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BACKGROUND OF THE INVENTION
1. Field of the Invention
N,N, disubstituted p-phenylenediamine color developing agents, their
incorporation as a principal functional component of a liquid packaged
developer concentrate, their incorporation in color developing working
solutions (baths) and their use in the color development of colored film.
2. Description of the Prior Art
The formation of colored negative or positive images from exposed
sensitized silver halide color emulsions is a demanding process which
requires a high degree of purity in the color developing solutions. The
chemistry and physics of the process are described by J. R. Thirtle and D.
M. Zwick in Kirk-Othmer "Encyclopedia of Chemical Technology", Volume 5,
pages 812-845 (2nd edition). The process is applicable to the developing
of photographic color negatives, photographic color positives,
photographic color plates and colored cinematographic films. The
developers currently and for many years past used in the trade to process
such emulsions contain as the color developing agent N,N disubstituted
p-phenylenediamines. In the course of color development, the color
developing agent reacts with phenolic or active methylene couplers that
are incorporated in sundry layers of the emulsion on a transparent base or
paper and forms non-diffusing dyes that constitute the final image.
Such color developing agents, when in contact with exposed silver halide,
distributed in three separate emulsion layers, undergo oxidation to
quinone diimines which, in turn, condense with the three different color
couplers, each of which is present in a different emulsion layer. The
amount of quinone diimine formed is directly proportional to the amount of
silver halide that has been exposed and, therefore, determines the amount
and, hence, the intensity, of dye that is formed. This process is known as
oxidative coupling. The combination of the layers of yellow, cyan and
magenta dyes in amounts determined by the exposed silver halide can be
made to reproduce with a high degree of faithfulness the colors of the
photographed subject.
Any degradation of the color developing agent affects the amount of dye
formed and the degradation products may adversely affect the color of the
dye formed and also the degraded color agent may diffuse throughout a
given layer to develop color in non-exposed areas. It will be appreciated
by those skilled in the art that N,N, disubstituted p-phenylenediamines as
color developing agents are characterized by their ability to condense
with color couplers in the immediate vicinity of exposed silver halide
grains and not to diffuse, whereas degradation products may not be
characterized by such non-diffusibility and, hence, can result in
non-selective dye formation.
From a practical point of view, the choice of developing agents is limited
because of the characteristics demanded of the dyes, among others, optimum
spectral characteristics and resistance to fading, bearing in mind that
the most widely distributed color films are made by and under the control
of a single manufacturer, so that the color developing agents are
specifically tailored to the existing color couplers present in such
emulsions in order to form the correct dyes, or because of characteristics
demanded of the color developing agents such as non-allergenicity.
One particular N,N, disubstituted p-phenylenediamine color developing agent
has gained wide acceptance in the trade and is the color developing agent
recommended by the single manufacturer for color developing its color
film. This is 4-amino-N-ethyl, N-beta methanesulfonamidoethyl-m-toluidene,
hereinafter denominated as AEMT. This compound also is known as 4-amino,
3-methyl,N-ethyl,N-beta methanesulfonamidoethyl aniline. AEMT has the
following structural formula:
##STR1##
As a sesqui-sulfate monohydrate of the aforesaid free base, the color
developing agent is marketed under the designation CD-3 and is used in a
majority of color photographic processes developed by Eastman Kodak
Company. Other N,N, disubstituted p-phenylenediamine color developing
agents have been proposed, but none has found as wide an acceptance as
CD-3 and, in the present market, CD-3 is the color developing agent of
choice despite the fact that other N,N, disubstituted p-phenylenediamines
are well known for the sample purpose. Typical of other N,N, disubstituted
p-phenylenediamine color developing agents that form non-diffusing dyes
with phenolic and active methylene couplers are N,N
diethyl-p-phenylenediamine monohydrochloride [known in the trade as CD-1];
4-amino-3-methyl-N-ethyl-N-beta hydroxyethyl aniline sulfate [the free
base, as distinguished from the sulfate salt, is known as AMEHEA, the
sulfate salt is known in the trade as CD-4];
2-amino-5-diethyl-amino-toluene [known as ADAT, the hydrochloride salt is
known in the trade as CD-2]; and similar N,N, disubstituted
p-phenylenediamine color developing agents such, for example, as those
disclosed in U.S. Pat. Nos. 2,552,241; 2,566,271 and 3,658,525, and in an
article entitled "CHEMICAL CONSTITUTION, ELECTROMECHANICAL, PHOTOGRAPHIC
AND ALLERGENIC PROPERTIES OF p-AMINO-N-DIALKYL-ANILINES" (sic) published
in the Journal of the American Chemical Society, Volume 73, Pages
3100-3125 (1951).
As mentioned above, the color developing agent of primary commercial
interest is, and for some time past has been, the sesqui-sulfate
monohydrate of AEMT. This salt is itself a color developing agent.
However, it does not constitute, as such, a color developer, that is to
say, a working bath for the color development of a color film, but is a
necessary ingredient of a color developer. In some commercial color
processes it is the practice to segregate different constituents of a
working color developer bath into separate components (compositions), each
of which is concentrated as far as is practical, and each of which is
liquid to facilitate mixing and dilution with water (upon occasion some of
the components may be dry), and each of which is compartmented, that is to
say packaged in a receptacle separate from other packaged components, all
of the packaged components of a developer usually being contained in a
single box. Any given component need not be, and usually is not, composed
of a single ingredient such, for example, as a color developing agent. It
is common, for example, to include a liquid solvent which may be water
and/or an organic solvent and/or a solubilizing agent and/or a mixture of
different liquids as an ingredient of each component. The organic solvent
and/or solubilizing agent, if present, may have as their sole function
that of a carrier or they also may have a photographic function such, for
example, as boosting the dye formed when the color developing agent reacts
with a color coupler. Additionally, there are various adjuvants which are
used in a working color developer bath, examples of which are pH buffering
systems, preservatives, sequestrants, anti-foggants, enhancers, and the
like. Some of these require different solvent systems and, for such
reason, are separately compartmented. Others tend to be unstable when kept
for periods of time in the same compartment with different ones of the
compounds used. Others have a tendency to react with different ones of the
compounds used. Others require the presence of co-solvents, etc. Hence,
separate compartmenting of different components is an accepted practice in
the art. The principles involving separate compartmentation and
concentrating and allocation of different compounds to different
compartments, as well as the concept of mixing the different compartmented
compounds and diluting the same with water at the time of use, are well
known.
In connection with the color developing agent of principal interest, CD-3,
the color developing component which includes the color developing agent
is, in its concentrated form, dissolved in water and pre-packaged;
subsequently, the concentrated color developing component is, as indicated
above, added to other concentrated components and diluted with water to
form a working bath. It has been found that when CD-3 is used, a
protective agent must be employed in the color developing component
(concentrate) containing the same to prevent immediate initiation of the
decomposition of the color developing agent by aerial oxidation.
Conventionally, this has been done by adding an alkaline bisulfite or
sulfite, usually an alkaline metal bisulfite or sulfite, to the color
developing component as an element thereof. The term "alkaline" includes
such moieties as alkali metals, quaternary ammoniums, amines, etc.
A color developing concentrated component so composed and stored in a fully
closed container undergoes slow decomposition and this decomposition is
accelerated if the concentrate has its temperature raised by storage in a
warm or even hot environment. Such slow decomposition is inevitable in
commercial practice because, after the concentrate is prepared at a
factory, it is conventional to store the same at a warehouse near the
point of manufacture, then to ship it to distribution points where, again,
it is stored until withdrawn upon order. Thereafter, it is trucked to a
retail outlet where it is put in a back room for a considerable time,
after which it is moved onto retail shelves where it awaits purchase by
members of the public or by photographic processors. The prevailing
temperature at each of its points of repose obviously is beyond the
control of the manufacturer and, because of extremely wide geographic
distribution, the color developing concentrate inevitably is subjected to
warm and hot environments so that decomposition, if it is to take place,
must occur. The exact nature of such decomposition is not fully understood
by the present inventors, but it is theorized that it involves reactions
between the sulfur/oxygen moieties present in the concentrate which, in
turn, may in part turn upon the proportions between the color developing
agent and the preservative. In any event, the photographic consequences of
the decomposition are easily measured and it is these consequences which
limit the shelf life of such concentrates, to wit, of a CD-3/sulfite
concentrate.
When a container having such a CD-3/sulfite concentrate is opened and
exposed to air, two disadvantageous reactions occur in addition to the
previous in-package slow decomposition. One of these further reactions is
that the liquid concentrate immediately evolves sulfur dioxide gas and, at
the same time, the sulfite (or bisulfite) in the solution starts to
decompose continuously and rapidly at a rate much faster than
decomposition took place in the closed container. This decomposition
proceeds until the sulfite or bisulfite is fully depleted. The second
reaction is that exposure to air causes oxidation of the color developing
agent. Initially, decomposition is comparatively slow due to the
protective effect of the sulfite or bisulfite, but as this anti-oxidant
depletes, the oxidation of the developing agent accelerates quite quickly
until the decomposition proceeds very rapidly when the bisulfite/sulfite
in the container diminishes to zero.
The decomposition of the color developing agent leads to the production of
false colors, non-selective dye formation and fog in any color emulsion
which is developed therewith. The evolution of sulfur dioxide gas from the
concentrate when the container is opened is considered highly
objectionable due to both the sharp pungent odor of the gas and to its
lacrimating action.
The decomposition of the color developing agent and of the preservative
could be somewhat reduced if the color developing component were not
highly concentrated, but manufacturers and users find it advantageous, for
reasons mentioned earlier, to make and use a color developing component
which is as concentrated as it is reasonably possible to make. The
concentration is limited practically by factors such as increase in
viscosity to the point that the concentrate cannot be poured out of its
container with ease, or there is too much of a tendency to retain some of
the concentrate as a thick film on the walls of the container, or the
viscosity becomes so high that dilution with water to form the working
bath becomes overly difficult. Increase in concentration is also limited
by the decomposition just discussed.
SUMMARY OF THE INVENTION
1. Purposes of the Invention
It is an object of the invention to provide a new type of color developing
agent which eliminates some of the foregoing drawbacks and substantially
reduces others.
It is another object of the invention to provide a new chemical compound
having as its presently-known primary use the employment thereof as a
color developing agent.
It is another object of the invention to provide a color developing
composition in concentrated liquid form having as a novel component
thereof a unique new color developing agent.
It is another object of the invention to provide a color developing working
bath which employs the new type of color developing agent in lieu of the
previous type of color developing agents but which can be used in place of
such former type of color developing agents without having any deleterious
photographic effects.
It is another object of the invention to provide a method of color
developing a color emulsion in which method the new type of color
developing agent is employed.
Other objects of the invention in part will be obvious and in part will be
pointed out hereinafter.
2. Brief Description of the Invention
The new color developing agent is an N,N, disubstituted p-phenylenediamine
salt of a phosphoric acid selected from the group consisting of
orthophosphoric acid, pyrophosphoric acid and polyphosphoric acid
containing the equivalent of from about 105% to about 115% orthophosphoric
acid. Such salt is far more stable than sulfuric and hydrochloric acid
salts of N,N, disubstituted p-phenylenediamines when incorporated in
aqueous concentrates. The new salt is quite stable even in the absence of
anti-oxidants such as ascorbic acid, sulfites and bisulfites, although its
stability is slightly improved by the presence of such antioxidants.
Working baths containing the new color developing agents produce true
color values and, where the concentrates are stored for a considerable
period of time prior to use, the deterioration thereof is so minimal that
when subsequently incorporated into a working color developer bath, the
differences in colors are so slight as to be acceptable and, indeed, are
considerably less than the differences in colors encountered with previous
color developing agents used either with or without an anti-oxidant.
The new salts may be formed by reacting an N,N, disubstituted
p-phenylenediamine free base with an acid of the type described, the acid
preferably being somewhat in excess, an accepted range being one mol to 3
mols of acid to one mol of the free base, and a preferred ratio being
about a 5% excess of the acid above the stoichiometric ratio. The
stability of the salt in a concentrated aqueous solution is somewhat
increased where the acid is present in excess of the stoichiometric
amount. The concentrate is in the form of an aqueous solution of the new
color developing agent. However, the solution also may include a
preservative or other adjuvants which can be dissolved in water and which
will not react with one another or with the color developing agent.
Additionally, co-solvents may be included both for their usefulness in the
working bath ultimately to be made and to enable additional compounds to
be included in the concentrate, so that the number of packages, the
contents of which are to be mixed together and diluted in water to make a
working solution, can be kept to a minimum. The working bath made with the
use of the concentrate containing the new color developing agent is
employed for color developing in a working bath in a manner which does not
differ from that practiced with working baths presently employed using
other color developing agents except, of course, that the fidelity of
color reproduction using the new color developing agent is considerably
less degraded by storage of the concentrate prior to use. It also is
within the scope of the present invention to employ derivatives of the new
type of concentrate, to wit, derivatives of phosphate salts of N,N,
disubstituted p-phenylenediamine, and specifically, alcoholates of such
salts, these being described and claimed in application Ser. No. 335,341
filed by Harry Kroll and Alderic R. Therrien on Feb. 23, 1973 for
ALCOHOLATES ORTHOPHOSPHATE SALTS OF 4-AMINO, 3-METHYL, N-ETHYL, N-BETA
METHANESULFONAMIDOETHYL ANILINE, now U.S. Pat. No. 3,875,227 granted Apr.
1, 1975. This type of derivative likewise is soluble in water and can be
used whenever the phosphate salts themselves can be employed. A maximum
workable concentration for the new salts in aqueous solution is about 50%
by weight.
The invention consists in the compounds, compositions, concentrates and
methods which will be hereinafter described and of which the scope of
application will be indicated in the appended claims.
PREFERRED EMBODIMENTS OF THE INVENTION
The primary novelty of the present invention resides in the unique
photographic characteristics of N,N, disubstituted p-phenylenediamine
salts of a phosphoric acid selected from the group consisting of
orthophosphoric acid, pyrophosphoric acid and polyphosphoric acid
containing the equivalent of from about 105% to about 115% orthophosphoric
acid and water-soluble derivatives of such salts. Their unique
characteristics make these salts highly advantageous for use as a color
developing agent, particularly in a concentrated aqueous solution thereof,
so that the same can replace N,N, disubstituted p-phenylenediamine salts
in present-day commercial use, specifically as a replacement for CD-3
which is the sesqui-sulfate monohydrate salts of 4-amino-N-ethyl, N-beta
methanesulfonamidoethyl-m-toluidene.
A suitable method of preparation for the new color developing agent is, at
ambient temperature and pressure, to dissolve 42.5 grams of 85%
orthophosphoric acid (a water solution containing 85% by weight of
orthophosphoric acid) in 100 milliliters of water, and then, at ambient
temperature and pressure, to dissolve in said dilute water solution of
phosphoric acid 100 grams of AEMT, adding enough water for the purpose of
further dilution to make up 200 milliliters of solution. The amount of
phosphoric acid employed is slightly in excess of the amount required
stoichiometrically to neutralize the free base AEMT. The AEMT and
additional water can be added gradually over a period of a few minutes or
they can be added all at once. Desirably, the water solution of the two
compounds is stirred to facilitate the neutralization reaction. There thus
is formed a concentrate subsequently, referred to as I, which contains 50%
weight per unit volume of AEMT on a free base basis. Reference is made to
this particular concentration because it subsequently will be compared
with similar concentrations of AEMT utilized in the form of CD-3, to wit,
a sesqui-sulfate monohydrate of AEMT both with and without an anti-oxidant
and with a concentrate of an alcoholate of the new phosphate salt.
The foregoing example is exemplificative of a suitable method for preparing
a color developing agent pursuant to the present invention. AEMT is only
one of many N,N, disubstituted p-phenylenediamines which can be similarly
prepared in the form of a phosphate salt by the foregoing method. Other
N,N, disubstituted p-phenylenediamines have been mentioned previously and
constitute N,N, diethyl-p-phenylenediamine;
4-amino-3-methyl-N-ethyl-N-beta hydroxyethyl aniline;
2-amino-5-diethyl-aminotoluene; and N,N, disubstituted p-phenylenediamine
color developing agents such as those disclosed in U.S. Pat. Nos.
2,552,241; 2,566,271 and 3,658,525, and in an article entitled "CHEMICAL
CONSTITUTION, ELECTROMECHANICAL, PHOTOGRAPHIC AND ALLERGENIC PROPERTIES OF
p-AMINO-N-DIALKYLANILINES" (sic) published in the Journal of the American
Chemical Society, Volume 73, pages 3100-3125 (1951).
The same reaction method between an acid and an N,N, disubstituted
p-phenylenediamine is practiced when preparing the other phosphate salts
of N,N, disubstituted p-phenylenediamine color developing agent such, for
instance, as pyrophosphoric salts and polyphosphoric salts of N,N,
disubstituted p-phenylenediamines. It has been found that where the
aqueous concentrate of N,N, disubstituted p-phenylenediamine phosphate
salts does not exceed 50% weight per unit volume, the concentrate is
sufficiently fluid for easy pouring out of a container in which the same
has been stored and is readily dilutable by mixing with water and other
concentrates to form a working color developing solution. However, with
phosphate salts, as the concentration of the salt rises from 50% to 60%
the concentrate starts to become viscous and, indeed, at 60% might be
considered to be too viscous for marketability, although the same can be
used, pursuant to the present invention, as, for example, by flushing out
with water the container in which the concentrate is stored. Indeed, the
concentration may even go up to as high as 65% with usable commercial
results.
The new salt also may be used in the form of a derivative and,
specifically, an alcoholate derivative, typical derivatives being an N,N,
disubstituted p-phenylenediamine phosphate alcoholates wherein the N,N,
disubstituted p-phenylenediamine is AEMT and wherein the alcoholate is of
a lower aliphatic alcohol selected from the group consisting of methyl
alcohol, ethyl alcohol, n-propyl alcohol and isopropyl alcohol, the
alcoholate of the salt having the formula
##STR2##
where R is CH.sub.3, C.sub.2 H.sub.5, CH.sub.3 CH.sub.2 CH.sub.2 or
##STR3##
AEMT phosphate alcoholates and their method of preparation are described
and claimed in co-pending application Ser. No. 335,341 filed Feb. 23, 1973
for "ALCOHOLATES OF ORTHOPHOSPHATE SALTS OF 4-AMINO, 3-METHYL, N-ETHYL,
N-BETA-METHANESULFONAMIDOETHYL ANILINE" by Harry Kroll and Alderic R.
Therrien now U.S. Pat. No. 3,875,227.
A typical color developer formulation for a working color developer bath
using the concentrate of the present invention hereinabove referred to as
I (the only constituents of this concentrate are the new color developing
agent, to wit, AEMT orthophosphate, and water) is as follows:
Concentrate I: 8.0 ml.
Benzyl alcohol: 5.5 ml.
Potassium bromide: 1.5 g.
Potassium metaborate: 50.0 g.
Sodium sulfite: 1.6 g.
Water q.s. to: 1 liter
Adjust pH to: 10.70
In order to demonstrate the superior characteristics of the new color
developing agent, the same was compared with two other developers made
from concentrates respectively denominated II and III, the formulations
for which are set forth below. The formulations for Concentrates II and
III differed from the formulation for Concentrate I in the following
respects. The formulation for Concentrate II contained AEMT but in the
form of the sesqui-sulfate monohydrate instead of the orthophosphate. The
amount of AEMT present was 31% weight per unit volume in contradistinction
to Concentrate I which contained AEMT (in the form of an orthophosphate
salt) as 50% weight per unit volume. Concentrate II did not include any
preservative. Concentrate III, which is a commercially available color
developer concentrate, contained as a color developing agent AEMT as a
sesqui-sulfate monohydrate as did Concentrate II and in the same
concentration as in Concentrate II, but unlike Concentrate II included an
anti-oxidant as a sulfite ion (the sulfite being present as sodium
sulfite) in a concentration of 1.3% weight per unit volume. Concentrate II
and III were incorporated into working color developer solutions in such a
manner that the solutions prepared from Concentrates II and III contained
the same concentrations of all ingredients including the amount of AEMT
and the amount of sodium sulfite. The formulations for the baths including
Concentrates II and III are set forth below.
Working Bath Solution Prepared with Concentrate II
Concentrate II: 14.0 ml.
Benzyl alcohol: 5.5 ml.
Potassium bromide: 1.5 g.
Potassium metaborate: 50.0 g.
Sodium sulfite: 1.6 g.
Water q.s. to: 1 liter
Adjust pH to: 10.70
Working Bath Solution Prepared with Concentrate III
Concentrate III: 14.0 ml.
Benzyl alcohol: 5.5 ml.
Potassium bromide: 1.5 g.
Potassium metaborate: 50.0 g.
Sodium sulfite: 1.4 g.
Water q.s. to: 1 liter
Adjust pH to: 10.70
A fourth concentrate, referred to as IV, was prepared with the following
formula to illustrate the use of the invention in the form of an
alcoholate.
Orthophosphoric acid (85%): 58.0 g.
AEMT phosphate monomethanolate: 148.0 g.
Water to 200.0 ml.
A working bath solution was prepared with Concentrate IV which was
identical to that prepared with Concentrate I except that Concentrate IV
was substituted on an equal volume basis for Concentrate I.
The four aforesaid developer solutions using Concentrates I, II, III and IV
were substituted for the developers supplied in the color negative process
as described by Eastman Kodak Co. for use in the trade. Standard "gray
scale" exposures on Kodak Kodacolor film were processed through these four
developer solutions. Their densities were determined and found to be
essentially photographically equivalent. In this developing process,
hereinafter denominated Process A, the development step was carried out
with working solutions employing the four freshly prepared concentrates,
these constituting controls for testing as to stability in connection with
the storing of concentrates for a period of weeks at a temperature
substantially above room temperature.
Four identically constituted concentrates, freshly prepared, were placed in
full, stoppered amber glass bottles which were stored (aged) at 50.degree.
C. for five weeks. At the end of that time working color developer
solutions were freshly made up from the four aged concentrates using the
same additional compounds in identical amounts to those above mentioned
and photographically evaluated in the manner described above and
denominated Process B. The red, green and blue density differences for
Processes A and B for four steps of an eleven-step [0-3 log E] gray scale
exposure are set forth below, thus providing a direct measurement of
density differences between a freshly prepared concentrate and a
concentrate that has been stored at a high temperature of 50.degree. C.
for five weeks.
__________________________________________________________________________
RED GREEN BLUE
Step 1 4 7 11 1 4 7 11 1 4 7 11
__________________________________________________________________________
Concentrate with
Developer I and IV
-.01
-.04
-.04
-.06
.00
-.02
-.02
-.04
+.01
-.03
-.04
-.03
II +.41
+.39
+.38
+.35
+.24
+.30
+.37
+.08
+.19
+.27
+.37
+.12
III +.06
+.24
+.18
+.04
+.08
+.11
+.08
-.02
+.13
+.07
+.05
.00
__________________________________________________________________________
From the foregoing date it is apparent that a concentrate made with the
sesqui-sulfate salt of AEMT requires sulfite ions to be present if it is
to be usable. The influence of the sulfite ions is seen by the differences
between the results obtained with the working color developer baths
including Concentrates II and III. However, a working color developer bath
containing Concentrate I or Concentrate IV without sulfite in the
concentrate demonstrates the distinctly superior stability of Concentrates
I and IV after storage at an elevated temperature. Indeed, it has been
observed that a working color developer bath containing Concentrate I or
IV after storage for several weeks at 50.degree. C. with a considerably
higher concentration of AEMT than the above baths containing Concentrates
II and III showed distinctly superior stability to the working color
developer bath containing Concentrates II and III stored for similar
periods of time at similar elevated temperatures.
That the group of phosphate salts listed above of N,N, disubstituted
p-phenylenediamines are uniquely advantageous as color developing agents
is readily ascertainable from other experimental data which were obtained
and which are set forth below.
Various acid salts of N,N, disubstituted p-phenylenediamines other than the
phosphate group mentioned above were tested in comparison with the
phosphate salts. It will be recalled that the necessary characteristics,
inter alia, for a color developing agent are considerable solubility in
water and good stability (reproduceable color effects within a small
latitude after storage at a high temperature for a protracted period of
time) with or without the addition of protective agents such as sulfites,
ascorbic acid, etc. to this concentrate.
Solutions of likely salts of N,N disubstituted p-phenylenediamines, and
specifically of AEMT, containing 50% by weight AEMT on a free base basis
were prepared by neutralizing the free base with slightly more than the
stoichiometric amount of acid, i.e. 5% excess. The acids used were
orthophosphonic acid, pyrophosphonic acid, polyphosphonic acid, nitrilo
triphosphonic acid, ethylenediamine tetraphosphonic acid, acetic acid,
hydroxyacetic acid, citric acid, gluconic acid, malic acid, formic acid,
hypophosphorous acid and orthophosphorous acid.
It was found that with the organophosphonic acids such as nitrilo
trimethylenephosphonic acid, ethylenediamine tetramethylenephosphonic acid
and like acids, the AEMT salts thereof when incorporated into water as a
solution became very viscous at a 30% or greater concentration weight per
unit volume and, hence, were not commercially useful, the concentration
being too low for desirable practical use.
Certain other of the AEMT salts decomposed either immediately upon
formation thereof or shortly after storage at 50.degree. C. and thus were
of no further interest. For example, the formate salt of AEMT decomposed
immediately. The hypophosphite and phosphite salts of AEMT decomposed
after a day or two of stoppered storage at 50.degree. C. with evolution of
hydrogen sulfide.
Other salts of AEMT showed poor photographic effects which appeared to be
due to the anionic constituent. For example, a working color developer
bath made with the acetate salt of AEMT had inferior photographic effects
colorwise when compared to a working color developer bath made with either
a sulfate or a phosphate salt of AEMT. Even discounting the initial
difference in photographic response, many of the salts of organic acids
other than the phosphates of the present invention showed considerable
instability upon prolonged storage at 50.degree. C. The method of testing
the sundry N,N disubstituted p-phenylenediamine salts of the acids that
did not perform well, as well as the salts of the phosphoric acids that
did and do perform well, was as follows:
A concentrate of the desired salt was prepared by adding the
stoichiometrically required amount of the acid for neutralization plus an
excess of about 5% and diluting the same with water to about 100 ml., then
dissolving 100 g. of AEMT in the solution and diluting with water to 200
ml., all at ambient temperature and pressure. For neutralization it was
calculated that each mole of AEMT required three moles of monobasic acid
and equivalently less of polybasic acids.
The concentrate so prepared contained 50% weight per unit volume of AEMT.
The concentrates of the various acids were stored at 50.degree. C. in
stoppered amber glass bottles for periods ranging from 8 to 21 days.
Concentrates were stored with and without a small amount of sodium
bisulfite as a preservative, the small amount being 0.4% by weight of the
AEMT content. After the above storage the various concentrates were
incorporated in a working color developer bath which included in addition
to the concentrate the further compounds and materials listed in
connection with the above described working color developer bath
containing Concentrate I with the exception that some of the baths
contained sodium sulfite and others did not, such difference being pointed
out below. Where sodium sulfite was employed it was present in the amount
previously mentioned, i.e. 0.4% by weight of sodium sulfite of the AEMT
content, the incorporation being for preservation purposes. For a
standard, i.e. control, a working color developer bath was made which was
the same as that given above for Concentrate I except that said
concentrate was replaced by 6.4 g. of AEMT sesqisulfate monohydrate. Both
the bath prepared with Concentrate I and the standard contained the same
amount of AEMT on a free base basis.
The developers were then incorporated into the Kodak Kodacolor process in
the manner described by Eastman Kodak Co. for use in the trade and said
developers were employed to develop Kodak Kodacolor film. The sequence and
times in a complete developing process were as follows:
______________________________________
Developer 14 minutes
Stop 4 minutes
Harden 4 minutes
Wash 4 minutes
Bleach 6 minutes
Wash 4 minutes
Fix 8 minutes
Wash 8 minutes
Wetting agent dip
Dry
______________________________________
All solution temperatures were 75.degree. F. The gray scale exposures, make
on Kodak Kodacolor film after processing the above using the working color
developer bath as determined by conventional densitometry, had certain
red, green and blue d | | |
