GB1453220A - Chain couplers for polyesterification and polyesters - Google Patents

Abstract

1453220 Polyesters MINNESOTA MINING & MFG CO 7 June 1974 [8 June 1973 7 March 1974] 25510/74 Heading C3R [Also in Division C2] A polyester contains within its polymer chain a residue of a chain coupling agent of the formula in which R<SP>1</SP>-R<SP>4</SP> may be the same or different and represent: (a) a hydrogen atom, (b) a phenoxycarbonyl group, (c) a bis(phenoxycarbonyl) phenylcarbonyl group, or (d) a bis(phenoxycarbonyl)phenylsulphino group, with at least 3 of R<SP>1</SP> to R<SP>4</SP> being (b), (c) and/or (d) with not more than one of either (c) or (d) being present in the compound and each of the (b), (c) and (d) groups present in the compound having not more than one adjacent (b), (c) and/or (d) group. The polyester may be prepared by reacting at least one polycarboxylic compound, preferably a dicarboxylic acid or diester, with at least one polyol, preferably a diol, and adding the chain-coupling compound to the reaction mixture after polyesterification has begun, preferably after the reaction mixture has reached an intrinsic viscosity of at least 0À2. Suitable chain coupling agents are triphenyl trimesate, triphenyl trimellitate, tetraphenyl pyromellitate and tetraphenyl - 3,4,3<SP>1</SP>,4<SP>1</SP> - benzophenone tetracarboxylate. In an embodiment the reaction may be stopped after the addition of the chain-coupling agent and the polymer recovered and used in a solid state polymerization process. In the examples polyethylene terephthalate is prepared by adding any one of the above chain couplers to a reaction mixture comprising dimethyl terephthalate, ethylene glycol, zinc acetate and Sb 2 O 3 , when the intrinsic viscosity of the reaction mixture reaches 0À3.