CA1216908A

CA1216908A - Electrical cable construction

Info

Publication number: CA1216908A
Application number: CA000453258A
Authority: CA
Inventors: Mitsuzo Shida; John Machonis, Jr.; Robert J. Zeitlin
Original assignee: Enron Chemical Co
Current assignee: Equistar Chemicals LP
Priority date: 1983-08-08
Filing date: 1984-05-01
Publication date: 1987-01-20
Also published as: JPS6056312A; FR2550656B1; GB2144901A; DE3425749C2; FR2550656A1; BE899985A; JPH0377604B2; DE3425749A1; GB8413918D0; NL8401556A

Abstract

ABSTRACT OF THE DISCLOSURE

An electrical cable construction which exhibits greatly improved structural stability over long periods of time and after exposure to moisture and greatly varying high and low temperatures. The electrical cable comprises a conductive core, a metallic shield extending around or through the core, and a protective polyolefin layer adhered directly to the shield by an adhesive blend. The adhesive blend comprises one or more of an ethylene homopolymer, a copolymer of ethylene and an .alpha.-olefin, and a copolymer of ethylene and at least one ethylenically unsaturated ester, blended with a graft or cograft copolymer which comprises a polyethylene backbone grafted with an ethylenically unsaturated dicarboxylic acid or acid anhydride or derivative thereof.

Description

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ELECTRIC~ ABLE CONST~UCTION

sAcKGRouND OF THE INVENTION
Field of the Invention This invention relates to improved electrical S cable constructions in which a metallic component is adhered directly to a protective polyolefin layer with an adhesive blend.

Description of the Art In the art of designing electrical cables, especially communication cables, conductors are generally assembled in a core and then surrounded by shield (such as a sheath) and a jacket.
One example of this construc-tion is the "Stalpeth" cable described by F. W. Horn in his book, "Lee's ABC of the Telephone", Vol. 5 (1974).
The shield is generally metallic, and the protective jacket is typically a polyolefin, such as polyethylene.
In the production of electrical cables a problem has always existed concerning the adhesion of the polyethylene jacket to the metal shield. Many attempts have been made to improve this adhesion and the use of ethylene/acrylic acid copolymers or ethylene/methacrylic acid copolymers as the adhesive layer has been one of the means by which this has been accomplished.
Even thouyh some measure of success has been obtained, the search continues for further improvements because of the effect observed on adhesion when the acrylic acid or methacrylic acid content of the polymer is increased. While an increase in the acrylic acid or methacrylic acid content of the polymer causes an increase in adhesion to the metal sheath, it has also resulted in a decrease in the adhesion to the polyethylene jacket.
The converse is also true, i.e. an increase in the adhesion to the polyethylene jacket can be accomplished by decreasing the acrylic acid or methacrylic acid content of the copolymer;
this, however, results in a decrease of adhesion to the metal sheath.

Excellent descriptions of the problems existing in the art of designing and constructing electrical cables, especially power and communication cables and cable shielding tapes are given in U.S. patent Nos. 4,292,463; 4,132,857;
4,049,904 and 3,935,374.

U.S. patent No. 4,132,857 discloses the use of a coextruded dual film laminate between the metal shield and the polyethylene jacket comprising 1) a first film layer of an ethylene-acrylic or methacrylic acid copolymer or known ionomer salts thereof and 2) a second film layer of either polyethylene, an ethylene-acrylyl ester copolymer or an ethylene-vinyl acetate copolymer. This composition gives some measure of improved jacketing resin adhesion at room temperature but not at high and/or low adhesion testing temperatures.

Great Britain published patent application 2,091,168A
provides improved high and low temperature adhesion by substituting a blend of a random copolymer of ethylene with an ethylenically unsaturated carboxylic acid and at least one different olefin polymer resin for the second layer of U.S. patent No. 4,132,857.

The patents described above have also attempted to improve performance by adding a layer between a metal-adherent adhesive layer and the jacket. Although this provides some improvement, it is highly desirable to obtain much higher levels of adhesion, both initially after preparation and after aging.
SUMMARY OF _HE INVENTION
It is an object of the invention to overcome one or more of the problems described above.
According to the invention, polyethylene or ethylene copolymers grafted with an ethylenically unsaturated dicarboxylic acid or acid anhydride, or derivatives, are blended with one or more 1) homopolymers of ethylene, 2) a-olefin copolymers of ethylene or 3) ethylene copolymers with ethylenically unsaturated esters. The resulting adhesive blend may also contain suitable elastomers, if desired.
These blends are us~d as the adhesive to form metal/ethylene polymer laminates and cable constructions.
These blends exhibit excellent adhesion to both metal and ethylene polymers, thus providing excellent adhesion of the ethylene polymer to the metal shield. The cable constructions of this invention have excellent high and low temperature structural integrity, both initially and after aging, which is surprisingly superior to that of any constructions known before.
Thus broadly, the invention contemplates an electrical cable comprising a conductive core, a metallic shield extending around or through the core, and a protective polyolefin layer adhered ~,irectly to the shield with an adhesive. The adhesive ~omprises a,blend of a graft or cograft copolymer comprising an ethylene homopolymer or copolymer backbone grafted with a grafting m~nomer comprising an ethyl,enically unaaturated,dicarboxylic acid or acid anhydride or a derivative thereof, and at least'--one of a homopolymer of et~ylene,or a copolymer of ethy~ene and an~~-olefinr or a copolymer of ethylepe~and~a-t least one ethylenically unsaturated ester. The blend contains between about 5.6 x 10 6 and about 8 x io 3 mo1es of-the acid, acid anhydride or derivative per hundred grams of the blend.

BRIEF DESCRIPTION OE' _IE DRAWINGS
Fig. 1 is a cutaway perspective view of an end of a communication cable illustrating one embodiment of the present invention; and, Fig. 2 is a diagrammatic cross-sectional view of a cable illustrating a second embodiment of the present invention.

DETAILED DESCRIPTION_OF_THE INVENTION
In the constructlon of electrical cables, especially telecommunication cables such as telephone cables, insulated conductors are typically assembled in a core and surrounded by a shield and a jacke-t. The shield may comprise a sheath, a screen, a shielding tape, etc.
and, as used herein, these terms denote a relatively thin layer of any metal, bare or coated, which can provide mechanical protection and electrostatic and electromagnetic screening for the conductors in the cable core.
Typically, the protective jacket comprises a layer of a polyolefin material, such as polye-thylene.
When cables are installed underground, these jackets may be subjected to damage due to the rigors of installation, or by rocks, rodents, weather conditions, etc. The underlying shield may, therefore, be exposed to water and consequently there is a possibility of corrosion. Also, exposure to widely varying high and low temperatures is encountered.
Thus, it is very important that the protective jacket be adhered very well to the metallic shield in order to provide maximum protection against the elements.
In some cables, especially where the number of conductors in the core is very large or the cable very long, an additional shield, usually comprising a ribbon of metal such as aluminum, extends through the multiconductor core. The ribbon is intended to prevent crosstalk between cable pairs of the core. The ribbon can be in the shape of an S, Z, D, or T, or any other appropriate configuration.
In both types of shields described above, the shield is generally closed by a longitudinally extending seam comprising the respective, overlapping edges of the shield. It is extremely important that these edges are adhered together strongly, in addition to the adhesion of the polyolefin layer to the metal itself.
The Figures illustrate two types of electrical cable constructions which embody the present invention.
Referring first to Fig. 1, a typical multipair conductor communications cable 10 is illustrated. The cable 10 comprises, for example, an inner core of multiple pairs of insulated conductors 12 bundled in a plastic core wrap 14 of, for example, polypropylene or polyethylene terephthalate, which is securely bound by a binder tape 16. Each insulated conductor 12 comprises a plastic coated copper wire, for example.
The bundle is enclosed in a metallic shield 18, which preferably comprises a longitudinally folded tube having a sealed overlapping seam 20.
An outer protective jacket 22, preferably of a polyolefin such as polyethylene, is disposed about the shield 18, and is preferably bonded thereto wi-th an adhesive according to the invention, as described below.
Fig. 2 illustrates a telephone cable 40 which comprises an alternative embodiment of the invention.
The cable 40 comprises a plurality of conductors 42 for transmitting messages in one direction, and a second plurality of concluctors 44 for transmi-tting signals in another direction. The illustrated groups of conductors 42 and 44 are each of generally semicircular cross-section, and the conductors of each group are bound together by plastic core wrap 46 and 48, respectively.
Preferably, the core wraps 46 and 48 comprise a plastic tape.
Metal shields 50 and 52, respectively, are disposed outwardly of the core wraps 46 and 48, and are preferably corrugated and in contact with the core wraps 46 and 48.
The metal shields 50 and 52 serve the dual purpose of improving isolation between the opposite directions of transmission, as well as protecting against lightning and water. Both shields 50 and 52 may be of aluminum, or another metal, and may be coated on both sides with an adhesive of the invention, so as to adhere to each other along the portions thereof which extend across the diameter of the cable in contact with each other.
A plastic jacket 54 surrounds the shields 50, 52 about the entire circumferential surfaces thereof, and is adhered to the outside surfaces thereof by an adhesive according to the invention.
Strong adhesion between the plastic jacket 54 and the shields 50, 52 is very important in providing the cable with mechanical strength and protection against water.
The various metal/plastic bonds encountered in 30 the structures of Fig. 1 and Fig. 2 are effected by the application of an adhesive blend of this invention - between the metal and plastic. This can be carried out by any suitable method known to one skilled in the art ~2~
~ 7 --and by any sequence of steps convenient to the fabri-cator. Examples of such methods include, but are not necessarily limited to, extrusion coating, extrusion lamination, dry lamination of monolayer or coextruded film, coextrusion coating, or a combination of these methods or any other suitable method for joining plastic resin to metals.
Although the laminate can be as simple as metal/adhesive/polyolefin, there is no reason why another polymer or polymers adherent to both the adhesive and the polyolfin cannot be inserted between the two materials.

The Shielding Material The metallic substrates (e.g~, sheets, strips, etc.) which comprise the cable shielding of the present invention can be of any of a wide variety of metallic materials such as, for example, aluminum, aluminum alloys, alloy-clad aluminum, copper, surface modified copper, bronze, steel, tin-free steel, tin plate steel, aluminized steel, aluminum-clad steel, stainless steel, copper-clad stainless steel r copper-clad low carbon ; steel, terne-plate steel, galvanized steel, chrome plated or chrome treated steel, lead, magnesium, tin and the like. Such metals can, of course, be surface treated or have conversion coatings on the surface thereof if desired.
Particularly preferred metallic substrates for use herein include chrome/chrome oxide coated steel (also commonly referred to in the art as tin-free steel), stainless steel, aluminum and copper.

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The Jacketing Materlal Olefin polymer materials useful for the jacketing material in cable structures of this invention include various ethylene homopolymers (e.g., low, medium and high density polyethylenes), copolymers comprising a major proportion of ethylene with a minor proportion of known copolymerizable monomers such as higher (e.g., C3 to about C12) ~-olefins and ethylenically unsaturated ester monomers (e.g., vinyl acetate, ethyl acrylate, etc.). Ethylene homopolymers and ethylene/higher~~olefin copolymers are particularly preferred.

The Adhesive Blend . . _ ~ . .
According to this invention, excellent structural integrity between the metallic shield and the protective polyolefin jac~et of an electrical cable is obtained by the use of an adhesive blend. This integrity is evident both directly after molding, and after prolonged exposure to both high and low temperatures.
The adhesive blend of the invention comprises a blend of one or more ethylene homopolymers, ethylene copolymers with an ~-olefin, or an ethylene ester copolymer, along with a graft or cogra~t copolymer of a polyethylene backbone and a grafting monomer which comprises an ethylenically unsaturated dicarboxylic acid ~5 or acid anhydride, or derivatives, or a monomer which undergoes ring closure to produce such an anhydride or imide.
It is believed that the excellent structural ir.tegrity of the invention is achieved because the adhesive is very closely related to the plastic material of the jacket. This close relationship is possible because very few polar groups (e.~., only about 10 6 to ~;2~L6~0~
g --10 3 moles of anhydride groups per 100 g. of the polymer blend, depending on the particular anhydride) are required to obtain excellent adhesion to metal and the desirable aging properties of this invention. That such a low concentration of reactive groups is required is surprising in view of statements made in the prior art (see, for example, U.S. Patent No. 4,292,463).
It is preferred in this invention first to prepare a graft copolymer and then use this graft co-polymer in combination with a wide variety of non-grafted polyolefins and elastomers so that the properties of the adhesive blend can be controlled. The amount of grafting monomer in the adhesive composition is determined by the amount required to attain maximum performance of the laminate, and may be in the range of about 5.6 x 10 6 to about g x 10 3 moles of dicarboxylic acid, dicarboxylic acid anhydride, or derivatives thereof per hundred grams of the polymer blend. The preferred range is about 1.6 x 10 4 to about 1.6 x 10 3 moles of dicarboxylic acid, dicarbo~ylic acid anhydride, or derivatives thereof per hundred grams of the pol~mer blend.
A number of adhesive blends which are believed to provide suitable levels of adhesion to both metallic shielding materials and plastic jacketing materials and which are believed to exhibit the desirable aging properties of the invention, are described in U.S. Patent Nos. 4,087,587 (Shida et al), 4,087,588 (Shida et al) and 4,298,712 (Machonis), all assigned to the assignee hereof. Suitable adhesive blends are also described in the following patent applications: Adur et al Canadian Ser.
No. 415,153, filed November 9, 1982, Shida e-t al Canadian Serial No. 420,654 filed February 1, 1983, and Adur et al, Canadian Serial No. 423,713, filed March 16, 1983, all of which are also assigned to the assignee hereof.
Another patent which discloses blends which are believed to be useful in this invention is U.S. Patent No. 4,230,830 (Tanny et al).

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Other U.S. patents which disclose blends which are believed to be useful ln the invention include 3,342,771 (Cheritat); 3,658,148 (McConnell); 3,856,889 (McConnell);
3,953,541 (Fuji); 4,058,647 (Inoue); 4,111,988 (Inayoshi et al); 4,134,927 (Tomoshize); 4,198,327 (Matsumoto et al);
4,198,369 (Yosikawa et al); 4,284,541 (Takeda et al); 4,350,740 (Coran et al); 4,350,797 (Marzola et al); and 4,370,388 (Mi-to).

The Graft Copolymer The graft copolymers used in this invention are prepared by reacting unsaturated dicarboxylic acids or acld anhydrides, or derivatives thereof, with polyethylene or ethylene copolymer backbones.

The ethylenically unsaturated dicarboxylic acid anhydrides useful as grafting monomers include compounds such as maleic anhydride, itaconic anhydride, 4-methyl cyclohex-4-ene-1,2-dicarboxylic acid anhydride, bicyclo(2.2.2)oct-5-ene-2,3-dicarboxylic acid anhydxide, 1,2,3,4,5,8,9,10-octahydronaphthalene-2,3-dicarboxylic acid anhydride, 2-oxa-1,3-diketospiro~4.4)non-7-ene, bicyclo(2.2.1)hept-5-ene-2,3-dicarboxylic acid anhydride, tetrahydrophthalic anhydride, x-methylbicyclo(2.2.1)-hept-5-ene-2,3-dicarboxylic acid anhydride, x-methyl-norborn-5-ene-2,3-dicarboxylic acid anhydride, norborn-5-ene-2,3-dicarboxylic acid anhydride, Nadic 6~

anhydride, Nadid~ methyl anhydride, Himic~ anhydride, and methyl Himic~ anhydride.
Monomers which ring close to form anhydrides or imides when subjected to heat, e.g., maleic acid, fu~aric acid, citric acid and monoalkyl maleates and maleamic acids, may also be used in this invention.
Maleamic acids useful in this invention are substituted maleamic or fumaramic acids of the formulas:
O o O
ll ll ll a) R"OCCH=CHCNH-R"'-COR
where R' is a straight or branched alkylene radical of 1-18 carbon atoms, a cycloaliphatic or aromatic ring, and R'' and R''' are H or a straight or branched alkylene cycloaliphatic, heterocyclic or aromatic radical; and, O O
ll ll b) (R"OCCH=CHCNH)2 Rn where n is ei-ther zero or one and R' and R'' are as described above.
Among the dicarboxylic acids and acid anhydrides particularly useful in the grafted copolymers of this invention are maleic anhydride, fumaric acid, x-methylbicyclo52.2.1)hept-5-ene-2,3-dicarboxylic acid anhydride and bicyclo(~.2.1)hept-5-ene-2,3-dicarboxylic acid anhydride.
Other monomers which modify the physical and chemical properties of the graft copolymers may be cografted to the polymer backbone, if desired.
For example, conjugated unsaturated esters and amides can be used as cograft monomers. Included among the conjugated unsaturatd esters suitable for cografting are dialkyl maleates, dialkyl fumarates, dialkyl L6~

itaconates, dialkyl mesaconates, dialkyl citraconates, alkyl acrylates, alkyl crotonates, alkyl tiglates and alkyl methacrylates where alkyl represent aliphatic, aryl-aliphatic and cycloaliphatic groups containing 1-12 carbon atoms. Esters particularly useful in the cografted copolymers of this invention are dibutyl maleate, diethyl fumarates and dimethyl itaconate.
It is often desirable to use more than one grafting monomer in either or both classes of monomers in order to control the physical properties of the final products.
Grafting is accomplished, in general, by heating a mixture of the polymer or polymers and the monomer or monomers with or without a solvent. The mixture can be heated to above the melting point of the polyolefin with or without a catalyst. Thus, the graft-ing occurs in the presence of air, hydroperoxides, or other free radical catalysts or, preferably,in the eseential absence of those materials where the mixture is maintained at elevated temperatures and (if no solvent is used) preferably under high shear.
The term "polyethylene" used herein in reference to the graft copolymer backbone includes ethylene homopolymers, and copolymers of ethylene with propylene, butene and other unsaturated aliphatic hydrocarbons containing at least 50 mole percent ethylene. It is preferable sometimes to use mixtures of two or more of the above homopolymers or copolymers. Especially preferred for the graftin~ backbone are high density polyethylenes with a density of 0.94 to 0.96-~ and ethylene-~-olefin copolymers with a density of 0.915 to 0.939 (known as linear low density polyethylene, LLDPE).

The Ethylene Homopolymer or Copolymer The adhesive blends of this invention may contain one or more of the ethylene homopolymers or copolymers of ethylene mentioned above. Especially preferred are ethylene-~ -olefin copolymers with a density of 0.915 - 0.939 (LLDPE).

The Ethylene-Ester Copolymer The adhesive blends of this invention may also contain one or more ethylene-ester copolymers. The term "ethylene-ester copolymers" as used herein denotes copolymers of ethylene with ethylenically unsaturated monomers which contain an ester grouping. Especially preferred ethylene-ester copolymers are ethylene-vinyl acetate copolymers, ethylene-ethyl acrylate copolymers and ethylene-methyl acrylate copolymers, e-thylene-ethyl methacrylate copolymers and ethylene-methyl methacrylate copolymers.

Additional Ingredients Also, the adhesive blends of this invention may contain one or more elastomers. The term 'lelastomer" as used herein denotes homopolymers of isobutylene, copolymers of isobutylene, elastomeric copolymers of ethylene and ~-olefins, elastomeric terpolymers of ethylene, ~-olefins and a diene, homopolymers of chloroprene, copolymers of a diene and a vinyl aromatic compound, block copolymers of a diene vinyl aromatic compound, hydrogenated block copolymers of a diene and vinyl aromatic compound, homopolymers of butadiene, and copolymers o~ an ethylenically unsaturated nitrile and diene.

EXA~PLES

The following Examples illustrate the enhanced adhesion in electrical cable constructions of the adhesive blends of the invention. The Fxamples are illustrative only, and are in no way to be regarded as limiting the scope of the invention.
Adhesive blends were prepared in an electrically heated ~rabender mixer using a scroll type mixer at a mixing temperature of 325F, a rotor speed of 120 rpm, and total mixing time of ten minutes.
The resulting adhesive blends were then com-pression molded into films approximately 0.006 inch thick at 350F.
other adhesives were prepared in a Banbury type intensive mixer under the following conditions: 320F
drop temperature, 110 rpm and total mixing time of 3 minutes. Blown films were prepared with a thickness of about 0.0025-0.003 in.
In order to simulate conditions and construction of actual cable, the following procedure was used: a 6" X 6" X 0.075" plaque of polyethylene cable jacketing compound was prepared. A layer of an adhesive blend prepared as described above and a layer of steel 0.010" thick, or of aluminum 0.008" thick, are placed in a press at 350F. The laminate is heated for one minute and cooled. The polymer coated steel is then adhered to the cable jacketing in a press preheated at 420F for 3 minutes with light contact and one minute under pressure.
The adhesion of the assembly was tested according to ASTM D 1876 at 2 in/min. The adhesion values were obtained at several temperatures before and ~2~

after aging in deioni~ed water for 7 days at 140F -145F (60-62C).

Example 1 X-methyl bicyclo(2.2.1)hept-5-ene-2,3-dicarboxylic acid anhydride (XMNA) was reacted with a high-density polyethylene homopolymer whose melt index under high load is 3.0 g/10 minutes and whose density is 0.961 g/cc to give a graft copolymer containing 1.5 wt.%
XMNA and a melt index of 1.5 g/10 minutes.
This graft copolymer was blended with a linear low-density polymer (LLDPE) having a melt index of 2 and a density of 0.919 in a ratlo of 1:9. The xesultant adhesive was adhered to a plate of single reduced electrolytically coated chrome steel and to a polyethylene cable jacketing compound as described above.
The resulting laminates were tested for adhesion initially and after aging for one week as also described above. The results are shown in Table I.

Comparative Example 1 An ethylene-acrylic acid copolymer containing 8% acrylic acid (MI 5.5, density 0.932) was adhered to the same steel and polyethylene as Example 1. The results are shown in Table I.

Example 2 An adhesive consisting of a HDPE graft copolymer and LLDPE in a ratio of 15:85 prepared as in Example l was laminated to steel and cable jacketing.
The laminate was tested for bond strength before and after aging. The results are shown in Table I.

Example 3 Maleic anhydride was reacted with a high-density polyethylene homopolymer whose high load melt index was 7~0 g/lO min~ and whose density was 0.961 g/cc to give a graft copolymer. This graft copolymer was blended and tested as in Example l. The results are shown in Table I.

Example 4 An adhesive consisting of the graft copolymer of Example 1, a HDPE (MI 18, density 0.955~ and polyisobutylene (Vistanex L80) in the ratio 8:64:28 was tested as described in Example l. The results are shown in Table I.

Example 5 XMNA is reacted with a linear low density polyethylene (high load melt index 2.6, density 0.917) to give a graft copolymer containing 1.3 wt.% XMNA and an MI
of 6.3. This graft copolymer was used in a composite structure as described in Example l.

The results in Table I clearly shown that the laminates of this invention are superior to those containin~ EAA copolymer a-t both high and low temperature.

Example 6 The adhesive of Example 1 was adhered to aluminum (Type 1100-0) and the polyethylene jacket compound of Example 1. The adhesion of the laminate was tested as previously described. The results are shown in Table II.

Compara ive Example 2 An ethylene-acrylic acid copolymer as in Comparative Example 1 was adhered to the same aluminum and polyethylene as described in Example 6 and adhesion was tested. The results are shown in Table II.

Example 7 An adhesive blend of the graft copolymer described in Example 1 and an ethylene-vinyl acetate copolymer (EVA) (melt index 1.0, 5 wt.% vinyl acetate) at a ratio 3:97 was used as the adhesive between an aluminum alloy (Type 1100-0) and polyethylene and adhesion was tested. The results are shown in Table II.

Example 8 An adhesive blend of the graft copolymer described in Example 1 with an ethylene-vinyl acetate copolymer containing 8 wt.~ vinyl acetate and an MI of 3.0 was prepared at a ratio of 1:9. An aluminum laminate as described in Example 6 was tested. The results are shown in Table II.

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The results shown in Table II illustrate that the laminates of this invention maintain -their structural integrity at low or elevated temperatures even after aging; whereas the adhesion of the laminate containing EAA declines at low temperature.

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GLOSSARY OF TERMS
______ EAA - Ethylene-acrylic acid copolymer HDPE - High density polyethylene LLDPE - Linear low density polyethylene MI - Melt index XMNA - X-methylbicyclo(2.2.13hept-5-ene-2,3-dicarboxylic acid anhydride Nadic anhydride - trademark (Buffalo Color Corp.) for bicyclo(2.2.1)hept-5-ene-2,3-dicarboxylic anhydride Nadic methyl anhydride-trademark (Buffalo Color Corp.) for x-methyl-bicyclo (2.2.1)hept-5-ene-2,3-dicarboxylic anhydride Himic anhydride - trademark (Hitachi Chemical Co.) for bicyclo(2.2.1)hept-5-ene-2,3-dicarboxylic anhydride Methyl Himic anhydride - trademark (Hitachi Chemical Co.) for x-methyl-bicyclo(2.2.1)hept-5-ene-

2,3-dicarboxylic anhydride

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An electrical cable comprising a conductive core, a metallic shield extending around or through said core, and a protective polyolefin layer adhered directly to said shield with an adhesive comprising a blend of:
a) a graft or cograft copolymer comprising an ethylene homopolymer or copolymer backbone grafted with a grafting monomer comprising an ethylenically unsaturated dicarboxylic acid or acid anhydride or a derivative thereof, and at least one of b) a homopolymer of ethylene; or, c) a copolymer of ethylene and an .alpha.-olefin;
or, d) a copolymer of ethylene and at least one ethylenically unsaturated ester, wherein said blend contains between about 5.6 x 10-6 and about 8 x 10-3 moles of said acid, acid anhydride or derivative per hundred grams of said blend.

2. The cable of claim 1 wherein said shield comprises a metal chosen from the group consisting of chrome coated steel, chrome oxide coated steel, stainless steel, aluminum and copper.

3. The cable of claim 1 wherein said protective polyolefin layer comprises low, medium or high density polyethylene or copolymers having greater than about 50 wt.% ethylene with olefins of 3-12 carbon atoms.

4. The cable of claim 1 wherein the backbone of (a) comprises at least one ethylene homopolymer or copolymer of ethylene with an unsaturated aliphatic hydrocarbon.

5. The cable of claim 4 wherein said backbone comprises LLDPE or an ethylene homopolymer having a density of 0.94 to 0.96.

6. The cable of claim 1 wherein said grafting monomer is chosen from the group consisting of maleic anhydride, itaconic anhydride, 4-methyl cyclohex-4-ene-1,2-dicarboxylic acid anhydride, bicyclo(2.2.2)oct-5--ene-2,3-dicarboxylic acid anhydride, 1,2,3,4,5,8,9,10-octahydronaphthalene-2,3-dicarboxylic acid anhydride, 2-oxa-1,3-diketospiro(4.4)non-7-ene, bicyclo(2.2.1)-hept-5-ene-2,3-dicarboxylic acid anhydride, tetra-hydrophthalic anhydride, x-methylbicyclo(2.2.1)hept-5-ene-2,3-dicarboxylic acid anhydride, x-methylnor-born-5-ene-2,3-dicarboxylic acid anhydride, norborn5-ene-2,3-dicarboxylic acid anhydride, Nadic anhydride, methyl Nadic anhydride, Himic anhydride, methyl Himic anhydride, maleic acid, fumaric acid, citric acid, monoalkyl maleates and maleamic acids.

7. The cable of claim 6 wherein said backbone is further grafted with a cograft monomer selected from the group consisting of dialkyl maleates, dialkyl fumarates, dialkyl itaconates, dialkyl mesaconates, dialkyl citraconates, alkyl acrylates, alkyl crotonates, alkyl tiglates, and alkyl methacrylates where alkyl is aliphatic, aryl-aliphatic or cycloaliphatic groups containing 1-12 carbon atoms.

8. The cable of claim 1 wherein said ethylene homopolymer of (b) comprises high density polyethylene.

9. The cable of claim 1 wherein said copolymer of (c) comprises LLDPE.

10. The cable of claim 1 wherein said copolymer of (d) is selected from the group consisting of ethylene-vinyl acetate copolymers, ethylene-methyl acrylate copolymers, ethylene-ethyl acrylate copolymers, ethylene-methyl methacrylate copolymers and ethylene-ethyl methacrylate copolymers.

11. The cable of claim 1 wherein said adhesive blend further includes one or more elastomers.

12. The cable of claim 11 wherein said elastomer is chosen from the group consisting of homopolymers of isobutylene, copolymers of isobutylene, elastomeric copolymers of ethylene and .alpha.-olefins, elastomeric terpolymers of ethylene, .alpha.-olefins and a diene, homopolymers of chloroprene, copolymers of a diene and a vinyl aromatic compound, block copolymers of a diene and a vinyl aromatic compound, hydrogenated block copolymers of a diene and a vinyl aromatic compound, homopolymers of butadiene, and copolymers of an ethylenically unsaturated nitrile and a diene.

13. The cable of claim 1 wherein said backbone of (a) is HDPE or LLDPE and said grafting monomer is selected from the group consisting of maleic anhydride, fumaric acid, x-methylbicyclo(2.2.1)hept-5-ene-2,3-dicarboxylic acid anhydride and bicyclo(2.2.1)hept-5-ene-2,3-dicarboxylic acid anhydride.

14. The cable of claim 1 wherein said shield, said adhesive and said protective layer are formed by one or more methods selected from the group consisting of extrusion coating, extrusion lamination, dry lamination of monolayer or coextruded film, or coextrusion coating.

15. The cable of claim 1 wherein said blend contains between about 1.6 x 10-4 and about 1.6 x 10-3 moles of said acid, acid anhydride, or derivative per 100 grams of said blend.

16. The cable of claim 1 wherein said adhesive blend comprises a blend of said graft copolymer, a high density ethylene homopolymer or a copolymer of ethylene with an .alpha.-olefin, and polyisobutylene.

17. The cable of claim 16 wherein said blend comprises an XMNA graft copolymer with a high density polyethylene backbone, a high density polyethylene homopolymer, and polyisobutylene.

18. The cable of claim 1 wherein said blend comprises an XMNA graft copolymer with a high density polyethylene backbone and LLDPE.

19. The cable of claim 18 wherein the weight ratio of said graft copolymer to said LLDPE is about 1:9.

20. The cable of claim 18 wherein the weight ratio of said graft copolymer to said LLDPE is about 15:85.

21. The cable of claim 1 wherein said blend comprises a blend of a graft copolymer of maleic anhydride and a high density polyethylene homopolymer backbone, and LLDPE.

22. The cable of claim 1 wherein said blend comprises a blend of an XMNA graft copolymer with an LLDPE backbone, and LLDPE.