DD154937A3 - METHOD FOR PRODUCING CHIPBOARDS WITH LOW FORMALDEHYDE CODING - Google Patents

Abstract

The object is to produce from wood chips and urea-formaldehyde glues such chipboard by pressing, which correspond to the requirements of environmental protection by a significantly reduced form splitting. This concerns both the reduction of formaldehyde removal in the production of chipboard as in their application in interior design. The object is achieved by adding a mixture of 0.5 to 1.5 parts by weight of urea and melamine and 1 to 2 parts by weight of ammonium sulfate, based on 100 parts of urea-formaldehyde binder, to the spaene binder. Mixture satisfies before pressing.

Description

2 1 95 5 1 '-4-

VEB Leuna-Werke Merseburg

»Walter Ulbricht« Dr * Bti./Sh '.

LP 8002 title of the invention

Process for the production of chipboard with low formaldehyde removal

Field of application of the invention

The invention relates to a process for the production of particleboard with low formaldehyde separation from wood or woody vegetable fibers using urea-formaldehyde resins as binder.

In the world, most of the chipboards produced are made from wood shavings or lignified vegetable fibers using urea-formaldehyde resins as a binder. These resins are based on their chemical, physical and performance properties as well as the ease of fabrication from relatively cheap raw materials especially for this purpose «

With'. Particleboard made of urea-foraialdehyde resins is mostly used in the furniture industry and for interior decoration *

- 2 LP 8002

Characteristic of the known technical solutions

In more recent times, special demands have been placed on chipboard due to the increasing environmental protection requirements. Due to the incomplete reaction between urea and formaldehyde in the production of chipboard is after completion ^ pressing of the chipboard constantly split off a small amount of formaldehyde, which is particularly harassing persons and improper handling of the particle board to harassment and in part to injury of the human organism.

The approval of particleboard, especially for interior work, is increasingly dependent on the release of formaldehyde. "The different levels of standardization of emission limits in individual countries are forcing particleboard producers to adapt to these demands and to the commercial types of glue by changing the molar ratios of the starting components and by adding Forsaaldehydakzeptoren to modify.

To reduce the formaldehyde during the curing process and from the finished chipboard numerous products and methods are known, such as the use of a natural resin (Quebracho), modified sulfite waste liquor or urea and mixtures of urea and styrene butyl acrylate. These products and processes have the disadvantage that certain physical properties of the particle boards are adversely affected, for "B ₆ fall in Festigkeitsxierte (bending strength and transverse tensile strength), increase in the thickness swelling and water absorption ·

In particular, the addition of urea to chip-binder mixture has found technical interest (DE- "AS 2 7 ^ 0 207) * wherein the addition is made as technically difficult to handle dispersion«

-3- 2 19551

LP 8002

Object of the invention

The aim of the invention is to develop a method which allows in a simple and economical manner, using the usual chip production plants, binders and additives in a small amount of time to produce a chipboard, which retains the usual physical strength values and during the manufacturing process and thereafter has a low formaldehyde elimination »

Explanation of the essence of the invention

The object of the invention is to add a formaldehyde-reducing component to the swarf-binder mixture.

This object is achieved in that in the production of particle board using a urea-formaldehyde binder as a formaldehyde-reducing component erfindungsgeraäß a mixture of 0.5 to 1.5 parts by weight of urea, 0.5 to 1, 5 wt. Parts of melamine and 1 to 2 parts by weight, Aßimoniurasulfat, based on 100 parts of binder is added before the mixture is compressed in a conventional manner under heat.

Due to the previously known results was to be feared that occurs by the addition of urea, a decrease in strength of the manufactured chipboard. Surprisingly, however, this is not the case when using the mixture of urea, melamine and ammonium sulfate.

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Lp 8002 embodiments

Example 1 100 parts by weight of flat wood chips of 0.3 to 0.4 mm thick, 3.0 to 5 mm wide and 20 to 30 ram in length were placed in a mixing drum and by spraying with. 14.26 parts by weight of a Loira fleet "

The Leirnflotte consisted of:

100 parts by weight of a particle board on the

Base urea-fornialdehyde with a pesticide content of 68 <$>

5 parts by weight of water

6 weight "parts by a ^ O $ weight paraffin emulsion h weight" parts by a ^ O ^ aqueous hardener

solution, consisting of a mixture of:

25 parts by weight of ammonium chloride, 20 parts by weight of hexamethylenetetramine and 55 parts by weight of urea »

1.14 Geiie parts urea 1.14 Gextf. parts melamine and 1.71 parts by weight _e Amtnonsulfat _β

In a 750 l χ 300 ram bulk load, 2.9 kg of the treated chips were evenly distributed. This chip cake was compressed in a hydraulic Keiaplattenpresse with a pressing pressure of 1.5 M Pa perpendicular to the plane of the plate to a thickness of 20 mm. The pressing pressure was maintained for 7 minutes, the temperature of the press plates was 150 ° C.

  - 5- 2 1955 1

LP 8002

The chipboard obtained had the following physical characteristics:

density kg / m- ' N / cm 604 flexural strength there N / cm 23.9 soundness there 0.60 Swelling 2h i> 5.05 perforator 0,010

After the procedure described, a second chipboard was prepared, but without the addition

, 1.14 parts by weight of urea 1.14 parts by weight of melamine and 1.71 parts by weight of ammonium sulfate

Add the glue-hardener mixture.

The chipboard obtained had the following physical characteristics;

density kg / m ³ 610 flexural strength there N / cm 24.5 soundness there N / cm 0.58 Swelling 2h * 5.32 perforator 0,020

The specified physical characteristics of the two plates are the same. They differ only within the Meßfehlerbereic'he test method. The release of formaldehyde from the finished chipboard was reduced by $ 50

The tests of the physical characteristics were carried out according to the following standards:

Density according to TGL 11369

ΤΓ.Τ. 1

- 6 - 2 19S5 1

LP 8002

Lift-off strength according to TGL 8767

Thickness swelling according to TGL 11370

Perforator value according to EN 120, draft GEN / TR 91

Example 2 100 parts by weight flat chips of pine wood of 0.3 to 0.4 mm thickness, 3> 0 to 5 mm wide and 20 to 30 mm in length were placed in a mixing drum and by nozzles with 13> 8O wt * parts a gluing fleet »

The Leirnflotte consisted of:

100 parts by weight of a Spanplattenleitnes on the

Base urea-formaldehyde with a solid resin content of $ 67

6 parts by weight of a 40% paraffin emulsion 6 parts by weight of a 20% solution of amorphous chloride 0.5 part by weight, - Parts of urea 1.5 parts by weight of melamine and 1.5 parts by weight of ammonium sulfate.

In a bulkhead with the dimensions 750 χ 300 mm xrarden 2.9 kg of the treated chips evenly distributed. This chip cake was compressed in a hydraulic hot plate press with a pressure of 1.5 M Pa perpendicular to the plane of the plate to a thickness of 20 mm. The pressing pressure was maintained for 7 minutes, the temperature of the press plates was 165 C "The chipboard obtained had the following physical characteristics:

density kg / m ^J 602 Flexural strength. there N / cm 21.9 soundness there N / cm 0.519 Swelling 2h 1" 5.07 perforator % 0,010

-7-219551

LP 8002

After the procedure described, a second chipboard was prepared, but without the addition

0.5 parts by weight of urea 1.5 parts by weight of melamine and 1.5 parts by weight of ammonium sulfate

Add the glue-hardener mixture.

The chipboard obtained had the following physical characteristics;

density kg / ra ³ 600 flexural strength there N / cm 21, 1 soundness there N / cm 0.519 Swelling 2h i 5.05 perforator * 0,020

The specified physical characteristics of the two plates are the same «They differ only within the measuring error range of the test method · The formaldehyde cleavage from the finished chipboard has been reduced by $ 50»

During the pressing process, the formaldehyde elimination was determined approximately 1 m from the press with the Dräger gas detector and the Dräger test tube of formaldehyde 0.5 / a, and the following values were determined:

0.5 ppm with the addition of 0.5% urea 1.5 melamine and 1.5% ammonium sulfate

1.0 ppm without the addition of 0.5% urea 1, 5% melamine and 1.5% ammonium sulfate

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LP 8002

The formaldehyde elimination with the described additive is lower during the pressing process *> Q fo .

Claims (1)

- 9 - 21 955 1 LP 8002 Erf indtingsanspruc h A process for the production of particle board with low formaldehyde elimination using a urea-formaldehyde resin as a binder and incorporating a urea-containing mixture as a formaldehyde reducing component before the mixture is compressed in a conventional manner under Vfärmeeinwirkung, characterized in that the chip-binder A mixture of O ₅ 5 to 1.5 parts by weight of urea, o, 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 binder, is added "