Title of Invention

STABILIZATION OF PEARL LUSTRE PIGMENTS.

Abstract Pearl lustre pigments which possess a first, inner layer, consisting of a platelet-shaped substrate,a second layer, comprising one or more metal oxides, the first and second layers forming a calcined base pigment, a third layer, comprising the corresponding uncalcined oxide, hydroxide or oxide hydrate of the oxide of the second layer, a fourth layer, comprising oxides, hydroxides and/or oxide hydrates of silicon or aluminium, a fifth layer, comprising oxides, hydroxides and/or oxide hydrates of silicon, aluminium, zirconium and/or cerium, this layer differing from the fourth layer, and a sixth layer, comprising one or more organofunctional coupling reagents. Also described are a preparation process, and the use of the pigments in paints, inks, plastics, coatings and cosmetics.
Full Text Stabilization of pearl lustre pigments
The invention relates to aftercoated pearl lustre pigments and to a process for preparing them. The invention further relates to the use of these pigments.
EP 0 632 109 BI discloses pearl lustre pigments which for use in coating compositions are subjected to an aftertreatment in order to enhance their stability.
The pearl lustre pigments known from EP 0 632 109 possess the following general layer sequence: the first "layer" is formed by the substrate, e.g. mica, the second layer is a metal oxide layer, e.g. titanium dioxide or iron (III) oxide, and these two layers form the base pigment. Atop the calcined base pigment, beginning with a third layer, the aftercoating, as it is known, is applied. The third layer comprises oxides, hydroxides and/or oxide hydrates of silicon or aluminium, the fourth layer comprises oxides, hydroxides and/or oxide hydrates of silicon, aluminium, zirconium and/or cerium, and is different from the third layer, and the fifth layer comprises organofunctional coupling agents, e.g. silanes or zirconium aluminates.
Despite the stabilizing aftercoating of layers three to five described above, the pearl lustre pigments, especially those based on mica and coated in the second layer with iron (III) oxide, are unsuitable for use in all fields, since under extreme stresses even higher stability of the pigments would be necessary.
Similar comments apply, in particular, to the micabased pearl lustre pigments coated in the second layer with titanium dioxide or other metal oxides, such as chromium oxide, zirconium dioxide, tin dioxide or zinc oxide; although they are in many cases more stable than

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the iron(III) oxide-coated micas, they likewise cannot be used without restrictions.
The aftercoated pearl lustre pigments known from the prior art, furthermore, possess the disadvantage that their orientation in coating films is not optimal; in other words, an improvement in the parallel alignment of the pigments with respect to the film coat would be desirable in order to enhance the lustre properties.
One of the objects of the invention was to increase the stability of such pigments and to provide pigments which possess improved orientation within coating films.
This object has been achieved in accordance with the invention by the provision of pigments having the following layer sequence:
a first layer, consisting of a platelet-shaped
substrate,
a second layer,
comprising one or more metal oxides,
the first and second layers forming a calcined
base pigment, a third layer, comprising the corresponding
uncalcined oxide, hydroxide or oxide hydrate of
the oxide of the second layer, a fourth layer, comprising oxides, hydroxides and/or
oxide hydrates of silicon or aluminium, a fifth layer, comprising oxides, hydroxides and/or
oxide hydrates of silicon, aluminium, zirconium
and/or cerium, this layer differing from the
fourth layer, and a sixth layer, comprising one or more organofunctional
coupling agents.
The third layer in this sequence adopts the function of an adhesion promoter and embraces preferably from 0.1

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to 10% by weight, more preferably from 1 to 5% by weight, based on the base pigment.
Suitable platelet-shaped substrates for the base pigment are the substrates specified in EP 632 109 81, such as mica, kaolin or glass, for example. Particular preference is given, however, to mica as the base
substrate.
Suitable metal oxides of the second layer are, for example, iron(III) oxide and/or titanium dioxide or other metal oxides, such as chromium oxide, zirconium dioxide, tin dioxide or zinc oxide, and the oxides may also be present in mixtures. Particularly high improvements over the pearl lustre pigments known from EP 632 109 Bl are achieved in the case of the iron(III) oxide-coated substrates.
Suitable coupling agents are the coupling agents disclosed in EP 632 109 Bl. They include, in particular, silanes, zirconium aluminates, zirconates or titanates, the silanes preferably possessing the structure Y-(CH2)n-SiX3 in, which Y is an organofunctional group, e.g. an amino, methacrylic, vinyl and/or epoxy group, and X is a silicon-functional group which following its hydrolysis reacts with active sites of an inorganic substrate or by condensation with other silicon compounds. The group in question may comprise, for example, an alkoxy group.
In addition to these substantially hydrophilic coupling agents, it is also possible to use hydrophobic silanes, especially the aryl-, alkyl- and fluoroalkylsubstituted di- and trimethoxysilanes. These include, for example, phenethyltrimethoxysilane, propyltrimethoxysilane, butyltrimethoxysilane, isobutyltrimethoxysilane, hexyltrimethoxysilane, octyltrimethoxysilane, 1H,1H,2H,2H-perfluorodecyltrimethoxysilane and (3, 3, 3-trifluoropropyl)methyldimethoxysilane.

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A further object was to provide a process for obtaining the pearl lustre pigments of the invention.
This object has been achieved by the provision of a multistage process in which the calcined, platelet-shaped substrate coated with one or more metal oxides is suspended in water, heated at from 25 to 100°C, preferably from 40 to 80°C, and adjusted to a pH of from 3 to 11, preferably from 5 to 9, in a first stage one or more water-soluble metal salts are added which correspond to the calcined metal oxides of the metal oxide coating of the platelet-shaped substrate, these salts are deposited in whole or in part as oxide, hydroxide and/or oxide hydrate, followed by heating at from 30 to 100°C, preferably from 40 to 75°C, and adjustment to a pH of from 3 to 9, preferably from 6 to 7, in a second stage a water-soluble silicate and/or aluminium salt is added, and is deposited in whole or in part as oxide, hydroxide and/or oxide hydrate, in a third stage, by adding at least one water-soluble silicate, aluminium salt, cerium salt and/or zirconium salt at a pH in the range from 3 to 9, preferably from 6 to 7, the corresponding oxides, hydroxides or oxide hydrates thereof are deposited, it being necessary for these to differ from those of the second stage, and in a fourth stage at least one organic coupling agent is added and is deposited at a pH of from 3 to 9, preferably from 6 to 8.
As calcined platelet-shaped substrates coated with metal oxides it is possible to use the substrates already mentioned above with the abovementioned metal oxide coatings, which are available commercially under the designation Iriodin® (manufacturer; B. Merck, Darmstadt).
A suitable water-soluble silicate is preferably sodium silicate; suitable water-soluble aluminium salts,

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cerium salts and zirconium salts are, in general, all
water-soluble salts of these metals, although the
readily obtainable halides and halide hydrates, for
example, are appropriate.
Coupling reagents used are preferably those mentioned above.
The aftercoating process of the invention may be carried out as described above in one operation without isolating and working up the pigment after the first precipitation reaction (first stage). However, it is also possible to isolate the pigment after the first stage, i.e., after the application of the adhesion-promoting layer.
The pearl lustre pigments coated in accordance with the invention are employed in particular in connection with the pigmenting of inks, such as printing inks, for example, and plastics, such as polymer films, for example, and also coating compositions, such as paints, for example. However, they are also employed in other areas in which the abovementioned improved properties play a part, such as"' in the pigmentation of cosmetics, for example.
In the text below, the invention is illustrated with reference to examples.
Examples
Different pearl lustre pigments were aftercoated by means of the aftertreatment process of the invention.
a) Iron oxide pigment without isolation (prepared in a reactor)

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100 g of Iriodin® 504 Red are suspended in 900 ml of deionized water and heated to 40°C with vigorous stirring.
The suspension is adjusted to a pH of 9.0 using 2.5% NaOH (all stated pH values are determined using appropriate pH indicator paper).
Over the course of approximately 30 minutes, a solution of 18.66 g of FeCl3 in 74.64 g of deionized water (corresponding to a 3% FeCl3 solution) is added dropwise to the suspension. The pH falls over the course of 5 minutes to 3.2 and is kept constant at this level using 10% sodium hydroxide solution. After the endpoint has been reached, the pigment suspension is adjusted to a pH of 5.0 and is subsequently stirred for approximately 15 minutes.
Subsequently, over the course of 30 minutes, a solution of 2.7 ml of sodium silicate (370 g of Si02 per litre) in 150 ml of deionized water is added dropwise to the pigment suspension. The pH.is kept constant using 2.5% hydrochloric acid. After the end of the addition, stirring is continued at 40°C for 15 minutes. Thereafter the pH is adjusted to 6.5 over the course of 10 minutes using 2.5% hydrochloric acid and the suspension is subsequently stirred at 40°C for 15 minutes. Then 1-35 g of sodium sulfate, 2.30 g of aluminium chloride hexahydrate and 1.10 g of cerium(II) chloride heptahydrate, as solids, are added to the suspension, the pH dropping to 4.0.
Subsequently, over the course of 20 minutes, the suspension is heated to 75°C and stirred at 75°C for a further 75 minutes, the pH dropping to 3.3. Subsequently, 3.0 g of Dynasilan AMMO (3-aminopropyltrimethoxysilane from Huls) in pure form are added over the course of 10 minutes and the pH is kept constant using the abovementioned hydrochloric acid. After the end of the addition, stirring is continued at 75°C for 2 h, during which the silane hydrolyses fully and reacts with the pigment surface.

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Subsequently, the system is adjusted to a pH of 8.0
using 2.5% sodium hydroxide solution very slowly over
the course of 60 minutes. During this procedure, the
oxides and/or oxide hydrates and the silane are
deposited completely in the form of a mixed
precipitation.
Subsequently, stirring is continued at 75°C for 1 h for
afterreaction, the pH falling to 7.0.
The product is filtered off over a suction filter,
washed salt-free with deionized water and dried at
140°C for approximately 16 h.
b) Iron oxide with isolation
100 g of Iriodin® 504 Red are suspended in 900 ml of deionized water and heated to 40°C with vigorous stirring.
The suspension is adjusted to a pH of 9.0 using 2.5%
sodium hydroxide solution (all stated pH values are
determined using appropriate pH indicator paper).
Over the course of approximately 30 minutes, a solution
of 18.66 g of FeCl3 in 74.64 g of deionized water
(corresponding to a 3% FeCl3 solution) is added
dropwise to the suspension. The pH falls over the
course of 5 minutes to 3.2 and is kept constant at this
level using 10% sodium hydroxide solution. After the
endpoint has been reached, the pigment suspension is
adjusted to a pH of 5.0 and is subsequently stirred for
approximately 15 minutes.
The pigment is isolated (filtered off with suction),
washed with approximately 12 1 of deionized water and
dried at 110°C for approximately 16 h.
The modified pigment thus obtained is suspended in
900 ml of deionized water, heated to 40°C with vigorous
stirring, and adjusted to a pH of 9.0 using 2.5% sodium
hydroxide solution.
Subsequently, over the course of 30 minutes, a solution
of 2.7 ml of sodium silicate (370 g of SiO2 per litre)

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in 150 ml of deionized water is added dropwise to the pigment suspension. The pH is kept constant using 2.5% hydrochloric acid. After the end of the addition, stirring is continued at 40°C for 15 minutes. Thereafter the pH is adjusted to 6.5 over the course of 10 minutes using 2.51 hydrochloric acid and the suspension is subsequently stirred at 40°C for 15 minutes. Then 1.35 g of sodium sulfate, 2.30 g of aluminium chloride hexahydrate and 1.10 g of cerium(II) chloride heptahydrate, as solids, are added to the suspension, the pH dropping to 4.0.
Subsequently, over the course of 20 minutes, the suspension is heated to 75°C and stirred at 75°C for a further 75 minutes, the pH dropping to 3.3. Subsequently, 3.0 g of Z6040 (3-glycidyloxypropyltrimethoxysilane from Dow Corning) in pure form are added over the course of 10 minutes and the pH is kept constant using the abovementioned hydrochloric acid. After the end of the addition, stirring is continued at 75°C for 2 h, during which the silane hydrolyses fully and reacts with the pigment surface.
Subsequently, the system is adjusted to a pH of 8.0 using 2.5% sodium hydroxide solution very slowly over the course of 60 minutes During this procedure, the oxides and/or oxide hydrates and the silane are deposited completely in the form of a mixed precipitation.
Subsequently, stirring is continued at 75°C for 1 h for afterreaction, the pH falling to 7.0.
The product is filtered off over a suction filter, washed salt-free with deionized water and dried at 140°C for approximately 16 h.
c) Titanium oxide pigment without isolation (prepared
in a reactor)
100 g of Iriodin® 225 Rutile Pearl-blue are suspended in 900 ml of deionized water and heated to 40°C with vigorous stirring.



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The suspension is adjusted to a pH of 9.0 using 2.5%
NaOH (all stated pH values are determined using
appropriate pH indicator paper).
Over the course of approximately 30 minutes, a solution of 20.54 g of TiCl4 in 74.64 g of deionized water is added dropwise to the suspension. The pH falls over the course of 5 minutes to 3.2 and is kept constant at this level using 10% sodium hydroxide solution. After the endpoint has been reached, the pigment suspension is adjusted to a pH of 5.0 and is subsequently stirred for approximately 15 minutes.
Subsequently, over the course of 30 minutes, a solution of 2.7 ml of sodium silicate (370 g of SiO2 per litre) in 150 ml of deionized water is added dropwise to the pigment suspension. The pH is kept constant using 2.5% hydrochloric acid. After the end of the addition, stirring is continued at 40°C for 15 minutes. Thereafter the pH is adjusted to 6.5 over the course of 10 minutes using 2.5% hydrochloric acid and the suspension is subsequently stirred at 40 °C for 15 minutes. Then 1.35 g of sodium sulfate, 2.30 g of aluminium chloride hexahydrate and 1.10 g of cerium(II) chloride heptahydrafe, as solids, are added to the suspension, the pH dropping to 4.0.
Subsequently, over the course of 20 minutes, the suspension is heated to 75°C and stirred at 75°C for a further 75 minutes, the pH dropping to 3.3. Subsequently, 3.0 g of Dynasilan MEMO (3-methacryloxy-trimethoxysilane from Dequssa-Huls AG) in pure form are added over the course of 10 minutes and the pH is kept constant using the abovementioned hydrochloric acid. After the end of the addition, stirring is continued at 7S°C for 2 h, during which the silane hydrolyses fully and reacts with the pigment surface.
Subsequently, the system is adjusted to a pH of 8,0 using 2.5% sodium hydroxide solution very slowly over the course of 60 minutes. During this procedure, the oxides and/or oxide hydrates and the silane are

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deposited completely in the form of a mixed
precipitation.
Subsequently, stirring is continued at 75°C for 1 h for
afterreaction, the pH falling to 7.0.
The product is filtered off over a suction filter,
washed salt-free with deionized water and dried at
140°C for approximately 16 h.
Results of the weathering tests
The pigment specimens a) to c) were incorporated into an aqueous coating system based on an acrylate/methacrylate binder and the test specimens were prepared by spray application.
The specimens a) to c) were weathered by means of a condensation test in accordance with DIN 50017 and were evaluated one hour after the end of exposure.
The blistering was evaluated visually in accordance with DIN 53209. "m" here is a measure of the number of blisters per unit area, while "g" is a measure of the size of the blisters. The evaluation scale ranges from 0 (very good) to 5 (very poor).
The swelling was likewise assessed visually in accordance with DIN 53230. The relative evaluation scale ranges from 0 (unchanged) to 5 (very severely changed).
The adhesion was determined visually in accordance with DIN 53151, the relative evaluation scale ranging from 0 (very good) to 5 (very poor).
The table contains the test results of specimens a) to c) , and also the comparative samples with Iriodin® 22 5 WR II and Iriodin® 504 WR II and a pigment-free blank sample as aqueous clearcoat. The pigments Iriodin® 225 WR II (titanium dioxide pigment) and Iriodin® 504 WR II

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(iron oxide pigment) are prior art and do not possess the adhesion-promoting interlayer of the invention.
Table: Weathering results of the aftertreated pigments
Example No. Blistering Swelling Adhesion
a) m 1 / g 1 Q 1 1
b) m 1 / g 1 Q 1 1
c) m 0 / g 0 Q 0 0
Iriodin® 225 WR II m 2 / g 1 Q 1-2 1-2
Iriodin® 504 WR II m 3 / g 4 Q 3-4 4
Blank sample m 0 / g 0 Q 0 0

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WE CLAIM
1. Pearl lustre pigments comprising
a first, inner layer, consisting of a plateletshaped substrate,
a second layer,
comprising one or more metal oxides,
the first and second layers forming a calcined
base pigment,
a third layer, comprising the corresponding
uncalcined oxide, hydroxide or oxide hydrate of the oxide of the second layer,
a fourth layer, comprising oxides, hydroxides and/or oxide hydrates of silicon or aluminium,
a fifth layer, comprising oxides, hydroxides and/or
oxide hydrates of silicon, aluminium, zirconium and/or cerium, this layer differing from the fourth layer, and
a sixth layer, comprising one or more organofunctional coupling reagents.
2. Pearl lustre pigment according to Claim 1, characterized in that the substrate is mica.
3. Pearl lustre pigment according to either of Claims 1 and 2, characterized in that the metal oxide of the second layer is iron(III) oxide or titanium dioxide.
4. Pearl lustre pigment according to one or more of Claims 1 to 3, characterized in that the organic coupling reagent is a silane, zirconium aluminate, zirconate or titanate.

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5. Process for preparing a pearl lustre pigment
according to one of Claims 1 to 4, characterized
in that a calcined, platelet-shaped substrate
coated with one or more metal oxides is suspended
in water, heated at from 25 to 100°C, preferably
from 40 to 80°C, and adjusted to a pH of from 3 to
11, preferably from 5 to 9, in a first stage one
or more water-soluble metal salts are added which
correspond to the calcined metal oxides of the
metal oxide coating of the platelet-shaped
substrate, these salts are deposited in whole or
in part as oxide, hydroxide and/or oxide hydrate,
followed by heating at from 30 to 100°C,
preferably from 40 to 75°C, and adjustment to a pH
of from 3 to 9, preferably from 6 to 7, in a
second stage a water-soluble silicate and/or aluminium salt is added, and is deposited in whole or in part as oxide, hydroxide and/or oxide hydrate, in a third stage, by adding at least one water-soluble silicate, aluminium salt, cerium salt and/or zirconium salt at a pH in the range from 3 to 9, preferably from 6 to 7, the corresponding oxides, hydroxides or oxide hydrates thereof are deposited, it being necessary for these to differ from those of the second stage, and in a fourth stage at least one organic coupling agent is added and is deposited at a pH of from 3 to 9, preferably from 6 to 8.
6. Process according to Claim 5, characterized in that after the first stage and before the second stage is carried out the pigment is isolated, washed and dried.
7. Process according to either of Claims 5 and 6, characterized in that after the third stage the pigment is separated off by sedimentation, washing and filtration and is dried at from 80 to 160°C, preferably from 120 to 160°C.

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8. Process according to one of claims 5 to 7, characterized in that the calcined, platelet-shaped substrate coated with one or more metal oxides is a mica coated with iron(lll) oxide and/or titanium dioxide. 9. Process according to one or more of claims 5 to 7, characterized in that the organic coupling reagent is a sllane, zirconium aluminate, ziroconate or tltanate.
Paints, inks, plastics, coatings and cosmetics pigmented with a pearl luster pigment according to one of more of claims 1 to 4.
Dated this 17th day of OCTOBER 2001.
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Pearl lustre pigments which possess a first, inner layer, consisting of a platelet-shaped substrate,a second layer, comprising one or more metal oxides, the first and second layers forming a calcined base pigment, a third layer, comprising the corresponding uncalcined oxide, hydroxide or oxide hydrate of the oxide of the second layer, a fourth layer, comprising oxides, hydroxides and/or oxide hydrates of silicon or aluminium, a fifth layer, comprising oxides, hydroxides and/or oxide hydrates of silicon, aluminium, zirconium and/or cerium, this layer differing from the fourth layer, and a sixth layer, comprising one or more organofunctional coupling reagents. Also described are a preparation process, and the use of the pigments in paints, inks, plastics, coatings and cosmetics.


Documents:

00596-cal-2001-abstract.pdf

00596-cal-2001-claims.pdf

00596-cal-2001-correspondence.pdf

00596-cal-2001-description(complete).pdf

00596-cal-2001-form-1.pdf

00596-cal-2001-form-18.pdf

00596-cal-2001-form-2.pdf

00596-cal-2001-form-3.pdf

00596-cal-2001-form-5.pdf

00596-cal-2001-g.p.a.pdf

00596-cal-2001-latters patent.pdf

00596-cal-2001-priority document others.pdf

00596-cal-2001-priority document.pdf


Patent Number 208808
Indian Patent Application Number 596/CAL/2001
PG Journal Number 32/2007
Publication Date 10-Aug-2007
Grant Date 09-Aug-2007
Date of Filing 17-Oct-2001
Name of Patentee MERCK PATENT GMBH
Applicant Address FRANKFURTER STRASSE 250,64293, DARMSTADT,
Inventors:
# Inventor's Name Inventor's Address
1 GLAUSCH RALF ALLEESTRASSE 22A,64367 MUHLTAL,
2 JEKEL MARITA TEICHHAUSSTRASSE 51,64287,DARMSTADT,GERMANY
PCT International Classification Number C 04B 14/20
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 DE10054980.2 2000-11-06 Germany