US2385800A

US2385800A - Paint

Info

Publication number: US2385800A
Application number: US380770A
Authority: US
Inventors: Douty Alfred; Frank B Freese
Original assignee: Amchem Products Inc
Current assignee: Henkel Corp
Priority date: 1941-02-27
Filing date: 1941-02-27
Publication date: 1945-10-02
Anticipated expiration: 1962-10-02
Also published as: ES172538A1

Description

Patented Oct. 2, 1945 PAINT Alfred Donty, Elkins Park, and Frank B. Freese, Lansdale, Pa., assignors to American Chemical Paint Oompany, Ambler, Pa., a corporation oi Delaware No Drawing.

Application February 27, 1941,

Serial No. 380,770

2 Claims.

This inventiom relates to siccative finishing compositions such as paint, varnish, lacquer, etc., and in the following disclosure and claims the term paint"will be employed as a generic term for compositions of this character.

The primary object of the invention is to provide a paint which will yield exceptionally adherent and strongly corrosion resistant finishes, especially on metal surfaces. A further object is to provide a primer which is particularly well adapted to serve as a foundation or base upon which to apply subsequent finishing coatings.

A still further object of the invention is to provide a metal primer which can be directly applied to surfaces which are contaminated with small amounts of rust, corrosion products, or rust stimulative materials like soluble chlorides, etc., without the necessity for preliminarily cleaning or otherwise treating the surface to be painted. More specifically our invention renders unnecessary certain preliminary treatments heretofore customary in the art, such, for example, as cleaning with phosphoric acid olutions, or the application to metal surfaces of phosphate base coatings.

Other objects of the invention include the provision of a paint which will greatly lessen the cost of a complete finishing Job as well as one which will materially increase the life of the finish.

Still other objects and advantages will appear to those skilled in this art as the description proceeds.

In its broadest aspect our invention consists in the provision of a paint or similar siccative finishing composition which includes a substantially water-insoluble or water immiscible film forming vehicle (either pigmented or unpigmented), which vehicle is emulsified as a dis persed internal phase in a continuous, aqueous acid external phase. The acid used in the external aqueous phase should react with some constituent of the particular surface to which the composition is to be applied to produce or leave behind only such residual end products as are stable, substantially water-insoluble and inert toward the deposited coating of film forming vehicle and for this reason we prefer phosphoric acid, especially where the paint is to be applied to metal surfaces because phosphoric acid is metal etching and non-corrosion stimulative.-

The emulsiflcation of the film-forming vehicle in the external acid aqueous phase may be accomplished by any means known to those skilled in the art, although we have found that very superior results are obtained when the emulsification is accomplished by means which includes a cationic surface active agent as will be more fully described hereinafter. However, entirely successful compositions have been prepared by means of other emulsifying agents such. for example, as hydrophile colloids, as well as combinations of surface active agents and hydrophile colloids.

Where our composition is to be employed in the finishing of metal surfaces, the aqueous external phase may also include, if desired, suitable regulators of the rapidity of reaction of the acid with the surface of the metal to which the paint is to be applied. Agents of this kind which may be used are, among others, inhibitors of acid attack on metal and/or bufier salts of metals not otherwise harmful either to the metal surface or to the finish which, after the evaporation of the water and the reaction of the acid with the metal surface, leave behind substantially water-insoluble residues only. Among such buffer salts may be mentioned the phosphates of zinc, magnesium, iron, calcium, manganese, cadmium, etc.

The internal dispersed phase may include, for example, drying oils, natural resins, synthetic resins, varnishes, cellulose others, etc.. in addition to pigments, fillers, solvents, diluents, etc. It must be so compounded that it remains sufficiently fluid to enable its discrete drops to flow on the surface and coalesce to a substantially continuous film which will remain in this condi tion until the water of the eitternal phase has evaporated and the reaction of the aqueous acid solution with the surface of the metal has substantially ceased. To this end, it is desirable, especially when the film-forming vehicle is high in resin solids, to have present in the dispersed phase a solvent or solvent system which evaporates more slowly than water and which, Just before the complete evaporation of the water, still remains in sufficient quantity to allow some "leveling" of the paint on the surface, so that the paint will not show "spatter marks if sprayed, nor brush marks if ibrushed. Moreover, the presence of such a solvent system yields an additional advantage in that it ensures the healing" of any holes left in the film by gas bubbles from the reaction of the acid aqueous solution with the surface of the metal, so that, as the paint film dries, any such holes due to the release of gas bubbles will be substantially eliminated in the final finish.

We have found that any oils, resins, or other vehicle solids may be used as the dispersed phase except such as are caused to gel or set" or are otherwise adversely affected by the acid environment in which the droplets of paint are suspended. Similarly, carbonates or other pigments or fillers which are easily affected by acids are not to be used, but otherwise no limitations in pigmentation have been encountered.

We have also found it desirable to add to our composition small amounts of an organic liquid blending agent somewhat soluble in the water of the aqueous phase and somewhat soluble also in the non-aqueous phase or film-forming phase and having the property of reducing the surface tension of both phases. Among agents of this character which we have found to be useful with our invention are the aliphatic alcohols 01' not more than eight carbon atoms and glycol others such as "cellosolve and "butyl cellosolve. These liquids, of which normal butyl alcohol, amyl alcohol (fusel oil) and secondary octyl alcohol are examples, have two desirable effects in our composition: first, they promote the dispersion of the substantially water-insoluble paint vehicle as the internal or dispersed phase in the aqueous liquid portion, so that the latter forms the continuous or external phase. This is sometimes diilicult to achieve in the absence of such blending agent, particularly when a relatively small amount of the aqueous phase is present as compared with the water-insoluble or oily" phase. This latter condition is encountered, for example, whenever it is desired to increase the viscosity or paint vehicle solids" of our composition, as. for instance, when it is to be applied by brushing instead of by spraying, or when increased film thickness of the final coating is desired. Second. such "blending agents promote leveling of the film of deposited paint.

In order to still further vary the stability or viscosity of the emulsions which constitute our compositions, it may further be desirable to incorporate therein a hydrophile colloid. Among such emulsion protective and thickening agents may be mentioned colloids such as glue, agar, solid colloidal agents like colloidal clay or bentonite; water soluble gums including cellulose others such as methyl cellulose, etc. These agents generally have a beneflcialeilect on the smoothness and texture of the deposited film.

Where metals are to be painted we have referred above to the use of the non-corrosion stlmulative phosphoric acid which is capable of etching the metal and of forming therewith or with any rust or surface contaminants which may be present thereon, relatively stable, substantially water-insoluble salts or basic salts of such a nature that their presence either on the metal itself or in the paint film does not stimulate corrosion by atmospheric agencies. In addition, the residual end reaction products of such acid is stable, substantially water-insoluble and inert toward the deposited coating of film-forming vehicle, as stated above.

The surface-active agents referred to above are in general organic substances which yield in aqueous solution ions that are strongly adsorbed on the surfaces of oily" materials with which the aqueous solution comes in contact. when such oily substances are broken up into fine droplets by mechanical or other means within such aqueous solutions, the droplets are prevented by their surface layers of adsorbed ions from coalescing; thus a more or less stable emulsion of the oil in the water results. The "oily" drops of our improved composition are the film-forming or paint vehicle, 1. e., the oils, resins, pigments, fillers and solvents originally composing the layer to be deposited on the surface to which the composition is to be applied.

Our experience has shown that for use in our compositions agents yielding positively charged surface active ions, so-called cationic surfaceactive agents are strongly indicated. Among the cationic-surface-active agents which we have found useful are a number of compounds defi nitely characterized chemically, and certain others known to use only by more general propcities and names. In general, the compounds found useful include amines and quaternary ammonium salts having at least one radical containing twelve or more carbon atoms; amidoamines or quaternary ammo-ammonium salts having radicals containing twelve or more carbon atoms; and ester-amines containing similar radicals.

Specifically, fatty acids esters of triethanoiamine, fatty acid amides of hydroxyethyl ethylene diamine, lauryl dimethylamine, etc. were found useful. In addition certain commercial materials, chemically characterized only as "amines." or "imines" were found satisfactory. One of these is known as "Amine E0," others as Acco Emulsifler #2 and #3.

In general, we have found operative a sumclent number of so-called cationic surface-active agents so that we believe that we are .iustified in concluding that the entire class of such materials is operative in the compositions of our invention.

An example of a quick-drying, pigmented composition according to our invention suitable for application to structural steel surfaces as a primer may be compounded as follows:

A varnish is prepared according to the following formula:

Formula N0. 1-Vomish Pounds Alkyd resin modified with oils and phen01 52.5 Modified phenolic resin, melting range 215-232 1" 17.5 Toluol 25.0 Secondary octyl alcohol 5.0

Total 100.0

Using this varninsh, a paste is prepared by grinding together, for instance, in a stone paint mill, the following:

Formula No. 2-Paste Pounds Varnish of Formula No. l 27.27 High flash solvent naphtha 27.27 Red iron oxide 13.64 Barytes 18.64 Asbestlne 18.18

Total 100.00

The composition ready for use is then prepared as follows:

Formula No. 3-Finished material Pounds Paste, Formula No. 2 40.00 Varnish, Formula No. 1 10.00 Phosphoric acid, 75% 1.72 Mono-oleyi ester of triethanolamine--- 2.78 Normal butanol 10.08 Water 35.42

Total 100.00

ii necessary. although water slightlyacidifled with phosphoric acid is preferable. as impurities, especially lime salts, in the water may have a deleterious eil'ect on the emulsion unless the water is ilrst slightly acidified.

. 'In the above composition, as in other compositions otour invention, other cationic surfaceactive agents may be used in place oi the monooieyl ester of triethanolamlne specified above. Successful preparations have been made with all the emulsifying agents enumerated above and others. As all emulsifying agents of this type are not of equal power, it may be desirable somewhat to vary the amounts used in the composition. In general it may be stated that it is preferable to use no more emulsifying agent than is necessary to produce an "oil-in-water" type emulsion of adequate stability.

ii, in attempting to prepare our compositions the emulsion forms initially as, or reverts on standing, to a water-in-oil type in which the "paint-like" portion of our preparation constitutes the external phase and the aqueous portion the internal or dispersed phase, the preparation is not satisfactory and must be discarded or retreated sb that the aqueous phase is the external or continuous and the oily" part the internal or dispersed phase. Many experiments have shown that our compositions, when properly prepared and applied, are highly superior to superflcially similar materials not made in accordance with our invention.

What we may term the acid emulsion primer" of this invention as exemplified by the foregoing examples, dries to a firm tough coat overnight, and under accelerated tests in the salt spray and high humidity cabinets as well as under outdoor exposure tests, it has proven itself to be much more resistant to corrosive influences than is any other primer with which we are familiar. In addition, multi-coat finishing systems embodying one of our compositions as a primary coat, have exhibited vastly improved results over similar systems embodying conventional primers, even when these are of so-calied "corrosion-resistant" pes.

The example of our composition given in Formula No. 3 is merely illustrative of a pigmented, air-drying material made in accordance with this invention, and embodying a synthetic resin vehicle. As stated above, various natural and artificial oils and resins may be used in place of synthetic resins such as are embodied in Formula No. 3. As an example of a composition embodying a natural drying oil only, we may cite the following:

Formula No. 4

Pounds China-wood oil 20.90 Gum turpentine 10.00 Red iron oxide 5.45 Barytes 5.45 Asbestine 7.27 Amine E 2.78 Butyl alcohol 10.08 75% phosphoric acid 1.72 Distilled water 35.45

Total 100.00

This is a commercial high molecular weight amine cationic surface active agent made by the Carbide and Carbon Chemicals Corporation.

oil; then mixingtogether the paste, the rest of the oil. and the Amine E0, and emulsifying the mixture in the water in which the acid has been dissolved.

As previously indicated, the pigment composition of Formula No. 3 and Formula No. 4 may be altered as desired to change the color or other properties of the deposited film as will be apparent to the paint chemist, provided only that the pigment be stable in the presence of the acid solution. A similar preparation may be made by substituting in the material of Formula No. 4 an equal weight of boiled linseed oil for the Chinawood oil of the formula.

The drying properties of our preparations are, of course. affected by the composition of the vehicle with respect to oils, resins, etc. For instance, the composition of Formula No. 4 dries fairly hard overnight at room temperature, whereas a similar composition containing boiled linseed oil requires several days to dry. However, in general, whatever the siccative coating agent in our compositions, the coatings produced from our acid emulsions dry much more rapidly than non-acid emulsions of identical "non-volatile solids" content.

It has been found, however, that maximum drying speed and adhesion of films produced with our coating compositions is often obtained at acid contents higher than the minimum necessary to produce a stable oil-in-water type emulsion with cationic surface active agents. This effect 01' free acidity on the drying time of a coating composition similar to that of Formula No. 3 will now be illustrated:

Two compositions were prepared having the following formulas:

Formula No. 5

Both the above compositions were compounded in the same way as was Formula No. 3 above.

It will be seen that Formulas No. 5 and No. 6 are identical except for the fact that Formula. No, 6 contains more phosphoric acid and correspondingly less water than Formula No. 5. The amount oi phosphoric acid in No. 5 is only willcient to combine with, neutralize, and bring into solution in the water, the Amine E0; while the amount of phosphoric acid in No. 6 is suillcient to have in the aqueous phase a considerable excess of free acid.

When these two preparations were sprayed onto clean steel and galvanized iron panels, the coats produced with No. 6 were dry and tough at the temperature of the room inside of 16 hours.

The coats produced with No. 5 were still tacky" after 116 hours.

The above effect of free acidity in our compositions has been noted for numerous formulations and is very striking. It has been found, in general, that even traces of free acidity yielding a pH of 4.5 or below in the aqueous phase are effective in producing satisfactory acid-emulsion paints, according to our invention. However, a somewhat higher free acidity such as approximately 0.1 normal is useful in reducing the drying time of the preparations. No sharp upper limits of acidity have been formed for the allowable acidity of our preparations. Too high an acidity may give rise to an increased susceptibility of the coatings produced to failure in atmospheres of high humidity, but the seriouness of this effect varies with the metal to which the coating is applied, the nature of the vehicle, degree of pigmentation, etc. We prefer compositions having a free acidity corresponding to an aqueous phase 0.1 to 1.0 normal in free acidity as determined, for example, by titration of a portion of the aqueous phase with standard caustic soda solution to an end-point pH of about 4.5.

As stated above, the action of the acid on the metal may be regulated or controlled by adding to the composition various regulating agents, among which may be included buffer salts, inhibitors, etc., as long as these leave no soluble rust-stimulative, or otherwise harmful, residues. The buffer salts are preferably salts of nonrust-stimulative acids, as, for example, phosphoric, arsenic, and oxalic acids.

Examples of compositions suitable for quickdrying, as, for instance, by baking in an oven at 350' i for 30 minutes are given below. The compositions of Formulas Nos. ll, 12 and 13 contain, as regulators or acid action, respectively, sine phosphate, manganese phosphate, and arsenious oxide.

Formula. No. 7Zinc Phosphate solution Pounds Zinc oxide 1.500 Phosphoric acid, 75% 6.720 Water 4.115

Total 12.335

The zinc oxide is suspended in the water, the phosphoric acid gradually run in, and the whole stirred until all the zinc oxide is dissolved.

Formula No. 8-Manoanese phosphate sodlution 1 Pounds Manganous carbonate 1.750 Phosphoric acid, 75% 5.050 Water 1 5.460

Loss of carbon dioxide 0.67

Total 11.500

This is made like No. 7, except that manganous carbonate is used instead of zinc oxide.

Formula No. 9Low an alkyd resin paste assasoo The paste was made in conventional fashion.

Formula number 10 11 I2 13 Ingredient pounds pounds pounds pounds Paste Formula No. 0 40. 00 low-oil modified alkyd resin, w m m m 40 Af l% soiids in xylol 11.65 ll. 65 11.05 ll. 65 2. 78 2. 78 2. 78 Phosphoric acid. 757 1.12 1.72 1.72 i: Zinc hosphate solution (Fori m a No. 7) 1. 35 Manganese phos hate solutlon (Formula 0. 8) l. 72 Arsonious oxide 0 38 Normal butanol 10. 08 10.08 in. 08 10.! WBW 33. 71 31. 92 32. 06 33. M

100. O0 100. (X) [00. (I) 100. (I)

All of these preparations are prepared by emulsiiying the mixture oi the paste and alkyd resin in an admixture of the rest of the ingredients as described for Formula No. 3.

The above compositions Nos, 10, 11, 12 and 13 were compared by spraying them onto cold rolled steel panels, allowing the coatings to dry thoroughly and exposing them in salt spray cabinet maintained at 05 1''. for a period of 240 hours. In addition, a further conventional paint was prepared by mixing together Paste No. 9 and the same low-oil alkyd resin in the same proportions as used in the above formulas. but substituting for all of the other ingredients an equal total weight of toluene as a thinner. This material, then, contained exactly the same pigment and non-volatile paint vehicle as the emulsions of Formulas Nos. 10 to 13, and in the same amounts. It constituted (and will be referred to as) a "conventional" paint. This paint was applied to, dried, and tested on similar metal panels simultaneously with the "acid emulsion paints" of Formulas Nos. 10 to 13, inclusive.

After 240 hours of exposure in the salt spray, the results were as follows:

Conventional paint 95% failure Acid emulsion paints Little or no failure Little purpose would be served by multiplying the number of formulas found to be suitable for the compositions of our invention. Suillce it to say that wide variations, obvious to the paint chemist, are permissible in the compositions according to our invention. The paint-like portion of our preparation, constituting the dispersed phase, may be formulated with wide variations with respect to the relative proportions of vehicle solids, solvents, thinners, pigments and fillers, and these variations may be expected to produce results in the deposited paint film similar to those well understood by the paint chemist in the case of conventional paints. For example:

(a) Compositions suitable for baking or accelerated drying, as well as for air drying, are easily prepared.

(12) Compositions giving clear varnish or lacquer films have been prepared with success equal to that obtained with pigmented compositions.

(c) Pigmented compositions giving films of various colors are easily made.

(at) Compositions suitable for brushing as well as spraying, have likewise been readily formulated. As stated previously. omission of some of the water is often all that is required to make a material of brushing instead of spraying consistency. Methyl cellulose and other thickening materials have likewise been added to the aqueous phase to improve "body" and brush-ability.

(e) Compositions embodying cooked varnishes and lacquers instead of oils or "solution varnishes" are readily made.

In general, with due regard only to the requirement that the acid aqueous phase does not deleteriously react with the vehicle resin or pigment, the formulation of our improved composition is almost as flexible and unlimited as the formulation of a conventional paint. The paint chemist will readily comprehend the limitations inherent in such compositions.

As examples of the widerange of vehicle solids which it has been found possible to incorporate into our compositions, we may mention, among the oils, linseed oil, tung oil, soya bean oil, oiticica oil, castor oil, dehydrated castor oil, etc. Nondrying oils have been incorporated for special purposes; among the resins we have used alkyd resins of various degrees of oil modification, pure phenolic resins both heat hardening and nonheat-hardening, modified phenolic resins, vinyl polymers, hydrocarbon polymers such as coumarone and indene resins, ester gum, rosin, natural resins, such as copal, congo, kauri, etc. The urea resins as well as the melamine resins are known to be extremely sensitive to acids, even to acidic pigments. Since they are immediately set" by acids the paint chemist would be immediately aware that they should not be used in our compositions.

Ester and ethers of cellulose such as nitrocellulose, cellulose acetate, ethyl cellulose, cellulose aceto-butyrate, etc. are also useful in our improved compositions.

Among the pigments are fillers we have found useful are fibrous talc or asbestine, silica, barytes, blanc flxe, titanium dioxide, titanated gypsum and titanated barytes, carbon black, lampblaclr, red iron oxide, black iron oxide, chrome green oxide, smalt, etc. whiting or other carbonates are inapplicable because of their well known reactivit with acids. Red lead may be used if the emulsions are freshly made Just before use. On

long standing red lead reacts deleteriously with acidity of 1.0 normal.

the acid in our compositions.

Ordinary driers and plasticizers may be present in our composition, and, in general, perform their usual functions.

Our invention has been found particularly useful on metals such as iron, steel, zinc and alloys thereof, although it has also been found useful on cadmium, lead, copper and aluminum. In addition, our compositions have yielded excellent results on concrete or cement surfaces and when painting such surfaces the preferable acids are, of course, those which are capable of forming with the lime of the cement substantially waterinsoluble, inert and stable salts.

We claim:

1. A siccative paint including organic filmforming material emulsified as a dispersed phase in a continuous aqueous phase including phosphoric acid, together with a cation-active emulsifying agent; an organic liquid blending agent from the class consisting of aliphatic alcohols of not more than eight carbon atoms and glycol ethers; a solvent in the dispersed phase which evaporates more slowly than water; and a pigment substantially unaflectcd by the phosphoric acid; the concentration of free acidity in the aqueous phase being suflicient to impart to that phase a pH of 4.5 but not more than enough to yield a free acidity of 1.0 normal.

2. A siccative paint for use on metals including organic film-forming material emulsified as a dispersed phase in a continuous aqueous phase including phosphoric acid and a buffer salt from the class consisting of the phosphates of iron, zinc, manganese, calcium, cadmium and magneslum, together with a cation-active emulsifying agent; an organic liquid blending agent from the class consisting of aliphatic alcohols of not more than eight carbon atoms and glycol ether-s; a solvent in the dispersed phase which evaporates more slowly than water; and a pigment substantially unaffected by the phosphoric acid; the concentration of free acidity in the aqueous phase beingsuilicienttoimparttothatphaseapfloi' 4.5 but not more than enough to yield a free GER'l'IFICliTE or comc'rzos.

Patent No. 2,385,800.

October 2, 19 6.

ALFRED DUUTY, ET AL- It is herebycertified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 2,

column, line 75, for use" read --us--; and

page 5, first column, line 35, for "are" read "and";

read --aci.d-;

first second column, line 9, for"aci.ds"

and

second column, line a, beginning with "and when" strike out all to and including the word "salts" in line 12; and that the said Letters Patent should be read with this correction therein that the some may conform to the record of the case in the Patent Office.

(Seal) i. o. 191L6- Leslie Frazer First Assistant domissioner of Patents.

long standing red lead reacts deleteriously with acidity of 1.0 normal.

the acid in our compositions.

We claim:

Patent No. 2,385,800.

October 2, 19 6.

column, line 75, for use" read --us--; and

page 5, first column, line 35, for "are" read "and";

read --aci.d-;

first second column, line 9, for"aci.ds"

and

(Seal) i. o. 191L6- Leslie Frazer First Assistant domissioner of Patents.