| 摘要 |
1. Method for concentrating carbamide-formaldehyde resins obtained by condensation of carbamide with formaldehyde, containing 40-60% parts by weight of dry matter, through distillation of those under reduced pressure in evaporators to over 60% parts by weight of dry matter, with evaporation from the evaporators of vapours containing steam, methanol vapour, gaseous formaldehyde and frayed, fine resin droplets, characterised in that the vapours are under adiabatic conditions rinsed with hot aqueous solution of carbamide of concentration 20-70% parts by weight, preferably 30-50%, when the solution is pre-alkalised to pH 7.4-9.0, preferably 8.2, by adding sodium or potassium hydroxide to the carbamide solution, but the amount of fresh carbamide solution supplied to the dribbling fluid is adjusted so that the molar ratio of formaldehyde to carbamide in the circulating solution was less than 0.5:1, preferably 0.1:1.<IMAGE>
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