Drug – bio-affecting and body treating compositions – Inorganic active ingredient containing – Phosphorus or phosphorus compound
Reexamination Certificate
2002-06-06
2004-06-22
Pak, John (Department: 1616)
Drug, bio-affecting and body treating compositions
Inorganic active ingredient containing
Phosphorus or phosphorus compound
C424S613000, C424S614000, C424S615000, C424S616000, C424S646000, C424S647000, C424S648000, C424SDIG001, C424SDIG001, C514S184000, C514S185000, C514S186000, C514S188000, C514S372000, C514S373000, C514S502000, C514S574000
Reexamination Certificate
active
06753016
ABSTRACT:
BACKGROUND
The present invention involves the chemical treatment of wood materials. More specifically, the invention involves a method of treating wood materials with iron salts and an oxidant to maintain dimensional stability and surface integrity of the wood material. Optionally, microbicidal and pesticidal agents may be incorporated to control contamination and degradation of the treated materials by microorganisms and pests.
Preservation of wood materials has long been of interest to mankind; however, chemicals that were found to provide the best preservative properties often posed a significant hazard to the environment. Various water-soluble salts have been used to provide wood preservative properties, such as borax, copper and chromium salts, zinc chlorides, mercuric chloride, nickel salts, sodium fluoride and sodium fluorosilicate. These salts offer the advantages of protection against both fungi and insect infestation, ease of handling (due to the ability to transport in solid form), and susceptibility to later treatment with paints or fire retardants.
Unfortunately, wood treated with these types of water-soluble inorganic salts are susceptible to leaching of the preservatives out of the wood with consequent contamination of the surrounding environment, and the treated wood becomes susceptible to microbial or insect attack over time as salt concentration decreases in the treated wood. Chromium salts are relatively resistant to leaching because these salts form complexes with materials in the wood.
Chromated-copper-arsenic (CCA) compositions are used in the conventional treatment of wood products. The arsenic provides protection from insects (such as termites), the copper provides fungicidal activity, and the chromium(VI) species forms stable compounds with the copper and arsenic that are leach resistant. Hence, CCA acts as a preservative and also protects the wood surface from softening when exposed to sun and rain. However, chromium and arsenic salts are highly toxic and any leaching action contaminates the surrounding environment.
Weathering studies of wood surfaces treated with aqueous solutions of chromium trioxide and ferric salts (nitrate, chloride) showed that the iron(III) treatments caused significant weight and strength loss in the treated wood samples compared to conventional chromium(VI) treatment and that treatment of wood with ferric chloride does not have a protective effect: “A Quantitative Weathering Study of Wood Surfaces Modified by Chromium VI and Iron III Compounds,” P. D. Evans and K. J. Schmalzl; Holzforschung, Volume 43, pp 289-292 (1989).
EP 1,034,903 discloses the treatment of wood by impregnation with a mixture of lignin (and/or lignin derivatives) and metal compounds (preferably copper) as an improved method for reducing the leaching of metal components from the treated wood; the reaction products of the lignin (lignin derivatives) and the metal compound are fixed into the wood substrate by macromolecularization or oxidation.
Unlike water-soluble salts, organic chemicals used to treat wood do not tend to leach out of treated lumber to a significant extent over time; however, organic wood preservatives present other problems. Although organic chemical preservatives, such as pentachlorophenol or creosotes, are effective as biocidal agents that prevent infestation by wood-degrading microorganisms and insects, these materials are generally toxic, generate objectionable odors and do not provide satisfactory surface integrity (hardness) to the treated wood.
Most chemicals in use today for wood preservation, whether aqueous or organic, are highly toxic to a broad spectrum of microorganisms. Wood treated with these traditional chemicals, such as CCA or creosote, pose a serious threat to the environment through either leaching or the need for later special disposal procedures.
The present invention seeks to improve upon the prior art wood treatment methods by a providing a treatment that is not toxic to higher organisms, does not leach active ingredient out of impregnated wood materials significantly over time, yet effectively maintains the dimensional stability and surface integrity of the treated wood materials, while preferably also protecting the treated materials from degradation by microorganisms.
STATEMENT OF INVENTION
The present invention provides a method for treatment of wood material comprising (a) contacting wood material with an aqueous treatment solution comprising an iron salt and an oxidant to provide impregnated wood material, and (b) separating the impregnated wood material from the aqueous treatment solution.
In another embodiment the present invention provides the aforementioned method wherein the aqueous treatment solution of step (a) further comprises a 3-isothiazolone selected from one or more of 2-n-octyl-3-isothiazolone and 4,5-dichloro-2-n-octyl-3-isothiazolone.
In a further embodiment the present invention provides a method for microbicidal treatment of wood material comprising (a) contacting the wood material with a first aqueous treatment solution comprising an iron salt and an microbicidal agent to provide impregnated wood material, (b) removing residual first aqueous treatment solution from the impregnated wood material, (c) further contacting the impregnated wood material with a second aqueous treatment solution comprising an oxidant to provide further impregnated wood material, and (d) separating the further impregnated wood material from the second aqueous treatment solution. In a preferred embodiment, the present invention provides the latter method further comprising subjecting the impregnated wood material to a pressure treatment during one or more of step (a) and step (c).
DETAILED DESCRIPTION
We have discovered that wood and other wood materials may be treated to maintain dimensional stability and surface integrity for extended periods of time after exposure to UV light and water without the use of conventional chromium (VI) salts by treatment with an iron salt and an oxidant for at least 15 seconds at temperatures from 15° C. and 100° C. This discovery also allows further protection of wood materials from attack by microorganisms by incorporating a microbicidal agent into the aforementioned treatment process that results in retention of the microbicidal agent in the treated wood for extended periods of time. In most cases, the oxidant may be added before, during or after the wood material has been contacted with the iron salt; however, in situations where the iron salt and oxidant may interact rapidly with each other during treatment, the oxidant is preferably added after the wood material has been impregnated with iron salt or iron salt and microbicidal agent.
As used herein, the following terms have the designated definitions, unless the context clearly indicates otherwise. All percentages referred to will be expressed in weight percent (%), based on total weight of polymer or composition involved, unless specified otherwise. The following abbreviations are used herein: g=grams, L=liters, mm=millimeters, cm=centimeters, pressure is in kiloPascals (kPa). Unless otherwise specified, ranges listed are to be read as inclusive and combinable and temperatures are in degrees Celsius (° C.).
As used herein, “wood,” “wood material” and “wood substrate” shall mean all forms of wood, for example, solid wood (such as timber or lumber in the form of logs, beams, planks, sheets and boards), wood composite materials (such as wood fiber board, chip board and particle board) and all products made from wood and wood-composite materials (such as mill frames, decking, siding, siding cladding, roof shingles and utility poles).
As used herein, “surface integrity” shall refer to the property of the wood materials and resultant treated wood materials related to hardness and impenetrability, that is, resistance to deformation and softening of the wood surface. As used herein, “dimensional stability” shall refer to the property of the wood materials and resultant treated wood materials related to resista
Crimaldi Kenneth
Howell Thomas J.
Pak John
Rohm and Haas Company
LandOfFree
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