EP3170635B1 - Osb (oriented strand board) - wood material board with improved properties and method for producing same - Google Patents

Description

The present invention relates to a process for the production of OSB wood-based panels according to the preamble of claim 1, OSB wood-based panels produced by the method according to claim 11 and the use of torrefected wooden strands according to claim 15.

description

Coated boards, also known as OSB (Oriented Strand Boards), are wood-based panels made from long strands. However, the OSB boards originally obtained as waste products of the veneer and plywood industry are increasingly being used in wood and prefabricated house construction, since OSB boards are lightweight and nevertheless fulfill the structural requirements set on construction boards. For example, OSB boards are used as building boards and as wall or roof planking or in the floor area.

The production of OSB boards is carried out in a multi-stage process, wherein initially the chips or strands of debarked roundwood, preferably coniferous wood, are peeled off in the longitudinal direction by rotating blades. In the subsequent drying process, the natural moisture of the beach is reduced at high temperatures. The degree of moisture of the strands may vary depending on the adhesive used, and the humidity should be well below 10% in order to avoid breakers during later compression. Depending on the adhesive, wetting may be more favorable on rather wet beaches or on dry beaches. In addition, as little moisture as possible should be present in the strands during the pressing process, in order to reduce the vapor pressure generated during the pressing process as far as possible, as this could otherwise cause the raw plate to burst.

Following the drying of the strands they are introduced into a gluing device in which the glue or adhesive is applied finely distributed to the chips. For gluing predominantly PMDI (polymeric diphenylmethane diisocyanate) or MUPF glues (melamine-urea-phenol-formaldehyde) are used. The glues can also be mixed in the OSB boards. These glues are used because the OSB boards are often used for structural applications as mentioned above. There must be used moist or moisture-resistant glues.

After gluing, the glued strands are scattered in scattering apparatuses alternately along and across 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 deviate from the scattering direction of the middle layer. Also, the strands used in the top and middle layers differ from each other. Thus, the strands used in the outer layers are flat and the strands used in the middle layer are less flat up to span-shaped. Usually, two strands of material are used in the manufacture of the OSB boards: one with flat strands for the later cover layers and one with "chips" for the middle layer. Accordingly, the strands in the middle layer may be qualitatively inferior because the flexural strength is generated substantially by the cover layers. Therefore, fines produced during machining can also be used in the middle layer of OSB boards.

Following the scattering of the strands, continuous compression of the same under high pressure and temperature of e.g. 200 to 250 ° C.

Not least because of their sustainability, OSB boards are enjoying increasing popularity and diverse applications, for example as a construction element in house construction or as formwork in concrete construction. The inherent hygroscopic properties of wood-based materials, however, have a detrimental effect in some applications.

Especially when using indoor OSB, the escape of wood constituents is viewed critically. This is particularly problematic in OSB pine panels, as they show very high emission of volatile organic compounds.

In the course of the production of wood-based panels and in particular due to the production process of the wood strands arise or a variety of volatile organic compounds are released. Volatile organic compounds, also called VOCs, include volatile organic compounds that readily evaporate or are already present as gas at lower temperatures, such as room temperature.

The volatile organic compounds VOC are either already present in the wood material and are released during workup from this or they are formed according to the current state of knowledge by the degradation of unsaturated fatty acids, which in turn are decomposition products of wood. Typical conversion products that occur during processing, for example, pentanal and hexanal, but also octanal, octenal or 1-heptenal. In particular, softwoods from which OSB boards are predominantly produced contain large amounts of resin and fats which lead to the formation of volatile organic terpene compounds and aldehydes. However, VOCs and aldehydes, such as formaldehyde, can also be formed or released when certain adhesives are used for the production of wood-based materials.

The emission of ingredients in OSB boards is critical mainly because this material is predominantly used uncoated. This allows the ingredients to exude unhindered. In addition, the OSB boards are often used for cladding / paneling of large areas, which usually results in a high space loading (m ² OSB / m ³ room air). This leads in addition to a concentration of certain substances in the room air.

To solve the problem of VOC emission, various approaches have been described in the past. So goes out of the EP 2 615 126 B1 show that a reduction in VOC emission in OSB plates can be achieved through the use of nanoparticles modified with silane compounds. However, the use of such nanoparticles in OSB boards is associated with relatively high costs.

It is therefore desirable to develop further solutions which reduce the release of volatile organic compounds from OSB wood-based panels.

Another problem in the production of OSB boards is the swelling tendency of the wood strands, which can lead to a reduction in the technological values such as strength values of the OSB wood-based boards. One approach to reducing swelling is in eg US 6098679 described. Here, a method and apparatus is shown for pre-treating or post-treating OSB panels to reduce swelling. For this purpose, the OSB plate is charged with superheated steam in a vacuum chamber.

The invention is now based on the technical object to improve the known per se method for the production of OSB material boards to produce OSB material plates with a significantly reduced emission of volatile organic compounds (VOCs) and with improved swelling values simply and safely. If possible, the manufacturing process should be changed as little as possible and the cost do not rise disproportionately. Furthermore, the solution should include the greatest possible flexibility. Finally, environmental aspects should also be considered, ie the solution should not cause additional energy consumption or generate additional waste.

This object is achieved by a method for producing OSB wood-based panels with the features of claim 1 and an OSB wood-based panel made therefrom according to claim 11.

1. a) Herstellen von Holzstrands aus geeigneten Hölzern,
2. b) Torrefizieren von zumindest einem Teil der Holzstrands;
3. c) Beleimen der torrefizierten Holzstrands und nicht-torrefizierten Holzstrands mit mindestens einem Bindemittel;
4. d) Aufstreuen der beleimten Holzstrands auf ein Transportband; und
5. e) Verpressen der beleimten Holzstrands zu einer OSB-Holzwerkstoffplatte.

Accordingly, there is provided a process for producing OSB wood-based panels, in particular OSB wood-based panels having reduced emission of volatile organic compounds (VOCs), comprising the following steps:

1. a) making wooden strips of suitable woods,
2. b) Torrefying at least a portion of the wooden strands;
3. c) gluing the torrefied wooden strands and non-torrefied wooden strands with at least one binder;
4. d) sprinkling the glued wooden strands onto a conveyor belt; and
5. e) pressing the glued wooden strands into an OSB wood-based panel.

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

By providing the present method, there are several advantages. Thus, a simple production of OSB wood-based panels is possible without substantially influencing the usual process chain without the classical drying process with significantly reduced emission of volatile organic compounds from the OSB. The produced OSB wood-based panels also have a significantly lower swelling and higher dimensional stability. Also, through the use of torrefied beaches, which have a very low humidity, simple products are produced, which are produced by the addition of aqueous formulations, with an adjustment of the water balance is possible.

Torrefaction is a thermochemical treatment process in which the material to be torrefied is heated in an oxygen-reduced or oxygen-free gas atmosphere at atmospheric pressure. Due to the lack of oxygen, the material does not burn, instead there is a mass loss due to the decomposition of wood components, which are degraded to volatile compounds at Torrefizierungsstemperaturen. These are mainly hemicelluloses and lignins. In addition, low molecular weight compounds such as formic acid, terpenes, hydrocarbons, etc. driven out. Torrefied material is hydrophobic and therefore less susceptible to ambient humidity, so that the risk of rotting torrefected material is extremely low.

The tanning step of the wood strands may be provided in various ways in the present process.

In one embodiment of the present method, at least a portion of the wood strands used to make the OSB boards are dried prior to torrefying, i. in this case dried or pre-dried wood strands, e.g. subjected to a degree of moisture of 5 to 15% moisture, preferably 5 to 10% moisture of Torrefizierung.

In a further second embodiment of the present method at least a portion of the wood strands are torrefied with a humidity of 20-50% by weight, i. Here no previous drying of the wooden strands, but the wood strands are fed without further pretreatment after chipping the Torrefizierungsvorrichtung.

Accordingly, the present method enables torrefaction of wet or dry wood strands. In particular, the torrefaction of wet wood strands is advantageous because the drying step is saved.

In another embodiment of the present method, torrefined wood strands or a mixture of torrefied wood strands and untreated (ie non-torrefied) wood strands are used as the middle layer and / or top layer of the OSB material board.

Accordingly, in one variant, a complete substitution of the wood strands is possible, the torrefizierten wood strands are used only in the middle layer, only in one or both cover layers or in all layers. In this variant, the use of a dryer is eliminated.

In another variant it is possible to form only the middle layer of torrefied wood strands and to use dried and non-tinted wood strands for one or both cover layers. Since torrefected strands have a brown color, it may be advantageous to use torrefied strands only in the middle layer.

In yet another variant, only one or both cover layers are formed of torrefied wood strands, and for the middle layer, dried and untorn wood strands are used.

In yet another variant, it is conceivable and possible to use for the middle and outer layers in each case a mixture with any ratio of torrefizierten wooden strands and non-torrefected wooden strands. In such a case, the mixture may comprise between 10 and 50% by weight, preferably between 20 and 30% by weight of untreated or non-torrefied wood strands and between 50 and 90% by weight, preferably between 70 and 80% by weight of torrefied wood strands.

In a further embodiment, the step of Torrefizierens the wood strands can be performed separately from the manufacturing process of OSB wood-based panels. Thus, in this embodiment of the present method, the torrefaction step occurs outside the overall process or process line. The wood strands are thereby discharged from the manufacturing process and introduced into the torrefying apparatus (e.g., torrefying reactor). Subsequently, the Torrefizierten wood strands may, after an intermediate storage, for example. be returned to the conventional manufacturing process immediately before gluing. This allows a high flexibility in the manufacturing process.

The Torrefizierungsschritt the wood strands can be integrated in yet another embodiment variant in the manufacturing process of the OSB wood-based panels, ie the Torrefizierungsschritt is incorporated into the overall process or process line and takes place online.

In this case, the torrefaction can be carried out immediately after the cutting and provision of the wooden strands, or only after the sifting and separation of the wooden strands according to the use of the wooden strands for the middle or top layer. In the latter case, a separate torrefaction of the wooden strands can be made according to the torrefaction requirements for the wooden strands used in the middle and top layers.
The wood strands used herein may have a length of 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 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 wood strands, for example, have a length between 150 and 200 mm, a width between 15 and 20 mm, a thickness between 0.5 and 1 mm and a moisture content of max. 50% up.
In a further variant of the present method, the torrefaction of the wood strands is carried out in at least one Torrefizierungsreaktor, preferably in two Torrefizierungsreaktoren. The Torrefizierungsreaktor used here can be present as a batch system or as a continuously operated system or work.
As noted above, the torrefaction of wood strands used for the middle layer and topsheets of the OSB wood-based panel may each be performed separately in at least two torrefying reactors. This makes it possible to adapt the Torrefizierungsgrades the torrefizierten wooden strands used in the middle and / or top layer to the respective requirements and customer requirements.
The two Torrefizierungsreaktoren used are preferably connected in parallel or arranged in this case. According to the invention, the wood strands are torrefied by heating in an oxygen-poor or oxygen-free atmosphere under atmospheric pressure at a temperature between 150 ° C and 300 ° C, preferably between 200 ° C and 280 ° C, particularly preferably between 220 ° C and 260 ° C. It can be torrefied under atmospheric pressure in the presence of an inert gas, preferably nitrogen as the reaction gas or gas stream. It is also possible to use saturated steam, in which case the Torrefizierungsprozess runs at temperatures between 160 ° C and 200 ° C and pressures of 6 bar to 16 bar.

The process of Torrefizierens is preferably terminated at a loss of mass of the wood strands of 10 to 30%, preferably 15 to 20%. The duration of the process varies depending on the amount and type of the starting material used and can be between 1 and 5 h, preferably between 2 and 3 h.

The pyrolysis gases released during the torrefaction process, essentially from hemicelluloses and other low molecular weight compounds, are used to generate process energy. The amount of gas mixture formed as gaseous fuel is sufficient to operate the process energetically self-sufficient.

It is also preferred if the torrefied wooden strands are cooled in water before gluing with a suitable binder. Thus, the torrefected wooden strands can be cooled in a water bath, which ensures complete wetting with water. A wetting agent which facilitates the wetting of the hydrophobic strands can be added to the water.

The contacting of the wood strands with the at least one binder in step c) is preferably carried out by spraying or atomizing the binder onto the wood strands. Many OSB systems work with rotating coils (drums with atomizer gluing). A 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 a binder which is selected from the group consisting of formaldehyde adhesives, polyurethane adhesives, epoxy adhesives, polyester adhesives. As the formaldehyde condensate adhesive, in particular, a phenol-formaldehyde resin adhesive (PF), a cresol / resorcinol-formaldehyde resin adhesive, urea-formaldehyde resin adhesive (UF) and / or melamine-formaldehyde resin adhesive (MF) can be used.

In the present case, the use of a polyurethane adhesive is preferred, wherein the polyurethane adhesive based on aromatic polyisocyanates, in particular Polydiphenylmethane diisocyanate (PMDI), tolylene diisocyanate (TDI) and / or diphenylmethane diisocyanate (MDI) is present, with PMDI being particularly preferred.

In the case of using PMDI adhesives, the torrefied and non-torrefied wood strands having a binder amount of 1.0 to 5.0% by weight, preferably 2 to 4% by weight, especially 3% by weight (based on the total amount of wood strands) glued.

In a further embodiment of the present method, it is also possible to use more than one polymer adhesive. Thus, as the first polymer adhesive at least one polycondensation adhesive such as a polyamide, a polyester, a silicone and / or a formaldehyde condensate adhesive, in particular a phenol-formaldehyde resin adhesive (PF), a cresol / resorcinol formaldehyde resin adhesive , Urea-formaldehyde-resin adhesive (UF) and / or melamine-formaldehyde-resin adhesive (MF) are used, and as the second polymer adhesive at least one polyaddition adhesive such as an epoxy resin, polycyanurate and / or a polyurethane adhesive, in particular a polyurethane adhesive based on polydiphenylmethane diisocyanate (PMDI) can be used. Such hybrid adhesive systems are known from EP 2 447 332 B1 known.

The following binder variants are particularly preferred: phenol-formaldehyde adhesive (PF); Melamine-urea-formaldehyde-resin adhesive (MUF); Melamine-urea-phenol formaldehyde resin adhesive (MUPF); PMDI adhesives and a combination of MUF / MUPF and PMDI adhesives. In the latter case, preference is given to using PMDI for the middle layer and as binder in the outer layers MUF or MUPF. Particularly preferred is the use of PMDI adhesives for all layers, i. for the cover layers and the middle layer.

It is also possible to supply at least one flame retardant to the wood strands together or separately with the binder.

The flame retardant may 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 wood strands.

Typical flame retardants are selected from the group comprising phosphates, borates, in particular ammonium polyphosphate, tris (tri-bromneopentyl) phosphate, zinc borate or boric acid complexes of polyhydric alcohols.

The glued (torrefied and / or non-torrefied) wood strands are scattered onto a conveyor belt to form a first cover layer along the transport direction, then to form a middle layer transversely to the transport direction and finally to form a second cover layer along the transport direction.

After sprinkling, the glued wooden 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,
• Torrefizieren der Holzstrands ohne vorherige Trocknung der Holzstrands;
• Sichten und Separieren der torrefizierten Holzstrands in Holzstrands geeignet zur Verwendung als Mittelschicht und Deckschicht;
• Beleimen der separierten torrefizierten Holzstrands;
• Aufstreuen der beleimten torrefizierten 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 process for producing an OSB wood-based panel with reduced VOC emission comprises the following steps:

• Making wooden strips of suitable woods, in particular by means of cutting suitable woods,
• Torrefying the wooden strands without first drying the wooden strands;
• Sifting and separating the torrefied wooden strands in wooden strands suitable for use as a middle layer and topcoat;
• Gluing the separated torrefected wooden strips;
• Sprinkling the glued torrefied wooden strands on a conveyor belt in the order of first lower cover layer, middle layer and second upper cover layer; and
• Pressing the glued wooden strands into an OSB wood-based panel.

• Herstellen von Holzstrands aus geeigneten Hölzern, insbesondere mittels Zerspanen von geeigneten Hölzern;
• ggfs. Trocknen der Holzstrands;
• Sichten und Separieren der Holzstrands in Holzstrands geeignet zur Verwendung als Mittelschicht und Deckschicht;
• Torrefizieren der für die Mittelschicht vorgesehenen Holzstrands und/oder Torrefizieren der für die Deckschicht(en) vorgesehenen Holzstrands;
• Beleimen der separierten torrefizierten Holzstrands;
• Aufstreuen der beleimten torrefizierten 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 process for producing an OSB wood-based panel with reduced VOC emission comprises the following steps:

• Manufacture of wooden strips of suitable woods, in particular by means of cutting of suitable woods;
• if necessary, drying the wooden strips;
• Sifting and separating the wooden strands in wooden strands suitable for use as a middle layer and topcoat;
• Torrefying the wooden strands provided for the middle layer and / or torrefying the wood strands provided for the cover layer (s);
• Gluing the separated torrefected wooden strips;
• Sprinkling the glued torrefied wooden strands on a conveyor belt in the order of first lower cover layer, middle layer and second upper cover layer; and
• Pressing the glued wooden 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) comprising torrefied wood strands.

The OSB wood-based panel produced by the present method has in particular a reduced emission of aldehydes released during wood pulping, in particular pentanal or hexanal, organic acids such as acetic acid and / or terpenes, in particular carene and pinene. In this regard, reference is also made to the comments below.

The present OSB wood-based panel may consist entirely of torrefied wooden strands or of a mixture of torrefied and non-torrefied wooden strands.

The present OSB board has a reduced swelling value, in particular one of 20% to 50%, preferably 30% to 40%, compared to OSB boards made entirely of non-torrefied wood strips. reduced source value by 35%. The swelling tendency of the present OSB wood-based panel is between 5 and 30%, preferably between 10 and 25%, particularly preferably between 15 and 20% (after 24 hours of water storage).

The present OSB wood-based panel may 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 may be between 5 and 50 mm, preferably between 10 and 40 mm, wherein in particular a thickness between 15 and 25 mm is preferred.

The object of the present invention is also achieved with the use of torrefied wood strands to reduce the emission of volatile organic compounds (VOCs) from OSB wood-based panels.

In a preferred variant, the torrefected wood strands are used for reducing aldehydes, organic acids and / or terpenes released during the wood pulping, in particular the cutting of the woods in strands.

Accordingly, in the present case, the torrefied wood strands are preferably used for reducing the emission of organic acids, in particular for reducing the emission of acetic acid from OSB wood-based panels. Organic acids are produced in particular as cleavage products of the wood constituents cellulose, hemicelluloses and lignin, alkanoic acids such as acetic acid and propionic acid or aromatic acids preferably being formed.

It is also desirable to use the torrefied wood strands to reduce the emission of aldehydes from OSB wood-based panels. As already explained above, there is a release of aldehydes during the hydrolytic workup of wood or lignocellulose. In this case, 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 liberated during the partial hydrolytic exclusion of lignin. Accordingly, the Torrefizierten wood strands to reduce the emission of C1-C10 aldehydes, particularly preferably from formaldehyde, acetaldehyde, pentanal, hexanal or furfural used in OSB wood-based panels.

In another embodiment of the present invention, the torrefied wooden strands are used to reduce the emission of terpenes. For example, the torrefied wood strands can be used to reduce liberated terpenes, in particular C10 monoterpenes and C15 sesquiterpenes, particularly preferably acyclic or cyclic monoterpenes.

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-menthane, terpeninol, limonene or carvone, and typical representatives of the bicyclic terpenes are caran, pinane, bornan, in particular 3-carene and α-pinene being of importance. Terpenes are components of the tree resins and therefore especially in very resinous tree species such as pine or spruce.

Figur 1

eine schematische Darstellung einer ersten Ausführungsform des erfindungsgemäßen Verfahrens, und

Figur 2

eine schematische Darstellung einer zweiten Ausführungsform des erfindungsgemäßen Verfahrens.

The invention will be explained in more detail with reference to the figure of the drawing of an embodiment. Show it:

FIG. 1

a schematic representation of a first embodiment of the method according to the invention, and

FIG. 2

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

In the FIG. 1 shown first embodiment of the method according to the invention describes the individual process steps, starting with the provision of the wood output product to the finished OSB wood-based panel.

Accordingly, in step 1 suitable wood starting material for the production of the wood strands is first provided. As wood source material all conifers, hardwoods or mixtures thereof are suitable.

The debarking (step 2) and the cutting (step 3) of the wood starting material takes place in suitable chippers, wherein the size of the wood strands can be controlled accordingly. After comminution and provision of the wood strands, they are optionally subjected to a predrying process, with a moisture content of 5-10% being set with respect to the initial moisture content of the woodchips (not shown).

In the case of in FIG. 1 In the embodiment shown, the wooden strands are introduced into a torrefying reactor (step 4). The torrefaction of the wooden strands takes place in a temperature range between 220 ° and 260 ° C. The resulting pyrolysis gases or Torrgase be used to generate the necessary energy for the process plant.

After completion of the torrefaction, which in the present case takes about 2 hours, the torrefected wooden strands are watered, sighted and separated (step 5).

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

The glued Torrefizierten wood strands are scattered onto a conveyor belt in the order first lower cover layer, middle layer and second upper cover layer (step 7) and then pressed to form an OSB wood-based panel (step 8).

In the in FIG. 2 As shown in the second embodiment, the wood starting material is analogous to FIG. 1 initially provided (step 1), debarked (step 2) and machined (step 3). The strands of wood may be subjected to a predrying process, with a humidity of 5-10% being adjusted in relation to the initial moisture content of the strands of wood (step 3a). In contrast to the variant of the FIG. 1 a separation in wood strands is already carried out after the optional drying for use as a middle layer or as a cover layer (step 5).

This is followed by torrefaction of the wood strands provided for the middle layer (step 4a) and / or torrefaction of the wood strands (step 4b) provided for the cover layer (s) in a suitable torrefaction reactor. The torrefaction of the wooden strands takes place in a temperature range between 220 ° and 260 ° C. Torrefaction can be set to the desired torrefaction level for the center and top layers.

The resulting pyrolysis gases or Torrgase be used to generate the necessary energy for the process plant.

After completion of the torrefaction, which takes in the present case about 2 hours, the Torrefizierten wooden strands are glued (steps 6 a, b).

The glued Torrefizierten wood strands are scattered onto a conveyor belt in the order first lower cover layer, middle layer and second upper cover layer (step 7) and then pressed to form an OSB wood-based panel (step 8).

In the finishing, the obtained OSB wood-based panel is assembled in each case in a suitable manner.

Embodiment:

Strands are produced from pine logs and torrefied in a continuous torrefaction apparatus at 180 ° C to a mass loss of about 20%. This takes place under saturated steam. In the process, the beaches turn from light yellow to light brown. The beaches are then cooled in water.

Subsequently, the binder (PMDI, about 3% by weight) in a gluing machine (Beleimtrommel, for example, the Fa. Coil) finely distributed on the torrefizierten wooden strands applied. The glued torrefied stands are sprinkled in an OSB plant as a middle layer.

The cover layer is formed from strands which have been dried in a tumble dryer. These have also been glued with PMDI as a glue (about 3% by weight). The beaches are not z. As a paraffin emulsion additionally hydrophobic, so as not to interfere with the subsequently performed tests by the hydrophobing agent. The scattered strands are pressed in a Contipresse to OSB plates.

The percentage distribution between middle and top layer is at least 70% to 30%. The strands are pressed into slabs with a density of about 570 kg / m ³ .

After a storage time of about one week, the test plate was tested together with a standard plate in the same strength in a micro-chamber on the VOC delivery.

Chamber parameters: temperature 23 ° C; Humidity 0%; Air flow 150 ml / min; Air exchange 188 / h; Load 48.8 m ² / m ³ ; Sample surface 0.003 m ² , chamber volume: 48 ml

The values of the quantitatively most important parameters are shown in Table 1. Table 1 parameter Test plate μg / m ² xh Standard plate μg / m ² xh hexanal 1093 3164 3-Carene 388 1962 α-Pinene 322 1174 pentanal 78 354 β-pinene 98 314

As can be seen from the results, the emissions of the quantitatively most important parameters are reduced by a factor of 3 to 5.

In addition, the thickness swelling was determined. Table 2 test drive standard plate Swelling (24 h) in% 18.3 27.44

As can be seen from the table, the source values are reduced by about 35% through the use of torrefied strands.

Claims (15)

1. Process for the production of OSB-wood-composite boards, in particular of OSB-wood-composite boards with reduced emission of volatile organic compounds (VOCs), comprising the following steps:

   a) production of wood strands made of suitable woods,

   b) torrefaction of at least a portion of the wood strands via heating in a low-oxygen-content or oxygen-free atmosphere under atmospheric pressure or elevated pressure at a temperature of from 150°C to 300°C;

   c) gluing of the torrefied wood strands and non-torrefied wood strands with at least one binder;

   d) application, by scattering, of the glued wood strands to a conveyor belt; and

   e) pressing of the glued wood strands to give an OSB-wood-composite board.
2. Process according to Claim 1, characterized in that at least a portion of the wood strands is dried before torrefaction.
3. Process according to Claim 1, characterized in that at least a portion of the wood strands is torrefied with moisture content of from 20 to 50% by weight.
4. Process according to any of the preceding claims, characterized in that torrefied wood strands, or a mixture of torrefied wood strands and non-torrefied wood strands, are/is used as middle layer and/or outer layer of the OSB-wood-composite board.
5. Process according to any of the preceding claims, characterized in that the wood strands are torrefied in at least one torrefaction reactor, preferably in two torrefaction reactors.
6. Process according to any of the preceding claims, characterized in that wood strands used for the middle layer and the outer layers of the OSB-wood-composite board are respectively torrefied separately in at least two torrefaction reactors.
7. Process according to any of the preceding claims, characterized in that the wood strands are torrefied via heating in a low-oxygen-content or oxygen-free atmosphere under atmospheric pressure or elevated pressure at a temperature of from 200°C to 280°C, with particular preference from 220°C to 260°C.
8. Process according to any of the preceding claims, characterized in that, before gluing with a suitable binder, the torrefied wood strands are cooled in water.
9. Process according to any of the preceding claims, characterized in that the quantity of binder used to glue the torrefied and non-torrefied wood strands is from 1.0 to 5.0% by weight, preferably from 2 to 4% by weight, in particular 3% by weight (based on the total quantity of the wood strands).
10. Process according to any of the preceding claims, characterized in that the glued wood strands are pressed at temperatures of from 200 to 250°C, preferably from 220 to 230°C, to give an OSB-wood-composite board.
11. OSB-wood-composite board with reduced emission of volatile organic compounds (VOCs) which can be produced in a process according to any of the preceding claims comprising torrefied wood strands.
12. OSB-wood-composite board according to Claim 11, characterized by reduced emission of terpenes and/or organic acids and/or aldehydes liberated during wood digestion.
13. OSB-wood-composite board according to Claim 11 or 12, characterized by a swelling value reduced in comparison with that of an OSB-wood-composite board produced entirely from non-torrefied wood strands, in particular a swelling value reduced by from 20% to 50%, preferably from 30% to 40%.
14. OSB-wood-composite board according to any of Claims 11 to 13, characterized in that this is composed entirely of torrefied wood strands or of a mixture of torrefied and non-torrefied wood strands.
15. Use of torrefied wood strands for reducing emission of volatile organic compounds (VOCs) from OSB-wood-composite boards.

Images