JP2018070667A - Rubber composition for oil sealing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition for oil sealing having sufficient strength, having excellent rubber moldability with a rise in Mooney viscosity inhibited, and having a low specific gravity.SOLUTION: A rubber composition for oil sealing at least contains a rubber component, silica, and powdery cellulose. A compounding ratio of the rubber component, silica, and powdery cellulose is [rubber component: silica: powdery cellulose=100:20-60:10-40 (pts.wt.)].SELECTED DRAWING: None

Description

The present invention relates to a rubber composition for oil sealing.

  Since the rubber composition for an oil seal is used for a seal part that involves sliding, in addition to oil resistance, strength against abrasion (abrasion resistance) is required (Patent Document 1). As a method for improving the strength of a rubber composition, it is known to add carbon black or silica to rubber (Patent Document 2).

JP2012-97213 Japanese Patent Application No. 2012-538891

  As described above, a filler such as carbon black or silica is generally added as a measure to prevent the oil seal rubber composition from being worn by repeated sliding and preventing oil leakage. However, since the specific gravity of the rubber composition increases due to the addition of fillers such as carbon black and silica, there arises a problem that the energy efficiency is lowered. Moreover, the problem that the moldability by the increase of the viscosity (Mooney viscosity) of a rubber composition also falls by addition of fillers, such as carbon black and a silica, also arises.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a rubber composition for oil sealing having a sufficient strength and a low specific gravity which is excellent in moldability of rubber with suppressed increase in Mooney viscosity.

The present invention provides the following [1] to [3].
[1] A rubber composition comprising at least a rubber component, silica, and powdered cellulose, wherein the blending ratio of the rubber component, silica, and powdered cellulose is rubber component: silica: powdered cellulose = 100: 20 to 60:10 to 40 (parts by mass) A rubber composition for oil sealing.
[2] The rubber composition for oil sealing according to [1], wherein the rubber component is ethylene propylene diene rubber.
[3] The rubber composition for oil sealing according to [1] to [2], wherein the silica is silica treated with a silane coupling agent.

ADVANTAGE OF THE INVENTION According to this invention, the rubber composition for oil sealings which has sufficient intensity | strength and is excellent in the moldability of the rubber | gum which suppressed the raise of the Mooney viscosity and low specific gravity can be provided.

  The rubber composition for oil sealing of the present invention is a rubber composition comprising a rubber component, silica, and powdered cellulose, and the mixing ratio of the rubber component, silica, and powdered cellulose is rubber component: silica: powdered. It is characterized by being cellulose = 100: 20-60: 10-40 (mass part).

(Rubber component)
The rubber component that can be used in the present invention is not particularly limited. Natural rubber, synthetic rubber: isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene rubber (SBR), chloroprene rubber (CR) Nitrile rubber (NBR), polyisobutylene (butyl rubber IIR), ethylene propylene rubber (EPM), ethylene propylene butadiene rubber (EPDM), chlorosulfonated polyethylene (CSM), acrylic rubber (ACM), fluoro rubber (FKM), epichlorohydrin Examples thereof include rubber (CO, ECO), urethane rubber (U), and silicone rubber (Q). In these, it is preferable to use the ethylene propylene butadiene rubber which made ethylene and propylene copolymerize various diene components in small quantities.

(silica)
The silica that can be used in the present invention can be exemplified by natural silica, synthetic silica (precipitated silica, dry silica, wet silica) and the like, and is not particularly limited. For example, it is used as a tire filler. Silica can be used.

  By treating the surface of silica with a silane coupling agent, the affinity for various rubbers is improved. Therefore, in the present invention, it is preferable to treat silica with a silane coupling agent. The silane coupling agent is not particularly limited. For example, bis (3-triethoxysilylpropyl) tetrasulfide, bis (2-triethoxysilylethyl) tetrasulfide, bis (4-triethoxysilylbutyl) tetra Sulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, bis (4-trimethoxysilylbutyl) tetrasulfide, bis (3-triethoxysilylpropyl) trisulfide, Bis (2-triethoxysilylethyl) trisulfide, bis (4-triethoxysilylbutyl) trisulfide, bis (3-trimethoxysilylpropyl) trisulfide, bis (2-trimethoxysilylethyl) trisulfide, bis ( 4-tri Toxisilylbutyl) trisulfide, bis (3-triethoxysilylpropyl) disulfide, bis (2-triethoxysilylethyl) disulfide, bis (4-triethoxysilylbutyl) disulfide, bis (3-trimethoxysilylpropyl) disulfide Bis (2-trimethoxysilylethyl) disulfide, bis (4-trimethoxysilylbutyl) disulfide, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-triethoxysilylpropyl-N, N -Dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N, N-dimethylthiocarbamoyl tetrasulfide, 2-trimethoxysilylethyl-N, N-dimethylthiocarbamoyl tetrasulfide, -Sulfide systems such as trimethoxysilylpropylbenzothiazolyl tetrasulfide, 3-triethoxysilylpropylbenzothiazole tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, 3-mercapto Mercapto type such as propyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, vinyl type such as vinyltriethoxysilane, vinyltrimethoxysilane, 3-amino Propyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3- (2-aminoethyl) aminopropyltriethoxysilane, 3- (2-aminoethyl) E) Amino-based aminopropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropylmethyl Glycidoxy type such as dimethoxysilane, nitro type such as 3-nitropropyltrimethoxysilane, 3-nitropropyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, 2-chloroethyltrimethoxysilane And chloro-based compounds such as 2-chloroethyltriethoxysilane. These may be used alone or in combination of two or more.

(Powdered cellulose)
The average particle size of the powdery cellulose used in the present invention is 25 to 70 μm, more preferably 35 to 55 μm. Replacing part of silica with powdered cellulose reduces Mooney viscosity and improves moldability, but the larger the average particle size, the less the Mooney viscosity reduction effect and the more the moldability improvement effect. Although less, the effect of improving mechanical properties is increased. On the other hand, when the average particle size is reduced, the Mooney viscosity is greatly reduced and the moldability is improved, but the effect of reinforcing the mechanical properties is reduced. Accordingly, the range of 35 to 55 μm is most preferable.

  The degree of polymerization is in the range of 250 to 1400, more preferably 600 to 1200. When the degree of polymerization is high, the average particle size increases accordingly, and the moldability deteriorates. On the other hand, when the degree of polymerization is reduced, the effect of reinforcing the mechanical properties is reduced. Therefore, the range of 600 to 1200 is most preferable.

  The degree of crystallinity is in the range of 70 to 90, more preferably 80 to 90. The crystallinity of the powdery cellulose is mainly affected by the raw material pulp and the production method, and the powdery cellulose produced only by mechanical treatment without performing acid treatment has a low crystallinity. When the degree of crystallinity is low, the time required for heat vulcanization is long, workability is deteriorated, and mechanical properties are also deteriorated. If the crystallinity is 80 or more, the influence on the vulcanization rate is hardly confirmed.

  The apparent specific gravity is preferably in the range of 0.15 to 0.5, more preferably 0.18 to 0.35. When the apparent specific gravity is 0.15 or less, the powder is bulky and does not mix well when mixed with rubber, silica, or the like, which causes poor dispersion. If it is 0.5 or more, since the powder is low in volume and compact, the dispersibility is good, but since the average particle diameter of the powder becomes small, the effect of reinforcing the mechanical properties becomes small.

  The angle of repose is 45 to 60 °, more preferably 48 to 58 °. When the angle of repose is 60 ° or more, the powder fluidity is poor, which is not preferable for work. When the angle is 45 ° or less, the powder falling speed is fast, but on the other hand, the powder powder is bad, which is not preferable in terms of work.

  The moisture is preferably 5% or less, more preferably 3% or less. When the moisture of the powdery cellulose is high, it causes a vulcanization delay when the rubber is heated and vulcanized. In addition, it adversely affects the mechanical properties after molding. Therefore, the lower the moisture content, the better, and 3% or less is particularly preferable.

  In this invention, the compounding quantity of a powdery cellulose is 10-40 mass parts with respect to 100 mass parts of rubber components, Preferably it is 20-35 mass parts.

(Method for producing powdery cellulose)
The method for producing powdered cellulose that can be used in the present invention is not particularly limited. For example, raw pulp is subjected to an acid hydrolysis treatment with a mineral acid such as hydrochloric acid, sulfuric acid, and nitric acid, and then neutralized, washed, and removed. Manufactured by pulverization and classification through a liquid / drying process. Moreover, it is also possible to produce only by mechanical pulverization without performing acid hydrolysis treatment.

The raw material pulp can be any of hardwood-derived pulp, softwood-derived pulp, or non-wood pulp, and the pulping method (digestion method) is not particularly limited. Examples include cooking methods, soda / quinone cooking methods, organosolv cooking methods, and the like.

  The conditions for the acid hydrolysis treatment were as follows: a dispersion having a pulp concentration of 3 to 10% by weight (in terms of solid content) adjusted to an acid concentration of 0.10 to 1.2N, a temperature of 80 to 100 ° C., and a time of 30 minutes to 3 hours. Process with conditions.

  After the hydrolysis of the pulp, solid-liquid separation is performed on the pulp hydrolyzed in the dehydration step and the waste acid. The hydrolyzed pulp is neutralized by adding an alkaline agent and washed. Then, it is dried with a dryer and mechanically pulverized and classified to a specified size with a pulverizer.

  The grinding machine is a cutting mill: mesh mill (manufactured by Horai Co., Ltd.), Atoms (manufactured by Yamamoto Hyakuma Mfg. Co., Ltd.), knife mill (manufactured by Palman), cutter mill (manufactured by Tokyo Atomizer Manufacturing Co., Ltd.), CS cutter (Mitsui) Mining Co., Ltd.), rotary cutter mill (manufactured by Nara Machinery Co., Ltd.), pulp crusher (manufactured by Ruiko Co., Ltd.), shredder (manufactured by Shinko Pantech Co., Ltd.), etc., hammer type mill: jaw crusher (manufactured by Makino Co., Ltd.) , Hammer crusher (manufactured by Hadano Sangyo Co., Ltd.), impact mill: Pulverizer (manufactured by Hosokawa Micron Corporation), fine impact mill (manufactured by Hosokawa Micron Corporation), super micron mill (manufactured by Hosokawa Micron Corporation), Inomizer (manufactured by Hosokawa Micron Corporation) , Fine Mill (Japan New Made by Matic Kogyo Co., Ltd., CUM type centrifugal mill (made by Mitsui Mining Co., Ltd.), Ixed Mill (made by Hadano Sangyo Co., Ltd.), Ultraplex (made by Hadano Sangyo Co., Ltd.), Contraplex (made by Hadano Sangyo Co., Ltd.), Coro Plex (manufactured by Sagano Sangyo Co., Ltd.), sample mill (manufactured by Seisin Co., Ltd.), bantam mill (manufactured by Seisin Co., Ltd.), atomizer (manufactured by Seisin Co., Ltd.), tornado mill (manufactured by Nikkiso Co., Ltd.), Neamill (manufactured by Dalton Co., Ltd.) , HT type fine crusher (made by Horai Co., Ltd.), free crusher (made by Nara Machinery Co., Ltd.), New Cosmizer (made by Nara Machinery Co., Ltd.), gather mill (made by Nishimura Machinery Co., Ltd.), spar powder Mill (made by Nishimura Machinery Co., Ltd.), Blade Mill (made by Nissin Engineering Co., Ltd.) , Super Rotor (Nisshin Engineering Co., Ltd.), Npa Crusher (Misho Industry Co., Ltd.), Willet Crusher (Miki Co., Ltd.), Pulp Crusher (Zuiko Co., Ltd.) Jacobson Fine Crusher (Shinko Pan) Tech Co., Ltd.), Universal Mill (Tokusu Kosakusho Co., Ltd.), Airflow Mill: CGS Jet Mill (Mitsui Mining Co., Ltd.), Micron Jet (Hosokawa Micron Co., Ltd.), Counter Jet Mill (Hosokawa Micron Co., Ltd.) ), Cross jet mill (manufactured by Kurimoto Steel Corporation), supersonic jet mill (manufactured by Nippon Pneumatic Industry Co., Ltd.), current jet (manufactured by Nissin Engineering Co., Ltd.), jet mill (manufactured by Sanjo Industry Co., Ltd.) , Ebara Jet Micronizer (Manufactured by Ebara Corporation) ), Ebara Triad Jet (Made by Ebara Manufacturing Co., Ltd.), Selenium Mirror (Masuyuki Sangyo Co., Ltd.) New Micro Sicto Mat (Masuno Mfg. Co., Ltd.), Kryptron (Kawasaki Heavy Industries Co., Ltd.), Sakai Type Roller mill: Vertical roller mill (manufactured by Shinion Co., Ltd.), vertical roller mill (manufactured by Schaeffler Japan Co., Ltd.), roller mill (manufactured by Kotobuki Giken Kogyo Co., Ltd.), VX mill (manufactured by Kurimoto Steel Corporation), KVM type Examples are Sakaigata Mill (Earth Technica Co., Ltd.) and IS Mill (IHI Plant Engineering Co., Ltd.). Among these, a tornado mill (made by Nikkiso Co., Ltd.), a blade mill (made by Nisshin Engineering Co., Ltd.), a free crusher (made by Nara Machinery Co., Ltd.), a turbo mill (made by Freund Sangyo Co., Ltd.), which has excellent pulverization properties. ) Is preferably used.

In addition, powdered cellulose raw materials and other organic and / or inorganic components can be mixed singly or in any proportion in any proportion for the purpose of imparting functionality or improving functionality, and pulverizing It is. Moreover, it is possible to perform a chemical process in the range which does not impair the polymerization degree of the natural cellulose used for a raw material significantly.

  When the powder is produced only by mechanical pulverization without performing acid hydrolysis, it is preferable to use a vertical roller mill with high pulverization. In the present invention, the vertical roller mill is a centrifugal vertical grinder belonging to the roller mill, and is pulverized by grinding with a disk-shaped turntable and a vertical roller. The biggest feature of the vertical roller mill is that it is excellent in fine pulverization. The reason is that the raw material is pulverized by the force of compressing the raw material between the roller and the table and the shearing force generated between the roller and the table. To do. Conventional crushers include vertical roller mills (manufactured by Shinion Co., Ltd.), vertical roller mills (manufactured by Schaeffler Japan Co., Ltd.), roller mills (manufactured by Kotobuki Giken Kogyo Co., Ltd.), VX mills (co., Ltd.) Kurimoto Works), KVM type vertical mill (Earth Technica Co., Ltd.), IS mill (IHI Plant Engineering Co., Ltd.), etc.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present application is, of course, not limited to such examples. The test method in the Example of this application is shown next.

<Average particle size measurement>
Measurement was performed using a Microtrac particle size analyzer (Spectris Co., Ltd., Malvern Division). As a measurement principle, a laser scattering method is used, and the particle size distribution is expressed as an accumulation distribution, and a value at which the accumulation distribution is 50% is defined as an average particle diameter.

<Degree of polymerization>
The cellulose polymerization degree was calculated | required by the viscosity measuring method using the copper ethylenediamine of the 16th revision Japanese Pharmacopoeia commentary and the crystalline cellulose confirmation test (2) description.

<Crystallinity>
The crystallinity was determined by measuring the X-ray diffraction of the sample. For the measurement of X-ray diffraction, an appropriate amount of sample was placed on a glass cell, and an X-ray diffraction measurement apparatus (RAD-2C system, manufactured by Rigaku Corporation) was used. The crystallinity is calculated by the method of Segal et al. (L. Segal, JJ Greery, et al, Text. Res. J., 29, 786, 1959) and the method of Kamide et al. (K. Kamide et al. , Polymer J., 17, 909, 1985), and using the diffraction intensity of 2θ = 4 ° to 32 ° of the diffraction diagram obtained from the X-ray diffraction measurement as a baseline, the diffraction intensity of the 002 plane and 2θ = 1 From the diffraction intensity of the amorphous portion at 18.5 °, the following formula was used.

Xc = (I _002C -Ia) / I _002C × 100
Xc: degree of crystallinity of cellulose (%)
I _002C : 2θ = 22.6 °, 002 plane diffraction intensity Ia: 2θ = 18.5 °, diffraction intensity of amorphous part

<Apparent specific gravity measurement>
According to a conventional method, 10 g of a sample was put into a 100 ml graduated cylinder, the bottom of the graduated cylinder was struck, and continued until the height of the sample was not lowered, and the scale on the flat surface was read and measured. Higher values mean that the powder is more compact.

<Repose angle>
Measurement was made using a powder tester (PT-N type, manufactured by Hosokawa Micron Corporation), and the angle of repose was taken as the angle of repose as an index of powder fluidity. That is, the smaller this value, the better the powder flowability.

<Moisture>
About 5 g of the sample was precisely weighed in a weighing bottle of known weight, and the weighing bottle containing the sample was dried for 2 hours with a dryer at 100 to 105 ° C. After 2 hours, the sample was transferred to a desiccator, cooled for 1 hour, weighed with an analytical balance, and calculated from the weight of the sample before and after drying.

<Mooney viscosity (ML (ML _{1 + 4} )>
Using a Mooney viscometer (SMV-300, manufactured by Shimadzu Corporation), the sample was preheated at 100 ° C. for 1 minute, and after 4 minutes from the start of rotation, the value measured with the Mooney viscometer is shown.

<Vulcanization characteristics>
An unvulcanized rubber sheet was prepared as a sample and measured using a curast meter (manufactured by JSR Corporation). A vulcanization curve for 10 minutes was measured at a measurement temperature of 160 ° C., the torque on the vertical axis and the horizontal axis on the graph, and the torque after 10 minutes (N · m) was determined.

<Specific gravity>
Measured according to ISO M6519.

<Rubber hardness>
Measured according to ISO M6518.

<400%, 600% tensile stress>
Measured according to ISO M6518.

<Compression set>
In accordance with JIS K6262, the measurement conditions were 70 ° C. and 24 hours.

<Example 1>
Using ethylene propylene diene rubber (manufactured by KUMHO PETROCHEMICAL, product name: KEP570P (Mooney viscosity 53)), 40 parts by weight of silica (manufactured by Rhodia, product name: Z-175) with respect to 100 parts by weight of ethylene propylene diene rubber , Powdered cellulose (manufactured by Nippon Paper Industries Co., Ltd., product name: W-50 (average particle size 43 μm, polymerization degree 1100, crystallinity 83%, apparent specific gravity 0.20 g / ml, repose angle 58 °, moisture 2.5) %)), 10 parts by weight of zinc oxide (manufactured by Sakai Chemical Industry Co., Ltd., zinc oxide for rubber), 4 parts by weight of silane coupling agent (manufactured by Evonik Degussa, product name: Dynasylan Si-69), 4 parts by weight of polyethylene glycol (manufactured by Toho Chemical Co., Ltd., product name: PEG 4000) and 1 of stearic acid (manufactured by CMB) Part by weight, anti-aging agent (manufactured by Chemutra, product name: Nagard 445), 2 parts by weight, crosslinking aid (manufactured by Kawaguchi Chemical Industry, product name: trialic), 3.6 parts by weight, kneader and open roll The Mooney viscosity of the kneaded product kneaded in (5) was 52 N · m, and the vulcanization characteristic was 1.6 N · m. The kneaded product was press-vulcanized at 160 ° C. for 12 minutes to obtain a plate-shaped test piece. The obtained specimen had a specific gravity of 1.08, a rubber hardness of 76 Shore A, a 400% tensile stress of 65 kgf / cm ² , a 600% tensile stress of 150 kgf / cm ² and a compression set of 33%.

<Example 2>
Using ethylene propylene diene rubber (manufactured by KUMHO PETROCHEMICAL, product name: KEP570P (Mooney viscosity 53))), 30 weights of silica (manufactured by Rhodia, product name: Z-175) with respect to 100 parts by weight of ethylene propylene diene rubber. Parts, powdered cellulose (manufactured by Nippon Paper Industries Co., Ltd., product name: W-50 (average particle size 43 μm, polymerization degree 1100, crystallinity 83%, apparent specific gravity 0.20 g / ml, repose angle 58 °, moisture 2. 5%)) 20 parts by weight, zinc oxide (manufactured by Sakai Chemical Industry Co., Ltd., zinc oxide for rubber) 5 parts by weight, silane coupling agent (Evonik Degussa, product name: Dynasylan Si-69) 3.2 Parts by weight, 3.2 parts by weight of polyethylene glycol (manufactured by Toho Chemical Co., Ltd., product name: PEG 4000), stearic acid (CMB) 1 part by weight, 2 parts by weight of an anti-aging agent (Chemutra, product name: Naugard 445), 3.6 parts by weight of a crosslinking aid (manufactured by Kawaguchi Chemical Industries, product name: Trialic), The Mooney viscosity of the kneaded material kneaded with a kneader and an open roll was 46 N · m, and the vulcanization characteristic was 1.9 N · m. The kneaded product was press-vulcanized at 160 ° C. for 12 minutes to obtain a plate-shaped test piece. The obtained specimen had a specific gravity of 1.06, a rubber hardness of 77 Shore A, a 400% tensile stress of 80 kgf / cm ² , a 600% tensile stress of 170 kgf / cm ² and a compression set of 31%.

<Comparative Example 1>
Using ethylene propylene diene rubber (manufactured by KUMHO PETROCHEMICAL, product name: KEP570P (Mooney viscosity 53)), 30 weight of silica (manufactured by Rhodia, product name: Z-175) with respect to 100 parts by weight of ethylene propylene diene rubber. Parts, 5 parts by weight of zinc oxide (manufactured by Sakai Chemical Industry Co., Ltd., zinc oxide for rubber), 2.4 parts by weight of silane coupling agent (manufactured by Evonik Degussa, product name: Dynasylan Si-69), polyethylene glycol (Toho) 2.4 parts by weight of Chemical Industry Co., Ltd., product name: PEG 4000), 1 part by weight of stearic acid (manufactured by CMB), 2 parts by weight of anti-aging agent (manufactured by Chemutra, product name: Naugard 445), 3.6 parts by weight of a crosslinking aid (manufactured by Kawaguchi Chemical Industry Co., Ltd., product name: Trialic), kneader Mooney viscosity of the kneaded product was kneaded with an open roll 43N · m, Vulcanization characteristics were 1.1 N · m. The kneaded product was press-vulcanized at 160 ° C. for 12 minutes to obtain a plate-shaped test piece. The obtained specimen had a specific gravity of 1.00, rubber hardness of 66 Shore A, 400% tensile stress of 52 Kgf / cm ² , 600% tensile stress of 125 Kgf / cm ² , and compression set of 35%.

<Comparative example 2>
Ethylene propylene diene rubber (manufactured by KUMHO PETROCHEMICAL, product name: KEP570P (Mooney viscosity 53)) is used, and 50 parts by weight of silica (manufactured by Rhodia, product name: Z-175) with respect to 100 parts by weight of ethylene propylene diene rubber. Parts, 5 parts by weight of zinc oxide (manufactured by Sakai Chemical Industry Co., Ltd., zinc oxide for rubber), 4 parts by weight of silane coupling agent (manufactured by Evonik Degussa, product name: Dynasylan Si-69), polyethylene glycol (Toho Chemical Industries) Co., Ltd., product name: PEG 4000) 4 parts by weight, stearic acid (manufactured by CMB) 1 part by weight, anti-aging agent (Chemutra, product name: Naugard 445) 2 parts by weight, crosslinking aid ( 3.6 parts by weight of Kawaguchi Chemical Co., Ltd., product name: Trialic), kneader and The Mooney viscosity of the kneaded product was kneaded with Nroru the 55N · m, Vulcanization characteristics were 1.3 N · m. The kneaded product was press-vulcanized at 160 ° C. for 12 minutes to obtain a plate-shaped test piece. The obtained specimen had a specific gravity of 1.10, a rubber hardness of 75 Shore A, a 400% tensile stress of 62 kgf / cm ² , a 600% tensile stress of 140 kgf / cm ² and a compression set of 37%.

Claims (3)

  A rubber composition comprising at least a rubber component, silica, and powdered cellulose, wherein the compounding ratio of the rubber component, silica, and powdered cellulose is rubber component: silica: powdered cellulose = 100: 20-60: 10 A rubber composition for oil sealing, characterized in that it is -40 (parts by mass).   The rubber composition for oil sealing according to claim 1, wherein the rubber component is ethylene propylene diene rubber.   The rubber composition for oil sealing according to claim 1 or 2, wherein the silica is silica treated with a silane coupling agent.