US3391010A - Gold decorating compositions and method - Google Patents

Description

United States Patent 3,391,010 GDLD DECORATING COMPOSITIONS AND METHOD Anna P. Hauel, West Orange, N.J., assignor to Engelhard Industries, Inc., Newark, N..l., a corporation of Delaware No Drawing. Filed Nov. 18, 1965, Ser. No. 508,575

11 Claims. (Cl. 106-1) ABSTRACT OF THE DISCLOSURE Process for forming gold films from gold mercaptide decorating compositions under less severe conditions than heretofore known by thermally decomposing such compo.- sitions in the presence of a halogen agent, and new improved decorating compositions for effecting such process.

This invention relates to new and improved gold decorating compositions, and is particularly concerned with gold decorating compositions which can be converted to decorative metallic gold films at temperatures substantially below those employed with compositions heretofore known in the art.

Gold decorating compositions are compositions that form a film of metallic gold when applied to various surfaces and heated. The gold compounds in such compositions have been derivatives of cyclic terpenes and sulfur, originally in the form of sul-foresinates and more recently in the form of cyclic terpene mercaptides. For example, gold decorating compositions containing gold sulforesinates prepared by reacting a gold salt with a sulfurized terpene such as sulfurized Venetian turpentine have been described by Chemnitius, J. Prakt. Chem. 117, 245 (1927). Gold cyclic terpene mercaptides have been described in US. Patent 2,490,399.

More recently, gold decorating compositions comprising gold primary, secondary and tertiary mercaptides have been developed as described in US. 2,994,614, US. 3,163,- 665 and US. 2,984,575. Certain of these gold mercaptides, particularly the secondary and tertiary mercaptides, provide certain advantages over the previously known gold compounds used in gold decorating compositions in that relatively low temperatures are required to form a metallic film therefrom, thus extending the use of such decorating compositions to a wide range of heat-sensitive substrates such as plastics, plastic laminates, wood, paper, textiles and the like. For example, the secondary gold mercaptides of US. 3,163,665 can be employed to produce decorative gold coatings at temperatures as low as 145 C., and certain of the gold tertiary mercaptide decorating compositions of US. 2,984,575 are converted into bright, conductive gold films by heating at temperatures of 150-160 C.

While certain of the known gold mercaptide compounds employed in gold decorating compositions can be converted to gold films at relatively low firing temperatures, it must be recognized that conversion of thin films of the decorating composition to gold films may require substantial periods of time, e.g. of the order of an hour or more, and that further advantages would accrue from availability of gold decorating compositions which can be more rapidly converted to gold films at temperatures heretofore employed. Additionally, gold decorating compositions which can be fired at even lower temperatures than heretofore employed in the art would be useful, e.g. in gold coating of temperature-sensitive materials such as heat-deformable plastics and the like.

It has now been discovered that the thermal decomposition of gold decorating compositions containing organic gold mercaptide compounds can be accelerated and/or 3,391,010 Patented July 2, 1968 effected at reduced temperatures by contact with a free halogen selected from the group consisting of iodine, bromine, and interhalo'gen compounds of iodine and bromine. The halogen agents which are used apparently destabilize the gold mercaptides so that gold films can be formed at lower temperatures. The halogen can be introduced, e.g. as vapors in a closed system, during firing. However, in a preferred embodiment of the invention, the gold formulations are mixed with the halogen just prior to application on a substrate in order to avoid undesirable destabilization of the gold solution in normal storage which would reduce the shelf life of the decorating solution. It should be understood, however, that the destabilization temperature of the halogen-containing solution will vary, depending upon the particular organic gold mercaptide compound employed, and that such solutions are within the scope of the invention.

The gold decorating solutions to which halogen agents are added according to the present invention are known per se, and generally comprise an organic gold mercaptide dissolved in a suitable organic vehicle. As hereinbefore described, such organic gold mercaptides may comprise gold resinates, cyclic terpene mercaptides, or primary, secondary or tertiary gold mercaptides of alkyl, cycloalkyl, aryl or aralkyl mercaptans. Generally speaking, the preferred mercaptans contain from one to about 20 carbon atoms in the molecule. 7

In addition to the gold compound, gold decorating compositions usually include a diluent therefor and may include a gold flux. The choice of diluent controls the behavior of the composition before firing and is dictated by the method by which the composition is to be applied. The diluent may be a simple solvent, but it will usually include mixtures of essential oils, terpenes, resins, and the like, carefully chosen to impart specific physical properties to the composition. These properties, such as oiliness, viscosity, evaporation rate, surface tension and tack, will vary for different methods of application. The requisite properties and the diluents required to produce them are well known to those skilled in the art of making enamels, paints and lacquers.

In addition to the diluent or solvent for the gold mercaptide, gold decorating compositions may contain a gold fiux which determines the behavior of the gold film during and after firing, and is usually dictated by the composition of the article to be decorated and the use for which it is intended. The gold flux usually includes salts or resinates of bismuth, lead, boron or silicon or mixtures thereof. Salts or resinates of chromium, cadmium, tin, copper, cobalt, antimony or uranium may be employed. The gold flux improves the adherence of the gold film and its resistance to abrasion and corrosive chemicals. Other ingredients may be added to alter the color of the gold film. Silver salts and resinates, for example, give a green gold, anildpalladi-um or platinum salts or resinates give a White go The halogen agent which is added to the gold decorating composition may be iodine, bromine or interhalogen compounds such as ICl, IBr, BrCl and the like. Generally, free chlorine and interhalogen compounds containing fluorine are to be avoided since they may adversely react with the containers and application equipment. The halogen agent is preferably dissolved in a solvent which is miscible with the gold decorating composition, e.g., ether, chloroform or the like, and the solution of halogen agent added to provide from about 1% to about by weight, of halogen agent, based on the Weight of gold in the mixture.

As mentioned hereinbefore, the addition of the halogen agent to the gold decorating composition lowers the temperature at which the gold mercaptide can be converted to metallic gold. While the halogent agent can EXAMPLE 1 A gold decorating solution containing 1.87% by weight gold was prepared by admixing the following (all percentages by weight):

Percent Ether 78.15 Gold t-dodecyl mercaptide solution in n-heptane and chloroform containing 28% gold 6.65 n-Hexanol 4.00 IBr in chloroform (10%) 11.20

The gold solution was sprayed on a thin (0.0 thick) sheet of cellulose acetate and heated by means of an infrared lamp held about /2 inches from the sample. A gold coating with a highly reflective surface was developed in 5-10 minutes, and the temperaturesensitive substrate (deformation temperature 100 C.) was not deformed. Similar films were developed on this substrate in constant temperature ovens at 80-90 C.

EXAMPLE 2 A gold solution containing 3.75% by weight gold was prepared by admixing the following:

Percent Ether 66.10 Gold t-dodecyl mercaptide solution in n-heptane and chloroform containing 28% gold 13.35 Oil of peppermint 4.00 IBr in chloroform (10%) 16.55

Thin sheets of cellulose acetate were immersed in this solution and heated at 80-90 C. to produce highly reflective gold films.

4 EXAMPLE 3 The following gold solution containing 2% gold was sprayed on a thin sheet of cellulose acetate:

Percent Oil of peppermint 6.25 Gold t-dodecyl mercaptide solution in n-heptane and chloroform containing 28% gold 7.13

Chloroform 86.62

The coated substrate was exposed to radiation from a 250 watt infrared lamp at adistance of 8 inches. After 10 minutes, a dark film having some metallic appearance, but containing large iridescent purple areas, resulted. This film had only slight electrical conductivity, indicating that considerable organic matter was present in the film. Further heating under the same conditions resulted in extreme deformation of the substrate without significant improvement in the film.

EXAMPLE 4 A gold solution containing 1.87% by weight gold was prepared from the following:

Percent IBr in chloroform (solution of 10%) 1.35 I in chloroform (solution of 2.6%) 0 64 Ether 8736 Oil of peppermint 4.00 Gold t-dodecyl mereaptide solution in n-heptane and chloroform containing 28% gold 6.65

This solution was sprayed on a thin sheet of cellulose acetate and heated in an oven at C. for 1 /2 hours. A highly reflective gold film was formed on the substrate.

EXAMPLES 5-18 A series of gold decorating solutions containing various organic gold rnercaptides was prepared and tested for their ability to deposit a decorative metallic gold film. In each case, the solutions were applied to either a thin cellulose acetate sheet or, for higher temperature trials to glazed porcelain and the coated substrate placed in a preheated oven at the indicated temperature for the time period indicated. The composition of the solutions and the results are shown in the following table.

Example Composition Weight Temp., C. Time (Hrs.) Quality of Film Percent Gold-Z-pinanyl mercaptide 6. 0 2. 5 No gold deposit. 5 Benzene 90. 0 O11 ot'pepperrnint... 4.0

(Total gold 2.4%.) glution of Example 5 87. 0 120 2. 5 Bright gold, conductive.

r 0. 13 6 Ohloroform 12. 87

(Total gold 2.1%.) Gold dlphenylmethyl meroaptide... 4. 0 2. 5 No gold deposit. Toluene. 50. 0 300 1 Do. 7 1. Ether 40. 0 400 1 Bright gold, conductive.

Oil of peppermint" 6.0

(Total gold 1.9%.) Gold diphenylmethyl mercaptide 4. 0 Bright gold. Eth 40. 0 150 2. 5 Ohlorolorm 47. 97 8 Oil of peppermint 6. 0

I 63 IBr 1. 40

(Total gold 1.9%.) Gold-l-methyldodecyl meroaptide in toluene 8. 0 120 1 No gold deposit. Ethel 50. 0 150 1 Do. 9 Ohloroform 38. 0 Oil of peppermint 4. 0

(Total gold 2.2%.) Solution of Example 9 Bnght gold, conductive. 1o IBr Do.

"""""""""""" Cholroform (Total gold 1.9%.) Gold-p-tert.-butyl phenyl mereaptide 6. 0 150 1 No gold deposit. Ether 50.0 11 Chloroform 40. 0 Oil of peppermint 4. 0

(Total gold 3.3%.) Solution of Example 11 87. 00 120 1 Bright gold, conductive. 12 I131 13 150 Do.

Chloroform 12. 87

(Total gold 29%.) GoId-tert.-tetradeeyl mercaptide 6. 0 150 1 N 0 gold deposit. Ether 50. O 300 1 Bright gold, conductive. 13 Chloroform 40. 0 Oil ofpeppennin 4.0

(Total gold 2.6%.

Example Composition Weight Temp., C. Time (Hrs) Quality of Film Percent Solution of Example 13 87. 120 1 Bright gold, not conductive. 14 IBr 13 150 Bright gold, conductive.

""""""""""" Chlorotorm 12.87

(Total gold 2.3%.) Gold-tert.-nonyl mercaptide 7. 150 1 No gold deposit. Ether 50. 0 300 1 Gold, conductive. 15 Chloroform 37. 5 011 of peppermmg- 5. 0

(Total gold 4.0%.) Solution of Example 15 87. 00 150 1 Bright gold, conductive. 16 1B1 13 Chloroform- (Total gold 3.5%.) Gold alpha-methylbenzyl mercaptide 4.0 120 1 No gold deposit. 17 Benzene 90.0 150 1 Do.

""""""""""" Oil ofpeppermint.-. 6.0

(Total gold 2.0%.) Solution of Example 17... 87. 00 120 1 No gold deposit. 18 IBr .13 150 1 Bright gold, conductive.

""""""""""" Chloroform r 1 .87

(Total gold 1.7%.)

The results shown in the table demonstrate that gold decorating compositions containing various gold mercaptide compounds are converted, in the presence of added halogen, to bright conductive gold films more rapidly and at substantially lower temperatures than are effective in the absence of the halogen agent.

What is claimed is:

1. A gold decorating composition comprising an organic gold mercaptide dissolved in an organic vehicle, said gold mercaptide being selected from the group consisting of gold resinates, cyclic terpene mercaptides, and primary, secondary, and tertiary gold mercaptides of alkyl, cycloalkyl, aryl, and aralkyl mercaptans containing from 1 to about 20 carbon atoms in the molecule, and said composition containing from about 1% to about 100% by weight, based on the weight of gold, of a free halogen selected from the group consisting of iodine, bromine and interhalogen compounds of iodine and bromine.

2. Composition of claim 1 wherein the mercaptide is a gold terpene mercaptide.

3. Composition of claim 2 wherein the organic gold mercaptide is gold Z-pinanyl mercaptide.

4. Composition of claim 1 wherein the organic gold mercaptide is a tertiary alkyl mercaptide having up to 20 carbon atoms in the molecule.

5. Composition of claim 4 wherein the tertiary mercaptide is t-dodecyl gold mercaptide.

6. Composition of claim 4 wherein the gold mercaptide is t-nonyl gold mercaptide.

7. Composition of claim 4 wherein the gold mercaptide is t-tetradecyl gold mercaptide.

8. Composition of claim 1 wherein the organic gold mercaptide is a gold secondary alkyl mercaptide having up to 20 carbon atoms in the molecule.

9. Composition of claim 1 wherein the organic gold mercaptide is a gold aryl mercaptide having up to 20 carbon atoms in the molecule.

organic gold I 10. In the method for forming a decorative gold film by coating a substrate with a gold decorating composition containing an organic gold mercaptide selected from the group consisting of gold resinates, cyclic terpene mercaptides, and primary, secondary, and tertiary gold mercaptides of alkyl, cycloalkyl, aryl, and aralkyl mercaptans containing from 1 to about 20 carbon atoms in the molecule, and heating the coated substrate to thermally decompose the gold compound to metallic gold, the improvement of effecting said thermal decomposition of the gold compound in contact with a free halogen selected 'from the group consisting of iodine, bromine and interhalogen compounds of iodine and bromine.

11. In the method for forming a decorative gold film by coating a substrate with gold decorating composition containing an organic gold mercaptide selected from the group consisting of gold resinates, cyclic terpene mercaptides, and primary, secondary, and tertiary gold mercaptides of alkyl, cycloalkyl, aryl, and aralkyl mercaptans containing from 1 to about 20 carbon atoms in the molecule, and heating the coated substrate to thermally decompose the gold compound to metallic gold, the improvement of adding to the gold decorating composition prior to use thereof of a free halogen selected from the group consisting of iodine, bromine and interhalogen compounds of iodine and bromine, such free halogen being added in the amount of 1% to about by weight of halogen based on the weight of gold.

References Cited UNITED STATES PATENTS 2,984,575 5/1961 Fitch 106l 2,994,614 8/1961 Fitch 106-1 3,092,504 6/1963 Langley et al. 106l 3,245,809 4/1966 Fitch 106-1 JAMES A. SEIDLECK, Primary Examiner.

L. B. HAYES, Assistant Examiner.