US3434890A - Composition and process for forming patina - Google Patents

Description

United States Patent US. Cl. 148--6.14 16 Claims ABSTRACT OF THE DISCLOSURE Formation of patina by wetting a copper-base alloy with a solution ocntaining a predominant proportion of a volatile water-soluble organic solvent and a minor proportion of an inorganic acid salt of a primary amine, for instance, monoethanolamine hydrochloride, and allowing the solution to stand in contact with said alloy until patina formation occurs.

This application is a continuation-in-part of application Ser. No. 364,266, now abandoned, filed May 1, 1964.

My invention is concerned with an improved process for forming patina and to novel compositions therefor.

Natural patina and the desirable virtues thereof from a decorative and protective standpoint have long been known. Because of a number of disadvantages in the natural process of producing patina as well as in the properties of natural patina, extensive efforts have been made over a period of many years to develop processes for artificially producing patina, for instance, on newly laid copper roofs and similar copper surfaces with a number of objectives in view including the production of a patina simulating natural patina in a short period of time by chemical procedures. Such efforts have been characterized by indifferent success. At the present time, the process of producing artificial patina which is perhaps best known is one which involves first carefully cleaning the copper or copper-base alloy surface to remove dirt, oil and grease therefrom, then spraying the cleaned surface with an aqueous ammoniacal solution of ammonium sulfate and copper sulfate, some five or six sprayings with alternate dryings between sprayings being carried out. The development of color depends upon suitable weather conditions, ideal weather conditions following the afore said treatment being a moderate to heavy dew, a light mist or fog, or other condition of high atmospheric moisture content with a relative humidity of 80% or more. Not infrequently, the foregoing process does not produce successful results.

In accordance with my present invention, artificial patina is produced rapidly and in a simple manner, which provides good resemblance to natural patina, and, when the process is carried out in the specified manner, consistently good results are obtained which are essentially independent of weather conditions and, therefore,not generally subject to the vagaries of weather.

In the practice of my invention, the surface to be treated, namely, copper or copper-base alloy such as brass or bronze, should first be cleaned to remove any dirt, dust, oil or grease. This cleaning step can be carried out with hot water or detergent solutions. While acid or alkaline cleaners can be utilized, it is preferred to use alkaline cleaners but, in any event, the cleaned metal surface should be carefully rinsed with water to insure removal of any adhering acid or alkaline material. Instead of using such cleaners, the patina coloring compositions described below can be used to clean the metal surface by rubbing said surface with a cloth dampened with the said compositions.

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The cleaned metal surface is then contacted with a solution, in a volatile water-miscible or water-soluble organic solvent (hereafter called volatile water-soluble organic solvent) of an inorganic salt of a primary amine containing not more than 12 carbon atoms, said solution advantageously containing a minor proportion of water. The contact may be effected in any suitable manner as, for instance, by spraying, by dipping, by brushing or by rubbing with a cloth wet with said solution. The volatile Water-soluble organic solvent may be removed by evaporation by standing at lower than room temperature but, more advantageously, at temperatures of the order of 70 to degrees F. It is preferred to use said slightly elevated temperatures since, at lower temperatures, there is a tendency toward streakiness. Generally, only a single coating on the metal is required and the patina will appear within a very few minutes, depending upon the temperature to which the coated metal surface is subjected. At room temperature or thereabouts, patina formation will usually take place in from 5 to 10 minutes, at somewhat elevated temperatures, for instance '70 to 90 degrees F., patina formation commonly occurs in about a minute or two depending upon the particular composition utilized. in certain instances, if patina formation does not occur within about 5 minutes, depending upon temperature, a second coating may be applied and, after drying, the coated metal is allowed to stand until patina formation takes place. It may be noted, here, and as stated above, that patina formation pursuant to my present invention is in no way dependent upon atmospheric or weather conditions but only on temperature considerations which may be simply controlled as desired.

While various volatile water-soluble organic solvents can be utilized in the compositions of my invention, as, for example, lower alcohols and ketones such as acetone, I find it especially advantageous to use monohydric aliphatic alcohols such as methyl alcohol, isopropyl alcohol and especially ethyl alcohol, and mixtures of volatile water-soluble organic solvents. By volatile water-soluble organic solvents, I mean those which have a boiling point of not in excess of about 200 degrees F. at atmospheric pressure. I find it particularly desirable to utilize those volatile water-soluble organic solvents which have boiling points in the range of to degrees F.

The primary amines whose inorganic salts are used in the compositions of my invention are advantageously soluble in the volatile water-soluble organic solvent utilized or, where water is incorporated in the composition, in said organic solvent-water solution, but, in any event, the inorganic acid salts of said amines must be soluble in said organic solvent or organic solvent-water solution. The primary amines which are preferably employed, generally speaking, contain not more than l2 carbon atoms, are of aliphatic character and they maybe straight chain or branched chain. Especially preferred are water-soluble aliphatic primary amines or aliphatic hydroxy primary amines such as monoethanolamine, monoisopropanolamine, ethylene diamine, diethylene triamine, ethyl amine, propyl amine, isopropylamine, amyl amine, hexyl amine, cyclohexylamine, heptyl amine, octyl amine, nonyl amine, decyl amine, undecyl amine, dodecyl amine, 2-amino-2- methyl-l propanol and the like, although aromatic primary amines such as benzyl amine and aniline can be used but are not preferred. I have found that monoethanolamine is outstandingly satisfactory for the purposes of my invention.

The acids which are used to form the salts of the aforesaid amines in the compositions of my invention are of inorganic character and include, by way of example, hydrochloric acid, hydrobromic acid, hydrofluoric acid, sulfuric acid, nitric acid and phosphoric acids. The nature and color of the patina which is obtained by the practice of my invention, and the speed with which such patina forms, are influenced by both the particular amine utilized and by the particular inorganic acid employed in conjunction therewith. Thus, for example, when amine salts such as monoethanolamine sulfate or monoethanolamine orthophosphate are utilized, the coloration obtained is of relatively dull bluish or greenish character which does not fully desirably simulate natural patina. I have found that salts of monoethanolamine and hydrochloric acid or hydrobromic acid or hydrofluoric acid, especially monoethanolamine hydrochloride, are exceptionally satisfactory and their use represents particularly important, though limited, embodiments of my invention.

The inorganic acid salts of the primary amines can be preformed and then incorporated With the volatile watersoluble organic solvent, and water where water is used in the compositions, to form a solution, with or without shellac or similar ingredients, or, alternatively, the inorganic acid and the primary amine can be added as such to the aforesaid organic solvent, or organic solvent-water solution, and admixed to form the inorganic acid salt of the primary amine in situ in the composition. I find it more desirable 'to perform the salt and add it to the organic solvent, or organic solvent-water solution, with stirring and, if desired, slight heating to hasten solubility if necessary.

The compositions of my invention, as stated above, may, and advantageously do, include a minor proportion of water which may range from about 2% to 20%, particularly desirably from 5 to 12%, by weight of the composition. The use of water in the compositions aids in the production of a coloring or shade of patina more closely resembling natural patina. The water need not, however, be included in the composition since the water may be supplied by a water-moistened or water-wetted surface of the copper or copper-base alloy upon which the patina is to be formed.

While the proportions of the other ingredients in the compositions of my invention are variable within reasonable limits, generally speaking, the volatile water-soluble organic solvent will constitute the major ingredient, ranging in proportions from about 60 to 95%, particularly from 75 to 90%, by weight of the composition. The inorganic acid salt of the amine constitutes a minor ingredient of the compositions, being present generally in proportions of about 2 to by weight of the compositions, with from 5 to 12% representing a particularly preferred range.

It is also desirable to include in the patina-forming compositions a small proportion, for instance, 3 to 7%, preferably about 4%, by weigh-t of the composition, of shellac or similar resin since this provides for greater adhesion of the composition to the metal surface and tends to inhibit washing off of the coating composition in case of rain occurring before patina formation occurs, and it also aids in causing better adherence of the patina to the metal surface after it is formed. In this same connection, although rain does not too adversely affect the patina, it is desirable to apply a transparent protective coating to the metal surface after the patina or color has formed. Suitable protective coatings are, in general, transparent synthetic plastics and resins such as the methacrylates, cellulose esters such as cellulose acetobutyrates, polyvinylidene chlorides, chlorinated rubbers, and the like. I find particularly satisfactory chlorinated rubbers, an illustrative example of which is Parlon (Hercules Powder Co.) in the form of a toluene or xylene solution which may be sprayed on the patina, the organic solvent evaporating rapidly and leaving a transparent protective coating on the patina.

The following examples are illustrative of compositions falling within the scope of my invention. Other specific embodiments will readily occur to those skilled in the art in the light of the guiding teachings and principles disclosed herein. All parts listed are by weight.

4 Example 1 Parts Ethyl alcohol -a 100 Water 10 Monoethanolamine hydrochloride 10 Example 2 Ethyl alcohol 100 Water 10 Monoethanolamine hydrochloride l0 Shellac 5 Example 3 Ethyl alcohol 100 Water 12 Monoethanolamine hydrobromide 11 Example 4 Methyl alcohol 100 Monoisopropanolamine hydrochloride 8 Water 10 Example 5 Ethyl alcohol 100 Ethylenediamine hydrochloride 8 Water 10 Example 6 Ethyl alcohol 100 Monoethanolamine hydrochloride 10 Example 7 Ethyl alcohol 100 Monoethanolamine hydrobromide l0 Shellac 3 Example 8 Ethyl alcohol 100 Octyl amine hydrochloride 10 Example 9 Ethyl alcohol 100 Dodecyl amine hydrochloride 10 For simplicity of expression in the claims, the term coppenbase alloy is used to include copper as Well as copper-base alloys which are susceptible to patina formation.

What is claimed is:

1. A process for forming patina which comprises wetting a copper-base alloy with a solution containing as essential ingredients, by weight, from about 60 to of volatile water-soluble organic solvent, and from about 2 to 20% of inorganic acid salt of a primary amine containing not more than 12 carbon atoms, and allowing the solution to stand in contact with said alloy until patina formation occurs.

2. A process according to claim 1 in which the organic solvent is an alcohol, and the primary amine is an aliphatic amine.

3. A process according to claim 2 in which the inorganic salt is a member selected from the group consisting of hydrochloric, hydrobromic and hydrofluoric acid salts of said amine.

4. A process according to claim 1 in which the organic solvent is a water-soluble aliphatic alcohol containing from 1 to 3 carbon atoms, and in which said solution con tains from 5 to 12% water, and from 5 to 12% of hydrohalide salt of a water-soluble hydroxy primary amine, said hydrohalide being selected from the group consisting of hydrochloride, hydrobromide and hydrofluoride.

5. A process according to claim 1 in which the organic solvent is ethyl alcohol and in which the inorganic salt of the primary amine is monoethanolamine hydrochloride.

6. A process according to claim 1 in which the organic solvent is ethyl alcohol, and in which said solution contains from 5 to 12% water, and from 5 to 12% of a hydrochloric acid salt of a water-soluble hydroxy primary amine.

7. A process according to claim 1 in which said solution contains the following ingredients in substantially the stated proportions by weight to each other:

Ethyl alcohol 100 Monoethanolamine hydrochloride 5-12 Water 5-12 8. A process according to claim 1 in which said solution contains the following ingredients in substantially the stated proportions by Weight to each other:

Ethyl alcohol 100 Monoethanolamine hydrochloride 5-12 Water 5-12 Shellac 3-7 9. A composition for forming patina on a copper-base alloy comprising a solution containing as essential ingreclients, by weight, from about 60 to 95% of volatile water-soluble organic solvent, and from about 2 to 20% of inorganic salt of a primary amine containing not more than 12 carbon atoms.

10. A composition according to claim 9 in which the organic solvent is an aliphatic alcohol containing from 1 to 3 carbon atoms, and in which the inorganic salt of the primary amine is a hydrohalide salt of a water-soluble hydroxy primary amine, said hydrohalide being selected from the group consisting of hydrochloride, hydrobromide and hydrofluoride.

11. A composition according to claim in which the hydrohalide is a hydrochloride and in which said Watersoluble hydroxy primary amine hydrochloride comprises from 5 to 12% of the solution, said solution also containing from 5 to 12% of water, said percentages being by weight of said solution.

12. A composition according to claim 9 in which the organic solvent is ethyl alcohol and in which the inorganic acid salt of the primary amine is a water-soluble hydroxy primary amine hydrochloride, said solution also containing a minor amount of water.

13. A composition according to claim 12 in which said solution contains, by weight, about parts of ethyl alcohol and in which the hydroxy primary amine is monoethanolamine, the monoethanolamine hydrochloride comprising from 5 to 12 parts, by weight, of said solution.

14. A composition according to claim 13 which includes about 5 to 12 parts water.

15. A composition according to claim 14 which includes about 3 to 7 parts shellac.

16. A composition according to claim 15 in which the solution contains, by weight, about 100 parts of ethyl alcohol, about 10 parts Water, about 10 parts monoethanolamine hydrochloride, and about 5 parts shellac.

References Cited UNITED STATES PATENTS 2,166,971 7/1939 Schoudt et al. 265-578 ALFRED L. LEAVITT, Primary Examiner.

A. GRIMALDI, Assistant Examiner.

US. Cl. X.R.