JPH06184385A - Tetrafluoroethylene resin composition - Google Patents

Abstract

PURPOSE:To provide a resin composition which has excellent wearing resistance and does not mar a mating material even when it is a soft metal, e.g. aluminum, by incorporating calcium sulfate into a tetrafluoroethylene resin. CONSTITUTION:This resin composition comprises preferably 50-99vol.% tetrafluoroethylene resin and preferably 1-50vol.% calcium sulfate. The sulfate may be anhydrous or a hydrate, and may be made up of single crystals of any of various shapes having particle sizes (maximum dimensions) of desirably 1-200mum, preferably 5-100mum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tetrafluoroethylene resin composition as a material for sliding parts of various devices.

[0002]

2. Description of the Related Art Generally, tetrafluoroethylene resin (hereinafter referred to as
(This is abbreviated as PTFE) not only has excellent heat resistance and chemical resistance, but also has a small coefficient of friction and self-lubricating properties. Therefore, materials for sliding parts such as bearings and gears, pipes, valves, etc. It has been widely used in various fields as a representative of so-called engineering plastics such as molded products of.

However, this one is not always satisfactory in wear resistance and has a large deformation (creep) under load,
Use under high load or high temperature is limited.

In order to improve such a defect of abrasion resistance of PTFE, it has been attempted to add various fillers. Examples of such fillers include glass fiber powder, glass beads and carbon fiber. Inorganic fillers such as graphite and molybdenum disulfide, organic fillers such as aromatic polyester, polyimide, polyphenylene sulfide, and aromatic polyamide.

[0005]

However, even the PTFE composition containing the above-mentioned various fillers cannot sufficiently improve the wear resistance, and in particular, the mating material which slides on the PTFE is soft. In the case of metal aluminum, the aluminum is damaged and abrasion powder is generated immediately after the start of sliding, and the aluminum powder attacks PTFE, so that there is a problem that the abrasion is accelerated.

[0006] Therefore, the present invention solves the above-mentioned problems and makes the PTFE composition excellent in wear resistance, and further, when a soft metal such as aluminum is used as a sliding mating material, The challenge is not to damage it.

[0007]

In order to solve the above problems, the present invention employs a means for preparing a tetrafluoroethylene resin composition obtained by adding calcium sulfate to a tetrafluoroethylene resin. The details will be described below.

First, PTFE according to the present invention has a molecular weight of 300 containing tetrafluoroethylene as a repeating unit.
Since it is a polymer of 10 to 10 million and has a high melt viscosity at a melting point of 327 ° C. or higher, compression molding is possible at the time of molding, but ordinary injection molding is impossible.
Commercially available PTFE is manufactured by Italy Montedison Co., Ltd .: Algoflon, DuPont Co .: Teflon, UK IC
Fluoron manufactured by Ai Co., Ltd., and Algoflon manufactured by Daikin Industries.

The calcium sulfate used in the present invention may be either anhydrous or hydrated, and may be in various single crystallized forms. That is, calcium sulfate can be obtained in various shapes such as powder, spheres, and fibers depending on the production method, and it can be used without particular limitation. The size (maximum dimension) of various shapes is preferably in the range of 1 to 200 μm, more preferably 5 to 100 μm. This is because if the size is less than 1 μm, the moldability of the composition is impaired, and if the size exceeds 200 μm, the friction and wear properties of the composition are not stable, which is not preferable.

The above-mentioned addition amount of calcium sulfate to PTFE is 1 to 50 with respect to 50 to 99% by volume of PTFE.
It is preferably% by volume. This is because if the amount is less than 1% by volume, the desired effect on the friction and wear properties is not observed, and if the amount exceeds 50% by volume, the moldability of the composition is significantly impaired.

Various fillers may be added to such a PTFE composition as long as the effects of the present invention are not impaired. As the filler used in that case, for example, polyamideimide resin, polyetherimide resin, polyarylene sulfide resin, aromatic polyether ketone resin, polyarylene ether sulfone resin, phenolic resin, aromatic polyester resin, polyimide resin, silicone Including heat-resistant polymer materials such as resins and molten fluorocarbon resins, heat-resistant inorganic single fibers such as graphite fibers, wollastonite, potassium titanate fibers, composite fibers such as magnesium sulfate-based fibers, aromatic amide fibers, etc. Heat-resistant organic fiber, inorganic powder for improving lubricity such as molybdenum disulfide, graphite, carbon, mica, talc, molybdenum trioxide, iron oxide, cadmium sulfide,
There are many examples such as inorganic pigments for coloring such as cadmium selenide and carbon black.

When these raw materials are mixed and molded, PT containing a filler, which has been widely used in the past, is used.
The molding may be performed under known FE molding conditions. As such a method, for example, dry mixing is performed with a mixer such as a tumbler mixer and a Henschel mixer, and the mixture is put into a mold, preformed by applying a pressure of 380 to 600 kg / cm ² , and then taken out from the mold. 3 compression molded products
A method of sintering at 70 ° C., a method of compression-molding batchwise while applying heat or a pressure, or a continuous molding method using a ram extruder can be adopted.

[0013]

The calcium sulfate added in the present invention improves the wear resistance of PTFE and protects the mating material by forming a strong transition film on the surface of the mating sliding material such as soft metal.

[0014]

EXAMPLES The raw materials used in Examples and Comparative Examples are collectively shown below. The abbreviations or chemical symbols are shown in [], and the mixing ratios are all volume%.

(1) Tetrafluoroethylene resin [PTFE] Teflon 7J manufactured by Mitsui DuPont Fluorochemicals (2) Calcium sulfate [CaSO ₄ ] Franklin Fiber A-3 manufactured by Dainichi Seika Kogyo Co., Ltd.
0 (3) Lithium phosphate [Li ₃ PO ₄ ] Wako Pure Chemical Industries, Ltd .: Reagent (4) Copper oxide [CuO] Wako Pure Chemical Industries, Ltd .: Reagent (5) Lead oxide [PbO] Mitsui Metal Industry Co., Ltd .: Resurge Y (6) Zinc oxide [ZnO] Made by Matsushita Electric Industrial Co., Ltd .: Panatetra (7) Calcium carbonate [CaCO ₃ ] Made by Nihon Kogyo Co., Ltd .: NA600 (8) Aromatic polyester resin [OP] Sumitomo Chemical Co., Ltd .: Econol E101M The above raw materials were blended in the proportions shown in Table 1 and dry-blended, then put in a mold and preformed at a pressure of 500 kg / cm ² , and the compression molded product was fired at 370 ° C. From this molded body, a test piece having a predetermined shape and dimensions used for the following test method or was prepared, and the physical property values were measured. The results are also shown in Table 1.

Friction coefficient and wear coefficient Using a pin-on disk type friction and wear tester, sliding speed 8.3 m / min, load 700 gf, disk type mating material: aluminum alloy A5056 (surface roughness 3.2S), no lubrication The friction coefficient of the pin type test piece (diameter 8 mm, radius of curvature of pin tip: R50) under the condition of
And 120 minutes later. Further, the wear coefficient (cm ³ / kgf · m) was calculated from the weight change and the specific gravity of the material after the test machine was operated for 120 minutes and before the operation.

After the test of the damage degree of the mating material, the surface roughness shape of the sliding surface was measured, and it was evaluated in two stages of no damage (marked with ◯) and damage (marked with x).

[0018]

[Table 1]

As is clear from the test results of Table 1, in Examples 1 and 2, the mating material was not damaged at all, the friction coefficient during the test time and the wear coefficient before and after the test were stable and low, and It exhibited excellent wear properties.

On the other hand, among Comparative Examples in which compounds other than calcium sulfate were added and mixed, Comparative Examples 1, 2 and 4
Nos. 6 to 6 damaged the mating material, and Comparative Example 3 had a poor wear coefficient, and none of them satisfied both desired wear resistance and mating material damage resistance.

[0021]

[Effects] As described above, the present invention provides a tetrafluoroethylene resin composition in which calcium sulfate is added to a tetrafluoroethylene resin. It has excellent properties, and has the advantage that even if a soft metal such as aluminum is used as a sliding partner material, it will not be damaged. In particular, it can be said that it is optimal as a material for sliding parts such as bearings.

Claims (1)

[Claims] 1. A tetrafluoroethylene resin composition obtained by adding calcium sulfate to a tetrafluoroethylene resin.