Patented Mar. 2, 1954 2,671,022

UNITED STATES PATENT OFFICE

GRAPHIC SILVER HALIDE. EMULSIONS CONTAINING BERYLLILUM.’ .CUMEOUNDST. Donald2 E. ‘Sargent, Eastom, Pam and 101x110’; Bail'arrlra- Urbano, Ill.,..assignors to General; Aniline=*&w Gorporation,,.New York, N'..» Y.,, amorporation of‘ Delaware No. Drawing: Application June" 2'4; 19:49, Seriat No. for-,2“ l3~ Glaims. (Cl. 95-7) 1 2 The present invention relates to vthe perpara~ It will? noted trom‘; this formula thatalter oi“ polyvinyl alcohol- gels and to such gels hate. carbon: atomsare substitutedé'by hydroxyl whion constitute, inter alia, colloids useful. in groups. It is to these. hydroxyl groups. that. the photography. of the product is: attributable; is Welt known, natmiaii gelatihs- are almost : There. isyinteraction»(hydrogen.bonding.) between universally employed as the protective ‘colloid in these. hydroxyl groups and. water and between-the photographic’: emulsions; Despite this fact,1the'se. hydroxyl groups of adjacent chains so- that the natural products have-seriousshortcornings which solutions in water" show an appreciable viscosity. have kindled- a'strong desire in the art for the Unfortunately, however, these forces arenotsui-x creation of- gelatin substitutes free from the oh~ 10 ?cient vper se to cause the productto gel on stand: jeetions- to‘ gelatin. lng at. room temperature or“ upon cooling. Among- the‘ shortcomings of‘ gelatin are varia Considerable work has been done in an eitort bility» in physical‘: properties\‘ and in chemical cont to convert polyvinyl alcohol into amateriall which position which lead to‘ variations in the physical would possess. the properties. aforesaid and would and photographic propertiesiof the ?nished pho serve, as an effective gelatin. substitute. For the tographie emulsion and‘to variations» in the sus most part, this workwas predicated upon the-use ceptiioility of the silver halides: thereof to sensitiz oforganic compound'sas the gelling agents. QTne. ing and desensitizing" substances, developing exceptionis provided USP 2,376,371‘ which sug agents, and the like: brittleness when dryso that gests. the employment. of‘ boron compounds, such photographic products carrying lemulsion layers 20 as borie. acid, and‘ the like, for gelling polyvinyl containing»gelatin»crack‘ratherzeasily; particularly alcohol. This. action was to be expected for the printing" papers so- prepared; low: resistance to’ the reason that it is known that boric-acid and similar action o-f‘bacteri'a and molds; susceptibility to the boron derivatives undergo ester or com-plexfoiuna action of‘ strongly‘ alkaline’ reagents; low “melt tion with polyhydroixy compounds,‘ such as'gl-ycer ing; points” when wet, making it'necessary» to-proc- “ ine; carbohydrates; and the like (see; for; example see the photographic material at relatively low the bottom of’ page 1699 of "Organic Chemistry” temperature, e., on theorder-of 1-5 to‘ 25‘L 6; by‘ Gilman, vol’. II, second edition). It could Any useful gelatin substitute shouldpossess' the therefore be"“ assumed that the'hsame action would gel-forming and‘ protective colloid‘ action of'gela be portrayed in connection with; polyvinyl alcohol2 tin but belfree from the aforementioned; disad- ~ and that such action could. easily lead to» a cross vantages. Such a, material should‘ have fairly linked or gelled structure. constant physical and chemical properties allow We have now found,:suprisingly, that beryliium ing emulsions of- constant properties" to" :be pre compounds possess the‘abiIi-ty‘to~ge15po1yvihy1 al pared, should be, superior to gelatin as a- ?lm cohol in‘ conjunction with’ a basic material man formingymateri'al, anct should‘ not be attacked by even- greater degree than do boron compounds, bacteria- or’molds. such as boric acid despiteithemarked difference Polyvinyl alcohol; is- athigh- molecular weight, between these two types‘ of compounds. The‘cl-if»v waterhsoluble‘ polymer which yields tough trans ferenceis illustrated by fact that it is well known parent ?lms when’ its aqueous solutions are dried; that boron is distinctly non-metallic (‘see for‘ exF-r It'i's readily available and the chemical and 40' ample, Lati'mer‘ and Hildebrand, Reference Book physical‘ properties of any given» grade arefairly of'lhorganic Chemistry; The McMillan Company; constant; Commercial-1y‘ it‘is‘ manufactured by New York‘, I940‘, page 80, second paragraph)‘ hydrolyzing- polyvinyl acetate partially or " com‘ whilelberyl-lium is‘ classi?ed as a- metal- (ihi'd, page pletel-‘y- to give» a: variety of‘ products: The» term 57). Because of this,’ the hydroxide- of‘ boron “polyvinyl alcohol” as. herein used also includes (5B [301E191 is an: acid while the hydroxide of‘ he water-soluble hydrolyzed polyvinyl esters having rylli‘umiBeEOHlzl is a base; Furthermore; boron apoiyvinyll ester content‘ of less- the-n25 %' ', the re never appears "as'the- Bl|i++ oationwhen'its mainder" being‘ poly-vinyl alcohol. ‘ The» structure compound‘siare dissolved in water, but always; oc» of a completely. hydrolyzed; polyvinyLester-may be curs" in ananion comhi'nation" with another represented schematically by the following 60' noni'metal‘ such as. oxygen tort example the- B021-> formula: andYB4O'r.—— anions. By way of'contrast beryl» l-iunri. compounds in. aqueous solution; readily yield v \ /C.Er_~ fcge. fCHe. the.- Be++ cation which. is typical of-ithe behavior on. on (EH; \ o?saltsrofthemetalsi. 'in' one on ltzmayialsoa be: noted that. appears: Ii 4 the same group of the periodic system with mag carbonate, or the like. Alternatively, the solu nesium, calcium, strontium, barium, zinc and tion of the polyvinyl alcohol and beryllium com cadmium. Like the hydroxide of beryllium, the pound may be coated on a suitable support and hydroxides of these other metallic elements ex gelation effected by fuming the .coating' with a hibit the characteristics of bases. Because of this, CR volatile base such as ammonia or an organic it was to be presumed that the gelling action of amine such as methylamine, ethylamine, ethyl beryllium compounds would be comparable to enediainine, or the like, or by dipping the coated that of similar compounds of the metalsmost I support into an aqueous solution of a base, either closely related thereto, i. e., of those which have organic or inorganic, of the type previously men the same valence and appear in the same group 10 tioned. - - _, of the periodic system. Investigation has shown - Any water ‘soluble beryllium compound may however that aqueous solutions of the salts of be usedvfor the intended purpose. Examples of magnesium, calcium, strontium, barium, zinc and, such compounds are beryllium nitrate, beryllium cadmium when added to an aqueous solution of chloride, beryllium , or the like. polyvinyl alcohol, followed by addition of a basic ' The quantity. of the beryllium compound which material effect very little or no gelling action on is employed may vary and will generally range the polyvinyl alcohol. In face‘with magnesium from about 1/2 to 10% by weight of the polyvinyl and calcium compounds, the hydroxides may pre ' ‘alcohol used. For the best results it is preferred cipitate. With zinc and cadmium compounds, on ‘to employ the beryllium compound in an amount the other hand, while, semi-opaque heterogeneous ranging from about 1 to 5% by weight of the masses are formed which may precipitate and polyvinyl alcohol. The exact amount used may which exhibit few of the desirable characteristics depend upon the molecularweight of the poly of a clear tough homogeneous gel. It was there vinyl alcohol used and the properties desired in fore suprising, that solutions of beryllium com the finished product. - _ _ pounds, unlike those of its congeners form gels 25 The aforesaid polyvinyl alcohol-beryllium with polyvinyl alcohol upon treatment with a compound complexes may be conveniently em basic material. . ployed for the preparation of light sensitive pho Furthermore it is well known that compounds tographic silver halide elements by adding to an of beryllium are often similar to compounds of aqueous solution of polyvinyl alcohol an alkali aluminum in both physical and chemical prop 30 metal halide such as ,‘ sodium erties. Never-the-less the above-noted gelling chloride, , potassium chloride, action of beryllium compounds is not shared by or the like, and precipitating therein a silver hal aluminum compounds. ‘ > » ide in a ?nely dispersed state by the addition of The beryllium compound-polyvinyl alcohol gel a soluble silver salt such as silver nitrate, while are even stronger than those formed with boron continuously stirring the mass. A water soluble compounds. This is probably attributable to the beryllium compound is then added, while stirring, fact that in many cases the boron compounds, and the resulting composition is coated on a suit being derived from a trivalent element, form able support and gelled by treatment with a basic structures which are too highly cross-linked and material as previously outlined. Following the are therefore rigid and too easily shared, where 40 addition of the soluble silver salt, it may be de as the beryllium compounds, being derived from sirable to ripen the emulsion by stirring it at a an element which is only divalent, form more somewhat elevated temperature, i. e., 35 to 75° C. elastic gel structures. for a short time or to add auxiliary agents such . Our discovery, which as noted, is quite unex~ as sensitizers, desensitizers, ripening agents, dis pected, involves the preparation of colorless gels persing agents, and the like. Flourescing agents having a very high mechanical strength and emi such as those described by Sargent in copending nently suitable for the preparation of photo applications Serial Nos. 69,841 ?led January 7, graphic emulsions by adding to polyvinyl alcohol 1949., now Patent No. 2,582,357; 72,2?7 ?led Janu solutions a solution of a water soluble beryllium‘ ary 22, 1949, now Patent No.2,555,138; and ‘75,738 compound followed by treatment with a basic filed February 10, 1949, now Patent No. 2,571,706, material. This gelling action may be due to the mayalso be added; ’ ‘ formation of beryllium hydroxide in situ from f It is to be understood that the above proce-. the beryllium compound and the reaction of the dure need not be strictly followed in producing hydroxide with the chain-like molecules of the the light sensitive silver halide elements. Thus polyvinyl alcohol. It is to be understood, how-_ beryllium compound may be added prior to the ever, that this explanation is. merely given as a addition of the alkali metal halide and the solu possible illustration of the mechanism of the re ble silver salt with equally good’ results. action and is not being submitted as an actual The remarkable gelling action of the beryllium indication of the reaction which takes place. compound is demonstrated by the fact that coat Clear, tough, high melting polyvinyl alcohol 69 ings prepared with the polyvinyl alcohol-beryl gels containing soluble beryllium compounds and lium compound complexes are proof against boil a basic substance and the preparation of such ing water, whereas if the beryllium compounds gels constitute the purposes and objects of the are omitted in the preparation of the coatings, present invention. - " , solution in boiling water occurs quite readily. The gels contemplated herein are produced by 65 adding to a water solution of polyvinyl alcohol, a Erample I water soluble compound'of beryllium and‘then .f'i‘o 100 parts of a 10% solution of polyvinyl modifying the pH of the resulting mixture by alcohol (Dupont Elvanol 52-22) are added 5' parts treatment with a water‘ soluble basic material. of a 10% solution of beryllium nitrate ‘ Such treatment may be e?ected in various ways. 70 One method involves the addition to the mixture (nanomsmoi of the polyvinyl alcohol and the beryllium com with continuous stirring until a homogeneous so pound, a solution of a watersoluble basic mate lution results/1O parts of a 10%.sodium hy rial such as sodium hydroxide, potassium by". droxide solution are then added with stirring droxide, sodium carbonate, ammonia, ammonium 75 whereupon the solution is__ almost instantaneous 2,071,022 '

1y converted into a sti?, colorless, transparent treating the mixture with a water soluble in gel which does not dissolve readily in boiling organic basic material. water. 2. The method of preparing a tough, colorless Example II gel which comprises mixing an aqueous solution of polyvinyl alcohol with a water soluble inor To a solution of 125 parts of a 10% polyvinyl ganic beryllium salt in a gelling amount and alcohol solution (Dupont Elvanol 52-22), is treating the mixture with a basic material se added, with stirring, a solution of 0.9 part of so- - lected from the class consisting of water solu dium chloride and 0.5 part of beryllium nitrate ble inorganic bases and volatile nitrogenous wa dissolved in 25 parts of distilled water. The solu ter soluble organic bases. tion is heated to 50° C. and, in yellow light, a solu 3. The process as de?ned in claim 2 wherein tion of 1.875 parts of silver nitrate in 15 parts of the mixing of the ingredients is effected with distilled water is added with continuous stirring. out heating. After stirring in yellow light for 15 minutes at 4. The process of producing a light sensitive 15° C., the resulting ?uid silver chloride emulsion 15 photographic element comprising a silver halide is coated on a paper base and allowed to cool. uniformly dispersed in a tough, colorless gel of The base is then exposed to ammonia fumes un polyvinyl alcohol which comprises adding to an - til the coating sets to a tough water-insoluble aqueous solution of polyvinyl alcohol, an alkali gel. The coating is then dried in the dark. The metal halide, adding silver nitrate while con light sensitive element so prepared is very suit 20 tinuously stirring the mass, incorporating a wa able for making prints from photographic nega ter soluble inorganic beryllium salt in a gelling tives and is not adversely aifected by the usual amount, and treating the composition with a treating baths as is unmodi?ed polyvinyl alcohol basic material selected from the class consistingr emulsion coatings. of water soluble inorganic bases and volatile ni Example 111 25 trogenous water soluble organic base. The procedure is the same as in Example H 5. The method of preparing a tough, colorless excepting that the coating is fumed with methyl gel which comprises mixing an aqueous solution amine rather than with ammonia. The results of polyvinyl alcoholwith beryllium nitrate in an . obtained are substantially the same as those of amount ranging from about 1A; to 10% by weight Example II. 30 of the polyvinyl alcohol and treating the mix Example IV ture with a water soluble inorganic basic ma terial. The procedure is the same as in Example 11 6. The process of producing a light sensitive excepting that the coating is effected on cellu photographic element comprising a silver halide lose acetate base and is set by bathing the coat 35 uniformly dispersed in a tough, colorless gel ing for a short time in a 5% solution of sodium of polyvinyl alcohol which comprises adding to hydroxide, followed by water washing, and dry an aqueous solution of polyvinyl alcohol, an al ing kali metal halide, adding silver nitrate while con Example V tinuously stirring the mass, incorporating a wa The procedure is the same as in Example I 40 ter soluble inorganic beryllium salt in a gelling excepting that the beryllium nitrate is replaced amount, coating the composition on a support by an equivalent amount of . and treating it with ammonia. ~ The gel obtained resembles that of Example I. 7. The process as de?ned in claim 4, wherein the berryllium salt is beryllium nitrate. Ezample VI 45 8. The process as de?ned in claim 4, wherein The procedure is the same as in Example I the beryllium salt is beryllium bromide. excepting that the beryllium nitrate is replaced 9. The product of the process of claim 1. by an equivalent amount of beryllium bromide. 10. The product of the process of claim 2. A clear, tough gel also results in this case. 11. The product of the process of claim 4. It should be understood that the gels formed 50 12. The product of the process of claim 6. as herein noted can be used for purposes other 13. The product of the process of claim 6. than the preparation of photographic products. DONALD vE. SARGENT. Such gels may be employed, for example, as thick ening and gelling agents in water paints, print JOHN C. BAILAR, JR. ing inks, and many other applications where 55 thickening or gelling compositions are required. References Cited in the file of this patent Various modi?cations of the invention will UNITED STATES PATENTS occur to persons skilled in this art, and we there Number Name Date fore do not intend to be limited in the patent 2,412,200 Blum ______Dec. 10, 1946 granted except as necessitated by the appended 60 2,439,108 Staehle ______Apr. 6, 1948 claims. We claim: OTHER REFERENCES 1. The method of preparing a tough, colorless gel which comprises mixing an aqueous solution PVA Publication, Dupont R 8: H Technical of polyvinyl alcohol with a water soluble inor Bulletin, 7 pp., copyright 1940, page 3 cited. ganic beryllium salt in a gelling amount and