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
1998-07-10
2003-09-30
Lipman, Bernard (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...
C525S141000
Reexamination Certificate
active
06627702
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
Generally, the present invention relates to a rubber composition containing EPDM rubber (ethylene-propylene-diene copolymer rubber) as its main component. More particularly, the present invention relates to a rubber composition which does not bloom vulcanizing accelerator in vulcanizing the vulcanizing accelerator-added EPDM rubber with sulfur so that paper-feeding rubber rollers, comprising the rubber composition, of laser beam printers, electrostatic copying machines, facsimiles and automatic deposit/payment machines (ATM) have a high friction coefficient and a high wear resistance.
2. Description of the Related Art
A rubber composition comprising the EPDM rubber (ethylene-propylene-diene copolymer rubber) contained therein as its main component has been hitherto used in large quantities for a paper-feeding roller of OA equipments such as laser beam printers, electrostatic copying machines, and facsimiles; and automatic deposit/payment machines (ATM). This is because paper-feeding rollers of the OA equipments and the automatic deposit/payment machines comprising the rubber composition are highly resistant to wear and are not deteriorated fast by ozone which is generated in the OA equipments when they are operated to form images. That is, the rubber composition is highly resistant to the ozone. In order to obtain a high coefficient of friction in the friction between the paper-feeding roller comprising the rubber composition and paper, softening agent such as process oil is added to the EPDM rubber to reduce the hardness of the paper-feeding roller. Further, in order to improve the wear resistance of the paper-feeding roller, oil-extended EPDM rubber is used to compose the rubber composition.
The EPDM rubber is used by vulcanizing it with vulcanizing agent such as sulfur or organic peroxide to increase its physical property (in particular, mechanical property). In a mixture material comprising the EPDM rubber, the softening agent such as the process oil, plasticizer, and the like, the reaction of the organic peroxide is inhibited by the softening agent. Thus, sulfur is practically used. The EPDM rubber does not have a double bond in its main chain. The double bond is present only in third components such as DCPD (dicyclopentadiene), 1,4-HD (1,4-hexadiene), and ENB (ethylidene norbornene) which are added to the EPDM rubber as a diene component. Further, the technique of polymerizing the third component with the polymer has a limitation. Thus, even though the EPDM rubber having the greatest iodine number (iodine number: 35) is vulcanized with sulfur, the vulcanizing speed thereof is lower than that of a diene polymer such as NR (natural rubber) or BR (butadiene rubber). In order to increase the vulcanizing speed of the EPDM rubber, vulcanizing accelerator has been hitherto added to the EPDM rubber in addition to the sulfur (vulcanizing agent) by selecting an appropriate kind of the vulcanizing accelerator and optimizing the addition amount thereof.
However, because the vulcanizing accelerator has a high polarity, it is difficult for it to be present in the EPDM rubber having a low degree of polarity. Thus, the vulcanizing accelerator is not dispersed uniformly in the EPDM rubber which has not been vulcanized. Consequently, in a product obtained after vulcanizing the EPDM rubber, the vulcanizing accelerator and reaction product thereof bloom. The blooming of the vulcanizing accelerator and reaction product thereof causes the reduction in the friction coefficient of the paper-feeding roller of the OA equipments and the automatic deposit/payment machine (ATM) formed by molding the product (EPDM rubber), into a roller shape, containing the vulcanizing accelerator and the reaction product thereof which bloom.
A method of suppressing the blooming by adding filler such as silica having a preferable adsorbing property to the EPDM rubber is known. The method is capable of suppressing the generation of the blooming of the vulcanizing accelerator and the reaction product thereof, but causes the hardness of the rubber composition to be increasingly high as the addition amount of the filler increases. Therefore, the paper-feeding roller comprising the EPDM rubber molded into a roller shape and containing much amount of the filler cannot be allowed to have a high friction coefficient for paper.
A method of suppressing the blooming of the vulcanizing accelerator by adding a small amount of polyalkylene glycol or polyoxyethylene alkylene ether to the EPDM rubber is known. But these methods are incapable of providing satisfactory blooming-suppressing effect and in addition, cause the polyalkylene glycol or the polyoxyethylene alkylene ether to be separated out from the vulcanized rubber composition.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above-described situation. Therefore, it is an object of the present invention to provide a rubber composition containing EPDM rubber, as its main component, which can be vulcanized efficiently without generating blooming of vulcanizing accelerator added thereto so that a rubber roller comprising the rubber composition has a high friction coefficient and a high wear resistance.
In order to solve the above-described problem, there is provided a rubber composition comprising EPDM rubber contained therein as a main component thereof. Vulcanizing accelerator and 0.3-5.0 parts by weight of phenol resin are added to 100 parts by weight of the EPDM rubber. A mixture thereof is vulcanized with sulfur. The phenol resin is obtained through a two-step reaction, namely, addition reaction and condensation reaction of phenols and aldehydes.
Furthermore, there is provided a rubber composition comprising EPDM rubber contained therein as a main component thereof. Vulcanizing accelerator and 0.3-10.0 parts by weight of halogenated phenol resin are added to 100 parts by weight of the EPDM rubber. A mixture thereof is vulcanized with sulfur. The halogenated phenol resin consists of aldehyde units of the phenol resin and at least one halogen atom bonded to each of the aldehyde units. The halogenated phenol resin is indicated by a structural formula (Chemical formula 1) shown below:
[Chemical Formula 1]
where X is halogen element, Z is halogen element or —OH and R is hydrogen element or alkyl group having 1-10 carbons.
The above-described construction prevents blooming of the vulcanizing accelerator without making the vulcanization speed of the EPDM rubber slow and deteriorating the physical property of the rubber composition. Consequently, when the rubber composition is molded into the shape of a roller to use the roller as a paper-feeding roller of OA equipments and automatic deposit/payment machines (ATM), the paper-feeding roller can be allowed to have a much higher friction coefficient in the friction between it and paper than that composed of the conventional rubber composition.
The reason why the above-described construction prevents the blooming of the vulcanizing accelerator is because the phenol resin (halogenated phenol resin) having a higher polarity than the EPDM rubber is compatible with the EPDM rubber, thus increasing the polarity of the entire rubber composition. As a result, the compatibility of the vulcanizing accelerator having a high polarity with the rubber composition can be improved. Because the phenol resin is a polymer of phenols and aldehydes copolymerized uniformly with each other, thus having uniformity in its molecular weight, physical property, and reactivity, the rubber composition obtained by vulcanizing the EPDM rubber has a uniform physical property in comparison with a EPDM rubber comprising the conventional ingredients. Thus, there is no variation in its performance and wear resistance of a paper-feeding roller comprising the rubber composition.
The reason why 0.3-5.0 parts by weight of the phenol resin is added to 100 parts by weight of the EPDM rubber is because if the addition amount of the phenol resin is less than 0.3 parts by weight, the ru
Arent Fox Kintner & Plotkin & Kahn, PLLC
Lipman Bernard
Sumitomo Rubber Industries Ltd.
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