Process for preparing urea-formaldehyde resins

A method of forming a urea formaldehyde resin by the condensation of urea with formaldehyde resin, comprising the steps of:

• (a) heating solid paraformaldehyde to a temperature of 60 to 120.degree. C.;
• (b) adding urea, dicyandiamide and melamine in corresponding molar quantities to the heated paraformaldehyde to form a urea mixture;
• (c) intensively dry-mixing and heating the urea mixture for approximately 15 minutes until a temperature of 80 to 110.degree. C. has been reached;
• (d) after step (c), adding a methanolic quanine base in the corresponding molar ratio to the urea mixture to form a quanine-urea-formaldehyde mixture and heating for approximately 10 minutes until the quanine-urea-formaldehyde mixture is liquefied and cooled to 65.degree. C.;
• (e) after step (d), heating the quanine-urea-formaldehyde mixture further to approximately 103 to 110.degree. C., until it boils;
• (f) when the temperature of the quanine-urea-formaldehyde mixture reaches 90.degree. C. in step (e), condensing the quanine-urea-formaldehyde mixture for a period of 30 to 100 minutes;
• (g) after step (f), adding additional urea and dicyandiamide in a corresponding molar ratio to the quanine-urea-formaldehyde mixture while it is boiling to form a urea enriched mixture;
• (h) condensing the urea enriched mixture for 90 to 180 minutes at a condensation temperature of 105 to 120.degree. C.;
• (i) after step (h), buffering the urea enriched mixture with lactic acid to form a buffered mixture;
• and
• (j) cooling the buffered mixture for approximately 120 minutes, to reach a temperature of approximately 25.degree. C.