Coating processes – With post-treatment of coating or coating material – Heating or drying
Patent
1994-11-21
1996-12-10
Beck, Shrive
Coating processes
With post-treatment of coating or coating material
Heating or drying
427297, 4273933, 4273934, 427440, 252380, 252607, B05D 302
Patent
active
055828710
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/FI94/00127, filed Mar. 31, 1994.
The invention is a method according to the preamble of claim 1 for preserving wood against undesirable reactions caused by microorganisms.
According to such a method, wood is treated with a substance capable of preventing the growth of microorganisms, whereby wood is impregnated at least essentially deeper than superficially with said substance.
The invention also concerns a wood according to the preamble of claim 17, said wood being preserved against undesirable reactions caused by microorganisms.
To preserve wood against decay and damage caused by microorganisms, different types of methods and preserving substances have been developed. The most common method is to impregnate wood as deep as possible with substances capable of preventing growth of microorganisms in wood. Such preserving substances typically are so-called creosote oils which provide at least a satisfactory degree of presentation. A disadvantage of such materials is, however, their general toxicity necessitating the handling of such preservative residues and wood blocks treated with them as hazardous waste.
The prior art also knows approaches in which organic complexing agents or their salts are used to preserve samples of cellulose derivatives against fungal damages caused by Fungi imperfecti fungi. For instance, Rao and Kumar [J. Archaelogical Chem. 4 (1986), pp. 11-15] have investigated the inhibitory power of such complexing agents as 8-acetyl-4-methyl umbelliferone (AMU) and dehydroacetate-(3-acetyl-6-methyl-12H-pyran-2,4-(3H)dione (DHA) and copper salts thereof on the hydrolytic effect of enzymes isolated from the Aspergillus niger and Trichoderma viride mold strains on a sodium carboxymethyl cellulose substrate. The results indicate that in small concentrations the chelating agents have a relatively weak effect as such, while their copper salts achieved 15-25% inhibition effect at concentrations as low as 50 ppm. According to Rao and Kumar, the inhibitory effect exhibited by the chelating agents and particularly their metal salts is based on their reactions with the active groups of enzymes.
It is an object of the present invention to provide an entirely novel method for preserving wood such as sawn wood against undesirable reactions caused by microorganisms.
The invention is based on two basic principles. Firstly, a complexing agent is used as a substance preventing the growth of microorganisms, said agent being capable of binding transition metals contained in wood. Thus, the invention utilizes the fact that through binding iron and other transition metals in wood materials into chelates, an extremely significant inhibitory effect on the growth and spreading of fungi and molds. It has been found that the decay of crystalline cellulose by rot fungi, for instance, takes place via a decay path based on oxidating reactions in which the transition metals contained in wood have a crucial part. Transition metals have a similar role in the growth of molds and blue-stain fungi. Most important of the transition metals contained in wood to the growth of microorganisms are iron (F), particularly trivalent iron, and manganese (Mn).
Complexing agents used for binding transition metals are mostly water-soluble, thus permitting their leaching away from treated wood by rainwater. Therefore, according to the second basic idea of the invention, a solid-phase "reserve depot" of precipitated complexing agent is formed in wood to cater for later entry of metal compounds and moisture into the wood. According to the invention, said reserve depot is provided comprising impregnation of the complexing agent into the wood in the form of an aqueous solution, and after the impregnation step, the complexing agent penetrated into the wood is precipitated from the aqueous phase.
More specifically, the method in accordance with the invention is principally characterized by what is stated in the characterizing part of claim 1.
Furthermore, the wood preserved according to the invention is characterized
REFERENCES:
patent: 4090000 (1978-05-01), Hatcher
patent: 4382105 (1983-05-01), Amundsen
Rao, et al., "A Non Conventional Method of Wood Preservation", Journal of Archaeological Chemistry, vol. 4, pp. 11-15 (1986).
Chemical Abstracts, vol. 108, No. 2, p. 89 (1988) (citing Rao, et al.).
Ritschkoff Anne-Christine
Silenius Petri
Viikari Liisa
Beck Shrive
Kymmene Oy
Talbot Brian K.
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