Recycling polyols are derived from polyurethane soft foams by the combination of glycosylsis and aminolysis.In this process the cleavage of the urethane bonds results in urea groups and the hydroxyl compounds.The polyureas from the water reaction of the polyisocyanate are in general not cleaved due to short reaction times and moderate temperatures.By this process homogeneous polyols of low glycol content are obtained the hydroxyl number of which is adjusted to the properties of the coatings aimed at and is in the range of 180 to 300 mg KOH/g depending on the Shore hardness to be produced.The primary amine content,a limting parameter for distribution in Europe,is lower than one percent leading to no limitations in this respect.The viscosity of the recycling polyols is in the range of 3000 to 6000 mPas (25 deg C) with some influence of the amount of dissolved polyureas originating from the reaction mentioned above.Coatings are produced by simple mixing of the recycling polyols plus additives in low concentrations with a di-or polyisocyanate.The coating is either sprayed by gun onto films or by applying a knife for thin film techniques using the Mathis LabDryer~(TM) for knife coating and hardening.The films of 0.2 to 4 mm thickness thus produced are hardened either at room temperature being tack-free after 30 to 120 minutes depending on catalysis or by applying warm air of 70 deg C in the LabDryer~(TM) for five to 30 minutes.Hardness and elasticity of the coatings can be adjusted by simply varying the isocyanate index.The coatings and produced have better tensile strength than current trade products,an optimal elongation behavior and can be used in the temperature range of -20 to +60 deg C.
展开▼
