Patent Publication Number: US-3877979-A

Title: Process of treating wood against stain and decay

Description:
STAIN AND DECAY lnventor: Trevor P. Clark, North Vancouver,  
 British Columbia, Canada C.B.M. Enterprises Ltd., New Westminster, British Columbia, Canada Filed: Sept. 8, 1972 Appl. No.: 287,537  
 Assignee:  
 US. Cl 427/337; 21/7; 106/15 R, 428/541; 428/907; 424/146 Int. Cl 827k 3/00; B44d 1/26; B44d l/44 Field of Search 117/147, 149, 57, 59, 116, 117/148; 21/7; 106/15 R References Cited UNITED STATES PATENTS 5/1939 Carswell 21/7 [451 Apr. 15, 1975 2,209,970 8/1940 Hay 117/147 2,331,268 10/1943 Flenner et a1 3,039,843 6/1962 Chamberlain et a1. 21]? 3,061,508 10/1962 Morriss ,et a1 21/7 3,070,494 12/1962 Goldstein et a1 1 17/147 3,281,318 10/1966 Stutz;... 21/7 3,305,298 2/1967 Chapman ,et a1 117/57 3,473,947 10/1969 Story...., 21/7 3,702,784 1l/1972 Farquahar et a1. 21/7 Primary Examiner-William R. Trenor Attorney, Agent, or Firm-Fetherstonhaugh &amp; Co.  
 [57] ABSTRACT Wood is treated by the application thereto of an aqueous solution of a chlorophenol salt in an emulsion of resin-like material, followed by the application of a solution containing a water soluble metal salt of an organic or inorganic acid.  
 12 Claims, No Drawings PROCESS OF TREATING WOOD AGAINST STAIN AND DECAY This invention relates to processes of treating newly cut wood and similar cellulosic materials in order to protect them against stain, decay, fungi, insect attack and the like.  
  When wood is first cut into boards and the like, it has a fresh, pleasant and natural appearance, but the problem isthat it does not retain this for very long. Many unsuccessful efforts have been made to preserve the freshcut appearance of wood for relatively,v long periods during storage, shipment and varying climatic conditions. The wood is often stored and transported in the open, and it fairly rapidly changes color due to sap stain, decay, mold fungi and insect attack. Another problem results from the fact that the wood is very often wet when cut, and frequently is immediately piled outside for storage. Thus, the wood often and particularly in some areas having a damp climate, is subjected to rain when or soon after it is first put outside.  
  entachlorophenol is known to be a good wood preservative. Pentachlorophenol is soluble in organic solvents and may be applied to wood in various solutions where thepentachlorophenol is soluble in that solution, but is only very slightly soluble by itself in water and, therefore, will be activated by water but will not dissolve in water and wash off the wood when unprotected from the weather. Some eluting of the pentachlorophenol will occur by the physical washing action of water over the wood surface when exposed to the weather.  
  Solutions containing pentachlorophenol are relatively costly due to the cost of the organic solvents used. Also the solvents are flammable and give off a heavy concentration of fumes. For these reasons producers preserving wood produced at the mill level have not used pentachlorophenol in organic solvents, although it has been used when specifications require that wood be treated with a preservative for a particular end use.  
  Manufacturers have been using the salt of pentachlorophenol which is readily soluble in water to treat lumber at .the mill level. Thus water has been the inexpensive carrying agent in treating the huge volumes of lumber being cut by mills in order to maintain the fresh appearance of the wood. The problem has been that since the salt is water soluble it dissolves and is flushed off the wood by rain when left exposed to the weather. Thus the preserving effect exists for only a short time and the lumber is left unprotected from decay and staining.  
  The present invention overcomes or greatly reduces the above problems. it utilizes the inexpensive carrying agent, water, containing the salt of pentachlorophenol. However, by use of a second solution applied to the treated lumber, the water soluble salt of pentachlorophenol is, precipitated out and returned to the crystaline form of pentachlorophenol which is not water soluble. Therefore, rain water, ,does no&#39;t&#39;dilute the crystals of pentachlorophenol &#34;and flush off the wood. By adding resins and the like to the first solution the crystals of pentachlorophenol are sealed to the fibres of the wood and thus retard the physical washing off of the pentachlorophenol from the wood. Because the pentachlorophenol is only very slightly soluble in water, it is immediately active in killing fungi and other microorganisms that attack wood from the time it is stored.  
  An object of the present invention is the provision of processes for preserving wood and similar cellulosic materials either in rough or dressed state, in green or dry condition, against attack by sap stain, decay, mold fungi and other micro-organism in an economical and efficient manner.  
  Another object is the provision of processes of treating wood against stain and decay which is effective when the wood is wet or relatively dry, and which will protect the wood for long periods of exposure to rain and other varying climatic conditions.  
  The process according to the present invention comprises a first stage of applying a first water solution to the wood by spraying, flowing or dipping, said solution having dissolved therein a preservative that will protect the wood against stain, decay, fungi and insect attack. and a binding material adapted to cause the preservative to adhere to the wood fibre, but in such a form that it will readily penetrate into without unduly adhering to the wood along with the dissolved preservative. The second stage of this process is applying by spraying, flowing or dipping, a second solution to the treated wood, which converts the wood preservative to a form in which it is only slightly soluble in water, at which time said binding material acts as an adhesive to bind the converted preservative to the wood fibres. The wood preservative is now distributed within the wood fibres at and below the surface of the wood, is in a form in which it will dissolve only very slowly when subjected to water while performing its wood preserving job, and is secured to the wood fibres by the binding material so that it cannot be washed away by rain or other free flowing water.&#39;Thus, this process overcomes the problems pointed out above. In addition, the water solution of the first stage will carry the preservative and binding material into the wood even when the latter is very wet, and the treated wood can be put outside in the rain immediately after treatment.  
  The process of treating wood according to the present invention includes applying to the surfaces of said wood, a first aqueous solution comprising chlorophenol salt which preferably is an ammonium, morpholine, sodium or potassium salt, in an emulsion of a resin-like material, which preferably is a water resistant adhesive compound, such as rosin, polyvinyl acetate, styrenebutadiene, rubber, synthetic resin, or hydrocarbon resin. Although not absolutely necessary, it is preferable that this is an anionic emulsion. The application of the first solution is followed by applying to the surfaces of the treated wood a second solution which precipitates the chlorophenol as substantially insoluble compounds and the resin-like material within the fibres of the wood, this resin-like material binding the chlorophenol compounds to the fibres to prevent leaching thereof from the wood.  
  The chlorophenol used in the first solution is preferably pentachlorophenol, but it may be tetrachlorophenol, trichlorophenol or chloro ortho phenyl phenol. Ths salts of ammonium, moropholine, sodium and potassium are soluble in water so that they are carried into the fibres of the wood when the solution is applied thereto.  
 The resin-like material is provided for binding purposes, and preferably is rosin, polyvinyl acetate,  
 emulsifiers, such as ammonium, morpholine, or triethanolamine soaps made from oelic or stearic acid or both, although other suitable emulsifiers may be used. The resins or plastic emulsions are miscible in water, but while the solution is in emulsion form, the resins or plastics cannot interfere with the penetration of the chlorophenol salt into the wood fibres and, in fact, the resin or plastic also penetrate the wood.  
  The second solution contains water soluble salts, such as zinc, aluminum, mercury, calcium, magnesium and lead salts. This is preferably a water solution, and the salts are preferably zinc acetate, zinc chloride, zinc sulfate, alum, acetic acid or phosphoric acid. The second solution also penetrates into the wood and mixes with the first solution and the metallic salts convert the saltsof the firstsolution to substantially insoluble salts, such as, for example, zinc chlorophenate. If the second solution contains one of the specified acids, the salt of the first solution is converted to chlorophenol which is in substantially crystalline form and is only very slowly soluble in water. At the same time, the emulsion of the first solution is broken down and the resin-like material precipitates on to and into the wood fibres and acts as a binding material to bind the very slowly soluble chlorophenate or chlorophenol to the fibres so that they cannot be physically washed away by rain or free flowing water.  
  If desired, rosin and some waxes can be used in the form of an ammonium, morpholine or triethanolamine soap in or as the emulsion in the first aqueous solution.  
  It is desirable to add corrosion inhibitors, except when phosphoric acid is used, to prevent corrosion of machinery used for lumber for the spray, flow or dipping equipment. Any compatible corrosion inhibitor can be used such as, for example, morpholine or Magna compounds. A compatible fungicide can also be included in the mixture, such as mercuric chloride. It is preferable to include a compatible antifoam agent, such as a silicone emulsion or other silicone oils. The antifoam material must be emulsified. It is also desirable to add materials that can form water repellents, such as alums or other soluble aluminum salts, or soluble salts of calcium and magnesium. These react with the soaps and will promote water repellancy in the coating remaining on the wood after this treatment.  
  The aqueous first solution and the second solution readily penetrate the wood regardless of whether it is wet or relatively dry. One of the advantages of this process is that no drying time is required to fix the preservative in the wood, since the resin-like material, after the application of the second solution, immediately functions to bind the preservative to the wood fibres, the salt of chlorophenol having been converted to the relatively insoluble chlorophenol or insoluble zinc, aluminum or lead compound. On the other hand, if an interval of drying does take place prior to exposure to water, no harm is done and, in fact, stronger adhesion develops.  
 The zinc chloride when used is in itself a good wood preservative as it reacts with the cellulose to produce a fungicide compound. Silicone-emulsions act not only as antifoam agents, but are water repellants to further retard leaching and reduce checking of the lumber. Wood flour and sawdust contamination in either solution does not adversely affect the solution.  
  The following examples illustrate combinations of chemicals that can be used in the first and second solutions of this process:  
 EXAMPLE I First Solution Water 81 l grams Sodium Pentachlorophenate 13.9 grams Resin Emulsion (T.M. Latex Plasticiser A-l2) 7.5 grams Resin Emulsion (T.M.  
  Piccopale A-ZO Emulsion) l7.5 grams Silicone Emulsion Trace Preparation The sodium pentachlorophenate was dissolved in water in a ratio of 13.9 grams of pentachlorophenate to 81 1 cc of water. 7.5 grams of the first resin emulsion (latex plasticiser A-l2) were added to water solution of the sodium peneachlorophenate. Then 17.5 grams of the second resin emulsion (piccopale A-20) were added to the solution containing the sodium pentachlorophenate and plasticiser A-l2. The antifoam agent was added in small amounts until no foaming was apparent under vigorous stirring.  
 Second Solution Aqueous Zinc Chloride (ZnCI l7r Acetic Acid 0.571 Mercuric Chloride 0.00471 Procedure Tests Samples of dressed hemlock wood measuring X 3 k X 15 inches were used for the test. The moisture content on the outer one-sixteenth inch of the surface of these samples was found to be about 34.6 percent prior to treatment.  
  The first solution was sprayed on to the lumber and followed immediately by the spraying of the second solution. Five minutes after this treatment, a portion of these samples was given a quick, copius rinse with cold water and then placed to air dry for 4 days. The remainder of the samples, 5 minutes after treatment were placed in 2 inch deep trays with the treated face down, and a tap was run into the tray to provide a steady overflow of water for 16 hours. After 16 hours of this water elution, these samples were air dried in the same manner as the other samples. All of the air dried samples as well as a blank control of untreated hemlock, were analyzed for moisture content and for pentachlorophenol content by the NITRIC ACID OXIDATION METHOD FOR DETERMINATION OF&#34; PENTA CHLOROPHENOL&#39;, TETRACI-ILOROPI-IENOL AND THEIR SALTS by Monsanto Canada Ltd. Only the treated area of wood to a depth &#39;of one-eighth. inch was used for analysis. The results of the tests are set out&#39;in the table below which also includes the results of ,Ex-  
 Preparation The sodium pentachlorophenate was dissolved in water.  
 in a ratio of l3.9 grams of pentachlorophenate to 811 c.c of water. 7.5 grams of the first resin emulsion (latex plasticiser A-l 2) were added and mixed with the water solution of sodium pentachlorophenate. 17.5 grams of the second resin emulsion (piccopale A-) were then added to this mixture and stirred well. The antifoam agent was added in small amounts until no foaming was apparent under vigorous stirring.  
 Second Solution l percent Aqueous Phosphoric Acid (H PO solution made by dissolving 12 (2.0. of 85 percent phosphoric acid in 988 cc. of water.  
 The preparation of samples and tests were exactly the same as those of Example I.  
  TEST OF TABLE OF RESULTS No. of Type of Treatment C Test l T.M. Dowicidc G and 29.1 0.064 0.026  
  Resin mixture plus zinc chloride solution 2 TM. Dowicide G and 2l 2 0.035 0.0l4  
 Resin mixture plus phosphoric acid solution &#34;/1 by weight equivalent to sodium pentachlorophenate retained by wood. Calculated as percentage of the amount of sodium pentachlorophenate applied. This basis of calculation is used only as a convenience to relate to the material applied. This applies to B.C.D. following.  
 &#34;/1 by weight equivalent to sodium pentachlorophenate calculated as percentage of dry Vs inch wood layer. Amount retained after brief water wash.  
  7: by weight equivalent to sodium pentachlorophenate retained after l6 hours of water flushing. Calculated as percentage by weight in the Vs inch wood layer. Amount equivalent to sodium pentachlorophenate retained after washing 16 hours. Calculated as percentage by weight of the amount of material originally deposited on the wood.  
 conditions that are normally encountered in storage,  
 transportation, and end use. For example, the preservation treatment of wood eaves troughs may require more concentrated solutions in order to obtain the desired 6 pic &#39;it ctive coatingrwhereas lumber to be stored briefly in a low rainfall area may require less concentratedsolutions to obtain th&#39;desired protection from stain, rot, fungi andmicro organisrns; I I  
  he co&#39;iicehtrationbf&#39;the chlorophenol salts, such as ammonium, morpholine, sodium or potassium salts, can be :fromapproxirn&#39;ately 0.05 percent of the active ingi&#39;edients&#34;to about 10 percent in the first-&#34;solution. The concentration of the resin-like material the er&#39;ntilsion df the first solution ma range from approximately 0.1.IQ about 40 percent The emulsifiers may range froiriabo&#39;ut 0.l&#39; to about percent of the resin solid content in the first solution. The quantities of silicone emulsions may range from about 0.1 to about 3.0 percent of the first solution.  
  The concentration of the chemicals of the second solution can range anywhere from about 0.004 percent up to the point of saturation of each chemical. The minimum concentrations would produce protection for very short periods only. However, it is desirable for economical reasons to use as little of the second solution chemicals as possible, and only sufficient to provide for a desired protection period.  
 What is claimed is:  
  l. The process of treating wood against stain, decay, fungi and insect attack, which comprises applying to the surfaces of wood a first aqueous solution comprising a chlorophenol salt selected from the group consisting of the salts of ammonium, morpholine, sodium and potassium, from about 0.057 to about 10 percent of the active ingredients, in an emulsion of resin-like material selected from the group consisting of rosin, polyvinyl acetate, rubber and hydrocarbon resin in from about 0.1 to about 40 percent concentration of the resin-like material, said emulsion being such as to result in a solution which is normally stable but is unstable when mixed with predetermined salts, said aqueous mixture of chlorophenol salt and resin-like material penetrating the surface fibres of the wood as an emulsion; and applying to the surfaces of said treated wood a second solution containing at least one of such predetermined salts comprising water soluble salt of an organic or inorganic acid in concentration from about 0.004 percent up to saturation and which is such as to immediately precipitate the chlorophenol salt as substantially insoluble compounds and at the same time to break the emulsion and precipitate the resin-like material within the fibres of the wood, said resin-like material binding the chlorophenol compounds to the fibres to prevent leaching thereof from the wood.  
  2. The process as claimed in claim 1 in which said second solution comprises water soluble salts selected from the group consisting of zinc, aluminum, mercury, calcium, magnesium, and lead salts.  
  3. The process as claimed in claim 1 in which said second solution comprises a water solution of chemicals selected from the group consisting of zinc acetate, zinc chloride, zinc sulfate, alum, acetic acid and phosphoric acid.  
  4. The process as claimed in claim 2 in which said second solution comprises a water solution of chemicals selected from the group consisting of zinc acetate, zinc chloride, zinc sulfate, alum, acetic acid and phosphoric acid.  
  5. The process as claimed in claim I in which said chlorophenol is selected from the group consisting of 8 patible antifoam agent in said mixture.  
  10. The process as claimed in claim 1 including an antifoam agent selected from the group consisting of silicone emulsion and silicone oils.  
  1]. The process as claimed in claim 1 including mercuric chloride in said mixture.  
  l2. The process as claimed in claim 1 including a compatible water repellent in said mixture selected from the group consisting of soluble salts of alum, aluminum, calcium and magnesium.  
  M ll