KR20130134461A - Composition for automotive hub bearing seal - Google Patents

Abstract

The present invention relates to a rubber composition for a bearing seal containing 100 parts by weight of nitro butadiene rubber, 30-60 parts by weight of carbon black, 1-15 parts by weight of zinc oxide, 3-10 parts by weight of plasticizer, 0.5-3 parts by weight of vulcanizing agent, and 5-10 parts by weight of vulcanizing promotion agent. The rubber composition for the bearing seal provides the bearing seal which has improved oil resistance, cold resistance, and abrasion resistance, vulcanizing time, crosslinking efficiency, and 100% modulus, and has enhanced kinetic characteristics for the continuous strain deformation. [Reference numerals] (AA) Bearing seal

Description

Technical Field [0001] The present invention relates to a rubber composition for automotive hub bearing seals,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition for bearing seals, and more particularly, to a rubber composition for automotive hub bearing seals.

Hub bearing seals for automobiles are mounted on four wheels of the drive shaft, and they are a key functional part that maximizes the driving efficiency through smooth operation by securing the airtightness of the bearing part by blocking muddy water and foreign substances that flow into the wheel bearing when driving. In recent years, the automobile industry has been replaced by automobile fuel sources such as hybrid and fuel cells, with the aim of low carbon eco-friendly and energy saving. However, the driving wheel parts are lightweight for improving fuel economy in the current system, Modularity, and performance enhancement for long-term durability are highlighted as key issues.

In particular, the bearing seal, which is a core component of the drive wheel, is located in the hub bearing of FIG. 1 and has a direct correlation with the durability of the drive wheel and the drive efficiency. When foreign substances are introduced due to lack of durability and defects of bearing seals, driving efficiency may be threatened due to reduction in driving efficiency due to lack of lubricity at the bearing part, and driving failure due to adhesion of bearing part.

In addition, since the oil in contact with the bearing in the vehicle goes up to 100 ° C, the bearing seal must have good heat resistance together with oil resistance. In addition, with the recent prolongation of the quality assurance period of vehicle parts, the required properties of the finished vehicle maker in severe conditions become more complicated, and the standards of heat resistance and durability of the bearing seals become more difficult. To solve such a problem, many techniques such as Korean Patent Laid-Open No. 10-2012-0040845 (Patent Document 1) have been known. Development of a bearing seal shape that requires high performance and high performance, and development of a rubber compounding composition are required.

Korean Patent Publication No. 10-2012-0040845

Disclosure of the Invention The present invention has been made to solve the above-mentioned problems, and has an object to provide a rubber composition for a bearing seal which has improved heat resistance and oil resistance as well as improved cold resistance and wear resistance and improved vulcanization time and crosslinking efficiency, And to produce a rubber composition.

In order to attain the above object, the present invention provides a rubber composition comprising 30 to 60 parts by weight of carbon black, 1 to 15 parts by weight of zinc oxide, 3 to 10 parts by weight of a plasticizer, 0.5 to 3 parts by weight of a vulcanization agent, 3 to 10 parts by weight of a rubber composition for a bearing seal.

Specifically, the present invention relates to a rubber composition comprising 30 to 60 parts by weight of carbon black, 1 to 15 parts by weight of zinc oxide, 3 to 10 parts by weight of a plasticizer, 0.5 to 3 parts by weight of a vulcanizing agent, And 3 to 10 parts by weight of a vulcanization accelerator containing a thiuram-based accelerator.

At this time, the content ratio of the benzothiazole-based promoter and the thiuram-based promoter may be 1: 0.6 to 1.

The nitrobutadiene rubber is characterized in that the content of acrylonitrile is 15 to 50%.

The carbon black may be selected from N110, N330, N332, N472, N550, N630, N642, N650, N762, N770, N907, N908, N990 and N991.

The plasticizer may be one or more selected from diester compounds, polyetherester compounds, naphthenic oils, aromatic oils, paraffin wax, castor oil, linseed oil and pine oil.

The vulcanizing agent may be one or more selected from sulfur (free sulfur), amine disulfide, polymeric polysulfide and sulfur olefin adducts.

The benzothiazole-based accelerator may be at least one selected from the group consisting of 2-mercaptobenzothiazole, dibenzotartil disulfide, sodium-2-mercaptobenzothiazole, zinc salt 2- mercaptobenzothiazole, cyclohexylamine salt 2- mercaptobenzothiazole , N-cyclohexyl-2-benzothiazole sulfenamide, N-tert-butyl-2-benzothiazole sulfenamide and N-oxydiethylene-2-benzothiazole sulfenamide, The thiuram-based accelerator may be selected from one or more selected from tetramethylthiuram monosulfide, tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide and dipentamethylthiuram disulfide.

The composition may further comprise a filler and an antioxidant.

Further, bearing seals including the rubber composition for bearing seals according to the present invention are included in the scope of the present invention.

The constitution of the rubber composition for a bearing seal according to the present invention will be described in detail below.

First, the nitrobutadiene rubber (NBR) has good oil resistance, and functions to prevent leakage of oil and prevent intrusion of foreign dust.

The nitrobutadiene rubber is characterized by an acrylonitrile (ACN) content of 15 to 50, more specifically 15.9 to 46.2%. Nitrobutane diene rubbers according to the present invention can be used as long as they satisfy the acrylonitrile content. For example, representative acrylonitrile rubbers commercially available from The Goodyear Tire & Rubber Company include Chemigum TM N206 (Mooney viscosity 55-70 and ACN 46.2%), Chemigom TM N300 (Mooney viscosity 50-63 and ACN 40%), Chemigom TM N318 (Mooney viscosity 68-82 and ACN 40%), Chemigom TM N328 Viscosity of 65-80 and ACN 41.5%), Chemigom TM N386B (Mooney viscosity 55-65 and ACN 40.5%), Chemigom TM N608 (Mooney viscosity 63-75 and ACN 33.4%), Chemigom TM N612B 30, and ACN 33.4%), Chemigom TM N615B (Mooney viscosity 47-60 and ACN 33.4%), Chemigom TM N624B (Mooney viscosity 38-50 and ACN 32.9%), Chemigom TM N628B (Mooney viscosity 68-85 (Mooney viscosity 45-55 and ACN 33.4%), Chemigom TM N687B (Mooney viscosity 65-75 and ACN 33.4%), Chemigom TM N683B (Mooney viscosity 25-35 and ACN 33.4%), Chemigom TM N685B 33.4%), ke (Mooney viscosity 45-55 and ACN 27.7%), Chemigom TM TM N715 (Mooney viscosity 45-63 and ACN 29.3%), Chemigom TM N785B (Mooney viscosity 45-55 and ACN 27.7% Such as Chemigom TM (TM) N926 (Mooney viscosity 55-70 and ACN 15.9%), and Chemigom TM N984B (Mooney viscosity 35-45 and ACN 20.0%), A product sold by Kumho Petrochemical Co., Ltd. may be used.

When the content of acrylonitrile is 33% or more and 50% or less, heat resistance and abrasion resistance are excellent, but cold resistance and workability are deteriorated. If it exceeds 50%, the workability becomes extremely poor.

If the content of acrylonitrile is 15% or more and less than 33%, it can be used because it exhibits excellent cold resistance. If it is less than 15%, the adhesion with the iron ring deteriorates and the mixing workability also deteriorates. It is therefore desirable to select an appropriate acrylonitrile content for the required properties within the range of acrylonitrile

Next, carbon black is described in detail.

Carbon black is used to increase the abrasion and stiffness of rubber composite materials. It is appropriate to select grades with low particle size and structure, but if it is too small, it may cause rubber heating due to continuous deformation stress caused by rotational motion This is taken into consideration.

Typically used carbon blacks include N110, N330, N332, N472, N550, N630, N642, N650, N762, N770, N907, N908, N990 and N991. For example, the N330 grade, which has a small particle size and an improved structure, has high abrasion resistance and stiffness increase effect, but it can generate rubber heat due to the continuous deformation stress generated by the rotational motion. Therefore, The composition should be designed.

The content of the carbon black may be 30 to 60 parts by weight, more specifically 30 to 55 parts by weight, based on 100 parts by weight of the nitrobutadiene rubber. When the content is less than 30 parts by weight, the hardness of the vulcanized product is low, The hardness is increased and a problem of workability occurs due to heat generation during mixing. Also, the flowability of the rubber composition during molding operation is lowered, and the surface of the product is not smooth.

The zinc oxide (ZnO) is a vulcanization auxiliary added to activate the crosslinking reaction during the vulcanization reaction, which is added in order to increase the crosslinking speed while preventing the side chain reaction and increase the crosslinking density. The content of zinc oxide is 1 to 15 parts by weight based on 100 parts by weight of the nitrobutadiene rubber. When the amount is less than 1 part by weight, the activation of the crosslinking reaction is insignificant. When the amount is more than 15 parts by weight, the mechanical properties of the vulcanized product may be deteriorated due to the residual zinc oxide.

As the vulcanization auxiliary agent, in addition to the zinc oxide, stearic acid and silane coupling additives may be included.

The plasticizer is added to soften the polymer and improve the flowability and cold resistance. It is appropriate to use 3 to 10 parts by weight based on 100 parts by weight of the nitrobutadiene rubber. If the amount is less than 3 parts by weight, the effect on the flowability and cold resistance of the rubber composition is insignificant, and if it exceeds 10 parts by weight, the plasticizer may be eluted and volatilized from the vulcanized product. The plasticizer may be selected from diester compounds, polyetherester compounds, naphthenic oils, aromatic oils, paraffin waxes, castor oils, flaxseed oils and pine oils, and most preferably polyetherester compound plasticizers Is good. In the present invention, RS-700 of Adeka Japan was used as an example, but the present invention is not limited thereto.

The vulcanizing agent functions to chemically bond the molecular chains of the nitrobutadiene rubber when the rubber composition is heated to an appropriate temperature. The vulcanizing agent according to the present invention may comprise sulfur vulcanizing agents such as elemental sulfur (free sulfur), amine disulfides, polymeric polysulfides and sulfur olefin adducts. The amount of the vulcanizing agent is preferably from 0.5 to 3 parts by weight based on 100 parts by weight of the nitrobutadiene rubber although it depends on the type of rubber and the specific type of vulcanizing agent.

The vulcanization accelerator preferably has a function of lowering the vulcanization reaction temperature and shortening the vulcanization time as well as improving the physical properties of the vulcanized product and preferably 5 to 10 parts by weight based on 100 parts by weight of the nitrobutadiene rubber.

When the content of the vulcanization accelerator is less than 5 parts by weight, the crosslinking efficiency deteriorates and the dynamic characteristics of the vulcanized product deteriorate. When the content of the vulcanization accelerator exceeds 10 parts by weight, the hardness of the vulcanized product due to the formation of excessive cross- In addition, when unreacted vulcanization accelerator remains and is exposed to an additional reaction environment, the vulcanization reaction proceeds to cause a change in physical properties of the vulcanized product.

The rubber composition for bearing seals according to the present invention proceeds under an EV system, i.e., a system having a high sulfur-accelerator content. The effective flow system has excellent storage stability of the rubber composition, secures fast vulcanization time, and prevents the bluing phenomenon in which the blend agent penetrates the rubber surface and the flower pattern is drawn. In addition, there is no discoloration of metal products due to the residual sulfur when in contact with metal, and it exhibits excellent dynamic characteristics of rubber composite material due to the shape of yellow cross. More specifically, the content ratio of the sulfur: promoter, which is a vulcanizing agent, can be used within the range of 1: 1.5 to 20.

At this time, it is better to use a benzothiazole-based accelerator and a thiuram-based accelerator as a vulcanization accelerator.

The present invention has been accomplished by discovering that by adding a benzothiazole-based promoter and a thiuram-based promoter, it is possible to improve 100% modulus and to induce CSC bonding to improve the dynamic characteristics of the nitrobutadiene rubber against continuous stress strain .

It is more preferable to add a thiuram-based accelerator to the benzothiazole accelerator in a ratio of 1: 0.6 to 1. If the thiuram promoter is less than 0.6, there is a problem of vulcanization efficiency and lowering of the reaction rate. If it exceeds 1, a scorch problem may occur during product molding due to a rapid vulcanization reaction, and the bonding energy is weaker C-Sx-C bonds and C-Sx bonds, leading to problems of dynamic properties and mechanical properties of vulcanized products.

The rubber composition for bearing seals according to the present invention ensures an efficient vulcanization time and efficiency by applying an effective flow system using a vulcanization accelerator at an appropriate ratio.

The present invention uses a benzothiazole-based accelerator and a thiuram-based accelerator in the above-mentioned effective flow-rate system, and more preferably, by adding a ratio of a benzothiazole-based accelerator: thiuram-based accelerator of 1: 0.6 to 1, And the CSC bond can be induced to improve the dynamic characteristics against the continuous stress strain of the nitrobutadiene rubber, thereby completing the present invention. By doing so, the viscoelastic properties of the nitrobutadiene rubber with respect to the continuous deformation stress of the rubber composition for a bearing seal according to the present invention are maintained.

Thiazole is one of the most widely used accelerators. It includes 2-mercapto benzo thiazole (MBT), dibenzothazyl disulfide (MBTS), sodium-2-mercapto Sodium-2-mercaptobenzo thiazole (Na MBT), zinc salt 2-mercaptobenzothiazole (Zn-Salt MBT, Zn MBT), cyclohexylamine salt 2-mercaptobenzothiazole 2-mercaptobenzo thiazole, CMBT), N-cyclohexyl-2-benzothiazoyl sulfenamide (CBS), N-tert-butyl-2-benzothiazolesulfenamide -butyl-2-benzothiazoyl sulfenamide (BBS), and N-oxydiethylene-2-benzothiazole sulfenamide (OBS).

The thiuram-based accelerator is an ultrahigh-strength promoter, and its kind includes tetramethylthiuram monosulfide (TMTM), tetramethylthiuram disulfide (TMTD), tetraethylthiuram disulfide (TETD), tetraethylthiuram disulfide Tetrabutylthiuram disulfide (TBTD), dipentamethylene thiuram tetra sulfide (DPTT), and the like.

The two accelerators have superior 100% modulus characteristics when used alone, unlike the case where they are used alone. Thus, the present invention has been completed. Further, when the content ratio of the benzothiazole-based promoter: thiuram-based promoter was set to 1: 0.6 to 1, it was found that the best effect was exhibited.

The rubber composition for a bearing seal according to the present invention may further contain an inorganic filler and an antioxidant as necessary.

The inorganic filler is used for improving the heat resistance and lubricating the rubber compound. It is used for improving the adhesion between the nitrobutadiene rubber and the iron ring, and improving the workability and reinforcement. It may be any one selected from the group consisting of graphite, molybdenum disulfide (MoS ₂ ), titanium dioxide (TiO ₂ ), silicon dioxide (SiO ₂ ), talc, wollastinite and combinations thereof And 10 to 60 parts by weight based on 100 parts by weight of nitrobutadiene rubber. Among them, talc is an inorganic material having a flaky particle shape and can be added to the rubber composition according to the present invention to improve heat resistance and abrasion resistance and thus can be usefully used.

The anti-aging agent is also referred to as an antioxidant, and is added to prevent the oxidation of the rubber component, and is not limited to any kind of antioxidant used for preparing a rubber component. For example, a quinoline antioxidant may be used in the present invention. For example, TMQ (polymerized 2,2,4-trimethyl-1,2-dihydroquinoline) was used in the present invention. This is useful for improving the durability of the bearing seals according to the present invention. However, it is not limited thereto. The antioxidant preferably has 1 to 5 parts by weight based on 100 parts by weight of the polymer.

The bearing seals including the rubber composition for bearing seals according to the present invention thus fabricated are included in the scope of the present invention. Further, the rubber composition according to the present invention can be applied not only to automotive hub bearing seals but also to various fields requiring the above properties.

The rubber composition for a bearing seal according to the present invention provides a bearing seal which improves oil resistance, cold resistance and abrasion resistance, improves vulcanization time and crosslinking efficiency, improves 100% modulus and improves dynamic characteristics against continuous stress deformation. Further, the rubber composition for a bearing seal according to the present invention can be applied not only to an automotive hub bearing seal, but also to various seal fields requiring the above properties.

Figure 1 shows a photograph showing the position of the hub bearing and the bearing seal contained therein.

Hereinafter, the present invention will be described in detail with reference to preferred embodiments of a rubber composition for a bearing seal according to the present invention. However, the present invention is not limited by the following examples.

≪ Example 1 >

Were prepared in a conventional manner to prepare rubber compositions for bearing seals in the amounts listed in Table 2 below. In order to measure the physical properties of the prepared composition, square specimens having a length of 150 mm, a width of 150 mm and a thickness of 2 mm were compression molded and then cooled to prepare specimens.

The prepared specimens were measured by the following measurement methods and evaluated for their physical properties.

1. Rheometer: The vulcanization rate and the degree of crosslinking were evaluated by rheometer in accordance with ASTM regulations.

2. Hardness: The hardness was evaluated in accordance with Clause 7 of KS M6518.

3. Tensile strength: It was evaluated according to 5 of KS M6518, KS standard.

4. 100% modulus: The modulus was measured with a tensile tester manufactured by Instron, by cutting the specimen into a dumbbell shape having a length of 100 mm, an outer width of 25 mm, and an inner width of 5 mm. The 100% modulus represents the tensile strength of the test specimen when the test specimen is elongated at 100%.

5. Elongation (elongation): It was evaluated according to 5 of KS M6518, KS standard.

6. Aging test: After aging at a temperature of 100 캜 for 70 hours, the hardness, the tensile and the rate of elongation were measured.

7. Oil resistance test: The oil resistance was evaluated at 100 ° C for 70 hours, and the oil resistance was tested using ASTM No. 1 and No. 3 oils.

8. Grease test: The test was carried out at a temperature of 100 ° C for 70 hours and tested using a lithium grease.

9. Cold resistance (TR-10): Low temperature recovery test was carried out according to KS M 6724, KS standard.

10. Compression Permanent Ratio (C / S) Test: The test was conducted at a temperature of 100 ° C for 70 hours and evaluated according to Clause 11 of KS M6518.

11. Taber Type Wear Test (weight loss, g): Wear amount was evaluated according to KS M ISO 5470-1, KS standard, and wear wheel was H22.

12. Product Durability Performance Evaluation (Dust rotation durability test): The evaluation was made as follows.

  - Test Evaluation Equipment: Performance evaluation of internal pressure and RPM by using environment durability tester

  - Test method: Fill the case with muddy water and drive in chamber to test

  - Test conditions: Table 1 shows.

[Table 1]

[Table 2]

≪ Examples 2 to 4 >

Were prepared and evaluated in the same manner as in Example 1 with reference to the contents in Table 2 above.

≪ Comparative Example 1 &

Were prepared and evaluated in the same manner as in Example 1 with reference to the contents in Table 2 above.

The rubber composition for a bearing seal according to an embodiment of the present invention has a Shore A of 70 or more and a high tensile strength characteristic of 150 kgf / cm 2 or more and is added together with a benzothiazole-based accelerator and a thiuram-based accelerator, which are features of the present invention It is confirmed that the rubber elastic modulus of elasticity against the continuous deformation stress is maintained by having 100% modulus of 30 kgf / ㎠ or more. In addition, the rubber composition for a bearing seal according to the present invention shows a cold resistance which can withstand even at a subzero temperature of -25 ° C. Also, the rubber composition for a bearing seal according to the present invention exhibits durability over 180 hours and exhibits good leakage characteristics. Among them, Example 2 exhibits the most excellent durability over 240 hours, and it can be confirmed that the characteristics required in the bearing seals according to the present invention are best satisfied. On the other hand, Comparative Example 1 using only a benzothiazole-based accelerator shows that 100% modulus and durability do not satisfy the properties required in the present invention.

Claims (10)

For bearing seals containing 30 to 60 parts by weight of carbon black, 1 to 15 parts by weight of zinc oxide, 3 to 10 parts by weight of plasticizer, 0.5 to 3 parts by weight of vulcanizing agent and 5 to 10 parts by weight of vulcanization accelerator, based on 100 parts by weight of nitro butadiene rubber. Rubber composition. The method of claim 1,
Wherein the vulcanization accelerator is a benzothiazole-based accelerator and a thiuram-based accelerator. 3. The method of claim 2,
Wherein the content ratio of the benzothiazole-based promoter and the thiuram-based promoter is 1: 0.6 to 1. The method of claim 1,
The nitro butadiene rubber is a rubber composition for a bearing seal, characterized in that the content of acrylonitrile is 15 to 50%. The method of claim 1,
Wherein the carbon black is one or more selected from N110, N330, N332, N472, N550, N630, N642, N650, N762, N770, N907, N908, N990 and N991. The method of claim 1,
Wherein the plasticizer is at least one selected from diester compounds, polyetherester compounds, naphthene oils, aromatic oils, paraffin wax, castor oil, linseed oil and pine oil. The method of claim 1,
Wherein the vulcanizing agent is one or more selected from sulfur (free sulfur), amine disulfide, polymeric polysulfide and sulfur olefin adduct. 3. The method of claim 2,
The benzothiazole-based accelerator may be at least one selected from the group consisting of 2-mercaptobenzothiazole, dibenzotartil disulfide, sodium-2-mercaptobenzothiazole, zinc salt 2- mercaptobenzothiazole, cyclohexylamine salt 2- mercaptobenzothiazole , N-cyclohexyl-2-benzothiazole sulfenamide, N-tert-butyl-2-benzothiazole sulfenamide and N-oxydiethylene-2-benzothiazole sulfenamide, A thiuram-based accelerator is one or more selected from tetramethylthiuram monosulfide, tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide and dipentamethylthiuram disulfide. The method of claim 1,
Wherein the composition further comprises an inorganic filler and an antioxidant. A bearing seal comprising the rubber composition for bearing seals of claim 1.

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