Improvements in Electric Insulating Compounds.
Year: 1890

page_text: Date of Application, 4th Feb., 1890-Accepted 5th Apr., 1890
COMPLETE SPECIFICATION.
Improvements in Electric Insulating Compounds.
I JAMES B. WILLIAMS, Electrician of Oakland, Alameda County, California in the
United States of America do hereby declare the nature of this invention and in
what manner the same is to be performed to be particularly described and ascertained
in and by the following statement :-
My invention relates to compounds designed to insulate electric conductors and
consists briefly in the combination with india rubber and paraffine wax of a resinous
body and sulphur to which may be added what may be designated as inert material
which serves to harden the compound and lessen its cost.
By paraffine wax is meant ozocerite or mineral wax or more particularly speaking a
substance having the consistency of wax, the main constituents of which are hydro-
carbons of the formula Cn H 2n + 2. By a resinous body is meant one of the
vegetable products commonly called resius or gum resins such as shellac, copal
colophony, sandarach etc. The inert material to which I refer above is silica or an
equivalent such as glass, asbestos, steatite, kaolin talc, various carbonates, silicates,
alkaline earths and bitumenous matter which is solid and brittle when cold. The paraffine
which I prefer to use is that which is obtained from ozocerite or mineral wax the resin
is shellac and the inert material is silica or a silicate though other paraffines, resins
and inert materials than those above designated may be used instead of the ones stated
as preferred with good results.
To make my insulating compound I usually take of indiarubber 60 (sixty) parts by
weight, of paraffine 10 (ten) parts by weight, of shellac 22 (twenty two) parts by
weight and of sulphur 8 (eight) parts by weight. If a harder and stiffer compound is
desired for instance one to be applied to conductors which are to be placed in conduits
where they are expected to remain in one position for a length of time a quantity of the
inert material is added varying with the degree of hardness required. I prefer to keep the
quantity of inert material below about 30 per cent. of the whole composition after the inert
material is added when the compound is to be applied to electric conductors to insulate
them but if it is to be used in the manufacture of telegraphic insulators or substitutes
for hard rubber the inner material may equal 50 per cent. of the whole after the
inert material is added. 1 do not restrict myself to the use of the exact proportions
above given as they are relative only and may be varied somewhat without notably
Neither do I
changing the efficiency of the compounds as an insulating material.
restrict myself to the use of silica or its equivalent or bitumenous matter taken separately
because the two may be combined in various proportions with good results but in case
both are used the quantity of the two when combined should not be greater than the
quantity of either if taken separately.
The above compound is suitable for ordinary purposes of insulation but in cases
where flexibility is not desired as for instance when the insulating material is to be
placed in tubes to insulate and maintain electric conductors in a fixed position the
indiarubber may be used in smaller proportions than those specified; in cases where
greater flexibility and elasticity is desired the indiarubber may be used in larger
proportions than those specified.
The manner of making my improved compound is as follows. The different
ingredients are first cleaned of all foreign matters which they may contain by any
of the processes well known to the art and the bitumenous matter when used is freed
from volatile and aqueous matters by subjecting it in a powdered state to a temperature
of from 300° to 400° Fahrenheit in a suitable vessel, care being taken not to char or
burn it.
The indiarubber is then dissolved in a volatile solvent such as benzole or petroleum

page_text: naphtha in a strong metallic vessel provided with tight fitting metallic cover and
surrounded by a steam jacket by means of which the solution is heated to a tempera-
ture below the boiling point of the solvent used. As the kind of vessel to he used
and the process of making solutions of indiarubber are well known in the art I need
not further describe them. I find that about one half a pound of india rubber to
every gallon of solvent used is a convenient proportion to handle during the process
of incorporating the indiarubber and paraffine hereinafter described. After the india-
rubber has been dissolved and the solution is cooled the proper quantity of paraffine is
added in a coarsely divided state and thoroughly mixed with it by stirring. The
vessel is again covered and heat applied by means of the steam jacket until the
paraffine is dissolved which will usually require from five to fifteen minutes time.
The solution of indiarubber and paraffine is then allowed to cool and when cool it is
transferred to a suitable distilling apparatus, the volatile solvent being distilled at
a temperature of about 200° Fahrenheit and condensed and retained for future use.
By this method of combining the india rubber and the paraffine the former is reduced
to a proper condition for incorporation with the remaining ingredients without
subjecting it to a high temperature. The compound of indiarubber and paraffine is
then incorporated with the remaining ingredients which are first reduced to a
finely divided state by mixing all together upon rollers heated by steam during
which process any of the solvent remaining in the compound of indiarubber and
paraffine is driven off.
Excellent insulating compounds may be made by incorporating with the india-
rubber and paraffine used in any proportions and combined in the manner just stated
a resinous body in any proportions such as shellac or colophony and applying
it to the electric conductors without the addition of sulphur or subsequent
vulcanization.
All of the ingredients of which the compound is composed may be incorporated
together by mixing them in a finely divided state upon hot rollers but by so doing the
indiarubber is liable to deteriorate rapidly afterwards and also lose its insulating
properties whereas by combining it with the other ingredients substantially in the
manner specified such subsequent deterioration is largely prevented.
Before the electric conductors are coated with the insulating compound they should
be covered with a layer of cotton fibre and the fibre saturated with a varnish of
shellac to prevent as far as possible the sulphur in the insulating compound from
coming in contact with or acting upon the materials of which the conductors are
composed during the vulcanizing process and also to prevent as much as possible
moisture from creeping in between the conductors and the insulating compound while
the former are in use.
After the varnish has become thoroughly dry the insulating compound is applied
to the conductors in the same manner and by the same means as is usually employed
in coating electric wires with insulating compounds which become plastic when
heated.
The conductors thus coated are then covered with one or more braids of cotton or
other suitable fibre and thus covered they are saturated with the insulating compound
by passing them through a suitable vessel containing it and in which it is kept in a
liquid condition by heat. The insulating compound is then vulcanized under pressure
in a suitable chamber, by steam to a temperature of from 270° to 280° Fahrenheit for
from one to three hours.
Besides being used as an insulating covering for electric conductors the compound
herein described can be used in the manufacture of condensors, substitutes for hard
rubber and insulators for telegraph and other electric wires.
I do not claim at any part of my invention any of the ingredients above named;
taken separately as their insulating properties are well known but it will be found
that the compounds herein described are easily applied to electric conductors are very
durable will maintain their insulating properties at very high temperatures and are
anhygroscopic under ordinary conditions.

page_text: Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is.
1. An electric insulating compound consisting of indiarubber paraffine and a resinous
body substantially as described.
2. An electric insulating compound consisting of india rubber, paraffine a resinous
body sulphur and silica or its equivalent substantially as described.
3. An electric insulating compound consisting of india rubber paraffine, a resinous
body, sulphur and bitumenous matter which is solid and brittle when cold sub-
stantially as specified.
4. An electric insulating compound consisting of india rubber, paraffine, a resinous
body sulphur silica or its equivalent and bitumenous matter which is solid and brittle
when cold substantially as specified.
5. The process of making the insulating compound above described which consists
first, dissolving india rubber in a volatile solvent, second dissolving paraffine in the
indiarubber solution thus obtained, third, distilling from the solution of indiarubber
and paraffine the volatile solvent, fourth, incorporating the resulting compound of
india rubber and paraffine with one or all of the remaining ingredients substantially
as specified.
Dated this 4th day of February 1800
HERBERT & Co.,
18, Buckingham Street, Strand, London, W.C., Agents to Applicant.