Carbon fiber reinforced soybean protein adhesive as well as preparation method and application thereof

Abstract

The invention discloses a carbon fiber reinforced soybean protein adhesive as well as a preparation method and application thereof, the adhesive comprises modified carbon fibers and a soybean protein matrix, and the modified carbon fibers are dispersed in the soybean protein matrix; the surface of the modified carbon fiber is rich in at least one active functional group of hydroxyl, carboxyl or epoxy group. According to the adhesive, the modified carbon fibers are combined with the soybean protein matrix, the bonding strength of the adhesive is enhanced, and when the adhesive is used for bamboo product bonding, the mechanical strength of bamboo products is improved, and the service life of the bamboo products is prolonged.

Description

Technical Field

[0001] The invention belongs to the technical field of bamboo product adhesives, and particularly relates to a carbon fiber reinforced soybean protein adhesive and a preparation method and application thereof. Background Art

[0002] Soy protein adhesives use the amino, carboxyl and other reactive groups contained in the basic amino acid structure of soy protein to interact with wood fibers to form an effective bonding layer, and are widely used in the wood adhesive industry. Compared with cereal and nut plant proteins, beans have the highest protein content, and the protein content after defatting is more than 40%, making them the best choice for preparing plant protein adhesives. In addition, soybeans are one of the most planted bean products. The original soy protein adhesive, as a natural plant glue, was obtained by a series of physical and chemical modifications of soy protein powder. However, the soy protein adhesive prepared by this method has the disadvantages of high viscosity, poor fluidity, low bonding strength, and poor water resistance, and is only involved in the wood processing and wood-based panel industries. In recent years, due to the excessive consumption of petroleum resources and the increase in people's environmental awareness, plant protein adhesives, mainly modified soy protein adhesives, have once again become a research hotspot. Zhang et al. (DOI: 10.1016 / j.jclepro.2020.120336) proposed a simple and clean physical high-pressure homogenization method for treating soybean meal (SM), which reduced the particle size of SM by 62%, improved the quality of soybean meal, made the particle size distribution uniform, and significantly improved the stability of the adhesive. In addition, the high-pressure homogenization method exposes many active functional groups in soy protein, increasing their reactivity with cross-linking agents. This helps to form a dense covalent network bonding system, improves the water resistance of soy protein adhesives, and plywood bonded with modified soy protein adhesives has a shear strength 212% higher than that of untreated plywood.

[0003] The modification methods of soy protein include physical modification, chemical modification and bio-enzyme modification. 1. Physical modification: changing the molecular structure, conformation or aggregation state of soy protein through physical means such as heat treatment, ultrafiltration, ultrasound, adding plasticizers, etc. Specific methods include: (1) Heat treatment: Appropriate heating of soy protein can unfold the protein molecules, expose more active groups, and enhance its solubility, emulsification and other functional properties. (2) Ultrafiltration treatment: using the screening effect of ultrafiltration membrane to separate and screen soy protein molecules according to their size and molecular weight, some impurities and unnecessary components can be removed, the purity and quality of soy protein can be improved, and its molecular weight distribution can also be changed, affecting its functional properties. (3) Ultrasonic treatment: the cavitation and mechanical effects of ultrasound can destroy the molecular structure of soy protein, reduce its molecular weight, increase its solubility and dispersibility, and improve its gelation and emulsification. (4) Adding plasticizers: plasticizers can be inserted between soy protein molecules, increase the distance and flexibility between molecules, and improve the plasticity and processing performance of soy protein. 2. Chemical modification: using chemical reagents to react with amino, hydroxyl, carboxyl and thiol side chain groups on soybean protein molecules to change the molecular structure and chemical properties of the protein, thereby improving its functional properties. Specific methods include: (1) Cross-linking modification: using bifunctional or multifunctional cross-linking agents to react with amino, hydroxyl and other side chain groups in soybean protein molecules to form cross-linked structures within or between protein molecules, thereby enhancing its mechanical properties such as water resistance, hardness and tensile strength, such as formaldehyde, glutaraldehyde and furfural. (3) Grafting modification: by adding specific chemical reagents to induce protein molecules to produce primary free radicals, and then grafting and copolymerizing olefin monomers on protein molecules, so as to give soybean protein new properties. This method can regulate parameters such as grafting monomers, grafting density and branch length to obtain the desired protein molecular material properties. (4) Acylation and esterification modification: acylation or esterification of amino and hydroxyl groups in protein molecules to allow protein molecules to obtain new functional groups and improve their performance. 3. Bioenzyme modification: using the specificity and high efficiency of bioenzymes to hydrolyze, crosslink or modify soy protein, thereby changing its molecular structure and functional properties. Specific methods include: (1) using different types of enzymes, including animal proteases (such as pepsin, etc.), plant proteases (such as papain, etc.) and microbial proteases (such as neutral proteases, etc.). These enzymes can specifically hydrolyze the peptide bonds in soy protein molecules, making the protein molecules smaller and exposing more hydrophobic groups and active sites, thereby improving its solubility, emulsification, foaming and other functional properties. (2) Enzyme synergy: multiple enzymes can be used in combination in a certain proportion and order to exert the synergistic effect of enzymes and improve the modification effect of soy protein.(3) Enzyme membrane reactor method, which couples enzyme catalytic reaction and membrane separation, integrates the in-situ separation and concentration of biological reaction and reaction products and the recovery and utilization of enzymes. It can change the reaction process, control the reaction process, reduce the formation of by-products, increase product yield, realize continuous production of enzymatic hydrolysis process and reuse of enzymes.

[0004] However, at present, when soybean protein adhesive is used to bond bamboo products, there is still the problem of poor adhesion. Summary of the invention

[0005] The inventors have found that ultra-short carbon fibers have good heat resistance and can maintain good structural stability and performance stability in high temperature environments. Ultra-short carbon fibers refer to carbon fiber materials that have been specially processed and are relatively short in length. They have the high strength and high modulus characteristics of carbon fibers themselves, as well as high mechanical strength and rigidity. Their strength is greater than that of steel, and they can provide excellent reinforcement effects for composite materials when subjected to tensile, bending, and compression loads. Adding ultra-short carbon fibers to matrix materials such as plastics, rubbers, and resins can significantly improve the mechanical properties of the materials, such as strength, stiffness, and wear resistance.

[0006] In order to overcome the problems of poor bonding performance of soybean protein adhesive and insufficient static bending strength of bamboo product board when used for bamboo product bonding, the present invention proposes a carbon fiber reinforced soybean protein adhesive and its preparation method and application. The adhesive adopts carbon fiber combined with soybean protein matrix for bonding bamboo products, and the surface of the carbon fiber is rich in active oxygen-containing functional groups such as hydroxyl, carboxyl, epoxy, etc. after oxidation treatment, and the carbon fiber has short length and excellent properties such as high strength, high modulus, and high temperature resistance. It is evenly dispersed in the soybean protein matrix, which can significantly enhance the mechanical properties of the adhesive and make up for the shortcomings of insufficient mechanical properties of the soybean protein adhesive itself. In the preparation of the bamboo product of the present invention, in the molding process, part of the carbon fiber will be inserted into the bamboo product under a large pressure to form a three-dimensional mesh structure across the interface layer of the bamboo product and the adhesive, and at the same time, the soybean protein adhesive is partially drained, the interaction between bamboo fiber and soybean protein is enhanced, and stress is effectively transmitted, so that the overall strength of the adhesive is greatly improved. When used for bonding bamboo products, it can withstand greater external forces to ensure the structural stability of the bamboo products. It can be used to bond various bamboo products such as bamboo chopsticks, bamboo mats, bamboo boards, etc.

[0007] The technical solution of the present invention is as follows:

[0008] A carbon fiber reinforced soybean protein adhesive, the adhesive comprising modified carbon fiber and soybean protein matrix, the modified carbon fiber being dispersed in the soybean protein matrix;

[0009] The surface of the modified carbon fiber is rich in at least one active functional group among hydroxyl, carboxyl or epoxy groups.

[0010] According to an embodiment of the present invention, the length of the modified carbon fiber is 50-500 μm, the diameter of the monofilament is 5-20 μm, and the density of the monofilament is 1.70-1.75 g / cm 3 .

[0011] According to an embodiment of the present invention, the modified carbon fiber is obtained by activating a carbon fiber matrix, and the carbon fiber matrix is ​​at least one of polyacrylonitrile (PAN)-based carbon fiber, asphalt-based carbon fiber, and viscose-based carbon fiber, for example, polycarbonate carbon fiber.

[0012] Preferably, the activation pathway includes oxidation or acidification. Oxidation and acidification are well known in the art. Oxidation can be achieved by adding potassium permanganate in batches to oxidize a mixed solution of sulfuric acid and sodium nitrate to achieve oxidation of the carbon fiber. Acidification can be achieved by treating the carbon fiber with an acidifier such as sulfuric acid, nitric acid, etc.

[0013] According to an embodiment of the present invention, the modified carbon fiber is uniformly dispersed in the soybean protein matrix.

[0014] According to an embodiment of the present invention, the mass ratio of the modified carbon fiber to the soybean protein matrix is ​​(0.05-0.6):10, preferably (0.05-0.4):10.

[0015] According to an embodiment of the present invention, the source of the soy protein matrix is ​​defatted soy flour.

[0016] According to an embodiment of the present invention, the soy protein matrix can also be modified and then composited with the modified carbon fiber; that is, the adhesive includes the modified carbon fiber and the modified soy protein matrix, and the modified carbon fiber is dispersed in the modified soy protein matrix.

[0017] Preferably, the soy protein matrix can be modified by methods known in the art, for example, at least one of physical modification, chemical modification and bioenzyme modification can be used.

[0018] The present invention also provides a method for preparing the carbon fiber reinforced soybean protein adhesive, the method comprising:

[0019] (1) preparing or preparing modified carbon fiber;

[0020] (2) The modified carbon fiber is mixed with a soybean fiber matrix to obtain the adhesive.

[0021] According to an embodiment of the present invention, in step (1), the modified carbon fiber is prepared by a method known in the art so that the surface of the modified carbon fiber is enriched with at least one active functional group of hydroxyl, carboxyl or epoxy.

[0022] For example, the preparation method of the modified carbon fiber is:

[0023] (S1) mixing a carbon fiber matrix with an acid, and then adding potassium permanganate and continuing to mix;

[0024] (S2) adding water to the mixed solution of step (S1) and mixing, then adding a hydrogen peroxide solution and mixing, allowing to stand, collecting a precipitate, and obtaining the modified carbon fiber.

[0025] According to an embodiment of the present invention, in step (2), during the mixing process of the activated modified carbon fiber and the soybean fiber matrix, an auxiliary agent may be added, wherein the auxiliary agent is selected from at least one of a leveling agent, a defoaming agent, a dispersant, a surfactant, a thickener and a preservative.

[0026] Preferably, the thickener is polyvinyl alcohol. Preferably, the mass of the thickener is 1-10% of the soy protein matrix.

[0027] Preferably, the leveling agent is selected from organic silicon compounds, such as polydimethylsiloxane, modified organic siloxane; acrylic polymers, such as polyacrylate, acrylic copolymer, etc. Preferably, the mass of the leveling agent is 0.1-1% of the soy protein matrix.

[0028] Preferably, the defoamer is selected from alcohols such as octanol, amyl alcohol, etc.; ethers such as nonyl (octyl) phenol polyoxyethylene ether, etc.; soap salts such as soap substances such as sodium fatty acid and potassium fatty acid; hydroxyl-containing macromolecular substances such as hydroxypropyl methylcellulose and polyvinyl alcohol, etc. Preferably, the mass of the defoamer is 0.05%-0.5% of the soy protein matrix, preferably 0.08%-0.5%. For example, the defoamer is AFE-1410.

[0029] Preferably, the dispersant is selected from natural polymers, such as xanthan gum, guar gum, carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC) and other cellulose ethers.

[0030] Preferably, the surfactant is selected from nonionic surfactants such as fatty alcohol polyoxyethylene ethers and alkylphenol polyoxyethylene ethers; anionic surfactants such as sodium dodecyl sulfate and sodium dodecylbenzene sulfonate; synthetic polymers such as polyacrylic acid and its copolymers and polyethylene glycol. Preferably, the mass of the surfactant is 1-10%, preferably 2-6% of the soy protein matrix.

[0031] Preferably, the preservative is selected from potassium sorbate. Preferably, the mass of the preservative is 0.1-1% of the soy protein matrix.

[0032] According to an embodiment of the present invention, in step (2), the viscosity of the adhesive is 10-20000 mPa.s, preferably 10000-20000 mPa.s, and is measured using the rotational viscometer method in accordance with the national standard GB / T 2794-2022.

[0033] As an exemplary embodiment of the present invention, step (2) is specifically:

[0034] The soy protein matrix is ​​mixed evenly with a defoamer, a leveling agent, a preservative, a thickener and a surfactant, and then the modified carbon fiber is added and mixed to obtain the adhesive.

[0035] As an exemplary embodiment of the present invention, step (2) is specifically: uniformly mixing the modified soy protein matrix with a defoamer, a leveling agent, a preservative, a thickener and a surfactant, and then adding the modified carbon fiber to mix to obtain the adhesive.

[0036] The present invention also provides the use of the carbon fiber reinforced soybean protein adhesive in bamboo products, for example, as a binder in bamboo carbon boards, bamboo fiber boards, bamboo plywood, particle boards, etc.

[0037] The present invention also provides a bamboo product, on which the above adhesive is coated.

[0038] The present invention also provides a method for preparing a bamboo product, the method comprising:

[0039] The adhesive is coated on a bamboo product substrate, and the bamboo product is obtained by heating and pressurizing.

[0040] According to an embodiment of the present invention, the heating temperature is 120-140° C.; the applied pressure is 1-5 MPa, and the pressurizing time is 5-15 min.

[0041] Beneficial effects of the present invention:

[0042] 1) The modified carbon fiber in the adhesive of the present invention is combined with the soybean protein matrix, which enhances the bonding strength of the adhesive. When the adhesive is used for gluing bamboo products, the mechanical strength and service life of the bamboo products are increased;

[0043] 2) The preparation method of the adhesive of the present invention is relatively simple. It only needs to add the treated fiber to the soybean protein matrix and perform sufficient and effective blending (the effective blending means that the adhesive after blending has a uniform texture, no obvious agglomeration phenomenon, and exhibits good fluidity) to obtain the adhesive. The adhesive uses activated modified carbon fibers, and the active functional groups such as hydroxyl, carboxyl, and epoxy groups on its surface are rich in properties similar to the active functional groups of the soybean protein matrix, have good compatibility, and are not prone to agglomeration or phase separation. When the adhesive is used to prepare bamboo products (such as bamboo carbon boards, bamboo fiberboards, and bamboo plywood), in the molding process, the carbon fibers can also be inserted into the interior of the bamboo products to form a three-dimensional network structure spanning the interface layer between the bamboo products and the adhesive. The surface active functional groups of the modified carbon fibers react chemically with the soybean protein matrix and the bamboo products to form stable covalent bonds, thereby increasing the bonding strength of the bamboo products, improving the bonding properties of the adhesive, and improving the static bending strength of the bamboo products.

[0044] 3) The main raw materials used in the present invention, carbon fiber and soybean protein, are both environmentally friendly materials and meet environmental protection requirements;

[0045] 4) The adhesive of the present invention can be used not only in the field of bamboo product processing, but also in the field of processing various wood-based panels, meeting the application requirements in different wood-based panel fields;

[0046] 5) The carbon fiber used in the adhesive of the present invention can also give bamboo products certain conductive and wave-absorbing functions, and can be used in supercapacitors, sensors, electronic communications, medical treatment, military and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 The figure is a schematic cross-sectional view of the bonding structure of bamboo products after the adhesive of the present invention is used.

[0048] Figure 2 This is a scanning electron microscope (SEM) photograph of the ultrashort carbon fiber in Example 1. DETAILED DESCRIPTION

[0049] The technical scheme of the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only exemplary descriptions and explanations of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are included in the scope that the present invention is intended to protect.

[0050] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0051] Example 1

[0052] In the first step, 15g of ultra-short carbon fiber (10-500μm, polycarbonate, such as Figure 2 ), 4.6g sodium nitrate (NaNO3, Aladdin) and 220mL concentrated sulfuric acid (H2SO4, 97%, Sinopharm) were added to a 1000mL three-necked flask and stirred for 60min (200r / min) under ice bath conditions (below 5°C). Then, under vigorous stirring (500r / min), 18.0g potassium permanganate (KMnO4, Aladdin) was slowly added in batches, while keeping the temperature of the reaction system below 15°C, and stirred for 90min. The temperature was raised to 50°C and the reaction continued for 60 minutes. 500mL deionized water was slowly added (the temperature of the reaction system needs to be kept below 70°C). After all the deionized water was added to the three-necked flask, the system was heated to 98°C and maintained for 30min. Subsequently, the resulting mixture was added to 900mL hydrogen peroxide solution (600mL water + 300mL H2O2, hydrogen peroxide purchased from Sinopharm, 30%), and attention was paid to stirring while pouring. After pouring, stirring was continued for 120min. Then, the mixture was allowed to settle and the supernatant was discarded. After adding an appropriate amount of deionized water and stirring thoroughly, the mixture was filtered and washed with deionized water for 5 times until the mixture was neutral. The mixture was filtered and dried to obtain the activated modified ultra-short carbon fiber for use.

[0053] In the second step, 200g defatted soy flour (Hongrun Baoshun, protein content ≥45.0%, amino acid ≥2.50%, moisture ≤10.0%, protein residual oil ≈0.96%) is added to a beaker containing 600ml deionized water, stirred evenly, and a soy flour suspension is formed. Slowly add sodium hydroxide (NaOH, Aladdin) alkaline solution, adjust the pH value of the system to 10, stir at room temperature for 60 minutes, so that the soy protein is fully dissolved, and the structure of the protein molecules is unfolded during this process, exposing more active groups. After diluting with concentrated hydrochloric acid (HCl, Aladdin), a 0.1mol / L acid solution is obtained, and the pH value of the system is slowly adjusted to pH 5, so that the soy protein is precipitated. After precipitation, let it stand for a period of time to allow the protein to fully precipitate. Centrifuge or filter the precipitate to collect the soy protein precipitate, which is the soy protein matrix.

[0054] In the third step, 20g of the soy protein precipitate obtained in the second step is redispersed in 50ml water to form a soy protein dispersion, and stirred for 20 minutes. 1.4g of thickener polyvinyl alcohol (PVA, PVA1788, Chinese medicine), 0.4g of surfactant sodium dodecylbenzene sulfonate (Aladdin), 0.1g of silicone defoamer (AFE-1410, Dow Corning), and 0.1g of preservative potassium sorbate (Tianjin Polyhengda Chemical Co., Ltd.) are added in sequence, and stirred at room temperature for 30 minutes at a stirring speed of 300 (rev / min) with a mechanical stirrer. Subsequently, 0.35g of the modified ultra-short carbon fiber obtained in the first step is added to the stirring system and stirred for 20 minutes. Finally, 2.1g of cross-linking agent epichlorohydrin (purity ≥ 99.5%, Aladdin) is added and stirred for 10 minutes. After stirring evenly, an ultra-short carbon fiber reinforced soy protein adhesive with a viscosity of 15000mPa·s is obtained.

[0055] In the fourth step, select bamboo strips and apply ultra-short carbon fiber reinforced soybean protein adhesive on all surfaces of the bamboo strips. Arrange the bamboo strips in three layers in the arrangement direction of 0° / 90° / 0° (each layer uses adhesive), and hot press for 10 minutes at a temperature of 130°C and a pressure of 3MPa to obtain a bamboo plywood bonded with short carbon fiber reinforced soybean protein bamboo product adhesive and bamboo pieces. The cross-sectional diagram of the bonding structure is shown in FIG. Figure 1 .

[0056] Bending strength / bonding strength test

[0057] The bamboo plywood prepared in Example 1 was cut into standard sizes for the test specimens (a total of 6 specimens with a length of 1000 mm and a width of 49-51 mm were cut according to the thickness size, and they were numbered and recorded), and placed in an environment with a temperature of 25°C and a relative humidity of 70% for 24 hours of equilibrium treatment. The samples were tested for static bending strength using a universal testing machine (AGX-100plus, Shimadzu, Japan) in accordance with the "Test Methods for Physical and Chemical Properties of Artificial Boards and Facing Artificial Boards" (GB / T 17657-2022), and the average static bending strength of the bamboo plywood was measured to be 96.7 MPa. The bonding strength test was carried out in accordance with the "Bamboo Woven Plywood" (GB / T 13123-2003), and the average bonding strength of the bamboo plywood was measured to be 1.2 MPa.

[0058] Example 2

[0059] The difference between Example 2 and Example 1 is that: in the third step of Example 2, 0.15 g of the modified ultra-short carbon fiber after activation is added, and the viscosity of the prepared ultra-short carbon fiber reinforced soybean protein adhesive is 14300 mPa·s.

[0060] The average static bending strength of the bamboo plywood prepared by the adhesive of Example 2 is 91.3 MPa; the average bonding strength is 0.9 MPa.

[0061] Example 3

[0062] The difference between Example 3 and Example 1 is that: in the third step of Example 3, 0.7 g of the modified ultra-short carbon fiber after activation is added, and the viscosity of the prepared ultra-short carbon fiber reinforced soybean protein adhesive is 16100 mPa·s.

[0063] The average static bending strength of the bamboo plywood prepared by the adhesive of Example 3 is 101.1 MPa; the average bonding strength is 1.3 MPa.

[0064] Example 4

[0065] In the fourth step, the ultra-short carbon fiber reinforced soybean protein adhesive in Example 1 is brushed on all surfaces of the bamboo strips, and the bamboo strips are arranged in three layers in the arrangement direction of 0° / 90° / 0°. The bamboo strips are hot-pressed at a temperature of 130° C. and a pressure of 1 MPa for 10 minutes to obtain a bamboo plywood.

[0066] The average static bending strength of bamboo plywood is 75.3MPa. The average bonding strength of bamboo plywood is 0.82MPa.

[0067] Example 5

[0068] In the fourth step, bamboo strips are selected and the ultra-short carbon fiber reinforced soybean protein adhesive in Example 1 is brushed on all surfaces. The bamboo strips are arranged in three layers in the arrangement direction of 0° / 90° / 0°, and hot pressed for 10 minutes at a temperature of 130°C and a pressure of 4MPa to obtain a bamboo plywood.

[0069] The average static bending strength of bamboo plywood is 100.9MPa. The average bonding strength of bamboo plywood is 1.44MPa.

[0070] The above is an exemplary description of the embodiments of the present invention. However, the protection scope of the present invention is not limited to the above embodiments. Any modification, equivalent substitution, improvement, etc. made by those skilled in the art within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A carbon fiber reinforced soybean protein adhesive, characterized in that: The adhesive comprises modified carbon fibers and a soybean protein matrix, wherein the modified carbon fibers are dispersed in the soybean protein matrix; The surface of the modified carbon fiber is rich in at least one active functional group among hydroxyl, carboxyl or epoxy groups.

2. The adhesive according to claim 1, characterized in that: The length of the modified carbon fiber is between 50-500 μm, the diameter of the single fiber is between 5-20 μm, and the density of the single fiber is 1.70-1.75 g / cm 3 .

3. The adhesive according to claim 1, characterized in that: The modified carbon fiber is obtained by activating a carbon fiber matrix, and the carbon fiber matrix is ​​at least one of polyacrylonitrile-based carbon fiber, asphalt-based carbon fiber, and viscose-based carbon fiber. Preferably, the activation pathway comprises oxidation or acidification treatment.

4. The adhesive according to claim 1, characterized in that: The modified carbon fibers are uniformly dispersed in the soybean protein matrix. Preferably, the mass ratio of the modified carbon fiber to the soybean protein matrix is ​​(0.05-0.6):

10. Preferably, the soy protein matrix is ​​sourced from defatted soy flour.

5. The method for preparing the adhesive according to any one of claims 1 to 4, characterized in that: The method comprises: (1) preparing or preparing modified carbon fiber; (2) The modified carbon fiber is mixed with a soybean fiber matrix to obtain the adhesive.

6. The preparation method according to claim 5, characterized in that: In step (2), during the mixing process of the modified carbon fiber and the soybean fiber matrix, an auxiliary agent may be added, wherein the auxiliary agent is selected from at least one of a leveling agent, a defoaming agent, a dispersant, a surfactant, a thickener and a preservative. Preferably, in step (2), the viscosity of the adhesive is 10-20000 mPa.s.

7. Use of the adhesive according to any one of claims 1 to 4 in bamboo products, for example, as a binder in bamboo carbon board, bamboo fiberboard, bamboo plywood or particleboard.

8. A bamboo product, characterized in that: The bamboo product is coated with the adhesive according to any one of claims 1 to 4.

9. The method for preparing bamboo products according to claim 8, characterized in that: The method is: The adhesive is coated on a bamboo product substrate, and the bamboo product is obtained by heating and pressurizing.

10. The preparation method according to claim 9, characterized in that: The heating temperature is 120-140° C.; the applied pressure is 1-5 MPa, and the pressurizing time is 5-15 min.

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