U.S. patent application number 11/712393 was filed with the patent office on 2007-09-13 for effect pigments based on coated glass flakes.
Invention is credited to Klaus Ambrosius, Ralf Anselmann, Marcus Mathias.
Application Number | 20070212487 11/712393 |
Document ID | / |
Family ID | 8177370 |
Filed Date | 2007-09-13 |
United States Patent
Application |
20070212487 |
Kind Code |
A1 |
Anselmann; Ralf ; et
al. |
September 13, 2007 |
Effect pigments based on coated glass flakes
Abstract
The present invention relates to effect pigments based on thin
glass flakes and to a method for the production of such pigments.
The resulting pigment can be used in any application for which
pearlescent pigments have been heretofore used-such as, for
example, in plastics, paints, inks, cosmetic formulations, coatings
including solvent or waterborne automotive paint systems, powder
coatings, inks and agriculture foils.
Inventors: |
Anselmann; Ralf; (Ramsen,
DE) ; Ambrosius; Klaus; (Dieburg, DE) ;
Mathias; Marcus; (Gernsheim, DE) |
Correspondence
Address: |
MILLEN, WHITE, ZELANO & BRANIGAN, P.C.
2200 CLARENDON BLVD.
SUITE 1400
ARLINGTON
VA
22201
US
|
Family ID: |
8177370 |
Appl. No.: |
11/712393 |
Filed: |
March 1, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10473710 |
Nov 10, 2003 |
7226503 |
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PCT/EP02/04020 |
Apr 11, 2002 |
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11712393 |
Mar 1, 2007 |
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Current U.S.
Class: |
427/255.11 ;
106/415; 106/489 |
Current CPC
Class: |
C01P 2002/02 20130101;
C01P 2004/84 20130101; C09C 1/0024 20130101; C09C 1/0015 20130101;
C09C 2200/301 20130101; Y10T 428/2993 20150115; Y10T 428/2996
20150115; C09C 2200/102 20130101; C09C 1/0021 20130101; C09D 5/36
20130101; C09C 2220/10 20130101 |
Class at
Publication: |
427/255.11 ;
106/415; 106/489; 106/489 |
International
Class: |
C23C 16/00 20060101
C23C016/00; C04B 14/04 20060101 C04B014/04; C04B 14/22 20060101
C04B014/22; C09C 1/00 20060101 C09C001/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 9, 2001 |
EP |
01111320.6 |
Claims
1. Effect pigments based on glass flakes with a thickness of
.ltoreq.1.0 .mu.m characterized in that the glass flakes are coated
with one or more layers with a high and/or low refractive
index.
2. Effect pigments according to claim 1, characterized in that the
softening point of the glass flakes is .gtoreq.800.degree. C.
3. Effect pigments according to claim 1, characterized in that the
glass flakes are coated with one or more layers of metal oxides,
metal suboxides, metal oxyhalides, metal fluorides, metal
chalcogenides, metal nitrides, metal sulfides, metal carbides, or
mixtures thereof.
4. Effect pigments according to claim 3, characterized in that the
metal oxide is TiO.sub.2, Fe.sub.2O.sub.3, TiFe.sub.2O.sub.5, Ti
suboxides, Fe.sub.3O.sub.4, Cr.sub.2O.sub.3, Al.sub.2O.sub.3,
SiO.sub.2, ZrO.sub.2, ZnO, SnO.sub.2, CoO, Co.sub.3O.sub.4,
VO.sub.2, V.sub.2O.sub.3, Sn(Sb)O.sub.2 or mixtures thereof.
5. Effect pigments according to claim 4, characterized in that the
glass flakes are coated with TiO.sub.2, Fe.sub.2O.sub.3 or a
mixture of TiO.sub.2 and Fe.sub.2O.sub.3.
6. Effect pigments according to claim 4, characterized in that the
TiO.sub.2 is in the rutile modification.
7. Effect pigments according to claim 3, characterized in that the
coatings are metal sulfides selected from sulfides of tin, silver,
lanthanum, rare earth metals, chromium, molybdenum, tungsten, iron,
cobalt and/or nickel.
8. Effect pigments according to claim 1, characterized in that the
glass flakes are coated with one or two layers.
9. A method of preparing an effect pigment according to claim 1
which comprises coating of the glass flakes by wet chemical
coating, by chemical or physical vapor deposition or electroless
plating and optionally calcining the coated glass flakes.
10. Use of the effect pigments according to claim 1 in plastics,
coatings, powder coatings, paints, inks printing inks, glasses,
ceramic products, agriculture foils and in cosmetic
formulations.
11. Use of the effect pigments according to claim 1 as conductive
pigments, as magnetic pigments or as dopants for the laser-marking
of papers and plastics.
12. Formulations containing the effect pigments according to claim
1.
Description
[0001] This application is a divisional of U.S. application Ser.
No. 10/473,710 filed on Nov. 10, 2003, which is incorporated
entirely by reference herein.
[0002] The present invention relates to effect pigments based on
thin glass flakes, to a method for the production of such pigments
and their use in plastics, paints, coatings, powder coatings, inks,
printing inks, glasses, ceramic products, agriculture foils, and in
cosmetic formulations.
[0003] Since more than 40 years iridescent luster effects can be
achieved using so called nacreous or pearlescent pigments. Various
alternative techniques have been developed to create colour/lustre
effects. The most important, economic and common way to make these
pigments is to coat a platelet shaped carrier with high refractive
substances like TiO.sub.2, Fe.sub.2O.sub.3, SnO.sub.2, ZrO.sub.2,
Cr.sub.2O.sub.3 or combinations of these or with alternating layers
of high and/or low refractivity. So far the nearly exclusively used
carrier is wet ground muscovite mica. It is cheap, readily
available and easy to cleave into smooth and very thin platelets.
These can be classified into any desired particle size
distribution. Additionally, pigments based on mica are very stable
towards chemical, mechanical or thermal treatment. But there are
some disadvantages of mica, since it is a natural product and shows
inconsistencies from source to source and even from batch to batch.
This has to be overcome by adjusting the processing parameters.
Natural mica contains impurities like quartz which makes the
processing more complicated (abrasion of grinding tools, waste) or
like Fe, Mn, Cu which makes the masstone yellowish grey rather than
white. When ground it yields platelets showing a broad distribution
of thicknesses and diameters. This can be reduced by proper
classification but will never lead to uniform shape.
[0004] In the past researchers tried to find corresponding
alternatives to mica which keep the advantages of it but did not
contain the above mentioned disadvantages.
[0005] A wide variety of other platy materials have been proposed
as substitute for mica in the patent literature. These include
non-soluble inorganic materials such as glass, enamel, china clay,
porcelain, natural stones or other silicaceous substances, metal
objects and surfaces of organic polymer materials such as
polycarbonate as disclosed for example in U.S. Pat. Nos. 3,123,485,
3,219,734, 3,616,100, 3,444,987, 4,552,593 and 4,735,869. While
glass has been mentioned as a possibility on many occasions, for
instance in U.S. Pat. No. 3,331,699, commercial pearlescent
products are not made using glass and experience has shown that
products made using glass as the platelet substrate have rather
poor quality.
[0006] U.S. Pat. No. 3,331,699 discloses that glass flakes may be
coated with a translucent layer of particles of a metal oxide
having a high index of refraction, such as titanium dioxide,
provided there is first deposited on the glass flakes a nucleating
substance which is insoluble in the acidic solution from which the
translucent layer of metal oxide is deposited. The patent does not
mention the necessity of a smooth transparent film, not particles,
being necessary for quality interference pigments to be developed.
The patent teaches that the nature of the glass is not critical,
but that the presence of the nucleated surface is critical. It is
further stated that there are only a small number of metal oxide
compounds which are insoluble in the acidic solution and capable of
forming a nucleated surface on the glass flakes; tin oxide and a
fibrous boehmite form of alumina monohydrate are the only two such
materials disclosed. As demonstrated in the examples below,
products prepared according to the teachings of this patent are
poor in quality.
[0007] U.S. Pat. No. 5,436,077 teaches a glass flake substrate
which has a metal covering layer on which is formed a dense
protective covering layer of a metal oxide such as titanium
dioxide. In this patent, the nature of the glass is unimportant,
the metallic coating provides the desired appearance and the
overcoating of the metal oxide is present to protect the metallic
layer from corrosive environments.
[0008] EP 0 912 640 B1 teaches the coating of thick flakes of C
glass having a first coating comprising iron oxide or rutile
titanium dioxide thereon. The disadvantage of C glass is the
limited thermal stability. As disclosed in the EP 0 912 640 B1 the
rutile pigments prepared according to the corresponding examples
were calcined at temperatures not higher than 600.degree. C. It is
well known that the calcining temperature is of essential
importance for the stability of rutile pigments, especially for
outdoor applications. To yield sufficiently stabilized rutile
TiO.sub.2 layers on a substrate calcining temperatures of at least
800.degree. C. are requested.
[0009] For the preparation of pearlescent pigments the transparency
and the thickness of the platy substrate are very important. For
the first time EP 0 289 240 B1 discloses the manufacturing of
extremely thin glass flakes at reasonable costs. According to the
claimed process the glass flakes cannot be only made in any desired
composition, e.g., from pure SiO.sub.2, but also in any thickness
tailored for the application wanted down to below 0.8 .mu.m.
[0010] It is an object of the present invention to overcome the
problems of the prior art and to provide novel effect pigments
which have advantageous application properties. This object is
achieved by the inventive effect pigments based on very thin glass
flakes having the following characteristics:
[0011] (1) thickness of the glass flakes .ltoreq.1.0 .mu.m
[0012] (2) high temperature and mechanical stability
[0013] (3) smooth surfaces
[0014] The present invention relates to effect pigments based on
glass flakes with a thickness of .ltoreq.1.0 .mu.m coated with one
or more layers with a high and/or a low reflective index. The
thickness of the glass flakes is preferably .ltoreq.0.8 .mu.m and
especially .ltoreq.0.5 .mu.m. Especially preferred are thin glass
flakes with a softening point .ltoreq.800.degree. C.
[0015] Glass can be classified for example as A glass, C glass, E
glass, ECR glass. For the present invention quartz glass is
preferred but the production of this glass is very expensive. Glass
types which fulfill the feature of the requested softening point
are quartz glass, and any other glass composition having a
softening point of .gtoreq.800.degree. C. Glass flakes which
fulfill the requirements are special glasses like e.g. Schott Duran
or Supremax types The softening point in the present invention is
defined, according to ASTM C 338 as the temperature at which a
uniform fiber of glass with a diameter of 0.55-0.75 mm and a length
of 23.5 cm increases its length by 1 mm/min when the upper 10 cm is
heated at a rate of 5.degree. C./min.
[0016] Suitable glass flakes preferably prepared according to EP 0
289 240 B1 are characterized in that they contain an average
particle size in the range of 5-1000 .mu.m, preferably in the range
of 5-150 .mu.m. Preferred glass flakes have an average particle
size in the range of 5-150 .mu.m and a thickness of 0.1-0.5 .mu.m,
preferably of 0.1-0.3 .mu.m. The aspect ratio of glass flakes is in
the range of 10-300, preferably in the range of 50-200.
[0017] The glass particles can be coated with one or more layers
selected from the group consisting of metal oxides, metal
suboxides, metal fluorides, metal oxyhalides, metals chalcogenides,
metal nitrides, metal sulfides, metal carbides, or mixtures
thereof.
[0018] Examples of suitable metal oxides are TiO.sub.2,
Fe.sub.2O.sub.3, TiFe.sub.2O.sub.5, Ti suboxides, Fe.sub.3O.sub.4,
Cr.sub.2O.sub.3, Al.sub.2O.sub.3, SiO.sub.2, ZrO.sub.2, ZnO,
SnO.sub.2, CoO, Co.sub.3O.sub.4, VO.sub.2, V.sub.2O.sub.3,
Sn(Sb)O.sub.2 or mixtures thereof. The TiO.sub.2 layer tan be in
the rutile or anatase modification, preferably the TiO.sub.2 layer
is rutile. Especially preferred are glass flakes coated with
TiO.sub.2 and/or Fe.sub.2O.sub.3.
[0019] Metal sulfide coatings on glass flakes are preferably
selected from sulfides of tin, silver, lanthanum, rare earth
metals, preferably cerium, chromium, molybdenum, tungsten, iron,
cobalt and/or nickel.
[0020] The glass flakes can be coated in the same way as e.g. mica
based pearl lustre pigments. Coatings with a metal oxide may be
accomplished by any known methods, such as hydrolysis of a metal
salt by heating or alkali, which deposits hydrated metal oxide,
optionally followed by calcination.
[0021] In general, the procedure involves the dispersing of the
thin glass flake particles and combining that dispersion with a
precursor which forms a hydrous metal oxide film coating on the
flakes.
[0022] After the glass is dispersed in water and placed in an
appropriate vessel, the appropriate metal salts are added. The pH
of the resulting dispersion is maintained at an appropriate level
during the addition of the metal salts by simultaneous feeding a
suitable base, for example sodium hydroxide, to cause precipitation
of the hydrous metal dioxide on the glass flakes. An aqueous acid,
for example hydrochloric acid, tan be used for adjusting the pH.
The coated platelets can, if desired, be washed and dried before
being calcined to the final pigment. The procedure is described in
detail in U.S. Pat. No. 5,433,779 and in the German Patents 14 67
468, 19 59 998, 20 09 566, 22 14 545, 22 15191, 22 44 298, 23 13
331, 25 22 572, 31 37 808, 31 37 809, 31 51 343, 31 51 354, 31 51
355, 32 11 602 and 32 53 017.
[0023] The effect pigments of the present invention are preferably
prepared by wet-chemically coating of the glass flakes or by gas
phase decomposition of volatile metal compounds (CVD, PVD) or
electroless plating.
[0024] The effect pigments obtained in this way are characterized
in that one or more homogeneous layers enrobing the uniform thin
glass flakes.
[0025] Preferred effect pigments of the present invention are given
in the following: [0026] glass flake+TiO.sub.2 (rutile) [0027]
glass flake+Fe.sub.2O.sub.3 [0028] glass flake+Fe.sub.3O.sub.4
[0029] glass flake+TiFe.sub.2O.sub.5 [0030] glass
flake+Cr.sub.2O.sub.3 [0031] glass flake+ZrO.sub.2 [0032] glass
flake+Sn(Sb)O.sub.2 [0033] glass flake+BiOCl [0034] glass
flake+Al.sub.2O.sub.3 [0035] glass flake+Ce.sub.2S.sub.3 [0036]
glass flake+MOS.sub.2
[0037] In general, the layer thickness ranges from 0.1 to 1000 nm,
preferably from 0.2 to 300 nm. The optical layer thickness will in
general be adapted to the particular application. Preferred
pigments are coated with one or two layers.
[0038] To enhance the light and weather stability it is frequently
advisable, depending on the field of application, to subject the
coated glass flakes to a surface treatment. Useful surface
treatments include for example the processes described in DE-C 22
15 191, DE-A 31 51 354, DE-A 32 35 017 or DE-A 33 34 598, DE 40 30
727 A1, EP 0 649 886 A2, WO 97/29059, WO 99/57204, U.S. Pat. No.
5,759,255. This surface treatment further enhances the chemical
stability of the pigments and/or facilitates the handling of the
pigment, especially its incorporation into various application
media.
[0039] The effect pigments of the present invention are
advantageous useful for many purposes, such as the coloring of
plastics, glasses, ceramic products, agriculture foils, decorative
cosmetic formulations and in particular coatings, especially
automotive coatings, and inks, including printing inks. All
customary printing processes can be employed, for example offset
printing, intaglio printing, bronze printing, flexographic
printing. Furthermore they can be used as functional pigments like
conductive pigments, as magnetic pigments or to make media, for
example plastics, board products and papers, laser-markable.
[0040] The effect pigments of the present invention are also
advantageously useful for these applications in admixture with
filler pigments or transparent and hiding white, colored and black
organic and inorganic pigments and also with conventional
transparent, colored and black luster pigments based on metal oxide
coated mica, TiO.sub.2 flakes, SiO.sub.2 flakes or Al.sub.2O.sub.3
flakes and coated or uncoated metal pigments, BiOCl pigments,
platelet shaped iron oxides, or graphite flakes.
[0041] Additionally, the inventive pigment mixtures can contain
organic or inorganic colourants, thixotropy agents, wetting agents,
dispersing agents, water, organic solvent or solvent mixtures,
etc.
[0042] The pigment mixtures of the invention are simple and easy to
handle. The pigment mixtures can be incorporated into the system in
which it is used by simple mixing. Laborious milling and dispersing
procedures for the pigments are not necessary.
[0043] The coated glass flakes of the invention can be used for
pigmenting and/or coating materials, printing inks, plastics,
agricultural films, button pastes, for the coating of seed, for the
colouring of food, coatings of foods, medicaments or cosmetic
formulations. The concentration of the pigments in the system in
which it is to be used for pigmenting is generally between 0.01 and
50% by weight, preferably between 0.1 and 5% by weight, based on
the overall solids content of the system. This concentration is
generally dependent on the specific application.
[0044] Plastics comprising the pigment mixture of the invention in
amounts of 0.1 to 50% by weight, in particular from 0.5 to 7% by
weight, are frequently notable for a particular brilliance.
[0045] In the coating sector, especially in automotive finishing,
the glass flakes are employed in amounts of 0.5 to 10% by
weight.
[0046] In the pigmentation of binder systems, for example for
paints and printing inks for intaglio, offset or screen printing,
the pigment is incorporated into the printing ink in amounts of
2-50% by weight, preferably 5-30% by weight and in particular 8-15%
by weight.
[0047] The invention likewise provides pigment preparations
comprising coated glass flakes, optionally effect pigments, binders
and, if desired, additives, the said preparations being in the form
of substantially solvent-free, free-flowing granules. Such granules
contain up to 95% by weight of the inventive pigments. A pigment
preparation in which the glass flakes of the invention are pasted
up with a binder and with water and/or an organic solvent, with or
without additives, and the paste is subsequently dried and brought
into a compact particulate form, e.g. granules, pellets,
briquettes, a masterbatch or tablets, is particularly suitable as a
precursor for printing inks.
[0048] The present invention therefore also provides formulations
containing the pigments of the invention.
[0049] In order to further illustrate the invention, various
non-limiting examples are set forth below. In these, as well as
throughout the balance of this specification and claims, all parts
and percentages are by weight and all temperatures are in degrees
centigrade unless otherwise indicated.
EXAMPLES
Example 1
(Rutile Silver Pigment) Prior Art
[0050] 200 g flakes of E-glass (thickness: 5 .mu.m; diameter: 10-40
.mu.m; specific surface area: approximately 0.2 m.sup.2/g) are
suspended in 2 l of deionized water. With vigorous stirring the
suspension is heated 80.degree. C. After having adjusted the pH to
2.0 with dilute HCl a first layer of SnO.sub.2 is precipitated onto
the glass flakes by feeding a solution of 3 g SnCl.sub.4.times.5
H.sub.2O (in 10 ml conc. HCl plus 50 ml of DI water) into the
suspension under simultaneous neutralization with 110% NaOH over a
period of about 1 h. To complete the reaction the suspension is
kept stirring for another 15 min. The coating is continued by
adjusting the pH to 1.8 with dilute HCl and then titrating 63.5 ml
of TiCl.sub.4-solution (400 g TiCl.sub.4/l DI water) against 10%
NaOH over a period of about 3 h. Having reached the desired layer
thickness the coating is stopped, stirred for another 15 min,
filtered, washed with DI water and dried. After calcination at
800.degree. C. for 30 min a silverwhite rutile pigment is
yielded.
Example 2
Rutile Silver Pigment
[0051] 200 g flakes of E-glass (thickness: 0.5 .mu.m; diameter:
10-40 .mu.m; specific surface area: approximately 1.7 m.sup.2/g)
are suspended in 2 l of DI water. The coating is carried out the
same way as in example 1. Titration periods keep the same, only the
amounts of solutions are adjusted to the different base
material:
[0052] 5 g SnCl.sub.4.times.5 H.sub.2O (in 15 ml conc. HCl plus 75
ml DI water) 196.3 ml of TiCl.sub.4 solution (400 g TiCl.sub.4/l DI
water)
[0053] After calcination at 800.degree. C. for 30 min a brilliant
silverwhite rutile pigment is yielded.
Examples 3 and 4
Rutile Interference Green Pigment
[0054] The coatings are started in the same ways as for examples 1
and 2, only the amount of TiO.sub.2 (400 g TiCl.sub.4/l DI water)
coated was increased to yield green interference type pigments. The
further steps are again carried out as described in examples 1 and
2.
[0055] To evaluate their properties draw down cards are made from
all of these pigments. Additionally sprayed panels were prepared.
The pigments based on glass flakes with a thickness of 5.0 .mu.m
and 0.5 .mu.m are checked for their coloristics and their visual
performance.
Results:
[0056] draw downcards and panels pigments with a thickness of 5.0
.mu.m showed very weak performance making a "dilute" impression.
For the silver little brilliance and little hiding effect was
observed while for the green a dull colour and little brilliance
are found;
[0057] a little better is the effect in the sunlight as some larger
flakes show a kind of sparkle;
[0058] completely different is the situation with a thickness of
0.5 .mu.m pigments: They exceeded comparable mica pigments
regarding brilliance, luster and (for the green) chroma;
[0059] particularly impressing is the high transparency combined
with clear color;
[0060] looking with the microscope shows that the surfaces of all
pigments are well and uniformly coated and that the differences
result mostly from the imperfect orientation of the 5 .mu.m
particles;
* * * * *