Improvements in and relating to the Manufacture of Vulcanized Plastic Compounds.
Year: 1890

page_text: Date of Application, 24th June, 1890-Accepted, 2nd Aug., 1890
COMPLETE SPECIFICATION.
Improvements in and relating to the Manufacture of Vulcanized
Plastic Compounds.
A communication from WILLIAM KIEL, residing at Butler, in the County of Morris,
and State of New Jersey, United States of America.
I, ALFRED JULIUS BOULT of 323 High Holborn in the County of Middlesex,
M.I.M.E., 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 :-
The object of this invention is to produce hard vulcanized plastic rubber compounds
which can be used in the place of hard rubber or other plastic compounds, wood,
bone, ivory, &c. and which possesses valuable qualities hitherto unknown.
The ingredients of the new compound are crude rubber, sulphur and oil preferably
mineral oil such as petroleum or kerosene, but with less satisfactory results vegetable
or animal oils may be used. The exact proportions of these ingredients are not
invariable for the reason that the proportions and quantities vary with the results to be
obtained.
Equal weights of sulphur and rubber are preferably used but a larger or smaller
quantity of sulphur can be used but the sulphur at any time is not reduced to below
approximately 80 per cent. of the rubber by weight.
When using sulphur in a quantity in weight greater than the crude rubber used
it is preferred to add to the compound before vulcanization what is known as rubber
dusi (that is waste hard rubber compound ground to a powder) in the proportion of
1 lb. of dust for each pound of sulphur in excess of the weight of the crude
rubber.
The new compound can be made either hard and rigid or hard and flexible and
its flexibility depends upon the quantity of mineral oil used and upon the vulcanization
to which it is subjected. The proportion of mineral oil used in the new compound
varies with the quantity of sulphur and varies in weight from 1 to 3 of the weight
of the sulphur used.
To produce the new compound in its hard, stiff form there is preferably used.
with the other ingredients mineral oil in weight from to of that of the sulphur.
To produce it in its more flexible form there is preferably used mineral oil in.
weight from to 3 of that of the sulphur. A large proportion of oil increases the
flexibility but reduces the elasticity of the finished product.
To prepare the new compound the mineral oil for example petroleum is preferably
mixed first with the sulphur in any convenient vessel and then the mass thus obtained
is mixed with the crude rubber upon heated rollers such as are commonly used in.
the manufacture of rubber compounds. When the ingredients are thoroughly united.
the new compound is ready to be put into moulds or otherwise treated to produce
any desired form and then vulcanized.
To vulcanize the new compound it is necessary to commence with a pressure or
temperature in the vulcanizer not less than that at which the vulcanization of hard
rubber usually ends; that is approximately 60 pounds corresponding to about
308° Fahrenheit.
The pressure during the process of vulcanization is retained constant during the
entire process if the vulcanization lasts less than three hours; or it is reduced
gradually after the third hour, if the vulcanization continues longer than three
hours.
Whenever the pressure is herein referred to I mean the pressure of steam in the
vulcanizer and the corresponding temperature. Vulcanization by steam heat is the
most advantageous method.

page_text: The following is the manner of producing the new compound in its hard and rigid
form.
With equal or with approximately equal weights of sulphur and rubber and the
proportionate quantity of mineral oil the ingredients of the new compound are
vulcanized for seven hours with an initial pressure of about 60 pounds to the square
inch. This pressure is kept constant for three hours and is then gradually reduced.
About seven hours is the longest time necessary for complete vulcanization of the
new compound.
The inventor can equally advantageously vulcanize the ingredients of the new
compound in the above proportions for one hour with an initial pressure of
100 pounds. This pressure remains constant during the process of vulcanization.
It will be seen that the time of vulcanization is reduced at the rate of one and one-
half hours for each 10 pounds of increased pressure above 60 pounds.
The inventor has not found it advantageous to go above 100 pounds pressure when
not using more than approximately equal weights of sulphur and rubber.
When the sulphur is greater in weight than the rubber up to about 150
per cent.
the ingredients in the new compound can be vulcanized for the period of one hour
at 100 pounds pressure. It has not been found practicable to go below this pressure
with the ingredients in this proportion.
The inventor can increase the pressure and shorten the time until. at 125 pounds
pressure the vulcanization lasts but one half-hour.
The following is the manner of producing the new compound as a hard but flexible
substance; the time which has before been stated as necessary for the production of
the new compound as a hard and rigid substance is shortened and the pressure is
retained as before or the pressure is reduced without shortening the time, or both the
pressure may be reduced and the time shortened.
A pressure of 60 lbs. for a period of 3 hours or a pressure of 80 lbs. for a period
of one hour will produce the new compound in its hard and flexible form when the
same proportions of ingredients are used as before; but the pressure at any time is
not reduced below about 60 lbs.
The new compound can be made as hard and rigid as the hardest hard rubber
or hard and flexible to a degree unknown in hard vulcanized rubber compounds as
heretofore made.
In its hard and rigid form the new compound is of a rich, deep, jet-black color
throughout, superior to that of hard vulcanized compounds, as now usually made,
and it is especially superior to such hard vulcanized compounds in that it can be
easily and more highly polished, than any of such compounds now known. It is at
ordinary temperatures far more flexible than the hard vulcanized compounds hereto-
fore made and when warmed becomes considerably more pliable than such compounds
when subject to the same heat. It is less brittle than such compounds and particularly
so when mineral oil is used and it is always cheaper. It has a different fracture in
its being more glassy than that of other hard vulcanized compounds now known.
It can be turned in a lathe with greater facility and with less injury to the tools
used than any such compounds; it gives a clean long shaving and this shows that it
possesses qualities which are of the greatest value when nicety and fineness of work-
manship upon the lathe are required.
When in the shape of a hard flexible substance the new compound is so flexible
that a rod or tube of it can be bent or twisted into any shape without injury to the
material. This would be impossible with a like article of any other known hard
vulcanized: compound. At the same time it can also be polished though to a some-
what less degree than the new compound in its hard and rigid shape; it is impervious
to moisture and can be used to great advantage as an insulating substance for
electric wires.
By the use of a large proportion of sulphur entering into the new compound a very
considerable saving in rubber can be effected (which as is well known is the most
expensive ingredient entering into rubber compounds) without using any foreign
solid substance not entering into ordinary bard rubber as now made. At the same

page_text: time the time of vulcanization of hard vulcanized compounds, as now produced is
reduced fromto of the time now required, a matter of great importance as it
considerably increases the production of the vulcanizers,
The method applied in the hitherto well known processes of vulcanizing hard rubber
compounds is reversed by beginning the vulcanization at a pressure (or temperature)
which is not less than that at which at present vulcanization of hard rubber compounds
ends, and by retaining it constant for not over three hours and then gradually
reducing it. This process if applied to the manufacture of hard rubber as now made,
produces a porous imperfect article, and in like manner, if the well known process
of manufacturing hard rubber, as now made is applied to this new compound, an
insufficiently vulcanized, porous and non-homogeneous mass is produced.
The inventor states that he is aware that it has been proposed to produce vulcanized
soft rubber, in which all the sulphur (not over 34%) is chemically combined with
the rubber, by exposing the rubber with sulphur to a minimum heat of 330 Fahrenheit;
but this is not the present invention; and the inventor does not claim it as such; and
moreover the inventor is aware that petroleum and some of its products have been
used as solvents of rubber, and that petroleum has been used in a process of reclaiming
rubber from old and waste vulcanized rubber, and utilizing the same in the manu-
facture of soft rubber goods; but that again is quite distinct from the present invention
and is not herein claimed.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed, as communicated to
me by my foreign correspondent, I declare that what I claim is :-
1. The herein described process of manufacturing vulcanized, plastic, rubber
compounds, consisting in mixing together sulphur and rubber, the sulphur being in
the proportion of not less than about 80 per cent. of the rubber, by weight, and
vulcanizing the compound with an initial temperature of not less than about 300 degrees
Fahrenheit, and for the period of time set forth, substantially as described.
2. The herein described process of manufacturing vulcanized, plastic, rubber
compounds, consisting in mixing together sulphur, rubber and oil, the sulphur being
in the proportion of not less than about 80 per cent. of the rubber, by weight, and
vulcanizing the compound with an initial temperature of not less than about
300 degrees Fahrenheit, and for the period of time set forth, substantially as
described.
3. The herein described hard vulcanized, plastic compound, consisting of crude
rubber, sulphur and oil, the sulphur being in the proportion of not less than
approximately 80 per cent. of the rubber by weight, united by vulcanization
substantially as described.
4. The herein described hard vulcanized plastic compound, consisting of crude
rubber, sulphur and mineral oil, the sulphur being in the proportion of not less than
approximately 80 per cent. of the rubber by weight, united by vulcanization,
substantially as described.
Dated this 23rd day of June 1800
W. P. THOMPSON & BOULT,
Agents for the Applicant.