JPH0881608A - Fluororesin composition - Google Patents

Abstract

PURPOSE: To provide high abrasion resistance to a fluororesin and improve also abrasion resistance of opposite material of sliding. CONSTITUTION: This fluororesin composition is composed of 99-40 pts.wt. of a fluororesin such as polytetrafluoroethylene and 1-60 pts.wt. of a carbon fiber having 50-320kgf/mm<2> Vickers hardness Hv by thin film hardness meter. The carbon fiber having the hardness is obtained by (1) a method for carrying out infusibilization treatment of a non-liquid crystal pitch-based fiber capable of providing a carbon fiber and then carrying out graphitization treatment of the carbon fiber at 2800-3300 deg.C maximum arriving temperature or (2) a method for carrying out infusibilization treatment of a liquid crystal pitch-based fiber capable of providing carbon fiber and then carrying out graphitization of the carbon fiber at 1700-3000 deg.C maximum arriving temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluororesin composition having excellent mechanical strength and slidability, especially abrasion resistance.

[0002]

2. Description of the Related Art Polytetrafluoroethylene (hereinafter referred to as P
(TFE) is not only excellent in heat resistance and chemical resistance, but also has a small friction coefficient and excellent sliding characteristics. However, the wear resistance is not always sufficient.

Therefore, glass fiber, glass powder or beads, carbon fiber, graphite, molybdenum disulfide, metal lubricant, metal oxide, and other fillers are added to PTFE. The resin composition containing these fillers has a lower friction coefficient and a smaller amount of wear than the matrix resin alone. Therefore, the resin composition is widely used for various industrial sliding members such as bearings, gears, sealing materials such as bushes and packings, piston rings, ball seats, sliding bands and the like.

However, in order to improve the energy transmission efficiency and to make it maintenance-free, even a molded product using a carbon fiber as a sliding member, which has high wear resistance and low wear resistance against the mating material However, the above requirements have not been met yet. For example, a molded product using a general-purpose carbon fiber (GPCF), which has an oligopoly on the market, as a filler has a high hardness, so that the molded product has a low wear resistance and an aluminum material which is becoming the mainstream of the counterpart material. However, low wear resistance against the mating material cannot be fully exhibited. Furthermore, in a molded product using polyacrylonitrile (PAN) -based carbon fiber as a filler, the hardness of the PAN-based carbon fiber is higher than that of general-purpose carbon fiber (GPCF), so that the aluminum material that is the counterpart material is damaged, The low wear resistance of and the low wear resistance of the mating material cannot be satisfied.

JP-A-5-32842 and JP-A-5-43763 disclose resin compositions containing carbon fibers oxidized and treated with a fluorine resin in the presence of an oxygen-containing gas. By using such a carbon fiber, it is possible to improve the affinity and wettability with respect to the fluororesin and improve the wear resistance. However, there is a limit in reducing not only the wear resistance of the molded product but also the wear resistance of the mating material. As described above, when the wear resistance of the molded product itself is improved, the mating material is easily worn, and it is difficult to enhance the wear resistance of both the molded product and the mating material.

[0006]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a fluororesin composition capable of obtaining a molded article having excellent sliding characteristics, especially abrasion resistance.

[0007] Another object of the present invention is to provide a fluororesin composition which can also reduce the wear resistance to the mating material.

[0008]

[Means for Solving the Problems] In order to achieve the above object, the inventors of the present invention have diligently studied to reduce the wear coefficient of a molded article made of a fluororesin composition and the wear coefficient of a mating material. The inventors have found that the use of carbon fibers having properties significantly reduces the sliding characteristics (especially wear resistance) of the fluororesin composition and the wear coefficient of the mating material, and completed the present invention.

That is, the fluororesin composition of the present invention is
Fluorine resin and Vickers hardness Hv5 by thin film hardness tester
It contains 0 to 320 kgf / mm ² of carbon fiber.

In the present specification, the "Vickers hardness" means the hardness Hv of the diametrical cross section perpendicular to the axial direction of the carbon fiber, and the fiber bundle of the carbon fiber is a softer acrylic than the carbon fiber. It is a value measured by fixing it on a base with resin, NBR (acrylonitrile butadiene rubber) or the like, and applying a load to the diametrical cross section of the carbon fiber using a thin film hardness meter.

The present invention will be described in detail below.

Examples of the fluororesin contained in the fluororesin composition of the present invention include fluorine-containing monomers such as tetrafluoroethylene, chlorotrifluoroethylene, vinyl fluoride, vinylidene fluoride, hexafluoropropylene and perfluoroalkyl vinyl ether. A homo- or copolymer of: a fluorine-containing monomer,
Copolymers with copolymerizable monomers such as ethylene, propylene and various acrylates are included. More specifically, examples of the fluororesin include homopolymers such as polytetrafluoroethylene, polychlorotrifluoroethylene, and polyvinylidene fluoride; tetrafluoroethylene-ethylene copolymers, chlorotrifluoroethylene-ethylene copolymers. Polymer, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene-hexafluoropropylene copolymer,
Tetrafluoroethylene-hexafluoropropylene-
Examples thereof include copolymers such as a perfluoroethylene copolymer and a tetrafluoroethylene-hexafluoropropylene-perfluoroethylene-chlorotrifluoroethylene copolymer. These fluororesins can be used alone or in combination of two or more.

Among these fluororesins, preferred resins include tetrafluoroethylene homopolymers, tetrafluoroethylene-ethylene copolymers, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers and other tetrafluoroethylene copolymers. Includes coalescence. Particularly preferred fluororesins include tetrafluoroethylene homopolymer.

The fluororesin composition of the present invention contains carbon fibers having specific properties. This carbon fiber has a Vickers hardness Hv of 50 to 320 kg measured by a thin film hardness meter.
f / mm ² , preferably 75 to 300 kgf / mm ² ,
More preferably about ^{85~300kgf / mm 2, 100~290kgf / mm} 2 ( e.g., 100
270 kgf / mm ² ) in most cases. When Hv is less than 50 kgf / mm ² , worn carbon powder is present in the sliding surface, and wear easily occurs, and Hv is 320 kg.
If it exceeds f / mm ² , the wear of the mating material tends to increase.

The fiber diameter and the fiber length of the carbon fibers are not particularly limited, but they are usually used as short fibers having a fiber diameter of about 1 to 20 μm and a fiber length of 10 μm or more. The fiber length is often about 50 μm to 5 mm (for example, 50 μm to 1 mm).

The ratio of the fluororesin to the carbon fiber is
Although it can be selected depending on the use of the molded product, it is usually fluororesin / carbon fiber = 99/1 to 40/60 (parts by weight), preferably 95/5 to 60/40 (parts by weight), and more preferably 92/8. It is about 65/35 (parts by weight). When a resin composition having such a composition ratio is molded, sliding characteristics,
A molded product having a well-balanced mechanical strength and moldability can be obtained, and the molded product is particularly excellent in wear resistance.

The fluororesin composition of the present invention is, for example, other carbon fibers, glass fibers, aramid fibers, boron fibers, silicon carbide fibers or other short fibers and long fibers, whiskers, etc. within a range that does not impair the characteristics. Fibrous reinforcing agents coated with metals such as nickel, aluminum and copper; reinforcing agents composed of fillers such as carbon black, graphite, molybdenum disulfide, mica, talc and calcium carbonate; Sn, Pb, Cu , Zn, Li and metal lubricants composed of these alloys, Zn, Al, Sb, C
Metal oxides such as o, Si, Cu, Pb and Co-Al ₂
It may contain various additives such as complex metal oxides such as O ₃ , colorants and stabilizers.

The resin composition of the present invention can be molded into a molded product by a conventional molding method. For example, (1) the fluororesin and the carbon fiber are uniformly mixed using a mixer such as a Henschel mixer, the mixture is compression-molded in a mold, and the obtained molded body is melted with the fluororesin. A method of performing heat treatment (annealing) at a temperature equal to or higher than a temperature, and (2) an extrusion molding method or an injection molding method of heating the mixture and molding the mixture in a molten state can be used. In the former molding method of preparing a molded body in advance, it is important to mix the fluororesin and the carbon fiber more uniformly. The extrusion molding method or the injection molding method can be performed at a temperature at which the fluororesin in the mixture can be melted.

The carbon fiber used in the present invention has only to have the above-mentioned characteristics, and the method for producing the carbon fiber is not particularly limited. The carbon fibers can be produced, for example, by firing carbon fiber-forming fibers (particularly pitch-based fibers) and carbonizing or graphitizing, especially graphitizing. Carbon fibers are manufactured without oxidation treatment after or during the firing process. Further, it is preferable that the fibers capable of forming carbon fibers are subjected to infusibilization or flameproofing treatment prior to firing.

The infusibilizing treatment means that pitch-based fibers are
In the presence of oxygen, for example, it is heated at a temperature of about 200 to 450 ° C to form a heat resistant layer on the surface to prevent melting at the time of firing. Flame-proofing means carbon fiber other than pitch-based fibers can be formed. It is said that such fibers are treated in the same manner as above.

The carbon fiber is a fiber which has been carbonized or graphitized. The carbonization treatment means that the fibers that can be carbonized are fired at a temperature of, for example, about 450 to 1500 ° C. The graphitization treatment is, for example, 1500 to 330.
This means firing at a temperature of about 0 ° C., and even if it does not have a graphite crystal structure, it is treated as graphitized when treated at the above temperature.

Examples of the raw material of the carbon fiber include coal tar pitch, coal pitch such as coal liquefied oil, petroleum pitch such as ethylene tar and decant oil pitch, and modified pitch obtained by modifying the pitch (for example, Hydrogenated pitch, pitch modified by heat treatment, pitch fractionated by solvent, pitch fractionated by distillation or pitch reformed by combining these methods), synthesized from aromatic hydrocarbons such as naphthalene and its derivatives Pitches such as pitch (for example, naphthalene pitch heat-treated using a Friedel-Crafts catalyst); polymers such as cellulose, polyacrylonitrile, rayon, and phenol resin.

Of the above raw materials, pitch (for example, coal tar pitch, coal pitch such as coal liquefied oil, petroleum pitch such as ethylene tar and decant oil pitch, reformed pitch obtained by modifying the pitch) is used. It is preferable to use carbon fiber that can be used as a raw material. The carbon fiber that can be made into carbon fiber using pitch as the raw material may be a non-liquid crystal pitch fiber or a liquid crystal pitch fiber using a mesophase pitch, an anisotropic pitch, or the like.

When a non-liquid crystalline pitch-based carbon fiber capable of being converted into carbon fiber is used, the carbon fiber having the above-mentioned properties is, for example,
After infusibilizing the fibers that can be made into carbon fibers, the maximum attainable temperature is 2800 to 3300 ° C, preferably 2900 to 330.
It can be produced by graphitizing at 0 ° C, more preferably 3000 to 3300 ° C. The holding time at the maximum temperature can be appropriately selected and is, for example, 2 to 48 hours, preferably about 4 to 12 hours.

In the case of using liquid crystal pitch type carbon fiber which can be made into carbon fiber, the carbon fiber having the above-mentioned properties can be obtained, for example, by infusibilizing the carbon fiber which can be made into carbon fiber, and then attaining the maximum attainable temperature of 1700 to 3000 ° C. Preferably 1800-2
It can be produced by graphitizing at 800 ° C., more preferably 2000 to 2800 ° C., especially about 2200 to 2800 ° C. The holding time at the highest temperature reaches, for example, 2
~ 48 hours, preferably about 4-12 hours.

In the production of the carbon fibers, if the firing process (graphitization process) or the oxidation process after the firing process is performed, the wear resistance of the molded product is improved and the wear property of the mating material is reduced as described above. Is difficult. for that reason,
The carbon fiber having the Vickers hardness is manufactured without a oxidization treatment during or after the firing (graphitization treatment).

Since the fluororesin composition of the present invention is excellent in heat resistance, chemical resistance, sliding characteristics, especially abrasion resistance, it can be used as a molding material for various molded articles, especially sliding members.

[0028]

EFFECTS OF THE INVENTION Since the fluororesin composition of the present invention contains a specific carbon fiber, it is possible to obtain a molded article having excellent sliding properties, especially abrasion resistance. In particular, not only the wear resistance of the composite material itself formed by the fluororesin composition,
Abrasion resistance to the mating material can also be reduced.

[0029]

The present invention will be described in more detail based on the following examples, but the invention is not intended to be limited by these examples.

Comparative Example 1 10 parts by weight of carbon fiber [SG-241 (average fiber diameter 13 μmφ, average fiber length 130 μm) manufactured by Donac Co., Ltd.] and PTFE [M-12] manufactured by Daikin Industries Ltd. 90
Parts by weight were mixed with a super mixer. The obtained powdery mixture was put into a mold and pressed at 600 kg / cm ² , to obtain a molded product (50 mmφ × 62 mm). A sliding test piece was prepared by cutting this molded product.

The Vickers hardness of the carbon fiber measured by a thin film hardness meter was 399 kgf / mm ² .

Comparative Example 2 Instead of the carbon fiber of Comparative Example 1, carbon fiber [manufactured by Toray Industries, Inc., MLD100 (average fiber diameter 7 μmφ, average fiber length 1
00 μm)] was used to obtain a sliding test piece (carbon fiber / fluorine resin = 10/90 (weight ratio)) in the same manner as in Comparative Example 1. The Vickers hardness of carbon fiber is 6
It was 05 kgf / mm ² .

Comparative Example 3 Instead of the carbon fiber of Comparative Example 1, carbonized carbon fiber [manufactured by Donac Co., S-241 (average fiber diameter 13 μm
φ, average fiber length 130 μm)] was used in the same manner as in Comparative Example 1 except that carbon fibers fired at 2500 ° C. for 2 hours in a nitrogen gas atmosphere containing 200 ppm oxygen were used. = 10/90 (weight ratio)) was obtained. The Vickers hardness of the obtained carbon fiber is 340k.
It was gf / mm ² .

Comparative Example 4 20 parts by weight of carbon fiber [S-244 (average fiber diameter 13 μmφ, average fiber length 700 μm) manufactured by Donac Co., Ltd.],
Tetrafluoroethylene-ethylene copolymer resin (ET
80 parts by weight of FE) [Aflon COP manufactured by Asahi Glass Co., Ltd.] was kneaded at 300 ° C. using a twin-screw extruder, and a sliding test piece was prepared using an injection molding machine. The Vickers hardness of the carbon fiber was 455 kgf / mm ² .

Comparative Example 5 20 parts by weight of carbon fiber [S-244 (average fiber diameter 13 μmφ, average fiber length 700 μm) manufactured by Donac Co., Ltd.],
80 parts by weight of tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resin (PFA) [Teflon PFA manufactured by Mitsui DuPont Fluorochemical Co., Ltd.],
Kneading was performed at 380 ° C. using a twin-screw extruder, and sliding test pieces were produced using an injection molding machine. The Vickers hardness of the carbon fiber was 455 kgf / mm ² .

Example 1 A carbon fiber mat made from anisotropic pitch as a raw material [made by Petka Co., Ltd. (average fiber diameter 11 μmφ)] was used to obtain an average fiber length of 130
Grind and classify to μm, under argon gas atmosphere, 2350 ℃
10 parts by weight of the carbon fiber calcined in step 10 and 90 parts by weight of PTFE [M-12 manufactured by Daikin Industries, Ltd.] were mixed with a super mixer. The obtained powdery mixture is put into a mold 6
By applying a pressure of 00 kg / cm ² , a molded product (50
mmφ × 62 mm) was obtained. A sliding test piece was produced by cutting the obtained molded product. The Vickers hardness of the carbon fiber was 115 kgf / mm ² .

Example 2 In place of the carbon fiber of Example 1, carbonized carbon fiber [manufactured by Donac Co., S-241 (average fiber diameter 13 μm
φ, average fiber length 130 μm)] was used in the same manner as in Example 1 except that carbon fibers fired at 3000 ° C. for 5 hours in an argon gas atmosphere were used. Sliding test pieces (carbon fibers / fluorine resin = 10/90 ( Weight ratio)) was obtained. The Vickers hardness of the carbon fiber was 151 kgf / mm ² .

Example 3 A carbon fiber mat made of anisotropic pitch as a raw material [manufactured by Petka Co., Ltd. (average fiber diameter 11 μmφ)] was used to obtain an average fiber length of 700.
Grind and classify to μm, under argon gas atmosphere, 1800 ℃
20 parts by weight of carbon fiber calcined with tetrafluoroethylene-ethylene copolymer resin (ETFE) [Asahi Glass Co., Ltd.
Manufactured by Aflon COP] 80 parts by weight at 300 ° C. for 2
Kneading was performed using a shaft extruder, and sliding test pieces were produced using an injection molding machine. The Vickers hardness of the obtained carbon fiber was 240 kgf / mm ² .

Example 4 A carbon fiber mat made of anisotropic pitch as a raw material [made by Petka Co., Ltd. (average fiber diameter: 11 μmφ)] was used to obtain an average fiber length of 700.
Grind and classify to μm, under argon gas atmosphere, 1800 ℃
Biaxially extruding 20 parts by weight of the carbon fiber calcined at 80 parts by weight of tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resin (PFA) [Teflon PFA manufactured by Mitsui DuPont Fluorochemical Co., Ltd.] at 380 ° C. Kneading was performed using a machine, and sliding test pieces were produced using an injection molding machine. The Vickers hardness of the obtained carbon fiber is 2
It was 40 kgf / mm ² .

Then, the sliding characteristics of the sliding test pieces obtained in Examples and Comparative Examples were measured using a Suzuki type friction and wear tester. The test pieces obtained in Comparative Examples 1 to 3 and Examples 1 and 2 were measured under the conditions of mating material JIS ADC12, load 4 kgf / cm ² , speed 1.0 m / sec, and test time 20 hours. On the other hand, for the test pieces obtained in Comparative Examples 4 to 5 and Examples 3 and 4, the mating material JIS S4 was used.
The measurement was performed under the conditions of 5 C, a load of 4 kgf / cm ² , a speed of 1.0 m / sec, and a test time of 8 hours. The results of the sliding characteristics are shown in the table together with the Vickers hardness Hv of the carbon fiber.

In the table, the unit of Vickers hardness is kg.
f / mm ² , the unit of wear coefficient is (10 ^-5 × mm / km)
/ (Kgf / cm ² ), and the wear coefficient of the mating material is (1
0 ⁻³ × mg / km).

[0042]

[Table 1] As is clear from the table, in comparison with the test piece obtained in the comparative example, the test piece (molded article) obtained in the example has not only high wear resistance of the molded article itself, but also wear against the mating material. Since the property is small, there is no risk of damaging the mating material.

Claims (6)

[Claims] 1. A fluororesin composition comprising a fluororesin and carbon fiber having a Vickers hardness Hv of 50 to 320 kgf / mm ^{2 as} measured by a thin film hardness meter. 2. The fluororesin composition according to claim 1, which comprises 99 to 40 parts by weight of fluororesin and 1 to 60 parts by weight of carbon fiber. 3. The fluororesin composition according to claim 1, wherein the fluororesin is a homopolymer or copolymer of tetrafluoroethylene. 4. A fluororesin composition comprising 92 to 65 parts by weight of fluororesin and 8 to 35 parts by weight of carbon fibers having a Vickers hardness Hv of 75 to 300 kgf / mm ² . 5. The fluororesin composition according to claim 4, wherein the fluororesin is polytetrafluoroethylene, a tetrafluoroethylene-ethylene copolymer, or a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer. 6. The carbon fiber is a fiber obtained without being subjected to an oxidation treatment during or after the firing process, and (1) the non-liquid crystal pitch-based carbon fiber capable of being converted into the infusible carbon fiber reaches the maximum. The fiber which is graphitized at a temperature of 2800 to 3300 ° C., or (2) the infusibilized liquid crystal pitch-based carbon fiber-forming fiber which is graphitized at a maximum temperature of 1700 to 3000 ° C. 3. Alternatively, the fluororesin composition according to item 4.