Electrical cable and method of making same

An electrical cable includes a first layer, a second layer, and a tie layer, disposed between the first layer and the second layer, for bonding the first layer to the second layer. A method of making an electrical cable includes applying a tie layer to an inner layer, the tie layer being miscible with the inner layer, and bonding an outer layer to the tie layer via one of a chemical reaction therebetween and a physical bond therebetween. An electrical cable includes a first layer, a second layer immiscible with the first layer, and a tie layer disposed between the first layer and the second layer, wherein the tie layer is miscible with the first layer and is capable of bonding with the second layer.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to electrical cabling and, more particularly, to an electrical cable having a tie layer disposed between a first layer and a second layer and a method for manufacturing same.

2. Description of Related Art

Many electrical cables, such as seismic, oceanographic, and wireline cables, are sometimes used in corrosive environments at pressures that may range from atmospheric to very high and at temperatures that may range from arctic to very high. Accordingly, the insulating and jacketing materials used in such cables must be able to withstand these harsh environments, as well as have the dielectric and capacitive properties desirable for the cables. Polymers belonging to the polyolefin family, such as polyethylene, polypropylene, and polyethylene propylene co-polymer, and polymers belonging to the fluoropolymer family, such as ethylene tetrafluoroethylene, fluorinated ethylene propylene, polytetrafluoroethylene/perfluoromethylvinylether co-polymer, and perfluoroalkoxy polymer, are commonly used as insulating materials in these cables.

It is often desirable to have multiple layers of insulating and jacketing materials surrounding the conductors in seismic, oceanographic, and other electrical cables so that the cable will have the desired electrical properties and be able to withstand the environment in which it is used. Generally, it is also desirable to bond or “pot” the insulating layers to a connector or the like within a cable termination to inhibit moisture or other contaminants from penetrating between the insulating layers and/or from entering the connector. Polyolefin and fluoropolymer materials, however, may not bond well to conventional epoxy, nitrile, ester, or urethane-based potting compounds. In general, only cyanoacrylate adhesives are effective in bonding these materials in electrical cable applications. Cyanoacrylate adhesives, however, may be brittle and may be unable to withstand the pressure and/or temperature cycling encountered by such cables.

Primers have been used to enhance the bonding, but they are not as effective on polyolefin and fluoropolymer materials as on other polymeric materials. Surface treatments, such as flame treatment, corona discharge, and solvent etching, have been used to enhance the bonding characteristics of polyolefin and fluoropolymer materials. These techniques, however, may be time consuming and impractical in certain situations. For example, it may be difficult to apply these treatments to large numbers of small, insulated conductors that are bundled together. As a result, such surface treatments may provide results that are less than optimal.

Multiple layers of different potting materials have also been used to overcome the bonding problems of polyolefin and fluoropolymer materials. However, this process has proven to be difficult and time consuming. In some situations the layers of potting material may not effectively bond together, which provides the potential for moisture ingression. Further, a longer length cable termination results from this process, which is generally undesirable.

When the insulating layer and the jacketing layer are not properly bonded together, such as in a cable having a polyvinylchloride insulating layer with a nylon jacketing layer, a small, often microscopic void or voids may exist between the insulating layer and the jacketing layer, which may allow wicking of fluids therein. Moreover, mechanical flexing of such layers having a void or voids therebetween may cause wrinkling and separation of the layers, inhibiting the usefulness of the cable.

Some conventional electrical cables have utilized insulating and jacketing materials that have better bonding characteristics than polyolefin and fluoropolymer materials, such as nylon and thermoplastic polyester elastomers (e.g., Hytrel®, manufactured by E. I. du Pont de Nemours and Company of Wilmington, Del., U.S.A.). However, such materials generally have electrical properties that are inferior to polyolefin materials.

BRIEF SUMMARY OF THE INVENTION

In one aspect of the present invention, an electrical cable is provided. The electrical cable includes a first layer, a second layer, and a tie layer, disposed between the first layer and the second layer, for bonding the first layer to the second layer.

In another aspect of the present invention, a method of making an electrical cable is provided. The method includes applying a tie layer to an inner layer, the tie layer being miscible with the inner layer, and bonding an outer layer to the tie layer via one of a chemical reaction therebetween and a physical bond therebetween.

In yet another aspect of the present invention, an electrical cable is provided. The electrical cable includes a first layer, a second layer immiscible with the first layer, and a tie layer disposed between the first layer and the second layer, wherein the tie layer is miscible with the first layer and is capable of bonding with the second layer.

In another aspect of the present invention, an electrical cable is provided. The electrical cable includes a first layer and a second layer bonded to the first layer comprising a polymer and at least one of an unsaturated anhydride, an acrylic acid, a carboxyl acid, a silane, and a vinyl acetate.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1depicts, in cross-section, a first illustrative embodiment of an electrical cable according to the present invention. In the illustrated embodiment, an electrical cable100includes a plurality of electrical conductors102, an insulating layer104, and a tie layer106. The plurality of electrical conductors102may be individually-insulated conductors (e.g., a plurality of twisted pairs), strands of an electrical conductor, or a combination of both. The insulating layer104electrically isolates the plurality of electrical conductors102and is disposed between the plurality of electrical conductors102and the tie layer106. The insulating layer104may be made of any chosen polyolefin, polyolefin co-polymer, or fluoropolymer material suitable for electrically isolating the plurality of electrical conductors102, e.g., polyethylene, polypropylene, ethylene propylene co-polymer, ethylene vinyl acetate, methylpentene co-polymer, e.g., TPX® from Mitsui Chemicals America, Inc. of Purchase, New York, U.S.A., polytetrafluoroethylene/perfluoromethylvinylether co-polymer, ethylene tetrafluoroethylene, perfluoroalkoxy polymer, or fluorinated ethylene propylene.

It is often desirable to bond potting material layers to insulating layers in electrical cable terminations or to bond jacketing layers to insulating layers. However, polyolefin and fluoropolymer materials are not readily bonded, except with cyanoacrylate adhesives, and such adhesives are often brittle and are not capable of withstanding the temperature and/or pressure cycling requirements of some electrical cables, such as seismic, oceanographic, and wireline cables. Accordingly, the illustrated embodiment shown inFIG. 1includes the tie layer106, which is miscible with the insulating layer104and readily bonds to potting materials and jacketing layer materials. In various embodiments, the tie layer106may comprise a material in the same polymer family as the insulating layer104that has been modified to include a functional group capable of interacting physically (e.g., via polar bonds) or chemically (e.g., via a chemical reaction) with the potting material or jacketing layer materials.

For example, as shown inFIG. 2, a potting material layer202is disposed between the tie layer106and, for example, a connector204for bonding the cable100to the connector204. In various embodiments, the potting material202may comprise epoxy-, nitrile-, ester-, or urethane-based potting materials. In on embodiment, the insulating layer104comprises polyethylene and the tie layer106comprises a modified polyethylene material grafted with an unsaturated anhydride (e.g., maleic anhydride or norbornene-2, 3-dicarboxylic anhydride), an acrylic acid, a carboxyl acid, or a silane. In another embodiment, the insulating layer104comprises polypropylene and the tie layer106comprises a modified polypropylene material grafted with an unsaturated anhydride, an acrylic acid, a carboxyl acid, or a silane.

In yet another embodiment, the insulating layer104comprises ethylene-propylene co-polymer and the tie layer106comprises a modified ethylene propylene co-polymer material grafted with an unsaturated anhydride, an acrylic acid, a carboxyl acid, or a silane. In still another embodiment, the insulating layer104comprises ethylene vinyl acetate and the tie layer106comprises an ethylene vinyl acetate material modified with, for example, a carboxyl acid or an acrylic acid. In yet another embodiment, the insulating layer104comprises methylpentene co-polymer and the tie layer106comprises a modified methylpentene co-polymer material grafted with an unsaturated anhydride or a silane.

Still referring toFIG. 2, it may be desirable for the insulating layer104to comprise a fluoropolymer. In one embodiment, the insulating layer104comprises ethylene tetrafluoroethylene and the tie layer106comprises a modified ethylene tetrafluoroethylene material grafted with a carboxyl, a carboxyl salt, a carboxyl acid, or an unsaturated anhydride.

Alternatively, it may be desirable to bond the insulating layer104to a polymeric jacketing layer302, comprising a material such as, for example, nylon, polyphenylene sulfide, polyurethane, or ethylene vinyl alcohol co-polymer, as shown in FIG.3. Such jacketing materials are advantageous in that they are resistant to attack by many chemicals and, thus, are capable of protecting the insulating layer104from degradation. In various embodiments, the insulating layer104comprises polyethylene and the jacketing layer302comprises nylon, polyphenylene sulfide modified with a functionalized polyethylene group (e.g., Fortron SKX-382®, provided by Ticona of Summit, N.J. U.S.A.), polyurethane, or ethylene vinyl alcohol co-polymer. In such embodiments, the tie layer106may comprise materials as shown in Table 1.

In other embodiments, the insulating layer104comprises polypropylene and the jacketing layer302comprises nylon, polyphenylene sulfide modified with a polyethylene functional group, polyurethane, or ethylene vinyl alcohol co-polymer. In such embodiments, the tie layer106may comprise materials as shown in Table 2.

Alternatively, the insulating layer104may comprise ethylene propylene co-polymer and the jacketing layer302may comprise nylon, polyphenylene sulfide modified with a polyethylene functional group, polyurethane, or ethylene vinyl alcohol co-polymer. In such embodiments, the tie layer106may comprise materials as shown in Table 3.

In other embodiments, the insulating layer104comprises ethylene vinyl acetate and the jacketing layer302comprises nylon, polyphenylene sulfide modified with a polyethylene functional group, polyurethane, or ethylene vinyl alcohol co-polymer. In such embodiments, the tie layer106may comprise materials as shown in Table 4.

TABLE 4Tie layer 106 materials for an insulatinglayer 104 comprising ethylene vinyl acetate.Jacketing layer 302Tie layer 106NylonEthylene vinyl acetate grafted with an unsaturatedanhydride, an acrylic acid, or a carboxyl acid.Polyethylene modifiedEthylene vinyl acetate grafted with an unsaturatedpolyphenylene sulfideanhydride, an acrylic acid, a carboxyl acid, or asilane.PolyurethaneEthylene vinyl acetate grafted with an unsaturatedanhydride.Ethylene vinyl alcoholEthylene vinyl acetate grafted with an unsaturatedco-polymeranhydride, an acrylic acid, a carboxyl acid, or asilane.

In yet other embodiments, the insulating layer104comprises methylpentene co-polymer and the jacketing layer302comprises nylon, polyphenylene sulfide modified with a polyethylene functional group, polyurethane, or ethylene vinyl alcohol co-polymer. In such embodiments, the tie layer106may comprise materials as shown in Table 5.

In other embodiments, the insulating layer104comprises ethylene tetrafluoroethylene and the jacketing layer302comprises nylon, polyphenylene sulfide modified with a polyethylene functional group, or ethylene vinyl alcohol co-polymer. In such embodiments, the tie layer106may comprise ethylene tetrafluoroethylene grafted with a carboxyl, a carboxyl salt, a carboxyl acid, or an unsaturated anhydride, e.g., Tefzel HT-2202, provided by E. I. du Pont de Nemours and Company.

Alternatively, it may be desirable to bond the insulating layer104to a metallic jacketing layer402, comprising a material such as, for example, aluminum, stainless steel, and tin-plated steel, as shown in FIG.4. Such jacketing materials are advantageous in that they are capable of protecting the insulating layer104from mechanical damage. In various embodiments having a metallic jacketing layer402, the insulating layer104may comprise polyethylene, polypropylene, ethylene propylene co-polymer, methylpentene co-polymer, or ethylene tetrafluoroethylene. In such embodiments, the tie layer106may comprise the material of the insulating layer104(e.g., polyethylene, polypropylene, ethylene propylene co-polymer, methylpentene co-polymer, or ethylene tetrafluoroethylene) grafted with an unsaturated anhydride, an acrylic acid, a carboxyl acid, or a silane.

It may be desirable in certain applications to pot or attach the cable100ofFIG. 3orFIG. 4to a connector. Accordingly,FIG. 5illustrates a potting layer502disposed between the jacketing layer302and a connector504. While the jacketing layer302is illustrated inFIG. 5as comprising a polymeric material, the present invention is not so limited. Rather, the connector504may be attached via the potting layer502to a metallic jacketing layer, such as the metallic jacketing layer402of FIG.4. The potting layer502may comprise a material corresponding to the potting layer202ofFIG. 2, or another material.

It may also be desirable in certain situations to incorporate a tie layer material, such as that of the tie layer106, into the insulating layer104(shown inFIGS. 1-5) and/or the jacketing layer302(shown in FIGS.3and5). Accordingly,FIG. 6depicts a second illustrative embodiment of a cable600according to the present invention. The cable600comprises a plurality of conductors602, which may correspond to the conductors102ofFIGS. 1-5. The cable600further comprises an insulating layer604disposed around the conductors602and a jacketing layer606disposed on the insulating layer604.

Still referring toFIG. 6, in one embodiment, a tie layer material is included in one of the insulating layer604and the jacketing layer606as a mixture. In various embodiments, one of the insulating layer604and the jacketing layer606may comprise a polymer and at least one of an unsaturated anhydride, an acrylic acid, a carboxyl acid, a silane, and a vinyl acetate. In one embodiment, one of the insulating layer604and the jacketing layer606comprises nylon and the other layer comprises a mixture of polyethylene and a polyethylene grafted with an unsaturated anhydride. In another embodiment, one of the insulating layer604and the jacketing layer606comprises nylon and the other layer comprises a mixture of ethylene propylene co-polymer and an ethylene propylene co-polymer grafted with an unsaturated anhydride.

In yet another embodiment, one of the insulating layer604and the jacketing layer606comprises polyethylene and the other layer comprises a mixture of nylon and a polyethylene grafted with an unsaturated anhydride. In another embodiment, one of the insulating layer604and the jacketing layer606comprises ethylene propylene co-polymer and the second layer comprises a mixture of nylon and an ethylene propylene co-polymer grafted with an unsaturated anhydride. In each of the embodiments relating toFIG. 6, the insulating layer604or the jacketing layer606may comprise a polymer grafted with an unsaturated anhydride within a range of about 20 weight percent of the layer to about 80 weight percent of the layer containing the mixture.