WO2006032267A1

WO2006032267A1 - Timber or derived timber product, method for producing the same

Info

Publication number: WO2006032267A1
Application number: PCT/DE2005/001717
Authority: WO
Inventors: Karsten Aehlig
Original assignee: Institut für Holztechnologie Dresden gGmbH
Priority date: 2004-09-21
Filing date: 2005-09-21
Publication date: 2006-03-30
Also published as: EP1793972A1

Abstract

The invention relates to timber or derived timber products, especially from fatty acid ester-containing timber, which have no off-odor caused by the degradation products of the fatty acid esters and which emit unsaturated aldehydes in a concentration of not more than 2 νg/m3. For this purpose, the fatty acid esters already contained are cleaved, inhibited or oxidized during production of the timber or derived timber products.

Description

Wood or wood-based material, process for their preparation

The invention relates to wood or wood-based materials, in particular fatty acid esterhaltϊgen woods that have no malodour caused by degradation products of the fatty acid esters and methods for their preparation.

Wood materials are z. B. plywood but also chip, fiber, MSB and OSB boards, which are made of wood particles by pressing with binders. The woods are according to the invention timbers and solid wood panels. The products according to the invention are used in a wide variety of fields.

In addition to the physico-mechanical properties of these materials, home hygiene parameters are increasingly influencing the application possibilities of the materials. This applies in particular to products that are used in the interior. These include z. As beams and roof structures made of solid wood panels, "classic" wood materials for partitions in home construction and interior, products for the floor, for furniture and panels.

The basis for the hygienic evaluation of such products are the concentrations of volatile organic compounds (VOC) determined under standardized conditions (DIN ISO 13419 Part 1-3 in conjunction with ISO 16000 Parts 3 and 6).

The evaluation of these VOCs can be done as a sum parameter (total VOC concentration) and, depending on voluntary agreements (eco-labels and other quality labels), a certain concentration of VOCs should not be exceeded. In addition, "hazardous" substances, which include, in particular, CMT substances of category 1 and 2. Since October 2004, emission from construction products has been toxicologically assessed according to the AgBB scheme based on NIK values (lowest concentration of interest) Exceeding the toxicological limit R of 1 will result in the non-approval of the construction product subject to registration, and it is clear that other interior products are also increasingly being subjected to this assessment.

Selected woods such as pine, birch, spruce linden or poplar contain fatty acid esters that are used in the manufacture of aldehydes and organic products Acids can be degraded without this can be prevented by changing technological parameters. Own investigations have shown that z. B. in birch 2315 mg / kg, linden 7544 mg / kg, pine 5807 mg / kg or spruce 1894 mg / kg of fatty acids may be included.

Both classes of compounds, aldehydes and organic acids, are odor-intensive. For consumers, products with increased emissions of odor-intensive compounds have a negative impact, causing complaints and also adverse health effects, solely due to the smell. The odor thresholds in these compounds may be 20 μg / m ³ and below.

In the production of wood particles (chips, fibers and OSB strands) in particular fatty acid ester-containing woods, such as. As the pine, it comes during the manufacturing process, especially during drying, to form odorous as well as toxicologically harmful compounds.

Since wood particles of fatty acid wood are the basis for the production of wood-based materials and wood-based materials are increasingly subject to residential hygiene requirements, such wood materials, which emit in particular saturated and unsaturated aldehydes, organic acids and other odorous compounds, difficult to deduct.

During production, this begins in particular already during the drying of the wood particles, the unsaturated fatty acid esters are split by the effect of temperature (up to about 700 ⁰ C drier inlet temperature). Among other things, odor-intensive aldehydes and organic acids as well as toxicologically relevant unsaturated aldehydes are formed.

Even with the classic wood drying of solid wood, it can be used to split unsaturated fatty acid esters and to form the o. G. smell-intensive or toxicologically relevant compounds come.

It is therefore an object of the invention to provide wood or wood-based materials that emit fission products of fatty acid esters only in very small amounts barely perceptible odor and to provide methods for their preparation. According to the invention, the object is achieved by wood or wood-based materials, in particular wood containing fatty acid esters, which have no malodour caused by degradation products of the fatty acid esters and emit unsaturated aldehydes in a concentration of not more than 2 μg / m ³ . This is achieved by cleaving, inhibiting or oxidizing the already contained fatty acid esters during their production. Malodor means an odor impression, which is generally perceived as unpleasant and leads to product rejection or irritation.

Degradation products of the fatty acid esters are in particular organic acids such as propionic, butanoic and hexanoic acid and / or aldehydes such as propanal, hexanal, nonanal, 2-octenal, heptenal, decenal or octanal. In particular, the degradation products of the fatty acid esters propanal, hexanal, propionic acid, butyric acid and hexanoic acid cause a false odor. The odor thresholds in these compounds are 20 μg / m ³ and below. Unsaturated aldehydes, such as. B. 2-octenal, decenal, heptenal or Nonenal set the woods or wood materials according to the invention in a maximum concentration of 2 ug / m ³ free.

The fatty acid ester-containing woods include wood species such as pine, birch, linden or poplar. Wood materials according to the invention are chip, fiber, MSB and OSB boards which are produced from wood particles by compression with binders and also plywoods. The woods are according to the invention timbers and solid wood panels.

According to the invention contains the wood or the wood material

wood or wood particles treated with antioxidants or solutions thereof,

or treated with alkaline compounds such as sodium carbonate, or ammonia or alkalis, or treated with oxidizing agents such as sodium dithionite or hydrogen peroxide wood or treated wood particles.

or wood particles treated with phenolic extractives of wood or bark. When using antioxidants, the wood or wood-based material contains antioxidants in a concentration of at least 0.1 μg / ml of ascorbic acid equivalent.

The woods or wood-base materials according to the invention can be produced by a process in which fatty acid esters contained in the wood or in the wood particles are already inhibited, split or oxidized during the drying of freshly cut solid wood or during or after the production of the wood particles.

The advantages of the method according to the invention are that either by inhibiting the cleavage of the fatty acid esters by antioxidants or phenolic extractives, the cause of the formation of odorous toxicologically harmful compounds is largely prevented or by the cleavage or oxidation (by means of fatty acid ester decomposing oxidant) of the fatty acid esters already In the manufacturing process, the odor-intensive, toxicologically questionable compounds are formed and eliminated immediately, so that they can no longer be emitted later from wood or wood-based material.

Furthermore, residual contents, in particular of antioxidants in wood or wood-based material, prevent or delay the subsequent formation of toxicologically relevant, odor-intensive compounds. Appropriate treatment of solid wood against drying prevents the formation o.g. Connections significantly.

Investigations by the inventors have shown that the odor-intensive and also toxicologically relevant compounds arise mainly during the drying of the wood particles. Thus, from a technological point of view, simple treatment solutions are possible, such as the use of appropriate chemical additives during the technological step of wood particle production (e.g., OSB strands) of round or solid wood or spraying with specially adjusted solutions prior to drying the wood particles.

In a preferred embodiment of the invention, the wood particles or the solid wood are treated with antioxidants, for example salts of gallic acid, citrates or 2,6-di-tertiary-butyl-4-methyl-phenol (BHT) or solutions thereof. The treatment is carried out by impregnation with or spraying the appropriate Solutions. At higher temperatures, volatile compounds (antioxidants) can also be superficially applied to the wood particles or the solid wood in the gas phase.

In an alternative embodiment of the process, the solid wood or wood particles are treated with fatty acid ester decomposing chemicals or their solutions prior to drying. In a further embodiment, alkaline compounds, such as sodium carbonate or sodium dithionite-containing solutions or alkalis or ammonia are used. The treatment is carried out by soaking the wood particles with the appropriate solutions. During drying, the resulting fission products are removed via the dryer exhaust air and thus no longer emit from wood or wood-based materials.

In a further embodiment of the process, phenolic extractives of wood or bark are used to treat the solid wood or the wood particles. For this purpose, barks or wood containing tannin are extracted and the extraction solution is associated with the wood particles or the solid wood in a suitable form. The wood particles or the solid wood can be dipped for a short time or the extraction solution can be applied to the particles or the solid wood by spraying before drying.

The process results in a wood or wood-based material without malodour due to breakdown products of the fatty acid esters. Furthermore, the wood thus produced or the wood particles thus produced emit unsaturated aldehydes at a maximum concentration of 2 μg / m ³ .

Reference to subsequent embodiments, the invention will be explained in more detail.

Embodiment 1

In a 1.5% dispersion of gallic acid propyl ester are immersed for about 10 min juice fresh pine beaches. This is followed by drying at 220 ^° C.

To demonstrate the success of treatment, the Kiefemstrands are comminuted to a particle size <1, 5 mm and determined by headspace gas chromatography, the contents of saturated and unsaturated aldehydes. 1 shows a gas chromatogram of an untreated pine wood sample dried at 220 ^° C. FIG. 2 shows a gas chromatogram of the pine wood sample treated with gallic acid propyl ester before drying and subsequently dried at 220 ^° C.

The relevant compounds can be taken from the gas chromatograms according to FIGS. 1 and 2:

Propanal retention time 1, 74 min

Acetic acid retention time 3.15 min

Hexanal retention time 5.59 min

Octanal retention time 14.37 min

2-octenal retention time 17.25 min

Nonanal retention time 17.95 min

As can be seen from the chromatograms according to FIGS. 1 and 2, the addition of gallic acid propyl ester prevents the formation of critical compounds during the drying process. This is especially true for hexanal, octanal, 2-octenal and nonanal. 2-Octenal is no longer determinable as emission in the treated product.

If the drying is carried out under room air conditions, the treatment of the wood with propyl gallate has the same effect as with drying at 220 ^° C. The emission of critical compounds from the wood is prevented or reduced. The smell was also investigated according to the following method:

The wood material sample is 48 hours at 23 ⁰ C and 65% rel. Humidity conditioned. For the detection of a false odor, 50 g of sample material are placed in a tightly closed odorless 11-glass vessel and stored for 24 hours at 23 ⁰ C.

The odor test is carried out in accordance with the VDA recommendation 270 with a panel of probands of at least 5 test persons on 3 samples each. There is an odor assessment in 6 notes.

Grade 1 - imperceptible; Grade 2 - perceptible / not disturbing; Grade 3 - clearly perceptible but not disturbing Grade 4 - disturbing; Grade 5 - very disturbing; Grade 6 - unbearable

The smell test shows whether the smell is product-typical, not disturbing or whether a non-product-typical disturbing smell emanates from the product.

While the untreated air-dried Kiefemstrand probe reached a level of 3.5 (noticeably a little disturbing smell) when it came to checking the odor, the treated beach sample came to 2.5 (noticeable to distinct smell).

Embodiment 2

In a 1, 5% solution of sodium citrate are for about 10 min juice fresh

Kiefemstrands bathed. Subsequently, the so treated beaches in the

Drying oven dried to a final moisture of 3 to 6%. The initial temperature is 220 ⁰ C.

To prove the success of the treatment, the pine strands on a

Grain size <1, 5 mm crushed and using headspace gas chromatography

Levels of saturated and unsaturated aldehydes determined.

Compared with untreated but analogously dried beaches could the critical

Aldehydes hexanal, nonanal and 2-octenal are not detected. The treated beach sample gave an odor note of 2.0 (noticeable odor).

Embodiment 3

In a 2.5% solution of sodium carbonate for about 10 min juice fresh Kiefemstrands immersed. Subsequently, the thus treated strands are dried in the drying oven temperature programmed to a final moisture content of 3 to 6%. The initial temperature is 218 ⁰ C and the drying time 75 min. To demonstrate the success of the treatment, the pine strands are comminuted to a particle size of <1.5 mm and the contents of saturated and unsaturated aldehydes are determined by headspace gas chromatography.

Compared with untreated but similarly dried strands, the critical aldehydes nonanal and 2-octenal could not be detected.

The hexanal and octanal contents could be reduced by 65 to 80% compared to untreated samples.

The treated beach sample gave an odor rating of 3.0 (more noticeable, not yet offensive odor).

Embodiment 4

In a 1.0% dispersion of octyl gallate, juice-fresh blanks made predominantly of pine heartwood in the dimensions 20 mm × 20 mm × 100 mm are immersed for about 10 minutes. Subsequently, the specimens thus treated are dried at room temperature to a final moisture content of 10 to 14%. To demonstrate the success of the treatment, drilling chips are taken from the surface of the specimens to a depth of about 2 mm and the contents of saturated and unsaturated aldehydes are determined by headspace gas chromatography.

Compared with untreated but analogously dried strands, the critical aldehydes hexanal, nonanal and 2-octenal could not be detected. No odor test was performed on this sample.

Embodiment 5

The treated with propyl gallate under laboratory conditions pine strands (drying at 220 ⁰ C) were bonded single layer under laboratory conditions with a polymeric isocyanate adhesive (PMDI) under known pressure conditions. The OSB laboratory plates measuring 500 mm x 500 mm x 20 mm were stored in a 1 m ³ test chamber to determine VOC emission and emissions were determined after 24 hours and 28 days. The odor determination was carried out according to the method already described. The following table shows selected results.

Table - Selected parameters of treated and untreated pine OSB boards after 28 days

nn - undetectable (<1 μg / m ³ at loading 1m ² / m ³ and air exchange 1 h ^"1 )

Claims

claims

1. Wood or wood-based material in particular fatty acid wood, characterized in that the wood or the wood material has no malodour caused by degradation products of fatty acid esters and does not emit unsaturated aldehydes in a concentration greater than 2 ug / m ³ .

2. wood or wood material according to claim 1, characterized in that the degradation products are organic acids such as propionic, butanoic and hexanoic acid and / or aldehydes such as propanal, hexanal, nonanal, 2-octenal, heptenal, decenal or octanal.

3. wood or wood material according to claim 1 or 2, characterized in that the wood or the wood material containing antioxidants or solutions thereof treated wood or wood particles.

4. Wood or wood-based material according to one of claims 1 or 2, characterized in that the wood or the wood material with alkaline compounds such as sodium carbonate, or ammonia or alkalis, or treated with oxidizing agents such as sodium dithionite or hydrogen peroxide treated wood or wood particles.

5. Wood or wood-based material according to one of claims 1 or 2, characterized in that the wood material contains wood particles which have been treated with phenolic extractives of wood or bark.

6. wood or wood material according to claim 3, characterized in that the wood or the wood material contains antioxidants in a concentration of at least 0.1 ug / ml ascorbic acid equivalent.

7. A process for the production of wood or wood materials from in particular fatty acid ester wood or wood particles, characterized in that already in the production of dried solid wood or during or after the production of the wood particles in the wood or in the wood particles contained fatty acid esters are inhibited, split or oxidized.

8. The method according to claim 7, characterized in that the solid wood or the wood particles are treated with antioxidants or their solutions.

9. The method according to claim 7, characterized in that the solid wood or the wood particles are treated before drying with fatty acid ester decomposing chemicals or their solutions.

10. The method according to claim 7, characterized in that as the fatty acid ester decomposing chemicals are used alkaline or strongly oxidizing compounds such as sodium carbonate or sodium dithionite containing solutions or hydrogen peroxide, or bases or ammonia.

11. The method according to claim 7, characterized in that obtained by extraction phenolic extractives from wood or bark used for the treatment of solid wood or wood particles.