Патент USA US2256390код для вставки
Patented Sept. 16, 1941 ' 2,256,390‘ UNITED STATES PA'E'EN'E' OFFIQE 2,256,390 METHOD OF PREVENTING PRECIPITATION. 0F ALKALBNE-EARTH METAL SALTS IN GELATW ‘ Edward Hewitson, Rochester, N. Y2, assignor, by mesne assignments, to Eastman Kodak Com pany, Rochester, N. Y., a. corporation of New Jersey _ No Drawing. Application August 19, 1936, Serial No. 96,855 2 Claims. (Cl. 95-7) action involved may be explained in the follow This invention relates to photographic gelatin ing way: When sodium metaphosphate is heated and emulsions and particularly to a method for to a temperature of about 620° C., it passes into preventing precipitation of insoluble salts in gel the hexametaphosphate according to the follow atin solutions and emulsions. ing reaction: Di?iculties have often been encountered when certain solutions, emulsions, or suspensions are added to gelatin solutions or photographic emul When the sodium hexametaphosphate is added sions used for coating light sensitive plates, ?lms, to a solution containing a calcium or other al and papers, by reason of the separation of insol uble calcium, magnesium, or other alkaline-earth 10 kaline-earth metal compound, a double salt of sodium and calcium or other alkaline-earth metal salts which are formed by the interaction metal is formed according to the following re of soluble salts of these metals contained in the gelatin solution or photographic emulsion with . action: some constituent of the solution, emulsion, or suspension added. This effect is undesirable for 15 a number of reasons. The coatings, produced by This double salt of sodium and calcium ionizes in the gelatin or photographic emulsion in which solution to sodium ions and calcium hexameta a soluble salt has been precipitated, are cloudy phosphate ions both of which are soluble. The or hazy and not fully transparent as desired for calcium ions are bound up in the hexameta photographic uses, and another objection is that 20 phosphate radical and are not produced as free the active ingredients of the solution added to calcium ions in the solution. This ionization the gelatin or photographic emulsion may be may be represented as follows: wholly or partially precipitated and thereby pre vented from having the desired effect on the 25» In addition to sodium hexametaphosphate, gelatin solution or photographic emulsion. It is, therefore, an object of the present inven other alkali-metal salts of hexametaphosphoric tion to provide a method for preventing precipi acid may be employed such as the lithium and tation‘of insoluble salts of alkaline-earth metals potassium salts. ' in gelatin solutions and emulsions. A further This property of the alkali-metal salts of hexa object is to provide a method for the clari?cation 30 metaphosphoric acid may be taken advantage of of gelatin solutions and emulsions. A still fur in a number of ' ways in connection with photo ther object is an improved photographic emul graphic. gelatin and emulsions. One use is the sion free from haze. Other objects will appear clari?cation ‘ of gelatin solutions. Many solu from the following description of my invention. -tions of gelatin are cloudy or hazy due to the These objects are accomplished by adding an 35 presence of ?nely suspended matter, which in alkali-metal salt of hexametaphosphoric acid to many cases consists largely of insoluble calcium the gelatin solution or photographic emulsion or salts. The addition of sodium hexametaphos to the solution or emulsion to be added to the phate to a gelatin’ solution containing a. haze of such material lowers the concentration of cal The alkali-metal salts of hexametaphosphoric 40 cium ions in the‘ solution to such an extent that acid have the property of forming soluble com a greater amount of calcium salt dissolves. This gelatin solution or photographic emulsion. plex ions with ions of calcium, magnesium and other alkaline earth metals and this results in process is repeated until ?nally all of the calcium salt passes into solution and the gelatin becomes lowering the concentration of these metallic~ions - clear. The amount of sodium hexametaphos to such a value that they are no longer precipi 45 phate necessary to achieve this result will vary tated by acidic ions or radicals such as carbonate, with the condition of the gelatin and the amount sulphate, oxalate, oleate, and other fatty acid of calcium saltpre'sent. In general, about 8.0% radicals etc. Other heavy metal ions such as of sodium hexametaphosphate as reckoned on ' iron and aluminum also form complex ions with the amount of gelatin, will be su?icient. This hexametaphosphates which are soluble in solu 50 amount may vary, however, from %% to about tion, but these complex ions are formed to a 20.0%, depending on the quantity of calcium, or lesser degree. 1' ‘ I other alkaline earth metals, present. Although I do not wish to commit myself to Another important use of this property of the the following explanation of the reason for this alkali-‘metal hexametaphosphate is in connec-v effect; I believe that the mechanism of the re- 55 tion with the addition of wax ‘emulsions to photo 2 2,256,390‘ graphic emulsions for the manufacture of self p. make solution A. To this is added the wax emul lubricating ?lms. The addition of wax emul sions to photographic emulsions for this pur pose is described in the patent of E. J. Ward, sion B slowly with stirring. The mixture of A and B is then added slowly with stirring to the photographic emulsion C. In- the above examples, I have referred to mix ing the wax emulsion with sensitive photographic emulsions. It should be understood, however, No. 2,059,829, granted November 3, 1936. Wax emulsions are readily ?occulated and coagulated by small amounts of ions of calcium, magnesium, and other alkaline-earth metals and in fact, that the wax emulsion may be mixed with gelatin most heavy metals. Photographic emulsions and solutions for use as backings, undercoats, or over gelatin solutions, however, rarely contain more 10 coating layers for photographic ?lms. than slight traces of metallic ions other than Another use of alkali-metal hexametaphos those of magnesium and the other alkaline-earth phates according to my invention, is in the manu group; and it is in connection with this group facture of the suspension of ?nely divided man that the hexametaphosphates are most effective. ganese dioxide by the reduction of potassium per I have found that the ?occulation of wax 15 manganate. When manganese dioxide is manu emulsions upon addition to photographic emul factured in this way, carbon dioxide is frequently sions or gelatin solutions may be prevented by liberated and if the suspension is mixed with adding sodium hexametaphosphate to the wax gelatin, the carbon dioxide thus produced pre emulsion or to the photographic emulsion or cipitates insoluble carbonates from the gelatin gelatin solution before the mixture is. made. 20 solution since the gelatin frequently contains The sodium hexametaphosphate must be added alkaline-earth metal compounds. The precipita in su?icient amount to react with all of the metal tion of these insoluble salts may be prevented ions which tend to ?occulate the wax emulsion. by the addition of the hexametaphosphate to the The following formulas have been found satis gelatin solution before the reduction of the factory. 25 Three solutions or emulsions are made up as follows: A. B. potassium permanganate takes place. A further use for the compounds according to my invention is in the incorporation of certain dyes in gelatin solutions or emulsions. Dyes such Emample I as sulfonated aryl amino ethyl alcohols of the ' Grams 30 Ionamine type are precipitated by calcium and Sodium hexametaphosphate _________ __ 9 similar ions. This property has heretofore Water ______________________________ __ 81 I limited the use of these dyes in photographic gelatin. With the aid of sodium hexametaphos Photographic emulsion ______________ __ 5000 phate, such precipitation can be readily prevented C. Wax emulsion (20% wax) ___________ __ 100 either by adding the hexametaphosphate to the Water _____________________________ __ 210 dye solution or to the emulsion or solution of In making up the ?nished photographic emulsion containing wax, the solution A, which is made is added to the photographic emulsion B. The gelatin to which the dye solution is to be added. It is to be understood that my invention may be used in other ways and that the compounds may be employed in other proportions than those wax emulsion is added to water to form the emul speci?cally mentioned in the preceding descrip sion C,-which is then added slowly to the mixture of A and B with stirring. Any suitable natural tion of my invention. I intend my invention to be limited only by the scope of the appended claims. by dissolving the hexametaphosphate in water, or synthetic wax such as that disclosed in the Ward Patent No.‘ 2,059,829 may be used. A pre 45 I claim: I - 1. The method of incorporating wax in a gela ferred wax is carnauba wax. tin photographic emulsion, which comprises add Example II ing an alkali metal salt of hexametaphosphoric acid to the gelatin emulsion, and mixing the wax Solutions or emulsions are made up as follows: Grams 50 emulsion with the gelatin emulsion. 2. The method of incorporating wax in a gela A. Sodium hexametaphosphate _________ __ 9 Water _____________________________ __ 291 B. Wax emulsion (20% wax) ___________ __ 100 . Photographic emulsion ______________ __ 5000 The hexametaphosphate is dissolved in water to tin photographic emulsion, which comprises add ing sodium hexametaphosphate to the gelatin emulsion, and mixing the wax emulsion with the 55 gelatin emulsion. EDWARD HEWITSON.