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). In the recycled carbon fibers (A), an oxygen content is 5.0 mass% or more. The thermoplastic resin (B) contains polyolefin resin with a melting point of 100°C or higher (excluding the case when it is an acid-modified thermoplastic resin) and at least one of acid-modified polypropylene (b-1) and thermoplastic elastomer (b-2) with a melting point of 130°C or higher.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% based on 100 mass% of the thermoplastic resin composition. [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), The oxygen content in the recycled carbon fiber (A) is 5.0% by mass or more, The thermoplastic resin (B) is a thermoplastic resin composition containing a polyolefin resin having a melting point of 100°C or higher (excluding acid-modified thermoplastic resins), and at least one of an acid-modified polypropylene (b-1) and a thermoplastic elastomer (b-2) having a melting point of 130°C or higher. (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.) [2]: The acid-modified polypropylene (b-1) is subjected to a shear rate of 1.2 × 10 3 sec -1 2. The thermoplastic resin composition according to claim 1, wherein the melt viscosity ηc is 10 to 500 Pa·s. [3]: The thermoplastic resin composition according to claim 1 or 2, 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. [4]: The bulk density of the recycled carbon fiber (A) is 0.03 to 1.0 g / cm 3 The thermoplastic resin composition according to any one of [1] to [3], wherein: (However, the bulk density is a value obtained in accordance with JIS K5101.) [5]: The thermoplastic resin composition according to any one of [1] to [4], wherein the polyolefin resin having a melting point of 100° C. or higher is a homopolymer of polypropylene. [6]: The thermoplastic resin composition according to any one of [1] to [5], wherein the thermoplastic resin (B) comprises an acid-modified polypropylene (b-1) having a melting point of 130°C or higher and a thermoplastic elastomer (b-2). [7]: A molded article obtained by molding the thermoplastic resin composition according to any one of [1] to [6]. [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 carbon fiber reinforced thermoplastic resin composition (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 r-CF(A) has an oxygen content of 5.0 mass% or more, and the thermoplastic resin (B) contains a polyolefin resin having a melting point of 100°C or more, and at least one of an acid-modified polypropylene (b-1) and a thermoplastic elastomer (b-2), each having a melting point of 130°C or more.

[0013] As a result of extensive research, the inventors have found that by combining r-CF (A) having an oxygen content of 5.0% by mass or more with a polyolefin resin having a melting point of 100°C or more and a thermoplastic resin (B) containing at least one of acid-modified polypropylene (b-1) and a thermoplastic elastomer (b-2), both of which have melting points of 130°C or more, the compatibility of the olefin resin with the recycled carbon fiber is significantly improved, resulting in improved adhesion between the polyolefin resin and the recycled carbon fiber. The thermoplastic resin composition of this embodiment improves tensile strength, modulus of elasticity, impact strength, deflection temperature under load, and productivity. Furthermore, the excellent compatibility between the resin and the recycled carbon fiber can suppress deposits on the die of the 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 r-CF (A) can increase tensile strength, modulus of elasticity, impact strength, and deflection temperature under load. As a result, it is expected that parts that have previously been made from metal materials will be replaced with r-CFRP, which has excellent lightness. 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. The r-CF(A) of this embodiment has an oxygen content of 5.0% by mass or more. The oxygen content in this specification refers to a value obtained by measurement 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.

[0015] By combining the thermoplastic resin (B) described below with r-CF (A) having an oxygen content of 5.0% by mass or more, the mutual compatibility can be significantly improved. The upper limit of the oxygen content of 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.

[0016] 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.

[0017] 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.

[0018] 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%).

[0019] From the viewpoint of improving the adhesion between the r-CF (A) and the 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 the r-CF (A) is less than 6. -2θ=25° in CF(A) represents diffraction from the (002) plane, and 44° represents diffraction from the (10) plane.

[0020] In the heat treatment step in the recycling production process from CFRP, 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) can be improved. Meanwhile, 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, and more preferably 600 to 900. By adjusting the treatment time in the 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° as observed by X-ray diffraction is less than 6.

[0021] 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 3 By 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.

[0022] 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.

[0023] <Thermoplastic resin (B)> A thermoplastic resin is a resin that softens and becomes plastic when heated to an appropriate temperature and solidifies when cooled. The thermoplastic resin (B) according to this embodiment includes a polyolefin resin having a melting point of 100°C or higher (excluding acid-modified thermoplastic resins), and at least one of an acid-modified polypropylene (b-1) and a thermoplastic elastomer (b-2) having a melting point of 130°C or higher, and preferably includes both an acid-modified polypropylene (b-1) and a thermoplastic elastomer (b-2) having a melting point of 130°C or higher.

[0024] Among these, it is preferable to contain an acid-modified polypropylene (b-1) and an acid-modified thermoplastic elastomer (b-2x) having a melting point of 130° C. or higher, since this can improve adhesion to the r-CF (A).

[0025] The term "acid-modified thermoplastic resin" refers to a thermoplastic resin into which an acidic functional group has been introduced by graft polymerization or the like. Furthermore, thermoplastic resins other than polyolefin resins having a melting point of 100°C or higher, acid-modified polypropylenes (b-1) having a melting point of 130°C or higher, and thermoplastic elastomers (b-2) may be used as long as they do not impair the effects of the present invention, but it is preferable that the main component is a polyolefin resin having a melting point of 100°C or higher (excluding acid-modified thermoplastic resins). The main component refers to the thermoplastic resin that is contained in the largest amount among the components that make up the thermoplastic resin (B). The melting point of the polyolefin resin having a melting point of 100° C. or higher is preferably 100 to 180° C., more preferably 105 to 170° C. When the melting point is within the above range, the compatibility with the acid-modified polypropylene (b-1) and the thermoplastic elastomer (b-2), which will be described later, is improved, and the dispersibility of the acid-modified polypropylene (b-1) and the thermoplastic elastomer in the polyolefin resin is improved, resulting in excellent adhesion between the thermoplastic resin (B) and the r-CF (A). The melting point in the present invention is a value measured by differential scanning calorimetry (DSC) (a measured value obtained at a heating rate of 10° C. / min using a differential scanning calorimeter DSC6200 manufactured by Seiko Instruments Inc.).

[0026] The content of the polyolefin resin having a melting point of 100°C or higher in the thermoplastic resin (B) is preferably 50 to 99 mass%, more preferably 52 to 98 mass%, and even more preferably 55 to 97 mass%, based on 100 mass% of the thermoplastic resin (B), since this can increase the strength and elastic modulus.

[0027] [Polyolefin resin] Examples of polyolefin resins include homopolymers of α-olefins having about 2 to 8 carbon atoms, such as ethylene, propylene, and 1-butene, and (co)polymers of these α-olefins with other α-olefins having about 2 to 18 carbon atoms, such as ethylene, propylene, 1-butene, 3-methyl-1-butene, 1-pentene, 4-methyl-1-pentene, 4,4-dimethyl-1-pentene, 1-hexene, 4-methyl-1-hexene, 1-heptene, 1-octene, 1-decene, and 1-octadecene. The polyolefin resin used in the present invention is not limited as long as it has a melting point of 100°C or higher.

[0028] Specific examples include ethylene homopolymers such as linear low-density polyethylene resin (LLDPE), low-density polyethylene resin (LDPE), and high-density polyethylene resin (HDPE); ethylene copolymers such as ethylene-propylene copolymers, ethylene-1-butene copolymers, ethylene-propylene-1-butene copolymers, ethylene-4-methyl-1-pentene copolymers, ethylene-1-hexene copolymers, ethylene-1-heptene copolymers, and ethylene-1-octene copolymers; and propylene copolymers such as propylene homopolymers (homo PP), propylene-ethylene block copolymers (block PP), propylene-ethylene random copolymers (random PP), propylene-ethylene-1-butene copolymers, propylene-ethylene-4-methyl-1-pentene copolymers, and propylene-ethylene-1-hexene copolymers. These polyolefin resins may be used alone or in combination of two or more. Propylene-based resins are preferred because they can achieve high mechanical properties, and among them, propylene homocopolymers (homo PP) are more preferred because they can increase the deflection temperature under load.

[0029] The MFR (melt flow rate) of the thermoplastic resin (B) in the present invention is preferably 0.1 to 100 g / 10 min, more preferably 10 to 80 g / 10 min, and even more preferably 20 to 60 g / 10 min. When the MFR of the thermoplastic resin (B) is within the above range, the r-CF (A) is not destroyed during kneading, and high physical properties can be exhibited. The MFR in the present invention is a value measured in accordance with JIS K-7210-1:2014.

[0030] Specific examples of thermoplastic resins include Prime Polypro J229E (random PP, MFR 50 g / 10 min, manufactured by Prime Polymer Co., Ltd.), Prime Polypro J708UG (block PP, MFR 45 g / 10 min), and SunAllomer PM900A (homo PP, MFR 30 g / 10 min, manufactured by SunAllomer Co., Ltd.).

[0031] [Acid-modified polypropylene resin (b-1)] The acid-modified polypropylene resin (b-1) is blended to improve the adhesion between the r-CF (A) and the thermoplastic resin (B). The acid-modified polypropylene resin (b-1) is an acid-modified polypropylene resin having a melting point of 130°C or higher as measured by a DSC method, and is obtained by introducing an acidic functional group into a propylene-based resin by graft polymerization or the like. Examples of the acidic functional group include cyclic acid anhydrides such as succinic anhydride, maleic anhydride, glutaric anhydride, and phthalic anhydride. The melting point of the acid-modified polypropylene resin (b-1) is preferably 130 to 200°C, more preferably 135 to 180°C. By using an acid-modified polypropylene resin having a melting point within the above range, the difference in melting point with the thermoplastic resin (B) is reduced, improving the dispersibility of the acid-modified polypropylene resin (b-1) in the thermoplastic resin (B), thereby improving the adhesion between the thermoplastic resin (B) and the r-CF (A). The melting point in the present invention is a value measured by differential scanning calorimetry (DSC) (a measured value obtained at a heating rate of 10° C. / min using a differential scanning calorimeter DSC6200 manufactured by Seiko Instruments Inc.).

[0032] The acid-modified polypropylene resin (b-1) in the present invention is also3 sec -1 The melt viscosity ηc at 220°C is preferably 1 to 500 Pa·s, more preferably 10 to 500 Pa·s, even more preferably 20 to 400 Pa·s, and particularly preferably 50 to 300 Pa·s. When the melt viscosity at 220°C is within the above range, the difference in melt viscosity with the thermoplastic resin (B) during kneading is reduced, improving the dispersibility of the acid-modified polypropylene resin (b-1), thereby improving the interfacial adhesion between the r-CF (A) and the thermoplastic resin (B). Furthermore, the elastic modulus and deflection temperature under load are improved, and even when recycled carbon fibers are used, molded articles containing recycled carbon fibers can be produced with excellent productivity and impact resistance. The melt viscosity in the present invention is determined according to JIS K7199:1999 at 220°C and a shear rate of 1.2 x 10 3 sec -1 The values ​​are those measured at .

[0033] The acid value of the acid-modified polypropylene resin (b-1) is preferably 0.1 to 100 mgKOH / g, more preferably 1 to 50 mgKOH / g. When the acid value of the acid-modified polypropylene resin (b-1) is within the above range, the interfacial adhesion between the r-CF (A) and the thermoplastic resin (B) can be improved without causing aggregation of the r-CF (A). The acid value in the present invention is a value measured in accordance with JIS K-0070.

[0034] From the viewpoint of achieving both tensile strength and deflection temperature under load, the amount of the acid-modified polypropylene resin (b-1) is preferably 1 to 40 mass%, more preferably 1 to 30 mass%, and even more preferably 5 to 20 mass%, based on 100 mass% of the thermoplastic resin composition. When the amount of the acid-modified polypropylene resin (b-1) is within this range, the interfacial adhesion between the r-CF (A) and the thermoplastic resin (B) can be improved, and the occurrence of deposits at the die tip can be further suppressed.

[0035] The amount of the acid-modified polypropylene resin (b-1) is preferably 3 to 80 parts by mass, more preferably 5 to 75 parts by mass, and particularly preferably 10 to 40 parts by mass, relative to 100 parts by mass of the polyolefin resin. When the amount of the acid-modified polypropylene resin (b-1) relative to the polyolefin resin is within the above range, both strength and deflection temperature under load can be achieved.

[0036] Specific examples of the acid-modified polypropylene resin (b-1) include Admer QB550 (manufactured by Mitsui Chemicals, Inc., melt viscosity 200 MPa·s, acid value 2.3 mgKOH / g) and Modic P-908 (manufactured by Mitsubishi Chemical Corporation, melt viscosity 150 MPa·s, acid value: 12.8 mgKOH / g). The acid value of the acid-modified polypropylene resin (b-1) can be determined by measurement in accordance with JIS K-0070.

[0037] [Thermoplastic elastomer (b-2)] The thermoplastic elastomer (b-2) is blended to improve the adhesion between the r-CF (A) and the thermoplastic resin (B). The thermoplastic elastomer (b-2) can be classified into acid-modified thermoplastic elastomers (b-2x) and non-acid-modified thermoplastic elastomers (b-2y). In order to further enhance the adhesion to the r-CF (A), it is preferable to use an acid-modified thermoplastic elastomer (b-2x). 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 incorporating r-CF (A), a polyolefin resin as the thermoplastic resin (B), and the thermoplastic elastomer (b-2), compatibility is significantly improved, making it possible to produce 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] The acid value of the acid-modified thermoplastic elastomer (b-2x) 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-2x) 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.

[0039] 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).

[0040] 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.

[0041] Commercially available acid-modified thermoplastic elastomers (b-2x) include maleic anhydride-modified isoprene rubbers such as LIR-403 (manufactured by Kuraray Co., Ltd.); modified isoprene rubbers such as LIR-410 (manufactured by Kuraray Co., Ltd.); carboxy-modified nitrile rubbers such as Krynac 110, 221, and 231 (manufactured by Polycer Corporation); maleic anhydride-modified polybutenes such as Nisseki Polybutene (manufactured by Nippon Oil Corporation); ethylene methacrylic acid copolymers such as Nucrel (manufactured by DuPont-Mitsui Polychemicals Co., Ltd.); ethylene methacrylic acid copolymers such as Yukalon (manufactured by Mitsubishi Chemical Corporation); maleic anhydride-modified ethylene-propylene rubbers such as Tafmer M (MA8510 (manufactured by Mitsui Chemicals Co., Ltd.) and TX-1215 (manufactured by Mitsui Chemicals Co., Ltd.); and maleic anhydride-modified ethylene-propylene rubbers such as Tafmer M (MH7020 (manufactured by Mitsui Chemicals Co., Ltd.)). Examples of suitable rubbers include ethylene-butene rubber, maleic anhydride-modified polyethylenes such as the HPR series (maleic anhydride-modified EEA manufactured by DuPont-Mitsui Polychemicals), Bondine (maleic anhydride-modified EEA manufactured by Atofina), Tuftec (maleic anhydride-modified SEBS, M1943 manufactured by Asahi Kasei), Kraton (maleic anhydride-modified SEBS, FG1901X manufactured by Kraton Polymers), Tufprene (maleic anhydride-modified SBS, 912 manufactured by Asahi Kasei), Septon (maleic anhydride-modified SEPS manufactured by Kuraray), Rexpearl (maleic anhydride-modified EEA, ET-182G, 224M, 234M manufactured by Japan Polyolefins), and Aurouren (maleic anhydride-modified EEA, 200S, 250S manufactured by Nippon Paper Chemicals).

[0042] Commercially available non-acid-modified thermoplastic elastomers (b-2y) include, for example, ethylene methacrylic acid copolymers such as Nucrel (manufactured by DuPont-Mitsui Polychemicals); ethylene methacrylic acid copolymers such as Yukalon (manufactured by Mitsubishi Chemical Corporation); α-olefin copolymers such as Tufmer (manufactured by Mitsui Chemicals); SEBS such as Tuftec (manufactured by Asahi Kasei Corporation); SBS such as Tufprene (manufactured by Asahi Kasei Corporation); SEPS such as Septon (manufactured by Kuraray Co., Ltd.); and EEA such as Rexpearl (manufactured by Japan Polyolefins Co., Ltd.).

[0043] A particularly suitable example of the acid-modified thermoplastic elastomer (b-2x) is a maleic anhydride-modified styrene-ethylene-butadiene-styrene copolymer. Commercially available acid-modified styrene-ethylene-butylene-styrene block copolymers include Asahi Kasei Chemicals' Tuftec M1911 (acid value 2 mg CHONa / g, MFR 4.5 g / 10 min), Asahi Kasei Chemicals' Tuftec M1913 (acid value 10 mg CHONa / g, MFR 5.0 g / 10 min), and Asahi Kasei Chemicals' Tuftec M1943 (acid value 10 mg CHONa / g, MFR 8.0 g / 10 min).

[0044] The thermoplastic elastomer (b-2) can increase the impact strength of the resulting r-CFRP, and therefore 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 thermoplastic elastomer (b-2) is not particularly limited, and any elastomer that does not break can be suitably used.

[0045] The average MFR of the thermoplastic elastomer (b-2) is preferably 1.0 g / 10 min or more, more preferably 5.0 g / 10 min or more. When the average MFR of the thermoplastic elastomer (b-2) 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.

[0046] The amount of thermoplastic elastomer (b-2) added 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.

[0047] The blending amount of the thermoplastic elastomer (b-2) is preferably 3 to 30 mass %, more preferably 5 to 25 mass %, and even more preferably 7 to 20 mass %, based on 100 mass % of the thermoplastic resin (B). When the blending amount of the thermoplastic elastomer (b-2) in the thermoplastic resin (B) is within the above range, both impact strength and deflection temperature under load can be achieved.

[0048] When the composition contains an acid-modified polypropylene (b-1) and a thermoplastic elastomer (b-2) having a melting point of 130°C or higher, the total content of the acid-modified polypropylene (b-1) and the thermoplastic elastomer (b-2) having a melting point of 130°C or higher is preferably 3 to 30 parts by mass, more preferably 5 to 25 parts by mass, and even more preferably 7 to 20 parts by mass, per 100 parts by mass of the polyolefin resin having a melting point of 100°C or higher, since high physical properties can be achieved in terms of strength, impact strength, and deflection temperature under load.

[0049] When the resin composition contains an acid-modified polypropylene (b-1) and a thermoplastic elastomer (b-2) each having a melting point of 130°C or higher, the amount of the acid-modified polypropylene (b-1) is preferably 3 to 30% by mass, more preferably 5 to 25% by mass, and even more preferably 7 to 20% by mass, based on 100% by mass of the thermoplastic resin (B), because high physical properties can be achieved in terms of strength, impact strength, and deflection temperature under load. In this case, the amount of the thermoplastic elastomer (b-2) is preferably 3 to 25% by mass, more preferably 5 to 20% by mass, and even more preferably 7 to 15% by mass.

[0050] <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.

[0051] <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.

[0052] 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.

[0053] 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 to dilute the masterbatch during molding can be one 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), so it can be stably molded even when it is made into a high-concentration resin composition such as a masterbatch.

[0054] 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.

[0055] <<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]

[0056] 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.

[0057] 《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 acceleration voltage of 15 kV and a field magnification of 3000 times. 2) Measurement of diffraction intensities I1 (2θ = 25°) and I2 (2θ = 44°) of r-CF(A), etc. Using XRD (X-ray Diometer) with Cu-Kα as the radiation source, the diffraction intensities of pulverized and powdered r-CF in the range of 5° < 2θ < 110° were measured. 3) Measurement of the bulk density of r-CF(A), etc. The bulk density of r-CF(A), etc. was measured in accordance with JIS K5101. 4) Measurement of the MFR of thermoplastic resin (B), etc. The MFR of thermoplastic resin (B), etc. was measured in accordance with JIS K7210-1. 5) Measurement of the melt viscosity of acid-modified polypropylene (b-1) In accordance with JIS K7199:1999, the melt viscosity of acid-modified polypropylene (b-1) was measured at 220 °C and a shear rate of 1.2×10 3 sec <00​​​​​​​​​​​​​​​​​​​ <<Manufacturing Example 2>> The recycled carbon fiber r-CFB according to Manufacturing Example 2 was obtained in the same manner as in Manufacturing Example 1, except that the CFRP derived from aircraft end materials was changed to CFRP derived from automotive part waste materials.

[0060] <<Manufacturing Example 3>> The recycled carbon fiber r-CFC according to Manufacturing Example 3 was obtained using the same materials and manufacturing method as in Manufacturing 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.

[0061] <<Raw Materials>> <00​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​b-1-II: UMEX 1001 (manufactured by Sanyo Chemical Industries, Ltd., melt viscosity 1 MPa·s, acid value 26 mgKOH / g, melting point: 142°C) [Thermoplastic elastomer (b-2), etc.] b-2x-I: Acid-modified SEBS, Tuftec M1943 (manufactured by Asahi Kasei Chemicals Corporation, acid value 10 mg CH3ONa / g, MFR 8.0 g / 10 min) b-2y-II: SEBS, Tuftec H1221 (Asahi Kasei Chemicals Corporation, MFR 5.0 g / 10 min, not acid-modified) b-2x-III: Acid-modified ethylene-propylene rubber, Tafmer MP0610 (Mitsui Chemicals, MFR 0.6 g / 10 min) b-2y-IV: Ethylene-propylene rubber, Tafmer DF640 (Mitsui Chemicals, MFR 3.6 g / 10 min, not acid-modified)

[0062] <Production of Thermoplastic Resin Composition> Example 1 10 parts by mass of A-1 as r-CF (A), 87 parts by mass of polyolefin resin (B-1) as thermoplastic resin (B), and 3 parts by mass of acid-modified polypropylene (b-1-I) were extruded at 280°C using 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).

[0063] (Examples 2 to 33, Reference Examples 1 and 2, 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 Tables 1 and 2. Tables 3 and 4 show the physical properties of the r-CF (A) and thermoplastic resin (B) in each example.

[0064] [Table 1]

[0065] [Table 2]

[0066] [Table 3]

[0067] [Table 4]

[0068] <Evaluation of Thermoplastic Resin Composition> The thermoplastic resin compositions according to the respective Examples were evaluated as follows. The results are shown in Tables 5 and 6. 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.

[0069] <Production of Molded Product> The thermoplastic resin compositions of each example were molded using an injection molding machine (manufactured by Toshiba Machine Co., Ltd.) to obtain A1 type dumbbell test pieces and B2 type strip test pieces in accordance with JIS K7139:2019.

[0070] <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 tensile strength The tensile strength of the obtained dumbbell-shaped test pieces of each example was measured in accordance with JIS K7161-1:2014. The higher the measured value, the better the tensile strength. The evaluation criteria for strength were as follows: +++: 80 MPa or more. Excellent. ++: 60MPa or more, less than 80MPa. Good. +: 40MPa or more, less than 60MPa. Practical range. NG: Less than 40 MPa. Poor. For applications requiring high strength, such as automobile parts, the tensile strength is preferably 60 MPa or more.

[0071] δ) 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.

[0072] ε) 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 / m 2Less 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.

[0073] ζ) Evaluation of heat deflection temperature (HDT) The deflection temperature under load was measured using the obtained rectangular test pieces of each Example, etc. in accordance with JIS K7191-2:2015. The evaluation criteria were as follows: +++: 140℃ or higher. Excellent. ++: 120℃ or higher, but lower than 140℃. Good. +: 100℃ or higher, but lower than 120℃. Practical range. NG: Less than 100°C. For applications requiring high heat resistance, such as automobile parts, a deflection temperature under load of 120°C or higher is preferred.

[0074] [Table 5]

[0075] [Table 6]

[0076] Molded articles formed from a thermoplastic resin composition combining r-CF (A) having an oxygen content of 5.0 mass% or more, a polyolefin resin, and at least one of acid-modified polypropylene (b-1) and a thermoplastic elastomer (b-2) having a melting point of 130°C or more, are excellent in productivity and in tensile strength, elastic modulus, impact strength, and deflection temperature under load, as shown in the examples in Tables 5 and 6. It was confirmed that these molded articles exhibit excellent effects equivalent to those of the molded article of Reference Example 1 formed from a thermoplastic resin composition combining CF and a thermoplastic resin (B).

Claims

1. A thermoplastic resin composition for carbon fiber reinforcement containing recycled carbon fibers (A) and a thermoplastic resin (B), The oxygen content in the recycled carbon fiber (A) is 5.0% by mass or more, The thermoplastic resin (B) includes a polyolefin resin having a melting point of 100°C or higher (excluding acid-modified thermoplastic resins), and an acid-modified polypropylene (b-1) or a thermoplastic elastomer (b-2) having a melting point of 130°C or higher, In 100% by mass of the thermoplastic resin composition, 10 to 50 mass% of recycled carbon fiber (A), 40 to 87% by mass of a polyolefin resin (excluding acid-modified thermoplastic resins) having a melting point of 100°C or higher, A thermoplastic resin composition containing 3 to 30 mass % of an acid-modified polypropylene (b-1) or a thermoplastic elastomer (b-2). (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.)

2. The acid-modified polypropylene (b-1) was subjected to a shear rate of 1.2×10 at 220°C. ３ sec －１ 2. The thermoplastic resin composition according to claim 1, wherein the melt viscosity ηc is 10 to 500 Pa·s.

3. 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 3. The thermoplastic resin composition according to claim 1, wherein the tensile strength is less than 6.

4. The bulk density of the recycled carbon fiber (A) is 0.03 to 1.0 g / cm ３ 4. The thermoplastic resin composition according to claim 1, wherein (However, the bulk density is a value obtained in accordance with JIS K5101.)

5. 5. The thermoplastic resin composition according to claim 1, wherein the polyolefin resin having a melting point of 100° C. or higher is a homopolymer of polypropylene.

6. The thermoplastic resin composition according to any one of claims 1 to 5, wherein the thermoplastic resin (B) comprises an acid-modified polypropylene (b-1) having a melting point of 130°C or higher and a thermoplastic elastomer (b-2).

7. A molded article obtained by molding the thermoplastic resin composition according to any one of claims 1 to 6.

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