AU2013203215A1 - Wood coating compositions and/or methods of treating wood - Google Patents

Abstract

The invention relates to coating compositions for use on wood. The coating compositions are specially formulated so that they can be applied to wood prior to the wood being treated with one or more wood preservatives. The coating compositions are sufficiently permeable so as to not hinder the penetration of the preservative(s) into the wood, so the wood will still meet required industry wood preservation standards. The coating compositions comprise at least one binder selected from the group consisting of resin polymer emulsions in an amount of about 30 - 70% by weight, one or more pigments, and one or more excipients selected from the group comprising antifoaming agents, antimould agents, dispersing agents, wetting agents, surfactants, thickening agents, fillers, UV blockers, stabilising agents, anti-tannin agents, and rheological additives. The invention also relates to a method of treating wood wherein the method comprises a first step of coating the surface of the wood with a coating composition of the invention, and a second subsequent step of treating the coated wood with one or more wood preservatives, such as a LOSP, which penetrates into the coated wood.

Description

- 1 WOOD COATING COMPOSITIONS AND/OR METHODS OF TREATING WOOD Field of the Invention The present invention relates generally to wood or timber coating compositions and methods for treating timber or wood. Background of Invention 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. Treatment of wood to protect it from such elements has been practiced since ancient times. There are a number of different chemical preservatives and processes that can extend the life of wood, timber, wood structures or engineered wood. These have been developed to improve the durability and working lifetime of wood and resistance of the wood to destruction by insects and/or fungus. To treat and prevent infestations, timber is often impregnated with a preservative such as a fungicide or insecticide. The treatment of timber or wood products with preservative compounds involves the introduction of stable chemicals into the cellular structure of the wood. This, in turn, protects the wood from hazards such as fungi, insects and other wood destroying organisms. Preservative treatments may also include the introduction of chemicals that improve resistance to degradation by fire. The preservatives commonly used in timber treatment can be characterised according to the carrier or vehicle used to carry the preservatives into the timber, and by the active chemicals used to protect against the various hazards. Chemical preservatives can be classified into three broad categories: water-borne preservatives, such as inorganic boron compounds, chromated copper arsenate (CCA), alkaline copper quaternary (ACQ), copper azoles and other copper compounds, pyrethrins and synthetic pyrethroids; oil-borne preservatives such as pentachlorophenol, creosote and linseed oil; and light organic solvent preservatives (LOSPs). LOSPs comprise a light organic solvent, typically white spirits, to carry the preservative into the wood. Excess fluid is drawn out in the final vacuum stage of treatment, with the required -2 level of preservative remaining within the wood. With LOSP treatment the preservative(s) remain in solution so that the excess fluid drawn out at the final vacuum stage is virtually unaltered in strength and may even become a little stronger due to solvent vaporisation. Typical preservatives include: synthetic pyrethroids such as permethrin, bifenthrin or deltamethrin, which are typically used as insecticides; and copper, tin, zinc and azoles (such as propiconazole and tebuconazole) which are typically used as fungicides. As the use of water-based carriers has been found to increase the moisture content of the wood, resulting in undesirable swelling of the wood, and necessitating a further drying process after treatment, many current methods of treating and protecting wood typically rely on the use of a solvent, such as the LOSPs. LOSP treatment is particularly suited for the protection of machine moulded timber components such as finger-jointed weatherboards and fascia boards, where dimensional stability is of utmost importance. LOSP treatment may also be considered for decking and other structural timber components, such as posts, handrails, bearers and joists, although the demand for dimensional stability may not be so precise. There are many known methods of application of wood-preservatives to timber and wood products. These can generally be divided into non-pressure processes such as brushing, spraying, dipping, soaking, steeping or hot and cold bath; and pressure processes which force the preservative into the pores of the wood. Pressure processes are currently the most widespread and effective processes used. The various pressure processes that are used today differ in details, but the general method is the same, and involves the application of applied pressure and/or vacuum. The treatment is carried out in closed cylinders into which the timber or wood is loaded. The cylinders are then set under pressure often with the addition of higher temperature. A vacuum step is frequently performed to extract excess preservatives, and pressure/vacuum cycles can be repeated to achieve better penetration of the preservative. LOSP treatments often use a vacuum impregnation process. The goal of modern day wood preservation is to ensure a deep, uniform penetration of preservative at a reasonable cost, and with minimal harm to the environment and to human safety. In most countries, the treatment of timber is covered by appropriate wood -3 preservation standards, for example, in the United States this is regulated by the American Wood Protection Association (AWPA), in Australia by Australian Standard "AS 1604-2010" series, in New Zealand by the "NZS 3640" series, and in Europe by the European BS/EN 335 standards. In Australia, the Australian Standard Hazard Class H3 is defined as being for protection against "moderate fungal decay and termite hazard for decking, fascia, cladding, window reveals, and exterior structure timber". The timber is exposed to the weather or not fully protected. It is clear from the ground and the area is well drained and ventilated. H3 treatment is designed to prevent attack by insects, including termites, and decay. "Penetration" is defined under the H3 Standards as: "All preservative-treated wood shall show evidence of distribution of the preservative in the penetration zone in accordance with the following requirements: (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; (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; (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; (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". With any wood preservation treatment, sufficient penetration of the preservative into the wood must be achieved, in order to provide an effective barrier against infestation. The treatment may provide for "complete penetration", or "incomplete penetration", often referred to as an "envelope treatment" in which one or more preservatives penetrate only partially the cross section of the timber in question. Once timber has been treated, it commonly requires priming, painting or staining prior to use. However, before the timber can be primed, painted or stained, it must be completely dry. Drying should occur in the open air, not when the timber is stacked and stored. It can take between four weeks and six months before it is sufficiently dry to enable priming, painting or staining. If the timber or wood is not dry enough, the primer, paint or stain will not adhere -4 properly. In addition, with LOSP treated timber, it is necessary to allow the residual solvent to flash-off before priming, painting or staining. The time required for solvent flash-off is dependent upon storage and drying conditions, but may take up to four weeks or more in a particularly cold and/or damp environment. This delay due to flash-off and drying time is inconvenient, time-consuming and can be costly for manufacturers, distributors and retailers of treated timber and wood products. Furthermore, in situations where priming of LOSP treated wood is required, it is generally recognised that the use of solvent based alkyd resin formulations are best suited for this purpose, which can be an additional inconvenience, particularly when a water based acrylic paint regime is specified, because even with prolonged flash-off, the level of residual solvent may be sufficient to soften the acrylic resin in the primer composition and cause serious adhesion between layers of stacked wood. Also, the water repellents in the LOSP treated wood may cause surface defects and imperfections during the application of acrylic primers, for example, cissing (fisheyes), or subsequent delamination of the paint film. There is therefore a need for an improved coating composition, and/or an improved method of treating timber or wood which overcomes at least some of the shortcomings of the prior art. Definitions: It is acknowledged that the term 'comprise' may, under varying jurisdictions, be attributed with either an exclusive or an inclusive meaning. For the purpose of this specification, and unless otherwise noted, the term 'comprise' shall have an inclusive meaning - i.e. that it will be taken to mean an inclusion of not only the listed components it directly references, but also other non-specified components or elements. This rationale will also be used when the term 'comprised' or 'comprising' is used in relation to one or more steps in a method or process. All percentage weights expressed herein refer to the weight of the component as a percentage of the total weight of the concentrated liquid composition, prior to any dilution.

-5 Object of the Invention It is an object of the invention to provide an improved wood or timber coating composition and/or an improved method of treating timber or wood, that ameliorates at least one of the disadvantages and limitations of the known art, or which at least provides the public with a useful choice. Summary of Invention In a first aspect the invention broadly resides in a water based coating composition formulated for application to wood prior to the wood being treated with one or more wood preservatives, wherein the coating composition will not hinder the penetration of said preservative(s) into the wood. The coating composition can be used as a primer or undercoat, or as a top-coat. Preferably the coating composition comprises at least one binder selected from the group consisting of resin polymer emulsions, one or more pigments, and one or more excipients selected from the group comprising antifoaming agents, antimould agents, dispersing agents, wetting agents, surfactants, thickening agents, fillers, UV blockers, stabilising agents, anti tannin agents, and rheological additives. Preferably the resin polymer emulsion is selected from the group comprising styrene acrylic copolymer emulsions, PVA acrylic copolymer emulsions, vinyl acetate vinyl versatate acrylate (VEOVA VAM) copolymer emulsions, pure acrylic copolymer emulsions (such as BA-MMA copolymers), and combinations thereof. Preferably the composition comprises from about 30 - 70% by weight of the binder. More preferably the binder or resin is present in an amount of from about 50 - 60% by weight. Preferably the coating composition further comprises potassium ferrocyanide. Alternatively, it may comprise a blue pigment. Preferably the potassium ferrocyanide when present in the composition is in an amount of about 1.0 - 2.0% by weight.

-6 Preferably the coating composition further comprises ammonia, or an ammonium releasing compound. Preferably the ammonia is present in the composition in an amount of about 0.1 0.5% by weight. The composition comprises one or more pigment(s). These pigments can be prime pigments, filler pigments or active pigments. Preferably the pigment(s) is/are selected from the group comprising inorganic pigments, such as chrome oxide green, titanium dioxide, iron oxide (yellow, red, brown and black), ultramarine blue, nickel-titanium yellow, carbon black, and organic pigments such as phthalocyanines, arylides, anthraquinones, quinacridones and naphthamides, and combinations thereof Preferably the composition comprises from about 3 - 30% by weight (in total) of one or more pigments. Preferably the composition comprises one or more thickening agents. Preferred thickening agents include all types of cellulose gums. For example, preferred thickening agents include hydroxyethyl cellulose and hydroxypropyl methylcellulose. Other thickening agents which can be used include diatomaceous earth, clays, and water-based polyurethane formulations such as hydrophobically modified ethylene oxide urethanes (known as HEUR rheology modifiers), polyether urea polyurethane polymers and non-ionic polyether polyols. Preferably the thickening agent is present in an amount in the range of about 0.1 - 10% by weight. Preferably the composition comprises at least one antifoaming agent in an amount of about 0.1 - 0.5% by weight. Preferred antifoaming agents include silicone based antifoaming agents, for example, emulsified blends of polydimethylsiloxane and silicon dioxide. Preferably the composition comprises at least one antimould agent in an amount of about 0.1 - 0.2% by weight. Preferred antimould agents include IPBC (3-iodo2-propynyl butylcarbamate), and isothiazolinone based compounds such as OIT (n-octyl isothiazolinone), EDDM (ethylenedioxydimethanol) and PMBO (polymethoxy bicyclic oxazolidine).

-7 Preferably the composition comprises one or more fillers. Preferred fillers include calcium carbonate, silicon dioxide, silica flour, barium sulphate, talc, zinc oxide, hydrated magnesium silicate, and combinations thereof These may also be used as rheological additives. In a second aspect the invention broadly resides in a method of treating untreated wood, wherein the method comprises a first step of coating the surface of the wood with a coating composition according to the first aspect of the invention, and a second subsequent step of treating the coated wood with one or more wood preservatives. Preferably the coated wood is treated with one or more preservatives selected from the group comprising LOSPs. In a further aspect the invention broadly resides in treated timber or a treated wood product when so-treated by a method according to the second aspect of the invention. In a further aspect the invention broadly resides in a method of treating wood comprising (a) applying a coating composition to the surface of the wood to be treated to form surface coated wood, and (b) applying a wood preservative treatment composition to the surface coated wood. Preferably the coating composition is a composition according to the first aspect of the invention. Preferably the wood preservative treatment composition is penetrated into the surface coated wood. Preferably the wood preservative treatment composition is a LOSP composition. In a further aspect the invention broadly resides in treated wood prepared by applying a coating composition according to the first aspect of the invention to the surface of the wood to be treated to form surface coated wood, and subsequently applying a wood preservative treatment composition to the surface coated wood. Preferably the wood preservative treatment composition is penetrated into the surface coated wood. Preferably the wood preservative treatment composition is a LOSP composition.

-8 Description of the Preferred Embodiment(s) The following description will describe the invention in relation to preferred embodiments of the invention. The invention is in no way limited to these preferred embodiments as they are purely to exemplify the invention only and it should be understood that possible variations and modifications which would be readily apparent are intended to be included without departing from the scope of the invention. The invention relates to a coating composition which is specially formulated for application to timber or wood prior to the timber or wood being treated with one or more wood preservatives, such that the coating composition does not hinder the penetration of the preservative(s) into the timber or wood. The compositions of the invention are water based or aqueous compositions, or compositions which are capable of being diluted with water. This is important as it is desired to keep environmental pollution to a minimum. The main component of the coating composition is one or more binders or resins which is/are selected from the group comprising resin polymer emulsions. These emulsions generally consist of fine suspensions in water, based on one or more of the following principal monomers: acrylic esters, acrylonitrile, fumaric and maleic diesters, methacrylic esters, ethylene, styrene, vinyl acetate and higher vinyl esters, vinyl chloride and vinylidene chloride. Plasticizers such as dibutyl phthalate and benzyl butyl phthalate may also be present in the emulsions. Preferred resin polymer emulsions include styrene acrylic copolymer emulsions, PVA acrylic copolymer emulsions, vinyl acetate vinyl versatate acrylate (VEOVA VAM) copolymer emulsions, pure acrylic copolymer emulsions (such as a BA-MMA copolymers), and combinations thereof. The amount of binder or resin included in the composition is important as the composition must be sufficiently permeable in order to allow for adequate penetration of the wood preservative(s) into the wood to the desired level to meet required industry standards. Standard wood coating compositions contain high levels of resin which would impede the ingress of wood preservatives, and would therefore be unsuitable for use in the invention. The binder or resin used in the compositions of the invention contributes to the provision of an open permeable lattice. If the resin content is too high, an impervious coating would be -9 produced, whilst if the resin content is too low, a very weak coating with limited durability and service life would be produced. Thus it is important that the composition comprises the correct balance between the binder or resin content and the remaining components to ensure adequate penetration of the wood preservative(s) into the wood, but also a sufficiently durable coating with a reasonable service life. The binder or resin is preferably present in the concentrated compositions of the invention in an amount of from about 30 - 70% by weight. Preferably the binder or resin is present in an amount of from about 50 - 60% by weight. The compositions of the invention also comprise one or more pigments selected from the group consisting of prime pigments, filler pigments and active pigments. Prime pigments impart colour and opacity. The choice of prime pigments is generally determined by the end user and by the specific application, and is not limited. For example, the pigment(s) may selected from inorganic pigments, such as chrome oxide green, titanium dioxide, iron oxide (yellow, red, brown and black), ultramarine blue, nickel-titanium yellow, carbon black, and organic pigments such as phthalocyanines, arylides, anthraquinones, quinacridones and naphthamides, and combinations thereof If one or more pigments are to be included in the composition, preferably the composition comprises from about 3 - 30% by weight (in total) of one or more pigments. Coating compositions which are to be used as primers or undercoats will typically comprise lower pigment levels of a far less obtrusive colour range, for example, pastel yellows, blues or off-whites, while coating compositions which are to be used as top-coats will generally comprise more intense pigment combinations. The compositions of the invention may also comprise potassium ferrocyanide. This is present for pigmentation purposes, as it reacts in ammoniacal solution to form Prussian blue. Alternatively, a blue pigment could be used if desired. Preferably the potassium ferrocyanide, when included, is present in the composition in an amount of about 1.0 - 2.0% by weight. The compositions of the invention may also comprise ammonia or an ammonium releasing compound. Aqua ammonia which is a solution of ammonia in water (also known as ammonia solution, ammonium hydroxide, ammonia water, ammoniacal liquor, ammonia - 10 liquor, aqueous ammonia, or simply ammonia) may be used. This component can be used when using potassium ferrocyanide for pigmentation purposes to facilitate the formation of Prussian blue. In addition, ammonia may be used to adjust the pH of the composition to at least pH 8.0, in order to ensure maximum emulsion stability. This is because acrylic resin emulsions are stabilised in alkaline solution so when an adjustment of pH is required to greater than 8.0, addition of ammonia is the quickest and most cost effective option. Ammonium carbonate would also suffice, as it dissociates and releases ammonia when added to an aqueous solution. Some acrylic emulsion compositions of the invention may already have a sufficiently high pH so as not to require additional ammonia, but when adjustment is required, then ammonia, or an ammonium releasing compound is a suitable choice. Preferably the ammonia, when included, is present in the composition in an amount of about 0.1 - 0.5% by weight. The compositions of the invention also comprise one or more excipients selected from the group comprising antifoaming agents, antimould agents, dispersing agents, wetting agents, surfactants, thickening agents, fillers, UV blockers, stabilising agents, anti-tannin agents, and rheological additives. The inclusion of these excipients will influence the viscosity, wetting power, dispersibility, stability, foaming, flow and levelling properties, and brush drag/rheology properties of the compositions, and therefore are carefully selected to suit particular uses and applications. For example, coating compositions designed to be used as primers do not need to be formulated to have durable, finished surfaces like top-coat compositions, so they can instead be formulated to have improved filling and binding properties with the surface of the wood to be coated. Therefore primer compositions generally contain higher amounts of fillers and thickening agents. For compositions which are formulated for use as top-coats, preferably at least one thickening agent, at least one antifoaming agent and at least one antimould agent are included in the compositions of the invention. For compositions which are formulated for use as primers or undercoats, preferably at least one thickening agent, at least one antifoaming agent and at least one filler are included in the compositions of the invention. Preferred thickening agents include all types of cellulose gums; for example, hydroxyethyl cellulose and hydroxypropyl methylcellulose. Other thickening agents which can be used include diatomaceous earth, clays, and water-based polyurethane formulations such as - 11 hydrophobically modified ethylene oxide urethanes (known as HEUR rheology modifiers), polyether urea polyurethane polymers and non-ionic polyether polyols. Preferably the thickening agent is present in an amount in the range of about 0.1 - 10% by weight. For compositions which are to be used as primers or undercoats, the amount of thickening agent(s) included in the composition is generally in the higher end of the range, while for top-coat compositions, generally a lesser amount of thickening agent(s) is/are included in the composition. Preferred antifoaming agents include silicone based antifoaming agents, for example, emulsified blends of polydimethylsiloxane and silicon dioxide. Alternatively non-silicone based antifoaming agents may be used, comprising an oil carrier of possibly mineral oil, vegetable oil, white oil or any other oil that is insoluble in the preparation. An oil based antifoaming agent may also contain a wax and/or hydrophobic silica to enhance performance. Typical waxes are ethylene bis-stearamide (EBS), paraffin waxes, ester waxes and fatty alcohol waxes. These additives might also have surfactants to improve emulsification and dispersion in the coating composition. Preferably about 0.1 - 0.5% by weight of one or more antifoaming agents is/are included in the composition. Preferred antimould agents include IPBC (3-iodo2-propynyl butylcarbamate), and isothiazolinone based compounds such as OIT (n-octyl-isothiazolinone), EDDM (ethylenedioxydimethanol) and PMBO (polymethoxy bicyclic oxazolidine). Preferably about 0.1 - 0.2% by weight of one or more antimould agents is/are included in the composition. Other excipients such as pigment dispersants and/or wetting agents can also be included in the compositions of the invention in order to aid in dispersing the pigments through the compositions. Preferred pigment dispersants are dependent upon pigment type, but some examples include APEs (alkyl phenol ethoxylates) or FAEs (fatty alcohol ethoxylates). The compositions of the invention may contain one or more fillers. Preferred fillers commonly used to enhance film build (thickness) include calcium carbonate, silicon dioxide, silica flour, and hydrated magnesium silicate. These can also be used as rheological additives. In coating compositions that are to be used as primers or undercoats, at least one filler, and preferably a combination of several fillers are used in the composition. Examples - 12 of fillers which are preferred in primer compositions are calcium carbonate, barium sulphate, talc and zinc oxide. The coating compositions of the invention are specially formulated so as to provide a primer or undercoat or a top-coat (protective coloured coating or decorative finish) to untreated timber or machined or rough sawn wood or wood products prior to the timber or wood undergoing wood preservation treatment with solvent based chemical preservatives, namely LOSPs. In contrast to the conventional in-situ application of primer, paint or stain to timber or wood products that have already been treated with preservative(s), the method of the present invention allows a specially formulated protective coating to be applied to the timber or wood prior to preservation treatment without hindrance to the ingress (penetration and retention) of the preservative(s) in the timber or wood. Accordingly, the timber or wood product is still in full compliance with industry wood preservation standards. That is, the coating composition is sufficiently permeable to enable the usual efficacy of the wood preservation treatment to be achieved and to meet required industry standards. The permeability of the coating compositions of the invention to chemical preservatives will be maintained for a period of at least 7 days after application of the preservative(s). The coating compositions are effective, i.e. permeable to the preservative(s), as a result of the particular balance of the components in the composition. It is important to get the balance of the components correct in order to produce a sufficiently permeable coating which allows for effective penetration of preservative(s) into the wood to the required levels, and also to provide a sufficiently durable coating which has a reasonable service life. In particular the selected binder or resin polymer contributes to the permeability of the composition by providing a composition with an open permeable lattice structure. An incorrect balance of this component in the composition could produce an impervious coating (without the required degree of porosity to allow penetration of the wood preservative into the wood) or a weak coating with limited durability and service life.

- 13 Preferred Formulations The following examples show both primer and top-coat coating compositions according to preferred embodiments of the invention. These compositions were formulated by mixing the ingredients using known paint manufacturing techniques and processes. For example, firstly the pigments are dispersed in water or a water based medium, generally with one or more surfactants and/or dispersants to separate pigment agglomerates, then the pigment dispersion is added to the binder and the combination is mixed to ensure all components are fully incorporated. Excipients are then added to the composition as required in order to achieve the desired thickness, viscosity, stability and other desired characteristics of the composition. The compositions are generally made in concentrated form and are designed to be diluted with water to the required working strength prior to application. The dilution rate may vary according to the application, but is typically 1 part concentrate to 1.5 parts water. Example 1 - Top-coat Formulation Ingredients % by Weight Binder (resin polymer emulsion) 50 - 60 Thickening Agent (hydroxyethyl cellulose) 0.1 - 0.5 Aqua ammonia 0.1 -0.5 Potassium ferrocyanide 1.0 -2.0 Antifoaming Agent 0.1 -0.2 Antimould Agent or biocide 0.1 -0.2 Pigment(s) 20-30 Water (to balance) 10-20 In the above example, the composition was formulated by adding the resin polymer emulsion to a mixing vessel, then adding the pre-dispersed pigments and mixing for 10 minutes, then - 14 adding the water and mixing for 5 minutes, then adding the thickening agent and mixing for a further 5 minutes before adding the aqua ammonia and mixing for a further 10 minutes. In a separate vessel the potassium ferrocyanide was dissolved in warm water (14%), then this solution was added to the mixing vessel and mixed for 10 minutes, after which the antifoaming agent and the antimould biocide were added and mixed for 10 minutes, and finally water was added to volume and the composition was mixed for a further 20 minutes. The composition was held overnight before checking the viscosity. Example 2 - Top-coat Formulation Ingredients % by Weight Binder (acrylic polymer) 25 - 30 Binder (acrylic resin) 25 - 30 2-buyoxyethanol (solvent for acrylic resin) 5 - 10 Filler (calcium carbonate) 5 - 10 Filler (hydrated magnesium silicate) 5 - 10 Filler (silica flour) 5-10 Iron (III) oxide-hydroxide (yellow iron oxide) 5- 10 Iron (III) oxide (pigment red 101) 5- 10 Manganese ferrite black spinel (pigment black 33) 5 - 10 Antifoaming Agent 0.1 -0.2 Antimould Agent or biocide 0.1 -0.2 Water (to balance) 10 - 20 - 15 Example 3 - Top-coat Formulation Ingredients % by Weight Binder (resin polymer emulsion) 30 Thickening Agent (hydroxyethyl cellulose) 0.5 Aqua ammonia 0.1 -0.5 Potassium ferrocyanide 1.0 Antifoaming Agent 0.1 Antimould Agent or biocide 0.2 Pigment(s) 25 - 30 Water (to balance) 3 8-43 Example 4 - Top-coat Formulation Ingredients % by Weight Binder (resin polymer emulsion) 70 Thickening Agent (hydroxyethyl cellulose) 0.2 Aqua ammonia 0.5 Potassium ferrocyanide 1.0 Antifoaming Agent 0.1 Antimould Agent or biocide 0.2 Pigment(s) 20 Water (to balance) 8 - 16 Example 5 - Top-coat Formulation Ingredients % by Weight Binder (acrylic polymer) 20 Binder (acrylic resin) 20 2-buyoxyethanol (solvent for acrylic resin) 5 Filler (calcium carbonate) 5 Filler (hydrated magnesium silicate) 5 Filler (silica flour) 5 Iron(III) oxide-hydroxide (yellow iron oxide) 5 Iron (III) oxide (pigment red 101) 5 Manganese ferrite black spinel (pigment black 33) 5 Antifoaming Agent 0.1 -0.2 Antimould Agent or biocide 0.1 -0.2 Water (to balance) 25 - 17 Example 6 - Top-coat Formulation Ingredients % by Weight Binder (acrylic polymer) 30 Binder (acrylic resin) 30 2-buyoxyethanol (solvent for acrylic resin) 5 Filler (calcium carbonate) 5 Filler (hydrated magnesium silicate) 5 Filler (silica flour) 5 Iron(II) oxide-hydroxide (yellow iron oxide) 5 Iron (III) oxide (pigment red 101) 5 Manganese ferrite black spinel (pigment black 33) 5 Antifoaming Agent 0.1 -0.2 Antimould Agent or biocide 0.1 -0.2 Water (to balance) 5 - 18 Example 7 - Primer Formulation Ingredients % by Weight Binder (vinyl/acrylic copolymer) 31.6 Demineralised Water 19.8 Dispersing Agent (polymeric non-ionic) 1.4 Co-solvent (propylene glycol) 3.3 Wetting Agent (fluorine modified) 0.1 Antifoaming Agent (non-silicone) 0.3 Thickening Agent (HEUR rheology modifier) 1.4 TiO2 pigment/filler 10.6 Thickening/matting agent (diatomaceous earth) 4.2 Filler (calcium carbonate) 8.6 Filler (barium sulphate) 7.5 Filler (talc) 4.2 Filler (zinc oxide) 0.7 Anti-tannin agent (optional) 2.2 Thickening Agent (anti-settling organo-clay) 4.0 - 19 Example 8 - Primer Formulation Ingredients % by Weight Part A (pre-mix) Water (deionised) 5.54 DPM (co-solvent) 4.00 Dispersing & wetting agent 3.60 Wetting agent (non-ionic surfactant) 0.65 Antifoaming agent 0.23 Iron Oxide (red synthetic Fe 2 0 3 ) 3.47 Filler (calcium carbonate) 16.94 Part B Water (deionised) 24.93 Antifoaming agent (polysiloxane) 0.02 Ammonia (25%) 0.13 Thickening Agent (polyether urea polyurethane polymer) 0.23 Thickening Agent (non-ionic polyether polyol) 0.32 Binder (styrene acrylic polymer emulsion) 39.94 In the above example, the composition was formulated by adding the Part A (pre-mix) components separately to a pre-mix vessel in the order listed and dispersing them for 20 minutes with a high speed Silverson-type mixer. The Part B components were then added to a different main mixing vessel in the order listed with continuous paddle mixing at a slow to medium speed in order to avoid excessive air entrainment. When the individual preliminary mixing of Parts A and B was completed, the Part A pre-mix was slowly pumped over to the main mixing vessel during continuous operation of the paddle mixer. Mixing was maintained for at least one hour until the complete blending of Parts A and B was achieved.

- 20 Preferred Methods The method of the invention comprises at least two steps. The first step involves coating the timber or wood with a coating composition as described herein. The coating compositions of the invention may be applied to the timber or wood by any of the conventional or known methods including vacuum coating, dipping, spraying (including air pressure or airless spraying), brushing, rolling, or flood coating. The excipients in the formulation can obviously be modified in order to suit a particular method of application. Vacuum coating is preferred for application of top-coat formulations as it provides greater uniformity and control in achieving the optimum wet film thickness (WFT) which is about 125 ptm. This optimum coating thickness would normally be achieved with a single application, however this is dependent upon the nature of the wood surface, and in some cases a second coating may be required. Any excess coating composition should be allowed to drain or should be removed from the timber or wood product with brushes, air knives or suction nozzles. The coated timber or wood product should be allowed to dry (for example by stacking and filleting), which can take as little as 10 to 15 minutes on a warm dry day, but over an hour in cold humid conditions. A dry film thickness (DFT) of approximately 80 pim is preferably achieved. After the timber or wood has been coated, and the coating has dried (usually within one hour), the second step of the method of the invention involves treating the timber or wood with one or more wood preservatives. Preferably, solvent based wood preservatives, i.e. LOSPs, are used. The pre-coated timber or wood products may be stored for an indefinite period before preservation treatment. For LOSP treatment the process is in principle similar to that adopted for uncoated timber or wood products. However, depending on the thickness of the coating, the treatment could be modified slightly to a more robust treatment schedule. Treatment can be performed by a standard, unmodified LOSP treatment plant and treatment fluid, and using traditional processes such as Rueping, Lowry and Bethel or proprietary modifications, including Vac Vac, Vac-Vac P, Pneu-Vac, Pneu-Press or Tri-Vac. A typical LOSP treatment schedule ensures that the penetration and retention of the preservative(s) complies with the set -21 standards (for example H3 of AS 1604.1 and H3.1 of NZS 3640) with nominal fluid uptake. An example of a typical LOSP treatment schedule is as follows: Initial Vacuum/Pressure: -30 kPa Hold Time: 60 seconds Flood: Hold Time: 10 seconds Second Vacuum/Pressure: +30 kPa Hold Time: 60 seconds Drain: Final Vacuum: -85 kPa Hold time: 12 minutes Anticipated Uptake 45 litres/m3 Efficacy Trials Efficacy trials were conducted in order to determine the fluid uptake and biocide retention of timber (100% sapwood suitable for decking) that was firstly coated with a coating composition of the invention and then treated with a LOSP wood-preservative, by a pressure process. The trial results are shown in Tables 1 and 2 below. Table 1 LOSP (triazole/permethrin) treatment of pre-coated decking timber Sample Width Depth Length Volume Weight Weight Weight Fluid Total Perm. ID (mm) (mm) (mm) (M 3 ) 1 (g) 2 (g) gain uptake Azole % (g) (Lt/m 3 ) % (m/m) (m/m) 13a 90 20 282 0.0005 248 266 18 44 0.109 0.036 14a 90 20 282 0.0005 295 311 16 39 0.081 0.027 13b 90 20 299 0.0005 288 312 24 56 0.125 0.042 14b 90 20 299 0.0005 313 331 18 42 0.086 0.029 13c 90 20 295 0.0005 288 312 24 56 0.125 0.042 14c 90 20 295 0.0005 310 329 19 45 0.092 0.031 13d 90 20 298 0.0005 298 325 27 63 0.136 0.045 14d 90 20 299 0.0005 289 312 23 53 0.119 0.040 13e 90 20 298 0.0005 289 313 24 56 0.125 0.042 14e 90 20 298 0.0005 283 304 21 49 0.111 0.037 13f 90 20 296 0.0005 283 310 27 63 0.143 0.048 14f 90 20 295 0.0005 281 303 22 52 0.117 0.039 15b 90 20 297 0.0005 263 290 27 63 0.154 0.051 17a 90 20 284 0.0005 290 310 20 49 0.103 0.034 15a 90 20 299 0.0005 273 297 24 56 0.132 0.044 17b 90 20 299 0.0005 308 330 22 51 0.107 0.036 - 22 Table 2 LOSP (triazole/permethrin + CuN) treatment of pre-coated decking timber Sample Width Depth Length Volume Weight Weight Weight Fluid Total Perm. ID (mm) (mm) (mm) (M 3 ) 1 (g) 2 (g) gain uptake Azole % % (g) (Lt/m 3 ) (m/m) (m/m) 3/3 90 21 2010 0.0038 1726.5 1811.4 84.9 28 0.074 0.025 3/4 90 21 2014 0.0038 1672. 5 1839.6 167.1 55 0.150 0.050 3/11 90 21 2008 0.0038 1881.5 1986.9 105.4 35 0.084 0.028 4/5 90 21 2016 0.0038 1609.9 1709.9 100.0 33 0.093 0.031 4/6 90 21 2016 0.0038 1655.2 1758.5 103.3 34 0.094 0.031 4/7 90 21 2016 0.0038 1746.9 1831.5 84.6 28 0.073 0.024 4/8 90 21 2011 0.0038 1556.1 1621.9 75.8 22 0.063 0.021 4/13 90 21 2012 0.0038 1782.7 1905.9 123.2 40 0.104 0.035 4/14 90 21 2010 0.0038 1625.8 1705.1 80.3 26 0.073 0.024 4/15 90 21 2012 0.0038 1575.0 1742.0 167.0 55 0.159 0.053 4/16 90 21 2008 0.0038 1594.9 1683.9 89.0 29 0.084 0.028 A selection of the timber samples listed in Table 1 above were then analysed in a laboratory to determine the extent of biocide retention and depth of penetration in accordance with the H3 specified requirements of Australian Standard 1604.1. The results of this analysis are represented in Table 3 below. Table 3 Chemical Analysis of LOSP (triazole/permethrin) treated pre-coated decking timber Sample ID Tebuconazole Propiconazole Total Azole Permethrin Penetration % (m/m) % (m/m) % (m/m) % (m/m) % 13a 0.078 0.076 0.154 0.06 Positive 13c 0.088 0.086 0.174 0.067 Positive 13d 0.093 0.091 0.184 0.071 Positive 14b 0.061 0.057 0.119 0.045 Positive 16a 0.040 0.037 0.077 0.030 Positive 17c 0.039 0.037 0.076 0.029 Positive These results demonstrate that the coating compositions of the invention have no adverse impact or effect on the LOSP fluid uptake and subsequent penetration and retention of the preservative(s) in the wood. This shows that the coating compositions of the invention can be applied to timber or wood prior to it being treated with one or more preservative(s). The coating compositions of the invention are sufficiently permeable to enable full penetration of the preservative(s) and they do not hinder fluid uptake, penetration or retention of the preservative(s) in the wood in any way. Advantages The coating compositions described herein can be used to coat wood before the wood is treated with a chemical preservative. The preservative can be applied soon after the coating composition has been applied to the wood. If the coating composition applied is a top-coat, - 23 then because the treated wood has been pre-painted and finished, after preservative treatment, the wood is a finished product available for use straight away, without any time delay (resulting from having to wait for the wood to dry and/or solvent to flash-off before coating). The invention therefore provides a sufficiently permeable coating composition which does not hinder or interfere with the usual penetration and retention properties of the preservative which is applied after coating. Treated timber still meets appropriate wood preservation standards. The method of the invention therefore cuts out the drying step and waiting time which was necessary in prior art processes, therefore providing a much more convenient, efficient and cost-effective process. If the coating composition applied is a primer, sufficient time must still be allowed after LOSP treatment for the LOSP solvent to flash-off before subsequent application of one or more decorative top-coats. While the standard waiting time is experienced here, the advantage is that an option is now provided to enable the use of an acrylic primer with LOSP treated wood without the risk of surface defects or paint film delamination. Variations It will of course be realised that while the foregoing has been given by way of illustrative example of this invention, all such and other modifications and variations thereto as would be apparent to persons skilled in the art are deemed to fall within the broad scope and ambit of this invention as is hereinbefore described.

Claims (18)

1. A water based coating composition formulated for application to wood prior to the wood being treated with one or more wood preservatives, wherein the coating composition will not hinder the penetration of said preservative(s) into the wood, said coating composition comprising at least one binder selected from the group consisting of resin polymer emulsions in an amount of about 30 - 70% by weight, one or more pigments, and one or more excipients selected from the group comprising antifoaming agents, antimould agents, dispersing agents, wetting agents, surfactants, thickening agents, fillers, UV blockers, stabilising agents, anti-tannin agents, and rheological additives.

2. The coating composition as claimed in claim 1, wherein the resin polymer emulsion is selected from the group comprising styrene acrylic copolymer emulsions, PVA acrylic copolymer emulsions, vinyl acetate vinyl versatate acrylate copolymer emulsions, pure acrylic copolymer emulsions, and combinations thereof.

3. The coating composition as claimed in claim 1 or 2, wherein the composition comprises from about 50 - 60% by weight of the binder.

4. The coating composition as claimed in any one of the previous claims, wherein the coating composition further comprises potassium ferrocyanide in an amount of about 1.0 - 2.0% by weight.

5. The coating composition as claimed in any one of the previous claims, wherein the coating composition further comprises ammonia, or an ammonium releasing compound, in an amount of about 0.1 - 0.5% by weight.

6. The coating composition as claimed in any one of the previous claims, wherein the pigment(s) are present in a total amount of about 3 - 30% by weight. -25

7. The coating composition as claimed in any one of the previous claims, wherein the pigment(s) is/are selected from the group comprising inorganic pigments, such as chrome oxide green, titanium dioxide, iron oxide (yellow, red, brown and black), ultramarine blue, nickel-titanium yellow, carbon black, and organic pigments such as phthalocyanines, arylides, anthraquinones, quinacridones and naphthamides, and combinations thereof.

8. The coating composition as claimed in any one of the previous claims, wherein the coating composition comprises a thickening agent in an amount in the range of about 0.1 - 10% by weight.

9. The coating composition as claimed in claim 8, wherein the thickening agent is selected from the group comprising cellulose gums, diatomaceous earth, clays, water-based polyurethane formulations, polyether urea polyurethane polymers and non-ionic polyether polyols.

10. The coating composition as claimed in any one of the previous claims, wherein the composition comprises an antifoaming agent in an amount of about 0.1 - 0.5 % by weight.

11. The coating composition as claimed in any one of the previous claims, wherein the composition comprises an antimould agent in an amount of about 0.1 - 0.2% by weight.

12. The coating composition as claimed in any one of the previous claims, wherein the composition comprises one or more fillers selected from the group comprising calcium carbonate, silicon dioxide, silica flour, barium sulphate, talc, zinc oxide, hydrated magnesium silicate, and combinations thereof.

13. A method of treating wood comprising (a) applying a coating composition as claimed in any one of the previous claims to the surface of the wood to be treated to form surface coated wood, and (b) applying a wood preservative treatment composition to the surface coated wood. - 26

14. The method as claimed in claim 13, wherein the wood preservative treatment composition is penetrated into the surface coated wood.

15. The method as claimed in claim 13 or 14, wherein the wood preservative treatment composition is a LOSP composition.

16. Treated wood prepared by the method as claimed in any one of claims 13 to 15.

17. A water based coating composition substantially as herein described with reference to the examples.

18. A method of treating wood substantially as herein described with reference to the examples.