EP2853648B1 - Use of leather particles in wood-based panels for reducing the emission of volatile organic compounds (VOCs) - Google Patents

Description

The present invention relates to the use of leather particles in wood fiber insulation boards according to claim 1, a wood fiber insulation board containing leather particles according to claim 10 and a method for producing this wood fiber insulation board according to claim 12.

description

For the production of wood fiber insulation boards, materials made of lignocellulose, such as wood fibers or wood chips, are currently being used as renewable raw materials. Lignocellulose includes as components cellulose, hemicellulose and lignin. Cellulose is a long-chain macromolecule composed of glucose units, hemicellulose a short-chain, branched macromolecule of pentoses and lignin a three-dimensional macromolecule of methoxyphenylpropane units. Cellulose and hemicelluloses form the skeletal substance of the cell wall, while lignin as a filling substance in the cell structure causes the lignification.

The production of wood fiber insulation panels has received more and more environmental attention in recent years. In addition to the fact that wood is available as a renewable resource unlimited, are also aspects of lower energy consumption and ease of disposal of interest.

However, when using wood fiber insulation panels, especially indoors, there is still a source of health stress due to the emission of volatile organic compounds formed during the production process of the wood fibers. Volatile organic compounds (VOCs) include volatile organic compounds that evaporate easily or are already gaseous at low temperatures, such as at room temperature. In general, the volatile compounds either accumulate as by-products during the manufacturing process or are formed during growth of the tree. These are then released more or less quickly to the environment. Both processes lead to specific Problems that may make the entire manufacturing process more expensive and / or cause odors in the use of wood fiber insulation boards.

The problem of emission of volatile organic components from wood fiber boards, especially aldehydes, is all the more serious, the lower the density of the wood-based panels produced. While in the case of a fiber board with increased density (HDF) or a medium-density fiberboard (MDF) no increased values of the volatile organic components can be determined, wood fiber boards below a gross density of about 250 kg / m ³ , such as the wood fiber insulation panels, a significant VOC Due to the low density, diffusion processes can be accelerated. Above all, this contributes to the rapid release of organic compounds from the insulation materials.

To solve the problem of VOC emission, various approaches are conceivable. On the one hand there is the possibility of wood fibers with other natural fibers such. Wool, hemp salmon, which behave more favorably with regard to their emission behavior, in order to obtain an ecological insulation material with improved emission characteristics. A disadvantage here, however, is the high costs associated with these fibers and limited availability, since in some cases higher-value applications exist for the corresponding fiber types, suggesting a different use.

For the above reasons, therefore, it is desirable to develop suitable solutions by which the release of volatile organic compounds from wood-based panels, especially from Holzfaserdämmstoffplatten is reduced. For this purpose, various approaches are known. Thus, by adding alkaline substances, the pH in the wood matrix can be increased so as to prevent or reduce the acid-catalyzed reactions taking place in the wood matrix ( Roffael, E., et al, Holzzentralblatt 1990, 116: 1684-1685 ). Further possibilities in the reduction of the emission of volatile organic compound consist in the addition of zeolite ( WO 2010/136106 ), Bisulfites or pyrosulfites ( US2009 / 0130474 A1 ) as aldehyde scavengers or in the addition of polyamines for reducing aldehydes and organic acids released during aqueous wood pulping ( EP 2 567 798 ). document EP 2 135 892 A2 discloses a use of leather particles in wood-based panels, wherein the wood-based panels contain formaldehyde-free binders (tannins, lignins). document EP 2 135 892 A2 also discloses a wood-based panel comprising 10 to 90% by weight of wood fibers, 10 to 90% by weight of leather particles, at least one flame retardant and at least one bicomponent binder based on a plastic fiber (eg polyethylenimines (PEI) together with lignin).

The present invention is based on the technical object of further increasing the emission of volatile organic compounds (VOCs) from wood fiber insulating boards reduce without this resulting in loss of technical properties of the insulation material for thermal conductivity or density.

Accordingly, the present invention was the technical object of finding a suitable raw material, which is used in combination with wood fibers and has a favorable emission behavior.

The object is achieved by the use of leather particles in wood fiber insulation panels according to the features of claim 1.

According to the present invention, leather particles are used in wood fiber insulation panels which result in a reduction in the emission of volatile organic compounds (VOCs) from wood fiber insulation panels.

The use of leather particles as a renewable raw material in wood-based panels has recently become increasingly the focus. So will in the European Patent Application 13 169 863 described the possibility of producing wood-based panels from a mixture of wood fibers and leather particles. Leather pulp used here is a material made of shavings, for example chrome shavings and comminuted, vegetable-tanned leather residues from the leather-processing industry. Leather residues are produced in large quantities during the processing of leather or the production of various products. Of the leather obtained after the tanning process to a thickness of more than 1 cm, usually only a few millimeters can be used. The remainder is waste and is used only to a small extent, for example for the production of shoe soles. Another advantage is that the leather in the various processing processes already obtained in comminuted form as so-called shavings, so that the mechanical effort for fiber production significantly reduced.

Leather is predominantly composed of collagen, a polypeptide that forms three-dimensional fiber structures. The amino acids glycine, proline, 4-hydroxyproline and 5-hydroxylysine are particularly common in the polypeptide, with almost every third residue in the collagen molecule being glycine.

The leather particles used herein are preferably leather fibers, which are obtained from reduced, vegetable tanned leather residues of the leather processing industry. Such leather fibers typically have a length of up to 20 mm, preferably 5 to 15 mm and a thickness of up to 1 mm, preferably 0.5 to 1 mm. In particular, Lederfalzspänne be used mainly for the production of insulation boards, resulting from the tanning of leather using other tannins. Excluded are leather creases that occur during the tanning of leather using chrome-containing tannins. Accordingly, the use of chrome rebates is excluded for ecological reasons.

The Lederfalzspäne can occur in the tanning and processing of leather at various points. The leather particles can be produced as a relatively moist material directly in the tanning process (moisture: about 50% by weight) or at the end of the leather production process (moisture <10%). Both materials can be used for use in insulation production. Although drying is unnecessary, it consumes energy and causes higher costs for the raw material.

In one embodiment, the leather particles have a moisture content of 20 to 70%, preferably 30 to 60%, particularly preferably 45 to 55%. A typical moisture value of the leather particles or leather fibers used is 50%.

The leather particles are used here to reduce the emission of organic acids, in particular to reduce the emission of acetic acid from wood fiber insulation panels. Organic acids are produced in particular as cleavage products of the wood constituents cellulose, hemicelluloses and lignin, alkanoic acids such as acetic acid and propionic acid or aromatic acids preferably being formed.

It is also desirable to use the leather particles to reduce the emission of aldehydes from wood fiber insulation panels. In this case, it is particularly preferred if the leather particles are used to reduce aldehydes released during the aqueous wood pulping process. As already explained above, there is a release of aldehydes during the hydrolytic workup of wood or lignocellulose. The aldehydes are formed from the basic building blocks of cellulose or hemicellulose. For example, the aldehyde furfural is formed from mono- and disaccharides of cellulose or hemicellulose, while aromatic aldehydes can be liberated during the partial hydrolytic exclusion of lignin. Accordingly, the leather particles are used to reduce the emission of C1-C10 aldehydes, particularly preferably formaldehyde, acetaldehyde, pentanal, hexanal or else furfural in wood-based panels.

In another embodiment of the present invention, the leather particles are used to reduce the emission of terpenes. So can the leather particles for Reduction of terpenes released from the wood shavings or wood fibers used in the wood-based panel, in particular C10-monoterpenes and C15-sesquiterpenes, in particular preferably acyclic or cyclic monoterpenes.

Typical acyclic terpenes are terpene hydrocarbons such as myrcene, terpene alcohols such as gerianol, linaool, ipsinol and terpene aldehydes such as citral. Typical representatives of the monocyclic terpenes are p-menthane, terpeninol, limonene or carvone, and typical representatives of the bicyclic terpenes are caran, pinane, bornan, in particular 3-carene and α-pinene being of importance. Terpenes are components of the tree resins and therefore especially in very resinous tree species such as pine or spruce.

In the present case, the leather particles are used in wood fiber insulating panels, which comprises 40 to 65% by weight, preferably 45 to 60% by weight, in particular 45 to 55% by weight of wood fibers.

Wood particles in the present case are lignocellulose-containing comminution products, such as e.g. Wood fibers, wood shavings or wood strands to understand. In the case of the use of wood fibers, according to the invention, in particular in the use of wood fibers in wood fiber insulation boards, in particular dry wood fibers having a length of 1 mm to 20 mm, preferably from 1.5 mm to 10 mm and a thickness of 0, 05 mm to 1 mm for use. The present wood fiber insulation board comprises 5 to 30% by weight, preferably 10 to 20% by weight, of leather particles or leather fibers.

In the present invention, a suitable binder is added to the mixture of wood fibers and leather particles or leather fibers in order to ensure a cohesive connection of the particles with one another.

Formaldehyde-free binders in the form of liquid or powdery adhesive components as well as in the form of binder fibers, such as isocyanates or synthetic fibers, can be used as binders for the wood-fiber / leather particle mixture which are not suitable for the invention as starting mixture for the production of wood fiber insulation boards.

In the case where an isocyanate is used as the binder, it is selected from a group containing aliphatic and aromatic isocyanates. As aliphatic isocyanates, for example, hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI) and / or 1,4-cyclohexyl diisocyanate (CHDI) can be used. Typical suitable aromatic isocyanates are, for example, diphenylmethane diisocyanate (MDI) or tolylene diisocyanate (TDI) or also polymeric diphenylmethane diisocyanate (PMDI), the latter being particularly preferred. The isocyanate is subject to two chemical reactions when used as a binder. First, it forms polyurea in the presence of water. Parallel to this, the binding to the wood particles and leather particles takes place by the reaction of the isocyanates with free hydroxyl / amino groups on the surface of the wood particles and / or leather particles to form a urethane or polyurea bond.

As already mentioned, according to the invention, plastic fibers are also used as binders for the wood particle-leather particle mixture. The plastic fibers according to the invention are bicomponent fibers. The thermally activatable plastic or binder fibers carry out both a binding and a support function in the matrix of wood fibers and leather particles due to their spatial distribution.

Bicomponent fibers (also referred to as biko support fibers) typically consist of a carrier filament or a core fiber made of a plastic with higher temperature resistance, in particular polyesters, which are coated or sheathed by a plastic with a lower melting point, in particular polyethylene. The shell or the jacket allows after melting a cross-linking of the wood particles and / or leather particles with each other.

The wood fiber insulating panels produced using the leather particles accordingly comprise 40 to 65% by weight, preferably 45 to 60% by weight, particularly preferably 45 to 55% by weight of wood fibers, 5 to 30% by weight, preferably 10 to 20% by weight of leather particles, at least one flame retardant and at least one binder.

The flame retardant may be added in an amount between 5 and 20% by weight, preferably between 8 and 10% by weight. Typical flame retardants are selected from the group comprising phosphates, borates, in particular ammonium polyphosphate, tris (tri-bromneopentyl) phosphate, zinc borate or boric acid complexes of polyhydric alcohols.

The present wood fiber insulation panels are characterized by a reduced volatile compounds (VOCs) compared to wood-based panels without leather particles. The reduction in VOC emission, in particular of organic acids, is up to 50%, preferably 45%, in particular 40% lower than in comparison with conventional wood-based panels.

The wood fiber insulation board according to the invention is preferably characterized by a reduction of the emission of organic acids, in particular acetic acid, of aldehyde and / or terpenes.

1. a) Herstellen von Holzfasern aus Holzhackschnitzeln,
2. b) Vermischen der Holzfasern mit Lederpartikeln, Flammschutzmittel und Kunststofffasern als Bindemittel, wobei die Kunststofffasern mit den Holzfasern und/oder Lederpartikel nach deren Trocknung gemischt werden,
3. c) Streuen der Mischung aus Holzfasern, Lederpartikeln, Flammschutzmittel und Kunststofffasern als Bindemittel auf ein Transportband, und
4. d) Verdichten und Erwärmen der gebildeten Fasermatte.

The present wood fiber insulation board containing leather particles is produced in a process with the following process steps:

1. a) producing wood fibers from woodchips,
2. b) mixing the wood fibers with leather particles, flame retardants and plastic fibers as binders, the plastic fibers being mixed with the wood fibers and / or leather particles after they have been dried,
3. c) spreading the mixture of wood fibers, leather particles, flame retardants and plastic fibers as a binder on a conveyor belt, and
4. d) compacting and heating the fiber mat formed.

To produce the wood fibers according to step a), the wood chips are first cleaned, then defibered and dried.

The mixing of the wood fibers with the leather particles can take place during various process steps. Thus, the leather particles can be added before or during the defibration process of the wood chips, eg in the digester or refiner. It is also generally possible to bring the leather particles into contact with the wood fibers in the blow-line or during the fiber mixing process. The wood fibers are used depending on the type of equipment and method used before or after mixing with the leather particles with plastic fibers as Binder additionally applied. After scattering the mixture of wood fibers, leather particles and plastic fibers as a binder on a conveyor belt and the formation of a wood fiber mat is first carried out a pre-pressing, in which the thickness of the mat is reduced in the context of a cold pre-compression. Then a mat trimming is performed while the side panel is separated from the fiber mat and the side panels returned to the process.

As previously mentioned, bicomponent fibers are used as binders. In the case of the use of liquid or powdery adhesive components, these are mixed with the wood fibers and / or leather particles, spread on a conveyor belt and then pressed in a hot pressing process to a plate. The mixing of the leather particles with the liquid and / or powdery adhesive component may e.g. during dosing in the blow-line feed. The mixture of leather particles and adhesive component is then injected into the wood fiber stream. However, the leather particles and the binder can also be contacted successively with the wood fiber stream. It is also conceivable to introduce the leather particles during the damping of wood chips or to add in the refiner

In the case of using according to the invention, the mixing derselbigen with the wood fibers and / or Lederpartiklen after drying of the wood fibers and / or leather particles is carried out in a separate process. The mixture of wood fibers, leather particles and binder fibers is scattered on a conveyor belt. The sprinkled mixture or fleece is then introduced into a hot air oven, in which the fleece formed from wood fibers, binder fibers and leather particles is flowed through by hot air, wherein the binding fibers are heated and melted and it comes to matting. At the furnace exit or end of the furnace, the mat can be calibrated.

The activating of the binder or of the bico fibers in the wood fiber mat associated with the compacting (or pressing) and / or heating is preferably carried out at temperatures between 100 ° C and 250 ° C, preferably 130 ° C and 220 ° C, in particular at 200 ° C.

During the passage of the fiber cake through the oven, activation of the binder typically occurs, eg, melting of the thermoplastic shell of bicomponent fibers whereby a firm connection between the wood fibers, leather particles and the binder are produced. In particular, in the case of the use of bicomponent fibers, a construction of a support framework arises from the bicomponent fibers, into which the wood fibers and leather particles are embedded or adhesively bonded.

During finishing, the fiber mat is finally reduced to the required dimensions and cooled.

It is also conceivable that more than one binder is used. Thus, in addition to the already mentioned binder, in particular of aldehyde-free binders from the group of isocyanates and bicomponent fibers, further binders such as a granulate of plastic may be added. Such a granulate may be a plastic granulate as obtained in the recycling of plastic articles from the dual system.

The invention will be explained in more detail using an exemplary embodiment.

Embodiment:

Wood fibers, bicrofibers (polyester fibers encased in polyethylene) and moist leather shavings (tanned with glyoxal, moisture content: approx. 50%) were mixed in the premix of the insulation system. The proportion of bicafiber serving as scaffold was kept constant at 20% by weight. The proportions of wood fiber were reduced depending on the dosage of the shavings.

Subsequently, the premixed fibers were scattered to a fiber bed and passed through the heating furnace. The BiCo fibers melt and create a support matrix. Depending on the quantity of shavings that were to be metered, the insulation materials produced with leather shavings showed a partly clearer coloration.

The insulating materials were then tested in a test chamber according to the AgBB scheme (Committee for the Health Assessment of Construction Products) on their VOC emission, with only the acetic acid value is given as a guide parameter. The emission levels of the other acids and aldehydes have been reduced in similar percentages. variant Wood fiber weight% Flame retardant wt% Bicafiber wt.% Leather cuttings weight%, atro Acetic acid emission after 7d in yg / m ³ O-sample 73.0 7 20 0 1426 1 64.4 7 20 8.6 925 2 55.8 7 20 17.2 741

As can be seen from the results, the acetic acid emissions are significantly reduced, with the reduction of the acetic acid emission being significantly higher than the percentage of leather fibers. The leather fibers thus actually cause an emission reduction.

The examination of the other production parameters showed no abnormalities.

Claims (13)

1. Use of leather particles in wood fibre insulation boards for reducing the emission of volatile organic compounds (VOCs) in the form of aldehydes and/or organic acids liberated during the aqueous digestion of wood from the wood fibre insulation boards, wherein the wood fibre insulation boards contain formaldehyde-free binders.
2. Use of leather particles in wood fibre insulation boards according to Claim 1, characterized in that the leather particles are present in the form of leather fibres, in particular leather shadings.
3. Use of leather particles in wood fibre insulation boards according to either of the preceding claims, characterized in that the leather particles have a moisture content of from 20 to 70%, preferably from 30 to 60%, particularly preferably from 45 to 55%.
4. Use of leather particles in wood fibre insulation boards according to any of the preceding claims for reducing the emission of alkanoic acids, in particular acetic acid, from wood fibre insulation boards.
5. Use of leather particles in wood fibre insulation boards according to any of the preceding claims for reducing the emission of formaldehyde, acetaldehyde, pentanal, hexanal or furfural from wood fibre insulation boards.
6. Use of leather particles in wood fibre insulation boards according to any of the preceding claims for reducing the emission of terpenes.
7. Use of leather particles in wood fibre insulation boards according to any of the preceding claims, characterized in that the wood fibre insulation board comprises from 40 to 65% by weight, preferably from 45 to 60% by weight, particularly preferably from 45 to 55% by weight, of wood fibres.
8. Use of leather particles in wood fibre insulation boards according to any of the preceding claims, characterized in that the wood fibre insulation board comprises from 5 to 30% by weight, preferably from 10 to 20% by weight, of leather particles.
9. Use of leather particles in wood fibre insulation boards according to any of the preceding claims, characterized in that the wood fibre insulation board contains polymer fibres as binder.
10. Wood fibre insulation board characterized by
    from 40 to 65% by weight, preferably from 45 to 60% by weight, particularly preferably from 45 to 55% by weight, of wood fibres,
    from 5 to 30% by weight, preferably from 10 to 20% by weight, of leather particles,
    at least one flame retardant and polymer fibres in the form of bicomponent fibres as binder,
    having a reduction of up to 50%, preferably 45%, in particular 40%, in the emission of volatile compounds (VOCs) in the form of aldehydes and/or organic acids liberated during the aqueous digestion of wood compared to wood fibre insulation boards without leather particles.
11. Wood fibre insulation board according to Claim 10, characterized by a reduction in the emission of alkanoic acids, in particular acetic acid, formaldehyde, acetaldehyde, pentanal, hexanal or furfural and/or terpenes.
12. Process for producing a wood fibre insulation board according to either Claim 10 or 11, characterized by the following process steps:

    a) production of wood fibres from wood chips,

    b) mixing of the wood fibres with leather particles, flame retardants and polymer fibres as binder, with the polymer fibres being mixed with the wood fibres and/or leather particles after drying thereof,

    c) scattering of the mixture of wood fibres, leather particles, flame retardants and polymer fibres as binder onto a conveyor belt and

    d) compaction and/or heating of the fibre matter formed.
13. Process according to Claim 12, characterized in that the compaction and/or heating of the mixture scattered on in step c) is carried out at temperatures in the range from 100°C to 250°C, preferably from 130°C to 220°C, in particular at 200°C.