Formaldehyde-free high-moisture-proof anti-deformation all-bamboo shaving board and preparation method thereof

Abstract

The invention discloses a preparation method of a formaldehyde-free high-moisture-proof anti-deformation all-bamboo shaving board. The preparation method comprises the following steps: (1) preparing materials; (2) drying; (3) screening; (4) sizing; (5) hot pressing; and (6) edge cutting. The invention further discloses the formaldehyde-free high-moisture-proof anti-deformation all-bamboo shaving board prepared through the preparation method. According to the preparation method, a polyfunctional group additive is used in a drying and / or sizing process, so that the moisture resistance, the deformation resistance and the dimensional stability of the bamboo shaving board are remarkably improved, meanwhile, the environment-friendly standard of formaldehyde-free addition is kept, the overall performance of the board is improved, the production process is simplified, the production efficiency and the economic benefit are enhanced, and the production cost is reduced. The method is suitable for the field of high-quality home building materials and has wide application prospects.

Description

Technical Field

[0001] The invention relates to the technical field of artificial board production, and in particular to a formaldehyde-free, highly moisture-proof and deformation-resistant full-bamboo particleboard and a preparation method thereof. Background Art

[0002] In recent years, bamboo particleboard made from bamboo has effectively solved the problem of low strength and easy water absorption and swelling of traditional wood particleboard due to its high strength, high toughness and low water absorption. However, there are a large number of hydrophilic groups in the cell wall of bamboo, and large-format and ultra-long particleboard is prone to bending and deformation during use, which has become a technical problem that needs to be overcome in the home building materials industry. Therefore, if bamboo particleboard can achieve a significant improvement and technical breakthrough in moisture resistance and anti-deformation performance, it can accelerate the promotion of differentiated applications of bamboo in the home building materials industry.

[0003] CN115805637A discloses a production process for high static bending strength particleboard, but it uses a honeycomb particleboard substrate and a combination of impregnated kraft paper for pressing, and the process is complicated and requires special mold equipment.

[0004] CN116277323A discloses a method for preparing a highly moisture-proof bamboo particleboard, wherein the bamboo shavings are immersed in a paraffin-ammonia-dissolved quaternary ammonium copper mixture for 1 to 2 hours before drying, and then dried and sizing. However, the soaking treatment increases the moisture content of the shavings from 40% to 100%, greatly increasing the heat energy required for drying, and the wet shavings need to be aged for a period of time before drying, which is time-consuming and labor-intensive. In addition, particleboard factories are usually not equipped with cooking tanks, which further reduces the operability of the invention.

[0005] CN117621215A discloses a method for preparing a highly moisture-proof bamboo particleboard, but the bamboo pieces need to be carbonized at a high temperature and high pressure of 180-220°C, 0.6-1.2 MPa, and 2-4 hours. This process is difficult to implement in conventional particleboard factories and is costly. In addition, the urea-formaldehyde resin used in the sizing results in a high formaldehyde content in the board.

[0006] Therefore, it is urgent to solve the above problems and accelerate the application of bamboo in the home building materials industry. Summary of the invention

[0007] In order to solve the above technical problems, the present invention aims to provide a formaldehyde-free, highly moisture-proof and deformation-resistant all-bamboo particleboard and a preparation method thereof, so as to solve the current problem that the all-bamboo particleboard is easy to absorb water and swell and is easy to bend and deform, and has the characteristics of simple process, high industrial applicability, significant performance improvement, and green environmental protection.

[0008] To achieve the above object, the first aspect of the present invention provides a first preparation method:

[0009] A method for preparing a formaldehyde-free, highly moisture-proof and deformation-resistant all-bamboo particleboard comprises the following steps:

[0010] (1) Material preparation: using raw bamboo or residues from bamboo product processing as raw material, wherein the moisture content of the raw material is 30-50%, and chipping and slicing the raw material to obtain wet bamboo shavings;

[0011] (2) Drying: spraying the wet bamboo shavings obtained in step (1) with a multifunctional additive, and drying the wet bamboo shavings to obtain dry bamboo shavings having a moisture content of 2.0 to 5.0%, wherein the multifunctional additive is used to promote efficient flow and chemical catalysis of bamboo fiber cell walls;

[0012] (3) Screening: Sorting the dried bamboo shavings obtained in step (2) to obtain a surface layer material and a core layer material;

[0013] (4) Gluing: applying pure lignin-based adhesive or lignin-based adhesive modified by the multifunctional additive, as well as a waterproofing agent and a curing agent to the surface material and the core material obtained in step (3), respectively, to obtain surface glue-mixed wood chips and core glue-mixed wood chips;

[0014] (5) hot pressing: laying the surface-layer glue-mixed wood chips and the core-layer glue-mixed wood chips obtained in step (4) in layers according to proportion, hot pressing and forming, and obtaining a board after cooling;

[0015] (6) Edge trimming: The board obtained in step (5) is edge trimmed to produce the formaldehyde-free, highly moisture-proof and deformation-resistant all-bamboo particleboard.

[0016] The first preparation method proposed by the present invention is to add a special multi-functional auxiliary agent in the drying section alone, or to add a special multi-functional auxiliary agent in both the drying section and the sizing section. The auxiliary agent is composed of polyvinyl alcohol, terminal epoxy polyether silicone oil, dodecyl dimethyl ammonium chloride, vinyl polydimethylsiloxane and water. This auxiliary agent can promote the efficient flow and chemical catalysis of bamboo fiber cell walls, improve the reaction activity of lignin-based adhesives with bamboo fibers, thereby enhancing the moisture resistance of the board, improving the deformation resistance and improving the dimensional stability.

[0017] The use of lignin-based adhesives instead of traditional urea-formaldehyde resins in the gluing process ensures that the formaldehyde emissions of the boards meet high environmental standards without the addition of formaldehyde.

[0018] The entire production process does not rely on special equipment or molds and can be implemented on a conventional particleboard production line, improving the plant's practical operability and economic benefits.

[0019] The second aspect of the present invention provides a second preparation method:

[0020] A method for preparing a formaldehyde-free, highly moisture-proof and deformation-resistant all-bamboo particleboard comprises the following steps:

[0021] (1) Material preparation: using raw bamboo or residues from bamboo product processing as raw material, wherein the moisture content of the raw material is 30-50%, and chipping and slicing the raw material to obtain wet bamboo shavings;

[0022] (2) Drying: directly drying the wet bamboo shavings obtained in step (1) to obtain dry bamboo shavings having a moisture content of 2.0 to 5.0%;

[0023] (3) Screening: Sorting the dried bamboo shavings obtained in step (2) to obtain a surface layer material and a core layer material;

[0024] (4) Gluing: applying a lignin-based adhesive modified by a multifunctional additive, a waterproofing agent, and a curing agent to the surface material and the core material obtained in step (3) to obtain surface glue-mixed wood shavings and core glue-mixed wood shavings, wherein the multifunctional additive is used to promote efficient flow and chemical catalysis of the bamboo fiber cell wall;

[0025] (5) hot pressing: laying the surface-layer glue-mixed wood chips and the core-layer glue-mixed wood chips obtained in step (4) in layers according to proportion, hot pressing and forming, and obtaining a board after cooling;

[0026] (6) Edge trimming: The board obtained in step (5) is edge trimmed to produce the formaldehyde-free, highly moisture-proof and deformation-resistant all-bamboo particleboard.

[0027] The second preparation method proposed by the present invention is to add a special multi-functional auxiliary agent separately in the sizing stage. The auxiliary agent is composed of polyvinyl alcohol, terminal epoxy polyether silicone oil, dodecyl dimethyl ammonium chloride, vinyl polydimethylsiloxane and water. This auxiliary agent can promote the efficient flow and chemical catalysis of bamboo fiber cell walls, improve the reaction activity of lignin-based adhesives and bamboo fibers, thereby enhancing the moisture resistance of the board, improving its deformation resistance and improving its dimensional stability.

[0028] The use of lignin-based adhesives instead of traditional urea-formaldehyde resins in the gluing process ensures that the formaldehyde emissions of the boards meet high environmental standards without the addition of formaldehyde.

[0029] The entire production process does not rely on special equipment or molds and can be implemented on a conventional particleboard production line, improving the plant's practical operability and economic benefits.

[0030] A third aspect of the present invention provides:

[0031] A formaldehyde-free, highly moisture-proof and deformation-resistant all-bamboo particleboard is prepared by the first preparation method or the second preparation method as described above.

[0032] The beneficial effects of the present invention are:

[0033] 1. By adding a special multi-functional additive in the drying section alone, or adding a special multi-functional additive in both the drying section and the sizing section, or adding a special multi-functional additive in the sizing section alone, it is possible to promote the efficient flow and chemical catalysis of the bamboo fiber cell wall, and improve the reaction activity of the lignin-based adhesive with the bamboo fiber, thereby enhancing the moisture resistance of the board, improving the deformation resistance and improving the dimensional stability.

[0034] 2. Without significantly changing the conventional drying process and sizing process, the moisture-proof and deformation-resistant properties of the board are significantly improved, and no special processing equipment and molds are required. The production process is simple and has strong feasibility in industrial production.

[0035] 3. The gluing process uses lignin-based adhesives instead of traditional urea-formaldehyde resins, ensuring that the formaldehyde emission of the board meets high environmental protection standards without adding formaldehyde. DETAILED DESCRIPTION

[0036] The embodiments of the present invention will be described in detail below in conjunction with the examples, but it should be understood by those skilled in the art that the following examples are only used to illustrate the present invention and should not be considered as limiting the scope of the present invention. If no specific conditions are specified in the examples, they are carried out according to normal conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased from the market.

[0037] The present invention provides a method for preparing a formaldehyde-free, highly moisture-proof and deformation-resistant all-bamboo particleboard, comprising the following steps:

[0038] (1) Material preparation: using raw bamboo or residues from bamboo product processing as raw material, wherein the moisture content of the raw material is 30-50%, and chipping and slicing the raw material to obtain wet bamboo shavings;

[0039] (2) Drying: spraying the wet bamboo shavings obtained in step (1) with a multifunctional additive, and drying the wet bamboo shavings to obtain dry bamboo shavings having a moisture content of 2.0 to 5.0%, wherein the multifunctional additive is used to promote efficient flow and chemical catalysis of bamboo fiber cell walls;

[0040] (3) Screening: Sorting the dried bamboo shavings obtained in step (2) to obtain a surface layer material and a core layer material;

[0041] (4) Gluing: applying pure lignin-based adhesive or lignin-based adhesive modified by the multifunctional additive, as well as a waterproofing agent and a curing agent to the surface material and the core material obtained in step (3), respectively, to obtain surface glue-mixed wood chips and core glue-mixed wood chips;

[0042] (5) hot pressing: laying the surface-layer glue-mixed wood chips and the core-layer glue-mixed wood chips obtained in step (4) in layers according to proportion, hot pressing and forming, and obtaining a board after cooling;

[0043] (6) Edge trimming: The board obtained in step (5) is edge trimmed to produce the formaldehyde-free, highly moisture-proof and deformation-resistant all-bamboo particleboard.

[0044] In the above step (4), the surface material and the core material obtained in step (3) are respectively applied with a pure lignin-based adhesive or a lignin-based adhesive modified by the multifunctional auxiliary agent, as well as a waterproofing agent and a curing agent to obtain surface-layer glue-mixed wood chips and core-layer glue-mixed wood chips, that is, the surface material obtained in step (3) is respectively applied with a pure lignin-based adhesive or a lignin-based adhesive modified by the multifunctional auxiliary agent, as well as a waterproofing agent to obtain surface-layer glue-mixed wood chips, and the core material obtained in step (3) is respectively applied with a pure lignin-based adhesive or a lignin-based adhesive modified by the multifunctional auxiliary agent, as well as a waterproofing agent and a curing agent to obtain core-layer glue-mixed wood chips. It should be noted that the surface layer material and the core layer material can be simultaneously applied with a pure lignin-based adhesive or simultaneously applied with a lignin-based adhesive modified by the multi-functional auxiliary agent, or one of the surface layer material and the core layer material can be applied with a pure lignin-based adhesive, and the other can be applied with a lignin-based adhesive modified by the multi-functional auxiliary agent.

[0045] The multifunctional auxiliary agent plays an important role in the preparation process, and improves the reaction activity of the lignin-based adhesive and the bamboo fiber by promoting the efficient flow and chemical catalysis of the bamboo fiber cell wall.

[0046] Specifically, the multifunctional additive helps reduce the accumulation of stress in the board and effectively reduces the water absorption of the particleboard. The test results show that the 24-hour water absorption thickness expansion rate is significantly reduced in the embodiment, proving that it helps the board have better moisture resistance.

[0047] The addition of the multifunctional additive and the pretreatment of the bamboo shavings graft more active groups into the bamboo fibers, which increases the reactivity of the bamboo fiber cell walls, effectively softens the cell walls of the bamboo shavings at high temperatures, and makes it easier to crosslink with the lignin-based adhesive, thereby making the board structure more uniform and significantly improving the deformation resistance. For example, key mechanical indicators such as static bending strength and elastic modulus are enhanced.

[0048] After applying the multifunctional additive, the board sample exhibits a smaller length and width change rate under dry and wet environment changes, indicating that the multifunctional additive can make the all-bamboo particle board have good dimensional stability and ensure the stability and durability of the board in actual use.

[0049] In one embodiment, the multifunctional auxiliary agent is prepared by mixing 30 to 40 parts of polyvinyl alcohol, 8 to 10 parts of terminal epoxy polyether silicone oil, 5 to 8 parts of dodecyl dimethyl ammonium chloride, 2 to 3 parts of vinyl polydimethylsiloxane and 40 to 50 parts of water, and stirring at 30 to 50° C. and 300 to 400 r / min for 20 to 30 minutes.

[0050] The above-mentioned multifunctional additive formula significantly improves the performance of bamboo particleboard through the synergistic effect of various components. For example:

[0051] As a water-soluble high molecular polymer, 30 to 40 parts of polyvinyl alcohol can provide good film-forming and adhesion properties, help enhance the bonding strength between lignin-based adhesives and bamboo fibers, improve the overall strength and density of the board, and help improve moisture-proof properties.

[0052] Epoxy-terminated polyether silicone oil has good surface activity and lubricity. 8 to 10 parts of epoxy-terminated polyether silicone oil can form a protective film on the surface of bamboo fiber, which can reduce water penetration and promote the sliding between fibers, which is beneficial to the uniform dispersion and full contact of fibers during the mixing process, and helps to reduce excessive extrusion internal stress during fiber laying.

[0053] As a cationic surfactant, 5 to 8 parts of dodecyl dimethyl ammonium chloride can neutralize the negative charge on the surface of bamboo fiber, promote good dispersion between fibers, and have certain antibacterial and antistatic functions. It improves the uniformity and stability of the mixture, prevents particle aggregation, and further reduces the internal stress generated during the hot pressing process, thereby ensuring the consistency and reliability of the board structure.

[0054] As an organic silicon compound, 2-3 parts of vinyl polydimethylsiloxane has excellent thermal stability and low surface tension, can maintain fluidity and reduce interfacial tension at high temperatures, and promote compatibility between different materials. It helps achieve more uniform distribution and better cross-linking effect during hot pressing, further enhancing the mechanical properties of the sheet and the stability of the internal structural units.

[0055] Water is used as a solvent, and 40 to 50 parts of water ensure that other components can be fully dissolved and mixed evenly, ensuring the stability and ease of use of the additive system.

[0056] In one embodiment, in step (2), the amount of the multifunctional additive added is 1-3% of the mass of the wet bamboo shavings in an absolutely dry state. Controlling the amount of the multifunctional additive added to 1.0-3.0% of the mass of the wet bamboo shavings in an absolutely dry state not only helps to optimize the physical and mechanical properties of the board, such as static bending strength, elastic modulus and internal bonding strength, but also effectively improves its moisture resistance and dimensional stability, ensuring the stability and economy of the production process.

[0057] In one embodiment, the pH range of the multifunctional auxiliary agent is 6.5-7.5, and the solid content range is 46-53%. The pH range of the multifunctional auxiliary agent is 6.5-7.5, and the pH value is close to neutral, which helps to maintain a good reaction environment for the active groups in the cell wall of bamboo fiber, is conducive to the grafting reaction between the multifunctional auxiliary agent and bamboo fiber, improves the reactivity of bamboo fiber, and enables the cell wall of bamboo shavings to be effectively softened at high temperature, making it easier to cross-link and bond with lignin-based adhesives. The solid content range of the multifunctional auxiliary agent is 46-53%, which not only ensures that the effective ingredients of the auxiliary agent are sufficient, but also avoids the problem of operating difficulties caused by too high solid content or too low solid content affecting the effect. For example, when added in the drying section, due to the small amount and high solid content, the moisture content of the bamboo shavings will not increase too much, thereby not affecting the subsequent drying process and energy consumption. By using multifunctional additives under appropriate pH and solid content conditions, stress accumulation in the board can be effectively reduced, and the moisture resistance (such as reducing the 24-hour water absorption thickness expansion rate) and deformation resistance (such as improving dimensional stability, static bending strength, elastic modulus and internal bonding strength) of the board can be improved, while maintaining the uniformity and stability of the board structure.

[0058] In one embodiment, in step (2), the drying temperature is 180-220°C, the drying medium is flue gas, and the moisture content of the dried bamboo shavings is 1.5-2.5%. At a higher temperature (180-220°C), the multifunctional additive can react chemically with the bamboo fiber more effectively, increasing the grafting amount of the active group. This helps to increase the reactivity of the bamboo fiber cell wall, making it easier to cross-link with the lignin-based adhesive. The moisture content of the dried bamboo shavings is controlled at 1.5% to 2.5%, which is an optimized range that can not only ensure good dispersibility and bonding effect of the adhesive in the subsequent sizing process, but also prevent the bamboo fiber from becoming more brittle due to too low a moisture content, thereby affecting the quality of the final board.

[0059] In one embodiment, in step (4), the amount of the multifunctional auxiliary agent added is 0.1-0.5% of the mass of the wet bamboo shavings in an absolutely dry state. The amount of the multifunctional auxiliary agent added is set to 0.1-0.5% of the mass of the wet bamboo shavings in an absolutely dry state to accurately control the reactivity of the bamboo fiber and the adhesive, optimize the moisture resistance and dimensional stability of the board, and ensure economy and environmental protection. Appropriate addition helps to improve the dispersibility and fluidity of the adhesive, enhance the overall performance of the board, and also avoid the cost increase and environmental burden caused by excessive use. The addition amount within this range can achieve the best comprehensive performance and production process benefits.

[0060] In one embodiment, in step (4), the amount of pure lignin-based adhesive or lignin-based adhesive modified by multifunctional additives is 6-8% of the mass of wet bamboo shavings in an absolutely dry state, and the solid content of pure lignin-based adhesive or lignin-based adhesive modified by the multifunctional additives is 40-53%. The amount of lignin-based adhesive or lignin-based adhesive modified by multifunctional additives is controlled to be 6-8% of the mass of wet bamboo shavings in an absolutely dry state, and the solid content is 40-53%, which can ensure sufficient bonding strength and good processing performance. The right amount of adhesive can ensure sufficient bonding between bamboo shavings, improve the mechanical properties and durability of the board, and at the same time, the appropriate solid content helps to optimize the fluidity and drying efficiency during the gluing process, and avoid the cost increase and environmental burden caused by excessive use. The parameter setting within this range achieves the best comprehensive performance and production benefits.

[0061] In one embodiment, in step (4), the waterproofing agent is fully refined solid paraffin and emulsified emulsified paraffin liquid, and the solid content is 40-42%. The waterproofing agent is selected from fully refined solid paraffin and emulsified emulsified paraffin liquid, and the solid content is set to 40-42%. This setting is intended to provide excellent waterproof performance while ensuring good dispersibility and processability. The appropriate solid content ensures the uniform distribution of the waterproofing agent in the adhesive system, effectively reduces the water absorption rate of the bamboo particle board, improves its moisture resistance and dimensional stability, thereby enhancing the overall durability and applicability of the board. Fully refined solid paraffin and emulsified emulsified paraffin liquid are selected as waterproofing agents because they can form an effective waterproof protective film on the surface of bamboo shavings, reduce moisture penetration, and improve the moisture resistance and dimensional stability of the board. Emulsified paraffin liquid also has good dispersibility and fluidity, which is convenient for uniform application, ensuring the efficiency and stability of the sizing process. This combination not only improves the performance of the board, but also meets environmental protection requirements.

[0062] In one embodiment, in step (4), a multifunctional additive, a waterproofing agent, a lignin-based adhesive, a curing agent and water are applied to the surface material and the core material in sequence. The multifunctional additive, the waterproofing agent, the lignin-based adhesive, the curing agent and water are applied to the surface material and the core material in sequence. This arrangement can ensure that each additive can fully exert its function and cooperate with each other. First, the multifunctional additive is added to improve the reaction activity, then the waterproofing agent is added to enhance the moisture-proof performance, then the lignin-based adhesive is applied to provide bonding strength, the curing agent accelerates the gluing process, and finally water is used to adjust the fluidity of the mixture to ensure uniform distribution of each layer and optimal bonding effect, thereby improving the overall performance and stability of the board.

[0063] In another embodiment, for the above preparation method, the multifunctional auxiliary agent can also be added only in the sizing stage, that is:

[0064] A method for preparing a formaldehyde-free, highly moisture-proof and deformation-resistant all-bamboo particleboard comprises the following steps:

[0065] (1) Material preparation: using raw bamboo or residues from bamboo product processing as raw material, wherein the moisture content of the raw material is 30-50%, and chipping and slicing the raw material to obtain wet bamboo shavings;

[0066] (2) Drying: directly drying the wet bamboo shavings obtained in step (1) to obtain dry bamboo shavings having a moisture content of 2.0 to 5.0%;

[0067] (3) Screening: Sorting the dried bamboo shavings obtained in step (2) to obtain a surface layer material and a core layer material;

[0068] (4) Gluing: applying a lignin-based adhesive modified by a multifunctional additive, a waterproofing agent, and a curing agent to the surface material and the core material obtained in step (3) to obtain surface glue-mixed wood shavings and core glue-mixed wood shavings, wherein the multifunctional additive is used to promote efficient flow and chemical catalysis of the bamboo fiber cell wall;

[0069] (5) hot pressing: laying the surface-layer glue-mixed wood chips and the core-layer glue-mixed wood chips obtained in step (4) in layers according to proportion, hot pressing and forming, and obtaining a board after cooling;

[0070] (6) Edge trimming: The board obtained in step (5) is edge trimmed to produce the formaldehyde-free, highly moisture-proof and deformation-resistant all-bamboo particleboard.

[0071] The following examples will describe in detail the application of any of the above-mentioned preparation methods in industrial production:

[0072] Example 1 - Adding multifunctional additives in the drying section

[0073] (1) The bamboo raw materials obtained by raw bamboo chips and shavings are cured and piled until the moisture content is about 30-40%, so that the moisture content of bamboo shavings tends to be consistent and part of starch and sugar substances are degraded.

[0074] (2) Prepare a multifunctional auxiliary agent for use alone in the wood shavings drying process: 35 parts of polyvinyl alcohol, 8 parts of terminal epoxy polyether silicone oil, 6 parts of dodecyl dimethyl ammonium chloride, 3 parts of vinyl polydimethylsiloxane and 48 parts of water are mixed by weight and stirred in a water bath at 40°C at a speed of 300 r / min for 20 minutes. The pH value is 6.5 and the solid content is 52.0%.

[0075] (3) The multifunctional additive is sprayed evenly on the surface of the bamboo shavings at the entrance of the shavings drying feeder in a spraying manner, and the amount used is 2.0% of the mass of the shavings in an absolutely dry state. The flow rate of the nozzle is adjusted according to the belt conveying speed. Due to the small amount and high solid content, the moisture content of the bamboo shavings will not be excessively increased and the drying energy consumption will not be increased. In addition, during the conveying process of the drum dryer, the multifunctional additive on the surface layer penetrates downward, so that the bamboo shavings, the additive, and the hot air are fully contacted and heated to carry out a heat treatment reaction. At the same time, the drum body speed and the inlet and outlet temperatures are controlled, and the drying time is about 15 minutes.

[0076] (4) Dry the wet bamboo shavings after the heat treatment reaction of the additive to a moisture content of about 2.5%, and obtain the core layer and surface layer dry bamboo shavings through a winnowing machine and a super sieve. Layered gluing is performed according to the surface shavings weight accounting for 40%: the surface layer lignin glue dosage is 8.0%, the waterproofing agent dosage is 0.8%, and the curing agent dosage is 0.5%; the core layer lignin glue dosage is 6.0%, the waterproofing agent dosage is 0.6%, and the curing agent dosage is 0.5%.

[0077] (5) The wet wood chips after mixing with glue are quantitatively laid in three layers of surface-core-surface, and then subjected to a hot pressing process at 180-230° C., 4.5-1.7 MPa, five-stage step pressure, and 8-10 s / mm to obtain a finished bamboo formaldehyde-free particleboard.

[0078] The all-bamboo formaldehyde-free high moisture-proof and anti-deformation particleboard prepared in Example 1 has significantly improved moisture-proof performance, anti-deformation ability and high environmental protection. By adding a multifunctional additive in the drying stage, the reactivity of the lignin-based adhesive and the bamboo fiber is improved, the accumulation of internal stress of the board is reduced, and the board structure is made more uniform, thereby enhancing the static bending strength, elastic modulus and internal bonding strength. In addition, while ensuring high strength and excellent moisture-proof performance, the board maintains a high environmental protection level without formaldehyde addition, showing high environmental protection characteristics.

[0079] Example 2 - Adding multifunctional additives in the sizing process

[0080] (1) The bamboo raw materials obtained by raw bamboo chips and shavings are cured and piled until the moisture content is about 30-40%, so that the moisture content of bamboo shavings tends to be consistent and part of starch and sugar substances are degraded.

[0081] (2) Drying the wet bamboo shavings to a moisture content of 2.5% by a pipeline dryer, and then obtaining core layer and surface layer dry bamboo shavings by an air separator and a super sieve.

[0082] (3) Prepare a multifunctional auxiliary agent for use alone in the wood sizing process: 35 parts by weight of polyvinyl alcohol, 10 parts by weight of epoxy-terminated polyether silicone oil, 7 parts by weight of dodecyl dimethyl ammonium chloride, 2 parts by weight of vinyl polydimethylsiloxane and 46 parts by weight of water are mixed and stirred in a water bath at 40°C at a speed of 300 r / min for 20 minutes to obtain a pH value of 6.5 and a solid content of 53.0%.

[0083] (4) Apply glue in layers according to the weight of the surface wood chips accounting for 40%. Adjust the position of the glue gun in the order of multifunctional additive, waterproofing agent, lignin adhesive, curing agent, and water, and apply glue in sequence.

[0084] (5) The amount of multifunctional additive in the surface layer is 0.3%, the amount of waterproofing agent is 0.6%, the amount of lignin glue is 8.0%, and the amount of curing agent is 0.5%; the amount of multifunctional additive in the core layer is 0.3%, the amount of waterproofing agent is 0.4%, the amount of lignin glue is 6.0%, and the amount of curing agent is 0.5%.

[0085] (6) The wet wood chips after mixing with glue are quantitatively laid in three layers of surface-core-surface, and then subjected to a hot pressing process at 180-230° C., 4.2-1.7 MPa, five-stage step pressure, and 6-8 s / mm to obtain a finished bamboo formaldehyde-free particleboard.

[0086] The all-bamboo formaldehyde-free high moisture-proof and anti-deformation particleboard prepared in Example 2 has significantly improved moisture-proof performance, anti-deformation ability and high environmental protection. By adding a multifunctional additive in the gluing process, the reactivity of the lignin-based adhesive and the bamboo fiber is improved, the accumulation of stress in the board is reduced, and the board structure is made more uniform, thereby enhancing the static bending strength, elastic modulus and internal bonding strength. In addition, while ensuring high strength and excellent moisture-proof performance, the board maintains a high environmental protection level without formaldehyde addition, showing high environmental protection characteristics.

[0087] Example 3 - Adding multifunctional additives in the drying and sizing process

[0088] (1) The bamboo raw materials obtained by raw bamboo chips and shavings are cured and piled until the moisture content is about 30-40%, so that the moisture content of bamboo shavings tends to be consistent and part of starch and sugar substances are degraded.

[0089] (2) Prepare a multifunctional auxiliary agent for use in the wood shavings drying process: 32 parts by weight of polyvinyl alcohol, 9 parts by weight of epoxy-terminated polyether silicone oil, 6 parts by weight of dodecyl dimethyl ammonium chloride, 3 parts by weight of vinyl polydimethylsiloxane and 50 parts by weight of water are mixed and stirred in a water bath at 40°C at a speed of 300 r / min for 20 minutes to obtain a pH value of 6.5 and a solid content of 50.0%.

[0090] (3) The multifunctional additive is sprayed evenly on the surface of the bamboo shavings at the entrance of the shavings drying feeder in a spraying manner, and the amount used is 2.0% of the mass of the shavings in an absolutely dry state. The flow rate of the nozzle is adjusted according to the belt conveying speed. Due to the small amount and high solid content, the moisture content of the bamboo shavings will not be excessively increased and the drying energy consumption will not be increased. In addition, during the conveying process of the drum dryer, the multifunctional additive on the surface is allowed to penetrate downward, so that the bamboo shavings, the additive, and the hot air are fully contacted, heated evenly, and the heat treatment reaction is sufficient. At the same time, the drum body speed and the inlet and outlet temperatures are controlled, and the drying time is about 15 minutes.

[0091] (4) Drying the wet bamboo shavings after the heat treatment reaction of the additive to a moisture content of about 2.5%, and obtaining core layer and surface layer dry bamboo shavings through an air separator and a super sieve.

[0092] (5) Apply glue in layers according to the weight of the surface wood chips accounting for 40%, adjust the position of the glue gun in the order of multifunctional additive, waterproofing agent, lignin adhesive, curing agent, and water, and apply glue in sequence.

[0093] (6) The amount of multifunctional additives in the surface layer is 0.2%, the amount of waterproofing agent is 0.6%, the amount of lignin glue is 8.0%, and the amount of curing agent is 0.5%; the amount of multifunctional additives in the core layer is 0.2%, the amount of waterproofing agent is 0.4%, the amount of lignin glue is 6.0%, and the amount of curing agent is 0.5%.

[0094] (7) The wet wood chips after mixing with glue are quantitatively laid in three layers of surface-core-surface, and then subjected to a hot pressing process at 180-230° C., 4.0-1.8 MPa, five-stage step pressure, and 6-8 s / mm to produce a finished bamboo formaldehyde-free particleboard.

[0095] The all-bamboo formaldehyde-free high moisture-proof and anti-deformation particleboard prepared in Example 3 has significantly improved moisture-proof performance, anti-deformation ability and high environmental protection. By adding multifunctional additives in the drying section and the sizing section, the reactivity of the lignin-based adhesive and the bamboo fiber is more significantly improved, the accumulation of stress in the board is reduced, and the board structure is made more uniform, thereby enhancing the static bending strength, elastic modulus and internal bonding strength. In addition, while ensuring high strength and excellent moisture-proof performance, the board maintains a high environmental protection level without formaldehyde addition, showing high environmental protection characteristics.

[0096] Comparison Example

[0097] (1) The bamboo raw materials obtained by raw bamboo chips and shavings are cured and piled until the moisture content is about 30-40%, so that the moisture content of bamboo shavings tends to be consistent and part of starch and sugar substances are degraded.

[0098] (2) Drying the wet bamboo shavings to a moisture content of 2.5% by a pipeline dryer, and then obtaining core layer and surface layer dry bamboo shavings by an air separator and a super sieve.

[0099] (3) Apply glue in layers according to the weight of the surface wood chips accounting for 40%, and apply glue in the order of waterproofing agent, lignin adhesive, curing agent, and water.

[0100] (4) The amount of surface waterproofing agent is 0.8%, the amount of lignin glue is 8.0%, and the amount of curing agent is 0.5%; the amount of core waterproofing agent is 0.6%, the amount of lignin glue is 6.0%, and the amount of curing agent is 0.5%; the solid content of lignin glue adhesive is 52.0%.

[0101] (5) The wet wood chips after mixing with glue are quantitatively laid in three layers of surface-core-surface, and then subjected to a hot pressing process at 180-230° C., 4.5-1.8 MPa, five-stage step pressure, and 9-11 s / mm to obtain a finished bamboo formaldehyde-free particleboard.

[0102] The particleboards prepared in the above Examples 1-3 and the control example were tested according to the methods specified in 4.7, 4.11, 4.9, 4.6, and 4.35 of GB / T 17657-2022 "Test methods for physical and chemical properties of wood-based panels and veneer wood-based panels", and the results are as follows:

[0103] Table 1

[0104]

[0105] Table 2

[0106]

[0107] Table 3

[0108]

[0109] From the above test results, it can be seen that whether adding multifunctional additives alone or jointly in the drying or sizing process can promote the efficient flow and chemical catalysis of bamboo fiber cell walls and effectively reduce the accumulation of stress in the board, which is manifested in:

[0110] (1) The reaction activity of lignin-based adhesive and bamboo fiber was improved, the water absorption of particleboard was effectively reduced, and the moisture resistance of the board was improved, which can be seen in the three performance indicators of 24h water absorption thickness expansion rate, static bending strength after immersion at 70℃, and dimensional stability.

[0111] (2) The addition of multifunctional additives and the pretreatment of bamboo shavings graft more active groups into the bamboo fibers, thereby increasing the reactivity of the bamboo fiber cell walls, effectively softening the cell walls of the bamboo shavings at high temperatures, making them easier to crosslink and bond with lignin-based adhesives, and making them more compact, making the board structure more uniform. The static bending strength, elastic modulus, and internal bonding strength of the embodiment are all enhanced compared with the previous embodiment, thereby increasing the base point for the board to resist stress relaxation and elastic creep during later use, and effectively improving the board's anti-deformation performance.

[0112] (3) The addition of multifunctional additives did not affect the formaldehyde emission of whole bamboo shavings, and the high environmental protection property of no formaldehyde was still maintained.

[0113] (4) Enhanced mechanical properties: The static bending strength, elastic modulus and internal bonding strength of Examples 1, 2 and 3 are all better than those of the control example. In particular, Example 3 performs best in these indicators, indicating that the mechanical properties of the board can be more effectively improved by adding multifunctional additives in the drying and sizing stages.

[0114] (5) Improved moisture resistance: From the static bending strength after immersion at 70°C and the 24-hour water absorption thickness expansion rate, the examples with the addition of multifunctional additives are significantly better than the control examples, indicating that the additives significantly improve the moisture resistance of the particleboard. For example, the 24-hour water absorption thickness expansion rate of Example 3 is the lowest, only 3.46%, which is much lower than 7.43% of the control example.

[0115] (6) Improved dimensional stability: The dimensional changes (shrinkage and swelling) tested under different humidity environments show that the addition of multifunctional additives helps to improve the dimensional stability of the board. In particular, Example 3 has the smallest shrinkage and swelling in the L and W directions, showing better dimensional stability.

[0116] (7) Maintaining high environmental protection: The formaldehyde emission of all tested samples was 0.3 mg / 100 g, which meets the high environmental protection standard of no formaldehyde addition. This shows that even if multi-functional additives are added, it does not affect the environmental performance of the board, ensuring its safety and environmental protection as a formaldehyde-free product.

[0117] The above description is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solutions and concepts of the present invention within the technical scope disclosed by the present invention, and they should be covered by the protection scope of the present invention.

Claims

1. A method for preparing a formaldehyde-free, highly moisture-proof and deformation-resistant all-bamboo particleboard, characterized in that: The following steps are involved: (1) Material preparation: using raw bamboo or residues from bamboo product processing as raw material, wherein the moisture content of the raw material is 30-50%, and chipping and slicing the raw material to obtain wet bamboo shavings; (2) Drying: spraying the wet bamboo shavings obtained in step (1) with a multifunctional additive, and drying the wet bamboo shavings to obtain dry bamboo shavings having a moisture content of 2.0 to 5.0%, wherein the multifunctional additive is used to promote efficient flow and chemical catalysis of bamboo fiber cell walls; (3) Screening: Sorting the dried bamboo shavings obtained in step (2) to obtain a surface layer material and a core layer material; (4) Gluing: applying pure lignin-based adhesive or lignin-based adhesive modified by the multifunctional additive, as well as a waterproofing agent and a curing agent to the surface material and the core material obtained in step (3), respectively, to obtain surface glue-mixed wood chips and core glue-mixed wood chips; (5) hot pressing: laying the surface-layer glue-mixed wood chips and the core-layer glue-mixed wood chips obtained in step (4) in layers according to proportion, hot pressing and forming, and obtaining a board after cooling; (6) Edge trimming: The board obtained in step (5) is edge trimmed to produce the formaldehyde-free, highly moisture-proof and deformation-resistant all-bamboo particleboard.

2. The method for preparing the formaldehyde-free, highly moisture-proof and deformation-resistant all-bamboo particleboard according to claim 1, characterized in that: The multifunctional auxiliary agent is prepared by mixing 30-40 parts of polyvinyl alcohol, 8-10 parts of terminal epoxy polyether silicone oil, 5-8 parts of dodecyl dimethyl ammonium chloride, 2-3 parts of vinyl polydimethylsiloxane and 40-50 parts of water, and stirring the mixture at 30-50° C. and 300-400 r / min for 20-30 minutes.

3. The method for preparing the formaldehyde-free, highly moisture-proof and deformation-resistant all-bamboo particleboard according to claim 1, characterized in that: In the step (2), the amount of the multifunctional auxiliary agent added is 1 to 3% of the mass of the wet bamboo shavings in an absolutely dry state.

4. The method for preparing the formaldehyde-free, highly moisture-proof and deformation-resistant all-bamboo particleboard according to claim 1, characterized in that: In the step (2), the drying temperature is 180-220° C., the drying medium is flue gas, and the moisture content of the bamboo shavings after drying is 1.5-2.5%.

5. The method for preparing the formaldehyde-free, highly moisture-proof and deformation-resistant all-bamboo particleboard according to claim 1, characterized in that: In the step (4), the amount of the multifunctional auxiliary agent added is 0.1 to 0.5% of the mass of the wet bamboo shavings in an absolutely dry state.

6. The method for preparing the formaldehyde-free, highly moisture-proof and deformation-resistant all-bamboo particleboard according to claim 1, characterized in that: In the step (4), the amount of pure lignin-based adhesive or lignin-based adhesive modified by a multifunctional additive is 6-8% of the mass of wet bamboo shavings in an absolutely dry state, and the solid content of pure lignin-based adhesive or lignin-based adhesive modified by the multifunctional additive is 40-53%.

7. The method for preparing the formaldehyde-free, highly moisture-proof and deformation-resistant all-bamboo particleboard according to claim 1, characterized in that: In the step (4), the waterproofing agent is fully refined solid paraffin and emulsified paraffin liquid, and the solid content is 40-42%.

8. The method for preparing the formaldehyde-free, highly moisture-proof and deformation-resistant all-bamboo particleboard according to claim 1, characterized in that: In the step (4), a multifunctional auxiliary agent, a waterproofing agent, a lignin-based adhesive, a curing agent and water are applied to the surface layer material and the core layer material in sequence.

9. A method for preparing a formaldehyde-free, highly moisture-proof and deformation-resistant all-bamboo particleboard, characterized in that: The following steps are involved: (1) Material preparation: using raw bamboo or residues from bamboo product processing as raw material, wherein the moisture content of the raw material is 30-50%, and chipping and slicing the raw material to obtain wet bamboo shavings; (2) Drying: directly drying the wet bamboo shavings obtained in step (1) to obtain dry bamboo shavings having a moisture content of 2.0 to 5.0%; (3) Screening: Sorting the dried bamboo shavings obtained in step (2) to obtain a surface layer material and a core layer material; (4) Gluing: applying a lignin-based adhesive modified by a multifunctional additive, a waterproofing agent, and a curing agent to the surface material and the core material obtained in step (3) to obtain surface glue-mixed wood shavings and core glue-mixed wood shavings, wherein the multifunctional additive is used to promote efficient flow and chemical catalysis of the bamboo fiber cell wall; (5) hot pressing: laying the surface-layer glue-mixed wood chips and the core-layer glue-mixed wood chips obtained in step (4) in layers according to proportion, hot pressing and forming, and obtaining a board after cooling; (6) Edge trimming: The board obtained in step (5) is edge trimmed to produce the formaldehyde-free, highly moisture-proof and deformation-resistant all-bamboo particleboard.

10. A formaldehyde-free, highly moisture-proof and anti-deformation all-bamboo particleboard, characterized in that: The compound is prepared by the preparation method according to any one of claims 1 to 8 or the preparation method according to claim 9.

Images