US2184324A - Paint - Google Patents

Description

Patented Dec. 26, 1939 UNITED. STATES Frank A. Strauss, New

Brighton, Staten Island,

N. Y., assignor to Wailes Dove-Hermiston Corporation, New York, New York N. Y., a corporation of Nb Drawing. Application January 19, 1987, Serial No. 121,285

larly to so-called metallic" paints which contain a metal powders. The invention contemplates an improved metallic paint and improvements in the method of manufacturing metallic paint, and aims to provide a metallic paint which may be applied directly to a surface without first applying the customary priming coat, but without sacrificing the additional protection which the priming coat affords.

The use of metal powders as pigments in paints is well known, theprincipal metals employed in this way being aluminum, copper, and the alloys of either of these metals. Thus it has been proposed heretofore to employ metal powders in the form of flakes mixed with a small amount of lubricating and polishing material. Such flakes, when mixed with a suitable vehicle and applied as a film to a surface, tend to leaf or float" to the outer surface of the film while the latter is still in a liquid condition, thus forming a layer of oriented overlapping scales on the outer surface. When the film dries the flakes become affixed to the surface and form a continuous coating having a metallic lustre. Such coatings evitable, it has been the heretofore customary practice first to apply a priming coat which will offer protection to the underlying surface in the event of a break in the metallic paint applied over the priming coat. Such priming coats usually contain a pigment having corrision-inhibiting properties, by which I mean the ability to protect metal upon which the pigment is applied even in the event that small portions of the metal become exposed.

As a result of my investigations I have discovered that relatively large proportions of corrosion-inhibiting pigments may be incorporated directly into a metallic paint, with the result that while the paint is still liquid they form a corrison-inhibiting fllm underneath the layer of overlapping metal plates but are completely obscured by the layer, so that in eifect the priming coat and the finishing coat are applied together i and afterward separate of themselves; the separation being sufliciently complete that the priming coat is completely obscured by the metallic coat. The labor employed heretofore to apply the priming coat separately is thus eliminated, 1 without sacrificing the additional protection which the priming coat alfords. The corrosioninhibiting pigments which I employ in the prac-' tice of my invention are those which manifest little or no tendency to float out of the vehicle into which they have been incorporated, with the result that they remain underneath while the metal flakes float to the surface to form the desired lustrous coating. The proportions of corrison-inhibiting pigments as compared with the quantity of metallic powder in the paint of my invention is such that substantially none of the pigment appears at the outer surface of the dried paint film. The paint thus dries in two layers, an outer one which has high decorative value but slight protective value once it has become ruptured, and an inner layer which has high protective value even when ruptured. The inner layer is not so decorative'as the outer one, but this is relatively unimportant because 3 the outer layer obscures it.

The terms float and leaf are used herein to describe that property of solid bodies (pos-. sessed by metal flakes which have been appropriately treated) which causes the bodies to mi- 5 grate to the outer surface of a film of appropriate liquid. The terms are not necessarily limited to thedescription of an actual rising of the bodies, since. migration will occur in other directions toward the outer surface of the fllm. 4

When corrosion-inhibiting pigments such as zinc chromate, basic lead chromate, red lead, zinc oxide and red iron oxide are employed, the amount of the corrosion-inhibiting pigment should be less than about 15% by weight of the 4 metal. powder in the paint, in order to ensure that the pigment layer is substantially completely obscured by the layer of overlapping metal flakes. When said pigments are employed in quantities substantially in excess of 15% by l weight of the metal particles in the paint there is a tendency for the pigment to appear on the outside surface. If no more than 15% of these pigments on the weight of the metallic powder is included in the paint, the lustre of the dried paint filament is unimpaired and the dried film is equal to that of a similar metallic paint containing no corrision-resistant pigment,

In preparing a paint containing both flaked metal particles and a corrision-inhibiting pigment I have found it desirable to incorporate the pigment into the vehicle before the metal particles, because in this way a thorough incorporation of metal particles and pigments is obtained with minimum effort.

From the foregoing it will be clear that the paint of my invention comprises a vehicle, metal flakes capable of floating to the outside surface of a film of said vehicle, and a finely divided corrosion-inhibiting pigment less capable than the metal flakes of floating to the outside surface of a film of said vehicle, the proportion of pigment to metal flakes in the paint being such that the metal floats to the outside surface of the vehicle and substantially completely obscures the pigment. My invention also contemplates an improvement in the method of making metallic paint containing metal flakes in a vehicle capable of floating them which comprises incorporating into the vehicle (prior to the introduction of the metal) a finely divided corrosion-inhibiting pigment which is incapable of floating in the vehicle, at least to the extent to which the metal is capable of floating, the amount of the pigment thus incorporated being such that its presence in the paint can be obscured with substantial completeness by the metal flakes after these latter have floated to the outside surface of the metallic paint.

The fact that the metal particles tend to float in the vehicle to a greater extent than do the pigment particles is probably due to the fact that the pigment particles are wetted by the vehicle to a greater extent than the metallic particles, a phenomenon somewhat analogous to that observed in flotation processes employed to separate particles having metallic surfaces from particles which have non-metallic surfaces and which are wetted while the particles having metallic surfaces are not.

When ,both corrosion-inhbiting pigment and metal flakes are included in a paint, there appears to be some tendency for the former to interfere with the segregation of the latter. The fact that there are proportions of pigment to metal particles in the paint at or below which the latter will completely obscure the former. I attribute to the hypothesis that at or below the aforementioned proportions the interference offered by the pigment is insufficient to prevent a high degree of segregation of the metalparticles. Whatever be the explanation, the fact remains that when the proportions of pigment to metal particles is maintained below a certain point the pigment will be completely obscured by the metal particles after a paint film containing them has been allowed to dry relatively slowly. If the proportions are substantially ex ceecied, the pigments are not completely obscured and the metallic appearance of the final fllm is impaired. As indicated hereinbefore the critical proportion with most of the corrosion-inhibiting pigments is about 15% of pigment by weight of the metal particles. It may well be, however, that critical proportions for some corrosion-inhibiting pigments are greater or less than 15%. They may be determined simply by continuing the introduction of known increments of pigment into a metallic paint containing a known quantity of metallic powder until the pigment appears at the outer surface of the paint film upon setting. Consequently my invention is not limited to the use of 15% of the pigment by weight of the metallic powder or to any other specific percentage.

These and other aspects of my invention will be understood more thoroughly in the light of the following detailed description of my presently preferred practices.

The paint is prepared by incorporating in the vehicle, prior to the introduction of the metallic powder, an amount of corrosion-inhibitive pigment preferably not in excess of 15% by weight of the metallic pigment which is to be employed. After the protective pigment is thoroughly incorporated either by efficient agitation or by grinding in a pebble, roller, buhrstone or colloid mill, the metallic pigment is added. The metallic pigment is incorporated simply by mixing or stirring, without excessive agitation or grinding which tends to impair its leaflng powers and to reduce the luster of the final film. The paint thus prepared can be applied by any of the known methods. such as brushing or spraying.

Any of the vehicles hitherto employed for metallic paints is suitable, provided that the metal flakes tend to float in it and provided that there is little or no tendency for the corrosion-inhibitive pigment to float in the vehicle. A satisfactory type of vehicle is a long oil spar varnish which may be made from ester gum and chinawood oil, with or without the admixture of other drying oils, such as linseed, perilla or soya bean oil. Other natural or artificial resins may be substituted in whole or in part for the ester gum. Rosin and Congo copal are examples of natural resins which may be used, while the soluble phenolformaldehyde condensation prodnets are examples of the synthetic resins. A

ratio of 100 lbs. of resin to from 25 to 60 gallons of oil generally will result in a satisfactory vehicle, but for certain purposes more or less than thisproportion may be desirable. The varnish may be thinned with mineral spirits, turpentine -or other solvents to a kinematic viscosity of between .4 and 1.5 poises at 25 C. Suitable soluble metallic driers should be added.

Other vehicles may also be employed in the practice of my invention. Such vehicles include kettle bodied or heavy bodied blown linseed oil, thinned to the requisite viscosity with solvent and containing metallic driers; air-drying solutions of alkyd resins; nitrocellulose lacquers; solutions of chlorinated or isomerized rubber suitably thinned with volatile solvents; and solutions of other synthetic resins with or without plasticizing and modifying agents.

As indicated hereinbefore, the term corrosion-inhibitive pigments" is used herein to describe pigments which exert a protective influence on metal surfaces to which they are applied which is more than a mere blanketing or covering effect. Corrosion-inhibitive pigments exert a marked chemical effect upon coated metal and will retard its corrosion, even after the paint film has failed partially.

As corrosion-inhibitive pigments for the practice of my invention, zinc chromate, basic lead chromate and red lead are especially suitable. Other pigments of value are zinc oxide and certain forms of iron oxide. Auxiliary pigments such as finely ground fibrous magnesiumsilicate may also be incorporated to advantage in small quantities for the purpose of preventing the corrosion-inhibitive pigment from settling hard or caking upon long standing. The pigments are most conveniently incorporated by grinding in concentrated paste form and subsequently thinning the proper amount of the paste with thebulk of the paint. vehicle. With reactive pigments suchas red lead, which react and thicken with certain types of vehicles, it may be desirable to incorporate the pigment with the vehicle Just prior to use. When the combination of pigment and vehicle used is non-reactive, the composition may be prepared at any time in advance and stored until needed. I Y

The metallic powders used are those well known in the art, specially prepared for paint purp ses. Aluminum and copper bronze are the metals'most often used. The metals are in the form of extremely fine flakes,to which are added a small percentage of leafing or polishing agent such as stearic acid. The metallic pigment may. be as in dry powder form or, in the'case of aluminum, in the form of a paste which usually contains approximately 65% of metal and of volatile mineral spirits and polishing agent. In order to secure the maximum metallic luster, with many 30 forms of vehicle it is desirable to mix the metal powder into the paint just prior to its use. With certain vehicles and powders, however, it is possible to make a ready-mixed paint which will retain the leafing powers of the metal for a con- ;5 siderable time. The proportions of metal usually employed may vary between and 2% lbs. of .metallic pigment per gallon of vehicle containing the corrosion-inhibiting pigments. When "aluminum bronze is used in powder form. 2 lbs. per

gallon is suitable in most cases. When paste aluminum bronze is used; 2 lbs. of paste containing approximately 1.3 lbs. of metal per gallon is often suitable.

The following are examples of paints produced Mineral spirits (turpentine substitute) -gals..-

To this varnish is added soluble lead and cobalt drier in the proportion of 2% by weight metallic lead and .02% metallic cobalt. The

finished varnish should have a viscosity of between .50 and .85 poise at 25 C. In one gallon of this varnish, 2 oz. of basic lead chromate is incorporated by grinding in a pebble mill. To this pigmented varnish is then added 2 lbs. of aluminum powder, "Standard Varnish grade. The finished paint is suitable for application to structural iron or steel for exterior exposure. It dries in eighteen hours to give a lustrous metallic coating, indis- 55 tinguishable in appearance from the same type of paint containing no basic lead chromate. It possesses marked corrosion-inhibitive qualities and may be used directly over the bare metal, al-

though added protection may be obtained if a priming paint is first applied. Additional protection may also be obtained by applying two coats' Y of this aluminum paint, one over the other.

Example 2 A varnish vehicle is prepared. according to the following formula:

Oil soluble 100% phenol-formaldehyde resin 5 of the oil non-reactive type "lbs..- 100 Tung nil male 5Q Lead naphthenate lbs.. 2.2 Manganese naphthenate solution (4% metal) lbs" 4: m Mineral spirits al: "10

This varnish is prepared by cooking in the usual manner and has a viscosity of .50 to .85 poise.

A pigment paste is prepared having the following composition:

' g Pounds Zinc chromate 75 Finely ground fibrous magnesium silicate 10 Light kettle bodied linseed oil 45 a The paste is given a fine grind in a buhrstone mill.

To each gallon of the above-yehicle, 4 ozs. of the above pastels added and is incorporated with thorough agitation. 25

At the time of use, the finished paint is prepared by adding one gallon of the above pigmented vehicle to 2 lbs. of aluminum powder paste containing approximately metallicpowder and of the aluminum paint may be used.

The paints described above conveniently may be 4 packed in two-compartment cans, one compartment containing the metallic powder or paste, and the other the pigmented vehicle. The contents ofthe two compartments may be mixed together by the consumer at the time'of use. 45

I claim:

1. A paint which comprises a mixture containing a liquid vehicle which forms a relatively hard permanent film, metal flakes coated with a leafing agent that float from a film of the freshly 50 applied paint to form a substantially continuous layer of oriented overlapping flakes, and a nonmetallic corrosion. inhibiting pigment which re-- mains dispersed in said film from which the metal flakes float, the proportion of pigment being sub- 55 stantial but not exceeding about 15% by weight of the metal flakes.

2. A paint comprising, in admixture, a liquid vehicle which forms a relatively hard permanent film, metal flakes coated with a leafing agent 00 that float to the exposed surface of a film of the freshly applied paint to form a substantially continuous layer of oriented overlapping flakes, and a non-metallic corrosion inhibiting pigment that remains dispersed in said film, said pigment being 55 selected from the group consisting of red lead,

basic lead chromate, zinc chromate, zinc oxide,

iron oxide, and being present in substantial proportions but not to exceed about 15% by weight of the metal flakes.

FRANK A. STRAUSS.