A method was developed for producing terephthalic acid (TPA) from secondary polyethylene terephthalate by alkaline hydrolysis when heated in a solvent medium, which is flotation agent oxal T-92 (a cheap byproduct of isoprene production). As a result of alkaline hydrolysis, sodium terephthalic acid is obtained, which is then transferred to terephthalic acid by treatment with hydrochloric acid.
Patent No. 2616299 "The method of alkaline hydrolysis of polyethylene terephthalate waste with the production of terephthalic acid" was obtained for the method of extracting TPA from polyethylene terephthalate.
The obtained TPA is used to synthesize a plasticizer according to the technologies described above.