SU1766659A1 - Compressed wood production method - Google Patents

Description

one

(21) 4868037/15 (22) 9/21/90 (46) 10/07/92. Bul №37

(71) Voronezh Forestry Institute

(72) M.V. Tsykhmanov, VA Shamaev, N.I. Vinnik and S.A. Burlov

(56) USSR Author's Certificate No. 456734, cl. B 27 M 1 / 02,1973

USSR author's certificate No. 1703464 positive decision on application 4453764/15, cl. В27М 1/02, 1988, dated 07.27.90

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(54) METHOD FOR OBTAINING PRESSED WOOD

(57) The use of the woodworking industry, pressed wood in the form of bars and planks, The essence of the invention: wood harvesting moisture of 20-60% is placed in the mold. The blanks are compacted with a flat wedge at a pressure of 8-12 MPa. The speed of the wedge is 10-30 mm / min. The pressed blanks are dried at a temperature of 125-140 ° C for 4-5 h. The density of treated wood is 1100-1200 kg / m3, humidity 5 -6% 4 tabl

The invention relates to the woodworking industry and concerns the production of pressed wood in the form of bars and planks.

The purpose of the invention is to improve the performance of physical and mechanical properties of compressed wood.

The method is carried out as follows.

Wood billets in the form of bars or boards with a humidity of 20-60% are placed in a mold and pressed using a flat wedge to a density of 1000-1200 kg / m3.

If the moisture content of the workpieces is less than 20%, the hardness of the wood significantly increases and microcracks form during compression, reducing the strength of the wood. If the moisture content of the wood is more than 60%, then when the wedge moves, even at low speed, the moisture does not have time to leave the wood and breaks the partitions of the vessels and cells, which also reduces mechanical properties (table 1)

The speed of movement of the wedge depends on the moisture content of the wood. The greater the humidity, the slower the speed. The optimum speed of movement, ensuring the preservation of high strength properties of wood, 10-30 mm / min (Table 2)

As can be seen from Table 2, at a wedge movement speed of more than 30 min / mm, the strength of compressed wood decreases, and a decrease in wedge movement speed less than 10 mm / min does not affect strength properties, but does not justifiably prolong the wood pressing cycle

The specific pressure during compression depends on a number of factors, mainly on the final density of pressed wood (Table 3).

After the pressing process is completed, the workpiece is dried at a temperature of 125-140 ° C for 4-5 hours. Pressing with a wedge allows the wood to be pressed in such a way that the compression of vessels and cells occurs smoothly, without

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characteristic flattening that is present when compressed in other ways. Therefore, the channels for moisture release during drying only decrease in cross section, but do not completely overlap. This allows drying at higher temperatures while maintaining the strength properties of pressed wood. It should be noted that after pressing, almost all the free moisture from the blanks is squeezed out, therefore, if the humidity of the rolls was more than 30%, then after pressing, the moisture fluctuates between 28-32%. If the drying temperature is more than 140 ° C, tbTtressovanny wood turns out to be dark in color and there is a decrease in the strength of the pressed wood. Using a drying temperature of less than 125 ° C is impractical because the process is unnecessarily delayed (production of compressed wood (Table 4).

As can be seen from table 4, with a drying time of 4-5 hours, the moisture content of pressed wood lies within the limits required by GOST 9629-89 (5-8%)

Examples of the implementation of the method of obtaining compressed wood.

Example 1 Birch wood blanks with a moisture content of 20% and dimensions of 60x80x300 mm (hereinafter the last dimension along the fibers) are placed in a mold and pressed across the fibers with a flat wedge to a compression ratio of 50% at a specific pressure of 12 MPa and a wedge movement speed of 30 mm / min The pressed billets are dried at 140 ° C for 4 h, then removed from the molds. The dimensions of the resulting bars 60x40x300 mm, density 1200 kg / m, humidity 5.8%.

Example 2 Aspen wood blanks with a moisture content of 40%, dimensions 60x80x300 mm are placed in a mold and compacted across the fibers with a flat wedge to a compression ratio of 53% at

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a specific pressure of 10 MPa and a wedge movement speed of 20 mm / min. Pressed blanks are dried at a temperature of 132 ° C for 4.5 hours. The dimensions of the resulting bars are 60x38x300 mm, the density is 1100 kg / m, the humidity is 6%,

Example 3. Pine wood blanks with a moisture content of 60% and dimensions of 60x80x300 mm are placed in a mold and compacted across the fibers with a flat wedge to a compression ratio of 48% at a specific pressure of 8 MPa and a wedge movement speed of 10 mm / min. The pressed billets are dried at 125 ° C for 5 h. The dimensions of the obtained bars are 60x42x300 mm, the density is 1000 kg / m, the humidity is 6%.

Below are indicators of the physicomechanical properties of compressed wood.

Density, kg / m3

Humidity before pressing,%

after pressing,%

Strength at

compression, MPa

along the fibers

across the fibers

Shock viscosity

kJ / m2

Face hardness,

MPa

1000-1200

20-60 5-6

145-155 32-47

98-110

160-175

Claims (1)

The invention The method of obtaining compressed wood, comprising pressing wood with a flat wedge and drying it in a compressed state, characterized in that, in order to improve the performance of physical and mechanical properties, pressing is carried out at. wood moisture 20-60% and specific pressure 8-12 MPa with a wedge movement speed of 10-30 mm / min, and drying is carried out at 125-140 ° C for 4-5 hours Table 1 table 2 Table 3 Table 4