Southern Clay Products, Inc.

Carl J Bauer

Benjamin W Knesek

John D Boothe

Clois E Powell

Harry Ryan Dennis

Dwaine E Siptak

Terrence P Brennan

Frank S Scimecca

A stable aqueous pigment slurry and a process for preparing same. The slurry contains about 50 to 90 wt. %, based on the weight of the slurry, of a pigment such as titanium dioxide and about 0.2 to 3.0 wt. %, based on the weight of the slurry, of a smectite clay such as bentonite, hectorite or montmorillonite. Preferably, the pigment slurry also contains about 0.1 to 2.0 wt. %, based on the weight of the slurry, of a dispersant. The process involves admixing a pigment slurry and a smectite clay slurry and preferably also the dispersant by milling the three components together under high shear conditions.

TiO.sub.2 slurry stabilization

An improved process for preparing an aqueous clay slurry having superior gellation properties. The process involves the bead milling of the clay in an aqueous medium for a period of about 0.5 to 20 minutes at an energy input level of about 44 to 146 kilowatt-hours per metric ton of dry clay. The milling may carried out using any suitable horizontal or vertical sand mill or ball mill such as the 'Morehouse Cowles Sandmill' or the 'Polymill' containing a grinding medium such as zirconium silicate or zirconium oxide. The clay is preferably a smectite clay such as montmorillonite and is present in the slurry in the range of about 3 to 30 wt. %, based on the total weight of the slurry. The aqueous clay slurry is useful as a rheological additive in water-based coating formulations.

Method for producing rheological additives and coating compositions

Organoclay compositions which comprise the reaction product of a smectite-type clay having an ion exchange capacity of at least 50 meq. wt. per 100 g. clay (active basis), and an alkoxylated quaternary ammonium compound having one or two alkoxylated chains containing 0-10 moles ethylene oxide and 3-15 moles of propylene or butylene oxide residues are useful thixotropic materials, especially for the preparation of aqueous systems.

Formulations including improved organoclay compositions

Unusually high loading levels of smectite minerals are found to provide excellent pigment spacing in aqueous-based coatings, as will enable desired improved hiding, thereby extending the pigment. The level of smectite used in accordance with the invention is sufficiently high that the high gelling efficiency smectites previously used as thixotropes would be inappropriate, and would yield viscosities so high as to render the aqueous coating composition lacking in desired flowability properties. Thus in accordance with the present invention, there is mixed with the aqueous carrier and pigment at least 0.5% by weight of the total composition, of a particulate water swellable smectite which has a gelling efficiency such as to display a 20 rpm Brookfield viscosity of less than 900 cps when subjected to the standard gelling test herein, with the amount of the smectite in the composition not exceeding that which would raise the viscosity of the composition above 110 Krebs Units (KU).

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Gonzales, TX, United States of America

Carl J Bauer