EP0815291B1 - Solution for use in the electrolytic deposition of zinc or zinc-alloy coatings - Google Patents

Abstract

The invention concerns an aqueous alkaline cyanide-free solution for use in the electrolytic deposition of lustrous and blister-free zinc or zinc-alloy coatings of uniform layer thickness on substrate surfaces. Electrolytic zinc- or zinc-alloy baths are used for depositing zinc or zinc-alloy coatings. The layers are partly decorative and for that reason the layers must have an even lustre across a wide current density range. However, sufficiently uniform layer thicknesses cannot be obtained on complex workpiece surfaces with sharp-edged structures and concave surface regions, and zinc and zinc-alloy layers deposited on such workpieces tend in addition to be more prone to blistering. These disadvantages are eliminated by a coating solution containing, in addition to the normal bath components, diallyl ammonium-sulphur dioxide copolymers of general structural formula (I) shown, and/or diallyldimethyl ammonium monomers.

Description

The invention relates to an aqueous alkaline, cyanide-free electrolytic solution Deposition of shiny and bubble-free zinc or zinc alloy coatings with uniform layer thickness on curved substrate surfaces.

Electrolytic zinc or zinc alloy baths are used to deposit zinc coatings or their alloys. On the one hand, the layers fulfill a decorative task. Therefore, the layers have to be evenly shiny. This includes that in a wide current density range, for example from 0.1 A / dm ² to 15 A / dm ² , no coarse-grained metal layers (so-called scorching) are deposited and that no matt zinc layers and no pores form in the coating.

Above all, zinc and zinc alloy layers are used as corrosion protection for less noble and corrosion-prone substrate materials are used, such as Ferrous metals. In particular, products made of wire and screws, Nuts, metal fittings, for example for engine parts, made of iron or Steel is coated with zinc layers to protect them against rust.

The corrosion protection is in many cases by post-treatment of the Zinc and zinc alloy layers improved with chromating solutions, whereby Chromate layers form on the zinc layers. These are colored and can vary depending on the composition of the chromating solutions Color tones are generated. This creates further decorative design options opened. The zinc layers must therefore also have a enable good chromatability. This includes the chromate layer adheres well to the zinc layer and does not form cracks because of the corrosion resistance the chromated zinc and zinc alloy layers otherwise would be very low.

It is also very important that the deposited zinc coatings are well on the base adhere and do not form bubbles.

Zinc baths for the electrolytic deposition of such zinc coatings are described in described in various publications.

Cyanide bath types in which zinc salts are known as cyanide complexes have long been known are solved. These baths are strongly alkaline. The one from these Solutions deposited layers are sufficiently smooth and shiny, especially when organic additive compounds, such as gelatin, Peptones, sodium sulfite, thiourea, polyvinyl alcohol, aldehydes, ketones or salts of organic acids can be used.

Because of the high toxicity of these solutions and because of the associated high work safety requirements when dealing with these solutions however, these types of baths are no longer used for wastewater treatment practical. Therefore, cyanide-free solutions have been developed.

DE 25 25 264 C2 describes an alkaline cyanide-free zinc bath containing a Zinc salt, alkali hydroxide, at least one organic additive and that Reaction product of an unsaturated heterocyclic, at least two nitrogen atoms with ring containing hydrocarbon compound with a Epihalohydrin or with a glycerol halohydrin.

With this bath you can use shiny to high-gloss, leveled zinc coatings be deposited.

enthalten. Mit diesen Bädern können gleichmäßig glänzende, Oberflächenrauheiten des Substrats einebnende Zinkschichten erzeugt werden. Außerdem werden den Cyanidbädern vergleichbare Abscheidungsgeschwindigkeiten für die Zinküberzüge bei vorgegebener kathodischer Stromdichte erreicht.In US-A 40 30 987 cyanide-free baths for the deposition of zinc are described, which, in addition to the zinc compounds and alkali hydroxide for setting a high pH value, are brighteners from the group of aromatic aldehydes and a diallylammonium-sulfur dioxide copolymer with the general structural formula

contain. These baths can be used to produce evenly shiny zinc layers that level the surface of the substrate. In addition, comparable deposition rates for the zinc coatings are achieved for the cyanide baths at a given cathodic current density.

In US-A 41 34 804 cyanide-free baths are disclosed which are in addition to Zinc compounds and alkali hydroxide those described in US-A 40 30 987 Contain diallylammonium sulfur dioxide copolymers. In addition to the Diallylammonium sulfur dioxide copolymers contain those described there Baths instead of aldehydes a quaternary pyridine compound, for example N-benzyl-3-methylcarboxylate pyridinium chloride and nicotinic acid N-oxide.

In US-A 38 56 637 are cyanide-free or largely cyanide-free zinc baths described, containing soluble zinc compounds, a brightener and a alkaline metal silicate to avoid dull, greasy or dirty Metal coatings. Alkaline amine-epichlorohydrin reaction products, for example, are used as brighteners specified.

In US-A 38 69 358 an aqueous alkaline zinc bath is disclosed, the less contains as 15 g cyanide / liter solution and additionally a soluble zinc compound and at least one water-soluble compound with tertiary and / or quaternary amine groups, which are formed by polymerizing an aliphatic Amine is produced with epihalohydrin.

With the aforementioned zinc baths shiny, but none evenly thick zinc coatings are deposited.

Especially for workpieces to be coated, which on the one hand have sharp edges are and / or have tips and corners and on the other hand the anodes have opposite concave surface areas, if possible uniformly thick layers will be separated so that the total to be deposited The amount of metal is as small as possible. A distinction is made for thicker layers on the different surface areas with different Curvature are therefore with the known baths under unfavorable conditions in some places very thick layers have already been created, while the zinc coating has hardly formed in other places. With thin Layers cannot provide sufficient leveling on the substrate surface existing roughness can be achieved. Therefore, with the conventional Baths are usually deposited large amounts of metal, so that the Operation with these baths is expensive. The workpieces must also treated for a long time in the electroplating bath, and large amounts of the Bath additives consumed.

In addition, long electrolytic metallization times lead to increased Tendency to blister. Because inevitably at some points on the workpiece relatively thick layers of zinc are formed, the adhesive strength of the Zinc coating on the workpiece base reduced. Among other things, this can caused by low internal stresses in the deposited zinc layer become.

German Offenlegungsschrift 37 21 416 describes a process for described galvanizing of objects made of metals, at which uses a cyanide-free, alkaline galvanizing bath, which as organic additive contains a product which by polymerization of Dimethylammonium chloride or bromide in the presence of sulfur dioxide as a polymerization stimulator at a temperature between 85 and 115 ° C is produced.

The present invention is therefore based on the problem, the disadvantages to avoid in the prior art and an aqueous electrolytic solution Separate shiny and bubble-free zinc or zinc alloy coatings even after tempering to find and in particular a uniform layer thickness distribution the zinc coatings can also be produced on curved surfaces.

The problem is solved by the solution and the use of the solution according to claims 1 and 15. Preferred embodiments the invention are specified in the subclaims.

mit einem mittleren Molekulargewicht von 240 g/Mol bis 10.000 g/Mol, wobei R1 und R2 unabhängig voneinander gewählt werden und Wasserstoff, Alkyl, Hydroxyalkyl, Alkenyl, Alkinyl, Aralkyl oder Phenyl und X^- = F-, Cl^-, Br^-, I^- sind.The object is achieved in particular by an aqueous alkaline cyanide-free solution for the electrolytic deposition of zinc or zinc alloy coatings at least containing
a zinc ion source, an alkalizing agent, and a diallylammonium sulfur dioxide copolymer having the general structural formula

with an average molecular weight of 240 g / mol to 10,000 g / mol, R1 and R2 being selected independently of one another and hydrogen, alkyl, hydroxyalkyl, alkenyl, alkynyl, aralkyl or phenyl and X ^- = F-, Cl ^- , Br ^- , I ^- are.

Furthermore, the solution can also be an amine-epichlorohydrin copolymer, which by Reaction of epichlorohydrin with compounds selected from the group of amines, diamines and triamines are available.

   wobei R1 und R2 unabhängig voneinander gewählt werden und Wasserstoff, Alkyl, Hydroxyalkyl, Alkenyl, Alkinyl, Aralkyl oder Phenyl sind, X^- = F^-, Cl^-, Br^-, I^- und
   0 ≤ y ≤ 20 ist, enthalten.Amine-epichlorohydrin copolymers with the general structural formula are particularly suitable

where R1 and R2 are selected independently of one another and are hydrogen, alkyl, hydroxyalkyl, alkenyl, alkynyl, aralkyl or phenyl, X ^- = F ^- , Cl ^- , Br ^- , I ^- and
0 ≤ y ≤ 20 is included.

The diallylammonium sulfur dioxide copolymers and Amine-epichlorohydrin copolymers are added to the bath as basic additives.

With this bathroom solution it is possible to work with even complex shaped work pieces essentially uniform layer thickness at all points on the workpiece surface to coat. Especially on sharp-edged surfaces, For example, high metal layer thicknesses are usually found at tips and corners generated while the layer thicknesses of the opposite of the anodes concave surface areas when using conventional Baths can be extremely small. With the aforementioned bath on the other hand, essentially uniform at the designated surface points get thick layers.

To determine the uniformity of the layer thickness distribution, for example the thicknesses of zinc or zinc alloys on metal sheets coated in a so-called Hull cell can be determined at different points which have been coated with different current densities. The ratio of the thickness of a layer deposited at a high current density (for example 3 A / dm ² ) to a layer deposited at a low current density (for example 0.5 A / dm ² ) is high in conventional bath types. In the case of the specified current densities, this ratio reaches values of at least 3.4.

With the bath according to the invention at the designated points in the Hull cell test coated sheet metal layers with layer thickness ratios of less than 2.4 and often less than 2. This means that in relation to places on complex shaped work pieces, which have high current densities due to sharp-edged surface structures train, even in places with low current density, for example the concave surface areas opposite the anodes are sufficient thick zinc or zinc alloy layer can be produced.

Furthermore, it is possible with the bath according to the invention, in a large Deposition of glossy layers without any bubbles. The layers have no veils within a large current density range no coarse crystalline coatings are produced and the adhesion of the layers is high enough on the substrate surface so that bubbles and others Do not create any lifts between the layer and the base.

In addition, the layers are ductile. Therefore coated in this way Workpieces can be processed mechanically without problems, for example by bending. The corrosion resistance of the layers is very good both against the formation of so-called white rust, i.e. the layer itself is stable against corrosion, as well as against red rust, which when coating Iron substrates can occur and are caused by corrosion of the substrate becomes.

The layers are also easy to chromate. The one formed on the layers Chromating layer adheres well and has a high corrosion resistance. Blue, yellow, green and black chromate layers can be used be generated.

Another advantage of the bath according to the invention is the high stability of the additive compounds used. When the bathroom is idle the effectiveness of these compounds is not reduced. The bathroom solution can at high, for example at 35 ° C to 40 ° C, or low temperatures, for example, room temperature or below. By suitable Choice of the concentration of the additive compounds contained and more suitable other compounds can be both high-gloss and semi-gloss Coatings are generated. The current efficiency in metal deposition is very high even with zinc contents of 8 g / l to 10 g / l solution. Of the Working area is with 4 g zinc ions / l to 40 g / l solution without causing burns form, and in particular from 5 g / l to 18 g / l solution, at very good layer thickness distribution in the entire current density range very good. It is it is also possible to create layers up to 30 µm thick without the formation of bubbles to separate.

In a preferred embodiment of the invention, a coating solution used in the diallylammonium sulfur dioxide copolymers with an average molecular weight of 240 - 10,000 g / mol or a little above and preferably with a molecular weight of 500 g / mol to about 6000 g / mol are included. Diallylammonium sulfur dioxide copolymers are particularly suitable with n ≥ m> 0 and with R1 = R2 = methyl. At Use of diallylammonium sulfur dioxide copolymers with too high Molecular weight increases the tendency of the bubbles to form in the layers. For example can with a bath in which diallylammonium sulfur dioxide copolymers with a molecular weight of 100,000 are included, none bubble-free coatings can be obtained.

Diallyldimethylammonium chloride-sulfur dioxide copolymer is particularly suitable as a diallylammonium sulfur dioxide copolymer.

   mit einem mittleren Molekulargewicht von 500 bis 100.000,
   wobei R1 und R2 unabhängig voneinander gewählt werden und Wasserstoff, Alkyl, Hydroxyalkyl, Alkenyl, Alkinyl, Aralkyl oder Phenyl sind, sowie
von der Herstellung der Diallylammonium-Schwefeldioxid-Copolymere und der homopolymeren Verbindungen herrührendes, in der Reaktion nicht umgesetztes Diallyldimethylammoniumhalogenid und Diallyldimethylammonium-Hydrogensulfit, welches sich bildet bei der Herstellung des Diallyldimethylammonium-Schwefeldioxid-Copolymeren aus Diallyldimethylammonuimhalogenid und eingeleitetem Schwefeldioxid,enthalten.The coating solution can also be a homopolymeric compound with the general structural formula

with an average molecular weight of 500 to 100,000,
where R1 and R2 are selected independently of one another and are hydrogen, alkyl, hydroxyalkyl, alkenyl, alkynyl, aralkyl or phenyl, and
unreacted diallyldimethylammonium halide and diallyldimethylammonium bisulfite resulting from the production of the diallylammonium sulfur dioxide copolymers and the homopolymeric compounds, which is formed in the production of the diallyldimethylammonium sulfur dioxide copolymers from diallyldimethylammonium containing sulfur halide.

In the group of compounds selected from the diallylammonium sulfur dioxide copolymers, the homopolymers and the reaction unreacted monomers, for example diallyldimethylammonium chloride are the diallylammonium sulfur dioxide copolymers in a proportion of 1 % By weight to 100% by weight, based on the mixture of the compounds in of this group. The proportion of homopolymers is 0% by weight to 60 wt .-%, based on the mixture of compounds, and the proportion of unreacted monomers 0% by weight to 70% by weight. Typical blends of these compounds contain 80% by weight of diallylammonium sulfur dioxide copolymer, 5% by weight homopolymer and 15% by weight not reacted monomer or 70% by weight diallyl ammonium-sulfur dioxide copolymer, 5 wt .-% homopolymer and 25 wt .-% unreacted Monomer.

Alternatively, 100% monomers can also be used for a sufficient layer thickness distribution, although no glossy coatings are achieved.
In many cases it was found that the copolymers alone, for example XP-104 according to Example 11, did not give a significantly improved layer thickness distribution, ie better than 2.4 to about 1.6, even with increased addition. By slight addition of monomers, such as. B. diallyldimethylammonium chloride and in the acidic synthesis solution, for example at pH values of 1-2 after the end of the reaction, diallyeldimethylammonium bisulfite, the layer thicknesses could be further compared to index values below 1.6.

The reaction solution containing copolymers can also be treated that the polymers precipitate as a crystalline solid in which no free diallyldimethylammonium is contained, but only the pure copolymer.

The claimed diallylammonium sulfur dioxide copolymers contain heterocyclic ring structures in a 5-ring system. Only these are suitable to produce the layers with the required uniform layer thickness. Similar diallylammonium sulfur dioxide copolymers, such as the polyamine sulfones described in US Pat. No. 4,134,804 with 6-ring systems, do not have the same advantages. In particular it is not possible with these connections, layers with the required uniformity to separate. There is also a tendency to blister significantly reduced the compounds disclosed in the U.S. patent.

Such diallylammonium sulfur dioxide copolymers with a 5-ring system are by appropriate reaction and substitution of the monomers available in their manufacture. In particular, these connections are obtained by polymerization in water as a solvent. Also the choice of the polymerization starter could form the 6-ring in US patents have led. When using ammonium persulfate instead of others Peroxide starters, for example di-tert-butyl peroxide or di-benzoyl peroxide, become the diallylammonium sulfur dioxide copolymers according to the invention educated.

The formation of the 5-ring systems can easily be detected by nuclear magnetic resonance spectroscopy (NMR). For example, the NMR spectra of the 5-ring structures and the 6-ring structures can easily be distinguished from one another in a ¹³ C-NMR spectrum. This has already been demonstrated in Lancaster, Baccei and Panzer in Polymer Letters, Edition 14 , page 549 (1976).

Instead of the halides, preferably the chlorides, can be used as counterions suitable other anions, e.g. B. also nitrates, chlorates, perchlorates and sulfates be applied.

The amine-epichlorohydrin copolymer contained in the solution preferably has an average molecular weight of more than 500 giMol and in particular of about 1500 g / mol. The amine-epichlorohydrin copolymers are prepared by known processes by polycondensation, for example of 3-dimethylamino-1-propylamine with epichlorohydrin. Coating solutions with copolymers of amines, diamines, triamines, hydrazines and / or nitrogen-containing heterocyclic compounds with bis-electrophilic compounds, such as, for example, bis-glycidyl ether, di-haloalkanes and epihalohydrins, are particularly suitable. 3-Dimethylamino-1-propylamine-epichlorohydrin copolymer is particularly well suited as an amine-epichlorohydrin copolymer. In this case, R1 and R2 are each methyl groups and X ^- is chloride in the aforementioned general structural formula II.

The solution can also be used to produce a high-gloss zinc or zinc alloy layer additionally 1-benzylpyridinium-3-carboxylate as brightener contain. The lower carboxylates are the carboxylates Alkanoic acids, such as acetate in question. Sulfonate betaines, such as N-benzylpyridinium sulfonate, are also effective compounds represents.

Zinc oxide is usually used as the zinc ion source alkaline coating bath as zincate dissolves. In principle, however, it can also other sources of zinc ions, such as zinc salts, are used, if other anions, which get into the bath by adding the zinc salts, do not interfere with the separation. Zinc sulfate, for example, is suitable.

Additional metals with zinc can be used to deposit zinc alloy layers be deposited together. For example, it is possible to use zinc layers with nickel, cobalt or iron admixtures. For this purpose, the In addition to the source of zinc ions, baths also contain compounds of these metals. In addition, there are coordinated complexing agent combinations in the coating solution required to control the deposition potential. Such Combinations are known.

Sodium hydroxide in a concentration is usually used as the alkalizing agent from 50 g / l to 200 g / l solution and in particular from 80 g / l to 150 g / l Solution added. However, other alkali and alkaline earth metal hydroxides are also as well as tetraalkylammonium hydroxides. However, in the latter If care is taken that a possible complexing effect of the Ammonium hydroxides do not impair the deposition effect.

In addition to the specified compounds, the coating solutions according to the invention contain further components that make the bathroom different Be added for purposes.

For example, the bath can be used to control and stabilize the pH additionally contain sodium carbonate. To reduce the sensitivity of the Bades against foreign ions, especially against calcium and magnesium in Tap water, the bath can also contain sodium gluconate or other complexing agents contain. Aldehydic aromatic compounds, such as Anisaldehyde can be added to the bath as a brightener. In certain circumstances these compounds deteriorate the layer thickness distribution. This Compounds are preferably used in the form of their bisulfite adducts, to increase their solubility in the bathroom. Thio compounds, such as Thiourea, mercaptobenzthiazole and mercaptotriazoles are used in the bath added to level the metal deposit in the low current density range to achieve.

The temperature of the bath can be set in a wide range. For example be good results with temperatures from 15 ° C to 40 ° C receive.

The current density that can be used is between 0.01 A / dm ² and 15 A / dm ² , preferably in the range from 0.1 A / dm ² to 6 A / dm ² . In this area, glossy, leveled, uniformly thick and bubble-free coatings are obtained.

The cathodic current efficiency of the bath is between 80% and 95%, based on the amount of metal deposited with pure zinc coatings.

The solution according to the invention can be used for coating workpieces be used in the so-called frame technology, in which the workpieces can be immersed in a fixed frame in the bathroom. Small parts are not due to the complex assembly technology with the rack technology metallized, but with a drum process in which the to Metallized parts filled in a drum in the bath solution and be metallized in the drum. This procedure is also included the solution according to the invention possible without any problems.

Both soluble zinc anodes and insoluble anodes, for example made of iron, iron alloyed with nickel or titanium become.

To even out the layer thickness distribution on the surface to be coated Workpiece and in the case of the frame technology also on the individual at the same time Workpieces to be coated can contain air in the coating solution blown in and the solution set in violent motion become.

Some examples are shown below to illustrate the invention.

Example 1:

A cyanide-free alkaline bath with the composition: Zinc as zinc oxide 10 g, Sodium hydroxide 130 g, sodium 20 g per liter of aqueous solution as a basic composition and 1-benzylpyridinium-3-carboxylate 40 mg, Mercaptobenzthiazole 0.1 g per liter of aqueous solution as additives
was used for zinc deposition.

The bath was tested by depositing zinc on sheet iron cathodes in a Hull cell at 22 ° C with a total current of 1A for 15 minutes. The layer thickness distribution at different current densities was determined by zinc dissolution at one point on the coated iron sheet, at which zinc was deposited with a current density of 3 A / dm ² , and at another point, at the zinc with a current density of 0.5 A / dm ² was determined. An index was calculated as a measure, which gives the ratio of the layer thickness deposited at 3 A / dm ² to the layer thickness deposited at 0.5 A / dm ² .

The base bath was 5 ml / l of a 25 wt .-% aqueous solution of diallyldimethylammonium chloride-sulfur dioxide copolymer in water and 0.5 ml / l of a 38 wt .-% aqueous solution of 3-dimethylamino-1-propylamine-epichlorohydrin Copolymer added. Uniformly coated, semi-gloss zinc coatings were obtained. The layer thicknesses at the measuring points were 5.7 µm (3 A / dm ² ) and 3.3 µm (0.5 A / dm ² ). The index was 1.7.

Example 2 (comparative example):

The experiment of Example 1 was repeated. Instead of connections Diallyldimethylammonium chloride-sulfur dioxide copolymer and 3-dimethylamino-1-propylamine-epichlorohydrin copolymer became other bath additives used, which is also described in the publication DE 25 25 264 C2 (5 ml of a 35 wt .-% aqueous solution of imidazole-epichlorohydrin copolymer (IMEP), 1-benzylpyridinium-3-carboxylate, thiourea, Anisaldehyde bisulfite adduct per liter of bath).

The iron sheets were coated with a shiny zinc layer. The layer thicknesses were 5.9 µm (3 A / dm ² ) and 2.0 µm (0.5 A / dm ² ), the index 3.0.

Example 3:

The experiment of Example 1 was repeated. In addition, 1-benzylpyridinium-3-carboxylate added to the bath solution in a concentration of 80 mg / l.

A shiny zinc coating was obtained in the entire current density range with an even layer thickness distribution. After one hour of treatment of the coated sheet were in the tempering furnace at 120 ° C. the sheets were unchanged and showed no bubbles.

Example 4:

The experiment of Example 1 was repeated. The temperature at the deposition was increased to 30 ° C.

There were shiny to shimmering zinc coatings without burns receive. The layer thickness distribution was also uniform.

Example 5:

The experiment of Example 1 was repeated in a 5 liter beaker with pure zinc anodes. The iron sheet cathodes were bent several times at right angles and were coated with zinc at an average current density of 2 A / dm ^{2 for} one hour. During this time, air was passed through the coating solution.

The layer thicknesses varied from 25 µm to 32 µm. The layer was semi-glossy to shiny.

Subsequent blue chromating with the ICP 33L chromating bath Company Atotech Espana, S.A., Spain, which has haxavalent chromium compounds and contains inorganic salts and produces a bluish finish can be done easily.

After one hour of treatment of the coated sheet in the tempering furnace at 120 ° C the sheets were unchanged and showed no bubbles.

Example 6:

The experiment of Example 3 was repeated. However, the coating solution an additional 50 mg / l anisaldehyde bisulfite adduct was added. The Coating was carried out at a total current of 1 A in the Hull cell a coating time of 15 minutes.

A shiny, even zinc coating was obtained. The layer thicknesses were 5.8 µm (3 A / dm ² ) and 3.3 µm (0.5 A / dm ² ), the index 1.7. No bubbles were visible even after heating in the oven.

Example 7:

To the basic composition of Example 1 were added per liter of aqueous solution 6 ml of diallyldiethylammonium chloride-sulfur dioxide copolymer, 1 ml of 3-dimethylamino-1-propylamine-epichlorohydrin copolymer, 50 mg of 1-benzylpyridinium-3-carboxylate and 100 mg of thiourea added.

At a temperature of 30 ° C. and a total current of 1 A, after 15 minutes of coating time in a Hull cell, a uniformly thick zinc coating was obtained, with good leveling and without scorching. The sheet was completely covered with zinc and had layer thicknesses of 6.6 µm (3 A / dm ² ) and 5.4 µm (0.5 A / dm ² ). The index was 1.3.

The zinc layer could be easily using the yellow chromating bath ZP1C from Atotech España, S.A., which hexavalent chromium compounds and contains inorganic salts and gives an iridescent finish and did not show any after tempering treatment Bubbles on.

Example 8:

Example 7 was repeated. The concentration of 1-benzylpyridinium-3-carboxylate in the bath was increased to 100 mg / l. The coating conditions corresponded to those of Example 7.

The zinc layer was high-gloss without blistering, even after an annealing treatment. The determined layer thickness index was 1.6 to 1.7.

Example 9:

Following Example 8 were 4 ml / l of a solution of 35 wt .-% imidazole-epichlorohydrin copolymer (IMEP) added to the bathroom.

The galvanized sheet was high-gloss without blistering after an annealing treatment. The layer thickness distribution index was 1.6 to 1.7.

Example 10:

a) 1,3-Tetramethyldiaminopropan-Epichlorhydrin-Copolymer in Wasser oder

b) Diethylentriamino-Epichlorhydrin-Copolymer in Wasser

eingesetzt.Die Schichten wiesen eine ähnlich gute Schichtdickenverteilung wie die nach Beispiel 1 hergestellten Schichten auf.A zinc layer was deposited using a bath according to Example 1. However, instead of 3-dimethylamino-1-propylamine-epichlorohydrin copolymer, one of the compounds

a) 1,3-tetramethyldiaminopropane-epichlorohydrin copolymer in water or

b) Diethylenetriamino-epichlorohydrin copolymer in water

The layers had a similar layer thickness distribution as the layers produced according to Example 1.

Example 11

(Layer thickness distribution using various diallyldimethylammonium chloride-sulfur dioxide copolymers): Bath composition: Zinc as zinc oxide 10 g, Sodium hydroxide 130 g, sodium 20 g, 1-benzylpyridinium-3-carboxylate 10 mg, Sodium gluconate 1.5g, 3-mercapto-1.2.4-triazole 0.1 g, Addition: 3-dimethylamino-1-propylamine-epichlorohydrin copolymer 0.5 ml per liter of aqueous solution

The diallyldimethylammonium chloride-sulfur dioxide copolymers (XP 1xx) were prepared with varying amounts of sulfur dioxide and initiator (see synthesis example) and used as 25% by weight solutions in water. The compounds PAS A5 and PAS 92 are products of the company Nitto Boseki Co., Ltd., Tokyo, Japan, and according to the manufacturer are also diallyldimethylammonium chloride-sulfur dioxide copolymers, but with a 6-ring system not according to the invention (according to structural formula IV ).

The coating results are given below using a Hull cell. The coating conditions correspond to those of Example 1. The values in Table 1 give the layer thickness distribution indices. concentration 4.0 ml / l 6.0 ml / l 8.0 ml / l 10.0 ml / l PAS A5 3.04 3.0 2.94 2.8 PAS 92 3.85 3.82 3.67 3.62 XP 101 2.1 2.0 2.0 1.8 XP 103 2.3 2.0 2.0 2.1 XP 104 2.0 1.9 1.9 1.6 XP 105 2.1 2.0 1.8 2.1 XP 106 2.4 2.0 1.9 2.0 XP 114 2.3 2.5 2.2 1.9

Example 12:

The same bath composition as in Example 11 was used. However, various compounds and combinations of compounds according to the table below were used as additives (BP3C: 1-benzylpyridinium-3-carboxylate, IMEP: imidazole-epichlorohydrin copolymer, Verb. II : 3-dimethylamino-1-propylamine-epichlorohydrin copolymer) . The coating conditions correspond to those of the previous example.

The layer thickness indices are again given in Table 2, combination No. 5 being a comparative example not according to the invention: Comb. XP 104 [ml / l] BP3C [mg / l] IMEP [ml / l] Verb. II [ml / l] Layer thickness index 1 5 - - - 2.0 2nd 5 40 - - 1.6 3rd 5 80 - - 1.6 4th 5 80 - 0.5 1.65 5 - 40 - 0.5 2.86 6 5 - 0.3 - 1.85 7 5 - 0.6 - 1.95 8th 5 - 0.6 0.5 2.20 9 5 - 1.0 0.5 2.05 10th 5 - 2.0 0.5 2.0

Example 13

Synthesis example of diallyldimethylammonium chloride-sulfur dioxide copolymer of the type XP 104:
A 60% by weight aqueous solution of 1260 g of diallyldimethylammonium chloride (company Aldrich, Germany) was diluted with 540 ml of water. 200 g of sulfur dioxide were slowly introduced at up to 30 ° C. into this solution. At 28 ° C, 8.7 g of ammonium peroxodisulfate in 43 ml of water were added as an initiator. After 2.5 hours, a further 13 g of ammonium peroxodisulfate, dissolved in 65 ml of water, were added. The mixture was then heated at 70 ° C for 5 hours.
A product with an average molecular weight of about 1400 g / mol in the polymeric portion is obtained. The molecular weight was determined by gel permeation chromatography (GPC) with Ultrahydrogel 120/250; refractometric determination, pullulan and maltooligosaccharide standard.

For the other compounds listed in Table 1 (XP1xx), the synthesis data can be found in Table 3 below; unless otherwise noted, the preparation is carried out according to the synthesis example above for XP 104. Type Diallyldimethyl ammonium chloride SO ₂ Ammonium persulfate Reaction conditions XP 101 87 g of a 60% solution with 37 ml of water 13.3 g 0.6 g in 3 ml of water 24 hours at 50 ° C XP 103 85 g of a 60% solution with 25 ml of water 9.1 g 0.4 g in 2 ml of water, then 0.6 in 3 ml of water 16 hours at 67 ° C XP 105 87 g of a 60% solution 13.9 g 0.6 g in 3 ml of water 16 hours at 68 ° C XP 106 69.6 g of a 60% solution with 15 ml of water 10.9 g 0.5 g in 2.4 ml of water 18 hours at 106 ° C XP 114 58 g of a 60% solution with 50 ml of water 9.4 g 0.6 g in 3 ml of water 26 hours at 77 ° C

Analogous to the measuring method described in Lancaster, Baccei and Panzer in Polymer Letters, Edition 14 , page 549 (1976), the chemical structure of the compound obtained was determined in D ₂ O as solvent and trimethylsilylpropanesulfonate (TSP) as standard. The compound gave signals in the ¹³ C-NMR spectrum which must be assigned to a 5-ring:

¹³C-NMR (D₂O,TSP):

34,9 (Ring-CH-),
54,5 1-CH₂-SO₂-),
55,5, 57,1 und 57,7 (CH₃-N⁺-),
71,1 und 71,4 (Ring-CH₂-).

A typical example is given below:

¹³ C-NMR (D ₂ O, TSP):

34.9 (ring-CH-),
54.5 1-CH ₂ -SO ₂ -),
55.5, 57.1 and 57.7 (CH ₃ -N ⁺ -),
71.1 and 71.4 (ring CH ₂ -).

These signals are in good agreement with those cited in the above Reference indicated NMR data for 5-ring polymers.

The assignment to a 5-ring system is further supported regarding the number and position of the signals by agreement of the measured spectra with calculated spectra.

In addition, the signals for the monomer diallyldimethylammonium chloride and for a poly-diallyldimethylammonium chloride sequence or a diallyldimethylammonium chloride homopolymer were recognizable in the ¹³ C-NMR spectra.

¹³C-NMR (D₂O,TSP):

29,2 (Gerüst-CH₂-)
41,0 und 41,4 (Ring-CH-),
55.2 und 56,9 (CH₃-N⁺-),
73,2 (Ring-CH₂-).

Poly-diallyldimethylammonium chloride signals:

¹³ C-NMR (D ₂ O, TSP):

29.2 (framework CH ₂ -)
41.0 and 41.4 (Ring-CH-),
55.2 and 56.9 (CH ₃ -N ⁺ -),
73.2 (ring CH ₂ -).

Example 14

1,088 kg 3-Dimethylamino-1-propylamin

0,709 kg Epichlorhydrin

2,7 Liter Wasser

Synthesis example of 3-dimethylamino-1-propylamine-epichlorohydrin copolymer:

1.088 kg of 3-dimethylamino-1-propylamine

0.709 kg epichlorohydrin

2.7 liters of water

3-Dimethylamino-1-propylamine was presented. With stirring, water became added in 500 ml portions. Epichlorohydrin was also added in portions while stirring to the reaction mixture. The reaction vessel was then heated to 100 ° C internal temperature and the reaction mixture Stirred for 5 hours. The mixture was then adjusted to pH with sulfuric acid 4 brought.

The total weight of the reaction mixture was then 7.25 kg Polymer content 1.8 kg, the total volume 6.4 liters and the dry weight of the product 38% by weight of the reaction mixture.

Example 15

Bath composition per liter of solution zinc 10 g / l Sodium hydroxide 130 g / l sodium 25 g / l Sodium gluconate 1.2 g / l 3-mercaptotriazole 0.1 g / l 3-dimethylamino-1-propylamine-epichlorohydrin copolymer, 38% by weight 0.5 ml / l XP-104, 25% by weight 4ml / l 1-benzylpyridinium-3-carboxylate 40 mg / l Rest of water

On a Hull cell plate, coated at 1 ampere, the shows after 15 min Layer thicknesses of 6.35 and 3.8 µm each with high and low current density. The layer thickness ratio is 1.65.

Example 16

1 ml / l of XP-104 was added to the bath according to Example 15. The measured Layer thicknesses were 6.41 and 3.86 µm with analog treatment, the resulting layer thickness ratio is 1.66.

Example 17

Example 16 was repeated, but became diallyldimethylammonium chloride (DADMAC) added as a 60% by weight solution to 0.2 ml / l. The measured Layer thicknesses after 15 min were 6.21 and 4.38 µm; that corresponds to one Layer thickness ratio of 1.4.

Example 18

To the bath composition according to Example 16, but without dimethylaminopropylamine-epichlorohydrin copolymer, XP-104 and benzylpyridinium carboxylate, 2-20 ml / l (DADMAC) were added. The results are shown in Table 4 below: DADMAC Layer thickness µm at current density Distribution / relative ml / l high low 2nd 1.27 1.05 1.21 1.21 4th 1.29 3.97 0.32 3.13 8th 1.14 3.96 0.28 3.57 12th 2.37 3.82 0.62 1.61 20th 8.12 2.18 3.72 3.72

This example shows that monomers alone have a thick layer distribution can influence, so that the sample additions of 2 and 12 ml / l are still below the solution according to the invention fall. However, the version of the example is 17 the preferred embodiment, since according to example 17 shiny and uniform coatings were achieved, while in Example 18 this The result on a Hull cell sheet was worse than the coating were dull and dark and partially burned on with high monomer additions were found. There was also a deposit of powdery Determine zinc on the sheet.

Example 19

This example shows the effect of the pure polymer.

A reaction solution of XP-104, prepared according to Example 12, was added to Partly lyophilized with a moist oil and with the multiple volume of methanol transferred. A crystalline solid precipitated out. It is separated off and crystallized then from methanol water. According to H-NMR, the colorless crystals were free of diallyldimethylammonium monomer and contained only that Diallyl dimethyl ammonium chloride-sulfur dioxide copolymer. The average molecular weight was 5,300 g / mol, determined according to that already described Method.

This material, XP-104 recrystallized, was subjected to a Hull cell test at 1A, 15 minutes and 24 ° C as previously described. Bath composition per liter of solution zinc 10 g / l Sodium hydroxide 130 g / l Sodium carbonate 25 gil Trilon D (complexing triacetic acid from BASF), instead of sodium gluconate 1.25 ml / l 3-mercaptotriazole 0.1 g / l XP-104 recrystallized in divergent amounts with divergent results according to Table 5 Rest of water XP-104 Umkr. Layer thickness µm at current density index Coating feature coating length 100 mm g / l high low 0.36 8.34 3.5 2.38 gray-matt up to 90-95 mm 0.50 8.25 3.65 2.26 gray-matt up to 70-75 mm 0.75 7.06 3.43 2.05 semi-glossy to glossy 1.0 7.09 4.09 1.93 evenly

The last coating is considered to be technically satisfactory in the sense of the invention and, as the organic bath matrix, contains only one component, 3-mercaptotriazole, in addition to the claimed polymer XP-104.
The complexing compounds gluconate or Trilon D are used by the expert for water softening and are not an inherent part of the bath matrix

Examples 20 to 22:

50 ppm of iron as iron sulfate, based on zinc, are added to the bath according to Example 1.
The bath was tested in the same way as that of Example 1.
The layer thicknesses at the measuring points were 5.7 to 3.4 µm. The index was 1.7; the Fe content of the coating was 0.55%.
A semi-glossy and even coating was produced which can be easily chromated with Ecopas Black 8000, a bath from Atotech Espana SA containing chromium salt and inorganic acids. A uniform black decorative finish is created.

Example 20 was repeated as examples 21 and 22, but once with an addition of 50 ppm iron as iron saccharate and once with iron gluconate. The results corresponded to those of Example 20.

Example 23:

50 ppm of iron as iron sulfate, based on zinc, are added to the bath according to Example 3.
A uniform and semi-gloss coating was created.
The layer thickness was 6.8 to 5.5 µm; the index was 1.2. The iron content of the coating was 0.65%.

The coating is easily chromated within 30 seconds with Tridur Yellow, a bath containing chromium salts from Atotech Espana SA, to produce a yellow iridescent color.
After the coated sheets according to Examples 20 to 22 had been treated in an annealing oven at 180 ° C. for one hour, the sheets were unchanged and had no bubbles.

Claims (15)

1. Aqueous, alkaline, cyanide-free solution for the electrolytic deposition of zinc or zinc alloy coatings on substrate surfaces, at least containing
   a zinc ion source, an alkalising agent and a diallylammonium-sulphur dioxide copolymer having the general structural formula

   

   having an average molecular weight of between 240 g/mol and 10,000 g/mol,
   in which R1 and R2 are selected independently of each other and are hydrogen, alkyl, hydroxyalkyl, alkenyl, alkinyl, aralkyl or phenyl, and
   X^- = F^-, Cl^-, Br^-, I^-.
2. Solution according to claim 1, characterised by an additionally contained amine-epichlorohydrin copolymer, obtainable by reacting epichlorohydrin with compounds, selected from the group of amines, diamines and triamines.
3. Solution according to one of the preceding claims, characterised by an additionally contained amine-epichlorohydrin copolymer having the general structural formula

   

   in which R₁ and R₂ are selected independently of each other and are hydrogen, alkyl, hydroxyalkyl, alkenyl, alkinyl, aralkyl or phenyl,
   X^- = F^-, Cl^-, Br^-, I^- and
   0 is ≤ y ≤ 20.
4. Solution according to one of the preceding claims, characterised by diallylammonium sulphur dioxide copolymers having an average molecular weight of between 240 g/mol and 6000 g/mol, preferably greater than 1000 g/mol.
5. Solution according to one of the preceding claims, characterised by diallylammonium sulphur dioxide copolymers with n ≥ m > 0.
6. Solution according to one of the preceding claims, characterised by diallylammonium sulphur dioxide copolymers with R1 = R2 = methyl.
7. Solution according to one of the preceding claims, characterised by an additionally contained homopolymeric compound having the general structural formula

   

   having an average molecular weight of between 500 and 100,000 g/mol, in which R1 and R2 are selected independently of each other and are hydrogen, alkyl, hydroxyalkyl, alkenyl, alkinyl, aralkyl or phenyl.
8. Solution according to one of the preceding claims, characterised by diallyldimethylammonium halide and/or diallylmethylammonium hydrogen sulphite, which is contained additionally or on its own instead of the copolymers and/or homopolymers.
9. Solution according to one of the preceding claims, characterised by an amine-epichlorohydrin copolymer having an average molecular weight greater than 500 g/mol and preferably of substantially 1500 g/mol.
10. Solution according to one of the preceding claims, characterised by 3-dimethylamino-1-propylamine-epichlorohydrin compolymer as the amine-epichlorohydrin copolymer.
11. Solution according to one of the preceding claims, characterised by additionally contained betaines, containing at least one pyridinium group and carboxylate and/or sulphonate groups.
12. Solution according to one of the preceding claims, characterised by additionally contained 1-benzylpyridinium-3-carboxylate.
13. Solution according to one of the preceding claims, characterised by additionally contained thio compounds.
14. Solution according to claim 8, characterised in that, instead of the halide ions, one or more negative ions are used, selected from the group formed from nitrates, chlorates, perchlorates and sulphates.
15. Use of an aqueous solution according to one of claims 1 to 14 for the electrolytic deposition of shiny and bubble-free zinc or zinc alloy coatings of a uniform layer thickness on curved substrate surfaces.