Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
1998-12-15
2001-02-06
Nutter, Nathan M. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S194000, C525S240000, C525S241000, C425S543000, C425S383000, C425S392000, C264S230000
Reexamination Certificate
active
06184295
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a rubber composition, a rubber roller comprising the rubber composition and a method of manufacturing the rubber composition. More particularly, the present invention relates to a modification of the rubber composition for use in paper-feeding rubber rollers of office appliances such as laser printers, electrostatic copying machines, facsimiles using ordinary paper and automatic deposit payment machines (ATM).
2. Description of the Related Art
The rubber composition for use in the paper-feeding rollers of office appliances such as laser printers, electrostatic copying machines, facsimiles and automatic deposit payment machines (ATM) is demanded to have high wear resistance and friction coefficient. In recent years, especially office appliances for personal use are in wide use and various kinds of paper are used therefor. Thus, the rubber roller is demanded to have high wear resistance and friction coefficient to feed various kinds of papers reliably. When the surface of the paper-feeding rubber roller is worn owing to repeated use, the friction coefficient thereof deteriorates, and hence slip occurs, which deteriorates the paper-feeding force greatly. Further, it is necessary that the rubber roller does not deteriorate in its performance applying a load at a high temperature. That is, the rubber roller is required to have a low permanent compression set.
Thus, in order to provide the rubber roller with a high friction coefficient and a high wear resistance, there have been proposed rubber rollers comprising a rubber composition formed of a sulfur-vulcanized mixture of a rubber material and thermoplastic elastomer. For example, it is known that EPDM rubber is used as the rubber material and urethane thermoplastic elastomer (TPU) is used as the thermoplastic elastomer. Further it is known that styrene butadiene rubber (SBR) is used as the rubber material and urethan thermoplastic elastomer (TPU) is used as the thermoplastic elastomer.
However, because the TPU is hard, the hardness of each of the rubber rollers composed of these rubber compositions cannot be lowered to an appropriate degree and hence the it is impossible to provide the rubber rollers with a preferable paper-feeding performance. In the rubber rollers, the rubber composition vulcanized with sulfur has blooming to a high extent, which causes the friction coefficient of the rubber roller to deteriorate.
Further, because matrix resin consists of urethane, it is necessary to reduce the amount of the matrix resin to allow the rubber roller to have a low hardness required for roller use. Thus, a problem occurs in kneadability. Further, there is another problem that because the friction coefficient of urethane is not so high, the rubber roller is prevented from having an appropriate friction coefficient.
Further, it is known that a rubber composition comprises thermoplastic crystalline poly-olefin and EPDM rubber vulcanized with phenol resin vulcanizing agent. However, when a rubber roller comprising the rubber composition is used as a paper-feeding roller, generation of blooming can be restrained. But the poly-olefin serving as forming matrix, namely, polyethylene and polypropylene are hard. Thus, it is impossible to reduce the hardness of the rubber roller sufficiently and hence the rubber roller is incapable of having a preferable paper-feeding performance.
As described above, efforts have been made to enhance the friction coefficient of the rubber composition or the rubber roller and reduce a permanent compression set by blending vulcanized rubber such as vulcanized EPDM rubber and thermoplastic resin or thermoplastic elastomer with each other. But a paper-feeding rubber roller which is so soft as to obtain a high friction coefficient for contact of paper and does not give rise to blooming and is superior in wear resistance has not been developed. It is described in the above patent publication that the permanent compression set can be improved. But as a result of examination, it was revealed that the paper-feeding performance of the rubber roller was not reliable when it was left with applying a load thereto at a high temperature, supposing that the rubber rollers are transported to a client.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above-described object. It is an object of the present invention to inexpensively provide a rubber composition which can be molded into a paper-feeding rubber roller, which has a high friction coefficient, is superior in wear resistance, does not give rise to blooming, and has a low permanent compression set for use in office appliances, automatic deposit payment machines (ATM) and the like.
In order to achieve the object, the present inventors have energetically made researches and found that it is possible to improve a paper-feeding rubber roller for use in office appliances, automatic deposit payment machine (ATM), and the like in its wear resistance, friction coefficient, and permanent compression set and to provide a rubber composition molded into the rubber rollers at a low cost when the rubber of the paper-feeding rubber roller containing a specified amount of a mixture of hydrogenated styrene thermoplastic elastomer and poly-olefin used as forming matrix is dynamically vulcanized by resin vulcanization.
That is, the rubber composition according to the present invention contains 100 parts by weight of rubber, a mixture of hydrogenated styrene thermoplastic elastomer and poly-olefin in the range from 20 parts by weight to 200 parts by weight. The rubber is dynamically vulcanized with a resin vulcanizing agent to disperse it in the mixture of the hydrogenated styrene thermoplastic elastomer and the poly-olefin.
When the rubber composition is molded into a roller shape for using a rubber roller, the rubber roller can be used as a paper-feeding roller having preferable wear-resistance , friction coefficient, and permanent compression set and capable of preventing blooming, thus having superior paper-feeding performance.
As a method of producing the rubber composition, 100 parts by weight of rubber, a mixture of the hydrogenated styrene thermoplastic elastomer and the poly-olefin in the range from 20 parts by weight to 200 parts by weight, and the resin vulcanizing agent are heated while all of these materials are being kneaded to vulcanize the rubber dynamically. As a result, it is possible to obtain the rubber composition in which vulcanized fine particles of the vulcanized rubber are dispersed in the kneaded material. The method allows the rubber composition to be produced with ease and high productivity.
According to another present invention, 100 parts by weight of rubber, a mixture of the hydrogenated styrene thermoplastic elastomer, the poly-olefin, and a softener in the range from 20 to 300 parts by weight. The softener is added to the rubber in the range from 10 parts by weight to 200 parts by weight. The rubber is dynamically vulcanized with the resin vulcanizing agent to disperse it in the mixture of the hydrogenated styrene thermoplastic elastomer and the poly-olefin.
In the rubber composition to be thus produced, the dispersibility of the vulcanized rubber contained in the mixture of hydrogenated styrene thermoplastic elastomer and the poly-olefin is improved in the dynamic vulcanization. Thus, a rubber roller comprising the rubber composition molded into the shape of a roller has a higher wear resistance than a rubber roller comprising the rubber composition in above-mentioned rubber composition without the softener. Further, injection molding allows the fluidity of the rubber composition to be improved in molding it into the rubber roller, thus improving the moldability of injection molding.
As a method of manufacturing the rubber composition, 100 parts by weight of rubber, a mixture of the hydrogenated styrene thermoplastic elastomer, the poly-olefin, and a softener in the range from 20 parts by weight to 300 parts by weight. The softener is added to
Arent Fox Kintner Plotkin & Kahn
Nutter Nathan M.
Sumitomo Rubber Industries Ltd.
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