KR100681937B1 - Rubber composition of high pressure oil seal for power steering system - Google Patents

Abstract

The present invention relates to a high pressure oil seal rubber composition used in a power steering system, more specifically 100 parts by weight of hydrogenated nitrile rubber (H-NBR) containing 20 to 30 mol% of acrylonitrile, di By including 2 to 10 parts by weight of octyl adipate and 6 to 8 parts by weight of dicumyl peroxide, the oil seals have improved cold resistance, heat resistance, and compression set. The present invention relates to a high pressure oil seal rubber composition used in a power steering device, which is improved to prevent oil leakage due to cracking and to improve sealing functionality.

Power Steering System, High Pressure Oil Seal, Hydrogenated Nitrile Rubber, Compressive Permanent Shrinkage

Description

Rubber composition of high pressure oil seal for power steering system

The present invention relates to a high pressure oil seal rubber composition used in a power steering system, more specifically 100 parts by weight of hydrogenated nitrile rubber (H-NBR) containing 20 to 30 mol% of acrylonitrile, di By including 2 to 10 parts by weight of octyl adipate and 6 to 8 parts by weight of dicumyl peroxide, the oil seals have improved cold resistance, heat resistance, and compression set. The present invention relates to a high pressure oil seal rubber composition used in a power steering device, which is improved to prevent oil leakage due to cracking and to improve sealing functionality.

The Power Steering Oil Seal is mounted on the steering system which changes the rotational movement to linear movement by hydraulic power and transmits it to the tire when the driver rotates the steering wheel. do. In more detail, the steering gear which controls the driver's steering force according to the driving conditions and transfers the driving direction by changing the movement direction, that is, the power steering gear is installed in the power steering gear. Sealing function that prevents the cylinder tube from going out of the power steering gear.

The power steering oil seal is divided into low pressure and high pressure according to the strength of hydraulic power. High pressure oil seals should be selected to withstand high pressures above 120 bar compared to low pressure oil seals, and should have excellent oil resistance, heat resistance, cold resistance and abrasion resistance. In addition, the high pressure oil seal should be excellent in the sealing function for mineral oil, such as the power steering hydraulic fluid.

Hydrogenated nitrile rubber (H-NBR) has been used as a rubber for high pressure oil seals. Hydrogenated nitrile rubber (H-NBR) is prepared by subjecting acrylonitrile-butadiene rubber (NBR) to hydrogenation. H-NBR has been in the spotlight as a high pressure oil seal rubber due to its excellent oil resistance, heat resistance, cold resistance and abrasion resistance.

However, the conventional rubber has an inadequate acrylonitrile (ACN) content and the vulcanization characteristics of the oil seal is inadequate. The polymer chain has a high content of acrylonitrile, which has a polar group to prevent swelling, and thus has resistance to mineral oils such as hydraulic oil of the power steering system, resulting in shrinkage of the oil seal, and long-term exposure at low temperatures (below -30 ° C). Due to the crystallization of the polymer by the crystallization (Crystallization) phenomenon, the stiffness is increased and the elasticity is lost, hardening and cracking (CRACK) occurs at low temperatures, and thus oil leakage (LEAK) may occur.

 Accordingly, the present inventors have studied and tried to solve such a conventional problem, and as a result, the present invention includes hydrogenated nitrile rubber (H-NBR) containing 20 to 30 mol% of acrylonitrile as a polymer, and dioctyl adipate as a plasticizer. It is found that the rubber composition comprising dicumyl peroxide as an organic crosslinking agent improves the cold resistance, heat resistance and compression set of the oil seal, thereby preventing shrinkage and oil leakage and improving sealing functionality. The invention has been completed.

Accordingly, the present invention provides a high pressure oil seal rubber composition for use in a power steering apparatus including hydrogenated nitrile rubber (H-NBR) containing 20 to 30 mol% of acrylonitrile, dioctyl adipate and dicumyl peroxide. There is this.

The present invention provides a high pressure oil seal rubber for a power steering apparatus including 100 parts by weight of hydrogenated nitrile rubber containing 20 to 30 mol% of acrylonitrile, 2 to 10 parts by weight of dioctyl adipate, and 6 to 8 parts by weight of dicumyl peroxide. The composition is characterized by that.

The present invention will be described in more detail as follows.

The present invention includes 100 parts by weight of hydrogenated nitrile rubber (H-NBR) containing 20 to 30 mol% of acrylonitrile, 2 to 10 parts by weight of dioctyl adipate, and 6 to 8 parts by weight of dicumyl peroxide, thereby providing cold resistance of the oil seal. The power steering system is improved to prevent oil leakage due to hardening and cracking of rubber and hardening and cracking of the rubber at high and low temperatures by improving heat resistance and compressive permanent shrinkage. It relates to a high pressure oil seal rubber composition used in the steering system).

As the rubber of the present invention, hydrogenated nitrile rubber (H-NBR) containing 20 to 30 mol% of acrylonitrile is used. It has excellent oil resistance, heat resistance, cold resistance and abrasion resistance than the conventional nitrile-based hydrogenated nitrile rubber, and is suitable for use in high pressure oil seals.

The filler of the present invention can be used without limitation in the manufacture of the high pressure oil seal used in the power steering device, but it is best to use carbon black and silica (SiO ₂ ) simultaneously.

The carbon black is not limited to a specific carbon black, and carbon black FEF having a particle diameter of 40 to 48 nm is particularly preferable. By adding carbon black, physical property improvement effects, such as rubber strength, are produced.

It is preferable that carbon black contains 40-50 weight part with respect to 100 weight part of hydrogenated nitrile rubber containing 20-30 mol% of acrylonitrile. When the carbon black content exceeds 50 parts by weight, the rubber is improved, but cracks are more likely to occur due to external impact and elasticity may be reduced. When the carbon black content is less than 40 parts by weight, the strength of the rubber is inferior.

Another filler for use with carbon black includes silica (SiO ₂ ).

Silica (SiO ₂ ) is called white carbon and has similar reinforcement as carbon black. In the present invention, when used together with carbon black FEF, it is preferable to use silica having a particle diameter of 6 to 7 μm.

The silica is preferably contained 5 to 10 parts by weight based on 100 parts by weight of the hydrogenated nitrile rubber containing 20 to 30 mol% of acrylonitrile. When the content of silica is more than 10 parts by weight, the physical properties of the basic rubber such as tensile strength and elongation may be lowered. When the content of silica is less than 5 parts by weight, the reinforcement and abrasion improvement effects do not appear.

The plasticizer of the present invention is added to improve the cold resistance, flowability and processability of the rubber. Dioctyl adipate of the present invention is excellent in cold resistance as fatty acid-based plasticizer and can improve durability and cold resistance by improving the resistance to migration, oil resistance and the like.

Dioctyl adipate is contained in an amount of 2 to 10 parts by weight based on 100 parts by weight of hydrogenated nitrile rubber containing 20 to 30 mol% of acrylonitrile. If the content of dioctyl adipate is less than 2 parts by weight, the effect of improving the cold resistance, flowability and processability of the rubber is insignificant, and if it is more than 10 parts by weight, it may cause excessive shrinkage of the material and an excessive amount of plasticizer may be extracted into the oil. It is not suitable for use in power steering.

The crosslinking agent of the present invention is used to make crosslinks between polymer chains when the blended rubber is heated to an appropriate temperature. Since the rubber composition of the present invention has a form in which the polymer structure is almost saturated, organic peroxide is used instead of sulfur as a crosslinking agent.

The organic peroxide used in the present invention is disilyl peroxide. Disulmilyl peroxide, unlike sulfur, decomposes at crosslinking temperatures to form free radicals (R ·). These free radicals extract hydrogen atoms from the polymer chain (PH) to form RH and form polymer radicals (P ·). Adjacent polymer radicals combine with each other to form a carbon-carbon crosslink (P-P) between the polymers.

The crosslinking agent may be included 6 to 8 parts by weight based on 100 parts by weight of hydrogenated nitrile rubber containing 20 to 30 mol% of acrylonitrile. If the content of the cross-linking agent exceeds 8 parts by weight, the cross-linking is made, if less than 6 parts by weight is not cross-linking is the cause of the oil leakage of the power steering oil seal due to deterioration of the physical properties it is difficult to properly function the power steering device.

The composition of the present invention may include a certain amount of crosslinking aid to help the role of the crosslinking agent. The crosslinking aid can be used without limitation, which can be used for crosslinking of the organic peroxide conventionally, for example, zinc oxide, stearic acid and the like.

The crosslinking aid is preferably included 1 to 6 parts by weight based on 100 parts by weight of hydrogenated nitrile rubber containing 20 to 30 mol% of acrylonitrile.

In addition, the rubber composition of the present invention may include an anti-aging agent. Anti-aging agent is good considering the function of the high pressure oil seal of the power steering system, it is good to select the excellent heat resistance and durability that can withstand high temperatures.

The anti-aging agent is not limited to a specific one, and 2,2,4-trimethyl-1,2-dihydroquinoline polymer, 2-mercaptobenzimidazole-based compound, etc., which is an amine anti-aging agent having excellent heat resistance, and the like It can be used, it is possible to use a wax-based (such as SUNNOC) that is an anti-aging agent for cracking.

Antioxidant is preferably included 2 to 4 parts by weight based on 100 parts by weight of hydrogenated nitrile rubber containing 20 to 30 mol% acrylonitrile. If the content is more than 4 parts by weight, mechanical properties may be lowered. If the content is less than 2 parts by weight, aging of the rubber may occur due to internal or external factors.

The manufacturing method of the high pressure oil seal rubber composition used for the power steering apparatus of this invention is not specifically limited. For example, it is possible to produce the above components of the present invention by a conventional mechanical kneading method. Specifically, a method using a general kneader such as a kneader, a banbury mixer, or an open mill can be employed. At this time, the kneading temperature is preferably carried out at 100 ~ 140 ℃. In addition, in the case of the molding process for the composition of the present invention includes all cutting, extrusion molding, etc., of which extrusion molding is most suitable.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to Examples.

Examples and Comparative Examples

Next, the high pressure oil seal rubber composition used in the power steering apparatus was prepared according to the composition and content of Table 1.

Ingredients (parts by weight) Example Comparative example Rubber Low Nitrile H-NBR ¹⁾ 100 - Medium Nitrile H-NBR ²⁾ - 100 Filler Carbon Black FEF ³⁾ 50 50 Celite N219 ⁴⁾ 10 10 Plasticizer DOA ⁵⁾ 10 - DOP ⁶⁾ - 10 Crosslinking agent Percumill D ⁷⁾ 7.5 - F-40 ⁸⁾ - 6 Crosslinking aid ZnO ⁹⁾ 5 5 ST / A ¹⁰⁾ One One Anti-aging TMQ ¹¹⁾ 2 2 Antage MB ¹²⁾ - One SUNNOC ¹³⁾ One One  1. Low nitrile-based H-NBR: ZETPOL 3310, ZEON (ACN: 24%) 2. Medium nitrile-based H-NBR: ZETPOL 2020, ZEON (ACN: 36%) 3. Carbon black FEF: N550, particle size 40 to 48 nm, TONGYANG STEEL CHEMICALS 4. Celite N219: Silica, particle size 6-7 µm, Celite Korea 5. DOA: Dioctyl adipate, BAYER 6. DOP: Dioctyl phthalate, Aekyung emulsification 7. Percumil D: Dicumylper Oxide, Shinkwang Chemical 8. F-40: diisopropylbenzene, oil and fat in Japan 9. ZnO: zinc oxide, sambo zinc 10. ST / A: stearic acid, micro-composite acid 11. TMQ: 2,2,4-trimethyl- 1,2-dihydroquinoline, Flexsys. Co 12.Antage MB: 2-mercaptobenzimidazole, Kawaguchisa 13.SUNNOC: Waxes, emerging

Experimental Example

Hardness, tensile strength, elongation, heat resistance, oil resistance, compression set and cold resistance were measured using the specimens prepared from the rubber compositions of Examples and Comparative Examples by the following method and the results are shown in Table 2 below.

1. Hardness: According to KS M6518, Clause 7

2. Tensile strength: According to KS M6518, Clause 5

3. Elongation: According to KS M6518, Clause 5

4. Heat resistance: According to KS M6518, Clause 8 of KS Standard

5. Oil resistance: According to KS M6518, Clause 13

6. Compressed permanent shrinkage: in accordance with Clause 11 of KS M6518, KS Standard

7. TR TEST: According to ASTM D1329-1998

As shown in Table 2, the present invention shows an effect of equal or more in the state properties showing mechanical properties compared to the prior art, in particular the tensile strength is higher than the conventional, the change in the properties of hardness, tensile strength, elongation at heat resistance In particular, the hardness change was reduced by 4 points from +5 to +1, resulting in an improvement of 75%.

The volume change rate of the low nitrile hydrogenated nitrile improved rubber composition was changed from -4.3% to +2.5% from (-) to (+), and the compression set decreased from 19% to 15%. It has been reduced by 26% to improve the sealing function. Also in cold resistance, TR-10 value improved from 25 degreeC to 34 degreeC, and the effect of cold resistance improved about 36%.

As described above, the high pressure oil seal rubber composition used in the power steering apparatus of the present invention includes 100 parts by weight of hydrogenated nitrile rubber (H-NBR) containing 20 to 30 mol% of acrylonitrile, and 2 to 10 parts by weight of dioctyl adipate. And 6 to 8 parts by weight of dicumyl peroxide to improve cold resistance, heat resistance and compressive permanent shrinkage of the oil seal, thereby preventing oil leakage due to shrinkage phenomenon of the hydraulic power of the power steering system and hardening and cracking of rubber at high and low temperatures. This has the effect of improving the sealing functionality.

Compared with the prior art, hardness, tensile strength, elongation, and the like of the physical properties were satisfactory to satisfy the requirements of the high pressure oil seal of 120 bar, and exhibited excellent physical properties in the heat and cold resistance test results at high and low temperatures. . The most important properties of the power steering high pressure oil seal are the sealing and compression set. In addition, satisfactory results can be obtained in the deposition test for the power steering hydraulic fluid used as the counterpart oil.

Therefore, the power steering high pressure oil seal rubber composition proposed in the present invention is characterized in that the hardening and cracking at high and low temperatures due to the improvement of the sealing function and the heat resistance and the cold resistance are improved according to the shrinkage phenomenon of the power steering hydraulic fluid used as the counterpart oil. It can improve the oil leak (LEAK) problem.

Claims (6)

100 parts by weight of hydrogenated nitrile rubber containing 20 to 30 mol% of acrylonitrile; 2 to 10 parts by weight of dioctyl adipate; 6-8 parts by weight of dicumyl peroxide; 40 to 50 parts by weight of carbon black; And 5 to 10 parts by weight of silica; High pressure oil seal rubber composition used in the power steering device comprising a. delete The high pressure oil seal rubber composition according to claim 1, wherein the carbon black has a particle diameter of 40 to 48 nm. The high pressure oil seal rubber composition according to claim 1, wherein the silica has a particle diameter of 6 to 7 µm. According to claim 1, wherein the acrylonitrile further comprises 1 to 6 parts by weight selected from the group consisting of zinc oxide and stearic acid based on 100 parts by weight of hydrogenated nitrile rubber containing 20 to 30 mol%. High pressure oil seal rubber composition used in power steering. The 2,2,4-trimethyl-1,2-dihydroquinoline polymer and 2-mercaptobenzimidazole type according to claim 1, based on 100 parts by weight of the hydrogenated nitrile rubber containing 20 to 30 mol% of acrylonitrile. A high pressure oil seal rubber composition for use in a power steering apparatus further comprising 2 to 4 parts by weight selected from the group consisting of a compound and a wax-based anti-aging agent.