US2393731A - Nonleafing aluminum paste and method of making same - Google Patents

Description

Patented Jan. 29, 1946 NONLEAFING ALUMINUM PASTE AND DIETHOD OF MAKING SAME Gordon M. Babcock, Louisville, Ky, as'slgnor to Reynolds Metals Company, New York, N. Y., a corporation of Delaware so Drawing. Application June 20, 1944, a Serial No. 542,243

" 4 Claims. (01. 106-290) This invention relates to metallic pigment pastes for use inthe preparation of polychromatlc coatings or finishes and non-leaflng aluminum metallic finishes as distingushed from substantially unwetted inetallic powders, on the one hand, and paints. lacquers, enamels and the like including a coating base or vehicle as well as a pigment, on the other hand. More particularly this invention relates to non-leafing aluminum pastes and their methods of manufacture. The present application is a continuation in part of my application Serial No. 456,417, filed August 27, 1942, which in turn was a division of my application Serial No. 360,501, filed October 9, 1940, which issued January 26, 1943, as Patent No. 2,309,377, both for Non-leaflng aluminum paste and method of making same.

It has been known for some time that a nonleafing finish can be prepared by carefully grinding an ordinary leafing pigment, in the form of a powder or a paste, either in a liquid carrier or solvent which is compatible with the coating base with which the pigment is adapted ,o'be used, or in the base itself. Such a grinding operation so alters the urface of. the pigment by mechanical action as to make it non-leaflng.

The grinding, however, not only increases the electric constants (see Industrial Chemistry of Colloidal and Amorphous Materials, by Lewis,

Squires and Broughton, MacMillan 00., page 15) such scale being readily derivable from standard chemical texts and handbooks. It is believed that the deleafing action of the polar-active material is due'to a rearrangement of the orient'ed molecules of stearlc acid already present on the flakes of the powder, so that by virtue of what is thought to be a preferential wetting action, the surfaces ,of the powder particles are readily wetted by the vehicle when the paste so made is thereafter mixed to provide a coating material, such as a paint, lacquer, enamel or the like. It has been found that a paste of this character disperses more readily than others when mixed with the base of a polychromatic paint, enamel The carrier of the paste may be selected as desired from among the many available, having due regard to its compatibility with the coating base to which the paste will thereafter ultimateily be added, although it is generally preferred to use either xylol or toluol because ofthe wide range of paints, lacquers, enamels and the like with which they are compatible. The group of suitable carriers also includes the straight chain leaflng aluminum paste which has the capacity 40 hydrocarbon thinners marketed as mineral of at once'producing a non-leailng coating material, whenmixed with a suitable coating base or film-forming vehicle, without the long delay which is unavoidable if reliance is placed on the reaction of the vehicle or some ingredient therecentages of aromatics.

of on a leafing pigment in order ultimately to obtain a non-leafing effect. Y

Inasmuch as the paste produced by the metho herein disclosed is itself of novel composition, the invention also encompasses the product as well as the process by which it is made.

The basis of the present invention resides in the discovery that certain highly polar materials, especially when in solution, have the property of chemically destroying the leafing characteristics of otherwise full leafing aluminum powder when combined with such powder to form a paste. The term "highly polar material" is used herein to mean a material having a displrits, kerosene, gasoline, petroleum naphtha, and the like, as well as aromatic thinners such as benzol and coal tar naphthas, and hydrogenated peroleum naphthas containing high per- The following is one example of a working formula which has proven to be quite successful in practice in producing a non-leaflng aluminum paste according to the present invention:

/ Pounds Aluminum powder (fully polishedand leaf- This formula may be varied by substituting for the ethyl acetate such other highly polar electric constant of at least 10 or higher, and materials from the group composed of alcohols,

some instances, however, it may deleaflng reaction.

2 esters, ketones and aldehydes, as methyl, etll or butyl alcohol, butyl acetate. ethyl lacta glycerolabiatate, acetone, benzaldehyde, etc., the speed of reaction being largely dependent upon the amount of the acetate or other deleafing agent relative to that of the toluol or whatever other carrier may be used compatibly with the color base. For example, another working formula is:

Pounds Aluminum powder (full leafingi 65 Benzaldehyde Xylol 3 acetone, methyl alco- In lace oi benzaldehyde,

p be substituted with hol, or glycerolabiatate can equally good results.

A liquid carrier embodying a relatively high percentage of alcohol, ethyl acetate, acetone, or the like, will also provide the desired deleaflni; action, the highly polar liquid being either used alone. or dissolved in a'thinner compatible with the coating in which the paste is to be dispersed.

action may be decreased by diminishing the reia-.

tive proportions of the deleaflng agents, and the speed of reaction may also be increased by increasing the relative proportions of the deleafing agents, or by using a small amount of alcohol in addition to one or more of the other deleafing agents referred to. 1

In practicing the method of the present invention, the usual procedure is to first dissolve or suspend the deleafing agent or agents in the carto the liquid mixture thus to form a paste. In be preferred to to a previously rier, and then add formed the leafing powder simply add the deleafing agent otherwise treatingthe material to render it nonleaflng and without thelong delay that is unavoidable if reliance is placed on the vehicle of the coating material to effect ultimately a nonleafing eflect. Not only does a paste prepared in accordance with the present invention disperse more rapidly in the coating base and provide greater covering than ordinary leaflng materials. but it has also been round that, because of the fact that the pigment is all within the film, rather than partially on top thereof, it can be applied without giving rise to the well known, objectionable smudging effect which results when some object is accidentally drawn across the air dried surface or the paint.

Although the method of preparing, and-the composition oi, the non-leafing paste of the present invention have been described herein in some detail, and a specific formula has been set forth as exemplary of its practical application, it is to be expressly understood that the invention is not limited to the particular examples given, but that the ingredients of the paste, their relative propertions and the particular mode of preparation or the paste may be varied within limits which will be clearly' apparent to those skilled in the art without departing from the underlying concept -of the invention. Reference is'ther'efore to be formed paste composed of leafing powder and carrier. Under normal conditions of temperature, pressure, humidity and the like, the leafing characteristics or a paste conforming to the present formula above recited will be almost completely, if not entirely, destroyed in less than 48 hours after the paste has been formed. This time may be decreased by varying the proportions and/or materials of the deleafing agents, as above indicated, or by increasing the temperature at which the mixture of carrier and deleafing agent or agents is permitted to act upon the leafing aluminum pigment. Agitation of the materials when forming the paste, or agitation ofthe paste itself, will also decrease the time required for the There is thus provided tion a novel, simple and economical method of producing a non-ieafing aluminum paste which is susceptible of direct dispersion in a wide variety of coating bases for the production of polychromaticfinishes. The paste, which is also novel in composition, may be directly dispersed in a color base to produce a non-leaflng polychromatic coating without the necessity for grinding or by the present invenhad to the appended claims for a definition oi the scope of the invention.

a What is claimed is:

1. A method of making a pigment in the form 01' a non-leaflng aluminum paste from a normally-leafing aluminum powder while retaining the shape and size of, the aluminu p rti l s.

which comprises combining without grinding a deleaflng agent composed of at least one material selected fromjthe group consisting of the relative highly polar alcohols, esters, ketones and aldehydes, a hydrocarbon thinner and, a normally-leafing aluminum powder in such proportions as to form a pigment paste to substantially destroy the leaflng characteristics of said powder by the chemical action of the deleafing' agent thereon and produce a paste which when mixed with a vehicle will at once provide a non-leafing coating material.

2. A method of making a pigment in the form of a non-leaflng aluminum paste from a normally-leailng aluminum powder while retaining the shape and size of the aluminum particles, comprising the steps or dissolving in a hydrocarbon thinner a deleaflng agent composed 01' at least one material from the group consisting of the relatively highly polar alcohols, esters, ketones and aldehydes, and then combining without grinding the liquid mixture thus formed with'a normally-leafing aluminum powder to form a pigment paste and destroying the leafing characteristics of said powder by the chemical action of the deleafing agent thereon to produce a paste which when mixed with a vehicle will at once provide a non- -leafin'g coating material.

3. The methodof making a pigment in the form of a non-leafing aluminum paste from paste composed of a normally-leaiing aluminum powder and a hydrocarbon thinner, while retaining the shape and size of the aluminum particles, which comprises adding to said paste a deleaflng agent composed of at least one material selected'from the group consisting of the relatively highly polar alcohols, :esters, ketones and aldehydes in such proportionsas to form a pigment paste to destroy the leafing characteristics of the aluminum powder by the chemical action of the deleafing mixedwith a fllm-torming'vehicle to produce non-leafing paints, enamels and lacquers, comprising a. normally-leaflng aluminum powder whose leafing film is mechanically left intact, a hydrocarbon thinner and at least one dele'aflng material selected from the group consisting of.

highly polar alcohols, esters, ketones and aldehydes, the aluminum powde constituting more I than 50% of the total weight of the paste and the thinner and .deleafing constituent of the paste Y being sufllcient to completely wet the powder Darticles.

GORDON M. BABCOCK.