- 1 -

N-ALKYLHYDROXYLAMINE DERIVATIVES AND THEIR USE AS ANTIOXIDANTS IN PHOTOGRAPHIC COLOR DEVELOPERS AND

PROCESSING METHODS

The present invention relates to color photographic developer compositions and to their use in the processing of silver halide color photographic materials. More specifically, it relates to a color developer composition having certain water-soluble substituted dialkylhydroxylamines as antioxidants which provide stability for the color developer. These compositions and methods are useful in the field of photography. The invention also relates to a novel class of hydroxylamines. Photographic color developing compositions are used to process color photographic materials such as color photographic films and papers to provide the desired color images. Such compositions generally contain developing agents, for example 4-amino-3- methyl-N- (β-methane sulfonamidoethy1) aniline, as reducing agents to react with suitable color forming couplers to form the desired dyes. However, such developing agents are susceptible to oxidation by dissolved oxygen. An antioxidant is conventionally included in the developer compositions to preserve the oxidation state of the color developer and thereby maintain useful color developer activity.

Many classes of compounds have been employed as color developer solution antioxidants, including hydroxylamines, hydroxamic acids, oxi es, nitroxy radicals, hydraz ^' ines, hydrazides, phenols, saccharides, various simple amines, polyamines, quaternary ammonium salts, -hydroxy ketones, alcohols, diamides and disulfonamides . To be used in practice, however, antioxidants must be soluble in aqueous media, non- toxic to living organisms, low cost and non-silver

halide developers. Further, it is desirable that antioxidants react slowly with oxygen and rapidly with oxidized color developer, but not so rapidly that color development is retarded. Yet another concern is that the antioxidant must not be able to promote bacterial growth.

All of these considerations greatly limit the number and classes of compounds that practically can be used as antioxidants or stabilizers in color developer solutions. One class of compounds often used as antioxidants are hydroxylamines . They exhibit excellent characteristics by having a slow rate of aerial oxidation, being non-silver halide developers, and relatively inexpensive to produce. There are considerable publications describing such compounds. While there is considerable literature describing various water-soluble hydroxylamines which can be used as antioxidants, most of them have a number of disadvantages. For example, making them with the requisite solubilizing groups may be difficult or expensive. In addition, even when generally water- soluble, they may still emit an unpleasant odor which is offensive to users in the photoprocessing industry. For example, US-A-4, 892, 804 describes a number of dialkylhydroxylamines useful as color developer antioxidants, including N,N- diethylhydroxylamine, which are improvements over the unsubstituted or mono-substituted hydroxylamines. US- A-4,876,174 describes a lengthy list of substituted hydroxylamines believed useful as antioxidants in color developer compositions, but the compounds actually used emit unpleasant odors. In US-A-5, 354, 646, water- solubilizing groups, such as carboxy and sulfo are shown on dialkylhydroxylamines. Specifically illustrated compounds include N-ethyl-N-ethylsulfonyl- hydroxylamine and N, -ethylsulfonylhydroxylamine.

As the antioxidants shown in the art have varying and unpredictable effect, there remains a need to find relatively inexpensive, odorless and consistently effective antioxidants for color developer compositions.

The problems noted above with conventional color developer compositions are overcome with a photographic color developer composition having a pH of from 9 to 13 and comprising a primary aromatic amine color developing agent, the composition characterized as further comprising a hydroxylamine derivative as defined below.

This invention also provides a method for .processing a color photographic element comprising developing an imagewise exposed color photographic element with the photographic color developer composition described above.

This invention provides novel hydroxylamine derivatives characterized as having the formula [R-CH(R ¹ )] _m -N(OH)-[R ² -X] _n

1 wherein R and R are independently alkyl of 1 to 8 carbon atoms provided the total carbon atoms for R and

1

R is no greater than 9,

2

R is alkylene of 2 to 6 carbon atoms or phenylene,

₃ X is sulfo, carboxy, phosphono, -SO NR R or

3 4 3 4

-CONR R wherein R and R are independently hydrogen or alkyl of 1 to 3 carbon atoms, m is 0 or 1, and n is 1 to 2, provided that when ή is 1, m is 1, and when n is 2, m is 0 and X is -CONR ³ R ⁴ . The color developer composition of this invention provides a number of significant advantages including less or no odor and improved stability of the color developer. The improved stability is evidenced

by either reduced loss in color developing agent activity or reduced decrease in pH (pH drop) , or both. These advantages are provided by the use of certain water-soluble N-alkylhydroxylamines of the noted formula as the antioxidants. The use of such compounds provides a surprising improvement in antioxidant activity in comparison to similar substituted hydroxylamine derivatives having straight chain alkyl groups attached to the nitrogen atom. FIGURE 1 is a graphical representation of the change in color developer agent activity over time for various color developer compositions as described below in Example 3.

FIGURE 2 is a graphical representation of the change in color developer composition pH over time for various color developer compositions as described below in Example 3.

The novel compounds of this invention that are useful as antioxidants in the present invention can be represented by the formula:

[R-CH(R ¹ ) ] _m -N(OH)-[R ² -X] _n i wherein R and R are independently alkyl (linear or branched) of 1 to 8 carbon atoms (such as methyl, ethyl, n-propyl, isopropyl, isobutyl, t-butyl, n- butyl, pentyl, hexyl, 2-ethylhexyl and octyl) . The ι total number of carbon atoms for both R and R is no

1 greater than 9. Preferably, each of R and R has 1 to

3 carbon atoms, and more preferably, each is methyl i or ethyl. Most preferably, each of R and R is methyl. It is clear from the noted formula that certain embodiments, one substituent of the nitrogen atom is a branched alkyl group wherein the carbon atom directly connected to the nitrogen has one and only one hydrogen atom.

1 Each of R and R can be substituted with one of more substituents other than sulfo or carboxy

groups, as long as such substituents do not adversely affect the antioxidant properties of the compound.

1

Preferably, each of R and R is an unsubstituted alkyl group (linear or branched) .

2 In the noted formula, R is a substituted or unsubstituted, branched or linear alkylene group of 2 to 6 carbon atoms (such as ethylene, trimethylene, isopropylene, tetramethylene and hexamethylene) and preferably, it has only 2 or 3 carbon atoms. Most

2 preferably, R is substituted or unsubstituted

2 ethylene. The R group can also be a substituted or unsubstituted phenylene group. The substituents that

2 can be attached to R include hydroxy, carbonamido, carboxy, sulfo, halo, sulfonamido or phosphono.

2 Preferably, R is an unsubstituted, linear alkylene group of 2 to 4 carbon atoms or

2 unsubstituted phenylene. More preferably, R is unsubstituted alkylene of 2 or 3 carbon atoms, and most preferably, it is unsubstituted ethylene. In the noted formula, X is sulfo, carboxy,

3 4 _{3 4} phosphono, -SO.NR R or -CONR R , and more preferably, it is sulfo, carboxy or -CONR ³ R ⁴ . The noted acid forming groups can be present as free acids, salts or esters (having a suitable cation or ester group) .

3 4 R and R are independently hydrogen, or a substituted or unsubstituted alkyl of 1 to 3 carbon

3 4 atoms. Preferably, R and R are both hydrogen or the same alkyl group of 1 or 2 carbon atoms, and more preferably, they are each hydrogen or methyl. In the noted formula, m is 0 or 1, and n is

1 or 2 , provided that when n is 1, m is also 1, and when n is 2, m is 0 and X is -CONR ³ R .

Thus, in one embodiment of this invention, m is 1 and n is 1, so that the compounds have a branched alkyl substituent attached to the nitrogen

2 atom as well as the -R -X group attached to the nitrogen atom.

In another embodiment, m is 0 and n is 2 so that the compounds have symmetrical -R ² -X groups. However, in this embodiment, X is -CONR ³ R ⁴ only.

Suitable monovalent cations or ester groups for the free acids include ammonium (including quaternary amines) , alkali metal ion (such as sodium, potassium or lithium) , alkyl having 1 to 4 carbon atoms (such as methyl, ethyl, n-propyl, isopropyl, n- butyl and t-butyl) , pyridinium, tetraethylammonium and tetramethylammonium, as well as other cations and ester groups which would be readily apparent to one skilled in the art. Preferably, methyl ester, ethyl ester or an alkali metal salt form is used.

Representative compounds useful in the practice of this invention include N-isopropyl-N- ethylsulfonic acid hydroxylamine, N-isopropyl-N- isopropylsulfonic acid hydroxylamine, N-isopropyl-N- n-propylsulfonic acid hydroxylamine, N-isopropyl-N- t- butylsulfonic acid hydroxylamine, N-sec-butyl-N- ethylsulfonic acid hydroxylamine, N-sec-butyl-N- isopropylsulfonic acid hydroxylamine, N-sec-butyl-N- n-butylsulfonic acid hydroxylamine, N-N-ethylsulfonic acid, N-2-octyl-N-n-propylsulfonic acid, N-isopropyl- N- (sulfonamidoethyl)hydroxylamine, N-isopropyl-N- (p- carboxybenzyl)hydroxylamine, N-isopropyl-N-propionic acid hydroxylamine, N-isopropyl-N- (N,N-dimethyl- sulfonamidoethyl)hydroxylamine, N-isopropyl-N- (N,N- diethylsulfonamidoethyl)hydroxylamine, N-isopropyl-N- (2-carboxymethylene-3-propionic acid) ydroxylamine, N-sec-butyl-N-propionic acid hydroxylamine, N- isopropyl-N-carbonamidoethyl)hydroxylamine, bis (N,N- carbonamidoethyl)hydroxylamine, bis (N,N- carbonamidopropyl)hydroxylamine, bis(N,N- methylcarbonamidoethyl)hydroxylamine, bis (N,N-

dimethylcarbonamidoethyl)hydroxylamine and salts (e.g., alkali metal) or esters of the free acids in this list.

Of the foregoing compounds, N-isopropyl-N- ethylsulfonic acid hydroxylamine, N-isopropyl-N- propionic acid hydroxylamine, N-isopropyl-N- (carbonamidoethyl)hydroxylamine, bis (N,N- carbonamidoethyl)hydroxylamine, N-isopropyl-N- (N,N- dimethylsulfonamidoethyl)hydroxylamine are preferred, along with salts or esters of the free esters.

The compounds described herein as useful antioxidants can be readily prepared using published procedures, such as those described in US-A- 3,287,125, US-A-3,778,464, US-A-5, 110, 985 and US-A- 5,262,563. In general, one useful synthetic procedure for sulfo-substituted compounds comprises reacting an N-alkylhydroxylamine with a vinylsulfonate in a suitable solvent (such as water, an alcohol, tetrahydrofuran or methyl ethyl ketone) . For the alkali metal salts of vinylsulfonates, water is the best solvent. In cases where the hydroxylammonium salt is available, an equivalent of a base must be used to liberate the free N-alkylhydroxylamine. The antioxidant is included in the color developer composition of this invention in an amount of at least 0.001 mol/1, and a preferred amount is from 0.005 to 0.5 mol/1. More than one antioxidant can be used in the same color developer composition if desired, but preferably, only one is used.

In solution, the pH of the color developer composition is generally from 9 to 13 (preferably from 9 to 11) , as provided by the addition of one or more weak or strong bases (such as a hydroxide) or buffers in amounts readily known in the art.

Particularly useful buffers include, but are not

limited to, carbonates, borates, tetraborates, phosphates, glycine salts, leucine salts, valine salts, proline salts, alanine salts, aminobutyric acid salts, lysine salts, guanine salts and hydroxybenzoates .

The color developer compositions of this invention include one or more color developing agents, of which there are hundreds of possibilities. Useful classes of such materials include, but are not limited to, aminophenols, p-phenylenediamines

(especially N, -dialkyl-p-phenylenediamines) and others which are well known in the art, such as EP 0 434 097A1 and EP 0 530 921A1. It may be useful for the color developing agents to have one or more water-solubilizing groups as are known in the art. Further details of such materials are provided in Research Disclosure, publication 36544, pages 501-541 (September, 1994) . Research Disclosure is a publication of Kenneth Mason Publications Ltd. , Dudley House, 12 North Street, Emsworth, Hampshire

PO10 7DQ England (also available from Emsworth Design Inc., 121 West 19th Street, New York, N.Y. 10011) . This reference will be referred to hereinafter as " Research Disclosure" . The color developer composition can be easily prepared by mixing a suitable color developer (in a suitable solution) with an antioxidant as described above (in a suitable aqueous solution) . Water can be added to the resulting solution to provide the desired concentrations of an aqueous solution, and the pH can be adjusted as noted above.

The composition can also include one or more of a variety of other addenda which are commonly used in such compositions, such as alkali metal halides (such as potassium chloride, potassium bromide, sodium bromide and sodium iodide) , metal

sequestering agents (such as polycarboxylic or aminopolycarboxylic acids or polyphosphonates) , buffers (as noted above) , other preservatives (such as sulfites) , anti-foggants, development accelerators, optical brighteners, wetting agents, stain reducing agents, surfactants, defoaming agents, and water-soluble or water-dispersible color couplers, as would be readily understood by one skilled in the art (see for example, Research Disclosure, noted above and US-A-4, 814,260) . The amounts of such additives are well known in the art also. For example, the amounts of halides can be varied widely, but are preferably in the range of

-7 from 5 x 10 to 0.3 mol/1 for chloride ion and from 5

-7 x 10 to 0.1 mol/1 for bromide ion. Iodide ion may be totally absent, or present up to an amount of 0.001 mol/1. A preferred color developing composition is described below in Example 1. The color developing composition is preferably formulated and used as an aqueous solution, either as the working developer solution or a replenishing solution. However, as is known in the art, color developer composition can also be formulated as used as dry tablets. The technology for this embodiment is readily known in the art, such as US-A-5,362, 610, US-A-5, 376, 509 and EP-A-0 611 986A1.

The color developing composition of this invention has obvious utility to provide color development in an imagewise exposed color photographic element comprising a support and one or more silver halide emulsion layers containing an imagewise distribution of developable silver halide emulsion grains. A wide variety of types of photographic elements (both color films and papers) containing various types of emulsions can be

processed using the present invention, the types of elements being well known in the art (see Research Disclosure, noted above) . In particular, the invention can be used to process color photographic papers of all types of emulsions, including so-called "high chloride" and "low chloride" type emulsions, and so-called tabular grain emulsions as well. The color developer solution can also be used in color reversal processing. The present invention is particularly useful to process high chloride (greater than 70 mole % chloride and preferably greater than 90 mole % chloride) emulsions in color photographic papers. Such color photographic papers can have any useful amount of silver coated in the one or more emulsions layers, and in some embodiments, low silver elements

2

(that is, having less than 0.8 g total silver/m ,

2 e.g., from 0.3 to 0.7 g silver/m ) are processed with the present invention. The layers of the photographic elements can have any useful binder material or vehicle as it known in the art, including various gelatin and other colloidal materials . One useful binder material is acid processed gelatin which can be present in any layer in any suitable amount.

Development is carried out by contacting the element under suitable time and temperature conditions, in suitable processing equipment, to produce the desired developed image. 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. Useful processing steps, conditions, materials and amounts useful therefor are

well known (see for example, Research Disclosure and references cited therein) .

The photographic elements processed in the practice of this invention can be single or multilayer color elements. Multilayer color elements typically contain dye image-forming units sensitive to each of the three primary regions of the visible spectrum. Each unit can be comprised of a single emulsion layer or multiple emulsion layers sensitive to a given region of the spectrum. The layers of the element can be arranged in any of the various orders known in the art . In an alternative format, the emulsions sensitive to each of the three primary regions of the spectrum can be disposed as a single segmented layer. The elements can also contain other conventional layers such as filter layers, interlayers, subbing layers, overcoats and other layers readily apparent to one skilled in the art. A magnetic backing can be used as well as conventional supports . Considerable details of element structure and components, and suitable methods of processing various types of elements are described in Research Disclosure, noted above. Included within such teachings in the art are the use of various classes of cyan, yellow and magenta color couplers (including pyrazolotriazole magenta dye forming couplers) which can be used with the present invention. In addition, the present invention can be used to process color photographic papers having pigmented resin-coated paper supports which are prepared with the usual internal and external sizing agents (including alkylketene dimers and higher fatty acids) , strengthening agents and other known paper additives and coatings.

Particularly useful color photographic papers that can be used in the practice of this invention include, but are not limited to, KODAK EKTACOLOR EDGE ^®

2 Paper, KODAK EKTACOLOR PORTRA ^® II Paper, AGFACOLOR PROFESSIONAL SIGNUM Paper, AGFACOLOR Paper Type 10, FUJICOLOR SUPER FA Type P Paper, KONICA COLOR QA Paper Type A6 and KONICA COLOR QA Paper Professional Type P5. The elements are typically exposed to suitable radiation to form a latent image and then processed to form a visible dye image. Processing includes the step of color development in the presence of a color developing agent to reduce developable silver halide and to oxidize the color developing agent. Oxidized color developing agent in turn reacts with a color-forming coupler to yield a dye.

Processing according to the present invention can be carried out using conventional deep tanks holding processing solutions. Alternatively, it can be carried out using what is known in the art as "low volume thin tank" processing systems, or LVTT, which have either a rack and tank or automatic tray design. Such processing methods and equipment are described, for example, in US-A-5,436, 118 and publications noted therein.

The length of time and temperatures used for each processing step of the present invention are generally those conventionally used in the art. For example, development is generally carried out at a temperature of from 20 to 50 °C. The overall processing time (from development to final rinse or wash) can be from 30 seconds to 40 minutes, and each step can be from 10 to 450 seconds. Short overall processing times, that is, less than 140 seconds, are desired for processing color photographic papers. It is particularly desirable that the time for development using the color developing composition of this invention be less than 200 seconds, and preferably, less than 120 seconds, but longer or shorter times may be useful under particular conditions .

The following examples are provided to illustrate the practice of this invention and not to limit it in any way. Unless otherwise indicated, percentages are by weight.

Preparation of N-isopropyl-N-ethylBulfonic acid hydroxylamine;

Isopropyl hydroxylamine (330 g of 15% in water, 0.665 mol) was combined with sodium vinylsulfonate (350 g of 25% in water, 0.665 mol) and sodium hydroxide (0.4 g, 0.01 mol) . The resulting solution was refluxed for four hours, after which no starting materials were detected by thin layer chromatography. The reaction mixture was cooled to room temperature and precipitated into eight liters of stirred isopropanol. The resulting white solid was dried in a vacuum oven prior to use. HNMR (δ, ppm)2.9-3.1 (br,CH ₂ CH ₂ , 4H) , 2.85 (septet, i-Pr, IH) , 0.95 (d, i-Pr, 6H) confirmed the structure, and ion chromatography revealed no chloride ion and 1.2% sulfate.

Alternative Preparation of N-isopropyl-N-(2- ethanesulfonic acid)hydroxylamine. Sodium Salt An aqueous solution (420 ml) of vinylsulfonic acid, sodium salt (25%) was heated to reflux. While at reflux, an aqueous solution (480 g) of isopropyl hydroxylamine was linearly added over a period of two hours. During the next five hours, water (600 g) was removed linearly by distillation. After cooling the reaction solution to 20 °C, isopropanol (500 ml) was added with good mechanical stirring to keep the resulting white solid suspended. This solid was collected on a sintered glass funnel, rinsed with additional fresh isopropanol (100 ml) , and dried overnight at 50 °C under vacuum for

analysis. N-isopropyl-N- (2-ethanesulfonic acid) - hydroxylamine, sodium salt was isolated as a white powder. However, the product could have been left in the reaction solution for later use if desired. All analyses were consistent with the

1 structure of the desired compound. The H NMR in D 0 had peaks at 4.8(NOH) , 3.2-2.9 (isopropyl methine and two methylenes of the ethylsulfonato sodium salt moiety) , and 1.1 ppm (two methyls of the isopropyl

13 group) . The C NMR had peaks at 59.4, 52.4, 49.9 and 19.2 ppm. The sodium analysis was 11.5%.

Preparation of N-isopropyl-N- (3-propionic Acid)- hvdroxylamine Acrylic acid (120 g) was added to an aqueous solution (825 g) of isopropylhydroxylamine (15%) and methanol (1250 ml) at room temperature with vigorous mechanical stirring. Upon completion of the addition, the reaction solution was heated to 60 °C and maintained at that temperature overnight. Upon cooling to room temperature and concentration of the reaction solution by evaporation, a yellow oil crystallized upon standing. Isopropanol and ether were added to facilitate collection of the resulting product by suction filtration for analysis. The resulting white granular solid was dried overnight under vacuum to give 155 g.

The analyses were consistent with the

1 desired structure. The H NMR in dimethylsulfoxide-d6 had peaks at 7.0(NOH) , 2.7 (isopropyl methine plus methylene group ^" of the propionic acid moiety) , 2.35 (methylene of propionic acid moiety) , and 0.9 ppm(two methyls of the isopropyl group) . The mass spectrum was consistent with the desired compound.

Preparation of N-isopropyl-N-(2-carboxymethylene-3- propionic acid)-hydroxylamine

Methanol (300 ml) was added to an aqueous 15% solution (400 ml) of N-isopropylhydroxylamine (0.8 moles) , followed by addition of itaconic acid (104 g, 0.8 moles) in portions as a solid. Additional methanol (100 ml) was used to rinse the itaconic acid into the flask. After all of the solid acid had dissolved, the mixture was stirred at room temperature for 6 days, and filtered to collect the resulting white solid product. This material was dried under mild vacuum to a weight of 142 g (m.p. 136-8 °C) . NMR analysis was consistent with the structure of the desired compound. Similarly, N-isopropyl-N-

(sulfonamidoethyl)hydroxylamine, N-isopropyl-N- (N,N- dimethylsulfonamidoethyl)hydroxylamine, and N- isopropyl-N- (N,N-diethylsulfonamidoethyl) - hydroxylamine were prepared using similar conditions and slightly varying solvent mixtures of water and methanol, water and tetrahydrofuran or tetrahydrofuran and N,N-dimethylformamide. These compounds were prepared by reacting vinylsulfonamide, N,N-dimethyl vinylsulfonamide or N,N-diethyl vinylsulfonamide with N-isopropylhydroxylamine, as would be appropriate.

Preparation of N.N-Bis(N.N- dimethylcarbonamidoethyl)hydroxylamine Methanol (200 ml) was added to a methanically stirred aqueous solution (66 g) of hydroylamine (50%) . N,N-dimethylacrylamide (198 g) was added dropwise to the resulting cloudy suspension over a period of several hours . The reaction solution became warm and clear. Upon cooling to

50 °C, the reaction mixture became an orange, viscous

mixture, which was transferred to another vessel and allowed to cool to room temperature. After 14 hours, the mixture had solidified. The solid was collected and dried under vacuum overnight to give 105 g of white solid for analysis.

All analyses were consistent with the desired structure. The H NMR spectrum in dimethylsulfoxide-d6 had peaks at 7.8(NOH), 2.9, 2.7 (amide methyl groups) , 2.73 (methylene group) and 2.43 (methylene group) .

Example 1: Color Developer Composition

This example demonstrates the preparation of a preferred aqueous photographic color developer composition according to this invention.

The components of the composition as shown in Table I below, were mixed together.

TABLE I

Component Concentration/liter

Lithium salt of sulfonated polystyrene (30% w/w) 0.25 ml Triethanolamine 5.5 ml

KODAK EKTAPRINT™2 Stain Reducing Agent l g N-isopropyl-N-ethylsulfonic acid hydroxylamine, 0.041 mol sodium salt antioxidant

Lithium sulfate 2 g

1-Hydroxyethylidene-l-diphosphonic acid (60% w/w) 0.6 ml

Potassium chloride 6.4 g

Potassium bromide 0.028 g 4-Amino-3-methyl-N-ethyl-N-(β- 4.35 g methanesulfonamido-ethyl)aniline

Potassium carbonate 25 g

Water to 1 liter solution pH adjusted to 10.12 with sodium hydroxide or sulfuric acid

Example 2: Processing of Photographic Element

The color developer composition of Example

TM

1 was used to process samples of KODAK EKTACOLOR Color Paper which had been imagewise exposed by a step tablet varying exposure by 0.1 logE over 20 steps. Densitometry data were obtained using conventional procedure, showing acceptable color development using the color developer composition of Example 1.

Example 3: Stability Comparisons The color developer composition of Example

1 was compared to three compositions known in the art for stability, that is, loss in color developer and change in pH which are indicative of instability.

A Control A composition was like Example 1 except that the antioxidant was omitted. The Control B composition contained N,N-diethylhydroxylamine as the antioxidant. The Control C and D compositions contained N,N-diethylsulfonic acid hydroxylamine and N-ethyl-N-ethylsulfonic acid hydroxylamine, respectively, as the antioxidants.

Each color developer composition was subjected to an "aeration" test designed to measure the concentration of color developer as a function of time as the composition (1 liter) was continuously

3 aerated at a rate of 0.014 m /hr. The concentration of color developer (g/1) was measured by high performance liquid chromatography as a function of time (hours) . The results of these tests are shown in FIGURE 1.

In addition, the pH of the compositions was measured over time. The results are shown in FIGURE

2. The results in color developing agent loss and pH change are also presented below in Table II.

TABLE II

Composition 2-Day Loss 4-Day 2-Day pH 4-Day pH

Loss Change Change

Example 1 0.65 g 2.95 g 0.12 0.17

Control A 4.00 g 4.20 g 0.13 0.20

Control B 1.40 g 4.00 g 0.13 0.16

Control C 1.25 g 3.65 g 0.16 0.24

Control D 2.70 g 3.90 g 0.16 0.24

It can be seen in FIGURE 1 that the concentration of color developer dropped less quickly with using the present invention. The color developer loss is considered to be significantly less

with the practice of this invention compared to the use of similar art-recognized antioxidants (Controls B-D) . Without an antioxidant (Control A) , the loss of color developer is also significant. It is apparent from FIGURE 2 that the change in pH (that is, pH decrease) is significantly less over time with the present invention compared to the use of compositions containing no antioxidant or similar sulfo-substituted antioxidants (Controls A, C and D) . The Control B composition had a similar pH drop over time, but the combined data shown in both FIGURES indicates that the present invention showed considerable overall improvement in performance.

Examples 4-10: Additional Stability Comparisons

Color developer compositions like that in Example 1 except with various antioxidants were compared as to their stability, that is, the loss in color developing agent activity, and pH drop. Each color developer composition was subjected to an accelerated aerial oxidation as follows:

A 50 ml volume of the color developer solution was placed into a 50 ml graduated cylinder (2 cm diameter, 21 cm height) . A glass tube (0.4 cm inner diameter, 0.6 cm outer diameter) was placed into the solution and suspended so that the tip was held 1 cm above the bottom of the graduated cylinder. Water saturated air was passed through the glass tube at a rate of 25 ml/min. The color developer solution was sampled every 24 hours and the concentration of color developing agent and pH were determined. Generally the color developer solution was nearly exhausted after 5 days of aeration and the test was halted. East test was done in duplicate, and the results were averaged.

- 20 -

The loss in color developer activity and pH drop were measured at 1, 2, 3 and 4 day intervals during the accelerated aerial oxidation tests . The results are shown in Table III below. The various antioxidants tested for the examples and controls were as follows:

Example 4: N-isopropyl-N- (N,N- dimethylsulfonamidoethyl)hydroxylamine. Control E: bis(N,N- dimethylsulfonamidoethyl)hydroxylamine.

Example 5: N-isopropyl-N- (p- carboxybenzyl)hydroxylamine.

Control F: bis(N,N-p- carboxybenzy1)hydroxylamine.

Example 6: N-isopropyl-N-propionic acid hydroxylamine.

Control G: bis (N,N-propionic acid)hydroxylamine. Example 7: N-isopropyl-N-ethanesulfonic acid hydroxylamine.

Control H: bis (N,N-ethanesulfonic acid)hydroxylamine.

Example 8: N-isopropyl-N- (2-carboxymethylene-3- propionic acid)hydroxylamine.

Control I: bis (N,N-2-carboxymethylene-3- propionic acid)hydroxylamine.

Example 9 : N-isopropyl-N- (carbonamidoethyl)hydroxylamine. Example 10: bis(N,N- carbonamidoethyl ^" )hydroxylamine. Control J: N-n-propyl-N- (carbonamidoethyl)hydroxylamine.

Table III

Color Developing Agent pH Drop Loss ( % ) -Hours- -Hours-

Experiment 24 48 72 96 24 48 72 96

Example 4 7 28 72 97 0.17 0.28 0.32 0.30

Control E 13 35 63 89 0.24 0.36 0.40 0.38

Example 5 9 29 80 91 0.10 0.13 0.20 0.20

Control F 4 42 83 93 0.1 1 0.16 0.20 0.20

Example 6 17 34 50 67 0.19 0.28 0.38 0.41

Control G 14 32 51 67 0.18 0.32 0.43 0.48

Example 7 1 1 35 69 89 0.1 1 0.17 0.24 0.25

Control H 1 1 49 78 91 0.14 0.20 0.26 0.27

Example 8 19 44 69 87 0.13 0.18 0.24 0.26

Control I 27 52 70 82 0.20 0.29 0.37 0.38

Example 9 7 26 44 68 0.32 0.35 0.46 0.42

Example 10 9 28 51 72 0.35 0.46 0.51 0.47

Control J 6 31 60 81 0.24 0.27 0.40 0.31

In general, the hydroxylamine derivatives useful in the present invention provided improved color developing agent stability or less drop in pH or both than the comparable hydroxylamine derivatives in the "Control" experiments.

Example 11: Comparison With Non-Branched Compound

The color developer composition described in Example 1 was compared to a similar composition in which N-isopropyl-N-ethylsulfonic acid hydroxylamine, sodium salt was replaced with N-n-propyl-N- ethylsulfonic acid hydroxylamine, sodium salt (Control K) . These two compositions were compared to the ability of the two hydroxylamine derivatives to reduce the loss in color developing agent over a period of

time. Each color developer composition was subjected to accelerated aerial oxidation as described for Examples 4-10 above.

The loss in color developer activity was measured after 2 days during the accelerated aerial oxidation test for both compositions. The results are shown in the following Table IV.

TAB:E IV

Color Developer Composition Color Developing Agent Loss After 2 Days (%)

Example 1 37

Control K 61

It is apparent that the loss in color developing agent activity was much greater when the linear alkyl (n-propyl) -substituted hydroxylamine derivative was used as an antioxidant compound compared to the present invention. This almost 65% greater loss in activity is highly unacceptable.