CA1039891A - Cable filling compositions consisting of blends of low density polyethylenes - Google Patents

Abstract

ABSTRACT

This invention provides cable filling com-pounds, e.g., for telecommunications cables, which are blends of low density polyethylenes having major pro-portion of low molecular weight and minor proportion of high molecular weight polyethylenes. The compounds are advantageously prepared from a melt blend at a temperature above the melting point by quickly cooling the blend to a temperature below 90°C, preferably from a temperature above 135°C to below 75°C, to form a grease-like material useful in filling cables by cold filling processes. The filling compound resists flowing out of the filled cable at temperatures up to 80°C.

Description

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This invention provides improved cable-filling compositions which have grease-like consistency and can be p~lmped to cable-filling means but which resist flowing ;, or draining out of the finished cable even at elevated test temperature. It also provides a method of making such compositions and further provides cables, especially telecommunication cables, filled with such compositions.
The cable-filling compositions of this inven-tion comprise a major proportion of low density poly-ethylene constituent A and a minor proportion of low ::
~ density polyethylene constituent B, constituent A having ~-,~-~" a melt flow rate value from 5 to 140 dg/min when measured by ASTM D-1238-70 at 50C and 2160 g total load using . .
0.0200 inch (0.5 mm) die orifice and constituent B having i~
a melt flow rate value from 0.2 to 250 dg/min when measured ;
by ASTM D-1238-70 at 190C and 2160 g total load using , 0.0825 inch ~2.1 mm) die orifice, the composition being a ~ -.-;:
melt blended mixture of the constituents A and B and having a melt flow rate value from 0.1 to 25 dg/min when measured by ASTM D-1238-70 at 50C and 2160 g total load using 0 0200 .. . 1, , inch ~0.5 mm) die orifice. Constituent A has weight average molecular weight from 800 to 3000, preferably from -~ 1500 to 2200. Constituent B has weight average molecular . . ~ . ..
weight from 70,000 to 300,000, preferably from 100,000 to -. 25 150,000.
The cable-filling compositions are prepared by `~
- thoroughly mixing together a major proportion of low l-.: . ..
; density polyethylene, constituent A, as above defined, and ~
,:,.` :
- a minor proportion of low density polyethylene, constituent B, as above defined, at a temperature above the melting , :~

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point of the mixture, usually above 105C and preferably `;
from 135C to 200C, but belo~ the decomposition tem-perature, and quickly cooling the resulting melt, pre-ferably with stirring, to below about 90C, preferably below 75C, to form the grease-like product. Thereafter, the grease can be allowed to cool to ambient room tempera-~- ture and used for cable filling in conventional manner ;
- and meanS. i~
r The resulting blends of constituents A and B ~ -are characterized as soft, semi-solid, grease-like materials ~- at normal room temperature.
Typical communications cables filled with this ~ ~ ;
composition pass standard drainage tests up to 80C and are flexible at low temperatures, e.g., down to -17.8C ~ -(0F). The filling composition shows no deleterious ;!`
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effects on plastic materials such as polyethylene commonly used in cables for insulation and jacketing and shows no tendency to exude oily material.
, The single figure of the drawing is a schematic representation in cross-section of a typical ~;
multi-paired communications cable with insulated con- `
ductors in a core with a surrounding core wrap, shield . .
and jacket, the interstitial spaces of which cable are filled with the cable-filling composition. Constituent ! ' A is usually present in from 80 to 99, preferably from 89 to 95, percent by weight, and constituent B is corres-pondingly present in from 1 to 20, preferably from 5 to ll, percent by weight based on the combined weights of ~`
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`~ constituents A and B. The molecular weights (~) of ~he constituents A and B are weight average molecular weights ~
-~ measured by gel permeation chromatography.

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The mel~ flow rate of constituent B is prefer-r ably from 20 to 50 dg/min.
The melt -flow rate of constituent A under the specified modified conditions is preferably from Z5 to 35 dg/min.
It will be understood that each of "constituent ,.,.: :~ ., .
; A" and "constituent B" can be composed of two or more ,, .
~- of such materials provided that each component of such ~ -: constituent has properties as specified herein for the :
respective constituents A or B and that the composite of ~
components, if plural, making up the particular constituent ;
complies with the description of that constituent.
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The low density polyethylene constituents required in the cable~Eilling composition of this invention are individually kn~wn kinds of materials made in known manner by polymeri~ation of ethylene ~-under high pressure and temperature in the presence of free-radical initiator such as molecular oxygen, ;
organo per-oxygen compounds or organo-a~o compounds.
By "low density polyethylene" is meant a polymer of ethylene made by such high pressure, high temperature -process with free-radical initiation of polymerization.
The density of such polymers is usually in the range ;~
from 0.85 to 0.53 g/cc at 25C. By "polyethylene" -it is meant to include polymers of ethylene obtained !', by polymerization of ethylene alone or of ethylene together with minor amounts of lower alkene, especially propylene and butene-l, or of ethylene together with -minor amounts of lower alkanes as telogen, such as ethane, propane or n-butane. The addition of lower - ;
alkene or lower alkane is a known expedient to decrease `
the molecular weight of the ethylene polymer product :
and is usually employed in making constituents A and B.
After thorough blending of the constituents, - the melt blended composition is cooled as rapidly as posslble with continued stirring from about 105C, - 25 preferably from above 135C, to a temperature below 90C, preferably below 75C, thereby forming a grease~ ~--like product. The cooling time should be not more than 30 minutes from 135C to 75C, and is pref-erably less than 15, more preferably less than 5 minutes. Thereafter, the product can be allowed to - 1',265/266-F -4-.. - , . : . ~ :
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cool, e.g., from 75C, to ambien~ room temperature without further stirring. It is usually convenient to draw off the grease from the mixing apparatus to ~: ' storage containers at warm temperature, e.g., 50~C.
The operations can be carried out in batches or in ,~ continuous manner.
Any apparatus capable of effecting rapid ~* cooling by heat-exchange with the initially hot molten polyethylene blend is suitable. Preferably, the cool-ing step is performed in a continuous manner on a ;i feed of melt blended polyethylene maintained at a ; temperature above 105C, preferably above 135C, pass-., ~.
ing a stream of the blend through a cooling zone with ~; the shortest possible residence time therein consistent ~ 15 with the lowest possible temperature of blend leaving ~.
r,- the cooling zone below 90C, preferably below 75C, and removing the resulting cooled blend.
~; Agitation or stirring during the cooling ;;
step is not necessary except as associated with rapid heat v, ~.
'~ 20 transfer, e.g., bringing the hot blend to, and moving ~
the cooled blend away from, the cooling surface. ~;
; ~ It is custom~ry to include in the compo-sition of starting constituents A and B small amounts of antioxidants and stabilizers such as 2,6-di-tert-~: 25 -butyl-4-methylphenol or 4,4'-thiobis(2-tert-butyl~
-5-methyl-phenol). Further amounts of such agents can also be added to the present blend compositions. `^~
Where needed or desired, other kinds of additaments ;
such as finely divided silica can be incorporated in the filler compound as known in the cable filling art~
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There can also be added to the present blend composition hollow, synthetic thermoplastic particles having gen-erally spherical con-figuration and diameters in the range from about 0.5 to about 200 microns. When used, ,. :.- .
such particles are dispersed in the present cable filler composition in proportions of up to about 10 parts -per 100 parts of the polyethylene blend, by weight~
Additaments can be incorporated into the polyethylene blend anytime prior to use as cable filler, but are ~-... .
-; 10 most conveniently admixed when the blend of polyethyl-- enes is being stirred as a melt before congealing to its grease-like consistency.
The resulting grease-like composition has physical properties dependent upon the kind and pro-' 15 portion of specific constituents blended together.
In general, the melt flow property of the blended -~
composition, tested by the modified ASTM procedure D-1238 as previously described herein using 50C, 2160 g total load and 0.0200 inch (0.508 mm) orifice, is ., ~
in the range from 0.1 to 25, preferably from 0.5 to -- 10, most preferably from 1 to 5, dg/minO
Cable-filling grease compositions as described which have been prepared by quick cooling in accordance with this invention can be stored indefinitely ; 25 before use in cable filling and then used as such in ~able filling by cold filling processes with good results in the filling step and excellent performance in the cable product, including resistance to drip, flow and drain from the cable at temperatures below 80C.
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.s 1~398~1 Alternatively, blended polyethylene compo-sitions of the formulation hexein d~scribed but which have not been quickly cooled, can be manufactured, stored and shipped without such treatment, then sub-jected to the treatment in accordance with this in-vention immediately prior to use. In one such embodi-ment, the blended polyethylene composition in the molten condition is placed in drums and allowed to cool slowly. In such condition, ik is suitable for ;~
use in hot filling cable processes but not suitable as - such for use in cold filling cable processes. How-.. .. .
- ever, if the composition as received in the cable manufacturing plant is heated above its melting point and then quickly cooled in accordance with this in-vention, the resulting grease product is suitable for use in cold filling cable processes. The heating and quick cooling steps can readily be carried out . . .
- in simple apparatus in conjunction with the usual cable line, and any surplusage of filler falling from the cable filling station can readily be returned -to the melting step. -In yet another embodiment, the initial blend ~- of polyethylenes in molten condition above its melting ~ ~-., ~, ~ .
` point, preferably above 135C, would be shipped in . . .
- 25 insulated tanks from the manufacturing site to the -cable filling site without significant intermediate cooling. At the cable manufacturing site, the hot melt blend would be taken from the shipping tank at ~ ;
appropriate rate integrated with the cable filling ` 30 facility, quick cooled and immediately used as cable : ..

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filler in cold filling processes. Even if some re- -heating were necessary to restore the high temperature before the quick cooling step, the practice could result in overall energy conservation.
The cable-filling composition of this in-. .. :.
vention can be used to fill cables such as communication cables, e.g., telephone cables, in conventional manner, using either hot filling or cold filling techniques.
As is known to the cable artisan, in the makin~ of multi-pair communication cables, a number of indi-vidually insulated twisted conductor pairs are brought together in a forming zone to form a bundle which will become the core of the cable. The core bundle may be composed of several sub-bundles, each held together with a spiral wound thread. In "filled"
cables, the conductor bundle is passed through a stuffing box or impregnator wherein the filler compound is forced into the bundle, displacing the air and - filling the interstitial spaces between the conductor and other mechanical elements of the bundle with the filling composition. In some instances, the forming ~ `
zone and the filling zone are in effect combined so that the filler is forced around and among the twisted conductor pairs as they are brought together to form a core bundle containing filler compound. In either case, the so-filled bundle then passes to subsequent operations of the cable manufacturing line to complete the cable construction, such as a zone where plastic film is wrapped or folded about the conductor bundle, a zone where a tape of metal foil such as aluminum ..

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11,265/266-F -8-3989~ ~
or copper is folded lo~gitudinally or wound helically about the core to provide a mechanical and electrical shield, and a zone where a crosshead extruder provides ' the cable with a seamless extruded plastic outer jacket. If desired, facilitiles can be provided on j~
the cable line to apply further amounts of filler -compound, e.g., over the plastic wrap before or to-gether with the metal shield, or over the metal shield - before the plastic outer jacket.
A typical filled cable is portrayed in the - drawing wherein a cable is shown in section. A plur-- ality of insulated conductors 1 are arranged in a generally cylindrical bundle surrounded by a core wrap 2 of tough plastic film and a metal shield 3 shown as a longitudinally folded tape with overlapped seam. A plastic outer jacket 4 surrounds the metal shield. A cable filler 5 composed of the composition of this invention is disposed in the interstices between the insulated conductors 1 within the core `~
wrap 2. The conductors 1 are generally of copper covered with polyethylene or other known insulation.
Core wrap 2 is usually poly(ethylene terephthalate) ~ -or polypropylene film. Shield 3 is usually of aluminum ~
or copper, or a plurality of shields can be used such -~ -as aluminum or copper next to the core wrap and a `~
steel tape folded thereover. The outer jacket may be composed of any suitable cable jacketing composition such as, for example, polyethylene, polymers of ethyl ene, polypropylene or chlorinated polyethylene, usually compounded with carbon black.
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- 1/,265/266-F -9-10`39~91 The shield 3 is advantageously formed of '- aluminum having an adhesive coating on at least the outer surface when placed over the core wrap for the purpose of providing a sealing bond in the lap seam of the shield and of bonding the shield to the outer plastic jacket. Suitable exemplary adhesives include random and graft copolymers of ethylene and ~
-ethylenically unsaturated carboxylic acids such as, for example, acrylic acid and methacrylic acid and ;~ 10 such copolymers which also include esters of such acids, partial salts of such acids (ionomers), and `` vinyl acetate.
: .
The filling compositions of this invention can also be used to fill electrical devices other than cable cores, for example, splice boxes, terminal boxes, junction boxes and like devices where it is desired to exclude water and/or to assist holding `~ component parts in spaced relationship. -~
The following examples further illustrate the invention.
,. . .
Example 1 A mixture is composed as follows:
92.86 parts by weiyht polyethylene A
6.99 parts by weight polyethylene B
0.15 part by weight 4,4'-thio-bis-(2-tert--butyl~5-methylphenol) Polyethylene A is a low molecular weight i polymer product of free-radical initiated polymeri-~- zation of ethylene in the presence of propylene and has melt flow rate of about 30 dg/min at 50C through ~`. ' : :
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- the extrusion plastometer o~ ASTM D-1238-70 when modified with 0.0200 inch die orifice using 2160 g -- total load. Polyethylene B is low density (D.915 g/cc) free-radical induced polymer of ethylene which `-; 5 has melt flow rate (Melt IndeK) of about 50 dg/min - by ASTM D-1238-70 Condition E. Starting polyethyl-ene B contains about 1500 ppm by weight of 2,6-di-- -tert-butyl-4-methylphenol.
The mixture was heated with stirring to a temperature between 150 and 200C until all of poly-ethylene B is melted and well blended with polyethylene A. One portion of the blend, at a temperature of about ~-~ 200C, was drawn off into large drums and allowed to cool slowly. After 24 hours, the drums and contents were still warm. Another portion was cooled rapidly with continued stirring and the blend temperature was quickly lowered to about 50C, forming a soft, semi-solid grease-like product.
Samples of both of the resulting blend prod-ucts have melt flow rates of about 1.9 dg/min through the extrusion plastometer of ASTM D-1238-70 modified with 0.0200 inch (0.5 mm) die orifice, at 50C with 2160 g total load. Other properties are as follows:
Property Method Value Viscosity at 135C Brookfield* 135 cp Visc., kinematic, 135C ASTM D 445 225 cs Melting point ASTM D 127 9noc Density at 23C 0 85 g/cc ~ at 135C 0.73 g/cc ; Dielectric Constant, 10 Hz ASTM D 150 2.2 Dissipation Factor, 10 Hz ASTM D 150 0.0005 *Model RV using No. 7 spindle at 100 rpm.

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The rapidly cooled composition just described is used to fill a multi-pairecl twisted conductor communication cable, pumping the composition at ambient ~- room temperature to a stuffing box as the conductor ~` 5 pairs are being formed into a core structure and forwarded to cable finishing operations for fabrication of aluminum shield and plastic outer jacket in conven tional fashion.
Examination of a sample piece of the re-sulting cable shows no swelling or other indication of adverse effect of the filler compound on the con-~ ductor insulation or plastic jacket.
- Twelve-inch (30.48-cm) lengths of the re- ~j ,....................................................................... ~ .
sulting cable are subjected to a drip test. From one end of the piece, the outer plastic jacket is removed to a length of 5 inches (12.7 cm). The exposed -, metal shield and core wrap are removed to 3 inches (7.62 cm~ from the end. The twisted pairs of con-ductors are separated and slightly flared apart.
The cable lengths are hung vertically, flared con-ductors end down, in a circulating air oven maintained ;
at I50F (65.5C). After 24 hours in such state and condition, there is no drip of filler compound from the cable or evidence of flow of such compound within .
. 25 the cable. Repeat of the test at oven temperature ~
` of 176F ~80C) shows no evidence of drip or flow. ;~;
Other test pieces of the cable are condi-~ tioned at 0F (-17.8C), tested by bending, and found `~ to be acceptably flexible.

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~ A portion of the polyethylene blend product t stored in the drums, identified as Sample l-D, was `
. taken and processed for one m:inute at room tempera-ture in a grease worker as descr.ibed in ASTM D-217 at a rate of 30 strokes per m.inute to make a worked material which is identified as Sample l-DW. Process-ing in a grease-worker simulates the shearing action which is encountered in pumps used in injecting greases --into cables.
- 10 Another lot of starting mixture having com-:, position first described above in this Example 1 was heated and melted, and its temperature was adjusted to about 135C. The melt was then fed continously to a scraped wall, water-cooled heat exchanger. The :: 15 residence time of the blend passing through the ex-changer was about three minutes, and its exiting tem-,:.,~ , . :.
:; perature was about 70C. A sample of the resulting ~
:; .. .
quick cooled product, identified as Sample l-QC, was ;~
taken and processed for one minute at room temperature - 20 in a grease worker as described in ASTM D-217 at a : rate of 30 strokes per minute to make a worked material -~
~ identified as Sample l-QCW. ~.
: The viscosities of portions of the respective samples were measured on a Brookfield Viscometer, ; 25 Model RV, using a No. 7 spindle and turning speed varying from Q.5 to 100 rpm appropriate to the vis-~ cosity and computing the viscosity in centipoises : (cp) from the corresponding scale. The resulting - data are recorded in Table 1.

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'- Portions of the respective samples were also tested in a simulated cable drip test. This test is more convenient to carry out on small sample~
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than are full scale filled ~able manufacture and testing, and has been found suitable for screening purposes and correlates well with results of full scale tests. The present tests were carried out by '- applying a liberal coating of the test sample cable -" filling composition to a piece about 6 or 8 inches long of typical twisted pair insulated telephone cable wire. The so-coated wire pair is hung vertically in a hot air circulating oven maintained at 160F
: .:
(71.1C) and examined after 24 hours. If any of the `- test filler compound has dripped from the wire, that compound has failed the test. If none of the test filler compound has dripped from the wire, that compound ~` has passed the test. The test is more rigorous than the standard cable filler flow test in that the stan-` dard test temperature is only 150F (65.5C). The .: ~
results with the present test compositions are shown , ' in Table 1.

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Sample Viscosity, Cp Wire Drip Test No. at 25C. _ at 71.1C
l-D 44,500 Fail l-DW 17,300 Fail l-QC 2.1 x 106 Pass l-QCW 250,000 Pass From these data it is seen that the samples (l-D and l-DW~ of drummed material (cooled slowly) failed the -` 30 drip test. The samples (l-QC and l-QCW) of material ,' .- ~

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which was quick cooled in accordance with the present invention, passed the drip test. It is also seen that the action of processing the material through standard grease working machinery has the effect of lowering the viscosity of the material at 25C, with-out adversely affecting the drip test resistance of sample l-QCW. The product of quick cooling and woxking (Sample l-QCW) simulates the cable filling compound that would be obtained in conventional cold filling ~;~
processes and provides cables which pass the standard , 150F (65.5C) flow test for cable filling compounds.
-.
- Example 2 A mixture is prepared similar to that de-, ~- scribed in Example 1 from the same kinds of ingredi-~.
ents, except as to the proportions thereof, as follows: `
.
89.86 parts by weight polyethylene A
~: 9.99 parts by weight polyethylene B
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0.15 part by weight 4,4'-thio-bis-(2-tert-' -butyl-5-methylphenol) The mixture is heated, melted, stirred, divided and ;
one portion quickly cooled and one portion drummed and slowly cooled as described in Example 1. The resulting compositions have melt flow rate of about 1.4 dg/min by ASTM D-1238-70 modified with 0.0200 -,~.~. .
; inch (0.5 mm) orifice die, at 50C and 2160 g total load. A cahle was filled with a portion of the quickly cooled material in the manner described in Example ` 1 except that the composition is preheated and the cable is filled hot, with substantially similar re-sults, i.e., no deleterious e~fects on the cable and - 1:,265/266-F -15-~¢;1 39~9~ ~-no drip or flow from the cable end by standard test up ~
to temperature of 80C (176F~. ~
A portion of the drwmmed material, 2-D~ was ::
worked in a grease worker as described in Example l;
' 5 the resulting worked material is identified as Sample

2-DW.
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Portions of the drummed material 2-D were : . placed in small jars, reheated and re-melted. The melt was then allowed to cool in air to a temperature of about 82C during a period less than 15 minutes.
The resulting quick cooled product is here identified as Sample 2-QC. A portion of that quick cooled ma- : :
terial 2-QC was taken and processed in a grease worker . as described in Example l; the resulting quick cooled .~ 15 and worked material is here identified as Sample 2-QCW.
~: The viscosities of portions of the respective samples were measured, and simulated cable drip tests ~` were carried out, all in accord with the descriptions :
in Example 1, with results shown in Table 2.

SampleViscosity, CpWire Drip Test ` No. at 25C at 71.1C
2-D 527,000 Pass 2-DW 52,000 Marginal*
`- 2-QC >8 x 106 Pass . 25 2-QCW 235,000 Pass `. ~' *Note: The test product tended to flow from the wire : where coated in a thick layer; thin layers did :` not flow .:
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The product of quick cooling is suitable for use as cable filling compound in cold filling processes and provides cables which pass the standard flow test for cable filling compounds. The quick cooled grease product can be pumped at ambient room temperature in `~ appropriate and conventional grease pumping equipment.
, Example 3 In a manner similar to that described in ; Example 1, a cable filling composition is prepared from a mixture of these constituents:
- 94.86 parts by wei~ht polyethylene AA
4.99 parts by weight polyethylene B
~- 0.15 part by weight 4,4'-thiobis-(2-tert- ~`
-butyl-5-methylphenol).
Polyethylene AA is a low molecular weight polymer product of free-radical initiated polymeri~ation of ethylene in the presence of propylene, similar to polyethylene A of Example 1, and has melt flow rate - of about 35 g/min at 50C through the extrusion plasto-meter of ASTM D-1238-70 modified with 0.0200 inch : .:
(0.5 mm) die orifice using 2160 g total load. Poly- -ethylene B is another portion of the same polyethylene B used in Example 1.
; The mixture is heated, melted, stirred and quickly cooled as described in Example 1. Cables are filled therewith in the manner described in Example 1 and otherwise well known in the art, with substan-tially the same results, i.e.~ no adverse effects on the cable insulation, plastic jacket or other ; 30 components, and no drip or flow of filler compound from the cable end by standard drip test up to tem-perature of about 80C (176F).

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Claims (9)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A filling composition for electrical cables and devices, which comprises a major proportion of low density polyethylene constituent A and a minor proportion of low density polyethylene constituent B, constituent A having a melt flow rate value from 5 to 140 dg/min when measured by ASTM D-1238-70 at 50°C and 2160 g total load using 0.0200 inch (0.5 mm) die orifice and constituent B having a melt flow rate value from 0.2 to 250 dg/min when measured by ASTM
D-1238-70 at 190°C and 2160 g total load using 0.0825 inch (2.1 mm) die orifice, the composition being a melt blended mixture of the constituents A and B and having a melt flow rate value from 0.1 to 25 dg/min when measured by ASTM D-1238-70 at 50°C and 2160 g total load using 0.0200 inch (0.5 mm) die orifice.

2. The filling composition of Claim 1 wherein constituent A has a melt flow rate of from 25 to 35 dg/min, constituent B has a melt flow rate from 20 to 50 dg/min, there are present in the filler composition, based on the combined weights of the constituents A and B, from 80 to 99 percent of con-stituent A and correspondingly from 1 to 20 percent of constituent B, and the melt blended mixture of constituents A and B has a melt flow rate from 0.5 to 10 dg/min.

3. The filling composition of Claim 2 wherein there are present in the composition, based on the combined weights of the constituents A and B, from 89 to 95 percent of constituent A and from 5 to 11 percent of constituent B, and the melt blended mixture of constituents A and B has a melt flow rate of from 1 to 5 dg/min.

4. A telecommunication cable comprising a plurality of insulated electrical conductors arranged in a core and a core wrap defining interstices within the core, characterized by having disposed within the interstices a filler composition in accordance with any one of Claims 1 to 3.

5. A method for making a filling compound for electrical cables and devices, the compound com-prising a major proportion of low density polyethylene constituent A and a minor proportion of low density polyethylene constituent B, constituent A having a melt flow rate value from 5 to 140 dg/min when measured by ASTM D-1238-70 at 50°C and 2160 g total load using 0.0200 inch (0.5 mm) orifice die and constituent B
having a melt flow rate value from 0.2 to 250 dg/min when measured by ASTM D-1238-70 at 190°C and 2160 g total load using 0.0825 inch (2.1 mm) orifice die, the compound being a melt blended mixture of the constituents A and B and having melt flow rate value from 0.1 to 25 dg/min when measured by ASTM D-1238-70 at 50°C and 2160 g total load using 0.0200 inch (0.5 mm) orifice die, characterized by quickly cooling the melt blended mixture of the constituents A and B from a temperature above the melting point of the mixture to a temperature below about 90°C.

6. Method of Claim 5 characterized in that constituent A has a melt flow rate of from 25 to 35 dg/min, constituent B has a melt flow rate of from 20 to 50 dg/min, and there are present in the filler compound, based on the combined weights of the con-stituents A and B, from 80 to 99 percent of constituent A and from 1 to 20 percent of constituent B, and the melt blended mixture of constituents A and B has a melt flow rate of from 0.5 to 10 dg/min.

7. Method of Claim 6 characterized in that there are present in the compound, based on the combined weight of the constituents A and B, from 89 to 95 percent of constituent A and correspondingly from 5 to 11 percent of constituent B, and the melt blended mixture of constituent A and B has melt flow rate from 1 to 5 dg/min.

8. Method of Claim 5 char-acterized in that the melt blended mixture of the constituents A and B is quickly cooled from a tempera-ture of at least 135°C to a temperature of at most 75°C in a time of not more than 30 minutes.

9. Method of Claim 8 characterized in that the time of cooling from 135°C to 75°C is not more than five minutes.