method of producing a film suitable for siegelfähige polypropylens

摘要

A C3H6 copolymer, (I), is produced in 2 steps, by (I) preparing a random copolymer having reduced specific viscosity, RSV, 4-8 dl./g., by copolymerising a mixt. contg. by wt., either (a) 94-5-99.5% C3H6 with 0.5-6.5% C2H4 or (b) 85-97.5% C3H6, 0.5-5% C2H4 and 2-10%, w.r.t. total mixt., of another l-olefin having formula CH2=CHR (where R is 2-6C alkyl) in the presence of H2 as mol. wt. regulator, a catalyst and opt. a dispersant, and (2) degrading the copolymer by melt extrusion at 200-300 degrees C. in the absence of O2 and radical-donors, to reduce mol. wt. to RSV 1.8-3.5 dl./g. The catalyst in (1) consists of a Ti-contg. solid component, an organic Al component and opt. 1 or more cpds. having electron-donor character. (I) forms foils which retain their sealability also after preliminary printing. By controlling RSV in step (1), soluble polymer quantity is no higher than that obtd. by C3H6 homoplymerisation. The suspension is easily pumped and polymer powder is easily separated.