Sheet or film prodn. from polymer powder - by compacting and coalescing in nip of contra:rotating rollers and withdrawn sheet under tension

摘要

Sheets or films are produced by feeding a thermoplastic or thermosetting powder to the nip between two rollers to compact and coalesce the powder particles and form a sheet or film, the peripheral speed of the rollers being equal to the linear speed of the sheet emerging from the nip. A mechanical tension is then applied to the sheet or film corresponding to a force which does not exceed the elastic limit of the sheet or film. The polymer is pref. a polyolefin, a phenolic resin or a urea formaldehyde resin. The rollers at a temp. lower than the m.pt. of the polymer. The mechanical tension applied is as high as possible without exceeding the elastic limit of the sheet or film. The process allows prodn. of sheets within a large range of thicknesses (63.5 microns to 1.25mm.) directly from a polymer powder.