Abstract:
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.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application claims priority from Provisional Application 60/409,563, filed Sep. 10, 2002, which is incorporated herein by reference. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    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.  
           [0004]    2. Description of Related Art  
           [0005]    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.  
           [0006]    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.  
           [0007]    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.  
           [0008]    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.  
           [0009]    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.  
           [0010]    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.  
           [0011]    The present invention is directed to overcoming, or at least reducing, the effects of one or more of the problems set forth above.  
         BRIEF SUMMARY OF THE INVENTION  
         [0012]    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.  
           [0013]    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.  
           [0014]    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.  
           [0015]    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. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]    The invention may be understood by reference to the following description taken in conjunction with the accompanying drawings, in which the leftmost significant digit in the reference numerals denotes the first figure in which the respective reference numerals appear, and in which:  
         [0017]    [0017]FIG. 1 is a cross-sectional view of a first illustrative embodiment of an electrical cable according to the present invention;  
         [0018]    [0018]FIG. 2 is a cross-sectional view of the electrical cable of FIG. 1 potted to a connector;  
         [0019]    [0019]FIG. 3 is a cross-sectional view of the electrical cable of FIG. 1 having a polymeric jacketing layer;  
         [0020]    [0020]FIG. 4 is a cross-sectional view of the electrical cable of FIG. 1 having a metallic jacketing layer;  
         [0021]    [0021]FIG. 5 is a cross-sectional view of the electrical cable of FIG. 3 potted to a connector; and  
         [0022]    [0022]FIG. 6 is a cross-sectional view of a second illustrative embodiment of a cable according to the present invention.  
     
    
       [0023]    While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but, on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0024]    Illustrative embodiments of the invention are described below. In the interest of clarity, not all features of an actual implementation are described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developer&#39;s specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.  
         [0025]    [0025]FIG. 1 depicts, in cross-section, a first illustrative embodiment of an electrical cable according to the present invention. In the illustrated embodiment, an electrical cable  100  includes a plurality of electrical conductors  102 , an insulating layer  104 , and a tie layer  106 . The plurality of electrical conductors  102  may be individually-insulated conductors (e.g., a plurality of twisted pairs), strands of an electrical conductor, or a combination of both. The insulating layer  104  electrically isolates the plurality of electrical conductors  102  and is disposed between the plurality of electrical conductors  102  and the tie layer  106 . The insulating layer  104  may be made of any chosen polyolefin, polyolefin co-polymer, or fluoropolymer material suitable for electrically isolating the plurality of electrical conductors  102 , 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.  
         [0026]    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 in FIG. 1 includes the tie layer  106 , which is miscible with the insulating layer  104  and readily bonds to potting materials and jacketing layer materials. In various embodiments, the tie layer  106  may comprise a material in the same polymer family as the insulating layer  104  that 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.  
         [0027]    For example, as shown in FIG. 2, a potting material layer  202  is disposed between the tie layer  106  and, for example, a connector  204  for bonding the cable  100  to the connector  204 . In various embodiments, the potting material  202  may comprise epoxy-, nitrile-, ester-, or urethane-based potting materials. In on embodiment, the insulating layer  104  comprises polyethylene and the tie layer  106  comprises 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 layer  104  comprises polypropylene and the tie layer  106  comprises a modified polypropylene material grafted with an unsaturated anhydride, an acrylic acid, a carboxyl acid, or a silane.  
         [0028]    In yet another embodiment, the insulating layer  104  comprises ethylene-propylene co-polymer and the tie layer  106  comprises 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 layer  104  comprises ethylene vinyl acetate and the tie layer  106  comprises an ethylene vinyl acetate material modified with, for example, a carboxyl acid or an acrylic acid. In yet another embodiment, the insulating layer  104  comprises methylpentene co-polymer and the tie layer  106  comprises a modified methylpentene co-polymer material grafted with an unsaturated anhydride or a silane.  
         [0029]    Still referring to FIG. 2, it may be desirable for the insulating layer  104  to comprise a fluoropolymer. In one embodiment, the insulating layer  104  comprises ethylene tetrafluoroethylene and the tie layer  106  comprises a modified ethylene tetrafluoroethylene material grafted with a carboxyl, a carboxyl salt, a carboxyl acid, or an unsaturated anhydride.  
         [0030]    Alternatively, it may be desirable to bond the insulating layer  104  to a polymeric jacketing layer  302 , 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 layer  104  from degradation. In various embodiments, the insulating layer  104  comprises polyethylene and the jacketing layer  302  comprises 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 layer  106  may comprise materials as shown in Table 1.  
                             TABLE 1                           Tie layer 106 materials for an insulating       layer 104 comprising polyethylene.                Jacketing layer 302   Tie layer 106                       Nylon   Polyethylene grafted with an unsaturated               anhydride, an acrylic acid, a carboxyl               acid, or a silane. Ethylene vinyl acetate               grafted with an unsaturated anhydride.           Polyethylene modified   Polyethylene grafted with an unsaturated           polyphenylene sulfide   anhydride, an acrylic acid, a carboxyl               acid, or a silane.           Polyurethane   Polyethylene or ethylene vinyl acetate               grafted with an unsaturated anhydride.           Ethylene vinyl alcohol   Polyethylene grafted with an unsaturated           co-polymer   anhydride, an acrylic acid, a carboxyl               acid, or a silane. Ethylene vinyl acetate               grafted with an unsaturated anhydride.                      
 
         [0031]    In other embodiments, the insulating layer  104  comprises polypropylene and the jacketing layer  302  comprises nylon, polyphenylene sulfide modified with a polyethylene functional group, polyurethane, or ethylene vinyl alcohol co-polymer. In such embodiments, the tie layer  106  may comprise materials as shown in Table 2.  
                         TABLE 2                           Tie layer 106 materials for an insulating       layer 104 comprising polypropylene.            Jacketing layer 302   Tie layer 106               Nylon   Polypropylene grafted with an unsaturated           anhydride, an acrylic acid, a carboxyl acid,           or a silane.       Polyethylene modified   Polypropylene grafted with an unsaturated       polyphenylene sulfide   anhydride, an acrylic acid, a carboxyl acid,           or a silane.       Polyurethane   Polypropylene grafted with an unsaturated           anhydride.       Ethylene vinyl alcohol   Polypropylene grafted with an unsaturated       co-polymer   anhydride, an acrylic acid, a carboxyl acid,           or a silane.                  
 
         [0032]    Alternatively, the insulating layer  104  may comprise ethylene propylene co-polymer and the jacketing layer  302  may comprise nylon, polyphenylene sulfide modified with a polyethylene functional group, polyurethane, or ethylene vinyl alcohol co-polymer. In such embodiments, the tie layer  106  may comprise materials as shown in Table 3.  
                         TABLE 3                           Tie layer 106 materials for an insulating       layer 104 comprising ethylene propylene co-polymer.            Jacketing layer 302   Tie layer 106               Nylon   Ethylene propylene co-polymer grafted with           an unsaturated anhydride, an acrylic acid,           a carboxyl acid, or a silane.       Polyethylene modified   Ethylene propylene co-polymer grafted with       polyphenylene sulfide   an unsaturated anhydride, an acrylic acid,           a carboxyl acid, or a silane.       Polyurethane   Ethylene propylene co-polymer grafted with           an unsaturated anhydride.       Ethylene vinyl alcohol   Ethylene propylene co-polymer grafted with       co-polymer   an unsaturated anhydride, an acrylic acid,           a carboxyl acid, or a silane.                  
 
         [0033]    In other embodiments, the insulating layer  104  comprises ethylene vinyl acetate and the jacketing layer  302  comprises nylon, polyphenylene sulfide modified with a polyethylene functional group, polyurethane, or ethylene vinyl alcohol co-polymer. In such embodiments, the tie layer  106  may comprise materials as shown in Table 4.  
                         TABLE 4                           Tie layer 106 materials for an insulating       layer 104 comprising ethylene vinyl acetate.            Jacketing layer 302   Tie layer 106               Nylon   Ethylene vinyl acetate grafted with an unsaturated           anhydride, an acrylic acid, or a carboxyl acid.       Polyethylene modified   Ethylene vinyl acetate grafted with an unsaturated       polyphenylene sulfide   anhydride, an acrylic acid, a carboxyl acid, or a           silane.       Polyurethane   Ethylene vinyl acetate grafted with an unsaturated           anhydride.       Ethylene vinyl alcohol   Ethylene vinyl acetate grafted with an unsaturated       co-polymer   anhydride, an acrylic acid, a carboxyl acid, or a           silane.                  
 
         [0034]    In yet other embodiments, the insulating layer  104  comprises methylpentene co-polymer and the jacketing layer  302  comprises nylon, polyphenylene sulfide modified with a polyethylene functional group, polyurethane, or ethylene vinyl alcohol co-polymer. In such embodiments, the tie layer  106  may comprise materials as shown in Table 5.  
                             TABLE 5                           Tie layer 106 materials for an insulating       layer 104 comprising methylpentene co-polymer.                Jacketing layer 302   Tie layer 106                       Nylon   Methylpentene co-polymer grafted with an               unsaturated anhydride.           Polyethylene modified   Methylpentene co-polymer grafted with an           polyphenylene sulfide   unsaturated anhydride.           Polyurethane   Methylpentene co-polymer grafted with an               unsaturated anhydride.           Ethylene vinyl alcohol   Methylpentene co-polymer grafted with an           co-polymer   unsaturated anhydride, an acrylic acid,               a carboxyl acid, or a silane.                      
 
         [0035]    In other embodiments, the insulating layer  104  comprises ethylene tetrafluoroethylene and the jacketing layer  302  comprises nylon, polyphenylene sulfide modified with a polyethylene functional group, or ethylene vinyl alcohol co-polymer. In such embodiments, the tie layer  106  may 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.  
         [0036]    Alternatively, it may be desirable to bond the insulating layer  104  to a metallic jacketing layer  402 , 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 layer  104  from mechanical damage. In various embodiments having a metallic jacketing layer  402 , the insulating layer  104  may comprise polyethylene, polypropylene, ethylene propylene co-polymer, methylpentene co-polymer, or ethylene tetrafluoroethylene. In such embodiments, the tie layer  106  may comprise the material of the insulating layer  104  (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.  
         [0037]    It may be desirable in certain applications to pot or attach the cable  100  of FIG. 3 or FIG. 4 to a connector. Accordingly, FIG. 5 illustrates a potting layer  502  disposed between the jacketing layer  302  and a connector  504 . While the jacketing layer  302  is illustrated in FIG. 5 as comprising a polymeric material, the present invention is not so limited. Rather, the connector  504  may be attached via the potting layer  502  to a metallic jacketing layer, such as the metallic jacketing layer  402  of FIG. 4. The potting layer  502  may comprise a material corresponding to the potting layer  202  of FIG. 2, or another material.  
         [0038]    It may also be desirable in certain situations to incorporate a tie layer material, such as that of the tie layer  106 , into the insulating layer  104  (shown in FIGS.  1 - 5 ) and/or the jacketing layer  302  (shown in FIGS. 3 and 5). Accordingly, FIG. 6 depicts a second illustrative embodiment of a cable  600  according to the present invention. The cable  600  comprises a plurality of conductors  602 , which may correspond to the conductors  102  of FIGS.  1 - 5 . The cable  600  further comprises an insulating layer  604  disposed around the conductors  602  and a jacketing layer  606  disposed on the insulating layer  604 .  
         [0039]    Still referring to FIG. 6, in one embodiment, a tie layer material is included in one of the insulating layer  604  and the jacketing layer  606  as a mixture. In various embodiments, one of the insulating layer  604  and the jacketing layer  606  may 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 layer  604  and the jacketing layer  606  comprises 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 layer  604  and the jacketing layer  606  comprises nylon and the other layer comprises a mixture of ethylene propylene co-polymer and an ethylene propylene co-polymer grafted with an unsaturated anhydride.  
         [0040]    In yet another embodiment, one of the insulating layer  604  and the jacketing layer  606  comprises 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 layer  604  and the jacketing layer  606  comprises 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 to FIG. 6, the insulating layer  604  or the jacketing layer  606  may 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.  
         [0041]    The particular embodiments disclosed above are illustrative only, as the invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the invention. Accordingly, the protection sought herein is as set forth in the claims below.