Process for the preparation of urea-formaldehyde resins

Details Process for the preparation of urea-formaldehyde resins Process for the preparation of urea-formaldehyde resins

C - Chemistry, Metallurgy

08

G

400/7331, 402/91

C08G 12/12 (2006.01) B32B 21/04 (2006.01) C08L 97/02 (2006.01) C09J 161/24 (2006.01)

Patent

CA 1290091

PROCESS FOR THE PREPARATION OF UREA-FORMALDEHYDE RESINS ABSTRACT Urea-formaldehyde resins which may be cured to give products having a low total extractable formaldehyde content are prepared by the following process: (i) aqueous 30-50% formaldehyde and urea are mixed in a formaldehyde:urea molar ratio of 2-3:1 at pH 6-11, (ii) this mixture is heated to at least 50°C, preferably to at least 80°C, (iii) a mineral or organic acid is added to bring the mixture to pH 0.5-3.5, (iv) the mixture is heated at a temperature between 80°C and the reflux temperature, preferably for 15 minutes to 1 hour, (v) keeping the temperature at or above 80°C, a base is added to bring the mixture to pH 6.5-9 and (vi) urea is added until the formaldehyde:urea molar ratio is within the range 0.8-1.8:1. In a modification of the process, solid particulate resins are obtained by reacting the mixture from step (v) with urea at a pH below 7 to increase the viscosity thereof, adding a base until the mixture reaches a pH of 6.5-9 and dehydrating the resulting mixture.

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