Abstract
For recycling use of cured phenolic resin wastes, a reclamation process based on an acid-fission-recombination reaction2) has been developed.
Phenolic materials tested are castings, moldings of one- and two-stage resins, and laminates (paperand cotton cloth-based). Epoxy resins cured with amine and acid anhydride were also used as materials. They were ground into fine particles and boiled with a large excess amount of phenol in the presence of catalytic amount of p-toluene sulfonic acid.
As the reaction proceeded, insoluble phenolic resin particles were gradually solubilized and a phenolic solution dissolving lower resin molecules was produced. For the both types of cured epoxy resins, the mode of solubilization was quite similar to produce phenolic solutions. It took 3-5 hrs to complete the perfect solubilization, but for cast resin it needed only several minutes. This result suggests that the type and density of cross-linkage of cured cast resin considerably differ from those of other kinds of phenolic resins.
Phenolic solutions of solubilized resins were then reacted with formaldenhyde to produce novolacs and they were formulated with hexamine, wood-flour and other additives to derive molding compounds by usual techniques. The mechanical and electrical properties of molding pieces obtained from these compounds were tested according to JIS K 6911, and the results showed that the properties of reclaimed resin moldings and of conventional two-stage rein moldings have almost the same level and no problem for practical use.
