PURPOSE: To obtain the title resin, having excellent storage stability and useful as a cement water-reducing agent, etc., by reacting melamine with formaldehyde in an aqueous medium, adding and reacting a specific amount of a sulfite and polycondensing the reaction product under specific condition.
CONSTITUTION: Melamine is primarily reacted with formaldehyde at 1.0:2.6W3.4 molar ratio and pH 3W10 in an aqueous medium and a sulfite (e.g. sodium bisulfite) in an amount of 0.7W1.3mol. based on 1mol. melamine is added. Secon dary reaction is carried out at 50W90°C and pH 9W13 for 1W5hr. A 2% sulfuric acid solution, etc., is then added thereto to adjust the pH to 3.5W6.5 and tertiary condensation reaction is carried out at 40W90°C for 1W5hr. A 20% aqueous solution of caustic soda, etc., is then added thereto to adjust pH to 9W13. A sulfite in an amount of 0.01W0.30mol. is further added to carry out quaternary reaction for 0W60min and afford the aimed resin.
DOI KIYOTO
ODAGIRI MASARU
MATSUNAGA KOJI
Next Patent: PRODUCTION OF MOLDING FROM POLYISOCYANATE POLYADDUCT