Reactive oil/copper preservative systems for wood products

Abstract

The specification describes preserved solid wood or wood composites including a copper ammonium acetate complex wood preservative and a drying oil. The wood preservative is present in the wood in an amount effective to improve the resistance of the treated wood to at least one type of decomposition, such as decay or insect attack. The drying oil is present in the wood in an effective amount to accomplish at least one useful end, such as reducing the water absorption or thickness swell of the treated wood or increasing its mechanical strength, even in a wood composite made using less binding resin than usual. Yet another aspect of the invention is a method of making the treated wood from green wood in solid or flaked form. A copper ammonium acetate complex wood preservative and optionally a drying oil are added to the green wood.

Description

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT Not applicable. BACKGROUND This invention relates to the incorporation of a drying oil and a copper containing preservative system into wood products, which may include lumber and plywood, and into wood and agricultural based composite products. Wood based composite products can include products such as oriented strandboard, medium density fiberboard, fiberboard, hardboard, and particle board. The invention also relates to the method of manufacturing wood based composite products whereby a drying oil and a wood preservative composition are added to the wood furnish (defined as wood strands, chips, particles, flakes and fiber), plywood (whether in the form of separate plies or a bound sheet), or solid wood prior to or after drying. Where a wood furnish or separate wood plies are treated, the wood is then formed and pressed into a finished board or panel product. The production of wood based composite panel products ha...

AI Technical Summary

Benefits of technology

The drying oil is present in the wood in an effective amount to accomplish at least one useful end. One useful end is to reduce the water absorption of the treated wood. An alternative useful end is to reduce the thickness swell of the treated wood.

The wood preservative again is present in the wood composite in an amount effective to improve the resistance of the treated wood composite to at least one type of decomposition.

The presence of a copper based wood preservative with a reactive agricultural oil or fish oil has the potential to provide biological efficacy against wood biodeteriogens. (A biodeteriogen is an organism that is capable of causing biodeterioration—an undesirable change in the properties of a material caused by the vital activities of living organisms.) Biodeteriogens for wood include decay fungi, termites and other insects. Complexation of the preservative with the reactive oil reduces the likelihood of leaching / depletion of the preservative in service.

The drying oil again is present in the wood in an effective amount to accomplish at least one useful end. For example, the drying oil may interact to enhance the dimensional stability or water repellency of the wood composite, and may function to reduce or eliminate the need for a separate binder resin.

Yet another aspect of the invention is a method of making treated wood composites. One step of the method is providing green wood in flaked form. Another step of the method is adding to the green wood a copper based wood preservative. The wood preservative again is added to the wood composite in an amount effective to improve the resistance of the treated wood composite to at least one type of decomposition. Another step of the method, alternatively carried out simultaneously with, before, or after the wood preservative treatment, is adding to the green wood a drying oil. The drying oil again is present in the wood composite in an effective amount to accomplish at least one useful end.

One advantage of the present method is that it allows the wood to be treated with the preservative while green, then dried once, instead of drying the wood, treating it with a water dispersion of the treating agent (thus rewetting the wood), then drying the wood a second time.

Problems solved by technology

However, these products are typically used in interior applications where attack from insects or decay fungi is limited and dimensional stability is not of great concern.

The expansion of wood fiber, particle and flake based composites into certain construction applications is hindered by limitations in the physical and mechanical properties of the manufactured panels, in particular excessive water absorption and propensity to swell, but also by their susceptibility to attack by biological agents such as decay fungi and termites.

Historically, attempts to incorporate chemical treatments into wood based composites using similar technology have failed for economic reasons or more commonly because of technical problems associated with irreversible and excessive swelling of the treated panels and severe loss of structural integrity.

Therefore, more solid wood and wood fiber can be channeled to new construction and not the replacement market.

This will limit the stress on the forest resources of North America, which have been shrinking over the last two decades due to land being tied up in “natural” status, which cannot be harvested.