The method of obtaining the modified wood

 

(57) Abstract:

The invention relates to chemical treatment of wood, in particular to the production of blanks for the woodworking industry from low-value wood. To obtain the modified wood are impregnated wood 30-40% aqueous solution of urea, followed by drying under mechanical pressure at the initial temperature 100S, and in the impregnating solution add forcontent urea-formaldehyde oligomer in an amount of 10-12% by weight of dry urea.

The invention relates to the field of chemical processing of wood, in particular to the production of blanks of the desired properties for the woodworking industry mainly of low-value wood. The prior art in this field is characterized by the fact that a method of obtaining modified wood, including impregnation of timber with a solution of urea and the control of its content in the wood of the subsequent drying under pressure at a temperature of 90-120%, and thermostabilization blanks [Shamayev Century A. Modification of wood. M.: Ecology, 1991, S. 38].

Also known cause impregnation of the wood with a solution of urea, containing 6-10% of methenamine by weight of dry urea at pH of solution, 6,4-6,5, drying under mechanical pressure at a temperature of 100-120With simultaneous thermostabilization [U.S. Pat. Of the Russian Federation No. 2131351, CL 27 To 3/50, 1999].

The technical disadvantages of this method are insufficient formostabilnost get wood, as well as the complexity of making the three-component aqueous solution (urea, methenamine, hydrochloric acid).

The technical problem on which the invention is directed, increased thermostability modified wood. To solve this problem, the impregnation of wood is carried out in a 30-40% aqueous solution of urea containing 10-12% of forcontent urea-formaldehyde oligomer relative to the dry weight of urea, and the temperature at the end of drying was adjusted to 130C. For modification of wood was used aqueous dispersion of urea-formaldehyde resins, and aqueous resins of urea and formaldehyde, leading to the formation of resins in the wood. The use of resin required to obtain formostabilnost wood introduction 70-100% of dispersion resin by weight of dry wood, in the region which had the effect because the reaction of polycondensation was uncontrollable, often starting back in the impregnating solution, and the percentage receiving forestablishing wood does not exceed 15%.

Using forcontent would eliminate the reaction polycondensation in the impregnating solution and to carry out it in only dry wood when the moisture content will be less than 30%. By this time the wood has passed the stage of pressing. Urea as a plasticizer has already played a role and it is further drying at a temperature of 120-130With reacts with forcompensation and components of the wood, forming in the reaction of polycondensation infusible and insoluble products knitting, giving promotability wood. The temperature increase at the end of drying over 130Since it is impractical, because it begins the process of degradation products of polycondensation and thermostability wood is reduced. The lower limit of the content of forcontent 10% due to the efficiency of thermostabilization pressure-treated wood in natural wood of firm breeds, i.e. 14-16%. The upper limit of 12% due to the fact that the higher concentration of forcontent reaction polik is(emission of 300 mg/l). Therefore, the content of forcontent in the wood should not exceed 1.5% of the mass of absolutely dry wood. The method is as follows. In 30-40% aqueous solution of urea add 10-12% by weight of dry urea of forcontent urea-formaldehyde oligomer (TU).

Procurement of raw wood is loaded into the solution and carry out the impregnation diffusion method to the content of urea 10-15% of the mass of absolutely dry wood. After that, the workpiece is dried under mechanical pressure of 0.6-1.0 MPa at an initial temperature of 100C and the final temperature of 130C to a moisture content of 4-5%. The result is a modified wood density 800-1100 kg/m3having a maximum volumetric swelling in water of 14-16%, i.e., 36% less than that of the prototype, and not exceeding the volumetric swelling natural hardwoods.

Example 1

A 40% aqueous solution of urea was added forcontent urea-formaldehyde oligomer in an amount of 10% by weight of dry urea. After stirring the resulting solution was loaded timber birch dimensions 80C and the final temperature of 130C, then cooled to room temperature. The density of the obtained product was 1100 kg/m3the maximum volumetric swelling in water of 16%.

Example 2

A 30% aqueous solution of urea was added forcontent urea-formaldehyde oligomer in the amount of 12% by weight of dry urea and stirred. In the resulting solution was loaded billet alder dimensions 501301200 mm humidity 88%. After 152 hours the content of urea was 11% relative to the weight of dry wood. The processed workpiece was dried under a pressure of 0.5 MPa to a moisture content of 5% at the initial temperature 100C and the final temperature of 130C, then cooled to room temperature. The density of the obtained product was 800 kg/m3the maximum volumetric swelling in water of 14%.

The method of obtaining the modified wood, including propedine, drying of the workpieces under mechanical pressure at 100-120With simultaneous thermostabilization, characterized in that the impregnation is carried out in an aqueous solution of urea containing 10 to 12% of forcontent urea-formaldehyde oligomer by weight of dry urea, and the temperature at the end of drying was adjusted to 130C.

 

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