US2296854A - Dielectric material - Google Patents

Description

Sept. 29, 1942. A, KEMP 2,296,854

DIELECTRIC MATERIAL.

Filed June 18, 1937 III/I POL YMER/ZED A L/PHA TIC MON0 OL E F INS AND RUBBER, GUTTA, EAL/1734,01? MINERAL WAX /N l/E N TOR ARKEMP BY A T TORNE V Patented Sept. 29, 1942.

nmuzc'raro Muslim J Archie a. Kemp, Westwoofl, N. 1., assignor to Bell Telephone Laboratories, Incorporated. New York, N. Y., a corporation of New York Application June 18, 1937, Serial No. 148,878

1 Claim.

This invention relates to electrical insulation and more particularly for dielectric materials employed for insulating electrical conductors.

An object of this invention is to insulate electrical apparatus effectively and eificiently.

A more particular objector this invention is an insulated electrical conductor, .the insulation of which has excellent dielectric properties, is

stable and is free from any corroding materials. Insulation for electrical apparatus, and ,more

particularly forxdrop wire, in addition topossessing desirable electrical characteristics, .must withstand the variousconditions towhich the apparatus is subjected andnot corrode theapparatus. For example, a temperature range between 40 F. to +140 F. prevails for drop wire employed extensively as a conductor in telephone communication systems and insulation for the drop wire must not flow or crack without healing in this temperature range. Then again, the insulation for submarine cables. must not be brittle at temperatures which obtain at the ocean bottom, must not corrode the con-' ductor and most important of all, must have low leakan'ce and a low dielectric constant.

In accordancejwith this invention, electrical apparatus, and more particularly submarine cable, is insulated by a medium which is not. brit tle at'low temperatures, which does not corrode the metallic parts to which it is 'applied and which possesses extremely desirable I electrical properties. This medium comprises polymerized aliphatic mono-olefins varying in physical characteristics from viscous liquids to tough elastic solids similar to crepe rubber. The leakance and dielectric "constants of these materials are particularly low and'they maybe'obt'a'ined commercially substantially airee mm any deleterious substance winch 'corrodes the conductor. or other 1 apparatus. 'F'u'rther, their physical characteristicsar'e such that they are adaptablerto use under a wide range of temperatures;

Chemically, the polymerized aliphatic olefins are among the most'highly stable high polymeric organic materials known. They are pure hydropercha or para gutta.

carbons and free from any wanna or con ducting substance. They have an extremely low water absorption which is almost negligible and they have an extreme resistance to oxidationand in this latter respect are superior to rubber, gutta This oxidation resistance is due primarily to the saturated nature of the polymerized aliphatic mono-olefin molecules.

The polymerized aliphatic mono-oleilns may be employed alone or as an ingredient in mixtures with other materials such as high melting point waxes, rubber, gutta percha or balata. The particular type of polymerized aliphatic monoolefins employed depends to a great extent upon the use to which the apparatus for which it serves as an insulating medium is subjected. When these substances are mixed with other materials to produce an insulation composition. the amount employed varies with the use of the composition. For example, the polymerized aliphatic mono-oleflns may be employed as a compounding ingredient in rubber mixtures used for coating conductors. In some cases the paramount consideration is the utilization of the superior electrical characteristics of the polymerized aliphatic mono-olefins which comprise a relatively high percentage of the composition,

halide as a catalyst such an anhydrous alumiv num chloride, stannic chloride, boron fluoride, titanium chloride, etc. For the polymerization the aliphatic mono-olefin or a mixture of aliphatic oleflns is dissolved in butane. Subsequent to the polymerizatidn reaction conducted for various periods of time at temperatures usually below --10 0., the catalyst is removed by filtration, washed and the butane distilled from the polymerization product. Preferably, the aliphatic mono-olefin contains from 4 to carbon atoms and branch chain mono-oleflns are likewise preferred over the straight chain variety since the former polymerize more quickly and are more readily obtainable commercially in large quantitiesthan the latter. Examples of the preferred aliphatic mono-olefins from which the polymerized products of this invention are employed are the isomers of butylene, amylene, hexylene, heptylene, octylene, nonylene and decylene. Isobutylene due to its relative cheapness and its ease of polymerization is particularly well adapted for large scale production of polymerized products. In the polymerization of the mono-olefins, the mono-olefins intermolecularly react to link together with the elimination of most of the double bond and the resulting product is substantially saturated. By the proper selection of a particular aliphatic mono-olefin or a mixture of aliphatic mono-olefins and by the control of the condition of polymerization such as temperature, polymerized products are obtained which vary in physical characteristics from viscous liquid to solid elastic materials. Perhaps the best criterion for differentiating the polymerization products from each other and for serving as an index of the physical characteristic of the polymerization product in the molecular weight as determined by the Staudinger viscosity method. Polymerized aliphatic monooleilns having a molecular weight of from 10,000 to 150,000 as-determined by this method are preferred for electrical insulation.

The polymerized mono-olefins may be em polymerized reaction product may be mixed with rosin or rosin oil or employed alone. I To illustrate the use of the polymerized mono- I2 of jute is placed over the insulation H. In Fig. 2 a copper electric conductor 20 is covered with an insulation 2| comprising polymerized aliphatic mono-oleflns and rubber, balata, gutta percha, high melting point hydrocarbon wax or other materials. The insulation It may be vulcanized by the continuous vulcanization process or the older pan method.

The insulation I I of the submarine cable shown in Fig. 1 or the insulation II of the insulated wire illustrated in Fig. 2 may comprise the polymerized aliphatic mono-oleilns alone or asan ingredient in mixtures with other insulating materials. Several examples are hereinafter described in which the polymerized aliphatic monoolefins are employed in compositions for insulating conductors and other electrical apparatus.

EXAMPLES or Comrosrrrorzs Commence GUTTA AND Pommaslzan ALIPHATIG MoNo-OLariNs The following compositions comprising the reaction product resulting from the polymerization of aliphatic mono-oleiins and gutta have been found satisfactory for electrical purposes:

Compo- Compositkm sition. B

Parts by Parts by weight might White leai gutta Polymerized all hatic mono-olefin (molecular weight 100,000? 35 Amorphous high melting point mineral wax (M. I. 160 F.)

' Percent Thick- Loss Spec. cond.

increase Dielectric Spec. res. Compound ness in (3/0 factor constant (mho. (ohm cm) (cm.) weight (i/o0 cmr TREATMENT BEFORE BOA KING White leaf gutta 0. 1485 0. 00 5.4 0. 00043 2. 53 1. 2X10 9. 3X10 ll White leaf gutta 0. 1505 0. 00 6. 3 0.00050 2. 47 1. 4X10 9. 2X10 Composition A 0.1512 0. 00 2. 7 0. 00022 2. 40 0. 58x10 9. 2X10 Composition B 0.1543 0.00 2.1 0. 00017 2. 39 0. 45x10 0. 0X10 ll TREATMENT AFTER BOAKINO TWO WEEK White leaf gutta 0. 1476 0. 05 9. 7 0. 00077 2. 54 2. 2X10 9. 6X10 White leaf gutta.-. 0. 1512 0. l3 6. 5 0. 00052 2. 52 1. 5X10 9. 3X10 Composition A. 0.1522 0.12 5. 7 0. 00045 2. 45 1. 2X10 9. 3X10 Composition B 0. 1548 0. 07 5. 2 0. 00041 2. 40 1. 1X10 0. lX l0 ll olefins for insulation, reference is made to the accompanying drawing in which:

Fig. 1 illustrates a submarine cable insulated with polymerized aliphatic mono-olefins; and

Fig. 2 shows an insulated conductor in which a rubber mixture comprising polymerized aliphatic mono-olefins is employed for the insulating material.

In Fig. l, a copper conductor I0 is insulated by polymerized aliphatic mono-olefins ll having a molecular weight of 50,000 to 150,000 as determined by the Staudinger method. A coating aeeaazsa.

ExAurLEs or Courosmon Courmsnvo Rosana AND Ponruaarznn ALmnA'rroMoNo-Omrme Compo- Compo- Compo- Composition G sition D sition E sition F Parts by Parts by Parts by Paris by weight weia weight weight Pale crepe rubber 30. 30.00 30.00 44. 75 Mineral rubber.. 12.00 15.00 Zinc oxide 3. 3. 00 31. 00 Lithoponc 29. 75 40. 00 Whiting 20. 00 Polymerized aliphatic mono-cleans (molecular weight 15,000) 2.00 2.00 3.00 6.00 Retarder (salicylic acid).- 0. 50 0.50 0. 50 S p ur 1.00 1.00 1.25 1.00 Accelerator (tetramethylthiuram-monosulphide) 0. 25 0. 25 0. 25 0. 50 Steer c acid 0. 25 0. 25 0. 25 0. 25 Ceresin wax 0. 26 0. 25 0.25 Anti-oxidant (phenylalphane hthylamme). 0. 50 0.50 0. 50 1.00 Carbon lack 0.50 0.50 1.00 Reclaimed rubber 20.00 Accelerator (diphenylguanidine) 0. 25 Lead oleate 0. 25

The ingredients of the compositions C, D, E or F are compounded together, vulcanized and applied to the conductors by any of the methods well known in the art. Other fillers, retarders, accelerators, and anti-oxidants may be employed instead or those used in the compositions C, D, E and F.

The relative amount of polymerized aliphatic mono-olefins in the compositions C, D, E andF varies from two to six per cent. These compositions illustrate the utilization of the plasticizing properties of the polymerized aliphatic olefins in rubber compounds. The resulting rubber insulation has superior dielectric properties tor insulating conductorsand possesses the necessary physical properties required of such conductors in the field.

As an example or a rubber composition which has a low leakance and low dielectric constant and in which the polymerized aliphatic monoolefins comprise the major portion, the following compound has been found satisfactory for insulating electric conductors:

Composition G Parts by weight Polymerized aliphatic mono-oleiins- (Molecular weight 100,000) 66. 00 Crepe rubber 34. 00 Zinc oxide 4. 00 Stcaric a 2. 00

Anti o x i d a n t (phenylalphanaphthylamine) 1. 50 A c 0 e1 e r a t o r (tetramethylthiuramdisulphide) 0. 20

Sulphur 2 00 Other anti-oxidants and accelerators may be employed instead of those specified in the above formula. The ingredients are mixed, vulcanized and applied to the conductor in the usual way.

A hard rubber composition having extremely desirable electrical and physical characteristics may also be prepared from these polymerized aliphatic mono-oleflns. For example, hard rubber compositions containing the following constituents may be mixed together and vulcanized for ten hours at approximately C.:

Compo- Composition H sition I Parts by Parts by weight weight Crepe rubber 70. 00 70. 00 Sulphur 30. 00 30. 00 Polymerlzed aliphatic mono-olefins (molecular weight 60,000) 10.00 20.00

EXAMPLE or COMPOSITION CoMr'nIsINe Wax AND POLYMEEIZED ALIPHATIO MONO-OLEFINS The polymerized aliphatic mono-olefins may also be employed with hydrocarbon waxes, such oleflns and the resulting compositions utilized for electrical insulation.

The molecular weight of the polymerized aliphatic mono-olefins specified in the compositions in all of the examples are the values obtained by the well-known Staudinger viscosity method.

While preferred embodiments of the invention have been illustrated and described, various modifications-may be made therein without departing from the scope of the appended claim.

What is claimed is:

An insulation for submarine cable comprising 66 parts by weight of polymerized aliphatic monooleflns having a molecular weight above 50,000, 34 parts by weight of crepe rubber and 2 parts by weight of sulphur.

. ARCHIE R. KEMP.

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