WO2015141442A1

WO2015141442A1 - Seal member and method for producing same

Info

Publication number: WO2015141442A1
Application number: PCT/JP2015/055800
Authority: WO
Inventors: 明宏大和田
Original assignee: 株式会社リケン
Priority date: 2014-03-18
Filing date: 2015-02-27
Publication date: 2015-09-24
Also published as: JPWO2015141442A1

Abstract

[Problem] To provide a seal member that has excellent sealing and sliding properties. [Solution] A seal member comprises a composite material that includes a fluorine-based elastomer and a fluororesin. The fluororesin includes at least one of polytetrafluoroethylene (PTFE), tetrafluoroethylene perfluoro alkyl vinyl ether copolymer (PFA), tetrafluoroethylene hexafluoropropylene copolymer (FEP), and tetrafluoroethylene ethylene copolymer (ETFE). The seal member has a compression set at 150°C of 90% or less.

Description

Seal member and manufacturing method thereof

The present invention relates to a sealing member used for hydraulic equipment and a method for manufacturing the same.

An automobile equipped with various hydraulic devices such as a hydraulic continuously variable transmission is known. In these hydraulic devices, a seal ring for sealing oil is used. For example, the seal ring is fitted into a shaft inserted through the housing, and seals between the housing and the shaft.

It is preferable that the seal ring can be in close contact with the housing and the shaft without any gap in order to realize high sealing characteristics between the housing and the shaft. For this reason, the seal ring may be formed of an elastomer having rubber elasticity.

Patent Documents

1 and 2 disclose a seal ring formed of an elastomer.

JP 2012-255495 A JP 2013-194484 A

In automobiles equipped with hydraulic equipment, reduction of hydraulic equipment drive loss is desired to improve fuel economy.

The seal ring slides back and forth with respect to the housing and shaft when the hydraulic equipment is driven. For this reason, a friction loss (friction loss) that is a driving loss due to a frictional force between the seal ring and the housing and a frictional force between the seal ring and the shaft is generated in the hydraulic device. Therefore, the seal ring preferably has high sliding characteristics in order to reduce friction loss of the hydraulic equipment.

However, elastomers are generally rich in rubber elasticity but have a high coefficient of friction. For this reason, a seal ring formed of an elastomer is easy to obtain high sealing characteristics, but it is difficult to obtain high sliding characteristics.

In view of the circumstances as described above, an object of the present invention is to provide a sealing member excellent in sealing characteristics and sliding characteristics and a manufacturing method thereof.

In order to achieve the above object, a sealing member according to an embodiment of the present invention is made of a composite material containing a fluorine-based elastomer and a fluorine resin.
The fluororesin includes polytetrafluoroethylene (PTFE), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene / hexafluoropropylene copolymer (FEP), and tetrafluoroethylene / ethylene. And at least one of copolymer (ETFE).
The compression set at 150 ° C. of the sealing member is 90% or less.
With this configuration, it is possible to provide a sealing member having excellent sealing characteristics and sliding characteristics.

The composite material may include 20 wt% or more and 40 wt% or less of the fluororesin.
With this configuration, it is possible to provide a seal member having a good balance between seal characteristics and sliding characteristics.

The particle size of the fluororesin may be 10 μm or less.
With this configuration, it is possible to provide a seal member that is further excellent in sliding characteristics.

The seal member may be formed in a ring shape.
With this configuration, it is possible to provide a seal ring having excellent sealing characteristics and sliding characteristics.

In the method for manufacturing a seal member according to one embodiment of the present invention, a fluorine-based elastomer having a compression set at 150 ° C. of 20% or less and a fluororesin are prepared.
The fluororesin includes polytetrafluoroethylene (PTFE), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene / hexafluoropropylene copolymer (FEP), and tetrafluoroethylene / ethylene. And at least one of copolymer (ETFE).
The fluorinated elastomer and the fluororesin are kneaded.
The material obtained by the kneading is formed.
With this configuration, it is possible to provide a manufacturing method of a sealing member that is excellent in sealing characteristics and sliding characteristics.

It is possible to provide a sealing member excellent in sealing characteristics and sliding characteristics and a manufacturing method thereof.

It is the graph which showed the compression set of the seal ring. It is the graph which showed the static friction coefficient of the seal ring. It is the graph which showed the dynamic friction coefficient of the seal ring. It is the graph which showed the Shore A hardness of the seal ring. It is the graph which showed the tensile strength of the seal ring. It is the graph which showed the elongation rate of the seal ring. It is the photograph which showed the surface of the seal ring before an abrasion test. It is the photograph which showed the surface of the seal ring after an abrasion test.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

The present invention is applicable to all seal members used in hydraulic equipment. Therefore, although the shape of the seal member is arbitrary, in this embodiment, a seal ring that is a ring-shaped seal member will be described as an example of the seal member.

[Seal ring]
The seal ring according to the present embodiment is made of a composite material including a fluorine-based elastomer that is a base material and a fluororesin that is a filling material.

Fluorine-based elastomer is advantageous as a material for a seal ring because it can achieve both a small compression set and a low friction coefficient as an elastomer. The compression set of the fluoroelastomer used as the base material is preferably as small as possible. Specifically, a fluorine-based elastomer having a compression set at 150 ° C. of 20% or less can be used.

The fluoroelastomer according to this embodiment is not particularly limited as long as it can be kneaded with a fluororesin before molding. Examples of such a fluorine-based elastomer include a thermosetting paste (liquid) and a thermoplastic elastomer.

Examples of the fluorine-based elastomer that can be used in the present embodiment include “SIFEL 3000 series” from Shin-Etsu Chemical Co., Ltd., “Diel G-101” from Daikin Industries, Ltd., “Cefal Soft” from Central Glass Co., Ltd., “THV” from Sumitomo 3M Limited and “AFLAS” from Asahi Glass Co., Ltd.

In particular, the SIFEL 3000 series of Shin-Etsu Chemical Co., Ltd. is preferable in that it has a low glass transition point and maintains stable performance in a wide temperature range of about −50 ° C. to 200 ° C.

In order to obtain a seal ring having sufficiently high sliding characteristics, the material forming the seal ring is required to have a lower friction coefficient than that of the fluorinated elastomer. Therefore, in the present embodiment, a fluororesin having a low coefficient of friction is used as a filling material that fills the fluoroelastomer that is the base material.

As the fluororesin, a material is selected that acts to reduce the friction coefficient of the fluoroelastomer, that is, to impart lubricity to the fluoroelastomer. The fluororesin may be composed of one type of material or may include a plurality of types of materials.

Examples of the fluororesin that can be used in this embodiment include polytetrafluoroethylene (PTFE), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), and tetrafluoroethylene / hexafluoropropylene copolymer (FEP). And ethylene-tetrafluoroethylene copolymer (ETFE).

Particularly, it has been confirmed that the sliding characteristics of the seal ring are improved when a fluororesin having at least one of PTFE, PFA, FEP, and ETFE is used.

In addition, the fluororesin is preferably in the form of a powder in order to improve dispersibility with respect to the fluoroelastomer. Furthermore, the fluororesin is preferably in the form of a fine powder having an average particle size of 10 μm or less, and more preferably 10 μm or less, in order to impart high lubricity to the fluoroelastomer. Specifically, the particle diameter of each particle in the fluororesin can be 10 μm or less, and the average particle diameter can be 4 to 8 μm.

Furthermore, the fluororesin preferably has a low molecular weight. A low molecular weight fluororesin is advantageous for making fine powders, and is less likely to be sticky and is less likely to be fibrillated, so that high dispersibility with respect to the fluoroelastomer can be obtained. Hereinafter, an example in which PTFE is used as the fluororesin will be described. However, the same results as in the case of PTFE shown below can be obtained when PTFE is replaced with another fluororesin.

In this embodiment, a composite material having a lower coefficient of friction than that of a fluorine elastomer alone was obtained by using PTFE having a low molecular weight and filling (adding) PTFE into the fluorine elastomer. In this composite material, when the amount of PTFE is 20% by weight or more, a more remarkable reduction in the friction coefficient is obtained.

In this composite material, as the amount of PTFE increases, the coefficient of friction decreases, but the compression set increases. In the present embodiment, the amount of PTFE in the composite material is determined within the range of compression set that provides sufficient sealing characteristics as a seal ring.

Specifically, when the compression set at 150 ° C. of the seal ring is 90% or less, high seal characteristics of the seal ring can be ensured. Therefore, it is possible to determine the amount of PTFE in the composite material so that the compression set at 150 ° C. of the seal ring is 90% or less.

In this embodiment, even when the amount of PTFE in the composite material is increased to 40% by weight by using a fluorine-based elastomer whose compression set at 150 ° C. is 20% or less, compression of the seal ring at 150 ° C. Permanent distortion can be suppressed to 90% or less. In addition, when the amount of PTFE in the composite material was increased to 50% by weight, the compression set at 150 ° C. of the seal ring increased to 95%.

In the composite material according to the present embodiment, it is particularly preferable that the compression set at 150 ° C. is 40% or less. In a composite material in which PTFE is added to a fluorine-based elastomer, generally, as the amount of PTFE with respect to the fluorine-based elastomer increases, compression set increases and the friction coefficient tends to decrease. In this regard, in this embodiment, it has been confirmed that the change in compression set with respect to the amount of PTFE is moderate when the compression set is 40% or less. That is, when the compression set is 40% or less, the friction coefficient can be satisfactorily reduced, but the adverse effect due to the increase in compression set is less likely to occur. This phenomenon is considered due to the high dispersion of PTFE in the fluorine-based elastomer.

The reason why high dispersion of PTFE with respect to the fluorine-based elastomer was obtained in this embodiment may be, for example, the use of PTFE powder having an average particle diameter of 10 μm or less and a low molecular weight. That is, since the PTFE powder is small, it hardly aggregates in the fluorine-based elastomer. Further, when PTFE has a low molecular weight, the initial viscosity and the initial elastic modulus are lowered, and therefore, the viscosity and the elastic modulus are less likely to increase due to rotational heat generated during mixing as compared with a high molecular weight. It is considered that PTFE is highly dispersed in the fluorine-based elastomer by these combined actions.

Further, in the composite material in which PTFE is added to the fluoroelastomer, the elongation hardly changes when the compression set is 40% or less, whereas when the compression set exceeds 40%, the compression set increases. Along with this, the elongation rate decreases. This phenomenon is considered to be caused by the fact that when the amount of PTFE is increased to such an extent that the compression set exceeds 40%, the limit of the amount of PTFE in the fluoroelastomer is exceeded, and PTFE aggregation starts.

As described above, in the composite material according to the present embodiment, by suppressing the amount of PTFE to an amount at which the compression set is 40% or less, an increase in compression set and a decrease in elongation are effectively suppressed. However, the coefficient of friction can be improved satisfactorily.

A seal ring formed of such a composite material has both a sufficiently low static friction coefficient and a dynamic friction coefficient, and has excellent sliding characteristics.

[Seal ring manufacturing method]
(Thermosetting)
When using a thermosetting fluorine-based elastomer as the base material, first, PTFE powder is added to the fluorine-based elastomer paste (liquid) before curing, and the fluorine-based elastomer and PTFE powder are sufficiently kneaded to obtain a kneaded body. The obtained kneaded body is poured into a mold, and the mold is heated to cure the kneaded body in the mold. After cooling the mold, a seal ring is obtained from within the mold.

(injection molding)
When a thermoplastic fluorine-based elastomer is used as the base material, first, PTFE powder is added to the fluorine-based elastomer, and the fluorine-based elastomer and the PTFE powder are sufficiently kneaded to obtain a kneaded body. The obtained kneaded body is heated, and the softened kneaded body is filled into a mold. After cooling the mold, a seal ring is obtained from within the mold.

[Production of seal ring]
In this example, “SIFEL3705A / B” manufactured by Shin-Etsu Chemical Co., Ltd., which has high Shore A hardness and excellent pressure resistance, was used as the fluorine-based elastomer. This fluorine-based elastomer is a two-component thermosetting paste. The average particle size of the PTFE powder was 4 μm. The amount of PTFE was 7 types of 0, 10, 20, 25, 30, 35, and 40% by weight.

First, kneading of one liquid of a fluorine-based elastomer, two liquids of a fluorine-based elastomer, and PTFE powder was performed. The kneading may be performed by using a kneader or by manual work as long as the fluoroelastomer and the PTFE powder are mixed well. Next, the kneaded body obtained by kneading was filled in a mold for a seal ring, and the mold was heated. In heating the mold, the mold was held at 150 ° C. for 5 to 10 minutes. As a result, seven types of seal rings having an outer diameter of 25.0 mm, an inner diameter of 19.6 mm, and a thickness of 3.2 mm and different amounts of PTFE were obtained.

[Examination of the amount of PTFE]
The amount of PTFE in the seal ring was examined from the viewpoint of compression set and coefficient of friction. Specifically, the compression set, static friction coefficient, and dynamic friction coefficient at 150 ° C. were measured for each seal ring.

(Measurement of compression set)
As a measurement sample for this measurement, a test piece having a length of 5 mm, a width of 15 mm, and a thickness of 2 mm obtained by injection molding was used.

In this measurement, first, a measurement sample sandwiched between spacers was compressed by 25% by applying a pressure between the spacers and held at 150 ° C. for 100 hours. Thereafter, the applied pressure between the spacers was released, and the measurement sample was allowed to stand at room temperature for 30 minutes. The compression set at 150 ° C. was calculated by the following formula.
(Compression set at 150 ° C.) = [(T ₀ −t ₂ ) / t ₀ −t ₁ ] × 100 [%]
(Where, t ₀ : thickness of the measurement sample before the test (mm), t ₁ : thickness of the spacer (mm), t ₂ : thickness of the measurement sample after the test (after standing at room temperature for 30 minutes) (Mm)

FIG. 1 is a graph showing compression set of each seal ring. The horizontal axis in FIG. 1 indicates the amount of PTFE. From FIG. 1, it can be seen that the compression set at 150 ° C. increases as the amount of PTFE increases.

On the other hand, if the compression set at 150 ° C. exceeds 90%, sufficient seal characteristics may not be obtained in the seal ring. Referring to FIG. 1, it can be seen that when the amount of PTFE is 40% by weight or less, the compression set at 150 ° C. is 90% or less.

Further, when the compression set at 150 ° C. is 60% or less, better sealing characteristics can be obtained in the seal ring. Referring to FIG. 1, it can be seen that when the amount of PTFE is 35% by weight or less, the compression set at 150 ° C. is 60% or less.

Furthermore, when the compression set at 150 ° C. is 45% or less, particularly good sealing characteristics can be obtained in the seal ring. Referring to FIG. 1, it can be seen that the compression set at 150 ° C. is 45% or less when the amount of PTFE is 30% by weight or less.

(Measurement of static friction coefficient and dynamic friction coefficient)
In this measurement, each seal ring was directly used as a measurement sample, and a vertical friction wear tester was used.

In this measurement, carbon steel S45C having an average roughness Rz of 6.3 μm was used as a counterpart material for sliding the measurement sample. In this measurement, the surface pressure of the measurement sample against the mating material is 0.65 MPa, the peripheral speed of the outer circumference of the measurement sample is 0.50 m / s, the PV value is 0.33 (MPa · m / s), At the expected temperature.

FIG. 2A is a graph showing the static friction coefficient of each seal ring, and FIG. 2B is a graph showing the dynamic friction coefficient of each seal ring. The horizontal axis in FIGS. 2A and 2B indicates the amount of PTFE. In FIG. 2A and FIG. 2B, the measurement sample in which the amount of PTFE is 40% by weight is omitted because the compression set at 150 ° C. is outside the allowable range of this example.

2A and 2B, it can be seen that both the static friction coefficient and the dynamic friction coefficient decrease as the amount of PTFE increases. In particular, it can be seen that the static friction coefficient decreases significantly in the region where the amount of PTFE is 20% by weight or more, and the dynamic friction coefficient decreases significantly in the region where the amount of PTFE is 25% by weight or more.

Also, when both the static friction coefficient and the dynamic friction coefficient are 0.45 or less, particularly good sliding characteristics can be obtained in the seal ring. Referring to FIGS. 2A and 2B, it can be seen that when the amount of PTFE is 20% or more, the static friction coefficient and the dynamic friction coefficient are both 0.45 or less.

(Consideration of the amount of PTFE)
From the measurement result of compression set at 150 ° C., the amount of PTFE in the seal ring is preferably 40% by weight or less, more preferably 35% by weight or less, and particularly preferably 30% by weight or less. . Further, from the measurement results of the static friction coefficient and the dynamic friction coefficient, the amount of PTFE in the seal ring is preferably 20% by weight or more, and more preferably 25% by weight or more.

[Evaluation of seal ring]
Each seal ring was evaluated from a viewpoint other than compression set and coefficient of friction. Specifically, each seal ring was measured for Shore A hardness, tensile strength, elongation rate, and wear amount.

(Measurement of Shore A hardness)
A measurement sample for this measurement was prepared by cutting each seal ring into an appropriate shape. About each measurement sample, the Shore A hardness was measured based on JISK7215 using the type A durometer.

FIG. 3 is a graph showing the measurement result of Shore A hardness. The horizontal axis in FIG. 4 indicates the amount of PTFE. The Shore A hardness is sufficiently high at 71 even for a measurement sample made of only a fluoroelastomer having a PTFE amount of 0% by weight. Further, it can be seen that the Shore A hardness increases with an increase in the amount of PTFE. That is, a sufficiently high Shore A hardness was obtained for all measurement samples.

(Measurement of tensile strength and elongation)
In this measurement, a dumbbell piece having a length of 75 mm, a width of 5 mm, and a thickness of 2 mm obtained by injection molding was used as a measurement sample. The tensile test was performed under the conditions that the distance between chucks was 20 mm and the test speed was 50 mm / min. The tensile strength (breaking strength) indicates the maximum stress in the tensile test, and the elongation (breaking elongation) indicates the elongation at break in the tensile test.

FIG. 4A is a graph showing the measurement result of tensile strength, and FIG. 4B is a graph showing the measurement result of elongation. The horizontal axis of FIGS. 4A and 4B indicates the amount of PTFE.

FIG. 4A shows that the tensile strength is greatly reduced in the measurement sample in which the amount of PTFE is 50% by weight. On the other hand, in the region where the amount of PTFE is 40% by weight or less, good tensile strength is obtained. In particular, a particularly good tensile strength was obtained with a measurement sample in which the amount of PTFE was 35% by weight or less.

From FIG. 4B, it can be seen that the elongation is greatly reduced in the measurement sample in which the amount of PTFE is 35 to 50% by mass. That is, in the region where the amount of PTFE is 30% by weight or less, good elongation is obtained in all cases. The elongation percentage of the measurement sample having a PTFE amount of 35% by weight and the measurement sample having a PTFE amount of 40% by weight was within an allowable range. Further, in FIG. 1, it was confirmed that a particularly good elongation was obtained in the region where the compression set of PTFE was 40% or less and the amount of PTFE was about 29% by weight or less.

(Measurement of wear)
In this measurement, a seal ring having an amount of PTFE of 25% by weight was directly used as a measurement sample, and a vertical friction and wear tester was used.

In this measurement, carbon steel S45C having an average roughness Rz of 6.3 μm was used as a counterpart material for sliding the measurement sample. In this measurement, the surface pressure of the measurement sample against the mating material is 0.65 MPa, the peripheral speed of the outer circumference of the measurement sample is 0.50 m / s, the PV value is 0.33 (MPa · m / s), A one hour wear test was carried out at the expected temperature.

FIG. 5A is a photograph of the surface (sliding surface) of the measurement sample before the wear test, and FIG. 5B is a photograph of the surface (sliding surface) of the measurement sample after the wear test. In FIG. 5B, no conspicuous sliding trace was observed, and it was confirmed that the measurement sample was smoothly sliding with respect to the counterpart material in the wear test.

Further, the wear amount of the seal ring obtained by the difference between the thickness of the measurement sample before the wear test and the thickness of the measurement sample after the wear test was 13 μm, which was very small. Thus, in the seal ring according to the present embodiment, it was confirmed that deterioration due to wear is suppressed by excellent sliding characteristics.

As mentioned above, although embodiment of this invention was described, this invention is not limited only to the above-mentioned embodiment, Of course, in the range which does not deviate from the summary of this invention, a various change can be added.

For example, the seal ring according to this embodiment is made of only a fluorine-based elastomer and a fluororesin. However, if the main component of the seal ring is a fluoroelastomer and a fluororesin, the object of the present invention can be achieved even if the seal ring contains subcomponents such as various additives.

Claims

Fluorine-based elastomer,
Polytetrafluoroethylene (PTFE), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene / hexafluoropropylene copolymer (FEP), tetrafluoroethylene / ethylene copolymer (ETFE) And a fluororesin having at least one of
A seal member having a compression set at 150 ° C. of 90% or less.
The seal member according to claim 1,
A sealing member having a compression set at 150 ° C. of 40% or less.
The seal member according to claim 1 or 2,
A sealing member in which the composite material includes 20% by weight to 40% by weight of the fluororesin.
The seal member according to any one of claims 1 to 3,
The fluororesin has a particle size of 10 μm or less.
The seal member according to any one of claims 1 to 4,
Seal member molded in a ring shape.
A fluorine-based elastomer having a compression set at 150 ° C. of 20% or less;
Polytetrafluoroethylene (PTFE), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene / hexafluoropropylene copolymer (FEP), tetrafluoroethylene / ethylene copolymer (ETFE) And a fluororesin having at least one of
Kneading the fluoroelastomer and the fluororesin,
A method for producing a sealing member, wherein the kneaded body obtained by the kneading is molded.