US3108026A - Coloring of oxide-coated aluminum - Google Patents

Description

United States Patent Ofiice 3,1il3fi2ii Patented Oct. 22, 1963 3,108,026 COLORENG F OXIDE-COATED ALUMINUM Rolf Dessauer, Braudywine Hundred, DeL, assignor to E. i. du Pont de Nernours and Company, Wilmington, Del., a corporation of Delaware No Drawing. Filed Oct. 10, 1960, Ser. No.

8 Claims. ((11. 148-61) This invention relates to colored aluminum and more particularly to a process of coloring oxide-coated alurninum so as to impart a light-fast green-yellow color thereto.

This application is a continuation-in-part of my copending application Serial No. 768,051, filed October 20, 1958, now abandoned.

The coloring of aluminum is old in the art. In one process the aluminum is anodized making it dye receptive and the anodized aluminum is then treated in an aqueous dyeing process with an organic dye containing sulfonic or carboxylic acid groups. In a more recent process for coloring anodized aluminum a printing technique is used. This is a more rapid process and has greater flexibility. For example, printing may be accomplished with several colors simultaneously by using appropriate printing rolls. In this printing technique the coloring agents are preferably applied from a nonaqueous vehicle and thus, colorants are required which have solubility or dispersibility in a non-aqueous vehicle. One of the difiiculties encountered in this desirable printing process is that no coloring agents are available which are soluble or dispersible in a non-aqueous vehicle and which impart a light-fast green-yellow color to the alu minum.

It is an object of the present invention to provide 4 oxide-coated aluminum having a lightfast, green-yellow color. A further object is to provide a process for imparting a light-fast, grcen-yellow color to anodized aluminum by means of a printing technique. Other objects will appear hereinafter.

These and other objects of this invention are accomplished by a process of coloring oxide-coated aluminum with a non-aqueous ink which comprises imparting a green-yellow color to the aluminum by using as the coloring agent an o-hydroxybenzophenone of the formula R OH | 0 I ll 3 X OX l I Y Y wherein R is hydrogen or hydroxy, X is hydrogen, hydroxy or a lower alkoxy radical, X is hydrogen or a lower alkyl radical, Y is hydrogen, a tertiary lower alkyl radical or acyl radical, R'CO-, wherein R is a lower alkyl radical or a phenyl radical, with the proviso that Y need not necessarily be the same in each occurrence. The process of the present invention consists in the use of the o-hydroxybenzophenone as the coloring agent in the coloring of oxide-coated aluminum whereby a greenyellow color is imparted to the aluminum.

The process of printing anodized aluminum with a nonaqueous printing vehicle is well known in the art. In

general this process comprises the steps of printing on an anodized aluminum surface with an ink comprising a dye dissolved or dispersed in a film-forming vehicle and then sealing the color on the surface by treating with boiling water.

In one method of carrying out this invention the coloring agent, i.e., the o-hydroxybenzophenone, is dispersed in an inert vehicle and the dispersion is printed with conventional oil-set printing equipment .onto oxide-coated aluminum. Any conventional vehicle may be used which is inert to the coloring agent and the aluminum. Representative vehicles include a varnish, linseed oil and nitrocellulose dissolved in methyl butyl ketone. The printed article is subsequently heated at temperatures of C. to C. for about 15 to 30 minutes to bond the coloring agent to the substrate. Then the aluminum is immersed in an aqueous bath in which it is heated at the boil for about 15 minutes or longer. This treatment serves to seal the oxide-coated aluminum surface. Any unreacted ink is then removed by a solvent wash. Representative solvents which may 'be used for this wash include alcohols, lower ketones, etc.

If desired, the coloring agent may be dissolved in a solvent, such as dimethylformamide, butanol, Z-methoxy (or ethoxy) ethanol, etc. and then printed onto the oxidecoated aluminum. In lieu of printing said solutions of the hyd-roxybenzophenones onto said aluminum, they may be applied by well-known spraying, dipping or painting techniques to obtain solid colorations. For this purpose one may employ mixtures of the above-named solvents, or these solvents which are diluted with lower alcohols or lower ketones.

The coloring agents which may be used in the present invention to impart a green-yellow color to the oxidecoated aluminum are selected from the class of ohydroxybenzophenones described above. Representative compounds include 2,4-dihydroxyrbenzophenone; S-tert. ibutyl-2,4-dihydroxybenzophenone; 2,2',4 trihydroxybenzophenone; 5-tert.butyl 2,2,4 trihydroxybenzophenone; 2,2-dihydroxy-4-rnethoxybenzophenone; 2,2 dihydroxy- 4 butoxybenzophenone; 2,2,4,4'-tetrahydroxybenzophenone; 5,S-di-tert.1butyl 2,2',4,4 tetrahydroxybenzophenone; 2,2 dihydroxy 4,4 di-methoxy'benzophenone; 5,5-di-tert.butyl 2,2 dihydroxy-4,4-dimethoxybenzophenone; 2,2'-dihydroxy 4 methoxy-4-ethoxybenzophenone; 2,2,4-trihydroxy 5 (/3-methyl heptyD-benzophenone; 4,6-dibenzoyl resorcinol; 4,6-diacetyl resorcinol. These o-hydroxybenzophenones are either colorless or essentially colorless compounds and it is, therefore, quite surprising that when used in a process for coloring oxidecoate-d aluminum, they impart a green-yellow color to the aluminum. The color imparted to the aluminum as a result of using these compounds has excellent light 'fastness.

The green-yellow color imparted to the oxide-coated aluminum is believed to be due to a chemical combination between the coloring agent and the aluminum oxide surface, and this chemical combination causes a bathochromic shift in the hue of the colorant. It appears that the oxide-coated aluminum contains on its surface an aluminum chelate of the o-hydroxybenzophenone. The green-yellow colored =oxide-coated aluminum has a wide variety of uses such as in automobile trim, printed signs, drinking tumblers, and interior and exterior decorations.

The following examples will better illustrate the nature of the present invention; however, the invention is not intended to be limited to these examples. Parts are by weight unless otherwise indicated.

Example 1 A printing paste is prepared by milling parts of 2,2,4,4'-tetrahydroxybenzophenone into 40 parts of linseed oil until a homogeneous paste is obtained. This paste is then used on a two roll ofl-set printing press and anodized aluminum is printed in the usual manner. Then, the printed aluminum is heated at 110 C. for minutes to remove the vehicle and the color is fixed onto the metal surface by immersing it in boiling water for 15 minutes. The colored metal is removed and dried. It has a green-yellow color which exhibits excellent light fastness.

Example 2 Example 1 is repeated using 2,2' dihydroxy-4,4-dimethoxybenzophenone in a vehicle of linseed oil. The dyed aluminum is colored green-yellow and exhibits excellent light fastness.

Example 3 Example 1 is repeated using 2,2',4,4'-tetrahydroxy-5,5'- di-tert.butyl-benzophenone. The aluminum is colored green-yellow and exhibits excellent light fastness.

Example 4 When 4,6dibenzoyl resorcinol is used as colorant in the process of Example 1, a green-yellow dyed aluminum is obtained.

Example 5 (a) One part of 5 tert.butyl 2,2,4 trihydroxybenzophenone is dissolved in 1 part of dimethylformamide and the solution is stirred into 3 parts of silk screen base (a solution of nitrocellulose in methyl ethyl ketone). The resulting paste is brushed onto a piece of freshly anodized aluminum (0.8 mil oxide coating), and the aluminum article is heated at 110 C. for minutes. The piece of aluminum is then immersed in boiling water for 30 minutes. The surface of the colored aluminum is cleaned by rinsing with dimethylformamide, then with acetone. The green-yellow coloration thus obtained exhibits excellent light fastness.

Similar results are obtained when the 5-tert.butyl- 2,2,4-trihydroxybenzophenone employed in this example is replaced by an equal amount of any of the following colorants: 5,5 di-tert.butyl 2,2,4,4 tetrahydroxybenzophenone, 2,2 dihydroxy 4,4 dimethoxybenzophenone, 2,2',4,4 tetrahydroxybenzophenone, 2,2,4- trihydroxybenzophenone and 2,2-dihydroxy-4-methoxy- 4-ethoxybenzophenone.

(b) When 1 part of 2,3,4-trihydroxybenzophenone (Alizarin Yellow A) is employed as the colorant in part (a) of this example, one obtains a green-yellow coloration having extremely poor light fastness.

Example 6 One part of 5-tert.butyl-2,2',4-trihydroxybenzophenone is dissolved in 65 parts of dimethyl-formamide. A strip of anodized aluminum (0.8 mil oxide coating) is immersed in said solution for 5 minutes. The strip is removed from the solution, heated at 110 C. for 20 minutes and then immersed in boiling water for 30 minutes. The aluminum article is cleaned by rinsing with dimethylformamide, then with acetone. A light-fast, green-yellow coloration is obtained.

The amount of solvent employed in this example may be varied from 20 parts to 100 parts per part of colorant, depending on the depth of shade desired.

Other solvents may be substituted for the dimethylformamide, e.g. diethylformamide, dimethylacetarnide, diethylacetamide and dimethylsulfoxide, giving similar results.

As many widely different embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that this invention is not limited to the specific embodiments thereof except as defined in the appended claims.

What is claimed is:

1. In the process of coloring oxide-coated aluminum With a non-aqueous ink so as to impart a light-fast, greenyellow color thereto, the step which comprises applying to said oxide-coated aluminum an ink comprising a non-aqueous vehicle and a coloring agent contained therein, said coloring agent being an o-hydroxybenzophenone of the formula R OH I O I II o wherein R is selected from the group consisting of hydrogen and a hydroxy radical; X is selected from the group consisting of hydrogen, a hydroxy radical and a lower alkoxy radical; X is selected from the group consisting of hydrogen and a lower alkyl radical; each Y is independently selected from the group consisting of hydrogen, a tertiary lower alkyl radical and an acyl radical, RCO, wherein R is selected from the group consisting of a lower alkyl radical and a phenyl radical.

2. The process of claim 1 wherein the coloring agent is 5-tert.butyl-2,2',4-trihydroxybenzophenone.

3. The process of claim 1 wherein the coloring agent is 2,2',4,4'-tetrahydroxybenzophenone.

4. The process of claim 1 wherein the coloring agent is 2,2'-dihydroxy-4,4-dimethoxybenzophenone.

5. The process of claim 1 wherein the coloring agent is 2,2'-dihydroxy-4-methoxy-4-ethoxybenzophenone.

6. The process of claim 1 wherein the coloring agent is 4,6-dibenzoyl resorcinol.

7. Green-yellow colored oxide-coated aluminum containing on the surface thereof a coating of an aluminum chelate of an o-hydroxybenzophenone of the formula wherein R is selected from the group consisting of hydrogen and a hydroxy radical; X is selected from the group consisting of hydrogen, a hydroxy radical and a lower alkoxy radical; X is selected from the group consisting of hydrogen and a lower alkyl radical; each Y is independently selected from the group consisting of hydrogen, a tertiary lower alkyl radical and an acyl radical, RCO, wherein R is selected from the group consisting of a lower alkyl radical and a phenyl radical.

8. In the process of coloring oxide-coated aluminum with a non-aqueous ink so as to impart a light-fast, green yellow color thereto, the step which comprises printing on said oxide-coated aluminum an ink comprising a nonaqueous vehicle and a coloring agent contained therein, said coloring agent being an o-hydroxybenzophenone of the formula wherein R is selected from the group consisting of hydrogen and a hydroxy radical; X is selected from the References Cited in the file of this patent group consisting of hydrogen, a hydroxy radical and 2. UNITED STATES PATENTS lower al koxy radical; X is selected from the group consisting of hydrogen and a lower alkyl radical; each Y 160mg 2 i 1 is independently selected firom the group consisting of 5 2250473 i er 3 3 hydrogen, a tertiary lower alkyl radical and an acyl radi- 576 3 y 1957 cal, ROO--, wherein R is selected from the group con- 2927872 f f m 3;; 1960 slstmg of a lower alkyl rachcal and a phenyl radical. 1, 3 43 Dessauer Jam 1962 10 3,066,054 McNamara Nov. 27, 1962 OTHER REFERENCES Organic Chemistry, Furon and Snyder, pp. 68 and 69'. Copyright 1942. Copy on Examiners desk.

Claims (1)

1. IN THE PROCESS OF COLORING OXIDE-COATED ALUMINUM WITH A NON-AQUEOUS INK SO AS TO IMPART A LIGHT-FAST, GREENYELLOW COLOR THERETO, THE STEP WHICH COMPRISES APPLYING TO SAID OXIDE-COATED ALUMINUM AN INK COMPRISING A NON-AQUEOUS VEHICLE AND A COLORING AGENT CONTAINED THEREIN, SAID COLORING AGENT BEING AN O-HYDROXYBENZOPHENONE OF THE FORMULA