Radiation imagery chemistry: process – composition – or product th – Nonradiation sensitive image processing compositions or... – Developer
Reexamination Certificate
2001-10-13
2003-04-22
Le, Hoa Van (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Nonradiation sensitive image processing compositions or...
Developer
Reexamination Certificate
active
06551767
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for preparing solutions of p-phenylenediamine color developers in a concentrated free-base form. More particularly the present invention is an improvement in preparing solutions of p-phenylenediamine color developers in a concentrated free-base from a sulfate or chloride acid salt precursor, in a photographically inactive and compatible, water miscible or water soluble, organic solvent.
2. Background of the Invention
The basic processes for obtaining useful color images from exposed color photographic silver halide materials include several steps of photochemical processing such as color development, silver bleaching, silver halide fixing and water washing or dye image stabilizing using appropriate photochemical compositions. Photographic color developing compositions are used to process color photographic materials such as color photographic films and papers to provide the desired dye images early in the photo processing method. Such compositions generally contain color developing agents which act as reducing agents to react with suitable color forming couplers to form the desired dyes.
Color development of an image exposed photographic silver halide element is carried out by contacting the exposed color paper with a color developing composition prepared from the color developer concentrate of the present invention and under suitable time, temperature conditions, and in suitable processing equipment, to produce the desired developed image such as a color print. Additional processing steps can then be carried out using conventional procedures, including but not limited to, one or more development stop, bleaching, fixing, bleach/fixing, washing or rinsing, stabilizing and drying steps, in any particular desired order as would be known in the art.
Suitable color developing agents that are known in the art include aromatic amino color developing agents such as p-phenylenediamines, and particularly the N,N-dialkyl-p-phenylenediamines in which the alkyl groups or the aromatic nucleus can be substituted or unsubstituted. The p-phenylenediamine color developers most commonly present in photofinishing compositions include: N,N-diethyl-2-methyl-p-phenylenediamine monohydrochloride (CD-2); N-ethyl-N-2-(methanesulfonylaminoethyl)-2-methyl-p-phenylenediamine sesquisulfate monohydrate (CD-3); and N-ethyl-N-(2-hydroxyethyl)-2-methyl-p-phenylenediamine sulfate (CD-4), listed here in the commonly used acid salt form.
The photographic finishing industry is comprised of three primary segments: the manufacture of photographic chemicals to supply photochemical formulators, the formulation of these chemicals into useful compositions for photochemical processing, and the processing of sensitized photographic color elements. Formulated photographic processing (photofinishing) solutions provided to the processors are complex, multi-part, multi-component mixtures, the specific compositions of which vary significantly according to the intended use and the formulator.
Color developing compositions are commonly supplied in multiple parts or solutions because of the requirement to separate components which are reactive or unstable over extended periods of time. One part normally includes an acid salt of a p-phenylenediamine color developer, typically in the form of a stabilized aqueous solution. These solutions are acidic since the color developer is formulated in this part as the acid salt. Another part typically contains a base or combination of bases which, upon mixing of the parts, serves to neutralize the acid associated with the part containing the color developer and to establish the desired alkalinity of the mixed color developing composition. These solutions are typically mixed immediately before use. Upon combination of all parts and water, a homogeneous color developing composition can usually be obtained for the working strength solution in the processing machine.
The free-base forms of these color developers are presently industrially processed in solutions as prepared from the acid salt form of the p-phenylenediamine. The free base form of the color developer is prepared by mixing an aqueous solution of the color developer salt with an alkali metal hydroxide, typically sodium hydroxide. For example, U.S. Pat. No. 6,017,687 issued to Darmon et al. on Jan. 25, 2000 and U.S. Pat. No. 6,077,651 issued to Darmon et al. on Jun. 20, 2000 disclose a homogeneous, single-part, color developing concentrate that is prepared using a critical sequence of steps. In the first step, an aqueous solution of the color developing agent containing a preservative is prepared typically from the sulfate salt and an alkali metal base to provide a stoichiometric proportion of alkali metal ions to render the color developer in a free base form in a liquid phase. The addition of an alcohol or glycol solvent forces precipitation of the sulfate salts, which are subsequently removed by filtration. It has been found that due to the particle size of the precipitate, filtration is inefficient, time consuming and generally results in some residual sulfate ions in solution, which these patents teach is detrimental to the composition stability of a photofinishing solution.
The use of such combined photofinishing solutions results in simplicity of operation with a reduction in the potential of mixing errors and poor photo processing results. The major incompatibility of the traditional parts of photofinishing solutions is that between the acidic aqueous part, containing the acid salt of the p-phenylenediamine color developer, and the alkaline part, containing the base or combination of bases. Since the active color developer in the final, mixed photofinishing composition is the free base form of the color developer, full consolidation of parts to produce a single-part formulation requires a source of the p-phenylenediamine color developer in free base form as the necessary ingredient. As used herein, the term “free-base” refers to phenylenediamine compounds devoid, or essentially devoid, of acid addition salts of phenylenediamines.
The industry has investigated the use of both concentrates and solid mixtures (including powders and tablets). In most cases, concentrates are convenient to use but may have high packaging costs compared to powders. Powders permit high concentration, but not every photochemical composition can be dried into a stable powder. Powders present problems with dust, separate packaging needs and more troublesome metering or mixing procedures. In addition not every dry formulation is readily dissolved in water.
Accordingly, there is a need for a method for preparing a single-part color developing composition that is homogeneous, concentrated and stable. Such compositions would reduce the cost of shipping and storage of diluted solutions, avoid the need for mixing multiple parts or agitation of multi-phase compositions, and offer the user a more attractive product. The present invention is directed to meeting this long felt need.
SUMMARY OF THE INVENTION
The present invention provides a method for preparing a homogeneous, aqueous single-part color developing concentrate having at least 0.06 mol/l of color developing agent in the free-base form, an antioxidant and a water soluble hydroxy-substituted organic solvent. The method includes a critical sequence of steps after contacting a sulfate or chloride salt of the color developer with an alkali metal hydroxide comprising: (a) forming liquid free-base and water layers in a suitable container; (b) separating the liquid free-base layer from the water layer; and (c) mixing the liquid free-base with a water miscible or water soluble hydroxy organic solvent. The method may optionally include the step(s) of: (d) heating the liquid free-base and water layers, and (e) water washing the liquid free-base layer after the separating step and separating the wash water from the liquid free-base layer. Preferably, the resulting concentrate is essentially sulfate ion free, that is, th
Boldea Lucian
Hudnall Phillip Montgomery
Niziurski-Mann Renee Ellen
Salyer Michael Wayne
Eastman Chemical Company
Graves, Jr. Bernard J.
Le Hoa Van
Wood Jonathan D.
LandOfFree
Process for preparing p-phenylenediamine color developers in... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for preparing p-phenylenediamine color developers in..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for preparing p-phenylenediamine color developers in... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3040864