Abstract: A process for producing poly(1,3-propylene terephthalate) from the reaction of either terephthalic acid or a lower dialkyl ester of terephthalic acid and 1,3-propanediol and polymerization of the monomer produced therefrom using a novel catalyst system. The novel catalyst composition includes employing an effective catalytic amount tin in the polycondensation reaction. Using the catalyst system and Hostaperm.RTM. pigments allows for the production of poly(1,3-propylene terephthalate) having yellowness of less than 4 and an IV of at least 0.80 dl/g.

Abstract: A process for removing inorganic compounds from glycol recovery still bottoms resulting from the manufacture of poly(ethylene terephthalate), the novel process using a small amount of phosphoric acid to precipitate the antimony and then removing the titanium dioxide and antimony compound by a centrifuge. The novel process for removing the inorganic compounds from the recovery polyester bottoms includes the steps of distilling ethylene glycol from the spent glycol until the remaining bottoms have a solids concentration from about 15% to about 45%; adding phosphoric acid to the bottoms to form an antimony compound and removing the antimony and titanium precipitates from the bottoms by a centrifuge.

Abstract: A process is disclosed for the preparation of polymeric butanediol ester of terephthalic acid by means of ester interchange process having improved rates of polymerization to produce polyesters having improved color. The process employs the neat addition of terephthalic acid on completion of the ester interchange reaction and maintains the ratio of glycol to dimethyl terephthalate in the ratio of not more than 1.3 to 1. Preferably the process is conducted with titanium containing catalysts and has a polymerization rate greater than 700 deciliters per hour.

Abstract: There is disclosed a process for reducing the reaction time in the hydrolysis of a condensation polymer wherein molten condensation polymer is intimately admixed with a depolymerizing agent which is either (i) one of the products resulting from the complete hydrolytic depolymerization of the condensation polymer; or (ii) water. The depolymerization agent is present in the mixture in an amount which is less than the weight of the condensation polymer and the materials are intimately admixed for a time sufficient that the molecular of the condensation polymer is reduced by at least 50%. The treated condensation polymer of lower molecular weight is thereafter subjected to neutral hydrolysis. In addition to decreasing the overall time required to effect complete hydrolytic depolymerization, this process additionally permits the use of a smaller hydrolysis vessel, thereby reducing the fabrication cost of the hydrolysis unit.

Abstract: A process is described for reducing the amount of low molecular weight oligomers formed during the hydrolysis of a condensation polymer. This process comprises the neutral aqueous hydrolysis of a condensation polymer in which conditions are controlled such that the following two conditions are met:(1) the amount of water and the condensation polymer present in the hydrolysis zone are such that the least soluble final depolymerization product would not exceed its solubility limits, assuming all of the polymer is converted to final depolymerization products; and(2) temperature conditions and aqueous concentration of final depolymerization products are controlled so that at equilibrium, the amount of low molecular weight oligomers is no greater than 7% of the theoretical, based on the amount of polymer added.

Abstract: There is disclosed an improved modified polymer suitable for use in making hollow containers by conventional extrusion blow molding. It is a specific type of end-capped and branched polyethylene terephthalate polymer or copolymer. In the improvement, the end-cap comprises the reacted component of a difunctional acid or alkali metal salt of a difunctional acid having the formula: ##STR1## wherein: X has a valency of 6 and is selected from sulfur, selenium, and tellurium;M is an alkali metal or hydrogen; andY is hydrogen or an aliphatic group containing from 1 to 18 carbon atoms.The preferred difunctional acid is m-sulfobenzoic acid. The product typically contains few large gels having diameters greater than 0.1 mm.