WO2007116126A1

WO2007116126A1 - Reinforced wood panel and a method for manufacturing thereof

Info

Publication number: WO2007116126A1
Application number: PCT/FI2007/050180
Authority: WO
Inventors: Esa Lappalainen; Juha Patovirta
Original assignee: Upm-Kymmene Wood Oy
Priority date: 2006-04-10
Filing date: 2007-04-02
Publication date: 2007-10-18
Also published as: FI20060347A0; FI20060347A; DE112007000900T5

Abstract

This invention relates to a wood panel, which has been formed of a number of veneer layers (2), which have been joined together by means of a glue. In accordance with the invention to the wood panel (1) it is included at least one reinforcing layer (3), which includes resin and reinforcement fibre, which is bound with resin, and the reinforcing layer (3) is arranged between two veneer layers (2). Additionally the target of the invention is a method for manufacturing the wood panel described above.

Description

REINFORCED WOOD PANEL AND A METHOD FOR MANUFACTURING THEREOF

FIELD OF INVENTION

This invention relates to a wood panel specified in the preamble of claim 1 and to a method specified in the preamble of claim 13 for manufacturing the wood panel.

BACKGROUND OF THE INVENTION Different reinforcing materials or laminates used to reinforce different structures are known from the prior art. Using of the reinforcing materials is known in the prior art e.g. to reinforce plywood or other wood panels and to enhance bending strength and stiffness of the wood panels. Conventionally reinforcing material is placed to the surface of a wood panel or plywood to-be-reinforced. In the prior art methods reinforcing material is fastened in a separate gluing phase to a wood panel or plywood to-be-reinforced.

In addition, prior art publication JP 07214506 discloses an arrangement of fibreglasses to an adhesive layer of the panel structure to provide strength to the adhesive layer and to the thereby formed panel. Earlier the problem of known reinforcing materials has been the fact that the reinforcing materials have been fastened to the wood panel or plywood in a separate working phase. In addition, reinforcing material arranged to the surface of a wood panel or plywood causes a number of technical problems in the manufacturing, e.g. panel manufacturing becomes slower and a risk of damage to the panel or coating is high during the manufacturing. Further, finishing machining of the panel becomes difficult since the surface material of the panel changes.

Earlier such reinforcing material was not known, which could have replaced one or more veneer layers in conjunction with the manufacturing of a wood panel or plywood.

TARGET OF THE INVENTION The target of the invention is to remove above-mentioned disadvantages. Particularly the target of the invention is to introduce a new type of reinforced wood panel structure and a method for manufacturing thereof.

SUMMARY OF THE INVENTION A wood panel in accordance with the invention and a method for manufacturing thereof are characterised by the features presented in the claims. The invention is based on a wood panel, which has been formed of a number of veneer layers, which have been joined together by means of a glue. In accordance with the invention the wood panel includes at least one reinforcing layer, which includes resin and reinforcement fibre, which are bound by resin. A reinforcing layer is arranged between two veneer layers.

By "wood panel" we here refer to any wood panel product, plywood product, composite product, joist, pressed panel product formed of veneer and veneer layers or a similar product, which has been mainly formed of wood-based materials and wherein veneers have been piled one on the other and glued together. By "veneer layer" we here refer to any material layer, conventionally thin material layer, which is used to form a layered panel. The material layer may be formed of wood-based material or any other material suitable for use.

By "reinforcing layer" we here refer to any reinforced fibre bearing reinforcing material, which are bound by resin to a reinforcing layer, which will be suited to reinforce a wood panel and to replace one or more veneer layers and which enables to obtain a desired strength to the wood panel. Reinforcement fibre increases the natural strength of the tree. By "binding resin" we here refer to reinforcement fibre impregnation, saturation or absorption or no any binding by resins. Additionally, the invention is based on a method for manufacturing a wood panel in accordance with the invention, in which method it is formed of a number of veneers a wood panel with multiple veneer layers so that the veneer layers are piled up one on the other and joined together by means of a glue. In accordance with the invention between two veneer layers it is arranged a reinforcing layer, which includes resin and reinforcement fibre, which is bound by resin. Preferably the veneer layers are piled up one on the other and the glue is arranged between the veneer layers. The reinforcing layer is arranged in the product formed of veneers, between other veneer layers, to replace at least one veneer layer and/or additionally in conjunction with the manufacturing and more spefically in conjunction with the piling and gluing of the veneers. In an application the wood panel is pressed in the subjection of heat and pressure after the piling and gluing to form a desired type of wood panel.

In an application a reinforcing layer is essentially dry, e.g. precured, at that point when it is being piled up and glued between the veneer layers to form the wood panel. In an application the reinforcing layer is dried at least partially or completely prior to the gluing. In an alternative application the reinforcing layer may be non-precured at that point when it is being piled up between the veneer layers to form the wood panel. The piling of veneers, gluing to each other and other conventional stages for manufacturing the wood panel can be preferably rendered in a manner known per se in the field.

In an application of the invention the wood panel includes one reinforcing layer. In another application the wood panel includes at least two reinforcing layers.

In a preferred application of the invention the reinforcing layer is arranged in conjunction with the manufacturing of the wood panel preferably as close to the surface of the wood panel as possible, in an application under the first or first few veneer layers, in the vicinity of a top surface and/or lower surface of the panel, hi this case, achieved benefit of the reinforcing layer is biggest.

In an application of the invention the reinforcing layer is arranged close to a drive side surface of the wood panel. In an application of the invention the reinforcing layer is arranged close to a pressing side surface of the wood panel.

If the wood panel includes e.g. two reinforcing layers, so in a preferred application the first reinforcing layer is close to the drive side surface and the second reinforcing layer is close to the pressing side surface. Reinforcing layers can be arranged within same distances from drive side and pressing side surfaces, but they do not need to be equally far away from the drive side and pressing side surfaces.

In a preferred application one reinforcing layer replaces one veneer layer. In an application of the invention the reinforcing layer includes fibreglass, which is preferably a reinforcement fibre.

In an application of the invention the reinforcing layer includes carbon fibre, which is preferably a reinforcement fibre.

In an application the reinforcing layer may include in addition to the resin a curing agent, softener or other suitable and desired additive.

In an application of the invention epoxy resin is used as a resin. Other suitable resins include for example different polyester, including unsaturated polyester, or vinyl ester based resins.

In a preferred application resin included in reinforcing layer serves as a binder by binding reinforcement fibres, e.g. glass or carbon fibres or similar, and/or other elements in a desired way and to a desired form to form a reinforcing layer. The resin may function at the same time as so-called carrier in the reinforcing layer.

In an application reinforcement fibres, e.g. fibreglasses and/or carbon fibres, can be in the reinforcing layer as thin fibres, which have been arranged to a netlike web and bound together with a resin-based binder, e.g. with epoxy resin. In an application the reinforcing layer may be epoxy resin coated. In an application of the invention the reinforcing layer is formed of glassfibre-carbon fibre compound impregnated with epoxy resin.

A reinforcing layer is a replacing layer for the veneer layer, which can be laminate, web, non-woven web, net, film, nano fibre material and/or composite material or alike. hi an application of the invention the reinforcing layer is arranged in the form of a netlike web. In an application of the invention as a glue it is used a liquid phenolic resin or a derivative thereof, which is water soluble. Heat-setting phenolic resin is preferably used for the gluing. Epoxy or polyester based resin used as a reinforcing layer resin or binder is solvent soluble. However, is has been noticed that epoxy and polyester based resin and phenolic resin based adhesive go well together, and do no cause any rejection reaction together. As a solvent for the resin any suitable solvent can be used, to which the resin is soluble. In an application the resin for the reinforcing layer can function also as an adhesive. In a preferred application of the invention the same glue is used to fasten the reinforcing layer to other veneer layers as in fastening veneer layers to each other.

A wood panel in accordance with the invention may include veneer layers of various thicknesses. The thicknesses of the veneer layers may vary. In an application of the invention the reinforcing layer may be of a same thickness as some of the veneer layers or it may be thinner or thicker than the veneer layer. Veneer layers can be arranged to the desired position that is, in a transverse or longitudinal direction in a desired order. The wood panel in accordance with this invention can be used in different structures requiring strength and high load endurance for example, as a surface material. The wood panel in accordance with this invention can be used e.g. in supporting structures in the transport equipment industry and construction industry. Due to the invention load-carrying capacity and strength of the wood panel, especially bending strength, can be increased. At the same time wood panel structure can be made thinner, which reduces material requirement and on the other hand increases uses of the wood panel. Due to the invention with a thinner wood panel it is possible to accomplish the same or better load-carrying capacity and strength properties as with the prior art wood panels. Additionally, grammages of the thinner wood panels are lower than in the prior art panels, which, for example, reduces the load weight in the transportations of the panels or on the other hand increases transport capacity.

The advantage of this invention is that the reinforcing material may be added as a part of the veneer built wood panel between the veneer layers already in the process of manufacture of the wood panel, and no separate working phases are needed for the reinforcement of the wood panel. Due to the invention a wood panel is generated, which has a good load endurance as well as bending and breaking strength.

DETAILED DESCRIPTION OF THE INVENTION The invention is described in the following by means of detailed application examples with a reference to accompanying Figures 1 and 2, where plywoods in accordance with the invention are shown.

Example 1 In the experiment of this example load endurance and bending strength of two plywoods in accordance with the invention shown in Figure 1 were studied and they were compared with the corresponding ones of the prior art plywood or reference plywood. In the experiment, two plywood panels in accordance with the invention were manufactured: 22.9 mm plywood (Fig. 1), which had 16 wood veneer layers and a reinforcing layer, and 20.1 mm plywood, which had 14 wood veneer layers and a reinforcing layer.

In the experiment, as a reinforcing layer it was used a glassfibre-bearing reinforcing material laminate impregnated with epoxy resin in plywoods in accordance with the invention. The reinforcing material was arranged in the form of a netlike web so that thin fibreglasses and carbon fibres had been arranged to the netlike form and bound together by means of a epoxy resin to a non- woven web. Used reinforcing material was a commercial product by Exel Oyj, which included 54 - 75% of fibreglass, 3 - 23% of carbon fibre, 13% of epoxy resin and 11% of curing agent. The reinforcing material did not include evaporable components. In the manufacture of plywood 0.5 mm thick dry reinforcing material 3 was arranged to one layer between the dry veneer layers 2 of 1,1 - 1,4 mm formed of birch in conjunction with the piling and gluing of the veneer layers. Veneer layers 2 were piled up one on the other and reinforcing material layer 3 was added to the pile in the vicinity of the drive side surface as a third layer from the top (Fig. 1). Veneer layer 2 and reinforcing layer 3 were attached to each other by gluing with a liquid phenolic resin to form a plywood panel. In the experiments, a prior art plywood (reference plywood) of 27.4 mm was tested and compared, which had 20 wood veneer layers and had a grammage of 18,6 kg/m², with thinner plywoods of 22.9 mm in accordance with the invention, which had 16 veneer layers and one reinforcing layer and which had a grammage of 15.6 kg/m , and with ones of 20.1 mm in accordance with the invention, which had 14 veneer layers and one reinforcing layer and which had a grammage of 13.7 kg/m . Figure 1 shows a plywood of 22.9 mm in accordance with the invention.

In the experiments, load endurances and bendings of different plywoods were measured and compared. In the testing, a wheel load test in accordance with ISO R 1496 was used, which is used to test load-carrying capacity of floor panels. In the wheel load test as a press a rubber coated wheel is used, which has a width of 80 mm and a length of 180 mm. Floor panel bending and breaking load are registered in the test, hi general, a wheel load carrying capacity of at least 2730 kg is required of the floor. The bending is measured with a load of 2730 kg. As a result with a span length of 390 mm the following were obtained: maximum load endurance of the reference plywood was approximately 5250 kg and bending (with a load of 2730 kg) approximately 6.5 mm, a plywood of 22.9 mm in accordance with the invention had the maximum load endurance of approximately 5900 kg and bending (with a load of 2730 kg) approximately 10 mm and a plywood of 20.1 mm in accordance with the invention had the maximum load endurance of approximately 4800 kg and bending (with a load of 2730 kg) approximately 13 mm.

On the basis of the tests one could discover that 27.4 mm reference plywood could be replaced with thinner plywoods of 22.9 mm and 20.1 mm in accordance with the invention on the basis of the load-carrying capacity. The reinforcing material added the plywood's load-carrying capacity as much as 20 %. Additionally, one could discover that the thinner structures will bend more, but do not break so easily.

Example 2

In the experiment of this example load endurance and bending strength of two plywoods in accordance with the invention shown in Figure 2 were studied and they were compared with the corresponding ones of the prior art plywood or reference plywood.

In the experiment, two plywood panels in accordance with the invention were manufactured: 26.4 mm plywood (Fig. 2), which had 19 wood veneer layers and two reinforcing layers of 0.5 mm thickness, and 26.2 mm plywood, which had 19 wood veneer layers and two reinforcing layers of 0.8 mm thickness, a reference plywood of 27.5 mm thickness had 21 wood veneer layers. In the manufacture of the plywoods in accordance with the invention and also of the reference plywoods used birch veneer layers were approximately 1.55 mm thick.

In the experiment, as reinforced layers it had been used the glassfibre-carbon fibre bearing reinforcing material laminate impregnated with epoxy resin in accordance with the example 1. In the manufacture of plywood reinforcing materials 3 were arranged to two veneer layers between dry birch veneer layers 2 in conjunction with the piling and gluing of the veneer layers. Veneer layers 2 were piled up one on the other and the reinforcing material layers 3 were added to the pile and in the vicinity of surfaces of both the drive side and the pressing side as a third layer from the top (Fig. 2) relative to the drive side and pressing side surfaces. Veneer layers 2 and the reinforcing layers 3 were fastened to each other by gluing with a liquid phenolic resin.

In the experiments, reference plywoods of 27.5 mm having a grammage of 20.1 kg/m² were tested and compared with the reinforced plywoods of 26.4 mm in accordance with the invention having a grammage of 19.1 kg/m , and with the ones of 26.2 mm in accordance with the invention having a grammage of 20,6 kg/m². In the experiments, load endurances and bendings of different plywoods were measured and compared. In the testing, a wheel load test in accordance with ISO R 1496 was used. As a result with a span length of 350 mm the following were obtained: maximum load endurance of the reference plywood was approximately 46.6 kN and bending (with the maximum load) approximately 14.4 mm, a plywood of 26.4 mm in accordance with the invention had the maximum load endurance of approximately 49.1 kN and bending (with the maximum load) approximately 14.3 mm and a plywood of 26.2 mm in accordance with the invention had the maximum load endurance of approximately 55.1 kN and bending (with the maximum load) approximately 13 mm.

As a result with a span length of 500 mm the following were obtained: maximum load endurance of the reference plywood was approximately 35.9 kN and bending (with the maximum load) approximately 18.0 mm and a plywood of 26.4 mm in accordance with the invention had the maximum load endurance of approximately 41.6 kN and bending (with the maximum load) approximately 24.4 mm.

On the basis of the tests one could discover that 27.5 mm reference plywood had worse load-carrying capacity than the plywoods in accordance with the invention. As the span length increased it was emphasised that clearly better load-carrying capacity was achieved with the plywoods in accordance with the invention than with the reference plywoods.

Example 3

In the experiment of this example load endurance and bending strength of the plywood in accordance with the invention were studied and they were compared with the corresponding ones of the prior art plywood or reference plywood. In the experiment, a plywood panel in accordance with the invention was manufactured: 27.4 mm plywood, which had 19 wood veneer layers and a reinforcing layer. In the experiment, as a reinforcing layer it was used a commercial Isoglass product by Isosport. In the manufacture of plywood a dry reinforcing material of 0.5 mm thickness 3 was arranged to one layer between the veneer layers 2 of 1.1 - 1.4 mm formed of birch in conjunction with the piling and gluing of the veneer layers. Veneer layers 2 were piled up one on the other and reinforcing material layer 3 was added to the pile in the vicinity of the drive side surface as a third layer from the top. Veneer layers 2 and reinforcing layer 3 were fastened to each other by gluing with a liquid phenolic resin. In the experiments, a prior art plywood (reference plywood) of 27.4 mm was tested and compared, which had 20 wood veneer layers, with the plywood of 27.4 mm in accordance with the invention, which had 19 veneer layers and one reinforcing layer. In the experiments, load endurances and bendings of different plywoods were measured and compared. In the testing, a wheel load test in accordance with ISO R 1496 was used. As a result with a span length of 395 mm the following were obtained: the average maximum load endurance of the reference plywood was approximately 4333 kg and bending (with a load of 2730 kg) approximately 8.8 mm and the average maximum load endurance of the plywood in accordance with the invention was approximately 5960 kg and bending (with a load of 2730 kg) approximately 9.0 mm. On the basis of the results one could discover that also with the reinforcing material presented herein a reinforcement bearing plywood was obtained with a better load endurance than with the prior art reference plywood.

A wood panel in accordance with the invention is suitable to be used in different applications and in different uses, particularly in targets requiring a high load endurance. A method in accordance with the invention can be used to manufacture wood panels of any type, where the reinforcing layer is one of the veneer layers within the structure. Applications of the invention are not to be limited to disclosed examples, but they may vary within the scope of the accompanying claims.

Claims

1. A wood panel, which has been formed of a number of veneer layers (2), which have been joined together by means of a glue, characterised in that to a wood panel (1) it is included at least one reinforcing layer (3), which includes resin and reinforcement fibre, which is bound with resin, and the reinforcing layer (3) is arranged between two veneer layers (2).

2. The wood panel according to claim 1, characterised in that to the wood panel (1) at least one reinforcing layer (3) is included.

3. The wood panel according to claim 1 or 2, characterised in that to the wood panel (1) at least two reinforcing layers (3) are included.

4. The wood panel in accordance with any of claims 1-3, characterised in that the reinforcing layer (3) is arranged close to the surface of the wood panel (1).

5. The wood panel in accordance with any of claims 1-4, characterised in that the reinforcing layer (3) is arranged close to the surface of the drive side of the wood panel (1).

6. The wood panel in accordance with any of claims 1-5, characterised in that the reinforcing layer (3) is arranged close to the surface of the pressing side of the wood panel

(1).

7. The wood panel in accordance with any of claims 1-6, characterised in that the reinforcing layer (3) contains fibreglass.

8. The wood panel in accordance with any of claims 1-7, characterised in that the reinforcing layer (3) contains carbon fibre.

9. The wood panel in accordance with any of claims 1-8, characterised in that the reinforcing layer (3) is arranged to a form of a netlike web.

10. The wood panel in accordance with any of claims 1-9, characterised in that resin is epoxy-, polyester- and/or vinyl ester based resin.

11. The wood panel in accordance with any of claims 1-10, characterised in that the reinforcing layer (3) is a fibreglass-carbon fibre layer impregnated with epoxy resin.

12. The wood panel in accordance with any of claims 1-11, characterised in that glue is a liquid phenolic resin or a derivative thereof.

13. A method for manufacturing a wood panel, in which it is formed of a number of veneers the wood panel with multiple veneer layers so that the veneer layers are piled up one on the other and joined together by means of a glue, characterised in that a reinforcing layer is arranged, which includes resin and reinforcement fibre, which is bound with resin, between two veneer layers.

14. A method according to claim 13, characterised in that it is arranged one reinforcing layer between the veneer layers.

15. A method according to claim 13 or 14, characterised in that it is arranged at least two reinforcing layers between the veneer layers.

16. The method in accordance with any of claims 13-15, characterised in that the reinforcing layer is arranged close to the wood panel surface.

17. The method in accordance with any of claims 13-16, characterised in that the reinforcing layer is arranged close to a surface of a drive side of the wood panel.

18. The method in accordance with any of claims 13-17, characterised in that the reinforcing layer is arranged close to a pressing side surface of the wood panel.

19. The method in accordance with any of claims 13-18, characterised in that as a glue phenolic resin or a derivative thereof is used.

20. The method in accordance with any of claims 13-19, characterised in that the reinforcing layer is arranged between the veneer layers essentially in conjunction with the piling and gluing of the veneer layers.