A process for separatiing polyolefin fractions from solid polymer material mixtures by molar mass fractionation

A process for separating polyolefin fractions from solid polymer material mixtures by molar mass fractionation, the process comprising the steps of:

• A) providing a solid polymer material mixture comprising at least 75 wt % of polyolefin material, based on the total weight of the solid polymer material mixture, wherein the polyolefin material comprises polypropylene and/or polyethylene;
• B1) contacting the solid polymer material mixture with a non-polar solvent comprising at least one n-alkane comprising from 5 to 10 carbon atoms, to form a first composition (C1) comprising the solid polymer material mixture and the solvent;
• C1) heating the first composition (C1) at a first dissolution temperature (T1) in the range of 80 to 120° C. and a first pressure (P1) in the range of 0.1 to 1.1 MPa abs. for a first period (M1) of from 5 min to 2 h, to obtain a first solution (S1) comprising the solvent and a first polyolefin fraction (F1), the first polyolefin fraction (F1) being dissolved in the solvent, and a first undissolved material (U1);
• D1) separating the first undissolved material (U1) from the first solution (S1);
• E1) separating the first polyolefin fraction (F1) from the first solution (S1) to obtain a solidified first polyolefin fraction (F1) having a first weight average molecular weight (Mw), and optionally recovering the solvent;
• B2) contacting the separated first undissolved material (U1) with a non-polar solvent comprising at least one n-alkane comprising from 5 to 10 carbon atoms, to form a second composition (C2) comprising the separated first undissolved material (U1) and the solvent;
• C2) heating the second composition (C2) at a second dissolution temperature (T2) in the range of 90 to 160° C., with the proviso that the second dissolution temperature (T2) is higher than the first dissolution temperature (T1), and a second pressure (P2) in the range of 0.1 to 1.1 MPa abs. for a second period (M2) of from 5 min to 2 h, to obtain a solution (S2) comprising the solvent and a second polyolefin fraction (F2), the second polyolefin fraction (F2) being dissolved in the solvent, and, optionally, a second undissolved material (U2);
• D2) optionally, separating the second undissolved material (U2) from the second solution (S2);
• and
• E2) separating the second polyolefin fraction (F2) from the second solution (S2) to obtain a solidified second polyolefin fraction (F2) having a second weight average molecular weight (Mw) that is higher than the first weight average molecular weight (Mw) of the first polyolefin fraction (F1), and optionally recovering the solvent.