Published: Kem. Ind. 51 (10) (2002) 431–436
Paper reference number: n/a
Paper type: Review
J. Sadadinović and Z. Iličković
The problem of polyurethane waste recycling has major technological, ecological and economical significance since polyurethane is relatively expensive, and its disposal whether by burning or landfill is also costly. This paper gives the overwiev of existing options of PUR-recycling with industrial practice, as well as the review of the alternative options of recycling of PUR-waste that might be realized in practice in the near future. Polyurethane may be recycled using physical and chemical methods. Several physical methods for polyurethane have been developed such as grinding, compression molding, adhesive pressing. Grinding has a special importance in this field, because it's starting operation of almost all PUR-recycling methods. Grinding transform PUR-foam waste into powders allows to be used in the production of new foam. Two methods for grinding PUR-waste have been developed. Cryogenic grinding based on liquid nitrogen and grinding upon ambient conditions. Adhesive pressing is a technique where polyurethane granule are mixed with PUR-binder and then cured under heat and pressure. In USA, annually over 300 000 tons of flexible polyurethane foam scrap are recycled into carpet underlay, using this method. Some type of polyurethanes (elastomers) can be reshaped by compression molding at temperatures just below the point at which degradation commences. Chemical recycling based on converting of PUR-polymer into a starting compounds, may be used to produce a new PUR-products. Most frequently used options are glycolysis and hydrolysis. The reagent used for hydrolysis process is steam. Hydrolysis can produce polyols and amine but their reuse requires additional purification. Glycolysis is a process where polyurethane reacts with diols (alifatic glycols) at elevated temperature to produce a glycolysates-polyols, which can be used as a part of major polyol component in new PUR-foam production. ICI-split phase glycolysis and BASF-method are the best known glycolysis processes used on industrial scale. Incineration with energy recovery presents a validity option of PUR-recycling, especially because of fact that PUR has an energy value of about 35 MJ kg-1. Hydrogenation and pyrolysis are the promising techniques theoretically applicable for PUR-recycling. Those processes can break down polyurethane waste (and other plastics) to a valuable petrochemical feedstocks, using heat, pressure and hydrogen.
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polyurethanes, recycling, glycolysis, glycolysate, polyurethane foams