US2992108A - Gelatin coating compositions - Google Patents

Description

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Patented July 11, 1961 ice 2,992,108 GELATIN COATING COMPOSITIONS William J. Knox, Jr., and John Stenberg, Rochester, N.Y., assignors to Eastman Kodak Company, Rochester, N .Y., a corporation of New Jersey No Drawing. Filed Oct. 21, 1957, Ser. No. 691,125 Claims. (Cl. 96-85) This invention relates to gelatin coating solutions particularly for photographic purposes and the employment of those solutions in the manufacture of photographic products.

In the application of gelatin coating compositions such as of photographic emulsions or of protective coatings, to film base or to paper the addition of a coating aid such as saponin to the coating composition permits the application of a smooth, even coating. Furthermore, the presence of saponin in an emulsion coating enables the emulsion while wet and in a chilled, set condition to be overcoated with a protective gelatin coating (weton-wet coating process).

If saponin or some other suitable coating aid is omitted from a coating composition which is applied to film base or paper as a single layer thereon (wet-on-dry process) the coating thus laid down is prone to develop deficiencies such as the presence of repellencies, mottle and streakiness and a subsequent application of a protective gelatin coating thereover at reasonable speeds by a wet-on-wet coating process will be impossible.

Saponin although quite useful as a coating aid in applying gelatin layers in preparing photographic products, is nevertheless a naturally occurring substance and may show decided variations in quality from batch to batch. These variations are such that some batches of saponin may cause fog increase or a change in photographic sensitivity or may cause no improvement in the coating properties of the system to which the saponin has been added. Because of these variations of the quality of various saponins, it is preferred that synthetic surfactants which are reproducible from batch to batch both in chemical composition and in behavior, be employed as coating aids in gelatin coating compositions either alone or in admixture with other suitable coating aids.

Coating techniques have been developed for the application of gelatin layers which involve the simultaneous application of two or more gelatin layers to film base or to paper. In those techniques saponin has often been found to be not particularly satisfactory. In those procedures where saponin has been used, the ratio of the bulk concentrations of saponin in the various layers appears to be critical and frequently products free from streaks and other defects such as skips and repellencies are difiicult to obtain when saponin has been employed as the coating aid. This is also true of many other surfactant materials which have been considered.

This invention has for one object to provide an improved method for applying aqueous gelatin coatings. Another object of our invention is to provide gelatin coating compositions which can be applied to supports therefor without exhibiting the disadvantages which have been found in attempts to coat previous gelatin coating compositions. A further object of our invention is to provide an improved coating procedure whereby an undried first coating of gelatin may be followed by further gelatin coatings thereon with good results. Other objects of our invention will appear herein.

We have found surfactants which, when used as coating aids in various photographic emulsions and gelatin coating compositions, are effective in at least 2 if not all 3 of the following particulars: (1) in controlling repellency and other coating deficiencies (2) in enabling high speed wet-on-wet coating and (3) in enabling the satisfactory simultaneous application to fihn base or paper of two or more gelatin layers independent of the concentration ratio of the surfactants in any two contiguous layers. These materials have indicated their superiority to saponin as coating aids in the preparation of photographic products involving the application of gelatin layers therein.

We have found that certain related compounds having both amide and carboxylic acid groups therein have shown themselves to be very useful as coating aids in the preparation of coating compositions. These compounds are prepared by the reaction of high molecular weight amines with reagents which will supply carboxylic acid groups to the resulting product. One class of surfactant materials which has been found to be useful in this connection has the structural formula:

CH CONHR OHCO ONa SOaNa in which formula R is an alkyl group of 8 to 18 carbon atoms or some other hydrophobic like radical such as oleyl, abietyl or alkyl and having a molecular weight equivalent to at least 12 carbon atoms. Examples of long chain alkyl groups of 8 to 18 carbon atoms straight or branch chain are octyl, laury-l, octadecyl or trimethyl nonyl. An example of an alkylaryl group is dodecyl phenyl. In the above formula Na can be replaced with some other alkali radical such as potassium, lithium or ammonium. The preparation of compounds of this type is described in US. Patent No. 2,252,401 of Alphonse O. Jaeger.

Another class of compounds of this type the members of which are useful for incorporating into gelatin coating compositions as coating aids are those having the following formula:

CHrCO OX CHCO OX CHzOON XOaSOHGO OX R in which R represents any of the groups which are represented by R in the preceding formula and X is an alkali substituent such as NH Na, K or Li. The preparation of compounds of this type is described in US. Patent No. 2,438,092. For example, a suitable coating aid of this type may be prepared by the following pro cedure using a high molecular weight amine in that procedure:

To a solution of 71 parts of laurylamine in 250 parts of t-butanol was added 65.5 parts of diethyl maleate.-

The mass was allowed to stand for 72 hours at room temperature and was then warmed to 60 C. and 39.5 parts of maleic 'anhydride was added in small portions with stirring. The solution was stirred for one hour at 90 C. to complete the acylation. The solution was then slowly poured with stirring into a hot solution of 50 parts of sodium sulfite in 188 parts of distilled water. Heating was continued for 15 minutes. The resulting clear solution was evaporated to dryness at a reduced pressure. The residue was dissolved in a liter of absolute alcohol and added to a liter of alcohol to which had been added a solution of 31 parts of sodium hydroxide in 60 parts of distilled water. A pinkish solid separated which lightened in color on stirring for several hours in a 60 bath. After cooling, the solid material was collected, washed with ethyl ether and dried. The coating aid was obtained in the form of a white powdery solid.

Another group of the compounds of this type are analogues of the preceding, the preparation of which involves adding the amine to diethyl maleate, acylating the product with maleic anhydride and hydrolyzing the product thus obtained. These compounds have the following formula:

C170 CH=CHC OX RN-CHGOOX OHrCOOX in which R is a long chain alkyl of .8-18 carbon atoms, an alkyl aryl group of an abietyl group such vas have been referred to previously as being represented by R in the formulas herein. X represents Na, K, Li, or NH These compounds are prepared as described in U.S. Patent No. 2,438,092. The following example illustrates the preparation of one of these compounds:

65.5 parts of diethylmaleate was mixed with a solution of 71 parts of laurylamine in 125 parts of tertiary butanol. The mixture was allowed to stand for three days at room temperature. The solution was then warmed to 60 C. and 39.5 parts of maleic anhydride was added in small portions with stirring. The solution was heated to 85-90 C. and maintained thereat for an hour to complete the acylation whereupon the mass was evaporated to dryness at reduced pressure. The residue was dissolved in 500 parts of ethanol and was added to 1000 parts of ethanol containing a solution of 48 parts of sodium hydroxide in 100 parts of Water. The mass was stirred for two hours at 60 C. A solid was collected and the coating aid was obtained by drying this material to a fine powder.

In the use of the gelatin coating compositions in accordance with our invention, if a film base is to be coated, it may be composed of any of the usual conventional film base materials. This may be a sheet of cellulose nitrate, or of an organic acid ester of cellulose such as cellulose acetate, cellulose acetate propionate or cellulose acetate butyrate. It is often desirable first to apply a subbing layer to the cellulose ester base to facilitate adhesion of the photographic emulsion thereto; this practice of subbing being well known in the art. As for the photographic paper a description thereof is found in Kodak Data Book, 5th edition, Kodak Papers, pages 3 and 4. A base material of the type described there would preferably be employed for preparing photographic paper in accordance with the present invention.

The coating procedure outlined may comprise any of the standard procedures employed in the industry. As an instance of such procedure, paper base to be coated is passed through a trough or other reservoir whereby a coating is applied to the paper base. The coating is applied in greater thickness than desired and the surface is then subjected to the action of some leveling means such as a doctor blade or an air brush which causes run back of the coating composition and results in an even surface. In some cases it may be desirable to apply several coatings simultaneously in the manner described in US. Patent No. 2,761,791 of T. A. Russell. In some cases the coating method may involve a hopper technique in which the thickness of the layer is regulated by the rate at which the coating composition is deposited upon the base which is moved along adjacent thereto. We have found that the coating aids in accordance with our invention are effective when used in gelatin compositions over a wide range such as from as little as .001%, based on the weight of the gelatin, up to as much as 5 or even more on that basis. We have found that the presence of excessive coating aid as described herein causes no discoloration or the like in coating operations and therefore there is no upper limit which can be regarded as critical as amounts of coating aid even up as much as 50% of the weight of the gelatin can be employed even though the economics of the coating process makes proportions of this order impractical. The following examples illustrate coating procedures employing compositions in accordance with our invention:

Example 1 A gelatin silver halide emulsion was applied to paper in a hopper type coating operation which emulsion contained various amounts of surfactant; The surfactant employed unless otherwise designated was N-oc-tadecyl disodium sulfosuccinamate. This coating operation was carried out at normal coating speed. This coating aid was employed in amounts from 0.13 gram to 1 gram per pound of emulsion. A product which was free from streaks or coating defects was obtained.

Surfactant Sample No. Concentra- Repellencies Photograph tion (gm/ Projection 0.00 0 O.K Sap onin r Standard 0 O.K P 0.13 1 O.K 0.25 O O.K 0. 5 0 O.K

Example 2 There was applied to paper simultaneously a layer of silver halide gelatin emulsion and a clear gelatin overcoating using as the coating aid N-octadecyl disodium sulfosuccinamate. The results obtained were as follows:

Surfactant Surfactant Photo- Gone. in Gene. in Repclgraph Pro- Emulsion Overcoat lencies jection -I (a /1b.)

0. l3 0. l3 0 O.K. 0. 25 0; 13 0 O.K. 0. 5 0. 13 0 O.K. 1. 0 0. l3 0 O.K. O. 13 0. 25' 0 O.K. 0. 25 0. 25 0 O.K. 6. 5 0. 25 0 O .K. 1.0 0. 25 0 O.K. 0. 13 0. 50 0 O.K. 0. 25 0. 5 0 O.K. 0. 5 0. 5 O O.K. 1. 0 0. 5 0 O .K. 0. l3 1. 0 0 O.K. 0. 25 1. 0 0 O.K. 0. 5 l. 0 0 O K. 1. 0 l. 0 0 O .K.

Example 3 A wet-on-wet coating operation involving X-ray type silver halide emulsion and gelatin overcoating was run. N-octadecyldisodium sulfosuccinamate was used at the rate of 1 gram to 2.5 pounds in the emulsion and 1 gram to 7.7 pounds in the overcoating over the emulsion layer. The overcoat was applied to the wet emulsion layer by a hopper technique using normal coating speed. In this wet-on-wet coating procedure the results obtained were excel-lent.

Example4 A run was carried out similar to that in the preceding example except that the lauryl analogue was used as the coating aid. Similar excellent wet-on-wet coating results were obtained.

Example 5 A gelatin silver halide photographic emulsion was applied to paper on a wet-on-dry application procedure using a knife technique. Normal coating speed was used. The surfactant which was employed in the emulsion composition was tetra sodium N-(1,2 dicarboxyethyl)-N- octadecyl sulf osuccinamat'e. The concentration of surfactant and the results obtained were as follows:

Surfactant Repellencles Photographic Concentration (7.5 sq. ft.) Properties 0.00 2 O.K. 0.13 3 OK. 0.25 O.K. 0.5 0 OK. 1.0 0 O.K.

Example 6 A gelatin-silver halide emulsion and a clear gelatin overcoat were applied simultaneously to paper support by a hopper technique in which tetra sodium N-(1,2 dicarboxyethyl) N-octadecyl sulfosuccinamate was employed as the surfactant in both layers. The proportions used and the results obtained in the finished products were as follows:

Surfactant Surfactant Gone. in Gone. in Repcllencies Emulsion Overcoat (7.5 sq. ft.)

(is-l s-/ 0. 13 0. l3 0 0. 25 0. l3 0 0. 5 07 13 1 1. 0 0. 13 0 0. 13 O. 25 0 0. 25 O. 25 0 0. 5 0. 25 0 1. 0 0. 25 0 0. l3 0. 50 0 0. 25 0. 50 0 0. 50 O. 50 0 1. 0 0. 50 0 0. 13 1. 0 0 0. 25 1. 0 0 0. 5 1. 0 0 1. 0 1. 0 0

Example 7 A wet-on-wet coating run was carried out involving X-ray type gelatin photographic emulsion. The ratios of tetra sodium N-(l,2 dicarboxyethyl) N-octadecyl sulfosuccinamate to total composition were 1. 0, 0.4, 0.2 and 0.1 gram to 2.5 pounds of emulsion and 1.0, 0.5, 0.2 and 0.1 gram per 7.7 pounds of gelatin overcoat. The ease of wet-on-wet coating at high speeds was found to be even better than has been obtained in previous coating experiments using coating aids which have been regarded as satisfactory in those operations. The coating operation was carried out using a hopper coating technique.

Commonly in multiple coating operations applied simultaneously the concentration of surfactant in a given layer must be equal to or greater than that in the layer below to avoid serious coating defects with the coating aids as used above. With the coating aids designated herein successful coating is obtained in simultaneous multiple coating operations independent of the concentration ratios of the coating aids (surfactants) in the two contiguous layers. Successful simultaneous coatings have even been carried out when the surfactant was in the lower layer only.

Example8 A wet-on-wet coating operation was carried out in which the coating aid used was tetrasodium N-(1,2 dicarboxyethyl) N-lauryl sulfosuccinamate. The coating aid was used in the emulsion in the proportion of 1 gram to 2.5 pounds of emulsion and 1 gram to 7.7 pounds of gelatin overcoat. The ease of wet-on-wet coating at high speeds was outstanding.

Example 9 In a simultaneous application of gelatin silver halide emulsion and clear gelatin overcoat to paper by a hopper technique the following results were obtained wher'f N-(alkyl-i-alkenyl) N-maleyl sodium aspartate was used as the coating aid. This coating aid was prepared by using as the amine in its preparation a commercial product consisting of a mixture of hexadecyl, octadecyl and octadecenylamines which supplies the (alkyl-l-alkenyl) portion of the surfactant:

Cone. of Cone. of Photosurfactant surfactant (7.5 ft?) graphic in emulin overcoat Repel- Propsion (gm./1b.) lencies erties -l 0. 13 0. 13 0 OK. 0. 25 0. 13 0 OK. 0. 5 0. 13 O O.K. 1. 0 0. 13 0 OK. 0. 13 0.25 0 OK. 0. 25 0.25 0 O.K. 0. 5 0.25 0 O.K. 1. 0 0. 25 0 O.K. 0. l3 0. 5 0 O.K. 0. 25 0. 5 0 OK. 0. 50 0. 5 0 OK. 1.0 0. 5 0 O.K. 0. 13 1. 0 0 OK. 0. 25 1.0 1 O.K. 0. 5 1. 0 0 O.K. 1. 0 1. 0 1 OK.

In a similar run the sodium salt of N-maleyl-N-abietyl aspartic acid was used as a coating aid. Coatings of good photographic properties and good repellencies were obtained.

Example 10 In a dry wet-on-dry application of gelatin silver halide emulsion to paper by a hopper technique the following results were obtained when the sodium salt of N-malely- N-lauryl aspartic acid was used as the coating aid:

In a wet-on-wet coating run employing a gelatin photographic emulsion of the X-ray type and N-maleyl-N- (a1kyl+alkenyl) aspartic acid, sodium salt, as the coating aid, the ease of coating was equivalent to that obtained with the best coating aids known for this purpose at the present time.

In a run similar to the preceding, N-maleyl N-lauryl aspartic acid, sodium salt, was used as the coating aid. The results obtained were superior to those which are obtained using coating aids which have up to now been found to be best for this purpose.

In addition to the compounds having both amide and carboxylic groups therein in accordance with our invention there has also been some interest shown in the use of certain sulfonated compounds as coating aids for the coating out of aqueous gelatin compositions including photographic emulsions. For instance, compounds having the formula SOaNa C(CHahCH wherein R represents hydrogen or an alkyl of 1-4 carbon atoms and n=1-18 have been found to be suitable in many situations for use as coating aids. These compounds prepared by the action of fatty acids on orthophenylene diamine followed by sulfonation thereof have been described. in French Patents 774,018 and 818,919 and. German Patent 6335818. These surfactantshave beenfound.

to beuseful as coating aids in the coating out. of. Xeray' emulsions andin wet-on-wet coating. processes usinglthose emulsions as well as in wet-on-dry processes. Some corn.- pounds of this type useful in coating operations. are 2-n.- pentadecylbenzimidazole sodium sulfonate Z-n-tridecyl benzimidazole sodium sulfonate and 2-n-und ecyl benzimidazole sodium sulfonate. These coating aids,.however, have certain characteristics which render them inferior to the compounds containing amide and carboxylic groups in accordance with our invention.

Another type of material which has been of some interest for aiding in coating operations involving aqueous gelatin coating compositions are the alkylarylguanamin sulfonates, such as those having the structural formula in which formula R represents an alkyl group of 1-18 carbon atoms and R represents hydrogen or an alkyl group" of 14 carbon atoms. Using a hopper technique these coating aids are superior to saponin in wet-on-wet coating operations. However, both these and the coating aids referred to in the preceding paragraph are not useful in all types of photographic emulsions. In certain types of photographic emulsions it has been noted that these coating aids cause a speed loss of 25-30% while in other types of emulsions losses in speed do not occur. Also with coating aids ofthe. type of thosediscussed in the last two paragraphs it is necessary in simultaneous multiple coating operations such as described in US. Patent No. 2,761,791 of T. A. Russell that the coating aid be higher in the overlayer than in the lower layer to produce a smooth uniform coating in both layers. If the order of concentration is reversed a non-uniform flow results which contributes to the obtaining of a coating of inferior characteristics. In contrast the coating aids of the invention give satisfactory effects when used in simultaneous multiple coating operations of the type described in the Russell patcnt irrespective of the ratio of coating aids used in the two adjacent layers in that process. Coating aids of the type described and claimed in this application do not cause desensitization of silver halide emulsions such as results in the case of certain emulsions when alkylaryl guanamin sodium sulfonates and the benzimidazole sulfonates are used as coating aids therein.

We claim:

1. A photographic element comprising a support and a light-sensitive silver halide emulsion layer, said element having a gelatin overcoat layer upon the emulsion layer, one of which layers contains a small amount of a compound selected from the group consisting. of the compounds having the following structural formulas:

C J HCOOX CHCOOX RNOHCOOX SOsX CHzCON-R OHQOOOX IHC'OOX SOaX in which formulas R is an alkyl radical of at least. 8-carbon atoms and X is an alkali metal substituent,

2. A photographic element comprising a support and a light-sensitive silver halide emulsion layer, said element having over the emulsion layer a gelatin overcoat layer, one of which layers contains a small amount of a com- CH2OONHR CHOOOX in which R is an alkyl radical of at least 8- carbon atoms and X is an alkali metal substituent.

3. A photographic element comprising a support and a light-sensitive silver halide emulsion layer, said element having over the emulsion layer a gelatin overcoat layer, one of which layers contains a small amount of a compound having the formula:

CHzOOOX OHCOOX CHzCON-R (IJHCOOX in which R is an alkyl radical of at least 8 carbon atoms and X is an alkali metal substituent.

4. A photographic element comprising a support and a light-sensitive silver halide emulsion layer, said element having over the emulsion layer a gelatin overcoat layer, one of which layers contains a small amount of a compound having the formula:

O=CCH=GH(JOOX RNCHCOOX CHzCOOX in which R is an alkyl radical of at least 8 carbon atoms and X is an alkali metal substituent.

5. A photographic element comprising a support and a light-sensitive silver halide emulsion layer, said element having over the emulsion layer a gelatin overcoat layer which layers contain a small amount of N-octadecyl disodium sulfosuccinamate.

References Cited in the file of this patent UNITED STATES PATENTS 2,252,401 Jaeger Aug. 12, 1941 2,383,130 Jaeger et al Aug. 21, 1945 2,438,092 Lynch Mar. 16, 1948 2,527,260 Hart et al Oct. 24, 1950 2,739,891 Knox et al Mar. 27, 1956 2,823,123 Knox et al Feb. 11, 1958 2,843,487 Knox et al July 15, 1958 OTHER REFERENCES Schwartz et al.: Surface Active Agents and Detergents, pp. 732-733, vol. II (1958), Interscience Publishers Inc., New York.

Websters New International Dictionary, p. 1067, item glue, 1956 ed., Merriam Co. Publishers, Springfield, Mass.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,992,108 Jill 11, 1961 William J. Knox, Jr., et al.

ified that error appears in the above numbered pat- It is hereby cert on and. that the said Letters Patent, should read as ent requiring correcti "corrected below. 1

Column 8, line 7, after "oom" insert the following line: pound having the formula:

(SEAL) Attest:

ERNEST W. SWIDER Attesting Officer DAVID L. {LADD Commissioner of Patents USCOMM-DC-

Claims (1)

1. A PHOTOGRAPHIC ELEMENT COMPRISING A SUPPORT AND A LIGHT-SENSITIVE SILVER HALIDE EMULSION LAYER, SAID ELEMENT HAVING A GELATIN OVERCOAT LAYER UPON THE EMULSION LAYER, ONE OF WHICH LAYERS CONTAINS A SMALL AMOUNT OF A COMPOUND SELECTED FROM THE GROUP CONSISTING OF THE COMPOUNDS HAVING THE FOLLOWING STRUCTURAL FORMULAS: