A new type of binder for wood particles or fibres was developed using a recycled polyol from polyurethane or PET wastes and a polyisocyanate as raw materials. The binders developed with various ratios of hydroxyl and isocyanate groups are solid at room temperature with melting points between 40 and 60°C. Between 5 and 20% of these were mixed with the wood products and compression-moulded at temperatures between 80 and 100°C and 0.75 to 2.05 kp/mm² pressure to give composites of tensile strength up to 47 N/mm2 or flexural strength up to 58 N/mm2.