A wet-state maintaining plant protein adhesive as well as a preparation method and application thereof

Abstract

The present application relates to the technical field of adhesive, and provides a wet-state maintaining type plant protein adhesive, a preparation method and application thereof, wherein the hyperbranched catechol polymer adhesive filler is prepared by ring-opening reaction of the epoxy groups of neopentyl glycol diglycidyl ether and pentaerythritol tetraglycidyl ether with the amino group of dopamine hydrochloride.Meanwhile, the plant protein adhesive is prepared by plant protein, a crosslinking agent and the above adhesive filler in a certain proportion.The adhesive filler and the corresponding plant protein adhesive can solve the defects of insufficient product performance caused by poor moisture retention of the bio-based adhesive, especially the plant protein adhesive.

Description

Technical Field

[0001] This invention relates to the field of adhesive technology, and in particular to a moisture-retaining plant protein adhesive, its preparation method, and its application. Background Technology

[0002] With the increasing popularity of environmental protection concepts and the growing demand for sustainable development, the application of traditional petroleum-based polymer materials in many fields is gradually being limited, especially in the adhesive industry. The shortcomings of petroleum-based adhesives in terms of environmental protection, resource consumption, and biodegradability are prompting the industry to continuously seek green and renewable alternative materials.

[0003] Natural bio-based adhesives, such as plant protein adhesives, are an ideal alternative to traditional synthetic adhesives due to their wide availability, environmental friendliness, and excellent biodegradability. In recent years, bio-based adhesives have attracted widespread attention and research from various industries, including wood processing, paper products, textiles, and packaging, due to their superior performance and low-carbon characteristics.

[0004] Despite the significant advantages of bio-based adhesives in terms of environmental friendliness, they still face certain technical challenges in practical applications. This is mainly because bio-based adhesives have relatively poor moisture retention, which can easily affect production efficiency and product quality during long-term storage or transportation.

[0005] Therefore, this invention is proposed. Summary of the Invention

[0006] This invention provides a moisture-retaining plant protein adhesive, its preparation method, and its application, to address the shortcomings of existing bio-based adhesives, especially plant protein adhesives, in terms of insufficient product performance due to poor moisture retention.

[0007] Specifically, the present invention provides an adhesive filler comprising: a hyperbranched catechol polymer (HBP) obtained by ring-opening reaction of the epoxy groups of neopentyl glycol diglycidyl ether and pentaerythritol tetraglycidyl ether with the amino group of dopamine hydrochloride. The hyperbranched catechol polymer includes phenolic hydroxyl groups and a hydrophobic carbon skeleton.

[0008] This invention proposes an adhesive filler containing the hyperbranched catechol polymer described above. Because this hyperbranched catechol polymer possesses abundant phenolic hydroxyl groups, it can form extensive hydrogen bonds with water molecules, exhibiting excellent hydrophilicity. When used as an adhesive filler, it forms covalent crosslinks and a large number of hydrogen bonds with the crosslinking agent TGA, resulting in a uniform distribution within the adhesive system. The hydration process of this hyperbranched catechol polymer also enhances the wettability of the adhesive and reduces interfacial tension. Furthermore, the hydrophobic carbon skeleton of this hyperbranched catechol polymer disrupts the hydration layer on the adhesive surface, exposing the bonding surface and promoting hydrogen bond interactions between the hydrophilic hydroxyl groups of the hyperbranched catechol polymer and the substrate. Finally, π-π interactions are also formed between the hydrophobic carbon skeleton and the matrix. With the aid of hydrogen bonding and π-π interactions, the synergistic effect of the polar hydroxyl groups and nonpolar carbon skeleton of this hyperbranched catechol polymer improves the wettability and adhesion of the prepared adhesive, enabling it to be uniformly distributed on the substrate surface, filling micro-grooves, and improving the pre-compression strength and wet and dry shear strength of the adhesive.

[0009] Therefore, the hyperbranched catechol polymer of the present invention gives the adhesive a certain degree of hygroscopicity. Moreover, the hyperbranched catechol polymer can easily form a multi-crosslinked network structure with other components in the adhesive system, thereby improving the overall performance of the adhesive, such as its moisturizing properties and mechanical properties, on the basis of hygroscopicity.

[0010] According to the adhesive filler provided by the present invention, the Mn of the hyperbranched catechol polymer is 80,000 to 150,000 Da; Preferably, the Mw / Mn value of the hyperbranched catechol polymer ranges from 0.8 to 1.2; Preferably, the hyperbranched catechol polymer is in a high viscosity state at 273K and reaches a high elastic state at temperatures above 298K.

[0011] In a second aspect, the present invention also provides a method for preparing the adhesive filler as described above, comprising: reacting the epoxy groups of neopentyl glycol diglycidyl ether (NGDE) and pentaerythritol tetraglycidyl ether (PTE) with the amino group of dopamine hydrochloride (DOPA) to obtain the hyperbranched catechol polymer.

[0012] Studies have found that, compared to other reactive raw materials such as tannins and gallic acid, the dopamine hydrochloride (DOPA) used in this invention exhibits stronger intermolecular crosslinking ability in the preparation of the hyperbranched catechol polymer due to the unique coexistence of phenolic hydroxyl and amino groups. The amino and hydroxyl groups in DOPA play a dual role in the polymerization reaction: on the one hand, the amino group participates in the polymerization reaction, forming stable molecular chains with the epoxy backbone and crosslinking agent respectively; on the other hand, the phenolic hydroxyl group synergistically interacts with other functional groups in the molecule through hydrogen bonds, thereby significantly improving the adhesive's moisture retention and pre-compression strength. Therefore, this hyperbranched catechol polymer based on dopamine hydrochloride possesses the aforementioned structural advantages, thus significantly improving the overall application performance of plant protein adhesives.

[0013] According to the preparation method of the adhesive filler provided by the present invention, the mass ratio of neopentyl glycol diglycidyl ether to dopamine hydrochloride is (0.1~2):1, preferably (0.5~2):1; And / or, the mass ratio of the pentaerythritol tetraglycidyl ether to dopamine hydrochloride is (0.1~2):1, preferably (0.1~1):1; According to the preparation method of the adhesive filler provided by the present invention, the ring-opening reaction is carried out under the action of an alkaloid catalyst; Preferably, the alkaloid catalyst is selected from 1,5,7-triazabicyclo[4,4,01-5-ene (TBD). More preferably, the mass ratio of 1,5,7-triazabicyclo[4,4,01-5-ene] to dopamine hydrochloride is (1~2):1, more preferably (1~1.5):1.

[0014] Research has found that using 1,5,7-triazabicyclo[4,4,01-5-ene] as a catalyst has greater technological advantages.

[0015] The method for preparing the adhesive filler according to the present invention includes: Dopamine hydrochloride and ethanol are mixed to obtain a mixed solution; preferably, the mass ratio of dopamine hydrochloride to ethanol is 1:(1~20), more preferably 1:(1.5~15), and even more preferably 1:(1.5~10). The alkaloid catalyst is mixed with the mixed solution to obtain a first mixture; preferably, the alkaloid catalyst is added to the mixed solution in two or more batches to obtain the first mixture. Neopentyl glycol diglycidyl ether and pentaerythritol tetraglycidyl ether were mixed to obtain a second mixture; The first mixture and the second mixture are mixed and reacted at 50~100℃ for 0.5h~1.5h to obtain the adhesive filler; preferably, the product obtained after the reaction of the first mixture and the second mixture is subjected to rotary evaporation treatment to obtain the adhesive filler; more preferably, the drying temperature is 40~80℃.

[0016] In the preparation process of the hyperbranched catechol polymer of the present invention, using ethanol as the reaction medium is beneficial for the ring-opening reaction, the control of the reaction degree, and the subsequent product acquisition. The reaction principle is as follows: Figure 1 As shown. The purpose of drying in this invention is to remove ethanol from the product. The drying can be carried out by rotary evaporation, which can be performed under normal pressure.

[0017] Preferably, the preparation of the hyperbranched catechol polymer is carried out under nitrogen protection.

[0018] Thirdly, the present invention also provides a plant protein adhesive, comprising plant protein and a crosslinking agent, and further comprising adhesive filler as described above, or adhesive filler prepared by the preparation method described above.

[0019] Plant proteins contain no toxic substances, are low in cost, and are suitable for industrial applications. However, improving the moisturizing properties of plant proteins while maintaining their environmentally friendly characteristics has long been a key technical challenge for the industry. Research has found that by using the aforementioned adhesive fillers, combined with cross-linking agents, they can be uniformly mixed with the plant protein system. The adhesive fillers are distributed within the plant protein system, forming covalent and hydrogen bonds, thus creating a multi-crosslinked network structure. This promotes stress balance, synergistically improves the moisturizing performance of the adhesive, and contributes to the uniformity and stability of the adhesive system.

[0020] In the plant protein adhesive provided by the present invention, the crosslinking agent is selected from triglycidylamine.

[0021] In this invention, the choice of crosslinking agent has a certain impact on the application performance of the plant protein adhesive. When using the above-mentioned adhesive filler, the crosslinking agent is preferably triglycidylamine. The above-mentioned adhesive filler and triglycidylamine can undergo ring-opening grafting chemical crosslinking, thereby improving the intermolecular interaction force and internal structural stability of the plant protein adhesive.

[0022] According to the plant protein adhesive provided by the present invention, the plant protein is selected from one or more combinations of soybean meal protein, peanut meal protein, cottonseed meal protein and corn alcohol meal protein; more preferably, the protein content of the plant protein is 90-98 wt%, preferably 93-95 wt%.

[0023] For plant protein adhesives, the proteins in plant proteins can provide abundant functional groups such as amino and carboxyl groups, which play a crucial role in the cross-linking reaction. Therefore, their content has a significant impact on the cross-linking density of the adhesive. Studies have found that the adhesive filler of this invention has greater application advantages for plant proteins with a protein content of over 90%.

[0024] According to the plant protein adhesive provided by the present invention, the mass ratio of the plant protein to the triglycidylamine is 1:(0.2~2), preferably 1:(0.2~1).

[0025] According to the plant protein adhesive provided by the present invention, the mass ratio of the plant protein to the adhesive filler is 1:(0.2~2), preferably 1:(0.2~1).

[0026] Fourthly, the present invention also provides a method for preparing the plant protein adhesive as described above, comprising: mixing adhesive filler, triglycidylamine, plant protein and water to obtain the adhesive; Preferably, the mass ratio of the plant protein to the water is 1:(20~80), more preferably 1:(20~50). More preferably, the preparation method includes the following steps: The first product is obtained by mixing plant protein and water; The first product is mixed with an adhesive filler to obtain the second product; The second product is mixed with a crosslinking agent to obtain the plant protein adhesive.

[0027] The second product is mixed with the crosslinking agent by mechanical stirring; the mechanical stirring conditions are: 800~1200 rpm, 0~40℃, stirring for 0.1~1.5 hours; preferably, the mechanical stirring conditions are: 800~1000 rpm, 15~35℃, stirring for 0.5~1 hours.

[0028] The method for preparing adhesives according to the present invention is simple, efficient, releases no harmful substances, produces highly reactive products, has good processability, and exhibits stable performance across batches.

[0029] Fifthly, the present invention also provides a plywood comprising the plant protein adhesive as described above, or the plant protein adhesive prepared by the preparation method described above.

[0030] This invention provides a moisture-retaining plant protein adhesive, its preparation method, and its application. A specific hyperbranched catechol polymer is obtained through the ring-opening reaction of neopentyl glycol diglycidyl ether, pentaerythritol tetraglycidyl ether, and dopamine hydrochloride. This hyperbranched catechol polymer can be used as an adhesive filler.

[0031] Furthermore, this invention also prepares a plant protein adhesive by combining an adhesive filler containing a hyperbranched catechol polymer, a crosslinking agent, and a plant protein. This plant protein adhesive has excellent moisturizing properties. Compared with traditional functional fillers, the adhesive filler of this invention is more conducive to improving the moisturizing properties of the plant protein adhesive. Its quality retention rate can reach 73.53% after exposure in a controlled environment (25°C, 60% relative humidity) for 40 hours, its open time can reach 2.5 hours, and its pot life can reach 80 hours.

[0032] Moreover, by optimizing the ratio of each raw material, the overall performance of the plant protein adhesive can be improved. When the plant protein adhesive is applied, the processing conditions are mild and the curing is fast. It has been verified that its lap shear strength can reach 1.29 MPa, pre-compression strength can reach 1.31 MPa, dry shear strength can reach 2.1 MPa, and wet shear strength can reach 1.45 MPa. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in this 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 some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0034] Figure 1 This is a schematic diagram illustrating the reaction principle of the adhesive filler provided by the present invention.

[0035] Figure 2 ai is the microstructure characterization result and reaction process analysis diagram of the adhesive filler prepared in Example 1A of the present invention.

[0036] Figure 3 This is a state diagram of the adhesive filler prepared in Example 1A of the present invention at a temperature of 273K; Figure 4 This is a state diagram of the adhesive filler prepared in Example 1A of the present invention at a temperature of 298K; Figure 5 This is a state diagram of the adhesive filler prepared in Example 1A of the present invention at a temperature of 313K. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0038] The following is combined with Figures 1-5 This invention describes a moisture-retaining plant protein adhesive, its preparation method, and its application.

[0039] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0040] In this invention, the percentage sign "%" refers to the mass percentage unless otherwise specified; however, the percentage of a solution, unless otherwise specified, refers to the number of grams of solute contained in 100 ml of the solution; the percentage between liquids refers to the ratio of their volumes at 20°C.

[0041] The plant protein used in the embodiments of this invention has a protein content of 95% and a particle size of 250 mesh, and was purchased from Shandong Yuwang Ecological Food Industry Co., Ltd.

[0042] Neopentyl glycol diglycidyl ether, pentaerythritol tetraglycidyl ether, dopamine hydrochloride and 1,5,7-triazabicyclo[4,4,01-5-ene were provided by Science Compass Testing Platform Co., Ltd., located in Hangzhou, China.

[0043] The crosslinking agent triglycidylamine, polyamide epichlorohydrin resin, and wood boards with a moisture content of 7% to 10% were purchased from Shandong Qiansen Group Co., Ltd.

[0044] Example 1A This embodiment provides an adhesive filler, the preparation method of which is as follows: (1) Under nitrogen protection, add 4g of dopamine hydrochloride and 10g of ethanol to a three-necked flask and stir to mix.

[0045] (2) Continue to add 8g of 1,5,7-triazabicyclo[4.4.01-5-ene (1,5,7-triazabicyclo[4.4.01-5-ene was added in three equal parts) into a three-necked flask and stir for 4 hours while maintaining the reaction temperature at 60℃.

[0046] (3) Slowly mix 3g of neopentyl glycol diglycidyl ether and 1g of pentaerythritol tetraglycidyl ether and stir thoroughly. Then, transfer the resulting mixture to a three-necked flask and react it with dopamine hydrochloride, ethanol and 1,5,7-triazabicyclo[4,4,01-5-ene at 60°C and 300 rpm for 3 hours.

[0047] (4) The obtained product was dried (pressure: 0.1MPa; temperature: 60℃) for 0.5 hours to obtain adhesive filler.

[0048] Example 2A This embodiment provides an adhesive filler, the preparation method of which is as follows: (1) Under nitrogen protection, add 4g of dopamine hydrochloride and 10g of ethanol to a three-necked flask and stir to mix.

[0049] (2) Continue to add 4g of 1,5,7-triazabicyclo[4.4.01-5-ene (1,5,7-triazabicyclo[4.4.01-5-ene was added in three equal parts) into a three-necked flask and stir for 4 hours while maintaining the reaction temperature at 60℃.

[0050] (3) Slowly mix 3g of neopentyl glycol diglycidyl ether and 1g of pentaerythritol tetraglycidyl ether and stir thoroughly. Then, transfer the resulting mixture to a three-necked flask and react it with dopamine hydrochloride, ethanol and 1,5,7-triazabicyclo[4,4,01-5-ene at 60°C and 300 rpm for 3 hours.

[0051] (4) The obtained product was dried (pressure: 0.1MPa; temperature: 60℃) for 0.5 hours to obtain adhesive filler.

[0052] Example 3A This embodiment provides an adhesive filler, the preparation method of which is as follows: (1) Under nitrogen protection, add 4g of dopamine hydrochloride and 10g of ethanol to a three-necked flask and stir to mix.

[0053] (2) Continue to add 8g of 1,5,7-triazabicyclo[4.4.01-5-ene (1,5,7-triazabicyclo[4.4.01-5-ene was added in three equal parts) into a three-necked flask and stir for 4 hours while maintaining the reaction temperature at 60℃.

[0054] (3) Slowly mix 4g of neopentyl glycol diglycidyl ether and 2g of pentaerythritol tetraglycidyl ether and stir thoroughly. Then, transfer the resulting mixture to a three-necked flask and react it with dopamine hydrochloride, ethanol and 1,5,7-triazabicyclo[4,4,01-5-ene] at 60°C and 300 rpm for 3 hours.

[0055] (4) The obtained product was dried (pressure: 0.1MPa; temperature: 60℃) for 0.5 hours to obtain adhesive filler.

[0056] Examples 1B~3B This embodiment provides a method for preparing a moisturizing plant protein adhesive. The process is as follows: 15 kg of plant protein is added to 85 kg of dispersion medium water and mechanically stirred for 6 minutes. Then, 10 kg of adhesive filler from Examples 1A to 4A and 10 kg of triglycidylamine are added and mechanically stirred for another 30 minutes until a uniform paste is produced, thus obtaining the moisturizing plant protein adhesive.

[0057] In particular, Example 1B uses the adhesive filler from Example 1A.

[0058] Example 2B uses the adhesive filler from Example 2A.

[0059] Example 3B uses the adhesive filler from Example 3A.

[0060] Example 4B This embodiment provides a method for preparing a moisturizing plant protein adhesive. The process is as follows: 15 kg of plant protein is added to 85 kg of dispersion medium water and mechanically stirred for 6 minutes. Then, 8 kg of adhesive filler from Example 4A and 8 kg of triglycidylamine are added and mechanically stirred for another 30 minutes until a uniform paste is produced, thus obtaining the moisturizing plant protein adhesive.

[0061] Example 5B This embodiment provides a method for preparing a moisturizing plant protein adhesive. The process is as follows: 15 kg of plant protein is added to 85 kg of dispersion medium water and mechanically stirred for 6 minutes. Then, 6 kg of adhesive filler from Example 4A and 3 kg of triglycidylamine are added and mechanically stirred for another 30 minutes until a uniform paste is produced, thus obtaining the moisturizing plant protein adhesive.

[0062] Comparative Example 1 This comparative example provides a method for preparing an adhesive, the process of which is as follows: 30 kg of soybean meal is added to 70 kg of dispersion medium water, mechanically stirred for 6 minutes, then 10 kg of adhesive filler from Example 1A and 10 kg of triglycidylamine are added and mechanically stirred for another 30 minutes until a uniform paste is produced.

[0063] Comparative Example 2 This comparative example provides an adhesive, the process of which is as follows: 15 kg of plant protein is added to 85 kg of dispersion medium water, mechanically stirred for 6 minutes, then 10 kg of adhesive filler from Example 1A and 10 kg of polyamide epichlorohydrin resin are added and mechanically stirred for another 30 minutes until a uniform paste is produced.

[0064] Comparative Example 3 This comparative example provides an adhesive filler, the preparation method of which is as follows: (1) Add 4g gallic acid and 10g ethanol to a three-necked flask and stir to mix.

[0065] (2) Slowly mix 4g of neopentyl glycol diglycidyl ether and 2g of pentaerythritol tetraglycidyl ether and stir thoroughly. Then, transfer the resulting mixture to a three-necked flask and react it with dopamine hydrochloride, ethanol and 1,5,7-triazabicyclo[4,4,01-5-ene] at 60°C and 300 rpm for 3 hours.

[0066] (3) The obtained product was dried (pressure: 0.1MPa; temperature: 60℃) for 0.5 hours to obtain adhesive filler.

[0067] This comparative example also provides an adhesive, which is prepared in the same way as in Example 1, except that the adhesive filler is replaced with the adhesive filler prepared in Comparative Example 3.

[0068] Comparative Example 4 This comparative example provides an adhesive filler, the preparation method of which is as follows: (1) Add 4g of tannin and 10g of ethanol to a three-necked flask and stir to mix.

[0069] (2) Slowly mix 4g of neopentyl glycol diglycidyl ether and 2g of pentaerythritol tetraglycidyl ether and stir thoroughly. Then, transfer the resulting mixture to a three-necked flask and react it with dopamine hydrochloride, ethanol and 1,5,7-triazabicyclo[4,4,01-5-ene] at 60°C and 300 rpm for 3 hours.

[0070] (3) The obtained product was dried (pressure: 0.1MPa; temperature: 60℃) for 0.5 hours to obtain adhesive filler.

[0071] This comparative example also provides an adhesive, which is prepared in the same way as in Example 1, except that the adhesive filler is replaced with the adhesive filler prepared in Comparative Example 4.

[0072] Test case The adhesive filler prepared in Example 1A was subjected to microstructure testing, and the results are as follows: Figure 2 b shows the FTIR spectra of DOPA, NGDE, PTE, and HBP (adhesive fillers). In epoxy resin, 899 cm⁻¹ -1The absorption peak at 1650-1500 cm⁻¹ was attributed to the epoxy group. The disappearance of this peak after the grafting reaction indicates that the epoxy groups in NGDE and PTE reacted with the amino group of DOPA, thereby generating HBP. Specifically, in the FTIR spectrum of DOPA, the peak at 1650-1500 cm⁻¹... -1 and 900-770cm -1 The peaks between these points correspond to the stretching vibration and out-of-plane deformation vibration of NH in primary amines, respectively. Furthermore, the peaks at 1230-1030 cm⁻¹... -1 The CN stretching vibration peak further confirmed the presence of primary amines in DOPA. However, in the HBP spectrum, the absorption peaks associated with primary amines disappeared, replaced by secondary and tertiary amine peaks.

[0073] Figure 2 c shows the 1H NMR spectra of DOPA and HBP in DMSO-D6. In the DOPA spectrum, the resonance peak at 1.6 ppm is attributed to the absorption peak of H in the primary amine. In the 1H NMR spectrum of HBP, this peak disappears, but a strong absorption peak (3.7 ppm) belonging to H in the secondary amine appears. This indicates that the terminal amino group is converted to a secondary amine group. These changes verify that DOPA chemically covers the terminal epoxy group of the epoxide compound, supporting the success of the grafting reaction.

[0074] The molecular weights of DOPA and HBP were determined by GPC. For example... Figure 2 d. The Mn of PTE is 6165 Da and the Mw is 6382 Da. After the grafting reaction, the Mn of HBP is 106826 Da and the Mw is 261289 Da, indicating that the synthesis of HBP was successful. The polydispersity of the sample corresponds to the relative molecular weight distribution, i.e., Mw / Mn. After the grafting reaction, the Mw / Mn of HBP increases. Therefore, the polydispersity of HBP relative to PTE decreases from 2.446 to 1.035, indicating the randomness of the reaction and the narrowing of the molecular weight distribution range after grafting.

[0075] like Figure 2 As shown in the image, the surface of HBP exhibits a smooth and dense structure, which is significantly different from the layered structure of DOPA as seen in SEM images. Furthermore, EDS spectroscopy analysis revealed that nitrogen (N) and oxygen (O) elements are uniformly dispersed on the HBP surface, further confirming the successful incorporation of DOPA into the hyperbranched polymer. At room temperature, solidified HBP can be observed as elongated, viscous fibers between rubber gloves. Figure 2 h).

[0076] To better understand the reaction processes in the system (such as...) Figure 2 As shown in Figure a), the changes in charge distribution before and after curing of the hyperbranched polymer are discussed. Figure 2The negative interaction energy of DOPA@TBD indicates an attractive force between the particles. Clearly, TBD (1,5,7-triazabicyclo[4,4,01-5-ene) acts as an alkaloid catalyst, facilitating the spontaneous conduction of the click reaction and improving the stability of the reaction system. Charge distribution calculations show ( Figure 2 i) In DOPA@TBD, the negative charge of the nitrogen atom in the amino group (-0.8930 eV) is greater than the negative charge of the oxygen atom in the phenolic hydroxyl group (-0.4520 eV), indicating that the negatively charged N atom in TBD facilitates the preferential adsorption and activation of the amino group in DOPA. By comparing the electrostatic charge distribution of the amino group before and after the click reaction, it was found that the amino group of DOPA@TBD reacts with the epoxy end group in the epoxy compound to generate a hydroxyl group. In this process, the nitrogen atom transfers more negative charge to the oxygen atom, thus significantly reducing the charge of the nitrogen atom to -0.5610 eV. This change proves the successful synthesis of HBP.

[0077] like Figures 3-5 It can be seen that the viscosity of molecules changes with temperature, especially at 273K, the system exhibits a high viscosity state, gradually transitioning to a high elastic state at 298K.

[0078] Furthermore, the adhesives obtained in the above embodiments and comparative examples were also tested. All tests were repeated three times, and the average value was taken.

[0079] Open time refers to the maximum time that the mixed resin and hardener can remain on the substrate before bonding. Generally, the open time can be calculated as the time it retains 80% of the final tensile strength that would have been achieved immediately after application. Pot life refers to the time during which the mixed adhesive can be used for application after the resin and hardener are mixed. Pot life considers the time before the adhesive is applied to the substrate, while open time considers the time after application.

[0080] Moisture retention test: The adhesive was placed in a constant temperature and humidity chamber at 25℃ and 60%RH for 40 hours, and then its mass retention rate was calculated. The calculation method is as follows: Quality retention rate = Wt / W0 × 100%, where Wt is the weight of the adhesive at 40 hours and W0 is the initial weight of the adhesive.

[0081] Lap shear test: The test was conducted using a universal testing machine (UTM, Instron 3365, Norwood, Massachusetts) at a loading rate of 10 mm / min and ambient temperature. The adhesive was compressed between two poplar strips (100 mm × 25 mm), with a bonded area of ​​25 mm × 25 mm, at a loading rate of 180 g / m². 2The coating should be applied evenly. The overlap shear strength is calculated by dividing the force at failure by the overlap area. For each adhesive, at least six measurements should be performed to obtain the average overlap shear strength.

[0082] Pre-compression strength test: The pre-compression bonding strength of the adhesive was tested using poplar veneer (200×200×1.5mm³) as the substrate for plywood manufacturing. Different adhesive formulations were tested at 180g / m². 2 The coating density was uniformly applied to one side of the veneer. Then, following the principle of perpendicular arrangement of adjacent veneers, uncoated veneers were stacked between two coated veneers and pressed for 15 minutes at 25°C and 1 MPa. After pressing, the plywood was immediately cut into test samples. Pre-compression strength tests were performed on a UTM equipped with a 5 kN force sensor at a loading rate of 10 mm / min until failure. Pre-compression strength was calculated by dividing the force at failure by the overlap area; all measurements were repeated six times.

[0083] Dry and wet shear strength tests: To evaluate the bonding performance of the mixed adhesives, poplar veneer (200×200×1.5mm³) was used as the substrate for plywood fabrication. Adhesives of different formulations were uniformly applied to one side of the veneer at a coating density of 180 g / m². Uncoated veneers were then stacked between two coated veneers, with adjacent veneers arranged perpendicularly. The plywood assembly was pressed for 6 minutes at 120°C and 1.0 MPa in a hot press. After pressing, the plywood was placed at 20°C for 24 hours and then cut into test specimens. The shear strength of the plywood was tested using a universal testing machine (CMT4202, China New Sansi Enterprise Development Co., Ltd.) according to Chinese National Standard GB / T17657-2013. The dry shear strength of three-layer plywood specimens (100×25 mm) was measured at a loading rate of 10 mm / min. In the wet shear test, the specimen was immersed in water at 63°C for 3 hours, then cooled to room temperature for 10 minutes before the test was conducted. Each specimen was tested six times, and the average value was recorded.

[0084] The test results are shown in Table 1.

[0085] Table 1

[0086] Based on the above test results and comparing the examples with Comparative Examples 1-4, it is evident that the materials in the examples exhibit superior performance in several key parameters. Regarding open time and pot life, Example 1 shows a more significant advantage. Furthermore, the example demonstrates significantly higher lap shear strength and pre-compression strength than the comparative examples, indicating superior moisture retention properties. In addition, the example also exhibits superior mass retention, further confirming its excellent moisture retention performance. Moreover, the example demonstrates good performance in dry shear strength and wet shear strength, clearly showing that improving moisture retention can significantly optimize its mechanical properties. In conclusion, the examples demonstrate excellent performance in moisture retention, pre-compression strength, and mechanical strength, exhibiting significant application prospects and technological advantages.

[0087] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An adhesive filler, characterized in that, It is a hyperbranched catechol polymer obtained by ring-opening reaction of the epoxy groups of neopentyl glycol diglycidyl ether and pentaerythritol tetraglycidyl ether with the amino group of dopamine hydrochloride; the mass ratio of neopentyl glycol diglycidyl ether to dopamine hydrochloride is (0.1~2):1; the mass ratio of pentaerythritol tetraglycidyl ether to dopamine hydrochloride is (0.1~2):

1. The hyperbranched catechol polymer includes phenolic hydroxyl groups and a hydrophobic carbon skeleton; The Mn of the hyperbranched catechol polymer is 80,000 to 150,000 Da.

2. The adhesive filler according to claim 1, characterized in that, The hyperbranched catechol polymer exhibits high viscosity at 273K and high elasticity at temperatures above 298K.

3. A method for preparing the adhesive filler according to claim 1 or 2, characterized in that, The epoxy groups of neopentyl glycol diglycidyl ether and pentaerythritol tetraglycidyl ether undergo a ring-opening reaction with the amino group of dopamine hydrochloride to obtain the hyperbranched catechol polymer.

4. The method for preparing adhesive filler according to claim 3, characterized in that, The mass ratio of neopentyl glycol diglycidyl ether to dopamine hydrochloride is (0.5~2):

1.

5. The method for preparing adhesive filler according to claim 3, characterized in that, The mass ratio of pentaerythritol tetraglycidyl ether to dopamine hydrochloride is (0.1~1):

1.

6. The method for preparing the adhesive filler according to any one of claims 3 to 5, characterized in that, The ring-opening reaction is carried out in the presence of an alkaloid catalyst.

7. The method for preparing adhesive filler according to claim 6, characterized in that, The alkaloid catalyst is selected from 1,5,7-triazabicyclo[4.4.0]dec-5-ene.

8. The method for preparing adhesive filler according to claim 7, characterized in that, The mass ratio of 1,5,7-triazabicyclo[4.4.0]dec-5-ene to dopamine hydrochloride is (1~2):

1.

9. The method for preparing adhesive filler according to claim 8, characterized in that, The mass ratio of 1,5,7-triazabicyclo[4.4.0]dec-5-ene to dopamine hydrochloride is (1~1.5):

1.

10. The method for preparing adhesive filler according to any one of claims 3-4 and 7-9, characterized in that, include: Dopamine hydrochloride and ethanol were mixed to obtain a mixed solution; The alkaloid catalyst is mixed with the mixed solution to obtain a first mixture; Neopentyl glycol diglycidyl ether and pentaerythritol tetraglycidyl ether were mixed to obtain a second mixture; The first mixture and the second mixture are mixed and reacted at 50~100℃ for 0.5h~1.5h to obtain the adhesive filler.

11. The method for preparing adhesive filler according to claim 10, characterized in that, The mass ratio of dopamine hydrochloride to ethanol is 1:(1~20).

12. The method for preparing adhesive filler according to claim 11, characterized in that, The mass ratio of dopamine hydrochloride to ethanol is 1:(1.5~15).

13. The method for preparing adhesive filler according to claim 12, characterized in that, The mass ratio of dopamine hydrochloride to ethanol is 1:(1.5~10).

14. The method for preparing adhesive filler according to claim 10, characterized in that, The alkaloid catalyst is added to the mixed solution in two or more batches to obtain the first mixture.

15. The method for preparing adhesive filler according to claim 10, characterized in that, The adhesive filler is obtained by drying the product obtained after reacting the first mixture with the second mixture.

16. The method for preparing adhesive filler according to claim 15, characterized in that, The drying temperature is 40~80℃.

17. A plant protein adhesive, comprising plant protein and a cross-linking agent, characterized in that, It also includes the adhesive filler according to claim 1 or 2, or the adhesive filler prepared by the preparation method according to any one of claims 3 to 16; the protein content of the plant protein is 90 to 98 wt%. The crosslinking agent is selected from triglycidylamine; The mass ratio of the plant protein to the triglycidylamine is 1:(0.2~2). The mass ratio of the plant protein to the adhesive filler is 1:(0.2~2).

18. The plant protein adhesive according to claim 17, characterized in that, The plant protein is selected from one or more of soybean meal protein, peanut meal protein, cottonseed meal protein, and corn alcohol meal protein.

19. The plant protein adhesive according to claim 18, characterized in that, The plant protein has a protein content of 93-95 wt%.

20. The plant protein adhesive according to claim 17, characterized in that, The mass ratio of the plant protein to the triglycidylamine is 1:(0.2~1).

21. The plant protein adhesive according to claim 17, characterized in that, The mass ratio of the plant protein to the adhesive filler is 1:(0.2~1).

22. A method for preparing the plant protein adhesive according to any one of claims 17-21, characterized in that, include: The adhesive filler, triglycidylamine, plant protein and water are mixed together to obtain the product.

23. A type of plywood, characterized in that, Includes the plant protein adhesive according to any one of claims 17 to 21, or the plant protein adhesive prepared by the preparation method according to claim 22.

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