Thermoplastic resin composition, method for producing thermoplastic resin composition, and molded body

Abstract

Provided is a thermoplastic resin composition which provides a molded body having excellent thermal conductivity and excellent mechanical characteristics. A thermoplastic resin composition which contains (A) a thermoplastic resin, (B) pitch carbon fibers and (C) graphite, and wherein: the content of the graphite (C) is from 1% by mass to 20% by mass (inclusive) relative to 100% by mass of the thermoplastic resin composition; and a molded body, which is obtained by molding this thermoplastic resin composition and has a thickness of 1 mm, has a thermal conductivity of 10 W/mK or more as determined by a hot wire method.

Claims

1. A method for producing a thermoplastic resin composition, comprising feeding a pitch-based carbon fiber (B) having a mass average fiber length of 2 mm or longer and 20 mm or shorter to a thermoplastic resin (A) in a molten state, wherein the thermoplastic resin composition comprises: the thermoplastic resin (A); the pitch-based carbon fiber (B); graphite (C); and a PAN-based carbon fiber (D), wherein the thermoplastic resin (A) is a polyamide resin, a content of the thermoplastic resin (A) is 39% by mass or more and 69% by mass or less with respect to 100% by mass of the thermoplastic resin composition, a content of the pitch-based carbon fiber (B) is 30% by mass or more with respect to 100% by mass of the thermoplastic resin composition, a mass average fiber length of the pitch-based carbon fiber (B) in the thermoplastic resin composition is 0.1 mm or longer and 0.3 mm or shorter, a content of the graphite (C) is 1% by mass or more and 20% by mass or less with respect to 100% by mass of the thermoplastic resin composition, a mass average fiber length of the PAN-based carbon fiber (D) in the thermoplastic resin composition is 0.1 mm or longer and 0.9 mm or shorter, a content of the PAN-based carbon fiber (D) is 1% by mass or more and 30% by mass or less with respect to 100% by mass of the thermoplastic resin composition, and the only resin in the thermoplastic composition is the thermoplastic resin (A).

2. The method according to claim 1, wherein the content of the graphite (C) is 2% by mass or more and 12% by mass or less with respect to 100% by mass of the thermoplastic resin composition.

3. The method according claim 1, wherein a thermal conductivity of the pitch-based carbon fiber (B) is 400 W/mK or less.

4. The method according to claim 1, wherein the thermoplastic resin is poly(m-xylene adipamide).

5. The method according to claim 1, wherein a thermal conductivity of a molded body which is obtained by molding the thermoplastic resin composition and which has a thickness of 1 mm as measured by a hot wire method is 10 W/mK or more.

6. The method according to claim 1, wherein a tensile strength of a molded body obtained by molding the thermoplastic resin composition measured in conformity to ISO 527 is 100 MPa or more.

7. A molded body obtained by molding the thermoplastic resin composition obtained by the method according to claim 1.

8. A method for producing a molded body, the method comprising injection-molding the thermoplastic resin composition obtained by the method according to claim 1.

9. The method according to claim 1, wherein the mass average fiber length of the pitch-based carbon fiber (B) in the thermoplastic resin composition is 0.12 mm or longer and 0.2 mm or shorter.

10. The method according to claim 1, wherein the content of the pitch-based carbon fiber (B) is 32% by mass or more and 55% by mass or less with respect to 100% by mass of the thermoplastic resin composition.

11. The method according to claim 1, wherein the content of the pitch-based carbon fiber (B) is 34% by mass or more and 50% by mass or less with respect to 100% by mass of the thermoplastic resin composition.

12. The method according to claim 1, wherein the content of the graphite (C) is 3% by mass or more and 8% by mass or less with respect to 100% by mass of the thermoplastic resin composition.

13. The method according to claim 1, wherein a content of the thermoplastic resin (A) is 43% by mass or more and 65% by mass or less with respect to 100% by mass of the thermoplastic resin composition.

14. The method according to claim 1, wherein a content of the thermoplastic resin (A) is 47% by mass or more and 61% by mass or less with respect to 100% by mass of the thermoplastic resin composition.

15. The method according to claim 1, wherein a diameter of the pitch-based carbon fiber (B) is 4 μm or more and 15 μm or less.

16. The method according to claim 1, wherein a diameter of the pitch-based carbon fiber (B) is 8 μm or more and 12 μm or less.

17. The method according to claim 1, wherein the polyamide comprises is one selected from the group consisting of nylon 6, nylon 66, nylon 69, nylon 610, nylon 612, nylon 46, nylon 11, nylon 12, poly(hexamethylene terephthalamide), and poly(hexamethylene isophthalamide).

Description

EXAMPLES

(1) Hereinafter, the invention will be specifically described with reference to Examples, but the invention is not limited to these Examples.

(2) (Measurement of Thermal Conductivity)

(3) The thermoplastic resin compositions obtained in Examples and Comparative Examples were injection-molded under the conditions of a cylinder temperature of 300° C. and a mold temperature of 80° C. using an injection molding machine (model name “IS55” manufactured by TOSHIBA MACHINE CO., LTD.) to obtain molded bodies (width: 100 mm, length: 100 mm, thickness: 1 mm).

(4) The molded body thus obtained and the box type probe were superposed on a reference plate having a known thermal conductivity in this order such that the fine wire which was a heat source of the box type probe was orthogonal to the flow direction of the molded body in injection molding, and the measurement was conducted using a rapid thermal conductivity meter (model name “QTM-500” manufactured by KYOTO ELECTRONICS MANUFACTURING CO., LTD.).

(5) The thermal conductivity of the molded body was calculated by interpolating the results obtained when the measurement was conducted using a plurality of reference plates so that the difference from the reference plate became zero.

(6) (Measurement of Melt Volume Rate (MVR))

(7) The melt volume rate (MVR) of the thermoplastic resin compositions obtained in Examples and Comparative Examples was measured in conformity to ISO 1133-1 using a melt flow index tester (model name “LABO-MI” manufactured by YASUDA SEIKI SEISAKUSHO, LTD.).

(8) Incidentally, the melt volume rate was measured at 300° C. and 21 N for a thermoplastic resin composition using a thermoplastic resin (A-1) which was a polyamide resin, at 330° C. and 21 N for a thermoplastic resin composition using a thermoplastic resin (A-2) which was a polyphenylene sulfide resin, and at 230° C. and 21 N for a thermoplastic resin composition using a thermoplastic resin (A-3) which was a polypropylene resin.

(9) (Measurement of Flexural Strength and Flexural Modulus of Elasticity)

(10) The thermoplastic resin compositions obtained in Examples and Comparative Examples were injection-molded under the conditions of a cylinder temperature of 300° C. and a mold temperature of 80° C. using an injection molding machine (model name “IS55” manufactured by TOSHIBA MACHINE CO., LTD.) to obtain molded bodies (width: 10 mm, length: 80 mm, thickness: 4 mm). The molded bodies thus obtained were subjected to a three-point bending test in conformity to ISO 178 to measure the flexural strength and flexural modulus of elasticity.

(11) (Measurement of Charpy Impact Strength)

(12) The thermoplastic resin compositions obtained in Examples and Comparative Examples were injection-molded under the conditions of a cylinder temperature of 300° C. and a mold temperature of 80° C. using an injection molding machine (model name “IS55” manufactured by TOSHIBA MACHINE CO., LTD.) to obtain molded bodies (width: 10 mm, length: 80 mm, thickness: 4 mm). The molded bodies thus obtained were subjected to a Charpy impact test in conformity to ISO 179 to measure the Charpy impact strength of the molded bodies without a notch. In addition, a V notch was imparted to the molded bodies thus obtained, and the molded bodies were subjected to a Charpy impact test in conformity to ISO 179 to measure the Charpy impact strength of the molded bodies with a notch.

(13) (Measurement of Tensile Strength)

(14) The thermoplastic resin compositions obtained in Examples and Comparative Examples were injection-molded under the conditions of a cylinder temperature of 300° C. and a mold temperature of 80° C. using an injection molding machine (model name “IS55” manufactured by TOSHIBA MACHINE CO., LTD.) to obtain dumbbell-shaped molded bodies (width: 10 mm, length: 80 mm, thickness: 4 mm). The molded bodies thus obtained were subjected to a tension test in conformity to ISO 527 to measure the tensile strength.

(15) (Measurement of Mass Average Fiber Length)

(16) The thermoplastic resin compositions obtained in Examples and Comparative Examples were heated at 600° C. for 3 hours in an air atmosphere to remove the thermoplastic resin (A) and the like by thermal decomposition, and the fiber length of remaining arbitrary 100 carbon fibers was measured using an optical microscope to calculate the mass average fiber length.

(17) The thermoplastic resin compositions obtained in Examples and Comparative Examples were injection-molded wider the conditions of a cylinder temperature of 300° C. and a mold temperature of 80° C. using an injection molding machine (model name “IS55” manufactured by TOSHIBA MACHINE CO., LTD.) to obtain molded bodies width: 10 mm, length: 80 mm, thickness: 4 mm). The molded bodies thus obtained were heated at 600° C. for 3 hours in an air atmosphere to remove the thermoplastic resin (A) and the like by thermal decomposition, and the fiber length of remaining arbitrary 100 carbon fibers was measured using an optical microscope to calculate the mass average fiber length.

(18) (Raw Materials)

(19) Thermoplastic resin (A-1): a resin composition in which 88% by mass of a polyamide resin (poly(m-xylene adipamide) (trade name “MX nylon 6007” manufactured by MITSUBISHI GAS CHEMICAL COMPANY, INC.), 10% by mass of nylon 66 (trade name “E2000SL-1” manufactured by UNITIKA LTD.), and 2% by mass of other additives (including a release agent, a nucleating agent, and carbon black) are blended.

(20) Thermoplastic resin (A-2): polyphenylene sulfide resin (trade name “DSP C-115” crosslinked polyphenylene sulfide resin manufactured by DIC Corporation)

(21) Thermoplastic Resin (A-3): a resin composition in which 95% of a polypropylene resin (trade name “NOVATEC-PP MA04A” manufactured by Japan Polypropylene Corporation) and 5% of a modified polypropylene resin (trade name “UMEX 1001” manufactured by Sanyo Chemical Industries, Ltd.) are blended.

(22) Thermoplastic resin (A-4): polybutylene terephthalate resin (trade name “NOVADURAN 5008” manufactured by Mitsubishi Engineering-Plastics Corporation)

(23) Thermoplastic resin (A-5): a resin composition in which 75.9% by mass of a polycarbonate resin (trade name “NOVAREX. 7020IR” manufactured by Mitsubishi Engineering-Plastics Corporation), 19.0% by mass of a polybutylene terephthalate resin (trade name “NOVADURAN 5008” manufactured by Mitsubishi Engineering-Plastics Corporation), 4.7% by mass of an impact modifier (trade name “METABLEN S2006” manufactured by Mitsubishi Rayon Co., Ltd.), and 0.4% by mass of an antioxidant are blended.

(24) Pitch-based carbon fiber (B-1): pitch-based carbon fiber (trade name “DIALEAD K6371T” manufactured by Mitsubishi Plastics, Inc., fiber length: 6 mm, thermal conductivity: 140 W/mK, tensile modulus of elasticity: 640 GPa, tensile strength: 2600 MPa)

(25) Pitch-based carbon fiber (B-2): pitch-based carbon fiber (trade name “DIALEAD K223HE” manufactured by Mitsubishi Plastics, Inc., fiber length: 6 mm, thermal conductivity: 550 W/mK, tensile modulus of elasticity: 900 GPa, tensile strength: 3800 MPa)

(26) Pitch-based carbon fiber (B-3): pitch-based carbon fiber (trade name “DIALEAD K237SE” manufactured by Mitsubishi Plastics, Inc., fiber length: 6 mm, thermal conductivity: 140 W/mK, tensile modulus of elasticity: 640 GPa, tensile strength: 2600 MPa)

(27) Graphite (C-1): expanded graphite (trade name “GRAFOIL Powder GFP-100” manufactured by GrafTech International LID, pulverized product of expanded graphite sheet, average particle diameter: 0.1 mm)

(28) PAN-based carbon fiber (D-1): (trade name “PYROFIL TR06NL” manufactured by Mitsubishi Rayon Co., Ltd., fiber length: 6 mm, tensile modulus of elasticity: 230 GPa or more, tensile strength: 3720 MPa or more)

(29) PAN-based carbon fiber (D-2): (trade name “PYROFIL TR06UL” manufactured by Mitsubishi Rayon Co., Ltd., fiber length: 6 mm, tensile modulus of elasticity: 230 GPa or more, tensile strength: 3720 MPa or more)

Example 1

(30) Using a co-rotating twin screw extruder (model name “TEX44αII” manufactured by The Japan Steel Works, LTD.) having a main raw material feeder and a side feeder, 60 parts by mass of the thermoplastic resin (A-1), 35 parts by mass of the pitch-based carbon fiber (B-1), and 5 parts by mass of the graphite (C-1) were melt-kneaded to obtain a thermoplastic resin composition. The evaluation results are presented in Table 2.

Examples 2 to 7 and Comparative Examples 1 to 4

(31) Thermoplastic resin compositions were obtained by conducting the operation in the same manner as in Example 1 except that the composition was changed as presented in Table 1. The evaluation results are presented in Table 2.

(32) Incidentally, in all Examples and Comparative Examples of Examples 1 to 7 and Comparative Examples 1 to 4, the feeders of the extruder were installed such that the main raw material feeder, the side feeder 1, and the side feeder 2 were disposed from the upstream side, and the zones were disposed at four places in total, namely, at two places between the main raw material feeder and the side feeder 1, one place between the side feeder 1 and the side feeder 2, and one place between the side feeder 2 and the die.

(33) In addition, in all Examples and Comparative Examples of Examples 1 to 7 and Comparative Examples 1 to 4, the extrusion conditions were set to have a screw rotation number of 200 rpm and a discharge rate of 80 kg/hour. The cylinder temperature was set to 300° C. when the thermoplastic resin (A) was a polyamide resin and 330° C. when the thermoplastic resin (A) was a polyphenylene sulfide resin.

(34) Furthermore, in all Examples and Comparative Examples of Examples 1 to 7 and Comparative Examples 1 to 4, the thermoplastic resin (A) and the graphite (C) were fed through the main raw material feeder, the pitch-based carbon fiber (B) was fed through the side feeder 2, and the PAN-based carbon fiber (D) was fed through the side feeder 1.

Example 8

(35) Using a co-rotating twin screw extruder (model name “PCM-30” manufactured by Ikegai Corp) having a main raw material feeder and a side feeder, 50 parts by mass of the thermoplastic resin (A-4), 35 parts by mass of the pitch-based carbon fiber (B-3), and 5 parts by mass of the graphite (C-1) were melt-kneaded to obtain a pellet, meanwhile, 50 parts by mass of the thermoplastic resin (A-4), 10 parts by mass of the PAN-based carbon fiber (D-2), and 5 parts by mass of the graphite (C-1) were melt-kneaded to obtain a pellet, and these two kinds of pellets were dry blended at a ratio of 7:2 to obtain a thermoplastic resin composition.

Example 9

(36) Using a co-rotating twin screw extruder (model name “PCM-30” manufactured by Ikegai Corp) having a main raw material feeder and a side feeder, 50 parts by mass of the thermoplastic resin (A-5), 35 parts by mass of the pitch-based carbon fiber (B-3), and 5 parts by mass of the graphite (C-1) were melt-kneaded to obtain a pellet, meanwhile, 50 parts by mass of the thermoplastic resin (A-5), 10 parts by mass of the PAN-based carbon fiber (D-2), and 5 parts by mass of the graphite (C-1) were melt-kneaded to obtain a pellet, and these two kinds of pellets were dry blended at a ratio of 7:2 to obtain a thermoplastic resin composition.

Example 10

(37) Using a co-rotating twin screw extruder (model name “PCM-30” manufactured by Ikegai Corp) having a main raw material feeder and a side feeder, 50 parts by mass of the thermoplastic resin (A-2), 35 parts by mass of the pitch-based carbon fiber (B-3), and 5 parts by mass of the graphite (C-1) were melt-kneaded to obtain a pellet, meanwhile, 50 parts by mass of the thermoplastic resin (A-2), 10 parts by mass of the PAN-based carbon fiber (D-1), and 5 parts by mass of the graphite (C-1) were melt-kneaded to obtain a pellet, and these two kinds of pellets were dry blended at a ratio of 7:2 to obtain a thermoplastic resin composition.

(38) Incidentally, in all Examples of Examples 8 to 10, the feeders of the extruder were installed such that the main raw material feeder and the side feeder were disposed from the upstream side, and the kneading zones were disposed at three places in total, namely, at two places between the main raw material feeder and the side feeder and one place between the side feeder and the die.

(39) In addition, in all Examples, the extrusion conditions were set to have a screw rotation number of 200 rpm and a discharge rate of 15 kg/hour. The cylinder temperature was set to 250° C. when the thermoplastic resin (A) was the polybutylene terephthalate resin (A-4) and 270° C. when the thermoplastic resin (A) was the polycarbonate/polybutylene terephthalate alloy resin (A-5).

(40) Furthermore, in all Examples, the thermoplastic resin (A) and the graphite (C) were fed through the main raw material feeder and the pitch-based carbon fiber (B) and the PAN-based carbon fiber (D) were fed through the side feeder.

(41) TABLE-US-00001 TABLE 1 Thermoplastic resin (A) Pitch-based carbon fiber (B) Graphite (C) PAN-based carbon fiber (D) Content rate Content rate Content rate Content rate Kind (% by mass) Kind (% by mass) Kind (% by mass) Kind (% by mass) Example 1 (A-1) 60 (B-1) 35 (C-1) 5 — — Example 2 (A-1) 50 (B-1) 45 (C-1) 5 — — Example 3 (A-1) 60 (B-2) 35 (C-1) 5 — — Example 4 (A-1) 50 (B-2) 45 (C-1) 5 — — Example 5 (A-2) 60 (B-1) 35 (C-1) 5 — — Example 6 (A-1) 50 (B-3) 35 (C-1) 5 (D-1) 10 Example 7 (A-3) 50 (B-3) 35 (C-1) 5 (D-2) 10 Example 8 (A-4) 50 (B-3) 35 (C-1) 5 (D-2) 10 Example 9 (A-5) 50 (B-3) 35 (C-1) 5 (D-2) 10 Example 10 (A-2) 50 (B-3) 35 (C-1) 5 (D-1) 10 Comparative (A-1) 70 (B-1) 25 (C-1) 5 — — Example 1 Comparative (A-2) 60 — — (C-1) 5 (D-1) 35 Example 2 Comparative (A-2) 70 (B-2) 30 — — — — Example 3 Comparative (A-1) 25 (B-3) 35 (C-1) 40 — — Example 4

(42) TABLE-US-00002 TABLE 2 Evaluation results Mass average fiber length (mm) of pitch-based Mass average Flexural Charpy Charpy impact carbon fiber length modulus impact strength fiber (B) in (mm) of pitch- Thermal Flexural of strength (kJ/m.sup.2) when Tensile thermoplastic based carbon conductivity MVR strength elasticity (kJ/m.sup.2) when not having strength resin fiber (B) in (W/mK) (cm.sup.3/10 min) (MPa) (GPa) having notch notch (MPa) composition molded body Example 1 13.8 8.6 231 31.9 3.7 19 165 0.172 0.158 Example 2 12.2 7.4 237 35.4 3.9 19 164 0.162 0.133 Example 3 25.6 12.7 164 32.1 3.2 12 116 0.152 0.113 Example 4 26.0 7.0 180 39.4 3.1 10 119 0.143 0.126 Example 5 16.9 17.0 174 29.6 2.4 11 118 — — Example 6 15.8 10.4 261 38.7 4.2 18 170 — — Example 7 12.3 4.6 127 21.7 4.7 18 80 — — Example 8 16.8 — 140 29.0 3.2 14 78 — — Example 9 16.7 — 164 28.1 4.1 16 106 — — Example 10 17.5 — 180 34.2 2.7 10 128 — — Comparative 6.5 10.0 204 23.2 3.7 20 159 0.184 0.165 Example 1 Comparative 4.8 0.9 275 33.4 6.5 19 164 — — Example 2 Comparative 7.3 17.5 150 28.3 2.6 8 99 — — Example 3 Comparative — — — — — — — — — Example 4

(43) The thermoplastic resin compositions obtained in Examples 1 to 10 exhibited excellent moldability and molded bodies thereof exhibited excellent mechanical properties and thermal conductivity.

(44) On the other hand, the thermoplastic resin composition obtained in Comparative Example 1 had a low content rate of the pitch-based carbon fiber (B) and a molded body thereof exhibited poor thermal conductivity. In addition, the thermoplastic resin composition obtained in Comparative Example 2 exhibited poor moldability since a PAN-based carbon fiber was used therein instead of the pitch-based carbon fiber (B), and a molded body thereof exhibited poor thermal conductivity. Furthermore, the graphite (C) was not used in the thermoplastic resin composition obtained in Comparative Example 3 and a molded body of the thermoplastic resin composition thus exhibited poor thermal conductivity. In Comparative Example 4, feeding failure occurred in the feeder since the graphite (C) was bulky, and a thermoplastic resin composition was not obtained.

INDUSTRIAL APPLICABILITY

(45) The invention can provide a thermoplastic resin composition which provides a molded body exhibiting excellent thermal conductivity and mechanical properties.