AU2012202186A1

AU2012202186A1 - Improved Surface Treatment for Wood and Wood Products

Info

Publication number: AU2012202186A1
Application number: AU2012202186A
Authority: AU
Inventors: Javier Romero
Original assignee: Osmose Australia Pty Ltd
Current assignee: Koppers Performance Chemicals Australia Pty Ltd
Priority date: 2002-12-05
Filing date: 2012-04-16
Publication date: 2012-05-03
Anticipated expiration: 2023-12-05
Also published as: AU2012202186B2

Abstract

A method and apparatus for the surface treatment of wood using synthetic pyrethroids such as bifenthrin as well as wood products made from using those treatments. - 16-

Description

5 IMPROVED SURFACE TREATMENT FOR WOOD AND WOOD PRODUCTS FIELD OF THE INVENTION The invention pertains to wood treatments, and more particularly to superficial surface treatments of wood. 1o The invention has been developed primarily for use as method and apparatus for applying a superficial surface treatments of wood using synthetic pyrethroids at a sawmill, and will be described hereinafter with reference to this application. However, it will be appreciated that the invention is not limited to this particular field of use. 15 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, 20 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 25 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 Coptotermes acinaciformis, the most economically important termite species in Australia, and Mastotermes darwiniensis, the most voracious species in Australia and around 30 the world. The rates for controlling these termite species are 5 and 20 g/m3 respectively. -1 - 5 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 10 to treat wood. Penetration of preservatives can also be achieved by diffusion, a process which involves less expensive equipment but requires much more time and higher levels of stock holding. The wood's moisture content is one of the most important parameters in controlling diffusion times. Wet wood is required to achieve diffusion within commercial expectancy. Full penetration of the 15 preservative into a 90 mm thick sample of radiata pine green sapwood can be achieved between 4 to 8 weeks. Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of the common general knowledge in the field. 20 OBJECTS OF THE INVENTION It is an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative. Accordingly it is an object of the present invention in a preferred form to provide a method and apparatus for the surface treatment of wood using synthetic 25 pyrethroids such as bifenthrin. It is also an object of the present invention in a preferred form to provide wood products made using these surface treatments. In a preferred embodiment, the surface treatment comprising an application of between 4 and 38 g/m3 of timber product. -2- 5 SUMMARY OF THE INVENTION According to an aspect of the invention there is provided a method of timber product preservation when performed at a sawmill, the method comprising the steps of: applying a superficial treatment of a water based formulation of bifenthrin to 10 the timber product; the water based formulation further comprising a colorant; the superficial treatment comprising an application of between 4g/m3 and 38g/m3 of timber product; and wherein the timber product does not require redrying. 15 Preferably, the method is performed at the sawmill in-line with sawing operation of the timber product. More preferably, the superficial treatment occurs after stress grading of the timber product. Preferably, the application of the superficial treatment is by spraying. More preferably, the application of the superficial treatment is by transverse spraying 20 after a docking saw operation. Preferably, the superficial treatment is an envelope treatment. More preferably, the superficial treatment comprises an application of between 4 g/m3 and 23g/m3 of timber product. Preferably, the bifenthrin is applied as a formulated product in a carrier. 25 Preferably, the water based formulation further comprises an additive selected from any one of the group comprising: a fire retardant, a water repellent or a resin. Preferably, applying a superficial treatment does not require use of a vacuum pressure to achieve penetration. 30 Preferably, the application of the a superficial treatment occurs while the timber product is warmer than room temperature. -3- 5 Preferably, the method further comprising a treatment against attack by Coptotermes acinaciformis or Mastotermes darwiniensis. According to an aspect of the invention there is provided an apparatus when used at a sawmill to preserve a timber product, the apparatus comprising: an application means to apply a superficial treatment of a water based 10 formulation of bifenthrin to the timber product; the water based formulation further comprising a colorant; the superficial treatment comprising an application of between 4g/m3 and 38g/m3 of timber product; the superficial treatment being applied such that the timber product does not 15 require redrying. Preferably, applies the superficial treatment in-line with sawing operation of the timber product. More preferably, the apparatus applies the superficial treatment after stress grading of the timber product. Preferably, the apparatus applies the superficial treatment by transverse spray 20 after a docking saw operation. Preferably, the application means applies the superficial treatment in accordance with an embodiment method as herein disclosed. According to an aspect of the invention there is provided a timber product having been preserved, wherein the timber product is treated at a sawmill in accordance 25 with an embodiment method as herein disclosed. Preferably, the timber product is a housing timber or material. Preferably, the timber product retains significant insecticide/acaricide properties above 25 degrees centigrade. Preferably, the timber product is treated against attack by Coptotermes 30 acinaciformis or Mastotermes darwiniensis. -4- 5 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 10 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 25 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 15 protect the timber. Other actives, such as Deltamethrin, which have been trialed in similar applications, were found to cause occupational health and safety ("OH&S") problems at both the treating site and the construction site. These also degrade rapidly when exposed to UV light. In OH&S studies conducted in 1998-1999 using timber treated with Deltamethrin, all workers who handled the treated timber 20 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 25 significant penetration was not required to protect the active against degradation through exposure to either UV or heat. Owing to Bifenthrin's stability and 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 3o Bifenthrin is significantly greater than that of Permethrin. These two attributes of bonding & water insolubility, together with the above mentioned stability against heat or UV exposure result in the chemical staying on the timber despite exposure to rain, sunlight, temperature or handling. No other chemicals used in the past have such characteristics that would allow a mere superficial treatment. -5- 5 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 10 g/m3 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. 15 Table 1 Evaluation scale for radiata pine samples exposed to termites in the field 20 Rating Condition of the Specimen 1 Sound 2 Superficial attack-grazing 3 Penetration - >3mm in depth 25 4 Attack Slight -10-25 % mass loss 5 Attack Moderate 25-50 % mass loss 6 Attack Severe 50-70 % mass loss 7 Attack Destroyed 75-100 % mass loss 30 - 6- 5 Table 2 Mean scores for radiata pine commercial samples treated superficially with bifenthrin and exposed to Mastotermes darwiniensis in the field Treat No Treatment Mean Range Pass or Fail 1 Untreated control 6.7 6-7 Fail 10 3 .007% m/m permethrin (LOSP) 2.2 2-3 Fail 4 .013% m/m permethrin (LOSP) 2.2 1-4 Fail 5 0.02% m/m permethrin (LOSP) 1.8 1-2 Pass 10 Bifenthrin 4 g/m3 3.3 2-6 Fail 11 Bifenthrin 8 g/m3 2.2 2-3 Fail 15 12 Bifenthrin 15 g/m3 2.0 1-3 Fail 13 Bifenthrin 23 g/m3 1.7 1-2 Pass 17 Bifenthrin 38 g/m3 1.0 1-1 Pass 20 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 25 2 Solvent control (white spirit) 7b 7-7 Fail 3 ).007% m/m OD permethrin 2 1-3 Fail 4 ).013% m/m OD permethrin 1.8 1-3 Fail 5 0.02% m/m OD permethrin 1.3 1-2 Pass 30 8 Determite 4 g/m3 1.0 1-1 Pass 9 Determite 8 g/m3 1.0 1-1 Pass 10 Determite 15 g/m3 1.5 1-1.5 Pass 11 Determite 23 g/m3 1.0 1-1 Pass 35 -7- 5 House frame building practices were incorporated in a test to demonstrate the efficacy of bifenthrin superficial treatments. The ends of the samples were not treated. The simulated frames were exposed to 120,000 termites. After six months of exposure all untreated simulated frames were attacked. The treated frames were not attacked despite signs of termite activity within the frame. 1o Superficial treatments can be applied, for example, by dipping, rolling, brushing, deluging, misting or spraying. Superficial treatment systems can be installed in different areas of a sawmill, either in-line with the sawmill or as a process separate to the sawmill. For example, the situation of a spray unit will depend on the lay out of the production line or lines of a given sawmill. A longitudinal and 15 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 or docking saw. Transverse spraying may 20 occur after the docker or docking 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, 25 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 30 Coptotermes acinaciformis. - 8- 5 Table 4 Mean scores for radiata pine commercial samples treated superficially with bifenthrin and water 10 repellent and exposed to Coptotermes acinaciformis in the field Treatment Meana Range Success rating (Pass or Fail) Untreated control 7.0 7-7 Fail Solvent control (white spirit) 7 .ob 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/m3 + water 1.2 1-2 Pass repellents Bifenthrin 8 g/m3 + water 1.3 1-2 Pass repellents Bifenthrin 15 g/m3 + water 1.2b 1-2 Pass repellents Bifenthrin 23 g/m3 + water 1.2 1-2 Pass repellents - 9- 5 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. 10 4. The invention eliminates the operating costs associated with conventional treatments. 5. 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. 15 6. Additives can be included in the concentrate or working solution, to add different characteristics to the final product. These additives can include, for example, colors, fire retardants and water repellents. Experiments have been conducted, to date, with radiata pine. However, the 20 experiments do not exclude other pinus species, other softwood, hardwoods and broadleaves timber species or engineering and re-constituted wood products. Engineering or re-constituted wood products include, without limitation, plywood, Laminated Veneer Lumber, Oriented Stranded Boards (OSB), particleboards, Medium Density Boards (MDF), Glue laminated Lumber 25 (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 30 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. - 10- 5 Table 5 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.ob 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 Partial penetration more than 1.0 1-1 Pass 3mm. Bifenthrin 6-12 g/m3 Partial penetration more than 1.0 1-1 Pass 3mm. Bifenthrin 13-20 g/m3 10 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 15 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. - 11 - 5 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. 1o 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 15 process. -12-

Claims

1. A method of timber product preservation when performed at a sawmill, the method comprising the steps of: applying a superficial treatment of a water based formulation of bifenthrin to the timber product; the water based formulation further comprising a colorant; the superficial treatment comprising an application of between 4g/m3 and 38g/m3 of timber product; and wherein the timber product does not require redrying.

2. The method according to claim 1, wherein the method is performed at the sawmill in-line with sawing operation of the timber product.

3. The method according to any one of the preceding claims, wherein the superficial treatment occurs after stress grading of the timber product.

4. The method according to any one of the preceding claims, wherein application of the superficial treatment is by spraying.

5. The method according to any one of the preceding claims, wherein the application of the superficial treatment is by transverse spraying after a docking saw operation.

6. The method according to any one of the preceding claims, wherein the superficial treatment is an envelope treatment. - 13-

7. The method according to any one of the preceding claims, wherein the superficial treatment comprises an application of between 4 g/m3 and 23g/m3 of timber product.

8. The method according to any one of the preceding claims, wherein the bifenthrin is applied as a formulated product in a carrier.

9. The method according to any one of the preceding claims, wherein the water based formulation further comprises an additive selected from any one of the group comprising: a fire retardant, a water repellent or a resin.

10. The method according to any one of the preceding claims, wherein applying a superficial treatment does not require use of a vacuum pressure to achieve penetration.

11. The method according to any one of the preceding claims, wherein the application of the a superficial treatment occurs while the timber product is warmer than room temperature.

12. The method according to any one of the preceding claims, wherein the method further comprising a treatment against attack by Coptotermes acinaciformis or Mastotermes darwiniensis.

13. An apparatus when used at a sawmill to preserve a timber product, the apparatus comprising: an application means to apply a superficial treatment of a water based formulation of bifenthrin to the timber product; the water based formulation further comprising a colorant; the superficial treatment comprising an application of between 4g/m3 and 38g/m3 of timber product; - 14 - the superficial treatment being applied such that the timber product does not require redrying.

14. The apparatus according to claim 13, wherein the apparatus applies the superficial treatment in-line with sawing operation of the timber product.

15. The apparatus according to claim 13 or claim 14, wherein the apparatus applies the superficial treatment after stress grading of the timber product. 15. The apparatus according to any one of claims 13 to 15, wherein the apparatus applies the superficial treatment by transverse spray after a docking saw operation.

16. The apparatus according to claim 13, wherein the application means applies the superficial treatment in accordance with a method according to any one of claims 1 to 12.

17. A timber product having been preserved, wherein the timber product is treated at a sawmill in accordance with a method according to any one of claims 1 to 12.

18. The timber product according to claim 17, wherein the timber product is a housing timber or material.

19. The timber product according to claim 17 or claim 18, wherein the timber product retains significant insecticide/acaricide properties above 25 degrees centigrade.

20. The timber product according to any one of claims 17 to 19, wherein the timber product is treated against attack by Coptotermes acinaciformis or Mastotermes darwiniensis. - 15-