A Method of and Apparatus for the Purifying of Gutta-percha.
Year: 1891

page_text: Date of Application, 1st June, 1891-Accepted, 3rd Oct., 1891
COMPLETE SPECIFICATION.
A Method of and Apparatus for the Purifying of Gutta-percha.
I, REGINALD HADDAN of the firm of Herbert & Co. Patent Agents of
18 Buckingham Street Strand W.C. in the County of London, Civil Engineer do
hereby declare the nature of this invention a communication to me from abroad by
Alexandre Grammont of Pont de Chérui, Isère, France, Manufacturer of Telephonic
and Telegraphic Cables, and in what manner the same is to be performed to be
particularly described and ascertained in and by the following statement:-
Up to the present the purification of gutta-percha has been performed mechanically,
all the operations necessary being long and costly, and in spite of care and time
given to the process it is difficult to obtain an absolutely pure product.
The improved method which forms the subject of this invention consists broadly
in dissolving the raw gutta percha in a suitable solvent and treating it to successive
purifications while in solution.
This refining process consists of three principal operations which take place
substantially in an automatic manner in the apparatus used for this process and
which also forms part of this invention.
These three operations are, first, the extraction of matters foreign to the ordinary
composition of the gutta percha such as carthy matter, sand, wood, water, secondly,.
the extraction and separation of the oxidized gutta percha, giving product No. 1,
and thirdly, the extraction and separation of the resinous matters contained in
product No. 1 and also in product No. 2 being the residue that remains after
extracting product No. 1.
The method is carried out as follows:-
The gutta-percha to be treated is triturated to reduce it to small fragments and
placed in an iron or wooden receiver in which are movable pallets or mixing devices.
Bisulphide of carbon is then allowed to flow into this receiver from a tank placed
on a higher level. The agitator or mixer is then moved to stir together the
bisulphide of carbon and the crude gutta percha until the soluble matter therein
is all dissolved. A cock at the base of the receiver is then opened and the solution
passes into a filter which retains the solid matters not dissolved in the bisulphide
of carbon which foreign matters are thus separated from the gutta percha. The
solution passes into a series of depositing vessels, in these vessels the oxydized
gutta-percha separates gradually from the pure gutta-percha by reason of a difference
in density. The pure gutta-percha is drawn off into a lower vessel in which the
bisulphide of carbon is evaporated leaving only pure gutta-percha containing
however still some resinous matter.
The vapour of the bisulphide of carbon is carried off and condensed in a worm
and returned to its storage tank to be used again for dissolving crude gutta-
percha.
Two products are thus obtained, one being oxydised gutta-percha containing
resin, the other non-oxydised gutta-percha also containing resin.
Before treatment to remove the resin the oxydised gutta-percha requires to be
de-oxydised which may be done by passing carbonic oxide gas into the vessel
containing the solution of oxydised gutta-percha. The carbonic oxide gas removes
the oxygen, being converted in carbonic dioxide or carbonic acid gas. The resulting
deoxydised gutta percha may be mixed with the non oxydised gutta percha or these
two products may be treated separately for removal of the resin according to the
quality of the ultimate product required.
To remove the resin, an apparatus is used similar to that employed for the first
part of this process, or even the same apparatus may be used if desired. Instead

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however of using bisulphide of carbon as a solvent, benzine, or essence of thérébentine,
or any other essential oil which dissolves resin, is used.
The solution is made in the mixer as before, passes through the filter into the
depositing vessels, where the resin. separates, from the gutta, percha so that by
simply drawing off at proper levels, the two products are separated. The gutta-
percha solution is carried to the evaporator where the solvent is evaporated to be
re-condensed for use again, and the pure gutta-percha is.left.in.the apparatus.
The oxydised gutta-percha after de-oxydation is treated in the same manner and
forms a product of secondary quality.
The drawing illustrates the apparatus employed. A is the receiver or mixer.
B the filter. CCC the series of depositing chambers. D the evaporator, E a
-cooler containing a worm. Freservoir tank for the solvent,
These are connected by pipes with cocks as shown so that the circulation, is
effected, so to speak, automatically under control of the cocks.
Having now particularly described and ascertained the nature of this said inven-
tion and in what manner the same is to be performed I declare that what I
claim is
1) The method of purifying or refining crude or raw gutta percha by solution
in bisulphide of carbon and in an essential oil, or other suitable solvent and separating
the foreign matters and resins as herein described.
2) The apparatus as described herein and illustrated for the carrying out of the
above process or method.
Dated this 1st day of June 1891.
HERBERT & Co.,
Agents to Applicant..