Protein Borates as Non-Toxic, Long-Term, Wide-Spectrum, Ground-Contact Wood Preservatives

Abstract

Wood preservatives based on protein borates and in particular albumin borate greatly retarded the leaching of boron from treated timber. Accelerated biological tests indicated that boric acid partially fixed to timber by formation of a salt with albumin and other proteins which are 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 borates, and particularly albumin borate, can be classified as long-term, wide-spectrum, ground-contact, heavy-duty wood preservatives, and are only composed of boric acid, a non-toxic to mammals biocide and of a non-toxic, natural, sometimes waste material, namely a protein. Investigation of the chemical mechanisms of boric acid fixation by the protein indicated that both acid-base salt formation occurs, as well as the further formation at increasing boric acid proportions of additional boric acid/protein complexes. The mechanism is hence only one of partially reversible rather than totally irreversible fixation of boron, leaving at all times small amounts of boron free to exercise its antifungal activity, but drastically diminishing its tendency to leach and greatly retarding its leaching. Boric acid leaching as a function of exposure time appears to tend 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 just leaching of the protein borate coagulum.

Environmentally friendly wood preservatives formulated with enzymatic-hydrolyzed okara, copper and/or boron salts

“…For example, the treatability of OK/CC/B (104.87%) was much higher than that of OK/CC (79.32%), and this was attributed to the difference of molecular weights between the complexes, formed in the OK/CC and OK/CC/B formulations. Thevenon et al [8] suggested that the molecular weight of the OK-B and CC-B complexes might be smaller than that of the OK-CC complexes, thereby lowering the treatability of OK/CC compared to that of OK/CC/B.…”

“…However, due to the high cost of these biocides compared to CCA, several researchers have investigated the development of new effective and economically practicable, preservation systems. For example, natural resources, such as egg albumin, milk casein [8] and soy protein products [9,10], and industrial wastes, such as lignin [11,12] and tannin [13], were used as a raw material in their preservative formulations, because these resources are readily available in large quantities with preservative complexes retained from aqueous solutions, and might have a potential as inexpensive adsorbents. However, in Korea, such resources are unsuitable as ingredients in newly developed preservation systems because of their high cost or rarity.…”

Glycerol/Glyoxal: A New Boron Fixation System for Wood Preservation and Dimensional Stabilization

“…An alternative to this drawback concerns the use of water repellents or polymer systems which reduce leaching in treated timber . More recently, new wood preservatives based on protein borates have been described to greatly retard the leaching of boron from treated timber (Thevenon et al 1997(Thevenon et al , 1998. In a similar manner, we describe here the development of a new low cost boron preservation system for hazard class III involving glycerol/glyoxal and H 3 BO 3 mixtures capable of improving not only the durability but also the dimensional stability of timber treated with them.…”

Chemical improvement of surfaces. Part 1: Novel functional modification of wood with covalently bound organoboron compounds

“…The above-mentioned approaches to wood protection by boron-containing chemicals suffer from subsequent leaching of biologically active agent, even though fixation of boric acid by esterification to some extent has been published in the literature (Pizzi and Baecker 1996;Thevenon et al 1998;Yalinkilic et al 1998b). Mixed ammonium salts comprising two types of anions, namely borate and oleate (Lyon et al 2007), have also been applied.…”