GB993121A - Linear superpolyester production - Google Patents

Abstract

Linear superpolyesters are prepared by subjecting to solid-phase polymerization in the presence of certain titanium catalysts, particles of at least one prepolymer having an inherent viscosity of 0.1-0.45 which particles pass substantially through a 20-mesh screen with less than 25% passing a 200 mesh screen; the polymerization being effected at 175-350 DEG C. at 5-80 DEG C. below the melting point of the prepolymer and in the presence of a gas at about atmospheric pressure which flows through the polymerization zone at 10-1000 ml. of gas per minute per gram of the particles, any particles more than 5 mm. from the surface being agitated into contact with the inert gas. The superpolyesters produced melt at 180-350 DEG C., have an inherent viscosity of at least 0.5, and are those of at least one glycol and at least one dicarboxylic acid of which at least 50 mole per cent is a dicarboxylic acid having its two carboxylic groups attached to at least one carbocyclic nucleus having 4-6 carbon atoms per ring. The catalysts are those of formula <FORM:0993121/C3/1> wherein R is an alkyl radical containing 1-6 carbon atoms; R1, R2 and R3 are alkyl radicals containing 1-6 carbon atoms or aryl radicals containing 6-9 carbon atoms; M is an alkali metal; and M1 is magnesium, calcium or strontium compound. It may be used in admixture with a lead and/or antimony compound. The prepolymer particles may be prepared by grinding prepolymer obtained (a) by casting molten prepolymer as a thick sheet and allowing it to cool slowly or (b) by passing molten prepolymer into water. Prepolymers as prepared in Specification 993,122 may be used. The crystallinity of the prepolymer particles may be enhanced by treating them with a volatile organic liquid (e.g. acetone). The gas used in the solid-phase polymerization may be substantially inert (i.e. containing less than 2% oxygen), whereby colourless superpolyesters are produced, or it may be air, whereby coloured, superpolyesters result. Polymerization may be effected in a horizontal or slightly tilted tube (which may rotate) or in an upright fluidized blender. The prepolymer may be polymerized in the presence of a high molecular weight polyester to produce an ordered copolymer. Examples describe the solid-phase polymerization of (1)-(5) and (11)-(17) the polyester of 4,41-sulphonyl dibenzoic acid, succinic acid and 1: 5-pentanediol; (6) the polyester of 4,41-sulphonyl dibenzoic acid, terephthalic acid and 1: 5-pentanediol; (7) polyethylene terephthalate; (8) polyethylene isophthalate in the presence of high molecular weight polyethylene terephthalate; (9) the polyester of Example 1 in the presence of poly-N-tert.-butylacrylamide (to improve the dyeability); (10) the polyester of Example 1 viscosity stabilized with methyl benzoate. Specifications 777,216 and 818,157 also are referred to.