GB2144901A - Electrical cable construction - Google Patents

Abstract

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

Description

SPECIFICATION Electrical cable construction This invention relates to electrical cable constructions in which a metallic component is adhered directly to a protective polyolefin layer with an adhesive blend.

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.

On example of this construction 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 of this kind 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 an adhesive layer between the two has been one of the means by which this has been accomplished.

Even though 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, that is an increase in the adhesion to the polyethylene jacket can be obtained 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 desigting and constructing electrical cables, especially power and communication cables and cable shielding tapes are given in U.S. Patents No. 4,292,463; 4,132,857; 4,049,904and 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.

British 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 referred to 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.

We have found that certain polymeric adhesive blends, that is blends of a polyethylene or ethylene copolymer backbone grafted with an ethylenically unsaturated dicarboxylic acid or acid an hydride, or derivative thereof, with one or more 1) homopolymers of ethylene, 2) a-olefin copolymers of ethylene or 3) ethylene copolymers with ethylenically unsaturated esters, exhibit excellent adhesion to both metal and ethylene polymers, thus providing excellent adhesion of an ethylene polymer sheath to the metal shield in a cable construction. 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 known cable constructions.

According to the present invention, there is provided an electrical cable which comprises a conductive core, a metallic shield extending around or through the core, and a protective polyolefin layer adhered to the shield with an adhesive blend comprising: a) a graft or cograft copolymer comprising an ethylene homopolymer or copolymer backbone grafted with a grafting monomer which is an ethylenically unsaturated dicarboxylic acid or acid anhydride or a derivative thereof, and at least one of b) a homopolymer of ethylene; c) a copolymer of ethylene and an a-olefin; or, d) a copolymer of ethylene and at least one ethylenically unsaturated ester, the adhesive blend containing from 5.6 x 10-6 to 8 X 10-3 moles of said acid, acid anhydride or derivative per hundred grams of the blend.

In the construction of electrical cables, particularly telecommunication cables such as telephone cables, insulated conductors are typically assembled in a core and surrounded by a shield and a jacket. The shield may comprise a sheath, a screen, a shielding tape, etc. and, as used herein, these terms deonote 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 polyethylene. 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, particularly 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 aluminium, extends through the multi-conductor core. The ribbon is intended to prevent cross-talk 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.

In order that the invention may be more fully understood, preferred embodiments thereof will now be described, by way of example, with reference to the accompanying drawing, in which Figure 1 is a cutaway perspective view of a communication cable illustrating one embodiment of the present invention; and, Figure 2 is a diagrammatic cross-sectional view of a cable illustrating a second embodiment of the present invention.

Referring first to Fig. 1, a typical multi-pair conductor communications cable 10 is illustrated.

The cable 10 comprises, for example, an inner core of multiple pairs of insulated conductors 1 2 bundled in a plastic core wrap 14 of, for example, polypropylene or polyethylene terephthalate, which is securely bound by a binder tape 1 6. Each insulated conductor 1 2 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 bonded thereto with an adhesive according to the invention, as described below.

Fig. 2 illustrates a telephone cable 40 which comprises an alternative embodment of the invention. The cable 40 comprises a plurality of conductors 42 for transmitting messages in one direction, and a second plurality of conductors 44 for transmitting 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 aluminium, 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 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 and by any sequence of steps convenient to the fabricator. 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 polyolefin cannot be inserted between the two materials.

The Shielding Material The metallic substrates (e.g., sheets, strips, etc.) which form the cable shielding of the present invention can be of any of a wide variety of metallic materials such as, for example, aluminium, aluminium alloys, alloy-clad aluminium, copper, surface modified copper, bronze, steel, tin-free steel, tin plate steel, aluminized steel, aluminium-clad steel, stainless steel, copper-clad stainless steel, copper-clad low carbon steel, terne-plate steel, galvanized steel, chrome plated or chrome treated steel, lead, magnesium, and tin. 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, aluminium and copper.

The Jacketing Material 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) a-olefins and ethylenically unsaturated ester monomers (e.g., vinyl acetate, ethyl acrylate, etc.). Ethylene homopolymers and ethylene/higher a-olefin copolymers are particularly preferred.

The Adhesive Blend As already indicated, the present invention is based on the discovery that excellent structural integrity between the metallic shield and the protective polyolefin jacket of an electrical cable can be obtained by the use of an adhesive blend as already described. This integrity is evident both directly after moulding, and after prolonged exposure to both high and low temperatures.

It is believed that this excellent structural integrity 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.g., only about 10-6 to 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 4,292,463).

It is preferred first to select a suitable graft copolymer and then use this graft copolymer 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, within the range specified above, is determined by the amount required to attain maximum performance. The preferred range is from 1.6 x 10-4 to 1.6 x 10-3 moles of dicarboxylic acid, dicarboxylic acid anhydride, or derivative thereof per hundred grams of the polymer 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. Patents 4,087,587, 4,087,588 and 4,298,712. Suitable adhesive blends are also described in British Patent Applications 2113696A, 21 16187A and 2119389A. Another patent which discloses blends which are believed to be useful in this invention is U.S. Patent 4,230,830.

Other U.S. patents which disclose blends which are believed to be useful in the invention include 3,342,771; 3,658,148; 3,856,889; 3,953,541; 4,058,647; 4,111,988; 4,134,927; 4,198,327; 4,198,369; 4,284,541; 4,350,740; 4,350,797; and 4,370,388.

The Graft Copolymer The graft copolymers used in the adhesive blends are prepared by reacting unsaturated dicarboxylic acids or acid anhydrides, or derivatives thereof, with polyethylene or ethylene copolymer backbones.

The ethylenically unsaturated dicarboxylic acid anhydrides useful as grafting monomers include, for example, maleic anhydride, itaconic anhydride, 4-methyl cyclohex-4-ene-1,2dicarboxylic acid anhydride, bicyclo(2 .2. 2)oct-5-ene-2, 3-dicarboxylic acid anhydride, 1,2,3,4,5,8,9,1 0-octahydronaphthalene-2, 3-dicarboxylic acid anhydride.2-oxa-l, 3-diketospi- ro(4.4)non-7-ene,bicyclo(2.2.1)hept-5-ene-2,3-dicarboxylic acid anhydride, tetrahydrophthalic anhydride, x-methylbicyclo(2.2. l)-hept-5-ene-2, 3-dicarboxylic acid anhydride,x-methyl-norborn 5-ene-2, 3-dicarboxylic acid an hydride, norborn-5-ene-2, 3-dicarboxylic acid anhydride, Nadic anhydride, Nadic methyl anhydride, Himic anhydride, and methyl Himic anhydride ("Nadic" and "Himic" are Trade Marks).

Monomers which ring close to form anhydrides or imides when subjected to heat, for example maleic acid, fumaric acid, citric acid and monoalkyl maleates and maleamic acids, may also be used in the grafting monomer.

Maleamic acids useful for this purpose are substituted maleamic or fumaramic acids of the formula:

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,

where n is either 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 the blend are 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.

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.

Suitable conjugated unsaturated esters suitable for this purpose include, for example, dialkyl maleates, dialkyl fumarates, dialkyl itaconates, dialkyl mesaconates, dialkyl citraconates, alkyl acrylates, alkyl crotonates, alkyl tiglates and alkyl methacrylates, in all of which alkyl represents aliphatic, aryl-aliphatic and cycloaliphatic groups containing 1-1 2 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, in general effected 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. Grafting may be effected in the presence of air, hydroperoxides, or other free radical catalysts or, preferably, in the essential 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 sometimes preferred to use mixtures of two or more of the above homopolymers or copolymers. Preferred backbone polymers are high density polyethylenes with a density of 0.94 to 0.96 + and ethylene-a-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 ethylene homopolymers or copolymers of ethylene mentioned above. Ethylene-a-olefin copolymers with a density of 0.915-0.939 (LLDPE) are particularly preferred.

The Ethylene-Ester Co polymer 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. Preferred ethyleneester copolymers are, for example, ethylene-vinyl acetate copolymers, ethylene-ethyl acrylate copolymers and ethylene-methyl acrylate copolymers, ethylene-ethyl methacrylate copolymers, and ethylene-methyl methacrylate copolymers.

Additional Ingredients The adhesive blends used according to the invention may contain one or more elastomers, the term "elastomer" being used herein to denote homopolymers of isobutylene, copolymers of isobutylene, elastomeric copolymers of ethylene and a-olefins, elastomeric terpolymers of ethylene, a-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 of an ethylenically unsaturated nitrile and diene.

In order that the invention may be more fully understood, the following examples are given by way of illustration.

In these examples, adhesive blends were prepared in an electrically heated Brabender mixer using a scroll type mixer at a mixing temperature of 325"F (163"C) a rotor speed of 120 rpm, and total mixing time of ten minutes. The resulting adhesive blends were then compression moulded into films approximately 0.006 inch (0.1 5 mm) thick at 350"F (177"C).

Other adhesives were prepared in a Banbury type intensive mixer under the following conditions: 320"F (160"C) drop temperature, 110 rpm and total mixing time of 3 minutes.

Blown films were prepared with a thickness of 0.0025-0.003 in. (0.064-0.076 mm).

In order to simulate conditions and construction of actual cable, the following procedure was used: a 6" x 6" x 0.075" (152 mm X 152 mm X 1.91 mm) 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" (0.25 mm) thick, or of aluminium 0.008" (0.20 mm) thick, are placed in a press at 350"F (177"C). 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 420"F (216"C) 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 (51 mm/min). The adhesion values were obtained at several temperatures before and after aging in deionized water for 7 days at 140"F-145"F (60-62"C).

Example I 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 ratio of 1:9. The resultant 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 1 was laminated to steel and cable jacketing. The laminate was tested for bond strength before and after aging. The results are shown in Table Example 3 Maleic anhydride was reacted with a high-density polyethylene homopolymer whose high load melt index was 7.0 g/10 min. and whose density was 0.961 g/cc to give a graft copolymer.

This graft copolymer was blended and tested as in Example 1. The results are shown in Table 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 1.

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 Ml of 6.3. This graft copolymer was used in a composite structure as described in Example 1.

The results in Table I clearly shown that the laminates of this invention are superior to those containing EAA copolymer at 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.

Comparative 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 Ml 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.

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.

TABLE I ADHESION AT INDICATED TESTING TEMPERATURE1 0 F(-18 C) RoomTemp2 140 F(63 C) 160 F(71 C) Laminate3 Initial Aged Initial Aged Initial Aged Initial Aged Example 1 30 30 36 30 70 65 40 404 Comparative Example 1 16 6 24 17 17 19 7 6 Example 2 34 31 50 49 70 56 -- - Example 3 28 36 27 42 29 42 -- - Example 4 35 44 31 42 30 40 -- - Example 5 24 21 30 21 19 27 -- - NOTES: 1 Adhesion in lb/in.

2 Room temperature = 72 F(22.2 C).

3 Laminate composition: chrome steel/adhesive/polyethylene jacketing compound 4 Plastic peeling tab tears without separation of plastic from the metal.

TABLE II ADHESION AT INDICATED TESTING TEMPERATURE1 0 F(-18 C) Room Temp2 140 F(63 C) Laminate3 Initial Aged Initial Aged Initial Aged Example 6 16 16 16 16 18 18 Example 7 11 10 11 12 10 11 Comparative Example 2 6 5 14 14 14 14 Example 8 10 11 12 13 13 10 NOTES: 1 See Table I, Note 1.

2 See Table I, Note 2.

3 Laminate composition: aluminum/adhesive/polyethylene jacketing compound.

GLOSSARY OF TERMS EAA-Ethylene-acrylic acid copolymer HDPE-High density polyethylene LLDPE-Linear low density polyethylene Mi-Melt index XM NA-X-methylbicyclo(2 .2.1 )hept-5-ene-2, 3-dicarboxylic acid anhydride Nadic anhydride-trademark (Buffalo Color Corp.) for bicyclo(2.2.1)hept-5-ene-2,3-dicarboxy- lic anhydride Nadic methyl anhydride-trademark (Buffalo Color Corp.) for x-methyl-bicyclo (2.2.1)hept-5ene-2,3-dicarboxylic anhydride Himic anhydride-trademark (Hitachi Chemical Co.) for bicyclo(2 .2.1 )hept-5-ene-2, 3-dicar- boxylic anhydride Methyl Himic anhydride-trademark (Hitachi Chemical Co.) for x-methyl-bicyclo(2.2. 1 )hept-5- ene-2, 3-d icarboxylic anhydride

Claims (18)

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

2. A cable according to claim 1, in which the metallic shield is formed of chrome coated steel, chrome oxide coated steel, stainless steel, aluminium or copper.

3. AA cable according to claim 1 or 2, in which the protective polyolefin layer is a low, medium or high density polyethylene or copolymer containing more than 50 wt.% ethylene with one or more olefins having from 3 to 1 2 carbon atoms.

4. A cable according to any of claims 1 to 3, in which the backbone of (a) is at least one ethylene homopolymer or copolymer of ethylene with an unsaturated aliphatic hydrocarbon.

5. A cable according to claim 4, in which the backbone is LLDPE or an ethylene homopolymer having a density of 0.94 to 0.96.

6. A cable according to any of claims 1 to 5, in which the grafting monomer is maleic anhydride, itaconic anhydride, 4-methyl cyclohex-4-ene-1 2-dicarboxylic acid anhydride, bicy clo(2.2.2)oct-5-ene-2, 3-dicarboxylic acid anhydride, 1,2,3,4,5,8,9,1 0-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-methylnorborn-5-ene-2, 3-dicarboxylic acid anhydride, norborn-5-ene-2,3-dicarboxylic acid anhydride, Nadic anhydride, methyl Nadic anhydride, Himic anhydride, methyl Himic anhydride, methyl Himic anhydride, maleic acid, fumaric acid, citric acid, a monoalkyl maleate, or maleamic acid.

7. A cable according to any of claims 1 to 6, in which the backbone is further grafted with a cograft monomer which is a dialkyl maleate, dialkyl fumarate, dialkyl itaconate, dialkyl mesaconate, dialkyl citraconate, alkyl acrylate, alkyl crotonate, alkyl tiglate, or alkyl methacrylate, in all of which alkyl is an aliphatic, aryl-aliphatic or cycloaliphatic group containing 1-12 carbon atoms.

8. A cable according to any of claims 1 to 7, in which the ethylene homopolymer of (b) is high density polyethylene.

9. A cable according to any of claims 1 to 8, in which the copolymer of (c) is LLDPE.

1 0. A cable according to any of claims 1 to 9, in which the copolymer of (d) is an ethylenevinyl acetate copolymer, ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene-methyl methacrylate copolymer or an ethylene-ethyl methacrylate copolymers.

11. A cable according to any of claims 1 to 10, in which the adhesive blend further includes one or more elastomers.

1 2. A cable according to claim 11, in which the elastomer is a homopolymer of isobutylene, a copolymer of isobutylene, an elastomeric copolymer of ethylene and an a-olefin, an elastomeric terpolymer of ethylene, an a-olefin and a diene, a homopolymer of chloroprene, a copolymer of a diene and a vinyl aromatic compound, a block copolymer of a diene and a vinyl aromatic compound, a hydrogenated block copolymer of a diene and a vinyl aromatic compound, a homopolymer of butadiene, or a copolymer of an ethylenically unsaturated nitrile and a diene.

1 3. A cable (according to any of claims 1 to 12, in which the blend contains from 1.6 X 10-4 to 1.6 x 10-3 moles of said acid, acid anhydride, or derivative per 100 grams of the blend.

14. A cable according to any of claims 1 to 13, in which the adhesive blend comprises the graft copolymer, a high density ethylene homopolymer or a copolymer of ethylene with an a- olefin, and polyisobutylene.

1 5. A cable according to any of claims 1 to 14, in which the blend comprises an XMNA graft copolymer with a high density polyethylene backbone, a high density polyethylene homopolymer, and polyisobutylene.

1 6. A cable according to any of claims 1 to 13, in which the blend comprises an XMNA or maleic anhydride graft copolymer with a high density polyethylene or LLDPE backbone, and LLDPE.

1 7. A cable according to claim 16, in which the weight ratio of the graft copolymer to the LLDPE is from 1:5.6 to 1:9.

18. An electrical cable according to claim 1, substantially as herein described in any of the Examples.