U.S. patent application number 09/323632 was filed with the patent office on 2001-07-12 for corrosion-stable aluminum pigments and process for the production thereof.
Invention is credited to KAUPP, GUNTER, OSTERTAG, WERNER, SOMMER, GUNTER.
Application Number | 20010007696 09/323632 |
Document ID | / |
Family ID | 7804119 |
Filed Date | 2001-07-12 |
United States Patent
Application |
20010007696 |
Kind Code |
A1 |
KAUPP, GUNTER ; et
al. |
July 12, 2001 |
CORROSION-STABLE ALUMINUM PIGMENTS AND PROCESS FOR THE PRODUCTION
THEREOF
Abstract
In aluminum-based metal pigments produced by physical vapor
deposition of a metal film and subsequent crushing of the metal
film metal surfaces which are exposed after the operation of
crushing the metal film and in particular fracture surfaces thereof
are covered with a passivating protective layer to afford corrosion
stability of those metal pigments.
Inventors: |
KAUPP, GUNTER; (NEUHAUS,
DE) ; OSTERTAG, WERNER; (GRUNSTADT, DE) ;
SOMMER, GUNTER; (LAUF, DE) |
Correspondence
Address: |
CHARLES R HOFFMANN ESQ
HOFFMANN & BARON LLP
6900 JERICHO TURNPIKE
SYOSSET
NY
11791
|
Family ID: |
7804119 |
Appl. No.: |
09/323632 |
Filed: |
June 1, 1999 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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09323632 |
Jun 1, 1999 |
|
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08910978 |
Aug 7, 1997 |
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Current U.S.
Class: |
427/216 ;
427/220; 427/250; 427/327 |
Current CPC
Class: |
C01P 2004/84 20130101;
C08K 9/02 20130101; C08K 9/08 20130101; C09C 1/648 20130101; C09C
1/642 20130101; C23C 14/58 20130101; C08K 9/04 20130101; Y10T
428/2991 20150115; Y10T 428/2993 20150115; C09D 5/103 20130101;
C23C 14/0005 20130101; C23C 22/05 20130101; C01P 2004/61 20130101;
C01P 2004/86 20130101; C23C 14/20 20130101; C09D 11/037
20130101 |
Class at
Publication: |
427/216 ;
427/220; 427/327; 427/250 |
International
Class: |
B05D 003/12; B05D
007/00; C23C 016/00 |
Claims
What is claimed is:
1. Aluminum-based metal pigment produced by physical vapor
deposition (PVD) of a metal film and crushing thereof, wherein all
metal surfaces which are exposed after the step of crushing the
metal film produced by PVD are covered with a passivating
protective layer.
2. Metal pigment as set forth in claim 1 wherein said metal
surfaces include fracture surfaces of the metal pigment
particles.
3. Metal pigment as set forth in claim 1 which to produce variable
color effects has a multi-layer structure of the type M'TMTM',
wherein M' is a semi-transparent aluminum layer, T is a transparent
low-refracting dielectric and M is a highly reflecting opaque
aluminum layer, and wherein the passivating protective layer is
additionally applied to the layer M' and also extends over fracture
surfaces of the pigment particles.
4. Metal pigment as set forth in claim 3 wherein at least one of
said aluminum layers is an aluminum-based metal layer.
5. Metal pigment as set forth in claim 1 wherein the passivating
protective layer comprises at least one substance selected from the
group consisting of carboxylic acids, phosphoric acids, phosphonic
acids and derivatives of said substances with between 8 and 20
C-atoms and salt-like compounds of the substances of said
group.
6. Metal pigment as set forth in claim 1 wherein the passivating
protective layer comprises at least one metal oxide layer of at
least one metal of the group consisting of B, Al, Sn, Ti, V, Cr,
Mo, Zn and Ce.
7. Metal pigment as set forth in claim 1 wherein the passivating
protective layer comprises at least one metal oxide hydrate layer
of at least one metal of the group consisting of B, Al, Sn, Ti, V,
Cr, Mo, Zn and Ce.
8. Metal pigment as set forth in claim 1 wherein the passivating
protective layer comprises a substance from the group consisting of
organically modified silicate, titanate, zirconate and aluminum
zirconate.
9. Metal pigment as set forth in claim 1 wherein the passivating
protective layer comprises an organic polymer based on at least one
acrylate.
10. Metal pigment as set forth in claim 1 wherein the passivating
protective layer comprises an organic polymer based on at least one
methacrylate.
11. Metal pigment as set forth in claim 3 wherein at least one said
metal layer comprises a corrosion-stable aluminum alloy.
12. Metal pigment as set forth in claim 11 wherein said aluminum
alloy is a chromium-bearing aluminum alloy.
13. A process for producing a corrosion-stable aluminum-based metal
pigment comprising producing a metal film by means of physical
vapor deposition (PVD) and subsequent crushing of the metal film
produced, wherein the pigment obtained by the crushing operation is
treated with at least one substance selected from the group
consisting of carboxylic acids, phosphonic acids, phosphoric acids,
phosphomolybdic acid, alcohols, amines, amides and derivatives of
said substances to produce a passivating protective layer on the
free metal surfaces of the pigment.
14. A process as set forth in claim 13 wherein the pigment is
treated with a derivative having between 8 and 20 C-atoms of said
substances.
15. A process as set forth in claim 13 wherein the pigment is
treated in a solution of at least one salt-like compound of said
substances.
16. A process as set forth in claim 13 wherein the pigment is
treated in a solution of at least one salt-like compound of said
derivatives.
17. A process for producing a corrosion-stable aluminum-based metal
pigment comprising producing a metal film by means of physical
vapor deposition (PVD) and subsequent crushing of the metal
produced, wherein at least one of a metal oxide layer and a metal
oxide hydrate layer is deposited as a passivating protective layer
on the free metal surfaces of the pigment obtained by the crushing
operation, by hydrolysis of at least one of salts and metal acid
esters from the group consisting of B, Al, Sn, Ti, V, Cr, Mo, Zn
and Ce.
18. A process for producing a corrosion-stable aluminum-based metal
pigment comprising producing a metal film by means of physical
vapor deposition (PVD) and subsequent crushing of the metal film
produced, wherein a layer of a substance from the group consisting
of an organically modified silicate, titanate, zirconate and
aluminum zirconate layer is applied as a passivating protective
layer to the free metal surfaces of the pigment obtained by the
crushing operation from a suitable organic solution.
19. A process for producing a corrosion-stable aluminum-based metal
pigment comprising producing a metal film by means of physical
vapor deposition (PVD) and subsequent crushing of the metal film
produced, wherein a layer of a substance from the group consisting
of an organically modified silicate, titanate, zirconate and
aluminum zirconate layer is applied as a passivating protective
layer to the free metal surfaces of the pigment obtained by the
crushing operation by hydrolysis of a suitably modified metal acid
ester.
20. A process for producing a corrosion-stable aluminum-based metal
pigment comprising producing a metal film by means of physical
vapor deposition (PVD) and subsequent crushing of the metal film
produced, wherein an organic polymer layer based on at least one
substance selected from acrylates and methacrylates is applied as a
passivating protective layer to the free metal surfaces of the
pigment obtained by the crushing operation by radical
polymerization in solution.
21. A process as set forth in claim 13 wherein the operation of
applying the passivating protective layer to the free metal
surfaces of the pigment particles is effected during the operation
of crushing the metal film produced by PVD.
22. A process as set forth in claim 17 wherein the operation of
applying the passivating protective layer to the free metal
surfaces of the pigment particles is effected during the operation
of crushing the metal film produced by PVD.
23. A process as set forth in claim 18 wherein the operation of
applying the passivating protective layer to the free metal
surfaces of the pigment particles is effected during the operation
of crushing the metal film produced by PVD.
24. A process as set forth in claim 19 wherein the operation of
applying the passivating protective layer to the free metal
surfaces of the pigment particles is effected during the operation
of crushing the metal film produced by PVD.
25. A process as set forth in claim 20 wherein the operation of
applying the passivating protective layer to the free metal
surfaces of the pigment particles is effected during the operation
of crushing the metal film produced by PVD.
26. A process as set forth in claim 13 wherein a substance forming
at least a component of the passivating protective layer forms a
release layer in production of the aluminum pigment by means of PVD
and wherein during the operation of crushing the metal film the
release layer is detached and applied as a protective layer to the
free metal surfaces of the metal particles.
27. A process as set forth in claim 17 wherein a substance forming
at least a component of the passivating protective layer forms a
release layer in production of the aluminum pigment by means of PVD
and wherein during the operation of crushing the metal film the
release layer is detached and applied as a protective layer to the
free metal surfaces of the metal particles.
28. A process as set forth in claim 18 wherein a substance forming
at least a component of the passivating protective layer forms a
release layer in production of the aluminum pigment by means of PVD
and wherein during the operation of crushing the metal film the
release layer is detached and applied as a protective layer to the
free metal surfaces of the metal particles.
29. A process as set forth in claim 19 wherein a substance forming
at least a component of the passivating protective layer forms a
release layer in production of the aluminum pigment by means of PVD
and wherein during the operation of crushing the metal film the
release layer is detached and applied as a protective layer to the
free metal surfaces of the metal particles.
30. A process as set forth in claim 20 wherein a substance forming
at least a component of the passivating protective layer forms a
release layer in production of the aluminum pigment by means of PVD
and wherein during the operation of crushing the metal film the
release layer is detached and applied as a protective layer to the
free metal surfaces of the metal particles.
31. A process as set forth in claim 13 wherein a substance forming
at least a component of the passivating protective layer forms a
release layer in production of the aluminum pigment by means of PVD
and wherein during the operation of crushing the metal film the
release layer is detached and by the addition of a suitable
protective layer component reacted with same and the resulting
reaction product is applied as the protective layer.
32. A process as set forth in claim 17 wherein a substance forming
at least a component of the passivating protective layer forms a
release layer in production of the aluminum pigment by means of PVD
and wherein during the operation of crushing the metal film the
release layer is detached and by the addition of a suitable
protective layer component reacted with same and the resulting
reaction product is applied as the protective layer.
33. A process as set forth in claim 18 wherein a substance forming
at least a component of the passivating protective layer forms a
release layer in production of the aluminum pigment by means of PVD
and wherein during the operation of crushing the metal film the
release layer is detached and by the addition of a suitable
protective layer component reacted with same and the resulting
reaction product is applied as the protective layer.
34. A process as set forth in claim 19 wherein a substance forming
at least a component of the passivating protective layer forms a
release layer in production of the aluminum pigment by means of PVD
and wherein during the operation of crushing the metal film the
release layer is detached and by the addition of a suitable
protective layer component reacted with same and the resulting
reaction product is applied as the protective layer.
35. A process as set forth in claim 20 wherein a substance forming
at least a component of the passivating protective layer forms a
release layer in production of the aluminum pigment by means of PVD
and wherein during the operation of crushing the metal film the
release layer is detached and by the addition of a suitable
protective layer component reacted with same and the resulting
reaction product is applied as the protective layer.
36. Use of a metal pigment as set forth in claim 1 in paints,
lacquers, printing inks and plastic materials.
Description
FIELD OF THE INVENTION
[0001] The present invention concerns corrosion-stable aluminum
pigments produced by physical vapor deposition and a process for
the stabilization thereof.
BACKGROUND OF THE INVENTION
[0002] Pigments which are produced by way of physical vapor
deposition (PVD) of single-layer or multi-layer films on a carrier,
subsequent detachment and then crushing of the films or film packs
are becoming of increasing interest in very recent times because of
their special optical properties. Thus for example single-layer
aluminum pigment which is produced by way of PVD and which is known
under the name METALURE (registered mark) is highly valued in the
printing and paints industry because of its outstanding mirror
shine while multi-layer so-called optically variable pigments which
have brilliant interference colors and which produce pronounced
angle-dependent color shade variations are increasingly used in
paints, plastic materials and in bond printing.
[0003] The single-layer aluminum scales or flakes with a very high
degree of shine of the above-mentioned aluminum pigment are
produced by vacuum deposition on a substrate provided with a
release layer, subsequent detachment of the aluminum film, and
mechanical crushing thereof. The thickness of the film particles is
generally less than 100 nm. The scale or flake surface is
mirror-smooth and is of the highest level of perfection. The flake
or scale surface can however also have a hologram-like embossing
(WO 93/23481). Depending on the embossing involved such flakes
appear in variable colors.
[0004] The basic structure of optically variable multi-layer
pigments is as follows: following a central highly reflective metal
layer M, towards each side, is a transparent low-refractive layer T
and then a semi-transparent metal layer M'. Films which involve a
multi-layer structure of the type M'TM have been known for many
years (see Optical Acta 20, 925-937 (1973) and U.S. Pat. No.
3,858,977). Pigments which embody the optical principle which is
applicable in respect of films and which have the above-mentioned
layer sequence M'TMTM' were first described in U.S. Pat. No.
3,438,796. The flake-like pigment particles, envisaged for the area
of use of decorative paints and lacquers, exhibit brilliant colors
and comprise a highly reflective, central aluminum layer which is
at least 60 nm in thickness and which is accompanied in an outward
direction by a respective SiO.sub.2-layer which is between 100 and
600 nm in thickness and which is then followed by a
semi-transparent aluminum layer which is between 5 and 40 nm in
thickness. Thereover there is also an SiO.sub.2-protective layer.
The production of such pigments is effected by vapor deposition of
subsequent layers and then crushing of the multi-layer film to the
particle size of special-effect pigments. So as to facilitate
detachment of the film from the substrate it is covered with a
release layer. The color of the pigments produced in that way
depends on the thickness of the SiO.sub.2-layers. Each color shade
of the spectrum can be specifically set by way of the choice of the
thickness of the SiO.sub.2-layers. Higher-order interference colors
are also possible.
[0005] Pigments involving a similar structure and a similar
production process are described in U.S. Pat. No. 5,135,812 and
EP-A227 423. Those pigments have a multi-layer structure, wherein
the central opaque layer comprises a highly reflective metal layer,
generally aluminum, the transparent layers which follow it in an
outward direction comprise MgF.sub.2 or SiO.sub.2 (refractive index
n<1.65) and a semi-transparent or semi-opaque metal layer. The
area of use is printing inks for forgery-resistant banknotes. The
pigments are produced by physical vapor deposition in a vacuum and
then crushing of the multi-layer film, generally in an ultrasonic
crusher, to pigment particle size.
[0006] The pigments described in the above-indicated patents suffer
from the disadvantage that they are susceptible to corrosion by
virtue of exposed metal surfaces. Admittedly the pigments which are
produced from films manufactured by vapor deposition in a
multi-layer structure can already be passivated on the large
surfaces of the pigment particles by the production of a protective
layer in the vapor deposition process, as was effected in
accordance with U.S. Pat. No. 3,438,796. The operation of crushing
the multi-layer film however also gives rise to fresh fracture
locations which, due to the procedure involved, are unprotected and
are therefore highly sensitive to corrosion. Particularly in the
presence of moisture, acids or bases, the chemical reactivity of
the fresh fracture locations results in corrosion and thus
inevitably results in an impairment in the brilliance and
coloristics of the pigment scales or flakes. That represents a
serious problem in terms of technical application. U.S. Pat. No.
5,498,781 described an initial attempt at passivating optically
variable pigments for aqueous coating systems. The ready-for-sale,
optically variable pigment powder was thereafter surface-coated
with a silane compound of the type R.sub.3 Si--A--X, specifically
(CH.sub.3CH.sub.2O).sub.3 Si(CH.sub.2).sub.3 NH.sub.2 in an aqueous
alcohol solution, tempered at 110.degree. C. and then reacted in an
alcohol solution with a polymer bearing functional isocyanate
groups.
[0007] The result is a finished lacquer or paint as is used for the
decorative surface coating of motor vehicles. Thus the passivation
operation described in U.S. Pat. No. .sub.5,498,781 leads to a
single system of use and lacks the multiple and varied use options
of a passivated pigment. A further disadvantage of that passivation
process is that the corrosion processes have already begun at the
endangered fracture edges of the optically variable pigments when
treatment of the finished pigment powder begins.
SUMMARY OF THE INVENTION
[0008] An object of the present invention is to improve the
corrosion characteristics of pigments produced by PVD and
subsequent crushing of the films.
[0009] Another object of the invention is to provide pigments
produced by PVD and then crushing, which remain substantially
stable even in aggressive aqueous such as acid or alkaline or
solvent-based agents.
[0010] A further object of the invention is to provide that fresh
fracture locations which are produced by a film-crushing operation,
in relation to optically variable multi-layer pigments, more
especially fracture locations of a central, highly reflective
aluminum layer, are passivated.
[0011] A still further object of the invention is a process for the
stabilization of aluminum-based metal pigments manufactured by
physical vapor deposition and subsequent crushing of the metal film
produced.
[0012] In accordance with the invention the foregoing and other
objects are attained by an aluminum-based metal pigment produced by
physical vapor deposition (PVD), wherein all metal surfaces and in
particular fracture surfaces of the metal pigment particles, which
are exposed after the step of crushing a metal film produced by
PVD, are covered with a passivating protective layer.
[0013] In regard to the process aspect the foregoing and other
objects are attained by a process for producing corrosion-stable
aluminum-based metal pigment manufactured by means of physical
vapor deposition (PVD) and subsequent crushing of the metal film
produced. The pigment obtained by the crushing operation is treated
with one or more substances of the group consisting of carboxylic
acids, phosphonic acids, phosphoric acids, phosphomolybdic acid,
alcohols, amines, amides and derivatives of said substances.
Alternatively a metal oxide and/or metal hydroxide layer is
deposited as a passivating protective layer on the free metal
surfaces of the pigment obtained by the crushing operation, by
hydrolysis of salts or metal acid esters from the group consisting
of B, Al, Sn, Ti, V, Cr, Mo, Zn and Ce. Alternatively again an
organically modified silicate, titanate, zirconate or aluminium
zirconate layer is applied as a passivating protective layer to the
free metal surfaces of the pigment obtained by the crushing
operation from suitable organic solutions or by hydrolysis of
suitably modified metal acid esters. A further alternative is that
an organic polymer layer based on acrylates and/or methacrylates is
applied as a passivating protective layer to the free metal
surfaces of the pigment obtained by the crushing operation by
radical polymerization in solution.
[0014] As will be seen in greater detail hereinafter from examples
the invention provides that all exposed metal surfaces are covered
with a very firmly adhering passivating layer with a barrier
function. In that respect it is preferred that, in terms of the
process of the invention, the passivating layer is applied during
the film crushing step, that is to say therefore it is formed in
situ directly in the production of fresh fracture edges. The
chemically applied passivating protective layer must be of a nature
such that - insofar as the large surfaces of the pigment particles
are unprotected - the protective layer is deposited on the large
surfaces of the pigment particles but also in particular covers
over the fracture surfaces. As indicated above a number of
compounds and operating procedures can be used for that
purpose.
[0015] Thus the passivating protective layer can comprise
substances of the group consisting of long-chain carboxylic acids,
phosphonic acids, phosphoric acids, alcohols, amines, amides and
derivatives of said substances with between 8 and 20 C-atoms and
salt-like compounds of said substances. Those substances may be
applied to the pigment particles either from suitable solutions or
by direct treatment.
[0016] The protective layer however may also comprise at least one
metal oxide layer and/or metal hydroxide layer of the group B, Al,
Sn, Ti, V, Cr, Mo, Zn and Ce. That layer is precipitated by
controlled hydrolysis of suitable salts or metal acid esters.
[0017] The protective layer may also comprise organically modified
silicates, titanates, zirconates or aluminum zirconates and can
also be applied from suitable organic solutions or by hydrolysis of
suitably modified metal acid esters.
[0018] Another possible protective layer is an organic polymer
layer based on acrylates and/or methacrylates which are applied by
radical polymerization in solution. That protective layer can be
applied to the pigments or in a particular configuration during the
actual film crushing operation.
[0019] It is possible to conceive of a protective layer which is
afforded by combinations of the above-listed substances and
procedures.
[0020] Tests have also shown that it is advantageous, instead of
pure aluminum, to use aluminum alloys with a higher level of
resistance to corrosion. Particular emphasis is to be laid on the
seawater-resistant aluminum alloy `Hydronalium` (with 7% by weight
of magnesium and a little silicon) and chromium-bearing aluminum
alloys.
[0021] Operation is conducted in known manner in the production of
the multi-layer pigments. In a roll coater which is a vacuum
coating apparatus with an internally disposed foil roll which can
be rolled up and unrolled, a foil which is firstly provided with a
release layer is successively coated by way of physical vapor
deposition with a semi-transparent aluminum layer, for example of
between 5 and 40 nm in thickness, then a transparent
SiO.sub.2-layer for example of between 100 and 600 nm in thickness,
then an opaque aluminum layer of >60 nm in thickness and then
again with a transparent SiO.sub.2-layer of for example between 100
and 600 nm in thickness and finally with a semi-transparent
aluminum layer of for example between 5 and 40 nm in thickness.
Instead of pure aluminum, aluminum-based alloys can also be used
for the central aluminum layer and/or for the two semi-transparent
aluminum layers. Vapor deposition of the aluminum or aluminum-based
metal is effected electrically by way of resistance-heated boats or
by sputtering. Sputtering is preferred for optically variable
pigments. Sputtering is also the preferred method for the vapor
deposition of SiO.sub.2-layers or SiO.sub.2-bearing layers. Mixing
SiO.sub.2 with cryolite is found to be advantageous as the
SiO.sub.2/cryolite layer is built up very much more quickly than
the build-up of a pure SiO.sub.2-layer and cryolite has
approximately the same refractive index as SiO.sub.2.
[0022] To produce the pigment from the multi-layer film, firstly
the release layer is dissolved by means of a solvent, the film is
peeled off the substrate and the film fragments which are produced
in that case are crushed, possibly after washing and filtering. The
operation of crushing the film fragments to pigment size is
effected by ultrasound or mechanically by high-speed agitators in a
liquid medium or after drying thereof in an air jet crusher with a
sifter wheel. The free metal surfaces of the pigment which occurs
in a particle size of between 5 and 60 .mu.m, preferably between 12
and 36 .mu.m, are coated with a passivating protective layer during
the crushing operation or subsequently thereto by one of the
above-mentioned processes according to the invention, depending on
whether the pigment crushing operation is effected in a liquid
medium or dry.
[0023] If the passivation operation is effected during the crushing
operation, for example carboxylic acid, phosphoric acid or
phosphoric acid ester or chromic acid is added to the liquid medium
in which the film fragments are present in the crushing treatment.
In that respect the medium must have at least a certain solution
property for the respectively added passivation agent. Passivation
of the dry powder, for example by adding for example metal oxides,
polymers, higher fatty acids or phosphoric acid esters in finely
divided form is also possible, as well as passivation in the
gaseous phase, for example in the procedure for crushing film
fragments in an air jet crusher, but it is less preferred. The
preferred situation involves using carboxylic acids, phosphoric
acids, phosphomolybdic acid or phosphoric acid ester, chromic acid
or also mixtures of a plurality of passivation agents in aqueous,
alcohol, ketone-type, alkane-type, ether-type or other organic
solvents such as tetrahydrofuran, propylacetate or toluene or also
mixtures thereof. In regard to the carboxylic acids, higher fatty
acids such as stearic acid, oleic acid, myristic acid or for
example salts such as for example sodium stearate or zinc stearate
are particularly suitable. Dicarboxylic acid or salts thereof can
also be used.
[0024] Phosphoric acid can also be used in the form of a monobasic
or polybasic acid. Among the possible phosphoric acid esters, those
based on higher fatty alcohols are particularly preferred. Chromic
acid (CrO.sub.3) is desirably applied in the form of a 20% aqueous
solution.
[0025] The concentration of the passivating agent in the liquid
medium is selected to be between 5 and 30% by weight under normal
circumstances. In the exceptional case of liquid passivation agents
it is also possible to operate in a 100% concentrate, thus for
example when using oleic acid. The passivating treatment in a
liquid medium itself is preferably effected over a period of
between 1 and 5 hours. During that period the pigment-bearing
suspension is carefully stirred. After the treatment the pigment is
filtered off, possibly washed and dried. The need for the washing
operation arises only in relation to CrO.sub.3-treatment. All
experience indicates that a `post-maturing phase`, during which the
pigment is exclusively stored for between 3 and 4 weeks, increases
the quality of passivation. Analyses show that, depending on the
particle size, between 0 and 30% by weight of the passivating agent
is firmly `attached` to the surface of the pigment.
[0026] The corrosion-stable single-layer and multi-layer pigments
according to the invention are used for material coloring purposes,
in particular for coloring decorative coatings in the lacquer,
varnish, paint, plastic material, printing and ceramic sectors.
[0027] The boiling test in water described in DE-A 40 30 727 for
example serves for quickly checking the effectiveness of
passivation, that is to say the water-resistance of the pigments.
In that procedure, 1.5 g of the metal or multi-film pigment to be
tested is pre-dispersed in the form of paste in 10 g of butyl
glycol and then introduced with 150 g of water into a gas-tightly
closable apparatus. The mixture is then heated until boiling occurs
and the time required until 400 ml of hydrogen is developed is
recorded.
[0028] Non-stabilised pigments react within a few minutes. The
pigments produced according to the invention on the other hand
requires boiling times of at least 15 hours until 400 ml of
hydrogen is developed.
[0029] The following Examples serve to further describe the
invention and by means of the above-indicated tests illustrate the
achieved passivation and corrosion resistance of the pigments
according to the invention.
EXAMPLES
[0030] Production of metal-bearing particles as a starting product
for pigment production.
[0031] A. In a roll coater, a 90 nm thick aluminum layer is applied
by vapor deposition of molten aluminum, to a polyester foil coated
with an acrylic resin-based release layer. The aluminum layer is
removed from the roll coater and peeled off by means of acetone by
dissolving away the release layer. The fragments of the layer are
decanted off and washed with white spirit (300% residual
solvent).
[0032] B. In a roll coater, the following layers are applied by
sputtering in succession one upon the other, to a polyester foil
coated with an acrylic resin-based release layer:
[0033] 1. (M') a 10 nm thick semi-transparent aluminum layer
[0034] 2. (T) a 500 nm thick transparent SiO.sub.2-layer
[0035] 3. (M) a 60 nm thick opaque aluminum layer
[0036] 4. (T) a 500 nm thick transparent SiO.sub.2-layer
[0037] 5. (M') a 10 nm thick semi-transparent aluminum layer.
[0038] The result obtained is a multi-layer film having a clear
green/red color flop. That film is removed from the roll coater and
peeled off the substrate with solvent (THF/water/ethanol=1:1:1, or
acetone). The fragments are filtered off.
[0039] C. Procedure as in A above with the difference that layers
1. (M'), 3. (M) and 5. (M') do not comprise pure aluminum but an
aluminum/chromium alloy comprising 95% by weight of Al and 5% by
weight of Cr.
[0040] D. Procedure as in A with the difference that the layers 1.
(M'), 3. (M) and 5. (M') do not comprise pure aluminum but a
Hydronalium alloy comprising 92.9% by weight of Al, 7% by weight of
Mg and 0.1% by weight of Si.
[0041] Passivation of the fragments
Example 1
[0042] Coating of single-layer pigments
[0043] The slurry in accordance with Example A, containing solvent
and aluminum film fragments, is introduced into a chromic acid
(CrO.sub.3)-bearing aqueous solution which contains 12% by weight
of CrO.sub.3 and 88% by weight of water. The suspension is then
treated in an ultrasonic crusher over a period of 60 minutes at
30.degree. C. The pigment is then decanted, washed a plurality of
times with isopropanol and finally put into the definitive form of
a ready-for-sale isopropanol-bearing paste.
Example 2
[0044] Coating with oleic acid solution
[0045] The multi-layer film fragments produced in B are introduced
in a solvent-moist condition into an oleic acid
(C.sub.17H.sub.33COOH)-contain- ing alcohol solution (30% by weight
of oleic acid, 70% by weight of ethanol) and then treated in a
commercially available ultrasonic crusher over a period of about 1
hour. After that, the particle size is between 3 and 60 .mu.m. The
particles are then also carefully stirred over a further period of
4 hours. Thereafter, cooling is effected, followed by filtration,
washing with a solution comprising 95% by weight of ethanol and 5%
by weight of oleic acid, and drying at 50.degree. C. in a vacuum
drying chamber. The powder is then stored at ambient temperature
for 4 weeks.
[0046] The pigment powder passivated in that way has a C-proportion
of 4% by weight.
Example 3
[0047] Coating with phosphate solution
[0048] The multi-layer film fragments produced in B are introduced
in solvent-moist condition into a triethylphosphate
((C.sub.2H.sub.5) PO.sub.4)-containing alcohol solution (20% by
weight of triethylphosphate, 77% by weight of ethanol and 3% by
weight of H.sub.2O) and then treated in an ultrasonic crusher over
a period of about 1 hour. After this, the particle size is between
3 and 60 .mu.m. The particles are then carefully agitated for a
further period of 3 hours at 50.degree. C. After that, cooling is
effected, followed by drying at 50.degree. C. in a vacuum drying
chamber. The powder is stored at ambient temperature over a period
of 4 weeks.
[0049] The pigment powder passivated in that way has a P-proportion
of 0.4% by weight.
Example 4
[0050] Coating with chromate solution
[0051] The multi-layer film fragments produced in B are introduced
in a solvent-moist condition into a chromic acid
(CrO.sub.3)-bearing aqueous solution. The solution contains 10% by
weight of CrO.sub.3 and 90% by weight of H.sub.2O. The fragments
are then adjusted to particle sizes of between 3 and 60 .mu.m in an
ultrasonic crusher over a period of about 1 hour. After that, the
suspension is carefully agitated at 40.degree. C. over a period of
2 hours, then the pigment is filtered and washed with water. Drying
is effected at 60.degree. C. in a vacuum drying chamber and the
powder is stored for 2 weeks.
[0052] The pigment contains 1.4% by weight of chromium.
Example 5
[0053] Coating with zinc stearate solution.
[0054] The multi-layer film material produced in C is dried in a
vacuum drying chamber at 50.degree. C. and then introduced into a
water/xylene-bearing zinc stearate solution (10% by weight of zinc
stearage, 5% by weight of water, 85% by weight of xylene) and
brought to particle sizes of between 5 and 50 .mu.m in an
ultrasonic crusher. After this, the suspension is heated for 2
hours at 80.degree. C., with careful agitation. The pigment is then
filtered off, dried in a vacuum drying chamber at 50.degree. C. and
stored for 4 weeks.
Example 6
[0055] Coating with chromate solution
[0056] The multi-layer film fragments produced in D are introduced
in a solvent-moist condition into chromic acid (CrO.sub.3)-bearing
solution (15% by weight of CrO.sub.3 and 85% by weight of H.sub.2O)
and brought to particle sizes of between 5 and 60 .mu.m in an
ultrasonic crusher. After this, the suspension is agitated for 2
hours at 40.degree. C. The pigment is then filtered off, washed
with H.sub.2O, at 60.degree. C., dried in a vacuum drying chamber
at 50.degree., and stored for 4 weeks.
Example 7
[0057] Polymer coating in solution
[0058] 125 g of single-layer pigment particles produced by PVD with
a mean particle size of 18 .mu.m is dispersed in 1300 g of white
spirit and heated to 120.degree. C. Firstly 7.6 g of
3-methacryloxypropyltrimethoxys- ilane in 20 g of white spirit is
added followed by 0.3 g of vinyl phosphonic acid in 20 g of white
spirit, 0.3 g of water and 5.0 g of butan-2-ol and stirred for 1
hour at 120.degree. C. After this, 12 g of
trimethylolpropanetrimethacrylate in 20 g of white spirit and then
within 30 minutes a slurry of 0.4 g of 2.2-azobis(2-methylpropane
nitrile) in 10 g of white spirit are added. Agitation is effected
for 5 hours at 120.degree. C., the reaction mixture is left to cool
down and the coated pigment is separated off by way of a suction
filter. The filter cake obtained is freed of solvent in the vacuum
drying chamber.
[0059] In the boiling test the pigment only developed 100 ml of
hydrogen after 22 hours.
Example 8
[0060] Polymer coating in solution
[0061] Using the mode of operation of Example 7 corrosion-stable
pigments are produced using 0.2 g of 2-carboxyethane phosphonic
acid and 0.2 g of aminoethane phosphonic acid respectively, instead
of 0.3 g of vinyl phosphonic acid.
[0062] In the boiling test the pigments produced in that way
develop 120 ml and 125 ml of hydrogen respectively after 20
hours.
Example 9
[0063] Coating with phosphate using a CVD process
[0064] 100 g of single-layer pigment particles (mean particle size
20 .mu.m) is fluidised in a fluidised bed reactor by introducing a
total of 800 1/h nitrogen as a fluidization gas, and heated to
200.degree. C. A flow of 200 1/h of the fluidization gases is
passed through an absorption bulb heated to 70.degree. C. and
loaded with 20 ml of POCl.sub.3. A further 200 1/h of nitrogen is
loaded with water vapor in a second absorption bulb heated to
50.degree. C. and charged with water, and transferred into the
reactor. The remainder of the fluidization gases is blown directly
through the lower opening of the reactor by way of the frit
bottom.
[0065] The total POCl.sub.3-amount was consumed after about 2
hours. Analysis showed 0.82% by weight of P in the passivated
pigment. In the boiling test the pigment developed 90 ml of
hydrogen after 22 hours.
Example 10
[0066] Coating with phosphite using a CVD process.
[0067] A similar procedure as in Example 9 is adopted, but using 24
ml of trimethylphosphite with an absorption bulb temperature of
20.degree. C. and with a reaction time of 3 hours.
[0068] The finished pigment contains 2.8% by weight of P; in the
boiling test it develops 60 ml of hydrogen after 24 hours.
Example 11
[0069] Coating with vanadate using a CVD-process
[0070] A similar procedure as in Example 9 is employed, but using
28 ml of VOCl.sub.3 with an absorption bulb temperature of
20.degree. C. and a reaction time of 5 hours.
[0071] The pigment coated in that way contains 13% by weight of V;
360 ml of hydrogen is formed in 22 hours in the boiling test.
Example 12
[0072] Coating with molybdic acid in solution
[0073] 200 g of pigment particles (mean particle size 15 .mu.m) is
dispersed in 2000 ml of propyleneglycolmonomethylether and mixed at
15 to 20.degree. C. with a pH-value of 9 with an aqueous solution
of 20 g of ammonium paramolybdate (NH.sub.4).sub.6Mo.sub.7O.sub.24.
4 H.sub.2O in 400 g of deminerealized water, by a dropwise
procedure. After a reaction time of 1 hour the reaction product is
isolated by means of a suction filter and washed a plurality of
times with demineralized water in order to remove ammonium salts
and unreacted molybdate. The pigment coated in that way contains
5.2% of Mo and developed 85 ml of hydrogen in the boiling test
after 24 hours.
Example 13
[0074] Coating with cerium silicate solution
[0075] 100 g of pigment powder (mean particle size of 12 .mu.m) is
dispersed in 600 ml of propyleneglycolmonobutylether and stirred
with an aqueous solution of 50 g of cerium silicate for 15 hours at
ambient temperature. The pigment is then separated off by way of a
suction filter.
[0076] The pigment powder obtained contains 14.0% by weight of Ce
and in the boiling test forms 150 ml of hydrogen after 22
hours.
Example 14
[0077] Coating with organophophites (RO).sub.2 PHO
[0078] 100 g of pigment powder is dispersed in 1000 g of white
spirit and mixed with 8 g of dioctylphosphite in 100 g of white
spirit at abient temperature and intensively stirred for 24 hours.
The pigment is then separated off by means of a suction filter and
dried at 90.degree. C. in a vacuum drying chamber. The pigment
coated in that way contains 0.76% by weight of P and in the boiling
test develops a 90 ml of hydrogen after 20 hours.
Example 15
[0079] Coating with modified titanates in solution
[0080] 100 g of pigment powder is homogeneously dispersed in 800 g
of ethylacetate, mixed with a solution of 20 g of
isopropyltri(dioctyl)pyro-- phosphatotitanate (KR 38S, from the
company Kenrich) in 100 g of ethylacetate and intensively stirred
for 24 hours at ambient temperature. The pigment is then separated
from the solvent and dried in a vacuum drying chamber at 50.degree.
C.
[0081] The pigment coated in that way contains 0.5% by weight of Ti
and 2.2% by weight of P and in the boiling test develops 70 ml of
hydrogen after 24 hours.
[0082] It will be appreciated that the foregoing Examples of
compositions and procedures according to the invention have only
been set forth by way of illustration thereof and that various
other modifications and alterations may be made therein without
thereby departing from the invention.
* * * * *