Abstract: A continuous process for manufacturing a polyester includes introducing reactant components including a terephthalic acid slurry having an ethylene glycol to terephthalic acid molar ratio of about 2 and a TiO2 slurry to an initial reactor vessel and stirring the reactant components at greater than 0 to 200 rpm to form an oligomer; transferring the oligomer, phosphoric acid, and at least one additive (carbon black, 5-sulfoisophthalic acid, 5-sulfoisophthalic acid dimethyl ester, and/or 5-sulfoisophthalic acid diglycolate) to an intermittent reactor vessel and stirring at 400 rpm to 1000 rpm to form an intermediate, wherein the oligomer, the at least one additive, and the phosphoric acid have a residence time of from 1 minute to 5 minutes in the intermittent vessel; and polymerizing the intermediate in a final reactor vessel at a temperature of 285° C. to 320° C., and in the absence of a polyethylene glycol, to obtain the polyester.

Abstract: A continuous polymerization process where one or more stirred vessels (intermittent reactor vessels) are employed in oligomer transfer line for mixing additives. An additive is added in the stirred vessel either as a solution or as slurry. The additive may or may not be reactive with the other monomer of the polyester molecule. The additive reacts with the monomer and incorporates in the polymer backbone in one of the embodiment. One or more further additives are mixed with the pre-reactor monomer mix and are charged in the first reactor or charged through the stirred vessel in the form of single slurry or solution or multiple slurries or solutions. Any further vessels employed provide higher residence time proportionate to output and use of such vessels in reactor system is independent of the any further additives.