Rubber composition and sealing material molded from the rubber composition

Abstract

To provide a rubber composition that is well prevented from fixing to a counterpart material in a low-temperature environment and also has excellent moldability.SOLUTION: A rubber composition contains (A) an ethylene propylene diene polymer and (B) a block copolymer having a silicone chain and a polymer block other than the silicone chain. Relative to 100 pts.mass of the (A) ethylene propylene diene polymer, the content of the (B) block copolymer having a silicone chain and a polymer block other than the silicone chain is 0.30 pt.mass or more and less than 9.0 pts.mass.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a rubber composition containing an ethylene propylene diene polymer and a block copolymer having a silicone chain, and in particular to a rubber composition which can give a molded material which has excellent moldability and resistance to sticking to mating materials in low-temperature environments. [Background technology]

[0002] Compositions containing ethylene propylene diene (EPDM) polymer as a main component are used as sealing materials such as O-rings and packings, for example, sealing materials used in valve bodies (shutoff valves) of valves that require water resistance, because of their excellent water resistance and mechanical properties. A valve that shuts off a fluid opens to allow the fluid to flow under certain conditions, and closes to shut off the flow of the fluid under other conditions.

[0003] However, when the shutoff valve of a valve is left in a closed state for an extended period of time, the adhesiveness of the sealing material, whose main component is EPDM polymer, means that while the shutoff valve is closed, it may stick to the mating material, such as a flow path component through which the fluid flows, making it difficult to open smoothly.In addition, since the shutoff valve of a valve is generally in a closed state when the valve is stored, when a product equipped with the valve is stored for an extended period of time, the valve body of the valve may stick to the mating material, making it difficult to open smoothly.

[0004] In view of this, a rubber molding has been proposed that is used in contact with a metal surface as a mating material, in which a release coating made of an olefin-based hydrocarbon compound having a melting point of 100° C. to 160° C. is integrally formed on the surface of the rubber molding (Patent Document 1). It is claimed that the rubber molding in Patent Document 1 can be used as a sealing material for valve bodies and can be prevented from sticking to mating materials even when in contact or pressure contact with a metal surface as a mating material for a long period of time.

[0005] However, when the shutoff valve of the valve is used in a low-temperature environment, the adhesiveness of the sealing material further increases, and the shutoff valve of the valve may strongly stick to the mating material and become fixed while the valve is closed. Even if the rubber composition of Patent Document 1 is used as a sealing material for the valve body, when the valve is closed for a long period of time in a low-temperature environment, the shutoff valve may still stick to the mating material, and there is a need for improvement in preventing sticking to the mating material in a low-temperature environment. In addition, since the adhesiveness of the sealing material further increases in a low-temperature environment, the rubber composition of Patent Document 1 has a problem that it cannot prevent the sticking between the mating material and the shutoff valve of the valve from becoming stronger during long-term storage of a product equipped with a valve, making it even more difficult to open the valve than when the product is stored in a normal temperature environment.

[0006] Furthermore, the rubber molding in Patent Document 1 is prepared by adding 3 to 20 parts by mass of an olefinic hydrocarbon compound having a melting point of 100°C to 160°C to 100 parts by mass of a rubber compound, vulcanizing and molding the composition to obtain a rubber molding, and then heating and maturing the rubber molding at a temperature equal to or higher than the melting point of the olefinic hydrocarbon compound to cause the olefinic hydrocarbon compound to exude onto the surface of the rubber molding, which is then cooled and solidified to integrally form a release coating, which poses the problem that molding the rubber molding is complicated and difficult.

[0007] Also, it has been considered to prevent the valve body from sticking to the mating material by performing a surface treatment or coating to prevent sticking. However, in the case of surface treatment or coating of the sealing material, problems may occur in the valve body's anti-sticking performance due to missing surface treatment or uneven application, so there was still a need to improve the ability to prevent the valve body from sticking to the mating material in a low-temperature environment. In addition, there was a problem that productivity could not be obtained because it was necessary to perform a surface treatment or coating on the sealing material separately.

[0008] On the other hand, when a shutoff valve of a valve is used in a low-temperature environment, it has been proposed to adopt a sub-valve structure that is resistant to factors that inhibit the return movement, such as adhesion of synthetic rubber, when returning from a closed valve to an open valve, even if the force with which the synthetic rubber valve body adheres to the valve seat increases at low temperatures (Patent Document 2).

[0009] However, even in Patent Document 2, there was still room for improvement in preventing adhesion to the valve seat, which is the mating material, in a low-temperature environment. Also, in order to prevent the valve body from sticking to the mating material by improving the valve structure as in Patent Document 2, there were problems such as the complexity of the valve design. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Application Publication No. 8-302045 [Patent Document 2] Japanese Patent Application Publication No. 9-303601 Summary of the Invention [Problem to be solved by the invention]

[0011] In view of the above circumstances, an object of the present invention is to provide a rubber composition which is excellent in preventing adhesion to a mating material in a low-temperature environment and which also has excellent moldability. [Means for solving the problem]

[0012] The gist of the configuration of the present invention is as follows. [1] A polymer composition comprising: (A) an ethylene propylene diene polymer; and (B) a block copolymer having a silicone chain and a polymer block other than a silicone chain; A rubber composition comprising (B) 0.30 parts by mass or more and less than 9.0 parts by mass of a block copolymer having a silicone chain and a polymer block other than a silicone chain, per 100 parts by mass of (A) the ethylene propylene diene polymer. [2] The rubber composition according to [1], wherein the (B) block copolymer having a silicone chain and a polymer block other than a silicone chain is (B1) a block copolymer having a silicone chain and a polyolefin chain. [3] The block copolymer (B1) having a silicone chain and a polyolefin chain, The following formula (1) [a1]-[b]-[a2] (1) (wherein, [a1] and [a2] each independently represent a polyolefin chain, and [b] represents a silicone chain), [4] The rubber composition according to any one of [1] to [3], wherein the block copolymer (B) having a silicone chain and a polymer block other than the silicone chain forms a complex with a polyolefin portion containing a polyolefin. [5] The rubber composition according to any one of [1] to [4], comprising 0.90 parts by mass or more and 6.0 parts by mass or less of the block copolymer (B) having a silicone chain and a polymer block other than the silicone chain, per 100 parts by mass of the ethylene propylene diene polymer (A). [6] The rubber composition according to [2] or [3], wherein the polyolefin chain contains a structural unit derived from an olefin having 2 to 20 carbon atoms. [7] The rubber composition according to any one of [1] to [6], further comprising a silicone oil. [8] The rubber composition according to any one of [1] to [7], which is used as a sealing material for a valve. [9] A molding material formed from the rubber composition according to any one of [1] to [8].

[10] The molding material according to [9], which is a valve sealing material. Effect of the Invention

[0013] According to an embodiment of the rubber composition of the present invention, the rubber composition includes (A) an ethylene propylene diene polymer and (B) a block copolymer having a silicone chain and a polymer block other than the silicone chain, and the rubber composition has excellent anti-sticking properties with respect to the mating material in a low temperature environment and has excellent moldability by including 0.30 parts by mass or more and less than 9.0 parts by mass of the block copolymer having a silicone chain and a polymer block other than the silicone chain relative to 100 parts by mass of the (A) ethylene propylene diene polymer. Therefore, when a molded body molded from the rubber composition of the present invention is attached to various equipment as a sealing material, for example, there is no need to perform a surface treatment or coating for preventing sticking on the sealing material, and the occurrence of problems in the anti-sticking performance of the sealing material can be prevented. In addition, the rubber composition of the present invention does not require a complicated molding process for the rubber molded product, and molding can be simplified. Furthermore, by using the rubber composition of the present invention, there is no need to change the design of equipment such as valves to impart anti-sticking properties to the mating material, and therefore the complication of equipment such as valves can be prevented.

[0014] According to an embodiment of the rubber composition of the present invention, the block copolymer (B) having a silicone chain and a polymer block other than the silicone chain is represented by the following formula (1): [a1]-[b]-[a2] (1) (wherein, [a1] and [a2] each independently represent a polyolefin chain, and [b] represents a silicone chain), the triblock copolymer further improves the ability to prevent adhesion to the mating material in a low-temperature environment, and also makes it possible to reliably obtain a rubber composition having excellent moldability.

[0015] According to an embodiment of the rubber composition of the present invention, the block copolymer (B) having silicone chains and polymer blocks other than silicone chains forms a complex with a polyolefin portion containing a polyolefin, thereby improving the dispersibility of the block copolymer (B) having silicone chains and polymer blocks other than silicone chains in the rubber composition, reliably improving the prevention of adhesion to the mating material in low temperature environments, and more reliably providing a rubber composition with excellent moldability.

[0016] According to an embodiment of the rubber composition of the present invention, by containing 0.90 parts by mass or more and 6.0 parts by mass or less of the block copolymer (B) having a silicone chain and a polymer block other than the silicone chain per 100 parts by mass of the ethylene propylene diene polymer (A), it is possible to achieve a well-balanced improvement in anti-sticking properties with respect to the mating material in a low temperature environment and moldability. [Brief description of the drawings]

[0017] [Figure 1] 1 is a side cross-sectional view illustrating a test method for evaluating anti-sticking properties in a low-temperature environment in the examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] The rubber composition of the present invention will be described in detail below. The rubber composition of the present invention contains (A) an ethylene propylene diene polymer and (B) a block copolymer having a silicone chain and a polymer block other than the silicone chain, and contains 0.30 parts by mass or more and less than 9.0 parts by mass of the block copolymer having a silicone chain and a polymer block other than the silicone chain per 100 parts by mass of the ethylene propylene diene polymer (A). In the rubber composition of the present invention, the ethylene propylene diene polymer is blended as a base polymer.

[0019] (A) Ethylene propylene diene polymer Ethylene propylene diene polymer is a ternary copolymer of ethylene, propylene and diene monomer. The diene monomer is a crosslinking monomer. The diene monomer used in the ethylene propylene diene polymer is not particularly limited, and examples thereof include cyclic dienes such as 5-ethylidene-2-norbornene, 5-propylidene-5-norbornene, dicyclopentadiene, 5-vinyl-2-norbornene, 5-methylene-2-norbornene, 5-isopropylidene-2-norbornene, and norbornadiene; and linear non-conjugated dienes such as 1,4-hexadiene, 4-methyl-1,4-hexadiene, 5-methyl-1,4-hexadiene, 5-methyl-1,5-heptadiene, 6-methyl-1,5-heptadiene, and 6-methyl-1,7-octadiene. These diene monomers may be used alone or in combination of two or more. The ethylene propylene diene polymer may include ethylene propylene diene rubber.

[0020] The Mooney viscosity (ML1+4 100°C) of the ethylene propylene diene polymer is not particularly limited, but the lower limit is preferably 30, particularly preferably 35, from the viewpoint of imparting flexibility to the molded article of the rubber composition of the present invention. On the other hand, the upper limit of the Mooney viscosity (ML1+4 100°C) of the ethylene propylene diene polymer is preferably 100, particularly preferably 70, from the viewpoint of preventing the molded article of the rubber composition of the present invention from becoming hard. The Mooney viscosity is a measure of the viscosity of the ethylene propylene diene polymer measured with a Mooney viscometer.

[0021] The content of the diene monomer in the ethylene propylene diene polymer is not particularly limited, but the lower limit is preferably 2.0 mass %, particularly preferably 5.0 mass %, from the viewpoint of imparting flexibility to the molded article of the rubber composition of the present invention, while the upper limit of the content of the diene monomer in the ethylene propylene diene polymer is preferably 20 mass %, particularly preferably 15 mass %, from the viewpoint of durability of the molded article of the rubber composition of the present invention.

[0022] (B) Block copolymer having silicone chains and polymer blocks other than silicone chains A block copolymer having a silicone chain and a polymer block other than the silicone chain (hereinafter, sometimes simply referred to as "block copolymer (B)") is a block copolymer having a silicone chain block and a polymer block other than the silicone chain. In addition, in the rubber composition of the present invention, 0.30 parts by mass or more and less than 9.0 parts by mass of the block copolymer (B) are blended with 100 parts by mass of the (A) ethylene propylene diene polymer. By blending 0.30 parts by mass or more and less than 9.0 parts by mass of the block copolymer (B) with 100 parts by mass of the (A) ethylene propylene diene polymer, a rubber composition having excellent anti-sticking properties with respect to a mating material in a low-temperature environment and excellent moldability can be obtained. Therefore, when a molded body molded from the rubber composition of the present invention is attached to various equipment such as a valve body as a sealing material, for example, there is no need to perform a surface treatment or coating for preventing sticking on the sealing material, and problems with the anti-sticking performance of the sealing material can be prevented. In addition, the rubber composition of the present invention does not require a complicated molding process for a rubber molded product, and molding can be simplified. Furthermore, by using the rubber composition of the present invention, it is no longer necessary to change the design of equipment such as valves in order to impart anti-sticking properties to the mating material, and therefore it is possible to prevent the equipment such as valves from becoming complicated.

[0023] Examples of polymer blocks other than silicone chains include polyolefin chains (olefin polymer blocks), and polymer blocks ((meth)acrylic polymer blocks) having as their constituent units monomers containing at least one (meth)acrylic monomer selected from the group consisting of acrylic acid, methacrylic acid, acrylates, and methacrylates. Among these, (B1) block copolymers having silicone chains and polyolefin chains are preferred from the viewpoint of reliably improving anti-sticking properties with respect to mating materials in low-temperature environments and moldability, and (B1) block copolymers having silicone chains and polyolefin chains are those represented by the following formula (1) from the viewpoint of further improving anti-sticking properties with respect to mating materials in low-temperature environments and reliably obtaining a rubber composition having even more excellent moldability: [a1]-[b]-[a2] (1) Particularly preferred is a triblock copolymer represented by the formula: (wherein [a1] and [a2] each independently represent a polyolefin chain, and [b] represents a silicone chain).

[0024] Examples of the olefins constituting the polyolefin chains of [a1] and [a2] include olefins having from 2 to 50 carbon atoms. Examples of the olefins having from 2 to 50 carbon atoms include ethylene, propylene, and α-olefins having from 4 to 50 carbon atoms. Examples of α-olefins having 4 to 50 carbon atoms include 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, 3,4-dimethyl-1-pentene, 4-methyl-1-hexene, 3-ethyl-1-pentene, 1-octene, 3-ethyl-4-methyl-1-pentene, 3,4-dimethyl-1-hexene, 4-methyl-1-heptene, 1-nonene, 3,4-dimethyl-1-heptene, 1-decene, 1-dodecene, 1-tridecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosene, vinylcyclohexane, etc. Among these, olefins having 2 to 20 carbon atoms are preferred, olefins having 2 to 12 carbon atoms are more preferred, ethylene, propylene, and α-olefins having 4 to 8 carbon atoms are even more preferred, and ethylene is particularly preferred. The olefins constituting the polyolefin chain may be used alone or in combination of two or more kinds.

[0025] The number average molecular weight of the polyolefin chain is not particularly limited, but is preferably from 100 to 500,000, more preferably from 200 to 100,000, even more preferably from 500 to 50,000, and particularly preferably from 700 to 10,000. The number average molecular weight is a molecular weight measured by gel permeation chromatography using orthodichlorobenzene as a solvent and expressed as a polyethylene equivalent value.

[0026] The polyolefin chains of [a1] and [a2] may be made up of the same or different olefin species, and the number average molecular weights of the polyolefin chains of [a1] and [a2] may be the same or different.

[0027] The triblock copolymer represented by formula (1) may be a graft copolymer in which a polyolefin chain (polymer block of olefin) is graft-polymerized to the silicone chain of [b]. The polyolefin chain graft-polymerized to the silicone chain of [b] may be a polyolefin chain composed of the above-mentioned olefin. The number-average molecular weight of the polyolefin chain graft-polymerized to the silicone chain of [b], as analyzed by gel permeation chromatography, is not particularly limited, but is preferably 100 to 500,000, more preferably 200 to 100,000, even more preferably 500 to 50,000, and particularly preferably 700 to 10,000. The polyolefin chain graft-polymerized to the silicone chain of [b] may be the same as or different from the olefin species constituting the polyolefin chain of [a1]. The polyolefin chain graft-polymerized to the silicone chain of [b] may be the same as or different from the average molecular weight of the polyolefin chain of [a1]. The polyolefin chain grafted onto the silicone chain of [b] may be the same as or different from the olefin species constituting the polyolefin chain of [a2]. The polyolefin chain grafted onto the silicone chain of [b] may be the same as or different from the average molecular weight of the polyolefin chain of [a2].

[0028] The ratio of the mass of the silicone chain to the mass of the polyolefin chain in the triblock copolymer represented by formula (1) is not particularly limited, but from the viewpoint of reliably improving the prevention of adhesion to the mating material in a low-temperature environment, it is preferably 5:95 to 95:5, and particularly preferably 10:90 to 90:10.

[0029] The block copolymer (B) may also be a block copolymer composite formed with a polyolefin portion containing polyolefin. The block copolymer (B) forms the block copolymer composite, which improves the dispersibility of the block copolymer (B) in the rubber composition, reliably improves the adhesion prevention with the mating material in a low-temperature environment, and further reliably obtains a rubber composition having excellent moldability. An example of the block copolymer composite is an embodiment in which the block copolymer (B) is wrapped in a membrane-like polyolefin portion. The polyolefin forming the polyolefin portion is a polyolefin chain that does not contain a silicone chain in its chemical structure, which is different from the polyolefin chain of the block copolymer (B). The block copolymer composite may maintain the structure of the block copolymer composite in the rubber composition of the present invention, or may not maintain the structure of the block copolymer composite, such as the block copolymer (B) being separated from the polyolefin portion.

[0030] Examples of the olefin forming the polyolefin portion include ethylene, propylene, and α-olefins having 4 to 20 carbon atoms. Examples of the α-olefins having 4 to 20 carbon atoms include 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, 3,4-dimethyl-1-pentene, 4-methyl-1-hexene, 3-ethyl-1-pentene, 1-octene, 3-ethyl-4-methyl-1-pentene, 3,4-dimethyl-1-hexene, 4-methyl-1-heptene, 1-nonene, 3,4-dimethyl-1-heptene, 1-decene, 1-dodecene, 1-tridecene, 1-tetradecene, and 1-hexadecene. Among these, ethylene, propylene, and α-olefins having 4 to 8 carbon atoms are preferred, and ethylene is particularly preferred. The olefins constituting the polyolefin portion may be used alone or in combination of two or more.

[0031] The ratio of the mass of the block copolymer (B) to the mass of the polyolefin portion in the block copolymer composite is not particularly limited, but is preferably 10:90 to 50:50, particularly preferably 20:80 to 40:60, in order to reliably improve the dispersibility of the block copolymer (B) in the rubber composition.

[0032] The amount of the block copolymer (B) is not particularly limited as long as it is in the range of 0.30 parts by mass or more and less than 9.0 parts by mass per 100 parts by mass of the ethylene propylene diene polymer (A), but the lower limit is preferably 0.60 parts by mass, more preferably 0.90 parts by mass, even more preferably 1.2 parts by mass, and particularly preferably 2.0 parts by mass, per 100 parts by mass of the ethylene propylene diene polymer (A), from the viewpoint of reliably improving the anti-sticking property with the mating material in a low-temperature environment. On the other hand, the upper limit of the amount of the block copolymer (B) is preferably 8.7 parts by mass, more preferably 8.0 parts by mass, per 100 parts by mass of the ethylene propylene diene polymer (A), from the viewpoint of reliably obtaining a rubber composition having excellent moldability, and more preferably 7.5 parts by mass, and particularly preferably 6.0 parts by mass, from the viewpoint of further improving the moldability of the rubber composition.

[0033] Optional ingredients In the rubber composition of the present invention, in addition to the ethylene propylene diene polymer (A) and the block copolymer (B) having a silicone chain and a polymer block other than the silicone chain, other components such as silicone oil may be blended as necessary. By blending silicone oil, the rubber composition can be excellent in anti-sticking property with the mating material in a warm environment and moldability, and the friction coefficient of the molded article of the rubber composition can be reduced.

[0034] Examples of silicone oils include dimethylpolysiloxane, methylphenylpolysiloxane, etc. Silicone oils are silicone chains that do not contain polymer blocks other than silicone chains in their chemical structure, and therefore differ from the silicone chains of the block copolymer (B).

[0035] In addition, in the rubber composition of the present invention, other components such as various additives, release agents, extenders, colorants, etc. may be appropriately added as required.

[0036] Examples of the various additives include crosslinking agents, crosslinking promoters, antiaging agents, plasticizers, UV stabilizers, antioxidants, deodorants, flame retardants, weather resistance agents, antistatic agents, slip agents, and ion exchange agents.

[0037] Method for preparing rubber composition Examples of the method 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, a Brabender, etc. Furthermore, if necessary, the above-mentioned components may be pre-kneaded before mixing and melt-kneading.

[0038] Rubber composition molding material The shape of the molded material of the rubber composition of the present invention is not particularly limited, and examples thereof include sheet, film, ring, ribbon, block, etc. The manufacturing method of the molded material 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 by using a known molding method such as extrusion molding, injection molding, injection compression molding, melt casting, inflation molding, compression molding, transfer molding, cast molding, etc. to manufacture the molded material.

[0039] Uses of rubber compositions The use of the rubber composition of the present invention is not particularly limited, and examples thereof include sealing materials used for valve bodies of valves such as solenoid valves, and materials for sealing members such as O-rings and packings. Therefore, examples of mating materials for moldings molded from the rubber composition of the present invention include flow path members through which fluids flow, and examples of the mating materials include metals such as stainless steel. From the above, it is possible to manufacture moldings, such as sealing materials for valve bodies of valves, and sealing members such as O-rings and packings, from the rubber composition of the present invention. EXAMPLES

[0040] Next, examples of the present invention will be described, but the present invention is not limited to these examples as long as the gist of the present invention is not exceeded.

[0041] Examples 1 to 7, Comparative Examples 1 to 2 The components shown in Table 1 below were mixed in the mixing ratios shown in Table 1 below, and melt-kneaded for 60 minutes using a kneader to prepare rubber compositions used in Examples 1 to 7 and Comparative Examples 1 to 2. The prepared rubber compositions were molded into square sheets (dimensions 200 mm x 200 mm) by press molding, and then subjected to primary vulcanization at 170°C for 10 minutes and secondary vulcanization at 150°C for 2 hours. Thereafter, the square molded bodies were punched to prepare hollow cylindrical test samples with a diameter of 15 mm, a hollow diameter of 9.9 mm, and a thickness of 2 mm. The numbers in Table 1 below indicate parts by mass.

[0042] Details of each component in Table 1 are as follows.

[0043] (A) Ethylene propylene diene polymer · NORDEL 6530XFC: High diene EPDM with 55% ethylene and 8.5% diene, manufactured by DOW.

[0044] (B) Block copolymer having silicone chains and polymer blocks other than silicone chains Exfora PE3027: A block copolymer complex in which a triblock copolymer represented by a polyethylene chain-silicone chain-polyethylene chain (corresponding to block copolymer (B)) is wrapped in a polyethylene film (corresponding to the polyolefin part), mass of the triblock copolymer represented by a polyethylene chain-silicone chain-polyethylene chain: mass of the polyethylene film = 30:70, Mitsui Chemicals Fine Co., Ltd.

[0045] The common components used in preparing the test samples of Examples 1 to 7 and Comparative Examples 1 and 2 and the amounts of the components blended are as follows: Body conditioning agent Silicon dioxide: 25 parts by weight.

[0046] The following components are various additives. -Anti-aging agent: 3.0 parts by mass. Crosslinking promoter: 7.3 parts by mass.

[0047] Plasticizer: 6.0 parts by mass. Coupling agent: 2.0 parts by mass. Crosslinking agent: 6.0 parts by mass.

[0048] The evaluation items of the test sample are as follows. (1) Prevention of adhesion to mating materials in low-temperature environments (anti-adhesion at low temperatures) The anti-sticking property of the test sample at low temperature was evaluated using an adhesion test jig. Fig. 1 is a side cross-sectional view explaining a test method using an adhesion test jig for evaluating anti-sticking property in a low temperature environment in the examples. Specifically, as shown in Fig. 1, a test sample 11 was set on the lower side in the direction of gravity of a ring-shaped protrusion protruding downwards of a metal plate 10 provided on the adhesion test jig 1. The contact area between the test sample 11 and the metal plate 10 was 1 cm2. 2The adhesion test jig 1 was set to 5 g. A stainless steel member weighing 5 g was used as the metal plate 10 functioning as the mating material in the adhesion test jig 1. A weight of 500 g (not shown) was further placed on the upper side of the metal plate 10 in the gravity direction, so that a stress F was applied from the metal plate 10 to the test sample 11. In this state, the test sample 11 was left in a thermostatic chamber at -40°C for 2 hours. After leaving it for 2 hours, the adhesion test jig 1 was immediately turned upside down, and a push-pull gauge was used to measure the load when the metal plate 10 peeled off from the test sample 11. The above load was measured for three test samples 11, and the low-temperature adhesion prevention property was evaluated from the average value.

[0049] Based on the load measurement results, the low-temperature adhesion prevention property was evaluated according to the following three-level criteria: When the test sample 11 was not adhered to the metal plate 10 and the metal plate 10 fell under its own weight, the load was set to 0 kgf. ◎: 1.00Kgf or less ○: More than 1.00Kgf but less than 1.50Kgf ×: More than 1.50Kgf

[0050] (2) Formability The moldability was evaluated by a press molding method using a mold, and was rated according to the following three-level criteria. ◎: No problems with molding ○: Moldable, but some release agent must be applied during molding. ×: Cannot be molded or requires application of conventional amount of release agent during molding

[0051] The evaluation results are shown in Table 1 below.

[0052] [Table 1]

[0053] As shown in Table 1 above, in the rubber compositions of Examples 1 to 7 in which 0.30 parts by mass or more and less than 9.0 parts by mass of a polyethylene chain-silicone chain-polyethylene chain triblock copolymer was blended with 100 parts by mass of ethylene propylene diene polymer, the low-temperature adhesion prevention of the molded body was evaluated as ◯ or higher, and a molded body excellent in adhesion prevention with a mating material in a low-temperature environment was obtained. In addition, in the rubber compositions of Examples 1 to 7, the moldability was also evaluated as ◯ or higher, and excellent moldability was obtained. In particular, in the rubber compositions of Examples 2 to 7 in which 0.90 parts by mass or more and less than 9.0 parts by mass of a polyethylene chain-silicone chain-polyethylene chain triblock copolymer was blended with 100 parts by mass of ethylene propylene diene polymer, the low-temperature adhesion prevention of the molded body was evaluated as ◎, and the adhesion prevention with a mating material in a low-temperature environment was further improved. Furthermore, in the rubber compositions of Examples 4 to 7, in which 3.0 parts by mass or more and less than 9.0 parts by mass of a polyethylene chain-silicone chain-polyethylene chain triblock copolymer was blended with 100 parts by mass of ethylene propylene diene polymer, the molded body did not adhere to the metal plate 10, and the metal plate 10 fell under its own weight, providing even better low-temperature sticking prevention properties.

[0054] Furthermore, in the rubber compositions of Examples 1 to 6 in which 0.30 parts by mass or more and 6.0 parts by mass or less of a polyethylene chain-silicone chain-polyethylene chain triblock copolymer was blended per 100 parts by mass of ethylene propylene diene polymer, the moldability was rated as ⊚, and the moldability was further improved.

[0055] On the other hand, as shown in Table 1 above, the rubber composition of Comparative Example 1, which did not contain a polyethylene chain-silicone chain-polyethylene chain triblock copolymer, did not provide low-temperature adhesion prevention, and it was found that when the amount of the polyethylene chain-silicone chain-polyethylene chain triblock copolymer to 100 parts by mass of ethylene propylene diene polymer was less than 0.30 parts by mass, adhesion prevention with the mating material in a low-temperature environment was not provided. Also, the rubber composition of Comparative Example 2, which contained 9.0 parts by mass of a polyethylene chain-silicone chain-polyethylene chain triblock copolymer to 100 parts by mass of ethylene propylene diene polymer, did not provide moldability. [Industrial Applicability]

[0056] The rubber composition of the present invention has excellent anti-sticking properties to mating materials in low-temperature environments, and can also have excellent moldability. Therefore, the rubber composition can be used in a wide range of fields, and is particularly useful in the fields of sealing materials such as valve bodies for valves used in low-temperature environments, and sealing members such as O-rings and packings. [Explanation of symbols]

[0057] 1. Sticking test fixture 10 Metal Plate 11 Test Sample

Claims

1. (A) an ethylene propylene diene polymer; and (B) a block copolymer having a silicone chain and a polymer block other than a silicone chain, A rubber composition comprising 0.90 parts by mass or more and less than 9.0 parts by mass of the block copolymer (B) having a silicone chain and a polymer block other than the silicone chain, per 100 parts by mass of the ethylene propylene diene polymer (A), the block copolymer (B) having a silicone chain and a polymer block other than the silicone chain is formed as a complex wrapped in a membrane-like polyolefin, the block copolymer (B) having a silicone chain and a polymer block other than a silicone chain is a block copolymer (B1) having a silicone chain and a polyolefin chain, The rubber composition, wherein the polyolefin chain contains a structural unit derived from an olefin having 2 to 20 carbon atoms.

2. The block copolymer (B1) having a silicone chain and a polyolefin chain is The following formula (1) [a1]-[b]-[a2] (1) 2. The rubber composition according to claim 1, which is a triblock copolymer represented by the formula: (wherein, [a1] and [a2] each independently represent a polyolefin chain, and [b] represents a silicone chain).

3. 3. The rubber composition according to claim 1 or 2, comprising 0.90 parts by mass or more and 6.0 parts by mass or less of the block copolymer (B) having a silicone chain and a polymer block other than the silicone chain, per 100 parts by mass of the ethylene propylene diene polymer (A).

4. The rubber composition according to claim 1 , further comprising a silicone oil.

5. The rubber composition according to any one of claims 1 to 4, which is used as a sealing material for a valve.

6. A molding material produced from the rubber composition according to any one of claims 1 to 5.

7. The molding material according to claim 6, which is a valve sealing material.

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