ETHYLENE POLYMER COMPOSITION FOR CABLE APPLICATIONS

Abstract: The present invention discloses a cable comprising a layer of a polyethylene composition characterized in that the polyethylene composition comprises: (A) from 5 percent to 95 percent by weight of the total composition of at least one first polymer which is an ethylene/ alpha -olefin interpolymer having: (i) a density from 0.865 g/cm<3> to 0.95 g/cm<3>, (ii) a molecular weight distribution (Mw/Mn) from 1.8 to 3.5, (iii) a melt index (I2) from 0.001 g/10 min. to 10 g/10 min., and (iv) a CBDI greater than 50 percent, (B) from 5 percent to 95 percent by weight of the total composition of at least one second polymer which is a heterogeneously branched ethylene polymer or homogeneously branched ethylene homopolymer having a density from 0.9 g/cm<3> to 0.965 g/cm<3>. The cable of the present invention has superior mechanical properties and processability relative to conventional cable using current polymers such as low density polyethylene (LDPE), linear low density polyethylene (LLDPE), and polyvinylchloride (PVC).

Description: ETHYLENE POLYMER COMPOSITION FOR CABLE APPLICATIONS The present invention relates to cable applications, such as a coating on a fiber optical cable, coaxial cable, or telecommunications cable, comprising a layer of a specific polyethylene composition. More specifically, the polyethylene composition used in the cable of the present invention comprises a particular type of ethylene /α-olefin interpolymer, especially a homogeneously branched ethylene/α olefin interpolymer, and most preferably a homogeneously branched substantially linear ethylene/α-olefin interpolymer; and a heterogeneously branched ethylene/α-olefin interpolymer (or linear ethylene homopolymer). The cable of the present invention may have good mechanical properties such as abrasion resistance and flexibility, and good processability, moreover, may be less environmentally harmful (as compared with polyvinyl-chloride (PVC) based cables) when disposed. Various types of thermoplastic polymer have been used for wire and cable jacketing applications. Especially, polymer compositions based on ethylene homopolymer via high pressure polymerization processes (low density polyethylene (LDPE)), and polyvinyl-chloride (PVC) have been used conventionally. Various mechanical properties are desired for the cable jacketing application, for example, mechanical properties such as abrasion resistance, flexibility and reduced notch sensitivity are highly required. Moreover, good processability is also required for production efficiency and good appearance or quality of produced cable. However, the above resins ( that is LDPE, PVC) have several deficiencies. For example, LDPE may be acceptably flexible ( that is low stiffness) but very often has low abuse resistance; moreover, since PVC contains chlorine, PVC-based cables release environmentally harmful gas such as hydrochloride gas when combusted. Furthermore, considering environmental adaptability, polymers such as PVC, especially those containing lead stabilizers, tend to release environmental harmful materials (for example, lead leached into ground water) when combusted or landfilled and should be avoided for this application. In addition, when the plasticizers leach out of a PVC formulation, the cable becomes brittle which leads to premature failure. Linear polyethylene has also been used as a layer in a cable application, but these linear polyethylene polymers do not have adequate abuse resistance in combination with the necessary flexibility; that is, to increase abuse resistance in a linear polyethylene, one merely has to increase the density of the polyethylene, however raising the density reduces the flexibility. Reduced flexibility hampers installation of the cable, especially where the cable must be routed through numerous bends and twists/turns Jacket or sheath damage resulting from poor flexibility usually results in cable failure. In view of the above deficiencies, a resin composition which satisfies the above vanous mechanical properties, processability and environmental adaptability has been long awaited One aspect of the present invention is a cable compπsing a layer of a polyethylene composition characterized in that the polyethylene composition compπses: (A) from 5 percent (by weight of the total composition) to 95 percent (by weight of the total composition) of at least one first polymer which is an ethylene/α-olefm interpolymer having: (i) a density from 0.865 g cm^ to 0.95 g/cm^, (ii) a molecular weight distπbution (M w /M„) less than 3.5, especially from 1.8 to 2.8, (iii) a melt index (I2) from 0.001 g/lOmin. to 10 g/10min., (iv) a CDBI of greater than 50 percent; and (B) from 5 percent (by weight of the total composition) to about 95 percent (by weight of the total composition) of at least one second polymer which is a heterogeneously branched ethylene/α-olefin inteφolymer or a homogeneously ethylene homopolymer having a density from 0.9 g/cm- , preferably from 0.93 g/cm^ to 0.965 g/ciτA Most preferably, the cable composes a layer of a polyethylene composition characterized in that the polyethylene composition comprises about 40 percent (by weight of the total composition) of the at least one first polymer which is characteπzed as having: (1) a density from 0.91 to 0.92 g/cm^, (ii) a molecular weight distribution (M w M n ) of about 2, (iii) a melt index (I2) of about 0.1 g/10 min., and (iv) a CBDI greater than 50 percent; and about 60 percent (by weight of the total composition) of the at least one second polymer which is characteπzed as having heterogeneously branched ethylene/α-olefin inteφolymer: (1) a density of about 0.96 g/cm^, (ii) a melt index (I 2 ) of about 6 g/10 min., and (iii) a CDBI less than 50 percent. Another aspect of the present invention is a cable jacket compπsing the polyethylene composition of the invention which has at least 10 percent, preferably at least 20 percent, more flexibility than a cable made using conventional heterogeneous linear ethylene polymer having about the same density as the inventive polyethylene composition Yet another aspect of the invention is a cable comprising a thermoplastic cable jacket having a thickness from 80 to 90 mils (2 0 to 2 3 mm) in contact with a metal shield creating a notch in said jacket, wherein a sample of said notched jacket taken in a circumferential direction, in accordance with ASTM D 638, has less than 55 percent loss of elongation than an un-notched cable jacket sample from said cable Still another aspect of the invention is a cable comprising a thermoplastic ethylene polymer cable jacket composition, wherein a plaque having a single notch, a thickness from 70 to 80 mils (1 8 to 2 0 mm) made from said jacket composition has at least 100 percent, preferably at least 200 percent, more preferably at least 300 percent, especially at least 400 percent, and most especially at least 500 percent, ultimate tensile elongation, wherein the notch has a depth of at least 10 mils (0.25 mm), a radius from 0 275 mm to 0 55 mm, preferably 0 3 mm to 0525 mm, and especially from 0 38 mm to 051 mm, and wherein said ethylene polymer composition has a density of at least 0 945 g/cm 1 In still another aspect, the invention is a cable compπsing at least one layer of a thermoplastic polymer, especially a polyethylene polymer composition of the invention, wherein the thermoplastic polymer has a strain hardening modulus, Gp, greater than 1 6 MPa, preferably greater than 1.7 MPa, especially greater than 1 8 MPa, and can be as high as 2 MPa, wherein Gp is calculated according to the following equations (I) σ, = σ Eπg λ (III) G p =f The strain hardening modulus (Gp) is calculated from the conventional tensile stress-strain curve using the theory of rubber elasticity More specifically, the true stress, σ,, is calculated from the engmeeπng stress, θnn g , and draw ratio, λ, as shown in Equation (I) For cable jacket resins. Equation (II) was used to calculate the strain hardening modulus, where λ„ and σ* represent the natural draw ratio and engmeeπng draw stress, respectively The natural draw ratio was determined by measuπng the elongation of a grid pattern which was pπnted on the tensile dogbones As shown in Equation (III), the strain hardening modulus is inversely related to the molecular weight between entanglements, M-, that is, the molecular weight of the tie-molecules between crystalline domains and p is the density of the resin Figure 4, for example, shows strain hardening modulus as a function of density of the ethvlene polymer composition For examples E, En, A, and An, the strain hardening modulus relationship can be approximated by the following equation (IV) Gp = -98 57 + (208 89)(p) - (108 73)(p) 2 where p = density of the ethylene polymer composition (including carbon black in the density calculation if appropπate) and Gp is the strain hardening modulus Note that polymers B and Bn fall above the line, which is believed to be attributed to higher levels of long chain branching ( that is, the I10 I2 melt flow ratio is higher for the homogeneous component for resm Bn than for the homogeneous component of resins En and/or An For comparative polymers J, D, I and G, the strain hardening modulus follows a different relationship descπbed by equation (V) (V) Gp = -438 03 + (921 96)(p) - (483 46)(p) 2 . Note that the line for the comparative polymers is much lower than that for the polymer compositions of the invention Preferably, the polyethylene composition used in the cable of the present invention is prepared by a process compπsing the steps of (I) reacting by contacting ethylene and at least one α-olefm under solution polymeπzation conditions in at least one reactor to produce a solution of the at least one first polymer which is a homogeneously branched ethylene/α-olefin inteφolymer, preferably a substantially linear ethylene/α-olefin inteφolymer, (II) reacting by contacting ethylene and at least one α-olefin under solution polymeπzation conditions in at least one other reactor to produce a solution of the at least one second polymer which is a heterogeneously branched ethylene polymer, (III) combining the solution prepared in steps (1) and (11), and (iv) removing the solvent from the polymer solution of step (in) and recovering the polyethylene composition T e cables of the present invention have good flexibility, mechanical properties and good processability, furthermore, are environmentally less harmful when disposed relative to cables compπsing conventional PVC An important aspect of the present invention is the fact that cables, where the outer cable jacket comprises the compositions disclosed in this invention, have improved flexibility relative to comparative cables where the jacket is produced from conventional heterogeneous linear low density polyethylenes (LLDPE) Cable flexibility is an important performance criteria, since more flexible cables are easier to install and bend around corners Cable flexibility was measured by clamping a piece of cable hoπzontally in an Instron tensile machine and measuπng the force required to deflect the cable in the upward direction Lower deflection forces demonstrate improved flexibility, as shown in Figure 1 Cable jackets produced from the copolymers of this invention are preferably 10 percent more flexible, and more preferably 20 percent more flexible than comparative cables made using conventional heterogeneous linear low density ethylene polymers having about the same density ( that is, the density of each polymer is within 10 percent of the other) These and other embodiments are more fully descπbed below, and in conjunction with the Figures, wherein FIG 1 is a plot of deflection force (kg) versus cable deflection (mm) for example A and comparative example G, FIG 2 is a plot of ultimate tensile elongation (percent) versus notch number in the test sample for example B and for comparative example G, FIG 3 is a plot of change in the relative tensile elongation versus temperature for example A and comparative example G, FIG 4 is a plot of strain hardening modulus (MPa) versus polymer and composition density for example polymers A, An, B, Bn, E, and En, and for comparative examples D, G, I and J, FIG 5 is a surface roughness scan of a cable jacket made from example B, FIG 6 is a surface roughness scan of a cable jacket made from comparative example G, and FIG 7 is a schematic representation, in perspective and party broken away, showing one cable of the present invention The "substantially linear" ethylene/α-olefm inteφolymers useful in the present invention are not "linear" polymers in the traditional sense of the term, as used to descπbe linear low density polyethylene (Ziegler polymeπzed linear low density polyethylene (LLDPE)), nor are they highly branched polymers, as used to descπbe low density polyethylene (LDPE) The "substantially linear" ethylene/α-olefin inteφolymers have long chain branching, wherein the backbone is substituted with 0 01 long chain branches/ 1000 carbons to 3 long chain branches/ 1000 carbons, more preferably from 001 long chain branches/1000 carbons to 1 long chain branches/1000 carbons, and especially from 0 05 long chain branches/1000 carbons to 1 long chain branches/1000 carbons Note that the long chain branches are not the same as the short chain branches resulting from incoφoration of the comonomer Thus, for an ethylene/ 1-octene copolymer, the short chain branches are six carbons in length, while the long chain branches for such a substantially linear ethylene/ 1- octene copolymer are at least seven carbons in length, but usually much longer than seven carbons The substantially linear ethylene/α-olefin inteφolymers of the present invention are herein defined as in U S patent 5,272,236 (Lai et al ) and 5,278,272 (Lai et al ) Long chain branching is defined herein as a chain length of at least 7 carbons, above which the length cannot be distinguished using '^C nuclear magnetic resonance (NMR) spectroscopy The long chain branch can be as long as the length of the polymer backbone For ethylene homopolymers and ethylene/C C 7 alpha-olefin copolymers, long chain branching can be determined by C NMR spectroscopy and can be quantified using the method of Randall (Rev Macromol Chem Phys , C29 (2&3), p 285-297) Union Carbide, in EP 0659773 Al, used a 1990 paper (Mirabella et al ) to quantify long chain branching Exxon used "viscous energy of activation" to quantify long chain branching in PCT Publication WO 94/07930 Both the homogeneous linear and the substantially linear ethylene/α-olefin inteφolymers useful for forming the compositions of the present invention are those in which the comonomer is randomly distπbuted within a given inteφolymer molecule and wherein substantially all of the inteφolymer molecules have the same ethylene / comonomer ratio within that inteφolymer, as descπbed in USP 3,645,992 (Elston) The homogeneity of the inteφolymers is typically descπbed by the SCBDI (Short Chain Branching Distπbution Index) or CDBI (Composition Distπbution Branch/Breadth Index) and is defined as the weight percent of the polymer molecules having a comonomer content within 50 percent of the median total molar comonomer content The CDBI of a polymer is readily calculated from data obtained from techniques known in the art, such as, for example, temperature nsing elution fractionation (abbreviated herein as "TREF") as descπbed, for example, in Wild et al, Journal of Polvmer Science. Polv Phvs Ed . Vol 20, p 41 (1982), in U S patent 4,798,081 (Haz tt et al ), or in U S patent 5,089,321 (Chum et al ) The SCBDI or CDBI for the homogeneous ethylene/α-olefin inteφolymer used in the present invention is greater than 50 percent, more preferably greater than about 70 percent, and especially greater than about 90 percent The homogeneous ethylene/α-olefin inteφolymers used in the present invention essentially lack a linear polymer fraction which is measurable as "high density" fraction by the TREF technique ( that is homogeneously branched ethylene/α-olefin inteφolymers do not contain a polymer fraction with a degree of branching less than or equal to 1 methyl/1000 carbons) For homogeneous linear or substantially linear ethylene/α-olefin inteφolymers, especially ethylene/ 1-octene copolymers, having a density from about 0 88 g/cm and higher, these inteφolymers also do not contain any highly short chain branched fraction ( that is the homogeneously branched ethylene/α-olefm polymers do not contain a polymer fraction with a degree of branching equal to or more than about 30 methyls/ 1000 carbons) The homogeneous linear or substantially linear ethylene/α-olefin inteφolymer for use in the present invention typically are inteφolymers of ethylene and at least one C3-C20 α- olefm and/or C4-C]g diolefm, preferably inteφolymers of ethylene and C3-C20 α-olefins, more preferably a copolymer of ethylene and a C4-C8 α-olefin, most preferably a copolymer of ethylene and 1-octeπe The term inteφolymer is used herein to indicate a copolymer, or a teφolymer, or the like That is, at least one other comonomer is polymeπzed with ethylene to make the inteφolymer Ethylene polymeπzed with two or more comonomers can also be used to make the homogeneously branched substantially linear inteφolymers useful in this invention Preferred comonomers include the C3-C20 ot-olefins, especially propene, isobutylene, 1 -butene, 1-hexene, 4-methyl- 1 -pentene, 1-heptene, 1-octene, 1-nonene, and 1- decene, more preferably 1 -butene, 1-hexene, 4-methyl- 1 -pentene and 1-octene The homogeneously branched linear and substantially linear ethylene/α-olefin inteφolymers used in the present invention have a single melting peak, as determined using differential scanning caloπmetry (DSC) using a second heat and a scanning range from -30°C to 140°C at 10°C/mιnute, as opposed to traditional heterogeneously branched Ziegler polymeπzed ethylene/α-olefin copolymers having two or more melting peaks, as determined using DSC The density of the homogeneously branched linear or substantially linear ethylene/α- olefin inteφolymers (as measured in accordance with ASTM D-792) for use in the present invention is generally from 0 865 g/cπ to 0 95 g/cm-\ preferably from 0 89 g/cm^ to 0 94 g/cm^, and more preferably from 0 9 g/cm^ to 0935 g/cm^ The amount of the homogeneously branched linear or substantially linear ethylene/α- olefin inteφolymer incoφorated into the composition used in the cable of the present invention varies depending upon the heterogeneously branched ethylene polymer to which it is combined However, preferably from 5 to 95 percent, more preferably from 20 to 80 percent, most preferably from 25 to 45 percent (by weight of the total composition ) of the homogeneous linear or substantially linear ethylene/α-olefin polymer may be incoφorated in the polyethylene composition for use in the cable of the present invention The molecular weight of the homogeneously branched linear or substantially linear ethylene/α-olefin polymer for use in the present invention is conveniently indicated usine melt index measurement according to ASTM D- 1238, condition 190°C/2 16 kg (formerly known as "condition (E)", and also known as h) Melt index is inversely proportional to the molecular weight of the polymer, although, the relationship is not linear The homogeneously branched linear or substantially linear ethylene/α-olefin inteφolymers useful herein will generally have a melt index of at least 0001 grams/10 minutes (g/10 min ), and preferably at least 0.03 g/10 mm. The homogeneously branched linear or substantially linear ethylene/α-olefin inteφolymer will have a melt index of no more than lOg/10 mm , preferably less than about 1 g /10 min., and especially less than 0.5 g/10 mm. Another measurement useful in charactenzing the molecular weight of the homogeneously branched substantially linear ethylene/α-olefin inteφolymers is conveniently indicated in melt index measurement according to ASTM D- 1238, condition 190°C/10 kg (formerly know as "Condition (N)" and also known as I I ). The ratio of the I JQ and I2 melt index is the melt flow ratio and is designated as I10 I2 Generally, the I10 I2 ratio for the homogeneously branched linear ethylene/α-olefϊn inteφolymers is about 5.6. For the homogeneously branched substantially linear ethylene/α-olefin inteφolymers used in the polyethylene composition of the present invention, the I JQ 12 ratio indicates the degree of long chain branching, that is, the higher the I10 I2 ratio, the more long chain branching in the inteφolymer. Generally, the I10/I2 ratio of the homogeneously branched substantially linear ethylene/α-olefin inteφolymers is at least 6, preferably at least 7, especially at least 8 or above, and can be as high as 20. For the homogeneously branched substantially linear ethylene/α-olefm inteφolymers, the higher the I]( l2 ratio, the better the processability The molecular weight distnbution of the substantially linear ethylene inteφolymer in the present invention may be analyzed by gel permeation chromatography (GPC) on a Waters 150°C high temperature chromatographic unit equipped with three mixed porosity columns (Polymer Laboratoπes 10 3 , 10 4 , \(fi and 10 6 ), operating at a system temperature of 140°C The solvent is 1 ,2,4-tπchlorobenzene, from which 0 3 percent by weight solutions of the samples are prepared for injection. The flow rate is 1.0 mL/minutes and the injection size is 100 microliters A differential refractometer is being used as the detector The molecular weight determination is deducted by using narrow molecular weight distπbution polystyrene standards (from Polymer Laboratoπes) m conjunction with their elution columns The equivalent polyethylene molecular weights are determined by using appropriate Mark-Houwmk coefficient for polyethylene and polystyrene ( as descπbed by Williams and Ward in Journal of Polymer Science. Polymer Letters, Vol 6, (621) 1968, incoφorated herein by reference) to derive the following equation. polyethylene =a *( polystyrene) • In this equation, a=0.4316 and b=1.0. Weight average molecular weight, Mw, is calculated in the usual manner according to the following formula: Mw=∑ wι*Mι, where wi and Mi are the weight fraction and molecular weight, respectively, of the i tn fraction eluting from the GPC column. For the homogeneously branched linear and substantially linear ethylene/α-olefin inteφolymers, the molecular weight distribution (M w /M„) is less than 3.5, preferably from 1.8 to 2.8, more preferably from 1.89 to 2.2 and especially about 2. The ethylene polymer to be combined with the homogeneously branched linear or substantially linear ethylene/α-olefin inteφolymer is a heterogeneously branched ethylene polymer, preferably a heterogeneously branched (for example, Ziegler polymerized) inteφolymer of ethylene with at least one C3-C20 α-olefin (for example, linear low density polyethylene (LLDPE)). Heterogeneously branched ethylene/α-olefm inteφolymers differ from the homogeneously branched ethylene/α-olefin inteφolymers primaπly in their branching distribution. For example, heterogeneously branched LLDPE polymers have a distπbution of branching, including a highly short chain branched portion (similar to a very low density polyethylene), a medium short chain branched portion (similar to linear low density polyethylene) and often a linear ( that is, non-short chain branched) portion. The amount of each of these fractions vanes depending upon the whole polymer properties desired. For example, linear homopolymer polyethylene has no short chain branching. A very low density heterogeneous polyethylene having a density from 0.89 g/cm 3 to 0.915 g/cm 3 (such as Attane copolymers, sold by The Dow Chemical Company and Flexomer M sold by Union Carbide Coφoration) has a higher percentage of the highly short chain branched fraction, thus loweπng the density of the whole polymer. Preferably, the heterogeneously branched ethylene polymer is a heterogeneously branched ethylene/α-olefin inteφolymer, most preferably Ziegler polymerized ethylene/α- olefin copolymer. The α-olefin for such ethylene inteφolymer may include α-olefin having 3 to 30 carbon atoms, more preferably an α-olefin having 4 to 8 carbon atoms, most preferably 1 -octene More preferably, the heterogeneously branched ethylene polymer is a copolymer of ethylene with a C -C20 α-olefin, wherein the copolymer has (I) a density from 0 9 g/cm 3 to 0 965 g/cm 3 , (II) a melt index (I 2 ) from about 0 1 g/10 min to about 500 g/lOmin The heterogeneously branched ethylene/α-olefm inteφoiymers and/or copolymers. especially those having a density of less than 0 95 (excluding, of course, ethylene homopolymers having a single melting peak) also have at least two melting peaks as determined using Differential Scanning Caloπmetry (DSC), using the same scanning rate and temperature range descπbed earlier herein The compositions disclosed herein can be formed by any convenient method, including dry blending the individual components and subsequently melt mixing or by pre- melt mixing in a separate extruder (for example, a Banbury mixer, a Haake mixer, A Brabender intemal mixer, or a twin screw extruder) Another technique for making the compositions in-situ is disclosed in PCT applications WO 92/1 1269 and WO 94/01052. PCT applications WO 92/11269 and WO 94/01052 describe, inter alia, inteφolymenzations of ethylene and C3-C20 α-olefins using a homogeneous catalyst in at least one reactor and a heterogeneous catalyst in at least one other reactor The reactors can be operated in seπes or in parallel. A preferred density of the polyethylene composition used for the cable of the present invention may depend upon desired stiffness of the finished cable However, typical densities will preferably be from 0.91 to 0 96 g/cm 3 , more preferably from 0 92 to 096 g/cm 3 A preferred melt index ( that is I2) of the polyethylene composition disclosed herein may depend upon process conditions and desired physical properties However, generally, the melt index of the polyethylene composition disclosed herein may be from 0.1 to 50 g/10 minutes for all categones of cable, preferably not greater than 04 g/10 minute for category five (5), preferably from 04 to 1 g/10 minutes for category four (4), preferably greater than 1 to 10 g/10 minutes for category three (3), and preferably greater than 10 to 25 g/10 minutes for category two (2), and greater than 25 g/10 minutes for category one (1) These general categories are found in ASTM D 1248, and are also included in the Standard Specifications for Plastic, Molding and Extrusion However, if the I2 of the polyethylene composition disclosed herein is lower than about 0 1 g/10 minutes, the polyethylene composition is often difficult to extrude and may cause melt fracture on the surface of the finished cable Likewise, if the l of the polyethylene composition disclosed herein is higher than the above ranges, the molten polymer tends to have a low melt viscosity and melt tension, thus may be difficult to fabricate into the desired cable. The I i(/l2 °f tne polyethylene composition disclosed herein may be preferably from 7 to 16. more preferably from 9 to 14, most preferably from 10 to 13. If the Iiφ or" tne polyethylene polymer disclosed herein is lower than the above range, surface quality of the finished cable tends to be deteriorated, and processability of the cable may become unacceptably low. The resin composition of the present invention may comprise any known additives and or fillers to the extent that they do not interfere with the enhanced formulation properties discovered by Applicants. Any additives commonly employed in polyolefin compositions, for example, cross-linking agents, antioxidants (for example, hindered phenolics (for example, Irganox 1010 made by Ciba Geigy Coφ.), phosphites (for example, Irgafos™ 168 also by Ciba Geigy Coφ.), flame retardants, heat stabilizers, ultra-violet absorbents, anti-static agents, slip agents, process aids, foaming agents, plasticizers, dyes, miscellaneous fillers such as clay and pigments can be included in the formulation. A preferable additive of the present invention may include, for example, carbon black, and an antioxidant such as Irganox™ 1010 and Irgafos™ 168. The composition of the present invention may be further fabricated into desired cable of the present invention by using any known fabrication method. The composition of the present invention may be used not only for cable jacketing, but also cable insulation or any layer of a cable. For example, the composition described herein may be heated, melted, kneaded and extruded by a mono- or bi-axial extruder through an extrusion die such as a cross-head die so as to be applied onto a core substrate, and then it may be subjected to a cooling step, or the next coating step if desired. Multiple layers of polymers may be applied onto the core substrate if desired. The core substrate may comprise any known materials in the art, for example, control cables comprising any conductive material such as copper, and aluminum, insulating material such as low density polyethylene, polyvinyl-chloride, polyethylene compositions including compositions described herein, conductive or semiconductive shields such as aluminum, copper, and steel, usually in form of tape, foil, screen, net or any combinations thereof, and any reinforcement material. Various cables and cable designs may include, as at least one layer, the polyethylene compositions disclosed herein. For example, USP 3,638.306 (Padowicz) shows a communications cable which has a water proof core of conductors and a sheath including an unsoldered steel layer. Figure 7 herein shows such a structure: the steel layer (1 ) is stretch- formed to attain a tightly registered longitudinal seam which eliminates the necessity of soldeπng or other means of mechanically joining the seam A cable 101 includes a plurality of conductors or conductor pairs 4 within a cable core 2 The conductors 4 are surrounded by and the interstitial spaces therebetween are filled with a wateφroof filler material 6 About core 2 is a core wrap 8 which may be a suitable plastic or other matenal A binder can be placed around core wrap 8 to hold it in position about core 2, a layer of conductive metal is placed about the core A thin aluminum layer 10 having a longitudinal seam 14 therein advantageously can be used for lightning protection and shielding Longitudinal seam 14 is not required to be soldered or otherwise mechanically joined, a steel layer 20 having unsoldered overlapping edges 16 and 18 forming a longitudinal seam 17 is longitudinally wrapped about aluminum layer 10 to provide protection from mechanical forces such as abrasion The use of an unsoldered seam 17 for steel layer 20 is possible, since the cable core 2 is wateφroof Steel layer 20 and aluminum layer 10 advantageously can be transversely corrugated and meshed with each other to provide a more flexible sheath Steel layer 20 is stretch-formed and cold- orked as it is wrapped about aluminum layer 10 and edges 16 and 18 are closely meshed to provide a tightly registered overlapping seam 17 The stretch-forming and cold-working insure that edges 16 and 18 retain their respective positions without the necessity for external holding forces after the forming forces have been removed Thus, the tightly registered seam 17 is maintained Edges 16 and 18 will retain their positions and maintain the tightly registered seam 17 even when cable 101 is would on a reel The outer or overlying edge 16 of steel layer 20 advantageously can be turned slightly inward toward core 2 to insure that no shaφ edges are presented by steel layer 20 Corrosion protection for steel layer 20 and added protection against water penetration are provided by hot-melt flooding each side of steel layer 20 with respective coatings 12 and 22 of a corrosionproof, wateφroof matenal (such as a Pπmacor™ Adhesive Polymer made by The Dow Chemical Company) This readily can be accomplished by drawing cable 101 through a bath of appropπate matenal as layer 20 is being applied Coatings 12 and 22 advantageously might be the same material as is utilized for filler matenal 6 Protection against water penetration is obtained since coatings 12 and 22, respectively, fill all spaces between steel layer 20 and the adjacent layers 10 and jacket 24 of the cable sheath Jacket 24 is desirably made using the ethylene polymer compositions disclosed herein Seam 17 is also sealed against water ingress by coatmgs 12 and 22 being drawn into seam 17 by capillary action of the tightly registered seam Added mechanical strength is also obtained from the adhesive forces of coatings 12 and 22 which tend to adhere steel layer 20 to adjacent layers 10 and jacket 24 For added corrosion protection of layer 20 and for additional mechanical and moisture protection, an exterior ethylene polymer composition jacket 24 advantageously is extruded around the exterior surface of layer 20 Thus, the cable sheath compπsing an aluminum layer 10, an unsoldered steel layer 20 and a thermoplastic layer or jacket 24 joined by corrosion coatings 12 and 22 provides mechanical, rodent, and wateφroof protection at a cost substantially less than the sheaths of prior art cables In Figure 7, vanous layers may compπse the ethylene polymer compositions disclosed herein, including jacket 24, layers 22, 12 and 8, further any or all of these layers may compπse the ethylene polymer compositions disclosed herein Other United States Patents disclosing useful cable structures enhanced by use of a layer compnsing the polyethylene compositions layer of the present invention include US Patent 4,439,632 (Aloisio, Jr et al ), US Patent 4,563,540 (Bohannon, Jr et al ), US Patent 3,717,716 (Biskeborn et al ), and US Patent 3,681,515 (Mildner) The present invention will be more clearly understood with reference to the following examples Cable Example 1 A cable was produced by using polymer A which was an in-situ blend made according to PCT Publications WO 92/1 1269 and WO 94/01052, wherein 36 weight percent of the total composition of a homogeneously branched substantially linear ethylene/ 1-octene copolymer having a density of 0915 g/cm 3 was made in a first reactor, and 64 weight percent of the total composition of a heterogeneously branched linear ethylene/1-octene copolymer having a density of 0955 g/cm 3 was made in a second reactor Polymer A had a melt index (12) of 0 78 g/10 minutes, Iχθ^2 of 11 9, a density of 0 958 g/cm 3 (note that polymer A contained 2 6 weight percent carbon black and 400 ppm of a fluoroelastomer) and 0039 long chain branches/ 10,000 carbons (0 39 long chain branches/1000 carbons) as determined using a kinetic model, and a M w M„ of 7 5 The polymer was extruded onto a cable by using a cable manufactuπng line equipped with an extruder having a diameter of 6 35 cm, length to diameter ratio of 20 to 1 with a 5 turn meteπng screw having a compression ratio of 3 66 to 1 , with a crosshead die having a die diameter of 2 04 cm, die-tip inside diameter of 1 73 cm, a die gap of 0 318 cm, and 0 cm land length The cable was produced by forming corrugated steel over a poly vinylchloπde jacketed control cable and extruding the polymeπc jacket over the steel sheath The extruder speed was approximately 55 φm and the cable line speed was held constant at 760 cm/minutes The melt temperature was 232°C to 240°C using the following temperature profile zone 1, 166°C, zone 2. 171 °C, zone 3, 188°C, zone 4, 205°C, cross head, 219°C, die, 227°C Pressure, amps, melt temperature and cable melt strength were evaluated subjectively (for example, the cable jackets did or did not have the required melt strength dunng extrusion as reported in Table 1 ) The surfaces of the cable jackets were evaluated visually and assigned a numencal surface rating, where the highest quality surface was given a rating of 100 The results are also reported m Table 1 The finished cable was subjected to physical properties test described below Cable Example 2 A cable was produced by using polymer B which was an in-situ blend made according to PCT Publications WO 92/11269 and WO 94/01052, wherein 41 weight percent of the total composition of a homogeneously branched substantially linear ethylene/ 1-octene copolymer having a density of 0915 g/cm 3 was made in a first reactor, and 59 weight percent of the total composition of a heterogeneously branched linear polymer ethylene/1-octene copolymer having a density of 0 955 g/cm 3 was made in a second reactor The polymer B had a melt index of 0 89 g lOminutes, 2 or" 1 1 - 3 > density of 0.957 g cm 3 (note that polymer B contained 2.6 weight percent carbon black and 400 ppm of a fluoroelastomer), 0 18 long chain branches/ 10,000 carbon atoms (1.8 long chain branches/ 1000 carbon atoms) as calculated using a kinetic model, and molecular weight distnbution ( that is M w /M n ) of 5 01 The polymer was extruded onto cable as desenbed in Example 1. The finished cable was sub j ected to the physical property tests desenbed below Melt tension and cable surface rating were measured by the methods descπbed in Example 1 , and are reported m Table 1 Cable Example 3 An cable is produced by using polymer C which was an in-situ blend ethylene/ 1- octene copolymer produced by the same process descπbed in Example 1 , having a melt index of 0 87 g/lOminutes, I10 I2 of 1 47 and density of 0.952 g/cm 3 (note that polymer C contained 26 weight percent carbon black and 400 ppm of a fluoroelastomer) and a M M n of 5 22 The polymer was extruded onto cable as descπbed in Example I Surface rating is reported in Table 1 The finished cable was subjected to physical properties tests descπbed below Comparative Cable Example 4 A cable was produced by using polymer D, which is a currently available polyethylene (for example UCC 8864 by Union Carbide) having melt index of 0 76 g/lOminutes, lio/Io of 12 3. density of 0 942 g/cm 1 , and M w /M n of 3 7, and no long chain branching Polymer D also contained 2.6 weight percent carbon black and about 400 ppm of a fluoroelastomer The polymer was extruded onto cable as described in Example 1 Melt tension data and cable surface rating are reported in Table 1 Cable Example 5 A cable was produced by using polymer E which was an in-situ blend ethylene/ 1- octene copolymer produced by the same process described in Example 1, having a melt index of 0.58 g/lOminutes, I JO/I 2 of 11.03, and density of 0.944 g/cm 3 , and M w /M n of 5.1 Polymer E also contained 2.6 weight percent carbon black and 400 ppm of a fluoroelastomer. The polymer was extruded onto cable as desenbed in Example 1. Melt tension and surface rating are reported in Table 1. The finished cable was subjected to physical properties test descπbed below Cable Example 6. A cable was produced by using polymer F which was an in-situ blend ethylene/ 1- octene copolymer produced by the same process described in Example 1, having a melt index of 0.88 g/lOmmutes, Ijo 12 of 10 I 3 < density of 0.94 g/cm 3 , and a M w M n of about 4.6. Polymer F contained 2.6 weight percent carbon black and 400 ppm of a fluoroelastomer The polymer was extruded onto cable as descπbed in Example 1 and subjected to physical properties tests described below Melt tension and surface rating are reported in Table 1 Comparative Cable Example 7 A cable was produced by using polymer G, which is a currently available polyethylene (for example UCC 3479 by Union Carbide) having melt index of 0.12 g ]0mιnutes, I10 I2 of 294, density of 0.958 g cm 3 , M w /M n of 5.6, and no long chain branching. Polymer G contained 2.6 weight percent carbon black and about 400 ppm of a fluoroelastomer. The polymer was extruded onto cable as desenbed in Example 1 and subjected to physical properties tests descπbed below. Melt tension and surface rating are reported in Table 1 Table 1 Visual Surface Melt Strength Used to (g/lOmin.) Density (g/cnr ) Rating (cN) Resin* Make Cable I10 I2 Polymer A Example 1 0.78 11.9 0.958 90 - Polymer B Example 2 0.89 11.3 0.957 100 3.69 Polymer C Example 3 0.87 10.47 0.952 75 - Polymer D Comp. Ex 4 0.76 12.26 0.942 95 6.57 Polymer E Example 5 0.58 11.03 0.948 65 4.5 Polymer F Example 6 0.88 10.13 0.940 70 4.2 Polymer G Comp. Ex 7 0.12 29.4 0.958 80 7.1 * All of these resins contained 2.6 wt percent carbon black and 400 ppm fluoroelastomer Surface Profilometry The surface roughness of Example 2 and comparative Example 7 was quantified using surface profilometry. More specifically, the average surface roughness of theses cables was measured using a Surftest 402 Surface Roughness Tester, produced by Mitutoyo. This analyzer computes various surface roughness parameters given a scan of the cable surface with a diamond tipped stylus. Surface roughness is quantified by the statistical parameter, R a , known as the average roughness. This quantity is the arithmetic mean of all departures of the roughness profile from the average mean line as in Equation (V), (v) R α = ^∑ =1 | w| where N is the number of digitized data points within the length of cable used for the measurement and /fa) is the vertical departure from the mean surface line at each data point. The average roughness of Example 2 was 28.0 ± 1.4 μ in. (0.71 ± 0.036 microns), while the average roughness of comparative example 7 was 60.5 ± 2.1 μ in (1.54 ± 0.053 microns). The surface roughness of the copolymers described in this invention is less than half the roughness of the comparative sample. Typical profilometer traces from the surface of cable Example 2 and Example 7 are shown in Figures 5 and 6. This surface roughness data is suφrising, given the Iιo/I 2 values, for example, 1 1.3 for Example 2 and 29.4 for comparative Example 7. More specifically, it is well known that processability improves and surface roughness (melt fracture) decreases as I 10 I 2 increases. In other words, the very smooth cables produced by the copolymers of this invention were suφrising, given their relatively low L0/I2 values. Circumferential and Longitudinal Tensile Tests Circumferential tensile samples were cut from the finished cables peφendicular to the cable axis with no metal seam impressions within gauge length Longitudinal tensile samples were cut parallel to the cable axis with no metal seam impressions within gauge length The tensile test was earned out according to ASTM D 638, using Die V (5) (for example microtensile), with a 2 54 cm jaw separation and pulling at 1.27 cm/minutes The tensile strength data are reported in Table 2 Table 2 " ■ Comparative Example Notched circumferential tensile tests Circumferential tensile samples were cut peφendicular to the cable axis from the finished cables prepared as descπbed above, and the notch (due to the metal overlap) was centered withm the gauge length. The test was earned out as desenbed in ASTM D638 using Die V (5) (for example microtensile), with a 2.54 cm jaw separation and puling at 5.08 cm/minute. The results are reported in Table 3. Table 3 * a Sample Cracked Reduced Notch Sensitivity (Cables) An important aspect of the present invention is the fact that cables, where the outer cable jacket is composed of the compositions disclosed in this invention, have reduced notch sensitivity relative to comparative cable jackets It is well known that the tensile properties of polyethylenes are sensitive to notches or surface imperfections Duπng the cable jacketing process, notches are generally produced at the shield overlap In the case of poor or incomplete shield overlap, severe notches are produced in the jacket which can result in failures under relatively mild impact or tensile forces The reduced notch sensitivity of the cable j ackets of this invention is shown in Table 4 For example, due to the notch, the cable jackets of this invention lost 26 to 54 percent of their tensile elongation, that is, the tensile elongation with no notch present In contrast, 90 percent of the tensile elongation was lost for cable jackets produced from a comparative polyethylene (Example G) Thus, cable jackets produced from the copolymers of this invention have reduced notch sensitivity Reduced notch sensitivity means the cables are easier to install, for example, the cables do not fail (split) during the bending and/or twisting which occurs during the installation process Table 4 Percent (%) Cable Jacket Cable Jacket Notched Loss of Sample Circumferential Circumferential Elongation due Tensile Elongation Tensile Elongation to Notch Example A 380 280 26 Example B 450 220 51 Example C 540 250 54 Comparative 400 40 90 Example G Cable Flexibility Cable flexibility of the final cable jacket bonded to corrugated steel was determined by measuring the amount of force required to deflect the cable. A cable having a length of 33 cm was cut, the cable core was discarded, and each end, approximately 3 cm in length, was flattened. The cable was inserted through the upper grip assembly of the Instron tensile machine and the flattened ends were clamped to the frame of the Instron tensile machine. The cable samples were deflected at a rate of 12.7 cm/minutes, and the force required to deflect the cable 5, 10, 15 and 20 mm was recorded and reported in Table 5. Lower force indicates greater flexibility This test is described in detail in "Chemical Moisture Barner Cable for Underground Systems" by K.E. Bow and Joseph H. Snow, presented at IEEE/PCIC Conference, held Sept. 1981 in Minneapolis, MN, pp. 1-20, especially pages 8-10. Table 5 The cables made from polymer A (density: 0.958 g/cm 3 ), polymer B (density: 0.957 g/cm 3 ) and polymer C (density: 0.952 g/cm 3 ) showed greater flexibility ( that is lower force at deflection) than cable made from Polymer G (density: 0.958 g cm 1 ), where these samples are of similar density. Especially, the cable made from polymer A showed supenor flexibility than the cable made from polymer G, despite the density of the both polymers being about the same. The results for these two trials are also shown graphically in FIG. 1 The results shown in Table 5 indicate the cables of the present invention have superior flexibility than the cable made from the current polymer. For example, the data show that it takes less force to deflect a cable of the mvention for a given distance (for example, 5, 10, 15 or 20 mm as shown in the table), than for a cable made from currently commercially available polyethylene, even at similar densities. Shπnkback Samples of jacket were removed from the finished cable prepared above, and the shπnkback was measured in accordance with ASTM D 4565 As an exception to ASTM D 4565. 4 specimens having 5 1 cm length parallel to the cable axis and 6 4 mm width were cut from the cable One of the specimens was cut from a portion of the cable lying directly over the outer shield overlap and the other three were cut at successive 90 degree increments to the overlap Cables should not shnnk back more than 5 percent, preferably not more than 2 percent, after 4 hours in an oven at 100°C The results are reported in Table 6 Table 6 Resin percent Shnnkback Polymer A 1 5 Polymer B 0.5 Polymer C 0.5 Polymer G* 1.0 Polymer E 1.0 Polymer F 1.0 " ■ Comparative Example Melt Index Drift The melt index of the cable jacket, after extrusion, was determined according to ASTM D 1238 The percent dnft in melt index ( that is, the change in melt index as a result of extrusion) (percent M dnft) was determined using the following equation percent MI dπft = (MI cable -MI , tιal ) / MI ιmtιal wherein MI lπ,tιa ^ represents a melt index of the resin pnor to extrusion, and Mjcable represents a melt index after extrusion The change in melt index as a result of extrusion indicates the amount of crosslinking that may take place dunng extrusion, normally, minimal change is desired The results are reported in Table 7 Table 7 Resin {yjj cable jyl j initial percent MI drift Polymer A 0.83 0.78 6.4 Polymer B 0.94 0.89 5.6 Polymer C 0.96 0.87 10.3 Polymer G* 0.16 0.12 33.3 Polymer E 0.75 0.58 29.3 Polymer F 0.96 0.88 9.1 *Comparative Example The results shown in Table 7 indicate that the melt index drift of the resin used in the present invention was generally lower than that of commercially available currently used resin G*. Jacket Bond Test The jacket bond test was conducted according to ASTM D 4565 for cables with a bonded steel sheath. A section of the cable jackets prepared as described above was removed by slitting the jacket longitudinally along the shield overlap. The cable was ringed circumferentantially with a knife, flexed at the cut point to break the steel shield at the ring. The metal sheath was opened, flattened, and the cable core was discarded. The specimen strip was cut in the circumferential direction. Three strips having a width of 13 mm were cut for each strip. For each specimen, the jacket was separated from the shield or armor only of a length sufficient to permit forming a tab of each sheath component. Three specimens were tested for each cable sample at a crosshead speed of 50 mm / minute. The results are reported in Table 8. Table 8 Circumferential Longitudinal Overlap Bond Bond Bond Strength Failure Strength Failure Strength Resin (N/m) Mode (N/m) Mode (N/m) Polymer A 4, 136 Jacket 6,1 10 Metal / 6.366 Jacket Polymer B 10,246 Jacket / 7,299 Metal 3,929 Metal Polymer G 6,523 Jacket 7,721 Metal / 1.160 Jacket Polymer E 5,963 Metal 5,825 Metal 4,224 Polymer D 6,601 Jacket / 6,110 Metal 6,091 Metal Bend Tests. Hot. Room Temperature and Cold A cold bend test was conducted according to ICEA specification S-84-608- 1988 which calls out ASTM 4565 for the specifics on the test procedure Samples were equilibrated in a cold room at - 30°C for 4 hours, pnor to the testing A cable sample having length of 91 4 cm was bent in a 180° arc around a mandrel having a diameter of 8 times the cable diameter, then the sample was straightened, rotated 180°, and then bent again 180° Upon completion of the second bend, the cable was straightened, rotated 90° and bent m a 180° arc Upon completion of the third bend, the cable was straightened, rotated 180° and then bent for the fourth time A room temperature bend test was conducted m a manner similar to ASTM 4565 The cable samples were conditioned at 20°C for 4 hours pnor to testing A cable sample was bent in the same manner as the cold bend test as desenbed above, except the sample was bent around a mandrel having a diameter of 20 times the cable diameter A hot bend test was conducted in a manner similar to ASTM 4565 The cable samples were conditioned at 60°C for 4 hours pnor to testing A cable sample was bent in the same manner as the cold bend test as desenbed above, except the sample was bent around a mandrel having a diameter of 10 times that of the cable diameter After bending each cable sample, the surface area of the samples were inspected for cracks in the bent area using normal or corrected to normal vision Results of the cold, room temperature and hot bend test are reported in Table 9 Table 9 Resin -30°C bend 20°C bend 60°C bend Polymer A no visual change no visual change no visual change Polymer B no visual change no visual change no visual change Polymer D* no visual change no visual change no visual change Polymer E no visual change no visual change no visual change Polymer G* no visual change no visual change no visual change " • Comparative Example Cold impact test According to ASTM D-4565, the cable samples were conditioned at -20°C for 4 hours and tested for impact resistance A 045 kg weight was dropped onto the cable samples from a height of 0 9 m, and inner and outer surfaces of the cable samples were inspected with normal or corrected to normal vision The results are reported in Table 10 Table 10 Resin -20°C bend Polymer A no visual change Polymer B no visual change Polymer D* no visual change Polymer E no visual change Polymer G* no visual change * Comparative Example Cable Torsion Cable samples having length of 152 cm were conditioned more than 24 hours at a temperature of 18 to 27°C One end of the straight sample was fixed in a vise and the other end was rotated in a direction opposite to the overlap in the steel sheath without bending dunng the test, by an angle φ defined below in Equation (IV), UN) φ=540-3 5(OD) wherein OD is an outer diameter of the cable in mm The results are reported in Table 1 1 Table 1 1 Resin Torsion Result Polymer A no visual change Polymer B no visual change Polymer D* no visual change Polymer E cable zippered Polymer G* no visual change Example 8, 9, 10, 12 and 14, and Comparative Example 1 1 and 1 , Abrasion Resistance The abrasion resistance of Polymers A, B, C and F (which are the same polymers used in Examples 1, 2, 3 and 6), and Polymer H which is an in-situ blend produced by the same process desenbed in Example 1 (polymer H is an ethylene/ 1-octene copolymer biend), are summanzed in Table 13 Examples 8, 9 and 10 are summanzed in Table 12 The Taber abrasion data is detailed in Table 13, which measurements were determined using abrading wheel H 18 with a 1000 g load and 1000 cycles on molded plaques Table 12 Density Example No Resin (g/lOmin.) IιoΛ 2 (g/cm 1 ) Example 8 Polymer An* 0.92 1 1.87 0.94 Example 9 Polymer Bn* 0.89 11.35 0 94 Example 14 Polymer H** 0.82 1 1.45 0.952 * "n" denotes natural version of these polymers, that is, no carbon black or fluoroelastomer * *Sample contains 2.6 wt percent carbon black and 400 ppm of fluoroelastomer Table 13 Taber Abrasion (g Example No. Resin* lost / 1000 revolutions) Example 8 Polymer An 0.033 Example 9 Polymer Bn 0.031 Example 10 Polymer C 0.033 Comparative Example 11 Polymer G 0.029 Example 12 Polymer F 0.039 Comparative Example 12 Polymer D 0031 Example 14 Polymer H 0.029 * "n" denotes natural version of these polymers, that is, no carbon black or fluoroelastomer As the data of Table 1 indicate, the polymer compositions disclosed in the present invention have similar abrasion resistance relative to the currently available polymers Examples 15, 16, 18 and 19, and Comparative Examples 17 and 20, Notch Sensitivity Plaque samples for standard microtensile test according to ASTM D-l 708, Die V (5) were prepared using a special mold containing four ridges with the dimensions desenbed in Table 14 These ridges produced well defined notches m the final plaques Microtensile dogbone samples were cut from the plaque, with the notch centered within the gauge length The tensile test was conducted according to ASTM D 638 at 25 4 cm mmutes cross-head speed (pull rate) with 2.5 cm jaw separation at three temperatures, for example -30°C, 0°C and 25°C, using each notched sample and control samples having no notch The results are reported in Table 15 Table 14 Notch Depth Notch Radius/Depth (mm) Radius (mm) Ratio Notch 1 0.251 0.508 2.02 Notch 2 0.249 0.381 1.53 Notch 3 0.254 0.254 1.00 Notch 4 0.257 0.127 0.50 Table 15 Polymer / Density Elongation at Break (percent) Stress at Break (kg/cm 2 ) Example No (g/cm') Notch 20°C [)°C -30°C 20°C 0°C -30°C Example 15 Polymer B / Control 546 452 279 229 8 237 3 231 8 0 957 Notch 1 529 180 32 212 6 157 1 232 3 Notch 2 230 41 24 138 7 173 9 242 6 Notch 3 44 24 17 55 9 176 8 220 8 Notch 4 34 20 13 52 9 1500 220 4 Example 16 Polymer C / Control 627 458 150 236 0 216 3 224 2 0952 Notch 1 439 392 26 195 0 191 0 203 8 Notch 2 452 53 21 203 0 1820 203 3 Notch 3 48 26 20 75 5 183 5 21 1 1 Notch 4 38 29 17 41 3 54 1 163 6 Comparative Polymer G / Control 637 304 128 173 3 197 1 224 1 Example 17 0958 Notch 1 53 25 16 1099 73 9 276 1 Notch 2 29 22 52 156 2 128 9 211 6 Notch 3 20 18 52 179 4 64 8 211 4 Notch 4 22 19 12 104 9 55 5 394 5 Example 18 Polymer E / Control 624 505 472 252 1 284 9 299 9 0948 Notch 1 543 497 310 2107 281 1 2760 Notch 2 508 471 30 1906 265 9 223 5 Notch 3 218 43 23 1404 104 7 223 2 Notch 4 44 35 16 53 5 67 2 241 6 Example 19 Polymer F / Control 671 573 452 261 0 215 1 270 8 0940 Notch 1 574 524 326 2084 281 2 253 4 Notch 2 542 493 33 1960 2627 2107 Notch 3 273 45 22 128 8 127 3 216 1 Notch 4 47 35 26 57 1 64 7 79 2 Comparative Polymer D / Control 923 739 372 259 7 297 6 230 1 Example 20 0 942 Notch 1 759 683 405 216 1 285 8 225 4 Notch 2 73f 652 454 209 5 277 3 2424 Notch 3 685 43Ϊ 21 202 8 205 9 199 0 Notch 4 7 4' 1 15 > 83 2 84 1 207 1 As shown in Table 15, the polymers used in the cable of the present invention (for example polymer B, C, E and F) were less notch sensitive than the polymers currently available in the industry (for example Polymer D and G), comparing at about same density, for example. Polymers B and C have the higher elongation at break than Polymer G, and polymers E and F have the higher elongation at break than Polymer D, at almost all temperatures. Reduced Notch Sensitivity (Compression Molded Plaques) Improved notch sensitivity of the copolymers of this invention was also demonstrated by the tensile properties of compression molded plaques, as described in "Notched Tensile Low-Temperature Brittleness Test for Cable Jacketing Polyethylene" by R. Bernie McAda, as appeared in the May 1983 issue of Wire Journal International Magazine. Well defined notches were produced in compression molded plaques using a special "notched" mold. In general, as shown in Figure 2, tensile elongation decreased as the severity of the notch increased (for example, Notch 2 was more severe than Notch 1, etc.). Figure 2 also shows that the copolymer described in this invention (Example B) is much less notch sensitive than comparative Example G. In fact, Notch 1 had no effect on the ultimate tensile elongation of Example B (within experimental error), while comparative Example G failed catastrophically at all four notches. Improved Low Temperature Tensiles (Compression Molded Plaques) The copolymers useful in this invention also have improved low temperature tensile properties. For example, as shown in Figure 3, the reduction in tensile elongation for Example A was 18 percent at 0°C and 56 percent at -30°C. In contrast, the reduction in tensile elongation for comparative Example G was 52 percent at 0°C and 80 percent at -30°C. Thus, relative to comparative samples, the copolymers of this invention have improved tensile properties at low temperature. As a result, the cables of this invention are easier to install at low temperatures, for example, less susceptible to failures (splitting) at low temperatures.

Claims: 1 A cable compnsing a layer of a polyethylene composition characterized in that the polyethylene composition compnses (A) from 5 percent to 95 percent by weight of the total composition of at least one first polymer which is an ethylene/α-olefin interpolymer having (I) a density from 0 865 g/cm 3 to 0 95 g/cm 3 , (n) a molecular weight distnbution (M w /M„) from 1 8 to 3 5, (in) a melt index (I2) from 0001 g/10 mm to 10 g/lOmin , and (iv) a CBDI greater than 50 percent, (B) from 5 percent to 95 percent by weight of the total composition of at least one second polymer which is a heterogeneously branched ethylene polymer or homogeneously branched ethylene homopolymer having a density from 0 9 g/cm 3 to 0.965 g/cm 3 2. The cable of Claim 1 wherein the polyethylene composition compπses from 20 to 80 percent by weight of the total composition of the at least one first polymer of component (A) 3. The cable of Claim 1 wherein the polyethylene composition compnses from 25 to 45 percent by weight of the total composition of the at least one first polymer of component (A) 4 The cable of any of the preceding claims wherein the at least one first polymer of component (A) is a substantially linear ethylene polymer having long chain branching or a homogeneous linear ethylene polymer having an absence of long chain branching 5. The cable of any of the preceding claims wherein the polyethylene composition is further charactenzed as having a melt flow ratio, I 10 I 2 from 7.0 to 160 6 The cable of any of the preceding claims wherein the polyethylene composition is further charactenzed as having a density of 0 91 to 0.96 g/cm 3 7. The cable of any of the preceding claims wherein at least one of the at least one first polymer of Component (A) and the at least one second polymer of component (B) is an inteφolymer of ethylene with at least one C3-C20 α-olefin 8 The cable of claim 1 wherein the polyethylene composition has a processability as indicated by cπtical shear stress at onset of gross melt fracture of at least 3.5 x 10 6 dyne/cm" (0.35 MPa) 9 A cable jacket compπsing the polyethylene composition of any of the preceding claims having at least 10 percent more flexibility than a cable made using a heterogeneous linear ethylene polymer having the same density as the polyethylene composition. 10 The cable of any of the preceding claims characteπzed in that the polyethylene composition comprises about 40 percent (by weight of the total composition) of the at least one first polymer of component (A) which is further charactenzed as having (1) a density from 0 91 to 0 92 g/cm 3 , (n) a molecular weight distπbution (Mw/Mn) of about 2, (in) a melt index (b) of about 0 1 g/10 mm , and (iv) a CBDI greater than 50 percent, and about 60 percent (by weight of the total composition) of the at least one second polymers of component (B) having (0 a density of about 0 96 g/cm 3 , (n) a melt index (I 2 ) of about 6 g/10 min , and (in) a CDBI less than 50 percent 1 1 A cable of any of the preceding claims, characteπzed m that the polyethylene composition has a strain hardening modulus, Gp, greater than 1 6 MPa wherein Gp is calculated according to the following equation where λ„ and Od r represent the natural draw ratio and engmeenng draw stress, respectively. 12 The cable of any of the preceding claims, wherein the polyethylene composition is prepared by a process compnsing the steps of (I) reacting by contacting ethylene and at least one α-olefin under solution polymenzation conditions in at least one reactor to produce a solution of the at least one first polymer of component (A), (n) reacting by contacting ethylene and an optional α-olefin under solution polymenzation conditions in at least one other reactor to produce a solution of the at least one second polymer of Component (B), (in) combining the solutions prepared in steps (I) and (n), and (iv) removing the solvent from the polymer solution of step (in) and recovenng the polyethylene composition 13 A cable compπsing a thermoplastic cable jacket having a thickness from about 80 to about 90 mils in contact with a metal shield creating a notch in said jacket, wherein a sample of said notched jacket taken in a circumferential direction, in accordance with ASTM D 638, has less than 55 percent loss of elongation than an un-notched cable jacket sample from said cable wherein the cable jacket comprises the polyethylene composition of any of the preceding claims 14. A cable comprising a thermoplastic ethylene polymer cable jacket composition, which comprises the polyethylene composition of any of the preceding claims wherein a plaque having a single notch, a thickness from 70 to 80 mils made from said jacket composition has at least 100 percent ultimate tensile elongation, wherein the notch has a depth of 10 mils or more, a radius from 0.275 mm to 0.55 mm and wherein said ethylene polymer composition has a density of 0.945 g/cm 1 or more. 15. The cable of claim 19 wherein the ultimate tensile elongation is at least 200 percent.

Inventors: BOW KENNETH E, IACCINO TRUDY L, KALE LAWRENCE T, MCADA RICHARD B, BOW, KENNETH, E., IACCINO, TRUDY, L., KALE, LAWRENCE, T., MCADA, RICHARD, B.
Applicants: BOW KENNETH E, DOW CHEMICAL CO, IACCINO TRUDY L, KALE LAWRENCE T, MCADA RICHARD B, BOW, KENNETH, E., IACCINO, TRUDY, L., KALE, LAWRENCE, T., MCADA, RICHARD, B., THE DOW CHEMICAL COMPANY
Application year: 1997
Main classification: H01B3
IPC codes: C08F2, C08F6, C08L23, H01B3, H01B9