TUBULAR MEMBRANE MATRICES

Abstract: A tubular membrane comprising a substantially cylindrically shaped fabric member having been coated with an alpha -cyanoacrylate monomer containing composition. The fabric is characterized as being substantially inert to and insoluble in the alpha -cyanoacrylate monomer containing composition. The membrane is ideally suited for the joinder of linear geometrically shaped objects such as electrical conductors as substitutes for prior shrink fit tubing.

Description: Description Tubular Membrane Matrices Technical Field of Invention The present invention deals with an alternative to currently available shrink-fit tubing and other means for splicing wires and connecting rods and tubes. As the tubular membrane of the present invention is convenient to use and does not require the use of heat or an open flame to complete the splice or connection, the present invention provides increased flexibility for those wishing to join linear geometrically-shaped devices. Background of the Invention For as long as wires, tubes and rods have been cut and spliced to make new connections, improved tech¬ niques have been sought to enhance- the connection or splicing operation. Splices of non-electrically conducting rods, wires or tubes have traditionally been accomplished by butt-cementing the free ends of these materials with conventional adhesives followed by wrapping with tape. Tapes found appropriate for use in the splicing operation were generally those extruded i from polyethylene, polypropylene and cither material films or knitted or woven structures which were coated with water-based or solvent-based adhesives of all sorts. The adhesives were generally of the type derived from polymerized acrylic acids and their esters or derivatives or polymerized ethylene products and their derivatives or synthetic rubbers such as polybutadiene and their derivatives or natural rubbers such as latexes. It was common practice to cut a splicing material from flat, wide-woven goods which were previously impregnated or coated with suitable adhesives prior to the splicing operation. Regarding the splicing of electrically conductive wires, rods or tubes, and particularly splicing for the shielding of electrical connectors, conventional tapes have proven unsatisfactory due to the high temperatures experienced at the splice. It has not been uncommon to experience temperatures which are high enough to melt or burn conventional splicing tapes. Recognition of this problem has led to the development of irradiated polyethylene tubes which essentially have no melting point due to the cross-linked nature of the polyolefin. As a natural extension to the development of heat resistant polyolefin tubes was the invention of shrink- fit tubing. This was accomplished by overexpanding polyolefin tubes subsequent to the irradiating of the tubes after the cross-linking operation. The tubes in an expanded state were then placed on a bare wire connection and with the application of heat via a flame or hot air, etc. could be shrunk onto the splice. The thermal energy provided for the release of strains imposed within the polyolefin tube during its fabrication and thus allowed the tube to shrink accordingly. Although shrink-fit t'ubing represented an improve¬ ment in the state of the art, the use of such materials was not without its drawbacks. For example, one could not use shrink-to-fit tubing in installations where combustible materials were present as an open flame could ignite such materials. It was further recognized that the high melting point tubing did not enhance the structural integrity of the splice nor did it aid in the exclusion from the splice point of environmental elements which could corrode the conductor at the point of connection. Occasionally, it was noted that the tubing did not properly shrink onto the wire insulator and in many cases areas were noted between the shrink tubing and bare wire insulator which were unprotected and open. Although the wire could be coated with an insulating material prior to the application of the shrink-fit tubing, such a process is expensive and does not properly function in all cases. It has been found that suitable adhesives stick to the insulator and tend to "walk around" the cylinder as it shrinks onto the connector. Also, many sealants do not exhibit melting points which are sufficiently high, and thus break down under the application of heat necessary to shrink the polyolefin tubing. It is thus an object of the present invention to provide a tubular membrane for joining two or more substantially linear geometrically-shaped objects which is improved over prior splicing materials described above. It is yet another object of the present invention to provide a tubular membrane for joining together two or more substantially linear geometrically-shaped objects without the requirement for the application of heat- and which substantially protects the splice from the environment and enhances the integrity and continuity of the splice. These and other objectsfof the present invention will be more readily appreciated when considering the following description and appended drawings wherein: Figs. IA through IE depict the sequential steps employing the tubular membrane of the present invention in completing the joining together of two linear geometrically-shaped objects. Summary of the Invention In its broadest terms, the present invention involves a tubular membrane and a method of using said membrane for the joining together of two or more substantially linear geometrically shaped objects. The membrane comprises a cylindrically-shaped fabric member having been coated with an α-cyanoacrylate monomer containing composition. As such, the fabric, making up the membrane, should be substantially inert to and insoluble in the α-cyanoacrylate monomer containing composition. Detailed Description of the Invention Figs. IA through IE show a typical application for the invention claimed and disclosed herein. In this illustration, electrically conductive wires 10 and 20 have been prepared for the splice by removing insula- tive coatings 4 and 5 exposing bare metal sections 2 and 3. Prior to the joining of wires 10 and 20, tubu- lar membrane 6 is applied over one of the wires, in Fig. IB tubular membrane 6 has been applied over wire 20. Tubular membrane 6 comprises a cylindrically- shaped fabric member which must be .substantially inert to and insoluble in the later applied α-cyanoacrylate monomer containing composition. Ideally, the fabric is a member selected from the group consisting of poly- olefins, polyesters, polyamides, polytetrafluoro- ethyleηe and mixtures thereof. In view of their inert- ness and relative availability, it has been found that polypropylene fibers sold under the trade designation "Type 153" from Hercules Chemical Company which is produced from thermally polymerized feed stock are most advantageous for use in practicing the present invention. In certain applications use of Kodel® texturized polyester yard available from Eastman Kodak Co. can be employed herein. The fibers themselves can be knitted, woven or thermally bonded as an unwoven mat in configuring the cylindrically-shaped fabric member of the present iηvention. For the sake of a compliant, easy to use fabric member, it is preferred that the fabric be knitted. Ideally, fabrics manufactured pursuant to the teachings of U.S. Patent Applications Serial Nos. 06/467,913, 06/504,892, and 06/532,352 can be used herein, such as those which have been thermally bonded to one another to make a composite structure. Such fabrication methods are notoriously well known in the art such as taught in the texts entitled "Non-Woven Fabrics" by Buresh and "Non-Woven Textiles" by Casper, the disclosures of which are incorporated herein by reference. Suitable for use herein are the spun-bonded olefins sold by Du Pont under the trademark Tyvek®, as well as membranes produced by calendering, thermally bonding a needle punched web and thermally bonding of an arachne web. It is further contemplated, as a preferred embodi¬ ment, that the cylindrically-shaped fabric member be pre-treated with a sensitizer to promote the catalytic polymerization of the α-cyanoacrylate monomer contain¬ ing composition. The polymerization of the monomer can take ^ place without an externally-applied catalyst, however, the process can be enhanced by providing a sensitizer in the fabric bodγ during its manufacture. Sensitizers can ideally comprise an anionic or cationic detergent or surfactant. Alternatively, any alkaline generating material can be employed such as, for example, sodium bicarbonate. As illustrative, an amine, such as an aryl alkyl amine, sold by Pacer Technology, Inc. as a solution in trichlorotrifluoro- ethane can be employed. Rather than sensitizing the fabric, catalytic agents, particularly the amines, can be oversprayed onto the tubular membrane after the application of the α-cyanoacrylate monomer containing composition. Referring again to the figures, the bare metal ends 2 and 3 are next brought into overlapping contact (Fig. 1C) and either held in position mechanically or by means of an adhesive. Although mere overlap of ends 2 and 3 is depicted as a simplistic means of illustrat¬ ing the present invention, the ends could have been twisted or otherwise mechanically joined to one another or a chemical agent such as an α-cyanoacrylate monomer containing adhesive applied to chemically stabilize the joint. Once the joinder has been made, the cylindrically- shaped fabric 6 is then slid over joint 7 to ideally completely cover the bare metal ends as well as some of the adjacent insulative sleeves 4 and 5 (Fig. ID). The tubular membrane of the present invention is clearly superior to prior art sleeves in that the present membrane is capable of isolating the spliced area from the surrounding environment once the α-cyanoacrylate monomer containing composition has been applied thereto. As such, it is most desirable in practicing the present invention to provide a suitable length of cyli drically-shaped fabric to fully encompass not only the bare spliced area but also adjacent insulated areas for complete environmental isolation. Once the cylindrically-shaped fabric has been drawn over the spliced area, the α-cyanoacrylate mono¬ mer containing composition can be applied as coating 8 (Fig. 1E). Generally, virtually any commercially available α-cyanoacrylate monomer containing composi- tion can be employed. As a preferred embodiment of the present invention, the fabric can be used as a support for the application of α-cyanoacrylate acid esters of the following structure: CH_ = C - C - 0 - R 2 CIN I0I wherein R is a member selected from the group consisting of an alkyl from approximately 1 to 18 carbon atoms; phenyl, cyclohexyl, alkoxy, allyl and furfuryl groups and mixtures thereof. Compositions which include the α-cyanoacrylate monomers can be used at viscosities between approximately 5 to 10,000 cps. When used in the 50 to 500 cps range, materials available from Pacer Technology sold under the trademarks PX-50 and PX-500 can be employed which, when applied, soak in and fully saturate the cylindrically- shaped fabric. Alternatively, a gel having a viscosity between approximately 5,000 to 20,000 cps can be employed, such as that shown in co-pending U.S. Patent Application Serial No. 639,340 , the disclosure of which is incorporated herein by reference. More specifically, the gelled product is intended to contain a dry colloidal fumed silica such as that available from Cabot Corporation sold under the trademark CAB-0- SIL N 70 TS. The composition further is intended to include a plasticizer comprising a member selected from the group consisting of monofunctional aliphatic esters, difunctional aliphatic esters, difunctional aromatic esters, phosphate esters and phosphonate esters. Viscosity enhancers , rcan also be used to increase the viscosity at the lower level and increase the melting point of the composition. Suitable viscosity enhancers include polymethylmethacrylate, polyethyl cyanoacrylate and acrylonitrile butadiene styrene copolymer. These enhancers should be employed in levels between approximately 0.25% and 10.0%, and more preferably between approximately 1.0% and 8.0% and most ideally between approximately 4.0% to 6.0%. Further contained within the gelled α-cyano¬ acrylate monomer containing composition is a stabilizer which ideally comprises a member selected from the group consisting of sulfur dioxide, hydrogen fluoride. nitrogen oxide, phosphoric acid, phosphorous acid, boron trifluoride, stannic chloride, ferric chloride, sultones and aromatic sulfonic acid«s. A free radical scavenger is also included in such a composition which preferably is a member selected from the group consist¬ ing of hydroquinone, monomethylether of hydroquinone, butylated hydroxyanisole, butylated hydroxytoluene and t-butyl hydroquinone. It is also contemplated that filled α-cyano- acrylate monomer containing compositions be employed such as those disclosed in co-pending U.S. Application Serial No. 639,339 r the disclosure of which is incorporated herein by reference. Such materials not only exhibit the properties of a gel, but are also thixotropic. It is preferred that a gel-like product be employed, whether filled or unfilled, as these compositions generally exhibit improved high tempera¬ ture break down properties and are. more waterproof and resistant to the elements than are their low viscosity counterparts. The gelled hardener and particularly those which have been filled with inert fibers or spheres pursuant to the teachings of U.S. Application Serial No. 639,339 are further resistant to cracking as they do not exhibit the brittleness which is generally exhibited, by 'low viscosity commercially available α-cyanoacrylate monomer containing compositions. By practicing the present invention, one achieves a highly desirable connection or splice which exhibits the properties of a high temperature insulator and adds structural integrity to the splice. As the α-cyano¬ acrylate monomer containing composition is applied, it bonds right to the wire, tube or rod and the surround¬ ing insulating materials and serves to occlude the environment from the joined objects to reduce the potential for corrosion. The present invention can be employed not only in environments where it is unsafe to generate a flame or spark but also in environments where it is unpractical to support -a flame or heat generating device necessary in employing the shrink-fit tubing of the prior art.

Claims: Claims 1. A tubular membrane for th« joining together of two or more substantially linear geometrically shaped objects comprising a substantially cylindrically-shaped fabric member having been coated with an α-cyanoacrylate monomer containing composition. 2. The tubular membrane of claim 1 wherein said fabric is characterized as being substantially inert to and insoluble in said α-cyanoacrylate monomer containing composition. 3. The tubular membrane of claim 2 wherein said fabric is comprised of a member selected from the group consisting of polyolefins, polyesters, polyamides, polytetrafluoroethylene and mixtures thereof. 4. The tubular membrane of claim 1 wherein said α-cyanoacrylate monomer containing composition comprises: A. an α-cyanoacrylate monomer of the formula wherein R is a member selected from the group consisting of an alkyl from approximately 1 to 18 carbon atoms; phenyl, cyclohexyl, alkoxy, allyl and furfuryl groups and mixtures thereof; B. dry colloidal fumed silica; C. a plasticizer; D. a stabilizer; and E. a free radical scavenger. 5. The tubular membrane of claim 1 wherein said fabric further comprises a sensitizer for catalyzing polymerization of the α-cyanoacryla«te monomer containing composition. 6. The tubular membrane of claim 5 wherein said sensitizer comprises a member selected from the group consisting of an amine, an anionic detergent, a cationic detergent, a surfactant, an alkaline generator and mixtures thereof. 7. The tubular membrane of claim 6 wherein said alkaline generator comprises sodium bicarbonate. 8. The tubular membrane of claim 7 wherein said amine comprises an aryl alkyl amine. 9. The tubular membrane of claim 4 wherein said plasticizer comprises a member selected from the group consisting of ' monofunctional aliphatic esters, difunctional aliphatic esters, difunctional aromatic esters, phosphate esters and phosphonate esters. 10. The tubular membrane of claim 4 wherein said stabilizer comprises a meπber selected from the group consisting of sulfur dioxide, hydrogen fluoride, phosphorous acid, boron trifluoride, stannic chloride, ferric chloride, sultones and aromatic sulfonic acids. 11. The tubular membrane of claim 4 wherein said free radical scavenger comprises a member selected from the group consisting of hydroquinone, monomethylether of hydroquinone, butylated hydroxyanisole, butylated hydroxytoluene and t-butyl hydroquinone. 12. The tubular membrane of claim 3 wherein said polyolefins comprise a member selected from the group consisting of polypropylene and polyethylene. 13. The tubular membrane of claim 4 wherein said composition further comprises a viscosity enhancer. 14. The tubular membrane of claim 13 wherein said viscosity enhancer is a member selected from the group consisting of polymethylmethacrylate, polyethyl cyanoacrylate and acrylonitrile butadiene styrene copolymer. 15. A method of joining together two or more substantially linear geometrically shaped objects comprising inserting a free end of each of said objects within the interior of a cylindrically shaped fabric member and applying to said fabric.member an α-cyanoacrylate monomer containing composition. 16. The method of claim 15 wherein said substantially linear geometrically shaped objects comprise members selected from the group consisting of rods, wires and tubes. f 17. The method of claim 15 wherein said fabric further comprises a sensitizer for catalyzing polymerization of the α-cyanoacrylate monomer containing composition. 18. The method of claim 15 wherein a catalyst to enhance the polymerization of the α-cyanoacrylate monomer containing composition is applied to said cylindrically shaped fabric member after the application of said composition. 19. The method of claim 15 wherein said substantially linear geometrically shaped objects comprise insulated electrical conductors. 20. The method of claim 19 wherein the joinder of said electrical conductors is made where insulation has been removed therefrom. 21. The method of claim 20 wherein said cylindrically shaped fabric member extends beyond the point of joinder to overlap said insulation on each of said linear geometrically shaped objects. 22. The method of claim 15 wherein said α-cyanoacrylate monomer containing composition is further employed to adhesively join the free ends of said linear geometrically shaped objects.

Inventors: HONEYCUTT TRAVIS W, HONEYCUTT, TRAVIS, W.
Applicants: ISOPEDIX CORP, ISOPEDIX CORPORATION
Application year: 1985
Main classification: H01B13
IPC codes: C09J5, H01B3, H01R4