CA1290883C - Cable-filling compounds - Google Patents

Abstract

ABSTRACT OF THE INVENTION
Filling compounds having plastic flow behavior for electrical components and light-wave conductors comprising (a) a non-polar, water-immiscible hydrocar-bon organic liquid, (b) an organic polymeric thickening agent therefor, (c) pyrogenic silica, and when used for electrical cables or optionally for optical cables, (d) hollow micro-bodies dispersed in the filling compounds.

Description

~29(~83 ~ PATENT
; Case D 7354 CABLE-FILLING COMPOUNDS
BACKGROUND OF THE INYENTION
; -- --1. Field of the Invention This invention relates to filling compound~ or ; sealing compound~ for electrical components, such as cableq, light-wave conductors, terminal qtripQ or plugs~ The filling compounds consist of a polymer solution in which pyrogenic silica is dispersed and which may also contain hollow bodies (e.g., hollow beads). The hollow bodies are optional when the filling compounds are used for llght-wave conductors.
; The filling compounds protect cables and light-wave conductors against the penetration of contaminants, particularly water, and al~o against mechanical damage during laying~or through the effects of~temperature.

2. Description of Related Art It i~ known that communication~ cables and also light-wave conductor~ encounter the danger that any moisture penetrating at a given point ~preads out axially and not only reduceQ the qerviceability of the line, but also has a corrosive effect thereon. There has ; never been any 3hortage~0f attempts to~overcome this 25- problem by the provision of suitable sealing compounds.
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, ~. ~ ; . .:. ~ : . , For example, German patent 3 150 909 de~cribes a filling compound consi~ting of a vi~cou3 water-immiscible ~ubstance and elastic hollow bodies finely di3persed therein, the hollow bodies being of ~uch a nature that they can be compressed to a ~maller volume by relatiYely qtrong forces and thereafter reassume their original volume as the forces diminish.
Although ~uch ~illing compounds afford a number of advantages by virtue of their relatively low dielectric con~tant~ there i5 nevertheles~ a danger at relatively high operating temperatures that the filling compound may e~¢ape from the cable through sheath damage or that at lea3t oil leakages may occur These effeot~ may be counteracted to a certain extent by increasing the pro-portion of elastic hollow bodies to such an extent that the compounds are only able to flow under pressure, i.e., when the ela~tic hollow bodie3 are compressed to a 3maller volume. Although it is pos~ible in this way to make cables having 31ightly better propertie3, the ~; 20 pro¢edure involved is ¢ompli¢ated on a¢count of the high pres~ure~ under which the filling compound has to ~; be introduced To improve the thermal stability under load of the illing compound~ according to German patent 31 50 909, attempts have been made to stabilize the hollow beads by cross-linking. Thus, it i3 propo~ed in German patent 32 13 783 to cros~-link the beadq by electron beam treatment. Although the thermal stability limit of the hollow bodie~ is thus increased by about 10~C, the filling materials thus treated still show very poor thermal stability under load.
Accordingly, there is a need for filling materials for cables or light-wave conductors which do not e~cape ; from damaged~ parts of a cable even at operating tem-peratures of about 80C or slightly above and which ' : ~ ,.
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show plastic ~low over the entire temperature range of importance In practice, i.e., the filling materials are unable to ~low up to a certain shear ~traln. Neverthe-less, the filling material~ are intended to show the favorable propertie~ of the known materials containing hoIlow bodies, particularly in that their dielectric constant i~ < 2Ø Finally, the filling compounds are intended to be proce~ible under the conditions nor-mally applied in cable manufacture.
; 10 DESCRIPTION OF THE INVENTION
It i9 an object of this invention to providè
filling materials which ~how the above described range t5 of properties.
Accordingly, the present invention relates to filling materials for the longitudinal sealing of electrical and/or optical cables and terminal strips ba~ed on a non-polar, water-immiscible hydrocarbon 20 organic liquid component characterized in that the organic liquid contains, in solution at room tem-perature, an organic thickener based on a polymer (and, optionally a dispersant), and dispersed in this hydro-carbon liquid thickener, pyrogenic ~ilica and, ~; 25 optionalIy for light-wave conductors and required for electrical conductors, gas-filled micro-hollow bodies from ~5 to 500 um in diameter wherein amounts of the subqtance~ di~persed in the liquid thickener is from about 10 to about 80S by volume whereby the filling 30 material qhows pla~tic flow behavior.
In a general embodiment, the invention relates to filling materials based on ~ a non-polar, water-~;~ immiscible hydrocarbon liquid which is thickened by an organic polymer and shows plastic flow behavior and 35 which contain mioro-hollow bodie~ to give a low , :
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More particularly, the invention provides a Pilling compound having plastic flow behavior for electrical components and light-wave conductors comprising: (a) from about 65 to about 90% by weight of a non-polar, water-immiscible hydrocarbon organic liquid having a pour point below 0C and a kinematic vi~cosity of from about 2 to about 600 cSt measured at about 20C; (b) from about 2 to about 25% by weight o~
an organic polymer ~elected from the group con~isting of a copolymer of ethylene and propylene, a copolymer of ethylene and ~-butylene, a copolymer of propylene and ~-butylene, and a terpolymer of propylene,~
-butylene and ethylene; and tc) from about 2 to about 10% by weight of pyrogenic silica; said filling compound having a dielectric constant at 20C of less than about 2.0, a specific breakdown resistance of more than about 10 Ohm.cm, a specific gravity of less than about 1.0 g/cm3, a cable filling capacity at room~temperature, is Pree from leakage at a temperature of up to about 90C, and is free from cracks i~ after 10 free~e-thaw cycles.
Accordingly, the filling materials according to the invention contain a liquid hydrocarbon as an important component. The quantity of hydrocarbon is generally from about 65 to about 90% by weight and preferably from about 75 to about 88% by weight. In certain cases, particularly where the percentage content of hollow beads or dispersed silica is relatively highj quantities of hydrocarbon liquid of from ,~
about 50 to 65% by weight may be sufficient. Suitable non-polar hydrocarbons are primarily mineral oils. Of these, substances having a .

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~ 291~)8~33 pour point below 0C are preferred. In the ca~e of ~ubstance~ having a higher pour point, it is advisable to u~e ~tandard pour point depre~ant~. The den~ity of the non-pol~r hydrocarbon~ ~hould be between about 0.8 and about 0.95 g/l and preferably between about 0.81 and about 0.91 g/l. An important selection criterion i~ the kinematic vi~co~ity which should be in the range of from about 2 to about 600 cSt (mm2 ~ 1) a~ measured at 20~C. Preference i3 attributed to non-polar hydrocarbon~, particularly mineral oil~, having a kinematic viscosity of from about 15 to about 300 cSt, and more e~pecially from about 50 to about 250 cSt.
Another important component o~ the filling materials according to the invention i~ the organic ;

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9 0 ~3 thickener~. Suitable organic thickeners are polymers which are soluble in the non-polar hydrocarbon~ and who~e ~olutions show special rheological propsrties, i.e., the solutions should show plastic flow behavior either on their own or after addition of the other com-ponents of the filling materials, the viscosity of the ~olution~ undergoing little or no reduction with increasing temperature at temperature~ of up to about 100C .
Among the polymers suitable for use as organic thickeners, polyolefins are particularly suitable.
Poly- ~ -olefins and copolymers thereof, including in particular i~otatic poly-C~-olefins are preferred.
In one preferred embodiment of the invention, from about 2 to about 25~ by weight, and more e~pecially from about 5 to about 20S by weight, of an ~-olefin copolymer is used.
d~-Olefin copolymers which have been produced by low-pres~ure polymerization u~ing Ziegler-Natta cata-ly~t~ are particularly ~uitable a~ organic thickeners herein. Thus, suitable copolymers are, for example, copolymers of ethylene and propylene, copolymers of ethylene and ~ -butylene and copolymer~ of one of the above-mentioned olefin~ with ~ -olefin3 having a chain length of from Cs to C7~ Terpolymers of at least one of the above-mentioned olefin~ may also be used. It i~
known to the arti~an that the propertie~ of ~ -olefin copolymers may be varied through the choice of the -~ catalyst and the polymerization temperature and according to the ratio in which the monomers are u~ed.
Even with different preconditions, however, the material~ obtained are often virtually identical in regard to their end properties. ~ -Olefin copolymer~
-~ having a Brookfield melt vi~cosity of from about 30 to 70 Pa at 190~C and more especially from about 40 to , .

~ 2'~'30~383 about 60 Pas are particularly preferred for the pur-po~es of the invention. In this regard, it i~ desired ~ that their 30ftening point be in the ranBe of from ; about gO to about 160C, and more especially in the range of from about 100 to 125C, and that their den-sity be from about o.83 to about 0.9 g/cc.
A particularly preferred cla~s ofoC-olefin copoly-mers are copolymer~ of propylene anddC-butylene having a C3 component of from about 55 to about 90~ by weight, and more especially from about 60 to about ô5~ by weight. These copolymers may additionally contain from about 2 to about 10~ by weight, and more especially from about 2 to about 5~ by weight, of ethylene group~.
Among the laqt-mentioned oC-olefin copolymers, co-isotactic products are preferred.
The filling materials according to the invention contain as a further constituent from about 2 to about 10X by weight, and preferably from about 3 to about 7S
by weightj of highly di~persed ~ilica. Highly dispersed silicas having a particle size of from about 0.007 to ,~ about 0.5 micron, and a powder density of from about 20 to about 120 g/l are ~uitable. However, it i~ pre-ferred to use lilica having a powder denqity of from about 35 to about 40 g/l and a particle si3e of from about 0.007 to about 0.014 micron.
Although optional, but preferred, for light con-ducting cables, when u~ed with electrioal cables the filling materials according to the invention will con-; ~ tain as a further con~tituent from about 0.2 to about 10S by weight, and preferably from about 0.5 to about 5S
by weight, of micro-hollow bodies. Among the possible micro-hollow bodies, hollow microbeads are preferred.
i It i~ po~sible to use hollow microbeads on the one hand of inorganic material~, such as for example hollow glas~ bead~, more especially of silicate glasses, and , .
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':. ' ~ ~9~)~83 on the other hand even organic hollow microbead~ having elastic walls. The hollow beads should have a diameter of from about 10 to about 150 um, and more especially of from about 40 to about 60 um. It is particularly preferred to use lightweight materialq having a powder density o~ lesg than about 100 kg/m3, and more espe-cially below 50 kg/m3- In addition to the inorganic hollow microbeads mentioned, organic hollow microbeads are particularly preferred. Thus, hollow microbeads ba~ed on a copolymer of acrylonitrile and vinylidene chloride may be successfully used. For example, pro-ducts ranging from 40 to 60 um in diameter are commer-cially available and suitable. It i~ also possible to use, for example, hollow polymer microbeads based on acrylonitrile-vinylidene chloride, which are filled with an inert gas, such as isobutane. If deqired, it is also possible to use hollow beads of which the walls have been crosslinked through the u~e of polyfunctional monomers or which have been subsequently crosslinked by ionizing radiation. In any event, the quantity in which the hollow bead~ are used has to be gauged in such a way that the beads in the final filling material occupy leq3 qpace under normal presYure than close packed sphereq. Accordingly, the quantity of beadq in the final filling material should be less than about 90~ by volume, preferably less than 70S by volume, and more especially less than 50~ by volume because other-wise the cable sheath~ could only be filled with the ~ ~ ~ filling material after compression of the particles by ; 30 high pre~ure.
The filling materials according to the invention may also contain dispersants. Suitable di~persants include polymers, particularly polycondensates, par-ticularly polycondenqates based on hydrophobic and 35~ hydrophilic components. Thus, it i~ posqible to use '~' " ' ~

~9C~383 polycondensates ~ynthesized at lea~t partly from dimer fatty acids or the corre~ponding diamines. Suitable condensates are polyamides of dimer fatty acids and diamines or polye~ter~ of dimer fatty acid~ and poly-functional alcohol3 (functionality 2 or 3, e.g.,oligomer~). Mixed- types may also be u~ed.
Polycondensate~ containing terminal amino groups are preferred. Thu~, suitable polyconden~ates are, for example, polycondensate~ of a long-chain dicarboxylic acid with one or more diamines or triamines, more e3pe-cially conden3ate~ of dimer fatty acid~j trimer fatty acids, monomeric fatty acid3 and primary or secondary diamine3 containing from 2 to 36 carbon atoms (dimer fatty amine). Polyconden~ates o~ dicarboxylic acids ; 15 with cyclic amine~, uch a~ piperazine, may al~o be u~ed. The dimer fatty acids may al30 be replaced to a minor extent by ~hort-chain dicarboxylic acids, for example, sebacic acid or adipic aci~d. In any event, it is preferred for the polyconden~ates to contain ter-minal amino groups. Suitable amine number~ are in the range o~ from 80 to 400, and more preferably, in the range of from 190 to 230. For example, a preferred material has theqe characteri~tics and, in addition, a ~ visco~ity of from 0.3 to 4 PaQ at 75C, while other ;; ~ 25 ~uitable productq have a visco3ity of from 0.7 to 1.2 Pa~ at 150C. If de~ired, the oligomeric diqpersants may be completely or partly replaced by fatty acid e~ters andtor fatty alcohol ether3.
The ~illing material~ according to the invention may contain a~ further con~tituent3 any of the variou~
auxiliaries normally u~ed in preparation~ of the type in que~tion. For example, they may contain antioxi-dantq, dyes or even corro~ion inhibitors.
The filling materials according to t-he invention may be u~ed for protecting electrical component~ of :., :

290~83 various kind~, such a~, for example, oable3, plug~, ter-minal 3trip3, communicatlon~ cable~ or even light-wave conductors, again3t the penetration of contaminant~
and, in particular, moi~ture. The filling material~
are al30 quitable, particularly where they contain organic hollow bodie~, for protecting light-wave con-ductor3 of gla3~ against mechanical damage such as can occur during laying through bending and the effects of temperature. In addition, the filling material3 according to the invention may al~o be used aQ repair ~ealing compound~, for example, where electrical line3 or component~ have been deinsulated or damaged in the oour~e of laying work.
The filling material3 ~how many outstanding tech-nical propertie~. For example, their in3ulation reqistance i~ high, and their Qpecific volume re~i3tance factor i~ large~ In addition, by virtue of the hollow beads, their dielectric con3tant i3 low, ` i.e., value~ below 2.3 and in particular even below 2, may be adju~ted according to the quantity of hollow beads u~ed. The 3pecific gravity of the preferred filling oompounds is below about 1. They are com-j~ patible with the variou~ pla3tic~ u3ed in electrical components and cables. Thu3, the con~tituents of the filling compound3 do not penetrate into 3uch pla~tic~, nor do they affect the u~ual cable 3heath material3.
The filling compounds are completely stable at tem-peratures of up to 90C and do not beco~e thin-flowing;
even in the event of damage at those temperatures, no leaking occurs. In addition, the filling compound3 are flexible and remain flexible at temperatures down to -40C without any draQtic change in their flow proper-~`~ tie~ and without developing any cracks under ~tre3Q at low temperature3. In addition, the ~illing materials according to the invention are readily proce~ible, .

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~ L2~0~83 i.e., even at temperat~res below 70C, they may be introduced under moderate pres3ure into the cable ~heaths to be ~illed, reachLng even difficult places.
EXAMPLES
_ ~` The ~ollowing component~ ~ere used in the Examples:
A) a mineral oil liquid at room temperature having the following analytical data:
; 10 density at 15C according to ASTM D941: 0.886, viscosity at 20C in cSt according to ASTM D445: 242;
B) propylene-C~-butylene copolymer containing from 2 to 5~ ethylene units as additional comonomer to reduce crystallinity, characterized by Brookfield melt vi~cosity at 190C: 50,000 mPa.s, so~tening point (R+B) according to DIN 52011: 107-110C, density at 23C according to DIN 53 479: 0.87, break elongation according to DIN 53455, test bar 4: approximately 1250;
C) highly di~persed ~ilica particle size in microns: 0.007, powder density: approximately 40 g/l;
D) hollow microbeads o~ acrylonitrile-vinylidene :~ :
chloride copolymer particle size: 40-60 um, filled with isobutane - . , ttrade mark Expancel DE, a product of Kema Nobel Nord);
E) oligoamide prepared by condensation of dimer fatty acid with ethylene diamine; char~acteristics:
- amine number: 190-230, ~ ; ; Brookfield visco~ity: 35 poises at 75C.
;s;~ ~ In the following examples, all quantities are ~ ~ 35 expre~sed in part~ by weight.

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`~ ~lX908~3 Although not recited in the example~, the examples all contain up to 25~ by weight antioxidant~, i.e. mix-ture~ of Irganox(~) 1035, 1010j and 1024 and triphe-nylpho3phine. The quantities in parts by weight are baqed on 100 without taking the anti-oxidant con-sitituent~ into account.
The Pilling compounds may be prepared using any effective, but non-damaging mixing units ~hich provide for effective mixing even at low speeds, for example ` 10 turbulence mixers and khe like.
The introduction of the compound~ into a normal telephone cable wa~ evaluated using a conventional barrel meltlng unit. The compounds of Example~ 1 and 2 were transported at 60C. All other Examples illustrating the inventi~on could be tran~ported without difficulty at room temperature without any separation or air pocket~ being observed during tran~port. By contrast, the compoundq o~ the Comparison Exampleq ~eparated under the ~ame transport conditions.
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The products were tested for ~everal hours under a ~`~ nitrogen exces~ pres~ure of 12 bar. No destruction of thé materials occurred. The contraction in volume was le~s than 1~ for the compounds containing hollow microbeads.
; 25 15 parts~ of the o~-olefin copolymer (component B) were di~solved while 3tirring at 130C in 80 parts of mineral oil (component A). The mixture was cooled to 70C. 5 partq of the highly disperse silica (component C) were then added in small portions and incorporated by mixing in such a way that a homogeneouq mixture wa~
obtained. The mixture waq deaerated under a vacuum of 1.5 kPa.
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9()8~33 A mixture wa~ prepared as de~cribed in Example 1, except that 1.5 parts of the oligoamide (component E) were additionally introduced.

; A mixture of 85.8 part3 mineral oil (component A), 9.0 part~ OC -olefin copolymer (component B), and 5 part~ highly disper~ed ~ilica (component C) wa~ pre-pared a~ de~cribed in Example 1. 0.2 part hollow microbead~ (component D) were incorporated in thi~ mix-ture at a temperature o~ from 50C to 70C. After deaeration and cooling to room temperature, the material wa~ Ytored for 24 hours at room temperature before te~ting ~o that the hollow microbead~ could be completely "encap~ulated" in the silica network.

A mixture was prepared a3 de~cribed in Example 3, except that 1.5 part~ of the oligoamide (component E) were additionally introduced.

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A filling compound having the following com-position wa~ prepared a~ de cribed in Example 3 with 85 parts of component A, 10 parts of component B, 3 parts component C, and 2 parts of component D.
., A filling composition wa~ prepared a~ in Example 5, but also containing 0.5 part of component E.
All the filling compound~ according to the inven-tion satisfy the following requirement :
fla~h point in C according to DIN 51584: >200C, dielectric constant at 20C according to DIN
53483: <2.3, and volume resi~tivity at 100C in cm according to DIN 53482: ~101.

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~l29~)8~33 . , Individual dielectric con~tants:
EXAMPLE DC
~ 5 1 2.1 ; 2 2.3 3 1.9 4 2.0 1.7 6 1.7 The f~vorable ~low propertie~ of the compounds may be demon~trated by a flow curve and a visco~ity curve.
All the produots have a pronounced flow li~it at 800C
and are therefore stable under load.
Example 1 show~ rare ~flow behavior. L~ke the other Lxampleq, the compound ha~ structural visco~ity and is pla~tic, but 3how~ dilatance-like flow behavior, ` i.e.~ vi~cosity increases, albeit only ~lightly, with increasing shear load. Accordingly, the compound does `~ ~ not leak, even at relatively high temperatures and under the effect of force~.
,~ COMPARISON EXAMPLES
- -A filling compound wa~ prepared as de~cribed in ^~; Example 1 from 77 part~ atactic polypropylene, 20 part~
mineral oil tcomponent A) and 3 part3 highIy di~persed sil1ca (component C). The product had the following characteri~tics:
; density: 0.86 g/cm3-~; melt viscosity at 190C, rotational viscosimeter:
;r :~ ~ 6500 mPa ~.

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~.~29~ 3 A compound was prepared from 7 part~ hollow micro-beads (component D) and 94 parts mineral oil (component A). The compound thus prepared is extremely paqty.
In order to demonstrate the favorable properties, particularly in regard to low-temperature flexibility, stability under load, and stability on mixing, the com-pounds of Examples 1 to 6 according to the invention were compared with the comparison compounds of Examples 7 and 8.
The following test method~ were used:
Method I - Leakage te~t (accelerated dropping point determination) The sealing/filling compoundq are introduced into 8 mm diameter, 1 cm long glass tubes open at both ends.
The tubes are then placed on polyamide netting having a diameter of 0 2 mm and introduced into a precision-controlled heating cabinet. Beginning at +40C, the temperature is increased by 10C every two hourq. The temperature quoted i~ the temperature at which there is still no leakage of the compound (no dripping).
Method II - Drainage and leakage beha~ior (phase separation) of filling compounds on vertical glass surfaces A hemi~pherical, 2 ml large blob is applied to a 20 x 20 cm glas~ plate which has been cleaned with acetone. The glas~ plate i~ positioned vertically in a recirculating air cabinet in such a way that the com-` 30 poundq to be tested are situated at the upper end of the test plate. The drainage and leakage behavior i~
assessed after a residence time of 16 hours at 90C.
Leaka6e is understood to mean that, for example, thinly liquid constituent~ egress from the compounds and appear as a nose beneath the blob.

~, 908~33 Method III - Low-temperature behavior of sealing/
filling compound~
The compound to be te3ted i~ in~ected bubble-free by means of a syringe into a 4 mm diameter, 100 mm long ~ilicone ho~e. The ends are clo~ed by mean~ of ho~e clipq and the teQt specimens ~tored for 24 hours at -40C.
After ~torage, the test specimen i~ bent at an acute angle and ~traightened out again. The filling compound should neither break nor crack.
Method IV - Alternating temperature test The procedure is as described for method III. The silicone ho~e~ filled with the compound to be tested are alternately qtored for 16 hour~ at -40C, then bent and then ~traightened out again. They are then stored for 16 hours at room temperature, bent and then qtraightened out again, ~ollowed by ~torage at -40C, bending and straightening and so on for a total of 10 cycles. The compound i~ inspected for cracks; the number of cycles after which cracks appear is also determined.
The re~ults of these test~ on the Examples according to the in~ention are compared in Table 1 with the re~ults on the Comparison Examples.

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Claims (13)

1. A filling compound having plastic flow behavior for electrical components and light-wave conductors comprising: (a) from about 65 to about 90% by weight of a non-polar, water-immiscible hydrocarbon organic liquid having a pour point below 0°C and a kinematic viscosity of from about 2 to about 600 cSt measured at about 20°C; (b) from about 2 to about 25% by weight of an organic polymer selected from the group consisting of a copolymer of ethylene and propylene, a copolymer of ethylene and ? -butylene, a copolymer of propylene and ?-butylene, and a terpolymer of propylene, ?-butylene and ethylene, wherein said organic polymer is soluble in said hydrocarbon organic liquid and is a thickening agent therefor; and (c) from about 2 to about 10 by weight of pyrogenic silica; said filling compound having a dielectric constant at 20°C of less than about 2.0, a specific breakdown resistance of more than about 1010Ohm.cm, a specific gravity of less than about 1.0 g/cm3, a cable filling capacity at room temperature, is free from leakage at a temperature of up to about 90°C, and is free from cracks after 10 freeze-thaw cycles.

2. A filling compound in accordance with claim 1 wherein said pyrogenic silica is dispersed in said organic polymer.

3. A filling compound in accordance with claim 1 including (d) hollow micro-bodies.

4. A filling compound in accordance with claim 3 wherein said micro-bodies have a diameter of from about 5 to about 500 microns.

5. A filling compound in accordance with claim 3 wherein said micro-bodies are present in an amount of from about 0.2 to about 10 percent by weight, based on the weight of said filling compound.

6. A filling compound in accordance with claim 1 wherein said hydrocarbon organic liquid comprises mineral oil having a pour point below 0°C, a density of between about 0.8 and about 0.95 g/l, and a kinematic viscosity of from about 15 to about 300 cSt measured at about 20°C.

7. A filling compound in accordance with claim l wherein said organic polymer has a Brookfield melt viscosity of from about 30 to about 70 Pas at 190°C, a softening point of between about 90°C and about 160°C, and a density of from about 0.83 to about 0.9 g/cc.

8. A filling compound in accordance with claim 1 wherein said silica has a particle size of from about 0.007 to about 0.5 micron, and a powder density of from about 20 to about 120 g/l.

9. A filling compound in accordance with claim 3 wherein said hollow micro-bodies are selected from inorganic materials and organic materials.

10. A filling compound in accordance with claim 9 wherein said micro-bodies comprise glass beads.

11. A filling compound in accordance with claim 9 wherein said micro-bodies comprise gas-filled polymer beads.

12. A filling compound having plastic flow behavior for electrical components and light-wave conductors comprising: (a) from about 65 to about 95 percent by weight of a non-polar, water-immiscible hydrocarbon organic liquid having a pour point below 0°C and a kinematic viscosity of from about 2 to about 600 cSt measured at about 20°C; (b) from about 2 to about 25 percent by weight of an organic polymer selected from the group consisting of a copolymer of propylene and ?-butylene and a terpolymer of propylene, ?-butylene, and a terpolymer of propylene, ?-butylene and ethylene; (c) from about 2 to 10 percent by weight of pyrogenic silica, wherein said hydrocarbon organic liquid comprises mineral oil having a kinematic viscosity of from about 15 to about 300 cSt measured at about 20°C; and (d) from about 0.2 to about 10 percent by weight of hollow micro-bodies, all weights being based on the weight of said filling compound; said filling compound having a dielectric constant at 20°C of less than about 2.0, a specific breakdown resistance of more than about 1010Ohm.cm, a specific gravity of less than about 1.0 g/cm3, a cable filling capacity at room temperature, is free from leakage at a temperature of up to about 90°C, and is free from cracks after 10 freeze-thaw cycles.

13. A filling compound in aeeordanee with claim 12 wherein said organic polymer has a Brookfield melt viscosity of from about 30 to about 70 Pas at 190°C, a softening point of between about 90°C and about 160°C, and a density of from about 0.83 to about 0.9 g/cc.