WO2019120421A1

WO2019120421A1 - Fire retardant impregnation of wooden plates

Info

Publication number: WO2019120421A1
Application number: PCT/DK2018/050377
Authority: WO
Inventors: Paw Christian FÆLLED; Mayra Melián RODRÍGUEZ; Jesper HENRIKSEN; John ENGQVIST GRIEM; Jimmie REE; Knud Jørgen RASMUSSEN; Finn MØLGÅRD POULSEN
Original assignee: Burnblock Holding Aps
Priority date: 2017-12-20
Filing date: 2018-12-19
Publication date: 2019-06-27
Also published as: EP3727771A1; RU2020123687A; EP3727771A4

Abstract

The present invention relates to a system and method for very fast fire retardant impregnation of wooden plates with a chemical composition. The system comprises weighing systems, humidity sensors for performing measurement of humidity in the plates, drying modules for drying of the plates, a spraying device with a plurality of spray nozzles placed both under and over the plate for spraying with the chemical composition. With this very fast system, it is possible to carry out the impregnation of wooden plates at extremely high speed compared to previous impregnation systems.

Description

Fire retardant impregnation of wooden plates

Field of the Invention

The present invention relates to a system for fire retardant impregnation of veneers and other types of wooden plates/boards, which system comprises a first weighing system, which system comprises a first humidity sensor for performing a first meas- urement of humidity in plates, which system comprises a spraying device for spraying with a chemical composition, which system comprises a second weighing system, which system comprises veneers and other types of wooden plates/boards.

Background of the Invention

US 7,736,549 discloses a chemical composition to be applied to materials to impart flame retardancy. The composition includes a mixture of ingredients that is not harm ful to humans or the environment. The ingredients of the composition can include a phosphorous containing material, an acidic material, a material that serves as a pre- servative, and an aqueous solvent.

Other chemical compositions of fire retardant can also be used to impregnate the dif ferent types of wood.

US3935341 A disclose a system in which system wood can be rendered fire resistant by impregnating the wood with a solution of a monomer, such as a phenol, and a fire- inhibiting salt, drying the wood and thereafter treating the wood with a solution of a second monomer, such as formaldehyde, polymer rizable with the first monomer. Heating to dryness causes polymerization of the monomers. The fire resi stant proper ties of wood treated this way are not affected by exposure to moisture. Prior to the first impregnation, after the first impregnation and after treatment with the second monomer the wood being treated is dried to a moisture content below about 4 percent. Object of the Invention

It is the object of the pending patent application to achieve fast and effective flame retardancy in different types of wood. A further object of the pending patent application is to achieve non-toxic flame retard- ancy both during production and by end use of veneer.

Description of the Invention

The object can be fulfilled by a system as disclosed in the preamble to clam 1 and further modified in that the spraying device comprises a plurality of spray nozzles placed over (and dependent on purpose also under) the type of wood, which system comprises a drying module for performing a drying process (with drying panels placed over (and dependent on purpose also under) the type of wood), which system com prises of various measuring sensors throughout the entire process line.

Hereby a very fast impregnation can be achieved with a chemical composition as pre viously disclosed. By this very fast process it is possible to perform impregnation of veneer in an extremely high speed in relation to previous methods of impregnation. To be able to ensure the right impregnation different types of input data is required.

This includes specie, size and humidity of the type of wood as well as the concentra tion of the fire retardant, speed of the process line, heat and water/liquid pressure. During the next step of the process spraying is performed by a plurality of soft spray ing nozzles. The pressure in the nozzles has to be kept adjustable in order not to per- form any harm at the wood surfaces (varies across types of wood). All the surfaces have to be covered by the spraying as the chemical composition will penetrate the surface of the plate and penetrate the open cells in the wood and thereby perform a highly effective impregnation. Further, a drying process is performed in order to re duce humidity which has been used as carrier for the chemical composition. There- fore, the humidity is being removed in the drying process and leaving the chemical composition inside the cells of the wood. Both during and after the impregnation pro cess further measures can be made to ensure the right intake and humidity level. In that way it is possible to control the amount of the chemical composition that is occu- pied by the plate in the wood cells.

In a preferred embodiment for the invention the system comprises one or more com- puters, which computers receive input from e.g. roller bans including a weighing sys- tem, from a humidity sensor, from a spraying device, from the drying module.

Hereby can be achieved that all measured parameters automatic are communicated to the computer system, where all measured values can be stored in a database. From that database it is possible for every production lot that has been produced by the system to get full information about the process that has been performed. The computer system also gives the possibility for the personnel who are operating the system that they can perform different kind of adjustment according to the information from the computers. Also for quality documentation the computer system can deliver complete description of the quality that is achieved during the process, in fact it should be possible for each single plate to document the uptake of the chemical composition in the wood.

In a further preferred embodiment for the invention the computers can perform docu- mentation from at least processes performed by the system. Hereby different kind of documentation can be achieved by the computer system. Quality documentation can be transmitted to a customer so that the quality documentation is achieved long time before the lot of wood which has been sent through the process. In a further preferred embodiment for the invention the system comprises a conveyor system for transporting plates through the system. Each of the different modules com prises a conveyor system inside the single modules, e.g. in the drying module there is a conveyor and also in the spraying module there is a conveyor. Further, in the drying process there is further a conveyor inside the module. Also between modules there are placed different conveyors; many of them comprise in the same time a weighing sys- tem so that the weight of each single plate is measured and transmitted to the comput- er system. By having access to the weight of the different types of wood and at the same time the humidity in the plate, it is possible to measure how much of the chemi cal composition that has taken place inside the type of wood. In a further preferred embodiment for the invention the conveyor system comprises at least the first, second and third weighing system. Hereby can be achieved that weigh ing of each single plate automatically takes place during the operation of the system. In a further preferred embodiment for the invention the system comprises one or more video cameras for video inspection of plates before and after the processes. Hereby can be achieved that an automatic control of the plates can be performed by camera technology before and after the process. By video control it is possible to find differ ent kind of cracks or other failures in plates before the process is started. In some situ- ations there can be some cracks that are so critical that the plate has to be removed immediately; then there is no need for sending a plate through the process. The video inspection afterwards could also indicate failures in the plate, because the plate has been sent through a drying process, has been sprayed with a chemical composition, probably together with water and hereafter a new drying process, it is possible that some cracks could occur in plates and they thereafter have to be removed from the production lot. Further, it is possible for the computer system to have pictures of each single plate that has been sent through the system. This could be a further good docu mentation for quality analyses. In a further preferred embodiment for the invention the system can receive a mixture of water and chemical composition from a water source such as a tank and from a tank for the chemical composition, which water tank comprises a first pump, which tank for the chemical composition comprises a second pump, which first pump is via a first flow measuring device connected to a mixer, which second pump is via a second flow measuring device connected to the mixer, from which mixer the liquid flows through a aerometer, from which aerometer the liquid flows through lines and to the nozzles. Hereby an effective supply of the mixture of the chemical composition and water to the nozzles can be achieved. In a further preferred embodiment for the invention the invention is described as a method for operating a system for fire retardant impregnation of different types of wood in the following steps of operation: a. perform measurement of weight of the plates, b. perform measurement of humidity in the plates, c. perform drying on one or both sides of the type of wood, d. perform spraying of a chemical composition from one or both sides of the types of wood, e. remove liquid drops from the surfaces of the types of wood, f. perform a drying process on one or both sides of the types of wood, g. perform measurement of weight of the types of wood. By the method as disclosed it is possible to perform impregnation of the types of wood where at first the humidity content of the plate is measured together with the weight of the plate and drying is performed. After drying and the control of the hu- midity in the type of wood the spraying process can be performed by a plurality of nozzles placed over and/or under the plate during a conveyor movement through the process. After spraying a new weighing measure should be performed. Hereafter is drying performed which could be performed in different ways. It is possible in a rela- tive short machine by infrared light to perform the drying. Another possibility will be a very long machine where hot air can perform the drying. After the drying process the weight is controlled once again. If the humidity is well-known before together with the increasing weight, it is then an indication for the intake of the chemical com position. Because all these results from the different sensor systems are sent to a com puter it is possible to perform full documentation for the method.

Definition of types of wood: veneer, plywood, panel products (eg. MDF, gipson, LVL) with veneer on top. Definition of chemical composition: The composition can include a phosphorous con taining material, an acidic material, a material that serves as a preservative and an aqueous solvent as disclosed in US 7,736,549. Other compositions are also possible. Hereby a new and more efficient and effective solution for impregnation into veneers for plywood production in a high-quality can be achieved. The system can provide the desired intake of impregnation into the veneers. Furthermore, the impregnated veneers can leave the system with an average humidity of 3-5%.

The system will be able to document the intake in the veneer and thereby optimize the use of impregnation and at the same time ensure a constant surveillance of the quality.

Due to the gentle impregnation and the great quality in the final product, it is expected that the process line can treat both top veneers as well as core and scarf jointed ve neers. Both solve existing challenges with fire retarding top veneer on plywood boards as well as optimizing the use of veneers (inch core and scarf jointed veneers) in fire retardant plywood.

IMPREGNATION SYSTEM A possible production line is composed by:

• Spray unit

• Conveyor units

• Catalytic Infrared Radiation (CIR) oven / Drying unit

• Digital data registration

The purpose of the spray system is to ensure a uniform intake of impregnation, ac cording to the specified quantity, by means of a (double sided) spray system, spraying the type of wood while being conveyed through the spray machine.

One possible drying process can be performed by a CIR-oven emits infrared radiation, having a wavelength of 2-10 pm, transferring energy into the veneer material, which has reception properties corresponding to a wavelength of 6-8 pm. By utilizing the above-mentioned energy transfer properties, it is possible to speed the drying process.

As such the invention consists of different units. The units can be combined in differ ent ways depending on the condition and type of the wood, the required treatment

required measures on concentration of fire retardant, intake of fire retardant, humidity of wood and speed of process line. Below a number of examples of different combinations of the units:

Example 1 : Roller unit - Spray unit - Roller unit - Drying unit - Roller unit

Example 2: Spray unit

Example 3 : Roller ban - Drying unit - Roller ban - Spray unit - Roller ban - Drying unit - Roller ban

About Wood

Types of wood relevant for this patent application:

- Veneer: thin slices of wood (typically peeled from logs). The veneer is usually thinner than 3 mm.

Green veneer: Fresh veneer just peeled from a log and still containing humidi- ty·

- Plywood: Plywood consists of three or more layers of veneer. Normally, each is glued with its grain at right angles to adjacent layers for strength.

- Panel products (e.g. plywood, MDF, gipson, LVL) with veneer on top.

Wood is a natural material and as such not uniform. Some of the differences are:

• Wood species

· Wood density

• From where is the sample taken in the log

• Knots and holes

• Veneer thickness

• Initial Humidity

As a consequence the intake of chemical composition and the humidity will be differ ent even across the individual veneer. The first version of Spray-CIR oven is composed by a unique process, where first the veneers can be weighed, and the moisture can be measured before entry in the spray. The process can be followed by an impregnation using a spray machine. After im pregnation, the veneers can be weighed again to control ire-retardant intake. Then they are followed to a CIR-oven, where the veneers are dried. After the drying process, veneers are weighed again and the moisture at the end of the process is controlled.

The spray and CIR-oven can be two separate lines. In future, one line may however still be possible.

Veneers can be weighed and the moisture can be measured before entry in the spray. The process can be followed by an impregnation using a spray machine. Then, the veneers can be weighed to control fire-retardant intake. Veneers can be weighted by lots before and after. It is not a requirement to weigh veneer by veneer.

Veneers can be dried inside the CIR-oven. The moisture can be controlled by weigh after the drying process and compare the data with previous information obtained in the spray process.

A blower can be installed after the spray process to remove the excess of fire-retardant in the following steps in the system, and to have a more accuracy in the weigh after being impregnated.

Adjustable Parameters

The process line can be adjusted and thereby optimized to achieve the desired perfor mance.

Spray Machine:

Operating speeds

Liquid volume

Liquid pressure CIR-oven:

• Operating speeds

• Temperature

• IR distance

• Ventilation

Description of the Drawing

Fig. 1 shows a possible embodiment of the invention in a schematic view.

Fig. 2 shows a spraying device.

Fig. 3 shows a conveyor system 38.

Fig. 4 shows one possible heating device for drying of the plates.

Fig. 5 shows a spraying device connected by a conveyor towards a drying device. Fig. 6 shows a conveyor.

Fig. 7 shows an enlarged view of the drying module.

Fig. 8 shows a possible embodiment of the invention in a schematic view.

Fig. 9 shows a possible embodiment for a spray line.

Fig. 10 shows a separated spray device.

Fig. 11 shows a possible embodiment for a drying module.

Detailed Description of the Invention

Fig. 1 shows a possible embodiment of the invention in a schematic view. At fig. 1 is indicated a number of plates 4, which are placed at a first weighing system 6, further there is a second weighing system 12 and a third weighing system 24. The weighing systems are integrated in a conveyor 38, which is indicated during the process. Fur ther, humidity sensors 8 are indicated. There could be more humidity sensors in the system. Further is indicated a drying unit 10, which by drying is removing humidity of the plates 4 before they are sent further in the process. The second weighing system 12 also placed together with the conveyor 38 is weighing the plate 4 once again and probably once again humidity is measured. Hereafter is the plate 4 sent into the spray- ing unit 14. Here is a chemical composition 16 sprayed at the plate 4 from one or both sides through a plurality of nozzles (not shown at fig. 1). Afterwards the plates 4 are transported further to the conveyor where the weight of the plate 4 is registered. Hereafter is the plate 4 sent through a drying unit 20. After drying the plate 4 is now prepared with the chemical composition 16 and sent to the conveyor 38. Here is the plate 4 once again sent to a weighing system at the conveyor 38. All data which are measured by e.g. a weighing unit 6, 12, 24 and humidity sensors 8,22 are transmitted to the computer 26. The computer 26 performs storage in the storage 42. The output from the storage could be any kind of report and documentation for the process that is performed at the plates.

Fig. 2 shows a spraying device 14, which comprises a plurality of nozzles, which are able to perform a soft spraying at the plates 4 when they are sent through by an inter nal conveyor. Because the soft spraying takes place both from top and below the plate, it will in that way be totally covered with a liquid, which contains the chemical com position 16. Because the plate is relative dry before the process is starting, the chemi cal composition will penetrate the surface and take up open space in the wood cells because the chemical composition is solved in water. The spraying process is a con tinuously process where plate after plate can be sent through the spraying device.

Fig. 3 shows a conveyor system 38.

Fig. 4 shows one possible heating device for drying the plates. The heating device 20 as disclosed here is a CIR-oven that emits infrared radiation having a wavelength of 2- 10 pm and the material of the plate has reception properties corresponding to a wave length of 6-8 pm. Hereby a highly effective heating and drying can be performed.

Fig. 5 shows a spraying device 14 connected by a conveyor 38 towards a drying de vice 20 as previously disclosed.

Fig. 6 shows a conveyor 38.

Fig. 7 shows an enlarged view of the drying module 20.

Fig. 8 shows a possible embodiment for the system 2. At fig. 8 is indicated a plate 4 partly passing through a spraying device 14, which comprises spray nozzles 18. Fur- ther is indicated a water tank 44 and a tank 46 for the chemical composition 16. The water tank 44 comprises a pump 48 and the tank 46 for the chemical composition 16 comprises a pump 50. The pump 48 is by a line connected to a flow measuring device 52 and the pump 50 is by a line connected to a flow measuring device 54. The flow measuring devices 52 and 54 are combined in a mixer 56, which mixer 56 is further connected to an aerometer/conductivitymeter 58, from which there are further lines 60 and 62, which are connecting the nozzles 18.

Hereby a total control of the mixture of water and chemical composition can be achieved. By controlling the pumps 48 and 50 based on measuring results from the flow measuring devices 52 and 54, it is possible to generate a mixture in the mixer 56, which fulfils the specifications for impregnation. The aerometer 58 is controlling the mixture so that there is an extra control in that the mixture sent through the lines 60 and 62 to the nozzles 18 has the correct composition.

Fig. 9 discloses a possible embodiment for a spray line. Veneers 4 are weighed, and the moisture is measured before entry in the spray device 14. The process is followed by an impregnation using a spray device 14. Then, the veneers 4 are weighed to con trol fire-retardant intake. Veneers 4 can be weighted by lots before and after. It is not a requirement to weigh veneer by veneer.

Fig. 10 discloses a separated spray device 14 where the spray and CIR-oven can be two separate lines. In future, one line may however still be possible. Veneers 4 are weighed, and the moisture is measured before entry in the spray device 14. The pro- cess is followed by an impregnation using a spray device 14. Then, the veneers 4 are weighed to control fire-retardant intake. Veneers 4 can be weighted by lots before and after. It is not a requirement to weigh veneer by veneer.

Fig. 11 discloses a possible embodiment for drying module 20 such as a CIR oven comprising blower means. Veneers 4 are weighed, and the moisture is measured be- fore entry in the spray device 14. The process is followed by an impregnation using a spray machine. Then, the veneers 4 are weighed to control fire-retardant intake. Ve- neers can be weighted by lots before and after. It is not a requirement to weigh veneer by veneer. Reference signs:

System (2)

plates, veneer (4)

first weighing system (6)

first humidity sensor (8)

drying module (10)

second weighing system (12) spraying device (14)

chemical composition (16)

spray nozzles (18)

drying module (20)

second humidity sensor (22)

third weighing system (24)

computers (26)

conveyor system (38)

video cameras (40)

storage (42)

water tank (44)

tank for chemical composition (46) pump (48) for water tank

pump (50) for chemical composition tank first flow measuring device (52) second flow measuring device (54) mixer (56)

aerometer (58)

line (60)

line (62).

Claims

1. System (2) for fire retardant impregnation of plates (4) such as veneer, which sys- tem (2) comprises a first weighing system (6), which system (2) comprises a first hu- midity sensor (8) for performing a start measurement of humidity in plates (4), which system comprises a spraying device (14) for spraying with a chemical composition (16), characterized in that the spraying device (14) comprises a plurality of spray nozzles (18) placed both under and over the plate (4), which system comprises a dry ing module (20) for performing a drying process, which system (2) comprises a third weighing system (24).

2. System (2) according to claim 1, characterized in that the system (2) comprises a pre-drying system (2a) connected to the inlet of the system (2), which pre-drying sys- tem (2a) comprises a drying module (10) for drying the plates (4) before impregna- tion, which system comprises a second weighing system (12).

3. System (2) according to claim 1 or 2, characterized in that the system comprises one or more computers (26), which computers receive input from at least a first weighing system (6), from a first humidity sensor (8), from a second weighing system (12), from a spraying device (14), from a third weighing system (24), from a drying module (20) and from a fourth weighing system (24).

4. System (2) according to claim 1- 3, characterized in that the computers (26) per form a documentation at least from processes (6,8,12,14,20,22,24) performed by the system (2).

5. System (2) according to claim 1-4, characterized in that the system comprises a conveyor system (38) for transporting plates (4) through the system (2).

6. System (2) according to claim 1-5, characterized in that the conveyor system (38) comprises at least the first (6), second (12) and third (24) weighing system.

7. System (2) according to claim 1-6, characterized in that the system comprises one or more video cameras (40) for video inspection of plates (4) before and after the pro- cesses.

8. System (2) according to claim 1-6, characterized in that the system (2) is receiving a mixture of water and chemical composition (16) from a water source such as a tank (44) and from a tank (46) for the chemical composition (16), which water tank (44) comprises a first pump (48), which tank (46) for the chemical composition (16) com prises a second pump (50), which first pump (48) is via a first flow measuring device (52) connected to a mixer (56), which second pump (50) is via a second flow measur ing device (54) connected to a mixer (56), from which mixer (56) the liquid flows through an aerometer (58), from which aerometer (58) the liquid flows through lines (60) and (62) to the nozzles (18).

9. Method for operating a system for fire retardant impregnation of plates (4) as dis closed in the claims 1-8 characterized in the following steps of operation: a. perform measurement of weight of the plates (4), b. perform measurement of humidity in the plates (4), c. repeat step a to assure weight and humidity in the plates is reduced to a level where impregnation can be performed, d. perform spraying of a chemical composition from one or both sides of the plates

(4), e. remove liquid drops from the surfaces of the plates (4), f. perform a drying process, g. perform measurement of weight of the plates (4).