JP2023045474A - Rubber composition for sealing member of rolling bearing - Google Patents

Abstract

An object of the present invention is to provide a rubber composition for producing a rolling bearing sealing member having excellent electrical conductivity and wear resistance, and a rolling bearing sealing member produced from the rubber composition. A rubber composition for forming a sealing member of a rolling bearing, comprising 100 parts by mass of rubber containing acrylic acid ester as a main component and carbon black 20 having a DBP oil absorption of 200 ml/100 g or more and 500 ml/100 g or less. 40 parts by mass, and does not contain carbon black having a DBP oil absorption of less than 200 ml/100 g. [Selection figure] None

Description

TECHNICAL FIELD The present invention relates to a rubber composition for forming a sealing member of a rolling bearing and a sealing member using the rubber composition.

Automotive parts, such as auxiliary equipment around the engine (alternator, air conditioner, etc.) and bearings used in undercarriage parts, are designed to prevent grease leakage, rain, bad roads, etc., and prevent muddy water or dust from entering. For this purpose, a ring-shaped metal core is covered with a rubber molding on the surface of the sealing member. Rubber moldings are used.

Here, rubber moldings used for sealing members used in rolling bearings are required to have physical properties that can withstand harsh environments such as high temperature and high humidity, in which rubber tends to degrade.
For example, as a sealing member that is excellent in heat resistance and conductivity and has good releasability from the mold during production, the rubber molded product contains 100 parts by mass of rubber (A) containing acrylic acid ester as the main component, and a carbon material. A carbon material ( B) is carbon black (B2) having a DBP oil absorption of 150 ml/100 g or more and 1000 ml/100 g or less, and the rubber molding has a volume resistivity of 1×10 ⁶ Ω·cm or less. It is known (Patent Document 1).

Japanese Patent Application Laid-Open No. 2020-152796

However, the inventors of the present invention have found that a rubber molded product containing carbon black having a DBP oil absorption of less than 200 ml/100 g has a problem that it does not have sufficient resistance (wear resistance) against wear due to rotation of rolling bearings. found for the first time.

Accordingly, an object of the present invention is to provide a rubber composition for producing a rolling bearing sealing member having excellent electrical conductivity and wear resistance, and a rolling bearing sealing member produced from the rubber composition. .

As a result of intensive studies by the present inventors in order to solve the above problems, instead of carbon black having a DBP oil absorption of less than 200 ml / 100 g, by blending a specific amount of carbon black having a specific DBP oil absorption, The present invention was completed by discovering that a sealing member for a rolling bearing having excellent electrical conductivity and wear resistance can be produced.

That is, the gist of the present invention is
[1] A rubber composition for forming a sealing member of a rolling bearing,
Carbon black containing 100 parts by mass of rubber containing acrylic acid ester as a main component and 20 to 40 parts by mass of carbon black having a DBP oil absorption of 200 ml/100 g or more and 500 ml/100 g or less and having a DBP oil absorption of less than 200 ml/100 g A rubber composition for a sealing member of a rolling bearing, characterized in that it does not contain
[2] The rubber composition for a sealing member of a rolling bearing according to [1] above, wherein the acrylic acid ester is an acrylic acid ester having a carboxyl group;
[3] The rubber composition for a sealing member of a rolling bearing according to [1] or [2], further comprising 5 to 100 parts by mass of a white filler.
[4] The rubber composition for a sealing member of a rolling bearing according to any one of [1] to [3], further comprising 0.1 to 5 parts by mass of a coupling agent;
[5] A bearing seal member molded from the rubber composition according to any one of [1] to [4],
The present invention relates to a bearing sealing member characterized by having a volume resistivity of 100Ω·cm or less.

By using the rubber composition for a sealing member of a rolling bearing of the present invention, a sealing member of a rolling bearing having excellent electrical conductivity and wear resistance can be produced.
By arranging the sealing member of the rolling bearing of the present invention in automobile parts, for example, bearings used in auxiliary equipment around the engine (alternator, air conditioner, etc.) and suspension parts, etc., automobiles can be used in harsh environments. However, the reliability of the rolling bearing can be maintained.

BRIEF DESCRIPTION OF THE DRAWINGS It is explanatory drawing which shows the structure of the rolling bearing which mounted the sealing member for rolling bearings which concerns on embodiment of this invention, (a) is sectional drawing of the whole rolling bearing, (b) is principal part enlarged sectional drawing. It is explanatory drawing which showed the implementation method of a wear resistance test.

The present invention will be described in more detail below. It should be noted that the present invention is not limited to the forms shown in the attached drawings, and includes all embodiments that satisfy the requirements described in the scope of claims.

[Rolling bearing]
FIG. 1 is an explanatory view showing the configuration of a rolling bearing equipped with a rolling bearing seal member according to an embodiment of the present invention, showing a deep groove ball bearing as an example. Further, FIG. 1(a) is a cross-sectional view of the entire rolling bearing 1, and FIG. 1(b) is an enlarged cross-sectional view of a main part.

In FIG. 1, a rolling bearing 1 has an inner ring 2 and an outer ring 3 that rotate relative to each other via rolling elements 5 held by a retainer 4. is filled with grease 10 as a lubricant. Further, on the left and right sides of the rolling elements 5 in the bearing width direction, seal members 11, which are substantially annular in front view and close the annular opening A between the inner ring 2 and the outer ring 3, and peripheral members 11 formed on the outer peripheral surface of the inner ring 2, are provided. A sealing device constituted by a groove 6 is provided. The seal member 11 is attached to at least one of the annular openings A, A on the left and right sides in the bearing width direction between the inner ring 2 and the outer ring 3 of the rolling bearing 1 . (Instead of the double-shielded type that seals both sides of the rolling bearing 1 as shown in FIG. 1, a single-shielded type that seals only one side of the rolling bearing 1 may be used depending on the location of use.) Then, as shown in FIG. As shown, the sealing member 11 is formed by coating an elastic body 13 such as synthetic rubber by vulcanization adhesion continuously to the outer and inner peripheral parts of an annular core metal 12 made of a steel plate or the like. The lip structure consists of an inner main lip 14 and an outer dust lip 15 on the inner peripheral side (inner ring 2 side) and an outer diameter lip 16 on the outer peripheral side (outer ring 3 side).
The main lip 14 prevents the grease 10 filled inside the bearing 1 from leaking and also prevents foreign matter from entering from the outside. is intended to reduce Further, the outer diameter lip 16 is fitted in an outer ring circumferential groove 7 formed in the inner circumferential surface of the outer ring 3 to position and fix the seal member 11 with respect to the bearing 1, and prevents the seal member 11 from the outer diameter portion. This is to prevent foreign matter from entering. Furthermore, the dust lip 15 is formed with a groove 15A, and the sealing member 11 also has the function of facilitating the discharge of water or muddy water that has entered between the dust lip 15 and the main lip 14. As shown in FIG.

[Rubber composition]
The rubber composition of the present invention is a rubber composition for forming a sealing member of a rolling bearing,
Carbon black containing 100 parts by mass of rubber containing acrylic acid ester as a main component and 20 to 40 parts by mass of carbon black having a DBP oil absorption of 200 ml/100 g or more and 500 ml/100 g or less and having a DBP oil absorption of less than 200 ml/100 g It is characterized by not containing

The rubber containing acrylic acid ester as a main component used in the rubber composition of the present invention may be a commercially available acrylic acid ester polymer or copolymer having a cross-linking point such as a carboxyl group, active chlorine, or epoxy group. Any of these commercially available products can be used in the present invention. Ethylene-acrylic rubber (AEM), which is a copolymer with ethylene, and acrylic rubber (ANM) containing AN (acrylonitrile) composition can be used as the rubber containing acrylic acid ester as a main component. The type of acrylic rubber is also not particularly limited. For example, "Nipol" (trade name) manufactured by Nippon Zeon Co., Ltd. is an acrylic ester polymer having an epoxy group, such as "AR12" if it is an acrylic ester polymer or copolymer having a carboxyl group. Alternatively, copolymers such as "AR31", "AR42W", "AR54", etc., and polymers or copolymers of acrylic acid esters having active chlorine groups such as "AR71", "AR72LS", etc. may be mentioned. Examples of AEM include "VAMAC" (registered trademark) manufactured by DuPont.
Among these, in addition to heat resistance and water resistance, carboxyl Acrylic acid ester copolymers having groups are preferred.

The DBP oil absorption of carbon black indicates the amount (mL) of dibutyl phthalate (DBP) that can be absorbed by 100 g of carbon black (according to JIS K 6217-4). The DBP oil absorption increases as the structure of aggregates and agglomerates is developed in carbon black. A carbon material having excellent conductivity generally has a large DBP oil absorption.
The DBP oil absorption of carbon black used in the present invention is 200 ml/100 g or more, preferably 300 mL/100 g or more. On the other hand, if the DBP oil absorption exceeds 500 mL/100 g, the fluidity of the rubber composition may deteriorate.

As the carbon black having a DBP oil absorption of 200 ml/100 g or more and 500 ml/100 g or less, for example, "Ketjen Black EC300J" and "Ketjen Black EC600JD" manufactured by Lion Specialty Chemicals Co., Ltd. can be suitably used.

The rubber composition of the present invention contains 20 to 40 parts by mass of carbon black having a DBP oil absorption of 200 ml/100 g or more and 500 ml/100 g or less with respect to 100 parts by mass of rubber containing acrylic ester as a main component. , it is possible to impart electrical conductivity to the sealing member. If the content is less than 20 parts by mass, the electrical conductivity will not be sufficient, which is not preferable in terms of causing deterioration in electrical conductivity due to kneading. This is not preferable because it tends to cause poor molding of the bearing seal.

Further, the rubber composition of the present invention is characterized in that it does not contain carbon black having a DBP oil absorption of less than 200 ml/100 g.
When a rolling bearing is produced using a rubber composition for a sealing member containing carbon black with a DBP oil absorption of less than 200 ml/100 g, as described in Comparative Examples below, it is difficult to say that the wear resistance is sufficient. It becomes impossible.
In the present invention, the above-mentioned "does not contain" means that it does not substantially contain.

The rubber composition of the present invention contains 5 to 100 parts by mass of a white filler with respect to 100 parts by mass of a rubber containing acrylic acid ester as a main component, from the viewpoint of improving the adhesion between the rubber molded article and the metal core. may contain.

More preferably, the content of the white filler is 70 parts by mass or less.

The type of white filler is not particularly limited, and fillers commonly used in rubber compositions can be used. Such fillers include inorganic fillers such as silica, clay, calcium carbonate, diatomaceous earth, wollastonite, barium sulfate and titanium oxide, and organic fillers such as cellulose powder, regenerated rubber and powdered rubber. Among them, silica, clay, calcium carbonate, and diatomaceous earth are more preferably used as inorganic fillers and from the viewpoint of improving adhesiveness. As the white filler, two or more kinds may be used in combination.

The rubber composition of the present invention may further contain 0.1 to 10 parts by mass of a coupling agent from the viewpoint of improving the reinforcing properties of the rubber.

The content of the coupling agent is more preferably 0.1 parts by mass or more, and more preferably 5 parts by mass or less.

The coupling agent is not particularly limited as long as it is used as a coupling agent for acrylic rubber. Examples include vinyl silane coupling agents, amino silane coupling agents, and epoxy silane coupling agents. , a mercapto-based silane coupling agent, and a zirconia-based silane coupling agent.

In addition to the above components, the rubber composition of the present invention usually further contains a cross-linking agent, a vulcanizing agent, a plasticizer, a reinforcing agent, a metal oxide, a softening agent, an anti-aging agent, a processing aid, a flame retardant, Various additives such as ultraviolet absorbers can be blended in an appropriate amount within a range that does not impair the effects of the present invention.

The cross-linking agent is not particularly limited as long as it is for acrylic rubber, and a known cross-linking agent can be used as appropriate. Examples of common cross-linking agents include diamine-based cross-linking agents such as hexamethylenediamine, sulfur and organic peroxides.

Moreover, when using the cross-linking agent, a cross-linking accelerator, a cross-linking aid, or the like can also be used. Examples of cross-linking accelerators include N-cyclohexyl-2-benzothiazolylsulfenamide, N-oxydiethylene-2-benzothiazolylsulfenamide, N,N-diisopropyl-2-benzothiazolylsulfenamide and the like. 2-mercaptobenzothiazole, 2-(2',4'-dinitrophenyl)mercaptobenzothiazole, 2-(4'-morpholinodithio)benzothiazole, dibenzothia Thiazole compounds such as dil disulfide; Guanidine compounds such as diphenylguanidine, diorthotriylguanidine, diorsonitrileguanidine, orthonitrile biguanide, and diphenylguanidine phthalate; acetaldehyde-aniline reaction products, butyraldehyde-aniline Condensates, aldehyde amines such as hexamethylenetetramine and acetaldehyde ammonia, or aldehyde-ammonia compounds; imidazoline compounds such as 2-mercaptoimidazoline; thiocarbanilide, diethylthiourea, dibutylthiourea, trimethylthiourea, diorthotolylthiourea, etc. Thiuram compounds such as tetramethylthiuram monosulfide, tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide, tetraoctylthiuram disulfide, and pentamethylenethiuram tetrasulfide; ferric dimethyldithiocarbamate, dimethyldithiocarbamine dithioate compounds such as sodium acid salt, selenium dimethyldithiocarbamate and tellurium dimethyldithiocarbamate; xanthate compounds such as zinc dibutylxanthate; and compounds such as zinc oxide.

Vulcanizing agents include, for example, primary aliphatic and primary aromatic amines. Examples of aliphatic amines include hexamethylenediamine, hexamethylenediamine carbamate, tetramethylenepentamine, hexamethylenediamine-cinnamaldehyde adducts and hexamethylenediamine-dibenzoate salts. Examples of aromatic amines include 4,4'-methylenedianiline, 4,4'-oxyphenyldiphenylamine, m-phenylenediamine, p-phenylenediamine, 4,4'-methylenebis(o-chloroaniline). etc. As a vulcanizing agent, zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc di-n-butyldithiocarbamate, zinc ethylphenyldithiocarbamate, zinc butylphenyldithiocarbamate, and the like can also be used.

Examples of plasticizers include phthalates such as dimethyl phthalate, diethyl phthalate, dibutyl phthalate, diisobutyl phthalate, dioctyl phthalate, butyl octyl phthalate, di-(2-ethylhexyl) phthalate, diisooctyl phthalate, and diisodecyl phthalate; Adipate, diisobutyl adipate, di-(2-ethylhexyl) adipate, diisooctyl adipate, diisodecyl adipate, octyldecyl adipate, di-(2-ethylhexyl) azelate, diisooctyl azelate, diisobutyl azelate, dibutyl sebacate, di - Fatty acid esters such as (2-ethylhexyl) sebacate and diisooctyl sebacate, trimellitic acid isodecyl ester, trimellitic acid octyl ester, trimellitic acid n-octyl ester, trimellitic acid-based isononyl ester In addition to mellitic acid esters, di-(2-ethylhexyl) fumarate, diethylene glycol monooleate, glyceryl monoricinoleate, trilauryl phosphate, tristearyl phosphate, tri-(2-ethylhexyl) phosphate, epoxidized soybean oil, polyether esters etc. These can be used alone or in combination of two or more.

Examples of metal oxides include zinc white, active zinc white, surface-treated zinc white, zinc carbonate, composite zinc white, composite active zinc white, surface-treated magnesium oxide, magnesium oxide, calcium hydroxide, ultrafine calcium hydroxide, Examples include lead monoxide, red lead, and white lead. These can be used alone or in combination of two or more.

Examples of softening agents include petroleum softening agents and vegetable oil softening agents. Examples of petroleum softeners include aromatic softeners, naphthenic softeners, and paraffin softeners. Vegetable softeners include, for example, castor oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, palm oil, coconut oil, peanut oil, and Japan wax. These can be used alone or in combination of two or more.

Anti-aging agents include, for example, naphthylamine-based, diphenylamine-based, p-phenylenediamine-based, quinoline-based, hydroquinone derivative-based, mono-, bis-, tris-, polyphenol-based, thiobisphenol-based, hindered phenol-based, and phosphite-based. , imidazole-based, nickel dithiocarbamate-based, and phosphoric acid-based anti-aging agents. These can be used alone or in combination of two or more.

Processing aids include, for example, stearic acid, oleic acid, lauric acid, zinc stearate, calcium stearate, potassium stearate, sodium stearate, stearylamine and the like. These can be used alone or in combination of two or more.

The method for producing the rubber composition of the present invention is not particularly limited. For example, rubber containing the above acrylic acid ester as a main component, carbon black having a DBP oil absorption of 200 ml/100 g or more and 500 ml/100 g or less, and optionally white fillers, coupling agents, other additives, etc. are combined, preferably at 10 to 200 ° C., more preferably 20 to 170 ° C., after kneading with a mixer such as a Banbury mixer, Brabender mixer, intermixer, kneader, transferred to a roll or the like and a vulcanizing agent or heat It can be produced by adding an unstable vulcanization aid or the like to , and then performing secondary kneading, preferably at a temperature of 10 to 80°C.

[Bearing seal member]
By cross-linking the rubber composition of the present invention containing the above-described components, a rubber molded article to be used as a bearing sealing member can be obtained. For cross-linking, for example, the rubber composition may be vulcanized based on a known technique, and then a rubber molded article can be obtained by molding such as sheet molding. It is preferable that the vulcanization treatment is divided into primary vulcanization and secondary vulcanization. The temperature conditions for the vulcanization treatment are not particularly limited, but a range of 140 to 180° C. is preferable for both primary vulcanization and secondary vulcanization. The vulcanization treatment time is not particularly limited, but it is preferable to perform the primary vulcanization for 10 to 30 minutes and the secondary vulcanization for 1 to 10 hours.

As the vulcanization means, steam vulcanization, press vulcanization, oven vulcanization, and other general methods used for vulcanization of rubber can be appropriately selected.

The bearing seal member of the present invention is characterized by having a volume resistivity of 100 Ω·cm or less. When the volume resistance is 100 Ω·cm or less, electromagnetic noise can be effectively suppressed. The volume resistance value is preferably 10 Ω·cm or less.
The volume resistance value is a value obtained by measurement conforming to JIS K6271-2 Method 3.

In particular, the bearing sealing member of the present invention has the advantage that the surplus material generated can be re-kneaded and used because the decrease in volume resistance value is small even when preforming is performed.

The bearing sealing member of the present invention obtained as described above has excellent electrical conductivity and wear resistance.

Next, the present invention will be described with reference to examples, but the present invention is not limited to these examples.

The components used in Examples and Comparative Examples described later are as follows.
Acrylic acid ester copolymer (1): "AR12" (manufactured by Nippon Zeon, containing carboxyl group)
Acrylic acid ester copolymer (2): "ANM" (manufactured by Nippon Zeon, epoxy group-containing)
Processing aid (1): stearic acid, "Tsubaki Stearate" (NOF Corporation)
Antiaging agent: 4,4'-bis(α,α-dimethylbenzyl)diphenylamine, "Nocrac CD", Ouchi Shinko Chemical Industry Co., Ltd. Processing aid (2): Stearylamine, "Lipomin 18D", Lion Specialty Co., Ltd. Chemicals Carbon Black (1): "Ketchin Black EC300-J", Lion Specialty Chemicals DBP oil absorption 360ml/100g
Carbon black (2): "FT carbon" DBP oil absorption 20ml/100g or more and less than 150ml/100g White filler (1): Silicon dioxide "Nipsil ER", Tosoh Silica White filler (2): Diatomaceous earth Celite #499", Tokyo Diatomaceous Earth Co., Ltd. White filler (3): Silicon dioxide and aluminum oxide "Satinton No. 5", BASF Co. Coupling agent (1): γ-aminopropyltriethoxysilane, "A-1100 "Nippon Unicar coupling agent (2): γ-glycidoxypropyltrimethoxysilane, "A-187" Nippon Unicar vulcanizing agent (1): hexamethylenediamine carbamate, "Diak-1" DuPont cross-linking accelerator ( 1): 1,3-di-O-tolylguanidine "Noccera-DT", Ouchi Shinko Kagaku Kogyo Co., Ltd. vulcanizing agent (2): Zinc dimethyldithiocarbamate "Noccera-PZ", Ouchi Shinko Kagaku Kogyo Co., Ltd. Cross-linking accelerator Agent (2): Ferric dimethyldithiocarbamate "Noxera-TTFE", Ouchi Shinko Chemical Industry Co., Ltd.

(Example 1)
Raw materials were pressed with pressure rolls so as to have the composition shown in Table 1, and then mixed with a sealed mixer to prepare a rubber composition.
Next, after kneading the obtained rubber composition with a mixing roll, primary vulcanization (150 to 180°C, 10 to 15 minutes) and secondary vulcanization (150 to 180°C x 1 to 10 hours) are performed. A rubber sheet (rubber molding) having a thickness of 2 m was obtained by molding into a sheet.

(Examples 2-6, Comparative Examples 1-7)
A rubber composition was prepared in the same manner as in Example 1, except that the raw materials were mixed so as to have the formulation shown in Table 1, and then a rubber sheet (rubber molding) was obtained.

The physical properties of each rubber composition and rubber sheet obtained as described above were evaluated according to the following evaluation methods. Those results are shown in Table 1.

(Conductivity)
The rubber sheet was measured according to JIS-K6271-2 Method 2 to obtain the volume resistivity of the material.
Next, the rubber composition was reprocessed (re-kneaded) with an 8-inch roll machine at a roll temperature of 50 degrees, a rotation ratio of 12:10, and a roll gap of 1.0 mm. The volume resistance value of the material was determined for each number of times of reworking, and it was confirmed whether or not the electrical conductivity was maintained compared to before reworking.

(hardness)

The durometer hardness (Shore A hardness) of the rubber sheet was measured according to JIS K6253.

(strength)
The tensile strength (Mpa) of a No. 3 dumbbell test piece of the rubber sheet was measured according to JIS K6251.

(stretch)
JIS. The elongation (%) of a No. 3 dumbbell test piece of the rubber sheet was measured according to K6251.

(Heat-resistant)
A heat aging test was performed.
Specifically, according to JISK6257, a heat aging test was started on a rubber sheet at 170° C., and the change in hardness (ΔHS) and change in elongation (ΔEB) from the initial value after 70 hours from the start were calculated.
Judgment criteria ◯: change amount ΔHS = within ±10 points, elongation change rate ΔEB within ±30%. Satisfied with both.
x: Amount of change ΔHS = within ±10 points, rate of change in elongation ΔEB within ±30%. Not happy with either.

(water resistant)
According to JIS K 6258, the rubber sheet immersed in water was allowed to stand at 100° C. for 72 hours, and then hardness change (ΔHS) and elongation change (ΔEB) were determined in the same manner as the heat resistance test. Also, the volume change rate was obtained from the volume after immersion at 100° C. for 72 hours and the volume before immersion.
Judgment criteria ◯: change amount ΔHS = within ±10 points, elongation change rate ΔEB within ±30%, volume change rate within 8%. Satisfactory x: Amount of change ΔHS = within ±10 points, rate of change in elongation ΔEB within ±30%, rate of volume change within 8%. Not happy with either.

(compression set)
It was measured at 150°C for 72 hours according to JIS K 6262.
Judgment Criteria ◯: The amount of change is 50 or less.
x: The amount of change is 50 or more.

(wear resistance)
A dummy seal (test piece, n = 4) was prepared using a rubber composition, and a wear resistance tester as shown in Fig. 2 was used to rotate the test piece while applying a load with a friction plate, The amount of wear (mm) was confirmed.
Load: 400 gf, Rotational speed: 5000 rpm, 1 hour
Judgment criteria ◯: 0.02 mm or less △: More than 0.02 mm and less than 0.023 mm ×: 0.03 mm or more and less than 0.10 mm XX: 0.10 mm or more

(Metal rust evaluation)
The rubber sheet was crimped onto an SPCC steel plate (size 20 mm×100 mm×2 mm).
Next, place it in an environment with a relative humidity of 95% or more at 85 ° C. for 24 hours, and visually check the surface of the crimped SPCC steel plate. x” was evaluated.

From the results shown in Table 1, it can be seen that the rubber sheets obtained in Examples 1 to 6 are all excellent in electrical conductivity and abrasion resistance.
Above all, the rubber sheets obtained in Examples 1 to 5 are excellent in heat resistance, water resistance, distortion resistance, and metal rust prevention of the core metal portion to which the rubber sheet is fixed. .
On the other hand, the rubber sheets obtained in Comparative Examples 1 to 4, which contain carbon black with a DBP oil absorption of less than 200 ml/100 g, have better wear resistance than the rubber sheets obtained in Examples 1 to 6. was inferior.
In addition, compared with the rubber sheets obtained in Examples 1 to 6, the rubber sheets obtained in Comparative Examples 5 to 7, which have a low carbon black content and have a DBP oil absorption of 200 ml/100 g or more and 500 ml/100 g or less, are: The electroconductivity was poor, such as a decrease in current due to repeated application.

1 Rolling bearing 2 Inner ring 3 Outer ring 4 Cage 5 Rolling element 6 Inner ring circumferential groove 7 Outer ring circumferential groove 10 Grease 11 Seal member 12 Core metal 13 Elastic body 14 Main lip 15 Dust lip 15A Groove 16 Outer diameter lip A Annular opening

Claims (5)

A rubber composition for forming a sealing member of a rolling bearing,
Carbon black containing 100 parts by mass of rubber containing acrylic acid ester as a main component and 20 to 40 parts by mass of carbon black having a DBP oil absorption of 200 ml/100 g or more and 500 ml/100 g or less and having a DBP oil absorption of less than 200 ml/100 g A rubber composition for a sealing member of a rolling bearing, characterized in that it contains no 2. The rubber composition for a sealing member of a rolling bearing according to claim 1, wherein said acrylic acid ester is an acrylic acid ester having a carboxyl group. 3. The rubber composition for a sealing member of a rolling bearing according to claim 1, further comprising 5 to 100 parts by mass of a white filler. The rubber composition for a sealing member of a rolling bearing according to any one of claims 1 to 3, further comprising 0.1 to 5 parts by mass of a coupling agent. A bearing seal member molded from the rubber composition according to any one of claims 1 to 4,
A sealing member for a bearing, characterized by having a volume resistivity of 100Ω·cm or less.

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