Resin composition and molded article thereof

Abstract

To provide a resin composition capable of obtaining a molded article that is lightweight, and has a small mechanical property change depending on molding conditions.SOLUTION: There is provided a resin composition that comprises: (A) a thermoplastic resin and (B) reinforcing fibers, in which reinforcing fibers of the component (B) contain (B-1) organic fibers and (B-2) carbon fibers, and do not contain glass fibers, polyethylene terephthalate fibers and polyethylene naphthalate fibers; a content ratio of the component (A) is 40 to 95 mass%, and a content ratio of the component (B) is 60 to 5 mass% in a total of 100 mass% of the components (A) and (B); a volume ratio of the component (B-1) is 10 to 99% in a total volume of 100% of the reinforcing fibers of the component (B); and a specific gravity of the resin composition is 0.95 to 1.20.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a resin composition from which a molded article that is lightweight and exhibits little change in mechanical properties depending on molding conditions can be obtained, and to a molded article made from the resin composition. [Background technology]

[0002] Molded products obtained by blending multiple types of fibers with thermoplastic resins or thermosetting resins are used. Patent Document 1 describes an invention related to a fiber-reinforced thermoplastic resin molded product containing carbon fiber, organic fiber, and a thermoplastic resin, which is suitable for automotive parts such as instrument panels, door beams, undercovers, lamp housings, pedal housings, radiator supports, spare tire covers, front end modules, etc. It also describes applications for the product in parts for home and office electrical appliances such as telephones, facsimiles, VTRs, copy machines, televisions, microwave ovens, audio equipment, toiletries, LaserDiscs (registered trademark), refrigerators, and air conditioners, as well as housings for personal computers and mobile phones, and components for electrical and electronic devices such as keyboard supports that support keyboards inside personal computers. As the organic fibers, fibers obtained by spinning polyolefin resins such as polyethylene and polypropylene, polyamide resins such as nylon 6, nylon 66 and aromatic polyamide, polyester resins such as polyethylene terephthalate and polybutylene terephthalate, and resins such as polyether ketone, polyether sulfone, polyarylene sulfide and liquid crystal polyester are described.

[0003] Patent Document 2 describes an invention of a fiber-reinforced plastic for automotive components that contains fibers including natural fibers and glass fibers and a thermoplastic resin, and states that the content of natural fibers in the fibers is 30 to 70% by weight. Examples of natural fibers include bast fibers such as ramie, kenaf, linen, hemp, and jute; vein fibers such as Manila hemp, sisal hemp, and pineapple; petiole fibers such as Manila hemp and banana; fruit fibers such as coconut; and seed hair fibers such as cotton and kapok.

[0004] Patent Document 3 describes an invention of a long fiber reinforced composite resin composition containing a propylene-based resin, long organic fibers, and carbon fibers, and describes applications for the composition in vehicles, construction and civil engineering, machine parts, electronic parts, etc. As organic long fibers, polyester fibers, polyamide fibers, polyurethane fibers, polyacrylonitrile fibers, kenaf, and cellulose fibers are described. Among these, polyester fibers or polyamide fibers are preferred from the viewpoints of handling / processability and mechanical properties, and polyethylene terephthalate (PET) fibers (melting point 260°C, glass transition temperature 67°C) and polyethylene naphthalate (PEN) fibers (melting point 272°C, glass transition temperature 113°C) are described as being particularly preferred. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 5633660 [Patent Document 2] Patent No. 5589465 [Patent Document 3] Patent No. 5238939 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present disclosure is to provide a resin composition from which a molded article can be obtained that is lightweight and exhibits little change in mechanical properties (tensile strength) depending on molding conditions, and to provide a molded article made from the resin composition. [Means for solving the problem]

[0007] The present disclosure provides a thermoplastic resin composition comprising (A) a thermoplastic resin and (B) reinforcing fibers, the reinforcing fibers of the component (B) contain (B-1) organic fibers and (B-2) carbon fibers, but do not contain glass fibers, polyethylene terephthalate fibers, or polyethylene naphthalate fibers; The content of component (A) is 40 to 95 mass% and the content of component (B) is 60 to 5 mass% out of a total of 100 mass% of component (A) and component (B), The volume ratio of the (B-1) component is 10 to 99% of the total volume of the reinforcing fibers of the (B) component, 100%; The present invention provides a resin composition having a specific gravity of 0.93 to 1.25, and a molded article thereof. [Effects of the Invention]

[0008] Molded articles obtained from the resin composition of the present disclosure are lightweight and show little change in mechanical properties (tensile strength) due to differences in molding conditions. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 2 is a diagram for explaining a method for measuring a molding shrinkage ratio in the examples. DETAILED DESCRIPTION OF THE INVENTION

[0010] <Resin composition> Examples of the thermoplastic resin of component (A) include polyamide resins, olefin resins, styrene resins, polycarbonate resins, polyvinyl chloride, polyvinylidene chloride, polycarbonate resins, acrylic resins, methacrylic resins, polyester resins, polyacetal resins, and polyphenylene sulfide resins.

[0011] The thermoplastic resin of component (A) is preferably selected from polyamide resins and olefin resins. The polyamide resin may be selected from aliphatic polyamides and aromatic polyamides. Examples of aliphatic polyamides include polyamide 6, polyamide 66, polyamide 69, polyamide 610, polyamide 1010, polyamide 612, polyamide 46, polyamide 10, polyamide 11, and polyamide 12. Examples of aromatic polyamides include those obtained from aromatic dicarboxylic acids and aliphatic diamines, or aliphatic dicarboxylic acids and aromatic diamines, such as nylon MXD10 (metaxylylenediamine and sebacic acid), nylon MXD6 (metaxylylenediamine and adipic acid), nylon 6T (hexamethylenediamine and terephthalic acid), nylon 6I (hexamethylenediamine and isophthalic acid), nylon 9T (nonanediamine and terephthalic acid), nylon 5MT (methylpentadiamine and terephthalic acid), and nylon 10T (decamethylenediamine and terephthalic acid). Among these, polyamide 6, polyamide 10, polyamide 11, polyamide 12, polyamide 612, polyamide 610, polyamide 1010, and nylon MXD10, which have a melting point of 250° C. or less, are preferred.

[0012] Examples of polyolefin resins that can be used include polypropylene, high-density, low-density, and linear low-density polyethylene, poly-1-butene, polyisobutylene, copolymers of ethylene and propylene, ethylene-propylene-diene terpolymers (diene components as raw materials are 10% by mass or less), polymethylpentene, random, block, and graft copolymers of ethylene or propylene (50% by mole or more) with other copolymerizable monomers (vinyl acetate, alkyl methacrylate esters, alkyl acrylate esters, aromatic vinyl, etc.), etc. Among these, polypropylene is preferred.

[0013] The reinforcing fibers of the component (B) include (B-1) organic fibers and (B-2) carbon fibers, but do not include glass fibers, polyethylene terephthalate fibers, or polyethylene naphthalate fibers. Glass fibers are not used because when the resin composition and its molded articles are incinerated, combustion residues are generated that must be treated.

[0014] The organic fiber of component (B-1) can be selected from cellulose fiber, aramid fiber, polyphenylene sulfide (PPS) fiber, and polyparaphenylene benzobisoxazole (PBO) fiber, and among these, cellulose fiber is preferred. The cellulose fiber may be a natural product or an industrial product, and may be hemp fiber, bamboo fiber, cotton fiber, wood fiber (such as wood pulp from softwood or hardwood), kenaf fiber, hemp fiber, jute fiber, banana fiber, coconut fiber, or the like.

[0015] The carbon fiber of component (B-2) is The carbon fiber may be made of known polyacrylonitrile, pitch, rayon, or the like.

[0016] The organic fibers of component (B-1) can be made into fiber bundles as needed. When forming a fiber bundle, it is preferable to use a bundle of cellulose fibers bundled in the lengthwise direction, which is impregnated with a thermoplastic resin and integrated into a single bundle (resin-impregnated organic fiber bundle) having a length of 3 to 50 mm. The organic fiber bundle may be a bundle of approximately 1,000 to 30,000 organic fibers. When a resin-impregnated organic layer is used as component (B-1), it also contains a thermoplastic resin, and therefore can be used as a layer containing both component (A) and component (B-1). Even when resin-impregnated cellulose fiber bundles are used as component (B-1), the thermoplastic resin of component (A) can be contained separately from the resin-impregnated organic fiber bundles of component (B-1) in order to adjust the content ratio of the thermoplastic resin of component (A) and the organic fiber of component (B-1).

[0017] The carbon fiber of the component (B-2) is preferably a carbon fiber bundle having a length of 3 to 50 mm, which is obtained by impregnating carbon fiber bundles bound in the lengthwise direction with a thermoplastic resin to integrate them (resin-impregnated carbon fiber bundle). The carbon fiber bundle may be a bundle of approximately 1,000 to 50,000 carbon fibers. When resin-impregnated carbon fiber bundles are used as component (B-2), they also contain a thermoplastic resin, and therefore can be used as a bundle containing both component (A) and component (B-2). Even when resin-impregnated carbon fiber bundles are used as the component (B-2), the thermoplastic resin of the component (A) can be contained separately from the resin-impregnated carbon fiber bundles of the component (B-2) in order to adjust the content ratio of the thermoplastic resin of the component (A) and the carbon fiber of the component (B-2).

[0018] The resin-impregnated organic fiber bundle and the resin-impregnated carbon fiber bundle can be produced by a well-known production method using a die. For example, in addition to paragraph 7 of JP-A-6-313050 and paragraph 23 of JP-A-2007-176227, manufacturing methods described in JP-B-6-2344 (Method for manufacturing and molding resin-coated long fiber bundles), JP-A-6-114832 (Fiber-reinforced thermoplastic resin structures and methods for manufacturing the same), JP-A-6-293023 (Manufacturing methods for long fiber-reinforced thermoplastic resin compositions), JP-A-7-205317 (Method for removing fiber bundles and method for manufacturing long fiber-reinforced resin structures), JP-A-7-216104 (Manufacturing methods for long fiber-reinforced resin structures), JP-A-7-251437 (Manufacturing methods and manufacturing apparatus for long fiber-reinforced thermoplastic composite materials), and JP-A-8-118490 (Manufacturing methods for crosshead dies and long fiber-reinforced resin structures) can be applied. It should be noted that polyethylene terephthalate fibers and polyethylene naphthalate fibers have too low tensile strength at temperatures near the melting point of the thermoplastic resin, so that resin-impregnated fiber bundles cannot be produced by a production method using a die.

[0019] Of the total 100% by mass of component (A) and component (B), The content of component (A) is 40 to 95 mass%, preferably 50 to 90 mass%, and more preferably 60 to 85 mass%, The content of the component (B) is 60 to 5% by mass, preferably 10 to 50% by mass, and more preferably 15 to 40% by mass.

[0020] Of the total volume of the reinforcing fibers of the (B) component (100%), the volume (Vof) of the organic fibers of the (B-1) component is 10 to 99%, preferably 30 to 95%, and the volume (Vcf) of the carbon fibers of the (B-2) component is 90 to 1%, preferably 70 to 5%. The volume ratio is calculated from the following formula: Vof / (Vof+Vcf)×100.

[0021] In addition to the components (A) and (B), the resin composition may contain other known flame retardants, flame retardant auxiliaries, heat stabilizers, lubricants, light stabilizers, antioxidants, colorants, release agents, antistatic agents, and the like, within the scope of the problems of the present disclosure.

[0022] The specific gravity of the resin composition is 0.93 to 1.25, preferably 1.00 to 1.20, and more preferably 1.05 to 1.15, in order to reduce the weight of molded articles obtained from the resin composition.

[0023] <Molded products> The molded article is made of the above-mentioned resin composition, and the shape, size, etc. can be determined depending on the application. The molded article can be produced by a known resin molding method such as injection molding or extrusion molding.

[0024] The molded article has a molding shrinkage ratio (MD / TD) of 0.6 to 1.4, preferably 0.75 to 1.25, and more preferably 0.85 to 1.15. The molding shrinkage ratio is determined by the measurement method described in the Examples, and indicates the ratio of dimensional changes expressed in 1 / 1000.

[0025] When the molded article is an injection molded article, the rate of change between the tensile strength (ISO527-1) (ts1) of an injection molded article molded at a back pressure of 5 MPa and the tensile strength (ISO527-1) (ts2) of an injection molded article molded at a back pressure of 15 MPa, as calculated from the following formula: (ts1-ts2) / ts1×100, is preferably 15% or less, and more preferably 12% or less. The molding conditions were the same except for the back pressure, and the back pressure of 15 MPa was significantly higher than the back pressure under normal molding conditions. Even when the molding conditions are changed (e.g., back pressure of 15 MPa) to a level that far exceeds the normal molding conditions (e.g., back pressure of 5 MPa), the change in the tensile strength of the molded product is small, so molded products of stable quality can be obtained as long as the equipment and operating errors are within the range of normal molding conditions.

[0026] Molded articles obtained from the resin composition of the present disclosure can be used as substitutes for metal materials used in electrical and electronic devices, communication devices, automobile parts, building materials, daily necessities, etc., as well as for shoes (preferably the soles of sports shoes such as running shoes and walking shoes), bicycle saddle parts (preferably the base member of a bicycle saddle), and pedal parts. A bicycle saddle has components including a pad (the part that comes into contact with a person's buttocks when riding), a base (also called a "shell") that is located below the pad, and a metal rail that is also fixed to part of the base and is used to attach the saddle to the bicycle body. Molded products obtained from the resin composition of the present disclosure are suitable as the base member.

[0027] Each feature disclosed herein may be combined with any other feature disclosed herein. The configurations and combinations thereof in each embodiment are merely examples, and additions, omissions, substitutions, and other modifications of the configurations are possible as appropriate within the scope of the gist of the disclosure of the present invention. The present disclosure is not limited by the embodiments, but is limited only by the claims. [Example]

[0028] The components used in the examples and comparative examples are as follows: Polyamide 12: Daiamide L1600 (manufactured by Daicel-Evonik Co., Ltd.) Cellulose fiber bundle: CR500 (manufactured by Cordenka GmbH & Co. KG) Aramid fiber bundle: Technora T-241K (manufactured by Teijin Limited) Carbon fiber bundle 1: Torayca T700SC-12000 (manufactured by Toray Industries, Inc.) Carbon fiber bundle 2: Torayca T700SC-24000 (manufactured by Toray Industries, Inc.)

[0029] (1) Tensile strength (MPa) Measurements were performed in accordance with ISO527-1. (2) Charpy impact strength (kJ / m 2 ) The notched Charpy impact strength was measured in accordance with ISO179 / 1eA. (3) Mold shrinkage ratio After injection molding a flat plate (150 x 150 mm, 3 mm thick) with a fan gate (the triangular part in Figure 1) as shown in Figure 1, the dimensions in the direction of resin flow (MD) and the direction perpendicular to the direction of resin flow (TD) were measured at the center, and the shrinkage ratio relative to the mold dimensions was calculated and expressed in 1 / 1000. The dimensions were measured using a three-dimensional measuring machine (SP600A manufactured by Tokyo Seimitsu Co., Ltd.).

[0030] Production Example 1 (Production of resin-impregnated cellulose fiber bundle) A cellulose fiber bundle (outer diameter 12 μm, bundle of approximately 2,700 cellulose fibers) was passed through a crosshead die, to which molten polyamide 12 was supplied from a twin-screw extruder, so that the cellulose fiber bundle was impregnated with polyamide 12. The fiber was then shaped using a shaping nozzle at the crosshead die outlet, shaped using a molding roll, and cut into 7 mm pieces using a pelletizer to obtain pellet-shaped (cylindrical) resin-impregnated cellulose fiber bundles (PA12-RF bundles: resin composition with a cellulose fiber content of 40% by mass). The resin-impregnated cellulose fiber bundle thus obtained was cut lengthwise and checked, and it was found that the cellulose fibers were almost parallel to the lengthwise direction.

[0031] Production Example 2 (Production of resin-impregnated aramid fiber bundle) A resin-impregnated aramid fiber bundle (PA12-aramid bundle: resin composition with 30 mass% aramid fiber content) was obtained in the same manner as in Production Example 1, except that aramid fiber (outer diameter 12 μm, bundle of 5,300 aramid fibers) was used instead of cellulose fiber and the pellet length was cut to 6 mm. The resin-impregnated aramid fiber bundle thus obtained was cut in the lengthwise direction and checked, and it was found that the aramid fibers were almost parallel to the lengthwise direction.

[0032] Production Example 3 (Production of resin-impregnated carbon fiber bundles) Carbon fiber bundle 1 (a bundle of 12,000 carbon fibers) was passed through a crosshead die, to which molten polyamide 12 was supplied from a twin-screw extruder, so that the carbon fiber bundle was impregnated with polyamide 12. Thereafter, the fiber was shaped using a shaping nozzle at the exit of the crosshead die, and after shaping using a forming roll, it was cut into 9 mm pieces using a pelletizer to obtain pellet-shaped (cylindrical) resin-impregnated carbon fiber bundles (PA12-CF bundle 1: resin composition with a carbon fiber content of 15% by mass). Carbon fiber bundle 2 (a bundle of 24,000 carbon fibers) was also produced in the same manner as the PA12-CF bundle 1 to obtain a resin-impregnated carbon fiber bundle (PA12-CF bundle 2: a resin composition containing 40% by mass of carbon fiber). Both resin-impregnated carbon fiber bundles thus obtained were cut in the lengthwise direction and examined, and it was found that the carbon fibers in both bundles were almost parallel to the lengthwise direction.

[0033] Examples 1 to 6, Comparative Example 1 In each example, a combination of fiber bundles corresponding to components (A) and (B) shown in Table 1 and a comparative fiber bundle was injection molded to prepare ISO test pieces and flat molded products, and the above-mentioned measurement tests were carried out. Injection molding was carried out as follows. The results are shown in Table 1.

[0034] (Injection molding conditions 1) Molding machine: FANUC ROBOSHOT α-S150iA Back pressure: 5 MPa Cylinder temperature: 250℃ Mold temperature: 100℃ Screw diameter: 44mm Gate shape: 20mm wide side gate

[0035] (Injection molding conditions 2) Molding machine: FANUC ROBOSHOT α-S150iA Back pressure: 15MPa Cylinder temperature: 250℃ Mold temperature: 100℃ Screw diameter: 44mm Gate shape: 20mm wide side gate (flat plate forming conditions) Molding machine: Toyo Machinery & Metal Co., Ltd. Si-180-6 Back pressure: 5 MPa Cylinder temperature: 250℃ Mold temperature: 100℃ Screw diameter: 50mm Gate shape: 150mm wide fan gate

[0036] [Table 1]

[0037] In Examples 1 to 6, the change in mechanical properties (tensile strength) due to differences in molding conditions (back pressure) was small. [Industrial Applicability]

[0038] Molded articles obtained from the resin composition of the present invention can be used as substitutes for metal materials used in electrical and electronic devices, communication devices, automobile parts, building materials, daily necessities, etc., as well as for shoes (preferably the soles of sports shoes such as running shoes and walking shoes) and bicycle saddle parts (preferably the base member of a bicycle saddle).

Claims

1. (A) thermoplastic resin and (B) reinforcing fiber are contained, the reinforcing fibers of the component (B) contain (B-1) organic fibers and (B-2) carbon fibers, but do not contain glass fibers, polyethylene terephthalate fibers, or polyethylene naphthalate fibers; the content of component (A) is 40 to 95 mass% and the content of component (B) is 60 to 5 mass% based on a total of 100 mass% of component (A) and component (B), The volume ratio of the (B-1) component is 10 to 99% of the total volume of the reinforcing fibers of the (B) component, 100%; A resin composition having a specific gravity of 0.93 to 1.25, The organic fibers of the component (B-1) are cellulose fibers, and are 3 to 50 mm long, in which organic fiber bundles are bundled in the length direction and impregnated with a thermoplastic resin to form an integrated bundle; and the carbon fibers of the component (B-2) are 3 to 50 mm long, in which carbon fiber bundles are bundled in the length direction and impregnated with a thermoplastic resin to form an integrated bundle. Resin composition.

2. The resin composition according to claim 1, wherein the rate of change calculated from the following formula: (ts1 - ts2) / ts1 x 100 between the tensile strength (ISO527-1) (ts1) of an injection-molded product molded at a back pressure of 5 MPa and the tensile strength (ISO527-1) (ts2) of an injection-molded product molded at a back pressure of 15 MPa is 15% or less.

3. 3. The resin composition according to claim 1, wherein the volume ratio of the component (B-1) to the total volume of the reinforcing fibers of the component (B) is 30 to 95%.

4. The resin composition according to any one of claims 1 to 3, wherein the specific gravity of the resin composition is 1.00 to 1.

15.

5. 5. The resin composition according to claim 1, wherein the thermoplastic resin of component (A) is selected from the group consisting of polyamide resins and olefin resins having a melting point of 250° C. or less.

6. A molded article made from the resin composition according to any one of claims 1 to 5.

7. The molded article according to claim 6, wherein the mold shrinkage ratio (MD / TD) of the molded article is 0.9 to 1.

2.

8. 8. The molded product according to claim 6 or 7, which is selected from the group consisting of bicycle saddle parts and pedal parts.

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