| 摘要 |
Beaded carbon black is produced by subjecting the black to a preliminary dry beading operation as defined, crushing the resulting beads of density within the range 15-28 lbs./cu. ft. thus formed, and reforming the resultant black into beads by a wet beading process as defined, with subsequent drying. Dry, finelypowdered black of density say 3-15 lbs./cu. ft. is fed into the upper end of an inclined cylindrical drum rotating at 2-20 r.p.m. until the black agglomerates into beads having the required density. Beads pass from the lower end of the drum over an annular dam which maintains a residual, predetermined level of beads within the drum, to be screened to separate "fines" which are subsequently recycled to the process, the proportion of separated "fines" to acceptable beaded black varying from 1 : 1 to 5 : 1 usually 2 : 1. A small proportion of water, not above 8% wt. may be incorporated into the dry black before the dry beading process. The dry beads may be crushed by a separate treatment before entering the wet beading process or be transferred directly to the web-beading apparatus where they are crushed during mixing with the added water, the amount of which may vary from 50-130% wt. Apparatus employed in the wet beading process may comprise a horizontal trough fitted with a longitudinal rotatable shaft having agitator pins attached normal thereto and arranged in a spiral around the shaft, and water sprays mounted vertically above the trough at 12-inch intervals. Carbon black is introduced at one end of the trough and is mixed and crushed with a proportion of water required to form wet beads which may be passed subsequently through a series of similar troughs supplied with varying amounts of water depending on the amount already added, the beads being finally dried to a moisture content not exceeding 1%, preferably 0.1%. Specifications 652,139 and 839,919 are referred to. |
