Water-resistant lignin-based environment-friendly adhesive and preparation process thereof

Abstract

The invention relates to the technical field of functional material development, in particular to a water-resistant lignin-based environment-friendly adhesive and a preparation process thereof. The water-resistant lignin-based environment-friendly adhesive comprises the following components: 200-300 parts of modified sodium lignin sulfonate; 50 to 80 parts of tannic acid; 100 to 150 parts of an acrylate emulsion; 5 to 10 parts of a silane coupling agent; 2 to 5 parts of nano cellulose crystal; 5 to 10 parts of zinc borate; 3-7 parts of magnesium hydroxide; 1 to 3 parts of ethylene diamine tetraacetic acid; 1 to 2 parts of a polyoxyethylene ether surfactant; 0.5 to 1 part of an organic silicon defoaming agent; 2 to 5 parts of nano cellulose; and 1-3 parts of natural plant extract tea polyphenol. The water-resistant lignin-based environment-friendly adhesive provides excellent water resistance and mechanical strength through optimized combination of various natural and synthetic materials, is suitable for efficient bonding of wood and other materials, and has the advantages of being green and environmentally friendly.

Description

Technical Field

[0001] The present invention relates to the technical field of functional material development, in particular to a water-resistant lignin-based environmentally friendly adhesive and a preparation process thereof. Background Art

[0002] As a new material, water-resistant, environmentally friendly adhesives show broad application prospects in wood processing, furniture manufacturing, architectural decoration, and other fields. In the pursuit of sustainable development, the development of high-performance, environmentally friendly adhesives has become a key technological need. Applications include bonding outdoor timber structures, interior decorative panels, and various composite materials, meeting the demand for environmentally friendly and high-performance materials in modern architecture and home decoration.

[0003] Currently, a targeted solution to this technical need is an environmentally friendly adhesive based on polyvinyl alcohol (PVA). This adhesive combines PVA with various additives to form a composite material with excellent bonding properties and a certain degree of water resistance. Furthermore, by adding appropriate amounts of crosslinkers and functional additives, its water resistance and mechanical strength can be further enhanced to meet the requirements of specific application scenarios.

[0004] Although environmentally friendly adhesives based on polyvinyl alcohol modification have achieved performance improvements to a certain extent, there are still some shortcomings:

[0005] Insufficient water resistance: Although the water resistance of polyvinyl alcohol can be improved by adding cross-linking agents, the adhesive is still prone to water absorption and expansion in a long-term humid environment, resulting in a significant decrease in bonding strength.

[0006] Low mechanical strength: Due to the molecular structure of polyvinyl alcohol, its mechanical strength is relatively low, making it difficult to withstand high stress and shear forces. This limits its use in high-strength applications, such as large timber structures or heavy furniture manufacturing. Low mechanical strength can also cause the adhesive layer to crack or peel during use, affecting the stability and safety of the overall structure.

[0007] Single function: Existing polyvinyl alcohol modified adhesives mainly provide basic bonding functions and lack multifunctional integration capabilities. Summary of the Invention

[0008] In view of the deficiencies in the prior art, the present invention provides a water-resistant lignin-based environmentally friendly adhesive and a preparation process thereof, which solves the problems of the above-mentioned background technology.

[0009] According to a first aspect of the present invention, there is provided a water-resistant lignin-based environmentally friendly adhesive comprising the following components in parts by mass:

[0010] Modified sodium lignin sulfonate: 200-300 parts;

[0011] Tannic acid: 50-80 parts;

[0012] Acrylate emulsion: 100-150 parts;

[0013] Silane coupling agent: 5-10 parts;

[0014] Nanocellulose crystals: 2-5 parts;

[0015] Zinc borate: 5-10 parts;

[0016] Magnesium hydroxide: 3-7 parts;

[0017] Ethylenediaminetetraacetic acid: 1-3 parts;

[0018] Polyoxyethylene ether surfactant: 1-2 parts;

[0019] Silicone defoamer: 0.5-1 part;

[0020] Nanocellulose: 2-5 parts;

[0021] Natural plant extract tea polyphenols: 1 to 3 parts.

[0022] Tannic acid (TA) is used to improve the water resistance and antibacterial properties of adhesives.

[0023] Acrylate Emulsion (AE) is used to enhance the flexibility and weather resistance of adhesives.

[0024] Silane coupling agent (SCA) helps to improve the interfacial bonding strength between adhesives and other materials.

[0025] Nanocrystalline Cellulose (NCC): has high strength and high modulus, and can form a reinforced network structure in adhesives to improve their mechanical properties and heat resistance.

[0026] Zinc borate (ZB): decomposes into boric acid and zinc oxide at high temperatures. These products can inhibit the free radical chain reaction during the combustion process and increase the flame retardancy and fire resistance of the adhesive.

[0027] Magnesium hydroxide (MH) is used to enhance the flame retardant effect of adhesives and provide smoke suppression function.

[0028] Ethylenediaminetetraacetic Acid (EDTA): It can form stable complexes with various metal ions, preventing these ions from interfering with the chemical reactions of the adhesive or affecting its physical properties, thereby ensuring the long-term stability of the adhesive.

[0029] Polyoxyethylene ether surfactants: They reduce interfacial tension, promote uniform mixing of components, and improve the fluidity and coating properties of adhesives.

[0030] Organosilicone Defoamer (OSD) is used to eliminate bubbles generated during the preparation of adhesives to ensure the uniformity of the adhesive.

[0031] Nanocellulose (NC): It has an extremely high aspect ratio and high strength, and can form a three-dimensional network structure in the adhesive, significantly improving its mechanical properties and toughness.

[0032] Natural plant extract Tea Polyphenols (TP): Rich in polyphenol compounds, it has strong antioxidant and antibacterial capabilities, can effectively inhibit the growth of microorganisms, extend the service life of adhesives and improve their stability.

[0033] According to an embodiment of the present invention, the modified sodium lignin sulfonate is sodium lignin sulfonate modified by epichlorohydrin grafting;

[0034] Wherein, the mass ratio of the sodium lignin sulfonate to the epichlorohydrin is 10:1-13:1.

[0035] Modified Sodium Lignosulfonate (MSL): As the main bonding matrix, it provides excellent bonding performance and certain water resistance.

[0036] According to the embodiments of the present invention, epichlorohydrin introduces more hydrophilic and hydrophobic functional groups into the sodium lignin sulfonate molecular chain through a cross-linking reaction, enhancing the intermolecular interactions and the stability of the network structure. This not only improves the initial bonding strength of the adhesive, but also enhances its water resistance and durability in humid environments. Furthermore, the modified sodium lignin sulfonate is more compatible with other components (such as tannic acid and acrylate emulsions), forming a more uniform and stable mixed system, thereby further enhancing the overall mechanical strength and weather resistance.

[0037] According to an embodiment of the present invention, the acrylic ester emulsion is a copolymer emulsion formed by copolymerization of butyl acrylate and methyl methacrylate;

[0038] Wherein, the mass ratio of the butyl acrylate to the methyl methacrylate is 2:1-4:1.

[0039] According to the embodiments of the present invention, the copolymerization of butyl acrylate and methyl methacrylate not only balances the conflicting demands of flexibility and rigidity, but also forms a denser and more stable network structure between the molecular chains, thereby improving the overall strength and durability of the adhesive. Furthermore, the copolymer solution has good film-forming properties and adhesion, and can form a uniform and stable mixed system with other components (such as modified sodium lignin sulfonate and nanocellulose), further enhancing the adhesive's bonding properties and weather resistance.

[0040] According to an embodiment of the present invention, the polyoxyethylene ether surfactant is a polyoxyethylene ether copolymer solution formed by polymerization of polyoxyethylene ether and ethylene oxide;

[0041] Wherein, the mass ratio of the polyoxyethylene ether to the ethylene oxide is 1:2-1:5.

[0042] According to the embodiments of the present invention, the synergistic effect of polyoxyethylene ether and ethylene oxide not only optimizes the fluidity and coating properties of the adhesive, but also improves its wettability and adhesion to the substrate. Furthermore, the resulting stable emulsion structure prevents particle sedimentation and agglomeration, ensuring the consistency of the adhesive during storage and use. Therefore, through the copolymerization of these two components, the polyoxyethylene ether surfactant improves the rheological properties, dispersibility, and adhesion of the adhesive, resulting in excellent overall performance in a variety of application scenarios.

[0043] According to a second aspect of the present invention, a water-resistant lignin-based environmentally friendly adhesive is provided, such as Figure 1 As shown, the following steps are included:

[0044] S1: preparing modified sodium lignin sulfonate solution;

[0045] S2: preparing acrylic emulsion;

[0046] S3: uniformly mixing the modified sodium lignin sulfonate solution, tannic acid and acrylic acid ester emulsion to prepare a base mixed solution;

[0047] S4: uniformly mixing the silane coupling agent and the nanocellulose crystals to prepare a reinforcing agent mixture;

[0048] S5: mixing the enhancer mixture with the base mixture to prepare an intermediate mixture;

[0049] S6: adding the zinc borate, magnesium hydroxide, ethylenediaminetetraacetic acid, polyoxyethylene ether surfactant, silicone defoamer, nanocellulose and natural plant extract tea polyphenols to the intermediate mixture in sequence to obtain a lignin-based environmentally friendly adhesive.

[0050] According to an embodiment of the present invention, the preparation of the modified sodium lignin sulfonate solution comprises:

[0051] The sodium lignin sulfonate is added to a 5% sodium hydroxide solution and stirred at room temperature until dissolved to obtain an alkaline solution;

[0052] The epichlorohydrin is slowly added to the alkaline solution at a stirring speed of 40-80 r / min, and reacted at 60-80° C. for 2-3 hours, and then cooled to room temperature to obtain the modified sodium lignin sulfonate solution.

[0053] According to an embodiment of the present invention, the specific preparation process of the modified sodium lignin sulfonate solution is as follows:

[0054] The sodium lignin sulfonate is added to a 5% sodium hydroxide solution and stirred at room temperature until dissolved to obtain an alkaline solution;

[0055] During the addition of epichlorohydrin to the alkaline solution, ensure that the reaction system temperature remains between 40-80°C. Control the temperature by heating in a water bath or oil bath, ensuring that the temperature fluctuation does not exceed ±2°C. At the same time, continuously monitor the pH value and maintain it within the range of 10-12 by slightly adjusting the sodium hydroxide solution.

[0056] React at 60-80°C for 2-3 hours.

[0057] After the reaction is completed, the reaction system is cooled naturally to room temperature (20-25° C.), and stirring is maintained during the cooling process to prevent local overcooling from causing precipitation.

[0058] The cooled modified sodium lignin sulfonate solution can be vacuum filtered or centrifuged to remove insoluble matter. Subsequently, the filter cake is washed multiple times with deionized water to remove residual sodium hydroxide and other impurities.

[0059] According to an embodiment of the present invention, the step of uniformly mixing the modified sodium lignin sulfonate solution, tannic acid, and acrylic ester emulsion to prepare a basic mixed solution comprises:

[0060] heating the modified sodium lignin sulfonate solution to 60-80° C., then adding the tannic acid to the heated modified sodium lignin sulfonate solution, and stirring at a speed of 50-70 r / min for 5-10 minutes to obtain an initial mixed solution;

[0061] The acrylic ester emulsion is added to the initial mixed solution, stirred for 20-30 minutes, and then ultrasonically treated for 10 minutes to obtain the basic mixed solution.

[0062] According to embodiments of the present invention, after adding the acrylic emulsion to the initial mixed solution, continued stirring and ultrasonic treatment ensures uniform dispersion of the components. The polymer chains in the acrylic emulsion form a complex crosslinked network with the modified sodium lignin sulfonate and tannic acid, enhancing the adhesive's flexibility and weather resistance. Ultrasonic treatment further refines the particle size in the base mixture, enhancing the uniformity and stability of the system.

[0063] According to an embodiment of the present invention, the step of uniformly mixing the silane coupling agent and the nanocellulose crystals to prepare a reinforcing agent mixture comprises:

[0064] At room temperature, the nanocellulose crystals are added to the silane coupling agent, and stirred at a rotation speed of 40-80 r / min for 10-20 minutes to obtain the reinforcing agent mixed solution.

[0065] According to the embodiments of the present invention, nanocellulose crystals form a three-dimensional network structure in the adhesive, significantly improving the mechanical strength and toughness of the adhesive. Gradual addition and uniform mixing ensure uniform dispersion of the components, avoiding performance degradation caused by localized concentration unevenness.

[0066] According to an embodiment of the present invention, the mixing of the enhancer mixed solution with the base mixed solution to prepare the intermediate mixture comprises:

[0067] The enhancer mixed solution is slowly added to the basic mixed solution, stirred at a speed of 40-80 r / min for 10-20 minutes under room temperature, and then ultrasonically treated for 5 minutes to obtain the intermediate mixture.

[0068] According to an embodiment of the present invention, after the reinforcing agent mixture is mixed with the base mixture, the silane coupling agent tightly combines the nanocellulose crystals with the organic polymer in the base mixture through chemical bonding, significantly enhancing the interfacial bonding force and improving the bonding strength and durability of the adhesive.

[0069] According to an embodiment of the present invention, the zinc borate, magnesium hydroxide, ethylenediaminetetraacetic acid, polyoxyethylene ether surfactant, silicone defoamer, nanocellulose and natural plant extract tea polyphenols are sequentially added to the intermediate mixture to obtain a lignin-based environmentally friendly adhesive, comprising:

[0070] Adding the zinc borate and the magnesium hydroxide to the intermediate mixture, stirring at a speed of 40-80 r / min for 10 minutes to obtain a first mixture;

[0071] Adding the ethylenediaminetetraacetic acid, polyoxyethylene ether surfactant and silicone defoamer successively to the first mixture and continuing stirring for 5 minutes to obtain a second mixture;

[0072] Slowly adding the nanocellulose to the second mixture, stirring for 10 minutes, and then ultrasonically treating for 10 minutes to obtain a third mixture in which the nanocellulose is uniformly dispersed;

[0073] The natural plant extract tea polyphenols is added to the third mixture, and the mixture is stirred in a magnetic stirrer at a speed of 40-80 r / min for 30-60 minutes to obtain the lignin-based environmentally friendly adhesive.

[0074] According to embodiments of the present invention, the lignin-based environmentally friendly adhesive exhibits excellent water resistance, mechanical strength, and environmental friendliness. Polyoxyethylene ether surfactants optimize rheological properties and dispersibility, while silicone defoamers eliminate bubbles and ensure uniformity. Nanocellulose enhances mechanical strength and toughness, while tea polyphenols provide antioxidant and antibacterial properties. This adhesive not only performs well in a variety of environments but also exhibits good biodegradability and low toxicity, making it suitable for applications in wood processing, furniture manufacturing, architectural decoration, and other fields.

[0075] The present invention has the following beneficial effects:

[0076] The present invention significantly enhances its water resistance and mechanical strength through the synergistic effect of multiple ingredients. Modified sodium lignin sulfonate, as the primary bonding matrix, not only provides excellent initial bonding strength but also maintains good stability in humid environments. The addition of tannic acid further enhances the adhesive's water resistance and antibacterial properties, enabling it to perform well in high-humidity or outdoor applications. The introduction of nanocellulose crystals and nanocellulose forms a reinforced network structure, significantly improving the adhesive's overall mechanical properties and toughness.

[0077] The present invention significantly enhances its flame retardancy and smoke suppression properties by adding zinc borate and magnesium hydroxide. Zinc borate decomposes at high temperatures to produce boric acid and zinc oxide, effectively inhibiting the free radical chain reaction during combustion, thereby improving the fire resistance of the adhesive. Magnesium hydroxide further enhances the flame retardancy and provides smoke suppression, ensuring safety during use under extreme conditions. This dual flame retardancy makes the adhesive suitable for applications requiring high fire protection.

[0078] This invention utilizes a variety of natural and renewable resources as key ingredients, such as modified sodium lignin sulfonate, tannic acid, and tea polyphenols, a natural plant extract. These ingredients not only reduce environmental impact but also impart excellent biodegradability to the adhesive. The addition of EDTA ensures effective chelation of metal ions, preventing interference with adhesive properties and further enhancing its long-term stability. Overall, this adhesive adheres to the principles of green chemistry and is suitable for projects with high environmental requirements.

[0079] Due to its comprehensive performance advantages, the present invention is widely applicable to a variety of fields such as wood processing, furniture manufacturing, and architectural decoration. Its excellent bonding properties, weather resistance, and multifunctional characteristics make it an ideal choice for high-performance, environmentally friendly materials. Whether used indoors or outdoors, it can demonstrate excellent performance. In addition, the antioxidant and antibacterial properties provided by tea polyphenols extend the service life of the adhesive and improve its stability, further broadening its scope of application. This versatility enables the adhesive to play an important role in a variety of complex application scenarios.

[0080] Of course, any product implementing the present invention does not necessarily need to achieve all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0081] Figure 1 Flow chart of the preparation method of an embodiment of the present invention. DETAILED DESCRIPTION

[0082] The embodiments of the present application provide a water-resistant lignin-based environmentally friendly adhesive through the present invention.

[0083] Example 1: Standard formula water-resistant lignin-based environmentally friendly adhesive

[0084] Modified sodium lignin sulfonate: 250 parts;

[0085] Tannic acid: 65 parts;

[0086] Acrylate emulsion: 125 parts;

[0087] Silane coupling agent: 7.5 parts;

[0088] Nanocellulose crystals: 3.5 parts;

[0089] Zinc borate: 7.5 parts;

[0090] Magnesium hydroxide: 5 parts;

[0091] Ethylenediaminetetraacetic acid: 2 parts;

[0092] Polyoxyethylene ether surfactant: 1.5 parts;

[0093] Silicone defoamer: 0.75 parts;

[0094] Nanocellulose: 3.5 parts;

[0095] Natural plant extract tea polyphenols: 2 parts.

[0096] Example 2: Increasing the content of modified sodium lignin sulfonate Modified sodium lignin sulfonate: 300 parts;

[0097] Tannic acid: 60 parts;

[0098] Acrylate emulsion: 125 parts;

[0099] Silane coupling agent: 7.5 parts;

[0100] Nanocellulose crystals: 3.5 parts;

[0101] Zinc borate: 7.5 parts;

[0102] Magnesium hydroxide: 5 parts;

[0103] Ethylenediaminetetraacetic acid: 2 parts;

[0104] Polyoxyethylene ether surfactant: 1.5 parts;

[0105] Silicone defoamer: 0.75 parts;

[0106] Nanocellulose: 3.5 parts;

[0107] Natural plant extract tea polyphenols: 2 parts.

[0108] Example 3: Reducing Tannic Acid Content

[0109] Modified sodium lignin sulfonate: 250 parts;

[0110] Tannic acid: 50 parts;

[0111] Acrylate emulsion: 125 parts;

[0112] Silane coupling agent: 7.5 parts;

[0113] Nanocellulose crystals: 3.5 parts;

[0114] Zinc borate: 7.5 parts;

[0115] Magnesium hydroxide: 5 parts;

[0116] Ethylenediaminetetraacetic acid: 2 parts;

[0117] Polyoxyethylene ether surfactant: 1.5 parts; silicone defoamer: 0.75 parts;

[0118] Nanocellulose: 3.5 parts;

[0119] Natural plant extract tea polyphenols: 2 parts. Example 4: Modified sodium lignin sulfonate to enhance water resistance and flame retardancy: 270 parts;

[0120] Tannic acid: 80 parts;

[0121] Acrylate emulsion: 125 parts;

[0122] Silane coupling agent: 7.5 parts;

[0123] Nanocellulose crystals: 3.5 parts;

[0124] Zinc borate: 10 parts;

[0125] Magnesium hydroxide: 7 parts;

[0126] Ethylenediaminetetraacetic acid: 2 parts;

[0127] Polyoxyethylene ether surfactant: 1.5 parts; silicone defoamer: 0.75 parts;

[0128] Nanocellulose: 3.5 parts;

[0129] Natural plant extract tea polyphenols: 2 parts.

[0130] Example 5: Optimizing mechanical strength

[0131] Modified sodium lignin sulfonate: 250 parts;

[0132] Tannic acid: 65 parts;

[0133] Acrylate emulsion: 125 parts;

[0134] Silane coupling agent: 10 parts;

[0135] Nanocellulose crystals: 5 parts;

[0136] Zinc borate: 7.5 parts;

[0137] Magnesium hydroxide: 5 parts;

[0138] Ethylenediaminetetraacetic acid: 2 parts;

[0139] Polyoxyethylene ether surfactant: 1.5 parts; silicone defoamer: 0.75 parts;

[0140] Nanocellulose: 5 parts;

[0141] Natural plant extract tea polyphenols: 2 parts.

[0142] Example 6: Enhanced antibacterial properties

[0143] Modified sodium lignin sulfonate: 250 parts;

[0144] Tannic acid: 80 parts;

[0145] Acrylate emulsion: 125 parts;

[0146] Silane coupling agent: 7.5 parts;

[0147] Nanocellulose crystals: 3.5 parts;

[0148] Zinc borate: 7.5 parts;

[0149] Magnesium hydroxide: 5 parts;

[0150] Ethylenediaminetetraacetic acid: 2 parts;

[0151] Polyoxyethylene ether surfactant: 1.5 parts; silicone defoamer: 0.75 parts;

[0152] Nanocellulose: 3.5 parts;

[0153] Natural plant extract tea polyphenols: 3 parts.

[0154] Comparative Example 1: 250 parts of sodium lignin sulfonate modified without tannic acid;

[0155] Acrylate emulsion: 125 parts;

[0156] Silane coupling agent: 7.5 parts;

[0157] Nanocellulose crystals: 3.5 parts;

[0158] Zinc borate: 7.5 parts;

[0159] Magnesium hydroxide: 5 parts;

[0160] Ethylenediaminetetraacetic acid: 2 parts;

[0161] Polyoxyethylene ether surfactant: 1.5 parts; silicone defoamer: 0.75 parts;

[0162] Nanocellulose: 3.5 parts;

[0163] Natural plant extract tea polyphenols: 2 parts.

[0164] Comparative Example 2: Sodium lignin sulfonate modified without silane coupling agent: 250 parts;

[0165] Tannic acid: 65 parts;

[0166] Acrylate emulsion: 125 parts;

[0167] Nanocellulose crystals: 3.5 parts;

[0168] Zinc borate: 7.5 parts;

[0169] Magnesium hydroxide: 5 parts;

[0170] Ethylenediaminetetraacetic acid: 2 parts;

[0171] Polyoxyethylene ether surfactant: 1.5 parts; silicone defoamer: 0.75 parts;

[0172] Nanocellulose: 3.5 parts;

[0173] Natural plant extract tea polyphenols: 2 parts.

[0174] Comparative Example 3: Sodium lignin sulfonate modified without nanocellulose crystals: 250 parts;

[0175] Tannic acid: 65 parts;

[0176] Acrylate emulsion: 125 parts;

[0177] Silane coupling agent: 7.5 parts;

[0178] Zinc borate: 7.5 parts;

[0179] Magnesium hydroxide: 5 parts;

[0180] Ethylenediaminetetraacetic acid: 2 parts;

[0181] Polyoxyethylene ether surfactant: 1.5 parts;

[0182] Silicone defoamer: 0.75 parts;

[0183] Nanocellulose: 3.5 parts;

[0184] Natural plant extract tea polyphenols: 2 parts.

[0185] Comparative Example 4: No polyoxyethylene ether surfactant

[0186] Modified sodium lignin sulfonate: 250 parts;

[0187] Tannic acid: 65 parts;

[0188] Acrylate emulsion: 125 parts;

[0189] Silane coupling agent: 7.5 parts;

[0190] Nanocellulose crystals: 3.5 parts;

[0191] Zinc borate: 7.5 parts;

[0192] Magnesium hydroxide: 5 parts;

[0193] Ethylenediaminetetraacetic acid: 2 parts;

[0194] Silicone defoamer: 0.75 parts;

[0195] Nanocellulose: 3.5 parts;

[0196] Natural plant extract tea polyphenols: 2 parts.

[0197] Experimental example:

[0198] The performance of the above examples 1-6 and comparative examples 1-4 was measured, and the results are shown in Table 1.

[0199] 1. Water resistance test

[0200] According to GB / T 17657-2013 standard, the plywood samples (double-sided glue amount 300g / m 2 ) were boiled in 100°C boiling water for 4 hours, dried and boiled again for 4 hours, and the tensile shear strength was tested (overlap area 25 mm × 25 mm).

[0201] 2. Flame retardant performance test

[0202] An oxygen index tester (ASTM D2863 standard) is used to measure the oxygen index (LOI) of the adhesive after curing, which reflects the minimum oxygen concentration required for the material to burn in air.

[0203] 3. Mechanical properties test

[0204] The elongation at break (%) of the adhesive cured specimens was measured using a universal material testing machine (testing speed 5 mm / min).

[0205] 4. Antibacterial performance test

[0206] Using Escherichia coli (E. coli) as the test strain, the adhesive was immersed in an agar plate containing a bacterial suspension, and the diameter (mm) of the inhibition zone was measured after 24 hours of incubation.

[0207] 5. Bond strength test

[0208] According to GB / T 14074-2006 standard, the tensile shear strength (MPa) of the adhesive on wood is tested, and the glue application amount is 300g / m2 on both sides. 2 .

[0209] 6. Environmental performance test (formaldehyde emission)

[0210] According to GB / T 17657, the formaldehyde emission of adhesive was determined by climate chamber method (mg / m 3 ).

[0211] Table 1. Experimental data of Examples 1-6 and Comparative Examples 1-4 of the present invention

[0212]

[0213] As shown in Table 1, water resistance:

[0214] The enhanced water resistance and flame retardancy (Example 4) showed the best performance (2.1 MPa), which was attributed to the synergistic effect of zinc borate and magnesium hydroxide.

[0215] The water resistance of the sample without tannic acid (Comparative Example 1) dropped significantly to 1.2 MPa, indicating that tannic acid is crucial to water resistance.

[0216] Flame retardant properties:

[0217] The oxygen index of Example 4 reaches 32%, which is much higher than that of other examples, verifying the synergistic effect of the flame retardant filler.

[0218] The oxygen indexes of Comparative Examples 1-4 are all lower than 29%, indicating that the key components (such as tannic acid and silane coupling agent) have an auxiliary effect on flame retardancy.

[0219] Mechanical properties:

[0220] The elongation at break of the optimized mechanical strength (Example 5) is 20%, which is significantly better than the other formulations, and is attributed to the strengthening effect of the nanocellulose crystals and the silane coupling agent.

[0221] The elongation at break of the sample without nanocellulose crystals (Comparative Example 3) was only 11%, and the mechanical properties were obviously insufficient.

[0222] Antimicrobial properties:

[0223] Enhanced antibacterial performance (Example 6) The diameter of the inhibition zone reached 18 mm, which was much higher than that of other examples, which was attributed to the antibacterial synergistic effect of tea polyphenols.

[0224] The diameter of the inhibition zone without tannic acid (Comparative Example 1) is only 7 mm, indicating that the synergistic antibacterial effect of tannic acid and tea polyphenols is irreplaceable.

[0225] Bond strength:

[0226] The bonding strength of Example 4 reached 2.8 MPa, verifying the positive effects of improved flame retardancy and water resistance on bonding strength.

[0227] Environmental performance:

[0228] The formaldehyde emission of all examples was less than 0.04 mg / m 3 , in line with environmental protection standards, among which Examples 3 and 6 performed best (0.01 mg / m 3 ).

[0229] Without polyoxyethylene ether surfactant (Comparative Example 4), the formaldehyde emission increased to 0.04 mg / m 3 , indicating that surfactants have an auxiliary effect on environmental performance.

[0230] Based on the above-mentioned integrated experimental data, lignin-based environmentally friendly adhesives, with their sustainability, high water and heat resistance, high bond strength, and high bacterial resistance, are poised to become core products in the green building materials sector, driving the industry's transformation and upgrading towards low-carbon, environmentally friendly, and high-value-added development. These adhesives are primarily suitable for use in construction, furniture manufacturing, and wood processing, with particular strength in bonding wood materials such as plywood, fiberboard, and particleboard. They can also be expanded into emerging areas such as packaging materials and new energy materials.

[0231] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0232] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A water-resistant lignin-based environmentally friendly adhesive, characterized in that: The composition is as follows in parts by mass: Modified sodium lignin sulfonate: 200-300 parts; Tannic acid: 50-80 parts; Acrylate emulsion: 100-150 parts; Silane coupling agent: 5-10 parts; Nanocellulose crystals: 2-5 parts; Zinc borate: 5-10 parts; Magnesium hydroxide: 3-7 parts; Ethylenediaminetetraacetic acid: 1-3 parts; Polyoxyethylene ether surfactant: 1-2 parts; Silicone defoamer: 0.5-1 part; Nanocellulose: 2-5 parts; Natural plant extract tea polyphenols: 1 to 3 parts.

2. The lignin-based environmentally friendly adhesive according to claim 1, characterized in that: The modified sodium lignin sulfonate is sodium lignin sulfonate modified by epichlorohydrin grafting; Wherein, the mass ratio of the sodium lignin sulfonate to the epichlorohydrin is 10:1-13:

1.

3. The lignin-based environmentally friendly adhesive according to claim 1, characterized in that: The acrylic ester emulsion is a copolymer emulsion formed by copolymerization of butyl acrylate and methyl methacrylate; Wherein, the mass ratio of the butyl acrylate to the methyl methacrylate is 2:1-4:

1.

4. The lignin-based environmentally friendly adhesive according to claim 1, characterized in that: The polyoxyethylene ether surfactant is a polyoxyethylene ether copolymer solution formed by polymerization of polyoxyethylene ether and ethylene oxide; Wherein, the mass ratio of the polyoxyethylene ether to the ethylene oxide is 1:2-1:

5.

5. A method for preparing the lignin-based environmentally friendly adhesive according to any one of claims 1 to 4, characterized in that: The steps include: preparing a modified sodium lignin sulfonate solution; preparing an acrylic emulsion; uniformly mixing the modified sodium lignin sulfonate solution, tannic acid and acrylic ester emulsion to prepare a base mixed solution; uniformly mixing the silane coupling agent and the nanocellulose crystals to prepare a reinforcing agent mixed solution; mixing the enhancer mixture with the base mixture to prepare an intermediate mixture; The zinc borate, magnesium hydroxide, ethylenediaminetetraacetic acid, polyoxyethylene ether surfactant, silicone defoamer, nanocellulose and natural plant extract tea polyphenols are sequentially added to the intermediate mixture to obtain a lignin-based environmentally friendly adhesive.

6. The preparation method according to claim 5, characterized in that: The preparation of the modified sodium lignin sulfonate solution comprises: The sodium lignin sulfonate is added to a 5% sodium hydroxide solution and stirred at room temperature until dissolved to obtain an alkaline solution; The epichlorohydrin is slowly added to the alkaline solution at a stirring speed of 40-80 r / min, and reacted at 60-80° C. for 2-3 hours, and then cooled to room temperature to obtain the modified sodium lignin sulfonate solution.

7. The preparation method according to claim 5, characterized in that: The step of uniformly mixing the modified sodium lignin sulfonate solution, tannic acid and acrylic ester emulsion to prepare a basic mixed solution comprises: heating the modified sodium lignin sulfonate solution to 60-80° C., then adding the tannic acid to the heated modified sodium lignin sulfonate solution, and stirring at a speed of 50-70 r / min for 5-10 minutes to obtain an initial mixed solution; The acrylic ester emulsion is added to the initial mixed solution, stirred for 20-30 minutes, and then ultrasonically treated for 10 minutes to obtain the basic mixed solution.

8. The preparation method according to claim 5, characterized in that: The step of uniformly mixing the silane coupling agent and the nanocellulose crystals to prepare a reinforcing agent mixed solution comprises: At room temperature, the nanocellulose crystals are added to the silane coupling agent, and stirred at a rotation speed of 40-80 r / min for 10-20 minutes to obtain the reinforcing agent mixed solution.

9. The preparation method according to claim 5, characterized in that: The step of mixing the enhancer mixed solution with the base mixed solution to prepare the intermediate mixture comprises: The enhancer mixed solution is slowly added to the basic mixed solution, stirred at a speed of 40-80 r / min for 10-20 minutes under room temperature, and then ultrasonically treated for 5 minutes to obtain the intermediate mixture.

10. The preparation method according to claim 5, characterized in that The zinc borate, magnesium hydroxide, ethylenediaminetetraacetic acid, polyoxyethylene ether surfactant, silicone defoamer, nanocellulose and natural plant extract tea polyphenols are sequentially added to the intermediate mixture to obtain a lignin-based environmentally friendly adhesive, comprising: Adding the zinc borate and the magnesium hydroxide to the intermediate mixture, stirring at a speed of 40-80 r / min for 10 minutes to obtain a first mixture; Adding the ethylenediaminetetraacetic acid, polyoxyethylene ether surfactant and silicone defoamer successively to the first mixture and continuing stirring for 5 minutes to obtain a second mixture; Slowly adding the nanocellulose to the second mixture, stirring for 10 minutes, and then ultrasonically treating for 10 minutes to obtain a third mixture in which the nanocellulose is uniformly dispersed; The natural plant extract tea polyphenols is added to the third mixture, and the mixture is stirred in a magnetic stirrer at a speed of 40-80 r / min for 30-60 minutes to obtain the lignin-based environmentally friendly adhesive.

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