NO332904B1 - Process for manufacturing glued wood parts or wood components and use thereof. - Google Patents

Abstract

A process for producing glued wood components (10) comprises uniformly warming the wooden component cross section (8) in an electromagnetic field (9) before gluing. The field consists of high frequency radiation of 13.56MHz or 27.12MHz. The components are warmed to 30-95degreesC. The adhesive is applied along with a hardener. Duroplastic condensation adhesives are used to join the components. A process for producing glued wood components (10) comprises uniformly warming the wooden component cross section (8) in an electromagnetic field (9) before gluing. The field consists of high frequency radiation of 13.56MHz or 27.12MHz. The components are warmed to 30-95degreesC. The adhesive is applied along with a hardener. Duroplastic condensation adhesives, eg formaldehyde resin, or thermoplastic adhesives, eg PVA, are used to join the components. The adhesive is applied using a line application (42) or film application (43) technique.

Description

The present invention relates to a method for the production of glued wooden parts and wooden components, for example, wooden components with relatively small dimensions (standard cross-section) and their use.

The application of the glue is of fundamental importance for a good result when gluing. The glue is usually applied to one of the two surfaces to be bonded together. The glue is applied by casting strings. The glue and a hardener are mixed together before application. This process has the disadvantage that, depending on the required working time until pressing, the resin mixture with the curing agent must be adjusted to a relatively long curing time since the reaction process is already initiated by the mixture before application to the wooden surface. On the other hand, this necessitates relatively long press times and consequently long total processing times, so that the operating resources are relatively poorly utilised. After a certain working time, the entire apparatus, which is contaminated with the manufactured glue/hardener mixture, must also be thoroughly cleaned to prevent the hardening of glue residues in the application plant.

DE 24 16 032 C3 shows a method for gluing wooden parts. A liquid resin and a liquid hardener are applied in each case separately by means of a "strip distributor". A disadvantage of this process is the fact that, apart from the formation of defects, local insufficient mixing of curing agent and resin can also occur, with the possible formation of wetted areas which only cure insufficiently, if they cure at all. Therefore, the bonding is weakened in the area with these defects or the bonding area where the hardener and the liquid resin are insufficiently mixed.

DE 38 34 026 A1 deals with a method for the separate application of a liquid two-component adhesive system to the surface of wooden parts. According to this solution, one of the two components of the two-component adhesive system is applied as a molding film and the other component of the two-component adhesive system is applied as a molding strand. At least one of the two components of the two-component adhesive system is kept in circulation. For this purpose, one of the two components can be kept in constant circulation via a storage container, a casting head which is equipped with a guide element, below which a supply device for the wooden parts can be arranged and above a collection vessel.

DE 38 34 027 A1 relates to a method for applying a ready-to-use adhesive to the surface of wooden parts. For this purpose, a ready-to-use glue is kept in constant circulation within a circulation circuit comprising a molding head equipped with a guide element and placed above a supply device, and a collection vessel, so that the ready-to-use glue can be applied as a molding film to the surface of the wooden parts. For this purpose, the adhesive is tempered to a temperature of from 5°C to 30°C before application. For example, urea/formaldehyde, melamine/urea/formaldehyde, melamine/urea/phenol/formaldehyde, phenol/resorcinol/formaldehyde, resorcinol/formaldehyde, phenol/formaldehyde, polyvinyl acetate glue types and mixtures thereof and additional glue types that are common in wood processes are applied as ready-to-use glue to the surface of the wooden parts. DE 38 34 027 A1 shows tempering of the glue to a temperature between 5° to 30°C before application to the surface of the wooden parts. According to this process, only brief heating can be achieved to the surface of the wooden components to be glued. Applying an adhesive at a temperature between 5°C to 30°C does not affect the curing time of the applied adhesives.

DE 41 26 712 A1 shows an insulating board comprising a wooden base material and a method for its production. According to the manufacturing process, especially for the continuous production of insulation boards comprising a wood base material, the wood base material is moistened with a heat-setting binder and introduced into a plate mold during the time for the binder to react under the action of heat and/or pressure, or placed on a conveyor belt passing through heating zones. The wood base material is pre-dried with the supply of energy and, after wetting with the binder, it is brought into the pallet or formed into a string, especially a continuous string, on the conveyor belt. It is then structurally stabilized by means of at least one press, in particular a through-flow press, under the action of pressure and/or heat energy and the plate or strand is heated by means of microwaves. The microwave energy is supplied in the form of microwaves that have a wavelength of from 1 mm to 1000 mm and a frequency of around 2500 MHz.

Fl 103490 describes a method for assembling wooden parts by gluing. The glue is applied to at least one of the surfaces of wooden parts to be glued together, and at least one wooden part is heated before applying the glue so that the heat accumulates in it.

In light of the solutions known from prior art, it is an aim of the invention to achieve a shortening of the pressing times of wooden parts and wooden components and consequently to achieve an increase in the capacity of facilities for the production of glued structural wooden parts or wooden components.

According to the invention, this task is solved by a method for the production of glued wooden parts or wooden components using adhesive systems, in which the gluing of the heated wooden parts or wooden components is carried out by separate application of laminating resin and hardener (binder) or by an adhesive system mixed from laminating resin and curing agent, in which uniform heating of the entire cross-section of the wooden parts or wooden components is carried out by microwave radiation before the gluing of the wooden parts or wooden components.

The complete heating of the entire cross-section of the wooden component or of the wooden part before gluing ensures that the inherent specific heat capacity Cp of the wooden part or wooden component after the process is utilized as a heat storage, which results in a considerable reduction in the curing time of the applied glue or of the applied glue components and consequently a considerable reduction in the required minimum pressing times for the wooden components or for the wooden parts. By means of the inventive process, the reactivity of the applied adhesive or of the applied adhesive systems is considerably increased, with the result that the curing time can be dramatically reduced. A tension-free adhesive joint is achieved by the proposed means according to the invention; furthermore, a reduction in the amount of adhesive applied can be achieved from about 400 g/m<2>to 300 g/m<2>with uniform preheating of the entire cross-section due to the higher reactivity of the applied adhesive or adhesive system. This increase in the temperature of the entire cross-section of the wooden part or wooden component further reduces the viscosity of the glue or of the glue system used so that a more uniform distribution of the glue or of the glue system is established. This is accompanied by a beneficial effect on adhesion and a better joint quality of the adhesive joints obtained. Due to smaller glue residues that swell over the glue joints and that remain on the outside of the wooden component, or wooden part, the wear of tools, in subsequent processing steps, for example planers, is dramatically reduced. The wear of the planer blades becomes significantly less, with the application of the method proposed according to the invention, due to less excess glue in the joint region, the planer blades now process the component, and they do not wear out prematurely due to protruding stuck-on dried glue residues. Furthermore, due to the limited swelling of glue in the joint area, less contamination of the construction parts is achieved.

By means of the proposed process, it is possible in total to have a beneficial influence on the storage behavior of the manufactured wooden parts or wooden components.

The heating of the three-part or three-component cross-sections to be glued before the glue application is carried out by microwave radiation. This allows short pressing times in facilities for the production of glued plate or structural wood parts. For this purpose, the wooden parts or wooden components prepared for gluing pass through a heating station. The wood parts or wood components to be glued together can be supplied to the heating station either continuously or in a cyclical manner at a plant for the production of plate-shaped or structural wood parts, for example glued laminated wood, structural solid wood, duolam or triolam. Good results are achieved in particular by heating the entire cross-section of the wooden component or wooden part to temperatures between SO^C and 95°C. Preferably, a tempering of the entire cross-section of the wooden components or wooden parts takes place to temperatures between 40<<>>C and 70<*>0. Particularly preferably, the entire cross-section of the wooden component or wooden part is heated to a temperature between 45°C and 60°C.

After heating the wood cross-sections prepared for gluing, conventional glue types used for wood gluing are used, for example, for glued laminated wood (BSH), preferably condensation glue or condensation resin glue types based on urea, melamine, phenol/resorcinol and formaldehyde, for example, urea/formaldehyde, melamine/urea/formaldehyde, melamine/urea/phenol/formaldehyde, phenol/resorcinol/formaldehyde, resorcinol/formaldehyde and phenol/formaldehyde glue types or phenol/formaldehyde resin glue types and polyvinyl acetate glue types, EPI glue types, mixtures thereof, and further common glue types in woodworking, such as for example, single- or multi-component polyadducts with which both load-bearing and non-load-bearing wood components or wood parts are glued to each other.

Through the total combination of all measures according to the present method, the pressing times of the wooden parts or wooden components to be glued together can be considerably reduced. In the case of conifers, for example, spruce, fir, larch and pine, pressing times can be reduced from, typically, 8 to 12 hours at 20<>C to about one hour. In the case of hardwoods, which are generally difficult to glue, such as beech, oak, ash, birch, maple and also tropical wood species, improved glue quality can be achieved in addition to a considerable reduction in pressing time. Using the proposed short-cycle method, the pressing time is dramatically reduced at the process step of heating the entire cross-section of the wooden component or wooden parts before gluing.

The processing step which follows the heating of the entire cross-section of the wooden components or of the wooden parts inside a heating station and includes the application of glue to the wooden surfaces to be glued together, can be carried out by application methods in which condensation resin systems comprising a laminating resin and associated curing agents are used especially in the case of structural wood components. The adhesive application can be carried out either with mixed adhesive liquid or with individual components of an adhesive system to be applied separately from each other. Both string application and film application can be chosen as an application technique. In the case of separate application of the adhesive components, any desired combination of strand application and film application may be used. Due to the increased substrate temperature due to uniform preheating of the wood parts or wood components to be glued together, the viscosity of the glues or glue components to be applied can be reduced, resulting in better adhesion. The heating of the entire cross-section to a temperature between 30°C and 95°C, preferably to a temperature between 40°C and 70°C and particularly preferred to a temperature between 45°C and 60°C, allows a reduction in the amount glue to be applied, since a better distribution of the glue or of the components used in the glue systems over the glued surfaces can be achieved by heating the entire wood cross-section.

By means of the method proposed according to the invention, it is possible to increase the capacity of facilities for the production of plate-shaped, single or multi-layer solid wood panels or structural wood parts, such as glued laminated wood (BSH), construction solid wood or duolam or triolam wood parts, planks or edge table. Furthermore, chipboard, fibreboard (HDF/MDF), OSB boards and plywood can be glued together. In the case of sandwich elements, for example components equipped with insulating polystyrene layers or components coated with PU foam, a considerable acceleration of the gluing can be achieved. The method proposed according to the invention is particularly suitable for use in the production of structural wooden components with relatively small dimensions, i.e. for the production of standard cross-sections.

The method proposed according to the invention is described more precisely in the following with reference to a drawing.

It shows:

Figure 1 a plan section of a plant for the processing of wooden components

and thirds and

Figure 2 the schematic presentation of a press station.

After the preparation of the surfaces of the wooden parts or wooden components 10 to be glued, i.e. after their surface treatment to produce a smooth surface and after possible cleaning of the surface, the wooden parts or wooden components 10 are taken to a heating station 3. The wooden parts/wooden components 10 to be glued is taken either continuously or cyclically to the heating station 3.

The wooden parts/wooden components 10 prepared for gluing are supplied to a heating station 3 before glue application. In the heating station 3, a microwave radiation is generated, by which uniform heating of the entire cross-section 8 of the individual wood parts/wooden components 10 which are fed continuously or cyclically to the heating station 3.1 the heating station 3, is a heating space limited by an upper side 4 and a underside and side walls 5. Radiation devices 6 can be arranged both on the upper side 4 and on the underside and on the side walls 5 of the heating room, the radiation devices uniformly expose the material to be heated on the inside of the heating station 3 to shortwave radiation, and ensure microwave radiation from these sides. The radiation devices 6 comprise individual radiators which can emit completely different radiation performances. The wooden components or wooden parts 10 supplied to the heating room are supplied in flow direction 2. As is obvious from the diagram in figure 1, the entire cross-section of the wooden parts/wooden component 10 is heated by the radiation device 6 which is held on the side walls 5 of the heating room. Since a uniform irradiation of all sides of the wooden parts/wooden components 10 inside the heating station 3 is ensured, uniform heating is established in the interior of the entire cross-section 8 of each wood part/wooden component 10 passing through the heating station 3. Depending on the residence time and the intensity of the microwave irradiation, a temperature between 30°C and 95°C is established within the entire cross-sections 8 of the wooden parts/wooden components 10. When the entire cross-section 8 of the wood parts/wooden components 10 is heated to a temperature between 40°C and 10°C, it is possible to achieve a shortening of the pressing time after gluing the wooden components or wooden parts 10, which are heated uniformly across their cross-section 8, in a gluing station 12 upstream of the heating station 3. Particularly preferably, a heating of the entire cross-section 8 of the wooden components or wooden parts 10 is carried out to a temperature between 45 and 60° C.

When passing through the heating station 3, the heat storage potential inherent in the wood parts/wood components 10, given by the specific heat capacity Cp, is utilized for the storage of heat, which allows a considerable reduction in the curing time of the applied glue or glue systems and thereby a significant reduction of the required minimal pressing time. The gluing of the wooden parts or wooden components 10 heated over their entire cross section is carried out by separate application of laminating resin and hardener or binder of a glue system. The application of the components of the adhesive system can be carried out either by the string application method or by the film casting method; furthermore, any combination of process steps of both application methods with each other is conceivable. It is also possible for a mixture made from laminating resin and hardener to be applied using the strand or film casting method. It is possible to achieve a reduction in pressing times and consequently an increase in the plant's capacity for the production of glued sheet-like, for example single-layer, or multi-layer solid wood panels or structural wood parts, for example, glued laminated wood, structural solid wood and/or duolam or triolam wood parts . With the help of the method proposed according to the invention, which includes a thorough heating of the entire cross-sections 8 of wooden parts/wooden components 10 to be glued by the short-cycle method, it is in principle possible to process all conventional types of wood. In the case of conifers, for example, spruce, fir, larch and pine, the pressing times in a pressing station downstream of a heating station 3 with downstream glue application can be dramatically reduced from, typically, 8 to 12 hours at 20°C to about one hour. In the case of hardwoods, which are generally more difficult to glue, such as for example beech, oak, ash, birch, maple and also tropical wood species, it is possible, in addition to a reduction in pressing times, to also achieve improved glue quality, because on due to the heating of the entire cross-section 8 of the wood parts/wood components 10, the viscosity of the applied glue or a component of a multi-component glue system can be reduced so that a better glue distribution in the joint and consequently better adhesion with simultaneous optimization of the applied glue quantity can be achieved. A further advantage of the total combination of all measures in the method proposed according to the invention can be seen in the fact that a stress-free glue joint can be achieved and the amount of the glue system applied to the components to be glued together can be reduced. A better joint quality in the area of the glue joint is established, which has a very partial influence on the lifetime of tools with which the wooden parts or wooden components produced by the process proposed according to the invention are later processed. The application of the process proposed according to the invention reduces the pressing times both in the processing of conifers and in the processing of hardwoods.

The short-cycle method proposed according to the invention is particularly suitable for the production of solid wood cross-sections, either boards, planks or edge boards, for example, glued laminated wood, duolam or triolam, structural solid wood (KVH), single-layer boards, and multi-layer solid triple boards. These materials, i.e. boards, planks, edge boards, glued laminated wood, duolam, triolam, construction solid wood (KVH), single-layer boards, and multi-layer solid triple boards could also be glued to each other using the process proposed according to the invention.

Furthermore, the short cycle method can be used in a way that has a positive effect on processing times, for the production of sandwich elements it is possible that the sandwich elements have insulation of polystyrene or PU foam or of layers that positively affect the insulation properties of the sandwich elements.

On the outlet side of the heating station 3 shown in figure 1, the uniformly heated wood parts/wood components 10 leave the heating room.

The outlet side of the heating space in the heating station 3 is equipped with a transport device, with which the uniformly heated wooden parts or wooden components 10 coming out of the outlet side of the heating station 3 are transported to a gluing station 12. In the gluing station 12, the wooden parts/wooden components 10 are glued. In the case of structural wooden components or wooden parts 10, condensation resin systems comprising a laminating resin and a curing agent are preferably used. The application of glue to the wooden parts/wooden components prepared for gluing and heated over the entire cross-section 8 can be carried out either with mixed glue liquid or with individual components that are applied separately. In the application method, a distinction is made between strand application and film application. For the gluing of wooden components or wooden parts 10 which are uniformly heated over the entire cross-section 8, urea/formaldehyde resin (UF), melamine/urea/formaldehyde resin (MUF), melamine/urea/phenol/formaldehyde resin (MUPF), phenol/resorcinol are used /formaldehyde resin (PRF), resorcinol/formaldehyde, phenol/formaldehyde glue types and polyvinyl acetate glue types, EPI glue types, mixtures thereof and additional glue types that are common for woodworking, for example single- or multi-component polyadducts, both for the bonding of load-bearing and for the bonding of non- -bearing wooden components 10.

The gluing and pressing plant 1 shown in figure 1 comprises the heating station 3 through which wooden components or wooden parts 10 are passed in the flow direction 2. The gluing and pressing plant 1 can be controlled by an operator from a control table 52.

The gluing station 12 comprises a first application device 13 and a second application device 14, which can either be operated individually or can be operated in parallel with each other. Therefore, a film of an adhesive or of an adhesive component can be applied by one of the application devices 13 or 14, while a string of an adhesive or of an adhesive component can be applied to a wooden component or wooden part 10 by means of the remaining application devices 13 or 14 in the gluing station 12. After passing through the gluing station 12, the wood components/wood parts 10 are coated with a mixed glue liquid or with glue transported by means of transport bodies 21, for example in the form of rollers to a press station.

While the heating phase in the processing sequence 20 of the wooden components/wooden parts 10 is denoted by reference number 17, the phase comprising the application of the glue or of the glue components in the case of glue systems, which is carried out in the glue station 12, is denoted by reference number 18. The phase comprising the application of the glue or of the glue components in a glue system is followed by the pressing phase 19 within the processing sequence 20. The length of the wooden component/wooden part 10 is denoted by reference number 16, while reference number 15 denotes the width of the wooden components/wooden parts 10. During the pressing phase identified by reference number 19, it takes place a reaction of the glue applied in the glue station 12 or of the glue components in an applied glue system. The correspondingly produced wooden components/wooden parts 10 are fed in the transverse direction 22 to a pressing device 23. There, individual wooden components/wooden parts 10 which have the length 16 and the width 15 are arranged in layers on top of each other. After a stack height 28 has been reached, one or more pressing pistons 24 are placed on a structural wooden component 10 formed in such a way. The press pistons 24 held on a press layer 25 by the press device 23 can be subjected to a certain well-defined pressure force by means of hydraulic or pneumatic parts actuated together or separately in each case. The compressive force exerted on the glued wooden components or wooden parts 10 can be effectively applied either in the vertical direction as well as in the horizontal direction, it is also possible that the compressive force is applied simultaneously in both planes. Usually the pressing pistons 24 in the pressing device 23 are arranged at a distance between 30 and 50 cm.

Figure 2 shows a front section of the pressing unit which is shown in plan section in Figure 1, in which the wooden components/wooden parts prepared for pressing are placed in a sequence of layers.

The diagram according to figure 2 shows that an individual component prepared for pressing and equipped with an adhesive layer is stacked on top of a carrier 30 which is formed on the underside of the pressing layer 25.1 the diagram according to figure 2 comprises the wooden component/wood part 10 placed in the pressing device 23 for pressing and drying, a first individual component 34, a second individual component 35, a third individual component 36, a fourth individual component 37, a fifth individual component 38, a sixth individual component 39, and at the bottom, a seventh individual component 40. According this sequence of layers, for example, glued laminated timber is produced which is used as load-bearing components for multi-purpose halls and similar purposes. After the individual components 34 to 40 have been arranged in a stack to maximize stack height 28, there follows the use of a hydraulic or pneumatic unit 31 which operates a press piston 24. Instead of a hydraulic or pneumatic unit 31 shown schematically in Figure 2 and is connected with a supply line system 32 for a pressure medium, mechanically driven spindle presses can also be used to set the press piston 24 to the upper side of the glued wood component/wood part 10 to be pressed. The pressure force 33 which via the piston surface 26 of the press piston 24 is introduced to the wooden component/wooden part 10 is introduced coaxially with the symmetry axis 27 of the stacked wooden component/wooden part 10.1 addition, a pressure force which acts in the horizontal direction on the layer arrangement of the wooden component or wooden part 10 can be used to prevent the stack to be pressed during the pressing process acting in the vertical direction from tipping over or slipping. The maximum width of the wooden component/wood part 10 to be pressed is denoted by reference number 29 in the diagram according to figure 2.

By means of the short cycle method proposed according to the invention for the production of structural or plate-shaped wooden components/wood parts 10, the residence time required to harden the glue or the glue system within a press apparatus according to the schematic diagram in Figure 2 can be considerably reduced and in individual cases even more than halved. By means of the short cycle method proposed according to the invention, on the one hand shorter processing and pressing times and on the other hand a reduction in the quantity of glue used - either the individual quantity of an individual glue used or the quantities of the components of a glue system used - can be achieved by uniform heating of the entire cross-section 8 of the components/wood parts 10 to be glued together.

Both factors contribute to a considerable increase in the productivity of a gluing and pressing plant 1 according to the diagram in Figure 1.

List of reference numbers

1. Glue and pressing plant

2. Flow direction

3. Heating station

4. Upper side of heating station

5. Side wall of heating station

6. Radiator device

7. Inlet side

8. Cross section of wood component/wood part 10

9. Radiation field

10. Three component/three part

11. Transport device

12. Lime station

13. First application device

14. Other application device

15. Width of wooden component/wood part 10

16. Length of wooden component/wooden part 10

17. Warm-up phase

18. Application phase

19. Drying and pressing phase

20. Processing flow

21. Transport body

22. Discharge direction

23. Press device

24. Press stamp

25. Pressure layer

26. Traverse

27. Axis of symmetry

28. Stack height of wooden component/wood part 10

29. Maximum width

30. Carrier

31. Hydraulic/pneumatic unit

32. Supply line for pressure medium

33. Pressure-force direction

34. First individual component

35. Other individual component

36. Third individual component

37. Fourth individual component

38. Fifth individual component

39. Sixth individual component

40. Seventh individual component

52. Control board.

Claims (10)

1. Method for the production of glued wooden parts or wooden components (10) using adhesive systems, in which the gluing of the heated wooden parts or wooden components (10) is carried out by separate application of laminating resin and curing agent (binder) or by an adhesive system mixed from laminating resin and hardener, in which uniform heating of the entire cross-section (8) of the wooden parts or wooden components (10) is carried out by microwave radiation before the gluing of the wooden parts or wooden components (10). 2. Method according to claim 1, in which the entire cross-section (8) of the wooden parts or wooden components (10) is uniformly heated to a temperature between 30°C and 95°C. 3. Method according to claim 2, in which the entire cross-section (8) of the wooden parts or wooden components (10) is preferably uniformly heated to a temperature between 40°C and 70°C. 4. Method according to claim 2, in which the entire cross-section (8) of the wooden parts or wooden components (10) is particularly preferably uniformly heated to a temperature between 45° and 60°C. 5. Method according to claim 1, in which the gluing of the heated wooden parts/wooden components (10) is carried out with mixed glue liquid. 6. Method according to claim 1, wherein the application of the separate or mixed components of a multi-component adhesive system is carried out by the string application method (42) or by the film casting method (43). 7. Method according to claim 1, wherein separate application of the laminating resin and curing agent is carried out by means of the strand casting method (42), the film casting method (43) or any desired combination of the strand casting method (42) with the film casting method (43). 8. Method according to claim 1, in which duroplastic condensation adhesive types, for example, urea/formaldehyde resin (UF), melamine/urea/formaldehyde resin (MUF), melamine/urea/phenol/formaldehyde resin (MUPF), phenol/resorcinol/formaldehyde resin (PRF), or en- component or multi-component addition glue types or thermoplastic glue types, such as poly-vinyl acetate glue types (PVAc) and EPI glue types, and mixtures thereof are used to glue the wood parts or wood components (10) which are uniformly heated over the entire cross-section (8). 9. Use of a method according to any one of claims 1 to 8, in which solid wood cross-sections, boards, planks, edge boards, glued laminated wood, duo-lam boards, trio-lam boards, structural solid wood (KVH), single or multi-layer solid triple boards, fiber boards (MDF/HDF), sandwich structural elements that have insulating layers of polystyrene or PU are produced foam arranged on one or both sides. 10. Use of a method according to any one of claims 1 to 8, in which solid wood cross-sections, boards, planks, edge boards, glued laminated wood, duo-lam boards, trio-lam boards, structural solid wood (KVH), single or multi-layer solid triple boards, fiber boards (MDF/HDF), sandwich structural elements that have insulating layers of polystyrene or PU foam arranged on one or both sides are glued together in any desired combination.