Ethylene/α-olefin/non-conjugated polyene random copolymer rubbers such as EPDM generally have excellent weathering resistance, heat resistance and ozone resistance, so that they are used for automobile industrial parts, industrial rubber products, electric insulating materials, building and civil engineering materials, rubberized fabrics and the like.
The conventional ethylene/α-olefin/non-conjugated polyene random copolymer rubbers are, however, inferior to silicone rubbers in the compression set resistance.
In order to remove this defect, utilization of peroxide crosslinking instead of sulfur vulcanization is effective. In this method, however, there is a problem that when hot-air crosslinking such as HAV (hot air vulcanization vessel) or UHF (ultra high frequency electromagnetic wave) is carried out, the rubber surface is not crosslinked or undergoes degradation, and as a result, the scratch resistance is markedly lowered. This is caused by that the peroxide does not participate in crosslinking and the rubber surface is brought into contact with oxygen to accelerate degradation. Therefore, if a crosslinking method wherein oxygen is blocked, such as steam crosslinking or lead covering crosslinking, is carried out, the scratch resistance of the rubber surface can be improved, but this method is disadvantageous in the production cost.
In Japanese Patent Laid-Open Publication No. 154855/1992, an olefin rubber composition comprising an EPDM/SiH/Pt compound, which is crosslinkable by hot air in HAV, is disclosed, but this rubber composition is not satisfactory in the scratch resistance and the compression set resistance.
In Japanese Patent Laid-Open Publication No. 33924/1995, it is described that a rubber capable of undergoing hot-air crosslinking and having excellent scratch resistance can be obtained by subjecting a rubber composition comprising an ethylene/propylene/diene copolymer rubber and a polysiloxane having at least one reactive group to peroxide crosslinking.
The present inventors have examined the invention described in this publication, and as a result, they have confirmed that though the crosslinking efficiency is increased by adding peroxide to the rubber composition, the peroxide radical causes addition reaction of siloxane and simultaneously produces polymer radical, so that the scratch resistance of the surface of the rubber product after crosslinking is not bearable in the practical use.
Depending upon uses of the rubber compositions comprising ethylene/α-olefin/non-conjugated polyene random copolymer rubbers, the rubber compositions are required to have excellent adhesion to rubbers or metals and to be free from softening deterioration after heat aging, namely, excellent in oil resistance after aging (after environmental deterioration).
In the uses of the rubber compositions comprising ethylene/α-olefin/non-conjugated polyene random copolymers rubbers, there are many parts manufactured by adhesion bonding of molded products of the rubber compositions to crosslinked rubbers or metals, and therefore adhesion properties are very important. For example, automobile weatherstrip materials are generally manufactured by vulcanizing extrusion-molded unvulcanized rubber in a continuous vulcanization vessel such as HAV or UHF, cutting the vulcanized rubber and bonding the in rubber. Therefore, a rubber of low adhesion strength may have a problem of break when fitted to automobile. Some constructional gaskets and automobile weatherstrip materials are manufactured by coextruding different rubber compositions to bond them utilizing crosslinking reaction.
On the other hand, rubbers of softening deterioration type whose degree of crosslinking is decreased after environmental deterioration become worse in the oil resistance with decrease of the degree of crosslinking.
By the way, a rubber product is generally designed in its compounding according to the hardness of the product. Therefore, in order to obtain a certain hardness, carbon black, silica, talc, clay, calcium carbonate or the like is used in consideration of a balance between cost and product properties. The reinforcements and fillers enumerated above contribute to increasing the product hardness in greater or lesser degree, but they increase a viscosity of a compounded rubber to thereby impair processability thereof. Further, these reinforcing agents and fillers also have a property of lowering extensibility that is important for rubber products.
On this account, techniques to increase the hardness of a rubber product and to decrease the viscosity of a compounded rubber are desired to be established.
By the way, the rubber products are desired to have excellent abrasion resistance in addition to the properties described above. The reason why the abrasion resistance is required is that, for example, automobile glass run channel or wiper blade is abraded on the portion which is slidably contacted with glass and as a result the product life is shortened.
In press molding or injection molding, the rubber composition is required to have excellent non-staining properties to mold.
As one cause of stain on the mold, accumulation of deteriorated rubber or compounding ingredients on the mold surface is known. With increase of the accumulated substances, the surface of the crosslinked rubber product is scratched, and the appearance thereof becomes bad. On this account, the mold must be frequently cleaned, and this cleaning time leads to increase of the production cost.
As a means to cope with stain on the mold, it is described in Japanese Patent Laid-Open Publication No. 116811/1999 that a silicone rubber is blended with an ethylene/α-olefin/non-conjugated polyene random copolymer rubber to provide a rubber composition hardly causing stain on the mold.
This rubber composition hardly stains the mold undoubtedly but has a defect of somewhat poor strength properties. As a reason of decrease of the strength properties, it is considered that, in the use of an organic peroxide crosslinking agent, the crosslinking rate of the ethylene/α-olefin/non-conjugated polyene random copolymer rubber is lower than that of the silicone rubber and has poor co-crosslinkability.
Accordingly, there is desired development of:                an ethylene/α-olefin/non-conjugated polyene random copolymer rubber composition which is capable of undergoing hot-air crosslinking (e.g., HAV or UHF) that is advantageous in the production cost and which has excellent scratch resistance and compression set resistance;        an ethylene/α-olefin/non-conjugated polyene random copolymer rubber composition which is capable of undergoing hot-air crosslinking (e.g., HAV or UHF) that is advantageous in the production cost and which is excellent in scratch resistance, compression set resistance, adhesion properties and oil resistance after environmental deterioration;        an ethylene/α-olefin/non-conjugated polyene random copolymer rubber composition which is capable of undergoing hot-air crosslinking (e.g., HAV or UHF) that is advantageous in the production cost and which is excellent in scratch resistance, compression set resistance, abrasion resistance and flowability; and        an ethylene/α-olefin/non-conjugated polyene random copolymer rubber composition which is capable of undergoing hot-air crosslinking (e.g., HAV or UHF) that is advantageous in the production cost, which is excellent in scratch resistance, compression set resistance and abrasion resistance and which exhibits excellent non-staining properties to mold and strength properties when subjected to press crosslinking molding or injection crosslinking molding.        
Moreover, there is also desired development of the following rubber compositions and uses thereof:                (1) a crosslinkable rubber composition for rubber vibration insulator, which has a high crosslinking rate and excellent productivity, is capable of undergoing hot-air crosslinking such as HAV (hot air vulcanization vessel) or UHF (ultra high frequency electromagnetic wave), and is capable of producing crosslinked rubber molded products having hitherto unknown excellent compression set resistance at low cost; and vibration insulating rubber products formed from the composition;        (2) a crosslinkable rubber composition for glass run, which has a high crosslinking rate and excellent productivity, is capable of undergoing hot-air crosslinking such as HAV (hot air vulcanization vessel) or UHF (ultra high frequency electromagnetic wave), and is capable of producing glass run products having good appearance free from stain by bleeding of a crosslinking agent or a vulcanizing agent and being mild to environment because of no release of a nitrosoamine compound suspected to be so-called carcinogenic material; and glass run products formed from the composition;        (3) a zinc oxide-free crosslinkable rubber composition for hose, which has a high crosslinking rate and excellent productivity, is capable of undergoing hot-air crosslinking such as HAV (hot air vulcanization vessel) or UHF (ultra high frequency electromagnetic wave), and is capable of producing crosslinked rubber molded products having excellent compression set, strength properties and heat aging resistance; and various hoses made from the rubber composition, such as automobile water hose, automobile brake hose, industrial air hose, water hose and steam hose;        (4) a crosslinkable rubber composition for weatherstrip sponge, which has a high crosslinking rate and excellent productivity, is capable of undergoing continuous crosslinking such as HAV (hot air vulcanization vessel) or UHF (ultra high frequency electromagnetic wave), and is capable of producing weatherstrip sponges having excellent compression set resistance and scratch resistance; and weatherstrip sponges which are crosslinked and expanded products of the rubber composition;        (5) a crosslinkable rubber composition for highly expanded sponge, which has a high crosslinking rate and excellent productivity, is capable of undergoing hot-air crosslinking such as HAV (hot air vulcanization vessel) or UHF (ultra high frequency electromagnetic wave), and is capable of producing highly expanded sponges of crosslinked rubber expanded products having excellent compression set resistance, expandability, non-staining properties (e.g., non-staining properties to metals) and strength properties; and highly expanded sponges of the composition (crosslinked rubber expanded products);        (6) a crosslinkable rubber composition for electric or electronic part, which has a high crosslinking rate and excellent productivity, is capable of undergoing hot-air crosslinking such as HAV (hot air vulcanization vessel) or UHF (ultra high frequency electromagnetic wave), and is capable of producing crosslinked rubber molded products for electric or electronic parts having excellent compression set resistance, electrical properties and strength properties; and electric or electronic parts comprising the composition, e.g., insulating electric or electronic parts such as electric wire covering materials and electric insulating rubber parts, and semi-conducting electric or electronic parts;        (7) a crosslinkable rubber composition for hydraulic cylinder seal, which has a high crosslinking rate and excellent productivity, is capable of undergoing hot-air crosslinking such as HAV (hot air vulcanization vessel) or UHF (ultra high frequency electromagnetic wave), and is capable of producing crosslinked rubber molded products having excellent heat aging resistance, compression set resistance, liquid resistance (ΔV) and strength properties; and hydraulic cylinder parts formed from the composition;        (8) a crosslinkable rubber composition for seal packing, which has a high crosslinking rate and excellent productivity, is capable of undergoing hot-air crosslinking such as HAV (hot air vulcanization vessel) or UHF (ultra high frequency electromagnetic wave), and is capable of producing crosslinked rubber molded products having excellent strength properties, scratch resistance, heat aging resistance, compression set resistance, chemical resistance and non-staining properties to mold; and seal packing parts formed from the composition;        (9) a rubber composition for constructional gasket, which has high glass holding power, is excellent in weathering resistance, creep resistance and colorability, and is stable to temperature change through the whole year; and construction gaskets produced from the rubber composition; and        (10) a rubber composition which is capable of producing polyolefin rolls having excellent heat resistance and elasticity; and rubber rolls produced from rubber composition.        
The present invention is intended to solve such problems associated with the prior art as mentioned above, and it is an object of the invention to provide a crosslinkable rubber composition, which has a high crosslinking rate and excellent productivity, is capable of undergoing hot-air crosslinking such as HAV (hot air vulcanization vessel) or UHF (ultra high frequency electromagnetic wave), and is capable of producing crosslinked rubber molded products having excellent compression set resistance, strength properties, heat resistance, weathering resistance and abrasion resistance. It is another object of the invention to provide automobile weatherstrip, hose, rubber vibration insulator, belt, sealing material, expanded product, covered electric wire, electric wire joint, electric insulating part and household rubber product each of which is formed from the rubber composition.
Further objects of the invention are as follows:
(1) To provide a crosslinkable rubber composition, which has a high crosslinking rate and excellent productivity, is capable of undergoing hot-air crosslinking (e.g., HAV or UHF), and is capable of producing crosslinked rubber molded products having excellent scratch resistance, compression set resistance, adhesion properties and oil resistance after deterioration; and to provide uses thereof (molded products thereof).
(2) To provide a crosslinkable rubber composition excellent in flowability, which has a high crosslinking rate and excellent productivity to produce crosslinked rubber molded products, is capable of undergoing hot-air crosslinking such as HAV or UHF, and is capable of producing crosslinked rubber molded products (including expanded products) having excellent compression set resistance, strength properties, heat resistance and weathering resistance; and to provide uses thereof.
(3) To provide a crosslinkable rubber composition excellent in non-staining properties to mold, which has a high crosslinking rate and excellent productivity to produce crosslinked rubber molded product, is capable of undergoing hot-air crosslinking (e.g., HAV or UHF), and is capable of producing crosslinked rubber molded products having excellent compression set resistance, strength properties, heat resistance, weathering resistance and abrasion resistance; and to provide uses thereof.
(4) To provide a crosslinkable rubber composition for vibration insulating rubber, which has a high crosslinking rate and excellent productivity, is capable of undergoing hot-air crosslinking such as HAV (hot air vulcanization vessel) or UHF (ultra high frequency electromagnetic wave), and is capable of producing crosslinked rubber molded products having hitherto unknown excellent compression set resistance at low cost; and to provide vibration insulating rubber products thereof.
(5) To provide a crosslinkable rubber composition for glass run, which has a high crosslinking rate and excellent productivity, is capable of undergoing hot-air crosslinking such as HAV or UHF, and is capable of producing glass run products having good appearance free from stain by bleeding of a crosslinking agent or a vulcanizing agent and being mild to environment because of no release of a nitrosoamine compound suspected to be so-called carcinogenic material; and to provide glass run products thereof.
(6) To provide a zinc oxide-free crosslinkable rubber composition for hose, which has a high crosslinking rate and excellent productivity, is capable of undergoing hot-air crosslinking such as HAV (hot air vulcanization vessel) or UHF (ultra high frequency electromagnetic wave), and is capable of producing crosslinked rubber molded products having excellent compression set, strength properties and heat aging resistance; and to provide various hoses formed from the composition, such as automobile water hose, automobile brake hose, industrial air hose, water hose and steam hose.
(7) To provide a crosslinkable rubber composition for weatherstrip sponge, which has a high crosslinking rate and excellent productivity, is capable of undergoing continuous crosslinking such as HAV (hot air vulcanization vessel) or UHF (ultra high frequency electromagnetic wave), and is capable of producing weatherstrip sponges having excellent compression set resistance and scratch resistance; and to provide weatherstrip sponges which are crosslinked and expanded products thereof.
(8) To provide a crosslinkable rubber composition for highly expanded sponge, which has a high crosslinking rate and excellent productivity, is capable of undergoing hot-air crosslinking such as HAV (hot air vulcanization vessel) or UHF (ultra high frequency electromagnetic wave), and is capable of producing highly expanded molded sponges of crosslinked rubber expanded products having excellent compression set resistance, expandability, non-staining properties (e.g., non-staining properties to metals) and strength properties; and to provide highly expanded sponges thereof (crosslinked rubber expanded products).
(9) To provide a crosslinkable rubber composition for electric or electronic part, which has a high crosslinking rate and excellent productivity, is capable of undergoing hot-air crosslinking such as HAV (hot air vulcanization vessel) or UHF (ultra high frequency electromagnetic wave), and is capable of producing crosslinked rubber molded products for electric or electronic parts having excellent compression set resistance, electrical properties and strength properties; and to provide electric or electronic parts formed from the composition, e.g., insulating electric or electronic parts such as electric wire covering materials and electric insulating rubber parts, and semi-conducting electric or electronic parts.
(10) To provide a crosslinkable rubber composition for hydraulic cylinder seal, which has a high crosslinking rate and excellent productivity, is capable of undergoing hot-air crosslinking such as HAV (hot air vulcanization vessel) or UHF (ultra high frequency electromagnetic wave), and is capable of producing crosslinked rubber molded products having excellent heat aging resistance, compression set resistance, liquid resistance (ΔV) and strength properties; and to provide hydraulic cylinder parts formed from the composition.
(11) To provide a crosslinkable rubber composition for seal packing having excellent non-staining properties to mold, which has a high crosslinking rate and excellent productivity, is capable of undergoing hot-air crosslinking such as HAV (hot air vulcanization vessel) or UHF (ultra high frequency electromagnetic wave), and is capable of producing crosslinked rubber molded products having excellent strength properties, scratch resistance, heat aging resistance, compression set resistance and chemical resistance; and to provide seal packing parts thereof.
(12) To provide a rubber composition for constructional gasket, which has high glass holding power, is excellent in weathering resistance, creep resistance and colorability, and is stable to temperature change through the whole year; and to provide construction gaskets produced from the rubber composition.
(13) To provide a rubber composition which is capable of producing polyolefin rolls having excellent heat resistance and elasticity; and to provide rubber rolls produced from rubber composition.