Study on phosphorus-containing polyol by degradation of waste rigid polyurethane foam

Rigid Polyurethane Foam (RPUF) has been applied as the insulation material in many fields, so the amount of polyurethane waste was accumulated gradually to pollute the environment seriously. How to degrade and apply it for high value-added is a concern for the whole of society now. In this paper, the waste RPUF was degraded by an alcoholysis reaction with Ethylene Glycol (EG) and Propylene Glycol (PG) to recover polyol. Then the polyol was reused to synthesize a phosphorus-containing polyol (P-polyol) via a transesterification reaction with diethyl ethylphosphate (DEEP). Furthermore, P-polyol was introduced into Rigid Polyurethane Foam (RPUF) by in-situ chemical reaction to obtain flame retarded RPUF to add value to the recovery technique. The reaction effect of alcoholysis and transesterification on the hydroxyl value and viscosity of polyol and P-polyol were studied. The optimal condition of alcoholysis is as follows: a mass ratio of EG, PG, and waste foam was 25:30:45 at 175 °C-200 °C. The viscosity of polyol was about 600 mPaꞏs with hydroxyl values ranging between 950 mg and 1050 mg KOH/g. The optimal transesterification condition of P-polyol is as follows: butyldihydroxychlorostannane as a catalytic agent, the mass ratio of DEEP to polyol was 1:4 at 120 °C-170 °C, the yield was over 85%, the apparent viscosity of P-polyol was 1300 mPaꞏS with the hydroxyl value about 540 mg KOH/g. It can be used in flame retarded RPUF. It provides an experimental basis for solving waste RPUF treatment and realizing a circular economy.