Polyamide resin composition and molded article containing the polyamide resin composition

Abstract

The present invention provides a polyamide resin composition which has high fluidity and has excellent mechanical properties and slidability when used as a molded article.　The polyamide resin composition comprises 60-85 mass% of an aliphatic polyamide resin (A), 0.5-9 mass% of a copolymer fluororesin (B) which may have a functional group, 5-20 mass% of carbon fiber (C), and not more than 34.5 mass% of other components (D), with respect to 100 mass% of the polyamide resin composition.

Description

[Technical Field]

[0001] The present invention relates to a polyamide resin composition and a molded article containing the polyamide resin composition. [Background technology]

[0002] Polyamide resins have excellent physical and chemical properties, such as mechanical properties, electrical properties, and oil resistance, and are therefore widely used as engineering plastics in applications such as automobiles and electrical and electronic equipment. In particular, polyamide resins with excellent oil resistance are often used in automobile applications.

[0003] Furthermore, although polyamide resins have excellent sliding properties, their use as materials for hydraulic equipment components such as pistons, cylinders, drive shaft washers, etc. requires even higher sliding properties, more precise dimensional stability, and mechanical properties such as greater rigidity, etc. A known method for solving these problems is to add fibrous reinforcing materials such as fluororesins and carbon fibers to polyamide resins.

[0004] As such a polyamide resin composition, a polyamide resin composition containing polyamide resin, fluororesin, carbon fiber, and fibrous xonotlite in specified proportions has been proposed, and it has been shown that this composition has high sliding properties and dimensional stability in addition to the oil resistance, thermal stability, mechanical properties, and moldability inherent to polyamide resin (see, for example, Patent Document 1).

[0005] Also proposed is a polyamide resin composition obtained by melt-kneading a polyamide resin composed of terephthalic acid units and aliphatic diamine units having 6 to 18 carbon atoms, a fluororesin having predetermined physical properties, and a fibrous filler and / or an acicular filler in predetermined proportions, and it has been shown to have excellent productivity during pellet production, sliding properties, mechanical properties, etc. (See, for example, Patent Document 2.) Furthermore, a rolling bearing cage has been proposed that contains a polyamide resin composed mainly of terephthalic acid and 1,10-decanediamine, glass fiber or carbon fiber, and a fluororesin in predetermined proportions, and it has been shown that the cage has high rigidity and can prevent seizure and breakage during high-speed rotation (See, for example, Patent Document 3.). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 10-324801 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-106917 [Patent Document 3] Japanese Patent Application Laid-Open No. 2017-57956 Summary of the Invention [Problem to be solved by the invention]

[0007] Although molded articles of the polyamide resin compositions described in Patent Documents 1 to 3 exhibit certain mechanical properties and sliding properties, there is a demand for polyamide resin compositions that can further improve these properties. Also, from the viewpoint of injection moldability of large molded articles, there is a demand for polyamide resin compositions with improved flowability.

[0008] An object of the present invention is to provide a polyamide resin composition which has high flowability and is excellent in mechanical properties and sliding properties when molded into a molded article. [Means for solving the problem]

[0009] The present inventors have conducted extensive research into polyamide resin compositions containing a fluororesin and carbon fiber, and have found that a polyamide resin composition containing a specific fluororesin in a specific ratio has high fluidity and, when formed into a molded article, is excellent in mechanical properties and sliding properties.

[0010] The present invention relates to the following [1] to

[12] . [1] A polyamide resin composition comprising, relative to 100% by mass of the polyamide resin composition, 60 to 85% by mass of an aliphatic polyamide resin (A), 0.5 to 9% by mass of a copolymer fluororesin (B) which may have a functional group, 5 to 20% by mass of carbon fiber (C), and 34.5% by mass or less of other components (D). [2] The polyamide resin composition according to [1], wherein the mass ratio of the carbon fiber (C) to the copolymerized fluororesin (B) which may have a functional group is more than 1.0 and less than 20. [3] The polyamide resin composition according to [1] or [2], wherein the mass ratio of the copolymerized fluororesin (B) which may have a functional group to the aliphatic polyamide resin (A) is greater than 0.005 and less than 0.12. [4] The polyamide resin composition according to any one of [1] to [3], wherein the fluororesin copolymer (B) which may have a functional group is an α-olefin / tetrafluoroethylene copolymer. [5] The polyamide resin composition according to any one of [1] to [4], wherein the functional group of the copolymerized fluororesin (B) which may have a functional group is a carboxyl group, a carboxylic acid ester group, and / or an acid anhydride group. [6] The polyamide resin composition according to any one of [1] to [5], wherein the copolymerized fluororesin (B) which may have a functional group is an α-olefin / tetrafluoroethylene copolymer having a group derived from maleic anhydride bonded thereto. [7] The polyamide resin composition according to any one of [1] to [6], which is substantially free of fibrous xonotlite. [8] The polyamide resin composition according to any one of [1] to [7], wherein the polyamide resin composition is injection molded using a mold having a width of 15 mm, a length of 360 mm, and a thickness of 1 mm under the conditions of a pressure of 100 MPa, a cylinder temperature of 285°C, a mold temperature of 80°C, an injection speed of 38 mm / sec, an injection time of 4 seconds, and a cooling time of 15 seconds, and the molded article obtained has an injection flow length of 150 mm or more. [9] The polyamide resin composition according to any one of [1] to [8], which is used for sliding parts.

[10] A molded article comprising the polyamide resin composition according to any one of [1] to [9].

[11] The molded product according to

[10] , which is a sliding part.

[12] A method for producing a sliding part, comprising molding the polyamide resin composition according to any one of [1] to [9]. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a polyamide resin composition which has high flowability and is excellent in mechanical properties and sliding properties when molded into a molded product. DETAILED DESCRIPTION OF THE INVENTION

[0012] In this specification, the content of each component in a composition means the total amount of the multiple substances present in the composition when multiple substances corresponding to each component are present in the composition, unless otherwise specified.

[0013] The polyamide resin composition of the present invention contains, relative to 100% by mass of the polyamide resin composition, 60 to 85% by mass of an aliphatic polyamide resin (A), 0.5 to 9% by mass of a copolymer fluororesin (B) which may have a functional group, 5 to 20% by mass of carbon fiber (C), and 34.5% by mass or less of other component (D). By setting the proportions of each component within the above ranges, it is possible to provide a polyamide resin composition which has high fluidity and, when formed into a molded product, is excellent in mechanical properties and sliding properties.

[0014] <Aliphatic polyamide resin (A)> The polyamide resin composition contains an aliphatic polyamide resin (A), which has excellent toughness, heat resistance, oil resistance, solvent resistance, chemical resistance, abrasion resistance, and moldability. The aliphatic polyamide resin (A) can be selected from aliphatic homopolyamide resins (A-1) and aliphatic copolyamide resins (A-2), and can be one or a combination of two or more.

[0015] (Aliphatic homopolyamide resin (A-1)) The aliphatic homopolyamide resin (A-1) refers to a polyamide resin in which the monomer component constituting the aliphatic polyamide resin is a single type. The aliphatic homopolyamide resin (A-1) may be composed of at least one type of lactam and an aminocarboxylic acid that is a hydrolyzate of the lactam, or may be composed of a combination of one type of aliphatic diamine and one type of aliphatic dicarboxylic acid. Here, when the monomer components constituting the aliphatic polyamide resin are a combination of an aliphatic diamine and an aliphatic dicarboxylic acid, the combination of one type of aliphatic diamine and one type of aliphatic dicarboxylic acid is considered to be one type of monomer component.

[0016] Examples of the aliphatic homopolyamide resin (A-1) include aliphatic homopolyamide resins made from aliphatic diamines and aliphatic dicarboxylic acids, and aliphatic homopolyamide resins made from lactams or aminocarboxylic acids.

[0017] Examples of the monomer components constituting the aliphatic homopolyamide resin (A-1) include a combination of an aliphatic diamine having 2 to 20 carbon atoms, preferably 4 to 12 carbon atoms, and an aliphatic dicarboxylic acid having 2 to 20 carbon atoms, preferably 6 to 12 carbon atoms, a lactam or aminocarboxylic acid having 6 to 12 carbon atoms, and the like.

[0018] Examples of aliphatic diamines include ethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, undecamethylenediamine, dodecamethylenediamine, tridecanediamine, tetradecanediamine, pentadecanediamine, hexadecanediamine, heptadecanediamine, octadecanediamine, nonadecanediamine, eicosanediamine, 2-methyl-1,8-octanediamine, and 2,2,4 / 2,4,4-trimethylhexamethylenediamine. Examples of aliphatic dicarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedionic acid, dodecanedionic acid, tridecanedionic acid, tetradecanedionic acid, pentadecanedioic acid, hexadecanedioic acid, octadecanedioic acid, and eicosanedioic acid.

[0019] Examples of combinations of aliphatic diamines and aliphatic dicarboxylic acids include a combination of hexamethylenediamine and adipic acid, a combination of hexamethylenediamine and sebacic acid, and a combination of hexamethylenediamine and dodecanedioic acid, and equimolar salts of these combinations are preferably used.

[0020] Examples of lactams include ε-caprolactam, enantholactam, undecane lactam, dodecane lactam, α-pyrrolidone, and α-piperidone. From the viewpoint of productivity, the lactam is preferably ε-caprolactam, undecane lactam, or dodecane lactam. Examples of aminocarboxylic acids include 6-aminocaproic acid, 7-aminoheptanoic acid, 9-aminononanoic acid, 11-aminoundecanoic acid, and 12-aminododecanoic acid.

[0021] Specific examples of the aliphatic homopolyamide resin (A-1) include polycaprolactam (polyamide 6), polyenantholactam (polyamide 7), polyundecane lactam (polyamide 11), polylauryllactam (polyamide 12), polyhexamethylene adipamide (polyamide 66), polytetramethylene dodecamide (polyamide 412), polypentamethylene azelamide (polyamide 59), polypentamethylene sebacamide (polyamide 510), polypentamethylene dodecamide (polyamide 512), polyhexamethylene azelamide (polyamide 69), polyhexamethylene sebacamide (polyamide 610), polyhexamethylene dodecamide (polyamide 612), polynonamethylene Examples of the polyamide include methylene adipamide (polyamide 96), polynonamethylene azelamide (polyamide 99), polynonamethylene sebacamide (polyamide 910), polynonamethylene dodecamide (polyamide 912), polydecamethylene adipamide (polyamide 106), polydecamethylene azelamide (polyamide 109), polydecamethylene decamide (polyamide 1010), polydecamethylene dodecamide (polyamide 1012), polydodecamethylene adipamide (polyamide 126), polydodecamethylene azelamide (polyamide 129), polydodecamethylene sebacamide (polyamide 1210), polydodecamethylene dodecamide (polyamide 1212), and polyamide 122.

[0022] From the viewpoints of toughness, heat resistance, oil resistance, and abrasion resistance, the aliphatic homopolyamide resin (A-1) is preferably one or more selected from the group consisting of polyamide 6, polyamide 66, polyamide 610, polyamide 612, polyamide 11, and polyamide 12, and particularly preferably polyamide 6 and / or polyamide 66.

[0023] The aliphatic homopolyamide resin (A-1) may be one type or a combination of two or more types.

[0024] (Aliphatic copolyamide resin (A-2)) The aliphatic copolyamide resin (A-2) refers to a polyamide resin in which the monomer components constituting the aliphatic polyamide resin are a combination of two or more types. The aliphatic copolyamide resin (A-2) is a copolymer of two or more types selected from the group consisting of a combination of an aliphatic diamine and an aliphatic dicarboxylic acid, a lactam, and an aminocarboxylic acid. Here, the combination of an aliphatic diamine and an aliphatic dicarboxylic acid is considered to be one type of monomer component, with one type of aliphatic diamine and one type of aliphatic dicarboxylic acid being the combination.

[0025] Examples of the aliphatic diamine include the same as those exemplified as the raw materials for the aliphatic homopolyamide resin (A-1).

[0026] Examples of the aliphatic dicarboxylic acid include the same as those exemplified as the raw materials for the aliphatic homopolyamide resin (A-1).

[0027] Examples of lactams include those exemplified as raw materials for the aliphatic homopolyamide resin (A-1). Examples of aminocarboxylic acids include those exemplified as raw materials for the aliphatic homopolyamide resin (A-1).

[0028] These aliphatic diamines, aliphatic dicarboxylic acids, lactams and aminocarboxylic acids may be used alone or in combination of two or more.

[0029] Specific examples of the aliphatic copolymer polyamide resin (A-2) include caprolactam / hexamethylenediaminoadipic acid copolymer (polyamide 6 / 66), caprolactam / hexamethylenediaminoazelaic acid copolymer (polyamide 6 / 69), caprolactam / hexamethylenediaminosebacic acid copolymer (polyamide 6 / 610), caprolactam / hexamethylenediaminoundecanedicarboxylic acid copolymer (polyamide 6 / 611), caprolactam / hexamethylenediaminododecanedicarboxylic acid copolymer (polyamide 6 / 612), caprolactam / hexamethylenediaminododecanedicarboxylic acid copolymer (polyamide 6 / 613), caprolactam / hexamethylenediaminoadipic acid copolymer (polyamide 6 / 614), caprolactam / hexamethylenediaminoadipic acid copolymer (polyamide 6 / 615), caprolactam / hexamethylenediaminoadipic acid copolymer (polyamide 6 / 616), caprolactam / hexamethylenediaminoadipic acid copolymer (polyamide 6 / 617), caprolactam / hexamethylenediaminoadipic acid copolymer (polyamide 6 / 618), caprolactam / hexamethylenediaminoadipic acid copolymer (polyamide 6 / 619), caprolactam / hexamethylenediaminoadipic acid copolymer (polyamide 6 / 620), caprolactam / hexamethylenediaminoadipic acid copolymer (polyamide 6 / 621), caprolactam / hexamethylenediaminoadipic acid copolymer (polyamide 6 / 622), caprolactam / hexamethylenediaminoadipic acid copolymer (polyamide 6 / 623), caprolactam / hexamethylenediaminoadipic acid copolymer (polyamide 6 / 624), caprolactam / hexamethylenediaminoadipic acid copolymer (polyamide 6 / 625), caprolactam / hexamethylenediaminoadipic acid copolymer (polyamide 6 / 626), caprolactam / hexamethylenediaminoadi Examples of such copolymers include caprolactam / aminoundecanoic acid copolymer (polyamide 6 / 11), caprolactam / lauryllactam copolymer (polyamide 6 / 12), caprolactam / hexamethylenediaminoadipic acid / lauryllactam copolymer (polyamide 6 / 66 / 12), caprolactam / hexamethylenediaminoadipic acid / hexamethylenediaminosebacic acid copolymer (polyamide 6 / 66 / 610), and caprolactam / hexamethylenediaminoadipic acid / hexamethylenediaminododecanedicarboxylic acid copolymer (polyamide 6 / 66 / 612).

[0030] The aliphatic copolyamide resin (A-2) may be one type or a combination of two or more types.

[0031] The aliphatic polyamide resin (A) preferably has a relative viscosity of 2.61 to 2.85, as measured at 25°C by dissolving 1 g of the aliphatic polyamide resin (A) in 100 ml of 96% sulfuric acid in accordance with JIS K 6920. By setting the relative viscosity of the aliphatic polyamide resin (A) within the above range, the fluidity of the polyamide resin composition can be increased, and the mechanical properties can be improved. The relative viscosity of the aliphatic polyamide resin (A) is preferably 2.63 to 2.83, more preferably 2.65 to 2.81.

[0032] When the aliphatic polyamide resin (A) contains two or more polyamide resins with different relative viscosities, the relative viscosity of the aliphatic polyamide resin (A) is preferably measured as described above. However, when the relative viscosity of each polyamide resin and its mixing ratio are known, the relative viscosity of the aliphatic polyamide resin (A) may be determined by adding up the values ​​obtained by multiplying each relative viscosity by the mixing ratio.

[0033] The terminal amino group concentration of the aliphatic polyamide resin (A), as determined by dissolving the resin in a mixed solvent of phenol and methanol and subjecting it to neutralization titration, is preferably 15 μmol / g or more, more preferably 20 μmol / g or more and 110 μmol / g or less, and particularly preferably 30 μmol / g or more and 70 μmol / g or less. Within this range, molded articles using the polyamide resin composition have good moldability.

[0034] When the aliphatic polyamide resin (A) contains two or more polyamide resins having different terminal amino group concentrations, the terminal amino group concentration in the aliphatic polyamide resin (A) is preferably measured by the neutralization titration method described above. However, when the terminal amino group concentration of each polyamide resin and its mixing ratio are known, the terminal amino group concentration of the aliphatic polyamide resin (A) may be determined by adding up the values ​​obtained by multiplying each terminal amino group concentration by the mixing ratio.

[0035] Examples of the production apparatus for the aliphatic polyamide resin (A) include known polyamide production apparatuses, such as batch-type reaction vessels, single- or multi-vessel continuous reaction vessels, tubular continuous reaction vessels, kneading reaction extruders such as single-screw kneading extruders and twin-screw kneading extruders. Known polymerization methods, such as melt polymerization, solution polymerization, and solid-phase polymerization, can be used, and polymerization can be carried out by repeating operations such as normal pressure, reduced pressure, and increased pressure. These polymerization methods can be used alone or in appropriate combination.

[0036] <Fluorocopolymer resin (B) which may have a functional group> By blending the polyamide resin composition with a fluorocopolymer (B) which may have a functional group, the flowability and the mechanical properties and sliding properties of a molded article are improved compared to when a homopolymer of a fluorine-containing monomer such as tetrafluoroethylene is blended. The fluorocopolymer (B) which may have a functional group may be one type or a combination of two or more types.

[0037] The fluororesin copolymer (B) which may have a functional group is a copolymer having at least one repeating unit derived from a fluorine-containing monomer and at least one repeating unit derived from a non-fluorine-containing monomer. The functional group means a group which reacts with the terminal amino group of the aliphatic polyamide resin (A), and specific examples thereof include a carboxyl group, an acid anhydride group, a carboxylic acid ester group, a carboxylic acid metal salt, a carboxylic acid imide group, a carboxylic acid amide group, and an epoxy group. The fluoropolymer resin having no functional group means a copolymer having no functional group that reacts with the terminal amino group of the aliphatic polyamide resin (A). The fluoropolymer resin having a functional group means a copolymer obtained by copolymerizing a monomer having a functional group, or by reacting the copolymer having no functional group with a compound having a functional group to introduce a functional group.

[0038] Fluorine-containing monomers include tetrafluoroethylene (TFE), trifluoroethylene, vinylidene fluoride (VDF), vinyl fluoride (VF), chlorotrifluoroethylene (CTFE), trichlorofluoroethylene, hexafluoropropylene (HFP), and CF2=CFOR. f1 (where R f1 represents a perfluoroalkyl group having 1 to 10 carbon atoms which may contain an etheric oxygen atom), CF2=CF-OCH2-R f2 (where R f2 represents a perfluoroalkyl group having 1 to 10 carbon atoms which may contain an etheric oxygen atom), CF2=CF(CF2) p OCF=CF2 (where p is 1 or 2), CH2=CX 1 (CF2) n X2 (where X 1 and X 2 are each independently a hydrogen atom or a fluorine atom, and n is an integer of 2 or more and 10 or less.) These can be used alone or in combination of two or more.

[0039] The general formula CF2=CFOR f1 Specific examples include perfluoro(alkyl vinyl ethers) (hereinafter sometimes referred to as PAVE) such as CF2=CFOCF3 (perfluoro(methyl vinyl ether): PMVE), CF2=CFOCF2CF3 (perfluoro(ethyl vinyl ether): PEVE), CF2=CFOCF2CF2CF3 (perfluoro(propyl vinyl ether): PPVE), CF2=CFOCF2CF2CF2CF3 (perfluoro(butyl vinyl ether): PBVE), and CF2=CFO(CF2)8F (perfluoro(octyl vinyl ether): POVE). These may be used alone or in combination. Of these, CF2=CFOCF3 and CF2=CFOCF2CF2CF3 are preferred.

[0040] In addition, the general formula CH2=CX 1 (CF2) n X 2 (where X 1 and X 2are each independently a hydrogen atom or a fluorine atom, and n is an integer of 2 or more and 10 or less. In the compound represented by (), n is an integer of 2 or more and 10 or less, from the viewpoint of ensuring the effect of modifying the copolymeric fluororesin (B) which may have a functional group (for example, suppressing the occurrence of cracks during molding of the copolymer and in molded articles) and obtaining sufficient polymerization reactivity. Specific examples include CH2=CF(CF2)2F, CH2=CF(CF2)3F, CH2=CF(CF2)4F, CH2=CF(CF2)5F, CH2=CF(CF2)8F, CH2=CF(CF2)2H, CH2=CF(CF2)3H, CH2=CF(CF2)4H, CH2=CF(CF2)5H, CH2=CF(CF2)8H, CH2=CH(CF2)2F, CH2=CH(CF2)3F, CH2=CH(CF2)4F, CH2=CH(CF2)5F, CH2=CH(CF2)8F, CH2=CH(CF2)2H, CH2=CH(CF2)3H, CH2=CH(CF2)4H, CH2=CH(CF2)5H, CH2=CH(CF2)8H, etc. These may be used alone or in combination. Among these, from the viewpoint of the balance between the chemical barrier property and environmental stress cracking resistance of the copolymer fluororesin (B) which may have functional groups, CH2=CH(CF2) n F or CH2=CF(CF2) n Compounds represented by H are preferred, and n in the formula is more preferably 2 or more and 4 or less.

[0041] Non-fluorine-containing monomers include ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, 1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-nonadecene, 1-eicosene, 3-methyl-1-butene, 3-methyl-1-pentene, 3-ethyl-1-pentene, 4-methyl-1-pentene, 4-methyl-1-hexene, 4,4-dimethyl-1-hexene, Examples of suitable vinyl ethers include α-olefins such as 4,4-dimethyl-1-pentene, 4-ethyl-1-hexene, 3-ethyl-1-hexene, 9-methyl-1-decene, 11-methyl-1-dodecene, and 12-ethyl-1-tetradecene; olefins other than α-olefins such as isobutene; vinyl chloride, vinylidene chloride; vinyl esters such as vinyl acetate, vinyl chloroacetate, vinyl lactate, vinyl butyrate, vinyl pivalate, vinyl benzoate, and vinyl crotonate; methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, and methyl crotonate; and vinyl ethers such as methyl vinyl ether (MVE), ethyl vinyl ether (EVE), butyl vinyl ether (BVE), isobutyl vinyl ether (IBVE), cyclohexyl vinyl ether (CHVE), and glycidyl vinyl ether. These may be used alone or in combination. Among these, α-olefins such as ethylene and propylene and vinyl acetate are preferred, with ethylene being particularly preferred.

[0042] From the viewpoint of flowability and mechanical properties when molded into a molded article, the copolymerized fluororesin of copolymerized fluororesin (B) which may have functional groups is preferably an α-olefin / tetrafluoroethylene copolymer, more preferably an α-olefin / tetrafluoroethylene copolymer having 2 to 4 carbon atoms, and particularly preferably an ethylene / tetrafluoroethylene copolymer.

[0043] The copolymerized fluororesin having a functional group is a copolymer obtained by copolymerizing a monomer having a functional group, or by reacting the copolymer not having a functional group with a compound having a functional group to introduce a functional group. The functional group is preferably a carboxyl group, a carboxylic acid ester group, and / or an acid anhydride group, from the viewpoint of reactivity with the terminal amino group of the aliphatic polyamide resin (A). It is also possible to use a copolymer obtained by copolymerizing a monomer having a carboxyl group, a carboxylic acid ester group, an acid anhydride group, and / or a functional group other than these and then reacting and introducing a compound having a carboxyl group, a carboxylic acid ester group, and / or an acid anhydride group into the copolymer. The functional group-containing fluorocopolymer resin may have a plurality of types of functional groups, and the functional groups may be located at either the terminals or in the chain of the fluorocopolymer resin.

[0044] Examples of the monomer and / or compound having a carboxyl group include acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, crotonic acid, mesaconic acid, citraconic acid, glutaconic acid, cis-4-cyclohexene-1,2-dicarboxylic acid, and endobicyclo-[2.2.1]-5-heptene-2,3-dicarboxylic acid. Examples of the monomers and / or compounds having a carboxylic acid ester group include alkyl esters, hydroxyalkyl esters, and aminoalkyl esters of the above-mentioned monomers and / or compounds having a carboxyl group. Examples of monomers and / or compounds having an acid anhydride group include dicarboxylic acid anhydrides having an α,β-unsaturated bond, such as maleic anhydride, itaconic anhydride, citraconic anhydride, and endobicyclo-[2.2.1]-5-heptene-2,3-dicarboxylic anhydride. These may be used alone or in combination. Among these, dicarboxylic acid anhydrides having an α,β-unsaturated bond are preferred, with maleic anhydride and itaconic anhydride being more preferred, and maleic anhydride being particularly preferred.

[0045] From the viewpoint of increasing the reactivity with the terminal amino groups of the aliphatic polyamide resin (A) and improving the fluidity of the resin composition, the copolymerized fluororesin (B), which may have functional groups, is preferably an α-olefin / tetrafluoroethylene copolymer into which maleic anhydride has been introduced, i.e., an α-olefin / tetrafluoroethylene copolymer to which a group derived from maleic anhydride has been bonded, and particularly preferably an ethylene / tetrafluoroethylene copolymer to which a group derived from maleic anhydride has been bonded.

[0046] Examples of the apparatus for producing the copolymeric fluororesin (B) which may have a functional group include a single- or multi-tank stirring polymerization apparatus, a tubular polymerization apparatus, etc., and the copolymeric fluororesin (B) can be produced as a batch or continuous operation. The polymerization method is not particularly limited, and for example, a polymerization method using a commonly used radical polymerization initiator can be used. As the polymerization method, known methods can be used, such as bulk polymerization, solution polymerization using an organic solvent such as a fluorohydrocarbon, a chlorohydrocarbon, a chlorofluorohydrocarbon, an alcohol, or a hydrocarbon, suspension polymerization using an aqueous medium and, if necessary, an appropriate organic solvent, and emulsion polymerization using an aqueous medium and an emulsifier.

[0047] <Carbon fiber (C)> The polyamide resin composition contains carbon fibers (C), which can improve the mechanical properties and sliding properties of a molded article. The carbon fibers (C) may be one type or a combination of two or more types.

[0048] Examples of the carbon fiber (C) include PAN-based carbon fiber obtained by carbonizing polyacrylonitrile fiber, and pitch-based carbon fiber obtained by carbonizing pitch fiber obtained from coal tar or heavy petroleum fractions as a raw material.

[0049] The fiber length of the carbon fibers may be short or long, reaching 1,000 mm, depending on the application. From the viewpoint of productivity, the fiber length before kneading is preferably 0.1 to 20 mm, and more preferably 1.0 to 15 mm.

[0050] The fiber diameter of the carbon fibers is not particularly limited, but is preferably 5 to 15 μm, more preferably 6 to 9 μm, from the viewpoints of mechanical properties and productivity. It is preferable to use fine carbon fibers because a masterbatch in which a resin is previously made to contain a high amount of carbon fibers or granulated carbon fibers is less likely to defibrate during the production of a polyamide resin composition.

[0051] The carbon fiber may be surface-treated. That is, the carbon fiber may be a surface-treated carbon fiber. Specific examples of the surface treatment agent include a silane coupling agent, a titanate coupling agent, and an aluminate coupling agent. Only one of the above surface treatment agents may be used, or multiple types of surface treatment agents may be mixed and used.

[0052] <Other ingredients (D)> The polyamide resin composition may contain other components (D) to the extent that the objectives of the present invention are not impaired. Examples of other components (D) include polyamide resins other than the aliphatic polyamide resin (A), such as polyamide resins having an alicyclic or aromatic group in the main chain or side chain; thermoplastic resins other than component (B); fibrous fillers other than carbon fiber (C), plasticizers, antioxidants, heat resistance agents, UV absorbers, light stabilizers, weather resistance agents, foaming agents, lubricants, particulate inorganic or organic fillers, antistatic agents, flame retardants, flame retardant assistants, crystal nucleating agents, crystallization accelerators, and colorants. The polyamide resin composition is preferably substantially free of fibrous xonotlite. "Substantially free" means that the xonotlite is not intentionally added, except in cases where it is inevitably mixed in with industrial raw materials, for example. Specifically, the content of fibrous xonotlite in 100% by mass of the polyamide resin composition is less than 0.1% by mass, preferably less than 0.05% by mass, and more preferably less than 0.03% by mass. The other component (D) is not the aliphatic polyamide resin (A), the copolymer fluororesin which may have a functional group (B), or the carbon fiber (C).

[0053] Among these, the polyamide resin composition preferably contains at least one selected from the group consisting of antioxidants and heat-resistant additives as the other component (D). Examples of the antioxidant include phenolic antioxidants, phosphorus-based antioxidants, and thioether-based antioxidants. Among these, the antioxidant is preferably a phenolic antioxidant or a phosphorus-based antioxidant.

[0054] Examples of heat-resistant agents include metal halide compounds such as potassium iodide, potassium bromide, potassium chloride, sodium iodide, sodium chloride, cuprous chloride, cupric chloride, cuprous bromide, cupric bromide, cuprous iodide, and cupric iodide, and triazine ring compounds such as melamine. Among these, the heat-resistant agent is preferably a mixture of cuprous iodide and a potassium halide, a mixture of cuprous bromide and a potassium halide, melamine, or a mixture thereof, and particularly preferably a mixture of cuprous iodide and potassium iodide, a mixture of cuprous bromide and potassium bromide, melamine, or a mixture thereof. Among these, the heat-resistant agent is preferably a mixture of cuprous iodide, a potassium halide, and melamine, or a mixture of cuprous bromide, a potassium halide, and melamine, and particularly preferably a mixture of cuprous iodide, potassium iodide, and melamine, or a mixture of cuprous bromide, potassium bromide, and melamine.

[0055] The antioxidant and the heat-resistant agent may each be one kind or a combination of two or more kinds.

[0056] [Composition of polyamide resin composition] The polyamide resin composition contains, relative to 100% by mass of the polyamide resin composition, 60 to 85% by mass of an aliphatic polyamide resin (A), 0.5 to 9% by mass of a copolymer fluororesin (B) which may have a functional group, 5 to 20% by mass of carbon fiber (C), and 34.5% by mass or less of other components (D). By setting the proportions of each component within the above ranges, a polyamide resin composition with high fluidity and excellent mechanical properties and sliding properties when molded into a molded product can be obtained. If the proportion of component (A) is less than 60% by mass, it will result in a decrease in mechanical properties and fluidity, and if it exceeds 85% by mass, it will result in a decrease in mechanical properties. If the proportion of component (B) is less than 0.5% by mass, it will result in a decrease in fluidity and sliding properties, and if it exceeds 9% by mass, it will result in a decrease in mechanical properties. If the proportion of component (C) is less than 5% by mass, the required mechanical properties and sliding properties will not be met, and if it exceeds 20% by mass, molding may become difficult. If the proportion of component (D) is more than 34.5% by mass, it will be impossible to ensure fluidity and the mechanical properties and sliding properties of the molded product.

[0057] The polyamide resin composition preferably contains 70 to 85 mass% of component (A), 0.8 to 5.0 mass% of component (B), 10 to 20 mass% of component (C), and 5.0 mass% or less of component (D), relative to 100 mass% of the polyamide resin composition, and more preferably contains 80 to 85 mass% of component (A), 1.0 to 3.0 mass% of component (B), 12.5 to 17.5 mass% of component (C), and 1.5 mass% or less of component (D). It is more preferable that the composition contains 80 to 85 mass% of the (A) component, 1.1 to 3.0 mass% of the (B) component, 12.5 to 17.5 mass% of the (C) component, and 1.5 mass% or less of the (D) component, and it is particularly preferable that the composition contains 80 to 85 mass% of the (A) component, 1.5 to 3.0 mass% of the (B) component, 12.5 to 17.5 mass% of the (C) component, and 1.0 mass% or less of the (D) component.

[0058] The polyamide resin composition may be a composition containing only an aliphatic polyamide resin (A), a copolymerized fluororesin (B) which may have a functional group, and carbon fiber (C). In this case, the polyamide resin composition preferably contains 71 to 85 mass% of component (A), 0.5 to 9 mass% of component (B), and 6 to 20 mass% of component (C), more preferably 79.5 to 85 mass% of component (A), 1.0 to 3.0 mass% of component (B), and 12.5 to 17.5 mass% of component (C), and particularly preferably 79.5 to 85 mass% of component (A), 1.1 to 3.0 mass% of component (B), and 12.5 to 17.5 mass% of component (C), relative to 100 mass% of the polyamide resin composition.

[0059] The mass ratio of carbon fiber (C) to copolymer fluororesin (B) which may have a functional group is preferably more than 1.0 and less than 20, since the carbon fibers are likely to be uniformly dispersed in the polyamide resin composition. The mass ratio of carbon fiber (C) to copolymer fluororesin (B) which may have a functional group is more preferably 3.0 to 18, further preferably 4.0 to 16, and particularly preferably 4.0 to 14.

[0060] The mass ratio of the fluororesin (B) which may have a functional group to the aliphatic polyamide resin (A) is preferably more than 0.005 and less than 0.12, since the fluororesin (B) which may have a functional group is easily dispersed uniformly in the polyamide resin composition. The mass ratio of the fluororesin (B) which may have a functional group to the aliphatic polyamide resin (A) is more preferably 0.008 to 0.060, even more preferably 0.010 to 0.040, and particularly preferably 0.013 to 0.040.

[0061] [Preferred embodiment] The polyamide resin composition is preferably injection molded using a mold having a width of 15 mm, a length of 360 mm, and a thickness of 1 mm under conditions of a pressure of 100 MPa, a cylinder temperature of 285°C, a mold temperature of 80°C, an injection speed of 38 mm / sec, an injection time of 4 seconds, and a cooling time of 15 seconds, with an injection flow length of 150 mm or more, as this facilitates filling into the mold. The injection flow length is an index for evaluating the fluidity of a resin composition using an injection molding machine and a mold, and is the length of a molded article when the resin is injected and filled at a constant temperature and pressure. A larger injection flow length indicates better fluidity of the resin composition. The injection flow length is more preferably 150 mm or more, and particularly preferably 180 mm or more. There is no particular upper limit to the injection flow length, but in practice it is 500 mm or less, preferably 300 mm or less.

[0062] [Method of producing polyamide resin composition] The method for producing the polyamide resin composition is not particularly limited, and the following method can be applied, for example. When mixing the aliphatic polyamide resin (A), the copolymerized fluororesin (B) which may have a functional group, the carbon fiber (C), and the other component (D), a commonly known melt-kneading machine such as a single-screw or twin-screw extruder, a Banbury mixer, a kneader, or a mixing roll is used. For example, any of the following methods may be used: a method in which all raw materials are blended using a twin-screw extruder and then melt-kneaded; a method in which some raw materials are blended and then melt-kneaded, and then the remaining raw materials are blended and melt-kneaded; or a method in which some raw materials are blended and then the remaining raw materials are mixed using a side feeder during melt-kneading. The carbon fibers (C) may be mixed in advance with the aliphatic polyamide resin (A) and used as a masterbatch.

[0063] [Uses of polyamide resin composition] The polyamide resin composition can be used to produce molded articles by any known method, without any particular limitation. Specifically, the polyamide resin composition can be used to produce molded articles by injection molding, extrusion molding, blow molding, rotational molding, etc.

[0064] Molded articles containing polyamide resin compositions not only possess the excellent properties inherent to polyamide resins, such as oil resistance, but also have high slidability and mechanical properties, making them suitable for use as sliding parts, particularly sliding parts requiring oil resistance. Examples of such sliding parts include cylinder head covers, various oil reservoirs, crankcase covers, power tool-related parts, and hydraulic equipment parts. Examples of hydraulic equipment parts include those used in the vehicle and general-purpose equipment parts fields. In the vehicle field, the polyamide resin composition can be used for piston-related parts of hydraulic equipment parts such as clutches, brakes, bearings, and power steering. In the general-purpose equipment parts field, the polyamide resin composition can be used for parts such as vises, jacks, and thrust washers. Preferred uses are in the vehicle and general-purpose equipment parts fields as hydraulic equipment parts. Particularly preferred uses are parts in the vehicle field. A further embodiment of the present invention is a method for producing a sliding part, comprising molding a polyamide resin composition. [Example]

[0065] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0066] [Materials used] 1. Aliphatic polyamide resin (A) Polyamide 66 (Leona (registered trademark) 1200, manufactured by Asahi Kasei Corporation)

[0067] 2. Fluoropolymer resin (B) which may have a functional group Acid anhydride group-containing ethylene / tetrafluoroethylene copolymer (AGC Corporation, Fluon® LM-ETFE, a copolymer in which maleic anhydride has been introduced into an ethylene / tetrafluoroethylene copolymer) Ethylene / tetrafluoroethylene copolymer (AGC Corporation, Fluon (registered trademark) ETFE)

[0068] 2'. Non-functional group-containing homopolymer fluororesin (B') Polytetrafluoroethylene (AGC Corporation, Fluon (registered trademark) PTFE)

[0069] 3. Carbon fiber (C) Teijin Limited, Tenax (registered trademark) HT type (average fiber diameter: 7 μm, average fiber length: 6 mm)

[0070] 4. Other ingredients (D) / heat-resistant agent Mixture of metal halide compounds and melamine: Mixture of cuprous iodide / potassium iodide / melamine = 2 / 5 / 1 (mass ratio)

[0071] Examples 1 to 7 and Comparative Examples 1 to 2 Using a twin-screw kneader ZSK32McPlus (manufactured by Coperion Co., Ltd., screw diameter 32 mm), all of the components listed in Table 1 except for the carbon fiber were added from the top, while the carbon fiber was added using a side feeder. Melt-kneading was carried out at a cylinder temperature of 300°C, a screw rotation speed of 400 rpm, and a discharge rate of 60 kg / h to produce polyamide resin composition pellets for Examples 1 to 7 and Comparative Examples 1 and 2, respectively. The units of composition in the table are mass %, and the entire resin composition is taken as 100 mass %.

[0072] [Table 1]

[0073] The pellets of Examples 1 to 7 and Comparative Examples 1 and 2 were used in the following property evaluations.

[0074] [Evaluation method] Preparation of test specimens All test pieces for evaluating the mechanical properties and sliding properties were molded using an SE100D-C160S injection molding machine manufactured by Sumitomo Heavy Industries, Ltd.

[0075] 1.Mechanical property test method Tensile breaking stress, nominal tensile breaking strain and tensile modulus Test pieces were prepared using the pellets of Examples 1 to 7 and Comparative Examples 1 and 2 in accordance with ISO 527-1 and 2, and the tensile stress at break, nominal tensile strain at break, and tensile modulus were measured. The pass criteria for the tensile stress at break, nominal tensile strain at break, and tensile modulus were set at 150 MPa or more, 5% or less, and 10 GPa or more, respectively.

[0076] Flexural strength and flexural modulus Using the pellets of Examples 1 to 7 and Comparative Examples 1 and 2, test pieces were prepared and measured for flexural strength and flexural modulus in accordance with ISO 178. The pass criteria for flexural strength and flexural modulus were set at 200 MPa or more and 10 GPa or more, respectively.

[0077] Rockwell hardness Test pieces were prepared in accordance with ISO 2039-2 using the pellets of Examples 1 to 7 and Comparative Examples 1 and 2, respectively, and the Rockwell hardness (M scale) was measured. The pass criterion for Rockwell hardness was set at 100 or more.

[0078] Charpy impact strength Test pieces were prepared in accordance with ISO 179 / 1eA using the pellets of Examples 1 to 7 and Comparative Examples 1 and 2, respectively, and the Charpy impact strength was measured. The pass criterion for Charpy impact strength was 4 kJ / m 2 That's all.

[0079] Deflection temperature under load Test pieces were prepared in accordance with ISO 75-2 using the pellets of Examples 1 to 7 and Comparative Examples 1 and 2, and the deflection temperature under load (measurement load: 1.8 MPa) was measured. The pass criterion for the deflection temperature under load was set at 200°C or higher.

[0080] Mold shrinkage Test pieces were prepared in accordance with ISO 294-4 using the pellets of Examples 1 to 7 and Comparative Examples 1 and 2, respectively, and measurements were carried out using a measuring microscope (STM7) manufactured by Olympus Corporation. The molding shrinkage in the MD and TD directions was calculated using the following formula. Mold shrinkage rate = (distance between scribed lines on mold - distance between scribed lines on test piece) / distance between scribed lines on mold x 100 The acceptance criteria for molding shrinkage in the MD and TD directions were set at 0.2% or less and 1.0% or less, respectively.

[0081] 2. Test method for injection flow length Using an injection molding machine (manufactured by Nissei Plastic Industrial Co., Ltd., product name: PS40E) equipped with a bar flow mold with a cavity thickness of 1 mm, width of 15 mm, and length of 360 mm, the pellets of Examples 1 to 7 and Comparative Examples 1 and 2 were each injection molded under molding conditions of injection pressure 100 MPa, cylinder temperature 285°C, mold temperature 80°C, injection speed 38 mm / sec, injection time 4 seconds, and cooling time 15 seconds. The total length from the gate exit of the molded article obtained by injection molding was measured as the L / T flow length. The flowability of the polyamide resin composition was then evaluated according to the following criteria. ◎: L / T flow length is 180mm or more ○: L / T flow length is 150 mm or more and less than 180 mm ×: L / T flow length is less than 150 mm

[0082] 3. Sliding property test method Coefficient of dynamic friction Using the pellets of Examples 1 to 7 and Comparative Examples 1 and 2, test pieces of 60 mm x 40 mm x 3 mm were prepared in accordance with JIS K7218A method, and measurements were carried out using a Suzuki-type friction and wear tester (manufactured by Orientec Co., Ltd., EFM-III-EN), and the dynamic friction coefficient was calculated using the following formula. Coefficient of dynamic friction = (friction force x fulcrum distance) / (spring pressure force x average radius of sample) The acceptance standard for the dynamic friction coefficient was set at 0.10 or less.

[0083] Limit PV value Using a Sumitomo Heavy Industries, Ltd. SE100D-C160S injection molding machine, 200 x 30 x 3 mm test specimens were prepared and left to stand at 23 °C for at least 48 hours. The test specimens thus obtained were subjected to a Suzuki-type friction and wear tester (manufactured by Orientec Co., Ltd., EFM-III-EN) in accordance with JIS K7218. A cylindrical ring made of S45C carbon steel, measuring 25.6 mm in outer diameter, 20.0 mm in inner diameter, and 15.0 mm in height, was used. The ring-on-plate method was used, the test speed was 350 mm / s, and an initial load of 25 kgf (245 N) was applied at the start, with the load increasing by 25 kgf (245 N) every 10 minutes. The critical PV value was calculated using the load (applied pressure) just before the test specimen melted by 2 mm using the following formula: Limit PV value = pressure force per square centimeter x peripheral speed The limiting PV value of the resin composition was evaluated according to the following criteria. ◎: Limit PV value is 6,000 kg / cm 2 ·cm / sec or more ○: Limit PV value is 4,000 kg / cm 2 ·cm / sec or more 6,000kg / cm 2 Less than cm / sec ×: Limit PV value is 4,000 kg / cm 2 Less than cm / sec

[0084] Table 2 shows the evaluation results of the pellets of Examples 1 to 7 and Comparative Examples 1 and 2.

[0085] [Table 2]

[0086] Table 2 shows that Examples 1 to 7, which used polyamide resin compositions containing 60 to 85 mass% of aliphatic polyamide resin (A), 0.5 to 9 mass% of copolymer fluororesin (B) which may have functional groups, 5 to 20 mass% of carbon fiber (C), and 34.5 mass% or less of other components (D) relative to 100 mass% of the polyamide resin composition, had high fluidity and excellent mechanical properties and sliding properties when molded into articles. Comparisons between Examples 2 and 6, 3 and 5, and 4 and 7 reveal that Examples 2 to 4, which used copolymer fluororesin having functional groups, had longer injection flow lengths and better fluidity than Examples 5 to 7, which used copolymer fluororesin without functional groups. Furthermore, Examples 1, 2, 4, 6, and 7, which contained 2.0 mass% or more of copolymer fluororesin (B) which may have functional groups relative to 100 mass% of the polyamide resin composition, had a critical PV value of 6,000 kg / cm. 2 -cm / sec or more, providing excellent sliding properties.

[0087] Comparative Example 1, which uses polytetrafluoroethylene instead of the fluoropolymer resin (B) which may have functional groups, is inferior in fluidity and mechanical properties. Comparative Example 2, which uses the fluoropolymer resin (B) having functional groups but whose content is outside the range of the present invention, is inferior in mechanical properties and sliding properties.

[0088] The pellets obtained in Example 1 were evaluated for weight retention as shown below. Using a TA Instruments TGA Q5000, the pellets were rapidly heated from room temperature to 300°C under air flow conditions, and after reaching 300°C, the temperature was maintained for 10 minutes. After that, the temperature was lowered to room temperature and the pellets were left to stand at 23°C and 50% RH for 48 hours. The weight retention was calculated from the weight before and after heating. The weight retention rate of the pellets in Example 1 (residual weight after heating at 300°C (held for 10 minutes)) was extremely high at 99.34%. [Industrial Applicability]

[0089] The polyamide resin composition of the present invention can be used to produce various molded articles by injection molding, extrusion molding, blow molding, rotational molding, etc.

Claims

1. The polyamide resin composition contains, relative to 100% by mass, 70 to 85% by mass of an aliphatic polyamide resin (A), 0.5 to 9% by mass of a copolymer fluororesin (B) which may have a functional group, 5 to 20% by mass of carbon fiber (C), and 5.0% by mass or less of other component (D), The polyamide resin composition, wherein the fluororesin copolymer (B) which may have a functional group is an α-olefin / tetrafluoroethylene copolymer.

2. 2. The polyamide resin composition according to claim 1, wherein the mass ratio of the carbon fiber (C) to the copolymerized fluororesin (B) which may have a functional group is more than 1.0 and less than 20.

3. 3. The polyamide resin composition according to claim 1, wherein the mass ratio of the copolymerized fluororesin (B) which may have a functional group to the aliphatic polyamide resin (A) is more than 0.005 and less than 0.

12.

4. The polyamide resin composition according to any one of claims 1 to 3, wherein the functional group of the copolymerized fluororesin (B) which may have a functional group is a carboxyl group, a carboxylic acid ester group, and / or an acid anhydride group.

5. The polyamide resin composition according to any one of claims 1 to 4, wherein the copolymerized fluororesin (B) which may have a functional group is an α-olefin / tetrafluoroethylene copolymer having a group derived from maleic anhydride bonded thereto.

6. The polyamide resin composition according to any one of claims 1 to 5, which is substantially free of fibrous xonotlite.

7. The polyamide resin composition according to any one of claims 1 to 6, wherein the polyamide resin composition is injection molded using a mold having a width of 15 mm, a length of 360 mm, and a thickness of 1 mm under conditions of a pressure of 100 MPa, a cylinder temperature of 285°C, a mold temperature of 80°C, an injection speed of 38 mm / sec, an injection time of 4 seconds, and a cooling time of 15 seconds, and the resulting molded product has an injection flow length of 150 mm or more.

8. The polyamide resin composition according to any one of claims 1 to 7, which is used for sliding parts.

9. A molded article comprising the polyamide resin composition according to any one of claims 1 to 8.

10. The molded article according to claim 9, which is a sliding part.

11. A method for producing a sliding part, comprising molding the polyamide resin composition according to any one of claims 1 to 8.

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