EP2159024A1 - Method for manufacturing a body made of wooden material - Google Patents

Abstract

The method involves molding a wood material e.g. wood chip, to a pressing material (4) e.g. continuous strand mat. The material is pressed to a wood product body (1) in a pressing device (3). A set-point value for a physical state variable of the material is stored before pressing the material. A sensor (5) e.g. pressure sensor, is integrated in the material, and a value for the physical state variable is determined by the sensor. The value is compared with the set-point value, and a parameter e.g. pressing temperature, of a pressing device is controlled on basis of the comparison. Independent claims are also included for the following: (1) a device for manufacturing a wood product body (2) a wood product body i.e. plate shaped wood product body.

Description

The invention relates to a method for producing a wooden material body in a device having a pressing device, comprising the following steps: providing comminuted wood material, in particular wood chips and / or fibers, forming the wood material into a pressed material and pressing the material to a wood material body in the press facility. Furthermore, the invention relates to a corresponding device for producing a wood material body with a pressing device for pressing a molded material from crushed wood material and a corresponding wood material body.

In the following, the term wood material body means a body made of pressed wood particles, for example a plate-shaped body, in particular a wood-based panel. By a wood-based panel according to the invention is meant any form of particle or fiberboard of shredded wood material such as medium density fiberboard (MDF), high density fiberboard (HDF) or very low density fiberboard (LDF). Also plywood boards, blockboards, veneered boards, chipboards or OSB boards (Oriented Strands Board) fall under the term wood board. A wood-based panel may consist of several layers, which have been spread one after the other and then fed to the press, or of several, glued together Single plates, which were each taken from a press exist.

For the purposes of the invention, the term wood chips means chips, shavings or comparable particles of any shape and size produced by comminution, in particular machining. The term wood fibers describes by shredding shredded wood material of any shape and size.

It is known from the prior art to produce wood-based panels, for example OSB panels, from one or more layers of wood chips provided with a binder and pressed. An essential criterion for the quality of particular plate-shaped wood material bodies are their strength properties. These depend essentially on the used Spangeometrie, the binder used and the parameters set during the pressing process parameters of the pressing device.

An essential parameter of the pressing device is the pressing pressure, ie the pressure exerted externally on the pressed material during the pressing process. Another essential parameter is the pressing temperature, ie the temperature prevailing during the pressing process, which is exposed to the material to be pressed when passing through the pressing device. Another essential parameter of the pressing device is, for example in a continuously operating press such as a double belt press, to call the pressing speed, ie the driving speed in the pressing device, that is, the transport speed with which the pressed material transported by the pressing device becomes. In any press, especially in a platen press, the pressing time is an essential parameter of the pressing device, ie the period in which the pressed material is exposed to the pressing pressure.

During the pressing process, a certain vapor pressure, also called internal pressure, inevitably builds up in the pressed material due to the evaporating moisture. However, at the end of the pressing time, this vapor pressure may only be so high that, when the press is opened or when the pressed material is removed from the pressing device due to the now possible expansion of the vapor, the plate will not burst. The height of the existing when opening the press or at the outlet from the continuous press vapor pressure results as a result of the aforementioned parameters and the prevailing Ausdampfverhalten. Platzer, also called Dampfspalter, have their cause in an excessively high vapor pressure in the finished plate compared to given under the prevailing conditions transverse tensile strength. This can be caused, inter alia, by too high a moisture content of the glued chips, too high pressing temperatures, especially in the outlet region of a continuous press, poor evaporation behavior of the material to be pressed, for example as a result of too high a mat weight, too high a fines content of the middle layer, edges that are too high too large a plate width, as well as by an unfavorable pressure profile, in particular a too long pending high pressing pressure and an insufficient duration of the Lüftphase, and by a too long press time, especially for low-formaldehyde binders.

On the subsequent end product but also have too low humidity, too low pressing temperature and too short Press time negative impact. In particular, there may be insufficient curing of the binder and insufficient plasticization of the wood material, which, inter alia, adversely affects the mechanical and technological properties of the plate.

It is known from the prior art for optimizing the manufacturing process to obtain information on the thermodynamic conditions in the interior of the pressed material by means of a mobile measuring system which has a steel cannula which is connected to a miniature pressure transducer and a data logger. The measurement data obtained are used to generate statistics with regard to the expected physical properties of a finished plate. The use of such a measuring system is relatively complicated and requires precise handling, especially when placing the probe or signal generator in the pressed material. Another disadvantage is that the signal generator must be removed from the pressed material again, and this without damaging the pressed material. Finally, due to the limited length of the cannula, the application is limited to a certain plate thickness, usually a maximum of 10 mm.

Starting from the prior art described above, it is the object of the present invention to provide a method and a corresponding apparatus for producing a wooden material body, with which the physical properties of the finished product are optimized. Further, it is the task to create a corresponding wood material body.

The previously derived and indicated object is achieved according to a first teaching of the present invention in a method of the type mentioned in that before the step of pressing at least one setpoint for at least one physical state variable of the material to be pressed is stored that at least one sensor in the pressed material is integrated, that the at least one sensor determines at least one actual value for the at least one physical state variable, and that the at least one actual value is compared with the at least one setpoint based on the comparison of actual and setpoint value at least a parameter of the pressing device is adjustable.

By a sensor or a plurality of sensors is provided in the pressed material, which allow a wireless and in particular non-contact measurement data transmission and therefore can remain in the finished product, and a comparison between the actual values determined by the sensors and predetermined target values is performed is allows the press device to be adjusted and readjusted - manually or automatically - for optimized physical properties of the finished product. The measured data determined by the sensors flow directly into the production process and, while the wood-based material body is still being produced, lead to an optimization of those parameters of the pressing device which influence the essential physical state variables of the pressed material. By regulating the parameters of the pressing device is to be achieved that the actual value approaches the predetermined target value for the at least one physical state variable of the pressed material. In other words, according to the invention, the manufacturing process automatically monitored and any deviations from the optimum, that is the preset target values, can be compensated immediately.

In particular, the at least one physical state variable is the pressure, in particular the vapor pressure, the temperature and / or the degree of moisture of the material to be pressed, in particular in the interior of the material to be pressed, preferably in the center of the material to be pressed. Accordingly, the at least one sensor may be a pressure sensor, a temperature sensor and / or a moisture sensor. Pressure, temperature and degree of humidity are physical state variables which, in addition to many other parameters such as type of wood, shape and dimensions of the wood particles, type and amount of binder, etc., significantly influence the physical properties of the finished product. The said physical state variables can be determined several times, in particular regularly, during the production process and be adjusted to a desired value by regulating one or more parameters of the pressing device.

The at least one parameter of the pressing device can be the pressing pressure, the pressing temperature, the pressing speed and / or the pressing duration. The inventive method makes it possible in this way to operate the pressing device with a pressing speed such that the vapor pressure in the pressed material, so the internal pressure due to the evaporating water, does not exceed the level which would lead to bursting of the finished product. Preferably, this is achieved as follows: immediately after the entry of the material to be pressed into the pressing device The entire cross-section of the pressed material should be heated as quickly as possible to a temperature above 100 ° C. In this way, on the one hand, the crosslinking reaction of the binder is set in motion, on the other hand, however, the residual moisture required for the heat transport is transferred as quickly as possible into the vaporous state. This is favored by an increased pressure is selected at the beginning of the press line. If the entire material to be pressed, including the middle layer, but reaches a temperature of slightly more than 100 ° C, prevents a high pressure, the removal of the evaporating residual moisture. The result is too high content of residual moisture or too high a vapor pressure at the end of the press, which can lead to the so-called bursters. With the help of the method according to the invention, the information can be obtained for the first time from when a certain required temperature is reached in the cross section of the material to be pressed, so that the pressing pressure can be withdrawn at the earliest possible time, whereby the remaining pressing section for evaporation of the residual moisture remains. As a result, the existing press length, for example, a double belt press can be optimally used.

In the case of the production method according to the invention, the actual value for one or more physical state variables can be determined before, during and / or after the pressing of the material to be pressed. Preferably, an actual value, for example, for the vapor pressure, determined in predetermined, in particular regular, distances from the respective sensor, for example, the first time immediately before the inlet to the pressing device or immediately before the start of the pressing operation and then at least once again during the pressing process. Even after pressing, measured data, For example, regarding the internal pressure, are determined and incorporated directly into the current manufacturing process.

According to one embodiment of the method according to the invention, monitoring and / or regulation of the parameters of the pressing device is started only after completion of the start-up phase of the pressing device. In particular, at least one actual value is determined only after the startup phase has ended, the at least one actual value is compared with the at least one desired value and / or the at least one parameter of the pressing device is regulated. In other words, monitoring begins only after a predetermined time, namely the start-up phase, since in the start-up phase the final operating temperatures, operating pressures, etc. of the production device are often not yet present.

The pressed material can be shaped according to yet another embodiment as a mat, in particular endless mat. In this way, after passing through the pressing device, an endless plate-shaped wood material body, from which then individual plates can be made by cutting to length.

According to yet another embodiment of the manufacturing method according to the invention, the pressing device operates continuously. Although a clocked process is conceivable. However, the continuous process has the advantage of a higher throughput and thus a higher production speed.

In the method according to the invention, additionally or alternatively to the regulation of the at least one parameter of the pressing device, the result of the comparison of actual and desired value can also be used to produce a prognosis with regard to the physical properties of the finished plate.

The object is further achieved according to a second teaching of the present invention in a device of the type mentioned, in particular for carrying out a method as described above, characterized in that a detection device for wireless and in particular non-contact detection of measurement data, namely at least one actual Value for the at least one physical state variable is provided by at least one sensor integrated in the material to be pressed, for example a pressure, temperature and / or humidity sensor, as well as a memory and a comparator. The detection device is arranged outside the material to be pressed, in particular laterally thereof.

The device according to the invention allows for the first time, as already explained with reference to the method according to the invention, an optimization of the physical properties of the finished product by already during the passage of the material to be pressed by the manufacturing device monitoring relevant physical state variables of the material to be pressed and based on an immediate control of the state variables influencing Parameters of the pressing device such as pressing pressure, pressing temperature, pressing speed and / or pressing time can be done.

According to one embodiment of the production device according to the invention, the device is preceded by a device for integrating the at least one sensor into the product to be pressed. In particular, the integration takes place automatically, preferably at regular intervals. In principle, however, it is also conceivable to admit the sensors to the pressed material by hand. The sensor or sensors are preferably connected to the sensor body, i. the component which determines the physical properties, placed in the middle of the material to be pressed, with respect to a direction transverse to the transport direction (longitudinal plate direction), with any antenna of the sensor being aligned in particular pointing towards the edge.

According to yet another embodiment of the manufacturing device according to the invention, a device for applying a binder to the comminuted wood material is provided, which is preferably connected upstream of the device for integrating the at least one sensor. The latter has the advantage that the sensor is optimally provided with the binder and is securely fixed in the layer structure of the finished wood material body. However, it is also conceivable that the sensor is coated in a device with a separate adhesive, in particular adhesive film, which may be different from the binder.

The pressing device is again provided according to another embodiment with a heating unit, that is designed as a hot press. In this case, the press plates of the pressing device, which may have a double-belt press or platen press, be heated. It is also conceivable to heat by steam injection or by induction in the pressed material produce. The pressing temperature can then be varied depending on the measured data acquired. The same applies to the pressing pressure, the pressing speed and / or the pressing duration of the pressing device, which can also be varied. Preferably, pressing pressure and / or pressing temperature at different intervals of the pressing device, in particular the double belt press, regulated independently of the adjacent sections. A cooling zone may also be provided, which may likewise be subject to a temperature control on the basis of the acquired measured data.

According to yet another embodiment of the manufacturing device according to the invention, a display device may be provided, which is connected downstream of the comparator. A display device ensures that the operating personnel are immediately informed about a deviation of the respective actual value from the target value, so that it can then carry out a manual control of the at least one parameter of the pressing device or can control an automatic control. For automatic control, in addition to or as an alternative to the display device, it is conceivable to provide a control device which is connected downstream of the comparator and can transmit data for controlling the corresponding parameters of the pressing device, for example pressing pressure, pressing temperature and / or pressing speed or duration to the pressing device.

For example, after the compaction properties, the diffusion properties or the properties of the heat conduction significantly from the material used such as sawdust, cutting chips, the use of recycled wood etc., the method according to the invention and the device according to the invention represent an essential aid for choosing the optimal setting of a pressing device, in particular with a double belt press, in the production of wood-based material bodies.

The object is finally achieved according to a third teaching of the present invention by a wood material body, in particular plate-shaped wood material body, which is produced by a method as described above.

Fig. 1

eine schematische Darstellung einer Vorrichtung zur Herstellung eines Holzwerkstoffkörpers und

Fig. 2

eine Schnittansicht eines mit der Vorrichtung aus Fig. 1 hergestellten Holzwerkstoffkörpers.

There are now a large number of possibilities for designing and developing the method according to the invention, the device according to the invention and the wood-based material body according to the invention. For this purpose, reference is made, on the one hand, to the claims subordinate to patent claim 1, and, on the other hand, to the description of exemplary embodiments in conjunction with the drawing. In the drawing shows:

Fig. 1

a schematic representation of an apparatus for producing a wood material body and

Fig. 2

a sectional view of one with the device Fig. 1 produced wood material body.

In the Fig. 1 illustrated device 2 is used to produce an endless, plate-shaped wood material body 1, from which many individual plates can be produced by cutting the compressed pressed material.

The device 2, which operates continuously in the transport or longitudinal direction of the plate, has a pressing device 3 for pressing a pressed material 4 formed from comminuted wood material, which is provided on a conveying device 15 in the form of wood shavings and / or fibers and, after passing through a device 10 for Applying a binder of a double belt press 12 of the pressing device 3 is supplied.

The pressing device 3 further comprises a multi-part heating unit 11 and a plurality of mutually opposite, individually controllable pressing plates 16.

A detection device 6, which is arranged here for better depictability above the device 2 or the conveyor belt, but can also be arranged laterally thereof, is used for measurement data, in this case actual values of vapor pressure, temperature and moisture level in the interior of the material 4 to detect, which are of integrated into the pressed material 4 sensors 5, after the sensors 5 were preferably excited from outside by a transmitting device (not shown), are determined and transmitted to the detection device 6. In this case, the sensors 5 are automatically integrated by a device 9 at predetermined regular intervals in the presently shaped as a mat 4a pressed material 4. The device 9 is connected upstream of the device 10 for applying the binder, so that the sensors 5 are provided with the binder and fixed optimally and permanently in the pressed material 4.

The production by a continuous process, in particular with a double belt press 12, has the advantage that the measurements can be carried out simultaneously at different locations within the device 2 and need not be carried out at different times, as in the case of a platen press.

Furthermore, a memory 7 is provided, in which target values for the vapor pressure, the temperature and the degree of moisture of the material to be pressed 4 are stored.

Furthermore, a comparator 8 is provided which receives the actual values from the detection device 6 and compares them with the desired values read from the memory 7.

On the basis of the comparison of actual and desired value, the pressing device 3 is then automatically controlled. For this purpose, a control device 14 is provided, which is connected downstream of the comparator 8 and transmits corresponding control data to the pressing device 3. On the basis of the transmitted data in the pressing device 3, if necessary, the pressing pressure, the pressing temperature and / or the pressing speed are varied so that a possible difference between the actual and desired value can still be compensated during the pressing process.

Finally, a display device 13 is provided, which indicates to the operator when the actual value measured in each case deviates from the associated desired value. In particular, larger deviations outside a predetermined permissible range are visually and / or acoustically displayed here.

Fig. 2 shows finally a section through the finished plate-shaped wood material body 1. In the present case, the wood material body 1 is an OSB board, which is composed of two cover layers 1a and 1b and a middle layer 1c arranged therebetween. In the middle layer 1c, a sensor 5, in this case a pressure sensor, is integrated, which regularly sends measured data regarding the height of the vapor pressure in the plate in the form of an actual value to the detection device 6 during the production method according to the invention. The sensor 5 remains even after completion of the wood material body 1 permanently inside the plate.

Claims (15)

Method for producing a wood-based material body (1) in a device (2) having a pressing device (3), comprising the following steps: - providing shredded wood material, in particular wood chips and / or fibers, - Forming the wood material into a pressed material (4) and - Pressing the pressed material (4) to a wood material body (1) in the pressing device (3),
characterized, that at least one desired value for at least one physical state variable of the material to be pressed (4) is stored before the step of pressing, - That at least one sensor (5) is integrated into the pressed material (4), - That the at least one sensor (5) determines at least one actual value for the at least one physical state variable, and - That the at least one actual value is compared with the at least one desired value, wherein based on the comparison of actual and desired value at least one parameter of the pressing device (3) is controllable. A method according to claim 1, characterized in that the at least one physical state variable of the pressure, in particular steam pressure, the temperature and / or the degree of moisture of the pressed material (4), in particular in Interior of the material to be pressed (4), preferably in the middle of the material to be pressed (4). A method according to claim 1 or 2, characterized in that the at least one sensor (5) is a pressure sensor, a temperature sensor and / or a moisture sensor. Method according to one of the preceding claims, characterized in that the at least one actual value before, during and / or after the pressing of the pressed material (4) is determined. Method according to one of the preceding claims, characterized in that the at least one parameter of the pressing device (3) is the pressing pressure, the pressing temperature, the pressing speed and / or the pressing duration. Method according to one of the preceding claims, characterized in that only after completion of the start-up phase of the pressing device (3) determines the at least one actual value, the at least one actual value compared with the at least one desired value and / or the at least one parameter the pressing device (3) is regulated. Method according to one of the preceding claims, characterized in that the pressed material (4) as a mat (4a), in particular endless mat, is formed. Method according to one of the preceding claims, characterized in that the pressing device (3) operates continuously. Device (2) for producing a wooden material body (1), in particular for carrying out a method according to one of the preceding claims, with a pressing device (3) for pressing a pressed material (4) formed from comminuted wood material, characterized in that a detection device (6) for acquiring measured data from at least one sensor (5) integrated into the pressed material (4), as well as a memory (7) and a comparator (8). Device (2) according to claim 9, characterized in that the pressing device (3) is preceded by a device (9) for integrating the at least one sensor (5) into the pressed material (4). Device (2) according to claim 9 or 10, characterized in that a device (10) for applying a binder is provided on the comminuted wood material, which is preferably upstream of the means (9) for integrating the at least one sensor (5). Device (2) according to one of claims 9 to 11, characterized in that the pressing device (3) is provided with a heating unit (11). Device (2) according to one of claims 9 to 12, characterized in that the pressing pressure, the pressing temperature, the pressing speed and / or the pressing time of the pressing device (3) is variable. Device (2) according to one of claims 9 to 13, characterized in that a display device (13) and / or a control device (14) is provided, which is connected downstream of the comparator (8). Wood material body (1), in particular plate-shaped wood material body (1), produced by a method according to one of claims 1 to 8.

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