Improvements in the Treatment of Gutta-percha and like I Substances.
Year: 1898

page_text: 2..
Date of Application, 15th Mar., 1898-Accepted, 23rd Apr., 1898
COMPLETE SPECIFICATION.
Improvements in the Treatment of Gutta-percha and like
I
Substances.
I, WILLIAM RAMSAY, "F.R.S., of the University College, Gower Street, in the
County of London, Professor of Chemistry, 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:-
7
My invention relates to the treatment of gutta-percha and like substances, such
as the West Indian gutta, known as balata, one object of the invention being to
effect the purification of, the gutta-percha by the separation therefrom from the
deleterious substances which it.contains. A further, object of the invention is to
improve the quality of; the purified gutta-percha by subjecting the same to a process
which changes or varies the polymerisation of the constituents so that it becomes
harder and tougher and will not soften so readily under the action of heat as it
would do before treatment.
"
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Gutta-percha as obtained say from the Isonandra gutta-percha, is.of various
qualities, depending on the part of the tree from which it is extracted, on the age.
of the tree, and on the method of extraction. It consists mainly of a hydrocarbon,
possessing, a.composition expressible by the empirical formula CH. Its molecule
contains however many more atoms of carbon than 5 (the exact number has not
been ascertained) and may be termed a polymeride of the substance expressed by
the above formula, which is usually termed "isoprene." Besides containing this
hydrocarbon, commercial gutta-percha also contains products formed by oxidation
whilst, in the tree or in the leaves. The principal of these substances is known as
albane"; but there are others of less importance. The difference in the quality
of different samples of gutta-percha results from one of the following two reasons,
that is to say the said samples may contain different amounts of such oxidation-
products, or they may contain different polymerides of the fundamental.
substance CH. At the present time, samples of gutta-percha, suitable for any
specific purpose, are obtained by mixing together certain proportions of the various
qualities which happen to be available in the market.
Now an important feature of my invention consists in the employment, as
purifying agents, of toluene or toluol and acetone, which enable both the mechanical
and also the oxidation products to be separated from the true gutta-percha, as
hereinafter described.
A further important feature of the invention consists in effecting a change
in the chemical constitution of the true gutta-percha, by varying the
polymerisation of the constituent atoms or effecting a re-arrangement of them, so
as to convert gutta-percha having only indifferent qualities, into gutta-percha equal
to and identical with the better classes of gutta.
The resolution of gutta-percha into simpler molecules does not appear to lead to
results of commercial value, but the formation of more complex molecules and the
change in the relations of the atoms in the molecule, leads to modifications in the
properties of the gutta-percha, which I find improve its qualities for various
purposes.

page_text: According to my invention the crude gutta-percha which may be in the state in
which it is imported, is cut into small pieces; and warmed with toluol or toluene in
suitable vessels. The resulting solution is separated from the insoluble portions by
straining or filtering, and inay if desired be mixed with acetone or other suitable
agent, in order to precipitate the mixed gums which form what is termed "gutta-
percha "and which all have the empirical formula C, H, in different degrees of
polymerisation. The said mixed gums are then separated from the liquids from
which they are precipitated, preferably by the use of a filter-press, and the
precipitate constitutes, after washing with acetone or other solvent, the gutta-percha
which it is the object of this part of the invention to obtain:
After the filtration of the precipitated gutta-percha, the filtrate is submitted to
distillation for the purpose of separating and recovering the acetone and toluene.
The material obtained in the above manner is next heated in closed vessels, or
digesters, under pressure, with some suitable polymerising agent, for example dilute
hydrochloric or muriatic acid, or certain salts, such as common salt, or calcium
chloride, or even pure water. I find hydrochloric or muriatic acid, however, to
yield the best results. The strength of the acid employed for the above purpose
does not materially influence the result; but I have found that good results are
obtained with 5 per cent. of true acid. The temperature of the liquid is raised in
the closed vessels or digesters, preferably to between 180° to 200° Centigrade, and
should be maintained for about 12 hours. The change, however, may be produced
at a higher temperature in a shorter time, or at a lower temperature in a longer time.
The polymerised gutta-percha obtained by the above treatment is kneaded, under
hot water, in a macerator or in a dry state at a temperature higher than 100° C., in
the usual manner, and may be fashioned into any desired form, or applied to the
covering of telegraph cables or for other purposes.
The result of preparing gutta-percha by my improved process is that it becomes
very tough, and, moreover, does not soften until a much higher temperature is
reached than before such treatment. By varying the temperature, and with it the
pressure and the time of heating, and also the acid or salt dissolved in the water, I
find that gutta-percha of different qualities can be obtained, sometimes more,
sometimes less tough and resistant.
It will be readily understood that I may employ any other suitable purification
process than that above indicated, as a preliminary to the polymerisation process.
It will also be understood that I may use the purification process alone in
cases where the gutta obtained thereby happens to be of the quality required for
the purpose it is intended for, the polymerising treatment being in such cases
obviously unnecessary.
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. In the treatment of gutta-percha and like substances, the employment of toluol
and acetone, the former as a solvent, and the latter to precipitate the pure gutta-
percha therefrom, substantially as hereinafter described."
2. In the treatment of gutta-percha and like substances, the method of improving
the qualities of the same by increasing the polymerisation, or altering the arrange-
ment of the atoms, by digestion with a suitable polymerising agent, substantially as
described.
3. The treatment of gutta-percha and like substances which consists in first
separating the true gutta-percha gums, and then changing the chemical constitution
of the latter, substantially as hereinbefore described and for the purposes set forth.
111
1000
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.