WO2012001483A1

WO2012001483A1 - Multi-layered panel made of wood material, plant to make said multi-layered panel and relative method of production

Info

Publication number: WO2012001483A1
Application number: PCT/IB2011/001479
Authority: WO
Inventors: Antonio Dal Ben
Original assignee: Pal Srl
Priority date: 2010-06-28
Filing date: 2011-06-27
Publication date: 2012-01-05
Also published as: ITUD20100129A1

Abstract

Multi - layered panel (10) made of wood material, plant and method to produce said multi - layered panel (10). The multi - layered panel (10) comprises two external layers (1 1) and an internal layer (12) disposed in an intermediate position between the external layers (1 1). Each external layer (1 1) is made of a plurality of first elements made of virgin wood material and fibers, positioned according to a determined orientation and glued to each other. The internal layer ( 12) is made of a plurality of second elements made of wood material and fibers from recycling, and comprises a percentage in weight of glue between about 3% and about 8%. The mass of the internal layer (12) constitutes at least 50% of the overall mass of the panel (10).

Description

"MULTI-LAYERED PANEL MADE OF WOOD MATERIAL, PLANT TO MAKE SAID MULTI-LAYERED PANEL AND RELATIVE METHOD OF

PRODUCTION" FIELD OF THE INVENTION

The present invention concerns a multi-layered panel made of wood material, or wood substitute, in which there are at least two external layers, and at least an intermediate layer, assembled so as to have mechanical characteristics similar to those of a panel of the same size made in a single layer. In particular, the multi- layered panel according to the present invention is partly made of virgin wood materials, and partly of wood materials deriving from recycling.

The present invention also concerns a plant and method to make the multi- layered panel.

BACKGROUND OF THE INVENTION

Multi-layered panels made of wood material are known, for example of the type which can be used in making walls, supports, shelves, packaging or other, which substantially consist of so-called virgin wood fibers, or made from plants or trees and never before used for making artifacts. Normally these virgin wood materials can be traced to their origins.

An example of this type of known panels are those known by the acronym

OSB (Oriented Strand Boards), in which a plurality of fine virgin wood chips are oriented and glued together to define a panel.

This type of panel has good mechanical characteristics, which can substantially be summed up as:

- density of about 620 to about 680 kg/ m³;

- resistance to flexion in length of about 18 to about 22 N/mm2;

- resistance to flexion in width of about 9 to about 1 1 N/mm2;

- elasticity modulus in length of about 3,500 N/mm2;

- elasticity modulus in width of about 1,400 N/mm2;

- internal cohesion of about 0.3/0.4 N/mm2 (depending on the thickness).

This type of known panel in wood material has, however, high production costs due mainly to a widespread use of glues to guarantee the correct connection of the fine chips of wood, and to the time for the oriented deposition of the wood chips, and also to the cost of the virgin materials used which make up the whole panel.

Multi-layered panels provided with a central layer made of a wood substitute material such as chipboard are also known, which are surface covered by enhancing layers.

This type of known multi-layered panels, even though they cost less compared to OSB panels, have mechanical and structural characteristics which cannot be compared to the known OSB panels, given the same sizes.

From DE-A- 10024543 a method is known to produce continuously a multi- layered panel made of wood material, which provides to make a first layer with virgin wood chips (strands) directly resting on a molding belt. A second layer consisting of a mix of fibers, or small chips, made from waste materials, is then made on the first layer. A third layer is then made on the second layer in a similar way to that in which the first layer was made, that is, using strands of virgin wood. The second layer, that is, the internal one, has a thickness comprised between 0.3 mm and 1.5 mm and its weight, in a ratio to the total weight of the panel, is very small, so that the panel produced with this known method is very similar, even in cost, to that of the OSB type, which is made completely of chips of virgin wood (strands).

One purpose of the present invention is to make a multi-layered panel which costs much less, in the range of at least 20% less, than a similar panel of the OSB type, but which has similar mechanical characteristics to the latter.

Further purpose of the present invention is to produce a plant and perfect a method which allow to make a multi-layered panel which obviates the shortcomings of the state of the art.

The Applicant has devised, tested and embodied the present invention to overcome the shortcomings of the state of the art and to obtain these and other purposes and advantages.

SUMMARY OF THE INVENTION

The present invention is set forth and characterized in the independent claims, while the dependent claims describe other characteristics of the invention or variants to the main inventive idea.

In accordance with the above purposes, a multi-layered panel according to the present invention comprises two external layers and at least one internal layer disposed in an intermediate condition between the two external layers.

According to a characteristic feature of the present invention, each external layer is made with a plurality of first elements in virgin wood material and fibers glued to each other.

According to the present invention the internal layer is made with a plurality of second elements in wood material and fibers deriving from recycling and therefore not virgin, amalgamated and glued to each other.

According to the invention the internal layer comprises a percentage in weight of glue comprised between about 3% and 8% in order to define an amalgam between the materials and fibers deriving from recycling. Advantageously the mass of the internal layer constitutes at least 50% of the overall mass of the panel. Moreover the internal layer has a density which is less than that of each of the external layers, for example comprised between 500 Kg/ m 3 and 580 Kg/m 3. In this way, the multi-layered panel according to the present invention has an overall density equal to or less than that of known products, thanks to the limited use of glues, to the consistent mass and to the reduced density of the internal layer. Moreover, the multi-layered panel according to the present invention has a cost reduced by at least 30-40 % with respect to a traditional panel completely made with virgin material and fibers, since almost a half of it is made of fibers or wood materials deriving from recycling.

Moreover the use of materials and fibers deriving from recycling reduces the environmental impact due to the production steps of the panel.

The Applicant has found that a multi-layered panel according to the present invention, in which 50% of the volume is made of a wood material or fibers deriving from recycling, has similar mechanical characteristics to that of traditional panels made of fibers, and in particular:

- density of about 620-650 kg/ m³;

- resistance to flexion in length of about 30-40 N/mm2;

- resistance to flexion in width of about 14-19 N/mm2;

- elasticity modulus in length of about 6,000-7,500 N/mm2;

- elasticity modulus in width of about 1,900-2,900 N/mm2;

- internal cohesion of about 0.4/0.5 N/mm² (depending on the thickness). According to a variant, the virgin materials and fibers of each of the two external layers have a humidity level of less than about 5%.

According to another variant, the materials and fibers deriving from recycling of the internal layer also have a humidity level of less than about 5%.

According to another variant, each external layer comprises a percentage in weight of glue comprised between about 8% and about 20%.

It comes within the field of the present invention to provide a plant in which a first operating area is provided to make the external layers, comprising gluing and positioning means configured to glue and position the virgin materials and fibers according to a predetermined orientation.

The plant also comprises a second operating area to make the internal layer, comprising gluing means configured to glue, by means of resining, the materials and fibers deriving from recycling with the glue, in which the glue has a percentage in weight comprised between about 3% and about 8%.

The plant also comprises a third operating area for molding and pressing comprising, in its turn, pressing means, in which the external layers made in the first operating area and the internal layer made in the second operating area are assembled and pressed together to define the multi-layered panel.

It also comes within the field of the present invention to provide a method in which a first step is provided during which the lower external layer is made, by means of gluing and positioning chips of virgin wood material and fibers according to a predetermined orientation; a second step during which the internal layer is made, by means of resining of the materials and fibers deriving from recycling with the glue, in which the glue has a percentage in weight comprised between about 3% and about 8%, and molding of the internal layer; a third step during which the upper external layer is made; and a fourth step during which the external layers made in the first and third steps and the internal layer made in the second step are assembled and pressed together to define the multi-layered panel.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other characteristics of the present invention will become apparent from the following description of a preferential form of embodiment, given as a non-restrictive example with reference to the attached drawings wherein:

- fig. 1 shows a partial and sectioned three-dimensional view of a multi- layered panel according to the present invention;

- fig. 2 shows a first example of the orientation of the chips of virgin wood material in an external layer;

- fig. 3 shows a second example of the orientation of the chips of virgin wood material in an external layer;

- fig. 4 shows a third example of the orientation of the chips of virgin wood material in an external layer;

- fig. 5 shows a fourth example of the orientation of the chips of virgin wood material in an external layer;

- fig. 6 schematically shows a plant to make the multi-layered panel according to the present invention.

To facilitate comprehension, the same reference numbers have been used, where possible, to identify identical common elements in the drawings.

DETAILED DESCRIPTION OF A PREFERENTIAL FORM OF EMBODIMENT

With reference to fig. 1, a multi-layered panel 10 according to the present invention comprises two external layers 1 1 and an intermediate layer 12 interposed between the two external layers 1 1.

Each external layer 1 1 comprises a plurality of first elements consisting of thin chips of virgin wood.

The thin chips of virgin wood which make up the two external layers 1 1 indicatively have thicknesses between 0.3 mm and 2 mm, length between 100 mm and 230 mm, are reciprocally orientated according to defined directions and are held together by glue, in this case an MUF glue (Melanin Urea Formaldehyde) with a percentage in weight comprised between about 8% and about 20 %.

Advantageously the MUF glue has a melanin content comprised between about 10% and about 30%, with 2% hardener on dry glue and water dilution in a ratio of 65%-35% dry glue/water.

The thin chips of virgin wood have a humidity level of less than about 5%.

The overall mass of the two external layers 11 is less than about 50% of the overall mass of the panel 10, in this case about 40%, and the same can be said in approximate terms for the volume and therefore for the thicknesses of the layers. The intermediate layer 12 comprises a plurality of second elements consisting of fibers and wood elements deriving from recycling, both urban and/or industrial and waste from sawmills, held in an amalgam by a glue with a percentage in weight comprised between about 3% and about 8%.

Advantageously, the glue is of the PMDI type (Poly methylene Diisocyanate, isocyanate), but can also be urea glue.

Advantageously, the wood materials and fibers deriving from recycling also have a humidity level of less than about 5% (after drying) and are worked in advance to maximize the production of long shavings used to give the product a determinate mechanical characteristic. The sizes can be those as exiting from sifting using sieves with 2x2 mm and 10x10 mm square mesh, in the fraction >2mm, <10mm.

In the case shown, the internal layer 12 occupies a volume of about 60% (thicknesses of about 3 mm - 9 mm - 3 mm for a total of about 15 mm) with respect to the overall volume of the panel 10.

In this condition the Applicant has found that the panel 10 produced has the following mechanical characteristics:

- density of about 620 kg/ m³;

- resistance to flexion in length of about 36 N/mm2;

- resistance to flexion in width of about 14 N/mm2;

- elasticity modulus in length of about 6,500 N/mm2;

- elasticity modulus in width of about 1,900 N/mm2;

- internal cohesion of about 0.4 N/mm2 (depending on the thickness).

There follows a description of the plant 20 and the method according to the present invention to make the panel 10.

With reference to fig. 6 the plant 20 substantially comprises three operating areas, respectively, a first area 21 to make the external layers 1 1 , a second area 22 to make the internal layer 12, and a third or final operating area 40. The first two zones 21 and 22 of the plant 20 converge toward a forming belt 28 of the third operating area 40, where the lower external layer 1 1 (fig. 1), the internal layer 12 and the upper external layer 1 1 are formed to define the sandwich mattress which will then be pressed in a pressing station 23 (fig. 6) in the same third operating area 40. The latter, as well as the forming belt 28 and the pressing station 23, also comprises a pair of molding machines or heads 30a and 30b to mold the virgin chips to make the external layers 1 1 and a molding machine 37 to mold the chips or shavings deriving from recycling to make the internal layer 12.

According to a variant, not shown in the drawings, the pair of molding heads could be substituted by a single molding head.

In this case, the first operating area 21 of the plant 20 comprises a bark stripping machine 24, a chipper device 25, a drying member 26, a riddle 27 and a gluing member 29.

In particular, the bark stripping machine 24 is substantially of a known type and allows to remove possible peripheral parts of bark from the pieces, or slabs of virgin wood from which to start the production of the external layer 1 1.

The chipper device 25 is also of a substantially known type and is configured as a knife ring flaker in order to reduce into substantially uniform chips the pieces or slabs of virgin wood coming from the bark stripping machine 24.

The chips thus produced are put into the drying member 26 inside which the percentage of humidity is reduced to at least below 5%.

The dried chips are then sent inside the riddle 27 to separate the fine particles from the chips. The riddle 27 can be for example of the type described in the European Patent EP-B- 1358020 in the name of the Applicant.

Once the chips have been sieved they are soaked in glue by the gluing member 29, according to the weight percentage specifications indicated above.

The gluing member 29 comprises, for example according to some variants, a spray-type delivery device, a spreading system or other known systems for the correct and efficient depositing of the glue onto the chips.

The chips thus glued are sent to the molding machine 30, in which the chips are reciprocally disposed, with respect to each other, according to a determinate planned pattern, for example coherent with the types schematically shown and given only as an example in figs. 2, 3, 4 and 5.

The Applicant has found that the reciprocal positioning and orienting of the chips influences the mechanical characteristics of the multi-layered panel 10, in particular as regards the resistance to flexion and the elasticity modulus in length and in width.

Merely to give an example, the pattern of orientation of the chips as illustrated in fig. 2, that is, substantially parallel to the length of the panel 10 (in the direction of production, that is, the forming belt 28), confers on the panel 10 good characteristics of resistance to flexion and elasticity modulus in length.

The pattern of orientation of the chips as illustrated in fig. 3, that is, substantially perpendicular to the length (that is, direction of production flow), confers on the panel 10 good characteristics of resistance to flexion and elasticity modulus in width.

The pattern of orientation of the chips as illustrated in fig. 4, that is, disposed substantially oblique, confers on the panel 10 good mechanical characteristics similar for both directions.

The pattern of orientation of the chips as illustrated in fig. 5, that is, disposed substantially at random, confers inferior mechanical characteristics on the panel 10.

Since the external layers 1 1 have their total thickness (for example 6 mm) inside the sandwich of the panel, equal to about 40% of the overall thickness of the whole panel (for example 15 mm), there are always more sub-layers of chips inside the upper and/or lower external layer, so that there can be chips oriented alternatively sub-layer by sub-layer in length (direction of production flow) or in width, achieving the best mechanical properties possible.

In parallel, or at least in a differentiated way and not necessarily in sequence, the internal layer 12 is made by means of the second operating area 22.

In this case, the second operating area 22 of the plant 21 comprises a grinder device 31, a crushing mill 32, a drying member 33, a riddle 35 and a gluing member 36.

In particular, the grinder device 31 is predisposed with crushing members, known and not shown, which carry out a first, coarse crushing of the wood materials deriving from recycling, so as to make the sizes substantially uniform.

These materials are then introduced into the crushing mill 32 so as to be reduced to chips.

According to a variant, two or more crushing mills are provided in series, depending on the sizes and characteristics provided for the chips of wood material.

The chips thus produced are put into the drying member 33, inside which the percentage of humidity is reduced to at least below 5%.

The dried chips are then sent inside the riddle 35, to eliminate the fine particles and the sizes which are too big for the process.

Once sieved, the chips are soaked in glue by the gluing member 36, according to the weight percentages specifications indicated above.

As in the first operating area 21, the gluing member 36 comprises, for example according to some variants, a spray-type delivery device, a cylinder with mixing rotor or other known systems for the correct and efficient depositing of glue on the chips.

The chips thus glued are sent to the molding machine 37, in which the chips are assembled so as to make a homogenous layer, and so that, interposed between the two external layers 1 1 , it guarantees the equidistance and the panel 10 thus made responds in an efficient manner to the mechanical stresses.

The sandwich mattress is constituted by overlapping the three layers in sequence on the single forming belt 28. In substance the sequence of formation is: external layer 1 1 exiting from the molding machine 30a - internal layer 12 exiting from the molding machine 37 - external layer 1 1 exiting from the molding machine 30b.

The external layers 1 1 and the internal layer 12 thus made are then introduced into the pressing station 23, in which, by means of a press of a substantially known type, the layers 1 1 and 12 are pressed together according to the sequence provided, to form the multi-layered panel 10.

It is clear that modifications and/or additions of parts or steps may be made to the panel 10, the plant 20 and the method as described heretofore, without departing from the field and scope of the present invention.

It is also clear that, although the present invention has been described with reference to some specific examples, a person of skill in the art shall certainly be able to achieve many other equivalent forms of multi-layered panel in wood material, plant for the production of said multi-layered panel and relative production method, having the characteristics as set forth in the claims and hence all deriving within the field of protection defined thereby.

Claims

1. Multi-layered panel comprising at least two external layers (1 1) each made with a plurality of first elements made of virgin wood material and fibers glued to each other, and at least an internal layer (12) disposed in an intermediate position between said external layers (1 1), characterized in that said internal layer (12) is made of a plurality of second elements made of wood material and fibers deriving from recycling, comprises a percentage in weight of glue comprised between about 3% and 8% in order to define an amalgam between said second elements, and has a mass which constitutes at least 50% of the overall mass of said panel (10).

2. Panel as in claim 1, characterized in that the mass of the internal layer ( 12) constitutes 60% of the overall mass of said panel (10).

3. Panel as in claim 1 or 2, characterized in that the density of said internal layer (12) is comprised between 500 kg/m and 580 kg/m .

4. Panel as in claim 1 , 2 or 3, characterized in that it comprises a resistance to flexion in length comprised between 30 N/mm2 and 40 N/mm2.

5. Panel as in any claim hereinbefore, characterized in that it comprises a resistance to flexion in width comprised between about 14 N/mm2 and about 19 N/mm2.

6. Panel as in any claim hereinbefore, characterized in that it comprises an elasticity modulus in length comprised between about 6,000 N/mm2 and about 7,500 N/mm2.

7. Panel as in any claim hereinbefore, characterized in that it comprises an elasticity modulus in width comprised between about 1 ,900 N/mm2 and about 2,900 N/mm2.

8. Panel as in any claim hereinbefore, characterized in that it comprises an internal cohesion comprised between about 0.4 N/mm2 and about 0.5 N/mm2, according to the thickness of said panel (10).

9. Panel as in any claim hereinbefore, characterized in that the virgin materials and fibers of each of the two external layers (1 1) have a degree of humidity less than about 5%.

10. Panel as in any claim hereinbefore, characterized in that the materials and fibers of the internal layer (12) deriving from recycling have a degree of humidity less than about 5%.

1 1. Panel as in any claim hereinbefore, characterized in that each external layer (1 1) comprises a percentage in weight of glue comprised between 8% and 20%.

12. Plant to make a multi-layered panel made of wood material, comprising at least two external layers (1 1) and at least an internal layer (12) disposed in an intermediate position between said external layers (1 1), characterized in that it comprises at least a first operating area (21) to make said external layers (1 1), comprising gluing means (29) configured to glue the virgin wood materials and fibers, a second operating area (22) to make said internal layer (12), comprising gluing means (36) configured to glue the materials and fibers deriving from recycling with the glue, wherein the glue has a percentage in weight comprised between 3% and 8%, a third operating area (40) which comprises molding means (30a, 37, 30b) and pressing means (23), wherein said external layers (1 1) are able to be formed according to predetermined pattern, and wherein said internal layer (12) and said external layers (1 1) and are pressed so as to define said panel (10).

13. Method to make a multi-layered panel made of wood material formed by at least two external layers (1 1) and at least an internal layer (12) disposed in an intermediate position between said external layers (1 1), characterized in that it provides a first step during which a first of said external layers (1 1) is made, by gluing virgin wood materials and fibers and positioning them according to a predetermined orientation; a second step during which said internal layer (12) is made, on top of said first external layer (1 1), by gluing wood materials and fibers deriving from recycling with the glue, wherein the glue has a percentage in weight comprised between about 3% and about 8%; a third step during which a second of said external layers (1 1) is made, on top of said internal layer (12), by positioning and gluing virgin wood materials and fibers according to a predetermined orientation; and a fourth step during which the forming and pressing is carried out of said external layers (1 1) with said internal layer (12) interposed, in order to define said panel (10).