Fluororubber composition

Abstract

A fluororubber composition in which 10 parts by weight to 60 parts by weight of wollastonite having an aspect ratio of 7 to 15 and 2 parts by weight to 20 parts by weight of diatomaceous earth are blended per 100 parts by weight of a fluororubber having a hardness Hs of 75 to 85. The fluororubber composition is suitable for use as a molding material for an oil seal for forward / reverse rotation, said oil seal being capable of satisfactorily and continuously sealing a fluid even under high-temperature conditions of use ambient temperatures such as 100-200 DEG C, and even under high-speed rotation of 8000-15000 rpm during forward / reverse rotation operation.

Description

Technical Field

[0001] The present invention relates to a fluororubber composition, and more particularly to a fluororubber composition suitable for use as a vulcanization molding material for an oil seal for forward and reverse bidirectional rotation. Background Art

[0002] Oil seals are widely used as important mechanical parts in the fields of automobiles, industrial machinery, etc. Among them, bidirectional rotating oil seals (whose purpose is to continue to seal fluid even during the forward and reverse bidirectional rotation of various components) are used in a wide range of fields as components such as pumps, vehicle differential gears, agricultural machinery, and railway vehicles.

[0003] As cars become electric, the prime mover is shifting from the engine to the electric motor. When the electric motor is used as the prime mover, the rotation of the shaft changes in the direction of the car's travel. Conventional engine seals have a fixed rotation direction, so when they are rotated in the opposite direction, seal oil may leak.

[0004] In order to avoid the above-mentioned undesirable situation, for example, the following oil seal is proposed in Patent Document 1, in which screw parts are alternately arranged in groups on the inclined surface on the opposite side of the sealing object of the oil seal lip which is bonded to the first annular part embedded in a component and slides in close contact with other components, and the screw parts have a specific tilt angle relative to the rotation direction of the above-mentioned other components when rotating in the forward direction and in the reverse direction, wherein auxiliary screw parts are arranged in pairs with each of the above-mentioned screw parts, and the auxiliary screw parts have a specific tilt angle relative to the rotation direction in which each of the above-mentioned screw parts is arranged and the opposite rotation direction. However, only by such a structure in which the auxiliary screws and the screw parts are arranged in pairs, in the case of repeated forward and reverse rotation, the state of the sealing surface will be somewhat undesirable due to wear, and there is a possibility of sealing leakage during reverse rotation.

[0005] In addition, as a research from the material aspect, a rubber material containing wollastonite with an aspect ratio of 8 or more has been proposed (Patent Document 2). However, since the electric motor of a hybrid vehicle or electric vehicle is the prime mover, it has a higher circumferential speed. As a result, the lubrication state between the rotating shaft and the oil seal becomes strict, and leakage is easily generated in the reverse motion after the forward motion. In addition, in an environment where noise is generated during driving, such as in the case of a railway vehicle, the abnormal noise caused by the oil seal that is not noticeable becomes noticeable. Here, the main reason for the abnormal noise of the oil seal is that the lubrication state deteriorates with high rotation.

[0006] In addition, as a fluororubber composition having excellent durability such as heat resistance and wear resistance and fully satisfying lubricating oil resistance and sealing properties, a fluororubber composition has been proposed, wherein 3 to 60 parts by weight of at least one of diatomaceous earth, wollastonite, talc, graphite, mica and carbon fiber having an average particle size of 6 μm to 35 μm are contained per 100 parts by weight of a fluororubber composed of a 1,1-difluoroethylene-hexafluoropropylene-tetrafluoroethylene-ethylene-perfluoro(alkyl vinyl ether) 5-member copolymer (Patent Document 3). However, in the recent forward and reverse bidirectional rotation under more severe environments, there is a situation where the sealing is insufficient.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Publication No. 2006-125454

[0010] Patent Document 2: Japanese Patent No. 5294551

[0011] Patent Document 3: Japanese Patent Application Publication No. 2016-14092 Summary of the invention

[0012] Technical problem to be solved by the invention

[0013] An object of the present invention is to provide a fluororubber composition suitable for use as a vulcanization molding material for an oil seal for forward and reverse bidirectional rotation, wherein the oil seal can continue to seal a fluid well during forward and reverse bidirectional rotation even under high temperature conditions of an operating environment temperature of, for example, 100°C to 200°C and even under high speed rotation of 8,000 rpm to 15,000 rpm.

[0014] Solutions to Solve Problems

[0015] The above-mentioned object of the present invention is achieved by a fluororubber composition, in which 10 to 60 parts by weight of wollastonite with an aspect ratio of 7 to 15 and 2 to 20 parts by weight of diatomaceous earth are mixed for every 100 parts by weight of fluororubber with a hardness Hs of 75 to 85.

[0016] Effects of the Invention

[0017] The fluororubber composition of the present invention, which is suitable for forming the sliding surface of the oil seal for forward and reverse bidirectional rotation, is formulated with wollastonite having an aspect ratio of 7 to 15 and 2 to 20 parts by weight of diatomaceous earth, so that its vulcanized molded product has resistance to deformation due to the shape effect. That is, by suppressing the deformation of the oil seal sliding surface in the sliding direction, it is possible to significantly seal and retain the fluid in the forward and reverse bidirectional rotation direction compared to materials that are not formulated with wollastonite and diatomaceous earth or materials formulated with fillers of other shapes. As a result, in the forward and reverse bidirectional rotation action, even under high temperature conditions such as 100°C to 200°C in the operating environment temperature and at high speeds of 8,000rpm to 15,000rpm, it is possible to achieve an excellent effect of continuously sealing the fluid well. DETAILED DESCRIPTION

[0018] As fluororubber, fluororubber having a hardness Hs (JIS K6253:1997 standard corresponding to ISO 7619-1) of 75 to 85 is used. In fact, commercially available products such as DuPont·Dow Elastomers Japan products VitonA-500, DAIEL-G801, DAIEL-GBR-6002, Viton B-600, Viton GBL-600S, Viton GLT-600S, etc. can be used directly. Fluororubber can be used for a long time even at a high temperature of 100°C to 200°C in the use environment. Here, when fluororubber having a hardness Hs outside this range is used, seal leakage will occur when used as a forward and reverse bidirectional rotating seal, so it is not ideal.

[0019] As wollastonite (CaO·SiO2), wollastonite with an aspect ratio of 7 to 15, preferably 8 to 13, can be used directly. In fact, commercial products such as NYGLOS4W, NYGLOS8, NYGLOS12 of IMERYS, Tremin939-600 of Quarzwerke, WFA60, WFA70, WFB5 of Talc of Japan, etc. can be used. Wollastonite surface-treated with a silane coupling agent can also be used. When wollastonite with an aspect ratio smaller than this range is used, the desired sealing property cannot be ensured. On the other hand, when wollastonite with an aspect ratio larger than this range is used, the molding processability is deteriorated.

[0020] The above-mentioned wollastonite is used in a ratio of 10 to 60 parts by weight, preferably 20 to 40 parts by weight, per 100 parts by weight of fluororubber. When used in a ratio less than this range, the desired effect such as sealing during high-speed rotation cannot be obtained, while when used in a ratio greater than this range, the molding processability is significantly deteriorated.

[0021] As diatomaceous earth, diatomaceous earth having an average particle size (measured by laser scattering method) of 4 to 16 μm is preferably used. In practice, commercially available products such as Radiolite F manufactured by Shaohe Chemical Industry Co., Ltd. and Silica #6B manufactured by Chuo Silika can be used directly.

[0022] The diatomaceous earth is used in an amount of 2 to 20 parts by weight, preferably 5 to 15 parts by weight, per 100 parts by weight of the fluororubber. When the amount is less than the above range, humming noise may occur and the desired effect may not be obtained. On the other hand, when the amount is greater than the above range, the molding processability may be significantly deteriorated.

[0023] It should be noted that a fluororubber composition is proposed in Patent Document 3, wherein every 100 parts by weight of the fluororubber composed of a specific 5-membered copolymer contains 3 to 60 parts by weight of at least one of diatomaceous earth, wollastonite, talc, graphite, mica and carbon fiber with an average particle size of 6 μm to 35 μm, but in its embodiments, only compositions using diatomaceous earth, wollastonite, talc, graphite and carbon fiber separately are disclosed, and there is no record of the effect of using wollastonite and diatomaceous earth in a specific amount, and no teaching or suggestion is given. For the case disclosed in the document where talc or graphite is used alone without using wollastonite, as shown in Comparative Examples 4 to 5 described later, it is difficult to ensure the oil seal performance, for example, in the case of a forward and reverse rotation test.

[0024] To the fluororubber composition composed of the above essential ingredients, various compounding agents required for vulcanization, physical properties and functions may be added, such as polyol-based, sulfur-based, and organic peroxide-based vulcanizing agents, vulcanizing aids, reinforcing agents such as carbon black, fillers, divalent metal oxides, hydroxides or acid acceptors such as hydrotalcite, and other necessary compounding agents corresponding to the type of fluororubber used, to form a fluororubber composition.

[0025] The fluororubber composition is prepared by using any kneading means such as an open roll or a kneading machine, and is vulcanized and molded into a sliding surface of an oil seal for forward and reverse bidirectional rotation by hot pressing at 160°C to 200°C for 3 minutes to 30 minutes and secondary vulcanization at 150°C to 250°C for 0.5 hours to 24 hours as needed.

[0026] Example

[0027] Hereinafter, the present invention will be specifically described by way of examples. It should be noted that the present invention including its effects is not limited to these examples.

[0028] Example 1

[0029]

[0030] The above ingredients were mixed using a closed mixer, and subjected to primary vulcanization at 170°C for 15 minutes and secondary vulcanization at 200°C for 22 hours, and vulcanized into a sheet with a thickness of 6 mm, and the normal physical properties (hardness Hs) were measured. In addition, under the same vulcanization conditions, an oil seal with an inner diameter of 65 mm, an outer diameter of 80 mm, and a width of 8 mm was vulcanized and used for oil seal sealing test and whistling test.

[0031] Normal physical properties (hardness Hs): In accordance with JIS K6253:1997 corresponding to ISO 7619-1, the instantaneous hardness was measured using a type A durometer.

[0032] Oil seal test: Use oil seal lubricant (JX Energy Products AW-2) to perform the following a) or b) operation. Immediately after the operation, visually check for oil leakage.

[0033] a) Run the machine forward at 90°C and 4,500 rpm (15 m / s) for 24 hours, stop it for 2 minutes, and then run it reversely at 2,700 rpm (9 m / s) for 1 hour; or

[0034] b) Perform forward operation for 24 hours at a temperature of 140°C and a rotation speed of 15,000 rpm (51 m / sec), stop for 2 minutes, and then perform reverse operation at 6,000 rpm (20 m / sec) for 1 hour;

[0035] The evaluation of no oil leakage was ○, and the evaluation of oil leakage was ×

[0036] Noise test: Use oil seal lubricant (AW-2) and run forward at 120°C and 15,000 rpm. Reduce the amount of oil to 20 mm above the lower end of the rotating shaft and check whether there is any abnormal noise when the lubrication condition deteriorates.

[0037] The evaluation of no abnormal sound was ○, and the evaluation of abnormal sound was ×

[0038] Example 2

[0039] In Example 1, the same amount (30 parts by weight) of IMERYS product NYGLOS 8 (aspect ratio: 13) was used as wollastonite.

[0040] Example 3

[0041] In Example 1, the amount of wollastonite was changed to 45 parts by weight.

[0042] Example 4

[0043] In Example 1, the amount of wollastonite was changed to 15 parts by weight.

[0044] Example 5

[0045] In Example 1, the amount of diatomaceous earth was changed to 6 parts by weight.

[0046] Example 6

[0047] In Example 1, the amount of diatomaceous earth was changed to 2 parts by weight.

[0048] Example 7

[0049] In Example 1, the amount of diatomaceous earth was changed to 14 parts by weight.

[0050] Comparative Example 1

[0051] In Example 1, the amount of wollastonite was changed to 10 parts by weight, and the amount of diatomaceous earth was changed to 30 parts by weight.

[0052] Comparative Example 2

[0053] In Example 1, the amount of wollastonite was changed to 5 parts by weight, and the amount of diatomaceous earth was changed to 20 parts by weight.

[0054] Comparative Example 3

[0055] In Example 1, diatomaceous earth was not used.

[0056] Comparative Example 4

[0057] In Example 2, diatomaceous earth was not used.

[0058] Comparative Example 5

[0059] In Comparative Example 3, the same amount (30 parts by weight) of IMERYS product NYAD 400 (aspect ratio of 5) was used as wollastonite.

[0060] Comparative Example 6

[0061] In Comparative Example 3, 25 parts by weight of talc (Talc H manufactured by Asada Milling Co., Ltd.) was used instead of wollastonite.

[0062] Comparative Example 7

[0063] In Comparative Example 3, 20 parts by weight of graphite (Nichiden Carbon product C-1) was used instead of wollastonite.

[0064] Comparative Example 8

[0065] In Comparative Example 3, the amount of wollastonite was changed to 15 parts by weight.

[0066] Comparative Example 9

[0067] In Comparative Example 3, the amount of wollastonite was changed to 70 parts by weight, but kneading was not possible.

[0068] The results obtained in the above examples and comparative examples 1 to 8 are shown in the following table. In the material evaluation, materials satisfying the performance required as a forward and reverse bidirectional rotation oil seal material were evaluated as ○, and the others were evaluated as ×.

[0069] surface

[0070]

[0071] Based on the above results, the summary is as follows.

[0072] (1) Even when wollastonite and diatomaceous earth were used in combination, when they were used in amounts outside the prescribed amount range, leakage was confirmed in the oil seal sealing test (forward and reverse rotation test) and a humming sound was also generated (Comparative Examples 1 and 2).

[0073] (2) In the case of a material using wollastonite having an aspect ratio of less than 7, leakage was confirmed in the oil seal sealing test (forward and reverse rotation test) (Comparative Example 5).

[0074] (3) For the material to which 2 parts by weight or more of diatomaceous earth was not added, a buzzing sound was produced at a position 20 mm above the lower end of the shaft (Comparative Examples 3 to 8).

[0075] Industrial Applicability

[0076] The fluororubber composition of the present invention is suitable as a vulcanization molding material for bidirectionally rotating oil seals because the oil seal obtained by vulcanization molding can continue to seal the fluid well even in forward and reverse bidirectional rotation.

Claims

1. A fluororubber composition, wherein: For every 100 parts by weight of fluororubber having a hardness Hs of 75 to 85, 10 to 60 parts by weight of wollastonite having an aspect ratio of 7 to 15 and 2 to 20 parts by weight of diatomaceous earth are mixed.

2. A sealing material formed by vulcanization molding of the fluororubber composition according to claim 1. The sealing material according to claim 2 , which is used as an oil seal.

4. The sealing material according to claim 3, which is used as an oil seal for forward and reverse bidirectional rotation.

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