Grinding of materials in grinders having rolls with stepwise-increasing speeds

Claim 1

A PROCESS FOR THE PREPARATION OF PIGMENTS BY THE METHOD OF LIQUID SUBSTITUTION KNOWN AS THE "FLUSHING PROCESS" USING A GRINDER HAVING A CHARGING HOPPER ADAPTED TO RECEIVE MATERIAL AND A SERIES OF ROLLS ROTATING AT SPEEDS INCREASING STEPWISE FROM ROLL TO ROLL, PRESSED ONE AGAINST THE OTHER AND BETWEEN WHICH THE MATERIAL PASSES, COMPRISING THE STEPS OF: (A) INTRODUCING INTO THE HOPPER A COMPOSITION CONSISTING OF A MIXTURE OF WATER AND PRECIPITATED PIGMENTS TOGETHER WITH THE SUBSTITUTION LIQUID, (B) CAUSING THE COMPOSITION TO PASS BETWEEN THE ROLLS AND ALLOWING IT TO RETURN TO THE HOPPER IN A CLOSED CIRCUIT WHILE ADJUSTING THE TEMPERATURE, THE SPEED AND THE PRESSURE OF THE ROLLS ONE AGAINST THE OTHER IN CONCOMITANCE, FOR A TIME SUFFICIENT FOR THE COMPOSITION TO BECOME A PASTE CONSTITUTED BY A DISPERSION OF THE PIGMENTS IN THE SUBSTITUTION LIQUID AND HAVING THE DESIRED QUALITY OF DISPERSION, AND (C) REMOVING THE PASTE BY CAUSING IT TO PASS BETWEEN THE ROLLS FOR THE LAST TIME AND DETACHING IT FROM THE LAST ROLL OF THE SERIES.