METHOD OF PRODUCING UREA-FORMALDEHYDE RESIN FOR MANUFACTURE OF FOAMED PLASTICS Russian patent published in 2005 - IPC

FIELD: polymer production.

SUBSTANCE: condensation of urea with formaldehyde is conducted at starting urea-to-formaldehyde molar ratio 1:(2.0-2.2) in several steps in a medium with variable acidity on heating in presence of modifying additive, namely aqueous solution of polyvinyl alcohol. As formaldehyde-containing component of condensation, urea-formaldehyde concentrate is utilized. Starting reaction mixture contains 54-60% total formaldehyde, 20-24% total urea, and water in balancing amount. Process is carried out in presence of viscosity adjuster: demineralized water and 1-3 wt parts modifier per 100 wt parts urea. Reaction mixture is first heated to 90±2°C at pH 7.5-8.5, kept for 20 min, and, after lowering temperature to 82-85°C, kept at pH 4.5-5.0 for 20-50 min and then neutralized to pH 7.5-6.0. After addition of additional urea to urea-to-formaldehyde molar ratio 1:1.5, reaction mixture is kept for further 60 min at 65-70°C.

EFFECT: eliminated production of waste water and increased productivity of equipment.

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