フェノール系樹脂に関する研究 (第3報)

レゾールを用いるロジン変性フェノール樹脂の合成

抄録

For improvement of oil-solubility, authors have studied about the preparative methods of resol and rosin-modified phenolics using the resol as follows :
1) Phenol resol was obtained by the reaction of acid condensation at pH 15 and at 50°C for eight to ten hours from the methylolated phenol which was prepared by the reaction of phenol (1mol) with formaldehyde (0.83.0mol) in the presence of sodium hydroxide (0.2mol, 45% concentration) at room temperature for a day. Average composition of the resol is shown by the _??_OH CH₂ OH CH₂OH formula in case of the mole-ratio of phenol to formaldehyde being 1 : 1.
2) Some kinds of rosin-modified phenolics were prepared by heating rosin, resol and glycerine, and the relations of oil-solubility and softening point of the resins to the properties and contents of the resol were examined. Oil-solubility of the rosin-modified phenolics prepared is solely affected by the resol content and is independent for the kinds of the resol prepared under various conditions.
The limit of resol content allowing oil-solubility is 25% by weight. When the resol to be used is left for more than ten days, the lowering of softening point of the resins can be seen, compared with the case using the resol soon after the preparation.
The rosin-modified phenolics prepared here have shown excellent oil-solubility inspite of their high softening points (140180°C).