EP0815291A1

EP0815291A1 - Solution for use in the electrolytic deposition of zinc or zinc-alloy coatings

Info

Publication number: EP0815291A1
Application number: EP96907440A
Authority: EP
Inventors: Gonzalo Dr. Urrutia Desmaison; Santiago Torre Noceda
Original assignee: Atotech Deutschland GmbH and Co KG
Current assignee: Atotech Deutschland GmbH and Co KG
Priority date: 1995-03-10
Filing date: 1996-03-11
Publication date: 1998-01-07
Anticipated expiration: 2016-03-11
Also published as: CA2215048A1; ATE179465T1; ES2132899T3; DE19509713C1; KR19980702896A; DE59601779D1; JPH11501699A; BR9607363A; WO1996028590A1; EP0815291B1

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

Solution for the electrolytic deposition of zinc or zinc alloy coatings

description

The invention relates to an aqueous, alkaline, cyanide-free solution for the electrolytic deposition of shiny and bubble-free zinc or zinc alloy coatings with a 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 uniformly shiny. This includes that area in a wide Stromdichte¬, for example, 0, 1 A / dm ² to 1 5 A / dm ^2, no coarse-grained metal layers (so-called burn marks) are deposited, that no matte zinc layers and no Form pores in the coating

Above all, zinc and zinc alloy layers are used as corrosion protection for less noble and corrosion-sensitive substrate materials, such as, for example, ferrous metals. In particular, products formed from wire, as well as screws, nuts, metal fittings, for example for engine parts, made of iron or

Steel is coated with zinc layers to protect them against rust

Corrosion protection is improved in many cases by post-treatment of the zinc and zinc alloy layers with chromate solutions, whereby chromate layers form on the zinc layers. These are colored and can be produced in different colors depending on the composition of the chromating solutions. As a result, other decorative designs are possibilities opened up. The zinc layers must therefore also allow good chromability. This includes that the chromating layer adheres well to the zinc layer and does not form any cracks, since the corrosion resistance of the chromated zinc and zinc alloy layers would otherwise be very low.

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

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

Cyanide bath types in which zinc salts are dissolved as cyanide complexes have long been known. These baths are strongly alkaline. The layers deposited from these solutions are sufficiently smooth and shiny, especially when organic additive compounds such as gelatin, peptones, sodium sulfite, thiourea, polyalcohol, aldehydes, ketones or salts of organic acids are used.

However, because of the high toxicity of these solutions and because of the associated high expenditure on occupational safety when handling these solutions and when treating wastewater, these types of baths are no longer 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 metal hydroxide, at least one organic brightener and the reaction product of an unsaturated heterocyclic hydrocarbon compound containing at least two nitrogen atoms with a ring, with an epihalohydrin or with a glycerol halohydrin.

This bath can be used to deposit glossy to high-gloss, leveled zinc coatings. US Pat. No. 4,030,987 describes cyanide-free baths for separating zinc, which, in addition to the zinc compounds and alkali metal hydroxide to set a high pH, provides brighteners from the group of aromatic aldehydes and a diallylammonium-sulfur dioxide copolymer with the general structural formula

contains. 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 for a given cathodic current density.

In US-A 41 34 804 cyanide-free baths are disclosed, which in addition to the zinc compounds and alkali hydroxide described in US-A 40 30 987

Contain diallylammonium-sulfur dioxide copolymers. In addition to the diailylammonium sulfur dioxide copolymers, the baths described therein contain a quaternary pyridine compound, for example N-benzyl-3-methylcarboxylate-pyridinium chloride and nicotinic acid N-oxide, instead of aldehydes.

In US-A 38 56 637 cyanide-free or largely cyanide-free zinc baths are described, containing soluble zinc compounds, a brightener and an alkaline metal silicate to avoid matt, greasy or dirty metal coatings. Alkaline amine-epichlorohydrin reaction products, for example, are given as gloss agents. US Pat. No. 3,869,358 discloses an aqueous alkaline zincate bath which contains less than 15 g of cyanide / liter of solution and additionally a soluble zinc compound and at least one water-soluble compound with tertiary and / or quaternary amine groups, which are obtained by polymerization an aliphatic amine with epihalohydπn is produced

The aforementioned zinc baths can be used to deposit shiny, but not uniformly thick, zinc coatings.

In particular in the case of workpieces to be coated, which on the one hand have sharp edges and / or have tips and corners and on the other hand have concave surface areas opposite the anodes, layers which are as uniformly thick as possible must be deposited so that the total amount of metal to be deposited is as small as possible. With larger layer thicknesses - different on the different surface areas with different

With known baths, curvature is therefore already produced in very thick layers under unfavorable conditions in some places, while the zinc coating has scarcely formed in other places. With thin layers it is not possible to achieve a sufficient leveling of roughness on the substrate surface. Therefore, with the conventional

Large quantities of metal are usually separated from bathers, so that operation with these bathers is expensive. The workpieces also have to be treated in the electroplating bath for a long time, and large amounts of the bath additives are consumed.

In addition, long electrolytic metallization tents lead to an increased tendency to form bubbles, since relatively thick zinc layers are inevitably formed at some points on the workpiece, the adhesive strength of the zinc coating on the workpiece base is reduced. This can be caused, among other things, by low internal stresses in the deposited zinc layer. The present invention is therefore based on the problem of avoiding the disadvantages in the prior art and of finding an aqueous solution for the electrolytic deposition of shiny and bubble-free zinc or zinc alloy coatings, and in particular a uniform layer thickness distribution of the zinc coatings can also be produced on curved surfaces.

The problem is solved by claims 1 and 1 5. Preferred embodiments of the invention are specified in the subclaims.

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 source of zinc ions, an alkalizing agent, and a diallyl ammonium

Sulfur dioxide copolymer with 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 am.

Furthermore, the solution can also contain an amine-epichlorohydrin copolymer which can be obtained by reacting epichlorohydrin with compounds selected from the group of the nurses, diamines and triamines. Amine-epichlorohydrin copolymers with the general structural formula are particularly suitable

where R 1 and R2 are selected independently of one another and are hydrogen, alkyl, hydroxyalkyl, alkenyl, alkynyl, aralkyl or phenyl,

X- = F \ oil ^" , Br \ I ^' and 0 ≤ y ≤ 20 is included.

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

With this bath solution it is possible to coat even complex-shaped workpieces with an essentially uniform layer thickness at all points on the workpiece surface. In particular at sharp-edged surface points, for example at tips and corners, high metal layer thicknesses are usually produced, while the layer thicknesses at the concave surface areas opposite the anodes can be extremely small when using conventional baths. With the aforementioned bath, however, essentially uniformly thick layers are obtained at the designated surface points.

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 form a layer, deposited at a low current density (for example 0.5 A / dm ² ), has a high value for conventional bath types. In the case of the specified current densities, this ratio reaches values of at least 3, 4th

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

Furthermore, it is possible with the bathroom according to the invention, in a large one

Current-density area to deposit glossy layers without bubbles. The layers have no veils within a large current density range, no coarsely crystalline coatings are produced, and the adhesion of the layers to the substrate surface is sufficiently high that bubbles and other lift-offs do not form between the layer and the base

In addition, the layers are ductile. Workpieces coated in this way can therefore 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 resistant to corrosion, as well as to red rust, which can occur when coating iron substrates and is caused by corrosion of the substrate.

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 chromating layers can be used be generated.

Another advantage of the bath according to the invention is the high stability of the additive compounds used. The effectiveness of these compounds is not reduced when the bath is idle. The bath solution can be used at high temperatures, for example at 35 ° C. to 40 ° C., or at low temperatures, for example room temperature or below. By suitable choice of the concentration of the additive compounds contained and suitable further compounds, both high-gloss and semi-gloss coatings can be produced. The current yield in the metal deposition is very high even with zinc contents of 8 g / l to 10 g / l solution. The working range is very good with 4 g zinc ions / l to 40 g / l solution, without the formation of burns, and in particular from 5 g / l to 18 g / l solution, with a very good layer thickness distribution in the entire current density range. It is also possible to deposit layers up to 30 μm thick without the formation of bubbles.

In a preferred embodiment of the invention, a coating solution is used in which diallylammonium-sulfur dioxide copolymers with an average molecular weight of 240-10000 g / mol or slightly above and preferably with a molecular weight of 500 g / mol to about 6000 g / Moles are included. Diallyiammonium sulfur dioxide copolymers with n _ m> 0 and with R1 = R2 = methyl are particularly suitable. When using diallylammonium sulfur dioxide copolymers with too high

Molecular weight increases the tendency of the bubbles to form in the layers. For example, bubble-free coatings cannot be obtained with a bath containing diallylammomum-sulfur dioxide copolymers with a molecular weight of 100,000.

Diallyldimethylammonium chloride-sulfur dioxide copolymer is particularly well suited as a diallylammonium-sulfur dioxide copolymer. The coating solution can also additionally be a homopolymeric compound with the general structural formula

with an average molecular weight of 500 to 100,000, where R 1 and R2 are selected independently of one another and are hydrogen, alkyl, hydroxyalkyl, alkenyl, alkynyl, aralkyl or phenyl and

diallyldimethylammonium halide and diallyidimethylammonium hydrogen sulfite, which is formed in the production of the diallyldimethyiammonium-sulfur dioxide-sulfur dioxide-copolymers from diallyldimhalogenamide from monodimedimhalogenamides from diallyldimethylammonium-sulfur dioxide-copolymers derived from the production of the diallylammonium-sulfur dioxide copolymers and the homopolymeric compounds. contain

In the group of compounds selected from the diallylammonium sulfur dioxide copolymers, the homopolymers and the unreacted monomer, for example diallyldimethylammonium chloride, the diallylammonium sulfur dioxide copolymers are present in a proportion of 1

% By weight to 100% by weight, based on the mixture of the compounds in this group. The proportion of homopolymers is 0% by weight to 60% by weight, based on the mixture of the compounds, and the proportion of unreacted monomer is 0% by weight to 70% by weight. Typical mixtures of these compounds contain 80% by weight. Diallylammonium

Sulfur dioxide copolymer, 5% by weight homopolymer and 15% by weight unreacted monomer or 70% by weight dialiylammonium sulfur dioxide Copolymer, 5% by weight homopolymer and 25% by weight unreacted monomer.

Alternatively, you can also for a sufficient layer thickness distribution

100% monomers are used, but no glossy coatings are achieved.

In many cases it has been found that the copolymers alone, e.g. XP-1 04 according to Example 1 1, even with increased addition no significantly improved layer thickness distribution, i. H. was better than 2.4 to about 1.6. By slight addition of monomers, such as. B. diallyldimethylammonium chloride and the diallydimethylammonium hydrogen sulfite which occurs in the acidic synthesis solution, for example at pH values of 1-2 after the end of the reaction, the layer thicknesses could be further compared to index values below 1.6.

The reaction solution containing copolymers can also be treated in such a way that the polymers precipitate out as a crystalline solid, in which no free diallyl-dimethylammonium 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 for producing the layers with the required uniform layer thickness. Similar diallylammonium sulfur dioxide copolymers, such as, for example, the polyamine sulfones with 6-ring systems described in US Pat. No. 4,134,804, do not have the same advantages on. In particular, it is not possible with these compounds to deposit layers with the required uniformity. In addition, the tendency to form bubbles is markedly reduced compared to the compounds disclosed in the US patent.

Such diallylammonium sulfur dioxide copolymers with a 5-ring system are possible by suitable reaction control and substitution of the monomers available in their manufacture. In particular, these compounds are obtained as a solvent by polymerization in water. The choice of the polymerization starter could also have led to the formation of the 6-ring in the US patents. When ammonium persulfate is used instead of other peroxide initiators, for example di-tert-butyl peroxide or di-benzoyl peroxide, the diallylammonium-sulfur dioxide copolymers according to the invention are formed.

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 in a ¹³ C-NMR spectrum easily distinguishable from each other. This has already been demonstrated in Lancaster, Baccei and Panzer in Polymer Letters, Edition 1 4, page 549 (1 976).

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

The amine-epichlorohydrin copolymer contained in the solution preferably has an average molecular weight of more than 500 g / mol and in particular of about 1,500 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 nurses, diamines,

Tπamines, hydrazines and / or nitrogen-containing heterocyclic compounds with bis-electrophilic compounds, such as bis-glycidyl ether, di-haloalkanes and epihalohydrins. Particularly suitable is 3-dimethylamino-1-propylamine-epichlorohydrin copolymer as an amine-epichlorohydrin copolymer. In this case, R 1 and R2 are each methyl groups and X is chloride in the general structural formula II described above. The solution can also contain 1-benzyl pyridium 3-carboxylate as a gloss agent to produce a high-gloss zinc or zinc alloy layer. Particularly suitable carboxylate groups are carboxylates of the lower alkanoic acids, such as acetate. Sulfonate betaines, such as, for example, N-benzylpyπdinium sulfonate, are also effective compounds.

Zinc oxide is usually used as the source of zinc ions, which dissolves in the alkaline coating bath as zincate. In principle, however, other sources of zinc ions, such as zinc salts, can also be used, provided that further antones which enter the bath by adding the zinc salts do not impair the deposition is, for example, zinc sulfate

To deposit zinc alloy layers, other metals can be deposited together with zinc. For example, it is possible to produce zinc layers with additions of nickel, cobalt or iron. For this purpose, the bathers also contain compounds of these metals in addition to the zinc ion source. In addition, coordinated complexing agent combinations are required in the coating solution in order to control the deposition potentials. Such combinations are known.

Sodium hydroxide is usually added as an alkalizing agent in a concentration of 50 g / l to 200 g / l solution and in particular from 80 g / l to 150 g / l solution. However, other alkali and alkaline earth metal hydroxides and tetraalkylammonium hydroxides are also suitable. However, in the latter

Care should be taken to ensure that any complexing action of the ammonium hydroxides does not impair the deposition action.

In addition to the specified compounds, the coating solutions according to the invention also contain further components which are added to the bath for various purposes. For example, the bath can additionally contain sodium carbonate to control and stabilize the pH. To reduce the sensitivity of the bath to foreign ions, in particular to calcium and magnesium in tap water, the bath can also contain sodium gluconate or other complexing agents. Aldehydic aromatic compounds, such as, for example

Anisaldehyde can be added to the bath as a brightener. Under certain circumstances, these compounds worsen the layer thickness distribution. These compounds are preferably used in the form of their bisulfite adducts in order to increase their solubility in the bath, such as thiourea, mercaptobenzothiazole and mercaptotπazoles, are added to the bath in order to level the metal precipitate in the low current density range

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

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 range, shiny, leveled, uniform thicknesses are obtained and get bubble-free coatings

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

The solution according to the invention can be used both for coating workpieces in the so-called rack technology, in which the workpieces are immersed in the bath, firmly mounted on a rack. Due to the complex assembly technology, however, clamp parts are not metallized using the rack technology, but rather using a drum method in which the parts to be metallized are filled into a drum in the bath solution and metallized in the drum. This procedure is also easily possible with the solution according to the invention. Both soluble zinc anodes and insoluble anodes, for example made of iron, nickel-alloyed iron or titanium, can be used as anodes.

To even out the layer thickness distribution on the workpiece to be coated and, in the case of the frame technology, also on the individual workpieces to be coated at the same time, air can be blown into the coating solution and the solution can be set in vigorous motion in this way.

Some examples are shown below to illustrate the invention.

Example 1 :

A cyanide-free alkaline bath with the composition:

Zinc as zinc oxide 1 0 g, sodium hydroxide 1 30 g,

Sodium carbonate 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 1 A 1 for 5 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 basic bath was 5 ml / l of a 25% by weight aqueous solution of diallyldimethylammonium chloride-sulfur dioxide copolymer in water and 0.5 ml / l of a 38% by weight 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 _. 7th

Example 2 (comparative example):

The experiment of Example 1 was repeated. Instead of the compounds diallyldimethylammonium chloride-sulfur dioxide copolymer and 3-dimethylamino-1-propylamine-epichlorohydrin copolymer, other bath additives were used, which are also described in DE 25 25 264 C2 (5 ml of a 35% by weight aqueous solution 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-benzyl pyridium 3-carboxylate was added in a concentration of 80 mg / l to the bath solution

A zinc coating with a uniform layer thickness distribution was obtained in the entire current density range. After the coated sheet had been treated in the tempering furnace at 1 20 ° C. for one hour, the sheets were unchanged and showed no bubbles.

Example 4-

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

Shiny to semi-shiny zinc coatings without burns were obtained. 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 glossy. Subsequent blue chromating with the chromating bath ICP 33L from Atotech Espaήa, SA, Spain, which contains haxavalent chromium compounds and inorganic salts and produces a blue finish, could be carried out without any problems.

After the coated sheet had been treated for 1 hour in a tempering furnace at 120 ° C., the sheets were unchanged and showed no bubbles.

Example 6:

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

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

At a temperature of 30 ° C and a total current of 1 A was after

1 5 minutes of coating time in a Hull cell to obtain a uniformly thick zinc coating, 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 coated without any problems using the yellow chromating bath ZP1 C from Atotech Espaήa, S.A., which contains hexavalent chromium compounds and inorganic salts and gives an iridescent finish, and did not show any bubbles even after an annealing treatment.

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 a tempering treatment. The determined layer thickness index was 1.6 to 1.7.

Example 9:

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

The galvanized sheet was high-gloss without blistering after a tempering treatment. The layer thickness distribution index was 1.6 to 1.7. Example 1 0:

A zinc layer was deposited using a bath according to Example 1. However, instead of 3-dimethylamino-1-propylamine-epichlorohydrin copolymer was one of the compounds

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

b) Diethylenetriamino-epichlorohydrin copolymer in water

used. The layers had a layer thickness distribution similar to that of the layers produced according to Example 1.

Example 1 1

(Layer thickness distribution using various diallyldimethylammonium chloride-sulfur dioxide copolymers)

Bath composition:

Zinc as zinc oxide 1 0 g,

Sodium hydroxide 1 30 g, sodium carbonate 20 g,

1-benzylpyridinium-3-carboxylate 1 0 mg,

Sodium gluconate 1, 5g,

3-mercapto-1.2.4-triazole 0.1 g, additive: 3-dimethylamino-1-propylamine-epichlorohydrin copolymer 0.5 ml

per liter of aqueous solution The diallyldimethylammonium chloride-sulfur dioxide copolymers (XP 1 xx) were prepared with varying amounts of sulfur dioxide and initiator (see synthesis example) and used as 25% by weight solutions in water. The connections 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 indicate the layer thickness distribution indices.

Table 1

Concentration 4.0 ml / l 6.0 ml / l 8.0 ml / l 1 0.0 ml / l

PAS A5 3.04 3.0 2.94 2.8

PAS 92 3.85 3.82 3.67 3.62

XP 1 01 2, 1 2.0 2.0 1, 8

XP 1 03 2.3 2.0 2.0 2, 1

XP 1 04 2.0 1, 9 1, 9 1, 6

XP 1 05 2, 1 2.0 1, 8 2, 1

XP 1 06 2.4 2.0 1, 9 2.0

XP 1 1 4 2.3 2.5 2.2 1, 9 Example 1 2:

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:

Table 2

Comb. XP 1 04 BP3C IMEP Verb. II layer thickness index

[ml / l] [mg / l] [ml / l] [ml / l]

1 5 - - - 2.0

2 5 40 - - 1, 6

3 5 80 - - 1, 6

4 5 80 - 0.5 1, 65

5 - 40 - 0.5 2.86

6 5 - 0.3 - 1.85

7 5 - 0.6 - 1, 95

8 5 - 0.6 0.5 2.20

9 5-1.0 0.5 2.05

1 0 5 - 2.0 0.5 2.0 Example 1 3

Synthesis example of diallyldimethylammoniumchloride sulfur dioxide copolymer of the type XP 1 04:

A 60% by weight aqueous solution of 1,260 g of diallyldimethylammonium chloride (Aldpch, Germany) was diluted with 540 ml of water. 200 g of sulfur dioxide were slowly passed into this solution at up to 30 ° C. 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 1,400 g / mol in the polymeric portion is obtained. The molecular weight was determined by gel permeation chromatography (GPC) with Ultrahydrogel 1 20/250; refractometric determination, Pullulan and Maltooligosacchaπd standard.

For the other compounds listed in Table 1 (XPI xx), 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 1 04.

Table 3

Type diallyldimethyl-am-S0 ₂ ammonium reaction conditions monium chloride persulfate gene

XP 101 87 g a 1 3.3 g 0.6 g in 3 ml 24 hours at 50 ° C 60% solution with water 37 ml water

XP 1 03 85 g of a 60% 9, 1 g 0.4 g in 2 ml 1 6 hours at 67 ^0C solution with 25 ml water, then water 0.6 in 3 ml water XP 1 05 87 g a 60% 1 3.9 g 0.6 g in 3 ml 1 6 hours at 68 ° C solution water

XP 1 06 69.6 g of a 60% 1 0.9 g 0.5 g in 2.4 1 8 hours when dissolved with 1 5 ml ml of water 1 06 ° C water

XP 1 1 4 58 g of a 60% 9.4 g 0.6 g in 3 ml 26 hours at 77 ° C solution with 50 ml water water

Analogous to the measuring method described in Lancaster, Baccei and Panzer in Polymer Letters, Edition 1 4, page 549 (1 976), the chemical structure of the compound obtained was determined in D-0 as solvent and trimethylsilyl propane sulfonate (TSP) as standard. The compound gave signals in the ¹³ C-NMR spectrum which must be assigned to a 5-ring:

A typical example is given below:

13 C-NMR (D, O, TSP): 34.9 (ring CH-),

54.5 (-CH ₂ -SO).

55.5, 57, 1 and 57.7 (CH ₃ -N ^'

71, 1 and 71, 4 (ring-CHj-).

These signals are in good agreement with the NMR data for 5-ring polymers given in the above-cited literature reference.

The assignment made to a 5-ring system is further supported with regard to the number and position of the signals by matching 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.

Poly-diallyldimethylammonium chloride signals:

¹³ C NMR (D ₂ 0, TSP): 29.2 (framework CH _r )

41, 0 and 41, 4 (ring-CH-), 55.2 and 56.9 (CH ₃ -N ⁺ -),

73.2 (ring CH, -).

Example 1 4

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

1, 088 kg 3-dimethylamino-1-propylamine 0.709 kg epichlorohydrin 2.7 liters of water

3-Dimethylamino-1-propylamine was submitted. Water was added in 500 ml portions with stirring. Epichlorohydrin was also added in portions to the reaction mixture with stirring. The reaction vessel was then heated to an internal temperature of 100 ° C. and the reaction mixture

Stirred for 5 hours. The mixture was then brought to pH 4 with sulfuric acid.

The total weight of the reaction mixture was then 7.25 kg, the 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 1 5

Bath composition per liter of solution

Zinc 10 g / l

Sodium hydroxide 1 30 g / l

Sodium carbonate 25 g / l

Sodium gluconate 1.2 g / l

3- mercaptotriazole 0.1 g / l

3-dimethylamino-1 - -propyl; amine

Epichlorohydrin copolymer, 38% by weight 0.5 ml / l

XP-1 04, 25 wt% 4ml / l

1 -Benzylpyridinium- 3-carboxylate 40 mg / l

Rest of water

On a Hull cell sheet, coated at 1 ampere, the layer thicknesses 6.35 and 3.8 μm after 1 5 min each show a high and low current density. The layer thickness ratio is 1.65.

Example 1 6

1 ml / l of XP-1 04 was added to the bath according to Example 1 5. The measured layer thicknesses in the case of analog treatment were 6.41 and 3.86 μm, the resulting layer thickness ratio is 1.66.

Example 1 7

Example 1 6 was repeated, but diallyldimethylammonium chloride (DADMAC) was added as a 60% by weight solution to 0.2 ml / l. The measured Layer thicknesses after 15 minutes were 6.21 and 4.38 μm; this corresponds to a layer thickness ratio of 1.4.

Example 1 8

To the bath composition according to Example 1 6, but without dimethylaminopropylamine-epichlorohydrin copolymer, XP-1 04 and benzyipyridinium carboxylate, 2-20 ml / l (DADMAC) were added. The results are shown in Table 4 below:

Table 4

DADMAC layer thickness μm with current density distribution / relative ml / l high low

2 1, 27 1, 05 1, 21 1, 21

4 1, 29 3.97 0.32 3, 1 3

8 1, 1 4 3.96 0.28 3.57

1 2 2.37 3.82 0.62 1.61

20 8, 1 2 2, 1 8 3.72 3.72

This example shows that monomers alone can have a strong influence on a layer thickness distribution, so that the additions of 2 and 12 ml / l are still included in the solution according to the invention. However, the version of example 1 7 is the preferred embodiment since glossy and uniform coatings were achieved according to example 1 7, whereas in example 1 8 the result on a Hull cell sheet was worse in that the coating was matt and dark and burns were sometimes noticeable with high monomer additions. There was also a build-up of powdered zinc on the sheet. Example 1 9

This example shows the effect of the pure polymer.

A reaction solution of XP-1 04, prepared according to Example 1 2, was partially lyophilized to a moist OL and mixed with a multiple volume of methanol. A crystalline solid precipitated out. It is separated off and then recrystallized from methanol-water. According to H-NMR, the colorless crystals were free from diallyldimethylammonium monomer and contained only the diallyldimethylammonium chloride-sulfur dioxide copolymer. The average molecular weight was 5,300 g / mol, determined by the method already described.

This material, XP-1 04-Umkπstallιsιert, was, as previously described, subjected to a Hull cell test at 1 A, 1 5 min and 24 ° C.

Bath composition per liter of solution

Zinc 10 g / l sodium hydroxide 1 30 g / l

Sodium carbonate 25 g / l

Tπlon D (complexing Tπessigsaure from

BASF), instead of sodium gluconate 1, 25 ml / l

3-Mercaptotπazol 0.1 g / l XP-1 04-Umkrιstallιsιert in divergent amounts with divergent results according to Table 5

Rest of water Table 5

XP-1 04 Schiel thickness μm at lnd> coating feature

-Umkr Strorr dense coating -long 1 00 mm g / ι 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 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 bathroom matrix

Examples 20-22.

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 and the Fe content of the coating was 0.55%.

A semi-glossy and uniform 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 the 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 S.A., to produce a yellow iridescent color.

After one hour of treatment of the coated sheets according to the examples

20 to 22 in the tempering furnace at 180 ° C., the sheets were unchanged and showed no bubbles.

Claims

Solution for the electrolytic deposition of zinc or zinc alloy coatings

1 . Aqueous, alkaline, cyanide-free solution for the electrolytic deposition of zinc or zinc alloy coatings on substrate surfaces, at least containing

a source of zinc ions, an alkalizing agent, and a diallyl ammonium

Sulfur dioxide copolymer with the general structural formula

with an average molecular weight of 240 g / mol to 10 000 g / moi, where R 1 and R2 are selected independently of one another and hydrogen, alkyl, hydroxyalkyl, alkenyl, alkynyl, aralkyl or phenyl and X- = F, Cr, Br , I am.

2. Solution according to claim 1, characterized by an additionally contained amine-epichlorohydrin copolymer, obtainable by reacting epichlorohydrin with compounds selected from the group of the nurses, diamines and triamines.

3. Solution according to one of the preceding claims, characterized by an additionally contained amine-epichlorohydrin copolymer with the general structural formula

where R 1 and R2 are selected independently of one another and are hydrogen, alkyl, hydroxyalkyl, alkenyl, alkynyl, aralkyl or phenyl, X = F, Cl, Br, I and

4. Solution according to one of the preceding claims, characterized by

Diallylammonium sulfur dioxide copolymers with an average molecular weight of 240 g / mol to 6000 g / mol, preferably greater than 1000 g / mol.

5. Solution according to one of the preceding claims, characterized by diallylammonium sulfur dioxide copolymers with n ≥ m> 0

6. Solution according to one of the preceding claims, characterized by diallylammonium sulfur dioxide copolymers with R 1 = R2 = methyl.

7. Solution according to one of the preceding claims, characterized by an additionally contained homopolymeric compound having the general structural formula

with an average molecular weight of 500 to 100,000, R1 and R2 being selected independently of one another and being hydrogen, alkyl, hydroxyalkyl, alkenyl, alkmyl, aralkyl or phenyl.

8. Solution according to one of the preceding claims, characterized by diallyldimethylammonium halide and / or diallyldimethylammonium hydrogen sulfite, additionally or solely instead of the copolymers and / or homopolymers.

9. Solution according to one of the preceding claims, characterized by a

Amine-epichlorohydrin copolymer with an average molecular weight greater than 500 g / mol and preferably about 1,500 g / mol.

1 0. Solution according to one of the preceding claims, characterized by 3-dimethylamino-1-propylamine-epichlorohydrin copolymer as amine

Epichlorohydπn copolymer

1 1. Solution according to one of the preceding claims, characterized by additionally contained betaines, containing at least one pyπdinium group and carboxylate or sulfonate groups.

1 2. Solution according to one of the preceding claims, characterized by additionally contained 1 -benzylpyrιdinιum-3-carboxyiat.

1 3. Solution according to one of the preceding claims, characterized by additionally contained thio compounds.

1 4. Solution according to claim 8, characterized in that one or more counterions from the group formed from nitrates, chlorates, perchlorates and sulfates are used instead of the halide ions.

1 5. Use of an aqueous solution according to one of claims 1 to 1 4 for the electrolytic deposition of shiny and bubble-free zinc or zinc alloy coatings with a uniform layer thickness on curved substrate surfaces.

1 6. Water-based alkaline, cyanide-free solution for the electrolytic deposition of zinc or zinc alloy coatings, characterized by individual or all new features or a combination of the disclosed features.