Rubber composition

Abstract

To provide a rubber composition that enables production of a rubber member exhibiting superior operability in reciprocating motion and sealability in reciprocating motion under a low-temperature environment without causing deterioration in mechanical strength and elongation properties at room temperature.SOLUTION: A rubber composition comprises an oil-extended ethylene-butene-diene rubber having an ethylene content of 42 mass% or more and 59 mass% or less and a diene content of 2.0 mass% or more and 13 mass% or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a rubber composition, and more particularly to a rubber composition that can provide rubber parts having excellent properties in low-temperature environments without impairing mechanical strength and elongation properties at room temperature. [Background technology]

[0002] Automobiles and other devices are sometimes equipped with rubber components that undergo reciprocating motion, such as release valves, check valves, and diaphragms. Furthermore, because automobiles and other devices are likely to be used not only in warm regions but also in cold regions, rubber components that undergo reciprocating motion and are installed in automobiles and other devices are required to maintain their reciprocating motion and sealing properties even in low-temperature environments.

[0003] However, materials that have traditionally been used for rubber components, such as ethylene propylene diene rubber, acrylonitrile-butadiene copolymer rubber, hydrogenated nitrile rubber, and fluororubber, have problems in that, for example, the balance between elongation characteristics and strength deteriorates in low-temperature environments, resulting in a decrease in the properties required of rubber components, such as reciprocating motion operability and sealing ability.

[0004] Therefore, a rubber composition has been proposed in which 2.5 to 7.5 parts by mass of an ethylene-α-olefin copolymer having a melting point of 100°C or higher and a glass transition temperature of -55°C or lower is used per 100 parts by mass of ethylene-butene-diene copolymer rubber (Patent Document 1).The rubber composition in Patent Document 1 claims that adding a predetermined amount of hydrocarbon polymer oil to the ethylene-butene-diene copolymer rubber makes it possible to obtain rubber members with excellent sealing properties in low-temperature environments.

[0005] However, rubber members using the rubber composition containing the hydrocarbon polymer oil of Patent Document 1 still exhibit reduced properties required of rubber members, such as reciprocating motion operability and sealing performance during reciprocating motion, in extremely low-temperature environments such as -40°C, and there was a need to improve low-temperature properties. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2019 / 216311 Summary of the Invention [Problem to be solved by the invention]

[0007] In view of the above circumstances, an object of the present invention is to provide a rubber composition from which a rubber member having excellent reciprocating motion operability and sealing property in reciprocating motion in a low-temperature environment can be obtained without impairing the mechanical strength and elongation characteristics at room temperature. [Means for solving the problem]

[0008] The gist of the rubber composition of the present invention is as follows. [1] A rubber composition comprising an oil-extended ethylene butene diene rubber having an ethylene content of 42% by mass or more and 59% by mass or less and a diene content of 2.0% by mass or more and 13% by mass or less. [2] The rubber composition according to [1], further comprising a non-oil-extended ethylene butene diene rubber. [3] The rubber composition according to [2], wherein the non-oil-extended ethylene butene diene rubber has an ethylene content of 42% by mass or more and 59% by mass or less and a diene content of 2.0% by mass or more and 13% by mass or less. [4] The rubber composition according to [2] or [3], comprising 1.0 part by mass or more and 2500 parts by mass or less of the non-oil-extended ethylene butene diene rubber per 100 parts by mass of the rubber component of the oil-extended ethylene butene diene rubber. [5] The rubber composition according to [2] or [3], comprising 5.0 parts by mass or more and 1,000 parts by mass or less of the non-oil-extended ethylene butene diene rubber per 100 parts by mass of the rubber component of the oil-extended ethylene butene diene rubber. [6] The rubber composition according to any one of [1] to [3], further comprising carbon black. [7] The rubber composition according to [1], further comprising 10 parts by mass or more and 100 parts by mass or less of carbon black per 100 parts by mass of the rubber component of the oil-extended ethylene butene diene rubber. [8] The rubber composition according to [1], further comprising 26 parts by mass or more and 70 parts by mass or less of carbon black per 100 parts by mass of the rubber component of the oil-extended ethylene butene diene rubber. [9] The rubber composition according to [2], further comprising 10 parts by mass or more and 80 parts by mass or less of carbon black per 100 parts by mass of the rubber component of the oil-extended ethylene butene diene rubber and the non-oil-extended ethylene butene diene rubber combined.

[10] The rubber composition according to [2], further comprising 26 parts by mass or more and 55 parts by mass or less of carbon black per 100 parts by mass of the rubber component of the oil-extended ethylene butene diene rubber and the non-oil-extended ethylene butene diene rubber combined.

[11] The rubber composition according to [6], wherein the carbon black has an arithmetic mean particle size of 20 nm or more and 50 nm or less.

[12] The rubber composition according to any one of [1] to [3], which is for a rubber umbrella valve constituting a check valve device. [Effects of the Invention]

[0009] According to an embodiment of the rubber composition of the present invention, by containing oil-extended ethylene butene diene rubber having an ethylene content of 42% by mass or more and 59% by mass or less and a diene content of 2.0% by mass or more and 13% by mass or less, it is possible to obtain a rubber member that has excellent reciprocating motion operability and sealing properties during reciprocating motion in a low-temperature environment without compromising mechanical strength and elongation properties in a room-temperature environment.

[0010] According to an embodiment of the rubber composition of the present invention, the rubber composition further contains non-oil-extended ethylene butene diene rubber, thereby reliably improving the operability during reciprocating motion and the sealing performance during reciprocating motion in a low-temperature environment.

[0011] According to an embodiment of the rubber composition of the present invention, the ethylene content of the non-oil-extended ethylene butene diene rubber is 42% by mass or more and 59% by mass or less, and the diene content is 2.0% by mass or more and 13% by mass or less, thereby further reliably improving the operability of reciprocating motion and the sealing performance during reciprocating motion in a low-temperature environment.

[0012] According to an embodiment of the rubber composition of the present invention, the rubber composition contains 1.0 part by mass or more and 2500 parts by mass or less of the non-oil-extended ethylene butene diene rubber per 100 parts by mass of the rubber component of the oil-extended ethylene butene diene rubber, thereby more reliably improving the operability in reciprocating motion and the sealing performance during reciprocating motion in a low-temperature environment.

[0013] According to an embodiment of the rubber composition of the present invention, the rubber composition contains 5.0 parts by mass or more and 1,000 parts by mass or less of the non-oil-extended ethylene butene diene rubber per 100 parts by mass of the rubber component of the oil-extended ethylene butene diene rubber, thereby reliably improving the operability in reciprocating motion and the sealing performance during reciprocating motion in a low-temperature environment, and further improving the mechanical strength and elongation properties in a room-temperature environment.

[0014] According to an embodiment of the rubber composition of the present invention, by further containing carbon black, mechanical strength in a room temperature environment can be more reliably obtained.

[0015] According to an embodiment of the rubber composition containing the oil-extended ethylene butene diene rubber of the present invention, the rubber composition further contains 10 parts by mass or more and 100 parts by mass or less of carbon black per 100 parts by mass of the rubber component of the oil-extended ethylene butene diene rubber, whereby mechanical strength under room temperature conditions can be more reliably obtained.

[0016] According to an embodiment of the rubber composition containing the oil-extended ethylene butene diene rubber of the present invention, the rubber composition further contains 26 parts by mass or more and 70 parts by mass or less of carbon black per 100 parts by mass of the rubber component of the oil-extended ethylene butene diene rubber, whereby the mechanical strength and elongation properties under room temperature environment are further improved.

[0017] According to an embodiment of the rubber composition of the present invention containing the oil-extended ethylene butenediene rubber and the non-oil-extended ethylene butenediene rubber, the rubber composition further contains 10 parts by mass or more and 80 parts by mass or less of carbon black relative to a total of 100 parts by mass of the rubber component of the oil-extended ethylene butenediene rubber and the non-oil-extended ethylene butenediene rubber, thereby reliably improving the operability and sealing performance during reciprocating motion in a low-temperature environment and more reliably obtaining mechanical strength in a room-temperature environment.

[0018] According to an embodiment of the rubber composition of the present invention containing the oil-extended ethylene butenediene rubber and the non-oil-extended ethylene butenediene rubber, the rubber composition further contains 26 parts by mass or more and 55 parts by mass or less of carbon black relative to 100 parts by mass of the total of the rubber component of the oil-extended ethylene butenediene rubber and the non-oil-extended ethylene butenediene rubber, thereby reliably improving the operability in reciprocating motion and the sealing performance during reciprocating motion in a low-temperature environment, while further improving the mechanical strength and elongation properties in a room-temperature environment.

[0019] According to an embodiment of the rubber composition of the present invention, the arithmetic mean particle diameter of the carbon black is 20 nm or more and 50 nm or less, whereby the operability of reciprocating motion and sealing performance during reciprocating motion in a low-temperature environment are reliably improved, while mechanical strength in a room-temperature environment can be more reliably obtained. DETAILED DESCRIPTION OF THE INVENTION

[0020] The rubber composition of the present invention will be described in detail below.

[0021] The rubber composition of the present invention contains an oil-extended ethylene butene diene rubber (oil-extended EBDM) having an ethylene content of 42% by mass or more and 59% by mass or less and a diene content of 2.0% by mass or more and 13% by mass or less. According to an embodiment of the rubber composition of the present invention, the inclusion of the oil-extended ethylene butene diene rubber having an ethylene content of 42% by mass or more and 59% by mass or less and a diene content of 2.0% by mass or more and 13% by mass or less makes it possible to obtain a rubber member that exhibits excellent reciprocating motion operability and sealing ability during reciprocating motion in a low-temperature environment without impairing the mechanical strength and elongation properties in a room-temperature environment.

[0022] Each component of the rubber composition of the present invention will be described in detail below.

[0023] <Oil-extended ethylene butene diene rubber (oil-extended EBDM)> In the rubber composition of the present invention, an oil-extended ethylene butene diene rubber having an ethylene content of 42% by mass or more and 59% by mass or less and a diene content of 2.0% by mass or more and 13% by mass or less is blended as the oil-extended ethylene butene diene rubber. That is, as the rubber component of the oil-extended ethylene butene diene rubber, an ethylene content of 42% by mass or more and 59% by mass or less and a diene content of 2.0% by mass or more and 13% by mass or less is used.

[0024] The ethylene content of the ethylene butenediene rubber is not particularly limited as long as it is in the range of 42% by mass or more and 59% by mass or less, but the lower limit is preferably 45% by mass, and particularly preferably 47% by mass, from the viewpoint of reliably improving the reciprocating motion operability and sealing performance in a low-temperature environment while obtaining mechanical strength and elongation properties in a room-temperature environment. On the other hand, the upper limit of the ethylene content of the ethylene butenediene rubber is preferably 57% by mass, and particularly preferably 55% by mass, from the viewpoint of reliably improving the reciprocating motion operability and sealing performance in a low-temperature environment while obtaining mechanical strength and elongation properties in a room-temperature environment of a rubber member obtained from the rubber composition of the present invention.

[0025] The diene content of the ethylene butene diene rubber is not particularly limited as long as it is in the range of 2.0% by mass or more and 13% by mass or less. However, from the viewpoint of reliably improving the reciprocating motion operability and sealing performance of the rubber member obtained from the rubber composition of the present invention in a low-temperature environment, the diene content is preferably 2.5% by mass or more and 10% by mass or less, and particularly preferably 3.0% by mass or more and 8.0% by mass or less.

[0026] The amount of oil extension (phr) of the oil-extended ethylene butene diene rubber is not particularly limited, but from the viewpoint of ensuring that the rubber member obtained from the rubber composition of the present invention has mechanical strength and elongation properties in a room temperature environment while reliably improving the operability of reciprocating motion and sealing performance in a low temperature environment, the amount of oil extension is preferably 10 parts by mass or more and 50 parts by mass or less, and particularly preferably 20 parts by mass or more and 40 parts by mass or less, per 100 parts by mass of the ethylene butene diene rubber.

[0027] Mooney viscosity (ML) of oil-extended ethylene butene diene rubber 1+4 , 125°C) is not particularly limited, but the lower limit thereof is preferably 30, particularly preferably 40, from the viewpoint of reliably improving the mechanical strength and elongation properties in a room temperature environment. 1+4 , 125°C) is preferably 65, particularly preferably 55, from the viewpoint of processability. 1+4 , 125°C) are values ​​measured in accordance with JIS K-6300-1.

[0028] Examples of the oil type of the oil component of the oil-extended ethylene butene diene rubber include mineral oil.

[0029] <Non-oil-extended ethylene butene diene rubber (non-oil-extended EBDM)> The rubber composition of the present invention may further contain, in addition to the oil-extended ethylene butenediene rubber, a non-oil-extended ethylene butenediene rubber, if necessary. By including the non-oil-extended ethylene butenediene rubber, the mechanical strength at room temperature is improved, and the operability in reciprocating motion and the sealing performance during reciprocating motion at low temperatures are reliably improved.

[0030] The ethylene content of the non-oil-extended ethylene butenediene rubber is not particularly limited, but the lower limit is preferably 42% by mass, more preferably 45% by mass, and particularly preferably 47% by mass, from the viewpoint of further improving reciprocating operability and sealing performance in a low-temperature environment while maintaining mechanical strength and elongation properties in a room-temperature environment. On the other hand, the upper limit of the ethylene content of the non-oil-extended ethylene butenediene rubber is preferably 59% by mass, more preferably 57% by mass, and particularly preferably 55% by mass, from the viewpoint of further improving reciprocating operability and sealing performance in a low-temperature environment while maintaining mechanical strength and elongation properties in a room-temperature environment.

[0031] The diene content of the non-oil-extended ethylene butene diene rubber is not particularly limited, but from the viewpoint of further reliably improving the operability of reciprocating motion and the sealing performance during reciprocating motion in a low-temperature environment, it is preferably from 2.0% by mass to 13% by mass, more preferably from 2.5% by mass to 10% by mass, and particularly preferably from 3.0% by mass to 8.0% by mass.

[0032] Mooney viscosity (ML) of ethylene butene diene rubber 1+4 , 100°C) is not particularly limited, but the lower limit thereof is preferably 15, particularly preferably 20, from the viewpoint of reliably improving the mechanical strength and elongation properties in a room temperature environment. On the other hand, the Mooney viscosity (ML 1+4 , 100°C), is preferably 50, particularly preferably 40, from the viewpoint of processability.

[0033] The amount of non-oil-extended ethylene butene diene rubber is not particularly limited, but the lower limit thereof is preferably 1.0 part by mass, more preferably 5.0 parts by mass, and even more preferably 20 parts by mass, relative to 100 parts by mass of the rubber component of the oil-extended ethylene butene diene rubber, from the viewpoint of improving the mechanical strength in a room temperature environment while more reliably improving the operability in reciprocating motion and the sealing performance during reciprocating motion in a low temperature environment, and particularly preferably 50 parts by mass, from the viewpoint of improving the operability in reciprocating motion and the sealing performance during reciprocating motion in a low temperature environment in a balanced manner. On the other hand, the upper limit of the amount of non-oil-extended ethylene butene diene rubber per 100 parts by mass of the rubber component of oil-extended ethylene butene diene rubber is preferably 2500 parts by mass from the viewpoint of more reliably improving the operability in reciprocating motion and the sealing performance during reciprocating motion in a low-temperature environment, more preferably 1000 parts by mass from the viewpoint of further improving the mechanical strength and elongation properties in a room-temperature environment while reliably improving the operability in reciprocating motion and the sealing performance during reciprocating motion in a low-temperature environment, even more preferably 500 parts by mass from the viewpoint of further improving the operability in reciprocating motion in a low-temperature environment, and particularly preferably 90 parts by mass from the viewpoint of improving the operability in reciprocating motion in a low-temperature environment and the sealing performance during reciprocating motion in a balanced manner.

[0034] <Carbon black> The rubber composition of the present invention may further contain carbon black in addition to the oil-extended ethylene butene diene rubber, if necessary. By including carbon black, mechanical strength at room temperature can be more reliably obtained.

[0035] The amount of carbon black is not particularly limited, but for example, when the non-oil-extended ethylene butene diene rubber is not required, the lower limit is preferably 10 parts by mass per 100 parts by mass of the rubber component of oil-extended ethylene butene diene rubber from the viewpoint of more reliably obtaining mechanical strength at room temperature, and particularly preferably 26 parts by mass from the viewpoint of further improving mechanical strength and elongation properties at room temperature. On the other hand, when the non-oil-extended ethylene butene diene rubber is not required, the upper limit of the amount of carbon black is preferably 100 parts by mass, more preferably 70 parts by mass, and particularly preferably 60 parts by mass per 100 parts by mass of the rubber component of oil-extended ethylene butene diene rubber from the viewpoint of reliably improving reciprocating motion operability and sealing performance during reciprocating motion at low temperatures.

[0036] Furthermore, when a non-oil-extended ethylene butenediene rubber is further contained, the amount of carbon black is not particularly limited, but the lower limit is preferably 10 parts by mass, per 100 parts by mass of the rubber component of the oil-extended ethylene butenediene rubber and the non-oil-extended ethylene butenediene rubber, from the viewpoint of more reliably obtaining mechanical strength in a room temperature environment, and 26 parts by mass is particularly preferred from the viewpoint of further improving mechanical strength and elongation properties in a room temperature environment. On the other hand, when a non-oil-extended ethylene butenediene rubber is further contained, the upper limit of the amount of carbon black is preferably 80 parts by mass, per 100 parts by mass of the rubber component of the oil-extended ethylene butenediene rubber and the non-oil-extended ethylene butenediene rubber, from the viewpoint of reliably improving reciprocating motion operability and sealing performance during reciprocating motion in a low-temperature environment, and 55 parts by mass is particularly preferred. In the rubber composition of the present invention, since it further contains non-oil-extended ethylene butene diene rubber, excellent tensile strength can be obtained in the normal state even when the amount of carbon black compounded is reduced, and as a result, the operability in reciprocating motion and the sealing performance during reciprocating motion in a low-temperature environment are reliably improved.

[0037] The arithmetic mean particle size of the carbon black is not particularly limited, but is preferably 20 nm or more and 50 nm or less, and particularly preferably 22 nm or more and 45 nm or less, from the viewpoint of reliably improving the operability of reciprocating motion and the sealing performance during reciprocating motion in a low-temperature environment while more reliably obtaining mechanical strength in a room-temperature environment.

[0038] <Various additives> The rubber composition of the present invention may contain various additives as needed, such as a processing aid, a co-crosslinking agent, and a peroxide vulcanizing agent.

[0039] Examples of co-crosslinking agents include ethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, triallyl isocyanurate, 1,2-polybutadiene, N,N'-m-phenylene bismaleimide, etc. Examples of peroxide vulcanizing agents include dicumyl peroxide, tert-butyl peroxide, 2,5-dimethyl-2,5-di-tert-butylperoxyhexane, 2,5-dimethyl-2,5-di-tert-butylperoxyhexyne-3, tert-butylcumyl peroxide, 1,3-di-tert-butylperoxyisopropylbenzene, 2,5-dimethyl-2,5-dibenzoylperoxyhexane, ketone peroxide, peroxyketal, hydroperoxide, dialkyl peroxide, diacyl peroxide, peroxyester, peroxydicarbonate, etc.

[0040] Furthermore, various additives other than the processing aid, co-crosslinking agent, and peroxide vulcanizing agent may be added as necessary, such as a crosslinking accelerator, an antioxidant, a plasticizer, an antioxidant, and a flame retardant.

[0041] Next, a method for preparing the rubber composition of the present invention will be described. Examples of methods for preparing the rubber composition of the present invention include a method in which the above-mentioned components are mixed and melt-kneaded using a mixing / kneading means such as a single-screw extruder, a twin-screw extruder, a kneader, a roll mixer, a Banbury mixer, a tumbler mixer, or a Brabender. Furthermore, if necessary, the above-mentioned components may be pre-kneaded before being mixed and melt-kneaded.

[0042] Next, the molded material of the rubber composition of the present invention, i.e., the rubber member obtained from the rubber composition of the present invention, will be described. The shape of the molded material of the rubber composition of the present invention, i.e., the shape of the rubber member, is not particularly limited, and examples thereof include umbrella-shaped, cylindrical, sheet-shaped, film-shaped, ring-shaped, ribbon-shaped, and block-shaped. The method for producing a rubber member using the rubber composition of the present invention as a material is not particularly limited, and for example, the rubber composition prepared as described above can be molded into a predetermined shape using a known molding method such as extrusion molding, injection molding, injection compression molding, melt flow molding, inflation molding, compression molding, transfer molding, or cast molding to produce a rubber member.

[0043] The uses of the rubber composition of the present invention are not particularly limited, and examples thereof include rubber components that reciprocate within a predetermined space and rubber components that slide against other components. Specific examples include rubber umbrella valves that constitute check valve devices. Other uses of the rubber composition of the present invention include diaphragms, duckbill valves, gaskets, O-rings, packing, and vibration-isolating rubber. [Example]

[0044] Next, examples of the present invention will be described, but the present invention is not limited to these examples as long as the spirit of the present invention is not exceeded.

[0045] Examples 1 to 11, Comparative Examples 1 to 6 The components shown in Table 1 below were blended in the blending ratios shown in Table 1 below and kneaded using a kneader for 40 minutes to prepare rubber compositions used in Examples 1 to 11 and Comparative Examples 1 to 6. The numbers in Table 1 below indicate parts by mass.

[0046] Details of each component in Table 1 are as follows:

[0047] Non-oil exhibition EBDM K-9330M: Ethylene content 50% by mass, diene content 7.1% by mass, Mooney viscosity (ML 1+4 , 100℃)30, oil extension amount 0 mass%, Mitsui Chemicals, Inc. EPDM EPT-9090M: Non-oil extended ethylene propylene diene rubber, ethylene content 41% by mass, diene content 14% by mass, Mooney viscosity (ML 1+4 , 125℃)58, Mitsui Chemicals, Inc. oil exhibition ebdm K-8370EM: Ethylene content 51% by mass, diene content 4.7% by mass, Mooney viscosity (ML 1+4 , 125℃) 50, oil extension amount 30 mass%, Mitsui Chemicals, Inc.

[0048] Carbon Black Seast G-116 Carbon: Arithmetic mean particle diameter 38nm, Tokai Carbon Co., Ltd. · SEAT 6: Arithmetic mean particle size 22nm, Tokai Carbon Co., Ltd.

[0049] polymer oil Lucant LX-004: Ethylene and α-olefin co-oligomer (hydrocarbon polymer oil), Mitsui Chemicals, Inc.

[0050] Peroxide vulcanizing agent · Percumyl D-40: Dicumyl peroxide, NOF Corporation.

[0051] The evaluation items are as follows: (1) Normal tension test (normal tension) Tests were conducted in accordance with JIS K6251, and the tensile strength (mechanical strength) and elongation at room temperature were evaluated using the obtained tensile strength and elongation at break results according to the following criteria. Evaluation criteria for tensile strength at room temperature ×: Less than 10.0 MPa △: 10.0 MPa or more and less than 12.0 MPa 〇: 12.0 MPa or more and less than 16.0 MPa ◎: 16MPa or more Evaluation criteria for elongation at room temperature ×: Less than 200% △: 200% or more but less than 300% ○: 300% or more but less than 400% ◎: 400% or more

[0052] (2) Gehman torsion test Gehman torsion tests were conducted in accordance with JIS K 6261-3. Specifically, test specimens were prepared based on JIS K 6250, and the temperatures T2 (°C) and T10 (°C) corresponding to the torsion angle at 23±2°C and the torsion angles corresponding to moduli 2 and 10 times the torsion angle were measured. Using the T2 (°C) results, the operability in low-temperature environments was evaluated according to the following criteria. Evaluation criteria for operation in low temperature environments ×: Over -45.0℃ 〇: -50.0℃ or more -45.0℃ or less ◎: Less than -50℃

[0053] (3) TR test (low-temperature elastic recovery test) A TR test was conducted in accordance with JIS K 6261-4. Specifically, a test specimen was prepared based on JIS K 6250, and the resulting test specimen was cooled to -70°C while elongated by 50%, and then the temperature was increased to measure the temperature (TR10: unit °C) at which the specimen contracted 10% from the 50% elongation length (i.e., a 10% contraction rate). Using the results of T10 (°C) and TR10 (°C) from the Gehman torsion test, the sealing ability in a low-temperature environment was evaluated according to the following criteria. Note that the lower of the T10 and TR10 evaluation results was used to evaluate the sealing ability in a low-temperature environment. Evaluation criteria for sealing performance in low temperature environments T10 evaluation criteria ×: Over -56.5℃ 〇: -60.0℃ or more -56.5℃ or less ◎: Less than -60.0℃ TR10 evaluation criteria ×: Over -57.0℃ 〇: -60.0℃ or more -57.0℃ or less ◎: Less than -60.0℃

[0054] The measurement results are shown in Table 2 below, and the evaluation results are shown in Table 3 below.

[0055] [Table 1]

[0056] [Table 2]

[0057] [Table 3]

[0058] As shown in Tables 1 to 3, Examples 1 to 11, which are rubber compositions containing oil-extended ethylene butene diene rubber having an ethylene content of 42% by mass or more and 59% by mass or less and a diene content of 2.0% by mass or more and 13% by mass or less, had excellent tensile strength and elongation at room temperature, and also had excellent operability and sealing properties in low-temperature environments. From the above, Examples 1 to 11 had excellent tensile strength and elongation at room temperature, and also had excellent low-temperature properties.

[0059] In particular, in Examples 3 to 11, which are rubber compositions containing oil-extended ethylene butene diene rubber and non-oil-extended ethylene butene diene rubber having an ethylene content of 42% by mass or more and 59% by mass or less and a diene content of 2.0% by mass or more and 13% by mass or less, it was found that excellent tensile strength could be obtained under normal conditions even when the amount of carbon black compounded was reduced compared to Examples 1 and 2, which did not contain non-oil-extended ethylene butene diene rubber, and as a result, operability and sealing performance in low-temperature environments were reliably improved.

[0060] Furthermore, a comparison between Examples 3 to 10 and Example 11 shows that by containing 900 parts by mass or less of non-oil-extended ethylene butene diene rubber per 100 parts by mass of the rubber component of oil-extended ethylene butene diene rubber, the operability and sealing performance in low-temperature environments were reliably improved, while the mechanical strength and elongation properties in room-temperature environments were further improved.

[0061] Furthermore, Examples 3 to 10, which contain 27 parts by mass or more and 53 parts by mass or less of carbon black per 100 parts by mass of the total of the rubber component of oil-extended ethylene butene diene rubber and the non-oil-extended ethylene butene diene rubber, showed further improved mechanical strength and elongation properties at room temperature compared to Example 11, which contains 25 parts by mass of carbon black per 100 parts by mass of the total of the rubber component of oil-extended ethylene butene diene rubber and the non-oil-extended ethylene butene diene rubber.

[0062] On the other hand, in Comparative Examples 2 to 6, which were rubber compositions containing no oil-extended ethylene butenediene rubber, it was not possible to achieve both operability in low-temperature environments and sealing performance in low-temperature environments, and low-temperature properties could not be obtained.Furthermore, in Comparative Examples 1 and 4, which contained no oil-extended ethylene butenediene rubber and had a reduced amount of carbon black, it was not possible to obtain mechanical strength in a room-temperature environment. [Industrial Applicability]

[0063] The rubber composition of the present invention can provide rubber members that have excellent reciprocating motion operability and sealing properties during reciprocating motion in low-temperature environments without compromising mechanical strength and elongation properties in room-temperature environments. Therefore, the rubber composition of the present invention is highly useful in the field of rubber members that require reciprocating motion operability and sealing properties during reciprocating motion in extremely low-temperature environments such as -40°C.

Claims

1. A rubber composition comprising an oil-extended ethylene butene diene rubber having an ethylene content of 42% by mass or more and 59% by mass or less and a diene content of 2.0% by mass or more and 13% by mass or less.

2. The rubber composition according to claim 1, further comprising a non-oil-extended ethylene butene diene rubber.

3. The rubber composition according to claim 2, wherein the non-oil-extended ethylene butene diene rubber has an ethylene content of 42% by mass or more and 59% by mass or less and a diene content of 2.0% by mass or more and 13% by mass or less.

4. The rubber composition according to claim 2 or 3, comprising 1.0 part by mass or more and 2500 parts by mass or less of the non-oil-extended ethylene butene diene rubber per 100 parts by mass of the rubber component of the oil-extended ethylene butene diene rubber.

5. The rubber composition according to claim 2 or 3, comprising 5.0 parts by mass or more and 1000 parts by mass or less of the non-oil-extended ethylene butene diene rubber per 100 parts by mass of the rubber component of the oil-extended ethylene butene diene rubber.

6. The rubber composition according to any one of claims 1 to 3, further comprising carbon black.

7. The rubber composition according to claim 1, further comprising 10 parts by mass or more and 100 parts by mass or less of carbon black per 100 parts by mass of the rubber component of the oil-extended ethylene butene diene rubber.

8. The rubber composition according to claim 1, further comprising 26 parts by mass or more and 70 parts by mass or less of carbon black per 100 parts by mass of the rubber component of the oil-extended ethylene butene diene rubber.

9. The rubber composition according to claim 2, further comprising 10 parts by mass or more and 80 parts by mass or less of carbon black per 100 parts by mass of the rubber component of the oil-extended ethylene butene diene rubber and the non-oil-extended ethylene butene diene rubber combined.

10. The rubber composition according to claim 2, further comprising 26 parts by mass or more and 55 parts by mass or less of carbon black per 100 parts by mass of the total of the rubber component of the oil-extended ethylene butene diene rubber and the non-oil-extended ethylene butene diene rubber.

11. The rubber composition according to claim 6, wherein the carbon black has an arithmetic mean particle size of 20 nm or more and 50 nm or less.

12. The rubber composition according to any one of claims 1 to 3, which is used for a rubber umbrella valve constituting a check valve device.

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