Polymer Composition for Bonding to Copper

The copper laminates of the present invention have a wide variety of uses and some of such uses will be described with reference to the accompanying drawings, wherein:

FIG. 1 is a simplified representation of a cable including a laminate of the present invention;

FIG. 2 is a simplfied representation of another cable including a laminate of the present invention;

FIG. 3 is a simplified representation of a transmission cable formed from a laminate of the present invention; and

FIG. 4 is a simplified representation of a pipe formed from a laminate of the present invention.

The laminates of the present invention can be used, as known in the art, as a water-tight cable sheathing for transmission cables. Referring to FIG. 1, there is shown the transmission cable strands forming the cable core 10 held together, as known in the art, by a winding 12 of paper, plastic or other suitable material. A water-tight cable sheathing of a preformed laminate of the present invention comprised of a copper band 14 having bonded to one or both of its surfaces a layer 12 of a copolymer or ionic copolymer, including a copper stabilizer or deactivator is wound above and around the winding 12. An outer plastic coating 15, such as polyethylene, surrounds the cable sheathing. The copper band 14 having the layer 13 bonded thereto is longitudinally placed around the cable core with a small overlap and the plastic coating 15 is extruded thereon. The heat of extrusion is sufficient to bond together the laminate of the copper band 14 and layer 13 at the overlap and to also establish a firm bond between the band 14 annd the sheathing 15.

The production of such cables is generally known in the art (e.g., U.S. Pat. Nos. 3,206,541; 3,233,036; and 3,459,877) and such teachings are especially applicable to the production of cables including a copper-polymer laminate of the present invention.

Referring to FIG. 2, there us illustrated an alternate method of providing a transmission cable having a watertight cable sheathing formed of a copper laminate of the present invention. In accordance with the embodiment of FIG. 2, the cable core 21 is surrounded by a suitable winding 22 and then by copper foil 23 placed lengthwise around the core. The edges of the copper foil 23 are bent upwards, welding and then folded, as shown. Alternatively, the band edges of the copper foil 23 could be welded. After providing the welded copper foil layer 23, a layer 24 of a copolymer or ionic copolymer, including a copper stabilizer or deactivator, of the present invention, is extruded over and bonded to the copper foil layer 23 to provide a water-tight sheathing. The outer plastic sheathing 25 is then formed as known in the art.

The laminates of the present invention can also be used to advantage to provide transmission cables with damping dependent on frequency. In accordance with the present invention, the massive inner core is replaced by a laminate of the present invention comprised of an inner member formed of a copolymer or ionic copolymer including a copper stabilizer of the present invention, and a copper foil outer member bonded to the inner member.

Referring to FIG. 3, there is shown a solid inner member 31 formed from a copolymer or ionic copolymer having incorporated therein a copper stabilizer, as hereinabove described, surrounded lengthwise by a thin copper band 32. The copper band is heated and forced under pressure over the inner member 31 to form an adhesive bond therebetween. The edges of the copper band 32 are, for example, welded along the longitudinal seam. A plastic coating 33, as known in the art, is extruded over the copper band 32. Accordingly, the massive inner core has been replaced with a thin copper tube and through the skin effect, all of the energy transmitted is through the copper layer 32.

The laminates of the present invention may also be used for producing pipe for the transportation of various materials, including heated or refrigerated, liquid or gaseous media. Thus, as shown in FIG. 4, a pipe 41 is comprised of a copper tube 42 having bonded to its exterior surface a layer 43 of a copolymer or ionic copolymer including a copper stabilizer, of the present invention. The copper tube 42 may be preformed and the layer 43 subsequently bonded thereto, for example, by an extrusion technique. Alternatively, copper sheets having one or both surfaces covered with the copolymer or ionic copolymer, including a copper deactivator, of the present invention bonded thereto may be formed with the edges thereof free of the polymer layer. The tube is then formed from the copper laminate, and the polymer free edges welded together.

It is also to be understood that the copolymer and/or ionic copolymer including a copper stabilizer or deactivator may be used for bonding together copper surfaces. Thus, for example, the composition may be used between an overlapping seam portion of a copper strip in which case the composition functions as an adhesive for providing an effective bond.

The invention is further illustrated by the following examples, but it is to be understood that the scope of the invention is not to be limited thereby.

An ethylene-acrylic acid-copolymer further including acrylate units, sold under the Lupolen mark KR-1285 by BASF was uniformly mixed with the copper stabilizer N-salicylidene-N' salicyloyl hydrazide (CHEL-180) in amounts of 0.2% and 0.5%, by weight. A layer 1.5 mm. thick was applied to a previously degreased sheet of copper with a thickness of 0.28 mm. by application of a pressure of about 200 atm. at 180.degree. F.

A similar sheet was also prepared from Lupolen KR-1285 without stabilizer.

The initial peel strength was about 9 kp./cm. and the initial peel strength of the 0.2% and 0.5% deactivated polymers were about 4 kp./cm. and 2 kp./cm., respectively.

The strips were kept in distilled water at 70.degree. C. inside a drying cabinet.

The laminate strips without stabilizer exhibited a very dramatic decrease in adhesive strength which completely deteriorated after 13-15 days.

The laminate strips with stabilizer did not exhibit any notable decrease in peel strength over a period of 90 days.

In the following examples, a copper laminate is prepared, as in Example I, having a total thickness of 0.4 mm., with the thickness of the polymer layer being 0.04 mm. The resulting laminates are found to resist delamination.

Copper laminates are prepared, as in Example I, using Surlyn 1800 (an ethylene-carboxylic acid ionomer containing zinc as the major cation and including an antioxidant) as the polymer and 0.4 wt. percent of the copper deactivators of Examples I-VI.

The laminates have a total thickness of 0.4 mm., with the thickness of the polymer layer being 0.04 mm. The resulting laminates are found to resist delamination.

The present invention is particularly advantageous in that the polymeric compositions may be effectively bonded to copper, and the resulting laminate, resists delamination even at those conditions at which delamination is to be expected. The results of this invention are particularly surprising in that the polymers of the composition are not known to be susceptible to degradation by copper, and accordingly, the resulting resistance to delamination, resulting from the use of copper stabilizers or deactivators, is completely unexpected.

The present invention is further advantageous in that the polymer composition can also function as an adhesive for bonding other plastics to copper.

Numerous modifications and variations of the present invention are possible and, therefore, within the scope of the appended claims the invention may be practiced other than as described.