Modified aminated lignin cured epoxidized soybean oil adhesive as well as preparation method and application thereof

Abstract

The invention provides a modified aminated lignin cured epoxidized soybean oil adhesive as well as a preparation method and application thereof, and belongs to the technical field of adhesives. The adhesive comprises a water-in-oil type stable system formed by compounding a component A, a component B and a component C, the component A is aminated lignin obtained through plasma activation and chemical grafting modification, the component B is epoxidized soybean oil, and the component C is a nonionic emulsifier; the composition comprises the following components in parts by weight: 25-35 parts of a component A, 65-75 parts of a component B and 1-2 parts of a component C, according to the invention, a ternary co-curing system is constructed. The obtained adhesive has the characteristics of full biomass, zero formaldehyde, high bonding strength and the like, and the preparation process is clean, low in cost and suitable for large-scale industrial production.

Description

Technical Field

[0001] This invention relates to the field of adhesive technology, specifically to a modified amino-modified lignin-cured epoxy soybean oil adhesive, its preparation method, and its application. Background Technology

[0002] Wood adhesives are a core technology in the engineered wood products industry, and their performance directly determines the mechanical strength, weather resistance, and environmental performance of products such as plywood, particleboard, and fiberboard. For a long time, the engineered wood products industry has heavily relied on formaldehyde-based resins (FBR). Although FBR resins have significant advantages such as low cost, fast curing speed, and abundant active functional groups, they inevitably release free formaldehyde during production and use, posing a significant threat to human health. With the World Health Organization classifying formaldehyde as a Group 1 carcinogen and increasingly stringent standards for formaldehyde release from engineered wood products, the development of "all-biomass, zero-formaldehyde, high-performance" environmentally friendly adhesives has become a global strategic issue.

[0003] In the process of biomass substitution, epoxidized soybean oil has attracted much attention due to its renewability and has been widely used in the field of plasticizers, which has laid the raw material foundation for its application in the field of adhesives. However, the epoxy groups of ESO are located inside the long carbon chain, and due to the steric hindrance effect of the triglyceride skeleton, its curing reaction is extremely slow, requiring several hours to form a film under normal conditions. Conventional small molecule amine or acid anhydride curing agents usually require several hours or even tens of hours at 100-200 °C to form a film, which cannot meet the requirements of the wood industry for curing within minutes.

[0004] Lignin, an abundant aromatic polymer, is mainly derived from byproducts of papermaking and biorefining. Traditional alkali lignin, due to its complex three-dimensional network structure, strong intermolecular hydrogen bonds, and the constraint of β-O-4 ether bonds, has most of its chemically active sites (such as phenolic hydroxyl groups and C5 active sites) in a hidden state. This invention aims to break the lignin constraint and introduce high-density amino groups through the synergistic effect of plasma physical activation and Mannich chemical grafting, constructing a highly efficient amino-modified lignin curing system to achieve rapid industrial-scale curing of epoxidized soybean oil.

[0005] Plasma, rich in high-energy electrons, ions, free radicals, and excited-state molecules, can efficiently induce bond breaking and group generation on polymer surfaces without altering the chemical composition. This invention fully utilizes the bond-breaking and oxygen-containing group generation capabilities of plasma to achieve the active release of the C5 site of alkaline lignin and the introduction of active groups into the adhesive substrate. Summary of the Invention

[0006] The purpose of this invention is to overcome the technical problems of low curing efficiency of epoxidized soybean oil, poor lignin reactivity, and insufficient water resistance of biomass adhesives. It provides an amino-based lignin-cured epoxidized soybean oil wood adhesive prepared through the synergistic effect of a physical field (plasma) and a chemical reaction field (Mannich grafting).

[0007] This invention is based on the following scientific logic: First, low molecular weight lignin with the highest reactivity is screened through solvent fractionation, and its β-O-4 ether bonds are broken by the high-energy impact of dielectric barrier discharge plasma, thereby significantly increasing the phenolic hydroxyl content and activating the C5 active site. Second, a high-density polyamine functional group is introduced into the lignin skeleton through the Mannich reaction using an imine intermediate pre-prepared from glyoxal and diethylenetriamine. This aminated lignin, as a macromolecular crosslinking agent, has a high density of nucleophilic groups (-NH2 and -NH-) that can effectively overcome the steric hindrance of the epoxy groups inside ESO, inducing ring-opening polymerization to generate β-amino alcohol structures, thereby achieving rapid crosslinking and curing of the adhesive. This is combined with the interfacial activation of the wood surface by sliding arc discharge plasma. The reactive oxygen species generated by GAD can attack the chemical components on the surface of the wood veneer, causing lignin oxidation and exposing more cellulose oxygen-containing groups, forming activated wood surface (AWS). AWS interface functional groups and AL jointly participate in the open-loop reaction of ESO, building an integrated "ESO-AL-AWS" co-curing network, which significantly improves the adhesive's peel resistance and wet strength. Figure 1 The reaction formula summarizes the reaction mechanism. Figure 2 and 3 Infrared spectral characterization of the sample confirmed the reaction mechanism.

[0008] The technical solution of this invention is implemented as follows: This invention provides a modified amino-modified lignin-cured epoxidized soybean oil adhesive, the adhesive comprising a water-in-oil stable system composed of component A, component B and component C, wherein component A is amino-modified lignin obtained by plasma activation and chemical grafting modification, component B is epoxidized soybean oil, and component C is a nonionic emulsifier; the component ratio by weight is: component A 25-35 parts, component B 65-75 parts, and component C 1-2 parts.

[0009] As a further improvement of the present invention, the amine value of component A, the amino-modified lignin, is 200-500 mg. KOH / g Between them, in its molecular skeleton, an amino functional group branch chain formed by the condensation of diethylenetriamine and glyoxal is grafted at the C5 position of the lignin benzene ring; the epoxy value of component B, epoxidized soybean oil, is ≥6.0; component C is at least one of Tween-20, Tween-40, Tween-60, Tween-80, and Tween-85, preferably Tween-80 and / or Tween-85.

[0010] This invention further protects a method for preparing the above-mentioned modified amino-modified lignin-cured epoxy soybean oil adhesive, comprising the following steps: (1) Lignin screening: Alkali lignin was added to anhydrous acetone, stirred and extracted, the acetone-soluble part was collected and vacuum rotary evaporated to obtain a low molecular weight lignin component solid powder. (2) Physical activation by dielectric barrier discharge: The tray obtained in step (1) is treated with dielectric barrier discharge plasma in an air atmosphere; (3) Preparation of imine intermediate: Under the condition of 0-5℃, glyoxal aqueous solution is added dropwise to diethylenetriamine. After the addition is completed, the mixture is stirred continuously to obtain a stable Schiff base imine intermediate solution. (4) Mannich high-temperature grafting: Dissolve the lignin powder activated in step (2) in an alkaline aqueous solution, adjust the pH, add the intermediate solution obtained in step (3), first contact and stir at room temperature, and then heat and reflux reaction. (5) Product purification and adhesive compounding: After the reaction solution is cooled, the pH is adjusted to allow the aminated lignin to precipitate completely. After centrifugation, washing and drying, aminated lignin powder is obtained. The obtained dry powder is sheared and emulsified with component B and component C in proportion to obtain modified aminated lignin-cured epoxidized soybean oil adhesive.

[0011] This invention employs a combined physical and chemical approach. First, low-molecular-weight lignin components are obtained through solvent fractionation screening. Then, dielectric barrier discharge plasma is used to break the β-O-4 ether bonds of the lignin molecules and activate the C5 position. Combined with a Schiff base reaction-prepared imine intermediate, Mannich grafting is performed to prepare a high-amine-value aminated lignin. This aminated lignin is used as a curing agent in combination with epoxidized soybean oil. During the sizing stage, sliding arc discharge plasma is used to activate the interface of the wood veneer to increase adhesive strength. This invention constructs an "ESO-AL-Activated Wood Surface (AWS)" ternary co-curing system. The resulting adhesive is characterized by being entirely biomass-based, formaldehyde-free, and possessing high bonding strength. Furthermore, the preparation process is clean and low-cost, making it suitable for large-scale industrial production.

[0012] As a further improvement of the present invention, in step (1), the alkali lignin is G-type lignin, and the solid-liquid mass ratio of alkali lignin and anhydrous acetone is 1:5-15; in step (3), the mass fraction of glyoxal solution is 30-50%; and the molar ratio of glyoxal to diethylenetriamine is 0.5-1.5:0.5-1.5.

[0013] As a further improvement of the present invention, in step (2), the discharge power of the dielectric barrier discharge plasma treatment is 1500-2500W, the treatment time is 5-10min, and the thickness of the powder after spreading is controlled to be ≤1.0mm; in step (4), the pH is adjusted to 10.5-11.5, the room temperature stirring time is 30-90min, the heating reflux reaction temperature is 85-90℃, the time is 4-6h, and the molar ratio of lignin to imine intermediate is 1:1-1.5.

[0014] As a further improvement of the present invention, in step (5), the pH is adjusted to 5.0-5.5, and the high-speed shear emulsification speed is 8000-12000 rpm for 20-40 min.

[0015] This invention further protects the application of the above-mentioned modified amino-modified lignin-cured epoxy soybean oil adhesive in the bonding of boards.

[0016] As a further improvement to the present invention, the following steps are included: S1. Activation treatment of board interface: The surface of the wood veneer to be glued is activated by sliding arc discharge plasma; S2. Adhesive application process: Apply the modified aminated lignin-cured epoxy soybean oil adhesive as described in claim 1 or 2 evenly to the surface of the activated veneer; S3. Hot pressing: The assembled veneer is placed into a hot press for hot pressing.

[0017] As a further improvement of the present invention, in step S1, the power of the activation treatment is set to 1500-2500W, the distance between the nozzle and the single board is 2-3 cm, and the treatment time is 30-60 s; in step S2, the amount of adhesive applied is 150-200 g / m² per side. 2 The sizing process must be completed within 30 minutes after surface activation; in step S3, the hot-pressing temperature is 140-180℃, the pressure is 0.8-1.2MPa, and the hot-pressing time is 5-15 minutes. The sliding arc discharge plasma (GAD) treatment aims to break the chemical bonds of the lignin components on the veneer surface, increasing oxygen-containing active groups such as -OH and -COOH, enabling them to participate in the ring-opening curing reaction of epoxidized soybean oil and form interfacial chemical bonds.

[0018] As a further improvement of the present invention, the board material is a man-made board.

[0019] The present invention has the following beneficial effects: 1. High curing efficiency: Through physical and chemical synergistic methods, lignin is converted into a high amine value curing agent, successfully enabling ESO, a traditionally difficult-to-cure oil, to reach industrial-grade bonding strength within 5-10 minutes.

[0020] 2. Environmentally friendly throughout the entire life cycle: It completely achieves zero formaldehyde and biomass substitution. The raw material sources are not only low-cost, but also in line with the "carbon neutral" forestry development goal.

[0021] 3. Interface strength transition: The interfacial chemical bonding formed by GAD treatment increases the curing efficiency of ESO and effectively improves the bonding force between the adhesive layer and the substrate, greatly enhancing the moisture resistance of the board.

[0022] 4. Strong industrial compatibility: Plasma technology can be seamlessly integrated with existing automatic sizing production lines, and the absence of a special atmosphere effectively controls production costs. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 The reaction equations for plasma-co-modified aminated lignin-cured epoxidized soybean oil adhesive are as follows: a. Synthesis of imine intermediates. b. Preparation of aminated lignin. c. ESO-AL-AWS co-curing reaction.

[0025] Figure 2 This is the FT-IR image of amino-modified lignin.

[0026] Figure 3 The image shows the FT-IR spectrum of the ESO-AL cured product. Detailed Implementation

[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Example 1 The present invention discloses a plasma-synergistic modified aminated lignin-cured epoxidized soybean oil adhesive, wherein the adhesive comprises component A, component B (epoxidized soybean oil), and component C (Tween-80), and is made of three-layer plywood using poplar veneer with a thickness of 2 mm.

[0029] The preparation method of the plasma-synergistic modified aminated lignin-cured epoxy soybean oil adhesive of the present invention includes the following steps: (1) Add a certain mass of alkali lignin to anhydrous acetone, stir and extract at a solid-liquid mass ratio of 1:10, filter, and vacuum rotary evaporate the acetone-soluble part to obtain lignin reaction precursor powder.

[0030] (2) Spread the powder obtained in step (1) on a tray with a thickness of ≤1.0 mm, and treat it with DBD in an air atmosphere. The discharge power is set to 2000 W and the treatment time is 10 min.

[0031] (3) In an ice bath environment at 0 ℃, a 40% glyoxal aqueous solution was slowly added dropwise to DETA at a molar ratio of 1.0:1.0. The dropping rate was controlled at 10 s / drop. After the dropping was completed, the mixture was stirred for 60 min to obtain the intermediate solution.

[0032] (4) Dissolve the activated lignin powder from step (2) in an alkaline aqueous solution, adjust the pH to 11, and add the intermediate solution obtained in step (3), wherein the molar ratio of lignin to imine intermediate is 1.0:1.1. First, contact and stir at 25 °C for 30 min, and then heat to 90 °C for reflux reaction for 5 h.

[0033] (5) After the reaction solution cools down, adjust the pH to 5.5. AL is completely precipitated. After filtration, centrifugation, washing and drying, AL dry powder is obtained, which is component A.

[0034] (6) Mix 30 parts of component A with 70 parts of component B, and introduce 1.5% of component C by total mass. Perform high-speed shear emulsification at a high shear speed of 10,000 rpm for 30 min to obtain a stable oil-in-water adhesive ESO-AL.

[0035] The method of using the plasma-synergistic modified aminated lignin-cured epoxy soybean oil adhesive of the present invention includes the following steps: (1) The wood surface was treated with GAD for 50 seconds.

[0036] (2) After plasma activation, the wood surface is treated with 180 g / m 2 Apply ESO-AL evenly and let stand for 5 minutes.

[0037] (3) After the veneer is assembled, it is placed in a hot pressing environment at a temperature of 160 ℃ and a pressure of 1 MPa for 5 min to obtain a 3-layer plywood.

[0038] Example 2 The present invention discloses a plasma-synergistic modified aminated lignin-cured epoxidized soybean oil adhesive, wherein the adhesive comprises component A, component B (epoxidized soybean oil), and component C (Tween-80), and is made of three-layer plywood using poplar veneer with a thickness of 2 mm.

[0039] The preparation method of the plasma-synergistic modified aminated lignin-cured epoxy soybean oil adhesive of the present invention includes the following steps: (1) Add a certain mass of alkali lignin to anhydrous acetone, stir and extract at a solid-liquid mass ratio of 1:10, filter, and vacuum rotary evaporate the acetone-soluble part to obtain lignin reaction precursor powder.

[0040] (2) Spread the powder obtained in step (1) on a tray with a thickness of ≤1.0 mm, and process it with DBD in an air atmosphere. The discharge power is set to 2000 W and the processing time is 5 min.

[0041] (3) At 5℃, a 40% glyoxal aqueous solution was slowly added dropwise to DETA at a molar ratio of 1.0:1.0. The dropping rate was controlled at 10 s / drop. After the dropping was completed, the mixture was stirred for 60 min to obtain the intermediate solution.

[0042] (4) Dissolve the activated lignin powder from step (2) in an alkaline aqueous solution, adjust the pH to 10.5, and add the intermediate solution obtained in step (3), wherein the molar ratio of lignin to imine intermediate is 1.0:1.1. First, contact and stir at 25 °C for 30 min, and then heat to 85 °C for reflux reaction for 5 h.

[0043] (5) After the reaction solution is cooled, adjust the pH to 5.0. AL is completely precipitated. After filtration, centrifugation, washing and drying, AL dry powder is obtained, which is component A.

[0044] (6) Mix 28 parts of component A with 72 parts of component B, and introduce 1.5% of component C by total mass. Perform high-speed shear emulsification at a high shear speed of 10,000 rpm for 30 min to obtain a stable oil-in-water adhesive ESO-AL.

[0045] The method of using the plasma-synergistic modified aminated lignin-cured epoxy soybean oil adhesive of the present invention includes the following steps: (1) The wood surface was treated with GAD for 30 seconds.

[0046] (2) After plasma activation, the wood surface is treated with 180 g / m 2 Apply ESO-AL evenly and let stand for 5 minutes.

[0047] (3) After the veneer is assembled, it is placed in a hot pressing environment at a temperature of 160 ℃ and a pressure of 1 MPa for 10 min to obtain a 3-layer plywood.

[0048] Example 3 The present invention discloses a plasma-synergistic modified amino-modified lignin-cured epoxidized soybean oil adhesive, wherein the adhesive comprises component A, component B (epoxidized soybean oil), and component C (Tween-80), and is made of three-layer plywood using elm veneer with a thickness of 2 mm.

[0049] The preparation method of the plasma-synergistic modified aminated lignin-cured epoxy soybean oil adhesive of the present invention includes the following steps: (1) Add a certain mass of alkali lignin to anhydrous acetone, stir and extract at a solid-liquid mass ratio of 1:10, filter, and vacuum rotary evaporate the acetone-soluble part to obtain lignin reaction precursor powder.

[0050] (2) Spread the powder obtained in step (1) on a tray with a thickness of ≤1.0 mm, and treat it with DBD in an air atmosphere. The discharge power is set to 2000 W and the treatment time is 10 min.

[0051] (3) At 1 ℃, a 40% glyoxal aqueous solution was slowly added dropwise to DETA at a molar ratio of 1.0:1.0. The dropping rate was controlled at 10 s / drop. After the dropping was completed, the mixture was stirred for 60 min to obtain the intermediate solution.

[0052] (4) Dissolve the activated lignin powder from step (2) in an alkaline aqueous solution, adjust the pH to 11.5, and add the intermediate solution obtained in step (3), wherein the molar ratio of lignin to imine intermediate is 1.0:1.1. First, contact and stir at 25 °C for 30 min, and then heat to 88 °C for reflux reaction for 5 h.

[0053] (5) After the reaction solution cools down, adjust the pH to 5.5. AL is completely precipitated. After filtration, centrifugation, washing and drying, AL dry powder is obtained, which is component A.

[0054] (6) Mix 31 parts of component A with 69 parts of component B, and introduce 1.5% of component C by total mass. Perform high-speed shear emulsification at a high shear speed of 10,000 rpm for 30 min to obtain a stable oil-in-water adhesive ESO-AL.

[0055] The method of using the plasma-synergistic modified aminated lignin-cured epoxy soybean oil adhesive of the present invention includes the following steps: (1) The wood surface was treated with GAD for 60 s.

[0056] (2) After plasma activation, the wood surface is treated with 180 g / m 2 Apply ESO-AL evenly and let stand for 5 minutes.

[0057] (3) After the veneer is assembled, it is placed in a hot pressing environment at 180 ℃ and 1 MPa for 8 min to obtain a 3-layer plywood.

[0058] Example 4 The present invention discloses a plasma-synergistic modified amino-modified lignin-cured epoxidized soybean oil adhesive, wherein the adhesive comprises component A, component B (epoxidized soybean oil), and component C (Tween-80), and is made of three-layer plywood using pine veneer with a thickness of 2 mm.

[0059] The preparation method of the plasma-synergistic modified aminated lignin-cured epoxy soybean oil adhesive of the present invention includes the following steps: (1) Add a certain mass of alkali lignin to anhydrous acetone, stir and extract at a solid-liquid mass ratio of 1:10, filter, and vacuum rotary evaporate the acetone-soluble part to obtain lignin reaction precursor powder.

[0060] (2) Spread the powder obtained in step (1) on a tray with a thickness of ≤1.0 mm, and treat it with DBD in an air atmosphere. The discharge power is set to 2000 W and the treatment time is 10 min.

[0061] (3) At 1 ℃, a 40% glyoxal aqueous solution was slowly added dropwise to DETA at a molar ratio of 1.0:1.0. The dropping rate was controlled at 10 s / drop. After the dropping was completed, the mixture was stirred for 60 min to obtain the intermediate solution.

[0062] (4) Dissolve the activated lignin powder from step (2) in an alkaline aqueous solution, adjust the pH to 11, and add the intermediate solution obtained in step (3), wherein the molar ratio of lignin to imine intermediate is 1.0:1.1. First, contact and stir at 25 °C for 30 min, and then heat to 85 °C for reflux reaction for 5 h.

[0063] (5) After the reaction solution cools down, adjust the pH to 5.5. AL is completely precipitated. After filtration, centrifugation, washing and drying, AL dry powder is obtained, which is component A.

[0064] (6) Mix 32 parts of component A with 68 parts of component B, and introduce 1.5% of component C by total mass. Perform high-speed shear emulsification at a high shear speed of 10,000 rpm for 30 min to obtain a stable oil-in-water adhesive ESO-AL.

[0065] The method of using the plasma-synergistic modified aminated lignin-cured epoxy soybean oil adhesive of the present invention includes the following steps: (1) The wood surface was treated with GAD for 60 s.

[0066] (2) After plasma activation, the wood surface is treated with 180 g / m 2 Apply ESO-AL evenly and let stand for 5 minutes.

[0067] (3) After the veneer is assembled, it is placed in a hot pressing environment at a temperature of 180 ℃ and a pressure of 1 MPa for 10 min to obtain a 3-layer plywood.

[0068] Example 5 The present invention discloses a plasma-synergistic modified aminated lignin-cured epoxidized soybean oil adhesive, wherein the adhesive comprises component A, component B (epoxidized soybean oil), and component C (Tween-80), and is made of two overlapping layers of bamboo veneer with a thickness of 2 mm.

[0069] The preparation method of the plasma-synergistic modified aminated lignin-cured epoxy soybean oil adhesive of the present invention includes the following steps: (1) Add a certain mass of alkali lignin to anhydrous acetone, stir and extract at a solid-liquid mass ratio of 1:10, filter, and vacuum rotary evaporate the acetone-soluble part to obtain lignin reaction precursor powder.

[0070] (2) Spread the powder obtained in step (1) on a tray with a thickness of ≤1.0 mm, and treat it with dielectric barrier discharge (DBD) plasma in an air atmosphere. The discharge power is set to 2000 W and the treatment time is 10 min.

[0071] (3) At 3℃, a 40% glyoxal aqueous solution was slowly added dropwise to DETA at a molar ratio of 1.0:1.0. The dropping rate was controlled at 10 s / drop. After the dropping was completed, the mixture was stirred for 60 min to obtain the intermediate solution.

[0072] (4) Dissolve the activated lignin powder from step (2) in an alkaline aqueous solution, adjust the pH to 11.5, and add the intermediate solution obtained in step (3), wherein the molar ratio of lignin to imine intermediate is 1.0:1.1. First, contact and stir at 25 °C for 30 min, and then heat to 85 °C for reflux reaction for 5 h.

[0073] (5) After the reaction solution is cooled, adjust the pH to 5.5. AL is completely precipitated. After filtration, centrifugation, washing and drying, AL dry powder is obtained, which is component A.

[0074] (6) Mix 33 parts of component A with 67 parts of component B, and introduce 1.5% of component C by total mass. Perform high-speed shear emulsification at a high shear speed of 10,000 rpm for 30 min to obtain a stable oil-in-water adhesive ESO-AL.

[0075] The method of using the plasma-synergistic modified aminated lignin-cured epoxy soybean oil adhesive of the present invention includes the following steps: (1) The surface of the wood was treated with sliding arc discharge plasma for 40 s.

[0076] (2) After plasma activation, the wood surface is treated with 180 g / m 2 Apply ESO-AL evenly and let stand for 5 minutes.

[0077] (3) The assembled veneer is placed in a hot pressing environment at 160 ℃ and 1 MPa for 8 min to obtain the overlapping veneer.

[0078] Experimental Example 1 Plywood prepared in Examples 1-5 were tested for physical and mechanical properties according to the national standard GB / T 17657-2022 "Test Methods for Physical and Chemical Properties of Wood-based Panels and Decorative Wood-based Panels", using the mechanical strength test standard for Class II water-resistant plywood. The specific results are as follows: the dry shear strength of the specimens reached 2.6-3.8 MPa, and the wet bonding strength of the specimens after soaking in hot water at 63±3 ℃ for 3 h was 1.8-2.4 MPa, which meets and exceeds the national standard (≥0.7 MPa).

[0079] Table 1: Dry / Wet Shear Strength of Plates from Examples 1-5

[0080] Comparative Example 1 The patent, "A Preparation Method of Hyperbranched Polyamine-Modified Lignin Adhesive" (Patent No.: ZL202111227864.3), describes a method for chemically demethoxylating lignin with sodium sulfite, followed by physical blending with hyperbranched polyamines. The significant differences between this invention and the patent are as follows: First, the comparative patent increases the hydroxyl content through a wet chemical reaction, which is a "linear incremental" activation, while this invention directly breaks the β-O-4 ether bonds of the lignin skeleton through DBD plasma and introduces high-density branched amine groups through Mannich chemical grafting, thereby achieving branching reinforcement of the molecular structure. Second, the comparative patent involves a long hot water bath chemical reaction, resulting in a long production cycle, while this invention uses plasma dry treatment, which greatly increases the reactivity and is more environmentally friendly and cleaner. Third, the comparative patent uses lignin aqueous solution as the main component, while this invention introduces epoxidized soybean oil as a continuous phase, utilizing its long carbon chain structure to construct a natural hydrophobic barrier. Finally, the comparative patent has a maximum wet strength of 1.63 MPa, while this invention increases the wet strength to over 1.8 MPa through the "ESO-AL" co-curing system, making it more suitable for the manufacture of high-performance water-resistant structural panels.

[0081] Comparative Example 2 The patent, titled "A dual-aldehyde lignin and dual-aldehyde protected lignin adhesive, its preparation method and application" (Patent No.: CN202510561699.7), describes a compound of dual-aldehyde lignin and gelatin, cured via an aldehyde / amino Schiff base condensation reaction. The significant differences between this invention and the patent are as follows: First, the patent constructs Schiff base bonds (C=N) that are prone to hydrolysis, while this invention initiates epoxy ring-opening polymerization through aminated lignin, forming a β-amino alcohol structure with extremely high cohesive strength and hydrothermal stability. Second, the patent uses a traditional aqueous alkaline solution for dissolution and mixing, while this invention uses a high-shear emulsification process to uniformly embed AL particles into the ESO system to form a stable water-in-oil emulsion, significantly improving sizing wettability. Third, the patent relies on animal-based proteins (gelatin), which suffers from easy mold growth and high cost, while this invention utilizes all-plant-based ESO, possessing natural anti-corrosion and anti-insect properties. Finally, in terms of performance, the wet strength of the patent is usually difficult to exceed 1.2 MPa, while the wet strength of this invention has been increased to over 1.8 MPa, giving the board excellent moisture resistance and a wider hot-pressing process window.

[0082] Comparative Example 3 Compared to the patent "A Plasma-Modified Chitosan-Curing Epoxy Soybean Oil Wood Adhesive and Its Preparation Method and Application" (Patent No.: ZL 202410260521.4), which uses chitosan as a curing agent and physically modifies the chitosan film coated on the veneer surface through sliding arc plasma, the significant differences between this invention and that patent are as follows: First, this invention uses plant-based lignin as a raw material, whose aromatic skeleton has better natural compatibility with wood fibers; second, in terms of modification depth, the patent only uses plasma physical means to break down long-chain chitosan into smaller molecules, while this invention actively constructs high-density branched amine groups on the lignin skeleton through a dual approach of "DBD activation + Mannich chemical grafting," whose nucleophilic ring-opening efficiency for ESO epoxy groups is much higher than that of the amino groups in chitosan itself; third, in terms of the compounding process, the patent applies components A and B in steps, while this invention achieves pre-mixed and stable emulsification of components A and B, resulting in a simpler process and more uniform dispersion. Finally, compared with the patent, the wet strength is stable at 1.6 MPa, while the wet strength of the present invention under the same test standard is improved to more than 1.8 MPa, which fully demonstrates the progress of the present invention in bonding effect.

[0083] Comparative Example 4 Compared to the patent "A Co-curing Epoxy Soybean Oil-Based Wood Adhesive and Its Plasma Reinforcement Method and Application" (Patent No.: ZL 202110377994.9), which uses urea-formaldehyde resin (UF) as the co-curing component of ESO and utilizes the hydroxymethyl group in UF to initiate the ring-opening of ESO, the significant differences between this invention and that patent are as follows: First, a qualitative change in environmental performance; the patent system still contains formaldehyde, while this invention achieves formaldehyde-free replacement using all biomass. Second, optimization of the curing mechanism; the hydroxymethyl group in UF has weak nucleophilicity, and the wet strength of the cured product is usually between 1.2-1.4 MPa, while the aminated lignin introduced in this invention contains a large number of secondary and primary amine groups, with extremely strong nucleophilic ring-opening ability, and the measured wet shear strength can be stably maintained above 1.8 MPa. Finally, an advancement in modification logic; the patent only activates the veneer interface, while this invention achieves comprehensive physical field enhancement from the curing agent itself (DBD powder activation) to the interface (GAD veneer activation).

[0084] Comparative Example 5 The patent, "Method for Producing Plywood Using Lignin Adhesives" (Patent No.: ZL 201410634438.5), utilizes the reaction of sulfonated lignin with phenol and introduces petrochemical-based crosslinking agents such as isocyanates. The significant differences between this invention and the patent are as follows: First, while the patent heavily relies on the strong chemical crosslinking of petrochemical components, this invention utilizes plasma physical field activation to directly induce ring-opening of biomass oils, resulting in a more efficient and simpler mechanism. Second, the patent involves cumbersome processes such as sulfonation, concentration, and three-roll milling, while this invention significantly simplifies the process and facilitates continuous production. Third, the patent contains toxic phenol and expensive isocyanates, while this invention achieves an environmentally friendly leap of "all biomass, zero formaldehyde." Finally, while achieving significantly superior performance (the highest dry shear strength of the patent is only 1.67 MPa), this invention significantly reduces raw material costs and eliminates the release of free toxic substances from engineered wood products, meeting the stringent environmental requirements of the high-end solid wood composite furniture market.

[0085] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A modified amino-modified lignin-cured epoxy soybean oil adhesive, characterized in that, The adhesive comprises a water-in-oil stable system composed of components A, B, and C, wherein component A is aminated lignin obtained through plasma activation and chemical grafting modification, component B is epoxidized soybean oil, and component C is a nonionic emulsifier; by weight, its component ratio is: component A 25-35 parts, component B 65-75 parts, and component C 1-2 parts.

2. The modified amino-amined lignin-cured epoxy soybean oil adhesive according to claim 1, characterized in that, The amine value of component A, the amino-modified lignin, is between 200 and 500 mg. KOH / g Between them, in its molecular skeleton, an amino functional group branch chain formed by the condensation of diethylenetriamine and glyoxal is grafted at the C5 position of the lignin benzene ring; the epoxy value of component B, epoxidized soybean oil, is ≥6.0; component C is at least one of Tween-20, Tween-40, Tween-60, Tween-80, and Tween-85.

3. A method for preparing the modified amino-amined lignin-cured epoxy soybean oil adhesive as described in claim 1 or 2, characterized in that, Includes the following steps: (1) Lignin screening: Alkali lignin was added to anhydrous acetone, stirred and extracted, the acetone-soluble part was collected and vacuum rotary evaporated to obtain a low molecular weight lignin component solid powder. (2) Physical activation by dielectric barrier discharge: The tray obtained in step (1) is treated with dielectric barrier discharge plasma in an air atmosphere; (3) Preparation of imine intermediate: Under the condition of 0-5℃, glyoxal aqueous solution is added dropwise to diethylenetriamine. After the addition is completed, the mixture is stirred continuously to obtain a stable Schiff base imine intermediate solution. (4) Mannich high-temperature grafting: Dissolve the lignin powder activated in step (2) in an alkaline aqueous solution, adjust the pH value, add the intermediate solution obtained in step (3), first contact and stir at room temperature, and then heat and reflux reaction. (5) Product purification and adhesive compounding: After the reaction solution is cooled, the pH value is adjusted to allow the aminated lignin to precipitate completely. After centrifugation, washing and drying, aminated lignin powder is obtained. The obtained dry powder is sheared and emulsified with component B and component C in proportion to obtain modified aminated lignin-cured epoxidized soybean oil adhesive.

4. The preparation method according to claim 3, characterized in that, In step (1), the alkali lignin is G-type lignin, and the solid-liquid mass ratio of alkali lignin and anhydrous acetone is 1:5-15; in step (3), the mass fraction of glyoxal solution is 30-50%; the molar ratio of glyoxal to diethylenetriamine is 0.5-1.5:0.5-1.

5.

5. The preparation method according to claim 3, characterized in that, In step (2), the discharge power of the dielectric barrier discharge plasma treatment is 1500-2500W, the treatment time is 5-10min, and the thickness of the powder after spreading is controlled to be ≤1.0mm; in step (4), the pH is adjusted to 10.5-11.5, the room temperature stirring time is 30-90min, the temperature of the heating reflux reaction is 85-90℃, the time is 4-6h, and the molar ratio of lignin to imine intermediate is 1:1-1.

5.

6. The preparation method according to claim 3, characterized in that, In step (5), the pH is adjusted to 5.0-5.5, and the high-speed shear emulsification speed is 8000-12000 rpm for 20-40 min.

7. The application of the modified aminated lignin-cured epoxy soybean oil adhesive as described in claim 1 or 2 in the bonding of boards.

8. The application according to claim 7, characterized in that, Includes the following steps: S1. Activation treatment of board interface: The surface of the wood veneer to be glued is activated by sliding arc discharge plasma; S2. Adhesive application process: Apply the modified aminated lignin-cured epoxy soybean oil adhesive as described in claim 1 or 2 evenly to the surface of the activated veneer; S3. Hot pressing: The assembled veneer is placed into a hot press for hot pressing.

9. The application according to claim 8, characterized in that, In step S1, the power of the activation treatment is set to 1500-2500W, the distance between the nozzle and the single board is 2-3 cm, and the treatment time is 30-60 s; In step S2, the amount of adhesive applied is 150-200 g / m² on one side. 2 The adhesive application process must be completed within 30 minutes after surface activation; in step S3, the hot pressing temperature is 140-180℃, the pressure is 0.8-1.2MPa, and the hot pressing time is 5-15 minutes.

10. The application according to claim 7, characterized in that, The board material is a man-made board.

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