WO2011144729A2

WO2011144729A2 - Preservative composition

Info

Publication number: WO2011144729A2
Application number: PCT/EP2011/058241
Authority: WO
Inventors: Risto Rahkola
Original assignee: Kemira Oyj
Priority date: 2010-05-21
Filing date: 2011-05-20
Publication date: 2011-11-24
Also published as: WO2011144729A3; CL2012002364A1; BR112012029235A2; FI20105562A; AU2011254537B2; FI20105562A0; AU2011254537A1

Abstract

The present invention provides a preservative composition for treating materials, said composition containing rosin dissolved in a mixture of alkyl borate and alcohol. The present invention also provides a method for treating materials, such as wood or non-wooden porous material, such as concrete.

Description

Preservative composition Field of the invention

The present invention relates to a preservative composition. More specifically the present invention relates to a preservative composition containing rosin dissolved in a mixture of alkyl borate and alcohol. The preservative composition may be used for treating wood and other porous materials.

Background of the invention

In the past pentachlorophenol (PCP) or chromated copper arsenate (CCA) were superior wood preservatives, but environmental and health concern have been changing legislation to ban any chlorophenols or arsenic compounds in this application. CCA was banned by the European Union in 2006. Creosote is remembered from railway sleepers and transmission poles but also from polluted treatment sites. Its use is heavily controlled by authorities.

Still, current preservatives contain heavy metals and other toxic materials, which are harmful to environment. For example, US EPA represents copper as priority pollutant, which at concentration over 3.1 micrograms/liter is not considered safe for marine life.

Borates are considered acceptable wood preservatives from a human health and ecological perspective because of very low toxicity to both mammalian and aquatic organisms. Borates are effective preservatives against both fungi and insects and even considered more effective than copper or zinc compounds.

Borates are inexpensive, colorless, odorless and non-corrosive. Unfortunately borate solubility reduces its use in outdoor applications, since high moisture will dissolve boron from wood. There are small differences in classification of wood in different countries when treated with preservative. Below are listed EU requirements according to EN 335: (according to Ullmann's Encylopedia of Industrial Chemistry, Wiley-VHC).

Use Class 1 - above ground, covered (dry)

Use Class 2 - above ground, covered (risk of wetting)

Use Class 3 - above ground, not covered

Use Class 4 - in contact with ground or fresh water

Use Class 5 - in salt water In principle boric acid or borate is suitable to be used in class 1 , when wood is in dry atmosphere without risk of wetting. If boron would be fixed properly in the wood the treated wood would be applicable in any class.

Boron in wood is typically expressed as boric acid equivalent (BAE) and it represents all boron compounds in wood preservation including borates, polybo- rates etc. In numerous researches the effective level of BAE is typically between 0.2-1 .0 BAE % (wt/wt) depending on the wood material, boron preservative and wood attacking organism.

According to New Zealand standard NZS 3640, treatment level of 0.8% BAE (wt/wt) meets the hazard class 3.1 (exposed to the weather, above ground), if sufficient protective surface treatment has been done.

When considering wood preservation in industrial scale traditional treatment methods have been the Bethell, Lowry and Rueping processes.

The Bethell process starts with initial vacuum to draw air from wood cells. During the vacuum the cylinder is flooded with preservative. After that follows -15 bar pressure from 15 minutes to several hours before preservative solution is drained off. The final step is a vacuum to draw excessive preservative out of the wood.

The Lowry process is similar to the Bethell process but without the initial vacuum step. The Rueping process uses initial pressure during flooding of the cylinder and otherwise it resembles the Bethell process. This treatment method is used for creosote oils to limit net uptake compared to other processes.

There are also modifications of the above processes and special treatments exist for example oscillating pressure, vacuum and diffusion methods. Robinson et al. (US2007/087213) describes a method where wood is treated with inorganic borate preservative and also with a rosin component. One step treatment is based on water soluble rosin salt and its effect on boron fixing is questionable. Secondly, the proposed two step treatment requires large volumes of aqueous boron solution as well as solvent, for example toluene. Treatment effec- tiveness is probably based on water repellence, not fixing boron. This method is hardly competitive with present high throughput preservative systems. Similar two step impregnation by boric acid and tall oil derivatives were examined by Temiz et al. in Journal of Bioresource Technology vol 99 (2008) pages 2102-2106.

TrialkyI borate has been known as wood preservative for over 50 years (NZ1 15464). Its reactivity with hydroxyl compounds can be used as advantage since organic boron will form mainly boric acid with wood moisture and polybo- rates with some wood compounds. TrialkyI borate is easily impregnated in wood structure as gas or liquid. Several modifications of the basic process have been disclosed: Vinden et al. (US2009/01 10842), Staminoroff (US2009/0069271 ), Na- sheri (US5871817), Yasuhisa et al. (JP07-047515), Murphy et al. (US5330847), Vinden et al. (US5024861 ), Akio et al. (JP03-021401 ), Schroeder et al. (US4354316) and Martin (US3342629). All the documents referred to herein are incorporated by reference. This method is limited to certain above ground applications under cover since boric acid solubility in water is not solved in these applications. The wood is typically dried in kiln to reduce moisture content before impreg- nation. The treated wood is then conditioned by steam to avoid cracks.

Borate based materials may also be used for the treatment of non-wood materials, as described for example in US2005/0196628 A1 . In said publication man-made structures made with non-wood materials are protected from termite damages.

It is also known that boric acid - alcohol diffusion ability is much less than of reac- tive trialkyi borate (US5871817) and the required high pressure or long treatment time may result in severe swelling of the wood.

Rosin can be dissolved in trialkyi borate, namely in trimethyl borate, since it is not soluble in higher molecular weight trialkyi borates. Unfortunately maximum solubility of rosin in trimethyl borate is only -13 g / 100g and this concentration is most likely not enough to prevent boron leaching from wood.

There is still need for a non-leachable boron preservative which is competitive with present technologies and which could be used in moist applications. It would significantly reduce the environmental risks of traditional preservatives making it an appealing alternative in the wood preserving industry. Wood preservative or treated wood should meet several requirements (Suolahti, Osmo: Laho ja sen torjunta. Porvoo, Helsinki WSOY (1961 ), pages 75-76): effective against wood destroying organisms and insects; harmless for mammals, vertebrates and cultivated plant; easily and fast impregnated into the core of wood; non-toxic, non-flammable for wood handlers; effective in service for years or even decades; non-corrosive for metals which are in contact with wood or which are used in impregnation; not deteriorating mechanical properties of wood; not affecting ignition properties and in case of fire it should not release toxic gases; odorless, colorless, non-staining; not preventing painting or other post treatment; easily analyzed at least qualitatively; relatively cheap and available for large scale; non toxic waste after use; easily reclaimed for example as energy.

It is likely that there is no wood preservative that meet all the requirements. But interestingly many of them are met by present invention and there are means to affect to the rest of them. It is an aim of the invention to provide a composition for treating several materials that is safe (not harmful); is absorbed by or penetrates well all different kinds of porous materials, such as wood materials, but remains in the wood substantially without leaching out; preserves the materials both against mould and fungi, such as wood-rotting fungi and blue stain fungi; can be used against damage caused by insects, such as borers and termites; protects the wood from dimensional changes and cracking; and is not harmful for the structure of the materials after the treatment, even in long-term use. When considering wooden materials the aim is also to improve the performance of the wood in demanding environment, such as protection against for example decay, insects and fire. Summary of the invention

This invention relates to a preservative composition solution, where alkyl borate acts as precursor for boric acid based preservative and rosin is functioning as preservative and fixing agent for boric acid. It has been surprisingly discovered that rosin, for example tall oil rosin, has very high solubility in alkyl borate azeotrope or other alcohol composition at room temperature and the thus formed solution has unique properties, for example as a wood preservative.

The present invention provides a preservative composition for treating materials, said composition containing rosin dissolved and/or emulsified in a mixture of alkyl borate and alcohol. The present invention also provides a method for treating materials by bringing the material into contact with the preservative composition of the invention. One advantage of the present invention is that the composition penetrates easily into different materials and further remains in the material. In addition to fixing agent, rosin is also a well known fungicide.

Another advantage of the present invention is that such a preservative composi- tion is environmentally beneficial. Firstly, boric acid as preservative is considered safe for mammals and when fixed in wood it is harmless for the environment.

Secondly, the preservative can be produced totally without heavy metals or petrochemicals. Rosin is a known product of natural origin. Even if bio-based methanol was not available it can be totally recycled back to trialkyl borate production. Still another advantage of the present invention is the low energy consumption since it is not necessary to dry the wood below outdoor equilibrium moisture content, which is between 10-20% for wood in Nordic countries. In addition to this, conditioning to ambient atmosphere is enough and no additional steaming or wetting is needed for treated wood. Still another advantage of the present invention is that the composition may be cooled or let be cooled to any temperature, which is advantageous in storage and transportation.

Brief description of the drawings

Figure 1 shows rosin solubility in trimethyl borate - methanol Figure 2 shows rosin solubility in triethyl borate - ethanol Figure 3 shows rosin solubility in triisopropyl - isopropanol Detailed description of the invention

The present invention provides a preservative composition for treating materials, said preservative composition containing rosin dissolved in a mixture of alkyl bo- rate and alcohol. In another embodiment the rosin is emulsified in the mixture of alkyl borate and alcohol. The composition may also contain both dissolved and emulsified rosin. The present invention also provides methods for preparing said preservative compositions as described herein.

"Alkyl" as used herein refers to any suitable mono-, di-, tri-, tetra- or polysubsti- tuted alkylic compound. Examples of alkyls are disclosed in US2009/01 1842 para- graph [0063]. In one embodiment the alkyl borate is trialkyi borate. Generally the composition is in the form of a solution.

Surprisingly it has been found that rosin, such as tall oil rosin, dissolves in alkyl borate and alcohol solution in a very high percentage, much more than in alkyl borate or in alcohol alone (Figures 1 -3). As a preservative composition it penetrates very fast into materials, such as wood, even without pressure. Alkyl borate acts as precursor for boron preservative and soluble rosin is a fixing agent when alcohol is evaporated off.

Thus the major advantage of the present invention is that the composition contain- ing alkyl borate and rosin penetrates easily into different materials and further remains in the material. As an example trialkyi borate reacts with moisture in wood and solidifies as boric acid, at the same time rosin is no longer soluble and it becomes solid as well. Rosin contains high amount of abietic type of acids and its melting point is over 1 50^QC. After the treatment the wood will have water repellent properties and boric acid is fixed against dissolution.

Some non-limiting examples of useful alkyl borates include trimethyl borate, trie- thyl borate, triisopropyl borate, diglyceryl borate and mixtures thereof.

The alcohol may be selected for example from water soluble C-I-C-I_O alcohols as for example monovalent alcohols, such as methanol, ethanol, propanol, butanol, pentanol, hexanol and derivatives thereof; multivalent, such as divalent or trivalent alcohols. In some embodiments the alcohol is a water soluble C₂-C₇ alcohol. In other embodiments the alcohol is multivalent, aliphatic, water soluble C₂-C₅ alcohol, such as diole and triole. In still other embodiments the alcohol is glycerol, ethylene glycol or propylene glycol. Also a mixture of said alcohols may be used. In some preferred embodiments the alcohol is selected from methanol, ethanol, isopropanol, glycerol and mixtures thereof.

In one embodiment the rosin is dissolved or emulsified in a mixture of diglyceryl borate and glycerol. In such emulsification process heat may be used to promote the forming of the emulsion. Also another alcohol, such as ethanol, may be further added. When glycerol is used, the solvent may be methanol-free which is less toxic and the preparation of the composition is easier. The poor solubility of rosin to glycerol may be overcome by rising the temperature over the melting point of rosin (for example to 1 00-1 20^QC) to obtain a useful emulsion (for example creosote impregnation is carried out at this temperature). In another embodiment the rosin is dissolved or emulsified in a mixture of diglyceryl borate and ethanol. In still another embodiment the rosin is dissolved or emulsified in a mixture of diglyceryl borate, glycerol and ethanol.

In another embodiment the rosin is dissolved or emulsified in a mixture of trimethyl borate and methanol. In still another embodiment the rosin is dissolved or emulsified in a mixture of triethyl borate and ethanol. In still another embodiment the rosin is dissolved or emulsified in a mixture of triisopropyl borate and isopropanol.

In one embodiment the alkyl borate is in the form of azeotrope with an alcohol. Alkyl borate - alcohol azeotrope is produced when boric acid and alcohol react in a reaction column. Azeotrope is distilled as overflow and side product water is withdrawn from column bottom.

In one embodiment the rosin is dissolved or emulsified in an azeotrope of trimethyl borate in methanol. In one embodiment the rosin is dissolved or emulsified in an azeotrope of triethyl borate in ethanol. In one embodiment the rosin is dissolved or emulsified in an azeotrope of triisopropyl borate in isopropanol.

Trimethyl borate azeotrope contains approximately 70% trimethyl borate in methanol, triethyl borate azeotrope approximately 30% triethyl borate in ethanol and triisopropyl borate azeotrope approximately 5% triisopropyl borate in isopropanol. One advantage of the azeotrope solution is that it is less expensive than pure alkyl borate as boric acid equivalent. In case of high moisture in wood, alkyl borate will react to form solid boric acid just at the surface and prevent diffusion across the material. Such a situation will be avoided by azeotrope where alcohol acts as vehicle into deeper parts of wood (see US2009/01 10842 paragraph [0005]). Alkyl borate azeotrope is an electricity conductive solution, but alkyl borate is an insulat- ing liquid. In pure form alkyl borate easily creates electrostatic discharges during pumping or transferring, which poses a safety risk.

Rosin is a solid form of resin obtained from pines and some other plants, mostly conifers, produced by heating fresh liquid resin to vaporize the volatile liquid ter- pene components. In the embodiments of the present invention the rosin is se- lected e.g. from wood rosin, gum rosin, tall oil rosin or mixtures thereof.

Tall oil rosin is considered as a low cost side product from the distillation of crude tall oil (CTO). Crude tall oil is a by-product obtained from the kraft paper making process. Normal delivery form is hot molten, but in this application tall oil rosin can be used as solid. Alternative rosin is obtained from aged pine stumps which are chipped and soaked in a solvent; this extracted form of rosin is called wood rosin. Yet applicable rosin in a preservative is gum rosin obtained from living trees.

It is known that tall oil derivatives are effective preservatives against decay especially with high loading in wood. In the invention boron concentration may be less with rosin additive than would be in bare boron-based preservative to reach required preservative properties.

In this context, the term wood refers to all materials and products containing ligno- cellulosic material, including raw timber, sawn timber, wooden construction materials and elements and wood-plastic composite products, and further, various processed wood products such as round logs, all sawn timber such as boards, planks, laths, flat elements such as laminates, for example chipboard, plywood or LVL products (Laminated Veneer Lumber), panels, slabs, wall elements and the like, furniture for indoors and outdoors, and other wooden articles and objects. The wood product to be treated may also be present in immobile structures, particularly outdoors, such as wooden buildings, fences, framings, pillars, bridges, piers etc.

The composition is suitable for the treatment of both processed timber and raw timber, and the treatment can be given for example at wood storage sites or in a separate processing mill for timber, wherein the treatment composition and the wood can be brought into contact in a variety of ways. Similarly, the invention is suitable for the preservation of stationary structures already erected, particularly outdoors, wherein primarily spraying and brushing of the surfaces can be used. It should be noted that thanks to the safety of the composition, it can be used for the treatment of erected wooden structures in their locations of use without particular safety measures. The composition is also suitable for products consisting not only of wood but of a combination of wood and another material. The composition may also be used to other non-wooden porous materials, such as concrete, tiles and cotton batting. The embodiments explained herein with wood treatment applications may also be applied to these materials as well. Prior to the treatment of the material, the treatment composition may be diluted with alcohol to give the concentration required by the treatment.

The present invention provides a method for treating materials by bringing the material into contact with the preservative composition of the invention to protect the material and to obtain preserved material, such as wood. Any suitable method may be used to promote the composition to enter the material. The composition may be in the form of a solution or an emulsion.

The composition may be contacted to the material to be treated and absorbed over the whole thickness thereof, or to a certain depth from the surface, for exam- pie by impregnation, immersion, spraying, or by application with a brush (painting). Physical properties of the composition such as viscosity may be adjusted according to the type and purpose of the treatment. In case of some emulsions the composition may be as a (solid) suspension when stored (in room temperature) and it will be entered to the material in a melted form. The composition suits particularly well for treatment processes requiring good penetrability into material such as wood, for example impregnation. The composition can be entered into the wood, for example, in the known pressure impregnation process, in which the wood is at first kept under negative pressure to remove water from its inside, after which the composition is brought into contact with the wood and its penetration into the wood is enhanced by overpressure.

The composition of the invention may be heated and/or elevated temperature may be used in the process, thus further improving the absorption. Absorption is also improved by sub- and superatmospheric pressures as is known for conventional CCA impregnation. Contrary to heating the composition may be cooled or let be cooled to any temperature. Testing of the composition at -20^QC affected turbidity and thickness, but it still remained pumpable. Heating the turbid liquid to room temperature made it a clear solution again. This is a real benefit in transportation or storage e.g. in Nordic countries at winter time. Common waterborne preservatives do not tolerate freez- ing.

The invention makes it possible to treat materials in a light and cost-efficient way, and the treatment can be easily included in other present-day steps of wood treatment. The process may be one step in a processing line of timber or wooden objects comprising successive steps. In the following, practical examples will be given of methods how the treatment composition can be used for the treatment of wood and how the treatment can be integrated in a wood material processing line in mills for wood processing. Any other porous materials other than wood can be applied as well. 1 ) Pressure impregnation

A conventional method for entering great amounts of impregnation substance in wood, and thereby providing the most effective treatment by means of different steps (negative pressure and overpressure, elevated temperature). By this me- thod, the best penetrability of compositions is obtained, and the wood can normally be impregnated to the core. The composition according to the invention has a very good penetrability, wherein it is possible to reduce the negative pressures/overpressures used in conventional CCA impregnation and thereby to improve the cost-effectiveness of the process. Also, a tighter-grained type of wood, such as spruce, can be pressure impregnated with the composition according to the invention, which has not been possible with conventionally used substances.

2) Immersion impregnation

The penetrability of the composition according to the invention is good, and in some cases, mere immersion impregnation is also possible. This method is simple but it requires separate immersion basins and is carried out in batch processes, like the pressure impregnation.

3) Spraying

The composition according to the invention can be sprayed onto the surface of wood, for example, in connection with the planing of sawn timber. In this way, pre- servation against microorganisms can be achieved during storage and delivery before a surface treatment (painting etc.) later on.

4) Painting or other surface treatment line

The composition according to the invention may also be added into the wood in connection with a painting or another surface treatment line. From a paint dosing tank, a wooden board can be impregnated with the solution under overpressure or negative pressure through a separate painting unit. Depending on the pressure and the speed of the line, relatively good penetrability and thereby a reasonable resistance to weather and fire can be achieved by this method.

5) Drying of the wood and the control of final moisture content In the processing of timber in sawmills, it is more and more important that the final moisture content of the wood is suitable to prevent cracking and dimensional changes, as well as to prevent being too good a substrate for biological life. In connection with the drying, the wood often dries to a moisture content that is lower than desired. At the end, the moisture content can be adjusted, for example, by a technique based on spraying with water. In this step, it is very easy to add the composition according to the invention into the wood, wherein it is possible to elim- inate cracking and dimensional changes due to the drying of wood. Furthermore, this method can be used to improve fire resistance of the material, and to provide at least a short-term preservation against microorganisms.

For the fire resistance purposes it is important that the borate content in the material, such as in wood, is high enough. Generally the concentration of about 7% (w/w) BAE in the wood (see for example US2009/01 10842 [0016]) is required for fire resistance. Typically for protection against insects about 0.25% (w/w) BAE and for fungicidal protection about 0.75% (w/w) BAE are required according to US2009/01 10842. For example the BAE of trimethyl borate azeotrope is about 43%, so the solution may be diluted as long as the minimum required level in the material can still be obtained, for example said 7% for the protection against fire.

Basic reaction of trialkyl borate with wood moisture can be expressed by the equation:

B(OR)₃ + 3 H₂0→ H₃BO₃ + 3 ROH (R = CH₃, C₂H₅ or C₃H₇)

In addition to boric acid alcohol is formed as by-product. Trialkyl borate or boric acid may react also with wood hydroxyl groups forming borate esters as described by Muhammed in Journal of Tropical Forest Science 21 (4): 345-352 (2009). The most cost effective solution is methanol azeotrope of trimethyl borate in the above equation.

In one embodiment of the invention alkyl borate azeotrope is used as tall oil rosin dissolving compound to treat wood in an industrial way and the alcohol is evaporated to recycle it from the treatment. Conventional pressure treatment chambers can also be utilized. In another embodiment of the invention ethyl borate azeotrope is used as tall oil rosin dissolving compound to treat wood in household applications. Evaporated ethanol is not toxic. Even painting of the solution on the surface of the wood would give high resistance to water and (micro)biological barrier for fungi or termites.

In some embodiments of the invention the wood is treated in outdoor/ambient atmosphere without any pre-treatment, which may be energy consuming methods, such as drying, e.g. kiln drying. The treated wood may also be normalized at am- bient conditions. The wood may be softwood or hardwood or even refractory wood.

Inventive solution has unique properties depending on the composition and treatment process. Since rosin is not soluble in methanol it will solidify when methyl borate is reacted with wood moisture. This allows wood loading with very high concentration of rosin. In case of ethanol or isopropanol less rosin is deposited in wood since it will easily flow back during kickback of the treatment. In this case boron concentration is high in relation to rosin.

In one embodiment of the invention wood is dual-treated with the inventive com- position and creosote. This concept is reported in Norfolk Southern, RTA Showcase Long-Term Research, Crossties, March/April 2010, and the idea on 1987 was to partner creosote with a diffusible wood preservative containing boron in a dual-treatment process to extend and maximize the useful life of hardwood cross- ties in track. It was hypothesized that the borates would penetrate and protect the interior against wood-destroying organisms (decay, termites, etc.), while the traditional creosote treatment would weatherproof the outer portion of the treated product. The site was monitored for several years, and in 2002 several white oak ties were pulled for destructive testing. During that testing, it was learned that even in these most severe conditions the white oak test ties were all in virtually perfect condition. There were no signs of decay, spikes were all tight, and the ancillary benefit of no iron degradation of the wood by rusting spikes was observed. Borates are corrosion inhibitors as well as excellent wood preservatives.

With said dual-treatment method the amount of creosote may be decreased to minimum and it can be applied only to surface treatment. The boron-containing composition of the invention is well applicable to said dual-treatment method.

In the following, the invention will be described in more detail by means of examples on the preservation of wood with the wood treatment composition according to the invention. The examples are provided to illustrate and not to limit the invention. Examples

Examples 1 -4 relate to the preparation of preservative solution

Example 5 relates to preservative impregnation of wood

Example 6 relates to boron leaching from wood Example 1

Tall oil rosin (FOR85) was dissolved in trimethyl borate and methanol in different concentrations. The rosin solubility in trimethyl borate - methanol is presented in Figure 1 . Example 2

Tall oil rosin (FOR85) was dissolved in triethyl borate and ethanol in different concentrations. The rosin solubility in triethyl borate - ethanol is presented in Figure 2.

Example 3

Tall oil rosin (FOR 85) was dissolved in triisopropyl borate and isopropanol in dif- ferent concentrations. The rosin solubility in triisopropyl borate - isopropanol is presented in Figure 3.

Example 4.

A mixture of 35 g boric acid (0.57 mol) and 120 g 87% glycerol (1 .14 mol) was heated and stirred in a flask. Water of the esterification reaction distilled out until reaching final temperature 227°C. After that the content of the flask was cooled down and analyzed. IR analysis peaks were identical to literature reference for diglyceryl borate. Boron was titrated by 0.5 M NaOH with mannitol and phenolph- talein as indicator. Boron content was 5.58%.

According to a KF (Karl Fischer) analysis the product contained under 1 % water. Solubility of diglyceryl borate in 99.5% ethanol was determined to be 184 g/100g. Rosin solubility in pure ethanol was already tested in example 2 and it was 52 g/100g. Combining these two solutions resulted diglyceryl borate 42.2% (13.5% BAE) and 1 1 .9% rosin in ethanol.

Example 5

Scots pine sawn boards of size 28 mm x 95 mm x 4000 mm were conditioned in moisture of 15% ± 4% before treatment. Boards were placed in a treatment chamber which was then sealed. Treatment solution was allowed to flow to the chamber from upper storage vessel. Time recording for the impregnation started when suit- able amount of preservative was filled. At the end of the treatment all the liquid was drained out and after that vacuum was used to evaporate residual treatment solution and by-product methanol. Analysis of boron was done by ICP-AES and heartwood was excluded from analysis by procedure described in NWPC Document no. 3:1998. Rosin content was calculated from weigh differences. Boron pe- netration was determined in cross-section of the board including heartwood by curcumin/salisylic acid solution (standard BS 5666-2:1980: Methods of analysis of wood preservatives and treated timber. Qualitative analysis). The treatments and results are shown in Tables 1 -3.

Table 1

Table 2

Impregnation test 2 Pressure Temperature Time BAE % Rosin % Boron penetra(bar (g)) (^SC) (min) (wt/wt) (wt/wt) tion %

Chamber pressure 0 20 0

during filling

Impregnation pres0 20 60

sure

Final vacuum -0.95 20 30

Results 1 .6 2.7 50 Table 3

Example 6

Accelerated weathering tests:

10 boards were impregnated as described in example 4, table 3. Samples were cut from original boards and they were analyzed as reference in groups of 2 or 3. The same boards were cut to length 700 mm and placed to accelerated weather- ing test chamber. Test chamber was one cubic meter in size and it included two sprinklers. Four 300 W lamps gave UV radiation for boards. Heartwood was excluded from analysis by procedure described in NWPC Document no. 3: 1998. Analysis of boron is done by ICP-AES.

Tested boards were passed through the following cycle:

1 . Conditioning 13 days at 20 °C, RH = 65%

2. High moisture/ water spray 1 day at 20 °C, RH = 90%, 1 minute water spray once an hour (~ 2.5 l/m²)

3. Freezing 1 day at -10°C.

4. Hot and dry atmosphere/ UV-radiation 1 day at 80 °C, RH = 30%

First cycle (2-3) was done according to above mentioned but two following cycles were 3 days on counts 2 and 4. The total test period was 30 days. The results are shown in Table 4. Table 4

Claims

1 . A preservative composition for treating materials, said composition containing rosin dissolved or emulsified in a mixture of alkyl borate and alcohol.

2. The preservative composition of claim 1 , characterized in that the rosin is selected from wood rosin, gum rosin, tall oil rosin or mixtures thereof.

3. The preservative composition of claim 1 or 2, characterized in that the alkyl borate is trialkyl borate.

4. The preservative composition of claim 1 , characterized in that the alkyl borate is selected from trimethyl borate, triethyl borate, triisopropyl borate, diglyceryl borate and mixtures thereof.

5. The preservative composition of any of the preceding claims, characterized in that the alcohol is selected from water soluble C-I-C-I_O alcohols as for example monovalent alcohols, such as methanol, ethanol, propanol, butanol, pentanol, hexanol and derivatives thereof; multivalent, such as divalent or trivalent alcohols; multivalent, aliphatic, C₂-C₅ alcohols, such as diole and triole; glycerol, ethylene glycol and propylene glycol, and mixtures thereof.

6. The preservative composition of claim 5, characterized in that the alcohol is selected from methanol, ethanol, isopropanol, glycerol and mixtures thereof.

7. The preservative composition of any of the preceding claims, characterized in that the rosin is dissolved or emulsified in a mixture of diglyceryl borate and glycerol.

8. The preservative composition of any of the preceding claims, characterized in that the rosin is dissolved or emulsified in a mixture of diglyceryl borate and ethanol.

9. The preservative composition of any of the preceding claims, characterized in that the rosin is dissolved or emulsified in a mixture of diglyceryl borate, glycerol and ethanol.

10. The preservative composition of any of the preceding claims, characterized in that the alkyl borate is in the form of azeotrope with an alcohol.

1 1 . The preservative composition of claim 10, characterized in that the rosin is dissolved or emulsified in an azeotrope of trimethyl borate in methanol.

12. The preservative composition of claim 10, characterized in that the rosin is dissolved or emulsified in an azeotrope of triethyl borate in ethanol.

13. The preservative composition of claim 10, characterized in that the rosin is dissolved or emulsified in an azeotrope of triisopropyl borate in isopropanol.

14. The preservative composition of any of the preceding claims, characterized in that the material is wood.

15. The preservative composition of any of the claims 1 -13, characterized in that the material is non-wooden porous material, such as concrete, tile or cotton batting.

16. A method for treating materials, characterized by bringing the material into contact with the preservative composition of any of the preceding claims.

17. The method of claim 16, characterized in that the material is wood.

18. The method of claim 17, characterized in that the wood is dual-treated with the preservative composition of any of the claims 1 -15 and creosote.

19. The method of claim 16, characterized in that the material is non-wooden porous material, such as concrete, tile or cotton batting.

20. The method of any of the claims 16-19, characterized in that the composi- tion is contacted to the material to be treated by impregnation, immersion, spraying, or by application with a brush.

21 . The method of any of the claims 16-17 and 18-19, characterized in that the wood treatment is carried out at outdoor atmosphere without any pre-treatment, such as drying.