JP2001348460A - Lubricative rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oil-bleeding lubricative rubber composition excellent in roll kneading properties and abrasion characteristics. SOLUTION: This lubricative rubber composition comprises a diene rubber and, incorporated therewith, a silicone oil having a mol.wt. of not higher than about 20,000 and a silicone gum having a mol.wt. of at least about 100,000.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a lubricating rubber composition. More particularly, it relates to a lubricating rubber composition having excellent roll kneading properties and friction characteristics.

[0002]

2. Description of the Related Art Generally, rubber materials have a high coefficient of friction and are often used for slip prevention. However, in sliding material applications that require elasticity such as dynamic seals, problems such as heat generation due to high frictional force, stick slip, squeal, startup torque, increased power consumption, and damage due to frictional wear And problems such as malfunctions occur.

[0003] In order to solve such problems caused by friction and wear, it has been practiced to apply oil or grease to sliding material products, but such measures increase the process load and increase the cost. Not only that, there is a problem that the oil runs out when used for a long time and the effect is lost, and in applications where sliding characteristics are required, the lubricity of the rubber material itself is strongly required to be improved.

Conventionally, oil bleed types, solid lubricant addition types, surface treatment methods, and the like have been studied in order to reduce the friction coefficient of rubber materials, but the following problems are observed in these countermeasures. . Oil bleed type: Effective for initial reduction of friction coefficient, but has no sustained effect because oil bleeds out over time. Solid lubricant added type: Polytetrafluoroethylene type, silicone Numerous proposals have been made to reduce friction by adding a solid lubricant such as a system, but the addition of a solid lubricant causes an increase in hardness and a decrease in sealability, and is often insufficient for practical use. Surface treatment method: A typical method is a polytetrafluoroethylene coating method. However, a rubber material and polytetrafluoroethylene lack adhesion, and when used under a high pressure condition for a long time, a sufficient peeling occurs. No effect

Further, in the case of the solid lubricant addition type and the surface treatment method, depending on the raw material price and the process load due to the post-treatment, etc.
When applied to inexpensive diene rubber, the cost of the material increases, which is also undesirable in this respect. The oil bleed type is most preferable in terms of cost, and the addition of silicone oil is most effective from the viewpoint of imparting lubricity.

In this case, it is effective to add a large amount of silicone oil in order to ensure the durability of the lubricating effect. However, if the amount is too large, the compatibility with the diene rubber becomes poor, resulting in poor dispersion. And bagging (the phenomenon in which the rubber band that has passed through the roll gap rises off the roll)
There is a problem that the kneading workability is significantly reduced.
Therefore, when emphasis is placed on workability and productivity, there is a limit in the amount of addition by itself, and in reality it is not possible to add a sufficient amount for imparting lubricity.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide an oil bleed type lubricating rubber composition having excellent roll kneading properties and friction characteristics.

[0008]

SUMMARY OF THE INVENTION The object of the present invention is as follows.
The lubricating rubber composition is obtained by adding a silicone oil having a molecular weight of about 20,000 or less to a diene rubber and a silicone gum having a molecular weight of about 100,000 or more.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Diene rubbers include nitrile rubber, hydrogenated nitrile rubber, styrene butadiene rubber,
Isoprene rubber, chloroprene rubber, butadiene rubber,
Synthetic rubber such as butyl rubber or natural rubber is exemplified. Silicone oil and silicone gum are added to these diene rubbers.

As a silicone oil, a molecular weight of about 20
000 or less, generally about 5,000 to 20,000 dimethyl silicone oil, straight silicone oil such as phenylmethyl silicone oil or non-reactive modified silicone oil such as alkyl, alkyl / aralkyl, fluorinated alkyl, etc. Also advantageous dimethyl silicone oil is used. In practice, commercially available products are used as they are, and in the case of dimethyl silicone oil, Dow Corning Toray having various molecular weights (viscosity)
Silicone products SH200, Shin-Etsu Chemical product KF96, Toshiba silicone products TSF451 and the like are used. In the case of phenylmethyl silicone oil, Toray Dow Corning silicone products SH510, SH550, SH710 and the like are used, respectively. When a silicone oil having a molecular weight higher than this is used, the lubricating effect cannot be obtained.

As the silicone gum, an ultrahigh-viscosity grade having a molecular weight of about 100,000 or more, generally about several hundred thousand in silicone oil is used.

The silicone oil is used in an amount of about 1 to 20 parts by weight, preferably about 5 to 15 parts by weight, per 100 parts by weight of the diene rubber. If the addition ratio is lower than this, the kneadability is good but the frictional characteristics are deteriorated. On the other hand, if the addition ratio is higher than this, the kneadability is deteriorated and processing becomes difficult. The silicone gum is used in an amount of about 1 to 20 parts by weight, preferably about 5 parts by weight, per 100 parts by weight of the diene rubber.
It is used in a proportion of up to 15 parts by weight. If the addition ratio is lower than this, the effect of improving the friction characteristics is lost, while if used at a higher ratio, the dispersibility of the rubber decreases and the kneading property deteriorates.

The composition containing the above components as essential components includes a reinforcing agent, a processing aid, an antioxidant, a plasticizer, a crosslinking agent,
A crosslinking aid or the like is appropriately blended and used.

The rubber reinforcing agent also functions as a filler, and for example, carbon black, silica, clay, talc, silicic acid, silicate, calcium hydroxide, calcium carbonate and the like are used. As the processing aid, for example, zinc oxide, stearic acid, polyethylene glycol, liquid polybutadiene and the like are used. Examples of anti-aging agents include, for example, 2,6-di-tert-butyl-4-methylphenol, N-isopropyl-N'-phenyl-p-phenylenediamine, polymerized (2,2,4-trimethyl-1,2-dihydro (Quinoline), 2-mercaptoimidazole and the like. As the plasticizer, for example, process oil, dioctyl phthalate,
Dibutyl carbitol adipate, vegetable oil and the like are used.

As the cross-linking agent, a sulfur-based cross-linking agent such as powdered sulfur, precipitated sulfur, colloidal sulfur, or insoluble sulfur or a peroxide-based cross-linking agent is used depending on the type of diene rubber used. As the peroxide-based crosslinking agent,
For example, 1,3-bis (tert-butylperoxyisopropyl) benzene, 1,4-bis (tert-butylperoxyisopropyl)
Benzene, tertiary butyl hydroxy peroxide, dicumyl peroxide, 2,5-dimethylhexane-2,5-dihydroperoxide, 1,1-bis (tertiary butyl peroxy)-
3,3,5-trimethylcyclohexane and the like are used. When a peroxide-based crosslinking agent is used, for example, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, triallyl isocyanurate, triallyl cyanurate, diallyl phthalate, N, Nm-phenylenedimaleimide as a crosslinking aid It is preferable to use a polyfunctional unsaturated compound such as

Further, for example, powdered graphite, spheroidal graphite, molybdenum disulfide, powdered polytetrafluoroethylene,
Solid lubricants such as glass fibers and carbon fibers can also be used in the composition.

[0017]

According to the lubricating rubber composition of the present invention, by using a silicone oil and a silicone gum together, a large amount of lubricating components can be blended without impairing the kneading properties of the roll, and the lubricating rubber composition has excellent lubricity. It is possible to provide a rubber material at low cost. In addition, since the composition is simple, adverse effects on other physical properties can be avoided.

Such a lubricating composition has a very low coefficient of friction on the surface of a vulcanized rubber molded product because the silicone oil bleeds out moderately during vulcanization molding. Low wear properties are continuously exhibited,
Since the torque is reduced, the product life can be extended. Further, even if oil or grease is not applied, the insertion resistance is low, and the product mounting property is good.

The lubricating composition of the present invention having such characteristics can be effectively used as a molding material such as an oil seal, a toner seal, an O-ring, and a packing which requires sliding characteristics.

[0020]

Next, the present invention will be described with reference to examples.

Example 1 Hydrogenated nitrile rubber (Zepol 2020L manufactured by Nippon Zeon) 100 parts by weight SRF carbon black (Tokai Carbon Product Seast S) 35 亜 鉛 zinc oxide 5 ス テ stearic acid 1 ジ オ dioctyl phthalate 5 シ リ コ ー ン silicone oil (Toray Co., Ltd.) Dow Corning silicone products 5 〃 SH-200; molecular weight 5000) Silicone gum (molecular weight about 400000) 10 〃 dicumyl peroxide 7 〃 Each of the above ingredients is kneaded using a closed kneader and open roll, and the kneaded material is mixed. After press vulcanization at 170 ° C for 15 minutes, oven vulcanization was performed at 150 ° C for 1 hour, and the thickness was 2 mm.
To obtain a vulcanized rubber sheet.

With respect to the obtained vulcanized rubber sheet, the following items were evaluated and measured. Roll kneading property: When it is judged that kneading with a roll can be carried out without any difference from ordinary rubber material, it is evaluated as "x". When it is judged that kneading of rolls is difficult due to bagging of rubber material, it is evaluated as x. Friction coefficient: Shinto Kagaku surface Measured with a 10 mm diameter steel ball indenter under the conditions of a load of 50 g and a moving speed of 50 mm / min using a property measuring machine Tribogear type 14. Normal physical properties: JIS K-6251, -6253 compliant Compression set: JIS K-6262 Compliant (120 ° C, 70 hours)

Example 2 In Example 1, the same amount of silicone oil having a molecular weight of 10,000 (SH200) was used in place of the silicone oil having a molecular weight of 5,000.

Comparative Example 1 In Example 1, no silicone oil or silicone gum was used.

Comparative Example 2 In Example 1, no silicone gum was used.

Comparative Example 3 In Example 2, the amount of silicone oil was changed to 10 parts by weight, and no silicone gum was used.

Comparative Example 4 In Example 1, no silicone oil was used.

Comparative Example 5 In Example 1, the amount of silicone gum was changed to 15 parts by weight, and no silicone oil was used.

The evaluation and measurement results in each of the above Examples and Comparative Examples are shown in the following table. Table Evaluation / Measurement Items Actual-1 Actual-2 Ratio-1 Ratio-2 Ratio-3 Ratio-4 Ratio-5 Roll Kneading 〇 〇 〇 × × 〇 × Coefficient of Friction 0.2 0.2 1.2 0.1 0.2 1.0 0.4 Physical Properties Hardness ( (Duro A) 70 70 70 70 70 69 68 Tensile strength (MPa) 19.9 20.6 22.5 22.2 21.1 21.5 20.9 Elongation (%) 440 420 300 320 370 380 440 Compression set (%) 15 13 10 10 11 13 15

From the above results, the following can be said. (1) Each example shows a very low coefficient of friction while exhibiting the same kneading properties as ordinary rubber. (2) In each comparative example, those with good kneading properties have a high friction coefficient.
(Comparative Examples 1 and 4), on the other hand, those having a low coefficient of friction show poor kneading properties (Comparative Examples 2, 3 and 5).

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Claims (2)

[Claims] 1. A lubricating rubber composition comprising a diene rubber and a silicone oil having a molecular weight of about 20,000 or less and a silicone gum having a molecular weight of about 100,000 or more. 2. The lubricating rubber composition according to claim 1, which is used as a molding material for a sliding material.