Polybutylene naphthalate resin composition and molded member obtained by molding the same

Abstract

To provide a polybutylene naphthalate resin composition for a transportation device having excellent heat resistance and low thermal conductivity in the thickness direction and a molded member using the same.SOLUTION: There is provided a polybutylene naphthalate resin composition for a transportation device which is a resin composition comprising (B) 35 to 65 pts.wt. of a glass fiber (B component) and (C) 10 to 35 pts.wt. of a polytetrafluoroethylene (C component) having no fibril-forming capability based on (A) 100 pts.wt. of a polybutylene naphthalate resin (A component), wherein the content of a resin other than A component is less than 1 pt.wt. and the content of a filler other than B component is less than 1 pt.wt..SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a polybutylene naphthalate resin composition for a conveying device, which has excellent heat resistance and low thermal conductivity in the thickness direction, and to a molded member obtained by molding the same. [Background technology]

[0002] Thermoplastic polyester resins have traditionally been widely used in electrical and electronic components, semiconductors, home appliances, and automotive parts due to their excellent low water absorption, low impurity content, low volatility, and chemical resistance. Furthermore, because the addition of fibrous fillers can relatively easily improve rigidity and heat resistance, their application to molded components for transport devices such as conveyors, robot arms, and rollers has been considered. Building highly clean transport devices that take advantage of the properties of thermoplastic polyester resins is extremely useful in the manufacturing or transporting of precision parts.

[0003] When attempting to transport high-temperature objects over 200°C, the molded parts for the transport device must have heat resistance so that they do not bend even at high temperatures, and, depending on the device configuration, they must also have appropriate thermal conductivity. In particular, when high-temperature objects are transported frequently using a robot arm, the molded parts accumulate heat over time due to heat transfer from the high-temperature objects to the molded parts, so it may be preferable to reduce the thermal conductivity of the molded parts to suppress heat transfer from the high-temperature objects.

[0004] Adding fibrous fillers such as glass fiber and carbon fiber is a widely known method for imparting heat resistance to thermoplastic polyester resins. For example, Patent Documents 1 and 2 disclose resin compositions consisting of glass fiber and a resin primarily composed of polybutylene terephthalate resin, but there is room for improvement in terms of heat resistance. Furthermore, because the addition of fillers increases thermal conductivity, it has been difficult to achieve both heat resistance and low thermal conductivity using thermoplastic polyester resins. Patent Document 3 discloses a resin composition consisting of polybutylene naphthalate resin, polytetrafluoroethylene, glass fiber, and carbon fiber, but does not disclose heat resistance or thermal conductivity, and further improvement is needed. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 11-92640 [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-323784 [Patent Document 3] Japanese Patent Publication No. 2023-15635 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a polybutylene naphthalate resin composition for a conveying device, which has excellent heat resistance and low thermal conductivity in the thickness direction, and a molded member obtained by molding the same. [Means for solving the problem]

[0007] As a result of extensive research into solving the above-mentioned problems, the inventors discovered that the above-mentioned object could be achieved by blending polybutylene naphthalate resin, glass fiber, and polytetrafluoroethylene that does not have fibril-forming ability in specific proportions, and setting the content of resins other than polybutylene naphthalate resin and fillers other than glass fiber to less than 1 part by weight, thereby arriving at the present invention.

[0008] That is, the present invention is as follows. 1. A resin composition containing 35 to 65 parts by weight of (B) glass fiber (component B) and 10 to 35 parts by weight of (C) polytetrafluoroethylene having no fibrillating ability (component C) with respect to 100 parts by weight of polybutylene naphthalate resin (component A), wherein the content of resins other than component A is less than 1 part by weight and the content of fillers other than component B is less than 1 part by weight. A polybutylene naphthalate resin composition for a conveying device, characterized in that 2. The resin composition according to item 1 above, wherein the intrinsic viscosity of component A is 0.90 or more. 3. The resin composition according to item 1 or 2 above, wherein the 50% average particle diameter of component C is 1 to 10 μm. 4. A molded member for a conveying device formed by molding the resin composition according to any one of items 1 to 3 above. 5. A molded member manufactured by injection molding, having no weld portion, and a surface parallel to the resin flow direction being used in contact with the conveyed object. A molded member for a conveying device according to item 4 above, characterized in that

Effects of the Invention

[0009] The polybutylene naphthalate resin composition for a conveying device of the present invention is excellent in heat resistance and has a low thermal conductivity in the thickness direction. Therefore, a molded product obtained from the resin composition of the present invention can be suitably used as a molded member for a conveying device, such as a conveyor, a robot arm, a pad, a guide, a rail, a retainer, a roller, and a member for a container.

Modes for Carrying Out the Invention

[0010] Hereinafter, the details of the present invention will be further described.

[0011] <Regarding 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. If a polyester resin other than polybutylene naphthalate resin is used as component A, the heat resistance decreases and the thermal conductivity in the thickness direction increases.

[0012] The naphthalenedicarboxylic acid component is primarily 2,6-naphthalenedicarboxylic acid or 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 the amount can be selected as desired 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 primarily 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 the amount can be selected as desired depending on the purpose. The amount of ester-forming derivatives of other dicarboxylic acids used is preferably 30 mol % or less, more preferably 20 mol % or less, based on the total ester-forming derivative components of dicarboxylic acids.

[0013] A small amount of a tri- or higher functional dicarboxylic acid component such as trimellitic acid, an acid anhydride such as trimellitic anhydride, or a small amount of a hydroxycarboxylic acid or an alkyl ester thereof such as lactic acid or glycolic acid may also be used, and these can be selected arbitrarily depending on the purpose.

[0014] The glycol component is primarily 1,4-butanediol, but other glycol components can be used in combination as long as the properties are not impaired. Examples of other glycol components include 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. These can be selected arbitrarily depending on the purpose. A small amount of a polyhydric alcohol component such as glycerin may also be used. A small amount of an epoxy compound may also be used. The amount of other glycol components used is preferably 30 mol % or less, more preferably 20 mol % or less, based on the total glycol components.

[0015] The amount of the glycol component used is preferably 1.1 to 1.4 times by mole 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 mole, the esterification or transesterification reaction may not proceed sufficiently, which is not preferred. If the amount of the glycol component used is more than 1.4 times by mole, the reaction rate may slow down, although the reason is unclear, and the excess glycol component may produce a large amount of by-products such as tetrahydrofuran, which is also not preferred.

[0016] 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 a mixture of these titanates may also be used. Among these titanium compounds, tetra-n-propyl titanate, tetraisopropyl titanate, and tetra-n-butyl titanate are particularly preferred, with tetra-n-butyl titanate being the most preferred. The amount of titanium compound added is preferably 10 ppm to 60 ppm, more preferably 15 ppm to 30 ppm, in terms of the titanium atom content in the resulting polybutylene naphthalate resin. A titanium atom content of more than 60 ppm in the resulting polybutylene naphthalate resin may result in a decrease in the color tone and thermal stability of the resin composition of the present invention, which is undesirable. On the other hand, a titanium atom content of less than 10 ppm may result in poor polymerization activity, making it difficult to obtain a polybutylene naphthalate resin with a sufficiently high intrinsic viscosity, which is undesirable. The polybutylene naphthalate resin of the present invention is preferably produced via an esterification or transesterification reaction step in the presence of a titanium compound between a dicarboxylic acid component primarily composed of naphthalenedicarboxylic acid and / or its ester-forming derivative and a glycol component primarily composed of 1,4-butanediol, followed by a polycondensation reaction step. 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. A temperature above 220°C at the end of the esterification or transesterification reaction increases the reaction rate, but may result in increased by-products such as tetrahydrofuran, which is undesirable. Furthermore, a temperature below 180°C may prevent the reaction from proceeding.The reaction product (bis glycol ether and / or its low polymer) obtained by esterification or transesterification reaction is preferably polycondensed under a reduced pressure of 0.4 kPa (3 Torr) or less at a temperature not lower than the melting point of the polybutylene naphthalate resin and not higher than 270 °C. When the polycondensation reaction temperature exceeds 270 °C, the reaction rate rather decreases and coloring may increase, which is not preferable.

[0017] The intrinsic viscosity of the polybutylene naphthalate resin measured in orthochlorophenol at 35 °C is preferably 0.90 or more, more preferably 0.95 or more, and still more preferably 1.00 or more. When the intrinsic viscosity is less than 0.90, the heat resistance may decrease. Although the upper limit of the intrinsic viscosity is not particularly limited, it is preferably 1.30 or less.

[0018] <Regarding Component B> As the glass fiber used as Component B of the present invention, any glass fiber may be used as long as it is generally referred to as glass fiber. The glass compositions such as A glass, C glass, E glass are not particularly limited, and those containing components such as TiO2, SO3, P2O5, etc. may be used depending on the case. However, it is more preferable when E glass (alkali-free glass) is blended with the polybutylene naphthalate resin. The glass fiber is obtained by rapidly cooling molten glass while stretching it by various methods into a predetermined fibrous shape. The rapid cooling and stretching conditions in such a case are not particularly limited either. Also, in addition to the circular cross-section shape, shapes other than circular such as elliptical, mayu-shaped, three-lobed-shaped, etc. may be used. When adding glass fiber, glass fiber having an elliptical cross-section shape may be used to suppress the anisotropy of physical properties. In the present invention as well, glass fiber having an elliptical cross-section shape may be used from the same viewpoint, and those having a major diameter of 15 to 45 μm, a minor diameter of 3 to 15 μm, and an aspect ratio of 1.8 to 6 are preferably used. Furthermore, a mixture of circular glass fiber and glass fiber having a shape other than circular may also be used. The glass fiber may be coated or bundled with a resin such as an ethylene / vinyl acetate copolymer, polyurethane, and epoxy resin.

[0019] The content of Component B is 35 to 65 parts by weight, preferably 40 to 60 parts by weight, more preferably 42 to 58 parts by weight, based on 100 parts by weight of Component A. When the content of Component B exceeds 65 parts by weight, the thermal conductivity in the thickness direction increases. On the other hand, when it is less than 35 parts by weight, the heat resistance decreases.

[0020] <Regarding Component C> The polytetrafluoroethylene as Component C of the present invention is a polytetrafluoroethylene having no fibril-forming ability. Polytetrafluoroethylene having fibril-forming ability has an extremely high molecular weight and tends to form fibers by bonding polytetrafluoroethylenes to each other by an external action such as shear force, and its number average molecular weight is in the range of 1.5 million to tens of millions. When such polytetrafluoroethylene having fibril-forming ability is used, when added in the content described in the present invention, the dispersibility in the resin is insufficient, resulting in strand breakage and difficulty in extrusion. The polytetrafluoroethylene having no fibril-forming ability used in the present invention is a low molecular weight polytetrafluoroethylene having a number average molecular weight of 10,000 to 1.2 million. By using such polytetrafluoroethylene and polybutylene naphthalate resin in a specific ratio, even when glass fiber is added thereto, the heat resistance can be improved without increasing the thermal conductivity in the thickness direction. The reason for this is not clear, but it is presumed that the orientation of the glass fiber in the flow direction is promoted, resulting in suppression of the increase in the thermal conductivity in the thickness direction.

[0021] The fibril-forming ability of polytetrafluoroethylene can be confirmed by a paste extrusion test, and the criterion for this is whether a continuous extrudate is obtained. The paste extrusion test is performed using the following method described in Japanese Patent Laid-Open Publication No. 4-154842. First, 50 g of polytetrafluoroethylene and 10.8 g of a hydrocarbon oil extrusion aid (Idemitsu Petrochemical Co., Ltd., product name IP1620) are mixed in a glass bottle and aged for 1 hour at room temperature (25±2°C). Next, the mixture is filled into an extrusion die (having an orifice with an inner diameter of 2.54 mm and a land length of 7 mm at the lower end, with a constriction angle of 30°) equipped with a cylinder (inner diameter 25.4 mm), and a load of 60 kg is applied to the piston inserted into the cylinder and held for 1 minute. Immediately after this, the mixture is extruded at room temperature at a ram speed (piston depression speed) of 20 mm / min, and it is determined whether a continuous extrudate is obtained. If continuous extrudates are not obtained, it is determined that the polytetrafluoroethylene does not have the ability to form fibrils.

[0022] Examples of such polytetrafluoroethylenes include Lubron L-2, Lubron L-5, and Lubron L-5F from Daikin Industries, Ltd., and KTL-620, KTL-610, KTL-450A, KT-600M, KT-400M, and KT-300M from Kitamura Co., Ltd., and these are readily available.

[0023] The polytetrafluoroethylene can be either fired or unfired polytetrafluoroethylene. However, since polytetrafluoroethylene is prone to reagglomeration, a powdered material subjected to a firing treatment or the like is preferred to make it difficult to reagglomerate. Particularly, polytetrafluoroethylene fired at a firing treatment temperature of 360 °C or higher is preferred. The melting point of the polytetrafluoroethylene is preferably 320 to 335 °C, more preferably 325 to 335 °C, measured by the DSC method to make it difficult to reagglomerate. Also, the 50% average particle diameter of the polytetrafluoroethylene is preferably 1 to 10 μm, more preferably 3 to 9 μm. When the 50% average particle diameter is less than 1 μm, the workability such as raw material conveyance and cleaning during extrusion may deteriorate. When it exceeds 10 μm, the thermal conductivity in the thickness direction may increase. Here, the 50% average particle diameter is a value calculated as being equal to the particle diameter corresponding to 50% of the obtained cumulative particle size distribution measured using the laser diffraction particle size distribution measurement method.

[0024] The content of the C component is 10 to 35 parts by weight, preferably 11 to 30 parts by weight, more preferably 12 to 25 parts by weight, based on 100 parts by weight of the A component. When the content is less than 10 parts by weight, the heat resistance decreases and the thermal conductivity in the thickness direction increases. On the other hand, when it exceeds 35 parts by weight, strand breakage frequently occurs during extrusion, making extrusion difficult.

[0025] <Resin other than A component> In the resin composition of the present invention, the content of the resin other than the component A is less than 1 part by weight, preferably less than 0.8 part by weight, more preferably less than 0.6 part by weight, and still more preferably 0 part by weight. When the content of the resin other than the component A is 1 part by weight or more, the crystallization of the polybutylene naphthalate resin is inhibited, so the heat resistance is lowered. The resin referred to here means a polymer of a monomer that does not correspond to the component A, and its number average molecular weight is 2000 or more. Examples of the resin other than the component A include polyethylene naphthalate resin, polyethylene terephthalate resin, polybutylene terephthalate resin, polystyrene resin, brominated polystyrene resin, polyamide resin, polycarbonate resin, polyethylene resin, polypropylene resin, polyphenylene sulfide resin, rubber, and thermoplastic elastomer.

[0026] <Filler other than component B> In the resin composition of the present invention, the content of fillers other than component B is less than 1 part by weight, preferably less than 0.8 parts by weight, more preferably less than 0.6 parts by weight, and even more preferably 0 part by weight. When the content of fillers other than component B is 1 part by weight or more, the thermal conductivity in the thickness direction increases. The filler other than component B is not particularly limited, and examples thereof include inorganic fibers such as carbon fiber, alumina fiber, silicon carbide fiber, ceramic fiber, potassium titanate whisker, wollastonite, titanium oxide whisker, and zinc oxide whisker, as well as metal-coated versions of these fibers, as well as metal fibers such as iron, stainless steel, nickel, copper, silver, gold, and titanium fibers, zeolite, sericite, kaolin, mica, clay, pyrophyllite, bentonite, asbestos, talc, alumina silicate, and silicate compounds such as layered silicates represented by montmorillonite, metal compounds such as alumina, silicon oxide, magnesium oxide, zirconium oxide, titanium oxide, and iron oxide, carbonates such as calcium carbonate, magnesium carbonate, and dolomite, sulfates such as calcium sulfate and barium sulfate, hydroxides such as magnesium hydroxide, calcium hydroxide, and aluminum hydroxide, glass beads, ceramic beads, boron nitride, silicon carbide, and silica. These materials not only have high thermal conductivity as simple materials, but when added to the resin composition of the present invention, it is presumed that they disrupt the orientation of the glass fibers in the flow direction, thereby increasing the thermal conductivity in the thickness direction.

[0027] The resin composition of the present invention may contain various additives, such as antioxidants, impact modifiers, plasticizers, flame retardants, colorants, light stabilizers, heat stabilizers, antistatic agents, antiblocking agents, lubricants, dispersants, flow modifiers, and crystal nucleating agents, as needed, within the scope of the present invention.

[0028] <Method of manufacturing resin composition> Any method can be used to produce the resin composition of the present invention. For example, the components and optionally other components can be premixed, followed by melt-kneading and pelletizing. Examples of premixing methods include a Nauta mixer, a V-blender, a Henschel mixer, a mechanochemical device, and an extrusion mixer. Premixing can also be performed using an extrusion granulator or briquetting machine. After premixing, the components are melt-kneaded in a melt mixer, typically a vented twin-screw extruder, and pelletized using a pelletizer or other device. Other examples of melt mixers include a Banbury mixer, a kneading roll, and a thermostatically stirred vessel. A vented twin-screw extruder is preferred. Alternatively, the components and optionally other components can be fed independently to a melt mixer, typically a twin-screw extruder, without premixing.

[0029] <Molded components for conveying devices> Molded conveying device components made from the resin composition of the present invention can be obtained by molding the pellets produced as described above. Suitable methods include injection molding and extrusion molding, with injection molding being preferred. Injection molding includes not only conventional molding methods but also injection compression molding, injection press molding, gas-assisted injection molding, foam molding (including supercritical fluid injection), insert molding, in-mold coating molding, adiabatic mold molding, rapid heating and cooling mold molding, two-color molding, multi-color molding, sandwich molding, and ultra-high-speed injection molding. Molding can be performed using either a cold runner or hot runner system. In extrusion molding, a molded conveying device component can be obtained by extruding a round bar and then cutting it into a disk, or by extruding a thick sheet and then punching it into the desired shape.

[0030] When a molded part for a conveying device is obtained by injection molding using the resin composition of the present invention, it is preferable that the molded part for a conveying device has a shape free of welds in order to maintain low thermal conductivity in the thickness direction. Methods for achieving a product shape free of welds include using a single gate, not providing a through-hole, reducing the diameter of the through-hole, and not providing a sudden difference in thickness. Furthermore, it is preferable that the molded part for a conveying device be used with the surface parallel to the resin flow direction in contact with the object to be conveyed. If the surface not parallel to the resin flow direction comes into contact with the high-temperature object to be conveyed, heat transfer from the object to the molded part is promoted, which may result in the molded part accumulating heat over time.

[0031] In the present invention, the molded article may be used as a molded member for a conveying device as is, or may be subjected to additional cutting processing before being used as a molded member for a conveying device. Examples of cutting processing include cutting a flat plate into the actual product shape after molding by injection molding, removing the skin layer on the surface of the molded article, and finishing to the desired surface roughness. In these cases, it is preferable that the surface that comes into contact with the object to be conveyed is parallel to the flow direction of the resin.

[0032] <About usage> The resin composition of the present invention is used exclusively for conveying devices. When used in conveying devices, the resin composition may or may not come into direct contact with the object to be conveyed; however, direct contact is preferred because the effects of the present invention are more pronounced. Specifically, the resin composition can be suitably used in conveyors, robot arms, pads, guides, rails, retainers, rollers, and container components used in the manufacturing and conveying processes of sheets, fibers, solar panels, liquid crystal panels, semiconductors, food, steel plates, and paper, but is not limited thereto. [Example]

[0033] Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples. Physical properties were evaluated by the following methods.

[0034] [Evaluation of Resin Composition] (1) Thermal conductivity The pellets obtained using the method described below were dried at 120°C for 6 hours and then injection-molded 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 to obtain tensile dumbbell specimens (compliant with ISO standards ISO 527-1 and ISO 527-2). The center of this specimen was cut to the specified size (100 mm x 10 mm x 3 mm). The thermal diffusivity in the flow direction and thickness direction of the sample was measured using a laser flash device (NETZSCH, Xenon Laser Flash Analyzer, LFA447) to calculate the thermal conductivity. The thermal conductivity in the thickness direction must be 0.27 W / m·K or less.

[0035] (2) Heat resistance The pellets obtained by the method described below were dried at 120°C for 6 hours and then injection-molded 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 to obtain strip test pieces (Type B1) as specified in JIS K 7139. Using these test pieces, the deflection temperature under load was measured at a bending stress of 1.80 MPa in accordance with ISO-75-1 and ISO 75-2. The test was performed three times, and the average value was used as an index of the heat resistance of the composition. The deflection temperature under load must be 218°C or higher.

[0036] [Examples 1-7, Comparative Examples 1-8] Component A and component C were separately fed into a twin-screw extruder through the first feed port according to the amounts shown in Table 1. Here, the first feed port refers to the feed port at the base. Component B was fed through 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 The Japan Steel Works, Ltd.) was used. The extrusion was performed at a screw rotation speed of 200 rpm, a set temperature of 280°C, a discharge rate of 20 kg / h, and a vent vacuum of 3 kPa to obtain pellets by melt-kneading. The pellets were used to carry out the above evaluations. The results are shown in Table 1. In Comparative Examples 4 and 6, frequent strand breakage occurred, making it impossible to obtain pellets.

[0037] (Component A) A-1: Polybutylene naphthalate resin obtained in Production Example I <Manufacturing 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 reactor, and the ester exchange reaction was carried out for 150 minutes while the temperature of the ester exchange reactor was raised to 210°C. The resulting reaction product was then transferred to a polycondensation reactor to initiate the polycondensation reaction. The polycondensation reaction was carried out by gradually reducing the pressure in the polycondensation reactor from atmospheric pressure to 0.13 kPa (1 torr) or less over 40 minutes, while simultaneously raising the temperature to the 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). After 140 minutes had elapsed, the polycondensation reaction was terminated, and the polybutylene naphthalate resin was extracted in the form of strands and cut into chips using a cutter while cooling with water. Next, the obtained polybutylene naphthalate resin was subjected to solid-state 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 having an intrinsic viscosity of 1.05. A-2: Polybutylene naphthalate resin obtained in Production Example II <Manufacturing example II> 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 reactor, and the ester exchange reaction was carried out for 150 minutes while the temperature of the ester exchange reactor was raised to 210°C. The resulting reaction product was then transferred to a polycondensation reactor to initiate the polycondensation reaction. The polycondensation reaction was carried out by gradually reducing the pressure in the polycondensation reactor from atmospheric pressure to 0.13 kPa (1 torr) or less over 40 minutes, while simultaneously raising the temperature to the specified 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). After 140 minutes had passed, the polycondensation reaction was terminated, and the polybutylene naphthalate resin was extracted in the form of strands, which were then cut into chips with a cutter while being cooled with water, yielding a polybutylene naphthalate resin with an intrinsic viscosity of 0.78. A-3 (Comparative Example): Polybutylene terephthalate resin (manufactured by Polyplastics Co., Ltd., DURANEX 500FP (product name))

[0038] (B component) B-1: Glass fiber (manufactured by Nitto Boseki Co., Ltd., CS-3PE944 (product name), round cross section, fiber diameter 13 μm, cut length 3 mm)

[0039] (C component) C-1: Polytetrafluoroethylene without fibril-forming ability (manufactured by Daikin Industries, Ltd., Lubron L-5 (trade name), melting point 326 to 328°C, 50% average particle size 5 to 7 μm) C-2: Polytetrafluoroethylene without fibril-forming ability (Kitamura Co., Ltd., KT-600M (trade name), melting point 325 to 335°C, 50% average particle size 14 μm) C-3 (Comparative Example): Polytetrafluoroethylene having fibril-forming ability (manufactured by Daikin Industries, Ltd., Polyflon MPA FA-500H (trade name), melting point 327°C)

[0040] (Other ingredients) D-1: Polycarbonate resin (Teijin Limited, Panlite L-1225WP (product name)) E-1: PAN-based carbon fiber (Teijin Limited, IM P303 (product name), cut length 3 mm, average fiber diameter 5 μm, epoxy-based sizing agent)

[0041] [Table 1]

[0042] <Examples 1 to 7> Since the composition is within the scope of the present invention, it has excellent heat resistance and low thermal conductivity in the thickness direction. <Comparative Example 1> Since the content of component B was below the lower limit, the heat resistance was poor. <Comparative Example 2> Since the content of component B exceeded the upper limit, the thermal conductivity in the thickness direction was high. <Comparative Example 3> Since the content of component C was below the lower limit, the heat resistance was poor and the thermal conductivity in the thickness direction was high. <Comparative Example 4> Because the content of component C exceeded the upper limit, strand breakage occurred frequently and pellets could not be obtained. <Comparative Example 5> Since component A was not a polybutylene naphthalate resin, the heat resistance was poor and the thermal conductivity in the thickness direction was high. <Comparative Example 6> Since component C was not polytetrafluoroethylene, which does not have fibril-forming ability, strand breakage occurred frequently and pellets could not be obtained. <Comparative Example 7> Since the content of resins other than component A exceeded the upper limit, the heat resistance was poor. <Comparative Example 8> Since the content of fillers other than component B exceeded the upper limit, the thermal conductivity in the thickness direction was high.

Claims

1. A polybutylene naphthalate resin composition for conveying devices, characterized in that it contains 35 to 65 parts by weight of (B) glass fiber (component B) and 10 to 35 parts by weight of (C) polytetrafluoroethylene (component C) that does not have fibril-forming ability, relative to 100 parts by weight of (A) polybutylene naphthalate resin (component A), wherein the content of resins other than component A is less than 1 part by weight and the content of fillers other than component B is less than 1 part by weight.

2. 2. The resin composition according to claim 1, wherein the intrinsic viscosity of component A is 0.90 or more.

3. 2. The resin composition according to claim 1, wherein the 50% average particle size of component C is 1 to 10 μm.

4. A molded member for a conveying device, obtained by molding the resin composition according to any one of claims 1 to 3.

5. The molded member for a conveying device according to claim 4, characterized in that it is a molded member manufactured by injection molding, has no weld portion, and is used so that a surface parallel to the resin flow direction comes into contact with the object to be conveyed.

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