EP1575744B1 - Combination material and method for the production thereof - Google Patents

Abstract

The invention relates to a combination material which is produced from a mixture of non-melting fibrous and/or chip-shaped particles and meltable thermoplastic particles and/or duroplastic particles in a prehardened condition by applying heat and pressure. The inventive combination material contains thermally crosslinking binders based on aminoplast resins and/or phenolic resins.

Description

The invention relates to a combination material containing wood fibers or wood chips or both, and a method for its production. With the invention of claim 1 and 5 environmentally friendly arbitrarily shaped components are produced, which have over the known materials produced in presses increased moisture resistance.

Engineered wood products such as chipboard, Oriented Chipboard (OSB), High Density Fiberboard (HDF), and Medium Density Fibreboard (MDF) are currently produced from relatively high value wood grades, with the addition of custom-fit binders, usually dry. Special additives can impart properties such as reduced water absorption and thus reduced thickness swelling, low flammability and / or conditional resistance to biological damage to the materials. Binder formulations based on urea-formaldehyde resin (UF), melamine-urea-formaldehyde resin (MUF), melamine-urea-phenol-formaldehyde resin (MUPF), phenol-formaldehyde resin (PF) or polymeric diisocyanates (PMDI) are used for industrial wood-based material production , To improve water repellency, up to 1.5% of water repellents (eg paraffin) are added. The solids content of the binders in the UF, MUF, MUPF or PF resins is 5 to 20%, in the PMDI adhesives about 2 to 6%, in each case based on atro wood particle mass / Deppe, Ernst 1996: MDF - medium-density fiberboard, DRIN-Verlag Weinbrenner GmbH & Co., Leinfelden-Echterding s; Deppe, Ernst 2000: Taschenbuch der Spanplattentechnik, 4th edition, DRW-Verlag Weinbrenner GmbH & Co., Leinfelden-Echterding en / .

More recently, solutions have also been developed to work through the commonly used resins in fibrous or particulate based materials Lackkoagulate or powder coating waste to replace, for example, for insulating mats or door lining elements in the automobile ( DE 3936974 C1 ), Nonwoven molded parts ( DE 4441765 A1 . US 6,008,150 A ) or wood particle materials ( DE 10129750 A1 . WO 02/100616 A1 ). It reveals DE 4441765 A1 ostensibly a binder composition for producing nonwoven molded articles comprising at least 70% by weight of powder coating waste and up to 30% by weight of phenolic resin. The nonwoven moldings are made by chemically bonding nonwoven fabrics in molds with the binder. For this purpose, the binders are added to the fiber webs, wherein the curing of the binder during the shaping of the fiber webs can be accelerated to moldings in a hot mold by the use of superheated steam. The superheated steam can be introduced into the mold at a pressure of 1 to 15 bar. The disadvantage of these solutions is that higher pressing temperatures and / or uneconomically long pressing times are required for the production of the materials because of the heat energy required for crosslinking the substitutes.

Out US 6,344,504 B1 For example, a wood-like material prepared by extrusion is known which contains at least 16% of a thermoplastic material, preferably polyolefins. The use of polyolefins leads to improved moisture resistance. In FR 2 679 482 A1 It is proposed to use in such a material polyolefins, which are obtained from recycled material.

Since the materials are made by extrusion, the shape of the parts made of the material is based on profile shapes, i. limited to molded parts that are linear in at least one direction.

Furthermore, in US 5,435,945 A a method in which wood particles with plastic particles, which are made of a thermoplastic material and are preferably obtained from recycled material, mixed become. The mixture is then pressed at a temperature at which the plastic particles melt, in a hot press to form a combination material. In one variant, it is also proposed to add 3% of pulverulent PF resin to the mixture as adhesive.

On the one hand, the method has the disadvantage that it is difficult to prevent segregation of the pulverulent constituents before pressing, which can result in comparatively poor homogeneity of the composite material.

The invention has for its object to provide a combination material from which arbitrarily shaped parts can be produced, which should be cheaper and more environmentally friendly to produce and have a better moisture resistance.

This object is solved by the features of claims 1 and 5. Advantageous embodiments will become apparent from the claims 2 to 4.

According to the invention, a combination material is provided, which is made of a mixture of wood fibers and / or wood chips and meltable thermoplastic resin particles and / or thermosetting plastic particles in a precured state by means of a press under the action of heat and pressure and amplification 4 to 15% contains thermally crosslinking binders based on amino and / or phenoplast resins.

The meltable thermoplastic particles may consist of powdery or granular polyolefins. The polyolefins are preferably polyethylene or polypropylene.

The pulverulent or granular polyolefins are, in a particularly preferred embodiment, comminuted recycling material, the comminuted recycling material advantageously having a purity of at least 90%.

The thermosetting plastic particles are preferably made of thermosetting powdery or granular resins such as acrylates, epoxy resins, polyesters and polyurethanes or mixtures of these resins.

The binders used for reinforcement are expediently products based on urea-formaldehyde resin, melamine-formaldehyde resin, phenol-formaldehyde resin or mixed condensates of these resins or mixtures of these binders.

The combination material according to the invention has improved properties. Of particular importance is the reduced hygroscopicity of the materials according to the invention containing wood fibers and / or wood chips.

According to the invention, moreover, a method for producing the composite material according to the invention is provided in which the non-meltable fibrous and / or chip-shaped particles are dried, glued with the thermally crosslinking binders used for reinforcement, mixed with the meltable thermoplastic and / or thermosetting plastic particles and then heated and compacted in a press, wherein the pressing temperature above the softening temperature of the thermoplastic resin particles and above the melting and reaction temperature of the thermosetting binder is and the pressing time is at least as long as the crosslinking time of the binder.

Conveniently, the polyolefins are comminuted prior to mixing into grains, powders, flakes, Schnipseln or agglomerates.

By gluing the non-meltable particles with the thermally crosslinking binder, a high cold tack and in particular ensures that the plastic particles stick to the chip-shaped particles during subsequent mixing, whereby segregation of the various particles is prevented. The resulting higher homogeneity leads to a general improvement of the material properties of the finished pressed composite material.

Further features and advantages of the invention will become apparent from the following examples.

embodiments

The invention will be explained in more detail below with reference to two exemplary embodiments.

example 1

A pine wood pulp for MDF in deep-tilling quality produced under standard industry cooker settings (temperature 175 ° C., residence time 4 min) is mixed with urea-formaldehyde resin with a solid resin content of 4% by mass and an addition of 1% by mass of paraffin dispersion (proportions in each case based on atro Wood fibers) glues. This is followed by a homogeneous mixing of the glued wood fibers with powdered polyolefins (recycled material) with a proportion of 150% by mass, based on atro wood fibers. After drying in a known manner, the fiber fleece formation, the pre-compression and compression with pressing time factors of 15 s / mm and pressing temperatures of 240 ° C to 4 mm thick, single-layer MDF. Comparatively, plates were also made without recycling material. After air conditioning in normal climate 20 ° C and 65% relative humidity, the following material properties were determined: with 150% recycled material without recycling material Bulk density kg / m ³ DIN EN 323 714 773 Transverse tensile strength N / mm ² DIN EN 319 0.84 0.44 Thickness swelling after 24 h water storage% DIN EN 317 6.3 37.1 Moisture content% DIN EN 322 3.9 7.9

Example 2

After being dried to a moisture content of about 2%, pinewood topcoat chips produced by industrial analogy are glued with urea-formaldehyde resin having a solid resin content of 4% by weight and an addition of 1% by weight of paraffin dispersion (proportions in each case based on atro wood chips). This is followed by a homogeneous mixing of the glued chips with powdered polyolefins (recycled material) with a share of 150% by weight, based on atro wood chips. Following the web formation and pre-compaction, the chip mats, which have a very good cold tack, are pressed with press time factors of 15 s / mm and pressing temperatures of 240 ° C. into 4 mm thick, single-layer fine chipboard. For comparison, plates were also prepared without polyolefin addition.

After conditioning in a standard climate of 20 ° C and 65% relative humidity, the following material properties were determined: with 150% recycled material without recycling material Bulk density kg / m ³ DIN EN 323 680 676 Transverse tensile strength N / mm ² DIN EN 319 1.11 0.38 Thickness swelling after 24 h water storage% DIN EN 317 5.7 52.1 Moisture content% DIN EN 322 3.7 9.2

Summary

The invention relates to a combination material. It is envisaged that the material is made from a mixture of wood fibers and / or wood particles and meltable thermoplastic resin particles and / or thermosetting plastic particles in a pre-cured state by means of a press under the action of heat and pressure and 4 to 15% reinforcing thermally crosslinking binder based on amino and / or phenoplast resins. The thermoplastic plastic particles consist of pulverulent or granular polyolefins in the form of comminuted recycled material. From the combination material environmentally friendly arbitrarily shaped components can be produced, which have an increased moisture resistance compared to the known materials produced in presses.

Claims (5)

1. A combination material, produced in presses under the action of heat and pressure from a mixture made of wood fibers and/or wood chips and thermoplastic particles, or a mixture of thermoplastic and duroplastic particles composed of thermally curing powdery or granular resins, wherein the thermoplastic particles are made of powdery or granular polyolefins in the form of comminuted recycling material, and for reinforcement purposes the combination material contains thermally cross-linking binding agents based on aminoplast and/or phenoplast resins having a mass content of 4 to 15%.
2. The material according to claim 1, characterized in that the polyolefins used are polyethylene or polypropylene.
3. A material according to claims 1 and 2, characterized in that the comminuted recycling material has a purity level of at least 90%.
4. The material according to claim 1, characterized in that the thermally curing powdery or granular resins are acrylates, epoxy resins, polyesters or polyurethanes or are composed of mixtures of these resins.
5. A method for producing the material according to claims 1 to 4, in which the wood fibers and/or wood chips are dried, glued with the thermally cross-linking binding agents used for reinforcement, mixed with the thermoplastic particles or a mixture of thermoplastic and duroplastic particles, and subsequently heated and compressed in a press, wherein the pressing temperature is above the softening temperature of the thermoplastic particles and above the melting and reaction temperatures of the thermally cross-linking binding agents, and the pressing duration is at least as long as the cross-linking duration of the binding agents, wherein the polyolefins made of recycling material are comminuted before being admixed.