JP2010156398A - Sliding material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sealing material having a rate of thermal expansion almost equal to that of a rotation shaft, improving a low torque performance and abrasion resistance, and preventing leakage of fluid from a sealed part of the rotation shaft. <P>SOLUTION: The sealing material is obtained by steps of: molding fluororesin composite composed of 10-60 wt.% fluororesin, 37-60 wt.% natural graphite powder, and 2-30 wt.% carbon fiber to form a sealing material with pores; and sealing the pores with thermosetting resin by impregnating and hardening it. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a sliding material made of a fluororesin. More specifically, it is made of a fluororesin having a thermal expansion coefficient substantially equal to the thermal expansion coefficient of the rotating shaft, improving low torque and wear resistance, and preventing fluid leakage from the rotating shaft sealing portion. It relates to a sliding material.

  As the sliding material used in the shaft seal portion of various rotating devices becomes high speed, high pressure, and high temperature, leakage of fluid (water, oil, various chemicals, etc.) from the shaft seal portion is likely to occur. This is often due to the fact that the thermal expansion coefficient of the material used as the sliding material is different from the thermal expansion coefficient of the material of the rotating shaft or due to wear of the sliding material. In, the tendency is remarkable.

  As the usage environment becomes severe, the rotating shaft sealing portion (sliding portion) has a rotating shaft sealing portion (sliding portion) and a sliding material due to the difference in thermal expansion coefficient between the rotating shaft material and the fixed portion material. The space (clearance) changes during the period, i.e., the space (clearance) increases and the wear of the sliding surface of the shaft seal portion increases. As a result, the sealing function decreases and the fluid leaks.

  Proposals have been made to solve these phenomena. For example, Japanese Patent Laid-Open No. 2001-294720 proposes a polytetrafluoroethylene resin composition in which graphite and carbon fibers are blended with a polytetrafluoroethylene resin. However, in the sliding material made of this resin composition, the spatial change due to the difference in thermal expansion coefficient between the rotating shaft material and the fixed part material is large, and the sliding sliding surface is less worn, but a large amount of graphite or carbon fiber is used. When added to, there is a problem that the gap increases and the fluid permeates (vents) the sliding material. Japanese Patent Laid-Open No. 11-21406 proposes a tetrafluoroethylene resin composition in which tetrafluoroethylene, a modified tetrafluoroethylene resin, carbon fiber, and expanded graphite are blended. However, in the sliding material made of this resin composition, the gap of the sliding material is low and the fluid permeation (ventilation) is small, but the spatial change due to the difference in the thermal expansion coefficient between the rotating shaft material and the fixed part material is large. There is a problem that the sealing function is lowered and the fluid flows out.

JP 2001-294720 A Japanese Patent Laid-Open No. 11-21406

As a result of developing a sliding material having improved characteristics in order to solve the problem of the sliding material, the present inventor has found a sliding material capable of preventing leakage of fluid from the rotating shaft seal, The present invention has been achieved.
An object of the present invention is a sliding having a thermal expansion coefficient substantially equal to the thermal expansion coefficient of the rotating shaft, improving low torque and wear resistance, and preventing leakage of fluid from the rotating shaft sealing portion. To provide materials.

  In the present invention, the voids in the sliding material obtained by molding a specific fluororesin composition are impregnated with a thermosetting resin and cured to seal the voids. It is based on the discovery that leakage can be prevented, has a thermal expansion coefficient substantially equal to the thermal expansion coefficient of the rotating shaft, improves low torque and wear resistance, and from the rotating shaft sliding portion. It is intended to provide a sliding material in which leakage of the fluid is prevented.

That is, the present invention relates to fluorine comprising at least one selected from 10 to 70% by weight of fluororesin, 30 to 60% by weight of graphite powder, and / or 2 to 30% by weight of carbon fiber, zinc oxide, and glass fiber. Provided is a sliding material in which a void in a sliding material obtained by molding a resin composition is impregnated with a thermosetting resin and cured.
The above-described sliding material in which the thermosetting resin is a thermosetting resin that cures at a temperature lower than the softening point of the fluororesin is a preferred embodiment of the present invention.

  The above-described sliding material in which the thermosetting resin that cures at a temperature lower than the softening point of the fluororesin is at least one selected from a phenol resin, a furan resin, and an epoxy resin is a preferred embodiment of the present invention.

  The above-described sliding material in which the thermosetting resin is a phenol resin is a particularly preferable aspect of the present invention.

  A sliding material in which the fluororesin is a polymer or copolymer of a monomer selected from tetrafluoroethylene, hexafluoropropylene, and perfluoro (alkyl vinyl ether) is a preferred embodiment of the present invention.

  It is a preferable aspect of the present invention that the sliding material is a sliding material used for a rotating shaft sealing portion (sliding portion) of a rotating device.

  According to the present invention, there is provided a sliding material having a thermal expansion coefficient substantially equal to the thermal expansion coefficient of the rotating shaft, improving low torque and wear resistance, and preventing leakage of fluid from the rotating shaft sealing portion. Provided.

  The present invention provides a void in a sliding material obtained by molding a fluororesin composition comprising 10-60 wt% fluororesin, 37-60 wt% graphite powder, and 2-30 wt% carbon fiber. A sliding material impregnated with a thermosetting resin and cured is provided.

  Examples of the fluororesin used in the present invention include polymers or copolymers of perfluoromonomers such as tetrafluoroethylene (TFE), hexafluoropropylene (HFP), and perfluoroalkyl vinyl ether (PAVE). . Specific examples of the perfluorofluororesin include polytetrafluoroethylene (hereinafter referred to as PTFE), TFE / PAVE copolymer (hereinafter referred to as PFA), TFE / HEP copolymer (hereinafter referred to as FEP), Examples thereof include a TFE / HEP / PAVE copolymer (hereinafter referred to as EPE). Among these, in the copolymer of tetrafluoroethylene and perfluoro (alkyl vinyl ether), the alkyl group of perfluoro (alkyl vinyl ether) preferably has 1 to 5 carbon atoms, particularly 1 to 3 carbon atoms. Further, these polymers or copolymers may be blended and used.

  Preferred fluororesins include TFE polymers or copolymers, more preferably PTFE or modified PTFE modified with 1 wt% or less of the above fluorine-containing monomer.

As the shape of the fluororesin, powder, granule, or granulated granule can be used. Even if it is directly powdered by suspension polymerization or emulsion polymerization, the bulk polymer is pulverized. It may be a thing.
The average particle diameter of the fluororesin in the present invention is preferably 5 to 100 μm, more preferably 10 to 50 μm. As such a fluororesin, a commercially available fluororesin powder produced by a conventionally known method can be appropriately selected and used.

  The fluororesin in the fluororesin composition is preferably 10 to 70% by weight. When the amount of the fluororesin is too small, the strength tends to decrease and the pores tend to increase. When the amount is too large, the ratio of graphite and carbon fibers is lowered, so that low torque characteristics are hindered.

  The graphite powder used in the present invention is preferably natural graphite having 95% or more of fixed carbon. More preferred is scaly natural graphite. The average particle size of the graphite powder used in the present invention is preferably 2 to 100 μm, more preferably 3 to 30 μm.

  The graphite powder in the fluororesin composition is preferably 30 to 60% by weight. When the amount is too small, low torque cannot be obtained, which is not preferable. When the amount is too large, strength is decreased and voids are increased.

  The carbon fiber used in the present invention is a pitch-based or PAN-based carbon fiber, and preferably has a fiber length of 20 to 1000 μm, a fiber diameter of 5 to 20 μm, and an aspect ratio of 4 to 80.

The manufacturing method and shape of zinc oxide used in the present invention are not particularly limited, and examples thereof include zinc oxide whiskers having a tetrapot-like three-dimensional structure described in JP-A-2004-210839. . The surface of the zinc oxide whisker may be treated with a silane-based, chromium-based, or titanium-based coupling agent. In particular, when the zinc oxide whisker is surface-treated with a silane coupling agent, the dispersibility in the polytetrafluoroethylene polymer particles can be improved.

The glass fiber that can be used in the present invention is not particularly limited, and the characteristics (eg, melting point, length, thickness, etc.) of the glass fiber can be appropriately selected according to the purpose of use. If the glass fiber is less than the predetermined amount, the resin composition is abruptly worn during sliding, and if the amount of glass fiber added exceeds the predetermined amount, the glass fiber in the composition significantly wears the counterpart metal.

  At least one selected from carbon fiber, zinc oxide, and glass fiber in the fluororesin composition is preferably 2 to 30% by weight. When the amount is too small, the wear resistance cannot be improved, which is not preferable. When the amount is too large, the ratio of the fluororesin or graphite is decreased and the low torque characteristics may be hindered.

The method for obtaining the fluororesin composition of the present invention is not particularly limited, and at least one selected from fluororesin, graphite powder, carbon fiber, carbon fiber, zinc oxide, and glass fiber is mixed by a conventionally known method. Can be obtained. For example, after adding graphite powder and carbon fiber to the fluororesin of the present invention, it can be mixed uniformly using a Henschel mixer to obtain the fluororesin material composition of the present invention.

  In the present invention, examples of the thermosetting resin that is impregnated and cured in the voids in the sliding material include a phenol resin, a furan resin, and an epoxy resin. At least one selected from a phenol resin, a furan resin, and an epoxy resin is a preferable thermosetting resin, and a phenol resin is particularly preferable.

  As the phenol resin, a resol type phenol resin is preferable. Such a phenol resin can be appropriately selected from commercially available ones.

  Furan resins and epoxy resins can also be used by appropriately selecting from commercially available ones. Preferable examples of the furan resin and the epoxy resin include EXA-850CRP (epoxy resin) manufactured by DIC Corporation.

In the fluororesin composition of the present invention, one or more various additives such as a solid lubricant, an oxidation stabilizer, a heat resistance stabilizer, a weather resistance stabilizer, a flame retardant, and a pigment are impaired. You may mix | blend suitably in the range which is not. For example, MoS _2, talc, may be appropriately blended a filler such as a pigment.

As a method for molding the fluororesin composition of the present invention into a sliding material, a conventionally known method such as a compression molding method or an extrusion molding method is used, and it is not particularly limited. For example, a so-called free baking, in which a fluororesin composition is compression-molded using a mold to form a preform, and then fired at a temperature equal to or higher than the melting point of the fluororesin (330 ° C. to 390 ° C. in the case of PTFE). The molded body obtained by cooling after performing the above can be processed into a desired sliding material by cutting or the like.

  As a method of impregnating the sliding material obtained by molding the fluororesin composition of the present invention with a phenol resin, the sliding material is put in a vacuum chamber and deaerated, and the sliding material in the vacuum chamber is completely removed. It is preferable to impregnate with pressure after injecting the phenolic resin until it sinks. When the degree of vacuum is insufficient, the deaeration is preferably performed until the degree of vacuum is 200 Pa or less because the impregnation effect may be impaired by the air remaining in the open pores of the sliding material.

  The pressure impregnation is preferably performed at a pressure of 3 to 10 MPaG.

  The pressure is 3 to 10 MPaG and the voids are sufficiently impregnated with a thermosetting resin such as a phenol resin.

  As a method for curing the phenolic resin pressure-impregnated into the sliding material obtained by molding the fluororesin composition of the present invention, it is preferable to use a hot-air circulating firing furnace. As a preferable effect example, there can be mentioned a method in which the temperature is increased to 200 ° C. at a temperature increase rate of 30 ° C./hour and held at 200 ° C. for 1 hour to cure the impregnated phenol resin.

  In addition, the voids on the surface of the sliding material obtained by molding the fluororesin composition of the present invention can be impregnated by curing or impregnating the thermosetting resin after coating or brushing the thermosetting resin.

  Since the space | gap on the surface of the sliding material obtained by shape | molding the fluororesin composition of this invention is sealed by impregnating a thermosetting resin, it is thought that the effect of this invention is acquired.

The sliding material of this invention can be used conveniently for the rotating shaft sealing part of rotary equipment.
Since the sliding material of the present invention has a low coefficient of thermal expansion equivalent to that of the metal that is the material of the rotating shaft, for example, stainless steel, particularly when used for a split-type axial-circumferential segment seal, the sliding performance is remarkably improved. appear. This is because the shaft packing (segment seal) divided into the expansion (shrinkage) of the shaft (sleeve) due to heat follows, and the space (clearance) between the shaft and the shaft packing is always kept constant. It makes it possible to maintain sex for a long time.

  Further, when the sliding material of the present invention is used for a mechanical seal, the sliding material of the present invention has a low coefficient of thermal expansion. It becomes possible to prevent leakage. The sliding material of the present invention can be applied not only to a rotation motion but also to a shaft seal portion (sliding portion) such as a reciprocating motion or a motion combining a rotation and a reciprocating motion.

  The sliding material of the present invention has a thermal expansion coefficient substantially equal to the thermal expansion coefficient of the rotating shaft, improves low torque and wear resistance, and prevents fluid from flowing out of the rotating shaft seal. Therefore, it is most suitable for the use of the rotary shaft seal device of the rotating equipment. For example, it can be suitably used for a shaft type split segment seal, a mechanical seal, and the like.

The present invention will be described more specifically with reference to examples and comparative examples below, but the present invention is not limited to these examples.
In the present invention, each physical property was measured by the following method.

A. Measurement of physical properties (1) Open porosity The open porosity was measured according to JIS (R1634).
(Sliding material is impregnated with water (saturated weight) and calculated by the following formula)
Pb = (W3-W1) / (W3-W2) × 100
Pb: Open porosity (%)
W1: Dry weight (g)
W2: Weight in water (g)
W3: Saturated weight (g)

(2) Tensile strength Tensile strength was measured according to JIS (K7161).
(Test piece was processed into JISK7161 1 (1/2) type, and tensile strength was measured with Autograph AGS-5KND manufactured by Shimadzu Corporation, test speed 1 mm / min)
(3) Bending strength Bending strength was measured according to JIS (K7171).
(A test piece with a width of 10 mm, a length of 80 mm, and a thickness of 4 mm is processed, and the bending strength is measured with an autograph AGS-5KND manufactured by Shimadzu Corporation. Test speed is 2 mm / min)
(4) Thermal expansion coefficient The thermal expansion coefficient was measured according to JIS K7197.
A test piece having a width of 5 mm, a length of 10 mm, and a thickness of 5 mm was processed, and the temperature was increased from 30 to 100 ° C. at 2 ° C./min to calculate an average coefficient of thermal expansion.

(5) Friction / wear / leakage test (mechanical seal testing machine)
The sliding surface of the mechanically-inserted PTFE composite material (sliding material) for the mechanical seal obtained in the examples and comparative examples is lapped so that the flatness is 0.2 μm or less and the surface roughness Ry is 2 μm, and then the shaft diameter φ 60 The unbalanced mechanical seal tester was set and the friction, wear, and leakage were measured under the following test conditions.
The coefficient of friction was calculated from the torque during operation.
The amount of wear was calculated based on the height of the PTFE composite material before and after operation.
The amount of leakage was measured with a flow meter.
Mating material (rotating ring): Alumina stationary ring: PTFE composite material Number of rotations 1.0 (m / s)
Pressure 0.3 (MGPa)
Operation time: 50hr

(6) Leak test (segment seal)
The segment seal obtained in the examples and comparative examples (shaft-circular seal, a device that combines and seals a segmented ring on a rotating shaft) is mounted on a shaft diameter of φ300 (mm) and leaks under the following test conditions Was measured.
The amount of leakage was measured with a flow meter.
Mating material (shaft material): SUS304
Number of revolutions: 20 (m / s)
Pressure: 0.2 (KPaG)

B. Raw materials The raw materials used in Examples and Comparative Examples of the present invention are as follows.
(1) Fluororesin PTFE powder (average particle size: 5 to 100 μm) obtained by suspension polymerization, manufactured by Mitsui DuPont Fluorochemicals.
(2) Natural graphite manufactured by Nippon Graphite Industries Co., Ltd., special CP
(3) Artificial graphite ATNo. 10 、 average particle size 20μm
(4) M2007S manufactured by Kureha Co., Ltd.
(5) Zinc oxide Amtech Co., Ltd. Product name: WZ-0501
(Tetrapot type zinc oxide whisker with needle-like short fiber diameter of 0.2-30 μm and needle-like short fiber length of 2-50 μm)
(6) Glass fiber manufactured by Nitto Boseki Co., Ltd., glass fiber having an average fiber diameter of 10.5 μm and an average fiber length of 20 μm (7) impregnating resin liquid phenol resin

(Example 1-7)
The mixture was mixed at 25000 rpm for 3 minutes using a high-speed rotary mixer (tilting pulverizer) so that the total amount was about 500 g at the weight ratio shown in Table 1. The obtained mixed powder was molded with a mold of Φ100 × 0 (mm) at a molding pressure of 1.5 t / cm ² to obtain a molded body of Φ100 × 0 × 30 (mm). The obtained molded body was heated up to 370 ° C. at a heating rate of 50 ° C./hour in a hot-air circulating firing furnace (H-100 manufactured by Asahi Kagaku Co., Ltd., temperature distribution ± 5 ° C. or less) and held at 370 ° C. for 3 hours. Thus, a PTFE composite material 1 was obtained.

  The obtained PTFE composite material 1 was machined into an unbalanced mechanical seal insert shape with a shaft diameter of φ60. Next, the insert-shaped PTFE composite material is put in a vacuum chamber, deaerated until the degree of vacuum is 200 Pa or less, and then liquid phenol resin is injected until the insert-shaped PTFE composite material is completely submerged in the vacuum chamber. Then, pressure impregnation was performed at a pressure of 5 MPa. Thereafter, the PTFE composite material in the form of a phenol resin impregnated mechanical seal is heated to 200 ° C. at a heating rate of 30 ° C./hour in a hot air circulation type firing furnace (H-100 manufactured by Asahi Kagaku Corporation, temperature distribution ± 5 ° C. or less). The temperature was raised, and the impregnated phenol resin was cured by maintaining at 200 ° C. for 1 hour. The open porosity of the obtained PTFE composite material (sliding material 1) in the form of a phenol resin-impregnated mechanical seal was measured and subjected to a friction / wear / leakage test. The results are shown in Table 1.

Moreover, the mixed powder obtained above was molded at a molding pressure of 1.5 t / cm ² with a mold of Φ100 × 0 (mm) to obtain a segment seal shape molded body of Φ100 × 0 × 20 (mm). The obtained molded body was heated up to 370 ° C. at a heating rate of 50 ° C./hour in a hot-air circulating firing furnace (H-100 manufactured by Asahi Kagaku Co., Ltd., temperature distribution ± 5 ° C. or less) and held at 370 ° C. for 3 hours. Thus, a segment seal-shaped PTFE composite material 2 was obtained. The obtained PTFE composite material 2 was deaerated in the same manner as described above and impregnated and cured with a phenol resin, and the tensile strength, bending strength and heat of the obtained segment seal-shaped PTFE composite material (sliding material 2) were obtained. The expansion rate was measured and a wetting test was performed. The results are shown in Table 1.

(Comparative Example 1-7)
A mixed powder was obtained in the same manner as in Example 1 so that the total amount was about 500 g at the weight ratio shown in Table 2. A PTFE composite material 3 and a PTFE composite material 4 were obtained in the same manner as the PTFE composite material 1 and the PTFE composite material 2 of Example 1 using the obtained mixed powder. Using the obtained PTFE composite material 3 and PTFE composite material 4, an PTFE composite with an unbalanced mechanical seal insert shape with a shaft diameter of φ60 was used in the same manner as in Example 1 except that the phenol impregnation curing operation was omitted. A material (sliding material 3) and a segment-shaped PTFE composite material (sliding material 4) were obtained. The open porosity of the sliding material 3 was measured, a friction / wear / leakage test was performed, and the tensile strength, bending strength, and thermal expansion coefficient of the sliding material 4 were measured, and a leak test was performed. The results are shown in Table 2.

From the results of Table 1 and Table 2, it can be seen that the phenol resin-impregnated products shown in Examples 1 to 7 have improved leakage and strength compared to the phenol resin non-impregnated products shown in Comparative Examples 1 to 7. .
Further, there was no change in thermal expansion due to the impregnation treatment with the phenol resin.

  The sliding material provided by the present invention has a thermal expansion coefficient substantially equal to the thermal expansion coefficient of the rotary shaft, improves low torque and wear resistance, and allows fluid to flow out of the rotary shaft seal. Since it is prevented, it is most suitable for the use of the rotary shaft sealing part of a rotating device. For example, axial division type segment seals, mechanical seals and the like can be mentioned.

Claims (5)

  Thermosetting properties in the voids in the sealing material obtained by molding a fluororesin composition comprising 10 to 60% by weight of fluororesin, 37 to 60% by weight of natural graphite powder, and 2 to 30% by weight of carbon fiber A sealing material in which the void is sealed by impregnating and curing a resin.   The sealing material according to claim 1, wherein the thermosetting resin is a thermosetting resin that cures at a temperature lower than the softening point of the fluororesin.   The sealing material according to claim 1 or 2, wherein the thermosetting resin is at least one selected from a phenol resin, a furan resin, and an epoxy resin.   The sealing material according to claim 1, wherein the fluororesin is a polymer or copolymer of a monomer selected from tetrafluoroethylene, hexafluoropropylene, and perfluoro (alkyl vinyl ether).   The sealing material in any one of Claims 1-4 whose sealing material is a sealing material used for the rotating shaft sealing part of rotary equipment.