AU2007101011B4 - Superficial Treatment for Wood and Wood Products - Google Patents

Description

SUPERFICIAL TREATMENT FOR WOOD AND WOOD PRODUCTS O FIELD OF THE INVENTION The invention pertains to wood treatments, and more particularly to surface treatments of wood using synthetic pyrethroids.

BACKGROUND OF THE INVENTION Bifenthrin is a synthetic pyrethroid insecticide/ acaracide and is classified as a non-cyano pyrethroid. The active ingredient is efficacious for targeting pests through both contact and stomach action. As with most synthetic pyrethroids, bifenthrin is active against a wide range of pests including Coleoptera, Diptera, Heteroptera, Hymenoptera, Homoptera, Isoptera and Lepidoptera, Orthoptera, as well a number of species of Acarina. Bifenthrin is currently registered in a number of countries throughout the world for the control of a wide range of pests.

Bifenthrin is used extensively in many industries. For example: Cotton, grain, turf, pest control, flower, home garden and mosquito control. However it has not been used in the timber industry.

Tests have demonstrated that within the standard practice in the timber industry, very low rates of bifenthrin are required to protect timber against Cop to term es acinaciform is, the most economically important termite species in Australia, and Mastoterm es darw iniensis, the most voracious species in Australia and around the world. The rates for controlling these termite species are 5 and g/m 3 respectively.

Standard treatment methods in Australia and around the world currently require some penetration into the timber by a preservative. This can be achieved by vacuum pressure. A vacuum system requires a treatment vessel and expensive peripheral and computerized equipment. The process time required to treat the timber varies depending on the product, but it generally takes at least 45 minutes to treat wood. Penetration of preservatives can also be achieved by diffusion, a process which involves less expensive equipment but requires much more time 5 and higher levels of stock holding. The wood's moisture content is one of the most ('4 Simportant parameters in controlling diffusion times. Wet wood is required to O achieve diffusion within commercial expectancy. Full penetration of the preservative into a 90 mm thick sample ofradiata pine green sapwood can be achieved between 4 to 8 weeks.

OBJECTS AND SUMMARY OF THE INVENTION Accordingly it is an object of the present invention to provide a method and apparatus for the surface treatment of wood using synthetic pyrethroids such as bifenthrin. It is also an object of the present invention to provide wood products ('4 made using these surface treatments.

BEST MODE AND OTHER EMBODIMENTS OF THE INVENTION Until this invention, adequately protecting timber against termite attack required significant penetration of a preservative into the sapwood. This was the case due to the fact that other available active ingredients degraded very quickly when exposed to increased temperatures and Ultra Violet (UV) light. Penetration was required to protect the active ingredient ("active") from the degradation. The most commonly used active in the 1990's which penetrated the timber was Permethrin.

Permethrin has been shown to degrade when exposed to temperatures above degrees centigrade. Permethrin also has a very low resistance to UV light. Thus, Permethrin must penetrate into the timber, otherwise it would degrade and not protect the timber. Other actives, such as Deltamethrin, which have been trialed in similar applications, were found to cause occupational health and safety problems at both the treating site and the construction site. These also degrade rapidly when exposed to UVlight. In OH&S studies conducted in 1998-1999 using timber treated with Deltamethrin, all workers who handled the treated timber complained of a parasthesia or skin irritation. This problem was so severe that it made the use of Deltamethin unviable.

It has been confirmed through extensive OH&S testing that, due to the chemical composition of Bifenthrin, exposure to Bifenthrin treated timber does not produce any skin irritation. Extensive testing done with Bifenthrin showed that a S 5 significant penetration was not required to protect the active against degradation Sthrough exposure to either UV or heat. Owing to Bifenthrin's stability and O repellent effects, only a superficial treating of the timber is needed.

Useful in superficial applications, Bifenthrin it has the ability to form strong bonds to the timber, and is virtually insoluble in water. The bonding co-efficient of 0Bifenthrin is significantly greater than that of Permethrin. These two attributes of 0 bonding water insolubility, together with the above mentioned stability against heat or UV exposure result in the chemical staying on the timber despite exposure Sto rain, sunlight, temperature or handling. No other chemicals used in the past have such characteristics that would allow a mere superficial treatment.

Recent studies have demonstrated that applying bifenthrin superficially to radiata pine sapwood of commercial sizes, by very short dipping (4 seconds) or spraying at very low rates, protects the pine timber against termite attack. The rates required to superficially treat and protect a surface of 35 x 90 mm radiata pine, against Coptotermes acinaciformis and Mastotermes darwiniensis, are 4 and 23 g/m 3 respectively. These studies were conducted using the drum test described by the AWPA protocols. Table 1 shows the evaluation scale used during the inspection of specimens tested. Tables 2 and 3 respectively show the inspection results of surface treated specimens that were exposed to Mastotermes and Coptotermes.

Table 1 Evaluation scale for radiata pine samples exposed to termites in the field Rating Condition of the Specimen 1 Sound 2 Superficial attack-grazing 3 Penetration >3mm in depth 4 Attack Slight -10-25 mass loss Attack Moderate 25-50 mass loss 6 Attack Severe 50-70 mass loss 7 Attack Destoyed 75-100 mass loss Table 2 Mean scores for radiata pine commercial samples treated superficially with bifenthrin and exposed to Mastotermes darwiniensis in the field Treat No rreatment Mean Range Pass or Fail 1 Untreated control 6.7 6-7 Fail 3 .007% m/m permethrin (LOSP) 2.2 2-3 Fail 4 .013% m/m permethrin (LOSP) 2.2 1-4 Fail 0.02% m/m permethrin (LOSP) 1.8 1-2 Pass Bifenthrin 4 g/m 3 3.3 2-6 Fail 11 Bifenthrin 8 g/m 3 2.2 2-3 Fail 12 Bifenthrin 15 g/m 2.0 1-3 Fail 13 Bifenthrin 23 g/m 3 1.7 1-2 Pass 17 Bifenthrin 38 g/m 3 1.0 1-1 Pass Table 3 Mean scores for radiata pine commercial samples treated superficially with bifenthrin and exposed to Coptotermes acinaciformis in the field Treat No Treatment Mean Range Pass or Fail 1 Untreated control 7.0 7-7 Fail 2 Solvent control (white spirit) 7b 7-7 Fail 3 0.007% m/m OD permethrin 2 1-3 Fail 4 0.013% m/m OD permethrin 1.8 1-3 Fail 0.02% m/m OD permethrin 1.3 1-2 Pass 8 Determite 4 g/m 3 1.0 1-1 Pass 9 Determite 8 g/m 3 1.0 1-1 Pass Determite 15 g/m 3 1.5 1-1.5 Pass 11 Determite 23 g/m 3 1.0 1-1 Pass House frame building practices were incorporated in a test to demonstrate the efficacy of bifenthrin superficial treatments. The ends of the samples were not 0 O 5 treated. The simulated frames were exposed to 120,000 termites. After six months of exposure all untreated simulated frames were attacked. The treated O frames were not attacked despite signs of termite activity within the frame.

Superficial treatments can be applied, for example, by dipping, rolling, brushing, deluging, misting or spraying. Superficial treatment systems can be installed in O different areas of a sawmill, either in-line with the sawmill or as a process separate O to the sawmill. For example, the situation of a spray unit will depend on the lay- Sout of the production line or lines of a given sawmill. A longitudinal and O transversal spray unit in a sawmill is contemplated. Spraying can occur, for example, by application with a linear sprayer after stress grading. Timber is then arranged on a conveyor and graded and marked by hand (or automatically).

Boards that are marked during grading are detected by a scanner and then cut to the appropriate length by the docker saw. Transverse spraying may occur after the docker saw operation. Ending rolls may be used to treat the ends of the boards as required.

Bifenthrin can be used as a dust or as a formulated product such as suspension concentrate, emulsion concentrate or microemulsion. Bifenthrin can be applied in a concentrate form or diluted in a variety of carriers. Carriers may include water, organic solvent, oils from different sources, diesel, gasoline, petroleum and other non polar solvents.

Additives, for example, colors, fire retardants, water repellents and resins, can be incorporated during the application of bifenthrin. Table 4 demonstrates that the addition of water repellents did not mask the repellent effect of bifenthrin against Coptotermes acinaciformis.

Table 4 Mean scores for radiata pine commercial samples treated superficially with bifenthrin and water repellent and exposed to Coptotermes acinaciformis in the field Treatment Meana Range Success rating (Pass or Fail) Untreated control 7-7 Fail Solvent control (white spirit) 7.0 b 7-7 Fail 0.007% m/m OD permethrin 2.0 1-3 Fail 0.013% m/m OD permethrin 1.8 1-3 Fail 0.02% m/m OD permethrin 1.3 1-2 Pass Bifenthrin 4 g/m 3 water 1.2 1-2 Pass repellents Bifenthrin 8 g/m 3 water 1.3 1-2 Pass repellents Bifenthrin 15 g/m 3 water 1.2b 1-2 Pass repellents Bifenthrin 23 g/m 3 water 1.2 1-2 Pass repellents The benefits of the invention include that: 1. Low rates of chemical usage are obtained.

2. The application of the invention does not require expensive equipment.

3. The invention allows synthetic pyrethrins to be applied in a sawmill as an in-line process or a stand alone process.

4. The invention eliminates the operating costs associated with conventional treatments.

Wood treated according to the invention does not require re-drying after the treatment. Normal process requires re-drying when the end use is framing.

O 5 6. Additives can be included in the concentrate or working solution, to add different characteristics to the final product. These additives can include, O for example, colors, fire retardants and water repellents.

Experiments have been conducted, to date, with radiata pine. However, the experiments do not exclude other pinus species, other softwood, hardwoods and O broadleaves timber species or engineering and re-constituted wood products.

O Engineering or re-constituted wood products include, without limitation, plywood, Laminated Veneer Lumber, Oriented Stranded Boards (OSB), O particleboards, Medium Density Boards (MDF), Glue laminated Lumber (GlueLam), flake boards and plastic-wood.

The superficial treatments may be modified by a partial introduction of bifenthrin into the wood. This results in an envelope around the cross section of the timber board or wood product, or just a partial penetration. Tests conducted following a method similar to that described above strongly suggest the modified treatments are also effective in protecting timber against termite attack. Table 5 shows the assessment results for commercial sizes of radiata pine partially penetrated with bifenthrin.

Table Mean scores for radiata pine commercial samples partially penetrate with bifenthrin and exposed to Coptotermes acinaciformis in the field Treatment Meana Range Success (Pass or Fail) rating Untreated control 7.0 7-7 Fail Solvent control (white spirit) 7.0b 7-7 Fail 0.007% m/m OD permethrin 2.0 1-3 Fail O 0.013% m/m OD permethrin 1.8 1-3 Fail 0.02% m/m OD permethrin 1.3 1-2 Pass Partial penetration more than 1.0 1-1 Pass 3mm. Bifenthrin 6-12 g/m 3 Partial penetration more than 1.0 1-1 Pass 3mm.

Bifenthrin 13-20 g/m 3 When added protection of the timber's faces is required, a pressed product can be treated by spraying the faces before the product has cooled down. The warmth in the product will create a hot-cold effect that will draw the applied formulation deep into the faces. Face treatments can also be applied onto a cold face. In this case, the lathe checks are used as pathways for the penetration of the chemical.

The sprayed chemicals penetrate a warm face more effectively than a cold face.

Penetration of the chemicals into a cold face can be improved, and probably matched to a warm face penetration. The improvement may be made by increasing the concentration of the chemical, increasing the uptake area by wetting more of the faces, or adding surfactants and chemicals that help the solution penetrate the faces better.

The surface treatments of faces can be done by dipping, rolling, brushing, deluging, misting and spraying. These systems can be installed in different areas of the LVL, plywood or any other mill that produces engineered and reconstituted products. Depending on the lay-out of the production line or lines of a given mill, the systems can be installed in-line with the production lines or as a separate process.

Claims (4)

1. A method of timber product preservation comprising the step of: n applying an envelope treatment of a water based formulation of bifenthrin to the timber product by spraying.

2. The method of claim 1, wherein: 0 0. the bifenthrin further comprises an additive selected from any one of the group S comprising: a colorant, a fire retardant, a water repellent or a resin.

3. The method of either of claims 1 or 2, wherein: the spray occurs at a sawmill site and does not require a re-drying step.

4. The method of any one of claims 1- 3, wherein: the application concentration of the formulation is between 4 and 38 g of bifenthrin per cubic meter of timber. A timber product having insecticide/acaricide properties, comprising: a timber substrate onto which has been sprayed a water based formulation of bifenthrin, the formulation being according to any one of claims 1-4. 9 COMS ID No: ARCS-172219 Received by IP Australia: Time 13:35 Date 2007-12-13