AU2007304870B2 - Insect and subterranean-termite resisting settable-polyurethane foam - Google Patents

Description

WO 2008/040047 PCT/AU2007/000182 1 INSECT AND SUBTERRANEAN-TERMITE RESISTING SETTABLE POLYURETHANE FOAM BACKGROUND OF THE INVENTION, Many methods of preventing termite entry to buildings across the perimeter 5 cavity have been proposed. These include the use of stainless steel mesh, aluminium strips and layers of plastic sheeting with a layer of a termiticide impregnated fibre matrix sandwiched between the plastic sheets. All these methods suffer from the disadvantage that while the mesh or sheeting laid across the cavity may be highly resistant to termite ingress, the systems are 10 dependent on applying a termite resisting glue to attach the mesh or sheeting to the construction materials. Any failure of this glue during or after installation compromises the system. Often the application of the glue or parging material, as it is also called, requires elaborate and meticulous preparation of the construction materials to ensure 15 good adhesion. A further disadvantage of these systems in the case of mesh and metal strips is that the barrier materials are relatively rigid and difficult to form Into the contours of the building- This puts further strain on the glue or parging material and increases the likelihood of gaps being left in the barrier through which termite 20 entry can occur. In the case of plastic sheeting materials, glues that adhere both to plastic and construction materials are notoriously difficult to formulate. Typically, glues that adhere well to construction materials will have little or no affinity for plastic and vice versa. 25 In some plastic sheeting systems, the sheeting is nailed to the substrate and relies on the repellency of the termiticide incorporated into the plastic sheet WO 2008/040047 PCT/AU2007/000182 2 preventing termite entry through the gap between the sheeting and the substrate. In this situation, too large a gap between the sheet and substrate compromises the system. Patent application No AU2003212117 describes an acrylic based termite 5 resistant sealant that overcomes these difficulties, The acrylic based sealant forms an extremely strong bond to common construction materials such as brick and concrete and can form a seal or damp-course layer A disadvantage of Patent application No AU200321 2117 and to a greater extent with other methods of termite-proofing buildings such as stainless steel mesh 10 aluminium and plastic sheeting is that a high degree of detail is required in the installation of the system and, where complex or non-uniform construction methods are used, installation may be slow and time consuming. BRIEF DESCRIPTION OF THE INVENTION. There is provided according to the invention a method of preventing or deterring 15 the entry of insects and subterranean termites into a building the method including the step of installing a foam barrier in situ around the building and across construction joints and gaps in the building. Preferably the foam is a closed cell polyurethane foam and is formed in situ and includes an insecticide and a termiticide. 20 Preferably the ingredients are mixed on site and dispensed by a high pressure system, or dispensed from a single use can or from a refillable, reusable canister system. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a view of the invention applied to a wall cavity, the foam supported 25 by a cardboard former, and WO 2008/040047 PCT/AU2007/000182 3 Figure 2 is a further view of the invention applied to a wall cavity DETAILED DESCRIPTION OF THE INVENTION Polyurethane foams have been known for a long time. They are widely used in the manufacture of flexible foam for furniture, carpets, automobiles and a wide 5 range of industrial applications including sealants and adhesives. By careful selection of the monomers and catalysts used to control the cross-linking that occurs, a wide variety of desirable mechanical properties can be built into the final product. Polyurethane is formed by the chemical reaction between a diisocyanate and a 10 polyol. Diisocyanates have the general formula O=C=N-R-CH 2 -R'-N=C=O. Both aliphatic and aromatic diisocyanates can be used; those made with aromatic diisocyantes are less stable to light and tend to yellow with age. It is the structure of the polyol that exerts the greatest influence on the final properties of the polyurethane. Softer, elastic and more flexible products are 15 formed when linear difunctional polyethylene glycol monomers, usually called polyether polyols, are used. More rigid products result if polyfunctional polyols are involved as these create three-dimensional cross-linked structures. To create even more rigid foams special catalysts known as trimerisation catalysts are used to promote the formation of cyclic structures within the 20 matrix. Foams formed in this way are known as polyisocyanurate foams and are commonly used in construction materials. Polyurethane is formed into foam as a result of the addition of small amounts of water to the polyol. The water reacts with the diisocyanate to form carbon dioxide in relatively uniform bubbles throughout the liquid. These harden as 25 polymerisation progresses eventually forming a solid foam matrix.

WO 2008/040047 PCT/AU2007/000182 4 There are two main variations to the basic polyurethane foam: Either the bubbles (cells) remain closed or the cells open at a crucial stage in the reaction allowing trapped gases to escape. In general, flexible foams have open cells rigid foams have closed cells. In the 5 latter case, the gas retained in the cells (such as the fluorocarbon blowing agent) may play a key role in imparting desirable properties, such as thermal insulation, to the foam. In this invention the preferred form is a closed cell structure as this is less likely to provide a pathway for termite ingress. Volatile chemicals known as blowing agents are another common additive used 10 in polyurethane foams. These can be simple volatile chemicals such as acetone or dichloromethane or more sophisticated fluorocarbons which are used to impart desirable performance characteristics such as thermal insulation. In the preferred form of this invention, the amount of blowing agent is maximised at the expense of the addition of water in order to minimise the 15 volume of carbon dioxide present in the closed foam. Many other additives can be added to polyurethane foams to further enhance the desired properties of the end product- These additives include chain extenders, cross-linkers, surfactants, foam stabilisers, pigments, flame retardants and additives such as denatonium salts to deter rats and mice. 20 This invention describes the incorporation of an insecticidally and termiticidally active compound or compounds into polyurethane foam to render the foam resistant to insect and termite attack. With'the exception of the addition of an insecticidal and termiticidal constituent to the foam, all of the foregoing description of polyurethane foams is well-known 25 to those skilled in the art. Indeed the number of possible combinations of diisocyanate and polyol and the possible variations of additives is innumerable.

WO 2008/040047 PCT/AU2007/000182 5 Regardless of the details of the composition, the method of introducing an insecticidal and termiticidal compound into the foam is relatively simple in principle. The insecticidal or termiticidal compound is pre-blended with either the diisocyanate or polyol or pre-blended with both the diisocyanate and the 5 polyol. When the diisocyanate and polyol are mixed the polymerisation reaction takes place and the insecticidal and termiticidal compound is evenly distributed throughout the polymer matrix. The insecticidal and termiticidal compound can be chosen from any of the organic insecticide groups including carbamates, dhloronicotinyls such as 10 imidacloprid, organochlorines, organophosphorus compounds, phenyl pyrazoles such as fipronil, naturally occurring or synthetic pyrethroids, and other naturally occurring insecticides. Preferably, the pesticide is selected from the pyrethroid group (bifenthrin, cypermethrin, deltamethrin, etc.), fipronil, imidacloprid or one of the naturally occurring pesticides such as pyrethrins. 15 In principle, inorganic insecticides such as arsenic compounds, boron compounds, etc. could be used in place of an organic insecticide. These compounds have the advantage that they do not degrade overtime. The disadvantage is that inorganic compounds, especially boron compounds are generally only effective at much higher concentrations than organic insecticides 20 and are generally more difficult to incorporate into polyurethane foam i.e. they must be incorporated as solids since they do not easily dissolve in the monomer precursors. For these reasons organic insecticides are the preferred method of rendering the foam termite resistant. It is obvious that one or more insecticidal and termiticida compounds could be 25 used in any combination of organic and/or inorganic compounds. Indeed, one compound or mixture of compounds could be added to one precursor material and the other compound or mixture of compounds could be added to the other or the mixture of compounds could be added to both precursors or to only one precursor. In the preferred form of this invention only one insecticidal or WO 2008/040047 PCT/AU2007/000182 6 termiticidal compound is used and is added preferentially to the polyol precursor. In principle, the insecticidal and termiticidal compound can be added either to the diisocyanate or polyols or both. The preferred method is to add the 5 insecticidal and termiticidal compound to the polyol only. The preferred method of addition is to pre-dissolve the insecticidal or termiticidal compound in the polyol together with the other minor additives in the formulation. If this is not possible then the compound is dissolved in a suitable solvent and the concentrated solution so formed added to the polyol. 10 Many solvents are suitable for this purpose; the selection will depend on the solubility properties of the particular insecticidal and termiticidal compound. A preferred method is to use the solvent N-methylpyrrolidone (NMP) in which many pesticidal active compounds are highly soluble. Yet another preferred method of dissolving the active compound is to form a 15 solution in one of the minor additives present in the formulation such as the blowing agent. This solution is then blended with the polyol and other minor constituents. Regardless of the procedure, a key objective of this method is to obtain a stable solution of the active constituent in the polyol blend together with the other minor constituent that form part of the formulation. 20 If the compound is not readily Soluble by any of the above methods or is present in too high a concentration to be dissolved by any of the above methods, then the preferred method of addition is to add the compound as a powder. Even more preferred is to mill the compound to an average particle size of <2pm (99% <10pm) and pre-blend with the polyol. 25 The powder can be milled by any suitable method including wet and dry milling methods. The preferred method is to wet mill the compound and add the wet milled compound to the polyol such that the water in the wet milled compound WO 2008/040047 PCT/AU2007/000182 7 constitutes the water required to generate the carbon dioxide reaction that is essential to creating the foam. In this form of the invention the wet-milled product must be carefully controlled and is preferably used immediately after milling to minimise the possibility of re 5 agglomeration or separation of the milled compound from the suspension. In the preferred form of this invention the dilsocyanate is an alkylene diaryl 4,4' diisocyanate preferably methylene diphenyl 4,4'- diisocyanate. The preferred polyol blend component is an aromatic ether polyol and/or an aromatic polyester polyol. Also, in the preferred form of the invention the minor 10 additives (catalysts, chain extenders, cross-linkers, surfactants, foam stabilisers, pigment, flame retardants, anti-vermin compounds, insecticides' and termiticides) are pre blended with the polyol blend component. The preferred range of typical additives is shown in the Table 1 below; however, these values are not intended as limitations on any component as it is possible i5 for those skilled in the art to devise functional products in which one or more of the individual components lie outside these ranges.

WO 2008/040047 PCT/AU2007/000182 8 Table 1 Aromaticpolyetherpolyowl Aromatic polyester polyol 35-50 Aromatic polyester polyol 35 -50 Hydrogen containing fluorocarbon (HFC) 10-15 Water 1-5 Catalysts 0.1-2 Chain Extenders -- 5 Cross-linking agents 1-5 Surfactants 1-5 Foam Stabilisers 1 -5 Pigments 1-5 Flame Retardants 10-15 InsecticidefTermiticide 0.01-5 Anti-Vermin compounds 0.001 -5 Solvent 0.1 -5 15 Table 2 Typical examples of the polyol blend composition. 1% - 5 _______________________ 1.2. 3. Aromatic polyether polyol 40 27 20 Aromatic polyester polyol 156 26 32 Hydrogen containing fluorocarbon (HFC) 12 12.5 13 Water 3.0 3.6 2.7 Catalysts 0.5 1.5 0.9 Chain Extenders 3.5 3.9 4.5 Crosslinking agents 2.2 2.0 3.9 1.7 1.0 3.2 Aoamaiplyser 2.5 1.9 4.1 Wat 3.5 2.4 1.7 Clat anyt 15 12 9 Insecticidenermiticide 0.25 2.0 4.0 Ant-Vermin corunds 0.01 1.8 4 Solvents 0.25 2.4 1.0 WO 2008/040047 PCT/AU2007/000182 9 The diisocyanate and polyol blend can be combined in any ratio from 100 parts diisocyanate to 100 parts polyol blend (100:100 diisocyanate:polyol) to 140 parts diisocyanate to 100 parts polyol blend (140:100 dilsocyanate:polyol). However, it is possible to form acceptable products outside these ratios. The 5 preferred ratio is 100 parts diisocyanate to 100 parts polyol blend (100:100 diisocyanate:polyol). This invention describes a method of installing a foam barrier around the perimeter of buildings and across other large construction joints and gaps in an economical and speedy fashion. The invention is based on a closed cell 10 polyurethane foam formed in situ that incorporates an insecticide and termiticide to discourage insect and particularly termite activity from breaching the barrier. The foam ingredients can be mixed on site by hand, dispensed via a large scale high pressure mixing system, dispensed from a single use can or from a refillable, reusable canister system. The ingredients of the formulation when 15 combined react to generate a foam barrier that is laid down in the cavity in slab on-ground or infill slab construction methods or sprayed into larger holes or openings to completely fill those openings. To minimise the volume of foam required to cross a wall cavity or other large opening a simple cardboard former is placed in the cavity (Figures 1 and 2) 20 such that the inverted V-shape of the former holds it in position and prevents it from moving as the foam is applied. Of course, the invention is not limited to the perimeter cavity in slab-on-ground construction methods. The foam can be used to seal cracks, fissures, construction joints, etc. of practically any size- Equally it can be used to fill wall 25 cavities, underfloor spaces, and large openings of any shape or size where it is desirable to exclude termites or other insect pests.

WO 2008/040047 PCT/AU2007/000182 10 It is not essential when treating the perimeter cavity in slab-on-ground construction methods to limit the amount of foam by the use of cardboard or other formers. The total void can be filled with foam if desired. The essential feature of this invention is that any cavity or opening must be 5 completely sealed leaving no gaps or fissures to allow passage of termites or other insect pests, The minimum thickness of foam necessary to prevent termite ingress will vary with the amount of pesticide incorporated into the foam, the type of pest and the type of building construction. Typically the minimum foam thickness will be from 10 to 50mm. The preferred thickness is 40mm in 10 the cavity of slab-on-ground constructions, In some situations a lesser thickness may be adequate; in other situations a greater thickness may be desirable. The properties of the foam are such that it readily adheres to construction materials, is flexible enough to withstand the normal live and dead loads 15 associated with building movement and is sufficiently rigid and waterproof to act as both a barrier to termite ingress and as a moisture barrier. Referring now to Figure 1 showing one example of the application of the invention. The foundation 1 supports the outer wall 2 and the inner wall 3. The floor slab 4 is supported between a row of bricks of the inner wall. To support 20 the foam a former 5 is positioned between the two walls, the former having side walls 6 to frictionally engage the two walls to hold the former in position whilst the foam 7 is sprayed into the cavity to have its upper surface at the end face of the floor slab, preferably just below the upper surface of the floor slab. A further refinement of the invention is to coat the upper surface of the foam 25 barrier with a layer of sealant 8 or to make an even more efficacious termite barrier with damp-coursing characteristics to form a damp-course and to protect it from external agencies and to further reduce the likelihood of termite ingress due to any deficiencies in the foam layer such as gaps, physical damage or in WO 2008/040047 PCT/AU2007/000182 11 the event that too thin a layer of foam is applied. The sealant may an acrylic or non-acrylic sealant and preferably a sealant as described in Australian Patent No 2003212117. In the example as shown in Figure 2, the floor slab 4 rests on the foundation 1, 5 the inner wall 3 being erected on the floor slab. In this example a former is not required the foam being sprayed direct onto the foundation between the outer wall 2 and the edge of the floor slab. Also the upper surface is covered by the sealant, In both instances a fibreglass or hardened plastic seal 9 is provided to seal brick 10 cord holes when that type of brick is incorporated into the construction. Other coatings including water-based acrylics, non-acrylic coatings or solvent based sealants can be applied to the foam to protect it from mechanical damage moisture or for aesthetic reasons; however, these materials do not afford the additional termite protection that the sealant described in Patent 15 application No AU2003212117 would confer. In general, water based sealants are preferred to solvent-based sealants because of the potential damage to the integrity of the foam from the solvent. The concentration of insecticide or termiticide added to the foam depends on the specific materials used to form the foam, the target insect and the selection 20 of insecticide or termitioide. in the preferred form of this invention the target species are termites and the preferred insecticide I termiticide is the synthetic pyrethroid bifenthrin. Field trials have indicated that the optimum concentration of termiticide based on the weight of foam solids is 1 - 2 g/kg (0.1 - 0.2% w/w). However, the application is not limited to this range. 25 Synthetic pyrethroids such as bifenthrin are preferred because these compounds have adequate thermal and chemical stability to provide long term insect and termite proofing to the foam compounds. Furthermore, the structure of the foam and the manner of its use provide a protected environment ensuring WO 2008/040047 PCT/AU2007/000182 12 that the insecticidal and termiticidal compound remains active for a long period of time. At the preferred rate of addition, the amount of insecticidal and termiticidal compound used does not adversely affect the physical or chemical properties of 5 the foam. The following examples illustrate the invention, with particular reference to the incorporation of bifenthrin to prevent ingress of termites. Example 1: Polyol blends with the compositions shown in Table 2, Composition 2 and 3 10 above, were prepared on a laboratory scale using bifenthrin technical grade active constituent with a.purity of 97%. The bifenthrin was pre-dissolved in a minimum quantity of NMP prior to blending with the polyol components. Laboratory trials showed that within experimental error the bifenthrin was stable in the polyol blend for at least two years using standard accelerated test 15 methods (54 ± 2"C for 14 days). A'1OO:100 parts by weight mixture of the above polyol blends and methylene diphenyl 4,4'-diisocyanate were mixed by hand in polyethylene containers. The mixtures were allowed to polymerise and expand without restriction. The experiment was repeated several times. Core samples were taken from the 20 polymerised materials and tested to determine the bifenthrin content. The results showed that bifenthrin concentrations were within the expected range within the limits of experimental error. Foam samples subjected to an accelerated stability trial (54 ± 2 0 C for 14 days), also showed no observable change in bifenthrin content within the limits of 25 experimental error. Example 2: WO 2008/040047 PCT/AU2007/000182 13 The objective of this experiment was to determine the performance of polyurethane foams prepared as described in Example 1 against field populations of the subterranean termites Mastotermes darwiniensis, and Coptotermes acinacaformis 5 Test Product Standard concrete building blocks (approx. dimensions 400 x 190 x 190 mm) divided into two sections were prepared as follows (Figure 3): One section of each block was filled with the test polyurethane foam to a thickness of 40mm within the opening cavity of the block. The foam was cut off 10 level with the face of the block and a water based acrylic paint coated on the outside of the foam. This section of the block was then filled with Tasmanian Oak billets and the other end of the section sealed with stainless steel mesh glued to the concrete block using a termite proof glue (such as that described in Patent application No AU2003212117). The other section of the block was filled 15 with Tasmanian Oak (Eucalyptus regnans) billets and sealed at both ends with chicken wire. Control blocks were prepared exactly as described above using an identical polyurethane foam omitting only the bifenthrin. Site Preparation 20 Sites were selected close to well established termite nests (Mastotermes darwiniensis in northern'Western Australia and Coptotermes acinacaformis in northern New South Wales). At each location a trench was dug with approx. dimensions 1800 x 500 x 400 mm deep and the trench floor lined with a layer of bait wood (Tasmanian Oak 25 and Pine).

WO 2008/040047 PCT/AU2007/000182 14 Concrete Block Installation Concrete blocks prepared as described above were placed lengthways on top of plain untreated masonry blocks filled on both sides with bait wood. The polyurethane foam treated sections of the blocks were placed such that the 5 foam treated sections faced upwards to simulate the conditions that would exist in a house. Timber boards were placed lengthways on top of the blocks and around the blocks totally encasing the test materials in bait wood. Site Closure The test materials were covered with a layer of black plastic sheet, held down 10 with soil to a depth of approx. 50mm around the edges of the sheet. Shade cloth was placed over the soil and the area gently compacted. Finally, an irrigation water drip system was installed in the immediate area around the trench for use during dry periods to minimise the risk of termite withdrawal. Number of Trial Blocks 15 Four trial blocks and one control block were prepared at each trial site. Two of the trial blocks were prepared with a bifenthrin concentration of 0.1% w/w (Table 2 Composition 2) and two with a concentration of 0.2% w/w (Table 2 Composition 3). These trial sites were set up-in 2006. After five months from establishment, 20 termite activity in the northern New South Wales trial was massive. Inspection of the trial blocks showed that the bait wood in the control block was totally consumed, with the foam itself totally destroyed by'the termites. The treated foam showed minimal damage by termite activity and no loss of bait wood protected by the treated foam. 25 After four months, termite activity in the northern Western Australian trial was well established, with extensive muddying of the bait wood. Damage to the WO 2008/040047 PCT/AU2007/000182 15 untreated foam in the control block was slight with evidence of termite activity within the foam protected section. There was no activity around the treated foam. These trials indicate that bifenthrin at a concentration of 0.1 - 0.2% w/w 5 provides adequate protection against extreme termite pressure. Activity around treated foam was limited to minor surface damage. METHODS OF DISPENSING THE FOAM HAND MIXING The simplest method of forming the foam is to hand mix the diisocyanate and 10 polyol blend on site by hand or with a power drill to ensure efficient mixing. The resulting mixture is quickly poured into the cavity to be filled and the expansion of the foam ensures that all the voids are taken up and the cavity is filled. HIGH PRESSURE DISPENSER Specialised equipment such as Gusmer® allows the diisocyanate and polyol 15 blend to be thoroughly mixed and dispensed under high pressure. The process is very fast and most of the expansion of the foam takes place after the mixture leaves the machine i.e. in the voids to be filled. In the hands of a skilled operator this system is fast and efficient; however, there is a considerable capital cost involved in the acquisition of the equipment and the system is best 20 suited to large scale operations. PRESSURISED CYLINDERS Polyurethane foams can be packaged and dispensed from small aerosol type cans. This method lends itself to small scale operations.

WO 2008/040047 PCT/AU2007/000182 16 Fomo Products USA has developed a more practical version of the aerosol can in which the precursors are packaged in pressurised cylinders and the product is dispensed through disposable hoses and gun. The pressurised cylinders contain sufficient material to treat several domestic buildings and are re 5 useable. In addition, because the product is pre-packaged in the pressurised cylinders, there is no need for the operator to handle directly any pesticide containing material substantially increasing the safety of the system. There is also no substantial capital outlay with this system as there is with the Gusmer® type equipment and the degree of control that can be attained by a skilled 10 operator is similar to that which can be achieved with the Gusmer® system. This is the preferred method of dispensing the foam.

Claims (8)

1. A method of preventing or deterring the entry of insects and subterranean termites into a building, the method including the step of installing a closed cell fast curing foam barrier containing an insecticide and/or mixture of insecticides and/or 5 termiticides in situ at least partly around the building and across construction joints and gaps in the building through which termites may enter the building and wherein the foam is formed from a diisocyanate and a polyol and the insecticide and/or mixture of insecticides and/or termiticides blended with the diisocyanate and the polyol which when mixed polymerise and the insecticidal and/or termiticidal 1o compounds are evenly distributed throughout the resulting polymer.

2. A method as defined in claim 1 including the step of pre-dissolving the insecticidal and/or termiticidal compound or mixture of insecticidal and/or termiticidal compounds in the polyol.

3. A method as defined in claim 3 including the step of dissolving the insecticidal 15 and/or termiticidal compound or mixture of insecticidal and/or termiticidal compounds in a suitable solvent and mixing the resulting solution in the polyol .

4. A method as defined in claim 3 including the step of wet or dry milling the insecticidal or termiticidal compounds prior to mixing in the polyol.

5. A method as defined in claims wherein the insecticidal and termiticidal 20 compound is selected from organic insecticide groups including carbamates, organochlorines, organophosphorus compounds, phenyl pyrazoles, nicotinyls, naturally occurring or synthetic pyrethroids.

6. A method as defined in claim 1 including the step of mixing the diisocyanate and polyol blend by hand and pouring the mix into the desired cavity whereby 25 expansion of the foam ensures that all voids are taken up. 18

7. A method as defined in claim 1 including mixing the diisocyanate and polyol blend in a mixed and dispensing the mixture under high pressure.

8. A method as defined in claim 1 including the step of dispensing the foam from pressurised cylinders.