1. Field of the Invention
This invention relates to chain extenders for polyester elastomers, and, more particularly, to a process for preparing 2,3-bis(hydroxyethoxymethyl) bicyclo [2,2,1] heptane (BHEMBCH) for use in the preparation of polyester elastomers therewith.
2. Description of the Prior Art
2,3-Bis(hydroxymethyl) bicyclo [2,2,1] heptane (BHMBCH) has been described in the literature. See Birch et al., J. of Org. Chem. 21, 970-974 (1956). The Birch synthesis involved three separate steps, namely, (1) a Diels-Alder condensation of cyclopentadiene and maleic anhydride to form an unsaturated anhydride; (2) reduction of the anhydride with lithium aluminum hydride to produce an unsaturated diol; and (3) hydrogenation over a palladium catalyst to provide the saturated diol. However, in the process, a considerable quantity of undesirable by-products were obtained during step (2), and, accordingly, four crystallizations of the crude unsaturated diol were required before the hydrogenation step (3) could be carried out effectively.
French Patent No. 857,937 described the preparation and isolation of the unsaturated diol intermediate only. The process comprised reaction between cyclopentadiene and 1,4-butenediol in dioxane solvent. However, dioxane is extremely toxic and difficult to remove completely from the reaction product.
U.S. Pat. No. 3,492,330 disclosed reactions of bridged-ring olefins, including the unsaturated diol with functional alkanes. The patentee said the unsaturated diol could be prepared from cyclopentadiene and 1,4-butenediol by a classical Diels-Alder reaction.
The aformentioned copending patent application describes an improved process over the stated prior art for making BHMBCH and a polyester product made therefrom. In this invention, a more advantageous chain extender (BHEMBCH) for making polyesters is prepared for use in the synthesis of polyesters.
USPTO Backgrounds
USPTO Backgrounds