METHOD FOR PRODUCING CONCENTRATED CARBAMIDE-FORMALDEHYDE PRODUCTS Russian patent published in 1998 - IPC

FIELD: production of concentrated carbamide-formaldehyde products. SUBSTANCE: aqueous formaldehyde solution comprising formaldehyde and methanol (their molar ratio is not less than 2:1) is concentrated by distillation. Steam from distillation stage is fed for absorption which is carried out with the help of carbamide solution at pH 3-10. Upper product of absorption is discharged, and lower product of absorption is mixed with concentrated solution of formaldehyde from distillation stage, mixing is carried out at 20-110 C and at pH 3-10 till stable solution of concentrated carbamide-formaldehyde products is obtained. According to one of alternatives of the method portion of carbamide solution is mixed with concentrated formaldehyde solution from distillation stage and with lower product of absorption. According to other alternative method solution of carbamide is prepared by using of upper product of absorption. EFFECT: improved efficiency. 3 cl