 or less, and even more preferably 1 or more and 4 or less.

[0041] As such an acetylene-based surfactant (B1), for example, commercially available products such as the Olfin (registered trademark) series (Olfine (registered trademark) E-1010, Olfin (registered trademark) E-1004, etc.) and the Surfynol (registered trademark) series (Surfynol (registered trademark) 104PG50, Surfynol (registered trademark) DF110BC, etc.) manufactured by Nissin Chemical Industry Co., Ltd. may be used.

[0042] The content of the acetylene surfactant (B1) is preferably 0.1 to 30 parts by mass, with the total content of the resin (A) and the surfactant (B) being 100 parts by mass. When the acetylene surfactant (B1) is a mixture, the total content of each component constituting the mixture is referred to as the content of the acetylene surfactant (B1). The content of the acetylene surfactant (B1) is more preferably 0.3 parts by mass or more. Furthermore, the content of the acetylene surfactant (B1) is more preferably 27 parts by mass or less.

[0043] The aromatic surfactant (B2) is a surfactant containing an aromatic ring in the molecule. The aromatic surfactant (B2) is, for example, a compound in which an alkylene oxide is added to an alcohol containing an aromatic ring. The aromatic surfactant (B2) may be one type of aromatic surfactant or a mixture of multiple types of aromatic surfactants.

[0044] Examples of alcohols containing an aromatic ring include phenol, phenol derivatives (such as tristyrenated phenol, nonylphenol, and distyrenated phenol), and benzyl alcohol.

[0045] Examples of alkylene oxides include ethylene oxide and propylene oxide. The alkylene oxide residue of the aromatic surfactant (B2) may be a single type of alkylene oxide residue, or may contain multiple types of alkylene oxide residues. Furthermore, when multiple types of alkylene oxide residues are contained, the multiple types of alkylene oxide residues may be introduced in a block form or may be introduced randomly.

[0046] The content of the aromatic surfactant (B2) is preferably 5 to 50 parts by mass, with the total content of the resin (A) and the surfactant (B) being 100 parts by mass. When the aromatic surfactant (B2) is a mixture, the total content of each component constituting the mixture is referred to as the content of the aromatic surfactant (B2). The content of the aromatic surfactant (B2) is more preferably 10 parts by mass or more. The content of the aromatic surfactant (B2) is more preferably 48 parts by mass or less.

[0047] (non-ionic polyester resin) When the sizing agent according to the present embodiment contains a nonionic polyester resin (D), the nonionic polyester resin (D) preferably has, in its molecule, at least one partial structure selected from the group consisting of a bisphenol A skeleton and a bisphenol F skeleton. The nonionic polyester resin (D) may be a single resin or a mixture of multiple types of resins.

[0048] As such nonionic polyester resin (D), for example, a compound obtained by esterifying a commercially available product such as the Newpol (registered trademark) series manufactured by Sanyo Chemical Industries, Ltd. (Newpol (registered trademark) BPE-20, Newpol (registered trademark) BPE-40, Newpol (registered trademark) BPE-100, etc.) with an acid such as maleic acid, fumaric acid, or adipic acid may be used.

[0049] (Other ingredients) The sizing agent according to this embodiment may contain components other than the resin (A), surfactant (B), and nonionic polyester resin (D). Examples of such components include, but are not limited to, organic solvents and preservatives contained in commercially available products of the resin (A), surfactant (B), and nonionic polyester resin (D). The sizing agent according to this embodiment may also contain an antistatic agent, an antioxidant, an ultraviolet absorber, an antifoaming agent (e.g., modified silicone), and the like.

[0050] The content of the other components may be 0.05 to 30 parts by mass (so-called outer multiplier value) when the total content of the main components of the sizing agent (resin (A), surfactant (B), and nonionic polyester resin (D)) is taken as 100 parts by mass. When there are multiple types of other components, the content of the other components refers to the total content of each component.

[0051] [Method for producing sizing agent] The sizing agent according to this embodiment can be obtained by mixing the resin (A), the surfactant (B), the nonionic polyester resin (D) which may be added optionally, and other components which may be added optionally, by a known method.

[0052] For example, a sizing agent can be produced by heating a mixture of the raw materials to 100°C and mixing uniformly, then cooling to, for example, 70°C or below, and gradually adding water while mixing. The concentration of the active ingredient in the sizing agent can be adjusted by appropriately selecting the ratio by weight of the raw materials to the weight of water.

[0053] [How to use sizing agent] The sizing agent according to this embodiment is used in a sizing treatment of inorganic fibers (carbon fibers are used as an example in this embodiment). The sizing treatment is a treatment in which the sizing agent is applied to a fibrous material, and any method commonly used in the art for applying this type of sizing agent to a fibrous material can be used. That is, an immersion oiling method, a spray oiling method, a roller oiling method, a guide oiling method, and the like can be used. When applying each method, the sizing agent can be appropriately diluted with a solvent such as water.

[0054] The amount of sizing agent attached to the inorganic fibers is not particularly limited, but is preferably 0.1% by mass to 3% by mass of the total amount of sizing agent attached to the inorganic fibers.

[0055] When the sizing agent according to the present embodiment is applied in the production of carbon fibers, carbon fibers having the sizing agent attached thereto are obtained. These carbon fibers are an example of inorganic fibers according to the present invention. Furthermore, the application of the sizing agent according to the present embodiment in the production of carbon fibers is an example of a method for producing carbon fibers according to the present invention, and is also an example of the use of the sizing agent for inorganic fibers according to the present invention.

[0056] Other Embodiments In the above embodiment, an example in which the inorganic fiber sizing agent according to the present invention is applied to carbon fibers has been described. However, the application of the inorganic fiber sizing agent according to the present invention is not limited to carbon fibers, and it can also be applied to inorganic fibers such as glass fibers, ceramic fibers, metal fibers, mineral fibers, rock fibers, and slag fibers.

[0057] Regarding other configurations, it should be understood that the embodiments disclosed in this specification are illustrative in all respects and that the scope of the present invention is not limited thereby. Those skilled in the art will easily understand that appropriate modifications are possible without departing from the spirit of the present invention. Therefore, other embodiments modified without departing from the spirit of the present invention are naturally included in the scope of the present invention.

[0058] (Other means to solve the problem) The sizing agent for inorganic fibers according to the present invention is characterized by containing a resin (A) containing at least one selected from the group consisting of epoxy resins, vinyl ester resins, polyolefin resins, polyurethane resins, and acrylic resins, and a surfactant (B) containing an acetylene-based surfactant (B1).

[0059] The inorganic fibers according to the present invention are characterized in that the above-mentioned sizing agent for inorganic fibers is attached thereto.

[0060] These configurations can improve adhesion and wettability to the matrix resin compared to conventional sizing agents.

[0061] Furthermore, the method for producing carbon fibers according to the present invention is characterized by comprising a step of adhering to carbon fibers a sizing agent for inorganic fibers, the sizing agent containing: resin (A) including at least one selected from the group consisting of epoxy resins, vinyl ester resins, polyolefin resins, polyurethane resins, and acrylic resins; and surfactant (B) including an acetylene-based surfactant (B1).

[0062] This configuration can improve the adhesion and wettability of the carbon fibers to the matrix resin compared to when a conventional sizing agent is used.

[0063] Preferred embodiments of the present invention will be described below, but the scope of the present invention is not limited to the preferred embodiments described below.

[0064] In one aspect of the sizing agent for inorganic fibers according to the present invention, the content of the acetylene-based surfactant (B1) is preferably 0.1 parts by mass or more and 30 parts by mass or less, relative to 100 parts by mass of the total content of the resin (A) and the surfactant (B).

[0065] This configuration provides particularly significant improvements in adhesiveness and wettability.

[0066] In one aspect of the sizing agent for inorganic fibers according to the present invention, it is preferable that the resin (A) contains at least one selected from the group consisting of epoxy resins and vinyl ester resins, and the surfactant (B) further contains an aromatic surfactant (B2).

[0067] This configuration can further improve the adhesiveness.

[0068] In one aspect of the sizing agent for inorganic fibers according to the present invention, the content of the aromatic surfactant (B2) is preferably 5 parts by mass or more and 50 parts by mass or less, relative to 100 parts by mass of the total content of the resin (A) and the surfactant (B).

[0069] This configuration further significantly improves adhesiveness.

[0070] In one embodiment, the sizing agent for inorganic fibers according to the present invention further contains a nonionic polyester resin (D), and it is preferable that the resin (A) contains at least one selected from the group consisting of epoxy resins and vinyl ester resins.

[0071] This configuration can further improve wettability.

[0072] In one embodiment of the sizing agent for inorganic fibers according to the present invention, the nonionic polyester resin (D) preferably has, in its molecule, at least one partial structure selected from the group consisting of a bisphenol A skeleton and a bisphenol F skeleton.

[0073] According to this configuration, the improvement in wettability is even more remarkable.

[0074] In one embodiment, the sizing agent for inorganic fibers according to the present invention is preferably for carbon fibers.

[0075] According to this configuration, a carbon fiber reinforced resin having excellent strength can be obtained.

[0076] Use of the sizing agent for inorganic fibers according to the present invention in the production of carbon fibers is also an aspect of the present invention.

[0077] This configuration can improve the adhesion and wettability of the carbon fibers to the matrix resin compared to when a conventional sizing agent is used. [Example]

[0078] The present invention will be further described below by way of examples, but the present invention is not limited to these examples.

[0079] [Preparation of sizing agent] The sizing agents of Examples 1 to 30 and Comparative Examples 1 to 6 shown in Tables 2 to 4 below were obtained by the following method.

[0080] (1) Reagents (1-1) Resin The resins listed below were used. Of the listed resins, all except for polyester resin PEs-1 correspond to resin (A) in the above embodiment. Furthermore, of the listed resins, various polyolefin resins, various polyurethane resins, and polyester resins were used in the form of resin emulsions, while various acrylic resins were used in the form of aqueous resin solutions. For each material, the nonvolatile content in the emulsion or aqueous solution is shown. The nonvolatile content is determined by measuring the weight of each material before and after heating at 105°C for 2 hours, and expressing the ratio of the weight after heating to the weight before heating as a percentage.

[0081] (epoxy resin) EP-1: jER (registered trademark) 828 (manufactured by Mitsubishi Chemical Corporation, a bisphenol A-based bifunctional epoxy resin) EP-2: jER (registered trademark) 1001 (manufactured by Mitsubishi Chemical Corporation, bisphenol A-based bifunctional epoxy resin) EP-3: Denacol (registered trademark) EX-421 (manufactured by Nagase ChemteX Corporation, diglycerol polyglycidyl ether)

[0082] (vinyl ester resin) VE-1: a reaction compound of jER (registered trademark) 828 (above) with methacrylic acid (bisphenol A diglycidyl ether methacrylic acid adduct) VE-2: Acrylic acid adduct of bisphenol A with 2 moles of ethylene oxide VE-3: 2-Acryloyloxyethyl-2-hydroxyethyl-phthalate

[0083] (Polyolefin resin) PO-1: MGP-1650 (Maruyoshi Chemical Co., Ltd., emulsion of modified polypropylene resin, non-volatile content: 30%) PO-: Hi-Tec (trademark) P-9018 (manufactured by Toho Chemical Industry Co., Ltd., emulsion of modified polypropylene resin, non-volatile content: 35%)

[0084] (Polyurethane resin) PU-1: Superflex (registered trademark) 650 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., polyurethane resin emulsion, non-volatile content: 45%) PU-2: Adeka Bontiter (registered trademark) HUX-564 (manufactured by ADEKA Corporation, polyurethane resin emulsion, non-volatile content: 40%) PU-3: MELUSI (registered trademark) 6900 (manufactured by Toyo Polymer Co., Ltd., polyurethane resin emulsion, non-volatile content: 30%)

[0085] (acrylic resin) AC-1: 23% aqueous solution of ammonia-neutralized copolymer of maleic anhydride and n-butyl methacrylate (60 / 40 by mass) AC-2: 30% aqueous solution of sodium-neutralized copolymer of acrylic acid and 2-hydroxyethylacrylamide (mass ratio 15 / 85)

[0086] (polyester resin) PEs-1: Vylonal (registered trademark) MD-1480 (manufactured by Toyobo Co., Ltd., emulsion of modified polyester resin, non-volatile content: 25%)

[0087] (1-2) Surfactants The surfactants listed below were used.

[0088] (acetylene surfactant) As the acetylene-based surfactant, the following acetylene-based surfactants B1-1 to B1-4 were used, all of which correspond to the acetylene-based surfactant (B1) in the above embodiment. B1-1: Olfine (registered trademark) E-1010 (manufactured by Nissin Chemical Industry Co., Ltd., an adduct of 2,4,7,9-tetramethyl-5-decyne-4,7-diol with 10 moles of ethylene oxide) B1-2: Olfine (registered trademark) E-1004 (manufactured by Nissin Chemical Industry Co., Ltd., an adduct of 2,4,7,9-tetramethyl-5-decyne-4,7-diol with 4 moles of ethylene oxide) B1-3: Surfynol (registered trademark) 104PG50 (manufactured by Nissin Chemical Industry Co., Ltd., a mixed solution of 50% 2,4,7,9-tetramethyl-5-decyne-4,7-diol and 50% propylene glycol) B1-4: Surfynol (registered trademark) 1DF110BC (manufactured by Nissin Chemical Industry Co., Ltd., a mixed solution of 50% 2,5,8,11-tetramethyl-6-dodecyne-5,8-diol and 50% 2-butoxyethanol)

[0089] In Tables 2 to 4 shown below, for examples using acetylene surfactant B1-3, 2,4,7,9-tetramethyl-5-decyne-4,7-diol, which falls under the acetylene surfactant category, is shown as B1-3-A, and propylene glycol, which does not fall under the acetylene surfactant category, is shown as B1-3-S, and their respective contents are shown separately.Similarly, for examples using acetylene surfactant B1-4, 2,5,8,11-tetramethyl-6-dodecyne-5,8-diol is shown as B1-4-A, and 2-butoxyethanol, which does not fall under the acetylene surfactant category, is shown as B1-4-S, and their respective contents are shown separately.

[0090] (aromatic surfactants) As the aromatic surfactant, the following aromatic surfactants B2-1 to B2-3 were used, all of which correspond to the aromatic surfactant (B2) in the above embodiment. B2-1: Tristyrenated phenol with 30 moles of ethylene oxide and 5 moles of propylene oxide at random adduct B2-2: Nonylphenol with 10 moles of ethylene oxide B2-3: Random adduct of distyrenated phenol with 27 moles of ethylene oxide and 3 moles of propylene oxide

[0091] (Other surfactants) The surfactants listed below were used. B3-1: Tetradecyl alcohol adduct with 10 moles of ethylene oxide and 5 moles of propylene oxide B3-2: 10 moles of ethylene oxide adduct of dodecyl alcohol

[0092] (1-3) Nonionic polyester resin As the nonionic polyester resin, the following nonionic polyester resins D-1 to D-3 were used, all of which correspond to the nonionic polyester resin (D) in the above embodiment. D-1: A polyester resin obtained by esterifying Newpol (registered trademark) BPE-20 (manufactured by Sanyo Chemical Industries, Ltd., an adduct of 2 moles of ethylene oxide with bisphenol A) and maleic acid in a molar ratio of hydroxyl value / acid value of 4 / 3. D-2: A polyester resin obtained by esterifying Newpol (registered trademark) BPE-40 (manufactured by Sanyo Chemical Industries, Ltd., an adduct of bisphenol A with 4 moles of ethylene oxide) and fumaric acid in a molar ratio of hydroxyl value / acid value of 5 / 4. D-3: A polyester resin obtained by esterifying Newpol (registered trademark) BPE-100 (manufactured by Sanyo Chemical Industries, Ltd., an adduct of 10 moles of ethylene oxide with bisphenol A) and adipic acid in a molar ratio of hydroxyl value / acid value of 6 / 5.

[0093] (1-4) Other ingredients In the examples and comparative examples, no other components were added to the system alone, except for propylene glycol (B1-3-S) contained in the acetylenic surfactant B1-3 and 2-butoxyethanol (B1-4-S) contained in the acetylenic surfactant B1-4, which correspond to other components in the above embodiments.

[0094] (2) Preparation of sizing agent (Preparation of Example 1) 65 parts by mass of epoxy resin EP-1, 5.0 parts by mass of acetylene surfactant B1-1, 20 parts by mass of aromatic surfactant B2-1, and 10 parts by mass of nonionic polyester resin D-1 were weighed out, heated to 100°C, and mixed uniformly. The mixture was then cooled to below 70°C, and water was gradually added while mixing to obtain a uniform sizing agent solution. The solids concentration of the resulting sizing agent solution was 2% by mass.

[0095] (Preparation of Examples 2 to 23 and Comparative Examples 1 and 2) The sizing agents of Examples 2 to 23 and Comparative Examples 1 and 2 were prepared using the same procedures and conditions as in Example 1, except that the type of resin, the presence or absence and type of acetylene-based surfactant, the presence or absence and type of aromatic-based surfactant, the presence or absence and type of other surfactants, the presence or absence and type of nonionic polyester resin, and the presence or absence and type of other components were changed.

[0096] Preparation of Example 24 95 parts by mass of polyolefin resin PO-1 (based on nonvolatile content) and 5.0 parts by mass of acetylene surfactant B1-1 were weighed out and mixed with water to obtain a homogeneous sizing agent solution. The solids concentration of the obtained sizing agent solution was 2% by mass.

[0097] (Preparation of Examples 25 to 30 and Comparative Examples 3 to 6) The sizing agents of Examples 25 to 30 and Comparative Examples 3 to 6 were prepared using the same procedures and conditions as in Example 23, except that the type of resin, the presence or absence and type of acetylene-based surfactant, the presence or absence and type of aromatic-based surfactant, the presence or absence and type of other surfactants, the presence or absence and type of nonionic polyester resin, and the presence or absence and type of other components were changed.

[0098] [Evaluation of sizing agents] (1) Adhesiveness One carbon fiber was taken out from the carbon fiber bundle to which the sizing agent of each example and comparative example had been applied, and both ends of the fiber were fixed to a holder with an adhesive so that the carbon fiber was in a tensioned state. A matrix resin (described below) in the form of resin droplets with a diameter of 90 to 110 μm was attached to the carbon fiber fixed to the holder to prepare a test specimen.

[0099] The matrix resins used are as follows: The matrix resins used correspond to the resins contained in each of the Examples and Comparative Examples, and the matrix resins used for adhesiveness evaluation are indicated by the following symbols in Tables 2 to 4 shown below. M-1: Epoxy resin (jER (registered trademark) 828 (manufactured by Mitsubishi Chemical Corporation), triethylene is used as a curing agent) M-2: Vinyl ester resin (Lipoxy (registered trademark) R-804B (Showa Denko K.K.), methyl ethyl ketone peroxide (manufactured by Showa Denko K.K.) was used as a curing agent. M-3: Polyamide resin (UBE nylon 1011FB (UBE Corporation)) M-4: Polypropylene resin (2% maleic anhydride modified polypropylene)

[0100] Each sample piece was sandwiched between two blades, which were moved in the fiber axial direction at a speed of 0.05 mm / min, and the maximum stress F generated when the resin droplets peeled off from the carbon fiber was measured with a load cell. The interfacial shear strength τ was calculated using the measured value according to equation (5).

number

[0101] In equation (5), F is the maximum stress (unit: kgf) generated when the resin droplet peels off from the carbon fiber, D is the diameter (unit: mm) of the carbon fiber used as the test specimen, and L is the diameter (unit: mm) of the resin droplet in the test specimen in the fiber axis direction.

[0102] The interfacial shear strength τ was measured by the above procedure 20 times for each of the Examples and Comparative Examples, and the interfacial shear strength τ was divided into three levels based on the average value obtained (Table 1).

[0103] Table 1: Evaluation criteria for each matrix resin [Table 1]

[0104] (2) Wettability For each of the test pieces prepared in the above section "(1) Adhesion" for each of the Examples and Comparative Examples, the contact angle of the resin droplets with the carbon fiber was measured. For each matrix resin, the contact angle of the resin droplets with the carbon fiber to which no sizing agent was applied was also measured. The contact angle θ for each of the Examples and Comparative Examples and the contact angle θ with the carbon fiber to which no sizing agent was applied were compared. ref The difference between Δθ(=θ ref -θ), the following three levels were determined: Evaluation A: Δθ is 2° or more. Rating B: Δθ is 1° or more and less than 2°. Rating C: Δθ is less than 1°.

[0105] 〔result〕 For each of the Examples and Comparative Examples, the type and content of the reagents used, as well as the evaluation results of adhesion and wettability, are shown in Tables 2 to 4. When the resin material used is in the form of an emulsion or aqueous solution, the ratio (percentage) of the weight of the non-volatile content contained in the emulsion or aqueous solution used to the total weight of the sizing agent is calculated as a value in parts by mass.

[0106] Table 2: Evaluation results of sizing agents (Examples 1 to 19) [Table 2]

[0107] Table 3: Evaluation results of sizing agents (Examples 20 to 30) [Table 3]

[0108] Table 4: Evaluation results of sizing agents (Comparative Examples 1 to 6) [Table 4] [Industrial Applicability]

[0109] The present invention can be used, for example, in the production of carbon fibers.

Claims

1. A resin (A) containing at least one selected from the group consisting of a vinyl ester resin, a polyolefin resin, and a polyurethane resin; and a surfactant (B) including an acetylene-based surfactant (B1).

2. 2. The sizing agent for carbon fiber according to claim 1, wherein a content of the resin (A) is 10 parts by mass or more and 97 parts by mass or less, relative to 100 parts by mass of the total content of the resin (A) and the surfactant (B).

3. 3. Carbon fiber having the sizing agent for carbon fiber according to claim 1 or 2 attached thereto.

4. A resin (A) containing at least one selected from the group consisting of a vinyl ester resin, a polyolefin resin, and a polyurethane resin; A method for producing carbon fibers, comprising a step of adhering to carbon fibers a sizing agent for carbon fibers, the sizing agent containing a surfactant (B) including an acetylene-based surfactant (B1).

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