GB1565835A - Creation of Inventions and Patents with Artificial Intelligence

GB1565835A – Retardation of flow of filler into cellular insulation
– Google Patents

GB1565835A – Retardation of flow of filler into cellular insulation
– Google Patents
Retardation of flow of filler into cellular insulation

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Publication number
GB1565835A

GB1565835A
GB4200976A
GB4200976A
GB1565835A
GB 1565835 A
GB1565835 A
GB 1565835A
GB 4200976 A
GB4200976 A
GB 4200976A
GB 4200976 A
GB4200976 A
GB 4200976A
GB 1565835 A
GB1565835 A
GB 1565835A
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GB
United Kingdom
Prior art keywords
petroleum jelly
cable
volume
cellular
insulation
Prior art date
1975-11-14
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)

Expired

Application number
GB4200976A
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Phillips Cables Ltd

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Phillips Cables Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
1975-11-14
Filing date
1976-10-08
Publication date
1980-04-23

1976-10-08
Application filed by Phillips Cables Ltd
filed
Critical
Phillips Cables Ltd

1980-04-23
Publication of GB1565835A
publication
Critical
patent/GB1565835A/en

Status
Expired
legal-status
Critical
Current

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Classifications

H—ELECTRICITY

H01—ELECTRIC ELEMENTS

H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES

H01B11/00—Communication cables or conductors

H—ELECTRICITY

H01—ELECTRIC ELEMENTS

H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES

H01B3/00—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties

H01B3/18—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances

H01B3/20—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances liquids, e.g. oils

H01B3/22—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances liquids, e.g. oils hydrocarbons

H—ELECTRICITY

H01—ELECTRIC ELEMENTS

H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES

H01B7/00—Insulated conductors or cables characterised by their form

H01B7/17—Protection against damage caused by external factors, e.g. sheaths or armouring

H01B7/28—Protection against damage caused by moisture, corrosion, chemical attack or weather

H01B7/282—Preventing penetration of fluid, e.g. water or humidity, into conductor or cable

H01B7/285—Preventing penetration of fluid, e.g. water or humidity, into conductor or cable by completely or partially filling interstices in the cable

Description

(54) RETARDATION OF FLOW OF FILLER INTO
CELLULAR INSULATION
(71) We, PHILLIPS CABLES LIMITED, a company organised and existing under the laws of Canada, of King Street West, Brockville, Province of Ontario, Canada, K6V 5WA, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:
This invention relates to communication cables.
Communication cables generally comprise a plurality of conductors which may or may not be individually or collectively insulated and which may or may not include a core, enclosed within a water-proof sheath; the interstices between the conductors and between the conductors and the sheath being filled from end to end of the cable length with a water-impervious medium. The water-impervious medium should not drain under the influence of gravity or such hydrostatic pressure as may arise in the event of damage to the cable or sheath, as this would leave an incompletely filled cable along which moisture might travel and the medium should further permit relative sliding movement of the conductors over one another during such bending of the cables as occurs during manufacture and installation of the cable.
In many such communication cables in use today the conductors are individually or collectively insulated with a cellular insulating material and it is with these cables that the present invention is concerned.
A preferred water-impervious medium for cable filling is petroleum jelly, however, petroleum jelly has a tendency to seep from the cable ends or from a flaw developed in the cable at elevated temperature to which the cable might be subjected.
It has now been found that the inclusion of a siliceous material in the petroleum jelly has the advantage, in the case where the electric conductors in the cable are individually or collectively insulated with a cellular insulating material of reducing migration of filler composition into the cells.
The cellular insulation conventionally used in such communication cables comprises a blown synthetic polymer, for example, polyolefins, particularly polyethylene and polypropylene. Flowable materials based on petroleum jelly with a conventional additive such as microcrystalline wax migrate into cellular insulating materials such as polyethylene to varying extents and the petroleum jelly itself may swell the carcass of the cell. In the case of cellular insulating materials, for example, cellular polyethylene, this migration may continue until the cells of the inslating material are filled. The filling of the cells affects the electrical properties of the cable particularly the capacitance.
It has now been found that the inclusion of small amounts of siliceous material in the petroleum jelly results in a filling composition in which migration of the petroleum jelly based filler composition into the cellular material is considerably reduced, particularly in comparison with the conventional petroleum jelly filler compositions containing microcrystalline waxes. The invention thus provides for the production of a communication cable having cellularly insulated conductors of stable electrical properties.
The present invention provides a communication cable comprising a sheath enclosing a plurality of electrical conductors electrically insulated with a cellular insulation comprising cells having a cell diameter of from 10 to 30 microns and a cell volume of 15% to 60% of the volume of the insulation, the interstices between the insulated conductors and between the insulated conductors and the sheath being filled with a composition comprising petroleum jelly having a siliceous material dispersed therein in an amount of 2% to 6% by volume of the petroleum jelly.It also provides a method of stablizing the physical and electrical properties of a communication cable comprising a plurality of conductors electrically insulated with a cellular insulating material and surrounded by a sheath, the cellular insulation having a cell diameter of from 10 to 30 microns and a cell volume of 15% to 60% of the volume of the insulation, the method comprising filling the interstices between the individual cellularly insulated conductors and between the cellularly insulated conductors and the sheath with a filling composition comprising petroleum jelly having a siliceous material dispersed therein in an amount of 2 to 6%, by volume, of the petroleum jelly, to provide a filled cable electrically insulated with a celllular insulating material.
In this specification, the term “petroleum jelly” includes synthetic petroleum jelly, and naturally-occurring petroleum jelly, and mixtures of the two.
Synthetic petroleum jelly is well known and is generally obtained by mixing various heavy petroleum lubricating oils with a low melting point paraffin wax.
Naturally-occurring petroleum jelly is well known and may be a purified mixture of semi-solid hydrocarbons obtained by the distillation of high boiling petroleum fractions and having a density in the range of about 0.81 to 0.88 at 60″C and a melting point of between 38 to 60″C or derived by fractional distillation of still residues from the steam distillation of paraffin wax petroleum, or from steam-reduced amber crude oils, the latter being oils from which the light fractions have been removed.
The term “siliceous material” in this specification includes diatomaceous earth, colloidal silica, pyrogenic silica, silica aerogel and similar silica containing siliceous materials having a relatively large surface area to mass ratio.
By way of example one suitable siliceous material is that sold under the trade mark
CAB-O-SIL by the Cabot Corporation. CAB-O-SIL is defined in Modern Plastics
Encyclopedia (1968) page 405, as consisting of particles averaging in diameter by grade from 70 to 140 Angstroms, sintered together in chain-like formations, the chains being branched and having surface areas of 200m2/g to 400m2/g.
The amount of siliceous material added to the petroleum jelly is an amount which is effective to reduce the mobility of the petroleum jelly at temperatures up to about 70″C and to avoid the problem of migration of the filler composition into the cellular insulation at temperatures to which the cable might be subjected during use, as compared with more conventional fillers based on petroleum jelly containing micro-crystalline waxes as the additive.
It is found that mobility of the petroleum jelly is appropriately reduced and the problem of migration experienced with the more conventional filling compositions is largely overcome even at temperatures as high as 70″C which would be a severe temperature for cable use and which probably represents an upper limit of temperatures to which the cable might be subjected. Of course, in many environments, temperatures as high as 70″C would never be encountered. However, there are hot countries in the world where cables might be subjected to such high temperatures. particularly if left in storage for prolonged periods under a hot sun.
In practice amounts of siliceous material of 2% by volume to 6% by volume and preferably 2% to 4% by volume of the petroleum jelly have proved satisfactory with cellular insulation even at temperatures as high as 70″C. A particularly preferred content of siliceous material is about 3% by volume of the petroleum jelly.
It is found to be convenient to measure the quantities by volume rather than by weight, but, on a weight basis 2 to 4 vol. % of siliceous material is 1 to 6% by weight of the petroleum jelly.
The cellular insulation may be any of those cellular insulations conventionally used in communication cables and which permit the migration of conventional petroleum jelly filler composition thereinto. Preferred cellular insulations are poly-olefins, for example, polyethylene and polypropylene with polyethylene being a preferred insulator.
Such cellular insulations used according to the invention have a cell diameter of from 10 to 30 microns (a typical cell diameter being 20 microns), and the volume of the cellular insulation which is composed of the cells is in the range from 15% to 60%; suitably about 25% by volume of the cellular insulation will be constituted by cells,
In the case where the conductors of the cable are individually insulated with cellular insulation the thickness of the insulation will generally be in the range of 0.07 to 0.4 mm and preferably from 0.11 to 0.33 mm. In such an insulation the cells will be in the interior of the insulation, the cellular insulation having an outer solid skin in contact with the petroleum jelly filling composition which may be from 1 to 3 mil thick.
Initially migration of the petroleum jelly filler composition into a cellular insulating material proceeds at the same rate as into a non-cellular, solid form of the same insulating.
material. This is presumably due to the fact that initially the filling composition has to migrate through a skin of the solid insulating material before reaching the outer cells.
In making a cable according to the teachings of the invention the sheath is suitably an aluminium tape which is preferably applied longitudinally or helically about the plurality of cellular insulated conductors such that contiguous margins overlap and can be bonded together.
The interstices between the individual conductors and between the conductors and the sheath are suitably filled with the composition before the edges of the sheath are bonded together.
The aluminium sheath provides an electrical shield for the conductors and is impervious to the petroleum jelly. A jacket of polyethylene or polypropylene may be extruded around the aluminium sheath in a conventional manner as desired.
The sheath could also comprise other material for example polyethylene tape, however, this has the disadvantage of being pervious to the petroleum jelly and the possibility exists of the composition migrating in certain conditions into and under the polyethylene sheath, thus creating an incompletely filled cable along which moisture may travel.
The petroleum jelly filling composition may optionally include additives conventionally used in cable filling compositions for example, oxidation inhibitors, e.g. phenyl–naphthyl- amine and metal deactivators, e.g. NN’disalicylidene ethylene diamine. Suitable amounts of such compounds are up to 0.2% by weight of the composition of the oxidation inhibitor and up to 0.02% by weight of the composition of the metal deactivator.
In one method for preparing the filling composition, the well known masterbatch technique is found to be suitable. In this technique the siliceous material is subjected to an intensive mixing, preferably in an Ink Mill or Ball Mill, with a liquid vehicle having high surfactant or wetting properties and which is compatible with the petroleum jelly.
The intensive mixing produces a concentrate which is then mixed into the petroleum jelly to produce a composition in which the siliceous material is uniformly distributed throughout the composition.
A suitable liquid vehicle is polybutene, however, other liquid vehicles having the requisite wetting and compatability properties can also be used. Suitably the siliceous material is added to polybutene in an amount of about 30 parts by weight siliceous material to 70 parts by weight polybutene.
The filling composition can also be prepared by adding the siliceous material directly to the petroleum jelly without the aid of the liquid vehicle or the petroleum jelly itself could be used as the liquid vehicle.
In the manufacture of the communication cable the filling composition may be inroduced into the cable by a vacuum impregnation process as a final step in the manufacture of the cable. Generally, however, it is preferred to introduce the composition as the cable is being manufactured, for example, as a step preceding or immediately following the application of each layer of cellularly insulated conductors or pairs or quads to the underlying assembly of cellularly insulated conductors, pairs or quads. In the latter case, the filling composition may be introduced into the cable at a die, which is modified to provide an annular space allowing the filling composition to flow completely around each layer of cellularly insulated conductors.Excess filling composition may be removed by a snuggering die and an insulating tape, for example, of paper, may be wound around the outer layer of cellularly insulated conductors.
In another embodiment pairs of cellularly insulated conductors may be passed into a tank into which the filling composition is pumped; the filling compositon is thus coated onto to the cellularly insulated conductors as they twist about each other more closely. The cellularly insulated conductors then pass into a wiping die that compresses together the coated but slightly separated conductors and removes excess filling composition from the insulated conductors. A sheath may then be wrapped about the insulated conductors.
The invention is further illustrated by reference to the accompanying drawings in which:
Figure 1 schematically represents a communication cable part cut away;
Figure 2 is an exploded cross-section, part cut away, on line 2-2 of Figure 1;
Figure 3 illustrates graphically the weight take-up by cellular insulation of three cable filling compositions at 700C; Figure 4 illustrates graphically the increase in density of cellular insulation treated with three cable filling compositions after aging at 70″C; and
Figure 5 illustrates graphically the variation in capacitance with time of cellular insulation treated with three cable filling compositions at 70″C.
With reference to Figures 1 and 2, a communication cable 1 comprises a plurality of copper or aluminium conductors 2 each having an insulating coating 3 of cellular polyethylene. A sheath 4 of aluminium tape is wrapped longitudinally about the conductors 2 to form a complete envelope; and an extruded jacket of polyethylene surrounds the sheath 4.
The interstices between the individual cellularly insulated conductors 2 and between the conductors 2 and the sheath 4 are filled throughout the length of the cable 1 with a water impermeable medium comprising petroleum jelly containing 3%, by volume of the petroleum jelly, of CAB-O-SIL (trade mark) thoroughly dispersed therein.
Various tests were carried out on cellularly insulated conductors treated with different cable filling compositions including the one employed in the present invention. The results of the tests demonstrate the advantages obtained by the invention.
In the tests described below cellularly insulated conductor wires were employed in which the cellular insulation was a medium density polyethylene in which the cells comprised 25% by volume; the outer diameter of the insulated conductor wires was 45.5 mils and the wall thickness of the cellular insulation was 10.1 mil.
The polyethylene employed in the manufacture of the insulated wires is available from Union Carbide under the manufacturer’s designation U.C. 8890; this product includes a blowing agent which on heating decomposes to produce gas bubbles which form the cells.
The cellular insulation can also be produced by the method described in U.K. Patent specification No. 1,428,891.
Three cable filling compositions were employed identified by the trade marks Dusseks 3215, Dusseks 2852 and Imperial QS-3091E, hereinafter termed Imperial E. Dusseks 3215 is a formulation employed in accordance with the present invention and comprises 4% by volume of CAB-O-SIL (trade mark) in petroleum jelly. Dusseks 2852 comprises a base petroleum jelly with a relatively large content of microcrystalline wax which conveniently is in the range of 15% to 35% by weight. Imperial E. comprises a petroleum jelly base with amorphous polypropylene as the additive.
In the following tests the test specimens (cellularly insulated conductors, as described above) were placed in pans and a large quantity of the filling composition was poured over them. After a predetermined immersion time the test specimen is removed from the pan and composition adhering to the surface of the specimen is removed by passing the specimen through a specially tooled die and the appropriate test carried out.
Test I
Weight-uptake
The filling compositions migrate into the cellular insulation by differing amounts depending on the temperature, the immersion time and the nature of the filling composition. The type of polymer is also significant but in the present test this was not varied, being polyethylene in each case.
In order to determine the weight take-up, six foot lengths of specimen wound into loose coils were employed. Each specimen was weighed before and after immersion and ten such results averaged to obtain a figure. The weighings were carried out after different periods of immersion at a temperature of 70″C.
The reuslts for the three filling compositions are shown graphically in Figure 3, in which the immersion period is plotted against the average weight take-up expressed in mg/6 ft.
length (left hand ordinate) and as a wt. 5 > o of the polyethylene (right hand ordinate).
In the case of Dussek 2852 it would appear that maximum take-up (cell filling) is reached in about 150 days. It is also clear that while the other two fillings have penetrated the cellular insulations to a certain extent, the degree of weight up-take has levelled off at a fraction of that with Dussek 2852.
It is apparent that a significant decrease in migration was obtained using Dussek 3215 according to the invention particularly when compared with Dussek 2852 which is widely used as a filling for communication cables.
Since 70″C is a fairly severe temperature the tests were repeated at 60″C; the weight up-take in milligrams per 6 ft. with time is tabulated in Table I below, from which it will be seen that the use of Dussek 3215 according to the present invention still shows a marked improvement.
TABLE I
Weight up-take (mg) at 600C
Time Filling Composition
Days 2852 Imperial E 3215 94 190 150 130 150 250 190 170 225 270 185 155 300 280 155 140
At 60″C the up-take levels off at about 150 mg in the embodiment according to the present invention, although for Dussek 2852 weight up-take is continuing even after 300 days.
In this test the weighing was carried out using a Mettler H-8 (trademark) balance accurate to + 0.5 mg.
Test 2
Swelling of Insulation
The swelling caused by exposure to the filling composition increased rapidly in the first few days and reached a constant state. Table II below summarizes the result
TABLE II
Swelling (mils) – Increase in diameter
Temperature Filling Composition
2852 Imperial E 3215 60″C 2.1 1.9 1.6 70″C 2.3 1.8 1.9
Swelling of the insulation is significant since it affects the capacitance increase of the cable due to cell filling.
Test 3
Density In crease
Density increase is significant since it is an indicator of the degree of cell filling.
The initial and final densities were determined by an established method involving weighing the sample in air and then in water. The results were cross-checked by a different procedure by determining the ratio of weight to volume as calculated from the weight up-take and swelling data; the results of both methods were found to be in close agreement.
The results on the test specimens at 700C are shown in Figure 4. In the case of Dussek 2852 insulation density had increased by 40% after 250 days exposure at which point measurements were discontinued since complete cell filling had occurred. Density increase is significantly less in the embodiment according to this invention.
The test was repeated at 60″C, at which temperature Dussek 2852 gave a density increase of 16% after 300 days whereas Dussek 3215, used according to the invention gave an increase of only 3.5%.
Test 4
Trough Capacitance Change
The procedure for this test is similar to that for weight up-take. A specimen is pulled through a filling composition and a selected die and the coaxial or trough capacitance is measured. The specimen is then re-exposed to filling composition and the measurement repeated after prolonged periods of exposure.
The results at 70″C for the three filling compositions are shown in Figure 5. A comparison with the figures obtained at 60″C is tabulated in Table III below.
TABLE III
Temperature Filling Composition
Initial CapacitancelFinal Capacitance in pF/foot
2852 Imperial E 3215 70″C 52.0/62.7 52.8/56.3 53.1/54.7 60″C 52.0/55.7 52.6/53.8 53.0/53.7
The results demonstrate a smaller change in coaxial or trough capacitance and hence an increase in electrical stability in the embodiment according to the invention,
Test 5
Tensile strength (T) and elongation at break (E)
The tensile strength and elongation at break of specimens were measured according to
ASTM procedures after being exposed to the filling compositions for varying time periods.
The exposed insulation was removed from the conductor by stretching the conductor and then stripping the insulation. The insulation was tested at 20 ins/min. and a percent retention of elongation at break based on that of the unexposed specimen, was determined.
The results are tabulated in Table IV below.
TABLE IV
% Retention after long exposure period
Temperature Filling Composition
2852 Imperial E 3215
T E T E T E 70″C 90 58 93 72 97 73 60″C 95 75 98 82 100 82
The results demonstrate that tensile strength is retained with all filling compositions although Dussek 3215 shows the best results. On the other hand, the drop in elongation is more significant with Dussek 2852 which results in a drop to 58% of the initial value at 70″C compared with 73% in the case of Dussek 3215.
A similar test was carried out using similar specimens in which the outer diameter was 45 mil and the wall thickness was 9.85 mil and wherein the cells of the insulations comprised 30% by volume.
Table V below shows the values for the tensile strength and elongation of the specimens at different time intervals after exposure to the filling composition at 70″C.
TABLE V
Ultimate Tensile Strength and Elongation
at 700C (Tensile/Elongation)
Time Filling Composition (Days) 2852 Imperial E 3215 0 3452/457 3452/457 3452/457 1 3083/430 2967/430 3092/440 13 2881/374 2825/380 3016/387 60 2398/340 2688/390 2756/390 90 2600/300 2700/370 2850/370 120 2672/290 2963/360 2920/350 153 2588/270 2811/360 2704/330 208 2540/290 2760/370 2870/370
Like the results tabulated in Table IV, these results demonstrate the superior nature of cables made according to this invention particularly in comparison with cables employing micro-crystalline wax (Dussek 2852) as additive.
The results of the tests described above demonstrate that by employing a filling composition according to the method of the present invention in a communication cable having cellular insulation of the conductors, improved stability is obtained; and this improves control of the manufacture of a communication cable having predetermined physical and electrical properties. It will be understood that communication cables are manufactured for long life, usually about 30 to 35 years, and it is thus important that the properties remain substantially uniform.
Example I
A siliceous material available under the trade mark CAB-O-SIL was intensively mixed with polybutene (M.W. 400 to 1000 on the MECROLAB SCALE) in an amount of 30 parts by weight of CAB-O-SIL to 70 parts by weight of the polybutene in an Ink Mill to produce a concentrate. The resulting concentrate was added to petroleum jelly in an amount to provide a 2% volume of CAB-O-SIL in the petroleum jelly based on the volume of petroleum jelly and was intensively mixed therein to uniformly distribute the CAB-O-SIL throughout the petroleum jelly.
The resulting composition was used as a filling composition for a communication cable in which the copper conductors were insulated with cellular polyethylene having a cell volume of 25% and reel diameter of 20 microns and sheathed with a longitudinally applied aluminium tape. No seepage occurred when the cable was subjected to elevated temperatures of the order of 70″C and the resulting cable was found to be of good stability over prolonged periods.
Example 2
CAB-O-SIL siliceous material was introduced directly to petroleum jelly in an amount of 3% by volume of the petroleum jelly. The petroleum jelly with the CAB-O-SIL was subjected to an intensive mixing to distribute the CAB-O-SIL uniformly throughout the petroleum jelly.
The resulting composition was used as a filling composition for a communication cable of the kind described in Example 1; a cable of improved electrical and physical properties was thus obtained.
In pursuance of the provisions of Section 9 of the Patents Act 1949 reference is directed to U.K. Patents Nos. 1 419 860 and 1 448 617.
WHAT WE CLAIM IS:
1. A communication cable comprising a sheath enclosing a plurality of electrical conductors electrically insulated with a cellular insulation comprising cells having a cell diameter of from 10 to 30 microns and a cell volume of 15% to 60% of the volume of the insulation, the interstices between the insulated conductors and between the insulated conductors and the sheath being filled with a composition comprising petroleum jelly having a siliceous material dispersed therein in an amount of 2% to 6% by volume of the petroleum jelly.
2. A communication cable according to claim 1 wherein the cellular insulation is from 0.07 to 0.4 mm thick and has an outer solid skin 1 to 3 mil. thick.
3. A cable according to claim 1 or 2 wherein the cellular insulation comprises polyethylene or polypropylene.
4. A cable according to any of claims 1 to 3 wherein the siliceous material has surface area of about 200 m2/g to about 400 m2/g.
5. A cable according to any preceding claim wherein the siliceous material is present in an amount of 2% to 4% by volume of the petroleum jelly.
6. A method of stabilizing the physical and electrical properties of a communication cable comprising a plurality of conductors electrically insulated with a cellular insulating material and surrounded by a sheath, the cellular insulation having a cell diameter of from 10 to 30 microns and a cell volume of 15% to 60% of the volume of the insulation, the method comprising filling the interstices between the individual cellularly insulated conductors and between the cellularly insulated conductors and the sheath with a filling composition comprising petroleum jelly having a siliceous material dispersed therein in an amount of 2 to 6%, by volume, of the petroleum jelly, to provide a filled cable.
7. A method according to claim 6 wherein the cellular insulation is a polyolefin.
8. A method according to claim 7 wherein the cellular insulation is selected from polyethylene and polypropylene.
9. A method according to claim 6, 7 or 8 wherein the siliceous material has a surface area in the range of about 200 m2/g to about 400 m2/g.
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (13)

**WARNING** start of CLMS field may overlap end of DESC **. Like the results tabulated in Table IV, these results demonstrate the superior nature of cables made according to this invention particularly in comparison with cables employing micro-crystalline wax (Dussek 2852) as additive. The results of the tests described above demonstrate that by employing a filling composition according to the method of the present invention in a communication cable having cellular insulation of the conductors, improved stability is obtained; and this improves control of the manufacture of a communication cable having predetermined physical and electrical properties. It will be understood that communication cables are manufactured for long life, usually about 30 to 35 years, and it is thus important that the properties remain substantially uniform. Example I A siliceous material available under the trade mark CAB-O-SIL was intensively mixed with polybutene (M.W. 400 to 1000 on the MECROLAB SCALE) in an amount of 30 parts by weight of CAB-O-SIL to 70 parts by weight of the polybutene in an Ink Mill to produce a concentrate. The resulting concentrate was added to petroleum jelly in an amount to provide a 2% volume of CAB-O-SIL in the petroleum jelly based on the volume of petroleum jelly and was intensively mixed therein to uniformly distribute the CAB-O-SIL throughout the petroleum jelly. The resulting composition was used as a filling composition for a communication cable in which the copper conductors were insulated with cellular polyethylene having a cell volume of 25% and reel diameter of 20 microns and sheathed with a longitudinally applied aluminium tape. No seepage occurred when the cable was subjected to elevated temperatures of the order of 70″C and the resulting cable was found to be of good stability over prolonged periods. Example 2 CAB-O-SIL siliceous material was introduced directly to petroleum jelly in an amount of 3% by volume of the petroleum jelly. The petroleum jelly with the CAB-O-SIL was subjected to an intensive mixing to distribute the CAB-O-SIL uniformly throughout the petroleum jelly. The resulting composition was used as a filling composition for a communication cable of the kind described in Example 1; a cable of improved electrical and physical properties was thus obtained. In pursuance of the provisions of Section 9 of the Patents Act 1949 reference is directed to U.K. Patents Nos. 1 419 860 and 1 448 617. WHAT WE CLAIM IS:

1. A communication cable comprising a sheath enclosing a plurality of electrical conductors electrically insulated with a cellular insulation comprising cells having a cell diameter of from 10 to 30 microns and a cell volume of 15% to 60% of the volume of the insulation, the interstices between the insulated conductors and between the insulated conductors and the sheath being filled with a composition comprising petroleum jelly having a siliceous material dispersed therein in an amount of 2% to 6% by volume of the petroleum jelly.

2. A communication cable according to claim 1 wherein the cellular insulation is from 0.07 to 0.4 mm thick and has an outer solid skin 1 to 3 mil. thick.

3. A cable according to claim 1 or 2 wherein the cellular insulation comprises polyethylene or polypropylene.

4. A cable according to any of claims 1 to 3 wherein the siliceous material has surface area of about 200 m2/g to about 400 m2/g.

5. A cable according to any preceding claim wherein the siliceous material is present in an amount of 2% to 4% by volume of the petroleum jelly.

6. A method of stabilizing the physical and electrical properties of a communication cable comprising a plurality of conductors electrically insulated with a cellular insulating material and surrounded by a sheath, the cellular insulation having a cell diameter of from 10 to 30 microns and a cell volume of 15% to 60% of the volume of the insulation, the method comprising filling the interstices between the individual cellularly insulated conductors and between the cellularly insulated conductors and the sheath with a filling composition comprising petroleum jelly having a siliceous material dispersed therein in an amount of 2 to 6%, by volume, of the petroleum jelly, to provide a filled cable.

7. A method according to claim 6 wherein the cellular insulation is a polyolefin.

8. A method according to claim 7 wherein the cellular insulation is selected from polyethylene and polypropylene.

9. A method according to claim 6, 7 or 8 wherein the siliceous material has a surface area in the range of about 200 m2/g to about 400 m2/g.

10. A method according to any of claims 6 to 9 wherein the amount of siliceous material
is 2% to 4% by volume of the petroleum jelly.

11. A method according to any of claims 6 to 10 wherein the cellular insulation is from 0.07 to 0.4 mm thick and has an outer solid skin 1 to 3 mil. thick

12. A communication cable incorporating a filling composition, the filled cable being subsutially as hereinbefore described in Example 1 or 2.

13. A method according to claim 6 and substantially as hereinbefore described in Example 1 or 2 or with reference to the accompanying drawings.

GB4200976A
1975-11-14
1976-10-08
Retardation of flow of filler into cellular insulation

Expired

GB1565835A
(en)

Applications Claiming Priority (1)

Application Number
Priority Date
Filing Date
Title

CA239,681A

CA1030624A
(en)

1975-11-14
1975-11-14
Improvement in cellularly insulated communication cables

Publications (1)

Publication Number
Publication Date

GB1565835A
true

GB1565835A
(en)

1980-04-23

Family
ID=4104523
Family Applications (1)

Application Number
Title
Priority Date
Filing Date

GB4200976A
Expired

GB1565835A
(en)

1975-11-14
1976-10-08
Retardation of flow of filler into cellular insulation

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Country
Link

CA
(1)

CA1030624A
(en)

GB
(1)

GB1565835A
(en)

1975

1975-11-14
CA
CA239,681A
patent/CA1030624A/en
not_active
Expired

1976

1976-10-08
GB
GB4200976A
patent/GB1565835A/en
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Expired

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Publication date

CA1030624A
(en)

1978-05-02

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