US2323424A - Process of forming insoluble and adherent nonmetallic films on metals - Google Patents

Description

Patented July 6, 1943 PROCESS OF FORMING IN SOLUBLE AND ADHERENT NONMETALLIG FILMS. ON

METALS George Schore, New York, N. Y.

No Drawing.

11 Claims.

This invention relates to the art of forming tenaciously adherent and insoluble non-metallic coatings or films on metals such as copper, nickel and comparable metals,-and more particularly, but not exclusively, to the preparation of photogravure printing forms of the flat or cylinder type, so as to permit any such forms to receive upon the coated surfacethereof, as effected by my treatment, a relatively large number of separate and successive electrodepositions of a metal, which said depositions, sometimes called shells, are readily strippable from the form without appreciable injury to or other adverse effect upon the integrity of said film or coating. It is thus within the contemplation of my invention to electrodeposit upon the base metal, coated by the process of this invention a shell or layer of metal, whereby said'shell or layer may be stripped therefrom without affecting the film thereon, and to permit such successive depositions and strippings at least five or six times, before it becomes necessary to reform the said film.

At the present time a form and process now more or less extensively employed in the printing trade in preparing rotogravure forms consists in electrodepositing on a steel cylinder a layer of copper, thence electroplating thereon a layer of nickel,-which is polished, and thereafter electrodepositing on said nickel layer a predetermined or desired thickness-of copper (or other metal) which is to receive the intaglioed impression. Ordinarily, the outer layer of electrodeposited copper remains more or less adherent to the layer of nickel beneath so that it is not possible to remove the outer thickness of copper by stripping without injuring the nickel plate, and redepositing a satisfactory new thickness of copper thereon unless, before the outer thickness of copper is deposited, the surface of Application August 31, 1940, Serial No. 355,028

the nickel is provided with a film of oil so as to keep the outer deposited thickness of copper from adhering to the underlying. nickel-plate.

Furthermore, when employing the above described nickel-plating process, it is the practice to extend the nickel-plated layer only part way across the width of the cylinder while the outer electrodeposited copper thickness isdeposited clear across the entire width of the cylinder, 'so that the nickel-plate is "locked in place.

According to my invention, instead of providing a plating of nickel on the surface of the roller (base metal), I apply to the surface of said roller a chemical solution or reagent which reacts with said surface to form an insoluble compound of extreme-thinness, which has the appearance of, and may be regarded to all in-' tents and purposes, as a film, which said film is smooth, remarkably tenaciousand adherent and resists the action of acids aswell as abrasion, permitting the successive applications and strippings of electrodeposited metals above described.

The solutions which I prefer to use in treating the surface of the desired metal in order to form thereon. the said adherent and insoluble film or coating contain a metal-etching ingredient or compound, and one or more salts or other chemical which reactswith the metal to form an insoluble, smooth and tenaciously adhering film. The etching substance is preferably an oxygen-containing acid, such as sulphuric or nitric acid, which, as the term implies, has the effect of etching or reacting on the surface of the metal to which it is applied to give a grained surface of such fineness as to be indistinguishable as such by the naked eye, which finely grained surface accounts in large part for the tenacity with which the superformed'film adheres to the metal. The salts which I prefer to use and which give the best results are metal compounds having an oxygen-containing complex negative radical, such as sulphates or nitrates, and where the metal to be treated with my solution is copper or nickelthe said salts may consist of copper sulphate or copper or nickel nitrate. Y

The treating solution may contain as an original product the oxygen-containing acid, or, the oxygen-containing acid may be formed or be present as the result of the reaction of some other acid with, for example, a sulphate or nitrate salt. The important point is that the treatingsolution have available the necessary oxygen-containing or other acid for the etching action.

Solutions which I have found satisfactory for the purposes of my invention contain:

(1) Hydrochloric acid, copper nitrate and copper sulphate in water solution; or

(2) Cadmium sulphide, sulphuric acid and copper sulphate in water solution; or

(3) Copper sulphate, nitric acid, hydrochloric acid and bismuth sulphate in water solution; or

(4) Nickel nitrate, copper nitrat, nitric acid and black antimony sulphide or tellurium dioxide in water solution.

In the case of solution (1) the oxygen-containing acid is supplied by the reaction of hydrochloric acid with copper sulphate and copper nitrate. To said solution (1) I preferably add some ammonium sulphate to promote the reaction; sodium chloride for the purpose of increasing the galvanic action, and a dye or coloring substance, such as methyl orange or selenium dioxide, to enable me to determine by the appearance of the film. when the reaction has reached its most satisfactory stage. Thus, when using solution (1) when the film assumes a brownish to dark brown appearance I know that the reaction has gone far enough, and ,wash oil or otherwise remove the remaining solution from the metal.

To solution (2) I prefer to add some ammonium sulphate for a purpose similar to that in the case of solution (1), and also a coloring substance, such as potassium permanganate or selenious acid, as an indicator of when the filmformation process has proceeded far enough.

In the case of solution (3) the bismuth sulphate is not absolutely essential, but controls the rate of reaction, so that etching does not-proceed too fast or too far. To said solution (3) I also prefer to add a coloring agent, such as barium sulphide or selenium oxychloride, as an indicator for the purpose stated above with respect to the other indicators.

With respect to solution (4) the black antimonysulphide serves a dual function,-

above formulae without departing from the scope of the invention.

Also, while the invention has been described in connection with its particular utility in the art of electroforming, photogravure or rotogra- .vure work, nosuch limitation on the scope oi.

the invention is intended.

The precise constitution of the film formed by my treatment. is not known to me with any certainty. It is insoluble in nitric acid as well as insoluble in sulphuric acid, though soluble in cyanide solutions; and the probability is that the film is a complex or double salt or oxide.

What I claim is:' I

1. In printing forms of the class wherein a metallic shell is electroplated on a metal base of the group consisting of copper and nickel, the

combination of a metal base of said group and an'adherent film thereon produced by the action upon the base of an acidic aqueous solution consisting essentially of the ions 01-, SO4- NO:-, and Cu".

2. In the art of producing printing forms of the class wherein a metallic shell is .electroplated over an adherent film on a metal base of the group consisting of copper and nickel, the method of producing said adherent film comprising the step of applying on said base an that of indicator and as a source of sulphateions, while tellurium dioxide (if used) acts mainly as an indicator. V

It will thus be seen that in each instance the solution serves two functions (a) that of etching the surface of the metal and (b) that of providing, by reaction with .the metal, an insoluble, adherent, non-metallic film.

Appended herebelow are the complete formuacidic aqueous solution consisting essentially of the ions 01-, N03, .SOr '3 and CW.

3. In the art of producing printing forms of the class wherein a metallic shell is electroplated over an adherent film on a metal base of the group consisting of copper and nickel, the

methodof producing said adherent film compris-,

ingthe step of applying on said base an acidic aqueous solution of hydrochloric acid, copper lae of solutions which I have found satisfactory:

Hydrochloric acid ounces 10 Copper nitrate'. do Copper sulphate do Ammonium sulphate do 7 Sodium chloride do 1 Water gallon 1 Methyl orange (or selenium dioxide) ounce 1':

Cadmium sulphide ounces y, Suphuric acid do 10 Copper sulphate do 3 Ammonium sulphate do I 1 Water gallon 1 Potassium permanganate (or selenious acid) ounce III Copper sulphate ounces 1 ,5 Nitric acid do 6 Hydrochloric acid do 3 Bismuth sulphate do V Waterallon 1 Barium sulphide (or selenium oxychloride) ounce Nickel nitrate ounces 2 Copper nitrate do 6 Nitric acid do 3 Waterallon" 1 Black antimony sulphide or tellurium dioxide ounce Obviously known equivalents may be substituted for some of the substances specfled in the nitrate, and copper sulphate.

4. In the art of producing printing forms of the class wherein a metallic shell is electroplated over an adherent film'gon a metal base of .the group consisting of copper and nickel, the method of producing said adherent film comprising the step of applying on saidbase an acidic aqueous solution of hydrochloric acid, nitric acid, and-copper sulphate.

5. In the art of producing printing forms of the class wherein a metallic shell is electroplated over an adherent film on a metal base of the group consisting of copper and nickel, the method of producing said adherent film comprising the step of applying on said base a solution having the composition:

Hydrochloric acid ounces 10 Copper nitrate do Copper sulphate a do- Ammonium sulphate do Sodium chloride do '1 Water gallons 1 Copper sulphate ounces 1 Nitric acid do 6 Hydrochloric acid do 3 Bismuth sulphate do /4 Water galions l 7. In the art of producing printing forms of the class wherein a metallic shell is deposited on a metal base of the group consisting of copper and nickel, and wherein the base is provided with a film to-permit stripping of the metallic shell without injury to the surface of the base, a solution for producing said film which comprises: an acidic aqueous solution consisting essentially of the ions, 01-, N03, SOr and Cu++.

8. In the art of 'producing'printing forms of the class wherein a metallic shell is deposited on a. metal base of the group consisting of copper and nickel, and wherein the base is provided with a film to permit stripping of the metallic shell without injury to the surface of the base, a. solution for producing said film which comprises: an acidic aqueous solution {of hydrochloric acid, copper nitrate and copper sulphate.

9. In the art of producing printing forms of the class wherein a, metallic shell is deposited on a metal base of the group consisting of copper and nickel, and wherein the base is provided with a film to permit stripping of the metallic shell without injury-to the surface of the base, ,a. solution for producing said film which comprises: an acidic aqueous solution of hydrochloric acid, nitric acid and copper sulphate.

10. In the art of producing printing forms of the class wherein a metallic shell is deposited on a metal base of thegroup consisting of copper and nickel, and wherein the base is provided with a film to permit stripping of the metallic shell without injury to the surface of the base, a'solution for producing said'filmconsisting of Hydrochloric acid. ounces.. 10- Copper nitr h do /2 Copper sulphate do Ammonium sulphaten" do A, Sodium chlor do 1= Water allon 1 11. In the art of producing printing forms of the class wherein a metallic shell is deposited on a metal base of the group consisting of copper and nickel, and wherein the base is provided with a film to permit stripping of the metallic shell without injury to the surface of the base, a

solution for producing saidiilm consisting of: Copper sulphate ounces 1 /2 Nitric arid do 61 Hydrochloric acid f do 3 Bismuth sulph e n 4 Water allon" 1 GEORGE SCHORE.