System for controlling the composition of color coupler on a real-time basis

A system for controlling the composition of color coupler on a real time basis, the system comprises a mixer for mixing the color coupler with a non-permanent solvent for forming a preliminary solution. A heat exchanger receives the preliminary solution for altering the temperature of the preliminary solution, and a separator receives the preliminary solution from the heat exchanger for separating the preliminary solution into a color coupler solution suitable for use in producing photographic paper and into a residual vapor. An in-line viscometer receives the color coupler solution from the separator for determining the viscosity of the color coupler solution, and a process control system alters the temperature of the heat exchanger in response to a signal received from the viscometer for optimizing the composition of the color coupler solution.

FIELD OF THE INVENTION 
The invention relates generally to the field of color coupler for use in 
producing photographic paper and, more particularly, to a system for 
controlling on a real-time basis the composition of such color coupler 
during its production. 
BACKGROUND OF THE INVENTION 
A typical process for producing color coupler includes inserting a 
composition of color coupler, any permanent organic solvent, ethyl 
acetate, water, gel and surfactant into a heat exchanger for controlling 
its temperature. A flash separator receives the above-described 
composition for separating it into a color coupler solution that is 
suitable for use in producing photographic film and into a residual vapor, 
ethyl acetate and water. The color coupler is passed out of the separator 
via a drain pipe to a dispersion tank for storing it for later use in 
producing photographic film. The residual vapor is vented out of the 
separator to a recovery system via a vapor pipe. 
A pressure sensor and a temperature sensor are both connected to the vapor 
pipe of the separator for respectively measuring the pressure and 
temperature of the residual vapor. These process measurements of the 
residual vapor are substantially the same as the color coupler solution, 
and this, consequently, permits these process variables to be used as an 
indication of the pressure and temperature of the color coupler solution. 
A programmable logic controller (PLC) receives both of these signals for 
determining if they are within predetermined ranges, and if they are not, 
the PLC sends a signal for modifying them. In regard to the temperature, 
the PLC sends a signal to a control valve attached to the heat exchanger 
for modifying the vapor temperature of the mixture passing therethrough 
for altering it so that it is within its range. To modify the pressure, 
the PLC sends a signal to an air bleed valve that is attached to the vapor 
pipe for altering the pressure so that it is in its range. 
Although the presently known and utilized system for controlling the 
production of color coupler solution is satisfactory, it is not without 
shortcomings. The actual impact of the modification of either process 
parameter (i.e., temperature or pressure) on the color coupler 
composition, although theoretically known, is immeasurable for verifying 
the theoretical results. Hence, process disturbances may lead to 
unpredictable variations in the final color coupler concentration. In 
addition, such control schemes include time delays because of the 
limitations of devices used for measuring the process. 
Consequently, a need exists for improvements in the process control system 
and its mode of operation so as to overcome the above-described 
shortcomings. 
SUMMARY OF THE INVENTION 
The present invention is directed to overcoming one or more of the problems 
set forth above. Briefly summarized, according to one aspect of the 
present invention, the invention resides in a system for controlling the 
composition of color coupler on a real time basis, the system comprising 
(a) means for mixing the color coupler with a non-permanent solvent for 
forming a preliminary solution; (b) a heat exchanger which receives the 
preliminary solution for altering the temperature of the preliminary 
solution; (c) a separator for separating the preliminary solution into a 
color coupler solution suitable for use in producing photographic paper 
and into a residual vapor; (d) an in-line viscometer which receives the 
color coupler solution from said separator for determining the viscosity 
of the color coupler solution; and (e) means for altering the temperature 
of said heat exchanger in response to a signal received from said 
viscometer for optimizing the composition of the color coupler solution. 
It is an object of the present invention to provide a process of producing 
color coupler solution which includes real time process control. 
It is an object of the present invention to provide a method of producing a 
color coupler solution which provides for direct product measurement and 
control. 
It is an advantage of the present invention to provide a process control 
system which is easily and efficiently retrofitted with the present 
invention. 
It is a feature of the present invention to provide an in-line viscometer 
which receives the color coupler solution from the separator for 
determining the viscosity of the color coupler solution. 
The above and other objects of the present invention will become more 
apparent when taken in conjunction with the following description and 
drawings wherein identical reference numerals have been used, where 
possible, to designate identical elements that are common to the figures.

DETAILED DESCRIPTION OF THE INVENTION 
Referring to FIG. 1, there is illustrated a system 10 for producing color 
coupler. An oil phase solution including a coupler, a permanent solvent 
and ethyl acetate non-permanent solvent is inserted into a homogenizer 
vessel 20 for mixing it with an aqueous phase solution of water, gel and 
surfactant, which is also inserted into the vessel 20. The vessel 20 mixes 
the solution and passes it into a heat exchanger 30 for providing the 
mixed solution with a predetermined temperature and pressure. 
A temperature control scheme system 40 is attached to the heat exchanger 30 
for permitting control of the temperature within the heat exchanger 30. In 
this regard, a hot water heat exchanger 50 is attached to the heat 
exchanger 30 via a circulation loop 60, and includes water therein for 
circulating the water through the heat exchanger 30. Steam is injected 
into the water heat exchanger 50 for enabling the water temperature to 
become higher, and consequently, raising the temperature of the mixed 
solution passing therethrough. A motorized control valve 80 is inserted 
into a portion of the circulation loop 60 for controlling the flow of the 
water therethrough. This permits the water temperature of the heat 
exchanger to be lowered by restricting the flow of water through the 
circulation loop 60. The pressure is monitored by a pressure sensor 81 
which sends a signal to a PLC 82 for controlling the pressure by an air 
bleed valve 83 connected to a vacuum pump 84, as well known in the art. 
A flash separator 90 is connected to the heat exchanger 30 via a process 
pipe 100 for receiving the mixed solution therefrom. The separator 90 
vents a residual vapor including ethyl acetate and water to a recovery 
system (not shown) via a vent pipe 110, and passes a liquid solution, 
color coupler solution, which is useful in the production of conventional 
photographic film to a dispersion tank 120 via an outlet pipe 130. 
An in-line viscometer 140 is inserted into the outlet pipe 130 for 
measuring the viscosity of the color coupler solution. The preferred 
viscometer 140 is a "SOFRASER" viscometer, although any suitable 
viscometer may be used. In-line, when describing the viscometer, is 
defined herein as meaning direct measurement of the final product of the 
liquid of interest. The viscosity is used as an indication of the 
composition of the color coupler solution passing therethrough because of 
known relationship between viscosity and oil phase volume fraction of the 
color coupler solution. Referring briefly to FIG. 2, a chart is 
illustrated showing viscosity versus oil phase volume fraction for 
graphically illustrating this known relationship. Referring back to FIG. 
1, a signal representative of the measured viscosity is sent to a 
programmable logic controller (PLC) 150 for comparing the received signal 
with a predetermined range that is pre-programmed into the PLC 150. The 
predetermined range is determined from the chart of FIG. 1 so that the 
viscosity range is set to correspond to the desired oil phase volume 
fraction range and, consequently, to the desired composition of the color 
coupler solution. One skilled in the art will readily recognize how to 
determine the range so that it is suitable for their particular use. 
If the viscosity is out of the predetermined range, for example the 
viscosity is higher than the desired viscosity, the PLC 150 sends a signal 
to the motorized control valve 80 for instructing it to further close for 
restricting the flow therethrough. This, in turn, lowers the temperature 
of the vapor in the flash separator 90 and, consequently, the mixed 
solution therethrough. As a result, the viscosity of the mixed solution is 
lowered or, in other words, its composition is altered to the desired 
composition. 
If the viscosity of the color coupler passing through the viscometer 140 is 
lower than the desired viscosity, the PLC 150 signals the control valve 80 
to further open for permitting less restricted flow therethrough. This, 
ultimately, permits the composition of any incoming mixture to the 
separator 90 to be altered to the desired composition of color coupler 
solution. 
The invention has been described with reference to a preferred embodiment. 
However, it will be appreciated that variations and modifications can be 
effected by a person of ordinary skill in the art without departing from 
the scope of the invention. 
Parts List: 
10 system 
20 vessel 
30 heat exchanger 
40 control scheme 
50 hot water exchanger 
60 circulation loop 
80 control valve 
81 pressure sensor 
82 PLC 
83 valve 
84 vacuum pump 
90 flash separator 
100 process pipe 
110 vent pipe 
120 dispersion tank 
130 outlet pipe 
140 viscometer 
150 programmable logic controller