JP4518788B2 - Rubber composition for low hardness seal - Google Patents

Description

  The present invention relates to a rubber composition for low-hardness seals mainly used as a sealing material for closures of electric wires and optical fiber cables.

  In the case of an electric wire, an optical fiber, etc., it is common to ensure insulation and waterproofness by winding the electric wire or optical fiber with a closure sealing material. The sealing material is excellent in airtightness and waterproofness, and a low hardness material having a rubber hardness of 0 to 10 degrees according to a type A durometer is widely used. The sealing material is not only excellent in airtightness and waterproofness, but also needs to be able to be easily peeled off and wound again when changing the connection of an electric wire or an optical fiber. Furthermore, it is necessary that the sealing performance does not deteriorate even under low temperature and high temperature use conditions.

  For example, Patent Document 1 proposes a waterproof rubber composition containing high molecular weight ethylene-propylene-diene rubber having a Mooney viscosity above a certain level, paraffinic oil, and organic peroxide as essential components. The rubber composition is excellent in elasticity and can be reused.

  Patent Document 2 proposes a rubber composition for a low-hardness sealing material containing paraffin oil, a low-temperature stabilizer, sulfur and a sulfur compound with respect to ethylene-propylene-diene rubber. Here, the low-temperature stabilizer is liquid and is compatible with ethylene-propylene-diene rubber and has an unsaturated bond. Since this rubber composition has low hardness and elasticity, it is excellent in airtightness and waterproofness, and furthermore, the presence of a low temperature stabilizer effectively suppresses bleeding of paraffin oil at low temperatures.

However, the pour point of paraffinic oil is around -50 to -10 ° C, and the glass transition temperature (Tg) of ethylene-propylene-diene rubber generally used as a rubber composition for sealing is -59 to -50 ° C. Higher than that. Therefore, when paraffinic oil is mixed with ethylene-propylene-diene rubber, the low-temperature characteristics of the ethylene-propylene-diene rubber itself deteriorates, and there is a problem that airtightness is lowered under the use conditions exposed to low temperature, and it is exposed to high temperature. There is also a problem that paraffinic oil bleeds out from the rubber composition under certain use conditions.
Japanese Patent Laid-Open No. 4-126789 JP-A-11-302478

  The present invention solves the above-mentioned problems and provides a rubber composition for low-hardness sealing that can maintain airtightness and waterproofness at high levels under low and high temperature use conditions.

In the present invention, the mixing ratio (A) / (B) of the ethylene-propylene-diene rubber (A) and the butyl rubber (B) is within the range of 100/0 to 20/80 (A) and (B). Including 100 parts by weight of base rubber mixed with 100 parts by weight, 100 to 400 parts by weight of hydrocarbon oil having a pour point of -80 to -50 ° C, and 1 to 4 parts by weight of sulfur and / or sulfur compounds. The present invention relates to a rubber composition for hardness sealing. Further, the pour point of hydrocarbon oils wherein the pour point is -80 to-50 ° C. is preferably relates to low hardness sealing rubber composition is -80 to-50 ° C.. The mixing ratio (A) / (B) of ethylene-propylene-diene rubber and butyl rubber is more preferably in the range of 80/20 to 20/80.

  In the present invention, the glass transition temperature of ethylene-propylene-diene rubber is preferably in the range of −70 to −40 ° C., and the glass transition temperature of butyl rubber is preferably in the range of −80 to −60 ° C.

The rubber composition for low-hardness sealing of the present invention comprises a hydrocarbon oil having a pour point of −80 to −50 ° C. to a base rubber composed of ethylene-propylene-diene rubber or a mixture of ethylene-propylene-diene rubber and butyl rubber. By mixing, airtightness can be sufficiently maintained even after a cycle test that is repeatedly exposed to low and high temperatures. Therefore, excellent airtightness and waterproofness can be exhibited under use conditions exposed to low temperature or high temperature.

In the rubber composition of the present invention , a hydrocarbon oil having a pour point of −80 to −50 ° C. as a softening agent is added to a base rubber composed of ethylene-propylene-diene rubber or a mixture of ethylene-propylene-diene rubber and butyl rubber. To maintain airtightness during repeated cycles of low and high temperatures.

  In the base rubber used in the present invention, the mixing ratio (A) / (B) of the ethylene-propylene-diene rubber (A) and the butyl rubber (B) is 100/0 to 20/80, preferably 80/20 to It is set within the range of 20/80.

  When butyl rubber (B) is contained in the base rubber, the mechanical strength and impact resistance of the rubber composition are improved, and good workability is obtained and the durability is improved. However, if the content of butyl rubber (B) is more than 20/80 of (A) / (B), the rubber composition becomes too hard, and the workability deteriorates and the airtightness and waterproofness decrease. End up.

  The ethylene-propylene-diene rubber of the present invention preferably has a glass transition temperature of -70 to -40 ° C. When the glass transition temperature is −70 ° C. or higher, the rubber composition has sufficient hardness, and is excellent in workability and durability. Further, when the glass transition temperature is −40 ° C. or lower, the rubber composition has sufficient flexibility, so that it can be easily processed and good airtightness and waterproofness can be obtained.

  The ratio (a) / (b) between the ethylene structure content (a) and the propylene structure content (b) in the ethylene-propylene-diene rubber is preferably in the range of 50/50 to 70/30. In this case, the glass transition temperature of the ethylene-propylene-diene rubber can be lowered, and a certain level of physical strength can be ensured.

  The butyl rubber of the present invention preferably has a glass transition temperature of -80 to -60 ° C. The glass transition temperature is more preferably −75 ° C. or higher, and preferably −63 ° C. or lower. When the glass transition temperature is −80 ° C. or higher, the rubber composition has sufficient hardness and is excellent in processability and durability. Moreover, when it is -60 degrees C or less, a rubber composition has sufficient softness | flexibility, and is excellent in workability, airtightness, and waterproofness.

  The glass transition temperature can be measured, for example, by a DSC (Differential Scanning Calorimetry) method.

As an ethylene-propylene-diene rubber used in the present invention, a non-conjugated diene such as ethylidene norbornene (ENB), dicyclopentadiene (DCPD) or 1,4-hexadiene is added as a third component to form an unsaturated bond. Can be introduced. When a non-conjugated diene is used as the third component, vulcanization is accelerated by introducing an unsaturated bond into the molecule, and a rubber composition having good physical properties can be obtained. Among the ethylene-propylene-diene rubbers of the present invention, ENB-based copolymers are particularly preferable because they are superior in heat aging resistance compared to DCPD-based copolymers.

The low-hardness rubber composition for sealing of the present invention contains 100 to 400 parts by mass of hydrocarbon oil having a pour point of −80 to −50 ° C. with respect to 100 parts by mass of the base rubber. When the content of the hydrocarbon oil having a pour point of −80 to −50 ° C. is less than 100 parts by mass, the rubber composition becomes too hard, so that sufficient airtightness and waterproofness cannot be exhibited. On the other hand, when the amount is more than 400 parts by mass, the rubber composition becomes too soft, so that the physical properties become insufficient, the workability becomes worse and the durability is lowered.

The olefin liquid hydrocarbon oil is added as an essential component in order to maintain sufficient flexibility even when exposed to a low temperature of, for example, about −20 ° C., and to ensure airtightness and waterproofness. In the rubber composition of the present invention, the flow temperature of hydrocarbon oil having a pour point of −80 to −50 ° C. is relatively close to the glass transition temperature of ethylene-propylene-diene rubber and butyl rubber which are base rubbers. ing. Therefore, the low temperature stability can be remarkably improved as compared with the case where oil having a relatively high pour point such as paraffin hydrocarbon oil is used. In addition, hydrocarbon oils having a pour point of −80 to −50 ° C. have good compatibility with ethylene-propylene-diene rubber and butyl rubber, so that the pour point is −80 to −50 ° C. even under high temperature conditions. Hydrogen oil bleed is effectively suppressed. Therefore, the rubber composition of the present invention maintains stable physical properties under both low temperature and high temperature use conditions, and has excellent airtightness and waterproofness.

The pour point of hydrocarbon oils having a pour point of -80 to -50 ° C is preferably -80 ° C or higher, more preferably -75 ° C or higher, particularly -70 ° C or higher, and -50 ° C or lower, particularly -60. It is preferable that it is below ℃. When the pour point is −80 ° C. or higher, the rubber composition does not become too soft, so that sufficient durability can be obtained, and the pour point under high temperature conditions is −80 to −50 ° C. Oil bleed is prevented. Further, when the temperature is −50 ° C. or lower, sufficient flexibility can be imparted to the rubber composition, which facilitates processing and improves airtightness and waterproofness.

The pour point of a hydrocarbon oil having a pour point of −80 to −50 ° C. can be measured by, for example, a method according to JIS-K2269.

Examples of the hydrocarbon oil having a pour point of −80 to −50 ° C. particularly preferably used in the present invention include Barrel Process Oil “P-18” manufactured by Matsumura Oil Co., Ltd.

  In the rubber composition of the present invention, 1 to 4 parts by mass of sulfur and / or a sulfur compound is blended with respect to 100 parts by mass of the base rubber. When the blending amount of sulfur and / or sulfur compound is less than 1 part by mass, the rubber composition is too low in crosslink density, and the rubber composition cannot obtain sufficient physical properties. Since the rubber composition has a too high crosslinking density and the rubber composition becomes hard, sufficient airtightness and waterproofness cannot be obtained in any case.

  In addition, as sulfur compounds, tetramethyltylium disulfide (TMT), tetraethyltyramium disulfide (TET), tetrabutyltylium disulfide (TBT), and other tyrames such as dipentamethylenethiuram tetrasulfide, selenium diethyldithiocarbamate, Dithio acid salts such as tellurium diethyldithiocarbamate and selenium dimethyldithiocarbamate, and compounds such as morpholine disulfide and alkylphenol disulfide can be preferably used.

In the rubber composition of the present invention, a vulcanizing agent or a vulcanization accelerator other than sulfur and / or a sulfur compound is added alone or as a mixture of two or more kinds for the purpose of improving the physical properties by crosslinking the rubber component. Is possible.

  As the vulcanizing agent, oxime compounds such as p-quinonedioxime and p, p′-dibenzoylquinonedioxime, organic peroxides, and the like can be blended. For example, organic peroxides contribute to the crosslinking of rubber molecules in the same way as sulfur or sulfur compounds, but the binding of rubber molecules crosslinked by organic peroxides is compared to the binding of rubber molecules crosslinked by sulfur or sulfur compounds. And flexible. Therefore, when a rubber composition containing an organic peroxide is used for sealing an electric wire or an optical fiber, it has excellent coverage and adhesion, so that good airtightness can be obtained.

  Specific examples of the organic peroxide include benzoyl peroxide, dicumyl peroxide, di-t-butyl peroxide, t-butylcumyl peroxide, 2,5-dimethyl-2,5-di (t-butyl peroxide). Oxy) hexane, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, t-butylperoxybenzene, 2 , 4-dichlorobenzoyl peroxide, 1,1-di-t-butylperoxy-3,3,5-trimethylcyclohexane or n-butyl-4,4-di-t-butylperoxyvalerate. .

Examples of the vulcanization accelerator include guanidines such as diphenylguanidine, cyclohexylbenzothiazylsulfenamide (CZ), N-oxydiethylenebenzothiazyl-2-sulfenamide (NS), Nt-butyl-2- Sulfenamides such as benzothiazole sulfenamide (BNS), 2-mercaptobenzothiazole (M), dibenzothiazyl disulfide (DM), zinc salt of 2-mercaptobenzothiazole (MZ), 2-mercaptobenzothiazole Thiazole compounds such as cyclohexylamine salt (MH), sodium salt of 2-mercaptobenzothiazole (M-Na), 2- (2,4-dinitrophenyl) mercaptobenzothiazole (DBM), tetramethyltyrium disulfide (TMT) Tetraethyltyradium disulfide (TET), tetramethyltyrium monosulfide (TS), dipentamethylenetyramium tetrasulfide (TRA), etc., thiourea such as ethylenethiourea, diethylthiourea, zinc dimethyldithiocarbamate (PZ), diethyl In addition to dithiocarbamate compounds such as zinc dithiocarbamate (EZ), zinc di-n-butyldithiocarbamate (BZ), zinc ethylphenyldithiocarbamate (PX), tellurium diethyldithiocarbamate (TTTE), aldehyde-amines, Compounds such as aldehyde-ammonia, imidazoline, xanthate, and the like can be used.

  To the rubber composition of the present invention, an anti-aging agent such as an ozone-resistant agent or an antioxidant can be added for the purpose of imparting stability that can withstand long-term use. For example, specific antioxidants include aldol-α-naphthylamine (C), 1,2-dihydro-2,2,4-trimethylquinoline (RD), N-isopropyl-N′-phenyl-P-phenylenediamine. (3C), phenyl-β-naphthylamine (D), N, N′-diphenyl-P-phenylenediamine (DP) and the like.

In addition to these, inorganic fillers such as zinc white, talc and clay, color powder and the like may be added to the rubber composition as necessary. Further, a softening agent other than hydrocarbon oil having a pour point of −80 to −50 ° C. can be further added.

The rubber composition of the present invention can be produced, for example, by the following method. That is, first, after mixing the blended components of the rubber composition excluding hydrocarbon oil having a pour point of −80 to −50 ° C. with a kneader, a Banbury mixer, etc., carbonization having a pour point of −80 to −50 ° C. Hydrogen oil is kneaded while being added in 3 to 5 times, and formed into a tape shape or a sheet shape by compression molding or the like. Subsequently, for example, 150 to 170 ° C.
When the rubber component is crosslinked by heating for 20 to 60 minutes, a rubber composition rich in elasticity and elasticity can be obtained.

Alternatively, a hydrocarbon oil having a pour point of −80 to −50 ° C. may be previously contained in the rubber component, and then kneaded and molded together with other compounding components.

  Although the aspect which uses the rubber composition of this invention as a sealing material is not limited, For example, the method etc. which are used as composite materials with reinforcement materials, such as cloth with a rough mesh structure, are employable. In this case, it is particularly preferable because the wire or optical fiber can be wound uniformly with an appropriate tightening force, stable airtightness and waterproofness can be secured over a long period of time, and peeling and reuse are easy.

<Example>
(1) were kneaded with three liters kneader component pour point excluding the hydrocarbon oil is -80 to-50 ° C. from the ingredients of the composition of Preparation Table 1 (parts by mass) of the rubber composition, pour point A hydrocarbon oil having a temperature of −80 to −50 ° C. was added in three portions, and then kneaded. Subsequently, vulcanization molding was carried out at 160 ° C. for 60 minutes using a compression mold having a mold with a diameter of 35 mm and a width of 3 mm.

(Note 1) Non-oil extended rubber is EPDM (Ethylene-propylene-diene rubber “Esprene 532” manufactured by Sumitomo Chemical Co., Ltd. (mass ratio of ethylene structure / propylene structure = 50/50, glass transition temperature = about −62). ° C).
(Note 2) Paraffin-based oil and oil-extended rubbers are EPDM (Esylene-propylene-diene rubber “Esplen 670F” manufactured by Sumitomo Chemical Co., Ltd.) and paraffin-based Diana process oil “PW-380” manufactured by Idemitsu Kosan Co., Ltd. (Pour point -15 ° C., viscosity 381.6 cSt (40 ° C.)) 100 PHR oil extended rubber.
(Note 3) Butyl rubber is “IIR268” (glass transition temperature = −74 ° C.) manufactured by ExxonMobil.
(Note 4) The hydrocarbon oil having a pour point of −80 to −50 ° C. is a barrel process oil “P-18” manufactured by Matsumura Oil Co., Ltd., having a pour point of −65 ° C. and a viscosity of 18 cSt (40 ° C. ).
(Note 5) Paraffinic hydrocarbon oil is Diana Process Oil “PX-90” manufactured by Idemitsu Kosan Co., Ltd., having a pour point of −45 ° C. and a viscosity of 110 cSt (40 ° C.).
(Note 6) Carbon black (ISAF) is “Dia Black I” manufactured by Mitsubishi Chemical Corporation.
(Note 7) Carbon black (FEF) is “Seast SO” manufactured by Tokai Carbon Co., Ltd.
(Note 8) Zinc flower is “Zinc oxide type 2” manufactured by Mitsui Mining & Smelting Co., Ltd.
(Note 9) Stearic acid is “paulownia stearate” manufactured by NOF Corporation.
(Note 10) White gloss flower is "White gloss flower CC" manufactured by Shiraishi Kogyo Co., Ltd.
(Note 11) Antioxidant A is “Irganox 1010” (tetrakis- [methylene-3- (3,5-di-tert-butyl-4′-hydroxyphenyl) manufactured by Ciba Specialty Chemicals Co., Ltd. ) Propionate] methane).
(Note 12) Antioxidant B is “Irganox MD1024” (N, N′-bis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) manufactured by Ciba Specialty Chemicals Co., Ltd. ) Propionyl] hydrazine).
(Note 13) Powdered sulfur is “fine powdered sulfur 200 mesh” manufactured by Tsurumi Chemical Co., Ltd. (Note 14) The vulcanization accelerator (M) is “Noxeller M” (2-mercaptobenzothiazole) manufactured by Ouchi Shinsei Chemical Co., Ltd.
(Note 15) Vulcanization accelerator (TET) is “Noxeller TET” (tetraethylthiuram disulfide) manufactured by Ouchi Shinsei Chemical Co., Ltd.
(Note 16) The vulcanization accelerator (BZ) is “Noxeller BZ” (zinc dibutyldithiocarbamate) manufactured by Ouchi Shinsei Chemical Co., Ltd.
(Note 17) The vulcanization accelerator (TTTE) is “Noxeller TTTE” (tellurium diethyldithiocarbamate) manufactured by Ouchi Shinsei Chemical Co., Ltd.
(Note 18) The tackifier is “Tackol 250-III” manufactured by Taoka Chemical Industry Co., Ltd.

(2) Evaluation of tensile strength (TB) TB was measured based on JIS-K6251.

(3) Evaluation of elongation at break (EB) EB was measured based on JIS-K6251.

(4) Evaluation of Shore A hardness Shore A hardness was measured based on JIS-K6253.

(5) Evaluation of Asker C hardness Asker C hardness was measured based on JIS-K6253.

(6) Measurement of internal pressure of closure box Four test pieces each having a diameter of 35 mm and a width of 3 mm were stacked and attached to the seal portion of the closure box, and a 6 mm diameter optical fiber was passed through the center of the test piece. In this state, the internal pressure of the closure box is kept at 0.4 kg / cm 2, the temperature is raised from −20 ° C. to 60 ° C., and again −20 ° C.
The operation of lowering the temperature was repeated 100 cycles as one cycle. Of the 100 treatments, the number of treatments in which the closure box internal pressure could be maintained was evaluated. The results are shown in Table 1.

  In the examples, the internal pressure of the closure box remained even after 100 treatments, and significantly higher results were obtained compared to 1 to 35 in the comparative example. Therefore, it was confirmed that the rubber composition according to the present invention can maintain good hermeticity even under long-time low temperature-high temperature cycle conditions.

  The rubber composition for low-hardness seals of the present invention can exhibit excellent airtightness and waterproofness under use conditions exposed to low or high temperatures.

Claims (3)

A base material obtained by mixing (A) and (B) so that the mixing ratio (A) / (B) of ethylene-propylene-diene rubber (A) and butyl rubber (B) is in the range of 80/20 to 20/80. Rubber composition for low-hardness seals comprising 100 parts by weight of rubber, 100 to 400 parts by weight of hydrocarbon oil having a pour point of -80 to -50 ° C, and 1 to 4 parts by weight of sulfur and / or sulfur compounds object.   The rubber composition for low-hardness sealing according to claim 1, wherein the ethylene-propylene-diene rubber has a glass transition temperature in the range of -70 to -40 ° C. The rubber composition for low-hardness sealing according to claim 1 or 2 , wherein the butyl rubber has a glass transition temperature in the range of -80 to -60 ° C.