Mildew-proof, flame-retardant, oxidation-resistant and strong soybean protein adhesive, and preparation method and application thereof

Abstract

The present application relates to the technical field of high polymer materials, and particularly relates to a strong and tough soybean protein adhesive with mildew resistance, flame resistance and oxidation resistance, and a preparation method and application thereof. The soybean protein adhesive comprises the following raw material components: soybean protein, water, nano reinforcing agent and modifier. The nano reinforcing agent is obtained by surface functionalization modification of alginate nanofiber with gallic acid. The modifier is a metal ion compound. The interface platform of gallic acid forms a fiber-reinforced covalent bond and a hydrogen bond crosslinking network with the alginate nanofiber and the soybean protein. The metal ion forms a sacrificial chelate bond with other components in the adhesive, thereby constructing a stable multi-crosslinking fiber-reinforced biomimetic hierarchical structure, improving the adhesive strength, toughness, initial adhesion and water resistance of the adhesive. In addition, the adhesive also has excellent mildew resistance, antibacterial property, flame resistance and oxidation resistance, and the process operation is simple and easy to popularize and apply.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a functionalized nanofiber reinforcing agent and a metal ion-modified, mildew-resistant, flame-retardant, antioxidant, and tough soybean protein adhesive, as well as its preparation method and application. Background Technology

[0002] Adhesives are a crucial component of engineered wood products. Petroleum-based formaldehyde adhesives account for over 90% of the market share, but they also cause over-reliance on petrochemical resources and a series of environmental problems such as formaldehyde release. Developing high-performance, renewable, and environmentally friendly bio-based adhesives to replace petroleum-based formaldehyde adhesives is of paramount importance for addressing the depletion of petrochemical resources and formaldehyde pollution.

[0003] Soy protein adhesives, as one of the most representative bio-based adhesives, have attracted widespread attention due to their easy availability, low cost, and good biocompatibility. However, their poor bonding strength, adhesive layer toughness, initial tack, and water resistance limit their practical applications.

[0004] Furthermore, the flammability of soybean protein adhesives poses a potentially fatal fire risk; simultaneously, soybean protein is susceptible to bacterial and mold growth, severely shortening the adhesive's lifespan; additionally, soybean protein adhesives are prone to bonding failure after oxidation. Therefore, developing strong and tough soybean protein adhesives with good water resistance, flame retardancy, mildew resistance, antibacterial properties, and antioxidant properties is crucial for the development of wood adhesives.

[0005] Many materials in nature exhibit both excellent strength and toughness, especially mussel byssal silk, which possesses a tensile strength exceeding 100 MPa and a tensile fracture deformation exceeding 100%. The superior mechanical properties of mussel byssal silk primarily stem from its ordered hierarchical structure composed of a fibrous core surrounded by a protective cuticle. This cuticle contains numerous particles that store a large amount of catechol derivatives, dopamine, and iron ions. Iron ions and dopamine form coordination bonds, while dopamine self-polymerizes into polydopamine, forming covalent and hydrogen bonds. The internal fibrous core provides structural stability, and the covalent bonds within the particles further reinforce the stability of the mussel byssal silk. On the other hand, the coordination and hydrogen bonds act as sacrificial bonds, dispersing fracture energy and thus generating tremendous fracture toughness.

[0006] Seaweed nanofibers possess excellent mechanical properties, are environmentally friendly, and non-toxic, showing great potential for preparing high-performance composite materials. However, the chemical inertness of the seaweed nanofiber surface leads to poor interfacial bonding with the matrix. Mussel-inspired catechin chemical modification has been widely used to improve the surface reactivity of materials. The phenolic hydroxyl groups of catechol derivatives such as dopamine and gallic acid can be oxidized to quinones, which then undergo Schiff base or Michael addition reactions with nucleophiles, while simultaneously forming free radical couplings with other catechols or amines. Therefore, utilizing catechol groups to improve the interfacial interaction between seaweed nanofibers and the matrix is ​​an effective design approach. Seaweed nanofibers with catechol groups can also serve as catechol donors to construct catechol-metal ion multi-crosslinked fiber-reinforced biomimetic hierarchical structures. Summary of the Invention

[0007] Purpose of the invention: The technical problem to be solved by the present invention is to address the shortcomings of the prior art by providing a nano-reinforcing agent and its preparation method, as well as a mildew-resistant, flame-retardant, antioxidant, and tough soybean protein adhesive prepared therefrom, and its preparation method and application.

[0008] Invention Concept: This invention modifies soybean protein adhesive using a multi-crosslinked fiber reinforcement system based on hydrogen bonds, covalent bonds, and metal ion chelate bonds. Inspired by the hierarchical structure of catechol-iron ion multi-crosslinked fibers in mussel byssal silk, this invention utilizes seaweed nanofibers to replace the byssal silk core, plant-derived gallic acid to replace dopamine in the byssal silk cuticle, ferric chloride to replace iron ions in the byssal silk cuticle, and soybean protein to replace the protein matrix in the byssal silk cuticle, thus constructing a multi-crosslinked fiber-reinforced biomimetic hierarchical structure. Gallic acid serves as a functionalized interface platform grafted onto seaweed nanofibers, enhancing the reactivity and interfacial interaction between the seaweed nanofibers and the soybean protein matrix. The functionalized seaweed nanofibers act as a reinforcing agent, forming hydrogen bonds, covalent bonds, and a fiber reinforcement structure with the soybean protein. The introduced iron ions act as a modifier, forming metal ion chelate bonds with other components in the adhesive. A stable fiber-reinforced covalent cross-linked network improves the strength and water resistance of the adhesive. Sacrificial chelate bonds and hydrogen bonds enhance the toughness of the adhesive. Hydrogen bonds and coordination effects increase the viscosity of the adhesive to improve its initial tack. The introduced gallic acid enhances the adhesive's anti-mildew, antibacterial, and antioxidant properties. Inorganic iron ions enhance the adhesive's flame retardancy. Based on the biomimetic hierarchical structure of multiple cross-links, a mildew-resistant, flame-retardant, antioxidant, and tough soybean protein adhesive was prepared, which meets national standards for use in engineered wood products.

[0009] To solve the above-mentioned technical problems, the present invention discloses the following technical solution:

[0010] In a first aspect, the present invention provides a nano-reinforcing agent, which is prepared by surface functionalization modification of gallic acid using seaweed nanofibers as templates.

[0011] Preferably, the nano-reinforcing agent is made from raw materials comprising the following parts by weight: 285-315 parts water, 3.6-10.4 parts seaweed nanofibers, and 1.8-2.4 parts gallic acid; more preferably, 290-310 parts water, 3.8-9.2 parts seaweed nanofibers, and 1.9-2.2 parts gallic acid; or more preferably, 300 parts water, 4-8 parts seaweed nanofibers, and 2 parts gallic acid; the water is preferably deionized water.

[0012] Seaweed is abundant in nature and inexpensive. Using seaweed nanofibers to prepare high-performance composite materials not only realizes the high-value utilization of seaweed, but also reduces the eutrophication of seawater and ecological damage caused by seaweed overgrowth. Furthermore, seaweed fibers themselves have high rigidity and can serve as a core skeleton to increase the stability of the material.

[0013] Preferably, the above-mentioned seaweed nanofibers are obtained by treating natural seaweed with alkali to remove impurities and then acid hydrolyzing it; preferably, the natural seaweed is added to a NaOH aqueous solution, stirred, washed and dried, and then added to sulfuric acid, stirred and washed; preferably, 10-15g of natural seaweed is added to 200-240mL of 5-8wt% NaOH aqueous solution, stirred at 21-27℃ for 24-28h, washed and dried to obtain 5-8g of alkali-treated seaweed, and 5-7g of the obtained seaweed is added to 300-370mL of 55-60wt% sulfuric acid, stirred at 21-27℃ for 12-17h, washed and dried to obtain 2.4-3.6g of the seaweed nanofibers; preferably, alkali treatment is performed first to remove impurities, and 10-15g of natural seaweed is added to 200-240mL of NaOH aqueous solution. The seaweed was treated with alkali by stirring continuously at 500-900 rpm for 24-28 hours in a NaOH aqueous solution (5-8 wt%) at 21-27°C. After washing 3-7 times with water, the seaweed was vacuum dried to obtain 5-8 g of alkali-treated seaweed. Then, acid hydrolysis was performed, and 5-7 g of the alkali-treated seaweed was added to 300-370 mL of sulfuric acid (55-60 wt%). The mixture was stirred continuously at 800-1200 rpm for 12-17 hours at 21-27°C, and washed 5-8 times with water. The seaweed nanofibers were further optimized to have a length of 500-750 nm and a width of 30-62 nm. After vacuum drying, 2.4-3.6 g of seaweed nanofibers were obtained. Preferably, the weight of the natural seaweed in the alkali treatment was 10-12 g, the volume of the NaOH aqueous solution was 200-220 mL, and the concentration of the NaOH aqueous solution was 5-6 wt%. The temperature is 22-25℃, the stirring speed is 500-800 r / min, the stirring time is 24-26 h, the water is preferably deionized water, and the washing frequency is 3-5 times; the weight of the pretreated seaweed in the acid hydrolysis is 5-6 g, the sulfuric acid volume is 300-335 mL, the sulfuric acid concentration is 55-58 wt%, the stirring temperature is 22-25℃, the stirring speed is 800-1000 r / min, the stirring time is 12-14 h, the water is preferably deionized water, and the washing frequency is 5-7 times; preferably, the seaweed nanofibers have a length of 500-630 nm and a width of 30-47 nm; the natural seaweed can be any one or a combination of several of Sargassum, Fucus vesiculosus, Rhododendron simsii, Porphyra, and Gracilaria; preferably, the natural seaweed is Sargassum. Research has shown that when Sargassum is used, the prepared seaweed nanofibers have better overall performance, especially tensile strength.

[0014] In some embodiments of the present invention, the gallic acid-functionalized seaweed nanofiber raw material also includes a pH buffer regulator, such as Tris buffer solution.

[0015] The principle of gallic acid-functionalized seaweed nanofibers in this invention is that gallic acid has a catechol structure similar to dopamine, which can be adsorbed and grafted onto the surface of seaweed nanofibers through intermolecular hydrogen bonds and electrostatic interactions, providing more reactive sites for seaweed nanofibers and increasing their interaction with the matrix.

[0016] In a second aspect, the present invention provides a method for preparing the nano-reinforcing agent described in the first aspect above, which utilizes gallic acid to functionalize surface-modified seaweed nanofibers, comprising: mixing seaweed nanofibers with water in parts by weight to obtain a seaweed nanofiber suspension, adjusting the pH to 7.0-8.5, then adding gallic acid, stirring continuously for 5.6-7.8 h, washing repeatedly with water, and vacuum drying to obtain gallic acid-functionalized seaweed nanofibers.

[0017] Further, specifically: seaweed nanofibers are added to water (preferably deionized water) according to a predetermined weight ratio and mixed evenly. The pH is adjusted to 7.5-8 using Tris buffer solution (1-1.8M). Gallic acid is then added in a specific proportion, and the mixture is continuously stirred at 600-1000 r / min for 6.1-7.3 h at 23-29℃. The mixture is washed 3-5 times with water and vacuum dried to obtain 3.3-8.4 g of gallic acid-functionalized seaweed nanofibers.

[0018] Preferably, the Tris buffer solution is 1-1.4M, the pH is adjusted to 7.8-8.2, the stirring temperature is 25-27℃, the stirring speed is 600-800r / min, the stirring time is 6.7-7.1h, the water is preferably deionized water, and the washing is performed 3-4 times to obtain 3.6-7.8g of gallic acid-functionalized seaweed nanofibers.

[0019] The present invention has found that nano-reinforcing agents prepared using the above-mentioned optimized process parameters exhibit better uniformity, dispersibility, and reinforcing effect.

[0020] Thirdly, the present invention also provides a modified soybean protein adhesive comprising the above-mentioned gallic acid-functionalized seaweed nanofibers. The gallic acid-functionalized seaweed nanofibers are used as the fiber core and catechin donor, and metal ions are added to construct a mussel byssal silk structure, which solves the problems of low adhesive strength, poor adhesive layer toughness, low initial tack, weak water resistance, poor mildew resistance, poor antibacterial properties, low flame retardancy, and poor antioxidant properties of the adhesive.

[0021] This invention relates to catechin-Fe from mussel byssal silk. 3+ Inspired by the multi-crosslinked fiber-reinforced hierarchical structure, we used seaweed nanofibers to simulate the fibrous core in mussel byssal silk, gallic acid to simulate dopamine in byssal silk, and metal ions to simulate Fe in byssal silk. 3+Soybean protein was used to mimic the protein matrix in mussel byssal silks to prepare a mildew-resistant, flame-retardant, antioxidant, and tough soybean protein adhesive based on a mussel byssal silk-like structure. Algae nanofibers covalently cross-linked with soybean protein molecules through a gallic acid interfacial reactive platform, constructing a covalent cross-linked network. Simultaneously, the catechin groups of gallic acid formed hydrogen bonds at the wood substrate interface, and the adhesive formed adhesive staples, increasing the adhesive's cohesiveness, adhesion to the substrate interface, and internal cross-linking hydrophobic stability, thereby improving bonding strength and water resistance. Metal ions formed chelate bonds with functionalized algae nanofibers and soybean protein; during stretching, these chelate bonds act as sacrificial bonds to dissipate energy, improving the adhesive layer's toughness. The formed hydrogen bonds and chelate bonds enhanced the adhesive's shear resistance. This increases viscosity and improves the initial tack of the adhesive; the catechin groups of gallic acid can adhere to fungal cells and change the permeability of the fungal cell membrane, killing the fungi and thus improving the antifungal and antibacterial properties of the adhesive; the phenolic hydroxyl groups of gallic acid, especially the ortho-hydroxyl groups, exert a strong antioxidant effect through the transfer of hydrogen atoms and single electrons, thus improving the antioxidant properties of the adhesive; inorganic metal ions promote the dehydration and carbonization of soybean protein molecules during combustion to form a coke layer. The coke layer acts as a physical fire barrier, hindering the penetration of external oxygen and delaying the decomposition of the internal combustible matrix, thereby improving the flame retardancy of the adhesive.

[0022] More specifically, the modified soybean protein binder provided by the present invention comprises: soybean protein, water, reinforcing agent and modifier.

[0023] Further, the modified soybean protein adhesive comprises the following raw material components in parts by weight: 2-7 parts soybean protein, 14-25 parts water, 0.4-1.2 parts nano-reinforcing agent, and 0.2-0.8 parts modifier; preferably, the raw material composition of the modified soybean protein adhesive comprises in parts by weight: 2.5-5 parts soybean protein, 16-21 parts water, 0.6-1.0 parts nano-reinforcing agent, and 0.4-0.6 parts modifier; preferably, the raw material composition of the modified soybean protein adhesive comprises in parts by weight: 3 parts soybean protein, 17 parts water, 0.6-1.0 parts nano-reinforcing agent, and 0.4-0.6 parts modifier.

[0024] Preferably, the modifier is a metal ion, such as Fe. 3+ Al 3+ Cr 3+ One or more of the following. Preferably, the modifier is Fe. 3+ (Preferably FeCl3), the present invention has found through research that when FeCl3 is used, the overall performance of the adhesive, especially the bonding strength, adhesive layer toughness and flame retardancy, is better.

[0025] Preferably, the soy protein is soy protein isolate with a protein content of 91-98 wt%, preferably 93-95 wt%; the particle size is 150-350 mesh, preferably 220-260 mesh; it can be one or more of high-temperature dissolved soy protein isolate, low-temperature dissolved soy protein isolate, and defatted soy protein isolate; the water is preferably deionized water.

[0026] Fourthly, the present invention also provides a method for preparing the above-mentioned modified soybean protein adhesive, comprising a process of mixing and stirring soybean protein, water, reinforcing agent and modifier in predetermined weight parts.

[0027] Preferred options include:

[0028] 1) Slowly add soy protein to water and mix with it. Stir at a constant rate until homogeneous to obtain a soy protein gel. 2) Slowly introduce the reinforcing agent into the soy protein gel and stir at a constant rate until homogeneous to obtain an enhanced soy protein gel. 3) Slowly introduce the modifier into the enhanced soy protein gel and stir at a constant rate until homogeneous to obtain a modified soy protein gel. Preferably, the first stirring is continuous stirring at a speed of 900-1900 r / min at a temperature of 25-35℃ for 20-35 min; preferably, the second stirring is continued stirring at a speed of 600-1400 r / min at a temperature of 25-33℃ for 15-25 min; preferably, the third stirring is continued stirring at a speed of 500-1200 r / min at a temperature of 25-30℃ for 10-20 min; preferably, the nano-reinforcing agent is added to the reaction system in 3-7 portions, preferably with an interval of 1-4 min between each addition, preferably with each addition being 1 / number of the total amount; preferably, the modifier is added to the reaction system in 1-3 portions, preferably with an interval of 5-10 min between each addition, preferably with each addition being 1 / number of the total amount.

[0029] Preferred options include:

[0030] 1) Slowly add soy protein to water and mix with water. Stir continuously at a speed of 900-1900 r / min and a temperature of 25-35℃ for 20-35 min to obtain soy protein gel.

[0031] 2) The reinforcing agent is slowly introduced into the soybean protein solution in 3-7 batches (each batch is 1 / 3 of the total amount, with an interval of 3-6 minutes between each batch), and then stirred for 15-25 minutes at a speed of 600-1400 r / min and a temperature of 25-33℃ to obtain the reinforced soybean protein solution.

[0032] 3) The modifier is slowly introduced into the above-mentioned enhanced soybean protein solution in 1-3 times (each time adding 1 / 3 of the total amount, with an interval of 5-10 min each time), and then stirred for 10-20 min at a speed of 500-1200 r / min and a temperature of 25-30℃ to obtain the modified soybean protein solution.

[0033] The method described above is beneficial for forming catechin-Fe in biomimetic mussel byssal threads. 3+ The multi-linked fiber-reinforced hierarchical structure helps to better increase the bonding strength, adhesive toughness, initial tack, water resistance, mildew resistance, antibacterial properties, flame retardancy, and antioxidant properties of modified soybean protein adhesives.

[0034] Further optimization, the preparation method of the modified soybean protein binder specifically includes:

[0035] 1) Slowly add soy protein to water and mix with water. Stir continuously at 1100-1600 r / min and 25-31℃ for 20-28 minutes to obtain soy protein gel.

[0036] 2) The reinforcing agent is slowly introduced into the soybean protein solution in 3-5 batches (each batch is 1 / 3 of the total amount, with an interval of 3-5 minutes between batches), and then stirred for 15-22 minutes at a speed of 900-1100 r / min and a temperature of 25-29℃ to obtain the reinforced soybean protein solution.

[0037] 3) The modifier is slowly introduced into the above-mentioned enhanced soybean protein solution in 2-3 times (each time adding 1 / time of the total amount, with an interval of 5-8 minutes between each time), and then stirred for 12-18 minutes at a speed of 500-800 r / min and a temperature of 25-27℃ to obtain the modified soybean protein solution.

[0038] Preferably, the water used in the above preparation process is deionized water.

[0039] The present invention has found that modified adhesives prepared using the above-mentioned optimized process parameters have better overall performance, especially mechanical properties and water resistance.

[0040] Fifthly, this invention also provides the application of the modified soybean protein adhesive in formaldehyde-free engineered wood products. The adhesive in this invention is environmentally friendly, containing no formaldehyde or other harmful components; it also possesses high performance and multifunctionality, improving the adhesive's service life during the engineered wood product manufacturing process; the prepared engineered wood product meets strength requirements; the high toughness of the adhesive layer prevents edge chipping and cracking during sawing and shaping; the high viscosity and high initial tack of the adhesive prevent delamination after board assembly; the prepared engineered wood product remains firmly bonded even in humid environments; the prepared engineered wood product has strong flame retardancy, reducing the risk of fire; the adhesive layer of the prepared engineered wood product is mildew-proof and antibacterial during use, reducing damage to the adhesive layer from mold and bacteria and improving the stability of the engineered wood product; simultaneously, the adhesive layer of the prepared engineered wood product has strong antioxidant properties, preventing adhesive failure due to oxidation and extending the service life of the engineered wood product. Preferably, the above-mentioned engineered wood product can be one or more of plywood, medium-density fiberboard, particleboard, and blockboard.

[0041] In a sixth aspect, the present invention also provides a method for producing formaldehyde-free plywood using the above-mentioned modified soybean protein adhesive, comprising: applying the adhesive to a wood veneer, and then assembling and hot-pressing the plywood.

[0042] Preferably, the plywood preparation process includes: according to 180g / m 2 The modified soybean protein adhesive was applied to one side of a 400mm×400mm×1.6mm wood veneer using an adhesive roller. The core layer veneer was then assembled and grouped with its adjacent upper and lower layers vertically. The assembled veneer was then placed on a metal pad to secure it, and subsequently placed on a CGYJ-100 hot press. The press parameters were adjusted to 1MPa pressure, 120℃ temperature, and 315s time for hot pressing.

[0043] Preferably, the wood veneer used can be one or more of poplar veneer, eucalyptus veneer, pine veneer and fir; preferably, the moisture content of the wood veneer is controlled at 8-12%.

[0044] The technical solution provided by this invention uses seaweed as raw material to obtain seaweed nanofibers, achieving high-value utilization. Simultaneously, compared to macromolecular polyphenols, this invention uses small-molecule gallic acid to perform hydrogen bonding grafting on the fiber surface. In addition to phenolic hydroxyl groups, the fiber surface also has carboxyl groups. These carboxyl groups form complexes with soybean protein molecules, increasing the stability of the cured structure and improving the initial tack with the wood interface. This results in better pre-pressing performance of the plywood, preventing delamination of the assembled board during transportation. It is suitable for gluing high-moisture-content veneers into boards, improving the processability of the actual manufacturing process of engineered wood products.

[0045] The beneficial effects of this invention include:

[0046] 1) Based on the layered and ordered structure of mussel byssal silk, this invention proposes an effective biomimetic method to modify soybean protein adhesive. It utilizes seaweed nanofibers to mimic the fibrous core of byssal silk, gallic acid to mimic dopamine in byssal silk, and metal ions to mimic Fe in byssal silk. 3+ Soy protein mimics the protein matrix in byssal silk. Gallic acid, acting as an interface platform, enhances the interaction between the reinforcing agent and soy protein. Gallic acid-functionalized seaweed nanofibers and soy protein form a fiber-reinforced covalent and hydrogen-bonded cross-linked network. Metal ions form sacrificial chelate bonds with other components, thereby constructing a stable multi-crosslinked fiber-reinforced biomimetic hierarchical structure. This solves the problems of low adhesive strength, poor water resistance, and poor toughness of adhesives, ensuring that the strength and water resistance meet national standards, and that the adhesive layer is tough enough to withstand breakage. The multiple bonds improve the viscosity and initial tack of the adhesive, making it less prone to delamination in plywood after adhesive coating and preventing misalignment during transportation. The catechol groups of gallic acid disrupt the membrane structure of fungi, extending the service life of the adhesive and solving the problems of poor anti-mildew and antibacterial properties. The phenolic hydroxyl groups of gallic acid endow the adhesive with effective antioxidant properties, solving the problem of poor antioxidant properties. The inorganic hybrid system of metal ions promotes the formation of a fire-retardant carbonized layer in the adhesive layer, solving the problem of poor flame retardancy of the adhesive.

[0047] 2) The adhesive prepared by this invention is green and pollution-free, and will not produce harmful components such as formaldehyde, and will not cause harm to the environment and human health.

[0048] 3) The adhesive used in this invention uses sustainable raw materials, without the use of petroleum-based raw materials, thus reducing the overuse of non-renewable resources.

[0049] 4) The soybean protein and seaweed nanofiber in this invention are made from industrial food by-products and natural waste, which reduces the waste of resources and is conducive to the high-value utilization of resources.

[0050] 5) The adhesive raw materials in this invention are inexpensive and do not require the addition of other expensive additives and crosslinking agents, which is beneficial to improving social and economic benefits.

[0051] 6) The process in this invention is easy to operate, requires no complex machinery or equipment, and is conducive to practical industrial application. Attached Figure Description

[0052] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, and the advantages of the present invention in the above and / or other aspects will become clearer.

[0053] Figure 1This is a graph showing the dry bonding strength results of the adhesives in Comparative Examples 1-6 and Examples 1-5 of this invention.

[0054] Figure 2 These are the fracture toughness results of the adhesives in Comparative Examples 1-6 and Examples 1-5 of this invention.

[0055] Figure 3 This is a graph showing the viscosity results of the adhesives in Comparative Examples 1-6 and Examples 1-5 of this invention.

[0056] Figure 4 This is a graph showing the wet bonding strength results of the adhesives in Comparative Examples 1-6 and Examples 1-5 of this invention.

[0057] Figure 5 This is a graph showing the anti-mildew effect of the adhesives in Comparative Examples 1-6 and Examples 1-5 in this invention.

[0058] Figure 6 This is a graph showing the antibacterial rate results of the adhesives in Comparative Examples 1-6 and Examples 1-5 of this invention.

[0059] Figure 7 This is a graph showing the flame retardancy results of the adhesives in Comparative Examples 1-6 and Examples 1-5 of this invention - limiting oxygen index.

[0060] Figure 8 This is a graph showing the flame retardancy results of the adhesives in Comparative Examples 1-6 and Examples 1-5 of this invention - maximum heat release rate.

[0061] Figure 9 This is a graph showing the absorbance of the antioxidant properties of the adhesives in Comparative Examples 1-6 and Examples 1-5 of this invention.

[0062] Figure 10 This is a graph showing the antioxidant properties of the adhesives in Comparative Examples 1-6 and Examples 1-5 of this invention – total antioxidant capacity. Detailed Implementation

[0063] Unless otherwise specified, the experimental methods described in this invention are all conventional methods.

[0064] Unless otherwise specified, all materials or reagents used in this invention can be obtained through legitimate commercial channels.

[0065] In this invention, soybean protein powder (protein content 95%, particle size 220-260 mesh) was purchased from Anhui Shuai Nuo Biotechnology Co., Ltd., seaweed was purchased from Guangdong Dianmei Biotechnology Co., Ltd., gallic acid was purchased from Shanghai Siyu Chemical Technology Co., Ltd., and ferric chloride (FeCl3, 99%) was provided by Fujian Beiwan Reagent Co., Ltd.

[0066] This invention provides a soybean protein adhesive modified with a nano-reinforcing agent (functionalized seaweed nanofiber) and metal ions, which is mildew-resistant, flame-retardant, antioxidant, and tough, and its preparation method is as follows. Specific embodiments are as follows.

[0067] Example 1

[0068] This embodiment provides a soybean protein binder with nano-reinforcing agents, anti-mildew, flame-retardant, antioxidant, and tough properties, and its preparation method, as follows:

[0069] The preparation method of the nano-reinforcing agent (functionalized seaweed nanofibers) in Example 1 is as follows:

[0070] 1) First, the natural Sargassum was treated with alkali. 10g of natural Sargassum was added to 200mL of NaOH aqueous solution (5wt%) and stirred continuously at 500r / min for 24h at 25℃. The mixture was washed repeatedly with water 3 times to remove impurities and then vacuum dried. Then, the seaweed was acid hydrolyzed. 5g of the alkali-treated seaweed was added to 300mL of sulfuric acid (55wt%) and stirred continuously at 800r / min for 12h at 25℃. The mixture was washed repeatedly with water 5 times to make the pH of the fiber neutral. The seaweed nanofibers were further optimized to have a length of 500-600nm and a width of 30-45nm. After vacuum drying, 2.4-2.7g of seaweed nanofibers were obtained. This preparation process was repeated to obtain sufficient seaweed nanofibers and stored at 5℃ for later use.

[0071] 2) Add 4g of seaweed nanofibers to 300mL of deionized water and mix well to obtain a suspension. Adjust the pH of the suspension to 8 using Tris buffer solution (1M). Then add 2g of gallic acid to the suspension and stir continuously at 600r / min for 7h at 25℃. Wash with deionized water 3 times and then vacuum dry to obtain 3.8g of gallic acid-functionalized seaweed nanofibers.

[0072] The anti-mildew, flame-retardant, antioxidant, and tough soybean protein adhesive in Example 1 and its preparation method, with the following raw material weight ratios:

[0073]

[0074] The preparation method of the above adhesive is as follows:

[0075] 1) First, add 17 parts of water to a reaction vessel equipped with a stirring function. Then, slowly add 3 parts of soy protein to the reaction vessel and mix with the water. Then, stir continuously at 1200 r / min and 25℃ for 25 min to obtain soy protein gel.

[0076] 2) The prepared 0.6 parts of reinforcing agent (functionalized seaweed nanofiber) was slowly added to the above soybean protein solution in 3 portions (1 / 3 of the total amount each time, with an interval of 3 minutes each time). Then, the mixture was stirred at 1000 r / min at 25°C for 20 minutes to obtain the enhanced soybean protein solution.

[0077] 3) The prepared 0.4 parts of modifier (FeCl3) were slowly introduced into the above-mentioned enhanced soybean protein solution in two portions (1 / 2 of the total amount each time, with an interval of 5 min each time). Then, the mixture was stirred at 800 r / min at 25℃ for 15 min to obtain the modified soybean protein solution.

[0078] Example 2

[0079] This embodiment provides a soybean protein binder with nano-reinforcing agents, anti-mildew, flame-retardant, antioxidant, and tough properties, and its preparation method, as follows:

[0080] The preparation method of the nano-reinforcing agent (functionalized seaweed nanofiber) in Example 2 is the same as that of the nano-reinforcing agent in Example 1.

[0081] The anti-mildew, flame-retardant, antioxidant, and tough soybean protein adhesive in Example 2 and its preparation method, with the following raw material weight ratios:

[0082]

[0083]

[0084] The preparation method of the above adhesive is as follows:

[0085] 1) First, add 17 parts of water to a reaction vessel equipped with a stirring function. Then, slowly add 3 parts of soy protein to the reaction vessel and mix with the water. Then, stir continuously at 1200 r / min and 25℃ for 25 min to obtain soy protein gel.

[0086] 2) The prepared 0.8 parts of reinforcing agent (functionalized seaweed nanofiber) was slowly added to the above soybean protein solution in 4 portions (1 / 4 of the total amount each time, with an interval of 3 minutes each time). Then, the mixture was stirred at 1000 r / min at 25°C for 20 minutes to obtain the enhanced soybean protein solution.

[0087] 3) The prepared 0.4 parts of modifier (FeCl3) were slowly introduced into the above-mentioned enhanced soybean protein solution in two portions (1 / 2 of the total amount each time, with an interval of 5 min each time). Then, the mixture was stirred at 800 r / min at 25℃ for 15 min to obtain the modified soybean protein solution.

[0088] Example 3

[0089] This embodiment provides a soybean protein binder with nano-reinforcing agents, anti-mildew, flame-retardant, antioxidant, and tough properties, and its preparation method, as follows:

[0090] The preparation method of the nano-reinforcing agent (functionalized seaweed nanofiber) in Example 3 is the same as that of the nano-reinforcing agent in Example 1.

[0091] The anti-mildew, flame-retardant, antioxidant, and tough soybean protein adhesive in Example 3 and its preparation method, with the following raw material weight ratios:

[0092]

[0093] The preparation method of the above adhesive is as follows:

[0094] 1) First, add 17 parts of water to a reaction vessel equipped with a stirring function. Then, slowly add 3 parts of soy protein to the reaction vessel and mix with the water. Then, stir continuously at 1200 r / min and 25℃ for 25 min to obtain soy protein gel.

[0095] 2) The prepared 1.0 part of reinforcing agent (functionalized seaweed nanofiber) was slowly added to the above soybean protein solution in 5 portions (1 / 5 of the total amount each time, with an interval of 3 min each time). Then, the mixture was stirred at 1000 r / min at 25℃ for 20 min to obtain the reinforced soybean protein solution.

[0096] 3) The prepared 0.4 parts of modifier (FeCl3) were slowly introduced into the above-mentioned enhanced soybean protein solution in two portions (1 / 2 of the total amount each time, with an interval of 5 min each time). Then, the mixture was stirred at 800 r / min at 25℃ for 15 min to obtain the modified soybean protein solution.

[0097] Example 4

[0098] This embodiment provides a soybean protein binder with nano-reinforcing agents, anti-mildew, flame-retardant, antioxidant, and tough properties, and its preparation method, as follows:

[0099] Nano-reinforcing agents (functionalized seaweed nanofibers) were synthesized using different preparation methods. By changing the proportions, different nano-reinforcing agents were synthesized. The specific process is as follows:

[0100] The preparation method of the nano-reinforcing agent in Example 4 is the same as that in Example 1, except that: in this example, 2) 6g of seaweed nanofibers are added to 300mL of deionized water and mixed evenly to obtain a suspension. The pH of the suspension is adjusted to 8 using Tris buffer solution (1M). Then, 2g of gallic acid is added to the suspension and stirred continuously at 600r / min for 7h at 25℃. The suspension is washed 3 times with deionized water and then vacuum dried to obtain 5.4g of gallic acid-functionalized seaweed nanofibers.

[0101] The anti-mildew, flame-retardant, antioxidant, and tough soybean protein adhesive in Example 4 and its preparation method, with the following raw material weight ratios:

[0102]

[0103] The different nano-reinforcing agents obtained in Example 4 above were used to prepare anti-mildew, flame-retardant, antioxidant and tough soybean protein adhesives. The method for preparing soybean protein adhesives was the same as in Example 2.

[0104] Example 5

[0105] This embodiment provides a soybean protein binder with nano-reinforcing agents, anti-mildew, flame-retardant, antioxidant, and tough properties, and its preparation method, as follows:

[0106] Nano-reinforcing agents (functionalized seaweed nanofibers) were synthesized using different preparation methods. By changing the proportions, different nano-reinforcing agents were synthesized. The specific process is as follows:

[0107] The preparation method of the nano-reinforcing agent in Example 5 is the same as that in Example 1, except that: in this example, 2) 8g of seaweed nanofibers are added to 300mL of deionized water and mixed evenly to obtain a suspension. The pH of the suspension is adjusted to 8 using Tris buffer solution (1M). Then, 2g of gallic acid is added to the suspension and stirred continuously at 600r / min for 7h at 25℃. The suspension is washed 3 times with deionized water and then vacuum dried to obtain 7.2g of gallic acid-functionalized seaweed nanofibers.

[0108] The anti-mildew, flame-retardant, antioxidant, and tough soybean protein adhesive in Example 5 and its preparation method, with the following raw material weight ratios:

[0109]

[0110] The different nano-reinforcing agents obtained in Example 5 above were used to prepare anti-mildew, flame-retardant, antioxidant and tough soybean protein adhesives. The method for preparing soybean protein adhesives was the same as in Example 2.

[0111] Comparative Example 1

[0112] This comparative example provides a soybean protein binder and its preparation method, as follows:

[0113] The soybean protein binder prepared in Comparative Example 1 differs from that in Example 2 in that no reinforcing agent (functionalized seaweed nanofibers) and modifier (FeCl3) are added during the preparation process; otherwise, they are the same.

[0114] The soybean protein binder in Comparative Example 1 and its preparation method, with the following raw material weight ratios:

[0115] 3 servings of soy protein

[0116] 17 parts water

[0117] The preparation method of the above adhesive is as follows:

[0118] First, add 17 parts of water to a reaction vessel equipped with a stirring function. Then, slowly add 3 parts of soy protein to the reaction vessel and mix with the water. Then, stir continuously at 1200 r / min and 25℃ for 25 min to obtain a soy protein gel.

[0119] Comparative Example 2

[0120] This comparative example provides a nano-reinforcing agent and a modified soybean protein binder, as well as their preparation method, as follows:

[0121] Common seaweed nanofibers (unfunctionalized) were prepared using ordinary seaweed nanofibers as nano-reinforcing agents. The specific process is as follows:

[0122] The preparation process of the nano-reinforcing agent in Comparative Example 2 is the same as that in Example 2, except that step 2 is omitted in the preparation process of the nano-reinforcing agent in this comparative example.

[0123] The soybean protein adhesive prepared in Comparative Example 2 differs from that in Example 2 in that ordinary seaweed nanofibers (unfunctionalized) are used as nano-reinforcing agents to modify the soybean protein adhesive during preparation, and no modifier (FeCl3) is added during the preparation process; otherwise, they are the same.

[0124] The modified soybean protein binder in Comparative Example 2 and its preparation method, with the following raw material weight ratios:

[0125] 3 servings of soy protein

[0126] 17 parts water

[0127] 0.8 parts of reinforcing agent

[0128] The preparation method of the above adhesive is as follows:

[0129] 1) First, add 17 parts of water to a reaction vessel equipped with a stirring function. Then, slowly add 3 parts of soy protein to the reaction vessel and mix with the water. Then, stir continuously at 1200 r / min and 25℃ for 25 min to obtain soy protein gel.

[0130] 2) The prepared 0.8 parts of reinforcing agent (ordinary seaweed nanofiber) was slowly added to the above soybean protein solution in 4 portions (1 / 4 of the total amount each time, with an interval of 3 minutes each time). Then, the mixture was stirred at 1000 r / min at 25°C for 20 minutes to obtain the reinforced soybean protein solution.

[0131] Comparative Example 3

[0132] This comparative example provides a nano-reinforcing agent and a modified soybean protein binder, as well as their preparation methods, as follows:

[0133] The preparation method of the nano-reinforcing agent (functionalized seaweed nanofiber) in Comparative Example 3 is the same as that of the nano-reinforcing agent in Example 2.

[0134] The soybean protein binder prepared in Comparative Example 3 differs from that in Example 2 in that no modifier (FeCl3) is added during the preparation process; otherwise, they are the same.

[0135] The modified soybean protein binder in Comparative Example 3 and its preparation method, with the following raw material weight ratios:

[0136] 3 servings of soy protein

[0137] 17 parts water

[0138] 0.8 parts of reinforcing agent

[0139] The preparation method of the above adhesive is as follows:

[0140] 1) First, add 17 parts of water to a reaction vessel equipped with a stirring function. Then, slowly add 3 parts of soy protein to the reaction vessel and mix with the water. Then, stir continuously at 1200 r / min and 25℃ for 25 min to obtain soy protein gel.

[0141] 2) The prepared 0.8 parts of reinforcing agent (functionalized seaweed nanofiber) was slowly added to the above soybean protein solution in 4 portions (1 / 4 of the total amount each time, with an interval of 3 minutes each time). Then, the mixture was stirred at 1000 r / min at 25°C for 20 minutes to obtain the enhanced soybean protein solution.

[0142] Comparative Example 4

[0143] This comparative example provides a soybean protein binder and its preparation method, as follows:

[0144] The soybean protein binder prepared in Comparative Example 4 differs from that in Example 2 in that no reinforcing agent (functionalized seaweed nanofibers) is added during the preparation process; otherwise, they are the same.

[0145] The soybean protein binder in Comparative Example 4 and its preparation method, with the following raw material weight ratios:

[0146] 3 servings of soy protein

[0147] 17 parts water

[0148] Modifier 0.4 parts

[0149] The preparation method of the above adhesive is as follows:

[0150] 1) First, add 17 parts of water to a reaction vessel equipped with a stirring function. Then, slowly add 3 parts of soy protein to the reaction vessel and mix with the water. Then, stir continuously at 1200 r / min and 25℃ for 25 min to obtain soy protein gel.

[0151] 2) The prepared 0.4 parts modifier (FeCl3) was slowly introduced into the above-mentioned enhanced soybean protein solution in two portions (1 / 2 of the total amount each time, with an interval of 5 min each time). Then, the mixture was stirred at 800 r / min at 25℃ for 15 min to obtain the modified soybean protein solution.

[0152] Comparative Example 5

[0153] This comparative example provides a nano-reinforcing agent and a modified soybean protein binder, as well as their preparation methods, as follows:

[0154] The preparation method of the nano-reinforcing agent (functionalized seaweed nanofiber) in Comparative Example 5 is the same as that of the nano-reinforcing agent in Example 2.

[0155] The soybean protein binder prepared in Comparative Example 5 differs from that in Example 2 in that another modifier (AlCl3) was added during the preparation process, while the rest were the same.

[0156] The anti-mold, flame-retardant, antioxidant, and tough soybean protein adhesive in Comparative Example 5 and its preparation method are described below, with the following raw material weight ratios:

[0157]

[0158] The preparation method of the above adhesive is as follows:

[0159] 1) First, add 17 parts of water to a reaction vessel equipped with a stirring function. Then, slowly add 3 parts of soy protein to the reaction vessel and mix with the water. Then, stir continuously at 1200 r / min and 25℃ for 25 min to obtain soy protein gel.

[0160] 2) The prepared 0.8 parts of reinforcing agent (functionalized seaweed nanofiber) was slowly added to the above soybean protein solution in 4 portions (1 / 4 of the total amount each time, with an interval of 3 minutes each time). Then, the mixture was stirred at 1000 r / min at 25°C for 20 minutes to obtain the enhanced soybean protein solution.

[0161] 3) The prepared 0.4 parts of modifier (AlCl3) was slowly introduced into the above-mentioned enhanced soybean protein solution in two portions (1 / 2 of the total amount each time, with an interval of 5 min each time). Then, the mixture was stirred at 800 r / min at 25℃ for 15 min to obtain the modified soybean protein solution.

[0162] Comparative Example 6

[0163] This comparative example provides a nano-reinforcing agent and a modified soybean protein binder, as well as their preparation methods, as follows:

[0164] The preparation method of the nano-reinforcing agent (functionalized seaweed nanofiber) in Comparative Example 6 is the same as that of the nano-reinforcing agent in Example 2.

[0165] The soybean protein binder prepared in Comparative Example 6 differs from that in Example 2 in that another modifier (CrCl3) was added during the preparation process; otherwise, they are the same.

[0166] The anti-mold, flame-retardant, antioxidant, and tough soybean protein adhesive in Comparative Example 6 and its preparation method are described below, with the following raw material weight ratios:

[0167]

[0168] The preparation method of the above adhesive is as follows:

[0169] 1) First, add 17 parts of water to a reaction vessel equipped with a stirring function. Then, slowly add 3 parts of soy protein to the reaction vessel and mix with the water. Then, stir continuously at 1200 r / min and 25℃ for 25 min to obtain soy protein gel.

[0170] 2) The prepared 0.8 parts of reinforcing agent (functionalized seaweed nanofiber) was slowly added to the above soybean protein solution in 4 portions (1 / 4 of the total amount each time, with an interval of 3 minutes each time). Then, the mixture was stirred at 1000 r / min at 25°C for 20 minutes to obtain the enhanced soybean protein solution.

[0171] 3) The prepared 0.4 parts modifier (CrCl3) was slowly introduced into the above-mentioned enhanced soybean protein solution in two portions (1 / 2 of the total amount each time, with an interval of 5 min each time). Then, the mixture was stirred at 800 r / min at 25℃ for 15 min to obtain the modified soybean protein solution.

[0172] Experimental Example 1

[0173] Three-layer plywood was prepared using the soybean protein adhesives obtained in Examples 1-5 and Comparative Examples 1-6 above. The specific preparation process is as follows:

[0174] Poplar veneer measuring 400mm × 400mm × 1.6mm was used as the plywood substrate. The moisture content of the poplar veneer was controlled at 8%-12%, and it was prepared at 180g / m³. 2 The amount of glue applied is modified soybean protein adhesive applied to one side of the veneer substrate using a glue roller. When assembling the three-layer plywood, the core layer veneer is arranged and assembled perpendicularly with its adjacent upper and lower layer veneers. The hot pressing parameters are set to a pressure of 1 MPa, a temperature of 120°C, and a time of 315 seconds. After continuous hot pressing, the prepared three-layer plywood is taken out from the press.

[0175] Adhesive bonding performance, toughness and water resistance testing:

[0176] According to GB / T 17657-2013, the test methods for physical and chemical properties of wood-based panels and veneer wood-based panels were used to test the dry bond strength, fracture toughness, and wet bond strength of plywood prepared with adhesives. Fracture toughness reflects the toughness of the adhesive, and wet bond strength reflects the water resistance of the adhesive. The test results are shown in [Figure number missing]. Figure 1 , Figure 2 , Figure 4 .

[0177] Adhesive viscosity test:

[0178] The viscosity of the adhesive was measured using a parallel plate fixture with a diameter of 20 mm on an RST-CPS rheometer. During measurement, the distance was set to 1 mm, and the shear rate was set from 1 to 50 rad / s. Viscosity reflects the initial tack of the adhesive. The test results are shown below. Figure 3 .

[0179] Adhesive anti-mildew performance test:

[0180] 15g of uncured adhesive was placed in petri dishes and stored at 30℃ and 80% relative humidity. The mold growth and decomposition of the adhesive samples were observed daily, and the anti-mold effectiveness period was recorded and tallied by day. The test results are shown below. Figure 5 .

[0181] Adhesive antibacterial performance test:

[0182] The antibacterial rate was determined using a colony counting method. The adhesive was first dried to constant weight at 120℃ and ground into a 200-mesh powder. The adhesive powder sample was then dissolved in sterile water to prepare a solution with a concentration of 20 mg / mL. The bacterial strains were activated after incubation at 37℃. The activated bacteria (0.5 × 10⁻⁶) were then... 5 The CFU / mL solution was placed in 5 mL of PBS buffer containing the adhesive solution and incubated at 37°C for 4 h. The resulting bacterial culture was diluted 10-fold, and 40 μL was spread onto Luria-Bertani (LB) agar medium. After incubation at 37°C for 4 h, the colony count was determined. The antibacterial rate of the adhesive was calculated as N2 / N1 and converted to a percentage, where N1 is the number of colonies in the untreated sample and N2 is the number of colonies in the treated sample. The results are shown in […]. Figure 6 .

[0183] Adhesive flame retardant performance test:

[0184] The limiting oxygen index of the adhesive samples was measured using an oxygen index flammability tester (HC-2C) according to GB / T 5454-1997; the maximum heat release rate of the adhesive samples was tested on an FTT cone calorimeter according to ISO 5660-1, with a heat flux of 55 kW / m³. 2 The test results are shown below. Figure 7 and Figure 8 .

[0185] Adhesive antioxidant performance test:

[0186] The antioxidant activity of the adhesive was determined using the azo-bis(ethylbenzothiazole)-6-sulfonate diammonium salt (ABTS) method. The dried adhesive was ground into a 200-mesh powder, and a 50 μg / mL sample solution was prepared using ultrapure water. An ABTS radical solution was obtained by mixing equal volumes of 7.4 mM ABTS and 2.6 mM potassium persulfate. Then, 2 mL of the ABTS radical solution and 2 mL of different sample solutions were mixed thoroughly in a 5 mL container, and the absorbance of the resulting solution was measured at 731 nm. The total antioxidant capacity of the adhesive was determined according to (A0-A...). i The absorbance of the solution after ultrapure water treatment is calculated and converted to a percentage, where A0 is the absorbance of the solution after ultrapure water treatment, and A... i The absorbance of the solutions obtained after different sample treatments is shown in the figure. Figure 9 and Figure 10 .

[0187] from Figure 1It can be seen that the dry bonding strength of the adhesives in Examples 1-5 is significantly improved compared with that of the adhesive in Comparative Example 1. In particular, the dry bonding strength of Example 2 is improved to 2.71 MPa. This is because the functionalized seaweed nanofibers, as a cross-linking framework, form covalent bonds and hydrogen bonds with soybean protein through the phenolic hydroxyl and quinone groups of the gallic acid interface platform, which increases the intermolecular cohesive force and thus improves the dry bonding strength of the adhesive.

[0188] from Figure 1 It can be seen that the dry bonding strength of the adhesives in Examples 1-5 is significantly increased compared with that in Comparative Example 2. This is because, compared with ordinary seaweed nanofibers, gallic acid in functionalized seaweed nanofibers acts as an interface platform, which improves the interfacial interaction between seaweed nanofibers and soybean protein and constructs a more stable cross-linked structure.

[0189] from Figure 1 It can be seen that the dry bonding strength of the adhesives in Examples 1-5 is further improved compared with that of Comparative Example 3. This is because of the introduced Fe. 3+ It forms chelate bonds with functionalized seaweed nanofibers and soybean protein, increasing the cross-linking density of the adhesive.

[0190] from Figure 1 It can be seen that the dry bonding strength of the adhesives in Examples 1-5 is increased compared with that in Comparative Example 4. This is because the gallic acid functionalization platform plays an interfacial crosslinking role and the seaweed nanofibers play a skeletal reinforcement role, giving the adhesive a denser and stronger cured structure.

[0191] from Figure 2 It can be seen that the adhesives in Examples 1-5 exhibit significantly improved fracture toughness compared to the adhesives in Comparative Examples 1-4, especially Example 2, whose fracture toughness increased to 1.42 MJ / m. 3 This is because the functionalized seaweed nanofibers in the adhesive inhibit crack propagation during mechanical strain through various crack damping effects such as crack bridging, crack deflection, and crack locking, thereby increasing the toughness of the adhesive. Fe 3+ Metallic chelate bonds were constructed in the adhesive as sacrificial bonds to dissipate energy, further improving the adhesive's toughness.

[0192] from Figure 3 It can be seen that the adhesives of Examples 1-5 have significantly increased viscosity compared to the adhesives of Comparative Examples 1-4, especially Example 2, whose viscosity increased by 4.1 times. This is because the functionalized seaweed nanofibers and Fe in the adhesives... 3+ Hydrogen bonds and coordination bonds are formed between the adhesive and soy protein. These multiple bonds can improve the adhesive's shear resistance and prevent shear thinning, thereby improving the adhesive's initial tack.

[0193] from Figure 4 It can be seen that the adhesives in Examples 1-5 exhibit significantly improved wet bonding strength compared to the adhesives in Comparative Examples 1-4, reaching the Class II plywood standard (≥0.7 MPa). In particular, the wet bonding strength of Example 2 increased to 1.39 MPa. This is attributed to the functionalized seaweed nanofibers and Fe... 3+ The adhesive forms a stable fiber-reinforced, multi-crosslinked, biomimetic hierarchical structure with soybean protein through covalent bonds, hydrogen bonds, and chelate bonds. This structure acts as a waterproof barrier, inhibiting the intrusion of moisture and thus improving the water resistance of the adhesive.

[0194] from Figure 5 As can be seen, compared with the adhesives in Comparative Examples 1-4, the anti-mold effect of the adhesives in Examples 1-5 is significantly extended, especially that of Example 2, which has increased to more than 63 days. This is because gallic acid in the functionalized seaweed nanofibers has effective anti-mold properties. The phenolic hydroxyl groups of gallic acid, especially the ortho-hydroxyl groups, can adhere to bacterial cells, destroy or deform the bacterial membrane, increase the permeability of the bacterial membrane, and kill the bacteria, thereby improving the anti-mold properties of the adhesive. At the same time, the dense biomimetic layered structure of the adhesives in Examples helps to prevent the penetration and proliferation of moisture and bacteria, thus extending the anti-mold effect.

[0195] from Figure 6 As can be seen, compared with the adhesives of Comparative Examples 1-4, the adhesive samples of Examples 1-5 showed significantly improved antibacterial rates against the two bacteria. In particular, the antibacterial rate of the sample of Example 2 against the two bacteria increased to 97.7% and 98.6%, respectively. This is because the introduced gallic acid has an effective antibacterial effect, and the dense biomimetic hierarchical structure inhibits the invasion of moisture and the proliferation of bacteria, thereby improving the antibacterial properties of the adhesive.

[0196] from Figure 7 and Figure 8 As can be seen, compared with the adhesives of Comparative Examples 1-4, the adhesives of Examples 1-5 showed a significantly higher limiting oxygen index and a significantly lower maximum heat release rate, demonstrating that the flame retardancy of the adhesives was enhanced. In particular, the limiting oxygen index of Example 2 increased to 35.9%, and the maximum heat release rate of Example 2 decreased to 217.2 kW / m³. 2 This is because inorganic Fe 3+ During combustion, soybean protein molecules are induced to dehydrate and carbonize to form a fire-resistant char layer. This char layer acts as a physical barrier, preventing the penetration of external oxygen and delaying the thermal decomposition of the internal combustible matrix, thus inhibiting the continued spread of the flame and improving the flame retardancy of the adhesive. Simultaneously, the gallic acid-functionalized seaweed nanofibers in this embodiment increase the density and cross-linking degree of the adhesive, improving its thermal stability.

[0197] from Figure 9 and Figure 10 As can be seen, compared with the adhesives in Comparative Examples 1-4, the adhesives in Examples 1-5 exhibit significantly enhanced antioxidant properties, a markedly reduced absorbance, and improved overall antioxidant capacity. In particular, the overall antioxidant capacity of Example 2 increased to 95.6%. This is because gallic acid contains abundant phenolic hydroxyl groups, especially the ortho-hydroxyl groups, which can achieve an antioxidant effect through the transfer of hydrogen atoms and single electrons, thereby enhancing the antioxidant properties of the adhesive. Simultaneously, the dense cross-linked structure of the examples also helps to prevent oxygen from damaging the internal structure of the adhesive, further improving its antioxidant properties.

[0198] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A soybean protein binder, characterized in that, The raw material components include: soybean protein, water, nano-reinforcing agent, and modifier; the nano-reinforcing agent is obtained by surface functionalization modification of seaweed nanofibers with gallic acid; the modifier is a metal ion compound; the metal ion compound contains Fe. 3+ Al 3+ and Cr 3+ Compounds of any one or more metal ions.

2. The soybean protein binder according to claim 1, characterized in that, The raw material components include the following parts by weight: 2-7 parts soybean protein, 14-25 parts water, 0.4-1.2 parts nano-reinforcing agent, and 0.2-0.8 parts modifier.

3. The soybean protein binder according to claim 1, characterized in that, The raw material components include the following parts by weight: 2.5-5 parts soybean protein, 16-21 parts water, 0.6-1.0 parts nano-reinforcing agent, and 0.4-0.6 parts modifier.

4. The soybean protein binder according to claim 1, characterized in that, The raw material components include the following parts by weight: 3 parts soybean protein, 17 parts water, 0.6-1.0 parts nano-reinforcing agent, and 0.4-0.6 parts modifier.

5. The soybean protein binder according to claim 1, characterized in that, The soy protein is soy protein isolate; the soy protein has a protein content of 91-98 wt%; and the soy protein has a particle size of 150-350 mesh.

6. The soybean protein binder according to claim 1, characterized in that, The soy protein is one or a combination of several of the following: high-temperature dissolved soy protein isolate, low-temperature dissolved soy protein isolate, and defatted soy protein isolate; the protein content of the soy protein is 93-95 wt%; and the particle size of the soy protein is 220-260 mesh.

7. The soybean protein binder according to claim 1, characterized in that, The nano-reinforcing agent is made from the following raw materials in parts by weight: 285-315 parts water, 3.6-10.4 parts seaweed nanofibers, and 1.8-2.4 parts gallic acid.

8. The soybean protein binder according to claim 1, characterized in that, The nano-reinforcing agent is made from the following raw materials in parts by weight: 290-310 parts water, 3.8-9.2 parts seaweed nanofibers, and 1.9-2.2 parts gallic acid.

9. The soybean protein binder according to claim 1, characterized in that, The nano-reinforcing agent is made from the following raw materials in parts by weight: 300 parts water, 4-8 parts seaweed nanofibers, and 2 parts gallic acid.

10. The soybean protein binder according to any one of claims 6-9, characterized in that, The preparation method of the nano-reinforcing agent includes: mixing seaweed nanofibers with water in proportion to weight to obtain a seaweed nanofiber suspension, adjusting the pH to 7.0-8.5, adding gallic acid and stirring for 5.6-7.8 h, washing with water and drying to obtain the final product.

11. The soybean protein binder according to claim 10, characterized in that, The preparation method of the nano-reinforcing agent includes: adding seaweed nanofibers to water according to the weight parts and mixing evenly to obtain a seaweed nanofiber suspension; adjusting the pH to 7.5-8 using a pH buffer adjuster; adding gallic acid; stirring at 600-1000 r / min at 23-29 ℃ for 6.1-7.3 h; washing with water and drying to obtain the final product.

12. The soybean protein binder according to claim 1, characterized in that, The metal ion compound is FeCl3.

13. A method for preparing the soybean protein binder according to any one of claims 1-12, characterized in that, The soybean protein binder is obtained by blending and stirring soybean protein, water, nano-reinforcing agent and modifier.

14. The preparation method according to claim 13, characterized in that, Soy protein is added to water and stirred for the first time to obtain a soybean protein adhesive; a nano-reinforcing agent is added to the obtained soybean protein adhesive and stirred for the second time to obtain a reinforced soybean protein adhesive; a modifier is added to the obtained reinforced soybean protein adhesive and stirred for the third time to obtain a soybean protein binder.

15. The preparation method according to claim 14, characterized in that, The first stirring is performed at a speed of 900-1900 r / min at 25-35 ℃ for 20-35 min; the second stirring is performed at a speed of 600-1400 r / min at 25-33 ℃ for 15-25 min; and the third stirring is performed at a speed of 500-1200 r / min at 25-30 ℃ for 10-20 min. The nano-reinforcing agent is added to the reaction system in 3-7 batches, with an interval of 1-4 minutes between each batch, and the amount added each time is 1 / batch of the total amount; the modifier is added to the reaction system in 1-3 batches, with an interval of 5-10 minutes between each batch, and the amount added each time is 1 / batch of the total amount.

16. The application of the soybean protein adhesive according to any one of claims 1-12 or the soybean protein adhesive prepared by the method according to any one of claims 13-15 in formaldehyde-free engineered wood panels.

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