Preparation method of wide-temperature-range recoverable eutectic solvent adhesive

Abstract

The invention relates to a preparation method of a recoverable deep-eutectic solvent adhesive with a wide temperature range, which comprises the following steps: synthesizing bola type amine oxide with different carbon chain lengths, and successfully preparing the recoverable deep-eutectic solvent adhesive with the wide temperature range by taking the bola type amine oxide as a hydrogen bond acceptor and citric acid as a hydrogen bond donor. The eutecticevaporate solvent adhesive prepared by the preparation method disclosed by the invention shows excellent comprehensive performance in engineering application. Aiming at various substrates such as glass, metal, plastic and the like, the material shows more excellent bonding capacity, and the problem that a traditional adhesive is not uniform in adhesive force among different materials is effectively solved. And a glued product is ensured to be stable in structure, the visual attractiveness can be kept, and the requirement of modern precision manufacturing on the appearance of a finished product is perfectly met.

Description

Technical Field

[0001] This invention relates to a method for preparing a wide-temperature-range recyclable eutectic solvent adhesive, belonging to the field of supramolecular adhesive technology. Background Technology

[0002] The advent and application of adhesives have played an irreplaceable role throughout human history. In ancient times, people prepared adhesives from natural raw materials collected from plants and animals. With the development of the chemical industry, especially the petrochemical industry, binary polymerizable adhesives have flourished. The bonding process of polymerizable adhesives often involves the formation of covalent bonds, physical entanglement, and supramolecular interactions, enabling strong adhesion on common substrates. Compared with natural adhesives and single-component adhesives, they have many advantages, including high adhesive strength, good long-term stability, and lower cost. However, polymerizable adhesives also have a series of problems, such as difficulty in removing adhesives after bonding, non-recyclability, and the unavoidable use of harmful solvents (including benzene, toluene, xylene, formaldehyde, and other volatile organic compounds) during the preparation process.

[0003] To overcome the aforementioned drawbacks, there has been a pressing need in recent years for supramolecular adhesives with recyclable properties, especially low-toxicity / non-toxic adhesives. Eutectic solvents are supramolecular assembly systems composed of hydrogen bond donors and acceptors connected by hydrogen bonds, capable of forming viscous liquids in the absence of solvents. These properties make them ideal for use as supramolecular adhesives. However, most eutectic solvent adhesives have glass transition temperatures above 0°C, making them difficult to use in low-temperature environments and limiting their application range.

[0004] To overcome the aforementioned drawbacks, the market has seen a strong demand in recent years for recyclable supramolecular adhesives, especially low-toxicity / non-toxic adhesives. Eutectic solvents are supramolecular systems assembled from hydrogen bond donors and acceptors through hydrogen bonding, forming viscous liquids in the absence of solvents. These properties make them ideal for use as raw materials in the preparation of supramolecular adhesives or directly as supramolecular adhesives. However, most eutectic solvent adhesives have glass transition temperatures above 0°C, making them difficult to apply at low temperatures and limiting their operating temperature range. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for preparing a wide-temperature-range recyclable eutectic solvent adhesive.

[0006] The method of this invention is simple, has high atom utilization, uses inexpensive and readily available hydrogen bond donors, and is easy to prepare on a large scale. The prepared adhesive has strong adhesion and a wide operating temperature range, exhibiting strong adhesion ability in the range of -50℃ to 50℃. It also shows excellent performance at low temperatures, with a bonding strength of 140MPa at -50℃, which is significantly better than similar adhesives.

[0007] The technical solution of the present invention is as follows:

[0008] The first objective of this invention is to provide a method for preparing a hydrogen bond acceptor.

[0009] A method for preparing a hydrogen bond acceptor includes the following steps:

[0010] (1) Mix tertiary amine and ethanol, stir and heat to obtain mixture a;

[0011] (2) Hydrogen peroxide was slowly added dropwise to mixture a, the temperature was kept warm, and the reaction was stopped to obtain mixture b;

[0012] (3) Mixture b is concentrated by vacuum rotary evaporation, and then recrystallized with organic solvent to obtain white bola-type amine oxides with different carbon chain lengths, which are hydrogen bond acceptors.

[0013] According to a preferred embodiment of the present invention, in step (1), the tertiary amine is N,N,N',N'-tetramethylethylenediamine, N,N,N',N'-tetramethylbutanediamine or N,N,N',N'-tetramethylhexanediamine.

[0014] According to a preferred embodiment of the present invention, in step (1), the molar ratio of the tertiary amine to the volume of ethanol is (1-50):(10-300), in mmol / mL.

[0015] According to a preferred embodiment of the present invention, in step (1), the heating temperature is 30-80°C.

[0016] According to a preferred embodiment of the present invention, in step (2), the molar ratio of hydrogen peroxide to tertiary amine is (10-60):(1-50).

[0017] According to a preferred embodiment of the present invention, in step (2), the heat preservation reaction time is 6-24 hours.

[0018] According to a preferred embodiment of the present invention, in step (3), the organic solvent selected for recrystallization is a mixture of ethyl acetate and petroleum ether, and the volume ratio of ethyl acetate to petroleum ether is 5:1 to 1:5.

[0019] A second objective of this invention is to provide a method for preparing a wide-temperature-range recyclable eutectic solvent adhesive.

[0020] A method for preparing a wide-temperature-range recyclable eutectic solvent adhesive, comprising the following steps:

[0021] The hydrogen bond acceptor and hydrogen bond donor prepared above are mixed, dissolved in water, and the water in the mixture is removed to obtain a eutectic solvent adhesive.

[0022] According to a preferred embodiment of the present invention, the hydrogen bond donor is an organic carboxylic acid.

[0023] According to a preferred embodiment of the present invention, the organic carboxylic acid is citric acid.

[0024] According to a preferred embodiment of the present invention, the molar ratio of hydrogen bond donor to hydrogen bond acceptor is 2:1 to 1:3.

[0025] A further preferred embodiment is that the molar ratio of hydrogen bond donor to hydrogen bond acceptor is 3:2.

[0026] According to the present invention, the preferred methods for removing water are: natural evaporation, rotary evaporation, and freeze drying.

[0027] A wide-temperature-range recyclable eutectic solvent adhesive was prepared using the method described above.

[0028] The adhesive prepared by this invention is essentially a novel eutectic solvent containing carboxyl, hydroxyl, and other groups. It has a large number of high-density hydrogen bonds, which can form hydrogen bonds with substrates such as glass, iron, and plastic, resulting in high adhesion strength, superior to similar adhesives currently reported. The adhesive is transparent and will not affect the appearance of the bonded objects. The bonded effect is aesthetic and structurally stable. The adhesive can be used in both wet and dry applications and is easily recyclable. There is no need to worry about embrittlement or failure at low temperatures.

[0029] Technical features and beneficial effects of the present invention:

[0030] 1. The hydrogen bond acceptor used in the eutectic solvent adhesive of this invention is independently designed and synthesized. Then, a novel recyclable eutectic solvent adhesive is obtained through the self-assembly of small organic molecules. The process is simple, with high atom utilization, and the hydrogen bond donor is inexpensive, readily available, and suitable for large-scale preparation. The self-assembly of small organic molecules successfully yields…

[0031] 2. The eutectic solvent adhesive prepared by this invention has a wide operating temperature range, exhibiting strong adhesion ability in the range of -50℃ to 50℃, and still showing excellent performance at low temperatures, with a bonding strength of 140 MPa at -50℃, which is significantly better than similar adhesives.

[0032] 3. The eutectic solvent adhesive prepared by this invention has a good service life, retains strong adhesion even after one year, and can be used for a long time even under conditions where air is not isolated.

[0033] 4. The eutectic solvent prepared by this invention has recyclability, is easy to depolymerize without leaving any trace, and can be depolymerized by repeated rinsing with running water. The adhesive strength remains basically unchanged after multiple recycling cycles, which is in line with the current concept of sustainable development and green chemistry, is environmentally friendly, and greatly reduces the environmental burden of waste disposal.

[0034] 5. The adhesive based on deep eutectic solvent of this invention still maintains a certain degree of flexibility and fluidity at low temperatures, overcoming the low-temperature embrittlement disadvantage of traditional adhesives, and will be more widely used in polar engineering, aerospace and low-temperature electronic packaging and other fields.

[0035] 6. The adhesive of the present invention has strong adhesion to different substrates and is easy to use; it can be directly applied to the substrate. Attached Figure Description

[0036] Figure 1 The molecular structure of the hydrogen bond acceptor prepared in this invention is shown.

[0037] Figure 2 The images show the SEM morphology of the bola-type amine oxide, citric acid, and the prepared eutectic solvent adhesive in Example 1 of this invention.

[0038] Figure 3 Rheological test diagrams of the eutectic solvent adhesives obtained by the methods provided in Examples 4-6;

[0039] Figure 4 The above is a statistical chart showing the adhesion strength of the eutectic solvent adhesives obtained by the methods provided in Examples 4-6 on glass.

[0040] Figure 5 Comparison of 1H NMR spectra of the eutectic solvent adhesives obtained by the methods provided in Examples 4-6, and Bola-type amine oxides and citric acid;

[0041] Figure 6 Infrared, thermogravimetric, DSC and XRD test images of the eutectic solvent adhesives obtained by the methods provided in Examples 4-6;

[0042] Figure 7 This is a statistical graph showing the adhesion strength of the eutectic solvent adhesive to different substrates (glass, iron, and PVC) at different temperatures in Experiment Example 3.

[0043] Figure 8 This is a statistical graph of the macroscopic bonding behavior during the load test in Experiment Example 4;

[0044] Figure 9 The graph shows the adhesion strength of the eutectic solvent adhesive in Experiment Example 5 after immersion in water for different times.

[0045] Figure 10This is a statistical graph showing the adhesion strength of the eutectic solvent adhesive in Experiment Example 5 after immersion in organic solvent for different times.

[0046] Figure 11 This is a statistical graph showing the adhesion strength of the eutectic solvent adhesive in Experiment Example 6 after being placed for different times.

[0047] Figure 12 This is a statistical graph showing the adhesion strength of the eutectic solvent adhesive after multiple recycling cycles in Experiment Example 7. Detailed Implementation

[0048] To better understand the present invention, specific embodiments are described below.

[0049] Unless otherwise specified, the experimental methods used in the examples are conventional methods.

[0050] Unless otherwise specified, all materials and reagents used in the examples are commercially available.

[0051] In the examples, bola-type amine oxides are collectively referred to as TMEAO, TMBAO, and TMHAO.

[0052] Example 1

[0053] Preparation of hydrogen bond acceptor TMEAO

[0054] In a 250 mL round-bottom flask, N,N,N',N'-tetramethylethylenediamine (10 mmol, 1.16 g) and ethanol (100 mL) were added. The reaction mixture was stirred thoroughly and heated to 50 °C. Subsequently, hydrogen peroxide (30 mmol, 2.04 g) was slowly added dropwise, and the mixture was stirred at 50 °C for 18 hours. The resulting mixture was concentrated by vacuum rotary evaporation, and recrystallized with ethyl acetate and petroleum ether to obtain a white solid with a yield of 96%, abbreviated as TMEAO. The molecular structure is shown in [reference needed]. Figure 1 .

[0055] Example 2

[0056] Preparation of hydrogen bond acceptor TMBAO

[0057] In a 250 mL round-bottom flask, N,N,N',N'-tetramethylbutanediamine (10 mmol, 1.44 g) and ethanol (100 mL) were added. The reaction mixture was stirred thoroughly and heated to 50 °C. Subsequently, hydrogen peroxide (30 mmol, 2.04 g) was slowly added dropwise, and the mixture was stirred at 50 °C for 18 hours. The resulting mixture was concentrated by vacuum rotary evaporation, and recrystallized with ethyl acetate and petroleum ether to obtain a white solid with a yield of 95%, abbreviated as TMBAO. The molecular structure is shown in [reference needed]. Figure 1 .

[0058] Example 3

[0059] Preparation of hydrogen bond acceptor TMHAO

[0060] In a 250 mL round-bottom flask, N,N,N',N'-tetramethylhexanediamine (10 mmol, 1.72 g) and ethanol (100 mL) were added. The reaction mixture was stirred thoroughly and heated to 50 °C. Subsequently, hydrogen peroxide (30 mmol, 2.04 g) was slowly added dropwise, and the mixture was stirred at 50 °C for 18 hours. The resulting mixture was concentrated by vacuum rotary evaporation, and recrystallized with ethyl acetate and petroleum ether. The final product was a white solid with a yield of 93%, abbreviated as TMHAO. The molecular structure is shown in [reference needed]. Figure 1 .

[0061] Example 4

[0062] A method for preparing a recyclable eutectic solvent adhesive with a wide temperature range, comprising the following steps:

[0063] Weigh TMEAO and citric acid (molar ratios of 2:1, 3:2, 1:2, and 1:3) prepared in Example 1 at room temperature (25°C) into a 100 mL beaker, add 50 mL of distilled water, stir for 0.5 hours to dissolve, sonicate for 1 hour, freeze dry for 24 hours to obtain a viscous adhesive (TMEAO-CA).

[0064] like Figure 1 As shown, the bola-type amine oxide TMEAO and citric acid prepared in Example 1 are both white powders with uneven SEM morphology images. In contrast, the prepared adhesive TMEAO-CA exhibits fluidity at room temperature, with a smooth and dense surface and a uniform microphase structure. The adhesion to the substrate can be assessed using a standard tensile test, with the adhesive thickness approximately 0.05-0.1 mm. The bonded adhesive portion is transparent and colorless, ensuring the aesthetic appeal of the final product.

[0065] Example 5

[0066] The preparation method of the eutectic solvent adhesive described in Example 4 differs from that in that:

[0067] Replace TMEAO with the hydrogen bond acceptor TMBAO prepared in Example 2, and follow the same steps as in Example 4. Freeze-dry for 24 hours to obtain a viscous adhesive (TMBAO-CA).

[0068] Example 6

[0069] The preparation method of the eutectic solvent adhesive described in Example 4 differs from that in that:

[0070] Replace TMEAO with the hydrogen bond acceptor TMHAO prepared in Example 3, and follow the same steps as in Example 4. Freeze-dry for 24 hours to obtain a viscous adhesive (TMHAO-CA).

[0071] Experimental Example 1

[0072] The rheological properties and adhesive strength to glass of the eutectic solvent adhesives obtained by the methods provided in Examples 4-6 are as follows: Figure 3-4 As shown.

[0073] from Figure 3 It can be seen that in stress scanning and frequency scanning, the G” value is greater than the G' value, indicating that the adhesive is always in an inelastic state during the test and exhibits viscous fluid characteristics. The composite viscosity decreases with increasing frequency, indicating that the sample has shear dilution characteristics. Moreover, regardless of the magnitude and duration of the applied shear rate, its viscosity changes very little, indicating that there is no molecular entanglement. When the ratio of Bola-type amine oxide to citric acid is 3:2, the mechanical strength of the adhesive is the highest.

[0074] from Figure 4 It can be seen that when the ratio of the three types of blea-type amine oxides to citric acid is 3:2, the adhesive has the highest bonding strength to glass.

[0075] Experiment Example 2

[0076] Nuclear magnetic resonance (NMR) was performed on the bola-type amine oxide TMEAO and citric acid prepared in Example 1, as well as the samples prepared in Examples 4-6 with a bola-type amine oxide to citric acid ratio of 3:2. Figure 5 ), infrared ( Figure 6 ), thermogravimetric analysis ( Figure 6 ), DSC ( Figure 6 ) and XRD ( Figure 6 )test.

[0077] Thermogravimetric analysis (TGA) results showed that the water content in the sample was approximately 10% by mass. Bola-type amine oxide and citric acid were solids at room temperature, while the melting point of the mixture sample was below 0°C, reaching as low as -18°C. XRD patterns showed a broad diffraction peak centered at 2θ = 21°, indicating an amorphous structure, confirming that the sample was a low-co-solubility solvent. Comparison of infrared spectroscopy and 1H NMR confirmed the presence of hydrogen bonds. Compared to pure citric acid and Bola-type amine oxide, the characteristic peaks of the active hydrogen in citric acid shifted to higher fields, while those of the active hydrogen in Bola-type amine oxide shifted to lower fields, confirming the existence of hydrogen bonds. Correspondingly, the asymmetric stretching vibration peak of the carboxyl group in citric acid shifted to higher wavenumbers in the low-co-solubility solvent. The hydrogen bonds, through interaction with the O atoms of the carboxyl group, lowered the bond order of the C=O bond, leading to a significant low-wavenumber shift, increased intensity, and increased bandwidth, further supporting this conclusion.

[0078] Experimental Example 3 The adhesion strength of samples prepared in Examples 4-6 with a ratio of 3:2 of Bola-type amine oxide and citric acid was tested, and then a tensile test was conducted to quantitatively evaluate the adhesion strength to different substrates (glass, iron, and PVC). Figure 7 As shown, the bonding strength with glass is strongest within the temperature range of −50℃ to 50℃. At -50℃, the adhesion strength of TMEAO-CA adhesive reaches 140 MPa, the adhesion strength with iron reaches 70 MPa, and the adhesion strength with PVC is the weakest, only 8 MPa. The adhesion strength gradually decreases with increasing temperature. The study investigated the adhesion properties of adhesives prepared with bola-type amine oxides of different carbon chain lengths. With increasing carbon chain length, the adhesion strength of the adhesive on all surfaces decreases. When the carbon chain extends from 4 carbons to 6 carbons, the adhesion increases again, showing an overall trend of first decreasing and then increasing. Therefore, the adhesion performance is affected by the monomer ratio and carbon chain length; an appropriate carbon chain length is beneficial for intermolecular interactions.

[0079] Experiment Example 4

[0080] The adhesive TMEAO-CA prepared in Example 4 was placed in a cold circulation system and cooled to -25°C. After 24 hours, it was removed, heated to room temperature, and subjected to a load test. It was then stored at -25°C for another 24 hours, and this process was repeated 100 times. The sample stored at low temperature was uniformly coated onto an ultra-thick glass slide, and a load weight of 25 kg was applied. No displacement of the glass slide was observed, based on macroscopic adhesive behavior (…). Figure 8 ) and adhesion strength ( Figure 7 The experimental results show that the adhesive exhibits good adhesion at low temperatures. When the entire system is heated to room temperature, the adhesion remains good, which well proves that the eutectic solvent adhesive we prepared belongs to a high-performance supramolecular adhesive material with an ultra-wide temperature range.

[0081] Experimental Example 5

[0082] a. The sample prepared by the ratio of bola-type amine oxide to citric acid of 3:2 in Examples 4-6 was evenly coated on the glass and immersed in water. When left to stand, the sample will show a layering phenomenon. Record the immersion time.

[0083] b. Apply the adhesive TMEAO-CA prepared in Example 4 evenly to the glass, immerse it in ethanol, and observe the layering phenomenon when it is left to stand. Record the immersion time.

[0084] c. Apply the adhesive TMEAO-CA prepared in Example 4 evenly to the glass, immerse it in ethyl acetate. When left to stand, it will show a layering phenomenon. Record the immersion time.

[0085] d. Apply the adhesive TMEAO-CA prepared in Example 4 evenly to the glass, immerse it in dichloromethane, and observe the layering phenomenon when it is left to stand. Record the immersion time.

[0086] According to the ab treatment, the eutectic solvent adhesive was tested in water ( Figure 9 ) and different solvents ( Figure 10 The adhesion strength was measured by immersion in the solution for different durations. Figure 9 , Figure 10 As can be seen, the adhesive can remain in a static solvent for a short period of time. With prolonged soaking time, the adhesive strength gradually weakens, and after a certain soaking time, the adhesive almost completely dissolves. This adhesive exhibits strong adhesive force for a certain period and has a higher tolerance to organic solvents than water, making it a promising fast-dissolving adhesive.

[0087] Experimental Example 6

[0088] The adhesive TMEAO-CA prepared in Example 4 was placed at room temperature, and the placement time was recorded. The adhesion strength of the eutectic solvent adhesive at different placement times was tested. Figure 11 As shown, the adhesive still has strong adhesion after a year and can be used for a long time even without being isolated from air.

[0089] Experimental Example 7

[0090] The samples prepared in Examples 4-6 with a ratio of 3:2 of Bola-type amine oxide and citric acid were redissolved in water, freeze-dried for 24 hours, and then the water was removed. This cycle was repeated 5 times. The adhesion strength of the eutectic solvent adhesive after multiple cycles was tested, such as... Figure 12 As shown, the eutectic solvent adhesive prepared by the present invention can be easily recycled. The adhesive strength of the three adhesives remained essentially unchanged after 5 recycling cycles, indicating that they have good recyclability.

Claims

1. A method for preparing a hydrogen bond acceptor, comprising the following steps: (1) Mix tertiary amine and ethanol, stir and heat to obtain mixture a; (2) Hydrogen peroxide was slowly added dropwise to mixture a, the temperature was kept warm, and the reaction was stopped to obtain mixture b; (3) Mixture b is concentrated by vacuum rotary evaporation, and then recrystallized with organic solvent to obtain white bola-type amine oxides with different carbon chain lengths, which are hydrogen bond acceptors.

2. The preparation method according to claim 1, characterized in that, In step (1), the tertiary amine is N,N,N',N'-tetramethylethylenediamine, N,N,N',N'-tetramethylbutanediamine or N,N,N',N'-tetramethylhexanediamine, the molar ratio of the tertiary amine to the volume of ethanol is (1-50):(10-300), the unit is mmol / mL, and the heating temperature is 30-80°C.

3. The preparation method according to claim 1, characterized in that, In step (2), the molar ratio of hydrogen peroxide to tertiary amine is (10-60):(1-50), and the reaction time is 6-24 hours.

4. The preparation method according to claim 1, characterized in that, In step (3), the organic solvent selected for recrystallization is a mixture of ethyl acetate and petroleum ether, with a volume ratio of 5:1 to 1:

5.

5. A method for preparing a wide-temperature-range recyclable eutectic solvent adhesive, comprising the following steps: The hydrogen bond acceptor prepared according to claim 1 is mixed with the hydrogen bond donor, dissolved in water, and the water in the mixture is removed to obtain a eutectic solvent adhesive.

6. The preparation method according to claim 5, characterized in that, The hydrogen bond donor is an organic carboxylic acid, and the organic carboxylic acid is citric acid.

7. The preparation method according to claim 5, characterized in that, The molar ratio of hydrogen bond donor to hydrogen bond acceptor is 2:1 to 1:3, and the water removal methods are: natural evaporation, rotary evaporation, and freeze drying.

8. A wide-temperature-range recyclable eutectic solvent adhesive, prepared by the method of claim 5.

9. The wide temperature range recyclable eutectic solvent adhesive according to claim 8, characterized in that, The substrates for the load are glass, iron, and plastic. It can be directly applied to the substrate. It has a wide operating temperature range, with strong adhesion in the range of -50℃ to 50℃. It still exhibits excellent performance at low temperatures, with a bonding strength of 140 MPa at -50℃. The adhesive can exist in a static solvent for a short time and has strong adhesion.

10. The wide temperature range recyclable eutectic solvent adhesive according to claim 8, characterized in that, The eutectic solvent adhesive still has strong adhesion after a year, and can be used for a long time even without isolating it from air. It is easy to de-adhere without leaving any traces; it can be de-adheded by repeatedly rinsing with running water. The adhesive strength remains basically unchanged after multiple recycling cycles, and the adhesive maintains flexibility and fluidity at low temperatures.

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