Resin composition and molded body

Abstract

The present invention provides a resin composition having excellent moldability from which a molded body excellent in mechanical characteristics and surface smoothness can be obtained, and a molded body thereof.　The resin composition of the present invention comprises a melt-moldable fluororesin and polyacrylonitrile-based carbon fibers. The carbon atom content of the polyacrylonitrile-based carbon fibers is from 90 mass% to less than 99 mass%. The average fiber length of the polyacrylonitrile-based carbon fibers is 1 mm or less, and the mass ratio of the fluororesin to the polyacrylonitrile-based carbon fibers is 60 / 40 to 95 / 5.

Description

Resin composition and molded article

[0001] The present invention relates to a resin composition and a molded article.

[0002] Fluorine resins have excellent heat resistance, flame retardancy, chemical resistance, weather resistance, non-stickiness, low friction, low dielectric properties, etc., and are therefore used in a wide range of applications, such as corrosion-resistant piping materials in chemical plants, agricultural greenhouse materials, release coating materials for kitchen utensils, and electrical wire covering materials. On the other hand, fluororesins may be inferior to general engineering plastics in mechanical properties such as tensile strength and flexural strength (Patent Document 1).

[0003] Patent Document 1 proposes the following resin composition that is excellent in mechanical properties and can give highly elastic molded articles: A resin composition containing one or more melt-moldable fluororesin and inorganic fibers, wherein the fluororesin accounts for 60 to 95 mass% of a total of 100 mass% of the fluororesin and the inorganic fibers, and the inorganic fibers account for 5 to 40 mass% of a total of 100 mass% of the fluororesin and the inorganic fibers, the inorganic fibers have a sizing agent adhered to at least a portion of their surfaces, and the inorganic fibers have a mass loss rate of 3% or less as calculated by a specific method.

[0004] International Publication No. 2023 / 286801

[0005] However, according to the investigations of the present inventors, the resin composition of Patent Document 1 has room for improvement in moldability when producing a molded article, particularly in the surface smoothness of the molded article.

[0006] The present invention provides a resin composition that is excellent in moldability and that can give a molded article that is excellent in mechanical properties and surface smoothness, and a molded article that is excellent in mechanical properties and surface smoothness.

[0007] The present invention has the following aspects. [1] A resin composition comprising a melt-moldable fluororesin and polyacrylonitrile-based carbon fiber, wherein the carbon atom content of the polyacrylonitrile-based carbon fiber is 90% by mass or more but less than 99% by mass, the average fiber length of the polyacrylonitrile-based carbon fiber is 1 mm or less, and the mass ratio of the fluororesin to the polyacrylonitrile-based carbon fiber is 60 / 40 to 95 / 5. [2] The resin composition according to claim 1, wherein the fluororesin has units based on a fluorine-containing monomer, and the fluorine-containing monomer is at least one selected from the group consisting of a fluoroolefin, a fluorine-containing compound having a ring structure, a compound represented by the following formula (1), a compound represented by the following formula (2), a compound represented by the following formula (3), a compound represented by the following formula (4), and a compound represented by the following formula (5). CF ２ =CFOR ｆ１ ... (1) CH ２ =CX １ (CF ２ ) ｐ X ２ ... (2) CF ２ =CFOR ｆ２ SO ２ X ３ ... (3) CF ２ =CFOR ｆ３ CO ２ X ４ ... (4) CF ２ =CF(CF ２ ) ｑ OCF = CF ２ ...(5) In formula (1), R ｆ１ is a perfluoroalkyl group having 1 to 10 carbon atoms which may have an etheric oxygen atom between carbon atoms, and in formula (2), X １ is a hydrogen atom or a fluorine atom, p is an integer of 2 to 10, and X ２ is a hydrogen atom or a fluorine atom, and in formula (3), R ｆ２ is a perfluoroalkylene group having 1 to 10 carbon atoms which may have an etheric oxygen atom between the carbon atoms, and X ３ is a halogen atom or a hydroxyl group, and in formula (4), R ｆ３is a perfluoroalkylene group having 1 to 10 carbon atoms which may have an etheric oxygen atom between the carbon atoms, and X ４ is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and in formula (5), q is 1 or 2. [3] The resin composition according to [1] or [2], wherein the fluororesin is at least one selected from the group consisting of a copolymer having units based on tetrafluoroethylene and units based on ethylene, a copolymer having units based on chlorotrifluoroethylene and units based on ethylene, a copolymer having units based on tetrafluoroethylene and units based on hexafluoropropylene, a copolymer having units based on tetrafluoroethylene and units based on a compound represented by the following formula (1), and a copolymer having units based on tetrafluoroethylene, units based on a compound represented by the following formula (2), and units based on ethylene. CF ２ =CFOR ｆ１ ... (1) CH ２ =CX １ (CF ２ ) ｐ X ２ ...(2) In formula (1), R ｆ１ is a perfluoroalkyl group having 1 to 10 carbon atoms which may have an etheric oxygen atom between carbon atoms, and in formula (2), X １ is a hydrogen atom or a fluorine atom, p is an integer of 2 to 10, and X ２is a hydrogen atom or a fluorine atom. [4] The resin composition according to [3], wherein the fluororesin is at least one selected from the group consisting of a copolymer having units based on tetrafluoroethylene and units based on ethylene, a copolymer having units based on tetrafluoroethylene and units based on the compound represented by formula (1), and a copolymer having units based on tetrafluoroethylene, units based on the compound represented by formula (2), and units based on ethylene. [5] The resin composition according to any of [1] to [4], wherein the fluororesin has at least one functional group selected from the group consisting of a carbonyl group-containing group, a hydroxy group, an epoxy group, an amide group, an amino group, and an isocyanate group. [6] The resin composition according to any of [1] to [5], wherein the melt flow rate of the fluororesin is 0.1 to 100 g / 10 min. [7] The resin composition according to any of [1] to [6], wherein the carbon atom content of the polyacrylonitrile-based carbon fiber is 90 to 98 mass%. [8] The resin composition according to any one of [1] to [7], wherein the polyacrylonitrile-based carbon fibers have an average fiber diameter of 1 to 20 μm. [9] The resin composition according to any one of [1] to [8], wherein the proportion of the fluororesin is 50 to 95 mass% of the total amount of the resin composition.

[10] The resin composition according to any one of [1] to [9], wherein the proportion of the polyacrylonitrile-based carbon fibers is 1 to 40 mass% of the total amount of the resin composition.

[11] The resin composition according to any one of [1] to

[10] , wherein the resin composition has a melt flow rate of 2.5 g / 10 min or more at a temperature of 297°C and a load of 49 N.

[12] The resin composition according to any one of [1] to

[11] , wherein s, calculated by the following formula, is 4.0 or more and less than 6.0. s = t / u In the formula, t is the bending strength (MPa) of a 4 mm thick injection-molded article of the resin composition, and u is the content (mass%) of the polyacrylonitrile-based carbon fiber in the total of the fluororesin and the polyacrylonitrile-based carbon fiber in the resin composition.

[13] A molded article obtained by molding the resin composition according to any one of [1] to

[12] .

[14] The molded article according to

[13] , wherein the bending strength of the molded article is 50 MPa or more.

[15] The molded body according to

[13] or

[14] , wherein the surface roughness of the molded body is 10 μm or less.

[0008] The resin composition of the present invention has excellent moldability and can be used to obtain a molded article having excellent mechanical properties and surface smoothness. The molded article of the present invention has excellent mechanical properties and surface smoothness.

[0009] The meanings of the terms are as follows. A compound represented by formula (n) is referred to as "compound (n)." n is a natural number. "Monomer" refers to a compound having a polymerizable carbon-carbon double bond. "Unit based on a monomer" is a collective term for an atomic group formed directly by polymerization of one monomer molecule and an atomic group obtained by chemically converting a portion of the atomic group. A unit based on a monomer is also simply referred to as a "monomer unit." "Melt-processable" means exhibiting melt fluidity. "Exhibiting melt fluidity" means that there is a temperature at which the melt flow rate is 0.1 to 1,000 g / 10 min at a temperature at least 20°C higher than the melting point of the resin under a load of 49 N. "Etheric oxygen atom" refers to an oxygen atom that forms an ether bond (-O-) between carbon atoms. "Melting point" refers to the temperature corresponding to the maximum value of the melting peak measured by differential scanning calorimetry (DSC). "Melt flow rate" is the melt mass flow rate (MFR) defined in JIS K 7210:1999 (ISO 1133:1997). "Carbon atom content," "average fiber length," and "average fiber diameter" are determined by the methods described in the Examples. "Surface roughness," "flexural strength," and the like are determined by the methods described in the Examples. The symbol "to" indicating a numerical range means that the numerical values ​​before and after "to" are included as the lower and upper limits. The lower and upper limits of the numerical ranges disclosed in this specification can be arbitrarily combined to form a new numerical range.

[0010] [Resin Composition] The resin composition of the present invention contains a melt-moldable fluororesin and polyacrylonitrile-based carbon fiber (hereinafter also referred to as "PAN-based CF"). The carbon atom content of the PAN-based CF is 90% by mass or more but less than 99% by mass, and the average fiber length of the PAN-based CF is 1 mm or less. The mass ratio of the fluororesin to the PAN-based CF is 60 / 40 to 95 / 5. Several embodiments will be described in detail below.

[0011] (Fluororesin) The fluororesin is a fluoropolymer having a fluorine-containing monomer unit, and is not particularly limited as long as it is melt-moldable. The fluorine-containing monomer is not particularly limited as long as it is a fluorine-containing compound having one polymerizable carbon-carbon double bond. Examples of the fluorine-containing monomer include fluoroolefins, fluorine-containing compounds having a ring structure, compound (1) (hereinafter also referred to as "PAVE"), compound (2) (hereinafter also referred to as "FAE"), compound (3), compound (4), and compound (5). However, the fluorine-containing monomer is not limited to these examples. Furthermore, two or more types of fluorine-containing monomers may be used in combination.

[0012] CF ２ =CFOR ｆ１ ... (1) CH ２ =CX １ (CF ２ ) ｐ X ２ ... (2) CF ２ =CFOR ｆ２ SO ２ X ３ ... (3) CF ２ =CFOR ｆ３ CO ２ X ４ ... (4) CF ２ =CF(CF ２ ) ｑ OCF = CF ２ ...(5)

[0013] In formula (1), R ｆ１ is a perfluoroalkyl group having 1 to 10 carbon atoms which may have an etheric oxygen atom between the carbon atoms. １is a hydrogen atom or a fluorine atom, p is an integer of 2 to 10, and X ２ is a hydrogen atom or a fluorine atom. ｆ２ is a perfluoroalkylene group having 1 to 10 carbon atoms which may have an etheric oxygen atom between the carbon atoms, and X ３ is a halogen atom or a hydroxyl group. ｆ３ is a perfluoroalkylene group having 1 to 10 carbon atoms which may have an etheric oxygen atom between the carbon atoms, and X ４ is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. In formula (5), q is 1 or 2.

[0014] Examples of the fluorine-containing compound having a ring structure include perfluoro(2,2-dimethyl-1,3-dioxole), 2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxole, and perfluoro(2-methylene-4-methyl-1,3-dioxolane).

[0015] As the fluorine-containing monomer, from the viewpoint of mechanical properties, fluoroolefin, PAVE and FAE are preferred, and fluoroolefin and PAVE are more preferred.

[0016] Examples of fluoroolefins include tetrafluoroethylene (hereinafter also referred to as "TFE"), vinyl fluoride, vinylidene fluoride (hereinafter also referred to as "VdF"), trifluoroethylene, chlorotrifluoroethylene (hereinafter also referred to as "CTFE"), hexafluoropropylene (hereinafter also referred to as "HFP"), and hexafluoroisobutylene. Among these, from the viewpoints of moldability and mechanical properties, TFE and HFP are preferred, and TFE is more preferred.

[0017] Examples of PAVE include CF ２ = CFOCF ２ CF ３ , C.F. ２ = CFOCF ２ CF ２ CF ３ , C.F. ２ = CFOCF ２ CF ２ CF ２ CF３ , C.F. ２ = CFO (CF ２ ) ６ Among them, CF is the most suitable from the viewpoint of mechanical properties. ２ = CFOCF ２ CF ２ CF ３ (hereinafter also referred to as "PPVE") is preferred.

[0018] Examples of FAE include CH ２ =CF(CF ２ ) ２ F, CH ２ =CF(CF ２ ) ３ F, CH ２ =CF(CF ２ ) ４ F, CH ２ =CF(CF ２ ) ５ F, CH ２ =CF(CF ２ ) ６ F, CH ２ =CF(CF ２ ) ２ H, CH ２ =CF(CF ２ ) ３ H, CH ２ =CF(CF ２ ) ４ H, CH ２ =CF(CF ２ ) ５ H, CH ２ =CF(CF ２ ) ６ H, CH ２ =CH(CF ２ ) ２ F (hereinafter also referred to as "PFEE"), CH ２ =CH(CF ２ ) ３ F, CH ２ =CH(CF ２ ) ４ F (hereinafter also referred to as "PFBE"), CH ２ =CH(CF ２ ) ５ F, CH ２ =CH(CF ２ ) ６ F, CH２ =CH(CF ２ ) ２ H, CH ２ =CH(CF ２ ) ３ H, CH ２ =CH(CF ２ ) ４ H, CH ２ =CH(CF ２ ) ５ H, CH ２ =CH(CF ２ ) ６ Examples include H.

[0019] The FAE is preferably the compound (2-1). ２ =CH(CF ２ ) ｐ１ X ２ In formula (2-1), p1 is 2 to 6, preferably 2 to 4, and X ２ is a hydrogen atom or a fluorine atom.

[0020] Compound (2-1) includes PFEE, CH ２ =CH(CF ２ ) ３ F, PFBE, CH ２ =CF(CF ２ ) ３ H, CH ２ =CF(CF ２ ) ４ H is preferred, and PFBE and PFEE are more preferred.

[0021] The fluororesin may further have a non-fluorine monomer unit in addition to the fluorine-containing monomer unit. The non-fluorine monomer is not particularly limited as long as it is a monomer that does not have a fluorine atom. Examples include olefins such as ethylene, propylene, and 1-butene, vinyl esters such as vinyl acetate, and monomers having a functional group f described below. When the fluororesin has a non-fluorine monomer unit, two or more types of non-fluorine monomers may be used in combination. As the non-fluorine monomer, ethylene, propylene, and 1-butene are preferred, and ethylene is particularly preferred, from the viewpoint of excellent mechanical properties and the like of the molded article.

[0022] The fluororesin may be a homopolymer having a fluorine-containing monomer unit, a copolymer having two or more kinds of fluorine-containing monomer units, or a copolymer having one or more kinds of fluorine-containing monomer units and one or more kinds of non-fluorine-containing monomer units. The resin composition may contain two or more kinds of these homopolymers or copolymers as the fluororesin.

[0023] When the fluororesin is a copolymer having fluorine-containing monomer units and non-fluorine-containing monomer units, the proportion of the fluorine-containing monomer units is preferably 40.0 to 99.5 mol %, more preferably 45 to 99 mol %, based on the total of the fluorine-containing monomer units and non-fluorine-containing monomer units. When the proportion of the fluorine-containing monomer units is equal to or greater than the lower limit of the above-mentioned range, the flame retardancy, chemical resistance, and moldability of the fluororesin are improved. When the proportion of the fluorine-containing monomer units is equal to or less than the upper limit of the above-mentioned range, the mechanical properties are improved.

[0024] As the fluororesin of homopolymer, for example, polyvinylidene fluoride, polychlorotrifluoroethylene, polyhexafluoropropylene can be enumerated.As the fluororesin of copolymer, for example, the copolymer having TFE unit and ethylene unit, the copolymer having CTFE unit and ethylene unit, the copolymer having TFE unit and HFP unit, the copolymer having TFE unit and PAVE unit, the copolymer having TFE unit, FAE unit and ethylene unit can be enumerated.Among them, from the viewpoint of mechanical properties and high elasticity, the copolymer having TFE unit and ethylene unit, the copolymer having TFE unit, FAE unit and ethylene unit, the copolymer having TFE unit and PAVE unit are preferred.In addition, as long as the fluororesin can be melt-molded, it is not limited to these examples, and it can also be various other homopolymers or copolymers.

[0025] When the fluororesin is a copolymer having TFE units and ethylene units, the TFE units are preferably 30 to 70 mol%, more preferably 40 to 60 mol%, based on the total monomer units of the copolymer. When the fluororesin is a copolymer having TFE units, FAE units, and ethylene units, the TFE units are preferably 40 to 64 mol%, the FAE units are 1 to 5 mol%, and the ethylene units are preferably 35 to 59 mol%, based on the total monomer units of the copolymer, or more preferably 45 to 59 mol%, the FAE units are 1 to 4 mol%, and the ethylene units are preferably 40 to 54 mol%. When the fluororesin is a copolymer having TFE units and PAVE units, the TFE units are preferably 80.0 to 99.5 mol%, more preferably 90 to 95 mol%, based on the total monomer units of the copolymer.

[0026] The melting point of the fluororesin is preferably 160 to 350°C, more preferably 200 to 320°C, and even more preferably 220 to 280°C. When the melting point of the fluororesin is equal to or higher than the lower limit of the above-mentioned range, heat resistance is improved. When the melting point of the fluororesin is equal to or lower than the upper limit of the above-mentioned range, general-purpose equipment can be used to produce the molded article. In addition, molded articles with excellent mechanical properties are likely to be obtained.

[0027] The melt flow rate of the fluororesin is preferably 0.1 to 100 g / 10 min, more preferably 0.5 to 80 g / 10 min, and even more preferably 1 to 50 g / 10 min. When the melt flow rate is equal to or greater than the lower limit of the above-mentioned range, the fluororesin has excellent moldability. When the melt flow rate is equal to or less than the upper limit of the above-mentioned range, a molded article having excellent mechanical properties is likely to be obtained.

[0028] The fluororesin may be a fluororesin (hereinafter referred to as "fluororesin A") having at least one functional group (hereinafter referred to as "functional group f") selected from the group consisting of a carbonyl group-containing group, a hydroxy group, an epoxy group, an amide group, an amino group, and an isocyanate group. The fluororesin A may have two or more functional groups f. The resin composition may contain the fluororesin A and a fluororesin not having the functional group f.

[0029] The fluororesin A has an adhesive functional group f, which can improve adhesion to PAN-based CF. From the viewpoint of adhesion to PAN-based CF, the functional group f is preferably present in at least one of a terminal group and a pendant group of the main chain of the fluororesin A.

[0030] From the viewpoint of adhesiveness to PAN-based CF, the fluororesin A preferably has at least a carbonyl group-containing group as the functional group f. Examples of the carbonyl group-containing group include a group having a carbonyl group between carbon atoms of a hydrocarbon group, a carbonate group, a carboxy group, a haloformyl group, an alkoxycarbonyl group, and an acid anhydride group.

[0031] Examples of hydrocarbon groups in groups having a carbonyl group between carbon atoms include alkylene groups having 2 to 8 carbon atoms. The number of carbon atoms in the alkylene group does not include the carbon atoms constituting the carbonyl group. The alkylene group may be linear or branched.

[0032] A haloformyl group is represented by -C(=O)-X (wherein X is a halogen atom). Examples of the halogen atom in a haloformyl group include a fluorine atom and a chlorine atom. Of these, a fluorine atom is preferred. That is, a fluoroformyl group (also called a carbonyl fluoride group) is preferred as a haloformyl group.

[0033] The alkoxy group in the alkoxycarbonyl group may be linear or branched. The alkoxy group in the alkoxycarbonyl group is preferably an alkoxy group having 1 to 8 carbon atoms, and particularly preferably a methoxy group or an ethoxy group.

[0034] The content of functional group f in fluororesin A is 1×10 ６The number of functional groups f is preferably 10 to 60,000, more preferably 100 to 50,000, even more preferably 100 to 10,000, and particularly preferably 300 to 5,000. When the content of functional group f is equal to or greater than the lower limit of the above-mentioned range, the adhesiveness to PAN-based CF is further improved. When the content of functional group f is equal to or less than the upper limit of the above-mentioned range, the adhesiveness to PAN-based CF is improved even if the temperature during melt molding is lowered.

[0035] The content of the functional group f can be measured by methods such as nuclear magnetic resonance (NMR) analysis, infrared absorption spectroscopy, etc. For example, as described in JP-A-2007-314720, the proportion (mol %) of units having the functional group f among all units constituting the fluororesin A can be determined using a method such as infrared absorption spectroscopy, and the content of the functional group f can be calculated from the proportion (mol %) of units.

[0036] Examples of fluororesin A include the following, depending on the production method. Fluororesin A1: a fluoropolymer having a functional group f derived from at least one selected from the group consisting of a monomer, a chain transfer agent, and a polymerization initiator used in producing the polymer (hereinafter also referred to as "fluoropolymer A1"). Fluororesin A2: a fluororesin obtained by introducing a functional group f into a fluororesin not having the functional group f by surface treatment such as corona discharge treatment or plasma treatment. Fluororesin A3: a fluororesin obtained by graft polymerizing a monomer having a functional group f onto a fluororesin not having the functional group f.

[0037] As the fluororesin A, fluoropolymer A1 is preferred for the following reasons: In fluoropolymer A1, the functional group f is present in at least one of the terminal group of the main chain and the pendant group of the main chain of fluoropolymer A1, which further improves the adhesion to PAN-based CF. Since the functional group f in fluororesin A2 is formed by surface treatment, it is unstable and tends to disappear over time.

[0038] When the functional group f in the fluoropolymer A1 is derived from a monomer used in the production of the fluoropolymer A1, the fluoropolymer A1 can be produced by the following method (1). In this case, the functional group f is present in a monomer unit formed by polymerization of a monomer during the production. Method (1): When the fluoropolymer A1 is produced by polymerization of a fluorine-containing monomer, a monomer having the functional group f is copolymerized.

[0039] When the functional group f in the fluoropolymer A1 is derived from the chain transfer agent used in the production of the fluoropolymer A1, the fluoropolymer A1 can be produced by the following method (2). In this case, the functional group f is present as a terminal group of the main chain of the fluoropolymer A1. Method (2): Fluoropolymer A1 is produced by polymerizing a fluorine-containing monomer in the presence of a chain transfer agent having the functional group f.

[0040] Examples of chain transfer agents having the functional group f include acetic acid, acetic anhydride, methyl acetate, ethylene glycol, and propylene glycol.

[0041] When the functional group f in the fluoropolymer A1 is derived from the polymerization initiator used in the production of the fluoropolymer A1, the fluoropolymer A1 can be produced by the following method (3). In this case, the functional group f is present as a terminal group of the main chain of the fluoropolymer A1. Method (3): Fluoropolymer A1 is produced by polymerizing a fluorine-containing monomer in the presence of a polymerization initiator such as a radical polymerization initiator having the functional group f.

[0042] Examples of the radical polymerization initiator having the functional group f include di-n-propyl peroxydicarbonate, diisopropyl peroxycarbonate, tert-butyl peroxyisopropyl carbonate, bis(4-tert-butylcyclohexyl) peroxydicarbonate, and di-2-ethylhexyl peroxydicarbonate.

[0043] When the functional group f in the fluoropolymer A1 is derived from two or more of the monomer, chain transfer agent and polymerization initiator used in the production of the fluoropolymer A1, the fluoropolymer A1 can be produced by using two or more of the above methods (1) to (3) in combination.

[0044] As the fluorine-containing polymer A1, a fluorine-containing polymer A1 having a functional group f derived from a monomer produced by the method (1) is preferred, since it is easy to control the content of the functional group f and to adjust the adhesiveness to PAN-based CF.

[0045] The monomer having the functional group f is preferably a monomer having a carboxy group, a monomer having an acid anhydride group, a monomer having a hydroxyl group, or a monomer having an epoxy group. Furthermore, the monomer having the functional group f is preferably a non-fluorine-containing monomer.

[0046] Examples of monomers having a carboxy group include maleic acid, itaconic acid, citraconic acid, and undecylenic acid. Examples of monomers having an acid anhydride group include itaconic anhydride (hereinafter also referred to as "IAH"), citraconic anhydride (hereinafter also referred to as "CAH"), 5-norbornene-2,3-dicarboxylic anhydride (hereinafter also referred to as "NAH"), and maleic anhydride. Examples of monomers having a hydroxyl group include hydroxybutyl vinyl ether. Examples of monomers having an epoxy group include glycidyl vinyl ether. However, the monomer having the functional group f is not limited to these examples. Furthermore, two or more types of monomers having the functional group f may be used in combination.

[0047] As the fluorine-containing polymer A1 having a functional group f derived from a monomer, the following fluorine-containing polymer A11 is particularly preferred, from the viewpoint of further improving adhesion to PAN-based CF. Fluorine-containing polymer A11: A fluorine-containing copolymer having units based on TFE or CTFE (hereinafter also referred to as "units u1"), units based on a cyclic hydrocarbon monomer having an acid anhydride group (hereinafter also referred to as "acid anhydride group-containing cyclic hydrocarbon monomer") (hereinafter also referred to as "units u2"), and units based on a fluorine-containing monomer (excluding TFE and CTFE) (hereinafter also referred to as "units u3"). Here, the acid anhydride group in unit u2 corresponds to the functional group f.

[0048] Examples of the acid anhydride group-containing cyclic hydrocarbon monomer constituting the unit u2 include IAH, CAH, NAH, and maleic anhydride. Two or more types of acid anhydride group-containing cyclic hydrocarbon monomers may be used in combination.

[0049] As the acid anhydride group-containing cyclic hydrocarbon monomer, IAH, CAH, and NAH are preferred. When IAH, CAH, or NAH is used, a fluorine-containing copolymer A11 having an acid anhydride group can be easily produced without using a special polymerization method (see JP-A-11-193312) that is required when maleic anhydride is used. As the acid anhydride group-containing cyclic hydrocarbon monomer, IAH and NAH are preferred from the viewpoint of further improving the adhesion to PAN-based CF.

[0050] Examples of the fluorine-containing monomer constituting unit u3 include fluoroolefins (excluding TFE and CTFE), fluorine-containing compounds having a ring structure, PAVE, FAE, compound (3), compound (4), and compound (5). The fluoroolefins, fluorine-containing compounds having a ring structure, PAVE, FAE, compound (3), compound (4), and compound (5) constituting unit u3 include the same compounds as those exemplified above as the fluorine-containing monomers constituting the fluororesin. The preferred embodiments are also the same. From the viewpoints of mechanical properties, high elasticity, and moldability, PAVE and FAE are preferred as the fluorine-containing monomer constituting unit u3.

[0051] The preferred proportions of each unit in the fluorine-containing polymer A11 are as follows. The proportion of units u1 is preferably from 90 to 99.89 mol%, more preferably from 95 to 99.47 mol%, and even more preferably from 96 to 98.95 mol%, based on the total of units u1, units u2, and units u3. The proportion of units u2 is preferably from 0.01 to 3 mol%, more preferably from 0.03 to 2 mol%, and even more preferably from 0.05 to 1 mol%, based on the total of units u1, units u2, and units u3. The proportion of units u3 is preferably from 0.1 to 9.99 mol%, more preferably from 0.5 to 9.97 mol%, and even more preferably from 1 to 9.95 mol%, based on the total of units u1, units u2, and units u3.

[0052] The fluorine-containing polymer A11 may further have, in addition to the units u1 to u3, units based on a non-fluorine monomer (excluding acid anhydride group-containing cyclic hydrocarbon monomers) (hereinafter also referred to as "units u4"). When the units u4 are ethylene units, the preferred proportions of each unit are as follows. The proportion of units u1 is preferably 25 to 80 mol%, more preferably 40 to 65 mol%, and still more preferably 45 to 63 mol%, based on the total of units u1, units u2, units u3, and units u4. The proportion of units u2 is preferably 0.01 to 5 mol%, more preferably 0.03 to 3 mol%, and still more preferably 0.05 to 1 mol%, based on the total of units u1, units u2, units u3, and units u4. The proportion of units u3 is preferably 0.2 to 20 mol %, more preferably 0.5 to 15 mol %, and even more preferably 1 to 12 mol %, based on the total of units u1, u2, u3, and u4. The proportion of units u4, i.e., ethylene units, is preferably 20 to 75 mol %, more preferably 35 to 50 mol %, and even more preferably 37 to 55 mol %, based on the total of units u1, u2, u3, and u4.

[0053] When the proportion of units u1 is within the above-mentioned range, the flame retardancy, chemical resistance, etc. of the molded product are further improved. When the proportion of units u2 is within the above-mentioned range, the amount of acid anhydride groups becomes appropriate, so that the adhesion to PAN-based CF is further improved. When the proportion of units u3 is within the above-mentioned range, the moldability is further improved. The proportion of each unit can be calculated by melt NMR analysis, fluorine content analysis, infrared absorption spectroscopy analysis, etc. of the fluoropolymer A11.

[0054] The fluoropolymer A11 may contain units based on dicarboxylic acids corresponding to the acid anhydride group-containing cyclic hydrocarbon monomers (itaconic acid, citraconic acid, 5-norbornene-2,3-dicarboxylic acid, maleic acid, etc.) as a result of hydrolysis of part of the acid anhydride groups in the units u2. In this case, the proportion of units based on dicarboxylic acids corresponding to the acid anhydride group-containing cyclic hydrocarbon monomers is included in the proportion of the units u2.

[0055] Examples of the fluorine-containing polymer A11 include copolymers having a TFE unit, an NAH unit and a PPVE unit, copolymers having a TFE unit, an IAH unit and a PPVE unit, copolymers having a TFE unit, a CAH unit and a PPVE unit, copolymers having a TFE unit, an IAH unit and a HFP unit, copolymers having a TFE unit, a CAH unit and a HFP unit, copolymers having a TFE unit, an IAH unit, a PFBE unit and an ethylene unit, copolymers having a TFE unit, a CAH unit, a PFBE unit and an ethylene unit, copolymers having a TFE unit, an IAH unit, a PFEE unit and an ethylene unit, copolymers having a TFE unit, a CAH unit, a PFEE unit and an ethylene unit, copolymers having a TFE unit, an IAH unit, a HFP unit, a PFBE unit and an ethylene unit.

[0056] Fluororesins can be produced by conventional methods. For example, they can be produced by polymerizing a monomer component containing at least a fluorine-containing monomer. The monomer component may further contain a non-fluorine monomer and a monomer having a functional group f, as necessary. Polymerization methods include, for example, bulk polymerization, solution polymerization using an organic solvent (fluorohydrocarbon, chlorohydrocarbon, fluorochlorohydrocarbon, alcohol, hydrocarbon, etc.), suspension polymerization using an aqueous medium and, if necessary, a suitable organic solvent, and emulsion polymerization using an aqueous medium and an emulsifier. Among these, solution polymerization is preferred.

[0057] (PAN-based CF) The carbon atom content of PAN-based CF is 90% by mass or more and less than 99% by mass. Another type of carbon fiber is pitch-based carbon fiber, but in the case of pitch-based carbon fiber, if the carbon atom content is 90% by mass or more and less than 99% by mass, the mechanical properties are insufficient. In the case of PAN-based CF, the mechanical properties are good even if the carbon atom content is 90% by mass or more and less than 99% by mass.

[0058] The carbon atom content of the PAN-based CF is not particularly limited, but is preferably 90 to 98 mass%, more preferably 93 to 98 mass%, even more preferably 94 to 97 mass%, and particularly preferably 95 to 96 mass%. When the carbon atom content of the PAN-based CF is equal to or greater than the lower limit of the above-mentioned range, the strength of the PAN-based CF is likely to be improved. When the carbon atom content of the PAN-based CF is equal to or less than the upper limit of the above-mentioned range, a molded product with excellent mechanical properties is likely to be obtained.

[0059] The average fiber length of the PAN-based CF is 1 mm or less. The average fiber length of the PAN-based CF is preferably 0.8 mm or less, more preferably 0.4 mm or less, and even more preferably 0.15 mm or less. If the average fiber length of the PAN-based CF is equal to or less than the upper limit, a molded article with excellent surface smoothness is likely to be obtained. The lower limit of the average fiber length of the PAN-based CF is not particularly limited, but may be, for example, 0.01 mm, 0.02 mm, 0.05 mm, etc.

[0060] The average fiber diameter of the PAN-based CF is not particularly limited, but may be, for example, 1 to 20 μm, 2 to 15 μm, or 4 to 10 μm. When the average fiber diameter of the PAN-based CF is equal to or greater than the lower limit of the above-mentioned range, a molded article having excellent mechanical properties is likely to be obtained. When the average fiber diameter of the PAN-based CF is equal to or less than the upper limit of the above-mentioned range, dispersibility is improved.

[0061] The aspect ratio of the fiber length to the diameter of the PAN-based carbon fiber is not particularly limited. The aspect ratio is preferably 2 to 1500, more preferably 5 to 1200, and even more preferably 10 to 100. When the aspect ratio is equal to or greater than the lower limit of the above-mentioned range, a molded product having excellent mechanical properties is likely to be obtained. When the aspect ratio is equal to or less than the upper limit of the above-mentioned range, the dispersibility of the PAN-based carbon fiber is likely to be improved.

[0062] The cross-sectional shape of the PAN-based CF is not particularly limited. The cross-section of the PAN-based CF may be circular, elliptical, polygonal, or irregular. The cross-sectional shape of the PAN-based CF can be appropriately selected depending on the desired physical properties.

[0063] (Other Components) The resin composition may further contain other components in addition to the fluororesin and PAN-based CF, as long as the effects of the invention are not impaired. Examples of other components include inorganic fibers (excluding PAN-based CF), inorganic fillers, metal soaps, surfactants, UV absorbers, lubricants, and silane coupling agents. However, the other components are not limited to these examples.

[0064] Examples of inorganic fibers include glass fibers, silicon carbide fibers, silicon nitride fibers, alumina fibers, silicon carbide fibers, boron fibers, and metal fibers, such as aluminum fibers, brass fibers, and stainless steel fibers.

[0065] (Composition) The mass ratio of the fluororesin to the PAN-based CF (fluororesin / PAN-based CF) is 60 / 40 to 95 / 5. Because this mass ratio is equal to or greater than the lower limit of the above-mentioned range, the molding processability of the resin composition is improved. In addition, the surface smoothness of the molded article is improved. Because this mass ratio is equal to or less than the upper limit of the above-mentioned range, the mechanical properties of the molded article are improved. The mass ratio is preferably 65 / 35 to 90 / 10, more preferably 70 / 30 to 90 / 10, and even more preferably 70 / 30 to 85 / 15.

[0066] The proportion of the fluororesin is preferably 50 to 95 mass%, more preferably 60 to 90 mass%, and even more preferably 70 to 85 mass% of the total amount of the resin composition. When the proportion of the fluororesin is equal to or greater than the lower limit of the above-mentioned numerical range, the molding processability of the resin composition is likely to be improved. Furthermore, the surface smoothness of the molded article is likely to be improved. When the proportion of the fluororesin is equal to or less than the upper limit of the above-mentioned numerical range, the mechanical properties of the molded article are likely to be improved.

[0067] The proportion of PAN-based CF is preferably 1 to 40 mass% of the total amount of the resin composition, more preferably 10 to 35 mass%, and even more preferably 15 to 30 mass%. When the proportion of PAN-based CF is equal to or greater than the lower limit of the above-mentioned range, the mechanical properties of the molded article are likely to be improved. When the proportion of PAN-based CF is equal to or less than the upper limit of the above-mentioned range, the moldability of the resin composition is likely to be improved. In addition, the surface smoothness of the molded article is likely to be improved.

[0068] The total proportion of the fluororesin and PAN-based CF is preferably 50 to 100 mass%, more preferably 60 to 95 mass%, even more preferably 70 to 90 mass%, and may even be 100 mass% of the total amount of the resin composition. When the total proportion of the fluororesin and PAN-based CF is equal to or greater than the lower limit of the above-mentioned range, the molding processability of the resin composition is likely to be improved. Furthermore, molded articles with excellent mechanical properties and surface smoothness are likely to be obtained. When the total proportion of the fluororesin and PAN-based CF is equal to or less than the upper limit of the above-mentioned range, when the resin composition further contains other components, the properties of the other components are likely to be imparted to the resin composition.

[0069] When the resin composition of the present invention further contains other components, if the proportion of the other components is 1% by mass or more of the total amount of the resin composition, the properties of the other components can be easily imparted. The proportion of the other components relative to the resin composition is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less. If the proportion of the other components is equal to or less than the upper limit, the molding processability of the resin composition is easily improved. Furthermore, molded articles with excellent mechanical properties and surface smoothness can be easily obtained.

[0070] (Properties of Resin Composition) The melt flow rate of the resin composition at a temperature of 297°C and a load of 49N is preferably 2.5 g / 10 min or more, more preferably 3 g / 10 min or more, and even more preferably 4 g / 10 min or more. If the melt flow rate of the resin composition is equal to or greater than the lower limit, a molded article having excellent surface smoothness is likely to be obtained. In addition, moldability is likely to be improved. The upper limit of the melt flow rate of the resin composition is not particularly limited, but may be 300 g / 10 min, 100 g / 10 min, etc. If the melt flow rate of the resin composition is equal to or less than the upper limit, a molded article having excellent mechanical properties is likely to be obtained.

[0071] For the resin composition, s calculated by the following formula (6) is preferably 4.0 or more and less than 6.0, more preferably 4.3 to 5.8, and even more preferably 4.5 to 5.5. When s is equal to or greater than the lower limit of the above-mentioned range, a molded article having excellent mechanical properties is likely to be obtained. When s is equal to or less than the upper limit of the above-mentioned range, the effect of improving mechanical properties is likely to be obtained with a smaller amount of PAN-based CF. Therefore, a molded article having excellent mechanical properties and surface smoothness is likely to be obtained.

[0072] s = t / u (6) In formula (6), t is the bending strength (MPa) of an injection-molded article of the resin composition having a thickness of 4 mm, and u is the content (%) of PAN-based CF in the total content of the fluororesin and PAN-based CF in the resin composition.

[0073] (Method for Producing Resin Composition) The resin composition can be produced by melt-kneading a fluororesin, a PAN-based CF, and optionally other components. The resin composition containing the molten fluororesin and the PAN-based CF can be extruded into a strand shape, and the strand can be cut into pellets using a pelletizer.

[0074] The melt-kneading device is not particularly limited. The melt-kneading device may be equipped with a screw having a high kneading effect. A single-screw extruder or a twin-screw extruder is preferred, a twin-screw extruder is more preferred, and a twin-screw extruder equipped with a screw having a high kneading effect is particularly preferred. As a screw having a high kneading effect, a screw that exerts a sufficient kneading effect and does not apply excessive shear force can be selected. Examples of the melt-kneading device include a Labo Plastomill kneader (manufactured by Toyo Seiki Seisakusho Co., Ltd.) and a KZW series twin-screw kneading extruder (manufactured by Technovel Co., Ltd.).

[0075] As a method for supplying PAN-based CF to the melt-kneading device, the PAN-based CF may be added before melt-kneading the fluororesin, or may be added after melt-kneading the fluororesin. However, from the viewpoint of mechanical properties, it is preferable to add the PAN-based CF after melt-kneading the fluororesin. When other components are to be contained in the resin composition, the other components may be added before melt-kneading the fluororesin, or may be added after melt-kneading the fluororesin.

[0076] The temperature when melt-kneading the fluororesin is equal to or higher than the melting point of the fluororesin, and preferably is equal to or higher than the melting point of the fluororesin + 5°C and equal to or lower than the melting point of the fluororesin + 100°C. The extrusion shear rate and the residence time of the fluororesin in the melt-kneading device when melt-kneading the fluororesin are not particularly limited, and conditions can be appropriately adopted depending on the desired application, etc. The extrusion shear rate is preferably set according to the melt viscosity of the fluororesin at the melt-kneading temperature.

[0077] (Mechanism of Action) In the resin composition described above, the carbon atom content of the PAN-based CF is 90% by mass or more but less than 99% by mass, and the mass ratio of the fluororesin to the PAN-based CF is 95 / 5 or less. This improves the mechanical properties of the molded article. In addition, the average fiber length of the PAN-based CF is 1 mm or less, and the mass ratio of the fluororesin to the PAN-based CF is 60 / 40 or more. This improves the moldability of the resin composition and the surface smoothness of the molded article. Therefore, the resin composition has excellent moldability. Furthermore, molded articles with excellent mechanical properties and surface smoothness can be obtained.

[0078] (Uses) The resin composition can be used, for example, as a raw material for a molded article. A molded article molded from the resin composition of the present invention has excellent mechanical properties and surface smoothness, and is therefore preferably used in applications requiring these properties.

[0079] The flexural strength of the molded body is preferably 50 MPa or more, more preferably 65 MPa or more, and even more preferably 80 MPa or more. If the flexural strength of the molded body is equal to or greater than the lower limit, the mechanical properties are further improved. The upper limit of the flexural strength of the molded body is not particularly limited, but may be, for example, 120 MPa.

[0080] The surface roughness of the molded body is preferably 10 μm or less, more preferably 5 μm or less, and even more preferably 2 μm or less. If the surface roughness of the molded body is equal to or less than the upper limit, the surface smoothness is further improved. The lower limit of the surface roughness of the molded body is not particularly limited, but may be, for example, 0.1 μm.

[0081] Examples of uses of the molded body are given below, but the following description is merely an example and the uses of the molded body are not limited to the examples given below.

[0082] Applications of the molded article include, for example, housings for portable electronic devices, connecting members for portable electronic devices, sliding members, three-dimensional circuit components, gears, actuators, pistons, bearings, aircraft interior materials, bushings, tubes (for fuel, etc.), hoses, tanks, seals, wires, insulating coating materials for electrical wires (wires, cables, etc.), films, sheets, bottles, and fibers. Portable electronic devices are used by hand, and therefore are prone to adhesion of liquids such as oils contained in food and cosmetics, beverages, sweat, and sebum. The molded article of the present invention is resistant to discoloration and deterioration due to these adhesions, and is therefore suitable for use as housings and connecting members for portable electronic devices. Examples of portable electronic devices include mobile phones, mobile terminals, laptop computers, tablet computers, radios, cameras, camera accessories, watches, calculators, music players, global positioning system receivers, portable games, hard drives, portable recording devices, portable playback devices, and portable radio receivers.

[0083] Examples of the form of the housing of a portable electronic device include a back cover, a front cover, an antenna housing, a frame, and a backbone of the portable electronic device. The housing may be a member consisting of a single component of the molded article of the present invention, or a member consisting of multiple components. Here, the backbone is a member to which components of the portable electronic device, such as electronics, a microprocessor, a screen, a keyboard, a keypad, an antenna, and a battery socket, are attached. When the housing is inside the portable electronic device, the housing may not be visible from the outside of the portable electronic device, or may be partially visible from the outside of the portable electronic device. The housing, such as a cover for protecting and supporting the internal structure, may be exposed to the outside of the portable electronic device.

[0084] Examples of the form of the coupling member for a portable electronic device include a snap-type connector between a circuit board, a microphone, a speaker, a display, a battery, a cover, an electrical connector, an electronic connector, a hinge, an antenna, a switch, and a switch pad of the portable electronic device. The coupling member is suitably applicable to portable electronic devices such as a mobile phone, a personal digital assistant (PDA), a music storage device, a bug, a portable DVD player, an electric multimeter, a portable electronic game console, and a portable personal computer (e.g., a notebook computer).

[0085] Three-dimensional circuit components are components in which a circuit pattern is formed on the surface of a resin component molded into a three-dimensional shape, and are used as antenna components for mobile electronic devices and components for in-vehicle electronic devices. The circuit pattern is formed using a laser direct structuring (LDS) method, in which the circuit pattern is etched with a laser and then plated. The molded article of the present invention has excellent low dielectric properties and can be suitably used for three-dimensional circuit components.

[0086] Examples of uses for tubes, hoses, tanks, seals, and wires include those described in International Publication No. 2015 / 182702. Examples of uses for tubes and hoses include tubes for drilling for energy resources such as oil, natural gas, and shale oil. Of these, tubes for oil drilling are preferred. Examples of uses for tubes include medical catheters, electrical wire coatings, and piping for analytical equipment.

[0087] Examples of applications of the insulating coating material for electric wires include electric wires or rectangular copper wires for motor coils, particularly insulating coating materials for rectangular conductors in drive motors for hybrid electric vehicles (HEVs) and electric vehicles (EVs). The insulating coating material for rectangular conductors is preferably in the form of a film. Examples of applications of the insulating coating material for electric wires include insulating coating materials for downhole cables used in drilling for energy resources (oil, natural gas, shale oil, etc.). Among these, insulating coating materials for downhole cables used in oil mining are preferred.

[0088] Applications of the film and sheet include speaker diaphragms, trauma and fracture plates, insulating paper for various electrical insulating adhesive tapes (e.g., motor insulating paper), sealing tape for oil and natural gas pipes, and release films used in the molding of thermosetting and thermoplastic composites. Particularly preferred applications of the film include speaker diaphragms, wire coating films, flexible printed circuit boards, heat-resistant rolls for office automation equipment, and films for impregnating other fiber composites. The film thickness is preferably 1 to 100 μm, more preferably 2 to 80 μm, and even more preferably 5 to 50 μm. When the film thickness is equal to or greater than the lower limit of the aforementioned numerical range, the film strength is improved. When the film thickness is equal to or less than the upper limit of the aforementioned numerical range, the film is easy to handle in subsequent processes. Applications of the fiber include protective clothing and various filters.

[0089] Other applications in the semiconductor industry include components, attachments, and transport components used in manufacturing equipment. These may be, for example, extrusion-molded products, injection-molded products, compression-molded products, machined products, and the like. Examples include containers, chemical tanks, wafer cases, screws, bolts, nuts, packing, O-rings, valves, fittings, filters, diaphragms, retainer rings, wire coatings, tubes, hoses, joints, piping, joining members, and duct members. The molded articles are also suitable for use as magnetic pump components. For example, the molded articles are used for impellers, casings, split plates, and gaskets.

[0090] Examples of molding methods include injection molding, extrusion molding, co-extrusion molding, blow molding, compression molding, transfer molding, and film molding, but the molding method is not limited to these examples.

[0091] The following examples will explain the embodiments in more detail. However, the present invention is not limited to the following examples. Examples 1 and 2 are working examples, and Examples 3 to 7 are comparative examples.

[0092] [Measurement Method] (Melting Point of Fluororesin) Using a differential scanning calorimeter (DSC device, manufactured by Seiko Instruments Inc.), the melting peak was recorded when the temperature of the polymer was raised at a rate of 10°C / min, and the temperature corresponding to the maximum value was taken as the melting point.

[0093] (Fluororesin Melt Flow Rate) Using a melt indexer (manufactured by Techno Seven Co., Ltd.), the mass of polymer flowing out from a nozzle having a diameter of 2 mm and a length of 8 mm for 10 minutes was measured under conditions of 297° C. and a load of 49 N.

[0094] (Average Fiber Length of Carbon Fibers) In a planar photograph taken with an optical microscope at a magnification of 50, the lengths of 100 to 300 carbon fibers are measured, and the average value is taken as the average fiber length of the carbon fibers. The carbon fibers used for length measurement are those located on the diagonal of an observation area of ​​3000 μm length × 5000 μm width.

[0095] (Average fiber diameter of carbon fibers) In a planar photograph taken with an optical microscope at a magnification of 50 times, the widths of 100 to 300 carbon fibers in the planar photograph are considered to be diameters and measured, and the average value is taken as the average fiber diameter of the carbon fibers. The carbon fibers used for width (diameter) measurement are those located on the diagonal of an observation area of ​​3000 μm length × 5000 μm width.

[0096] (Carbon atom content of carbon fiber) The surface composition of the carbon fiber measured by X-ray photoelectron spectroscopy (XPS) is taken as the carbon atom content.

[0097] (Density of Carbon Fiber) The value calculated by a method in accordance with JIS R 7603 is defined as the density of the carbon fiber.

[0098] (Melt Flow Rate of Resin Composition) Using a melt indexer (manufactured by Techno Seven Co., Ltd.), the mass of polymer flowing out from a nozzle having a diameter of 2.095 mm and a length of 8 mm in 10 minutes was measured under conditions of 297° C. and a load of 49 N.

[0099] (Preparation of Injection-Molded Article for Evaluation) Using an injection molding machine (ROBOSHOT α-50C, manufactured by Fanuc Corporation), the resin composition was injection-molded at a mold temperature of 100° C. and a cylinder temperature of 340° C. to obtain an injection-molded article for evaluation having a thickness of 4 mm.

[0100] (Surface Roughness) A test piece having a length of 80 mm and a width of 10 mm was cut out from the injection-molded article for evaluation. The surface roughness (Ra) of the test piece was measured using a surface roughness measuring device ("Surfcom NEX100" manufactured by Tokyo Seimitsu Co., Ltd.). The measurement length was 4 mm.

[0101] (Linear expansion coefficient) The linear expansion coefficient of the injection-molded article for evaluation was measured using a thermomechanical analyzer (SS6100, manufactured by Hitachi High-Tech Science Corporation) in both the MD and TD directions of the injection molding machine used to produce the injection-molded article for evaluation.

[0102] (Shrinkage Rate) The shrinkage rate (%) of the injection-molded article for evaluation was calculated using the following formula. Measurements were made in both the MD and TD directions of the injection molding machine used to prepare the injection-molded article for evaluation. Shrinkage rate (%) = ((mold dimensions - dimensions of injection-molded article for evaluation) / (mold dimensions)) x 100 In the formula, the mold dimensions are the length of one side of the mold used to prepare the injection-molded article for evaluation, and the dimensions of the injection-molded article for evaluation are the length of one side corresponding to the mold.

[0103] (Bending test) A test piece having a length of 80 mm and a width of 10 mm was cut out from the injection-molded article for evaluation. The bending strength [MPa] and bending modulus [GPa] of the test piece were measured using TENSILON (A&D, RTF-1350) in accordance with JIS K7171, with a load cell rating of 1 kN, a support distance of 64 mm, and a speed of 2 mm / min.

[0104] (Izod Impact Strength) A test piece measuring 80 mm in length and 10 mm in width was cut out from the injection-molded article for evaluation. A notch was made at a height of 40 mm in the injection-molded article for evaluation to obtain a test piece. The Izod impact strength [J / m] of the test piece was measured in accordance with ASTM D256 using an Izod tester (manufactured by Toyo Seiki Seisakusho, Ltd.) under conditions of a hammer capacity of 2.75 J and a distance from the axis to the impact point of 33 cm. The measurement was carried out at 23°C.

[0105] (Tensile Test) The tensile strength [MPa], tensile elongation [%], and tensile modulus [MPa] of the injection-molded articles for evaluation were measured using a TENSILON (manufactured by A&D Co., Ltd., model: RTF-1350) in accordance with JIS K 7161, with a load cell rating of 10 kN, a chuck distance of 115 mm, and a speed of 50 mm / min. The tensile modulus was measured in both the MD and TD directions of the injection molding machine used to produce the injection-molded articles for evaluation.

[0106] [Raw Materials] (CF1) CF1 was a PAN-based carbon fiber "CF PX30MF0150" manufactured by ZOLTEK. The average fiber length, average fiber diameter, carbon atom content, and density of CF1 are shown in Table 1.

[0107] (CF2) PAN-based carbon fiber "CF PX35MF0150" manufactured by ZOLTEK was used as CF2. The average fiber length, average fiber diameter, carbon atom content, and density of CF2 are shown in Table 1.

[0108] (CF3) CF3 was a pitch-based carbon fiber "CF SC-2415" manufactured by Osaka Gas Co., Ltd. The average fiber length, average fiber diameter, carbon atom content, and density of CF3 are shown in Table 1.

[0109] (CF4) PAN-based carbon fiber "PXCA0250-83" manufactured by ZOLTEK was used as CF4. The average fiber length, average fiber diameter, carbon atom content, and density of CF4 are shown in Table 1.

[0110] (Fluororesin 1) Fluororesin 1 not having functional group f was used. Fluororesin 1 had TFE units, ethylene units, and PFBE units, with a molar ratio of TFE units / ethylene units / PFBE units of 54 / 46 / 1.4. Fluororesin 1 had a melting point of 260°C and a melt flow rate of 12 g / 10 min.

[0111] [Examples 1 to 7] A fluororesin was added to the base end of the screw of a twin-screw extruder (manufactured by Technovel Co., Ltd., KZW15TW-45MG-NH (-1100), screw diameter: 15 mmΦ, L / D: 45) using a feeder to obtain the composition shown in Table 1. Carbon fiber was added from the middle of the twin-screw extruder barrel using a side feeder, and the mixture was kneaded under the following conditions: feed rate 3 kg / h, screw rotation speed 200 rpm, cylinder, die, and head temperature settings: C1 = 285 ° C, C2 = 285 ° C, C3 = 285 ° C, C4 = 285 ° C, C5 = 285 ° C, C6 = 285 ° C, D = 290 ° C. The strand extruded from the die tip was taken up on a belt conveyor, air-cooled, and then cut with a pelletizer to obtain pellets of the resin composition. Then, injection-molded articles for evaluation were obtained. The measurement results for each example are shown in Table 1.

[0112]

[0113] In Table 1, CF is an abbreviation for carbon fiber, and s is a value calculated by the following formula: s = t / u In the formula, t is the bending strength (MPa) of the injection-molded article for evaluation, and u is the content (mass%) of carbon fiber in the total of the fluororesin and carbon fiber in the resin composition.

[0114] In Examples 1 and 2, molded articles having excellent surface smoothness were obtained, with a surface roughness lower than that of Example 7. In addition, the molded articles of Examples 1 and 2 had better mechanical properties such as bending strength than those of Examples 2 to 6.

[0115] The resin composition of the present invention has excellent moldability and can be used to obtain a molded article having excellent mechanical properties and surface smoothness. The molded article of the present invention has excellent mechanical properties and surface smoothness.

[0116] This application claims priority based on Japanese Patent Application No. 2023-106630, filed on June 29, 2023, the entire contents of which are incorporated herein by reference.

Claims

1. A resin composition comprising a melt-moldable fluororesin and polyacrylonitrile-based carbon fiber, wherein the carbon atom content of the polyacrylonitrile-based carbon fiber is 90% by mass or more and less than 99% by mass, the average fiber length of the polyacrylonitrile-based carbon fiber is 1 mm or less, and the mass ratio of the fluororesin to the polyacrylonitrile-based carbon fiber is 60 / 40 to 95 / 5.

2. The resin composition according to claim 1, wherein the fluororesin has units based on a fluorine-containing monomer, and the fluorine-containing monomer is at least one selected from the group consisting of a fluoroolefin, a fluorine-containing compound having a ring structure, a compound represented by the following formula (1), a compound represented by the following formula (2), a compound represented by the following formula (3), a compound represented by the following formula (4), and a compound represented by the following formula (5). ２ =CFOR ｆ１ ... (1) CH ２ = C.X. １ (CF ２ ) ｐ X ２ ... (2) CF ２ =CFOR ｆ２ SO ２ X ３ ... (3) CF ２ =CFOR ｆ３ CO ２ X ４ ... (4) CF ２ = CF (CF ２ ) ｑ OCF = CF ２ ...(5) In formula (1), R ｆ１ is a perfluoroalkyl group having 1 to 10 carbon atoms which may have an etheric oxygen atom between the carbon atoms, １ is a hydrogen atom or a fluorine atom, p is an integer from 2 to 10, and X ２ is a hydrogen atom or a fluorine atom, ｆ２ is a perfluoroalkylene group having 1 to 10 carbon atoms which may have an etheric oxygen atom between the carbon atoms, ３ is a halogen atom or a hydroxyl group, and in formula (4), R ｆ３ is a perfluoroalkylene group having 1 to 10 carbon atoms which may have an etheric oxygen atom between the carbon atoms, ４ represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and in formula (5), q is 1 or 2.

3. The resin composition according to claim 1, wherein the fluororesin is at least one selected from the group consisting of a copolymer having units based on tetrafluoroethylene and units based on ethylene, a copolymer having units based on chlorotrifluoroethylene and units based on ethylene, a copolymer having units based on tetrafluoroethylene and units based on hexafluoropropylene, a copolymer having units based on tetrafluoroethylene and units based on a compound represented by the following formula (1), and a copolymer having units based on tetrafluoroethylene, units based on a compound represented by the following formula (2), and units based on ethylene. ２ =CFOR ｆ１ ... (1) CH ２ = C.X. １ (CF ２ ) ｐ X ２ ...(2) In formula (1), R ｆ１ is a perfluoroalkyl group having 1 to 10 carbon atoms which may have an etheric oxygen atom between the carbon atoms, １ is a hydrogen atom or a fluorine atom, p is an integer from 2 to 10, and X ２ is a hydrogen atom or a fluorine atom.

4. The resin composition according to claim 3, wherein the fluororesin is at least one selected from the group consisting of a copolymer having units based on tetrafluoroethylene and units based on ethylene, a copolymer having units based on tetrafluoroethylene and units based on the compound represented by formula (1), and a copolymer having units based on tetrafluoroethylene, units based on the compound represented by formula (2), and units based on ethylene.

5. The resin composition according to claim 1, wherein the fluororesin has at least one functional group selected from the group consisting of a carbonyl group-containing group, a hydroxy group, an epoxy group, an amide group, an amino group and an isocyanate group.

6. The resin composition according to claim 1, wherein the melt flow rate of the fluororesin is 0.1 to 100 g / 10 min.

7. The resin composition according to claim 1, wherein the carbon atom content of the polyacrylonitrile carbon fiber is 90 to 98 mass %.

8. The resin composition according to claim 1, wherein the polyacrylonitrile carbon fibers have an average fiber diameter of 1 to 20 μm.

9. The resin composition according to claim 1, wherein the proportion of said fluororesin is 50 to 95 mass % of the total amount of said resin composition.

10. The resin composition according to claim 1, wherein the proportion of the polyacrylonitrile carbon fiber is 1 to 40 mass % of the total amount of the resin composition.

11. The resin composition according to claim 1, wherein the melt flow rate of the resin composition at a temperature of 297° C. and a load of 49 N is 2.5 g / 10 min or more.

12. The resin composition according to claim 1, wherein s calculated by the following formula is 4.0 or more and less than 6.0: s = t / u In the formula, t is the bending strength (MPa) of an injection-molded article of the resin composition having a thickness of 4 mm, and u is the content (mass%) of the polyacrylonitrile-based carbon fiber in the total of the fluororesin and the polyacrylonitrile-based carbon fiber in the resin composition.

13. A molded article obtained by molding the resin composition according to any one of claims 1 to 12.

14. The molded article according to claim 13, wherein the molded article has a bending strength of 50 MPa or more.

15. The molded article according to claim 13, wherein the surface roughness of the molded article is 10 μm or less.