JPH10316761A - Modified fluororesin powder and modified fluororesin compact - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a resin powder having excellent frictional resistance by irradiating a fluoro resin in a state heated to its melting point or higher in the absence of oxygen with an ionizing radiation in a specified dosage and mechanically grinding the resin. SOLUTION: A fluoro resin in a state heated to a temperature 10-30 deg.C-above the crystalline melting point of the resin in the absence of oxygen is irradiated with an ionizing radiation selected, among γ-rays, electron beams and X-rays in a dosage of 1 kGy to 10MGy, and the resin is ground by e.g. mechanical grinding to obtain a modified fluoro resin powder having a particle diameter of 1 mm or below. 1-100 wt.% this powder is mixed with an unmodified polymeric material or an inorganic material, and the mixture is molded to obtain a molded product having a coefficient of friction at most 1/2 of that of a molded product molded from a mixture free from the resin powder. Materials used to form the modified fluoro resin powder include tetrafluoroethylene polymers, tetrafluoroethylene/perfluoro(alkyl vinyl ether) copolymers and tetrafluoroethylene/hexafluoropropylene copolymers.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a modified fluororesin powder capable of realizing sliding parts, sealing parts, packing, gaskets, containers and jigs for semiconductor production, etc. having excellent wear resistance and creep resistance. And a modified fluororesin molded article.

[0002]

2. Description of the Related Art Fluororesins are excellent in low friction, heat resistance, electrical properties and chemical resistance, and are widely used in various industrial and consumer applications. However, in some cases, the fluororesin cannot be used in a sliding environment or in a high-temperature compression environment due to large abrasion and creep deformation. For this reason, measures have been taken to improve wear and creep deformation by adding a filler to the fluororesin.

[0003]

However, in the method of adding a filler, the use range is often limited because the filler lowers the excellent properties inherent to the fluororesin.
It was not always satisfactory.

Accordingly, an object of the present invention is to provide a modified fluororesin powder and a molded article having excellent friction resistance, abrasion resistance, and creep resistance, and having good characteristics inherent to fluororesin. To provide.

[0005]

According to the present invention, in order to achieve the above object, a fluororesin is irradiated with ionizing radiation at a dose of 1 k in the absence of oxygen and heated to a temperature higher than its melting point.
An object of the present invention is to provide a modified fluororesin powder obtained by irradiating in the range of Gy to 10 MGy and then mechanically pulverizing, and a molded article comprising the modified fluororesin powder.

Under specific conditions, a method has been proposed for irradiating a tetrafluoroethylene polymer with ionizing radiation to thereby obtain a modified tetrafluoroethylene polymer in which elongation at break and deterioration of fracture strength are suppressed. However, according to the present invention, the form of the fluororesin modified by the radiation is made into a powder, which is molded or molded according to the intended use, as described in JP-A-6-116423, JP-A-7-118423, and JP-A-7-118424. The present invention places a special point on obtaining a molded article having improved abrasion resistance and creep resistance by being added to another resin or the like.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The fluororesin used in the present invention is a tetrafluoroethylene polymer (hereinafter referred to as PTF).
E), a tetrafluoroethylene-perfluoro (alkyl vinyl ether) -based copolymer (hereinafter referred to as PFA), or a tetrafluoroethylene-hexafluoropropylene-based copolymer (hereinafter referred to as FEP).

[0008] Among the above PTFE, perfluoro (alkyl vinyl ether), hexafluoropropylene,
Also included are those containing 1 mol% or less of polymerized units based on copolymerizable monomers such as (perfluoroalkyl) ethylene or chlorotrifluoroethylene. In the case of the copolymer type fluororesin, a small amount of the third component may be included in the molecular structure.

The modified fluororesin powder of the present invention comprises a sheet,
A block or other shaped fluororesin molded body may be subjected to ionizing radiation and then mechanically pulverized, or a fluororesin powder may be mechanically pulverized after being irradiated with ionizing radiation. It may be. In any case, the particle size of the powder after irradiation is preferably 1 mm or less in consideration of moldability, processability, and the ability to be added to other resins.
Further, a single fluororesin may be irradiated with ionizing radiation, or two or more kinds of fluororesin mixtures may be irradiated with ionizing radiation.

Irradiation with ionizing radiation for modifying the fluororesin powder is performed in the absence of oxygen, and the irradiation dose is in the range of 1 KGy to 10 MGy. In the present invention, as the ionizing radiation, γ-ray, electron beam, X-ray,
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. That is, for example, PT
When FE is used, the crystal melting point of this material, 3
It is necessary to irradiate ionizing radiation with the fluororesin heated to a temperature higher than 27 ° C. Alternatively, when applying PFA or FEP, the former is 310
C., the latter being heated to a temperature higher than the crystalline melting point specified at 275.degree. Heating the fluororesin above its crystalline melting point activates the molecular motion of the main chain constituting the fluororesin, and as a result, it is possible to efficiently promote a cross-linking reaction between molecules. However, excessive heating, on the contrary, causes the breaking and decomposition of the main chain of the molecule. Therefore, from the viewpoint of suppressing the occurrence of such a depolymerization phenomenon, the heating temperature is 10 to 30 times higher than the crystal melting point of the fluororesin. Should be kept in the high range. Further, when irradiating the powder, the heating temperature is raised to the melting point or higher, and as the temperature rises, the fluidity increases, and it becomes difficult to pulverize after irradiation. It is desirable to keep the temperature within a range higher by 30 ° C.

A desired molded product can be produced by pressure molding (compression molding or ram molding) of the modified fluororesin powder. In this case, a single or two or more kinds of modified fluororesin powders may be molded, or a mixture of these modified fluororesin powders and an unmodified polymer material or inorganic material may be molded. Is also good.

The unmodified polymer material is preferably a material having heat resistance similar to the fluororesin used for the modified fluororesin powder, specifically, a tetrafluoroethylene-based polymer or Tetrafluoroethylene-perfluoro (alkyl vinyl ether) -based copolymer, tetrafluoroethylene-hexafluoropropylene-based copolymer, ethylene-tetrafluoroethylene-based copolymer, ethylene-chlorotrifluoroethylene-based copolymer, propylene- Fluorine-containing copolymers such as tetrafluoroethylene copolymers, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymers, or polyimides, aromatic polyamides, polyarylene sulfides, aromatic polyesters, etc. it can.

Inorganic materials are mixed for the purpose of improving mechanical strength, heat resistance, abrasion resistance, preventing oxidation, absorbing ultraviolet light, imparting conductivity, coloring, and the like. , Boron fibers, silicon carbide fibers, asbestos, rock wool, fibers such as metal (stainless steel) fibers, or spherical bodies such as glass beads, carbon beads, shirasu balloons, or graphite, mica, talc, clay, diatomaceous earth, and alumina , Hydrated alumina, calcium carbonate, boron nitride, zinc oxide, wollastonite, graphite fluoride, lead monoxide, bronze powder, powder such as boron nitride, or calcium sulfate whisker, potassium titanate whisker, titanium oxide whisker , Short fibers such as zinc oxide whiskers, calcium carbonate whiskers, or copper, lead, tin, molybdenum Metals, alloys, oxides, can be exemplified those such sulfides, but is not limited thereto.

It should be noted that within a range not to impair the object of the present invention,
An antioxidant, a heat stabilizer, an ultraviolet absorber, a flame retardant, a colorant, and the like may be appropriately blended.

The modified fluororesin powder according to the present invention can be used in a wide range of applications such as thick blocks, sliding parts having complicated shapes, and containers containing highly oxidizing chemicals, which are difficult to apply by conventional methods. Can be expected. In addition, low friction and low abrasion resistance can be obtained by adding solid lubricants and non-adhesives to liquids such as engine oil and ink, semi-solid or solid polymer materials such as grease and wax, and various paints. Various properties such as abrasion, non-adhesion, water repellency, and oiliness can be imparted.

More specifically, it is applied to various sliding parts by being added to general-purpose plastics, engineering plastics, super engineering plastics, etc., and is added to various types of lubricating rubbers by being added to elastomers such as general-purpose rubber, oil-resistant rubber, and fluororubber. Applied to seal parts. The clarity of typeface by adding to ink etc. and the lowering of viscosity by adding to engine oil can be realized. The modified product by adding to various resins, rubber paints, enamels, varnishes, etc. has low friction and abrasion resistance. As a part, it can be widely applied to applications such as machinery, precision, transportation, information and communication, electric machinery, chemical plants, food, and medical equipment for coating of non-adhesive, water-repellent, and icing prevention of adhesive substances.

[0018]

【Example】

Example 1 An electron beam was applied to PTFE molding powder (trade name: G-163, manufactured by Asahi Glass Co., Ltd., average particle size: 40 μm) under a vacuum of 0.1 torr or less and a heating temperature of 350 ° C. After irradiation of 100KGy, about 20μ
The modified fluororesin powder was obtained by pulverizing with a jet mill until the average particle diameter reached m. The modified fluororesin powder was compression-molded at 360 ° C. and a pressure of 30 MPa for 1 hour to obtain a block having a thickness of 10 mm.

[Examples 2 to 6] PTFE molding powder (trade name: G-163, manufactured by Asahi Glass Co., Ltd., average particle size: 40 μm) was applied under a vacuum of 0.1 torr or less under vacuum.
After irradiating an electron beam at a heating temperature of 100 ° C. with a dose of 100 KGy, the modified fluororesin powder was obtained by grinding with a jet mill until the average particle size became about 20 μm. 5% by weight of each of the modified fluororesin powders in an unirradiated fluororesin powder (the same PTFE molding powder as above).
(Example 2) 10% by weight (Example 3), 20% by weight
(Example 4), 50% by weight (Example 5), 90% by weight
(Example 6) A fluororesin mixed powder was prepared by adding so as to be included, and the mixed powder was compression-molded at 360 ° C and a pressure of 30 MPa for 1 hour to obtain a block having a thickness of 10 mm.

Example 7 A PTFE molding powder composed of tetrafluoroethylene and perfluoro (alkyl vinyl ether) and having a molar ratio of 99.9 to 0.1 mol (trade name: Teflon 70J, Mitsui DuPont Fluorochemical Co., Ltd .;
After irradiation with an electron beam of 00 kGy, the particles were pulverized with a jet mill until the average particle diameter became about 20 μm to obtain a modified fluororesin powder. This modified fluororesin powder was added to unirradiated fluororesin powder (PTFE molding powder used in Example 1) so as to be contained at 50% by weight to prepare a fluororesin mixed powder. 360
C. and a pressure of 30 MPa for 1 hour to obtain a block having a thickness of 10 mm.

Comparative Example 1 PTFE used in Example 1
360 molding powders (not irradiated with electron beam)
C. and a pressure of 30 MPa for 1 hour to obtain a block having a thickness of 10 mm.

Comparative Example 2 PTFE used in Example 1
Modified fluororesin powder is obtained by irradiating the molding powder with an electron beam at a dose of 100 KGy at room temperature (25 ° C.) under a vacuum of 0.1 Torr or less, and then pulverizing with a jet mill to an average particle diameter of about 20 μm. I got This modified fluororesin powder was irradiated with unirradiated fluororesin powder (Example 1).
The PTFE molding powder used in the above was added so as to be contained at 50% by weight to prepare a fluororesin mixed powder, and the mixed powder was compression-molded at 360 ° C. and a pressure of 30 MPa for 1 hour to form a block having a thickness of 10 mm. I got

Comparative Example 3 PTFE used in Example 1
The molding powder was irradiated with an electron beam at 350 ° C. in air at a dose of 100 KGy, and then pulverized with a jet mill until an average particle diameter of about 20 μm was obtained to obtain a modified fluororesin powder. This modified fluororesin powder was added to unirradiated fluororesin powder (PTFE molding powder used in Example 1) so as to be contained at 50% by weight to prepare a fluororesin mixed powder. The mixed powder was compression molded at 360 ° C. and a pressure of 30 MPa for 1 hour to obtain a block having a thickness of 10 mm.

Table 1 shows the results of measurement tests of the coefficient of friction and the coefficient of wear performed on the molded blocks obtained in Examples 1 to 7 and Comparative Examples 1 to 3. For Example 6 and Comparative Example 1, compression creep was measured, and the results are also shown in Table 1.

In the test, a thrust type friction and wear test apparatus was used, and Examples 1 to 7 and Comparative Examples 1 to 3 were formed by using a SUS304 cylindrical ring (outer diameter 25.6 mm, inner diameter 20.6 mm) according to JIS K7218. A pressure of 2.5 kg / cm ² was applied to each of the test pieces at a speed of 0.5 m /
We went under the condition of sec. At this time, the multiplier PV value of the pressure and the speed was 1.25 kg · m / cm ² · sec.

After measuring the weight loss of the test object 2 hours after the test time, the reduced weight of the test object is converted into a reduced capacity, which is divided by the contact area of the cylindrical ring to obtain the wear depth. Was calculated. Wear coefficient K (msec / MPa / m /
hr × 10 ⁻⁶ ) was obtained by a relational expression of W = KPVT abrasion. In the equation, W is the wear depth (m), P is the load (M
Pa), V are speed (m / sec), and T is time (hr).

The measurement of compression creep is basically made by AST
Performed in accordance with MD621-64, length 10 mm, width 10
A square sample having a height of 5 mm and a height of 5 mm is placed in an atmosphere of 200 ° C. for 2 hours and preheated. After the preheating, a load of 70 kg / cm ² is applied for 24 hours. After removing the load, the sample is taken out and left at room temperature for 24 hours. The thickness of the sample was measured, and the compression creep was determined from the following equation.

Compressive creep = (L−Lt) × 100 / L L: Sample thickness at room temperature before test (mm) Lt: Sample thickness after standing at room temperature for 24 hours after completion of test (mm) The compression creep was determined for three points of the sample, and the average value is shown in Table 1.

[0029]

[Table 1]

[Examples 8 to 11] PTFE molding powder (trade name: G-163, manufactured by Asahi Glass Co., Ltd., average particle size: 40 μm) is applied to a 1 mm thick PTFE sheet under a vacuum of 0.1 torr or less. An electron beam was irradiated at a heating temperature of 335 ° C. at a dose of 100 KGy. This irradiation P
The average particle size of each TFE sheet is 0.3 mm (Example 8),
0.1 mm (Example 9), 50 μm (Example 10), 20
The modified fluororesin powder was obtained by pulverizing with a jet mill until the particle diameter reached μm (Example 11). This modified fluororesin powder was used as a non-irradiated fluororesin powder (PTFE used in Example 1).
Molding powder) was added so as to be contained at 10% by weight to prepare a fluororesin mixed powder.
1 hour compression molding at 60 ° C, pressure 30MPa, thickness 10
mm blocks were obtained.

The friction coefficients and the wear coefficients of the molded blocks of Examples 8 to 11 were measured in the same manner as in Examples 1 to 7 and Comparative Examples 1 to 3, and the results are shown in Table 2.

[0032]

[Table 2]

[0033]

According to the present invention described above, as is clear from the comparison between the examples and the comparative examples, the present invention shows a low coefficient of friction supporting good lubricity, and has excellent abrasion resistance. It becomes possible to realize a molded article having creep resistance, which greatly contributes to expanding the application range of the fluororesin.

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI // C08J 5/16 CEW C08J 5/16 CEW (72) Inventor Hiroo Kusano 5-1-1 Hidakacho, Hitachi City, Ibaraki Prefecture No. Power Systems Research Laboratory, Hitachi Cable, Ltd. Takasaki Research Institute (72) Inventor Shigetoshi Ikeda 1233 Watanukicho, Takasaki City, Gunma Prefecture Japan Atomic Energy Research Institute Takasaki Research Institute

Claims (7)

[Claims] 1. An ionizing radiation irradiation of 1 k in a state where a fluororesin is heated in the absence of oxygen and above its melting point.
A modified fluororesin powder characterized by being irradiated in the range of Gy to 10 MGy and then mechanically pulverized. 2. The method according to claim 1, wherein the powder has a particle size of 1 mm or less, and the powder is added to the unmodified polymer material at least at 1% by weight or more. 2. The modified fluororesin powder according to claim 1, which can be reduced to one part or less. 3. The fluororesin is a tetrafluoroethylene-based polymer, a tetrafluoroethylene-perfluoro (alkyl vinyl ether) -based copolymer, or a tetrafluoroethylene-hexafluoropropylene-based copolymer. Modified fluororesin powder. 4. An ionizing radiation exposure of 1 k in a state where the fluororesin is heated in the absence of oxygen and above its melting point.
A modified fluororesin molded product comprising a modified fluororesin powder which is irradiated in a range of Gy to 10 MGy and then mechanically pulverized. 5. The method of claim 1, wherein the powder has a particle size of 1 mm or less, and the powder is added to the unmodified polymer material at least at least 1% by weight to reduce the wear coefficient of the unmodified unmodified polymer compact. Half
The modified fluororesin molded product according to claim 4, which contains 1 to 100% of a modified fluororesin powder which can be as follows. 6. Modification having a powder particle size of 1 mm or less, and by adding at least 1% by weight or more of the powder to an inorganic material, it is possible to reduce the wear coefficient of a non-added compact to 1/2 or less. The modified fluororesin molded product according to claim 4, which contains 1 to 100% of a fluororesin powder. 7. The method according to claim 4, wherein the fluororesin is a tetrafluoroethylene-based polymer, a tetrafluoroethylene-perfluoro (alkyl vinyl ether) -based copolymer, or a tetrafluoroethylene-hexafluoropropylene-based copolymer. Modified fluororesin molding.