IMPROVEMENTS IN THE MANUFACTURE OF IMITATION LEATHER OR LEATHER CLOTH, AND IN APPARATUS THEREFOR
Year: 1880

page_text: PROVISIONAL SPECIFICATION left by Gerard Wenzeslaus von Nawrocki
"
at the Office of the Commissioners of Patents on the 20th December 1880.
A communication from Ewald Fischer, of Kaltwasser, near Wüste-Giersdorf,
and from the Firm of M. E. Cohn and Wollheim, of Berlin, both in the German
Empire.
GERARD WENZESLAUS VON NAWROCKI, of the Firm of J. Brandt and
G. W. v. Nawrocki, of 124, Leipzigerstrasse, Berlin, Germany, Patent Agent.
'IMPROVEMENTS IN THE MANUFACTURE OF IMITATION LEATHER OR LEATHER
CLOTH, AND IN APPARATUS THEREFOR." A communication from Ewald Fischer,
of Kaltwasser, near Wüste-Giersdorf, and from the Firm of M. E. Cohn and
Wollheim, of Berlin, both in the German Empire.
This new process for producing imitation leather differs from all processes as yet
known mainly through the peculiar combined application of baths which contain
chromic acid salts and such as contain leather glue mixed with glycerine, through
which baths the fabric serving as a backing to the imitation leather is drawn so
that the different substances are deposited on the same, which have to form the
artificial leather face or surface.
While these operations all take place in a dark room, or at least in a room to
which direct light is not accessible, the leather is, after the outward form has been
given to it by pressing and otherwise, exposed to the daylight, or to artificial
light, such as electrical light, which renders the chromglue or other compounds
insoluble.
It is of great importance that the leather should not be exposed to the light
before all other operations have been performed therewith, as only then the various
materials deposited thereon can enter into intimate combination. If, for instance,
a layer of chrome were put on afterwards and then again exposed to the light then
there would be no combination between the last layer and the previous one. As
the chromglue and the other materials are deposited direct on the fabric a more
intimate combination is obtained with the fibre than if the chromglue and materials
were first prepared and then put on as heretofore.
The fabric is drawn through a vessel in which there is a solution of 1 part
bichromate of kalium (K, Cr, O) in about 45 parts water of about 111° Fahrenheit.
The material is brought through this chrom bath at such a rate that it is
impregnated enough with chrom salt, while the superfluous solution is pressed out
by the material passing through the two rollers and flows back in the vessel.
Of course another bichromic salt could be used in the producing of the chrom bath,

page_text: but the bichromate of kalium is the most advantageous compound. Before
completely drying the material impregnated with the solution it is brought through
a second reservoir, in which there is a mixture of 1 part glue with 6 parts water
and 1 part glycerine.
For producing the glue waste pieces of leather may be used, and the constituent
parts of the second bath are previously equally distributed in the bath by a couple
of hours' boiling and kept at a temperature of about 167° Fahrenheit by a steam
pipe. The material coming out of this glue glycerine bath is passed through two
rollers, which remove all superfluous matter; after this the material passes over
a highly heated metal plate. The heating of the metal plate can either be produced
by direct heating or by means of steam or hot gas.
By the heat radiating from the plate the solution of glue and glycerine is nearly
freed from water.
If stronger leather has to be manufactured the prepared fabric is allowed to go
through a second glue glycerine bath and to dry; eventually a third and fourth
glue and glycerine bath can be used. To this second bath antiseptic means may
advantageously be added, such as salicylic acid, or birch tar, about 100 parts glue
to part of these substances, or 100 parts glue to 12 parts poppy seed oil, or
linseed oil, and 2 parts turpentine, by which means the leather is protected against
rotting and allows of being easily covered with fatty colors or blackings.
The material is now passed through a bath which contains a solution of tannin
(1 part tannin to 25-30 parts water), by which a weak preparatory tanning of the
glue takes place, so that the mass already deposited becomes somewhat more
consistent. The material then passes the pressing rollers and reaches the second
chrom bath, which contains 1 part bichromate of ammonium (NH, Cr, O,), 25 parts
water, 1 part sal ammoniac, and 1 part alcohol. This bath is kept at the temperature
of about 50° Fahrenheit by a cooling pipe in order to hinder the dissolving of the
glue layer. When the material comes out of this bath it is dried over the plate, it
is smoothed by rollers, after which it passes through two rollers heated by steam
or hot gas which are provided with the pattern on their surface that the leather is
to receive.
All these operations must take place in such manner that the material is not
exposed to the direct light, but the material may be exposed to a faint light before
passing through the pattern rollers.
The material is now wound up and then exposed to the direct sun or daylight
or another source of light which is able to effect the chemical change of the chrom
glue. This process lasts one or more days to 6 weeks or longer according to the
strength of the material, and of course the length of time depends essentially upon
the strength of the source of light, so that no general rule can be given.
Materials that only have to be prepared on one side must not go through the
glue and glycerine bath, but must be kept floating on the surface.
In the production of very fine glazed materials correspondingly large glass plates
are used, which are covered with a solution of 1 part wax in 50 parts benzine;
further, 1°, slightly nitrous cellulose is put in the last bath. Before the material is
put on the glass plate it is damped in a bath which contains 12 parts alcohol, 4 parts
sulphur ether; this bath has a weak dissolving action and gives the surface a
greater power of resistance.
The finished materials manufactured in the manner described have the property
that they do not dissolve in hot or cold water and are unaffected even by weak
acids. They are suitable as substitutes for real leather, for materials for water proof
capes, driving straps, packing and joint rings for hot and cold water hose pipes,
fire buckets, and many other useful articles.