Glycerol phthalate was the first synthetic polyester. It came into use around

World War I World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, the United States, and the Ottoman Empire, with fightin ...

. It was used for

waterproof Waterproofing is the process of making an object or structure waterproof or water-resistant so that it remains relatively unaffected by water or resisting the ingress of water under specified conditions. Such items may be used in wet environme ...

ing. This polyester does not form linear chains, but is built as a three-dimensional structure.Teegarden, David M. (2004) It was also sold by a German company as a varnish resin to replace Congo Copal, on account of its excellent colour. It became subsequently the starting point for one stop Alkyd manufacture. It became the back bone of the early Glyptal alkyd resins. The name alkyd is derived from the same root, acid /alcohol. The early alkyds were called Glyptal resins, since then, these have branched out to use out to use other dibasic acids and polyhydric alcohols.
Polymer chemistry: introduction to an indispensable science
NSTA Press. p. 232. , .

References

{{reflist Polyesters Plastics Phthalate esters