JPH0735476B2 - Polyamide resin composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a polyamide resin composition suitable for a sliding member, and more specifically, it has a low frictional force against a metal, self-wearing property, and wear of a mating material. TECHNICAL FIELD The present invention relates to a polyamide resin composition suitable for a sliding member, which has low mechanical properties, excellent mechanical properties, heat resistance, and fluidity during melting.

(Prior Art) Polyamide has been used as a useful resin for a long time. Among them, polytetramethylene adipamide resin (hereinafter referred to as nylon 4,6) has excellent heat resistance, toughness, and chemical resistance. Therefore, it is expected to be put to practical use as various structural materials. In particular, it is remarkably excellent in self-lubricating property as compared with other engineering resins, so that it is expected to be put to practical use in sliding parts such as bearing parts, gear parts, or machine parts requiring wear resistance.

Recently, plastic sliding members have expanded applications in fields such as bare links that are non-lubricated and subject to severe wear under severe loads, pushers used under high ambient temperature conditions, and thin sliding parts. Therefore, with the expansion of this application field, the required performance of the plastic sliding member has become severe.

Generally, when plastic is applied to sliding parts such as bearings, in addition to the sliding characteristics that the dynamic friction coefficient is small, the limit PV value is high, the amount of wear is small, and the mating material is not damaged, rigidity and creep resistance It is desirable to use a material having excellent mechanical properties such as heat resistance and heat resistance such as heat distortion temperature and continuous use temperature.

Polyamide resins, especially nylon 4 and 6, have extremely good mechanical properties and heat resistance.

However, under the present circumstances, nylon 4 and 6 alone cannot sufficiently satisfy the sliding characteristics such as low friction and abrasion resistance required for the above sliding parts.

As a method for improving the sliding characteristics of the above nylons 4 and 6, for example, a method of blending polytetrafluoroethylene and potassium titanate whiskers with nylons 4 and 6 has been proposed (JP-A-62-185747).

However, in recent years, the miniaturization and thinning of parts have been advanced along with the performance improvement of equipment, and the demand for sliding parts, especially thin parts, has been increasing. Nylon 4,6 is
For example, although the sliding characteristics are improved by the above improvements, it improves the miniaturization and thinning of molded parts, and the fluidity of molten resin may be inferior to that of other polyamides. There is a demand for a nylon 4,6 resin composition having good properties.

Generally, hydrocarbons such as paraffin and polyethylene wax, metal soaps such as lead stearate and calcium stearate, long-chain carboxylic acids such as stearic acid, palmitic acid amide, and ethylenebisstearylamide for the purpose of imparting fluidity to the molten resin. The method of adding amide compound, stearic acid monoglyceride, ester compound such as cetyl palmitate, alcohols such as mannitol and stearyl alcohol, and the method of adding polymers such as polyethylene, polypropylene and polyethylene oxide are widely known.

However, when low molecular weight compounds such as hydrocarbons, metal soaps, long-chain carboxylic acids, amide compounds, ester compounds and alcohols are added, it is easy to cause deterioration of surface appearance and mechanical properties, and polyethylene, polypropylene When such polymers are used, problems such as phase separation due to poor compatibility with nylon, deterioration of mechanical properties, and deterioration of heat resistance become problems. Further, since polyethylene oxide has a low thermal decomposition temperature of about 200 ° C, it cannot be used for nylon whose molding temperature exceeds 200 ° C.

(Problems to be Solved by the Invention) The present inventors have developed a resin composition in which the flowability of a molten resin is improved in order to improve the sliding characteristics of polyamide and to improve the miniaturization and thinning of molded parts. As a result of diligent study to develop, by blending polyamide with aromatic polyamide fiber and further with high-density polyethylene, excellent sliding properties, that is, mechanical properties, are achieved without causing deterioration of mechanical properties and heat resistance. In addition to heat resistance, there is no phase separation of polyethylene and it has the fluidity of molten resin,
It has been found that a resin composition capable of providing a sliding component having a thin wall can be obtained, and the present invention has been accomplished based on such findings.

(Means for Solving the Problems) That is, the present invention is based on 100 parts by weight of polyamide, 1 to 50 parts by weight of aromatic polyamide fiber, 3 to 80 parts by weight of polytetrafluoroethylene (hereinafter referred to as PTFE), and further higher. A resin composition comprising 1 to 20 parts by weight of high density polyethylene (hereinafter referred to as HDPE) is provided.

As the polyamide, nylon 6, nylon 66, nylon 12, nylon 11, nylon 612, etc. can be used,
Nylon 4 and 6 are preferable in terms of heat resistance and mechanical properties.

The nylon 4,6 is of the formula - a _{[NH- (CH 2) 4 -NH} -CO- (CH 2) 4- CO] polyamide consisting essentially of repeating structural units represented by -n.

For the production method of these nylons 4 and 6, see JP-A-56-14930.
No. 56, No. 56-149431, No. 58-83029, No. 60-28843
The method described in the issue etc. can be mentioned. Further, in order to obtain the resin composition of the present invention, nylon 4 having a relative viscosity (ηre; 30 ° C., 97% sulfuric acid, concentration: 10 ⁻² g / ml) of at least 1.5, preferably 2.5 to 5.0. It is advantageous to use 6,6.

The aromatic polyamide fiber used in the present invention is a so-called,
It is a fiber called "aramid fiber", such as "Kepler", "Nomex" (above made by DuPont), "Technora", "Conex", (above Teijin),
"Arenka" (manufactured by Akzo) and the like are commercially available and are available. Aromatic polyamide fiber used in the present invention,
It is preferably used in the form of short fibers, and the fiber diameter is not particularly limited, but is preferably 30 μm or less, more preferably 15 μm or less. When the fiber length exceeds 6 mm, the fluidity of the molten resin and the granulation property by an extruder are deteriorated, which is not preferable, and it is advantageous to use a fiber having a fiber length of 3 mm or less.

The addition amount of the aromatic polyamide fiber is polyamide 100
The amount is 1 to 50 parts by weight, preferably 2 to 30 parts by weight, and more preferably 3 to 20 parts by weight.

If the amount of the aromatic polyamide fiber added is less than 1 part by weight, improvement in mechanical strength and heat resistance cannot be expected, and improvement in self-wear amount during sliding with a metal is small. On the contrary,
If it exceeds 50 parts by weight, the fluidity cannot be improved by the method of the present invention.

The PTFE used in the present invention is preferably in powder form, and its average particle size is preferably 15 μm or less, more preferably 10 μm or less.
μm or less. There is no particular lower limit to the average particle size. If the average particle size exceeds 15 μm, the surface of the molded article produced from the composition of the present invention becomes coarse and unfavorable. PT
The amount of FE added is 3 to 80 parts by weight, preferably 5 to 50 parts by weight, from the viewpoints of addition effect, mechanical strength and dispersibility. If the amount of PTFE added is less than 3 parts by weight, the improvement of the dynamic friction coefficient will be insufficient. On the other hand, if the amount of PTFE added exceeds 80 parts by weight, the mechanical strength will decrease and the amount of self-wear when sliding on metal will increase, such being undesirable.

The amount of HDPE used in the present invention is 1 to 20 parts by weight, preferably 3 to 10 parts by weight. If the amount of HDPE added is less than 1 part by weight, the effect of improving the fluidity is not observed, and if it exceeds 20 parts by weight, the rigidity and heat resistance are remarkably lowered, and delamination of the injection-molded product is observed.

The compounding method of the resin composition of the present invention is not particularly limited, but examples thereof include a method of mixing with a Henschel mixer, a tumbler, etc., and further a method of melt mixing with a batch kneader, Banbury mixer, single or twin screw extruder. You can

Other inorganic or / and organic fillers may be added, if necessary, in order to provide the composition of the present invention with more excellent mechanical strength, heat resistance and sliding properties.

As the inorganic filler, a well-known reinforcing filler for rubber or plastics is used. The shape is not particularly limited as long as it is a solid, and may be in the form of powder, fibrous powder, fiber, whiskers, balloons, etc., while maintaining excellent low friction properties and abrasion resistance of the resin composition of the present invention. In order to obtain a sufficient reinforcing effect, a powdery or whisker-like one is preferable.

Specific examples of the filler include clay, calcined clay, talc, catalbot, silica, alumina, magnesium oxide, calcium silicate, asbestos, sodium aluminate, calcium aluminate, sodium aluminosilicate, magnesium silicate, and hydroxide. Aluminum, calcium hydroxide, barium sulphate, potassium tan, sodium ban, iron ban, shirasu balloon, glass balloon, carbon black, coke breeze, zinc oxide,
Antimony trioxide, boric acid, borax, zinc borate, metal powder, metal whiskers, mica, graphite, titanium oxide, wollastonite, carbon fiber, glass fiber, glass fiber powder, glass beads, calcium carbonate, zinc carbonate, hydrotalcite , Iron oxide and the like.

The aromatic polyamide fiber and the inorganic filler used in the present invention may be subjected to various surface treatments to further enhance the effects of the present invention. These inorganic fillers can be used alone or in combination of two or more.

The compounding method of the filler is not particularly limited, and the same compounding method as aromatic polyamide fiber, PTFE and HDPE can be mentioned.

Furthermore, other known polymers such as polybutadiene, butadiene-styrene copolymer, acrylic rubber, ethylene-propylene polymer, EPDM, modified depending on the required performance.
EPDM, styrene-butadiene block polymer, styrene-butadiene-styrene block polymer, styrene-butadiene-styrene radial teleblock polymer, polypropylene, butadiene-acrylonitrile copolymer,
Polyvinyl chloride, polycarbonate, PET, PBT, polyacetal, polyamide, polyester, epoxy resin,
Polyvinylidene fluoride, polysulfone, ethylene-vinyl acetate copolymer, polyisoprene, natural rubber, chlorinated butyl rubber, chlorinated polyethylene, PPS resin, polyether ether ketone, PPO resin, styrene-methyl methacrylate copolymer, styrene- Maleic anhydride copolymer,
Rubber-modified PPO resin, styrene-maleimide copolymer,
The rubber-modified styrene-maleimide copolymer and the like may be appropriately blended with the resin composition of the present invention.

These polymers may be used alone or in combination of two or more.

Other lubricants such as molybdenum disulfide and silicone oil, pigments, flame retardants, antioxidants, stabilizers, etc.
Antistatic agents and the like can be added.

The resin composition of the present invention has excellent sliding properties, and therefore has a pushing, a bearing, a scoop, a slipping,
Various sliding parts such as guide rails, sealing materials, switch parts, gears, cams can be provided.

(Examples) Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.

The resin compositions obtained in Examples and Comparative Examples were evaluated by the following test methods.

Test method Tensile test: Measured at a pulling speed of 50 mm / min in accordance with ASTM D638.

Bending test: Measured at a bending speed of 15 mm / min according to ASTM D790.

Heat distortion temperature: Friction and wear test measured at 264 psi according to ASTM D648: A Suzuki type friction and wear tester was used, and an aluminum material was used as a mating material. The test piece has an outer diameter of 25.6 mm and an inner diameter.
A hollow cylindrical test piece of 20.0 mm was used, and the mating material had the same shape.

(A) Dynamic friction coefficient It was measured under the conditions of a load of 10 kg (surface pressure of 5 kg / cm ² ) and a rotation speed of 60 rpm.

(B) Amount of wear 20000 rotations at a load of 10 kg and a rotation speed of 30 rpm (mileage 1.4K
The decrease in the weight of the test piece after m) was measured and defined by the specific wear amount calculated by the following expression (1).

Formula (1) Melt resin fluidity It was measured by the length of the spirally molded product (called slab flow length). The measurement conditions are as follows.

Molding temperature 320 ° C. (290 ° C. in Example 8) Mold temperature 80 ° C. Molded product wall thickness 2.0 mm Injection pressure 600 Kg / cm ² Injection speed 30 cm ³ / sec Examples 1 to 6 Relative viscosity 3.70 (30 ° C., 97% sulfuric acid) Medium, nylon 4,6 with a concentration of 10 ^-2 g / mI) and powdered polytetrafluoroethylene with an average particle size of 5 μm (PTFE, manufactured by Asahi Glass Co., Ltd., “Fluon”
L169 ”), aromatic polyamide fiber A (manufactured by Teijin Ltd.,“ Technora T-322 ”, fiber length 1 mm, fiber diameter 12 μm), and high density polyethylene (HDPE, Mitsui Petrochemical Co., Ltd.,“ Hi-Zex 3300F ”). The composition ratios shown in Table 1 were mixed in a tumbler, and then a twin-screw extruder (made by Ikegai Iron Works,
"Ikegai PCM45 II") was melt-mixed and pelletized. Molding temperature 300 ℃, mold temperature 8
Various test pieces were obtained by injection molding under the condition of 0 ° C., and the physical properties were measured by the above test methods.

As a result, as shown in Table 1, the resin compositions of Examples 1 to 6 have not only excellent mechanical strength, heat resistance and sliding characteristics, but also good flowability during melting, which is the object of the present invention. It turns out that it is a thing.

Example 7 Nylon 4,6, PTFE, HDPE and aromatic polyamide fiber B (manufactured by Teijin Ltd., “Conex”, fiber length 0.6 mm, fiber diameter 14 μm) shown in Examples 1 to 6 are shown in Table 1. The composition ratios shown were mixed, pelletized in the same manner as in Examples 1 to 6, and the physical properties thereof were measured. As a result, as shown in Table 1, this resin composition also has the same excellent mechanical strength, heat resistance, and sliding characteristics as in Examples 1 to 6, and also has good flowability during melting, which is the object of the present invention. It can be seen that it has both.

Example 8 Example 8 was repeated except that nylon 66 was used instead of nylon 4 and 6.

Comparative Examples 1 to 5 Nylon 4,6, PTFE, aromatic polyamide fiber and HDPE shown in Examples were mixed in the proportions shown in Table 1, pelletized in the same manner as in Examples, and the physical properties thereof were measured. . The results are shown in Table 2.

Comparative Example 1 is an example of a composition containing no HDPE, and the fluidity of the molten resin is insufficient.

In Comparative Example 2, the content of HDPE exceeds the range of the present invention, the mechanical strength and heat resistance are greatly reduced, and the surface of the molded product is delaminated, which is not preferable.

Comparative Example 3 is an example of a composition that does not contain PTFE, and the dynamic friction coefficient and the specific wear amount of resin and metal are large, which is not preferable.

Comparative Example 4 is an example containing no aromatic polyamide fiber and is inferior in tensile strength and heat resistance. Furthermore, HDPE is not preferable because it peels off on the surface of the molded product.

In Comparative Example 5, the content of the aromatic polyamide fiber exceeds the range of the present invention, and the dynamic friction coefficient and the specific wear amount of the metal increase, which is not preferable. Furthermore, the fluidity of the molten resin is poor, and the fluidity of the molten resin, which is the object of the present invention, cannot be improved.

Comparative Example 6 Comparative Example 6 uses polypropylene (“J 300” manufactured by Mitsui Petrochemical Co., Ltd.) instead of HDPE of Example 2, and has little effect of improving the fluidity of the molten resin. In addition, the coefficient of dynamic friction is high, which is not preferable.

Comparative Example 7 In Comparative Example 7, low-density polyethylene (“Yukaron YK-30” manufactured by Mitsubishi Yuka) was used in place of the HDPE of Example 2, and the mechanical strength and heat resistance were significantly reduced, which is preferable. Absent.

(Effects of the Invention) As shown in the above examples, the resin composition of the present invention is obtained by adding a specific amount of an aromatic polyamide fiber and a specific amount of polytetrafluoroethylene to a polyamide resin, and further adding a specific amount of By using the composition to which the density polyethylene is added, the mechanical strength, heat resistance and sliding characteristics are good, and the fluidity of the molten resin is excellent.

INDUSTRIAL APPLICABILITY The resin composition of the present invention has excellent mechanical strength, heat resistance, sliding characteristics, and exhibits excellent fluidity when melted, so that it is suitable for various applications such as sliding members such as small mechanical parts. It is useful and can provide various parts such as bearings, switches and gears. In the future, it is expected that small mechanical parts will become smaller and thinner, and resin compositions for obtaining such small and thin molded products are desired. It provides a suitable material.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location C08L 27:18 23:06) (72) Inventor Shuji Tsuchikawa 2-11, Tsukiji, Chuo-ku, Tokyo No. 24 within Japan Synthetic Rubber Co., Ltd. (72) Inventor Shinichi Kimura 2-11-24 Tsukiji, Chuo-ku, Tokyo Within Japan Synthetic Rubber Co., Ltd. (56) Reference JP-A-59-196394 (JP, A) JP-A-51-126246 (JP, A) JP-A-62-10165 (JP, A) JP-A-1-164810 (JP, A)

Claims (1)

[Claims] 1. A blend of (a) 1 to 50 parts by weight of aromatic polyamide fiber (b) 3 to 80 parts by weight of polytetrafluoroethylene (c) 1 to 20 parts by weight of high-density polyethylene with respect to 100 parts by weight of polyamide. A polyamide resin composition comprising: