TWI845760B - Polyamide resin composition for sliding parts, and sliding parts - Google Patents

Abstract

The purpose of the present invention is to provide a polyamide resin composition that has excellent moldability and heat resistance stability and is suitable for the molding of sliding parts that require sliding properties, especially wear resistance of particles with high hardness (hereinafter referred to as dust) and excellent sliding stability. The solution of the present invention is: 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), 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), and a mold release agent (E); the modified polyolefin resin (B) and 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

[The problem that the invention wants to solve]

The purpose of the present invention is to provide a polyamide resin composition having excellent moldability and heat resistance stability, and suitable for use in the molding of sliding parts requiring sliding properties, especially wear resistance of particles (hereinafter also referred to as dust) with high hardness, and excellent sliding stability. [Means for solving the problem]

The inventors of this case, in order to achieve the above-mentioned topic, conducted in-depth research and found that the addition of antioxidants and mold release agents to improve formability and heat resistance would improve the sliding properties, thereby achieving this invention.

That is, the present invention has the following structure. [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 the main chain amide group of the polyamide resin (A), 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), and a mold release agent (E); The modified polyolefin resin (B) and 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. [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] The polyamide resin composition for sliding parts as described in [1] or [2], wherein the reactive functional group is an anhydride group. [4] The 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 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 sliding part obtained from the polyamide resin composition for sliding parts as described in any one of [1] to [6]. [Effect of the invention]

The polyamide resin composition of the present invention not only has excellent moldability and heat resistance stability, but also has improved wear resistance and further improved sliding properties such as less variation in friction coefficient.

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)), 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), and a mold release agent (E).

The blending amount of each component is expressed as the mass parts when the total mass parts of all the resin components of the crystalline polyamide resin (A), the modified polyolefin resin (B), and the thermoplastic elastomer (C) 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 0.05-8% by mass, more preferably 0.1-5% 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 micro-domain with a particle size of less than 5 μm in the matrix of the polyamide resin (A). It is usually 0.5-10% by mass, preferably 1-8% by mass, and more preferably 2-6% by mass, relative to 100% by mass of the entire 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 0.05-8% by mass, more preferably 0.1-5% 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 0.1-10% by mass, preferably 1-7% 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 slip 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, etc. These may be used alone or in combination of two or more. In the case where the reactive functional groups of 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 to inactivate them.

The blending amount of the release agent (E) is preferably 0.05-1 mass part, more preferably 0.1-0.8 mass part, relative to 100 mass parts of the total resin components. If the blending amount of the release agent (E) 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.

In the polyamide resin composition of the present invention, in addition to the above-mentioned components (A) to (E), additives such as carbon black, copper oxide, alkali metal halide, light or heat stabilizer, crystal nucleating agent, lubricant, 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 microdispersion 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, 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 (E) 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 kneader, etc. The kneading device is preferably a two-screw extruder. In one embodiment, the above-mentioned (A) to (E) components and pigments depending on the application are mixed and put into a two-screw extruder. By uniformly kneading in a two-screw extruder, a polyamide resin composition with excellent slip can be produced. The kneading temperature of the two-screw extruder is preferably 220~300℃, and the kneading time is preferably about 2~15 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.)

[Examples 1 to 7, Comparative Examples 1 to 8] 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℃~300℃, and the mixing time was set at 5~10 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℃~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 the contraction 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] Embodiment 1 Embodiment 2 Embodiment 3 Embodiment 4 Embodiment 5 Embodiment 6 Embodiment 7 Composition (mass) Polyamide resin (A1) 92 93 89 96 90 Polyamide resin (A2) 92 Polyamide resin (A3) 92 Polyolefin resin (B1) 3 3 3 2 6 3 3 Polyolefin resin (B2) Thermoplastic elastomer (C1) 5 5 5 5 5 1 7 Thermoplastic elastomer (C2) Antioxidant (D1) 0.2 0.2 0.2 0.2 0.2 0.2 0.2 Antioxidant (D2) Release agent (E1) 0.4 0.4 0.4 0.4 0.4 0.4 0.4 Release agent (E2) Release agent (E3) Tensile properties Tensile strength(MPa) 70 69 69 72 68 76 68 Tensile modulus (GPa) 2.8 2.8 2.8 2.9 2.7 3.2 2.7 Tensile elongation (%) 65 65 65 63 67 56 70 Impact characteristics Charpy impact strength (kJ/m ² ) 8.7 8.5 8.3 8.1 9.0 6.8 9.4 Wear characteristics Wear loss (mg/km) 25 27 28 twenty three 29 twenty three 29 Dynamic friction coefficient 0.06 0.06 0.06 0.08 0.06 0.07 0.07 Dispersion diameter Particle size (μm) 2.6 2.8 2.8 2.5 3.2 2.1 3.5

[Table 2] Comparison Example 1 Comparison Example 2 Comparison Example 3 Comparison Example 4 Comparison Example 5 Comparative Example 6 Comparison Example 7 Comparative Example 8 Composition (mass) Polyamide resin (A1) 100 98 95 92 92 92 92 92 Polyamide resin (A2) Polyamide resin (A3) Polyolefin resin (B1) 2 3 3 3 3 Polyolefin resin (B2) 3 Thermoplastic elastomer (C1) 5 5 5 5 5 Thermoplastic elastomer (C2) 5 Antioxidant (D1) 0.2 0.2 0.2 0.2 0.2 0.2 0.2 Antioxidant (D2) 0.2 Release agent (E1) 0.4 0.4 0.4 0.4 0.4 Release agent (E2) 0.4 Release agent (E3) 0.4 0.4 Tensile properties Tensile strength(MPa) 81 78 73 73 73 71 72 68 Tensile modulus (GPa) 3.3 3.2 3.0 3.0 3.0 3.0 3.1 3.0 Tensile elongation (%) 50 51 60 56 51 54 51 57 Impact characteristics Charpy impact strength (kJ/m ² ) 4.5 5.3 7.2 6.6 5.7 5.9 5.5 6.4 Wear characteristics Wear loss (mg/km) 37 33 37 43 40 37 39 36 Dynamic friction coefficient 0.12 0.09 0.13 0.12 0.10 0.10 0.12 0.10 Dispersion diameter Particle size (μm) - 3.1 2.6 14.3 10.4 13.4 12.4 12.8

The Charpy impact strength of Examples 1 to 7 is all above 6 kJ/ ^m2 , and a composition with higher toughness is obtained compared to the unmodified polyamide. In addition, there is no significant loss in tensile modulus or tensile elongation. The wear amount and dynamic friction coefficient after the sliding test in the medium dust are also better than those of Comparative Examples 1 to 8. Comparative Examples 1 and 2 cannot suppress the brittle surface damage during sliding due to insufficient toughness, and the wear amount becomes larger. Although Comparative Example 3 has sufficient toughness, it is difficult to exert the sliding modification effect of the polyolefin resin. Comparative Example 4 is not suitable because it is difficult to form micro-dispersed micro-domains because the formula contains unmodified thermoplastic elastomers, and the particle size is not easy to show good physical properties. Comparative Examples 5, 6, and 7 use amine antioxidants and fatty acid metal salts, which react with the reactive functional groups of modified polyolefin resins or thermoplastic elastomers to inactivate the reactive functional groups, so micro-dispersed micro-domains cannot be formed. Comparative Example 8 is difficult to form micro-dispersed micro-domains because the formula contains unmodified polyolefin resins, and the sliding modification effect cannot be uniformly exerted on the surface, and the wear amount becomes large.

FIG1 is an image obtained by observing the cross section of Example 1 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 6 using a differential interference microscope. The above two modified materials are unevenly dispersed in the matrix of the polyamide resin, and no microdomains of microdispersion are formed. 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 with both excellent toughness and sliding properties. It is particularly suitable for sliding parts that require wear resistance of particles with high hardness and excellent 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.

[Figure 1] An image obtained by observing the cross section of the evaluation sample prepared in Example 1 using a differential interference microscope. [Figure 2] An image obtained by observing the cross section of the evaluation sample prepared in Comparison Example 6 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), 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), and a mold release agent (E); the modified polyolefin resin (B) and the thermoplastic elastomer (C) are dispersed in a microdomain with a particle size of less than 5 μm in the matrix of the polyamide resin (A). 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. The polyamide resin composition for sliding parts of claim 1 or 2, wherein the release agent (E) is a higher fatty acid ester compound. The polyamide resin composition for sliding parts of claim 1 or 2, wherein the thermoplastic elastomer (C) is a styrene-based and/or olefin-based thermoplastic elastomer. A sliding part is obtained from the polyamide resin composition for sliding parts as described in any one of claims 1 to 6.