Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Patent
1994-03-25
1997-11-18
Cooney, Jr., John M.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
521 54, 521 59, 521134, 264127, 264154, 2642888, C08J 924
Patent
active
056888368
DESCRIPTION:
BRIEF SUMMARY
(TECHNICAL FIELD)
The present invention relates to a polytetrafluoroethylene (which is, hereinafter, also referred to as "PTFE") porous material having improved properties, especially buckling resistance on bending and adhesion, and a process for the production of such a material.
(BACKGROUND ART)
A PTFE porous material has been used as for a number of medical treatments, especially for tubes of the medical treatments such as an artificial blood vessel since it has inherent properties such as excellent chemical resistance and heat resistance, its friction factor is small and further it is porous.
However, the tube made of the PTFE material has problems of buckling (collapse) on bending and also tearing along its longitudinal axial direction. In order to solve such problems, Japanese Patent Kokai Publication Nos. 49-22792, 50-102673 and 55-90347 disclose tape or fiber wrapping around the PTFE porous tube.
Alternatively, in order to overcome the above problems with respect to the PTFE porous tube, Japanese Patent Kokai Publication No. 55-52754 discloses application of a porous elastomer coating around the tube.
Since any solution as described above should further treat the PTFE tube, namely, it requires a further processing, it is not an economically advantageous solution. In addition, since such a solution does not change the properties of the PTFE tube itself, it highly depends on properties of the tape and the fiber, so that it is not always preferred.
Japanese Patent Kokai Publication No. 61-143124 discloses a method in which PTFE tubes which have been heat set are connected together by providing a separate heat fusible resin layer between them. When the PTFE tubes are connected by such a method, there occurs a problem that porosity of a portion where the connection is formed is not available.
The PTFE material is used as an insulation of an electric cable since it has an excellent electric insulating property in addition to the properties as described above. When the PTFE porous material is used as the cable insulation material, especially in the production of a flat cable, an adhesive is used so as to bond together the PTFE porous materials or an unsintered PTFE porous materials are heated to a temperature above their melting points so as to fuse the PTFE materials. However, the method using the adhesive is not satisfactory in the electrical properties and the heat resistance.
Japanese Patent Kokai Publication No. 56-149712 discloses a process for the production of a flat cable in which a plurality of conductors are sandwiched between unsintered PTFE porous films to form a resulted composite and then the resulted composite is pressed at a temperature above a melting point of the PTFE films. This process is based on an idea that the two sheets of the film are not bonded together unless the unsintered two sheets of the porous film are sintered while pressed. In such a process, the unsintered composite is less strong and change in its dimensions is large, so that a special apparatus is required in which such issues are taken into account.
Particularly, the flat cable is required to have flexibility. When the cable changes in its dimensions on bending thereof, especially when a large change in dimensions such as buckling occurs, electrical properties of the cable such as an impedance thereof is greatly changed in a portion where the dimension change occurs, which would cause a problem.
In order to prevent such change in dimensions, Japanese Patent Kokai Publication No. 57-7023 discloses a solution for such a problem in which a plastic layer is provided on an outer surface of a PTFE layer so that the change in dimensions and also the change in the electrical properties are prevented.
However, such a solution does not allow to increase a thickness of the plastic layer at the expense of the flexibility of the PTFE layer. Therefore, there is the problem that no change due to a stress from the outside is available.
(DISCLOSURE OF THE INVENTION)
As described above, it is difficult to adhere or bond the PT
REFERENCES:
patent: 4096227 (1978-06-01), Gore
patent: 4882113 (1989-11-01), Tu et al.
patent: 4891407 (1990-01-01), Mitchell
patent: 4973609 (1990-11-01), Browne
Onogi Hirofumi
Tanaka Osamu
Yamamoto Katsutoshi
Cooney Jr. John M.
Daikin Industries Ltd.
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