Value chain return process for the recovery and of polymeric methylene phenylene amine (pmda) as its hci salt from the depolymerization of spend polyurethane and polyisocyanurate rigid foams

2:

• The process according to claim 1, further comprising:
• e) performing phosgenation of the pMDA HCl salt to obtain pMDI.

3:

• The process according to claim 1, further comprising purifying.

4:

• The process according to claim 2, further comprising:
• d1) purifying the pMDA-HCl salt by washing with fresh solvents and/or drying under elevated temperatures and/or drying in vacuo.

5:

• The process according to claim 1, further comprising:
• e*) performing a condensation reaction of the pMDA HCl salt with formaldehyde to obtain pMDA.

(canceled)

7:

• The process according claim 1, wherein the catalytic active organic nitrogen compound is selected from the group consisting of pyridine, 1-methylimdazole, and triethylamine.

8:

• The process according to claim 1, wherein distillative removal of volatile compounds is carried out at a pressure of 1 bar to 0.001 bar and a temperature of 20° C. to 250° C.

9:

• The process according to claim 1, wherein the aprotic organic solvent (S1) is at least one selected from the group consisting of an aliphatic hydrocarbon, a halogenated hydrocarbon, an ether, an aromatic hydrocarbon, an ester, and a ketone.

10:

• The process according to claim 1, wherein HCl is added as a gas or a solution of HCl in solvent (S1).

11:

• A polymeric methylene phenylene amine (pMDA) obtained by the process of claim 1.

12:

• A polymeric methylenediphenyl diisocyanate (pMDI) obtained by the process of claim 1.

13:

• A method for preparing polyurethanes or polyisocyanurates, comprising reacting the polymeric methylenediphenyl diisocyanate according to claim 12.