U.S. patent application number 12/857722 was filed with the patent office on 2011-02-17 for process for coating metallic surfaces with a silane-rich composition.
Invention is credited to Heribert DOMES, Julia SCHNEIDER.
Application Number | 20110039115 12/857722 |
Document ID | / |
Family ID | 32928840 |
Filed Date | 2011-02-17 |
United States Patent
Application |
20110039115 |
Kind Code |
A1 |
DOMES; Heribert ; et
al. |
February 17, 2011 |
PROCESS FOR COATING METALLIC SURFACES WITH A SILANE-RICH
COMPOSITION
Abstract
A method for coating a metallic surface with an aqueous
composition for pretreating before applying another coating or for
treating said metallic surface. In addition to water, the
composition contains a) at least one hydrolysable or at least
partially hydrolyzed silane; b) at least one metal chelate, if
necessary, also c) at least one organic film former, d) at least
one long-chain alcohol that serves as a film forming aid or e) at
least one inorganic compound in particle form.
Inventors: |
DOMES; Heribert;
(Wellmunster, DE) ; SCHNEIDER; Julia; (Hamburg,
DE) |
Correspondence
Address: |
FULBRIGHT & JAWORSKI, LLP
666 FIFTH AVE
NEW YORK
NY
10103-3198
US
|
Family ID: |
32928840 |
Appl. No.: |
12/857722 |
Filed: |
August 17, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10546583 |
Oct 1, 2005 |
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PCT/EP2004/001828 |
Feb 25, 2004 |
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12857722 |
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Current U.S.
Class: |
428/447 ;
427/386; 427/387; 427/508; 524/311; 524/320; 524/394 |
Current CPC
Class: |
C09D 133/02 20130101;
C09D 133/08 20130101; Y02T 50/6765 20180501; C08K 5/5435 20130101;
Y02T 50/60 20130101; Y02T 50/67 20130101; Y10T 428/31663 20150401;
C09D 175/06 20130101; C09D 4/00 20130101; C23C 22/60 20130101; C23C
2222/20 20130101; C09D 5/08 20130101; C23C 22/53 20130101; C08K
3/36 20130101; C23C 22/68 20130101; C23C 22/83 20130101; C23C 22/50
20130101; C23C 22/74 20130101; C23C 22/82 20130101; C09D 7/61
20180101; C08K 5/0091 20130101; C09D 7/63 20180101; C23C 22/48
20130101; C09D 4/00 20130101; C08G 77/04 20130101; C09D 4/00
20130101; C08G 77/26 20130101 |
Class at
Publication: |
428/447 ;
427/387; 427/386; 427/508; 524/394; 524/320; 524/311 |
International
Class: |
B32B 27/00 20060101
B32B027/00; B05D 3/02 20060101 B05D003/02; C08F 2/48 20060101
C08F002/48; C08K 5/09 20060101 C08K005/09; C08K 5/10 20060101
C08K005/10 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 25, 2003 |
DE |
103 08 237.9 |
Jul 17, 2003 |
DE |
103 32 744.4 |
Claims
1-43. (canceled)
44. A process for coating a metallic surface with an aqueous
composition, which can be largely or completely free from chromium
(VI) compounds, for pretreatment before a further coating or for
treatment, wherein the metallic surface is at least one of clean,
pickled, cleaned or pretreated, comprising contacting said metallic
surface with the aqueous composition and forming a film on the
metallic surface; and drying and optionally curing the film;
wherein the dried and optionally cured film has a layer thickness
in the range from 0.01 to 10 .mu.m wherein the aqueous composition
comprises water and a) at least one of a hydrolyzable or at least
partly hydrolyzed silane; b) at least one alkali metal lactate; c)
at least one organic film-forming agent which contains at least one
of a water-soluble or water-dispersed organic polymer or copolymer
with an acid number in the range from 3 to 250, wherein the content
of organic film-forming agent, based on the solids content, is from
10 to 45 wt. %; and d) optionally at least one long-chain alcohol
as a film-forming auxiliary; wherein the aqueous composition is
free of Ti/Zr hexafluoride.
45. A process for coating a metallic surface with an aqueous
composition, which can be largely or completely free from chromium
(VI) compounds, for pretreatment before a further coating or for
treatment, wherein the metallic surface is at least one of clean,
pickled, cleaned or pretreated, comprising contacting said metallic
surface with the aqueous composition and forming a film on the
metallic surface; and drying and optionally curing the film;
wherein the dried and optionally cured film has a layer thickness
in the range from 0.01 to 10 .mu.m wherein the aqueous composition
comprises water and a) at least one of a hydrolyzable or at least
partly hydrolyzed silane; b) at least one chelate selected from the
group consisting of alkali metal lactate, ammonium lactate, a
citrate, a dialkyl citrate and a dialkylester citrate; c) at least
one organic film-forming agent which contains at least one of a
water-soluble or water-dispersed organic polymer or copolymer with
an acid number in the range from 3 to 250, wherein the content of
organic film-forming agent, based on the solids content, is from 10
to 45 wt. %; and d) optionally at least one long-chain alcohol as a
film-forming auxiliary; wherein the aqueous composition is free of
Ti/Zr hexafluoride.
46. The process according to claim 45, wherein the aqueous
composition further comprises at least one component e) selected
from the group consisting of e.sub.1) at least one inorganic
compound in particle form with an average particle diameter,
measured on a scanning electron microscope, in the range from 0.005
to 0.3 .mu.m diameter, e2) at least one lubricant, e3) at least one
organic corrosion inhibitor, e4) at least one anticorrosion
pigment, e5) at least one agent for neutralization or/and for
steric stabilization of the synthetic resins, e6) at least one
organic solvent, e7) at least one siloxane and e8) at least one
chromium (VI) compound.
47. The process according claim 45, wherein the organic
film-forming agent is a synthetic resin mixture of at least one
polymer, at least one copolymer which comprises a content of
synthetic resin based on acrylate, epoxide, ethylene,
urea-formaldehyde, phenol, polyester, polyurethane, styrene,
styrene-butadiene or vinyl.
48. The process claim 45, wherein the organic film-forming agent
comprises a synthetic resin having a content of an organic polymer,
a copolymer or mixtures thereof based on at least one of
polyethyleneimine, polyvinyl alcohol, polyvinylphenol,
polyvinylpyrrolidone or polyaspartic acid.
49. The process claim 45, wherein the organic film-forming agent
contains a content of at least one copolymer with an acid number in
the range from 3 to 80, to the extent of at least 50 wt. % of the
synthetic resins added.
50. The process claim 45, wherein the organic film-forming agent
contains at least one component based on at least one of
acrylic-polyester-polyurethane copolymer,
acrylic-polyester-polyurethane-styrene copolymer, acrylic acid
ester, acrylic acid ester-methacrylic acid ester, optionally with
free acids or/and acrylonitrile, ethylene-acrylic mixture,
ethylene-acrylic copolymer, ethylene-acrylic-polyester copolymer,
ethylene-acrylic-polyurethane copolymer,
ethylene-acrylic-polyester-polyurethane copolymer,
ethylene-acrylic-polyester-polyurethane-styrene copolymer,
ethylene-acrylic-styrene copolymer, polyester resins with free
carboxyl groups combined with melamine-formaldehyde resins, a
synthetic resin mixture or a copolymer based on acrylate and
styrene, a synthetic resin mixture or a copolymer based on
styrene-butadiene, a synthetic resin mixture or a copolymer of
acrylate and epoxide, based on an acrylic-modified polyester
containing carboxyl groups together with melamine-formaldehyde and
ethylene-acrylic copolymer, polycarbonate-polyurethane,
polyester-polyurethane, styrene, styrene-vinyl acetate, vinyl
acetate, vinyl ester or vinyl ether.
51. The process claim 45, wherein at least 30 wt. % of the organic
film-forming agent added comprises film-formable thermoplastic
resins.
52. The process claim 45, wherein the molecular weights of
synthetic resins in the aqueous composition added are in the range
of at least 1,000 u.
53. The process claim 45, wherein the organic film-forming agents
added comprise at least 40 wt. % of high molecular-weight
polymers.
54. The process claim 45, wherein the organic film-forming agents
comprise synthetic resins, wherein acid groups of synthetic resins
are stabilized with ammonia, an amine or an alkali metal
compound.
55. The process claim 45, wherein the aqueous composition contains
0.1 to 980 g/l of the organic film-forming agent.
56. The process claim 45, wherein the aqueous composition contains
an acyloxysilane, an alkoxysilane, a silane with at least one amino
group, a silane with a succinic acid group or a succinic acid
anhydride group, a bis-silyl-silane, a silane with at least one
epoxide group, a (meth)acrylato-silane, a multi-silyl-silane, an
ureidosilane, a vinylsilane, a silanol or a siloxane having a
composition which corresponds thereto.
57. The process claim 45, wherein the aqueous composition contains
at least one silane selected from the group consisting of
glycidoxyalkyltrialkoxysilane, methacryloxyalkyltrialkoxysilane,
(trialkoxysilyl)alkyl-succinic acid-silane,
aminoalkylaminoalkylalkyldialkoxysilane,
(epoxycycloalkyl)alkyltrialkoxysilane,
bis-(trialkoxysilylalkyl)amine, bis-(trialkoxysilypethane,
(epoxyalkyl)trialkoxysilane, aminoalkyltrialkoxysilane,
ureidoalkyltrialkoxysilane, N-(trialkoxysilylalkyl)alkylenediamine,
N-(aminoalkyl)aminoalkyltrialkoxysilane,
N-(trialkoxysilylalkyl)dialkylenetriamine,
poly(aminoalkyl)alkyldialkoxysilane, tris(trialkoxysilyl)alkyl
isocyanurate, ureidoalkyltrialkoxysilane and acetoxysilane.
58. The process claim 45, wherein the aqueous composition contains
at least one silane selected from the group consisting of
3-glycidoxypropyltriethoxysilane,
3-glycidoxypropyltrimethoxysilane,
3-methacryloxypropyltriethoxysilane,
3-methacryloxypropyltrimethoxysilane,
3-(triethoxysilyl)propyl-succinic acid-silane,
aminoethylaminopropylmethyldiethoxysilane
aminoethylaminopropylmethyldimethoxysilane,
beta-(3,4-epoxycyclohexyl)ethyltriethoxysilane,
beta-(3,4-epoxycyclohexyl)ethyltrimethoxysilane,
beta-(3,4-epoxycyclohexyl)methyltriethoxysilane,
beta-(3,4-epoxycyclohexyl)methyltrimethoxysilane,
gamma-(3,4-epoxycyclohexyl)propyltriethoxysilane,
gamma-(3,4-epoxycyclohexyl)propyltrimethoxysilane,
bis(triethoxysilylpropyl)amine, bis(trimethoxysilylpropyl)amine,
(3,4-epoxybutyl)triethoxysilane, (3,4-epoxybutyl)trimethoxysilane,
gamma-aminopropyltriethoxysilane,
gamma-aminopropyltrimethoxysilane,
gamma-ureidopropyltrialkoxysilane,
N-(3-(trimethoxysilyl)propyl)ethylenediamine,
N-beta-(aminoethyl)-gamma-aminopropyltriethoxy-silane,
N-beta-(aminoethyl)-gamma-aminopropyltrimethoxysilane,
N-(gamma-triethoxysilylpropyl)diethylenetriamine,
N-(gamma-trimethoxysilylpropyl)diethylene-triamine,
N-(gamma-triethoxysilylpropyl)dimethylene-triamine,
N-(gamma-trimethoxysilylpropyl)dimethylene-triamine,
poly(aminoalkyl)ethyldialkoxysilane,
poly(aminoalkyl)methyldialkoxysilane,
tris(3-(triethoxysilyl)propyl)isocyanurate
tris(3-(trimethoxysilyl)propyl)isocyanurate and
vinyltriacetoxysilane.
59. The process claim 45, wherein the content of the at least one
silane in the aqueous composition, including the reaction products
formed therefrom, is from 0.1 to 50 g/l.
60. The process claim 45, wherein the at least one metal chelate is
selected from chelate complexes based on acetylacetonates,
acetoacetates, acetonates, alkylenediamines, amines, lactates,
carboxylic acids, citrates or glycols, the content of the at least
one chelate in the aqueous composition, and any reaction products
formed therefrom.
61. The process claim 45, wherein the at least one metal chelate is
analkali metal lactate.
62. The process claim 45, wherein a finely divided powder, a
dispersion or a suspension is added as inorganic compound in
particle form.
63. The process claim 45, wherein the inorganic compound in
particle form comprising at least one compound of aluminum, barium,
cerium, calcium, lanthanum, silicon, titanium, yttrium, zinc or
zirconium.
64. The process claim 45, wherein particles based on at least one
of aluminum oxide, barium sulfate, cerium dioxide, silicon dioxide,
silicate, titanium oxide, yttrium oxide, zinc oxide or zirconium
oxide are added to the aqueous composition as an inorganic compound
in particle form.
65. The process claim 45, wherein the aqueous composition contains
0.1 to 500 g/l of the at least one inorganic compound in particle
form.
66. The process claim 45, wherein the aqueous composition contains
at least one organic corrosion inhibitor based on an amine, a
TPA-amine complex, an alkylaminoethanol, a zinc salt of
aminocarboxylate, a zinc salt of 5-nitro-isophthalic acid, a zinc
salt of cyanic acid, a polymeric amino salt with fatty acid, a
metal salt of a sulfonic acid, at least one amino and transition
metal complex of toluenepropionic acid,
2-mercapto-benzothiazolyl-succinic acid or an ammonium salt thereof
a conductive polymer, or a thiol, wherein the content of organic
corrosion inhibitor in the aqueous composition is in the range from
0.01 to 5 wt. %.
67. The process claim 45, wherein the aqueous composition contains
at least one basic crosslinking agent based on at least one of
titanium, hafnium or zirconium as a cation, a carbonate or ammonium
carbonate as an anion, and wherein the content of such crosslinking
agents in the aqueous composition is in the range of from 0.01 to 3
wt. %.
68. The process claim 45, wherein no inorganic acids or organic
carboxylic acids are added to the aqueous composition.
69. The process claim 45, wherein the film forming auxiliary is at
least one long-chain alcohol selected from the group consisting of
a diol, a butyl glycol a butyl diglycol, an esteralcohol, an
ethylene glycol, an ethylene glycol ether a glycol ether, a
polyether a polyethylene glycol, a polyethylene glycol ether, a
polyglycol, a polypropylene glycol, a propylene glycol, a propylene
glycol ether, a polypropylene glycol ether, a glycol ether,
trimethylpentanediol diisobutyrate or a derivative thereof, wherein
the content of long-chain alcohol in the aqueous composition is in
the range from 0.01 to 10 wt. %.
70. The process claim 45, wherein at least one wax selected from
the group consisting of paraffins, polyethylenes and
polypropylenes, is present as the lubricant, wherein the content of
waxes in the aqueous composition is in the range from 0.01 to 5 wt.
%.
71. The process claim 45, wherein the aqueous composition comprises
a lubricant, said lubricant comprising wax together with a polymer
mixture or a copolymer, said polymer or copolymer comprising
ethylene and acrylic acid as the lubricant.
72. The process claim 45, wherein the film is cured partly by
drying and film formation and partly by actinic radiation, cationic
polymerization or/and thermal crosslinking.
73. The process claim 45, wherein the aqueous composition contains
at least one additive selected from the group consisting a biocide,
a defoamer or a wetting agent.
74. The process claim 45, wherein the aqueous composition is
applied to the metallic surface at a temperature in the range from
5 to 50.degree. C.
75. The process claim 45, wherein the metallic surface is kept at
temperatures in the range from 5 to 60.degree. C. during
application of the film coating.
76. The process claim 45, wherein the coated metallic surface is
dried at a temperature in the range from 20 to 400.degree. C.
77. The process claim 45, wherein coated surface is on a strip is
wound up to a coil, optionally after cooling to a temperature in
the range from 40 to 70.degree. C.
78. The process claim 45, wherein the aqueous composition is
applied by rolling on, flooding, knife-coating on, spraying,
misting, brushing or dipping and optionally by subsequent squeezing
off with a roller.
79. The process claim 45, wherein the dried and optionally also
cured film has a pendulum hardness of 30 to 190 s, measured with a
Konig pendulum hardness tester in accordance with DIN 53157.
80. The process claim 45, wherein the dried and optionally also
cured film has a flexibility such that on bending over a conical
mandrel in a mandrel flex test substantially in accordance with DIN
ISO 6860 for a mandrel of 3.2 mm to 38 mm but without tearing the
test area longer than 2 mm that are detectable on subsequent
wetting with copper sulfate by a change in color due to deposition
of copper on the torn-open metallic surface are formed.
81. The process claim 45, wherein at least one coating of printing
ink, foil, lacquer, lacquer-like material, powder coating, adhesive
or/and adhesive carrier is applied to the dried and optionally also
cured film.
82. The process claim 45, wherein metal surface is on metal
components, strips or strip sections, and wherein the resultant
coated metal components, strips or strip sections are shaped,
lacquered, coated with a polymer printed, glued, hot-soldered,
welded or joined to one another or to other elements by clinching
or other joining techniques.
83. An aqueous composition for pretreatment of a metallic surface
before a further coating or for treatment of that surface, wherein
the composition comprises water and a) at least one hydrolyzable or
at least partly hydrolyzed silane, b) at least one chelate selected
from the group consisting of alkali metal lactate, ammonium
lactate, a citrate, a dialkyl citrate and a dialkylester citrate;
c) at least one organic film-forming agent which contains at least
one water-soluble or water dispersed organic polymer or copolymer
with an acid number in the range from 3 to 250, the content of
organic film-forming agent, based on the solids content, being 10
to 45 wt. %, and d) optionally at least one long-chain alcohol as a
film-forming auxiliary, wherein the amounts ratio of a) to b), in
each case including the reaction products formed therefrom, is in
the range from 0.1:1 to 10:1; wherein the aqueous composition is
free of Ti/Zr hexafluoride.
84. The aqueous composition according to claim 45, wherein the
composition also contains at least one inorganic compound in
particle form.
85. A substrate coated by the process according to claim 45,
wherein the substrate is a wire, strip, sheet metal or a component
for a wire coil, a wire braid, a steel strip, a metal sheet, a
lining, a screen, a vehicle body or a component of a vehicle body,
a component of a vehicle, trailer, mobile home or missile, a cover,
a housing, a lamp, a light, a traffic light element, a piece of
furniture or furniture element, an element of a domestic appliance,
a frame, a profile, a shaped component of complicated geometry, a
crash barrier, heater or fence element, a bumper, a component of or
with at least one tube or a profile, a window, door or bicycle
frame or an item of hardware or a spectacle frame.
86. The process of claim 45, wherein the organic film-forming agent
contains at least two component based on at least one of
acrylic-polyester-polyurethane copolymer,
acrylic-polyester-polyurethane-styrene copolymer, acrylic acid
ester, acrylic acid ester-methacrylic acid ester, optionally with
free acids or/and acrylonitrile, ethylene-acrylic mixture,
ethylene-acrylic copolymer, ethylene-acrylic-polyester copolymer,
ethylene-acrylic-polyurethane copolymer,
ethylene-acrylic-polyester-polyurethane copolymer,
ethylene-acrylic-polyester-polyurethane-styrene copolymer,
ethylene-acrylic-styrene copolymer, polyester resins with free
carboxyl groups combined with melamine-formaldehyde resins, at
least one of a synthetic resin mixture or copolymer based on
acrylate and styrene, at least one of a synthetic resin mixture or
copolymer based on styrene-butadiene, at least one of a synthetic
resin mixture or copolymer of acrylate and epoxide, based on an
acrylic-modified polyester containing carboxyl groups together with
melamine-formaldehyde and ethylene-acrylic copolymer,
polycarbonate-polyurethane, polyester-polyurethane, styrene,
styrene-vinyl acetate, vinyl acetate, vinyl ester or vinyl
ether.
87. The process of claim 45, wherein the organic film-forming
agents comprise synthetic resins.
88. A process for coating a metallic surface with an aqueous
composition, which can be largely or completely free from chromium
(VI) compounds, for pretreatment before a further coating or for
treatment, wherein the metallic surface is at least one of clean,
pickled, cleaned or pretreated, comprising contacting said metallic
surface with the aqueous composition and forming a film on the
metallic surface; and drying the film; wherein the dried film has a
layer thickness in the range from 0.01 to 10 .mu.m wherein the
aqueous composition comprises water and a) at least one of an
hydrolyzable or at least partly hydrolyzed silane; b) at least one
chelate selected from the group consisting of alkali metal lactate,
ammonium lactate, a citrate, a dialkyl citrate and a dialkylester
citrate; c) at least one organic film-forming agent having an acid
number in the range from 3 to 250, wherein the organic film-forming
agent, based on the solids content, is present in an amount of from
10 to 45 wt. % and is water soluble or water dispersible; and d) at
least one long-chain alcohol as a film-forming auxiliary; wherein
the aqueous composition is free of Ti/Zr hexafluoride.
89. The process of claim 87, wherein the aqueous composition
further comprises at least one component selected from the group
consisting of an inorganic compound in particle form with an
average particle diameter measured on a scanning electron
microscope in the range from 0.005 to 0.3 .mu.m diameter, a
lubricant, an organic corrosion inhibitor, an anticorrosion
pigment, and an organic solvent.
90. The process of claim 45, wherein the inorganic compound in
particle form comprising at least one compound of aluminum, barium,
cerium, calcium, lanthanum, silicon, yttrium, or zinc.
91. The process of claim 45, wherein particles based on at least
one of aluminum oxide, barium sulfate, cerium dioxide, silicon
dioxide, silicate, yttrium oxide, or zinc oxide are added to the
aqueous composition as an inorganic compound in particle form.
92. The process of claim 87, wherein the inorganic compound in
particle form comprising at least one compound of aluminum, barium,
cerium, calcium, lanthanum, silicon, yttrium, or zinc.
93. The process of claim 87, wherein particles based on at least
one of aluminum oxide, barium sulfate, cerium dioxide, silicon
dioxide, silicate, yttrium oxide, or zinc oxide are added to the
aqueous composition as an inorganic compound in particle form.
94. An aqueous composition for pretreatment of a metallic surface
before a further coating or for treatment of that surface, wherein
the composition has a solids content and comprises water and a) at
least one hydrolyzable or at least partly hydrolyzed silane, b) at
least one chelate selected from the group consisting of alkali
metal lactate, ammonium lactate, a citrate, a dialkyl citrate and a
dialkylester citrate; c) at least one water-soluble or water
dispersed organic polymer or copolymer with an acid number in the
range from 3 to 250, the content of organic film-forming agent,
based on the solids content, being 10 to 45 wt. %, and wherein the
ratio of a) to b) including the reaction products formed therefrom,
ranges from 0.1:1 to 10:1; wherein the aqueous composition is free
of Ti/Zr hexafluoride.
95. The process of claim 45, wherein the pH of the aqueous
composition is 6 to 10.5.
96. The aqueous composition according to claim 83, wherein the pH
of the aqueous composition is 6 to 10.5.
97. The aqueous composition according to claim 93, wherein the pH
of the aqueous composition is 6 to 10.5.
98. The process of claim 45, wherein the ratio of silane content to
chelate content is 0.2:1 to 5:1.
99. The aqueous composition of claim 83, wherein the ratio of
silane content to chelate content is 0.2:1 to 5:1.
100. The aqueous composition of claim 93, wherein the ratio of
silane content to chelate content is 0.2:1 to 5:1.
101. The process of claim 94, wherein the ratio of silane content
to chelate content is 0.2:1 to 5:1.
102. The aqueous composition of claim 96, wherein the ratio of
silane content to chelate content is 0.2:1 to 5:1.
103. The aqueous composition of claim 97, wherein the ratio of
silane content to chelate content is 0.2:1 to 5:1.
Description
[0001] This application is a continuation application of U.S. Ser.
No. 10/546,583 filed Oct. 1, 2005, which is a .sctn.371 of
PCT/EP2004/001828 filed Feb. 25, 2004, and claims priority from
German Patent Application 103 08 237.9 filed Feb. 25, 2003 and
German Patent Application 103 32 744.4 filed Jul. 17, 2003.
[0002] The invention relates to a process for coating metallic
surfaces with an aqueous composition containing silane and metal
chelate and optionally organic film-forming agent. The invention
furthermore relates to corresponding aqueous compositions and to
the use of the substrates coated by the process according to the
invention.
[0003] The processes most frequently employed hitherto on metals,
in particular metal strip, for surface treatment or pretreatment
before lacquering are based on the use of chromium(III) or/and
chromium(VI) compounds together with various additives. Because of
the toxicological and ecological risks which such processes
involve, and moreover because of the foreseeable legal restrictions
in respect of the use of chromate-containing processes,
alternatives to these processes have already been sought for a
relatively long time in all fields of metal surface treatment.
[0004] The use of silanes in aqueous compositions for the
preparation of siloxane-rich corrosion protection coatings is known
in principle. These coatings have proved themselves, but the
processes for coating with an aqueous composition containing
predominantly silane are in some cases difficult to use. This
coating is not always formed with optimal properties. Furthermore,
there may be problems in being able to characterize adequately the
very thin transparent silane coatings on the metal substrate and
defects thereof with the naked eye or with optical aids. The
corrosion protection and the lacquer adhesion of the siloxane-rich
coatings formed are very often, but not always, high and in some
cases not sufficiently high for particular uses even with suitable
application.
[0005] In designing silane-containing aqueous compositions, a small
or large added amount of at least one component chosen from the
group consisting of monomers, oligomers and polymers has moreover
proved appropriate. In such compositions the nature and amount of
the silane addition is sometimes of decisive importance for
success. However, the added amounts of silane for this purpose are
conventionally comparatively low--usually only up to 5 wt. %--and
then act as a "coupling agent", where the adhesion-promoting
action, in particular between the metallic substrate and lacquer
and optionally between the pigment and organic lacquer
constituents, should prevail, but in some cases also a low
crosslinking action may occur to a minor extent. Silane additions
are predominantly added to thermosetting resin systems.
[0006] Resin mixtures in which resins are blended with inorganic
acids in order also to achieve in this manner a pickling attack and
therefore a better contact of the resin layer directly with the
metallic surface are moreover also known. These compositions have
the disadvantage that because of the pickling attack during the
contact between the treatment liquid (dispersion) and the
substrate, contamination occurs. This leads to concentration of
metals in the treatment liquid and as a result to a permanent
change in the chemical composition of the treatment liquid, as a
result of which the corrosion protection is significantly impaired.
By the pickling attack, these metals are dissolved out of the
metallic surface of the substrates to be treated.
[0007] Another disadvantage is that the surfaces can discolour to a
dark colour, under certain circumstances to dark grey to
anthracite-coloured, specifically in the case of aluminium or
aluminium-containing alloys. The dark-discoloured metal surfaces
cannot be employed for decorative uses since the discoloration
itself is undesirable for aesthetic reasons. The dark coloration is
visible with varying intensity, depending on the thickness of the
layer applied. This effect, called darkening, should as far as
possible be avoided.
[0008] DE-A-198 14 605 describes a sealing composition for metallic
surfaces which contains, in addition to at least one solvent, at
least one silane derivative and colloidal silica or/and colloidal
silicate. In the examples, the content of silane(s) is 20 wt. %
(about 200 g/l) and that of silica sol or silicate in the range
from 10 to 40 wt. %. A suggested addition of wax to reduce the
coefficient of friction or of organic binder as a wetting agent,
such as e.g. polypropylene, polyethylene, polyethylene oxide or
modified polysiloxane, or for other reasons not mentioned with
binders not mentioned in more detail, was not employed in the
examples. The examples mention no polymeric substances beyond the
silanes.
[0009] The doctrine of DE-A1-41 38 218 is a solution containing
organofunctional polysiloxane and titanic acid esters and/or
titanium chelate for use as an after-dipping agent for chromated or
passivated zinc-containing layers on steel components.
[0010] U.S. Pat. No. 5,053,081 relates to a process for coating a
metallic surface, which has already been pretreated e.g. with a
phosphate layer, with an after-rinsing solution based on a content
of 3-aminopropyltriethoxysilane and, in comparison with this, a
significantly lower content of titanium chelate prepared with
tetraalkyl titanate, beta-diketone and alkanolamine.
[0011] DE-A1-101 49 148 describes aqueous coating compositions
based on organic film-forming agent, fine inorganic particles and
lubricant or/and organic corrosion inhibitor, which, in spite of
the absence of chromium compounds, produced outstanding results of
corrosion resistance, adhesive strength and shapability, inter alia
on GALVAMUME.RTM. (55% Aluminum-Zinc alloy coating sheet and strips
steel sheets, but nevertheless still showed an inadequate corrosion
resistance of an organic film of about 1 .mu.m layer thickness on
hot-galvanized, electrolytically galvanized, GALVALUME.RTM.-coated
or GALVAN.RTM. (alloy coating containing 95% zinc, 5% aluminium and
specific quantities of rare earth metals products) metallic strips,
that is to say on metallic surfaces which are difficult to protect
against corrosion. The compositions, their constituents and the
properties of the raw materials and coatings of this publication
are expressly included in this Application.
[0012] The object of the invention is to overcome the disadvantages
of the prior art, and in particular to propose a process for
coating metallic surfaces which is suitable both for coating the
surfaces of metallic bodies, e.g. by dipping or spraying, and for
high coating speeds such as are used for metallic strips, which can
be used largely or completely without chromium(VI) compounds and
which as far as possible can be employed easily. The object is in
particular to increase the corrosion resistance of chromate-free
organic coatings of less than 10 .mu.m, and in particular of less
than 3 .mu.m dry film thickness.
[0013] It has been found, surprisingly, that the addition of at
least one chelate, in particular a titanium and/or zirconium
chelate, to a silane-containing aqueous composition significantly
improves the corrosion resistance and also the lacquer adhesion of
the film formed therefrom. The addition of an organic corrosion
inhibitor can usually also be omitted here--except in the case of
coating of bright steel.
[0014] It has furthermore been found, surprisingly, that it was
possible also to improve the corrosion resistance of the film
formed from the aqueous composition containing at least one silane
but no organic polymer very significantly if at least one chelate,
in particular a titanium or/and zirconium chelate, is also
added.
[0015] The object is achieved with a process for coating a metallic
surface, in particular of aluminium, iron, copper, magnesium,
nickel, titanium, tin, zinc or alloys containing aluminium, iron,
copper, magnesium, nickel, titanium, tin or/and zinc, with an
aqueous composition, which can be largely or completely free from
chromium(VI) compounds, for pretreatment before a further coating
or for treatment in which the body to be coated
optionally--especially a strip, a strip section or a component--is
shaped after the coating, which is characterized in that the
composition contains, in addition to water, [0016] a) at least one
hydrolysable and/or at least partly hydrolysed silane and [0017] b)
at least one metal chelate, wherein the clean, pickled, cleaned
or/and pretreated metallic surface is brought into contact with the
aqueous composition and a film is formed on the metallic surface,
which is then dried and optionally is additionally cured, wherein
the dried and optionally also cured film has a layer thickness in
the range from 0.01 to 10 .mu.m, determined by detachment of a
defined area of the cured film and weighing or by determination of
the silicon content of the coating e.g. with x-ray fluorescence
analysis and corresponding conversion.
[0018] The object is moreover achieved with an aqueous composition
for pretreatment of a metallic surface before a further coating or
for treatment of that surface, which is characterized in that the
composition contains, in addition to water, [0019] a) at least one
hydrolysable or/and at least partly hydrolysed silane and [0020] b)
at least one metal chelate, wherein the amounts ratio of a) to b),
in each case including the reaction products formed therefrom, is
preferably in the range from 0.1:1 to 10:1.
[0021] The amounts ratio of a) to b), in each case including the
reaction products formed therefrom, is preferably in the range from
0.1:1 to 10:1, particularly preferably in the amounts ratio of
0.2:1 to 8:1, very particularly preferably in the amounts ratio of
0.3:1 to 7:1, in particular about 0.4:1, 0.6:1, 0.8:1, 1:1, 1.2:1,
1.6:1, 2:1, 3:1, 4:1, 5:1 or 6:1.
[0022] In each case amounts of silane(s) and chelate(s), in each
case including the reaction products formed therefrom,
independently of one another of 0.05 to 5 wt. %, based on the wet
film, are particularly preferred, very particularly preferably in
each case independently of one another amounts of 0.08 to 4 wt. %,
in particular about in each case independently of one another
amounts of 0.1, 0.2, 0.3, 0.5, 0.8, 1, 1.5, 2, 2.5, 3 or 3.5 wt.
%.
[0023] In each case amounts of silane(s) and chelate(s), in each
case including the reaction products formed therefrom,
independently of one another of 0.2 to 15 wt. %, based on the
solids content, are particularly preferred, very particularly
preferably in each case independently of one another amounts of 0.3
to 11 wt. %, in particular about in each case independently of one
another amounts of 0.5, 0.8, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5,
5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10 or 10.5 wt. %.
[0024] Preferably, at least one silane is chosen which is
compatible with water, i.e. that the at least one silane and, where
appropriate, its hydrolysis and condensation products are miscible
with the components of the aqueous composition without problems and
are stable for several weeks, and that it allows formation of a
defect-free wet film and dry film which, in particular, is closed,
uniform and free from craters. In particular, at least one silane
is chosen which renders possible a high corrosion resistance, in
particular in combination with the at least one chelate chosen.
[0025] Preferably, at least one chelate is chosen that is stable
for a duration of several weeks in aqueous dispersions in the
presence of the other components of the aqueous composition and
which renders possible a high corrosion resistance. It is
furthermore advantageous if both the at least one silane and the at
least one chelate on the one hand can bond chemically to the
intended metallic surface which is to be brought into contact
therewith and optionally can also bond chemically to the lacquer
subsequently to be applied. The at least one metal chelate is, in
particular, one of Al, B, Ca, Fe, Hf, La, Mg, Mn, Si, Ti, Y, Zn, Zr
or/and at least one lanthanide, such as Ce, or such as a
Ce-containing lanthanide mixture, particularly preferably chosen
from the group consisting of Al, Hf, Mn, Si, Ti, Y and Zr.
[0026] The concentrates of the aqueous compositions containing
predominantly silane and chelate and of the part components as the
starting substance for polymer-containing compositions preferably
have a water content in the range from 20 to 85 wt. %, in
particular 30 to 80 wt. %. The concentrates preferably contain the
at least one silane, including the reaction products formed
therefrom, in a content in the range from 1 to 60 wt. %,
particularly preferably in the range from 3 to 45 wt. %, very
particularly preferably in the range from 6 to 45 wt. %, above all
in the range from 8 to 40 to 35 or to 32 wt. %, in particular of
about 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30 or 32.5 wt. %,
and the at least one chelate, optionally including the reaction
products formed therefrom, in the range from 1 to 50 wt. %,
particularly preferably in the range from 2 to 40 wt. %, very
particularly preferably in the range from 3 to 30 wt. %, above all
in the range from 5 to 25 wt. %, in particular about 7.5, 10, 12,
14, 16, 18, 20 or 22.5 wt. %.
[0027] The bath compositions of the aqueous compositions containing
predominantly silane and chelate preferably have a water content in
the range from 80 to 99.9 wt. %, preferably in the range from 90 to
99.8 wt. %, particularly preferably in the range from 94 to 99.7
wt. %, above all in the range from 96 to 99.6 wt. %, in particular
of about 95, 95.5, 96, 96.5, 97, 97.5, 97.9, 98.2, 98.5, 98.8, 99.1
or 99.4 wt. %.
[0028] The bath compositions preferably contain the at least one
silane, including the reaction products formed therefrom, in a
content in the range from 0.01 to 10 wt. %, particularly preferably
in the range from 0.05 to 7 wt. %, very particularly preferably in
the range from 0.1 to 5 wt. %, above all in the range from 0.2 to 4
wt. %, in particular of about 0.4, 0.6, 0.8, 1.0, 1.1, 1.2, 1.3,
1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.4, 2.6, 2.8, 3.0,
3.2, 3.4, 3.6 or 3.8 wt. %, and the at least one chelate, including
the reaction products possibly formed therefrom, in the range from
0.01 to 10 wt. %, particularly preferably in the range from 0.05 to
7 wt. %, very particularly preferably in the range from 0.1 to 5
wt. %, above all in the range from 0.2 to 4 wt. %, in particular of
about 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4,
1.6, 1.8, 2.0, 2.2, 2.4, 2.6, 2.8, 3.0, 3.2, 3.4, 3.6 or 3.8 wt.
%.
[0029] The contents of the at least one silane and of the at least
one chelate, in each case including the reaction products formed
therefrom, in particular those of titanium, hafnium or/and
zirconium, preferably make up at least 20 wt. %, in particular at
least 30 wt. %, particularly preferably at least 40 wt. %, very
particularly preferably at least 50 wt. %, above all in each case
at least 60, 70, 80, 90, 94, 95, 96, 97, 98 or 99 wt. % of the
solids contents of this composition. This composition particularly
preferably substantially contains water, in each case at least one
silane and/or reaction products thereof, at least one chelate,
where appropriate including the reaction products formed therefrom,
and optionally contents of substances chosen from the group
consisting of alcohols, acids, such as carboxylic and fatty acids,
such as acetic acid, and/or mineral acids, and other substances
which influence the pH, such as ammonia, and additives and
impurities. The total content of further compounds, including
additives, in addition to silane and chelate is usually up to 20
wt. % of the solids content of silane and chelate, preferably up to
15 wt. %, particularly preferably up to 10 wt. %, very particularly
preferably up to 5 wt. %, above all up to 1 or 2 wt. %.
[0030] Although the ratio of the at least one silane, including the
reaction products formed therefrom, to the at least one chelate,
optionally including the reaction products formed therefrom, can
preferably be in the range from 0.8:1 to 1.2:1, it has surprisingly
become clear that this ratio can also be, in particular, in the
range from 0.2:1 to 0.5:1 or 2:1 to 5:1, since in certain
situations there may be an optimum there.
[0031] The pH of this bath composition can be, in particular, in
the range from 3 to 9.5, preferably in the range from 3.5 to 9, in
particular in the range from 4 to 8.8. To adjust the pH, inter
alia, an addition of a weak acid or of a dilute strong acid or an
acid mixture can be added. In particular, at least one acid, such
as carboxylic or fatty acids, such as acetic acid, or/and mineral
acids, and other substances which influence the pH, such as
ammonia, can be used. The bath composition can in some cases be
adjusted down to pH values of about 3.5 by addition of acid if the
chemical system tolerates the pH chosen and remains stable.
However, if the acid is added only for neutralization, no or
virtually no pickling attack takes place. A solvent, such as an
alcohol, can preferably also be added to stabilize the silane.
[0032] The coatings formed with these bath compositions typically
have a layer thickness in the range from 0.01 to 1 .mu.m or to 0.6
.mu.m, usually 0.015 to 0.25 .mu.m.
[0033] The addition of the at least one silane a) offers the
advantage that adhesion bridges are formed between the substrate
and the dried protective film and to lacquer layers or/and coatings
of plastic possibly subsequently applied, as a result of which an
improved lacquer adhesion is also achieved. A further advantage is
that suitable silanes/siloxanes generate crosslinkings like
adhesion bridges within the dried protective film, which
considerably improve the strength and/or the flexibility of the
coating composite and the adhesion to the substrate, as a result of
which an improved adhesion is achieved in many lacquer systems.
[0034] The aqueous composition which contains predominantly chelate
and silane or predominantly synthetic resin and in addition chelate
and silane preferably contains in each case at least one
acyloxysilane, one alkoxysilane, one silane with at least one amine
group, such as an aminoalkylsilane, one silane with at least one
succinic acid group or/and succinic acid anhydride group, one
bis-silyl-silane, one silane with at least one epoxide group, such
as a glycidoxysilane, one (meth)acrylato-silane, one
multi-silyl-silane, one ureidosilane, one vinylsilane or/and at
least one silanol or/and at least one siloxane of a composition
corresponding chemically to the abovementioned silanes. The
reaction products of the silanes are known in principle in such
systems and are therefore not mentioned individually. They are
therefore also not referred to further in the following, but are
included under the term "silane(s)".
[0035] The composition can contain e.g. at least one silane mixed
with a content of at least one alcohol, such as ethanol, methanol
or/and propanol, of up to 8 wt. %, based on the silane content,
preferably up to 5 wt. %, particularly preferably up to 1 wt. %,
very particularly preferably up to 0.5 wt. %. In particular, the
mixture can contain e.g. at least one silane chosen from at least
one amino-silane, such as e.g. bis-amino-silane, without or with at
least one alkoxy-silane, such as e.g.
trialkoxy-silyl-propyl-tetrasulfane, or at least one vinylsilane
and at least one bis-silyl-aminosilane or at least one
bis-silyl-polysulfur-silane and/or at least one
bis-silyl-aminosilane or at least one aminosilane and at least one
multi-silyl-functional silane. Those silanes/siloxanes which have a
chain length in the range from 2 to 5 C atoms and contain a
functional group which is suitable for reaction with polymers are
preferred in particular.
[0036] The aqueous composition preferably contains at least one
silane chosen from the group consisting of [0037]
glycidoxyalkyltrialkoxysilane, [0038]
methacryloxyalkyltrialkoxysilane, [0039]
(trialkoxysilyl)alkyl-succinic acid-silane, [0040]
aminoalkylaminoalkylalkyldialkoxysilane, [0041]
(epoxycycloalkyl)alkyltrialkoxysilane, [0042]
bis-(trialkoxysilylalkyl)amine, [0043] bis-(trialkoxysilyl)ethane,
[0044] (epoxyalkyl)trialkoxysilane, [0045]
aminoalkyltrialkoxysilane, [0046] ureidoalkyltrialkoxysilane,
[0047] N-(trialkoxysilylalkyl)alkylenediamine, [0048]
N-(aminoalkyl)aminoalkyltrialkoxysilane, [0049]
N-(trialkoxysilylalkyl)dialkylenetriamine, [0050]
poly(aminoalkyl)alkyldialkoxysilane, [0051]
tris(trialkoxysilyl)alkyl isocyanurate, [0052]
ureidoalkyltrialkoxysilane and [0053] acetoxysilane.
[0054] The aqueous composition preferably contains at least one
silane chosen from the group consisting of [0055]
3-glycidoxypropyltriethoxysilane, [0056]
3-glycidoxypropyltrimethoxysilane, [0057]
3-methacryloxypropyltriethoxysilane, [0058]
3-methacryloxypropyltrimethoxysilane, [0059]
3-(triethoxysilyl)propyl-succinic acid-silane, [0060]
aminoethylaminopropylmethyldiethoxysilane, [0061]
aminoethylaminopropylmethyldimethoxysilane, [0062]
beta-(3,4-epoxycyclohexyl)ethyltriethoxysilane, [0063]
beta-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, [0064]
beta-(3,4-epoxycyclohexyl)methyltriethoxysilane, [0065]
beta-(3,4-epoxycyclohexyl)methyltrimethoxysilane, [0066]
gamma-(3,4-epoxycyclohexyl)propyltriethoxysilane, [0067]
gamma-(3,4-epoxycyclohexyl)propyltrimethoxysilane, [0068]
bis(triethoxysilylpropyl)amine, [0069]
bis(trimethoxysilylpropyl)amine, [0070]
(3,4-epoxybutyl)triethoxysilane, [0071]
(3,4-epoxybutyl)trimethoxysilane, [0072]
gamma-aminopropyltriethoxysilane, [0073]
gamma-aminopropyltrimethoxysilane, [0074]
gamma-ureidopropyltrialkoxysilane, [0075]
N-(3-(trimethoxysilyl)propyl)ethylenediamine, [0076]
N-beta-(aminoethyl)-gamma-aminopropyltriethoxysilane, [0077]
N-beta-(aminoethyl)-gamma-aminopropyltrimethoxysilane, [0078]
N-(gamma-triethoxysilylpropyl)diethylenetriamine, [0079]
N-(gamma-trimethoxysilylpropyl)diethylenetriamine, [0080]
N-(gamma-triethoxysilylpropyl)dimethylenetriamine, [0081]
N-(gamma-trimethoxysilylpropyl)dimethylenetriamine, [0082]
poly(aminoalkyl)ethyldialkoxysilane, [0083]
poly(aminoalkyl)methyldialkoxysilane, [0084]
tris(3-(triethoxysilyl)propyl)isocyanurate, [0085]
tris(3-(trimethoxysilyl)propyl)isocyanurate and [0086]
vinyltriacetoxysilane.
[0087] The silanes contained in the aqueous composition
(concentrate or bath) are monomers, oligomers, polymers, copolymers
or/and reaction products with further components on the basis of
hydrolysis reactions, condensation reactions or/and further
reactions. The reactions take place above all in the solution,
during drying or optionally curing of the coating. In the context
of this Application, the term "silane" is used here for silanes,
silanols, siloxanes, polysiloxanes and reaction products and
derivatives thereof, which are often "silane" mixtures. Because of
the often very complex chemical reactions which occur here, and the
very expensive analyses and working, the particular further silanes
or other reaction products cannot be described.
[0088] Instead of a content of at least one fluorine-free silane in
the content of silanes, however, this content may contain only
fluorine-containing silanes, or at least, instead of fluorine-free
silanes, at least one fluorine-containing silane.
[0089] The aqueous composition preferably then contains at least
one silane chosen from the fluorine-containing silanes: from in
each case at least one acyloxysilane, one alkoxysilane, one silane
having at least one amino group, such as an aminoalkylsilane, one
silane having at least one succinic acid group or/and succinic acid
anhydride group, one bis-silyl-silane, a silane having at least one
epoxide group, such as a glycidoxysilane, one
(meth)acrylato-silane, one multi-silyl-silane, one ureidosilane,
one vinylsilane or/and at least one silanol or/and at least one
siloxane or polysiloxane of a composition which corresponds
chemically to the abovementioned silanes, which in each case
contains at least one group having one or having at least one
fluorine atom.
[0090] In particular, the aqueous composition then contains at
least one fluoroalkoxyalkylsilane, at least one silane having 1, 2,
3, 4, 5, 6, 7, 8, 9, 10, 11, 12 or 13 fluorine atoms per silane, at
least one perfluorinated silane, at least one mono-fluorosilane, at
least one fluorosilane based on ethoxysilane or/and based on
methoxysilane or/and at least one fluorosilane having at least one
functional group, such e.g. an amino group, in particular as a
cocondensate, such as e.g.
a fluoroalkyldialkoxysilane, a
fluoroaminoalkylpropyltrialkoxysilane, a fluoromethanesulfonate, a
fluoropropylalkyldialkoxysilane, a triphenylfluorosilane, a
trialkoxyfluorosilane, a trialkylfluorosilane or/and a
tridecafluorooctyltrialkoxysilane.
[0091] The composition particularly preferably then contains at
least one fluorine-containing silane which contains at least two
amino groups and at least one optionally fluorinated ethyl or/and
at least one optionally fluorinated methyl group.
[0092] The content of the at least one silane, including the
reaction products formed therefrom, in the aqueous composition is
preferably 0.1 to 80 g/l, in particular 0.2 to 50 g/l, particularly
preferably 0.3 to 35 g/l, very particularly preferably 0.5 to 20
g/l, above all 1 to 10 g/l.
[0093] Preferably, the bath compositions which have a relatively
low content of or are free from film-forming agent contain the
silanes, including the reaction products optionally formed
therefrom with other components, in a content in the range from
0.01 to 10 wt. %, particularly preferably in the range from 0.05 to
7 wt. %, very particularly preferably in the range from 0.1 to 5
wt. %, above all in the range from 0.2 to 4 wt. %, in particular of
about 0.4, 0.6, 0.8, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8,
1.9, 2.0, 2.1, 2.2, 2.4, 2.6, 2.8, 3.0, 3.2, 3.4, 3.6 or 3.8 wt. %,
and the at least one chelate, including the reaction products
optionally formed therefrom, in the range from 0.01 to 10 wt. %,
particularly preferably in the range from 0.05 to 7 wt. %, very
particularly preferably in the range from 0.1 to 5 wt. %, above all
in the range from 0.2 to 4 wt. %, in particular of about 0.3, 0.4,
0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.6, 1.8, 2.0,
2.2, 2.4, 2.6, 2.8, 3.0, 3.2, 3.4, 3.6 or 3.8 wt. %.
[0094] The content of the at least one metal chelate b), optionally
including the reaction products formed therefrom, in the aqueous
composition is preferably 0.05 to 80 g/l, in particular 0.1 to 50
g/l.
[0095] The at least one metal chelate is preferably chosen from
chelate complexes based on acetylacetonates, acetoacetates,
acetonates, alkylenediamines, amines, lactates, carboxylic acids,
citrates or/and glycols.
[0096] The at least one metal chelate is preferably based on [0097]
acetylacetonate, [0098] alkali metal lactate, [0099] alkanolamine,
[0100] alkyl acetoacetate, [0101] alkylenediamine tetraacetate,
[0102] ammonium lactate, [0103] citrate, [0104] dialkyl citrate,
[0105] dialkyl ester-citrate, [0106] dialkylenetriamine, [0107]
diisoalkoxybisalkyl acetoacetate, [0108] diisopropoxybisalkyl
acetoacetate, [0109] di-n-alkoxy-bisalkyl acetoacetate, [0110]
hydroxyalkylenediamine triacetate, [0111] trialkanolamine or/and
[0112] trialkylenetetramine.
[0113] These metal chelates serve in particular to stabilize the
organometallic compound in water and to bond to the metallic
surface or to the lacquer or to a corresponding coating applied.
They are particularly suitable if they have only a low reactivity
in the aqueous composition and if they are at least partly
decomposed within the process conditions used and the metal ions
for the bonding or/and chemical reaction are liberated. If they are
too reactive, the organometallic compounds react prematurely with
other chemical compounds, such as silanes.
[0114] Preferably, the chelates are hydrophilic, stable to
hydrolysis, stable to water or/and form stable hydrolysates.
Preferably, a silane or a chelate is chosen which is compatible
with water and moreover with the organic film-forming agent chosen
and which has the same properties as mentioned before for the
silane or chelate.
[0115] Preferably, the amounts ratio of a) to b), in each case
including the reaction products formed therefrom, is in the range
from 0.1:1 to 10:1, particularly preferably in the amounts ratio of
0.2:1 to 8:1, very particularly preferably in the amounts ratio of
0.3:1 to 7:1, in particular about 0.4:1, 0.6:1, 0.8:1, 1:1, 1.2:1,
1.6:1, 2:1, 3:1, 4:1, 5:1 or 6:1.
[0116] Particularly preferably, in each case amounts of silane(s)
and chelate(s), in each case including the reaction products formed
therefrom, are contained independently of one another in the range
from 0.05 to 5 wt. %, based on the wet film, very particularly
preferably in each case independently of one another amounts of
0.08 to 4 wt. %, in particular about in each case independently of
one another amounts of 0.1, 0.2, 0.3, 0.5, 0.8, 1, 1.5, 2, 2.5, 3
or 3.5 wt. %.
[0117] Particularly preferably, in each case amounts of silane(s)
and chelate(s), in each case including the reaction products formed
therefrom, are contained independently of one another in the range
from 0.2 to 15 wt. %, based on the dry substance content, very
particularly preferably in each case independently of one another
amounts of 0.3 to 11 wt. %, in particular about in each case
independently of one another amounts of 0.5, 0.8, 1, 1.5, 2, 2.5,
3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10 or 10.5
wt. %.
[0118] In particular, in the compositions having a comparatively
high film-forming agent content, an amounts ratio of components
[a)+b)]:c), in each case including the reaction products formed
therefrom and based on the wet film, of 2:70 to 20:70 is
particularly preferred, very particularly preferably in an amounts
ratio of 3.5:70 to 17:70, in particular about 5:70, 6:70, 7:70,
8:70, 9:70, 10:70, 11:70, 12:70 and 14:70. It may be preferable
here for either component a) to component b), or vice versa, to
assume values of the content which are higher by the factor 1.2 to
4 than that of the other component. An amounts ratio of components
[a)+b)]:c), in each case including the reaction products formed
therefrom and based on the solids content, of 2:70 to 20:70 is
particularly preferred, very particularly preferably in an amounts
ratio of 3.5:70 to 17:70, in particular about 5:70, 6:70, 7:70,
8:70, 9:70, 10:70, 11:70, 12:70 and 14:70.
[0119] In particular, in the compositions having a relatively low
film-forming agent content, however, the amounts ratio of
components [a)+b)]:c), in each case including the reaction products
formed therefrom and based on the wet film, can be particularly
preferably in the range from .gtoreq.0.2:7 and up to 20:7, very
particularly preferably in the amounts ratio of .gtoreq.0.5:7 and
up to 12:7 or of .gtoreq.1:7 and up to 8:7, in particular about
0.4:7, 0.6:7, 0.8:7, 1.2:7, 1.5:7, 2:7, 3:7, 4:7, 5:7, 6:7, 7:7,
9:7, 10:7, 11:7, 13:7, 14:7 and 16:7. It may be preferable here for
either component a) to component b) or vice versa to assume content
values which are higher than the other component by a factor of 1.2
to 4.
[0120] The contents of component a), including the reaction
products formed therefrom and based on the solids content, are
particularly preferably in the range from 0.4 to 10 wt. %, very
particularly preferably in the range from 0.8 to 8 wt. %, in
particular about 1.2, 1.5, 1.8, 2.1, 2.4, 2.7, 3, 3.3, 3.6, 3.9,
4.2, 4.5, 4.8, 5.1, 5.5, 6, 6.5, 7 or 7.5 wt. %.
[0121] The contents of component b), including the reaction
products formed therefrom and based on the solids content, are
particularly preferably in the range from 0.3 to 10 wt. %, very
particularly preferably in the range from 0.8 to 8 wt. %, in
particular about 1.2, 1.5, 1.8, 2.1, 2.4, 2.7, 3, 3.3, 3.6, 3.9,
4.2, 4.5, 4.8, 5.1, 5.5, 6, 6.5, 7 or 7.5 wt. %.
[0122] In particular, in the compositions having a comparatively
high film-forming agent content, the contents of component c),
based on the solids content, are particularly preferably in the
range from 10 to 95 wt. %, very particularly preferably in the
range from 30 to 90 wt. %, in particular about 35, 40, 45, 50, 55,
60, 63, 66, 69, 72, 75, 78, 81, 84 or 87 wt. %.
[0123] In particular, in the compositions having a comparatively
high film-forming agent content, the contents of component d)--at
least one long-chain alcohol--based on the solids content, are
particularly preferably in the range from 0.01 to 2 wt. %, very
particularly preferably in the range from 0.1 to 1 wt. %, in
particular about 0.12, 0.15, 0.18, 0.21, 0.24, 0.27, 0.30, 0.33,
0.36, 0.39, 0.42, 0.45, 0.48, 0.51, 0.55, 0.60, 0.65, 0.7, 0.75,
0.8, 0.9 or 0.95 wt. %.
[0124] In particular, the content of organic film-forming agent c),
based on the solids content of the composition, is 10 to 45 wt. %,
preferably 10 to 40 wt. %, particularly preferably 10 to 35 wt. %,
in particular 10 to 30, to 25 or to 20 wt. %. The aqueous
composition, which can serve as a bath composition or/and as a
concentrate, preferably contains the organic film-forming agent c)
in a content of 0.1 to 980 g/l, particularly preferably in a range
from 2 to 600 g/l, very particularly preferably 50 to 550 g/l, in
particular 150 to 450 g/l. Preferably, 2 to 100 parts of the
organic film-forming agent are added, particularly preferably 10 to
60 parts, very particularly preferably 15 to 45 parts, per 100
parts by weight of water. In particular, in the case of the
compositions having a relatively low film-forming agent content,
however, the aqueous composition, which can serve as a bath
composition or/and as a concentrate, preferably contains the
organic film-forming agent c) in a content of .gtoreq.0.01 and up
to 98 g/l, particularly preferably in a range from .gtoreq.0.1 and
up to 60 g/l, very particularly preferably from .gtoreq.0.5 and up
to 50 g/l, in particular from .gtoreq.2 and up to 45 g/l.
[0125] Under certain circumstances, the highest contents of organic
film-forming agent can occur in particular in UV-curing systems
without or in systems with only low volatile contents, such as
organic solvents or/and residual monomers. Coatings which are
predominantly or solely film-formed during drying or optionally
cured in part thermo-physically are particularly preferred for the
process according to the invention. In the context of this
Application, the term copolymers preferably also includes block
copolymers and graft copolymers.
[0126] The organic film-forming agent preferably contains at least
a proportion of at least one polymer or/and at least one copolymer
with an acid number in the range from 3 to 120, particularly
preferably in the range, from 3 to 80, very particularly preferably
in the range from 4 to 60.
[0127] The organic film-forming agent preferably contains at least
one proportion of at least one polymer or/and at least one
copolymer with a minimum film-forming temperature MFT in the range
from -10 to +99.degree. C., particularly preferably in the range
from 0 to 90.degree. C., in particular from 5.degree. C.; it is
very particularly advantageous if the organic film-forming agent
contains at least two in particular thermoplastic polymers or/and
copolymers at least in the initial stage--since the thermoplastic
constituents can at least partly lose or reduce their thermoplastic
properties during the further treatment and reaction--which--where
a minimum film-forming temperature can be stated--have a minimum
film-forming temperature in the range from 5 to 95.degree. C., in
particular of at least 10.degree. C., where at least one of these
polymers or/and copolymers, compared with at least a second of
these polymers or/and copolymers, A) has a minimum film-forming
temperature which differs from that of the other component by at
least 20.degree. C., B) has a glass transition temperature which
differs from that of the other component by at least 20.degree. C.,
or/and C) has a melting point which differs from that of the other
component by at least 20.degree. C. Preferably, one of these at
least two components has a film-forming temperature in the range
from 10 to 40.degree. C. and the other a film-forming temperature
in the range from 45 to 85.degree. C. Long-chain alcohols can help
here to lower the glass transition temperatures temporarily and
optionally also to match them somewhat to one another. After
application, the long-chain alcohols can escape and then leave
behind a film of higher glass transition temperature than during
the application. These dried films are then not too flexible and
too tacky. The glass transition temperatures and the melting points
of these synthetic resins are often about in the region of the
film-forming temperature, that is to say usually in the range from
0 to 110.degree. C.
[0128] In another preferred embodiment, a mixture of organic
film-forming agents in which at least some of the film-forming
agents have a glass transition temperature T.sub.g of substantially
the same or/and a similar T.sub.g can be employed. It is
particularly preferable here for at least some of the organic
film-forming agents to have a glass transition temperature T.sub.g
in the range from 10 to 70.degree. C., very particularly preferably
in the range from 15 to 65.degree. C., in particular in the range
from 20 to 60.degree. C. The organic film-forming agent then
preferably contains at least a proportion of at least one polymer
or/and at least one copolymer having a minimum film-forming
temperature MFT in the range from -10 to +99.degree. C.,
particularly preferably in the range from 0 to 90.degree. C., in
particular from 5.degree. C. or from 10.degree. C. It is
particularly preferable here for at least two, if not all, of the
organic film-forming agents to have a minimum film-forming
temperature in one of these temperature ranges--if a minimum
film-forming temperature can be stated.
[0129] It is particularly advantageous if all the organic
film-forming agents form a film during drying. It is particularly
preferable if synthetic resins which have thermoplastic properties
to the extent of at least 80 wt. %, in particular to the extent of
at least 90 wt. %, are added to the aqueous composition.
[0130] The organic film-forming agent is preferably formed from at
least one component in the form of in each case at least one
solution, dispersion, emulsion, microemulsion and/or suspension
which is added to the aqueous composition. The term dispersion here
also includes the sub-terms emulsion, solution, microemulsion and
suspension.
[0131] The acid number of the synthetic resins is preferably 3 to
100, particularly preferably 3 to 60 or 4 to 50. In particular,
copolymers with an acid number in the range from 3 to 50 are added
to the aqueous composition. The components of the organic
film-forming agent which are to be added are optionally already
partly neutralized. The organic film-forming agent can preferably
contain a proportion of at least one copolymer with an acid number
in the range from 3 to 80, in particular to the extent of at least
50 wt. % of the synthetic resins added. In a high range of the acid
number it is usually not necessary to stabilize a film-forming
agent cationically, anionically or/and sterically. At a low acid
number, however, such a stabilization is often necessary. It is
then advantageous to employ already (partly) stabilized synthetic
resins or mixtures thereof.
[0132] The aqueous composition preferably contains at least one
synthetic resin, such as organic polymer, copolymer or/and mixture
thereof, in particular a synthetic resin based on acrylate,
ethylene, polyester, polyurethane, silicone polyester, epoxide,
phenol, styrene, melamine-formaldehyde, urea-formaldehyde or/and
vinyl. The organic film-forming agent can preferably be a synthetic
resin mixture of at least one polymer or/and at least one
copolymer, which in each case independently of one another contains
a proportion of synthetic resin based on acrylate, epoxide,
ethylene, urea-formaldehyde, phenol, polyester, polyurethane,
styrene, styrene-butadiene or/and vinyl. This can also be here a
cationically, anionically or/and sterically stabilized synthetic
resin or polymer or/and dispersion thereof or even solution
thereof. The term acrylate in the context of this Application
includes acrylic acid ester, polyacrylic acid, methacrylic acid
ester and methacrylate.
[0133] The organic film-forming agent can preferably contain at
least one component based on [0134] acrylic-polyester-polyurethane
copolymer, [0135] acrylic-polyester-polyurethane-styrene copolymer,
[0136] acrylic acid ester, [0137] acrylic acid ester-methacrylic
acid ester, [0138] optionally with free acids or/and acrylonitrile,
[0139] ethylene-acrylic mixture, [0140] ethylene-acrylic copolymer,
[0141] ethylene-acrylic-polyester copolymer, [0142]
ethylene-acrylic-polyurethane copolymer, [0143]
ethylene-acrylic-polyester-polyurethane copolymer [0144]
ethylene-acrylic-polyester-polyurethane-styrene copolymer, [0145]
ethylene-acrylic-styrene copolymer [0146] polyester resins with
free carboxyl groups combined with melamine-formaldehyde resins,
[0147] a synthetic resin mixture or/and copolymer based on acrylate
and styrene, [0148] a synthetic resin mixture or/and copolymer
based on styrene-butadiene, [0149] a synthetic resin mixture or/and
copolymer of acrylate and epoxide, [0150] based on an
acrylic-modified polyester containing carboxyl groups together with
melamine-formaldehyde and ethylene-acrylic copolymer, [0151]
polycarbonate-polyurethane, [0152] polyester-polyurethane, [0153]
styrene, [0154] styrene-vinyl acetate, [0155] vinyl acetate, [0156]
vinyl ester or/and [0157] vinyl ether.
[0158] However, the organic film-forming agent can also preferably
contain as the synthetic resin a content of organic polymer,
copolymer or/and mixtures thereof based on polyethyleneimine,
polyvinyl alcohol, polyvinylphenol, polyvinylpyrrolidone or/and
polyaspartic acid, in particular copolymers with a
phosphorus-containing vinyl compound. A conductive polymer is
preferably also added to the aqueous composition.
[0159] A synthetic resin based on acrylate or based on
ethylene-acrylic acid with a melting point in the range from 60 to
95.degree. C. or a synthetic resin with a melting point in the
range from 20 to 160.degree. C., in particular in the range from 60
to 120.degree. C., is very particularly preferred.
[0160] Preferably, at least 30 wt. % of the organic film-forming
agent added can contain thermoplastic resins from which films can
be formed, particularly preferably to the extent of at least 50 wt.
%, very particularly preferably to the extent of at least 70 wt. %,
above all to the extent of at least 90 or to the extent of at least
95 wt. %. In addition, the organic film-forming agent can also
contain contents, in certain circumstances residual contents, of in
each case at least one monomer, oligomer, emulsifier, further
additive for dispersions, one curing agent, photoinitiator or/and
one cationically polymerisable substance. The content of monomer,
oligomer, emulsifier and further additive for dispersions is
usually less than 5 wt. %, often less than 2 wt. %, possibly less
than 1 wt. %. The composition of curing agents and correspondingly
crosslinkable substances then optionally also added and the
corresponding measures for this are known in principle.
[0161] The molecular weights of the synthetic resins added can
preferably be in the range of at least 1,000 u, particularly
preferably of at least 5,000 u, very particularly preferably from
20,000 to 200,000 u. The individual thermoplastic components of the
organic film-forming agent which are added to the aqueous
composition preferably have molecular weights in the range from
20,000 to 200,000 u, in particular in the range from 50,000 to
150,000 u.
[0162] The organic film-forming agent can preferably contain at
least 40 wt. % of high-molecular-weight polymers, particularly
preferably at least 55 wt. %, very particularly preferably at least
70 wt. %, above all at least 85 wt. %, in particular at least 95
wt. %. In particular, if at least 85 wt. % of the organic
film-forming agent comprises high-molecular-weight polymers, it is
usually not necessary to add curing agents, such as isocyanates, or
photoinitiators, such as benzophenones, for thermal or free-radical
crosslinking, and correspondingly crosslinkable synthetic resins in
order to achieve the outstanding properties of the coating
according to the invention, since it is then possible to form, by
the film formation, a closed, solid, high-quality film without
carrying out crosslinking.
[0163] During film formation, which takes place in particular
during drying, the organic microparticles add on to one another and
compact to form a closed pore-free film, if the choice of polymers
and film-forming auxiliary is suitable and the process is operated
under suitable conditions. The expert is familiar in principle with
these classes of substance and working conditions. The fact that
this film can have exceptionally high-quality properties, in spite
of such a low layer thickness, preferably in the range from 0.5 to
3 .mu.m, is demonstrated by the embodiment examples. To the
knowledge of the Applicant, no substantially organic, chromate-free
coating with a layer thickness of less than 4 .mu.m dry film
thickness has hitherto been disclosed for the coating on metallic
strips of such high lacquer adhesion and corrosion resistance which
predominantly contains polymers which have undergone film
formation. The coating according to the invention is at least
equivalent to a chromate-containing organic coating.
[0164] The final drying of such films can take many days, while
substantial drying can already be completed in a few seconds.
Curing here can, under certain circumstances, take several weeks
until the final drying and curing state is achieved if no thermal
or free-radical crosslinking occurs here. If required; the curing
can additionally be accelerated or intensified, as a result of
crosslinking, by irradiation, e.g. with UV radiation, or by
heating, or/and also to a small extent by addition of and reaction
with e.g. compounds containing free NCO groups with the hydroxyl
groups of the polymers containing hydroxyl groups.
[0165] The coating is preferably largely or completely cured by
drying and film formation. Alternatively, however, the coating can
be hardened or cured partly by drying and film formation and partly
by actinic radiation, cationic polymerization or/and thermal
crosslinking. In this case, at least one photoinitiator or/and at
least one curing agent and correspondingly crosslinkable resin are
optionally added to the aqueous composition.
[0166] The pH of the organic film-forming agent in an aqueous
formulation, without addition of further compounds, is usually in
the range from 0.5 to 12. The pH of the aqueous composition which
contains predominantly synthetic resins and also silane and chelate
as solids contents is preferably in the range from 1 to 6 or 6 to
10.5--depending on whether the procedure takes place in the acid or
rather basic range, particularly preferably in the range from 6.5
to 9.5, very particularly preferably in the range from 7 to
9.2.
[0167] In one embodiment variant, the organic film-forming agent
preferably contains only water-soluble synthetic resins, in
particular those which are stable in solutions with pH values of
.ltoreq.9, or/and the organic film-forming agent contains at least
one synthetic resin which contains hydroxyl groups. However, if the
pH should have fallen due to storage of the synthetic resins or
mixtures, it may be helpful to bring the pH, especially that of the
dispersion which is otherwise ready-to-use, back into a more
alkaline range e.g. by addition of sodium hydroxide solution. The
organic film-forming agent can also be of a composition such that
it contains--optionally only--water-soluble synthetic resin, in
particular one which is stable in solutions with pH values of
.ltoreq.5.
[0168] Preferably, the acid groups of the synthetic resins are
or/and will be neutralized with ammonia, with amines or
alkanolamines, such as e.g. morpholine, dimethylethanolamine,
diethylethanolamine or triethanolamine, or/and with alkali metal
compounds, such as e.g. sodium hydroxide. These additives then act
as a stabilizer.
[0169] Film formation is understood as meaning film formation from
a material with a high organic content, such as a polymer
dispersion, during which above all polymer particles are converted
into a uniform film, preferably at room temperature or slightly
elevated temperature. Fusion of the comparatively large polymer
particles is often referred to here. Film formation takes place
here from an aqueous medium during drying and optionally with
plasticizing of the polymer particles by the remaining film-forming
auxiliary. The film formation can be improved by the use of
thermoplastic polymers or copolymers or/and by addition of
substances which serve as temporary plasticizers. Film-forming
auxiliaries act as specific solvents which soften the surface of
the polymer particles and thus render possible fusion thereof. It
is advantageous here if these plasticizers on the one hand remain
in the aqueous composition for a sufficiently long period of time
to be able to act on the polymer particles for a long period of
time and then evaporate and thus escape from the film. It is
furthermore advantageous if a residual water content is also
present for a sufficiently long period of time during the drying
process. In a suitable film formation, a transparent film is
formed, but no milky-white or even pulverulent film, which is an
indication of an impaired film formation. For film formation which
is as perfect as possible, the temperature of the wet film applied
to a surface must be above the minimum film temperature (MFT),
since only then are the polymer particles soft enough to coalesce.
It is particularly advantageous here if these plasticizers do not
or virtually do not modify the pH of the aqueous composition. The
choice of suitable film-forming auxiliary is not easy here, a
mixture of at least two film-forming auxiliaries often being
necessary. Film-forming auxiliaries which are particularly
advantageous are so-called long-chain alcohols, in particular those
having 4 to 20 C atoms, such as a butanediol, a butyl glycol, a
butyl diglycol, an ethylene glycol ether, such as ethylene glycol
monobutyl ether, ethylene glycol monoethyl ether, ethylene glycol
monomethyl ether, ethyl glycol propyl ether, ethylene glycol hexyl
ether, diethylene glycol methyl ether, diethylene glycol ethyl
ether, diethylene glycol butyl ether, diethylene glycol hexyl
ether, or a polypropylene glycol ether, such as propylene glycol
monomethyl ether, dipropylene glycol monomethyl ether, tripropylene
glycol monomethyl ether, propylene glycol monobutyl ether,
dipropylene glycol monobutyl ether, tripropylene glycol monobutyl
ether, propylene glycol monopropyl ether, dipropylene glycol
monopropyl ether, tripropylene glycol monopropyl ether, propylene
glycol phenyl ether, trimethylpentanediol diisobutyrate, a
polytetrahydrofuran, a polyether-polyol or/and a polyester-polyol.
In contrast to film formation, temperatures of at least 120.degree.
C. are conventionally required for crosslinking for thermosetting
organic coatings.
[0170] In the processes according to the invention relating to
compositions which contain predominantly chelate and silane or
predominantly synthetic resin and in addition chelate and silane,
the aqueous composition can contain at least one component e)
chosen from the group consisting of [0171] e.sub.1) at least one
inorganic compound in particle form with an average particle
diameter, measured on a scanning electron microscope, in the range
from 0.005 to 0.3 .mu.m diameter, [0172] e.sub.2) at least one
lubricant, [0173] e.sub.3) at least one organic corrosion
inhibitor, [0174] e.sub.4) at least one anticorrosion pigment,
[0175] e.sub.5) at least one agent for neutralization or/and for
steric stabilization of the synthetic resins, [0176] e.sub.6) at
least one organic solvent, [0177] e.sub.7) at least one siloxane
and [0178] e.sub.8) at least one chromium(VI) compound.
[0179] Preferably, a finely divided powder, a dispersion or a
suspension, such as e.g. a carbonate, oxide, silicate or sulfate,
in particular colloidal or/and amorphous particles, is added as the
inorganic compound in particle form e.sub.1). Particles based on at
least one compound of aluminium, barium, cerium, calcium,
lanthanum, silicon, titanium, yttrium, zinc or/and zirconium are
preferably added as the inorganic compound in particle form.
Particles based on aluminium oxide, barium sulfate, cerium dioxide,
silicon dioxide, silicate, titanium oxide, yttrium oxide, zinc
oxide or/and zirconium oxide are preferably added as the inorganic
compound in particle form.
[0180] Preferably, particles with an average particle size in the
range from 6 to 200 nm are used as the inorganic compound in
particle form, particularly preferably in the range from 7 to 150
nm, very particularly preferably in the range from 8 to 90 nm, even
more preferably in the range from 8 to 60 nm, above all preferably
in the range from 10 to 25 nm. These particles can also be in the
form of a gel or sol. The particles can be stabilized e.g. under
alkaline conditions, in order to achieve a better dispersion. An
addition of boron for dispersing of the inorganic compound in
particle form was not necessary and also has not been used in the
examples. It is preferable for larger particles to have a rather
platelet-shaped or longitudinal grain form.
[0181] The aqueous composition, which can serve as a bath
composition or/and as a concentrate, preferably contains the at
least one inorganic compound in particle form in a content of 0.1
to 500 g/l, particularly preferably in a range from 10 to 200 g/l,
very particularly preferably 30 to 100 g/l, above all in the range
from 3 to 60 g/l. Preferably, 0.1 to 50 parts of the at least one
inorganic compound in particle form, particularly preferably 0.5 to
20 parts, very particularly preferably 0.8 to 10 parts, are added
per 100 parts by weight of water. Among the inorganic compounds in
particle form, those which maintain the transparency of the coating
according to the invention, that is to say are colourless or white,
such as e.g. aluminium oxide, barium sulfate, silicate, silicon
dioxide, colloidal silicon dioxide, zinc oxide or/and zirconium
oxide, are preferred in particular in order to maintain the visual
character of the metallic surface visibly as far as possible
without falsification.
[0182] Particles with a relatively high or high electrical
conductivity, which are optionally also added, such as those of
iron oxide, iron phosphide, tungsten, zinc and zinc alloy, can also
be chosen for use for welding so that they have an average particle
size such that they optionally project somewhat more out of the
layer according to the invention.
[0183] The ratio of the contents of organic film-forming agent to
contents of inorganic compounds in particle form in the aqueous
composition can vary within wide ranges; in particular, it can be
.ltoreq.25:1. Preferably, this ratio is in a range from
.gtoreq.0.05:1 and up to 15:1, particularly preferably in a range
from .gtoreq.0.2:1 and up to 12:1, very particularly preferably in
a range from .gtoreq.0.5:1 and up to 10:1, in particular in a range
from .gtoreq.1:1 and up to 8:1.
[0184] The ratio of the contents of at least one silane to contents
of inorganic compounds in particle form in the aqueous composition
can likewise vary within wide limits; in particular, it can be
.ltoreq.25:1. This ratio is preferably in a range from
.gtoreq.0.01:1 and up to 15:1, particularly preferably in a range
from .gtoreq.0.05:1 and up to 8:1, very particularly preferably in
a range from .gtoreq.0.08:1 and up to 4:1, in particular in a range
from .gtoreq.0.1:1 and up to 2:1.
[0185] Preferably, at least one wax chosen from the group
consisting of paraffins, polyethylenes and polypropylenes is used
as the lubricant e.sub.2), in particular an oxidized wax, the
content of waxes in the aqueous composition preferably being in the
range from 0.01 to 5 wt. %, particularly preferably in the range
from 0.02 to 3.5 wt. %, very particularly preferably in the range
from 0.05 to 2 wt. %. Preferably, the melting point of the wax
employed as a lubricant is in the range from 40 to 165.degree. C.,
particularly preferably in the range from 50 to 160.degree. C., in
particular in the range from 120 to 150.degree. C. It is
particularly advantageous to add, in addition to a lubricant with a
melting point in the range from 120 to 165.degree. C., a lubricant
with a melting point in the range from 45 to 95.degree. C. or with
a glass transition temperature in the range from -20 to +60.degree.
C., in particular in amounts of 2 to 30 wt. %, preferably 5 to 20
wt. % of the total solids content. However, the latter can also
advantageously be employed by itself.
[0186] It is particularly advantageous to employ the wax as an
aqueous or as a cationically, anionically or/and sterically
stabilized dispersion, because it can then easily be kept in
homogeneous distribution in the aqueous composition. The aqueous
composition preferably contains the at least one lubricant, which
optionally can also simultaneously be a shaping agent, in a content
in the range from 0.1 to 25 g/l and particularly preferably in a
content in the range from 1 to 15 g/l. However, a wax content is
usually only advantageous if the coating according to the invention
is a treatment layer, since the wax content in a pretreatment layer
can be a disadvantage during lacquering. A lubricant or/and shaping
agent can be added to reduce the coefficient of friction of the
coating, in particular during shaping. Paraffin, polyethylene and
oxidized polyethylene, inter alia, are recommended for this.
[0187] Preferably, at least one wax together with a polymer mixture
containing ethylene and acrylic acid or/and a copolymer, such as
ethylene/acrylic-acid copolymer, is employed as the lubricant,
optionally at least one further synthetic resin being added, in
particular in an amounts ratio of wax to the copolymer containing
ethylene and acrylic acid of 0.02:1 to 2:1, particularly preferably
0.05:1 to 1:1, very particularly preferably 0.1:1 to 0.5:1.
[0188] The ratio of the contents of organic film-forming agent to
contents of lubricant in the aqueous composition (bath composition)
can vary within wide ranges; in particular it can be .gtoreq.2:1.
Preferably, this ratio is in a range from 3:1 to 50:1, particularly
preferably in a range from 10:1 to 20:1.
[0189] The aqueous composition preferably contains at least one
organic corrosion inhibitor e.sub.3), in particular based on
amine(s), preferably at least one alkanolamine--preferably a
long-chain alkanolamine, at least one TPA-amine complex, such as
acid adduct-4-oxo-4-p-tolyl butyrate-4-ethylmorpholine, at least
one zinc salt of aminocarboxylate, of 5-nitro-isophthalic acid or
of cyanic acid, at least one polymeric ammonium salt with fatty
acid, at least one metal salt of a sulfonic acid, such as
dodecyl-naphthalenesulfonic acid, at least one amino and transition
metal complex of toluenepropionic acid,
2-mercapto-benzothiazolyl-succinic acid or at least one of its
amino salts, at least one conductive polymer or/and at least one
thiol, it being possible for the content of organic corrosion
inhibitors in the aqueous composition preferably to be in the range
from 0.01 to 5 wt. %, particularly preferably in the range from
0.02 to 3 wt. %, very particularly preferably in the range from
0.05 to 1.5 wt. %.
[0190] The at least one organic corrosion inhibitor is preferably
not readily volatile at room temperature. It may furthermore be
advantageous if it is readily soluble in water or/and readily
dispersible in water, in particular to the extent of more than 20
g/l. Compounds which are particularly preferred are, inter alia,
alkylaminoethanols, such as dimethylaminoethanol, and complexes
based on a TPA-amine, such as N-ethylmorpholine complex with
4-methyl-.gamma.-oxo-benzenebutanoic acid. This corrosion inhibitor
can be added in order to effect or to intensify still further a
relatively powerful corrosion inhibition. The addition of the at
least one organic corrosion inhibitor is usually necessary only for
metallic surfaces which are very difficult to protect, such as
bright steel surfaces, because of the very high
corrosion-inhibiting action of the compositions according to the
invention. It is advantageous if non-galvanized steel surfaces, in
particular cold-rolled steel (CRS), are to be coated.
[0191] The ratio of the contents of organic film-forming agent to
contents of at least one organic corrosion inhibitor in the aqueous
composition (bath composition) can vary within wide ranges; in
particular it can be .ltoreq.500:1. This ratio is preferably in a
range from 5:1 to 400:1, particularly preferably in a range from
10:1 to 100:1.
[0192] The aqueous composition preferably contains 0.1 to 80 g/l of
the at least one anticorrosion pigment e.sub.4). These include, in
particular, various silicates, based on aluminium silicates,
alumo-silicates, alumo-alkaline earth metal silicates and alkaline
earth metal silicates. The anticorrosion pigments preferably have
an average particle diameter, measured on a scanning electron
microscope, in the range from 0.01 to 0.5 .mu.m diameter, in
particular in the range from 0.02 to 0.3 .mu.m. The various types
of anticorrosion pigments are known in principle. However, an
addition of at least one of these pigments does not seem to be
necessary in principle, but renders alternative embodiment variants
possible.
[0193] The agents for neutralization and/or steric stabilization of
the acid groups of the synthetic resins with an acid number in
particular in the range from 5 to 50 e.sub.5) can be, inter alia,
slowly volatilizing alkanolamines and hydroxides, such as sodium
hydroxide solution and potassium hydroxide solution, but preferably
rapidly volatilizing alkanolamines, ammonia and compounds based on
morpholine and alkanolamines. They have the effect that the
neutralized synthetic resins become water-miscible or, at an acid
number from about 150, are also water-soluble.
[0194] At least one organic solvent e.sub.6) can optionally also be
added in the process according to the invention. At least one
water-miscible or/and water-soluble alcohol, one glycol ether or
N-methylpyrrolidone or/and water can be used as the organic solvent
for the organic polymers, and in the case of the use of a solvent
mixture, in particular a mixture of at least one long-chain
alcohol, such as e.g. propylene glycol, one ester-alcohol, one
glycol ether or/and butanediol with water. Preferably, however, in
many cases only water is added, without any organic solvent. If an
organic solvent is used, the content thereof is preferably 0.1 to
10 wt. %, in particular 0.25 to 5 wt. %, very particularly
preferably 0.4 to 3 wt. %. For strip production it is preferable
rather to employ only water and almost no or no organic solvent,
possibly apart from small amounts of alcohol.
[0195] It is furthermore advantageous to add at least one wetting
agent e.sub.7) in order to be able to apply the wet film uniformly
in the area extent and in the layer thickness as well as densely
and without defects. Many wetting agents are suitable in principle
for this, preferably acrylates, silanes, polysiloxanes, long-chain
alcohols, which reduce the surface tension of the aqueous
composition.
[0196] The coatings according to the invention can be largely or
completely free not only from chromium(VI) compounds but also from
chromium(III) compounds without thereby losing quality. Although it
is not normally intended in the context of the invention to add
environmentally hazardous chromium compounds e.sub.8), such as, in
particular, those of Cr.sup.6+, in rare cases of use this can
nevertheless be provided at the request of the customer. The
aqueous composition, which is preferably free or largely free from
chromium(VI) compounds, has only a chromium content of up to 0.05
wt. % on chromium-free metallic surfaces and a chromium content of
up to 0.2 wt. % on chromium-containing metallic surfaces; chromium
contents occurring in the bath can be dissolved out of the metallic
surface by pickling attack, can originate in traces from impurity
contents or can arrive carried in from previous baths or from tanks
and pipelines. Preferably, no chromium is consciously added to the
aqueous composition.
[0197] However, the process according to the invention can also
advantageously be employed with a content of at least one
chromium-containing compound if the corrosion protection is to be
retained in a wide range and with a high reliability, in particular
on damage to the protective layer which can be caused by mechanical
stresses during transportation, storage and assembly of the
substrates treated on the substrate surface with the treatment
liquid according to the invention. Sodium bichromate, potassium
bichromate or/and ammonium bichromate, for example, can then be
added. The content of chromium(VI) compounds is then preferably
0.01 to 100 g/l, particularly preferably 0.1 to 30 g/l.
[0198] Preferably, the aqueous composition can also contain at
least one basic crosslinking agent based on titanium, hafnium
or/and zirconium as the cation or/and based on carbonate or
ammonium carbonate as the anion, the content of such crosslinking
agents in the aqueous composition preferably being in the range
from 0.01 to 3 wt. %, particularly preferably in the range from
0.02 to 1.8 wt. %, very particularly preferably in the range from
0.05 to 1 wt. %.
[0199] Preferably, the aqueous composition contains at least one
additive, in particular at least one chosen from the group
consisting of at least one biocide, at least one defoamer or/and at
least one wetting agent.
[0200] Preferably, no acids, in particular no inorganic acids
or/and organic carboxylic acids, are added to the aqueous
composition--under certain circumstances with the exception of the
traces of acids contained hidden in the raw materials. In
particular, it is free or largely free from inorganic acids or/and
organic carboxylic acids, above all free from inorganic acids.
[0201] The aqueous composition according to the invention is
preferably free from additions of free fluoride, complex fluoride,
such as e.g. hexafluorotitanic acid or hexafluorozirconic acid,
or/and fluoride bonded in other ways.
[0202] Preferably, the aqueous composition is free or largely free
from heavy metals. In particular, contents of cadmium, nickel,
cobalt or/and copper should be kept extremely low and should not be
added. However, for the compositions according to the invention the
pickling attack is usually so low that no steel-refining agents,
such as e.g. chromium or nickel, can be dissolved out of a steel
surface.
[0203] Particularly advantageous compositions according to the
invention substantially contain, inter alia, at least one
copolymer, e.g. based on acrylic-polyester-polyurethane, styrene,
styrene-acrylate or/and ethylene-acrylate, as a film-forming agent,
at least one silane, at least one chelate, at least one
film-forming auxiliary based on a long-chain alcohol, at least one
inorganic compound in particle form, in particular based on
aluminium oxide, aluminium phosphide, iron oxide, iron phosphide,
mica, lanthanide oxide(s), e.g. based on cerium oxide, molybdenum
sulfide, graphite, carbon black, silicate, silicon dioxide,
colloidal silicon dioxide, zinc oxide or/and zirconium oxide,
optionally at least one lubricant, such as wax, optionally at least
one wetting agent, such as polysiloxanes, optionally at least one
organic corrosion inhibitor and optionally further additives, such
as, inter alia, a defoamer.
[0204] The metallic surface is preferably in a freshly produced,
clean or in a cleaned state. The term "clean metallic surface" here
means a non-cleaned metallic, e.g. freshly galvanized, surface on
which no cleaning is necessary, or a freshly cleaned surface.
[0205] Preferably, the aqueous composition is applied directly to
the metallic surface without applying a pretreatment composition
beforehand. For some uses it may nevertheless be advantageous to
apply at least one pretreatment layer, e.g. based on an alkali
metal phosphating, a zinc-containing phosphating, a pretreatment
containing rare earths, such as cerium, and/or at least one silane
beforehand.
[0206] To prepare the bath composition from a concentrate primarily
by dilution with water or for a topping-up solution for adjusting
the bath composition during relatively long operation of a bath,
aqueous compositions which contain most or almost all of the
constituents of the bath composition but as a rule not the at least
one organic compound in particle form, which is preferably kept
separately and added separately, are preferably used. Reaction and
drying accelerators, such as e.g. the morpholine salt of
paratoluenesulfonic acid, can also advantageously be added
separately. The concentrate and the topping-up solution preferably
have a concentration which is concentrated five times to ten times,
in respect of the individual constituents, as greatly as the bath
composition. In some cases, however, the "concentrate" can also be
used directly as the bath composition, optionally after a small
dilution by e.g. 5 to 30%.
[0207] In the process according to the invention, the aqueous
composition can preferably be applied to the metallic surface at a
temperature in the range from 5 to 50.degree. C., particularly
preferably in the range from 10 to 40.degree. C., very particularly
preferably in the range from 18 to 25.degree. C., or at 30 to
95.degree. C. In the process according to the invention, the
metallic surface can preferably be kept at temperatures in the
range from 5 to 60.degree. C. during application of the coating,
particularly preferably in the range from 10 to 55.degree. C., very
particularly preferably in the range from 18 to 25.degree. C., or
under certain circumstances also at 50 to 120.degree. C. In the
process according to the invention, the coated metallic surface can
preferably be dried at a temperature in the range from 20 to
400.degree. C. for the circulating air temperature, preferably in
the range from 40 to 120.degree. C., or in the range from 140 to
350.degree. C., very particularly preferably at 60 to 100.degree.
C. or at 160 to 300.degree. C. for the PMT (peak metal
temperature)--depending on the chemical composition of the organic
film-forming agent. The dwell time needed for drying is
substantially inversely proportional to the drying temperature:
e.g. for strip-like material 1 to 3 s at 100.degree. C. or 1 to 20
s at 250.degree. C., depending on the chemical composition of the
synthetic resins or polymers, or 30 min at 20.degree. C., while
polyester resins with free hydroxyl groups in combination with
melamine-formaldehyde resins cannot be dried at temperatures below
120.degree. C. On the other hand, coated shaped components, inter
alia depending on the wall thickness, must be dried for
significantly longer. Drying equipment based on circulating air,
induction, infra-red or/and microwaves are particularly suitable
for the drying. In the process according to the invention, the
coated strips can preferably be wound up to a coil, optionally
after cooling to a temperature in the range from 40 to 70.degree.
C.
[0208] In the process according to the invention, the aqueous
composition can preferably be applied by rolling on, flooding,
knife-coating on, spraying, misting, brushing or dipping and
optionally by subsequent squeezing off with a roller.
[0209] The layer thickness of the coating according to the
invention is preferably in the range from 0.1 to 6 .mu.m,
particularly preferably in the range from 0.2 to 5 .mu.m, very
particularly preferably in the range from 0.25 to 4 .mu.m, in
particular in the range from 0.3 to 2.5 .mu.m.
[0210] The coating properties of pendulum hardness and flexibility
are usually only of importance for coatings rich in organic
polymer/copolymer. The T-bend test is predominantly of importance
if the coating according to the invention is also provided
afterwards with at least one lacquer or with at least one
lacquer-like coating.
[0211] The dried and optionally also cured film preferably has a
pendulum hardness of 30 to 190 s, preferably 50 to 180 s, measured
with a Konig pendulum hardness tester in accordance with DIN 53157.
However, in some cases the Konig pendulum hardness is preferably in
the range from 60 to 150 s, particularly preferably in the range
from 80 to 120 s. Values of the pendulum hardness in the range from
100 to 150 s often occur in UV-crosslinkable coatings, while values
of the pendulum hardness in the range from 40 to 80 s may occur in
the coatings which are not UV-crosslinkable or are based e.g. on
polymer dispersions which do not or scarcely crosslink chemically.
The layers produced according to the invention are to be tested
only on test specimens with chemically the same but sufficiently
thick layers, but not on thin coatings in the range up to 10 .mu.m
thickness.
[0212] The dried and optionally also cured film preferably has a
flexibility such that on bending over a conical mandrel in a
mandrel flex test substantially according to DIN ISO 6860 for a
mandrel of 3.2 mm to 38 mm diameter--but without tearing the test
area--no cracks longer than 2 mm are formed that are detectable
during subsequent wetting with copper sulfate by a change in colour
as a result of deposition of copper on the cracked-open metallic
surface. The term "substantially" here means that thicker films are
conventionally characterized, and for this reason a copper sulfate
test also follows here, which can reveal the defects which
otherwise under certain circumstances are not visible.
Demonstration of the flexibility by using the mandrel flex test and
subsequent dipping of the regions shaped in this manner in a copper
sulfate solution to detect defects provides a reproducible test
result and has the advantage that no expensive corrosion tests,
e.g. lasting 240 h, which in some cases, depending on the chemical
composition and roughness of the metallic surface, can lead to
different results which therefore can be compared with one another
to only a limited extent, are necessary for this. In the case of
baser metallic surfaces, such as aluminium alloys, for this test it
is necessary first to clean the metallic surface once by pickling
before the coating, in order substantially to remove the oxide
layer.
[0213] The area proportions of the detached area in the T-bend test
on shaped components (metal sheets) coated according to the
invention and then with coil coating lacquer are preferably only up
to 8%, particularly preferably up to 5%, very particularly
preferably up to 2%, but the best values are at approximately 0%,
so that then usually only cracks occur. A coil coating lacquer
based on silicone polyester can preferably be employed for this, in
particular for comparative tests in tests typical for coated coils.
The absence of cracking or the size of the cracks here, however,
also depends largely on the nature of the lacquer employed.
[0214] In the process according to the invention, in each case at
least one coating of printing ink, foil, lacquer, lacquer-like
material, powder coating, adhesive or/and adhesive carrier can
preferably be applied to the dried and optionally also cured
film.
[0215] In each case at least one coating of lacquer, polymer,
paint, functional coatings of plastic, adhesive or/and adhesive
carrier, such as e.g. a self-adhesive film, can be applied to the
partly or completely dried or cured film, in particular a wet
lacquer, a powder coating, a coating of plastic, an adhesive, inter
alia for foil coating. The metal components coated according to the
invention with the aqueous composition, in particular strips or
strip sections, can be shaped, lacquered, coated with polymers,
such as e.g. PVC, printed, glued, hot-soldered, welded or/and
joined to one another or to other elements by clinching or other
joining techniques. These processes are known in principle for
coating of metallic strip for architectural uses. As a rule,
lacquering or coating of another type is first carried out, and
then shaping. If the coating according to the invention is
lacquered or coated with plastic, solder or weld connections
usually cannot be established without the coatings being removed at
least locally, unless, for electrical welding, a high content of
conductive particles or/and conductive polymer is incorporated into
the film according to the invention and the subsequent coating is
exceptionally thin.
[0216] The substrates coated according to the invention can
preferably be used as wire, strip, sheet metal or a component for a
wire coil, a braided wire, a steel strip, a metal sheet, a lining,
a screen, a vehicle body or a component of a vehicle body, a
component of a vehicle, trailer, mobile home or missile, a cover, a
housing, a lamp, a light, a traffic light element, a piece of
furniture or furniture element, an element of a domestic appliance,
a frame, a profile, a shaped component of complicated geometry, a
crash barrier, heater or fence element, a bumper, a component of or
with at least one tube or/and a profile, a window, door or bicycle
frame or an item of hardware, such as a screw, nut, flange, spring,
or a spectacle frame.
[0217] The process according to the invention is an alternative to
on the one hand the chromate-rich acid-free and on the other hand
acid-containing processes mentioned, in particular in the field of
surface pretreatment of metal strip before lacquering, and compared
with these gives comparably good results in respect of corrosion
protection and lacquer adhesion.
[0218] It is moreover possible to employ the process according to
the invention for treatment of metal surfaces cleaned in the
conventional manner but without subsequent after-treatment, such as
rinsing with water or a suitable after-rinsing solution. The
process according to the invention is particularly suitable for
application of the treatment solution by means of squeeze-off
rollers or by means of a so-called roll coater, it being possible
for the treatment solution to be dried directly after the
application without further intermediate process steps (Dry in
Place technology). By this means, the process is simplified
considerably e.g. compared with conventional spraying or dipping
processes, in particular those with subsequent rinsing operations,
such as e.g. a chromating or zinc phosphating, and only very small
amounts of rinsing water for cleaning the unit after the end of
work are produced, since no rinsing process after the application
is necessary, which also represents an advantage compared with the
already established chromium-free processes which operate by the
spraying process with after-rinsing solutions. These rinsing waters
can be added again to a new batch of the bath composition.
[0219] It is easily possible here to employ the polymeric,
optionally chromate-free coating according to the invention without
prior application of an additional pretreatment layer, so that an
outstanding permanent protection of the metallic surfaces, and in
particular on AlSi, ZnAl, such as GALFAN.RTM., AlZn, such as,
GALVALUME.RTM. ZnFe, ZnNi, such as GALVANNEAL.RTM. and other Zn
alloys as metallic coatings or Al and Zn coatings, is possible,
which can be achieved by application of a polymer-containing
coating. Moreover, the coating according to the invention has also
proved particularly suitable for metallic surfaces which are highly
susceptible to corrosion, such as those of iron and steel alloys,
in particular on cold-rolled steel, it then being advantageous to
add at least one corrosion inhibitor to the aqueous composition.
Flash rust formation during drying of the treatment liquid on
cold-rolled steel (CRS) can be suppressed by this means.
[0220] A less expensive and more environment-friendly corrosion
protection which also does not require an expensive UV curing but
can be cured adequately solely with drying and film formation and
optionally additionally with the "usual chemical" curing, which is
often called "thermal crosslinking", can thus be achieved. In some
cases, however, it may be of interest to obtain a harder coating
quickly in a particular process step. It can then be advantageous
if at least one photoinitiator is added and at least one UV-curable
polymer component is chosen in order to achieve a partial
crosslinking on the basis of actinic radiation, in particular UV
radiation. The coating according to the invention can then be cured
partly by actinic radiation and partly by drying and film formation
or by thermal crosslinking. This can be of importance in particular
during application to fast-running belt lines or for the first
crosslinking (=curing). The content of so-called UV crosslinking
here can be 0 to 50% of the total possible curing, preferably 10 to
40%.
[0221] The polymeric and largely or completely chromate-free
coating according to the invention furthermore has the advantage
that--especially at a layer thickness in the range from 0.5 to 3
.mu.m--it is transparent and light-coloured, so that the metallic
character and the typical structure e.g. of a galvanized or a
GALVALUME.RTM. surface can still be seen accurately and unchanged
or virtually unchanged through the coating. Furthermore, such thin
coatings can also be welded without problems.
[0222] The polymeric coating according to the invention moreover is
very readily shapable, so that it can be adjusted such that after
the coating, drying and optionally curing and optionally also in
the long term it is in a relatively plastic and not in a hard,
brittle state.
[0223] The polymer-containing coating according to the invention
can be readily over-lacquered with most lacquers or plastics. The
polymer-containing coating according to the invention can be
after-lacquered or coated with plastic, such as PVC, by application
processes such as e.g. powder coating, wet lacquering, flooding,
rolling, brushing or dipping. The cured coatings produced by this
means which are applied to the polymer-containing coating according
to the invention, it often also being possible to apply two or
three layers of lacquer or plastic, usually have a total layer
thickness in the range from 5 to 1,500 .mu.m.
[0224] The polymeric coating according to the invention can also be
foamed on the reverse without problems, e.g. with polyurethane
insulating foam, for the production of 2-sheet sandwich elements,
or can readily be glued with the conventional construction
adhesives such as are employed e.g. in vehicle construction.
[0225] The coatings according to the invention can be employed
above all as primer layers. They are outstandingly suitable
without, but also with, at least one previously applied
pretreatment layer. This pretreatment layer can then be, inter
alia, a coating based on phosphate, in particular ZnMnNi phosphate,
or based on phosphonate, silane or/and a mixture based on a
fluoride complex, corrosion inhibitor, phosphate, polymer or/and
finely divided particles.
[0226] Pretreatment layers or primer layers which, together with
the subsequently applied lacquer, resulted in a coating system
equivalent to the best chromium-containing coating systems are
achieved with the coatings according to the invention.
[0227] The process according to the invention furthermore has the
advantage over the processes described and/or practised to date
that on an aluminium-rich substrate or on a substrate coated with
an aluminium-containing alloy--in particular a substrate of
steel--it caused no darkening of the substrate surface and also no
milky-white matting of the substrate surface and can therefore be
employed for decoration of buildings or/and building components
without additional colouring lacquering. The aesthetics of the
metal surface remain unchanged.
[0228] The coatings according to the invention are exceptionally
inexpensive, environment-friendly and readily usable on a large
industrial scale.
[0229] It was surprising that in spite of a layer thickness of only
approx. 0.5 to 2 .mu.m, it was possible to produce an exceptionally
high-quality chromium-free film with a synthetic resin coating
according to the invention.
[0230] It was very surprising that by the addition of metal chelate
to the aqueous composition it was possible to achieve a significant
increase in the corrosion protection and also lacquer adhesion of
the film formed therefrom--both in the case of aqueous compositions
that contain predominantly chelate and silane and in the case of
those that contain predominantly synthetic resin and in addition
chelate and silane.
[0231] The adhesion-promoting action of the silanes and of their
reaction products, in particular between the metallic substrate and
lacquer and optionally between pigment and organic lacquer
constituents, should also prevail in the compositions such as are
described here in the embodiment examples, or even occur by itself,
as long as polymers and chelate are not simultaneously present. It
had not been expected that at high contents of
high-molecular-weight polymers and copolymers, without the presence
of low-molecular-weight organic contents, a significant improvement
in the film properties would be achieved by the addition of
chelate. The high-molecular-weight polymers and copolymers are
possibly crosslinked by the presence of chelate, which is
particularly advantageous in particular for those film-forming
systems which have no contents of curing agent and photoinitiator.
Exposure to relatively high temperatures, such as are otherwise
used for thermal crosslinking, and free-radical irradiation, which
are an additional expensive process step, can be avoided by this
means.
EXAMPLES AND COMPARISON EXAMPLES
[0232] The examples described below are intended to explain the
subject matter of the invention in more detail.
A) Compositions Substantially Based on Chelate and Silane:
[0233] For preparation of aqueous concentrates, at least one partly
hydrolysed silane was aged for at least two weeks and optionally
also thereby hydrolyzed. Thereafter, a metal chelate according to
table 1 was added. The concentrates were then diluted with water,
and an agent which adapts the pH, such as ammonia, was optionally
added in order to obtain ready-to-use treatment liquids. In each
case 3 metal sheets of hot-galvanized steel or of GALVALUME.RTM.
steel sheet were then brought into contact by rolling on and drying
on the corresponding treatment liquid at 25.degree. C. The metal
sheets treated in this way were dried here at 90.degree. C. PMT and
then tested for their corrosion protection.
[0234] Examples E 1 to E 8, including comparison example CE 4, show
the influence of the addition of chelate or of chelate and polymer
mixture. In examples E 9 to E 12 and E 13 to E 17, the amounts of
silane and chelate were increased and at the same time the addition
of inorganic particles was reduced, these two series differing by
different amounts of polymer mixture added. Finally, the layer
thicknesses were varied in examples E 9 and E 18 to E 20.
TABLE-US-00001 TABLE 1 Compositions based on chelate and silane and
in some cases also inorganic particles, data in wt. % for
concentrates and g/l for the treatment baths Examples/comparison
example E 1 E 2 E 3 CE 4 E 5 E 6 E 7 E 8 E 9 E 10 Concentrates
Organofunct. silane A 15 15 15 30 -- 15 15 3.3 1.7 5.1 Organofunct.
silane B -- -- -- -- 15 -- -- -- -- -- Titanium chelate D 17.5 17.5
17.5 -- -- -- -- 3.9 2 5.9 Zirconium chelate E -- -- -- -- 17.5 --
-- -- -- -- Zirconium chelate F -- -- -- -- -- 17.5 -- -- -- --
Titanium chelate G -- -- -- -- -- -- 17.5 -- -- -- SiO.sub.2
particles <0.2 .mu.m -- -- -- -- -- -- -- 11 13 9
Ethanol/methanol not added, may be formed Ammonia small amounts
added to adjust the pH to 8.3 Polymer mixture -- -- -- -- -- -- --
7 7 7 Water 67.5 67.5 67.5 70.0 67.5 67.5 67.5 74.8 76.3 73 Total
100 100 100 100 100 100 100 100 100 100 Batches for the treatment
baths Concentrate 10 20 30 20 20 20 20 53 53 53 Water 90 80 70 80
80 80 80 47 47 47 Treatment baths Water 968 936 904 936 936 936 936
866.6 874.5 857.0 Organometal comp. 17 34 51 -- 34 34 34 20.7 10.6
31.3 Silane 15 30 45 64 30 30 30 17.5 9.0 27.0 Acrylic-polyester-
-- -- -- -- -- -- -- 15 15 15 polyurethane copolymer
Styrene-acrylate copolymer -- -- -- -- -- -- -- 16.7 16.7 16.7
Colloidal SiO.sub.2 -- -- -- -- -- -- -- 58.3 68.9 47.7
Polysiloxane -- -- -- -- -- -- -- 1 1 1 Defoamer -- -- -- -- -- --
-- 1 1 1 Long-chain alcohol -- -- -- -- -- -- -- 3.3 3.3 3.3 pH 8.3
8.3 8.3 8.3 8.3 8.3 8.3 8.3 8.3 8.3 Film properties Layer weight,
g/m.sup.2 0.2 0.4 0.6 0.2 0.4 0.4 0.4 0.8 0.8 0.8 Salt spray test
48 h 10 <2 0 30 <2 <2 <2 0 0 0 ASTM B117-73: 96 h 20 10
<2 60 10 10 10 0 0 0 Area of corrosion 120 h 40 20 5 90 20 20 20
<2 0 <2 in % after 240 h 60 40 10 100 40 40 40 10 0 10 360 h
100 60 30 100 60 60 60 20 <2 30 Examples/comparison example E 11
E 12 E 13 E 14 E 15 E 16 E 17 E 18 E 19 E 20 Concentrates
Organofunct. silane A 7.5 11.6 2 1.2 3.3 5.1 7.8 1.7 1.7 1.7
Organofunct. silane B -- -- -- -- -- -- -- -- -- -- Titanium
chelate D 8.8 13.7 3.1 1.3 3.9 5.9 9.1 2 2 2 Zirconium chelate E --
-- -- -- -- -- -- -- -- -- Zirconium chelate F -- -- -- -- -- -- --
-- -- -- Titanium chelate G -- -- -- -- -- -- -- -- -- -- SiO.sub.2
particles <0.2 .mu.m 6 -- 7 9 6 4 -- 13 13 13 Ethanol/methanol
not added, may be formed Ammonia small amounts added to adjust the
pH to 8.3 Polymer mixture 7 7 4.5 4.5 4.5 4.5 4.5 7 7 7 Water 70.7
67.7 83.4 84 82.3 80.5 78.6 76.3 76.3 76.3 Total 100 100 100 100
100 100 100 100 100 100 Batches for the treatment baths Concentrate
53 53 53 53 53 53 53 40 27 13 Water 47 47 47 47 47 47 47 60 73 87
Treatment baths Water 844.8 828.9 912.2 915.3 906.3 896.8 886.7
905.1 936.1 969.3 Organometal comp. 46.6 72.6 16.4 6.9 20.7 31.3
48.2 8.0 5.4 2.6 Silane 39.8 61.5 10.6 6.4 17.5 27.0 41.3 6.8 4.6
2.2 Acrylic-polyester- 15 15 9.7 9.7 9.7 9.7 9.7 11.4 7.7 3.7
polyurethane copolymer Styrene-acrylate copolymer 16.7 16.7 10.7
10.7 10.7 10.7 10.7 12.6 8.4 4.1 Colloidal SiO.sub.2 31.8 -- 37.1
47.7 31.8 21.2 -- 52 35.1 16.9 Polysiloxane 1 1 0.6 0.6 0.6 0.6 0.6
0.8 0.5 0.2 Defoamer 1 1 0.6 0.6 0.6 0.6 0.6 0.8 0.5 0.2 Long-chain
alcohol 3.3 3.3 2.1 2.1 2.1 2.1 2.1 2.5 1.7 0.8 pH 8.3 8.3 8.3 8.3
8.3 8.3 8.3 8.3 8.3 8.3 Film properties Layer weight, g/m.sup.2 0.8
0.8 0.5 0.5 0.5 0.5 0.5 0.6 0.4 0.2 Salt spray test 48 h 20 30 0 0
0 30 40 0 0 0 ASTM B117-73: 96 h 30 40 0 0 0 40 60 0 0 <2 Area
of corrosion 120 h 50 60 0 0 0 50 80 0 <2 5 in % after 240 h 70
80 10 <2 10 70 100 <2 5 10 360 h 100 100 20 5 30 100 100 5 10
30
[0235] The film formed here was transparent, uniform and closed.
The films formed showed no coloration and showed no darkening of
the underlying metallic surface. This is particularly advantageous
in order to be able to see structure, gloss and colour of the
metallic surface practically unchanged through the coating. The
combination of chelate and silane already resulted in a very clear
improvement in the corrosion protection at very low layer
thicknesses compared with a composition which is free from
organometallic compounds. Further examples moreover showed that in
particular a higher addition of inorganic particles, in this case
based on SiO.sub.2 having an average particle size in the range
from 10 to 20 nm, made a further additional contribution to the
improvement in corrosion resistance. It was surprising here that
beyond small additions of such particles, an increase in the
content of inorganic particles also rendered possible a clear
increase in corrosion protection. Astonishingly, in spite of the
sometimes high content of inorganic particles, a closed and
nevertheless flexible film which was resistant to mechanical
influences was possible after the coating had formed a film. The
layer weight approximately divided by 1.1 gives the layer thickness
in .mu.m. The area proportions of the corrosion were estimated
visually. Due to the comparatively low contents of synthetic
resin(s), this thin film has rather the properties of a passivation
instead of a thin organic coating, which can be shaped. The film of
example 9 about 0.75 .mu.m thin is indeed thicker than a typical
chromate-rich inorganic passivation, but shows at least the same
good corrosion resistance and furthermore, in contrast to the
chromate-rich layer, can readily be shaped.
* * * * *