US3598598A

US3598598A - Fog stabilizers for photographic emulsions

Info

Publication number: US3598598A
Application number: US764332A
Authority: US
Inventors: Arthur H Herz
Original assignee: Eastman Kodak Co
Current assignee: Eastman Kodak Co
Priority date: 1968-10-01
Filing date: 1968-10-01
Publication date: 1971-08-10
Anticipated expiration: 1988-08-10
Also published as: GB1290868A; FR2019603A1; BE739709A

Abstract

A PHOTOGRAPHIC SILVER HALIDE EMULSION OR PHOTOGRAPHIC ELEMENT CONTAINING A FOG-STABILIZING AMOUNT OF A THIONAMIDE, E.G., A 3 SUBSTITUTED THIAZOLINE-2-THIONE, N,N-DISUBSTITUTED DITHIOCARBAMIC ESTER OF AN N,N,N'',N''-TETRASUBSTITUTED THIOUREA, WHICH CONTAINS AT LEAST ONE ACID GROUP IN THE MOLECULE IS DISCLOSED. THE ACID GROUP OR GROUPS CONTAINED IN THE THIONAMIDE MOLECULE SHOULD BE ONES WHICH WILL CONFER A NEGATIVE CHARGE TO THE THIONE AT A PH OR 5 OR BELOW AND IS EXEMPLIFIED BY CARBOXYLIC OR SULFONIC ACID GROUPS. SILVER HALIDE COMPLEXES OF THIONAMIDES AND DEVELOPING PHOTOGRAPHIC ELEMENTS ARE ALSO DESCRIBED.

Description

Un ited states Patent Olhce 3,598,598 Patented Aug. 10, 1971 3,598,598 FOG STABILIZERS FOR PHOTOGRAPHIC EMULSIONS Arthur H. Herz, Rochester, N.Y., assignor to Eastman Kodak Company, Rochester, N.Y. No Drawing. Filed Oct. 1, 1968, Ser. No. 764,332

Int. Cl. G03c N34 US. Cl. 96-109 20 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION Field of the invention This invention relates to new and improved antifoggants and stabilizers for photographic elements and to photographic silver halide emulsions containing said antifoggants and stabilizers therein. The invention also relates to silver halide complexes and to a process of developing photographic elements in the presence of new and improved antifoggants.

Description of the prior art During development of a silver halide emulsion, small amounts of silver halide are reduced to metallic silver regardless of whether or not they have been exposed. This reduction of silver ion produces a background fog which is more specifically referred to as chemical fog.

Chemical fog, apparent in most silver halide systems, has been reduced by prior art methods of processing exposed silver halide material in the presence of compounds which restrict development of unexposed silver halide. Such compounds can be incorporated in the silver halide emulsion or in the processing solutions for developing such silver halide emulsions. Compounds which have been found to have a chemical fog inhibiting effect on emulsions which have been subjected to high temperature and high humidity conditions are referred to as emulsion stabilizers. On the other hand, compounds which have been found to have chemical fog inhibiting effects on emulsions which have not been exposed to adverse storage conditions are referred to as antifoggants. Although a large number of emulsion stabilizers and anti foggants have been used in the prior art, many of these compounds cause undesirable losses in emulsion speed and contrast and others lack adequate compatibility with emulsion gelatin.

Thionamides have been used in the past as antifoggants in silver halide emulsions. Such compounds generally contain at least one hydrogen atom on the amidic nitrogen and exist in tautomeric equilibria between the thione and sulfhydryl structure. However, these compounds have a propensity to desensitize fast silver halide emulsions and, therefore, are generally used in concentrations of less than 50 milligrams per mole of silver to prevent objectionable loss of emulsion sensitivity.

SUMMARY OF THE INVENTION According to one embodiment of this invention, there is incorporated into the silver halide emulsion of aphotographic element or in a layer contiguous to the silver halide emulsion, a fog stabilizing amount of an acrylic or monocyclic thionamide, said thionamide containing at least one acid group which will confer a negative charge to the thionamide at a pH of 5 or below. These compounds stabilize the emulsion against fog when the dried emulsion has been subjected to a prolonged high humidity and temperature incubation period without adversely effecting other sensitometric properties.

According to another embodiment of the invention, a photographic element comprising a support coated with at least one silver halide emulsion layer is developed in the presence of one of the previously described thionamides. Preferably, the thionamide is present in the photographic element but it can be present elsewhere in the systeme.g., in the developer.

According to still another embodiment of this invention, there are provided wateror alkali-soluble silver complexes of the previously described thionamides.

DESCRIPTION OF THE PREFERRED EMBODIMENT Thionamides which are suitably used in the practice of this invention include those having the general formula wherein X represents sulfur, oxygen or an iso-electronic group, 'e.g., -CH=CH (where R and R are taken together) or =N'R where R is an aliphatic group or a substituted aliphatic group, R R and R when taken separately, are aliphatic groups or substituted aliphatic groups, R and R when taken together, represent an alkylene group, and R and R when taken together with the nitrogen atom to which they are attached, represent a heterocyclic group, at least one of the groups containing an acid substituent.

One group of thionamides which can be used in the practice of this invention are 3-substituted thiazoline-2 thiones which have the structure wherein R is an aliphatic group, e.g., an alkyl chain containing up to 10 carbon atoms which can be substituted with one or more groups such as carboxyl, sulfonyl, etc.; R and R can each be hydrogen, an aliphatic or substituted aliphatic radical, e.g., a keto group, a carboxyl group or an alkyl group containing up to 10 carbon atoms, which alkyl group can be further substituted with one or more other groups such as carboxyl, sulfonyl, hydroxy, an ester group, etc.; and at least one of R R and R contains an acid substituent such as a carboxylic or sulfonic acid group. Compounds having the above structure which can be used in the practice of this invention are set forth below wherein the groups R, R and R are as specified:

CH3 (H) -CHCOzH -CH; --C CH3 -CHuCHzSOaH- -CH3 -11 -CHCO2H CH3 CH CHzCOzH -CH3 -CH3 CO2H -CH -CH2COzH -H Another group of thionamides which can be used in the practice of this invention are N,N-disubstituted dithiocarbamic esters having the structure \N|J-S R1 R2 5 wherein R R and R are the same as defined above. Thus, the group and R can be a substituted aliphatic group having from 3 to carbon atoms and containing a carboxylic or sulfonic acid group such as Examples of such compounds include the following wherein the variable groups are as indicated:

Same as above.

A further group of thionamides which can be used are N,N,N,N'-tetrasubstituted thioureas having the structure groups containing an acid substituent such as a carboxylic or sulfonic acid group.

Other groups of thionamides which can be used include those having the general formulas wherein R, R R and R are the same as previously defined.

The thionamide can be incorporated into the silver halide emulsion of a photographic element or in a layer contiguous to the silver halide emulsion in any amount which Will stabilize the silver halide emulsion against fog. In general, a concentration of the thionamide in an amount of from about 0.05 to about 30, preferably about 0.6 to about 10.0 grams per mole of silver in the silver halide emulsion can be used with good results.

The preparation of photographic silver halide emulsions such as are suitably stabilized with the thionamide typically involves three separate operations: (1) emulsification and digestion of silver halide, (2) the freeing of the emulsion of excess water-soluble salts, suitably by washing with water, and (3) the second digestion or after-ripening to obtain increase demulsion speed or sensitivity. (Mees, The Theory of the Photographic Process, 1954.) The thionamide can 'be added to the emulsion before the final digestion or after-ripening or it can be added immediately prior to the coating.

The silver halide emulsion of a photographic element containing the antifoggants of this invention can contain conventional addenda such as gelatin plasticizers, coating aids, and hardeners such as aldehyde hardeners, e.g., formaldehyde, mucochloric acid, glutaraldehyde bis(sodium bisulfite), maleic dialdehyde, aziridines, dioxane derivatives and oxypolysaccharides. Spectral sensitizers which can be used are the cyanines, merocyanines, complex (trinuclear) cyanines, complex (trinuclear) merocyanines, styryls, and hemicyanines. Sensitizing dyes useful in sensitizing such emulsions are described, for example, in US. Pats. 2,526,632 of Brooker and White issued Oct. 24, 1950, and 2,503,776 of Sprague issued Apr. 11, 1950. Developing agents can also be incorporated into the silver halide emulsion if desired or can be contained in a contiguous layer. Various silver salts can be used as the sensitive salt such as silver bromide, silver iodide, silver chloride, or mixed silver halides such as silver chlorobromide, silver bromoiodide and the like. The silver halides used can be those which form latent images predominantly on the surface of the silver halide grains or those which form latent images inside the silver halide crystals such as described in US. Pat. 2,592,250 of Davey and Knott issued Apr. 8, 1952.

The silver halide emulsion layer of a photographic element containing the antifoggants of the invention can contain any of the hydrophilic, water-permeable binding materials suitable for this purpose. Suitable materials include gelatin, colloidal albumin, polyvinyl compounds, cellulose derivatives, acrylamide polymers, etc. Mixtures of these binding agents can also be used. The binding agents for the emulsion layer of the photographic element can also contain dispersed polymerized vinyl compounds. Such compounds are disclosed, for example, in US. Pats. 3,142,568 of Nottorf issued July 28, 1964; 3,193,386 of White issued July 6, 1965; 3,062,674 of Houck, Smith and Yudelson issued Nov. 6, 1962; and 3,220,844 of Houck, Smith and Yudelson issued Nov. 30, 1965; and include the water insoluble polymers of alkyl acrylates and methacrylates, acrylic acid, sulfoalkyl acrylates or methacrylates and the like.

The silver halide emulsion of a photographic element containing the antifoggants of the invention can be coated on a wide variety of supports. Typical supports are cellulose nitrate film, cellulose ester film, polyvinyl acetal film, polystyrene film, poly(ethylene terephthalate) film and related films or resinous materials as well as glass, paper, metal and the like. Supports such as paper which are coated with a-olefin polymers, particularly polymers of a-olefins containing two or more carbon atoms, as exemplified by polyethylene, polypropylene, ethylenebutene copolymers and the like can also be employed.

The sensitometric characteristics of the photographic emulsions containing the antifoggants of the invention can be further enchanced by including in the emulsions a variety of hydrophilic colloids such as carboxymethyl protein of the type described in U.S. Pat. 3,011,890 of Gates, Jr., Miller and Koller issued Dec. 5, 1961, and polysaccharides of the type described in Canadian Pat. 635,206 of Koller and Russell issued Jan. 23, 1962.

Photographic emulsions containing the antifoggants of the invention can also contain speed-increasing compounds such as quaternary ammonium compounds, polyethylene glycols or thioethers. Frequently, useful effects can be obtained by adding the aforementioned speed-increasing compounds to the photographic developer solutions instead of, or in addition to, the photographic emulsions.

Photographic elements containing the antifo ggants of the instant invention can be used in various kinds of photographic systems. In addition to being useful in X-ray and other non-optically sensitized systems, they can also be used in orthochromatic, panchromatic and infrared sensitive systems. The sensitizing addenda can be added to photographic systems before or after any sensitizing dyes which are used.

Silver halide emulsions containing the antifoggants of the invention can be used in color photography, for example, emulsions containing color-forming couplers or emulsions to be developed by solutions containing couplers or other color-generating materials, emulsions of the mixed-packet type such as described in U.S. Patent 2,698,- 794 of Godowsky issued J an. 4, 1955; in silver dye-bleach systems; and emulsions of the mixed-grain type such as described in U.S. Pat. 2,592,243 of Carroll and Hanson issued Apr. 8, 1952.

Silver halide emulsions containing the antifoggants of the invention can be sensitized using any of the wellknown techniques in emulsion making, for example, by digesting with naturally active gelatin or various sulfur, selenium, tellurium compounds and/or gold compounds. The emulsions can also be sensitized with salts of noble metals of Group VIII of the Periodic Table which have an atomic weight greater than 100.

Silver halide emulsions containing the antifoggants of the invention can be used in diffusion transfer processes which utilize the undeveloped silver halide in non-image areas of the negative to form a positive by dissolving the undeveloped silver halide and precipitating it on a receiving layer in close proximity to the original silver halide emulsion layer. Such processes are described in U.S. Patents 2,352,014 of Rott issued June 20, 1944; 2,543,181 of Land issued Feb. 27, 1951; and 3,020,155 of Yackel, Yutzy, Foster and Rasch issued Feb. 6, 1962. The emulsions can also be used in diffusion transfer color processes which utilize a diffusion transfer of an imagewise distribution of developer, coupler or dye, from a lightsensitive layer to a second layer, while the two layers are in close proximity to one another. Silver halide emulsions containing the antifoggants of the invention can be processed in stabilization processes such as the ones described in U.S. Pat. 2,614,927 of Broughton and Woodward issued Oct. 21, 1952, and as described in the article Stabilization Processing of Films and Papers by H. D. Russell, E. C.

Yackel and J. S. Bruce in P.S.A. Journal, Photographic Science and Technique, volume 16B, October 1950.

While it is preferred to utilize the antifoggants of the invention by incorporating them directly into a photographic element, the antifoggants could also be utilized by incorporating them into a photographic developer to control development fog.

The antifogging agents of this invention can be incorporated to advantage during manufacture in silver halide emulsions representing the variations described above. Moreover, fog control in binderless silver halide films prepared by vapor deposition of silver halide on a suitable support can be achieved by coating the antifogging agents of the invention over the vapor deposited layer of silver halide.

Combinations of all the above-mentioned addenda can be used if desired.

While the antifoggant action of the thionamide compounds of this invention are particularly advantageous, their ability to complex with metal ions, especially with silver ions, warrants their use in numerous photographic systems. Thus, they can be utilized in silver halide diffusion transfer systems; as silver halide grain growth agents to promote Ostwald ripening; as fixing agents; and as stabilization agents for unexposed silver halide in stabilization processing systems as described, for example, in Broughton et al. U.S. Patent 2,614,927 issued October 21, 1952. The thiones of this invention can also be used to form intramolecular salts or chelates with silver ions which, when coated in a suitable binder on a suitable support form light-sensitive layers as described in copending application Ser. No. 764,298 of Haist et al. entitled Photosensitive Compositions Comprising Silver Complexes of 3-Substituted-4-Thiazoline-2-Thiones and Photosensitive Elements Comprising Such Compositions filed concurrently herewith. The stability of these silver complexes will withstand extreme keeping conditions permitting their incorporation into photographic elements as a silver source for physical development and used, for example, in systems of the type described in Agfa British Pat. 920,- 277 issued Mar. 6, 1963; Kodak Belgian Pat. 672,283 issued Mar. 1, 1966; and copending application Ser. No. 764,330 of Bass entitled Photographic Element, Composition and Process filed concurrently herewith. The dual properties of stability and light sensitivity of these silverthione complexes allow them to be utilized with lightsenstive catalysts, which can or cannot be photoconductors, in a bifunctional photographic element containing two light-sensitive components which can be treated selectively to produce two independent images. Alternatively, these silver complexes can be utilized in image reproduction systems in combination with a reducing agent and a light-sensitive catalyst as described in Shepard et al. U.S. Pat. 3,152,903 issued Oct. 13, 1964.

The invention can be further illustrated by the following examples or preferred embodiments thereof, although it will be understood that these examples are included merely for purposes of illustration and are not intended to limit the scope of the invention.

In the following examples, the stabilizer compound is neutralized by the addition of a base before addition to the emulsion where it is necessary to maintain the pH of the emulsion constant.

EXAMPLE 1 Photographic emulsions .are prepared by adding thionamides having the formula wherein R is defined in Table 1, to separate portions of a high speed gold and sulfur sensitized bromoiodide emul- 8 sion. Each emulsion sample is coated on a cellulose ace- 50 at 68 F. for five minutes. The photographic results tate film support at a coverage of 350 milligrams of silver are set forth in Table 2.

TABLE 2 2 week incubation at 120 F. and 50% Stabilizer compound Fresh relative humidity Relative Relative R4 gJmole Ag speed Fog speed Fog Control 100 0.10 0.66 -CH2COZH 3.0 102 0.09 107 0.12 -OH2CHzCOzH.. 3.0 105 0.10 118 0.15 CH CHgOH2COzH 3.0 105 0.17 110 0.28

and 840 milligrams of gelatin per square foot. A sample EXAMPLE 3 f each film coating 18 exposed an lmenfilty S.cale Photographic emulsions are prepared by adding stabisitometer, processed for four minutes at 68 F. 1n Kodak lizer compounds having the formula Developer D-19, fixed, washed and dried. The photographic results obtained from these tests are listed in Table 1. 20 S TABLE 1 2 week lneu- N bation at Fresh sigl and R4 re a We Relative Fog hiimidity, wherein R and R are defined in Table 3 to separate por- Thlonamldel R4 Ag speed {0g tions of a high speed gold and sulfur sensitized bromo- Control 100 0 00 0. iodide emulsion containing a spectral sensitizer. Each :8g: 6 3; g; g g emulsion sample is coated on a cellulose acetate film support at a coverage of 350 milligrams of silver and 840 u 30 milligrams of gelatin per square foot. A sample of each It W111 be seen that the emu1s10n contammg a thionfilm coating is exposed on an intensity scale sensitomamide having a carboxyl substituent is much more effeceter, processed for five minutes at 68 F. in Kodak Detive in preventing the growth of incubauon fog than is a veloper DK50, fixed, washed and dried. The photographic thionamide which does not contain an and substituent. results obtained from these tests are listed in Table 3.

TABLE 3 Incubation at F. and relative humidity Stabilizer compound Fresh 1 week g./mole Relative Relative 2 Weeks, R4 R5 Ag speed Fog speed Fog fog Control 100 0.12 83 0. 34 1.12

-C]}HCO2H -CO2H 3.0 97 0.10 0.13 0.13

-CH2CH2C 02H CHzS O2(CH2)3CH3 0. 3 102 O. 11 97 0.17 O. 35

EXAMPLE 2 EXAMPLE 4 1 Process of Example 1 is repeatefi except that the 5 The process of Example 3 is repeated substituting for stabllizer compounds added to the emulsions have the forthe Stabilizer compounds therein a thionamide having the mula formula 8 s r mo CHzOzC-l HsC-KlTI/ HaC- wherein R is defined in Table 2. The emulsions also contain a spectral sensitizer and, in several samples, an 60 In several samples, an additional compound as indicated additional compound or compounds as indicated in Table in Table 4 is included. The photographic results obtained 2. Development is accomplished in Kodak Developer DK- 7 are hsted in Table 4.

TABLE 4 1 week incubation at 120 F. and 45% relative Fresh humidity Concentration of Additional compound stabilizer compound in and concentration Relative Relative ./mole Ag in gJmole Ag speed Fog speed Fog Control 100 0. 12 82 0. 34 3. 0 120 0. 14 0. 17 Control Poly(thi0diethylene 182 0. 24 1. 2

glutarate) (1.0). 3. 0 do 214 0. 21 178 0. 34 191 0. 21 1. 2 186 0. 19 151 0. 33

9 EXAMPLE The process of Example 3 is repeated using as the is also tested for its ability to stabilize an emulsion. The photographic results are set forth in Table 6.

TAB LE 6 Dithioearbamate Incubation at 120 F. and R3 50% relative humidity Fresh 1 week 2 Relative Relative Weeks, R R gJinole Ag Speed Fog Speed Fog Fog Control 100 0. 17 62 0. 41

m 0. 27 100 0.13 76 0. 0 N CH -C 02H Containing no acid 0.27 29. 5 0. 22 1. 0

group. Control 100 0.13 57 0. 48 1. 21

(C O CH2)2N-.-- 3.0 100 0. 09 91 0. 09 0. 09

CH2- C 0 2H Control 100 0. 16 0. 81

N on ong)zs 03 m CH stabilizer a thionamide having the formula EXAMPLE 7 I s H3O\ For the purpose of comparison, there is also tested an emulsion containing a non-acid group containing thionamide having the formula CH S The photographic results are set forth below in Table 7.

TABLE 7 s 40 Two weeks I an 0 H3 CHZC 02 CH? C Fresh relative humidit y Thiourea in Relative Relative 311 013 0 CH3 EJ g speed Fog speed Fog The photographic results obtained are set forth in Table 5. control- 100 0.14 54 0. 35 0.9- 8O 0. 11 65 0. 14

TABLE 5 Incubation at 120 F. and

% relative humidity Fresh 1 week 2 Relative Relative weeks, Thionamide G./mole Ag spee Fog speed Fog Fog Control 100 0. 12 59 0. 48 1. 16 Containing acid group 0.3 95 0. 11 94 0.14 0. 25 Containing no acid group.-- 0.3 78 0. 11 1. 0 1. 2

EXAMPLE 6 This example illustrates the use of dithiocarbamates containing acid groups as stabilizers for photographic emulsions. The process of Example 2 is repeated using as the stabilizer compound dithiocarbamates having the are as defined in Table 6. For purpose of comparison, a non-acid group containing dithiocarbamate having the Haze In the foregoing Table 4, the pyridinium salt used is 7,18-diazo-6,19 dioxotetracosane 1,24-bis(pyridinium perchlorate) The results in the above tables show that the compounds of this invention prevent the growth of incubation fog when incorporated in photographic emulsions.

Although the invention has been described in considerable detail with reference to certain embodiments thereof, it will be understood that variations and modifications can be effected without departing from the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

I claim:

1. A composition comprising a silver halide emulsion containing a fog-stabilizing amount of an acylic or monocyclic thionamide, said thionamide containing at least one carboxylic or sulfonic acid group which will confer a negative charge to the thionamide at a pH of 5 or below.

11 2. The composition of claim 1 wherein said thionamide is present in an amount of about 005 gram to about 30.0 grams per mole of silver in said silver halide emulsion.

3. The composition of claim 1 wherein said thionamide has the structure wherein X is sulfur, oxygen or an iso'electronic group, R R and R when taken separately, are aliphatic groups having up to 10 carbon atoms or substituted aliphatic groups, R and R when taken together, represent an alkylene group and R and R when taken together with the nitrogen atom to which they are attached, represent a heterocyclic group.

4. The composition of claim 1 wherein said thionamide has the structure /C=S R wherein R is an aliphatic group or a substituted aliphatic group containing up to carbon atoms and R and R are hydrogen, aliphatic groups or substituted aliphatic groups containing up to 10 carbon atoms, at least one of said groups containing a carboxylic or sulfonic acid substituent.

5. The composition of claim 3 wherein X in said thionamide is sulfur and at least one of said groups R R and R contains a carboxylic or sulfonic acid substituent.

6. The composition of claim 3 wherein X in said thionamide represents the group --NR, R being an. aliphatic or substituted aliphatic group having from 1-10 carbon atoms, and at least one of said groups R, R R and R contains a carboxylic or sulfonic acid substituent.

7. A photographic element comprising a support coated with a silver halide layer, said element containing a fog-stabilizing amount of an acylic or monocyclic thionamide, said thionamide containing at least one carboxylic or sulfonic acid group which will confer a negative charge to the thionamide at a pH of 5 or below.

8. The photographic element of claim 7 wherein said layer is a silver halide emulsion.

9. The photographic element of claim 8 wherein said thionamide is present in an amount of about 0.05 gram to about 30.0 grams per mole of silver in said silver halide emulsion.

10. The photographic element of claim 8 wherein said thionamide has the structure wherein X is sulfur, oxygen or an iso-electronic group, R R and R when taken separately, are aliphatic groups having up to 10 carbon atoms or substituted aliphatic groups, R and R when taken together, represent an alkylene group and R and R when taken together with the nitrogen atom to which they are attached, represent a heterocyclic group.

11. The photographic element of claim 8 wherein said thionamide has the structure wherein R is an aliphatic group or a substituted aliphatic group containing up to 10 carbon atoms and R and R are hydrogen, aliphatic groups or substituted aliphatic groups containing up to 10 carbon atoms, at least one of said groups containing a carboxylic or sulfonic acid substituent.

12. The photographic element of claim 10 wherein X in said thionamide is sulfur and at least one of said groups R R and R contains a carboxylic or sulfonic acid substituent.

13. The photographic element of claim 10 wherein X in said thionamide represents the group NR, R being an aliphatic or substituted aliphatic group having up to 10 carbon atoms, and at least one of said groups R, R R and R contains a carboxylic or sulfonic acid substituent.

14. The photographic element of claim 8 wherein said thionamide is present in said silver halide emulsion.

15. The photographic element of claim 8 wherein said thionamide is present in a layer contiguous to said silver halide emulsion.

16. In a process of developing a photographic element comprising a support coated with at least one silver halide emulsion layer, the improvement comprising developing said photographic element in the presence of an acyclic or monocyclic thionamide containing at least one carboxylic or sulfonic acid group which will confer a negative charge thereto at a pH of 5 or below.

17. The process of claim 16 wherein said thionamide has the structure wherein R is an aliphatic group or a substituted aliphatic group containing up to 10 carbon atoms and R and R are hydrogen, aliphatic groups or substituted aliphatic groups containing up to 10 carbon atoms, at least one of said groups containing a car-boxylic or sulfonic acid substituent.

19. The process of claim 17 wherein X in said thionamide is sulfur and at least one of said groups R R and R contains a carboxylic or sulfonic acid substituent.

20. The process of claim 17 wherein X in said thionamide represents the group -NR, R being an aliphatic or substituted aliphatic group having up to 10 carbon atoms, and at least one of said groups R, R R and R contains a carboxylic or sulfonic acid substituent.

References Cited UNITED STATES PATENTS 3,433,640 3/1969 Nishio et a]. 96109 WILLIAM D. MARTIN, Primary Examiner R. M. SPEER, Assistant Examiner