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Process for the modification of TiO2 nanoparticles

IP.com Disclosure Number: IPCOM000198940D
Publication Date: 2010-Aug-18

Publishing Venue

The IP.com Prior Art Database

Abstract

The present invention describes a process for the homogeneous dispersion of inorganic nanoparticles in two-component polyurethane coating materials with the aim of improving the scratch resistance of coatings obtained therefrom.

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Process for the modification of TiO2 nanoparticles

Description

The present invention describes a process for the homogeneous dispersion of inorganic nanoparticles in two-component polyurethane coating materials with the aim of improving the scratch resistance of coatings obtained therefrom.

In order to incorporate inorganic particles into organic coating materials, these particles are frequently prepared as milled or precipitated solids or a slurry or paste and then suspended in the organic coating material.

A disadvantage of this is that the particles cannot be transferred into an organic matrix without agglomerates by known methods, such as dry milling, wet milling, ultrasonic treatment or extrusion. In addition, for example, particles dispersed by wet milling tend to agglomerate after removal of the solvent, so that the particles are nonuniformly dis- tributed on introduction into a medium, such as, for example, a coating material. As a rule, this results in a loss of transparency of the coating material and, owing to the phase separation of the coating material, leads to abrasion-labile coatings having little hardness.

Since a particular embodiment of the present invention is to use aqueous inorganic nanoparticle sols as inorganic filler for organic coating materials, a suitable pretreat- ment of the particles is required in order to transfer them into the organic resin without agglomeration.

Direct suspension of the particles in the aqueous solvent in the organic coating materi- als is not possible, generally owing to the incompatibility of the solvents. However, it is necessary substantially to dispense with solvents since solvents constitute an addi- tional component in the finish system, and this would mean removal of the solvent by the end user. Ready-to-use, low-solvent coating materials which already comprises inorganic particles are therefore sought.

Development of nanotechnology has led a way to impart special properties (self clean- ing, antifogging, dirt repellent etc.) to conventional polymer coatings. However, the property enhancement highly depends on the intrinsic properties of nanoparticles such as particle size, particle size distribution and its shape, and the level of loading in the composition. For a transparent coating application incorporating nanoparticles it is al- ways important to avoid particle agglomeration due to the incompatibility between na- noparticles and the formulation ingredients. This can be achieved by a proper surface modification with an organic moiety that enhances the compatibility of nanoparticles to the polymer.

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US-A-2005/063,898 describes the process for preparation and modification of titanium dioxide nanoparticle and their dispersions in acrylate based polymers. Although the disclosed procedure provides transparent dispersion in acrylate, the process for modi- fying TiO2 nanoparticles requires a heating up to at least 50ÂșC.

US-B-5,858,077 d...