Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2000-03-31
2002-12-10
Henderson, Christopher (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C525S113000, C525S330400, C525S331800
Reexamination Certificate
active
06492454
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a rubber composition having high adhesiveness to a metal, high modulus, high compression set resistance and high heat resistance, which enables the production of rubber/metal composite products to be used in the fields that require heat resistance and oil resistance. The present invention further relates to the composition can be suitably used for the products such as hoses, belts, tires, rolls and mold goods, and a producing method thereof. The present invention also relates to a hose having excellent adhesiveness between an inner tube and the like comprising the rubber composition and a reinforcing layer and excellent heat resistance. The present invention further relates to a rubber compounding agent that is easy-handling and improves heat resistance and modulus of a rubber, and a rubber composition containing the same.
2. Description of the Related Art
In recent years, many rubber products such as hoses, belts, tires, rolls and mold goods come to be used under high temperature and high pressure and also together with an oil heated for a long time, and deterioration of rubber products under such conditions always brings significant problems. If deterioration of rubber products is remarkable, very much time and labor are needed for maintenance or replacement of such deteriorated rubber products. Sometimes deterioration of rubber products may cause a large accident.
Conventional polymers that can be durable to continuous use under such high temperature (about 120-150° C.) environment are acrylonitrile-butadiene copolymer rubber (NBR), ethylene-propylene copolymer rubber (EPM), ethylene-propylene-diene copolymer rubber (EPDM), acrylic rubber (ACM), ethylene-acrylic acid ester copolymer rubber (AEM), ethylene-acrylic acid ester-vinyl acetate copolymer rubber (ER), ethylene-vinyl acetate copolymer rubber (EVM), chlorosulfonated polyethylene rubber (CSM), chlorinated polyethylene rubber (CM) and hydrogenated acrylonitrile-butadiene copolymer rubber (HNBR) obtained by hydrogenating a conjugated diene portion of acrylonitrile-butadiene copolymer rubber (NBR).
In general, in rubber compositions, it is known that an organic peroxide-crosslinked rubber composition using an organic peroxide has excellent heat resistance as compared with a sulfur-vulcanized rubber composition using sulfur in vulcanization.
However, the organic peroxide-crosslinked rubber composition does not generally contain sulfur that reacts with a metal for adhesion. As a result, such an organic peroxide-crosslinked rubber composition has poor adhesiveness to a metal surface and does not adhere to a brass that is plated on a metal surface. Therefore, rubber products composed of a combination of such an organic peroxide-crosslinked rubber composition and a metal such as a brass-plated steel plate have defects in that separation occurs at the interface between a rubber layer and a plated layer, resulting in breakage of the goods.
Diene rubber widely used in rubber products have excellent adhesiveness to a metal but do not have excellent heat resistance if sulfur in an ordinary amount is used as a crosslinking agent and an adhesive promoter is also compounded for improving adhesiveness to a metal. Further, where an adhesive promoter is not compounded, the amount of sulfur compounded is decreased that the ordinarily used amount and a vulcanization accelerator such as a sulfur donor is used together, for the purpose of improving heat resistance, heat resistance is improved but adhesiveness to a metal is decreased, resulting in impairing adhesiveness. Also, if an organic peroxide is used as a crosslinking agent for the improvement of heat resistance, heat resistance is excellent but adhesiveness to a metal is poor.
On the other hand, non-diene rubbers have excellent heat resistance and hence are used in various uses. However, non-diene rubber is difficult for vulcanization with sulfur, and it is necessary to crosslink with an organic peroxide or the like. In other words, since sulfur giving good adhesiveness to a metal cannot be used as a crosslinking agent, it is extremely difficult to directly adhere non-diene rubber to a metal. Various proposals have been made on formulation for developing adhesiveness. For example, JP-A-55-125155 describes that a polymer composition comprising an organic peroxide-crosslinkable polymer, organic peroxide, an epoxy resin and 2,4-dimercapto-6-R-1,3,5-triazine has a good adhesiveness to brass. From the results of our investigation and the contents of description in examples of the JP-A, it is presumed that the good adhesiveness is due to utilization of a reaction of chlorine in a chlorine-containing polymer such as chlorinated polyethylene with 2,4-dimercapto-6-R-1,3,5-triazine, a reaction of 2,4-dimercapto-6-R-1,3,5-triazine with an epoxy resin and a reaction of 2,4-dimercapto-6-R-1,3,5-triazine with copper in brass. However, since a reaction for adhesion does not occur in the case of chlorine-free polymers, there is a defect that such an adhesiveness does not sufficiently satisfy the adhesiveness in the level presently required.
For example, wires used as a reinforcing material of rubber hoses are generally high carbon steel wires, and in many cases, the wires are plated with brass to improve adhesiveness to a rubber.
However, where hydrogenated acrylonitrile-butadiene copolymer rubber (HNBR) or ethylene-acrylic acid ester copolymer rubber (AEM) such as ethylene-methyl acrylate copolymer rubber, having excellent heat resistance are used as, for example, an inner tube of a hose, those rubber are non-diene rubber which do not have unsaturated bonds in the main chain or side chains, and therefore sulfur cannot be used as a crosslinking agent. As a result, the non-diene rubber does not adhere to a reinforcing layer comprising reinforcing steel wires plated with brass.
Thus, regardless of diene rubber or non-diene rubber, rubber is demanded to overcome the above-described problems and to satisfy both adhesiveness to a metal and heat resistance.
Further, from the point of light-weight of rubber compositions, demand for high rigidity of rubber compositions is increasing, and rubber compositions having high modulus are demanded. There are various techniques to improve modulus of rubber compositions but on the other hand, there is disadvantage of impairing other physical properties, particularly heat resistance. Thus, it is necessary to optimize the physical properties in every rubber composition while balancing the physical properties.
Crosslinking aids have conventionally be used in rubber compositions crosslinked with organic peroxide to improve modulus (ex. stress at 100% elongation). Bifunctional or multifunctional polymerizable monomers are generally used as the crosslinking aids. Of those, triallyl isocyanurate (TAIC) and triallyl cyanurate (TAC) are known as having high efficiency of co-crosslinking and particularly high effect to improve modulus. However, triallyl isocyanurate has a melting point in the vicinity of 25° C. and triallyl cyanurate has a melting point in the vicinity of 27° C. Therefore, there are the disadvantages that those compounds are liquid if temperature is high, which are difficult to mix with a solid material, and those compounds are solid if temperature is low, which are also difficult to mix with a solid material, thus handling properties are poor. It is thus desired to overcome those problems.
Further, where TAIC and/or TAC and silica are used together, handling properties not only TAIC and/or TAC but also silica become problem in many cases. Specifically, since silica has a strong hydrophilicity, there is the problem that it is difficult for silica to be uniformly dispersed in the case of mixing with a hydrophobic material, and there is also the problem that silica is scattered in air in working because of the bulkiness thereof.
On the other hand, there are many cases that organic peroxide-crosslinkable rubber compositions, particularly organic peroxide-crosslinkable rubber c
Ozawa Osamu
Saitoh Tomoji
Henderson Christopher
The Yokohama Rubber Co. Ltd.
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