Method for treating wood at the glass transition temperature the

Details Method for treating wood at the glass transition temperature the Method for treating wood at the glass transition temperature the

1998-03-23

1999-11-30

Bennett, Henry

Drying and gas or vapor contact with solids

Process

With nondrying treating of material

34388, 34398, F26B 700

Patent

active

059920432

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to a method for treating wood in the natural state as well as to a material obtained in accordance with this method.
It is known that, in the natural state, wood, or the wood fibers which are in contact with a humid atmosphere, tend to be logged with water, going as far as absorbing it up to the value of their own weight. Such absorption of water is accompanied, on the one hand, by a swelling and, on the other hand, by a loss of the mechanical qualities and the qualities of cohesion of the material which, in certain cases, can go as far as an advanced disintegration thereof. This is why the habit is taken, before every step of machining wood, of effecting a drying step which, by eliminating the water therefrom, improves its dimensional stability.
Although the drying step enables the water to be eliminated from the wood, it in no way modifies its hydrophilic nature, with the result that it is again likely to reabsorb the water eliminated during the drying, when it is again in a humid atmosphere.
In order to decrease the hydrophilic nature of the natural wood and thus give it a long-lasting dimensional stability, different techniques of heat treatment at high temperature have been proposed. For example, it has been proposed, particularly in French Patent FR-A-2 512 053, to heat a fragmented ligneous matter, possibly in an agglomerate form, under a neutral atmosphere to a temperature of between 200.degree. C. and 280.degree. C. Although such a treatment makes it possible to obtain a dimensionally stabilized wood, it reduces, on the other hand, the mechanical qualities of the material.
It has also been proposed to subject the natural wood to different treatment steps including in particular a drying in open circuit followed by a progressive heating and maintenance in closed circuit at a temperature included between 180.degree. C. and 280.degree. C. Apart from the fact that such a technique does not enable a dimensional stability and a decrease in the hydrophilic character of the treated wood to be constantly obtained, it is accompanied most of the time by the formation therein of cracking and splitting.
It is an object of the present invention to propose a method of treating wood which gives said wood a hygrophobic character and a good dimensional stability, without provoking the creation of cracking and splitting.
The present invention thus has for its object a method of treating wood, of the type in which a piece of wood to be treated is subjected to a heat treatment, of the so-called high-temperature type, for a determined time, characterized in that it comprises a step prior to the heat treatment during which the piece of wood is subjected to a temperature equal to its glass transition temperature, and said piece of wood is maintained at this temperature as long as it has not completely reached said glass transition temperature.
Applicants have thus established, by tests carried out in the laboratory on numerous different essences of wood, that, by maintaining the wood to be treated at its glass transition temperature for a determined time, sufficient for the whole of its mass to reach said temperature, all the phenomena of formation of splitting and cracking of the wood which usually occurred when the latter was subjected to a high-temperature treatment, were subsequently avoided.
Such a treatment may be effected in a chamber, and in that case the piece of wood to be treated may be subjected to a progressive, even linear, increase of the temperature. This treatment may also be effected by immersion of the wood to be treated in a heat-regulated bath, for example a liquid bath or a solid bath formed by fine solid particles.
It is known that the glass transition temperature of wood corresponds to the zone of temperature where the elements constituting said wood, i.e. those which give it its characteristics of rigidity, precisely lose this character of rigidity, so that the material passes from a rigid state to a supple state, which allows the internal stresses of the wood to be

REFERENCES:
patent: 4620373 (1986-11-01), Laskowski et al.
patent: 5030483 (1991-07-01), Drinkard, Jr.
patent: 5343913 (1994-09-01), Tanahashi et al.
patent: 5678324 (1997-10-01), Vittaniemi et al.
patent: 5752328 (1998-05-01), Yamamoto

Affiliated with

Also associated with

Rating

Method for treating wood at the glass transition temperature the does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Method for treating wood at the glass transition temperature the, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for treating wood at the glass transition temperature the will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-1657528