DE729069C - Production of cadmium red - Google Patents

Description

Production of Cad'mium Red It is known to use red pigments containing selenium by heating cadmium sulfide with selenium to high temperatures. Here finds a more or less extensive conversion to cadmium selenide and free sulfur instead of. The latter escapes due to the high reaction temperatures, see above that essentially a red mixed crystal of CdSie and CdS remains. This however, older method suffers from several disadvantages, most notably being through The high temperatures also volatilize copious amounts of selenium and thus go lost for implementation. Furthermore, undesirable coarsening of the grain occurs that have an unfavorable influence on the quality of the end product. This latter deficiency is increased by the fact that depending on the heating: gs: degree and the heating date fluctuating degrees of conversion can be achieved, so that non-uniform reaction products attack. However, as is well known, the inconsistency of the end products is precisely at Colors and pigments are particularly annoying and unpleasant, especially here on compliance a certain nuance is important.

It has now been found that one can be particularly advantageous valuable Ca & mium red can be produced if one mixes the cadrnium sulfide and selenium or release selenium: contain de substances, heated in the presence of such substances, which chemically bind and / or carry away the sulfur released during the reaction. As such substances come into consideration z. B. Oxidizing agents such as ammonium nitrate or other nitrates or nitrites or reducing agents, e.g. B. hydracine hydrate. Such substances oxidize the sulfur released during the reaction, d. H. converted into SO2 or reduced, d. H. in hydrogen sulfide or volatile Sulphides transferred, so that these substances from the reaction mixture during the reaction come off and thus achieved a complete removal of the sulfur released will. Similar effects can be achieved through the use of Phosphorus, Arsenic or antimony achieve as additives, the sulfides formed during escape the reaction.

There is a further embodiment of the previous method in that the reaction mixture is heated in the presence of such substances that the The sulfur released during the reaction is converted into compounds that act as such initially remain in the reaction mixture, but if they are subsequently washed out can be easily removed. Such substances are: nitrates and nitrites of alkali metals, also alkalis, e.g. B. Hydro @ yde or carbonate. Through this The sulfur released during the reaction is initially added in the form of alkali stilfates, -sulfites or polythionates bound. Other additives can be considered Light metals, e.g. B. Magnesium, able to bind sulfur, but without im essential to block selenium. On the other hand, reducing agents can also be used as additives add, e.g. B. Hvdride or Amicle of the alkali metals or i- # rlallcalinietalle. In this case, the sulfur released during the reaction is in the form of sulfhy Roast or sulfides bound. Organic substances can also be processed in an analogous manner send that combine with sulfur under the reaction conditions, z. B. Olfinic compounds (diolefin, terpenes and the like) or organic amines, e.g. B. Diphenylamine. Particularly advantageous effects are achieved when using Cvanides as sulfur-binding additives. yThese substances are here in Rhodanide transferred, which can subsequently be easily removed by washing with water are. Above all, however, the formation of cadmium red takes place in the presence of Cyanides, e.g. Potassium cyanide, sodium cyanide, calcium cyanide and the like; at especially low temperatures, which leads to the formation of particularly high-quality pigments is. : Ulan can also initially combine selenium with the cvanids to form Seienocyanirlen and make them react with the cadmium sulfide.

The sulfur compounds formed in this way are subsequently removed by washing them out with suitable solvents. So you can z. B. Remove sulfates, sulfites and sulfides by washing finitely water. Sometimes it is advantageous to use weak or dilute aqueous acids instead of water for this purpose, e.g. B. phosphoric acid, formic acid, acetic acid. The use of stronger acids or such higher concentrations is generally impractical, since this can result in partial decomposition of the calcium red. Furthermore, as a means of wash consider organic solvents tel, e.g. B. benzene. So the new procedure will be in the highest easily done by cad Niiumsulfirl or such containing mixtures -en together with selenium or selenium release- the substances and sulfur-binding resp. -Leading substances in a crucible or the like. be heated. As selenium-releasing substances for example, the se- lenides or polyselenides of the alkali metals or other metals. In this case it can da; s metallic cation at the same time as heavy field-binding agent in the sense of the present the invention work, so that in this Case the formation of cadmium red, under double pelter implementation takes place. = 11s wide- res example of a selenium-releasing substance - called selenious acid, but it is still finite a reducing agent is to be added finitely. In addition, the formation of ', @; i, lniiuni- red within the meaning of the present invention too in the further presence of lliiie! -alisators. z. B. \ atrium chloride. carried out «-erden. On the other hand, the implementation can also be present inert extenders, e.g. B. Barituti- sulfate. As has also been found, the implementation of the reaction mixture is effected finitely advantageously at lower temperatures than those previously used and were also required. In general, according to the invention, temperatures below about 600 °, advantageously between aoo and 500 °, can be used. Excellent results are achieved in the lower temperature ranges between about 200 and;> o-. This is made possible and achieved in particular by the addition of cvanides, as already mentioned above.

The new way of working leads to particularly fine powdery cadmium red. Because these particularly fine-grained pigments are particularly chemically active and they are Glowing with pyrophoric oxygen at moderately elevated temperatures is recommended it is the reactions or the subsequent cooling to the exclusion of ozvdierencler Gases, advantageously in the presence of inert or reducing gases such as carbonic acid, Nitrogen on the one hand. or hydrogen, carbon oxide and the like, on the other hand. You can by adding mineralizers or by appropriate choice of Temperature also get pigments of any grain size. In all cases and especially in the production of fine-grained cadmium red, pigments of the highest quality are obtained Intensity and purity of the colors. It is also possible according to the invention, under Keeping the Once working conditions have been established, pigments are always used consistent quality and color. Another significant one The advantage of the new process is that selenium losses are practically avoided can be.

The pigments produced according to the invention can be used as color pigments for paints, fillers and films, and also as color pigments for ceramic purposes, such as the manufacture of glasses and glazes, and finally as coloring fillers e.g. B. for plastic masses, synthetic resins and rubber.

Claims (1)

PATENT CLAIMS: i. Process for the production of calcium red by joint heating of cadmium sulphide and selenium, characterized in that mixtures: containing calcium sulphide and selenium or selenium-releasing substances are heated in the presence of substances which chemically remove the sulfur released during the reaction A process according to claim 1, characterized in that the heating is carried out in the presence of substances which convert the sulfur released in the reaction into compounds which are removed by subsequent washing out Claim i or characterized in that the heating is carried out at temperatures below 600 °, preferably between zoo and 500 ° .d .. Process according to Claims 1 to 3, characterized in that CSanide is used as the sulfur-binding agent.