The production of polyesters and copolyesters of dicarboxylic acids and aliphatic glycols has been carried out commercially for many decades. Among the earliest disclosures relating to the production of polyesters and copolyesters is the disclosure in U.S. Pat. No. 2,465,319, issued Mar. 22, 1949. Since this disclosure many variations have been made in the process and many catalysts have been discovered and patented. On Dec. 8, 1970, there issued U.S. Pat. No. 3,546,179, which is directed to the use of compounds containing both silicon and phosphorus atoms a compounds as a catalyst for the production of such polyesters and copolyesters.
The use of metal halides and certain silicon compounds as catalysts in the polycondensation of dicarboxylic acids and aliphatic glycols is disclosed in U.S. Pat. Nos. 4,143,057; 4,254,241; and Re-30,554. The metal halides employed in the examples therein are necessarily employed with solvent present. In addition these compounds tend to be hydrolytically unstable and, thus, require careful handling during their use. Thus, although these catalysts are highly advantageous it would be highly desirable to have a catalyst that may be of use without a solvent and which is hydrolytically stable.