EP1414629B1 - Panel consisting of a derived timber product and produced in an environmentally-friendly manner - Google Patents

Abstract

The invention relates to a method for producing a construction element, especially a panel, consisting of wood fibres, wood chips and/or sawdust. According to the inventive method, glue is applied to wood fibres, wood chips and/or sawdust, and the wood fibres, wood chips and/or sawdust provided with glue are compressed to form a construction element, especially a panel. The wood fibres, wood chips and/or sawdust are cooked in such a way that they decompose into solid and liquid constituents. The liquid constituents are separated and cooled in the sealed gastight system, before leaving the same. Odour pollution during the production is thus strongly reduced. The invention also relates to a device for carrying out the method and components which are produced according to said method.

Description

The invention relates to a manufacturing method together with an associated device for a made of pieces of wood such as fibers or chip component. The invention relates in particular to plates made of wood fibers.

A typical, well-known production process for the manufacture of a board made of wood fibers is known from the Journal HK 1/88, pages 74 to 75 , "Production of MDF boards", known. Cooked chips are fed to a so-called refiner. In the refiner, the wood chips are processed into fibers, with the application of temperature and pressure with the help of painting discs. From the refiner, the fibers are transported out with the help of steam and forwarded by means of a line called "blue-line". The vapor pressure is about 10 bar. The temperature is about 150 to 160 ° C. In the "Blue-Line" glue is added. The glue used is phenolic resins, urea resins or mixed resins of urea and melamine. Following the addition of the glue, the "Blue-Line" expands. A turbulence is caused by the expansion. The glue mixes with the fibers. The proportion of glue in relation to the fibers is about 22% by weight.

The "Blue Line" opens in the middle of a drying tube. The drying tube has a diameter of, for example, 2.60 m. Air is blown through the drying tube at a temperature of 160 ° C, maximum 220-240 ° C. In the drying tube, the moisture is reduced from 100% to 8 to 11%. The resulting steam is separated in subsequent cyclones from the fibers and fed through chimneys to the environment.

Disadvantageously, the steam is contaminated with foreign substances. Thus, odors are released in this way to the atmosphere. The environment is charged accordingly.

The fibers provided with glue are fed in layers to a molding machine. The fibers are pressed here in two phases. First, a pre-pressing takes place. The pre-pressed fibers are then pressed to the plate using high pressure and heat. The experts have found that the plates split when the temperature falls below 150 ° C during compression to the plate and is for example 140 ° C. The temperatures are therefore typically 180 ° C during compression.

A gluing device for the production of fiberboard is from the document EP 0 744 259 A2 known. A method for producing boards from a wood material is the document US 5,554,330 refer to. The publication GB 791,554 discloses a method for mixing solid and liquid components. A device for continuous gluing of wood chips is from the document DE 41 15 047 C1 out. Continuous mixing of chip and fibrous materials with binders is the document DE-OS 1956 898 refer to. The extraction of glue from wood components are the documents PCT / IB98 / 00607 and WO 98/37147 refer to. Pre-evaporation methods disclose the publications DE-OS 44 41 017 . US 11 17 95 and Danish patent application no. 0302/97 ,

The US 4,882,112 describes a method of making flexible sheets or other comparable articles from vegetable raw materials such as sawdust or rice bran or soybean meal. For this purpose, in a first step, glue is applied to the vegetable fibers and this mixture is pressed in a further step to form a component. The final compression should be carried out at pressures between 100 and 200 kg / cm ² and at temperatures between 70 and 200 C °.

The object of the invention is to provide a greener process for creating a device of the type mentioned and the provision of an associated device.

The object of the invention is achieved by one of the claimed methods. An apparatus for carrying out the method has the features of a first additional claim. Advantageous embodiments emerge from the subclaims.

In a wider Aüsführüngsform existing wood chips are first separated into solid and liquid components. The solid components are dried and provided with glue. The glued solid ingredients are pressed into a plate or other shaped body.

The liquid ingredients include in particular lignin and hemicellulose. These substances cause at the temperatures prevailing during drying emissions that cause an odor and thus environmental pollution. By separating these liquid components before drying, corresponding emissions during and / or after drying are reduced accordingly. The environmental impact on production is correspondingly lower.

The liquid components are preferably disposed of at temperatures and / or processed further, in which only small emissions occur. If the temperatures of the liquid constituents are high and in particular above 90 ° C., the liquid constituents are kept in a gastight system with respect to the environment until the temperatures have dropped sufficiently.

In a further embodiment of the invention, the liquid constituents, in particular lignin and hemicellulose, are used as glue, that is to say mixed according to the invention with the dried solid constituents. The solid components are preferably added Fibers or chips processed further. For example, the liquid components may be separated from the solid components in a so-called agitator. The aforementioned ingredients which are obtained are typically: 20 to 35% by weight of hemicellulose, 45 to 50% by weight of cellulose and 20 to 35% by weight of lignin. The cellulose is an integral part of the wood.

Wood chips are first added in an embodiment in a plug screw. From the plug screw from the wood chips arrive in the compressed state in a cooking container and are cooked here at high pressure. The cooking container is designed for high pressures. The pressure in the cooking vessel is in particular at least 1.2 to 2.2 MPa (12 to 22 bar). According to the prior art, wood chips are usually cooked at pressures of only 0.8 to 0.9 MPa. The thermal steam treatment separates the solid wood components (cellulose) from lignin and hemicellulose, which are liquid components. The cellulose is in solid form. The two other components lignin and hemicellulose are liquid and can basically be used as a glue. The bond strength is predominantly effected by the hemicellulose.

It is from the publication WO 98/37147 It is known to separate the lignin and hemicellulose contained in the wood from the solid constituents and then to use it as a glue in the production of MDF boards. Disadvantageous in this process are heavy emissions that pollute the environment of a production facility. The problem of emissions is inventively reduced in that the liquid components are separated in a gas-tight container from the solid components of the wood. The liquid components are separated and initially remain in a gas-tight system connected to the container, at least as long as the Liquid temperatures are so high that high emissions occur. After the separation of the liquid constituents, they cool significantly and are led out of the gas-tight system only at relatively low temperatures and, for example, further processed, that is sprayed onto the fibers in particular via nozzles. The liquid components are thus significantly cooled and in particular by at least 30 ° C, preferably by at least 50 ° C, before they leave the gas and thus odor-tight encapsulated system. In this relatively cool state, the odor development is significantly lower. It is then not critical to remove the liquid components from the gas-tight system.

The liquid ingredients can be used as a glue. This is environmentally friendly in that the liquid components of a wood only at low temperatures, especially at temperatures well below 100 ° C, especially below 70 ° C, more preferably below 50 ° C leave a gas and thus odor-tight encapsulated system and applied to the fibers in this cool state, for example. In this way, it is possible to reduce environmental pollution in a particularly economical way.

The .gasdichte system consists for example of the container and connected lines. Another container, which serves, for example, for cooling, may be part of the gas-tight system.

In particular, in the drying tube, the glue is undesirably exposed to a temperature treatment in an application according to the prior art, the glue. From about 80 ° glue is namely charged or activated disadvantageously. Activated glue is no longer applicable for the subsequent processing step, in which the glued solid wood components are pressed to the plate.

By the aforementioned prior art, the active part of the glue is reduced. Of the originally customarily used 22% by weight, only 1 to 8% by weight are ready for use when the fiber-glue mixture leaves the drying tube. This glue can be applied in a relatively cool state to solid wood components. A premature, unnecessarily extensive activation of glue is thus avoided.

For HDF, MDF and chipboard, glue is currently used on a formaldehyde-urea basis. If panels are made for the floor area, melamine is added to the glue. This is to prevent the swelling that can occur due to moisture.

Problem is so that a part of the glue is lost by the temperature treatment for the actual processing step. Disadvantageously, considerably more glue must be added to the fibers or chips than is required in order to press the fibers or the chips in a press under the supply of temperature and thus obtain the desired result, that is to say the MDF board. Currently, an MDF board has about 60 kg of glue per m ³ . This amount can be significantly reduced if glue is applied in a relatively cool state.

The liquid fractions hemicellulose and lignin obtained in the manner described above are mixed in another embodiment of the invention in the cooled or cool state with another glue. The other glue was therefore not extracted from liquid components of the wood. The proportion of hemicellulose and lignin in the glue mixture thus provided is preferably not more than 20% by weight. In addition, the mixture contains in particular reactive resins as a glue preferably on a formaldehyde-urea basis. Furthermore, the used in the prior art glues or resins.

If a glue mixture is used which contains more than 20% by weight of hemicellulose and lignin, the pressing time (with a complementary use of the currently available synthetic glues) becomes relatively long, while the glued fibers etc. become a plate be pressed. It is therefore more economical to mix hemicellulose and lignin with other glue or glue mixtures. In this way, on the one hand conventional glue can be saved and on the other hand, the process is not relatively long and thus less economical due to long press times. Of course, the upper limit for the proportions of hemicellulose and lignin that is economically viable depends on the reactivity of the glue with which the ingredients hemicellulose and lignin are mixed. The stated upper limit of 20% by weight therefore represents only a guideline value or a current empirical value.

The glue also contributes to emissions in the prior art. By no longer being exposed to the hot drying temperatures, but rather to the solid constituents at relatively cool temperatures, emissions resulting from the glue are also avoided. So it will dry in the dryer or drying tube only water, but no chemicals. This results in corresponding environmental benefits, since the dry air is not adversely affected with vapors that come from the glue according to the prior art becomes. Accordingly, environmentally friendly manages the production of the components. In addition, this embodiment has the advantage that portions of the glue are not disadvantageously activated during the drying process and thus are no longer available for the actual bonding of the wood components to the plate.

The solid constituents, which are present in particular in the form of fibers or chips and which are dried, are advantageously not contaminated with liquid constituents of the wood-based material and, in the aforementioned embodiment, also with glue. The corresponding liquid phases are therefore not dried in the dryer. Compared to the prior art, considerable amounts of energy are saved. The saving of energy not only results in considerable cost advantages, but also conserves natural resources and thus the environment.

By applying the glue to the wood components only after drying, the amount of glue needed for board production is reduced. It succeeds in reducing to 45 to 55 kg per m ³ plate. A typical value is 50 to 52 kg per m ³ plate.

An essential quantity to effect the proper gluing of fibers or chips is the "correct" ratio of solid components to glue. In a preferred embodiment of the method, the solid components are fed to a belt scale before gluing. On the belt scale, the solid components are transported on one side by means of a circulating conveyor belt, on the other side they are weighed. This will give the information as to what amount of glue is to be added to the solid components of the wood in the subsequent step.

The solid components are transferred to the subsequent device by means of the belt scale. Possible weight fluctuations of the supplied solid components are detected during transport, registered and stored in one embodiment. These data are processed and can serve as a manipulated variable for the amount of glue that is subsequently applied to the solid constituents.

In one embodiment of the invention, the transport speed at the belt scale is controlled so that a uniform amount of solid components of the subsequent gluing device (device in which the solid wood components are provided with glue) is supplied. By a change in speed of the feeder so a constant amount of material is supplied to the following facilities. The weight detection of the solid constituents, which may be in the form of fibers or chips, can be carried out in the smallest increments and allows a uniform feed of the solid constituents with an accuracy of, for example ± 1%.

It is not easy to properly coat the solid ingredients with glue, especially when the solid ingredients are in the form of fibers. Fibers tend to bunch up like cotton. It is then difficult to evenly distribute the glue on the fibers. In one embodiment of the invention, the gluing is therefore carried out in a mixer in which glue and solid constituents are mixed together.

The mixer has, in one embodiment of the invention, means for cooling its housing. For this purpose, in an especially simple embodiment, an at least partially double-walled housing, for example a double-walled tube, which is part of the housing of the mixer, is provided. A cooled liquid, such as chilled water, is passed through the double-walled housing to cool the mixer or its walls. By the Cooling is to be created inside a condensation layer on the walls. Accordingly, the cooling is interpreted. The condensed water layer does not cause glue containing solids to adhere to the walls and clog the mixer.

After the solid constituents have been dried, they are distributed over a surface area in one embodiment of the invention and a kind of curtain or mat is formed. This is especially the case when the solid constituents are in the form of fibers, since a mat or a curtain can easily be formed therefrom. Glue is then added, in particular sprayed into the curtain. Preferably, an air-glue mixture is sprayed in, so as to ensure the most uniform distribution of the glue. The formation of a curtain ensures that the glue is evenly distributed over the solid components. This is especially the case when the solid constituents are in the form of fibers.

A formed of solid components curtain or mat formed is introduced in one embodiment in the mixer. The curtain or mat is then blown through nozzles with an air-glue mixture. The glue is thus fed to the curtain or the mat via the nozzles. Subsequently, the curtain or the mat is preferably passed through the mixer without contact. Due to the contactless implementation, adhesion of the solid components to walls is advantageously avoided. Pollution problems and associated costs are reduced.

The glue is blown together with air, in particular at a temperature of 40 to 70 ° C, preferably at a temperature of 55 to 60 ° C in the dried solid components of the wood. This ensures that the glue reaches a dry outer skin. He will So minimal activated. This ensures that the subsequent mixture of solid wood constituents and glue does not stick to transport devices and devices, for example inside the mixer.

The glue is prepared in one embodiment of the invention so that it hardens after a predetermined time. Thus, the glue can be suitably adjusted by temperature treatment. Further, a hardener may be added or added after e.g. Cured for 60 seconds. The preparation of the glue is carried out in particular in the mixer or a hardener together with the glue immediately before the mixer added to the dried solid ingredients.

It has the advantage that when later pressing the solid ingredients to a plate, the glue immediately solidifies quickly. This allows you to realize shorter press times. In each individual case, the time of curing by the expert is specifically determined to get to particularly short pressing times. This represents a further significant economic advantage over the prior art, in which these short pressing times could not be realized due to the required curing times of the glue.

Because the glue is exposed to much lower temperatures than heretofore, it is possible to use more reactive sizes than the prior art. In addition, it is possible to add the ingredient to chemicals, e.g. Reduce formaldehyde. This results in further environmental benefits.

In one embodiment of the invention, the glue is vortexed with heated air and this air-glue mixture added to the dried solid components, so for example fibers or chips. The hot air, for example, via a cabin along with the glue and the dried solid ingredients is introduced into the mixer, the surfaces of the glue droplets produced thereby activates slightly. As a result, adhesion of solid constituents to downstream devices, for example to mixer walls, is suitably counteracted. Otherwise, for example, the mixer would have to be cleaned in no time. The production would then be stopped disadvantageously. Unwanted cleaning costs are also incurred accordingly. These significant economic drawbacks have to be weighed against the disadvantage that glue is activated a little and compared with each other. By means of a few tests, the person skilled in the art can determine how far the glue is to be activated on its surface in order to achieve an optimum economic result. The proportion of activated glue will always be low compared to the prior art.

After the addition of the glue to the dried solid components such as fibers or chips, in one embodiment of the invention the free surface of the glue is further activated by means suitable therefor so as to facilitate subsequent processing steps. After the addition of the glue to the dried solid components, ie z. As to fibers or chips, especially after leaving the mixer, the glue-containing solid constituents are therefore preferably in a riser, which is in particular 10 to 30 m, preferably about 20 m long. The diameter of the riser is in particular at 1 to 4 meters.

The riser is preferably also cooled and in turn is then, for example, double-walled to pass a cooling fluid between the two walls of a double wall. The objective is in turn the formation of a layer of condensation on the inner walls of the riser, so that the glued solid components do not adhere to the walls.

Through the riser the glued solid components can be particularly easily passed contactless through an air or gas stream.

It has been found that the solid components, especially if present in the form of fibers, should be passed through the riser at a rate of at least 25 meters per second, preferably at least 35 meters per second. If the speed is lower, fibers or chips remain adhered to the riser despite the aforementioned measures. This would dirty the riser unnecessarily fast. As lower speeds have been provided, the riser had to be cleaned already after 8 hours. By setting a suitable speed, the cycles could be extended to 7 to 8 days. So it just had to be cleaned every week the riser.

The maximum rate at which the glued solid ingredients are blown through the riser depends on the performance of the subsequent components or devices. It should be noted here that the subsequent components or devices must be able to process the incoming quantity of solid constituents. In practice, an upper limit of 40 meters per second could currently be realized without any problems. From 50 meters per second, the following components were overloaded. It goes without saying that the upper speed limit can be increased as soon as more powerful downstream components are available. Basically, higher transport speeds in the riser are advantageous, since then pollution problems and associated production stoppages are reduced accordingly.

By providing a riser it is achieved that the glue on the surface is further activated somewhat in order to be able to carry out subsequent processing steps in a suitable manner. The length of the riser is therefore adapted by the skilled person to the desired degree of glue activation. The expert will take into account the transport speed in the riser in the interpretation.

Following the addition of glue to the dried solid components, especially following the partial activation of the glue in the riser, the solid constituents, which are associated with glue, enter a cyclone. Here, the glue has now been activated sufficiently on the surface due to the aforementioned measures, so that it no longer adheres in the cyclone. In the cyclone, the solid components are separated and fed to the next processing step with a transport means such as a belt. The solid components are separated from the air in the cyclone. The transport means directs the solid components in one embodiment in a viewing device. In the vision unit, the solid components are examined for coarse constituents. The coarse ingredients are sorted out automatically. Coarse ingredients are, for example, glue lumps.

From the viewing device, the solid components are transported by a belt to the press and pressed here to the plate. The press is preferably made of pressed against each other, rotating press belts, which are suitably tempered. So can be pressed continuously. The temperature must be adjusted by the skilled person to the particular glue used. The amount of energy and the resulting temperatures for the two press belts are therefore chosen differently in one embodiment, so as to avoid a distortion in the produced plate.

The nozzles via which the glue is added to the solid components in one embodiment of the invention are preferably configured conical. By the cone tip, the glue then emerges droplet-like, so that in this way a uniform distribution of the glue advantageously promoted, that is improved.

It is advantageous to avoid cleaning work and a concomitant stoppage of production when the glue emerging from the nozzles, for example, does not contact subsequent tools, for example the tools located in the mixer. The glue is therefore preferably directed directly in the direction of the solid components, in particular injected, so as to achieve a uniform distribution as possible. Moreover, it is then in particular to ensure a sufficient distance between nozzles and subsequent tools in a mixer. In practice, it has been found that the distance between tools in the mixer and the nozzles should be at least 1 meter, preferably at least 2 meters, when the glue is injected horizontally. The solid components are then introduced perpendicular to the beginning of the mixer and transported horizontally in this. Of course, the specified distance values refer only to a specific individual case. They are not universal, because it depends on the speed at which the glue escapes from the nozzles.

If a glue-air mixture is injected in the direction of the solid constituents, an air stream is advantageously at the same time ready, with which the solid constituents are first blown as contactlessly as possible by subsequent devices such as a mixer or a standpipe and thus transported. In principle, another gas can be used instead of air.

As tools in a mixer stirring devices are used in particular, which cause mixing of the solid ingredients with the glue.

To achieve good results, the solid components come in the form of a curtain in front of the nozzles. As a result, in addition to the advantages already mentioned avoided that glue injected into the mixer and dirty tools here. Otherwise, the solid components would adhere to the tools and the mixer would clog in no time and would need to be cleaned at short intervals.

The tools in the mixer are fastened in one embodiment to a centrally mounted axis and consist of star-shaped protruding rods, which go similar to a rudder blade in a flat area. Overall, a star is formed from, for example, four tools. Each two tools thus include an angle of 90 °. Compared to the air flow that flows through the mixer, the rudder blades are tilted. As a result, a turbulence of the air is achieved and thus a good mixing of the solid ingredients with the glue. Several "stars" formed by tools are fixed at regular intervals on the axis. The solid components are then transported parallel to the axis by the mixer. In general, therefore, the tools are in particular so that in addition to the solid components air is swirled. Propeller-like or propeller-like tools are therefore to be preferred.

From the solid components, a curtain is preferably produced as follows.

A means of transport, such as a conveyor belt or a belt weigher is at the end with at least one, preferably with several Rollers provided. Through the roller (s), the solid components are passed. The rollers are pressed against each other in particular. Remains a gap between two rollers or a roller and an adjacent surface, this is basically harmless. This ensures that a kind of curtain or mat is formed from the solid components by the rollers. So it is the curtain shape generated by the rollers.

It is preferably used a conveyor belt, as this ensures a uniform supply of fibers to the rollers. When a belt weigher is used, in one embodiment, the speed of delivery to the rollers is controlled to provide the rollers with a particularly consistent amount of fiber. According to the state of the art, screws are used regularly to transport solid components in the production of plates. Solid components, however, leave snails relatively unevenly. A correspondingly uneven curtain formed from the solid components would result. A uniformly thick and wide curtain is an advantage to achieve a uniform glue distribution. In addition, it is achieved so that the curtain reliably separates injected glue from subsequent tools.

In particular, by the compressed or a gap wide spaced rollers for the production of the curtain is avoided that the solid components, especially if they are in the form of fibers, are transmitted in a cotton or lumpy manner. This would hinder the desired uniform gluing.

In order to be able to process a sufficiently large amount of solid components in a curtain and to achieve a particularly uniform curtain, more than two rollers are used in one embodiment, through the solid components to produce a Curtain are passed through. The rollers are preferably offset one above the other so arranged that an acute angle of the rollers is enclosed with a means of transport such as a conveyor belt or belt scale. As a result, enough material can be added to the means of transport, so for example be given to the belt scale to process a sufficiently large amount of solid components evenly.

In practice, it has hitherto been found that a total of four rollers are particularly advantageous in order to produce a curtain of the solid components, which is then glued mechanically.

The opening through which the solids-based curtain is inserted into or in front of the mixer in one embodiment preferably corresponds to the maximum width of the mixer housing, for example the diameter of said tube which at the same time forms the walls of the mixer. This ensures that the entire width in the mixer is covered by the curtain. Otherwise, glue could splash past the remaining openings laterally past the curtain into the interior of the mixer, and the aforementioned fouling problems would occur.

If the entire width of the mixer were not covered, then not only would glue splash into the mixer, but also solid constituents on the edge would increasingly be entrained, which clump together. This will affect the quality of the material. Corresponding production problems would be the result. A work-up of the material would have to be operated disadvantageously and cost-intensive.

The lateral walls of the mixer are preferably cooled in practice to 7 to 15 ° C, in particular to 10 to 12 ° C. In this way it is achieved that a condensation layer settles on the walls. The condensation layer prevents sticking.

The temperatures mentioned are also suitable for the formation of a condensation layer on the inner walls within the riser.

Since u.a. a gaseous medium such as air is provided for the transport of the fibers with the glue through the mixer, the nozzles for feeding glue in a configuration of the invention at a distance from the housing of the mixer. Before an opening of the mixer housing are then the nozzles. Between the nozzle and the opening thus remains a gap or annular gap, entrained by the air and can be supplied as suitable. Moreover, in this embodiment, the air introduced through the gap or annulus may be preheated to provide a desired temperature in the mixer, particularly so as to promote a desired activation of the glue on the surface.

Tools in the interior of the mixer are mounted in one embodiment on an axis. Annular around the axis are then arranged the nozzles for feeding glue, so as to provide fibers evenly with glue. The fibers or the curtain made of fibers are then preferably fed perpendicularly to the axis between nozzles and tools. Depending on the diameter of the mixer, nozzles are arranged annularly in one or more rows. With a correspondingly large diameter, the entire opening of the mixer is sprayed with glue by arranging a second row of nozzles in a ring around the axis.

In addition to the fibers consisting of solid wood constituents, glass fibers or synthetic fibers are additionally added in one embodiment of the invention. The addition takes place in particular in or immediately before the mixer. As a result, particularly well plate-like molded parts can be produced, which are provided for example as interior trim in a car. Such shaped plates can be used in the automotive industry, for example, as parcel shelf. It then suffices merely to pre-press the layer system. A final pressing step does not have to be carried out.

The automotive industry does not require as many moldings as fibers are usually economically produced on a large scale. Therefore, it is more economical to manufacture molded parts particularly used in the automobile industry together with MDF boards (intended for the manufacture of panels) so as to be able to use the quantities of fiber on an industrial scale. The intended for the production of panels MDF panels have a top and a bottom, which are parallel to each other and which are flat. These plates are a few millimeters thick. They usually have no plastic or glass fibers, since no special forms must be realized, which differ from a flat surface.

In the production of molded parts, sharp edges are problematic. These tend to rip. By reinforcing with fiberglass or plastic fibers, these problems are avoided or significantly reduced.

Moldings of the aforementioned type are also used in the furniture industry. Such moldings are z. B. needed for doors that are specially shaped for design reasons.

In contrast to plates consisting of fibers, for example MDF boards, which are intended for the production of panels, it is sufficient for the molded parts to merely pre-press them. The pre-pressing takes place at much lower pressures than the actual pressing step. The pre-pressure can be only one-third of the pressure that is used for the actual pressing step. The actual pressing step is carried out at pressures of 75 to 80 kg / cm ² .

The proportion of glass fibers and / or plastic fibers in a molding is up to 25 wt .-%, preferably up to 15 wt .-%, in order to arrive at cost-effective results. At least 1% by weight, more preferably at least 5% by weight, should be used on glass fibers.

Fibers for the production of molded parts to the fibers, which are used for the production of MDF or HDF panels for panels, in particular for floor panels, is also independent of the above-mentioned other measures and features according to the invention particularly economical compared to the prior art ,

In a further embodiment of the invention, provided with glue solid wood components - for example, on a conveyor belt - arranged in layers and subjected to hot steam, such as by steam. Subsequently, the layer is pressed in a press - so for example within two rotating against each other pressed bands - to the plate and indeed, for example, to a MDF, HDF or chipboard. The invention is particularly well suited for the production of fiberboard.

In one embodiment, the two outer main surfaces of the layer are vapor-deposited from outside. This can be done simultaneously with pre-compression or densification of the layer. For example, by means of a vapor-permeable conveyor belt, the layered solid wood components are transported between two rigid plates. One plate is then below the conveyor belt and the other above the conveyor belt. Of the Distance between the two plates can decrease in the transport direction so that thereby the layer is compressed. About in the plates located nozzles, the layer is acted upon by steam. The moisture in the surface region of the layer is then increased in particular by at least 2% by weight, for example up to 4% by weight and thus for example from 7% by weight to 9 to 11% by weight. The temperature of the steam is typically 100 to 130 ° C.

The evaporation increases the thermal conductivity to the middle of the layer. Overall, this causes a better pressing behavior and thus a reduction of the pressing time.

The layer or the already compacted layer of solid, glue-provided wood components can be divided in one embodiment, so that there are virtually two superimposed layers. For example, the layer is transported for this purpose on a conveyor belt. Above and across the conveyor belt, a belt or a rail is arranged so that this divides the layer located on the conveyor belt. The tape or the rail is followed by a steaming device, which is located in this way between the two layers. The adjacent sides of the two layers formed by division or at least one of them is steamed as described above, so as to allow faster pressing times. Following this evaporation, the top layer is on top of the bottom. The vaporized layers are transported to the press and pressed here to the plate.

The evaporation causes a direct or indirect rapid heating of the fibers provided with glue immediately and / or during pressing succeeds and thus pressing times can be shortened. The productivity is increased accordingly.

In the manufacture of panels of flooring, it is of interest that the panels have hard outer layers and a soft inner layer. As a result, for example, the impact sound can be advantageously reduced. If the surface is steamed and the interior area remains relatively dry, the surfaces are purposefully pressed. One of the reasons for this is that moist material can be pressed better than dry material. Surface areas are thus densely compressed. By pre-evaporation, it is also possible to control the temperature profile. This makes it possible to obtain in an improved way to harder outer layers compared to the middle layer.

If it is possible to reduce press times, the length of the double belt presses used can be shortened. The costs for the purchase of the presses are significantly reduced. It can be produced in a smaller space. Significant cost advantages are the result. By pre-evaporation, the pressing time can be reduced.

The steam may also be added additives that contribute to the curing. Thus, the desired hard surfaces are further improved when the surfaces are steamed before being pressed.

If there are harder surface layers, they may be relatively thin. Thus, a total of material can be saved at the same plate thickness, since the soft middle layer is made of relatively little material.

The invention will be further clarified with reference to the following figures.

FIG. 1 shows a section through a belt scale 1 and a subsequent mixer 2. As indicated by the arrow 3, dried fibers, which were made from wood chips, fed through an opening of a housing 4 of the belt scale 1. A slope 5 directs the incoming fibers onto the belt of the belt scale. The belt scale detects and controls the amount of material that is transported in the direction of the three rollers 6. The three rollers 6 are superposed and offset so arranged that they include α with the belt weigher 1 an acute angle. The fibers on the belt scale reach this acute angle. They pass through the rotating rollers 6. In this case, a curtain is formed from the fibers, which is transported vertically downward along the arrow 7 due to gravity. The curtain thus enters the mixer 2, specifically between a plurality of nozzles 8 and tools 9.

The mixer consists of a tubular housing. The housing is formed by a double wall 10 and 11. Central to the interior of the housing is an axle 12, on which the tools 9 are mounted. A tool 9 includes with the axis 12 a right angle. Each four rudder blade-like tools 9 are summarized in a star shape. Several of these combined tools are mounted at regular intervals on the axis 12. The front area into which the fiber curtain is inserted is free of tools. This ensures that a sufficiently large distance between the tools 9 and the nozzles 8 is present. This distance is provided so that from the nozzles 8 leaking glue does not impinge directly on the tools during operation.

The diameter of the housing of the mixer corresponds to the width of the opening through which the fiber curtain is inserted into the mixer. The width of the curtain is adapted to the width of the opening. The nozzles 8 are semicircular around the axis 12 in an upper area arranged. This causes on the one hand, the curtain is evenly provided with glue and on the other hand, the emerging from the nozzle 8 glue does not impinge directly on parts of the mixer. Between the nozzles 8 and the housing 10, 11 a distance is arranged, so that a kind of annular gap is formed. Air is sucked in via this annular gap. Not shown are means for heating the air, which is sucked. This creates a glue-air mixture. The glue-provided curtain (in other words, a mat formed of fibers) is transported by the air flow parallel to the axis 12 through the mixer 2. The axis rotates during transport and thus the tools 9. The glue is further mixed with the fibers. Between the two walls 10 and 11 of the double wall, a cooled liquid is introduced in order to create a condensation layer on its inner walls in the interior of the mixer.

In the FIG. 2 a plan view of the mixer parallel to the axis 12 is shown. For clarity, only two tools 9 are shown. Based on FIG. 2 In particular, a single-row, semi-circular arrangement of the nozzles in the upper area is illustrated.

In the FIG. 3 an embodiment of the method is illustrated in the overall context.

As a starting material deciduous or coniferous wood in the form of logs, branches and / or sawmill and Industrieresthölzer be used. The wood is first crushed into chips with a size of about 20 x 5 mm in a crusher 31. These chips can also come directly from the forest or from sawmills. They can be screened to separate too small or too large particles. If the chips are the right size, they can be washed to remove adherent foreign bodies, especially sand and earth). Cutting and other tools are spared and not damaged in the later manufacturing and processing process.

Sawdust is advantageously utilized, which is placed in a silo 32.

From the shredder 31 and the silo 32, the wood components are fed to a funnel-shaped Vampfampfbehälter means of conveyor belts.

The feed is typically in the ratio of about 6: 4 (60 wt .-% shavings, 40 wt .-% sawdust). In this way, sawdust is also recovered. Costs are lowered further. Resources of raw materials are spared. The proportion of shavings should predominate, as this produces fibers and later fiber mats, which stabilize mechanically. A lower limit for the sawdust content is therefore not to be observed.

In Vordampfbehälter 33, the wood components are mixed, pre-evaporated while 60 to 70 ° C heated. For example, by means of a plug screw, the wood components are then fed to a digester 34. In the digester 34, the wood components are cooked for about 2 to 3 minutes at a pressure of 11 to 16 bar and a temperature of 140 to 180 ° C. Pressure and temperature are chosen so that a splitting into liquid and solid wood components takes place.

The liquid components are separated from the solid and fed to a line 36 which is gastight connect to the cooker 34.

The solid wood components are fed to a defibering machine 36 (refiner). The defibering machine 36 typically includes a stator and a rotor that are driven by a motor. The solid components are broken down here into fibers.

The fibers, which in one embodiment are mixed with sawdust, are pneumatically fed to a drying tube 37. In the following, independently of fibers. In the drying tube 37, the fibers are dried at 160 to 220 ° C. The drying is relatively quick and inexpensive, since the liquid wood components have already been removed.

From the drying tube, the fibers enter cyclones 38. Here the steam is separated. Down the fibers are led out. The temperature of the fibers is then typically 50 ° C. The fibers are then mechanically glued in gluing devices 39 at comparatively cool temperatures. The subsequently glued fibers have a temperature of typically 35 to 40 ° C. The glued fibers pass into one or more vision devices 40. In one embodiment, the vision devices 40 include heaters to heat the fibers to 55 to 60 ° C. The increase in temperature is advantageous if the plates are to be pressed at temperatures above 150 ° C. The pressing step can be accelerated. Shorter press times lead to larger production capacities.

The pre-glued fibers are fed to one or more separation devices 41. From the separating devices 41, the pre-glued fibers reach a scattering station 42. The scattering station 42 applies the pre-glued fibers to a conveyor belt. The conveyor belt guides the fibers to a pre-press 44. Here, the fibers are typically pre-pressed 2/3. The pre-press includes a circulating belt between which the fibers are fed and thereby be pressed. The fibers then pass through a forming line 45 which has various means of ensuring that the fibers are in the desired shape. In one embodiment, the forming line leads to a vapor deposition device 46. Here, the fibers are vapor-deposited from above and / or below. The fibers can be split parallel to the conveyor belt and steamed in the "inside".

The fibers finally reach the main press 47, which consists of two circulating steel strips pressed against each other. Here typically the pressure takes place above 150 ° C. According to the invention, however, is pressed at temperatures below 60 ° C.

Subsequently, the plates are sawed by means of a saw 48 and fed to a holding device 49. In the holding device, the plates are held so that they do not touch. The plates are cooled in this way.

The separated liquid components which have been supplied to the line 35 are cooled within the gas-tight sealed system. If these liquid constituents have been sufficiently cooled, they are either disposed of or fed to the gluing device 39.

Subsequently, the plates are further processed, for example, to panels. The plates are for this example coated with papers, further sawn and provided with coupling elements by milling. The panels can serve as a covering for walls or floors.

Surprisingly, it has been found that during the compression of the fibers below 120 ° C, in particular below 90 ° C no cleavage occurs, which is observed in particular in the temperature range between 120 ° C and 150 ° C. The resins used then do not cure.

Claims (44)

1. Method for the manufacturing of a construction element, in particular of a board, made from wood fibers, wood chips and/or sawdust with the steps:

   - application of glue to wood fibers, wood chips and/or sawdust,

   - pressing of the wood fibers, wood chips and/or sawdust provided with the glue to form a construction element,
   characterized in that
   the pressing is performed at temperatures below 60°C and pressures from 75 to 80 Kg/cm².
2. Method according to claim 1, whereby the wood fibers, the wood chips and/or the sawdust is broken down into solid components and liquid components within a gas proof system, the liquid components are separated from the solid components and are led out of the gas proof system at temperatures of below 90°C, in particular of below 70°C.
3. Method according to any one of the two preceding claims, whereby the glue is applied to the wood fibers, wood chips and/or the sawdust at a temperature of below 100°C.
4. Method according to the preceding claim, characterized in that layers, in particular in form of paper and/or décor paper, which preferably are provided with resins, are provided below and/or above the board in particular for the manufacture of laminate panels and are pressed at temperatures of preferably above 150°C, particularly preferred above 180°C.
5. Method according to any one of the preceding claims with the steps:

   - drying of wood fibers, wood chips and/or sawdust in a drying device;

   - application of glue to dried wood fibers, wood chips and/or sawdust outside of the drying device at a cooled temperature;

   - pressing of the wood fibers, wood chips and/or sawdust provided with the glue to form a construction element.
6. Method according to any one of the preceding claims, characterized in that glue is applied to the wood fibers, wood chips and/or sawdust, by spraying a glue-gas-mixture to the fibers.
7. Method according to any one of the preceding claims, characterized in that the glue is applied in such quantity that 45 to 55 Kg of the glue is used per m³ of construction element.
8. Method according to any one of the preceding claims, characterized in that the wood fibers, wood chips and/or the saw dust are put onto a weighing conveyor before the application of glue and the weighing conveyor and the application of the glue are controlled so that the quantity ratio between the glue and the wood fibers, wood chips and/or the sawdust during the application of the glue is substantially constant.
9. Method according to any one of the preceding claims, characterized in that the wood fibers, wood chips and/or sawdust provided with glue are mixed together and/or are swirled and in fact in particular in a mixer (39) with cooled walls.
10. Method according to any one of the preceding claims, characterized in that the fibers are formed into a curtain or a mat and the glue is applied to the curtain or the mat or introduced into the curtain or into the mat.
11. Method according to any one of the preceding claims, characterized in that the glue together with heated air is applied to the wood fibers, wood chips and/or the sawdust and in fact in particular at an air temperature of 40 to 70 °C.
12. Method according to any one of the preceding claims, characterized in that the glue is applied to the wood fibers, wood chips and/or the sawdust together with a hardener.
13. Method according to any one of the preceding claims, characterized in that after being applied to the wood fibers, wood chips and/or the sawdust, the glue is activated to an extend limited only to its surface.
14. Method according to any one of the preceding claims, characterized in that the wood fibers, wood chips and/or the sawdust provided with glue are blown trough a rising tube.
15. Method according to any one of the preceding claims, characterized in that wood is broken down into solid components and liquid components, and liquid components are applied to the wood fibers, wood chips and/or the sawdust as glue.
16. Method according to any one of the preceding claims, characterized in that the liquid components are cooled down before being applied and in fact in particular by at least 30°C, preferably by at least 60°C.
17. Method according to any one of the preceding claims, characterized in that, Lignin and Hemicellulose are contained in the glue and in fact in particular in a proportion of up to 20% by weight.
18. Method according to any one of the preceding claims, characterized in that plastic fibers and/or glass fibers are added to the wood fibers, wood chips and/or the sawdust.
19. Method according to any one of the preceding claims, characterized in that the construction element is manufactured as a board-like shaped body.
20. Method according to any one of the preceding claims, characterized in that just before pressing, steam is applied to the wood fibers, wood chips and/or the sawdust.
21. Method in particular according to any one of the preceding claims, characterized in that MDF- and/or HDF-boards for flooring panels and shaped bodies are produced at the same time and the fibers used for this purposes originate from the same device, in particular from the same milling device.
22. Apparatus for the manufacture of a construction element, in particular of a board, prepared from wood fibers, wood chips and/or sawdust, with a drying device (37), in which the wood fibers, wood chips and/or the sawdust are dried, and with a glue-applying device (39), in which the wood fibers, wood chips and/or the sawdust are provided with glue, and with means (44, 47) for pressing the glued fibers or chips to form a construction element, in particular a board,
    characterized in
    a pressure- and temperature controlling device adapted to press the wood fibers, wood chips and/or the sawdust provided with glue at temperatures below 60°C and at pressures from 50 to 80 kg/cm².
23. Apparatus according to the preceding apparatus claim with transport means (1, 7), by which the wood fibers, wood chips and/or the sawdust are transported from the drying device to the glue-applying device (2, 8)
    characterized in that
    a press (47) is provided which comprises circulating pressing belts pressed towards one another.
24. Apparatus according to the preceding apparatus claim with a device (36) in which wood shavings are reduced to fibers and in fact in particular with the aid of heat and pressure and with the aid of milling disks.
25. Apparatus according to any one of the preceding apparatus claims, in which the drying device (37) comprises a tube together with means by which a gaseous medium is heated and blown trough the tube.
26. Apparatus according to any one of the preceding apparatus claims in which the transport means comprise a weighing conveyor (1).
27. Apparatus according to any one of the preceding apparatus claims, in which a mixer (2) is provided, in which glue and wood fibers, wood chips and/or sawdust are mixed together and in fact in particular mechanically by means of stirring tools (9) whereby the stirring tools are preferably arranged like the plates of oars or like propellers in order thereby to be able to cause turbulence of air in the mixer.
28. Apparatus according to any one of the preceding apparatus claims, in which a mixer (2, 39) together with means for cooling its housing (10, 11) is provided.
29. Apparatus to one of the preceding apparatus claims, in which a mixer (2, 39) is provided having at least partially a double-walled housing (10, 11), in fact in particular a double-walled tube.
30. Apparatus according to any one of the preceding apparatus claims, in which cooling means are provided for cooling a fluid, as well as means for cooling with the cooled fluid the housing of a mixer and/or of a rising tube.
31. Apparatus according to any one of the preceding apparatus claims, with means for producing a layer of condensed water on the inside walls of a mixer (2, 39) and/or of a rising tube.
32. Apparatus according to any one of the preceding apparatus claims, with means (6) for feeding the fibers to the glue-applying device (39) in form of a curtain or a mat.
33. Apparatus according to any one of the preceding apparatus claims, with means (6) for feeding the fibers to the glue-applying device (39) in form of a curtain or a mat, whereby these means comprise rollers (6) and whereby a transport band or a weighing conveyer (1) for supplying the fibers to the rollers is provided.
34. Apparatus according to any one of the preceding apparatus claims, with means (6) for feeding the fibers to the glue-applying device in form of a curtain or a mat, whereby these means comprise rollers (6) which are arranged one above another and offset, the rollers being arranged in particular so that they make an acute angle (α) with a conveyor belt or a weighing conveyor (1).
35. Apparatus according to any one of the preceding apparatus claims with nozzles (8) in particular of conical shape, by which the glue is applied to the fibers or chips.
36. Apparatus according to any one of the preceding apparatus claims, with means by which glue together with heated air is applied to the wood fibers, wood chips and/or the sawdust.
37. Apparatus according one of the preceding apparatus claims, with means by which glue together with a hardener is applied to the wood fibers, wood chips and/or the sawdust.
38. Apparatus according to any one of the preceding apparatus claims, with a substantially vertically extending rising tube which follows on the glue-applying device (39) and through which the wood fibers, wood chips and/or the sawdust are blown in a direction against gravity, whereby preferably means are provided for cooling the walls of the rising tubes.
39. Apparatus according to any one of the preceding apparatus claims, with a cyclone (41) in which fibers or chips provided with glue are precipitated out and/or an inspection station, at which the fibers or tubes provided with glue can be optically monitored.
40. Apparatus according to any one of the preceding apparatus claims with means for bringing fibers in the form of a curtain or a mat in front of the nozzles (8) from which glue emerges.
41. Apparatus according to any one of the preceding apparatus claims, with a mixer (2) and an opening through which a curtain made-up of fibers is introduced into or in front of the mixer, the opening corresponding to the maximum width of the mixer housing and the means for producing the curtain preferably being of dimensions such that the width of the curtain corresponds substantially to the width of the opening.
42. Apparatus according to any one of the preceding apparatus claims, in which a rising tube made of metal and/or a mixer made of metal is provided.
43. Apparatus according to any one of the preceding apparatus claims, in which means are provided for breaking down wood fibers, wood chips and/or sawdust inside of a gas proof system into solid and liquid components, and means for cooling and separating the liquid components from the solid components within the gas proof system.
44. Apparatus according to the preceding apparatus claim with means for applying the liquid components to the wood fibers, wood chips and/or the sawdust at least partially in particular in cooled condition.

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