BACKGROUND Timber products used in structural applications, particularly outdoor applications, must be durable, that is, resistant to attack from decay fungi organisms which can cause the timber to rot, as well as insects such as termites.

To enable many timbers to be used in outdoor applications, they are treated with chemical preservatives, water repellent chemicals and/or insecticides. In the case of laminated timbers, such as radiata pine laminates, current treatment processes typically involve either treating all the individual elements of the laminate prior to lamination, or treating the final laminated product. The former approach has the disadvantages that a higher proportion of the treated lamina is surfaced to waste when the lamina are prepared for lamination. The latter approach has the disadvantage that, because the whole finished laminate is being treated, it is difficult to achieve full penetration of the preservative solution into the core of the laminate. This means that high pressures and large quantities of toxic, undesirable solvents are typically required to achieve full penetration.

With this background, it is an object of the present invention to provide a process for preparing a laminated timber product which will go some way towards overcoming the above disadvantages, or at least to provide the public with a useful choice.

SUMMARY OF THE INVENTION Accordingly, in a first aspect the present invention provides a process of preparing a laminated timber product comprising two outer layers and at least one inner layer, the process comprising the steps of :

laminating the outer layers and the at least one inner layer together, wherein the inner layer or layers have been pre-treated with a first timber preservative solution; and treating the resulting laminated product with a second timber preservative solution.

Preferably, the layers are laminated together using an adhesive.

Preferably, the process includes the preliminary step of pre-treating the inner layer (s) with the first timber preservative solution.

Preferably, the first timber preservative solution, with which the inner layer (s) are pre-treated, is substantially free of water repellent chemicals, but may optionally contain one or more insecticides, such as a termiticide.

Preferably, the second treatment solution, with which the laminated product is treated, also contains a water repellent. Optionally, the second treatment solution also contains one or more insecticides, such as a termiticide.

Preferably, the first and second treatment solutions are non-aqueous solutions.

Preferably, the laminated timber product has three layers only.

In a further aspect, the present invention provides a laminated timber product obtainable by a process as defined above.

Although the invention is broadly as defined above, it is not limited thereto and also includes embodiments of which the following description provides examples.

DESCRIPTION OF THE DRAWINGS A better understanding of the invention will be gained with reference to the accompanying Figures 1A to 1E, which are a flow chart illustrating the details of the various steps involved in a preferred embodiment of the process of the present invention.

DESCRIPTION OF THE INVENTION As defined above, the present invention relates to a process of preparing a laminated timber product. In general terms, the process involves laminating together two outer layers and at least one inner layer to form a laminated product.

Prior to the laminating step, the inner layer (s) will have first been pre-treated with a timber preservative solution. The process also includes the step of treating the resulting laminated product with a timber preservative solution.

The process of the present invention may be used to prepare a laminate of any non- durable timber requiring preservative treatment and which is capable of absorbing and retaining preservative. By way of example, the process of the invention may be used to prepare laminates of timber species selected from pine species as included in the US"Southern Pines classification", Pinus radiata, Crytpmeria, japonica, Tsuga sieboldoo, Tsuga diversifolia, Tsuga heterophylla, Larix spp, Picea, Abies, Pinus densiflora, Pinus thundergii, Pseudotsuga menzil, and Diperocarpus species, as well as mixtures of any of the above.

It will be appreciated that the individual timber laminae can be prepared ready for use in the process of the invention using techniques known in the art. The particular combination of process steps used to initially prepare the laminae will depend to some extent on the required cosmetic, mechanical and other properties of the laminae, which will in turn depend on the end use to which the laminated product is to be put. Typically, preparation of the laminae may involve finger jointing shook into continuous ribbons of laminae, and surfacing and proof grading the laminae.

The process of the invention involves laminating two outer or external layers of timber and at least one inner or core layer together. It is generally preferred that the laminate be of three layers only, although laminates of four or more layers can also be prepared using the process of the invention.

In accordance with the present invention, the laminae intended for use as inner layers will first be pre-treated with a timber preservative solution. Where the final

laminated product is to contain two or more inner layers, different timber preservative solutions could be used. However, in practice, it is more likely that the same solution will be used to treat all inner layers.

The preservative solution will contain at least one preservative compound.

Compounds suitable for use as timber preservatives are well known in the art.

Examples of preservatives suitable for use in the process of the invention are emulsion types such as copper naphthenate, zinc naphthenate, zinc tri-carboxylate, azole-propetamphos compound, tributyl tin oxide, tributyl tin naphthenate, Iodo- Propynyl-Butyl-Carbamate, didesyldimethyl ammonium chloride and ammoniacal copper quaternaries, and oil borne types such as copper naphthenate and zinc naphthenate. Suitable carriers for the preservatives include white spirits, pine oil, liquid petroleum gas, methanol, carbon dioxide and freon.

One preferred preservative solution suitable for use in the process of the invention for pretreating the laminae intended for the inner layers of the laminate is didesyldimethylammonium chloride (DDAC) in a solution with a non-aqueous compound, typically white spirits.

It should be understood that the term"timber preservative solution", as used in this specification, will also include liquids in the form of emulsions or suspensions of the preservative compound.

It is generally preferred that the preservative solution is non-aqueous so that the solution is anhydrous, in order to avoid swelling of the wood and potentially damaging adhesion. However, aqueous carriers are not excluded from the scope of the present invention.

Where, as is preferred, the lamination is to be carried out using an adhesive (described in more detail below), it is preferred that the timber preservative solution used to treat the inner laminae does not contain a water repellent, as this may upset the glue bond between the laminae. It will be appreciated that it will not in any event be necessary to treat the inner layer (s) with a water repellent. The inner layers will largely be protected from water penetration by the external layers, which

will preferably themselves be treated with a timber preservative solution which does contain a water repellent, as will be described in more detail below.

The treatment of the inner laminae with the preservative solution may be carried out using processes known in the art. Conveniently this may be done in a suitable treatment vessel or enclave by drawing a vacuum to remove air from the timber cells, flooding treatment solution into the vessel under the vacuum, pressurising the fluid and then drawing a final vacuum to remove the excess solution. Following treatment, the treated laminae will be allowed to dry and stored in a dry environment prior to carrying out the lamination process.

Lamination of the laminae intended for the outer layers to the prepared inner laminae is preferably carried out using a suitable adhesive (such as a JAS approved Phenol Formaldehyde Resorcinol adhesive (Neste Resins Corp)) which is applied to the surface of the laminae. It may be desirable to surface the pretreated core laminae prior to lamination to ensure a satisfactory glue bond. Application of the adhesive is followed by compiling of the laminae and compression in a press. Upon release from the press, the laminated product is desirably stored for a sufficient period of time in a dry environment to allow the glue bond to be completed (typically a few days), before further processing.

It is not necessary for the laminae intended for the outer layers to be treated with a preservative solution prior to the lamination step, although this can be done if desired.

It will also be appreciated that other laminating techniques such as mechanical jointing may be employed instead of adhesive bonding.

Following the lamination step, the resulting laminate is then treated with a timber preservative solution. Again, suitable preservative compounds and carriers are known in the art and in particular may be selected from those listed above as suitable for pretreatment of the inner laminae. It will therefore be appreciated that the timber preservative solutions used to pretreat the inner laminae and the resulting laminate may be the same. It is however generally preferred that, in addition to a preservative compound, the solution used to treat the resulting

laminate includes a water repellent compound (such as a suitable acrylic or acrylic- based compound), in order to protect the laminate from moisture when in use. Alternatively, a water repellent may be applied separately to the preservative treated finished laminated product. The preservative solution may also desirably contain one or more insecticides, particularly termiticides.

One example of a preferred timber preservative solution for treating the resulting laminate is didesyldimethyl ammonium chloride in combination with a non- aqueous carrier such as white spirits and a water repellent compound.

The treatment of the laminated product with the preservative solution may conveniently be carried out in a similar manner to that described above for pretreatment of the inner laminae, that is, in a suitable treatment vessel or enclave, with the preservative solution being flooded in under vacuum.

The result of the above process is a laminated timber product which, because of the pre-treatment of the inner layer (s) with preservative solution, is fully treated throughout. It will also be appreciated that the process of the invention minimises the quantity of chemical required to achieve full treatment. This is because it is unnecessary to first pre-treat the outer layers of the laminate prior to lamination.

In addition, it is unnecessary to include water repellents and insecticides in the treatment solution used to pretreat the inner laminae.

The process of the present invention has particular application to preparing timber laminates intended for use as sub-floor products, in particular to laminates known as dodai. However, it will also be appreciated that the process of the invention is equally applicable to preparing timber laminates for other potential applications.

The process of the present invention will be described in more detail with reference to the following non-limiting examples.

EXAMPLES Example 1 Laminae for the core of the intended laminated product being of an accepted species, which is kiln dried and finger jointed, of the required dimension and specification (cosmetic and mechanical properties that accord with JAS 601) were packaged in batches in readiness for preservative treating. Packets of laminae were enclosed in a (certified) treating enclave. An initial vacuum of-20 kPa was drawn for a period of 5 minutes, following which a solution of preservative compound and carrier gravitated into the enclave from a storage reservoir which connected by valve to the treating enclave in which the-20kPa vacuum had been drawn. (The fluid was maintained at ambient temperature but above a minimum of 60C) During the flooding period the vacuum was maintained.

The solution comprised a mix of carrier and preservative the concentration of which had been regulated to ensure the minimum 4.5kg of active ingredient per m3 of lumber was retained in the laminae after the treating process. When the treating enclave had been flooded the vacuum was released. The solution was added to the treating enclave to compensate for the fluid being absorbed into the laminae so that the minimum fluid level remained above the height of the laminae.

After a period of 5 minutes the fluid was released from the enclave by a valve into a reservoir.

A vacuum of-85 kPa was drawn on the enclave, with this vacuum being maintained for 30 minutes from the time this minimum was attained. At the conclusion of this period, the enclave was opened and the packaged lamina removed.

A volume of 28 litres per m3 of laminae was retained in the laminae including the 4.5kg per m3 minimum of preservative.

The laminae was stored in a weather protected warm (17°C) environment for 2 days before being surfaced and mechanically (or visually) graded in accordance with JAS

601, in readiness for laminating. Laminae for the outer laminates of the intended product, being of an accepted species which is kiln dried (untreated) and finger jointed, of the required dimension and specification (cosmetic and mechanical properties that accord with JAS 601) were surfaced and mechanically (or visually) graded in accordance with JAS 601 (noting that JAS 601 requires where three or less laminae are combined they small be of the same lamina grade) in readiness for laminating.

Combinations of inner (pre treated) and outer laminae were past through the glue applicator where a premixed adhesive is applied to appropriate surfaces at a controlled rate (eg 250gms of mixed adhesive per m2 of glued surface). The respective laminae were then compiled and compressed in a press while being heated to accelerate the glue cure. Upon release from the press, the laminated product was stored for a period of four days in a dry environment while the glue bond completed. Packets of laminated product were then cut to length and surfaced into final dimension.

Packets of product in final dimensional form were then placed in the treating enclave.

An initial vacuum of-30 kPa was drawn for a period of 5 minutes, following which a solution of preservative compound, water repellent and carrier gravitated into the enclave from a storage reservoir which connected by valve to the treating enclave in which the-30kPa vacuum had been drawn. During the flooding period the vacuum was maintained. The solution comprised a mix of carrier water repellent and preservative, the concentration of which had been regulated to ensure the minimum 4.5kg of active ingredient per m3 of lumber was retained in the laminated product after the treating process.

When the treating enclave had been flooded the vacuum was released. Solution was added to the treating enclave to compensate for the fluid being absorbed into the laminated product so that the minimum fluid level remained above the height of the product.

After a period of 5 minutes the fluid was released from the enclave by a value into a reservoir.

A vacuum of-85 kPa was drawn on the enclave, with this vacuum being maintained for 30 minutes from the time this minimum was attained. At the conclusion of this period, the enclave was opened and the packaged product removed, having residual absorption of up to 70 litres of fluid per m3 of product and not less than 4.5 kg per m3 of preservative retained evenly throughout the outer laminae, the inner laminae having been penetrated from the preceding treating cycle.

The treated product was then stored for a period of seven days in a weather protected environment during which residual carrier evaporated.

Example 2 This example, together with the flow chart of Figures 1A to 1E, describes in detail an algorithm which would be followed in preparing laminated, kiln dried, non metallic preservative treated, water repelling sub-floor components in accordance with a preferred embodiment of the process of the present invention. The laminated components would be made in compliance with the Japanese Agricultural Standard 601 for Glued Laminated Timber and the Japanese Industrial Standard 9108, Foundation wood sill treated with preservatives by pressure processes.

1. Logs are selected as being suited for processing to produce feedstock for the target product. Criteria of selection might include a combination of species (mainly radiata pine), diameter, ovality, length, sweep, knot size, density, age, stress wave properties, propagation time.

2. Selected logs are sawn into dimension lumber the size of which is compatible with the lamina sizes required for the specific finished products, including size allowances for shrinkage and process loss.

3. Refuse is a by product of converting log to sawn timber.

4. Chip is a by product generated by chipping slab wood from which dimension lumber can not be recovered.

5. Bark is removed from the log prior to sawing.

6."Othe7 lumberis sawn dimension lumber that is of a grade or dimension not suited for the target product.

7. Feedstock for the target product is green sawn (high moisture content freshly sawn) dimension lumber of a size and grade suited for processing into the target product, sorted by respective sizes and packaged in fillet in readiness for kiln drying.

8. Kiln drying is where the green sawn dimension lumber is placed in a specially constructed enclave capable of being heated and where the speed of air flow, temperature and humidity can be controlled to dry the lumber to a prescribed uniform moisture content, typically 12 to 14%. The moisture content is defined as the weight of a lumber, less its bone dry weight expressed as a percentage. Typically stacks of filleted lumber will have weights placed upon them during the kiln drying process, to maintain the straightness of the lumber. During the kiln drying process the dimensions of the lumber will contract.

9. Moisture along with other extractives is that which is given off the lumber, during the kiln drying process.

10. Blanking is a process whereby lumber of one sawn dry dimension (at a time) is fed longitudinally through a planing or surfacing machine to remove irregularities in size to provide a smooth uniform dimensioned lumber feedstock for processing into the target product.

11. MSR is machine stress rating, where the blanked dry lumber is fed longitudinally through a purpose built machine which measures the modulus of elasticity of the lumber at increments along its length. This measure can be achieved from equipment that measures the stress wave propagation time by vibration analysis, or stress wave analysis (where the average modulus of elasticity of the entire lumber length is provided) or by measuring deflection by application of a mechanical bending force or

measuring the resistance to induced deflection as lumber passes through sets of rollers by Xray or acoustic analysis. Having been conveyed longitudinally through the machine stress rating device a record will be made of the mechanical properties of the lumber, to which will be added data relating to visual defects and blemishes. Identification of such defects and blemishes can be observed manually or detected by electronic devices using line scan cameras or laser cameras to identify blemish and defects and determine which are within or outside of grade by reference to pre programmed parameters pertaining to the specification required for any specific product as defined by regulation, producer or customer preference.

Moisture content can be monitored to enable lamina that falls outside the prescribed range to be identified for ejection and reprocessing.

12. Cross cutting is where the feedstock is fed through a saw capable of cutting long lengths of lumber into shook of various specifications as assessed by the machine stress grading, defect and blemish identification and moisture monitoring.

13. Sawdust is generated by the cross cut saw.

14. Sort shook is where shook has been generated at the cross cut saw according to criteria established by machine stress rating, visual defect scanning and moisture content monitoring. Shook (short lengths) will be specific to various products differentiated by prescribed grades, including; arising shook, (that to be applied to non target products including rejects which might be chipped) and to the target product in this instance"dodai".

15. The dodai shook will be that which conforms to the specifications for a specified finished product as required under JAS 601 in addition to those defined by the manufacturer or customer.

16. Core shook is a subset of the"dodai shook"and is classified as being suited for use in other than the outer lamina. (Caution should be exercised here since JAS 601 stipulates that where three or less lamina (plys) are combined in a laminated product, the manufacturer can not differentiate between the grade of lamina in the outer or core. (Where there are greater than three lamina in the element, this restriction lapses.)) Despite this it is

prudent to sort shook with cosmetically unattractive blemish or defects (that are within the acceptable parameters) into the core lamina where they do not detract from the appearance of the finished product.

17. Core shook will be fingerjointed in purpose built equipment that is established and operated in accordance with the plant JAS 601 Certification. In this process, fingers of a prescribed minimum length (JAS 601) are cut into each end of each shook. Adhesive, which normally comprises a two pot (resin and hardener) solution of a (JAS 601) prescribed type (eg, Malemine Urea Formaldehyde, or Phenol Resorcinol Formaldehyde) where the two ingredients (if applicable) are mixed in a prescribed ratio, immediately prior to use, is applied to the fingers prior to the shook being assembled longitudinally, so the fingers are mated. Following this the joints are compressed into a continuous longitudinal ribbon of lamina which is cross cut to prescribed lengths. Some wood fibre is lost in this process as the fingers are cut etc which is not described in this schematic.

18. Cure joint is where the adhesive used in the fingerjointing process is cured.

This can be achieved by leaving the lamina for a specific time at a temperature greater than the minimum at which cure for a specific glue type is effected. The cure time is capable of being accelerated by elevating the temperature of the wood and or adhesive in the region of the fingerjoint.

This can be achieved by use of radiant or conductive heat or use of microwave or radio frequency curing tunnels. Where micro wave curing is used a conductive compound must be added to adhesive to facilitate absorption of the heat energy.

19. Vacuum pressure treat LOSP/DDAC is where batches of lamina selected for use in the core, have been surfaced and proof graded are subject to preservation treatment in accordance with JIS 9108. Under this process the batches of lamina are placed in a purpose built enclave that has been approved for use by the Japanese Plywood Inspection Corporation (JPIC) (which culminates in the plant being granted"AQ"certification). In addition the plant must comply with the Human and Environmental Regulations pertaining to its establishment and use in the Country in which it is located. After placement in the enclave, the enclave is sealed. The ensuing

process of drawing a vacuum, flooding the enclave, pressurising the fluid, draining the enclave, drawing a final vacuum is performed in accordance with the AQ Certificate prescribing the use of the plant. The fluid used in this process is to be a mixture of didesyldimethyl ammonium chloride (DDAC) as defined in JIS 9018 (or other approved non-metallic preservative) mixed in a solution, of controlled concentration, with a non aqueous compound (typically, white spirits) as approved by the AQ plant certification.

After treating the lamina is removed from the enclave and stored in a dry environment while any residual solvent vaporises. The concentration of DDAC in the treating solution is to be such that the retention of compound in the lamina after treating is in accordance with JIS 9108, JIS 9002 or any other relevant regulation pertaining to this process.

20. All lamina, surface two faces, is where the fingerjointed lengths of lamina are fed longitudinally through a surfacing machine to produce a calibrated smooth surface on at least the two faces. (The two edges could also be surfaced, but this is not critical to the process). Shavings are generated as a by product of this process, not shown in the schematic.

21. Proof grade core lamina is where the lamina having been surfaced two faces is fed through a purpose built proof grader, installed and operated in accordance with the plant JAS 601 Certification. The equipment, typically, comprises a set of spaced rollers where a specified (JAS 601) load is applied to the lumber to induce deflection. Where the mechanical properties of the lamina will support this load the lamina is deemed to have passed the proof grading. (As an alternative, the proof grading process could be applied to the cured finger jointed lamina prior to it being surfaced two faces, so that lamina that fails can be reprocessed. Further, where this process is close coupled so that freshly (for example, radio frequency) cured fingerjoints are subject to proof grading, the load applied while grading can be decreased to recognise the degree of glue care on the fingerjoint at the time of proof grading).

22. Reject lamina is that which fails to withstand the load applied during proof grading. Where failure occurs the product is automatically paint marked to identify failure to facilitate manual rejection from the batch.

23. Assemble for laminating is where the now impregnated core lamina is brought into line as part for the ensuing laminating process.

24. Apply adhesive is where a mix of the adhesive (as described in function 25, 26,27) prescribed in JAS 601 as being suited for use in the specific product being laminated is applied to one or more of the surfaces of the core lamina prior to it being compiled with outer lamina in readiness for pressing. The rate of spread typically measured in grams of mixed adhesive per square meter of surface to which it is applied) is regulated and controlled.

25. Adhesive is the resin component of what is typically a two pot adhesive as prescribed in JAS 601 as being suited for use in the specific product.

26. Mix adhesive is where measured proportions of resin (25) and appropriate hardener (27) are mixed prior to application on the surface of the lamina by glue extruder, Curtin coater roller spreader or other glue applicator.

27. No function 28. Outer shook is where shook designated as being within the specification required for outer lamina are assembled prior to fingerjointing.

29. Finger joint outer lamina is where shook is fingerjointed as described in process 17.

30. Cure joint is where fingerjointed outer lamina has the adhesive cured as described in process 18.

31. Outer lamina is where the lengths of fingerjointed cured outer lamina have not less than their two faces thickness as described in process 20.

32. Proof grade outer lamina is where the lamina are subject to a bending test as described in process 32. Where lamina designated for use as outer lamina fail this test, they would automatically be identified for removal from the process and accumulated as reject as for process 22.

33. Assemble for laminating is where the proof graded surfaced outer lamina are placed in line in preparation for the ensuing lamination process.

34. Apply adhesive is as for process 24 where adhesive is applied to one of the two faces of each piece of lamina in readiness for compiling and pressing.

35. Compiling is where the successive pieces of outer and core lamina are assembled in the manner appropriate for the laminating configuration prescribed for the specific product.

36. Press, is where the compiled lamina are subject to compression in equipment installed and operated in compliance with the plant JAS 601 Certification. Under this process, pressure is applied to the set or sets of compiled lamina. The equipment can be capable of pressing a set or sets of lamina in a static or continuous mode, where the continuous mode can be by transverse or longitudinal passage through a pressurised zone.

37. Cure is provided during the period the set or sets of lamina remain compressed, at a temperature above the minimum at which any specific adhesive will cure, as defined by the adhesive manufacturer. As most adhesives are thermo setting the length of cure time is a function of temperature at the surface of the lamina adjacent to the glue line. Cure time can thus be accelerated by preheating the lamina before pressing, by radiant, conductive or micro wave heating and or heating the set (s) of laminated product while in the press by application of conductive heat and or radio frequency generated energy, where the radio wave conduct through the glue line, made possible by the addition of a conductive compound in the adhesive mix.

38. Cut to length, is where laminated sets of product are cut to length required by the customer. An allowance is made to the lamina length during processing to allow the laminated billet to be trimmed to length. This process may not be specified by the customer, and if required whether it be performed before or after step 39 is immaterial.

39. Surface four sides is where the laminated billet is fed longitudinally through planing equipment to remove a small thickness from each of the four sides of the billet to yield a smooth surfaced uniformed dimensioned product in a finished form. Shavings are generated as a by product of this process (not shown in schematic).

40. Rejects is where pieces of"finished form"product are rejected for non compliance with the JAS 601, manufacturer's or customer's specification.

41. Samples for destructive tests are where a JAS 601 specified minimum number of pieces are removed from the process for testing, where such tests include glue bond performance, modulus of elasticity and modulus of rupture tests.

42. Waste is where rejects and the product of destructive testing are accumulated.

43. Branding is where brand marks as required by relevant Standards (JAS 601, JIS 9108) or AQ Certification must be applied, along with any customer specified brands, including that of the manufacturer or licensed manufacturer.

44. Package is where product in finished dimension is prepared for process 45 and or dispatch.

45. Vacuum pressure treat LOSP/DDAC/Water Repellent is where the packaged product is placed in an enclave as described in process 19 or that of a similar enclave certified for use (JPIC/Howtec/RMA or equivalent) and licensed for use by the licensor to perform this function. The fluid for use in this process will be similar to that described in process 19 except that it will include a water repellent solution that will be impregnated along with the preservative (DDAC or other approved non metallic preservative) and carrier (white spirits or other as approved by JPIC). After completion of this process the now finished product will be stored in a weather proof environment to enable any residual treating fluid to vaporise prior to it being dispatched for use. As an alternative to the water repellent being added to the preservative solution used in process 45, the preservative treated finished product could have a water repellent applied by spraying or dipping providing such application does not increase the moisture content of the finished element.

46. Sample for destructive preservation tests is where treated product is removed to ensure the retention of preservative compound in the finished product is

in compliance with JIS 9201 Qualitative Standards and Testing Methods of Wood Preservatives or other Standards introduced to supersede this Standard.

47. Waste is material that accumulates as a result of destructive testing.

48. Dispatch of finished product is where product made in accordance with relevant Standards and conditions imposed by the manufacturer, or his licensee or the customer, in plant (s) Certifie for use by the relevant regulatory authorities are made available to customers.

49. No process 50. No process 51. No process 52. Bark is the bark from the trees generated as a by product of processing log into sawn lumber.

LOSP is Light Organic Solvent Process. This is a recognised process whereby a variety of preservative compounds are infused into wood product having being mixed with light organic solvents, which do not cause swelling of wood and which after evaporation, (normally at ambient temperatures) do not cause the moisture content of the kiln dried lumber to rise above the maximum permitted level, as is the case where water borne treating compounds are used.

INDUSTRIAL APPLICATION It is believed that a process in accordance with the present invention will find acceptance in the building industry as both an effective and economical method of preparing a fully-preservative treated timber laminate.

Although the invention has been described with reference to a particular embodiment, those persons skilled in the art will appreciate that various alterations and modifications can be made, and that the invention is limited only by the lawful scope of the appended claims.