JP2002338766A - Modified fluororesin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a modified fluororesin composition which is excellent in abrasion resistance and creep deformation prevention in a sliding environment without detriment to the chemical resistance and stain resistance (cleanness) inherent in a fluororesin. SOLUTION: This modified fluororesin composition is prepared by mixing a fluororesin, a radiation-modified fluororesin prepared by irradiating a fluororesin with an ionizing radiation to cross-link, and a melt-type fluororesin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a modified fluororesin composition.

[0002]

2. Description of the Related Art Fluororesins have excellent heat resistance, electrical properties, low friction, chemical resistance, non-staining properties (cleanliness), and the like. Is widely used in many fields.

[0003] However, the fluororesin has a drawback that the wear deterioration and the creep deformation are large in the sliding environment.

For this reason, several attempts have been made to improve the abrasion deterioration and creep deformation of a fluororesin in a sliding environment.

A conventional modification method for minimizing wear deterioration and creep deformation in a sliding environment of a fluororesin is a method of adding a filler to the fluororesin.

[0006]

However, the filler-improved fluororesin obtained by adding a filler to the conventional fluororesin has a reduced chemical resistance and non-staining property (cleanness). Was limited and not always satisfactory.

[0007] The present invention has been made in view of such a point, and an object thereof is to solve the above-mentioned disadvantages of the prior art and to provide the chemical resistance and non-contamination (cleanness) inherent to a fluororesin. It is an object of the present invention to provide a modified fluororesin capable of exhibiting excellent abrasion resistance and creep deformation resistance in a sliding environment without impairing the above.

[0008]

SUMMARY OF THE INVENTION The gist of the present invention is to mix a fluororesin, a radiation-modified fluororesin obtained by irradiating the fluororesin with ionizing radiation and crosslinking, and a melt-type fluororesin. A modified fluororesin composition characterized by comprising:

[0009]

Next, an embodiment of the modified fluororesin of the present invention will be described.

In the present invention, as the base fluororesin, PTFE, PFA, FEP, containing a heterogeneous fluoromonomer of the second component or a plurality of the third components within 1 mol% is used.
It is preferably one selected from THF / PDD.

Here, the PTFE contains a polymer unit based on a copolymer monomer such as perfluoro (alkyl vinyl ether), hexafluoropropylene, (perfluoroalkyl) ethylene and chlorotrifluoroethylene in an amount of 0.2 mol% or less. Is also included. In addition, these base fluororesins have a small amount of third
A monomer component may also be included.

In the present invention, as the radiation-modified fluororesin, a fluororesin having a melting point or higher and an oxygen concentration of 10 or more is used.
Irradiation dose of 1kG under atmosphere of torr or less
consisting of an ionizing radiation cross-linked product obtained by irradiation with y to 10 MGy,
The ionizing radiation crosslinked product has a heat of crystallization of 40 J /
g or less and a melting point of 325 ° C. or less.

The reason why the modified fluororesin is limited to a heat of crystallization of 40 J / g or less and a melting point of 325 ° C. or less is that the heat of crystallization is 40 J / g or more and the melting point is 325 ° C. This is because the above-mentioned modified fluororesin cannot provide a remarkable improvement in wear resistance and creep deformation resistance in a sliding environment.

When the fluororesin is PFA, the heat of crystallization is preferably 26 J / g or less and the melting point is preferably 305 ° C. or less. And FEP is FEP
, The heat of crystallization is 9 J / g or less and the melting point is 2
It is preferably at most 75 ° C.

In the present invention, the raw material fluororesin is preferably a blend of one or more selected from PTFE, PFA and FEP.

In the present invention, the thermal characteristics of the fluororesin were measured using a differential scanning calorimeter (DSC).

A. Temperature rise / fall speed The temperature rise / fall speed of the differential scanning calorimeter in the temperature range of 50 to 360 ° C. was set at 10 ° C./min, and the temperature rise / fall was repeated two cycles.

B. Melting point The melting point was defined as the endothermic peak of the DSC curve at the time of temperature rise in the second cycle.

C. Heat of crystallization The heat of crystallization was obtained by first determining the exothermic peak of the DSC curve and the peak area surrounded by the baseline at the time of the temperature decrease in the second cycle, and then calculating the heat of crystallization according to JIS K7122.

In the present invention, types of ionizing radiation include γ-ray, electron beam, X-ray, neutron beam, high energy ion beam and the like. The dose of this ionizing radiation is 1 kGy to 1
A range of 0 MGy is preferred.

When the raw material fluororesin is irradiated with ionizing radiation, it is effective to heat the raw material fluororesin to a temperature higher than its melting point. This is because heating the raw material fluororesin activates the movement of the molecular main chain, thereby efficiently performing a cross-linking reaction between molecules. Therefore, when irradiating the PTFE with ionizing radiation, the PTFE is heated to a temperature higher than the melting point of 327 ° C. When the PFE is irradiated with ionizing radiation, the irradiation is performed in a state where the PFE is heated to a temperature higher than the melting point of 310 ° C. When irradiating the FEP with ionizing radiation, the FEP is heated to a temperature higher than the melting point of 275 ° C. of the FEP.

However, excessive heating will cause the molecular backbone of the raw material fluorocarbon resin to be cut and decomposed, so that a desirable heating temperature is a temperature range higher by 10 to 30 ° C. than the melting point of the fluorocarbon resin.

In the present invention, the molten type fluororesin is preferably PFA or FEP.

In the present invention, applications of the modified fluororesin composition include sliding parts, semiconductor-related parts, and other industrial products.

[0025]

EXAMPLES Next, examples of the modified fluororesin composition of the present invention will be described together with a modified fluororesin composition of a conventional comparative example. (1) Material a. PTFE As PTFE, Asahi Glass P-192 (trade name of Asahi Glass) was used.

This P-192 has a heat of crystallization of 34 J /
g, the melting point is 319 ° C., and the average particle size is φ20 μm. b. PFA As PFA, NP-20 of Daikin Industries (trade name of Daikin Industries) was used. c. FEP Asahi Glass AP-210 (trade name of Asahi Glass) was used as the FEP. d. Polyamide resin As a polyamide resin, Zytel 101, which is nylon 66 manufactured by DuPont, was used. e. Carbon fiber Kureha T101S from Kureha Chemical Industry
Was used. (2) Preparation of radiation-modified fluororesin First, PTFE powder was heated at 360 ° C. and 50 MPa
Time compression molding, firing 50mm by 50m
m, a PTFE sheet having a thickness of 1 mm was formed.

Next, the obtained vertical 50 mm and horizontal 50 m
m, 1mm thick PTFE sheet 50mm long, 30mm wide,
It was cut to a thickness of 1 mm.

Next, a tension of 10 g per 10 mm is applied to the PTFE sheet prepared above on both sides in the longitudinal direction, and the PTFE sheet with the tension is heated to 340 ° C. in a nitrogen atmosphere having an oxygen concentration of 1 torr. Then acceleration voltage 2
Crosslinking was achieved by irradiation with an electron beam of MeV at 100 kGy.

Next, the crosslinked product thus obtained was pulverized to obtain a radiation-modified fluororesin finely pulverized product. (3) Preparation of Finely Pulverized Modified Fluororesin Composition The compositions of Examples and Comparative Examples were prepared. (4) Preparation of characteristic test sample a. Tensile property test Next, for the compositions of Examples and Comparative Examples, a thickness of 0.5 mm
In each case, three tensile test pieces were prepared.

Next, the prepared tensile test piece having a thickness of 0.5 mm was subjected to a pulling speed of 200 in accordance with JIS-K7161.
It was pulled at a rate of mm / min, and its tensile strength and elongation at break were measured.

The results are shown as an average of three samples. b. Abrasion Resistance Test Next, three abrasion resistance test pieces each having an outer diameter of 25.6 mm, an inner diameter of 20.6 mm, and a thickness of 1 mm were prepared for the compositions of Examples and Comparative Examples.

Next, the abrasion resistance test piece prepared above was attached to a SUS304 cylindrical ring of a thrust abrasion tester according to JIS-K7218.

Next, a SUS304 plate material (length 30 mm, width 30 mm, thickness 5 mm) was prepared as a mating plate material.

Next, the prepared SUS304 plate was rubbed for 24 hours at a pressure of 0.4 MPa and a speed of 128 m / min.

After 24 hours, the wear amount V of the wear-resistant test piece
(Weight loss) was measured.

Finally, the specific wear amount V _SA was calculated from the following equation.

V _SA = V / P · L V; abrasion amount P; test load L; average sliding distance c. Permanent Deformation Rate Test (Compression Creep Test) Next, for each of the compositions of Examples and Comparative Examples, five test pieces each having a length of 10 mm, a width of 10 mm, and a thickness of 1 mm were prepared. Next, ASTM-D6
According to 21-64, these five compression creep test specimens were superimposed, and the thickness of the five superimposed products was measured at room temperature.

Next, the five sheets were placed in air at 200 ° C. for 2 hours and preheated.

Next, a load of 7 MPa was applied and left for 24 hours.

After being left for 24 hours with a load, the load was removed and left for another 24 hours.

Next, after standing for 24 hours without a load, the thickness of the five superposed products was measured at room temperature.

Finally, the permanent deformation rate was calculated from the following equation.

ΔL = (L = L _t ) × 100 / l L; thickness of the five-layered product at room temperature before the test L _t ; thickness of the five-layered product at room temperature after the test ( Example 1) First, 60 parts by weight of PTFE, 30 parts by weight of a finely pulverized modified fluororesin composition, and 10 parts by weight of PFA were blended to obtain a modified fluororesin composition of Example 1.

Next, a tensile test piece, an abrasion resistance test piece and a compression creep test piece were prepared and tested for the modified fluororesin composition of Comparative Example 3 as described above. (Example 2) First, 40 parts by weight of PTFE, 40 parts by weight of the pulverized modified fluororesin composition, and 20 parts by weight of PFA were blended to obtain a modified fluororesin composition of Example 2.

Next, a tensile test piece, an abrasion resistance test piece, and a compression creep test piece were prepared and tested for the modified fluororesin composition of Example 2 as described above. Example 3 First, 65 parts by weight of PTFE, 20 parts by weight of a finely pulverized modified fluororesin composition, and 15 parts by weight of FEP were blended to obtain a modified fluororesin composition of Example 3.

Next, a tensile test piece and an abrasion resistance test piece were prepared and tested for the modified fluororesin composition of Example 3 as described above. Example 4 First, 60 parts by weight of PTFE, 20 parts by weight of a finely pulverized modified fluororesin composition, 15 parts by weight of PFA, and 5 parts by weight of carbon fiber are blended to obtain a modified fluororesin composition of Example 4. Was.

Next, a tensile test piece, an abrasion resistance test piece and a compression creep test piece were prepared and tested for the modified fluororesin composition of Example 4 as described above. (Example 5) First, 55 parts by weight of PTFE, 20 parts by weight of a finely-modified modified fluororesin composition, 15 parts by weight of PFA, and 10 parts by weight of carbon fiber are blended to obtain a mixture of Example 5
To obtain a modified fluororesin composition.

Next, a tensile test piece, an abrasion resistance test piece and a compression creep test piece were prepared and tested for the modified fluororesin composition of Example 5 as described above. Comparative Example 1 First, 60 parts by weight of PTFE and 40 parts by weight of a finely pulverized modified fluororesin composition were blended to obtain a modified fluororesin composition of Comparative Example 1.

Next, a tensile test piece, an abrasion resistance test piece, and a compression creep test specimen were prepared and tested for the modified fluororesin composition of Comparative Example 1 as described above. Comparative Example 2 First, 90 parts by weight of PTFE and 10 parts by weight of PFA were blended to obtain a modified fluororesin composition of Comparative Example 2.

Next, a tensile test piece, an abrasion resistance test piece, and a compression creep test piece were prepared and tested for the modified fluororesin composition of Comparative Example 2 as described above. Comparative Example 3 First, 60 parts by weight of PTFE, 30 parts by weight of a finely pulverized modified fluororesin composition, and 10 parts by weight of a polyamide resin were blended to obtain a modified fluororesin composition of Comparative Example 3.

Next, for the modified fluororesin composition of Comparative Example 3, a tensile test piece, a wear resistance test piece, and a compression creep test piece were prepared and tested as described above. (Test results) Table 1 shows the results of these tests.

[0052]

[Table 1]

As can be seen from Table 1, the modified fluororesin composition of Comparative Example 1 and the modified fluororesin composition of Comparative Example 2 do not contain a melt-type fluororesin, and thus a PTFE-modified fluororesin set is used. Has poor adhesion, resulting in voids at the interface, which results in significantly poor wear and creep resistance.

The modified fluororesin composition of Comparative Example 3 in which a polyamide resin which is not a molten type fluororesin is blended, the polyamide resin is thermally decomposed at the firing temperature, resulting in voids and extremely small elongation. And the wear resistance and creep resistance are considerably poor.

On the other hand, since the modified fluororesin compositions of Examples 1 to 5 contain a molten type fluororesin, the adhesion between the PTFE and the modified fluororesin group is excellent, and as a result, voids are formed at the interface. There were no occurrences, thereby showing excellent results in tensile properties, abrasion resistance and creep resistance.

[0056]

The modified fluororesin composition of the present invention can exhibit excellent tensile properties, abrasion resistance, creep resistance and the like, and is industrially useful.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Kenji Asano 5-1-1, Hidaka-cho, Hitachi City, Ibaraki Prefecture F-term in Hitachi Cable, Ltd. General Research Laboratory 4F070 AA24 AB17 AB23 AC79 HA04 HB02 HB06 4J002 BD15W BD15Y BD17X

Claims (5)

[Claims] 1. A modified fluororesin composition comprising a mixture of a fluororesin, a radiation-modified fluororesin obtained by irradiating and cross-linking the fluororesin with ionizing radiation, and a melt-type fluororesin. . 2. The method according to claim 1, wherein the base fluororesin has a second content of 1 mol% or less.
Polytetrafluoroethylene copolymer (hereinafter referred to as P)
TFE), a tetrafluoroethylene / perfluoro (alkyl vinyl ether) copolymer (hereinafter PFA)
1) selected from tetrafluoroethylene / hexafluoropropylene copolymer (hereinafter referred to as FEP) and polytetrafluoroethylene / perfluorodioxysole copolymer (hereinafter referred to as THF / PDD).
The modified fluororesin composition according to claim 1, which is a seed. 3. The radiation-modified fluororesin comprises an ionizing radiation crosslinked product obtained by irradiating the fluororesin with an irradiation dose of 1 kGy to 10 MGy in an atmosphere having a melting point or more and an oxygen concentration of 10 torr or less, The modified fluororesin composition according to claim 1, wherein the ionizing radiation crosslinked product has a heat of crystallization of 40 J / g or less and a melting point of 325 ° C or less. 4. The method according to claim 1, wherein the fluororesin is PTFE, PFA, FEP.
The modified fluororesin composition according to claim 1, wherein the composition is a blend of one or more selected from the group consisting of: 5. The modified fluororesin composition according to claim 1, wherein the molten type fluororesin is PFA or FEP.