An all-bio-based epoxy soybean oil-based adhesive and a preparation method thereof

Abstract

The application discloses a kind of full biological base adhesive based on epoxy soybean oil and preparation method thereof.Specifically, the method uses epoxy soybean oil as reaction base, citric acid as nucleophilic reagent to open the epoxy ring of epoxy soybean oil, tannic acid as catechol compound to provide adhesion after crosslinking polymerization, and constructs a biological base crosslinking network structure with excellent bonding performance. The present application is an environmentally friendly adhesive developed based on full biological base raw materials, with the outstanding features of non-toxic, renewable and environmentally friendly. The adhesive uses a one-pot synthesis process, which is simple and easy to implement industrial production. In terms of performance, it performs outstandingly, not only has excellent tensile strength and long-term stability, but also has outstanding water resistance and mildew resistance, making it stand out among similar products. In addition, the product has a wide range of raw materials, obvious cost advantage, and high performance and economic benefit.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of adhesive preparation, and particularly relates to a full-bio-based adhesive based on epoxy soybean oil and a preparation method thereof. BACKGROUND

[0002] As an indispensable key auxiliary material in industrial production, the application field of adhesives is continuously expanding with the rapid economic development, and the market demand is showing a sustained growth trend. However, the mainstream adhesive products on the current market are mostly made of harmful chemical substances such as petroleum, formaldehyde and toluene, which not only leads to the release of toxic substances during the use of the products, causing environmental pollution, but also may potentially harm human health. In addition, the permanent bonding characteristics of traditional adhesives also make it difficult to effectively recycle and utilize the materials, further exacerbating the problem of resource waste.

[0003] In order to overcome the limitations of traditional adhesives, researchers have developed various bio-based adhesives, but the existing technologies still have many deficiencies. For example, patent CN 201610999146.0 developed a high-performance full-bio-based epoxy soybean oil resin, which achieved bio-based substitution, but had the defect of large fluctuation in mechanical properties (tensile strength 5-38.5 MPa, elongation at break 55-356%). This may affect the stability of the product. In addition, this technology relies on decanedioic acid and decanediamine to prepare polyamide 1010 prepolymer, although the raw materials are renewable, but the scale production and cost-effectiveness still need to be optimized. The catalysts that may be needed in the curing process also increase the cost and environmental burden. Another patent CN 201811130480.8 proposes an amine curing agent modified polyurethane epoxy soybean oil adhesive, which improves the curing efficiency and bonding performance by introducing a secondary amino group, but still faces problems such as difficult reaction control (high activity of secondary amino group easily leads to rapid curing or side reactions), complex process (requires special polyurethane synthesis process) and strict storage conditions (requires strict moisture protection). These technical bottlenecks limit the industrial application and commercialization of bio-based adhesives.

[0004] Soybean oil, as an abundant agricultural byproduct, has become an ideal raw material to replace petroleum-based epoxy resin due to its renewability, biodegradability and environmental friendliness. Through green chemical processes, soybean oil can react efficiently with peroxymonocarbonate / peroxyacetic acid and other epoxidation reagents to convert into epoxy soybean oil with important application value. The active epoxy groups in the molecular structure of epoxy soybean oil endow it with excellent cross-linking reaction capability, while the long fatty chain structure can significantly enhance the toughness and impact resistance of the material. In addition, epoxy soybean oil also has safety features such as low toxicity and low volatility, further enhancing its environmental advantages and application safety.

[0005] In this system, citric acid exhibits a dual catalytic effect: on the one hand, its hydroxyl and carboxyl groups can activate the epoxy ring through protonation, promoting nucleophilic attack; on the other hand, as a nucleophile, it can directly initiate the ring-opening reaction of the epoxy ring to form a new C-H bond. At the same time, tannic acid, as a key functional component, not only forms a stable hydrogen bond network with epoxy soybean oil, effectively reducing the hydrophilicity of the material, but also inactivates enzymes and active proteins on the surface of mold cells through specific binding, thereby imparting excellent mold resistance to the material.

[0006] Based on the above synergistic effect, the adhesive prepared by the reaction of epoxy soybean oil, tannic acid and citric acid exhibits excellent comprehensive performance and has broad application prospects in the field of environmentally friendly bonding of materials. SUMMARY

[0007] To solve the problems in the above background art, the present application provides a full-bio-based adhesive based on epoxy soybean oil and a preparation method thereof.

[0008] To achieve the above-mentioned objectives, the present application adopts the following technical solutions:

[0009] The full-bio-based adhesive based on epoxy soybean oil according to the present application is prepared from epoxy soybean oil, tannic acid, citric acid and anhydrous ethanol.

[0010] Preferably, the mass ratio of the epoxy soybean oil to the tannic acid and the citric acid is 1:0.4-0.5:0.5-0.6.

[0011] A preparation method of a full-bio-based adhesive based on epoxy soybean oil, comprising the following steps:

[0012] S1: epoxy soybean oil, tannic acid and citric acid are weighed separately;

[0013] S2: tannic acid and citric acid are dissolved in anhydrous ethanol respectively to prepare solutions with a concentration of 0.5 g / mL;

[0014] S3: the epoxy soybean oil is placed in a reaction container and stirred at a constant temperature of 70°C until the system is uniform;

[0015] S4: the tannic acid solution is first added to the system, and after stirring for 5 min to mix uniformly, the citric acid solution is added dropwise;

[0016] S5: the reaction is terminated after stirring at 70°C for 6 h, and the adhesive product is prepared.

[0017] Preferably, the stirring speed in S3 is 1000 rpm, and the heating rate is 5°C / min.

[0018] Preferably, the dropping speed of the citric acid solution in S4 is 1 mL / min.

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

[0020] (1) The epoxy soybean oil-based full-bio-based adhesive prepared by the present application exhibits excellent bonding strength, which is mainly due to the formation of a multi-functional crosslinking network: the epoxy groups of epoxy soybean oil are ring-opened to form hydroxyl groups under the acidic conditions provided by tannic acid and citric acid, which further react with the phenolic hydroxyl groups of tannic acid or the carboxyl groups of citric acid to form covalent crosslinking structures; at the same time, the catechol groups of tannic acid enhance the cohesive strength through hydrogen bonding and metal coordination, and the carboxyl groups of citric acid participate in esterification to expand the crosslinking network. The synergistic effect of the three ultimately forms a high-density crosslinking system (covalent bond + hydrogen bond), significantly improving the mechanical strength and heat resistance of the adhesive.

[0021] (2) The epoxy soybean oil-based full-bio-based adhesive prepared by the present application has excellent water resistance and mildew resistance. In this system, tannic acid is an ideal choice for simulating the function of mussel byssin due to its structural characteristics of rich catechol groups. This special structure not only significantly reduces the hydrophilicity of the material surface, but also makes the key enzymes and functional proteins on the surface of mold cells lose their biological activity by specifically binding to them, thereby endowing the material with excellent mildew resistance. Citric acid plays a key role in this system, as its hydroxyl and carboxyl groups in the molecular structure can activate the epoxy ring through protonation effect, significantly enhancing the attack ability of nucleophiles. In addition, citric acid itself can also act as a nucleophile to directly participate in the reaction, inducing the ring-opening process of the epoxy ring and further promoting the formation of new C-H bonds.

[0022] (3) The adhesive uses full-bio-based raw materials, which are non-toxic and renewable. Its environmentally friendly formula ensures that it will not pollute the environment during production and use, and does not contain any toxic substances, which is harmless to human health. In addition, the adhesive is prepared by one-pot method, which is simple and easy to mass produce. The low cost of raw materials makes the overall production cost have a significant advantage, which is suitable for industrialized application. DETAILED DESCRIPTION

[0023] The technical solutions of the present application are further described below in conjunction with examples.

[0024] Example 1:

[0025] The preparation method of the epoxy soybean oil-based full-bio-based adhesive of the present application comprises the following steps:

[0026] Epoxy soybean oil (10 g), tannic acid (4 g) and citric acid (6 g) were weighed according to the mass ratio of 1:0.4:0.6. The tannic acid and citric acid were dissolved in ethanol respectively to prepare a solution of 0.5 g / mL. The epoxy soybean oil was heated in a constant-temperature magnetic stirrer (the rotation speed was set to 1000 rpm, and the heating rate was 5 ℃ / min) at 70 ℃ to reduce the viscosity, then the tannic acid solution was added, and stirred for 5 min to mix uniformly. Then the citric acid solution was slowly added (1 mL / min), and the reaction was continued for 6 h, finally an amber adhesive with syrup-like fluidity was prepared.

[0027] The epoxy soybean oil-based full-bio-based adhesive prepared in this example exhibited good coating performance, and the shear strength reached 5.178 MPa, showing excellent bonding performance.

[0028] Example 2:

[0029] The preparation method of the epoxy soybean oil-based full-bio-based adhesive of the present application comprises the following steps:

[0030] Epoxy soybean oil (10 g), tannic acid (5 g) and citric acid (5 g) were weighed according to the mass ratio of 1:0.5:0.5. The tannic acid and citric acid were dissolved in ethanol respectively to prepare a solution of 0.5 g / mL. The epoxy soybean oil was heated in a constant-temperature magnetic stirrer (the rotation speed was set to 1000 rpm, and the heating rate was 5 ℃ / min) at 70 ℃ to reduce the viscosity, then the tannic acid solution was added, and stirred for 5 min to mix uniformly. Then the citric acid solution was slowly added (1 mL / min), and the reaction was continued for 6 h, finally an amber adhesive with syrup-like fluidity was prepared.

[0031] The epoxy soybean oil-based full-bio-based adhesive prepared in this example exhibited good coating performance, and the shear strength reached 4.731 MPa, showing excellent bonding performance.

[0032] Example 3:

[0033] The preparation method of the epoxy soybean oil-based full-bio-based adhesive of the present application comprises the following steps:

[0034] Epoxy soybean oil (10 g), tannic acid (5 g) and citric acid (6 g) were weighed according to the mass ratio of 1:0.5:0.6. The tannic acid and citric acid were dissolved in ethanol respectively to prepare a solution of 0.5 g / mL. The epoxy soybean oil was heated in a constant-temperature magnetic stirrer (the rotation speed was set to 1000 rpm, and the heating rate was 5 ℃ / min) at 70 ℃ to reduce the viscosity, then the tannic acid solution was added, and stirred for 5 min to mix uniformly. Then the citric acid solution was slowly added (1 mL / min), and the reaction was continued for 6 h, finally an amber adhesive with syrup-like fluidity was prepared.

[0035] The epoxy soybean oil-based full-bio-based adhesive prepared in the embodiment exhibits good coating performance, and the shear strength reaches 4.271 MPa, showing excellent bonding performance.

[0036] Comparative Example 1

[0037] The preparation method of the epoxy soybean oil-based full-bio-based adhesive of the present application comprises the following steps:

[0038] Epoxy soybean oil (10 g), tannic acid (3 g) and citric acid (6 g) were weighed according to the mass ratio of 1:0.3:0.6. The tannic acid and citric acid were dissolved in ethanol respectively to prepare a solution of 0.5 g / mL. The epoxy soybean oil was heated in a constant-temperature magnetic stirrer at 70°C (the rotation speed was set to 1000 rpm, and the heating rate was 5°C / min) to reduce the viscosity, and then the tannic acid solution was added, and stirred for 5 min to mix uniformly. Then the citric acid solution was slowly added (1 mL / min), and the reaction was continued for 6 h, finally an amber adhesive with syrup-like fluidity was prepared.

[0039] The epoxy soybean oil-based full-bio-based adhesive prepared in the comparative example exhibits good coating performance, and the shear strength is 4.230 MPa. However, due to the insufficient amount of tannic acid, the ratio of epoxy groups to phenolic hydroxyl groups is imbalanced, and the crosslinking network density is reduced, resulting in poorer shear strength compared to the above-mentioned embodiment.

[0040] Comparative Example 2

[0041] The preparation method of the epoxy soybean oil-based full-bio-based adhesive of the present application comprises the following steps:

[0042] Epoxy soybean oil (10 g), tannic acid (3 g) and citric acid (6 g) were weighed according to the mass ratio of 1:0.3:0.6. The tannic acid and citric acid were dissolved in ethanol respectively to prepare a solution of 0.5 g / mL. The epoxy soybean oil was heated in a constant-temperature magnetic stirrer at 70°C (the rotation speed was set to 1000 rpm, and the heating rate was 5°C / min) to reduce the viscosity, and then the tannic acid solution was added, and stirred for 5 min to mix uniformly. Then the citric acid solution was slowly added (1 mL / min), and the reaction was continued for 6 h, finally an amber adhesive with syrup-like fluidity was prepared.

[0043] The epoxy soybean oil-based full-bio-based adhesive prepared in the comparative example exhibits good coating performance, and the shear strength is 4.230 MPa. However, due to the insufficient amount of tannic acid, the ratio of epoxy groups to phenolic hydroxyl groups is imbalanced, and the crosslinking network density is reduced, resulting in poorer shear strength compared to the above-mentioned embodiment.

[0044] Comparative Example 3:

[0045] The method for preparing the epoxy soybean oil-based full-bio-based adhesive of the present application comprises the following steps:

[0046] Epoxy soybean oil (10 g), tannic acid (5 g) and citric acid (7 g) were weighed according to a mass ratio of 1:0.5:0.7. The tannic acid and citric acid were dissolved in ethanol respectively to prepare a 0.5 g / mL solution. The epoxy soybean oil was heated in a constant-temperature magnetic stirrer (rotation speed set to 1000 rpm, heating rate 5°C / min) at 70°C to reduce the viscosity, and then the tannic acid solution was added and stirred for 5 min to mix uniformly. The citric acid solution was slowly added dropwise (1 mL / min), and the reaction was continued for 6 h to finally obtain an amber adhesive with syrup-like fluidity.

[0047] The epoxy soybean oil-based full-bio-based adhesive prepared in this comparative example exhibited good coating performance, and the shear strength was 4.184 MPa. However, the synergistic effect of excessive tannic acid and citric acid would compete for the epoxy groups, resulting in uneven crosslinking network structure, and finally the shear strength was poorer than that of the above-mentioned examples.

[0048] Table 1, Comparison of shear strength of adhesive of examples and comparative examples

[0049] Test piece Shear strength / MPa Example 1 5.178 Example 2 4.731 Example 3 4.271 Comparative Example 1 4.230 Comparative Example 2 4.005 Comparative Example 3 4.184

[0050] The parameter determination methods in the above examples and comparative examples are as follows:

[0051] 1. An aluminum substrate with a size of 75 mm (length) x 27 mm (width) x 2.5 mm (height) was used to accurately coat a square adhesive layer of 27 mm x 27 mm on its surface. The coated sample was aligned and covered with another aluminum plate of the same size, and a special clamp was used for fixation.

[0052] 2. The prepared sample was placed in an oven at 160°C for 72 h of curing treatment.

[0053] 3. The shear strength of the epoxy soybean oil-based full-bio-based adhesive prepared in Examples 1-3 and Comparative Examples 1-3 was tested. An electronic universal testing machine was used to determine the shear strength of the sample, 3 parallel samples were set for each group, the test data were taken as the arithmetic mean value, and the experimental data were processed by statistical analysis method.

[0054] As described above, the epoxy soybean oil-based full-bio-based adhesive prepared by the present application shows excellent coating performance and shear strength. The present application provides an epoxy soybean oil-based full-bio-based adhesive and a preparation method thereof, which significantly improves the adhesion performance of the adhesive by introducing tannic acid and citric acid, while maintaining the non-toxic and renewable characteristics. In addition, the adhesive is prepared by one-pot method, which is simple in process and easy to mass production, and is suitable for industrial application.

[0055] Although embodiments of the present application have been disclosed in connection with the above description and drawings, it should be understood that they are not limited thereto. Rather, they are applicable to various fields of endeavor within the general scope of the application. Those skilled in the art will readily devise additional modifications and variations without departing from the scope of the application. Accordingly, the application is not limited to the specific details described herein.

Claims

1. A fully bio-based adhesive based on epoxidized soybean oil, characterized in that, The raw materials for preparing the adhesive include epoxidized soybean oil, tannic acid, citric acid and anhydrous ethanol, wherein the mass ratio of epoxidized soybean oil to tannic acid and citric acid is 1:0.4:0.5-0.

6.

2. A method for preparing a fully bio-based adhesive based on the epoxidized soybean oil of claim 1, characterized in that, Includes the following steps: S1: Weigh out epoxidized soybean oil, tannic acid and citric acid respectively; S2: Dissolve tannic acid and citric acid separately in anhydrous ethanol to prepare a solution with a concentration of 0.5 g / mL; S3: Place the epoxidized soybean oil in a reaction vessel and stir at a constant temperature of 70°C until the system is homogeneous; S4: Add tannic acid solution to the system, stir continuously for 5 minutes to mix evenly, and then add citric acid solution drop by drop; S5: The reaction was terminated after continuous stirring at 70℃ for 6 hours to obtain the adhesive product.

3. The preparation method according to claim 2, characterized in that, The stirring speed in S3 is 1000 rpm, and the heating rate is 5℃ / min.

4. The preparation method according to claim 2, characterized in that, The dropping rate of the citric acid solution in S4 is 1 mL / min.