EP0049294A4

EP0049294A4 - A system for admixing photographic processing concentrates.

Info

Publication number: EP0049294A4
Application number: EP19810901235
Authority: EP
Inventors: Ross E Rumfola
Original assignee: Eastman Kodak Co
Current assignee: Eastman Kodak Co
Priority date: 1980-04-11
Filing date: 1981-04-10
Publication date: 1984-02-03
Also published as: BR8108311A; IT8121079A1; IT1137540B; IT8121079A0; EP0049294A1; WO1981002850A1; FR2480450A1

Abstract

A method and apparatus for admixing liquid with a shear-thinnable concentrate (11) of photographic processing composition to form a photographic processing solution, in which the concentrate is thinned by shear forces and contacted with the diluting liquid under turbulent mixing conditions to dissolve the concentrate in the liquid and thereby form the solutions. The concentrate, which does not flow and resists deformation under conditions of low shear, is displaced from a tube-like container (13) through an orifice (37) where conditions of high shear render it free-flowing and form a stream. One or more liquid jets (51, 53, 55) are directed at the stream with sufficient force to disperse the concentrate under turbulent mixing conditions. A mixer (57) then completes the dissolution of the concentrate in the liquid.

Description

A SYSTEM FOR ADMIXING PHOTOGRAPHIC PROCESSING CONCENTRATES

The present invention relates to a system for admixing photographic processing concentrates with liquids to form processing solutions, and more specifically for admixing shear-thinnable, processing concentrates having a paste-like consistency. The system comprises a method and apparatus for carrying out the method and a container for use in the method and apparatus. As used herein the term "photographic processing solution is intended to include developing solutions, replenisher solutions, starter solutions, and other working photographic solutions. It is well known to supply photographic processing compositions in concentrated form, including liquids, powders, tablets and even pastes and gels, which are diluted with water to form photographic processing solutions. Due perhaps to the simplicity of the dispensing and mixing equipment, liquid concentrates are generally preferred over the other forms of concentrates by professional photofinishers. In one approach, for example, the liquids are supplied in plastic bottles that are closed by a rupturable membrane and a protective cap. After removing the cap, each bottle is positioned upside-down over a receiving tank where a sharp probe pierces the membrane and releases the liquid. Water is added to dilute the mixture to the proper concentration for a photographic processing solution.

Although liquid concentrates nave been widely accepted, powders have certain advantages, particularly in connection with storage and shipping. Amateur photographers, for example, often prefer the powders for their compact form and long shelf life. Many of the powdered concentrates however are considered difficult to dissolve and dilute. While satisfactory equipment is certainly available for this purpose, it tends to be either bulky or suitable only for small batches, and is not particularly convenient for use by unskilled operators or with high volume automated processing equipment. Additionally, the powders tend to generate dust and spill easily during measuring and mixing.

Some of the problems associated with powders can be alleviated by compressing them into tablets. The tablets, however, are not a viable commercial alternative. The tablets cannot incorporate liquids, and many photographic processing compositions are not amenable to tablet formation. Those that are, usually incorporate binding agents which can make dissolution of the tablet difficult and/or cause undesirable sensitometric effects in processing.

Although effervescing agents have been employed to promote prompt dissolution, they are generally not very effective and introduce additional costs and complexity in the manufacturing operation. Proposals have been made in the past to formulate photographic processing concentrates as paste-like compositions. For example, British Patent 4689 describes black-and-white developer concentrates having the consistency of a paste or cream, Italian Patent 427,967 describes black-and-white developer concentrates which are prepared in paste form, U.S. Patent 2,735,774 describes fixer concentrates of paste-like consistency, and U.S. Patent 2,784,086 describes black-and-white developer concentrates that are formulated in the form of a smooth gel. Although photographic pastes and gels have been considered, the prior art failed to recognize how to use the pastes to obtain the full benefit of their use. The properties of paste formulations disclosed in the art have inhibited their use. It appears that pastes have been dispensed manually from their supply containers and mixed by manual stirring and similar techniques. For this and other reasons most pastes were relatively soft, and contained an undesirable amount of water. Pastes having reduced amounts of water were considered difficult to dissolve and possessed some of the disadvantages of tablets. It will become apparent from the following description that the present invention overcomes many of these disadvantages of the prior art and provides significant advantages not previously available.

In accordance with the present invention, a system is provided for admixing photographic processing concentrates having paste-like consistency with diluting fluids to form photographic processing solutions. The concentrates are stiff pseudo plastic pastes that behave in many respects like a solid, but have shear-thinning characteristics which greatly facilitate dispensing of the concentrates so that when shear thinned and then contacted with a diluting liquid under turbulent mixing conditions the concentrates will readily disperse and dissolve to form solutions.

In accordance with a preferred embodiment of the invention, the paste-like concentrate is discharged from a container through an orifice to form a flowing stream thinned by shear forces in the orifice. The stream passes through a primary mixing chamber where a diluting liquid is introduced in one or more jets that impinge on the stream with sufficient force to disperse the concentrate and bring about intimate contact between the concentrate and the liquid under turbulent mixing conditions. A mixer having internal stationary baffles is employed to effect secondary mixing and complete the dissolution of the concentrate in the liquid.

In the detailed description of the preferred and alternative embodiments presented below, reference is made to the accompanying drawings, in which:

Fig. 1 is a partially cross-sectioned view of a tube-like container of a photographic processing concentrate.

Fig. 2 is a cross-sectional view of a portion of the apparatus for displacing the processing concentrate through an orifice to thin the concentrate with shear forces and for contacting the thinned concentrate with a liquid to bring about intimate contact between the concentrate and the liquid to dissolve the concentrate in the liquid. Fig. 3 is a perspective view of apparatus for admixing a shear-thinnable photographic processing concentrate with a liquid to form a processing solution. Referring to the drawings, a preferred embodiment of a container is depicted in Fig. 1. The container includes a shear-thinnable photographic processing concentrate 11 in a dispenser tube 13 for delivering the concentrate to diluting apparatus 1 5 (Fig. 3).

The photographic processing concentrate includes continuous phases and discontinuous phases combined to form a concentrated highly viscous paste having a physical stability much like a solid. The paste is pseudo-plastic and shear thinnable, i.e. its viscosity is substantially reduced when subjected to shearing such as encountered when the concentrate is displaced through a constricting orifice. Under such conditions of high shear, the concentrate behaves hydraulically more like a fluid. It becomes free flowing and, in the manner described hereinafter, can be readily dispersed and dissolved in a liquid such as water. In other words, the concentrate is highly viscous under low shear conditions but has lower viscosity under high shear conditions.

The photographic processing concentrate per se is described more fully in commonly-assigned, copending U.S. Patent Application Serial No. 139,518 entitled PHOTOGRAPHIC PROCESSING CONCENTRATES, filed in the names of Richard W. Dillon and David A. Miro.ff. In general the processing concentrate contains solid and liquid phases. The continuous liquid phases can comprise a single liquid, or two or more liquids. It can be composed solely of water, or solely of one or more organic liquids, or it can be a mixed aqueous-organic system. The solid phases comprise one or more of the ingredients required for a processing concentrate which are normally solid materials. While liquid or solid ingredients which are not necessary components of the working strength processing solution can be incorporated in the concentrate when needed, it is frequently the case that the concentrate can be prepared solely from the necessary components of the processing solution, without the need to delete any ingredients that would be used in the prior art system of liquid concentrates nor to add any additional ingredients. In other words, formulation of the stable concentrate can be achieved solely by selection of the relative proportions of the ingredients, choice of the particle sizes of the ingredients, and control of the procedure whereby they are combined.

An important feature of the concentrate is its physical stability under conditions of low shear. In this state the concentrate behaves much like a solid. It resists deformation and will not easily spill or pour. These properties are, of course, very favorable for storing and shipping the concentrate, but would normally be thought to make dispensing of the concentrate difficult, especially on a volumetric basis. It has now been found, however, that other properties of the concentrate can be used to facilitate dispensing without requiring the addition of more water. When properly agitated, or otherwise subjected to shearing forces, the concentrate thins and becomes free flowing. The viscosity decreases, the concentrate is easily deformed for movement through tubes and conduits and can be readily dispersed and dissolved in water to form a photographic processing solution.

The particular viscosity and degree of shear-thinning exhibited varies greatly among the very wide range of different processing concentrates. For example, typical concentrates have an apparent viscosity in the range of from about 250 to about 1300 centipoises at a shear rate of 800 reciprocal seconds. At a shear rate of 45O0 reciprocal seconds, an apparent viscosity in the range of from about 100 to about 500 centipoises, respectively, would be typical. These values refer to viscosity measurements made in a HERCULES HI-SHEAR

VISCOMETER (rotational concentric cylinder type) at ambient temperature. During such measurements the rotor or inner cylinder (radius 1.95 cm., height 5.0 cm.) is rotated at a constant angular acceleration of approximately 5.49 rad/sec to a maximum angular velocity of 115 rad/sec. This rotation imparts an increasing rate of shear (maximum 4549 sec ^-1) to the sample which is contained in the annulus between the inner and outer cylinders (annulus width 0.5 cm.). The torque which is transmitted through the sample to the outer cylinder is measured and used in calculation of apparent viscosity as a function of rate of shear.

The term "photographic processing concentrate" is used herein to refer to a material used to develop or otherwise process a photographic element, for example, to develop, fix, bleach, harden, stabilize, and the like. Thus, the processing solutions prepared from the concentrates described herein can be any of the solutions used in processing photographic materials such as, for example, black-and-white developing solutions, color developing solutions, fixing baths, bleaching baths, stabilizing baths, stop baths, nucleating baths, monobaths, bleach-fixes, prehardeners, activators, conditioning baths, toners, neutralizers, and the like.

The container 13 is a relatively thin-walled plastic tube having a neck portion 19 including an opening 20 at one end of the tube, and a pressure applying device, such as a movable cup 21, which fits snuggly inside the body of the tube at its other end. Prior to use, the neck opening is closed by a rupturable membrane 23 and a protective cap 25 to render the container impervious to the inward diffusion of atmospheric gases and the outward diffusion of the concentrate. Thus, the tube protects the concentrate from deterioration and, as will become apparent from the following description, serves to dispense the concentrate to the diluting apparatus. When the cap is removed and the membrane ruptured the concentrate can be displaced from the tube through the opening 20 by applying a force against cup 21. Thus, in addition to the protection the tube provides during storage and shipping of the concentrate, it greatly facilitates dispensing of the concentrate directly to the diluting apparatus without use of intermediate holding canisters or the like. The tube also facilitates volumetric dispensing of the concentrate, i.e. it can easily be dispensed from the container in volumetrically metered quantities while still providing a high degree of uniformity of the active ingredients. Photographic processing chemicals must be dissolved in water or other liquid medium in very precise amounts in order to prepare working processing solutions. Thus, to be commercially useful, a photographic concentrate must not only possess features facilitating packaging, transport and storage, but must be capable of being dispensed in such a way as to ensure the necessary precision in the preparation of working processing solutions. It is particularly advantageous for the photographic processing concentrate to be "volumetrically dispensable." By the term "volumetrically dispensable," as used herein, is meant a concentrate which has flow properties such that it can be dispensed from a container in a metered amount on a volumetric basis, and which has a high degree of uniformity such that each unit volume dispensed contains essentially the same amount of active agents on a weight basis. With such a concentrate, it is possible to combine a predetermined volume of concentrate with a predetermined volume of liquid, e.g., 100 cubic centimeters of concentrate combined with one liter of water, and consistently obtain the same weight of active agents in the resulting working solution.

The dilution ratio employed with the processing concentrate, that is, the amount of water or other liquid used to convert the concentrate to a working processing solution, will vary greatly depending on the nature of the photographic element being processed, the processing procedure, and the particular processing formulation involved. In general, the dilution ratio will be in the range of 1 part of concentrate to 8 parts by weight of liquid to 1 part of concentrate to 100 parts by weight of liquid.

The opening in the tube is constricted relative to the tube body to permit a reasonably- compact configuration while restricting the cross-sectional area through which the concentrate is dispensed to the diluting apparatus. Additionally, and as will become more apparent from the following description of the diluting apparatus, the walls of the tube need not be sufficiently strong to withstand the forces necessary to displace the concentrate from the tube, since the diluting apparatus can provide additional support.

The container is adapted for use with a diluting apparatus including a receptacle 27 for receiving the container a shear thinning area 29 (Fig. 2), a pressure applying mechanism 3JL and one or more mixing chambers 33.

The receptacle includes a cylindrical sleeve 35 which. conforms generally to the configuration of the tube (13) and provides additional support so the tube will not distort under the pressure of the concentrate when it is displaced from the tube. The shear thinning area 29 includes an orifice depicted as a cone-shaped nozzle 37, coupled to the neck of the dispensing tube. In this preferred embodiment, the nozzle is intended to replace the protective cap on the tube. It should be understood, however, that the nozzle could be a part of the tube or it could be incorporated into the mixing apparatus. Similarly, the orifice could have other configurations than a nozzle, such as a circular opening of little or no longitudinal dimension. The nozzle configuration has the advantage of increasing the distance over which the processing concentrate is subjected to shearing, and, when the nozzle decreases in cross-section from the base to the tip, the shearing forces can be increased as the concentrate is thinned. Additionally, the tip of the nozzle can be clipped at a location selected to provide the desired final cross-sectional area. Thus, a single nozzle design could be used for different processing concentrates having different shear-thinning characteristics. Whatever type of orifice is used, it should function to substantially thin the concentrate so that it leaves the aperture as a flowing stream.

The pressure applying mechanism uses water pressure applied against the cup to plastically deform and shear-thin the concentrate while forcing it out of the opening in the neck of the tube through the nozzle. More specifically, cap 41 is clamped to the end of the cylindrical sleeve and engages the end of the tube 13 in a liquid tight seal so the water pressure is applied to the cup through tap hole 43 and water pressure line 45. The mixing chamber 33 actually includes two parts. The first part, a primary mixing chamber 47, has a primary inlet 49 through which the processing concentrate enters and at least one and preferably three secondary inlet jets 51, 53 and 55 for directing a diluting liquid into contact with the concentrate. In Fig. 3 the liquid is directed from the three jets against the center of the shear-thinned processing concentrate, which is dispensed from the end of the nozzle as a flowing stream. The liquid jets impinge on the stream with sufficient force to effect dispersion thereof and to being about intimate contact between the concentrate and the liquid under turbulent mixing conditions. The jets enter the mixing chamber at an angle approximately thirty (30) degrees to the stream of the processing concentrate and are aimed toward its center. Of course other arrangements might also be suitable. For example,, the jets could be oriented at ninety (90) degrees and tangential to the stream. The second part of the mixing chamber is a mixer 57 which communicates with the output of the primary mixing chamber (33) and effects secondary mixing to thereby complete the dissolution of the concentrate in the liquid. Mixer 57 has internal stationary baffles and may take the form of that shown in U.S. Patent 4,093,188.

From the mixing chamber (33), the diluted concentrate (now the processing solution) is directed through a hose 59 and into a collecting tank 61. where it is ready for use.

The method of the present invention in its preferred embodiment thus includes the steps of shearing a shear-thinnable photographic processing concentrate to thin the concentrate and then contacting the thinned concentrate with a diluting liquid under turbulent mixing conditions to form a photographic processing solution. Shearing is accomplished, for example, by forcing the concentrate through an orifice under pressure to form a flowing stream. The stream is dispersed by one or more liquid jets. The dispersed stream is then repeatedly divided in a mixer having internal stationary baffles to further dissolve the concentrate in the liquid.

In its simplest form a premeasured quantity of the concentrate is in the container. The entire contents of the container are then dispensed to the diluting apparatus, which adds a predetermined quantity of the diluting liquid. The addition of the diluting liquid begins preferably simultaneously with the dispensing of the concentrate, and continues for some period after the container is emptied, to ensure that all of the concentrate passes through the mixing chambers to the solution-collecting tank.

It should now be apparent that the system of the present invention provides important advantages for photographic processing that are not available from the teaching of the prior art. The processing concentrate can be supplied and used in a manner that possesses the advantages of both powders and liquids. Prior to thinning, the concentrate is almost like a solid that resists gravitational displacement or spilling and has excellent shipping and storage characteristics. After thinning, the concentrate is free flowing, moves easily through tubes and conduits and dissolves readily in liquids such as water when subjected to turbulent mixing conditions.

Claims

Claims:

1. A method for preparing a photographic processing solution from a shear-thinnable concentrate, said system comprising the steps of: displacing the concentrate from a container through an orifice to shear thin the concentrate and form a flowing stream of the concentrate; and contacting said shear-thinned concentrate with a liquid under turbulent conditions to dissolve said concentrate in said liquid and thereby form said solution.

2. A method according to claim 1 wherein the contacting step comprises impinging a jet of liquid upon said flowing stream of shear-thinned concentrate with sufficient force to disperse said concentrate; and mixing the dispersed concentrate with said liquid to dissolve the concentrate.

3. A method according to claim 2 wherein said jet of liquid is continued for a predetermined time after the container is emptied.

4. A method according to claim 1 wherein said concentrate is supplied in a premeasured quantity and a predetermined quantity of the liquid is added thereto. 5. A method according to claim 2 wherein said thinned concentrate is conveyed into a mixing zone; and at least one jet of liquid impinges on said shear-thinned concentrate with sufficient force to effect dispersion thereof and bring about intimate contact between the concentrate and the diluting liquid within said mixing zone under turbulent mixing conditions, effecting primary mixing of the concentrate with said liquid; and the effluent is directed from said mixing zone to a mixer for secondary mixing of said effluent to complete the dissolution of said concentrate.

6. An apparatus for effecting the method of claim 1 comprising means for forming a constricted orifice; means for moving the concentrate through said constricted orifice to shear thin the concentrate; and mixing means for contacting the shear-thinned concentrate with diluting liquid to disperse and dissolve the concentrate in the liquid and form said solution.

7. Apparatus according to claim 6 comprising a mixing chamber and means for simultaneously introducing the shear-thinned concentrate and the liquid into said chamber for turbulently mixing the concentrate and the liquid.

8. Apparatus according to claim 7 comprising a mixing chamber having a primary inlet adapted to receive said shear-thinned concentrate and at least one secondary inlet, and an outlet; means for introducing the liquid into said mixing chamber through said secondary inlet in the form of a jet which impinges upon said shear-thinned concentrate to effect dispersion thereof and bring about intimate contact between the concentrate and the liquid within said mixing chamber under turbulent mixing conditions; and a mixer, having internal stationary baffles, communicating with the outlet from said mixing chamber for effecting secondary mixing of the effluent from said mixing chamber to thereby complete the dissolution of the concentrate in the liquid.

9. A container of photographic processing concentrate for use with the method according to claim 1 comprising: a concentrate of a shear-thinnable photographic processing composition including at least in major part a discontinuous phase and a continuous phase in proportions which impart to said concentrate the consistency of a paste; a dispenser for delivering said concentrate to a diluting apparatus, said dispenser having a constricted exit opening and means for applying pressure to said concentrate by discharging said concentrate through said exit opening.

10. A container according to claim 9 wherein the exit opening of said dispenser provides a nozzle for cooperating with the diluting apparatus to direct said concentrate to the mixing chamber of said apparatus said nozzle acting to shear-thin said concentrate.

11. A container according to claim 9 wherein said dispenser includes a rupturable seal for closing said exit opening, such that with said seal intact, said container is impervious to the inward diffusion of atmospheric gases and the outward diffusion of said concentrate.

12. A container according to claim 11 wherein said concentrate entirely fills said container to exclude extraneous gases from said container.