Effects of alkyl chain length and the mixing of homologues with different alkyl chains on the leaching characteristics of benzalkonium chloride

Abstract

Benzalkonium chloride (BAC) is the active ingredient of ACQ-1, one of the most widely used wood preservatives in Japan. BAC in ACQ-1 comprises homologues with different alkyl chains: C12 comprises 74%; C14 26%; and C16 < 1%. To clarify the leaching characteristics and the factors affecting the leaching of BAC homologues, wood specimens treated individually with the C12, C14, and C16 homologues were used in a leaching experiment with distilled water (DW) and artificial sea water (SW). The leaching rates of the BAC homologues were accelerated by the SW, and the order of the leaching rate in both DW and SW was C12 > C14 > C16. When the specimens were treated with a mixture of two of the three homologues, the leaching rates of the C14 and C16 homologues from specimens treated with a solution containing C14 and C16 were lower than that from specimens treated with a solution containing the C14 or C16 homologue together with C12. From the adsorption isotherm of the homologues it is assumed that the formation of BAC aggregates on the treated wood is related to their leaching. BACs consisting of mainly C14 and C16 are thought to be suitable for reducing leaching, particularly in marine usage.