Compositions – Preservative agents – Anti-oxidants or chemical change inhibitants
Patent
1994-04-29
1996-07-23
Gibson, Sharon
Compositions
Preservative agents
Anti-oxidants or chemical change inhibitants
252397, 25240023, 106 1505, 424405, 424409, 427297, 4273934, 427393, 427397, 427440, 4285371, A01N 3300
Patent
active
055386709
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/FI92/00293, filed Oct. 30, 1992, published May 13, 1993, now WO 93/08971.
The present invention relates to a method for protecting wood against decay and similar degradation reactions caused by wood decay fungi and similar microorganisms which cause wood decay.
According to such a method, wood is treated with a preservative capable of preventing wood decay fungi and similar microorganisms, which have the capability of decomposing lignocellulosic compounds, from growing and spreading in wood.
The invention also concerns a wood preservative capable of preventing the growth and spread of wood decay fungi and similar microorganisms which cause wood decay.
Wood decay fungi and a number of other microorganisms can metabolically utilize the structural components of wood cells. Brown-rot fungi, for example, decompose only the cellulose and hemicellulose of the wood structure, while white-rot decay fungi can also utilize the lignin components of wood. Brown-rot decay is characterized by a rapid deterioration of strength properties of wood in the initial stage of decay even before any visible changes are evident. This fact is one of the reasons, why brown-rot wood decay fungi are the worst culprits in boreal climate zones for causing damages in timber and wood constructions, accounting for annual losses of several billions of Finnmarks through decay in sawn timber as well as residential and other buildings constructed with wooden components.
Wood can be protected chemically against damages caused by decay fungi by various preservation methods based on preservatives of varying efficacy. Wood preservatives employed in the art can be coarsely classified in three categories: 1) water-borne preservatives, 2) oil-borne preservatives and 3) creosote oil. An outline of each of these categories is given:
1) Fixing-type water-borne salt preservatives contain copper, chromium and arsenic (CCA preservatives) as the active components. Fixing-type preservatives are intended for a long-term protection of wood. Nonfixing salt-based preservatives employ various boron and fluorine compounds as the active components. The latter type of preservatives give a limited time of protection, since the protecting compounds are subject to leach-out by environmental moisture.
2) Oil-based preservatives contain one or more active constituents in an organic solvent, conventionally a light petroleum oil of the solvent naphtha grade. The active compounds can be tributyl tin naphthenate (TBTN), tributyl tin oxide (TBTO), mixtures of penta- and tetrachlorophenols, phoxim and dichlofluanid.
3) Creosote oil is a fraction of coal tar distilling above 200.degree. C. Analysis of creosote oil has identified about 300 different compounds, most of them occuring in very low concentrations. The efficacy of creosote oil in the inhibition of organism growth is based on the synergetic preservative effect of its components.
Conventional wood preservatives have appreciable drawbacks. For instance, they contain toxic compounds thus necessitating approval by authorities for their use. The toxic effect of preservatives is based on a general toxicity, which affects all vital metabolic functions of living organisms such as, e.g., cell respiration and production of a high energy compound, ATP. Due to the broad toxic spectrum of such preservatives, appreciable health (e.g., carcinogenicity) and environmental (soil and waterway contamination) risks are involved with the use of conventional wood preservatives. Health risks are imposed on all eucaryotic organisms including plants, animals and man. If the content of copper, arsenic and chromium in a CCA preservative were decreased, however, problems in fixing the preservative into wood result, with a significant reduction of the preservative's efficacy paralleling the reduction of heavy metal concentrations.
It is an object of the present invention to overcome the drawbacks prior-art technology and to achieve an entirely novel method of wood preservation against decay, said method being specifi
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Mattila-Sandholm Tiina
Paajanen Leena
Ritschkoff Anne-Christine
Viikari Liisa
Fee Valerie
Gibson Sharon
Koskisen Oy
Kymmene Oy
Metsalitto Osuuskunta
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