Lip seal

Abstract

To improve lubricity in a lip seal material using a hydrogenation nitrile rubber.SOLUTION: A lip seal made of a rubber-like elastic body is fixed to a housing and slides with a shaft relatively rotating with the housing. The lip seal comprises: a rubber-like elastic body containing a hydrogenation nitrile rubber, EPDM or a fluororubber; a reinforcing filler; and a non-reinforcing filler having an aspect ratio in a range of 1 or more and 30 or less. The lip seal contains 1 pt.wt. or more and 150 pts.wt. or less of the reinforcing filler, and 5 pts.wt. or more and 90 pts.wt. or less of the non-reinforcing filler based on 100 pts.wt. of the rubber-like elastic body.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a lip seal. [Background technology]

[0002] A sealing device that prevents fluid sealed inside a housing such as a water pump from leaking into the atmosphere is designed to have the lip portion of the seal member in sliding contact with the rotating shaft, and the lip portion is pressed against the rotating shaft by the pressure of the fluid, thereby improving sealing performance.

[0003] As a rubber material used for the lip portion of such a sealing device, Patent Document 1 discloses a rubber molded product obtained by kneading one or more rubber materials selected from nitrile rubber, hydrogenated nitrile rubber, fluororubber, silicone rubber, and ethylene propylene rubber with thermally expandable graphite, and then vulcanizing and molding the mixture. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2008-280366 A Summary of the Invention [Problem to be solved by the invention]

[0005] Lip seal materials using rubber materials such as those disclosed in Patent Document 1 may have insufficient lubricity during use. Insufficient lubricity may cause seizure, damage the lip seal, and cause leakage. Therefore, an object of the present invention is to improve the lubricity of lip seal materials using hydrogenated nitrile rubber, EPDM, and / or fluororubber among the above rubber materials. [Means for solving the problem]

[0006] The inventors conducted extensive research to solve the above problems, and discovered that the above problems can be solved by blending a specific amount of a non-reinforcing filler having a specific shape, thereby improving the lubrication between the rotating shaft and the lip seal, and thus completing the present invention.

[0007] That is, the present invention is a lip seal made of a rubber-like elastic material that is fixed to a housing and slides on a shaft that rotates relative to the housing, The lip seal includes a rubber-like elastomer containing hydrogenated nitrile rubber, EPDM and / or fluororubber, a reinforcing filler, and a non-reinforcing filler having an aspect ratio in the range of 1 or more and 30 or less, The lip seal includes a filler material having a reinforcing property of 1 part by weight or more and 150 parts by weight or less, and a non-reinforcing filler material having a non-reinforcing property of 5 parts by weight or more and 90 parts by weight or less, per 100 parts by weight of the rubber-like elastic body. Effect of the Invention

[0008] According to the present invention, a lip seal having improved lubricity can be provided in a lip seal material using hydrogenated nitrile rubber, EPDM and / or fluororubber. In addition, in a preferred embodiment, various properties of the lip seal can be improved. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The present invention will be described in detail below. The following description of the constituent elements of the present invention These are examples (representative examples) of embodiments, and the present invention is not limited to these contents, but can be practiced in various modified forms within the scope of the gist thereof.

[0010] The lip seal according to one embodiment of the present invention is a lip seal made of a rubber-like elastomer that is fixed to a housing and slides on a shaft that rotates relative to the housing, and includes a rubber-like elastomer containing hydrogenated nitrile rubber, EPDM and / or fluororubber, a reinforcing filler, and a non-reinforcing filler. The lip seal may contain only these components, or may contain components other than these components. Each will be described below in order.

[0011] (rubber-like elastic body) The rubber-like elastomer includes hydrogenated nitrile rubber (HNBR), EPDM and / or fluororubber. The hydrogenated nitrile rubber includes nitrile rubber (NBR) in which all or part of the conjugated diene units are hydrogenated, and is preferably butadiene-acrylonitrile copolymer rubber to which hydrogen has been added, but is not particularly limited thereto. The HNBR may be commercially available or may be produced by a known method.

[0012] The EPDM is not particularly limited as long as it is an ethylene-propylene rubber, and examples thereof include ethylene-propylene-dicyclopentadiene copolymer, ethylene-propylene-ethylidenenorbornene copolymer, ethylene-propylene-1,4-hexadiene copolymer, ethylene-propylene-methylenenorbornene copolymer, ethylene-propylene-methyltetrahydroindene copolymer, and the like, and these can be used alone or in combination of two or more kinds.

[0013] The fluororubber may be a rubber-like elastomer containing fluorine, and examples thereof include vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, vinylidene fluoride-perfluorovinyl ether-tetrafluoroethylene copolymer, tetrafluoroethylene-perfluorovinyl ether copolymer, vinylidene fluoride-propylene-tetrafluoroethylene copolymer, perfluorovinyl ether-ethylene-tetrafluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, and the like, and these may be used alone or in combination of two or more.

[0014] (Reinforcing filler) The reinforcing filler is a component that can form a chemical bond such as a covalent bond or a hydrogen bond with the rubber component to strengthen the rubber strength. Typical examples include carbon black and silica, but are not limited to these.

[0015] The content of the reinforcing filler is preferably in the range of 1 to 150 parts by weight, and more preferably in the range of 30 to 60 parts by weight, per 100 parts by weight of the rubber-like elastomer. By setting the content of the reinforcing filler in the above range, the physical strength of the lip seal can be improved.

[0016] (Non-reinforcing filler) The non-reinforcing filler is a component that does not form a chemical bond such as a covalent bond or a hydrogen bond with the rubber component, and exists as it is in the rubber component to strengthen the physical strength of the lip seal. Typical examples include silicates such as aluminum silicate, magnesium silicate, and calcium silicate, carbon fiber, iron oxide, zinc oxide, titania, alumina, barium sulfate, calcium carbonate, talc, clay, and diatomaceous earth. Among these, it is preferable to include silicates and / or carbon fiber from the viewpoint of improving lubricity. Also, it is preferable to include zinc oxide in order to improve compression set.

[0017] The non-reinforcing filler preferably has an aspect ratio of 1 or more and 30 or less. When the aspect ratio of the non-reinforcing filler is in the above range, unevenness is imparted to the seal surface, and the surface roughness is appropriately controlled. The aspect ratio of the non-reinforcing filler can be measured by observation with a microscope. Specifically, the aspect ratios of a plurality of non-reinforcing fillers are calculated, and the average value thereof can be used.

[0018] The average diameter of the non-reinforcing filler is not particularly limited, but is preferably in the range of 1 μm to 100 μm. When the average diameter of the non-reinforcing filler is within the above range, the lubricity of the lip seal can be effectively improved, and good rubber performance and sealing performance can be exhibited. The average diameter here means the average particle diameter when the non-reinforcing filler is a particle, and the average major axis when the non-reinforcing filler is a fiber. When the non-reinforcing filler includes a particulate filler and a fibrous filler, the average diameter can be calculated by the weighted average of the average particle diameter of the particulate filler and the average major axis of the fibrous filler.

[0019] When the non-reinforcing filler contains a silicate, the average particle size of the silicate is preferably in the range of 10 μm to 30 μm, and the average particle size is measured by observation with a SEM. When the non-reinforcing filler contains carbon fiber, the fiber diameter φ of the carbon fiber is preferably in the range of 1 μm to 30 μm, the fiber length is preferably in the range of 1 μm to 100 μm, and the average fiber length is preferably in the range of 1 μm to 50 μm. The fiber diameter and fiber length of the carbon fiber can be measured by SEM.

[0020] The content of the non-reinforcing filler is preferably 5 parts by weight or more and 90 parts by weight or less, and more preferably 5 parts by weight or more and 40 parts by weight or less, relative to 100 parts by weight of the rubber-like elastic body. By keeping the content of the non-reinforcing filler within the above range, the lubricity of the lip seal can be effectively improved.

[0021] (Plasticizer) The plasticizer may be any plasticizer commonly used in the art, and examples of the plasticizer include, but are not limited to, phthalic acid plasticizers, adipic acid plasticizers, sebacic acid plasticizers, trimellitic acid plasticizers, and the like. The content of the plasticizer is preferably more than 0 part by weight and not more than 15 parts by weight per 100 parts by weight of the rubber-like elastomer. By including the plasticizer in the above range, it is possible to impart low temperature durability to the lip seal.

[0022] (Anti-aging agent) As the antiaging agent, those generally used in the technical field can be used, and examples thereof include, but are not limited to, amine compounds, phenol compounds, imidazole compounds, and the like. The content of the antioxidant is preferably 0.5 parts by weight or more and 5 parts by weight or less, and more preferably 0.5 parts by weight or more and 3 parts by weight or less, relative to 100 parts by weight of the rubber-like elastomer. By including the antioxidant in the above content range, the heat resistance of the lip seal can be improved.

[0023] (Other ingredients) Other components that can be contained in the rubber composition may be appropriately contained within a range that does not impair the effect of the lip seal according to the present embodiment. Examples of other components include processing aids, process oils, and acid acceptors.

[0024] (Lip seal manufacturing) The rubber composition for molding the lip seal is prepared by mixing the components contained in the lip seal in a kneading machine such as an intermixer, a kneader, or a Banbury mixer, or by mixing the components in an open roll. The prepared rubber composition is molded in a molding machine and crosslinked by heating. Molding is performed using an injection molding machine or a compression molding machine, and the rubber composition is crosslinked by heating for about 3 to 60 minutes in an atmosphere having a temperature of, for example, 150° C. to 200° C. Secondary crosslinking may be performed as necessary.

[0025] (Lip seal characteristics) In the lip seal, the roughness Ra of the sliding surface is preferably 0.01 to 10 μm. When the lip seal is in the above range, appropriate irregularities are formed on the sliding surface when the lip seal is installed, and the fluid penetrates into the irregularities, promoting lubrication. More preferably, Ra is 0.01 to 1 μm. This allows a good lubricated state to be maintained and leakage to be suppressed. Here, Ra indicates the arithmetic mean roughness defined in JIS B 601.

[0026] In addition, in the lip seal, the interference in the sliding portion (the difference between the inner diameter dimension when installed and the inner diameter dimension before installation) dimension (A) divided by the inner diameter dimension before installation (B) (interference ratio: A / B) is preferably 1% to 30%, more preferably 10% or less. By having the lip seal in the above range, the unevenness of the sliding surface due to the surface roughness when the lip seal is installed can be maintained, and the fluid can appropriately penetrate the unevenness, promoting lubrication. The above interference ratios are values ​​measured at room temperature.

[0027] In addition, it is preferable that the lip seal has a radial thickness of 0.4 to 2 mm at the innermost diameter part at the sliding part before mounting on the shaft. This makes it possible to form the lip seal in a specified shape while maintaining the strength of the seal part, form a seal part that will not be damaged during sliding, and also to appropriately set the binding force of the lip seal, thereby maintaining a good lubricating state and suppressing leakage.

[0028] In addition, in the lip seal when not mounted on a shaft, the angle between the inner diameter surface forming the sliding part and the tip end surface of the lip seal in the axial cross section when the lip seal is mounted is preferably 90 to 120°. This makes it possible to maintain an appropriate sliding state without excessively increasing the axial area of ​​the sliding part even if the outer periphery of the sliding part is pressurized by the sealed fluid or the like, and also makes it easier for the sealed fluid to properly enter the sliding surface, so that the sealed fluid can reach the uneven parts of the sliding surface and maintain an excellent lubricated state.

[0029] Another aspect of the invention is a method of manufacturing a lip seal. The embodiment is a method for producing a lip seal, comprising the steps of blending a rubber-like elastomer containing hydrogenated nitrile rubber, EPDM or fluororubber, a reinforcing filler and a non-reinforcing filler having an aspect ratio in the range of 1 to 30, in an amount of 1 to 150 parts by weight of the reinforcing filler and 5 to 90 parts by weight of the non-reinforcing filler, preferably further blending an antioxidant in the range of 0.5 to 5 parts by weight and preferably further blending a plasticizer in the range of 15 parts by weight or less, to prepare a rubber composition, and molding the prepared rubber composition. The method may also include a step of crosslinking the lip seal during or after molding. EXAMPLES

[0030] The present invention will be described in more detail below using examples, but it goes without saying that the scope of the present invention is not limited to the descriptions of the examples. <Example 1> The components shown in Table 1 below were kneaded in a 10-inch roll to prepare a rubber composition. The kneaded product was then subjected to primary crosslinking at 180°C for 6 minutes, and then to oven vulcanization (secondary crosslinking) at 150°C for 1 hour. A bridge was then performed, and a rubber sheet (thickness: 2 mm) and a lip seal were vulcanization molded.

[0031] [Table 1]

[0032] The crosslinked product was subjected to the following measurements. The test pieces used were sheet rubber for the evaluation of physical properties and heat aging resistance, and lip seals for the torque test, sealing property, and surface roughness. The results are shown in Table 1. Physical property evaluation: Elongation at break was measured in accordance with JIS K6251, which corresponds to ISO37. Elongation at break of 150% or more was evaluated as ○, 150% or less but 140% or more was evaluated as △, and less than 140% was evaluated as ×. Torque test: Using water as the sealing fluid, a shaft with a diameter of 15 mm was rotated at a rotation speed of 0 to 5000 rpm to measure the torque. The torque was evaluated as being lower than that of Comparative Example 1, with an O, and the torque was evaluated as being equal to or higher than that of Comparative Example 1, with an X. · Sealing performance: Using an LLC aqueous solution (concentration 30% by volume) as the sealing fluid, a rotation test was carried out under conditions of 6000 rpm, 120°C, 0.15 MPa, and 50 hours, and the leakage rate (ml / hour) of the LLC aqueous solution was measured. Leakage rates of less than 0.2 ml / hour were evaluated as ○, and those of 0.2 ml / hour or more were evaluated as ×. Heat aging resistance: Measure the elongation change rate after aging test in air at 150℃ for 70 hours Surface roughness: The surface roughness Ra of the lip seal sliding surface was measured using a laser microscope.

[0033] <Example 2> In Example 1, the amount of carbon fiber was changed to 5 parts by weight, and a crosslinked product was obtained without blending aluminum silicate, magnesium oxide, and zinc oxide, and the test was performed.

[0034] <Example 3> In Example 1, the amount of carbon fiber was changed to 50 parts by weight, a crosslinked product was obtained, and a test was performed.

[0035] <Example 4> In Example 1, the carbon fibers having a fiber diameter of φ13 μm and an average fiber length of 40 μm were changed to the same amount of carbon fibers having a fiber diameter of φ1 μm and an average fiber length of 1 μm, and a crosslinked product was obtained and tested.

[0036] <Example 5> In Example 1, the carbon fibers having a fiber diameter of φ13 μm and an average fiber length of 40 μm were changed to 30 parts by weight of carbon fibers having a fiber diameter of φ3 μm and an average fiber length of 78 μm, and a crosslinked product was obtained and tested.

[0037] <Example 6> In Example 1, the hydrogenated NBR was changed to the same amount (100 parts by weight) of EPDM (EPT3045 manufactured by Mitsui Chemicals), a crosslinked product was obtained, and a test was performed.

[0038] <Example 7> In Example 1, the hydrogenated NBR was changed to the same amount (100 parts by weight) of fluororubber (Dai-el G901 manufactured by Daikin Industries), a crosslinked product was obtained, and a test was performed.

[0039] <Example 8> In Example 1, the amount of antioxidant was changed to 0.5 parts by weight, a crosslinked product was obtained, and the test was carried out.

[0040] <Example 9> In Example 1, the amount of antioxidant was changed to 5 parts by weight, a crosslinked product was obtained, and the test was carried out.

[0041] <Example 10> In Example 1, the amount of carbon black was changed to 1 part by weight, a crosslinked product was obtained, and a test was performed.

[0042] <Example 11> In Example 1, the amount of carbon black was changed to 150 parts by weight, a crosslinked product was obtained, and a test was performed.

[0043] <Example 12> In Example 1, the amount of antioxidant was changed to 0.1 parts by weight, a crosslinked product was obtained, and the test was carried out.

[0044] <Example 13> In Example 1, the amount of antioxidant was changed to 8 parts by weight, a crosslinked product was obtained, and the test was carried out.

[0045] <Comparative Example 1> In Example 1, the amount of carbon fiber was changed to 1 part by weight, and a crosslinked product was obtained without blending aluminum silicate, magnesium oxide, and zinc oxide, and the test was performed. The results of the comparative examples are shown in Table 2 below.

[0046] <Comparative Example 2> In Example 1, the amount of carbon fiber was changed to 70 parts by weight, a crosslinked product was obtained, and a test was performed.

[0047] <Comparative Example 3> In Example 1, the carbon fibers having a fiber diameter of φ13 μm and an average fiber length of 40 μm were changed to the same amount of carbon fibers having a fiber diameter of φ1 μm and an average fiber length of 60 μm, and a crosslinked product was obtained and tested.

[0048] <Comparative Example 4> In Example 1, no carbon black was added, and a crosslinked product was obtained and tested.

[0049] <Comparative Example 5> In Example 1, the amount of carbon black was changed to 170 parts by weight, a crosslinked product was obtained, and a test was performed.

[0050] [Table 2]

Claims

1. A lip seal made of a rubber-like elastic material is fixed to a housing and slides on a shaft that rotates relative to the housing, The lip seal includes a rubber-like elastomer containing hydrogenated nitrile rubber, EPDM, or fluororubber, a reinforcing filler, and a non-reinforcing filler having an aspect ratio in the range of 1 to 30, the non-reinforcing filler comprises zinc oxide; A lip seal comprising, per 100 parts by weight of the rubber-like elastic body, 1 part by weight or more and 150 parts by weight or less of the reinforcing filler and 5 parts by weight or more and 90 parts by weight or less of the non-reinforcing filler.

2. The lip seal of claim 1 , wherein the non-reinforcing fillers include carbon fiber and silicate.

3. 3. The lip seal according to claim 1, wherein the average diameter of the non-reinforcing filler is 1 μm or more and 100 μm or less.

4. The lip seal according to any one of claims 1 to 3, further comprising an antioxidant in the range of 0.5 parts by weight to 5 parts by weight.

5. The lip seal according to any one of claims 1 to 4, further comprising a plasticizer in an amount of 15 parts by weight or less.

6. The lip seal according to any one of claims 1 to 5, wherein the roughness Ra of the sliding surface of the lip seal is 0.01 to 10 µm.

7. The lip seal according to any one of claims 1 to 6, wherein the interference ratio (A / B) obtained by dividing an interference dimension (A) represented by a difference between an inner diameter dimension at the time of installation and an inner diameter dimension before installation in a sliding portion by an inner diameter dimension (B) before installation is 1% or more and 30% or less.

8. The lip seal according to any one of claims 1 to 7, wherein the radial thickness of the lip seal at its innermost diameter portion is 0.4 to 2 mm.

9. The lip seal according to any one of claims 1 to 8, wherein an angle between an inner diameter surface forming a sliding portion and a tip end surface of the lip seal is 90 to 120° in an axial cross section of the lip seal.

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