阅读说明：本技术 注射成型用聚酰胺系树脂组合物以及由其构成的滑动部件 (Polyamide resin composition for injection molding and sliding member comprising same ) 是由 岩村和树 吉村信宏 泷田宗利 于 2020-05-14 设计创作，主要内容包括：本发明提供了一种注射成型用聚酰胺系树脂组合物,适用于要求成型性、耐热稳定性优异,同时耐磨损性、滑动稳定性优异的滑动部件,该聚酰胺系树脂组合物含有结晶性聚酰胺树脂(A)以及具有液晶骨架的聚酯纤维(B),该结晶性聚酰胺树脂(A)的熔点优选为170℃以上,基于聚酰胺系树脂组合物的总质量,优选含有0.1～40质量％的具有液晶骨架的聚酯纤维(B)。(The present invention provides a polyamide resin composition for injection molding, which is suitable for sliding parts requiring excellent moldability and heat stability, and also excellent abrasion resistance and sliding stability, and which contains a crystalline polyamide resin (A) and a polyester fiber (B) having a liquid crystal skeleton, wherein the crystalline polyamide resin (A) preferably has a melting point of 170 ℃ or higher, and preferably contains 0.1 to 40 mass% of the polyester fiber (B) having a liquid crystal skeleton, based on the total mass of the polyamide resin composition.)

1. A polyamide resin composition for injection molding, characterized by containing a crystalline polyamide resin A and a polyester fiber B having a liquid crystal skeleton.

2. The polyamide resin composition for injection molding according to claim 1, wherein the crystalline polyamide resin A has a melting point of 170 ℃ or higher.

3. The polyamide resin composition for injection molding according to claim 1 or 2, wherein the polyester fiber B having a liquid crystal skeleton is contained in an amount of 0.1 to 40 mass% based on the total mass of the polyamide resin composition.

4. A sliding member comprising the polyamide resin composition according to any one of claims 1 to 3.

Technical Field

The present invention relates to a polyamide resin composition for injection molding, and more particularly to a polyamide resin composition for injection molding suitable for a sliding member.

Background

Polyamide resins are crystalline and therefore are molding materials having excellent sliding properties, but solid lubricants such as molybdenum disulfide, graphite, and fluorine resins, various lubricating oils, and liquid lubricants such as silicone oils are known to be blended in order to obtain more excellent sliding properties.

Among these sliding improvers, a large amount of solid lubricant is required to be mixed, which has a disadvantage of significantly reducing the toughness of the polyamide resin as a base material, and a liquid lubricant can impart efficient sliding properties in a relatively small amount, but in many cases, compatibility with the resin as a base material is poor, and the surface of a molded article is often contaminated with these liquid lubricants, which has a disadvantage of limited usefulness.

As a method for improving the disadvantages caused by mixing of various lubricants, a method of mixing carbon fibers and aramid fibers (patent document 1), a method of mixing modified polyethylene (patent document 2), and the like have been proposed.

According to the polyamide resin composition, a molded article having excellent sliding properties can be provided without the above-mentioned disadvantages. However, in recent years, due to the tendency of weight reduction of molded articles, complication of the shape of molded articles, and the like, higher-level characteristics such as improvement of sliding characteristics have been demanded. Further, from the viewpoint of complexity of products, abrasion between resin compositions as well as metals is more important. Therefore, the methods proposed so far cannot achieve satisfactory characteristics.

Documents of the prior art

Patent document

[ patent document 1] International publication No. WO2017/110323

[ patent document 2] International publication No. WO2008/075699

Disclosure of Invention

Problems to be solved by the invention

The invention provides a polyamide resin composition for injection molding, which is suitable for sliding parts requiring excellent moldability and heat resistance stability, and excellent abrasion resistance and sliding stability.

Technical scheme for solving problems

The present inventors have conducted intensive studies to solve the above problems and as a result, have found that an organic fiber having a liquid crystal skeleton, particularly a polyester fiber, affects sliding characteristics, and have completed the present invention.

Namely, the present invention has the following composition.

[1] A polyamide resin composition for injection molding, characterized by containing a crystalline polyamide resin (A) and a polyester fiber (B) having a liquid crystal skeleton.

[2] The polyamide resin composition for injection molding according to [1], wherein the crystalline polyamide resin (A) has a melting point of 170 ℃ or higher.

[3] The polyamide resin composition for injection molding according to [1] or [2], characterized by containing 0.1 to 40 mass% of a polyester fiber (B) having a liquid crystal skeleton, based on the total mass of the polyamide resin composition.

[4] A sliding member comprising the polyamide resin composition according to any one of [1] to [3 ].

Effects of the invention

The polyamide resin composition of the present invention is excellent in moldability and heat resistance stability, and further improved in sliding properties such as improved abrasion resistance and reduced dynamic friction coefficient.

Detailed Description

The present invention will be specifically described below.

The crystalline polyamide resin (a) in the present invention is not particularly limited as long as it is a crystalline polymer having amide bonds (-NHCO-) in the main chain, and examples thereof include polyamide 6(PA6), polyamide 66(PA66), polyamide 46(PA46), polyamide 11(PA11), polyamide 12(PA12), polyamide 610(PA610), polyamide 612(PA612), polymetaxylylene adipamide (PAMXD6), hexamethylenediamine-terephthalic acid polymer (PA6T), hexamethylenediamine-terephthalic acid-adipic acid copolymer (PA6T/66), hexamethylenediamine-terephthalic acid-epsilon-caprolactam copolymer (PA6T/6), trimethylhexamethylenediamine-terephthalic acid polymer (PATMD-T), isophthalic acid-isophthalic acid copolymer (PAMXD-6/I), and the like, Crystalline polyamide resins such as copolymers of trimethylhexamethylenediamine-terephthalic acid and epsilon-caprolactam (PATMD-T/6), copolymers of diaminodicyclohexylmethane (CA), and copolymers of isophthalic acid and laurolactam, and mixtures thereof, but the invention is not limited thereto.

The crystalline polyamide resin (A) is preferably a polyamide having a melting point of 170 ℃ or higher. If the melting point is less than the above-mentioned crystalline polyamide, the glass transition temperature is usually 40 ℃ or lower, and the surface may be softened by heat generated during sliding. The melting point of the crystalline polyamide resin (a) is more preferably 200 ℃ or higher, and still more preferably 220 ℃ or higher. The upper limit of the melting point of the crystalline polyamide resin (a) is preferably 350 ℃ or lower from the viewpoint of suppressing decomposition of the polyester fiber having a liquid crystal skeleton.

In the present invention, polyamide 6 and polyamide 66 are particularly preferable as the crystalline polyamide resin (a).

The relative viscosity of the crystalline polyamide resin (A) in the present invention is not particularly limited, and a solution of a 96% sulfuric acid solution (polyamide resin concentration of 1g/dl, temperature of 25 ℃) in the range of 2.0 to 5.0 can be used. The crystalline polyamide resin (A) preferably has a relative viscosity of 2.0 to 3.5, more preferably 2.1 to 3.4.

The amount (content) of the crystalline polyamide resin (a) is preferably 35% by mass or more, more preferably 60 to 99.9% by mass, even more preferably 70 to 99% by mass, and particularly preferably 75 to 98% by mass, based on the total mass of the polyamide resin composition.

The organic fiber (B) in the present invention is preferably a polyester fiber (B) having a liquid crystal skeleton (hereinafter referred to as a liquid crystal polyester fiber (B)). Examples of the polyester constituting the liquid crystal polyester fiber (B) include, but are not limited to, a polycondensate of ethylene terephthalate and p-hydroxybenzoic acid, a polycondensate of dihydric phenol and phthalic acid and p-hydroxybenzoic acid, and a polycondensate of 2, 6-hydroxynaphthoic acid and p-hydroxybenzoic acid, as long as the polyester is a synthetic resin having liquid crystal properties due to linear ordered arrangement of molecules and defined as a thermoplastic resin.

Examples of the polyester constituting the liquid crystal polyester fiber (B) include those composed of an aromatic dicarboxylic acid, an aromatic diol and/or an aromatic hydroxycarboxylic acid and derivatives thereof, and in some cases, copolymers of these with an alicyclic dicarboxylic acid, an alicyclic diol, an aliphatic diol and derivatives thereof. Here, examples of the aromatic dicarboxylic acid include: terephthalic acid, isophthalic acid, 4' -dicarboxybenzene, 2, 6-diacetoxynaphthalene, 1, 2-bis (4-carboxyphenoxy) ethane, or nucleophilic substitution of their alkyl, aryl, alkoxy, halogen groups. Examples of the aromatic diol include: hydroquinone, resorcinol, 4 '-dihydroxybenzophenone, 4' -dihydroxybenzoylmethane, 4 '-dihydroxybenzoethane, 2-bis (4-hydroxyphenyl) propane, 4' -dihydroxydiphenyl ether, 4 '-dihydroxybenzenesulfone, 4' -dihydroxydiphenyl sulfide, 2, 6-dihydroxynaphthalene, 1, 5-dihydroxynaphthalene, and the like, or nucleophilic substitution of their alkyl, aryl, alkoxy, halogen groups. Examples of the aromatic hydroxycarboxylic acid include: p-hydroxybenzoic acid, m-hydroxybenzoic acid, 2-hydroxy-6-naphthoic acid, 1-hydroxy-5-naphthoic acid, and the like, or nucleophilic substitution products of their alkyl, aryl, alkoxy, halogen groups. Examples of the alicyclic dicarboxylic acid include: trans-1, 4-dicarboxylcyclohexane, cis-1, 4-dicarboxylcyclohexane, and the like, or nucleophilic substitution products of alkyl, aryl, and halogen groups thereof. Examples of the alicyclic and aliphatic diols include: trans-1, 4-dihydroxycyclohexane, cis-1, 4-dihydroxycyclohexane, ethylene glycol, 1, 4-butanediol, benzenedimethanol, and the like.

The liquid crystal polyester fiber (B) may contain other polymers or additives or may be coated with a sizing agent within a range not to impair the object of the present invention.

The fiber length and fiber diameter of the liquid crystal polyester fiber (B) are not particularly limited, but the fiber diameter is preferably 0.1 to 50 μm and the fiber length is preferably 0.05 to 10 mm. The fiber diameter is more preferably 1 to 30 μm, still more preferably 8 to 25 μm, and particularly preferably 10 to 22 μm. The fiber length is more preferably 0.3 to 5mm, and a short cut type is preferably used.

As the liquid crystal polyester fiber (B), "Zxion (registered trademark)" manufactured by kbsieren, and "Vectran (registered trademark)" manufactured by KURARAY can be used.

The amount (content) of the liquid crystal polyester fiber (B) is preferably 0.1 to 40% by mass, more preferably 1 to 30% by mass, and still more preferably 2 to 25% by mass, based on the total mass of the polyamide resin composition. If the amount is less than 0.1% by mass, the effect of improving the sliding property is insufficient, while if it exceeds 40% by mass, the effect is saturated, which is not preferable, and the appearance of the molded article is deteriorated due to the liquid crystal polyester fiber floating.

In the present invention, the reason why the liquid crystal polyester fiber (B) is used to improve the sliding properties, particularly the sliding properties through the use of dust, is considered to be that the favorable frictional properties of the liquid crystal polyester fiber impart lubricity to the surface properties of the polyamide resin composition. In addition, the polyamide resin composition is damaged, and the liquid crystal polyester fibers present in the composition are detached and deposited on the surface. It is also suggested that the abrasive pulverization is carried out by shearing and chopping the fibers in the fiber direction, and an intermediate layer having lubricity is formed between the abrading body and the abraded body, thereby preventing direct contact with dust. Dust abrasion, caused by contact with grit or other inorganic matter, can cause severe damage to the outermost surface. Therefore, it is not sufficient to merely impart lubricity or to increase the elastic modulus of the surface of the resin composition. Therefore, forming an intermediate protective layer having lubricity is extremely effective in suppressing dust abrasion. As the organic fiber having a liquid crystal skeleton, aramid fiber can be mentioned, but compared with liquid crystal polyester fiber, which is cut in a fiber direction by shearing, shearing does not occur at a molecular wall interface, and therefore the same mechanism does not occur, and dust abrasion proceeds without forming an intermediate layer. In the carbon fiber, the fiber precipitated at the same time as the damage may become an intermediate of the abrasion resin composition, and the abrasion may be accelerated, which is not preferable. In addition, when the target wear member is made of resin, the target wear member may be worn.

In the present invention, the strength and rigidity can be greatly improved by further adding a filler. Examples of such a filler include: glass fiber, carbon fiber, metal fiber, aramid fiber, asbestos, potassium titanate whisker, wollastonite, glass flake, glass bead, talc, mica, clay, calcium carbonate, barium sulfate, titanium oxide, aluminum oxide, and the like.

The strength and rigidity are preferably considered when these fillers are mixed, and the amount (content) thereof is preferably 5 to 60% by mass, and particularly preferably 5 to 40% by mass, based on the total mass of the polyamide resin composition. When the sliding property is preferred, the amount (content) thereof is preferably 5% by mass or less based on the total mass of the polyamide resin composition.

In the present invention, by further adding a polyolefin resin and a thermoplastic elastomer, the toughness can be greatly improved. Examples of the polyolefin resin include olefin resins such as high-density polyethylene, low-density polyethylene, ultrahigh-molecular-weight polyethylene, linear low-density polyethylene, polypropylene, poly (1-butene), and poly (4-methylpentene). The thermoplastic elastomer includes styrene-based thermoplastic elastomers, olefin-based thermoplastic elastomers, polyamide-based thermoplastic elastomers, polyester-based thermoplastic elastomers, polyurethane-based thermoplastic elastomers, and the like.

When these are mixed, the amount (content) is preferably 0.5 to 10% by mass, more preferably 1 to 8% by mass, based on the total mass of the polyamide resin composition.

The polyamide resin composition of the present invention is free from problems in that carbon black, copper oxide and/or alkali metal halide, a light or heat stabilizer, a mold release agent, a crystal nucleating agent, a lubricant, an antistatic agent, a pigment, a dye, a coupling agent, and the like, which are generally used as a weather resistance improver for a polyamide resin composition, are blended in addition to the fillers (a) and (B), the above filler, the polyolefin resin, and the thermoplastic elastomer, within a range not inhibiting the sliding property and the moldability.

When these are mixed, the total amount (content) is preferably 0.1 to 5% by mass, more preferably 0.2 to 3% by mass, based on the total mass of the polyamide resin composition.

The method for producing the polyamide resin composition of the present invention is not particularly limited, and a single-screw extruder, a twin-screw extruder, a pressure kneader or the like, which is a general kneading apparatus, can be used.

In one embodiment, the above-mentioned (A) and (B) may be mixed with a pigment or the like according to the use and fed into a twin-screw extruder. The polyamide resin composition can be uniformly kneaded by a twin-screw extruder to produce a polyamide resin composition having excellent sliding properties. The kneading temperature of the twin-screw extruder is preferably 220 to 300 ℃ and the kneading time is preferably 2 to 15 minutes.

The polyamide resin composition of the present invention is suitable for extrusion molding, and can be widely used in various applications such as electric and electronic parts, automobile parts, building materials, industrial parts, and the like, which require slidability, particularly by extrusion molding. The bearing is useful as a bearing, a gear, a door checker, a chain guide, a fixing plate member, or the like.

[ examples ] A method for producing a compound

The present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

The raw materials used in the examples and comparative examples of the present invention are as follows.

Crystalline Polyamide resin (A)

A1: polyamide 66(RV 2.8), Vydyne 21FSR (produced by Ascend), melting point 265 deg.C

A2: polyamide 6(RV 2.6), ZISAMIDE TP4208 (manufactured by KAPPY CO., LTD.) having a melting point of 225 deg.C

A3: polyamide 12(RV 2.4), Rilsamid (manufactured by Acoma corporation), melting point 175 deg.C

Liquid crystal polyester fiber (B)

B1: Zxion-VS chopped fiber with a fiber diameter of 14 μm and a fiber length of 3mm (manufactured by KBSEIREN)

B2: Zxion-TS chopped fiber, fiber diameter 20 μm, fiber length 3mm (manufactured by KBSEIREN)

B3: Zxion-VS chopped and milled fiber having a fiber diameter of 14 μm and a fiber length of 0.3mm (manufactured by KBSEIREN)

Inorganic fiber (C)

C1: glass fiber, chopped fiber, T-275H, fiber diameter 11 μm, fiber length 3mm (manufactured by Nippon electric Nitri metric Co., Ltd.)

C2: carbon fiber CFUW, chopped fiber, fiber diameter 10 μm, fiber length 3mm (manufactured by Nippon Polymer industries Co., Ltd.)

Other organic fibers (D)

D: para-aramid fiber, chopped strand, Technora T322UR 3-12, fiber diameter 12 μm, fiber length 3mm (manufactured by Diren Ltd.)

Examples 1 to 11 and comparative examples 1 to 7

The samples were evaluated for production by weighing the respective raw materials in accordance with the mixing ratios of the polyamide resin compositions shown in tables 1 and 2, mixing the raw materials with a tumbler (tubler), and feeding the mixture to a twin-screw extruder. The set temperature of the double-screw extruder is 250-300 ℃, and the mixing time is 5-10 minutes. The obtained pellets were molded into various evaluation samples by an extrusion molding machine. The cylinder temperature of the extrusion molding machine is 250-290 ℃, and the mold temperature is 80 ℃.

Various evaluation methods are described below. The evaluation results are shown in tables 1 and 2.

1. Relative Viscosity (RV) of Polyamide resin (96% sulfuric acid solution method)

The measurement was carried out using a Ubbelohde viscosity tube in a 96 mass% sulfuric acid solution at 25 ℃ at a polyamide resin concentration of 1 g/dl.

2. Melting Point of Polyamide resin

The endothermic peak temperature was determined by measuring EXSTAR 6000, a differential scanning calorimeter, SEIKO INSTRUMENTS, Inc. at a temperature rise rate of 20 ℃ per minute.

3. Wear characteristics

A flat plate (size: 50 mm. times.50 mm) of a polyamide resin composition obtained by extrusion molding was brought into contact with a SUS round jig having a convex portion with a length of 8mm and a width of 1.3mm by using a push type abrasion tester, and a load of 48.9kgf/cm was applied for 20 minutes²And a speed of 15cm/sec,and continuously sliding. Then, based on the difference in mass between the flat plate and the cylindrical molded article before and after the abrasion and the total abrasion distance, the abrasion loss (mg/km) per unit distance was calculated, and the kinetic friction coefficient was calculated from the convergence load value at the time of the abrasion test.

4. Wear characteristics of dust-containing media

A flat plate (size: 50 mm. times.50 mm) of a polyamide resin composition was uniformly coated with 1mg of grease containing molybdenum disulfide, and then coated with 2mg of a mixture of silica sand and volcanic ash containing inorganic substances having different particle diameters and hardness in a mass ratio of 1: 1 mixing the prepared dust. This surface was brought into contact with a cylindrical molded article made of Polyoxymethylene (POM) under a load of 30kgf/cm for 30 minutes²Speed 40mm/sec, continuous sliding. Then, based on the difference in mass between the flat plate and the cylindrical molded article before and after the abrasion and the total abrasion distance, the abrasion loss (mg/km) per unit distance was calculated, and the kinetic friction coefficient was calculated from the convergence load value at the time of the abrasion test.

5. Formability

The mold was molded under the above molding temperature conditions using a mold equipped with a mold release force measuring device, and mold release forces from the 31 st injection molding to the 35 th injection molding were measured to obtain a mold release resistance value.

6. Stability against Heat

The test pieces were heat-treated in a recirculating air oven (manufactured by chant scientific machinery, hot air circulation dryer, NH-401S) according to the procedure described in ISO 2578. The test pieces were removed from the oven at 120 ℃ for the specified test time (250 hours), cooled at room temperature, and sealed in bags with aluminum foil liners until the test preparation was completed. Then, the tensile strength was measured in accordance with ISO527-1, 2, and the maintenance ratio before and after treatment was calculated from the average value obtained from three test pieces.

In examples 1 to 11, the abrasion test by contact with the SUS circular jig and the abrasion test with dust interposed had physical properties equal to or higher than those of comparative examples 1 to 7, and the abrasion characteristics were improved. In particular, this effect is remarkable in the abrasion test using dust. When the mold release resistance value is 1.0MPa or less, the moldability required for continuous extrusion molding is satisfied, and the level of heat resistance stability is also referred to as a level satisfying.

In comparative example 1, the polyamide 66 was not modified, and the abrasion loss was large. In comparative examples 2 and 3, although the wear property was contributed to the wear test by contacting the SUS circular jig, the effects equivalent to those of examples 1 to 11 were not exhibited. In addition, in the abrasion amount after the abrasion test through the dust, the abrasion amount could not be reduced, and as a result, the abrasion of the POM cylindrical molded article of the target material increased. It is understood that the inorganic fiber-reinforced material is not suitable for the case where the material to be contacted is a polymer, since the abrasion of the POM cylindrical molded article of the target material tends to increase in the abrasion test through the dust, as is observed also in comparative examples 4 and 5. Comparative examples 6 and 7, like patent document 1, do contribute to the abrasion resistance, but the contribution degree is lower than that of the composition of the present invention.

As the main modification mechanism of examples 1 to 11, it is suggested that the composition is damaged, and the polyester fiber having a liquid crystal skeleton present in the composition is sheared and chopped in the fiber direction to be abraded and pulverized, and an intermediate layer having lubricity is formed between the abraded body and the abraded body, thereby preventing direct contact. Further, it is also suggested that the effect of reducing the dynamic friction coefficient is exhibited on the surface by the low friction property of the liquid crystal polyester fiber itself.

Industrial applicability of the invention

The polyamide resin composition of the present invention is a molding material having excellent sliding properties. Particularly, the resin composition is suitable for sliding parts which are required to have high abrasion resistance and to withstand high surface pressure, and is expected to contribute greatly to the industry as an engineering plastic which can be used in a wide range of fields.