US3492145A - Heat or pressure-sensitive copying sheets - Google Patents

Description

United States Patent US. Cl. 11736.2 9 Claims ABSTRACT OF THE DISCLOSURE Improved copying sheet systems of the type utilizing a combination of a copper compound and a color-reactive organic compound, such as a dithiooxamide, are formulated using achromatous sodium cupric pyrophosphate as the source of copper. Use of this material virtually eliminates the blue background color attending the use of conventional copper compounds. The innovation is adaptable to both heat-sensitive and pressure-sensitive copying systems.

CROSS-REFERENCE TO RELATED APPLICATION This is a continuation-in-part of application Ser. No. 556,911, filed June 13, 1966, now abandoned.

BACKGROUND OF THE INVENTION This invention relates to image production and more particularly to copying sheets which are adapted to reproduce printed or other graphic images under the influence of either heat or pressure.

Briefly, the invention is directed to copying systems and copying sheets of the chemical type and more especially to compositions and sheets which are adapted to use in an image production process and which comprise a base material carrying achromatous sodium cupric pyrophosphate either per se or together with a compound reactive with achromatous sodium cupric pyrophosphate to produce a visibly distinct color change.

The use of color-reactive chemical combinations in image production systems such as heat-sensitive copying papers is well established, and the use of a copper compound as one component of such a system has been disclosed in, for example, US. Patents 2,663,656 and 3,111,- 423. These patents disclose the combination of a fusible copper compound, such as cupric stearate, and a substance, such as a dithiooxamide, which forms a colored compound with copper, in a heat-sensitive paper coating.

The use of color-reactive chemical combinations in pressure-sensitive copying papers and record materials is also well established, such systems being disclosed in, for example, US. Patents 2,548,366, 2,730,456, and 2,- 730,457 and Belgian Patent 627,711. These patents describe systems in which one of the color-reactive substances is enclosed in pressure-rupturable microcapsules which are carried by a copying sheet, for example, in proximity to particles of the other color-reactive substance so that, upon the application of pressure, the microcapsules are ruptured and a visibly distinct color change is produced by reaction of the two color-reactive substances.

Notwithstanding the long-known disclosure of Patent 2,663,656 (issued Dec. 23, 1954), copper-containing copying papers have never achieved any significant degree of commercial use. One reason for this is that copper compounds normally considered for such uses, such as cupric stearate, are distinctly colored, and, even in thin coatings,

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they impart a distinct bluish color to the coated sheet. Such colors are significantly more intense than those imparted by corresponding nickel compounds, such as nickel stearate, which have been commercially employed in preference to copper compounds, for such applications. However, for many copying applications, essentially white copying papers, resembling high grade writing or typing paper as much as possible, are preferred, and there remains an unfulfilled need for a color-reactive chemical combinkation which will impart little or no color to a copying s eet.

Also, in copying systems wherein the reaction between a copper or nickel compound and a dithiooxamide is utilized to form an image, there is an inherent advantage in the use of copper compounds, since it has been found that copper complexes with dithiooxamides are much more resistant to bleaching under ultraviolet irradiation than are the corresponding nickel complexes. However, as mentioned, there has not heretofore been found a copper compound satisfactory for use in copying systems.

Further, the images produced by copying systems utilizing a reaction between a nickel compound and a dithiooxamide have a blue or purple hue whereas, for commercial purposes, images more closely approaching black in color would be highly preferred.

In a study of pyrophosphates of several bivalent metals, Bassett et al., 1. Chem. Soc. (1936), 1412, prepared a number of pyrophosphate compounds of copper. In general, these contained varying proportions of sodium, and the products were believed to be double salts and/ or solid solutions of cupric pyrophosphate with sodium pyrophosphate. One unique compound was indicated to be a complex double salt, forming dark blue, readily water-soluble crystals. All the other products were quite water-insoluble and were essentially white or very pale blue. From a reading of the Bassett et al. publication, it is clear that a variety of products of the latter type, having somewhat differing compositions, is possible and that defining the precise nature of any particular product is difiicult. However, these products all contained sodium as well as copper, in addition to having no more than a very pale blue color and to being essentially insoluble in water.

SUMMARY OF THE INVENTION If, following the general scheme outlined by Bassett et al., referred to above, one carries out a series of precipitations by adding a solution of cupric sulfate to a solution of sodium pyrophosphate, the composition of the precipitated product and its color will vary somewhat, depending on the relative amounts of cupric sulfate and sodium pyrophosphate used. For example. equimolar quantities of the reactants produce a pale blue product, while a cupric sulfate/sodium pyrophosphate ratio of 2 produces a pale green product. As the ratio varies progressively from 1 to 2 the color of the resulting product varies from pale blue through an essentially white color to a pale green. Products with not more than a very slight bluish or greenish tint result when the cupric sulfate/ sodium pyrophosphate ratio is in the range of about 1.3 to about 1.6. An essentially white sodium cupric pyrophosphate results when the cupric sulfate/sodium pyrophosphate ratio is about 1.4. The gram-atomic ratio, Cu/ Na, in this product is about 7/ 6.

For convenience, in the present context, I have used the term achromatous sodium cupric pyrophosphate to designate a product having the following characteristics:

(1) It contains both sodium and copper, as well as pyrophosphate; but essentially no other metallic ions;

(2) It possesses not more than a pale blue or pale green color;

(3) It is essentially insoluble in water;

(4) It may be essentially anhydrous, or it may be hydrated to varying degrees.

As indicated above, one method of preparing achromatous sodium cupric pyrophosphate is to mix a solution of a cupric salt, such as cupric sulfate, with a solution of sodium pyrophosphate, the molar ratio of cupric salt to sodium pyrophosphate being in the range of about 1 to about 2, and recovering the precipitated product. Preferably, the cupric salt/sodium pyrophosphate ratio is in the range of about 1.3 to about 1.6, especially about 1.4.

Among the several objects of the invention, therefore, may be noted the provision of copying sheets which are substantially colorless rather than dominated by the characteristic blue or green colors of cupric compounds; the provision of such sheets which are adapted for use as either heat-sensitive sheets or pressure-sensitive sheets in the reproduction of graphic images; the provision of copying sheets of this type which provide images of a satisfactory, primarily black color; and the provision of copying sheets of the class described which may be readily prepared and used. Other objects and features of the invention will be in part apparent and in part pointed out hereinafter.

The invention accordingly comprises the products and methods hereinafter described, the scope of the invention being indicated in the following claims.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In acordance with the present invention, it has now been found that improved image-production systems of the color-reactive type can be produced by utilizing achromatous sodium cupric pyrophosphate, as defined above, as one component of a copying sheet system. Notwithstanding the more or less unique properties of achromatous sodium cupric pyrophosphate as compared with those of the more familiar cupric compounds, I have found that it reacts in characteristic fashion with many known reagents for cupric compounds to produce visiblydistinct products. Moreover, in those systems of the present invention which utilize achromatous sodium cupric pyrophosphate and a dithiooxamide to produce a visibly distinct color change, the images formed appear, upon casual inspection, to be essentially black in color. While these images are, upon closer inspection, found to be black with a slight brownish tinge, they more closely approach black than the images produced by the previously used copying systems employing a nickel compound and a dithiooxamide.

While the copying systems of the present invention are described below with particular reference to the use of various dithiooxamides as reagents which will react with cupric ions derived from achromatous sodium cupric pyrophosphate to form visible images of original graphic matter under the influence of heat or pressure, other substances capable of similar reactions with cupric ions may also be used. Many such substances are known, including diphenylthiocarbazone, benzoinoxime and salicylaldozime. These and other such substances are tabulated in US. Patent 2,663,656 of C. S. Miller and B. L. Clark as Well as in the other prior art patents mentioned above.

In preparing the heat-sensitive copying sheets of the present invention, the general procedures described in U.S. Patents 2,663,656 and 3,111,423 may be used. In accordance with the invention, it has been found that when the color-reactive substance incorporated for reaction with achromatous sodium cupric pyrophosphate is N,N' diphenethyldithiooxamide, N,N'-bis(o-chlorobenzyl)-dithiooxamide, N,N'-bis(p-chlorobenzyl) dithiooxamide or N,N-bis(carbododecyloxymethyl) dithiooxamide, the achromatous sodium cupric pyrophosphate and dithiooxamide compound may be conveniently and advantageously mixed together in an aqueous slurry and applied to paper as a single coating. If the mixture is applied within a short time (i.e., approximately 10 minutes) after formulation, no appreciable reaction between the two compounds occurs. The heat-sensitive copying sheets of the invention may be used in commercially available thermographic copying machines which operate at elevated temperatures on the order of 60 to C.

In preparing the pressure-sensitive copying sheets of the invention, the procedures described in US. Patents 2,730,456 and 2,730,457 may be used. In these procedures, a base material such as paper has applied thereto a dry coating including small particles of one colorreactive substance in proximity to pressure-rupturable microcapsules containing a water-immiscible oil having dissolved therein a second color-reactive substance. A1- ternatively, the pressure-sensitive copying sheets of my invention may be prepared by the procedures described in Belgian Patent 627,711. In these procedures, for example, pressure-rupturable microcapsules containing a dithioozamide compound and a dispersion of achromatous sodium cupric pyrophosphate in an aqueous solution of polyvinyl alcohol are added to a charge of wood pulp or fibrous matrices of paper to form a paste which is fed to a paper-making machine to form a continuous ribbon of sheets having therein the microcapsules and particles of achromatous sodium cupric pyrophosphate in close proximity to each other. In preparing pressure-sensitive copyingsheets according to my invention, I prefer to use N,N-bis(2-octanoyloxyethyl)-dithioozamide or N,N'-dioleyldithiooxamide as the encapsulated organic color-reactive substance. It will be understood, however, that any dithiooxamide or other organic compound which is adapted for microen'capsulation by the above procedures and which is rapidly reactive with achromatous sodium cupric pyrophosphate at room temperature, may be satisfactorily used in the practice of the invention.

In the formation of images by the reaction of achromatous sodium cupric pyrophosphate with a dithiooxamide, the development of maximum color intensity is accelerated by the presence of a basic material. Amines are particularly useful in this regard, primary amines being generally the most effective, then secondary, then tertiary amines. Either aromatic or aliphatic amines may be used. The selection of a particular amine for a given application 'will, to a large extent, be influenced by requirements dictated by such factors as microencapsulation or paper-coating technology used in applying the organic color-forming reagent or preparing it for such application.

Since the color-forming reaction between achromatous sodium cupric pyrophosphate and a dithiooxamide is an ionic reaction, an environment which encourages ionization of the reactants speeds color formation. In pressuresensitive compositions, this is most readily provided by including a small amount of water in the reaction envlronment.

The following examples illustrate the invention.

Example 1.Thermographic paper coated with achromatous sodium cupric pyrophosphate and N,N'-diphenethyldithiooxamide Achromatous sodium cupric pyrophosphate was prepared by a modication of the procedure described by Bassett et al., J. Chem. Soc. (1936), 1412. A solution of cupric sulfate (150 g. CuSO -5H O in 2 l. of water) was added to an equal volume of a solution of sodium pyrophosphate (167 g. of Na P O -10H O). (Molar ratio cupric sulfate/sodium pyrophosphate=l.6.) The mixture 5 was stirred well for 1 hour at room temperature and filtered and the product was reslurried in water (4 1.). Sulfur dioxide (0.5 lb.) was passed into the slurry with stirring. The slurry was then filtered and the product washed free of S and dried.

A paper coating slurry was prepared in the following manner. Achromatous sodium cupric pyrophosphate (0.6 g.), prepared as described above, was suspended in water (1.9 g.). An aqueous slurry of N,N-diphenethyldithio oxamide (0.6 g.) was prepared by ball-milling it for two days in an aqueous solution of a wetting agent (marketed under the trade designation Igepal CO630 by Antara Chemicals Division, General Aniline & Film Company) sufficient to provide a dispersion containing 16% by weight of the dithiooxamide derivative and l0% by weight of the wetting agent. A starch binder was prepared by cooking a (by weight) aqueous dispersion of starch (marketed under the trade designation Stayco M by A. E. Staley Manufacturing Company) on a steam bath for 3045 minutes, then replacing the evaporated water. The achromatous sodium cupric pyrophosphate slurry, the N,N-diphenethyldithiooxamide slurry and the starch binder (1.5 g.) were stirred with sufficient water to yield a pourable mixture. Within 10 minutes after formulation, this mixture was applied to ordinary bond paper by means of a No. 10 coating rod (R.D. Specialties Company, Webster, N.Y.). The coated paper was then air dried to yield an essentially white coated paper.

When a sheet of this paper is exposed to 145l50 C. heat for 5 seconds it turns black. When an unexposed sheet of this paper is placed, coated side up, on top of a typed or printed original and the combination is exposed to a heat source, such as a thermographic copying machine, sufficient to generate a temperature of 145150 C. for about 5 seconds by selective absorption, in the areas of the coated sheet immediately contiguous to the printed matter an opaque, a brown-black image of the original printed matter appears on the coated sheet. The blackened areas do not noticeably lighten after exposure to intense ultraviolet radiation for a period of 24 hours.

Example 2 Bond paper was coated with a formulation containing 0.3 g. N,N'-diphenethyldithiooxamide ground and dispersed as described in Example 1, 2.4 g. achromatous sodium cupric pyrophosphate and 0.3 g. magnesium stearate (clear melt, M.P. 115-120 C.). Upon exposure of this paper, as described in Example 1, to temperatures in the range of 120125 C. a visibly distinct dark color develops within five seconds. The color is somewhat less intense than that of the paper of Example 1.

Example 3 Thermosensitive coated copy papers similar to those described in Example 1 were prepared as described there, with the exception that the N,N-diphenethyldithooxamide specified in Example 1 was replaced with equivalent quantities of the following compounds, respectively:

(a) N,Nbis o-chlorobenzyl -dithiooxamide (b) N,N'-bis p-chlorobenzyl -dithiooxamide (c) N,N-bis (carbododecyloxymethyl -dithiooxamide These papers have thermographic copying properties similar to the paper .of Example 1.

In the following examples, the proportions given are by weight, unless otherwise specified.

Example 4 (a) A paper coating slurry is formulated from achromatous sodium cupric pyrophosphate (8 g.), synthetic latex (Dow Latex 636, containing 48% solids), (4 g.), and distilled water (17 ml.). A coating of this slurry is applied to paper by means of a No. 16 coating rod (R.D. Specialties Co.). The coated paper is air dried.

(b) Microcapsules of N,N'-bis (2-octanoyl-oxyethyl)- dithiooxamide are prepared by a method similar to that method described in US. Patent 2,730,457 of B. K. Green and L. Schleicher. Gum arabic (20 g.) is dissolved in water (160 g.), and into this is emulsified trichlorodiphenyl g.) containing 1.6% of N,N'-bis(2-octanoyloxyethyl)-dithiooxamide. With vigorous stirring, emulsification is carried on until the drop size of the oil is 2-5 microns. Next, pigskin gelatin (20 g.) is dissolved in water (160 g.) and mixed with the emulsion. The acidity of the mixture of colloid sols is adjusted to pH 6.5 by means of 20% sodium hydroxide solution. The resulting mixture (300 g.) is diluted with water (700 g.) at 50 C. with agitation. The diluted mixture is then acidified to approximately pH 4.5 by the addition of 10% aqueous acetic acid, which causes coacervation, resulting in the deposition of the colloid complex evenly and densely around each of the oil droplets. While the mixture is still at a temperature of 50 C., formaldehyde (2.19 g. of 37% w./w. solution in water) is added. No more than 20 minutes should elapse from the start of dilution to this point. Thereafter, gelation is commenced by placing the mixture in an ice bath with agitation until the temperature reaches 10 C. The mixture is then made alkaline (pH 9) by means of 20% sodium hydroxide solution, to promote the hardening of the capsules.

At this stage the compositionis a white fluid consisting of a slurry of microspcopic capsules of the hydrophilic complex colloid material, the individual capsules being several microns in diameter and containing one or more droplets of oil. The consistency of the slurry can be adjusted by removal or addition of water to attain that consistency most appropriate for the method of coating to be used. When the slurry is of the proper consistency it is applied to the achromatous sodium cupric pyrophosphate-coated paper described in paragraph (a) hereof by any commonly used paper coating method, such as roller, spray, brush, etc. It is then allowed to dry.

When the coated sheet is placed beneath a sheet of ordinary writing paper and the top sheet is subjected to printing and/or writing pressures, the original message imprinted thereon is duplicated as an intense brown-black image on the coated sheet.

To accelerate the development of maximum color intensity in the copy sheet, approximately 2-6% by weight of a relatively non-volatile amine, insoluble in aqueous solution at pH 4.5, is dissolved in the trichlorodiphenyl solution of the dithiooxamide prior to emulsification. Such an amine, for example, is l-hendecyldodecylamine.

Example 5 A pressure-sensitive copy paper containing achromatous sodium cupric pyrophosphate as one reactant is prepared, using the method of US. Reissue Patent 24,899 of B. K. Green to prepare microcapsules containing the coreactant. One gallon .of an oil-in-water emulsion of 20 parts, by weight, of a trichlorodiphenyl solution of 2-6% of N,N'-dioleyldithiooxamide and 26% of l-hendecyL dodecylamine, and parts, by weight, of a sol of 10% by weight pigskin gelatin in water is prepared, the emulsification continuing until the drop size of the oil solution is 25 microns. This material is kept at 50 C. to prevent the gelatin from gelling. At this temperature, coacervation is induced by slowly and uniformly adding to the emulsion 0.4 gal. of 20% solution of sodium sulfate. Uniform distribution of the salt solution is accomplished by continued agitation.

To gel the coacervate, the heated coacervation mixture is poured into 10 gallons of 7% aqueous sodium sulfate solution at 19 C. with agitation. The material is filtered and washed with water to remove the salt, the temperature being kept below the melting point of the gelatin. The filtered material is hardened by combining it with 2 gallons of a 37% solution of formaldehyde in water.

This hardened mass is then filtered and washed to remove the residual formaldehyde. The resulting filter cake is adjusted to the proper water content for paper coating and applied to a paper previously coated with achromatous sodium cupric pyrophosphate, as described in Example 4. The resulting coated paper has copying characteristics similar to that described in Example 4.

Example 6 The filter cake of microencapsulated N,N'-dioleyldithiooxamide prepared in Example 5, or a water slurry of it, is added to a water slurry of achromatous sodium cupric pyrophosphate and synthetic latex as described in Example 4(a). After thorough mixing the combined slurry is applied to paper in one coating operation. The resulting coated paper has copying characteristics similar to that described in Example 4.

Example 7 A first sheet of paper is coated with achromatous sodium cupric pyrophosphate as described in Example 4(a). A second sheet of paper is coated with microcapsules of an oil solution of a dithiooxamide, such as those whose preparation is described in Examples 4(b) and 5.

When the first coated sheet is placed beneath the second coated sheet, with the coated surfaces in contiguous relationship to each other, and the top sheet is subjected to printing and/or writing pressures, the original message imprinted thereon is duplicated as a colored image on the under-sheet, by virtue of the interreaction of the dithiooxamide liberated from ruptured capsules in the coating of the upper-sheet with achromatous sodium cupric pyrophosphate on the contiguous surface of the under-sheet.

Example 8 Soft wood pulp that is bleached by sulfite and has a 49 Schopper-Riegler freeness is used. A paste is prepared from 100 parts by weight of this pulp, 10 parts by weight of capsules and parts by weight of achromatous sodium cupric pyrophosphate wherein all weights given are dry weights. This mixture is made by diluting the wood pulp with sufiicient water to give 02-04% solids and then adding the capsules and the cupric salt to it.

Achromatous sodium cupric pyrophosphate is added in the form of a 15% solids dispersion in an aqueous solution of polyvinyl alcohol.

The capsules are formed by hollow envelopes of ureaformaldehyde and range in size from 5-30 microns. The capsules contain a liquid charge of 2.5% N,N'-bis(2- octanoyloxyethyl)-dithiooxamide in xylene, so that the weight of the liquid charge constitutes about two-thirds of the total weight of the capsule.

The paste containing wood pulp, capsules and cupric compound is fed to a Fourdrinier paper-making machine and a continuous ribbon of sheets of paper formed in the machine. The paper is then dried on hot plates and wound into rolls. Paper thus made is secure from premature rupture during winding of the rolls, subsequent unwinding and cutting of the paper into individual sheets. It is reactive to pressure in the manner indicated in foregoing examples of this application.

Example 9 In a variant of Example 8, the paper is formed from two different charges; a base charge is formed from soft wood paper that is sulfite treated and beaten to 375 (Canadian freeness). It is first deposited on a Fourdrinier grating in the form of an aqueous paste containing 0.2% solids at a speed suitable for forming a 20-pound per ream paper (3,000 sq. ft.).

A moist paper ribbon is made by passage of this paste into aspirator chests at the grating, after which there is deposited on the top surface of the paper thus formed a second charge formed from an aqueous paste of about 0.1% solid of a hardwood kraft pulp beaten to 575 (Canadian freeness). A sufiicient quantity of capsules filled with a 2% solution of N,N'-bis(2-octanoyloxyethyl)-dithiooxamide in xylene and achromatous sodium cupric pyrophosphate are included in this second paste to give a mixture of pulp, capsules and achromatous sodium cupric pyrophosphate in a weight ratio of -2525 on a dry basis. The resulting paper is then dried and Wound onto rolls as a 26-pound per ream paper (3,000 sq. ft.).

Example 10 Achromatous sodium cupric pyrophosphate was prepared by a method similar to that outlined in Example 1, using a cupric sulfate/ sodium pyrophosphate ratio of 1.4. The product was essentially white. Its analysis showed:

Percent Cu 27.3 Na 7.8 P 18.5 Loss on ignition 11.6

A thermographic paper formulated as described in Example 1 using this achromatous sodium cupric pyrophosphate had characteristics similar to the paper of Example 1. v

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results obtained.

As various changes could be made in the above products without departing from the scope of the invention, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. A copying sheet for the reproduction of graphic images which comprises a base material in sheet form carrying achromatous sodium cupric pyrophosphate and a compound reactive therewith to produce a visibly distinct color change, said visibly distinct color change being produced by reaction between the achromatous sodium cupric pyrophosphate and said reactive compound at elevated temperatures above about 60 C. or upon the application of pressure sufficient to cause rupturing of microcapsules containing the reactive compound, said achromatous sodium cupric pyrophosphate being prepared by reacting a solution of a cupric salt with a solution of sodium pyrophosphate, the molar ratio of cupric salt to sodium pyrophosphate being in the range of about 1 to about 2.

2. A copying sheet as set forth in claim 1 wherein said cupric salt is cupric sulfate and the molar ratio of cupric sulfate to sodium pyrophosphate is between about 1.3 and about 1.6.

3. A copying sheet as set forth in claim 2 wherein said achromatous sodium cupric pyrophosphate and reactive compound are coated on the base material and the visibly distinct color change is produced by reaction between the achromatous sodium cupric pyrophosphate and reactive compound at elevated temperatures above about 60 C.

4. A copying sheet as set forth in claim 2 wherein the said reactive compound is enclosed in microcapsules carried by said base material and the visbly distinct color change is produced by reaction between achromatous sodium cupric pyrophosphate and the reactive compound upon the application of pressure sufiicient to cause rupturing of said microcapsules.

5. A copying sheet as set forth in claim 2 wherein the reactive compound is a dithiooxamide compound and the base material is paper.

6. The copying sheet as set forth in claim 1 wherein the gram-atomic ratio of copper to sodium in said achromatic sodium cupric pyrophosphate is 7/ 6.

7. A copying sheet as set forth in claim 3 wherein the reactive compound is a dithiooxamide compound selected 9 from the group consisting of N,N-di-phenethyldithioox amide, N,N'-bis(o-chlorobenzyl)-dithiooxamide, N,N'- bis(p-chlorobenzyl)-dithiooxamide and N,N'-bis(carbododecyloxymethyl -dithiooxamide.

8. A copying sheet as set forth in claim 4 wherein the reactive compound is a dithiooxamide compound selected from the group consisting of N,N-bis(2-octanoxyloxyethyl)-dithiooxamide and N,N-dioleyldithiooxamide.

9. A copying system for the reproduction of graphic images which comprises a first base material in sheet form carrying achromatous sodium cupric pyrophosphate and a second base material in sheet form carrying a compound reactive with said achromatous sodium cupric pyrophosphate to produce a visibly distinct color change, said achromatous sodium cupric pyrophosphate being prepared by reacting a solution of a cupric salt with a solution of UNITED STATES PATENTS 2,663,656 12/1953 Miller et a1. ll736.8 3,063,863 11/1962 Holland et a1 l1736.8 3,111,423 11/1963 Ostlie 1l736.8 3,287,154 11/1966 Haas l1736.8

MURRAY KATZ, Primary Examiner US. Cl. X.R.