CZ287076B6 - Mineral pigment with hydrophilic surface finish - Google Patents

Abstract

In the present invention there is disclosed a mineral pigment with hydrophilic surface finish containing 0.005 to 1.0 percent by weight polyacrylate and/or pyrohydrolysis products thereof at a temperatures up to 350 degC, based on the pigment total weight. The polyacrylate can be represented a free polyacrylic acid or soluble salts or derivatives thereof, particularly copolymers with other olefinic compounds, preferably with maleate hydride. The polyacrylates can be applied individually or in combination with commonly used polyols and ethoxy derivatives thereof and/or products of their pyrohydrolysis. The polyols serve here as mainly as grinding intensifiers in steam jet mills. The invention can be employed for titanium white, pigments based on iron and other pigments.

Description

Inorganic pigment with hydrophilic coating

Technical field

The invention relates to an inorganic pigment with a hydrophilic coating of polyacrylates having improved dispersibility in water-dilutable systems.

BACKGROUND OF THE INVENTION

By treating the surface of the pigment particles with various organic substances, their pigment and processing properties are improved. For the application of pigments to water-borne coatings, it is common practice in the technical practice to coat such types of organic substances which impart hydrophilic character to the particles. The pigments thus treated are easier and faster to disperse in aqueous media. For this purpose, polyhydric alcohols, called polyols, such as trimethylolpropane and trimethylolethane, are most commonly used. In recent years, ethoxylated derivatives of polyols have been preferred for titanium dioxide because, unlike the original materials, they are liquid, so there is no need to prepare a solution and can therefore be applied directly undiluted. In addition, ethoxy derivatives have higher thermal stability than simple polyols and there is no danger of their decomposition when applied at higher temperatures with consequent reduction in whiteness.

Titanium dioxide is one of the most important inorganic pigments. In the case of its organic surface treatment, the organic additives can be dosed at several points in the production plant, but it is most advantageous to apply them directly to the steam jet mill. Indeed, many of the substances used for the organic coating of titanium dioxide improve the milling process and are therefore used as intensifiers for milling in a steam jet mill (GB 1022821). This is particularly true of polyols such as trimethylolpropane and trimethylolethane and their ethoxylated derivatives. Also alkanolamines, such as triethanolamine, are often used for this purpose.

The use of trimethylolpropane for the hydrophilic coating of titanium dioxide is described, for example, in DE 1767289 and CA 067303, the application of ethoxylated derivatives is disclosed in DE 1467442 and DE 4312035.

SUMMARY OF THE INVENTION

The present invention is based on an inorganic hydrophilic surface pigment characterized in that it contains from 0.005 to 1.0 wt. % polyacrylate and / or pyrohydrolysis products thereof, based on the weight of the pigment. The pigment may be anatase or rutile type titanium white or ferrous and ferric pigments, but also other types of pigments that may be inorganically surface treated but not.

As the polyacrylate, free polyacrylic acid or soluble salts or derivatives thereof may be used, the most suitable of which are copolymers with other olefinic substances, preferably maleic anhydride. The polyacrylates are either used alone or in combination with commonly used polyhydric alcohols and their ethoxy derivatives, since the polyols are more important here as milling intensifiers in a steam jet mill than for improving the pigment and processing properties of surface-treated inorganic pigments.

The preparation of the inorganic hydrophilic surface pigment according to the invention is carried out by first preparing an aqueous solution of the polyacrylate in question and introducing it into a steam jet mill in the form of an aerosol formed by superheated steam at a pressure of 0.2 to 2.5 MPa and temperature 200 to 350 ° C. Under these conditions, some substances undergo various pyrohydrolytic reactions and subsequently irreversibly bind the formed grafts to the surface of the pigment particles.

-1GB 287076 B6

In comparison with the hydrophilization methods used hitherto, the inorganic pigment with a hydrophilic coating of polyakiylates is more easily and rapidly dispersed in water-dilutable systems.

The described embodiments illustrate but do not limit the scope of the invention.

Examples

Example 1

First, an aqueous solution containing 15 wt. % polyacrylic acid. This solution was dosed at a rate of 12 kg / h into a stream of superheated water vapor (1.8 MPa pressure, 290 ° C) by a special nozzle and the aerosol formed was fed to a micronizer along with dried titanium dioxide which was dosed at 1800 kg / hr. h. The product obtained had a moisture content of 10 0.34 wt. % and contained 0.21 wt. % carbon.

Example 2

For comparison, titanium dioxide was prepared organically treated with a solution containing 15 wt. % of the sodium salt of maleic anhydride polyacrylic acid copolymer which was mixed with ethoxylated trimethylolpropane (M.h. 270) in a ratio of 2 to 1. This 15 mixture was dosed at 12 kg / h. The product obtained had a moisture content of 0.36 wt. % and contained 0.26 wt. % carbon.

Example 3

For comparison, the titanium white prepared organically with undiluted ethoxylated trimethylolpropane (M.h. 270) was prepared by the procedure of Example 1 and dosed at 20 12 kg / h. The product obtained had a moisture content of 0.31 wt. % and contained 0.38 wt. % carbon.

Example 4

The properties of titanium whites organically treated according to Examples 1 to 3 were compared to untreated starting whites. The following tests were performed:

Latex exam

This assay visually assesses the amount of non-dispersed aggregates in the water-dilutable system by subjecting it to a subjective scale of 1-5. A mixture of 52 g of pigment with 30 g of distilled water and 24 g of a suitable standard surfactant is dispersed for 30 seconds, 74 g of polyvinyl acetate are added and dispersed for a further 15 seconds. The mixture is applied on a hammer paper with a 0.12 mm slit ruler and allowed to dry. Evaluation is performed visually. Stage 1 represents a practically smooth coating without pigment, Stage 2 and 3 a small amount, and Stage 4 and 5 a large amount of non-dispersed lumps.

Research Institute of Consumer Chemistry

In this test, 15 g of titanium white is overlaid with 45 g of distilled water preheated to 30 ° C and mixed with a mechanical stirrer until complete dispersion. The time (in minutes) required for dispersion is measured.

Furthermore, the sedimentation rate of titanium dioxide from a water suspension in a measuring cylinder was compared. The highest sedimentation rate is numbered 1, the lowest number is 4.

-2GB 287076 B6

The results are summarized in the table below:

Type of titanium, white Latex, exam Dispersion Sedimentation Unedited 4 10 1 Example 1 1 1 4 Example 2 1 1.5 3 Example 3 2 3 2

PATENT CLAIMS

Claims (5)

An inorganic pigment with a superficial coating, characterized in that it contains from 0.005 to 1.0 wt. % of polyacrylate and / or its pyrohydrolysis products at temperatures up to 350 ° C based on the pigment weight. Inorganic pigment according to claim 1, characterized in that it is anatase or rutile type titanium white with or without inorganic surface treatment. Inorganic pigment according to claim 1, characterized in that it is a ferric and / or ferrous pigment based on oxo- and / or hydroxo- compounds with or without inorganic surface treatment. Inorganic pigment according to claims 1 to 3, characterized in that polyacrylic acid and / or its salts and / or derivatives and / or copolymers with other olefinic substances, preferably maleic anhydride, are used as the polyacrylate. Inorganic pigment according to Claims 1 to 4, characterized in that the polyacrylate is either used alone or in combination with commonly used polyhydric alcohols or their ethoxylated derivatives and / or their pyrohydrolysis products at temperatures up to 350 ° C.