JPH1095889A - Fluorocarbon resin composition and seal for swivel joint - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a highly durable joint seal for power shovels by mixing a hard copper alloy powder with an inorganic fiber, a solid lubricant or the like, and a terafluoroethylene/perfluoroalkyl vinyl ether copolymer. SOLUTION: A mixture comprising 30-50wt.% hard copper alloy powder (A), 0.5-5wt.% inorganic fiber (B), 1-5wt.% solid lubricant and a hard powder (C) and the balance (D) consisting of a tetrafluoroethylene/perfluoro(alkyl vinyl ether) copolymer is compression-molded to obtain a fluorocarbon resin composition for sealing the swivel joint of, e.g. a power shovel. Component D desirably has a perfluoro(3 or 4 C alkyl vinyl ether) content of 0.5-5wt.%. Component A is used in the form of a fine powder and is desirably bronze. Component B is desirably a glass fiber or a carbon fiber. Component C is desirably molybdenum disulfide, a Co-Al double oxide or the like. Because of the improved creeping resistance and abrasion resistance of the fluorocarbon resin, this composition can give durable seals.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluororesin composition, and more particularly to a fluororesin composition having improved wear resistance and creep resistance, and a seal for a swivel joint.

[0002]

2. Description of the Related Art FIG. 3 is a partial cross-sectional view of a swivel joint of a power shovel or the like, wherein 1 is a cylindrical housing, and 2 is a rotating shaft that rotates in close contact with an inner wall 11 of the housing 1. A ring-shaped recess 12 for sealing is provided on the inner wall 11 of the housing 1 at regular intervals, and a ring-shaped elastic body 13 made of a crosslinked elastomer and a ring-shaped fluorine on the recess 12 are provided in the recess 12. Resin seals 14 are stacked and installed. The housing 1 and the rotating shaft 2 are hermetically sealed by the fluororesin seal 14.

[0003] If a seal made of a conventionally known fluororesin or its composition is used as the fluororesin seal 14, the sealing performance is deteriorated after a short use, and oil leakage from the housing 1 and the rotary shaft 2 occurs. There is a problem that occurs. The fluororesin seal 14 is constantly pressed against the rotating shaft 2 by the elastic body 13, and a high oil pressure P is applied to the interface between the housing 1 and the rotating shaft 2 while the swivel joint is operating. According to the study of the present inventors, the fluororesin seal 1 was produced by the above-mentioned external force during operation.
4 is that the contact surface with the rotating shaft 2 is worn or deformed during long use, and a part of the seal enters the interface between the housing 1 and the rotating shaft 2 as shown in FIG. It has been found that a so-called overflow phenomenon occurs, and as a result, the oil leakage occurs.

Further studies have shown that seals made of fluororesin compositions with improved abrasion and creep resistance are:
New knowledge has been obtained that the seal 14 and the like for a swivel joint exhibit high performance.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a fluororesin composition having improved abrasion resistance and creep resistance, and a swivel joint seal comprising the composition.

[0006]

The present invention has the following features. (1) Hard copper alloy powder 30-50% by weight, inorganic fiber 0.5-
A fluororesin composition comprising 5% by weight, 1 to 5% by weight of a solid lubricant and / or hard powder, and a balance of a copolymer of tetrafluoroethylene and perfluoro (alkyl vinyl ether). (2) The fluororesin composition according to the above (1), wherein the copolymer of tetrafluoroethylene and perfluoro (alkyl vinyl ether) contains 0.1 to 10% by weight of perfluoro (alkyl vinyl ether). (3) Both the solid lubricant and the hard powder are contained, and the use ratio of both is 0.1 to 0.1 parts by weight of the hard powder per 1 part by weight of the solid lubricant.
3. The fluororesin composition according to the above 1 or 2, which is 2 to 2 parts by weight. (4) The fluororesin composition according to any one of the above (1) to (3), wherein the hard powder has a Mohs hardness of at least 5. (5) The fluororesin composition according to the above (4), wherein the hard powder is a composite oxide containing cobalt oxide and aluminum oxide. (6) The above 1-3, wherein the solid lubricant is a molybdenum-based compound
The fluororesin composition according to any one of the above. (7) The fluororesin composition according to the above (1) or (2), wherein the hard copper alloy powder is a bronze powder. (8) The fluororesin composition according to the above item 1 or 2, wherein the inorganic fibers are carbon fibers. (9) A seal for a swivel joint, comprising the fluororesin composition according to any one of the above (1) to (8).

[0007]

A copolymer of tetrafluoroethylene and perfluoro (alkyl vinyl ether) (hereinafter abbreviated as PFA-modified PTFE) is used as a fluororesin, and in addition to a large amount of hard copper alloy powder as described above, The above object is achieved by blending a small amount of inorganic fibers and a solid lubricant and / or hard powder. By adding only a large amount of hard copper alloy powder to the PFA-modified PTFE, it is possible to considerably improve the physical properties. However, the excessive use of the same may cause the mechanical properties of the PFA-modified PTFE composition, especially the tensile strength and the like. This leads to a decrease in elongation. On the other hand, by keeping the amount of the hard copper alloy powder within the above range and adding a small amount of inorganic fibers and a solid lubricant and / or hard powder, the mechanical properties of the PFA-modified PTFE composition can be improved. The wear resistance and creep resistance can be improved without lowering. The addition of a small amount of inorganic fibers is effective in improving the overall physical properties of the composition. Solid lubricants have the effect of imparting lubricity to the composition to reduce wear and creep due to friction of the composition, while hard powders have the same effect in improving the rigidity of the composition.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION As PFA-modified PTFE, a copolymer of at least one kind of perfluoro (alkyl vinyl ether) represented by the general formula RO-CF = CF ₂ and tetrafluoroethylene is used. As the perfluoro (alkyl vinyl ether), those in which R in the above formula is a perfluoroalkyl group having 3 to 4 carbon atoms, for example, perfluoro (propyl vinyl ether),
Perfluoro (butyl vinyl ether) is preferred. Further, PFA-modified PTFE containing 0.1 to 10% by weight, preferably 0.5 to 5% by weight of perfluoro (alkyl vinyl ether) is preferable.

As hard copper alloys, bronze, brass, phosphor bronze,
Various copper alloys such as nickel silver, lead bronze, etc. are exemplified, but bronze is particularly preferable from the viewpoint of load resistance.

As the inorganic fibers, various fibers are used apart from those having a particularly low tensile strength. For example, soda glass, alkali-free glass, glass fiber such as silica glass, ceramic fiber such as rock wool, steel,
Metal fibers of metals such as iron, aluminum, nickel, and copper; whiskers such as potassium titanate; and carbon fibers. Among them, glass fibers such as non-alkali glass and carbon fibers are preferable, and carbon fibers are particularly preferable from the viewpoint of further improving the load deformability of the composition of the present invention.

The inorganic fiber generally has a tensile strength of a single fiber of 200 kgf / mm ² or more, especially 300 kgf / mm ^2.
It is preferably ² or more and the average fiber diameter is 50 μm or less, particularly preferably 10 μm or less. The average length of the inorganic fibers is suitably from 10 to 1000 μm, especially from 50 to 150 μm, and the aspect ratio is from 1 to 80, especially from 5 to 50,
Further, 5 to 15 is appropriate. For carbon fibers, the average fiber diameter is 30 μm or less, especially 10 to 10 μm.
The average length is preferably 0.05 to 2 mm, particularly preferably 0.1 to 0.8 mm, and the aspect ratio is preferably 1 to 80, particularly preferably 5 to 50. In the present invention, it is particularly preferable to mix glass fibers and carbon fibers as the inorganic fibers. Thus, the creep resistance is further improved. Various carbon fibers can be used.

As the solid lubricant, those generally known as solid lubricants, for example, graphite, mica, soap stone,
Examples include zinc white, molybdenum-based compounds, and other inorganic powders. Above all, molybdenum compounds are preferred. The molybdenum-based compound includes various molybdenum disulfides and organic molybdenum compounds. Of these, examples of the molybdenum disulfide include natural hexagonal compounds and trigonal compounds. For the hexagonal material, lubricating high-grade conch having a purity of 99% or more obtained by a method such as flotation from ore produced from the United States, Chile, Canada or other countries, and ferroalloy having a purity of about 85% There are things. The other molybdenum disulfide is a synthetic orthorhombic material, a hexagonal material obtained by heat-treating the orthorhombic material, or the like. Examples of the organic molybdenum compound include molybdenum dialkyl diphosphate and molybdenum dialkyl dithiocarbamate.

[0013] As hard powder, Mohs hardness is low.
Also preferably 5, and especially at least 6. In general
Various inorganic powders known as abrasives, such as
Complex oxide containing aluminum and aluminum oxide, aluminum
Na, silicon carbide, boron carbide, diamond, emeral
Or natural products such as spinels, garnets, chins
Is an artificial product. Cobalt oxide and aluminum oxide
And 4CoO-3Al as a composite oxide containing_TwoO
_Three, CoO-nAl_TwoO_ThreeOxidation such as (1 ≦ n ≦ 5)
Double oxide of cobalt and aluminum oxide, Kovar oxide
And aluminum oxide and other inorganic oxides such as oxide oxide
A compound containing at least one of ROM, magnesium oxide, etc.
Composite oxide, for example, CoO-Al_TwoO_Three−Cr_TwoO_Three, C
oO-Al _TwoO_Three—MgO and the like. Various types
Baltic blue is a preferred example of such a composite oxide.
You.

In the present invention, the above-mentioned hard copper alloy, solid lubricant and hard powder are all used in the form of fine powder or fine powder. They generally have a particle size of 100% passing through a Tyler standard sieve 100 mesh, especially those passing 100% through a Tyler standard sieve 200 mesh, and furthermore a sieve 30
Those that pass 100% through 0 mesh are preferred.

The amount of the hard copper alloy powder is from 30 to 50% by weight. If it is less than 30% by weight, the effect of improving the creep resistance is poor, while if it is more than 50% by weight, the tensile strength and elongation decrease. Therefore, the preferred compounding amount of the hard copper alloy powder is 35 to 45% by weight.

The compounding amount of the inorganic fiber is 0.5 to 5% by weight. If it is less than 0.5, the effect of improving the abrasion resistance is poor, while if it is more than 5% by weight, there is a problem of a decrease in elongation. Therefore, the preferable blending amount of the inorganic fiber is 1 to 4% by weight, particularly 1 to 3% by weight.

In the present invention, the solid lubricant and the hard powder may be used alone, or preferably both. The compounding amount is 1 to 5% by weight both when used alone and when shared (in that case, the total amount of the solid lubricant and the hard powder). If it is less than 1% by weight, the effect of improving the wear resistance is poor, and if it is more than 5% by weight, the tensile strength and elongation decrease. Therefore, the preferred compounding amount of the solid lubricant and / or the hard powder is 2 to 4% by weight, particularly 2.5% by weight.
~ 3.5% by weight.

As described above, one or both of the solid lubricant and the hard powder may be used at the same time, but it is particularly preferable that both of them are used at the same time. In this case, the ratio of the solid lubricant and the hard powder used is 0.1 parts by weight of the hard powder per 1 part by weight of the solid lubricant.
To 2 parts by weight, preferably 0.2 to 1 part by weight.

In the present invention, in addition to the above-mentioned component materials, various materials usually compounded in the fluororesin composition, for example, an antioxidant, a pigment, a molding aid, and the like may be compounded as required. However, the total content of components other than PFA-modified PTFE in the fluororesin composition of the present invention,
When the content is in the range of 55 to 65% by weight, a decrease in tensile strength can be reduced.

The composition of the present invention comprises PFA-modified PTFE,
It can be produced by mixing a hard copper alloy powder, an inorganic fiber, a solid lubricant, a hard powder, and other compounding agents, if necessary, by a usual method. Then, the fluororesin composition can be molded into a desired shape by a method usually used for molding, for example, compression molding / sintering, ram extrusion, or the like.

The swivel joint seal of the present invention
The composition of the present invention can be manufactured by molding using the above-described method and the like, and the shape and dimensions may be those conventionally known.

[0022]

The present invention will be described below in more detail with reference to Examples and Comparative Examples.

Examples 1-5, Comparative Examples 1-5 PFA-modified PTFE (manufactured by Daikin Industries, trade name: Polyflon M112), PTFE resin (manufactured by Asahi Glass Co., trade name: Fluon G163), bronze powder (Fukuda Metal) Manufactured by Kogyo Co., Ltd., trade name: BRO-AT-W, particle size: 100% passing through Tyler standard sieve 350 mesh, carbon fiber (trade name: Kureha Chop M202S, manufactured by Kureha Chemical Co., average fiber diameter: 14.5 μm, average) Length: 0.20 mm), molybdenum disulfide (manufactured by Nippon Molybdenum Co., trade name: Nichimori C powder, average particle size: 100% passing through Tyler standard sieve 400 mesh), and cobalt blue (manufactured by Mitsubishi Materials Corporation, trade name: Cobalt blue No. 1202,
(Moth hardness: 6-7, particle size: 100% passing through 400 mesh of Tyler standard sieve) were used in combination and mixing ratio shown in Table 1, and they were used by using a Henschel mixer (manufactured by Mitsui Miike Kakoki). The material was dry-blended, preformed in a mold at a pressure of 600 kgf / cm ² , and then fired at 365 ° C. for 3 hours to prepare a material. Thereafter, a physical property evaluation sample having predetermined dimensions was prepared by machining.

The samples obtained from the examples were subjected to ASTM
The load deformation rate under the conditions of 14 MPa × 24 hours based on D621 and the tensile strength and elongation based on ASTM D1457 were measured. Table 1 shows the results.

Table 1 shows that the composition of the present invention has a
It has excellent properties in tensile strength and elongation. On the other hand, the compositions of Comparative Examples 1 and 2 using the PTFE resin instead of the PFA-modified PTFE resin were inferior in the load deformation ratio. Outer Comparative Examples 3-5
Is inferior in elongation.

[0026]

[Table 1]

Example 6 From the composition of Example 1, the thickness was 2.1 mm and the inner diameter was 100 m.
m and a seal for a swivel joint having an outer diameter of 105 mm were obtained.

Example 7 and Comparative Examples 6 and 7 In the same manner as in Example 6, a seal for a swivel joint having the same dimensions Example 7 (from Example 2) and Comparative Example 6 (Comparative Example 1)
) And Comparative Example 7 (from Comparative Example 2). Comparative Example 7 is a commercial product currently in use.

For each of Example 6, Example 7, and Comparative Example 6, the following bench test 1 was performed, and the results are shown in FIG. Bench test 1: Each seal to be tested was applied to a swivel joint shown in FIG. 3 having turbine oil turbine # 56 as working oil, working oil pressure: 10.3 MPa, fluctuation range of swing angle: +120 degrees to -120 degrees, Swing cycle: 13c
The cycle operation was performed under the condition of pm, and the total leakage amount (cc) of the hydraulic oil with respect to the increase in the swing cycle was measured.

From FIG. 1, it can be seen that the seal for the swivel joint of Comparative Example 6 has reached the end of its life with only 256 hours, whereas the seals of Examples 6 and 7 still function sufficiently after 1280 hours. ing. As is clear from the performances of Examples 6 and 7, the composition of the present invention and the seal for swivel joint are also excellent in abrasion resistance.

For each of Example 6 and Comparative Example 7, the following bench test 2 was performed, and the results are shown in FIG. Bench test 2: Each test seal was applied to the swivel joint shown in FIG. 3 having turbine oil turbine # 56 as working oil, and the working oil pressure fluctuation range: 0 to 34.3MP.
a, pressure cycle: 18 cpm, fluctuation range of swing angle: +
1080 degrees to -1080 degrees, swing cycle: 13 cpm
And the total leakage (cc) of the hydraulic oil with respect to the increase in the pressure cycle was measured.

FIG. 2 shows that the seal for the swivel joint of Example 6 has much better deterioration resistance than Comparative Example 7. By the way, when the disassembly inspection was performed after the test for 185 hours, no abnormal point was particularly found in Example 6, but in Comparative Example 7, some large damage was generated.

[0033]

The fluororesin composition of the present invention can be produced by the same method as in the prior art, and has excellent wear resistance, creep resistance, and especially compression creep resistance while maintaining good tensile strength and elongation. Therefore, it is suitable as a wear ring of a hydraulic or pneumatic cylinder, a bearing, a sliding member to which a high load is applied, a fixing member, and the like, particularly as a seal for a swivel joint. Further, the seal for a swivel joint of the present invention has excellent wear resistance and creep resistance, and has a longer life than conventional products.

[Brief description of the drawings]

FIG. 1 is a graph showing test results of a bench test 1 for each of Example 6, Example 7, and Comparative Example 6.

FIG. 2 is a graph showing test results of a bench test 2 for each of Example 6 and Comparative Example 7.

FIG. 3 is a partial cross-sectional view of a normal swivel joint in a power shovel.

FIG. 4 is an explanatory diagram of a sticking-out phenomenon of a seal in a swivel joint.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylindrical housing 2 Rotating shaft 12 Ring-shaped recess for sealing 13 Elastic body 14 Seal made of fluororesin

Claims (9)

[Claims] 1. Hard copper alloy powder 30 to 50% by weight, inorganic fiber 0.5 to 5% by weight, solid lubricant and / or hard powder 1 to 5% by weight, balance tetrafluoroethylene and perfluoro (alkyl vinyl ether) A fluororesin composition comprising a copolymer of 2. The copolymer of tetrafluoroethylene and perfluoro (alkyl vinyl ether) contains 0.1 to 10% by weight of perfluoro (alkyl vinyl ether).
The fluororesin composition according to claim 1, which comprises: 3. The fluorine according to claim 1, wherein both the solid lubricant and the hard powder are contained, and the use ratio of both is 0.1 to 2 parts by weight of the hard powder per 1 part by weight of the solid lubricant. Resin composition. 4. The fluororesin composition according to claim 1, wherein the hard powder has a Mohs hardness of at least 5. 5. The fluororesin composition according to claim 4, wherein the hard powder is a composite oxide containing cobalt oxide and aluminum oxide. 6. The fluororesin composition according to claim 1, wherein the solid lubricant is a molybdenum compound. 7. The hard copper alloy powder is bronze powder.
Or the fluororesin composition according to 2. 8. The method according to claim 1, wherein the inorganic fibers are carbon fibers.
Or the fluororesin composition according to 2. 9. A seal for a swivel joint, comprising the fluororesin composition according to claim 1.