PL168425B1 - Composition of noble metals, method of depositing a coating of such composition on a substrate and decalcomania containing such composition - Google Patents

Abstract

FIELD: chemical industry. SUBSTANCE: compositions which form noble metal films are useful for preparing decorative coatings from ceramic or glass substrates. The homogeneous composition comprises polymeric resin, 3-22 wt % of mercapto compound of gold, water and cosolvent. In this case, as composition gets dry on substrate and becomes gradually heated during roasting operation, water evaporates to form homogeneous composition of resin and mercapto compound of gold in cosolvent. Then, as cosolvent evaporates, it forms homogeneous composition of mercapto compound of gold in resin, and mercapto compound of gold decomposes to form gold, and resin evaporates simultaneously. EFFECT: improved properties of the homogeneous composition. 24 cl, 23 ex

Description

The present invention relates to a homogeneous composition for producing a noble metal coating on a substrate after firing.

Compositions that form a coating of noble metal (which herein are meant to be one or more metals selected from platinum, palladium, gold and silver) when fired are particularly useful for decorating ceramic or glass substrates.

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Commercially available liquids for this purpose are based on organic solvents and are complex mixtures containing (a) a noble metal compound that decomposes upon firing to form a noble metal, (b) metal compounds such as rhodium, bismuth or chromium, to improve the color, adhesion or gloss of the fired coating, and (c) a resin and an organic solvent for solvent (a) and (b) or as carriers (a) and (b).

It would be desirable to reduce or eliminate the organic solvent so as to reduce or eliminate the risk of environmental contamination posed by its presence, e.g., during the manufacture, transportation or use of a composition containing it, e.g. from fumes released after application of the composition or its firing. However, this is not a simple task as the compositions still need to be stable, easy to apply and have good coatings after firing. A water based composition rather than an organic solvent would have the added advantage that materials such as screen printing brushes or screens or stencils with which the composition is in contact could be cleaned with aqueous cleaners. Despite these advantages, the applicant is not aware of a gold composition providing glossy coatings which is an aqueous solution.

The object of the invention is to provide a composition containing water as a solvent.

British Patent Specification No. 2,097,811 discloses an overglaze paint for pottery which contains 15-40% by weight of polyvinylpyrrolidone or a mixture of polyvinylpyrrolidone and an aqueous solution of polyethylene oxide, 45-85% by weight of ethylene glycol and / or propylene glycol and optionally water. The description lists the coloring substances which may be oxides, gold and organic gold compounds.

It is known from British Patent Specification No. 2,216,536 to a polishable coating gold composition comprising 10-40% by weight of gold in the form of a powder and / or a poorly soluble gold compound, 2-20% by weight of polyvinylpyrrolidone, 3-30% by weight of water. an acrylate resin dispersion containing 30-60% by weight solids and 5-50% water.

The present invention relates to a homogeneous composition which forms a coating of noble metal on a substrate when fired, which is one or more metals selected from platinum, palladium, gold and silver. The composition according to the invention comprises a polymeric resin and a noble metal thiolate solution in water and a co-solvent in an amount of 3-22% by weight, the water content being up to 85% by weight.

The cosolvent, the resin, and the thiolate are such that as the composition on the substrate dries and is gradually heated during firing, the water evaporates to leave a homogeneous composition of the resin and thiolate in the cosolvent, then the cosolvent evaporates to leave a homogeneous composition of the thiolate and resin, and then the thiolate decomposes. to precious metal while the resin evaporates.

The formation of a noble metal coating on a substrate consists in applying the composition to the substrate, drying and firing the applied composition.

The composition may also be dried on a transfer substrate to make decals.

Some of the thiolates are new compounds, especially thiolate, which is a gold compound with the formula AuSR or its salt, where R has the meaning that HSR is 4,6-dihydroxy-2-mercaptopyrimidine or N- (mercaptoalkanoyl) glycine, wherein the alkane group contains 1 or 2 carbon atoms.

The method of producing the new thiolane consists in reacting a compound of formula AuCl (SR2) in a solvent with a thiol of formula HSR to form a gold sulfide of formula SR'2 in a solution of the compound.

The method of producing the new thiolate also involves the reaction of a tetrahalo-thiol with a HSR thiol to produce a gold compound.

Moreover, the method of producing a new thiolate consists in reacting a thiol of formula HSR with a complex of amine and gold (I) of formula R'2 NH-Au-Hal, in which Hal is a halogen atom and each of the substituents R 'which are the same or different, means an aliphatic group,

An aromatic or heterocyclic or two R 'groups together with the N atom represent a cyclic amine.

Although the composition of the present invention contains a co-solvent, it is a water-based composition. It can be diluted with water (water dispersible composition) and does not need to contain as much organic solvent as conventional liquid noble metal compositions. It is easy to apply and forms good coatings after firing.

It is surprising that a water-soluble (non-colloidal) noble metal compound can be used. The invention is based on the discovery that it can be used if the compound is a soluble thiolate and when the composition is gradually heated during firing, the noble metal compound remains in a homogeneous composition, preferably in solution, until the noble metal compound decomposes to form that metal, while the matrix, which is the carrier, evaporates.

For clarification, the invention is described as a heating process that leaves a homogeneous composition, preferably a noble metal thiolate solution in a co-solvent, and then a homogeneous composition, preferably a thiolate resin solution. It should be recognized, however, that the structure of the thiolate may change upon heating, but it is important that the noble metal compound, regardless of its later form, remains in a homogeneous composition, preferably in solution. Likewise, the resin may break down on volatilization.

The composition according to the invention remains homogeneous upon heating such that the thiolate does not precipitate prior to decomposition to the noble metal, while the resin volatilizes. In the starting composition, the thiolate is in solution, and preferably remains in solution during heating until it decomposes to a noble metal while the resin volatilizes. Preferably the composition comprises a solution in water and a co-solvent of a polymeric resin and a noble metal thiolate, the composition containing 3-22% by weight of the noble metal thiolate, and the co-solvent, resin and thiolate are such that when the composition on the substrate dries and is gradually heated during firing , the water evaporates to leave a solution of the resin and thiolate in the cosolvent, then the cosolvent evaporates to leave the thiolate solution in the resin, and then the thiolate decomposes to the noble metal and the resin volatilizes.

The composition according to the invention usually contains 5-85% water. Percentages are weight percentages. The composition can be diluted with water before use. The composition preferably comprises 15-70%, especially 40-55% water. It is particularly preferred that the composition comprises more water than the total of all organic solvents.

The precious metal usually includes gold or platinum, especially gold. Specific examples are:

a) gold, b) platinum, c) gold and platinum, d) gold and palladium, e) gold, platinum and palladium, and f) any of the metals a) -e) and silver.

Preferably, the noble metal is a), b), d) or any of them and silver.

The thiol is an organic compound that is an alcohol analog in which the oxygen atom in the hydroxyl group is replaced with a sulfur atom. The metal thiolate is a thiol derivative in which the hydrogen in the SH group is replaced with a metal atom. The noble metal thiolate must form a solution in the water / co-solvent mixture and must fulfill other desired functions. Usually the thiolate employed solubility in water at 293 K is at least ΐ0θ, preferably 200 - 300 g per dm ^3.

Preferably, the thiolate, usually in the form of a salt, is soluble in water alone. Preferably, a noble metal, especially gold, thiolate begins to decompose to a noble metal above 473K; such thiolates tend to form glossy rather than dull coatings after firing. Suitable thiolates are known compounds.

The thiolate may be aliphatic, aromatic or heterocyclic and preferably contains at least one group selected from nitro groups and groups of the formula -COOH, -SO2OH, -OH, -CONH2, -HN2 and -O-P (O) (OH) 2, in which the hydrogen atoms are optionally substituted, or their salts. Such thiolates are discussed below with reference to gold as the precious metal. Thus, a preferred group of thiolates are gold compounds with the formulas:

Au-SRH or Au-SRX or a salt thereof, in which X is a nitro group or a group of the formula -COOH, -SO2OH, -OH, -CONH2, -NH2 or -OP (0) (OH) 2, in which the hydrogen atoms are optionally substituted and R is a divalent organic group.

While gold compounds are typically described as single-core compounds of the formula Au-S-R-X, it should be understood that they may indeed have a multi-core formula and may be in the nature of 2-coordination gold (I) complexes.

The substituent on the X group will typically be an aliphatic, aromatic or heterocyclic group, or an optionally substituted amino group, e.g. mono or disubstituted with alkyl of 1-6 carbon atoms. The aliphatic group is typically an alkyl group of 1-6 carbon atoms, e.g., ethyl, isopropyl or n-butyl. The aromatic group is an optionally substituted phenyl wherein the common substituent is X as defined above, an alkyl of 1-6 carbon atoms, or a mercapto group in which the hydrogen atom is usually 'replaced with gold. The heterocyclic group is typically an optionally substituted purine, pyridine, or pyrimidine, and the substituent typically is X as defined above, an alkyl of 1-6 carbon atoms, or an aromatic group as described above. The group -CO.NH2 or -NH2 may be mono- or disubstituted, e.g. with an alkyl of 1-6 carbon atoms optionally substituted with X as defined above.

When R is a divalent aliphatic group (i.e. the group attached to S is aliphatic and not aromatic or heterocyclic), it will normally be a divalent hydrocarbon group with 1-7 carbon atoms (e.g. derived from an alkane with 1-6 carbon atoms or from toluene) optionally substituted with X which is as defined above, typically with one X or oxo group on a non-terminal carbon. When R is a divalent aromatic group (i.e. the group attached to S is aromatic rather than aliphatic or heterocyclic) it will typically be a benzene-derived divalent group optionally substituted with X as defined above, typically with one substituent X. When R is a divalent heterocyclic group ( i.e. the group linked to S is heterocyclic and not aliphatic or aromatic); usually it is a divalent group derived from pyrimidine, purine or pyridine, optionally substituted with X, as defined above (usually with one X) and / or phenyl (usually no more than one) and / or alkyl of 1-6 carbon atoms (usually no more than one such alkyl group).

X is preferably -COOH.

In a particular embodiment of the invention -RX is -CH2CH2X, -CH / CH3CO.NH.CH2X, -CH2CH2CO.NH.CH2X, -CH2C6H4-pX, -CH2COCH2CH2X, -CH / X / CH2X, -CH2CH / NH2 / X, -CH2CO .NH.CHX.CH 2.-C 3H 3N2, -CH 2CO.NH.CH 2CH 2CO.NH.CHX.CH 2.C 3H 3N2, -CH2CONH.CH2CH2CO.NH.CH2CO.NH.CH2X, -CH2CH / CO.NH.CH2XNH.CO.CH2CH2CH / NH2 / X or -CS.N / CH3 / CH2CH2X where X. is -COOH, C6H4 is a divalent group derived from benzene and C3H3N is imidazol-4-yl.

In another embodiment, -R-X is a -CH2CH2X or -CH2-C6H4-p-X group, wherein X is a nitro group or a group of the formula -SO2OH, -OH or -NH2, and C6H is a benzene-derived divalent group.

In yet another embodiment, the gold compounds of formula Au-S-R-H or Au-S-R-X, H-S-R-H, or H-S-R-X are:

4,5-diamino-6-mercapto-2-phenylpimidine, 2-amino-6-mercapto-8-methylpurine, 2-mercapto-4-aniiio-pyridopyrimidine, 2-mercaptopyridine, 2-mercaptobenzoxazole, 2-mercaptobenzimidazole, 5- mercapto-1-methyltetrazole, 4-mercaptopyridine, 2-mercapto-5-nitrobenzimidazole, or 4-amino-6-hydroxy-2-mercaptopyrimidine.

The sulfur atom bound to the gold atom in a preferred class of gold compounds is bound to the same carbon atom to which the substituted amide group is bound or is separated from that atom by one carbon atom, yes. that these compounds contain a group of formula 1 or 2.

Specific examples of this class of gold compounds are provided. compounds of the formula Au-S-R-H or Au-S-R-X which are such that they correspond to H-S-R-H or H-S-R-X which are:

N- (2-mercaptopropionyl) glycine, N- (3-mercaptopropionyl) glycine, N- (2-mercaptoacetyl) glycine, 2-mercaptoacetyl-L-histidine or 2-mercaptopropionyl-L-histidine.

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Another preferred class of gold compounds are compounds of Formula III, wherein n is 0 or an integer of at least 1, and Y is hydrogen or an alkanoyl group of 2-6 carbon atoms, which optionally may include one amino (carboxy) group. methyl If an amino / carboxy / methyl group is present, it is usually an alkanoyl group at the terminal carbon atom - Typically n is 0 or an integer 1-4 A specific example of this class of gold compounds are compounds of the formula Au-SRH or Au-SRX which are such that corresponds to HSRH or HSRX which are acetylcysteine, glutathione or L-cysteine A preferred gold thiolate is N- (2-mercaptopropionyl / glycine gold (I) of formula 4, which may alternatively be represented as a zwitterion of formula 5, although it is believed that the thiolate is should be multi-core as explained above. Reference is made to British Patent Specification No. 2,047,672 for this gold thiolate. This description is not related to the formation of the coating, but to the production of m of liquid containing ⁹⁵ m Au, adsorption of ^m Hg on a certain adsorption agent and then elution of the radioisotope derivative ^ "Au- In table 1 on page 5 of the above-mentioned description, combinations of adsorption agents and eluents are listed, and among the eluents is an aqueous solution of mercaptopropionylglycine- W the description does not show a specific use of this eluent and no specific data is given for the present gold thiolate - Example 2 describes a series of experiments in which liquids containing ¹⁹⁸ Au are passed through adsorptive agents - The example explains that the ¹⁹ 8 ^m Au isotope was used instead of a radioisotope ^{The ratio of} Au due to, inter alia, the short half-life of ^ "Au In the example it was found that liquids were prepared by dissolving 1-3 µg of gold containing ^1M Au in 1 cm ^{3 of an} aqueous solution having a pH of about 5-6 and containing 0.001-0 1 mole of one of the compounds in the table, called gold ion complexing agents - One of these agents is mercaptopropio nylglycine and the table shows that using it together with the SiOi / Ag adsorption agent leaves 88% ^1% Au unabsorbed - We believe that using mercaptopropionylglycine as a complexing agent would not give this gold thiolate but gold with residues strongly adsorbed on the metal surface and therefore not containing one gold atom per N- / 2-mercapto-propionyl / glycine ligand as is the case with the present gold thiolate In this specification, the disclosed or proposed gold-containing materials are radioactive - These materials would decay, becoming progressively less radioactive, but some radioactivity would remain - The gold in the gold thiolates used in the present invention is preferably naturally occurring gold which is not radioactive - Therefore preferably the gold in the present N- (2-mercaptopropionyl / glycine gold (I) or its salt is non-radioactive (and therefore not is a mixture of a non-radioactive form with a radioactive one) - Preferably all Any thiolates present, not only N- (2-mercaptopropionyl / glycine gold (I) or its salt, are non-radioactive. The optionally substituted sulfo group (-SO2OH) which may be X in these gold thiolates introduces more sulfur, which usually forms sulfur oxides during firing the composition to form a coating, whereby the meanings of X are less preferred - The nitro group and the optionally substituted hydroxyl group tend to form a thiolate that is less water soluble and less resistant to reduction, so X is less preferred - Typically X is most preferably represents an optionally substituted carboxyl group. Thiolane may be in the form of a salt. Salts may be prepared with bases via e.g. a carboxyl or sulfone group which are X-Thiolane which forms a salt with a base may be used in a basic solution in which a salt is formed. salt with ammonia or with an organic base, especially with an optionally substituted amine, wherein p the substituent is np-alkyl of 1-6 carbon atoms, optionally substituted with X groups, as defined above Particularly interesting substituted amines are triethylamine, ethanolamine, diethanolamine, triethanolamine, pyridine, morpholine or diisopropylamine, especially the first four of these New thiolates used in the present invention may prepared by known methods - When the thiolate is to be in the form of a salt, it can be prepared, for example, by reaction with a base.

When the thiolate is a gold compound of the formula AuSR or a salt thereof, where R is such that the HSR is N- (mercaptoalkanoyl / glycine) where the alkane group contains and or 2 carbon atoms, the N- / mercaptoalkanoyl / glycine may be:

N- (2-mercaptoacetyl) glycine, N- (3-mercaptopropionyl) glycine, or N- (2-mercaptoacetyl) glycine.

The glycine listed last is particularly suitable.

The thiolates can be prepared by the general method of A.K. Al-Sa'ady et al. Inorganic Synthesis, vol. 23, 191 (1985), determined by a general equation for gold.

[AuCl4 '+ 2SR' ₂ -> [AuCl (SR) ' ₂ ] + R' ₂ SO + 2HCl + Cl · [AuCl (SR ' ₂ ) j + HSR -> AuSR + HCl + SR'2

Au (III) in the form of the tetrachlorosilatate anion is reduced to Au (I) with a water-soluble sulfide of formula SR ' ₂ . The radicals R 'are the same or different and are preferably methyl, ethyl or 2-hydroxyethyl. Preferably the water-soluble sulfide is ethyl 2-hydroxyethyl sultide. Addition of a suitable thiol ligand via the HSR thiol, usually at ambient temperature, produces a good thiolate, usually as a white solid, although in the case of mercaptosuccinic acid as a yellow solution. The solvent used in the reaction is usually water, ethanol or isopropanol, preferably water, so that the soluble inorganic salts (e.g., NaCl) can be extracted by washing with water. The yields of gold thiolates can be as high as 80% or more (based on gold) with the residue being water soluble. The produced gold thiolates can be dissolved in water by adding a base, usually an organic base, e.g. an optionally substituted amine, to form the corresponding salt, in this case a substituted ammonium salt.

Gold thiolates can also be prepared by reacting a tetrachloro goldrate (especially a tetrachlorohydrate or tetrabromotholate) with a thiolate of formula HSR to produce a gold compound.

They can also be prepared by reacting a thiol of the formula HSR with a complex of the amine and gold of the formula R '"HNH-Au-Hal, where Hal is a halogen atom (preferably a chlorine or bromine atom) and each R" "is the same or different and is an aliphatic, aromatic or heterocyclic group, or preferably two R "" substituents together with the nitrogen atom represent a cyclic amine (such as benzotriazole or pyridine) to form a gold compound. The aliphatic, aromatic, or heterocyclic group that is R "" may be a group as discussed above as substituents in X.

The thiolates can also be generated in situ in the composition of the invention, e.g. by salification therein, e.g. as described above.

The composition according to the invention contains 3-22% of the noble metal in the form of a thiolate. The composition preferably contains 8-12% of noble metal, especially gold, in the form of thiolate. The composition usually comprises 10-40%, preferably 14-26%, of a thiolate, especially gold thiolate.

The polymeric resin must form a homogeneous composition with the other ingredients and must also meet the other desired characteristics. The resin preferably forms a solution in a mixture of water and a co-solvent, although it may form a dispersion or emulsion therein. Preferably, the resin is soluble or forms a clear dispersion in water itself. Suitable resins are known. Polyacrylic, polymethacrylic, polyvinylpyrrolidone, cellulose polyether, polyamide, polyethylene glycol, polyester, polyacrylamide, polyvinyl acetate, polyvinyl alcohol, alkyd, polyamine or polyurethane resins or mixtures thereof can be used. The resin may be in the form of a copolymer or a graft polymer. The resin may contain solubilizing groups, especially carboxylate and / or hydroxyl and / or amine, especially carboxylate, which increase the solubility of the resin in water. Preferably, the resin comprises one or more, usually one, polyvinylpyrrolidine resin, polymethacrylic resin and polyether cellulose, e.g. one or more, usually one, polymethacrylic resin and polyether cellulose. The resins tend to volatilize strongly in the temperature range used, more readily than all substances at the same temperature. Preferably, the resin is selected such that at least a major portion of it volatilizes in the range of 473-823K. Preferably the resin comprises polyvinylpyrrolidone, polymethacrylic resin, or polyether cellulose, which volatilize mostly in this range.

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The resin must satisfy the condition that, after firing, the thiolate forms a homogeneous composition therein, preferably a solution, whereupon the thiolate decomposes into the noble metal and the resin volatilizes. For example, if a composition similar to the inventive composition includes auramericaptosuccinic acid which decomposes to gold at about 423K, and the resin begins to evaporate at about 473-573K, no homogeneous composition (e.g. solution) of the thiolate is formed upon firing. in resin. Instead, gold disperses the resin prematurely. A cloudy coating forms. However, the same resin can be used successfully and create shiny gold coatings with the thiolate with which it meets these requirements; and the same thiolate can be used successfully and create shiny gold coatings with the resin with which these requirements are met. Na N- (2-mercaptopropionyl) glycine gold (I) starts to decompose at about 473K and decomposes to gold at about 473-573K; therefore it can be successfully used for the preparation of shiny gold coatings with resins which volatilize at about 553 - 573K and which could not be used with auramercaptosuccinic acid.

The composition of the invention may contain less than 5% resin, but typically 5-45%, especially 7-13% resin. The weight ratio of solid resin to noble metal, especially gold, in the thiolate may be e.g. at least 1: 1, e.g. at least 1.2: 1, e.g. at least 1.5: 1, since these ratios result in better free from foam and brighter films after firing. However, satisfactory glossy coatings with ratios of 0.1: 1 to 1.5: 1 were also obtained. In a typical composition, the ratio is 1: 1.

The co-solvent must, together with the water, dissolve the noble metal thiolate and form a homogeneous composition, preferably with the solution, with the resin, and must also meet other required requirements.

The co-solvent preferably boils at 373-553K, e.g. 373-493K. A preferred group of co-solvents are water-miscible alcohols, ethers or esters, especially water-miscible alcohols. Preferably the co-solvent comprises 1,2-propanediol, 1,3-propanediol, n-butanol, tetrahydrofuran acetate, glycerin, glycerol diacetate or ethyl lactate, especially 1,2-propanediol, 1,3-propanediol or ethyl lactate. The co-solvent may affect the gloss of the film after firing.

The composition usually comprises 5-45%, preferably 15-30%, e.g. 25-30% of a cosolvent.

It should be understood that the nature of the ingredients and their amounts are interdependent and that any potential material can be easily tested. For example, it has been found that when a cellulose resin is used as the resin, the cosolvent content of the composition is preferably 25-30%, while when an acrylic or methacrylic resin is used, the cosolvent content is preferably 15-30%.

The composition may contain a minorly added metal compound, such as palladium (e.g., palladium sulfate), rhodium, bismuth or chromium compounds, usually used in combination to improve the color, adhesion or gloss of a fired film, especially on pottery. A minority addition of a metal compound for the films, especially on glass, can be, for example, silver, vanadium or silicon compounds. For glossy coatings, additives are usually used in solution in the composition. The total content may be, for example, 0.01-5%, typically 0.1-0.4% of the composition. Such additives and their amounts and action are known and used in conventional liquid organic solvent based noble metal compositions.

Known metal compounds used as minor additives which are soluble in the mixture of water and the cosolvent according to the invention may be used, e.g., chromium trioxide or [CH2SO4], bismuth ammonium citrate or bismuth lactate; [RhCl (ox) (NH3)], [Rh (gly) 3], [Rh2 (oc ^ t ^; an) z ^ j, I '^ ił3fB ^ hi ((^ O3) Gj or [Rh (acac) COJ; MeaSiOMe; or [vO (acac) 2] wherein acac is acetylacetonate, ox is oxalate and gly is glycinate A particular embodiment uses rhodium, bismuth or silver as the same thiolate as the noble metal thiolate, e.g. - (2-mercaptopropionyl) glycine silver Thus, when the noble metal thiolate is a gold compound of formula Au-SRX or a salt thereof, the minor addition of rhodium may have the formula [Rh (SRX) 3j.

The composition must be homogeneous for ease of use, etc. In order to improve the rheology of the composition and to control the drying of the applied coating, the composition may contain an additional solvent such as a water miscible alcohol, e.g. isopropanol or n-hexanol water miscible. a ketone, e.g. butanone, or a water-miscible solid, e.g. 1,6-hexanediol. The additional solvent content is preferably 5-10% of the composition. The composition may contain a surfactant, e.g. in an amount of '0.05-0.5%, e.g. to improve brush applicability of the composition.

A specific composition according to the invention consists essentially of:

Polyvinylpyrrolidone 7-313%

Gold thiolate 14 - 263c

1.2- propanediol 15-33%

Water 40 - 55%

Isopropanol 5 - 10%

Minor metal additions 0.1 - 0.4%

A preferred composition of the invention consists essentially of:

Polyvinylpyrrolidone 7-13%

Gold thiolate 14 - 2 6 * 6

1.2- propanediol 15-03%

Ethyl lactate 15 - 30%

Water 30 0 - 5%

Isopropanol 5 - -003

Minor metal additions 0.1 - 0.4%

The composition of the invention may be UV curable due to the presence of a polymeric resin, which may be UV curable, or it may be thermally curable due to the presence of a thermosetting polymeric resin.

The polymeric composition can be applied to substrates and fired by any method known to them, and this is an advantage of the invention as conventional equipment and techniques can be used. The substrate on which the firing is carried out is preferably ceramic, such as tableware and arts, or glass. The composition can be applied directly to the substrate. Alternatively, it may be applied in the form of a desired pattern (e.g., a decorative pattern) to a transfer substrate, dried thereon to form a decal, which can then be used in the usual manner to transfer the pattern to a substrate, such as a ceramic substrate, on which it is fired. The composition can be applied e.g. by brush, steel or neoprene wheel, or by printing, e.g. injection printing, but preferably by mesh printing. The individual components of the composition correspond to a specific application procedure, and the specific composition used also depends on the procedure of its application, taking into account e.g. the desired rheology. The applied composition is typically dried, e.g., at ambient temperature, prior to firing. However, drying may be part of the heating step during firing. The compositions of the invention are typically fired at 473-1173K, 733-923K on a glass substrate, 923-1173K on a ceramic substrate, and 473-623K on a plastic substrate.

The composition according to the invention gives good coatings. Precious metal coatings are divided into 3 classes: polished, self-polished and glossy. Polished coating compositions that the name implies must be polished to provide the desired coating include a noble metal powder or, in some cases, an insoluble noble metal compound. The fired coatings usually contain more precious metal by weight than is needed for glossy coatings, but are cloudy and show little reflection. After firing, they are polished by mechanical abrasion, such as sand and water, to give them a matt appearance. Self-polishing coatings have recently been introduced. They contain an insoluble matting agent that gives the fired coating the appearance and durability of a polished coating without the need for polishing. The glossy coating compositions contain a soluble noble metal compound. Fired coatings give a very good reflection, often having mirror properties. The compositions of the invention may be of any of these types. Preferably, they provide a glossy coating after firing. The composition may additionally contain a powdered noble metal or an insoluble noble metal compound and then, after firing and polishing, produces a polished coating. Alternatively, compo10

The invention may additionally contain an insoluble matting agent and provide a self-polishing coating after firing.

The composition of the invention is preferably used for decorating a substrate, e.g. for making a decorated tableware. The composition can be used in electronics, e.g. to lay electrically conductive tracks on insulating materials.

The invention is illustrated by the following examples in which the rhodium complex has the formula Rh (acac) CO, where acac is acetylacetonate, the cellulose polyether is Natrasol resin from Aqualon Limited, UK, the polymethacrylate resin is Versicol K11 resin from Allied, unless otherwise stated. Colloids, Bradford, UK, polyvinylpyrrolidone is manufactured by Aldrich Chemicals, UK, and all coating compositions are in the form of solutions unless otherwise stated. Unless otherwise stated, the compositions were brush applied to glazed porcelain and then heated to a maximum temperature of 1053K for a 1 hour firing cycle with a 10 minute soak at maximum temperature.

Example 1 N- (2-mercaptopropionyl) glycine gold (I) was prepared in a 1000 cm 3 round bottom double neck flask as follows:

To a solution of 20.5 g of ethyl 2-hydroxyethyl sulfide in 200 ml of distilled water was slowly added to a solution of 35 g of sodium tetrachloro-solution in 200 cm3 of distilled water. After adding 5.21 g of solid mercaptopropionylglycine and stirring vigorously, mercaptopropionylglycine gold was obtained as a white solid in a yield of 85% in terms of gold.

Analysis: theoretically C 16.8 N 3.9 Found: C 16.15 N 3.65% Melting point: 503K (with decomposition)

Examples II-IV (comparative). Analogously to the method of Example 1, L-cystein gold, aura-2-mercaptoethanesulfonic acid and 2-mercaptoethanesulfonic acid and 2-mercaptopyridine gold were produced, each with a yield of more than 80% in terms of gold.

Example 5 (comparative). Auramercaptosuccinic acid was prepared in an analogous manner to Example 1, except that isopropanol was used instead of water and the gold complex was soluble in isopropanol, so it was isolated by evaporating the solvent under reduced pressure of 13.33 Pa and then triturating the resulting oil with diethyl ether and a white precipitate was obtained with a yield greater than 80% in terms of gold.

Example VI (comparative). 4-hydroxythiophenol gold was prepared by the method analogous to example 1 with a yield of more than 80% in terms of gold.

Analysis on C: theoretically 22.3% found: 22 ^%

Example VII. 4,6-dihydroxy-2-mercaptopyrimidine gold was prepared by the method analogous to example 1 with a yield of more than 80% in terms of gold:

Analysis on C: Theoretically 11.99% Found: 11.2%

Example VIII (comparative). The following composition was prepared by mixing the ingredients:

Parts

Cellulose polyether 10

Gold bis (ethylenediamine) chloride 22 (10.1 parts gold)

1,3-propanediol 15

Water 38

Isopropanol 15

Rhodium complex 0.05

Chromium trioxide 0.0) 0

In the examples these parts are parts by weight and the resin content is based on their dry weight.

The composition was applied with a brush to porcelain and heated to a maximum temperature of 1053K for 10 minutes during a 1-hour firing cycle. A film formed

168,425 cloudy and pitted - Film showed no adhesion; was removed by gentle rubbing It can be seen that the gold compound is not a gold thiolate according to the invention Example IX (comparative) - The following composition was prepared and used analogously to Comparative Example VIII:

Parts

Polymethacrylic resin 11 Gold salt of mercaptosuccinic acid 18 (11 gold parts) 1,3-Propanediol parts 15 Water 40 Isopropanol 15 Family complex 0.05 chromium trioxide 0.05 The resulting cloudy, sticky film - The cloudy nature of the film was due to pre-

early decomposition of the thiolate during firing to form an insoluble compound

Examples X-XII (comparative)

Compositions were prepared and used analogously to Comparative Example 9, replacing the gold thiolate used therein with the following gold thiolate, in an amount corresponding to 10 parts gold:

cystein gold (comparative example X) auramercaptobenzoic acid (comparative example XI)

2-mercaptopyridine gold (Comparative Example XII) In each case, the film formed cloudy - The cloudy nature of the film was due to the decomposition of thiolate during firing to form an insoluble gold compound - The film did not stick; could be removed by gentle rubbing Example XIII (comparative)

The following composition was prepared and used analogously to Comparative Example XIII:

Parts

Cellulose polyester 17

Aurathiobarbituric acid 17 (10 parts gold)

1,3-propanediol Parts 15 Ethyl lactate 15 Water twenty Isopropanol 15 Triethylamine 1 Family complex 0.05 Chromium trioxide 0.05 The resulting film was cloudy and pitted. The cloudy nature of the film was due to premature

by decomposing the thiolate during firing to form an insoluble gold compound, the film did not stick; it could be removed by gentle rubbing Example XIV- The following composition was prepared and used analogously to Comparative Example VIII:

Parts

Polymethacrylic resin 10

N- (2-mercaptopropionyl) glycine gold (I) 18.5 (10 parts of gold)

1,3-propanediol 15

Water 40

Isopropanol 15

Triethylamine 1

Rhodium complex 0.05

Chromium trioxide 0.05

168 425

A shiny, sticky film was formed.

It can be seen that the composition contains 10% gold as thiolate.

The composition was also applied with a steel wheel and a neoprene wheel. In both cases, the same result was obtained as when applied with a brush.

Examples XV-XVII. Example 14 was followed, with the difference that

The 1,3-propanediol was replaced with 15 parts of tetrahydrofuran acetate (Example XIV), glycerol diacetate (Example XVI) or ethyl lactate (Example XVII). In each case, the gold film produced had good adhesion and was shiny.

The composition was also applied with a steel and neoprene circle. In each case, a shiny, continuous coating was obtained after firing.

The following compositions were prepared and used analogously to Comparative Example VIII.

Example XVIII.

Cellulose polyether

N- (2-mercaptopropionyl) glycine gold (I)

1,2-propanediol

Ethyl lactate

Water

Triethylamine

Family complex

Chromium trioxide

Example XIX.

Polyvinylpyrrolidone - resin (MW 30,000) N- (2-mercapt.py'opionyl) glycine gold (I)

1,2-propanediol Ethyl lactate

Water

Triethylamine

Family complex

Chromium trioxide

Ammonium citrate bismuth salt Pr x y example XX

Parts

18.5 (10 parts of gold)

0.05

0.05

Parts

16.5 (9 parts of gold)

0.05

0.05

0.05

Parts

20,000)

18.5 (10 gold parts) 15 5

0.05

0.05

Polyethylene glycol - resin (molecular weight

N- (2-mercaptopropionyl) glycine gold (I)

1,2-propanediol Glycerin Ethyl lactate Water

Rhodium trioxide rhodium complex

A glossy, sticky coating was created in each case.

Example XXI (comparative). The following composition was prepared and used analogously to Comparative Example VIII:

Polyvinylpyrrolidone Parts 91 Aura-2-mercaptobenzimidazole 182 Water 273 1,2-propanediol 91 Ethyl lactate 227.5

168 425

Ammonia solution 45.5 (specific gravity 0.88) fRh ^ acetate) 4l 1

811

A dull, non-stick film was obtained after firing the composition. This was a result of the low solubility of the gold compound during the application (by brush) of the composition, leading to a non-uniform composition when heated. It is estimated that only 5% of the gold mercaptide dissolved in the original medium.

Examples XXII-XXVIII (comparative). Compositions were prepared and used as in Comparative Example 21 replacing the gold compound used therein with the following compounds:

XXII - Aura-5-mercapto-1-methyltetrazole

XXIII - Aura-2-mercapto-5-nitrobenzimidazole

XXIV - Aura-4-aminothiophenol

XXV - Aura-4-hydroxytiophenol

XXVI - aura-mercaptoacetic acid

XXVII - aura-2-mercaptopropionic acid

XXVIII - aura-mercapto-2,3-hydroxypropane.

All the films produced were not satisfactory. The compositions of Comparative Example XXII-XXIV were unsatisfactory for the same reason as that of Comparative Example 21, which gave cloudy coatings, often with severe pitting. In the compositions of Comparative Examples XXV-XXVIII, decomposition to gold powder too early during manufacture or use, leading to heterogeneous compositions. The gold compounds of Comparative Examples XXV-XXVIII and the corresponding general classes are inherently unstable in the presence of an organic base and are therefore unsuitable for making shiny gold coatings from water-based media.

Example XXIX. A liquid gold composition, an aqueous solution with a solid resin to gold ratio of 1:10, was prepared by mixing:

Parts

Polycellulose resin 9.1 (Natrasol 250GR by Aqualon, Great Britain) N- (2-mercaptopropionyl) glycine gold (I) 182 Water 273 1,2-propanediol 91 Ethyl lactate 182 Triethylamine 45.5 [Rh2 (acetate) 4] 1

783.6

It can be seen that the composition contains 1.2% by weight of resin.

A glossy and continuous coating was obtained after gently washing off any inorganic deposit remaining on the coating with water and drying with tissue paper.

Example XXX. The composition was prepared and used as in Example XXIX replacing the gold compound used therein with aura-acetylcysteine. The same result was obtained.

Example XXXI. A liquid gold composition of an aqueous solution containing aura- (7-lL-glutamoyl-L-cysteinyl-glycine), otherwise known as aura-glutathione, was prepared by mixing:

Polyvinylpyrrole idon Parts 72 Aura-glutathione 172 Water 290 1,2-propanediol 72 Ethyl lactate 91 Triethylamine 68

168,425 [Rh2 (acetate) 4]. 1

766

The resulting coating was glossy and continuous.

Example XXXII. A liquid gold composition of an aqueous solution containing gold and palladium to give a metallic (gray) appearance to the fired film was prepared by mixing:

Parts

Polyvinylpyrrolidone 50

N- (2-mercaptopropionyl) glycine gold (I) 100 Palladium sulphate 15

Water 150

1,2-propanediol 50

Ethyl lactate 100

Triethylamine 25

Polysulfide solution 12.5

RHCl (ox) N «33) 4] ._1_

503.5 ox = oxalate; polysulfide solution = 15% ammonium polysulfide solution in water (BDH, UK). A glossy and continuous coating was obtained.

Example XXXIII. A liquid gold composition in an aqueous solution, suitable for both fast and slow firing cycles, was prepared by mixing:

Parts

Polyvinylpyrrolidone thirty N- (2-mercaptopropionyl) glycine gold (I) 100 Water 240 1,2-propanediol thirty Ethyl lactate 125 n-butanol 5 Triethylamine 25 Polysulfide solution 12.5 [RhCl (ox) (NH3) 4] 1 Cr2 (SC> 4) 4 1.9 [Bi-citrate] 2.5 572.9

ox = oxalate; Bi-citrate from BDH, UK, in the form of ammonium bismuth citrate. Polysulfide solution as in Example XXXII. The following firing processes resulted in continuous reflective coatings: Fast firing: 40-minute cycle, maximum temperature = 1078K; 2 minutes of heating

Slow firing: 473K for 1 hour; maximum temperature = 823K; 10 minutes of heating.

The same composition was applied by brush to porcelain articles to give a glossy and continuous coating using the same firing cycle as in Comparative Example VIII.

The same composition, applied to porcelain products with a brush, was fired to a maximum temperature of 1173K; 40-minute cycle; 2 minutes of heating-in and a continuous and glossy coating was obtained.

Example XXXIV. A liquid gold composition, an aqueous solution suitable for application to glassware, was prepared by mixing:

Parts

Polymethacrylic 100 resin (Versicol K11, from Allied

Colloids, UK

N- (2-mercaptopropionyl) glycine gold (I) 200

Water 380

168 425

1,3-propanediol 20

2-propanol 100 [Rh (CO) (acac) J 2

C1-O3 1

Me ₃ SiOMe 1

Argenta-N- (2-mercaptopropionyl) glycine 734

The composition was applied by brush to glassware and fired for 1 hour to a maximum temperature of 893K, with a 10-minute holding time - A glossy and continuous coating was obtained. Example XXXV- A liquid gold composition, an aqueous solution suitable for inkjet printing, with a high concentration of water, prepared by mixing:

Parts

Polyvinylpyrrolidone 74

N- (2-mercaptopropionyl) glycine gold (I) 59

Water 314.4

Butanone 46 n-Butanol 39

Triethylamine 8

Polysulfide 10 [Rh (NH3) 6] Cl3 1 [Bi-lactate] 1.4 solution

614.4

The composition of this example contains 61% water - Polyvinylpyrrolidone resin has a molecular weight of 10,000 Daltons - Polysulfide solution as in Example XXXII The composition was sprayed onto flat tiles with a paint sprayer and fired; a shiny and continuous gold coating was obtained Example XXXVI- A liquid gold composition of an aqueous solution suitable for screen printing was prepared by mixing:

Parts

Polycellulose resin 45 N- (2-mercaptopropionyl) glycine gold (I) 181 Water 454

1,2-propanediol 181

Glycerin 91

Ethyl lactate 45 [Rh2 (acetate) 4] 1 [Cr ₂ (SO4) 2] ._18

999.8

The composition contains 4.5% of solid resin - The composition was printed through a sieve with a mesh size of 350 (t onto a glazed plate - The fired film was shiny and continuous - A small amount of inorganic residue that remained after firing was gently washed with water, then dried with tissue paper to obtain glossy and continuous coating Example XXXVII - A liquid gold composition of an aqueous solution which contains powdered gold and which is suitable for screen printing, was prepared by mixing:

Parts

Polycellulose resin 62

Powdered gold 400

N - (2-mercaptopropionyl) glycine gold (I) 250 Water 1000

1,2-propanediol 250

Ethyl lactate · 62

Glycerin 125

Triethylamine 62

168,425 [Rh2 (acetate) 4] 1

2212

The composition was applied analogously to Example XXXVI. The produced coating was rubbed to obtain a golden coating without gloss.

Example XXXVIL In the same manner as described for the composition of Example XXXVII, a brush gold composition was prepared resulting in a polished coating by simply reducing the concentration of the polycellulose resin to 25 parts.

Example XXXIX. In a manner analogous to that of Example 1, auro-N- (3-mercaptopropionyl) glycine was produced in a yield of more than 80% in terms of gold.

Analysis: Theoretical: C 16.8 N 3.9 Found: C 16.35 N 3.55%

1 / 1 1 S-C-C -N Au-S-C-C-C- I II \ 1 1 u 0 0 MODEL 1 PATTERN 2 Η Y \ / N H 0 1 1 II Au -S-CH <CC ² II - (N-CH ₂ -C) _n OH 0 PATTERN 3 0 0 II II Au-S-CH-C-NH-CI-LCOH 1 of ch ₃ MODEL 4 0 0 II II Au-S-CH-C-NH < CH _o C0 1 + zz ch ₃ PATTERN 5

Publishing Department of the UP RP. Circulation of 90 copies. Price PLN 1.50

Claims (14)

Patent claims A homogeneous composition for producing a noble metal coating which is one or more metals selected from platinum, palladium, gold and silver, after firing on a substrate, characterized in that it comprises a polymeric resin and a solution in water and a cosolvent of a noble metal thiolate in an amount 3-22% by weight, with the water content up to 85% by weight. 2. A composition according to claim 1 The process of claim 1, wherein the polymer resin and noble metal thiolate solution in water and co-solvent is 3-22% by weight, the water content being up to 85% by weight. 3. A composition according to p. A water according to claim 1 or 2, characterized in that it contains 5-85% by weight of water. 4. A composition according to p. A water according to claim 3, containing 40-55% by weight of water. 5. A composition according to p. The method of claim 1 or 2, characterized in that the precious metal is gold. 6. A composition according to p. 5. The thiolate according to claim 5, characterized in that the thiolate is a gold compound of formula Au-SRH or Au-SRX or a salt thereof, wherein X is a nitro group or a group of formula -COOH, -SO2OH, -OH, -CO, .NH2, - NH2 or -O-P (O) ((OH) 2, wherein the hydrogen atoms may be optionally substituted and R is a divalent organic group. 7. A composition according to p. A compound according to claim 6, characterized in that it contains a gold compound of formula Au-SRH or Au-SRX, corresponding to the compound HRSH or HSRX, which is: N- (2-mercaptopropionyl) glycine, N- (3-mercaptopropionyl) glycine; N-) 2 -mercaptoacetyl) glycine; 2-mercaptoacetyl-L-histidine, 3-mercaptopropionyl-L-histidine, L-cysteine; acetylcysteine or glutathione. 8. A composition according to p. The composition of claim 1 or 2, characterized in that it contains 8-12% by weight of the noble metal in the form of a thiolate. 9. A composition according to p. The resin according to claim 1 or 2, wherein the resin is polyvinylpyrrolidone, polymethacrylic resin or cellulose polyether, with the majority of these resins volatilizing in the range 473-823K. 10. The composition of claim 1 The resin according to any of the preceding claims, containing 5-45% by weight of resin. 11. The composition according to p. The method of claim 1 or 2, characterized in that the co-solvent has a boiling point in the range 373-493K. 12. The composition according to p. 2. The process of claim 1 or 2 wherein the co-solvent is a water-miscible alcohol, an ester or an ether. 13. A composition according to p. A pharmaceutical composition according to claim 12, characterized in that the alcohol is 1,2-propanediol or 1,3-propanediol. 14. The composition of claim 1 A co-solvent according to claim 1 or 2, characterized in that it contains 5-45 wt.