Improvements in the Manufacture of Methyleneditannic Acids from Formaldehyde and Tannin
Year: 1897

page_text: "Improvements in the Manufacture of Methyleneditannic Acids
from Formaldehyde and Tannin."
I, DR. ERNST HEINRICH CARL DÜRKOPF, of 52 Rossdorferstrasse, Darmstadt, in the
Empire of Germany, Chemist, do hereby declare the nature of this invention to be as
follows:-
By the method described in the specification of a former British Patent No. 816
of the 11th January 1896, methyleneditannic acids, that is to say products of
condensation from formaldehyde and tannins, are obtained by the mutual action of
formaldehyde and tannic acid upon each other in the presence of a condensing agent,
such as for instance concentrated hydrochloric acid.
By this method the formation of the products of condensation, which are designed
to be used as disinfecting agents and as initial material for the manufacture of
colouring matters, is effected by the condensing agent added thereto. Experiments
have shown that heating under pressure likewise effects the formation of such
products of condensation without adding special condensing agents, and may
therefore take the place of the latter. According to the present invention the agents
used in conformity with the aforesaid former Patent No. 81606 and designed to be
added as condensing agents are rendered superfluous by substituting pressure for the
heating of the two reaction materials mixed with each other (formaldehyde and
tannin).
It is then only necessary to heat the tannin (for instance gallotannic acid,
myrobalenetannic acid, quebrachotannic acid, ratanhiatannic acid or corresponding
aqueous vegetable extracts containing tannin) together with the molecular quantity
of paraformaldehyde (or the corresponding quantity of the customary 40% solution
of formaldehyde) in a boiler for several hours to about 100 degrees Centigrade,
whereupon the insoluble product which has been formed is freed from the remainder
of the liquor by washing and pressing. The products thus obtained and dried
resemble as regards their properties the compounds produced according to the method
described in the specification of the said patent No. 816 of 1896.
Example: 22 Kilogrammes of tannin and 1 Kilogramme of paraformaldehyde are
heated for hours in a boiler to 100 degrees Centigrade; then the product of reaction
which has cooled down is mixed with water, pressed in the filter press, washed, and
again pressed, whereupon the washed product is dried.
Dated this 12th dow of March 1897

page_text: 66
'Improvements in the Manufacture of Methyleneditannic Acids
from Formaldehyde and Tannin."
I, DR. ERNST HEINRICH CARL DÜRKOPF, of 52 Rossdorferstrasse, Darmstadt, in the
Empire of Germany, 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 :--
By the method described in the specification of a former British Patent No 816 of
the 11th January 1896, methyleneditannic acids, that is to say products of condensa-
tion from formaldehyde and tannins, are obtained by the mutual action of formalde-
hyde and tannic acid upon each other in the presence of a condensing agent, such as
for instance concentrated hydrochloric acid.
By this method the formation of the products of condensation, which are designed
to be used as disinfecting agents and as initial material for the manufacture of
colouring matters, is effected by the condensing agent added thereto. Experiments
have shown that heating under pressure likewise effects the formation of such
products of condensation without adding special condensing agents, and may there-
fore take the place of the latter. According to the present invention the agents used
in conformity with the aforesaid former Patent No. 816% and designed to be added
as condensing agents are rendered superfluous by substituting pressure for the
heating of the two reaction materials mixed with each other (formaldehyde and
tannin).
It is then only necessary to heat the tannin (for instance gallotannic acid, :
myrobalenetannic acid, quebrachotannic acid, retanhiatannic acid or corresponding
aqueous vegetable extracts containing tannin) together with the molecular quantity
of paraformaldehyde (or the corresponding quantity of the customary 40% solution
of formaldehyde) in a boiler for several hours to about 100 degrees Centigrade,
whereupon the insoluble product which has been formed is freed from the remainder
of the liquor by washing and pressing. The products thus obtained and dried
resemble as regards their properties the compounds produced according to the method
described in the specification of the said patent No 816 of 1896.
Example 22 Kilogrammes of tannin and 1 kilogramme of paraformaldehyde are
heated for 5 hours in a boiler to 100 degrees Centigrade; then the product of reaction
which has cooled down is mixed with water, pressed in the filter press, washed, and
again pressed, whereupon the washed product is dried.
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 :-
The method, described in the first claim of former patent No 816 dated the 11th
January 1896, of manufacturing methyleneditannic acids, that is to say products of
condensation from formaldehyde and tannins, modified in such a manner that the
mixture of formaldehyde and tannin solution is heated under pressure, thereby
enabling the addition of a condensing agent, such as for example concentrated
hydrochloric acid to be dispensed with.
HASELTINE LAKE & Co.
45 Southampton Buildings, London, W.C. Agents for the Applicant.