Plastic and nonmetallic article shaping or treating: processes – Forming electrical articles by shaping electroconductive...
Patent
1995-04-19
2000-10-31
Ortiz, Angela
Plastic and nonmetallic article shaping or treating: processes
Forming electrical articles by shaping electroconductive...
264114, 264115, 264128, B29C 4104, B29C 6724, B29C 7060
Patent
active
061397849
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a seamless belt having a substantially uniform volume or surface electric resistance value (hereinafter referred to sometimes as `electric resistance value`).
BACKGROUND ART
While a variety of electrically conductive seamless belts are heretofore available, most of them are not free of variation in electric resistance or are inadequate in mechanical and other properties. The cause is the poor and uneven blending of electrically conductive powders with organic polymer materials. In addition, there are cases in which the mechanical characteristics are adversely affected by the very addition of such conductive powders. The seamless belt of this kind is manufactured by extrusion molding, centrifugal molding or the like. However, extrusion molding generally tends to cause a variation in thickness or electric resistance as well as compromised mechanical properties and centrifugal molding tends to a cause a gradient in electric resistance between the external and internal surfaces of the belt due to a difference in specific gravity between the different materials admixed, hence causing the above-mentioned drawbacks.
The object of the present invention is to provide a seamless belt with a minimum of variation in electric resistance value and having very satisfactory mechanical and other physical properties.
DISCLOSURE OF THE INVENTION
The present invention is directed to (1) a seamless belt comprising a polyimide resin and an electrically conductive powder characterized in that the volume electric resistance values in various parts of the belt are within the range of 10.sup.-1 .about.10.sup.13 .OMEGA..multidot.cm and the maximum value of volume electric resistance is within the range of 1 to 10 times the minimum value (hereinafter referred to `seamless belt A`) and (2) a seamless belt comprising a polyimide resin and an electrically conductive powder as manufactured by centrifugal molding, characterized in that the surface electric resistance values in various parts of the external and internal surfaces of the belt are within the range of 1.about.10.sup.13 .OMEGA./.quadrature. (ohm/square units) and the maximum value of surface electric resistance is within the range of 1 to 100 times the minimum value (hereinafter referred to as "seamless belt B"). Each of these seamless belts A and B is further characterized in that compared with a seamless belt which is identical in shape but is manufactured from a raw material which does not contain said electrically conductive powder, its tensile strength value, 200.degree. C..times.1 hour thermal shrinkage rates in the transverse and circumferential directions thereof and flexurural resistance value can be controlled to preferably not less than 50% and more preferably not less than 75%. However, these values are not critical and may be any other values depending on the intended use.
In the present invention, the polyimide resin includes but is not limited to thermoplastic polyimide resins and thermosetting polyimide resins such as polyimides and polyamideimides. Moreover, precursors of such thermosetting polyimide resins are also subsumed in the concept of the thermosetting polyimide resin of the invention.
In the present invention, the electrically conductive powder may be any electrically conductive or semi-conductive powder, with no particular restriction, and a broad range of fine powders including carbon blacks such as kitchen black (contactive furnace carbon black), acetylene black, etc., stannic oxide, indium oxide, potassium titanate and other types of conductive and semi-conductive powders can be liberally employed. Among these powders, acetylene black which has a specific gravity of about 1.82 is generally preferred because of its excellent compatibility with polyimide resins. Kitchen black which has a specific gravity of about 1.95 is also tending to be used with advantage. In other words, it is preferable to employ an electrically conductive powder having a specific gravity close to that of the polyimide res
REFERENCES:
patent: 4606955 (1986-08-01), Eastman et al.
patent: 4681712 (1987-07-01), Sakakibara et al.
patent: 5021036 (1991-06-01), Tanaka et al.
patent: 5876647 (1999-03-01), Makise et al.
Omoto Kenichi
Oshima Tetsuhiro
Gunze Limited
Ortiz Angela
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