SE459647B - SET TO IMPREGNATE COUNTRY TREE WITH METAL SALTS - Google Patents

Description

459 647 10 15 20 25 30 35 l Y 1 s I i I I | 2 primarily as a satisfactory surface treatment, although a certain penetration is observed. Another pressure-free technique is the diffusion process with undried wood. The author suggests that the process requires a long treatment time due to low diffusion rates.

Although the literature on such treatment of wood is extensive and covers a period of at least 100 years, most of the procedures described for treating wood with preservatives and resin components, including pressure treatments, do not result in extensive uniform impregnation of the material. into the heart of the wood and / or the procedures require a long time to effect the penetration. The problem is particularly pronounced in the treatment of certain types of raw or incompletely dried wood, such as soft pine.

The use of liquid aromatic hydrocarbons to produce impregnation solutions gives the wood a strong odor and gives it a surface that is oily and difficult to paint.

In addition, liquid aromatic hydrocarbons are flammable materials, which require special handling and safety regulations, which increases the cost of wood treatment.

Wood treated with organic preservatives dissolved in petroleum distillate has the same disadvantages as wood treated with aromatic hydrocarbons. The use of low-boiling petroleum distillates, such as mineral spirits, as a solvent fails to eliminate the disadvantages completely. Prolonged air drying as a finishing treatment is often required to allow sufficient evaporation of the solvent if the wood is to be painted. During this air drying period, part of the preservative can migrate to the surface of the wood with the solvent and thus the retention of the preservative in the wood is reduced during what was the intention of the treatment.

A technique for utilizing aqueous systems with polyhalophenols is described in U.S. Patent 4,090,000. The method briefly involves the use of an aqueous solution containing a water-soluble salt of the polyhalophenol and an acid-forming material which may undergo a reaction in the solution to release an acid which displaces the polyhalophenol from the salt after the solution has been impregnated into the wood.

Regardless of the impregnation solution used, the most common commercial method of wood impregnation involves exposing the wood to the preservative under relatively high pressure, such as 1034-1379 kPa (150-200 psi) for a significant period of time, such as 1-24 hours.

The process may also require relatively high temperatures, such as from about 75 ° C to 90-95 ° C. Although an increase in pressure tends to increase the amount of preservative absorbed by the wood, it can make the penetration irregular or uneven. In addition, the application of pressure can cause compaction of the outer layer of the wood, especially after the wood has been weakened and softened by steam heating. Collapse of the wood cells tends to occur, especially when relatively soft, low density dry wood is treated. Upon collapse of the wood cells in an area, a relatively impermeable layer is formed, which restricts or even completely blocks the flow of preservative to the interior of the wood.

It has also been proposed to improve the pressure treatment method by first subjecting the wood to vacuum treatment. Examples of patents describing methods of wood impregnation using negative pressure followed by pressure treatment include U.S. Patents 2,668,779, 3,200,003 and 3,968,276.

U.S. Patent No. 3,677,805 discloses a modification of the printing treatment. In this method, the wood is immersed in a treatment liquid inside a pressure vessel and the pressure is increased to working pressure, whereupon the contents of the vessel are exposed to the action of a pulsating pump, which generates sinusoidal pressure pulses inside the vessel. In other words, the pressure pulses are applied repeatedly with modulated amplitude 459 647 10 15 20 25 30 35 4 to generate variable pressure peaks above and below the ambient pressure maintained in the pressure vessel. This method requires equipment, which includes a pulsating pump, which operates into a pressure carrier medium equipped with pressure release means.

The previous technique described above represents a small selection of the proposals that have been made for treating wood with preservatives to prevent rot. Despite these many suggestions in the prior art, there continues to be a need for a cheap, safe, non-toxic treatment, which is effective and which results in uniform penetration of preservatives and other chemicals into the core of the wood.

SUMMARY OF THE INVENTION Improved wood preservation using a process which does not require special and expensive equipment and which results in good penetration of the treatment chemicals into the wood is described. More particularly, in accordance with the present invention, a process for impregnating undried and raw wood with metal salts is described. This method comprises (a) contacting the raw wood with an aqueous system comprising (i) water, (ii) at least one oil-soluble metal salt, and (iii) at least one surfactant, for a period of time sufficient to to enable the metal salt to penetrate the wood, and (b) the wood is removed from contact with the aqueous system. Preferred metal salts are acidic, neutral or basic metal salts of organic carboxylic acids. In general, the aqueous mixture contains less than 20% of hydrocarbon solvent and may contain optional and desirable ingredients, such as flame retardants, colorants and insecticides. The process may be carried out under vacuum, at atmospheric pressure or at elevated pressure. DESCRIPTION OF PREFERRED EMBODIMENTS It has now been found that good penetration of desired treatment chemicals into raw or undried wood is obtained by the process of the invention, which does not require unusual or expensive equipment.

In accordance with the present invention, undried or raw wood can be impregnated with metal salts, which, preferably, act as fungicides when incorporated into the wood. The process of the present invention involves an aqueous system, thereby reducing, if not eliminating, the problems of many known processes based on organic solvents, which are flammable and often toxic. As mentioned above, the method of the present invention is further applicable to undried and straight wood. Accordingly, the method of the invention eliminates the need for expensive and time consuming drying and / or storage processes.

The aqueous system used in the process of the invention comprises (i) water, (ii) at least one oil-soluble metal salt, and (iii) at least one surfactant.

The aqueous systems comprise from about 50% to about 98% water and more particularly from about 67% to about 83% water.

The other essential component of the aqueous systems used in the present invention is at least one oil-soluble metal salt. The oil solubility of the metal salt according to the invention is believed to contribute greatly to the advantageous and desirable results obtained. Since the organic compound is oil-soluble and substantially hydrophobic, it has no tendency to be extracted or leached from the treated wood even for prolonged periods of time. .

Particularly preferred types of oil-soluble metal salts useful in the aqueous systems of the present invention are acidic, neutral and basic salts of organic carboxylic acids. These salts are known in the art as 'soaps'.

The choice of metal in the salts depends on the properties that it is desirable to impart to the wood being treated, as well as availability, cost and efficiency. Some metals are more commonly used in the process of the invention and these include copper, zinc, chromium, iron, antimony, lead and mercury. Salts containing a mixture of ions of two or more of these metals may also be used.

As mentioned, the salts may be acidic, neutral or basic. The acidic salts contain insufficient metal cation to neutralize the acid. The neutral salts contain a just sufficient amount of metal cation to neutralize the acidic groups present in the salt anion. The basic salts contain an excess of metal cation and are often referred to as overbased, hyperbasic or superbasic salts. These acidic, basic and neutral salts are preferably salts of oil-soluble organic carboxylic acids and mixtures of such acids. The carboxylic acids from which suitable acidic, neutral and basic salts can be prepared include aliphatic, cycloaliphatic and aromatic mono- and poly-basic carboxylic acids. The organic carboxylic acids may be either natural or synthetic or mixtures thereof. Examples of natural acids, although usually refined, include straight chain and branched carboxylic acids and mixtures such as tall oil acids and cyclic carboxylic acids such as naphthenic acids.

A variety of synthetic carboxylic acids, and in particular aliphatic carboxylic acids or mixtures thereof, are useful and generally contain 6 or more carbon atoms.

The metal salts or soaps can be prepared by fusing or precipitating methods. The soaps are normally prepared in an inert liquid medium, such as a hydrocarbon oil or a solvent. The organic carboxylic acids generally have at least 6 carbon atoms and as many as 30 carbon atoms, but when more than one carboxylic acid is used, carboxylic acids containing as few as 2 carbon atoms can be used as one of the acids of the mixture. Examples of useful organic carboxylic acids include acetic acid, propionic acid, butyric acid, isoP% nanoic acid, hexanoic acid, 2-ethylbutyric acid, nonyl acid, decanoic acid, 2-ethylhexanoic acid, isooctanoic acid, isononanoic acid, neodecanoic acid, lauric acid, lauric acid, lauric acid naphthenic acid, as well as commercially available mixtures of two or more carboxylic acids, such as naphthenic acid, tall oil acids, resin acids, etc.

Examples of acid salts are acid copper salts, which contain less than one stoichiometric equivalent of copper per acid equivalent. For metals other than copper, the basic salts or soaps are preferred, as these contain higher amounts of metal. For example, solutions of normal zinc salts of monocarboxylic acids, such as neodecanoic acid, contain about 6% zinc, while a solution of a basic zinc neodecanoate may contain up to about 16% or more zinc.

Basic metal salts or soaps of carboxylic acids can also be prepared by methods well known in the art. Examples of neutral and basic salts and metal salt complexes and their preparation are found in, for example, U.S. Pat. Nos. 2,251,798, 2,955,949, 3,723,152 and 3,941,606, which are incorporated herein by reference.

Some of the basic salts have been called complex, as they are not simple salts. For example, the basic compositions described in U.S. Patent No. 3,941,606 are referred to as "metal carboxylate-alkoxy alcoholate" complexes.

In the context of the present invention, such basic complexes are incorporated into the term metal salts or soaps, as such term is used in the present specification and claims. Specific examples of the salts or soaps useful in the process of the invention include those described in Table 1 and the following specific examples. in- TABLE 1 Carboxylate metal salts Component Metal Metal content (%) §! 5a Bl g Cu 16 neodecanoic acid B-2 Cu 11 neodecanoic acid B-3 Cu 6 naphthenic acid B-4 Zn 18 2-ethylhexanoic acid B-5 Zn 8 naphthenic acid B-6 Zn 10 mixture of ° s' ° 1s Preparation of the metal salts described above is illustrated by the following examples.

EXAMPLE B1 A mixture of 260 parts of neodecanoic acid, 103 parts of propionic acid, 400 parts of mineral spirits, 172 parts of copper powder, 91 parts of Methyl Cellosolve, 14 parts of dipropylene glycol, 70 parts of water, 10 parts of octyl-phenoxypolyethoxyethanol (Triton X-15 from Rohm a Haas Company) and 3 ael santoflex-77, are prepared and bubbled through with air under heating to a temperature of about 80 ° C. The reaction is continued under these conditions for about 6 hours. A small amount of boric acid (7 parts) was added and heating was continued at 80 ° C with air bubbling. The reaction was continued at this temperature until 180% acid neutralization was achieved (total 14 hours).

The mixture was heated for a further 2 hours at a temperature of about 150 ° C to 190% acid neutralization.

The air purge was terminated and an inert nitrogen atmosphere was used while the mixture was slowly heated to about 150 ° C over a period of 8 hours while removing excess water. _ _ __ »íí __._. »- 10 15 20 25 30 35 459 647 9 Four approximately equal parts of amyl phosphate, which made up a total of 176 parts, were added at 3 hour intervals while maintaining a temperature of about 145 ° C and a nitrogen atmosphere. The mixture was then cooled to 125 ° C, allowed to settle to remove excess copper, and filtered.

The filtered product can be heated under vacuum to a temperature of about 150 ° C to remove mineral spirits to give the desired metal concentration.

The remaining component examples B-2 to B-6 in Table 1 can be prepared according to methods similar to those described above for B-1 or by alternative methods known in the art.

EXAMPLE B-7 A mixture of 840 parts of distilled naphthenic acid, 176 parts of 2-ethylhexanoic acid, 512 parts of mineral spirits, 48 parts of Carbitol (a diethylene glycol ether, which is commercially available from Union Carbide Corp.), 4.8 parts of acetic acid, 1, 6 parts of water and 10.9 parts of an antifoam agent were charged to a reactor and the mixture was heated with stirring to a temperature of about 65 ° C.

The mixture was bubbled with carbon dioxide and 214.4 parts of zinc oxide were added to the mixture, which was then heated to a temperature of about 10 ° C. The reaction was continued at this temperature while periodic checks were made with respect to the percentage of zinc, the acid number and the percentage of water. If necessary, the acid number was adjusted to minus 33 to minus 38 for 10% zinc.

If the water content was above 0.4%, the mixture was dehydrated.

About 100 parts of filter aid were added with stirring to the mixture, which was then filtered. The filtrate was a clear liquid, which was adjusted to a zinc content of 1% using mineral spirits.

Carboxylate metal salts of the type described above are commercially available, such as from Mooney Chemicals, Inc., Cleveland, Ohio, 44113 under the general trade names TEN-CEM, CEM-ALL, NAP-ALL, HEX -CEM, LIN-ALL and.NEO-NAP. These mineral spirits can be adapted for use in preparing aqueous systems in accordance with the present invention by adjusting the mineral turpentine content (generally reducing the amount of mineral spirits) and mixing the mineral spirits with water and surfactants, as described below.

Water-dispersible solutions / dispersions of metal salts are also available from Mooney Chemicals, Inc., under the trademark HYDRO-NAF. The metal content of these salts also varies from about 4% to about 10%, but these solutions / dispersions already contain the desired surfactants and can be easily mixed with water to form the desired aqueous systems. Mixtures of carboxylic acid salts, such as those described in Table 1, are readily prepared and used in accordance with the invention.

Thus, for example, a mixture is prepared in accordance with the invention from equal parts of components B1 and B-6, which results in a mixture containing 8% copper and Q% zinc. A mixture of 2 parts of component B1 with 1 part of component B-6 contains 10.7% copper and 3.3% zinc.

Examples of other neutral and basic salts include lead naphthenate, lead neodecanoate, lead 2-ethylhexoate, lead tallate, zinc tallate, chromium-2-ethylheoate, chromium tallate, chromoleate, antimony octoate, antimonoleate, ferrous naphthenate, iron quicksilverolate, phenyl ether, phenyl ether.

In addition to the metal salts and soaps described above, the aqueous systems used in the process of the invention also contain at least one surfactant. Preferably, the surfactants are anionic or nonionic surfactants. Many such surfactants are known in the art. See, e.g., McCutcheon's "Detergents and Emulsifiers", 1979, North American Edition, published by McCutcheon's Division, MC Publishing 10 15 20 25 30 35 459 647 ll Corporation, Glen Rock, New Jersey, USA, especially pages 15-20, hereby referred.

In general, the nonionic surfactants, such as those containing ether linkages, are particularly useful. Examples of such ether-containing surfactants are those I of the general formula n1 - o - Hcazyn fl x fl where R1 is an aryl or alkyl group containing from about 6 to 20 carbon atoms, n is 2 or 3 and x is an integer between 2 and 100. Such surfactants are generally prepared by treating fatty alcohols or alkyl-substituted phenols with excess ethylene oxide or propylene oxide. The alkyl carbon chain may contain about 14-24 carbon atoms and may be derived from a long chain fatty alcohol, such as oleyl alcohol or stearyl alcohol.

Nonionic polyoxyethylene compounds of this type are described in U.S. Pat. No. 3,855,085. Such polyoxyethylene compounds are commercially available under the general trade name "Surfynol" from Air Products and Chemicals, Inc., Allentown, Pennsylvania, and under the name "Pluronic" or "Tetronic". "from BASF Wyandotte Corp., Wyandotte, Michigan. Examples of particular polyoxyethylene condensation products include" Surfynol 465 ", which is a product obtained by reacting about 10 moles of ethylene oxide with 1 mole of tetramethyldecyndiol. "Surfynol 485" is the product obtained by reacting 30 moles of ethylene oxide with tetramethyldecyndiol. "Pluronic L 35" is a product obtained by reacting 22 moles of ethylene oxide with polypropylene glycol, obtained by condensing 16 moles of propylene oxide. Atlox 1045A from ICI America, Inc., which is a polyoxyalkylene sorbitol oleate laurate blend, is also useful.

Amine-type, long-chain fatty amine-type, long-chain fatty acid-type, alkanolamine-type, diamine-type, amide-type, alkanolamide-type, and polycholine-type surfactants are also known in the art. One type that has been found to be particularly useful is the group obtained by adding a mixture of propylene oxide and ethylene oxide to diamines. More specifically, compounds formed by the addition of propylene oxide to ethylenediamine followed by the addition of ethylene oxide are useful and are commercially available from BASF Wyandotte Inc.

Chemical Group under the general trade name 'Tetronic'.

Carbowax-type wetting agents, which are polyethylene glycols with different molecular weights, have been found to give good results.

For example, Carbowax No 1000 has a molecular weight range from about 950 to 1050 and contains from 20 to 24 ethoxy units per molecule. Carbowax No. 4000 has a molecular weight range from about 3000 to 3700 and contains from 68 to 85 ethoxy units per molecule. Other known nonionic glycol derivatives, such as polyalkylene glycol ethers and methocipolyethylene glycols, which are commercially available can be used as surfactants in the compositions of the invention.

Anionic surfactants are also useful in the aqueous systems of the invention. Among the useful anionic surfactants are the well-known metal carboxylate soaps, organosulfates, sulfonates, sulfocarboxylic acids and their salts, and phosphates. Various anionic surfactants are commercially readily available and further information on anionic surfactants can be found in the text "Anionic Surfactants" Part II and III, compiled by WM Linfield, published by Marcel Dekker, Inc., New York, 1976. Examples of Anionic Surfactants agents available from ICI America, Inc. include Atlas G-2205, which is an aromatic phosphate, and Atlas G-3300, which is an alkylarylsulfonate. Examples of anionic surfactants available from Rohm and Haas Company, includes Triton 770, which is a sodium salt of an alkylaryl polyether sulfate, Triton GR-SM, which is a dioctyl sodium sulfate sulfate, 459 647 13 succinate, Triton K-55, which is a potassium salt of a phosphate surfactant, Triton W-30 and Triton X-200, which are sodium salts of alkylaryl polyether sulfonates, etc.

Mixtures of the nonionic and anionic surfactants can and are widely used in the aqueous systems of the present invention. The amount of surfactant present in the aqueous mixture can vary over a wide range, but is generally from 0.25% to about 7.5% and more preferably between 1% and 5%.

The aqueous systems of the present invention generally contain at least about 67% water and less than about 20% hydrocarbon solvent. Preferably, the amount of hydrocarbon solvent present in the aqueous mixture is maintained at a minimum and is generally less than about 15% of the aqueous system. The metal content of the aqueous systems can vary from about 0.2 to about 10% by weight.

The aqueous systems of the present invention can be prepared by mixing the metal salt and the surfactants with sufficient water. to achieve the desired levels of the constituents.

Alternatively and more preferably, the aqueous systems are prepared from water-dispersible additive concentrates which contain the desired metal salt, one or more surfactants and a hydrocarbon solvent. As mentioned above, such additive concentrates are commercially available, for example, from Mooney Chemicals, Inc. under the general tradename HYDRO-NAP. In addition, such water-dispersible additive concentrates can be prepared from commercially available solutions of metal salts and mineral spirits and by mixing the mineral turpentine solutions with the desired surfactants with or without additional hydrocarbon solvents, such as mineral oils.

A water dispersant resin additive concentrate can be prepared, for example, from the metal salt solutions of mineral turpentine, as illustrated above as Examples B-1 to B17, by thoroughly mixing the mineral turpentine solutions with mineral oil and surfactants. A specific example of such a process is mixing 800 parts of the product of Example B-7 with 100 parts of mineral oil, 75 parts of W Atlas G-3300 and 25 parts of Atlox-1045A. Corresponding water-dispersible additive concentrates can be prepared from compositions identified as B-1 to B-7 using the same or other surfactants.

The water-dispersible additive concentrates of the types described above can be converted into the aqueous systems used in the invention by dilution with water. This dilution is usually accomplished by standard mixing procedures. It offers a convenient method, as the additive concentrate can be shipped to the place of use before the water is added, thereby reducing the shipping cost.

The aqueous systems of the present invention may also contain other additives which impart desirable properties to the treated wood.

Thus, for example, the aqueous systems of the invention may contain (v) flame retardant compositions, (vi) colorants, (vii) insecticides and (viii) fragrances.

In general, these additives can be incorporated into the aqueous systems of the invention in the dispersed phase or dissolved in the water. The amount of such additives incorporated into the aqueous systems of the invention can vary within a fairly wide range, although amounts of from about 0.5 to about 5% of these compositions are generally satisfactory.

Inorganic flame retardant compositions are particularly useful in the aqueous systems of the invention. Examples of inorganic materials include diammonium phosphate, monoammonium phosphate, ammonium chloride, ammonium sulfate, borax and zinc chloride. Examples of organic flame retardants include a number of halogenated compounds and organophosphorus compounds, which may either be dispersed in the aqueous systems, as mentioned above, or solubilized by forming water-soluble salts. or solutions of the flame retardants which can then be mixed with the water-dispersible additive concentrates or the aqueous systems of the invention. For example, ammonium salts of organophosphorus compounds can be used in the aqueous systems of the invention. Examples include, in particular, ammonium salts of bis-dibromopropyl phosphate, diethyl phosphate, bis- (beta-chloroethyl) phosphate, bis (1,3-dichloropropyl) phosphate, etc. Other water-soluble organic flame retardants include aliphatic carboxylic acids containing more than 50% organically bound bromine, alkyl sulfamates, ammonium alkyl phosphates, antimony trichloride with tertiary amines such as ethanolamines, urea with ammonium phosphate and urea with sulfamic acid.

Although the various types of wood which can be treated in accordance with the method of the present invention generally have a satisfactory appearance for most purposes, the appearance can be modified if desired by imparting different color effects. The present invention involves the incorporation into the aqueous systems of coloring agents which are either soluble or dispersible in the aqueous systems of the invention. Any of the known oil-soluble, water-soluble or water-dispersible colorants can be used. These agents are mixed with either the water-dispersible additive concentrates of metal salts described above, or the aqueous systems, and when the wood is immersed in the aqueous systems of the invention containing coloring agents, the coloring agents penetrate the wood, the metal salts giving desirable color effects. many cases emphasize the grain of the wood. Examples of colorants that can be used depending on the desired result include: Bruco Creosote Brown RGY, available from Bruce Chemical Co., Iron Cem-All, available from Mooney Chemical Inc., and 459 647, 10 15 20 25 30 35 ~ Dow Chemical and Ficam 76 WP, -by brush ironing, spraying, 16 Pylaklor Red Brown LX-6249, Pylam Dye Co.

Insecticides can also be incorporated into the aqueous systems of the invention, and it is preferred that the insecticide be either soluble in oil, water or readily dispersible in water. Examples of such insecticides include Dursban TC, which is available from which is available from which is available from BFC Chemicals Inc.

Fragrances can be incorporated into the aqueous systems of the invention and a preferred fragrance is pine oil. Other water-soluble or dispersible compounds, which have the desired odor, can be incorporated into the aqueous systems.

The method of the invention involves contacting the raw wood with the aqueous systems for a sufficient time to allow the desired amount of metal salt to enter the wood. Contact between the wood and the aqueous system can be achieved by painting, immersion, etc. One of the surprising features and advantages of the present invention is that excellent results have been obtained when the raw wood is immersed in aqueous systems containing as little as 2% metal in as little as 5-10 minutes. In addition, subsequent analysis of the raw wood treated in accordance with this procedure reveals an excellent metal salt uptake with extremely good penetration of the metal salt into the wood. in a method of the present invention, the aqueous system in which the raw wood is immersed can be maintained at a temperature of from about 5 to about 9S ° C at atmospheric pressure. However, the method according to the invention can be carried out and is also preferably carried out at ambient temperature, thereby eliminating the need for equipment or materials for heating or cooling the aqueous systems. In some cases it may be advantageous to heat the aqueous systems to an elevated temperature to increase the rate of penetration.

As mentioned above, the wood is removed from contact with the aqueous system after the raw wood has been brought into contact with the aqueous systems of the invention for the desired period of time. The raw wood thus treated is ready for shipment, although in some cases it may be desirable to allow the wood to dry * at least in part before shipment.

It is surprising that desirable results can be obtained with such short contact times between the wood and the aqueous systems. It is believed that the aqueous systems used in the invention deposit the desired amount of material on and in the outer layers of the wood during the short contact to achieve the desired results even though the metal salts and other additives have not completed the penetration process into the wood.

After the treated logs have been removed from the aqueous system, the salts and other additives continue to penetrate the wood while the wood is being stored or transported. Accordingly, the invention provides a method of treating wood which not only uses inexpensive equipment (such as a large open tank), but in which the wood to be treated is in the equipment for a short time.

The method according to the invention can also be performed on wood, which is housed in a closed vessel under vacuum or pressure, or a combination thereof. The use of pressure to improve the penetration of various chemicals into all types of wood is well known in the art. In this technique, the raw wood is placed in a chamber, which is closed and evacuated in a regulated cycle, which is related to and determined with respect to the type of wood. In general, the evacuation period varies from about 15 minutes to 1 hour and the pressure in the closed chamber is brought to a level of about 5 cm Hg or less. The purpose of this step 459 647 10 15 20 25 30 35 1 l8 is to remove air and volatiles from the wood. The dilute aqueous systems of the invention. then inserted into the closed container and the amount of composition should be sufficient to completely immerse the wood; The pressurization of the vessel is then initiated and the pressure is maintained at a desired level for a given period of time. Initially, the pressure in the vessel drops when the aqueous system in the container penetrates the vessel. The pressure can be raised to maintain a desired level during the penetration period of the treatment.

Stabilization of the pressure in the vessel is an indication that there is no longer any penetration of liquid into the wood. At this point, the pressure can be released, the vessel emptied and the wood removed. The details of the printing process, including pressure ranges, concentration of aqueous composition and the cycle of vacuum and pressure with respect to particular types of wood can be readily determined by those skilled in the art from the following examples and also by following the method of the invention for the particular type of wood. the process parameters to achieve optimal results. Thus, for example, the pressures used in the pressure method described above can be as high as zosa kva (zoo psig) and are generally from about 345-1724 kPa (50-250 psig).

The method according to the invention can be performed on a large number of different types of wood. The actual contact time between the raw wood and the aqueous systems according to the invention varies depending on the amount of metal salt to be introduced into the wood and the difficulty of penetration into the different types of wood. Examples of woods that can be treated in accordance with the process of the invention include Western Red Cedar, Douglas fir, spruce, sugar maple, ash, walnut, cherry, white pine, red pine, birch, red oak, elm, hickory and linden. True wood is generally defined in the industry as wood containing 30% by weight or more of water, based on absolutely dry wood. 10 15 20 25 30 35 459 64.7 19 The following is a specific example of the process according to the invention carried out at atmospheric pressure in an open tank.

EXAMPLE A Stocks (debarked) were immersed in an aqueous system prepared by diluting Zinc Hydro-Nap (trademark), available from Mooney Chemicals, Inc., containing 8% zinc as zinc naphthenate, with water and stirring to provide an aqueous system containing about 2.67% zinc. The aqueous system was kept at ambient temperature and the logs were immersed in the aqueous system for about 6 minutes. The sticks were then removed from the aqueous system and allowed to drip dry. Examination of the logs treated in accordance with this procedure showed good zinc uptake and retention. Subsequent examination of the logs, which were treated in accordance with this procedure, also showed excellent penetration of the zinc salt into the logs, and there was no appreciable change in the original dimensions and surface texture of the wood. The metal salts that had penetrated the logs showed resistance to leaching with water.

The following are particular examples of the process according to the invention carried out at elevated pressure in a closed vessel.

EXAMPLE B Raw Norwegian logs were pressure treated with an aqueous system prepared by diluting Zinc Hydro-Nap (Mooney Chemicals), which contained 8% zinc as zinc naphthenate, with enough water to produce an aqueous system containing about 0.57%. zinc. The logs were immersed in the system in a closed pressure vessel. The pressure treatment was carried out at a maximum pressure of 1860 kPa (270 psig) for a total pressurization time of about 1 hour. The logs were then removed from the vessel and allowed to drip dry. The logs treated in this way contained zinc, which showed good retention properties. f. TW 459 647 EXAMPLE C The procedure of Example B was repeated, except that the dilute aqueous system contained 0.39% zinc and zinc naphthenate and that the maximum pressure was 2068 kPa (300 psig) for a treatment period of about 2 hours. was about 38%.

Claims (3)

10 15 20 459 647 21 PATENT REQUIREMENTS A method of impregnating raw wood with metal salts, characterized by, (a) contacting the raw wood with an aqueous system, comprising (i) water, (ii) at least one oil-soluble metal salt of an organic carboxylic acid, ( iii) at least one anionic or non-ionic surfactant or mixtures thereof, (iv) less than 20% of a hydrocarbon solvent and in addition optionally at least one additive from the group consisting of a flame retardant, a coloring agent and an insecticide, during a a period of time sufficient to allow the metal salt to enter the wood, and (b) the wood is removed from contact with the aqueous system. A method according to claim 1, wherein the metal content of the aqueous mixture is about 0.2-10% by weight. 3. A method according to claim 1, wherein the raw wood is immersed in an aqueous k n n e t e c k n a t k ä n n e t e c k n a t system, which is kept at a temperature of about 5-95 ° C.