| 摘要 |
Carbon black beads containing not more than 1% by weight of water, the outer portions of which are composed of carbon black particles bound together with rosin, are prepared by a modification of the process of Specification 824,589 whereby the outer portions only of preformed dry process beads as defined are uniformly wetted with water, in proportions within the range of 40 to 90 lb. of water per 100 lb. of beads, the beads being thereafter dried to a moisture content not exceeding 1% by weight, which comprises mixing with the water, prior to wetting the beads, an aqueous dispersion of rosin containing as dispersing agent an ammonium rosin soap which decomposes at the drying temperature subsequently employed in the drying of the beads. Aqueous dispersions of rosin which may have a pH of 8-10.5 may contain 40-45% weight of solid resin of particle sizes not more than 5 microns and preferably ranging from less than 1 micron to a maximum of 3, 90% of the particles being less than 1 micron are employed in proportion of 0.5-2% weight based on the weight of the carbon black. The proportion of ammonium rosin soap contained in the dispersion is merely that which is sufficient to maintain the rosin in suspension. |
