EA008833B1 - Enhancing silbertarnish-resistance - Google Patents

Abstract

An alkanethiol, alkyl thioglycollate, dialkyl sulfide or dialkyl disulfide may be used to surface treat of an alloy of silver containing an amount of germanium that is effective to reduce firestain and/or tarnishing. The treatment has been found to further reduce tarnishing of the alloy such that a sample can be supported close above a 20% solution of ammonium polysulphide for at least 30 minutes while retaining a generally untarnished appearance. The treatment may be carried out at the end of manufacturing a shaped article to give rise to an article that will preserve its untarnished appearance both during transit to a point of sale but during subsequent display for an extended period. The invention therefore also includes a method for manufacturing a tarnish-resistant silver article, which comprises the steps of forming a shaped article of an alloy of silver containing an amount of germanium that is effective to reduce firestain and/or tarnishing, surface treating the article with an alkanethiol, alkyl thioglycollate, dialkyl sulphide or dialkyl disulphide; and introducing the article into packaging. Also disclosed for use in treating an alloy of silver as aforesaid is a water-based composition comprising a treatment agent selected from an alkanethiol, alkyl thioglycollate, dialkyl sulfide or dialkyl disulfide and a mixture of an anionic surfactant and an amphoteric or nonionic surfactant in a concentration that is effective to solubilise the treatment agent.

Description

Field of Invention

The present invention relates to the use of organosulfur compounds to increase the tarnishing resistance of silver alloys, silver products with increased tarnishing resistance, surface-treated with organosulfur compounds, and methods for storing and displaying processed products. It also relates to aqueous formulations that can be used to process metal, which may be a silver alloy, but may also be another metal that needs surface treatment to increase tarnish resistance, such as copper, brass or nickel.

BACKGROUND OF THE INVENTION

Silver alloys and their tarnishing resistance

British standard silver (Sterling) provides manufacturers and jewelers with a versatile and reliable material, however, the products obtained inevitably require cleaning and polishing in order to remove unwanted tarnishing products from time to time. It is well known that in everyday contact with the atmosphere on silver and silver alloys, a gloss-destroying dark film is formed, known as tarnish.

Since ancient times, it was known that pure, "pure", silver is too soft for normal use, and therefore, additives of base metal were introduced into it to increase hardness and strength. British law, existing since the XIV century, establishes a minimum silver content in products for sale, equal to 92.5% (British Standard Sterling), but does not regulate its base metals. Years of experience have convinced jewelers that copper is the most suitable metal available. Modern silver plate manufacturers adhere to this composition, although sometimes, for greater ductility, part of the copper is replaced by cadmium. Sterling silver with a content of 2.5% cadmium is a standard material for molding and stamping. In many European countries, silver alloys of lower quality are commonly used for the manufacture of cutlery and tableware. Alloys of the 800th sample (800 parts Hell per thousand) are mainly used in Southern and Central Europe, while the standard 830 prevails in Scandinavia.

In all large manufacturing companies, most of the annealing and soldering operations necessary for assembling finished products or semi-finished products are carried out in the flame of a gas-air blowtorch. The oxidizing or reducing nature of the flame and the temperature of the products are regulated only by the art of the jeweler. Oxygen easily passes through pure silver, especially when it is heated red-hot. Silver itself does not oxidize in air, but copper in a silver / copper alloy is oxidized to mono- or divalent copper oxides. Etching of the oxidized surface of the product with hot dilute sulfuric acid removes external, but not deeply embedded copper oxide, resulting in a surface consisting of pure or pure silver covering the silver / copper oxide mixture. Pure silver is easily permeable upon further heating, which leads to the oxidation of copper deeper below the surface. The subsequent stages of annealing, cold working and etching create a silver luster surface after light polishing, but with more thorough polishing, dark and ugly spots, known as “heating spots” or “overheating”, appear. Soldering operations due to higher temperatures result in even more such deep spots. When the spot depth exceeds approximately 0.025 mm (0.010 in.), The alloy also cracks and is difficult to solder since the oxide surface is not wetted by solder and a regular metal junction is not formed.

Patent CB-B-2255348 (Ka1eai, A1beg1 apb 1oypz; Me1a1sitor Kessiese) disclosed a new silver alloy that retained the hardness and gloss characteristic of Ad-Cu alloys, but had fewer problems associated with the tendency of copper to oxidize. The alloys were Ad-Cu-Ce triple systems containing at least 92.5 wt.% Ad, 0.5-3 wt.% Ce and the rest, except for impurities, copper. It was stated that alloys do not fade in air under ordinary conditions during traditional manufacturing, processing and finishing operations, are easily deformed in a cold state, are easily soldered and do not give noticeable shrinkage during casting. It was also stated that the alloys have extraordinary ductility and extensibility and, after annealing, the necessary hardness. It was stated that germanium has a protective effect and is responsible for the successful combination of the properties of the new alloys, forming solid solutions with both the silver phase and the copper phase. It was said that the microstructure of the alloy includes two phases: a solid solution of germanium and copper in silver, which is surrounded by a filamentous solid solution of germanium, silver and copper. It was indicated that germanium in the copper-enriched phase inhibits the oxidation of the surface of this phase due to the formation of thin protective coatings of CeO or CeO ₂ , which prevent the formation of overheating spots during brazing and annealing in the flame as a result of oxidation of copper at high temperatures. Moreover, by adding germanium, tarnishing was suppressed and the surface became not black, but pale yellow, and tarnishing products were easily removed with tap water. It has been said that the alloy can be used, inter alia, in jewelry. However, the alloy disclosed in said patent has limitations since it contains large grains,

- 1 008833 which leads to weak deformability and the formation of large cavities from low-melting eutectics, and this causes local surface melting when the alloy is heated by a blowtorch.

Patents I8-A-6168071 and EP-B-0729398 Οοΐιηδ) disclose a silver / germanium alloy that contains at least 77 wt.% Silver and 0.4-7 wt.% Germanium and the rest, except for impurities, is copper, the alloy being contains elemental boron as an additive grinding grain at a concentration of more than 0 ppm, but less than 20 ppm Boron can be introduced into the alloy in the form of a copper / boron alloy with 2 wt.% Elemental boron. It was reported that with such a low concentration of boron, an excellent grain grinding effect in the silver / germanium alloy is achieved, which gives the alloy increased strength and ductility compared to the silver / germanium alloy without boron. Boron in the alloy inhibits grain growth even at temperatures used in brazing jewelry, and it was indicated that alloy samples are resistant to ulceration even when reheated to temperatures at which the copper / germanium eutectic in conventional alloys would already melt. Strong and aesthetically attractive joints between the individual elements of the alloy can be obtained without the use of an additive between the free surfaces of the two elements, and butt-to-butt or lap jointing can be carried out by a diffusion process or by the method of contact electric welding or laser welding. Compared to the weld in Sterling silver, the weld in the alloy described above contains, on average, finer grain, which increases the formability and ductility of the welds, and when processing the alloy of the 830th sample using plasma welding and polishing, grinding is not necessary.

Triple and quaternary alloys, for example Ad-Si-Ce and Ad-Si-2p-Ce, include two base metals, Cu and Ce, as the alloying elements, in the initial noble metal Ad. Upon contact with an oxidizing atmosphere, two oxidation reactions can be considered. First, the oxidation of copper to monovalent oxide of copper:

4 [Cu] alloy + 02 (g)> 2ССОО (tv) (1)

Secondly, the oxidation of germanium to (di) germanium oxide:

[Ce] alloy + O2 (g)> CeO2 (tv) (2)

The above equation indicates the formation of germanium oxide (GU) CeO ₂ , but germanium oxide (GH) CeO or an intermediate compound Ce _x O _y can also be formed, where x is 1 and y is greater than 1 but less than 2. Under standard conditions, i.e. e. when pure Cu and Ce react with pure oxygen at a pressure of 1 atm to form a pure oxide phase, both reactions are possible, and the chemical driving force of reaction (2) is 1.65 times higher than the driving force of reaction (1).

According to patent XVO 02/095082 (BoNPZ), the tarnishing resistance of ternary silver, copper and germanium alloys or quaternary silver, copper, zinc and germanium alloys can be increased by casting a molten mixture to form an alloy and anneal it to reduce grain thickness and recrystallize in the alloy moreover, annealing is carried out under a selectively oxidizing atmosphere, for example, H ₂ / H ₂ O or CO / CO ₂ , in order to promote the formation of CeO ₂ and to prevent the formation of Cso.

Processing compositions for removing or preventing tarnishing of silver

To remove tarnishing and / or inhibit tarnishing, various methods have been proposed for purifying or protecting Sterling silver and silver from other known samples.

Patent I8-A-2841501 discloses a composition for polishing silver based on abrasive powder and n-alkanethiol C ₁₂ -C ₂₀ , which is considered non-toxic, has a faint odor and protects silver from tarnishing due to the formation of a Ρ-8-Ad monomolecular layer. in which B represents an alkanethiol chain, wherein said layer forms a physical barrier between silver and reactive components of the atmosphere.

Patent CB-A-1130540 relates to the protection of the finished surface of Sterling or British silver at the manufacturing stage and discloses a method consisting of the following stages:

wetting the clean surface of silver in the product with a solution containing 99 wt.h. volatile organic solvent, for example trichlorethylene or 1,1,1-trichloroethane, and 0.1-1.8 wt.h. a solute containing an -8H group and capable of forming a transparent, colorless protective layer on the surface of silver, for example stearyl and cetyl mercaptan or triglycolate;

the interaction of the solution with the surface with the formation of such a layer and evaporation of the solvent; and washing the surface with a surfactant solution, rinsing the surface with hot water and drying.

It is stated that the above method provides "long-term finishing" for long-term storage of the product until it reaches the consumer.

It has been shown that halide derivatives of hydrocarbons are the most suitable solvents, but their use from an environmental point of view remains problematic. It was noted that ethers are flammable and toxic substances, and lower alcohols are poor solvents. Water is not mentioned as a solvent. The applicants saw on the Internet a message from ATOBGIA Syet1sa18 Gps. According to which the solubility of mercaptans in water is reduced

- 2 008833 from 23.30 g / l in the case of methyl mercaptan to 0.00115 g / l in the case of nonyl mercaptan, and the data for hexadecyl and octadecyl mercaptans (CA8 2885-00-9) show that they are insoluble in water.

Patent I8-A-6183815 (Yeshsk) also indicates that treatments of this type produce a self-forming coating of thiol compounds in which sulfur atoms are bonded to the metal surface and the alkyl groups are directed away from the metal surface. In the examples given there, fluoroalkylamides, for example CE ₃ (CE ₂ ) ₅ SOHN (CH ₂ ) ₂ 8H, in aqueous solutions of alcohols, for example aqueous isopropanol, are sprayed onto a silver surface, after which the surface is rinsed and dried with a soft cloth. Fluoroalkylamides have no pronounced odor and can dissolve in lower alcohols or in alcohol / water mixtures, although, as can be seen from the description and examples, not all alcohol solvents form good films.

Woisoid K1t e! a1. they report that the adsorption of thiols on silver proceeds through anodic oxidation, which causes a shift in the potential of the open circuit of the substrate metal in the negative direction or a peak in the anode current if the potential is fixed:

K8H + M (0) ^ K8-M (1) + H ⁺ + e ^- (M) (M = Au or Hell), see 1Wr: // \ y \ y \ u.e1es1gos11et / ogd / tee1td5 / pa51 / 200 / ab51gas15 / 5utro81a / N1/1026.rPG

Klgap K1t, Abzogrboi aib Keasboy OG Tho18 aib 8i1yebeb op Yobe Me1a18, Katay 8K8-2000, 14-17 Aidiz! 2000, Khaltei, Eitsai, Syia, yyr: //rgo88.ogd/1sog8kht/reg/kiaik1t.rbG, also discloses the production of self-forming monolayers and reports that alkanethiols, dialkyl sulfides and dialkyl disulfides self-form on silver surfaces with aliphatic dithiol formation two connections of Ad-8.

In contrast to the foregoing, literature data on the formation of germanium alkylthiols are relatively scarce. Dissociative adsorption of H ₂ 8 on the Ce (100) surface with the formation of adsorbed -8H groups and adsorbed hydrides was reported by No. 1 e! a1., Arrbeb 8shGase 8s1eise, 150, 65-72 (1999), see Lbr: //tete.set.t188sht.bi / Sgeeeeb / ribb / 00005797.rbG, see also the message Hrg. М1сяе1 СгеейеГ, Ишуегвюу ОГ М188шт-С1итЬ1а 1 Шр: // \ у \ у \ у / с11ет / т155шпеби / Сгееи11еГ / Ве8еагс11.1ит1 that dissociates upon Н ₂ 8 contact with the Ce (100) surface, which can be monitored by ultraviolet photoelectron spectroscopy. The reaction of alkanethiols with Ce to form a high-quality monolayer has been reported in the context of semiconductor and nanotechnology, Na e! A1., 1. At. S'No. 8oc., 123, 2422 (2001). In the described experiment, a thin sheet of Ce (111) is sonicated in acetone to dissolve organic impurities, then immersed in a concentrated solution of HE to remove residual oxide and a surface with terminal hydrogen atoms is obtained, after which a thin sheet is immersed in a solution of alkanethiol in isopropanol and sonicated in propanol and dried.

SUMMARY OF THE INVENTION

Although patent SV-A-1130540 claims to provide long-term processing, the experience of one of the authors, who is a jeweler, says that such processing does not solve all the tarnishing problems between production and delivery to the customer or user and suffers from many shortcomings. Although silver can be delivered to the seller in a tarnished condition, this is largely provided by packaging made by the manufacturer, which protects the product from air. As soon as the packaging is removed and the product is placed in the atmosphere of a store, for example, in a hotel, it comes in contact with air and is exposed to heat from artificial lighting, a traditional Sterling silver product might need to be refinished after a week, and after 2 weeks it usually is grows dull that it is impossible to sell. When the product is exposed, its life to noticeable tarnishing can be as little as 3-4 days. Re-polishing leads to wear and small scratches so that if the product could not be sold quickly, it loses its original appearance. The need to polish the exposed silver at short intervals increases the labor cost of the jewelers or merchants who were hired to sell products, rather than clean them. Therefore, tarnishing at the point of sale or exhibiting creates a serious problem that reduces the willingness of those involved in the supply and advertising of silver products, and which has not yet received an adequate solution.

When the product arrives at the customer, of course, it is desirable that the problem of removing the tarnish, if possible, is not often repeated and undemanding.

Silver alloys according to the patents CB-B-2255348 and EP-B-0729398 are now commercially available in Europe and the United States under the brand name Argentum, and the word “Argentum” as used herein refers to these alloys. Although they exhibit increased tarnishing resistance compared to, for example, Sterling silver and any tarnishes that form can be removed by simple washing, there are still opportunities to increase tarnishing resistance. This is true even when annealing is carried out in a selectively oxidizing atmosphere, as disclosed in \ ¥ 0/02/095082.

It has now been found that alkanethiol, alkylthioglycolate, dialkyl sulfyl or dialkyl disulfide can be used to treat the surface of a silver alloy containing some germanium, which effectively reduces overheating and / or tarnishing spots in order to reduce or further reduce the tarnishing of the alloy so that the sample can be exposed

- 3,008833 of hydrogen sulfide gas over a 20% solution of ammonium polysulfide for at least 30 minutes and usually 45-60 minutes at room temperature while maintaining a substantially unbleached appearance.

The invention therefore relates to a method for processing a finished product or a semi-finished product - cutlery, tableware or jewelry - from a silver / germanium alloy with a silver content of at least 77 wt.% And germanium 0.4-7%, the rest, mainly copper, to reduce or further reduce the tarnishing of the product so that the sample of the alloy from which the product is made can be placed near a 20% solution of ammonium polysulfide for at least 30 minutes, while maintaining a substantially unbleached appearance, the method comprising turning nostnuyu treating said products alkanethiol, alkiltioglikolyatom, dialkyl sulfide or dialkyl.

The specified method may include an additional step of packaging the product.

In addition, the invention provides a finished product or semi-finished cutlery, crockery or jewelry made of silver alloy containing an amount of germanium that is effective to reduce the overheating and / or tarnishing spot, and which has been treated with C1 ₂ -C ₂₄ alkanethiol, alkylthioglycolate, dialkyl sulfide or dialkyl disulfide, and which exhibits resistance to tarnishing so that the alloy sample from which the product is made can be placed near a 20% solution of ammonium polysulfide for at least 30 minutes while maintaining uu mainly undimmed species.

The above accelerated tarnishing test, in which the product is exposed to gaseous hydrogen sulfide from a solution of ammonium polysulfide, over which it is suspended at a height of, for example, 30 mm, corresponds to a period of one year or more at the point of sale where the product is exposed and exposed to the surrounding atmosphere and may be exposed to elevated temperatures. It is the combination of the protective function of germanium in the alloy with additional protection by the organosulfur compound that is considered responsible for the observed increase in tarnish resistance. The period during which the product retains its tarnished appearance under harsh conditions may be 3 or more times the corresponding period for the product not treated with the organosulfur compound. This is unexpected because the same accelerated tarnishing test, carried out under the same conditions with a standard Sterling silver product that does not contain protective germanium, did not show a significant increase in tarnishing time in the case of samples not treated and treated with an organosulfur compound. Accelerated tarnishing tests performed with Argentum silver and standard Sterling silver samples, which were immersed in octadecyl mercaptan and hexadecyl mercaptan solutions, showed that the protective thiol was removed from standard Sterling silver samples, but not from Argentum silver samples, when wiped with a cloth dampened with solvent ί (Ε 765 is a solvent based on n-propyl bromide, discussed below). During accelerated testing, the areas of standard Sterling silver, rubbed with a solvent, changed color faster than non-rubbed areas, while in the case of silver Argentum, there was no difference in the state of rubbed and non-rubbed areas, which suggests a stronger and more effective connection with thiol.

Accelerated tarnishing tests with Sterling from Argentum using ammonium polysulfide were reported by the American Society of Jewelers, see 1Wr: // \ y \ y \ y.5 | Xg5tTs1pp8.ot / 1agdspSht.1t4.1it. and in the benchmark test, Sterling from Argentum remained unfaded an hour later, while traditional Sterling silver faded in less than 15 minutes. However, in this test, 0.5 ml of a 20% solution of ammonium polysulfide was mixed with 200 ml of distilled water so that the test conditions were significantly less stringent than when the samples came in contact with the 20% solution itself. In the patent \ ¥ 0/02/095082, samples were placed close to above 20% ammonium polysulfide, but the exposure times were relatively short, and the first appearance of yellowness for Ad-Cu-Ce alloys was noted after 3-5 minutes. Other tests described in this patent included placing the samples in an desiccator containing micronized powders of sulfur and calcium nitrate, which had a less severe effect than polysulfyl ammonium.

In one section of the development program for improved formulations for processing agents described above, the authors unexpectedly found that processing agents can be dissolved or dispersed directly in an aqueous solution of a surfactant without first dissolving the processing agent in an organic solvent and then mixing the resulting solution with an aqueous liquid . Variants of the above compositions are optically transparent and stable when stored at ambient temperature for weeks or months. Therefore, the treatment compositions may be water-based and contain alkanethiol, alkylthioglycolate, dialkyl sulfyl or dialkyl disulfide and a mixture of an anionic surfactant with a neutral or amphoteric surfactant and water.

DETAILED DESCRIPTION OF THE INVENTION

Silver-copper-germanium alloys

Alloys that can be processed according to this invention include a silver alloy containing germanium in an amount effective to reduce overheating and / or tarnishing spots. Patent I8-A-6406664 (Όίαιηοηά) discloses that an amount of germanium of only 0.1 wt.% Can be effective provided that a noticeable amount of tin is present, and although examples of formulations are provided, but there are no test data for corrosion or overheating spots as for

- 4 008833 casts, and for products made from a sheet. The authors believe that the amount of 0.5 wt.% Ce provides a preferred and more realistic lower limit, and in practice the use of less than 1 wt.% Is undesirable. A two-component copper-free alloy may contain 99% Ag and 1% Ce, and a tarnish-free cast alloy for jewelry has been reported to contain 2.5% P1, 1% Ce and the rest of Ag, as well as optional contains Ζγ, δί or δη.

Triple alloys Ag-Cu-Ce and quadruple alloys Αβ-Ο'ιι-Ζη-Οο. which can be suitably processed by the method of the present invention, contain at least 30% silver, preferably at least 60%, more preferably at least 80% and most preferably at least 92.5 wt.%, and a maximum of not more than 98 %, preferably not more than 97% of the alloy. The germanium content in the Α§-Οι- (Ζη) -Οε alloys should be at least 0.1%, preferably at least 0.5%, more preferably at least 1.1%, and most preferably at least 1 , 5 wt.%, And most preferably not more than 6.5%, more preferably not more than 4%.

If desired, germanium can be substituted, in part, with one or more elements that have an oxidizing potential and are selected from A1, Ba, Be, Cc1. Co, Cr, Er, Ca, Ιη, Mg, Μη, Νί, Pb, Pc1. Ρΐ, 8ΐ, δη, Τί, V, Υ, Υό and Ζγ, provided that they do not adversely affect the ability of germanium to increase the resistance of the alloy to the appearance of overheating spots and tarnishing. The mass ratio between germanium and substitute elements may be in the range from 100: 0 to 60:40, preferably from 100: 0 to 80:20. Preferably, the germanium content consists entirely of germanium, i.e. the mass ratio is 100: 0.

The rest of the Ag-Cu-Ce ternary alloys, other than impurities and any grain grinder, will be copper, which should be present in an amount of at least 0.5%, preferably at least 1%, more preferably at least 2 % and most preferably at least 4% by weight of the alloy. For the triple alloy "800th test" is suitable, for example, a copper content of 18.5%. The rest of the quaternary alloys are Αβ-Οιι-Ζη-Οε. in addition to impurities and any grain grinder, will comprise copper, which must be present in an amount of at least 0.5%, preferably at least 1%, more preferably at least 2% and most preferably at least 4% by weight alloy, and zinc, which should be present in a mass ratio to copper of not more than 1: 1. Therefore, zinc is optionally present in silver-copper alloys in an amount of from 0 to 100 wt.% Of the copper content. For the fourth alloy of the “800th test”, for example, a copper content of 10.5% and a zinc content of 8% are suitable.

In addition to silver, copper and germanium, and optionally zinc, the alloys preferably contain a grain mill (grain grinding aid) to inhibit grain growth during processing of the alloy. Suitable grain grinders include boron, iridium, iron and nickel, but boron is a particularly preferred element. A grain shredder, preferably boron, may be present in Α§-Οι- (Ζη) -Οε alloys in an amount of from 1 to 100 ppm. (rrs), preferably from 2 to 50 ppm, more preferably from 4 to 20 ppm by weight of the alloy.

In a preferred embodiment, the alloy is a triple alloy, consisting, in addition to impurities and any grain grinder, from 80-96% silver, 0.1-5% germanium and 1-19.9% copper by weight of the alloy. In a more preferred embodiment, the alloy is a triple alloy consisting, in addition to impurities and any grain grinder, from 92.5-98% silver, 0.3-3% germanium and 1-7.2% copper by weight of the alloy, as well as from 1 to 40 ppm boron as a grinder of grain. In another preferred embodiment, the alloy is a triple alloy consisting, in addition to impurities and any grain grinder, from 92.5-96% silver, 0.5-2% germanium and 1-7% copper by weight of the alloy, as well as 1 up to 40 ppm boron as a grinder of grain.

Protective reagents

As a protective reagent, you can use a compound containing a long-chain alkyl group and a group -8H or -8-8-, for example alkanethiol, dialkyl sulfide or dialkyl disulfides, in which the carbon chain preferably consists of at least 10 carbon atoms and can represent C1 ₂ c ₂ to 4. The compounds or -8H -8-8- group, which may be used include saturated aliphatic straight-chain compound having 16-24 carbon atoms in the chain, eg cetyl mercaptan (hexadecyl mercaptan), stearyl (oktadetsilmerka tan) and cetyl steariltioglikolyaty and whose formulas are shown below.

about

8n

-5008833

Octadecyl mercaptan is a pale yellow waxy substance, insoluble in water and melting at 15-16 ° C. Hexadecyl mercaptan is also a white or pale yellow waxy substance that melts at 30 ° C.

Organic Solvent Compounds

The protective reagent can be used in the form of a solution in a solvent, for example in a non-polar organic solvent, such as an alcohol, for example methyl or ethyl alcohol, a ketone, for example acetone or methyl ethyl ketone, an ether, for example diethyl ether, an ester, for example n-butyl acetate, a hydrocarbon, a halogenated hydrocarbon, for example methylene chloride, 1,1,1-trichloroethane, trichlorethylene, perchlorethylene or HCEC 141b. The protective reagent may be 0.1-1 wt.% Solvent. You can use solvents based on alkyl or aryl halides, for example n-propyl bromide, which is currently preferred, due to the short life of this compound in the atmosphere, its relatively low toxicity compared to other halocarbons, its chemical and physical properties and boiling point, heat capacity and latent heat of vaporization.

Patent I8-A-5616549 discloses a solvent mixture containing from 90 to about 96.5% npropyl bromide; from 0 to about 6.5% terpenes mixture, which contains from 35 to about 50% cispinan and from 35 to about 50% trans-pinan; and from 3.5 to about 5% of a mixture of low boiling solvents that contains from 0.5 to 1% nitromethane, from 0.5 to 1% 1,2-butylene oxide and from 2.5 to 3% 1,3 dioxolane. The solvent mixture has the following advantages:

(ί) it is essentially stabilized against the action of any free acid that can form when the mixture is oxidized in air, when the mixture is hydrolyzed in the presence of water, and when the mixture is pyrolyzed by high temperature;

(ίί) it is non-flammable and does not have corrosive properties;

(iii) the various components of the solvent mixture are not governed by the requirements of I.8. C1eap Ay As !; and (ίν) none of the components of the solvent mixture is a known cancer-causing agent (i.e., the components are not included in the lists of Ν.Τ.Ι., 1.A.V.C and SaShogsh RgoroBYup 65 and are not regulated by O8NA )

Moreover, the solvent mixture has a high solubility and its co-attribute number exceeds 120 and more preferably exceeds 125. In addition, the solvent mixture has an evaporation rate of at least 0.96 (taking the evaporation rate of 1,1,1-trichloroethane as a unit). The non-volatile residue after evaporation of the solvent mixture (ΝνΒ) is less than 2.5 mg and more preferably the non-volatile residue does not remain at all. Solvents according to the aforementioned patent are available from ΕηνесΓθ-These 1p! o £ Me1goke Ragk, ΙΙΙίηοίδ, И8А under the trademark Εηδοίν.

Organic solvent and water based formulations

For many purposes, for example for small-scale industrial applications, it may be preferable to carry out anti-tarnishing treatment using a predominantly aqueous solvent system. For this purpose, the protective reagent can be dissolved in a water-immiscible organic solvent, for example in a solvent based on n-propyl bromide, the resulting solution can be mixed with a relatively concentrated water-based soap or detergent composition, which acts as a “carrier”, and then add to the resulting mix water and get an aqueous solution for processing or a combined solution for degreasing and processing. Thus, an aqueous solution for processing has the advantage that a solvent system for degreasing is not needed, the solution is easy to prepare and can be used cold, and all surfaces of immersed products can come into contact with stearyl mercaptan or other processing reagents, and Argentum only requires silver from 2 minutes to 1 hour in solution, and the products are easy to rinse and dry, since water droplets repel from the surface of polished silver, and the treatment solution can be easily used Start in production before sending products to sellers.

Preferred water-based detergents can be based on anionic, alkoxylated nonionic or water-soluble cationic surfactants or mixtures thereof and preferably have a pH of 7 or close to 7. Anionic surfactants can be based on alkyl sulfates and alkylbenzyl sulfonates, which are detrimental to skin with prolonged contact can be reduced due to the joint presence or use of alkyl ethoxysulfates (I8-A-3793233, Woke e! a1; 4024078 Syb; 4316824 Rapsyegs). Other known surfactants may also be present, see, for example, I8-A-4555360 (B155ey). A suitable formulation containing 5-15 wt.% Non-ionic surfactants and 15-30 wt.% Anionic surfactants is sold in the United Kingdom under the trademark Ea1gu Είςπίά (Prgosieg & Satbé).

An aqueous liquid can also be prepared by dissolving the treatment reagent in an inorganic solvent and adding a relatively concentrated aqueous detergent liquid, such as undiluted Ea1gu ΕίςπΕίς. This produces a detergent liquid, which has several advantages: soapy liquid is easy to prepare, liquid is easy to apply to silverware

- 6 008833

Using a wet sponge / cotton / cloth, etc., Argentum, liquid and foam allow stearyl mercaptan or other processing reagent to penetrate into such inaccessible areas of the product where the fabric does not have access, the products are easily rinsed and dried, as water droplets repel from polished silver surfaces, and the process can be easily used in the surrounding production atmosphere before the items are sent to sellers, and can also be easily used in the atmosphere of a store or at home. Further, the hydrophobic properties imparted to silver / silver alloy when treated with thiol-based reagents can alleviate or overcome the problems of stains from water and water etching resulting from rinsing processes in manufacturing or home use.

Compounds based on aqueous fluids

It was surprisingly found that formulations containing effective amounts of processing reagents can be prepared by dissolving them directly in aqueous liquids containing anionic and neutral or amphoteric surfactants and not containing water-immiscible organic solvents and preferably no other solvents. Processing reagents can be dissolved in relatively concentrated aqueous surfactant-containing liquids that can be used as such or after subsequent dilution with water, see, in particular, the instructions in the previous section.

Processing reagents may be contained in said composition prior to dilution in an amount of at least 0.1 wt.% And preferably at least 1 wt.%, The solids content of the composition being at least 5 wt.%, Usually 10-40 wt.% and possibly 50 wt.% or more. The fact that aqueous solutions of surfactants are capable of dissolving or dispersing relatively high concentrations of higher alkylthiols and other processing reagents that are known to be highly insoluble in water has not been previously described. The resulting concentrates can be diluted with water and get an aqueous solution for processing or a combined solution for degreasing and processing, used as described above. It was found that the treatment reagent can remain in solution or suspension after such dilution and can remain effective in treating the surface of silver-copper or silver-copper-germanium alloys and, possibly, other metals, such as copper, brass and nickel, when protective surface films can slow down corrosion. Especially good results in terms of stability and effectiveness can be obtained by mixing hexadecyl mercaptan (in liquid state) directly in the “carrier” of the surfactant and using the solution as such or after subsequent dilution with water.

In particular, the processing reagents of the present invention can be successfully dispersed in aqueous liquids containing mixtures of neutral and anionic surfactants with neutral surfactants, and for example, about 33 wt.% Of the total content of surfactants can be obtained. Processing reagents that can be dispersed in this way include n-hexadecylthiol and n-octadecylthiol. They can also be successfully dispersed in aqueous fluids containing mixtures of amphoteric or zwitterionic surfactants and anionic surfactants, and such mixtures can provide relatively stable storage of optically transparent solutions that exhibit a slight tendency to re-precipitate the treatment reagent or not at all showing such a trend. In this case, the mass ratio of amphoteric or zwitterionic surfactant to anionic surfactant can be from 1:10 to 10: 1, usually close to 1: 3.

Amphoteric or zwitterionic surfactants that can be used individually or in admixture with each other and / or with nonionic surfactants and / or with anionic surfactants can be derivatives of secondary or tertiary amines, derivatives heterocyclic secondary and tertiary amines or derivatives of quaternary ammonium, quaternary phosphonium or tertiary sulfonium compounds. The cationic atom in the quaternary compound may be part of a heterocyclic ring. All such compounds have at least one straight or branched chain aliphatic group containing from about 3 to 18 carbon atoms and at least one aliphatic substituent containing an anionic water-solubilizing group, for example, carboxy, sulfonate, sulfate, phosphate or phosphonate.

Examples of zwitterionic surfactants that can be used include betaine surfactants, which are preferred, imidazoline-based surfactants, aminoalkanoate surfactants, and iminodialkanoate surfactants. Such suitable surfactants include amidocarboxybetaines such as cocoamidodimethyl carboxymethyl betaine, laurylamidodimethyl carboxymethyl betaine, cetylamidodimethyl carboxymethyl betaine and cocoamido bis (2-hydroxyethyl) carboxymethyl betaine. Particularly preferred are betaines of the amidocarboxybetaine type of the formula below, wherein B is C ₈ -C ₈ alkyl, for example cocoamidopropyl betaine. This connection is generally considered safe: in the Lds5 test. performed by VL8R, it was not mutagenic with respect to indicator organisms 8a1toie11a and in the test for repeated spotted skin tests

- 7 008833 on damaged skin in humans (ΗΚΙΡΤ), it showed neither contact hypersensitivity, nor photoallergy (see data from MARO CAB on cocamidopropylaminobetaine published by VAZE):

Also applicable are sulfobetaine surfactants, for example amidosulfobetaines such as lauramidosulfopropyl betaine of the following formula

cocoamido-2-hydroxypropylsulfobetaine, cocoamidodimethylsulfopropyl betaine, stearylamidodimethylsulfopropyl betaine and laurylamido-bis- (2-hydroxyethyl) sulfopropyl betaine. Imidazoline-based surfactants can also be used, including glycinates and amphoacetates, for example cocoamphocarboxypropionate, cocoamphocarboxypropionic acid, cocoamphocarboxyglycinate and cocoamphoacetate, aminoalkanoates, for example n-alkylaminopropionates and n-amino acids, and M-lauryl-3-iminodipropionic acid and its salts.

Non-ionic surfactants that can be used alone or in a mixture include compounds obtained by condensation of alkylene oxide with an organic hydrophobic compound, which can be aliphatic or alkyl aromatic. The length of the hydrophilic or polyoxyalkylene moiety that condenses with any hydrophobic compound may be such as to produce a water-soluble compound having the desired balance between the hydrophilic and hydrophobic moieties. Semipolar nonionic surfactants, including amine oxides, phosphine oxides and sulfoxides, can also be used.

Suitable classes of compounds include the following.

Condensation products of polyethylene oxide with alkyl phenols.

These compounds include condensation products of alkyl phenols, the alkyl group of which contains from about 6 to 12 carbon atoms in a straight or branched chain, with ethylene oxide, wherein said ethylene oxide is present in an amount of 5-25 moles of ethylene oxide per mole of alkyl phenol. The alkyl substituent in such compounds can be obtained, for example, from the polymerization products of propylene, diisobutylene, octene or nonene.

Condensation products of aliphatic alcohols with ethylene oxide.

The alkyl chain of an aliphatic alcohol may be straight or branched and contain about 8-22 carbon atoms.

Condensation products of ethylene oxide with the reaction product of propylene oxide with ethylene diamine.

Amine oxide surfactants, such as dimethyldodecylamine oxide, dimethyltetradecylamine oxide, etilmetiltetradetsilaminoksid, tsetildimetilaminoksid, dimetilstearilaminoksid, tsetiletilpropilaminoksid, dietildodetsilaminoksid, dietiltetradetsilaminoksid, dipropildodetsilaminoksid, bis- (2-hydroxyethyl) dodetsilaminoksid, bis- (2-hydroxyethyl) -3-2--dodekoksi gidroksipropilaminoksid, (2-hydroxypropyl) methyltetradecylamine oxide, dimethyl oleyl amine oxide, dimethyl (2 hydroxy dodecyl) amine oxide and the corresponding decyl, hexadecyl minutes and octadecyl homologs of the above compounds.

Surfactants based on the phosphine oxide, e.g. dimetildodetsilfosfinoksid, dimetiltetradetsilfosfinoksid, etilmetiltetradetsilfosfinoksid, tsetildimetilfosfinoksid, dimetilstearilfosfinoksid, tsetiletilpropilfosfinoksid, dietildodetsilfosfinoksid, dietiltetradetsilfosfinoksid, dipropildodetsilfosfinoksid, bis (hydroxymethyl) dodetsilfosfinoksid, bis- (2-hydroxyethyl) dodetsilfosfinoksid, (2-hydroxypropyl) metiltetradetsilfosfinoksid, and dimetiloleilfosfinoksid dimethyl (2-hydroxy-dodecyl) phosphine oxide and the corresponding dec the full, hexadecyl and octadecyl homologues of these compounds.

Sulfoxide surfactants, for example, octadecylmethyl sulfoxide, dodecylmethyl sulfoxide, tetradecylmethyl sulfoxide, 3-hydroxytridecylmethyl sulfoxide, 3-methoxytridecylmethyl sulfoxide, 3-hydroxy-4-dodecoxybutylmethyl sulfoxide-octodecyl-ethyl-octodecyl-ethyl-octodecyl-ethyl octoxide.

-8008833

Ethanolamide-based surfactants, for example coconut oil fatty acid monoethanolamide or diethanolamide, in which K is C ₁₀ -C ₄₀ alkyl, mainly C ₁₂ -C ₁₈ alkyl, for example oleyl or coco. Further, surfactants can be based on quaternary ammonium derivatives of diethylene triamine (ΌΕΤΑ), such as diamidoamine ethoxylates and imidazolines and quaternized esters. As a class, quaternized esters can be derivatives of compounds including methyldiethanolamine (ΜΌΕΑ), triethanolamine (ΤΕΑ) and I, I-dimethyl-3-aminopropane-1,2-diol (ΌΜΑΡΌ).

A variety of alkyl sulfates can be used as anionic surfactants, including fatty alcohol sulfates, fatty acid ether sulfates, alkyl phenol ether sulfates, alkylaryl sulfonic acids and their salts, cumene, toluene and xylene sulfonates and their salts and alkyl sulfosuccinates, for example sodium or ammonium lauryl sulfates . However, the preferred class of anionic surfactants are sulfates of monoalkyl substituted ethers of polyols of the formula KO- (CH ₂ CH ₂ ) _n 80 ₃ M, in which K represents alkyl C ₁₀ C ₁₈ , η is 2-6 (preferably about 2-3) and M represents a monovalent cation. Such compounds are sulfonated ethoxylated C ₁₀ -C ₁₈ alcohols that can be obtained from coconut oil, solid animal fat, or synthetically. The sodium laureth sulfate, which the authors successfully used, is the Να-salt of lauryl ether sulfate ethoxylated in the ratio of, on average, 2 moles of ethylene oxide per mole of lauryl acid and sulfonated, general formula CH ₃ (CH ₂ ) ₁₀ CH ₂ (OCH ₂ CH ₂ ) ₂ O8O ₃ Na.

In addition to simple processing reagents, the above compositions can be incorporated into metal polishing compositions, for example for silver or brass. Such substances can be formulated as liquids, immersed in objects such as jewelry or cutlery. After immersion, objects are usually rinsed with water and dried with a soft cloth. Alternative formulations are available in the form of creams or pastes, which are applied with a soft cloth and then removed.

The active ingredients introduced into the composition for immersion are usually acids with pKa no higher than 5, for example phosphoric, citric, oxalic or tartaric, together with thiourea or its derivatives, for example with alkyl derivatives such as methyl or ethyl thiourea. Compositions for creams or pastes may contain about 25 wt.% Mild abrasive, such as precipitated chalk, infusoria, silica or γ-alumina (for example, a fraction of 0.05 μm). It is believed that these ingredients are compatible with surfactants and processing reagents and can be administered when convenient by simple mixing.

Processing techniques

Surface treatment can be carried out after completion of the stages of manufacturing a shaped product from an alloy. Products can be cutlery, dishes or jewelry. Manufacturing steps may include torsion, extrusion, forging, casting, engraving, embossing, sheet ironing, ironing, brazing or welding, annealing and polishing using a polishing wheel / washcloth and aluminum oxide or iron oxide.

The product to be treated can be degreased in various ways: steam degreasing with or without ultrasound; water degreasing with or without ultrasound;

degreasing with an organic solvent with or without ultrasound (for example, degreasing with ethanol or acetone before treatment with thiol, which can give very good accelerated tarnishing test results);

simultaneous degreasing and treatment with thiol, and thiol is included in an organic or aqueous medium for degreasing.

For example, the product can be degreased using ultrasound in a treatment bath, immersed in a bath containing a processing reagent, for example 1 wt.% Stearyl mercaptan in a solvent, for example in Εη8ο1ν, rinsed in one or more solvent baths and evaporated. It is preferable to rinse the excess thiol with the same solvent used for treatment with thiol so that thiols that have not reacted with the metal surface are removed and cannot react with anything else. The solvent should not leave any residue at all or practically leave it so that subsequent washing with water or aqueous solvents becomes unnecessary and the product can be allowed to dry. The product can then be packaged for delivery to the distribution industry. This operation may include packaging the product in one or more protective wrappers (molding), placing it in a decorative box, and packaging the decorative box in a protective wrapper, such as a plastic film with thermal crimping. Products treated with an organic compound containing the groups -8H or -8-8-, as described above, and packaged, should not only go on sale in good condition, but also, being exhibited, for example, on a shelf or in an office for a long time period, persist without showing noticeable tarnishing for at least 6 months and possibly 12 months or longer.

Alternatively, the products can simply be polished using a composition containing 1-5 wt.% Of an organosulfur compound, for example stearyl mercaptan, together with surfactants

- 9 008833 with a cleaning agent, such as diatomaceous earth in a solvent. Another alternative is that they can simply be polished with a cloth impregnated with an organosulfur compound, for example cetyl or stearyl mercaptan, for example impregnated with a treatment agent in an organic solvent, for example n-propyl bromide, followed by drying. The advantages of a cleaning cloth are that it is easy to manufacture, can be easily used in a store or at home and in general for Argentum silver care (if necessary).

The processing method of the present invention would be particularly useful for protecting against tarnishing of blanks for stamping money immediately before stamping, since it has been found that various versions of the films of the present invention can be largely or entirely preserved during stamping operations and can protect newly stamped coins from tarnishing. It is important that coins in the conditions of stamping (minting) are packed with minimal use of manual operations, as Each manual processing, such as polishing with a soft cloth, involves the risk of damage to the coin. The present invention reduces the risk of such damage and can provide long-lasting tarnishing of coins.

The following is a description of the invention only in the form of illustrations with reference to the following examples. In all examples, the term "increased tarnishing resistance" of samples treated with stearyl mercaptan refers to comparison with Argentum silver samples that were not treated with anything except polishing and degreasing.

Example 1. The use of immersion treatment in a solvent (samples degreased with solvent).

Solutions were prepared containing stearyl mercaptan (0.1, 0.5, and 1.0 g) in Εηδοίν 765 (100 ml). Argentum silver samples polished and degreased using ultrasound using Εηδοίν 765 for 2 minutes were each immersed in one of stearyl mercaptan solutions for 2, 5 and 15 minutes. Then the samples were polished with clean cotton.

To assess tarnish resistance, alloy samples were placed on a glass plate in a fume hood about 25 mm above the surface of a 20% ammonium polysulfide solution so as to be exposed to hydrogen sulfide released from the solution. All samples showed good tarnishing resistance during the 1-hour test, while they turned very slightly yellow after 45 minutes of exposure to hydrogen sulfide. The light film on the samples was easily removed with a cleaning cloth impregnated with stearyl mercaptan.

For comparison, a sample of standard Sterling silver began to change color immediately after it fell into the conditions of the specified test, and an hour later became dull in the form of strong blackening, which could not be removed with a cleaning cloth impregnated with stearyl mercaptan. The same results were obtained on the second sample of Sterling silver, which was wiped with a cleaning cloth, and the color change began immediately as soon as the sample was placed in the test conditions. Sterling Argentum silver alloy obtained according to patent EP-B-0729398 began to fade after 3 minutes. Another Sterling Argentum alloy annealed in a selectively oxidizing atmosphere, as described in \ ¥ 0/02/09502, began to fade after 6 minutes. A markedly increased delay at the beginning of tarnishing was unexpected in the absence of an increased delay in the case of a standard Sterling silver product.

Example 2. The effect of solvent cleaning after processing.

Example 1 was repeated with Argentum samples, except that instead of polishing with cotton after treatment with mercaptan, the samples were degreased using ultrasound with Εηδοίν 765 for 2 minutes. Then the samples were tested for tarnishing, as described in example 1, and it was found that they all had increased resistance to tarnishing. The ability of the protective effect from treatment with stearyl mercaptan to be preserved during ultrasonic cleaning with Εηδοίν 765 shows that tarnishing resistance is achieved due to the reaction on the surface with the participation of stearyl mercaptan and, possibly, germanium in Argentum silver, and not due to the formation of a fat or oil layer on the surface of Argentum.

Example 3. The use of treatment by immersion in an aqueous solution (samples, degreased with solvent).

A tarnish treatment solution was prepared from the following ingredients.

Stearyl mercaptan 1 g

Εηδοίν 765 5 ml

Detergent (Ga1gu bk | w <1) 40 ml

Deionized Water 100 ml

Saryl mercaptan was dissolved in Εηδοίν 765, then the resulting solution was mixed with a detergent (Ga1yu Ys. | Shb). diluted with water and received an aqueous solution for processing. Argentum silver samples were polished and degreased using ultrasound at Εηδοίν 765 for 2 min, immersed in the indicated aqueous solution for 2 min at ambient temperature and then rinsed with tap water. It was noted that water immediately drained from the polished surface and the samples remained dry. Samples were tested for tarnishing, as described in example 1, and all samples showed increased resistance to tarnishing.

- 10 008833

Example 4. The use of processing by immersion in aqueous solution 2 (samples degreased with detergent). Sterling Argentum samples were degreased with a 2% aqueous detergent solution (Ra1gu 1ls | shs1) and then immersed in the processing solution from Example 3. It was noted that the treated samples repelled water as described in Example 3. The samples were tested for tarnishing, as described in Example 1 , and they all found increased tarnishing resistance. This test was repeated, except that Ea1gu 1ls | ss1 in the treatment solution was replaced with liquid hand soap (40 ml). When exposed to a solution of ammonium polysulfide, the samples did not show increased resistance to tarnishing. Perhaps this is due to the fact that the soap for the hands was more diluted.

Example 5. Simultaneous degreasing and anti-tarnishing treatment.

The following solutions were prepared.

g stearyl mercaptan ml ΕηΞοΙν 765 ml of detergent (Ga1gu Εχφΐίά)

100 ml deionized water g stearyl mercaptan ml ΕηΞοΙν 765 ml detergent (Gahgu bafnd)

100 ml deionized water g stearyl mercaptan (preferred amounts) ml ΕηΒοΙν 765 ml detergent (Gahgu Εϊαριίά)

500 ml deionized water g stearyl mercaptan ml Εηδοίν 765 ml detergent (Rahgu Ιιίφΐίά)

1000 ml deionized water

The solution was heated to 50 ° C in a vessel for cleaning using ultrasound. Argentum polished silver samples were ultrasonically degreased in solutions for 2 minutes and rinsed with tap water. It was found that the first three treatment solutions caused the repulsion of water from samples that remained dry. Samples treated with the first three solutions were tested for tarnishing, as described in example 1, and they all found increased resistance to tarnishing. However, in the case of samples treated with the last two solutions, water at the rinsing stage did not flow from their surface. When drying, smudges (streaks) were found on the surface that changed the color of the sample during the tarnishing test. A sample treated with 500 ml of solution changed color less than a sample treated with 1000 ml of solution. These experiments show that Argentum silver can be degreased at the same time, and a protective film against tarnishing can be formed on it when using thiol treatment in an aqueous system, and the more concentrated the solution of stearyl mercaptan / Epgio / detergent / water, the higher the resistance of the samples to tarnishing.

Example 6. Direct use - undiluted detergent solutions (samples degreased with solvent / samples degreased with an aqueous system).

The following solutions were prepared.

g stearyl mercaptan ml ΕηΒοΙν 765 ml of detergent (Yatgu Είςιιΐά) (preferred quantities) g stearyl mercaptan ml Εη3ο1ν 765 ml of soap (liquid hand soap)

-11 008833

First, stearyl mercaptan was dissolved in Εηδοίν. Then the detergent was mixed with the solutions. Silver was polished and degreased with ultrasound in Εηδοίν 765 for 2 minutes. Then, stearyl mercaptan / Ep8O1u / detergent solutions were applied directly to the surface of Argentum samples using wet cotton wool and rubbed in a foam. After that, the samples were rinsed with tap water. In each case, it was noted that water completely drained from the polished surface, leaving the samples dry. The samples were tested for tarnishing, as in example 1, keeping them above an undiluted solution of ammonium polysulfide for 1 h. All of them showed increased resistance to tarnishing. The specified direct method for the use of stearyl mercaptan was tested on samples defatted in a 2% Ba1gu bk aqueous solution. | Shb. Again, increased tarnishing resistance was found.

Example 7. The use of tissue (samples, fat-free solvent).

Tissues were prepared by immersing flaps of clean cotton fabric in the following solutions and drying:

0.1 g of stearyl mercaptan dissolved in 100 ml of Εηδοίν;

0.5 g of stearyl mercaptan dissolved in 100 ml of Εηδοίν;

1.0 g of stearyl mercaptan dissolved in 100 ml of Εηδοίν (preferred).

Argentum silver samples (which were polished and ultrasonically degreased at 65ηδοίν 765 for 2 min) were wiped with a cloth and then wiped with clean cotton wool. The samples were tested for tarnishing, as in example 1, by keeping near the above solution of ammonium polysulfide for 1 h. All samples showed increased resistance to tarnishing.

Example 8. Hexadecyl- and octadecylmercaptans in Ba1gu bk. | Shb.

Liquid hexadecyl mercaptan (1 g) was mixed with Bayoux bk | sb (a surfactant containing anionic and nonionic surfactants) and with water in the amounts given below .______________________________________________________________________

Link Bayu Ytsshb, ml Deionized water, ml 8.1 40 Not 8.2 one hundred Not 8.3 200 Not 8.4 40 one hundred 8.5 40 200

As it turned out, the ingredients of solution 8.2 mix well without hexadecyl mercaptan if they are previously dissolved in an organic solvent. A Argentum silver sample was immersed in the resulting solution for 10 minutes and rinsed. The surface of the Argentum sample became hydrophobic, which suggests the formation of a layer of hexadecyl mercaptan attached to the silver surface of Argentum. When rinsing with water, no noticeable residue remains on the surface. A portion of the sample was wiped with cotton moistened with Εηδοίν 765 and tested for tarnishing with an undiluted solution of ammonium polysulfide for 45 minutes. The samples showed exceptional resistance to tarnishing without a significant difference between the area treated with участηδοίν 765 and the untreated area. Similar solutions were prepared from octadecyl mercaptan and Bayoux bk. | Shb. At first they were transparent, but less stable with the separation of the surface layer of octadecyl mercaptan after a few months.

Example 9. Hexadecyl mercaptan in a simple shower gel.

The liquid hexadecyl mercaptan was mixed with a simple shower gel (clear shower gel from Lssen Na Nei Ibn Bea1b L1b., Btrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr that are believed to contain sodium laureth sulfate and cocoamidopropylbetaine as the main surfactants along with cocamide ) and with water in the amounts given below ._____________

Link ΗΌΜ, g Simple gel, ml Deionized water, ml 9.1 one one hundred not 9.2 one one hundred one hundred 9.3 5 one hundred one hundred 9.4 one 200 one hundred

Shortly after mixing, solutions 9.1 and 9.4 were completely transparent viscous gels without a noticeable separation of hexadecyl mercaptan. Sample 9.2 was also completely transparent, but had a consistency close to that of water, and there was also no noticeable release of hexadecyl mercaptan. Sample 9.3, which also had a consistency close to that of water, looked like a milk emulsion when shaken, but when standing, it revealed detachments of hexadecyl mercaptan on the surface.

In a preliminary experiment, a Argentum silver sample was immersed in solution 9.1 for 10 min and rinsed. The surface of the Argentum sample became hydrophobic, which suggests the formation of a layer of hexadecyl mercaptan bound to the silver surface of Argentum. The silver pattern is well spread.

- 12 008833 nodded with water, leaving no noticeable residue on the surface after rinsing. When tested with undiluted ammonium polysulfide, exceptional tarnishing resistance was noted.

Samples of Argentum silver and traditional Sterling silver were prepared as follows. Each sample was polished with a polishing compound 81e1bn111 then crocus and ultrasonically degreased for 2 min in a 2% solution of Ea1bu bcc in water at 54 ° C. Then degreased for 5 min in ethanol and immersed at ambient temperature in the test solution. After the sample was removed, part of each sample was wiped with a cloth dampened with Εηδοίν 765 and tested for tarnishing with undiluted ammonium polysulfide for 45 minutes. Argentum silver samples showed exceptional tarnishing resistance and thiol binding, and especially good results were obtained with solutions 9.1 and 9.4 compared to solutions 9.2 and 9.3 with a higher water content. Solutions 9.1 and 9.4 appear to have some protective effect against tarnishing on standard Sterling silver as well, but the thiol layer can be easily removed, as follows from the differences between the untreated section and the section treated in Εηδοίν 765.

Example 10. Mixtures of cocoamidopropyl betaine (CPB) and sodium laureth sulfate (8L8).

These substances are supplied by 8GGAS11ET. ο £ ее Й Й 8 8, Ishiy Κίη ^ Ηοιη, in the form of a thick fluid aqueous liquid and a highly concentrated gelatinous liquid (70% of the active substance). Liquid hexadecyl mercaptan (1 ml) was mixed with these substances in the amounts shown below.

Link 8b8 ml SRV, ml Water ml 10.1 40 40 one hundred 10.2 40 twenty one hundred 10.3 thirty 10 one hundred 10.4 10 thirty fifty 10.5 thirty 10 160

To prepare a solution of 10.1, hexadecyl mercaptan was added to a thick mixture of sodium laureth sulfate and cocoamidopropyl betaine, after which water was added and the solution was cooled. The resulting mixture initially had a thick foamy white texture, which when standing turned into a transparent gel. Solution 10.2 was prepared similarly. Solution 10.3 was liquid and at first slightly transparent with bubbles above and became transparent after standing overnight. Solution 10.4 was mixed with gentle heating to about 35 ° C. Heating in some way facilitated mixing. After a few minutes of stirring, the mixture foamed strongly. The mixture was left overnight and a viscous solution was obtained. Solution 10.5 was heated to about 35 ° C with stirring. Water was added last. Stirring was facilitated by heating. The solution foamed, but after a few hours (up to 12 hours) the standing became transparent and somewhat thicker than water.

Argentum silver samples were prepared by polishing with 81E1Lpd1L polishing compound and then with crocus, ultrasonically degreased in a 2% aqueous solution of RaGu Idium, then degreased with acetone, immersed in the test solution at ambient temperature for 10 min and washed with cold tap water. A small portion of each sample was wiped with a cloth dampened with Εη8ο1ν, trying to remove any thiols, after which the sample was left standing for 45 minutes and accelerated tarnishing testing was carried out by keeping it close to undiluted ammonium polysulfide for 45 minutes.

All samples showed extremely good hydrophobic properties when rinsing, indicating the presence of thiols. Drops of water drained completely and there was no need to dry the sample. Samples successfully passed the tarnishing test and only a slight difference was observed between the rubbed and non-rubbed areas. It was concluded that hexadecyl mercaptan in each sample tested created a thiol layer on the Argentum silver surface to protect it from tarnishing.

Claims (23)

CLAIM 1. The method of processing the finished product or semi-finished cutlery, dishes or jewelry made of silver / germanium alloy with a silver content of at least 77 wt.% And germanium 0.4-7%, the rest is mainly copper, in order to reduce or additionally reduce the tarnish of the product so that the sample of the alloy from which the product is made can be placed near above a 20% solution of ammonium polysulfide for at least 30 minutes while maintaining the mostly non-tarnished form, including the surface treatment indicated of products alkanethiol, alkiltioglikolyatom, dialkyl sulfide or dialkyl. 2. The method according to claim 1, wherein the alkanethiol, alkylthioglycolate, dialkyl sulfide or dialkyl disulfide contains alkyl groups C12-C24. 3. The method according to claim 1 or 2, wherein the alkanthiol, alkylthioglycolate, dialkyl sulfide or dialkyl disulfide is in an organic solvent. - 13 008833 4. The method according to claim 3, wherein the solvent containing alkanethiol, alkylthioglycolate, dialkyl sulfide or dialkyl disulfide is substantially neutral. 5. The method according to claim 3 or 4, in which the alkanethiol, alkylthioglycolate, dialkyl sulfide or dialkyl disulfide are in a solvent based on n-propyl bromide. 6. The method according to claim 3 or 4, in which the alkanethiol, alkylthioglycolate, dialkylsulfide or dialkyl disulfide are (a) in the composition obtained by dissolving the indicated alkanthiol, alkylthioglycolate, dialkylsulfide or dialkyl disulfide in an organic solvent and adding to the solution in relation to the concentrated water in an organic solvent or dialkyl sulfide or dialkyl disulfide in an organic solvent and adding to the solution in relation to the concentrated water, dialkyl sulfide or dialkyl disulfide in an organic solvent detergent, or (b) in an aqueous dispersion obtained by dissolving said alkanethiol, alkylthioglycolate, dialkyl sulfide or dialkyl disulfide in an organic solvent, adding to the specified solution relative to a concentrated aqueous solution of soap or detergent and diluting the resulting mixture with water. 7. The method according to claim 1 or 2, wherein said alkanethiol, alkylthioglycolate, dialkylsulfide or dialkyl disulfide are in a composition obtained by dissolving said alkanethiol, alkylthioglycolate, dialkylsulfide or dialkyl disulfide directly in an aqueous mixture of anionic surfactant and neutral, amphoteric. -active substances, and this mixture does not contain other solvents except water. 8. The method according to claim 7, in which the specified composition contains betaine as a surfactant. 9. The method according to claim 8, in which the betaine is cocoamidopropyl betaine. 10. The method according to any one of claims 7 to 9, further comprising an anionic surfactant. 11. The method according to claim 10, in which the anionic surfactant has the formula KO (CH ₂ CH ₂ ) _p 8O ₃ M, in which K is C ₁₀ -C ₁₈ alkyl, η is 2-6 and M is monovalent cation. 12. The method according to claim 11, in which the anionic surfactant is a monovalent cationic salt of laureth sulfate. 13. The method according to any one of claims 7 to 12, in which the composition contains an amphoteric or zwitterionic surfactant and an anionic surfactant in a mass ratio of from 1:10 to 10: 1. 14. The method according to claim 9, wherein the aqueous mixture contains sodium laureth sulfate and cocoamidopropyl betaine. 15. The method according to any of the preceding claims, wherein the alkanethiol or alkylthioglycolate is selected from stearyl mercaptan (octadecyl mercaptan), cetyl mercaptan (hexadecyl mercaptan), stearyl thioglycolate and cetyl thiogly glycolate. 16. The method according to any of the preceding paragraphs, in which the alloy consists, in addition to impurities and a grain grinder, from 92.5-98% silver, 0.3-3% germanium and 1-7.2% copper by weight of the alloy, together with 1-40 ppm boron as a grinder grain. 17. The method according to p. 16, in which the ternary alloy consists, in addition to impurities and a grain grinder, from 92.5-96% silver, 0.5-2% germanium and 1-7% copper by weight of the alloy, together with 1- 40 ppm boron as a grinder grain. 18. The method according to any one of claims 1 to 15, in which the alloy is a quadruple alloy of silver, copper, zinc and germanium. 19. The method according to any of the preceding paragraphs, comprising the additional step of packaging the processed product. 20. The method according to claim 19, in which said package includes a decorative box. 21. The method according to claim 20, in which the package includes an overwrap for a decorative box. 22. Use of C1 ₂ -C ₂₄ alkanethiol, alkylthioglycolate, dialkyl sulfide or dialkyl disulfide in preparing a tarnishing inhibitor for a silver / germanium alloy product with a silver content of at least 77% by weight and germanium from 0.4 to 7%, the rest is mainly copper, in order to reduce the alloy tarnish so that the sample can be placed close over a 20% solution of ammonium polysulfide for at least 30 minutes while retaining the mostly non-tarnished form. 23. Finished product or semi-finished cutlery, dishes or jewelry made of silver alloy containing germanium in an amount that is effective for reducing the hot spot and / or tarnishing, which was treated with C1 ₂ -C ₂₄ alkanethiol, alkylthioglycolate, dialkyl sulfide or dialkyl disulfide and shows such resistance to tarnish, that the sample of the alloy from which the product is made can be placed near above a 20% solution of ammonium polysulfide for at least 30 minutes while maintaining epotusknevshego species.