Method for manufacture of products from composite materials, mostly cement wood

FIELD: technological processes.

SUBSTANCE: in method for manufacture of products from composite materials, mostly cement wood, which includes stages of wood filler and binder preparation, treatment of wood particles in electric field, preparation of cement wood mixture, moulding and thermal treatment, wood particles are treated in flow of orifice gas in discharge chamber at high frequency generator capacity of 200-600 W and underpressure of 100-130 Pa for 250-280 sec. Orifice gas used is air, and its flow rate makes 0.08-0.12 g/sec. Due to plasma treatment of wood particles, interface interaction at the border of wood and mineral binder is intensified as a result of surface loosening, opening of pores and capillaries.

EFFECT: increase of physical and mechanical properties of products from composite materials by modification of wood particle surface structure.

1 dwg, 2 tbl

 

The invention relates to the manufacture of products from composite materials based on waste wood processing industries and mineral binders that can be used as building materials in various industries. Mostly this invention can be used in the manufacture of products from arbolita.

A known method of manufacturing articles made of composite materials, including chipboard, namely, that the wood components are first mixed with powdered polyethylene, the resulting mixture to form a package in which evenly along its height distribute plenkoobrazovatel binder and the package is then heated and formed into a plate under pressure (see, for example, as the USSR №1666305, IPC B27N 3/02, 1991).

The disadvantages of this method is that it does not provide uniform encapsulating binder surface of the wood components, requires the use of film and excess consumption of binder to ensure high physical-mechanical characteristics. The high content of binder in the composition of the material leads to the fact that its properties and appearance close to the properties of plastics.

There is also known a method of manufacturing articles made of composite materials - arbolita, consisting of the stages of podgotovitelnaya, preparation of chemical additives, dosage of components, preparation of cement wood mixture, packing it in a mold and sealing, heat treatment of the formed articles and excerpts at positive temperatures (see, for example, the book Melnikova L.V. Technology of composite materials from wood. - M: at MSFU, 1999. - S.162-173).

The disadvantage of this technical solution is the low mechanical strength of the product.

This disadvantage is due to the inhomogeneous structure of the surface of the wood particles used as filler. Wood waste from different sources differ in the wettability of the surface and adhesive properties with respect to the solution of a mineral binder, which depend on the modes and methods of mechanical wood processing.

The closest in technical essence and the achieved result to the invention is a method of manufacturing a composite material, consisting in the preparation of wood filler and a binder, the processing of wood particles in an electric field, the preparation of cement wood mixture, forming and heat treatment (see, for example, patent RU 2076040, IPC B27N 3/00, B27N 3/14, 1997).

The disadvantage of this technical solution is the low mechanical strength of the composites due to uneven NAS is senjem fine polymer binder on the surface of the wood components of the fill.

Processing binder and wood filler is made of particles in chaotic movement of dispersed components. This leads to various charging conditions: particles closer to the electrodes acquire a greater electrical charge, compared to those particles that are removed from them. In addition, a wedge-shaped sections of wood particles can concentrate charged ions of the opposite sign (back-corona effect). Therefore, when mixing the components smaller particles of a polymeric binder in these areas will be recharged and build on the filler particles.

The technical task of the present invention is the improvement of physico-mechanical characteristics of composites, mainly arbolita, by modifying the surface structure of wood particles.

The problem is solved in that in the method of manufacturing of articles made of composite materials, mainly arbolita, including preparation of wood filler and a binder, the processing of wood particles in an electric field, the preparation of cement wood mixture, forming and heat treatment, it is new that the processing of wood particles is carried out in the flow of plasma gas in the discharge chamber when the high-frequency generator 200-600 watts and develop the position, equal 100-130 PA, for 250-280 with as a plasma-forming gas used air, and its consumption is 0.08-0.12 g/S.

When solving the above problem is achieved technical effect consists in the fact that due to the plasma treatment of wood particles is enhanced interfacial interaction on the border of the wood - mineral binder in the loosening surface, open pores and capillaries.

The invention is illustrated in the drawing, which shows a functional diagram of an installation for the implementation of the proposed method of manufacture of products from composite materials, for example arbolita.

The unit consists of a feed tank 1 with shredded wood filler, the plasma processing device 2 wood particles, an intermediate tank 3, tank for soaking 4 particles of filler mixer 5, water dispensers 6, cement 7, sand, 8, chemical additives 9, solution textured layer 10, the molding station 11, the press 12 and chamber heat treatment 13.

The plasma processing device 2 includes a vacuum chamber 14, a high-frequency generator 15, the compressed plasma-forming gas 16, the vacuum pump 17, the plasma torch 18, vacuum valves 19, 20, valve 21, the valve 22 to 24.

In the plasma torch 18 is installed electrodes 25 connected by an electric cable 26 with high fre is now a generator 15.

The cylinder with the working gas 16 is in communication with the vacuum chamber 14 through the control valve 27, the flowmeter 28, the valves 22, 23 and the plasma torch 18.

The vacuum chamber 14 is equipped with a gauging device 29 (gauge).

A method of manufacturing articles made of composite materials, mainly arbolita, as follows. Particles of wood filler from the supply tank 1 when the outdoor vacuum shutter 19 and the closed shutter 20 is served in the vacuum chamber 14. Vacuum the shutter 19 is closed, open the valve 24, and include a vacuum pump 17, which generate a vacuum in the vacuum chamber 14. After that, the vacuum chamber 14 through the plasma torch 18 at open valves 22, 23 sleuth working gas from the cylinder 16, by controlling and regulating the flow rate of 0.08-0.12 g/s) flowmeter 28 and valve 27. The specified residual pressure in the vacuum chamber 14 (100-130 PA) install control valve 24, is placed on the vacuum line and providing a given ratio between the performance of pumping systems and inlet working gas. Control the residual pressure in the working chamber vacuum gauge 29.

Include high-frequency generator 15 capacity of 0,2-0,6 kW and serves voltage to the electrodes 25. Between the electrodes, an electric arc with a high concentration of energy (plasma clot), which is what I heats the working gas to a state of low-temperature plasma. The surface of wood particles, placed in the flow of nonequilibrium low-temperature plasma is subjected to the bombardment of charged and excited atoms, UV radiation, heat flux and electromagnetic fields. As a result of plasma surface modification of wood particles is activated (cleaned from dirt, loosened, provided the disclosure of the pores and capillaries). The duration of the plasma treatment is 250-280 C.

After a predetermined period of time, disconnect the high-frequency generator 15, close the valves 22-24, turn off the vacuum pump 16, to open the valve 21 and increase the pressure in the vacuum chamber 14 to atmosphere. Wood particles surface modified with an open vacuum shutter 20 is unloaded from the vacuum chamber 14 in the intermediate tank 3 and is soaked in the tank 4.

Cement wood mixture produced in the mixer 5, which sequentially loads of wood filler, solutions, chemical additives, water (duration of mixing at least 180 C). Loading components and chemical additives to the mixer 5 is carried out by dosing 6-9.

Molded product of arbolita at station 11, and the mortar or fine concrete for textured layer is metered by the device 10. Then the product is subjected to the compaction press 12, th is the howl of the processing chamber 13 and the shutter speed.

The duration of plasma treatment 250-280 with due to the necessity of obtaining the required degree of activation of the surface of the wood particles. Reducing the time consuming process leads to a decrease of the parameters affecting the strength of the product: wettability and porosity. On the other hand, the increase in the duration leads to an increase in energy costs and reduce economic efficiency.

The reducing power of the high-frequency generator below 200 W leads to a decrease in the degree of activation of the surface of the particles, and the failure to comply with the upper limit on power (600 watts) - for intense impact of the jet discharge and contamination of the surface of wood particles by decomposition products.

The plasma gas flow is 0.06-0.12 g/s provides the most complete removal of the decomposition products from the reaction zone (0.06 g/s) and optimal energy costs to maintain the vacuum in the vacuum chamber (0.12 g/s).

The range of values for residual pressure 100-130 PA is due on the one hand (130 PA) changing properties of low-temperature plasma, leading to a deterioration in the quality of the treated wood particles, on the other (100 PA) - the increase in energy costs for the process.

As an example of a specific implementation of the method claimed as the invention was made about ASEC products made of composite material arbolita. For the manufacture of products were used waste after processing wood of coniferous and deciduous breeds on a milling machine with a maximum size up to 10 mm surface Treatment of wood particles was carried out low-temperature nonequilibrium plasma under the following operating parameters:

- power capacitive high-frequency generator is N=600 W;

residual pressure in the vacuum chamber - pOST=110-120 PA;

the plasma gas flow is G=0.1 g/s;

the voltage applied to the electrodes is U=320;

the generator frequency is f=13.5 MHz;

- duration of treatment - τ=280;

- plasma - forming gas is air.

Wood filler with a modified surface were investigated on the wettability of the liquid with a microscope equipped with an optical goniometer. The values of boundary corners of the wetting solutions of mineral binders on the surface of wood particles of various breeds before and after high-frequency plasma treatment are shown in table 1.

Table 1
The composition of the mineral binderWetting angle softwood (Θ, hail)Wetting angle of hardwood (Θ, hail)
before processingafter processingbefore processingafter processing
Portland cement, sand, water glass and aluminum sulfate25,412,828,314,1

Comparison of the results of the study allows to draw a conclusion about the improvement of the wettability of wood particles of coniferous and deciduous species with a modified surface.

Cement wood mixture were prepared according to the following recipe: wood filler - 21%; Portland cement M400 - 25,6%; liquid glass - 1,1%; water - 30%; sand - 16,3%; aluminum sulfate - 6%.

The formed product was compacted in a hydraulic press at a pressure of p=0.2 MPa, was subjected to heat treatment at a temperature of t=35-40°C and was maintained at a temperature of t=20°C for 5 days.

To evaluate the adhesion strength of a mineral binder to the wood filler is used the method of separation of the element, bonded to a layer deposited on the surface of the wood mineral binder, on a press machine of the type system Dubova-Regelii with optical dynamometer. Take-off speed when this was v=0,175 mm/min the results of the study the adhesion strength of mineral binding to the surfaces of the wood of coniferous and deciduous breeds before and after plasma treatment are shown in ABL.

Table 2
The composition of the mineral binderAdhesive strength for softwood (MPa)Adhesive strength for hardwood (MPa)
before processingafter processingbefore processingafter processing
Portland cement, sand, water glass, aluminum sulfate0,440,640,400,59

As can be seen from table adhesion of the mineral binder to the wood of coniferous and deciduous species, treated with low temperature plasma, increased respectively by 45% and 47%.

Maximum strength samples of the product from arbolita based wood filler with a modified surface on the compression was 7,46 MPa, and tensile - 1,29 MPa and increased in comparison with the strength of the samples based wood filler without surface treatment by 47.5% and 43%, respectively.

Thus, the method of manufacturing of articles made of composite materials, mainly arbolita, has the following advantages:

- improving the wettability of the surface of wood particles with a solution of mineral knitting is about;

- the increase of adhesion of the mineral binder for wood filler;

- improvement of physico-mechanical characteristics of the product.

A method of manufacturing articles made of composite materials, mainly arbolita, including preparation of wood filler and a binder, the processing of wood particles in an electric field, the preparation of cement wood mixture, forming and heat treatment, characterized in that the processing of wood particles is carried out in the flow of plasma gas in the discharge chamber when the high-frequency generator 200-600 watts and vacuum equal 100-130 PA for 250-280 with as a plasma-forming gas used air, and its consumption is 0.08-0.12 g/S.



 

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