1. Recycling by physical method: Polyurethane waste material refers to the method of directly using the waste material after changing its physical form. The physical recycling methods of PMI foam include thermo-compression molding, bonding pressure molding, extrusion molding and use as filler, etc., and bonding pressure molding is the main method.
2. Recycling of chemical methods: Since the polymerization reaction of PMI foam is reversible, the polymerization reaction can be reversed under certain reaction conditions, and it will be gradually depolymerized into the original reactant or other substances, and then passed through distillation and other equipment , Can obtain pure raw material monomer polyol, isocyanate, amine and so on. The process route of using chemical methods to treat waste polyurethane materials and recycling polyols as raw materials to prepare polyurethane again. Several sets of devices have been put into trial operation. This is one of the main directions for recycling waste polyurethane.
There are six types of chemical recovery technologies: alcoholysis, hydrolysis, alkaline hydrolysis, ammonolysis, pyrolysis, and hydrocracking. The decomposition products produced by various methods are different. The alcoholysis method generally generates a mixture of polyols; the hydrolysis method generates polyols and polyamines; the alkaline hydrolysis method generates amines, alcohols and corresponding alkali carbonates; the ammonolysis method generates polyols, amines, and ureas; pyrolysis generates a mixture of gaseous and liquid fractions; The main products of the hydrocracking process are oil and gas.
3. Combustion and recovery of heat energy: Polyurethane mainly contains carbon, hydrogen, oxygen, and nitrogen. When it burns with oxygen in the air, it produces a large amount of heat energy, about 25-28MJ per kilogram of polyurethane. Polyurethane waste is often used as fuel together with municipal solid waste, which can replace part of coal and be used as fuel for boilers. Polyurethane is a clean fuel. The gas produced by combustion contains only a small amount of NO2 and does not contain SO2, which is far superior to coal, oil and other fuels. However, it needs to be pointed out that if the PMI foam is not completely burned during the incineration process, toxic gases will be generated and the atmosphere will be polluted. Therefore, people's opposition to the incineration law is constantly rising.