| 摘要 |
<p>Polypropylene fibrils are made by suddenly releasing the pressure on a liq. mixt. comprising (a) molten polypropylene, (b) a preponderant amt. of an alkane and (c) a liq. non-solvent for the polypropylene. The soln. is passed at elevated temp. and pressure through an orifice into a relaxation chamber where the alkane is instantly vapourised and the polypropylene solidified. Short polypropylene fibrils can be made directly from polypropylene polymerisation solns. in alkanes such as pentane and hexane, and without using the more expensive halogenated solvents in prior art. The resulting fibrils are esp. useful as papermaking additives, giving excellent drainage on the wire and forming papers of high specific gravity, even after calendering.</p> |
