RU2541323C1 - Method of production of wood boards - Google Patents

Abstract

FIELD: woodworking industry.

SUBSTANCE: method of production of wood boards comprises placing the wood raw material in a container with water, which is subjected to cavitation treatment. At that the 40-60-fold cavitation treatment is carried out in a hydrodynamic disperser with radially directed channels to obtain fibre-split wood particles with the length of less than 1.5 mm, the thickness of 0.01 to 0.05 mm and the width of 0.03 to 0.06 mm, and a high content of active reaction centres on the surface.

EFFECT: method provides obtaining of hydrodynamically activated wood particles, which enables to obtain non-toxic high-density wood boards with high physical-mechanical properties.

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Description

The invention relates to the field of woodworking, and in particular to methods for producing wood boards without the use of medium density binders (from 650 to 1000 kg / m ³ ). The invention can be used for the production of building products: furniture, rough floors, wall panels, operated in variable humidity conditions.

A known method for the production of fibreboard wet method [1]. It consists in the following: at the first stage, round timber or lumpy woodworking wastes are crushed into technological chips of the PV grade, after which it is subjected to hydrothermal and chemical treatment. Chips are crushed by special machines (defibrators and refiners) into individual fibers, which in a mixture with water and additives make up the wood pulp for the boards.

The disadvantage of this method is that the manufacturing technology of plate materials does not allow to obtain finished products with a thickness of more than 5 mm The main negative point of the technology is determined by high energy costs. Most of the thermal energy is consumed in the process of hydrothermal processing of wood raw materials with the aim of plasticizing it before grinding. An insignificant disadvantage of wood-fiber boards is the low water resistance and form stability in variable humidity conditions.

A known method of manufacturing a wood board, in which wood bark is used as an adhesive with a fraction of 40 to 5000 microns, and a filler of cellulose fibers obtained from the recycling of waste paper from annual plants and pulp and paper waste [2].

The disadvantage of this method is that the filler are cellulose fibers. The manufacture of this type of raw material requires the use of chemical reagents, which has a significant impact on the toxicity of the finished product. The second negative point is that it is proposed to use only bark of birch wood of a certain fractional composition as a binder, which requires the use of additional grinding equipment, thereby increasing the cost of the finished product.

A known method of producing a composite of lignocellulosic material obtained by hydrothermal treatment [3]. The essence of this method is as follows: a solution of 0.1-15.0 parts by weight is applied to wood waste. hydrogen peroxide and treat them with superheated steam at a temperature of 170-180 ° C. Steamed wood waste during decompression turns into pulp wood pulp, which is dried to a moisture content of not more than 5% for subsequent processing. A pulp without the addition of binders is molded and cold pressed. Hot pressing is carried out at 120-160 ° C at a pressure of 4.0 MPa and a specific process duration of 1 min / mm

The disadvantages of this method include the complexity of the technological implementation, the high energy intensity of production, the density of the resulting material exceeds 1000 kg / m ³ .

The closest invention of the same purpose is a method for producing plate materials [4]. According to this invention, the press mass in the form of plant materials (sawdust, cereal straw, etc.) is obtained by cavitation treatment. Plant materials (with a moisture content of 3-8%, a fraction of up to 1.25 mm and 2 cm, respectively) are placed in a container with water (hydraulic module is 10) without or with the addition of a hydrolyzing agent - sulfuric acid (concentration up to 1%). The mass is subjected to cavitation for various periods of time (from 15 to 120 minutes). The process is accompanied by spontaneous heating of the mixture to 95 ° C.

The disadvantages of this method are the significant energy costs for drying the feedstock and the resulting pulp, the use of chemicals in the processing of plant materials. The recommended pressing temperature does not provide the conditions for the formation of bonds between the surface reaction centers of the ligno-carbohydrate complex, which does not allow to obtain medium-density material with high physical and mechanical properties. When the density of the plates is more than 1.5 times higher in comparison with materials manufactured with the addition of synthetic binders, their mechanical properties are of equal value. With prolonged exposure to water on the material obtained without the addition of adhesives, its complete destruction occurs.

The invention solves the problem of obtaining hydrodynamically activated wood particles allowing the manufacture of non-toxic wood boards with a density of 650 to 1000 kg / m ³ with high physical and mechanical properties.

The technical result consists in obtaining hydrodynamically activated wood particles with a length of at least 1.5 mm and a high content of active reaction centers on the surface, providing an optimal structure of the plates during further pressing, which allows obtaining non-toxic wood boards with a density of 650 to 1000 kg / m ³ with high physical -mechanical properties.

The specified technical result is achieved by the fact that in a method of manufacturing wood-based panels, including placing wood raw materials in a container with water, which is subjected to cavitation treatment, it is new that a 40-60-fold cavitation treatment is carried out in a hydrodynamic disperser with radially directed channels to obtain fibrous wood particles with a length of at least 1.5 mm, a thickness of 0.01 to 0.05 mm and a width of 0.03 to 0.06 mm, and a high content of active reaction centers on the surface.

This makes it possible to obtain hydrodynamically activated wood particles with a length of at least 1.5 mm with a high content of active reaction centers on the surface. The processing time is characterized precisely by the multiplicity of passage of wood particles through the dispersant (from 40 to 60 times), and not by the processing time, and was determined experimentally by the authors.

Multiplicity less than 40 times does not allow to obtain the required maximum content of particles with a length of at least 1.5 mm, a thickness of 0.01 to 0.05 mm and a width of 0.03 to 0.06 mm. Particles of these sizes have a minimum number of surface active centers, which in turn does not allow to obtain plate material with a density of 650 to 1000 kg / m ³ with acceptable physical and mechanical properties.

The multiplicity of processing in a hydrodynamic disperser with radially directed channels more than 60 times leads to an increase in the proportion of wood particles with a length of less than 0.25 mm to 30%, which significantly reduces the mechanical strength of the plate material in bending.

The fractional composition of wood pulp at various processing ratios is presented in table 1.

Table 1 Name Sieve diameter, mm 10 5 2.5 one 0.5 0.25 bottom The fraction fraction before grinding,% 30,0 8.25 37.75 5.00 6.47 - 12.53 The fraction fraction after 40 times processing in the dispersant,% 22.1 4.65 30,44 9.81 12.45 4.03 16.52

The fraction fraction after 60 times processing in the dispersant,% - - - 28,4 3.21 64.6 3.79

The use of rotary pulsation apparatus (rotary cavitators) does not allow to obtain wood particles with a length of more than 0.5 mm, this is due to the significant influence of mechanical stress during dispersion. Also, a significant drawback of producing particles in these devices is the low surface content of active reaction groups, which, when pressed, form bonds between themselves do not provide structure formation of plates with high physical and mechanical properties.

The use of a hydrodynamic dispersant with radially directed channels makes it possible to obtain fibrous wood particles with a length of at least 1.5 mm, a thickness of 0.01 to 0.05 mm and a width of 0.03 to 0.06 mm

There is no need for the process of drying wood after processing in a dispersant, since otherwise there will be a decrease in the reactivity of the ligno-carbohydrate complex of wood, which in turn will not allow to obtain a material with a density of 650 to 1000 kg / m ³ with high physical and mechanical properties.

Figure 1 presents a diagram of the pressing of wood boards; figure 2 is a flow chart of the manufacture of wood boards.

A device for implementing the method includes a sawdust bin 1; sieves with a mechanical drive 2; screw conveyor 3; mixing hopper 4; gear pump 5; hydrodynamic dispersant 6; capacity for pulp 7; a roller with a hydraulic drive for mechanical extraction 8; roller press 9; hot press 10; format-edging machine 11; lifting table for placing finished plates 12; forming machine 13.

A method of manufacturing wood boards as follows. Wood particles (sawdust) of coniferous or deciduous species with a moisture content of 8 to 100% are mixed with water with a mass ratio, m.h .: from 10 to 20 and from 80 to 90, respectively. After that, the resulting mass is piped to a hydrodynamic dispersant with radially directed channels. The processing time is determined by the multiplicity of passage of the mass through the active region of the dispersant. The multiplicity of processing is limited by increasing the proportion of wood fibers with a length of less than 0.25 mm, which negatively affects the mechanical properties of the finished boards. According to the proposed method, the processing ratio should vary from 40 to 60 times. The treated particles are pumped to a tank, from where they are fed to a mesh conveyor using a paddle batcher. During the movement of the mass on a mesh conveyor using rollers (force from 1.5 to 2 MPa), mechanical extraction is performed. The moisture content of the wood pulp is brought up to 180%. The formation of a fibrous carpet is carried out on mesh pallets (mesh diameter from 0.1 to 0.25 mm), the height of which should be no more than two thicknesses of the finished plates. The formed carpet is pressed in a roll press at a specific pressure of 0.5 MPa, while the height of the carpet is reduced to 1.5 times the thickness of the finished material. The resulting carpet on a mesh pallet is pressed in a hot flat press at a temperature of from 190 ° to 220 ° C and a specific pressure of 1.0 to 1.6 MPa, according to the diagram presented in figure 1 (1 stage - 60%, 2 stage - 20%, stage 3 - 20% of the pressing cycle). The specific pressing time depends on the process temperature and the initial moisture content of the wood pulp and varies from 0.8 to 1.5 min / mm.

Example 1

Wood particles (sawdust) of coniferous or deciduous species with a moisture content of 70% from hopper 1 are fed to sieves with a mechanical drive 2, where large fractions of wood and bark are separated. After which the sawdust with the screw conveyor 3 is sent to the mixing hopper 4 (volume from 3 to 15 m ³ ), where it is mixed with water in a mass ratio, m.h .: 20 and 80, respectively. After that, the resulting mass is piped through a pump 5 to a hydrodynamic dispersant 6, with radially directed channels and a channel cross-section of at least 0.81 cm ^{2 of a} rectangular shape. The multiplicity of processing is 50 times. After dispersion, the mass is pumped to the pulp container 7. After this, the treated particles are fed to the mesh conveyor 15. Using a roller press 14 with a force of 2 MPa, mechanical extraction is performed. The moisture content of the wood pulp is brought up to 180%.

The fibrous carpet is formed on mesh pallets with a mesh diameter of 0.25 mm, which are stacked on the conveyor 16. The formed carpet is pressed in a roller press 9 at a specific pressure of 0.5 MPa, the height of the carpet is reduced to 1.5 the thickness of the finished material.

The resulting carpet on a mesh pan is hot pressed in a hot press 10 at a temperature of 220 ° C and the specific pressure is varied from 1.0 to 1.6 MPa during the pressing process, according to the diagram shown in FIG. 1, for 1 min / mm.

Example 2

Analogously to example 1. Wood particles having a moisture content of 12% are mixed with water in a mass ratio, m.h .: 10 and 90, respectively. Then they undergo sixty-fold processing in a hydrodynamic dispersant 6, after mechanical extraction and carpet formation, the mats are pressed at a temperature of 190 ° C and a specific duration of 0.8 min / mm of plate thickness.

Physico-mechanical properties of the resulting plate materials are presented in table 2.

table 2 Name of indicator Value at density, kg / m 650 800 900 950 Strength in static bending, σ, MPa 9.25 12.36 13.8 14.01 The tensile strength perpendicular to the reservoir, σ _⊥ , MPa 0.53 0.6 0.69 0.75 Specific resistance to pulling screws, N / mm 36.54 37.00 37.87 38.24 Volumetric swelling in 24 hours, ΔV,% 11.39 8.95 9.41 9.55 Water absorption, ΔW,% 18,99 2.42 2,32 12.73

Table 3 presents the physico-mechanical properties of the obtained plate materials at different processing ratios in the dispersant.

Table 3 Name of indicator The multiplicity of processing in the dispersant (with a density of plates of 900 kg / m ³ ) thirty 60 90 120 Strength in static bending, σ, MPa 9.78 13.8 10.15 8.04 The tensile strength perpendicular to the reservoir, σ _⊥ , MPa 0.24 0.69 0.71 0.75

Specific resistance to pulling screws, N / mm 22.41 37.87 32,40 28.76 Volumetric swelling in 24 hours, ΔV,% 33.39 9.41 7.34 7.25 Water absorption, ΔW,% 28.64 2,32 2.26 2.10

The proposed method allows to obtain wood waste from sawmills with high physical and mechanical properties. In addition, reduced energy costs for obtaining wood-based panels.

Information sources

1. Integrated chemical processing of wood: textbook. for universities / I.N. Koverninsky, V.I. Komarov, S.I. Tretyakov; ed. I.N. Koverninsky; Arkhang.gos.tehn. un-t - Arkhangelsk: ASTU, 2002 .-- 347 p. - Bibliography: p. 342. - ISBN 5-261-00054-3 /

2. RU 2173256, IPC B27H 3/08, publ. 09/10/2001

3. RU 2152966, IPC C08L 97/02, B27K 9/00, B27N 3/04, B27N 3/18, publ., 07.20.2000.

4. RU 2381244, IPC C08L 97/02, B27K 9/00, B27N 3/04, publ. 01/09/2008.

Claims (1)

A method of manufacturing wood-based panels, including placing wood raw materials in a container of water, which is subjected to cavitation treatment, characterized in that a 40-60-fold cavitation treatment is carried out in a hydrodynamic disperser with radially directed channels to produce dispersed wood particles with a length of at least 1.5 mm , with a thickness of 0.01 to 0.05 mm and a width of 0.03 to 0.06 mm and a high content on the surface of active reaction centers.

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