JP2007332208A - Modified fluororesin composition and molded product thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a modified fluororesin composition excellent in long-term wear resistance under a high surface pressure and capable of retaining satisfactory properties inherent in a fluororesin. <P>SOLUTION: This modified fluororesin composition is produced by mixing at least one selected from a tetrafluoroethylene-based polymer, a tetrafluoroethylene-perfluoro(alkyl vinyl ether)-based polymer and a tetrafluoroethylene-hexafluoropropylene-based polymer, a fluororesin modified therefrom by irradiating an ionizing radiation, carbon fibers and stainless steel. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a modified fluororesin composition excellent in wear resistance and creep resistance under a high surface pressure made of a modified fluororesin, and the modified fluororesin composition, including sliding parts, seal products, and packings. Further, the present invention relates to a molded body obtained by molding a gasket, a semiconductor manufacturing container, jig, piping or the like.

  Rubber and plastics are used in a wide range of applications. Among them, fluororesins are excellent in low friction, heat resistance, electrical characteristics, chemical resistance and cleanliness (non-contamination), and are widely used in various industrial and consumer applications. It's being used.

  However, wear and creep deformation are large in a sliding environment or in a compression environment at a high temperature.

  For this reason, measures have been taken to improve wear and creep deformation by adding a filler such as glass fiber or carbon fiber to the fluororesin. In such a method, attention has been focused on the total wear amount including initial wear and steady wear, and improvements have been made.

JP 2003-26883 A

  However, when considering the actual use of the sliding material over a long period of time, the steady wear has a greater influence on the overall wear amount than the influence of the initial wear. For this reason, it is important to suppress steady wear.

  In various methods of adding a conventional filler, steady wear is not always small, and depending on the application, long-term wear resistance is not sufficient.

  Accordingly, an object of the present invention is to provide a modified fluororesin composition and a molded body that solve the above-mentioned problems, have excellent long-term wear resistance under high surface pressure, and can retain the original properties of the fluororesin. There is to do.

  In order to achieve the above object, the invention of claim 1 is characterized in that at least selected from a tetrafluoroethylene polymer, a tetrafluoroethylene-perfluoro (alkyl vinyl ether) polymer, and a tetrafluoroethylene-hexafluoropropylene polymer. A modified fluororesin composition comprising one or more types, a fluororesin modified with ionizing radiation, and a mixture of carbon fiber and stainless steel.

  The invention according to claim 2 is the modified fluororesin composition according to claim 1, wherein the polytetrafluoroethylene copolymer contains a second component or a plurality of third component different fluoromonomers within 1 mol%.

  A third aspect of the present invention is the modified fluororesin composition according to the first or second aspect, wherein the heat of crystallization is 40 J / g or less and the melting point is 325 ° C. or less.

  In the invention of claim 4, the modified fluororesin is irradiated with ionizing radiation in an inert gas atmosphere having an oxygen concentration of 10 torr or less and heated to the melting point or higher, and a dose range of 1 kGy to 10 MGy. 4. The modified fluororesin composition according to any one of claims 1 to 3, wherein the modified fluororesin composition is irradiated with a laser beam.

  In the invention of claim 5, the total weight of the fluororesin, carbon fiber and stainless steel modified by ionizing radiation is 10 to 50 parts by weight with respect to the total weight (100 parts by weight in total), Among them, the modified fluororesin is 5 to 30 parts by weight with respect to the total weight, the carbon fiber is 2 to 10 parts by weight with respect to the total weight, and the stainless steel is 3 to 10 parts by weight with respect to the total weight. The modified fluororesin composition according to any one of claims 1 to 4.

  The invention of claim 6 is a molded article characterized by being molded with the modified fluororesin composition according to any one of claims 1 to 5.

  According to the present invention, excellent wear resistance can be imparted under high surface pressure, which greatly contributes to expanding the application range of fluorine polymers.

  Hereinafter, a preferred embodiment of the present invention will be described in detail.

  The fluorine polymer used in the present invention is at least one selected from a tetrafluoroethylene polymer, a tetrafluoroethylene-perfluoro (alkyl vinyl ether) polymer, and a tetrafluoroethylene-hexafluoropropylene polymer. It is most preferable to use a fluororesin such as tetrafluoroethylene copolymer (PTFE), tetrafluoroethylene-fluoroalkoxytrifluoroethylene copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer. (FEP), polytetrafluoroethylene-perfluorodioxysol copolymer (THF / PDD).

  The PTFE includes those containing 0.2 mol% or less of a polymer unit based on a copolymerizable monomer such as perfluoro (alkyl vinyl ether), hexafluoropropylene, (perfluoroalkyl) ethylene or chlorotrifluoroethylene. It is. Moreover, in the case of the said fluororesin, a small amount of 3rd components can also be included in the molecular structure.

  In the present invention, the modified fluororesin molded article preferably has a melting point of 325 ° C. or less and a crystallization heat quantity of 40 J / g or less. If these exceed the specified values, the wear resistance and creep resistance are remarkably lowered. When the fluororesin is PFA, the melting point is preferably 305 ° C. or less and the heat of crystallization is preferably 26 J / g or less, and when FEP is used, the melting point is 275 ° C. or less and the heat of crystallization is 11 J / g or less. Is preferred.

  In the present invention, a differential scanning calorimeter (DSC) is used for evaluation of thermal characteristics, and the temperature is raised and lowered at a rate of 10 ° C./min. The endothermic peak temperature of the DSC curve at the time is taken as the melting point, and the amount of crystallization heat is determined from the exothermic peak at the second temperature drop and the peak area surrounded by the baseline according to JIS K7122.

  The modified fluororesin molded body of the present invention has a dose of 1 kGy to 10 MGy of ionizing radiation when the fluororesin molded body is heated in an inert gas atmosphere having an oxygen concentration of 10 torr or less and at a temperature higher than its melting point. It can manufacture by irradiating with.

  As the ionizing radiation in the present invention, γ-rays, electron beams, X-rays, neutron beams, high energy ions, or the like are used.

  When performing irradiation with ionizing radiation, it is necessary to heat the fluororesin molded body to a temperature higher than its crystalline melting point. For example, when PTFE is used as the fluororesin, it is necessary to irradiate at a temperature higher than the melting point of 327 ° C., and when PFA and FEP are used, the former is 310 ° C. and the latter is 275 ° C. Irradiation is carried out by heating to a temperature higher than the melting point specified in.

  Heating the fluororesin above its melting point activates the molecular motion of the main chain constituting the fluororesin, and as a result, the intermolecular cross-linking reaction can be efficiently promoted. However, excessive heating leads to cleavage and decomposition of the molecular main chain, so the heating temperature should be kept within a range of 10 to 30 ° C. higher than the melting point of the fluororesin.

  In the present invention, carbon fiber and stainless steel are added in addition to these.

  As a result of various studies on improvement of long-term wear resistance under high surface pressure, it has been found that long-term wear resistance is remarkably improved by using a modified fluororesin together with carbon fiber and stainless steel.

  The details of this are unclear, but the modified fluororesin makes it easier to form a transition film on the sliding surface mating material, and the carbon fiber and stainless steel increase the elastic modulus of the entire composition and prevent deformation at high surface pressure. It is presumed that the effect of suppressing the heat storage by suppressing the heat storage by suppressing the heat generated by the sliding by the stainless steel is effective. It is presumed that these effects express long-term wear resistance improvement.

  The carbon fiber and stainless steel used in the present invention are desirably powdery in view of dispersibility, and the carbon fiber preferably has a fiber length of less than 0.4 mm, and the stainless steel preferably has a particle size of 40 μm or less. Beyond this, dispersibility is inferior, resulting in a decrease in wear resistance.

  As a use of the modified fluororesin molding according to the present invention, a wide range of uses such as sliding parts and semiconductor-related manufacturing parts can be expected.

  The present invention will be specifically described based on Examples and Comparative Examples.

  Table 1 shows the compositions and sliding characteristics of Examples 1 to 7 and Comparative Examples 1 to 6.

  Each numerical value of each composition of each example and each comparative example indicates a blending amount with respect to a total amount of 100 parts by weight, and the unit is parts by weight.

  As PTFE, Asahi Glass trade name P-192 was used. This PTFE was modified by irradiating it with 100 kGy of an electron beam (acceleration voltage 2 MeV) at an oxygen concentration of 1 torr and a nitrogen atmosphere at a temperature of 340 ° C. This was finely pulverized to a mean particle size of 20 μm by a jet mill. Kureha Chemical Industries Kureka Chop M-2007S and M-201S were used as carbon fibers. As the stainless steel, the trade name St-S (average particle size 38 μm) of Fukuda metal foil powder was used.

  A mixer was used for mixing these materials, and the material temperature and the ambient temperature were 15 ° C. A hot homing method was used to produce a molded body of this compound. For compression molding, a mold having a diameter of 45 mm and a height of 80 mm was used, and compression molding was performed by applying a pressure of 50 MPa at room temperature. Subsequently, the block was produced by firing at 360 ° C. for 2 hours at atmospheric pressure, and then taking out the mold together at room temperature and compression molding at a molding pressure of 20 MPa.

  A test piece was prepared by cutting from the block thus prepared.

  The sample characterization is described next. The number of measurements was 3 points for each sample, and the arithmetic average of these was the average value.

For the wear resistance evaluation test, a ring-on-desk wear tester was used, and in accordance with JIS K7218, a test piece (outer diameter 25.6 mm, inner diameter) was formed on a SUS304 cylindrical ring (outer diameter 25.6 mm, inner diameter 20.6 mm). 20.6 mm, thickness 1 mm), and SUS304 plate (length 30 mm, width 30 mm, thickness 5 mm, surface roughness Ra 0.2 μm) was used as the mating material under conditions of pressure 4 MPa and speed 60 m / min. It was. The atmosphere was 20 ° C. in air.

  At that time, the wear thickness compensated for the thermal expansion due to the temperature rise of the sliding surface from the vertical movement distance of the shaft to which pressure is applied is measured with an eddy current non-contact displacement sensor, and this is graphed in relation to the sliding time. The amount of change per unit time (μm / h) was determined with the initial wear before the change of the slope of the graph and the steady wear after.

  FIG. 1 shows an example of the test results of the test time and the wear height. In the graph, the rising slope A is the initial wear, and the rising slope B is the steady wear.

  As shown in Examples 1 to 7, all of the molded bodies composed of PTFE, modified PTFE, carbon fiber, and stainless steel as a main component have a low coefficient of friction and excellent wear resistance.

  On the other hand, the comparative example 1 which does not contain carbon fiber but uses glass fiber has a high specific wear amount and is inferior in wear resistance. Comparative Example 6 containing carbon fiber but not containing stainless steel, Comparative Example 2 using bronze instead of stainless steel, Comparative Example 3 containing no carbon fiber and stainless steel, Comparative Example using bronze containing no carbon fiber and stainless steel No. 5 or Comparative Example 4 containing no modified fluororesin also has a high specific wear amount, indicating that the wear resistance is significantly inferior to Examples 1-7.

It is a figure which shows the example of the abrasion test result in the Example and comparative example of this invention.

Explanation of symbols

A Initial wear В Steady wear

Claims (6)

  At least one selected from a tetrafluoroethylene polymer, a tetrafluoroethylene-perfluoro (alkyl vinyl ether) polymer, and a tetrafluoroethylene-hexafluoropropylene polymer, and this was modified by ionizing radiation. A modified fluororesin composition comprising a fluororesin, and further a mixture of carbon fiber and stainless steel.   The modified fluororesin composition according to claim 1, wherein the polytetrafluoroethylene copolymer contains 1 mol% or less of a second component or a plurality of third component different kinds of fluoromonomers.   The modified fluororesin composition according to claim 1 or 2, which has a crystallization heat amount of 40 J / g or less and a melting point of 325 ° C or less.   The modified fluororesin is obtained by irradiating the fluororesin with an ionizing radiation within an irradiation dose range of 1 kGy to 10 MGy in an inert gas atmosphere having an oxygen concentration of 10 torr or less and being heated to the melting point or higher. Item 4. The modified fluororesin composition according to any one of Items 1 to 3.   The total weight of the fluororesin, carbon fiber and stainless steel modified by the ionizing radiation is 10 to 50 parts by weight with respect to the total weight. Among them, the modified fluororesin is 5 parts by weight with respect to the total weight. The modified fluororesin according to any one of claims 1 to 4, wherein -30 parts by weight, carbon fiber is 2 parts by weight to 10 parts by weight, and stainless steel is 3 parts by weight to 10 parts by weight with respect to the total weight. Composition. A molded article, which is molded with the modified fluororesin composition according to any one of claims 1 to 5.

Images