US2864719A - Stabilized copper bronze powders and method - Google Patents

Description

.bronzes 9f commerce.

United States Patent STABILIZED COPPER BRONZE POWDERS AND METHOD Victor M. Willis, Dolton, Ill., assignor to The Sherwinggiliams Company, Cleveland, Ohio, a corporation of No Drawin Application 18, 156 I 7 Serial No. 591,794

17 Claims. (Cl. 106-296) This invention relates to an improvement in copper bronze powders whereby coating compositions containing the same may be admixed for longer periods prior to use without deterioration of the fluidity necessary to application. More particularly, this invention relates to a method of treating copper containing bronze powders so as to impart additional stability to said powders when incorporated in solutions of nitrocellulose lacquers for coating purposes.

If copper bronze powders now available as standard articles of commerce are admixed with organic solvent solutions of nitrocellulose lacquers, within a brief time a green coloration develops and shortly thereafter the liquidity of the system is lost and the product undergoes a sol to gel transformation. This phenomena is peculiarly a characteristic of copper containing bronze powders, but in the case of other bronzing powders, such as aluminum bronzes, the difiiculty is not known to exist.

The principal object of this invention is, therefore, to provide a copper containing bronze powder characterized by improved stability when in contact with nitrocellulose lacquers in solution. The principal object of this invention can be accomplished at two different time intervals. It has been found preferable to accomplish the object of this invention by a special treatment of the copper containing bronze powder prior to its incorporation in lacquer containing protective and decorative coatings.

It is also possible, however, to obtain a similar result by incorporating into the nitrocellulose lacquer .solution a quantity of the protective additive prior to incorporating therein the copper bronze powder or within .a very brief but reasonable period subsequent to the incorporation of the copper bronze powder in the bronzing lacquer solution. Time of addition is not particularly critical. However, as previously indicated, it is preferred that the treatment take place prior to the incorporation of the copper bronze powder into liquid bronzing medium. It may be feasible to incorporate the herein described protective additive during the copper bronze powder manufacturing procedure, by addition at one or more stages in comminution of the metal particles as they are transformed from nodular particles into rela- 'tively thin larnellar flakes characteristic of the metal The essential components of this invention comprises-copper bronze containing powder, an organic compound selected iiGiTr the g p consisting of water insoluble long chain aliphatic and.

alicyclic hydrocarbon acids containing from 8 to about 32 carbon atoms as an ancillary agent in conjunction with the metallic copper bronze of from about one half percent to about five percent by weight of said bronze powder and at least about five-tenths of a percent but not more than about ten percent by weight of said metallic powder of a water insoluble rosinamine.

Ratio of fatty acid to amine may vary within appreciable limits. Where the ratio of acid to amine is within the range of 1:7 to 3:1 the range has been found satisfactory for the purposes of the invention. Preferably, the total ce l 2 amount of organic agent in conjunction with the metallic copper bronze powder has been found to be in excess of one percent but less than eight percent and the range of acid to amine within the ratio of from 1:5 to 2:1. From this range it can be seen that the proportions of r'os'inarnine to fatty acid need not be in stoichiometric equivalents. It is believed that the optimum range is quite close to stoichiometric equivalents, although this relation has not been established by scientific tests.

Copper containing metal, bronze powders for the purposes of this invention are generally prepared by subjecting the desired metal to a preliminary comminuting process to reduce the size of the metal to convenient but relatively large initial particle size. The comminuted metal particles are then placed in a ball mill, stamping mill, or other device together with fatty acid lubricant containing from eightto thirty carbon atoms and the metal powders subject ,to the internal forces of these mills until reduced to the requisite particle dimension. If it is intended that the final: powders be used as non leafing bronzes, the percentage of fatty acid may be of the order of one half percent but'ifffo'r leafing quality the percentage by weight ofthe metal is of the order of 2 to 5%. In certaininstances the product is also furnished as a metal paste. This general practice, in these instances,jto add volatile thinner to the extent of 20 to 4 0 percent ,to producemetal powder pastes.

In accomplishing t'heends of thisinvention it is unnecessaryto alter 'aippr'eciably the prior art processes for preparation of *therii'etal bronze powder. It is reasonable to assume that little difliculty is to be encountered in inclusion of the additive of this invention during bronze powder manufacturing. 'There'is evidence to indicate preferredresults are obtained if the metal powder, per se, is subject to treatment rather than to cause treatment to occur in the lapquer solutionupongformulation of bronze coatings. v i

In initial stages of development 'of this invention advantages of the adjuvant here disclosed were investigated b'y adding approxiinately 50 grams of commercially available copper containing bronze powders (already treated with from one and one half 'to five percent of fatty acid containing atleast 8 carbon atoms) in 150 parts of a standardbroiizingdacquer (lacquer made as set out in Example 1'); To the'thus prepared bronzing coating composition was added exploratorypercentages of various agents which weredeemed to have potential value in stabilizing the coating composition against changes in its viscosity and to prevent attendant gelation occurring shortly (1-4days) after mixing of the bronze powder with nitrocellulose lacquer solutions.

Through this series of tests it was found that a generic class of materials 'comrnonly described as rosinamines were useful in's'tabilizing the bronze containing lacquer coating. By the term rosinamine as used herein, it is intended to refer to commercially'available products in which the parent compound contains from about percent to 97 percent of the primary amino compound derived from rosin. 'The parent group of compounds includes rosinamine, dehydr'orosinamine, dihydrorosinamine, and v te rahysiroresinamine. A series f ag g tests has established the parent primary aniind compohhd to be preferred for the purposes of this invention. However, a more comprehensive testing of it and related compounds has also shown it to be within the scope of the invention to use secondary rosinamines which are alkylene oxide condensations of the parent primary rosinamine compound. is possible when the quantity of the alkylene oxide condensed with the parent primary rosinamine is small. In no case should enough alkylene 'oxide (ethylene oxide) be condensed with the rosinarnine to render the so diarived secondary rosinamine water soluble, or to interfere with the basic character of rosinamines. Thus, both primary and secondary rosinamines are useful for the purposes of this invention, although as stated previously, primary rosinamines appear to be more efiective. The non-substituted primary. and secondary rosinamines useful for the purposes of this invention are characterized by an organic residue of a structure similar to the structure of abietic acid, wherein vthe carboxyl group of the abietic acid issubstituted for with an amino group. While primary amines are preferred, the secondary rosinamines (whereinone of the active hydrogens of the parent amine is replaced by 'alkylene oxide condensation) are usef u1 to accomplish a similar result. The amount of ethylene oxide, which can be tolerated in condensation with the primary rosinamine, is insufiicient to render the so-formed secondary rosinamines water soluble. To illustrate, the limitation of the term water soluble" as it appliesto these compounds is as follows:

when 11 molesormore of ethylene oxide are condensed with one mole of ros inamine sufficient instability is observable in the resultant bronzinglacquer coatings to remove this agent from practi cal value and to eliminate it from consideration. for the purposes of this invention.

If seven moles of ethylene oxidearecondensed per mole of primary rosinamine, there isstill some water solubility and the usefulnessjs appreciably lostfor my purpose. However, if the arnount of ethylene oxide is reduced to five moles per molepf rosinamine, the secondary amines resulting are useful and the solubility iniwaterat this range is negligible. The expression ff'water insoluble rosinamine" has therefore beenjarbitiarfly'limited and does not embrace secondary rosinaniin es containing more than eleven moles of alkylene, oxide per mole of rosinamine. While experience hasgbe en primarily with ethylene oxide adducts-of rosinamine it is obvious that propylene oXideaddu tsareals potentially available. It should be pointed out ,that water solubility per se, is not known to be a detrimental quality in the; present application. Water solubility does provide, however, a convenient means of lirnitingand defining,the scope of rosinamines of secondary nature useful iforpurposes of the invention with practical accuracy in the hereinafter appended claims. a In A'review of the prior artwhigh relates 'to the production of metal pastes, pigments, aluminum; bronzcs, and copper containing bronze, powdersestabli shes that it is customary in the art of manufajcture'ofimetal powders for pigment use to employ long chain fatty acids to promote the leafing quality of the" metali powders and to lubricate the metal as it is transformed from the larger particle shrode state to.a fine particle lamellar powder state and to assist in polishing the surface of the finc metal powder particles to obtain optimum brilliance. The prior art discloses a numberof fatty acids useful during attenuation of metal toa finely powdered lamellar state. Among the organic compounds selected from the group consisting of water insoluble long chain aliphatic and alicyclic hydrocarbon acids containing from 8 to about 32 carbon atoms reportedly usedare sunflower oil acids, ricinoleic acids (castor oil a ids), Qleic acids, myristic acid, palmitic acidQnaphthenic acids, etc., which are characterized by their lubricity, water insolubility. and soap forming qualities. In the arts which relate to surface activity, it is generally recognized that surface active qualities of long chain aliphatic acids are of little moment until the fat-l1 acid contains. at -least 8'carbon atoms in its hydrocarbon chain. "Most surfacefactive agents contain from eight to about 32' carbon atoms in their longest hydrocarbon chain. For the purposes of this invention, long chain aliphatic and alicyclic hydrocarbon acids within this range are useful and essential in conjunction with the described rosinamines to accomplish'thecnds of the invention. 1

As will be shown in the examples, presence of rosinamine alone, in conjunction with the metallic copper bronze powder appears to hasten gelation when in conjunction with a dispersion of the metal powder in a solution of a nitrocellulose lacquer. It has been observed the presence of water in macroscopic quantity also hastens gelation of bronze-containing lacquers, independent of the treatment or method of treatment as described herein. However, it is known that quite small amounts of water are present in nitrocellulose as shipped commercially for it is wetted down with about 30 percent of ethyl alcohol. The ethyl alcohol in turn contains water. This water is carried into bronzing lacquer formulations. The amount so carried in appears not to interfere with the effectiveness of the treatment herein described.

A host of related amines have been used in comparative manner to the rosinamines herein described. These amines include alpha naphthol amine, paraphenylenediamine, and diphenylguanadine. In each test case the useful life of the completed bronzinglacquencontaining the recited amines was seriously diminished.

The following examples, while numerous, are by no means to be construed as exhaustive. They are included to illustrate the best methods of practice of the invention and to make clear, by comparison, limitations upon the invention and to illustrate the difference between what is here accomplished and what has been illustrated in the prior art. It is to be noted in passing that attempts to artificially accelerate the age rate of test samples by exposing them to elevatedtemperatures were in all cases unsatisfactory. This for the reason that-developed fluidity of the nitrocellulose suspending medium allowed rapid settling of the heavier metallic bronze powder into closer proximity of the individual metallic flakes and entrapment of thin films of nitrocellulose lacquer between relatively large active metallic surfaces of the copper bronze powder. These conditions appeared to cause very rapid reaction to take place. Increasereactionrates were observed at temperatures of the order of l25 F. Test results recorded herein were at room temperature and with in the range of 65 to 90 F. Partsare by weight unless otherwise identified.

EXAMPLE I EXAMPLE H (Control) Parts Cordova rich gold 49 Copper bronze powder Stearic acid L25 Lacquer of Exam le I 150 were aged together at room temperature.v At thecnd of 4 days, the previously liquid sample had undergone a sol to gel transformation and discolored to a characteristic copper-green color.

EXAMPLE III Parts Cordova rich gold 49 Copper bronze powder Stearic aoirl 1.25 Rosinamine 2.50

Lacquer of Example I 1S0 Acetone asserts were mixed together and aged at room temperature. At the end of 30 days the sample was still useful for'paint purposes.

EXAMPLE IV Part A 200 parts copper bronze were exhaustively extracted in a soxhlet apparatus for 2 hours with chloroform to PartB Parts Treated bronze from above 50 Std. lacquer solution 150 were mixed together. Upon overnight age, a solid gel formed. Control: gelled in 4 days. The example illustrates ineffectiveness of rosinamines alone.

EXAMPLE V Parts Copper bronze powder (2 /2% stearic acid) 5O were mixed together and after several hours the paste was heated and the acetone driven off by evaporation. The product remaining still containing some acetone was mixed with 150 parts lacquer of Example I. The lacquer-bronze mixture had not changed appreciably in viscosity at the end of days at room temperature and behaved normally upon application as a coating.

EXAMPLE v1v The following materials were tested, using 50 parts copper bronze powder, 2.5 parts'test material and 150 parts lacquer of Example I. The length of time of stability in each case was recorded as follows:

Rosinamine Identification Material a B-napt Control (No addition) 96 24 Carbon atom primary amine 60 EXAMPLE VIII Parts Metal powder (copper bronze) 50 Rosinamine 2 Water 2 Lacquer 150 Test was made to determine treatment effectiveness if water was present in substantial amount. terial gelled overnight. The test established that water in more than trace amounts cannot be tolerated in the system and precautions should be taken to maintain the bronzing lacquer system as dry as possible. That trace amounts of water can be tolerated apepars from the fact Test ma- 5 6 'that trace amounts of water are present in Bronzing lacquet solutions prepared as in Example 1.

EXAMPLE IX In a test series, 50 parts of copper bronze powder were treated with 2.5 parts, (a) rosinamine naphthenate, (b) rosinamine laurate, (c) rosinamine oc toate, (d) rosinamine oleate. The test runs were found to be in good condition after the control sample containing no rosinamine salt had gelled.

EXAMPLE X the metal containing nitrocellulose solution against gelation. With a molar ratio of 1:1 rosinamine-ethylene oxide adduct added the treated bronze gelled in 28 days, whereas the adduct containing 1 mol rosinamine to 11 mols ethylene oxide gelled in 14 days.

From the behavior of this series, as well as in a comparable series where the rosinamine-fatty acid condensa-- tions were of fatty acids containing from 2 to 5 carbon atoms, it was determined that rosinamine adducts useful for the purposes of the invention, again, were preferably limited to those of water-insoluble nature.

The percentage of rosinamine useful for the purposes of the invention was found to be within the range of about 0.5% to not more than about 10% by weight of the copper containing metal powder. While effective at higher percentages, the total length of time before gelation fell off rapidly as the amount of rosinamine present was increased above 10%. can use too great an amount of amine in relation to fatty acid lubricant inherently present in bronzes of commerce for test purposes.

In all theexamples, unless otherwise noted, it is to be observed that the copper bronze powders .used as illus trative contained from 2 to 3% of stearic acid.

While it is possible and satisfactory for the purposes of the invention to add the rosinamine solution to the lacquer solutions and to form rosinamine-fatty acid salts in situ in the bronzing liquid upon'addition of the bronze, it is preferred to form the fatty acid salt of rosinamine di rectly upon the copper bronze powder, and following this step to make the bronzing liquid by admixture of the treated bronze powder and lacquer solution.

Having described my invention, what I claim is:

1. A copper-containing bronze powder of improved stability characteristics which comprises a major quantity of a copper containing bronze powder and in intimate contact therewith at least 0.5% but not more than about 5% by weight of said metal powder of an organic compound selected from the group consisting of water insoluble long chain aliphatic and alicyclic hydrocarbon acids containing from 8 to about 32 carbon atoms and a waterinsoluble rosinamine.

2. A copper-containing bronze powder characterized by improved stability when in contact with nitrocellulose lacquers in solution in volatile organic solvents which comprises a copper containing bronze powder in intimate contact with a mixture containing at least 0.5% but not more than about 5% by weight of said powder of an organic compound selected from the group consisting of by improved stability when in contact wtih nitrocellulose In this series, it was determined that the This evidence suggests one Iacquers in solution in volatilqorganic solvents which comprises a copper containing bronze powder inintimate contact with at least five tenths of a percentbut 'not more than about five percent byweight of said powder of an organic compound selected from the group consisting of water; insolubledong chain aliphatic .and lalicyclic hydrocarbon acids containing from" 3 to aboutBZ-carbon atoms and a water insoluble rosinamine wherethe weight ratio of acid to amine is. within therange'offrom 1:5 to2:1."

4. As in claim 3, where the alicyclic hydrocarbon acid is napthenic acid.

5. As in claim}, where the long chair aliphatic acid is stearic acid. I

6. As in claim 3, Wherethe long chain aliphatic acid is myristic acid. r

7. As in claim 3, where thelong chain aliphatic acid is palmitic acid.

8. As in claim 3, where the long cbain aliphatic acid is lauric acid.

9. As in claim 3,

rosinamine.

10. A copper containing bronze powdercharacterized by improved stability whenin contact with nitrocellulose lacquers in solution which comprises a copper bronze containing powder, from one half a percent to not appreciably more than live percent of an organic compound selected from the group consisting of. water insoluble long chain aliphatic and alicyclic hydrocarbon acids containwhere the rosinamine is a primary ing from 8 to about 32 carbon atoms and from 0.5% to not morethan about. 10% by weight ofsaidpowder of a primary rosinamine.

11. As in claim 10,. .where the alicyclic hydrocarbon 15. In nitrocellulose lacquer solutions in organic solvents containing copper bronze metallic pigments coated with a lubricating organic acid selected from the group consisting of water insoluble long-chain aliphatic and alicyclic hydrocarbon acids containing from 8 to about 32 carbon atoms in association with said copper bronze powders, the method of increasing the useful life of the above described liquidcoating compositions which comprises including. therein during manufacture and prior to storage, from 0.5% to not more than about 8% by weight of the copper bronze powder in said coating composition of a water insoluble rosinamine.

16. A method of increasing the useful life of copper bronze powder-containing nitrocellulose lacquers in solution in organic solvents which comprises including with the copper bronze, nitrocellulose lacquer solution and the 0.5% to 5% by weight of said bronze of lubricating fatty acids associated with said copper bronzes from five tenths of a percent to not more than about 10 percent by weight of the copperbronze powder of a primary rosinamine.

17. A method of increasing the useful life of copper bronze powder containing nitrocellulose lacquers in solution in organic solvents which comprises including with the copper bronze, nitrocellulose lacquer solution and the 0.5% to 5% by weight of said bronze of stearic acid associated with said bronze from five tenths of apercent to not more than about eight percent by weight of said bronze .of a primary rosinarnine.

References Cited in the file of this patent UNITED STATES PATENTS 2,178,181 McMahan Oct. 31, 1939 2,445,374 Van Wyck July 20, 1948 2,525,280 Allen Oct. 10, 1950 2,561,892 Van Wyck July 24, 1951 2,709,160 Korejwa May 24, 1955 FOREIGN PATENTS 180,062 Switzerland Dec. 16, 1935

Claims (1)

1. A COPPER-CONTAINING BRONZE POWDER OF IMPROVED STABILITY CHARACTERISTICS WHICH COMPRISES A MAJOR QUANTITY OF A COPPER CONTAINING BRONZE POWDER AND IN INTIMATE CONTACT THEREWITH AT LEAST 0.5% BUT NOT MORE THAN ABOUT 5% BY WEIGHT OF SAID METAL POWDER OF AN ORGANIC COMPOUND SELECTED FROM THE GROUP CONSISTING OF WATER INSOLUBLE LONG CHAIN ALIPHATIC AND ALICYCLIC HYDROCARBON ACIDS CONTAINING FROM 8 TO ABOUT 32 CARBON ATOMS AND A WATERINSOLUBLE ROSINAMINE.