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Advertising supplement provided Jeld-Wen
Windows & Doors
The New Process
In 1998, a major Oregon-based window
and door manufacturer began investigating new alternatives
in wood preservation technology for millwork. The objective
was to find a reasonably priced system that increased decay
resistance and diminished environmental impact.
Water replaces petroleum-based solvents
as the carrier for the active ingredients—tebuconazole
as the fungicide. Tebuconazole is an organic triazole biocide,
that is stable and leach resistant in wood, effective against
wood decay fungi, but of uncertain effectiveness as an insecticide.
Therefore, a proven insecticide—imidacloprid—is
blended into the solution. Both tebuconazole and imidacloprid
are among ingredients certified by the Window and Door Manufacturers
Association’s Hallmark Certification Program. The repellant
is a proprietary emulsion that differs from paraffin-based
repellants commonly used throughout the industry.
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“From an environmental standpoint,
this system results in a 97 percent reduction in VOCs (volatile
organic compounds). That, alone, is a huge benefit,”
says the manufacturer’s technical director. “The
water-soluble process produces little or no wastewater, unlike
oil-based processes that produce both significant quantities
of process wastewater and metal-containing sludge.” In
addition, pressure treatment permits manufacturers to use
solutions with considerably lower chemical concentrations
to achieve comparable effect.
The process, referred to as “full-cell,”
is this:
- Treating chemicals are delivered and stored in holding
tanks.
- Chemicals and water are mixed in a treating solution.
- A charge of wood is sealed into an 84-ft.-long pressure
vessel and a vacuum is applied to remove air from the chamber—and,
as much as possible, from the wood.
- The vacuum is released, flooding the containment vessel
with chemical solution, and 150 psi pressure is applied
until the wood will take no more preservative.
- Pressure is released, the solution drained from the chamber,
and a final vacuum is applied to recover solution.
- The vacuum is released, the pressure vessel opened, and
wood removed. The process takes about two hours, and up
to 10,000 board feet can be treated in a single charge.
The system now produces up to 500,000 board feet of treated
lumber per week.
- Wood is transferred to a computer-controlled dehumidification
kiln.
Boards are immersed in the solution in the process, not merely
surface-treated. The result is that the solution penetrates
the wood, not merely coats it.
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