SU1675087A1 - Method for production of low-toxicity wood chipboards - Google Patents

Abstract

The invention relates to the woodworking industry and can be used in the manufacture of chipboard. The purpose of the invention is to reduce the toxicity of plates without reducing performance and deteriorating physical and mechanical properties. Aspen wood chips are ground on a DS-3 machine into chips. The chips are dried to a moisture content of 1-3% and sorted into fractions for the middle and outer layers of sandwich panels. After that, a binder is prepared by mixing carbamide-formaldehyde resin KF-MT-15 and an hardener — ammonium chloride. Before mixing with the ne binding chips, an aqueous solution of urea is applied in the amount of 0.45-1.00% of the dry weight of the chips in the outer layers and 0.4-0.8% in the middle layer. The concentration of the urea solution is 35- 50% and heated to 30-50 ° C. The amount of binder is 13.5% for the outer layers and 10.5% for the middle layer. Three-layer plates are pressed with a density of 650 kg / m3 at 165 ° C, a pressure of 2.5 MPa and a pressing time of 0.3 min / mm. 1 tabl Ј

Description

The invention relates to the woodworking industry and can be used in the manufacture of chipboard.

The purpose of the invention is to reduce the toxicity of plates without reducing performance and deteriorating physical and mechanical properties.

PRI me R 1. Chips of aspen are ground on the bed DS-3 in chips. The chips are dried to a moisture content of 1–3% and sorted into fractions for the middle and outer layers of sandwich panels. After that, a binder is prepared by mixing carbamide-formaldehyde resin KF-MT-15 according to GOST 14231-78 and an ammonium chloride hardener. in the outer layers and 0.4% in the middle layer. The concentration of the urea solution is 35% and is heated to 30 ° C.

The mixing of chips with a binder is carried out in a laboratory blender at the rate of its dosing on a completely dry residue,% relative to the mass of chips

Outer layers13,5

Middle layer 10, b

Content of the press mass by layers,%: External35

0

Vi ate about

00 VI

Average65

Three-layer plates are pressed with a density of 650 kg / m3 with the following operating parameters:

Temperature, ° С165

Pressure, MPa2.5

Duration, min / mm0,3. Testing the physical and mechanical properties of the plates is carried out according to GOST 10632-72. The content of free formaldehyde in the slabs is checked using the perforator method. Test data plates are shown in table.

EXAMPLE 2 Example 1, with the amount of urea applied to the surface of the chip being 1.0% in the outer layers, 0.8% in the middle layer, the temperature of the solution being 50 ° C, and a concentration of 50%.

Example The procedure is carried out as in Example 1, wherein the concentration of the urea solution is 40%, its temperature is 40 ° C, and the amount of urea in the layers is 0.6% on average and the outer layers.

Example 4 is carried out as in Example 1, the concentration of the urea solution is 30%, the temperature is 25 ° C, and the consumption of urea over the plates of the plates,%: in the outer layers 0.2; in the middle layer of 0.3.

Example 5: Carried out as in example 1, the concentration of the urea solution is 55%, the temperature is 60 ° C, and the consumption of urea over the layers is%: middle layer 0.9; outer layers 1.1.

The test results of experimental batches of plates are presented in the table.

The application of a heated aqueous solution of urea provides its penetration to the required depth into the wood, which in turn does not reduce the pressing performance and does not lead to a deterioration of the physical and mechanical properties of the plates.

Thus, the invention makes it possible to reduce the toxicity of the plates without reducing the performance and deterioration of their physical and mechanical properties.

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Claims (1)

Invention Formula Method for the production of low toxicity particle boards, including the manufacture, drying, sorting of wood particles, preparation binder based on urea-formaldehyde resin with free formaldehyde content of not more than 0.2%, mixing it with wood particles along the layers of the plates, forming a carpet and pressing the plates, characterized in that, in order to reduce the toxicity of the plates without decreasing the productivity and deteriorating the physicomechanical parameters, before mixing with the binder to the chip separately an aqueous solution of urea in the amount of 0.4-0.8% by dry residue for the middle layer and 0.45-1.00% for the outer layers is applied by spraying the layers of the plates, while the urea solution is used by concentration 35-50% and heated to 30-50 ° C.