U.S. patent application number 15/311342 was filed with the patent office on 2017-06-15 for method for producing a sandwich structure, sandwich structure produce thereby and use thereof.
The applicant listed for this patent is Chemetall GmbH, ThyssenKrupp Steel Europe AG. Invention is credited to Ingo Kluppel, Mark Leimkuhler, Norbert Maurus, Sophie Reisewitz, Gerrit Schullermann.
Application Number | 20170167030 15/311342 |
Document ID | / |
Family ID | 53189823 |
Filed Date | 2017-06-15 |
United States Patent
Application |
20170167030 |
Kind Code |
A1 |
Kluppel; Ingo ; et
al. |
June 15, 2017 |
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.
Inventors: |
Kluppel; Ingo; (Schwerte,
DE) ; Leimkuhler; Mark; (Recklinghausen, DE) ;
Maurus; Norbert; (Langen, DE) ; Reisewitz;
Sophie; (Schwerte, DE) ; Schullermann; Gerrit;
(Maintal, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Chemetall GmbH
ThyssenKrupp Steel Europe AG |
Frankfurt Am Main
Duisburg |
|
DE
DE |
|
|
Family ID: |
53189823 |
Appl. No.: |
15/311342 |
Filed: |
May 20, 2015 |
PCT Filed: |
May 20, 2015 |
PCT NO: |
PCT/EP2015/061039 |
371 Date: |
November 15, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B32B 2262/101 20130101;
B32B 2262/0269 20130101; C23C 22/188 20130101; B32B 15/08 20130101;
B32B 15/20 20130101; B32B 2419/00 20130101; B32B 27/12 20130101;
B32B 27/18 20130101; C23C 22/20 20130101; B32B 2260/046 20130101;
C23C 22/42 20130101; B32B 2255/26 20130101; B32B 5/02 20130101;
B32B 15/18 20130101; B32B 2479/00 20130101; B32B 27/34 20130101;
B32B 2255/06 20130101; B32B 2605/00 20130101; B32B 2307/718
20130101; B32B 27/08 20130101; B32B 27/32 20130101; B32B 2307/714
20130101; C23C 2222/10 20130101; B32B 15/14 20130101; B32B 2255/205
20130101; B32B 2262/106 20130101; B32B 2260/021 20130101; C23C
2222/20 20130101 |
International
Class: |
C23C 22/42 20060101
C23C022/42; C23C 22/20 20060101 C23C022/20; C23C 22/18 20060101
C23C022/18 |
Foreign Application Data
Date |
Code |
Application Number |
May 28, 2014 |
DE |
102014007715.2 |
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
[0001] The invention relates to a method for producing a sandwich
structure on the basis of at least one layer on the basis of
plastics with at least one layer on the basis of metallic material,
for example sheet steel, wherein a special adhesion-promoting and
conversion-protecting coating is undertaken on at least one
surface, the sandwich structure produced in this manner and the use
of the sandwich structure produced in this manner.
[0002] In automobile production and aircraft construction, but also
in many other construction types, metallic components are nowadays
used, in particular, as supporting parts. However, the weight of
such components is large and is to be further reduced in a number
of uses.
[0003] One route to weight reduction is the use of sandwich
structures in which a part of the usually heavy but typically
mechanically very stable metallic material is replaced with organic
material and with which a well-adhering composite in a stable
construction can be used.
[0004] Particularly preferred sandwich structures are, for example,
those on the basis of metal-plastics, metal-plastics-metal or
metal-plastics-metal-plastics-metal.
[0005] The coating of metallic surfaces for reasons of corrosion
protection and/or paint adhesion is basically known from many
publications. For this purpose, above all, conversion coatings are
used. Herein, it is above all decided whether passivations
(=treatments) which are intended to protect primarily a paint layer
against corrosion in the long term or whether pre-treatments should
be used before a further coating, for example, a paint or
adhesive.
[0006] EP 1 651 432 B1 teaches a metal laminate which comprises
between two outer metal sheets an adhesive polymer layer comprising
polyamide, a copolymer of ethylene and an unsaturated carboxylic
acid and/or a derivative thereof and a reactive copolymer which
comprises a styrene maleic anhydride copolymer, which has a
molecular weight from 1400 to 10000.
[0007] DE 102007046226 A1 relates to a composite component
consisting of a first and second metal sheet with at least one
polymer foam layer arranged between them.
[0008] DE 2627681 A1 teaches phosphating methods on the basis of
acidic metal phosphate solution in the presence of a water-soluble
polymer with monomer units of (methyl)acrylic acid and/or
(meth)acrylamide.
[0009] U.S. Pat. No. 3,721,597 relates to production methods of
laminates on the basis of aluminum panels, ethylene-acrylic acid
copolymer and HD-PE as the inner layer.
[0010] As compared with single or multi-layered paint coatings
which often have a thickness of the individual paint layer on metal
substrates in the region of 1 to 50 .mu.m, one or more layers of
organic polymer (=polymer layer) which are used for a sandwich
structure and are glued on as a layer and/or are pressed onto one
another, require a significantly greater thickness than a paint
layer, for example, a thickness in the region of 0.1 to 5 mm.
[0011] A high degree of adhesion between the individual layers of a
sandwich structure is necessarily required for the production, in
particular, of a stiffness-optimized sandwich structure, for
example, a metal-plastics-metal sandwich structure. Previously, it
has often been realized by means of a wet chemical application of a
thin surface-activating and/or adhesion-promoting intermediate
layer on the metallic surface of a metallic layer and the melting
on, in particular, of thermoplastic components of a polymer layer.
In order to apply the surface-activating and/or adhesion-promoting
intermediate layer onto the metallic surface of a metallic layer,
separate plant passes for pre-treatment, for example, of a metal
sheet in a coil coating plant are required. For example, galvanized
steel sheets, depending on their production method, for example,
hot-dip galvanized steel sheet Z or electrolytically galvanized
steel sheet ZE, require different process control, which entails
additional effort. Other metal substrates can be created with the
conventional method sometimes only with insufficient adhesion of
the layers of the sandwich structure. Whereas on similar metallic
surfaces as on ZE, a certain degree of adhesion has been achieved
by means of an acidic conversion composition to form a conversion
layer with approximately 30 mg Ti per m.sup.2, on Z, an
insufficient adhesion has been achieved. A sufficiently high level
of adhesion could only be achieved on Z when by additional process
steps with a first alkaline conversion composition, furthermore
with additional rinsing with water and then with a second acidic
conversion composition, a second conversion layer having
approximately 30 mg Ti per m.sup.2 was formed. When the manner of
zinc coating was changed from time to time, this was an
unacceptable disadvantage.
[0012] Furthermore, the conventionally used technique had the
disadvantage, in particular, for hot-dip galvanized steel sheets,
that the metal-plastics composite had only a limited adhesion in a
peel strength test.
[0013] For this reason, further wet-chemical conversion
compositions should be investigated. It would be advantageous if
the conventional wet-chemical coating method for surface activation
and/or adhesion-promotion could be more effectively adapted to the
plastics used. It was an aim to ascertain alternative wet-chemical
conversion compositions for all common metal substrates and, in
particular, for metallic-coated steel substrates. It was also an
aim to provide metallic layers for a sandwich structure with the
aid of a thin adhesion-promoting conversion coating which serves as
an intermediate layer of a sandwich structure and hereby to achieve
a sandwich composite adhesion of at least 300N/4 cm at 4 cm sample
width, which results in 75N/cm in the peel strength test according
to ISO 11339, 2010.
[0014] It was an object to improve the adhesion between the surface
of a layer on the basis of organic polymers, for example, a KTL
temperature-stable polymer layer and the surface of a metallic
layer, for example, as a cover panel, in order to produce a
sandwich structure, in particular on the basis of metal-plastics,
metal-plastics-metal, plastics-metal-plastics,
metal-plastics-metal-plastics or
metal-plastics-metal-plastics-metal. Sandwich structures, in
particular, stiffness-optimized metal-plastics-metal sandwich
structures, as planned under the trademark Litecor.RTM., are
particularly preferred.
[0015] Furthermore, it would be advantageous if the process
complexity of the existing method for manufacturing sandwich
structures could be improved by reducing the number of plant passes
and if the bath stability for preparing the metallic surface and/or
for adhesion-promotion could be increased and if the number of
treatment steps necessary for particular metallic surfaces could
also be reduced.
[0016] It has surprisingly been determined that with a special
conversion composition, a single-step and, in particular,
economical conversion coating can be carried out for all the
technically relevant metallic surfaces, which leads to a
sufficient, or even to an unexpectedly high level of adhesion of
the metal-plastics composite.
[0017] The object is achieved with a method for producing a
sandwich structure from at least one layer of metallic material and
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:
[0018] 0.5 to 20 g/l zinc, [0019] 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,
[0020] 0 or 0.01 to 5 g/l of the total as nickel and/or cobalt,
[0021] 0 or 0.01 to 5 g/l of the total as molybdenum, tantalum,
vanadium and/or tungsten, [0022] 2 to 100 g/l P.sub.2O.sub.5, which
corresponds to 2.68 to 133.8 g/l PO.sub.4, [0023] 0.1 to 10 g/l
polyacrylic acid, but not more than 25% of the content of the
composition of P.sub.2O.sub.5 in g/l, and [0024] 0 or 0.01 to 3 g/l
silane, but not more than 25% of the content of the composition of
P.sub.2O.sub.5 in g/l, in that the liquid film produced therewith
is dried on, in that the metallic layer coated in this manner is
cut, if required--in particular, into panels--and in that the thus
cut metallic layer 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.
[0025] Preferably, the organic polymer is a thermoplastic polymer
and/or a thermoplastic copolymer.
[0026] Before the coating of surfaces of the metallic layers, the
surfaces to be coated are typically cleaned and then rinsed with
water. If metallic layers are put into intermediate storage, they
are usually oiled. If oiled surfaces are to be treated or if the
plant is at least somewhat contaminated with oil, it is to be
recommended particularly to clean the surfaces with an alkaline
cleaner before the coating and then to rinse them with water in
order to remove adhering cleaning solution from the surface. A
surface that is not completely water-wettable can result in an
uneven no-rinse coating.
[0027] Before the application of the inventive aqueous conversion
composition, no activation is used, since it is desirable to
generate an extremely fine-grained and, at the same time, largely
or completely amorphous phosphate coating and as far as possible no
crystalline phosphate coating. The resulting conversion layer is
preferably completely X-ray amorphous or is X-ray amorphous with
slight crystalline fractions, which is unusual for a zinc phosphate
layer. It is important that the surface of the metallic layer is
wetted as completely and evenly as possible with the no rinse
conversion composition. On application with the aid of rollers as
coater rollers and/or as squeezing rollers, the condition of the
application roller is very important since it is intended to create
an even wet film preferably in the range from 0.5 to 10
ml/m.sup.2.
[0028] The inventive conversion coating method therefore takes
place without an activation step with a colloidal titanium
phosphate or with a surface conditioner on the basis of phosphate
particles, which is unusual for a typical zinc phosphating. This is
also a sign that the inventive conversion composition and its
coating method are no typical zinc phosphating.
[0029] Preferably, the aqueous conversion composition has a total
content of manganese, aluminum, chromium(III), iron(II), iron(III)
and/or magnesium in the region of 0.01 to 8 g/l, particularly
preferably in the range from 0.1 to 6 g/l, from 0.2 to 5 g/l, from
0.3 to 4 g/l, from 0.4 to 3 g/l, from 0.5 to 2 g/l or from 0.6 to 1
g/l.
[0030] Preferably, the aqueous conversion composition has the
following composition: [0031] 1 to 10 g/l zinc, [0032] 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, wherein the total of these elements/cations without
zinc preferably lies in the range from 0.01 to 8 g/l, [0033] 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, [0034] 0 or 0.01 to 5 g/l of the total of molybdenum and/or
vanadium, [0035] 8 to 60 g/l P.sub.2O.sub.5, which corresponds to
10.72 to 80.28 g/l PO.sub.4, [0036] 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 [0037] 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.
[0038] Particularly preferably, the aqueous conversion composition
has the following composition: [0039] 2 to 8 g/l zinc, [0040] 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, wherein the total of these
elements/cations without zinc preferably lies in the range from
0.01 to 8 g/l, [0041] 0 or 0.01 to 2 g/l nickel, [0042] 0 or 0.01
to 2 g/l cobalt, wherein the total of nickel and cobalt is not more
than 2.5 g/l, [0043] 0 or 0.01 to 5 g/l of the total of molybdenum
and/or vanadium, [0044] 9.5 to 50 g/l P.sub.2O.sub.5, which
corresponds to 12.73 to 66.9 g/l PO.sub.4, [0045] 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 [0046] 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.
[0047] Preferable herein is an initial aqueous conversion
composition in which the ratio by weight of zinc:PO.sub.4 lies in
the range from 0.02:1 to 0.6:1, from 0.05:1 to 0.5:1, from 0.08:1
to 0.4:1 or from 0.1:1 to 0.2:1 relative to the initial composition
before an uptake of steeped zinc which can become enriched in the
acidic solution over time.
[0048] Preferable herein is an aqueous conversion composition in
which the ratio by weight of zinc:PO.sub.4 lies in the range from
0.02:1 to 8:1, from 0.05:1 to 4:1, from 0.08:1 to 1.5:1 or from
0.1:1 to 0.8:1, related to the composition which has additionally
already taken up etched out zinc when used, for example, on
galvanized surfaces.
[0049] The ratio by weight of the aqueous conversion composition
and/or the coating produced therefrom of the total (Ni and Co):Zn
preferably lies in the range from 0.0001:1 to 1:1, from 0.002:1 to
0.7:1, from 0.01:1 to 0.4:1 or from 0.04:1 to 0.2:1. Depending on
the content of nickel and/or of cobalt, the corrosion-resistance of
the conversion coating created therewith can be influenced.
[0050] Preferably, the zinc content of the aqueous conversion
composition is 1.5 to 10 g/l, 2 to 8 g/l or 2.5 to 4.5 g/l.
Preferably, the manganese content of the aqueous conversion
composition is 0.5 to 6 or 1 to 5 g/l. Preferably, the nickel
content of the aqueous conversion composition is not more than 1.5
g/l, not more than 1 g/l, not more than 0.5 g/l or not more than
0.01 g/l. The Zn:Mn ratio by weight of the aqueous conversion
composition can vary within wide limits and preferably lies in the
range from 0.1:1 to 5:1 or from 0.8:1 to 3:1.
[0051] The aqueous conversion composition can possibly also contain
0.001 to 1 g/l NO.sub.2, 0.01 to 1 g/l NO.sub.3 and/or 0.001 to 2
g/l H.sub.2O.sub.2 as accelerant.
[0052] An addition of polyacrylic acid to the aqueous conversion
composition has proved to be useful since therewith significantly
better adhesion results are achieved, which had not previously
succeeded without polyacrylic acid. An addition of polyacrylic acid
provides the conversion coating with a greater adhesive strength,
which has a positive effect, in particular with materials on the
basis of polyethylene and/or polyamide. It is herein advisable to
add a water-soluble or water-dispersible polyacrylic acid to the
conversion composition. The polyacrylic acid preferably has a
molecular weight in the range from 5,000 to 120,000, from 30,000 to
90,000 or from 50,000 to 70,000. The conversion composition
preferably has a content of at least one water-soluble or
water-dispersible polyacrylic acid in the region of 0.2 to 8 g/l,
from 0.3 to 5 g/l or from 0.5 to 3 g/l. The addition of polyacrylic
acid has had positive effects with all the different metallic
surfaces, on the adhesion firstly to the metallic surface, and
secondly to the surface wetted with organic, particularly
thermoplastic, plastics. Preferably, the content of polyacrylic
acid and/or its reaction products in the dried-on and/or dried-on
and, during compaction, thermally loaded conversion coating is 0.05
to 15% by weight of the conversion coating.
[0053] If additionally at least one silane is added to the
conversion composition, the adhesion between adjacent layers of a
sandwich structure, measured here as the peel strength, can be
further improved by up to approximately 25%.
[0054] If the content in the aqueous conversion composition of
polyacrylic acid is successively increased and finally exceeds
approximately 25% of the P.sub.2O.sub.5 content in g/l, it can
arise that no further increase in the peel strength of the sandwich
structure than at lower content levels, or even a somewhat lower
peel strength, is achieved.
[0055] If the content of polyacrylic acid in the aqueous conversion
composition falls below approximately 2% of the P.sub.2O.sub.5
content in g/l, it can occur that a significant worsening in the
peel strength of the sandwich structure as compared with higher
levels of polyacrylic acid, results.
[0056] For the sake of simplicity, silane, silanol and siloxane are
often referred to below simply as silane. The reason is that
silane/silanol/siloxane if often also subject to a rapid sequence
of reactions, including in water, so that due to the changes and
due to the great effort for a suitable demonstration of the state,
a determination and a more precise specification are not
worthwhile.
[0057] As silanes, fundamentally many types are possible
individually or in combination with one another. They are
preferably put into a water-soluble or water-dissolved state.
Particularly preferably, they are partially or entirely
hydrolyzed.
[0058] Particularly preferable are conversion compositions with a
content of at least one aminosilane with at least one amino group
and of at least one aminosilane different therefrom with at least
two amino groups, at least one aminosilane, and at least one
epoxysilane with a content of at least one aminosilane and at least
one bis-silyl-silane with a content of at least one ureidosilane
and at least one bis-silyl-silane or with a content of at least one
epoxysilane and at least one bis-silyl-silane.
[0059] Particularly preferred are silanes with respectively at
least one amino, epoxy, glycidoxy, imino and/or ureido group.
Particularly preferred are mono-trialkoxysilanes,
bis-trialkoxysilanes, mono-silyl-silanes and/or bis-silyl-silanes,
wherein these particularly preferably have at least one amino,
epoxy, glycidoxy, imino and/or ureido group.
[0060] The conversion composition advantageously has a total
content of at least one silane in the range of 0.01 to 4, from 0.1
to 3, 0.3 to 2.5 or from 0.6 to 2 g/l.
[0061] If the content of silane(s) in g/l in the aqueous conversion
composition exceeds approximately 25% of the content of
P.sub.2O.sub.5 in g/l, it can occur that the adhesion worsens. If
the content of silane(s) in g/l in the aqueous conversion
composition falls below approximately 2% of the content of
P.sub.2O.sub.5 in g/l, it can occur that the adhesion worsens.
[0062] If the polyacrylic acid content in g/l in the aqueous
conversion composition exceeds approximately 25% of the of
P.sub.2O.sub.5 content in g/l, it can occur that the adhesion
worsens.
[0063] If the of polyacrylic acid content in g/l in the aqueous
conversion composition falls below approximately 2% of the
P.sub.2O.sub.5 content in g/l, it can occur that the adhesion
worsens.
[0064] Preferably, the content of at least one silane and/or
its/their reaction products in the dried-on and/or dried-on and,
during compaction, thermally loaded, conversion coating is 0.01 to
15% by weight of the conversion coating.
[0065] However, in some experiments, it has been found that the
polyacrylic acid content in the aqueous conversion composition
should preferably be not more than 25, not more than 20, not more
than 15 or not more than 10% of the P.sub.2O.sub.5 content in g/l
of the composition. Under some circumstances, no further
improvement of the peel strength can be achieved as compared with
compositions having less polyacrylic acid.
[0066] However, in some experiments, it has been found that the
content of at least one silane in the aqueous conversion
composition should preferably be not more than 25, not more than
20, not more than 15 or not more than 10% of the P.sub.2O.sub.5
content in g/l of the composition. Under some circumstances, no
further improvements of the peel strength can be achieved as
compared with compositions having less silane.
[0067] The aqueous conversion composition can preferably also
contain 0.001 to 20 g/l or 0.2 to 10 g/l of at least one further
water-soluble and/or water-dispersible organic polymer/copolymer
apart from polyacrylic acid.
[0068] If, furthermore, at least one further organic
polymer/copolymer is added to the aqueous conversion composition,
this is preferably selected from acid-resistant polymers and/or
copolymers, which are specifically stabilized, if relevant. These
include, in particular, acid-resistant polymers and/or copolymers
selected from those on the basis of poly(meth)acrylate,
polyacrylamide, polycarbonate, polyepoxide, polyester, polyether,
polyethylene, polystyrene, polyurethane, polyvinyl,
polyvinylpyrrolidone and modification(s) thereof, for example
cationic polyurethane resin, modified anionic
acrylate/polyacrylate, epoxy resin with amino groups and, if
relevant, also with phosphate groups and/or cationic copolymer on
the basis of polyester-polyurethane,
polyester-polyurethane-poly(meth)acrylate,
polycarbonate-polyurethane and/or
polycarbonate-polyurethane-poly(meth)acrylate.
[0069] It can herein be advantageous if the conversion composition
also has a content of at least one further organic
polymer/copolymer and at least one silane/silanol/siloxane. These
additives can contribute, for example, to increasing the adhesive
strength.
[0070] Preferably the aqueous conversion composition and, if
relevant, also the corresponding conversion coating has, in many
embodiments, no content of boron, chromium(VI), hafnium, titanium,
zirconium and/or niobium or no content of an intentionally added
compound of boron, chromium(VI), hafnium, titanium, zirconium,
niobium or of aluminum, boron, chromium(VI), hafnium, titanium,
zirconium, niobium, tantalum, vanadium and/or tungsten or no
content of an intentionally added compound of boron, chromium(VI),
hafnium, titanium, zirconium, niobium, tantalum and/or tungsten. In
particular, it is preferred that it has no content of a complex
fluoride, in particular of aluminum, boron, silicon, hafnium,
titanium and/or zirconium. In many variants, the inventive aqueous
conversion composition has no content of other organic polymers and
copolymers except from polyacrylic acid, a cross-linking agent, a
photoinitiator and/or a chromium(III) compound. Preferably, the
inventive conversion composition has no content of metallic and/or
inorganic particles, in particular such particles larger than 0.1
.mu.m.
[0071] In the conversion coating method, the pH value of the
conversion composition can lie in the range from 1 to 5, preferably
in the range from 2.2 to 4.5, particularly preferably in the range
from 2.8 to 4.
[0072] Particularly preferably, in the inventive method, as the
inorganic aqueous basic composition, one such is selected which
enables a "microphosphating" to be carried out with the aqueous
conversion composition. Microphosphating is herein referred to when
the layer weight of the conversion coating is less than or equal to
0.4 g/m.sup.2 or less than or equal to 0.3 g/m.sup.2. Therefore, in
the inventive method, a conversion coating with a layer weight of
up to 0.4 g/m.sup.2 is preferably formed. Herein, the zinc
phosphate is preferably present at least as partially X-ray
amorphous, since no typical zinc phosphating is carried out.
[0073] The inventive phosphate-rich conversion coating can be
largely or entirely amorphously configured in many embodiments, and
far finer than a typical finely crystalline zinc phosphate layer.
In the inventive conversion coating, neither particles nor the
finest hollow spaces can be discerned with the naked eye, so that
this coating makes a far more even and unified impression compared
with a typical "normal" zinc phosphate layer. This often succeeds
only if no activation and no surface conditioning has been used
before the conversion coating, if the wet film of the aqueous
conversion composition has been homogeneously formed on the surface
of the metallic layer and if the contact times with the aqueous
conversion composition until complete drying out were comparatively
short, in particular, shorter than 1 minute. The activation or
surface conditioning before a phosphate-rich conversion composition
serves to coat the surfaces to be coated with seed crystals for
forming phosphate crystals.
[0074] A typical zinc phosphating is introduced with an activation
or surface conditioning of the metallic surface and causes a longer
contact time of the zinc phosphate solution with the metallic
surface, specifically typically depending on the application type
by spraying and/or dipping and depending on the substrate type as a
band or as parts, of between 3 s and approximately 5 min. Herein,
typically bath temperatures in the range from 50 to 70.degree. C.
and substrate temperatures in the range from 15 to 40.degree. C.
are used. For typical zinc phosphating, squeezing is not used
except with band. For typical zinc phosphating, drying out is not
used, although rinsing is. Due to all these measures, the phosphate
layer of a typical zinc phosphating is unusually formed in crystals
of approximately 5 to 40 .mu.m. Their layer weight is herein
typically in the range from 1 to 25 g/m.sup.2.
[0075] In the inventive conversion coating method, it is preferred
to bring the inventive aqueous conversion composition into contact
with the metallic surface, in particular, of a band for 0.1 to 30 s
until water-free during drying-on, wherein the temperatures of the
metallic surface and of the band preferably lie in the region of 15
to 40.degree. C. Due to the omission of an activation or surface
conditioning and due to the shorter contact times and the possibly
also lower temperatures, the crystallization of the zinc phosphate
is largely or entirely suppressed so that it is predominantly or
entirely present amorphously and much finer than in a crystalline
zinc phosphate layer. These properties also characterize the
microphosphating.
[0076] Furthermore, it is preferred in many embodiments that the
liquid film applied is dried on without being rinsed therein or
thereafter with aqueous liquid. Alternatively, rinsing can be
performed with an aqueous solution, for example, of a salt and/or
another compound, for example, in order to improve the adhesion
still further.
[0077] In the inventive conversion coating method, the surfaces of
the metallic layer can preferably be coated at a peak-metal
temperature, PMT, in the range from 5 to 50.degree. C.,
particularly at 15 to 40.degree. C. The aqueous conversion
composition can have a temperature at the time point of the
application in the range from 15 to 50.degree. C. or from 20 to
40.degree. C., wherein a t temperatures of above 40.degree. C., it
must be noted whether precipitations possibly arise in the
conversion composition.
[0078] In the inventive conversion coating method, the contact
times until water-freedom when drying onto surfaces of the metallic
layer, particularly in the case of metallic band or metallic coil
are, in particular, 0.2 to 30 seconds. In the case of rolling
and/or spraying onto band, the time of contacting until
water-freedom can, under some circumstances, be reduced to less
than 1 second or to approximately 0.2 seconds. In particular, on a
conversion coated metallic band or coil, the drying can take place,
for example, in a heated air stream, by induction and/or by IR
and/or NIR heat radiation. The conversion coating of the metallic
layer takes place, above all, before the bringing together of this
layer with at least one polymer layer for compressing to a sandwich
structure.
[0079] The polymer layers can have thickness, for example, in the
range from 0.1 to 5 mm, from 0.2 to 4 mm, from 0.4 to 3 mm, from
0.6 to 2 mm, from 0.7 to 1.2 mm or of approximately 0.8 mm per
length. They preferably consist of compact plastics and not of
plastics foam.
[0080] For example, a plastics coil can be used as the polymer
layer. In moisture-sensitive plastics, this is possibly contained
vacuum-welded into film. This film is to be removed from the
polymer layer for compression. Many polypropylene-based plastics
have no moisture-sensitivity. Many types of polymer layer and also
the metallic layers are usually not to be further pre-treated. The
polymer layers and the metallic layers can often be compressed
after the bringing together and placing on one another in
advantageous manner without prior heating.
[0081] Two embodiments as to how lamination layers can be built up
and how they can function are described, by way of example, in WO
2009/043777 A2.
[0082] If a number of layers of metal and plastics are used for the
production of a sandwich structure, it is preferred that, firstly,
at least two, at least three or at least four metallic layers of
metal and/or metallic alloy and/or metallic layers with at least
one additional metal or alloy layer, for example, galvanized steel
and/or, secondly, at least two or at least three polymer layers
(=polymer layers), which can possibly also be coated on at least
one side and/or specially treated, for example, polarized by
flame-scorching, UV treatment, corona treatment or plasma
treatment, are used. Herein, it is particularly preferable that
each metallic layer alternates with a polymer layer.
[0083] Herein, for example, the following sequences of layers can
occur, wherein if two polymer layers adjoin one another, both
similar and different plastics or polymer layers can be used with
similar or different dimensions and/or properties independently of
one another: metal-plastics, metal-plastics-metal,
metal-plastics-plastics, metal-plastics-plastics-metal,
metal-plastics-plastics-plastics-metal,
metal-plastics-metal-plastics-plastics,
plastics-plastics-metal-plastics,
plastics-plastics-metal-plastics-plastics,
metal-plastics-plastics-metal-plastics,
metal-plastics-plastics-metal-plastics-plastics,
plastics-metal-plastics-plastics-metal-plastics,
plastics-metal-plastics-plastics-metal-plastics-plastics,
plastics-plastics-metal-plastics-plastics-metal-plastics-plastics,
metal-plastics-plastics-metal-plastics-metal or
metal-plastics-plastics-metal-plastics-plastics-metal.
[0084] Herein, more complex structures, structures with inlays
and/or structures without continuous layers and/or with hollow
spaces are also producible, wherein these peculiarities can each
relate to one or more metallic layers and/or respectively one or
more polymer layers. It is particularly preferred, however, that
the polymer layers and/or the metallic layers have no hollow spaces
and/or as far as possible no pores.
[0085] For the production of sandwich structures of one or more
metallic layers, for example, of metallic coil or sheet metal
sections and one or more polymer layers of organic, in particular
thermoplastic, polymer, for example, plastics coil or polymer
sections, gluing and/or compaction under pressure and/or
temperature are particularly suitable as joining methods.
[0086] Many types of organic polymers are suitable as polymer
layers, in particular also as polymer core layers between metallic
layers, wherein in particular, temperature-resistant and/or
mechanically loadable layers are preferred. Polymer layers of an
organic composite material (=compound) with proportions of
different plastics are herein preferred. In particular, layers of
thermoplastics, plastics with a proportion of thermoplastics and/or
fiber-reinforced thermoplastics can be used as layers of organic
polymer. If at least three polymer layers are used in contact with
one another, the at least one middle layer can alternatively also
consist of a plastics with a proportion of thermoplastics of less
than 50% by weight or even of thermosetting plastics, possibly
respectively also fiber-reinforced.
[0087] Plastics or thermoplastics that are suitable are, in
particular, those on the basis of polyamide, polyethylene and/or
polypropylene, which can possibly be fiber-reinforced, in
particular with aramide, glass, carbon and/or graphite fibers.
Preferably, the layer of organic polymer is a layer on the basis of
at least one thermoplastics and, in particular, on the basis of
plastics on the basis of polyamide, polyethylene and/or
polypropylene, which can possibly also be fiber-reinforced.
Particularly preferred are possibly fiber-reinforced thermoplastics
on the basis of polyamide, polyamide and polyethylene or polyamide
and polypropylene. In particular, polymer layers of a composite
material (compound) with a proportion of PA 6 and/or PE can be
used, which means a polyamide on the basis of .epsilon.-caprolactam
or .omega.-aminohexanoic acid and/or of polyethylene, which can
possibly also be fiber-reinforced. Particularly preferred is an
organic composite material of PA 6 with a proportion of PE, that
is, a polyamide on the basis of .epsilon.-caprolactam and/or
.omega.-aminohexanoic acid and of polyethylene.
[0088] These organic materials are particularly preferred since
they are temperature-resistant and/or mechanically loadable. These
composite materials can preferably contain additives, for example,
stabilizers, adhesion-promoters and/or compounds with adhesive
groups. These organic composite materials can preferably be made so
that the organic composite materials or layers of these organic
composite materials are preferably entirely pore-free and therefore
are not foam and/or are deep-drawing capable at a temperature of up
to approximately 100.degree. C. and/or are ductile at room
temperature or possibly up to 220.degree. C.
[0089] Herein, for large-scale manufacturing, it suggests itself to
use band as the metallic starting material, particularly as a coil
or as cut sheet, which is or has been coated in a coil coating
process and which is joined to at least one layer of a plastics
material.
[0090] Particularly preferred are metallic substrates as coil, band
and/or sheet, which often have a thickness of the layer in the
range, in particular, from 0.1 to 2 mm and, if required, can be
coated with a metallic protective layer and/or with at least one
protective layer, for example, on the basis of an adhesion
promoter, passivator or pre-treatment layer. A good compromise
between the weight and properties of the sandwich structure has
proved to be the use of a band/coil/sheet with a thickness in the
range from 0.05 to 1 or from 0.1 to 0.5 mm, preferably from 0.2 to
0.3 mm. Metallic coatings which are used in place of a metallic
layer or on a metallic layer can herein have a thickness in the
range from 1 to 80 .mu.m.
[0091] As metallic surfaces, in particular, those of aluminum,
iron, magnesium, titanium, zinc, tin and alloys thereof come into
question. As metallic substrates, in particular, those based on
aluminum, iron/steel/high-grade steel, magnesium, titanium, zinc,
tin and alloys thereof can be used. As the coating of a metallic
layer, for example metal such as e.g. zinc, an alloy containing
aluminum, magnesium and/or zinc, for example, a ZnMg alloy or a
chrome plating, in particular, on steel can be used.
[0092] As metallic bands, coils and/or sheets and in particular for
use as cover sheets, above all metallic layers can be used which
possibly can be coated with a metallic layer and/or with at least
one protective layer, for example, on the basis of an
adhesion-promoter, passivation or pre-treatment layer and which are
made of one of the following materials: electrolytically galvanized
steel sheet ZE, for example, electrolytically with a magnesium
and/or zinc-containing alloy, for example, steel sheet coated with
ZnNi, ZnCo, ZnMg, hot-dip galvanized steel sheet Z, by hot-dipping
in a molten aluminum-containing and/or zinc-containing alloy, for
example, a steel sheet coated with an Al, ZnAl, ZnMg and/or ZnAlMg
alloy, chrome-plated sheet, for example, chrome-plated steel sheet,
sheet metal made of aluminum, aluminum alloy, magnesium, magnesium
alloy and/or high-grade steel. If a metallic layer is coated, it
can be coated on one side or both sides. These coatings, depending
on the side, can be different or the same in their thickness and/or
characteristics and/or composition and can additionally have, for
example, at least one conversion layer and/or a passivation layer
on a metallic coating.
[0093] Layers of different materials can also be combined with one
another, for example, an upper layer of a high-grade steel sheet
with a lower layer of galvanized steel sheet or, for example, in a
combination of metal-plastics-metal-plastics-metal, on the outside,
high-grade steel sheets and as at least one middle layer, a
galvanized steel sheet and/or two different plastics types and/or
polymer layers with different properties.
[0094] The inventive method is particularly advantageous if at this
point in the method, following the bringing together and laying on
one another of at least one metallic layer with at least one
polymer layer for compression to a sandwich structure, only the
compression is still required. Preferably, panels or coils are used
as polymer layers and as metallic layers for compression, which
influences the type, design and size of the plant. If coils of
plastics and of metallic material are used, the compression can
preferably take place continuously and on compression of panels,
often discontinuously, for example, in a double band press.
Particularly in continuous methods, pre-heating of the individual
or combined layers can possibly be helpful. For a continuous
compression, preferably, a plant can be used in which the pressing
plates of the pressing tool remain static for the pressing time or,
if the transport speed is low, move along with the band plant.
[0095] The compression of the metallic layers and polymer layers
placed against one another preferably takes place at temperatures
of the pressing tool and particularly of the pressing plates in the
range from 100 to 260.degree. C., in particular from 120 to
240.degree. C. It is herein preferred that the temperature of the
pressing plates is kept as constant as possible. In a particularly
preferred method variant, during compression, the heated pressing
plates which are configured planar and arranged mutually parallel
can be pressed for a particular duration onto the planar structure
of the layers lying on one another, without the pressing plates
being lifted. The pressing duration is preferably 5 s to 20 min, 10
s to 8 min or 30 s to 8 min, wherein on compression of overall more
than two layers, a longer pressing duration and/or a slightly
raised temperature is/are rather used. During compression, a
sufficiently long action of the heat at or above the melting
temperature of at least one organic, in particular, thermoplastic
component of a compound or of the, in particular, thermoplastic
plastics of the polymer layer is to be ensured.
[0096] Preferably, the melt temperature of at least one component
of the compound or of the, in particular, thermoplastic plastics of
the polymer layer is reached or exceeded over at least 5 s and/or
up to 10 min. The melt temperature of at least one component of the
compound or of the plastics of the polymer layer often lies in the
range from 150 to 260.degree. C. or from 2 00 to 250.degree. C. The
plastics of the polymer layer herein melts at least partially,
attaches firmly to the conversion-coated surface of the metallic
layer and becomes adhesively connected thereto. The pressing
pressure during compression is preferably in the range from 0 to 10
bar or from 2 to 8 bar. In the inventive method, it is necessary
that the at least one metallic layer has a coating of the inventive
conversion coating on the surface that is to be joined to plastics,
said coating acting there as an adhesion promoter and as a
corrosion protection at the future cut edges. This is the case
because it has been found that the edge protection is generally
better if the adhesion of the inventive coating is increased.
[0097] If the pressing plates are lifted at the end of the
compression process, the sandwich structure can be cooled by
natural cooling and/or by forced cooling, for example, with cool
air. Until the beginning of the winding up of a laminated-together
coil or until the stapling of laminated-together panels, the
temperature should typically be below 90.degree. C.
[0098] When the metallic coils (bands) are coated with the
inventive conversion composition and dried they can be cut, if
necessary, into panels which can be compressed with the polymer
layers at a later time point, or the coils (bands) are continuously
compressed--in particular, in a laminating plant on passing through
with the polymer layer. It should herein be ensured that until the
joining with the polymer layer, the conversion coating is not
chemically or mechanically loaded, so as not to damage the
conversion coating therethrough. The inventive conversion coating
on the surface of the metallic layer which is preferably directly
joined to the polymer layer, provides the necessary adhesion for a
lasting bond between the solidified polymer layer and the metallic
layer.
[0099] In particular when such sandwich structures are further
coated as components or used as one of a plurality of components
and coated thereafter, a coating with respectively at least a
liquid paint, an electrocoat paint, for example, a cathodic KTL
electrocoating and/or a powder coating is fundamentally possible.
Coating with an electrocoat and/or a powder coating is particularly
advantageous herein since even hard-to-access and hidden sites can
be coated. Particularly preferred are polymer layers which can be
used as temperature-resistant polymer layers or as
temperature-resistant polymer core layers. Electrocoatings of this
type are often applied at temperatures in the range from 15 to
40.degree. C. and mostly at temperatures in the range from 25 to
30.degree. C. under the action of current. These electrocoatings
are subsequently baked in an oven, often at temperatures of
approximately 160 to 180.degree. C. Furthermore, within the most
varied of paint coatings, paints such as for example a finishing
paint, a filler, a clear lacquer or a powder coating are used which
can be baked at temperatures approximately in the range from 150 to
240.degree. C. Thus, the expression "temperature-resistant" for a
polymer layer of the present invention means that it withstands the
baking temperatures in the baking oven without any disadvantageous
influence on their properties. Therefore, overall, at least one
electrocoating, finishing paint, filler, clear lacquer and/or
powder coating can be applied onto at least one side of the
composite or laminate.
[0100] The inventive sandwich structure can, if required, be at
least once respectively coated, deformed, glued, compressed and/or
otherwise joined. From sandwich structures of this type, for
example, bodywork parts can be produced, for example, by cutting,
deforming, painting and/or joining, wherein the sequence of these
steps can be varied.
[0101] Unexpected Effects:
[0102] It was surprising that through the addition of polyacrylic
acid in the range from 1 to 3 g/l, significantly greater peel
strength values could be achieved than with the previously tested
and/or used conversion compositions.
[0103] It was also surprising that the conversion composition
generated a sufficient adhesion between the metallic surface and
the polymer layer on all such different metallic substrates such
as, for example, CRS, Z, ZE, ZnMg, ZnAlMg, high-grade steel and
Al.
[0104] It was further surprising that the conversion coating also
did not disrupt a subsequent cathodic electrocoating (KETL), even
on the side of the metal sheet not joined to a polymer layer.
[0105] It was advantageous that two successively performed
conversion coatings could be reduced to a single coating, such that
two to four process steps can be spared. Apart from this
simplification of the production process, a significant increase in
the peel strength could also be achieved.
[0106] The inventive production and the inventive sandwich
structures can be used in motor vehicle construction, aircraft
construction, space travel, apparatus construction, in building
construction, furniture production or as structural elements.
[0107] The inventive sandwich structures can be used, in
particular, as parts of motor vehicles, trailers, mobile homes or
aerodynamic vehicles, as parts of bodywork, as elements of doors,
rear hatches or engine hoods, as fenders, as crash barriers, for
electrotechnical equipment, for domestic appliances, external
claddings, facade elements, roof claddings, garage door elements,
fence elements, in interior fittings, as radiators, as lamps, for
furniture items or as furniture elements, for wardrobe elements or
shelving, as bands, as metal sheets, formed parts, coverings,
paneling, screens, frames, isolating elements, safety elements,
supports or as housings.
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.degree. 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.degree. C. for 20 to
30 s at a peak metal temperature PMT of 60.degree. 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 .epsilon.-caprolactam or
.omega.-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.degree. 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.
* * * * *