A Process and Apparatus for Recovering Volatile Solvents from Collodion Coatings of Paper.
Year: 1895

page_text: Date of Application, 15th July, 1895-Accepted; 17th Aug., 1895-
COMPLETE SPECIFICATION.
A Process and Apparatus for Recovering Volatile Solvents from
Collodion Coatings of Paper.
I, HECTOR DE GROUSILLIERS, of 24 Englische Strasse, Charlottenburg near
Berlin, in the Empire of Germany, Engineer, 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 :-
In coating paper with collodion film the substance used for the coating is first
dissolved in a volatile solvent, the resulting solution is then uniformly distributed
or caused to flow over the surface of the paper and, finally, the volatile solvent is
evaporated, leaving the paper coated with a coherent film or pellicle. In order to
recover the solvents, which usually are lost, the coated paper is, according to this
invention, passed through a closed chamber, in which the. vapours are kept in
continuous circulation, the air mixed with the vapours of the solvent being drawn
off to a condenser, and, after the solvent is condensed, the air is reheated and
returned to the closed chamber.
As the circulation takes place through a closed apparatus, very little of the
solvent vapour is lost. The circulation of the air and vapour promotes the drying
of the coating as the paper is drawn slowly through the evaporation chamber.
An apparatus for carrying out this process is shown by way of example, on the
accompanying drawing.
The paper to be coated is drawn from the roller A over the tension rollers a¹, a²,
a³, a' through the slot b into a chamber B; it is there carried along by the endless
felt apron c and finally passes through the slot d over roller e to the winding on
mechanism C.
Collodion solution in the vessel V flows through the pipe v, provided with cock,
on to the paper spreading out on it so as to form a thin coating; if necessary, the
adjustable distributing roller a may be brought into operation. Within the
chamber B, which is closed as tightly as possible, is arranged above the slowly
advancing paper a system of heating tubes, supplied with steam by the pipe f¹;
the chamber B is thus kept at the temperature necessary for evaporating the
solvent.
During the passage of the paper, thinly coated with collodion, through the heated
chamber B, a fan D draws off the air by the pipe h into the condensor F; the air
then returns through the heater E and pipe g into the chamber B, a continuous
circulation being thus carried on. The hot air entering through pipe 9 passes
through the chamber B in a direction contrary to that of the advancing paper and
thus becomes saturated with the solvent vapors arising from the paper coating
which are then carried along with the air to the condenser F, where the vapors
are almost wholly condensed, the liquid passing off through the pipe i into the
collector G.
The air, thus deprived of the solvent vapours, is then caused by the fan D to pass
through the pipe into the heater E where it is heated by steam entering at E¹
and leaving at E2. The air thus heated, containing very little solvent vapour,
passes by the pipe g into the chamber B.
By means of suitable valves, or dampers, the velocity of the circulating air and
vapours may be regulated as desired.
By means of this process and apparatus described not only is the solvent
recovered, except the insignificant loss arising from the apparatus not being

page_text: perfectly tight, but the evaporative action on the coated paper is promoted and
accelerated.
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. The herein described process for recovering volatile solvents used for
applying collodion to paper by passing the coated paper through a closed heated
chamber-B in which hot air entering at g circulates in a direction opposite to that
of the movement of the paper, and whence the air is drawn to a condenser F where
the solvent is condensed, the air then returning through a heater E into the
evaporation chamber B to be again charged with solvent vapour roall
2. The apparatus for carrying out the process set forth in Claim 1, and for
effecting a continuous circulation of air, comprising the evaporation chamber B with
steam pipes f the condenser F the fan D and heater. E and their connecting pipes,
substantially as described with reference to the drawing.
Dated this 15th day of July 1895. .