The gold bronze flake pigment thereby produced is found to be of superior brilliance, i.e. containing an advantageously lower proportion of fines than gold bronze made for example with stearic acid as a grinding agent;<a href="http://www.lightcrusher.com/solutions/used-ball-mill-for-sale.html">used ball mill for sale</a> of more uniform size than heretofore obtainable; and more readily classifiable into uniform size grades. In addition, with the present method a -gold-bronze product can be achieved having a significantly higher apparent density than the stearic acid product. That is to say, whereas gold bronze ground with stearic acid in a ball mill may have an apparent density of about 12 to 14 g./in. or up to about 16 g./in. or above when ground in a stamping mill, the product of the present method may have an apparent density ringing up to about 24 g./in. Because of this greater apparent density, the gold bronze flake produced by the present method exhibits desirably superior flowing properties when dispersed in an ink or like vehicle; that is to say, this pigment is more free-flowing and hence more readily transferred (in ink) from printing rolls to paper than the gold bronze products made with stearic acid. It is further found that with the described operation there can be produced a flake having good leafing properties.
These desirable properties are achieved by the present method without the necessity for such close or critical control of operating conditions as has heretofore been necessary in making gold bronze,<a href="http://www.lightcrusher.com/solutions/granite-machinery.html">Granite crushing machine for sale</a>. e.g. with stearic acid to avoid excessive fines in the product. Further, the invention provides these advantages even when the feed is socalled rich bronze feed (containing above about 25% zinc) which has heretofore been particularly difficult to grind to flake form without production of excessive fines.
The product of the above-described example of operation is a gold-bronze flake having thereon a surface coating of polytetrafluoroethylene, effective to provide leafing in typical surface-coating vehicles.