Wood treatment

Abstract

Compositions comprising one or more autoxidative catalysts for treating wood and reducing or preventing resin show-through or resin-bleed or both.

Claims

1. A method of reducing or preventing resin show-through in painted wood, the method comprising: impregnating unprimed, unpainted wood at a concentration of 8 to 50 g/m.sup.3 with one or more autoxidative catalysts in a liquid carrier before application of a primer coating to the wood, the one or more autoxidative catalysts comprising one or more metal compounds selected from one or more cobalt compounds, one or more manganese compounds, one or more cerium compounds, one or more vanadium compounds, or a combination of any two or more thereof, the liquid carrier comprising a water-based wood preservative, or a non-aqueous carrier, the wood being pine to reduce or prevent resin show-through in the wood after painting.

2. The method of claim 1, wherein the one or more autoxidative catalysts is an oxidative drying agent.

3. The method of claim 1, wherein the one or more metal compounds comprise one or more metal soaps of one or more carboxylic acids, one or more metal salts, or one or more metal coordination compounds, or any combination of any two or more thereof.

4. The method of claim 1, wherein the one or more metal compounds comprise cobalt or manganese, or a combination thereof.

5. The method of claim 1, wherein the one or more metal compounds comprises one or more carboxylate groups.

6. The method of claim 5, wherein the carboxylate group is selected from formate (C1), acetate (C2), propanoate (C3), butanoate (C4), pentanoate (C5), hexanoate (C6), heptanoate (C7), octanoate (C8), nonanoate (C9), decanoate (C10), undecanoate (C11), dodecanoate (C12), tridecanoate (C13), tetradecanoate (C14), pentadecanoate (C15), hexadecanoate (C16), heptadecanoate (C17), octadecanoate (C18), nonadecanoate (C19), eicosanoate (C20), heneicosanoate (C21), docosanoate (C22), tricosanoate (C23), and tetracosanoate (C24) groups, optionally substituted with one or more groups selected from hydroxyl, methyl, ethyl, n-propyl, isopropyl, n-butyl, t-butyl, isobutyl, and sec-butyl groups, optionally unsaturated with one or more double or triple bonds, and any combination of any two or more thereof.

7. The method of claim 1, wherein the one or more autoxidative catalysts comprises manganese-2-ethyl hexanoate, cobalt-2-ethyl hexanoate, cobalt napthenate, cobalt oleate, or cobalt acetate, or any combination of any two or more thereof.

8. The method of claim 3, wherein the one or more metal compounds comprise one or more metal salts selected from cobalt chloride or cobalt sulphate, or a combination thereof.

9. The method of claim 1, wherein the one or more autoxidative catalysts is applied or formulated with one or more secondary driers, one or more auxiliary driers, or one or more wood preservative compounds, or any combination of any two or more thereof.

10. The method of claim 9, wherein the one or more autoxidative catalysts is applied or formulated with one or more secondary driers selected from lead, zirconium, bismuth, barium, aluminum or strontium compounds, or any combination of any two or more thereof.

11. The method of claim 10, wherein the one or more autoxidative catalysts is applied or formulated with one or more secondary driers selected from an aluminium oxide and an aluminium carboxylate or a combination thereof.

12. The method of claim 1, wherein the liquid carrier is a non-aqueous carrier selected from an oil-based wood preservative, a hydrocarbon-based carrier, a light organic solvent preservative (LOSP), and an ester solution, or a combination thereof.

13. The method of claim 1, wherein the water-based wood preservative comprises a borate or triazole.

14. The method of claim 1, wherein the one or more autoxidative catalysts are impregnated into wood at concentration of about 20 to about 50 g/m.sup.3 on a metal-equivalent basis.

15. The method of claim 1, wherein the wood comprises logs, processed timber or composite wood products.

16. The method of claim 1, wherein the unprimed, unpainted wood is impregnated with the one or more autoxidation catalysts at a concentration of 10 to 50 g/m.sup.3.

17. The method of claim 1, wherein the unprimed, unpainted wood is impregnated with the one or more autoxidation catalysts at a concentration of 20 to 50 g/m.sup.3.

18. A method of reducing or preventing resin show-through in painted wood, the method comprising impregnating unprimed, unpainted wood by vacuum impregnation, pressure impregnation, or vacuum/pressure impregnation at a concentration of 8 to 50 g/m.sup.3 with one or more autoxidative catalysts in a liquid carrier, the one or more autoxidative catalysts comprising one or more metal compounds selected from one or more cobalt compounds, one or more manganese compounds, one or more cerium compounds, one or more vanadium compounds, or a combination of any two or more thereof, the wood being pine, the liquid carrier comprising a water-based wood preservative, or a non-aqueous carrier to reduce or prevent resin show-through in the wood after painting.

19. The method of claim 18, wherein the liquid carrier is a non-aqueous carrier selected from an oil-based wood preservative, a hydrocarbon-based carrier, a light organic solvent preservative (LOSP), and an ester solution, or a combination thereof.

20. The method of claim 18, wherein the water-based wood preservative comprises a borate or triazole.

21. The method of claim 18, wherein the one or more metal compounds impregnated into the wood comprise cobalt or manganese, or a combination thereof.

22. The method of claim 21, wherein the one or more metal compounds are impregnated into the wood at concentration of about 20 to about 50 g/m.sup.3 on a metal-equivalent basis.

23. The method of claim 18, wherein the unprimed, unpainted wood is impregnated with the one or more autoxidation catalysts at a concentration of 10 to 50 g/m.sup.3.

24. The method of claim 18, wherein the unprimed, unpainted wood is impregnated with the one or more autoxidation catalysts at a concentration of 20 to 50 g/m.sup.3.

25. A method of reducing or preventing resin show-through in painted wood, the method comprising impregnating unprimed, unpainted wood with one or more autoxidative catalysts at a concentration of 8 to 50 g/m.sup.3, the one or more autoxidative catalysts comprising one or more metal compounds selected from one or more cobalt compounds, one or more manganese compounds, one or more cerium compounds, one or more vanadium compounds, or a combination of any two or more thereof, the wood being pine, and applying a primer coating to the impregnated wood to reduce or prevent resin show-through in the wood after painting.

26. The method of claim 25, wherein the one or more metal compounds impregnated into the wood comprise cobalt or manganese, or a combination thereof.

27. The method of claim 26, wherein the one or more metal compounds are impregnated into the wood at concentration of about 20 to about 50 g/m.sup.3 on a metal-equivalent basis.

28. The method of claim 27, wherein the one or more metal compounds are impregnated into the wood in a liquid carrier selected from water, a water-based wood preservative, and a non-aqueous carrier.

29. The method of claim 25, wherein the unprimed, unpainted wood is impregnated with the one or more autoxidation catalysts at a concentration of 10 to 50 g/m.sup.3.

30. The method of claim 25, wherein the unprimed, unpainted wood is impregnated with the one or more autoxidation catalysts at a concentration of 20 to 50 g/m.sup.3.

Description

DETAILED DESCRIPTION OF THE INVENTION

(1) It has been discovered that certain chemical compounds added to wood have beneficial effects in preventing resin show-through. Such chemicals may be conveniently added to the wood prior to painting, including addition to wood during priming.

1. Definitions

(2) The term autoxidative catalyst refers to an agent capable of initiating or catalysing oxidation or polymerisation reactions of unsaturated carbon bonds of resin, fats and waxes or other polymerisable materials, including oxidation or polymerisation reactions in the presence of oxygen or UV radiation or both. Suitable autoxidative catalysts are reviewed by Gorkum, R. V., Bouwman, E., The oxidative drying of alkyd paint catalysed by metal complexes, Coord. Chem. Rev. (2005) 249:1709-1278, incorporated herein by reference. In various embodiments the autoxidative catalyst has two or more oxidation states or three or more oxidation states.

(3) The term comprising as used in this specification means consisting at least in part of When interpreting statements in this specification which include that term, the features, prefaced by that term in each statement or claim, all need to be present but other features can also be present. Related terms such as comprise and comprised are to be interpreted in the same manner.

(4) The phrase resin show-through refers to micro-blistering, bubbling, or in severe cases crocodiling (a crocodile skin appearance) of a painted surface. It is observed as paint shade differences revealing the resinous areas where the paint in the resinous areas appears bleached or washed out due to different light scattering effects associated with the comparatively uneven paint surfaces. Reference to resin show-through is also intended to include resin bleed.

(5) The phrase resin bleed refers to where wood resin may exude through a paint film to produce visible resin deposits on a painted surface.

(6) The phrase unpainted wood refers to wood that may have had a primer or other pre-treatment applied but has not yet had a topcoat of paint applied.

2. Compositions of the Invention

(7) A preferred chemical compound for inhibition of resin show-through is cobalt 2-ethyl hexanoate (also known as cobalt octoate)an autoxidative catalyst. In Example 1 below, cobalt octoate was added to wood at an equivalent of 36 g (cobalt metal equivalent) per cubic meter of wood to produce a major reduction of resin show-through.

(8) The mechanism or chemical pathway by which cobalt octoate inhibits resin show-through in wood has not been ascertained Cobalt octoate is used commercially as a paint drier in alkyd paint systems where it functions as a catalyst to promote resin autoxidation. Autoxidation is the direct reaction of oxygen with organic compounds to initiate free radical chain reactions, which lead to cross-linking and polymerization of the alkyd resin. A necessary requirement for autoxidation is the presence of unsaturated carbon bonds in the organic compound, but not all unsaturated compounds will autoxidise. Autoxidation of alkyd paint systems is described in detail by Gorkum, R. V., Bouwman, E., The oxidative drying of alkyd paint catalysed by metal complexes, Coord. Chem. Rev. (2005) 249:1709-1278, incorporated herein by reference.

(9) Many of the wood extractives, such as resin acids, fatty acid esters and terpenes, which are concentrated in wood resinous areas, have unsaturated carbon bonding with potential for autoxidation in the presence of cobalt catalyst. Such autoxidation may cause loss of chemical reactivity and/or physical stabilization of the extractives, so that interactions between extractives and the paint system are minimized and resin show-through does not develop.

(10) It may be predicted that other cobalt compounds capable of catalyzing autoxidation reactions, including, but not limited to, cobalt naphthenate, cobalt oleate and cobalt acetate may also be useful in preventing resin show-through.

(11) Other autoxidative paint driers may also prove beneficial in controlling resin show-through. Other metals capable of autoxidation in alkyd paint systems include compounds of iron, copper, manganese, titanium, vanadium and cerium.

(12) Autoxidative paint driers are commonly used in conjunction with secondary driers, incapable of autoxidation, to enhance crosslinking. The most commonly used secondary driers include compounds of aluminium, zirconium, zinc, calcium, lithium and potassium compounds. In particular, aluminium compounds, in conjunction with cobalt driers, greatly enhance crosslinking and produce films of significantly increased hardness. Secondary driers are reviewed by Gorkum, R. V., Bouwman, E., The oxidative drying of alkyd paint catalysed by metal complexes, Coord. Chem. Rev. (2005) 249:1709-1278, incorporated herein by reference.

(13) A preferred method of adding such chemicals to wood is in conjunction the wood preservative treatment, such as LOSP (light organic solvent preservative). Pine timber for exterior outdoor uses in NZ and Australia must be impregnated with chemical preservatives according to the relevant standards. For exterior paint grades, such as weatherboards, the most common treatment process is LOSP. This process utilizes white spirit as a carrier fluid for the active ingredients and impregnation produces no significant wood swelling, which is particularly advantageous for wood products which are dimensionally finished or profiled before treatment. After LOSP treatment, the wood is conditioned to allow evaporation of the white spirit from the wood.

(14) Although LOSP treatment is a commonly used wood preservative method for paint grade products, there exist alternative low uptake water based systems which allow diffusion of borate salts or emulsified triazole compounds. The metal catalysed autoxidation reactions are not limited to hydrocarbon solvent (white spirit) systems and therefore there is expected benefit in the addition of water solubilised or emulsified cobalt and/or other catalysts in such preservative formulations.

(15) Most primers used for painting exterior wood products are based on alkyd resin systems and as such, already contain suitable concentrations of cobalt and/or other primary driers and auxiliary driers to achieve optimal through drying of the coat. Drying rate issues may limit the addition of excess quantities of driers to alkyd resin systems.

(16) In contrast, acrylic primer systems, which are water emulsified and not cross linking, may accommodate metal based driers, which may precipitate in the surface layers of the wood. It is possible that some benefit in reducing show-through may accrue from this approach.

(17) The afore-mentioned methods of incorporating autoxidative catalysts and additional agents into wood via either the preservative fluid or primer composition have cost advantages because no additional wood processing steps are required. In some instances however, it may be advantageous to introduce the autoxidative catalysts and additional agents independently as, for instance, in a pre-primer application. This strategy may remove any formulation constraints imposed by the nature of the preservative fluid or primer compositions, and provide flexibility in terms of application method, which may include treating the wood by pressure and/or vacuum impregnation, dipping, spraying, roller, brush or other means, with the treatment composition.

(18) Various aspects of the invention will now be illustrated in non-limiting ways by reference to the following examples.

EXAMPLES

Example 1

(19) Eighteen highly resinous shooks, 90 mm19 mm400 mm, were selected for resin show-through trials, where the following three LOSP treatments were compared. (a) An azole based LOSP formulation, containing 0.6% tebuconazole, 0.6% propiconazole, 0.45% permethrin and 3% total resins and waxes in a predominantly white spirit solvent. (b) A tri-butyl tin naphthenate (TBTN) based LOSP formulation containing an equivalent 1.3% tin, 0.45% permethrin and 3% resins and waxes. (c) An azole formulation as above but also containing 0.12% (w/v) equivalent cobalt content (added as 2% of a 6% cobalt octoate solution).

(20) After LOSP impregnation with fluid uptakes of 30 L/m.sup.3, the shooks were air conditioned for five days to remove solvent, primed with a commercial alkyd primer, conditioned seven days and painted with two exterior acrylic topcoats of light reflective value (LRF) of 35.

(21) After further conditioning (minimum one week) the shooks were mounted on plywood sheets angled 45 degrees towards maximum sunlight during the summer months. Under these conditions board surface temperatures generally ranged between 15 and 55 C.

(22) The evaluation of resin show-through after 12 weeks exposure of the boards is shown in Table 1. The results clearly show the beneficial effect of the cobalt octoate additive where none of the shooks exhibited resin show-through, whereas a majority of the boards in the two standard treatments exhibited some show-through.

(23) TABLE-US-00001 TABLE 1 Twelve Week Resin Show-through Evaluation of Different LOSP Treatments LOSP Treatment Minor Major Solution Unaffected Show-through Show-through Azole 2 3 1 TBTN 1 5 0 Azole + 0.12% Co 6 0 0 octoate

(24) After 18 months exposure the shooks were re-evaluated for show-through and the results are shown in Table 2. The results confirm the longer term effectiveness of the cobalt octoate treatment.

(25) TABLE-US-00002 TABLE 2 Comparison of LOSP treatments after 18 months Minor Major Treatment Solution Unaffected Show-through Show-through Std LOSP azole 0 1 5 LOSP (TBTN) 0 1 5 Azole + 0.12% cobalt 6 0 0 octoate

Example 2

(26) An accelerated weathering test using a QUV weatherometer (ManufacturerQ Panel Lab. Products, Cleveland, Ohio, USA) was devised for investigations of resin show-through. This test consisted of a two-stage four-hourly alternating cycle of the following. An ultraviolet heating stage using short wavelength, UVB 313 nm radiation, where irradiance was controlled at 50% maximum by the four UV sensors. An air blower operates during the UV cycle and the temperature was controlled at 55 C. A condensation cycle where the UV lamps are off and the temperature is controlled at 40 C. by water heated in an underneath tray. In this cycle the board surfaces are continually wet once condensation is fully developed (after about one hour).

(27) The QUV sample positions were adapted to hold up to 24 shooks (310 mm90 mm) in the unit. Generally QUV exposures of 250-300 hours were sufficient to allow strong development of resin show-through in resinous shooks.

(28) A comparison of QUV exposures of shooks treated by the standard azole formulation and the same formulation with cobalt octoate added, as described in Example 1, is shown in Table 3. After LOSP treatment the shooks were conditioned, primed and top-coated as in Example 1.

(29) TABLE-US-00003 TABLE 3 Resin Show-through in QUV trials of Azole Treatments with and without Cobalt Octoate. LOSP Minor Major Treatment Unaffected Show-through Show-through Azole 1 3 8 Azole + Co octoate 8 2 2

(30) The QUV results support the finding of the outdoor exposure trial outlined in Example 1, that the presence of cobalt octoate has a major beneficial effect on the inhibition of resin show-through.

Example 3

(31) A larger scale exposure trial involving outdoor weathering of 850 resinous shooks distributed over five sites with differing local climates was undertaken to establish the effectiveness of cobalt octoate treatment. The shooks were cut to 300-350 mm long and finger-jointed to produce 6 m lengths.

(32) After moulding and longitudinally splitting into halves, the 6 m lengths of 90 mm18 mm pieces were re-examined to cull insufficiently resinous pieces or defects such as resin pockets, splits or knots. Finally 252 pieces of lengths 1.0-1.2 m were selected for the trial. Each length contained either three or four shooks or about 850 shooks in total.

(33) A pilot LOSP treatment plant, void volume 200 L and length 1.2 m was used for the trials. The average fluid uptake for the cobalt treatments was 27.3 L/m.sup.3 corresponding to a cobalt additive concentration of 32 g/m3 of wood. After treatment, the lengths were conditioned in fillet for eight days to remove solvent before priming with a commercial alkyd primer After a further 12 day conditioning period two coats of commercial semi-gloss exterior, acrylic topcoats were applied as described in Examples 1 and 2.

(34) The boards were backed with bitumen tape to prevent egress of water from trapped water behind the boards. The boards were attached to plywood panels (12 per panel) which were oriented in sunny positions approximately north at angles 45-60.

(35) Five different NZ sites ranging from the north of the North Island to the south of the South Island, New Zealand, both coastal and inland, to encompass differing temperatures and rainfall conditions.

(36) Inspections were made after six months exposure including a summer period. Three categories of resin show-through were distinguished: Major show-throughsufficiently evident to be unacceptable in a commercial situation; Minor show-throughevident on close inspection by an experienced observer; None.

(37) The results of the field trial assessments, shown in Table 4, confirm the efficacy of the cobalt octoate treatment.

(38) TABLE-US-00004 TABLE 4 Comparison of Standard and Cobalt additive Treated Boards at Five Sites Total Boards Exhibiting Treatment Show-through Location STD LOSP +32 g/m.sup.3 Cobalt Central 5 major 0 coastal 10 minor Central 8 major 0 inland 9 minor Northern 7 major 1 minor coastal 2 minor Southern 8 major 2 minor coastal 7 minor Southern 3 major 0 inland 5 minor

Example 4

(39) An accelerated weathering trial was carried under similar conditions to Example 2, to determine the efficacy of lower levels of the cobalt octoate additive. The results, shown in Table 5, indicate positive benefit at the higher levels of 9 g/m.sup.3 and 36 g/m.sup.3 cobalt contents in the wood.

(40) TABLE-US-00005 TABLE 5 Effect of lower Cobalt levels. % Shooks with No of Show-through Treatment Primer Shooks None Minor Major LOSP Alkyd 4 25 25 50 LOSP + 3.6 g/m.sup.3 Co Alkyd 6 33 17 50 LOSP + 9 g/m.sup.3 Co Alkyd 6 33 50 17 LOSP + 36 g/m.sup.3 Co Alkyd 6 83 0 17

Example 5

(41) An accelerated weathering trial under similar conditions to Example 2 was carried out to determine if the cobalt treatment would be effective for acrylic primed systems. Ten shooks treated with standard LOSP and (two coats) of acrylic primer were compared to ten similarly treated shooks but with cobalt octoate additive in the LOSP fluid to produce an equivalent cobalt concentration of 36 g/m.sup.3 in the wood. Both sets (and all sets in this research) were top coated with two coats of exterior acrylic.

(42) TABLE-US-00006 TABLE 6 Effect of Cobalt in Acrylic Primed Systems % Shooks with No of Show-through Treatment Prime Shooks None Minor Major LOSP Acrylic 10 40 40 20 LOSP + 36 g/m.sup.3 cobalt Acrylic 10 30 70 0 octoate

Further Examples

(43) A further six accelerated weathering trials were carried out at a higher weathering temperature (5 C. hotter) and longer weathering period (extended two days) to provide a greater challenge to the treatments compared to Examples 2, 4 and 5, which showed only minor differences between treatments. The results of the six trials are shown in Table 7.

(44) TABLE-US-00007 TABLE 7 QUV Results of Further Six Trials. % Shooks with Example/ Pre- No of Show-through Trial set Treatment prime Prime Shooks None Minor Major Reference LOSP Alkyd 21 10 20 71 Reference LOSP + 36 g/m.sup.3 Alkyd 22 50 32 18 Cobalt Example 6 LOSP + 18 g/m.sup.3 Alkyd 9 33 22 44 Cobalt Example 7 Borate Alkyd 8 13 38 50 Example 7 Borate + 8 63 38 36 g/m.sup.3 cobalt (emulsion) Example 8 LOSP Aq-Co- Alkyd 16 6 13 81 sulphate Example 8 LOSP Cobalt Alkyd 8 63 38 octoate Example 9 Presso Alkyd 9 33 33 33 Example 9 Presso 36 g/m.sup.3 Alkyd 9 56 33 11 Cobalt Example 10 LOSP + 36 g/m.sup.3 Alkyd 7 57 28 14 Mn-octoate Example 11 LOSP + Al Alkyd 7 14 43 43 isopropoxide Example 11 LOSP + Al Alkyd 7 71 28 0 isopropoxide + 36 g/m.sup.3 Cobalt

Example 6

(45) Example 6 investigated an intermediate concentration of the cobalt octoate additive at 18 g/m.sup.3 of wood. The results, shown in Table 7, indicate an effectiveness intermediate between no cobalt and the higher level of cobalt of 36 g/m.sup.3

Example 7

(46) Example 7 investigated the efficacy of the cobalt additive in aqueous borate preservative systems. Eight shooks treated by an aqueous borate process were compared with eight shooks similarly treated but with the addition of emulsified cobalt octoate in the borate fluid (to attain 36 g/m.sup.3 cobalt in the wood. After borate treatment and conditioning the shooks were alkyd primed and acrylic top coated according to earlier trials. The results, shown in Table 7, indicated a beneficial effect in reducing show-through by the presence of cobalt in the borate fluid.

Example 8

(47) Example 8 aimed to determine if cobalt could be effectively applied as a pre-primer treatment instead of incorporation in treatment fluids. This option would allow a targeted approach whereby LOSP treated resinous wood could be segregated and coated with a pre-primer prior to the standard primer process.

(48) Eight shooks were LOSP treated and pre-primed with diluted (in white spirit) cobalt octoate solution to provide a cobalt level of 36 g/m.sup.3 in the wood, similar to the quantity taken up in the LOSP treatments. After pre-priming the shooks were alkyd primed and acrylic top coated as in previous trials. A second set of sixteen shooks was pre-primed with an aqueous solution of cobalt sulphate to provide a similar level of cobalt uptake by the wood The results, shown in Table 7, indicated the solvent based cobalt octoate pre-primer provided more reduction of show-through than the aqueous cobalt treatment.

Example 9

(49) Example 9 aimed to determine if the cobalt octoate additive would be effective in an alternative solvent system which uses tertiary butyl acetate instead of white spirit as a carrier solvent. This system is known as the Presso ProcessrefWood Treatment Using Ester Compounds as Recoverable Carrier Solvents by F W Fraer and R C EddyProc. American Wood Preservers Association, Annual Meeting Nashville Tenn., USA., May 2012.

(50) Nine shooks were treated by the standard Presso fluid, which contains the same actives as standard LOSP. A further nine shooks were treated with standard Presso fluid containing 2% cobalt octoate. As shown in Table 7, both Presso treatments exhibited less resin show-through than the standard LOSP treatment. The presence of cobalt marginally improved the performance of the Presso treatment in controlling show-through.

Example 10

(51) Example 10 evaluated manganese octoate as an alternative to cobalt octoate for reduction of resin show-through. Seven shooks with manganese octoate incorporated into the LOSP fluid to give an equivalent concentration of 36 g/m.sup.3 in the wood were compared to LOSP treatments with and without cobalt octoate.

(52) The results, shown in Table 7, indicated a reduction in show-through for the manganese octoate doped LOSP treatment. The reduction in show-through was similar to the equivalent cobalt octoate treatment.

Example 11

(53) Example 11 aimed to determine if the combination of cobalt and aluminium driers could produce increased benefit in controlling show-through. As a source of organically soluble aluminium for this trial, aluminium isopropoxide was pre-dissolved in xylene (50 g/L) and the solution added to the LOSP fluid to generate a solution of 1 g/L aluminium in the fluid or 30 g/m.sup.3 in the treated wood. The trial consisted of

(54) 7 shooks treated in LOSP fluid with the Al drier only.

(55) 7 shooks treated in LOSP fluid with cobalt octoate only (36 g/m.sup.3) only.

(56) 7 shooks treated with the combination of the above Al and cobalt octoate additives.

(57) The results indicate that aluminium drier alone is not effective in preventing resin show-through. However the combination of aluminium and cobalt driers gave a very good result.

INDUSTRIAL APPLICABILITY

(58) The present invention relates to compositions for treating wood, and in particular to compositions and their use for reducing or preventing resin show-through or resin-bleed or resin show-through and resin-bleed, particularly in pine. These compositions have application in the building and decorating industries.

(59) Those persons skilled in the art will understand that the above description is provided by way of illustration only and that the invention is not limited thereto.