RU2041809C1 - Method of obtaining the pressed articles from the wood - Google Patents

Abstract

FIELD: wood-working industry. SUBSTANCE: packet consisting of several boards or beams greased between themselves is installed into the press-mold or into the casette, is pressed up to the requires density with the force of 50-70 MPa. Then it is kept under this charge during 1-2 min. along all the thickness of the pressed packet. Then the pressure is lowered up to 20-40 MPa. The pressed packet is fixed and is directed together with the casette into the chamber for drying and gluing. After that it is cooled. EFFECT: enhanced efficiency. 1 cl, 8 dwg, 2 tbl

Description

 The invention relates to the woodworking industry and can be used to produce pressed wood products such as bars, boards, bushings, rollers, parquet, furniture, etc.

 A known method of producing plasticized wood with contact heating in furnaces and on press plates in a stationary way (Nysenko N.T. and Genel S.V. Plasticization of whole wood, M.L. Goslesbumizdat, 1958, pp. 128-132, 140-144, 150-151).

 The disadvantage of this method is the inability to obtain pressed bars of large thickness, since when pressing the blanks between the plates of the press without lateral stops, their resolution is observed due to transverse deformation and the greater the magnitude of transverse deformation.

 The method of producing large-thickness glued boards by means of a separate-section double compaction (ibid., Pp. 226-232) is also very laborious and time consuming, requires a large consumption of electricity due to the repeated heating of individual sections and the entire package during final compaction.

 A known method of plasticization of wood with preliminary steaming (see ibid., P. 132, Khukhryansky PN, Wood pressing, M. Timber industry, 1964, p. 9, 167).

 The disadvantage of this method is that due to the high humidity of the workpieces after they are steamed in autoclaves (25-30% or more) at the time of pressing, for example, a package of individual boards or bars, moisture is squeezed out, which flushes the adhesive from the surfaces to be glued and, as a result, delamination is observed between individual workpieces when drying them.

In the case of one-piece compression bars with a large thickness after steaming vessel to a moisture content of 25-30% while drying to a final moisture content of 6-8% at 100-105 ^{° C} will be tens of hours, requiring a large power consumption, and quality of these bars will be much worse than from separately glued boards due to hydrolytic processes with decomposition of wood in the central parts of the bars due to the slower release of moisture compared to the peripheral parts.

 The closest in technical essence and the achieved result to the invention is a method for producing wood billets.

 According to this method, pressed blanks (bars, boards) are obtained with preservation of the porous structure and elastic properties due to the exclusion from the process of the operation of preheating or steaming the blanks before pressing them (in the cold). Moreover, the blanks themselves are pressed individually in mobile molds with almost uniformly distributed and optimal humidity over their cross-section and length (14-19%).

 However, this method allows to obtain pressed blanks of only a relatively small cross section. Obtaining pressed blanks with a large cross section in this way is impossible, since the large friction forces arising on the walls of the mold or cassette at the time of compaction are the reason for the uneven thickness density in the finished products, and therefore their unequal quality. The upper zones of such pressed bars have a density higher than in the middle and especially in the lower zones.

 The objective of the invention is to obtain large-sized pressed wood billets (bars, beams) with a uniform density in cross section and length for one technological cycle, improving the quality of bonding of individual billets to each other.

 This is done by installing blanks in the form of a stacked package consisting of several boards or bars smeared with glue, followed by pressing them to a predetermined density with a force of 50-70 MPa, holding them in a press under a load for 1-2 minutes per the entire thickness of the compressed bag, after which the pressure of the press is released to 20-40 MPa, the compressed bag is fixed and together with the cassette are placed for drying and gluing in the chamber, where it is dried and cooled according to known conditions, and the hardwood and softwood blanks radial arrangement of annual rings in relation to the pressing direction of the stack in the cassette with the core in contact with the core, with sapwood sapwood and the workpiece with the radially tangential direction, on the contrary, the core with sapwood.

 In FIG. 1-8 depict two main options for producing large-sized blanks, pressed or glued together boards or bars.

 Figure 1 shows 1-4 blanks of natural wood with a radial arrangement of annual layers in relation to the direction of pressing, 5 cassette, 6 mold (matrix), 7 pressure plate, 8 punch-pressure, 9 clamps.

 In FIG. 2 blanks 1-4 in the mold after pressing them and they are in the cassette 5 in a fixed state (figure 3); in Fig.4 pressed blanks (timber) after drying and gluing; 5, preforms 10-13 of natural wood with a radially tangential arrangement of annual layers with respect to the pressing direction; in Fig.6 the same blanks (timber) after pressing, drying and gluing.

 In Fig.7 blanks 1-10 of aspen wood before pressing in the cassette 10; on Fig the same blanks after pressing, drying and gluing.

PRI me R 1. Bars of 1-4 natural birch wood with a radial arrangement of annual layers in relation to the direction of pressing, with a density of 650 kg / m ³ , a moisture content of 15% with a cross section of 80 x 150 and a length of 500 mm were coated with heat-resistant adhesive and laid in cassette 5 so that the sapwood is in contact with the sapwood, and the core with the core. The total height of the installed package, consisting of 4 bars, was 320 mm.

After that, the cassette 5 was installed in the mold 6, a steel pressure plate 7 was applied to the bag and the punch 8 pressurized the press until the thickness of the lowermost bar was reduced to 50 mm and the density increased to 1040 kg / m ³ . Then, the total pressure of the press was measured by a manometer and the thickness of the remaining pressed bars 1, 2, 3 lying above the lower bar 4 was measured.

The total pressing force was 375, the specific pressure per cm ² area of the package is 50 MPa.

 The initial thickness of the bars and their density changed as follows (see table 1).

 After holding the pressed package in the press under the initial load for 2 minutes, the pressure of the press was released to 225 tons (30 MPa), while the three upper bars were partially decompressed and the thickness of each of them turned out to be close to 50 mm.

 The thickness of the lower bar has not changed. Thus, all four pressed bars were aligned in thickness, and therefore in density.

Then the pressed bag (Fig. 2) with a total height of 200 mm was fixed with steel rods 9, removed from the mold with the cassette 5 and in this state was placed for drying and gluing in a chamber, where 110 ^° C was dried to a moisture content of 8%, cooled to room temperature temperature and dismantled the cartridge. The size of the bar (figure 4) after drying amounted to the cross section: 196.5 x 147 length 500 mm, weight 14650 g, volume 14443 cm ³ , density 1010 kg / m ³ .

 No cracks were found along the glue joints, the beam looked like a monolithic one.

PRI me R 2. In a similar manner, a bar (Fig. 5) was made from birch wood bars with a density of 600 kg / m ³ , a moisture content of 15% and a radially tangential arrangement of annual layers with respect to the pressing direction. The difference was that bars 10-13 with such an arrangement of annual layers were placed in the cassette so that the least dense part of the bar (closer to the core) was in contact with the densest part of the bar (sapwood). This arrangement of the bars after compaction allows you to get finished products with a more uniform density in cross section and length, since the less dense part of the wood is compacted to a greater degree compared to denser (sapwood) wood and vice versa.

 Less dense parts of the bars were densified 3-5 mm more than dense. After reducing the initial load from 70 to 30 MPa, the sapwood parts of the bars increased (pressed out) their thicknesses more rapidly than those located closer to the core (sound, etc.).

The total thickness of the sapwood and core parts of the bars after pressing with a load of 70 MPa was 170-172 mm, and after reducing the load to 30 MPa, the total height of the package increased to 185 mm. After drying to a moisture content of 8% and gluing, the size of the bar (Fig.6) decreased: height 181 mm; width 147 mm, length remained the same 500 mm, volume 13304 cm ³ , weight 13523 g, density 1010 kg / m ³ . No cracks in the adhesive joints were found.

PRI me R 3. Boards made of natural aspen wood (Fig.7) with a radial arrangement of annual layers in relation to the direction of pressing with an initial average density of 500 kg / m ³ humidity 12%, thickness 50 mm, width 150 mm and length 1000 mm in the amount of 10 pieces were coated with glue and placed in the cassette 10 in the same manner as in Example 1 (Fig. 1).

After pressing the bag in the mold until the thickness of the lowest board halved and became equal to 25 mm, we measured the total pressure of the press by a manometer and measured the thickness of all the other boards lying above the lower board 10. The total pressing force was 675 t. specific pressure 45 MPa. The initial thickness of the boards (50 mm), the total height of 500 mm, and the density of 500 kg / m ³ changed as follows (see table 2).

 After holding the pressed package in the press under an initial load of 45 MPa for 2 min, the pressure of the press was released to 30 MPa, while the boards lying above board 8 began to be pressed and reached a thickness of 24.5-25.0 mm. Boards under 8-10 practically did not change in thickness. The total height of the package has become equal to 247 mm. Thus, all 10 pcs. the pressed boards are almost equal in thickness, and therefore in density.

 Then, the compressed bag was fixed in a cartridge, dried, and cooled similarly to examples 1, 2.

The size of the bar (Fig. 8) after drying to a moisture content of 7% was: height 244 mm, width 146.5 mm, length 1000 mm, volume 4574 cm ³ , weight 34891 g, density 980 kg / m ³ .

 On visual inspection, no cracks were found along the glue lines.

The proposed method for producing pressed wood products provides large-sized pressed glued billets (bars, beams) with a uniform density in cross section and length ranging from 800 to 1200 kg / m ³ depending on the initial applied load and its subsequent reduction to a certain value; increased quality of bonding between each individual blanks (boards or bars), since bonding occurs under high pressure (20-40 MPa) in cassettes in a fixed state; increase in productivity and economic efficiency due to the possibility of using various lumpy waste from sawmilling and woodworking as a raw material by pressing and gluing them into a solid monolithic beam with physical and mechanical properties not inferior to similar blanks.

 If there is a press equipment with a capacity of 600-1200 tons and a table size of 2 m long for installing a mold, the proposed method allows to obtain high-strength bars from boards of low-quality alder, aspen, poplar, etc. which can be successfully used in construction as beams, connecting 2-meter bars to each other with steel clamps.

 From pressed bars less than 1 m long, it is recommended to make the front cover of parquet boards, various kinds of sliding bearings, bushings, rollers, an end block for floors of industrial premises, shock-absorbing pads for concrete and wooden sleepers, sports equipment and much more.

Claims (2)

 1. METHOD FOR PRODUCING PRESSED PRODUCTS FROM WOOD, including cutting wood billets, drying them to a certain moisture content, applying glue to glued surfaces, cold pressing individually across the fibers in cassettes or molds, followed by drying and cooling, characterized in that the billets in the form of a stacked bag consisting of several layers of boards or bars, pressed to a predetermined density with a force of 50 70 MPa, then kept in the press under load for 1 2 min over the entire thickness of the pressed th packet, after which press pressure dropping to 20 to 40 MPa, a compressed packet and fixed together with the cassette placed on the drying chamber, where dried and cooled according to known modes.  2. The method according to p. 1, characterized in that the blanks of all deciduous and coniferous trees with a radial arrangement of annual layers in the pressing direction are placed in the cassette so that the core is in contact with the core, sapwood with sapwood, and vice versa core with sapwood.

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