US2710805A

US2710805A - Production of silver halide photographic emulsions containing a synthetic polypeptide derivative

Info

Publication number: US2710805A
Application number: US382874A
Authority: US
Inventors: Wood Henry Walter
Original assignee: Ilford Ltd
Current assignee: Ilford Imaging UK Ltd
Priority date: 1952-10-09
Filing date: 1953-09-28
Publication date: 1955-06-14
Anticipated expiration: 1972-06-14
Also published as: GB721067A; DE953575C

Description

United States atent Z,7lil,805

Patented June 14, 1955 PRODUCTION OF SILVER HALIDE PHOTO- GRAPHIC EMULSIONS CONTAINING A SYNTHETIC POLYPEPTIDE DERIVATIVE Henry Walter Wood, Ilford, England, assignor to Ilford Limited, Ilford, England, a British company No Drawing. Application September 28, 1953, i Serial No. 382,874

Claims priority, application Great Britain October 9, 1952 8 Claims. (Cl. 95-7) graphic emulsions the usual procedure is to cause precipitation of the required silver halide in an aqueous solution of gelatin by double decomposition between soluble silver salts and soluble halides, thereafter to set the emulsion obtained, ripen it, shred it and wash it. The washed emulsion is then redispersed in an aqueous medium, optionally with additional gelatin, digested and coated on paper, film, glass or other base to form a lightsensitive photographic material.

In British Patent No. 694,132 a process is described for the production of gelatino silver halide emulsions which comprises adding to an alkaline gelatino silver halide photographic emulsion a proportion of a synthetic polypeptide which is soluble in aqueous alkaline solutions but insoluble in acid solutions, acidifying the emulsion, separating the precipitate containing silver halide thus obtained, and redispersing the said precipitate in aqueous gelatin. The precipitate may be washed to remove soluble by-products formed in the preparation of silver halide before its redispersion in aqueous gelatin, and by suitably selecting the quantity and gelatin concen tration of the aqueous gelatin used for redispersion, emulsions may be obtained which have a high ratio of silver to gelatin. It is explained in the said patent that the chemical character of the synthetic polypeptide is not critical providing always that it is soluble in aqueous alkaline solutions and insoluble in aqueous acid solutions. The preferred compounds are polyglutamic acid and the copolymers of glutamic acid with other a-aminoacids. Corresponding compounds in which the glutamic acid is replaced by aspartic acid may also be employed. In all cases the optically active or racernic mirgtures of the compounds may be employed, including mixtures of different synthetic polypeptides.

It has now been discovered that there may be employed, in a process of the type just described, derivatives of synthetic polypeptides soluble in aqueous solutions at all pH values formed by reacting such a synthetic polypeptide with an aryl sulphonyl chloride or aroyl chloride or with an aryl isocyanate.

According to the present invention, therefore, a process for the production of silver halide photographic emulsions comprises adding to an alkaline silver halide photographic emulsion, of which the colloid dispersion medium is gelatin or polyvinyl alcohol, a proportion of a derivative of a waterand acid-soluble synthetic polypeptide, particularly an aryl sulphonyl, aroyl, or aryl carbamyl derivative, which is soluble in aqueous alkaline solutions but insoluble in acid solutions, acidifying the emulsions, separating the precipitate containing silver halide thus obtained, and redispersing the said precipitate in aqueous gelatin or polyvinyl alcohol, and preferably in whichever of such colloids was present in the original emulsion.

While not confining himself to a particular theory of reaction, the applicant believes, on the evidence available, that the derivatives attach themselves to the silver halide, which is precipitated on reducing the pH value, leaving the bulk of the gelatin or polyvinyl alcohol in solution.

The polypeptides may be produced by the methods generally indicated in British Patent No. 694,132, using an appropriate amino acid, such as lysine, which imparts to the polypeptide obtained the desired waterand acidsolubility. It is preferred to employ a polypeptide which is a copolymer of glutamic acid and lysine with or Without other amino acids. The polypeptides are prepared by condensation polymerisation of the carbonic anhydrides, and the gamma carboxy group of the glutamic acid residues is protected by esterification, whilst the e-amino group of the lysine is protected by a carbobenzyloxy radicle which is removable by treatment with phosphonium iodide (or more conveniently by treatment with hydriodic acid in glacial acetic acid) after polymerisation has been effected. After removal of carbobenzyloxy groups, the protective methyl groups are removed by making the aqueous solution alkaline. This also involves neutralising the hydriodic acid which is present partly in combination with the NHz groups of the polymer and partly as an unavoidable contamination from the reduction. The solution may be made alkaline with, for instance, NaOH or Ba(OH)2. The latter can subsequently be removed as insoluble B21504 if it is desired to prepare the pure polypeptide. However, NaOH is quite satisfactory since the presence of sodium ions is not a disadvantage and it is not necessary to isolate the polypeptide. The subsequent reactions proceed readily in the aqueous solution containing sodium iodide and the derivative is readily isolated by acidification.

The polymerisation may be effected in various solvents, but it is preferred to employ anhydrous dioxan containing ammonia as catalyst since this process yields polypeptides of high molecular weight especially suitable for conversion to derivatives suitable for use in the invention. Nevertheless, solvents such as benzene or pyridine may be employed. Alternatively, the polymerisation step may be effected by fusing the carbonic anhydrides together.

The following are illustrative procedures for the preparation of a polypeptide suitable for conversion to a polypeptide derivative for use in the present invention.

POLYPEPTIDE A 37 millimols each of e-N-carbobenzyloxy lysine anhye dride and 'y-methyl glutamate anhydride and 10 mM. each of glycine anhydride, leucine anhydride, phenylalanine anhydride and O-acetyl tyrosine anhydride were dissolved in 207 ml. sodium-dried dioxan, and 0.25 mM. ammonia, dissolved in dioxan, added as catalyst. After heating on the water-bath for 3 days, the viscous mix ture was precipitated with ether and the polymer collected and dried (12.6 g.). The carbobenzyloxy protective groups were removed from the lysine units by treatment in 150 ml. acetic acid under hydrogen with 24 g. phosphonium iodide. The resulting material was soluble in water and was purified by precipitating it from the aqueous solution by a mixture of 80 ml. alcohol and 900 ml. diethyl ether. After taking up again in Water,

i the pH of the solution was adjusted to 9, which resulted in the almost instantaneous removal of the protective ester groups of the glutamic units and acetyl groups of the tyrosine units. This solution, after standing for a day at room temperature, was used directly for the preparation of derivatives. Its content of polymer was estimated to be 9.3 g. The polymer is soluble at all pH values.

3 POLYPEPTIDE B A polypeptide was prepared by the method set forth above but using 20 millimols each of e-N-carbobenzyloxy lysine anhydride and 'y-methyl glutamate anhydride, and millimols each of glycine anhydride, leucine anhydride, phenylalanine anhydride and O-acetyl tyrosine anhydride.

POLYPEPTIDE C A polypeptide was prepared by the general method indicated above but omitting the minor proportions of amino acids so that it contained only lysine and glutamic acid residues in approximately equimolar proportions.

POLYPEPTIDE D 0.21 mol of 'y-methyl glutamate anhydride, 0.21 mol of e-N-carbobenzyloxy lysine anhydride and 0.28 mol of glycine anhydride were dissolved in 1.2 litres dry dioxan, with 1.37 mM. ammonia as catalyst, and heated for 3 days on a boiling water bath. The polypeptide was isolated by precipitation with ether and dried. Yield 93.5. It was worked up in batches, e. g. 15.5 g. dry polymer was suspended in 150 ml. glacial acetic acid containing g. anhydrous Hl. The mixture Was warmed, with mechanical stirring, for minutes on a boiling water bath. The red product was filtered off and dissolved in ml. water; a small amount of unreacted material was removed by filtration. The

solution was adjusted to pH 9, stood overnight, and then used directly for the preparation of Derivative G (hereinafter referred to). It was estimated to contain 11.8 g. polypeptide.

POLYPEPTIDE E The steps used in producing Polypeptide A were followed but using 28 mM. of -methyl glutamic anhydride, 26 mM. of e-N-carbobenzyloxy lysine anhydride, 39 mM. of glycine anhydride and 18 mM. of diamino sebacic di-anhydride. Diamino sebacic di-anhydride, m. pt. C., used in the production of this polypeptide, was prepared by the action of phosphorus pentachloride on the corresponding di-carbobenzyloxy compound, 111. pt. 136 C. It is notable for the fact that it is an amino acid which, so far as is known, does not occur naturally.

Derivatives of the synthetic polypeptides may be obtained by reacting the side-chain amino groups of the lysine units with an aryl sulphonyl chloride or aroyl chloride at a pH in the neighbourhood of 10, or by reacting these groups with an aryl isocyanate at a pH in the neighbourhood of 8. of the tyrosine units may be attacked by these reagents. The derivative-forming reagents are preferably employed in substantial excess, e. g. 50-100% excess, over the amount required on a theoretical basis to convert all the lysine amino groups, and it is believed that under these conditions all, or substantially all, of such amino groups are substituted.

The following are illustrative of the procedures used for the preparation of the polypeptide derivatives.

Derivative A 2.3 g. of Polypeptide A, dissolved in 20 ml. water, was treated with 0.9 ml. 10% KOH to bring the pH to 10. A solution of 3.3 g. naphthalene-Z-sulphonyl chloride in 5 ml. benzene was added and the mixture stirred at 50 C. The pH was maintained at about 10 by addition of 10% KOH, a total of 26 ml. being added. After 20 minutes, the visible reaction ceased and the mixture was acidified with mineral acid to precipitate the product. It was purified by repeated dissolution in alkali and precipitation with acid, and was obtained in a yield of 2.2 g.

Derivative B 2.6 g. of Polypeptide A in 22 ml. water was mixed In addition, the hydroxy groups Cal with 22 ml. of a phosphate buffer soltuion giving pH 8. 1.7 g. phenylisocyanate in 1.7 ml. benzene was added and the mixture stirred at 5 C. for 40 minutes and for 30 minutes more at room temperature. During this time the pH was maintained at 8 by the addition of 3.5 ml. N NaOH. The insoluble by-product, phenylurea, was filtered oif and the product worked up as for Derivative A. A yield of 2.8 g. was obtained.

Derivative C Polypeptide B was condensed with naphthalene-2- sulphonyl chloride as for Derivative A.

Derivative D Polypeptide B was condensed with B-naphthylisocyanate following the general procedure indicated for preparing Derivative B.

Derivative E Polypeptide C was condensed with naphthalene-2- sulphonyl chloride following the general procedure indicated for Derivative A.

Derivative F Polypeptide D was condensed with ,B-naphthoyl chloride. In this case, when the aqueous reaction mixture was acidified, some of the by-product, naphthoic acid, was co-precipitated with the product. It was removed by extraction with diethyl ether. It may be observed that this complication does not arise where the derivative-forming reagent is an isocyanate or a sulphonyl chloride. When isocyanates are used the byproducts are insoluble at all pH values and may be filtered off before the reaction mixture is acidified. When sulphonyl chlorides are used the by-products are soluble at all pH values and so do not come out of solution on acidification.

Derivative G Polypeptide E was condensed with fl-naphthyl isocyanate.

The polypeptide derivatives, although solids, cannot be characterised by melting points since they are infusible. Their nature may be understood from the following theory.

The parent polypeptides may be represented schematically thus:

i. e. as chains containing the peptide linkages, with sidechains terminating in cationic groups (from lysine residues) and anionic groups (from glutamic acid residues).

The polypeptide derivatives are prepared by reaction with compounds which are known to attack primary amino groups. It is assumed that the following occurs, in alkali:

NHz ArNCO -NH.CO.NH.Ar

isocyanate O O C- O O C- NH ArSOzCl NH.S02 Ar H01 sulphonyl chloride -0 O C- O O 0..

-NH: ArC OCl |NH.COAr H01 carboxyl chloride I -O O (3-; O O O- In this way the basic properties (capacity for combining with protons) of the parent compounds are nullified so that the derivatives are no longer ampholytic in nature, but are, in effect, polymeric acids, insoluble at low PH.

It may be observed that the composition of the initial polypeptides may be assessed in a semi-quantitative manner by hydrolysis and application of partition paper chromatography to the concentrated hydrolysate. Thus, by this method it is possible to detect all six of the amino acids used in Polypeptide A described above, the strengths of the individual spots giving an approximate idea of the relative proportions of these amino acids in the polypeptide. Paper electrophoresis has also proved very useful in checking the qualitative composition of the parent polypeptides.

The polypeptide derivatives of the present invention present an advantage over alkali-soluble, acid-insoluble polypeptides themselves, as described in Patent No.

694,132, in that in general a smaller quantity of the polypeptide derivative is required to achieve a similar result.

The invention is illustrated by the following examples which, however, are not to be regarded as limiting it in any way:

EXAMPLE 1 A normal type of gelatino silver iodobrornide photographic emulsion was produced having a gelatin content of 0.25%, a silver halide content of 9% w./v. and a pH of about 9. To 1 /2 litres of this emulsion was added 2.5 g. of Derivative C above dissolved in ml. water at pH 8, the emulsion being just warm. Sulphuric acid (100 ml. 5N.H2SO4) was then immediately added to the emulsion to neutralise the alkalinity of the emulsion and provide an excess of acid. (Acetic or hydrochloric acid may equally well be employed for this purpose.) After a few minutes standing, the precipitate which formed had collected on the bottom of the reaction vessel and the supernatant liquid was then decanted. The precipitate was then washed with neutral or weakly acid liquors.

The washed precipitate was then adjusted to pH 8.5-9 by addition of caustic alkali and stirred for five minutes at 115 F. It was then re-dispersed in an aqueous gelatin solution.

EXAMPLE 2 A normal type of gelatino silver iodobrornide photographic emulsion was prepared, having a gelatin content of 1.25% and a silver halide content of 9% w./v., and a pH of about 9. To 1 /2 litres of this emulsion was added 5 g. of Derivative G referred to above and the procedure of Example 1 was then followed, precipitation being effected by the addition of 100 ml. 5N.H2SO4.

EXAMPLE 2:

A silver bromide in polyvinyl alcohol photographic emulsion was prepared containing 3.5% silver bromide, 0.25% polyvinyl alcohol and 0.09 N ammonia. After ripening the emulsion there was added, to 2 litres of the emulsion, 2.5 g. of Derivative H. Precipitation was effected by adding ml. 5N.H2SO4 and the precipitate was separated as in the previous examples and re-dispersed in aqueous polyvinyl alcohol solution.

The precise technique employed will naturally vary with the nature of the silver halide emulsion being treated and with the precise character of the polypeptide derivative. However, in respect of gelatin emulsions it may be observed in general that the higher the gelatin content of the original emulsion, the greater is the quantity of the polypeptide derivative required. Where the initial emulsion contains sensitising dyes, these are carried with the silver halide into the precipitate. Where emulsions are prepared according to the present invention and do not contain sensitising dyes, such emulsions may be dyed in the usual way. It is a feature of the present invention that the precipitate containing silver halide may be re-dispersed in aqueous gelatin or aqueous polyvinyl alcohol of greater concentration than exists in the solution from which the precipitate is formed.

What I claim is:

l. A process for the production of silver halide photographic emulsions which comprises adding to an alkaline silver halide photographic emulsion of which the colloid dispersion medium is selected from the class consisting of gelatin and polyvinyl alcohol, a proportion of a derivative of a waterand acid-soluble synthetic polypeptide which is soluble in aqueous alkaline solutions but insoluble in acid solutions, said polypeptide being a copolymer including glutamic acid and lysine, said derivative being selected from the class consisting of aryl sulphonyl, aroyl, and aryl carbamyl derivatives of said polypeptide, acidifying the emulsion, separating the precipitate containing silver halide thus obtained, and redispersing the said precipitate in an aqueous medium containing a colloid selected from the class consisting of gelatin and polyvinyl alcohol.

2. A process for the production of silver halide photographic emulsions which comprises adding to an alkaline silver halide photographic emulsion of which the colloid dispersion medium is gelatin, a proportion of a derivative of a waterand acid-soluble synthetic polypeptide which is soluble in aqueous alkaline solutions but insoluble in acid solutions, said polypeptide being a copolymer including glutamic acid and lysine, said derivative being a naphthalene sulphonyl derivative of the said polypeptide, acidifying the emulsion, separating the precipitate containing silver halide thus obtained, and redispersing the said precipitate in an aqueous medium containing gelatin.

3. A process for the production of silver halide photographic emulsions which comprises adding to an alkaline silver halide photographic emulsion of which the colloid dispersion medium is polyvinyl alcohol, a proportion of a derivative of a waterand acid-soluble synthetic polypeptide which is soluble in aqueous alkaline solutions but insoluble in acid solutions, said polypeptide being a copolymer including glutamic acid and lysine, said derivative being a naphthalene sulphonyl derivative of the said polypeptide, acidifying the emulsion, separating the precipitate containing silver halide thus obtained, and redispersing the said precipitate in an aqueous medium containing polyvinyl alcohol.

4. A process for the production of silver halide photographic emulsions which comprises adding to an alkaline silver halide photographic emulsion of which the colloid dispersion medium is gelatin, a proportion of a derivative of a waterand acid-soluble synthetic polypeptide which is soluble in aqueous alkaline solutions but insoluble in acid solutions, said polypeptide being a copolymer including glutamic acid and lysine, said derivative being a naphthyl carbamyl derivative of the said polypeptide, acidifying the emulsion, separating the precipitate containing silver halide thus obtained, and redispersing the said precipitate in an aqueous medium containing gelatin.

5. A process for the production of silver halide photographic emulsions which comprises adding to an alkaline silver halide photographic emulsion of which the colloid dispersion medium is polyvinyl alcohol, a proportion of a derivative of a waterand acid-soluble synthetic polypeptide which is soluble in aqueous alkaline solutions but insoluble in acid solutions, said polypeptide being a copolymer including glutamic acid and lysine, said derivative being a naphthyl carbamyl derivative of the said polypeptide, acidifying the emulsion, separating the precipitate containing silver halide thus obtained, and redispersing the said precipitate in an aqueous medium containing polyvinyl alcohol.

6. A process for the production of silver halide photographic emulsions which comprises adding to an alkaline silver halide photographic emulsion of which the colloid dispersion medium is gelatin, a proportion of a derivative of a waterand acid-soluble synthetic polypeptide which is soluble in aqueous alkaline solutions but insoluble in acid solutions, said polypeptide being a copolymer including glutamic acid and lysine, said derivative being a naphthoyl chloride derivative of the said polypeptide, acidify ing the emulsion, separating the precipitate containing silver halide thus obtained, and redispersing the said precipitate in an aqueous medium containing gelatin.

7. A process for the production of silver halide photographic emulsions which comprises adding to an alkaline silver halide photographic emulsion of which the colloid dispersion medium is polyvinyl alcohol, a proportion of a derivative of a waterand acid-soluble synthetic polypeptide which is soluble in aqueous alkaline solutions but insoluble in acid solutions, said polypeptide being a copolymer including glutamic acid and lysine, said derivative being a naphthoyl chloride derivative of the said polypeptide, acidifying the emulsion, separating the precipitate containing silver halide thus obtained, and redispersing the said precipitate in an aqueous medium containing polyvinyl alcohol.

8. A photographic silver halide emulsion of which the dispersion medium is selected from the class consisting of gelatin and polyvinyl alcohol, containing an alkalisoluble, acid-insoluble derivative of a synthetic polypeptide which is itself waterand acid-soluble, said polypeptide being a copolymer including glutamic acid and lysine and said derivative being selected from the class consisting of aryl sulphonyl, aroyl and aryl carbamyl derivatives a said polypeptide.

References Cited in the file of this patent UNITED STATES PATENTS l,7l9,7ll Matthies et a1 July 2, 1929 2,454,001 Mueller Nov. 16, 1948 FOREIGN PATENTS 259,926 Great Britain Sept. 26, 1927 500,537 Belgium Jan. 31, 1951

Claims

1. A PROCESS FOR THE PRODUCTING OF SILVER HALIDE PHOTOGRAPHIC EMULSIONS WHICH COMPRISES ADDING TO AN ALKALINE SILVER HALIDE PHOTOGRAPHIC EMULSION OF WHICH THE COLLOID DISPERSION MEDIUM IS SELECTED FROM THE CLASS CONSISTING OF GELATIN AND POLYVINYL ALCOHOL, A PROPORTION OF A DERIVATIVE OF A WATER- AND ACID-SOLUBLE SYNTHETIC POLYEPTIDE WHICH IS SOLUBLE IN AQUEOUS ALKALINE SOLUTIONS BUT INSOLUBLE IN ACID SOLUTIONS, SAID POLYPEPTIDE BEING A COPOLYMER INCLUDING GLUTAMIC ACID AND LYSINE, SAID DERIVATIVE BEING SELECTED FRON THE CLASS CONSISTING OF ARYL SULPHONYL, AROYL, AND ARYL CARBAMYL DERIVATIVES OF SAID POLYPEPTIDE, ACIDIFYING THE EMULSION, SEPARATING THE PRECIPITATE CONTAINING SILVER HALIDE THUS OBTAINED, AND REDISPERSING THE SAID PRECIPITATE IN AN AQUEOUS MEDIUM CONTAINING A COLLOID SELECTED FROM THE CLASS CONSISTING OF GALATIN AND POLYVINYL ALCOHOL.