LV12494B - Production method of oak blanks stained with gaseous ammonia - Google Patents

Abstract

The object of an invention is production method of long-sized oak blanks, mainly parquetry flooring blanks, stained by chemical treatment with gaseous ammonia, heat-treatment and drying. The offered method is characterised in that the aforesaid treatment is carried out in the autoclave, preferably in the heatable autoclave, that is provided with vacuum pump, ammonia force feed system, induced circulation system of heat-transfer agent in the autoclave formed by mixture of ammonia, air and water vapours, as well as removal and regeneration system of waste ammonia that is not chemically fixed to wood substance and monitoring and control system of ammonia, heat-transfer agent and wood stack parameters in the autoclave. The essence of the invention: - oak blanks with initial moisture content within the limits 14-18 % are used; - the ammonia feed in the autoclave is ensured within the limits 3-6 % of absolutely dry wood stack mass retaining the temperature in the autoclave during the process within the limits 20-140 oC and ensuring periodical, best of all continuous, forced circulation of heat-transfer agent in the autoclave; - the pressure of gaseous medium in the autoclave during the active treatment with ammonia is retained within the limits 0,2-0,6 bar; - the total duration of the process is ensured within the limits 36-64 hours.

Description

TECHNICAL DESCRIPTION OF THE INVENTION

The invention relates to the chemical treatment of oak wood with ammonia and can be used for continuous (through) staining of oak wood (sometimes also referred to as etching or staining), providing the desired staining intensity and maintaining the specific texture of oak wood.

It is well known that the treatment of wood with ammonia stains the staining intensity (the color of the wood) depends on many factors (the initial humidity of the wood, the amount of ammonia introduced into the wood, the duration of the treatment with ammonia, treatment temperature, etc.).

The technique for staining oak wood / 3 / in a closed container such as an autoclave, aqueous ammonia solution and / or ammonia vapor is known using freshly cut oak wood blanks or humidified oak wood blanks with a moisture content of up to 70%. The disadvantage of this process is the significant consumption of ammonia, which reaches 8-10% by weight of the absolutely dry wood, and the continuous condensation with the ammonia dissolved therein, which is difficult to control and the processing time is very long, taking into account the need to a process in a closed system for the final production of environmentally friendly blanks in the absence of chemically unbound ammonia.

A virtually ecologically clean wood coloring process is known / 4 /, which comprises the following steps: treatment of wood with gaseous ammonia, removal of chemically unbound ammonia from the wood in the autoclave itself by means of a periodic vacuum treatment of the material by the following process:

- Wood treatment temperature with ammonia - 60-110 ° C;

- the amount of ammonia introduced into the wood - 2-10% by weight of absolutely dry wood;

- temperature of chemically modified wood after heat treatment including drying to complete removal of moisture and non-chemically bound ammonia -130-170 ° C;

- the duration of said heat treatment is 1 to 5 hours, provided that the initial humidity of the wood to be stained corresponds to that of the dry air of the wood under normal conditions.

It should be noted that for the protection of the environment, all techniques for chemical modification of wood with ammonia must be carried out in a closed system and in the process it is imperative to ensure removal of non-wood ammonia from wood such as / 5 / by heating chemically modified wood 110 ° C and after heating it under vacuum until the content of non-chemically bound ammonia in the wood does not exceed 0,1-0,4% of the weight of the absolutely dry wood, whereby the heating can be carried out cyclically by varying the cycle time and temperature.

The disadvantage of both of these techniques / 4; 5 / is that they do not reflect the specificity of oak wood blanks, which are mainly determined by the specific structure of the oak wood, and the size nomenclature for use primarily as parquet boards without additional wood sealing.

The object of the invention is to achieve a uniform staining intensity of oak wood longitudinal blanks, mainly parquet board blanks, throughout the thickness of the blanks, to reduce waste of ammonia during processing and to reduce the amount of chemically unbound ammonia to be recovered at the end of processing.

BACKGROUND OF THE INVENTION The present invention relates to a process for painting oak wood longitudinal blanks, mainly parquet board blanks, characterized in that the blanks are treated with gaseous ammonia as well as heat treatment and drying in a heated autoclave equipped with an ammonia feed system, and water vapor mixture), an autoclave system for the removal of non-wood ammonia from the autoclave and its regeneration system, and a system for controlling and regulating the ammonia, heat carrier and wood parameters.

The essence of the invention is as follows;

- oak blanks with an initial humidity of 14-18% are used for painting;

- the autoclave ammonia is fed in an amount of 3-6% by weight of the stack in the autoclave, based on the mass of the wood in the dry state, maintaining the autoclave temperature within the range of 20-140% during the process and ensuring periodic, preferably continuous

- ambient pressure in the autoclave is maintained at 0.2-0.6 bar during active treatment with ammonia;

- the overall duration of the process is ensured within 36-64 hours.

Sources of information:

1. The USSR a.a. 360220, SKI B27K3 / 04, 1968

2. USSR a.a. 317510, SKI B27K5 / 02, 1970.

3. USSR aa 899349, SKI ³ B27K5 / 02, 1980 (cnoco6 MopeHMfl fly6a); LV Patent 5603, 1994.

4. USSR aa 1376402, SKI ⁴ B27K5 / 02, 1986 (cnococh OKpaujMBaHMR flpeBecMHbi).

5. USSR aa 11055310, SKI ³ B27K3 / 02, 3/10, 1982 (cnoco6 XHMMHeCKOrO Μ0βΜφΜ14Ι / ΐρ0Β3ΗΜί1 flpeBeCMHbl M yCTpOMCTBO flilfl ΘΓΟ ocymecTBneHMfl).

Claims (4)

1. A method of staining oak wood longitudinal blanks, mainly parquet board blanks, characterized in that the blanks are treated with gaseous ammonia, as well as heat treatment and drying, in a heated autoclave equipped with an ammonia feed system, water vapor mixture) circulation system, autoclave and non-wood ammonia removal system, and ammonia, heat carrier and wood parameters control and regulation system, characterized in that chemical treatment is carried out with a starting humidity of 14-18% . 2. A process according to claim 1, wherein the autoclave ammonia is fed in an amount of 3-6% by weight of the stack in the autoclave, based on the weight of the wood in an absolutely dry state, maintaining the autoclave temperature during the process within 20-140%. periodic, preferably continuous, autoclaving of the heat carrier. 3. The method of claim 2, wherein the ambient pressure in the autoclave is maintained at 0.2-0.6 bar during active treatment with ammonia. 4. A process as claimed in any one of the preceding claims, wherein the total process duration is provided within a range of 36-64 hours.