CN104136179A - Lignocellulosic materials with lignocellulosic fibers in the outer layers and expanded plastics particles present in the core, and process and use thereof - Google Patents

Abstract

The invention relates to lignocellulosic materials having a core and two outer layers, comprising in the core A)30% to 98% by weight of lignocellulose particles; B) 1% to 25% by weight of expanded plastics particles having a bulk density in the range from 10 to 150 kg/m3, C) 1% to 50% by weight of one or more binders selected from the group consisting of phenoplast resin, aminoplast resin, and organic isocyanate having at least two isocyanate groups, and D) 0% to 30% by weight of additives and in the outer layers E)70% to 99% by weight of lignocellulose fibers, F) 1% to 30% by weight of one or more binders selected from the group consisting of phenoplast resin, aminoplast resin, and organic isocyanate having at least two isocyanate groups, and G) 0% to 30% by weight of additives.

Description

Lignocellulosic material with lignocellulosic fibers in the outer layer and expanded plastic particles in the core, method and use thereof

The present invention relates to a lignocellulosic material having a core and two outer layers, wherein the core comprises expanded plastic particles and the outer layers comprise lignocellulosic fibers.

CH-A-370 229 discloses compression moldings having both low weight and compressive strength and consisting of wood chips or wood fibres, binder and porous, expandable or partially expandable plastic as filler.

A disadvantage of these compression molded parts is that they do not have a plastic-free outer layer, which means that conventional coating techniques (for example lining with furniture foils or short-cycle coating with melamine films) lead to poor results.

DE-U-20 2007 017 713 discloses a reduced-weight particleboard obtained by combining wood chips with uniformly distributed expanded polystyrene beads in the middle layer of the board.

The disadvantage of these materials is that the flexural strength, screw pullout resistance and surface quality are not sufficient for all applications.

WO-A-2008/046890 discloses lightweight single- and multi-layer wood-based materials comprising wood particles, polystyrene and/or styrene copolymer fillers and binders with a bulk density of 10-100 kg/ ^m3 agent. The filler is advantageously evenly distributed in the wood-based material. The wood-based material is produced from veneers, chips or fibers, more particularly chips and fibers.

The disadvantage of these materials is that for a given board density the performance improvements can only be obtained with increased amounts of glue and/or polymer and thus increased cost.

It is therefore an object of the present invention to remedy the above-mentioned disadvantages, more particularly to provide light-weight lignocellulosic materials with improved flexural strength, improved screw pull-out values and/or good surface properties, which Continues to have good processability as conventional high-density wood-based materials.

A new and improved lignocellulosic material has thus been found having a core and two outer layers comprising or preferably consisting of the following components in the core:

A) 30-98% by weight lignocellulosic particles;

B) 1-25% by weight of expanded plastic granules with a bulk density of 10-150 kg/m ³ ,

C) 1-50% by weight of one or more binders selected from the group consisting of phenoplast resins, aminoplast resins and organic isocyanates having at least two isocyanate groups, and

D) 0-30% by weight of additives,

and comprising or preferably consisting of the following components in the outer layer:

E) 70-99% by weight lignocellulosic fibers,

F) 1-30% by weight of one or more binders selected from the group consisting of phenoplast resins, aminoplast resins and organic isocyanates having at least two isocyanate groups, and

G) 0-30% by weight additives.

The expressions of weight percentages of components A, B, C, D, E, F and G refer to the dry weight of said components as a proportion of the total dry weight. The sum of the weight percent values of components A, B, C and D is 100% by weight. The sum of components E, F and G is likewise 100% by weight. Furthermore, not only the outer layer but also the core contains water, which is not taken into account in the weight value. The water may originate from residual moisture present in the lignocellulosic particles, from the binder, from additional water added e.g. to dilute the binder or to wet the outer layer, or from additives such as an aqueous curing agent solution Either an aqueous paraffin emulsion or originating from expanded plastic particles when the expanded plastic particles are expanded, for example using steam. The water content of the core and the outer layer may be up to 20% by weight based on 100% by weight of the total dry weight, ie 0-20% by weight, preferably 2-15% by weight, more preferably 4-10% by weight. The ratio of the total dry matter of the core to the total dry matter of the outer layer is generally 100:1-0.25:1, preferably 10:1-0.5:1, more preferably 6:1-0.75:1, more particularly 4 :1-1:1.

The lignocellulosic material (lignocellular material) of the present invention can be produced as follows:

Usually the components for the core and the components for the outer layer are mixed separately from each other.

For the core, lignocellulosic particles A may be combined with components B, C and D and/or component constituents contained therein (i.e. for example two or more constituents from one component, such as substances or compounds) in any desired order. Components A, B, C and D may in each case consist of one, two (A1, A2 or B1, B2, or C1, C2 or D1, D2) or several components (A1, A2, A3 ,..., or B1, B2, B3,..., C1, C2, C3,..., or D1, D2, D3,...).

If the individual components consist of several constituents, these constituents can be added as a mixture or separately from one another. In the case of separate addition, the constituents may be added directly one after the other or at different points of time instead of directly one after the other. For example when component C consists of two components C1 and C2, this means that C2 is added immediately after C1 or that C1 is added immediately after C2, or one or more other components or components, such as component B, Add between additions of C1 and C2. It is also possible to premix the components and/or constituents with other components or constituents prior to addition. For example, additive component D1 can be added to binder C or added to binder component C1 and this mixture then added to the actual mixture.

Preferably, the expanded plastic particles B are first added to the lignocellulosic particles A, and the mixture is then mixed with the binder C or two or more binder components C1, C2, etc. When two or more binder components are used, they are preferably added separately from each other. Additive D is preferably partly mixed with binder C or binder components, ie components from this component, eg substances or compounds, and then added.

For the outer layer, lignocellulosic fibers E are mixed with components F and G and/or the constituent components present therein (ie components from one component, eg substances or compounds) in any desired order. The same mixture or two different mixtures, preferably the same mixture, can be used for the two outer layers.

When each component is composed of a plurality of constituent components, these components may be added as a mixture or separately from each other. At this point the constituents may be added directly one after the other or at different points in time instead of directly one after the other. Additive G is preferably partially mixed with binder F or binder components and then added.

The resulting mixtures A, B, C, D and E, F, G are laminated one on top of the other and compressed at elevated temperature by conventional methods to give lignocellulosic moldings. For this, a mat is produced on a carrier, said mat consisting of these mixtures in the sequence E, F, G/A, B, C, D/E, F, G ("sandwich construction") . Typically the mat is compressed at a temperature of 80-300°C, preferably 120-280°C, more preferably 150-250°C and a pressure of 1-50 bar, preferably 3-40 bar, more preferably 5-30 bar to form a molded article . In a preferred embodiment, the mat is cold pre-compressed prior to hot pressing. The compression can be carried out by any method known to the skilled person (cf. "Taschenbuch der Spanplatten Technik", H.-J. Deppe, K. Ernst, 4th edition, 2000, DRW – Verlag Weinbrenner, Leinfelden Echterdingen, pp. 232-254 pp. and examples in "MDF-Mitteldichte Faserplatten" H.-J. Deppe, K. Ernst, 1996, DRW-Verlag Weinbrenner, Leinfelden-Echterdingen, pp. 93-104). These methods make use of discontinuous pressing techniques, eg, on one- or multi-stage presses, or continuous pressing techniques, eg, on twin-belt presses.

The lignocellulosic material of the invention generally has an average density of 300-600 kg/m ³ , preferably 350-590 kg/m ³ , more preferably 400-570 kg/m ³ , more especially 450-550 kg/m ³ .

The lignocellulosic particles of component A are present in the lignocellulosic material of the core in an amount of 30-98% by weight, preferably 50-95% by weight, more preferably 70-90% by weight, and the base material thereof may be any Wood species or mixtures thereof, examples are spruce, beech, pine, larch, basswood, poplar, eucalyptus, locust, chestnut and fir wood or mixtures thereof, preferably spruce, beech or mixtures thereof, more particularly is spruce and may for example comprise wood parts such as planks, strips, chips, wood fibers, chips or mixtures thereof for the production of boards for particleboard, MDF (medium density fibreboard) and HDF (high density fibreboard), preferably Wood chips, wood fibers, wood chips and mixtures thereof, more preferably wood chips, wood fibers or mixtures thereof. The lignocellulosic particles can also be derived from woody plants such as flax, hemp, cereals or other annual plants, preferably flax or hemp. Particular preference is given to using wood chips of the type used for the production of particleboard. If a mixture of different lignocellulosic particles is used, for example a mixture of wood chips and wood fibers or a mixture of wood chips and wood chips, the proportion of wood chips is preferably at least 75% by weight, i.e. 75-100% by weight, more preferably at least 90% by weight, i.e. 90% by weight. -100% by weight. The average density of component A is generally 0.4-0.85 g/cm ³ , preferably 0.4-0.75 g/cm ³ , more particularly 0.4-0.6 g/cm ³ .

The raw materials for lignocellulosic pellets are generally wood from forestry thinning, forest residual, residual industrial wood and used wood, and also plants containing wood fibers. Processing to the desired lignocellulosic particles, for example wood particles such as wood chips or wood fibers, can be carried out according to known methods (for example M. Dunky, P. Niemz, Holzwerkstoffe und Leime, pp. 91-156, Springer Verlag Heidelberg, 2002) .

In the lignocellulosic material of the outer layer, the lignocellulosic fibers of component E are present in an amount of 70-99% by weight, preferably 75-97% by weight, more preferably 80-95% by weight, consisting of at least 75% by weight , ie 75-100% by weight of lignocellulosic fibers, preferably at least 85% by weight, ie 85-100% by weight, more preferably at least 95% by weight, ie 95-100% by weight. Most preferably only lignocellulose is used, ie 100% by weight lignocellulosic fibres. The raw materials used may be wood from all wood species or woody plants listed under component A. After mechanical comminution, fibers can be produced by grinding operations, for example after hydrothermal pretreatment. Fiber-forming methods are known, for example, from Dunky, Niemz, Holzwerkstoffe und Leime, Technologie und Einflussfaktoren, Springer, 2002, pp. 135-148. The average density of component E is generally 0.3-0.85 g/cm ³ , preferably 0.35-0.8 g/cm ³ , more particularly 0.4-0.75 g/cm ³ .

Component A may comprise 0-10% by weight, preferably 0.5-8% by weight, more preferably 1-5% by weight (at 0-0.5% by weight, preferably 0-0.4% by weight, more preferably 0-0.3% by normal small amount of water within the fluctuation range). The figures for this amount are based on 100% by weight of absolute dry wood matter and describe that component A is immediately after drying (by conventional methods known to the skilled person) together with the first component or the second component selected from B, C and D. The water content of a component or first mixture prior to mixing.

In a preferred embodiment, component E may comprise 0-10% by weight, preferably 0.5-8% by weight, more preferably 1-5% by weight (at 0-0.5% by weight, preferably 0-0.5% by weight, more preferably 0 A small amount of water in the normal low fluctuation range of -0.3% by weight). The figures for this amount are based on 100% by weight of absolute dry wood matter and describe that component E is immediately after drying (by conventional methods known to the skilled person) together with the first component or the first component selected from F and G The water content of the ingredients or first mixture prior to mixing.

In another preferred embodiment, component E may comprise 30-200% by weight, preferably 40-150% by weight, more preferably 50-120% by weight (at 0-20% by weight, preferably 0-10% by weight, more preferably 0-5% by weight fluctuation range) of water. The figures for this amount are based on 100% by weight absolute dry wood matter and describe the water content of component E immediately before mixing with the first component or first constituent ingredient or first mixture selected from F and G. In this embodiment, drying is carried out according to methods known to the skilled person after addition of all components and/or a part of the constituents; preferably the drying is performed after addition of all components.

Suitable expanded plastic particles (component B) include expanded plastic particles, preferably expanded thermoplastic particles, having a bulk density of 10-150 kg/m ³ , preferably 30-130 kg/m ³ , more preferably 35-110 kg/m ³ , more particularly 40-100 kg/m ³ (determined by weighing the defined volume filled with loose material).

The expanded plastic particles B are generally used in the form of spheres or beads having an average diameter of 0.01-50 mm, preferably 0.25-10 mm, more preferably 0.4-8.5 mm, more particularly 0.4-7 mm. In a preferred embodiment, the spheres have a small surface area per unit volume, eg in the case of spherical or spheroidal particles, and are advantageously closed-cell spheres. The proportion of open cells according to DIN ISO4590 is generally not more than 30%, ie 0-30%, preferably 1-25%, more preferably 5-15%.

Suitable polymers on which the expandable or expanded plastic particles are based are generally all known polymers which can be expanded or mixtures thereof, preferably thermoplastic polymers or mixtures thereof. Examples of highly suitable such polymers include polyketones, polysulfones, polyoxymethylenes, PVC (rigid and flexible), polycarbonates, polyisocyanurates, polycarbodiimides, polyacrylimides and Polymethacrylimides, polyamides, polyurethanes, aminoplast resins and phenolic resins, styrene homopolymers (hereinafter also referred to as "polystyrene" or "styrene polymers"), styrene copolymers, C ₂ -C ₁₀ olefin homopolymers, C ₂ -C ₁₀ olefin copolymers and polyesters. For the production of the olefin polymers, preference is given to using 1-alkenes, examples being ethylene, propylene, 1-butene, 1-hexene and 1-octene.

Polymers, preferably thermoplastic polymers, can additionally be mixed together or spatially separately with customary additives forming the basis of expandable or expanded plastic particles B) as auxiliaries, examples of the latter being UV stabilizers, antioxidants, Coatings, hydrophobizing agents, nucleating agents, plasticizers, flame retardants, soluble and insoluble organic and/or inorganic dyes, pigments and heat-impermeable particles such as carbon black, graphite or aluminum powder.

Component B can generally be obtained as follows:

Suitable polymers using or containing a foamable medium (also referred to as a "blowing agent") can expand by exposure to microwave energy, thermal energy, hot air, preferably steam, and/or pressure changes (the expansion typically Also known as "foaming") (Kuntstoff Handbuch 1996, Vol. 4, "Polystyrol", Hanser 1996, pp. 640-673 or US-A-5,112,875). During the course of this procedure, the blowing agent typically expands, increases in particle size, and forms a cellular structure. This expansion can be carried out in conventional foaming equipment commonly referred to as a "pre-foamer". Such pre-foamers may be permanently installed or may be portable. Expansion can be performed in one or more steps. In a one-step process, expandable plastic particles are usually expanded directly to the desired final size. In a multi-step process, the expandable plastic particles are generally first expanded to an intermediate size and then expanded to the desired final size via a corresponding number of intermediate sizes in one or more further steps. In contrast to expanded plastic particles, the aforementioned compact plastic particles, also referred to herein as "expandable plastic particles", generally do not have a cellular structure. The expanded plastic particles generally have a low residual blowing agent content of 0-5% by weight, preferably 0.5-4% by weight, more preferably 1-3% by weight, based on the total mass of plastic and blowing agent. The expanded plastic particles obtained in this way can be stored temporarily or can be used further without further intermediate steps for the production of component B according to the invention.

The expandable plastic particles can be expanded using all blowing agents known to the skilled person, examples of which are aliphatic _C3 - _C10 hydrocarbons such as propane, n-butane, isobutane, n-pentane, Isopentane, neopentane, cyclopentane and/or hexane and its isomers, alcohols, ketones, esters, ethers or halogenated hydrocarbons, preferably n-pentane, isopentane and cyclopentane , more preferably the commercially available pentane isomer mixtures of n-pentane and isopentane.

The amount of blowing agent in the expandable plastic particles is generally 0.01-7% by weight, preferably 0.01-4% by weight, more preferably 0.1-4% by weight, based in each case on the expandable plastic material containing the blowing agent particles.

A preferred embodiment uses styrene homopolymers (herein also referred to simply as "polystyrene"), styrene copolymers or mixtures thereof as the sole plastic in component B.

Such polystyrene and/or styrene copolymers can be prepared by any polymerization technique known to the skilled person; see for example Ullmann's Encyclopedia, 6th Edition, 2000 Electronic Release or Kunststoff-Handbuch 1996, Volume 4, "Polystyrol", No. 567 -598 pages.

Expandable polystyrene and/or styrene copolymers are generally produced in a conventional manner by suspension polymerization or by means of extrusion processes.

In the case of suspension polymerization, styrene can be polymerized, optionally with addition of further comonomers, in aqueous suspension in the presence of customary suspension stabilizers by means of free-radical-forming catalysts. Blowing agents and any other customary auxiliaries can be included in the initial charge of the polymerization or can be added to the batch during or after the polymerization. The resulting bead-shaped expandable styrene polymer impregnated with a blowing agent can be separated from the water phase, washed, dried and sieved after the end of the polymerization.

In the case of an extrusion process, the blowing agent can be mixed into the polymer, for example via an extruder, conveyed through a die plate and pelletized under pressure to form pellets or strands.

Preferred or particularly preferred abovementioned expandable styrene polymers or expandable styrene copolymers have a relatively low blowing agent content. Such polymers are also known as "low foaming agents". A process highly suitable for producing expandable polystyrene or expandable styrene copolymers with low blowing agent is described in US-A-5,112,875, which is hereby incorporated by reference.

As mentioned, styrene copolymers can also be used. Advantageously, these styrene copolymers contain at least 50% by weight, ie 50-100% by weight, preferably at least 80% by weight, ie 80-100% by weight, of copolymerized styrene, based on the plastic mass (without blowing agent). Examples of useful comonomers include α-methylstyrene, cyclohalogenated styrene, acetonitrile, esters of acrylic or methacrylic acid with alcohols having 1 to 8 carbon atoms, N-vinylcarbazole, maleic acid , maleic anhydride, (meth)acrylamide and/or vinyl acetate.

Polystyrene and/or styrene copolymers may advantageously comprise small amounts of copolymerized chain branching agents, in other words compounds having more than one double bond, preferably two double bonds, such as divinylbenzene, butadiene and/or Butylene Glycol Diacrylate. The branching agent is generally used in an amount of 0.0005 to 0.5 mol %, based on styrene. It is also possible to use mixtures of different styrene (co)polymers. Highly suitable styrene homopolymers or styrene copolymers are crystal-clear polystyrene (GPPS), high-impact polystyrene (HIPS), anionically polymerized polystyrene or high-impact polystyrene (A-IPS), styrene-alpha-methylstyrene copolymer, acrylonitrile-butadiene-styrene polymer (ABS), styrene-acrylonitrile (SAN), acrylonitrile-styrene-acrylate (ASA), methyl acrylate-butadiene-styrene (MBS), methyl methacrylate-acrylonitrile-butadiene-styrene (MABS) polymers or mixtures thereof, or with polyphenylene ether (PPE) use together.

Preference is given to using plastic particles, more preferably styrene polymers or styrene copolymers, more particularly styrene homopolymers, with a molecular weight of 70,000-400,000 g/mol, more preferably 190,000-400,000 g/mol, very preferably 210,000-400,000 g/mol mol.

These expanded polystyrene particles or expanded styrene copolymer particles can be used to produce lignocellulosic matter with or without other measures to reduce blowing agents.

Expandable polystyrene or expandable styrene copolymers or expanded polystyrene or expanded styrene copolymers are often provided with an antistatic coating.

The expanded plastic particles B are usually in a non-molten state even after compression to form the lignocellulosic material, which means that the plastic particles B usually do not penetrate or impregnate the lignocellulosic particles, but are distributed between them. Plastic particles B can usually be separated from the lignocellulosic by physical means, for example after comminuting the lignocellulosic material.

The total amount of expanded plastic particles B is generally 1-25% by weight, preferably 3-20% by weight, more preferably 5-15% by weight, based on the total dry matter of the core.

It has been found to be advantageous to match the dimensions of the aforementioned expanded plastic particles B to lignocellulosic particles, preferably wood particles A), or vice versa.

This matching is shown below by the correlation of the corresponding d' values (from the Rosin-Rammler-Sperling-Bennet function) of the lignocellulosic particles, preferably wood particles A, and expanded plastic particles B.

The Rosin-Rammler-Sperling-Bennet function is described, for example, in DIN66145.

The d' value is determined by first performing a sieve analysis analogously to DIN 66165 Parts 1 and 2 to determine the particle size distribution of the expanded plastic particles B and the lignocellulosic particles, preferably wood particles A.

The values from the sieve analysis were then plugged into the Rosin-Rammler-Sperling-Bennet function and d' was calculated.

The Rosin-Rammler-Sperling-Bennet function is:

R＝100*exp(-(d/d') ⁿ ))

The parameters are defined as follows:

R Residue remaining on the corresponding sieve tray (wt%)

d Granularity

d' Particle size at 36.8% by weight residue

n the width of the particle size distribution

Highly suitable lignocellulosic particles A, preferably wood particles, have a d' value according to Rosin-Rammler-Sperling-Bennet (d' is defined and determined as described above) of 0.1-5, preferably 0.3-3, more preferably 0.5 -2.75.

A highly suitable lignocellulosic material is obtained when lignocellulosic particles, preferably particles of wood particles A and expanded plastic particles B, satisfy the following relationship according to the d' value of Rosin-Rammler-Sperling-Bennet:

d' of granule A ≤ 2.5 x d' of granule B, preferably d' of granule A ≤ 2.0 x d' of granule B, more preferably d' of granule A ≤ 1.5 x d' of granule B, very preferably of granule A d' ≤ d' of particle B.

The total amount of binder C is 1-50% by weight, preferably 2-15% by weight, more preferably 3-10% by weight, based on the total mass of the core.

The total amount of binder F is 1-30% by weight, preferably 2-20% by weight, more preferably 3-15% by weight, based on the total dry mass of the outer layer.

The binders of components C and F can be selected from phenoplast resins, aminoplast resins and organic isocyanates having at least two isocyanate groups, wherein components C and F use the same or different binders or binders Mixtures, preferably different binders, particularly preferably the use of phenoplasts and aminoplasts in both cases. The weight figures in the case of aldolplast or aminoplast resins relate to the solids content of the respective component (according to Günter Zeppenfeld, Dirk Grunwald, Klebstoffe in der Holz-und by evaporating water at 120°C within 2 hours 2nd edition, DRW-Verlag, p. 268 determination), while in the case of isocyanates, more particularly PMDI (polymeric diphenylmethane diisocyanate), it concerns the isocyanate component itself, that is to say e.g. without solvent or emulsifying medium .

The term "bakelites" refers to synthetic resins or modified products obtained by condensation of phenols with aldehydes. In addition to unsubstituted phenol, derivatives of phenol are used in the manufacture of Bakelite resins. These include cresols, xylenols and other alkylphenols (such as p-tert-butylphenol, p-tert-octylphenol and p-tert-nonylphenol), arylphenols (such as phenylphenol and naphthol) and diphenols ( divalent phenol) (such as resorcinol and bisphenol A). The most important aldehyde component is formaldehyde, which is used in various forms, including aqueous solutions and solid paraformaldehyde, and also formaldehyde-derived compounds. Other aldehydes such as acetaldehyde, acrolein, benzaldehyde and furfural are used to a more restricted extent, as is the case with ketones. Bakelite resins can be modified by chemical reaction of methylol or phenolic hydroxyl groups and/or by physical dispersion in the modifier (EN ISO 10082).

Preferred phenoplast resins are phenol/aldehyde resins, most preferably phenol-formaldehyde resins. Phenol-formaldehyde resins (also called PF resins) are known, for example, from Kunststoff-Handbuch, 2nd edition, Hanser 1988, Vol. 10, "Duroplaste", pp. 12-40.

All aminoplast resins known to the skilled worker, preferably those known for the production of wood-based materials, can be used as aminoplast resins. Such resins and also their preparation are described, for example, in Ullmanns der technischen Chemie, 4th revised and expanded edition, Verlag Chemie, 1973, pp. 403-424 "Aminoplaste" and Ullmann's Encyclopedia of Industrial Chemistry, Vol. A2, VCH Verlagsgesellschaft, 1985, pp. 115-141 "Amino Resins ", also in M. Dunky, P. Niemz, Holzwerkstoffe und Leime, Springer 2002, pp. 251-259 (UF resins) and pp. 303-313 (MUF and UF with small amounts of melamine). In general, they are compounds having at least one amino or urea group optionally partially substituted with an organic group (urea groups are also called carboxamide groups), preferably urea groups, preferably urea or melamine, and aldehydes, preferably formaldehyde polycondensation products. Preferred polycondensation products are urea-formaldehyde resins (UF resins), melamine-formaldehyde resins (MF resins) or melamine-containing urea-formaldehyde resins (MUF resins), more preferably urea-formaldehyde resins, examples of which are ® from BASF SE Glue products.

Particularly preferred polycondensation products are those in which the molar ratio of aldehyde to amino and/or ureido groups optionally partially substituted with organic groups is from 0.3:1 to 1:1, preferably from 0.3:1 to 0.6:1, more preferably from 0.3:1 - 0.55:1, very preferably those from 0.3:1 to 0.5:1. When aminoplasts are used in combination with isocyanates, the molar ratio of aldehyde to amino and/or ureido groups optionally partially substituted with organic groups is from 0.3:1 to 1:1, preferably from 0.3:1 to 0.6:1, more preferably from 0.3 :1-0.45:1, very preferably 0.3:1-0.4:1.

The aminoplast resins are usually used in liquid form, usually as a solution with a concentration of 25-90% by weight, preferably as a solution with a concentration of 50-70% by weight, preferably as an aqueous solution, but can also be used in solid form.

The solids content of the liquid aqueous aminoplast resin can be determined according to Günter Zeppenfeld, Dirk Grunwald, Klebstoffe in der Holz-und 2nd Edition, DRW-Verlag, p. 268 Determination.

The components of binder C and binder F can themselves be used alone, ie for example aminoplast resins or organic isocyanates or PF resins as the sole components of binder C or binder F. In addition, however, it is also possible to use the resin components of binder C and binder F as combinations of two or more components of binder C and/or binder F; these combinations preferably comprise aminoplast resins and /or Bakelite resin.

In a preferred embodiment, a combination of aminoplast and isocyanate can be used as binder C. The total amount of aminoplast resin in the adhesive C here is 1-45% by weight, preferably 4-14% by weight, more preferably 6-9% by weight, based on the total dry mass of the core. Organic isocyanates, preferably oligomeric isocyanates with 2-10, preferably 2-8 monomer units and an average of at least one isocyanate group per monomer unit, more preferably PMDI. The total amount in the binder C is based on the core The total dry mass is 0.05-5% by weight, preferably 0.1-3.5% by weight, more preferably 0.5-1.5% by weight.

Components D and G may each independently of one another comprise different or identical, preferably identical, curing agents known to the skilled person, or mixtures thereof. If the adhesives C and/or F comprise aminoplast resins or phenoplast resins, these components are generally used. These curing agents are preferably added to the binders C and/or F at, for example, 0.01-10% by weight, preferably 0.05-5% by weight, more preferably 0.1-3% by weight, based on the total amount of aminoplast resin or phenoplast resin.

Curing agents for aminoplast resin components or phenoplast resin components are understood herein to include all compounds of any molecular weight which accelerate or cause the polycondensation of aminoplast resins or phenoplast resins. One class of highly suitable curing agents for aminoplast resins or phenol-formaldehyde resins are organic acids, inorganic acids, acidic salts of organic acids and acidic salts of inorganic acids, or acid-forming salts, such as ammonium salts or acidic salts of organic amines. Such components can of course also be used in mixtures. Examples are ammonium sulfate or ammonium nitrate or organic or inorganic acids such as sulfuric acid, formic acid or acid regeneration substances such as aluminum chloride, aluminum sulfate or mixtures thereof. A preferred class of curing agents for aminoplast or phenoplast resins are organic or inorganic acids such as nitric acid, sulfuric acid, formic acid, acetic acid, and polymers with acid groups such as homopolymers of acrylic or methacrylic acid or maleic acid compounds or copolymers.

Bakelite resins, preferably phenol-formaldehyde resins, can also be alkylenically cured. Preference is given to using carbonates or hydroxides such as potassium carbonate and sodium hydroxide.

Other examples of hardeners for aminoplast resins are known from M.Dunky, P.Niemz, Holzwerkstoffe und Leime, Springer 2002, pages 265-269, while hardeners for phenoplast resins, preferably phenol-formaldehyde resins Further examples are known from M. Dunky, P. Niemz, Holzwerkstoffe und Leime, Springer 2002, pp. 341-352.

The lignocellulosic material according to the invention may contain other commercially customary additives and additives known to the skilled person as component D in an amount of 0-10% by weight, preferably 0.5-5% by weight, more preferably 1-3% by weight and component G, which independently of one another are identical or different, preferably identical additives, examples being hydrophobizing agents such as paraffin emulsions, antifungal agents, formaldehyde scavengers such as urea or polyamines and flame retardants.

The thickness of the lignocellulosic material according to the invention with expanded plastic particles in the core and lignocellulosic fibers in the outer layer varies with the field of application and is generally 0.5-100 mm, preferably 10-40 mm, more particularly 15-20 mm .

In a preferred embodiment of the invention, the expandable plastic particles B are present in the core in a non-uniform distribution. This means that the weight ratio X of expanded plastic particles B to lignocellulosic particles A in the outer region of the core ("outer") is different than in the inner region of the core ("inner") expanded plastic particles B and lignocellulosic particles A The weight ratio Y of lignocellulosic particles A, in other words, is greater or smaller in the outer region ("outer") of the core than in the inner region ("inner") of the core. The inner region of the core is generally separated from the two outer regions of the core by a face extending parallel to the plane of the plate. The inner region of the core is understood to represent 20-80% by weight, preferably 30-70% by weight, more preferably 40-60% by weight, more particularly 45-55% by weight, very preferably 50% by weight, of the total dry mass of the core % and the region between two outer regions. The two outer regions can have the same mass, in other words in each case 25% by weight, or approximately the same mass, based on the total dry mass of the core, ie 25.01:24.99-25.99:24.01% by weight, preferably 25.01:24.99-25.8: 24.2%, more preferably 25.01:24.99-25.6:24.4%, more particularly 25.01:24.99-25.4:24.6%, or different masses, i.e. 26:24-40:10% by weight, preferably 26:24-30:20 % by weight, more preferably 26:24-27:23% by weight, more particularly 26:24-26.5:23.5% by weight. The sum of the inner region and the two outer regions of the core is 100% by weight. To determine the weight ratio X of expanded plastic particles B to lignocellulosic particles A in the outer regions of the core, all expanded plastic particles B and all lignocellulosic particles A contained in the two outer regions are used. The ratio X' describing the ratio of plastic particles B to lignocellulosic particles A in one of the two outer regions can then be different or the same as the ratio X" describing the ratio in the other of the two outer regions.

In the material of the invention, the weight ratio X of expanded plastic particles to lignocellulosic particles in the outer region ("outer") of the core is the same as in the inner region ("inner") of the core. The ratio Z between the weight ratios Y of the cellulose particles is 1.05:1-1000:1, preferably 1.1:1-500:1, more preferably 1.2:1-200:1. In a further preferred embodiment, the ratio Z is 0.001:1-0.95:1, preferably 0.002:1-0.9:1, more preferably 0.005:1-0.8:1.

A non-uniform distribution of plastic particles B in the core can be produced as follows:

Various mixtures of components A, B, C and D containing different mass ratios of components A and B can be produced. These mixtures can be dispersed sequentially. In this case, mixtures with different mass ratios of components A and B should generally only be lightly mixed or not mixed. As a result a non-uniform distribution of the expanded plastic particles in the core of the lignocellulosic material can be obtained. In this regard, both wood pellets A and plastic pellets B can be previously divided into different fractions, for example by sieving. Each mixture may contain different fractions of wood particles A and/or plastic particles B.

In another embodiment, a non-uniform distribution of the plastic particles B in the core can be achieved by separate dispersion. Dispersion takes place here using means which ensure that the balls, depending on size and/or weight, collect in the outer or inner region of the core. This can be achieved, for example, by dispersing the mixtures A, B, C, D using a screening system. In a preferred embodiment, the system is equipped with screens of different hole sizes, which are arranged mirror-symmetrically. It is particularly preferred that the support carrying the material of the lower outer layer is transported below the dispersing device in which the sieve system is arranged: at the beginning of the dispersing device (in the production direction) there is a sieve with a small hole size, wherein the holes of the sieve The size increases inwards towards the center of the scattering station and decreases again at the end of the station. The setting of the screen means that small lignocellulosic particles enter the outer regions of the core, which are close to the outer layer, while large lignocellulose particles enter the inner regions of the core. At the same time, small plastic particles enter the outer regions of the core, which are close to the outer layer, and large plastic particles enter the inner regions of the core. Depending on the size distribution of lignocellulosic particles and plastic particles, this results in different lignocellulosic particle A and plastic particle B mass ratios. Such decentralized stations are described in EP-B-1140447 and DE-C-19716130.

For example, a lignocellulosic particle dispersion station may include two metering silos, each housing a plurality of back-scraping rakes. A bulk material ("core mix") consisting of different large particles A and components B, C and D can be fed into the metering chamber (for example from above). Arranged on the underside of the individual metering chambers may be a bottom belt which runs over two deflection rollers and which in each case forms a discharge unit for the core mixture together with discharge rollers. Below each discharge drum there can be a continuous scraper belt which is guided on two deflection rollers and whose lower tower can be guided in each case on sieve arrangements of different hole sizes, thus forming different sieve arrangements. segment. The sieve device together with the scraping belt forms a classifying device by which the lignocellulosic particles A and plastic particles B of the core mixture can be classified according to their size. The segments of the sieve device can be arranged in such a way that the fine lignocellulose particles A and/or the plastic particles B are each dispersed in the lower outer layer in those areas of the dispersing table which are held externally in the transport direction of the web (web) on, while coarse lignocellulosic particles A and/or plastic particles B are dispersed on the outer layer via the inner region of the classifying device (see EP-B-1140447 for details).

According to another advantageous embodiment of the invention, at least a part of the distributing section comprises in each case abrasive elements which rest on the surface of the sieve device and are guided abrasively on the surface of the sieve device when the distributing section is moved. Abrasive elements bearing against the surface of the sieve means for each distribution section or at least some of the distribution sections under gentle pressure further enhance the cleaning effect which occurs when the distribution sections are moved over the surface of the sieve means. At the same time, the abrasive elements increase the force component acting on the particles in a direction perpendicular to the screen surface, thereby increasing throughput. The transport device is preferably designed as a scraping belt, more particularly as a continuous scraping belt. In this way, the transport device can be constructed particularly simply and inexpensively. It is advantageous here that the scraping belt preforms the particles at least in a subregion in a direction perpendicular to the surface of the sieve device, allowing the particles to be dumped from the metering chamber via its feed unit through the scraping belt and onto the sieve device . This obviates the need for any complex construction of the feed unit. According to another advantageous embodiment of the invention, the scraping belt comprises drives, more particularly plate-shaped drives, which are preferably provided at regular intervals on a chain-like or belt-like continuous support element. In this case, the support element can be mounted centrally on the drive in each case. However, it is also possible to provide several support elements, more particularly two chain or belt support elements, which are each fixed in the laterally outer edge region of the drive. This increases the stability of the scraping belt designed according to the invention. Preferably, the drive is detachably fastened to the support element or support elements and/or has an air-tight design. This ensures that on the one hand the drives used can be optimally adapted to the sieve arrangement used and on the other hand old drives can be replaced by new ones. According to a further advantageous embodiment of the invention, the abrasive elements are in each case formed by a section of the drive. In this way, the design of the device according to the invention is particularly cost-effective, since no separate components are required for the abrasive elements. In particular, at least in its section forming the abrasive element, the driver has a flexible design, for example made of hard rubber. This allows the abrasive element to conform to the surface of the sieve device, thereby ensuring that the abrasive element bears against the surface of the sieve device under a certain pressure over its entire width and also over its entire range of movement, even if there are some irregularities in the sieve surface . According to another preferred embodiment of the invention, the drive has an abrasion-resistant design, at least in its section forming the abrasive element, and more particularly has an abrasion-resistant coating, such as a Teflon coating. The driver section forming the abrasive element can be designed in one piece with the driver or as a separate component. When the abrasive elements are designed as separate components, they are preferably mounted detachably on the drive so that they can be replaced when worn. According to another advantageous embodiment of the invention, the driver is formed of a water-repellent, non-stick material at least in its section forming the abrasive element. This prevents the particles wetted by the binder from remaining stuck to the drive, which would limit the pickup capacity of the dispensing section. According to another preferred embodiment of the present invention, the sieve arrangement comprises a sieve section with different sieve openings, more particularly two sieve sections. In this way, particles of different sizes are classified with sieve zones having sieve openings of different sizes. In this regard, in particular the sieve sections are arranged one behind the other in the direction of movement of the distribution section which can be moved on the surface of the sieve device, and preferably the sieve sections which are located in the direction of movement of the distribution section have a screen opening which is larger than The sieve openings of the sieve zone located in the opposite direction to the direction of movement. This ensures that as they pass over the sieve surface, particles with a small diameter pass through the sieve arrangement first, while in the following sieve zone the next largest particles pass through the sieve last. Thus, depending on the number of sieve sections and the size of the sieve openings, the desired classification of the particles is achieved. These classified particles can be dumped according to the sieve section into different collection devices for different particle sizes, or can be dumped, for example, into the underside of the sieve device and can be produced thereon with different particle sizes in its thickness. Distributing the web on a moving conveyor belt.

According to another advantageous embodiment of the invention, the continuous scraping belt is guided via two deflection rollers and thus the lower belt section runs directly on the screen device surface, while the upper belt section runs at a certain distance from the screen device surface. running, more particularly in each case substantially parallel to the surface of the sieve device. In this way, a particularly compact design is possible for the device according to the invention. Preferably at this time at least at one end of the scraping belt, more particularly in the region of the turning drum, pick-up means are provided to pick up the discharged particles. These particles may be alien bodies present in loose material, such as screws or nails; alternatively, they may be aggregates that exceed the maximum allowable size and are expelled and withdrawn so that even the largest screen openings of the screen device do not become clogged bodies or particles. According to another preferred embodiment of the invention, an intermediate base is provided at least in the region between the upper and lower belt sections, and the driver rests on this intermediate base with its end opposite to the section forming the abrasive element, This means that the tips guide in an abrasive manner on the intermediate base when the dispensing section is moved. In this embodiment, the bulk material which is first applied to this intermediate base from the metering chamber via its feed unit can be fed in a defined manner into a specific position between the deflection rollers. At this time, according to a preferred embodiment, the intermediate base can extend from one turning roller to the other turning roller on the opposite side in the moving direction of the upper belt section; Between the ends of the intermediate base of the sieve, an area previously in a direction perpendicular to the surface of the sieve device is formed for the particles. Especially if this area is formed by another sieve arrangement with larger mesh openings, there can be a preliminary deposit of foreign bodies or particles of a size larger than these mesh openings. Only those particles that pass through the other sieve device fall onto the lower sieve device, on which they are moved by means of the conveying device. According to a further preferred embodiment of the invention, there are two scraping strips located one behind the other in the longitudinal direction and the scraping strips are arranged in particular mirror-symmetrical to each other. Here it is advantageous to arrange distribution devices downstream of the feed unit of the metering chamber, more particularly in the form of shuttle distributors, and they can be used to feed the particles taken from the metering chamber through the feed unit to the two scrapers Belts, more particularly alternate feeds. With this configuration, the particles can be distributed to two different scraping belts starting from one metering chamber. Especially when the two scraping belts can be driven in opposite directions and thus the two upper belt sections can be moved in a mutually divergent manner and an intermediate seat is provided between the upper and lower belt sections in the manner already explained, it is possible to use the The particles applied by the distribution means to the respective intermediate bases are conveyed to the ends of the scraping belts lying in the opposite direction, where they are applied in each case to the sieve means arranged below the scraping belts. Given a suitable size of the screen openings of these screen devices, especially when the size of the screen openings increases in the direction of movement of the lower belt section, the material of the core can be formed on the moving conveyor belt provided on the screen devices, and On which the lower outer layer has been dispersed, the core material is formed such that fine lignocellulose particles A and/or plastic particles B aggregate in the outer layer of the core, while coarse lignocellulose particles A and/or plastic particles B aggregate in the inner layer of the core. Instead of a distribution device, for example, there may also be two metering chambers, by means of which the two scraping belts are charged with granules. In all embodiments, the sieve device and/or other sieve devices are preferably designed as vibrating screens or vibrating shaker screens. At this point, the loose material fed into the sieve arrangement is loosened further, which means that fine particles and subsequently medium-sized particles at a distance from the sieve pass more quickly to the sieve openings and pass through them (see DE-C-197 16 130).

Another preferred embodiment is the use of roller dispersion systems (roller screens) with specially contoured rollers. It is also preferred here to choose a symmetrical configuration, which means that small lignocellulosic particles A and/or small plastic particles B enter the outer regions of the core, which are close to the outer layer, while large lignocellulosic particles A and/or large plastic particles B enters the inner region of the core. A particularly preferred embodiment is the use of one or more ClassiFormer(TM) devices. Suitable is, for example, the Classiformer CC from Dieffenbacher, which has a symmetrical construction. Alternatively two Classiformers C facing each other and arranged one after the other can be used.

Lignocellulosic materials, such as wood-based materials, are inexpensive and resource-conserving alternatives to solid wood and have become very important especially in furniture making, for laminate flooring and as building materials. Usually used as raw material are wood particles of different thicknesses, examples being wood chips or wood fibers from various wood species. Such wood particles are usually compressed with natural and/or synthetic binders and optionally with the addition of other additives to form wood-based materials in the form of boards or strips.

Light-weight wood-based materials are important for the following reasons: Light-weight wood-based materials lead to easier handling of the product by the end consumer, for example when packaging, transporting, disassembling or constructing furniture. The lightweight wood-based material results in lower shipping and packaging costs and can also save material costs when producing the lightweight wood-based material. The use of lightweight wood-based materials in transport means can lead, for example, to lower energy consumption of these transport means. In addition, material-intensive decorative parts, thick worktops and side panels, for example in kitchens, can be produced more cost-effectively using lightweight wood-based materials.

There are many applications, such as in bathroom or kitchen furniture parts or in interior fittings, where lightweight and economical lignocellulosic materials are sought, which have improved mechanical properties, such as improved flexural strength and screw pullout values. Furthermore, such materials should have an excellent surface quality to allow the application of coatings with good properties, such as paint or varnish finishes.

Example

1. Production of foamed polymer particles

Expandable polystyrene Polystyrol from BASF SE Light 200 was used as raw material. Polystyrene granules were treated with steam and expanded to a bulk density of 50 g/l in a batch pre-expander. The expanded polymer particles (component B) obtained in this way were stored in air-permeable cloth bags at room temperature for 7 days before further use.

2. Production of wooden materials

Three different mixtures of raw materials were produced for each wood material board.

Mixture 1: Components E, F, G, for cover layer

Mixture 2: Components A, B, C, D for the outer area of the core

Mixture 3: Components A, B, C, D for the inner region of the core

Component B was omitted for Comparative Example 1, ie mixtures 2 and 3 now contained only components A, C and D. For Comparative Example 2 and Inventive Example 3, Mixtures 2 and 3 were the same. In comparative examples 1 and 2, mixture 1 contained wood shavings as component E, whereas in all other examples contained wood fibers.

The mixtures were each produced in a laboratory mixer, in which first the solid ingredients were introduced and mixed. Liquid ingredients are premixed in containers and then sprayed.

For mixture 1, a fine covering layer was used, ie spruce shavings with a moisture content of 5.9% or wood fibers with a moisture content of 2.8% (component E).

For mixtures 2 and 3, an intermediate layer was used, ie wood shavings with a moisture content of 3.2% (component A).

67% solids from BASF SE Glue 347 was used as adhesive (components C and F). For mixture 1, 40 parts by weight of water and 1 part by weight of a 52% strength ammonium nitrate solution (based in each case on 100 parts by weight of Kaurit gum 347) were added to the gum and then applied to the solids content of the mixture. For mixtures 2 and 3, 4 parts by weight of a 52% strength ammonium nitrate solution (based on 100 parts by weight of Kaurit gum 347) were added to the gum and then applied to the solids content of the mixture.

For the cover layer (mixture 1 ), the amount of glue mixture was set such that a 10% glue addition was obtained, ie 10 parts by weight glue (based on solids) per 100 parts by weight E (based on solids).

For the core (for both the outer zone of the core - mix 2 - and the inner zone - mix 3), the amount of gum mix was set such that a gum addition of 8.0% was obtained, i.e. 8.0 parts by weight gum (based on solids) per 100 wt. Mixture of Parts A and B (solids basis).

The mixture is then placed one above the other in a 30 x 30 cm mold in a layered fashion to obtain a symmetrical structure consisting of 5 layers (sequence: mixture 1, mixture 2, mixture 3, mixture 2, mixture 1). wooden material pad. The amounts are chosen such that the weight ratio of the layers (based on dry matter) is in each case 15.5:20.5:28:20.5:15.5.

In all examples comprising Component B, the total amount of Component B contained in the inner 3 layers is the same mass ratio (on a solids basis) as the total amount of Component A contained in the inner 3 layers.

The total weight of the mat of wood material is chosen such that the desired density is obtained at the end of the pressing process at a specified thickness of 18.5 mm.

The wooden material mat is then cold pre-compacted and pressed in a hot press. Set a thickness of 16mm here. The pressing temperature was in each case 210° C. and the pressing time 210 s.

3. Detection of wooden materials

3.1 Density

Density was measured according to EN1058 24 hours after production.

3.2 Transverse tensile strength

The determination of transverse tensile strength is carried out according to EN319.

3.3 Flexural strength and E flexural modulus

The determination of flexural strength and E-flexural modulus is carried out according to DIN EN310.

3.4 Screw pullout resistance

The determination of screw pullout resistance is carried out according to DIN EN320. The screw pullout resistance of the surface is measured only.

3.5 Lift-off strength

The determination of the peel strength as a measure of the surface quality is carried out according to DIN EN311.

Example

Examples 1 and 2: Comparative examples using wood shavings in the cover (with and without expanded polymer particles in the core)

Embodiment 3-7: embodiment of the present invention

Claims (9)

1. A lignocellulosic material having a core and two outer layers, wherein in said core comprises: A) 30-98% by weight lignocellulosic particles; B) 1-25% by weight of expanded plastic granules with a bulk density of 10-150 kg/m ³ , C) 1-50% by weight of one or more binders selected from the group consisting of phenoplast resins, aminoplast resins and organic isocyanates having at least two isocyanate groups, and D) 0-30% by weight of additives, And in said outer layer include: E) 70-99% by weight lignocellulosic fibers, F) 1-30% by weight of one or more binders selected from the group consisting of phenoplast resins, aminoplast resins and organic isocyanates having at least two isocyanate groups, and G) 0-30% by weight additives. 2. A lignocellulosic material having a core and two outer layers, comprising in said core: A) 30-98% by weight lignocellulosic particles; B) 1-25% by weight of expanded plastic granules with a bulk density of 10-150 kg/m ³ , C) 1-50% by weight of one or more binders selected from the group consisting of phenoplast resins, aminoplast resins and organic isocyanates having at least two isocyanate groups, and D) 0-30% by weight of additives, and in said outer layer include: E) 70-99% by weight lignocellulosic fibers, F) 1-30% by weight of one or more binders selected from the group consisting of phenoplast resins, aminoplast resins and organic isocyanates having at least two isocyanate groups, and G) 0-30% by weight additives, Wherein the expanded plastic particles B are present in the core in a non-uniform distribution. 3. A lignocellulosic material having a core and two outer layers, wherein the core consists of: A) 30-98% by weight lignocellulosic particles; B) 1-25% by weight of expanded plastic granules with a bulk density of 10-150 kg/m ³ , C) 1-50% by weight of one or more binders selected from the group consisting of phenoplast resins, aminoplast resins and organic isocyanates having at least two isocyanate groups, and D) 0-30% by weight of additives, And the outer layer consists of the following components: E) 70-99% by weight lignocellulosic fibers, F) 1-30% by weight of one or more binders selected from the group consisting of phenoplast resins, aminoplast resins and organic isocyanates having at least two isocyanate groups, and G) 0-30% by weight additives, Wherein the expanded plastic particles B are present in the core in a non-uniform distribution. 4. A method of producing a lignocellulosic material according to any one of claims 1-3, comprising mixing components E, F and G for the outer layer and components A, F and G for the core B, C and D, where a heterogeneous mixture of components A and B is produced. 5. A method of producing a lignocellulosic material according to any one of claims 1-3, comprising mixing components E, F and G for the outer layer and components A, F and G for the core B, C and D, wherein the material for the core is dispersed in such a way that a heterogeneous mixture of components A and B is formed. 6. Process for producing lignocellulosic material according to claim 4 or 5, wherein said heterogeneous mixture of components A and B is obtained by successively dispersing different mixtures with different A/B ratios. 7. Process for producing lignocellulosic material according to any one of claims 4-6, wherein said heterogeneous mixture of components A and B is obtained by separately dispersing a mixture comprising A, B, C and D. 8. Use of lignocellulosic material according to any one of claims 1-4 in furniture making, laminate flooring and building materials. 9. Use of lignocellulosic material according to any one of claims 1-4 for the production of boards for furniture making, laminate flooring and building materials.