Synergistic catalyst composition containing a group ii metal salt and an arsenic compound for preparing condensation-type polyesters

Claim 1

A PROCESS FOR PREPARING A HIGHLY POLYMERIC LINEAR POLYESTER COMPRISING, (1) HEATING AT AN ELEVATED TEMPERATURE IN THE PRESENCE OF A CATALYST (1) A LOWER DIALKYL ESTER OF A BIFUNCTIONAL DICARBOXYLIC ACID WHICH IS PREDOMINANTLY COMPOSED OF AN AROMATIC ACID CONTAINING FROM 1 TO 2 BENZENE RINGS AND FROM 8 TO 20 CARBON ATOMS AND SAID ALKYL RADICALS CONTAIN FROM 1 TO 4 CARBON ATOMS, AND (2) A BIFUNCTIONAL GLYCOL CONTAINING FROM 2 TO 10 CARBON ATOMS, SAID HEATING BEING UNDER CONDITIONS FACILITATING REMOVAL OF THE LOWER ALKANOL FORMED FROM SAID LOWER DIALKYL ESTER BY ESTER EXCHANGE WITH SAID GLYCOL, WHEREBY A SUBSTANTIALLY MONOMERIC PROTOPOLYMER IS FORMED, AND (II) HEATING SAID PROTOPOLYMER IN THE PRESENCE OF SAID CATALYST UNDER CONDITIONS FACILITATING REMOVAL OF SUPERFLUOUS QUANTITIES OF SAID GLYCOL WHEREBY SAID HIGHLY POLYMERIC LINEAR POLYESTER IS FORMED SAID CATALYST BEING PRESENT IN BOTH OF STEPS I AND II IN A CONCENTRATION OF FROM 0.001 PERCENT TO 0.1 PERCENT BASED ON THE WEIGHT OF SAID LOWER DIALKYL ESTER, SAID CATALYST BEING ESSENTIALLY COMPOSED OF (1) A LOWER ALKANOATE SALT OF A METAL SELECTED FROM THE GROUP CONSISTING OF MAGNESIUM, CALCIUM, ZINC AND CADMIUM, SAID ALKANOATE RADICALS CONTAINING FROM 2 TO 6 CARBON ATOMS, AND (2) AN INORGANIC ARSENIC COMPOUND SELECTED FROM THE GROUP CONSISTING OF THE OXIDES, ACIDS, HALIDES AND NITRATES OF TRIVALENT AND PENTAVELENT, ARSENIC THE PROPORTIONS BEING SUCH THAT THERE ARE FROM ABOUT 0.7 TO 5 ATOMS OF SAID METAL FOR EACH ATOM OF ARSENIC, WHEREBY A COLORLESS, CLEAR, HIGHLY POLYMERIC POLYESTER CAN BE PREPARED IN LESS TIME THAN WHEN EITHER OF SAID CATALYSTIC COMPONENTS IS USED BY ITSELF IN THE SAME TOTAL CONCENTRATION.