EP2147762A1 - Composite wood board - Google Patents

Abstract

The timber material plates (10.1,10.2) have a circular boundary area and an internal area surrounded by the boundary area. The firmness of the boundary area is increased in relation to the internal area. A cross linked substance is made from an isocyanate polymer, a polyurethane polymer or an epoxy resin. The boundary area is stabilized for the increase of the firmness over a full thickness expansion (D) of the timber material plate with the cross linked substance. Independent claims are included for the following: (1) a floor panel with a connecting profile; and (2) a method for manufacturing a timber material plate.

Description

The invention relates to a wood-based panel having a peripheral edge region and an inner region surrounded by the edge region. According to a second aspect, the invention relates to a method for producing a floor panel.

Wood-based panels, for example HDF panels (high-density fiber board), are used, for example, in the production of floor panels or laminate floors. In the manufacture of floor panels must be introduced into the wood-based panel profiles, for example, are milled, so that two floor panels can be connected together. It is desirable to make floor panels particularly easy, as this requires less raw material and leads to easier to transport and handle floor panels. The reduction of the material thickness of the wood-based panel, however, limits, since the profiles must safely absorb the loads that arise when using the floor panels.

In order to be able to set lower material thicknesses or lower bulk densities in wood-based panels, in the production of floor panels, for example, aluminum strips are embedded in the profiles of the floor panels, which absorb a majority of the joining forces in use. However, this has the disadvantage that the aluminum strips can be introduced only with increased effort in the manufacture of the floor panel in the wood-based panel.

The invention has for its object to achieve lower densities and / or lower densities without the strength of a click connection suffers from made of wood-based panel floor panels suffers.

The invention solves the problem by a generic wood-based panel, in which the strength of the edge region is increased relative to the inner region. In this case, the edge region is to be understood in each case as the region in which the profiles for connecting the individual elements are later. This means that there is a plurality of impregnated areas on the output format, which may have a much larger dimension. In the following text, when referring to the edge region, this is generally the edge region / edge regions which are created by separating a large-format plate into the resulting blanks.

Preferably, to increase the strength of the edge region over a full thickness expansion of the wood-based panel is stabilized with a postcrosslinking substance.

According to a second aspect, the invention solves the problem by a method for producing a wood-based panel with the step of introducing a post-crosslinking substance in an edge region of the wood-based panel, so that the post-crosslinking substance in the wood-based panel cross-links and stabilizes the edge region. According to the invention, a method is also provided for producing a floor panel comprising the steps of: (a) producing a wood-based panel according to the invention and (b) introducing a profile into the edge area, wherein each point of the profile adjoins a layer of material having a predetermined minimum thickness.

An advantage of the invention is that wood-based panels can be used for the production of floor panels and laminate floors, which have a lower density. This means that the production facilities that produce the wood-based panels can produce much faster and more cost-effectively. Furthermore, for a consumer of the floor panel and the wood-based panel transport and handling are much more pleasant.

It is a further advantage that wood-based panels according to the invention can be produced with existing production facilities. In particular, a short-cycle coating is possible.

Another advantage is that even with reduced thickness or reduced density of the wood-based panel mechanically strong connections between two floor panels made of wood-based panels according to the invention are possible. It is also advantageous that the postcrosslinking substance, which increases the strength of the edge region, as a rule also acts as a water repellent, so that swelling in the edge region is avoided.

In the context of the present description, a post-crosslinking substance is understood as meaning a substance which reacts chemically after introduction into the edge region. For example, the post-crosslinking substance polymerizes or reacts with constituents of the wood-based panel, for example with wood chips.

The feature that the postcrosslinking substance increases the strength of the edge region is understood in particular to mean that a transverse tensile strength of the edge region after introduction of the postcrosslinking substance is significantly higher than before incorporation of the postcrosslinking substance and subsequent postcrosslinking.

It is possible, but not necessary, for post-crosslinking to be supported, for example by introducing microwave radiation, heat or the like.

An edge region is understood in particular to be a volume section of the wood-based panel which extends along the edge over a complete thickness of the wood-based panel. For example, the edge region has an extension of more than 1 cm from a peripheral edge of the wood-based panel. The wider the edge area, the cheaper the strength properties of the wood-based panel affected. At the same time, however, the costs for the postcrosslinking substance are increasing. The edge region is thus advantageously chosen to be so wide that further broadening of the edge region does not significantly increase the strength of a profile introduced for producing a floor panel.

According to a preferred embodiment, the edge region has a content of postcrosslinked substance such that its transverse tensile strength exceeds 2.3 N / mm ² , in particular 2.5 N / mm ² .

Postcrosslinking substances have proven to be particularly suitable which consist of at least one compound which has NCO groups, a relative proportion of the NCO groups in a molar mass of the compounds being more than 15%. The NCO groups or cyan groups of a molecule greatly contribute to a high strength of the post-crosslinked substance. The average relative proportion of NCO groups in the molar mass of the compounds is calculated by dividing the molecular weight of the NCO group by the molecular weight of the entire molecule. This procedure is carried out for all compounds present in the postcrosslinking substance and from the respective results a mean weighted with the molar portion of the respective compound is calculated.

Particularly suitable as postcrosslinking substances, isocyanate prepolymers, polyurethane polymers and / or epoxy resins have been found. These compounds are present in the finished wood-based panel as polymers, but usually they are introduced as prepolymers in the wood-based panel.

Particularly high strengths can be achieved if the edge region has a content of postcrosslinking substance of more than 500 g / m ² . It has been found that a content of postcrosslinking substance in the edge region of more than 1500 g / m ² generally brings no further advantages.

For given dimensions and for a given strength in the edge region, a particularly low mass of the wood-based panel is achieved if the bulk density in the edge region has a peripheral edge bulk density which is greater than an inside bulk density in the inner region. For example, the edge area bulk density is greater than 8% greater than the interior bulk density. The edge area density is preferably above 800 kg / m ³ . In addition, it is advantageous if the internal density of the inner region is below 750 kg / m ³ .

The consumption of postcrosslinking substance or of prepolymer is particularly low if substantially only the edge region contains postcrosslinking substance. This is to be understood as meaning that the concentration of a postcrosslinking substance in the edge area is significantly higher than in the interior area, for example more than 5 times as high. In particular, it is also possible to treat the interior area with postcrosslinked substance, but this is not necessary.

For example, a floor panel is obtained from the wood-based panel, in which a profile is introduced into the edge area for connection to other floor panels, in particular milled in and / or embossed.

As part of a process according to the invention, the postcrosslinking substance, d. H. the substance that polymerizes in the wood-based panel, for example, or combines with other ingredients, sucked under the influence of negative pressure in the wood-based panel. For this purpose, the post-crosslinking substance is applied, for example, on one side of the wood-based panel. On the opposite side is a squeegee, which sucks the applied post-crosslinking substance in the wood-based panel. Preferably, the postcrosslinked substance is applied exclusively in the edge region.

The wood-based panel may be an MDF or HDF board. The floor panel is preferably designed for glueless connection by means of tongue and groove.

Figur 1

eine schematische Ansicht einer erfindungsgemäßen Holzwerkstoff- platte und

Figur 2

ein erfindungsgemäßes Fußbodenpaneel.

In the following the invention will be explained in more detail with reference to the accompanying drawings. It shows

FIG. 1

a schematic view of a wood-based panel according to the invention and

FIG. 2

an inventive floor panel.

FIG. 1 shows a first wood-based panel 10.1 and a second material panel 10.2, which have been prepared by sawing a total wood-based panel along a cutting line 12. The wood-based panel 10.1 has an edge region 14.1, which extends along the cutting line 12 and extends over a full thickness extent along a thickness D of the wood-based panel 10.1. The edge region 14.1 has a width B of, for example, 1 to 3 cm. Similarly, the wood-based panel 10.2 has an edge region 14.2, which also adjoins the cutting line 12 and has the same width B. Beyond the edge regions 14.1, 14.2 extend respective inner regions 16.1 and 16.2 of the wood-based panels 10.1 and 10.2.

The edge regions 14.1, 14.2 contain a postcrosslinking substance, which gives them a higher strength in comparison to the inner regions 16.1, 16.2. The postcrosslinking substance is a polyurethane prepolymer which has bonded in the marginal areas 14.1., 14.2 with other constituents of the wood-based panels 10.1 and 10.2 during polymerization.

To introduce the postcrosslinking substance into the edge regions 14.1, 14.2, the postcrosslinking substance is applied to, for example, an upper side 18, for example brushed, sprayed, suspended or rolled up. In the region of the edge region 14.1, 14.2 is located on a bottom 19, a squeegee with their seals and generated in FIG. 1 below the edge region 14.1, 14.2 a negative pressure. By this negative pressure is applied to the top 18 postcrosslinking substance quickly absorbed into the edge area 14.1, 14.2.

The postcrosslinking substance is chosen so that it crosslinks after introduction into the edge region 14.1, 14.2 and increases the strength. For producing an HDF wood-based panel 10.1, 10.2, which may for example have a thickness D of less than 10 mm, for example 8 mm, the polyurethane prepolymer is introduced with a raw areal density of 750 kg / m ³ . In this polyurethane prepolymer, the content of NCO groups is more than 20%, resulting in a particularly large increase in strength results. In order to use as little as possible of the polyurethane prepolymer, it is only in the edge regions 14.1, 14.2, but not in the inner region 16. The edge region 14.1, 14.2 has introduced so that as little as possible polyurethane prepolymer must be used, a width of, for example less than 10 cm, especially less than 5 cm.

By introducing the postcrosslinking substance, in the present example in the form of the polyurethane prepolymer, a transverse tensile strength R _transversely to more than 2.5 N / mm ² . The transverse tensile strength is the strength in the transverse direction, which is indicated by the arrow Q. The transverse tensile strength R _transverse is an important measure of an achievable strength of a profile milled into the Rarnd region 14.1, 14.2 of a floor panel produced from the wood-based panel. Typical transverse tensile strengths for the HDF boards are R _transverse = 1.2 N / mm ² to 2.0 N / mm ² .

By increasing the transverse tensile strength R _transverse due to the postcrosslinking substance, it is possible to choose a gross density in the inner region ρ _{raw, inside} of less than 830 kg / m ³ , without resulting disadvantages in the subsequent processing. The bulk density in the edge area ρ _{raw, edge} can still be 850 to 900 per m ³ in order to increase the _transverse tensile strength R _across .

FIG. 2 shows floor panels 20.1, 20.2, which are made of the corresponding wood-based panels 10.1 and 10.2 by introducing respective profiles 22.1, 22.2. The profiles 22.1, 22.2 are for example milled or embossed.

Characterized in that the wood material plate 10 from which the floor panels are manufactured 20.1, 20.2, can be lowered in its central _medium density P, handling and transportation of the floor panel 20 can be facilitated, which is consumer-friendly. Furthermore, a reduction in the density leads to improved behavior with regard to footfall and room noise when walking.

The wood-based panels 10.1, 10.2 or the entire material panel can be easily produced by means of short-cycle coating, the first production step in the manufacture of floor panels. Even with the _raw densities ρ _raw specified above, further KT coatings are possible. Optionally, during production, production parameters such as pressure or temperature must be adjusted.

By introducing the postcrosslinking substance, moreover, the water absorption capacity of the edge region 14.1, 14.2 and thus of the profile 22.1, 22.2 is reduced. It should be noted, however, that the introduction of the postcrosslinking substance is not a surface impregnation of the profile, since impregnating agents have no strength-increasing effect and serve only to repel water. Further suitable postcrosslinking substances are isocyanate polymers, polyurethane polymers and / or epoxy resins, it also being possible to use mixtures.

LIST OF REFERENCE NUMBERS

10

Wood panel

12

cut lens

14

border area

16

interior

18

top

19

bottom

20

floor panel

22

profile

ρ _{raw, edge}

Density indoors

ρ _{raw, inside}

Density indoors

Q

transversely

R

strength

R _across

transverse tensile strength

Claims (15)

Wood-based panel with (a) a peripheral edge region (14) and (b) an inner region (16) surrounded by the edge region (14),
characterized in that (C) the strength (R) of the edge region (14) relative to the inner region (16) is increased. Wood material board according to claim 1, characterized in that for increasing the strength (R) of the edge region (14) over a full thickness dimension (D) of the wood material board (10) is stabilized with a post-crosslinking agent. Wood material board according to claim 2, characterized in that the edge region (14) having such content of post-crosslinking substance that its transverse tensile strength (R _crosswise) N / mm ^2, in particular 2.5 N / mm ^2, exceeds 2.3. Wood material board according to one of the preceding claims, characterized in that the postcrosslinking substance consists of at least one compound which has NCO groups, - Where a relative proportion of NCO groups in a molar mass of the compounds is more than 15% on average. Wood material board according to one of the preceding claims, characterized in that the postcrosslinking substance comprises an isocyanate polymer and / or a polyurethane polymer and / or epoxy resin. Wood material board according to one of the preceding claims, characterized in that in the transverse tensile strength (R _transverse ) in the inner region is at most 1.2 N / mm ² . Wood material board according to one of the preceding claims, characterized in that the edge region (14) has a content of postcrosslinking substance of more than 500 g / m ² . Wood material board according to one of the preceding claims, characterized in that the edge region (14) has a content of postcrosslinking substance of less than 1500 g / m ² . Wood material board according to one of the preceding claims, characterized in that a bulk density in the edge region (14) has an edge region density (ρ _edge ) which is greater than an inner region bulk density (ρ _inside ) in the inner region (16). Wood material board according to one of the preceding claims, characterized in that the edge area density (ρ _edge ) by more than 8% larger than the indoor bulk density (ρ _inside ). Wood material board, characterized in that the edge area density (ρ _edge ) is above 800 kg / m ³ . Wood-based panel, characterized in that the internal density (ρ _inside ) is below 750 kg / m ³ . Wood material board according to one of the preceding claims, characterized in that only the edge region (14) contains postcrosslinking substance. Floor panel made of a wood-based panel according to one of the preceding claims, which in the edge region (14) has a profile (22) for connection to other floor panels (20). Method for producing a wood-based panel (10), comprising the step: Introducing a post-crosslinking substance into an edge region (14) of the wood-based panel (10) so that the post-crosslinking substance in the wood-based panel (10) cross-links and stabilizes the edge region (14).

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