Patent ID: 6284921
Filing Date: 2001-09-04
Classification: C05C

Abstract:
A method for preparing an oligomethylene urea product comprising:a) introducing at least urea and an aqueous solution of formaldehyde into a first reactor in the overall molar ratio of urea to formaldehyde of 1:1-2:1, the reactor having a retention time of at least 0.5 h, a temperature maintained in the range of 40 to 95.degree. C. and a pH maintained in the range of 6.5 to 11, in order to produce a methylol urea composition,b) conducting the methylol urea composition to a second reactor, having a temperature maintained in the range of 5 to 35.degree. C. and a pH maintained in the range of 1.8 to 3.5, in order to produce a first oligomethylene urea slurry and, optionally,c) conducting the methylol urea composition or the first oligomethylene urea slurry to a third reactor, having a temperature maintained in the range of 5 to 35.degree. C. and a pH maintained in the range of 1.8 to 3.5, to produce a second oligomethylene urea slurry,d) conducting the oligomethylene urea slurry, which is selected from the first and the second oligomethylene urea slurries, to a filter and filtering it to form an oligomethylene urea precipitate and a filtrate,e) recycling the filtrate to the reactor, which is selected from the second and third reactor, andf) neutralizing and drying the oligomethylene urea precipitate and recovering it as said oligomethylene urea product.