Production process for hydroxyalkyl ester

A production process for producing a hydroxyalkyl ester in a production apparatus, said production process comprising

• washing an inside of said production apparatus subsequent to a previous production process of producing said hydroxyalkyl ester, said washing comprising washing said inside of said production apparatus with water, followed by washing with an aqueous basic solution and thereafter washing with water,
• drying said inside of said production apparatus under reduced pressure or by introducing hot air into said production apparatus to remove residual water and reactants from said production apparatus,
• introducing a carboxylic acid, an alkylene oxide and a catalyst into said production apparatus and reacting said carboxylic acid and alkylene oxide in the presence of said catalyst and producing said hydroxyalkyl ester, wherein said alkylene oxide contains 2 to 6 carbon atoms, said carboxylic acid is selected from the group consisting of acrylic acid, methacrylic acid, acetic acid, propionic acid, butyric acid, maleic acid, fumaric acid, succinic acid, benzoic acid, terephthalic acid, trimellitic acid and pyromellitic acid and where said catalyst is at least one member selected from the group consisting of chromium chloride, chromium acetylacetonate, chromium formate, chromium acetate, chromium acrylate, chromium methacrylate, sodium bichromate, chromium dibutyldithiocarbamate, iron powder, ferric chloride, iron formate, iron acetate, iron acrylate, iron methacrylate, trialkylamines and its quaternary ammonium salts, cyclic amines and its quaternary ammonium salts, and resins having a basic functional group.