Improvements in the Method of Manufacturing Non-blooming Vulcanized Soft Rubber.
Year: 1888

page_text: Date of Application, 10th Jan., 1888
Specification Accepted, 10th Feb., 1888
Improvements in the Method of Manufacturing Non-blooming
Vulcanized Soft Rubber.
I, FRANZ WILHÖFT, of the City and State of New York, United States of America,
Chemist, 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 :-
This invention relates to the manufacture of non-blooming vulcanized soft rubber.
By this I mean; vulcanized soft rubber in which the sulphur necessary for vulcani-
zation is permanently chemically combined with the rubber, in such a manner that
the sulphur cannot separate from the rubber by crystallization either on the exterior as
bloom, or in the interior as after vulcanization.
My method has for its object to produce under the ordinary degree of heat now
used in factories, vulcanized soft rubber, that will not bloom nor lose its elasticity by
crystallization of sulphur in its interior.
The following is a specification of this improved method :
Pure sulphur mixed with india-rubber, will, by the usual mode of vulcanization,
combine with one another, but the former will continue to effloresce from the moment
it leaves the vulcanizer. This efflorescence of sulphur (bloom) is nothing else than a
process of crystallization. To prevent this, the sulphur must be rendered amorphous.
This can be done, by subjecting the sulphurous rubber mass to a heat above
330° Fahrenheit in vulcanizing, or preferably by using a sulphur preperation or
sulphur compound in which the sulphur is already in a lastingly amorphous condition.
When this is used instead of sulphur, the ordinary low heat of 270°-280° Fahrenheit,
equal to about thirty to thirty five pounds steam pressure to the square inch in the
vulcanizer, is sufficient to chemically combine sulphur and rubber and prevent
blooming. Sulphur may be rendered lastingly amorphous, by fusing it with any fatty,
greasy, resinous or turpentine like body by the aid of heat under certain condition.
This means, that the sulphur must be heated to such a degree, that it becomes brown,
or so thick or tar-like that it would not flow from the vessel when upset. This
renders the sulphur amorphous temporarily--that is, not lastingly. Now the greasy,
fatty, resinous or turpentine like body is gradually added to it under continuous

page_text: Stirring of the mass, until samples of the bot mass, upon cooling, show no symptoms
of crystallization. This is done for the purpose of rendering the sulphur lastingly
amorphous.
When this point has been reached, the mass is poured out and after cooling,
broken up and ground. This preperation should have the color of moist clay, and
is of a pungent sulphurous odor.
The proportion of sulphur and of the greasy, fatty, resinous or turpentine-like bodies
differs, as a matter of course, and I use at present to one pound of sulphur, one fourth
of a pound of Canada balsam, although equal quantities may be used.
The quantity of sulphur compound to be used for vulcanization depends upon the
proportion of sulphur the compound contains. In my case I use from six to seven
per cent. of the weight of the rubber.
The fusing of the sulphur with the greasy, fatty, resinous and turpentine like bodies
causes the sulphur to assume a lastingly amorphous condition-that is to say, the
sulphur, which had previously a tendency to crystallize, has now lost such tendency
and can therefore not effloresce.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what
I claim is:
1. The compound consisting of amorphous sulphur and of a greasy, fatty, resinous
or turpentine like body and adapted to be used for the manufacture of non-blooming
soft rubber substantially as specified.
2. The process of making a preperation of sulphur, in which this body is in a
lastingly amorphous condition, which consists in fusing sulphur with a greasy, fatty,
resinous or turpentine like body substantially as specified.
3. The process of manufacturing non-blooming vulcanized soft rubber, which
consists in mixing rubber with a sulphur preperation in which this body is in a
lastingly amorphous condition by the addition of greasy, fatty, resinous or turpentine
like body and vulcanizing the mixture substantially as specified.
Dated this 10th day of January 1888.
HERBERT J. ALLISON,
Agent for the Applicant.