Separating different thermoplastic polymers from mixed waste - reducing particles size dry and treating suspension in successive hydrocyclones

摘要

Mixed thermoplastic waste materials of different density are sepd. for recovery by reducing the material to max. 20mm. particle (pref. 5mm. long), washing and sterilising if necessary, and suspending in a liquid. Successive hydrocyclones are appropriate are arranged in stages, with upper cylindrical parts through which the suspended materials are dropped; the ratio of the dias. of the overflow/underflow outlets is 1-4 (pref. 1-2.5), the ratio of the length/dia. of the top cylindrical part is 1-10 but increases with decrease in difference in density between the polymers and liquid. If the polymer's density exceeds that of the liquid, and if they are mainly film materials, the angle of the cyclone cone is 120-180 degrees; if the density of the polymers is only partly above that of the liquid this angle is 5-40 degrees. Continuous operation with high throughput is obtd.