DE102004024566A1 - Water-resistant wooden construction material, e.g. chipboard or fiberboard for furniture production, having binder comprising formaldehyde resin and modified and/or destructured cereal flour - Google Patents

Abstract

In a wooden construction material (I) consisting of wood particles, aggregate and a binder (typically contained at 5-20% of the dry weight of (I)), the binder comprises (a) a synthetic formaldehyde resin component and (b) a natural component consisting of dry chemically modified and/or extrusion-destructured cereal flour, in an amount of at least 20%. An independent claim is included for the preparation of a wooden construction material (I') consisting of wood particles, aggregate and a binder by glueing the wood particles (after comminution and drying) with the binder, where glueing is carried out using cereal flour as a binder component.

Description

The The invention relates to a wood material used for furniture and interior design as well for applications is suitable in construction and for Production of moldings can be used.

Of the Material consists in principle known manner of wood particles, binders and aggregates.

to Wood material production predominantly synthetic products such as urea-formaldehyde (UF), melamine-urea-formaldehyde (MUF) -, phenol-formaldehyde (PF), melamine-urea-phenol-formaldehyde (MUPF) resins and polymers Diisocyanates (PMDI) application.

Over 80% the produced wood materials are mixed with urea-formaldehyde or melamine reinforced Urea-formaldehyde resins produced. These adhesives are technical mature, very reasonably priced and now optimally adapted to the respective requirements. alternative Binders (e.g., tannin-formaldehyde resins) On the other hand, they could not yet prevail on the market, their share is less than 0.5%.

For the use of the wood materials in the wet or outdoor area must for Bonding polymeric diisocyanates, phenol, melamine-urea or Melamine-urea-phenol-formaldehyde resins are used.

The Requirements for the binders in the wood-based panel industry are high. superficial will the cheap Price-performance ratio called. The wood material manufacturers demand reactivities that enable a rational production. additionally is a small fluctuation range of the chemical composition as well as sufficient and long-term availability of outstanding Importance.

Although the synthetic binders currently in use for the manufacture of wood-based panels very well allow the production of wood-based materials with specific properties for different fields of use, they suffer from some disadvantages. In addition to the perspective decreasing availability of petroleum-based raw materials is the repeated emphasis formaldehyde release aminoplastgebundener chipboard when used indoors, although these now have a very low emission potential. In addition, increasing environmental awareness and skepticism about chemical manufacturing processes are increasing the trend towards using natural binders based on renewable resources for certain wood-based material applications. The use of renewable raw materials in the production of adhesives and binders helps to close the recyclable material cycle in the subsequent disposal of goods produced therefrom (eg paper, wood materials, cardboard) largely CO ₂ -neutral. The substitution of synthetic adhesives by binders based on renewable raw materials for wood-based material production is consequently also of great interest in regard to the disposal of both production residues and the wood-based materials themselves after expiry of their useful life.

When Episode in recent years, intensive studies on Use of natural Binder based on renewable raw materials for certain wood-based material applications carried out.

"Natural glues" on animal and Plant-based have been known since ancient times.

When alternative adhesives are natural soluble Suitable polymers, either thermally or by reaction with a reactive component to an insoluble form. The most common natural Binders can be broken down into proteins, polysaccharides (e.g., starch derivatives), Polyphenols (e.g., tannin, lignin) and resins and waxes.

From The carbohydrates, above all, the strength can be used as a binder become. To the strength, the consists of amylose and amylopectin, as a physically hardening To be able to use glue this must be available as a gel. Those existing in native strength Strong bonds are broken up by thermal or chemical means. Strengthen be u.a. as an adhesive and auxiliary for various gluing purposes - in particular in the paper industry - used.

Starch proved to be unsuitable as the sole binder for wood-based materials, since the crosslinking of the starches or carbohydrates requires relatively high temperatures and longer times. On the other hand, the use of starches as extender in UF resins has been beneficial for surface bonding proven, in addition to adhesive savings and glue punches can be avoided with very thin and porous veneers.

Likewise, the use of wheat flours as a filler in PF and UF resins has long been known; related sources and the discussion of advantages and disadvantages of such substitutions are out DE 102 53 455 A1 (P. 3, para. 0011 ff.).

With development of binders based on tannin-starch combinations Within the scope of a joint project, the WKI in Braunschweig and the IAP Teltow deals and possibilities the production and proportional use of native or chemical modified starches as a binder for Examined wood materials. Glue resins based on tannins and certain hydrolytically degraded starches were evident in the preparation of chipboard and MDF. Depending on the strength of starch different strength classes were achieved (N. N .: wood binder from renewable raw materials. Holz-Zentralblatt 125 (1999), p. 1579). in the As a result of this work, up to 20% of a tannin binder could be used by enzymatically degraded or acid-hydrolysed starches replace. However, micrographs show that no crosslinking of the Tannins with the starch hydrolyzate was achieved. The chipboard with tannin starch binder corresponded in terms of transverse tensile strength after 2 h boil and thickness swelling not the requirements for V 100 grades according to DIN 68763.

at Thole (Thole, V .: Development of novel pressing and hardening technologies for hydrous or water-needy Adhesive systems. In: Adhesives for woodworking materials and molded fiber parts - New developments, applications and analysis techniques. Schmidt-Druckerei, Braunschweig 1997) itself when using starch as a binder for Wood materials the problem of high water demand to swell the strength. It are elaborate chemical, physical and procedural measures necessary, Nevertheless, the Spanfeuchte before pressing is much higher than at the usual used technology. For the hot pressing starch-bound Particleboard with high chip moisture therefore becomes a three-phase pressure diagram required. It is sought by Thole, the press water requirement to reduce so far that Spanfeuchten below 20% for gluing suffice.

Studies on the suitability of potato starch substrate as a binder for insulation materials or packaging materials with densities of 150 to 250 kg / m ³ were the work of TU Dresden to the content. The material properties of the natural fiber insulating materials are comparable or even more favorable with mineral wool. However, the incorporation of protective agents (eg, quaternary ammonium salts) is necessary for the achievement of sufficient biological resistance.

Also when combined completely Binder based on synthetic raw materials natural Binders must be with a certain reduction in moisture resistance of binding (Fechtal, M., Riedl, B .: Use of Eucalyptus and Acacia mollissima Bark - Extract Formaldehyde in Particleboard Manufacture. Holzforschung 47 (1993), pp. 349-357). By Targeted selection and modification of natural binders can be this Loss of moisture resistance, also considering a reasonable price-performance ratio, as low as possible being held.

decisive Disadvantages of the natural Binders are therefore a for the wood-based material production too low moisture resistance the glued joint, the unfavorable rheological behavior and a relatively low biological resistance (Detlef Krug: Proteins suitable as binders for wood-based materials (With PF resin / wheat protein binders Wood materials of high moisture resistance with little formaldehyde) Holz-Zentralblatt 128 (2002), 12, 153-155, P. 1850).

Also showed as a major disadvantage of previous solutions for the development of natural binders for wood-based materials, that by the application of natural Adhesive components compared to conventional synthetic glue resins higher Commodity prices as well as higher Legal costs, especially because of the longer ones pressing times by the higher one Water requirement for the reaction, are required.

moreover have wooden materials made with such alternative binders Compared to wood materials with exclusive phenol-formaldehyde-resin or melamine-urea-formaldehyde - bond no improved properties, especially moisture resistance, on. Often leads the starch additive even to a property deterioration.

task The invention is to eliminate the disadvantages of the prior art. It should be specified in particular a material that is characterized by a lasting improved moisture resistance distinguishes. Such a Material, in particular based on particles, used for chipboard, MDF or OSB, should accordingly for a Use in damp and / or outdoor areas be suitable; that is, the thickness swelling of the material of FIG. 24 h water storage is ≤ 16% to lower.

According to the invention this Task by the claims 1 and 4 solved; expedient designs are the claims 2 and 3 and 5-10 refer to.

To proviso The invention is therefore a wood material for furniture and interior design as well for applications in construction and for Moldings, consisting of wood particles, binders and aggregates, provided, which is characterized in that the binder from a synthetic formaldehyde component and a natural Component of dry chemical modified and / or destructured by an extrusion process Corn meal exists. The binder content is typical but not exclusively 5-20% based on the dry total mass of the material; of the Proportion of the natural Binder is at least 20%.

It is in fact surprising succeeded, by combinations of industry-standard UF resins, dry chemical modified and / or in the extruder destructured cereal flour components and hydrophobizing additives high quality binder to find a production of particulate wood materials, such as Chipboard, MDF or OSB enable, the opposite high humidity relatively resistant and thus in the wet area can be used.

Medium density fiberboard, high density fiberboard (HDF) with densities of 800 kg / m ³ and light MDF (L-MDF) with densities ≤ 650 kg / m ³ and ultralight MDF (UL MDF) are included under MDF Bulk densities ≤ 550 kg / m ³ to understand [DIN EN 316].

The The method used for this purpose is accordingly characterized by that the Glueing using cereal flour as a binder component he follows.

When Formaldehyde resin component according to the invention is a urea-formaldehyde resin and / or melamine-urea-formaldehyde resin, phenol-formaldehyde resin, Melamine-urea-phenol-formaldehyde resin are also provided used polymeric diphenylmethane diisocyanates. The cornmeal is preferably obtained from rye grain.

process immanent is that the Cereal flour either directly applied in powder form or with a synthetic Binder mixed and then sprayed onto the particles. Furthermore, the gluing of the wood particles preferably by done that the in an extrusion process in Melt brought corn meal immediately after the extruder the wood particles is mixed. During the destruction process hydrophobizing additives and / or wood chips are after proviso the invention admixed. Feeding a small amount of Wood chip particles during the extrusion process, which are then carried along in the destruction process, especially with regard to low thickness swelling values the chipboard produced proved advantageous.

It is also advantageous that the Corn flour is finely reground after the destruction process. Further According to the essence of the invention, the gluing of the fibers in a two-step process be, first with the synthetic binder, if necessary with the addition of hydrophobicizing and other property-enhancing additives, in a blow-line glue and then the cereal flour is applied in powder form.

Finally sees the invention that the Process for the production of a wood-based material used for the production of fiberboard is used implies that the powdery dry chemical modified and / or destructured by an extrusion process Cereal flour directly into the cooker before defibration and / or during the Defibering in the refiner between the grinding discs and / or in the Connection to the defibration in the blow-line is added. Here are in a known manner, wood chips in a digester hydrothermally pretreated, shredded into fibers in a refiner and produced Glueing fibers in the blow-line with binders and then dried.

With the presented wood material are in the object of the invention assured requirements met; contributes to this, that with the method according to the invention reproducible material properties can be achieved.

The Invention will be explained in more detail below with reference to 2 embodiments.

example 1

It A gluing of spruce cutting chips with the binder according to the invention is carried out from urea-formaldehyde resin and destructured and dry chemical Modified rye flour with a solids content of 10% and an addition of 1% paraffin dispersion. The rye flour content is 10 mass%, rel. on dry Wood. After drying, the chip web formation and the compression follows with pressing time factors of 20 s / mm and pressing temperatures from 200 ° C to 10 mm thick, single-layer chipboard. The determined properties are part of Table 1.

Example 2

One under industry standard Cooker settings (temperature 170 ° C, residence time 4 min) produced pine wood pulp is after the defibration process with the binder according to the invention made of synthetic resin and destructured rye flour component with a solids content of 12% and an addition of 1% paraffin dispersion glued. There were three-layered variants, in which only in the outer layers Rye flour derivatives was used prepared. After drying The glued fibers in a known manner follows the fiber fleece formation and pressing with pressing time factors of 20 s / mm and pressing temperatures from 200 ° C to 16 mm thick, three-layered MDF. Selected properties are in Table 2 summarized.

Table 1:

Properties of 10 mm thick, single-layer chipboard from spruce wood chips using the inventively prepared binder urea-formaldehyde resin and dry-chemically modified and destructured by an extrusion process cereal flour, binder solids content in all variants 5% UF resin + 10% rye flour derivative, based on atro span:

Explanation:

• RDB 10:

  dry chemical modified Rye flour 1 + 10% additive, destructured

  RDB 14:

  dry chemical modified Rye flour 4 + 20% wood chips fraction A, destructured

  RMU 21:

  untreated rye flour + 10% wood chips fraction A + 1% water repellent, destructured

  WMU 1:

  untreated wheat flour + 10% wood chips fraction A + 1% water repellent, destructured

Table 2:

Characteristics of 16 mm thick, three-ply MDF made of pine wood pulp using the inventively prepared binder of phenol-formaldehyde resin and dry-chemically modified and / or destructured by an extrusion process rye flour, binder solids content in all variants in the MS 8% PF resin and in the DS 4% PF resin + 10% rye flour derivative, based on atro pulp:

Explanation:

• RM 4:

  dry chemical modified Rye flour, not destructured

  RMU 1:

  untreated rye flour, destructured

Claims (10)

Wood material for furniture and interior construction as well as for applications in building and for moldings, consisting of wood particles, binders and aggregates, with a typical, but not exclusive binder content of 5-20% based on the dry total mass, characterized in that the binder a synthetic formaldehyde resin component and a natural component of dry-chemically modified and / or destructured by an extrusion process cereal flour, the proportion of which is at least 20% exists. Wood material according to claim 1, characterized that the Formaldehyde resin component, a urea-formaldehyde resin and / or Melamine-urea-formaldehyde resin, Phenol-formaldehyde resin, melamine-urea-phenol-formaldehyde resin is and in addition polymeric diphenylmethane diisocyanates are used. Wood material according to Claims 1 and 2, characterized that this Cornmeal was obtained from rye grain. Method for producing a wood-based material, consisting of wood particles, binders and aggregates the wood particles after comminution and drying with binders glued, characterized in that the gluing using made of cereal flour as a binder component. Method according to claim 4, characterized in that that this Cereal flour either in powder form directly applied or with a mixed synthetic binder and then sprayed onto the particles. Method according to claim 4, characterized in that that the Glueing of the wood particles takes place in such a way that brought into an extrusion process in melt Grain flour immediately after the extruder with the wood particles is mixed. Method according to Claims 4 to 6, characterized that during the Destruction process hydrophobizing additives and / or wood chips be mixed. Method according to Claims 4 to 7, characterized that this Corn flour is finely reground after the destruction process. Method according to claims 4 to 8, characterized that the Gluing of the fibers takes place in two stages, with first with gluing the synthetic binder in a blow-line and then the cornmeal is applied in powder form. Method for producing a wood-based material, which is used for fiber board production, according to one of o. G. claims and in which wood chips are hydrothermally pretreated in a cooker, crushed into fibers and the fibers produced in a refiner glued in the blow-line with binders and then dried be characterized in that the powdered dry chemical modified and / or destructured by an extrusion process Cereal flour directly into the cooker before defibration and / or during the Defibering in the refiner between the grinding discs and / or in the Connection to the defibration in the blow-line is added.