JP2022088748A - Hydrogenated nitrile rubber composition - Google Patents

Abstract

To provide a hydrogenated nitrile rubber composition that is excellent in adhesion with a metal of an obtained sealing material, furthermore makes reduction of friction coefficient achieve without using a grease, and is suitably used as an oil sealing material for steering dust seal, in addition to use of hydrogenated nitrile rubber excellent in heat resistance and ozone resistance.SOLUTION: A hydrogenated nitrile rubber composition contains 5 to 10 pts.mass of a hydrocarbon-based or fatty acid amide-based wax having a melting point of 140°C or lower with respect to 100 pts.mass of hydrogenated nitrile rubber.SELECTED DRAWING: None

Description

The present invention relates to a hydrogenated nitrile rubber composition. More specifically, the present invention relates to a hydrogenated nitrile rubber composition for an oil seal used for a steering shaft that prevents foreign substances such as dust and rainwater from entering.

In a steering device of a vehicle such as an automobile, the steering shaft is inserted into a column hole opened in a dash panel separating the vehicle interior and the engine room, and the gap between the steering shaft and the column hole is sealed by a steering seal. (Patent Document 1). The steering dust seal prevents foreign substances such as dust and rainwater from entering the vehicle interior.

Conventionally, nitrile rubber has been used as the material for the oil seal for steering dust, and grease has been used to reduce the coefficient of friction of the molded product.

However, in recent years, there have been demands for improved heat resistance and adhesion to metals, as well as lower torque, due to the trend toward compactification of vehicles and the like for oil seals for steering dust.

WO2016 / 076186 Japanese Unexamined Patent Publication No. 2007-83732 Japanese Unexamined Patent Publication No. 2007-83733 WO2019 / 102864

An object of the present invention is to use hydrogenated nitrile rubber to improve heat resistance and ozone resistance, and the obtained sealing material has excellent adhesion to metal, and further reduces the coefficient of friction without using grease. It is an object of the present invention to provide a hydrogenated nitrile rubber composition.

The object of the present invention is achieved by a hydrogenated nitrile rubber composition in which 5 to 10 parts by weight of a hydrocarbon-based or fatty acid amide-based wax having a melting point of 140 ° C. or lower is blended with 100 parts by weight of hydrogenated nitrile rubber. ..

The hydrogenated nitrile rubber (HNBR) composition according to the present invention uses a specific hydrocarbon-based or fatty acid amide-based wax having a melting point of 140 ° C. or lower as the wax, and uses 5 to 10 parts by weight of HNBR. By blending in parts by weight, the adhesiveness of the hydrocarbon to the metal and the friction coefficient in the absence of grease are improved in a well-balanced manner, and it is particularly effective in reducing the friction coefficient in the low speed range of 1.5 mm / sec. It has excellent effects such as measures against squeal and stick slip.

Although a hydrocarbon-based or fatty acid amide-based waxed hydride nitrile rubber composition having a melting point of 140 ° C. or lower is disclosed (Patent Documents 2 to 4, etc.), the blending amount thereof is 100. The technical idea is that it is about 2 to 3 parts by weight with respect to the weight part, and by blending 5 to 10 parts by weight, in addition to heat resistance, the friction coefficient of the crosslinked product can be reduced without using grease. Not disclosed so far.

Hydrogenated nitrile rubber (HNBR) is a rubber obtained by selectively hydrogenating only carbon-carbon double bonds in acrylonitrile butadiene rubber, and has heat aging resistance, weather resistance, and weather resistance as compared with nitrile rubber. It is characterized by its significantly improved chemical properties. Further, as the HNBR, those having a medium-high nitrile to a high nitrile, and more preferably a medium-high nitrile are used. In the present invention, commercially available products such as ZEON products Zetpol 2010, Zetpol 4310, and Alan Seo products Therban 3629 can be used as they are. A specific wax is added to these HNBRs to prepare the HNBR composition according to the present invention.

As the wax, a hydrocarbon-based or fatty acid amide-based wax having a melting point (measured by a microwax and a petrolatum melting point tester) of 140 ° C or less is used, and this is a commercially available product such as Seiko Chemical Product Suntite R, Mitsubishi Chemical Product Slipax O, etc. Can be used as it is. Here, if a wax having a melting point higher than this is used, it becomes difficult to achieve a reduction in the coefficient of friction.

In addition, such wax is used in a ratio of 5 to 10 parts by weight with respect to 100 parts by weight of HNBR. If the wax is used in a higher proportion, the adhesiveness to the metal will deteriorate, while if it is used in a lower proportion, it will be difficult to achieve a reduction in the coefficient of friction.

In addition to wax, which is an essential component, hydrogenated nitrile rubber compositions include various compounding agents generally used in the rubber industry, such as inorganic fillers, cross-linking agents, cross-linking accelerators, acid receiving agents, and antiaging agents. Is appropriately added and used.

Inorganic fillers include wollastonite, white carbon (silica), basic magnesium carbonate, activated calcium carbonate, special calcium carbonate, ultrafine magnesium silicate, hard clay, carbon black, barium sulfate, talc, graphite, mica, etc. Kaolin or the like may be used alone or in combination. The addition of these inorganic fillers is effective in preventing the adhesive layer from peeling off during high-temperature immersion. Of these, wollastonite and graphite are preferably used, and commercially available products, Imerys product NYAD400, Nichiden carbon product graphite A-0 and the like can be used as they are.

These inorganic fillers are used in a proportion of 40 to 150 parts by weight, preferably 60 to 120 parts by weight, per 100 parts by weight of HNBR. If the proportion of the inorganic filler used is less than this, the flow of rubber will increase when used at high temperature and high surface pressure, while if it is used at a higher proportion, the rubber will easily peel off during air heating. Become.

In addition to the above essential components, the hydride nitrile rubber composition contains polyfunctional unsaturated compounds such as triallyl (iso) cyanurate, trimethylolpropane tri (meth) acrylate, and triallyl trimellitate, zinc oxide, and oxidation. Acid receiving agents such as magnesium and hydrotalcite, and plasticizing agents such as dioctyl sebacate are appropriately blended, and the preparation thereof is, for example, a uniaxial extruder, a twin shaft extruder, a roll, a Banbury mixer, a kneader, and a high shear type mixer. After kneading each component other than the cross-linking agent and the cross-linking aid using a kneading machine such as, the cross-linking agent, the cross-linking aid and the like are further added and kneaded.

Organic peroxides are used as the cross-linking agent, specifically 1,1-dithary butylperoxy-3,3,5-trimethylcyclohexane, dithird butyl peroxide, and third butyl cumyl peroxide. , Dicumyl peroxide, 2,5-dimethyl-2,5-di (third butylperoxy) hexane, 2,5-dimethyl-2,5-di (third butylperoxy) hexin-3,1, Examples thereof include 3-bis (third butylperoxyisopropyl) benzene. These organic peroxides are used in a proportion of about 1 to 20 parts by weight, preferably about 2 to 16 parts by weight, per 100 parts by weight of hydrogenated nitrile rubber.

As the cross-linking accelerator, triallyl isoianulate, triallyl cyanurate and the like are used in a proportion of 0.5 to 6 parts by weight, preferably 2 to 4 parts by weight per 100 parts by weight of hydrogenated nitrile rubber. If the amount of the cross-linking accelerator is larger than this, the storage stability of the unvulcanized rubber will be impaired.

The prepared composition is vulcanized and molded by, for example, press crosslinking at about 150 to 200 ° C. for about 3 to 30 minutes.

Next, the present invention will be described with respect to Examples.

Example 1
Hydrogenated nitrile rubber (Aranseo product Therban 3629) 100 parts by weight Wollastonite (Imeris product NYAD400) 30 〃
Graphite (Nichiden Carbon Product Graphite A-0) 30 〃
Anti-aging agent (Ouchi Shinko Chemical Product Nocrack MBZ) 0.5 〃
Wax (Seiko Chemical Product Santite R; 5 〃
Hydrocarbon wax, melting point 75 ℃)
Crosslinking agent (NOF PERCUMYL D) 3 〃
Crosslinking aid (Nihon Kasei Product Tyke M-60) 2 〃
Each of the above components was kneaded using a kneader and an open roll, applied onto a metal plate using the obtained hydrogenated nitrile rubber composition, and subjected to heat crosslinking at 180 ° C. for 10 minutes.

Using the obtained rubber laminated metal plate, the coefficient of friction of the rubber surface was evaluated and the adhesiveness between the metal and rubber was measured as follows. The coefficient of friction was evaluated as ○, and the residual rubber ratio was ○ (100). %)Met.
Coefficient of friction: Pin-on-disc test weighted 1N for test pieces 7 days after cross-linking,
Performed under the condition of 1.5 mm / sec, 0.9 or less is ◎, 1.5 or less is ○, and is larger than 1.5.
The case is evaluated as x. Rubber residual ratio: 180 ° C x 10 minutes Cross-linked product is peeled off from the metal and rubber layer with pliers.
Calculated by
If it is larger than 70%, it is evaluated as ○, and if it is 70% or less, it is evaluated as ×.

Example 2
In Example 1, when the same amount (5 parts by weight) of unsaturated fatty acid bisamide (Mitsubishi Chemical product Slipax 0; melting point 119 ° C) was used as the wax, the coefficient of friction evaluation was ○ and the rubber residual ratio was ○ (100%). there were.

Example 3
In Example 1, when the amount of wax was changed to 10 parts by weight and used, the coefficient of friction evaluation was ◯, and the rubber residual ratio was ◯ (95%).

Example 4
In Example 2, when the amount of wax was changed to 10 parts by weight and used, the coefficient of friction evaluation was ◯, and the rubber residual ratio was ◯ (95%).

Comparative Example 1
In Example 1, when no wax was used, the coefficient of friction evaluation was ×, and the rubber residual ratio was ◯ (100%).

Comparative Example 2
In Example 1, when the amount of wax was changed to 3 parts by weight and used, the coefficient of friction evaluation was × and the rubber residual ratio was ◯ (100%).

Comparative Example 3
In Example 1, when the amount of wax was changed to 13 parts by weight and used, the coefficient of friction evaluation was ⊚ and the rubber residual ratio was × (70%).

Comparative Example 4
In Example 2, when the amount of wax was changed to 3 parts by weight and used, the coefficient of friction evaluation was × and the rubber residual ratio was ◯ (100%).

Comparative Example 5
In Example 2, when the amount of wax was changed to 13 parts by weight and used, the coefficient of friction evaluation was ⊚ and the rubber residual ratio was × (70%).

Comparative Example 6
In Example 1, when the same amount (5 parts by weight) of saturated fatty acid bisamide (Mitsubishi Chemical product bisamide LA; melting point 142 ° C.) was used as the wax, the coefficient of friction evaluation was × and the rubber residual ratio was ○ (100%). rice field.

The crosslinked rubber using the hydrogenated nitrile rubber composition according to the present invention has good heat resistance and a reduced coefficient of friction without using grease, and is effectively used as an oil seal for steering dust seals.

Claims (4)

A hydrogenated nitrile rubber composition containing 5 to 10 parts by weight of a hydrocarbon-based or fatty acid amide-based wax having a melting point of 140 ° C. or lower with respect to 100 parts by weight of hydrogenated nitrile rubber. The hydrogenated nitrile rubber composition according to claim 1, further comprising 40 to 150 parts by weight of an inorganic filler. The hydrogenated nitrile rubber composition according to claim 1 or 2, which is used as an oil sealing material for a steering dust seal. An oil seal for a steering dust seal, which is a crosslinked molded product of the hydrogenated nitrile rubber composition according to claim 3.