Chemical apparatus and process disinfecting – deodorizing – preser – Process disinfecting – preserving – deodorizing – or sterilizing – Process of storage or protection
Reexamination Certificate
1999-08-23
2004-12-14
McKane, Elizabeth (Department: 1744)
Chemical apparatus and process disinfecting, deodorizing, preser
Process disinfecting, preserving, deodorizing, or sterilizing
Process of storage or protection
C044S541000, C034S380000, C034S417000
Reexamination Certificate
active
06830727
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a method for stocking and preserving green round wood and sawn timber, of both softwood and hardwood, over long periods without loss of quality.
Conventional general preserving methods concern mainly food which is sterilized by heating in the absence of air (bottling, canning), or fumigated in dry condition with carbon dioxide (protection of grain from pests), or gassed with protective gases having special compositions (storing and ripening of fruit in a nitrogen/carbon dioxide atmosphere), or cleared from insects under pure nitrogen (restoration of wood articles whose pigments would be attacked by carbon dioxide).
Methods used so far for preserving green round wood are based on storage in water or sprinkling with water. A wood moisture content of over 100% is aimed at in order to prevent fungal growth. Drawbacks are the high water consumption and the ground-water pollution due to wood substances, in connection with different moisture content in the interior of the wood stack, which results in fungal attack (Armillariella species).
Further, round wood and sawn timber can be preserved for a time using insecticides and fungicides. The application of pesticides involves endangering nature and mankind.
A safe method of preservation is to convert and season the wood as soon as possible. This, however, demands extensive conversion and seasoning capacities to be kept in reserve, in order to be capable of quickly processing large quantities of round wood (wind-fallen wood and other problems).
Also known are attempts to preserve green round wood in dry stacks. This method, however, involves high risks of fungal and insect attacks.
From DE-OS 28 57 355 and DEOS 34 34 551, methods are known of influencing the wood properties by means of fungal cultures.
According to DE-OS 28 57 355, a method is known of microbiologically modifying softwood using micro-organisms. These micro-organisms selectively modify the softwood whereby the temperature, the moisture content of the wood, the O
2
content and the CO
2
content are controlled in due consideration of the micro-organisms.
In DE-OS 34 34 551, the round wood is deliberately discolored by treatment with wood-destroying fungi. Discoloration occurs at those places where the fungus culture has been applied. Also the application of several fungus cultures is described which is associated with a beneficial boundary layer formation.
In the paper Mahler G.: Konservierung von Holz mit Schutzgas (Preservation of Wood Using Protective Gas), AFZ 47 (1992) 19, pp. 104-1025, experiments are reported to preserve wood using a protective gas. In these experiments wood with standardized dimensions was wrapped in silo films. The stacks were fumigated with both nitrogen and carbon dioxide; in each case, the threefold gas volume compared to the wood volume was required. Thereby the oxygen content was reduced to 4-5% and this content maintained over a longer-period of time (more than 6 months). After opening of the stack a fungal coating was found on the wood that is assumed to be an antagonist, which indicates that an attack from wood-destroying fungi can be prevented by the promotion of antagonistic fungi.
Disadvantages are the fumigating demand described and the relatively high residual oxygen content.
SUMMARY OF THE INVENTION
It is the objective of this invention to develop a method that enables to stock green round wood or sawn timber of all wood species over a longer period of time without deterioration of quality and strength properties without previously having the wood sterilized, moistened, dried or treated with special protective gases.
Initially, it is certainly surprising that humid, non-debarked wood is not going moldy and not rotting under a low-exchange atmosphere. Essential to the invention, however, is that resulting from respiratory processes of wood cells that are still alive, and metabolic processes of fungi, bacteria which have been fed into the covering through the green round wood, or sawn timber, respectively, a virtually oxygen-free atmosphere, enriched with carbon dioxide, is produced.
The airtight cover ensures that, on the one hand, no oxygen can enter from the exterior and, on the other hand, no carbon dioxide can exit from the cover.
Contrary to the interpretation in Mahler, G.: Konservierung von Holz mit Schutzgas (Preservation of Wood Using Protective Gas), AFZ 47 (1992) 19, pp. 1024-1025, it is not the action of the fungal antagonists which is decisive to prevent wood-destroying fungi from growth. It is rather the very low oxygen content of less than 0.1 vol.-% that is essential for permanent storage possibility.
This low oxygen content is achieved by the fact that after the respiratory processes as in fruit storing in which CO
2
and H
2
O are released and which end with the consumption of the O
2
, another cycle starts. In this cycle, fermentation processes occur in that additional CO
2
is set free so that the CO
2
content further rises.
The initiation of fermentation processes is another substantial advantage of the invention, compared to fruit storage. No degradation of cellulose or lignin takes place while only readily soluble sugars are degradated. Thus the strength of the round wood or timber, respectively, is remained.
The biotechnological process started after the sealing from air can be accelerated by minimization of the volume of the air within the cover.
In order to produce sealing from air, covering, advantageously a plastic film with a high diffusion resistance, is employed: To reduce the danger of leakage the film can be used in double layer. The benefit of a flexible covering consists in that the volume of the air can be minimized (by suction until the film tightly wraps the stack of wood or timber).
Sealing from air can also be obtained in purpose-prepared storehouses, containers, cargo holds, lined pits, silos, or mining tunnels.
After any short-time opening of the air-tight covering to take out some wood, or timber, respectively, the virtually oxygen-free atmosphere after resealing reproduces within a few days. The micro-organisms are able, independent of the time of the year, to reproduce those conditions that are favourable for them.
Additionally, CO
2
stored in the wood as a porous body and salved in the water bonded in the wood, call again be released to produce a new gas balance.
In film storage, scaling from air of the wood or timber stacks, in case of valuable (veneer) wood also of individual trunks, is achieved by a double weld at the enveloping film, or by gluing, respectively, or by clamping of the films webs straight lying on top of each other by means of strips of wood around which the film is tightly wrapped and secured with clips from unwinding.
The essential advantage of the method according to the invention is that in the preservation, storage needs no additional fumigation.
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patent: 5447686 (1995-09-01), Seidner
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patent: 2857355 (1980-05-01), None
patent: 3434551 (1985-04-01), None
patent: 267188 (1989-04-01), None
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patent: 6-39811 (1994-02-01), None
patent: 97/27034 (1997-07-01), None
Kozlik et al. Abstract of “Changes of the atmosphere during wood decay by fungi under conditions of stopped gas diffusion,” Drev. Vysk. (1974), 19(4), pp. 169-179.*
1992 “Preservation of Wood by Protective Gas” by Von Gerold Mahler pp. 1024-1025.
Gross Martin
Koenig Juergen
Mahler Gerold
Maier Thomas
Richter Christoph
Jordan and Hamburg LLP
McKane Elizabeth
Technische Universitaet Dresden
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