Wet state maintaining type vegetable protein adhesive as well as preparation method and application thereof

Abstract

The invention relates to the technical field of adhesives, and provides a wet state maintaining type vegetable protein adhesive as well as a preparation method and application thereof. The hyperbranched catechol polymer adhesive filler disclosed by the invention is prepared by carrying out ring-opening reaction on epoxy groups of neopentyl glycol diglycidyl ether and pentaerythritol tetraglycidyl ether and amino groups of dopamine hydrochloride. Meanwhile, the vegetable protein adhesive is prepared from vegetable protein, a cross-linking agent and the adhesive filler according to a certain proportion. According to the adhesive filler and the corresponding vegetable protein adhesive, the defect that in the prior art, a bio-based adhesive, especially a vegetable protein adhesive, is poor in product performance due to poor moisture retention can be overcome.

Description

Technical Field

[0001] The present invention relates to the technical field of adhesives, and particularly to a wet-state maintaining plant protein adhesive and its preparation method and application. Background Art

[0002] With the increasing popularity of environmental protection concepts and the continuous enhancement of the demand for sustainable development, the application of traditional petroleum-based polymer materials in multiple fields has been gradually restricted, especially in the adhesive industry. The deficiencies of petroleum-based adhesives in terms of environmental protection, resource consumption, and biodegradability have prompted the industry to continuously seek green and renewable alternative materials.

[0003] Natural bio-based adhesives, such as plant protein adhesives, have become an ideal choice to replace traditional synthetic adhesives due to their wide sources, environmental friendliness, and good biodegradability. In recent years, bio-based adhesives have received extensive attention and research in multiple industries such as wood processing, paper products, textiles, and packaging due to their good performance and low-carbon characteristics.

[0004] Although bio-based adhesives have significant advantages in terms of environmental friendliness, they still face certain technical challenges in the actual application process. This is mainly because the moisture retention of bio-based adhesives is relatively poor, which leads to the easy influence on production efficiency and product quality during long-term storage or transportation.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] The present invention provides a wet-state maintaining plant protein adhesive and its preparation method and application, aiming to solve the defect of insufficient product performance caused by poor moisture retention of bio-based adhesives, especially plant protein adhesives, in the prior art.

[0007] Specifically, the present invention provides an adhesive filler, comprising: a hyperbranched catechol polymer (HBP) obtained by the 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 comprises phenolic hydroxyl groups and a hydrophobic carbon skeleton.

[0008] The present invention provides an adhesive filler containing the hyperbranched catechol polymer as described above. Since the hyperbranched catechol polymer has abundant phenolic hydroxyl groups, it can form extensive hydrogen bonds with water molecules and exhibits excellent hydrophilicity. When used as an adhesive filler, through the crosslinking agent TGA, covalent crosslinking and a large number of hydrogen bonds are formed and evenly distributed in the adhesive system. The hydration process of the hyperbranched catechol polymer also enhances the wettability of the adhesive and reduces the interfacial tension. In addition, the hydrophobic carbon skeleton of the hyperbranched catechol polymer will disrupt the hydration layer on the bonding surface, expose the bonding surface, and promote the hydrogen bond interaction 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 assistance of hydrogen bonds and π-π interactions, the synergistic effect of the polar hydroxyl groups and the non-polar carbon skeleton of the hyperbranched catechol polymer improves the wettability and adhesion of the prepared adhesive, enabling it to be evenly distributed on the substrate surface, fill the microgrooves, and improve the pre-pressing strength and dry-wet shear strength of the adhesive.

[0009] Therefore, the above hyperbranched catechol polymer of the present invention endows the adhesive with certain hygroscopicity. Moreover, the hyperbranched catechol polymer easily forms a multi-crosslinked network structure with other components in the adhesive system, improving the comprehensive properties such as the moisture retention performance and mechanical properties of the adhesive 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 - 150,000 Da; Preferably, the value range of Mw / Mn of the hyperbranched catechol polymer is 0.8 - 1.2; Preferably, the hyperbranched catechol polymer is in a high-viscosity state at a temperature of 273 K and reaches a high-elastic state at a temperature above 298 K.

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

[0012] The research found that, compared with other reactive raw materials, such as tannins and gallic acid, etc., dopamine hydrochloride (DOPA) used in the present invention has a stronger intermolecular cross-linking ability in the preparation of the hyperbranched catechol polymer due to the unique characteristics of the coexistence of phenolic hydroxyl groups and amino groups. The amino group and hydroxyl group in DOPA can play a dual role in the polymerization reaction: on the one hand, the amino group participates in the polymerization reaction and forms stable molecular chains with the epoxy skeleton and the cross-linking agent respectively; on the other hand, the phenolic hydroxyl group produces a synergistic effect with other functional groups between molecules through hydrogen bonds, thereby significantly improving the moisture retention and pre-pressing strength of the adhesive. Therefore, this hyperbranched catechol polymer based on dopamine hydrochloride has the above structural advantages, thus significantly improving the comprehensive application performance of the plant protein adhesive.

[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 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[4.4.0]dec-5-ene (TBD); More preferably, the mass ratio of 1,5,7-triazabicyclo[4.4.0]dec-5-ene to dopamine hydrochloride is (1~2):1, preferably (1~1.5):1.

[0014] The research found that using 1,5,7-triazabicyclo[4.4.0]dec-5-ene as the catalyst has more technical advantages.

[0015] According to the preparation method of the adhesive filler provided by the present invention, it includes: Mix dopamine hydrochloride and ethanol to obtain a mixed solution; preferably, the mass ratio of dopamine hydrochloride to ethanol is 1:(1~20), preferably 1:(1.5~15), and more preferably 1:(1.5~10); Mix the alkaloid catalyst with the mixed solution to obtain a first mixture; preferably, the alkaloid catalyst is added to the mixed solution in more than two times to obtain the first mixture; Mix neopentyl glycol diglycidyl ether and pentaerythritol tetraglycidyl ether to obtain a second mixture; The first mixture and the second mixture are mixed, and reacted at 50-100° C. for 0.5 h-1.5 h to obtain the adhesive filler; preferably, the product obtained after the first mixture and the second mixture react is subjected to rotary evaporation to obtain the adhesive filler, and further preferably, the drying temperature is 40-80° C.

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

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

[0018] In a third aspect, the present invention further provides a plant protein adhesive, comprising plant protein and a cross-linking agent, and also comprising the adhesive filler as described above, or the adhesive filler prepared by the preparation method as described above.

[0019] Plant protein does not contain any toxic substances, is low-cost, and is conducive to industrial application. How to improve the moisture retention of plant protein while maintaining its green and environmentally friendly characteristics has always been a key technical problem that needs to be solved in the industry. Research has found that the use of the above-mentioned adhesive fillers, combined with the role of cross-linking agents, can be evenly mixed with the plant protein system. The adhesive fillers are distributed in the plant protein system to form covalent and hydrogen bond connections, thereby forming a multi-cross-linked network structure, which is beneficial to stress balance, and synergistically improves the moisture retention performance of the adhesive, and is beneficial to the uniformity and stability of the adhesive system.

[0020] According to the plant protein adhesive provided by the present invention, the cross-linking agent is selected from triglycidylamine.

[0021] In the present invention, the selection of the cross-linking agent has a certain influence on the application performance of the plant protein adhesive of the present invention. When the above-mentioned adhesive filler is used, the cross-linking agent is preferably triglycidylamine. The above-mentioned adhesive filler and triglycidylamine can undergo chemical cross-linking by ring-opening grafting, 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 a combination of two or more of soybean meal protein, peanut meal protein, cottonseed meal protein and corn alcohol meal protein; further preferably, the protein content of the plant protein is 90~98wt%, preferably 93~95wt%.

[0023] For plant protein adhesives, the proteins in plant proteins can provide abundant functional groups such as amino and carboxyl groups, and these groups play a key role in cross-linking reactions. Therefore, the content of these groups has a great influence on the cross-linking density of the adhesive. It has been found that the adhesive filler of the present invention has more application advantages for plant proteins with a protein content of more than 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 preparation method of the plant protein adhesive as described above, including: mixing the adhesive filler, triglycidylamine, plant protein and water to obtain the product. Preferably, the mass ratio of the plant protein to the water is 1:(20 - 80), preferably 1:(20 - 50). More preferably, the preparation method includes the following steps: Mixing the plant protein and water to obtain a first product; Mixing the first product with the adhesive filler to obtain a second product; Mixing the second product with the cross-linking agent to obtain the plant protein adhesive.

[0027] The mixing of the second product and the cross-linking agent is carried out by mechanical stirring; the conditions of the mechanical stirring are: stirring at a speed of 800 - 1200 rpm for 0.1 - 1.5 hours at 0 - 40 °C; preferably, the conditions of the mechanical stirring are: stirring at a speed of 800 - 1000 rpm for 0.5 - 1 hour at 15 - 35 °C.

[0028] The method for preparing the adhesive of the present invention is simple, has high efficiency, no release of harmful substances, high reactivity of the product, good processability, and stable performance of each batch.

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

[0030] A wet-state retention type plant protein adhesive, its preparation method and application provided by the present invention obtain a specific hyperbranched catechol polymer through the ring-opening reaction of neopentyl glycol diglycidyl ether, pentaerythritol tetraglycidyl ether and dopamine hydrochloride, and this hyperbranched catechol polymer can be used as an adhesive filler.

[0031] Furthermore, the present invention also prepares a plant protein adhesive through a combination of an adhesive filler containing a hyperbranched catechol polymer, a cross-linking agent, and a plant protein. It has excellent moisture retention performance. Compared with traditional functional fillers, the adhesive filler of the present invention is more conducive to improving the moisture retention performance of the plant protein adhesive. Its mass retention rate can reach 73.53% after being exposed for 40 hours in a controlled environment (25°C, relative humidity 60%), the open time can reach 2.5 h, and the pot life can reach 80 h.

[0032] Moreover, by optimizing the ratio of each raw material, the overall performance of the plant protein adhesive can be improved. When the obtained 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, the pre-pressing strength can reach 1.31 MPa, the dry shear strength can reach 2.1 MPa, and the wet shear strength can reach 1.45 MPa. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

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

[0035] Figure 2 a-i are the microscopic structure characterization results and reaction process analysis diagrams of the adhesive filler prepared in Example 1A provided by the present invention.

[0036] Figure 3 It is a state diagram of the adhesive filler prepared in Example 1A provided by the present invention at a temperature of 273K; Figure 4 It is a state diagram of the adhesive filler prepared in Example 1A provided by the present invention at a temperature of 298K; Figure 5 It is a state diagram of the adhesive filler prepared in Example 1A provided by the present invention at a temperature of 313K. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0037] To make the objectives, technical solutions, and advantages of the present invention clearer, the following will clearly and completely describe the technical solutions in the present invention in conjunction with the accompanying drawings in the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention without making creative efforts fall within the scope of protection of the present invention.

[0038] The following will describe Figures 1-5 a wet-state maintaining plant protein adhesive and its preparation method and application of the present invention.

[0039] The experimental methods used in the following examples are all conventional methods unless otherwise specified. The materials, reagents, etc. used in the following examples can all be obtained from commercial channels unless otherwise specified.

[0040] In the present invention, if the percentage sign "%" is involved, unless otherwise specified, it refers to the mass percentage; however, for the percentage of a solution, unless otherwise specified, it means the number of grams of solute contained in 100 ml of the solution; for the percentage between liquids, it refers to the volume ratio at 20°C.

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

[0042] Neopentyl glycol diglycidyl ether, pentaerythritol tetraglycidyl ether, dopamine hydrochloride, and 1,5,7-triazabicyclo[4.4.0]dec-5-ene are provided by Science Compass Testing Platform Co., Ltd. located in Hangzhou, China.

[0043] The crosslinking agent trisglycidylamine, polyamide epichlorohydrin resin, and wooden boards with a moisture content of 7% - 10% are purchased from Shandong Qiansen Group Co., Ltd.

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

[0045] (2) Continue to add 8 g of 1,5,7-triazabicyclo[4.4.0]dec-5-ene (the 1,5,7-triazabicyclo[4.4.0]dec-5-ene is added in three equal portions) to the three-necked flask and stir evenly for 4 hours, and keep the reaction temperature at 60°C.

[0046] (3) Slowly mix 3 g of neopentyl glycol diglycidyl ether and 1 g of pentaerythritol tetraglycidyl ether and stir well. Then, transfer the resulting mixture to a three-necked flask and react it with dopamine hydrochloride, ethanol, and 1,5,7-triazabicyclo[4.4.0]dec-5-ene at 60 °C and a rotation speed of 300 rpm for 3 hours.

[0047] (4) Dry the obtained product (pressure: 0.1 MPa; temperature: 60 °C) for 0.5 hours to obtain the adhesive filler.

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

[0049] (2) Continue to add 4 g of 1,5,7-triazabicyclo[4.4.0]dec-5-ene (added in three equal portions) to the three-necked flask and stir evenly for 4 hours, keeping the reaction temperature at 60 °C.

[0050] (3) Slowly mix 3 g of neopentyl glycol diglycidyl ether and 1 g of pentaerythritol tetraglycidyl ether and stir well. Then, transfer the resulting mixture to a three-necked flask and react it with dopamine hydrochloride, ethanol, and 1,5,7-triazabicyclo[4.4.0]dec-5-ene at 60 °C and a rotation speed of 300 rpm for 3 hours.

[0051] (4) Dry the obtained product (pressure: 0.1 MPa; temperature: 60 °C) for 0.5 hours to obtain the adhesive filler.

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

[0053] (2) Continue to add 8 g of 1,5,7-triazabicyclo[4.4.0]dec-5-ene (added in three equal portions) to the three-necked flask and stir evenly for 4 hours, keeping the reaction temperature at 60 °C.

[0054] (3) Slowly mix 4 g of neopentyl glycol diglycidyl ether and 2 g of pentaerythritol tetraglycidyl ether and stir well. Then, transfer the resulting mixture to a three-necked flask and react it with dopamine hydrochloride, ethanol, and 1,5,7-triazabicyclo[4.4.0]dec-5-ene at 60 °C and a rotation speed of 300 rpm for 3 hours.

[0055] (4) Dry the obtained product (pressure: 0.1 MPa; temperature: 60 °C) for 0.5 h to obtain the adhesive filler.

[0056] Examples 1B to 3B This example provides a method for preparing a moisture-retaining plant protein adhesive. The process is as follows: Add 15 kg of plant protein to 85 kg of water as the dispersion medium, mechanically stir for 6 minutes, then add 10 kg of the adhesive filler of Examples 1A to 4A and 10 kg of triglycidylamine, and continue mechanical stirring for 30 minutes until a uniform paste is discharged, thus obtaining the moisture-retaining plant protein adhesive.

[0057] Among them, the adhesive filler of Example 1A is used in Example 1B.

[0058] The adhesive filler of Example 2A is used in Example 2B.

[0059] The adhesive filler of Example 3A is used in Example 3B.

[0060] Example 4B This example provides a method for preparing a moisture-retaining plant protein adhesive. The process is as follows: Add 15 kg of plant protein to 85 kg of water as the dispersion medium, mechanically stir for 6 minutes, then add 8 kg of the adhesive filler of Example 4A and 8 kg of triglycidylamine, and continue mechanical stirring for 30 minutes until a uniform paste is discharged, thus obtaining the moisture-retaining plant protein adhesive.

[0061] Example 5B This example provides a method for preparing a moisture-retaining plant protein adhesive. The process is as follows: Add 15 kg of plant protein to 85 kg of water as the dispersion medium, mechanically stir for 6 minutes, then add 6 kg of the adhesive filler of Example 4A and 3 kg of triglycidylamine, and continue mechanical stirring for 30 minutes until a uniform paste is discharged, thus obtaining the moisture-retaining plant protein adhesive.

[0062] Comparative Example 1 This comparative example provides a method for preparing an adhesive. The process is as follows: Add 30 kg of soybean meal to 70 kg of water as the dispersion medium, mechanically stir for 6 minutes, then add 10 kg of the adhesive filler of Example 1A and 10 kg of triglycidylamine, and continue mechanical stirring for 30 minutes until a uniform paste is discharged.

[0063] Comparative Example 2 This comparative example provides an adhesive. The process is as follows: Add 15 kg of plant protein to 85 kg of water as the dispersion medium, mechanically stir for 6 minutes, then add 10 kg of the adhesive filler of Example 1A and 10 kg of polyamide epichlorohydrin resin, and continue mechanical stirring for 30 minutes until a uniform paste is discharged.

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

[0065] (2) Slowly mix 4 g of neopentyl glycol diglycidyl ether and 2 g of pentaerythritol tetraglycidyl ether and stir well. Then, transfer the obtained mixture to a three-necked flask and react with dopamine hydrochloride, ethanol, and 1,5,7-triazabicyclo[4.4.0]dec-5-ene at 60 °C at a rotation speed of 300 rpm for 3 hours.

[0066] (3) Dry the obtained product (pressure: 0.1 MPa; temperature: 60 °C) for 0.5 hours to obtain the adhesive filler.

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

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

[0069] (2) Slowly mix 4 g of neopentyl glycol diglycidyl ether and 2 g of pentaerythritol tetraglycidyl ether and stir well. Then, transfer the obtained mixture to a three-necked flask and react with dopamine hydrochloride, ethanol, and 1,5,7-triazabicyclo[4.4.0]dec-5-ene at 60 °C at a rotation speed of 300 rpm for 3 hours.

[0070] (3) Dry the obtained product (pressure: 0.1 MPa; temperature: 60 °C) for 0.5 hours to obtain the adhesive filler.

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

[0072] Test Example Perform microstructure testing on the adhesive filler prepared in Example 1A, and the results are as follows: Figure 2 b shows the FTIR spectra of DOPA, NGDE, PTE, and HBP (adhesive filler). In epoxy resin, 899 cm -1The absorption peak at [specific location] was attributed to the epoxy group. After the grafting reaction, the disappearance of this peak indicated that the epoxy groups in NGDE and PTE reacted with the amino groups of DOPA, thereby generating HBP. Specifically, in the FTIR spectrum of DOPA, the peaks between 1650 - 1500 cm -1 and 900 - 770 cm -1 corresponded to the stretching vibration and out-of-plane deformation vibration of N-H in primary amines, respectively. In addition, the C-N stretching vibration peak at 1230 - 1030 cm -1 further confirmed the presence of primary amines in DOPA. However, in the spectrum of HBP, the absorption peaks related to primary amines disappeared, and instead, the peaks of secondary amines and tertiary amines appeared.

[0073] Figure 2 Figure c shows the 1H NMR spectra of DOPA and HBP in DMSO-D6. In the DOPA spectrum, the resonance peak at 1.6 ppm was attributed to the absorption peak of H in primary amines. This peak disappeared in the 1H NMR spectrum of HBP, but a strong absorption peak belonging to H in secondary amines (3.7 ppm) appeared, indicating that the terminal amino group was partially converted to a secondary amino group. These changes verified that DOPA covered the epoxy groups at the ends of the epoxides through chemical reactions, supporting the success of the grafting reaction.

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

[0075] As shown in Figure 2 Figures e - f, the surface of HBP presented a smooth and dense structure, which was significantly different from the characteristics of the hierarchical structure of DOPA in the SEM images. In addition, EDS spectral analysis showed that nitrogen (N) and oxygen (O) elements were uniformly dispersed on the surface of HBP, further verifying that DOPA had been successfully introduced into the hyperbranched polymer. At room temperature, the solidified HBP could be observed as viscous fibers stretched between rubber gloves ( Figure 2 Figure h).

[0076] To better understand the reaction process in the system (as shown in Figure 2 Figure a), the changes in the charge distribution before and after the curing of the hyperbranched polymer were discussed. As shown in Figure 2i. The interaction energy of DOPA@TBD is negative, indicating an attractive force between the particles. Apparently, TBD (1,5,7-triazabicyclo[4.4.0]dec-5-ene) as an alkaloid catalyst helps the spontaneous progress of the click reaction and improves the stability of the reaction system. The charge distribution calculation shows that ( Figure 2 i) in DOPA@TBD, the negative charge (-0.8930 eV) of the nitrogen atom in the amino group is greater than the negative charge (-0.4520 eV) of the oxygen atom in the phenolic hydroxyl group, indicating that the negatively charged N atom in TBD helps the preferential adsorption and activation of the amino group in DOPA. By comparing the static charge distribution of the amino group before and after the click reaction, it is found that the amine group of DOPA@TBD reacts with the epoxy end group in the epoxide to form a hydroxyl group. In this process, more negative charges are transferred from the nitrogen atom to the oxygen atom, resulting in a significant decrease in the charge of the nitrogen atom to -0.5610 eV. This change proves the successful synthesis of HBP.

[0077] As Figures 3-5 can be seen, the viscosity transition of the molecule during temperature change, especially at 273 K, the system shows a high-viscosity state and gradually transitions to a highly elastic state at 298 K.

[0078] Furthermore, the present invention also tested the adhesives obtained in the above-mentioned examples and comparative examples. All tests were repeated three times and the average values were taken.

[0079] The open time refers to the maximum time that the mixed resin and curing agent can be placed on the substrate before bonding. Generally speaking, after applying the glue for a period of time and then bonding, if the final tensile force when bonding immediately after applying the glue is still 80%, it can be deduced as the open time. The pot life refers to the time during which the mixed adhesive can be used for construction after the resin and curing agent are mixed. The pot life considers the situation before the glue is applied to the substrate, while the open time considers the situation after the glue is applied to the substrate.

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

[0081] Lap shear test: Tested using a universal testing machine (UTM, Instron 3365, Norwood, Massachusetts) at a loading rate of 10 mm / min and normal temperature environmental conditions. The tested adhesive was compressed between two poplar strips (100 mm × 25 mm), and the bonding area was 25 mm × 25 mm, at 180 g / m 2The coating rate is evenly applied. The calculation method of the lap shear strength is to divide the force at failure by the overlap area. For each adhesive, at least six measurements are carried out to obtain the average lap shear strength.

[0082] Pre - pressing test: The pre - pressing bonding strength of the adhesive is tested by using poplar veneer (200×200×1.5 mm³) as the substrate for plywood manufacturing. Adhesives with different formulations are evenly coated on one side of the veneer at a coating density of 180 g / m 2 . Then, according to the principle of arranging adjacent veneers vertically, uncoated veneers are stacked between two coated veneers, and pressed at 25°C and 1 MPa for 15 min. After pressing, the plywood is immediately cut into test samples. The pre - pressing strength test is carried out on a UTM equipped with a 5 kN load cell at a loading rate of 10 mm / min until failure. The pre - pressing strength is calculated by dividing the force at failure by the lap area, and all measurements are repeated six times.

[0083] Dry - and - wet shear strength test: To evaluate the bonding performance of the hybrid adhesive, poplar veneer (200×200×1.5 mm³) is used as the substrate for plywood production. Adhesives with different formulations are evenly coated on one side of the veneer at a coating density of 180 g / m². Then, according to the principle of arranging adjacent veneers vertically, uncoated veneers are stacked between two coated veneers. The plywood assembly is pressed in a hot press at 120°C and 1.0 MPa for 6 min. After pressing, the plywood is placed at 20°C for 24 h and then cut into test samples. According to Chinese national standard GB / T17657 - 2013, a universal testing machine (CMT4202, Shenzhen Suns Technology Standards Co., Ltd., China) is used to test the shear strength of the plywood. The dry shear strength of a three - layer plywood specimen (100×25 mm) is measured at a loading rate of 10 mm / min. In the wet shear test, the specimen is immersed in water at 63°C for 3 h, then cooled to room temperature for 10 min before the test. Each specimen is tested six times and the average value is recorded.

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

[0085] Table 1

[0086] Based on the above test results, comparing the examples with Comparative Examples 1 to 4, it can be seen that the materials of the examples perform excellently in multiple key parameters. In terms of pot life and working life, the advantages of Example 1 are more significant. Moreover, in terms of lap shear strength and pre-compression strength, the examples are significantly higher than the comparative examples, indicating that their materials have more superior moisture retention performance. In addition, the examples also have excellent values in terms of mass retention rate, further confirming their superior moisture retention performance. In addition, the examples perform well in dry shear strength and wet shear strength, obviously improving the moisture retention can also greatly optimize their mechanical properties. In summary, the examples perform excellently in terms of moisture retention, pre-compression strength and mechanical strength, and have significant application prospects and technical advantages.

[0087] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing examples, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing examples, or perform equivalent replacements for some of the technical features; and these modifications or replacements 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: include: Hyperbranched catechol polymers obtained by ring-opening reaction of the epoxy groups of neopentyl glycol diglycidyl ether and pentaerythritol tetraglycidyl ether with the amino groups of dopamine hydrochloride: The hyperbranched catechol polymer includes phenolic hydroxyl groups and a hydrophobic carbon skeleton.

2. The adhesive filler according to claim 1, characterized in that: The Mn of the hyperbranched catechol polymer is 80,000 to 150,000 Da; Preferably, the Mw / Mn value of the hyperbranched catechol polymer is in the range of 0.8 to 1.2; Preferably, the hyperbranched catechol polymer is in a high viscosity state at a temperature of 273K, and reaches a high elastic state at a temperature above 298K.

3. The method for preparing the adhesive filler according to claim 1 or 2, characterized in that: include: The hyperbranched catechol polymer is obtained by ring-opening reaction between the epoxy groups of neopentyl glycol diglycidyl ether and pentaerythritol tetraglycidyl ether and the amino groups of dopamine hydrochloride.

4. The method for preparing the adhesive filler according to claim 3, characterized in that: 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 pentaerythritol tetraglycidyl ether to dopamine hydrochloride is (0.1-2):1, preferably (0.1-1):

1.

5. The method for preparing the adhesive filler according to claim 3 or 4, characterized in that: 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; Further preferably, the mass ratio of the 1,5,7-triazabicyclo[4.4.01-5-ene] to dopamine hydrochloride is (1-2):1, preferably (1-1.5):

1.

6. The method for preparing the adhesive filler according to any one of claims 3 to 5, characterized in that: include: Mixing dopamine hydrochloride and ethanol to obtain a mixed solution; preferably, the mass ratio of dopamine hydrochloride to ethanol is 1: (1-20), preferably 1: (1.5-15), and more preferably 1: (1.5-10); Mixing the alkaloid catalyst with the mixed solution to obtain a first mixture; preferably, the alkaloid catalyst is added to the mixed solution twice or more to obtain the first mixture; mixing neopentyl glycol diglycidyl ether and pentaerythritol tetraglycidyl ether to obtain a second mixture; The first mixture and the second mixture are mixed, and reacted at 50-100° C. for 0.5 h-1.5 h to obtain the adhesive filler; preferably, the product obtained after the first mixture and the second mixture react is dried to obtain the adhesive filler, and more preferably, the drying temperature is 40-80° C.

7. A plant protein adhesive comprising plant protein and a cross-linking agent, characterized in that: It also includes the adhesive filler described in claim 1 or 2, or the adhesive filler prepared by the preparation method described in any one of claims 3 to 6.

8. The plant protein adhesive according to claim 7, characterized in that: The cross-linking agent is selected from triglycidylamine; Preferably, the plant protein is selected from one or a combination of two or more of soybean meal protein, peanut meal protein, cottonseed meal protein and corn alcohol meal protein; further preferably, the protein content of the plant protein is 90-98wt%, preferably 93-95wt%; Preferably, the mass ratio of the vegetable protein to the triglycidylamine is 1:(0.2-2), preferably 1:(0.2-1); Preferably, the mass ratio of the plant protein to the adhesive filler is 1:(0.2~2), preferably 1:(0.2~1).

9. The method for preparing the plant protein adhesive according to claim 7 or 8, characterized in that: include: The adhesive filler, triglycidylamine, vegetable protein and water are mixed to obtain the adhesive; Preferably, the mass ratio of the vegetable protein to the water is 1:(20-80), preferably 1:(20-50); Further preferably, the preparation method comprises the following steps: Mixing vegetable protein and water to obtain a first product; mixing the first product with an adhesive filler to obtain a second product; The second product is mixed with a cross-linking agent to obtain the plant protein adhesive.

10. A plywood, characterized in that: It includes the plant protein adhesive according to claim 7 or 8, or the plant protein adhesive prepared by the preparation method according to claim 9.

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