MOKUZAI HOZON (Wood Protection)

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In this study, resistance to decay of acetylated wood produced with supercritical carbon dioxide was investigated. Specimens of treated wood were prepared from sugi (Cryptomeria japonica D. Don) heartwood and sugi sapwood for testing using a soil-buried test and a laboratory decay test, respectively. The oven-dried wood specimens were acetylated in supercritical carbon dioxide conditioned at 120 ˚C and 10-12 MPa for eight hours. The acetylated wood specimens were buried in soil for five years at two test sites in Japan, and theirweight loss was measured. The weight loss resulting from decay was minimal. The results of the soil-buried test showed that the acetylated wood produced with supercritical carbon dioxide has high durability and resistance to decay. It is possible that the extractives of sugi heartwood were extracted by acetylation in supercritical carbon dioxide. However, the removal of the extractives likely has little influence on resistance to decay. The results of the laboratory decay test also showed that the wood specimens acetylated in supercritical carbon dioxide featured high decay durability. It was considered that the wood specimens acetylated in supercritical carbon dioxide showed high acetylation at the core of the specimens.

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In the deep penetration treatment for wood preservation, the infiltration state of the active ingredient has been evaluated by using a dithizone-Zn color reaction by adding a Zn compound together with the active ingredient. However, it has not been clarified what kind of difference exists in the penetration and diffusion behavior of the active ingredient and Zn. In this study, in order to evaluate the penetration and diffusion behavior of both components in the deep infiltration treatment process, deep penetration treated Douglas fir (Pseudotsuga menziesii) kiln dried wood and Scots pine (Pinus sylvestris) laminated wood were analyzed by time-of-flight secondary ion mass spectrometry. The results showed that Zn was strongly detected in a few cells, while the active ingredient distributed more widely. Although both components to be treated at the same time should share the initial infiltration process, the microscopic infiltration and diffusion behavior in wood during the infiltration and drying process should be different, which causes a difference in the final distribution state. The active ingredient may distribute more uniformly over a wider region than the Zn compound.

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