METHOD OF PREPARING CARBIDE FORMALDEHYDE CONCENTRATE Russian patent published in 2001 - IPC

FIELD: large-ton production of carbide-formaldehyde concentrates. SUBSTANCE: concentrate is prepared by condensation of carbamide with formaldehyde used in the form of 40-45% aqueous solution containing not more than 2 % of weight of formaldehyde at carbamide to formaldehyde molar ratio of 1: 2.5-2.7 first in alkaline medium having pH of 7.5-9.0 at 80-85 C for 5-35 min, and then in acid medium having pH of 5.3-5.6 at 85-96 C for 60-90 min. The resulting product is concentrated in vacuum till refraction coefficient is attained, and cooled. Second embodiment envisages preparing carbide-formaldehyde concentrate when using other pH parameters of medium, process duration and ratio of components. Invention makes it possible to reduce content of free formaldehyde and methanol in concentrate and in air of zone of industrial premises. EFFECT: more efficient preparation method. 8 cl, 6 ex, 2 tbl