SU1546261A1 - Method of producing modified wood - Google Patents

Abstract

The invention relates to the woodworking industry. The purpose of the invention is to improve the physico-mechanical parameters. Rectangular-shaped softwood hardwood blanks with a moisture content of 10-15% are subjected to exhaustive acetylation with excess acetic anhydride for 48 hours. After that, acetic acid formed in wood and excess acetic anhydride is removed by drying in a drying chamber at a temperature of 80-100 ° C . The weight of acetyl groups is 25-30% (the conversion of wood hydroxyl groups is 85-95%). Instead of treatment with acetic anhydride, treatment with ketone can be used for 10 hours. In this case, the drying operation is no longer necessary. Dried billets are impregnated under pressure with aqueous solutions of phenol alcohols of 46% concentration to a weight gain of a solution of 80-100%. After that, they are dehydrated with phosphorus pentoxide to a moisture content of 10-12%. The weight gain of phenol alcohol in terms of dry wood is 36-42%. 2 tab.

Description

The invention relates to the production of modified wood and can be used in the woodworking industry.

The purpose of the invention is to improve the physico-mechanical parameters.

To implement the process, it is first necessary to block the hydroxyl groups of cellulose, hemicellulose and lignin, which are responsible for the hydrophilicity of wood, by exhaustively 1 acetylating the wood, for example, with acetic anhydride. Then it is necessary to sew cellulose micromolecules that form microfibrils, depriving them of the possibility of mutual displacement.

To do this, it is necessary to impregnate the wood with a monomer or oligomer penetrating into the cell wall, for example, phenol-formaldehyde oligomer (phenol alcohols), followed by. cure. The most difficult task arises when it is necessary to stabilize the cells of the wood, flattened as a result of pressing, since during their spreading the main deformation of the wood swelling occurs. The flattened cells and vessels are in a stressful state and, upon ingestion of moisture, tend to return to their natural form. To stabilize them you need to create

in lumens of a spatial two- or three-meter grid with the obligatory cross-linking of the grid with functional groups of wood. This cage is formed during curing phenol-alcohols, which react with the active groups of wood ingredients.

The method is carried out as follows.

Rectangular timber softwood species with a moisture content of 10–15% are subjected to exhaustive acetylation with excess acetic anhydride for 48 hours. Thereafter, the acetic acid formed in the woodfunction and excess acetic anhydride is removed by drying (in a drying chamber at 80-100 ° C. The weight of the acetyl groups is 25-30% (wood conversion degree of hydroxyl groups is 85-95%). Instead of treatment with acetic anhydride, ketone treatment can be used for 10 hours. drying operation disappears. These blanks are impregnated under pressure with aqueous solutions of phenol-alcohols of 46% concentration to a weight gain of 80-11) 0%, after which they are released over phosphorus pentoxide to a moisture content of 10-12%. The weight gain of phenol alcohol in terms of dry wood is 36-427.

The resulting material is pressed in a mold to a density of at least 1200 kg / me. If the wood pressing density is less than 1200 kg / m3, then the cell cavities are not sufficiently flattened and their phenol alcohols are not fully crosslinked with polycondensation products, as a result of which the stabilization wave effect cannot be achieved, as can be seen from Table. one.

Compressed blanks are subjected to heat treatment at 110-140 ° C. The curing time of phenol alcohols is 6–10 min per 1 mm of the thickness of the pressed billet (.6 min at 140 ° C and 10 min at 110 ° C) „

Example 1. A billet of birch wood with a cross section of 65x65 mm and a length of 200 mm was treated for 48 hours with acetic anhydride with a preliminary vacuum. After this, the preparations were dried at 80 ° C for 36 hours to remove the acetic acid that was formed. The content of acetyl groups was 307. Next, the preforms were impregnated in an autoclave with a solution of 0.

five

0

five

0

five

0

five

rum phenol-alcohols 46% concentration under a pressure of 15 atm. The ratio of phenol to formaldehyde in fenol alcohols is 1: 1.3. The weight of the solution was 90%. Impregnated blanks were dried over P205 and 12% moisture. The dried billets had a density of 810 kg / m. They were placed in a mold and pressed under a pressure of 30 Mlla to a density of 1200 kg / m. The degree of pressing was 40%. Compressed blanks were heat-treated in an oven at 140 ° C for 4 hours. Samples with dimensions of 10x10x5 mm were cut from blanks and the volume swelling was determined by water absorption and moisture absorption.

The limiting volumetric swelling of the modified wood was 0.6%, the limiting water absorption is 6%.

In tab. 2 shows the properties of wood obtained by the proposed and known methods.

The application of the proposed method reduces the water absorption of compressed wood by 5 times, and the swelling by 10 times compared to the known ones and provides an almost stable material, the shape of which is at the level of temperature materials.

Claims (1)

Invention Formula The method of obtaining modified wood, including impregnation with phenol alcohols, drying, pressing and heat treatment, characterized in that, in order to improve the physicomechanical characteristics of wood, prior to impregnation, the wood is subjected to acetylation with an excess of acetyl groups of 25-30% and degree of conversion hydroxyl groups of wood 85-95%, and pressing lead to a density of at least 1200 kg / me. Table 1 Table 2