JP7597588B2 - Polybutylene naphthalate resin composition and molded article using same - Google Patents

Description

The present invention relates to a polybutylene naphthalate resin composition that exhibits a low coefficient of friction during sliding under high load and has excellent bleed-out resistance, and to a molded article made using the same.

Thermoplastic aromatic polyester resins have traditionally been excellent in mechanical properties, heat resistance, and chemical resistance, and are widely used in electrical and electronic components, home appliances, and automotive parts. In particular, polybutylene naphthalate resins are used in various gear and polishing pad applications because they have superior sliding properties and hydrolysis resistance compared to polybutylene terephthalate resins and the like. However, in fields where sliding properties are required in operating environments under higher loads, it has been difficult to achieve a low coefficient of friction while maintaining the strength of the parts.

Patent Document 1 proposes a polybutylene naphthalate resin composition having excellent sliding properties and a sliding part using the same, which is a resin composition consisting of polybutylene naphthalate resin, high-density polyethylene resin, and acid-modified polyethylene resin. However, although the sliding properties under low loads are improved, the sliding properties under high loads are insufficient and further improvement is required. Patent Documents 2 and 3 propose a resin composition consisting of a synthetic resin, a fibrous filler, and an olefin wax or paraffin wax, and an attempt is made to improve the sliding properties of the resin. However, since the wax component bleeds out from the resin part over time, there are still problems with process contamination due to component separation during molding and stabilization of sliding performance over a long period of time. Furthermore, there is insufficient knowledge about the reduction of the friction coefficient during sliding under high loads. Patent Document 4 proposes a resin composition having excellent friction and wear properties consisting of a polyester resin, ultra-high molecular weight polyethylene, and carbon fiber, but there is also insufficient knowledge about the reduction of the friction coefficient during sliding under high loads, and further improvement is required.

JP 2010-111759 A Patent No. 4209666 Japanese Patent Application Publication No. 59-84990 Japanese Patent Application Publication No. 63-297455

The object of the present invention is to provide a polybutylene naphthalate resin composition that exhibits a low coefficient of friction during sliding under high load and has excellent resistance to bleed-out, and a molded article made using the same.

As a result of extensive research into solving the above problems, the inventors discovered that the above object could be achieved by blending polybutylene naphthalate resin with modified ultra-high molecular weight polyethylene, carbon fiber, and polyolefin wax in specific ratios, which led to the invention.

That is, the present invention is achieved by a resin composition comprising 100 parts by weight of (A) polybutylene naphthalate resin (component A), 5 to 30 parts by weight of (B) modified ultra-high molecular weight polyethylene (component B) modified with maleic anhydride and having an intrinsic viscosity of 5 to 28 dl/g as measured in decalin solvent at 135°C, (C) 2 to 9 parts by weight of carbon fiber (component C), and (D) 1 to 15 parts by weight of polyolefin wax (component D).

According to the present invention, it is possible to provide a polybutylene naphthalate resin composition that exhibits a low coefficient of friction under high load while appropriately suppressing bleeding out of the sliding material, and that has excellent stain resistance during the manufacturing process and long-term stability of sliding properties. The molded articles obtained from the resin composition of the present invention can be suitably used not only for electrical and electronic parts and automotive parts, but also for building materials that require high long-term stability of sliding properties.

The following provides further details about the present invention.

<About Component A>
The polybutylene naphthalate resin, which is component A of the present invention, can be produced using a dicarboxylic acid component mainly composed of naphthalenedicarboxylic acid and/or an ester-forming derivative of naphthalenedicarboxylic acid, and a glycol component mainly composed of 1,4-butanediol.

The naphthalenedicarboxylic acid component is mainly composed of 2,6-naphthalenedicarboxylic acid and 2,7-naphthalenedicarboxylic acid, but other dicarboxylic acids can be used in combination as long as the properties are not impaired. Examples of other dicarboxylic acids include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, 4,4'-diphenyldicarboxylic acid, diphenoxyethane-4,4'-dicarboxylic acid, diphenylsulfone-4,4'-dicarboxylic acid, and diphenylether-4,4'-dicarboxylic acid, aliphatic dicarboxylic acids such as adipic acid, sebacic acid, succinic acid, and oxalic acid, and alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid. One or more of these may be used, and can be selected arbitrarily depending on the purpose. The amount of other dicarboxylic acids used is preferably 30 mol% or less, more preferably 20 mol% or less, based on the total acid components. The ester-forming derivatives of naphthalenedicarboxylic acid are mainly composed of dimethyl 2,6-naphthalenedicarboxylate and dimethyl 2,7-naphthalenedicarboxylate, but ester-forming derivatives of other dicarboxylic acids can be used in combination as long as the properties are not impaired. Examples of ester-forming derivatives of other dicarboxylic acids include lower dialkyl esters of aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, 4,4'-diphenyldicarboxylic acid, diphenoxyethane-4,4'-dicarboxylic acid, diphenylsulfone-4,4'-dicarboxylic acid, and diphenylether-4,4'-dicarboxylic acid, lower dialkyl esters of alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid, and lower dialkyl esters of aliphatic dicarboxylic acids such as adipic acid, sebacic acid, succinic acid, and oxalic acid. One or more of these may be used, and can be selected arbitrarily depending on the purpose. The amount of the ester-forming derivatives of other dicarboxylic acids used is preferably 30 mol% or less, more preferably 20 mol% or less, based on the total dicarboxylic acid ester-forming derivative components.

A small amount of a trifunctional or higher dicarboxylic acid component such as trimellitic acid may be used, or a small amount of an acid anhydride such as trimellitic anhydride may be used. A small amount of a hydroxycarboxylic acid or its alkyl ester such as lactic acid or glycolic acid may also be used, and can be selected arbitrarily depending on the purpose.

The glycol component is mainly composed of 1,4-butanediol, but other glycol components can be used in combination within the range that does not impair the properties. As the other glycol component, for example, one or more alkylene glycols such as ethylene glycol, 1,3-propylene glycol, 1,2-propylene glycol, neopentylene glycol, hexamethylene glycol, decamethylene glycol, cyclohexanedimethanol, diethylene glycol, triethylene glycol, poly(oxy)ethylene glycol, poly(oxy)tetramethylene glycol, and poly(oxy)methylene glycol may be used, and can be arbitrarily selected depending on the purpose. Furthermore, a small amount of a polyhydric alcohol component such as glycerin may be used. A small amount of an epoxy compound may also be used. The amount of the other glycol component used is preferably 30 mol % or less, more preferably 20 mol % or less, based on the total glycol components.

The amount of the glycol component used is preferably 1.1 to 1.4 times by mol relative to the dicarboxylic acid or ester-forming derivative of the dicarboxylic acid. If the amount of the glycol component used is less than 1.1 times by mol, the esterification or transesterification reaction may not proceed sufficiently, which is not preferred. Also, if the amount exceeds 1.4 times by mol, the reaction rate may slow down, and the excess glycol component may produce a large amount of by-products such as tetrahydrofuran, which is not preferred, for reasons that are unclear.

In the production of polybutylene naphthalate resin, a titanium compound is used as a polymerization catalyst. The titanium compound used as a polymerization catalyst is preferably a tetraalkyl titanate, specifically tetra-n-propyl titanate, tetraisopropyl titanate, tetra-n-butyl titanate, tetra-sec-butyl titanate, tetra-t-butyl titanate, tetra-n-hexyl titanate, tetracyclohexyl titanate, tetraphenyl titanate, tetrabenzyl titanate, etc., and may be used as a mixed titanate. Of these titanium compounds, tetra-n-propyl titanate, tetraisopropyl titanate, and tetra-n-butyl titanate are particularly preferred, and tetra-n-butyl titanate is the most preferred. The amount of titanium compound added is preferably 10 ppm or more and 60 ppm or less, more preferably 15 ppm or more and 30 ppm or less, in terms of the titanium atom content in the resulting polybutylene naphthalate resin. If the titanium atom content in the resulting polybutylene naphthalate resin exceeds 60 ppm, the color tone and thermal stability of the resin composition of the present invention may decrease, which is not preferable. On the other hand, if the titanium atom content is less than 10 ppm, good polymerization activity may not be obtained, and a polybutylene naphthalate resin with a sufficiently high intrinsic viscosity may not be obtained, which is not preferable. The polybutylene naphthalate resin of the present invention is preferably produced through an esterification or transesterification reaction step and a subsequent polycondensation reaction step of a dicarboxylic acid component mainly composed of naphthalenedicarboxylic acid and/or its ester-forming derivative and a glycol component mainly composed of 1,4-butanediol in the presence of a titanium compound, and the temperature at the end of the esterification or transesterification reaction is preferably in the range of 180° C. to 220° C., more preferably 180° C. to 210° C. If the temperature at the end of the esterification or transesterification reaction exceeds 220° C., the reaction rate increases, but by-products such as tetrahydrofuran may increase, which is not preferable. Also, if the temperature is less than 180° C., the reaction may not proceed. The reaction product (bisglycol ether and/or its oligomer) obtained by the esterification or transesterification reaction is preferably polycondensed at a temperature between the melting point of the polybutylene naphthalate resin and 270°C under reduced pressure of 0.4 kPa (3 Torr) or less. If the polycondensation reaction temperature exceeds 270°C, the reaction rate will decrease and coloring will increase, which is not preferable.

<About Component B>
The modified ultra-high molecular weight polyethylene, which is the B component of the present invention, has an intrinsic viscosity [η] measured in a decalin solvent at 135° C. of 5 to 28 dl/g, preferably 8 to 28 dl/g, and more preferably 10 to 26 dl/g. If the intrinsic viscosity of the B component is less than 5 dl/g, the sliding properties under high load become insufficient, and if it exceeds 28 dl/g, the layers are easily peeled off during injection molding, and the toughness decreases. The intrinsic viscosity was measured by the following method. That is, 20 mg of a sample was dissolved in 15 mL of decalin solvent, and the specific viscosity ηsp was measured in an oil bath at 135° C. After diluting the decalin solution by adding 5 mL of decalin solvent, the specific viscosity ηsp was measured. This dilution operation was repeated two more times, and the value of ηsp/C when the concentration (C) of the modified ultra-high molecular weight polyethylene was extrapolated to 0 was taken as the intrinsic viscosity [η] of the modified ultra-high molecular weight polyethylene. Modified components used in the production of modified ultra-high molecular weight polyethylene include maleic anhydride and itaconic anhydride, with maleic anhydride being particularly preferred. The content of modified groups in the modified ultra-high molecular weight polyethylene is preferably 0.05 to 3% by weight. If the amount of modification is less than 0.05% by weight, the reactivity with polybutylene naphthalate resin is low, which may lead to layer peeling and reduced toughness, whereas if the amount of modification exceeds 3% by weight, the reactivity may become excessively high and gelation may occur. If unmodified ultra-high molecular weight polyethylene is used, the toughness will be reduced.

The content of component B is 5 to 30 parts by weight, preferably 7 to 25 parts by weight, and more preferably 10 to 20 parts by weight, per 100 parts by weight of component A. If the content is less than 5 parts by weight, the sliding properties under high load will be insufficient and the amount of bleed-out of the polyolefin wax will increase, while if it exceeds 30 parts by weight, the layers will peel off easily and the toughness will decrease.

<About Component C>
The carbon fiber used in the present invention may be any carbon fiber that is generally called carbon fiber, such as PAN-based carbon fiber made from polyacrylonitrile, pitch-based carbon fiber made from petroleum tar or petroleum pitch, vapor-grown carbon fiber made from hydrocarbons, and cellulose-based carbon fiber made from viscose rayon.

The fiber diameter of the carbon fibers is not particularly limited, but is preferably 1 to 15 μm, and more preferably 2 to 13 μm. Carbon fibers with an average fiber diameter in this range may be able to exhibit good sliding properties without impairing the appearance of the molded product.

The carbon fibers may be subjected to a bundling process from the viewpoint of productivity and mechanical strength. Examples of bundling agents include, but are not limited to, olefin resins, styrene resins, acrylic resins, polyester resins, epoxy resins, and urethane resins. From the viewpoint of processability, the preferred amount of bundling agent is 0 to 5% by weight, and more preferably 0.1 to 4% by weight. The carbon fibers may be coated with a metal layer on the surface thereof. Examples of metals include silver, copper, nickel, and aluminum, with nickel being preferred from the viewpoint of the corrosion resistance of the metal layer.

The content of component C is 2 to 9 parts by weight, preferably 3 to 9 parts by weight, and more preferably 4 to 8 parts by weight, per 100 parts by weight of component A. If the content of component C is less than 2 parts by weight, sufficient strength cannot be maintained under high load, and as a result, a low coefficient of friction during sliding under high load is not achieved. If the content exceeds 9 parts by weight, a low coefficient of friction during sliding under high load is also not achieved.

<About Component D>
The polyolefin wax used in the present invention may be any known one. Examples of the polyolefin wax include polyolefin waxes which are polymers of olefin monomers having 2 to 8 carbon atoms, such as ethylene, propylene, 1-butene, 1-pentene, isobutene, isobutylene, butadiene, or other such pyrolysates; oxidized polyolefin waxes which are obtained by bringing the above-mentioned polyolefin wax into a molten state at or above the melting point and introducing air, oxygen, or an oxygen-containing gas thereto to introduce functional groups through an oxidation reaction; unsaturated carboxylic acids having 3 to 8 carbon atoms, such as acrylic acid, methacrylic acid, vinyl acetate, vinyl propionate, maleic acid, maleic anhydride, itaconic acid, and maleic acid monomethyl ester, and those acids which are wholly or partly composed of sodium, potassium, lithium, zinc, magnesium, calcium, or the like; Preferred examples of the wax include metal salts neutralized with monovalent or divalent metal cations such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-propyl acrylate, n-propyl methacrylate, isobutyl acrylate, isobutyl methacrylate, n-butyl acrylate, n-butyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, monomethyl maleate, glycidyl acrylate, glycidyl methacrylate, vinyl acetate, acrylamine, and acid-modified polyolefin waxes obtained by copolymerizing, block-polymerizing, or graft-polymerizing functional group-containing monomers such as acrylamide, among which polyethylene wax, oxidized polyethylene wax, acid-modified polyethylene wax, or mixtures thereof are more preferred. As the acid-modified wax, maleic acid modification or maleic anhydride modification is particularly preferred. As the oxidized wax, it is preferred that a carboxyl group, a ketone group, and a hydroxyl group are introduced. The viscosity average molecular weight of the polyolefin wax is preferably 1,000 or more and less than 10,000, more preferably 1,500 or more and less than 8,000. If the viscosity average molecular weight is less than 1,000, separation between the resin and the wax may occur, and the processability during molding may decrease. If the viscosity average molecular weight is 10,000 or more, the performance as a solid lubricant may not be fully exhibited, and the sliding properties may be poor.

The content of component D is 1 to 15 parts by weight, preferably 1 to 13 parts by weight, and more preferably 2 to 10 parts by weight, per 100 parts by weight of component A. If the content of component D is less than 1 part by weight, the solid lubricating effect of the wax is insufficient, resulting in insufficient sliding properties under high loads, and if it exceeds 15 parts by weight, bleed-out resistance is poor.

In the present invention, the modified ultra-high molecular weight polyethylene and polyolefin wax are used in combination in the range of 5 to 30 parts by weight of the modified ultra-high molecular weight polyethylene and 1 to 15 parts by weight of the polyolefin wax per 100 parts by weight of component A, thereby making it possible to reduce the coefficient of friction under high load and suppress the amount of bleed-out from the resin composition compared to when each is contained alone. The reason for this is unclear, but it is thought that the intermolecular interaction between the modified ultra-high molecular weight polyethylene and the polyolefin wax produces an effect of appropriately suppressing bleed-out outside the matrix.

<About Component E>
The spherical silica used in the present invention may be any known one, and the manufacturing method is not particularly limited. For example, spherical silica manufactured by a gas phase method, a precipitation method, a gel method, a sol-gel method, or a deflagration method (VMC method) may be used. The sphericity of the spherical silica is preferably 0.7 or more, more preferably 0.8 or more. The sphericity is calculated by measuring the projected area and perimeter of a silica particle, and the sphericity is calculated as sphericity=4π×(projected area)/(perimeter) ^2. The average particle size of the spherical silica is preferably 1 to 15 μm in diameter, more preferably 3 to 12 μm, from the viewpoint of ensuring the sliding property and toughness of the molded body. The average particle size was measured by the following method. That is, the volume average diameter was calculated from the particle size distribution obtained by the laser diffraction scattering method according to JIS Z8825 and JIS Z8819-2, and was taken as the average particle size.

The content of component E is preferably in the range of 1 to 15 parts by weight, more preferably 2 to 10 parts by weight, per 100 parts by weight of component A. By including component E in the above range, the strength of the molded body under high load is maintained, and the surface unevenness resulting from the silica particles near the surface of the molded body reduces the contact area with the opposing sliding material, which may result in a low coefficient of friction.

The resin composition of the present invention may contain other thermoplastic resins, and may contain additives such as antioxidants, impact modifiers, plasticizers, inorganic fillers, non-halogen flame retardants, colorants, light stabilizers, antistatic agents, antiblocking agents, lubricants other than components B and D, dispersants, flow modifiers, and crystal nucleating agents, as necessary, within the scope of the spirit of the present invention.

<Method of producing resin composition>
Any method can be used to produce the resin composition of the present invention. For example, each component and optionally other components can be premixed, then melt-kneaded, and pelletized. Premixing means can include a Nauta mixer, a V-type blender, a Henschel mixer, a mechanochemical device, an extrusion mixer, and the like. In premixing, granulation can be performed using an extrusion granulator or a briquetting machine, etc. After premixing, the mixture is melt-kneaded using a melt kneader, typically a vented twin-screw extruder, and pelletized using equipment such as a pelletizer. Other examples of melt kneaders include a Banbury mixer, a kneading roll, and a thermostatic stirring vessel, but a vented twin-screw extruder is preferred. Alternatively, each component and optionally other components can be independently supplied to a melt kneader, typically a twin-screw extruder, without premixing.

<Regarding Molded Products>
The molded article made of the resin composition of the present invention can be obtained by molding the pellets produced as described above. It is preferably obtained by injection molding or extrusion molding. Injection molding can be performed not only by ordinary molding methods, but also by injection compression molding, injection press molding, gas-assisted injection molding, foam molding (including a method of injecting a supercritical fluid), insert molding, in-mold coating molding, heat-insulating mold molding, rapid heating and cooling mold molding, two-color molding, multi-color molding, sandwich molding, and ultra-high speed injection molding. In addition, molding can be performed using either a cold runner system or a hot runner system. In extrusion molding, a molded article can be obtained by extruding a round bar and then cutting it into a disk shape, or by extruding a thick sheet and then punching it into a predetermined shape.

The following examples are provided to explain the practice of the present invention, but the present invention is not limited to these. In addition, the physical properties were evaluated using the following methods.

[Evaluation of Resin Composition]
(1) Dynamic friction coefficient The pellets obtained by the following method were dried at 120 ° C for 5 hours, and then molded into hollow cylindrical test pieces having an outer diameter of 25.6 mm, an inner diameter of 20 mm, and a height of 15 mm in accordance with JIS K7218A method at a cylinder temperature of 280 ° C and a mold temperature of 120 ° C using an injection molding machine (Toshiba Machine Co., Ltd., EC130SXII-4Y). The dynamic friction coefficient was measured when the test piece was slid against a test piece of similar shape made of stainless steel (SUS304) in accordance with JIS K7218A method. The test was carried out using a friction and wear tester (EFM-3-G, Orientec Co., Ltd.) under conditions of a load of 4,000 N, a sliding speed of 200 mm / s, and a sliding distance of 12 m. It is necessary that the dynamic friction coefficient at the sliding distance of 12 m is 0.06 or less.

(2) Bleed-out Resistance Pellets obtained by the method described below were compressed in a press heated to the melting point of the pellets + 5°C to obtain a sheet-like test specimen. The test specimen was attached to a glass plate having a thickness of 1.5 mm, and then treated at 120°C for 4 hours. The test specimen was then peeled off from the glass plate, and the haze of the glass plate was measured using a haze meter (HR-100, manufactured by Murakami Color Research Laboratory Co., Ltd.). The haze of the glass plate must be 0.5 or less.

(3) Toughness The pellets obtained by the method described below were dried at 120°C for 5 hours, and then molded into test pieces using an injection molding machine (Toshiba Machine Co., Ltd., EC130SXII-4Y) at a cylinder temperature of 280°C and a mold temperature of 120°C. Tensile tests were carried out in accordance with ISO527-1 and ISO527-2 to evaluate the toughness based on the tensile breaking elongation. The tensile breaking elongation must be 2% or more.

[Examples 1 to 8, Comparative Examples 1 to 10]
According to the amounts of addition shown in Table 1, a mixture consisting of components A, B, D and E was separately fed to a twin-screw extruder from the first feed port. Such a mixture was obtained by mixing with a V-type blender. Here, the first feed port refers to the feed port at the base. Component C was fed from the second feed port using a side feeder. For extrusion, a vented twin-screw extruder with a diameter of 30 mm (TEX30α-31.5BW-2V manufactured by Japan Steel Works, Ltd.) was used, and the extrusion was melt-kneaded at a screw rotation speed of 200 rpm, a discharge rate of 20 kg/h, and a vent vacuum of 3 kPa to obtain pellets. The extrusion temperature was 280°C.

The following materials were used in the examples and comparative examples of the present invention.

(Component A)
AI: Polybutylene naphthalate resin obtained in Production Example I <Production Example I>
315.0 parts of 2,6-naphthalenedicarboxylic acid dimethyl ester, 200.0 parts of 1.4-butanediol, and 0.062 parts of tetra-n-butyl titanate were placed in an ester exchange reaction tank, and the ester exchange reaction was carried out for 150 minutes while the temperature of the ester exchange reaction tank was raised to 210 ° C. Then, the reaction product obtained was transferred to a polycondensation reaction tank to start the polycondensation reaction. The polycondensation reaction was carried out by gradually reducing the pressure in the polycondensation reaction tank from normal pressure to 0.13 kPa (1 torr) or less over 40 minutes, and at the same time raising the temperature to a predetermined reaction temperature of 260 ° C. Thereafter, the polycondensation reaction was carried out for 140 minutes while maintaining the polycondensation reaction temperature at 260 ° C. and the pressure at 0.13 kPa (1 torr). When 140 minutes had passed, the polycondensation reaction was terminated, and the polybutylene naphthalate resin was extracted in the form of a strand, and cut into chips using a cutter while cooling with water. Next, the obtained polybutylene naphthalate resin was subjected to solid-phase polymerization for 8 hours under conditions of a temperature of 213° C. and a pressure of 0.13 kPa (1 Torr) or less to obtain a polybutylene naphthalate resin.

(Component B)
B-I: Modified ultra-high molecular weight polyethylene obtained in Production Example II <Production Example II>
100 parts by weight of a polyethylene resin mixture of 80% by weight of ultra-high molecular weight polyethylene (Hi-Zex Million 630M manufactured by Mitsui Chemicals, Inc.) having an intrinsic viscosity of 31 dl / g measured in a decalin solvent at 135 ° C. and 20% by weight of polyethylene (Hi-Zex 2200J manufactured by Prime Polymer Co., Ltd.) having an intrinsic viscosity of 2 dl / g measured in a decalin solvent at 135 ° C., 0.8 parts by weight of maleic anhydride and 0.07 parts by weight of an organic peroxide (Perhexine-25B manufactured by Nippon Oil & Fats Co., Ltd.) were mixed in a Nauta mixer, and the resulting mixture was melt-kneaded in a single-screw extruder (EXT40m / m extruder manufactured by Isuzu Kakoki Co., Ltd.) set at 250 ° C. to obtain the B-I component. The intrinsic viscosity of the resulting modified ultra-high molecular weight polyethylene measured in a decalin solvent at 135 ° C. was 25 dl / g.

B-II: Ultra-high molecular weight polyethylene obtained in Production Example III <Production Example III>
A polyethylene resin mixture of 30% by weight of ultra-high molecular weight polyethylene (Hi-Zex Million 630M manufactured by Mitsui Chemicals, Inc.) having an intrinsic viscosity of 31 dl / g measured in a decalin solvent at 135 ° C. and 70% by weight of polyethylene (Hi-Zex 2200J manufactured by Prime Polymer Co., Ltd.) having an intrinsic viscosity of 2 dl / g measured in a decalin solvent at 135 ° C. was mixed in a Nauta mixer, and the resulting mixture was melt-kneaded in a single-screw extruder (EXT40m / m extruder manufactured by Isuzu Kakoki Co., Ltd.) set at 250 ° C. to obtain a B-II component. The intrinsic viscosity of the obtained ultra-high molecular weight polyethylene measured in a decalin solvent at 135 ° C. was 11 dl / g.

B-III: Modified polyethylene obtained in Production Example IV Production Example IV
100 parts by weight of polyethylene (Hi-Zex 2200J, manufactured by Prime Polymer Co., Ltd.) having an intrinsic viscosity of 2 dl/g measured in decalin solvent at 135°C was mixed with 0.8 parts by weight of maleic anhydride and 0.07 parts by weight of organic peroxide (Perhexine-25B, manufactured by Nippon Oil & Fats Co., Ltd.) in a Nauta mixer, and the resulting mixture was melt-kneaded in a single-screw extruder (EXT40m/m extruder, manufactured by Isuzu Kakoki Co., Ltd.) set at 250°C to obtain component B-III. The resulting modified polyethylene had an intrinsic viscosity of 1.8 dl/g measured in decalin solvent at 135°C.

B-IV: Modified ultra-high molecular weight polyethylene obtained in Production Example V <Production Example V>
100 parts by weight of ultra-high molecular weight polyethylene (Hi-Zex Million 630M manufactured by Mitsui Chemicals, Inc.) having an intrinsic viscosity of 31 dl/g measured in a decalin solvent at 135 ° C. was mixed with 0.8 parts by weight of maleic anhydride and 0.07 parts by weight of an organic peroxide (Perhexine-25B manufactured by Nippon Oil & Fats Co., Ltd.) in a Nauta mixer, and the resulting mixture was melt-kneaded in a single-screw extruder (EXT40m/m extruder manufactured by Isuzu Kakoki Co., Ltd.) set at 250 ° C. to obtain a B-IV component. The intrinsic viscosity of the resulting modified ultra-high molecular weight polyethylene measured in a decalin solvent at 135 ° C. was 30 dl/g.

(Component C)
C-I: Carbon fiber: PAN-based carbon fiber (IM P303 (product name) manufactured by Teijin Ltd., fiber diameter 7 μm, cut length 3 mm, epoxy-based bundling agent)
(Component D)
D-I: Polyolefin wax: Oxidized polyethylene wax (Mitsui Hiwax 310MP (product name), manufactured by Mitsui Chemicals, Inc., viscosity average molecular weight 3,000)
D-II: Calcium stearate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.)
(Component E)
E-I: Spherical silica (Admafine FE-975A (product name), manufactured by Admatechs Co., Ltd., average particle size 7 μm)

<Examples 1 to 8>
Since the composition was within the scope of the present invention, it exhibited a low dynamic friction coefficient under high load and was excellent in bleed-out resistance.

<Comparative Example 1>
Since the component D was not included, the coefficient of dynamic friction under a high load was high.

<Comparative Example 2>
Since component B was unmodified ultra-high molecular weight polyethylene, the results showed poor toughness.

<Comparative Example 3>
Since the component B was not contained, the dynamic friction coefficient under a high load was high and the bleed-out resistance was poor.

<Comparative Example 4>
Since the content of component B exceeded the upper limit, the toughness was poor.

<Comparative Example 5>
Since component D was not a polyolefin wax, the results showed poor bleed-out resistance.

<Comparative Example 6>
Since the content of the C component exceeded the upper limit, the coefficient of dynamic friction under a high load was high.

<Comparative Example 7>
Since the composition does not contain component C, the coefficient of dynamic friction under a high load was high.

<Comparative Example 8>
Since the content of component D exceeded the upper limit, the results showed poor bleed-out resistance.

<Comparative Example 9>
Since the intrinsic viscosity of component B was below the lower limit, the dynamic friction coefficient under high load was high.

<Comparative Example 10>
Since the intrinsic viscosity of component B exceeded the upper limit, the toughness was poor.

Claims (4)

A resin composition comprising 100 parts by weight of (A) polybutylene naphthalate resin (component A), 5 to 30 parts by weight of (B) modified ultra-high molecular weight polyethylene (component B) modified with maleic anhydride and having an intrinsic viscosity of 5 to 28 dl/g as measured in decalin solvent at 135°C, 2 to 9 parts by weight of (C) carbon fiber (component C), and 1 to 15 parts by weight of (D) polyolefin wax (component D). 2. The resin composition according to claim 1 , wherein component D contains at least one polyolefin wax selected from the group consisting of polyethylene wax, oxidized polyethylene wax and acid-modified polyethylene wax. The resin composition according to claim 1 or 2, characterized in that it contains (E) 1 to 15 parts by weight of spherical silica particles having an average particle diameter of 1 to 15 μm, which is a volume average diameter calculated from a particle diameter distribution obtained by a laser diffraction scattering method in accordance with JIS Z8825 and JIS Z8819-2 , relative to 100 parts by weight of component A. A molded article made of the resin composition according to any one of claims 1 to 3 .