Compositions – Electrically conductive or emissive compositions – Elemental carbon containing
Reexamination Certificate
2000-12-07
2003-06-03
Kopec, Mark (Department: 1751)
Compositions
Electrically conductive or emissive compositions
Elemental carbon containing
C252S502000, C252S511000, C521S112000, C521S129000, C521S137000, C521S159000, C521S174000, C521S176000, C355S025000, C493S960000, C206S823000, C510S144000
Reexamination Certificate
active
06572791
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an elastic member which is used in image formation equipment such as electro-photographic equipment, electrostatic recording equipment and toner flying recording equipment. More particularly, the present invention is concerned with an elastic member which is simultaneously imparted with excellent characteristics such as low hardness, fine cells, low residual compressive strain, high strength and the like; with image formation equipment equipped with the elastic member; and with toiletries such as a puffing material, a sponge and a scrubbing brush, and a bathing product each being composed of the polyurethane foam which constitutes the above-mentioned elastic member.
In addition, the present invention relates to an electroconductive elastic member which is used in image formation equipment such as electrophotographic equipment, electrostatic recording equipment and toner flying recording equipment. More particularly, the present invention pertains to an electroconductive elastic member which is simultaneously imparted with excellent characteristics such as low electric resistance, low hardness, fine cells, low residual compressive strain, high strength and the like; with image formation equipment equipped with the electroconductive elastic member.
2. Description of the Related Arts
In recent years, accompanying the advancement of electro-photographic technique, attention is paid to an intermediate-resistance elastic roller as a transfer member for dry electro-photographic equipment, a toner feeding member, an electrifying member and the like. Thus, there are used a transfer roller, a developing roller, a toner feeding roller, an electrifying roller and the like. Incidentally, there have heretofore been employed a high molecular elastomer and high molecular foam each having rubbery elasticity as a material constituting the aforesaid intermediate-resistance elastic roller.
Examples of the members which have hitherto been employed for the above-mentioned purpose include such elastomer or foam as NBR, EPDM, silicone rubber, polyurethane and the like, and as required, an electroconductive carbon such as carbon black, a metal oxide and a member imparted with electroconductivity with an ionic electroconductive agent or the like.
Of the elastomer or foam, polyurethane is preferably used in the above-mentioned member, since polyurethane can be made into a low hardness member well suited for the above-mentioned member, and can be made into a low hardness foam by a method using such a foaming agent as water and a compound having a low boiling point, a mechanical agitation method or the like method. It is possible to lower the hardness of polyurethane foam by selecting a material which determines the chemical constitution of polyurethane and its blending amount.
In the case where polyurethane foam is brought into usage in a member for image formation equipment such as a toner feeding roller, the foam is required to have a low hardness, a low resistance, fine cells, a low residual compressive strain, a high tensile strength, and to be inexpensive. Since in such usage, different electric resistances are required for elastic members according to the types and kinds of toners (developing agent) and developing members and the conditions on electric power source, elastic members having from a low resistance to a high resistance are manufactured and used by adding at need or without adding the electroconductive agent as mentioned hereinbefore.
There has heretofore been employed as the aforesaid elastic member, ester base polyurethane foam capable of easily achieving relatively fine cells by means of free foaming. However, the ester base polyurethane foam has been problematical in its liability to hydrolysis because of being ester base. On the other hand, ether base polyurethane foam which is not hydrolyzed is liable to form coarse cells by free foaming, necessitating pressurized mold foaming for the purpose of forming fine cells.
Moreover, the above-mentioned ester base polyurethane foam is in use also as a toiletry and a bathing product. However, the problem of durability has been raised in a puffing material for toiletry and a scrubbing brush for bathing each being composed of conventional polyurethane foam because of their liability to hydrolysis, whereby improvement of the polyurethane foam has been desired.
On the one hand, in the case of imparting electroconductivity to conventional polyurethane foam, it is necessary to add a large amount of electroconductive carbon thereto, since the electric resistance thereof is not sufficiently lowered even by the addition of an ionic electroconductive agent. Nevertheless, when a large amount of electroconductive carbon is added to the starting materials of polyurethane foam such as polyol, isocyanate, prepolymer and the like, there are brought up such problems as increasing the viscosity of the starting materials containing the electroconductive carbon added and dispersed, making it impossible to sufficiently mix or agitate the starting materials, as producing polyurethane foam having unfavorably coarse cells, and as making electric resistance less prone to be lowered.
In order to solve the above-mentioned problems, there is proposed a method for producing electroconductive polyurethane foam by mixing urethane prepolymer with water-dispersed carbon, a catalyst, a foam stabilizer and the like, and subjecting the resultant mixture to foaming with water.
There is proposed, for instance, as the above-mentioned method, a method which comprises mixedly reacting a hydrophilic prepolymer with an aqueous dispersion containing fine particles of electroconductive carbon under the conditions of chemical equivalent and excess of water, said prepolymer being produced by reacting an isocyanate with polyoxyethylene/polyoxypropylene copolymer made into a polyether polyol having a polyoxyethylene content of 60 to 100% by weight {Japanese Patent Application Laid-Open No. 69794/1974 (Showa-49) and Japanese Patent Publication No. 2086/1986 (Showa-61)}. The electroconductive polyurethane foam obtained by this method, although having a low resistance and fine cells, involves such problems as liability to shrinkage after foaming, high residual compressive strain and the like.
Likewise, there is proposed a method which comprises mixedly reacting a hydrophilic prepolymer with an aqueous dispersion containing fine particles of electroconductive carbon under the conditions of chemical equivalent and excess of water, said prepolymer being produced by reacting an isocyanate with oxyethylene/oxypropylene copolymer made into a polyether polyol having a polyoxyethylene content of at most 30% by weight (Japanese Patent Application Laid-Open Nos.228357/1990 (Heisei-2) and 251426/1998 (Heisei-10). The aforesaid method involves such problems that electroconductive polyurethane foam produced by free foaming under atmospheric pressure unfavorably increases cell size and causes liability to crack and roughness of the resultant cells.
SUMMARY OF THE INVENTION
It is an object of the invention to solve the problems with conventional elastic members and at the same time, to provide an elastic member constituted of polyurethane foam which is simultaneously imparted with excellent characteristics such as low hardness, fine cells, low residual compressive strain, high strength and the like, and also provide a toiletry and a bathing product each being composed of this polyurethane foam.
It is another object of the invention to solve the problems with conventional electroconductive elastic members and at the same time, to provide an electroconductive elastic member constituted of polyurethane foam which is simultaneously imparted with excellent characteristics such as low electric resistance, low hardness, fine cells, low residual compressive strain, high strength and the like.
Other object of the invention will be obvious from the text of this specification hereinafter disclosed.
In such circumstances,
Kawagoe Takahiro
Nakajima Tadashi
Sakata Junji
Yamazaki Hirotaka
Bridgestone Corporation
Kopec Mark
Vijayakumar Kallambella M
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