Soybean protein adhesive and preparation method thereof

Abstract

The invention belongs to the technical field of bio-based adhesives, and relates to a soybean protein adhesive and a preparation method thereof. According to the invention, a multi-scale structure of a dragonfly wing is referred, bionic design is taken as a starting point, an MXene-Ag component is adopted to simulate a reinforced venation of the wing and is combined with a soft SPI matrix (simulating an energy dissipation film), strong interface combination is realized through a Schiff base reaction and a hydrogen bond, and 3-carboxyphenylboronic acid is added for further optimization, so that the mechanical property of the wing is improved. A cross-linked network of amido bonds and boric acid ester bonds is formed, and the finally obtained multilevel structure adhesive shows excellent comprehensive properties including excellent toughness, mechanical strength and water resistance, and also has the characteristics of natural antibacterial property, mildew resistance and flame retardance.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of bio-based adhesives, and relates to a soy protein adhesive and a preparation method thereof. BACKGROUND

[0002] At present, in the fields of furniture manufacturing, floor laying and building construction, wood adhesives still rely heavily on chemical products derived from fossil fuels, among which formaldehyde-based (such as urea-formaldehyde resin, phenol-formaldehyde resin) and epoxy resin adhesives are representative. These adhesives, especially aldehyde-based products, continuously release volatile organic compounds (VOCs) such as formaldehyde and phenol in the whole life cycle of production and use, which not only poses a serious threat to indoor air quality and damages human health (such as causing respiratory diseases, allergies and even cancer), but also causes long-term pressure on the ecological environment due to the non-renewable raw material attribute and difficult-to-degrade waste. In the face of the dual challenges of global oil resources dwindling and environmental problems (including climate change and pollution) becoming increasingly serious, developing environmentally friendly adhesives based on natural resources that are renewable, biodegradable and have excellent processing performance has become an important research direction in the fields of material science and green manufacturing.

[0003] Soy protein isolate (SPI) as a widely available and low-cost agricultural byproduct has shown great potential as a sustainable adhesive in the manufacturing of wood-based panels. However, the presence of a large number of hydrophilic groups and nutrients in its molecules also leads to obvious deficiencies in water resistance, mechanical strength and storage stability of SPI adhesives. To overcome these limitations, researchers have tried various modification strategies, including protein denaturation, chemical crosslinking, biomimetic modification and nano-enhancement. Studies have shown that compounds containing epoxy groups such as polyamide-epichlorohydrin, epoxy silane coupling agent and epoxy resin can effectively improve the wet shear strength of adhesives, but these substances often exacerbate the brittleness of the adhesive layer while increasing the crosslinking density. The current mainstream modification scheme for SPI adhesives still relies on petroleum-based crosslinking agents and chemical fungicides, which not only introduces harmful chemicals but also may weaken the mechanical toughness of the material and increase production costs, thereby to some extent weakening the ecological and economic advantages of SPI as a bio-based material. Therefore, developing SPI adhesives with excellent water resistance, high strength, good toughness and efficient fungicidal performance has become a key issue in promoting the development of this field. SUMMARY

[0004] In view of the limitations of existing soy protein adhesives in water resistance, strength and toughness, and functionality, the present application provides a soy protein adhesive and a preparation method thereof. The method not only effectively improves the water resistance and mechanical properties of the adhesive, but also simultaneously endows it with excellent flame retardant and fungicidal properties.

[0005] The specific technical solutions are as follows:

[0006] A preparation method of a soybean protein adhesive, comprising the following steps:

[0007] S1 obtaining MXene nanosheets;

[0008] S2 preparing MXene / TA-Fe nanosheets: dispersing the MXene nanosheets obtained in step S1 in deionized water, then adding a tannic acid solution and a ferric chloride solution, and adjusting the pH to 9-10 with a tris base to react, and obtaining the MXene / TA-Fe nanosheets after the reaction is completed; 3+ Preparation of nanosheets: dispersing the MXene nanosheets obtained in step S1 in deionized water, then adding a tannic acid solution, a ferric chloride solution, and adjusting the pH to 9-10 with a tris base to react, and obtaining the MXene / TA-Fe 3+ nanosheets after the reaction is completed;

[0009] S3 preparing MXene-Ag nanosheets: dispersing the MXene / TA-Fe 3+ nanosheets obtained in step S2 in deionized water, then adding polyvinylpyrrolidone, glucose, and a silver ammine solution, and obtaining the MXene-Ag nanosheets after the reaction is completed;

[0010] S4 preparing a soybean protein adhesive: dispersing soybean protein in deionized water, then adding the MXene-Ag nanosheets obtained in step S3 and 3-carboxyphenylboronic acid, and uniformly mixing to obtain the soybean protein adhesive.

[0011] Further, in step S1, the MAX phase is mixed with a hydrofluoric acid solution, and the mixture is reacted at 50-70°C for 24-48h to obtain the MXene nanosheets. Preferably, in step S1, the mixing ratio of the MAX phase to the hydrofluoric acid solution is 10-20g:300mL, and the concentration of the hydrofluoric acid solution is 30-50wt%.

[0012] Preferably, in step S2, the concentration of the tannic acid solution is 0.02-0.06mg / mL, and the concentration of the ferric chloride solution is 0.005-0.02mg / mL; the mixing ratio of the MXene nanosheets, the tannic acid solution, and the ferric chloride solution is 30-60mg:1mL:1mL; and the mixing ratio of the MXene nanosheets to the deionized water during the dispersion of the MXene nanosheets in the deionized water is 40-60mg:100mL.

[0013] Preferably, in step S2, the reaction temperature is 25-50°C, and the reaction time is 1-2h.

[0014] Preferably, in step S3, the mixing ratio of the MXene / TA-Fe 3+ nanosheets to the polyvinylpyrrolidone, glucose, and silver ammine solution is 20-80mg:1-6mg:40-100mg:1-5mL, and the concentration of the silver ammine solution is 0.02-0.1mol / L; and the mixing ratio of the MXene / TA-Fe 3+In the process of dispersing the nanosheets in deionized water, MXene / TA-Fe 3+ The mixing ratio of the nanosheets to the deionized water is 20-60 mg:100 mL.

[0015] Preferably, in step S3, the reaction temperature is 25-50 DEG C, and the reaction time is 5-10 min.

[0016] Preferably, in step S4, the mixing mass ratio of the soy protein to the MXene-Ag nanosheets and 3-carboxyphenylboronic acid is 10-20 g:0.05-0.2 g:1-3 g; and the mixing mass ratio of the soy protein to the deionized water is 10-20 g:80-90 g.

[0017] Preferably, in step S4, the soy protein is soy protein isolate.

[0018] The second aspect of the present application provides a soy protein adhesive prepared by the above preparation method.

[0019] Compared with the prior art, the present application has the following beneficial effects:

[0020] The present application refers to the multiscale structure of dragonfly wings, takes bionic design as the starting point, uses MXene-Ag components to simulate the reinforced veins of the wings, combines with the soft SPI matrix (which simulates the energy dissipation film), realizes strong interface combination through Schiff base reaction and hydrogen bond, further optimizes through the addition of 3-carboxyphenylboronic acid, forms a crosslinking network of amide bond and borate ester bond, and finally obtains a multistage structure adhesive which exhibits excellent comprehensive performance, including excellent toughness, mechanical strength and water resistance. The adhesive also has the characteristics of natural antibacterial, mildewproof and flame retardant. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 A wet shear strength change graph of the adhesives obtained for Example 1 and Comparative Examples 1-3;

[0022] Figure 2 A force-displacement curve graph of the adhesives obtained for Example 1 and Comparative Examples 1-3;

[0023] Figure 3 A swelling rate comparison graph of the adhesives obtained for Example 1 and Comparative Examples 1-3;

[0024] Figure 4 An insoluble fraction graph of the adhesives obtained for Example 1 and Comparative Examples 1-3;

[0025] Figure 5 A heat release rate graph of the adhesives obtained for Example 1 and Comparative Examples 1-3;

[0026] Figure 6This is a graph showing the total heat release of the adhesives obtained in Example 1 and Comparative Examples 1-3;

[0027] Figure 7 The image shows a comparison of the anti-mildew properties of the adhesives obtained in Example 1 and Comparative Examples 1-3 under constant temperature of 30°C and 100% relative humidity. Detailed Implementation

[0028] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and should not be construed as limiting the scope of the invention. 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.

[0029] Example 1

[0030] A method for preparing a soybean protein adhesive includes the following steps:

[0031] S1 Obtaining MXene nanosheets: 15g of MAX phase powder was placed in 300mL of hydrofluoric acid solution (40wt%) and etched at 50℃ for 36h. After the reaction was completed, the product was subjected to ultrasonic exfoliation (600W, 30min), deionized water washing, centrifugation (3500r, 10min) in sequence, and finally freeze-dried to obtain MXene nanosheets.

[0032] S2 MXene / TA-Fe 3+ Preparation of nanosheets: 50 mg of MXene nanosheets obtained in step S1 were dispersed in 100 mL of deionized water, followed by the addition of 1 mL of tannic acid solution (0.04 mg / mL) and 1 mL of FeCl3 solution (0.01 mg / mL). The pH was adjusted to 9 with tris(hydroxymethyl)aminomethane, and the reaction was carried out at 25 °C for 1 h. After filtration and freeze-drying, MXene / TA-Fe was obtained. 3+ Nanosheets;

[0033] Preparation of S3 MXene-Ag nanosheets: 50 mg of MXene / TA-Fe obtained in step S2 was used... 3+ The nanosheets were uniformly dispersed in 100 mL of deionized water, and then 4 mg of polyvinylpyrrolidone, 80 mg of glucose and 1 mL of silver ammonia solution (concentration of 0.06 mol / L) were added. After reacting at 25 °C for 7 min, the product was washed with deionized water and finally obtained by freeze drying.

[0034] S4 Preparation of soybean protein adhesive: 15 g of soybean protein isolate was dispersed in 85 g of deionized water and mechanically stirred for 10 minutes; then, 0.15 g of MXene-Ag nanosheet and 2 g of 3-carboxyphenylboronic acid were added to the dispersion and stirred until uniformly mixed, finally obtaining the soybean protein adhesive SPI / MXene-Ag / CPBA.

[0035] Comparative Example 1

[0036] With reference to Example 1, the difference is that in step S4, no MXene-Ag nanosheet is added to obtain the soybean protein adhesive SPI / CPBA.

[0037] Comparative Example 2

[0038] With reference to Example 1, the difference is that in step S4, no 3-carboxyphenylboronic acid is added to obtain the soybean protein adhesive SPI / MXene-Ag.

[0039] Comparative Example 3

[0040] With reference to Example 1, the difference is that in step S4, no MXene-Ag nanosheet and 3-carboxyphenylboronic acid are added to obtain the soybean protein adhesive SPI.

[0041] Performance test

[0042] Figure 1 The wet shear strength change diagram of the adhesives obtained in Example 1 and Comparative Examples 1-3 is shown. The prepared adhesive was coated on poplar veneer with a sizing amount of 200 g / m² on one side, and was assembled into a three-layer structure with uncoated veneer according to the principle of vertical texture; then, hot pressing was performed at 120°C and 1.0 MPa for 6 minutes to form; according to the national standard, the standard test piece of 100×25 mm was cut, soaked in a constant temperature water bath at 63°C for 3 hours, then cooled at room temperature for 10 minutes, and then the wet shear strength was evaluated. From Figure 1 It can be seen that the introduction of MXene-Ag nanosheet can form an organic-inorganic hybrid structure inspired by the structure of dragonfly wings in the adhesive matrix, and this enhancement mechanism is mainly realized through the formation of Schiff base and strong hydrogen bond interaction, which synergistically improves the mechanical properties of the adhesive; the introduction of crosslinking agent CPBA significantly enhances the mechanical properties of SPI / MXene-Ag adhesive, and the wet shear strength reaches 1.19 MPa, which is increased by 108.8% compared with pure SPI adhesive, which is not only better than the system with only MXene-Ag or CPBA added, but also shows a significant synergistic enhancement effect. The addition of CPBA not only strengthens the crosslinking network structure of the adhesive through covalent bond, but also connects the polymer matrix and MXene-Ag nanosheet as a molecular bridge, thereby effectively improving the interfacial bonding and stress transfer efficiency. The debonding work and the fracture toughness of the cured adhesive show a positive correlation.Figure 2 The force-displacement curve of the adhesives obtained in Example 1 and Comparative Examples 1-3 was obtained by integrating the force-displacement curve. The adhesive work of the SPI / MXene-Ag / CPBA adhesive reached 0.359 J, which was 312.6% higher than that of the pure SPI adhesive (0.087 J). This significant enhancement effect, combined with the change of the breaking strain from 0.63 mm to 1.08 mm, indicated that the material fracture mode changed from brittle failure to more ductile and ductile fracture behavior. Figures 3-4 The swelling rate and insoluble fraction of the adhesives obtained in Example 1 and Comparative Examples 1-3 were compared, and it was found that the SPI / MXene-Ag / CPBA adhesive had lower swelling rate and higher insoluble fraction than the pure SPI adhesive, indicating that the addition of MXene-Ag and CPBA significantly improved the water resistance of the adhesive. To further evaluate the flame retardant performance of the SPI / MXene-Ag / CPBA adhesive, its heat release rate (HRR) and total heat release (THR) were tested. Figures 5-6 The heat release rate and total heat release of the adhesives obtained in Example 1 and Comparative Examples 1-3 were compared, and it was found that the peak HRR of the SPI / MXene-Ag / CPBA adhesive was significantly reduced from 143.7 W / g to 68.9 W / g, a decrease of 52.05% compared with the pure SPI adhesive; at the same time, the THR was also reduced from 9.3 kJ / g to 7.3 kJ / g. This was mainly due to the introduction of components with better heat resistance (CPBA) and the formation of stable interfacial bridging structure on the MXene nanosheet, which together enhanced the flame retardant performance of the SPI-based adhesive.

[0043] A certain amount of fully cured adhesive powder was placed uniformly in a disposable culture dish, and then the adhesive samples were placed in a constant temperature and humidity chamber with a temperature of 30°C and a relative humidity of 100% for observation and analysis. The state of the adhesive was observed every 12 hours, and the photographs were recorded with a mobile phone. Figure 7 The mold resistance test of the adhesives obtained in Example 1 and Comparative Examples 1-3 under the condition of constant temperature 30°C and 100% relative humidity was compared, and the results showed that the cured SPI adhesive had obvious mold spots within 7 days, while the cured SPI / MXene-Ag / CPBA adhesive had no mold growth even after 110 days, which indicated that CPBA and MXene-Ag could effectively inhibit fungal erosion through synergistic effect, and the adhesive had excellent mold resistance.

[0044] The above only describes the preferred embodiments of the present application and does not limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a soy protein adhesive, characterized by, The method comprises the following steps: S1: obtaining MXene nanosheets; S2 MXene / TA-Fe 3+ Preparation of nanosheets: the MXene nanosheets obtained in step S1 were dispersed in deionized water, then tannic acid solution, iron chloride solution were added, and the pH was adjusted to 9-10 with tris(hydroxymethyl)aminomethane for reaction, and MXene / TA-Fe was obtained after the reaction was completed 3+ nanosheets Preparation of S3 MXene-Ag nanosheets: The MXene / TA-Fe 3+ nanosheets obtained in step S2 were dispersed in deionized water, followed by the addition of polyvinylpyrrolidone, glucose and silver ammine solution, and MXene-Ag nanosheets were obtained after the reaction was completed; S4: preparing a soy protein adhesive: dispersing soy protein in deionized water, then adding the MXene-Ag nanosheets obtained in step S3 and 3-carboxyphenylboronic acid, and uniformly mixing to obtain the soy protein adhesive.

2. The production method according to claim 1, characterized by, In step S1, the MAX phase is mixed with a hydrofluoric acid solution, and the mixture is reacted at 50-70℃ for 24-48h to obtain MXene nanosheets.

3. The preparation method according to claim 1, characterized in that, In step S2, the concentration of the tannic acid solution is 0.02-0.06mg / mL, and the concentration of the ferric chloride solution is 0.005-0.02mg / mL; the mixing ratio of the MXene nanosheets, the tannic acid solution and the ferric chloride solution is 30-60mg:1mL:1mL.

4. The production method according to claim 1, characterized by, In step S2, the reaction temperature is 25-50℃, and the reaction time is 1-2h.

5. The method of claim 1, wherein, In step S3, MXene / TA-Fe 3+ The ratio of the nanosheet, polyvinylpyrrolidone, glucose and silver ammine solution is 20-80 mg: 1-6 mg: 40-100 mg: 1-5 mL, and the concentration of the silver ammine solution is 0.02-0.1 mol / L.

6. The method of claim 1, wherein, In step S3, the reaction temperature is 25-50℃, and the reaction time is 5-10min.

7. The preparation method according to claim 1, characterized in that, In step S4, the mixing mass ratio of the soy protein, the MXene-Ag nanosheets and the 3-carboxyphenylboronic acid is 10-20g:0.05-0.2g:1-3g.

8. The method of claim 1, wherein, In step S4, the soy protein is soy protein isolate.

9. A soy protein adhesive prepared by the preparation method according to any one of claims 1-8.

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