PROTEIN BORATES AS NONTOXIC, LONG-TERM, WIDE-SPECTRUM, GROUND-CONTACTWOOD PRESERVATIVES

Wood preservatives based on protein berates and in particular albumin berate greatly retarded the leaching of boron from treated limber. Acc elerated biological tests indicated that boric acid partially fixed to timber by formation of a salt with albumin and other proteins which a re then insolubilised by heat-induced coagulation can yield durability comparable to that obtained with CCA wood preservatives. The results of the biological tests show that protein berates, and particularly al bumin berate, can be classified as long-term, wide-spectrum, ground-co ntact, heavy-duty wood preservatives, and are only composed of boric a cid, a non-toxic to mammals biocide and of a non-toxic, natural, somet imes waste material, namely a protein. Investigation of the chemical m echanisms of boric acid fixation by the protein indicated that both ac id-base salt formation occurs, as well as the further formation at inc reasing boric acid proportions of additional boric acid/protein comple xes. The mechanism is hence only one of partially reversible rather th an totally irreversible fixation of boron, leaving at all times small amounts of boron free to exercise its antifungal activity, but drastic ally diminishing its tendency to leach and greatly retarding its leach ing. Boric acid leaching as a function of exposure lime appears to ten d to an equilibrium value which is different for each type of protein used and differs in the case of treated timber from that obtained by j ust leaching of the protein berate coagulum.