An environmentally friendly biomass-based underwater adhesive, its preparation method and application

Abstract

This invention relates to the field of adhesive technology, and discloses an environmentally friendly biomass-based underwater adhesive, its preparation method, and its applications. The adhesive is prepared by one-step melt copolymerization of three biomass raw materials: lipoic acid, caffeic acid, and cysteine. This system utilizes the ring-opening polymerization of lipoic acid to form a dynamic disulfide bond network providing cohesive force, the catechol groups of caffeic acid to provide various interfacial interactions with the substrate, and the thiol groups of cysteine ​​to simultaneously participate in network construction and inhibit catechol oxidation, thereby synergistically achieving high-strength and durable underwater adhesion. The adhesive achieves an underwater adhesion strength of up to 5.5 MPa on iron sheets, remains stable in various acid, alkali, and salt environments, and can be repeatedly recycled through hot melting. This invention uses entirely bio-based raw materials, employs a simple and non-toxic process, and is suitable for underwater remediation, marine engineering, and other fields.

Description

Technical Field

[0001] This invention relates to the field of adhesive technology, and in particular to a high-performance, environmentally friendly adhesive based on biomass raw materials that can be used in humid and underwater environments, and its preparation method. Background Technology

[0002] Adhesives are a class of polymeric materials that can tightly bond different material surfaces and transfer stress, and are widely used in modern industry and daily life. However, most existing adhesives are primarily suitable for air or dry environments; when bonding in fog, dew, damp surfaces, or underwater environments, the hydration layer on the substrate surface hinders sufficient contact between the adhesive and the substrate and reduces wettability, resulting in a significant decrease in adhesion strength. Even prolonged immersion in water can cause plasticization, swelling, degradation, and hydrolysis of the adhesive, ultimately leading to bond failure. Therefore, developing high-performance underwater adhesives has become an important research direction in this field.

[0003] While some research (such as hydrogels and synthetic polymer adhesives) has been dedicated to solving underwater adhesion problems, these solutions often have limitations in terms of raw material sourcing, environmental friendliness, complexity of preparation processes, or long-term stability, making it difficult to meet the needs of green and sustainable development. Specifically, existing high-performance underwater adhesive technologies still face prominent contradictions between environmental protection, cost, and process. For example, the fluorinated ionomer gel adhesive reported in authorized patent CN115895527B, although exhibiting excellent adhesion performance, has a long synthesis route and uses fluorine-containing raw materials, requiring improvements in cost and environmental friendliness. The adhesive reported in authorized patent CN114195651B achieves rapid adhesion, but its monomer synthesis and purification steps are complex, and the preparation process requires the use of organic solvents or ionic liquids. In addition, many mussel-inspired hydrogels suffer from problems such as easy oxidation of catechols and insufficient long-term stability. Therefore, developing an underwater adhesive with raw materials entirely derived from renewable biomass, a simple and rapid preparation process (requiring no complex synthesis or solvents), and simultaneously possessing high strength, long durability, and excellent environmental resistance has significant scientific and application value. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides an environmentally friendly biomass-based underwater adhesive and its preparation method.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] An environmentally friendly biomass-based underwater adhesive is obtained by heating and melting thioctic acid, caffeic acid and cysteine ​​to form a homogeneous melt system and then stirring and reacting. It is a hot-melt reactive adhesive that can be used for bonding in underwater or humid environments.

[0007] The core of this invention lies in the fact that three biomass raw materials—lipoic acid, caffeic acid, and cysteine—in a specific ratio, can form a eutectic system under heating conditions of 155℃-185℃, thereby forming the target adhesive through a one-step melt copolymerization reaction without the need for any external solvents. In this reaction system, each component has a clear function and synergistic effect: 1. Lipoic acid: As the main framework, it undergoes ring-opening polymerization upon heating, constructing a three-dimensional network with both strength and toughness through dynamic and reversible disulfide bond (-SS-) crosslinking, and endowing the material with inherent recyclability. 2. Caffeic acid: As a functional monomer, its catechol (catechol) group is a strong interfacial adhesion unit. It can effectively displace water molecules from the surface of the adhered object and form diverse non-covalent bonds (such as hydrogen bonds, coordination bonds, and π-π stacking) with various substrates such as metals, ceramics, and plastics, providing universal and strong interfacial adhesion. 3. Cysteine: As a key regulator, it plays a "dual-effect" role. Its thiol group (-SH) can participate in the ring-opening polymerization of lipoic acid, regulating the network crosslinking density and enhancing cohesion. More importantly, it can act as a highly efficient antioxidant, effectively inhibiting the oxidative deactivation of catechol groups in caffeic acid in an underwater environment, thereby significantly improving the long-term stability of the adhesion. The unique combination and synergy of these three components enable the adhesive of this invention to simultaneously achieve excellent properties that are difficult to achieve with traditional technologies, such as high strength (balance between cohesion and interfacial forces), long durability (antioxidant), wide environmental tolerance (water, acid, alkali and salt resistance), and green environmental protection throughout its entire life cycle (bio-based and recyclable).

[0008] Preferably, the adhesive raw material, by weight percentage, comprises: 60%~75% lipoic acid, 10%~23% caffeic acid, and 5%~20% cysteine; more preferably, it comprises 62.5%~71.5% lipoic acid, 14.25%~21.5% caffeic acid, and 7%~18.75% cysteine. Even more preferably, the mass ratio of lipoic acid, caffeic acid, and cysteine ​​in the adhesive raw material is 10:3:2.

[0009] The present invention also provides a method for preparing any of the above-mentioned environmentally friendly biomass-based underwater adhesives, comprising the following steps:

[0010] S1: Place the adhesive raw materials lipoic acid, caffeic acid, and cysteine ​​together in a reaction vessel;

[0011] S2: Place the reaction vessel at a heating temperature and heat it to 155℃~185℃ to form a homogeneous molten system of lipoic acid, caffeic acid, and cysteine;

[0012] S3: At the stated temperature, start stirring to carry out the reaction. After the reaction is complete, the adhesive can be obtained.

[0013] Preferably, the heating temperature is 155℃~185℃. Within this temperature range, the three raw materials, lipoic acid, caffeic acid, and cysteine, can form a eutectic mixture. The principle is that the interactions between different molecules (such as hydrogen bonds) interfere with the originally regular molecular lattice arrangement of each component, thereby significantly reducing the energy barrier that needs to be overcome for the overall melting of the mixture. A more preferred heating temperature is 165℃.

[0014] Preferably, the stirring speed is 400 r / min to 600 r / min (155℃ to 185℃). A low stirring speed will result in uneven stirring, while a high speed will easily cause splashing and waste. More preferably, it is 500 r / min.

[0015] Preferably, the stirring reaction time is 0.5h~1.5h (155℃~185℃), more preferably 1h.

[0016] Preferably, the adhesive exhibits an underwater adhesion strength of up to 5.5 MPa on the iron sheet substrate, and this adhesion strength is maintained for at least 4 weeks, demonstrating excellent continuous stability of high underwater adhesion strength. It can be recycled and reused at least 10 times underwater and in air, with a high recycling rate, and is adaptable to various environments such as air, underwater, and seawater, exhibiting excellent environmental applicability.

[0017] The present invention also provides an application of any of the above-mentioned environmentally friendly biomass-based underwater adhesives in the fields of adhesives and adhesives in liquid environments, especially in adhesives used in wet or underwater environments.

[0018] Preferably, the adhesive is suitable for substrates including common materials such as iron, copper, aluminum, stainless steel, and wood.

[0019] Compared with the prior art, the beneficial effects of the present invention are mainly reflected in:

[0020] (1) In a single material system, the biomass source of raw materials, the solvent-free simplification of the preparation process, and the high strength and long durability of the adhesive properties are achieved simultaneously. Specifically: ① In terms of raw material selection, the adhesive is composed entirely of three biomass derivatives: lipoic acid, caffeic acid, and cysteine, avoiding the dependence of existing technologies on non-biomass or difficult-to-degrade raw materials such as fluorinated compounds. ② In terms of preparation process, a eutectic system is formed at 155-185℃ using a specific ratio of the three, which can be directly prepared by one-step heating melt copolymerization without the need for external solvents, initiators, or complex subsequent purification, simplifying the multi-step synthesis and purification process in traditional schemes. ③ In terms of performance, by introducing cysteine, while utilizing the caffeic acid catechol groups to obtain high interfacial adhesion, the technical problem of easy oxidation and instability of such groups is effectively solved, enabling the adhesive to have both high initial strength (e.g., >4MPa) and long-term stability in an underwater environment.

[0021] (2) Based on a dynamic disulfide bond crosslinking network, the adhesive achieves both high-strength and durable bonding performance and closed-loop recyclability and reprocessing characteristics. The polymer backbone of the adhesive is composed of dynamically reversible disulfide bond crosslinks. This chemical structural feature enables it to exhibit excellent performance (high strength, environmental resistance) while allowing for multiple recycling and remolding through hot pressing. The recycled material retains good bonding performance, achieving a unification from high-performance adhesive to recyclable material.

[0022] In summary, the adhesive of this invention exhibits excellent underwater adhesion performance, synergistically achieving high-strength and durable underwater adhesion. The underwater adhesion strength of this adhesive on iron sheets can reach up to 5.5 MPa, remains stable in various acid, alkali, and salt environments, and can be repeatedly recycled through hot-melt processes. It also possesses outstanding environmentally friendly characteristics such as being made from entirely bio-based, biodegradable, widely available, capable of closed-loop recycling, and produced without toxicity, along with a simple and efficient production process. Compared to existing technologies, it has significant advantages, demonstrating broad market application prospects and large-scale industrial application potential. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the preparation of the adhesive sample in Example 1;

[0024] Figure 2 This is a schematic diagram of underwater bonding in Example 1;

[0025] Figure 3 This is the adhesion strength of test example 1 at different times underwater;

[0026] Figure 4 This is the adhesion strength of samples with different proportions in Test Example 2 under water for the same amount of time;

[0027] Figure 5 This is to test the adhesion strength of Example 3 in seawater at different times;

[0028] Figure 6 This is the adhesion strength of test example 4 at different times underwater;

[0029] Figure 7 This is to test the adhesion strength of Example 5 in the air at different times;

[0030] Figure 8 This is a schematic diagram of the recycling preparation in Example 7;

[0031] Figure 9 This refers to the adhesion strength of air and underwater recovery in Example 7;

[0032] Figure 10 This is the adhesion strength of test example 6 at different times underwater. Detailed Implementation

[0033] To better clarify and understand the objectives, process solutions, and advantages of this invention, the technical solutions and implementation methods of this invention will be further described clearly, completely, and in detail below through specific embodiments and in conjunction with the accompanying drawings. It should be understood that the embodiments described in this invention are implemented under the premise of the technical solutions of this invention, providing detailed implementation methods and specific operating procedures, but are only some embodiments of this invention, not all embodiments. The specific implementation methods described are limited to illustrating and explaining this invention and do not limit this invention. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0034] Unless otherwise specified, the experimental methods and conditions used in the embodiments of this invention are conventional methods and conditions. The materials, reagents, instruments, and equipment used in the embodiments, unless otherwise specified, are all conventional substances or equipment known to those skilled in the art and can be obtained commercially or prepared by conventional methods. The reaction conditions described in the invention's content can all achieve the stated reactions and obtain the desired products. Due to space limitations, some embodiments are listed below to further illustrate the advantages of the technical solution of this invention.

[0035] Example 1, TCB-1031

[0036] Weigh 1g of lipoic acid, 0.3g of caffeic acid, and 0.1g of cysteine ​​and mix them in a reaction flask. Place the reaction flask on a magnetic stirrer equipped with an oil bath and heat it to 165℃. Once the lipoic acid, caffeic acid, and cysteine ​​are completely melted, turn on the stirrer and set the speed to 500 rpm. Let it react for 1 hour to obtain a brownish-red liquid, which is TCB-1031 adhesive. Figure 1 As shown.

[0037] 0.5 mL of the prepared adhesive is drawn onto an iron sheet using a syringe. This is then used to cover another iron sheet underwater, which is then clamped in place with two clips to achieve underwater adhesion. Underwater adhesion can also be achieved using substrates such as copper and aluminum. Figure 2 As shown.

[0038] Example 2, TCB-1032

[0039] Weigh 1g of lipoic acid, 0.3g of caffeic acid, and 0.2g of cysteine ​​and mix them in a reaction flask. Place the reaction flask on a magnetic stirrer equipped with an oil bath and heat it at 165℃. When the lipoic acid, caffeic acid, and cysteine ​​are completely melted, turn on the stirrer and set the speed to 500 rpm. Let it react for 1 hour to obtain a brownish-red liquid, which is TCB-1032 adhesive.

[0040] Apply 0.5 mL of the prepared adhesive to an iron sheet using a syringe. Submerge another iron sheet underwater and secure it with two clips to achieve underwater adhesion. Underwater adhesion can also be achieved using copper or aluminum substrates.

[0041] Example 3, TCB-1033

[0042] Weigh 1g of lipoic acid, 0.3g of caffeic acid, and 0.3g of cysteine ​​and mix them in a reaction flask. Place the reaction flask on a magnetic stirrer equipped with an oil bath and heat it at 165℃. When the lipoic acid, caffeic acid, and cysteine ​​are completely melted, turn on the stirrer and set the speed to 500 rpm. Let it react for 1 hour to obtain a brownish-red liquid, which is TCB-1033 adhesive.

[0043] Apply 0.5 mL of the prepared adhesive to an iron sheet using a syringe. Submerge another iron sheet underwater and secure it with two clips to achieve underwater adhesion. Underwater adhesion can also be achieved using copper or aluminum substrates.

[0044] Example 4, TCB-1022

[0045] Take 1g of lipoic acid, 0.2g of caffeic acid, and 0.2g of cysteine ​​and mix them in a reaction flask. Place the reaction flask on a magnetic stirring table equipped with an oil bath and heat it at 165℃. When the lipoic acid, caffeic acid, and cysteine ​​are completely melted, turn on the stirrer and set the speed to 500 rpm. Let it react for 1 hour to obtain a brownish-red liquid, which is TCB-1022 adhesive.

[0046] Apply 0.5 mL of the prepared adhesive to an iron sheet using a syringe. Submerge another iron sheet underwater and secure it with two clips to achieve underwater adhesion. Underwater adhesion can also be achieved using copper or aluminum substrates.

[0047] Example 5, TCB-1042

[0048] Weigh 1g of lipoic acid, 0.4g of caffeic acid, and 0.2g of cysteine ​​and mix them in a reaction flask. Place the reaction flask on a magnetic stirrer equipped with an oil bath and heat it at 165℃. When the lipoic acid, caffeic acid, and cysteine ​​are completely melted, turn on the stirrer and set the speed to 500 rpm. Let it react for 1 hour to obtain a brownish-red liquid, which is TCB-1042 adhesive.

[0049] The prepared adhesive was drawn into a syringe at 0.5 mL and applied to an iron sheet. This was then used to cover another iron sheet underwater, which was then clamped in place with two clips to achieve underwater adhesion. Underwater adhesion can also be achieved using copper or aluminum substrates.

[0050] Example 6, TCB-1052

[0051] Weigh 1g of lipoic acid, 0.5g of caffeic acid, and 0.2g of cysteine ​​and mix them in a reaction flask. Place the reaction flask on a magnetic stirrer equipped with an oil bath and heat it at 165℃. When the lipoic acid, caffeic acid, and cysteine ​​are completely melted, turn on the stirrer and set the speed to 500 rpm. Let it react for 1 hour to obtain a brownish-red liquid, which is TCB-1052 adhesive.

[0052] The prepared adhesive was drawn into a syringe at 0.5 mL and applied to an iron sheet. This was then used to cover another iron sheet underwater, which was then clamped in place with two clips to achieve underwater adhesion. Underwater adhesion can also be achieved using copper or aluminum substrates.

[0053] Example 7, TCB-1032-1

[0054] Weigh 1g of lipoic acid, 0.3g of caffeic acid, and 0.2g of cysteine ​​and mix them in a reaction flask. Place the reaction flask on a magnetic stirrer equipped with an oil bath and heat it at 155℃. When the lipoic acid, caffeic acid, and cysteine ​​are completely melted, turn on the stirrer and set the speed to 500 rpm. Let it react for 1 hour to obtain a brownish-red liquid, which is TCB-1032-1 adhesive.

[0055] Apply 0.5 mL of the prepared adhesive to an iron sheet using a syringe. Submerge another iron sheet underwater and secure it with two clips to achieve underwater adhesion. Underwater adhesion can also be achieved using copper or aluminum substrates.

[0056] Example 8, TCB-1032-2

[0057] Weigh 1g of lipoic acid, 0.3g of caffeic acid, and 0.2g of cysteine ​​and mix them in a reaction flask. Place the reaction flask on a magnetic stirrer equipped with an oil bath and heat it at 185℃. When the lipoic acid, caffeic acid, and cysteine ​​are completely melted, turn on the stirrer and set the speed to 500 rpm. Let it react for 1 hour to obtain a brownish-red liquid, which is TCB-1032-2 adhesive.

[0058] Apply 0.5 mL of the prepared adhesive to an iron sheet using a syringe. Submerge another iron sheet underwater and secure it with two clips to achieve underwater adhesion. Underwater adhesion can also be achieved using copper or aluminum substrates.

[0059] Comparative Example 1, TC-103

[0060] 1g of lipoic acid and 0.3g of caffeic acid were weighed and mixed in a reaction flask. The reaction flask was placed on a magnetic stirring table equipped with an oil bath and heated to 165℃, at which temperature the two substances could melt. Once the lipoic acid and caffeic acid were completely melted, stirring was started at 500 rpm, and the reaction was allowed to proceed for 1 hour, yielding a brownish-red liquid, which is the TC-103 adhesive. Tests showed that the TC-103 adhesive exhibited very poor adhesion, almost zero, on the aluminum, iron, and copper sheets commonly used in this invention. The lack of cysteine ​​prevented the adhesive from forming amide bonds, making it even more difficult to form a three-dimensional network structure, thus hindering its adhesion. This highlights the importance of cysteine ​​in this invention. Correspondingly, increasing the amount of caffeic acid to 0.5g yielded the same effect as in this example, with virtually no adhesion.

[0061] Comparative Example 2, TB-102

[0062] Weigh 1g of lipoic acid and 0.2g of cysteine ​​and mix them in a reaction flask. Place the reaction flask on a magnetic stirrer equipped with an oil bath and heat it at 165℃. At this temperature, the two substances will melt. Once the lipoic acid and cysteine ​​have completely melted, turn on the stirrer and set the speed to 500 rpm. Let it react for 1 hour to obtain a yellow liquid, which is TB-102 adhesive.

[0063] The prepared adhesive was drawn into a syringe and applied to an iron sheet in 0.5 mL. The iron sheet was then covered underwater and clamped with two clips to achieve underwater adhesion.

[0064] Comparative Example 3, TCB-1032-3

[0065] Weigh 1g of lipoic acid, 0.3g of caffeic acid, and 0.2g of cysteine ​​and mix them in a reaction flask. Place the reaction flask on a magnetic stirring table with an oil bath and heat it at 100℃. Due to the low temperature, the three raw materials cannot form a eutectic mixture, thus failing to lower the energy barrier required for melting. Therefore, they cannot be completely melted and it is difficult to prepare TCB-1032-3 adhesive.

[0066] Comparative Example 4, TCB-10105

[0067] 1g of lipoic acid, 0.1g of caffeic acid, and 0.05g of cysteine ​​were weighed and mixed in a reaction flask. The reaction flask was placed on a magnetic stirring table equipped with an oil bath and heated to 165℃. Once the lipoic acid, caffeic acid, and cysteine ​​were completely melted, stirring was started at 500 rpm, and the reaction was allowed to proceed for 1 hour, yielding a brownish-red liquid, which is the TCB-10105 adhesive. Testing revealed that the TC-10105 adhesive exhibited very poor adhesion to the aluminum, iron, and copper sheets commonly used in this invention, showing almost no adhesion ability. Although some amide bonds could be formed, it was difficult to form a three-dimensional network structure, resulting in poor adhesion. This highlights the importance of the proper formulation in this invention.

[0068] The adhesives obtained in each embodiment and comparative example were subjected to underwater adhesion strength tests for 24 hours. The substrate was an iron sheet, and the specific test method was to place the iron sheet into a high and low temperature double column testing machine for tensile testing. The conditions and adhesion strength test results for each example are summarized in Table 1 below:

[0069] Table 1 Summary of conditions and underwater adhesion strength for each example

[0070]

[0071] As can be seen from the table, the adhesives within the specified feeding range of this invention all exhibit good adhesive properties, such as in Examples 1-4 and Examples 7-8. However, when the mass ratio of thioctic acid is less than 60% as in Example 6, or the mass ratio of caffeic acid is greater than 23% as in Example 5, the adhesive effect of the adhesive is even slightly lower than that of Comparative Example 2. It can be seen that the proportion of each substance has a significant impact on the adhesive effect of the adhesive, and there is no regularity to this effect.

[0072] Test Example 1

[0073] The adhesive prepared in Example 2 was applied to an iron sheet underwater for different durations: 1 hour, 6 hours, 12 hours, 24 hours, 48 ​​hours, and 72 hours. The adhesion strengths were 1.81 MPa, 2.95 MPa, 3.74 MPa, 5.48 MPa, 5.37 MPa, and 5.54 MPa, respectively, indicating that the adhesive of the present invention reaches its maximum curing degree after 24 hours. The adhesion strength is as follows... Figure 3 As shown.

[0074] Test Example 2

[0075] The adhesives prepared in Examples 1, 2, 3, 4, 5, and 6 were respectively bonded underwater onto aluminum sheets, iron sheets, and copper sheets; after 24 hours underwater, the adhesion strength was as follows: Figure 4 As shown.

[0076] Test Example 3

[0077] The adhesive prepared in Example 2 was bonded to an iron sheet in seawater for different periods: 1 week, 2 weeks, 3 weeks, and 4 weeks. The adhesion strengths were 4.66 MPa, 4.54 MPa, 3.84 MPa, and 2.73 MPa, respectively, indicating that the adhesive of the present invention has good adaptability in seawater. The adhesion strength is as follows... Figure 5 As shown.

[0078] Test Example 4

[0079] The adhesive prepared in Example 2 was bonded to an iron sheet in water for different periods: 1 week, 2 weeks, 3 weeks, and 4 weeks. The adhesion strengths were 5.43 MPa, 5.40 MPa, 5.55 MPa, and 5.53 MPa, respectively, indicating that the adhesive of the present invention has good adaptability in seawater. The adhesion strength is as follows... Figure 6 As shown.

[0080] Test Example 5

[0081] The adhesive prepared in Example 2 was placed on an iron sheet and bonded in air for different times: 1 day, 3 days, 5 days, and 7 days. The adhesion strengths were 4.56 MPa, 4.17 MPa, 4.85 MPa, and 5.22 MPa, respectively, demonstrating excellent adhesion strength and durability. The adhesion strength is as follows... Figure 7 As shown.

[0082] Test Example 6

[0083] The adhesive prepared in Comparative Example 2 was bonded to an iron sheet in water for different periods: 1 week, 2 weeks, 3 weeks, and 4 weeks. The adhesion strengths were 3.94 MPa, 3.06 MPa, 2.65 MPa, and 2.11 MPa, respectively. Compared with the TCB-1032 adhesive in Example 2, the adhesion strength and durability were worse. This is mainly due to the role of caffeic acid, which contains catechin groups. Catechol groups are widely used in underwater adhesion and can improve the adhesion strength and durability of adhesives. (The adhesive strength is as follows...) Figure 10 As shown.

[0084] Example 9, TCB-1032-4

[0085] The adhesive used in Example 2 was scraped off with a knife and placed back into the reaction flask. The reaction flask was placed on a magnetic stirrer equipped with an oil bath and heated to 165°C. Once the recovered sample was completely melted, stirring was started at 500 rpm for 1 hour, yielding a brownish-red liquid, which was the recovered adhesive TCB-1032-4. Figure 8 As shown.

[0086] The recycled adhesive TCB-1032-4 was placed in air and underwater for 24 hours for bonding, and its bonding strength was tested. This process was repeated ten times, with odd-numbered strengths measured underwater and even-numbered strengths measured in air. The bonding strengths for the 1st, 3rd, 5th, 7th, and 9th underwater bonding tests were 4.41 MPa, 3.93 MPa, 3.92 MPa, 4.16 MPa, and 4.11 MPa, respectively. The bonding strengths for the 2nd, 4th, 6th, 8th, and 10th air bonding tests were 4.84 MPa, 4.79 MPa, 4.44 MPa, 4.04 MPa, and 4.17 MPa, respectively. In summary, the adhesive exhibits excellent recyclability. (The bonding strength is shown in the image.) Figure 9 As shown.

[0087] Unless otherwise specified, the raw materials and equipment used in this invention are all commonly used in the field; unless otherwise specified, the methods used in this invention are all conventional methods in the field.

[0088] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, alterations, and equivalent transformations made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. An environmentally friendly biomass-based underwater adhesive, characterized in that: The adhesive is obtained by heating and melting lipoic acid, caffeic acid, and cysteine ​​to form a homogeneous melt system and then stirring the mixture. The adhesive, based on 100% of the total mass of the adhesive raw materials, contains 60%–75% lipoic acid, 10%–23% caffeic acid, and 5%–20% cysteine. The preparation method of the adhesive includes the following steps: S1, add lipoic acid, caffeic acid and cysteine ​​to the reaction vessel; S2, heated to 155℃~185℃ to form a homogeneous molten system; S3, stir and react at temperature S2 for 0.5h to 1.5h to obtain adhesive.

2. The environmentally friendly biomass-based underwater adhesive according to claim 1, characterized in that, Based on the total mass of the adhesive raw materials as 100%, the mass percentage of thioctic acid is 62.5%~71.5%, the mass percentage of caffeic acid is 14.25%~21.5%, and the mass percentage of cysteine ​​is 7%~18.75%.

3. The environmentally friendly biomass-based underwater adhesive according to claim 1, characterized in that, In the adhesive raw materials, the mass ratio of thioctic acid, caffeic acid, and cysteine ​​is 10:3:

2.

4. A method for preparing an environmentally friendly biomass-based underwater adhesive as described in any one of claims 1-3, characterized in that, Includes the following steps: S1, add lipoic acid, caffeic acid and cysteine ​​to the reaction vessel; S2, heated to 155℃~185℃ to form a homogeneous molten system; S3, stir and react at temperature S2 for 0.5h to 1.5h to obtain adhesive.

5. The preparation method according to claim 4, characterized in that: The heating temperature in step S2 is 165°C.

6. The preparation method according to claim 4, characterized in that: In step S3, the stirring speed is 400 r / min to 600 r / min.

7. The preparation method according to claim 4, characterized in that: In step S2, the heating temperature is 165℃, and in step S3, the stirring speed is 500r / min and the stirring time is 1h.

8. The use of the environmentally friendly biomass-based underwater adhesive as described in any one of claims 1-3 in bonding in wet or underwater environments.

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