JP2001082611A - Valve seat or packing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve abrasion resistance characteristic by including modified fluororesin which is formed by radiating ionizing radiation to fluororesin by a radiation quantity of a specified range in a condition heated than a melting point of fluororesin, under an atmosphere of an inert gas having an oxygen concentration not less than a specified value. SOLUTION: Ionizing radiation using γ-ray, electron ray, X-ray, neutron radiation, high energy ion or the like is radiated to fluororesin selected from tetrafluoroethylene polymer, tetrafluoroethylene-perfluoro copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, in the range of a radiation quantity of 1 kGy to 10 Mgy, in a condition heated more than a melting point of fluororesin, under an atomosphrere of an inert gas having an oxygen concentration of 100 torr or less. It is thus possible to improve abrasion resistance characteristic of a valve seat.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve seat or packing excellent in low friction and sealing properties and hardly damaging a mating member, and more particularly to a valve seat suitable for a ball valve ball seat or a gland packing. Or, it relates to packing.

[0002]

2. Description of the Related Art Valves are used in various environments, and with the diversification of fluids and automation of production, various types of valves are used. Among them, a ball valve that is frequently used in recent years is a ball valve, and the demand is increasing in the electric power industry, natural gas pipelines, petroleum refining, chemical plants, general chemical plants, and the like. The ball valve has features such as low fluid resistance, high fluid sealing property, structurally suitable for automation, compact valve shape, easy maintenance, etc. BACKGROUND ART A tetrafluoroethylene-based polymer (hereinafter, referred to as “PTFE”) having excellent heat resistance, chemical resistance, and the like is widely used.

[0003]

However, since the valve is repeatedly subjected to compression and pressure release, and receives much more dynamic resistance, there is a danger that the PTFE will be worn and fluid will leak out. It had to be replaced in a short time.
For this reason, there is a problem that production efficiency is reduced due to maintenance or a temporary stop of the production line. As a means to prevent abrasion, carbon fiber, graphite, etc.
There is a method of filling a large amount inside, but the friction coefficient increases, and as a result, the opening and closing force when opening and closing the valve increases,
There is a problem that the filler swells or elutes depending on the fluid.

Accordingly, an object of the present invention is to provide a valve seat or packing which is excellent in abrasion resistance and hardly damages a mating member.

[0005]

Means for Solving the Problems The fluororesin has an oxygen concentration of 1%.
Under an inert gas atmosphere of not more than 00 torr, a dose of ionizing radiation of 1 when heated to a temperature not lower than the melting point of the fluororesin.
Provided is a resin component valve seat or packing containing a modified fluororesin which is irradiated in the range of kGy to 10 MGy.

[0006] In the present invention, the modified fluororesin is PT
FE, a fluororesin selected from a tetrafluoroethylene-perfluoro (alkyl vinyl ether) -based copolymer (hereinafter referred to as “PFA”) and a tetrafluoroethylene-hexafluoropropylene-based copolymer (hereinafter referred to as “FEP”), In an inert gas atmosphere having a concentration of 100 torr or less, preferably 10 torr or less, a dose of ionizing radiation of 1 when heated to a temperature equal to or higher than the melting point of the fluororesin.
It can be obtained by irradiation in the range of kGy to 10 MGy.

[0007] Among the above PTFE, perfluoro (alkyl vinyl ether), hexafluoropropylene,
Those containing 0.2 mol% or less of polymerized units based on copolymerizable monomers such as (perfluoroalkyl) ethylene and chlorotrifluoroethylene are also included. In the case of the copolymer type fluororesin, a small amount of the third component may be included in the molecular structure.

As ionizing radiation, γ-rays, electron beams, X-rays
A wire, a neutron beam, a high energy ion or the like is used. When irradiating with ionizing radiation, it is necessary to heat the fluororesin above its crystalline melting point. For example, when PTFE is used as the fluororesin, it is necessary to irradiate ionizing radiation while heating the fluororesin to a temperature higher than the crystal melting point of 327 ° C. of this material, and use PFA or FEP. In this case, the former is heated to a temperature higher than the melting point specified at 310 ° C. and the latter at 275 ° C. for irradiation. Heating the fluororesin above its melting point activates the molecular motion of the main chain constituting the fluororesin, and as a result, it is possible to efficiently promote the cross-linking reaction between molecules. However, excessive heating, on the contrary, causes the breaking and decomposition of the main chain of the molecule, so from the viewpoint of suppressing the occurrence of such a depolymerization phenomenon, the heating temperature is 10 to 30 ° C. lower than the melting point of the fluororesin.
Should be kept within a high range.

As a method for obtaining the valve seat or the packing of the present invention, a method of molding a fluororesin into a predetermined shape and then irradiating it with ionizing radiation under a specific atmosphere, or a method of irradiating ionizing radiation under a specific atmosphere. And a method of molding fine powder of modified fluororesin into a predetermined shape.

[0010] The valve seat or packing of the present invention comprises:
When composed of the modified fluororesin alone, when composed of the modified fluororesin and at least one of unmodified fluororesin, polyimide and engineering plastics, when composed of the modified fluororesin and fibrous filler And any one of a case where it is composed of a modified fluororesin, at least one kind of unmodified fluororesin, polyimide and engineering plastics, and a fibrous filler.

A representative example of engineering plastics is polyoxybenzoyl ester. Further, as the fibrous filler, glass fiber or carbon fiber can be used. From the viewpoint of reducing the friction coefficient and minimizing the damage of the mating material, the content is 10%.
% By weight or less.

[0012]

[Embodiment 1] PT having a thickness of 1.0 mm
Oxygen concentration 1 torr and nitrogen concentration 755 to FE sheet
rr atmosphere and a heating temperature of 340 ° C.
Modification was performed by irradiation with 20 kGy to obtain a valve sheet.

Example 2 PTFE molding powder (trade name: G-163, manufactured by Asahi Glass Co., Ltd., average particle size: 40 μm)
m) in an atmosphere with an oxygen concentration of 1 torr and a nitrogen concentration of 755 torr at a heating temperature of 340 ° C. and an electron beam of 120 kG.
y Irradiation and modification. This modified PTFE is about 20 μm
And pulverized by a jet mill until the average particle size becomes. 20% by weight of this modified PTFE powder and PTFE molding powder (trade name: G-163, manufactured by Asahi Glass Co., Ltd., average particle size 20)
μm, unmodified) in a proportion of 80% by weight,
Molding was performed at 30 ° C. and a pressure of 30 MPa to obtain a valve sheet.

Example 3 15% by weight of the modified fluororesin powder obtained in Example 2 and 75% by weight of PTFE molding powder (trade name: G-163, manufactured by Asahi Glass Co., average particle size 20 μm, unmodified) % And polyoxybenzoyl ester (trade name: Econol S330, manufactured by Sumitomo Chemical Co., Ltd.), and molded at 360 ° C. and 30 MPa pressure to obtain a valve sheet.

Example 4 30% by weight of the modified fluororesin powder obtained in Example 2 and 70% by weight of PFA (340-J manufactured by Du Pont-Mitsui Fluorochemicals) were dry-blended with a Hensyl mixer and extruded 40 mm. The mixture was melt-kneaded in a machine and pelletized. Pellets are 300 to 3 using a hot press.
Molding was performed at 50 ° C. to obtain a valve sheet.

Comparative Example 1 PTFE molding powder (trade name: G-163, manufactured by Asahi Glass Co., Ltd., average particle size: 20 μm)
m, unmodified) at 360 ° C. and a pressure of 30 MPa to obtain a valve sheet.

Comparative Example 2 PTFE molding powder (trade name: G-163, manufactured by Asahi Glass Co., Ltd., average particle size 20 μm)
m, unmodified) in a ratio of 30% by weight of PFA (340-J manufactured by DuPont-Mitsui Fluorochemicals) and dry blending with a Hensyl mixer, and melt-kneaded with a 40 mm extruder to form pellets. Pellets are converted to 30 using a hot press.
Molding was performed at 0 to 350 ° C. to obtain a valve sheet.

Comparative Example 3 PTFE molding powder (trade name: G-163, manufactured by Asahi Glass Co., Ltd., average particle size: 20 μm)
m, unmodified) 75% by weight and glass fiber (Nittobo PFA)
-001) 25 wt% was dry blended with a Hensyl mixer and molded at 360 ° C. and a pressure of 30 MPa to obtain a valve sheet.

With respect to the valve seats obtained in the examples and comparative examples, the wear resistance and the damage to the mating member were evaluated, and the results are shown in Table 1. For the evaluation test, a strass-type friction and wear tester was used, and S was determined according to JIS K7218.
A test specimen having a thickness of 0.5 mm was attached to 45C, ADC12 was used as a mating material, pressure was 0.4 MPa, and speed was 1.5 m / m.
The test was conducted at room temperature for 5 hours under the condition of in.

[0020]

[Table 1]

[0021]

According to the present invention described above, as is clear from the comparison between the embodiment and the comparative example, a valve seat or packing excellent in abrasion resistance and hard to damage a mating member is realized. It is possible to do.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3H054 AA03 BB02 BB22 CB34 CE03 GG03 GG07 3J040 EA16 FA06 FA07 FA13 HA01 HA15 HA30

Claims (5)

[Claims] 1. A reforming method comprising irradiating a fluorocarbon resin with an ionizing radiation in an irradiation dose of 1 kGy to 10 MGy in an inert gas atmosphere having an oxygen concentration of 100 torr or less while being heated to a temperature higher than the melting point of the fluorocarbon resin. A valve seat or packing comprising a resin component containing a fluororesin. 2. The valve seat or packing according to claim 1, wherein the modified fluororesin alone is contained as a resin component. 3. The valve seat or packing according to claim 1, which comprises at least one of a modified fluororesin, an unmodified fluororesin, polyimide and engineering plastics as a resin component. 4. The valve seat or packing according to claim 1, further comprising a fibrous filler in addition to the resin component. 5. The fluororesin is at least one selected from a tetrafluoroethylene-based polymer, a tetrafluoroethylene-perfluoro (alkyl vinyl ether) -based copolymer and a tetrafluoroethylene-hexafluoropropylene-based copolymer. The valve seat or packing according to claim 1.