Thermoplastics esp. polyester recovery from mixed fibres - by stripping dye, selectively dissolving polyester and evaporating solvent without polyester pptn.

摘要

A polyester polymer is sepd. and recovered from a collective material contg. (i) polyester, including dyed polyester fibres, and (ii) materials other than polyester fibres. Process comprises (1) stripping the dye from the dyed polyester fibres, by contacting the collective material with a dye-stripping solvent at a temp. below the temp. for dissolving the polyester and above the temp. at which the crystalline polyester fibre lattice swells to release the dye; (2) removing excess dye-contg. dye-stripping solvent which is not absorbed by the collective material; (3) selectively dissolving the polyester component by contacting the remaining dye-contg. dye-stripping solvent-charged fibres with sufficient prim. solvent which is a non-solvent for the 2nd component; (4) sepg. the dissolved polyester component from the undissolved 2nd component; and (5) sepg. the residual dye-stripping solvent and the prim. solvent from the polyester component by evaporating the solvent(s) without pptn. of the polyester component from the soln. The recovered polyesters can be used in prepn. of new, undyed prods. e.g. fibres and films. Prevention of polyester pptn. reduces need for further sepn. of entrained solvent or dye. Some solvent can be used for dye stripping, polymer recovery and fibre sepn.