Method for reducing internal stress of bamboo tube filled hollow core slab

Abstract

A method for reducing the internal stress of a bamboo cylinder filled hollow board, comprising the following steps: step one, core layer filler production: bamboo with a diameter of less than or equal to 70 mm is used to cut the raw bamboo into bamboo cylinders with the same length (fiber direction), the length tolerance of each bamboo cylinder is controlled within the range of plus or minus 0.30 mm, the bamboo cylinders are dried and de-insected, the drying is performed in two stages, the moisture content is reduced to about 15% in the first stage, and the steam with a temperature of 120-230 DEG C is used to remove the insect pests in the bamboo cylinders in the second stage, the moisture content is adjusted after high-temperature treatment, and the final moisture content is controlled within the range of 7-13%; step two, production of two-layer surface plate: eucalyptus, poplar, birch and other logs are used to cut logs, veneers or plywood or medium-density fiberboard as the surface layer of the bamboo cylinder filled hollow board; step three, composite of the surface layer and the core layer: the moisture content of the two-layer surface plate is controlled to be basically consistent with the moisture content of the bamboo cylinder core layer, and the two are glued, assembled and formed; before the forming, the whole bamboo cylinder is rolled and cracked by a rolling knife, and a flexible adhesive is selected to adapt to the deformation of the bamboo tile in the drying and wetting process, so that the internal stress of the adhesive layer between the core layer and the surface layer veneer is effectively reduced, the board is guaranteed not to be opened due to the excessive internal stress of the adhesive layer caused by the cracking and deformation of the bamboo cylinder in the subsequent use, the flatness and service life of the board are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of artificial board, in particular to a method for reducing internal stress of bamboo tube filled hollow board. BACKGROUND

[0002] The patent application CN102615679A discloses a kind of light pressure-resistant bamboo-wood composite board and its production method, which is a three-layer structure of two surface layers (1) and one core layer (2). The core layer (2) is composed of horizontally arranged wood material (3) and vertically arranged bamboo filler (4) between the material. Each wood material (3) is composed of two lateral long materials (5) and a vertical short material (6) sandwiched in the middle. Each filler (4) is a bamboo segment with or without through holes. The production method includes four steps: manufacturing core layer material and the frame of the frame-shaped board, manufacturing core layer filler, fine processing of the core layer, and combining the surface layer with the core layer.

[0003] The utility model patent CN213928090U discloses a bamboo filled wooden door, which includes a door body and a bamboo core with equal thickness and weight of 15-40 kg. The bamboo core includes a main bamboo tube and a reinforcing tube, and the outer diameter of the reinforcing tube is less than or equal to 5 cm. The door body includes a wooden frame, an outer side plate, and an inner side plate. A cavity is formed in the door body, and the main bamboo tube is uniformly filled in the cavity. One end of the main bamboo tube and one end of the reinforcing tube are fixedly connected with the outer side plate and / or the inner side plate. The main bamboo tube with an inner diameter greater than or equal to 8 cm is filled with the reinforcing tube. The bamboo filled wooden door provided by the utility model saves bamboo materials, has stable weight, and has good compressive strength.

[0004] The utility model patent CN219132610U discloses a bamboo tube assembly board, which includes a board blank and a single board. The board blank is formed by horizontally arranging a plurality of bamboo tubes with an axial projection in the shape of a regular hexagon. The single board covers the circumferential surface of the board blank to form a cuboid frame. The utility model also discloses a telescopic base arranged at the bottom of the bamboo tube assembly board. The bamboo tube has low density and high strength, and is less susceptible to mold invasion than bamboo chips and bamboo shavings. The bamboo tube is cut into bamboo units in the shape of a polygon. The unit structure is more stable, which improves the stability of the overall board or structure. The surface gluing area is increased by removing the bamboo green, which greatly improves the bonding performance.

[0005] The utility model patent CN202788504U discloses a bamboo door composite door, which includes a bamboo framework, a bamboo tube, a gap, and a decorative layer. The bamboo framework is connected by two vertical bars and three horizontal bars. The gap is filled with crushed materials. The bamboo tube is vertically arranged and perpendicular to the decorative layer and is attached to the decorative layer by hot pressing. The decorative layer is a paint-free board, a bamboo skin, or a wood skin. The bamboo door composite door provided by the utility model uses bamboo materials as the framework and filler, which reduces the amount of wood used. The overall door is reliable in quality and achieves an aesthetic and decorative effect.

[0006] The utility model discloses a kind of bamboo door core door panels, which includes door panel body, and the door panel body is provided with hollow inner cavity, and reed door core is filled in the inner cavity of door panel body. The utility model fills reed door core in the inner cavity of door panel body, and the both ends of reed door core abut against the front and back of door panel body, thereby solving the problem of small external force resistance of the door panel in the prior art.

[0007] The above multiple patents fill the bamboo tube, which is low in cost, reduces the weight of the plate, and greatly improves the compression resistance of the plate body by bamboo tube filling, fully utilizing the advantage of bamboo tube in resisting compression along the grain.

[0008] However, bamboo has internal stress during growth, which is caused by uneven compression of bamboo poles due to changes in height growth, slope bending and wind and rain load, etc. In addition, the fiber distribution gradient changes greatly in the radial direction of the bamboo tube, with high fiber bundle content near the bamboo green surface and low content on the bamboo yellow surface. The difference in dry shrinkage and wet expansion is large. After drying and overall filling of the bamboo tube with glue, the difference in dry shrinkage and wet expansion still exists. In terms of a single bamboo tube, the bamboo green surface is prone to cracking during drying. The original filling of the bamboo tube will cause different shrinkage gaps in the subsequent use of the plate and act on the glued surface to form internal stress in the glue layer. When the internal stress exceeds the strength of the glue layer, delamination occurs, affecting the performance and use of the bamboo tube filled hollow plate. To this end, the present application provides a method for reducing the internal stress of a bamboo tube filled hollow plate based on theoretical analysis and test results. SUMMARY

[0009] The present application provides a method for reducing the internal stress of a bamboo tube filled hollow plate, aiming to solve the problems raised in the above background.

[0010] A method for reducing the internal stress of a bamboo tube filled hollow plate, comprising the following steps:

[0011] Step one, core layer filler production: bamboo with a diameter of ≤70mm is cut into bamboo tubes of the same length (fiber direction), and the length tolerance of each bamboo tube is controlled within ±0.30mm. The bamboo tubes are dried and de-insected. The drying process is divided into two stages: the first stage reduces the moisture content to about 13%, and the second stage uses steam at 120-230℃ to remove insect pests. After high-temperature treatment, the final moisture content is adjusted to 7-13%.

[0012] Step two, production of two-layer surface plate: eucalyptus, poplar, birch and other logs are rotary cut into log veneer or plywood or medium-density board as the surface layer of the bamboo tube filled hollow plate.

[0013] Step three, the combination of the surface layer and the core layer: control the moisture content of the two surface layers and the moisture content of the bamboo tube core layer to be basically the same, and glue, group, and glue into shape.

[0014] Preferably, a flexible adhesive is selected or modulated to slow down the inconsistent shrinkage (expansion) of the glue layer caused by the uneven distribution of radial fibers and the structural differences of bamboo, which causes the stress of the glue layer.

[0015] Preferably, after the core layer is dried, the bamboo tube is randomly filled and laid in the direction of the frame and the first surface plate. After the laying is completed, the surface (bamboo tube cross section) of the core layer is coated with a glue coating machine. After the glue coating is completed, the second surface plate is combined with the glued core layer and turned over. After turning over, the first surface plate is disassembled, leaving the second surface plate and the frame to coat the other end of the bamboo tube exposed (bamboo tube cross section). After the glue coating is completed, the bamboo tube is rolled in the fiber direction by a rolling knife, so that the bamboo tube with a diameter greater than the distance between the rolling knives is longitudinally cracked, and the bamboo tube is cracked into several pieces in a non-continuous whole state. After the bamboo tube is cracked, the first surface plate is combined with it to complete the combination with the core layer. After the combination, pressure is applied, the pressure is 0.6-1.5 MPa, and the glue is cured and formed. After the pressure is released, the bamboo tube filled hollow plate is made by cooling and aging.

[0016] Compared with the prior art, the advantages of the present application are:

[0017] 1. In the present application, the whole bamboo tube is rolled and cracked by a rolling knife before glue forming, and a flexible adhesive is selected to adapt to the deformation of the bamboo tile during dry shrinkage and wet expansion, which effectively reduces the internal stress of the glue layer between the core layer and the surface layer, ensures that the plate will not be glued due to excessive internal stress of the glue layer caused by bamboo cracking and deformation during subsequent use, and improves the flatness and service life of the plate.

[0018] 2. In the present application, the frame is used to temporarily fix the first surface plate during laying, and the bamboo tube is positioned by the frame, so that the glue coating machine can directly coat the bamboo tube cross section. At this time, the glue coating machine only coats the cross section (gluing surface) of the bamboo tube. Compared with the prior art, the glue application area is greatly reduced, and the amount of adhesive used is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 A flowchart of a method for reducing the internal stress of a bamboo tube filled hollow plate is provided for the present application;

[0020] Figure 2 A cross-sectional view of a raw bamboo tube and a bamboo tube with excessive internal stress leading to bamboo cracking is provided for the present application;

[0021] Figure 3 A partial composite schematic diagram of a method for reducing the internal stress of a bamboo tube filled hollow plate is provided for the present application.

[0022] Legend: 1, core layer; 2, surface layer. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application is further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application.

[0024] A method for reducing the internal stress of a bamboo cylinder filled hollow board, comprising the following steps:

[0025] Step one, preparation of core layer filler: bamboo with a diameter of ≤70 mm is used to cut the original bamboo into bamboo cylinders with the same length (fiber direction), and the length tolerance of each bamboo cylinder is controlled within ±0.30 mm. The bamboo cylinders are dried and de-insected, and drying is performed in two stages. In the first stage, the moisture content is reduced to about 13%, and in the second stage, steam at 120-230°C is used to remove the insect pests in the bamboo cylinders. After high-temperature treatment, the final moisture content is adjusted to 7-13%.

[0026] Step two, preparation of two layers of surface plates: eucalyptus, poplar, birch and other logs are used to cut logs into single logs or plywood or medium-density boards as the surface layer of the bamboo cylinder filled hollow board.

[0027] Step three, compounding of the surface layer and the core layer: the moisture content of the two layers of surface plates is controlled to be substantially the same as that of the core layer, and then glue is applied, the blanks are assembled, and the glue is formed.

[0028] A flexible adhesive is selected or prepared to slow down the stress on the glue layer caused by the inconsistent shrinkage (expansion) of the radial fiber distribution and the structural differences of the bamboo.

[0029] After the core layer is dried, the bamboo cylinders are randomly filled and laid in the direction of the first surface plate through the frame. After the laying is completed, the surface of the core layer (the cross section of the bamboo cylinder) is coated with glue by a glue coating machine. After the glue coating is completed, the second surface plate is assembled with the glued core layer and is turned over. After the turning, the first surface plate is disassembled, leaving the second surface plate and the frame to coat the other end of the bamboo cylinder exposed outside (the cross section of the bamboo cylinder) with glue. After the glue coating is completed, the bamboo cylinders are rolled in the fiber direction by a rolling knife, so that the bamboo cylinders with a diameter greater than the distance between the rolling knives are longitudinally cracked, and the cracks penetrate through the entire bamboo cylinder to become several pieces in a non-continuous whole state. After the bamboo cylinders are cracked, the first surface plate is assembled with the core layer to complete the assembly and compounding of the core layer. After the assembly, pressure is applied, the pressure is 0.6-1.5 MPa, and the glue is cured and formed. After the pressure is released, the bamboo cylinder filled hollow board is cooled and aged.

[0030] Example one, urea-formaldehyde glue + white latex + hot-press production method, select white latex to modulate urea-formaldehyde glue, improve its flexibility, the specific proportion of deployment is 100:12~18 (weight parts, 48~52% solid content of urea-formaldehyde glue, 32~38% solid content of white latex), add after stirring, make frame and the first plate connected, form a whole, fillable bamboo tube is randomly paved to the frame, until full; The end of the bamboo tube after paving is coated with glue, the amount of glue is 160~200g / m 2 , after the second plate and the core layer are assembled and turned over, the first plate is removed, leaving the second plate and the frame, then the other end of the bamboo tube exposed (bamboo tube cross section) is coated with glue, and the bamboo tube is rolled in the fiber direction after the glue is applied, so that the bamboo tube with a diameter greater than the distance between the rollers is longitudinally cracked, and the whole bamboo tube becomes several pieces in a non-continuous whole state. After the bamboo tube is cracked, the first plate is assembled with it, and hot pressing is carried out after assembly, the hot pressing pressure is 0.6~1.5MPa, the hot pressing time is 2~4min, the surface and core layer are glued into shape, and the bamboo tube filled hollow slab is made after cooling and aging.

[0031] Example two, production method of cold pressing glue of spliced board, select spliced board glue (PVAC emulsion adhesive), and add curing agent, the ratio of spliced board glue (PVAC emulsion adhesive) to curing agent is 100:12~18 (weight parts, the solid content of spliced board glue is 48~52%), add after stirring, through the operation of the above example one, the surface plate and the bamboo tube are assembled, and finally cold pressing machine is used for cold pressing, the pressure is 0.6~1.5MPa, and the cold pressing time is 3~6 hours, so that the surface and core layer are glued into shape, and the bamboo tube filled hollow slab is made.

[0032] Example three, production method of cold pressing glue of inorganic glue, select Jiangshan Huamujiang Home Co., Ltd. independently developed flame-retardant magnesium oxychloride adhesive (patent application number: 202410110879.9), the surface plate and the end face of the bamboo tube are glued and assembled, the cold pressing pressure is 0.6~1.5MPa, the cold pressing time is 3~6 hours, and the bamboo tube filled hollow slab is made.

[0033] The above description of the embodiments is to assist the person of ordinary skill in the art to understand and use the present application. It is obvious that the person of ordinary skill in the art can easily make various modifications to the embodiments and apply the general principles described herein to other embodiments without creative labor. Therefore, the present application is not limited to the above embodiments. Improvements and modifications made by the person of ordinary skill in the art based on the principles of the present application without departing from the scope of the present application should be within the scope of protection of the present application. The above description is only the preferred embodiments of the present application and is not used to limit the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application should be included in the scope of protection of the present application.

Claims

1. A method for reducing the internal stress of a bamboo cylinder filled hollow core slab, characterized in that, It comprises the following steps: step one: making of core layer filler; step two: making of two-layer surface layer; step three: compounding of surface layer and core layer; in the step one, bamboo with diameter ≤70 mm is used to cut the original bamboo into the same bamboo cylinder, the tolerance is controlled within ±0.30 mm, the bamboo cylinder is dried and de-insected, drying is carried out in two stages, the moisture content is controlled to 15% in the first stage, and the steam of 120-230°C is used to remove the insect pests in the bamboo cylinder in the second stage, and the final moisture content is controlled to 7-13%; the moisture content of the two-layer surface layer is consistent with that of the bamboo cylinder core layer; in the step three, after the drying of the core layer is completed, the core layer is laid through the frame and the first surface plate, after the laying is completed, the surface of the core layer is coated by the gluing machine, after the gluing is completed, the second surface plate is combined with the glued core layer and is turned over, at the same time, the frame and the first surface plate are disassembled, the other end of the bamboo cylinder exposed is coated, after the gluing is completed, the core layer is rolled by the rolling cutter, so that the bamboo cylinder is longitudinally cracked into tiles, after the bamboo cylinder is cracked, the first surface plate is combined with the core layer after the combining is completed, after the combining is completed, the pressure is applied, the pressure is 0.6-1.5 MPa, and the core layer is solidified and formed, after the pressure is released, the core layer is cooled and aged to make the bamboo cylinder filling hollow slab; the gluing machine selects the adhesive with good flexibility, and the adhesive layer is applied to slow down the dry shrinkage and wet expansion caused by the inconsistent distribution of radial fibers and the structural difference of bamboo.

2. The method for reducing the internal stress of the bamboo cylinder filled hollow slab according to claim 1, characterized in that: In the step two, the single board, plywood or medium fiber board made of eucalyptus, poplar or birch is used as the surface layer of the bamboo filling hollow slab.

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