EP2961580A1 - Wood and composite-material plate and method for production - Google Patents

Abstract

The invention relates to a wood and composite-material plate, comprising an intermediate layer made of popcorn and two cover layers having a high modulus of elasticity. The resulting plate is characterized by a very high flexural strength.

Description

 WOOD AND COMPOSITE MATERIAL PLATE AND METHOD FOR

 MANUFACTURING

The present invention relates to the field of wood and / or composites, in particular chipboard and fiberboard, insulation boards, boards and composite materials containing lignocellulose and popcorn. Wood and / or composite materials, in particular chipboard or fiberboard have been known for more than a hundred years as an alternative for solid wood in the furniture industry, construction, etc. For the quality of wood and / or composite materials, several factors play a role, in particular the bulk density, the transverse tensile strength and the thickness, but in many applications the flexural strength.

WO 2008/040747 discloses wood and composites containing popcorn. These have the advantage of a low density. However, it is the task of further improving the wood and / or composite material disclosed therein. This is achieved by a wood and / or composite panel according to the present invention. Accordingly, a wood and / or composite sheet is proposed, comprising an upper and a lower cover layer and an intermediate layer, wherein - the intermediate layer contains popcorn and - The upper and the lower cover layer consist of materials which have a modulus of elasticity (modulus of elasticity) of> 1 kN / mm ² to <70 kN / mm ² .

Surprisingly, it has been found that in this way the properties of the resulting wood and / or composite board, in particular the flexural strength and flexural modulus of elasticity, can be greatly increased compared to WO 2008/040747.

The term "wood and / or composite material" is understood to mean, in particular, materials which consist mainly of mechanically or thermomechanically, chemo-thermomechanically comminuted lignocellulose-containing material or popcorn, which are shaped after gluing with a synthetic or natural binder and added under temperature and pressure Wood and / or composites are pressed.

It should be noted that the wood and / or composite board according to the invention may contain even more than the three mentioned layers (upper and lower cover layer and intermediate layer). Usually, and thus according to a preferred embodiment, however, it is a three-layer wood and / or composite board. The individual layers of the wood and / or composite board according to the invention are explained in detail: a) Cover layers The cover layers of the wood and / or composite board according to the invention - as mentioned - each have a modulus of elasticity (modulus of elasticity) of> 1 kN / mm ² up to <70 kN / mm ² . The modulus of elasticity is preferably from> 1.5 kN / mm ² to <50 kN / mm ² , more preferably> 2 kN / mm ² to <40 kN / mm ² , and most preferably> 3 kN / mm ² to <30 kN / mm ² , and most preferably from> 5 kN / mm ² to <10 kN / mm ² . The modulus of elasticity for wood-based materials is measured according to DIN EN 310. The lower and / or upper cover layer preferably has a density of 0,5 0.5 g / cm ^{3 to} ≦ 3.0 g / cm ³ . This has proven itself in practice, since so the stability of the resulting wood and / or composite material plate according to the invention can be increased again. Even more preferably, the lower and / or upper cover layers have a density of 0,8 0.8 g / cm ³ to ≦ 2.5 g / cm ³ , more preferably from 0 0.9 g / cm ^{3 to} ≦ 1.5 g / cm ³

According to a preferred embodiment of the invention, the proportion of the cover layers is from 1 1% to ≦ 50% of the total wood and / or composite panel according to the invention (% by weight / weight). This has proved to be advantageous, since the density of the wood and / or composite board according to the invention remains low, but nevertheless the surprising increases in flexural strength can be observed. Even more preferably, the proportion of cover layers is from 10 10% to ≦ 30% of the total wood and / or composite panel of the invention (weight / weight). According to a preferred embodiment, the lower and / or upper cover layer consist predominantly of a material selected from the group consisting of wood chips or fibers, lignocellulose-containing chips and / or fibers (such as, for example, hemp, flax, etc.), or melamine film , HPL (High Pressure Laminate), CPL (Continuous Pressure Laminate), Chipboard (eg Thin Chipboard), Fiberboard (Thin HDF), Aluminum Sheet / Sheet, Metal Sheet / Sheet, Sheet Metal, Plywood, Veneer, Glass Fiber, Carbon Fiber, Carbon fiber, ceramic and possibly other additives such. As hydrophobing agents, anti-flame agents, binders and mixtures of all these materials.

The term "predominantly" in the sense of the present invention means in particular> 90% by weight, preferably> 95% by weight and most preferably> 98% by weight. B) Intermediate layer

The intermediate layer contains - as described - popcorn. The "popcorn" in the context of the present invention comprises in particular all materials which, like the puffed corn (Zea mays, convar Microsperma), if appropriate after adequate greasing, explode at high temperatures due to rapid heating by the water present in the seed evaporating abruptly Such behavior is known inter alia by quinoa grain, amaranth, rice or even wheat, materials based on these raw materials are explicitly referred to in the context of the present invention as "a foamy consistency." Popcorn "and includes, the term" popcorn "should not be limited to corn and was chosen especially for reasons of simplicity, clarity and readability.

The intermediate layer preferably comprises ≥ 60% (w / w), more preferably ≥ 80% (w / w), still more preferably ≥ 90% (w / w) and ≥ 95% (w / w) of popcorn and otherwise preferably predominantly of wood chips and / or wood fibers, preferably here. lignocellulosic chips and / or fibers (such as of hemp, flax, etc.) or plastics, thermoplastics, thermosets, plastic fibers, such as. As PP (polypropylene), PE (polyethylene), PVAc (polyvinyl acetate) or PP, PE supporting fibers), optionally with the addition of additives, such as. Hydrophobing agents, antiflaming agents, binders, etc. However, according to a preferred embodiment, the intermediate layer may consist of 100% popcorn.

According to a preferred embodiment of the invention, the popcorn has a particle size distribution in which ≥ 50% and ≤ 90% of the popcorn have a particle size of ≥ 2 mm and ≤ 10 mm.

This has proven advantageous for many applications within the present invention. Popcorn of larger grain size is often less suitable for processing into lignocellulose-containing moldings such as wood and / or composite materials. Popcorn of smaller grain size tends to be used in many applications within the present invention in the manufacture of the wood and / or composite material Absorb added binder or glue, which can degrade the quality of the wood and / or composite material.

Particularly preferably, the popcorn has a particle size distribution in which> 70% and <90% of the popcorn have a particle size of> 2 mm and <10 mm.

According to a preferred embodiment of the invention, the popcorn has a particle size distribution in which> 50% and <90%, particularly preferably> 70% and <90% of the popcorn have a particle size of> 4 mm and <10 mm.

According to a preferred embodiment of the invention, the popcorn has a particle size distribution in which> 50% and <80% of the popcorn have a particle size of> 3 mm and <8 mm. According to a preferred embodiment of the invention, the popcorn has an average particle size distribution of> 3 mm and <6 mm. This has been found to be beneficial for many applications within the present invention.

Particularly preferably, the popcorn has an average particle size distribution of> 3.5 mm and <5 mm.

According to a preferred embodiment of the invention, the fat content of the popcorn before processing is <10 (wt)%. By "fat content" of popcorn is not understood the total amount of fat in popcorn, but the proportion of fat, which was used to hydrophobize the seed epidermis, which leads to better inclusion of the water contained in the seed.

It has been found to be beneficial in many applications within the present invention to keep this fat content as low as possible, as this facilitates the further processing of the popcorn. Preferably, the fat content is <5 (wt)%, According to a particularly preferred embodiment, no fat is added to the consistency change (conversion) (= "puffing"). In this case, it is particularly preferred that the consistency change (= "puffing") takes place by means of microwaves, as will be explained below.

The present invention also relates to a method for producing a wood and / or composite board according to the invention, comprising the steps a) (optionally separate) lining of the outer layer and the intermediate layer precursor material

 b) presenting the glued topcoat and interlayer precursor materials

c) Pressing for Wood and / or Composite Material Board According to the Invention This process has proven particularly useful for wood and / or composite panels according to the invention, in which the cover layers receive wood fibers and / or wood chips. In this way, the wood and / or composite plate can be made directly by a single Verpressschritt. Step a) can be done by simply sprinkling fibers, chips and / or granules. In this case, in the intermediate layer, the popcorn granules are preferably either by the Bichsel method (WO 1999042005A1) or by Puffung, z. B. by the microwave method, and then crushed. Particularly suitable as binders are thermoplastics, thermosets, aminoplasts, phenoplasts, isocyanates, proteins, tannins, starch, synthetic binders or natural binders, or mixtures of binders, such as, for example, urea-formaldehyde resin, melamine-formaldehyde resin, melamine-reinforced urea-formaldehyde resin, tannin formaldehyde Resin, phenol-formaldehyde resin, polymeric diphenylmethane diisocyanate or mixtures thereof preferred. In addition, if necessary, additives such. As hydrophobing agents, anti-flaking agents, etc., are attached. Step c) can be carried out according to a preferred embodiment of the invention while introducing hot air / hot steam. Reference is made to DE 10 2012 101 716.6. Alternatively, the present invention also relates to a process for producing a wood and / or composite sheet according to the invention, comprising the steps of a) producing the intermediate layer

 b) bonding the intermediate layer with the cover layers

In this case, thus Verpressschritte run separately if necessary; in the event that the cover layers z. As aluminum included, here account for the Verpressschritte steps for the outer layers. In the intermediate layer, popcorn granules are preferably prepared as described above. Suitable binders are also the materials described above.

The abovementioned and the claimed components and components to be used according to the invention described in the exemplary embodiments are not subject to special conditions in terms of size, shape, material selection and technical design, so that the selection criteria known in the field of application can be used without restriction.

Further details, features and advantages of the subject of the invention will become apparent from the dependent claims and from the following description of the accompanying examples and drawings, in which - by way of example - several embodiments of inventive lignocellulose-containing moldings are shown. In the drawings, which refer to the examples, FIG. 1 shows a diagram of a particle size distribution of a popcorn granulate which was used in the examples according to the invention. I. Preparation of Popcom Granules

Starting material for the following material examples is grain corn; alternatively, however, other starchy grains may be used as well. For the production of a plate-suitable granulate with a low bulk density, feed corn kernels are first crushed and the grain fragments are subsequently expanded under pressure and temperature according to the Bichse method (WO 1999042005A1) to a defined process. The popcorn granules produced in this way are now fractionated, so that a granulate having particle sizes of 0.5 mm to 8 mm and a bulk density of about 30 kg / m ³ to 70 kg / m ³ is present. Alternatively, starchy grains may be expanded by means of a microwave oven or other common methods.

In order to obtain a comparable to the above-mentioned method granules, the expanded grain is comminuted in further steps and fractionated. FIG. 1 shows a grain size distribution suitable for producing expanded corn kernel-based composite materials and as used in the following examples.

Π. Production of the intermediate layer

For the preparation of the intermediate layer (bulk density of 200 kg / m ³ and 300 kg / m ³ ), the following procedure was used

In addition to the popcorn granules, a binder liquor based on urea-formaldehyde resin (UF resin) was used, as is commonly used for the industrial production of wood-based materials. In addition to the eigentlichem UF resin (. Eg KAURTT ^® 350 from BASF AG), these binders liquor contains ammonium sulfate solution (40% - strength) and in some cases water repellents (HYDROWAX 138 ^® SASOL GmbH). The glue liquor of the material plates described below consisted of popcorn granules, 8.0% UF solid resin relative to ator popcorn granules, 1% ammonium sulfate solution (hardener) based on dry solid resin. As alternative binders, other thermoset-curing binder liquors based on melamine-formaldehyde resin (MUF resin), phenol-formaldehyde resin (PF resin) and mixed resin systems prepared therefrom, natural binder systems based on tannins or proteins and isocyanates such. B. PMDI used. Two different processes were used to compress the glued popcorn granule cake: a) The glued popcorn granule cake is pressed under heat at 120 ° C. to 200 ° C. with a press time factor of 12 s / mm in a hot press with conductive heat transfer. b) The Popcomgranulatkuchen is pressed cold to the desired final dimensions.

The curing of the binder is then carried out by hot air / hot steam is passed through the pressed granules cake. In addition to thermosets, this process technology also makes it possible to use thermoplastic binders, such as, for example, PVAC or PP or PE supporting fibers. This process is particularly suitable for slab densities below 200 kg / m ³ , since it must be ensured that the cold pre-pressed granules cake can flow through with hot steam / hot air.

Method a)

The material plates prepared according to the point a) using a hot press with a plate density between 130 kg / m ³ and 300 kg / m ³ were examined with regard to their transverse tensile strength and thermal conductivity. The results are summarized in Tables 1 and 2.

Tab. 1: Some physico-technological properties of hot-pressed UFC resin (8.0% based on atro) bonded popcorn composite panels with a thickness of 20 mm

 Method b)

The material plates prepared according to the point b) using a hot air / hot steam press with a plate density between 80 kg / m ³ and 200 kg / m ³ were examined for their transverse tensile strength and thermal conductivity. The results are summarized in Tables 3 and 4. Of all plates under Example II, the flexural strengths were measured according to DIN EN 310; All produced material plates consistently have a low flexural strength of about 1.0 to 2.5 N / mm ² , so that applications with supporting functions are excluded.

ΙΠ. Production of the wood and / or composite panels according to the invention

The wood and / or composite panels of the invention were now starting from the under Π. produced intermediate layers, each with a weight fraction of 2 x 20% for the outer layers and 60% for the intermediate layer. a) Production in a one-step process

In this process, the coverstock material was glued separately. For this purpose, all binders mentioned above come into question, in the sequence (Table 5) UF resin is used as a binder as an example.

From the glued material is scattered in the order cover layer, intermediate layer, cover layer, a material cake and pre-compressed. The curing of the binder is finally carried out in a hot press at temperatures of 120 ° C to 200 ° C and a pressing time factor of 6 mm / s to 12 mm / s. The material cake was pressed using spacer strips to material plates with a thickness of 20 mm.

The determined strengths of the plates produced in this way (Table 6) show that the low bending strength of the material plates made of popcorn can be significantly increased by applying a cover layer of wood fibers / shavings, so that, for example, with cover layers made of wood fibers, a bending strength of approx. 16 N / mm ² , which clearly exceeds the requirements for chipboard for furniture construction of 11.0 N / mm ² according to EN 312.

Thus one can see the astonishingly increased bending strength of all plates according to the invention. b) Production in a two-stage process

For the production of bending-loadable material plates from popcorn granules in a two-stage process, the plates produced under Ex. 1 after their production and Conditioning first glued at a temperature of 20 ° C and a relative humidity of 65% using a suitable binder (epoxy resin, polyurethane, etc.) with cover layers of different materials. This results in a sandwich structure which has different properties depending on the cover layers used. As cover layers z. As thin slabs or thin-HDF, plywood, HPL or metal sheets in question. In the following Table 7 some mechanical-technological properties are listed for sandwich panels with a core layer of expanded maize and different cover layers:

Thus one can see the astonishingly increased bending strength of all plates according to the invention.

The individual combinations of the components and the features of the already mentioned embodiments are exemplary; the exchange and substitution of these teachings with other teachings contained in this document with the references cited are also expressly contemplated. The person skilled in the art recognizes that variations, Modifications and other embodiments described herein may also occur without departing from the spirit and scope of the invention.

Accordingly, the above description is illustrative and not restrictive. The word "comprising" used in the claims does not exclude other ingredients or steps The indefinite article "a" does not exclude the meaning of a plural. The mere fact that certain measures are recited in mutually different claims does not make it clear that a combination of these dimensions can not be used to advantage. The scope of the invention is defined in the following claims and the associated equivalents.

Claims

CLAIMS 1. Wood and / or composite board comprising an upper and a lower  Covering layer and an intermediate layer, wherein the intermediate layer contains popcorn and the upper and lower cover layers have a modulus of elasticity (modulus of elasticity) of 1 1 kN / mm ^{2 to} ≦ 70 kN / mm ² . 2. wood and / or composite board according to claim 1, wherein the lower and / or upper cover layer have a density of ≥ 0.5 g / cm ^{3 to} ≤ 3.0 g / cm ³ . 3. wood and / or composite board according to claim 1 or 2, wherein the proportion of the cover layers of ≥ 1% to ≤50% of the total wood and / or composite board according to the invention (wt / wt) is. The wood and / or composite panel according to any one of claims 1 to 3, wherein the intermediate layer is ≥60% (w / w) of popcorn. 5. Wood and / or composite board according to one of claims 1 to 4, wherein the popcorn has a particle size distribution, wherein ≥ 50% and ≤ 90% of Popcorns have a grain size of≥ 2 mm and≤ 10 mm. 6. wood and / or composite sheet according to one of claims 1 to 5, wherein the lower and / or upper cover layer predominantly of a material selected from the group consisting of wood chips or - fibers, lignocellulose-containing chips and / or fibers (such as. from hemp, flax, etc.), or from melamine foil, HPL (high pressure laminates), CPL (continuous pressure laminates), chipboard (eg thin chipboard), fibreboard (thin HDF), aluminum plate / sheet, metal plate / sheet metal, sheet metal, plywood, veneer, fiberglass, carbon fiber, carbon fiber, ceramic and possibly other additives such. 7. Wood and / or composite board according to one of claims 1 to 6, wherein the popcorn of the intermediate layer has a particle size distribution, wherein ≥ 50% and 8. The wood and / or composite panel according to any one of claims 1 to 7, wherein the popcorn of the intermediate layer has an average grain size distribution of ≥ 3 mm and ≤ 6 mm ≤ 90% of the popcorn. 9. A process for producing a wood according to the invention and / or  A composite panel comprising the steps of a) (optionally separately) coating the topcoat and interlayer precursor materials  b) presenting the glued topcoat and interlayer precursor materials  c) pressing to the wood and / or composite material plate according to the invention. 10. Process for producing a wood according to the invention and / or  Composite plate comprising the steps of a) producing the intermediate layer  b) bonding the intermediate layer with the cover layers