Resin composition and molded article

Abstract

Provided are a resin composition capable of producing a molded article having enhanced durability, and a molded article including the resin composition.SOLUTION: The resin composition contains a semi-aromatic polyamide having a structural unit represented by formula (1), carbon fibers, and a water-soluble carbodiimide. In Formula (1), Ar1 represents a phenylene or naphthylene group, and a plurality of Ar1 contained in the semi-aromatic polyamide may be the same as or different from each other. P is an integer of 4 to 12. [Chemical Formula 1] SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a resin composition and a molded article. [Background technology]

[0002] Polyamides have excellent abrasion resistance and strength and are widely used as molding materials for various components such as machine parts. Patent Document 1 discloses a resin composition for extrusion molding that contains a semi-aromatic polyamide and a carbodiimide compound in a specific ratio. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-10587 Summary of the Invention [Problem to be solved by the invention]

[0004] However, there is a demand for further improvement in the durability of molded articles containing conventional resin compositions containing semi-aromatic polyamides. The present disclosure has been made in consideration of the above circumstances, and aims to provide a resin composition that can be used to produce a molded article with improved durability, and a molded article containing this resin composition. [Means for solving the problem]

[0005] In order to solve the above problems, the present disclosure includes the following aspects.

[0006] [1] A resin composition comprising a semi-aromatic polyamide having a structural unit represented by the following formula (1), carbon fiber, and a water-soluble carbodiimide:

[0007] [ka] [In formula (1), Ar1 represents a phenylene group or a naphthylene group, and the plurality of Ar 1 may be the same or different, and p is an integer of 4 to 12.

[0008] [2] The semi-aromatic polyamide is Ar 1 The resin composition according to [1], which is a semi-aromatic polyamide having a structural unit represented by formula (1) in which represents a 1,4-phenylene group and p is 9 or 10.

[0009] [3] The resin composition according to [1] or [2], wherein the content of the water-soluble carbodiimide is 0.1% by mass or more and 15% by mass or less relative to the total mass of the resin composition. [4] The resin composition according to any one of [1] to [3], wherein the content of the carbon fiber is 5% by mass or more and 60% by mass or less with respect to the total mass of the resin composition. [5] The resin composition according to any one of [1] to [4], which is a resin composition for molding gears.

[0010] [6] A molded article comprising the resin composition according to any one of [1] to [5]. [7] The molded article according to [6], which is a gear. [Effects of the Invention]

[0011] According to the present disclosure, it is possible to provide a resin composition that can be used to produce a molded article with enhanced durability, and a molded article that includes this resin composition. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a photographed plan view of an example of a gear manufactured in an example. DETAILED DESCRIPTION OF THE INVENTION

[0013] (Resin composition) One embodiment of the resin composition contains a semi-aromatic polyamide having a structural unit represented by formula (1), carbon fiber, and a water-soluble carbodiimide.

[0014] <Semi-aromatic polyamide> The semi-aromatic polyamide in this embodiment has a structural unit represented by the following formula (1).

[0015] [ka] [In formula (1), Ar 1 represents a phenylene group or a naphthylene group, and the plurality of Ar 1 may be the same or different, and p is an integer of 4 to 12.

[0016] The semi-aromatic polyamide is a polycondensation product of an aliphatic diamine and an aromatic dicarboxylic acid. The aliphatic diamine may be an aliphatic diamine having 4 to 12 carbon atoms. Examples of aliphatic diamines having 4 to 12 carbon atoms include 1,4-butanediamine, 1,5-pentanediamine, 1,6-hexanediamine, 1,7-heptanediamine, 1,8-octanediamine, 1,9-nonanediamine, 1,10-decanediamine, 1,11-undecanediamine, and 1,12-dodecanediamine. The aliphatic diamines may be used alone or in combination of two or more. Examples of aromatic dicarboxylic acids include terephthalic acid, phthalic acid, isophthalic acid, naphthalenedicarboxylic acid, etc. The aromatic dicarboxylic acids may be used alone or in combination of two or more.

[0017] From the viewpoint of excellent durability and heat resistance of the resulting molded article, Ar 1 represents a phenylene group or a naphthylene group, and the plurality of Ar 1 may be the same or different, and p may be 9 or 10 from the viewpoint of being more excellent in low water absorbency.

[0018] From the viewpoint of obtaining a molded article with superior durability and heat resistance, Ar 1 represents a phenylene group or a naphthylene group, and the plurality of Ar 1 may be the same or different, and p may be 10 from the viewpoint of achieving a more excellent effect of improving durability by adding a water-soluble carbodiimide and a more excellent low water absorption.

[0019] The Ar 1 The phenylene group in Ar may be a 1,4-phenylene group or a 1,3-phenylene group. 1 The naphthylene group includes a 2,6-naphthylene group and a 2,7-naphthylene group.

[0020] Preferably, in the formula (1), Ar 1 represents a 1,4-phenylene group, and p may be an integer of 4 to 12. More preferably, in the formula (1), Ar 1 represents a 1,4-phenylene group, and p may be 9 or 10. Particularly preferably, in the formula (1), Ar 1 represents a 1,4-phenylene group, and p may be 10.

[0021] In the semi-aromatic polyamide, the content of the structural unit represented by the formula (1) is preferably 40% or more, more preferably 80% or more, and even more preferably 90% or more, relative to the total number of all structural units in the semi-aromatic polyamide (100%).

[0022] In the semi-aromatic polyamide, the structural unit represented by the formula (1) is Ar 1 represents a phenylene group or a naphthylene group, and the plurality of Ar groups contained in the semi-aromatic polyamide 1may be the same or different, and the content of structural units in which p is 9 or 10 is preferably 40% or more, more preferably 80% or more, and even more preferably 90% or more, relative to the total number of all structural units in the semi-aromatic polyamide (100%).

[0023] In the semi-aromatic polyamide, the structural unit represented by the formula (1) is Ar 1 The content of structural units in which represents a 1,4-phenylene group and p is 9 or 10 is preferably 40% or more, more preferably 80% or more, and even more preferably 90% or more, relative to the total number of all structural units (100%) in the semi-aromatic polyamide.

[0024] In the semi-aromatic polyamide, the structural unit represented by the formula (1) is Ar 1 The content of structural units in which represents a 1,4-phenylene group and p is 10 is preferably 40% or more, more preferably 80% or more, and even more preferably 90% or more, relative to the total number of all structural units (100%) in the semi-aromatic polyamide.

[0025] The melt mass flow rate (MFR) of the semi-aromatic polyamide, measured in accordance with JIS K 7210 at a test temperature of 330°C and a load of 2160 g, is preferably 150 g / 10 min or less, more preferably 125 g / 10 min or less, and even more preferably 100 g / 10 min or less. In another aspect, the MFR of the semi-aromatic polyamide, measured in accordance with JIS K 7210 at a test temperature of 330°C and a load of 2160 g, is preferably 80 g / 10 min or less, more preferably 50 g / 10 min or less, and even more preferably 30 g / 10 min or less. A resin composition containing a semi-aromatic polyamide having an MFR equal to or less than the above upper limit can produce a molded article having even better durability.

[0026] The MFR of the semi-aromatic polyamide measured in accordance with JIS K 7210 at a test temperature of 330°C and a load of 2160 g may be 5 g / 10 min or more, 10 g / 10 min or more, or 15 g / 10 min or more.

[0027] The upper and lower limits of the MFR of the semi-aromatic polyamides exemplified above can be freely combined.

[0028] The MFR of the semi-aromatic polyamide, measured in accordance with JIS K 7210 at a test temperature of 330°C and a load of 2160 g, may be, for example, 5 g / 10 min or more and 150 g / 10 min or less, 10 g / 10 min or more and 125 g / 10 min or less, or 15 g / 10 min or more and 100 g / 10 min or less. In another aspect, the MFR of the semi-aromatic polyamide, measured in accordance with JIS K 7210 at a test temperature of 330°C and a load of 2160 g, may be, for example, 5 g / 10 min or more and 80 g / 10 min or less, 10 g / 10 min or more and 50 g / 10 min or less, or 15 g / 10 min or more and 30 g / 10 min or less.

[0029] The MFR of the semi-aromatic polyamide can be controlled by appropriately adjusting conditions related to the reaction efficiency of the polycondensation reaction, such as the raw material monomer, catalyst, and reaction time.

[0030] The resin composition of the present embodiment may contain one type of semi-aromatic polyamide, or may contain two or more types of semi-aromatic polyamides. In the resin composition of this embodiment, the content of the semi-aromatic polyamide is, for example, 40 mass% or more relative to the total mass of the resin composition, and may be 40 mass% or more and 95 mass% or less, or 60 mass% or more and 85 mass% or less.

[0031] <Carbon fiber> The carbon fiber in this embodiment is a typical carbon fiber obtained by firing a precursor (a fiber used as a raw material for carbon fiber) called a precursor. For example, the precursor is first flame-retarded in an oxidizing atmosphere, and the resulting flame-retarded fiber is then fired in an inert gas atmosphere at about 800 to 2000°C. If necessary, the fiber is further fired in an inert gas atmosphere at a higher temperature. Carbon fibers are generally known to have a sizing agent applied to their surfaces.

[0032] Examples of types of carbon fibers include polyacrylonitrile-based (hereinafter sometimes referred to as "PAN-based"), petroleum / coal pitch-based (hereinafter sometimes referred to as "pitch-based"), rayon-based, and lignin-based carbon fibers.

[0033] Examples of PAN-based carbon fibers include "TORAYCA (registered trademark)" manufactured by Toray Industries, Inc., "PYROFIL (registered trademark)" manufactured by Mitsubishi Chemical Corporation, and "TENAX (registered trademark)" manufactured by Toho Tenax Co., Ltd. Examples of pitch-based carbon fibers include "DIALEAD (registered trademark)" manufactured by Mitsubishi Chemical Corporation, "DONACARBO (registered trademark)" manufactured by Osaka Gas Chemicals Co., Ltd., and "KUREKA (registered trademark)" manufactured by Kureha Chemical Industry Co., Ltd.

[0034] The carbon fiber is preferably a carbon fiber bundle in which a plurality of single fibers are bundled together, or chopped carbon fiber.

[0035] The number average fiber diameter of the carbon fibers may be 1 μm or more and 10 μm or less, or may be 5 μm or more and 8 μm or less. When the number-average fiber diameter of the carbon fibers is 1 μm or more, the carbon fibers are easily dispersed in the semi-aromatic polyamide. Furthermore, the carbon fibers are easy to handle during the production of the resin composition. On the other hand, when the number-average fiber diameter of the carbon fibers is 10 μm or less, the carbon fibers efficiently reinforce the semi-aromatic polyamide. Therefore, excellent mechanical strength can be imparted to a molded article obtained by molding the resin composition. The number average fiber diameter of the carbon fibers is determined by observing the carbon fibers under a scanning electron microscope (1000x magnification) and measuring the fiber diameters of 50 carbon fibers, and the number average value is used.

[0036] The fiber diameter of the carbon fibers in the resin composition or molded article is hardly changed by melt-kneading, and is usually the same as the fiber diameter of the carbon fibers before melt-kneading.

[0037] The number average fiber length of the carbon fibers in the resin composition may be 10 μm or more and 400 μm or less, or may be 100 μm or more and 350 μm or less. When the number average fiber length of the carbon fibers is equal to or greater than the above-mentioned lower limit, the durability of the molded article obtained by molding the resin composition is likely to be improved. On the other hand, when the number average fiber length of the carbon fibers is equal to or less than the above-mentioned upper limit, the reinforcement of the semi-aromatic polyamide by the carbon fibers is efficiently carried out.

[0038] [Method for measuring number average fiber length of carbon fibers in resin composition] The resin composition is heated at 450°C for 3 hours to remove the resin components, obtaining an ashing residue containing carbon fibers. 1 g of the ashing residue is mixed with 150 mL of acetone to obtain a sample solution. Next, approximately 5 mL of the sample solution is placed on a glass slide and allowed to dry naturally. The slide with the ashing residue is placed on a projector (microscope) and magnified 100 times to measure the fiber lengths of at least 400 carbon fibers, and the number-average fiber lengths of the measured carbon fibers are calculated.

[0039] The resin composition of the present embodiment may contain one type of carbon fiber, or may contain two or more types of carbon fibers. In the resin composition of this embodiment, the content of the carbon fiber is, for example, 5% by mass or more, or may be 5% by mass or more and 60% by mass or less, or 15% by mass or more and 40% by mass or less, relative to the total mass of the resin composition.

[0040] <Water-soluble carbodiimide> The water-soluble carbodiimide in this embodiment is a carbodiimide compound that has a carbodiimide group (—N═C═N—) and a hydrophilic segment in the molecule and is soluble in water. The term "water-soluble compound" used herein refers to a compound that can be dissolved in water at 25° C. at a concentration of 10% by mass or more. As the water-soluble carbodiimide, a carbodiimide compound that can be dissolved in water at 25° C. at a concentration of preferably 20% by mass or more, more preferably 35% by mass or more, is used. As the water-insoluble carbodiimide, a carbodiimide other than the water-soluble carbodiimide is used.

[0041] Examples of the hydrophilic segment include a structure containing at least one selected from the group consisting of an oxyalkylene group, an acetal structure, an imino group, a hydroxy group, an amino group, an epoxy group, and a carboxy group. The water-soluble carbodiimide may be a monocarbodiimide having one carbodiimide group in the molecule, or a polycarbodiimide having two or more carbodiimide groups in the molecule.

[0042] The water-soluble carbodiimide may be an aromatic carbodiimide, an alicyclic carbodiimide, or a chain aliphatic carbodiimide. The water-soluble carbodiimide may be an aromatic monocarbodiimide, an alicyclic monocarbodiimide, a chain aliphatic monocarbodiimide, an aromatic polycarbodiimide, an alicyclic polycarbodiimide, or a chain aliphatic polycarbodiimide. The water-soluble carbodiimide is preferably a polycarbodiimide from the viewpoint of having high reactivity with the semi-aromatic polyamide.

[0043] The carbodiimide group (-N=C=N-) equivalent of the water-soluble carbodiimide is preferably 300 g / mol or more, and may be 300 g / mol or more and 600 g / mol or less, or 350 g / mol or more and 500 g / mol or less.

[0044] The water-soluble carbodiimide used in this embodiment may be a known water-soluble carbodiimide or a commercially available product. Examples of commercially available products that can be used include water-soluble versions of Carbodilite (registered trademark), such as Carbodilite (registered trademark) V-02, V-02-L2, SV-02, V-04, and V-10 (all manufactured by Nisshinbo Chemical Inc.).

[0045] The resin composition of the present embodiment may contain one type of water-soluble carbodiimide, or may contain two or more types of water-soluble carbodiimides. In the resin composition of this embodiment, the content of the water-soluble carbodiimide is, for example, 0.1 mass% or more relative to the total mass of the resin composition, and may be 0.1 mass% or more and 15 mass% or less, 0.1 mass% or more and 12 mass% or less, or 0.2 mass% or more and 6 mass% or less.

[0046] <Other ingredients> The resin composition of the present embodiment may contain other components that do not fall under any of the above-mentioned semi-aromatic polyamides, carbon fibers, and water-soluble carbodiimides, as long as the effects of the present disclosure are not impaired. Examples of other components include fillers other than carbon fibers, additives, and resins that do not fall under the category of semi-aromatic polyamides (hereinafter sometimes referred to as "other resins"). The other components may be used alone or in combination of two or more.

[0047] The filler other than carbon fiber may be a fibrous filler or a granular filler, and may be an inorganic filler or an organic filler. Examples of the additives include stabilizers, release agents, antioxidants, heat stabilizers, ultraviolet absorbers, antistatic agents, surfactants, flame retardants, and colorants. Examples of other resins include thermoplastic resins such as polyester, polyphenylene sulfide, polyether ketone, polycarbonate, polyphenylene ether, polyetherimide, and fluororesin; and thermosetting resins such as phenolic resin, epoxy resin, polyimide resin, and cyanate resin.

[0048] In the resin composition of the present embodiment, the semi-aromatic polyamide having the structural unit represented by the above formula (1), the carbon fiber, the water-soluble carbodiimide, and other components are contained so that the total content (mass %) of these components is 100 mass %.

[0049] As described above, the resin composition of this embodiment uses a water-soluble carbodiimide in addition to the semi-aromatic polyamide having the structural unit represented by formula (1) and carbon fiber. The water-soluble carbodiimide has a functional group that can react with the semi-aromatic polyamide. The presence of this water-soluble carbodiimide strengthens the adhesion between the semi-aromatic polyamide and the carbon fiber at their interfaces. Therefore, it is believed that the resin composition of this embodiment improves the durability of molded articles.

[0050] The resin composition of the present embodiment is suitable as a molding material for machine parts such as gears, and is particularly suitable as a resin composition for molding gears, because it can enhance the durability of molded articles.

[0051] The durability of the molded article can be evaluated, for example, using the total number of rotations until the gear breaks in the below-described [Durability Test] as an index. [Durability test] A metal master gear as a driving gear is meshed with the gear to be tested and set in a power absorption gear running test machine specified in JIS B 1759. The test machine is operated under the following conditions: load torque on the gear is 8 N·m, rotation speed is 1000 rpm, no lubrication, temperature is 23°C, and relative humidity is 50% RH, and the total number of rotations until the gear breaks is measured. In this durability test, "breakage" of the gear refers to a state in which power cannot be transmitted from the metal master gear to the gear due to breakage of the gear teeth or the like.

[0052] [Method of producing resin composition] The resin composition of the above-described embodiment can be produced by mixing a semi-aromatic polyamide having a structural unit represented by formula (1), carbon fiber, a water-soluble carbodiimide, and other components as needed, such that the total content (% by mass) of the semi-aromatic polyamide, carbon fiber, water-soluble carbodiimide, and other components as needed in the target resin composition is 100% by mass. One embodiment of the method for producing such a resin composition is a production method including a step (S) of mixing a semi-aromatic polyamide having a structural unit represented by the formula (1), carbon fiber, and a water-soluble carbodiimide.

[0053] Another embodiment of the method for producing such a resin composition is a production method including a step (S1) of premixing carbon fibers and a water-soluble carbodiimide to prepare a mixture (M) of carbon fibers and a water-soluble carbodiimide, and a step (S2) of mixing the mixture (M) with a semi-aromatic polyamide having a structural unit represented by the formula (1).

[0054] In one embodiment of step (S1), an aqueous solution of a water-soluble carbodiimide is mixed with carbon fibers, and then the mixture is heated to remove water, thereby preparing a mixture (M) of carbon fibers and the water-soluble carbodiimide. The concentration of the water-soluble carbodiimide in the aqueous solution of the water-soluble carbodiimide is, for example, 30 to 50 mass %. The mixture (M) is in a solid form, such as a powder form.

[0055] In one embodiment of step (S2), the semi-aromatic polyamide and the mixture (M) prepared in step (S1) are fed into a twin-screw extruder and melt-kneaded to produce a resin composition in a desired shape, such as pellets.

[0056] According to the manufacturing method including the above-mentioned steps (S1) and (S2), a resin composition capable of producing a molded article with improved durability can be easily produced. This is because, in the step (S1), an aqueous solution of a water-soluble carbodiimide is mixed with carbon fibers in advance, so that the carbodiimide can be strongly bonded to the surface of the carbon fibers. This further strengthens the adhesion at the interface between the carbon fibers to which the carbodiimide is strongly bonded and the semi-aromatic polyamide, which is thought to further improve the durability of the molded article.

[0057] In another aspect, the present disclosure further includes the following embodiments.

[0058] [8] A resin composition containing a semi-aromatic polyamide having a structural unit represented by the following formula (1), carbon fiber, and a water-soluble carbodiimide, Relative to the total mass of the resin composition The content of the semi-aromatic polyamide is 40% by mass or more and 95% by mass or less, The content of the carbon fiber is 5% by mass or more and 60% by mass or less, The resin composition has a content of the water-soluble carbodiimide of 0.1% by mass or more and 15% by mass or less.

[0059] [ka] [In formula (1), Ar 1 represents a phenylene group or a naphthylene group, and the plurality of Ar 1 may be the same or different, and p is an integer of 4 to 12.

[0060] [9] A resin composition containing a semi-aromatic polyamide having a structural unit represented by the following formula (1), carbon fiber, and a water-soluble carbodiimide, Relative to 100 parts by mass of the semi-aromatic polyamide content, the content of the carbon fiber is 5 parts by mass or more and 160 parts by mass or less, preferably 20 parts by mass or more and 80 parts by mass or less, and more preferably 35 parts by mass or more and 50 parts by mass or less, A resin composition, wherein the content of the water-soluble carbodiimide is 0.1 parts by mass or more and 35 parts by mass or less, preferably 0.2 parts by mass or more and 15 parts by mass or less, and more preferably 0.3 parts by mass or more and 3 parts by mass or less.

[0061] [ka] [In formula (1), Ar 1 represents a phenylene group or a naphthylene group, and the plurality of Ar 1 may be the same or different, and p is an integer of 4 to 12.

[0062]

[10] The resin composition according to [8] or [9], wherein a mass ratio of the carbon fiber to the water-soluble carbodiimide is 1 / 7 to 160 / 1, preferably 8 / 1 to 120 / 1, and more preferably 10 / 1 to 100 / 1.

[0063]

[11] The semi-aromatic polyamide is Ar 1 is a semi-aromatic polyamide having a structural unit represented by formula (1) in which represents a 1,4-phenylene group and p is 9 or 10; The water-soluble carbodiimide is a carbodiimide compound that is soluble in water at 25°C at a concentration of 10% by mass or more; It has a carbodiimide group (-N=C=N-) and a hydrophilic segment in the molecule, the hydrophilic segment has a structure containing at least one selected from the group consisting of an oxyalkylene group, an acetal structure, an imino group, a hydroxy group, an amino group, an epoxy group, and a carboxy group, The resin composition according to any one of [8] to

[10] , which is a polycarbodiimide having a carbodiimide group (—N═C═N—) equivalent of 300 g / mol or more and 600 g / mol or less.

[0064] (Molded body) One embodiment of the molded article includes the resin composition of the above-described embodiment. An example of the molded article of this embodiment is a molded article containing the resin composition of the above-described embodiment.

[0065] The method for molding the resin composition into a molded article is not particularly limited, but melt molding is preferred, and examples include extrusion molding, T-die molding, blow molding, and injection molding, and the molding method can be selected depending on the shape of the molded article, etc.

[0066] The molded article of this embodiment can be used in any application to which a resin composition can generally be applied. Examples of the molded article of this embodiment include electrical and electronic components such as connectors, sockets, relay parts, coil bobbins, optical pickups, oscillators, printed wiring boards, circuit boards, semiconductor packages, and computer-related parts; semiconductor manufacturing process-related parts such as IC trays and wafer carriers; home electrical appliance parts such as VTRs, televisions, irons, air conditioners, stereos, vacuum cleaners, refrigerators, rice cookers, and lighting fixtures; lighting fixture parts such as lamp reflectors and lamp holders; audio product parts such as compact discs, laser discs (registered trademark), and speakers; communication equipment parts such as ferrules for optical cables, telephone parts, facsimile parts, and modems; separation claws and heater holders. copier and printer related parts; mechanical parts such as impellers, fan gears, gears, bearings, motor parts and cases; automotive parts such as automotive mechanism parts, engine parts, engine room parts, electrical parts, and interior parts, cooking utensils such as microwave cooking pots and heat-resistant tableware; heat insulation and soundproofing materials such as flooring and wall materials, supporting materials such as beams and pillars, building materials such as roofing materials, civil engineering and construction materials; aircraft, spacecraft, and space equipment parts; radiation facility components such as nuclear reactors, marine facility components, cleaning jigs, optical equipment parts, valves, pipes, nozzles, filters, membranes, medical equipment parts and medical materials, sensor parts, sanitary equipment, sporting goods, leisure goods, and cable ties.

[0067] The molded article of the present embodiment contains the resin composition of the above-described embodiment, and therefore has improved durability. Therefore, the molded article of the present embodiment is particularly suitable for sliding applications, and is particularly suitable for use as a mechanical part such as a gear, and is particularly suitable for use as a gear. Types of gears include spur gears, helical gears, racks, internal gears, worm gears, worm wheel gears, bevel gears, hypoid gears, and the like. [Example]

[0068] The present disclosure will be described in more detail below using examples, but the present disclosure is not limited to the following examples.

[0069] <Production of Resin Composition> The semi-aromatic polyamide, carbon fiber, and carbodiimide used were as follows:

[0070] Semi-aromatic polyamide Semi-aromatic polyamide (P1): Ar 1 A semi-aromatic polyamide having a structural unit represented by formula (1), in which is a 1,4-phenylene group and p is 10. Melt mass-flow rate (MFR) 24 g / 10 min. Semi-aromatic polyamide (P2): Ar 1 A semi-aromatic polyamide having a structural unit represented by formula (1), in which is a 1,4-phenylene group and p is 9. MFR: 20 g / 10 min. The MFR of the semi-aromatic polyamide was measured in accordance with JIS K 7210 at a test temperature of 330°C and a load of 2160 g.

[0071] Carbon fiber Mitsubishi Chemical Corporation's "Pyrofil (registered trademark) Chopped Fiber TR03M," fiber length 3 mm, number average fiber diameter 7 μm

[0072] Carbodiimide Carbodiimide (1): Aqueous solution of water-soluble carbodiimide, "Carbodilite SV-02" manufactured by Nisshinbo Chemical Co., Ltd., non-volatile content 40% by mass, carbodiimide group equivalent weight 430 g / mol Carbodiimide (2): non-water-soluble carbodiimide, "Stavaxol (registered trademark) P-100" manufactured by Rhein Chemie

[0073] [Method for measuring number average fiber length of carbon fibers in a resin composition in pellet form] Five grams of pellets were heated at 450°C for three hours to remove the resin components, yielding an ashing residue containing carbon fibers. One gram of the ashing residue was mixed with 150 mL of acetone to obtain a sample solution. Approximately 5 mL of the sample solution was then placed on a glass slide and allowed to dry naturally. The slide with the ashing residue was placed on a projector (microscope) and magnified 100 times to measure the fiber lengths of at least 400 carbon fibers, and the number-average fiber lengths of the resulting carbon fibers were calculated.

[0074] Example 1 1.25 parts by mass of carbodiimide (1) and 30 parts by mass of carbon fiber were mixed, and then heated to 120°C to remove water, thereby obtaining 30.5 parts by mass of a mixture (Ma) of carbon fiber and water-soluble carbodiimide. 30.5 parts by mass of the resulting mixture (Ma) and 69.5 parts by mass of the semi-aromatic polyamide (P1) were placed in a twin-screw extruder (PCM-30, manufactured by Ikegai Corporation) and melt-kneaded while degassing under conditions of a barrel temperature of 320-350°C, a screw rotation speed of 150 rpm, and a discharge rate of 5 kg / min. The mixture was discharged in the form of strands through a circular nozzle (discharge port), passed through a water-cooled belt conveyor, and pelletized with a strand cutter to obtain a resin composition in the form of pellets. The number average fiber length of the carbon fibers in the resulting pellets was 150 μm.

[0075] (Comparative Example 1) Except for using 30 parts by mass of carbon fiber alone instead of 30.5 parts by mass of the mixture (Ma) and changing the blending amount of semi-aromatic polyamide (P1) to 70 parts by mass, a resin composition in the form of pellets was obtained in the same manner as in Example 1. The number average fiber length of the carbon fibers in the obtained pellets was 154 μm.

[0076] (Comparative Example 2) 0.5 parts by mass of carbodiimide (2) and 30 parts by mass of carbon fiber were mixed and then heated to 120° C. to obtain 30.5 parts by mass of a mixture (Mb) of carbon fiber and water-insoluble carbodiimide. Next, except that 30.5 parts by mass of the mixture (Ma) was changed to 30.5 parts by mass of the mixture (Mb), a resin composition in the form of pellets was obtained in the same manner as in Example 1. The number average fiber length of the carbon fibers in the obtained pellets was 153 μm.

[0077] Example 2 Except for changing 69.5 parts by mass of the semi-aromatic polyamide (P1) to 69.5 parts by mass of the semi-aromatic polyamide (P2), a pellet-shaped resin composition was obtained in the same manner as in Example 1. The number average fiber length of the carbon fibers in the obtained pellets was 150 μm.

[0078] (Comparative Example 3) A pellet-shaped resin composition was obtained in the same manner as in Example 2, except that 30 parts by mass of carbon fiber alone was used instead of 30.5 parts by mass of the mixture (Ma) and the amount of semi-aromatic polyamide (P2) was changed to 70 parts by mass. The number average fiber length of the carbon fiber in the obtained pellets was 153 μm.

[0079] <Gear manufacturing example> The pellet-shaped resin composition was placed in an injection molding machine and injection molded to produce a gear under the following injection conditions: barrel temperature 320-340°C, mold temperature 120°C, back pressure 6 MPa, screw rotation speed 100 rpm, injection pressure 100 MPa, injection speed 30 mm / sec, injection time 6 seconds, dwell pressure 90 MPa, and cooling time 25 seconds. The gear was manufactured to have the following shape: spur gear, module 1, number of teeth 48, pressure angle 20°, reference diameter 48 mm, tip diameter 50 mm, root diameter 45.5 mm, face width 8 mm, transition coefficient 0, and spanning tooth thickness 16.909 (number of spanning teeth 6). An example of the manufactured gear is shown in Figure 1.

[0080] <Evaluation> The manufactured gears were subjected to the following durability test. [Durability test] A metal master gear [material: SCM420 carburized, quenched, and tempered (surface hardened), quench-hardened layer depth 0.8 to 1.2, hardness HRC 55 to 60, gear shape: spur gear, module 1, number of teeth 67, pressure angle 20°, reference circle diameter 67 mm, tip circle diameter 69 mm, root circle diameter 64.5 mm, face width 15 mm, transition coefficient 0, and spanning tooth thickness 23.079 (number of spanning teeth 8)] was installed as the drive gear in a power absorption gear operation test machine specified in JIS B 1759, and the manufactured gear was meshed with it. The manufactured gear was subjected to a load torque of 8 N m, a rotational speed of 1000 rpm, no lubrication, a temperature of 23°C, a relative humidity of 50% RH, and a normal backlash of 0.1 mm. The total number of rotations until the gear broke was measured. The results are shown in Table 1. The "destruction" of the gear refers to a state in which power cannot be transmitted from the metal master gear to the gear due to breakage of the gear teeth or the like.

[0081] [Table 1]

[0082] According to the results of the durability test, Example 1 containing a water-soluble carbodiimide had improved gear durability compared to Comparative Example 2 containing a non-water-soluble carbodiimide.

[0083] The durability tests were conducted under high-load conditions with a load torque of 8 N m, demonstrating that the pellet-shaped resin compositions of Examples 1 and 2 are useful molding materials that can be used to produce gears with excellent durability under high-load conditions.

[0084] The configurations and combinations thereof in each embodiment are merely examples, and modifications such as addition, omission, and substitution of configurations are possible within the scope of the spirit of this disclosure. Furthermore, this disclosure is not limited to each embodiment, but is limited only by the claims.

Claims

1. A semi-aromatic polyamide having a structural unit represented by the following formula (1): Carbon fiber and Water-soluble carbodiimide A resin composition comprising: 【Chemistry 1】 [In formula (1), Ar １ represents a phenylene group or a naphthylene group, and the plurality of Ar groups contained in the semi-aromatic polyamide １ may be the same or different, and p is an integer of 4 to 12.

2. The semi-aromatic polyamide is Ar １ The resin composition according to claim 1, which is a semi-aromatic polyamide having a structural unit represented by formula (1) in which represents a 1,4-phenylene group and p is 9 or 10.

3. The resin composition according to claim 1, wherein the content of the water-soluble carbodiimide is 0.1 mass % or more and 15 mass % or less relative to the total mass of the resin composition.

4. The resin composition according to claim 1, wherein the content of the carbon fiber is 5% by mass or more and 60% by mass or less with respect to the total mass of the resin composition.

5. The resin composition according to claim 1, which is a resin composition for molding gears.

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

7. The molded article according to claim 6, which is a gear.

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