Organic compounds -- part of the class 532-570 series – Organic compounds – Thiocarboxylic acids or salts thereof
Patent
1998-10-28
1999-11-09
Geist, Gary
Organic compounds -- part of the class 532-570 series
Organic compounds
Thiocarboxylic acids or salts thereof
205 65, C07C 51305
Patent
active
059817933
DESCRIPTION:
BRIEF SUMMARY
The present invention pertains to slightly water-soluble metal salts having the formula I ##STR3## wherein R.sub.1 and R.sub.2 are the same or different and represent hydrogen or a lower alkyl group of from 1 to 3 carbon atoms, M is the cation of a metal which forms slightly water-soluble sulfides, and n means 1 or 2, and mixtures thereof, a process for the preparation thereof, and the use thereof as gloss additives in the electrolytic deposition of metals.
From DE-PS-885 036, a process is known for the production of shining silver precipitates wherein sulfur-containing compounds, such as carbon disulfide (and other sulfur-containing compounds), are reacted with ketones and strong alkali, followed by acidification, precipitation and, optionally after redissolution with alkali and renewed precipitation with mineral acid, using them as additives for silver plating baths. Frequently, formaldehyde or Turkey red oil were also added to such silver plating baths.
From DE-PS 27 31 595, it is known that such baths can be improved if the condensation products of ketone, alkali hydroxide and carbon disulfide are admixed with water-soluble salts of naphthalenesulfonic acid/formaldehyde condensation products. Especially when added to cyanide-type silver plating baths, it is possible to thus prepare high-gloss silver precipitates.
From the works by Apitzsch, Berichte 37, 1599 (1904), and Berichte 38, 2888 (1905), as well as Berichte 41, 4028 (1908), it has been known that the condensation of ketones with carbon disulfide followed by acidification yields cyclic compounds having the formula: ##STR4##
To date, it has been considered that such cyclic compounds accounted for gloss generation in silver plating baths. Mass spectroscopical examinations of such reaction mixtures have now confirmed that the cyclic compounds actually form. In the past, it has been attempted to enrich this cyclic fraction in particular, to add it to the brighteners.
Intensive studies by Applicant have now yielded the surprising result that it is not these cyclic compounds which account for gloss formation, but the compounds of formula I formed as side-products prior to the acidification, wherein, however, M is the cation of a metal which forms sulfides readily soluble in water. In all methods for the preparation of condensation products of ketones with carbon disulfide described and practised to date, there were formed either the water-soluble alkali metal salts, or the slightly soluble cyclic compounds which can be precipitated with acids.
It has now further been established that these side-products, the compounds according to the invention, can be stabilized and separated in an undecomposed form if they are precipitated as slightly water-soluble salts. Slightly soluble salts are predominantly formed by the metals which also form slightly water-soluble sulfides. Thus, in addition to silver, these are in particular copper, lead, bismuth, antimony, cobalt, iron, zinc, palladium, molybdenum, tin, and gold.
It has further been established that these slightly soluble metal salts are not only essentially more stable than the side-products or cyclic compounds, which have been observed to be unstable, but that these slightly soluble metal salts are in addition excellently suited for acting as gloss additives. The usual primary brighteners, such as Turkey red oil and the condensation products of formaldehyde with naphthalenesulfonic acids, can even be dispensed with. At any rate, significantly improved gloss layers of silver are obtained with or without the addition of these known primary brighteners. It appears that these slightly soluble metal salts are capable of redissolving in electrolytes to such an extent that they can serve the function of a brightener.
The novel metal salts are effective in concentrations of 0.005 to 0.3 g/l already. Evidently, the other components of the electrolytes increase the solubility of the slightly soluble metal salts so that they become redissolved. The process for the preparation of the slightly soluble metal salts of f
REFERENCES:
patent: 1788632 (1931-01-01), Powers
patent: 2666738 (1954-01-01), Kardos
patent: 4455262 (1984-06-01), Detienne
Thuillier et al., Presentes a La Societe Chimique, "Composes organiques sulfures (*).V. --Condensation du sulfure de carbone et de l'acetone", No. 367, pp. 2182-2186.
Thuillier et al., Preesentes a La Societe Chimique, "Composes organiques sulfures (*).VI--Condensation du dulfure de carbone et des cetones aliphatiques", pp. 2187-2193.
Heyer Joachim
Kleinfeld Marlies
Knaak Eberhard
Van Wijngaarden Christel
Blasberg Oberflachentechnik GmbH
Geist Gary
Vollano Jean
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