US2992213A

US2992213A - Acid cooked pigskin gelatins for photographic subbing

Info

Publication number: US2992213A
Application number: US695205A
Authority: US
Inventors: Jr John W Gates; Paul E Miller; Robert R Phillips; Gale F Nadeau
Original assignee: Eastman Kodak Co
Current assignee: Eastman Kodak Co
Priority date: 1957-11-08
Filing date: 1957-11-08
Publication date: 1961-07-11
Anticipated expiration: 1978-07-11
Also published as: US3157506A; GB852446A

Description

sirable for the purpose.

United ttes atent 1 2,992,213 ACID COOKED PIGSKIN GELATINS FOR PHOTOGRAPHIC SUBBING John W. Gates, Jr., Paul E. Miller, Robert R. Phillips, and Gale F. Nadeau, all of Rochester, N.Y., assignors to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey No Drawing. Filed Nov. 8, 1957, Ser. No. 695,205 Claims. (Cl. 260-117) This invention relates to the treatment of acid cooked pigskin gelatin to adapt it to use for subbing photographic film base and the subbed film base and film obtained by its use.

In the manufacture of photographic film the finished product ordinarily consists of a transparent film base of a polymeric material such as cellulose acetate, cellulose acetate propionate, polystyrene, polyester, or the like, containing a layer of silver-halide-gelatin photographic emulsion thereon. To facilitate good adherence of the emulsion layer to the film base subbing layers are usually employed, of which gelatin is one of the important constituents. It is desirable that the gelatin employed have certain properties which make it suitable for this purpose. For instance, the gelatins usable as subbing materials in the preparation of photographic film bases should (1) Produce stable dispersions in the mixed solvents which are employed for applying the coatings thereto; g

(2) Produce subbing layers which will not allow stripping off of the emulsion layer either wet or dry and exhibit a high bonding strength to both the film base and the emulsion layer;

(3) Produce subbing layers having a high clarity and a minimum of color;

(4) Produce subbing layers with no wet haze. There are other properties of importance to this use such as photographic inertness to the emulsion layer applied thereon.

The gelatins which are ordinarily employed for subbing purposes have been developed by long years of experience and trial and are generally prepared from limed cattle hides and calf skins and are of necessity of very low ash content so as to obtain good compatability and dispersion in the mixture of non-aqueous solvents Which may be employed in applying the same to photographic film base.

The gelatins obtained from pigskins have been considered in this connection due to the generally high jelly strength of those gelatins. High jelly strength indicates that the gelatin has good adhesion to the film base.

-However, When deashed pigskin gelatins produced by means of the customary acid cooked procedure or those from limed pigskins have been employed for photographic layers the light transmission of those gelatins has been poor and their compatibility with mixed solvents as employed for subbing has not been considered satisfactory. Therefore, even though gelatins having a jelly strength above 260 grams shoom are readily obtained from pigskins either by a first run extraction or by a second run extraction thereof, nevertheless, those gelatins have shown properties which were not considered de- Ordinarily in the obtaining of gelatin from pigskins the acid cook procedure is employed which involves the extraction of gelatin with water at a pH within the range of 4-5. After the grease has been removed from the extractant thus obtained the resulting gelatin in aqueous solution can be made to gel by cooling giving products having a jelly strength above 260 shoom. It is to the use of those gelatins that the present invention is directed.

One object of our invention is to provide a procedure for treating pigskin gelatin to adapt it for use in subbing layers employed in the preparation of photographic films. Another'object of our invention is to provide a gelatin from pigskin which will give layers when applied to transparent polymeric sheeting having a high bonding strength thereto, whether in wet or dry condition. A further object of our invention is to prepare from high jelly strength pigskin gelatin a product which possesses good light transmission properties and the capacity for giving smooth layers when coated out from its solution in mixed solvents onto a support therefor; other objects of our invention will appear herein.

We have found that acid cooked pigskin gelatins of high jelly strength can be adapted to use for subbing purposes in the manufacture of photographic film if that gelatin is given an alkaline treatment within certain critical temperatures and pH ranges. The treatment of the pigskin gelatin which should have a jelly strength of at least 260 grams shoom may be with either aqueous am-' monia or with alkaline alkali metal compounds such as alkali metal hydroxide or alkali metal carbonate, for instance, sodium hydroxide, potassium hydroxide, sodium carbonate or the like. The treatment of the gelatin is carried out by leaching for a time such as 1-6 hours with the aqueous alkaline solution at a pH within the range of 8-9.5 and a temperature of 35-55 F. The length of time employed for this treatment may vary with the individual operator. The effectiveness of the treatment is the. criterion of the length of time which one will wish to employ. We have found that a 4 hour treatment is ordinarily sufiicient in every situation but if shortening of the time is desirable, in some cases the time used maybe as little as 1 hour and a satisfactory product may be obtained. After the treatment of the gelatin with the alkaline liquor it maybe employed directly for the subbing layers particularly following the ammonia treatment or it may be subjected first to a deashing treatment with aqueous acetic acid as is well known in the art, the latter ordinarily being desirable where the treatment of the gelatin has been with alkaline alkali metal compound solutions. After the gelatin has been treated either with.

the alkaline solution or with the combination of alkaline solution and deashing it is then thoroughly washed to remove water soluble salts or the like which might be present therein. using several changes of cold water which may involve 3 or 4 or more washings of the gelatin. Although it appears that the use of distilled or demineralized water in the alkaline treatment or in the washing operation or both produces a better product than where tap water is employed, nevertheless, the use of tap water in these operations has been found to be effective and its use is also included within the scope of the invention which we have made. To obtain gelatin of the best jelly strength the first run type of gelatins may be employed but many second run gelatins have a jelly strength above 260 grams shoom and may be employed in the coating of subbing layers or in admixture with first run gelatin for that purpose. It has been noted that the acid which has been employed in preparing the pigskin gelatin may be any one of several acids; for instance, acids such as hydrochloric, sulfuric, acetic or the like may be employed and the extracted gelatins obtained will be substantially equivalent in characteristics.

The ammonia treatment of the gelatin may be carried out by plumping the gelatin such as in the form of flakes or noodles approximately 4 hours in cold water which has been adjusted to a pH of 8.5 with ammonia and following this treatment the gelatin may then be subjected to successive treatments with cold water, each treatment being of approximately 4 hours duration. The gelatin may then be melted if desired, and treated with acetic This Washing operation is carried out acid, or may be employed without such treatment. In this treatment tap water may be used particularly if the gelatin employed is a first run pigskin gelatin or a blend of first and second run gelatins in which the first run gelatin predominates. lt is preferable when the gelatin treated is a second run gelatin that the water treatment be confined to the use of distilled water or demineralized water such as is obtained by the treatment of water with a zeolite or a Permutit base exchange resin.

Instead of the ammonia treatment the acid cooked pigskin gelatin may treated for 4 hours in cold water adjusted to a pH such as of 9 to 9.5 with sodium hydroxide. The gelatin can then be washed in water such as for 2 hours and deashed by treatment with changes of dilute aqueous acetic acid prepared with either demineralized Water or with tap water. This treatment is useful for the treatment of either first run gelatin, second run gelatin or a mixture of first and second run gelatins extracted from acid cooked pigskin providing of course that the jelly strength of the gelatin is above 260 grams shoom.

The pigskin gelatins obtained by the alkaline treatments described are suitable for use in any of the accepted formulas for coating compositions for the application of subbing formulas for coating compositions for the application of subbing layers to film supports which compositions include gelatin therein. The layers thus obtained exhibit good light transmission properties and give smooth surfaces when coated out as subbing layers indicating the good compatibility of the gelatin for the solvent mixtures which are employed in preparing the coating compositions.

The following examples illustrate the treatment of acid cooked pigskin gelatins to render them useful for subbing purposes and typical subbing operations in which those gelatins have been used to give layers of good properties.

Example 1 2 pounds of a second run acid cooked pigskin gelatin was immersed in 20 liters of 0.1% sodium hydroxide solution having a temperature of 40-45 F. for 2 hours with occasional stirring. The liquid was drained from the gelatin and a second addition of 20 liters of cold 0.1% sodium hydroxide solution was added to the gelatin and the mixture was stirred occasionally over a 2 hour period. The 0.1% sodium hydroxide solution had a pH within the range of 9-9.5. The liquid was drained from the gelatin and the gelatin was washed with distilled water with 3 one hour changes. The gelatin was then deashed with aqueous acetic acid and dried in a current of warm dry air.

The deashed gelatins which were employed as starting materials in several runs as described in Example 1 had light transmissions of 46.1%, 51.2% and 37.2%. After those gelatins were treated by the procedure described in Example 1 they exhibited light transmissions of 77.8%, 64.4% and 72.2%. When first run acid cooked pigskin gelatins were employed in such a procedure which gelatins when deashed had light transmissions of 45.2%, 37.8% and 53.4% they exhibited after the treatment as described in Example 1 light transmissions of 78.2%, 61.6% and 74%. Pigskin gelatins which had not been deashed could not be tested for light transmission because those gelatins would not even disperse in the solvents employed for the subbing procedure. The light transmission is determined by measuring the amount of light transmitted by sub solutions made with the various gelatins which values are all determined under the same conditions.

Example 2 2 /2 pounds of pigskin gelatin in noodle form were leached for 4 hours with 20 liters of water having a temperature of 40 F., the pH of the water being adjusted to 8.5 with 28% aqueous ammonia. Over the time of treatment the pH was maintained at 8.5 by occasional. am-

monia additions. The water was then drained from the gelatin and the latter was washed with four 4 hour 20 liter leaches with cold water. Some of the gelatin was dried by means of a current of warm dry air. The remainder of the gelatin was melted into solution, the pH thereof was adjusted to 4.65 with acetic acid and the mass was chilled and dried. The light transmission values of the gelatins thus obtained were found to be considerably improved over those of acid cooked pigskin gelatins which had not been given an alkaline treatment in accordance with our invention. It was noted that when subbing layers of pigskin gelatin in accordance with our invention were applied to photographic film base that the pigskin gelatin layers were characterized by 100% resistance to stripping of the emulsion from the photograph film base whereas in many cases of gelatins of other types having jelly strengths below 260 grams shoom stripping of the emulsion from the film base occurred.

Example 3 A batch of first run acid cooked pigskin gelatin was treated with successive amounts of cold tap water sufficient in each treatment to thoroughly cover the gelatin. The gelatin which was in the form of flakes was stirred occasionally in each step. In the first step ammonia had been added to the water to hold the pH at 8.5 and the A batch of first run acid cooked pigskin gelatin in flake form was treated with several successive changes of cold demineralized water which water had a minimum of 500,000 ohms resistance. In the first two water treatments sufficient sodium hydroxide had been added to hold the pH at 9.5 and the mass was stirred for 2 hours in each of the steps. After removal of the alkaline treating liquid from the gelatin flakes they were immersed in water and stirred for 3 hours. The water was removed and the gelatin was subjected to 7 successive changes of water in each case containing sufficient acetic acid to reduce the pH to 4-5. In each of these treatments the mass was stirred for 1 hour. The gelatin flakes were then removed and were dried on nets in the air. The gelatin obtained was found to have good light transmission properties, gave good smooth surfaces when employed in the form of subbing layers, and the photographic film prepared using this gelatin as at least one subbing layer exhibited high resistance to emulsion stripping.

The following examples are subbing compositions in which acid cooked pigskin gelatins have first been treated by procedures in accordance with our invention.

Example 5 triacetate film support while it was maintained at a ternpcrature of F. by means of a water tempered subbing drum. The sub coated support thus obtained was employed for preparing photographic film by coating silver halide-gelatin photographic emulsion thereon. This emulsion layer when driedwas found to be firmly bonded to .the film support.

B. Aphotographic filmsupport was prepared by coaling cellulose triacetatefilm support with a subbing composition as described in A and there was then applied to this surface an overooating layer of the following composition: 0.25% if deashed acid cooked pigskingelatin which had been treated in accordance with our invention, 0.25% of glacial acetic acid, 40% of methyl alcohol, of butyl alcohol and 49.5% of water. The subbed film support was kept at a temperature of 150 F. and the overcoat solution was also heated to this temperature and applied to the sub layer under these conditions. The product obtained was coated with a silver halide-gelatin photographic emulsion layer and that layer was found to be firmly bonded to the film support.

Example 6 This example illustrates the use of acid cooked pigskin gelatin treated as described herein for the preparation of compositions to apply subbing layers to film supports of cellulose acetate butyrate and cellulose acetate propionate.

A. A composition was prepared consisting of 1.25% acid cooked pigskin gelatin treated as described herein, 3% of sub type cellulose nitrate, 1% of glacial acetic acid, chromic chloride in an amount 1.5% by weight of the gelatin used, 50% acetone, 4% water and the balance methyl alcohol. The subbing layer was applied to a cellulose acetate butyrate film support by the bead method during which application the surface temperature of the support was maintained at 50 F. The resulting subbed film support was overcoated with a gelatin-silver halide emulsion which emulsion layer was found to be firmly bound to the cellulose acetate butyrate base.

B. Cellulose acetate butyrate support was coated as described in A and this subbed film support was then overcoated with an overcoating layer applied from a composition as deson'bed in B of the preceding example. To the subbed film base was applied on the subbed side of a gelatin-silver halide photographic emulsion. The emulsion layer was found to be firmly bound to the fihn support.

Example 7 This example relates to the preparation of polystyrene film support for the application of photographic emulsion layer thereto by applying thereto at least one subbing layer containing pigskin gelatin treated in accordance with the invention.

To a polystyrene film support having a temperature of 75 F. was applied a layer using the following composition: 2.25% n-butyl methacrylate, 2.25% isobutyl methacrylate, 25% methyl alcohol, 25% n-butyl alcohol and 65.5% hexane. Over this subbing layer a layer was applied while the support was held at 75 F. of the following composition: 2.5% cellulose nitrate, 10% methyl Cellosolve, 5% n-bu-tyl alcohol, and 82.5% methyl alcohol. There was then applied to the film support at 100 F. over this layer a layer from a composition as follows: 1.2% acid cooked pigskin gelatin which had been treated as described herein, 0.2% cellulose nitrate, 1.0% glacial acetic acid, chro-mic chloride in an amount 1.5% by weight of the gelatin, 10% of methyl cellosolve, 20% of water and the balance methyl alcohol. Each of these layers was applied by the bead method and the subbing layers were each dried before application of the succeeding sub layer. There was then applied to the subbed polystyrene film support a gelatin-silver halide photographic emulsion. The emulsion layer thus applied was found to be firmly bound to the polystyrene film support.

Example 8 There was applied to a polyethylene glycol tereph- 6 thalate film support a layer of a resin latex consisting .of a hydrosol obtained by polymerizing together 2 parts of itaconic acid, 15 parts of methylacrylate and 82 parts of vinylidene chloride. After drying the coated film was stretched 200% in both a lengthwise and crosswise direction and was then crystallized by means of heat. The subbed polyester film support was then overcoated with a composition consisting of 0.5% acid cooked pigskin gelatin which had been treated as described herein, 0.015% of a 10% solution of cetyl betaine, 0.017% of a 10% solution of chrome alum, 0.25% of urea and the balance water. The thus subbed polyester film support was heat cured for approximately 5 minutes at 250 F. There was then applied to the subbed polyester film support a layer of a photosensitive gelatin silver halide photographic emulsion. The emulsion layer was found to be firmly bound to the film support.

The firmness with which an emulsion layer is bound to film support is tested by a wet stripping test procedure in which the film is exposed to light and developed, fixed and washed as recommended for the photographic emulsion used. After washing the soft swollen emulsion is scored with .a sharp pointed instrument and an attempt is thereupon made with the tips of the fingers to remove the emulsion from the film base by rubbing across the score marks. In addition an attempt is made to remove the emulsion from the cut edge of wet processed film by rubbing with the balls of the fingers. In the case of photographic films including the use of subbing layers containing acid cooked pigskin gelatin which had been treated under the conditions of the invention described herein the emulsion layers were found to be resistant to this wet stripping procedure both when tested at the score marks and when tested at the cut edge of the sample.

We claim:

1. A method of treating acid cooked pigskin gelatin to adapt it for photographic subbing purposes which comprises leaching acid cooked pigskin gelatin having high jelly strength with aqueous alkali selected from the group consisting of the aqueous solutions of ammonia and of alkaline alkali metal compounds for 1-6 hours at a pH of 8-9.5 and a temperature within the range of 35-55 F. followed by washing to remove the alkali.

2. A method of treating acid cooked pigskin gelatin to adapt it for use for photographic subbing pmposes which comprises leaching pigskin gelatin having high jelly strength with aqueous ammonia for 1-6 hours at a pH of 8-9.5 and a temperature within the range of 35-55 F. followed by washing to remove the alkali.

3. A method of treating acid cooked pigskin gelatin to adapt it for use for photographic subbing purposes which comprises leaching acid cooked pigskin gelatin having high jelly strength with an aqueous alkaline alkali metal compound for 1-6 hours at a pH of 8-9.5 and a temperature within the range of 35-55 F. followed by washing to remove the alkali.

4. A method of treating acid cooked pigskin gelatin to adapt it for use for photographic subbing purposes which comprises leaching acid cooked pigskin gelatin having high jelly strength with aqueous alkali selected from the group consisting of the aqueous solutions of ammonia and of alkaline alkali metal compounds for 1-6 hours at a pH of 8-9.5 and at a temperature within the range of 35-5 5 F., and subsequently treating the leached gelatin with aqueous acetic acid and washing the thus treated gelatin with water.

5. A method of treating acid cooked pigskin gelatin to adapt it for use for photographic subbing purposes which comprises leaching acid cooked pigskin gelatin having high jelly strength with aqueous alkali selected from the group consisting of the aqueous solutions of ammonia and of alkaline alkali metal compounds for l-6 hours at a pH of 89.5 and at a temperature Within the range of 35-55 F., and subsequently treating the leached 7 gelatin with aqueous acetic acid and washing the thus 2,351,174 treated gelatin with demineralized water. 2,398,004 2,598,608 Reiereuges Cited in the file of this patent 2,834,771

UNITED STATES PATENTS 5 1,865,497 Atwood July 5, 193 625,873

8 Whitehead June 13, 1944 Houck et a1. Apr. 9, 1946 Sale May 27, 1952 Mitchell et a1. May 13, 1958 FOREIGN PATENTS Great Britain July 5, 1949

Claims

1. A METHOD OF TREATING ACID COOKED PIGSKIN GELATIN TO ADAPT IT FOR PHOTOGRAPHIC SUBBING PURPOSES WHICH COMPRISES LEACHING ACID COOKED PIGSKIN GELATIN HAVING HIGH JELLY STRENGTH WITH AQUEOUS ALKALI SELECTED FROM THE GROUP CONSISTING OF THE AQUEOUS SOLUTIONS OF AMMONIA AND OF ALKALINE ALKALI METAL COMPOUNDS FOR 1-6 HOURS AT A PH OF 8-9.5 AND A TEMPERATURE WITHIN THE RANGE OF 35-55* F. FOLLOWED BY WASHING TO REMOVE THE ALKALI.