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PROCESS FOR OBTAINING GLUES BASED ON UREOFORMALDEHYDE RESINS WITH IMPROVED COLD COLLECTION CAPACITY FOR THE PRODUCTION OF AGGLOMERATED PANELS
PROCESS FOR OBTAINING GLUES BASED ON UREOFORMALDEHYDE RESINS WITH IMPROVED COLD COLLECTION CAPACITY FOR THE PRODUCTION OF AGGLOMERATED PANELS
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机译:基于脲醛缩醛树脂的胶的制备工艺,该胶具有改进的冷收集能力,可用于生产凝结板
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摘要
Prodn. of urea-formaldehyde resin adhesives comprises first precondensing urea and HCHO in a molar ratio of 1:1.8-2.2 at 100-140 degrees C and elevated pressure in the presence of 0.5-5 wt.% (based on urea) of an acid (esp. HCOOH) for 10-100 min. to form a precondensate with a predetermined viscosity. The precondensate is neutralised or made weakly basic and condensn. is continued at 40-80 degrees C while adding urea until the final urea-HCHO molar ratio is 1:1.3-1.8. Water is opt. removed to obtain the required solids content. The adhesives are esp. useful for the mfr. of wood chipboard. They have good cold bonding properties, allowing continuous board prodn. by cold pressing to form a self-supporting rough board, which can then be passed for hot pressing without a support.
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