Method for Producing a Sandwich Structure, Sandwich Structure Produce Thereby and Use Thereof

Abstract

The invention relates to a method for producing a sandwich structure on the basis of at least one layer on the basis of metallic material and on the basis of at least one layer of organic polymer, wherein for coating of at least one metallic surface with at least one metallic layer to be combined with the layer on the basis of organic polymer, an aqueous conversion composition on the basis of zinc, additional cations, poly(acrylic acid), and optionally silane, is brought into contact, wherein the liquid film thereby produced is dried on and wherein the metallic layer coated in such manner is brought into contact with at least one layer on the basis of organic polymer and is combined into a sandwich structure by means of compaction under pressure and/or temperature. The invention also relates to such sandwich structures.

Claims

1.-16. (canceled)

17. A method for producing a sandwich structure on the basis of at least one layer of metallic material and on the basis of at least one layer of organic polymer, characterized in that at least one surface on at least one metallic layer which is to be combined with at least one layer of organic polymer is brought into contact with an aqueous conversion composition which contains: 0.5 to 20 g/l zinc, 0.01 to 10 g/l manganese, 0.01 to 10 g/l aluminum, 0.01 to 1 g/l chromium(III), 0.01 to 5 g/l iron(II), 0.01 to 5 g/l iron(III) and/or 0.01 to 5 g/l magnesium, 0 or 0.01 to 5 g/l of the total as nickel and/or cobalt, 0 or 0.01 to 5 g/l of the total as molybdenum, tantalum, vanadium and/or tungsten, 2 to 100 g/l P.sub.2O.sub.5, which corresponds to 2.68 to 133.8 g/l PO.sub.4, 0.1 to 10 g/l polyacrylic acid, but not more than 25% of the P.sub.2O.sub.5 content of the composition in g/l, and 0 or 0.01 to 3 g/l silane, but not more than 25% of the P.sub.2O.sub.5 content of the composition in g/l, in that a liquid film produced therewith is dried on, in that the metallic layer coated in this manner is cut, if required, and in that the metallic layer coated in this manner is brought into contact with at least one layer on the basis of organic polymer and is combined into a sandwich structure by means of compaction under pressure and/or temperature.

18. The method according to claim 17, characterized in that the aqueous conversion composition has the following composition: 1 to 10 g/l zinc, 0.5 to 6 g/l manganese, 0.01 to 0.5 g/l aluminum, 0.01 to 0.8 g/l chromium(III), 0.01 to 1 g/l iron(II), 0.01 to 1 g/l iron(III) and/or 0.01 to 1.5 g/l magnesium, 0 or 0.01 to 2.5 g/l nickel, 0 or 0.01 to 2.5 g/l cobalt, wherein the total of nickel and cobalt is 0 or lies in the range from 0.01 to 4 g/l, 0 or 0.01 to 5 g/l of the total as molybdenum, tantalum and/or vanadium, 8 to 60 g/l P.sub.2O.sub.5, which corresponds to 10.72 to 80.28 g/l PO.sub.4, 0.5 to 5 g/l polyacrylic acid, but not more than 25% of the P.sub.2O.sub.5 content of the composition in g/l, and 0 or 0.01 to 3 g/l silane, but not more than 25% of the P.sub.2O.sub.5 content of the composition in g/l and also no content of a complex fluoride of titanium or zirconium.

19. The method according to claim 17, characterized in that the aqueous conversion composition has the following composition: 2 to 8 g/l zinc, 1 to 5 g/l manganese, 0.01 to 0.2 g/l aluminum, 0.01 to 0.5 g/l chromium(III), 0.01 to 0.5 g/l iron(II), 0.01 to 0.5 g/l iron(III) and/or 0.01 to 0.8 g/l magnesium, 0 or 0.01 to 2 g/l nickel, 0 or 0.01 to 2 g/l cobalt, wherein the total of nickel and cobalt is not more than 2.5 g/l, 0 or 0.01 to 5 g/l of the total as molybdenum, and/or vanadium, 9.5 to 50 g/l P.sub.2O.sub.5, which corresponds to 12.73 to 66.9 g/l PO.sub.4, 0.5 to 3 g/l polyacrylic acid, but not more than 25% of the P.sub.2O.sub.5 content of the composition in g/l, and 0 or 0.01 to 2 g/l silane, but not more than 25% of the P.sub.2O.sub.5 content of the composition in g/l and also no content of a complex fluoride of titanium or zirconium.

20. The method according to claim 17, characterized in that the method takes place without an activation step with a colloidal titanium phosphate or with a surface conditioner on the basis of phosphate particles.

21. The method according to claim 17, characterized in that a wet film of the aqueous conversion composition is homogeneously formed on the metallic surface and that the contact time with the aqueous conversion composition until complete drying on is less than 1 minute.

22. The method according to claim 17, characterized in that the liquid film thereby produced is dried on without being rinsed herein or hereafter with aqueous liquid.

23. The method according to claim 17, characterized in that a conversion coating with a layer weight of up to 0.4 g/m.sup.2 is formed.

24. The method according to claim 23, characterized in that the conversion coating is formed in the form of a microphosphating.

25. The method according to claim 23, characterized in that the conversion coating is formed largely or entirely amorphous.

26. The method according to claim 17, characterized in that the at least one layer is made of organic thermoplastic polymer which is optionally fiber-reinforced.

27. The method according to claim 17, characterized in that the at least one layer of organic polymer is a polymer on the basis of polyamide, polyethylene and/or polypropylene, which is optionally made of thermoplastic plastics and/or is also fiber-reinforced.

28. A sandwich structure produced with a method according to claim 17.

29. The sandwich structure according to claim 28, characterized in that the content of polyacrylic acid and/or its reaction products in the dried-on and/or the dried-on and, during compaction, thermally loaded, conversion coating is 0.05 to 15% by weight of the conversion coating.

30. The sandwich structure according to claim 28, characterized in that the content of at least one silane and/or its/their reaction products in the dried-on and/or the dried-on and, during compaction, thermally loaded conversion coating is 0.01 to 15% by weight of the conversion coating.

31. The sandwich structure according to claim 28, characterized in that it is at least once respectively coated, deformed, glued, compressed and/or otherwise joined.

32. Use of the sandwich structure according to claim 28.

33. Use of the sandwich structure produced in accordance with the method according to the claim 17 in motor vehicle construction, in aircraft construction, in space travel, in apparatus construction, in machine construction, in building construction, in furniture production or as structural elements.

Description

EXAMPLES AND COMPARATIVE EXAMPLES

[0108] The subject matter of the invention will now be described in greater detail by reference to exemplary embodiments:

[0109] The examples below are based on the following substrates or method steps:

[0110] The following sheet metals were tested:

A) Aluminum alloy AlMg3 5754 W19,
B) Cold rolled continuous annealed steel sheet (CRS) from unalloyed steel DC04B,
C) Light gage electrolytically galvanized sheet steel (ZE) in automobile quality, grade DX54 DZ100,
D) hot-dip galvanized rerolled sheet (Z) from mild unalloyed steel, grade DX53 with at least 100 g/m.sup.2 zinc deposit,
E) High-grade steel (StS), grade 1.4301,
F) Magnesium alloy AZ31, and
G) Magnesium alloy AM50,
each with a thickness of approximately 0.2 to 1 mm, depending on the metallic material and test.
1. The substrate surfaces of the sheets were cleaned in a 2% aqueous solution of a strongly alkaline cleaner over 10 to 20 s at 55 to 60 C. and thoroughly degreased in the process.
2. This was followed by rinsing with mains water for 0.5 minutes at room temperature.
3. Different aqueous conversion compositions were prepared according to Table 1, all except VB37 having good bath stability. The salts used herein are given on the second and third pages of the tables, although always only one of a plurality of the zinc compounds given was added. As polyacrylic acid, an adhesion-promoting formulation dissolved in water with polyacrylic acid polymer having a mean molecular weight in the range from 50,000 to 70,000 was used. As epoxysilane 1, 3-glycidoxypropyltrimethoxysilane in the pre-hydrolyzed state was used. As aminosilane 1, N-(2-(aminoethyl)-3-aminopropyltrimethoxysilane in the prehydrolyzed state was used. The conversion compositions showed a pH value in the range from 2 to 3.
4. In many tests, a plurality of different metallic substrates were treated one after another and otherwise treated in the same manner and grouped together under a number of an example or comparative example for greater clarity in Table 1.
5. Thereafter, the surfaces of the different types of metal sheet given in Table 1 under substrates were coated at room temperature with a laboratory coater, wherein a wet film of approximately 3.5 ml/m.sup.2 was applied.
6. Then the coated substrates were dried in a drying oven at 180 C. for 20 to 30 s at a peak metal temperature PMT of 60 C., where in the wet film was dried on without prior rinsing.
7. On the dried conversion-coated substrates, the layer weight for the chemical element phosphorus was determined with an X-ray fluorescence analysis apparatus (RFA) to discover the P.sub.2O.sub.5 content. In examples B1 to B6, layer weights for the conversion coating in the range from 20 to 60 mg/.sup.2 P.sub.2O.sub.5 were tested, whereas in the further examples and comparative examples, a layer weight in the range from 10 to 150 mg/m.sup.2 P.sub.2O.sub.5 was used. Table 1 shows extracts therefrom.
8. As polymer layers, KTL temperature-resistant layers made of a composite material (compound) of polyamide PA6 with a proportion of PE, which means a polyamide on the basis of -caprolactam or -aminohexanoic acid and/or of polyethylene having a thickness in the range from 0.05 to 1.00 mm.
9. In each case, a polymer layer was pressed in a panel press as an intermediate layer between two identical metallic layers conversion-coated according to the invention without targeted pre-warming, under loading at a temperature possibly of up to 240 C. without pressure for 60 s and thereby combined to a durable sandwich structure. Herein, at least a part of the, in particular, thermoplastic material melted and, on cooling, formed a firm bond by means of the inventive conversion coating.
10. Following cooling, peel strength values to ISO 11339:2010 were determined, wherein triple measurements per sandwich structure were made on relevant samples. The portions used from the sandwich structure were 4 cm wide and 13 cm long and were expected to produce peel strength results of at least 300N/4 cm, i.e. at least 75N/cm in the peel strength test to ISO 11339:2010.

TABLE-US-00001 TABLE 1 Composition and properties of the aqueous conversion compositions, the conversion coatings and the sandwich structures produced therewith. B1 B2 B3 B4 B5 B6 B7 B8 B9 B10 B11 B12 Substrate Z/ZE CRS/StS Z/ZE/CRS/AL/StS Z/ZE Bath composition in g/l; remainder: water Zn 3.33 3.33 3.33 6.86 6.86 6.86 8.76 8.76 8.76 1.72 1.72 1.72 Mn 2.02 2.02 2.02 4.03 4.03 4.03 5.15 5.15 5.15 1.01 1.01 1.01 Ni 0.69 0.69 0.69 1.37 1.37 1.37 1.75 1.75 1.75 0.34 0.34 0.34 Mo 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 P.sub.2O.sub.5 19.15 19.15 19.15 38.30 38.30 38.30 48.86 48.86 48.86 9.57 9.57 9.57 PO.sub.4 25.62 25.62 25.62 51.24 51.24 51.24 65.39 65.39 65.39 12.81 12.81 12.81 Zn:PO.sub.4 0.13 0.13 0.13 0.13 0.13 0.13 0.13 0.13 0.13 0.13 0.13 0.13 Polyacrylic acid 1.28 2.56 1.59 1.28 2.56 1.59 1.28 2.56 1.59 1.28 2.56 1.59 Epoxysilane 1 1.56 1.56 1.56 1.56 Layer weight P.sub.2O.sub.5 20-60 40-120 50-150 10-30 mg/m.sup.2 Peel strength N/4 cm 500- 500- 400- 300- 300- 350- 300- 300- 350- 200- 200- 400- 700 750 500 400 400 650 400 400 650 350 350 500 B13 B14 B15 B16 B17 B18 B19 B20 B21 B22 B23 Substrate CRS/StS Z/ZE CRS/StS Z/ZE CRS/StS added as Bath composition in g/l; remainder: water Zn as ZnO + ZnCO.sub.3 3.33 3.33 3.33 3.33 6.86 3.33 3.33 3.33 6.86 6.86 6.86 Mn as Mn.sub.3(PO.sub.4).sub.2 2.02 2.02 2.02 2.02 4.03 2.02 2.02 2.02 4.03 4.03 4.03 Ni as NiCO.sub.3 0.69 0.69 0.69 0.69 0.69 0.69 1.37 1.37 1.37 Al as AlPO.sub.4 0.18 0.18 0.18 Cr(III) as Cr(NO.sub.3).sub.3 0.2 0.4 0.2 Mo 0.10 0.10 0.10 0.10 0.10 [(NH.sub.4).sub.6Mo.sub.7O.sub.24-4H.sub.2O] NO.sub.3 as NaNO.sub.3 0.60 0.60 P.sub.2O.sub.5 19.15 19.15 19.15 19.15 38.30 19.15 19.15 19.15 38.30 38.30 38.30 PO.sub.4 25.62 25.62 25.62 25.62 51.24 25.62 25.62 25.62 51.24 51.24 51.24 Zn:PO.sub.4 0.13 0.13 0.13 0.13 0.13 0.13 0.13 0.13 0.13 0.13 0.13 Polyacrylic acid 1.28 2.56 1.59 2.56 2.56 1.28 2.56 1.59 1.28 2.56 1.59 Epoxysilane 1 1.56 1.56 1.56 Aminosilane 1 0.20 Layer weight P.sub.2O.sub.5 20-60 20-60 20-60 20-60 40-120 mg/m.sup.2 Peel strength N/4 cm 400- 400- 400- 500-750 300-400 500-750 400-500 500 500 500 B24 B25 B26 B27 B28 B29 B30 B31 B32 B33 B34 Substrate Z/ZE/CRS/AL/StS Z/ZE CRS/StS Z/ZE added as Bath composition in g/l; remainder: water Zn as ZnO + ZnCO.sub.3 8.76 8.76 8.76 1.72 1.72 1.72 3.33 3.33 3.33 3.33 6.86 Mn as Mn.sub.3(PO.sub.4).sub.2 5.15 5.15 5.15 1.01 1.01 1.01 2.02 2.02 2.02 2.02 4.03 Ni as NiCO.sub.3 1.75 1.75 1.75 0.34 0.69 0.69 0.69 Co as Co(NO.sub.3).sub.2-4H.sub.2O 0.34 0.34 Fe(III)[Fe(NO.sub.3).sub.2.9H2O] 0.20 0.20 0.40 Mg as Mg.sub.3(PO.sub.4).sub.2 0.30 0.60 Mo 0.10 0.10 [(NH.sub.4).sub.6Mo.sub.7O.sub.24-4H.sub.2O] V as NaVO3-W 0.20 W 0.10 V as Na.sub.2WO.sub.4 H.sub.2O.sub.2 0.0002 0.0004 NO.sub.2 as NaNO.sub.2 0.002 NO.sub.3 as NaNO.sub.3 0.60 0.60 0.60 P.sub.2O.sub.5 48.86 48.86 48.86 9.57 9.57 9.57 19.15 19.15 19.15 19.15 38.30 PO.sub.4 65.39 65.39 65.39 12.81 12.81 12.81 25.62 25.62 25.62 25.62 51.24 Zn:PO.sub.4 0.13 0.13 0.13 0.13 0.13 0.13 0.13 0.13 0.13 0.13 0.13 Polyacrylic acid 1.28 2.56 1.59 1.28 2.56 1.59 1.28 2.56 1.59 2.56 2.56 Epoxysilane 1 1.56 1.56 1.56 Layer weight P.sub.2O.sub.5 50-150 10-30 20-60 40-120 mg/m.sup.2 Peel strength N/4 cm 300- 350- 200- 200- 400- 200- 200- 200- 300- 300- 400 650 350 350 500 320 320 320 420 400 B35 B36 VB37 B38 B39 B40 B41 B42 B43 VB44 VB45 VB46 B47 VB48 VB49 Z/ZE Substrate Bath composition in g/l; remainder: water Zn 1.28 6.41 12.81 3.33 3.33 3.33 3.33 3.33 3.33 3.33 3.33 3.33 3.33 3.33 3.33 Mn 2.02 2.02 2.02 2.02 2.02 2.02 2.02 2.02 2.02 2.02 2.02 2.02 2.02 2.02 2.02 Mo 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 P.sub.2O.sub.5 19.15 19.15 19.15 19.15 19.15 19.15 19.15 19.15 19.15 19.15 19.15 19.15 19.15 19.15 19.15 PO.sub.4 25.62 25.62 25.62 25.62 25.62 25.62 25.62 25.62 25.62 25.62 25.62 25.62 25.62 25.62 25.62 Zn:PO.sub.4 0.05 0.25 0.50 0.13 0.13 0.13 0.13 0.13 0.13 0.13 0.13 0.13 0.13 0.13 0.13 Polyacrylic acid 1.59 1.59 1.59 0.30 1.56 3.00 0.30 1.56 3.00 5.50 7.50 10.00 1.59 1.59 Epoxysilane 1 0.20 0.20 0.20 3.00 3.00 3.00 3.50 6.00 Layer weight P.sub.2O.sub.5 20-60 mg/m.sup.2 Peel strength N/4 cm 300- 300- 250- 400- 400- 250- 400- 300- 250- 200- 150- 400- 250- 150- 650 650 400 800 800 400 800 600 400 300 250 800 400 250

[0111] Table 1 illustrates that on all the very different metallic substrate materials, with the inventive aqueous conversion composition, sandwich structures with excellent or good values of peel strength were achieved and that even for nickel-free conversion compositions, very good values were achieved.

[0112] The examples B1 to B6 show excellent results, examples B7 to B17 show very good results. The examples B18 to B43 illustrate good results with a peel strength of more than 300 N/4 cm, so that overall good sandwich structures are producible in a broad chemical field of the aqueous conversion compositions. The comparative examples VB44 to VB46 and VB48 show less good results since clearly, for these aqueous compositions, excessively high levels of polyacrylic acid or of silane were added.

[0113] Lower layer weights herein typically produced a better peel strength than higher layer weights. The inventive sandwich structures showed an outstanding peel strength. They also met the very high standards of the automotive industry with regard to joining behavior, corrosion-resistance, formability and coatability, as determined in further tests (not shown here).

[0114] First tests with the inventive method, revealed that, under the same conditions and without an additional second conversion coating, the galvanized steel sheets Z and ZE can now both be successfully coated and further processed to sandwich structures. The process stability of the preparation of the metallic surfaces, of the aqueous conversion composition and of the conversion coating process was also greater than in the earlier tests, as was revealed by high peel strength values overall. There was found to be a greater bath stability of the conversion composition, which had the effect of more even coatings, which therefore also showed better property values.