EP2061325A1

EP2061325A1 - Enhanced penetration of biocides

Info

Publication number: EP2061325A1
Application number: EP07834837A
Authority: EP
Inventors: Nigel Paul Maynard
Original assignee: Mattersmiths Technologies Ltd
Current assignee: Mattersmiths Technologies Ltd
Priority date: 2006-08-28
Filing date: 2007-08-28
Publication date: 2009-05-27
Also published as: WO2008026941A1; AU2007289445A1

Abstract

The invention relates to compositions for, and methods of, delivering treatment compounds to lignocellulosic substrates, such as lumber. Preferably the composition includes water, a glycol solvent and a borate compound.

Description

ENHANCED PENETRATION OF BIOCIDES

FIELD

This invention relates to compositions for use in treating organic substrates and to methods of delivering compositions to organic substrates. In particular, the invention relates to compositions for, and methods of, delivering treatment compounds to lignocellulosic substrates, such as lumber. The methods may be for the purpose of prevention of growth of pest organisms, or for providing specific properties to the substrate, for example.

BACKGROUND

Lumber from many tree species lacks durability and frequently has inferior physical properties. These deficiencies are more likely to occur in lumber extracted from man- made plantation forests. Since durability and enhanced physical properties can be required it is typical for lumber processors to alter lumber properties.

It is well known to those versed in the art that these deficiencies can be remedied to a greater or lesser extent by impregnation of the lumber with preservatives, polymers and the like. Such impregnation processes have been used for many decades and most frequently involves impregnation with treating fluids.

A relatively modern trend is to treat lumber in its dry final ready to use form. This eliminates any contaminated waste streams (saw dust, shavings and the like), which would otherwise occur during subsequent processing of lumber treated in crude form.

When treating lumber it is preferable to have the lumber already dry, that is, with its cells empty. This is because space is required for the incoming treating fluid.

Those versed in the art will know that when the cells are empty the wood is either at fibre saturation or lower and there is no remaining free water, only that which is bound to the cell wall. Any change in moisture content below fibre saturation can cause a change in dimension of the lumber, either shrinkage or swelling. This can pose problems during subsequent treatment because any significant re-introduction of moisture can cause swelling and may necessitate re-drying. Typically lumber is treated with either waterborne preservatives, or with solvent fluids based on non-polar organic solvents such as white spirits (LOSP processes). Both processes are similar in that variations of vacuum and pressure are used.

A deficiency of known waterborne processes is that substantial uptakes are required to achieve full penetration. This in part is due to rewetting of the cell wall and to absorption of water into or onto the cell wall. Thus to overcome this absorption and ensure full penetration, uptakes can vary from 150 litres per cubic metre to 600 litres per cubic metre depending on the process used. Current treatment methods with waterborne solutions cause swelling which is undesirable. Once treated, the lumber must be redried and this is costly. However waterborne processes do enable use of inexpensive well proven inorganic biocides.

LOSP processes using non-polar organic solvents overcome the swelling problem and have quite low uptakes of around 30 to 40 litres per cubic metre. This is because there is no significant interaction between the solvent and the cell wall. That is, the solvent is non- polar and does not interact with or adsorb onto cellulose or lignin, which are polar. Uptakes can be as low as 30 to 50 litres per cubic metre. Drying in the normal sense is not required although the solvent must be allowed to evaporate. Whilst this process is effective for treating dry lumber the cost of solvent is high and eventually all the solvent escapes into the atmosphere thus becoming an environmental issue. Further, the solvent is manufactured from petroleum feedstocks thus it is not a renewable resource and is subject to significant price variations. However in favour of LOSP is the option to recover and recycle the solvent.

A major deficiency of LOSP processes is that they must use non-polar solvent soluble biocide systems. These are typically very expensive including the likes of, for example, complex triazoles and synthetic pyrethroids and which require expensive solvents or formulating techniques. Also typically used are Tri Butyl Tin compounds which are environmental poisons.

Many processes are known for the impregnation of lumber. These processes are adequately described in "Industrial Timber Preservation", 1979, J G Wilkinson, Associated Business Press.

Several such processes include those of: 1) Rueping: Pre-pressure with gas followed by pressure with preservative or chemical solution; 2) Lowry: Pressure impregnation with preservative or chemical solution; and 3) Bethel: Vacuum followed by pressure impregnation with preservative or chemical solution.

The Rueping process applies pre-pressure with gas prior to treatment with preservative fluids. This pre-pressure with gas fills the cells with a compressible medium such that after treatment with fluid the gas will expand forcing out any surplus fluid. However this can result in ongoing kickback of preservative contaminated fluid which may be hazardous and which kickback fluid may contain extractives which will interfere with preservative chemistry.

The Rueping and Lowry processes retain gas within the void spaces within the substrate. Thus, the impregnation process requires pumps to force fluid into the substrate against the back pressure of the gases in the voids.

The Bethel process removes all gases from the cells by application of a vacuum which cells then become completely filled with preservative fluid. When using aqueous fluid this method has the disadvantage that lumber is completely filled which cannot be sucked out again. Accordingly, the lumber takes considerable time to dry.

Another process is that described in WO 2004/054765 which involves irradiation of the substrate causing bound water to turn into vapour thus creating voids in the cells.

LOSP preservatives use a solvent known as a Stoddard solvent, otherwise commonly known as aliphatic white spirits or mineral spirits. The modern versions of this are refined to remove aromatic compounds to improve odour and reduce toxicity. Moreover, impregnation processes used to apply LOSP formulations have been developed and refined to limit the amount of solvent transferred to the wood whilst ensuring substantial penetration. An example of this would be the "Double-Vacuum" process, wherein the wood is evacuated and then flooded with preservative, the vacuum is released to atmospheric pressure for a short time, then the preservative is transferred away from the wood and a second vacuum is applied to remove excess preservative.

Despite these improvements costs continue to escalate and because of environmental concerns there is a growing trend away from products using LOSP preservatives. However because re-drying of the substrate is not required there still exists a potential market, particularly if any residual solvent could be recovered and recycled. To maximise longevity of treated lumber it is important that it be treated throughout its volume. Generally this is taken as when full penetration has occurred and when the retention of preservative exceeds a known standard. In New Zealand for example, the standard under NZ 3640 requires full sapwood penetration and average cross section retention of 0.4% mass/mass boric acid equivalent on oven dry wood weight to achieve Hazard class H1.2 for house framing.

Those versed in the art will be aware that use of high pH compositions on lumber causes degradation of appearance. For example, previously high pH antisapstain formulations were promoted. Whilst these provided excellent performance, lumber appearance quickly degraded from a bright white appearance to a very dull grey aged look. This likely involved degradation of lignin in the wood substance and may have lead to longer term wood stability issues. This pH effect apparently occurred at pH exceeding around 9.2, the natural pH for aqueous borax solutions.

More recently purveyors have promoted "spray on" borate containing compositions. Whilst these can easily provide sufficient retention, issues have arisen regarding penetration throughout the sapwood.

Typically the composition used comprises borate salts, equivalent to disodium octaborate dissolved in a glycol such as ethylene glycol. Ethylene glycol is a known poison and with escalating oil prices is becoming more expensive.

Since it is desirable to minimise uptake of water to mitigate any swelling which might occur, mixtures of these compositions with water have been used. Thus it has been a compromise between cost due to the glycol solvent, and swelling due to the water.

Use of glycerol is not known in the marketplace likely because it has been an expensive compound. More recently the price of glycerol has reduced and that of the likes of ethylene glycol and propylene glycol have escalated in line with oil prices.

Since penetration by current compositions is limited a composition offering enhanced penetration would offer the user a valuable alternative.

US 3993752 teaches "a wood preservative composition comprising (1) alkali metal cyanide, (2) water, (3) alkali metal hydroxide, (4) alkali metal borate, (5) alkanol, (6) an organic solvent which can include a glycol, (7) a halogenated phenol, (8) a heavy metal salt or oxide". The art clearly teaches a composition of very high pH because the alkali metal hydroxide concentration exceeds that of the alkali metal borate. Whilst pH is not expressly stated it will exceed 11. Whilst this may be appropriate for a superficial application to wood, any substantive impregnation will severely degrade wood appearance and may also degrade the wood substance.

US 4076871 teaches "a method of impregnating lumber with boric acid or boron oxide, which comprises applying thereto a boric acid ester of an organic alcohol".

US 4400298 teaches "a wood preservative composition for controlling sapstain and superficial mould comprising as active ingredient an alkali metal borate and a dithiocarbamate". Examples stress that pH is between 10.1 and 10.8. Those learned in the art will be aware that such pH may be biocidally effective but it severely degrades the appearance of the wood.

US 4620990 teaches "a method of impregnating a wooden structure by diffusion of boric acid wherein solid rods of disodium octaborate are supplemented by an hygroscopic liquid which can be a glycol".

US 4911988 teaches "a shaped preservative element in the form of a rod or pellet which contains a solid organic boron ester".

US 4610881 and EP 0046380, which have the same inventor, teach the use of "a hygroscopic liquid carrier for application to a porous substrate such as timber wherein the composition contains at least 20% equivalent of boric oxide". No mention is made at any time in these documents regarding pH of the fluid. This art also teaches a significant stoichiometric excess of borate ion over glycol. The inventor understands this is to be primarily to reduce cost.

In New Zealand and Australia, for example, compositions based on ethylene glycol plus disodium octaborate, or the equivalent ratio of borax and boric acid, that are in accordance with US 4610881 are the only approved compositions containing ethylene glycol for treating wood products.

However, the glycol is derived from oil and is still very costly. Thus the composition is no longer commercially acceptable for all uses, particularly when the glycol content is lowered due to cost and the penetration diminishes. US 6508869 teaches "a composition comprising an amine oxide and a boron compound." This combination is designed to enhance penetration of boron compounds into lumber.

Those versed in the art will be aware that boric acid compounds including borates and octaborates form spiroboronate complexes with vicinal diols such as glycols and in an aqueous medium this substantially reduces pH. This is typified in analytical chemistry wherein mannitol is added to borate solutions thus allowing the borate to be titrated as a strong acid. Thus the spiroboronate compound is a strong acid, that is, upon addition of the vicinal glycol, the pH of the borate solution is substantially depressed.

Disodium octaborate is a relatively expensive compound as also is boric acid. Since boron is mined from the ground primarily as sodium borate (sodium tetraborate) it is the most economic compound to use.

Those versed in the art will be aware of the composition and structure of spiroboronates. An example is shown below (Spiroboronate Example 1). Borates can form partial spiroboronates and an example is also shown below (Spiroboronate Example 2).

Spiroboronate Example 1

Spiroboronate Example 2

Partial spiroboronates are highly polar due to the exposed ionic borate centre. Spiroboronates themselves, however, have a sheltered borate centre and are therefore less polar.

As those skilled in the art would know, glycerol is a natural renewable glycol with a triple alcohol functionality within the same molecule. This is an advantage over, for example, the oil based product ethylene glycol, which has only two alcohol groups as the additional functionality contributes to further interaction with borate groups. Additionally, the use of glycerol is less expensive than ethylene glycol.

OBJECT

It is an object of the present invention to provide a composition and method for delivery of a treatment composition to organic substrates, particularly lignocellulosic substrates, or at least to provide the public with a useful choice.

STATEMENT OF INVENTION

In a first broad aspect, the present invention provides an organic substrate treatment composition including: water; a glycol solvent; and a borate compound; wherein the pH of the composition is selected and controlled to maximise penetration of the borate compound into the substrate, and wherein the choice of glycol solvent determines the range of appropriate pH selection.

Preferably, the organic substrate is lignocellulosic.

Preferably, the lignocellulosic substrate is lumber.

Preferably, the glycol solvent is ethylene glycol, propylene glycol or glycerol.

More preferably, the glycol is glycerol.

Preferably, the glycol to borate ion ratio is in a controlled stoichiometric ratio to further assist penetration.

Preferably, the stoichiometric ratio of glycol to borate ion is between about 1.5 and about 2.5 to 1.

More preferably, the stoichiometric ratio of glycol to borate ion is between about 1.8 and about 2.2 to 1.

Most preferably, the stoichiometric ratio of glycol to borate ion is about 2 to 1.

Preferably, the organic substrate is substantially dry lumber that is at or below fibre saturation.

Preferably, if the glycol is ethylene glycol the pH of the composition is at least about 6.2.

Preferably, if the glycol is propylene glycol the pH of the composition is at least about 6.0.

Preferably, if the glycol is glycerol the pH of the composition is at least about 5.8.

Preferably, the pH of the composition is below about 8.8 and more preferably below about 7.8.

Preferably, the composition may include one or more biocides.

In a second aspect the invention provides an organic substrate treatment composition including: water; a glycol solvent; and a borate compound; wherein the pH of the composition is selected and controlled to maximise penetration of the borate compound into the substrate and wherein the choice of glycol solvent determines the range of appropriate pH selection, and the glycol to borate ion ratio is in a controlled stoichiometric ratio to further assist penetration.

Preferably, the organic substrate is lignocellulosic.

Preferably, the lignocellulosic substrate is lumber.

More preferably, the glycol is glycerol.

Preferably, the stoichiometric ratio of glycol to borate ion is between abouti .5 and about 2.5 to 1.

Preferably, the composition may include one or more biocides.

The invention also relates to a process for treating an organic substrate wherein the composition as described in the first or second aspect of the invention above is applied to the substrate by dipping, spraying or vacuum pressure impregnation and optionally includes use of the treatment process described in WO 2004/054765.

Preferably, the composition is applied to the substrate by dipping, deluging, spraying, or brushing. Additionally, variations of vacuum or positive pressure impregnation may be used.

Preferably, the composition is applied at between ambient temperature and 100 Celsius.

Preferably, the composition is applied at ambient temperature.

Preferably, the composition is applied to the substrate using vacuum pressure impregnation. Preferably, the composition is applied to the substrate using a single vacuum impregnation.

Preferably, the composition is applied to the substrate which is at or below fibre saturation.

Preferably, any swell imparted to the substrate is at least minimised by the glycohwater ratio.

In another aspect, the invention provides a method of preparing a composition for timber treatment, wherein the composition includes a borate compound, and wherein the method includes the use of a solvent system which includes a combination of a glycol and water, wherein the pH of the composition is selected and controlled to maximise penetration of the borate compound into the substrate, and wherein the choice of glycol solvent determines the range of appropriate pH selection.

Preferably, if the glycol is glycerol the pH of the composition is at least 5.8.

Preferably, the pH is below about 8.8 and more preferably below about 7.8.

In another aspect, the invention relates to a method of treating an organic substrate using an organic substrate treatment composition including water, a borate compound and a glycol, the composition having a pH as described above but less than 8.8, wherein the pH of the composition is selected and controlled to maximise penetration of the borate compound into the substrate, and wherein the choice of glycol solvent determines the range of appropriate pH selection, the composition being applied to the substrate by dipping, spraying or vacuum pressure impregnation and optionally includes the treatment process described in WO 2004/054765.

In another aspect, the invention relates to a method of treating an organic substrate using an organic substrate treatment composition including water, a borate compound and a glycol, the composition having a stoichiometric ratio of glycol to borate of between about 1.5 and about 2.5 to 1 , the composition being applied to the substrate by dipping, spraying or vacuum pressure impregnation and optionally includes the treatment process described in WO 2004/054765.

In another broad aspect, the invention provides an organic substrate to which a composition according to the present invention has been delivered, preferably in accordance with a method of the invention.

The invention may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, in any or all combinations of two or more of said parts, elements or features, and where specific integers are mentioned herein which have known equivalents in the art to which the invention relates, such known equivalents are deemed to be incorporated herein as if individually set forth.

DETAILED DESCRIPTION OF INVENTION

The following is a description of the preferred forms of the present invention given in general terms in relation to the application of the novel method. While the description focuses particularly on the delivery of compositions to lignocellulosic materials, such as lumber or logs, it should be appreciated that the method may be applicable to other organic substrates.

In general terms, the invention relates to compositions and methods of delivering compositions to an organic substrate, preferably a lignocellulosic substrate. The method allows for absorption or impregnation of the organic substrate by a treatment compound without the necessity of employing systems with only non-polar solvents.

The method of the invention may be used to deliver borate compositions to the substrate but could also include biocides in the compositions as well. Persons of general skill in the art to which the invention relates will no doubt appreciate various compositions that may be applicable to the invention. However, by way of example, where treatment or prevention of infection or pre-infection by pest organisms is desired, compositions (biocide compositions) having pesticidal (fungicidal, bactericidal, insecticidal for example) or preservative properties may be used. It may include compounds of use in waterproofing a substrate or providing fire retarding properties. A combination of treatment compounds (e.g. biocide and fire retardant) would provide clearly beneficial properties to the substrate. Additionally, the compositions may contain certain dyes which may be used to colour the substrate. Suitable biocides and polymeric/prepolymeric compounds would be known to the skilled person.

Whilst not wishing to be constrained, biocides could include; copper compounds, quaternary ammonium compounds, organo-iodine compounds, triazoles, metal chelates such as oxine copper, boron compounds, insecticides such as synthetic pyrethroids and the like, or mixtures of these. Fire retardants could include phosphorous compounds, guanidine compounds, melamine compounds, boron compounds or mixtures of these. In certain circumstances a biocide and/or fire retardant might be used wherein the composition comprises an added emulsifier or surfactant to prepare an emulsion in the solvent combination. When the resin or polymer is incompatible with the biocide or fire retardant as in the case of boron compounds in combination with phenol formaldehyde resins, one or other component might be micro-encapsulated and then combined with the other component.

As used herein, "organic substrate" should be taken to mean any organic material which may be in need of delivery of a composition of some nature; for example for the purposes of protection or treatment to prevent or ameliorate growth of pest organisms. Such substrate is preferably lignocellulosic, for example living trees, wood products, lumber or logs. The invention may be applicable to substrates containing a level of moisture, or those which are substantially dry, at or below fibre saturation.

Again, at least in the case of lignocellulosic substrates, those which are "substantially dry" include lumber dried by traditional methods. Such lumber may contain moisture of approximately 1 to approximately 30 per cent as a weight proportion of the lumber dry weight. Substantially dry lignocellulosic substrates include lumber which has been processed via kiln drying, RF vacuum drying and the like and may have been milled to a final, or near final product, and may include for example a lumber composite material.

"Pests" or "pest organisms", as referred to herein, may include any organisms which may infect an organic substrate, such as wood. While the invention is particularly applicable to fungi, pest organisms may also include insects and the like. The fungi and pests will be well known to people skilled in this art.

When used herein, the term "treatment" should be taken in its broadest possible context. It should not be taken to imply that a substrate is treated such that pest organisms are totally removed, although this is preferable. Prevention and amelioration of growth of pest organisms is also encompassed by the invention.

The words "comprise" or "comprises" should be taken to be synonymous with "includes" or "including" unless the context clearly indicates otherwise.

In one preferred embodiment, the method of the invention comprises at least the step of applying a composition to a surface of an organic substrate in which the composition includes a water plus a glycol solvent and a borate compound, wherein pH of the composition is selected and controlled to maximise penetration of the borate into the substrate, and wherein the choice of glycol solvent determines the range of appropriate pH selection. Preferably the pH is selected and controlled between about 5.8 and about 8.8 and more preferably between about 5.8 and about 7.8. The selection of pH within this range is dependent on the glycol solvent being used. In particular, the pH is at a pH greater than about 6.2 if the glycol is ethylene glycol, 6.0 if the glycol is propylene glycol, about 5.8 if the glycol is glycerol, and less than about 8.8 (preferably less than about 7.8).

The appropriate selection and control of pH, which is dependent on the glycol solvent, would be apparent to one of skill in the art once in possession of this invention.

The preferred glycol is one or more of ethylene glycol, propylene glycol or glycerol although other glycols could be used as would be known to a skilled person once in possession of this invention.

In a particularly preferred embodiment of the invention, the composition comprises a solvent mixture comprising water plus glycerol.

Preferably the borate compound can be included as: Boric acid plus alkali (sodium hydroxide or other) Disodium oct a borate plus alkali (sodium hydroxide or other) Sodium tetraborate; although others could also be used.

If a higher pH is preferred, all the above may be adjusted further by addition of an alkali such as sodium hydroxide however it is preferred this be minimised to mitigate cost. The pH used will be somewhat dependent on the glycol used in the composition. Selection and control of the pH of composition at desired levels can be achieved by any known means. Options such as appropriate alkalis, buffers or the like can be used. Thus glycol solutions of the above can be considered equivalent to boric acid solution in glycerol plus water wherein the pH has been adjusted upward using an alkali, typically sodium hydroxide.

It will be appreciated that the solvent composition will depend on the physicochemical properties of the glycol borate interaction or any other additive included. It is known that different glycols can reduce pH significantly and therefore the selection of pH is dependent on the glycol solvent. It will be appreciated that a balance will be required between the aims of the process; higher glycohwater ratios favour lower residual moisture in the substrate and are also more conducive to dissolution of organic borates. Higher water content in the solvent system reduces cost but reduces stability of the borate solution and may increase moisture content further than desired. Such matters are within the skill and knowledge of the skilled person once armed with the knowledge of the present invention. Once formed the treatment composition may take the form of an emulsion or micro-emulsion depending on the combination of components contained within the composition.

The composition may be applied to a surface of the substrate using any known means of bringing a composition into contact with a material. By way of example, the composition is applied by dipping, deluging, spraying, or brushing. While the inventors do not believe it necessary to apply active pressure to effect delivery of a composition in accordance with the invention, there may be instances where active pressure systems (positive pressure or vacuum) may be used to assist with delivery. Reference is made to the delivery system described in WO 2004/054765 in this regard by way of example.

While the operating temperature of the composition may vary depending on the nature of the borate and glycol, for example its solubility and the like, the composition is preferably applied at or around ambient temperature. Temperatures of up to 100⁰C could be used depending on the components of the composition. Higher temperatures are less preferred due to cost of energy.

As mentioned hereinbefore, the method of the present invention is applicable to substrates which are substantially dry (i.e. at or below fibre saturation). Preferably, the composition is applied to the substrate which is at or below fibre saturation. In addition, it is preferable, that any swell imparted to the substrate is at least minimised by the glycohwater ratio. In known art, compositions which are water soluble are typically applied as fully aqueous solutions which significantly rewet the substrate. Where this wetting occurs, the subsequent removal of this water is problematic. A novel feature of the present invention is that it provides the choice of treating the substrate, for the purpose of controlling or limiting rewetting of the substrate.

Whilst not wishing to be bound by any particular theory, the inventors believe that the invention may work through some reduction of borate substrate interactions immediately following application possibly due to a polarity change. For example, compositions of US 4610881 have a stoichiometric ratio of glycol to borate of 0.8:1. This results in the formation of partial spiroboronates, such as referred to in Background section of this specification, these have a stoichiometric ratio of glycol to ion borate around 1 :1. These have substantial polarity and, since the cell wall in wood is highly polar, these will also be impeded from rapid movement into the substrate.

The inventor hypothesises that controlling the stoichiometric ratio of the glycol to the borate ion will provide further assistance to the penetration of the compositions into the substrate. This is particularly so if the substrate is lignocellulosic (e.g. lumber). It is preferred that the glycol: borate ion ratio is controlled between about 1.5 and about 2.5:1 , more preferably between about 1.8 and about 2.2:1 and more preferably the compositions will have a stiochiometric ratio about 2:1. This will have lower interaction with the cell wall due steric hindrance that is the highly polar boronate centre of the molecule is surrounded by a hydrocarbon chain and is thus less polar. The glycohborate ratio may be controlled by, for example, mixing the correct mass ratios of glycol with borate such that the final mole ratio of glycol to borate is as desired (e.g. 2:1) and agitation until dissolution is complete. Water can also be present if needed. Use of the compositions having the stoichiometric ratio described above individually forms an inventive contribution to the art. The combination of selection and control of pH levels, as discussed earlier, and controlled glycol:borate stoichiometric ratios is a particularly preferred aspect of the present invention.

It may also work through partial saponification of resins in ray parenchyma due to higher pH than prior art thus allowing substantial radial penetration into the lumber. Upon radial movement the borate compound is then able to diffuse further into its immediate environment. EXAMPLES

The invention will now be further described with reference to the following non-limiting examples.

Using the principles described in the invention, the inventors set out to study whether the invention was applicable to penetration of borate biocides and to learn the impact of pH on the level of penetration.

Example 1

The following table illustrates the pH of compositions of borate plus glycol. This Example uses the compositions of EP 0046380. The compositions were prepared using 20% boron source and 30% glycol source (a ratio of 0.8:1) and the remainder made up with water, except for where the glycol was glycerol

In the Example using glycerol, the mol ratio was adjusted to 2:1 glycol equivalent to borate ion, whilst retaining the same amount of boron in the overall composition as was in the ethylene glycol and propylene glycol compositions. Thus, in all samples the "boric acid equivalent" was equal.

Table 1

Sample 5 has had the pH adjusted by addition of sodium hydroxide.

Thus it can be seen that when using the same glycol in samples 1 , 2, and 3, propylene glycol, the pH rises in accord with the increasing ratio of Na₂OiB₂O₃ but does not match the native pH of borate compound in water without glycol, which is 9.2. This applies also to samples 4, 5 and 6 with glycerol and 8, 9, and 10 with ethylene glycol. It can also be seen that varying the glycol from propylene glycol to glycerol in samples 3 and 6 demonstrates that glycerol more strongly complexes borate resulting in a lower pH.

Example 2

The above samples were then applied to a pinus radiata lumber substrate. The method comprises gluing polyethylene tubes vertically to a horizontal lumber face. Subsequently identical 1 millilitre aliquots of the above solutions were inserted into each tube.

The wood samples were 90 mm x 45 mm with grain approximately diagonal to any face. After 48 hours the fluid had migrated into the lumber. The tubes were removed and the lumber cut at the cross section central to where the tube had been glued. Each section was spot tested using curcumin reagent and upon completion of the reaction, penetration distance was measured.

Surprisingly those samples of higher pH showed substantially greater penetration of the borate compound.

The following Table, Table 2, lists penetration versus pH.

Table 2

Thus it can be seen that pH has a profound effect on penetration of spiroboronate compounds into lumber and that glycerol imparted a significant benefit. In fact 53 mm penetration if occurring on flat sawn lumber would penetrate completely through the sample. The effect of pH control for glycerol including solvent is thus surprisingly significant, even when compared to the clearly advantageous penetration for propylene glycol including solvent at a pH of at least 6.0 (and in this Example 7.0).

The above Examples demonstrate the correspondence between penetration of the wood and the pH of the composition. This is further demonstrated in the graph of Figure 1. This graph shows the penetration into the wood in mm with increasing pH of the samples listed in Table 2. This graph clearly demonstrates that as pH increases for both glycerol and propylene glycol composition penetration is enhanced.

Example 3

When treating nearly dry lumber with low uptakes, say between 18 and 40 litres per cubic metre, penetration using traditional borate/glycol compositions can be problematic. A lower penetration necessitates higher uptake to achieve the required treatment standard. This has the disadvantageous effect of rewetting the previously dry wood.

To determine whether the enhanced level of penetration achieved by the compositions of the present invention could translate into a high quality treatment process without unduly rewetting lumber, three treatment schedules were undertaken using sodium tetraborate in a glycerol water solvent. Solution pH was 6.0.

28 pieces of high temperature kiln dried pinus radiata were selected from a packet of 90 mm x 45 mm x 3.6 m. Each length was assigned an individual number from 1-28. The lengths were then cut into 4 pieces; each 900 mm long and arranged equally into 4 packets.

The samples in each packet were arranged 4 wide by 7 pieces high.

Each sample was then weighed, moistures taken and dimensions noted. Each packet treated using the schedules given below with a solution containing approximately 9% Boric Acid Equivalent and from the weights taken following treatment the uptakes determined. Each sample spot tested for percentage heartwood in the cross section and Boron spot tested for evidence of compliance to the NZS3640:H1.2/Amendment 3 (similar to standards such as the Australian standard AS 1604). Schedule A

Vacuum -30Kpa for 2 minutes

Flooding with no vacuum held

Soak at atmospheric pressure for 2 minutes

Vacuum -45Kpa for 10 minutes

Results

The uptake in this Example is higher than that of Example 4 (below) due to the initial vacuum being at a lower pressure and for a greater period of time.

Example 4

Example 3 was repeated but using the following schedule;

Schedule B

Vacuum -20Kpa for 1 minute Flooding with no vacuum held Soak at atmosphere for 2 minutes Vacuum -90Kpa for 10 minutes

Results

Example 4b

In order to compare the level of treatment quality of Example 4 with prior art, similar treatments were undertaken using a disodium octaborate and ethylene glycol composition as described in US 4610881 and EP 0046380, and Schedule B above was applied. It was found that to achieve full penetration an uptake of 33 litres per cubic metre was required. This uptake, of 33 litres/m³ compared to 18.9 litres/m³, demonstrates the enhanced penetration of the compositions of the invention over the prior art.

Example 5

Example 3 was repeated but using the following schedule;

Schedule C

Vacuum -25Kpa for 2 minutes Flooding with vacuum held Soak at atmosphere for 2 minutes Vacuum -70Kpa for 10 minutes

Results

The Examples demonstrate that pH has a significant impact on penetration of borate glycol systems into lumber.

The treatment schedules used have very low uptake for a polar solvent system containing water and as a consequence the lumber can be treated to a high standard of retention and penetration and yet remain within the residual moisture content requirement of less than 20 per cent.

Example 6

This Example repeated Example 2, however the compositions were altered to allow a comparison of the effect on penetration of addition of trialkylamine oxide of US 6508869 to a composition of this invention, with the effect on penetration of addition of trialkylamine oxide of US 6508869 to a composition of US 4810881. US 6508869 claims to enhance the penetration of boron compounds into lumber.

No enhancement of penetration was achieved; in fact there was a reduction in lateral diffusion of borate through the wood substrate. Figure 2 illustrates the method wherein 1 mL aliquots of a borate solution are installed in individual chimneys and allowed to diffuse into the wood over a 36 hour period. The drawing of Figure 2a shows the chimneys standing on the wood test specimen. Figure 2b shows the distribution of boron within the centre of the test piece after treatment and spot testing using curcumin reagent. Sample 1 is a composition comprising disodium octaborate and ethylene glycol in accordance with US 4810881. Sample 1 has the least penetration. Sample 2 is a composition comprising disodium octaborate and ethylene glycol in accordance with US 4810881 and trialkylamine oxide of US 6508869. The penetration of disodium octaborate and ethylene glycol in accordance with US 4810881 does appear to have been enhanced slightly by the addition of trialkylamine oxide of US 6508869. Sample 3 is a composition of the present invention with a stoichiometric ratio of glycol:borate of 2:1 and a pH of 6. As can be seen the penetration of sample 3 is significantly greater than that of samples 1 and 2. The penetration of sample 4, which is a composition of sample 3 but with trialkylamine oxide of US 6508869 added to it, is not noticeably different to that of sample 3. It was surprisingly found that lateral movement was somewhat diminished by the addition of amine oxides to compositions of this invention.

Example 7

A comparison of the penetration of the wood by the composition of the invention relative to the prior art is shown in the picture of Figure 3. In particular, the relative penetration of spiroboronates of differing stoichiometric ratio was assessed. A test rig was assembled comprising small plastic chimneys glued to the radial face of flat sawn kiln dried pinus radiata lumber of cross section 90 mm by 45 mm as in Example 6 above. 2 millilitres of a glycerol: spiroboronate composition with a stoichiometric ratio of 2:1 and a pH of 6.0 according to the present invention was placed in one chimney, in another was placed a composition of US 4610881 with a stoichiometric ratio of mols of ethylene glycol to mols of borate of 0.8:1. The rig was left to stand for 36 hours. Subsequently a section was cut through and the cut face spot tested with curcumin reagent. It could be seen that product of US 4610881 had penetrated around 15 mm whereas the product of this invention with stoichiometric ratio of 2:1 had penetrated completely to the opposite face of the lumber; 45 mm. Figure 3a) shows the penetration of borax plus glycerol at pH 6.0 according to the present invention and Figure 3b) shows the penetration of disodium octaborate plus ethylene glycol according to US 4610881. As can be seen, full penetration has occurred with the product of this invention. The penetration of the prior art relative to this invention has been approximately halved. There was also evidence of complete penetration through ray parenchyma to the opposite untreated face (45mm). Example 8

Samples of kiln dried pinus radiata of cross section 90 mm by 45 mm were carefully end sealed and then treated with a composition of glycerol plus borax at a stoichiometric ratio of 2:1 using the following schedules

In every case complete penetration and distribution of the biocide throughout the cross section was demonstrated using curcumin spray reagent. This demonstrates very effective penetration and is at variance with currently available art.

Even more surprisingly this high level of penetration was achieved with very low uptake (30 litres per cubic metre or less) and resulted in minimal increase in moisture content to otherwise kiln dried lumber. Further, the minor increase in moisture content that did occur was rapidly lost by evaporation to the original level.

Thus it can be seen that compositions of this invention can readily treat lumber without use of high uptakes and wherein penetration is achieved without adversely affecting swelling, that is where traditional aqueous compositions require around 150 litres per cubic metre uptake, compositions of this invention are able to meet the standard at 18 to 40 litres per cubic metre with minimal swelling. The benefits of this process and composition are that treatment can be achieved very rapidly, for example in less than 15 minutes, compared to other processes taking perhaps 30 minutes or more. This entire process can be undertaken in the same treatment vessel thus reducing additional handling costs.

Thus it can be seen that the inventors have discovered a biocide solvent system including combinations which achieve economical and complete treatment of substrates and yet enables the user to process lumber rapidly without undue increase in moisture content or swelling. The key benefits over either other waterborne systems or fully non-polar systems, is a reduction in cost without the concerns for significant rewetting of the substrate.

Where, in the foregoing description, reference has been made to components have known equivalents, then such equivalents are incorporated herein as if individually set forth.

Reference to prior art documents and disclosures does not constitute an admission that these are necessarily common general knowledge in any particular jurisdiction.

Although the invention has been described by way of example with reference to a preferred embodiment, modifications and variations may be made to the invention without departing from the scope or spirit of the invention as defined in the attached claims.

Claims

WHAT WE CLAIM IS

1. An organic substrate treatment composition including: water; a glycol solvent; and a borate compound; wherein the pH of the composition is selected and controlled to maximise penetration of the borate compound into the substrate, and wherein the choice of glycol solvent determines the range of appropriate pH selection.

2. An organic substrate treatment composition according to claim 1 wherein the organic substrate is lignocellulosic.

3. An organic substrate treatment composition according to claim 2 wherein the lignocellulosic substrate is lumber.

4. An organic substrate treatment composition according to any one of the preceding claims wherein the glycol solvent is ethylene glycol, propylene glycol or glycerol.

5. An organic substrate treatment composition according to claim 4 wherein the glycol is glycerol.

6. An organic substrate treatment composition according to any one of the preceding claims wherein the glycol to borate ion ratio is in a controlled stoichiometric ratio to further assist penetration.

7. An organic substrate treatment composition according to any one of the preceding claims wherein the stoichiometric ratio of glycol to borate ion is between about 1.5 and about 2.5 to 1.

8. An organic substrate treatment composition according to any one of the preceding claims wherein the stoichiometric ratio of glycol to borate ion is between about 1.8 and about 2.2 to 1.

9. An organic substrate treatment composition according to any one of the preceding claims wherein the stoichiometric ratio of glycol to borate ion is about 2 to 1.

10. An organic substrate treatment composition according to any one of the preceding claims wherein the organic substrate is substantially dry lumber that is at or below fibre saturation.

11. An organic substrate treatment composition according to any one of claims 1 to 4 or 6 to 10 wherein if the glycol is ethylene glycol the pH of the composition is at least about 6.2.

12. An organic substrate treatment composition according to any one of claims 1 to 4 or 6 to 10 wherein if the glycol is propylene glycol the pH of the composition is at least about 6.0.

13. An organic substrate treatment composition according to any one of claims 1 to 10 wherein if the glycol is glycerol the pH of the composition is at least about 5.8.

14. An organic substrate treatment composition according to any one of the preceding claims wherein the pH of the composition is below about 8.8.

15. An organic substrate treatment composition according to any one of the preceding claims wherein the pH of the composition is below about 7.8.

16. An organic substrate treatment composition according to any one of the preceding claims wherein the composition may include one or more biocides.

17. An organic substrate treatment composition including: water; a glycol solvent; and a borate compound; wherein the pH of the composition is selected and controlled to maximise penetration of the borate compound into the substrate, and wherein the choice of glycol solvent determines the range of appropriate pH selection, and the glycol to borate ion ratio is in a controlled stoichiometric ratio to further assist penetration.

18. An organic substrate treatment composition according to claim 17 wherein the organic substrate is lignocellulosic.

19. An organic substrate treatment composition according to claim 18 wherein the lignocellulosic substrate is lumber.

20. An organic substrate treatment composition according to any one of claims 17 to 19 wherein the glycol solvent is ethylene glycol, propylene glycol or glycerol.

21. An organic substrate treatment composition according to any one of claims 17 to 20 wherein the glycol is glycerol.

22. An organic substrate treatment composition according to any one of claims 17 to 21 wherein the stoichiometric ratio of glycol to borate ion is between about 1.5 and about 2.5 to 1.

23. An organic substrate treatment composition according to any one of claims 17 to 22 wherein the stoichiometric ratio of glycol to borate ion is between about 1.8 and about 2.2 to 1.

24. An organic substrate treatment composition according to any one of claims 17 to 23 wherein the stoichiometric ratio of glycol to borate ion is about 2 to 1.

25. An organic substrate treatment composition according to any one of claims 17 to 24 wherein the organic substrate is substantially dry lumber that is at or below fibre saturation.

26. An organic substrate treatment composition according to any one of claims 17 to 20 or 22 to 25 wherein if the glycol is ethylene glycol the phi of the composition is at least about 6.2.

27. An organic substrate treatment composition according to any one of claims 17 to 20 or 22 to 25 wherein if the glycol is propylene glycol the pH of the composition is at least about 6.0.

28. An organic substrate treatment composition according to any one of claims 17 to 25 wherein if the glycol is glycerol the pH of the composition is at least about 5.8.

29. An organic substrate treatment composition according to any one of claims 17 to 28 wherein the pH of the composition is below about 8.8.

30. An organic substrate treatment composition according to any one of claims 17 to 29 wherein the pH of the composition is below about 7.8.

31. An organic substrate treatment composition according to any one of claims 17 to 30 wherein the composition may include one or more biocides.

32. A process for treating an organic substrate comprising the step of applying the composition of any one of the preceding claims to the organic substrate.

33. A process according to claim 32 wherein the composition is applied to the substrate by dipping, deluging, spraying, or brushing.

34. A process according to claim 32 or claim 33 wherein the process includes use of the treatment process described in WO 2004/054765.

35. A process according to any one of claims 32 to 34 wherein the composition is applied at between ambient temperature and 100 Celsius.

36. A process according to any one of claims 32 to 34 wherein the composition is applied at ambient temperature.

37. A process according to any one of claims 32 to 36 wherein the composition is applied to the substrate using vacuum pressure impregnation.

38. A process according to any one of claims 32 to 36 wherein the composition is applied to the substrate using a single vacuum impregnation.

39. A process according to any one of claims 32 to 38 wherein the composition is applied to the substrate which is at or below fibre saturation.

40. A process according to any one of claims 32 to 39 wherein any swell imparted to the substrate is at least minimised by the glycol:water ratio.

41. A method of preparing a composition for timber treatment, wherein the composition includes a borate compound, and wherein the method includes the use of a solvent system which includes a combination of a glycol and water, and wherein the pH of the composition is selected and controlled to maximise penetration of the borate compound into the substrate, and wherein the choice of glycol solvent determines the range of appropriate selection.

42. A method according to claim 41 wherein if the glycol is ethylene glycol the pH of the composition is at least about 6.2.

43. A method according to claim 41 wherein if the glycol is propylene glycol the pH of the composition is at least about 6.0.

44. A method according to claim 41 wherein if the glycol is glycerol the pH of the composition is at least about 5.8.

45. A method according to any one of claims 41 to 44 wherein the pH is below about 8.8.

46. A method according to any one of claims 41 to 45 wherein the pH is below about 7.8.

47. A method of treating an organic substrate using an organic substrate treatment composition including water, a borate compound and a glycol, wherein the pH of the composition is selected and controlled to maximise penetration of the borate compound into the substrate, and wherein the choice of glycol solvent determines the range of appropriate pH selection, wherein:

^■ if the glycol is ethylene glycol the pH of the composition is at least about 6.2;

^■ if the glycol is propylene glycol the pH of the composition is at least about 6.0; and

^■ if the glycol is glycerol the pH of the composition is at least about 5.8; and wherein the pH is below about 8.8, the composition being applied to the substrate by dipping, spraying or vacuum pressure impregnation and optionally includes the treatment process described in WO 2004/054765.

48. A method according to claim 47 wherein the pH of the composition is below about 7.8.

49. A method of treating an organic substrate using an organic substrate treatment composition including water, a borate compound and a glycol, the composition having a stoichiometric ratio of glycol to borate of between about 1.5 and about 2.5 to 1 , the composition being applied to the substrate by dipping, spraying or vacuum pressure impregnation and optionally includes the treatment process described in WO 2004/054765.

50. An organic substrate when treated according to the method of any one of claims 47 to 49.

51. An organic substrate when treated with an organic substrate treatment composition of any one of claims 1 to 31.

52. An organic substrate according to claim 50 or claim 51 wherein the organic substrate is lignocellulosic.

53. An organic substrate composition substantially as herein described with particular reference to any one of the Examples excluding prior art and comparative Examples.

54. A method of treating an organic substrate substantially as herein described with particular reference to any one of the Examples excluding prior art and comparative Examples.