Production or purification procedure bis- (beta) -hydroxyethyl terephthalate.

A process for producing bis-b-hydroxyethyl terephthalate and / or condensate under the above from an aromatic polyester comprising the steps of: heating the aromatic polyester comprising terephthalic acid as the component main dicarboxylic acid and ethylene glycol as component main glycol with bis-b-hydroxyethyl terephthalate and / or a low condensate prior containing no free ethylene glycol to pre-decompose the aromatic polyester; and then reacting the product pre-decomposed obtained with ethylene glycol in amount of 1 part by weight of the pre-decomposed product and between 3, 0 to 10 0 parts by weight of ethylene glycol to convert the terephthalic acid product component pre -descompuesto bis-hydroxyethyl terephthalate-b and / or a low condensate of the above, wherein said low condensate is a compound containing ethylene terephthalate as main constituent, and has an average degree of polymerization of 1 a10.