DE4238956A1 - Water-soluble organic cpds used as additives in electrolytic bath anolyte(s) - inhibit halogen gas formation during metal deposition, said cpds contg at least one double or triple bond and at least one hydrophilic group - Google Patents

Abstract

Water-soluble organic cpds. contg. at least one double or triple bond and at least one hydrophillic group are used as additives to anolytes used in electrolytic coating baths. Pref. cpds. are vinylsulphonic acid, sodium vinylsulphonate, allylsulphonic acid, sodium allylsulphonate, vinylacetic acid, potassium vinylacetate, propynylsulphonic acid, sodium propynylsulphonate, diethylpropynyl ammonium chloride, dimethylpropynyl ammonium hydrogen sulphate, 1,4-butyndiol or sodium alpha-hydroxypropynyl sulphonic acid, used at concns. of 0.01-10 g/l in Zn, Ni or Cu electrolytic baths contg. an inert electrode encased in a membrane impervious to liquid, said membrane being composed of an ionic exchange material or a plastic. ADVANTAGE - Halogens arising from the galvanic deposition process are adsorbed and undergo chemical reaction, thereby avoiding formation of toxic gases. The claimed additives do not break down in acidic Ni, Cu or Zn electrolytes. Cheaper material not resistant to halogens may be used as anodes. Additives do not effect the deposited metals.

Description

The invention relates to the use of water-soluble organic compounds as additives in the anolyte in galvanic metal deposition baths, wherein the Formation of toxic halogen gases on an inert Anode is prevented.

For depletion or for leveling the metal concentrates tration in galvanic baths such. B. in acidic Nickel, copper or zinc electrolytes become membranes moduloden used, consisting of a liquid-tight Housing in which an anolyte and an inert anode are stored (US Patent 4,778,572). This is separated Space through a nonporous membrane as an example Cation-exchange membrane, the galvanizing field is adapted. The proportion of these insoluble anode modules based on the proportion of the total current is approximately 5 to 35%. This is necessary because usually the Anodic current yield compared to the cathodic Current efficiency is higher, d. H. it will be more metal Anodically dissolved as cathodic deposited. Thereby increases the metal concentration in the bath and the Elek trolyte gets out of his workspace. This problem is through partial or complete use of inert anodes - especially by membrane module anodes - (see Figure 1), (Craig J. Brown, Eco-Tec Inc., Presented at SUR / FIN 1989, Cleveland, Ohio, June 1989).  

Another advantage of the inert anodes is that through This measure also regulates the pH of the electrolytes can be and thus a salination or enrichment is avoided by heavy metal salts. This is off Environmental protection aspects seen a very important point, because it does not cause any heavy metal-containing sludge that is recycled or must be stored in landfills.

Closed systems can work without the partial or complete use of inert anodes not currently be realized because there is no electrolyte, the has a 100% cathodic current efficiency.

The use of inert anodes are nowadays a few Disadvantages:

There are problems with halogen-containing electrolytes, such as they are mostly to be found. Despite the use of Cation exchange membranes migrate halogen ions into the Anode space and become healthy at the inert anode harmful halogen gases - especially fluorine, chlorine, Bromine or iodine gas - oxidized.

Usually it is harmful to avoid health installed an intensive suction on the anodes, which only shifts the problem. Be here then attached to the exhaust air scrubber, the ent adsorb or react with toxic halogenated gases. These solutions must then be specially cleaned or be disposed of.

In addition, there are only a few halogen-stable anode materials lien. The thus necessary frequent changes and you high price is a widely used application opposite.  

Prior art is (DE-OS 40 32 856, US-PS 4,778,572), that the membrane electrolysis modules in the "feed and bleed" Ver be operated. That means it will each time led fresh Anolytlösung in the Anolytekammer and in the Overflow method, the spent solution flows into the Sewage system. As a result, this anolyte solution can not to be recycled more for environmental reasons is disadvantageous.

The object of the invention is to compounds the baths not just add the resulting halogen adsorb, but chemically react and thus a Can avoid poison gas formation. Another task is it that the resulting product and the reagent of the Operation of the electrolyte itself does not hurt or the physical characteristics of the precipitate changed.

This task is solved by the doctrine of Claims.

Surprisingly, it has been found that aqueous Solutions that have connections with at least one double bond and / or with a triple bond and contain at least one hydrophilic substituent, the show desired effect and beyond in be did not disturb drawn electrolytes.

Suitable hydrophilic substituents are sulfonic acids, Sulfinic acids, carboxylic acids (optionally in the form of their alkali metal Salts z. As sodium, potassium, ammonium or magnesium Salts); but also alcohols, hydroxyethyl ethers and quaternary ammonium compounds.

Although the addition reaction of halogens with double or triple bonds known as a chemical reaction, however, use in electrolytes is in use inert anodes new.  

The advantage of these methods is that the inhibitors, which the electrolyte to his operation anyway must be added via the membrane electrolysis modules are added while doing an extraordinary oxidative decomposition of the inhibitors, as otherwise the inert anodes occur by the fast Exchange and movement within the module is avoided. The compounds of the invention interfere For example, not in acidic nickel, copper or Zinc electrolyte. It is noteworthy that the Substances according to the invention which bind the halogen gas, at the same time even used as additives in the electrolyte can be. Thus is also a closed Material cycle for the halogens secured.

In addition, when using the erfindungsge In addition, inexpensive anode materials are also used which are not halogen resistant.

The required concentration is 0.01 to 10 g / Liter, preferably between 50 and 500 mg / liter, and is surprisingly low.

In the following Table 1 are examples of the invention according to compounds to be used as well as their preferred Application concentration indicated in the anolyte:

connection preferred concentration mg / l Vinylsulfonic acid, sodium 150-250 Allylsulfonic acid, sodium 200-400 Vinylacetic acid, potassium 100-300 Propynesulfonic acid, sodium 180-250 Diäthy-propynyl-amonium chloride 100-280 Dimethyl-propynyl-ammonium bisulfate 140-300 Butynediol (1,4) 250-450 α-hydroxypropinsulfonic acid, sodium 80-200

The anolyte itself varies in its composition ever after used catholyte. It contains besides at least one of the compounds of the invention at least partly the same salts as the catholyte. In the Tables 2 to 4 below are inorganic compounds Anolyte for nickel, zinc and copper baths specified.  

Table 2

Composition of a nickel anolyte

Table 3

Composition of a zinc anolyte

Table 4

Composition of a copper anolyte

The following examples illustrate the invention:  

example 1

A nickel electrolyte according to Table 5 is with a inert anode surrounded by a membrane, operated to reduce the nickel content. generally known disturbs a nickel content of over 90 g / l and reduces the Leveling. After just a few minutes, the experiment must be stopped because the strong smell of chlorine makes further work impossible. Now you put that Anolyte 245 mg / l vinylsulfonic acid, sodium salt, added, so the smell of chlorine disappears instantly. The Effect lasts for several hours. Then again Vinylsulfonic acid, sodium salt added, wherein the over shot of the anolyte in the nickel electrolyte becomes. He creates no disturbances in it.

Table 5

Composition of a nickel electrolyte

Example 2

A zinc electrolyte according to Table 6 is provided with an in The anode, which is surrounded by a membrane, operates to reduce the zinc content. As you know, it bothers a zinc content of over 60 g / l and leads to frames in the bathroom. After just a few minutes, the experiment must be stopped because the strong smell of chlorine makes further work impossible. Now you put that Anolyte 530 mg / l allyl sulfonic acid, sodium salt added, so the smell of chlorine disappears instantly. The Effect lasts for several hours. Then again Allyl sulfonic acid, sodium salt added, with the excess of the anolyte is added to the zinc electrolyte. He does not generate any interference in it.

Table 6

Composition of a zinc electrolyte

Example 3

A copper electrolyte according to Table 7 is with a inert anode, which is surrounded by a membrane, and operated with a phosphorus alloyed copper anode to the Keep copper content constant during operation. generally known interferes with too high a copper content of over 24 g / l and reduces metal scattering. After just a few minutes the experiment must be stopped, as the smell of chlorine makes further work impossible. Now you put that Anolyte 245 mg / l butynediol (1.4) is added, so disappears the smell of chlorine instantly. The effect holds several Hours. Then butynediol (1,4) is added again, wherein excess anolyte in the copper electrolyte is given over the pumping circuit. He creates in it no disturbances.

Table 7

Composition of a copper electrolyte

Claims (6)

1. Use of water-soluble organic verbin at least double or triple bond and in each case at least one hydrophilic Substituents as additives in the anolyte in galvani metal deposition baths. 2. Use according to claim 1 of
Vinyl sulfonic acid, sodium,
Allyl sulfonic acid, sodium,
Vinylacetic acid, potassium,
Propynesulfonic acid, sodium,
Diethyl-propynyl-amonium chloride,
Dimethyl-propynyl-ammonium bisulfate,
Butynediol (1,4) or
α-hydroxypropinsulfonic acid, sodium. 3. Use of the compounds according to claims 1 or 2 in concentrations of 0.01 to 10 g / liter. 4. Use of the compounds according to claim 1 or 2 in zinc, nickel or copper metal deposit baths.   5. Use of the compounds according to claim 1 in Baths together with an inert anode in one liquid-tight housing. 6. Use according to claim 5, in a liquid sealed housing consisting of ion exchanger material or plastic.