Wood protectant technology

A new timber impregnation process has recently been developed to treat timber without releasing organic solvents into the atmosphere.

Timber preservation scientists at Queensland Primary Industries and Fisheries have teamed with engineers at a specialist solvent technology company to achieve this great advancement.

The new process is an alternative to the current Light Organic Solvent Preservative (LOSP) process widely used in Australia, New Zealand and Europe to treat timber in its final shape and form.

While LOSP treatments contain active ingredients to give protection against decay, termites and other insects, LOSP treated timber also contains around 30 litres of light organic solvent per cubic metre when it emerges from the treatment plant. This wasted solvent increases the cost of treatment and makes the timber smell of white spirit. It can also interfere with paint adhesion. When the solvent evaporates into the atmosphere, it can contribute to the formation of photochemical smog.

The new timber impregnation process uses compressed gas as carrier fluid for the wood preservative active ingredients. It operates at similar pressures to current waterborne treatments.

There has been very good success with compressed refrigerant gases, which can be very penetrative, making it possible to treat timber that is difficult or impossible to treat using LOSP treatment.

After the impregnation process has occurred, before the timber is removed from the treatment vessel, the pressure is reduced and the solvent in the timber turns back into a gas, which is easily pumped out of the vessel and recovered for re-use.

The benefit of the new timber impregnation process is that no solvent remains in the timber after treatment and no solvent is released into the atmosphere. The timber emerges dry from the treatment vessel with negligible change in shape or dimensions, and is ready for immediate painting or gluing.

Patent actions for the process are underway in Australia, New Zealand, Europe and United States. The process was announced to the local industry at the Timber Preservation 2009 conference in Brisbane in April 2009. It is also the subject of a scientific paper to be presented by Dr Michael Kennedy at the annual meeting of the International Research Group on Wood Protection, to be held in Beijing, May 24-28, 2009.

For more information on this project, contact Michael Kennedy michael.kennedy@dpi.qld.gov.au.