A method for the production of artificial lightweight structures, such as threads or fibres, of molten polyesters or mixed poly esters

摘要

In the manufacture of filaments, fibres, coatings and other shaped articles or forms from melts of highly polymeric linear polyesters or interpolyesters obtained from aromatic dicarboxylic acids and glycols, the polyesters are intensively dried before melting to expel water in any form and are maintained in the water-free condition during melting and up to the point of formation of the filaments or other articles. The exclusion of water obviates or reduces any molecular degradation of the polyester. Drying, which may be carried out in stages, is effected by heating the polyester at an elevated temperature below its melting point under a reduced pressure, preferably under a high vacuum, and the dried material is then melted under conditions such that water in any form does not come into contact therewith. A drying agent, e.g. magnesium or barium perchlorate, magnesium or calcium chloride, calcium, aluminium or phosphorus oxides or silica gel, may be employed in the vicinity of the polyester to facilitate the drying operation. Alternatively, drying may be facilitated by passing a stream of an oxygen-free gas, e.g. nitrogen, over the heated polyester. In addition to the manufacture of filaments and fibres, the dry polyesters may be used for the manufacture of films, mouldings, coatings and adhesive unions. Specified polyesters are those obtained from terephthalic acid and ethylene glycol, trimethylene glycol, tetramethylene glycol, hexamethylene glycol or decamethylene glycol; diphenoxyethane-4 : 41 - dicarboxylic acid, diphenoxypropane - 4 : 41-dicarboxylic acid, diphenoxybutane-4 : 41- dicarboxylic acid, diphenoxypentane - 4 : 41-dicarboxylic acid and ethylene glycol; diphenoxypentane-4 : 41-dicarboxylic acid and hexamethylene glycol; diphenoxyhexane - 4 : 41 - dicarboxylic acid and decamethylene glycol; naphthalene-2 : 6-dicarboxylic acid and hexamethylene glycol; diphenylmethane - 4 : 41 - dicarboxylic acid, a : d -diphenylbutane 4 : 41 - dicarboxylic acid, naphthalene-2 : 6-dicarboxylic acid, naphthalene-2 : 7-dicarboxylic acid, 1 : 4-diphenoxybenzene - 41 : 411 - dicarboxylic acid, 1 : 4 - bis - (phenoxymethyl) - benzene - 41 : 411 - dicarboxylic acid, (phenoxymethyl) - benzene - 4 : 41-dicarboxylic acid, phenoxybenzene-4 : 41-dicarboxylic acid, a : b -bis-(phenylthio)-ethane-4 : 41-dicarboxylic acid, or diphenylthioether-4 : 41-dicarboxylic acid and ethylene glycol. Examples are given in which in one case polyethylene terephthalate, and in another case polyethylene diphenoxyethane - 4 : 41 - dicar - boxylate is dried under reduced pressure at 90 DEG C., and then at 200 DEG C., and melt-spun into filaments. Specifications 578,079 and 579,462 are referred to.