US3539353A - Poly(sulfoalkyl) gelatin - Google Patents

Description

United States Patent O F 3,539,353 POLY(SULFOALKYL) GELATIN John W. Gates, Jr., and Paul E. Miller, Rochester, N.Y., assignors to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey No Drawing. Continuation-in-part of application Ser. No. 736,570, June 13, 1968, which is a continuation-in-part of application Ser. No. 364,784, May 4, 1964. This application Oct. 7, 1969, Ser. No. 864,556

Int. Cl. C09h 11/00; C08h 1/00; 07n 7/00 US. Cl. 96--114.8 Claims ABSTRACT OF THE DISCLOSURE New gelatin compounds having sulfoalkyl groups attached to the gelatin molecule, a process for making said compounds and photographic elements and emulsions containing said compounds are disclosed.

This application is a continuation-in-part of our copending application Ser. No. 736,570 filed June 13, 1968 now abandoned, which was a continuation-in-part of copending application Ser. No. 364,784 filed May 4, 1964, abandoned as of June 26, 1968.

BACKGROUND OF THE INVENTION Field of the invention The use in the photographic art of various materials as binding agents for light-sensitive materials such as silver halides is well known. While many hydrophilic polymers have been used as suspending media for light-sensitive materials and as extenders, no substance has been used with greater photographic acceptability than gelatin. The term gelatin, as will be readily understood to those skilled in the art, defines a manufactured product from collagen, which is a naturally occurring fibrous protein and a major protein component of skin, bone and certain other animal tissue. It has long been known that, depending upon its source, gelatin possesses both various desirable and undesirable physical and chemical characteristics when used in photographic elements and, more particularly, in light-sensitive emulsions. For various reasons, gelatin derived from cattle, and most desirably from cattle bone and hides, is most useful for photographic purposes because bindeds comprising said cattle-derived gelatin are relatively permeable to developing solutions, have good physical characteristics, permit reasonably short processing times, and form silver halide emulsions which exhibit higher speed and higher contrast in comparison to gelatin derived from other sources.

While it would be economically advantageous to utilize in photographic elements generally, and more particularly ice in high speed, negative emulsions, gelatin derived from skins and bones of animals other than the high priced and invariably imported cattle, heretofore this has not been possible. For example, the use of pig gelatin has not previously been satisfactory because of desensitizing effects and the restraint of physical development in photographic use of said pig gelatin. These objectionable results are even more pronounced in use with developers having a high salt content, for example. The photographic art would, therefore, be greatly enhanced by new gelatin compounds which are economically, commercially and photographically acceptable replacements for cattle gelatin.

SUMMARY OF THE INVENTION This invention relates to new gelatin compounds having sulfoalkyl groups attached to the gelatin molecule. Said compounds can be derived from pig and more particularly pigskin and are characterized by specific physical and chemical properties which distinguish them from all other pigskin gelatins.

These new gelatin compounds are particularly useful in photographic elements and as binders in light-sensitive photographic emulsions.

A significant feature of this invention is that our new sulfoalkyl gelatins possess photographic, sensitometric and physical properties heretofore thought available only through use of cattle-derived gelatin. By a process of chemically modifying pig gelatin, we have successfully introduced new groups into the complex gelatin polymer molecule which so unexpectedly and dramatically change the characteristics of said molecule that the restraint to physical development can be completely overcome and photographic acceptability achieved.

In one aspect our invention comprises providing a chemically modified pig and pigskin gelatin whose inherent detrimental characteristics, for example, its development restraint, have been removed while its other desirable physical characteristics have been retained within desirable and reproducible limits, as illustrated in Charts I and II hereafter.

By restraint to physical development we mean an inhibition by an exposed photographic emulsion to respond to development within the time desirably required to produce a visible image with corresponding good sensitometric effects.

Accordingly, it is an object of our invention to provide new photographic elements comprising chemically modified gelatins from previously less desirable sources. It is another object of our invention to provide processes for chemically modifying pig gelatin by introducing sulfoalkyl groups into gelatins complex polymeric molecule.

It is another object of our invention to provide poly- (sulfoalkylated) gelatin having improved physical and chemical characteristics as compared to the parent gelatin from which it is derived.

Other objects of this invention willbecome apparent from an examination of the specification and claims that follow.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In accordance with our invention, the above objects are attained with new chemically modified gelatin. Said gelatin is characterized, in part, by being chemically com- 3 bined with a plurality of sulfoalkyl units, that is, alkyls of 3 to 4 carbon atoms. Said sulfoalkyl units are chemically united in recurring numbers on the gelatin macromolecule by reacting upon gelatin in alkaline solution with an alkyl sultone.

These repeating sulfoalkyl units impart generally decreased development restraining properties to light-sensitive emulsions such as pig gelatin emulsions containing said units and corresponding decreased desensitizing effects in concentrations of greater than about 3 by weight of gelatin. In concentrations of about 4 to about 6% by weight, the resistance to development restraint is completely overcome, i.e., the gelatin is substantially photographically inert to physical development restraint.

Although gelatin is a naturally occurring protein composed of known alpha-amino acids, the composite structural arrangement and position of said acids in the gelatin molecule is largely unknown and at best speculative.

One of these alpha-amino acids present in the gelatin molecule is Lysine and is known to have a reactive omega-amino functional group substituted thereon.

Thus, While the highly complex gelatin molecule contains a multiplicity of reactive sites, some of which are known and identifiable, others are unknown and to date are unidentifiable since factors which contribute to the ultimate reactivity of a gelatin molecule-contained alphaamino acid, are contingent upon said acids unknown structural relationship to other alpha-amino acids present in the gelatin molecule.

Therefore, it can be fairly said that the present state of chemical and biochemical analytic technology has not yet advanced to the point where a determination of the range of reactive sites of the gelatin molecule can be absolutely determined and efforts to most specifically designate both all of the reactive sites and their range whereon sulfoalkylation occurs have been unsuccessful and the source of some speculation. (See Mees, Theory of the Photographic Process, MacMillan, 3rd edition, pages 4554.)

Consequently, while it is possible that not all of the reactive site can be presently determined due to the state of the art, we have, nevertheless, unequivocally chemically modified gelatin as shown hereafter on both the lysine and hydroxylysine sites. Example 3, which follows, describes the characteristics of the chromatograms of the modified and unmodified gelatin. The comparative data of these examples show with certainty that the poly sulfoalkylation of gelatin occurs substantially on those two recurring alpha-amino acid sites. Further, said poly sulfoalkylation appears to occur on the epsilon-amino group of each of said amino acid sites. By poly it will be understood by those skilled in the art to mean not only the numerous and substantial sulfoalkylation of these recurring sites but also the additional disubstitution of many of said recurring sites. Further by the use of the term recurring one skilled in the art will also understand this to mean repeating in a random fashion and not necessarily in an ordered and regularly repeating manner. Gelatin is specifically characterized along with other physical properties by its amino acid sites and compositions thereof, and each of these is subject to very small variations after modification of the molecule as shown herein. We have thus produced specific and reproducible changes by the chemical modification of poly sulfoalkylation, which changes are used to identify and fingerprint our new compounds. These gelatin compounds are characterized in terms of their jelly strength, viscosity, color clarity, isoelectric point, lysine and hydroxylysine content and degree of substitution and sulfoalkylation.

In particular a comparison of the data, representing the various chromatograms of both pure gelatin and gelatin chemically modified by substantially sulfoalkylat ing the lysine and hydroxylysine sites, indicates with marked clarity that the sulfoalkylysine sites, indicates with marked clarity that the sulfoalkylation produces new peaks on said amino acid sites to the substantial exclusion of all other amino acid sites. It is seen by comparing the differential of the lysine and hydroxylysine concentration in the various samples of plain gelatin and poly(sulfoalkylated) gelatin that We have efiected sulfoalkylation on the lysine site in ranges from about 30 to about and on the hydroxylysine site from about 50 to about The level of each amino acid present in the chemically unmodified gelatin remains relatively constant at about .281 micromole per milligram of lysine and about .062 micromole per milligram of hydroxylysine. The degree of sulfoalkylation recorded is thus dependent upon the initial values of the unmodified gelatin.

These various characterizing terms are well known in the art and can be determined in a variety of ways employing suitable means. For example, viscosity can be determined by the rolling ball test, which test employs a viscosimeter to determine the length of time in seconds required by a metal ball to fall through a given distance of a solution of gelatin. This can also be measured equally Well in terms of inherent viscosity in water at a concentration of 0.25 gram per 100 milliliters of solution at 25 C. Isoelectric point can be determined conveniently employing mixed resins according to the procedure of Janus, Kenchington and Ward described in Research, volume 4, page 247 (1951). Color clarity is the measured amount of light transmitted through various solutions and rated on a photometer, for example, a lumitron. A test for determining jelly strength is described hereafter.

A preferred embodiment of our invention comprises poly(sulfoalkyl) gelatin being characterized by having the following properties:

Shom jelly strength of about 200 to about 285;

Color clarity of about to about Isoelectric point of about 4.3 to about 5.7;

Viscosity of about 9.4 to about 12.7;

Lysine micromoles per milligram of about 100 to about 200; and

Hydroxylysine micromole per milligram of about .015

and about .025.

The novel sulfoalkylated polymers of our invention can be derived by reacting gelatin, such as pig and preferably pigskin and pig bone gelatin, With a suitable sulfoalkylating compound. This reaction is most effective in a wide pH range but it is preferred that said pH be alkaline, that is, greater than about 7 and preferably about 9 to about 11. This reaction between gelatin, such as pig gelatin, having inherent undesirable sensitometric and photographic characteristics, and a sulfoalkyl compound such as an alkyl sultone, for example, a propane or butane sultone, can be efiected equally well under either warm or cold conditions. In one preferred embodiment, the modified gelatin of our invention is pre pared by first plumping gelatin into cold water (that is, having a temperature of less than about 15 C.), raising the temperature to about 50 C. thereby melting the gelatin. The pH is then adjusted in the resulting solution or suspension to about 10.5 with an alkaline substance, such as sodium hydroxide, potassium bydroxide and the like. Alkyl sultone, previously dissolved in a suitable solvent such as acetone, alcohol, benzene and the like, is added preferably with agitation and the pH is maintained at greater than about 7 and preferably at about 9.5 to about 10.5. The chemically modified gelatin is conveniently recovered by acidifying the solution to a pH of less than about 6, for example, by the addition of dilute sulfuric acid, dilute hydrochloric acid and the like. In the final steps, the poly(sulfoalkyl) gelatin is then chilled, noodled and Washed with cold water as is well known to those skilled in the gelatin art.

Another preferred embodiment of our invention comprises sulfoalkylating gelatin under cold conditions and is effected by plumping flakes of gelatin, that is, pig gelatin, for example, into cold water (for example, distilled water) having a temperature of less than about 15 C. The pH is adjusted to about 9.5 to about 10 such as by the addition of magnesium oxide, for example, and the alkyl sultone, in water, is added to the plumped gelatin flakes. The temperature is depressed, for example, to about 7 C. for about four days. The poly(sulfoalkyl) gelatin thus prepared is washed to remove the alkaline substance, for example, magnesium oxide, and after leaching with dilute acetic acid, for example, is melted, filtered, chilled and dried.

The characteristics of these sulfoalkyl gelatins produced by either method are very similar, as indicated before, except that the jelly strength of the product obtained in the absence of heat, that is, by cold process, understandably exhibits a slightly higher jelly strength. By jelly strength is meant the firmness of resistance to deformation of a gel prepared under standard conditions. This is determined by use of a Bloom Gelometer and the values are customarily referred to as Bloom jelly strengths. By definition, this is the weight in grams required to produce by means of a plunger 12.7 mm. in diameter a depression of 4 mm. in the surface of a gel of a concentration of 6%% by weight, measured at 10 C.i0.1 C. for a period of 16-18 hours (see Photographic Gelatin, Croome and Clegg Focal Press, London 1965). Shoom jelly strength is a modification of the above valuation in that the concentration of the gelatin is more dilute, that is, reduced to about 6.1% by weight. In all other respects, these jelly strength tests are the same. For photographic purposes, a high jelly strength is desirable, that is, at least 150 and preferably between 200 and 295. Unmodified pigskin gelatin has a Shoom jelly strength of about 280 to about 260 but is possessed of heretofore unalterable and undesirable development restraint, and therefore is generally unsuitable in photographic applications.

When combined in photographic elements and in lightsensitive silver halide emulsions, our poly(sulfoalkyl) gelatins can contain photographic addenda such as gelatin plasticizers, coating aids, and hardeners such as aldehyde hardeners, e.g., formaldehyde, mucochloric acid, glutaraldehyde bis(sodium bisulfite), maleic dialdehyde, azirdines, dioxane derivatives, oxypolysaccharides, vinylsulfonyl ethers and the like. 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 11.5. Pats. 2,526,632 of Brooker et al. 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 or silver bromoiodide. 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 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 ct al. issued Apr. 8, 1952.

The silver halide emulsion layer of a photographic element containing the poly(sulfoalkyl) gelatins of our invention can contain combined with, and in addition to, our gelatins any of the hydrophilic, water-permeable binding materials suitable for this purpose. The concentration of our poly(sulfoalkyl) gelatins can vary from more than about to about 90%, by weight, of binding agent, e.g., gelatin used, and preferably is present in a concentration range of about 40 to about 75% by weight of total binder. Suitable materials include other gelatin, modified or unmodified, colloidal albumin, polyvinyl compounds, cellulose derivatives, acrylamide polymers, etc. Mixtures of these latter binding agents can also be used in combination with our sulfoalkyl gelatins.

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 U.S. Pats. 3,142,568 of Nottorf issued July 28, 1964; 3,193,386 of White issued July 6, 1965; 3,062,674 of Houck et al. issued Nov. 6, 1962; and 3,220,844 of Houck et al., issued Nov. 30, 1965; and include the water-insoluble polymers of alkyl acrylates and methacrylates, acrylic acid, sulfoalkyl acrylates or methacrylates and the like.

In addition, the novel poly(sulfoalkyl) gelatins of our invention are particularly useful in photographic elements and layers, for example, in various layers or protective coatings, and layers such as overcoats, antihalation layers, interlayers, and the like and in emulsion layers comprising light-sensitive materials as set forth herein.

The silver halide emulsion of a photographic element containing the chemically modified gelatins of our 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 alpha-olefins polymers, particularly polymers of alpha-olefins containing two or more carbon atoms, as exemplified by polyethylene, polypropylene, ethylene-butene copolymers and the like can also be employed.

The speed of the photographic emulsions containing the new gelatins of our invention can be further enhanced by including in the emulsions a variety of hydrophilic colloids such as carboxymethyl protein of the type described in US. Pat. 3,011,890 of Gates et al. issued Dec. 5, 1961, and polysaccharides of the type described in Canadian Pat. 635,206 of Koller et al. issued Jan. 23, 1962.

Photographic elements and emulsions containing the gelatins of the invention herein can also contain speedincreasing 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 our new gelatins 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 sulfoalkyl gelatins 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 US. Pat. 2,698,- 794 of Godowsky issued 1 an. 4. 1955; in silver dye-bleach systems; and emulsions of the mixed-grain type such as described in US. Pat. 2,592,243 of Carroll et al. issued Apr. 8, 1952.

Silver halide emulsions and elements containing the gelatins of the invention can be sensitized using any of the well-known 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 and elements containing the sulfoalkyl gelatins of our 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 silver layer in close proximity to the original silver halide emulsion layer. Such processes are 7 described in US. Pats. 2,352,014 of Rott issued June 20, 1944; 2,543,181 of Land issued Feb. 27, 1951; and 3,020,- 155 of Yackel et al. 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 light-sensitive layer to a second layer, while the two layers are in close proximity to one another. Silver halide emulsions and elements containing the gelatins of the invention can be processed in stabilization processes such as the ones described in US. Pat. 2,614,927 of Broughton et a1. issued Oct. 21, 1952, and as described in the article Stabilization Processing of Films and Papers by H. D. Russell et al. in P.S.A. Journal, Photographic Science and Technique, vol. 16B, October 1950.

The gelatins of this invention can be incorporated to advantage during manufacture in silver halide emulsions and elements representing the variations described.

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

The following examples are included for a further understanding of the invention.

EXAMPLE 1 900 grams of pigskin gelatin are dissolved in 9 liters of distilled water at 50 C. Sodium hydroxide is added so as to adjust the pH of the solution to 10.5. Added with stirring are 27 grams (3% by weight of the pig gelatin) of 1,3-propanesultone in solution in 75 milliliters of acetone. Stirring is continued for 30 minutes with the pH of the solution being maintained at 10.0 by addition of sodium hydroxide as needed. Thereupon, the pH of the solution is lowered to 6.0 by adding dilute sulfuric acid. The resulting chemically modified gelatin solution is chilled, noodled, Washed and dried in customary fashion.

EXAMPLE 2 Portions of the above chemically modified pigskin gelatin are chromatographically analyzed by a method of the type described by Moore and Stein in J. Bio. Chem., 192, 663-681 (1951). This procedure is as follows:

Each sample is dried at 60 C. in vacuum for 16 hours. A sample of each of about 4 milligrams weight is weighed S exactly and is hydrolyzed in 5.5 N hydrochloric acid for 22 hours at 110 C. in a sealed system. Each is evaporated to dryness in a vacuum desiccator and is dissolved at pH 2.2 in a citrate buffer A (pH 2.2) and is diluted to 5 milliliters with citrate buffer A. One milliliter of the diluted solution is placed on a water jacketed ion exchange column containing sulfonated polystyrene resin (Beckman type B resin), said column being 50 centimeters long and 0.9 centimeter in diameter. The equipment used is a Beckman model 120 B amino acid analyzer.

Then the column is eluted with citrate buffer B (pH of 3.28). The column temperature is in itially held at 30 C. changing to 50 C. after milliliters of eluent is passed through the column. Citrate buffer C (pH 4.5) is then used as the eluent and during the course of the elution, the column eluent is automatically mixed with minhydrin reagent and the stream is put through a heated reaction coil at C. to develop characteristic blue colors for each amino acid. The colors formed are monitored in a Stream Colorimeter whose output is recorded on a strip chart recorder. This gives a separation of the acidic and neutral amino acids.

For the purpose of separating the basic amino acids, second 1 milliliter aliquot portions of each of the hydrolyzed samples in solution in citrate buffer A are taken and placed on a jacketed column of 0.6 centimeter diameter and 10 centimeters length which contain sulfonated polystyrene resin (Beckman type 15A). The sample is eluted with citrate buffer D (pH 5.28). After passing 60 milliliters of eluent through the column the basic amino acids are completely separated. During the course of the elution, the column eluent is automatically mixed with ninhydrin reagent, the stream is put through a heated reaction coil at 100 C. and the colors formed are monitored in a Stream Colorimeter whose output is recorded on a strip chart recorder, the time value for which is set forth on the axis of the ordinate, reading from left to right. The citrate buffers are principally composed of aqueous solutions of a mixture of sodium citrate and hydrochloric acid whose proportions are adjusted to supply the desired pH.

The results obtained in this and the other following examples which employ various degrees of sulfoalkylation are tabulated as follows:

Nominal percent of Hydroxy- 71 116 32 sulfopropyl Hydroxylysine minute Lysine minute minute Sum Sample number substitution lysine 1 decrease 1 peak 1 Lysine I decrease 1 peak I peak 1 116+32 1 N0. 1: N L10fi-195-1. 0 062 281 L1061953 5 021 O41 036 175 .106 085 030 o. 4:

LNG-1954 7 017 O45 042 123 158 101 029 o. 5:

L106-156-1 3 0&6 018 039 193 O71 069 008 .073 o. 8:

L106-156-2 4 032 032 028 130 125 070 O13 088 N0. 9:

L106-156-3 5 028 036 O41 123 141 124 024 14 1 N0. 10:

L106-l56-4 6 023 0&1 O41 101 163 137 037 o. 11:

1 All valuw in mieromoles per milligram. 2 Not available.

Photocopies of the chromatograms of the samples of Example 2 and other examples which follow hereafter show the appearance of a new peak at each of the elution times of about 71 and 116 minutes. When each of these peaks is compared to the percentage substitution, they indicate a linearity in the to about range and a leveling off in the 7% to about range. The lysine content decreases linearly up to about 7% or, to a value of .120 to .193 micromole per milligram. This new peak at each elution time appears to represent a primary sulfoalkylation of said reactive receiving sites.

A barely visible third new peak is observed at 32 minutes in some of the chromatograms and appears to be due to additional new sulfoalkylation as the disubstitution of sulfoalkyl moieties on already monosulfolakylated amino acid sites.

This data clearly illustrates that samples 25 and 7-11 are poly(sulfoalkylated) gelatins, the chemically modified reaction product between propanesulfone and pigskin gelatin.

EXAMPLE 3 Example 1 is repeated but using 36 grams (4% by weight) of 1,3-propanesultone rather than the 27 grams.

EXAMPLE 4 Example 1 is repeated but 45 grams (5% by weight) of 1,3-propanesultone are used.

EXAMPLE 5 Example 1 is repeated but 54 grams (6% by weight) of 1,3-propanesultone are used.

The gelatin is chilled, noodled, washed and dried in the usual manner.

EXAMPLE 8 The preceding example is repeated but 15 grams of 2,4- butanesultone are added.

EMMPLE 9 Example 7 is repeated but grams of 2,4-butanesultone are added.

In the following two charts, we set forth various unique physical and photographic properties and identifying characteristics of our chemically modified gelatins, of Examples 1 and 36, as compared with their parent pigskin gelatin and the previously preferred cattle bone gelatin. It is seen, for example, in Chart I that, while the parent pigskin gelatin possesses excellent jelly strength, its restraint to physical development (shown in Chart II) renders it photographically unacceptable, shown in part by high relative speed.

The chemically modified sulfoalkylated gelatins, however, provide excellent sensitometric results and particularly good development restraint control within the time required for the various commercially available developers. In particular, our poly(sulfoalkyl) gelatin compares most favorably with cattle bone gelatin and in preferred ranges is inert to physical development restraint.

The following chart representing 6.1% by weight of the various gelatin solutions gives the unique physical properties and characteristics of the chemically modified gelatins obtained in Examples 1, 3, 4, 5, and 6 (modified by sulfoalkylation to the extent as shown by percentages) as compared to untreated igskin gelatin and other gelatin.

CHART I [Physical proprties] Jelly strength (shoom value in C olor Isoelectric Gelatm used Viscosity grams) clarity point Cattle bone gelatin 11. 9 278 80-98 4. 9 Parent pigskin gelatin 11. 8 205 87-98 8.8 Example 1 10. 4 246 87-100 5. 7 Example 4 10. 2 236 88-100 5. Example 5 10.0 222 86-99 4. 0 Example 6 9. 4 200 90-100 4. 3 Example 7 12. 7 255 87-100 5.

EXAMPLE 6 EXAMPLE 7 200 grams of pigskin gelatin are plumped and melted in 2 /2 liters of distilled water at 50 C. Sodium hydroxide is added to adjust the pH to 10.5. 10 grams of 2,4-butanesultone in solution in acetone are stirred into the solution. The solution is held for minutes with occasional addition of NaOH to maintain the pH at 10.0. Thereupon the pH is lowered to 6.0 by adding dilute sulfuric acid.

The gelatins obtained by the various examples are evaluated photographically by using the various modified and unmodified gelatins respectively as binders in a high speed silver bromoiodide (6 mole percent iodide) photographic emulsion. These various emulsions are coated on a cellulose acetate film base at a coverage of 540 milligrams of silver and 1225 milligrams of gelatin per square foot in which operation the coatings after application are chill set and dried. Each film strip is exposed on an Eastman Sensitometer Type IB and a continuous step wedge is used. The films are processed for the times specified in the following tables in Kodak Developer DK50 or in Developer D19 and are fixed for 5 minutes in Kodak Fixing Bath F5, washed and dried. The properties of these films when freshly processed and in some cases after a one-week incubation period holding at 50% relative humidity and 120 F. temperature are as follows:

CHART II 1 week incubation Fresh 5 DK-50 5 D 5 Fresh 12 DK-50 Fresh 4 D-19 Relative Relative Relative Relative Gelatin Used speed S Fog speed S Fog speed S Fog speed S Fog Cattle bone gelatin 100 1. 17 09 0. 81 46 1. 23 22 80 1. 15 06 Parent pigskin gelatin 71 1. 02 06 54 0. 94 12 63 1. 25 18 54 1. 04 05 Example 1 80 l. 17 12 54 0.77 52 83 1. 10 22 65 1. 07 10 Example 4 1.08 .10 68 0. 77 .36 129 1.10 18 94 1. 05 08 Example 5 129 1. 15 11 78 0.93 40 155 1. 20 19 102 1. 15 10 Example 6 1. 27 12 148 1. 20 20 102 1. 10 10 Example 7 120 1. 38 12 105 1. 41 10 The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

We claim:

1. Poly(sulfoalkyl) gelatin containing recurring lysine sites of which about to about are sulfoalkylated and hydroxylysine sites of Which about 50 to about are sulfoalkylated, said gelatin being poly(sulfoall ;ylated) substantially on the epsilon amino groups of said lysine and hydroxylysine sites.

2. Poly(sulfoalkyl) gelatin of claim 1 being characterized by having the following properties:

Shoom jelly strength of about 150 to about 285; Color clarity of about to about Isoelectric point of about 4.3 to about 5.7; Viscosity of about 9.4 to about 12.7; Lysine micromoles per milligram of about 100 to about 200; and Hydroxylysine micromoles per milligram of about .015 to about .030. 3. The poly(sulfoalkyl) gelatin of claim 1 in which said alkyl is propyl.

4. The poly(sulfoalkyl) gelatin of claim 1 in which said alkyl is butyl.

5. A photographic element comprising a support and layer containing the poly(sulfoalkyl) gelatin of claim 1.

6. A photographic gelatin silver halide emulsion comprising the poly(sulfoalkyl) gelatin of claim 1.

7. The poly(sulfoalkyl) gelatin of claim 1 derived from pig collagen.

8. A method of preparing a gelatin derivative which comprises reacting upon gelatin in alkaline solution with an alkyl sultone, the alkyl being of 3 to 4 carbon atoms.

9. The method of claim 8 in which said gelatin is pigskin gelatin and said alkyl sultone is propane sultone.

10. The method of claim 8 in which said gelatin is pigskin gelatin and said alkyl sultone is butane sultone.

References Cited UNITED STATES PATENTS 12/1965 Vrancken et al 9694 7/1969 Young 2608 US. Cl. X.R. 260-ll7