Method of reconditioning used wood

Details Method of reconditioning used wood Method of reconditioning used wood

1998-02-02

1999-03-16

Warden, Jill

Cleaning and liquid contact with solids

Processes

Using solid work treating agents

134 26, 134 28, 134 29, 134 30, 162 1, 162 63, 162 65, 162 81, 162 82, B08B 300, B08B 302, D21C 102, D21C 104

Patent

active

058824278

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
The invention relates to a method of reconditioning used wood in which contaminated surface portions are removed by mechanical and chemical operations.
2. The Prior Art
Utilization of used wood as a working material is often particularly problematic because of various contaminations. Most often, the wood is contaminated by organic and inorganic wood preservatives which as a rule are applied to the surface of the wood by drenching or immersion processes, or after construction. Because of the manner in which the wood preservatives have been applied and because of the structure of the wood these wood preservatives are directly fixed only to the surface of the wood, i.e. penetrating not more than few millimeters thereof. Moreover, used wood may be contaminated by inorganic or mineral contaminations from building materials such as, for example, cement, gypsum, concrete or tar paper. These contaminations, because of the nature of utilization of the wood, e.g. to form support or ceiling beams, are also restricted to the surface. In the case of building wood, demolition wood or pallets, nails, screws and staples of iron or ferrous materials are often present. In most cases, they are separated from the chips after cleaning of the wood by magnetic separators and air separators. Together with the types of contamination referred to above, one often encounters weather-induced wear occurring even in protected wood made perceptible by embrittlement and graying of the surface of the wood. In all of the cases described, removal of only a certain surface layer of a piece of wooden building material is necessary, and the remaining core may be used again as good untreated and undamaged wood material. Mechanical reprocessing of used wood by shaving off its surface has been recognized as possible. because of the different and irregular shapes of used wood and its varying sizes, such a process is, however, very complex and expensive. Moreover, machines used for such purposes are subjected to damage from attached minerals or metal parts. For that reason, an economic reconditioning of used wood has hitherto not been possible in cases where surfaces have had to be removed.


OBJECTS OF THE INVENTION

It is a task of the present invention to provide a process which makes it possible in a simple manner to remove the surface layer of used wood pieces regardless of their size and condition, and to leave the remaining wood untreated to such an extent, or to preserve it such that it may be worked with or utilized again.


DETAILED DESCRIPTION OF THE INVENTION

This task is accommodated by a chemo-thermal method wherein the surfaces of used wood building materials are in a first step mechanically roughened at all sides by toothed rolls and knife rolls and/or by treatment in a drum rotor. Wooden pieces with strongly weathered surfaces and edges, coarse cement and concrete contaminations as well as fungus and insect infections are separated from the wooden core which may be reused. If, for instance, the contaminations are removed in a rotating drum similar to those used, for instance, for barking new wood, roughening or breaking open or tearing open of the surfaces by incising or by toothed rollers before and/or after the rotor treatment is very effective for complete decontamination. Up to a certain extent, the proportion of removed contaminations is increased. Following the mechanical pretreatment the roughly precleaned used wood is soaked in water or in a solution of water and chemicals, and the chemicals dissolved therein may more easily penetrate into the roughened surface. Preferably, the wood is soaked until the water or solution in the surface portions to be removed has reached 30%. In this manner the surface is softened and swells. By adding chemicals to, or heating, the water this process may be enhanced. Penetration of the solution may be accelerated by surfactants. The process may also be accelerated by the application of a vacuum prior to the soaking, by placing the used wo

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