US2956036A

US2956036A - Certificate of correction

Info

Publication number: US2956036A
Authority: US
Publication date: 1960-10-11
Anticipated expiration: 1977-10-11

Description

2,956,036 COMPOSITION A. KING MICROCRYSTALLINE PETROLEUM WAX IMPREGNATING FOR INSULATED ELECTRIC CABLES Filed April 13, 1954 SVEHUNI United States Patentv lVIICROCRYSTALLINE PETROLEUM WAX IM- 'PREGNATING COMPOSITION FOR INSU- LATED ELECTRIC 'CABLES Albert King, 'Bexley Heath, Kent, England, assignor t0 British Insulated Callenders 'Cables Limited, London, England, a British company l Filed Apr. 13, 1954, Ser. No. 422,923 Claims priority, application Great Britain Apr. 30, 1953 25 Claims.` (Cl. 26028.5)

This invention relates to insulated electric cables having a dielectric of impregnated fibrous insulating material, generally paper, and in particular to fully impregnated non-draining cables of this kind and to impregnating compositions therefor which comprise micro-crystalline petroleum wax as the major ingredient or one of the major ingredients of the composition and which are hereinafter referred to as micro-crystalline'petroleum Wax impregnating compositions.

By stating that the cable is fully impregnated it is intended to imply that the cable is as full of impregnant as is possible, the paper or other fibrous material being impregnated and the spaces between the turns and layers thereof being filled with composition, the object being to ensure that the possibility of the existence of voids within the sheath which surrounds the dielectric is reduced to a minimum, and by a non-draining cable is meant a cable such that whena vertical length of 30 feet or more of the cable,V with open ends, is heated to its maximum rated conductor working temperature for 7 days or more the amount of impregnating composition drained from the cable does not exceed 0.1% by volume of the cubical capacity of the cable sheath.

In the specification of our prior Patent No. 2,586,345 i there is' described and claimed a fully impregnated nondraining cable in which the cable impregnant is a normally plastic solid composition consisting of micro-crystalline petroleum wax having a melting point of not less than 80 C. and of cable impregnating mineral oil or one of a group of plasticisers consisting of polyisobutene (polyisobutylene) having an average molecular weight of 20,000 to 100,000 and rosin or a mixture of such oil with one or both of such plasticizers, the proportion of micro-crystalline Wax in the composition being not less than 55% by weight. An improved form of such cable is described and claimed in our U.S. Patent No. 2,914,429 in which instead of the microcrystalline petroleum wax composition of the grade described in the specification of Patent No. 2,586,345 there is used micro-crystalline petroleum Wax having a melting point of about 88 C. and needle penetration values of about at 25 C. and about 35 at 70 C. or a blend of such wax with micro-crystalline petroleum waxes having higher penetration values' at high temperatures, having a melting point of 85-90 C. and needle penetration values varying from about 5 and 6 at 25 C. to between 35 and 50 at 70 C., the proportion of micro-crystalline wax in the composition being not less than about 48% by weight when wax having a needle penetration value of 35 at 70 C. is used and not less than about 50% by weight when the specified blend of wax is used.

` By the term micro-crystalline petroleum wax is meant wax of the petrolatum group of petroleum waxes, that is to. s'ay, petrolatum wax, and/or wax of the petroleum ceresin group of petroleum waxes (as defined and classified in the Journal of the Institute of Petroleum, vol. 29,

No. 240, 1943, pp. 361-3), which waxes have a relatively Small. crystal size compared with that of waxes of the ICC paraffin wax group. Such wax is currently known as micro-crystalline wax or amorphous wax and has a setting point generally not less" than 71 C. The needle penetration values referred to above and those referred hereinafter are needle penetration values as determined in accordance with method I.P.-49/46 of the Institute of Petroleum.

The cable impregnating mineral oils referred to in the aforesaid patent specifications and hereinafter are those which, at the date of the aforesaid Patent No. 2,586,345, were generally known amongst cable makers to be suitable for the impregnation of paper insulated electric cables. They are discussed, for instnace, in the symposium of papers on insulating oils in the Journal of the Institution of Electrical Engineers, part Il, pages 3-64, vol. 90, 1943. They vary in viscosity from oils having a viscosity of about 11,000 centistokes or higher at 0 C. to the then so-called hollow core cable oil having a viscosity of about 140 centistokes at 0 C.

We have now discovered that improved micro-crystal line petroleum wax impregnating compositions for nondraining cables can be obtained by the inclusion of a low dielectric loss synthetic hydrocarbon wax having a melting point within the range C. to 120 C., as a partial replacement of the micro-crystalline petroleum wax. By a low dielectric loss wax we mean a wax of which the power factor is not greater than 0.005 at C. when measured at 50 cycles per second and at a stres's of 8 kv./cm.

A preferred example of such a synthetic wax is that sold under the trade name of Super Hard Wax No. 105. This wax has a melting point of 108 C.-110 C. and is a product of the Fischer-Tropsch process. It has an average molecular weight of about 600. A second example of Isuch a synthetic wax is the wax sold under the trade name Alcowax. This is a polyethylene wax having a molecular weight of between 2,000 and 6,000 with a melting point of about 110 C.

The inclusion of such synthetic wax yields a composition which has a melting point higher to an unexpected degree than that of a composition having the same ingredients save that all the wax is micro-crystalline petroleum wax of the same grade. Consequently by the inclusion of the `synthetic wax we may obtain micro-crystalline petroleum wax compositions suitable for use in the manufacture of cables capable of operating at higher temperatures, using, if desired, micro-crystalline wax which, or a proportion of which, has a melting point of less than 80C. Alternatively, the synthetic wax may be used to obtain micro-crystalline wax impregnating compositions made from low melting point micro-crystalline waxes, having approximately the same melting points as those in which the wax content consists entirely of micro-crystalline wax having a melting point of 80 C. or higher.

The amount of low loss synthetic hydrocarbon wax lthat may in accordance with our invention be present in the improved micro-crystalline petroleum wax composition is from about 1% to about 40% by weight of the whole composition, the proportion depending upon the proportion and melting point of micro-crystalline petroleum wax, the nature of the cable impregnating mineral oil (if` any) and of course the form and operating conditions of the cable in which it is to be used. Generally the proportion of the synthetic wax will be greater the lower the melting point of the micro-crystalline wax. As previously mentioned t-he preferred synthetic wax is that sold under the trade name Super Hard Wax No. 105. We prefer to use Alcowax only in conjunction with a larger proportion of the aforesaid preferred synthetic wax, the quantity of Alcowax present preferably not exceeding 15% by weight of the composition.

Depending upon the nature, -in particular on the viscosity/temperature characteristics, of the oil and other ingredients (if any) used in the composition, the total wax content may vary from to 100% by weight of the whole composition, providing that where the total wax content lies at the lower end of the specied range, i.e. lies between 20% and 25%, the oil used has a viscosity of less than 600 Redwood seconds at 60 C. Preferably however the total wax content lies between and 60%, the viscosity/temperature characteristics of the oil used being such that the composition has a sufficiently low shear strength to permit of a cable impregnated with it to be laid at low ambient temperatures without risk of rupture of the fibrous dielectric.

We have found that the increase in melting points of micro-crystalline petroleum wax impregnating compositions obtained by the inclusion of a low dielectric loss synthetic hydrocarbon wax having a melting point within the range of 85 C. to 120 C. as a partial replacement of the micro-crystalline wax is greater than would be anticipated having regard to the extent of the replacement and to the higher melting point of the replacement material. The increase per unit replacement is most pronounced at the lower end of the range and falls as the proportion of synthetic wax increases. This will be apparent from the graphs shown in the accompanying drawing. Curve A of these graphs shows how the melting point of a micro-crystalline petroleum wax composition consisting of micro-crystalline petroleum wax having a melting point of 80 C. and a low loss synthetic hydrocarbon wax of melting point 108 C. (Super Hard Wax No. 105) varies with the proportion of such synthetic wax. For purposes of comparison, curve B shows how the melting point of micro-crystalline petroleum wax composition consisting of micro-crystalline petroleum wax of melting point 80 C. and microcrystalline petroleum wax of melting point 90.5 C. varies with the proportion of the latter. From curve B it will be seen that a composition containing equal proportions of micro-crystalline petroleum wax of M.P. 80 C. and micro-crystalline petroleum wax of M.P. 90.5 C., has an MP. of 86.7 C. which compares with the average MP. of the components of 85 C. -From curve A it will be seen that a composition containing equal proportions of micro-crystalline petroleum wax of M.P. 80 C. and low loss synthetic hydrocarbon wax of M.P. 108 C., has an MP. of 106 C. which'compares with the average MP. of the components of 94 C.-a difference of 12 C. It will be noted that when the proportion of synthetic wax reaches about 20% that curves A and B run parallel to one another. It will also be noted that after the mixture is about 70% synthetic wax the melting point is the same as for the synthetic wax alone. Thus the maximum or" synthetic wax to be added is 70% or, stated diifere-ntly, the mixture will have a minimum of of microcrystalline wax. From curve C obtained by plotting the ratio between the increase in melting points on curves A and B against the percentage of synthetic wax or high melting point micro-crystalline petroleum wax, it will be seen that the unexpected effectiveness of the synthetic wax as a melting point raiser of micro-crystalline wax compositions is most marked when the proportion is a few per cent and that the effect per unit proportion of synthetic wax added rapidly falls until th eproportion of synthetic waxe reaches about 20% by Weight at which point the curve ilattens out. On this account, where the securing of an increase in melting point temperature at a low cost is a primary consideration the amount of low loss synthetic hydrocarbon wax present preferably does not exceed 20% by weight of the impregnating composition.

In addition to its essential components, micro-crystalline petroleum wax and the aforesaid synthetic wax, and to cable impregnating mineral oil, our improved impregnating composition may include a minor proportion of one or more plasticisers such as, for example, polyisobutylene, rosin, polyethylene, and butyl rubber. The lamount of plasticiser that may be used will depend upon the required characteristic of the impregnating composition and the particular plasticiser or plasticisers used and will be determined experimentally as required. By way of example it is mentioned that we have found that we may use up to about 1% by weight, on the weight of the composition of polyisobutylene of molecular weight about 80,000 to increase the liquid phase viscosity of the composition but we may use up to 5% by Weight of polyethylene of molecular weight about 3,000 or up to 5% by weight of butyl rubber. Where rosin is the plasticiser we may use up to 30% by weight on the weight of the composition. Where two (or more) such plasticisers are used together the amount used of one will depend upon the amount used of the other, for instance if instead of using 5% of polyethylene of molecular weight 3,000, one uses 4%, one might use 1% of polyethylene (M.W. 3,000) instead of the 5% one might use if no other plasticiser were present.

Small proportions, namely from 0.01 to 1.0% of other ingredients such as anti-oxidants and metal sequestrators (de-activators) may be added if required. An example of the former is phenyl -naphthylamine which may be incorporated in proportions up to 0.2% by weight of the composition and au example of the latter is NN' disalicylidene ethylene diamine which may be incorporated in proportions up to 0.02% by weight of the composition.

The improved compositions may be made by simply heating together the required quantities of the microcrystalline petroleum wax and the low loss synthetic hydro--carbon wax and where, as will generally be the case, the composition is to include it, cable impregnating mineral oil, to a temperature of from 120 to 130 C. for about two to four hours with agitation. Mixing may be carried out in an inert atmosphere e.g. in an atmosphere of nitrogen `but this is not essential as the ingredients are resistant to oxidation. Polyethylene and/or rosin may be added without diiiiculty when required but when it is desired to add polyisobutylene of high molecular weight and/or butyl rubber they should be added as in the form of a master batch of either or both in micro-crystalline petroleum wax or other suitable wax. Micro-crystalline wax incorporating polyisobutylene is sold under the trade name Mycroply 30.

The following are examples of our improved microcrystalline petroleum wax impregnating compositions suitable for use in the manufacture of non-draining impregnated paper insulated cable.

Example 1 Parts by weight Micro-crystalline petroleum wax (M.P. C. and needle penetration values of 17 at 25 C. and greater than 200 at 60 C.) 99 Super Hard Wax No. 1

Example 2 Parts by weight Micro-crystalline petroleum wax (M.P. 88 C. and needle penetration values of 5 at 25 C. and 35 at 70 C.) 45 Super Hard Wax No. 105 5 Oil-lled cable oil (viscosity centistokes at 0 C.

and 7.3 centistokes at 60 C.) 50

This composition has a melting point of 89 C. and is suitable for cables operating at conductor temperatures o f up to about 75 C. Here the increase in melting pointA obtained by replacing a part of the micro-crystalline petroleum wax by. the synthetic wax to the extent indicated is 9 C.l (a composition consisting of 50 parts by weight of the stated petroleum wax and 50 parts by weight of the specified oil having a melting point of 80. C.). That is` to say the inclusion of 5% of the synthetic wax increases the melting point by 11%.

Example 3 1 Parts by weight Micro-crystalline petroleum wax as specified in EX- ample 2 i Y 40 Super Hard Wax No. 105 15 Oil-filled cableoil as specified in Example 2 45 v Example 4 Parts by weight Micro-crystalline petroleum wax as specified in Example 1 30 Super Hard Wax No. 105 30 Oil-filled cable oilas specified in Example 2 40 This composition has a melting point of 98 C. and is suitable for cables operating at conductor temperatures up to 87 C. A composition consisting of 60 parts by weight of the specified petroleum wax and 40 parts by weight ofthe specified oil-filled cable oil has a melting point of 75 C., so that the increase in melting point resulting from the replacement of lalf the petroleum wax by the synthetic wax is 23 C. or 31%.

Example 5 j v Parts by weight Micro-crystalline petroleum wax as specified in Example 1 23 Super Hard Wax No. 105 23 Alcowax (M.W. 27,000) 14 Oil-filled cable oil as specified in Example 2 40 This composition has a melting point of 98 C. and is suitable for cables operating at conductor temperatures of up to about 87 C. ItA compares very favourably with a composition containing 60 parts by weight of the petroleum wax specified inExample 1 and 40 parts by weight of the specified cable oil, which has a melting point of 73 C;

Example 6 Y... j, i Parts byweight Micro-crystalline petroleum wax, M.P. 75 C. 80 Super Hard Wax No. 105 20 This composition has a melting point of 93 C. although the melting point of the micro-crystalline petroleum wax is only 75 C. It is suitable for vcables operating at conductor temperatures of up to about 80 C.

Example 7 y Parts by weight Micro-crystalline petroleum wax of melting point 75 C. 65 Super Hard Wax No. 105 5 Oil-filled cable oil as specified in Example 2 30 This composition has a melting point of 76 C. and is suitable for cables operating at conductor temperatures of up to about 65 C. and is equivalent to a composition consisting of 30 parts by weight of such oil and 70 parts by weight of the micro-crystalline petroleum wax specified in Example l, i.e. wax having an M.P. of 80 C.

What l claim as my invention is:

1. A microcrystalline petroleum wax irnpregnating composition for use in the manufacture of fully impregnated non-draining electric cables comprising as its major ingredients from 20% to 100% by weight, on the weight of the composition of a mixture of microcrystalline petroleum wax and a synthetic hydrocarbon wax product of the Fischer-Tropsch process having a melting point within the range 85 C. to 120 C., the weight of said synthetic wax amounting to between 1% and 40% of the weight of the composition, and the microcrystalline wax constituting at least 30% of the wax mixture.

2. A microcrystalline petroleum wax impregnating composition for use in the manufacture of fully impregnated non-draining electric cables comprising as its major ingredients up to by weight, on the weight of the composition, of cable impregnating mineral oil and at least 20% -by weight, on the weight of the composition, of a mixture of microcrystalline petroleum wax and a synthetic hydrocarbon wax product of the Fischer- Tropsch process having a melting point within the range C. to 120 C., the weight of said synthetic wax amounting to between 1% and 40% of the weight of the composition, and the microcrystalline wax constituting at least 30% of the wax mixture.

3. A microcrystalline petroleum wax impregnating composition as described in claim 2, wherein said mixture of microcrystalline petroleum wax and a synthetic hydrocarbon wax is from 25% to 60% by weight, on the weight of the composition.

4. A microcrystalline petroleum wax impregnating composition as described in claim 2, wherein said mixture of microcrystalline petroleum wax and a synthetic hydrocarbon wax is from 25% to 60% by weight, of the composition, and in which said synthetic hydrocarbon wax lhas a melting point of 108 C. to 110 C. and an average molecular weight of about 600.

5. A microcrystalline petroleum wax impregnating composition as described in claim 2, in which the weight of said synthetic hydrocarbon wax product amounts to between 1% and 30% of the weight of the composition.

6. A microcrystalline petroleum wax impregnating composition as described in claim 2, in which the weight of said synthetic hydrocarbon wax product amounts to between 1% and 20% of the weight of the composition.

7. A microcrystalline petroleum wax impregnating composition Ias described in claim 2, in which the weight of said microcrystalline petroleum wax is at least equal to the weight of said synthetic hydrocarbon wax.

8. A microcrystalline petroleum wax impregnating composition as described in claim 2, in which the weight of Isaid microcrystalline petroleum wax is at least equal tothe weight of said synthetic hydrocarbon wax and in which the weight of said synthetic wax amounts to between 1% and 30% of the weight of the composition.

v9. A microcrystalline petroleum wax i-mpregnating composition as described in claim 2, wherein said wax mixture is from 25 to 60% by weight, on the weight of the composition, and wherein the weight of said microcrystalline petroleum ywax is at least equal to the weight i of said synthetic hydrocarbon wax.

Y10. A microcrystalline petroleum wax impregnating composition as described in claim 2, in which the synthetic hydrocarbon wax has a melting point of 108 C. to 110 C. and an average molecular weight of about 600.

11. A microcrystalline petroleum wax impregnating composition as kdescribed in claim 2, in which the synthetic hydrocarbon wax has a melting point of 108 C. to 110 C. and an average molecular weight of about 600 'and in which the weight of the synthetic hydrocarbon Wax amounts to between 1% and 30% of the weight of the composition.

12. A microcrystalline petroleum wax impregnating composition as described in claim 2, in which the synthetic hydrocarbon wax has a melting point of 108 C. to 110 C. and an average molecular weight of about 600 and in which the weight of the microcrystalline petroleum wax is at least equal to the weight of the synthetic hydrocarbon wax.

13. A microcrystalline petroleum wax impregnating composition as described in claim 2, in which the synthetic hydrocarbon wax has a melting point of 108 C. to 110 C. and an average molecular weight of about 600 and in which the weight of the microcrystalline petroleum wlax is at least equal to lche weight of the synthetic hydrocarbon wax and the weight of the synthetic hydrocarbon wax amounts to between 1% :1nd 30% o the weight of the composition.

14. A microcrystalline petroleum wax impregnating composition as described in claim 2, in which the synthetic hydrocarbon wax has a melting point of 108 C. to 110 C. and an average molecular weight of about 600 and in which the weight of the synthetic hydrocarbon wax amounts to be between 1% and 20% of the weight of the composition.

15. A microcrystalline petroleum wax impregnating composition as described in claim 2, in which the synthetic hydrocarbon wax has a melting point of 108 C. to 110 C. and an average molecular weight of about 600, in which the weight of said petroleum wax is at least equal to the weight of said synthetic wax and in which the weight of the synthetic hydrocarbon wax amounts to between 1% and 20% of the weight of the composition.

16. A microcrystalline petroleum wax impregnating composition as described in claim 2, in which the synthetic hydrocarbon wax has a melting point of 108 C. to 110 C. and an average molecular weight of about 600, in which the mixture of microcrystalline petroleum waX and a synthetic hydrocarbon wax is from 25% to 60% by weight, on the weight of the composition, and in which the weight of said petroleum wax is at least equal to the weight of said synthetic hydrocarbon wax.

17. A microcrystalline petroleum wax impregnating composition for use in the manufacture of fully impregnated non-draining electric cables comprising as its major ingredients from 20% to 100% by weight, on the weight of the composition, of a mixture of microcrystalline petroleum wax, a synthetic hydrocarbon wax product of the Fischer-Tropsch process having a melting point within the range of 85 C. to 120 C., and polyethylene wax having a molecular weight of between 2000 and 6000 and a melting point of about 110 C., the microcrystalline petroleum wax constituting at least 30% of the wax mixture, the aggregate weight of the Fischer-Tropsch wax and of the polyethylene wax amounting to between 1% and 40% of the weight of the composition and the weight of the polyethylene wax not exceeding by weight of the weight of the composition.

18. A microcrystalline petroleum wax impregnating composition for use in the manufacture of fully impregnated non-draining electric cables comprising as its major ingredients up to 80% by Weight, on the weight of the composition, of cable impregnating mineral oil and at least by weight, on the weight of the composition, of a mixture of microcrystalline petroleum wax, a synthetic hydrocarbon wax product of the Fischer-Tropsch Vprocess having a melting point within the range of 85 C. to 120 C., and polyethylene wax having a molecular weight of between 2000 and 6000 and a melting point of about 110 C., the microcrystalline petroleum wax constituting at least of the wax mixture, the aggregate 8 weight of the Fischer-Tropsch wax and of the polyethylene wax amounting to between 1% and 40% of the weight of the composition and the weight of the polyethylene wax not exceeding 15 by weight of the weight of the composition.

19. A microcrystalline petroleum wax impregnating composition as described in claim 18, in which the aggregate weigbt of the Fischer-Tropsch wax and the polyethylene wax amounts to between 1% and 20% of the weight of the composition.

20. A microcrystalline petroleum wax impregnating composition as described in claim 18, in which the syntbetic hydrocarbon wax product of the Fischer-Tropsch process has a melting point of 108 C. to 110 C.

21. A microcrystalline petroleum waX impregnating composition as described in claim 18, in which the aggregate weight of the Fischer-Tropsch' wax and the polyethylene wax amounts to between 1% and 20% of the weight of the composition and in which the synthetic hydrocarbon wax product of the Fischer-Tropsch process has a melting point of 108 C. to 110 C.

22. A microcrystalline petroleum wax impregnating composition as described in claim 18, in which the weight of said microcrystalline petroleum wax is at least equal to the weight of the Fischer-Tropsch wax.

23. A microcrystalline petroleum wax impregnating composition as described in claim 18, in which the weight of said microcrystalline petroleum wax is at least equal to the weight of the Fischer-Tropsch wax and in which the aggregate weight of said Fischer-Tropsch wax and the polyethylene wax amounts to between 1% and 20% of the weight of the composition.

24. A microcrystalline petroleum wax impregnating composition as described in claim 18, in which the wax mixture is from 25% to 60% by weight on the Weight of the composition.

25. A microcrystalline petroleum wax impregnating composition as described in claim 18, in which the wax mixture is from 25% to 60% by weight, on the weight of the composition, and in which the weight of said microcrystalline petroleum wax is at least equal to the weight of said Fischer-Tropsch wax.

References Cited in the le of this patent UNITED STATES PATENTS 2,185,031 MacLaren et al. Dec. 26, 1939 2,245,494 Padgett June 10, 1941 2,457,229 Hanford et al Dec. 28, 1948 2,504,400 Erchak Apr. 18, 1950 2,523,848 Schaerer et al Sept. 26, 1950 2,586,345 King Feb. 19, 1952 2,594,547 Fischer Apr. 29, 1952 2,640,040 Lehman May 26, 1953 2,698,309 Thwaites et al Dec. 28, 1954 2,758,100 Bailly et al. Aug. 7, 1956 2,773,053 Field et al. Dec. 4, 1956 2,857,350 Thompson et al Oct. 21, 1958 2,867,596 Bennett Jan. 6, 1959 OTHER REFERENCES Dunstan et al.: The Science of Petroleum, volume 2, 1938, page 994, published by Oxford University Press.

The Chemistry and Technology of Waxes, by Warth, published 1947 by Reinhold Publishing Corporation, pages 199, 266 and 274-276,

UNITED STATES PATENT OFFICE CERTIFICATE 0F CORRECTION Pai-,ent No., 2,956,036 october 11, 1960 Albert King roby'r certified that error appears in theprinted specification umbered It is he of the above n patent requiring correction and that the said Letters Patent should read as corrected below. T

Column 2, line 13, for "instnzilcen read instance column 3, line 64, for "waxe" read Wax column 6, line 32, after "by Weight," insert on the Weight 1- Signed and sealed this 4th day of April 1961.,

(SEAL) Attest: ERNEST W. SWIDER ARTHUR W. CROCKER Attosting Ocer Acting Commissioner of Patents UNITED STATES PATENT OFFICE CERTIFICATE 0F 4CORRECTITON Patent No., 2,956,036 October 11, 1960 Albert King Column 2, line 13, for "instnalcen read instance column 3, line 64, for l"waxe" read Wax column line 32, after by Weight, insert on the weight Signed and sealed this 4th day of April 1961.,

(SEL) Attest: ERNEST W. SWIDER ARTHUR W. CROCKER ttesting Ufficer Acting Commissioner of Patents

Claims

1. A MICROCRYSTALLINE PETROLEUM WAX IMPREGNATING COMPOSITION FOR USE IN THE MANUFACTURE OF FULLY IMPREGNATED NON-DRAINING ELECTRIC CABLES COMPRISING AS ITS MAJOR INGREDIENTS FROM 20% TO 100% BY WEIGHT, ON THE WEIGHT OF THE COMPOSITION OF A MIXTURE OF MICROCRYSTALLINE PETROLEUM WAX AND A SYNTHETIC HYDROCARBON WAX PRODUCT OF THE FISCHER-TROPSCH PROCESS HAVING A MELTING POINT WITHIN THE RANGE 85*C. TO 120*C., THE WEIGHT OF SAID SYNTHETIC WAX AMOUNTING TO BETWEEN 1% AND 40% OF THE WEIGHT OF THE COMPOSITION, AND THE MICROCRYSTALLINE WAX CONSTITUTING AT LEAST 30% OF THE WAX MIXTURE.