Preparation method of flexible polyurethane foam

A method for preparing a flexible polyurethane foam, comprising the following steps of:

• (1) subjecting an epoxidized vegetable oil, a benzoylformic acid, a basic catalyst, and an inert solvent to a ring-opening reaction in a first microchannel reactor of a microchannel reaction device to obtain a vegetable oil polyol;
• (2) subjecting the vegetable oil polyol obtained in the step (1), a propylene oxide and the inert solvent to an addition polymerization reaction in a second microchannel reactor of the microchannel reaction device to obtain a vegetable oil polyol for the flexible polyurethane foam, wherein the vegetable oil polyol for the flexible polyurethane foam comprises a hydroxyl value of 31-46 mg KOH/q and viscosity of 648-960 mPas at 25° C.;
• (3) using the vegetable oil polyol for the flexible polyurethane foam obtained in the step (2) as a unique polyol, preparing a formulation comprising the following components in parts by weight:
• 100 parts of the vegetable oil polyol for the flexible polyurethane foam obtained in the step (2);
• 8 parts of ethylene glycol;
• 0.5 parts of stabilizer silicone oil B8681;
• 1 part of water;
• 1 part of triethylene diamine;
• and 1.0 part of toluene diisocyanate;
• wherein preparing the formulation comprises:
• weighing the above components excluding the toluene diisocyanate by weight first, mixing thoroughly at 25° C., adding the measured toluene diisocyanate, and stirring for 10s, and
• (4) pouring the mixture produced in the step (3) into a foaming box for a foaming reaction and curing to obtain the flexible polyurethane foam,
• wherein a molar ratio of an epoxy group in the epoxidized vegetable oil in the step (1) to the propylene oxide in the step (2) is 1:(10-20), and
• wherein the produced flexible polyurethane foam is having the following properties:
• density of 30.2-52.2 kg/m3;
• indentation strength (25% IFD) of 85-136 N;
• resilience by ball rebound 51-61%;
• elongation at break of 115-144%;
• tensile strength of 103-121 kPa and
• tear strength of 351-412 N/m.