DE1771371B1 - CYANIDE-FREE ALKALINE ZINC BATH - Google Patents

Description

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The invention relates to cyanide-free or high gloss supplies. The invention consists in that a zinc compound containing essentially cyanide and the bath as a polymer contains a reaction product of a polymer with repeating amine bonds, alkylene polyamine with an epihalohydrin, containing, aqueous, alkaline zinc bath for electrical tertiary and / or quaternary amino groups and trolytic shutdown of shiny, metallic 5 has a molecular weight of more than 250.
Zinc coatings. The bath according to the invention is characterized by a

Most of the currently known zinc provides and provides good stability over long periods of time baths is formed from alkaline solutions that have a precipitate with a shine and a scatter-soluble zinc compound and substantial amounts of ability that is equal to or even better than that Contain sodium cyanide. io gloss and the throwing power of commercially available cyanide

Such a cyanide bath produces semi-glossy zinc-zinc baths.

Coatings, and it is necessary to use the galvanic As zinc compounds for the inventive

Add bad brighteners. The well-known gloss bath, all zinc compounds can be used Formers include, for example, compounds such as those soluble in an alkaline medium, which as Aldehydes, ketones, thioureas, salts of organic electrolytes are suitable for a galvanic bath. At-acids and similar games for such zinc compounds are zinc sulfate,

The use of the toxic cyanides in these zinc acetate and zinc oxide.

Baths obviously form a significant The amount of metallic zinc in the bath is not

Disadvantage and leads to considerable problems in the critical and can, as it is in electroplating, handling the baths. In particular, it is known, as is the case with other known zinc baths the use of used baths can be a significant factor. Preferably, however, the salary should the bath of metallic zinc according to the invention

With a view to disposal in particular, it should be around 8 to 30 g / l.

The amount of alkaline compound such as gnawing was required of the needed cyanide baths made to cyanide-free electrolytes to 25 trium hydroxide should of course be larger than that create through which this difficult removal amount that is required for the formation of the sodium zincate problem is avoided. There are some cyanide free wills. The amount of excess or free Na- or substantially cyanide-free galvanic zinc trium hydroxide is not critical as long as it is sufficient baths are known to keep the sodium zincate in solution with an excess of the entire amount of zinc and any shot contain sodium hydroxide. 30 prevent the precipitation of zinc.

Alkaline zinc baths with a high pH value The pH value of the electrolytes according to the invention give However, if you do not use brighteners or other solutions it will generally be essential Additives are used, matte, spongy lower- be larger than twelve.

hit with bad looks. It was proposed that the polymers used as additives to produce

Beat this disadvantage by adding 35 shiny zinc coatings are used To avoid glycolates, the too smoother, low-water-soluble polycondensates of an alkylene polyamide Beat should lead, however, in this way and an epihalohydrin. The molecular weight of the Economically viable, glossy coatings not polycondensate is greater than 250. Preferably be achieved. It has also been proposed that the condensates have a molecular weight greater than strongly alkaline zincate baths alkanolamines, and 40 than 1000, and it was found that polymers with either alone or in conjunction with Aide- a molecular weight between about 4000 and 5000 hyden, add to the precipitation a particularly well suited.

to give better shine. Baths of this type were polymer products of polyamines and compounds

However, not sufficiently stable, there were no host fertilizers that had functional parts that react with the amine commercially useful glossy deposits and 45 groups can according to the invention the electroplating area, in which shiny low-gloss materials are also used as additives, provided Impacts were achieved, was not comparable with that of the polymeric products known recurring amino, Cyanide groups and a molecular weight of more than 250 produce shiny precipitates, preferably baths. It is also known that the highly alkaline wise have over 1000.

Zincate baths Alkylenamines, such as Ethy- 50 Special products, which are particularly advantageous diamine, Diethylenetriamine, triethylenetetramine, or have shown that they are water-soluble Tetraethylene pentamine, either alone or together, quaternary condensation products of epichloromite to add an aldehyde compound. This hydrin and dimethylammopropylamm, which according to Baths, although made shiny deposits, have either of the following two methods deliver and are comparatively more stable than the above-55 can be.

called baths, still the considerable after- In the first process 102 g of dimethyl

part of a very narrow .... density range, in which aminopropylamine in a three-necked flask is shiny Precipitation occurs, as well as a small one, which contains 612 g of water. The piston is located Throwing power. in the water bath and is with a stirrer, a

In most cases, the manufacturing experience has shown 60 thermometers and a funnel with a stopcock that these are also provided with so-called cyanide-free. After the solution has been cooled, solutions or baths have small amounts of sodium and are kept at 25 ⁰ C, the aqueous solution contained in the flask will require cyanide in order for them to be practical in the course of an hour, especially with regard to shiny slowly 161 g Epichlorohydrin added. That mole precipitations. 65 ratio of epichlorohydrin and dimethyl. In contrast, the invention has the task of aminopropylamine is 1.75: 1. After the basic task of creating a zinc bath, to which the total amount of epichlorohydrin has been completely added, is free of cyanide and the zinc precipitates are with, the reaction is allowed to take place for a further 30 minutes.

Claims (1)

3 4 to run. After that, the reaction product is turned with the help, and are for a factory galvanizing of sulfuric acid at a pH of about 6, generally about 3 A / dm ² is recommended. acidified. The following are some examples of galvanic In the second method, 422 g of dimethyl zinc baths according to the invention are indicated. With all aminopropylamine in 820 ml of water with 368 g of Epi- 5 these baths were at a current density of about chlorohydrin in a flask in the same way 3 A / dm ² on steel cathodes shiny zinc low- implemented as was the case with the first procedure. hit scored. . . The molar ratio of epichlorohydrin and dimethyl- Example 1 aminopropylamine in this case is 0.9: 1. Post-metallic zinc as zinc sulfate 15 g / l When the reaction is complete, the sodium hydroxide is 200 g / l resulting product together with 110 g of sodium condensation product of epichlorohydro- hydroxide in an autoclave and in it under it and dimethylaminopropylamine, the Stirring heated to 50 ° C. Then 300 g of Me- are prepared according to method 1 and a methyl chloride under a pressure in the range of about molecular weight from about 4,000 to 5,000 2.8 to 3.5 kg / cm ² are used to exit the autoclave, which has 1.0 g / l to wash. The autoclave is then cooled and hydrobenzaldehyde 0.4 g / l its content is extracted. The obtained solution _R. . is based on a solids content of 50% and an example U pH adjusted to about 6. Metallic zinc as zinc oxide 22 g / l In general, the addition of 0.1 g / l of an epi-20 sodium hydroxide is 540 g / l chlorohydrin - dimethylaminopropylamine - condensa- Quaternized condensation product tion product to a sodium zincate bath, which is free of epichlorohydrin and dimethylamino- Contains sodium hydroxide, a semi-glossy top-propylamine, which is produced by procedure 2 surface of the zinc precipitate, in contrast has been produced and a molecular to the previously achieved matt white, which has no weight in the range from about 4000 to Has gloss. If further amounts of the polymer 5000 have 1.5 g / l are added, even glossier vanillin is 0.6 g / l Precipitation achieved. Optimal results were obtained with _R. . . an amount of 1 g / l of the specific B e 1 s ρ 1 e given above Polymers achieved. 30 Metallic zinc as zinc acetate Hg / 1 With the bath according to the invention, potassium hydroxide 190 g / l can still be used high-gloss and leveled precipitates generated condensation product of epichlorohydro- if the bathroom is also a conventional one and dimethylaminopropylamine that Aldehyde brightener is added. The combi according to method 2 has been produced ned gloss formation and leveling caused by the 35 and a molecular weight of about 4000 synergistic effect of the two additives is achieved, up to 5000 has 0.5 g / l was not to be expected because aldehyde brightener in anisaldehyde 0.2 g / l Zinc cyanide or other zinc baths do not have a leveling effect. Furthermore, it was established claims:
that the amount of aldehyde which is required to achieve the desired gloss is less than in a zinc compound and polymers with themselves again in the known zinc baths. Aqueous, containing amine bonds Suitable aldehyde brighteners are, for example, an alkaline zinc bath for electrolytic deposition Vanillin, hydroxybenzaldehyde, anisaldehyde, bisulphite formation of shiny, metallic zinc coatings, Compounds of aldehydes and the like. The additives according to 45, characterized in that they are used as of the invention are primary brighteners and are a reaction product of an alkylene polymer polymer needed in any case to get good results. contains amine with an epihalohydrin, wherein The above-mentioned secondary brighteners can make the polymer tertiary and / or quaternary amino can be used optionally if even more shiny groups and a molecular weight of more than Zinc coatings are desired. The amount of a 50 has 250. such secondary brightener, e.g. B. anisaldehyde, 2nd bath according to claim 1, characterized in that can be varied in a known manner within wide limits that the polymer will at least one again. For example, anisaldehyde can have linking tertiary or quaternary amino groups with the additives in amounts as small as 0.1 g / l. used up to amounts of 1 g / l and even more 55 3. Bath according to claim 1 or 2, thereby being indicates that it contains a polymer whose A small amount of cyanide, for example Na molecular weight greater than 1000. trium cyanide, can if desired also in connection 4. Bath according to claims 2 and 3, thereby can be used with the baths of the invention. characterized in that, as a polymer, it is a reaction However, the presence of cyanide is essential for the product of a polycondensation of epichloro generation of shiny zinc coatings according to the invention hydrin and dimethylaminopropylamine with one not essential. Contains molecular weight between 4000 and 5000. The baths can be operated with current densities. 5. Bath according to one of the preceding claims, as is customary in the case of galvanic zinc baths, characterized in that there are one. For example, current densities in the range 65 may contain secondary aldehyde brighteners,
from 0 to about 6 A / dm ² , as determined with the Hull cell 6th bath according to one of the preceding specifications, can be used. It is, however, characterized in that its pH-partial, current densities of about 3 to 6 A / dm ² to a value of more than 12.