Patent GB-747842-A (GB)
Title: Method of superficially treating very fine calcium carbonate powders
IPC: C08K3/04
Filed: 1953-12-01
Abstract: The particles of a very fine calcium carbonate powder are superficially coated with a quaternary ammonium salt or base in order to render the powder more suitable as a filler or pigment, e.g. for plastics, rubber, or lacquers  An aqueous colloidal suspension of the powder may be formed using an anionic or mationic deflocculating agent, and then an agent of opposite polarity added to form a precipitate; one of the agents used is the quaternary ammonium compound.  The precipitation may also be carried out in organic media; for example the powder may be dispersed in a nonpolar organic liquid, e.g. gasoline or benzene, using a fatty acid, e.g. oleic acid, as dispersing agent, and then precipitated with a quaternary ammonium base; or the powder may be dispersed with the quaternary ammonium base in a polar organic liqud, e.g. alcohol, ethyl acetate, or acetone, and precipitated by means of a fatty acid.  Treated mixtures of calcium carbonate with another substance may be obtained by using as the precipitant a dispersion of the other substances of opposite polarity; for example a dispersion of titanium oxide obtained with the aid of sodium silicate is added to a dispersion of calcium carbonate containing quaternary ammonium chloride, or a rubber latex is added to the calcium carbonate dispersion to obtain by precipitation a finely dispersed high filler content rubber mix. In examples (1) natural chalk is pulverized and dispersed in water with tetradecylpyridinium bromide; an aqueous solution of sodium oleate is added and the precipitate dried and milled; (2) chalk is dispersed in an aqueous solution of sodium trisilicate, and tetradecylpyridinium bromide is added, (3) the chalk dispersion of example (1) is mixed with a dispersion of titanium oxide containing sodium trisilicate to form a mixed precipitate; (4) stand oil is emulsified with sodium hydroxide and mixed with the chalk dispersion of example (1) to obtain an intimate mixture of stand oil and chalk, useful in the preparation of lacquers.  Instead of the precipitation process, the calcium carbonate may be treated by a dry process in which it is passed through a mill together with a fatty acid salt of a quarternary ammonium base; suitable salts are dimethyl-lauryl-benzylammonium stearate, methyl-butyl-stearylbenzylammonium oleate, tetradecylpyridinium oleate, dodecylpyridinium linoleate, and dodecylquinolinium oleate. The amount of salt may be from 0.1-5 per cent by weight of the calcium carbonate, and may be introduced before or during milling. In example (5) chalk is milled, and fused dimethyl-lauryl-benzyl-amonium oleate is sprayed into the mill.ALSO:Fillers for rubber comprise a finely powdered calcium carbonate, the particles of which have been coated with a quaternary ammonium salt or base (see Group III).  A rubber mix of high filler content is obtained by precipitation on adding rubber latex to a suspension of calcium carbonate containing the quaternary ammonium compound.  Example (3) describes the preparation of a filler consisting of calcium carbonate and titanium oxide by the mutual precipitation of a suspension of chalk containing tetradecylpyridinium bromide and a suspension of powdered titanium oxide containing sodium trisilicate.