EP3620282A1 - Method for the preparation of osb wood-base panels with reduced emission of volatile organic compounds (vocs) - Google Patents

Abstract

The present invention relates to a process for the treatment of wood strands suitable for the production of OSB boards, the wood strands being treated with water vapor after drying without drying, the water vapor having a temperature between 80 ° C. and 120 ° C. and a pressure between 0 , 5 bar and 2 bar over the wooden strands. The present invention also relates to a method for producing OSB wood-based panels, in particular OSB wood-based panels with reduced emissions of volatile organic compounds (VOCs), comprising the steps of a) producing wooden strands from suitable woods; b) treating at least part of the wooden beaches with steam; c) drying the steamed wooden beach; d) gluing the steam-treated and dried wooden strands and gluing non-steam-treated wooden strands with at least one binder; e) sprinkling the glued wooden beach on a conveyor belt; and f) pressing the glued wood strand into an OSB wood-based panel.

Description

The present invention relates to a method for treating wooden beaches with water vapor according to claim 1, a device for carrying out the water vapor treatment according to claim 7, a method for producing OSB wood-based panels according to claim 10 and a production line for producing OSB-based wood panels according to claim 14.

description

Coarse chipboard, also called OSB (oriented strand boards), are wood-based panels that are made from long chips (strands). OSB boards are increasingly used in timber and prefabricated houses, as OSB boards are light and still meet the structural requirements placed on building boards. OSB panels are used as building panels and as wall or roof cladding or in the floor area.

The OSB boards are produced in a multi-stage process, with the chips or strands made from debarked logs, preferably softwood, being peeled off in the longitudinal direction by rotating knives. In the subsequent drying process, the natural moisture of the beaches is reduced at high temperatures. The moisture level of the strands can vary depending on the adhesive used, whereby the moisture should be well below 10% in order to avoid splitting during later pressing. Depending on the adhesive, wetting on rather damp or dry strands may be cheaper. In addition, as little moisture as possible should be present in the beaches during the pressing process in order to largely reduce the steam pressure generated during the pressing process, since this could otherwise cause the raw plate to burst.

After the strands have dried, they are introduced into a gluing device in which the glue or adhesive is applied to the chips in finely divided form. PMDI (polymeric diphenylmethane diisocyanate) or MUPF (melamine-urea-phenol-formaldehyde) glues are predominantly used for gluing. The glues can also be used mixed in the OSB boards. These glues are used because, as mentioned above, the OSB boards are often used for structural applications. Moisture or moisture-resistant glues must be used there.

After gluing, the glued strands are scattered alternately lengthways and crossways to the production direction, so that the strands are arranged crosswise in at least three layers (lower cover layer - middle layer - upper cover layer). The scattering direction of the lower and upper cover layer is the same, but differs from the scattering direction of the middle layer. The beaches used in the top and middle layers also differ from one another. For example, the strands used in the cover layers are flat and the strands used in the middle layer are less flat to chip-like. Usually, two strands of material are used in the production of the OSB boards: one with flat strands for the later top layers and one with "chips" for the middle layer. Accordingly, the strands in the middle layer can be of poor quality, since the bending strength is essentially generated by the cover layers. That is why fines that are produced during machining can also be used in the middle layer of OSB panels. The percentage distribution between the middle and top layers is at least 70% to 30%. Following the spreading of the strands, the strands are continuously pressed under high pressure and high temperature, e.g. 200 to 250 ° C.

Last but not least, OSB panels are becoming increasingly popular and versatile due to their sustainability, for example as a construction element in house construction or as formwork in concrete construction. However, the hygroscopic properties inherent in the wood-based materials have a disadvantageous effect in some applications.

Escape of wood constituents is viewed critically, especially when using OSB indoors. This is particularly problematic with OSB boards made of pine wood, since they show particularly high emissions of volatile organic compounds.

In the course of the manufacture of wood-based panels and in particular due to the manufacturing process of the wooden strands, a large number of volatile organic compounds are or are released. The volatile organic compounds, also called VOCs, include volatile organic substances which evaporate easily or are already present as a gas at lower temperatures, such as at room temperature.

The volatile organic compounds (VOC) are either already present in the wood material and are released from it during processing or they become According to the current state of knowledge, it is formed by the degradation of unsaturated fatty acids, which in turn are decomposition products of the wood. Typical conversion products that occur during processing are, for example, pentanal and hexanal, but also octanal, 2-octenal or 1-heptenal. In particular, conifers, from which OSB boards are mainly manufactured, contain large amounts of resin and fats, which lead to the formation of volatile organic terpene compounds and aldehydes. However, VOC, like the aldehydes mentioned, can also arise or be released when using certain adhesives for the production of the wood-based materials.

The emission of ingredients in OSB material boards is particularly critical because this material is mainly used uncoated. This allows the ingredients to evaporate unhindered. In addition, the OSB panels are often used for cladding / planking large areas, which usually results in a high room load (m ² OSB / m ³ indoor air). This also leads to a concentration of certain substances in the room air.

Various approaches have been described in the past to solve the problem of VOC emissions.

In the past, attempts were made to at least reduce the emissions of the aldehydes by adding reducing agents. However, many of these reducing agents were sulfur-containing, which resulted in undesirable emissions of sulfur dioxide during plate production and later use.

One approach has been taken in the EP 1 907 178 B1 tracked. Here, wood chips or wood fibers are treated with a bisulfite compound, e.g. sodium or ammonium bisulfite, at a pressure of 6-12 bar in a saturated water vapor atmosphere or in a water vapor-saturated air for a period of 3-8 minutes before gluing. It is believed that the addition of bisulfite binds volatile substances in the shredded wood and suppresses the formation of volatile substances. However, the chemicals used not only make the process more expensive, they also sometimes lead to unpleasant smells in production.

The addition of activated carbon has also been tried, but is technologically unsatisfactory from a cost perspective.

Suitable VOC scavengers are almost always added after the strands have dried, as this or the temperature exposure in the press was thought to be the cause of the majority of the emissions. The VOC scavengers were added in liquid form via the gluing system, and solids were added at various points in the process (e.g. scattering). This required an additional installation of dosing stations, which should ensure a homogeneous distribution.

The invention is based on the technical problem of improving the known process for the production of OSB material boards in order to produce OSB material boards easily and safely with a significantly reduced emission of volatile organic compounds (VOCs). At least the emission of the terpenes should be reduced. If possible, the manufacturing process should be changed as little as possible and the costs should not increase disproportionately. Furthermore, the solution should include the greatest possible flexibility. Ultimately, ecological aspects should also be taken into account. H. the solution should not generate additional energy consumption or generate additional waste.

Another technical task was to design a system that enables easy treatment of the beaches to reduce VOC emissions. This should be integrated into the production process and not disrupt or make the production of the OSB more expensive. The technical effort for the treatment should also not lead to an increase in safety measures or contain a greater risk potential.

This object is achieved according to the invention by a method for treating wooden beaches with steam with the features of claim 1, a device for steam treatment according to claim 7, a method for producing OSB wood-based panels with the features of claim 10, and a suitable production line according to claim 14 solved.

Accordingly, a method for the treatment of wood strands suitable for the production of OSB boards, in particular with the aim of reducing the VOC emission from these wood strands, is provided, the wood strands being treated with steam after being obtained from suitable woods without drying, the Water vapor with a temperature between 80 ° C and 120 ° C and a pressure between 0.5 bar and 2 bar is passed over the wooden strands.

In one embodiment of the present method, the treatment of the wooden beaches with water vapor takes place in such a way that the water vapor has a temperature between 90 ° C. and 110 ° C., particularly preferably 100 ° C., at a pressure between 0.7 bar and 1.5 bar. is particularly preferably passed over the wooden strands at 1 bar (atmospheric pressure).

Thus, the water vapor treatment takes place at the temperature-dependent pressure with which the water vapor is introduced into the treatment device. In particular, steam treatment at normal pressure (temperature of the introduced steam of 100 ° C.) is preferred. Accordingly, the application of an additional (external) pressure (i.e. in addition to the pressure with which water vapor enters the system) can be dispensed with. This leads to a simplification of the device, since no pressure vessels (such as an autoclave or a pressure chamber) are necessary for the steam treatment.

Due to the preferred saturated water vapor atmosphere, the steam treatment of the wooden beaches is carried out in a low-oxygen atmosphere or with the greatest possible exclusion of oxygen.

The present steam treatment of the wooden beaches is carried out in a separate steam treatment device. The steam treatment takes place outside of a chipper (e.g. knife ring chipper or disc chipper) and is therefore not part of the chipping or shredding process for wood to produce wooden strands. It is also essential that the steam treatment can be carried out before the wooden beaches dry.

Also, no additives are added to the water vapor: in particular, no bleaching agents, such as bisulfites or oxygen-releasing substances, are added. But there is also no need to add other VOC scavengers to the binder.

In one embodiment of the present method, the steam treatment of the wooden beaches takes place over a period of 5 to 30 minutes, preferably 10 to 20 minutes, particularly preferably 15 minutes. The maximum amount of steam is 1 kg steam / kg strands (atro).

The duration of the water vapor treatment is primarily determined by the speed of the transport device on which the wooden strands are guided through the water vapor treatment device in a continuous manner.

In a particularly preferred embodiment, the water vapor is collected as condensate after passing through the wooden beaches. It is advantageous that the loading of the condensate with organic compounds is relatively low. The COD (chemical oxygen demand) was about 250 mg COD / I when one kilogram of booth was treated with one kilogram of steam.

The wooden strands used here can have a length between 50 to 200 mm, preferably 70 to 180 mm, particularly preferably 90 to 150 mm; a width between 5 to 50 mm, preferably 10 to 30 mm, particularly preferably 15 to 20 mm; and have a thickness between 0.1 and 2 mm, preferably between 0.3 and 1.5 mm, particularly preferably between 0.4 and 1 mm.

In one embodiment, the wooden beaches e.g. a length between 150 and 200 mm, a width between 15 and 20 mm, a thickness between 0.5 and 1 mm and a humidity of max. 50% on.

• mindestens ein Gehäuse, insbesondere ein rohrförmiges Gehäuse;
  • mindestens eine das Gehäuse durchlaufende Transportvorrichtung zum Transportieren der Holzstrands durch das Gehäuse; und
  • mindestens eine oberhalb der Transportvorrichtung Gehäuse vorgesehene Zuleitung für den Wasserdampf, wobei entlang der Zuleitung mindestens ein Sprühmittel zum Applizieren des Wasserdampfs auf die sich auf der Transportvorrichtung befindlichen Holzstrands angeordnet ist.

The steam treatment of the wooden beaches is carried out in a device that comprises the following elements or features:

• at least one housing, in particular a tubular housing;
  • at least one transport device passing through the housing for transporting the wooden beaches through the housing; and
  • at least one supply line for the water vapor provided above the transport device housing, at least one spray means for applying the water vapor to the wooden beach located on the transport device being arranged along the supply line.

In one variant, the at least one housing can be in the form of a metal tube or tubular body.

In one embodiment of the present device, the at least one transport device consists of at least one transport belt. The conveyor belt should Have perforations or other openings so that the water vapor can be guided from the top of the conveyor belt past the wooden beaches to the bottom of the conveyor belt. The wooden strands are distributed on the conveyor belt so that a homogeneous flow of water vapor through the wooden strands is possible.

In a further embodiment of the present device, more than one spray is provided on the water vapor feed line. The number of spraying agents is particularly dependent on the total length of the housing. The spraying means can also be controlled individually, so that the required amount of water vapor can be specifically adjusted. Nozzles or other suitable injectors can be used as spraying means, which enable uniform spraying and uniform distribution of the water vapor on and between the wooden beaches.

As already mentioned above, in a particularly preferred embodiment, the water vapor is collected as condensate after passing through the wooden beaches. For this purpose, at least one means for collecting the condensate is provided in the evaporation system below the conveyor belt (based on the direction of flow of the water vapor). For example, the tubular body can be angled upward in the feed direction.

The condensate collected in this way contains wood constituents washed out from the wooden beaches, in particular aldehydes, organic acids and / or terpenes, in particular those which have a certain water solubility.

After leaving the steam treatment device, the steam-treated beaches have a temperature of 80 to 90 ° C. At this temperature, the wood strands from the steam treatment station enter a dryer (as part of the production line for OSB panels), which leads to an increase in dryer performance. The energy that is used to remove wood constituents is then used for the drying process. In a normal process, the inlet temperature of the strands in the dryer is around 25 ° C.

1. a) Herstellen von Holzstrands aus geeigneten Hölzern;
2. b) Behandeln von zumindest einem Teil der Holzstrands mit Wasserdampf gemäß dem oben beschriebenen Verfahren;
3. c) Trocknen der mit dem Wasserdampf behandelten Holzstrands;
4. d) Beleimen der mit Wasserdampf behandelten und getrockneten Holzstrands und optional Beleimen von nicht mit Wasserdampf behandelten Holzstrands mit mindestens einem Bindemittel;
5. e) Aufstreuen der beleimten Holzstrands auf ein Transportband; und
6. f) Verpressen der beleimten Holzstrands zu einer OSB-Holzwerkstoffplatte.

A method for producing OSB wood-based panels with reduced emissions of volatile organic compounds (VOCs) is also provided, which comprises the following steps:

1. a) Making wooden beaches from suitable woods;
2. b) treating at least part of the wooden beaches with steam according to the method described above;
3. c) drying the steamed wooden beach;
4. d) gluing the steamed and dried wooden strands and optionally gluing the non-steamed wooden strands with at least one binder;
5. e) sprinkling the glued wooden beach on a conveyor belt; and
6. f) pressing the glued wood strand into an OSB wood-based panel.

The present method enables the production of OSB wood-based panels using steam-treated wooden strands, which are introduced into a known manufacturing process in addition or as an alternative to untreated wooden strands. An OSB wood-based panel produced with the method according to the invention and comprising steam-treated wooden strands has a reduced emission of volatile organic compounds, in particular of terpenes and aldehydes.

Various advantages result from the provision of the present method. This makes it easy to manufacture OSB wood-based panels without significantly influencing the usual process chain with significantly reduced emissions of volatile organic compounds from the OSB. In addition, the energy required to dry the wooden strands can be reduced, since the wooden strands already have an elevated temperature (e.g. of approx. 90 ° C) when they enter the dryer; i.e. the energy used in the steam treatment supports the drying process. It is also possible to dispense with the use of additional chemicals, which makes the overall process ecologically and economically advantageous.

In the present process, the production of OSB is changed compared to the conventional OSB production process in such a way that at least some of the strands used are treated with steam before they are dried. The beaches can be those intended for the top or middle class. After the treatment, the strands of the drying performed as standard. This is done e.g. B. immediately before the gluing, whereby a complete substitution or only a partial substitution of the standard beaches can take place.

In a further embodiment of the present method, steam-treated wood strands or a mixture of steam-treated wood strands and non-steam-treated wood strands are used as the middle layer and / or top layer of the OSB wood-based panel.

Accordingly, in one variant, a complete substitution of the wooden strands is possible, the steam-treated wooden strands being used in the middle layer and in one or both outer layers or in all layers.

In another variant, it is possible to form only the middle layer from steam-treated wooden beaches and to use non-steam-treated wooden beaches for one or both top layers. Since steam-treated wooden beaches have a lighter color, it can be advantageous to use steam-treated wooden beaches in the top layer. These give the OSB a more appealing color.

In yet another variant, only one or both cover layers are formed from water-vapor-treated wooden strands, and dried and non-steam-treated wooden strands are used for the middle layer.

In a still further variant, it is conceivable and possible to use a mixture with any ratio of water-steam-treated wooden beaches and non-steam-treated wooden beaches for the middle and top layers. In such a case, the mixture can comprise between 10 and 50% by weight, preferably between 20 and 30% by weight of untreated or non-steam-treated wooden beaches and between 50 and 90% by weight, preferably between 70 and 80% by weight of water-steam treated wooden beaches.

In a further embodiment variant, the step of steam treatment of the wooden beaches can be carried out separately from the manufacturing process of the OSB wood-based panels. Accordingly, in this embodiment variant of the present method, the water vapor treatment takes place outside the overall process or the process line. The wooden beaches are removed from the manufacturing process and into the Steam treatment device (eg steaming system) introduced. Subsequently, the steam-treated wooden beaches can be reinserted into the conventional manufacturing process, if necessary after intermediate storage, for example immediately before gluing. This enables a high degree of flexibility in the manufacturing process.

In yet another embodiment, the steam treatment of the wooden beaches can be integrated into the manufacturing process of the OSB wood-based panels, i.e. The steam treatment step is integrated into the overall process or process line and takes place online.

In this case, the steam treatment can i) take place immediately after the cutting and preparation of the wooden strands or ii) only after the sifting and separation of the wooden strands in accordance with the use of the wooden strands for the middle or top layer. In the latter case, a separate steam treatment of the wooden strands can be carried out according to the requirements for the wooden strands used in the middle and top layers.

In a further variant of the present method, the steam treatment of the wooden beaches is carried out in at least one steaming system, preferably in two steaming systems. The vapor deposition system used here can exist or function as a batch system or as a continuously operated system, a continuously operated system being preferred.

As already noted above, the steam treatment of wood strands used for the middle layer and the top layers of the OSB wood-based panel can each be carried out separately in at least two steaming systems. This enables the degree of water vaporization of the water vapor-treated wooden strands used in the middle and / or top layer to be adapted to the respective requirements and customer requirements. In this case, the two vapor deposition systems used are preferably connected or arranged in parallel.

The contacting of the wooden strands with the at least one binder in step d) is preferably carried out by spraying or spraying the binder onto the wooden strands. Many OSB systems work with rotating coils (drums with atomizer gluing). Mixer gluing would also be possible. The strands are intimately mixed with the glue in a mixer by rotating blades.

In one embodiment of the present method, a polymer adhesive is preferably used as the binder, which is selected from the group comprising formaldehyde adhesives, such as urea-formaldehyde resin adhesive (UF) and / or melamine-formaldehyde resin adhesive (MF), polyurethane adhesives , Epoxy resin adhesives, polyester adhesives. In the present case, the use of a polyurethane adhesive is preferred, the polyurethane adhesive being based on aromatic polyisocyanates, in particular polydiphenylmethane diisocyanate (PMDI), tolylene diisocyanate (TDI) and / or diphenylmethane diisocyanate (MDI), PMDI being particularly preferred.

In a variant of the present method, the steam-treated and non-steam-treated wooden strands are glued with a binder amount of 1.0 to 5.0% by weight, preferably 2 to 4% by weight, in particular 3% by weight (based on the total amount of the wooden strands).

It is also possible to add at least one flame retardant to the wooden beaches together or separately with the binder. The flame retardant can typically be added in an amount between 1 and 20% by weight, preferably between 5 and 15% by weight, particularly preferably ≥ 10% by weight, based on the total amount of the wooden beaches. Typical flame retardants are selected from the group comprising phosphates, sulfates, borates, in particular ammonium polyphosphate, tris (tri-bromoneopentyl) phosphate, zinc borate or boric acid complexes of polyhydric alcohols.

The glued (water vapor-treated and / or non-water vapor-treated) wooden strands are sprinkled onto a conveyor belt to form a first cover layer along the direction of transport, then to form a middle layer transverse to the direction of transport and finally to form a second cover layer along the direction of transport.

After sprinkling, the glued wood strands are pressed at temperatures between 200 and 250 ° C, preferably 220 and 230 ° C, to form an OSB wood-based panel.

• Herstellen von Holzstrands aus geeigneten Hölzern, insbesondere mittels Zerspanen von geeigneten Hölzern,
• Behandeln von der Holzstrands mit Wasserdampf mit einer Temperatur zwischen 80°C und 120°C bei einem Druck zwischen 0,5 bar und 2 bar, in sauerstofffreier oder sauerstoffarmer Atmosphäre;
• Trocknen der mit dem Wasserdampf behandelten Holzstrands;
• Sichten und Separieren der wasserdampfbehandelten Holzstrands in Holzstrands geeignet zur Verwendung als Mittelschicht und Deckschicht;
• Beleimen der separierten Holzstrands;
• Aufstreuen der beleimten wasserdampfbehandelten Holzstrands auf ein Transportband in der Reihenfolge erste untere Deckschicht, Mittelschicht und zweite obere Deckschicht; und
• Verpressen der beleimten Holzstrands zu einer OSB-Holzwerkstoffplatte.

In a first preferred embodiment, the present method for producing an OSB wood-based panel with reduced VOC emissions comprises the following steps:

• Manufacture of wooden beaches from suitable woods, in particular by cutting suitable woods,
• Treating the wooden beaches with steam at a temperature between 80 ° C and 120 ° C at a pressure between 0.5 bar and 2 bar, in an oxygen-free or low-oxygen atmosphere;
• Drying the steamed wooden beaches;
• Sifting and separating the steam-treated wooden strands into wooden strands suitable for use as a middle and top layer;
• Gluing the separated wooden beaches;
• Sprinkle the glued, steam-treated wooden beach onto a conveyor belt in the order of the first lower cover layer, middle layer and second upper cover layer; and
• Pressing the glued wood strands into an OSB wood-based panel.

• Herstellen von Holzstrands aus geeigneten Hölzern, insbesondere mittels Zerspanen von geeigneten Hölzern;
• Sichten und Separieren der Holzstrands in Holzstrands geeignet zur Verwendung als Mittelschicht und Deckschicht;
• Behandeln der für die Mittelschicht vorgesehenen Holzstrands und/oder der für die Deckschicht(en) vorgesehenen Holzstrands mit Wasserdampf mit einer Temperatur zwischen 80°C und 120°C bei einem Druck zwischen 0,5 bar und 2 bar, in sauerstofffreier oder sauerstoffarmer Atmosphäre;
• Trocknen der mit dem Wasserdampf behandelten Holzstrands;
• Beleimen der separierten wasserdampfbehandelten Holzstrands und Beleimen von nicht-wasserdampfbehandelten Holzstrands;
• Aufstreuen der beleimten wasserdampfbehandelten und nicht-wasserdampfbehandelten Holzstrands auf ein Transportband in der Reihenfolge erste untere Deckschicht, Mittelschicht und zweite obere Deckschicht; und
• Verpressen der beleimten Holzstrands zu einer OSB-Holzwerkstoffplatte.

In a second preferred embodiment, the present method for producing an OSB wood-based panel with reduced VOC emissions comprises the following steps:

• Manufacture of wooden beaches from suitable woods, in particular by cutting suitable woods;
• Sifting and separating the wooden strands into wooden strands suitable for use as a middle and top layer;
• Treating the wooden strands intended for the middle layer and / or the wooden strands intended for the top layer (s) with steam at a temperature between 80 ° C and 120 ° C at a pressure between 0.5 bar and 2 bar, in an oxygen-free or low-oxygen atmosphere;
• Drying the steamed wooden beaches;
• Gluing of the separated steam-treated wooden beaches and gluing of non-steam treated wooden beaches;
• Sprinkling the glued steam-treated and non-steam treated wooden strands onto a conveyor belt in the order of the first lower cover layer, middle layer and second upper cover layer; and
• Pressing the glued wood strands into an OSB wood-based panel.

Accordingly, the present method enables the production of an OSB wood-based panel with reduced emission of volatile organic compounds (VOCs), which comprises steam-treated wooden beaches.

The present OSB wood-based panel can consist entirely of steam-treated wooden strands or a mixture of steam-treated and non-steam-treated wooden strands. In one embodiment, both top layers and the middle layer of the OSB consist of steam-treated wooden strands, in a further embodiment the two top layers consist of non-steam-treated wooden strands and the middle layer consists of steam-treated wooden strands, and in a further embodiment the two top layers consist of steam-treated wooden strands and the middle layer from non-steam treated wooden beaches.

The present OSB wood-based panel can have a bulk density between 300 and 1000 kg / m ³ , preferably between 500 and 800 kg / m ³ , particularly preferably between 500 and 600 kg / m ³ .

The thickness of the present OSB wood-based panel can be between 5 and 50 mm, preferably between 10 and 40 mm, a thickness between 15 and 25 mm being preferred in particular.

The OSB wood-based panel produced with the present method has, in particular, a reduced emission of aldehydes released during the wood digestion, in particular pentanal or hexanal, and / or terpenes, in particular carene and pinene.

Aldehydes are released during the machining process and the associated aqueous processing and cleaning of the wooden beaches. Specific aldehydes can be formed from the basic building blocks of cellulose or hemicellulose. For example, the aldehyde furfural is formed from mono- and disaccharides of cellulose or hemicellulose, while aromatic aldehydes can be released from lignin. The aliphatic aldehydes (saturated and unsaturated) are formed by the fragmentation of fatty acids with the participation of oxygen.

Due to the use of steam-treated wooden beaches, there is a reduction in the emission of C ₂ -C ₁₀ aldehydes, particularly preferably acetaldehyde, pentanal, hexanal or furfural, and a reduction in released terpenes, in particular C ₁₀ monoterpenes and C ₁₅ sesquiterpenes, in particular preferably acyclic or cyclic monoterpenes in the OSB wood-based panels.

Typical acyclic terpenes are terpene hydrocarbons such as myrcene, terpene alcohols such as gerianol, linaool, ipsinol and terpene aldehydes such as citral. Typical representatives of the monocyclic terpenes are p-menthan, terpeninol, limonene or carvone, and typical representatives of the bicyclic terpenes are carane, pinane, bornane, 3-carene and α-pinene being of particular importance. Terpenes are constituents of tree resins and are therefore particularly present in tree species containing resin, such as pine or spruce.

The emission of organic acids, in particular the emission of acetic acid from OSB wood-based panels can also be reduced. Organic acids are obtained in particular as cleavage products of the wood constituents cellulose, hemicellulose and lignin, alkane acids such as acetic acid and propionic acid or aromatic acids preferably being formed.

In particular, the sharp reduction in aldehydes was in no way foreseeable by the person skilled in the art. It can be assumed, for example, that water accumulates on the double bonds of the unsaturated fatty acids during the steam treatment, thus preventing the formation of aldehydes. However, because of the low electrophilicity of water, such additions usually only take place in the presence of mineral acids (sulfuric acid, phosphoric acid, etc.) at higher temperatures.

• mindestens eine Vorrichtung zum Entrinden von geeigneten Holzstämmen;
• mindestens einen Zerspaner zum Zerspanen der entrindeten Holzstämmen in Holzstrands;
• mindestens eine oben beschriebene Vorrichtung zur Wasserdampfbehandlung von mindestens einem Teil der Holzstrands;
• mindestens einen Trockner zum Trocknen der wasserdampfbehandelten Holzstrands;
• mindestens eine Vorrichtung zum Sichten und Separieren der Holzstrands (wasserdampfbehandelt und nicht-wasserdampfbehandelt);
• mindestens eine Vorrichtung zum Beleimen der Holzstrands;
• mindestens eine Vorrichtung zum Streuen der beleimten Holzstrands auf ein Transportband, und
• mindestens eine Presse zum Verpressen der gestreuten Holzstrands zu OSB.

The present method is carried out in a production line for the production of an OSB board and comprises the following elements:

• at least one device for debarking suitable logs;
• at least one chipper for chipping the debarked logs in wooden strands;
• at least one device for steam treatment of at least part of the wooden beaches described above;
• at least one dryer for drying the steam-treated wooden beaches;
• at least one device for classifying and separating the wooden beaches (steam-treated and non-steam-treated);
• at least one device for gluing the wooden beaches;
• at least one device for spreading the glued wooden beach on a conveyor belt, and
• at least one press for pressing the spread wooden strands to OSB.

As already noted above, the vapor deposition system can be designed continuously. For this purpose, the wooden strands are applied to a conveyor belt, which guides the wooden strands through the steaming system at a predetermined speed. During the passage through the steaming system, the wooden strands are sprayed evenly with water vapor, which is introduced from nozzles provided above the conveyor belt.

The steaming system can be provided upstream (upstream) of the device for classifying and separating the wooden strands. In this case, all wooden beaches are subjected to steam treatment.

However, it is also possible for two vapor deposition systems to be provided behind (downstream) the device for classifying and separating the wooden beaches. In this case, one steaming system is used for steam treatment of the wooden strands that are provided for the middle layer, and the other steaming system is used for steam treatment of the wooden strands that are provided for the cover layers. This enables an optional steam treatment of the wooden strands for the middle layer or the wooden strands for the top layers.

Figur 1

eine schematische Darstellung einer Ausführungsform einer Vorrichtung zur Wasserdampfbehandlung von Holzstrands;

Figur 2

eine schematische Darstellung einer ersten Ausführungsform des erfindungsgemäßen Verfahrens zur Herstellung von OSB-Platten, und

Figur 3

eine schematische Darstellung einer zweiten Ausführungsform des erfindungsgemäßen Verfahrens.

The invention is explained in more detail below with reference to the figure of the drawing using an exemplary embodiment. Show it:

Figure 1

a schematic representation of an embodiment of a device for steam treatment of wooden beaches;

Figure 2

a schematic representation of a first embodiment of the method according to the invention for the production of OSB boards, and

Figure 3

is a schematic representation of a second embodiment of the method according to the invention.

Figure 1 shows a variant of a device 10 for steam treatment of wooden beaches. The device comprises a (thermally insulated) tubular body 11 with a perforated conveyor belt 12 passing through the tubular body 11. Above the conveyor belt 12 there is a feed line 13 for the water vapor, the feed line 13 having a plurality of nozzles 14 for spraying the water vapor onto the Conveyor belt 12 located wooden beach. Below the conveyor belt 12, a collecting means 15 is provided for the water vapor condensate that forms.

The present device 10 enables steam treatment of the strands before the strands are dried in the drum dryer. All or part of the beaches that are intended for the later production of the OSB can be treated. The treatment takes place at normal pressure and achieves the homogeneous treatment of the beaches with steam by using the conveyor belt 12 made of metal mesh.

The belt of the transport device is dimensioned so that the strands cannot fall through the gaps. The strands are transferred to the conveyor belt 12, which runs through the tubular body 11, directly after production. The strands are distributed on the conveyor belt 12 in such a way that a homogeneous flow of water vapor through the strands is possible. Separation stations positioned at regular intervals ensure that existing or forming beach heaps are dissolved.

Since the conveyor belt 12 is cooled by the condensate forming when the beaches are heated and has a relatively high mass compared to the beaches, heating of the conveyor belt must be provided before the beaches are sprinkled on. This accelerates the heating of the beaches and thus reduces the duration of the steam treatment. The heating can be done by resistance heating or by radiation.

Steam is then applied from above to the strands through nozzles 14. The steam has a temperature of approx. 100 ° C. The insulation of the metal tube 11 ensures that the heat losses are as low as possible. The condensate that forms is collected under the transport device 12, freed from suspended matter and returned to the system after a cleaning step to remove dissolved substances.

The dwell time of the beaches in the saturated steam atmosphere is 5 to 15 minutes. The progress of beach heating is determined at regular intervals by thermal sensors. The temperature of the beaches should be close to 90 ° C at the end of the treatment.

In the Figure 2 The first embodiment of the method according to the invention shown describes the individual method steps starting with the provision of the wood starting product up to the finished OSB wood-based panel.

Correspondingly, in step 1 suitable wood starting material for the production of the wooden beaches is provided. All softwoods, hardwoods or mixtures thereof are suitable as wood raw material.

The debarking (step 2) and the cutting (step 3) of the wood starting material is carried out in suitable chippers, whereby the size of the wooden beaches can be controlled accordingly. After shredding and preparation of the wooden strands, they may be subjected to a pre-drying process, with a humidity of 5-10% being set in relation to the initial moisture of the wooden strands (not shown).

In the case of the Figure 2 In the embodiment shown, the wooden strands are introduced into an evaporation system (step 4). The steam treatment of the wooden beaches takes place in a temperature range between 80 ° and 120 ° C at a pressure between 0.5 bar and 2 bar. The resulting condensate can be collected and the substances washed out of the wooden beaches (terpenes, aldehydes) can be used from the condensate for further use.

After completion of the steam treatment, which in this case takes about 10-20 minutes, the steam-treated wooden beaches are dried (step 9), viewed and separated (step 5).

There is a separation in wooden strands for use as a middle layer (step 6a) or as a top layer (step 6b) with respective gluing.

The glued, steam-treated wooden strands are sprinkled onto a conveyor belt in the order of the first lower cover layer, middle layer and second upper cover layer (step 7) and then pressed into an OSB wood-based panel (step 8).

In the in Figure 3 shown second embodiment, the wood raw material in analogy to Figure 1 First provided (step 1), debarked (step 2) and machined (step 3). The wooden strands are optionally subjected to a pre-drying process, with a moisture of 5-10% being set in relation to the initial moisture of the wooden strands (step 3a). In contrast to the variant of the Figure 2 Already after the optional drying, there is a separation in wooden beaches for use as a middle layer or as a top layer (step 5).

This is followed by the water vapor treatment of the wooden strands provided for the middle layer (step 4a) and / or water vapor treatment of the wooden strands provided for the cover layer (s) (step 4b) in a respectively suitable vapor deposition system. The steam treatment of the wooden beaches takes place in a temperature range between 80 ° and 120 ° C at a pressure between 0.5 bar and 2 bar. The resulting condensate can be collected and the substances washed out of the wooden beaches (terpenes, aldehydes) can be used from the condensate for further use.

It is also possible that only the wooden strands for the middle layer are subjected to steam treatment, while the wooden strands for the outer layers remain untreated.

After completion of the water vapor treatment, which in the present case takes about 10-20 minutes, the water vapor-treated wooden strands are dried (steps 9a, 9b) and glued (steps 6 a, b).

The glued water-treated wooden strands are sprinkled onto a conveyor belt in the order of the first lower cover layer, middle layer and second upper cover layer (step 7) and then pressed into an OSB wood-based panel (step 8).

In the final processing, the OSB wood-based panel obtained is suitably assembled in each case.

Example 1:

Strands are produced from pine trunks (length: max. 200 mm, width: 20 mm, thickness: max. 1 mm, humidity max. 50%) and treated in a continuous process with steam at around 100 ° C. During the treatment, the strands are loosely heaped up on a conveyor belt which has perforations and thus allows the steam to pass through after passing the strands. The steam treatment was preferably carried out from top to bottom. The conveyor belt is guided through a tubular body. Preferably above the conveyor belt with the loosely heaped up beaches Nozzles are attached that distribute the steam evenly over the beaches. The treatment with steam takes about 15 minutes. The steam treatment takes place with the greatest possible exclusion of oxygen, so that one can speak of a reductive process control.

The tube body has a diameter of 50 cm and a length of 3 m in order to achieve a dwell time of about 15 minutes. The conveyor belt was moved through the tubular body at a speed of about 2 m / 10 minutes. In the feed direction, the tube body was angled slightly upwards (2 to 10 degrees), so that the condensate that formed could easily be collected. This is a test facility with which the effect should be demonstrated. For a production plant, this can be enlarged and easily optimized by a specialist in terms of transport speed and quantity.

The strands are then dried in a conventional drum dryer. The energy consumption of the drum dryer is significantly reduced, since the strands already have a temperature of around 90 ° C when they enter the dryer. Then they are glued in a coil with adhesive, preferably with PMDI (approx. 3% by weight on dry wood).

The glued stands are spread in a conventional OSB system as top and middle layers. The percentage distribution between the middle and top layers is preferably 70% to 30%. The strands are pressed into sheets with a bulk density of around 570 kg / m3. After a storage period of one week, the test plate was tested for VOC release together with a standard plate of the same thickness in a micro-chamber.

Chamber parameters: temperature: 23 ° C; Humidity: 0%; Air flow: 150 ml / min; Air change: 188 / h; Loading: 48.8 m ² / m ³ ; Sample surface: 0.003 m ² ; Chamber volume: 48 ml. The values of the most important parameters in terms of quantity are shown in Table 1. Table 1 parameter Test plate [µg / m2 xh] Standard plate [µg / m2 xh] Hexanal 194 1474 3-carene 208 626 α-pinene 181 925 Pentanal - 155 β-pinene - 285 2-octenal 60 115

As can be seen from the results, the emissions of the most important parameters in terms of quantity are significantly reduced. Some parameters could no longer be detected. Surprisingly, this also applies to the saturated and unsaturated aldehydes, which should only be formed in the press at high temperatures in accordance with the educational path assumed to be correct and plausible. This means that either the previously assumed mechanism for the formation of the aldehydes is incorrect or the steaming of the precursors of the aldehydes is chemically converted so that the formation of the aldehydes is only possible to a limited extent. Originally it was expected that steam treatment would only reduce terpene emissions. In the process, these would be driven off like in a steam distillation.

Example 2:

Corresponds to embodiment 1, except that only strands for the middle class (about 70% of the OSB) were treated with steam, with the following result of the VOC test:
Chamber parameters: temperature: 23 ° C; Humidity: 0%; Air flow: 150 ml / min; Air change: 188 / h; Loading: 48.8 m ² / m3; Sample surface: 0.003 m ² ; Chamber volume: 48 ml. The values of the most important parameters in terms of quantity are shown in Table 2. Table 2 parameter Test plate [µg / m2 xh] Standard plate [µg / m2 xh] Hexanal 243 1474 3-carene 299 626 α-pinene 178 925 Pentanal - 155 β-pinene - 285 2-octenal 61 115

A significant reduction in emissions can also be observed here, even though the cover layer consists of standard beaches.

Claims (15)

Comprehensive OSB wood-based panel with reduced emissions of volatile organic compounds (VOCs)
steam-treated wooden beaches or a mixture of steam-treated wooden beaches and non-steam-treated wooden beaches as a middle layer and / or top layer,
whereby to provide the water vapor-treated wooden strands, wooden strands are treated with water vapor after drying without drying, the water vapor being passed over the wooden strands at a temperature between 80 ° C. and 120 ° C. and a pressure between 0.5 bar and 2 bar. OSB wood-based panel according to claim 1, characterized in that the steam-treated wooden strands are used in all layers of the OSB wood-based panel. OSB wood-based panel according to claim 1, characterized in that the steam-treated wood strands are used only in the middle layer and non-steam-treated wood strands in one or both cover layers of the OSB wood-based panel. OSB wood-based panel according to claim 1, characterized in that the steam-treated wood strands are used only in one or both cover layers and non-steam-treated wood strands in the middle layer of the OSB wood-based panel. OSB wood-based panel according to claim 1, characterized in that a mixture with any ratio of water vapor-treated wooden strands and non-steam-treated wooden strands is used in the middle and top layer of the OSB wood-based panels. OSB wood-based panel according to claim 5, characterized in that the mixture between 10 and 50% by weight, preferably between 20 and 30% by weight of untreated or non-steam-treated wooden beaches and between 50 and 90% by weight, preferably between 70 and 80% by weight. on steam-treated wooden beaches. OSB wood-based panel according to one of the preceding claims, characterized by a polymer adhesive as a binder which is selected from the group comprising formaldehyde adhesives, such as urea-formaldehyde resin adhesive (UF), melamine-urea-phenol-formaldehyde adhesive (MUPF ) and / or melamine-formaldehyde resin adhesive (MF), polyurethane adhesives, epoxy resin adhesives, polyester adhesives. OSB wood-based panel according to one of the preceding claims, characterized in that a polyurethane adhesive based on aromatic polyisocyanates, in particular polydiphenylmethane diisocyanate (PMDI), tolylene diisocyanate (TDI) and / or diphenylmethane diisocyanate (MDI) is used as the binder, OSB wood-based panel according to one of the preceding claims, characterized in that the water-vapor-treated and non-water-vapor-treated wooden beaches with a binder amount of 1.0 to 5.0% by weight, preferably 2 to 4% by weight, in particular 3% by weight (based on the total amount the wooden beach) are glued. OSB wood-based panel according to one of the preceding claims, characterized in that it contains at least one flame retardant, in particular in an amount between 1 and 20% by weight, preferably between 5 and 15% by weight, particularly preferably ≥10% by weight, based on the total amount of the wooden beaches . OSB wood-based panel according to one of the preceding claims, characterized by a reduced emission of aldehydes released during the wood digestion, in particular C ₂ -C ₁₀ aldehydes. OSB wood-based panel according to one of the preceding claims, characterized by a reduced emission of terpenes released during the wood digestion, in particular C ₁₀ monoterpenes and C ₁₅ sesquiterpenes. OSB wood-based panel according to one of the preceding claims, characterized by a reduced emission of organic acids, in particular of alkanoic acids. OSB wood-based panel according to one of the preceding claims, characterized in that for treating the wooden beaches with water vapor, the water vapor at a temperature between 90 ° C and 110 ° C, particularly preferably 100 ° C at a pressure between 0.7 bar and 1, 5 bar, particularly preferably at 1 bar (atmospheric pressure) is passed over the wooden strands. OSB wood-based panel according to one of the preceding claims, characterized in that the steam treatment of the wooden beaches takes place over a period of 5 to 30 minutes, preferably 10 to 20 minutes, particularly preferably 15 minutes.

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