Polyamide resin composition containing polyamide resin and recycled carbon fiber

Abstract

The present invention provides a polyamide resin composition that exhibits excellent tensile modulus and flexural strength, even when using recycled carbon fibers. [Solution] The polyamide resin composition contains 60-95% by mass of polyamide resin and 2-30% by mass of recycled carbon fiber, with the bulk density of the recycled carbon fiber being 0.250 g / cm³. 3 Super 0.300g / cm 3 The following applies:

Description

[Technical Field]

[0001] The present invention relates to a polyamide resin composition comprising a polyamide resin and recycled carbon fibers. [Background technology]

[0002] Carbon fiber reinforced materials, which contain short carbon fibers in thermoplastic resins, are used as parts for automobiles and other applications because they possess high strength, high rigidity, and are advantageous for weight reduction. From the perspective of economic efficiency and reducing the burden on the environment, there are attempts to manufacture carbon fiber composite materials using inexpensive recycled carbon fibers instead of expensive unused carbon fibers (hereinafter also called "virgin carbon fibers").

[0003] Patent Document 1 discloses a carbon fiber composite material comprising a resin such as polyamide 6 and recycled carbon fibers with specified aspect ratio and fiber length, wherein the recycled carbon fiber content is 50 to 70% by weight.

[0004] Patent Document 2 discloses a polyamide resin composition comprising a polyamide resin mixture containing polyamide 66 or polyamide 612 and an aromatic polyamide, and recycled carbon fibers coated with an acrylic copolymer, wherein the elongation at break of the resin composition is equivalent to that of virgin carbon fibers.

[0005] Patent Document 3 discloses that a polyamide resin composition comprising a polyamide resin (polyamide 6 or polyamide 66) having a specific average solubility parameter and recycled carbon fiber having a specific oxygen content exhibits excellent productivity even when recycled carbon fiber is used. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2020-189916 [Patent Document 2] Special Publication No. 2016-540067 [Patent Document 3] Patent No. 6977904 [Overview of the project] [Problems that the invention aims to solve]

[0007] However, Patent Documents 1 to 3 did not mention the difference in tensile modulus and flexural strength between cases using virgin carbon fibers and cases using recycled carbon fibers. Furthermore, according to the inventors' findings, there is room for improvement in achieving both tensile modulus and flexural strength in polyamide resin compositions containing recycled carbon fibers.

[0008] The present invention aims to provide a polyamide resin composition that exhibits excellent tensile modulus and flexural strength, even when using recycled carbon fibers. [Means for solving the problem]

[0009] The present invention relates to the following [1] to [3]. [1] A polyamide resin composition comprising 60 to 95% by mass of polyamide resin and 2 to 30% by mass of recycled carbon fiber, based on 100% by mass of the polyamide resin composition, The bulk density of the recycled carbon fiber is 0.250 g / cm³. 3 Super 0.300g / cm 3 The following: With respect to the tensile strength measured according to ISO 527-1,2 using an ISO multipurpose test specimen molded from the polyamide resin composition according to ISO 527-1,2, and the tensile strength measured according to ISO 527-1,2 using an ISO multipurpose test specimen molded from a composition containing virgin carbon fibers according to ISO 527-1,2, the ratio of the tensile strength of the polyamide resin composition to the tensile strength of the composition containing virgin carbon fibers is 100.0% or more. With respect to the flexural modulus measured according to ISO 178 using an ISO multipurpose test specimen molded from the polyamide resin composition according to ISO 178, and the flexural modulus measured according to ISO 178 using an ISO multipurpose test specimen molded from a composition containing virgin carbon fibers according to ISO 178, the ratio of the flexural modulus of the polyamide resin composition to the flexural modulus of the composition containing virgin carbon fibers is 100.0% or more. The composition containing the virgin carbon fibers is a composition in which the recycled carbon fibers contained in the polyamide resin composition are replaced with virgin carbon fibers in an equal amount. Polyamide resin composition. [2] The bulk density of the recycled carbon fiber is 0.280 g / cm³. 3 More than 0.300g / cm 3 The polyamide resin composition described in [1] is as follows: A molded article comprising the polyamide resin composition described in [3][1] or [2]. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a polyamide resin composition that exhibits excellent tensile modulus and flexural strength, even when using recycled carbon fibers. [Modes for carrying out the invention]

[0011] In this specification, the content of each component in a composition means the total amount of any multiple substances present in the composition, unless otherwise specified. In this specification, the "~" symbol indicating a numerical range means that the numbers before and after it are included as the lower and upper limits, respectively.

[0012] [Polyamide resin composition] The polyamide resin composition contains 60-95% by mass of polyamide resin and 2-30% by mass of recycled carbon fiber, based on 100% by mass of the polyamide resin composition. The bulk density of the recycled carbon fiber in the polyamide resin composition is 0.250 g / cm³. 3 Super 0.300g / cm 3 The following conditions apply: The polyamide resin composition has a tensile strength of 100.0% or higher when measured according to ISO 527-1,2 using an ISO multipurpose test specimen molded from the polyamide resin composition according to ISO 527-1,2, and when measured according to ISO 527-1,2 using an ISO multipurpose test specimen molded from a composition containing virgin carbon fibers according to ISO 527-1,2, with respect to the tensile strength of the polyamide resin composition relative to the tensile strength of the composition containing virgin carbon fibers (hereinafter also simply referred to as "tensile strength retention rate"). The polyamide resin composition has a flexural modulus of 100.0% or higher (hereinafter also simply referred to as "flexural modulus retention rate"), with respect to the flexural modulus of the polyamide resin composition measured according to ISO 178 using an ISO multipurpose test specimen molded from the polyamide resin composition according to ISO 178, and the flexural modulus of 100.0% or higher, measured according to ISO 178 using an ISO multipurpose test specimen molded from a composition containing virgin carbon fibers according to ISO 178. Here, the composition containing virgin carbon fibers is a composition in which the recycled carbon fibers contained in the polyamide resin composition are replaced with virgin carbon fibers having an equal amount of carbon fibers.

[0013] The polyamide resin composition has a retention rate of tensile strength and flexural modulus of elasticity of 100.0% or more. Therefore, even when recycled carbon fibers are used, the polyamide resin composition is excellent in tensile modulus of elasticity and flexural strength. In this specification, "excellent in tensile modulus of elasticity and flexural strength" means that, with respect to the tensile modulus of elasticity and flexural strength measured using a test piece molded from the polyamide resin composition and the tensile modulus of elasticity and flexural strength measured using a test piece molded from a composition containing virgin carbon fibers, the ratio of the tensile modulus of elasticity and flexural strength of the polyamide composition to the tensile modulus of elasticity and flexural strength of the composition containing virgin carbon fibers (hereinafter, also simply referred to as "retention rate of tensile modulus of elasticity and flexural strength") is 90% or more. Here, the "composition containing virgin carbon fibers" is as described above. Also, the specific measurement method for tensile modulus of elasticity and flexural strength is the method described in the examples. The polyamide resin composition can greatly contribute to reducing the discharge amount of various carbon fiber reinforced resin (CFRP) wastes through the recycling of carbon fibers, and from the perspective of reducing the energy required for the production of virgin carbon fibers and the energy generated by combustion during disposal, it can contribute to the achievement of Goal + 7 of SDGs (Sustainable Development Goals).

[0014] The polyamide resin composition has a retention rate of tensile strength of 100.0% or more. By having a retention rate of tensile strength of 100% or more, the polyamide resin composition has superior mechanical properties compared to the case of using a composition containing virgin carbon fibers. Therefore, the molded body of the polyamide resin composition has excellent functions and properties. When the retention rate of tensile strength is 90% or more and less than 100.0%, although the functions and properties are not impaired, the mechanical properties (especially the tensile modulus of elasticity) tend to be slightly inferior. Also, when the retention rate of tensile strength is less than 90%, the mechanical properties (especially the tensile modulus of elasticity) tend to be significantly inferior.

[0015] The polyamide resin composition has a retention rate of flexural modulus of elasticity of 100.0% or more. By having a retention rate of flexural modulus of elasticity of 100% or more, the polyamide resin composition has superior mechanical properties compared to the composition using virgin carbon fiber. Therefore, the molded body of the polyamide resin composition has excellent functions and properties. When the retention rate of flexural modulus of elasticity is 90% or more and less than 100.0%, the mechanical properties (especially flexural strength) tend to be inferior within the range where the functions and properties are not impaired. Also, when the retention rate is less than 90%, the mechanical properties (especially flexural strength) tend to be significantly inferior.

[0016] 〔Polyamide resin〕 Examples of the polyamide resin include an aliphatic polyamide resin (A) having no aromatic ring and an aromatic polyamide resin (B) containing an aromatic ring. Examples of the aliphatic polyamide resin (A) include an aliphatic homopolyamide resin (A-1) and an aliphatic copolymer polyamide resin (A-2). Also, examples of the aromatic polyamide resin (B) include an aromatic homopolyamide resin (B-1) and an aromatic copolymer polyamide resin (B-2).

[0017] <Aliphatic homopolyamide resin (A-1)> The aliphatic homopolyamide resin (A-1) means a polyamide resin in which the monomer components constituting the aliphatic polyamide resin are of one kind. Here, examples of the monomer components constituting the aliphatic polyamide resin include a combination of an aliphatic diamine and an aliphatic dicarboxylic acid, a lactam, or an aminocarboxylic acid. Also, when the monomer components constituting the aliphatic polyamide resin are a combination of an aliphatic diamine and an aliphatic dicarboxylic acid, it shall be regarded as one kind of monomer component as a combination of one kind of aliphatic diamine and one kind of aliphatic dicarboxylic acid.

[0018] The number of carbon atoms in aliphatic diamines is preferably 2 to 20, and particularly preferably 4 to 12. The number of carbon atoms in aliphatic dicarboxylic acids is preferably 2 to 20, and particularly preferably 6 to 12. The number of carbon atoms in lactams is preferably 5 to 12. The number of carbon atoms in aminocarboxylic acids is preferably 5 to 12.

[0019] Examples of aliphatic diamines include ethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, peptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, undecamethylenediamine, dodecamethylenediamine, tridecanediamine, tetradecanediamine, pentadecanediamine, hexadecanediamine, heptadecanediamine, octadecanediamine, nonadecanediamine, and eicosanediamine. 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, pentadecanedionic acid, hexadecanedionic acid, octadecanedionic acid, and eicosanedionic acid.

[0020] Examples of combinations of aliphatic diamine and aliphatic dicarboxylic acid include hexamethylenediamine and adipic acid, hexamethylenediamine and sebacic acid, and hexamethylenediamine and dodecanedionic acid. Preferably, the combination of aliphatic diamine and aliphatic dicarboxylic acid is an equimolar salt of the said combination.

[0021] Examples of lactams include γ-butyrolactam, δ-valerolactam, ε-caprolactam, enantractam, undecanelactam, and dodecanelactam. Examples of aminocarboxylic acids include 5-aminopentanoic acid, 6-aminohexanoic acid, 7-aminoheptanoic acid, 9-aminononanoic acid, 11-aminoundecanoic acid, and 12-aminododecanoic acid. From the viewpoint of productivity, the lactam is preferably ε-caprolactam, undecanelactam, or dodecanelactam.

[0022] Specific examples of aliphatic homopolyamide resins (A-1) include polyvalerolactam (polyamide 5), polycaprolactam (polyamide 6), polyenanthractam (polyamide 7), polyundecanelactam (polyamide 11), polylauryllactam (polyamide 12), polytetramethyleneadipamide (polyamide 46), polytetramethylenedodecamid (polyamide 412), and poly Pentamethylene adipamide (Polyamide 56), Polypentamethylene azeramide (Polyamide 59), Polypentamethylene sevacamide (Polyamide 510), Polypentamethylene dodecamide (Polyamide 512), Polyhexamethylene adipamide (Polyamide 66), Polyhexamethylene azeramide (Polyamide 69), Polyhexamethylene sevacamide (Polyamide 610), Polyhex Sameethylene dodecamide (polyamide 612), polynonameethylene adipamide (polyamide 96), polynonameethylene azeramide (polyamide 99), polynonameethylene sebaamide (polyamide 910), polynonameethylene dodecamide (polyamide 912), polydecamethylene adipamide (polyamide 106), polydecamethylene azeramide (polyamide 109), polydecamethylene deka Examples include polyamide 1010, polydecamethylene dodecamide (polyamide 1012), polydodecamethylene adipamide (polyamide 126), polydodecamethylene azeramide (polyamide 129), polydodecamethylene sevacamide (polyamide 1210), polydodecamethylene dodecamide (polyamide 1212), and polydodecamethylene oxamide (polyamide 122).

[0023] <Aliphatic copolymer polyamide resin (A-2)> Aliphatic copolymer polyamide resin (A-2) is an aliphatic polyamide resin in which the monomer components constituting the aliphatic polyamide resin are two or more types and the aliphatic polyamide resin does not have an aromatic ring. Therefore, an example of aliphatic copolymer polyamide resin (A-2) is an aliphatic copolymer polyamide resin which is a copolymer of two or more monomers selected from the group consisting of a combination of aliphatic diamine and aliphatic dicarboxylic acid, lactam and aminocarboxylic acid.

[0024] Specific examples of aliphatic copolymer polyamide resins (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 / hexamethylenediaminoundecanoic acid copolymer (polyamide 6 / 611), caprolactam / hexamethylenediaminododecanoic acid copolymer (polyamide 6 / 612), and caprolactam / aminoundecanoic acid copolymer (polyamide 6 / 11) Examples include caprolactam / lauryl lactam copolymer (polyamide 6 / 12), caprolactam / hexamethylenediaminoadipic acid / lauryl lactam copolymer (polyamide 6 / 66 / 12), caprolactam / hexamethylenediaminoadipic acid / hexamethylenediaminosebacic acid copolymer (polyamide 6 / 66 / 610), caprolactam / hexamethylenediaminoadipic acid / hexamethylenediaminododecanedicarboxylic acid copolymer (polyamide 6 / 66 / 612), hexamethylenediaminoadipic acid / caprolactam copolymer (polyamide 66 / 6), etc.

[0025] <Aromatic homopolyamide resin (B-1)> Aromatic homopolyamide resin (B-1) refers to a polyamide resin in which the monomer component constituting the aliphatic polyamide resin is of one type. Therefore, aromatic homopolyamide resin (B-2) can be a combination of an aliphatic and / or alicyclic diamine and an aromatic dicarboxylic acid, a combination of an aromatic diamine and an aliphatic and / or alicyclic dicarboxylic acid, or a combination of an aromatic diamine and an aromatic dicarboxylic acid. Here, the aliphatic diamine and aliphatic dicarboxylic acid are those mentioned above.

[0026] Examples of aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,4-phenylenedioxydiacetic acid, 1,3-phenylenedioxydiacetic acid, dibenzoic acid, 4,4'-oxydibenzoic acid, diphenylmethane-4,4'-dicarboxylic acid, diphenylsulfone-4,4'-dicarboxylic acid, and 4,4'-biphenyldicarboxylic acid. Examples of alicyclic dicarboxylic acids include 1,3-cyclopentanedicarboxylic acid and 1,4-cyclohexanedicarboxylic acid.

[0027] Aromatic diamines include p-phenylenediamine, m-phenylenediamine, p-xylenediamine, m-xylenediamine, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl sulfone, and 4,4'-diaminodiphenyl ether. Alicyclic diamines include cyclohexanediamine, methylcyclohexanediamine, and isophoronediamine.

[0028] Specific examples of aromatic homopolyamide resins (B-1) include polynonameethylene terephthalamide (polyamide 9T), polynonameethylene naphthalamide (polyamide 9N), polydecamethylene terephthalamide (polyamide 10T), polydecamethylene naphthalamide (polyamide 10N), polydodecamethylene terephthalamide (polyamide 12T), polydodecamethylene naphthalamide (polyamide 12N), polymetaxylylene succinamide (polyamide MXD4), polymetaxylylene glutamide (polyamide MXD5), ​​polymetaxylylene adipamide (polyamide MXD6), and polymetaxylylene sveramide (polyamide Examples include polyamide MXD8, polymetaxylylene azeramide (polyamide MXD9), polymetaxylylene sebamid (polyamide MXD10), polymetaxylylene dodecamide (polyamide MXD12), polyparaxylylene succinamide (polyamide PXD4), polyparaxylylene glutamide (polyamide PXD5), ​​polyparaxylylene adipamide (polyamide PXD6), polyparaxylylene sveramide (polyamide PXD8), polyparaxylylene azeramide (polyamide PXD9), polyparaxylylene sebamid (polyamide PXD10), and polyparaxylylene dodecamide (polyamide PXD12).

[0029] <Aromatic copolymer polyamide resin (B-2)> Aromatic copolymer polyamide resin (B-2) is an aromatic polyamide resin in which the monomer components constituting the aromatic polyamide resin are two or more types. Here, examples of aromatic copolymer polyamide resin (B-2) include aromatic polyamide resins that are copolymers of monomers selected from a combination of aliphatic and / or alicyclic diamines and aromatic dicarboxylic acids, a combination of aromatic diamines and aliphatic and / or alicyclic dicarboxylic acids, and a combination of aromatic diamines and aromatic dicarboxylic acids. Here, when the monomer components constituting the aromatic polyamide resin are a combination of diamines and dicarboxylic acids, a combination of one type of diamine and one type of dicarboxylic acid shall be considered as one type of monomer component. Here, aliphatic diamines, alicyclic diamines, aromatic diamines, aliphatic dicarboxylic acids, alicyclic dicarboxylic acids, and aromatic dicarboxylic acids are those mentioned above.

[0030] Specific examples of aromatic copolymer polyamide resins (B-2) include poly(tetramethylene terephthalamide / hexamethylene terephthalamide) copolymer (polyamide 4T / 6T), poly(tetramethylene terephthalamide / tetramethylene adipamide) copolymer (polyamide 4T / 46), poly(hexamethylene terephthalamide / hexamethylene isophthalamide) copolymer (polyamide 6T / 6I), poly(hexamethylene terephthalamide / 2-methylpentamethylene terephthalamide) copolymer (polyamide 6T / M5T), poly(hexamethylene terephthalamide / caproamide) copolymer (polyamide 6T / 6), and poly(hexamethylene terephthalamide / hexamethylene adipamide) copolymer (polyamide 6T / M5T). Examples include polyamide 6T / 66, poly(hexamethylene terephthalamide / hexamethylene sevacamide) copolymer (polyamide 6T / 610), poly(hexamethylene terephthalamide / hexamethylene dodecamide) copolymer (polyamide 6T / 612), poly(hexamethylene terephthalamide / hexamethylene isophthalamide / hexamethylene adipamide) copolymer (polyamide 6T / 6I / 66), poly(hexamethylene terephthalamide / hexamethylene isophthalamide / hexamethylene sevacamide) copolymer (polyamide 6T / 6I / 610), and poly(hexamethylene terephthalamide / hexamethylene isophthalamide / hexamethylene dodecamide) copolymer (polyamide 6T / 6I / 612).

[0031] Furthermore, specific examples of aromatic copolymer polyamide resins (B-2) include poly(nonamethylene terephthalamide / 2-methyloctamethylene terephthalamide) copolymer (polyamide 9T / M8T), poly(nonamethylene terephthalamide / 2-methyloctamethylene terephthalamide / undecaneamide) copolymer (polyamide 9T / M8T / 11), poly(nonamethylene terephthalamide / 2-methyloctamethylene terephthalamide / dodecaneamide) copolymer (polyamide 9T / M8T / 12), and poly(nonamethylene terephthalamide / 2-methyloctamethylene terephthalamide Lenterephthalamide / Nonameethylene isophthalamide / 2-Methyloctamethylene isophthalamide) copolymer (Polyamide 9T / M8T / 9I / M8I), Poly(Nonameethylene naphthalamide / 2-Methyloctamethylene naphthalamide) copolymer (Polyamide 9N / M8N), Poly(Nonameethylene naphthalamide / 2-Methyloctamethylene naphthalamide / Undecaneamide) copolymer (Polyamide 9N / M8N / 11), Poly(Nonameethylene naphthalamide / 2-Methyloctamethylene naphthalamide / Dodecaneamide) copolymer (Polyamide 9N / M8 N / 12), poly(decamethylene terephthalamide / undecanamide) copolymer (polyamide 10T / 11), poly(decamethylene terephthalamide / dodecanamide) copolymer (polyamide 10T / 12), poly(decamethylene terephthalamide / decamethylene sevacamide) copolymer (polyamide 10T / 1010), poly(decamethylene terephthalamide / decamethylene dodecamide) copolymer (polyamide 10T / 1012), poly(decamethylene terephthalamide / decamethylene isophthalamide / undecanamide) copolymer (polyamide 10T / Polyamide 10T / 10I / 12), Poly(decamethylene terephthalamide / decamethylene isophthalamide / dodecanamide) copolymer (polyamide 10T / 10I / 12), Poly(decamethylene terephthalamide / decamethylene isophthalamide / decamethylene sevacamide) copolymer (polyamide 10T / 10I / 1010), Poly(decamethylene terephthalamide / decamethylene isophthalamide / decamethylene dodecamide) copolymer (polyamide 10T / 10I / 1012), Poly(decamethylene naphthalamide / undecanamide) copolymer (polyamide 10N / 11),Poly(decamethylenenaphthalamide / dodecanamide) copolymer (polyamide 10N / 12), poly(decamethylenenaphthalamide / decamethylenesebacamide) copolymer (polyamide 10N / 1010), poly(decamethylenenaphthalamide / decamethylenedodecamide) copolymer (polyamide 10N / 1012), poly(decamethyleneterephthalamide / decamethylenenaphthalamide / undecanamide) copolymer (polyamide 10T / 10N / 11), Examples include poly(decamethylene terephthalamide / decamethylene naphthalamide / dodecanamide) copolymer (polyamide 10T / 10N / 12), poly(decamethylene terephthalamide / decamethylene naphthalamide / decamethylene sevacamide) copolymer (polyamide 10T / 10N / 1010), and poly(decamethylene terephthalamide / decamethylene naphthalamide / decamethylene dodecamide) copolymer (polyamide 10T / 10N / 1012).

[0032] Furthermore, specific examples of aromatic copolymer polyamide resins (B-2) include poly(dodecamethylene terephthalamide / undecaneamide) copolymer (polyamide 12T / 11), poly(dodecamethylene terephthalamide / dodecaneamide) copolymer (polyamide 12T / 12), poly(dodecamethylene terephthalamide / dodecamethylene sevacamide) copolymer (polyamide 12T / 1210), poly(dodecamethylene terephthalamide / dodecamethylene dodecamide) copolymer (polyamide 12T / 1212), and poly(dodecamethylene terephthalamide) Polyamide 12T / 12I / 11 (polyamide / dodecamethylene isophthalamide / undecaneamide), Poly(dodecamethylene terephthalamide / dodecamethylene isophthalamide / dodecaneamide) copolymer (polyamide 12T / 12I / 12), Poly(dodecamethylene terephthalamide / dodecamethylene isophthalamide / dodecamethylene sevacamide) copolymer (polyamide 12T / 12I / 1210), Poly(dodecamethylene terephthalamide / dodecamethylene isophthalamide / dodecamethylene dodecamide) copolymer (polyamide Polyamide 12N / 12, Poly(dodecamethylenenaphthalamide / undecaneamide) copolymer (polyamide 12N / 11), Poly(dodecamethylenenaphthalamide / undecaneamide) copolymer (polyamide 12N / 12), Poly(dodecamethylenenaphthalamide / dodecamamide) copolymer (polyamide 12N / 12), Poly(dodecamethylenenaphthalamide / dodecamamide) copolymer (polyamide 12N / 1210), Poly(dodecamethylenenaphthalamide / dodecamamide) copolymer (polyamide 12N / 1212), Poly(dodecamethyleneterephthalamide / dodecamethylenenaphthalamide / undecaneamide) copolymer Examples include polyamide 12T / 12N / 11, poly(dodecamethylene terephthalamide / dodecamethylene naphthalamide / dodecanamide) copolymer (polyamide 12T / 12N / 12), poly(dodecamethylene terephthalamide / dodecamethylene naphthalamide / dodecamethylene sevacamide) copolymer (polyamide 12T / 12N / 1210), and poly(dodecamethylene terephthalamide / dodecamethylene naphthalamide / dodecamethylene dodecamide) copolymer (polyamide 12T / 12N / 1212).

[0033] <Preferred embodiment> From the viewpoint of moldability, the polyamide resin is preferably an aliphatic polyamide resin (A), more preferably an aliphatic homopolyamide resin (A-1), and particularly preferably one or more selected from the group consisting of polyamide 5, polyamide 6, polyamide 46, polyamide 56, polyamide 510, polyamide 66, polyamide 610, polyamide 612, polyamide 11, and polyamide 12.

[0034] The polyamide resin conforms to JIS K 6920, and the relative viscosity measured at 25°C by dissolving 1 g of polyamide resin in 100 ml of 96% concentrated sulfuric acid is 1.9 or higher, preferably between 1.9 and 4.2, and more preferably between 2.3 and 3.2, from the viewpoint of moldability. If the polyamide resin contains two or more polyamide resins with different relative viscosities, the relative viscosity of the polyamide resin is preferably measured as described above. However, if the relative viscosity of each polyamide resin and its mixing ratio are known, the average value calculated by summing the values ​​obtained by multiplying each relative viscosity by its mixing ratio may be used as the relative viscosity of the polyamide resin.

[0035] The polyamide resin may consist of one component or a combination of two or more components.

[0036] [Recycled carbon fiber] Recycled carbon fiber refers to carbon fiber recovered by recycling waste materials of carbon fiber reinforced materials (such as scraps of carbon fiber reinforced polymer (CFRP) or CFRP waste). Carbon fiber reinforced materials include carbon fiber (CF) and matrix resin. Carbon fiber reinforced materials may be not only molded products but also intermediate products before molding (such as prepregs). Examples of matrix resins for CFRP include thermosetting resins and thermoplastic resins. The method for separating the resin from the carbon fiber contained in the carbon fiber reinforced material when recovering the carbon fiber is not limited. Examples of such methods include thermal decomposition and chemical dissolution. Recycled carbon fiber may also contain unused carbon fiber generated during manufacturing.

[0037] As a specific recycling method for recovering carbon fibers from waste carbon fiber reinforced materials, there is no particular limitation, and known methods can be appropriately used.

[0038] <Preferred embodiment> The bulk density of recycled carbon fiber is 0.250 g / cm 3 exceeding 0.300 g / cm 3 as follows. When the bulk density of the recycled carbon fiber is within this range, the recycled carbon fiber is likely to be uniformly dispersed in the polyamide resin composition, and the recycled carbon fiber is less likely to be damaged or broken. From the viewpoint of increasing the mechanical properties (particularly, tensile modulus and / or flexural strength) of the molded body formed from the polyamide resin composition, the bulk density of the recycled carbon fiber is 0.280 g / cm 3 or more and 0.300 g / cm 3 or less. The bulk density of the recycled carbon fiber can be measured by the method described in the examples.

[0039] The aspect ratio of the recycled carbon fiber is not particularly limited, but is preferably 3.4 to 4.0, and particularly preferably 3.5 to 3.9. The average fiber length (D50) of the recycled carbon fiber is not particularly limited, but is preferably 100 to 150 μm, and particularly preferably 105 to 12 μm. The average fiber length and aspect ratio of the recycled carbon fiber can be measured with an optical microscope or the like.

[0040] Examples of commercially available recycled carbon fibers include those manufactured by ELG Carbon Fibre (CARBISO (registered trademark) series), Carbon Fiber Recycling Industries (T8S103, 106 series), Procotex (CF.OS.A), Carbon conversions (re-Evo (registered trademark) series), etc. In addition, recycled carbon fibers described in JP-A-2019-136932, JP-A-2013-87269, JP-A-2021-138077, JP-A-2020-75493, etc. can be used. <好ましい態様> Recycled carbon fiber may consist of one component or a combination of two or more components. If two or more types of recycled carbon fiber are present, the bulk density, aspect ratio, and average fiber length shall be the average values ​​of the existing recycled carbon fiber.

[0041] [Other ingredients] The polyamide resin composition may contain components other than polyamide resin and recycled carbon fiber, to the extent that it does not impair the effects of the present invention. Examples of such components include other resins, inorganic compounds, nitrogen-containing compounds, plasticizers, heat-resistant agents, foaming agents, weather-resistant agents, crystal nucleating agents, antioxidants, crystallization accelerators, mold release agents, lubricants, antistatic agents, flame retardants, flame retardant additives, pigments, dyes, glass fibers, carbon fibers (excluding recycled carbon fiber), cellulose fibers, aramid fibers, and other functional additives.

[0042] Other resins include low-density, medium-density, and high-density polyethylene, polypropylene, polyolefin resins such as polybutene, polyester resins such as polyethylene terephthalate, polybutylene terephthalate, and polyester elastomers, vinyl aromatic resins such as polystyrene, ABS resin, and AS resin, polyurethane resin, acrylic resin, polycarbonate, polyacetal, polyvinyl alcohol, and rosin-based resins.

[0043] Examples of inorganic compounds include metal halides and inorganic compounds other than metal halides.

[0044] Metal halides are compounds of halogens and metals. Examples of halogens include fluorine, chlorine, bromine, and iodine. Examples of metals include Group 1 elements (alkali metals), Group 2 elements (alkaline earth metals), and Group 3 to Group 12 elements (e.g., transition metals). Preferably, the metal halide is one or more selected from the group consisting of alkali metal halides and copper halides. Examples of alkali metal halides when the metal is a Group 1 element (alkali metal) include potassium iodide, potassium bromide, potassium chloride, sodium iodide, or sodium chloride. Examples of copper halides include cuprous chloride, cupric chloride, cuprous bromide, cupric bromide, cuprous iodide, and cupric iodide. It is particularly preferable that the metal halide is potassium iodide and / or cuprous iodide.

[0045] Inorganic compounds other than metal halides include metals, metal oxides, metal hydroxides, metal nitrides, metal phosphates, metal phosphites, metal carbonates, metal silicates, metal titanates, metal borates, metal sulfates, and metal nitrates. Specific examples of inorganic compounds other than metal halides include talc, mica, synthetic mica, glass flakes, non-swelling mica, fullerenes, carbon nanotubes, carbon black, graphite, metal foil, ceramic beads, clay, sericite, zeolite, bentonite, aluminum hydroxide, dolomite, kaolin, silica, fine silica powder, feldspar powder, potassium titanate, shirasu balloons, calcium carbonate, magnesium carbonate, barium sulfate, calcium oxide, aluminum oxide, titanium oxide, and acids. Examples include magnesium oxide, aluminum silicate, silicon dioxide, magnesium hydroxide, gypsum, novaculite, dawsonite, white clay, glass fiber, carbon fiber, graphite fiber, metal fiber, potassium titanate whisker, aluminum borate whisker, magnesium-based whisker, silicon-based whisker, warlastenite, sepiolite, slag fiber, zonolite, elestadite, gypsum fiber, silica fiber, silica-alumina fiber, zirconia fiber, boron nitride fiber, silicon nitride fiber, and boron fiber.

[0046] Examples of nitrogen-containing compounds include melamine, benguanamine, dimethylolurea, and cyanuric acid.

[0047] Other functional additives not mentioned above include, for example, the components described in Japanese Patent Publication No. 2002-370551.

[0048] Other ingredients may be one ingredient or a combination of two or more ingredients.

[0049] [Content] The content of each component relative to 100% by mass of the polyamide resin composition is as follows. Note that in the polyamide resin composition, the total of the polyamide resin, recycled carbon fiber, and other components is 100% by mass.

[0050] The polyamide resin content is 60 to 95% by mass per 100% by mass of the polyamide resin composition. From the viewpoint of mechanical properties (particularly superior tensile modulus and / or flexural strength) and moldability, the polyamide resin content per 100% by mass of the polyamide resin composition is preferably 65 to 95% by mass, more preferably 65 to 90% by mass, and particularly preferably 70 to 85% by mass.

[0051] The recycled carbon fiber content is 2 to 35% by mass per 100% by mass of the polyamide resin composition. From the viewpoint of mechanical properties (particularly superior tensile modulus and / or bending strength) and moldability, the recycled carbon fiber content per 100% by mass of the polyamide resin composition is preferably 5 to 35% by mass, more preferably 10 to 35% by mass, and particularly preferably 15 to 30% by mass.

[0052] The content of other components is 0 to 38% by mass relative to 100% by mass of the polyamide resin composition. From the viewpoint of not impairing the functions and properties of the polyamide resin and recycled carbon fiber, the content of other components relative to 100% by mass of the polyamide resin composition is preferably 0 to 35% by mass, more preferably 0 to 30% by mass, and particularly preferably 0 to 15% by mass.

[0053] [Further properties of polyamide resin compositions] The polyamide resin composition preferably has a Charpy impact strength of 100.0% or more, and particularly preferably 110.0% or more, with respect to the Charpy impact strength measured using a test piece molded from the polyamide resin composition and the Charpy impact strength measured using a test piece molded from a composition containing virgin carbon fibers (hereinafter also referred to as the "Charpy impact strength retention rate"). Here, the "composition containing virgin carbon fibers" is as described above. Furthermore, the specific method for measuring Charpy impact strength is the method described in the examples. The test piece used for measuring Charpy impact strength may be V-notched. When the Charpy impact strength retention rate of the polyamide resin composition is 100.0% or more, the polyamide resin composition has superior impact resistance compared to the case where a composition containing virgin carbon fibers is used. Therefore, the molded article of the polyamide resin composition has superior functionality and properties.

[0054] The density of the polyamide resin composition is not particularly limited, but from the viewpoint of the mechanical strength of the molded article, it is 1.10 to 1.35 g / cm³. 3 Preferably, it is 1.15 to 1.30 g / cm³. 3 This is particularly preferable. The specific method for measuring density is the method described in the examples.

[0055] [Method for producing polyamide resin composition] There are no particular restrictions on the method for producing the polyamide resin composition, as long as it can knead each component. For example, methods using a twin-screw extruder, single-screw extruder, multi-screw extruder, etc., can be used.

[0056] [Molded articles of polyamide resin compositions] Polyamide resin compositions can be used in the manufacture of molded articles. Molded articles containing polyamide resin compositions can be obtained as molded articles having a desired shape by molding the polyamide resin composition. The molding method is not particularly limited and includes extrusion molding, injection molding, blow molding, etc. Molded articles containing polyamide resin compositions can be used as the molded article itself or as parts containing the molded article for various applications such as automobile parts, railway parts, machine parts, industrial materials, industrial supplies, electrical parts, electronic parts, medical parts, food packaging parts, household goods, office supplies, building material parts, and furniture parts. In parts used for various applications, components other than the molded article can be appropriately used from known components depending on the application. [Examples]

[0057] 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.

[0058] [Ingredients used] 1. Polyamide resin Polyamide 6: Polyamide 6 (UBE Corporation, product name: 1013B, relative viscosity: 2.47) 2. Recycled carbon fiber Recycled carbon fiber: Procotex, product name CF.OS.A, bulk density 0.289 g / cm³ 3 3. Virgin carbon fiber Virgin carbon fiber: Manufactured by Teijin Corporation, product name HT C415, bulk density 0.551 g / cm³ 3

[0059] [Examples 1-3, Comparative Examples 1-2] Each component listed in Table 1 was melt-kneaded with TEX34αIII manufactured by Japan Steel Works, Ltd. to produce the target polyamide resin composition pellets. Next, the obtained pellets were injection-molded at a cylinder temperature of 290°C and a mold temperature of 80°C to produce various test specimens, and their various physical properties were evaluated.

[0060] The measurements shown in the table were taken using the following method. (1) Tensile strength and tensile modulus Using the aforementioned pellets, ISO multipurpose test specimens were prepared in accordance with ISO 527-1,2. Tensile tests were then performed on these specimens in a 23°C atmosphere in accordance with ISO 527-1,2. (2) Bending strength and bending modulus Using the aforementioned pellets, an ISO multipurpose test specimen was prepared in accordance with ISO 178. A bending test was then performed on this specimen in a 23°C atmosphere in accordance with ISO 178. (3) Relative viscosity of polyamide resin In accordance with JIS K 6920, 1 g of polyamide resin was dissolved in 100 ml of 96% concentrated sulfuric acid, and the relative viscosity of the polyamide resin was measured at 25°C. (4) Bulk density of carbon fiber The bulk density of recycled carbon fiber and virgin carbon fiber was measured in accordance with JIS K 5101. (5) Density of molded product Using the aforementioned pellets, ISO multipurpose test specimens were prepared in accordance with ISO 1183, and density measurements were performed in accordance with ISO 1183. (6) Charpy impact strength (with notch) Using the aforementioned pellets, an ISO multipurpose test specimen was prepared in accordance with ISO 179 / 1eA and subjected to V-notch processing. Using this test specimen, a Charpy impact strength test was performed in a 23°C atmosphere in accordance with ISO 179 / 1eA. (7) Charpy impact strength (without notch) Using the aforementioned pellets, an ISO multipurpose test specimen was prepared in accordance with ISO 179 / 1eA. A Charpy impact strength test was performed on this specimen in a 23°C atmosphere in accordance with ISO 179 / 1eA.

[0061] The results are shown in Table 1.

[0062] [Table 1]

[0063] As can be seen from the results shown in Table 1, the polyamide resin compositions of the examples maintained tensile modulus and flexural strength at 90% or more of those of compositions containing virgin carbon fibers. In particular, a comparison between Example 1 and Example 2 showed that the tensile modulus and flexural strength were superior when the recycled carbon fiber content was higher.

Claims

1. A polyamide resin composition comprising 60 to 95% by mass of polyamide resin and 2 to 3% by mass of recycled carbon fiber, based on 100% by mass of the polyamide resin composition, The bulk density of the recycled carbon fiber is 0.250 g / cm³. ３ Super 0.300g / cm ３ The following: With respect to the tensile strength measured according to ISO 527-1,2 using an ISO multipurpose test specimen molded from the polyamide resin composition according to ISO 527-1,2, and the tensile strength measured according to ISO 527-1,2 using an ISO multipurpose test specimen molded from a composition containing virgin carbon fibers according to ISO 527-1,2, the ratio of the tensile strength of the polyamide resin composition to the tensile strength of the composition containing virgin carbon fibers is 100.0% or more. With respect to the flexural modulus measured according to ISO 178 using an ISO multipurpose test specimen molded from the polyamide resin composition according to ISO 178, and the flexural modulus measured according to ISO 178 using an ISO multipurpose test specimen molded from a composition containing virgin carbon fibers according to ISO 178, the ratio of the flexural modulus of the polyamide resin composition to the flexural modulus of the composition containing virgin carbon fibers is 100.0% or more. The composition containing the virgin carbon fibers is a composition in which the recycled carbon fibers contained in the polyamide resin composition are replaced with virgin carbon fibers having an equal amount of carbon fiber. Polyamide resin composition.

2. The bulk density of the recycled carbon fiber is 0.280 g / cm³. ３ 0.300g / cm or more ３ The polyamide resin composition according to claim 1, which is as follows:

3. A molded article comprising the polyamide resin composition according to claim 1 or 2.

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