MOKUZAI HOZON (Wood Protection)

The weatherability and combustibility of fire-retardant-impregnated wood during natural weathering for up to 60 months were evaluated. Fire-retardant chemicals used were modified guanidine phosphate with phenolic additives in order to retain chemicals against leaching. The ability of coating was also examined using four solvent-born coating systems：① penetrating；semi-transparent（brown）, ② thin-film-forming；semi-transparent（brown）, ③ film-forming；opaque（white）, ④ film-forming；transparent. The systems ① and ② consisted of 2 or 3-coat application of each single coating composition, whereas ③ and ④ employed specific wood-sealers as an undercoat to stabilize the surface of wood prior to the application of topcoat. Phenolic additives were effective to maintain chemical retention for a certain period. After 60-month-natural weathering, coated specimens and uncoated specimen were at a quasi-non-combustible material level and a fire-retardant material level, respectively. Fire performance of specimens coated with ③ and ④ were better than ① and ②.

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The purification method for wood extract and the acceleration of high-performance liquid chromatography（HPLC）analysis using core-shell columns were examined to quantitatively analyze bifenthrin in treated wood. A comparison of the chromatograms of bifenthrin solution and ultrasonically obtained methanol extracts of heartwood of Douglas fir, western hemlock, European red pine, spruce, Japanese cypress, Japanese cedar revealed that the extracted components of European red pine, Japanese cypress, and Japanese cedar overlapped with the peak of bifenthrin. The extracted components of European red pine could be removed via dispersive solid-phase extraction using primary-secondary amine（PSA）. The extracted components of Japanese cypress and Japanese cedar could be removed via solid-phase extraction using a silica gel cartridge. In the addition/recovery tests performed on the heartwood chips of each wood species, the recovery rate of bifenthrin was found to be 96% or higher. In HPLC analysis, by changing the particle size of the filler of the core-shell column from 5 to 2.6 mm and reducing the length and internal diameter of the column, the analysis could be completed in a shorter time and the consumption of the mobile phase could be reduced.

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