AU2022100113A4 - A pyrethroid envelope timber treatment - Google Patents

Abstract

According to the present invention there is provided a formulation and method for treating timber. The formulation comprises one or more preservatives and a water-based carrier. When combined, the preservative/s and the water provide for a protective "envelope" of preservative/s within the treated wood to a depth of about 2 mm. The present invention also provides a method of effecting treatment of wood using such a formulation, a concentrate of the one or more preservatives and a kit comprising same. (Figure 1)

Description

A PYRETHROID ENVELOPE TIMBER TREATMENT

Related Application

[001] This is a divisional application from Australian innovation patent application 2021107145.

Field of the Invention

[002] The present invention relates to preservative treatment of timber materials and particularly, to formulations and methods for delivering a protective envelope of preservative to the timber.

[003] Those skilled in the art will appreciate that although the invention has been described with reference to specific examples, it may be embodied in many other forms.

Background of the Invention

[004] 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 common general knowledge in the field.

[005] Wood is a staple construction material used throughout the world. However, it is prone to degradation from elements including the natural environment, weather events, insects, rot and fire.

[006] For instance, in countries such as Australia, timber is especially susceptible to termite attack. This has been counteracted to some degree by the treatment of wood with preservatives in the form of insecticides. Accordingly, a range of chemical treatments has been developed to improve the durability and available working lifetime of wooden structures. Application methods and approved chemicals vary significantly throughout the world.

[007] The treatment of timber or timber products with preservative compounds involves the introduction of stable chemicals into the cellular structure of the timber. This, in turn, protects the timber from hazards such as fungi, insects and other wood destroying organisms. The active chemical agent is usually dissolved in a solvent and the solutions generally are of relatively low viscosity in order to facilitate the penetration of the treatment solution. However, the preservative may also be present in the carrier as an emulsion. Preservative treatments may also include the introduction of chemicals that improve resistance to degradation by fire.

[008] Softwood timbers such as Pinus radiata,P. elliotti, and P. carribeaused as framing timber in Australia are especially susceptible to termite attack. Changes in Government regulations have limited the use of soil poisoning agents (e.g., banning of organochloride insecticides). This has unfortunately led to a higher incidence of termite attack in timber-framed houses. Accordingly, many countries continue to seek suitable cost-effective methods to combat this ever-increasing risk of termite attack.

[0091 One of the strategies to combat termite attack of softwood frames is the treatment of the timber with insecticides or more broad-spectrum wood preservatives. To this end, timber is often impregnated with a preservative such as a fungicide or insecticide. The preservative is typically present in a carrier, with the mixture being applied to the surface of the timber, for example by dipping, spraying, brushing or pressure-treatment, such that the carrier and preservative are absorbed into the timber.

[0101 Examples of commonly used insecticides include synthetic pyrethroids. These are axonic poisons that work by keeping the sodium channels open in the neuronal membranes of insects. The sodium channel is a small hole through which sodium ions are permitted to enter the axon and cause excitation. As the nerves cannot then de excite, the insect is rendered paralysed. Examples of commercial pyrethroids include allethrin, bifenthrin, cypermethrin, cyphenothrin, deltamethrin, permethrin, prallethrin, resmethrin, sumithrin, tetramethrin, tralomethrin, transfluthrin and imiprothrin.

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[0111 Permethrin (1) is an especially preferred preservative according to the present invention. It is known to bean effective insecticide, acaricide, and insect repellent. It functions as a neurotoxin, as related above. However, it generally has a low mammalian toxicity and is poorly absorbed by skin.

[0121 In Australia, the treatment of timber is covered by the Australian standard series "AS 1604-2021". The present invention is especially applicable to Hazard classes H1, H2 and H2F. Of these, Hazard class H2 is defined for borer and termites. Although the present invention is exemplified with respect to H2F requirements, it will be readily appreciated by those skilled in the art that the invention is equally applicable to H1 and

H2 requirements and penetration standards. The approved chemicals are shown in the following table (retention is measured in w/w [% m/m]).

Table 1 - Minimum preservative retention in the penetrationzone, H2

Waterborne Light Organic Solvent Preservatives Copper chrome Ammoniacal copper arsenic (CCA) quaternary Permethrin Cypermethrin Deltamethrin (Cu + Cr + As) (Cu + DDAC) 0.320 0.35 0.020 0.030 0.0020

Table 2 - Minimum preservative retention in the penetrationzone (H2F)

Preservative Permethrin Bifenthrin Imidacloprid Penetration zone 5 mma 2 mma 2 mma Retention in penetration zone 0.020% m/m 0.020% m/m 0.0078% m/m aPenetrated from each surface, excluding ends

[0131 "Penetration"is defined under the standard as:

[0141 All preservative-treated wood shall show evidence of distribution of the preservative in the penetration zone in accordance with the following requirements:

[015] (a) If the species of timber used is of natural durability class 1 or 2, the preservative shall penetrate all the sapwood. Preservative penetration of the heartwood is not required.

[0161 (b) If the species of timber used is of natural durability class 3 or 4, the preservative shall penetrate all of the sapwood and, in addition one of the following requirements shall apply:

[017] (i) Where the lesser cross-sectional dimension is greater than 35 mm, the penetration shall be not less than 8 mm from any surface. Where the lesser cross sectional dimension is equal or less than 35 mm, the penetration shall be not less than 5 mm from any surface.

[0181 (ii) Unpenetrated heartwood shall be permitted, provided that it comprises less than 20% of the cross-section of the piece and does not extend more than halfway through the piece from one surface to the opposite surface and does not exceed half the dimension of the side in the cross-section on which it occurs".

[0191 In order to provide for penetration of the preservative, a carrier must be used. As shown in the Australian standard (see, Tables 1 and 2, above), the carriers presently available can be characterised as "waterborne" or "solvent-bome" systems. A carrier must provide sufficient penetration of a preservative into the wood, thereby to provide an effective barrier against infestation. Other considerations in the choice of carrier include the desired rate of penetration, the cost and environmental and health and safety considerations. Increased penetration of a preservative solution can also be achieved by diffusion, which despite involving less expensive equipment does require a longer time period and greater levels of stock holding. Diffusion time is also influenced by the initial wood moisture content and often requires a pre-drying step so as to create a preferential diffusion gradient along which the preservative/carrier formulation may migrate.

[020] The preservatives commonly used in timber treatment can be characterised according to the carrier solvent used as the vehicle to carry preservatives into the timber, and by the active chemicals that provide the protection against the various hazards that compositions such as that of the present invention seek to counter. The final step in the preservation process is that the solvent (which may include water) must then be removed before the timber is made available for use.

[021] Waterbome carriers swell wood and hence treated timber needs to be re-dried prior to use in service. Building codes specify the maximum moisture content of pine framing; this level is around 15-18% w/w moisture content. The general process sequence is: i) dry the wood; ii) water treat the wood; and iii) re-dry the wood. This additional re-drying step adds complexity and expense to the treatment process and results in additional costs being passed on to the consumer. By comparison, solvent borne preservatives do not raise the moisture content and hence do not swell the wood because they are non-polar. Thus, the process sequence is: i) dry the wood; and ii) solvent treat the wood.

[022] Although the use of solvent-bome preservatives mitigates against the need for the re-drying step, the principal disadvantages of this treatment system are the relatively high cost of solvents (cf water) and the potential environmental concerns with, e.g. volatile organic compounds being released into the atmosphere.

[023] As mentioned above, the application of the preservative/carrier to the wood is often carried out by a batch process involving a pressure vessel. For water-borne preservatives, a vacuum pressure process (Bethell or full cell) is used. This facilitates complete sapwood penetration and adequate heartwood penetration, if required.

[024] Copper, chromium and arsenate (H 2 AsO 4 -), "CCA", is a leach-resistant wood preservative that has been used for some time to treat solid wood in external applications. CCA impregnates the timber in a water/salts carrier and is designed to react with the wood cell components so that the active elements copper, chromium and arsenic are "fixed" into the wood's structure. The arsenic component protects the sapwood from insect attack; the copper and arsenic from degradation due to fungi, whilst the chromium component chemically locks the elements into the timber, offering a relatively high resistance to leaching. Following such treatment, in order to give the treated timber dimensional stability, it must be re-dried. This process can decrease the strength and/or toughness of the timber, and invariably adds to the cost. However, due to environmental health and safety issues - and toxicity concerns relating to the constituent metals, especially arsenic, CCA is coming under increasing regulation and is thus becoming a less desirable treatment on both commercial and environmental bases.

[025] Inorganic boron compounds have been commonly used in Australia to protect the sapwood of susceptible hardwoods against lyctines or "powder post" borers. Such treatment consists in soaking freshly-sawn unseasoned timber in solutions of boron salts. The salts diffuse through the timber, thereby treating it; following such treatment, the timber is allowed to dry. However, boron salts are readily soluble in aqueous solutions and can be leached relatively easily from the wood once treated. This largely restricts boron-treated timber to interior uses such as flooring or joinery, wherein it is protected from the external environment.

[026] Light Organic Solvent-bome Preservatives (LOSPs) comprise a light organic solvent, typically white spirit, to carry the preservative chemicals into the timber. White spirit is a mixture of saturated aliphatic and alicyclic C 7-C 1 2 hydrocarbons with a w/w content of about 15-20% aromatic C 7 -C 12 hydrocarbons. The solvent is drawn out in the final stages of treatment, with the preservative remaining within the wood. Such preservatives are typically fungicides, having copper, tin, zinc, azoles and pentachlorophenols (PCPs) as major toxicants. One principal advantage of LOSP treatment is that the treated timber does not swell, making such treatment quite suitable for treatment of finished items such as mouldings and joinery. The majority of LOSPs used in wood treatment also contain insecticides and/or waxes so as to give the surface water repellent properties. However, odour and exposure to volatile organic compounds (VOCs) are significant environmental and occupational health and safety issues associated with the use of LOSPs in the timber treatment industry. Accordingly, whilst effective, such treatments are becoming increasingly undesirable.

[027] Alkaline Copper Quat (ACQ) contains copper and a quaternary ammonium compound. It is used to protect timber against decay fungi and insects. ACQ is applied as a water-borne preservative using an external pressure process. It is free of arsenic and is used to treat external timber applications.

[028] Copper azole is another of the new generation of arsenic-free preservative treatments that can be used in water-bome pressure treatment processes. It is a preservative that contains copper, boric acid and tebuconazole. Copper azole has been used in Australia as a replacement for CCA for treatments having external applications.

[029] Creosote and pigment emulsified creosote (PEC) are commonly-used oil-borne preservatives that are painted onto timber surfaces, but can also be applied in a pressure based process for better penetration. These compounds have volatile components and hence, a characteristic odour. This makes creosote and PEC only really suitable for use in external or industrial applications.

[030] As the use of water-based carriers has been found to increase the moisture content of the timber, resulting in undesirable swelling of the wood, and necessitating a further drying processes after treatment, many current methods of treating and protecting wood, for H2 and H3 end uses, rely on using non-aqueous solvents. Further, pressure plants are expensive to construct, and being batch processes, conventional treatments do not match well with continuous sawmill production and require a high level of operator control to maintain costs.

[031] US 7,361,215 discloses the use of a drying oil in combination with a high flash point solvent carrier to transport an insecticide into the wood. This formulation promotes the formation of a well-defined "envelope" of preservative, thereby treating and preventing infestations of termites and other insects. A preferred embodiment of this invention is a mixture of pale boiled linseed oil (PBLO) and narrow cut kerosene (NCK). This solution, when combined with a pyrethroid preservative has proven effective in giving the required protective envelope at low uptake (12 to 15 L/m 3). However, of late, the cost of both PBLO and NCK has risen as a result of the commodity boom and cost of mineral oil.

[032] US 5,846,305 discloses a liquid wood preservative solution including copper metal, liquid amine solvent, a boron compound and a glycol. Glycol has been used as a replacement for water in ancient timber restoration, or for dimensional stability in a technique known as "bulking" for many years. Boron is highly miscible in glycol and thus the movement of a glycol/boron solution into the wood is due to diffusion. Due to the length of time required for adequate diffusion into the wood, this type of preservative is required to be forced into the wood by vacuum pressure and is unsuitable for effective use in more time-effective techniques such as brushing, dipping or spraying.

[033] US 2004/0146733 relates to a method for the protective treatment of wood by means of thermal treatment at 60-250 °C and additional treatment using an amine and/or amine derivative and/or salt thereof. The wood treated according to such method has good resistance even to harmful organisms that cannot be reliably controlled by means of only a heat treatment. The method is carried out without compounds containing heavy metals and the wood treated in this way has no impact on the environment either during the use or during the disposal thereof. However, it will be appreciated that the initial heat-treatment step is relatively undesirable for cost-energy reasons.

[034] WO 2004/050783 summarises known methods for glue, glue-line resin systems and wood products incorporating glues with bifenthrin. The glues, when combined with bifenthrin are purported to be effective in preserving engineered wood products, with or without additional surface sprays. The bifenthrin is delivered to the wood in a water based formulation by spraying.

[035] WO 2012/027796 describes a formulation and method for treating timber. The formulation comprises one or more preservatives, such as permethrin, and a water carrier. When combined, the preservative and the water provide for a protective envelope of preservative within the treated wood to a depth of about 5 mm. In this patent, penetration of the active ingredient beyond the outer 2.5 mm was clearly shown, yet the moisture content did not increase beyond 2.5 mm.

[036] WO 2004/050316 teaches that permethrin is not suitable for use as a superficial treatment. In this document, it was reported (Table 3) that permethrin failed (treatments 3 and 4). In Table 2, the treatments were described as LOSP, meaning that the specimens were treated using a solvent-borne formulation and a vacuum/pressure process to enable full sapwood penetration. In Table 3 the LOSP term is omitted, but given that a solvent control was included it is likely that the permethrin treatments described were again LOSP treatments. Irrespective, this document categorically teaches that the permethrin treatments failed.

[037] Herein and throughout the specification and claims, the term "permethrin" should be taken to mean any one or more of its four stereoisomers (two enantiomeric pairs), arising from the two stereogenic centres in the cyclopropane ring; the trans enantiomeric pair is often termed "transpermethrin", e.g.,

0 0 trans-enantiomer/s

CI

ci N ' I cis-enantiomer

cii

o the other cis-enantiomer

[038] 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.

[0391 It is an object of an especially preferred form of the present invention to provide for a water-based composition and method for the preservative treatment of timber products, preferably Australian species such as Pinus radiata,that is effective in providing for an approximate 2 mm envelope of preservative within the treated wood.

[0401 Despite the many and varied techniques for the treatment of wood, there remains a need to satisfy the "dry after" requirement for treated timber, having less than 15% moisture content, whilst achieving the required penetration of active compounds into the wood. Additionally, remains a need for a material for treating wood that has relatively low odour, relatively minimal VOC emissions, and relatively less reliance on mineral spirits, whilst at once providing relatively good dimensional stability to the treated wood.

[041] Unless the context clearly requires otherwise, throughout the description and the claims, the words "comprise", "comprising", and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of "including, but not limited to".

[042] Although the invention will be described with reference to specific examples it will be appreciated by those skilled in the art that the invention may be embodied in many other forms.

Summary of the Invention

[043] A preferred embodiment of the present invention may be represented, at least in the Australian marketplace, by the registered trademark "Vacsol© T".

[044] According to a first aspect of the present invention there is provided a preservative concentrate for treating wood, the formulation comprising an insecticidally-effective concentration of one or more insecticides, wherein upon application to the wood, a protective envelope is formed in which the majority of the insecticide is found within the treated wood to a depth of about 2 mm, and at a predetermined concentration or retention of said one or more insecticides with respect to the treated wood.

[045] In an embodiment, the protective envelope maintains the insecticidally-effective concentration of the one or more preservatives over a period of about one to about ten years.

[046] In an embodiment, the one or more insecticides are selected from the group consisting of: acrinathrin; allethrin; bioallethrin; barthrin; bifenthrin; bioethanomethrin; cyclethrin; cycloprothrin; cyfluthrin; beta-cyfluthrin; cyhalothrin; gamma cyhalothrin; lambda-cyhalothrin; cypermethrin; alpha-cypermethrin; beta-cypermethrin; theta cypermethrin; zeta-cypermethrin; cyphenothrin; deltamethrin; dimefluthrin; dimethrin; empenthrin; fenfluthrin; fenpirithrin; fenpropathrin; fenvalerate; esfenvalerate; flucythrinate; fluvalinate; taufluvalinate; furethrin; imiprothrin; metofluthrin; permethrin; biopermethrin; transpermethrin; phenothrin; prallethrin; profluthrin; pyresmethrin; resmethrin; bioresmethrin; cismethrin; tefluthrin; terallethrin; tetramethrin; tralomethrin; transfluthrin; ctofcnprox; flufcnprox; halfcnprox; protrifcnbutc; silafluofen and mixtures thereof.

[047] In an embodiment, the one or more insecticides comprise permethrin.

[048] In an embodiment, the concentration of each of the one or more insecticides in the formulation is less than about 1% m/m.

[049] In an embodiment, the concentration of each of the one or more insecticides in the formulation is less than about 0.5% m/m.

[050] In an embodiment, the concentration of each of the one or more insecticides in the formulation is less than about 0.25% m/m.

[051] In an embodiment, the concentration of each of the one or more insecticides in the formulation is less than about 0.1% m/m.

[052] In an embodiment, the one or more insecticides are emulsified or dispersed in water.

[053] In an embodiment, penetration of the one or more preservatives within the wood is along the grain of the wood and/or across the grain of the wood.

[054] In an embodiment, the formulation further comprises one or more surfactants.

[055] In an embodiment, the formulation is for application to the wood by means selected from the group consisting of: spraying, dipping, brushing, rolling, painting, vacuum coating, roller coating, flood coatings, pressure application, autoclave, and combinations/variations thereof.

[056] In an embodiment, the one or more insecticides comprise a combination of at least one toxicant and at least one repellent.

[057] In an embodiment, the one or more insecticides comprise a combination of at least one pyrethroid and at least one neonicotinoid.

[058] In an embodiment, the at least one insecticide comprises permethrin and at least one neonicotinoid comprises thiacloprid or imidacloprid.

[059] In an embodiment, the formulation comrpises permethrin emulsified in water, when applied to wood to prevent attack by Australian wood-destroying termites other than Mastotermes darwiniensis.

[060] In an embodiment, the termites are C. acinaciformis.

[061] According to a second aspect of the present invention there is provided a method for treating wood, the method comprising the step of contacting the wood with a water based preservative formulation defined according to the first aspect of the invention.

[062] In an embodiment, the contacting is effected by means selected from the group consisting of: spraying, dipping, rolling, painting, brushing, vacuum coating, roller coating, autoclave application, and any combination or variation thereof.

[063] In an embodiment, the contacting is accompanied by one or more pressure and/or vacuum gradients.

[064] In an embodiment, the method further comprises a post-application drying step wherein at least some of the water is evaporated from the treated wood following formation of the protective envelope.

[065] In an embodiment, the method further comprises a preliminary conditioning step, wherein the wood is pre-conditioned to facilitate subsequent application of the preservative formulation.

[066] In an embodiment, the wood is dipped in the preservative formulation for a period of between a few seconds to several minutes.

[067] In an embodiment, the wood is dipped in the preservative formulation for a period of around five seconds to about sixty seconds.

[068] In an embodiment, the wood is contacted with a sufficient quantity of preservative and carrier to provide an uptake of between 5 to 100 L/m3 in the wood.

[069] In an embodiment, the wood is contacted with a sufficient quantity of preservative and carrier to provide an uptake of between 10 to 100 L/m3 of the wood.

[070] In an embodiment, the method is applicable to radiata pine heartwood and sapwood, slash pine (Pinuselliottii) heartwood and sapwood, Pinus caribaeaheartwood and sapwood, F1 hybrid heartwood and sapwood (Pinus elliottii/caribaeahybrid), maritime pine (Pinuspinaster) heartwood or sapwood, southern yellow pine heartwood and sapwood (group of species including loblolly, longleaf, shortleaf, and slash pines) and/or Douglas fir (Pseudotsugamenziesii) heartwood and sapwood and/or hardwood species.

[071] In an embodiment, the method is applicable to imported species such as Picea abies L. Karst, Baltic pine (like red and white Baltic pine), Pinus sylvestris and the like.

[072] In an embodiment, the method is applicable to wood composites/engineered wood products including particle board, plywood, laminated veneer lumber (LVL), plywood or oriented strand board (OSB).

[073] According to a third aspect of the present invention there is provided treated wood, when treated by a method according to the second aspect of the present invention there is provided.

[074] According to a fourth aspect of the present invention there is provided a concentrate comprising one or more insecticides, wherein following dilution with a diluent comprising a predetermined volume of water and subsequent application to wood, a protective envelope comprising an insecticidally-effective concentration of the one or more insecticides is formed within the wood to a depth of about 2 mm.

[075] According to a fifth aspect of the present invention there is provided a method of preparing a formulation for treating wood as defined according to the first aspect of the present invention, the method comprising the step of adding to a concentrate as defined according to the fourth aspect of the present invention, a diluent comprising a predetermined volume of water and optionally agitating or mixing.

[076] According to a sixth aspect of the present invention there is provided a kit comprising a concentrate defined according to the fourth aspect of the present invention; and instructions pertaining to diluting the concentrate with a diluent comprising water and/or applying the subsequently diluted concentrate to wood, thereby to provide for a protective envelope comprising an insecticidally-effective concentration of one or more insecticides within the wood.

[077] In an embodiment, the kit further comprises application means in the form of a sprayer, brush, roller, vessel for dipping, or the like.

[078] A wide variety of preservatives may also be used in combination with the carrier. Various insecticides and termiticides known in the art may be mixed with the carrier composition. Such insecticides and termiticides include synthetic pyrethroids such as permethrin, cypermethrin, etc., and imidacloprid.

[079] Fungicides and mouldicides may also be used, e.g. iodopropynylbutyl carbamate (IPBC), and the class of mouldicides known as isothiazolones. Other fungicides and mouldicides applicable to the present invention include iodopropynylbuthylcarbamate (IPBC), organic copper compounds such as copper-8-quinolinolate and copper naphthenate, organic zinc compounds, quaternary ammonium compounds, tertiary ammonium compounds, isothiazolones, triazoles such as tebuconazole, boron compounds such as boric acid, sodium tetraborate (and hydrated forms thereof), disodium octaborate tetrahydrate and trimethyl borate.

[080] The Inventor has surprisingly found that the above-disclosed formulation comprising a mixture of one or more preservatives and carrier provides an effective wood preservative which has the sought "envelope" effect to a depth of about 2 mm. While the depth of penetration of the protective envelope is described as being "about 2 mm" within this application, it will be appreciated and understood by those skilled in the art that the envelope could equally be less than 2 mm or even more. The key point to make is that the envelope is relatively shallow, in comparison with that described previously in WO 2012/027796 provides an alternative to conventional preservative techniques.

[081 In another embodiment, the present invention provides a method of treating wood comprising contact to the wood with the inventive formulation. The treatment step can be conducted using conventional pressure application techniques such as existing vacuum pressure systems known in light organic solvent plants. Alternatively, the Applicant has also found the inventive composition can be applied without the need for pressure application. Treatment can be accomplished by spraying, dipping, brushing, vacuum or flood coating etc., which, unlike previous conventional batch systems, are ideal for use in continuous production line facilities such as saw mills.

[0821By comparison with the Applicant's earlier patent document WO 2012/027796, a key point of difference relates not only to the depth of penetration of the insecticide, but also to the overall retention in the treated article (piece retention). For a piece of timber framing with cross section dimensions of 90 x 45 mm, a 5 mm envelope (ignoring end effects) on this cross section leads to treatment of-31% of the cross section, compared with just -13% of cross section being treated in the case of a 2 mm superficial envelope. Therefore, applying the same retention to the envelope results in distinct piece retentions, as shown in Table 3, below. In addition to the apparent 'weaknesses' of permethrin described in prior art referred to above, the 2 mm permethrin envelope has still been shown to be efficacious, at piece retentions significantly lower than those previously described to have failed.

Table 3 - Piece retention comparative datafor2 and 5mm envelope treatments

Cross section % Cross section Envelope Piece retention Envelope (mm) treated retention (g/m3) (g/m 3 )

5 mm 90 x 45 31 100 31 2 mm 90 x 45 13 100 13

Brief Description of the Figures

[0831 A preferred embodiment of the invention will now be described, by way of example only, with reference to the accompanying figures, which show the effect of an inventive treatment of permethrin/water on radiata pine sapwood, as follows:

[084] Figure 1 is a photograph of (a) Untreated radiata pine sapwood after exposure to C. acinaciformis; (b) Radiata pine sapwood treated with a 2 mm envelope of permethrin (0.02% m/m in the penetration zone), after exposure to C. acinaciformisin a field trial.

[0851 The Applicant has also found that the inventive formulation and method provides more than adequate protection without the need for the formation of a deep envelope, as has been described in WO 2012/027796. This shallow protective envelope is a move away from the envelope protection afforded by permethrin as described in AS1604, where the analytical zone in the case of permethrin is 5 mm from the surface of the treated timber.

[086] The following Examples should be viewed as representative only, and in no way limiting of the scope of the claims or efficacy of the present invention. Tests were conducted to verify the efficacy of the inventive formulation.

[087] As applied herein throughout the remainder of the specification, "Formulation A" is a comparative oil-borne/solvent-borne preservative formulation (optionally of permethrin), sold commercially by the Applicant as Tanalith© T (see, e.g., US 7,361,215). One skilled in the art will appreciate that any of solvent-borne, oil-borne and waterborne preservative formulations may be preferable depending on the specific circumstances of the required treatment scenario.

[088] As applied herein throughout the remainder of the specification, "Formulation B" is a comparative imidacloprid aqueous suspension concentrate, which is currently sold under the trade name Tanalith Ti. It is approved for use with a 2 mm analytical zone, hence is used a reference preservative for demonstrating the efficacy of a 2 mm envelope

Example 1

[089] The formulation defined according to the present invention can be applied to timber via conventional means, e.g. spray or other means to apply the preservative to the timber surface. The proprietary water-based formulation of permethrin used in Example 1 forms an approximate 2 mm preservative envelope.

[090] To test the efficacy of the envelope formed by the inventive formulation, a field trial was carried out by the Commonwealth Scientific and Industrial Research Organisation (CSIRO, Australia), in accordance with the ProtocolsforAssessment of Wood Preservatives. The details of the trial are summarised in Table 4, below. In this Example, the formulation comprised an emulsified permethrin concentrate (ca. 500 g/L), diluted in water to a suitable concentration.

[091] The field trial specimens were treated in longer lengths, then docked to 200 mm. Sections of the left-over material were retained, and submitted to the Chemical

Laboratory at Department Primary Industries and Fisheries, Queensland, Australia, for chemical analysis. The results are given in Table 5, below.

[0921 As reflected in Table 4, the inventive formulation used was an emulsifiable concentrate of permethrin (500 g/L), which was diluted with water prior to use to give a preservative solution having a permethrin concentration of approximately 0.24% m/m. Permethrin, like many synthetic pyrethroids (e.g., bifenthrin), has low solubility in water. However, it is able to be introduced to the wood as an emulsion (e.g. microemulsion). It will be appreciated that within the context of the present invention, alternative formulation types are also applicable. For instance, permethrin can be solubilised in water through addition of a clathrating agent such as a cyclodextrin; other variants include dispersions, etc.

Table 4 - Summary of details of CSIROfield trial

Research provider CSIRO Active ingredient Permethrin Envelope (outer 2 mm) retention 0.022% m/m Controls Untreated timber Reference preservative Formulation A (permethrin 0.02% m/m) Substrate Pinus radiata sapwood Specimen size 200 x 90 x 45 mm Treatment Superficial spray Retention verification Chemical analysis Specimen pre-conditioning Outdoor exposure (1 month), vacuum-oven drying (5 days) Replication Six specimens Field trial site Gunn Point, Northern Territory, Australia Trial method Above-ground technique Duration of trial 9 months Termite species present C. acinaciformis Method of assessment Visual assessment using CSIRO rating system. 8 - Sound 7 - Superficial attack or grazing by termites 6 - Surface attack to a depth exceeding treatment envelope 5 - Attack (slight) 10 - 25 % mass loss 4 - Attack (moderate) 25 - 50 % mass loss 3 - Attack (heavy) 50 - 75 % mass loss 2 - Attack (severe) 75 - 90 % mass loss 1 - Attack (destroyed) >90 % mass loss

[0931 After a period of nine months' exposure at CSIRO's field test site in the Northern Territory of Australia, all of the specimens in the six replicate drums showed evidence of contact by C. acinaciformis. There was little evidence of any remaining Eucalyptus regnans bait wood, and the untreated controls in each of the six drums had been destroyed by termites. The grading system used by CSIRO (see, Table 4, above) assigns a rating of between 8 ("sound") and 1 ("destroyed") to each of the specimens, where a rating of 7 or 8 must be achieved for an envelope treatment to be considered "successful".

[094] The results are summarised in Table 5, below. The untreated controls were all rated 1 (mass loss > 90%), demonstrating the substantial termite pressure achieved in each of the replicate drums. In contrast specimens treated with the inventive formulation were each sound, with evidence of minor grazing only, where each specimen was rated 7 or 8.

Table 5 - Summary offield test resultsfor 2 mm envelope treatment

Mean active Penetration Mean Range Result Treatment retention (% m/m) zone (mm) rating (Pass/fail) Untreated control - N/A 1.0 1-1 0/6 Permethrin 2 mm 0.0062 2 7.2 7-8 6/0 envelope Permethrin 2 mm 0.0147 2 7.3 7-8 6/0 envelope Inventive permethrin 2 0.0235 2 7.5 7-8 6/0 mm envelope Reference Preservative, 0.020 5 8.0 8-8 6/0 Formulation A ReferencePreservative (emulsified 0.020 5 8.0 8-8 6/0 permethrin)

[0951 The data clearly contradict the teaching of the prior art document, WO 2004/050316, which teaches that permethrin is not suitable for use as a superficial treatment. In this document, it was reported (Table 3) that permethrin failed (treatments 3 and 4). The retentions shown in Table 5 match the data shown in WO 2004/050316 reasonably well.

[0961 Formulation A (a comparative oil-borne/solvent-borne permethrin formulation sold commercially by the Applicant as Tanalith@ T), with a 5 mm treatment envelope, was included as a reference preservative. These specimens also all achieved ratings of 8. Images of an untreated specimen and a specimen treated with a 2mm permethrin envelope at the completion of the field trial are shown in the respective Figures 1(a) and 1(b).

[0971 According to the present invention, the formulation can be applied via any means. In particular, the most applicable and preferable of the methods known in the art include spray, dip, vacuum coating, roller coating etc., and variations thereof.

[0981 The Applicant's intention was to treat only the outer portion of the wood (e.g., the outer 2 mm region) and achieve at least an efficacious retention of the insecticide in the penetration zone. Accordingly, it can be seen that the inventive formulation provides not only adequate protection but does so in a more efficient and cost-effective manner than conventional techniques.

Table 6 - Summary of condition ofspecimens after exposure in afield test

Treatment Label Termite Condition No. rating 1 1 Destroyed - shell remaining 2 1 Destroyed 3 1 Destroyed Untreated control 4 1 Destroyed - shell remaining 5 1 Destroyed - shell remaining 6 1 Destroyed 13 8 Heavy mudding 80% cover - sound Formulation A 14 8 Heavy mudding 80% cover - sound (permethrin, 5 mm 15 8 Moderate mudding 60% cover - sound envelope) 16 8 Moderate mudding 60% cover - sound 17 8 Heavy mudding 80% cover - sound 18 8 Heavy mudding 80% cover - sound 49 8 Moderate mudding 30% cover - sound 50 7 Moderate mudding 30% cover - isolated grazing < 1 mm Permethrin 2 mm 51 7 Light mudding 10% cover- isolated grazing envelope < 1 mm (0.0235% m/m) 52 7 Light mudding 10% cover - one penetration to 1.5 mm 53 8 Moderate mudding 40% cover - sound 54 8 Light mudding 5% cover - sound

[099] According to the experimental data attained, the C. acinaciformistermites damaged only the untreated specimens and baitwood. All treatments appeared to protect the test specimens. The severity of the test protocol is evidenced by the amount of termite damage to the control specimens. The termite foraging pressure was severe and conditions suitable for sustained termite foraging.

[0100] These results demonstrate the efficacy of a preservative envelope delivered from a waterborne carrier to protect timbers from attack by C. acinaciformis.

[0101] A further surprising feature of the invention was the discovery that timber treated with the waterborne permethrin formulation was less contacted by termites than timber treated with Formulation A, an oil/solvent-borne formulation of permethrin. The

CSIRO researchers noted that the specimens treated with the inventive permethrin formulation were only lightly mudded (Table 6), with an average coverage of 21%. In comparison, the reference preservative treated specimens were heavily mudded, with an average coverage of 73%. Although the timber specimens are vacuum oven dried to remove residual solvent prior to exposure in the field, it can be seen in Table 5 that the oil/solvent carrier in Formulation A does provide some deterrence to termite feeding. The oil/solvent control specimens (i.e., those treated only with the oil/solvent carrier) in general suffered less attack than the untreated specimens. It is therefore surprising that the specimens treated with the waterborne permethrin formulation, where there is no contribution to feeding deterrence from the carrier, were substantially less mudded than the Formulation A treated specimens. From this observation, which has been made on several occasions in different field trials, it can be concluded that the inventive permethrin formulation renders treated timber more repellent to termite attack than Formulation A treated timber.

Table 7 - Analysis of envelope treatedfieldtrialspecimens

Treatment group Envelope penetration Retention zone (mm) (% m/m) 2 0.006 2 0.0058 Permethrin 2 mm envelope 2 0.0069 (mean retention 0.0062% 2 0.0071 2 0.005 2 0.0062 2 0.017 2 0.0104 Permethrin 2 mm envelope 2 0.016 (mean retention 0.00147% 2 0.0178 n/rn) 2 0.0171 2 0.0098 2 0.0182 2 0.0178 Permethrin 2 mm envelope 2 0.0184 (mean retention 0.0235% 2 0.0235 2 0.0346 2 0.0285

Example 2

[0102] The present invention also provides a means for protecting imported timbers from termite attack.

[0103] To test the effectiveness of the 2 mm envelope to protect imported timbers such as Picea abies L. Karst (commonly referred to as Norway spruce), a field trial was carried out in accordance with the ProtocolsforAssessment of Wood Preservatives. The experimental details of the trial are summarised in Table 8. Norway spruce is known to be refractory in nature, such that achieving anything beyond superficial penetration by non-pressure application methods is not possible.

Table 8 -Norway sprucefield trialagainst attack by C. acinaciformis

Substrate Picea abies L. Karst (Norway spruce) Specimen size 200 x 90 x 45 mm Active ingredient (2 mm Permethrin (0.01, 0.02, 0.03 % m/m) envelope analytical zone) Control Untreated control Reference preservative (2 mm Formulation B (imidacloprid 0.0078% m/m) envelope analytical zone) Treatment Momentary immersion Specimen pre-conditioning Outdoor exposure (1 month), vacuum-oven drying (5 days) Replication Six specimens Field trial site Humpty Doo, Northern Territory, Australia Trial method Drum technique Duration of trial 12 months Termite species present C. acinaciformis Method of assessment Mass loss (%)

Table 9 - Resultsfor imported timber, Picea abies L. Karst (Norway spruce)

Active retention (% m/m) Mean mass Result Treatment in 2 mm penetration zone loss(%) (Pass/fail) Untreated control 75.6 0/6 Permethrin 0.01 0.2 6/0 Permethrin 0.02 0.1 6/0 Permethrin 0.03 0.4 6/0 Formulation B 0.008 2.3 6/0

[0104] After a period of twelve months exposure in the Northern Territory, all of the specimens in the six replicate drums showed evidence of contact by Coptotermes acinaciformis. There was little evidence of any remaining Eucalyptus regnans bait wood, and the untreated controls in each of the six drums had been destroyed by termites. The grading system used in this study was mass loss. After the field test the specimens were returned to the laboratory, cleaned, dried, vacuum-oven dried and then weighed to determine mass loss. The results are given in Table 9.

[0105] The untreated controls sustained high mass loss (> 75%), demonstrating the substantial termite pressure achieved in each of the replicate drums. In contrast, the superficial envelope treated specimens were all sound, with a mean mass loss of less than 0.5% for the 2 mm permethrin-treated specimens, and a mean mass loss of 2.3% for the specimens treated with the imidacloprid-treated reference preservative "Formulation B" (available commercially as Tanalith© Ti). The results demonstrate the suitability of superficial surface applied permethrin to protect refractory timbers from termite attack in indoor, above-ground exposure conditions. Empirically, no penetration of active beyond the 2 mm analytical zone was observed (i.e., the notional 2 mm envelope was not breached).

[0106] The above results further demonstrate the efficacy of the preservative envelope to protect framing timbers from attack by C. acinaciformis.

Example 3

[0107] This Example demonstrates an exemplary treatment and analysis according to the present invention. In this Example, samples of 90 x 35 mm Eucalyptus nitens (E. nitens, Eucalyptic hardwood, shining gum) framing with air dry densities in the range 540-620 kg/m3 were dip treated in a permethrin containing formulation, targeting a 0.04% m/m permethrin retention in the 2 mm analytical zone. Uptakes were low (mean uptake 6.4 L/m 3 ), which is consistent with the refractory nature of Eucalypt heartwood. Selected samples were sectioned and exposed in an inside above-ground field test in Esk, Queensland. The field trial was conducted in accordance with the Protocolsfor Assessment of Wood Preservatives using the lunch box technique. After 25 weeks exposure, the samples were harvested, returned the laboratory where they were cleaned, dried and mass loss determined by weighing. The untreated controls had experienced substantial mass loss (mean mass loss 48%), while those treated with a superficial envelope of permethrin showed only traces of termite attack (mean mass loss 2.4%).

Example 4

[0108] In addition to timber, per se, the inventive formulation is suitable for engineered/composite wood products (EWPs). To illustrate this point, treatment of Norway Spruce laminated veneer lumber (LVL) was carried out and the test samples installed in a termite field trial.

[0109] LVL specimens measuring 250 mm long were momentarily immersed in a permethrin containing work solution, targeting a surface application equivalent to 0.02%m/m permethrin in a 2 mm analytical zone. Being LVL manufactured from a refractory species, the mean uptakes were found to be 2.4 L/m 3 . After drying thoroughly the test specimens were exposed for four weeks to natural weathering as would occur during the construction phase of a new house. In accordance with Hazard Level 2 requirements (as specified in the Australasian Wood PreservationCommittee Protocols for Assessment of Wood Preservatives),specimens were then artificially weathered in vacuum ovens for five days at 40 °C and 0.04 mBar.

Table 10 - Summary of details of CSIROfield trial ofNorway Spruce LVL

Research provider CSIRO Substrate Picea abies L. Karst (Norway spruce) LVL, 15 x 3.2 mm veneer Specimen size 200 x 200 x 45 mm (cut from 250 x 200 x 45 mm) Active ingredient Permethrin Envelope (outer 2 mm) retention 0.02% m/m Treatment Momentary immersion Controls Untreated LVL Specimen pre-conditioning Outdoor exposure (1 month), vacuum-oven drying (5 days) Replication Six specimens Field trial site Gunn Point, Northern Territory, Australia Trial method Above-ground technique Duration of trial 9 months Termite species present C. acinaciformis Method of assessment Mass loss

[0110] The test specimens were cut to a length of 200 mm, labeled and installed in an inside above-ground field trial in the Northern Territory, near Darwin. At the conclusion of the above-ground H2 field trial, all exposure containers had evidence of substantial contact by C. acinaciformis. Untreated mountain ash strips (E. regnans), used as an attractive food source for maintaining the presence of termites, had been destroyed. The specimens were returned to the laboratory, cleaned, vacuum oven dried and finally weighed. The results are summarised in Table 11.

[0111] Five of the six untreated control Norway spruce LVL test specimens were either heavily damaged or destroyed by C. acinaciformis.Unfortunately, due to an uneven distribution of termites in exposure container no. 3, one untreated control specimen was not contacted by termites. In contrast, while there was evidence of substantial contact by

C. acinaciformis,the Norway spruce LVL test specimens treated with permethrin were in good condition with all six replicates showing little mass loss. Empirically, no penetration of active beyond the 2 mm analytical zone was observed (i.e., the notional 2 mm envelope was not breached).

Table 11 - Summary of results of CSIROfield trial ofNorway Spruce LVL

Mean active Mean mass Result Treatment retention (% loss(%) (Pass/fail) m/m) Untreated control - 81.4 0/5a Permethrin 2 mm envelope 0.02 0.9 6/0 a Mean offive replicates. One untreated control was untouched in the drum.

Example 5

[0112] In a further example, cypermethrin was also shown to be efficacious when applied to the surface of solid wood. Rubberwood was treated with an emulsion of cypermethrin, where the cypermethrin depth of penetration was limited to about 1 mm. The targeted retention in the penetration zone was 0.03% m/m cypermethrin. Specimens were exposed to C. gestroi in an inside, above-ground field test for a period of about four months in Malaysia, after which the specimens were returned to the laboratory for evaluation. The untreated controls were attacked to varying degrees, with all controls having some degree of visually observable damage. In contrast the treated specimens were intact and had not suffered any termite attack.

Industrial Applicability

[0113] It can be seen that the present invention provides an industrially-significant means with which to counter, in particular, termite infestation of timber. Although the invention has been described with reference to specific examples it will be appreciated by those skilled in the art that the invention may be embodied in many other forms. For instance, although the present invention specifically targets the protection of wood from insect attack, primarily termites, it also includes combining a mouldicide for preventing mould on damp timber, and also a colorant (e.g., a pigment or dye) for identification purposes.

Claims (34)

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. A preservative concentrate for treating wood, the formulation comprising an insecticidally-effective concentration of one or more insecticides, wherein upon application to the wood, a protective envelope is formed in which the majority of the insecticide is found within the treated wood to a depth of about 2 mm, and at a predetermined concentration or retention of said one or more insecticides with respect to the treated wood.

2. A concentrate according to claim 1, wherein the protective envelope maintains the insecticidally-effective concentration of the one or more preservatives over a period of about one to about ten years.

3. A concentrate according to claim 1 or claim 2, wherein the one or more insecticides are selected from the group consisting of: acrinathrin; allethrin; bioallethrin; barthrin; bifenthrin; bioethanomethrin; cyclethrin; cycloprothrin; cyfluthrin; beta-cyfluthrin; cyhalothrin; gamma cyhalothrin; lambda cyhalothrin; cypermethrin; alpha-cypermethrin; beta-cypermethrin; theta cypermethrin; zeta-cypermethrin; cyphenothrin; deltamethrin; dimefluthrin; dimethrin; empenthrin; fenfluthrin; fenpirithrin; fenpropathrin; fenvalerate; esfenvalerate; flucythrinate; fluvalinate; taufluvalinate; furethrin; imiprothrin; metofluthrin; permethrin; biopermethrin; transpermethrin; phenothrin; prallethrin; profluthrin; pyresmethrin; resmethrin; bioresmethrin; cismethrin; tefluthrin; terallethrin; tetramethrin; tralomethrin; transfluthrin; ctofcnprox; flufcnprox; halfcnprox; protrifcnbutc; silafluofen and mixtures thereof.

4. A concentrate according to claim 3, wherein the one or more insecticides comprise permethrin.

5. A concentrate according to any one of the preceding claims, wherein the concentration of each of the one or more insecticides in the formulation is less than about 1% m/m.

6. A concentrate according to any one of the preceding claims, wherein the concentration of each of the one or more insecticides in the formulation is less than about 0.5% m/m.

7. A concentrate according to any one of the preceding claims, wherein the concentration of each of the one or more insecticides in the formulation is less than about 0.25% m/m.

8. A concentrate according to any one of the preceding claims, wherein the concentration of each of the one or more insecticides in the formulation is less than about 0.1% m/m.

9. A concentrate according to any one of the preceding claims, wherein the one or more insecticides are emulsified or dispersed in water.

10. A concentrate according to any one of the preceding claims, wherein penetration of the one or more preservatives within the wood is along the grain of the wood and/or across the grain of the wood.

11. A concentrate according to any one of the preceding claims, further comprising one or more surfactants.

12. A concentrate according to any one of the preceding claims, for application to the wood by means selected from the group consisting of: spraying, dipping, brushing, rolling, painting, vacuum coating, roller coating, flood coatings, pressure application, autoclave, and combinations/variations thereof.

13. A concentrate according to any one of the preceding claims, wherein the one or more insecticides comprise a combination of at least one toxicant and at least one repellent.

14. A concentrate according to any one of the preceding claims, wherein the one or more insecticides comprise a combination of at least one pyrethroid and at least one neonicotinoid.

15. A concentrate according to claim 13, wherein the at least one insecticide comprises permethrin and at least one neonicotinoid comprises thiacloprid or imidacloprid.

16. A concentrate according to claim 1, comprising permethrin emulsified in water, when applied to wood to prevent attack by Australian wood-destroying termites other than Mastotermes darwiniensis.

17. A concentrate according to claim 15, wherein the termites are C. acinaciformis.

18. A method for treating wood, the method comprising the steps of diluting the concentrate defined according to any one of the preceding claims and applying it to the wood, in which the majority of the insecticide is found within the treated wood to a depth of about 2 mm, and at a predetermined concentration of said one or more insecticides with respect to the treated wood.

19. A method according to claim 18, wherein the contacting is effected by means selected from the group consisting of: spraying, dipping, rolling, painting, brushing, vacuum coating, and any combination or variation thereof.

20. A method according to claim 18 or claim 19, wherein the contacting is accompanied by one or more pressure and/or vacuum gradients.

21. A method according to any one of claims 18 to 20, further comprising a post application drying step wherein at least some of the water is evaporated from the treated wood following formation of the protective envelope.

22. A method according to any one of claims 18 to 21, further comprising a preliminary conditioning step, wherein the wood is pre-conditioned to facilitate subsequent application of the preservative formulation.

23. A method according to any one of claims 18 to 22, wherein the wood is dipped in the preservative formulation for a period of between a few seconds to several minutes.

24. A method according to any one of claims 18 to 23, wherein the wood is dipped in the preservative formulation for a period of around five seconds to about sixty seconds.

25. A method according to any one of claims 18 to 24, wherein the wood is contacted with a sufficient quantity of preservative and carrier to provide an uptake of between 5 to 100 L/m 3 in the wood.

26. A method according to any one of claims 18 to 25, wherein the wood is contacted with a sufficient quantity of preservative and carrier to provide an uptake of between 10 to 100 L/m 3 of the wood.

27. A method according to any one of claims 18 to 26, wherein the method is applicable to radiata pine heartwood and sapwood, slash pine (Pinus elliottii) heartwood and sapwood, Pinus caribaeaheartwood and sapwood, F1 hybrid heartwood and sapwood (Pinuselliottii/caribaeahybrid), maritime pine (Pinuspinaster)heartwood or sapwood, southern yellow pine heartwood and sapwood (group of species including loblolly, longleaf, shortleaf, and slash pines) and/or Douglas fir (Pseudotsugamenziesii) heartwood and sapwood and/or hardwood species.

28. A method according to any one of claims 18 to 27, wherein the method is applicable to imported species such as Picea abies L. Karst, Baltic pine (like red and white Baltic pine), Pinus sylvestris and the like.

29. A method according to any one of claims 18 to 28, wherein the method is applicable to wood composites/engineered wood products including particle board, plywood, laminated veneer lumber (LVL), plywood or oriented strand board (OSB).

30. Treated wood, when treated by a method according to any one of claims 18 to 29.

31. A concentrate comprising one or more insecticides, wherein following dilution with a diluent comprising a predetermined volume of water and subsequent application to wood, a protective envelope comprising an insecticidally-effective concentration of the one or more insecticides is formed within the wood to a depth of about 2 mm.

32. A method of preparing a preservative concentrate for treating wood as defined according to claim 1, the method comprising the step of adding to a concentrate as defined according to claim 31, a diluent comprising a predetermined volume of water and optionally agitating or mixing.

33. A kit comprising a concentrate defined according to claim 31; and instructions pertaining to diluting the concentrate with a diluent comprising water and/or applying the subsequently diluted concentrate to wood, thereby to provide for a protective envelope comprising an insecticidally-effective concentration of one or more insecticides within the wood.

34. A kit according to claim 33, further comprising application means in the form of a sprayer, brush, roller, vessel for dipping, or the like.

Dated this 19th day of August 2022 Spruson & Ferguson Pty Ltd Attorneys for: Arch Wood Protection (Aust) Pty Ltd