TWI845761B - Polyamide resin composition for sliding parts, and sliding parts - Google Patents

Abstract

The object of the present invention is to provide a polyamide resin composition which has excellent formability, heat stability and toughness and is suitable for forming sliding parts requiring wear resistance and excellent sliding stability. The polyamide resin composition for sliding parts of the present invention comprises a crystalline polyamide resin (A), a modified polyolefin resin (B) having a reactive functional group capable of reacting with the terminal group and/or the main chain amide group of the polyamide resin (A) and/or a thermoplastic elastomer (C) having a reactive functional group capable of reacting with the terminal group and/or the main chain amide group of the polyamide resin (A), an antioxidant (D), a mold release agent (E), and a solid lubricant (F); the modified polyolefin resin (B) and/or the thermoplastic elastomer (C) are dispersed in a matrix of the polyamide resin (A) in microdomains with a particle size of less than 5 μm.

Description

Polyamide resin composition for sliding parts, and sliding parts

The present invention relates to a polyamide resin composition, and more particularly to a polyamide resin composition suitable for forming sliding parts.

Polyamide resin is a molding material with excellent sliding properties due to its crystalline properties. In order to obtain better sliding properties, it is known to be mixed with solid lubricants such as molybdenum disulfide, graphite and fluororesin, various lubricating oils, or liquid lubricants such as silicone oil.

Among these slip improvers, solid lubricants need to be blended in large quantities, which has the disadvantage of significantly reducing the toughness of the polyamide resin as the base. Liquid lubricants can provide high slip properties with a relatively small amount, but in most cases, they have poor compatibility with the polyamide resin as the base, and the surface of the molded product is easily contaminated by the liquid lubricant, which limits its use.

As methods for improving the disadvantages caused by the blending of various lubricants, some have proposed a method of blending a modified styrene polymer with a modified high-density polyethylene having a molecular weight within a specific range (Patent Document 1), a method of blending a modified polyolefin resin while using a high-viscosity crystalline polyamide resin, and the like (Patent Document 2).

Although such a polyamide resin composition can provide a molded product with excellent sliding properties without the above-mentioned disadvantages, in recent years, due to the trend of lightweight molded products and complex shapes of molded products, higher-level properties such as improved moldability, improved heat resistance stability, and improved sliding properties are required. [Prior art literature] [Patent literature]

[Patent document 1] Japanese Patent Publication No. 8-157714 [Patent document 2] WO2008/075699

[Identify the problem you want to solve]

The purpose of the present invention is to provide a polyamide resin composition having excellent moldability, heat stability and toughness, and suitable for use in the molding of sliding parts requiring excellent wear resistance and sliding stability. [Means for solving the problem]

The inventors of this case, in order to achieve the above-mentioned results of in-depth research, found that the addition of antioxidants and mold release agents to improve moldability and heat resistance will improve the sliding properties, and further improved the sliding properties by adding solid lubricants to the polyamide resin composition to maintain toughness, thereby achieving this invention.

That is, the present invention is constituted as follows. [1] A polyamide resin composition for sliding parts, comprising a crystalline polyamide resin (A), a modified polyolefin resin (B) having a reactive functional group capable of reacting with the terminal group and/or main chain amide group of the polyamide resin (A), and/or a modified polyolefin resin (B) having a reactive functional group capable of reacting with the terminal group and/or main chain amide group of the polyamide resin (A). A thermoplastic elastomer (C) having a reactive functional group that reacts with a chain amide group, an antioxidant (D), a mold release agent (E), and a solid lubricant (F); The modified polyolefin resin (B) and/or the thermoplastic elastomer (C) are dispersed in a micro-domain with a particle size of less than 5 μm in the matrix of the polyamide resin (A). [2] The polyamide resin composition for sliding parts as described in [1], wherein the antioxidant (D) and the mold release agent (E) are compounds that inhibit the deactivation of the reactive functional groups possessed by the modified polyolefin resin (B) and the thermoplastic elastomer (C). [3] A polyamide resin composition for sliding parts as described in [1] or [2], wherein the reactive functional group is an anhydride group. [4] A polyamide resin composition for sliding parts as described in any one of [1] to [3], wherein the antioxidant (D) is a hindered phenol antioxidant. [5] A polyamide resin composition for sliding parts as described in any one of [1] to [4], wherein the mold release agent (E) is a higher fatty acid ester compound. [6] A polyamide resin composition for sliding parts as described in any one of [1] to [5], wherein the thermoplastic elastomer (C) is a styrene-based and/or olefin-based thermoplastic elastomer. [7] A polyamide resin composition for sliding parts as described in any one of [1] to [6], wherein the solid lubricant (F) is a fluorine-based lubricant and/or an acrylic modified polyorganosiloxane. [8] A sliding part obtained from the polyamide resin composition for sliding parts as described in any one of [1] to [7]. [Effect of the invention]

The polyamide resin composition of the present invention not only has excellent formability, heat stability and toughness, but also has improved wear resistance, and further improved sliding properties such as less variation in friction coefficient. In addition, the polyamide resin composition of the present invention can have both low wear and low friction.

The present invention is described in detail below. The polyamide resin composition for sliding parts of the present invention contains a crystalline polyamide resin (A), a modified polyolefin resin (B) having a reactive functional group capable of reacting with the terminal group and/or the main chain amide group of the polyamide resin (A) (hereinafter, also referred to as the modified polyolefin resin (B)) and/or a thermoplastic elastomer (C) having a reactive functional group capable of reacting with the terminal group and/or the main chain amide group of the polyamide resin (A) (hereinafter, also referred to as the thermoplastic elastomer (C)), an antioxidant (D), a mold release agent (E) and a solid lubricant (F).

The blending amount of each component is expressed as the mass parts when the total mass parts of all resin components of crystalline polyamide resin (A), modified polyolefin resin (B), thermoplastic elastomer (C) and solid lubricant (F) are 100 mass parts. In the polyamide resin composition of the present invention, the blending amount is the content in the polyamide resin composition.

The crystalline polyamide resin (A) is not particularly limited as long as it is a crystalline polymer having an amide bond (-NHCO-) in the main chain, and examples thereof include polyamide 6 (NY6), polyamide 66 (NY66), polyamide 46 (NY46), polyamide 11 (NY11), polyamide 12 (NY12), polyamide 610 (NY610), polyamide 612 (NY612), poly(m-xylylene adipate) (MXD6), hexamethylenediamine-terephthalic acid polymer (6T) , hexamethylenediamine-terephthalic acid and adipic acid polymer (66T), hexamethylenediamine-terephthalic acid and ε-caprolactam copolymer (6T/6), trimethylhexamethylenediamine-terephthalic acid polymer (TMD-T), meta-phenylenediamine and adipic acid and isophthalic acid copolymer (MXD-6/I), tri-hexamethylenediamine and terephthalic acid and ε-caprolactam copolymer (TMD-T/6), diaminodicyclohexylmethane (CA) and isophthalic acid and lauryl lactam copolymer, etc. These can be used alone or in combination of two or more. Among these, polyamide 6 (NY6) and polyamide 66 (NY66) are preferably used.

The relative viscosity of the crystalline polyamide resin (A) is not particularly limited, but is preferably 2.0 to 5.0, more preferably 2.0 to 3.5, as measured with a 96% sulfuric acid solution (polyamide resin concentration 1 g/dl, temperature 25°C).

The modified polyolefin resin (B) is a polyolefin resin obtained by modification. Examples of the polyolefin resin include high-density polyethylene, low-density polyethylene, ultra-high molecular weight polyethylene, linear low-density polyethylene, polypropylene, poly(1-butene), poly(4-methylpentene), etc. These can be used alone or in combination of two or more. Among these, high-density polyethylene is preferably used.

In order to improve the compatibility with the crystalline polyamide resin (A), the modified polyolefin resin (B) has a reactive functional group with the terminal group (amino group or carboxyl group) and/or the main chain amide group of the polyamide resin (A). Examples of the reactive functional group include carboxyl group, acid anhydride group, epoxy group, oxazoline group, amine group, isocyanate group, etc. Among these, an acid anhydride group is preferred from the viewpoint of high reactivity with the polyamide resin (A).

The content of the reactive functional group in the modified polyolefin resin (B) is preferably 0.05 to 8% by mass, more preferably 0.1 to 5% by mass. The method for producing the modified polyolefin resin (B) having the reactive functional group is not particularly limited, and examples thereof include a method of reacting the compound having the reactive functional group in the step of producing the polyolefin resin, a method of mixing polyolefin resin pellets with the compound having the reactive functional group, and kneading the mixture by an extruder to cause the mixture to react, and the like.

The amount of the modified polyolefin resin (B) blended is not particularly limited as long as it is an amount that can be dispersed in a microdomain with a particle size of less than 5 μm in the matrix of the polyamide resin (A). It is usually 0.5 to 10% by mass, preferably 1 to 8% by mass, and more preferably 2 to 6% by mass, relative to 100% by mass of the total resin component.

The thermoplastic elastomer (C) is not particularly limited, and examples thereof include styrene-based thermoplastic elastomers, olefin-based thermoplastic elastomers, polyamide-based thermoplastic elastomers, polyester-based thermoplastic elastomers, polyurethane-based thermoplastic elastomers, etc. These may be used alone or in combination of two or more.

The styrene-based thermoplastic elastomer is not particularly limited, and examples thereof include styrene/butadiene/styrene block copolymer (SBS), styrene/ethylene-butylene/styrene block copolymer (SEBS) which is a hydrogenated product thereof, styrene/butadiene copolymer (SBR), styrene/ethylene/butylene copolymer (HSBR) which is a hydrogenated product thereof, styrene/isobutylene/styrene block copolymer (SIS), styrene/ethylene-propylene/styrene block copolymer (SEPS) which is a hydrogenated product thereof, and the like.

The olefin-based thermoplastic elastomer is not particularly limited, and examples thereof include rubbers such as ethylene/propylene/diene rubber (EPDM), ethylene/propylene rubber (EPR), butyl rubber (IIR), dynamically cross-linked olefin-based thermoplastic elastomers, and flexible ethylene-based copolymers.

The polyamide-based thermoplastic elastomer is not particularly limited, and examples thereof include polyetheresteramide and polyesteramide having a crystalline polyamide having a high melting point as a hard segment and a polyether or polyester having a low glass transition temperature as a soft segment.

The polyester-based thermoplastic elastomer is not particularly limited, and examples thereof include block copolymers of polyether polyester and polyester polyester, which have crystalline polyester with a high melting point as a hard segment and polyether or polyester with a low glass transition temperature as a soft segment.

The polyurethane-based thermoplastic elastomer is not particularly limited, and examples thereof include polyether polyurethane and polyester polyurethane having a crystalline polyester having a high melting point as a hard segment and a polyether or polyester having a low glass transition temperature as a soft segment.

Among these thermoplastic elastomers, from the viewpoint of the balance between the toughness improvement effect and the elastic modulus, styrene-based and/or olefin-based thermoplastic elastomers are preferred, styrene-based thermoplastic elastomers are more preferred, and SEBS is further preferred.

In order to improve the compatibility with the crystalline polyamide resin (A), the thermoplastic elastomer (C) has a reactive functional group that can react with the terminal group (amino group or carboxyl group) and/or the main chain amide group of the polyamide resin (A). Examples of the reactive functional group include a carboxyl group, anhydride group, epoxy group, oxazoline group, amine group, isocyanate group, etc. Among these, anhydride group is preferred from the viewpoint of high reactivity with the polyamide resin (A).

The content of the reactive functional group in the thermoplastic elastomer (C) is preferably 0.05 to 8% by mass, more preferably 0.1 to 5% by mass. The method for producing the thermoplastic elastomer (C) having the reactive functional group is not particularly limited, and examples thereof include a method of reacting a compound having the reactive functional group in the step of producing the thermoplastic elastomer, a method of mixing pellets of the thermoplastic elastomer and the compound having the reactive functional group and kneading them with an extruder to react, and the like.

There is no particular limitation on the amount of the thermoplastic elastomer (C) blended as long as the thermoplastic elastomer (C) can be dispersed in a micro-domain with a particle size of less than 5 μm in the matrix of the polyamide resin (A). Generally, the amount is 0.1 to 10% by mass, preferably 1 to 7% by mass, relative to 100% by mass of the total resin component.

The antioxidant (D) is preferably a compound that inhibits the deactivation of the reactive functional groups possessed by the modified polyolefin resin (B) and the thermoplastic elastomer (C). "Inhibiting the deactivation of the reactive functional groups" means "not reacting with the reactive functional groups". That is, the antioxidant (D) is a compound that does not hinder the microdispersion of the modified polyolefin resin (B) and the thermoplastic elastomer (C) in the matrix of the polyamide resin (A).

The antioxidant (D) is not particularly limited. For example, when the above-mentioned reactive functional groups of the modified polyolefin resin (B) and the thermoplastic elastomer (C) are acid anhydride groups, hindered phenol-based antioxidants, organic antioxidants such as sulfur-based antioxidants and phosphorus-based antioxidants, and thermal stabilizers that do not have functional groups that react with acid anhydride groups can be listed, and hindered phenol-based antioxidants are preferred. One of these can be used, or two or more can be mixed and used. As for the functional groups that react with acid anhydride groups, for example, amino groups and hydroxyl groups can be mentioned. In addition, the phenolic hydroxyl group of the hindered phenol structure should not be the functional group that reacts with the acid anhydride group. Amine-based antioxidants are not ideal because they react with the above-mentioned reactive functional groups to deactivate them.

The blending amount of the antioxidant (D) is preferably 0.01 to 1 part by mass, more preferably 0.1 to 0.5 parts by mass, relative to 100 parts by mass of the total resin component. If the blending amount of the antioxidant (D) is within the above range, it will not only contribute to improving the lubricity and toughness of the polyamide resin composition, but also prevent oxidative degradation over time according to the appropriate amount of the polyamide resin composition.

The release agent (E) is preferably a compound that inhibits the deactivation of the reactive functional groups possessed by the modified polyolefin resin (B) and the thermoplastic elastomer (C). "Inhibiting the deactivation of the reactive functional groups" means "not reacting with the reactive functional groups". That is, the release agent (E) is a compound that does not hinder the microdispersion of the modified polyolefin resin (B) and the thermoplastic elastomer (C) in the matrix of the polyamide resin (A).

The release agent (E) is not particularly limited, and examples thereof include higher fatty acid ester compounds, amide compounds, polyethylene wax, polysilicone, polyethylene oxide, and the like. One of these may be used alone, or two or more of these may be mixed and used. In the case where the reactive functional groups possessed by the modified polyolefin resin (B) and the thermoplastic elastomer (C) are anhydride groups, the release agent (E) is preferably a higher fatty acid ester compound. In addition, a higher fatty acid is a fatty acid having more than 10 carbon atoms, preferably a fatty acid having 11 to 30 carbon atoms. Metal salt compounds are less desirable because they react with the reactive functional groups and inactivate them.

The amount of the release agent (E) blended is preferably 0.05 to 1 part by mass, more preferably 0.1 to 0.8 part by mass, relative to 100 parts by mass of the total resin component. If the amount of the release agent (E) blended is within the above range, it not only contributes to the improvement of the slip and toughness of the polyamide resin composition, but also ensures appropriate demolding properties.

The antioxidant (D) and the mold release agent (E) do not interfere with the microdispersion of the modified polyolefin resin (B) and the thermoplastic elastomer (C) in the matrix of the polyamide resin (A). Therefore, the modified polyolefin resin (B) and the thermoplastic elastomer (C) react efficiently with the polyamide resin (A) and are microdispersed in the matrix of the polyamide resin (A) in a microdomain with a particle size of 5 μm or less. As a result, it is believed that the effect of improving the sliding property by the modified polyolefin resin (B) and the effect of improving the toughness by the thermoplastic elastomer (C) will work effectively, and the unique effect of the present invention will be exhibited. The particle size is preferably 4 μm or less, and more preferably 3.5 μm or less. The lower limit of the particle size is not particularly limited, but from the viewpoint of fluidity, it is preferably 1 μm or more, more preferably 2 μm or more.

The solid lubricant (F) has the effect of contributing to improving the surface friction characteristics while suppressing the reduction of toughness. It is considered that the unique effect of the present invention is exhibited by adding the solid lubricant (F) to the polyamide resin composition.

The solid lubricant (F) is not particularly limited, but is preferably a fluorine-based lubricant or an acrylic modified polyorganosiloxane, either of which may be used alone or in combination of two or more.

As for the above-mentioned fluorine-based lubricant, for example, tetrafluoroethylene resin (PTFE), perfluoro-alkoxy resin (PFA), tetrafluoroethylene-hexafluoropropylene copolymer resin (FEP), tetrafluoroethylene-ethylene copolymer resin (ETFE), vinylidene fluoride resin (PVDF), trifluorochloroethylene resin (PCTFE), etc. Among them, PTFE is preferred from the viewpoints of heat resistance, sliding properties, etc.

The average particle size of the fluorine-based lubricant is preferably 1 to 200 μm, more preferably 7 to 100 μm, and further preferably 10 to 50 μm. If the average particle size exceeds 200 μm, the dispersibility of the fluorine-based lubricant in the matrix of the polyamide resin (A) deteriorates, and the mechanical strength of the molded body tends to decrease. On the other hand, if the average particle size is less than 1 μm, the particles of the fluorine-based lubricant tend to produce secondary aggregation, and it becomes difficult to mix uniformly, and the mechanical strength of the molded body tends to decrease.

The acrylic modified polyorganosiloxane may be obtained by graft copolymerizing at least (meth)acrylate to polyorganosiloxane, and preferably by graft copolymerizing a mixture of 70% by mass or more of (meth)acrylate and 30% by mass or less of other copolymerizable monomers to polyorganosiloxane at a mass ratio of 5/95 to 95/5.

As for the above-mentioned (meth)acrylate, for example, there can be mentioned acrylates such as methyl acrylate, ethyl acrylate, isopropyl acrylate, n-propyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate, n-octyl acrylate, 2-hydroxyethyl acrylate, and 2-methoxyethyl acrylate; and methacrylates such as methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, n-lauryl methacrylate, 2-hydroxyethyl methacrylate, and 2-ethoxyethyl methacrylate. These can be used alone or in combination of two or more. Among these, it is preferable to use at least methyl methacrylate as one component.

As for the above-mentioned other copolymerizable monomers, there can be mentioned styrene compounds such as styrene, vinyl toluene, α-methyl styrene; unsaturated nitriles such as acrylonitrile and methacrylonitrile; halogenated olefins such as vinyl chloride and vinylidene chloride; vinyl esters such as vinyl acetate and vinyl propionate; unsaturated amides such as acrylamide, methacrylamide, and N-hydroxymethylacrylamide; monomers having one double bond such as unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and maleic anhydride; polyunsaturated monomers such as ethylene glycol dimethacrylate, propylene glycol dimethacrylate, 1,4-butanediol dimethacrylate, allyl methacrylate, triallyl cyanurate, and triallyl isocyanurate, etc. These monomers can be used alone or in combination of two or more.

The average particle size of the acrylic modified polyorganosiloxane is preferably 1 to 500 μm, more preferably 10 to 400 μm, and further preferably 30 to 350 μm. If the average particle size exceeds 500 μm, the dispersibility of the acrylic modified polyorganosiloxane in the matrix of the polyamide resin (A) becomes poor, and the mechanical strength of the molded body tends to decrease. On the other hand, if the average particle size is less than 1 μm, the particles of the acrylic modified polyorganosiloxane tend to produce secondary aggregation, becoming difficult to mix uniformly, and the mechanical strength of the molded body tends to decrease.

The amount of the solid lubricant (F) blended is preferably 0.1-20% by mass, more preferably 0.5-10% by mass, relative to 100% by mass of the total resin component. If it is 0.1% by mass or more, wear resistance, sliding stability, and surface lubricity are effectively improved. On the other hand, if it is 20% by mass or less, the mechanical properties of the polyamide resin composition are effectively improved, especially the toughness is effectively improved.

In the polyamide resin composition of the present invention, in addition to the above-mentioned components (A) to (F), additives such as carbon black, copper oxide, alkali metal halide, light or heat stabilizer, crystal nucleating agent, antistatic agent, pigment, dye, coupling agent, etc., which are conventionally blended in polyamide resin compositions as weather resistance improvers, can be blended as long as they do not interfere with the fine dispersion of the modified polyolefin resin (B) and the thermoplastic elastomer (C) in the matrix of the above-mentioned polyamide resin (A). In addition, by blending fillers within a range that does not impair the toughness of the polyamide resin composition, the strength and rigidity of the molded product can be greatly improved. Examples of fillers include glass fiber, carbon fiber, metal fiber, aramid fiber, sponge, potassium titanate whiskers, wollastonite, glass flakes, glass beads, talc, mica, clay, calcium carbonate, barium sulfate, titanium oxide, aluminum oxide, etc. In the polyamide resin composition of the present invention, the total amount of the above-mentioned components (A) to (F) preferably accounts for 70% by mass or more, more preferably 80% by mass or more, and further preferably 90% by mass or more.

The polyamide resin composition of the present invention can be produced by kneading the components using a kneading device such as a single-screw extruder, a two-screw extruder, a pressure extruder, etc. The kneading device is preferably a two-screw extruder. In one embodiment, the above-mentioned (A) to (F) components and pigments depending on the application are mixed and put into a two-screw extruder. A polyamide resin composition with excellent slip can be produced by uniformly kneading in a two-screw extruder. The kneading temperature of the two-screw extruder is preferably 220 to 300°C, and the kneading time is preferably about 2 to 15 minutes.

The polyamide resin composition of the present invention can be widely used as a raw material for sliding parts such as electrical and electronic parts, automobile parts, construction parts, and industrial parts that require sliding properties. Specifically, the sliding parts include bearings, gears, door checkers, chain guide parts, etc. [Example]

Hereinafter, the present invention will be specifically described using examples, but the present invention is not limited to these examples. In addition, the various physical properties of the polyamide resin molded products obtained in the following examples are measured based on the following test methods.

The raw materials used in the examples and comparative examples are as follows. As crystalline polyamide resin (A), (A1) to (A3) are used. (A1) Polyamide 66 (RV = 3.4): EPR34W (manufactured by Shanghai Shenma Plastic Technology Co., Ltd.), melting point 265°C (A2) Polyamide 66 (RV = 2.8): Vydyne 21FSR (manufactured by Ascend), melting point 265°C (A3) Polyamide 66 (RV = 2.4): EPR24 (manufactured by Shanghai Shenma Plastic Technology Co., Ltd.), melting point 265°C

As the modified polyolefin resin (B), (B1) and (B2) were used. (B1) Maleic anhydride-modified polyethylene: MODIC DH0200 (manufactured by Mitsubishi Chemical Co., Ltd.) (B2) Unmodified polyethylene: hi-zex 6203B (manufactured by Prime Polymer Co., Ltd.)

As the thermoplastic elastomer (C), (C1) and (C2) were used. (C1) Maleic anhydride modified SEBS: Tuftec M-1943 (manufactured by Asahi Kasei Corporation) (C2) Unmodified SEBS: Tuftec H-1221 (manufactured by Asahi Kasei Corporation)

As the antioxidant (D), (D1) and (D2) were used. (D1) Hindered phenol antioxidant: triethylene glycol-bis-3-(3-tert-butyl-4-hydroxy-5-methylphenyl) propionate (SONGNOX2450, manufactured by SONGWON) (D2) Amine antioxidant: NONFLEX DCD (manufactured by Seiko Chemical Co., Ltd.)

As the mold release agent (E), (E1) to (E3) were used. (E1) Aliphatic ester: Ricolb WE-40 (manufactured by Clariant Japan K.K.) (E2) Magnesium stearate: N.P.1500-S (manufactured by Tamnan Chemical Industry Co., Ltd.) (E3) Calcium octadecanoate: Licomont Cav102 (manufactured by Clariant Japan K.K.)

As solid lubricants (F), (F1) to (F3) were used. (F1) PTFE: KT-300M (produced by Kitamura Co., Ltd.), average particle size 15μm (F2) Acrylic modified polyorganosiloxane: CHALINE R-170S (produced by Nissin Chemical Industry Co., Ltd.), average particle size 30μm (F3) Polysilicone powder: KMP-590 (produced by Shin-Etsu Silicone Co., Ltd.), average particle size 2μm In addition, the average particle size was measured by the following method. Each solid lubricant was observed by a differential interference microscope and photographed. Ten particles in the microscopic photograph were randomly selected, the length diameters of the selected particles were measured, and the average value thereof was taken as the average particle size.

[Examples 1 to 13, Comparative Examples 1 to 15] The evaluation samples were prepared by weighing the raw materials according to the blending ratio of the polyamide resin composition shown in Tables 1 and 2, mixing them by rollers, and then feeding them into a two-axis extruder. The temperature of the two-axis extruder was set at 250℃ to 300℃, and the mixing time was set at 5 to 10 minutes. The obtained pellets were used to form various evaluation samples by an injection molding machine. The cylinder temperature of the injection molding machine was set at 250℃ to 290℃, and the mold temperature was set at 80℃.

The various evaluation and measurement methods are as follows. The evaluation and measurement results are shown in Tables 1 and 2. 1. Relative viscosity of polyamide resin (96% sulfuric acid solution method) Using an Oobleck viscometer, the measurement was performed at 25°C with 96 mass% sulfuric acid solution and a polyamide resin concentration of 1g/dl.

2. Melting point of polyamide resin A differential scanning calorimeter (Seiko Instruments Inc., EXSTAR 6000) was used to measure the temperature at a heating rate of 20°C/min to obtain the endothermic peak temperature.

3.Tensile strength, tensile modulus, and tensile elongation Measured in accordance with ISO178.

4. Impact resistance Measured in accordance with ISO179-1.

5. Sliding property Using a thrust wear tester, a cylindrical molded product made of polyoxymethylene (POM) was brought into contact with a polyamide resin plate on which a certain amount of dust prepared by mixing grease mixed with molybdenum disulfide, silica sand and volcanic ash in a mass ratio of 1:1:1 was evenly applied. The plate was continuously slid for 30 minutes at a load of 30kgf/ ^cm2 and a speed of 40mm/sec. The dynamic friction coefficient was then calculated from the weight difference before and after the wear and the wear load after convergence during the friction test.

6. Particle size Cut out the evaluation sample after forming, and make a cross section using a microtome equipped with a glass knife. Observe the obtained cross section with a differential interference microscope and take a photo. Among the microdomains of the modified polyolefin resin (B) and the thermoplastic elastomer (C) in the microscope photo, randomly select the 10 microdomains with the largest dispersion diameter, measure the length of the selected microdomains, and take the average value as the particle size.

[Table 1]

[Table 2]

Examples 1 to 13 can obtain a polyamide resin composition with a Charpy impact strength of more than 6 kJ/ ^m2 , low wear and dynamic friction coefficient, and both toughness and sliding properties. In addition, there is no significant loss in tensile modulus and tensile elongation. Comparative Examples 1 to 3 are due to insufficient toughness, and the brittle surface damage during sliding cannot be suppressed by the alloy of polyolefin resin alone, and the wear becomes larger. Comparative Examples 4 to 7 are sufficient in toughness, but the tensile modulus is insufficient, dust will enter the material surface, and it is still easy to wear, and it is difficult to exert the sliding modification effect of polyolefin resin. Comparative Examples 8 and 12 are not ideal because they contain unmodified polyolefin resins or unmodified thermoplastic elastomers, which make it difficult to form micro-dispersed micro-domains and result in a particle size that is difficult to exhibit excellent physical properties. Comparative Examples 9 to 11 use amine antioxidants or fatty acid metal salts, respectively, which react with the reactive functional groups of the polyolefin resins or thermoplastic elastomers to inactivate the reactive functional groups, and thus fail to form micro-dispersed micro-domains. Comparative Example 13 is mixed with a solid lubricant, but because it is simply polysilicone powder, agglomerates are easily formed in the polyamide resin composition, so brittle failure is easily generated at the interface between the polysilicone powder and the polyamide resin, and the wear amount becomes larger. Although Comparative Examples 14 and 15 are mixed with a solid lubricant, they are not mixed with polyolefin resin or thermoplastic elastomer, so although the dynamic friction coefficient is low, brittle failure cannot be suppressed and the wear amount cannot be reduced.

FIG1 is an image obtained by observing the cross section of Example 2 using a differential interference microscope. It can be seen that the polyolefin resin and the thermoplastic elastomer are uniformly dispersed in the matrix of the polyamide resin in microdomains with a particle size of less than 5 μm. On the other hand, FIG2 is an image obtained by observing the cross section of Comparative Example 10 using a differential interference microscope. The above two modified materials are unevenly dispersed in the matrix of the polyamide resin and are not microdispersed. In addition, there are large microdomains, which may concentrate stress during wear and become the starting point of wear. [Industrial Utilization]

The polyamide resin composition of the present invention is a molding material having both excellent toughness and sliding properties. It is particularly suitable for sliding parts requiring excellent wear resistance and sliding stability. As an engineering plastic that can be used in a wide range of fields, it is expected to make a great contribution to the industry.

without.

[Figure 1] An image obtained by observing the cross section of the evaluation sample prepared in Example 2 using a differential interference microscope. [Figure 2] An image obtained by observing the cross section of the evaluation sample prepared in Comparison Example 10 using a differential interference microscope.

Claims (7)

A polyamide resin composition for sliding parts, comprising a crystalline polyamide resin (A), a modified polyolefin resin (B) having a reactive functional group capable of reacting with the terminal group and/or the main chain amide group of the polyamide resin (A), and/or a thermoplastic polyamide resin (B) having a reactive functional group capable of reacting with the terminal group and/or the main chain amide group of the polyamide resin (A). Elastomer (C), antioxidant (D), release agent (E), and solid lubricant (F); the solid lubricant (F) is a fluorine-based lubricant and/or acrylic modified polyorganosiloxane, and the modified polyolefin resin (B) and/or the thermoplastic elastomer (C) are dispersed in the matrix of the polyamide resin (A) in micro-domains with a particle size of less than 5μm. The polyamide resin composition for sliding parts of claim 1, wherein the antioxidant (D) and the mold release agent (E) are compounds that inhibit the deactivation of the reactive functional groups possessed by the modified polyolefin resin (B) and the thermoplastic elastomer (C). A polyamide resin composition for sliding parts as claimed in claim 1 or 2, wherein the reactive functional group is an anhydride group. The polyamide resin composition for sliding parts of claim 1 or 2, wherein the antioxidant (D) is a hindered phenol antioxidant. A polyamide resin composition for sliding parts as claimed in claim 1 or 2, wherein the mold release agent (E) is a higher fatty acid ester compound. The polyamide resin composition for sliding parts as claimed in claim 1 or 2, wherein the thermoplastic elastomer (C) is a styrene-based and/or olefin-based thermoplastic elastomer. A sliding part obtained from a polyamide resin composition for sliding parts as claimed in any one of claims 1 to 6.