Thermoplastic resin composition and molded article

Abstract

To provide a thermoplastic resin composition containing recycled carbon fibers, which has excellent productivity and impact resistance even though the recycled carbon fibers are used, and to provide a compact.SOLUTION: A thermoplastic resin composition for carbon fiber reinforcement contains recycled carbon fibers (A) and a thermoplastic resin (B). The recycled carbon fibers (A) have an oxygen content of 5.0 mass% or more and an acid value of 0.002-0.080 mmol / g. The thermoplastic resin (B) has an average flow start temperature of 250°C or lower, and contains at least one of polyester resin and polycarbonate resin.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a thermoplastic resin composition containing recycled carbon fibers and a molded article using the same. [Background technology]

[0002] Carbon fiber reinforced plastics (hereinafter referred to as CFRP) reinforced with carbon fiber (hereinafter referred to as CF) are used in a wide range of industrial applications, including sporting goods and aircraft parts. Wind turbine rotor blades, which have traditionally used glass fiber composite materials, are now being replaced with lightweight, high-strength CFRP in order to achieve improved efficiency and larger size.

[0003] Used CFRP waste and scraps (prepreg, sheet molding compound, etc.) generated during the CFRP manufacturing process have traditionally been crushed and then disposed of in landfills, but a technology has been proposed to reuse them as recycled carbon fiber (hereinafter sometimes referred to as r-CF). Patent Document 1 discloses two methods for recovering r-CF: one in which CFPR is crushed into flakes and then dry distilled in a substantially non-oxidizing atmosphere at a temperature range of 300 to 1,000°C, and the other in which CFPR is dry distilled in a substantially non-oxidizing atmosphere at a temperature range of 300 to 1,000°C, and then dry distilled into flakes. Patent Document 2 also discloses a method for producing r-CF from carbon fiber reinforced plastic (CFRP) containing CF and a matrix resin, in which the carbon fiber reinforced resin is heated to pyrolyze the matrix resin, resulting in a heat-treated product with a resin residue content of 0.01 to 30.0% by mass, and the heat-treated product is then cut.

[0004] However, r-CF has poor compatibility with plastics, and even when trying to incorporate it into resin, extrusion is unstable. Therefore, recycled carbon fiber reinforced plastics (hereinafter sometimes referred to as r-CFRP) reinforced with r-CF have issues with productivity and mechanical strength.

[0005] To address these issues, Patent Document 3 discloses a resin composition obtained using a resin and recycled carbon fibers that have a fiber length variation coefficient of 20% or more and do not contain a sizing agent. However, the physical properties of the r-CFRP obtained using this technology are insufficient. Patent Document 4 also discloses a polyolefin resin composition containing recycled carbon fibers, a polyolefin resin, and a dispersant having a basic group. The recycled carbon fibers have an average fiber length of 0.05 to 15.0 mm, and the amount of recycled carbon fibers mixed is 1 to 50 mass% per 100 mass% of the thermoplastic resin composition. However, there is a market demand for the development of r-CFRPs with high physical properties using resins other than polyolefins. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 7-118440 [Patent Document 2] Japanese Patent Publication No. 2020-075493 [Patent Document 3] Japanese Patent Application Publication No. 2019-163354 [Patent Document 4] Japanese Patent Publication No. 2020-176244 Summary of the Invention [Problem to be solved by the invention]

[0007] In the manufacturing process of CFRP for automobiles and aircraft, where safety is a major concern, there is a large amount of scrap material from intermediate products. Since the lifespan of CFRP in machine parts is estimated to be about 20 years, CFRP waste will increase in the future. For this reason, there is a strong demand for the development of r-CFRP with excellent properties, which is made from recycled carbon fiber (hereinafter sometimes referred to as r-CF) recovered from CFRP waste.

[0008] The present invention has been made in view of the above background, and aims to provide a thermoplastic resin composition containing recycled carbon fiber and a molded article that are excellent in productivity and impact resistance, even when recycled carbon fiber is used. [Means for solving the problem]

[0009] As a result of extensive research, the present inventors have found that the problems of the present invention can be solved by the following aspects, and have thus completed the present invention. [1]: A thermoplastic resin composition for carbon fiber reinforcement containing recycled carbon fibers (A) and a thermoplastic resin (B), wherein the recycled carbon fibers (A) have an oxygen content of 5.0 mass% or more and an acid value of 0.002 to 0.080 mmol / g, and the thermoplastic resin (B) has an average flow initiation temperature of 250°C or less, and contains at least one of a polyester resin and a polycarbonate resin. (Note that the oxygen content is a value measured using an energy dispersive X-ray spectrometer attached to a scanning electron microscope (SEM) at an acceleration voltage of 15 kV and a field magnification of 3000 times.) The flow starting temperature is the temperature at which the melt viscosity of the thermoplastic resin becomes 4800 Pa s or less under a pressure of 9.8 MPa when evaluated using a flow tester. [2]: The thermoplastic resin composition according to [1], characterized in that the intensity ratio I1 / I2 of the diffraction intensity I1 at a Bragg angle 2θ=25° and the diffraction intensity I2 at 2θ=44° observed by X-ray diffraction of the recycled carbon fiber (A) is less than 6. [3]: The bulk density of the recycled carbon fiber (A) is 0.03 to 1.0 g / cm 3 The thermoplastic resin composition according to [1] or [2], wherein (However, the bulk density is a value obtained in accordance with JIS K5101.) [4]: The thermoplastic resin composition according to any one of [1] to [3], wherein the thermoplastic resin (B) contains an acid-modified thermoplastic elastomer (b-1). [5]: A molded article obtained by molding the thermoplastic resin composition according to any one of [1] to [4]. [Effects of the Invention]

[0010] According to the present invention, even when recycled carbon fibers are used, the excellent effect of being able to provide a thermoplastic resin composition and a molded article containing recycled carbon fibers that are excellent in productivity and impact resistance can be achieved. DETAILED DESCRIPTION OF THE INVENTION

[0011] An example of an embodiment to which the present invention is applied will be described below. Other embodiments are also included within the scope of the present invention as long as they conform to the spirit of the present invention. In this specification, a numerical range specified using "to" includes the numerical values ​​before and after "to." In this specification, recycled carbon fiber is referred to as r-CF, and carbon fiber (i.e., non-recycled carbon fiber) is referred to as CF. Furthermore, recycled carbon fiber reinforced plastic is referred to as r-CFRP, and carbon fiber reinforced plastic (i.e., non-recycled carbon fiber reinforced plastic) is referred to as CFRP. "Film" and "sheet" are not distinguished by thickness. Unless otherwise noted, the various components mentioned in this specification may be used independently, either singly or in combination. The numerical values ​​specified in this specification are values ​​determined by the methods disclosed in the examples.

[0012] 《Thermoplastic resin composition》 The thermoplastic resin composition for carbon fiber reinforcement (hereinafter referred to as thermoplastic resin composition) of this embodiment contains recycled carbon fibers (A) (hereinafter also referred to as r-CF(A)) and a thermoplastic resin (B). The recycled carbon fibers (A) have an oxygen content of 5.0 mass% or more and an acid value of 0.002 to 0.080 mmol / g, and the thermoplastic resin (B) is at least one of a polyester resin and a polycarbonate resin, each of which has a flow-initiation temperature of 250°C or less.

[0013] As a result of extensive research, the inventors have found that by combining r-CF (A) in which the oxygen content in the recycled carbon fiber (A) is 5.0 mass% or more and the acid value is 0.002 to 0.080 mmol / g with a thermoplastic resin (B) in which the average flow initiation temperature is 250°C or less and which contains at least one of a polyester resin and a polycarbonate resin, the compatibility of the resin and the recycled carbon fiber is significantly improved, and the adhesion between the resin and the recycled carbon fiber can be improved. The thermoplastic resin composition of this embodiment improves impact strength, productivity, and elastic modulus. Furthermore, the excellent compatibility between the resin and recycled carbon fiber can suppress deposits on the die of manufacturing equipment. By suppressing deposits, problems such as deposits being mixed into the product or deposits clogging the die holes, resulting in poor material discharge, can be suppressed, thereby improving productivity. Furthermore, the improved adhesion between the thermoplastic resin (B) and the r-CF (A) can increase the elastic modulus. As a result, it is expected that parts that have previously used metal materials can be replaced with r-CFRP, which has excellent lightweight properties. Each component is described in detail below.

[0014] <Recycled carbon fiber (A)> r-CF (recycled carbon fiber) is carbon fiber recovered by recycling CFRP (carbon fiber reinforced plastic) scraps or CFRP waste. CFRP, the raw material for r-CF, contains CF (carbon fiber) and a matrix resin, and includes not only molded products but also intermediate products before molding (prepreg, towpreg, sheet molding compound, stampable sheet, bulk molding compound, etc.). There are no particular limitations on the shape of the CFRP or the form of the CF contained therein. Thermosetting resins, thermoplastic resins, etc. are used as the matrix resin for CFRP.

[0015] The r-CF(A) of this embodiment has an oxygen content of 5.0% by mass or more and an acid value of 0.002 to 0.080 mmol / g. The oxygen content and acid value in this specification refer to values ​​obtained by measurements described in the Examples below. The contents of other elements can be determined by similar methods. As described above, r-CF(A) is a carbon fiber obtained by subjecting scraps, CFRP waste, etc. to heat treatment and / or heated steam treatment to pyrolyze (gasify, carbonize, etc.) the matrix resin. By adjusting the oxidizing atmosphere during the heating process, r-CF(A) with an oxygen content of 5.0% by mass or more can be obtained.

[0016] By combining a thermoplastic resin (B) (described below) having a flow initiation temperature of 250°C or less and containing at least one of a polyester resin and a polycarbonate resin with an r-CF (A) having an oxygen content of 5.0% by mass or more and an acid value of 0.002 to 0.080 mmol / g, the compatibility of the two resins can be significantly improved. The upper limit of the oxygen content of the r-CF (A) is preferably 20.0% by mass or less, from the viewpoint of maintaining good strength of the thermoplastic resin composition. A more preferred range is 5.0 to 15.0% by mass. The upper limit of the acid value of r-CF(A) is preferably 0.080 mmol / g or less, more preferably 0.005 to 0.060 mmol / g, from the viewpoint of maintaining good strength of the thermoplastic resin composition.

[0017] The carbon content of r-CF(A) is set to 95.0 mass% or less. From the viewpoint of maintaining good strength of the thermoplastic resin composition containing r-CF(A), the lower limit of the carbon content of r-CF(A) is preferably set to 80 mass% or more. Note that r-CF(A) may contain other elements such as nitrogen, silicon, sodium, and sulfur as long as the effects of the present invention are not affected.

[0018] The fiber length of r-CF(A) is preferably 0.05 mm or more from the viewpoint of improving impact resistance and elastic modulus. Although there is no particular upper limit, a length of 20 mm or less is preferable in consideration of availability.

[0019] Commercially available r-CF(A) products include, for example, the CARBISO MF series (average fiber length 0.08 to 0.1 mm, oxygen content 6%) and the CARBISO C series (average fiber length 3 to 10 mm, oxygen content 5%).

[0020] From the viewpoint of improving the adhesion between r-CF(A) and thermoplastic resin (B), it is preferable that the intensity ratio I1 / I2 between the diffraction intensity I1 at a Bragg angle 2θ=25° and the diffraction intensity I2 at 2θ=44° observed by X-ray diffraction of r-CF(A) is less than 6. 2θ=25° of r-CF(A) represents the diffraction of the (002) plane, and 2θ=44° represents the diffraction of the (10) plane.

[0021] During the heat treatment step in the CFRP recycling manufacturing process, an oxidizing atmosphere is used, generating oxygen-derived functional groups on a portion of the surface of the r-CF(A). The introduction of these oxygen-derived functional groups reduces the diffraction intensity of the (002) plane of the r-CF(A). By reducing the diffraction intensity of the (002) plane of the r-CF(A), adhesion to the thermoplastic resin (B) having an average solubility parameter of 10 to 15 can be improved. Considering the mechanical strength of the resulting thermoplastic resin composition, it is desirable that the diffraction intensity of the (10) plane of the r-CF(A) be as high as possible. The lower limit of the intensity ratio I1 / I2 is preferably 3 or greater, from the viewpoint of achieving excellent mechanical strength in the resulting thermoplastic resin composition. The intensity ratio I1 / I2 is more preferably in the range of 3 to 5.9, and even more preferably 4 to 5.9. The analytical intensity of I2 is preferably 500 to 1,000, more preferably 600 to 900. By adjusting the treatment time in an oxidizing atmosphere, it is possible to obtain r-CF(A) in which the intensity ratio I1 / I2 between the diffraction intensity I1 at a Bragg angle 2θ=25° and the diffraction intensity I2 at 2θ=44° observed by X-ray diffraction is less than 6.

[0022] From the viewpoint of further increasing the productivity of the thermoplastic resin composition of this embodiment, the bulk density of r-CF(A) is 0.03 to 1.0 g / cm 3By using r-CF(A) having a bulk density in this range, it is possible to effectively prevent fibers from remaining at the supply port when supplying r-CF(A) to production equipment in the production of a thermoplastic resin composition, thereby improving productivity. A more preferred range for the bulk density of r-CF(A) is 0.05 to 1.0 g / cm. 3 and a more preferred range is 0.1 to 1.0 g / cm 3 By adjusting the rotation speed of the grinder rotary blade and the opening of the classification mesh, a bulk density of 0.05 to 1.0 g / cm3 can be achieved. 3 can be obtained.

[0023] The amount of r-CF(A) blended is preferably 10 to 40 mass%, more preferably 15 to 35 mass%, and even more preferably 20 to 30 mass%, based on 100 mass% of the thermoplastic resin composition, from the viewpoint of achieving a balance between mechanical properties, processability, and productivity.

[0024] <Thermoplastic resin (B)> A thermoplastic resin is a resin that softens and becomes plastic when heated to an appropriate temperature and solidifies when cooled, and the thermoplastic resin (B) according to this embodiment has an average flow initiation temperature of 250° C. or less. The thermoplastic resin (B) can be used alone or in combination of two or more, and includes at least one of a polyester resin and a polycarbonate resin. When two or more types are used, it is not necessary for the flow initiation temperature of each thermoplastic resin to be in the range of 250°C or less, but it is sufficient that the average flow initiation temperature when the thermoplastic resins used are blended is in the range of 250°C or less. Here, the flow initiation temperature refers to the temperature at which the melt viscosity of a thermoplastic resin becomes 4800 Pa·s or less when passed through a capillary with a die hole diameter of φ1 mm and a die length of 1 mm under a pressure of 9.8 MPa, as determined by a flow tester.

[0025] The lower limit of the average flow temperature of the thermoplastic resin (B) is not particularly limited, and a more preferred range is 220 to 240° C. By combining the thermoplastic resin (B) having an average flow temperature of 250° C. or less with the r-CF (A), high productivity and mechanical properties can be obtained.

[0026] That is, it is sufficient that the average flow initiation temperature of the thermoplastic resin (B) after blending is 250°C or less, and from the viewpoint of more effectively improving the mechanical properties, it is more preferable that the flow initiation temperature of each resin used in the thermoplastic resin (B) is 250°C or less.

[0027] The thermoplastic resin (B) can increase the impact strength of the resulting r-CFRP, so that the Charpy impact strength measured in accordance with JIS K7111-1 is 3 kJ / m 2 It is preferable that the concentration is 5 kJ / m or more. 2 The upper limit of the Charpy impact strength of the thermoplastic resin (B), which is more preferably equal to or greater than this, is not particularly limited, and any resin that does not break can be suitably used.

[0028] From the viewpoint of fluidity, the content of polyester resin or polycarbonate resin in the thermoplastic resin (B) is preferably 50 to 100 mass %, more preferably 52 to 95 mass %, and even more preferably 60 to 90 mass %, based on 100 mass % of the thermoplastic resin (B).

[0029] The flow initiation temperature of the polyester resin or polycarbonate resin contained in the thermoplastic resin (B) is preferably 250°C or lower, more preferably 220 to 240°C, from the viewpoint of high productivity and mechanical properties.

[0030] Suitable polyester resins include, for example, thermoplastic resins made of saturated dicarboxylic acids and saturated dihydric alcohols. Examples of saturated dicarboxylic acids that can be used include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid, naphthalene-1,4- or 2,6-dicarboxylic acid, diphenyl ether-4,4'-dicarboxylic acid, diphenyl dicarboxylic acids, and diphenoxyethanediethanedicarboxylic acids; aliphatic dicarboxylic acids such as adipic acid, sebacic acid, azelaic acid, and decane-1,10-dicarboxylic acid; and alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid.

[0031] Examples of saturated dihydric alcohols that can be used include aliphatic glycols such as ethylene glycol, propylene glycol, trimethylene glycol, tetramethylene glycol, diethylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, hexamethylene glycol, dodecamethylene glycol, and neopentyl glycol; alicyclic glycols such as cyclohexanedimethanol; 2,2-bis(4'-β-hydroxyethoxyphenyl)propane; and other aromatic diols.

[0032] Specific examples of preferred polyester resins include PET-G, I-PET, polybutylene terephthalate (PBT), polycyclohexene dimethylene terephthalate (PCT), and polytrimethylene terephthalate (PTT).

[0033] The polycarbonate resin may be, for example, a resin that can be easily produced by reacting an aromatic dihydroxy compound with a carbonate precursor such as phosgene or a carbonate diester. The resin can be produced by a known reaction, for example, an interfacial method when phosgene is used, or a transesterification method in which a molten reaction is carried out when a carbonate diester is used.

[0034] Examples of aromatic dihydroxy compounds include bis(hydroxyaryl)alkanes such as 2,2-bis(4-hydroxyphenyl)propane (bisphenol A), bis(4-hydroxyphenyl)methane, 1,1-bis(4-hydroxyphenyl)ethane, 2,2-bis(4-hydroxyphenyl)butane, 2,2-bis(4-hydroxyphenyl)octane, bis(4-hydroxyphenyl)phenylmethane, 2,2-bis(4-hydroxy-3-methylphenyl)propane, 1,1-bis(4-hydroxy-3-t-butylphenyl)propane, 2,2-bis(4-hydroxy-3-bromophenyl)propane, 2,2-bis(4-hydroxy-3,5-dibromophenyl)propane, and 2,2-bis(4-hydroxy-3,5-dichlorophenyl)propane; Examples of suitable hydroxyaryl compounds include bis(hydroxyaryl)cycloalkanes such as 1,1-bis(4-hydroxyphenyl)cyclopentane and 1,1-bis(4-hydroxyphenyl)cyclohexane; dihydroxydiaryl ethers such as 4,4'-dihydroxydiphenyl ether and 4,4'-dihydroxy-3,3'-dimethyldiphenyl ether; dihydroxydiaryl sulfides such as 4,4'-dihydroxydiphenyl sulfide and 4,4'-dihydroxy-3,3'-dimethyldiphenyl sulfide; dihydroxydiaryl sulfoxides such as 4,4'-dihydroxydiphenyl sulfoxide and 4,4'-dihydroxy-3,3'-dimethyldiphenyl sulfoxide; and dihydroxydiaryl sulfones such as 4,4'-dihydroxydiphenyl sulfone and 4,4'-dihydroxy-3,3'-dimethyldiphenyl sulfone. These compounds may be used alone or in combination. In addition to these compounds, piperazine, dipiperidyl hydroquinone, resorcinol, and 4,4'-dihydroxydiphenyl compounds may also be used in combination. Furthermore, branched aromatic polycarbonate resins containing polyfunctional compounds such as phloroglucin can also be used.

[0035] Examples of the carbonate precursor to be reacted with the aromatic dihydroxy compound include phosgene, diaryl carbonates such as diphenyl carbonate and ditolyl carbonate, and dialkyl carbonates such as dimethyl carbonate and diethyl carbonate.

[0036] The average MFR of the thermoplastic resin (B) is preferably 10 g / min or more, more preferably 20 g / min or more. By making the average MFR of the thermoplastic resin (B) 10 g / min or more, the melt viscosity when the r-CF (A) and the thermoplastic resin (B) are kneaded decreases, and breakage of the r-CF (A) can be suppressed, thereby achieving high mechanical properties. The upper limit of the average MFR of the thermoplastic resin (B) is not particularly limited, but from the viewpoint of availability, it is usually 200 g / min or less.

[0037] [Acid-modified thermoplastic elastomer (b-1)] The thermoplastic resin (B) may contain an acid-modified thermoplastic elastomer (b-1). In this specification, the term "thermoplastic elastomer" refers to a polymer that softens and becomes plastic when heated to an appropriate temperature, exhibits elasticity when cooled, and does not exhibit a melting point as determined by the DSC method. By combining r-CF (A) with the thermoplastic resin (B) and further including the acid-modified thermoplastic elastomer (b-1) as the thermoplastic resin (B), compatibility is significantly improved, enabling the production of a thermoplastic resin composition with high impact resistance. An "acid-modified thermoplastic elastomer" refers to a thermoplastic elastomer into which an acidic functional group has been introduced by graft polymerization or the like. Suitable examples of acid-modified thermoplastic elastomers include acid-modified styrene-based elastomers and acid-modified olefin-based elastomers. Acid modification refers to the introduction of cyclic acid anhydride groups or carboxylic acid groups into the copolymer side chains using, for example, cyclic acid anhydrides such as succinic anhydride, maleic anhydride, glutaric anhydride, or phthalic anhydride.

[0038] Examples of the styrene-based elastomer include block copolymers composed of polystyrene blocks and polyolefin elastomer blocks, such as styrene-isoprene-styrene block copolymer (SIS), hydrogenated styrene-ethylene-butylene-styrene block copolymer (SEPS), styrene-butylene-styrene block copolymer (SBS), hydrogenated styrene-ethylene-butylene-styrene block copolymer (SEBS), styrene-butadiene-isoprene-styrene block copolymer (SBIS), and hydrogenated styrene-butadiene-isoprene-styrene block copolymer (SEEPS).

[0039] Examples of the olefin-based elastomer include ethylene-propylene copolymer, ethylene-butene-1 copolymer, ethylene-hexene-1 copolymer, ethylene-octene-1 copolymer, ethylene-ethyl acrylate copolymer, ethylene-methacrylate copolymer, ethylene-propylene-diene terpolymer, isoprene rubber, nitrile rubber, and polybutene rubber.

[0040] Commercially available products include, for example, maleic anhydride-modified isoprene rubber such as LIR-403 (manufactured by Kuraray Co., Ltd.); modified isoprene rubber such as LIR-410 (manufactured by Kuraray Co., Ltd.); carboxy-modified nitrile rubber such as Krynac 110, 221, and 231 (manufactured by Polycer Corporation); maleic anhydride-modified polybutene such as Nisseki Polybutene (manufactured by Nippon Oil Corporation); ethylene methacrylic acid copolymer such as Nucrel (manufactured by DuPont-Mitsui Polychemicals Co., Ltd.); ethylene methacrylic acid copolymer such as Yukalon (manufactured by Mitsubishi Chemical Corporation); maleic anhydride-modified ethylene-propylene rubber such as Tafmer M (MA8510 (manufactured by Mitsui Chemicals Co., Ltd.)) and TX-1215 (manufactured by Mitsui Chemicals Co., Ltd.); maleic anhydride-modified ethylene-butene rubber such as Tafmer M (MH7020 (manufactured by Mitsui Chemicals Co., Ltd.)); and HPR series (maleic anhydride-modified EEA ( Examples of maleic anhydride-modified polyethylenes include maleic anhydride-modified polyethylenes (manufactured by DuPont-Mitsui Polychemicals), Bondine (maleic anhydride-modified EEA (manufactured by Atofina)), Tuftec (maleic anhydride-modified SEBS, M1943 (manufactured by Asahi Kasei Corporation)), Kraton (maleic anhydride-modified SEBS, FG1901X (manufactured by Kraton Polymers)), Tufprene (maleic anhydride-modified SBS, 912 (manufactured by Asahi Kasei Corporation)), Septon (maleic anhydride-modified SEPS (manufactured by Kuraray Co., Ltd.)), Rexpearl (maleic anhydride-modified EEA, ET-182G, 224M, 234M (manufactured by Japan Polyolefins Co., Ltd.)), and Aurouren (maleic anhydride-modified EEA, 200S, 250S (manufactured by Nippon Paper Chemicals Co., Ltd.)); and maleic anhydride-modified polypropylenes (manufactured by Admer, QB550, LF128 (manufactured by Mitsui Chemicals, Inc.)).

[0041] A particularly suitable example of the acid-modified thermoplastic elastomer (b-1) is a maleic anhydride-modified styrene-ethylene-butadiene-styrene copolymer. Commercially available acid-modified styrene-ethylene-butylene-styrene block copolymers include Tuftec M1911 (manufactured by Asahi Kasei Chemicals Corporation) with an acid value of 2 mg CHONa / g and a MFR of 4.5 g / 10 min, Tuftec M1913 (manufactured by Asahi Kasei Chemicals Corporation) with an acid value of 10 mg CHONa / g and a MFR of 5.0 g / 10 min, and Tuftec M1943 (manufactured by Asahi Kasei Chemicals Corporation) with an acid value of 10 mg CHONa / g and a MFR of 8.0 g / 10 min.

[0042] The acid-modified thermoplastic elastomer (b-1) can increase the impact strength of the resulting r-CFRP, and the Charpy impact strength measured in accordance with JIS K7111-1 is 20 kJ / m 2 It is preferable that the concentration is 30 kJ / m or more. 2 The upper limit of the Charpy impact strength of the acid-modified thermoplastic elastomer (b-1) is not particularly limited, and any elastomer that does not break can be suitably used.

[0043] The average MFR of the acid-modified thermoplastic elastomer (b-1) is preferably 1.0 g / 10 min or more, more preferably 5.0 g / 10 min or more. When the average MFR of the acid-modified thermoplastic elastomer (b-1) is within the above range, the melt viscosity during processing is reduced, fiber breakage of the r-CF (A) during processing can be suppressed, and high physical properties can be achieved.

[0044] The amount of the acid-modified thermoplastic elastomer (b-1) to be blended is preferably 5 to 20 parts by mass, more preferably 5 to 15 parts by mass, and even more preferably 5 to 10 parts by mass, per 100 parts by mass of the thermoplastic resin composition, from the viewpoint of further improving both the modulus of elasticity and the impact strength.

[0045] The acid value of the acid-modified thermoplastic elastomer (b-1) is preferably 0.5 to 40 mg CH3ONa / g, more preferably 1 to 30 mg CH3ONa / g. When the acid value of the acid-modified thermoplastic elastomer (b-1) is in the range of 0.5 to 40 mg CH3ONa / g, the interfacial adhesion between the r-CF (A) and the thermoplastic resin (B) can be improved. The acid value in the present invention is a value measured in accordance with JIS K-0070.

[0046] <Optional ingredients> The thermoplastic resin composition of this embodiment may contain an inorganic filler as an optional component. Examples of inorganic fillers include silica, heat-dissipating fillers, talc, calcium silicate, wollastonite, montmorillonite, and hydrotalcite. Furthermore, if necessary, other additives conventionally used to modify resins may be added, such as weathering stabilizers, light resistance stabilizers, antioxidants, antioxidants, softeners, dispersants, fillers, colorants, lubricants, heat stabilizers, antistatic agents, UV absorbers, and flame retardants such as halogen-based, phosphorus-based, or metal oxide flame retardants. Metal soaps of alkali metals, alkaline earth metals, or zinc, nonionic surfactants, cationic surfactants, anionic surfactants, and amphoteric surfactants may also be added.

[0047] <Method of producing thermoplastic resin composition> The thermoplastic resin composition can be obtained by kneading the ingredients at a temperature at which the thermoplastic resin (B) melts. For example, r-CF (A), thermoplastic resin (B), and, if necessary, various additives and colorants can be added and kneaded using a batch mixer such as a kneader, roll mill, super mixer, high-speed mixer, ball mill, sand mill, attritor, or Banbury mixer, a single-screw extruder, a twin-screw extruder, or a rotor-type twin-screw mixer to produce a resin composition in the form of pellets, powder, granules, or beads. The method of pelletizing using a twin-screw extruder is preferred because of its strong kneading power and ease of subsequent molding.

[0048] The thermoplastic resin composition can be used as a masterbatch by diluting it with a molding resin during molding. Alternatively, a required amount of r-CF (A) may be blended with a thermoplastic resin (B) to form a compound that can be molded directly without diluting it with a molding resin.

[0049] The amount of r-CF(A) in 100% by mass of the masterbatch is 41 to 70% by mass, and more preferably 50 to 65% by mass. By setting the amount of r-CF(A) in the above range, the productivity and mechanical properties of the masterbatch can be improved. In the masterbatch, the resin used for dilution during molding can be any of those exemplified as the thermoplastic resin (B) described above. Because of its excellent compatibility, it is preferable to use the same resin as the thermoplastic resin (B) used to disperse the r-CF(A). The thermoplastic resin composition of this embodiment has excellent dispersibility of r-CF(A), and therefore can be stably formed even when made into a high-concentration resin composition such as a masterbatch. It can be shaped.

[0050] When the thermoplastic resin composition of this embodiment is made into a compound, the amount of r-CF(A) in 100% by mass of the compound is preferably 10 to 40% by mass, more preferably 15 to 35% by mass. By setting the amount of r-CF(A) in the above range, both productivity and moldability of the compound can be achieved.

[0051] <<Molded body>> The molded article according to this embodiment is obtained by molding the thermoplastic resin composition according to this embodiment. The molding method is not particularly limited, and the molded article can be produced by, for example, extrusion molding, injection molding, blow molding, etc. The thermoplastic resin composition according to this embodiment has excellent strength and moldability, and is therefore suitable for molding injection-molded articles such as automobile parts having complex shapes. [Example]

[0052] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples. Items without numerical values ​​in the tables indicate that the element is not contained.

[0053] 《Measurement method》 The physical properties of each raw material, Examples, Reference Examples and Comparative Examples (hereinafter referred to as Examples, etc.) were measured by the following methods. 1) Measurement of oxygen content in recycled carbon fiber The oxygen content of r-CF(A) was measured using an energy dispersive X-ray spectrometer attached to a scanning electron microscope (SEM) at an accelerating voltage of 15 kV and a field magnification of 3000 times. 2) Measurement of the acid value of recycled carbon fiber To measure the acid value of r-CF(A), accurately weigh approximately 1 g of sample into a stoppered Erlenmeyer flask, add 100 ml of a toluene / ethanol (volume ratio: toluene / ethanol = 2 / 1) mixture, and stir. Add phenolphthalein TS as an indicator and hold for 30 seconds. Then, titrate with 0.1 N alcoholic potassium hydroxide solution until the solution turns a pale pink color. The acid value was calculated using the following formula (unit: mgKOH / g). Acid value (mgKOH / g) = {(5.611 x a x F) / S} / (non-volatile content / 100) Where S: sample amount (g) a: Consumption of 0.1N alcoholic potassium hydroxide solution (ml) F: Potency of 0.1N alcoholic potassium hydroxide solution 3) Measurement of flow start temperature of thermoplastic resin (B) etc. The flow initiation temperature was measured using a flow tester in accordance with JIS K 7210. Specifically, using a thermal fluidity evaluation device CFT-500D (Shimadzu Corporation), the flow initiation temperature was determined as the temperature at which the melt viscosity of the thermoplastic resin became 4800 Pa s or less when passed through a capillary with a die hole diameter of φ1 mm and a die length of 1 mm under a pressure of 9.8 MPa. 4) Measurement of diffraction intensity I1 (2θ=25°) and diffraction intensity I2 (2θ=44°) of r-CF(A) etc. Using an XRD (X-ray Diometer) with Cu-Kα as the radiation source, the diffraction intensity of pulverized r-CF was measured in the range of 5°<2θ<110°. 5) Measurement of bulk density of r-CF(A) etc. The bulk density of r-CF(A) and the like was measured in accordance with JIS K5101. 6) Measurement of the average MFR of thermoplastic resin (B) etc. The MFR of the thermoplastic resin (B) etc. was measured in accordance with JIS K7210-1. 7) Measurement of the Charpy impact strength of thermoplastic resin (B) etc. and the molded body The acid-modified thermoplastic elastomer (b-1) and the Charpy impact strength of the molded body were measured in accordance with JIS K7111-1.

[0054] <Production of r-CF> <<Production Example 1>> The CFRP derived from aircraft end materials was heat-treated in a heated steam atmosphere at 750°C for 4 hours. Subsequently, it was heat-treated at 550°C for 6 hours in air to obtain a regenerated carbon fiber mass. The obtained regenerated carbon fiber mass was crushed with a cutting machine, and fibers of 4 - 15 mm were collected to obtain the regenerated carbon fiber r-CF-A according to Production Example 1.

[0055] <<Production Example 2>> The regenerated carbon fiber r-CF-B according to Production Example 2 was obtained in the same manner as in Production Example 1, except that the CFRP derived from aircraft end materials was changed to CFRP derived from automotive part waste materials.

[0056] <<Production Example 3>> The regenerated carbon fiber r-CF-C according to Production Example 3 was obtained using the same materials and production method as in Production Example 1, except that the step of crushing with a cutting machine was not performed and the step of pulverizing with a pulverizer was performed.

[0057] <<Production Example 4>> The CFRP derived from aircraft end materials was heat-treated at 450°C to burn off the resin component. Subsequently, a regenerated carbon fiber mass obtained by performing a DC electrolysis reaction of 3V with the anode as a carbon fiber aggregate and the cathode as a titanium electrode under an aqueous sodium hydroxide solution was crushed and classified with a crusher to obtain r-CF-D.

[0058] <<Raw Materials>> The raw materials used in the examples etc. are shown below. <r-CF(A) etc.>[[]]<0​​​​​​A-II: r-CF-B (oxygen content 6 mass%, acid value 0.004 mmol / g, I1 / I2 = 5.0, bulk density 0.10 g / cm 3 ) A-III: r-CF-C (oxygen content 6 mass%, acid value 0.060 mmol / g, I1 / I2 = 5.9, bulk density 0.0 3g / cm 3 ) ·A'-IV:r-CF-D (oxygen content 8% by mass, acid value 0.120mmol / g, I1 / I2=4.9, bulk density 0.23g / cm 3 ) A'-V: v-CF-A (manufactured by Mitsubishi Chemical Corporation, oxygen content 0 mass%, acid value 0.001 mmol / g, I1 / I2 = 6 .9, bulk density 0.53g / cm 3 ) <Thermoplastic resin (B) etc.> BI: Toraycon 1401 x 06 (Toray Industries, PBT (polyester resin), flow temperature: 224°C) B-II: Tritan GN071 (manufactured by Eastman Chemical Company, PET-G (polyester resin), flow temperature: 235°C) B-III: Iupilon E-2000 (Mitsubishi Engineering Plastics Corporation, PC (polycarbonate resin), flow temperature: 230°C) B-IV: Novalloy S1500 (manufactured by Daicel Polymers, PC (polycarbonate resin), flow temperature: 220°C) BV: Mitsui Pet SA135 (Mitsui Chemicals, PET (polyester resin), flow temperature: 253°C) B'-VI: SunAllomer PMA-60Z (manufactured by SunAllomer, PP (polypropylene resin), flow temperature: 140°C) [Acid-modified thermoplastic elastomer (b-1), etc.] b-1-I: Acid-modified SEBS, Tuftec M1943 (manufactured by Asahi Kasei Chemicals Corporation, acid value 10 mg CH3ONa / g, MFR 8.0 g / 10 min)

[0059] <Production of Thermoplastic Resin Composition> Example 1 Using 10 parts by mass of A-1 as r-CF (A) and 90 parts by mass of B-1 as thermoplastic resin (B), the mixture was extruded at 280°C in a twin-screw extruder (manufactured by The Japan Steel Works, Ltd.) and granulated to obtain a thermoplastic resin composition (D-1) (see Table 1). Table 2 shows the physical properties of r-CF (A) and thermoplastic resin (B).

[0060] (Examples 2 to 13, Reference Example 1, Comparative Example 1) Thermoplastic resin compositions were obtained in the same manner as in Example 1, except that the materials and blending amounts (parts by mass) were changed to those shown in Table 1. Table 2 shows the physical properties of the r-CF (A) and thermoplastic resin (B) in each example.

[0061] [Table 1]

[0062] [Table 2]

[0063] <Evaluation of Thermoplastic Resin Composition> The thermoplastic resin compositions according to the respective Examples were evaluated as follows. The results are shown in Table 3. α) Evaluation of productivity (deposits on the die tip) When 2 kg of the thermoplastic resin composition of each example was produced at a discharge rate of 20 kg / h, The amount of deposits generated on the end dies was evaluated according to the following criteria. +++: The weight of the deposit is less than 1g. Productivity is particularly good. ++: The weight of the deposit is between 1g and 3g. Productivity is good. +: The weight of the deposit is between 3g and 5g. Productivity is possible. NG: Weight of deposit is 5g or more. Productivity is poor. β) Evaluation of productivity (fiber retention) Similarly, regarding the fiber supplyability during extrusion processing of the thermoplastic resin compositions of each Example, the degree of fiber retention at the raw material supply port when the fibers were supplied at a discharge rate of 6 kg / h using a gravimetric feeder with a hopper capacity of 25 L was visually evaluated. +++: No retention occurs. Productivity is particularly good. ++: Slight retention occurs. Productivity is good. +: Retention occurs to a degree that does not affect extrusion processing. Productivity is possible. NG: Fiber is not supplied to the extruder due to retention. Productivity is poor.

[0064] <Production of Molded Product> The thermoplastic resin compositions of the respective Examples were molded using an injection molding machine (manufactured by Toshiba Machine Co., Ltd.) to obtain multipurpose test pieces measuring 80 mm in length, 10 mm in width, and 4 mm in thickness.

[0065] <Evaluation of molded products> The molded articles according to the respective Examples were evaluated as follows. The results are shown in Table 3. γ) Evaluation of elastic modulus The obtained multipurpose test pieces of each example were used to measure the flexural modulus in accordance with JIS K7171:2016. The higher the measured value, the better the strength. The evaluation criteria for the modulus were as follows: +++: 10,000 MPa or more. Excellent. ++: 8000 MPa or more and less than 10000 MPa. Good. +: 5000 MPa or more, but less than 8000 MPa. Practical range. NG: Less than 5000MPa. Poor. δ) Evaluation of Charpy impact strength The notched Charpy impact strength was measured according to JIS K7111-1:2012 using the obtained multipurpose test specimens of each Example, etc. Evaluation criteria were as follows. +++:15kJ / m 2 That's it. Excellent. ++7kJ / m 2 More than 15kJ / m 2 Less than. Good. +:5kJ / m 2 More than 7kJ / m2 Less than. Practical range. NG: 5kJ / m 2 less than. For applications requiring high strength such as automotive parts, a Charpy impact strength of 7kJ / m 2 It is preferable that this is equal to or greater than this.

[0066] [Table 3]

[0067] A thermoplastic resin composition for carbon fiber reinforcement containing recycled carbon fiber (A) and thermoplastic resin (B), wherein the recycled carbon fiber (A) has an oxygen content of 5.0 mass% or more and an acid value of 0.002 to 0.080 mmol / g, and the thermoplastic resin (B) has an average flow initiation temperature of 250°C or less, and a molded article formed from the thermoplastic resin composition containing at least one of a polyester resin and a polycarbonate resin, is excellent in productivity, elastic modulus, and impact strength, as shown in the examples in Table 3, and it has been confirmed that the molded article exhibits excellent effects equivalent to those of the molded article of Reference Example 1 formed from a thermoplastic resin composition combining CF and thermoplastic resin (B).

Claims

1. A thermoplastic resin composition for carbon fiber reinforcement containing recycled carbon fibers (A) and a thermoplastic resin (B), The recycled carbon fiber (A) has an oxygen content of 5.0% by mass or more and an acid value of 0.002 to 0.080 mmol / g, the thermoplastic resin (B) has an average flow initiation temperature of 250°C or less and contains at least one of a polyester resin and a polycarbonate resin; The amount of recycled carbon fiber (A) is 10 to 50 mass% based on 100 mass% of the thermoplastic resin composition. Thermoplastic resin composition. (Note that the oxygen content is a value measured using an energy dispersive X-ray spectrometer attached to a scanning electron microscope (SEM) at an acceleration voltage of 15 kV and a visual field magnification of 3000 times.) The flow starting temperature is the temperature at which the melt viscosity of the thermoplastic resin becomes 4800 Pa s or less under a pressure of 9.8 MPa when evaluated using a flow tester.

2. Diffraction intensity I at Bragg angle 2θ = 25° observed by X-ray diffraction of recycled carbon fiber (A) １ and the diffraction intensity I at 2θ=44° ２ Intensity ratio I １ / I ２ 2. The thermoplastic resin composition according to claim 1, wherein the .lambda. of the thermoplastic resin composition is less than 6.

3. The bulk density of the recycled carbon fiber (A) is 0.03 to 1.0 g / cm ３ 3. The thermoplastic resin composition according to claim 1, wherein (However, the bulk density is a value obtained in accordance with JIS K5101.)

4. The thermoplastic resin composition according to any one of claims 1 to 3, wherein the thermoplastic resin (B) contains an acid-modified thermoplastic elastomer (b-1).

5. A molded article obtained by molding the thermoplastic resin composition according to any one of claims 1 to 4.

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