DE2016989A1 - Process for single-layer enamelling of strips and sheets - Google Patents

Description

P 2ο 16 989.5-45

Hoesch Aktiengesellschaft, 46 Dortmund, Eberhardstrasse 12 Process for single-layer enamelling of strips and sheets

The invention relates to a multi-stage process for single-layer enamelling of steel strips and sheets, the Degreased strips and sheets between each process step rinsed in cold water and enamelled after an intermediate treatment. ■ "-..-.- ·

Processes for single-layer enamelling of sheet steel, i.e. processes in which no base enamel is used, are known. In one of these known processes (see British Patent specification 763 379) is the "sheet to be enamelled" first electrolytically degreased and after rinsing in water in Sulfuric acid or a mixture of formic acid and nitric acid acid chemically or electrolytically pickled and rinsed again. After pickling, the sheet is in a nickel bath Electrolytically plated with nickel and then enamelled. If the enamelling is not carried out in a short time after nickel-plating, the sheet to be nickel-plated becomes electrolytic Coated with a zinc layer, which is then enamelled before is removed again. However, sufficient adhesion between the steel sheet and the enamel coating is achieved by this method not reached.

109844/0670

According to another known method of enamelling Sheet metal (see DT-PS 828 626), electroplating of the sheet metal with nickel is also proposed, which is oxidizing annealed and then pickled. Instead of nickel (cf. DT-AS 1 ol7 876) cobalt or a Mixture of nickel and cobalt can be used. The oxidizing annealing at relatively high temperatures and subsequent cooling in a very specific atmosphere however, it requires a relatively large amount of effort, so that this known method is also unsatisfactory.

The invention is based on the object of the disadvantages to avoid known methods for single-layer enamelling of steel sheets or strips and in particular a method of this type, with which the treatment time shortened in a simple manner, a continuous treatment can also be carried out by steel belts and with the both steel sheets and belts with a normal carbon content as well as those that have previously undergone a decarburization treatment have been subjected to, can be produced with a flawless and very adhesive enamel coating.

9844/067

These objects are achieved according to the invention in a method of the type mentioned in such a way that the tape or sheet metal in 3 - 8% by volume nitric acid chemically or anodically pickled that on the prepared tape or sheet metal a metallic layer made of iron and one or two of the metals nickel, which can be wiped off when wet, Cobalt, manganese cathodically from one or more electrolytic baths at a temperature of room temperature to 8o ° C is deposited that one or two of the metals Nickel, cobalt, manganese the electrolyte up to a total concentration of 50 g / l of these foreign metals are added, and that the strip or sheet is chemically or anodically in acid post-treated and is then dried, after which there is a stoving coating of a varnish in which white or colored pigmented enamel frits are distributed, obtained, the paint in the form of a liquid mixture in organic solvents for use arrives, which is based on the solid state as essential Components

a) 1 to 98 percent by weight of an acrylate resin polymer, its structural elements

aa) an acrylic acid ester whose ester group consists of a straight or branched chain aliphatic hydrocarbon radical with 1 to 6 carbon atoms, and / or

2 01 6 S 8 v9

-A-

bb) a methacrylic acid ester, the ester group of which consists of an aliphatic straight-chain or branched hydrocarbon radical with 1 to 6 carbon atoms,

are linked in a polymer bond,

b) 1 to 98 percent by weight of another with the Component a compatible film-forming binder from the group of coumarone resins and / or the ketone resins, optionally in combination with a hydrogenated abietyl alcohol,

c) 1 to 4o percent by weight of a benzene dicarboxylic acid ester,

which is deformable after baking and completely and at the temperatures used for enamelling Depolymerized without residue with volatilization, with the enamel frits forming a uniform coating on the belt or melt sheet metal. In a preferred embodiment contains The paint, based on the solid, as essential components:

ä) 70 to 92 percent by weight of an acrylate resin polymer whose structural elements, towards methacrylic acid ester, whose ester group consists of an aliphatic straight-chain or straight-chain hydrocarbon radical with 1 to 6 carbon atoms, are linked in a polymeric bond,

b) 3 to 2o weight percent of another with which Component a compatible film-forming binder from the group of coumarone resins and / or the ketone resins, possibly in combination with a hydrogenated abiety alcohol,

c) 5 to 20 percent by weight of a benzene dicarboxylic acid ester.

As appropriate, it has been found thereby to bake the coating at a temperature of 15o to 35o ° C, preferably IGo to 3oo ° C, in a time of 3o min and 15 see and depolymerization at temperatures from 5oo C, preferably from 7oo ^o C to perform.

, 2016889

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For the mentioned pickling treatment it is depending on the following] Process steps advantageous, if the sheet metal or strip in 3 - 8% by volume nitric acid chemically at room temperature 3o to 6o see long, or the tape or sheet in 3-8% by volume nitric acid anodic at one current density

of Io A / dm at room temperature is about Io see.

In an expedient manner, an amount of 10% by volume sulfuric acid can be added to the bath and, during aridic pickling at a temperature of 40 to ⁰ ° C., the bath can consist only of 10% by volume sulfuric acid.

For the application of the wipeable metallic layer various advantageous embodiments possible. In preferred Way is on the sheet or strip after picking from a bivalent iron contained electrical

2 lytes of this at a current density of 5 to Io A / dm in one Time from Io to 3o see and subsequently from a non-inhibited one Nickel electrolytes, e.g. from Wattsehen or from

citric acid type, with a current density of 3 to Io A / dm nickel is deposited cathodically in a time of 6 to 15 seconds, however, instead of the nickel electrolyte, a cobalt-containing sulfate electrolyte can also be used.

2 turns and the cobalt at a current density of 3 to Io A / dm be deposited cathodically on the sheet or strip in a time of 6 to 15 seconds. Should be more beneficial in addition to iron Way at least one or at most two metals at the same time;

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are deposited, so it is advisable to use one on the strip or sheet of the divalent iron as well as one at the same time or two of the metals manganese in an amount of 1 to 20 g / l as manganese sulfate, nickel in an amount of 10 to 50 g / l, Containing cobalt in an amount of 10 to 50 g / l.

'2

Iytes, these at a current density of 5 to 2o A / dm in one Time to separate from Io to 3o see.

For the chemical post-treatment of the metallic Layered strip or sheet, it is advantageously in a 3-8% strength nitric acid Room temperature and immersed for a time of 5 to 20 seconds, while in an anodic post-treatment in

2 Io Vol% sulfuric acid has a current density of Io A / dm at a temperature of 4o to 8o C and a time of about Io see are required.

The advantages of the method according to the invention are to be seen in particular in the fact that a continuous, relatively short treatment of steel strips, both with normal C contents of around 0.04 to 0.100% as well as with very low carbon contents of around 0.06% in the the same way can be carried out, with flawless and very adhesive layers of enamel on these tapes or Sheets can be produced.

201698G

In the following, the method for single-layer enamelling of steel strips or sheets is based on particularly advantageous Workflows that have already proven themselves are described in more detail.

example 1

1. Anodic degreasing in sodium hydroxide solution at a temperature of 8o C and a current density of 15 A / dm in a time of 6 seconds

2. Rinse

3. Pickling at room temperature in 5% by volume nitric acid in a time of 3o see

4. Rinse

5. Cathodic deposition of iron, manganese and nickel from an electrolyte with the composition:

7o g / l ferrous sulphate

Io "manganese (II) sulfate

loo "nickel sulfate

2o "nickel chloride

ο6> ο

5o g / l magnesium sulphate 25 "ammonium sulphate 2o" boric acid,

its pH value adjusted to 2, ο with sulfuric acid

becomes, at a current density of Io A / dm, a temperature

of 6o ° C, in a time of Io see. Anode material: which carbon steel

6. Rinse

7. Post-treatment at room temperature in 5% by volume nitric acid for a period of 20 seconds

8. Rinse

B ice ρ 1 e 1

1. Anodic degreasing in caustic soda at one temperature of 8o C, a current density of 15 A / dm, in a time of 6 seconds

- Io -

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2Q16989

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2. Rinse

3. Pickling at room temperature in 3% by volume nitric acid in a time of 3o see

4. Cathodic deposition of Elsen at room temperature

from an electrolyte having the following composition;

14o g / i iron (II) sulphate loo "magnesium sulphate 5o" ammonium sulphate,

whose pH is adjusted to 2, ο with sulfuric acid, at a current density of Io A / dm, at a time from Io see.

Anode material: soft carbon steel

5. Rinse

6. Cathodic deposition of cobalt at room temperature from an electrolyte with the following composition:

3oo g / l cobalt sulfate 2o " sodium chloride 4o" boric acid,

- li -

its pH value with sulfuric acid to 2, ο one

2 is set, at a current density of Io A / dm, in a time of Io see

7. Rinse

8. Anodic aftertreatment at 6o C in 10% alcohol

2 sulfuric acid and a current density of Io A / dm, in a time of Io see

9. Rinse

Example 3

A treated according to process steps 1 to 8 of the example and process steps 1 to 9 of example 2 and then dried sheet metal is coated in a known manner, e.g. by painting, dipping, spraying, rolling Varnish applied in the white or colored pigmented enamel frits in an amount of 5o to 8o percent by weight are incorporated. The paint is applied in the form of a liquid mixture in organic solvents and contains related to the solid, as essential constituents

^share:

J C67O

- 12 -

a) 1 to 98 percent by weight of an acrylate resin polymer, its structural elements

aa) an acrylic acid ester whose ester group consists of a straight or branched chain aliphatic carbon

"hydrogen radical with 1 to 6 carbon atoms

exists, and / or

bb) a methacrylic acid ester, the ester group of which consists of an aliphatic straight-chain or branched-chain hydrocarbon radical with 1 to 6 carbon atoms,

are linked in a polymer bond,

b) 1 to 98 percent by weight of another film-forming binder compatible with component a from the group of the Cmnaron resins and / or the ketone resins, optionally in combination with a hydrogenated abietyl alcohol,

c) 1 to 4o percent by weight of a fienzoldicarbon-

13 -

201698G

The lacquer coating is subsequently applied at a temperature of from 150 to 35o C., preferably from 160 to 300 ° C. in a time of 3o min to 15 seconds burned into the sheet, with longer burn-in times and at the low temperatures mentioned correspondingly shorter baking times are to be used at the higher temperatures.

It should be noted that the temperature transition for the subsequent depolymerization of the paint components is continuous or flowing and therefore the baking temperatures, which are preferably about 20 ° C. higher than the melting point of the frit used, cannot be increased at will can, The paint film baked into the strip or sheet metal has a smooth, matt appearance, the color tone being from depends on the enamel frit incorporated in the lacquer. The burned-in paint film is also not mechanically vulnerable, scratch-resistant, impact-resistant and hard. But in particular the tape or sheet provided with the lacquer coating is deformable, preferably deep-drawable, so that the end user the desired shape can already be manufactured by the sheet metal or strip manufacturer.

At the consumer, the lacquer film becomes ^{complete in an oven at temperatures of about 1} K) OC, preferably from 700 C

/ U: J f ^ V / ( ^f) 6

- 14 -

BATH ORIGINAL

• - 14 -

and residue-free with volatilization of the paint components depolymerizes, whereby the enamel frit fuses to form a uniform, flawless enamel coating.

Claims (1)

P-2ο 16 989. 5-45 Hoesch Aktiengesellschaft, 46 Dortmund, Eberhardstrasse 12 Claims ' 1. Multi-stage process for single-layer enamelling of steel strips and sheets, the strips and sheets being degreased, rinsed in water between each process step and enameled after an intermediate treatment, characterized in that the tape or sheet is chemically in a 3-8% strength nitric acid or anodic pickling is carried out so that a metallic layer of iron and one or two of the metals nickel, cobalt, manganese, which can be wiped off when wet, is deposited cathodically from one or more electrolytic baths at a temperature from room temperature to 8o C on the prepared strip or sheet is that one or two of the metals nickel, cobalt, manganese are added to the electrolyte up to a total concentration of 5o g / l of these foreign metals, and that the strip or sheet is chemically or anodically aftertreated in acid in a time from Io to at most 2o see and then dried, after which it is a stoved coating of a varnish in which we iße or colored pigmented enamel frits are distributed, the lacquer being applied in the form of a liquid mixture in organic solvents, which is applied to the 2016S89- Solids-related, as essential components a) 1 to 98 percent by weight of an acrylate resin polymer, its structural elements aa) an acrylic acid ester, its ester group a straight or branched chain ^ aliphatic hydrocarbon radical with 1 to 6 carbon atoms, and / or bb) a methacrylic acid ester, the ester group of which consists of an aliphatic straight-chain or branched hydrocarbon radical with 1 to 6 carbon atoms, are linked in a polymer bond, b) 1 to 98 percent by weight of another film-forming binder compatible with component a from the group of coumarone resins and / or ketone resins, optionally in combination with one hydrogenated abietyl alcohol, 2016 38 3 c) 1 to 40 percent by weight of a benzene dicarboxylic acid ester included, which is deformable after baking and at the temperatures used for enamelling completely and depolymerized without residue with volatilization, whereby the enamel frits fuse to form a uniform coating on the strip or sheet. 2. The method according to claim 1, characterized in that the paint, based on the solid, is essential Components contains: a) 7o to 92 percent by weight of an acrylate resin polymer, its structural elements, a methacrylic acid ester, its Ester group from an aliphatic straight-chain or branched-chain hydrocarbon radical with 1 to 6 Carbon atoms are linked in a polymeric bond, b) 3 to 20 percent by weight of another with the component a compatible film-forming binder . the group of coumarone resins and / or ketone resins, optionally in combination with a hydrogenated abietyl alcohol,. 2016S89 c) 5 to 20 percent by weight of a benzene dicarboxylic acid ester. 3. The method according to claims 1 and 2, characterized in that that the coating at a temperature of I5o to 35o C, preferably 16o to 3oo ° C, in a time of Baked in for 30 minutes to 15 seconds and the depolymerization carried out at temperatures from 500 ° C, preferably from 700 ° C will. 4. The method according to claims 1 to 3, characterized in that that the strip or sheet metal in 3 - 8% by volume nitric acid chemically at room temperature 3o to 6o see is picked up for a long time. 5. The method according to claims 1 to 3, characterized in that that the tape or sheet in 3 - 8% by volume Nitric acid anodic at a current density of Io A / dm is pickled at room temperature for about Io see. 6. The method according to any one of claims 1 to 4, characterized in that that the bath for anodic pickling is Io vol% Sulfuric acid is added. 2016S89 7. The method according to claim 6, characterized in that the bath for anodic pickling from Io VoI% -iger
Sulfuric acid. 8. The method according to claims 1 to 7, characterized in that that on the sheet or strip after pickling from a divalent iron containing electrolyte 2
this at a current density of 5 to Io A / dm in a time from Io to 3o see and subsequently from one non-inhibited nickel electrolytes, e.g. of the Watt's or citric acid type, at a current density of 3 to Io A / dm in a time of 6 to 15 see nickel is deposited cathodically. 9. The method according to claims 1 to 8, characterized in that that instead of the nickel electrolyte, a cobalt-containing sulfate electrolyte is used and the cobalt at a current density of 3 to Io A / dm at a time from 6 to 15 see cathodically. is deposited. Io. Method according to one of Claims 1 to 9, characterized in that that on the strip or sheet of the bivalent iron and at the same time one or two of the metals, manganese - 6 ■■ * * in an amount of 1 to 20 g / l as manganese sulfate, nickel in an amount of 10 to 50 g / l, cobalt in an amount from 10 to 50 g / l containing electrolytes this at 2 a current density of 5 to 20 A / dm in a time of Io to 3o see are deposited. 11. The method according to any one of claims 1 to Io, characterized in, that the strip or sheet provided with the metallic layer is chemically dissolved in 3 - 8% by volume nitric acid is aftertreated at room temperature in a period of 5 to 20 seconds. 12. The method according to a dör claims 1 to Io, characterized in that that the strip or sheet provided with the metallic layer is anodized in 10% strength sulfuric acid at a current density of Io A / dm at one temperature post-treated from 4o to 8o ° C in a time of about Io see will. TT ORIGINAL INSPECTED