Verfahren zur Zersetzung von Polyaetherurethanen

摘要

Polyether-based polyurethanes are decomposed into the polyether and an amine derived from the polyisocyanate used as starting materials for the polyurethane by contacting the polyurethane at a temperature of less than 250 DEG C under normal or elevated pressure with at least one amine which is aliphatic, cycloaliphatic, aromatic or heterocyclic and at least one compound which is an alkali metal or alkaline earth metal oxide or hydroxide or aqueous solution thereof. Both polyurethane foam and polyurethane elastomers may be decomposed. In order to avoid separation of the amine resulting from the decomposition of the polyurethane from the amine used to decompose the polyurethane, the latter amine is suitably the same as that resulting from the decomposition. Numerous amines may be used and exemplified are monoethanolamine, a mixture of monoethanolamine and aniline, an 80:20 mixture of 2,4-diaminotoluene and 2,6-diaminotoluene, cyclohexylamine, pyridine, diethanolamine and triethanolamine. The amines may also serve as a solvent system, but inert organic solvents may be used including the same polyether as that which is to be produced from the decomposition reaction. Suitable oxides and hydroxides are lithium, sodium, potassium, calcium and magnesium hydroxides, lithium oxide, sodium peroxide, potassium peroxide, magnesium oxide, calcium oxide and barium oxide. The amines and alkali or alkaline earth metal compounds may be mixed and then used as such or alternatively the polyurethane can firstly be reacted with the amine followed by the alkali or alkaline earth metal compound. When the polyurethane is completely decomposed the liquid produced is subjected to distillation under reduced pressure preceded, if a two layer liquid is formed, by a separation step in order to recover both the amine and the polyether. The amines can be phosgenated to reform the polyisocyanate which can then be reacted with the recovered polyether to form a polyurethane.ALSO:Polyamines are produced by decomposing a polyurethane derived from a polyether and polyisocyanate at a temperature of less than 250 DEG C. under normal or elevated pressure by contact with at least one aliphatic, cycloaliphatic, aromatic or heterocyclic amine and at least one alkali or alkaline earth metal oxide or hydroxide or an aqueous solution thereof. The amine which is derived from the isocyanate group of the polyisocyanate used in the production of the polyurethane is separated along with the polyether which are further separated by conventional means. Suitably, the amine used to decompose the polyurethane is the same as that as will be obtained from the decomposition. In examples, a mixture of 2,4- and 2,6 - diaminotoluene and 2,4 - diaminotoluene alone are produced by decomposing polyurethanes derived from a mixture of 2,4- and 2,6-toluene diisocyanates and from 2,4-toluene diisocyanate respectively.