Thermoplastic resin composition

Abstract

To provide a molding (injection molding, etc.) having excellent rigidity, impact strength with notch and impact strength without notch, a thermoplastic resin composition capable of obtaining the same, and a resin pellet.SOLUTION: A thermoplastic resin composition and a resin pellet contain aliphatic polyamide (A) including a monomer unit having 10 or more carbon atoms and carbon fibers (B) having a tensile strength of 5.1 GPa or more, in which a content of the carbon fibers (B) is 20-160 pts.mass with respect to 100 pts.mass of the aliphatic polyamide (A).SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a thermoplastic resin composition. To things Regarding. [Background technology]

[0002] Thermoplastic resins are widely used as raw materials for molded products because of their good moldability and ease of mass production of molded products. The demand for higher performance from molded products is becoming more and more advanced. For example, due to the reduction in the number of parts to improve the productivity of various industrial products that use molded products, a single molded product has come to contain a mixture of non-notched parts such as flat parts and parts with notches due to complex shapes. Since the mechanical properties (impact strength, etc.) differ between the non-notched parts and the notched parts, a single molded product is required to have a wide range of mechanical properties.

[0003] A method for improving the mechanical properties of a molded article is known to include blending a fibrous filler such as glass fiber or carbon fiber with a thermoplastic resin. A method for increasing the rigidity of a molded article is to blend carbon fiber with a thermoplastic resin. In particular, a molded article made of a thermoplastic resin composition in which carbon fiber is blended with polyamide has an excellent balance between rigidity and impact strength.

[0004] As molded articles made of a thermoplastic resin composition in which reinforcing fibers are blended with polyamide, the following have been proposed. (1) A thermoplastic resin molded article having a flexural modulus of 35,000 MPa or more and a specific gravity of 1.4 or less, which is made of a thermoplastic resin composition containing 40 to 70 mass% of MXD6 nylon and 30 to 60 mass% of carbon fiber having substantially no wrinkles extending in the longitudinal direction on the surface of the single fiber (Patent Document 1). (2) A thermoplastic resin composition comprising nylon 6 and carbon fibers having (i) a wrinkle depth on the surface of a single fiber extending in the longitudinal direction of the single fiber of 90 nm or less, (ii) a strand modulus of elasticity of 230 to 370 GPa, and (iii) a ratio of the long axis to the short axis of the fiber cross section of the single fiber (long axis / short axis) of 1.00 to 1.02, the thermoplastic resin composition having a flexural modulus of elasticity of 5000 MPa or more and an unnotched impact strength of 90 kJ / m in a Charpy impact test. 2 The above is a thermoplastic resin molded product having a specific gravity of 1.4 or less (Patent Document 2). (3) Polyamide resin composition pellets comprising (A) a reinforcing fiber roving having a void ratio of 30% to 70% and (B) a polyamide resin, characterized in that after melt-kneading, 10 to 65 mass% of reinforcing fibers are contained in 100 mass% of the resin pellets of the obtained polyamide resin composition, the average fiber length of the reinforcing fibers is 3 to 30 mm, and the reinforcing fibers are arranged in a state of substantially the same length as the length direction of the composition (Patent Document 3). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 4609984 [Patent Document 2] Patent No. 4587445 [Patent Document 3] JP 2010-202759 A Summary of the Invention [Problem to be solved by the invention]

[0006] For the molded product of (1), a high rigidity with a flexural modulus of 35,000 MPa or more is obtained, and the examples also state unnotched Charpy impact strength, but notched Charpy impact strength is not taken into consideration. (2) For molded products, the flexural modulus is 5000 MPa or more, and the unnotched Charpy impact strength is 90 kJ / m 2Although the Charpy notched impact strength is higher than 100%, this does not take into account the Charpy notched impact strength. As for the molded product in (3), since it is a molded product made of a long fiber reinforced polyamide resin composition consisting of a specific reinforcing fiber roving and polyamide, it is expected that the notched Charpy impact strength will be high. However, the unnotched Charpy impact strength is not taken into consideration, and the impact strength may be limited in parts without notches such as flat parts. In addition, since the reinforcing fibers are long, moldability into molded products with complex shapes may also be an issue.

[0007] Thus, there is a demand for a technique that satisfies both notched impact strength and unnotched impact strength in molded articles made of thermoplastic resin compositions in which polyamide is blended with carbon fiber. The present invention provides a molded article (such as an injection molded article) that is excellent in rigidity, notched impact strength and unnotched impact strength, as well as a thermoplastic resin composition and resin pellets from which the same can be obtained. [Means for solving the problem]

[0008] The present invention has the following aspects. <1> A thermoplastic resin composition comprising: an aliphatic polyamide (A) containing a monomer unit having 10 or more carbon atoms; and a carbon fiber (B) having a tensile strength of 5.1 GPa or more, wherein the content of the carbon fiber (B) is 20 to 160 parts by mass per 100 parts by mass of the aliphatic polyamide (A). <2> The mass average fiber length of the carbon fibers (B) is 0.1 to 1.0 mm. <1> A thermoplastic resin composition. <3> The content of the carbon fiber (B) is 40 to 100 parts by mass based on 100 parts by mass of the aliphatic polyamide (A). <1> or <2> A thermoplastic resin composition. <4> The aliphatic polyamide (A) is either or both of PA11 and PA12. <1> ~ <3> 1. The thermoplastic resin composition of claim 1 . <5> The above <1> ~ <4> A molded article made of any one of the thermoplastic resin compositions, wherein the molded article has a notched Charpy impact strength of 13 kJ / m2 or more, and the unnotched Charpy impact strength of the molded product is 80 kJ / m 2 or more, and the molded article has a flexural modulus of 15 GPa or more. <6> A resin pellet comprising: an aliphatic polyamide (A) containing a monomer unit having 10 or more carbon atoms; and a carbon fiber (B) having a tensile strength of 5.1 GPa or more, the content of the carbon fiber (B) being 20 to 160 parts by mass per 100 parts by mass of the aliphatic polyamide (A). <7> The mass average fiber length of the carbon fibers (B) is 0.1 to 1.0 mm. <6> Resin pellets. <8> The content of the carbon fiber (B) is 40 to 100 parts by mass based on 100 parts by mass of the aliphatic polyamide (A). <6> or <7> Resin pellets. <9> The aliphatic polyamide (A) is either or both of PA11 and PA12. <6> ~ <8> Resin pellets of either type. <10> The above <6> ~ <9> The method for producing resin pellets according to any one of the above items 1 to 5, further comprising blending carbon fibers (B) having a length of 2 to 20 mm with the aliphatic polyamide (A) in a molten state. <11> The above <6> ~ <9> and the Charpy notched impact strength of the injection molded product is 13 kJ / m 2 or more, and the unnotched Charpy impact strength of the injection molded product is 80 kJ / m 2 and the flexural modulus of the injection-molded article is 15 GPa or more. Effect of the Invention

[0009] According to the thermoplastic resin composition of the first aspect of the present invention, it is possible to obtain a molded article having excellent rigidity, notched impact strength and unnotched impact strength. The molded article according to the second aspect of the present invention is excellent in rigidity, notched impact strength and unnotched impact strength. According to the resin pellets of the third aspect of the present invention, it is possible to obtain an injection molded article having excellent rigidity, notched impact strength and unnotched impact strength. According to the method for producing resin pellets which is the fourth aspect of the present invention, it is possible to produce resin pellets which can give injection molded articles excellent in rigidity, notched impact strength and unnotched impact strength. The injection molded article according to the fifth aspect of the present invention is excellent in rigidity, notched impact strength and unnotched impact strength. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The following definitions of terms apply throughout the specification and claims. "PA" stands for polyamide. "Notched Charpy impact strength" is a value measured in accordance with ISO179-1 / 1eA. "Unnotched Charpy impact strength" is a value measured in accordance with ISO179-1 / 1eU. The "flexural modulus" is a value measured by a three-point bending test in accordance with ISO178. The "tensile strength" and "tensile modulus" of carbon fiber are values ​​measured in accordance with ASTM D4018. The "mass average fiber length" of the carbon fibers contained in the thermoplastic resin composition or resin pellets is a value calculated by heating the thermoplastic resin composition or resin pellets in an air atmosphere at 600°C for 3 hours to remove the aliphatic polyamide (A) and the like by thermal decomposition, measuring the fiber length of each of 100 or more carbon fibers randomly selected from the remaining carbon fibers using an optical microscope, and calculating the value according to the following formula. Lw = ΣL 2 / ΣL Here, Lw is the mass average fiber length of the carbon fibers, and L is the fiber length of each carbon fiber. The "length" of the raw carbon fiber is the arithmetic mean of the lengths of 10 or more randomly selected carbon fiber bundles measured directly with the naked eye when the carbon fibers are in a bundle, or the arithmetic mean of the lengths of 10 or more randomly selected carbon fibers measured with an optical microscope when the carbon fibers are not in a bundle. The "circle equivalent diameter" (μm) of carbon fiber is related to the basis weight (mg / m), number of filaments (pieces) and density (g / cm 3 ) is calculated using the following formula: Equivalent circle diameter = (basis weight ÷ number of filaments ÷ density × 1000 ÷ 3.14) 1 / 2 ×2

[0011] <Thermoplastic resin composition> A first aspect of the present invention is a thermoplastic resin composition comprising a specific aliphatic polyamide (A) and specific carbon fibers (B), the content of the carbon fibers (B) being within a specific range.

[0012] (Aliphatic polyamide (A)) The aliphatic polyamide (A) contains a monomer unit having 10 or more carbon atoms, from the viewpoint of obtaining a molded article having high impact strength. Aliphatic polyamides (A) are classified into two types: those consisting mainly of monomer units derived from lactams, and those consisting mainly of monomer units derived from diamines and monomer units derived from dicarboxylic acids. From the viewpoint of obtaining molded products with high notched impact strength, aliphatic polyamides consisting mainly of monomer units derived from lactams are preferred.

[0013] Examples of the monomer unit having 10 or more carbon atoms include a monomer unit derived from a lactam having 10 or more carbon atoms, a monomer unit derived from a dicarboxylic acid having 10 or more carbon atoms, and a monomer unit derived from a diamine having 10 or more carbon atoms. When the monomer unit derived from a dicarboxylic acid has 10 or more carbon atoms, the monomer unit derived from a diamine may have 9 or less carbon atoms, and when the monomer unit derived from a diamine has 10 or more carbon atoms, the monomer unit derived from a dicarboxylic acid may have 9 or less carbon atoms. As the monomer unit having 10 or more carbon atoms, a monomer unit derived from a lactam having 10 or more carbon atoms is preferred from the viewpoint of obtaining a molded product with high impact strength. The number of carbon atoms of the monomer unit is preferably 12 or less from the viewpoint of availability of the aliphatic polyamide (A).

[0014] Examples of the aliphatic polyamide (A) include PA610, PA611, PA612, PA1010, PA1012, PA11, and PA12. From the viewpoint of obtaining a molded product with high impact strength, either one or both of PA11 and PA12 are preferred, and PA11 is more preferred. Examples of commercially available PA11 products include Rilsan (registered trademark) manufactured by Arkema Co., Ltd. Examples of commercially available PA12 products include Rilsamid (registered trademark) manufactured by Arkema Co., Ltd., UBESTA (registered trademark) manufactured by Ube Industries, Ltd., and DAIAMID (registered trademark) manufactured by Daicel-Evonik Co., Ltd.

[0015] (Carbon fiber (B)) From the viewpoint of increasing the notched impact strength of the molded article, the tensile strength of the carbon fiber (B) is 5.1 GPa or more, preferably 5.4 GPa or more, and more preferably 5.6 GPa or more. The higher the tensile strength of the carbon fiber (B), the better, and there is no particular upper limit.

[0016] From the viewpoint of improving the modulus of elasticity of a molded article, the tensile modulus of the carbon fiber (B) is preferably 260 GPa or more, more preferably 275 GPa or more. The higher the tensile modulus of the carbon fiber (B), the better, and there is no particular upper limit.

[0017] The carbon fiber (B) may be a PAN-based carbon fiber or a pitch-based carbon fiber, and from the viewpoint of mechanical properties of the molded product, the PAN-based carbon fiber is preferred. The PAN-based carbon fiber is mainly composed of filament fibers essentially made of carbon, which are produced by infusible and carbonized fibers made of polyacrylonitrile-based resin polymerized with acrylonitrile as the main component.

[0018] Examples of the form of the carbon fiber (B) include continuous fiber (long fiber), chopped fiber, and milled fiber. The carbon fiber (B) may be used alone or in combination of two or more types. The form of the carbon fiber (B) is preferably chopped fiber, from the viewpoint of excellent handleability of the carbon fiber (B) and easy control of the mass average fiber length. Examples of commercially available products of continuous fiber include Pyrofil (registered trademark) TRH50 18M, MR60H 24P, and MR70 12P manufactured by Mitsubishi Chemical Corporation. Examples of commercially available products of chopped fiber include Pyrofil (registered trademark) MR03NE BDE manufactured by Mitsubishi Chemical Corporation.

[0019] The mass average fiber length of the carbon fiber (B) in the thermoplastic resin composition is preferably 0.1 to 1.0 mm, more preferably 0.13 to 0.30 mm. When the mass average fiber length of the carbon fiber (B) is within the above range, the molded article has an excellent balance between the notched impact strength and the unnotched impact strength. In addition, the change in fiber length during molding of the thermoplastic resin composition is small, and a molded article with stable mechanical properties can be obtained.

[0020] The circle-equivalent diameter of the carbon fiber (B) in the thermoplastic resin composition is preferably 6.5 μm or less, more preferably 6.0 μm or less, from the viewpoint of increasing the notched impact strength of the molded product. The circle-equivalent diameter of the carbon fiber (B) in the thermoplastic resin composition is preferably 4.5 μm or more, more preferably 5.0 μm or more, from the viewpoint of increasing the unnotched impact strength. The thicker the carbon fiber (B), the fewer the number of carbon fibers (B) in the thermoplastic resin composition, and the better the dispersion of the carbon fiber (B) in the thermoplastic resin composition. If the carbon fiber (B) is too thick, the length relative to the circle-equivalent diameter becomes small, and the reinforcing effect of the carbon fiber (B) becomes small. The carbon fiber (B) does not necessarily have to be circular as long as the circle-equivalent diameter is within the above range.

[0021] The content of the carbon fiber (B) is 20 to 160 parts by mass, preferably 40 to 100 parts by mass, and more preferably 50 to 90 parts by mass, relative to 100 parts by mass of the aliphatic polyamide (A). When the content of the carbon fiber (B) is within the above range, the molded article has an excellent balance of flexural modulus (rigidity), notched impact strength, and unnotched impact strength.

[0022] (Other ingredients) The thermoplastic resin composition may contain a thermoplastic resin other than the aliphatic polyamide (A) as necessary within a range that does not impair the effects of the present invention. Examples of the thermoplastic resin other than the aliphatic polyamide (A) include aliphatic polyamides that do not contain a monomer unit having 10 or more carbon atoms, aromatic polyamides, and ABS resins. From the viewpoint of preventing the impact strength of a molded article from decreasing, polyamides other than the aliphatic polyamide (A) are preferred. Examples of the aliphatic polyamides that do not contain a monomer unit having 10 or more carbon atoms include PA6 and PA66. Examples of the aromatic polyamides include PAMXD6, PA6T, PA9T, and PA10T. The content of the thermoplastic resin other than the aliphatic polyamide (A) is preferably 80 parts by mass or less, and more preferably 30 parts by mass or less, per 100 parts by mass of the aliphatic polyamide (A), from the viewpoint of not impairing the notched impact strength and unnotched impact strength of the molded article.

[0023] The thermoplastic resin composition may contain, as necessary, carbon fibers other than the carbon fibers (B) within the scope of the present invention. The carbon fibers other than the carbon fibers (B) have a tensile strength of less than 5.1 GPa. The content of carbon fibers other than the carbon fibers (B) is preferably 200 parts by mass or less, and more preferably 120 parts by mass or less, per 100 parts by mass of the carbon fibers (B), so as not to impair the effects of the present invention.

[0024] The thermoplastic resin composition may contain additives other than thermoplastic resin or carbon fiber as necessary, within the scope of not impairing the effects of the present invention. Examples of additives include colorants, antioxidants, metal deactivators, carbon black, nucleating agents, release agents, lubricants, antistatic agents, light stabilizers, ultraviolet absorbers, inorganic fillers, glass fibers, impact resistance modifiers, processing aids, flame retardants, and plasticizers. The additives may be used alone or in combination of two or more.

[0025] <Molded products> A second aspect of the present invention is a molded article made of the thermoplastic resin composition according to the first aspect of the present invention. The molded article can be produced by molding the thermoplastic resin composition by a known molding method (injection molding, extrusion molding, press molding, blow molding, etc.).

[0026] The notched Charpy impact strength of the molded product is 13kJ / m 2 More than 15kJ / m 2 More than 20 kJ / m is preferable. 2 The above is more preferable. If the notched Charpy impact strength of the molded article is within the above range, the molded article is less likely to crack due to impact even if the molded article has a notch or other surface discontinuity. The higher the notched Charpy impact strength of the molded article, the better, and there is no particular upper limit.

[0027] The unnotched Charpy impact strength of the molded product is 80kJ / m 2 More than 90kJ / m 2 More than 95 kJ / m is preferable. 2The above is more preferable. If the unnotched Charpy impact strength of the molded article is within the above range, the molded article is less likely to crack due to impact in non-notched parts such as flat parts. The higher the unnotched Charpy impact strength of the molded article, the better, and there is no particular upper limit.

[0028] The flexural modulus of the molded article is 15 GPa or more, preferably 20 GPa or more, more preferably 22 GPa or more. If the flexural modulus of the molded article is within the above range, the elastic deformation of the molded article against static load is small. The higher the flexural modulus of the molded article, the better, and there is no particular upper limit.

[0029] <Resin pellets> A third aspect of the present invention is a resin pellet comprising a specific aliphatic polyamide (A) and specific carbon fibers (B), the content of the carbon fibers (B) being within a specific range. The resin pellets may contain, as necessary, a thermoplastic resin other than the aliphatic polyamide (A), a carbon fiber other than the carbon fiber (B), or an additive other than a thermoplastic resin or carbon fiber, as long as the effects of the present invention are not impaired.

[0030] Examples of the aliphatic polyamide (A) include the same ones as the aliphatic polyamide (A) in the thermoplastic resin composition of the first aspect of the present invention, and preferred embodiments are also the same. The carbon fiber (B) may be the same as the carbon fiber (B) in the thermoplastic resin composition according to the first embodiment of the present invention, and the preferred forms are also the same. Examples of the thermoplastic resin other than the aliphatic polyamide (A) include the same as the thermoplastic resin other than the aliphatic polyamide (A) in the thermoplastic resin composition of the first aspect of the present invention, and preferred embodiments are also the same. The additives include the same ones as those in the thermoplastic resin composition according to the first aspect of the present invention, and the preferred forms are also the same. The content of each component in the resin pellets is the same as the content of each component in the thermoplastic resin composition according to the first aspect of the present invention, and the preferred ranges are also the same. However, the thermoplastic resin composition in the description of the first embodiment is replaced with a resin pellet in the description of the third embodiment, and the molded article in the description of the first embodiment is replaced with an injection-molded article in the description of the third embodiment.

[0031] The resin pellets may be short fiber pellets or long fiber pellets, and short fiber pellets are preferred from the viewpoints of good dispersion of the carbon fibers (B) and high unnotched impact strength of the injection molded product. In the case of short fiber pellets, the mass average fiber length of the carbon fibers (B) in the resin pellets is 2 mm or less.

[0032] <Method of manufacturing resin pellets> A fourth aspect of the present invention is a method for producing resin pellets according to the third aspect of the present invention, which comprises blending carbon fibers (B) having a length of 2 to 20 mm with a molten aliphatic polyamide (A).

[0033] Since the aliphatic polyamide (A) is in a molten state, when the carbon fibers (B) are blended therewith, breakage of the carbon fibers (B) can be suppressed and the mass average fiber length of the carbon fibers (B) can be made to be 0.1 mm or more. By using carbon fibers (B) having a length of 2 to 20 mm, supply defects such as bridging are unlikely to occur when the carbon fibers (B) are supplied by a quantitative feeder, and stable quantitative supply becomes possible. The length of the carbon fibers (B) is preferably 7 mm or less, more preferably 4 mm or less, from the viewpoint of uniformly dispersing the carbon fibers (B) in the molten aliphatic polyamide (A).

[0034] When the carbon fiber (B) is blended with the molten aliphatic polyamide (A), it is preferable to use an extruder to melt-knead the aliphatic polyamide (A) and the carbon fiber (B). By using an extruder, resin pellets of stable quality can be continuously produced. The melt-kneaded aliphatic polyamide (A) and carbon fiber (B) are extruded from an extruder to form strands, which are then cut with a strand cutter to obtain resin pellets.

[0035] The mass average fiber length of the carbon fibers (B) in the resin pellets can be adjusted by controlling the melt kneading conditions such as the method of feeding the carbon fibers (B), the screw rotation speed of the extruder, the discharge amount, etc. In order to adjust the mass average fiber length of the carbon fibers (B) to a preferred range, it is preferable to side feed a part or all of the carbon fibers (B).

[0036] <Injection molded products> A fifth aspect of the present invention is an injection-molded article made of the resin pellets according to the third aspect of the present invention. The injection molded article can be produced by injection molding resin pellets. The injection molded article can be produced by injection molding the thermoplastic resin composition according to the first aspect of the present invention, but from the viewpoint of obtaining an injection molded article of stable quality, the method of injection molding resin pellets is preferred. Injection molding also includes injection compression molding.

[0037] The notched Charpy impact strength of injection molded products is 13kJ / m 2 More than 15kJ / m 2 More than 20 kJ / m is preferable. 2 The above is more preferable. If the notched Charpy impact strength of the injection molded article is within the above range, the injection molded article is unlikely to crack due to impact even if the injection molded article has a notch or other surface discontinuity. The higher the notched Charpy impact strength of the injection molded article, the better, and there is no particular upper limit.

[0038] The unnotched Charpy impact strength of injection molded products is 80kJ / m 2 More than 90kJ / m 2 More than 95 kJ / m is preferable. 2 The above is more preferable. If the unnotched Charpy impact strength of the injection molded product is within the above range, the injection molded product is less likely to crack due to impact at non-notched portions such as flat surfaces. The higher the unnotched Charpy impact strength of the injection molded product, the better, and there is no particular upper limit.

[0039] The flexural modulus of the injection molded product is 15 GPa or more, preferably 20 GPa or more, more preferably 22 GPa or more. If the flexural modulus of the injection molded product is within the above range, the elastic deformation of the injection molded product against static load is small. The higher the flexural modulus of the injection molded product, the better, and there is no particular upper limit. EXAMPLES

[0040] The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0041] <Measurement> (Mass average fiber length) The resin pellets were heated in an air atmosphere at 600°C for 3 hours to remove polyamide and the like by thermal decomposition. The fiber length of each of 100 or more carbon fibers randomly selected from the remaining carbon fibers was measured using an optical microscope, and the mass average fiber length was calculated using the following formula. The fiber length (Lw) was calculated by the following formula. Lw = ΣL 2 / ΣL Here, Lw is the mass average fiber length of the carbon fibers, and L is the fiber length of each carbon fiber.

[0042] (Flexural strength, flexural modulus) A bending test piece measuring 80 x 10 x 4 mm was cut out from the dumbbell test piece, and a three-point bending test was performed in accordance with ISO178 to measure the bending strength and bending modulus.

[0043] (Charpy notched impact strength) A notched test piece of 80 × 10 × 4 mm was cut out from the dumbbell test piece, and the notched Charpy impact strength was measured in accordance with ISO179-1 / 1eA.

[0044] (unnotched Charpy impact strength) Unnotched test pieces measuring 80 × 10 × 4 mm were cut out from the dumbbell test pieces, and the unnotched Charpy impact strength was measured in accordance with ISO179-1 / 1eU.

[0045] (specific gravity) The specific gravity was determined in accordance with ISO1183 using the end of a dumbbell test piece.

[0046] <Raw materials> (polyamide) PA11: Rilsan (registered trademark) manufactured by Arkema Corporation. PA1010: Hiprolon (registered trademark) 200NN, manufactured by Arkema Corporation. PA612: Hiprolon (registered trademark) 90NN, manufactured by Arkema Corporation. PA610: Hiprolon (registered trademark) 70NN, manufactured by Arkema Corporation. PAMXD6: MX nylon S6007, manufactured by Mitsubishi Gas Chemical Company, Inc. PA6: Novamid (registered trademark) 1007J manufactured by DSM was used. PAXD10: Lexter 8500, manufactured by Mitsubishi Gas Chemical Company, Inc. PA10T: Xecot (registered trademark) XN400, manufactured by Unitika Ltd.

[0047] (Carbon Fiber) Carbon fiber (B-1): Mitsubishi Chemical Corporation, PAN-based carbon fiber MR60H 24P (filament count 24,000, basis weight 960 mg / m, density 1.81 g / cm 3 , equivalent circle diameter 5.3μm, tensile strength 5.68GPa, tensile modulus 280GPa) was applied with a polyamide sizing agent and cut to 3mm. The amount of sizing agent attached was 3.0%. Carbon fiber (B-2): Mitsubishi Chemical Corporation, PAN-based carbon fiber TRW40 50L (filament count 50,000, basis weight 3,750 mg / m, density 1.81 g / cm 3 , equivalent circle diameter 7.3μm, tensile strength 4.12GPa, tensile modulus 240GPa) was applied with a polyamide sizing agent and cut to 6mm. The amount of sizing agent attached was 3.0%. Carbon fiber (B-3): Mitsubishi Chemical Corporation, PAN-based carbon fiber MR60H 24P (filament count 24,000, basis weight 960 mg / m, density 1.81 g / cm 3, equivalent circle diameter 5.3 μm, tensile strength 5.68 GPa, tensile modulus 280 GPa).

[0048] (Additives) Release agent: Pentaerythritol stearate. Colorant: Carbon black.

[0049] Example 1 Using a co-rotating twin-screw extruder (Ikegai Corporation, PCM-30) equipped with a main raw material feeder and a side feeder, 100 parts by mass of PA11 and 1.7 parts by mass of colorant were fed from the main raw material feeder, and 67 parts by mass of carbon fiber (B-1) were fed from the side feeder, melt-kneaded under conditions of 260 ° C, 200 rpm, and 15 kg / h, and the discharged strand was cooled in water and cut to a length of 4 mm with a strand cutter to obtain resin pellets. The mass average fiber length of the carbon fiber in the resin pellets is shown in Table 1. The resin pellets were dried at 120°C for 2 hours, and then injection molded using an injection molding machine (Toshiba Machine Co., Ltd., IS55) and an ISO mold type A at a cylinder temperature of 260°C and a mold temperature of 80°C to obtain dumbbell test pieces. The evaluation results are shown in Table 1.

[0050] (Examples 2 to 9, Comparative Examples 1 to 6) Resin pellets were obtained in the same manner as in Example 1, except that raw materials other than carbon fiber were fed from the main raw material feeder and carbon fiber was fed from the side feeder according to the composition shown in Table 1 or Table 2, and the extrusion temperature was changed according to the conditions shown in Table 1 or Table 2. The mass average fiber length of the carbon fiber in the resin pellets is shown in Table 1 and Table 2. Dumbbell test pieces were obtained in the same manner as in Example 1, except that the resin pellets were changed and the cylinder temperature and mold temperature during injection molding were changed according to the conditions shown in Table 1 or Table 2. The evaluation results are shown in Tables 1 and 2.

[0051] Comparative Example 7 100 parts by mass of PA6 was melted in a co-rotating twin screw extruder (PCM-30, manufactured by Ikegai Corporation), and then composited with 43 parts by mass of carbon fiber (B-3) at a line speed of 20 m / min using an impregnation die set at 270°C, cooled in water, and cut to a length of 8 mm to obtain resin pellets. The mass average fiber length of the carbon fiber in the resin pellets is shown in Table 2. Dumbbell test pieces were obtained in the same manner as in Example 1, except that the cylinder temperature and mold temperature during injection molding of the resin pellets were changed according to the conditions shown in Table 2. The evaluation results are shown in Table 2.

[0052] [Table 1]

[0053] [Table 2]

[0054] Comparative Examples 1 and 2 used carbon fibers having a tensile strength of less than 5.1 GPa, and therefore had lower notched impact strength and unnotched impact strength than Examples 1-9. Comparative Examples 3 to 6 used polyamides other than the aliphatic polyamide (A), and therefore had lower notched impact strengths than Examples 1 to 9. Also, those containing the same amount of carbon fiber (B) had lower unnotched impact strengths. In Comparative Example 7, the notched impact strength is high because the mass average fiber length of the carbon fiber (B) is long, but the unnotched impact strength is low compared to Examples 1 to 9 because a polyamide other than the aliphatic polyamide (A) was used. Examples 1 to 7 and 9, in which the content of carbon fiber (B) is within the preferred range, have higher unnotched impact strength than Example 8. Examples 1 and 9, which used PA11, have higher notched impact strength than Examples 2-8. As described above, in comparison with Comparative Examples 1-7, Examples 1-9 of the present invention are higher in either or both of the notched impact strength and the unnotched impact strength. [Industrial Applicability]

[0055] The injection molded article of the present invention is useful as a transportation equipment part, an electric equipment part, a portable equipment part, and an industrial equipment part.

Claims

1. an aliphatic polyamide (A) containing a monomer unit having 10 or more carbon atoms; and carbon fiber (B) having a tensile strength of 5.1 GPa or more; The aliphatic polyamide (A) is PA11, The thermoplastic resin composition, wherein the content of the carbon fiber (B) is 20 to 160 parts by mass per 100 parts by mass of the aliphatic polyamide (A).

2. The thermoplastic resin composition according to claim 1, wherein the mass average fiber length of the carbon fiber (B) is 0.1 to 1.0 mm.

3. The thermoplastic resin composition according to claim 1 or 2, wherein the content of the carbon fiber (B) is 40 to 100 parts by mass per 100 parts by mass of the aliphatic polyamide (A).

4. The thermoplastic resin composition according to any one of claims 1 to 3, wherein the carbon fiber (B) has a tensile modulus of 260 GPa or more.

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