GB1601043A

GB1601043A - Polyethylene composition containing talc filler for electrical applications

Info

Publication number: GB1601043A
Application number: GB22624/78A
Authority: GB
Original assignee: Union Carbide Corp
Current assignee: Union Carbide Corp
Priority date: 1977-05-26
Filing date: 1978-05-25
Publication date: 1981-10-21
Also published as: NO781829L; AU3642278A; NL7805716A; CA1115044A; AU524422B2; DE2822817A1; FR2401192A1; SE7806039L; JPS5416553A; NL184628C; SE443678B; IT1096232B; IT7823806A0; NO150377B; NL184628B; NO150377C; JPS5711570B2; DE2822817C3; DE2822817B2; FR2401192B1

Description

(54) A POLYETHYLENE COMPOSITION CONTAINING TALC FILLER FOR ELECTRICAL APPLICATIONS (71) We, UNION CARBIDE CORPORATION, a Corporation organised and existing under the laws of the State of New York, United States of America, of 270 Park Avenue, New York, State of New York 10017, United States of America, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to a composition for electrical applications based on an ethylene polymer containing a talc filler coated with metallic salt for a fatty acid containing from 8 to 20 carbon atoms.

Compositions which are employed in electrical wire and cable are, in many cases, prepared from compositions which are based on vulcanizable, or crosslinkable, ethylene polymers. These ethylene polymer-based compositions may be filled with various fillers, as well as coated fillers, as described, for example, in United States Patents Nos. 3,148,169, 3,832,326 3,922,422, 3470/22, 3835091 and 3960739, and in British Patent Specification No. 1297802.

The fillers, when added to ethylene-based polymer compositions, reduce the cost of the composition as well as increase the mechanical properties of the compositions, in that they toughen the materials, such as for example, increase the abrasion resistance. Additionally, the fillers decrease the flammability of the ethylene polymer by their addition thereto.

However, there are certain adverse effects in the use of filled ethylene polymer-based compositions. The problems encountered in the use of fillers include the fact that the insulation properties, for example, are more susceptible to moisture, i.e., the insulation on a finished wire or cable is more susceptible to moisture.

Additionally, the elongation is generally adversely affected by the use of a filler. Also, in order to process the ethylene-based compositions so as to adapt them to be placed as, for example, insulation, on the electrical conductor components of the wire and cable, it is usually necessary to admix the components of the compositions at high temperatures, and to extrude them, again at high temperatures, onto the electrical conductor. When certain fillers are used in combination with certain types of ethylene polymers or in certain types of ethylene polymer-based compositions, the entire curable composition is susceptible to scorching during the high temperature processing thereof prior to the vulcanization of the composition on the electrical conductor. Scorching is, in effect, the premature vulcanization of the insulation composition.This premature vulcanization usually occurs, when it occurs, in the barrel or die head of the extruder in which the insulation composition is being processed, at elevated temperatures, prior to its being extruded onto an electrical conductor, and prior to its intended vulcanization. When an insulation composition is scorched in the extruder, the extruded composition will have imperfections in the form of discontinuity and roughness in the surface of the extrudate, and lumps or surface ripples caused by gel particles in the body of the extrudate. In addition, excessive scorching may cause sufficient pressure build-up in the extrusion device to require a cessation of the extrusion operation entirely.

Talc itself is a poor filler, since the tensile and elongation properties of a talcfilled ethylene polymer-based composition are unacceptable. These unacceptable properties of tensile strength and elongation indicate incompatibility between the talc and ethylene polymer.

It has now been found that when an ethylene polymer-based composition which employs a talc filler is coated with at least one metallic salt of a fatty acid containing from 8 to 20 carbon atoms, the ethylene polymer and talc filler are rendered compatible.

In accordance with one aspect of the present invention there is provided a composition suitable for extrusion about wires and cables to be used in electrical applications consisting essentially of: (a) an ethylene polymer, and (b) at least 10 parts by weight of a talc filler per 100 parts by weight of the ethylene polymer the talc filler being coated with at least one metallic salt of a fatty acid (as hereinafter defined) containing from 8 to 20 carbon atoms wherein the metallic salt contains a metal selected from Groups Ia, lIa and Ilb of the Mendeleev Periodic Table of Elements.

In another aspect, the present invention also provides a composition suitable for extrusion about wires and cables to be used in electrical applications consisting essentially of: (a) an ethylene polymer, (b) a conductive carbon black having an N2 surface area of from 10 to 1100 m2/g, and (c) at least 10 parts by weight of a talc filler per 100 parts by weight of the ethylene polymer, the talc filler being coated with at least one metallic salt of a fatty acid (as hereinafter defined) containing from 8 to 20 carbon atoms, wherein the metallic salt contains a metal selected from Groups la, Ila and IIb of the Mendeleev Periodic Table of Elements.

The ethylene polymers which are used in the compositions of the present invention are solid (at 250C) materials which may be homopolymers, or copolymers of ethylene. The ethylene copolymers generally contain at least 30 weight percent of ethylene and up to about 70 weight percent of propylene, and/or up to about 50 weight percent of one or more other organic compounds which are interpolymerizable with ethylene. These other compounds which are interpolymerizable with ethylene are preferably those which contain polymerizable unsaturation, such as is present in compounds containing an ethylene linkage, > C=C < . These other interpolymerizable compounds may be hydrocarbon compounds such as, butene-l, pentene-l, isoprene, butadiene, bicycloheptene, bicycloheptadiene, and styrene, as well as vinyl compounds such as vinyl acetate and ethyl acrylate.

These copolymers thus include those containing > 0 to 70 weight percent of propylene and 30 to < 100 weight percent of ethylene; and > 0 to < 50 weight percent butene-l or vinyl acetate or ethyl acrylate and 50 to < 100 weight percent of ethylene; and > 0 to < 30 weight percent of propylene, > 0 to 20 weight percent of butene-l and 50 to < 100 weight percent of ethylene.

The ethylene polymers may be used individually, or in combinations thereof The ethylene polymers generally have a density (ASTM 1505 test procedure with conditioning as in ASTM D-1248-72) of from 0.86 to 0.96 and a melt index (ASTM D-1238 at 44 psi test pressure) of from 0.1 to 20 decigrams per minute.

The ethylene polymers may be curable. They are cured by irradiation with high-energy electron beams or through the use of a chemical curing agent.

The art of electron beam cross-linking is to highly developed that one skilled in the art is very familiar with this procedure and therefore no further details will be given.

The chemical curing agent is preferably an organic peroxide. The organic peroxide curing agent which can be used in the present invention includes all organic peroxides which are capable of providing free radicals for cross-linking the ethylene polymer under the cross-linking conditions employed for the compositions.

The organic peroxide compounds can be used individually or in combination with one another.

The preferred organic peroxide compounds which may be used in the compositions of the present invention may also be generally classified as those in which each oxygen atom of each peroxide group is directly bonded to a tertiary carbon atoms whose remaining valancies are attached to hydrocarbon group: the hydrocarbon group being an alkyl, cycloalkyl, aryl or aralkyl group. Peroxides of this type are generally disclosed in United States Patent No. 2,888,424.Examples of the organic peroxide compounds which may be used in the compositions of the present invention include: di - a - cumyl peroxide 2,5 - dimethyl - 2,5 - di(t - butyl peroxy) - hexyne - 3 2,5 - dimethyl - 2,5 - di(t - butyl peroxy) - hexane t-butyl cumyl peroxide di-t-butyl peroxide a,a' - bis(t - butyl peroxy) - p - di - isopropyl benzene 2,5 - dimethyl - 2,5 - di(benzoyl peroxy)-hexane t-butyl peroxy isopropyl carbonate.

Additionally, organic hydroperoxide compounds such as those disclosed in United States Patents Nos. 3,954,907 and 4,018,852 are suitable for use in the present invention.

The organic peroxide compounds are used in cross-linking effective amounts in the compositions of the present invention which may range from 0.1 to 8.0, and preferably from 0.3 to 5.0, parts by weight of organic peroxide compound per 100 parts by weight of ethylene polymer in the compositions.

The talc filler of the present invention is commercially available in different forms and grades. The filler generally has a medium particle size of from 0.10 to 10.0 microns, preferably from 0.80 to 3.0 microns.

The metallic salts of the fatty acids that are employed herein are selected from the Mendeleev Periodic Table of the Elements, Group Ia, IIa, or IIb metal salts, of saturated or unsaturated monobasic or dibasic, branched or straight chain aliphatic acids containing from 8 to 20 carbon atoms. This group of aliphatic acids will be referred to herein generally as "fatty acids". Examples of the fatty acids that may be included within the practice of this invention are palmitic, stearic, lauric, oleic, sebacic, ricinoleic, and palmitoleic.

The preferred fatty acid is stearic acid. The preferred metal salts are calcium stearate and zinc stearate.

The flame-retardant additives useful in this invention comprise a family of chemical compounds well known to those skilled in the art. Generally speaking, the more important of these compounds contain chemical elements employed for their ability to impart flame resistance, e.g., bromine, chlorine, antimony, phosphorus and nitrogen. It is preferred that the flame-retardant additive comprise a halogenated organic compound (brominated or chlorinated); a halogen-containing organic compound in admixture with an organic or inorganic antimony compound, e.g. antimony oxide; elemental phosphorus or a phosphorus compound; a halogencontaining compound in admixture with a phosphorus compound or compounds containing phosphorus-nitrogen bonds or a mixture of two or more of the foregoing.

Also, alkaline earth metal hydroxides such as calcium hydroxide and magnesium hydroxide, and aluminium trihydrate are suitable flame retardant additives. In general, however, the amount of additive may be from 0.5 to 100 parts by weight per hundred parts by weight of ethylene polymer. A preferred range is from 10 to 75 parts by weight and an especially preferred range is from 35 to 55 parts by weight of additive per 100 parts by weight of ethylene polymer. Smaller amounts of compounds highly concentrated in the elements responsible for flameretardance will be sufficient, e.g., elemental red phosphorus is preferred at from 0.5 to 10 parts by weight per hundred parts by weight of ethylene polymer while phosphorus in the form of triphenyl phosphate may be used at 5 to 25 parts by weight of phosphate per part by weight of ethylene polymer.Halogenated aromatic compounds may be used at from 5 to 45 parts by weight and synergists, e.g., inorganic or organic antimony compounds such as antimony oxide, may be used at from 2 to 20 parts by weight per 100 parts by weight of ethylene polymer.

The compositions of the present invention also advantageously include from 0.01 to 3.0 and, preferably 0.05 to 1.0, parts by weight of one or more suitable high temperature antioxidants for the ethylene polymer per 100 parts by weight of the ethylene polymer.

These antioxidants are preferably sterically hindered phenols. These compounds include: 1,3,5 - trimethyl- 2,4,6 - tris(3,5 - ditertiarybutyl- 4- hydroxy benzyl)benzene: 1,3,5 - tris(3,5 - ditertiary butyl - 4 - hydroxybenzyl) - 5 - triazine - 2,4,6 (1 lI,3H,5H)trione; tetrakis - [methylene - 3 - (3',5 - di - t - butyl - 4' - hydroxy phenyl) propionatelmethane; and di(2 - methyl - 4 - hydroxy - 5 - t - butyl phenyl) sulfide.

1,2 - dihydro - 2,2,4 - trimethylquinoline.

Polymerised 2,2,4 - trimethyl dihydroquinoline may also be used.

The antioxidants may be used individually, or in combination with one another.

The compositions of the present invention also advantageously include any electrically conductive carbon blacks, including furnace blacks, acetylene blacks, and channel blacks. The carbon should have a particle size of the order of from 10 to 60 millimicrons and an N2 surface area of from 10 to 1100 m2/g. From I to 25, and preferably from 2 to 16 parts by weight of the carbon black is used per 100 parts by weight of the ethylene polymer.

In addition to the ethylene polymer, talc, and metal salt, the compositions of the present invention may also contain other adjuvants of the types normally used in curable compositions for electric insulation.

These other adjuvants would include curing agents; flame retardant additives; antioxidants; carbon black; other fillers, blowing agents; nucleating agents for blown systems; lubricants; UV stabilizers; dyes and colorants; voltage stabilizers; metal deactivators; and coupling agents.

These adjuvants may be used in amounts designed to provide the intended effect in the resulting composition.

The compositions of the present invention may also be extended, or filled, with polymers other than the ethylene polymer which are compatible, i.e. can be physically blended or alloyed, with the ethylene polymer. The resulting compositions should contain at least 30 weight percent of interpolymerized ethylene in all the polymers that may be present in the composition, based on the total weight of the resulting composition. The other polymers which may be used include polyvinyl chloride and polypropylene.

The total amounts of adjuvants used will range from 0 to 60 weight percent based on the total weight of the composition.

All of the components of the present invention are usually blended or compounded together prior to their introduction into the extrusion device from which they are to be extruded onto an electrical conductor. The ethylene polymer and the other desired constituents may be blended together by any of the techniques used in the art to blend and compound thermoplastic materials to homogeneous masses. Prior to blending the constituents together, the talc filler is coated with the metal salt by known techniques. As regards blending, for instance, the components may be fluxed on a variety of apparatus including multi-roll mills, screw mills, continuous mixers, compounding extruders, and Banbury mixers, or dissolved in mutual or compatible solvents.

When all the solid components of the composition are available in the form of a powder, or as small particles, the compositions are most conveniently prepared by first making a blend of the components, say in a Banbury mixer or a continuous extruder, and then masticating this blend on a heated mill, for instance a two-roll mill, and the milling continued until an intimate mixture of the components is obtained. Alternatively, a master batch containing the ethylene polymer and the talc filler or talc filler and carbon black and, if desired, some or all of the other components, may be added to the mass of polymer.Where the ethylene polymer is not available in powder form the compositions may be made by introducing the polymer to the mill, masticating it until it forms a band around roll, after which a blend of the remaining components is added and the milling continued until an intimate mixture is obtained. The rolls are preferably maintained at a temperature which is within the range 800C to 1350C and which is below the decomposition temperatures of the first peroxide compound(s) if such are used. The composition, in the form of a sheet, is removed from the mill and then brought into a form, typically dice-like pieces, suitable for subsequent processing.

After the various components of the compositions of the present invention are uniformly admixed and blended together, they are further processed, in accordance with the process of the present invention, in conventional extrusion apparatus.

The compositions are then extruded onto a wire or cable, or other substrate. If the compositions of the present invention, are curable, they are extruded onto the wire or cable, or other substrate and vulcanized at elevated temperatures of > 180"C and preferably at > 200--2300C using conventional vulcanizing procedures.

The following Examples are merely illustrative of the present invention and are not intended as a limitation on the scope thereof. All parts and percentages are given on a weight basis.

EXAMPLES 1--17 The compositions of these Examples were prepared by mixing in a suitable mixer all of the components together and then transferring these into a Banbury mixer. Where the filler was precoated, the filler and coating material were separately blended to intimately coat the surface of the filler. Then, the coated filler was mixed with the other components as indicated.

The formulations of the compositions are set forth in Table I.

TABLE I 1 2 3 4 5 6 7 8 9 Ethylene Vinvyl Acetate Copolymer (a) 70.9 70.9 70.9 70.9 70.9 70.9 70.9 70.9 70.9 Ethylene Ethyl Acrylate Copolymer (b) - - - - - - - - - Talc 26.8 26.551 24.051 26.3 23.8 26.3 - - Aluminum Silicate - - - - - - 24.051 24.051 Calcium Carbonate - - - - - - - - 24.051 Amorphous Silica - - - - - - - - Aluminum Trihydrate - - - - - - - - Calcium Metasilicate - - - - - - - - Calcium Stearate - - - - - - - - 0.25 Zinc Stearate - 0.25 0.25 0.5 - - - - Silane (c) - - - - 0.5 0.5 0.25 - Siloxane (d) - - - - - - - 0.25 Antioxidant (e) 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 Carbon Black - - 2.5 - 2.5 - 2.5 2.5 2.5 Peroxide (f) 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 100 100 100 100 100 100 100 100 100 TABLE I (cont.).

10 11 12 13 14 15 16 17 Ethylene Vinyl Acetate Copolymer (a) 70.9 70.9 70.9 70.9 70.9 70.9 70.9 Ethylene Ethyl Acrylate Copolymer (b) - - - - - - - 71.2 Talc - - - - - - - 23.5 Aluminum Silicate - - - - - - - Calcium Carbonate 24.051 - - - - - - Amorphous Silica - 24.051 24.051 - - - - Aluminum Trihydrate - - - 24.051 24.051 - - Calcium Metasilicate - - - - - 26.8 24.05 Calcium Stearate 0.25 - - - - - - Zinc Stearate - - - - - - - 0.5 Silane (c) - 0.25 0.25 0.25 0.25 - 0.25 Siloxane (d) - - - - - - - Antioxidant (e) 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 Carbon Black 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 Peroxide (f) 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 100 100 100 100 100 100 100 100 (a) 9-11.5% vinyl acetate; Melt Index 3.0; (b) 18% ethyl acetate;Melt Index 4.5; (c) vinyl-tris (beta-methoxyethoxy)silane; (d) octamethylcyclotetrasiloxane; (e) 1,2-dihydro-2,3,4 trimethylquinoline; (f) di-α-cumyl peroxide 1indicates that the filler was precoated.

The compositions in Table I were processed into test specimens as required by the following test procedures and subjected to the following test procedures: Tensile strength and elongation ASTM-D41 2-68 Insulation resistance Underwriters Laboratory Subject 44 (November 24, 1969) Oxygen Index ASTM-D2863-70 Scorch Time A constant weight of material is added to a Brabender mixer maintained at 1500C and 50RPM and suitably adapted so that a torque measurement can be continuously measured on the material.

When the material reaches 1350C, torque measurement begins as measured by a Brabender Plastograph Recorder. Torque continues to decrease until a significant degree of cross-linking is occurring at which time torque measurement begins increasing. At the time that the torque curve intersects the zero point, scorch is considered to have occurred. The width of a bowl shaped curve described by the Plastograph Recorder is the scorch time measurement. The wider the bowl of this curve, the less is the scorching.

The results of these tests are set forth in Table II.

TABLE II Insulation Resistance (75 C/H2O) Megohms/1000' Tensile 1 12 24 36 Scorch Time Example Strength (psi) Elongation (%) week weeks weeks weeks Oxygen Index (mins) 1 1170 250 - - - - - 2 2960 525 - - - - - 3 2890 520 650 1118 312 41.6 21.25 5.50 4 2290 415 - - - - - 5 2160 360 832 286 .104 Failed after 21.25 5.05 25 weeks 6 1700 280 - - - - - 7 1930 295 6240 9000 31.2 2.4 20.25 4.50 8 1750 240 6500 4.16 0.1 - 20.75 4.55 9 2220 505 3640 1.0 0.1 - 20.65 4.50 10 2520 495 3640 1.4 0.1 - 20.75 4.10 11 2220 385 11440 1.66 0.1 - 20.75 4.10 12 1990 420 13 2410 505 3380 4940 2.86 0.18 21.25 4.05 14 2110 330 3640 4160 598 17.6 21.25 4.90 15 1560 395 1924 23.4 0.1 - 20.0 4.65 16 1970 400 7280 1.90 0.10 - 20.75 4.70 17 2540 570 - - - - 22.5 - These results indicate that the use of a talc filler coated with a metallic salt of the present invention (Examples 2 and 3) provides a superior combination of tensile strength, elongation, insulation resistance, flame and processing characteristics (scorch time) that are not attainable with other mineral fillers and the treated mineral fillers, particularly the silane treated fillers of the prior art.

EXAMPLES 18-20 The compositions of these Examples were prepared by the methods as in the previous Examples. The formulations of these compositions are set forth in Table III.

TABLE III 18 19 20 Ethyl-Vinyl Acetate 59.2 59.2 54.0 Copolymer (a) Talc 12.4' - - Clay - 12.4' Silica - - 17.21 Zinc Stearate 0.5 - Siloxane (b) - 0.5 Silane (c) - - 0.4 Flame retardant (d) 17.3 17.3 17.2 Antimony trioxide 8.0 8.0 8.5 Antioxidant (e) 0.5 0.5 0.5 Peroxide(f) 2.1 2.1 2.2 100 100 100 (a) 911.5% vinyl acetate;Melt Index 3.0; (b) octamethylcyclotetrasiloxane; (c) vinyl-tri-(beta-methoxyethoxy)silane; (d) high melting hydrocarbon material containing 65% chlorine manufactured by Hooker Chemical Co.; (e)l ,2-dihydro-2,Z,4-trimethylquinoline ; (f) di-a-cumyl peroxide indicates the filler was precoated.

The compositions in Table III were processed into test specimen as required by the following test procedures and subjected to the following test procedures: Tensile strength and elongation, ASTM-412-68; Modulus, ASTM-D882-758; Oxygen Index, ASTM D-2863-70.

The results of these tests are set forth in Table IV.

TABLE IV Tensile Modulus Oxygen Example Strength (psi) Elongation (%) (psi) Index 18 2180 440 15,000 28.5 19 1570 310 12,200 26.8 20 1690 395 14,200 27.5 These results indicate that the use of a talc filler coated with a metal salt of the present invention (Example 18) provides a superior combination of tensile strength.

elongation, modulus and oxygen index that are not attainable with other coated mineral fillers.

EXAMPLE 21 The composition of this Example was prepared by the methods as in the previous Examples. The formulation of this composition is as follows: Ethylene-Ethyl Acrylate Copolymer (a) 74.8 Talc 15.0' Carbon black (b) 10.0 Antioxidant (c) 0.2 100 (a) 13-16% ethyl acrylate; Melt Index 1.0-2.0; (b) Electrically conductive; surface area 1000 m2/g indicates that the filler was precoated.

The composition was extruded onto tape using a conventional type extruding machine and subjected to the following test procedures: Tensile strength and elongation; and tensile strength and elongation after aging in an oven for 7 days at 1000C, ASTM-412-68; Brittleness temperature, F > o, ASTM D-746: Volume resistivity at 23 and 900 C, ASTM D-746.

The results of these tests are as follows: Tensile strength (psi) as molded 1730 after heat aging 1690 Elongation (%) as molded 510 after heat aging 400 Brittleness temperature, F50 0 C Volume resistivity (ohm-cm) 23"C 630 90"C 5700 WHAT WE CLAIM IS: 1.A composition suitable for extrusion about wires and cables to be used in electrical applications consisting essentially of: (a) an ethylene polymer, and (b) at least 10 parts by weight of a talc filler per 100 parts by weight of the ethylene polymer, the talc filler being coated with at least one metallic salt of a fatty acid (as hereinbefore defined) containing from 8 to 20 carbon atoms, wherein the metallic salt contains a metal selected from Groups Ia, IIa and Ilb of the Mendeleev Periodic Table of Elements.

2. A composition suitable for extrusion about wires and cables to be used in electrical applications consisting essentially of: (a) an ethylene polymer, (b) a conductive carbon black having an N2 surface area of from 10 to 1100 m2/g, and (c) at least 10 parts by weight of a talc filler per 100 parts by weight of the ethylene polymer, the talc filler being coated with at least one metallic salt of a fatty acid (as hereinbefore defined) containing from 8 to 20 carbon atoms, wherein the metallic salt contains a metal selected from Groups Ia, IIa and IIb of the Mendeleev Periodic Table of Elements.

3. A composition as claimed in claim I or claim 2 wherein the metallic salt contains a metal selected from Groups IIa and IIb of the Mendeleev Periodic Table of Elements.

4. A composition as claimed in claim 3 wherein the metallic salt is calcium stearate.

5. A composition as claimed in claim 3 wherein the metallic salt is zinc stearate.

6. A composition as claimed in any one of the preceding claims wherein the ethylene polymer is an ethylene copolymer.

7. A composition as claimed in claim 6 wherein the ethylene polymer is an ethylene-vinyl acetate copolymer.

8. A composition as claimed in claim 6 wherein the ethylene polymer is an ethylene-alkyl acrylate copolymer.

9. A composition as claimed in claim 8 wherein the ethylene-alkyl acrylate copolymer is an ethylene ethyl acrylate copolymer.

10. A composition as claimed in any one of the preceding claims wherein the ethylene polymer is curable.

11. A composition as claimed in any one of the preceding claims wherein the metallic salt is present in an amount of from 0.05 to 5.0 parts by weight per 100 parts by weight of the talc.

12. A composition as claimed in claim 11 wherein the metallic salt is present in an amount of from 0.5 to 2,0 parts by weight per 100 parts by weight of the talc.

13. A composition as claimed in any one of the preceding claims wherein the talc is present in an amount of from 10 to 150 parts by weight per 100 parts by weight of the ethylene polymer.

14. A composition as claimed in claim 13 wherein the talc is present in an

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

The composition was extruded onto tape using a conventional type extruding machine and subjected to the following test procedures: Tensile strength and elongation; and tensile strength and elongation after aging in an oven for 7 days at 1000C, ASTM-412-68; Brittleness temperature, F > o, ASTM D-746: Volume resistivity at 23 and 900 C, ASTM D-746.

The results of these tests are as follows: Tensile strength (psi) as molded 1730 after heat aging 1690 Elongation (%) as molded 510 after heat aging 400 Brittleness temperature, F50 0 C Volume resistivity (ohm-cm) 23"C 630 90"C 5700 WHAT WE CLAIM IS: 1.A composition suitable for extrusion about wires and cables to be used in electrical applications consisting essentially of: (a) an ethylene polymer, and (b) at least 10 parts by weight of a talc filler per 100 parts by weight of the ethylene polymer, the talc filler being coated with at least one metallic salt of a fatty acid (as hereinbefore defined) containing from 8 to 20 carbon atoms, wherein the metallic salt contains a metal selected from Groups Ia, IIa and Ilb of the Mendeleev Periodic Table of Elements.
2. A composition suitable for extrusion about wires and cables to be used in electrical applications consisting essentially of: (a) an ethylene polymer, (b) a conductive carbon black having an N2 surface area of from 10 to 1100 m2/g, and (c) at least 10 parts by weight of a talc filler per 100 parts by weight of the ethylene polymer, the talc filler being coated with at least one metallic salt of a fatty acid (as hereinbefore defined) containing from 8 to 20 carbon atoms, wherein the metallic salt contains a metal selected from Groups Ia, IIa and IIb of the Mendeleev Periodic Table of Elements.
3. A composition as claimed in claim I or claim 2 wherein the metallic salt contains a metal selected from Groups IIa and IIb of the Mendeleev Periodic Table of Elements.
4. A composition as claimed in claim 3 wherein the metallic salt is calcium stearate.
5. A composition as claimed in claim 3 wherein the metallic salt is zinc stearate.
6. A composition as claimed in any one of the preceding claims wherein the ethylene polymer is an ethylene copolymer.
7. A composition as claimed in claim 6 wherein the ethylene polymer is an ethylene-vinyl acetate copolymer.
8. A composition as claimed in claim 6 wherein the ethylene polymer is an ethylene-alkyl acrylate copolymer.
9. A composition as claimed in claim 8 wherein the ethylene-alkyl acrylate copolymer is an ethylene ethyl acrylate copolymer.
10. A composition as claimed in any one of the preceding claims wherein the ethylene polymer is curable.
11. A composition as claimed in any one of the preceding claims wherein the metallic salt is present in an amount of from 0.05 to 5.0 parts by weight per 100 parts by weight of the talc.
12. A composition as claimed in claim 11 wherein the metallic salt is present in an amount of from 0.5 to 2,0 parts by weight per 100 parts by weight of the talc.
13. A composition as claimed in any one of the preceding claims wherein the talc is present in an amount of from 10 to 150 parts by weight per 100 parts by weight of the ethylene polymer.
14. A composition as claimed in claim 13 wherein the talc is present in an

amount of from 10 to 25 parts by weight per 100 parts by weight of the ethylene polymer.
15. A composition as claimed in claim 13 wherein the talc is present in an amount of from 25 to 45 parts by weight per 100 parts by weight of the ethylene polymer.
16. A composition as claimed in claim I or claim 2 substantially as hereinbefore described.
17. A composition as claimed in claim I or claim 2 substantially as hereinbefore described in any one of Examples 2, 3, 18 or 21.
18. An electric wire or cable when insulated with a composition as claimed in any one of the preceding claims.