Improvements in or relating to a Process for Reclaiming Rubber Waste.
Year: 1899

page_text: Date of Application, 29th May, 1899-Accepted, 1st July, 1899
COMPLETE SPECIFICATION.
Improvements in or relating to a Process for Reclaiming Rubber
Waste.
A communication from ARTHUR HUDSON MARKS, of Akron, County of Summit
and State of Ohio, United States of America, Superintendent.
I, ALFRED JULIUS BOULT, of 111, Hatton Garden, in the County of Middlesex,
Chartered Patent Agent, do hereby declare the nature of this invention and in
what manner the same is to be performed, to be particularly described and ascer-
tained in and by the following statement:-
-
The invention has for its object the devulcanization of the rubber in vulcanized
rubber waste, and the reclaiming of said rubber in such condition that it is
capable of being used for the various purposes for which fresh rubber is used, and
of being revulcanized. The invention consists in subjecting a mixture of the
ground rubber waste and a dilute alkaline solution, as, for example, a 3 per cent.
solution of caustic soda, to the action of great heat, say about 344° Fahrenheit,
more or less, for a considerable number of hours, say twenty hours, more or less,
in a sealed vessel.
In the best method now known to me for carrying out the process, the finely
ground rubber waste is put into a suitable vessel, together with a dilute alkaline
solution a 3 per cent. solution of caustic soda being preferred--there being
enough of the solution to permeate the rubber and preferably to completely
submerge it. This vessel is then sealed up and the contents of the vessel are
then heated to 344° Fahrenheit, more or less, and this temperature is maintained
for twenty hours, more or less. The smaller the percentage of sulphur which
the rubber contains, the less the heat required and the shorter the time it is
necessary to maintain the heat, but as a practical process to be used day in and
day out with vulcanized rubber waste of various sorts as it is for sale in the open
market, a temperature of 344° Fahrenheit (which is the temperature of steam at
125 pounds per square inch pressure) maintained for twenty hours has been found
to produce the result sought, viz., the devulcanizing of the rubber, and, inci-
dentally, the elimination of the fabric which the waste contained.
The product of the process is then thoroughly washed to remove the chemicals ;
and there remains devulcanized rubber having substantially the characteristics
of fresh rubber and capable of being used in like manner and for like purposes.
The drawing is a sectional view of an apparatus capable of use in carrying out
the process.
A represents the vessel into which the ground waste and the chemical solution
is placed, a being the cover thereof by which the vessel may be sealed.
B represents an outer receptacle capable of containing the vessel A and of being
sealed. Steam is let into the outer vessel, through a pipe C, at a pressure of 125
pounds, more or less, (equivalent to a temperature of 344° Fahrenheit), and is
kept at this pressure for the entire time necessary, say twenty hours. If the steam
pressure and resulting temperature is increased, the time necessary for the
production of the result sought will be reduced.

page_text: It is impossible to state exactly what degrees of heat above or below the
temperature of steam at 125 pounds pressure may be employed with good result,
because it necessarily varies with the different materials, as before stated. It
must always be very much above the boiling point;-but if too low a temperature
is employed, the rubber will not be devulcanized; if too high a temperature is
employed, the rubber may be disintegrated. Fairly good results have been
obtained with rubber, containing a small percentage of sulphur, by heating the
vessel with steam at 90 pounds pressure; and very good results have been obtained
by the use of steam at 175 pounds pressure. But, as before stated, satisfactory
results may always be obtained by heating the contents of the vessel to 344°
Fahrenheit and maintaining that heat for twenty hours.
Having now particularly described and ascertained the nature of the said
invention as communicated to me by my foreign correspondent, and in what
manner the same is to be performed, I declare that what I claim is :-
1. The process of treating vulcanized rubber waste substantially as herein
described.
2. The process of treating vulcanized rubber waste which consists of submerging
the finely ground rubber waste in a dilute alkaline solution in a sealed vessel,
and in heating the contents of that vessel to a temperature approximately equal
to the temperature of steam at 125 pounds per square inch pressure, more or less,
and in maintaining the heat for twenty hours, more or less, substantially as set
forth.
Dated this 20th day of Mar 1800
BOULT & WADE,
Agents for the Applicant.