| 摘要 |
The invention relates to a pourable water-based hardener for urea resins. It comprises 1-25 wt-% of an acidifier, 10-60 wt-% of a filler, 0.5-10 wt-% of a consistency improver and 0-50 wt-% of a formaldehyde absorbing substance. The hardener composition has a dry-matter content of 35-85% and a viscosity of 2000-12,000 mPa.sec. Polyvinyl alcohol is a suitable consistency improver, and kaolin is a particularly advantageous filler. In the process for the preparation of a polyvinyl alcohol- containing hardener composition, the polyvinyl alcohol is dissolved in water, and the acidifier and the filler are then added at a temperature which is lower than the temperature at which the polyvinyl alcohol is dissolved. The hardener composition is particularly suitable for mechanical mixing with urea resins having a dry-matter content of 55-80 wt-% and a viscosity of 500-20,000 mPa.sec, especially when using a mixing technique that involves the fine distribution of the components on a joint assembly surface. |
