Two-stage chemical recycling of polyurethanes

The method (100) according to any one of the previous claims, wherein step d) further comprises the steps:

• d2) providing an second alcohol G, either mono- or polyfunctional, different from the first alcohol B provided at step b);
• d3) conducting a transcarbamation reaction (201) on the carbamate C provided at step d), thereby obtaining a carbamate H of the second alcohol G provided at step d2), and the first alcohol B;
• d4) separating (202) the carbamate H obtained at step d3) from the first alcohol B.

The method (100) according to any one of the previous claims, wherein step e) comprises:

• e2) providing a solution or suspension in a solvent S, of the carbamate C or H provided at step d);
• e3) transferring to a thermolysis reactor, the solution or suspension provided at step e2);
• e4) performing the thermolysis reaction (103) in said thermolysis reactor.

The method (100) according to any one of the previous claims, wherein at step e) the thermolysis reaction (103) is performed at a temperature from about 200° C. to about 450° C., preferably from about 200° C. to about 300° C.

The method (100) according to any one of the previous claims, wherein at step a) the polyurethane A comprises at least two polyurethanes.

The method (100) according to any one of the previous claims, wherein at step f) the isocyanate E is separated from the alcohol F by distilling away the alcohol F at a temperature from about 100° C. to about 300° C., preferably from about 200° C. to about 250° C., more preferably from 210° C. to about 230° C.

The method (100) according to any one of the previous claims, wherein at step c) the alcoholysis reaction is performed at a temperature equal to or lower than the boiling point of alcohol B.

The method (100) according to any one of the previous claims, wherein the polyurethane A provided at step a) is a polyurethane made from MDI, and at step e) the thermolysis reaction is performed on a dicarbamate of MDI at a temperature from 230° C. to about 280° C., preferably from 240° C. to 270° C., more preferably around 250° C.

The method (100) according to any one of the previous claims, wherein at step b) and/or d2) the first alcohol B and/or the second alcohol G is a C1-C15 alcohol, preferably a C1-C10 alcohol, more preferably a C4-C8 alcohol.

The method (100) according to any one of the previous claims, wherein at step b) and/or d2) the first alcohol B and/or second alcohol G is selected from the list comprising:

• propanol, pentanol, isopropyl alcohol, butanol, hexanol, nonanol, octanol, glycerol, ethylene glycol, diethylene glycol, triethylene glycol.

The method (100) according to any one of the previous claims, wherein at step b) and/or d2) the first alcohol B and/or the second alcohol G is provided in excess, wherein the molar excess of said first alcohol B and/or second alcohol G with respect to the polyol D is at least 2:1, preferably exceeding 3:1, more preferably exceeding 4:1.

The method (100) according to any one of the previous claims, wherein at step e) the thermolysis reaction (103) is performed at a pressure from about 1 bara to about 10 mbara, preferably from about 1 bara to about 100 mbara, more preferably from about 1 bara to about 200 mbara, even more preferably from 1 bara to about 0.9 bara;

• or under an inert gas.