Excerpt from Transactions of the American Institute of Chemical Engineers, 1912, Vol. 5

If we first produce the pure crystalline phenol-alcohol, contain ing no excess Of phenol, for instance crystalline saligenin or oxybenzyl-alcohol, and if we heat it gently, it will simply dehydrate and be transformed in a fusible mass which on cooling, solidifies to a resinous product - a fusible saliretin resin. The latter, submitted to the further action of heat, polymerizes and becomes an infusible, insoluble saliretin. This polymerization is facilitated, by the pres ence of small amounts of catalyzers, for instance, hydrochloric acid. The presence of an excess of phenol retards polymerization; hence the infusibility induced by polymerization will be retarded, and this, until some way or another the excess Of phenol has been expelled. The infusible polymerized saliretin obtained by heating phenol-alcohols containing no free phenol, or by heating fusible saliretin containing no free phenol, is insoluble in alcohol, but swells in acetone; it softens decidedly on heating, although it is no longer fusible. Longer heating does not harden it further, nor make it more resistive. It is harder, stronger, and more resistant to physical and chemical agents than the fusible saliretin from which it is derived; in this respect, it surpasses even more the soluble fusible resins described by Blumer, delaire, Baekeland, and called phenol resin by Aylesworth. But even after polymerization or hardening has been carried as far as possible, it is considerably less hard and less strong and less resistant to physical and chemical agents than the polymerization products resulting from the reaction of phenol on a sufficiently large proportion of formaldehyde or equivalent substances.

In order to obtain the latter polymerization products of maxi mum strength. Hardness, and maximum resistivity, an adequately larger amount of methylen group must be introduced before or dur ing the act of polymerization. The introduction of this methylen group may be accomplished by at least three distinct methods.

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