DD156237A1 - METHOD FOR PRODUCING WOOD MATERIALS WITH LOW FORMALDEHYDE BREAKING - Google Patents

Abstract

The object is in particular to produce composite panels and veneer surface-coated chipboard using urea-formaldehyde glue, which correspond to the requirements of environmental protection by a significantly reduced formaldehyde elimination. This concerns both the reduction of Formaldehydabspaltung in the production of the plates as in their application in interior design. The object is achieved in that the glue is a mixture of 0.5 to 1.5 parts by weight of urea and melamine and from 1 to 2 parts by weight of ammonium sulfate, based on 100 parts of urea-formaldehyde glue is added ,

Description

227123

VEB Leuna-Werke Leuna,

"Walter Ulbricht!! , ,

LP 80123

Title of the invention

Process for the production of wood materials with low formaldehyde elimination

Field of application of the invention

The invention relates to a process for the production of wood-based materials, in particular composite panels and veneered chipboard made of wood or woody PJLanzlichen fibers using urea-formaldehyde resins as a binder, which have a low formaldehyde elimination.

Characteristic of the known technical solutions

Recently, special demands have been placed on wood-based materials due to the increasing environmental protection requirements.

Due to the incomplete reaction between urea and formaldehyde in the production and pberflaechaabeschichtung of plates ", after completion of pressing constantly a small amount of formaldehyde is split off,

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which can lead to the sensitization and partly to the damage of the human organism in the case of particularly sensitive persons and if the plate is handled incorrectly. The approval of Yerbund- and chipboard, especially for interior work, is made increasingly dependent on the release of formaldehyde. The varying standardization of emission limits in individual countries forces plate producers to adapt to these demands and to constantly modify the commercial types of glue by changing the MoI ratios of the starting components and by adding formaldehyde acceptors.

When particle board is given a surface coating (e.g., veneer in the furniture industry), it is coated with a urea-formaldehyde glue and the veneer is pressed under pressure and temperature.

The urea-formaldehyde glues used usually have a much higher formaldehyde content compared to the glues used for chipboard production. To reduce the formaldehyde during the Aushaertungsprozesses and from the finished plates numerous products and methods are known, such as the use of a natural resin (Quebracho), modified sulfite liquor or urea and mixtures of urea and styrene butyl acrylate. These products and methods have the disadvantage that certain physical properties of the plates are negatively affected, e.g. Decrease in the strength values and increase in water absorption.

In order to lower the release of formaldehyde, in particular the addition of urea has found technical interest (DE-AS 2740207), the addition being carried out as a dispersion which is technically difficult to handle.

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Object of the invention

The aim of the invention is to develop a process for the surface coating of particle board with veneer and for the production of composite panels, which allows in a simple manner to produce plates which have during the manufacturing process and after a small formaldehyde elimination,

Explanation of the essence of the invention

The object of the invention is to add a formaldehyde-reducing component to the urea-formaldehyde glue used.

This object is achieved in that the urea-formaldehyde glue as a formaldehyde-reducing component according to the invention a mixture of 0.5 to 1.5 parts by weight urea, 0.5 to 1.5 parts by weight of melamine and 1 to 2 Parts by weight of ammonium sulfate, based on 100 parts of glue is added. Due to the hitherto known invention was to be feared that occurs by the addition of urea, a decrease in strength of the composite plate or coated chipboard. Surprisingly, however, this is not the case when using the mixture of urea, melamine and ammonium sulfate. Although it has already been proposed (WP B 29J / 219551) to add a mixture of the same amounts of urea, melamine and ammonium sulfate to the binder in the production of uncoated chipboard. However, the binders used have much lower levels of formaldehyde, so that the inventive achieved reduction of formaldehyde cleavage was not expected even with the glue used here.

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Exemplary embodiments Example 1

A chipboard with a Formaldehydabspaltung of 0.025 measured by the FESYP perforator method is glued with a urea-formaldehyde-Leim-Haertergemisch and coated with a veneer.

Sample sizes Type of coating Coating material Glue application

Pressing temperature pressing pressure

press time

400 mm χ 50 mm all-round oak veneer, 0.7 mm thickness 150 g / m 413 K 6 MPa 30 see.

glue mixtures:

(MT means parts)

1. 100 MT HF glue, molar ratio 1: 1.8

Solid resin content 68 %

- MT formaldehyde reducing agent 15 MT rye flour 10 MT 15% ammonium chloride solution

2. 100 M HF-glue, molar ratio 1: 1.8

Solid resin content 68 % 4 MT formaldehyde reducing agent 15 MT rye flour 10 MT 15% strength ammonium chloride solution

3. 100 MT HF glue, molar ratio 1: 1.8

, · Solid resin content 68 %

6 MT formaldehyde reducing agent

15 MT of rye flour

  10 MT "15% ammonium chloride solution

.4. 100 MT HF glue, Ko:

, . · .- _ Pc: 8 MT formaldehyde 15 MT rye flour 10 MT 15 SSige Mv.

Composition of the For

100 MT Melamine 100 MT Urea 150 MT. Ammonium Sulphate ..

Formaldehyde cleavage c

Determination of the Fon • FESYP Gas Analysis Methodology of the M: Glue 1 ot t e Gas Anr **;

mg / h v ²

1 (O value) 39j 7

3 · 20 _s 7

Example 2

It is a 5-ply Γ means a urine is used.

Technical data of ¥.>. Plate size % plate construction? Wood species %

Wood thickness ι

Holsfeuchtigkeit ι glue order?

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Pressing temperature: 373 K pressing pressure: 20 MPa

Press time: 5 min

glue mixtures

1. 100 MT HF glue, molar ratio 1: 1.8

Pestharzanteil 68 % - MT iOrmaldehydreduzierungsmittel 4 MT Haerterloesung, ·

2. 100 MT HP glue, molar ratio 1: 1.8

Pestharzanteil 68 %

4 MT Pormaldehyde Reducing Agent 4 MT Haerterloesung

"3. 100 MT HP glue, molar ratio 1: 1.8

Pestharzanteil 68 % 6 MT Pormaldehydreduzierungsmittel 4 MT Haerterloesung

4. 100 MT HP glue, molar ratio .1: 1.8

Pest Resin 68% 8 MT Pormaldehyde Reducing Agent 4 MT Haerterloesung Composition of Pormaldehyde Reducing Agent:

100 MT melamine 100 MT urea 150 MT ammonium sulphate ·

Composition of the toner solution: 25 'MT ammonium chloride

55 MT urea

20M hexamine. ^ I 50 MT water:

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Formaldehyde elimination during the pressing process The 5-18-ply plywood board was placed in a press frame, through which no fumes can escape into the fiaumluft during the PressVorganges.

At 4 suction points, the resulting Pormaldehyddaempfe were sucked off and passed over wash bottles.

The titrimetrically determined amount of pormaldehyde refers to a plywood board of 300 mm χ 300 mm with 4 glue joints.

The amount of glue liquor used is 65 g.

Compilation of the measurement results

glue liquor Severed Pormal Reduction in 51 amount of dehydrogenation in g / plate % um 60 1 0174 70 2 0085 3 0070 4 0052

Claims (1)

- 8 - 22 7 12 3 invention claim A process for the production of wood materials with low formaldehyde elimination, in particular for the production of composite panels and surface-coated particleboard, using urea-formaldehyde glue and a urea-containing mixture as a formaldehyde reducing component, characterized in that the glue as a formaldehyde reducing component is a mixture of 0 , 5 to 1.5 parts by weight of urea, 0.5 to 1.5 parts by weight of melamine and 1 to 2 parts by weight of ammonium sulfate, based on 100 parts by weight of glue is added.