DE19858152A1 - Continuous press for wood or recycled thermoplastic boards has structured sections for heating and heating/cooling and cooling to ensure that finished board material has no water or vapor pockets - Google Patents

Abstract

The continuous press assembly, for the production of wood chip- and fiberboards, and plastics boards, has a press stretch (L) which is divided into a heated press stretch (LH) of 50-75% of the length, a heated/cooled press stretch (LH/K) of 15-25% of the length, and a press cooling stretch (LK) of 10-25% of the length. The continuous press assembly, for the production of wood chip- and fiberboards, and plastics boards, has a press stretch (L) which is divided into a heated press stretch (LH) of 50-75% of the length, a heated/cooled press stretch (LH/K) of 15-25% of the length, and a press cooling stretch (LK) of 10-25% of the length. Each section has its press plate system with a recirculating low friction unit (21,22). The press heated/cooled stretch has a single or multiple structure, where the segments (S1-S3) can be heated and/or cooled. A low friction support is at the transit (TB) between the two recirculating systems or press part-sections (I,II). The low friction units are roller rods (22) on chains (21) across the press width, or they are roller bearing carpets. The supports are in the wedge-shaped path section (TB) between the press sections (I,II), which are rotating roller bodies, static rollers, sliding shoes or hydrostatic press cushions, air or steam cushions. The low friction units are between the press cooling plates (18) and the steel belts (12,13), as a non-stick cladding or an air or steam cushion surface at the press plates (18). Additional vertical drillings at the cooling press plates (18) and the heating press plates (17) are at intervals in a number of rows across the press width, to deliver cold softened water at the low friction units (22) and the steel belts (12,13). The evaporated water is extracted as steam from the roller zone and/or flat through the drillings in the press plates or at the sides of the steel belts (12,13). Heat taken from the low friction units (22) at the press part section (I) is fed back through a heater. The low friction units (22) can be tubes. Insulation strips (37) are between the final press heated plates (16) and the leading press heated/cooled plate (17). The press plate cassettes are separated from each other by insulation strips (37) and against the adjacent press heated plate (16). Independent claims are also included for: (1) a continuous board press plate control where the press heated/cooled stretch within the press stretch is switched on when the temperature in the center of the pressed board material has achieved 85-95% of the bonding agent reaction temperature; (2) a continuous board press operation, where the press heated/cooled stretch (LH/K) has a number of working fields (S1-S3) with a variable action either for the heated (LH) or the cooling (LK) stretches to match the reaction temperature of the bonding agent and/or the type and consistency and thickness of the pressed board material. Preferred Features: The final moisture content of the pressed board material over the press cooled stretch is 0-3% below the initial moisture content level. The recovery of the heat loss from the press plate cooling, the cooling of the low friction units and the steel belts is used for initial heating of the water supply to be heated for steam at the initial warming of the board material and/or the water supply for the steam dryers at the wood chip/fiber preparation stages and/or as the heating medium for the press heated plates in the continuous press. The heat extracted from the press units in the press heated/cooled stretch (LH/K) is fed to the full height of the steel belts as they return to the start point, together with heating. The cooling of the low friction units and the steel belts is set according to the hardening temperature of the bonding agent at not more than 120 deg C for wood boards and not more than 100 deg C for plastics boards. The surfaces of the pressed board material are cooled by coolant fed through the drillings in the press cooled plates and/or by spraying cold water on the low friction units and the steel belts through vertical drillings at the press plate cassettes and/or the press cooled plates and/or by press cooled plates. The water delivered is only sufficient to give a volume of evaporated steam which can be extracted. The extracted steam is fed through a water basin to condense into water. Any oil residue is taken from the water surface by separation or suction, and the condensed water is recirculated in a closed water spray circuit.

Description

The invention relates to a continuously operating press Manufacture of wood-based panels and plastic panels after Preamble of claim 1 and a method for a continuous working press according to the preamble of claim 11.

Such a continuously operating press, from which the invention is based, is known from DE-OS 29 22 151.

In the conventional production of wood-based materials, for example with resin binders based on phenol-formaldehyde or urethane-formaldehyde, the H ₂ O moisture introduced into the chip or fiber mat is preferred as the heat transfer medium into the core through the transition of this moisture into the vaporous state of matter the mat (plate) is used, the reaction start temperature of the binder (glue) depending on the plate thickness along the pressing section being reached sooner or later in the middle of the plate. This steam pressure, which still acts in the finished plate at the end of the continuous pressing process, is in equilibrium or imbalance with the transverse tensile strength generated in the plate by the curing process. For example, if the production speed in the continuously operating press is too high, the plate will be destroyed by steam bursts when leaving the continuously operating press due to the imbalance of a plate that has not yet been completely glue-set and the increased steam pressure.

General disadvantages of the conventional continuously operating pressing process without an additional cooling zone is therefore the risk of bursting due to excessive steam pressure acting in the hot plate. An evaporation effect within such a continuously operating press is achieved by a press steam or press pressure relief section. A disadvantage of such a process control is necessary to state that escapes through the input pressure gradient to the atmosphere outside the continuously operating press steam, that is, the disk is moisture (H ₂ O) withdrawn in the range of 2% to 3%, which is unfavorable in view of the swelling behavior and thus the utility value of the wood-based panel, especially in climatic zones with a high percentage of air humidity.

As known from DE-OS 29 22 151, come in industrial practice previously preferred separate arrangements for the heating and cooling zone area to use. Each of these heating and cooling zones has self-sufficient circulation systems for the roll support elements between heating and cooling plates and the Steel strips with the advantage of efficient energy use for each of them separate procedural areas. Another serious disadvantage is that Fixation on only one optimal parameter setting, for example the Production speed for a certain sheet thickness. A disadvantage of This continuously operating press is that it is still a fixed one Assignment within the press section between the heating or cooling area consists. That is, the system is generally with fixed heating and cooling zones uneconomical when used for a wider range in the production of thin (2.5 mm) plates to thick (38 mm) plates.

Thin plates, which are produced at high production speeds, reach the reaction temperature necessary for the hardening of the binder after 50% of the pressing section, whereas thick plates only reach them shortly before the end of the press after about 85% of the pressing section. With this continuously operating press, the cooling section must therefore be made very short. The production of thin and medium board thicknesses results in overheating of the top layers and an excessive loss of moisture. The long-lasting high surface temperature leads to chemical decomposition and degradation of the binding power, especially with urethane-formaldehyde glues. The low residual moisture causes a high water absorption after the manufacturing process, which leads to the swelling of the boards and, in addition to the undesirable dimensional changes, also leads to the breaking of glue bridges and also negatively influences the strength properties of the board. Another disadvantage is that in such systems the temperature profile within the heating section can be influenced only insufficiently. In the first part of the press section, high steel strip temperatures are used to introduce as much heat as possible into the material to be pressed. It would then be desirable to steadily lower the surface temperature. However, this is not possible due to the high mass of the roller bars, which act like a heat accumulator. Heat is carried away from the roller bars in the direction of production and ensures that even when the heating circuits are switched off, the surface temperature hardly drops, as shown in FIG. 9, curve B. With increasing temperature, the vapor pressure in the pressed material increases. At the transition between the heating and cooling sections, there is a brief pressure relief due to the separate circulation systems. As the binder has not yet fully hardened at this point, there is an imbalance of forces and the plate is split.

This system with separate roller body circulation results in one abrupt reversal from heating to cooling. However, this has the disadvantage  a too high initial cooling, causing a high in the pressed material Temperature gradient arises, which in turn leads to harmful shear stresses can lead, which can destroy already set glue bridges. The high initial cooling is system-related and is due to the fact that the Roll body removed from the system at the end of the cooling section, cooled to a great extent and then fed back at the beginning of the cooling section. There they are initially significantly colder than the steel strip and the product and cause a shock-like initial cooling.

The invention has for its object a continuously operating press to create and specify a method by which the cooling within the Press line optimally to the needs of the respective production or each product can be customized and with the further along the Press section of the heating and cooling process on and within the mat can be controlled that the overall efficiency of the continuously working press increased and the physical utility of the manufactured plates can be precisely adapted to the desired requirements can as well as the production security against burst by monitoring Control / regulation of the steam pressure to improve.

The solution to this problem is characterized by. . . . . A1.  

The pressing heating section L _H and the pressing heating cooling section L _{H / K} lie within a first support body circulation system and the cooling section L _K within a second circulation system, the transition between the two circulation systems being provided with a wedge-shaped, friction-reducing support device which relieves the pressure on the material to be pressed prevents the prevailing vapor pressure in the plate. Due to the variable switchable heating and cooling fields in the press heating cooling section L _{H / K} , the surface temperature according to FIG. 9, curve C, can be optimally controlled along the pressing section. The pressing process can thus be carried out more gently, which results in higher strengths of the finished plate or it allows the production of equivalent plates with less binder and thus greater economy. The temperature can be steadily lowered as it passes through the continuously operating press, whereby the jump in temperature when entering the press cooling section L _K can be reduced and the harmful shear stresses can be reduced or eliminated entirely. The heat extracted from the roller bars of the first circulation system can be returned in the return via preheating systems so that the desired high surface temperature is available as quickly as possible in the inlet of the continuously operating press. In such a system, the heat extracted from the roller bars, the steel strips and the pressure plates in the first circulation system can advantageously be returned in full by using this heat to preheat the cooled steel strip. This is possible because the steel strip in the press cooling section L _{K is} cooled to 120 ° Celsius to 90 ° Celsius and thus a sufficient temperature potential is available at the end of the press heating cooling section L _{H / K} to the 130 ° Celsius to 160 ° Celsius to transfer the heat. In this way, the specific internal consumption can be reduced in comparison to conventional systems and the efficiency of the system increased. The heat extracted in the second circulation system can also be used via recovery systems, but due to the low temperature level it may be used for external processes such as building heating, classifier preheating etc.

With this structure of the continuously operating press, the control according to claim 10 and the method according to claim 11 according to the invention, the press heating section L _H or the press cooling section L _K can be targeted and exactly according to the thickness of the mat or the thickness of the finished plate, according to the Reaction temperature of the binder and in line with the consistency of the grit to be used from the press heating _/ cooling section L _{H / K can be} lengthened or shortened.

In order to achieve this, both the starting point of the cooling must be variable be designed, as well as the required technological cooling rate can be controlled specifically and over the length of the cooling section.  

The cooling can thus vary depending on the material to be pressed, the chip / fiber glue culture or the plastic used and the permeability behavior of the chip, fiber or granule geometry and the production speed set according to the invention in addition to the press cooling section L _K from the individual Segments S ₁ , S ₂ and / or S ₃ can be set. As a result, the continuously operating press and the method achieve a greater overall efficiency and the physical utility value of the plate produced can be adapted to the desired requirements, since the mechanical-technological properties of the individual cross-sectional areas can be influenced better than before.

The controlled cooling process also causes a vapor pressure drop, which in comparison to the conventional continuous press Activation of a steam pressure relief section with approximately 10% of the total Press section at the end of the press section is no longer necessary, that is approx 10% of the press section is used to increase production output to disposal. Since there is still a risk of space in the finished plate is excluded, due to the lower vapor pressure at the end of the Press cooling section the process speed of the continuously working Press can be increased by approximately 10% to 15%. So far this has not been the case possible, because in the continuous process of the continuously working press, in  Regarding the risk of bursting with an additional safety value production had to be driven safely. Overall, this results in one Production output increase of approximately 20% to 25%.

Contrary to the previous and prevailing opinion, the teaching of the invention also consists in not only starting the cooling process for reducing the vapor pressure inside the pressed material mat after the binder has completely hardened over the plate cross-section, but rather with cooling on the surfaces of the pressed material mat as soon as it is reached 85% to 95% of the reaction temperature T _R required for the hardening of the binder used to begin in the center of the material to be pressed T _M. This means that the knowledge of the invention and the solution to the problem must be further stated:
Due to the steadily increasing heat content inside the material to be pressed, the heating for the partial pressing section is switched off and the press cooling is switched on before the curing temperature of the binder used in the material to be pressed T _{M is} reached.

The technical application of the invention brings about a drastic reduction the steel strip temperature and thus the surface temperature of the Pressed goods. As a result, the binder (glue) is in the top layers exposed to extremely high temperature loads far less in time.  

So far, this had the degradation (decay) of the binder and thus the Reduction of the bending strength in the finished plate and is in the Usually compensated with the excessive addition of binder. As a result So can higher bending strengths or with less glue same bending and transverse tensile strengths can be achieved for the finished product.

The controlled cooling of the steel strips at the end of the press cooling section to 120 ° Celsius to a minimum of 100 ° Celsius has the further advantages that the inlet temperature of the steel strip in the press circulation is also greatly reduced and that from the inlet to the pressing process under high pressure of approximately 3 to 5 N. / mm ² and a high temperature of 220 ° Celsius no uncontrolled pre-hardening of the pressed material top layers can take place. This results in another advantage of reducing the grinding allowance by ≧ 20%.

The friction reducing elements can be made in a known manner Width of the roller bars, rolling elements or pipes reaching the press plates exist, which are in guide chains on the long sides in the partial presses I and II are circulating.

Another useful arrangement is that in the outgoing part the continuously operating press, in which there are no longer large pressures are required, the friction-reducing elements between the press plates and the steel belts of the cooling section sub-press II as a sliding surface  or as an air, vapor cushion or liquid sliding surface on the press plates are trained. This can be especially the case with overdetermined ones Applications with low pressure in the calibration area with cost advantages be connected.

The cooling according to the invention is also in chipboard / fiberboard Combination with thermoplastic as a binder with advantages applicable. Such combined materials as wood and thermoplastic Plastic in the quantity distribution of, for example, wood chips from 75% to 50% or thermoplastics from 25% to 50% preferably come in Recycling process used. The basic advantage is here also in the use of a cooling and adjustable to the pressing section in that for thermoplastic plastic panels or wood-based panels in Combination with, for example, thermoplastic binders according to the Thermal plasticization process of the thermoplastic and the press molding the molded mat under pressure, the shaped plate then through adaptable cooling effect solidified, that is, the state change point from plastic-liquid to solid state thermally below and thus the plate is demoldable, that is, in the final plate thickness state after Cooling section the finished plate leave the continuously working press can and wood-based panels in combination with plastics can with  the application advantage of an extremely low moisture absorption, getting produced.

Further advantages of the continuously operating press, the control and the method according to the invention are:

• - Depending on the quantity distribution, a variable connection of the heating and coolable press plates possible to the plasticizing area or Adjust the hardening range and depending on the plate thickness Production speed economically adjustable.
• - With the use of the continuously operating press according to the invention can be connected to downstream, apparatus-technically very complex thermal Post-conditioning, that is cooling by using, for example Star turners can be partially or completely dispensed with.
• - This goes hand in hand with the reduction in fixed investment costs and less space required for a corresponding system.

The following process operations are necessary for the continuously operating press according to the invention:

• - The steel belts will go through to the end of the press section Cooling withdrawn heat in the return flow by appropriate Heating fed again.  
• - By cooling the friction-reducing elements and the steel strips to 120 ° Celsius to 100 ° Celsius and the material temperature T _M ≧ 100 ° Celsius, a higher final moisture content of the finished plate can be produced.
• - This means that the panels with a higher final moisture content up to 8 Weight percent can be made if desired. With this higher Final moisture is also possible that the initial moisture of the finished plate over the press cooling section from 0% to approx. 3% below the input moisture can be adjusted to the continuously operating press.
• - The plate thickness can be moved more precisely because of the Post-shrink effect is reduced by more than 50%, and further the Reduced grinding thickness is controlled by less pre-hardening cooled steel belts and retention of the glue structure without decay due to temporal overheating.

In order to be able to optimally control the start of the cooling T _K according to its different position along the pressing section L, the continuously operating press according to the invention for controlling the reaction starting point T _R consists in the fact that within the potential connecting section, that is the pressing heating cooling section L _{H / K} Several press plate cassettes with partial lengths in the range of 1 to 2 m are installed, which can be supplied with either heating or cooling medium. Thermal insulation is provided between the respective heating or cooling cassettes.

An advantageous development of the continuously operating press according to the invention is that in the coolable press plates of the press cooling section L _K and possibly also in the press plates of the press heating and cooling section L _{H / K} , additional vertical holes in several rows e across the width b of the press plates are, by the softened water can be pressed onto the friction-reducing elements and the steel strips and can be discharged as steam from the rolling area flatly through suction bores arranged in the press plate or to the side of the steel strips. By using the evaporation enthalpy there is a rapid cooling. The extracted steam is condensed in a water bath with the advantage that entrained oil molecules can be separated on the surface of the water bath and the condensed water is returned to the vertical spray holes in a closed circuit.

The friction-reducing elements can do this in a known manner the width of the pressing plates reaching rolling rods, rolling elements or pipes consist.  

Further advantageous measures and refinements of the subject of Invention emerge from the subclaims and the following description with the drawing.

Show it:

Fig. 1 in side view, the invention continuously working press according to the invention,

Fig. 2 shows the 1 part of the region between the part pressing in a first embodiment according to FIG. As a support device for the steel strips,

Fig. 3 shows the portion between the partial pressing in a second embodiment according to Fig. 1 as a support device for the steel strips,

Fig. 4 to 1 part of the region between the part pressing in a third embodiment according to FIG. As a support device for the steel strips,

Fig. 5 shows the partial region between the partial pressing in a fourth embodiment according to FIG. 1 as a support device for the steel strips,

Fig. 6, 7, 8 and 9 are diagrams over the heating and cooling profile within the pressing zone according to the prior art in comparison to the the invention,

Fig. 10 shows a part of the continuously working press according to Fig. 1 with the arrangement Preßplattenkassetten and rolling rods,

Fig. 11 shows a detail E of Fig. 10 with the Preßplattenkassetten and

Fig. 12 shows the design of the press cooling plates with rinsing-showering device and steam extraction device.

The continuously operating press 1 according to the invention consists of the partial presses I and II with the stationary lower press bars 2 and 5 and the movable upper press bars 6 and 9 . To adjust the press nip 11 , the upper press bars 6 and 9 of hydraulic piston-cylinder arrangements (not shown) are moved up and down and locked in the selected position. The steel belts 12 and 13 are each guided over a drive drum 14 and a deflection drum 15 around all lower and upper press bars and pull the mat 10 through the continuously operating press 1 . To reduce friction between the mounted on the press bars 2, 5, 6 and 9 press plates 16, 17 and 18 and the rotating steel strips 12 and 13 are also circumferentially depending on an educated antifriction elements carpet, in the exemplary embodiment as a roller rods 22, are provided. Longitudinal and transverse bores 19 are made in the pressure plates 16 , 17 and 18 for the passage of heating or cooling media. The roller bars 22 , the axes of which extend transversely to the direction of belt travel, are joined on both longitudinal sides of the presses I and II in guide chains 21 with a predetermined pitch and on the pressure plates 16 , 17 and 18 on the one hand and on the steel belts 12 and 13 rolling from the steel belts 12 and 13 through the continuously operating press 1 , the entrained material mat 10 being pressed to the finished plate 20 . The introduction wheels 27 and the deflection wheels 28 serve for the roller bars 22 and the guide chains 21 as circulation devices.

Fig. 6 after curve e shows the course of the mean temperature of the pressed material when passing through a press with heating section L _H and with cooling section L _K according to the prior art of DE-OS 20 58 820 and continuous roller bar circulation. At the end of the heating section L _{H there} is a switch from heating to cooling. As can be seen, the mean temperature T _{M of} the material to be pressed initially continues to rise until the flow of heat reverses at point "A" and the actual cooling begins. In this case, cooling is initially carried out using only a small heat flow, which initially increases steadily and then runs asymptotically against a limit value. Fig. 6, curve f, on the other hand, shows the course of the mean pressed material temperature in a conventional system with separate roller bar circulation according to DE-OS 29 22 151. Here, the sudden reversal with the high initial cooling speeds is visible, which, however, entails the disadvantages described at the beginning. Industrial production plants are usually designed for a defined range of products. For the production of wood-based panels on continuously operating presses, the core spectrum is usually 6 mm according to Fig. 8, thin pressed material mat o, medium pressed material mat n and thick pressed material mat m, up to 38 mm, with the project-specific spectrum down to 2.5 mm and can be extended up to 40 mm. Depending on the product thickness, density, type of board (chip, OSB, MDF, LVL, plastic ...), the hotplate temperature, moisture content, type of binder and other measures influencing production, such as water spraying, preheating of the pressed material, etc., increases the initial temperature T _A according to Fig. 8 of the binder m to the reaction temperature T _R according to the thickness, n or o the press material mat 10, however, different in the continuously operating press 1, and thus must also the onset of cooling, as shown in Figs. 6, 7 and 8 Curve g shown, at about 85% -95% of the reaction temperature T _{R1 / o} , T _{R2 / N} or T _{R3 / M} , that is to say earlier and at different points T _{K1 / O} , T _{K2 / N} or T _{K3 / M} . Depending on the project, the range in which 85% -95% of the reaction temperature T _R in the middle of the plate can be reached or calculated by interpolation can be achieved by calculation and using empirical values from existing systems. Within this range, the cooling must be variable switched, that is, the continuously operating press 1 is to be fitted in the Preßheizkühlstrecke L _{H / K} of the partial presses I with one or more combination of segments S ₁ to S _3, wherein each of these segments S _1, S ₂ and S ₃ can be activated as fields of action either for heating or cooling. In front of this area, that is the press heating section L ₁ , the continuously operating press 1 can be designed without a cooling option and behind this area, that is to say the press cooling section L _K , without a heating option. The entire technological press length can thus be divided into 3 groups. On the inlet side, a pure heating section is first built up over a length L _H , in which the process heat required for the reaction of the binder is introduced into the pressed material. The length L _H will extend to 50% to 75% of the press length L. This is followed in the production direction by a combined heating / cooling section L _{H / K} with inside the partial press I, in which, from a variable point in accordance with the segmentation S ₁ to S _{4, it is possible} to switch from heating to cooling. The press heating cooling section L _{H / K} is usually carried out in a length of 15% to 25% of the press length L and divided into one to three heating / cooling segments S ₁ to S ₃ . This is followed by a pure cooling section with the remaining length L _K of 10% to 25% in proportion. A control system with ideal setting options with regard to the starting point of the cooling and controllability of the cooling rate can be generated by the press heating section L _H with the individual heating / cooling segments S ₁ to S _{3 of} the heating / cooling section L _{H / K} , and the subsequent pure cooling section L _K , each with a separate roller bar circulation. This makes it difficult with all possible variations that the energy stored in the roller bars 22 is carried away by the sub-press I into the cooling zone of the sub-press II, and this results in the disadvantages already described. The cooling rate can be regulated individually for each roll body circulation and can thus be adapted to the needs of the respective production. As shown in FIGS. 6 and 7, the steepness and course of the cooling curve can thus be controlled over a wide range. Due to the short roll bar revolutions, there are also lower temperature differences between the incoming roll bars 22 and the steel strips 12 and 13 at the beginning of a respective cooling segment S ₁ to S ₃ , whereby the initial cooling speeds can be reduced. For the press heating section L _H with the individual segments of the press heating cooling section L _{H / K} and the pure cooling section L _K , individual roll bar revolutions are created. Each of these cycles has its own chain tensioning and drive system. To avoid pressure relief in the sub-area T _B or the transition between the individual circulations, support devices 23 or 24 or 25 or 26 are provided which support the steel strips 12 and 13 . Such support variations can be designed as sliding shoes 23 , provided with a static or hydrodynamic lubricating film 25 , as a roller carpet 24 or with fixed support rollers 26 . For the pure cooling section L _K , it will be necessary to provide a heating or tempering option so that the heating plate temperature is set to the later steady state before the start of production. The cooling temperature set during production of, for example, 120 ° Celsius would otherwise be undershot when the production was stopped and would lead to rejects when production was resumed.

The continuously operating press 1 is shown in simplified form in FIG. 1 only for the movable upper press bars 6 and 9 with friction-reducing roller bars 22 fixed in guide chains 21 . Of course, the fixed lower press bars 2 and 5 of the continuously operating press 1 are designed with the same guide chains / roller bar systems 21 , 22 , the press plates 16 , 17 and 18 and the holes 19 made therein.

In order to be able to optimally control the start for the press cooling or the reaction starting point T _R along the pressing section L, there are several pressing plate cassettes 34 (instead of the pressing heating cooling plates 17 ) with partial lengths in the range of approximately 1 m to within the potential control area of the press heating cooling section L _{H / K} 2 m is provided, which can be optionally supplied with heating or cooling media, as shown in FIGS. 10, 11 and 12. An insulating strip 37 is provided between the respective heatable and coolable press plate cassettes 34 . Either oil or water is used as the heating or cooling medium, water being preferred because of the higher heat transfer value, especially in the cooling area.

Fig. 12 shows a water spray showering device, through vertical holes 35 in the press plate cassettes 34 and / or the press cooling plates 18 , which between the heating or cooling holes 19 across the width of the press plate cassettes 34 transversely to the direction of the steel strip in several rows e, for example in a narrow distance s of 50 mm to 150 mm are arranged. The water is thus sprayed over a wide area onto the approximately 220 ° Celsius hot rods 22 and the closed hot steel strips 12 and 13 and evaporated immediately. As a result, the stored heat in the roller bars 22 and steel strips 12 and 12 is suddenly removed by the evaporation enthalpy effect, and the temperature profile in the pressed material 10 changes very rapidly. According to FIG. 12, section F from FIG. 10, the resulting steam pressure is sucked off through a series of steam suction bores 35 (= the water feed bores), so that there is no direct influence on the material to be pressed 10 . It can be alternately of the holes 35 of water was added from a row of holes e and suction filtered through a bore row e of the holes 35 vapor. In this case, only as much water is expediently fed through the bores of the pressing / cooling plates as can be generated and discharged as steam.

The water supply through the water spray showering device through the vertical bores 35 and also the cooling through the bores 19 along the press cooling section L _K can take place until the temperatures on the roller rods 22 and the steel strips 12 and 13 are approximately at auf 120 ° Celsius are lowered. This ensures a controlled steam discharge through the steam suction holes 35 , so that no condensation can take place on the surfaces of the roller bars 22 , the press cooling plates 18 , the press plate cassettes 34 (instead of the press cooling plates 18 ) and the steel strips 12 and 13 in the rolling area 38 . An emulsifying effect to the lubricating oil film on these surfaces is prevented and the lubricating function and operational safety is further guaranteed. The extracted steam is condensed in a water bath and returned to the cooling process at around 95 ° Celsius. Oil molecules entrained by the steam collect on the surface of the water bath and are sucked off or separated from there.

The drawing shows the procedural options for controlling the moisture profile and for reducing the pressing factor when using cooling in accordance with the above embodiment. With a 16 mm thick MDF board, with a press section of 38 m and with a 7 m integrated cooling section, the temperature profile shifts from ≈170 ° Celsius to ≈140 ° at the end of the 38 m press length at the end of the 38 m press length Celsius and in the middle of the plate from 115 ° Celsius to ≈100 ° Celsius. After passing through the press cooling section L _K , the temperature of the material to be pressed T _M is reduced in comparison to the process without cooling from approximately 115 ° Celsius to ≧ 100 ° Celsius and the surface temperature of the material to be pressed on the cover layers is reduced from ≈170 ° Celsius to approximately 122 ° Celsius. Compared to the center temperature of the material to be pressed T _M ≈115 ° Celsius in the core of the material to be pressed 10 without cooling, the steam pressure within the MDF board has dropped dramatically to ≦ 1.1 bar due to the temperature being reduced to 100 ° Celsius. This completely eliminates the risk of bursting in the finished plate 20 . The roller rods 22 of the press part I have to be heated in the return pipe for the new entry in the continuously operating press 1 in a Rücklaufheizeinrichtung 36 again.

As can further be seen from FIG. 1, the heat energy extracted during cooling can be fed back via the heat extraction pipes 29 and 30 to the steel strips 12 and 13 , the press heating plates 16 and / or the roller bars 22 via the heat supply pipes 31 , 32 and 33 .

From the drawing it can also be seen how the connection or disconnection section, that is to say the press heating cooling section L _{H / K,} can be shortened by appropriate variable control in the number of press plate cassettes 34 or by switching off the pressing heating section L _H or the press cooling section L _{K can be} extended.

Reference list

1

continuously working press

2nd

lower press spar I

5

lower press spar II

6

upper press spar I

9

upper press spar II

10th

Pressed mat

11

Press nip

12th

Steel band below

13

Steel band at the top

14

Drive drum

15

Deflection drum

16

Press heating plates

17th

Press heat cooling plates

18th

Press cooling plates

19th

Holes in

16

,

17th

,

18th

20th

Finished plate

21

Leadership chain

22

Roller bars

23

Sliding shoe

24th

Roll carpet

25th

hydrodynamic press pad

26

Support rollers

27

Entry wheels

28

Deflection wheels

29

Heat exhaust pipes

30th

Heat exhaust pipes

31

Heat supply pipes

32

Heat supply pipes

33

Heat supply pipes

34

Press plate cassettes

35

Bores / water sprayer and steam extractor

36

Return heating device

37

Insulating strips

38

Taxi area
I, II partial presses
L press line
L _H

Press heating section
L _{H / K}

Press heating and cooling section
L _K

Press cooling section
S (n) segments of the press heating and cooling section
T _A

Press mat temperature at the beginning of the pressing process
T _B

wedge-shaped section
T _K

Start of cooling
T _M

Temperature in the center of the material to be pressed
T _R

Reaction temperature of the binder
e Temperature curve in a continuously operating press with an L _H

and L _K

f temperature profile in a continuously operating press according to DE-OS 29 22 151
g temperature profile in a continuously operating press according to the invention
m thick finished plate / mat
n medium finished plate / mat
o thin finished plate / mat

Claims (19)

1.Continuously working press for the production of wood-based panels such as chipboard, fiberboard and chipboard as well as plastic panels from a combined proportion of wood and plastic as well as plastic with and without reinforcing inserts, with the pressure transferring and the material to be pressed through the press, flexible endless steel belts that of drive drums and deflection drums are guided around a lower and upper press spar of two partial presses and which are supported with friction-reducing elements first against heated and subsequently cooled press plates of the press spars, the press spars of the partial presses arranged one behind the other in the press frame forming the press section, characterized by the division the pressing section (L) into a pressing heating section (L _H ) with a share of 50% -75%, a press heating cooling section (L _{H / K} ) with a share of 15-25% and a press cooling section (L _K ) with a share of 10 b is 25%, the press heating section (L _H ) with the press heating cooling section (L _{H / K} ) and the press cooling section (L _K ) each having their own press plate area with circumferential friction-reducing elements ( 21 , 22 ), within the press heating cooling section (L _{H / K} ) a plurality of segments (S ₁ , S ₂ , S ₃ ) are both heatable and / or coolable and the transition (T _B ) between the two circulation systems or the partial presses (I and II) is a friction-reducing support device ( 23 , 24 , 25 , 26 ) is arranged. 2. Continuously operating press according to claim 1, characterized in that the friction-reducing elements as over the press width (b) extending roller bars ( 22 ) with guide chains ( 21 ) or as a roller bearing carpet are executed. 3. Continuously operating press according to claim 1 and 2, characterized in that the friction-reducing support devices ( 23 , 24 , 25 , 26 ) in the wedge-shaped partial area (T _B ) between the partial presses (I, II) from rotating rolling elements or as a roller carpet ( 24 ) consist of stationary support rollers ( 26 ), are designed as sliding shoes ( 23 ) or consist of a hydrostatic press cushion ( 25 ), air or steam cushion. 4. Continuously operating press according to claims 1 to 3, characterized in that the friction-reducing elements between the press cooling plates ( 18 ) and the steel belts ( 12 and 13 ) of the cooling section sub-press (II) as a sliding surface or as an air or steam cushion sliding surface the press plates ( 18 ) is formed. 5. Continuously operating press according to claim 11, characterized in that in the coolable press plates ( 18 ) of the press cooling section (L _K ) optionally also in the heatable and coolable press plates ( 17 ) of the press heating cooling section (L _{H / K} ) additional vertical holes ( 35 ) in several rows (e) at a distance (s) across the width (b) of the pressure plates ( 17 and 18 ) through which softened cold water is applied to the friction-reducing elements ( 22 ) and the steel strips ( 12 and 13 ) can be pressed in and discharged as steam from the rolling area ( 38 ) and / or flatly through bores ( 35 ) arranged in the pressure plates or laterally of the steel strips ( 12 and 13 ). 6. Continuously operating press according to claims 11 and 12, characterized in that the friction-reducing elements ( 22 ) of the sub-press (I) are guided in the return via heating devices ( 36 ) and can be heated up again. 7. Continuously operating press according to claims 11 to 13, characterized in that the friction-reducing elements ( 22 ) are designed as tubes. 8. Continuously operating press according to claims 11 to 14, characterized in that between the last press heating plates ( 16 ) and the first press heating cooling plate ( 17 ) insulating strips ( 37 ) are arranged. 9. Continuously operating press according to claims 11 to 15, characterized in that the press plate cassettes ( 34 ) are separated from one another and to the next press heating plate ( 16 ) by insulating strips ( 37 ). 10.Control for a continuously operating press for the production of wood-based panels such as chipboard, fiberboard and chipboard as well as plastic panels from a combined proportion of wood and plastic as well as plastic with and without reinforcement inserts, with the pressure transferring and the material being pressed through the press, flexible endless Steel belts, which are guided by drive drums and deflecting drums around a lower and upper press spar of two partial presses and which are supported with friction-reducing elements first against heated and subsequently cooled press plates of the press spars, with the press spars of the partial presses arranged one behind the other in the press frame forming the press section by means of a control or regulation in which the press cooling section (L _K ) is switched on within the press heating cooling section (L _{H / K} ) when 85% to 95% of the reaction temperature is in the center of the pressed material mat (T _M ) tur (T _R ) of the binder is reached. 11. A process for the continuous production of wood-based panels such as chipboard, fiber and chipboard as well as plastic panels from a combined proportion of wood and plastic as well as plastic with and without reinforcing inserts, in which a starting mixture of a scattering station is used on a continuously moving scattering belt with a binder offset press mat is formed, which, after being introduced between the steel belts, brings a continuously working press according to claims 1 and a control according to claim 10, using pressure, heat and cooling, into the final shape of a plate and cures, characterized in that the press heating cooling section L _{H / K} with one or more fields of action S ₁ to S ₃ variable either the press heating section L _H or the press cooling section L _{K can be} switched on for adaptation to the respective reaction temperature of the binder and / or the type, consistency and thickness of the material to be pressed b between the pressed material mat. 12. The method according to claim 11, characterized in that that the output moisture of the finished plate over the press cooling section from 0% to about 3% below the input humidity. 13. The method according to claims 11 and 12, characterized by a recovery process of the heat loss from the press plate cooling, the cooling of the friction-reducing elements and the steel strip cooling, in which this heat loss for preheating

• a) of the feed water for steam generation during the preheating of pressed material and / or
• b) the feed water for the steam / dryer units in the chip / fiber processing and / or,
• c) the heating medium itself is used to heat the press heating plates in the continuously operating press.

14. The method according to one or more of claims 11 to 13, characterized in that the amount of heat withdrawn from the press elements of the press heating cooling section L _{H / K is} fed in full to the steel strips in the return. 15. The method according to one or more of claims 11 to 14, characterized in that the steel strips amount of heat withdrawn by cooling in the return through a appropriate heating is supplied again. 16. The method according to one or more of claims 11 to 15, characterized in that the cooling of the friction-reducing elements and the steel strips accordingly the curing temperature of the binder to ≦ 120 ° Celsius Wood-based panels and for plastic composite panels at ≦ 100 ° Celsius is done. 17. The method according to one or more of claims 11 to 16, characterized in that the cooling on the  Surfaces of the pressed material mat by feeding coolant into the Bores of the pressing / cooling plates and / or by spraying cold water on the anti-friction elements and steel strips through vertical holes in the press plate cassettes and / or Press heating plates and / or cooling plates. 18. The method according to one or more of claims 11 to 17, characterized in that only so much water through the holes of the pressing / cooling plates is fed as as steam can be generated and discharged. 19. The method according to one or more of claims 11 to 18, characterized in that the derived steam condensed in water by introduction into a pool of water, Oil residues are separated or sucked off at the water surface and the condensate water in a closed circuit Spray cooling is fed back.