| 摘要 |
<p>1. A process for producing aminoaldehyde binders containing, per mole of urea, from 0.2 to 0.8 moles of melamine, from 1.5 to 2.5 moles of formaldehyde, and from 0.05 to 0.5 mole of phenol, characterised in that in a first stage a precondensate of urea and formaldehyde with a molar ratio F/U between 3 and 6 is condensed in the presence of urea so that the molar ratio F/U at said first stage is between 1.8 and 3, the condensation being carried out at a temperature of between 40 and 100 C, firstly at a neutral pH then at an acid pH at most equal to 5.5, and that in a second stage all the phenol and the remaining urea are added, the condensation still being carried out at an acid pH at most equal to 5.5 and at a temperature of between 40 and 100 C, until the viscosity of the reaction mixture is between 200 and 1,200 m Pa . s at 20 C for a dry extract content of 52% and that in a third stage, after neutralisation to a pH of at least 8, all the melamine is added, the reaction medium being heated to between 40 and 100 C until the viscosity of the reaction mixture is between 200 and 1,500 m Pa . s for a dry extract of 60 % at 20 C.</p> |
