| 摘要 |
Improved resol resin compositions which are suitable for obtaining phenol foams having generally closed cells which have a K factor of less than 0.029 watts/(m.K), preferably from 0.017 to 0.024 watts/(m.K) of foam thickness when measured at 24 degree C are prepared, for which purpose a resol resin precursor is rectified to a water content of less than 7% by weight, preferably from 3 to around 6% by weight based on the weight of resin. Also included in a foam-forming formulation are a viscosity- adjusting quantity of a solvent such as phenol and 10 to 20% by weight of a polyglycol based on the weight of the resin. Surfactants, expanding agents and conventional acid catalysts are used to prepare the foams. The foams prepared using these resins do not in general have any tendency to self-oxidise when placed in a stove heated to a temperature of 250 degree C, and have better resistance to flame penetration.
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