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Pearlescent pigment for water-borne surface-coating systems

a surface coating and pearlescent technology, applied in the direction of pigment pastes, pigment treatment with organosilicon compounds, coatings, etc., can solve the problems of reducing the distinctness of images, adversely affecting the gloss and color, and unsuitable for use in water-thinnable surface coating systems, and achieve excellent weathering resistance

Inactive Publication Date: 2010-10-26
MERCK PATENT GMBH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0009]An object of the present invention is therefore to provide a pearlescent pigment having excellent weathering resistance which is suitable for various, chemically different water-thinnable surface coating systems.
[0041]The neutral-color pigments obtained in this way have very good weathering resistance, which is confirmed by the test results carried out below. The pigment is on the one hand readily free-flowing and on the other hand has very good suitability for water-thinnable surface-coating systems, in particular automotive paint systems, with respect to dispersibility, stability, coloristic properties, microbubble formation, swelling and gloss.

Problems solved by technology

However, they are not suitable for use in water-thinnable surface-coating systems, since they cause the formation of microfine bubbles in the coating film which significantly increases light scattering and thus adversely affects gloss and color.
In addition, the distinctness of image (DOI) is greatly reduced and the regeneration capacity of the coating film is impaired.
Attempts to modify the surface of pearlescent pigments with the aid of these organofunctional silanes in order to improve their weathering resistance and to make them suitable for water-thinnable surface-coating systems have given unsatisfactory results.
The strength of the bond between the silane and the surface of the substrate is limited.
A further disadvantage is that the coverage of the substrate surface by the silane is incomplete.

Method used

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  • Pearlescent pigment for water-borne surface-coating systems

Examples

Experimental program
Comparison scheme
Effect test

example 1

[0061]100 g of Iriodin® 504 Red (iron(III) oxide-coated mica pigment from E. Merck, Darmstadt) are suspended in 900 ml of demineralized water, and the suspension is heated to 40° C. with vigorous, stirring.

[0062]The pH is adjusted to 9.0 by means of 2.5% sodium hydroxide solution. All the pH values indicated are determined with the aid of suitable pH indicator paper.

[0063]A solution of 2.7 ml of sodium water glass (370 g of SiO2 per liter) in 150 ml of demineralized water is subsequently added dropwise over the course of 30 minutes to the pigment suspension. During this addition, the pH is kept constant by means of 2.5% hydrochloric acid. When the addition is complete, the mixture is stirred at 40° C. for a further 15 minutes. The pH is then adjusted to 6.5 over the course of 10 minutes by means of 2.5% hydrochloric acid, and the mixture is stirred at 40° C. for a further 15 minutes. 1.35 g of sodium sulfate, 2.30 g of aluminum chloride hexahydrate and 1.10 g of cerium(III) chloride...

example 2

[0069]100 g of Iriodin® 225 Rutile Pearlescent Blue (titanium dioxide-coated mica pigment from E. Merck, Darmstadt) are suspended in 900 ml of demineralized water, and the suspension is heated to 40° C. with vigorous stirring. The procedure of Example 1 is then followed as far as the addition of the coupling reagents.

[0070]3.0 g of pure Dynasilan AMMO (3-aminopropyltrimethoxysilane from Huls AG, Troisdorf) are then added over the course of 10 minutes. During this addition, the pH is kept constant at 3.3 by means of 2.5% hydrochloric acid.

[0071]5.0 g of pure Z 6040 (3-glycidoxypropyltrimethoxysilane from Dow Corning chemicals) are then added over the course of 10 minutes. During this addition, the pH remains constant at 3.3.

[0072]13.2 g of pure Manchem C (carboxyzirconium aluminate solution from Rhone-Poulenc Chemicals) are subsequently added over the course of 10 minutes. During this addition, the pH is kept constant at 3.3 by means of 2.5% hydrochloric acid. When the addition is co...

example 3

[0076]100 g of Iriodin® 225 Rutile Pearlescent Blue (titanium dioxide-coated mica pigment from E. Merck, Darmstadt) are suspended in 900 ml of demineralized water, and the suspension is heated to 40° C. with vigorous stirring. The procedure of Example 1 is then followed as far as the addition of the coupling reagents.

[0077]3.0 g of pure Dynasilan MEMO (3-methacryloxypropyltrimethoxysilane from Huls AG, Troisdorf) are then added over the course of 10 minutes. During this addition, the pH remains constant at 3.3.

[0078]In addition, 5.0 g of pure Z 6040 (3-glycidoxypropyltrimethoxysilane from Dow Corning chemicals) are then added over the course of 10 minutes. During this addition, the pH remains constant at 3.3.

[0079]13.2 g of pure Manchem C (carboxyzirconium aluminate solution from Rhone-Poulenc Chemicals) are subsequently added over the course of 10 minutes.

[0080]During this addition, the pH is kept constant at 3.3 by means of 2.5% hydrochloric acid. When the addition is complete, th...

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Abstract

A pearlescent pigment based on a metal oxide-coated, platelet-shaped substrate and a top layer on the metal oxide layer, where the top layer comprises silicon dioxide, at least one further metal hydroxide or metal oxide hydrate and at least one organic coupling reagent. The further metal hydroxides or metal oxide hydrates are hydroxides or oxide hydrates of cerium, aluminum or zirconium, or mixtures thereof. The coupling reagents employed are organofunctional silanes, zirconium aluminates or metal acid esters.

Description

[0001]The invention relates to surface-modified pearlescent pigments for water-borne surface-coating systems.BACKGROUND OF THE INVENTION[0002]It is known that titanium dioxide particles present as the pigment component in a surface-coating composition cause oxidative decomposition of the polymer on exposure to ultra-violet rays and moisture, known as whitening. In order to suppress this effect of titanium dioxide, it has been proposed to coat or dope titanium dioxide with compounds of chromium, silicon, aluminum, zinc, phosphorus or zirconium.[0003]EP-A-0 268 918 describes a weathering-resistant pearlescent pigment having a hydrated zirconium oxide coating on the titanium dioxide base pigment, this coating being obtained by hydrolysis of a zirconium salt in the presence of a hypophosphite.[0004]EP-A-0 342 533 describes a weathering-resistant pearlescent pigment having, on the titanium dioxide base pigment, a top layer comprising hydrated zirconium oxide obtained by hydrolysis in the...

Claims

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Application Information

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Patent Type & Authority Patents(United States)
IPC IPC(8): C09C1/00C09C1/36C04B14/20C04B14/04C09C1/14C08K9/04C08K9/06C09C3/08C09C3/12C09D5/36C09D7/12C09D17/00
CPCC08K9/04C09C1/0015C09C1/0021C09C1/0024C09C2200/102C09C2200/401C09C2200/408C09C2200/409C09C2220/10C09D5/36C09C3/08C09C3/12C08K9/06C01P2004/20C01P2004/84
Inventor DUSCHEK, JOACHIMGLAUSCH, RALF
Owner MERCK PATENT GMBH
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