EP1970177A1 - Method for treating wood for profiles - Google Patents

Abstract

The method involves feeding a heat-treating furnace with the wood which can be treated by heating the oven. The carburet hydrogen evolved during heating is evacuated. The water is injected for the production of an inert chamber atmosphere upon reaching a chamber temperature over 100 degree celcius, preferably over 130 degree celcius. The load is removed from the chamber area. The wood that is to be treated is trimmed, smoothened and glued to semi-finished products. An independent claim is also included for wooden window for buildings with wood profiles.

Description

The present invention relates to a method for the production of wood profiles for window and door construction and for other applications in which dimensionally stable profiles are made of durable wood, as well as a use of wood profiles.

In the following, reference is made to profiles for window construction. However, similar profiles can also be used for other applications, such as the construction of exterior doors.

Window profiles for wooden windows are currently produced almost exclusively from tropical woods. Currently the most common material is Meranti. For ecological reasons, this wood will be used to a lesser extent in the future, because on the one hand the stocks of tropical timber are endangered by unsustainable cultivation. On the other hand, the transport from the place of growth to the place of use is ecologically questionable. There are therefore already some Methods have become known with which native wood durable, ie weather-resistant, to be made.

Chemical methods of increasing durability have been used successfully. However, these lead to a negative impact on the mechanical properties of the desired durability. In particular, it is disadvantageous for the profiled wood area in window construction that the wood treated in this way becomes fragile.

Impregnated woods have the disadvantage that they have to be treated as polluted waste at the end of their useful life due to added substances. Therefore, there are concerns in the living area that harmful substances can escape. The acceptance of such preserved wood is therefore low for such applications.

From an ecological point of view, the thermal processes are therefore particularly advantageous. Here is primarily the method according to the French patent FR784.378 to mention. One of the embodiments in this patent describes the treatment of wood in an oven at atmospheric pressure. The temperature is slowly increased up to 220 ° C. The risk of fire and explosion is reduced by creating an inert atmosphere in the furnace by introducing steam. The duration of the heat treatment is chosen according to the given requirements. It depends in the prior art in particular on the type of wood and the water content of the wood. Details are not provided. The aim of the process is to increase the durability and artificial aging of the wood.

The European patent EP0695408B1 discloses a method for improving the resistance of wood to mildew and rot. In this process, the wood is first dried to a moisture content of less than 15%. Then the temperature is increased rapidly to over 150 ° C and the treatment at this temperature as long continued until a weight loss of at least 5% has taken place. The treatment takes place at atmospheric pressure in a moist oven fed with steam. In this method, laborious measurements are required to control the specified moisture levels and weight loss. In addition, the feeding of the wet oven with steam is associated with high energy consumption. The suitability of the thus treated wood for the production of profiled timber, especially in window construction, is not stated.

Numerous other processes for preserving native woods are known in which the treatment takes place under increased pressure. This is undesirable because of the expenditure on equipment.

It is therefore an object of the present invention to provide a method for the treatment of indigenous woods, which improves the durability, in particular with regard to the suitability for the window construction, and does not or only so far changed the mechanical properties of the wood that they are used for window construction stay fit.

This object is achieved by a method having the features of claim 1, by a use having the features of claim 9 and finally by a window having the features of claim 10.

Further advantageous embodiments and uses emerge from the dependent claims.

Hereinafter, embodiments of the present invention will be explained with reference to the description of the method.

• Frisch geschnittenes Buchenholz wird innerhalb von 0 bis etwa. 48 Stunden nach dem Einschnitt als Schnittholz ohne Latten oder mit Stapelleisten in eine Dämpfkammer gefahren. Nach dem Verschließen der Dämpfkammer wird die Temperatur des zu dämpfenden Schnittholzes möglichst rasch (innerhalb von etwa 6
  • 12 Stunden) auf 80 °C bis 95°C angehoben. Aufheizmedium ist Nassdampf mit einer Dampftemperatur von ca. 115 - 125°C mit dem entsprechenden Druck von 0,4 bis 0,6 bar.
• Dabei verliert das Schnittholz die ursprüngliche Festigkeitsstruktur und geht einen plastisch verformbaren Zustand über. Dabei entspannt sich das Holz und ist nach dieser Vorbehandlung wesentlich spannungsärmer.
• Dieser Effekt kommt der nachfolgenden thermischen Behandlungsmethode zu gute.
• Die so gedämpfte Buche kann nach geeigneter Trocknung als Brett- oder Bohlenware in den Längen von 1 Meter bis etwa 6 Meter in einen Wärmebehandlungsofen gegeben werden. Sind die Anforderungen an die Formbeständigkeit geringer, so kann Holz nach einer Lagerungszeit auch ohne diese Vorbehandlung als Ausgangsstoff in das folgende Verfahren gegeben werden. Dies gilt für Buche und insbesondere für Eschenholz.
• In dem Wärmebehandlungsofen laufen nun bei dem bevorzugten Ausführungsbeispiel folgende Verfahrensschritte ab:
  1. 1. Aufheizen des Ofenraums mit einem Temperaturanstieg von etwa 10°C pro Stunde bis zu einer Temperatur von 70°C; danach mit einer Geschwindigkeit von 4°C pro Stunde bis zu einer Temperatur von 120°C;
  2. 2. Absaugen des beim Erhitzen entstehenden Kohlenwasserstoffgases, welches gegebenenfalls nach Trocknung in dem für die Aufheizung des Ofenraums verwendeten Festbrennstoffofen mit verbrannt werden kann;
  3. 3. ab Erreichen einer Kammertemperatur von über 130°C Einspritzen von Wasser zur Erzeugung einer inerten Kammeratmosphäre;
  4. 4. ab Erreichen einer Temperatur von 180°C bis 200°C, bei Buche vorzugsweise 190°C, Halten dieser Temperatur für einen Zeitraum von 3 bis 6 Stunden;
  5. 5. während des Zeitraums kontinuierliches oder intervallartiges Absaugen der entstehenden Kohlenwasserstoffgase und weiteres Einspritzen von Wasser zur Aufrechterhaltung der inerten Atmosphäre;
  6. 6. nach Ablauf des Zeitraums Abkühlen des Kammerraums auf eine Temperatur von 100°C, danach 10 Stunden Kondensationszyklus. Danach weiteres Abkühlen auf 30°C und anschließendes Entnehmen der Charge aus dem Kammerraum;
  7. 7. Besäumen, Hobeln und Verleimen des so behandelten Holzes zu Zweischicht- oder Dreischichtlamellen in den gewünschten Abmessungen, insbesondere etwa 8cm x 8cm für Fensterprofile.

As a starting material for the production of weather-resistant profile wood, a native European hardwood is selected, with currently ash and especially beech are preferred. First, a method is described, can be pretreated with the beech wood. This process is currently achieving the best result. For this purpose, the beech wood is treated with the following process steps:

• Freshly cut beechwood will be within 0 to about. 48 hours after the incision as lumber without slats or with stacking ledges driven into a steam chamber. After closing the steam chamber, the temperature of the timber to be damped as quickly as possible (within about 6
  • 12 hours) to 80 ° C to 95 ° C. Heating medium is wet steam with a steam temperature of about 115 - 125 ° C with the corresponding pressure of 0.4 to 0.6 bar.
• The sawn timber loses its original structure and undergoes a plastically deformable state. The wood relaxes and is much less stressful after this pretreatment.
• This effect is the following thermal treatment method to good.
• The thus steamed beech, after suitable drying, can be placed in a heat treatment oven in the lengths of 1 meter to about 6 meters as a board or plank. If the dimensional stability requirements are lower, wood can be added to the following process as a starting material after a storage period even without this pretreatment. This applies to beech and especially for ash wood.
• In the heat treatment furnace, the following method steps now proceed in the preferred embodiment:
  1. 1. heating the furnace chamber with a temperature increase of about 10 ° C per hour up to a temperature of 70 ° C; then at a rate of 4 ° C per hour up to a temperature of 120 ° C;
  2. 2. sucking off the hydrocarbon gas formed on heating, which may optionally be burned after drying in the solid fuel furnace used for heating the oven space with;
  3. 3. from reaching a chamber temperature of over 130 ° C injection of water to produce an inert chamber atmosphere;
  4. 4. from reaching a temperature of 180 ° C to 200 ° C, with beech preferably 190 ° C, keeping this temperature for a period of 3 to 6 hours;
  5. 5. during the period continuous or intermittent suction of the resulting hydrocarbon gases and further injection of water to maintain the inert atmosphere;
  6. 6. after expiration of the period, cool the chamber to a temperature of 100 ° C, then 10 hours condensation cycle. Thereafter, further cooling to 30 ° C and then removing the charge from the chamber chamber;
  7. 7. Trimming, planing and gluing the wood thus treated into two-layer or three-layer lamellae in the desired dimensions, in particular approximately 8 cm × 8 cm for window profiles.

The process proceeds essentially at atmospheric pressure or as a result of the exhaustion of hydrocarbon gases at low negative pressure.

The further processing in step 7 can also be made to glue wood panels or beams or profiles in other dimensions.

The slats obtained in step 7 can then be further processed by milling to the desired window profiles or other profiles. These are then manufactured in a known manner windows or the like, which have the required durability against weathering and rotting. The durability class according to the classification EN 350 part 1 is improved from 5 - 6 to 2 - 4. Durability has been demonstrated by a standard procedure, both in accordance with the EN 252 field test demonstrating resistance to microorganisms and fungal attack, and in laboratory tests according to EN 113.

In addition, the window profiles have the required mechanical properties. The elastic modulus to be achieved for the window construction is at least achieved. Thus, the thermally modified wood is comparable in mechanical properties to e.g. Jaw.

The method described above thus makes it possible to produce profiles for window construction of native hardwood. The profiles are weather-resistant and suitable in mechanical properties for window construction. Neither chemical additives nor pressure treatments are used. The process itself is purely temperature- and time-controlled. A complex measurement of the residual moisture content and weight loss does not take place. Next can be dispensed with by the intended injection of water into the chamber chamber on the steam supply according to the prior art, whereby the equipment cost is kept lower. Finally, the energy consumption due to the extraction and combustion of the resulting hydrocarbon-containing gas in the balance compared to other thermal processes is particularly low.

Claims (10)

Process for the production of dimensionally stable and weather-resistant wood profiles with the following steps: a) loading a heat treatment furnace with the wood to be treated; b) heating the oven space; c) sucking off the hydrocarbon gas formed on heating; d) from reaching a chamber temperature of about 100 ° C, preferably about 130 ° C injection of water to produce an inert chamber atmosphere; e) from reaching a temperature of 180 ° C to 200 ° C, with beech preferably 190 ° C, keeping this temperature for a period of 3 to 6 hours; f) during the period continuous or intermittent suction of the resulting hydrocarbon gases and further injection of water to maintain the inert atmosphere; g) at the end of the period cooling the chamber space to a temperature of 100 ° C, h) Thereafter, further cooling to about 30 ° C and then removing the charge from the chamber chamber; i) trimming, planing and gluing the treated wood to semi-finished products. A method according to claim 1, characterized in that the heating of the furnace chamber in step b) with a temperature increase of about 10 ° C per hour up to a temperature of 70 ° C, then at a rate of 4 ° C per hour up to a Temperature of 120 ° C. Method according to one of the preceding claims, characterized in that the hydrocarbon gas from the steps c) and f) is optionally burned in the solid fuel furnace used for heating the furnace chamber, optionally after drying. Method according to one of the preceding claims, characterized in that a condensation cycle takes place between step g) and step h) for 10 hours. Method according to one of the preceding claims, characterized in that in step i) the gluing to two-layer or three-layer slats takes place in the desired dimensions, in particular about 8cm x 8cm for window profiles. Method according to one of the preceding claims, characterized in that before step a) freshly cut hardwood is driven within 0 to about 48 hours after the incision as lumber without slats or with stacking strips in a Dämpfkammer and there the temperature of the lumber to be damped as possible raised rapidly (within about 6 to 12 hours) to 80 ° C to 95 ° C. A method according to claim 6, characterized in that the heating medium is wet steam at a steam temperature of about 115 - 125 ° C at a pressure of 0.4 to 0.6 bar. Method according to one of the preceding claims,
characterized in that the wood is beech wood. Use of a wood profile produced according to one of claims 1 to 8 for window construction. Wooden window for buildings with wooden profiles made according to the method of one of the preceding claims 1 to 8.