SU1118655A1 - Composition for manufacturing fiber boards by dry method - Google Patents

Abstract

COMPO: ZITIUM FOR THE MANUFACTURE OF WOOD-FIBER TILES IN A DRY METHOD, containing wood fiber, paraffin and a binder, differs from the fact that, in order to reduce water absorption and swelling of the plates, it contains the condensation product of urea with ethylene glycol, as well as a mixture of the composition of the matrix, as well as swelling of the plates, and the swelling of the plates. : 0.5-3: 1, respectively, in the following ratio of components, wt.%: The condensation product of urea with ethylene glycol at a molar ratio of 3: 0.5-3: 1, respectively, 4-5 Paraffin1-2 Woody fiber The rest

Description

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The invention relates to woodworking industry, in particular to the production of fiberboard by the dry method.

Compositions for the manufacture of wood plates, containing wood fiber and binding, are known - resole phenol-formaldehyde or urea-formaldehyde resin in an amount of 10-15% by weight of G13 chips.

However, the use of compositions based on these resins is complicated by the premature and irreversible curing of the binders during drying, which makes it difficult to finish the plates due to the formation of loose surface layers. In addition, the plates obtained on the basis of these compositions are characterized by low strength properties and water resistance.

A known composition containing wood fiber and urea 2 J.

However, due to the low speed of the reaction between wood fiber and urea in the production of Plates on the basis of this composition, it is necessary to additionally include heat treatment chambers in the processing line. In addition, the disadvantage of such a composition is the low physico-mechanical properties of wood boards.

- The closest to the technical essence and the effect achieved is a composition for manufacture. dry boards 3J, containing, in May.%:

Urea4-5

Polyvinyl alcohol 0.005-0.010 H2NCONH2-1- НОСН2СН20Н Products formed as a result of condensation are oily, colorless liquids, completely soluble in water, pH 8.0-8.5, density at 20 ° С 1.1131, 302 g / cm . For the manufacture of the composition, aqueous solutions of condensation products with a concentration of about 30% are used, which are sent to the process stream in the usual way. Due to the free NH groups, these products can be condensed by thermal action with aldehyde groups present on the surface of wood fibers. The optimal amount of urea condensation products with ethylene glycol in the composition is 4-5 wt. A reduction in their amount is less than 4 wt. does not allow to obtain the desired effect. Use of Condens Products

Paraffin .l-li: 5

Wood Alocole Remaining The wood fiber plates obtained by hot pressing of this composition are characterized by high strength properties, but low water resistance (strong water absorption and swelling).

The purpose of the invention is to reduce water absorption and swelling of fibreboard. .

This goal is achieved in that the composition for making dry fibreboard containing wood fiber, paraffin and binder as a binder contains a condensation product of urea with ethylene glycol at a molar ratio of 3; 0.5-3: 1, respectively, in the following ratio of components , wt.%:

The condensation product of urea with ethylene glycol at a molar ratio of 3: 0.5-3: 1 respectively4-5

Paraffin1-2

Wood fiber Remaining Condensation of urea with ethylene glycol is carried out in a reactor at 100-1 € 0 ° C for 45-120 minutes at a molar ratio of urea to ethylene glycol of 3: 0.5 or 3: 1.

Characteristics of the products obtained are given in table. one

Schematically, the process of interaction of urea with ethylene glycol can be represented as follows: H NCOOCHjCHgOH mol. Avdccot JOf H NCOOCH CHjOCONH LLOA. T4c in the amount of more than 5 wt.% Also impractical because it does not lead to a further increase in water resistance. At the same time, the ratio of urea and ethylene glycol upon receipt of condensation products does not significantly affect the physical and mechanical properties of the plates. The optimum amount of paraffin is 1-2% by weight. Plates obtained by extrusion, compositions containing less than 1 wt.% Paraffin, have low physical and mechanical properties. An increase in the paraffin content in the composition of more than 2 wt.% Does not lead to an increase in the physicomechanical properties of fiberboard. The proposed composition is prepared as follows. Hardwood chips are steamed in a defibrator at a pressure of 0.6 -

1.0 MPa for 1 min and grind into fibers. In the process of grinding the mass is treated with molten paraffin (according to the usual technology). Condensation products of urea with ethylene glycol are applied to the obtained fiber in a bar-type mixer by spraying 30% aqueous solutions. The treated fiber is dried to a moisture content of 10-16%.

To obtain composite fiberboard, it is molded into a carpet on a vacuum forming machine. After cold pressing, the plates are pressed in a hot press at 180-22 ° C for min / mm thickness of the finished plate.

Example. Wood fibers (95 wt.%) With paraffin applied by a known technology (1 wt.%) Are treated in a drum mixer with a 30% aqueous solution of the product.

condensation at 45 moles of urea and 0.5 moles of ethylene glycol (4 wt.%) for 45 minutes.

The resulting mass is dried to a moisture content of 8-10% and molded by dry method on a periodic machine in the carpet. Pressing is carried out at 20 ° C for 1 min / mm of the thickness of the finished plate.

Analogously to example 1 using other ratios of the components receive fibreboard, the properties of which are given in table. 2

As can be seen from the data presented in table. 2, the use of the inventive composition allows the production of fibreboards with significantly lower water absorption and swelling than when using the known composition 3.

Urea condensation product with

4.0 ethylene glycol

Wood fiber

Paraffin

Urea condensation product with

ethylene glycol

table 2

55.0

20.8

16.2

59.0

15.0

10, .9

Continued table. 2

Claims (1)

COMPOSITION FOR MANUFACTURE OF WOOD FIBER BOARDS A DRY METHOD containing wood fiber, paraffin and a binder, characterized in that, in order to reduce water absorption and swelling of the plates, it contains as a binder a condensation product of urea with ethylene glycol at a ratio of 3 mol , 5-3: 1, respectively, with the following ratio of components, wt.%: Condensation product of urea with ethylene glycol at a molar ratio of 3: 0.5-3: 1, respectively Paraffin Wood fiber 4-5 1-2 Rest