US3549376A - Image-forming compositions containing polymer binding agents and coordination complexes of iron (iii) organic salts - Google Patents

Description

United States Patent IntrCl. G03c 1/64 US. Cl. 96--92 11 Claims .ABSTRACT OF THE DISCLOSURE Light-sensitive compositions, layers and elements capable of forming vesicular images by exposure to actinic radiation and heating comprising a macromolecular organic polymer binder having dispersed therein a ferric ammonium polycarboxylate, a photoinitiator of addition polymerization, e.g., a polynuclear quinone or a vicinal ketaldonyl compound, an oxidizing agent, e.g., mercury oxylate, and an' acid or acid salt, e.g., oxalic acid or ammonium oxalate.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to vesicular or light-scattering image-forming compositions, layers and elements, and to their preparation.

Description of the prior art Vesicular images are, of course, known and generally comprise incorporating a gas-producing agent such as a diazonium compound in a film-forming organic polymer binder coating composition which is coated onto a suitable support. ,It is known to use ferric ammonium oxalate and citrate for this purpose and, further, it is known to add a small amount of oxalic acid or citric acid and dicarboxylic acids of at least carbon atoms to this composition to increase the sensitivity of the system. Such compositions and elements are described in British patent specification 935,428, Herrick, US. 2,703,756, and the textbook by I. Kosar, Light Sensitive Systems, published by John Wiley & Sons, Inc., New York (1965). Although such systems have been used to make blueprints and scatter images, one of their main disadvantages has been their slow speed and image fading characteristics. The fading of the images is apparently due to the use of unmodified natural colloids such as gelatin as the binder for the gas producing agent. These natural colloids absorb moisture which in turn destroys the image. Synthetic binders such as hydrophobic vinyl polymers have been proposed and offer some advantages over gelatin in that they are substantially water-insensitive.

. SUMMARY OF THE INVENTION This invention pertains to the use of coordination complexes of ferric salts of organic acids to form light-scattering images and to the sensitization of such systems with 'photoinitiato'rs. In vthis system the decomposition of the complex iron oxalate, citrate or tartrate, for example, to carbon dioxide, results in the formation of minute bubbles. The coordination complexes of iron (III) organic salts are noted for their light sensitivity and as mentioned above, theyhave been used extensively in the making of blueprints. The addition of a small amount of oxalic acid to the system increases the speed of the coated layer to actinic light as does the addition of an oxidizing agent, 'gl, silvert oxalate, silver nitrate, mercury oxalate and 1,1,2,3,3,3-hexafiuoropropyl-1-silver sulfonate. The photoinitiators, e.g., quinones or acyloins, apparently reoxidize the iron:

In other words, the entire sensitized reaction on a photochemical basis is a 2-photon process. The mechanism for the entire reaction can be written as follows:

The above sequence of reactions may not be entirely correct although it has been shown that the photocatalysis of oxalic acid in the presence of photolyzed Fe(C O can give rise to the formation of Fe(C O and Fe(C O Both of these are photoactive in the visible region of the spectrum. The maximum concentration at which these complexes form is at a 1:3 to 1:2 ratio of Fe+:C O In this range, the fastest rate of photolysis is obtained leading to a quantum yield of 1.2. With the addition of the phenanthrenequinone, a number of oxalate species could be formed during the oxidation step. Of course, it will be appreciated that the foregoing discussion is in part theoretical, and it is not intended to limit the invention thereby.

A number of quinones and acyloins have been found to be effective as sensitizers in the system. l-ethylanthraquinone is somewhat more effective than 9,10-phenanthrenequinone. Benzophenone, anthraquinone and 2,7-dit-butylanthraquinone are also useful sensitizers. Other useful polynuclear quinones are those listed in Notley US. 2,951,758, Sept. 6, 1960. The pH of the system, while not at all critical, gives optimum results when it is adjusted to between 5.0 and 6.0.

The binder system to contain the photosensitive materials is important. The rigidity, gas diffusibility and permeability are important characteristics which should be carefully controlled. This aspect of making vesicular elements is well known in the art and is documented in the J. Kosar textbook that is referred to above. In the prior art systems, gelatin was used originally as a binder but because of its sensitivity to moisture it has the disadvantages that are discussed above. It does have the advantage, however, that systems using it can be coated without need of special facilities to recover organic vapors as do hydrophobic resins coated from organic solvents, although organic systems may be desirable in some cases. Gelatin can also absorb large amounts of salts without precipitation. It has been found that gelatin can be used if certain modifiers are added thereto such as various polymer latices in aqueous dispersions. Also, it has been found that water-soluble synthetic polymers could be used, particularly when modified by a small amount of a thermoplastic hydrophilic polymer. This does not, of course, preclude the use of organic solvents for coating the novel light-sensitive systems of this invention, particularly where organic solvent-soluble ferric alkyl ammonium and aryl ammonium oxalates and citrates are used.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The compositions of this invention comprise (1) a binder such as gelatin, vinyl polymers, polyamides and other macromolecular organic polymers, (2) a gas-pro ducing agent having the formula:

3 3 3 where X is Na, K,

where R is H, alkyl of 4 to 20 carbons; cycloalkyl of 6 to 12 carbons; aralkyl, e.g., benzyl and naphthylmethyl; aryl f 6 to 14 carbons and alkaryl where alk contains 1 to 4 carbon atoms and aryl contains 6 to 14 carbon atoms, and Y is a polycarboxylic anion, namely, oxalate, citrate or tartrate, (3) a photoinitiator of addition polymerization, e.g., substituted or unsubstituted polynuclear quinones, vicinal ketaldonyl compounds, acyloins and acyloin ethers and, optionally, (4) an oxidizer, e.g., an acid salt of silver, mercury, palladium or gold having a pKa53, e.g., 1,1,2,3,3,3-hexafluoropropyl-l-silver sulfonate, silver oxalate, silver nitrate and mercury oxalate, oxalic acid or ammonium oxalate. Those acid salts of metals which function in the system can oxidize ferrous ion to ferric, and the metals can be described in terms of half-cell potentials. For illustration, the following is shown:

By convention, a positive potential indicates that the reaction will take place as written. Any acid salt of a metal which fits this condition is suitable. Plasticizers, hardeners and coating aids may also be added. The composition is coated on a suitable support and dried. Image formation is obtained by exposing the coated material through a suitable stencil, e.g., a photographic negative, to actinic light and then subsequently heating to a temperature between 50 and 120 C. depending on the binder used. The heating may be carried out by means of a source emitting infrared or strong heat rays such as a heating plate. A second overall exposure or normal exposure to ambient room illumination allows the vesicular image to be fixed without heat.

Suitable hydrocarbon substituted compounds, constituent (2), are described in my copending application entitled Substituted Ammonium Salts, Ser. No. 680,013, filed Nov. 2, 1967, and now US. Pat. No. 3,504,004.

The novel complexes that are described in the justmentioned application can be represented by the formula:

wherein l to 4 of the radicals R is alkyl of 4 to carbon I atoms, cycloalkyl of 6 to 12 carbon atoms, aryl of 6 to 14 carbon atoms, aralkyl, e.g., benzyl or naphthylmethyl or alkaryl wherein alk contains 1 to 4 carbons and aryl contains 6 to 14 carbon atoms, and any remaining radicals R is hydrogen, and each of the 3 radicals Y is an oxalate, citrate or tartrate anion.

Suitable specific alkyl radicals include methyl, ethyl, propyl, hexyl, heptyl, octyl, decyl, dodecyl, hexadecyl and octadecyl. The aryl radicals can be phenyl, naphthyl, anthryl or phenanthryl.

Suitable cycloalkyl radicals include cyclohexyl, cycloheptyl and cyclooctyl. Among the useful alkaryl radicals are tolyl, xylyl, ethylphenyl, propylphenyl, butylphenyl and dodecylphenyl.

The novel complexes can be made in accordance with the invention by reacting an appropriate alkyl-, cycloalkyl-, aryl-, aralkylor alkarylammoniurn chloride, bromide or iodide in an aqueous medium, e.g., in water, of a water-ethanol solution with an oxalate, citrate or tartrate of a metal that forms an insoluble salt, more particularly a silver oxalate, citrate or tartrate. The insoluble metal salt that is formed is separated, usually by filtering the prepicitate, from the quaternary ammonium compound. The latter compound is then reacted with an appropriate ferric salt, e.g., ferric sulfate, in an aqueous ethanol solution, to form the desired ferric hydrocarbonsubstituted-ammonium carboxylate complex. Ferric sulfate can be used with barium chloride to form the complex. The reactions may be carried on simultaneously, that is, the hydrocarbon-substituted ammonium halide, ferric salt and silver carboxylate may be incorporated in the reaction solution.

The constituents of the image forming composition can be used in the following amounts:

Constituent: Parts by weight (1) 26.0 to 62.6 (2) 72.0 to 12.4 (3 .3 to 5.0 (4) 1.7 to 20.0

The invention is further illustrated by but is not limited to the following examples.

EXAMPLE I A composition was made up as follows:

Gelatin-20 g.

Water350 ml.

Gum arabic (10% aqueous solution)10 ml. Formaldehyde (concentrated)1 ml. 9,10-phenanthrenequinone (0.1 M in ethanol)50 ml. Sodium N-methyl-N-oleyl tauratel g.

Ferric ammonium oxalate-30 g.

Oxalic acid5 g.

pH adjusted to 5.86.0.

The composition was coated on a copolymer coated polyethylene terephthalate film of the type described in Alles, US. Pat. 2,627,088 and dried in a conventional manner. A control coating was made using the above composition minus the 9,10-phenanthrenequinone compound. Strips of the coated material were exposed through a /2 sensitometric step wedge to actinic light and simultaneously heated by means of a Model 60W Revolute Rockette exposing device manufactured by the Bruning Corporation at a setting of 5 to produce the image of the step wedge. The strip coated with the composition containing the 9,10-phenanthrenequinone showed a 7\/2 step increase in speed over the strip coated with the composition not containing the quinone compound. The image when viewed by transmitted light was black and white and of high contrast. By reflected light the image was yellow in appearance.

EXAMPLE II To the formulation disclosed in Example I there was added milligrams of 1,l,2,3,3,3-hexafluoropropyl-1- silver sulfonate. The material when coated with this formulation and exposed and heated as described in Example I showed a speed increase of one step of the 2 step wedge as compared to the composition in Example I containing only the phenanthrenequinone compound.

EXAMPLE III The composition of Example I was coated and dried as described therein. Over this coating here was applied an antiabrasion overcoating having the following composition:

Water-300.0 ml.

Gelatin-6.5 g.

Dimethylolurea (.7% aqueous soln.)6.0 ml.

Sodium hydroxide 3 N5.0 ml.

Chrome alum (10.0% aqueous soln.)--2.0 ml.

Sodium salt of alkyl aryl polyether sulfonate (Rohm 8;

Haas-Triton 200)-3.5 ml.

Saponin aqueous soln.)6.0 ml.

Polyethylene glycol monostearate (avg. mol. wt. 1000) (5% ethanol)1.0 ml.

Dioctyl sodium sulfosuccinate (1.0% H 0 soln.)6.0

The coating showed superior resistance to moisture and upon exposure and treating as described in Example XI below the element gave somewhat higher speed and contrast than Example I.

EXAMPLE IV A composition was made up as follows:

Poly(vinyl pyrrolidone/styrene) (viscosity range 1000 centipoises at C. Brookfield No. 3 spindle r.p.m.) solids in aqueous dispersionparticle size 0.5 micron)-- ml.

Gelatin (1.2% aqueous soln. containing 1% gum arabic)50 ml.

Ferric ammonium oxalate-45 g.

9,10-phenanthrenequinone (.01 M in ethanol)25 ml.

Sodium N-methyl-N-oleoyl taurate--l g.

Polyvinyl acetate aqueous dispersionBrookfield viscosity 4456)-15 ml.

The above composition was coated, dried, exposed and heated as described in Example I. The resulting vesicular element gave good image quality and high speed. The element also showed good Water resistance, gas permeability and diffusibility.

EXAMPLE V A coating composition was made as follows:

Polyvinyl alcohol (viscosity 45-55 in centipoises of a 4% aqueous solution at 20 C. determined by Hoeppler falling ball method)--26 g.

Poly(methylvinylether/rnaleic anhydride) (high molecular weight, viscosity 4000 centipoises of 10% aqueous solutionat 20 C.-Brookfield)-l4 g.

Polyacrylamide (viscosity 6 centipoises-Brookfield 1% aqueous soln. at 25 C.)--25 g. Sodium N-methykN-oleoyl taurate0.5 g. Water-1000 ml.

To 20 ml. of the above there was added 2 ml. of 0.1 M methanol solution of 9,10-phenanthrenequinone, 100 mg. of poly(vinylpyrrolidone) (M.W. 40,000) and 1.5 grams of ferric ammonium oxalate. The mixture was thoroughly stirred and coated and dried as described in Example I. Upon exposure and heating an image was obtained showing good resolution and speed and good resistance to moisture.

EXAMPLE VI A coating composition was made of the following ingredients:

Ferric ammonium oxalate25 g.

Oxalic acid5 g. V

Gelatin 20 g. I

Gum arabic (10% aqueous soln.)-10 m1. Ethylanthraquinone (0.1 M in ethanol)50 ml. Formaldehyde (10% aqueous soln.)-40 ml. Sodium N-methyl-N-ole'oyl taurate-2 g.

Wate'r-300 ml.

The above composition was coated and dried as described in Example I. The material together with a control wherein the above composition did not contain the ethylanthraquinone were exposed through a /2 step wedge, setting 2, in a Model W. Revolute Rockette exposing device manufactured by the Bruning Corporation. V A

The strip coated with the composition containing the phenanthrenequinone compound showed a speed increase of 2V2 steps as compared to the control strip not containing the quinone compound.

EXAMPLE VII A composition was formulated as follows:

The above dispersion was coated, dried, exposed and heated as disclosed in Example I. The V2 strip showed good contrast and the image had excellent quality. The

speed was 4V2 steps faster than the same formula without the phenanthrenequinone compound.

EXAMPLE VIII The following composition. was made:

Ferric ammonium oxalate25 .0 g.

Gelatin-40.0 g.

Gum arabic 10% aqueous soln.)10.0 ml.

Dimethylolurea-0.5 g.

Sodium-N-methyl-N-oleoyl taurate--3.0= g.

Oxalic acid-5.0 g.

Formaldehyde (conc.)l.0 ml.

9,10-phenanthrenequinone (.01 M ethanol soln.)25.0

pH adjusted to 5.4 (with 20% NaOH) The above composition was coated, dried, exposed and heated as described in Example I along with a control containing no phenanthrenequinone. The material sensitized with the quinone was 4V2 steps faster than the control.

EXAMPLE 1X Example VII was repeated except that in place of the polyarnide dispersion there was added 25 ml. of a 40% solids concentration of a methyl ethyl ketone solution of the copolymer of bisphenol A and epichlorohydrin having a molecular weight of about 200,000 was added to the composition. Images obtained from the coated element showed excellent speed and quality indicating good gas difiusibility and permeability.

EXAMPLE X The coating composition was formulated from the following:

Gelatin-20 g.

Water200 ml.

Dimethylolurea- -l g.

Ferric ammonium oxalate-20 g.

Sodium N-methyl-N-oleoyl taurate-2 g.

Nonyl phenoxy polyoxyethylene ethanol1 g.

9,10-phenanthrenequinone (0.1 M in ethanol)35 ml.

Formaldehyde (conc. 30%)1 ml.

Polyethyl acrylate (Procedure A in Nottorf, US. 3,142,-

568) (30% dispersion)-30 ml.

pH adjusted to 6.0 a

The composition was coated, dried, exposed and heated as described in Example I to give a vesicular image of good quality and reduced water sensitivity as compared to the same composition containing no polyethylacrylate dispersion and only gelatin as the sole binder in the'system. The speed was 5 /2 steps faster than a similar composition 'not containing the 9,10-phenanthrenequinone compound.

7 EXAMPLE XI A coating composition was formulated as follows:

Polyvinyl acetate (viscosity of 6.8% benzene soln. -7 centipoisesHoeppler Viscosimeter at 20 C.) (20% methanol solution)25 ml.

Tris(hexadecylammonium) iron (III) oxalate (Example V of U.S. Ser. No. 680,013)5 g.

9,10-phenanthrenequinone (0.01 M methanol soln.)2

Oxalic acid0.l g.

The resulting solution was coated and dried as described in Example I. A control not containing the quinone compound was also coated. Sample strips of both were exposed through a /2 step wedge by means of a Sylvania SQ-60 Sun Gun1000-watt at a distance of 16 inches and heated to 100 C. until visible images were formed. The coating containing the phenanthrenequinone showed double the speed of the coating not containing the quinone compound.

EXAMPLE XII A coating composition was formulated as follows:

Polyvinylidene chloride (viscosity of 20% soln. in methyl ethyl ketone at 25 C.approx. 1000 centipoises Brookfield) (25% solution in methyl ethyl ketone)- 25 ml.

Tris(trioctylammonium) iron (III) oxalate (Example III, U.S. Ser. No. 680,013)5 g.

9, l0-phenanthrenequinone0.1 g.

Oxalic acid0.l g.

The composition was coated and dried as described in Example 1. Upon exposure and heating as described in Example XI a good quality vesicular image was formed in the coated layer.

EXAMPLE XIII A coating composition was formulated as follows:

Poly-n-butylmethacrylate (25 soln. trichloroethylene) high molecular weight-viscosity 0.53 for a solution of 0.25 g. polymer in 50 ml. chloroform, measured at 20 C. using a No. 50 Cannon-Fenske Viscometer25 ml.

Tris(hexadecylammonium) iron (III), oxalate (Example V of U.S. Ser. No. 680,0l3)5 g.

9,10-phenanthrenequinone0.1 g.

Oxalic acid-0.1 g.

The resulting solution was coated, dried, exposed and heated as described in Example XII to give a good quality image.

EXAMPLE XIV A coating composition was formulated as follows: Styrene/acrylonitrile copolymer (Refractive Index No.

1,565ASTM-D5420 and specific gravity 1.08-

EXAMPLE XV A' coating solution was formulated as follows:

Gelatin-20 g.

Water300 ml.

Gum arabic (10% aqueous soln.)-l0 ml. Sodium ferric oxalate15 g. Formaldehyde (conc.)1 ml.

Sodium N-rnethyl-N-oleoyl taurate2 g.

8 Oxalic acid3 g. 9,10-phenanthrenequinone (0.1 M in ethyl acetate)50 The above composition was coated, dried and exposed as described in Example I except that the Rockette exposing device was set at l. The V2 step wedge image gave an image with a speed 2 /2 steps faster as compared to a control sample not containing the quinone sensitizer.

EXAMPLE XVI A coating solution was formulated as follows:

Gelatin20 g.

Water-300 ml.

Gum arabic (10% aqueous so1n.)10ml.

Potassium ferric oxalate-15 g.

Formaldehyde (conc.)-1 ml.

Sodium N-methyl-N-oleoyl taurate2 g.

Oxalic acid-3 g.

9,10-phenanthrenequinone (0.1 M in ethyl acetate)-50 The above composition was coated, dried and exposed as described in Example I with a setting of 1 on the Rockette exposing device. An image 1 /2 step faster than a control not containing a quinone was obtained.

EXAMPLE XVII A coating solution was formulated as follows:

Gelatin-20 g.

Water300 ml.

Gum arabic (10% aqueous soln.)-10 ml. Ferric ammonium oxalate20 g.

Oxalic acid-5 g.

Formaldehyde (conc.)-1 ml.

Sodium N-methyl N-oleoyl taurate2 g. pH adjusted to 5.9 with .1 N NaOH The solution was coasted, dried and exposed to Sylvania Sun Gun photoflood described in Example XI at a distance of 18 inches for 15 seconds. The image was made visible by passing the exposed element through rollers heated to C. A usable image was obtained.

(a) To the above coating composition there was added 0.5 gram of anthraquinone in ethyl acetate. An element coated with the composition and dried, exposed and heated gave an image /2 step faster than a control not containing the quinone sensitizer.

(b) To the coating composition above there was added 0.5 gram of 2,7-di-t-butylphenanthrenequinone in place of the quinone added in (a) and this gave an image having a speed 4 /2 steps faster than a control.

(0) To the coating composition above there was added 0.5 gram of Z-ethylanthraquinone which gave an image of 2 /2 steps faster than a control.

(d) To the coating composition above there was added 0.5 gram of benzoin methyl ether which gave an image of 4 /2 steps faster than a control.

(e) To the coating composition there was added 0.5 gram of benzoquinone which gave an image 6V2 steps faster than a control.

(f) To the coating composition above there was added 0.5 gram of 1-amino-4-bromo-anthraquinone-Z-sodium sulfonate which gave an image 5V2 steps faster than a control.

EXAMPL'E XVIII A coating composition was formulated as follows;

Polyvinyl acetate (viscosity of 6.8% benzene soln. 5-7 centipoisesHoeppler Viscosimeter--20 C.) (20% methanol solution)40 ml.

Tris (hexadecylammonium) iron (III) citrate (Example I Ser. No. 680.013)lO g.

9 9,lO- henanthrensequinone-O.5 g. Citric acid-2 g.

Formaldehyde (conc.)-1 ml. Sodium N-methyl-N-oleoyl taurate-Z g.

The solution was coated, dried, exposed and developed as described in Example XVII to give an image 3V2 steps faster than a control not containing the quinone compound.

EXAMPLE XIX Example X was repeated except that the coating composition was coated on the film support of the type described in Alles, U.S. Pat. 2,627,088 on which there had been coated a blue layer from the following composition:

Water-300 ml.

Gelatin-6.5 g.

Sodium N-methyl-N-oleoyl taurate-1.0 g.

Monastral Blue (in ml. acetone) (Colour Index No.

The resulting element when processed as described in Example I gave a good, clear, white image on a blue background.

EXAMPLE XX Example XIX was repeated except that the undercoating contained 10 grams of a 31% aqueous dispersion of carbon black in place of the Monastral Blue dye to give an element which upon exposure and treating as described above gave a white image on a black background.

The solution was coated, dried and handled as described in Example XIII to give a good quality vesicular image.

The coating compositions of the above examples may be coated on any suitable support in addition to the polyethylene terephthalate described in Example I, e.g., cellulose acetate, glass, paper and the like. Suitable specific other useful supports are listed in Notley 2,951,758.

The coated elements obtained by this invention have higher photographic speed than those heretofore known, probably due to the catalyst regeneration. The polynuclear quinones extend the spectral response into the visible region thus increasing the utility of the elements of the invention.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A vesicular image-forming composition comprising:

(1) a macromolecular film-forming organic polymer binding agent;

(2) a gas-producing ferric compound of the formula ]3 )s wherein X is a member selected from the group consisting of Na, K,

wherein 1 to 4 of the radicals R are alkyl of 4 to carbons and any remaining radicals R are hydrogen, or one of the radicals R is aryl of 6 to 14 carbon atoms and the remaining radicals R are selected from the group consisting of hydrogen and alkyl radicals of 4 to 20 carbon atoms, and each of the radicals Y is an oxalate, citrate or tartrate anion; (3) a photoinitiator of addition polymerization; and (4) as an oxidizing agent, an acid salt of a metal having a pKa less than or equal to 3 which is capable of oxidizing ferrous to ferric ion; constituents (1), (2), (3), and (4) being present in the respective parts by weight 26.062.6, 72.0l2.4, 0.3-5.0, and l.720.0.

2. A composition according to claim 1 in the form of a layer or film.

3. A composition according to claim 1 wherein said binding agent comprises gelatin.

4. A composition according to claim 1 wherein said photoinitiator is a polynuclear quinone.

5. A composition according to claim 1 wherein said oxidizing agent has an oxalate radical.

6. A composition according to claim 1 wherein said ferric hydrocarbon-substituted compound is a ferric hydrocarbon-substituted ammonium complex of the forwherein 1 to 4 of the radicals R are alkyl of 4 to 20 carbon atoms and the remaining radicals R are hydrogen, or one of the radicals R is aryl of 6 to 14 carbon atoms and the remaining radicals R are selected from the group consisting of hydrogen and alkyl radicals of 4 to 20 carbon atoms, and each of the radicals Y is an oxalate, citrate, or tartrate anion.

7. A composition according to claim 6 wherein said ferric complex is tris(triocty1ammonium) iron (III) oxalate.

8. A composition according to claim 6 wherein said ferric complex is tris(trihexylammoniurn) iron (III) oxalate.

9. A composition according to claim 6 wherein said ferric complex is tris(tetra-n-butylammonium) iron (III) oxalate.

10. An image-bearing element comprising a support bearing a layer of composition as defined in claim 1.

11. An element according to claim 10 wherein the binding agent comprises gelatin.

References Cited UNITED STATES PATENTS 1,939,232 12/1933 Sheppard et al. 117-34X 1,964,136 6/1934 Prufer et al. 96-92 2,197,809 4/ 1940 McQueen 117-34X 2,459,136 1/ 1949 Slifkin 96-49 2,699,392 1/1955 Herrick et al. 117-34X 2,703,756 3/1955 Herrick et a1. 9649X 3,032,414 5/1962 James et al. 96-75X 3,046,127 7/1962 Barney et al. 9687X 3,183,094 5/ 1965 Cerwonka et. al. 96-92 3,298,833 1/1967 Gaynor 9692X 3,368,900 2/1968 Burg 96115 FOREIGN PATENTS 665,649 1/ 1952 Great Britain 96-92 922,565 4/1963 Great Britain 9675 935,428 8/1963 Great Britain 96-75 WILLIAM D. MARTIN, Primary Examiner M. R. P. PERRONE, IR., Assistant Examiner U.S. Cl. X.R.

3 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2, 5 |-2 76 D t d Dec. 22, 1970 Inventor-(s) Leo Boos It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

r Col. 7, lines 5-46, "Tris (hexadecylammonium) iron 111),

oxalate (Example V of U.S. Ser. No. 680,013) 5 g. should read --Tris(trioctylammoniumg iron (III) oxalate (Example III, U.S. Ser. No. 680,013 5 g.

Signed and sealed this 20th day of April 1971.

(SEAL) Attest:

WILLIAM E. SCHUYLER, JR.

EDWARD M FLETC HER, JR

Commissioner of Patents Attesting Officer