A manufacturing method of an environmentally-friendly, precisely controllable, compressed, light-weight, high-strength laminated composite board

Abstract

The application discloses a manufacturing method of an environment-friendly precise controllable compression light-weight high-strength laminated composite board, and comprises the following steps: firstly, the moisture content of surface layer veneer and first layer veneer is adjusted to 10-15%, the moisture content of woven bamboo mat and the rest layer veneer is adjusted to 6-8%; then, adhesive is coated on the upper and lower surfaces of the woven bamboo mat and the first layer veneer of the core board, and the woven bamboo mat is respectively laid on the upper and lower surfaces of the first layer veneer of the core board to obtain a laminated composite core board; then, adhesive is coated on the upper and lower surfaces of the laminated composite core board, and the rest layer veneer of the core board is respectively laid on the upper and lower surfaces of the laminated composite core board, and the laminated composite core board is sequentially subjected to pre-compression forming and pre-heating treatment; after the treatment is completed, high-temperature hot-pressing treatment is carried out to obtain the compression light-weight high-strength laminated composite board. The composite board prepared by the method has balanced transverse and longitudinal bending strengths, high deformation resistance, a thick dense surface layer and good finishing effect after sanding treatment, and has good application potential in furniture manufacturing.

Description

Technical Field

[0001] This invention belongs to the field of the wood industry, and in particular relates to a method for manufacturing an environmentally friendly, precisely controllable, compressible, lightweight, high-strength laminated composite board. Background Technology

[0002] With the large-scale advancement of residential decoration in my country, the customized home furnishing industry has experienced rapid development, leading to a surge in demand for high-quality wood-based panels. Traditional furniture-grade engineered wood panels mainly include fiberboard, particleboard, and plywood. After years of development, the production processes and equipment for these three types of wood-based panels have become increasingly mature, resulting in a wide variety of products and large-scale production lines worldwide. Bamboo-wood composite panels for furniture are functional composite materials made by mixing bamboo and wood unit materials and hot-pressing them together. These functional composite panels fully utilize the strength advantages of bamboo, exhibiting superior comprehensive mechanical properties compared to traditional wood-based engineered wood panels. Product forms mainly include bamboo-wood composite fiberboard, bamboo-wood composite particleboard, and bamboo mat (or bamboo veneer) composite panels. Currently, bamboo-wood composite panels for furniture face the following challenges:

[0003] 1) Raw Material Preparation: The bamboo strips used to manufacture bamboo-wood composite fiberboard or particleboard cannot have their outer green and inner yellow parts removed during the preparation process. This places special demands on the adhesives used and requires the addition of anti-mildew agents. Compared to wood fiber or shavings processing, processing small-sized bamboo strips causes more severe wear on cutting tools. Thin bamboo strips mixed in with the bamboo strips and debris easily clog production equipment such as the screw conveyor and rotary feed valve. Furthermore, the production line has higher energy consumption and generates drying exhaust gas and wastewater emissions. The preparation of bamboo curtains (or bamboo mats) and wood veneer composite boards typically uses large-diameter moso bamboo to make thick bamboo strips or relatively thick bamboo stalks, which requires specific bamboo diameters and results in low material utilization.

[0004] 2) Raw material pretreatment: When preparing bamboo curtain (or bamboo mat) wood veneer composite board, in order to ensure good bonding of thick raw materials, a long-term impregnation with water-soluble adhesive is usually adopted so that the adhesive can penetrate into the material in advance. After impregnation, the material is dried to a certain moisture content before assembly and subsequent hot pressing can be carried out. This process is time-consuming, labor-intensive and inefficient.

[0005] 3) Environmental issues: Currently, water-soluble phenolic resin adhesives are commonly used to prepare structural panels. The production and use of phenolic resin will cause a certain degree of pollution to the environment. The main reason is that the phenol and formaldehyde required for its synthesis are both toxic. Concentrated phenol solutions are highly corrosive to the skin, while formaldehyde is highly irritating to the eyes and respiratory tract, causing allergies and diseases, which seriously threaten human health.

[0006] 4) Adhesive Formulation: Currently, most inventions involve a two-stage formulation of polymethylene polyphenyl isocyanate with other water-based polymer emulsion adhesives (such as vinyl acetate and polyvinyl alcohol resin) in a specific ratio. In this composite adhesive, isocyanate acts as a curing agent, while the water-based polymer emulsion adhesive serves as the main agent. This composite adhesive exhibits good initial tack and water resistance; however, the preparation process of the water-based polymer emulsion is complex, typically requiring heating and constant stirring. Otherwise, the emulsion dispersion is poor, resulting in rapid viscosity changes after formulation, short shelf life, and even failure to apply the adhesive. Furthermore, numerous experiments have shown that this simple two-stage mixing and formulation of composite adhesives is unsuitable for the preparation of high-strength bamboo-wood composite boards, particularly exhibiting poor bonding strength to bamboo. Therefore, a formaldehyde-free, environmentally friendly adhesive with good initial tack and high bonding strength to bamboo is needed.

[0007] 5) Composite Structure and Hot-Pressure Process: Currently, the preparation of bamboo-wood laminated panels generally uses raw materials with uniform moisture content and lays them as a single unit. High-strength bamboo mats (or bamboo strips) are typically placed as close as possible to the surface of the composite panel to improve its bending resistance. However, due to the numerous gaps and overlapping unevenness generated during weaving, the composite panel blank is compressed as a whole after traditional one-piece hot-pressing. Only a thin, dense layer is formed on the surface, while the core layer remains a medium-density compressed layer. This traditional one-piece hot-pressing technology results in poor softening and compression of the two veneer layers combined with the bamboo mat (or bamboo strip), making it difficult to effectively fill the woven overlap gaps under low compression conditions. This leads to numerous voids in the bonding layer between the woven bamboo and wood materials, making them prone to moisture absorption and expansion, resulting in delamination between the woven bamboo and wood materials. Furthermore, this traditional hot-pressing process compresses the entire panel blank, making it impossible to precisely control the density gradient distribution and position of the composite panel. Only a thin, dense layer is formed on the surface, while the core layer remains a medium-density compressed layer. The high-density, dense layer on the surface is too thin and is almost completely lost after sanding. As a result, the surface of the composite board is not smooth and has poor finishing properties. During use, the surface is prone to cracking and the board is prone to deformation, making it unsuitable for the manufacture of home furnishing products.

[0008] 6) Board density: To achieve ideal board strength, increasing density is usually used to improve the mechanical properties of the board. Bamboo curtains (or bamboo mats) use many layers, consuming a large amount of raw materials, and the resulting board density typically reaches 700-900 kg / m³. 3 In addition, the bulky materials also increase transportation and construction costs. Summary of the Invention

[0009] The purpose of this invention is to overcome at least one deficiency of the prior art and provide a method for manufacturing environmentally friendly, precise and controllable compression lightweight high-strength laminated composite panels.

[0010] The technical solution adopted in this invention is:

[0011] In a first aspect, the present invention provides a method for manufacturing an environmentally friendly, precisely controllable, compressible, lightweight, high-strength laminated composite board, comprising the following steps:

[0012] 1) Adjust the moisture content of the surface veneer and the first layer of the core veneer to 10-15%, and adjust the moisture content of the woven bamboo mat and the remaining layers of the core veneer to 6-8%;

[0013] 2) Apply adhesive to the upper and lower surfaces of the woven bamboo mat and the first layer of the core board, and then lay the woven bamboo mat on the upper and lower surfaces of the first layer of the core board to obtain a laminated composite core board.

[0014] 3) Apply adhesive to the upper and lower surfaces of the laminated composite core board, and then lay the remaining veneers of the core board on the upper and lower surfaces of the laminated composite core board to obtain the laminated composite board blank.

[0015] 4) The laminated composite board blank is subjected to pre-compression molding and preheating treatment in sequence. After the treatment is completed, it is subjected to high-temperature hot pressing treatment to obtain the compressed lightweight high-strength laminated composite board.

[0016] In some instances, the preheating temperature of step 3) is 140–170 °C.

[0017] In some instances, the preheating time in step 3) is 0.5 to 2 minutes.

[0018] In some instances, the temperature of the hot pressing process in step 3) is 140–170 °C.

[0019] In some instances, the pressure of the hot pressing process in step 3) is 4–6 MPa.

[0020] In some instances, the hot pressing process in step 3) takes 3 to 5 minutes.

[0021] In some instances, the adhesive comprises the following components by weight: 2.5–4.5% water-soluble adhesive powder, 15–30% crosslinking agent, 15–25% flour, 3.5–5.5% heavy calcium carbonate powder, with the balance being water.

[0022] In some instances, the method for preparing the adhesive includes the following steps:

[0023] 1) Add water-soluble adhesive powder to water and stir until the adhesive powder is fully dissolved to obtain an adhesive powder solution;

[0024] 2) Then add the crosslinking agent, flour, and heavy calcium carbonate powder in sequence, and stir until there are no obvious lumps to obtain the adhesive.

[0025] In some instances, the water-soluble adhesive powder is selected from at least one of polyvinyl alcohol, methylcellulose, hydroxypropyl methylcellulose, sodium carboxymethylcellulose, hydroxyethylcellulose, and xanthan gum.

[0026] The second aspect is the application of the compressed lightweight high-strength laminated composite board prepared by the manufacturing method described in the first aspect of the present invention in furniture.

[0027] The beneficial effects of this invention are:

[0028] 1) A scientifically sound bamboo-wood composite structure is adopted, in which woven bamboo mats are sandwiched between the surface veneer of the composite board. The two veneers bonded to the bamboo mats are precisely and controllably preheated and softened by a high-temperature steam system, which facilitates compression, compaction and shaping in this area, while the core veneer remains unaffected.

[0029] 2) By adopting precise and controllable compaction and strengthening compression technology, the surface veneer, woven bamboo mat and the first layer of core veneer (the two veneers that are bonded to the bamboo mat) are compacted and strengthened by controlling the hot pressing temperature, pressure and holding time. The remaining layers of veneer in the core are glued with a low compression rate, and finally a lightweight and high-strength bamboo-wood composite board is formed by integrally molding the high-strength compacted and strengthened bamboo-wood composite surface veneer and the low compression rate core board.

[0030] 3) The precise and controllable compaction strengthening technology fully utilizes the softness of poplar veneer to effectively fill the depressions in the bamboo mat, reducing internal pores and defects in the material. Simultaneously, due to the high hardness of the bamboo mat, it is not compressed and thus retains its high strength. The highly compressed veneer on both the upper and lower surfaces, when combined with the bamboo mat, further enhances the strength of this composite compression layer, while also strengthening the interlayer bonding performance between the wood veneer and the woven bamboo mat.

[0031] 4) The use of green, environmentally friendly, and formaldehyde-free water-based adhesives has solved the problems of high formaldehyde release, high density, and high production cost of traditional bamboo and wood composite boards, resulting in a lightweight, high-strength, green, environmentally friendly, water-resistant, and moisture-proof high-quality bamboo and wood composite board.

[0032] 5) Taking advantage of the lightweight and low density of fast-growing wood and the high strength and hardness of bamboo, high-strength bamboo and wood materials are combined in a multi-layer composite process. With the good processing performance of wood materials, the mechanical properties of the board are improved. This composite board has balanced bending strength in both the transverse and longitudinal directions, strong resistance to deformation, dense and thick surface layer, and good finishing effect after sanding. It has good application potential in furniture manufacturing. Attached Figure Description

[0033] Figure 1 This is a cross-sectional view of the composite plate of Example 10 and Comparative Examples 1-2. Detailed Implementation

[0034] The following disclosure provides many different implementations or examples for different ways of implementing the present invention.

[0035] The preparation methods of the environmentally friendly, precisely controllable compression lightweight high-strength laminated composite panels in Examples 1 and 2 of this invention are as follows:

[0036] 1) Moisture conditioning treatment for veneer and woven bamboo mats:

[0037] First, the surface veneer and the first layer of the core veneer undergo moisture conditioning to maintain a moisture content of 10-15%. Excessive moisture content can easily cause cracking of the surface compression layer, while insufficient moisture content results in significant instantaneous rebound. A suitable moisture content allows the veneer to soften well during preheating, facilitating precise control of its lamination, compression, and strengthening with the woven bamboo mat later. The remaining veneer layers of the woven bamboo mat and the core veneer are then dried to a moisture content of 6-8%.

[0038] 2) Preparation of formaldehyde-free adhesives:

[0039] First, take the amount of tap water specified in the formula and put it into the glue bucket. Turn on the mixer and the speed of the mixer should be greater than 1200 rpm.

[0040] The second step is to slowly and evenly add 3% of the total mass of water-soluble adhesive powder to the water and stir for 8 to 10 minutes to fully dissolve the adhesive powder into a viscous liquid without obvious lumps.

[0041] The third step is to slowly and evenly add 25% crosslinking agent and continue stirring for 2 to 3 minutes to ensure that the crosslinking agent is evenly mixed in the adhesive powder solution.

[0042] Finally, slowly and evenly add 20% flour and 4.5% heavy calcium carbonate powder as fillers (the amount of filler can be adjusted according to the actual viscosity), and continue to stir and disperse for 3 to 5 minutes until there are no obvious lumps and the adhesive is a viscous light brown emulsion.

[0043] The water-soluble adhesive powder is selected from at least one of polyvinyl alcohol, methylcellulose, hydroxypropyl methylcellulose, sodium carboxymethylcellulose, hydroxyethylcellulose, and xanthan gum.

[0044] The crosslinking agent is selected from at least one of toluene diisocyanate, diphenylmethane diisocyanate, or polymethylene polyphenyl isocyanate.

[0045] 3) Manufacturing of lightweight high-strength laminated composite panels:

[0046] The first step is to apply the prepared adhesive to both surfaces of the woven bamboo mat, and then attach the loose side of the first layer of wood veneer and the lower surface wood veneer with a higher moisture content to the upper and lower surfaces of the woven bamboo mat that have been coated with adhesive.

[0047] The second step is to apply glue to the remaining veneers of the core board with lower moisture content in sequence, and then lay them in a cross-layering manner on the upper surface of the first layer of wood veneer on the lower surface of the core board, with tight sides facing each other and loose sides facing each other.

[0048] The third step involves applying a prepared water-based adhesive to both surfaces of the upper woven bamboo mat. Then, the upper surface wood veneer and the loose side of the first layer of wood veneer on the core board with a higher moisture content are respectively attached to the upper and lower surfaces of the glued woven bamboo mat.

[0049] The fourth step is to pre-compress the laid-out laminated composite slabs using a pre-press machine to prevent misalignment of the slabs during transportation and to remove excess air between the layers, which will facilitate subsequent compression.

[0050] The fifth step involves placing the composite board blank in a steam sprayer and preheating it at a temperature of 140–170℃. This raises the temperature of the upper and lower surface layers that are bonded to the bamboo mat and the top and bottom veneers of the core board, achieving controlled softening of the veneers to be compressed under the combined effect of heat and moisture. The preheating time is controlled between 0.5 and 2 minutes.

[0051] Step 6: After preheating, the blank is transported to the hot press. The forming thickness of the composite board is controlled by the thickness gauge. High-temperature hot pressing is carried out according to the set hot pressing process parameters: hot pressing temperature 140-170℃, hot pressing pressure 4-6MPa, and hot pressing time 3-5min. This makes the surface veneer, woven bamboo mat and the first layer of core board dense and strengthened, while the remaining layers of core board are glued with low compression rate, forming a lightweight and high-strength laminated composite board with a high-strength, dense and strengthened bamboo and wood composite surface board and a low-compression rate core board integrally formed.

[0052] Example 1

[0053] The lightweight, high-strength bamboo-wood laminated composite board prepared by the above method has the following process conditions: veneer moisture content 10%, preheating at 140℃ for 0.5 minutes, hot-pressing temperature 140℃, hot-pressing pressure 4MPa, and hot-pressing time 3 minutes.

[0054] Example 2

[0055] The lightweight, high-strength bamboo-wood laminated composite board prepared by the above method has the following process conditions: veneer moisture content 13%, preheating at 140℃ for 0.5 minutes, hot-pressing temperature 140℃, hot-pressing pressure 4MPa, and hot-pressing time 3 minutes.

[0056] Example 3

[0057] The lightweight, high-strength bamboo-wood laminated composite board prepared by the above method has the following process conditions: veneer moisture content 15%, preheating at 140℃ for 0.5 minutes, hot-pressing temperature 140℃, hot-pressing pressure 4MPa, and hot-pressing time 3 minutes.

[0058] Example 4

[0059] The lightweight, high-strength bamboo-wood laminated composite board prepared by the above method has the following process conditions: veneer moisture content 13%, preheating at 150℃ for 0.5 minutes, hot-pressing temperature 140℃, hot-pressing pressure 4MPa, and hot-pressing time 3 minutes.

[0060] Example 5

[0061] The lightweight, high-strength bamboo-wood laminated composite board prepared by the above method has the following process conditions: veneer moisture content 13%, preheating at 160℃ for 0.5 minutes, hot-pressing temperature 140℃, hot-pressing pressure 4MPa, and hot-pressing time 3 minutes.

[0062] Example 6

[0063] The lightweight, high-strength bamboo-wood laminated composite board prepared by the above method has the following process conditions: veneer moisture content 13%, preheating at 170℃ for 0.5 minutes, hot-pressing temperature 140℃, hot-pressing pressure 4MPa, and hot-pressing time 3 minutes.

[0064] Example 7

[0065] The lightweight, high-strength bamboo-wood laminated composite board prepared by the above method has the following process conditions: veneer moisture content 13%, preheating at 150℃ for 1.0 minute, hot-pressing temperature 140℃, hot-pressing pressure 4MPa, and hot-pressing time 3 minutes.

[0066] Example 8

[0067] The lightweight, high-strength bamboo-wood laminated composite board prepared by the above method has the following process conditions: veneer moisture content 13%, preheating at 150℃ for 1.5 minutes, hot-pressing temperature 140℃, hot-pressing pressure 4MPa, and hot-pressing time 3 minutes.

[0068] Example 9

[0069] The lightweight, high-strength bamboo-wood laminated composite board prepared by the above method has the following process conditions: veneer moisture content 13%, preheating at 150℃ for 2.0 minutes, hot-pressing temperature 140℃, hot-pressing pressure 4MPa, and hot-pressing time 3 minutes.

[0070] Example 10

[0071] The lightweight, high-strength bamboo-wood laminated composite board prepared by the above method has the following process conditions: veneer moisture content 13%, preheating at 150℃ for 1.5 minutes, hot-pressing temperature 150℃, hot-pressing pressure 4MPa, and hot-pressing time 3 minutes.

[0072] Example 11

[0073] The lightweight, high-strength bamboo-wood laminated composite board prepared by the above method has the following process conditions: veneer moisture content 13%, preheating at 150℃ for 1.5 minutes, hot-pressing temperature 160℃, hot-pressing pressure 4MPa, and hot-pressing time 3 minutes.

[0074] Example 12

[0075] The lightweight, high-strength bamboo-wood laminated composite board prepared by the above method has the following process conditions: veneer moisture content 13%, preheating at 150℃ for 1.5 minutes, hot-pressing temperature 170℃, hot-pressing pressure 4MPa, and hot-pressing time 3 minutes.

[0076] Example 13

[0077] The lightweight, high-strength bamboo-wood laminated composite board prepared by the above method has the following process conditions: veneer moisture content 13%, preheating at 150℃ for 1.5 minutes, hot-pressing temperature 150℃, hot-pressing pressure 4MPa, and hot-pressing time 4 minutes.

[0078] Example 14

[0079] The lightweight, high-strength bamboo-wood laminated composite board prepared by the above method has the following process conditions: veneer moisture content 13%, preheating at 150℃ for 1.5 minutes, hot-pressing temperature 150℃, hot-pressing pressure 4MPa, and hot-pressing time 5 minutes.

[0080] Comparative Example 1

[0081] 1. Commercially available ordinary plywood.

[0082] Comparative Example 2

[0083] The difference between the process conditions of the lightweight high-strength bamboo-wood laminated composite board and those of Example 1 is that the fifth step is not performed in the manufacturing process of the lightweight high-strength laminated composite board in step 3).

[0084] Then, according to GB / T 17657-2013 "Test Methods for Physical and Chemical Properties of Wood-based Panels and Decorative Wood-based Panels", the examples and comparative examples were tested respectively. The test results are shown in Table 1 below. The cross-sectional views of the composite panels of Example 10 and Comparative Examples 1-2 are shown below. Figure 1 As shown.

[0085] Table 1

[0086]

[0087] Compared to Comparative Example 1, this invention uses a green, environmentally friendly, and formaldehyde-free water-based adhesive to solve the problems of high formaldehyde release, high density, and high production costs associated with traditional bamboo-wood composite boards. It also fully utilizes the softness of poplar veneer to effectively fill the depressions in the bamboo mat, reducing internal porosity and defects. Furthermore, due to the high hardness of the bamboo mat, it is not compressed and retains its high strength. The highly compressed veneer on both the upper and lower surfaces, when combined with the bamboo mat, further enhances the strength of this composite compression layer and strengthens the interlayer bonding performance between the wood veneer and the woven bamboo mat.

[0088] Compared to Comparative Example 2, this invention uses a high-temperature steam system to precisely and controllably preheat and soften the two layers of veneer combined with the bamboo mat, which facilitates compression, densification, and shaping at this point, while the core veneer remains unaffected. This effectively improves the mechanical properties of the board and has good application potential in furniture manufacturing.

[0089] The above is a further detailed description of the present invention and should not be considered as a limitation on the specific implementation of the present invention. For those skilled in the art, simple deductions or substitutions without departing from the concept of the present invention are all within the protection scope of the present invention.

Claims

1. A method for manufacturing an environmentally friendly, precisely controllable compression lightweight high-strength laminated composite board, characterized in that, Includes the following steps: 1) Adjust the moisture content of the surface veneer and the first layer of the core veneer to 10-15%, and adjust the moisture content of the woven bamboo mat and the remaining layers of the core veneer to 6-8%; 2) Apply adhesive to the upper and lower surfaces of the woven bamboo mat and the first layer of the core board, and then lay the woven bamboo mat on the upper and lower surfaces of the first layer of the core board to obtain a laminated composite core board. 3) Apply adhesive to the upper and lower surfaces of the laminated composite core board, and then lay the remaining veneers of the core board on the upper and lower surfaces of the laminated composite core board to obtain the laminated composite board blank. 4) A woven bamboo mat is sandwiched between the surface veneer of the composite board. The two veneers bonded to the bamboo mat are precisely and controllably preheated and softened by a high-temperature steam system to facilitate compression, compaction, and shaping. The core veneer is unaffected. The laminated composite board blank is pre-compressed and preheated in sequence. The preheating temperature is 140–170 °C and the preheating time is 0.5–2 min. After the preheating is completed, a high-temperature hot-pressing treatment is performed. The hot-pressing temperature is 140–170 °C and the hot-pressing pressure is 4–6 MPa to obtain the compressed lightweight high-strength laminated composite board. The adhesive has the following composition by mass: 2.5–4.5% water-soluble adhesive powder, 15–30% crosslinking agent, 15–25% flour, 3.5–5.5% heavy calcium carbonate powder, and the balance being water. The water-soluble adhesive powder is selected from at least one of polyvinyl alcohol, methylcellulose, hydroxypropyl methylcellulose, sodium carboxymethyl cellulose, hydroxyethyl cellulose, and xanthan gum. The crosslinking agent is selected from at least one of toluene diisocyanate, diphenylmethane diisocyanate, or polymethylene polyphenyl isocyanate. The preparation method of the adhesive includes the following steps: a) Add water-soluble adhesive powder to water and stir to fully dissolve the adhesive powder to obtain an adhesive powder solution; b) Then add the crosslinking agent, flour, and heavy calcium carbonate powder in sequence, and stir until there are no obvious lumps to obtain the adhesive.

2. The manufacturing method according to claim 1, characterized in that, The hot pressing process in step 4) takes 3 to 5 minutes.

3. The application of the compressed lightweight high-strength laminated composite board prepared by the manufacturing method of claim 1 in furniture.

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