| 摘要 |
<p>Adding the nitrogen cpd. (I) in conjunction with the acid catalyst to the phenolic resin-blowing agent mixt. Preferred cpd. (I) is cond. prod. of urea, dicyandiamide or melamine with formaldehyde. Acid catalyst is pref. HCl. The nitrogen cpd. and catalyst react together to give a stable soln. which can be added to the phenolic resin/blowing agent mixt. to give a homogeneous foam with good flame resistance, insulation properties and mechanical strength. Specifically claimed combination is dicyandiamide-formaldehyde resin with a molar ratio of 1.1-2.5 (esp. 1.3-1.8) and HCl, using an acid/nitrogen cpd. ratio of > 1. The foaming agent is pref. a low boiling aliphatic or chlorinated hydrocarbon. Foam stabilisers, esp. silicone oils as described in FR.1,462,228, may also be added, as well as resorcinol which reduces the amt. acid catalyst necessary and improves the mechanical props of the foam.</p> |
