MOKUZAI HOZON (Wood Protection)

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The authors examined a possibility of promoting the fixation of CCA treated wood by heating and clarified the fixing conditions by steaming.
The specimens (2cm×2cm×1cm Cryptomeria japonica) impregnated with CCA were stored under various conditions and were determined the amount of leached Cr in water. The preservative tested was CCA Type A (oxide type). In this case, the loss of chromium continued until the final stage of leaching. So that the chromium component was used as an indicator of fixation of the preservative.
A comparison was made between heating treated wood with high moisture content under a cover and heating one without any cover. The results obtained were considered that the former case was evidently faster than the latter on fixing speed. The difference within two cases seems to be attributable to the fact that a reaction between CCA and wood constituents becomes uneven and incomplete if moisture is evaporate before the fixation of CCA is accomplished. Therefore, it is proper to use steaming for accelerating the fixation of CCA.
The authors introduced the relationship between storage time and leaching rate of CCA when steamed under coverage at 40°C to 100°C. They were as follows:
i) The leaching rate at a constant temperature was inversely promotional to a logarithm of storage time.
ii) When the storage temperature was increased up to 10°C, the optional storage time decreased to about half level.
iii) The relation between the storage temperature and the complete fixation time was given by the following formula;
Y= 100-32 logX
where, Y is the storage temperature (40°C≤Y≤100°C)
X is the complete fixation time (h)

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