PRODUCTION OF ACID COLLOIDAL SOLUTIONS OF MELAMINE-FORMALDEHYDE RESINS

摘要

The process comprises precondensing melamine and HCHO (or a cpd forming HCHO) in an aqs. suspension at pH 4-9; followed by treatin gthe precondensate with excess HCHO in above pH range and finally acidifying the condensate suspension with HCl or an aliphatic carboxylic acid with apKa =3.5 and/or phosphoric acid. The soln. is storage stable for >=6 months without gelling and when incorporated in paper gives a prod. with superior wet strength than when prior art resins (as prepd by US 2986489) are used.