JP3315688B2 - Filler-containing polytetrafluoroethylene composition and molded article thereof - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a filler-containing polytetrafluoroethylene composition having excellent mechanical strength, creep resistance and friction and wear resistance, and this composition. And a molded article obtained by molding the same.

[Background of the Invention]

Polytetrafluoroethylene resin (hereinafter, also referred to as PTFE) has many excellent properties such as a small coefficient of friction, chemical stability, and excellent chemical resistance and heat resistance. Polytetrafluoroethylene resin having such properties is used for sliding materials, sealing materials (packing,
Widely used as gaskets).

By the way, performance required for a member used for a part that moves relatively to a mating member, such as various bearings and packings, generally includes mechanical strength (tensile strength,
Elongation), excellent abrasion resistance, excellent creep resistance, low coefficient of friction and stability, not attacking mating members, and excellent heat resistance and chemical resistance. No.

PTFE has a relatively low coefficient of friction on the surface and therefore low sliding resistance, so it has relatively good properties as a material for sliding and sealing materials. PEFE materials have the problem that the wear resistance is relatively low and the creep resistance is not always good. Therefore, when it is used for a sliding material or a sealing material, it has a disadvantage that it is easily worn in an environment where it repeatedly comes into contact with a mating member, or is easily deformed when it is slid for a long time while applying stress. .

Conventionally, while maintaining the excellent friction characteristics, chemical resistance, and heat resistance inherent in the PTFE material as described above, the above-mentioned wear resistance, mechanical strength, and creep resistance have been improved, Attempts have been made to mix organic or inorganic fillers with PTFE in order to approach the required properties as a sealing material or a sealing material (Japanese Patent Application Laid-Open Nos. 58-19397 and 57-10544).
No. 2 publication).

However, according to the knowledge of the present inventor, it is difficult to obtain a material having all the characteristics required for a sliding material or a sealing material harmoniously even by the method using various fillers as described above. It is. For example, as described above, the sliding material and the sealing material have excellent mechanical strength (particularly tensile strength and elongation) as well as excellent creep resistance while maintaining abrasion resistance and friction characteristics at a certain value or more. In particular, the creep resistance at high temperatures has not yet been solved by a method of blending various fillers. Further, in the conventional PTFE material, the mechanical strength and the creep resistance are properties that cancel each other out, and it has been difficult to obtain a material having both of these properties.

[Summary of the Invention]

The present invention has been made in view of the above-mentioned problems of the prior art, and has excellent mechanical strength characteristics, creep resistance characteristics, and abrasion and wear resistance, and a polytetrafluoroethylene composition excellent in any of the characteristics. It is an object of the present invention to provide a molded product obtained by molding the above.

The inventor of the present invention made the base material composed of polytetrafluoroethylene (PTFE) a composite system of PTFE and a modified PTFE, and furthermore, added an excessive amount of the modified PTFE to the PTFE, so that the sliding was performed. Found that a material having all the characteristics required for materials and sealing materials can be obtained harmoniously,
Based on this finding, the present invention has been completed.

That is, the filler-containing polytetrafluoroethylene composition of the present invention is obtained by modifying non-melt processability of a copolymer of tetrafluoroethylene and a small amount of monomer with respect to 1 part by weight of polytetrafluoroethylene powder. A mixture comprising 1 to 16 parts by weight of polytetrafluoroethylene powder is used as a base material, and a heat-resistant organic filler is added to the base material.

[Specific description of the invention]

 Hereinafter, the present invention will be described specifically.

In the composition of the present invention, the matrix consists of a mixture of polytetrafluoroethylene (PTFE) powder and modified PTFE powder. Here, the PTFE powder means powder of a homopolymer of PTFE. Specifically, for example, an average particle size of 20 to 900
Commercially available PTFE molding powder of μm can be used. These PTFE are usually
It is a PTFE homopolymer obtained by a suspension polymerization method.

The modified PTFE powder mixed with the above PTFE powder means a modified PTFE, for example, a copolymer of a small amount of monomer and PTFE having sufficient physical properties to maintain non-melt processability. It is preferably used. As the monomer in this case, for example, a compound having 3 to 3 carbon atoms such as hexafluoropropylene
6, perfluoroalkenes and C3-C6 perfluoroalkyl vinyl ethers. The copolymer obtained by modification with such a monomer is non-melt-processable, and is characterized by having an apparent melt viscosity at 380 ° C. of 1 × 10 ⁹ poise or more. Can be

The base material in the composition of the present invention comprises a mixed system in which 1 to 16 parts by weight of the modified PTFE powder and 1 to 10 parts by weight of the modified PTFE powder are added to 1 part by weight of the PTFE powder.

It is preferable that the mixing ratio is appropriately selected depending on the type of the filler to be added. According to the inventor's knowledge, the optimum value exists when the filler is a heat-resistant organic filler such as polyoxybenzoyl or polyphenylene sulfide. For example, when used as a polyoxybenzoyl filler, modified PT
The range of 1 to 4 parts by weight of the FE powder is preferable, and the range of 1 to 3 parts by weight is more preferable. In the case of polyphenylene sulfide, it is modified to 1 part by weight of PTFE powder.
PTFE powder is preferably in the range of 1 to 10 parts by weight, more preferably 1 to 5 parts by weight. When the blending ratio of the modified PTFE powder is less than 1 part by weight, the high-temperature creep characteristics are remarkably deteriorated, which is not preferable. On the other hand, the compounding ratio of the modified PTFE powder is
If the amount exceeds 16 parts by weight, the decomposition gas (particularly, the organic filler) caused by the contained filler is promoted to remain in the molded product at the time of molding, and therefore, the strength characteristics are remarkably deteriorated.

As the filler to be added to the base material, a heat-resistant organic filler is used. In addition, an inorganic filler can be appropriately added according to desired characteristics.

As the heat-resistant organic filler, an aromatic heat-resistant polymer such as polyoxybenzoyl (POB) or polyphenylene sulfide (PPS) is particularly preferably used. Preferable examples of the inorganic filler include graphite, glass fiber, carbon fiber, bronze powder, and the like, and it is desirable to appropriately select the filler depending on the characteristics of the counterpart material to be actually applied. For example, when the present composition is used as a sliding material when the mating material is a soft metal material, it is important to select a filler that does not wear the mating material.

The compounding ratio of the filler is preferably in the range of 5 to 40% by weight, more preferably 10 to 30% by weight, based on the total amount of the composition, including the case where the inorganic filler is added in a complex manner.
If the content of the filler is less than 5% by weight or more than 40% by weight, the desired effect of improving the properties cannot be obtained, and the moldability is also decreased, which is not preferable.

〔Example〕

 Each mixture having the composition and compounding ratio shown in Table 1 below was prepared.
Was. Preparation of the base material in the examples
Fluoroethylene (PTFE) resin powder (Polyflon M12: Da
Ikin Industries, Ltd.) and modified PTFE resin powder (TG-70J:
(Mitsui DuPont Fluorochemicals Co., Ltd.)
It is performed by combining.

 Next, a filler is blended with the base material thus obtained.
To obtain a raw material mixture. The filler in the table added in this case
As POB (polyoxybenzoyl)
Conor E101 (Sumitomo Chemical Co., Ltd.), PPS (Po
Riffon P-4)
(Toray Philips Oil Co., Ltd.), inorganic filling
As the agent, graphite ACP-1000 (Nippon Kurofune Co., Ltd.)
(Manufactured by Sharp Corporation).

Next, after filling the obtained raw material mixture into a cylindrical mold, it was subjected to pore forming under a condition of a molding pressure of 500 kg / cm ² to form a columnar block.

Further, the block obtained as described above was fired under the temperature condition of the melting point of PTFE or higher (327 ° C. or higher) to produce a fired PTFE block containing filler. This block was cut to obtain various test samples.

For each comparative example, each test sample was produced in the same manner as described above.

The samples thus obtained were subjected to an evaluation of a strength factor (tensile test), an evaluation of a deformation factor (creep test), and a friction and wear test.

 The measurement conditions of each test are as follows.

Tensile test: Based on ASTM measurement method D-1457.

 Measurement temperature 25 ± 2 ° C Tensile speed 50mm / min Dumbbell width 5mm Distance between chucks 22.2mm Creep test: In accordance with ASTM measurement method D-621.

(Normal temperature test) Measurement temperature 25 ± 2 ° C. Load 140 kg f / cm ^{2 The} creep rate was calculated from the creep amount (%) at 1 hour and 24 hours after load.

(High temperature test) Measurement temperature 100 ± 2 ° C Load 70 kg f / cm ² The creep rate was calculated from the creep amount (%) at 1 hour and 24 hours after loading at the above measurement temperature.

Friction and wear test: Conducted by a thrust test method using aluminum as a mating material.

Load 10kg f / cm ² Speed 0.5m / s Atmosphere In air, room temperature Counterpart material Alnium (A5052) Contact area 2cm ² Sliding distance Initial friction 10km Steady friction 30km Table 2 below shows the results of the tensile test and the results of the creep test. Are shown in Table 3 and the results of the friction and wear test are shown in Table 4.

As described above, as can be understood from the results of each test, the strength factor, the deformation factor, as well as having good characteristics in both friction and wear factors, compared to the comparative example in which the base material is composed of a single material, It can be seen that each characteristic is improved harmoniously.

[Effect of the Invention] In the filler-containing polytetrafluoroethylene composition of the present invention, the base material composed of polytetrafluoroethylene (PTFE) is a composite system of PTFE and a modified PTFE, and Since the amount of the modified PTFE is excessively added, all characteristics required for the sliding material and the sealing material are harmoniously provided.

Claims (7)

(57) [Claims] 1 to 16 parts by weight of a non-melt-processable modified polytetrafluoroethylene powder comprising a copolymer of tetrafluoroethylene and a small amount of monomer per 1 part by weight of polytetrafluoroethylene powder. A filler-containing polytetrafluoroethylene composition, characterized in that a mixture obtained by mixing is used as a base material, and a heat-resistant organic filler is added to the base material. 2. The filler-containing polytetrafluoroethylene composition according to claim 1, wherein the composition further contains an inorganic filler. 3. The filler content is 5 to 40% by weight.
The filler-containing polytetrafluoroethylene composition according to claim 1. 4. The filler-containing polytetrafluoroethylene composition according to claim 1, wherein the heat-resistant organic filler is polyoxybenzoyl or polyphenylene sulfide. 5. The method according to claim 1, wherein the inorganic filler is graphite.
The filler-containing polytetrafluoroethylene composition according to claim 2. 6. A molded article obtained by molding the filler-containing polytetrafluoroethylene composition according to claim 1 or 2 into a predetermined shape. 7. The molded article according to claim 6, wherein said molded article is a sliding member or a sealing material.