Imidazolium ionic liquid as well as preparation method and application thereof

Abstract

The invention relates to the technical field of adhesives, and discloses an imidazolium ionic liquid and a preparation method and application thereof, the preparation method comprises the following steps: reacting omega-bromoalcohol with 1-(methoxymethyl) imidazole in acetonitrile, and washing with methyl tert-butyl ether to obtain a target ionic liquid precursor; and dissolving the product in acetonitrile, adding 4-trifluoromethyl phenyl isocyanate, and washing with methyl tert-butyl ether after the reaction is finished, thereby obtaining the target imidazolium ionic liquid. The imidazolium ionic liquid disclosed by the invention is applied to a PVB (Polyvinyl Butyral) adhesive, and the PVB adhesive shows excellent adhesion strength in a macroscopic adhesion performance test on the basis of multiple interactions, and particularly has excellent adhesion strength on aluminum. The obtained adhesive can be universally adapted to various substrates such as metal substrates and macromolecule substrates, and finally high-strength and high-durability intelligent adhesion performance is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of adhesives, in particular to an imidazole ionic liquid and a preparation method and application thereof. BACKGROUND

[0002] Traditional adhesives mainly rely on high molecular polymers to form cohesive force through covalent bond network. Although its bonding strength is high, the entanglement of high molecular chain leads to large viscosity, poor flowability, and it is difficult to achieve full wetting on low surface energy substrate or complex microstructure surface, and it is easy to form defective interface. In addition, high molecular weight adhesives usually need high temperature curing or solvent assisted coating, which has the problems of high energy consumption, environmental pollution risk and thick adhesive layer waste. Low molecular weight organic matter can improve the wettability, but its intermolecular force is weak, and the cohesive energy and interfacial adhesion are difficult to synergistically improve, which limits its practical application.

[0003] Ionic liquid (Ionic Liquids, ILs) as a kind of molten salt composed of anion and cation, which is in liquid state at room temperature. Because of its almost zero vapor pressure, unique physical and chemical properties and adjustable anion and cation structure, it can be precisely controlled by designing different combinations of polarity, hydrogen bond ability and hydrophobicity, so as to adapt to various substrates. Small molecule ionic liquid is more convenient to adjust the structure than polymer ionic liquid, has lower molecular weight, stronger permeability and faster curing, and has good application prospect in the fields of flexible electronics and precision device bonding.

[0004] The present application is based on the unique advantages of small molecule ionic liquid, such as easy adjustment of structure, convenient processing and non-flammability, aiming to solve the shortcomings of traditional adhesives in practical application. Due to the high adjustability of the anion and cation composition, we design and synthesize an imidazole ionic liquid with high adhesion performance, and explore its application in the field of adhesives. SUMMARY

[0005] The present application aims to obtain a high adhesion adhesive by adjusting the structure of ionic liquid, and provides an imidazole ionic liquid and a preparation method and application thereof.

[0006] To achieve the above purpose, on the one hand, the present application provides an imidazole ionic liquid, the chemical structure general formula is shown as formula (1):

[0007] (1).

[0008] According to the second aspect of the present application, the present application further provides a preparation method of the imidazole ionic liquid of formula (1), comprising the following steps:

[0009] (1) Dissolve 1-(methoxymethyl)imidazolium in acetonitrile solvent, add ω-bromool under continuous inert gas to carry out the reaction, wash the reaction system with methyl tert-butyl ether after the reaction is completed, and dry it under vacuum to obtain the ionic liquid precursor.

[0010] (2) The ionic liquid precursor obtained above is dissolved in acetonitrile. Under the condition of continuous inert gas, 4-trifluoromethylbenzene isocyanate is added to carry out the reaction. After the reaction is completed, the reaction system is washed with methyl tert-butyl ether and dried under vacuum to obtain the target ionic liquid.

[0011] According to a third aspect of the present invention, the present invention also provides a PVB resin adhesive composition, wherein an imidazole ionic liquid of formula (1) is added to the PVB resin adhesive as an adhesive performance enhancing additive. The composition, by weight, comprises:

[0012] Polyvinyl butyral (PVB) 80-120 parts;

[0013] Ethyl cellulose (EC) 10-25 parts;

[0014] 220-400 parts of anhydrous ethanol;

[0015] 90-150 parts of isopropanol;

[0016] 5-30 parts of imidazole ionic liquid of formula (1).

[0017] As a further preferred embodiment of the present invention, the PVB resin adhesive composition further includes 10-25 parts of a plasticizer, wherein the plasticizer is one or more selected from dioctyl phthalate (DOP), dibutyl phthalate (DBP), diisononyl phthalate (DINP), diisodecyl phthalate (DIDP), dioctyl terephthalate (DOTP), tributyl citrate (ATBC), trioctyl phthalate (TOTM), epoxidized soybean oil (ESO), and epoxidized oleate.

[0018] According to a fourth aspect of the invention, the invention also provides a PVB resin adhesive prepared by the PVB resin adhesive composition of the third aspect.

[0019] As a further preferred embodiment of the present invention, the method for preparing PVB resin adhesive includes the following steps:

[0020] Polyvinyl butyral (PVB) and ethyl cellulose were added to a mixed solvent of anhydrous ethanol and isopropanol and stirred until the polyvinyl butyral was completely dissolved. Then, plasticizer and imidazole ionic liquid were added and stirred until homogeneous to obtain PVB resin adhesive.

[0021] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0022] In the imidazolium ionic liquid synthesized in this invention, the imidazolium cation strongly anchors polarity and a π-electron-rich substrate through electrostatic and cation-π interactions; the amide and ester groups act as hydrogen bond donors and acceptors, forming a dense hydrogen bond network that significantly enhances interfacial adhesion strength; the trifluoromethyl group enhances polarity and introduces hydrophobicity through a strong electron-withdrawing effect, significantly improving moisture resistance and interfacial stability; and the ion pairs (such as Br...) - The flexible alkyl chain synergistically optimizes cohesive energy and wettability, ensuring efficient stress transfer and preventing brittle fracture. This structure, integrating multiple powerful mechanisms, enables it to be universally adaptable to diverse substrates such as metals and polymers, ultimately achieving high-strength, high-durability smart adhesion performance. Attached Figure Description

[0023] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0024] Figure 1 The image shows the proton NMR spectrum of compound SIL-0 obtained in Example 1.

[0025] Figure 2 The image shows the proton NMR spectrum of the target product, imidazole ionic liquid IL-1, obtained in Example 1.

[0026] Figure 3 The image shows the proton NMR spectrum of compound SIL-2, which is the compound in Comparative Example 3.

[0027] Figure 4 After bonding experiments were conducted on stainless steel, glass, PVC and aluminum substrates using commercial adhesive AD 630 (Comparative Example 1), PVB-0 (Comparative Example 2) and PVB-SIL reinforced with SIL-1 (Example 2), the shear strength data of the bond was measured at room temperature.

[0028] Figure 5 The graph shows the overlap shear test curve of PVB-0 without ionic liquid reinforcement in Comparative Example 2.

[0029] Figure 6 The figure shows the overlap shear test curve of PVB-SIL reinforced with SIL-1 prepared in Example 2.

[0030] The objectives, features, and advantages of this invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0031] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0032] Unless otherwise defined, the technical terms used in the following embodiments have the same meanings as commonly understood by those skilled in the art to which this invention pertains. Unless otherwise specified, the experimental reagents used in the following embodiments are conventional biochemical reagents; and the experimental methods described are conventional methods.

[0033] Example 1

[0034] This embodiment provides a method for preparing imidazole ionic liquids, specifically including the following steps:

[0035] (1) Weigh 10 mmol of 1-(methoxymethyl)imidazol and dissolve it in 20 mL of acetonitrile. Under the condition of continuous inert gas purging, add 15 mmol of 7-bromo-1-heptanol and stir continuously at 60 °C for 12 h. After the reaction is completed, add the reaction system to methyl tert-butyl ether, pour off the supernatant, wash three times with methyl tert-butyl ether, and dry under vacuum at 70 °C to obtain a pale yellow oily ionic liquid with a yield of 88%. The product is named SIL-0 and its chemical structure is shown below:

[0036] .

[0037] (2) Weigh 1 mmol of the ionic liquid SIL-0 obtained above and dissolve it in 20 mL of acetonitrile. Under the condition of continuous purging of inert gas, 1.2 mmol of 4-trifluoromethylphenyl isocyanate was added, and the reaction was stirred continuously at 60 °C for 12 h. After the reaction was completed, the reaction system was added to methyl tert-butyl ether, the upper liquid was poured off, washed three times with methyl tert-butyl ether, and dried under vacuum at 70 °C to obtain the target imidazole ionic liquid with a yield of 80%. The product was named SIL-1, and its structural formula is shown below:

[0038] .

[0039] Figure 1 The image shows the proton NMR spectrum of compound SIL-0 obtained in step (1) of Example 1. Figure 2 The image shows the proton NMR spectrum of the target product SIL-1 obtained in step (2) of Example 1.

[0040] The following Examples 2 and Comparative Examples 2 and 3 provide methods for preparing PVB resin adhesives, and compare the bonding performance of the PVB resin adhesives with that of the existing commercial adhesive 3M AD 630 all-purpose adhesive provided in Comparative Example 1.

[0041] Comparative Example 1

[0042] 3M AD 630 all-purpose adhesive was selected.

[0043] Comparative Example 2

[0044] This comparative example provides a method for preparing a PVB adhesive without ionic liquids, specifically including:

[0045] By weight, 90 parts PVB and 10 parts ethyl cellulose were added to a mixed solvent of 360 parts anhydrous ethanol and 90 parts isopropanol, and stirred until PVB and ethyl cellulose were completely dissolved; then 10 parts plasticizer were added, and stirred for 2 hours after the addition was complete to obtain PVB adhesive, named PVB-0.

[0046] Example 2

[0047] This embodiment provides a method for preparing an ionic liquid-reinforced PVB adhesive, specifically including:

[0048] By weight, 90 parts PVB and 10 parts ethyl cellulose were added to a mixed solvent of 360 parts anhydrous ethanol and 90 parts isopropanol, and stirred until the PVB was completely dissolved. Then, 10 parts plasticizer and 10 parts imidazole ionic liquid SIL-1 were added, and stirred for 2 hours after the addition was complete to obtain PVB adhesive, which was named PVB-SIL.

[0049] Comparative Example 3

[0050] As a control experiment for Example 2, the only difference was the ionic liquid; the imidazole ionic liquid SIL-1 was replaced with the azole ionic liquid SIL-2, which has the following structure. All other operations remained the same as in Example 2. The structure of the azole ionic liquid SIL-2 is as follows:

[0051]

[0052] Figure 3 The image shows the 1H NMR spectrum of the SIL-2 molecule in Comparative Example 3. Experimental tests revealed that the vinyl ionic liquid in Comparative Example 3 exhibited very poor bulk adhesive properties, failing to form an effective bond. It detached upon manual application of external force, demonstrating very poor adhesion. Therefore, the adhesive strength of the three adhesive samples from Example 2 and Comparative Examples 1 and 2 was tested below. The test method was: ambient temperature 25°C, 10 mm / min... -1 An overlap shear test was conducted at the test speed, with an adhesion area of ​​1 cm². 2 The test results are as follows:

[0053] like Figure 4As shown, the shear strength data of the bonded joints were measured at room temperature after bonding experiments of three adhesives on stainless steel, PMMA, thermoplastic (PVC), and aluminum substrates (Al). The results show that the ionic liquid-reinforced adhesive PVB-SIL (Example 2) exhibits the best overall bonding performance, with tensile strengths of 2.8 MPa and 3.3 MPa on PVC and Al substrates, respectively, demonstrating excellent applicability. On stainless steel substrates, the strength of all three adhesives is not high, indicating that the surface properties of stainless steel (such as the inert oxide layer) are the key limiting factor for bond strength, rather than the adhesive itself. However, PVB-SIL is still stronger than PVB-0 and AD 630 all-purpose adhesive. To further investigate the reinforcing effect of imidazole ionic liquid SIL-1 as an additive in PVB adhesive systems, the solution based on the example was modified by increasing the amount of SIL-1. The resulting PVB adhesive showed improved bonding performance compared to Example 2, with the best effect achieved when the amount of SIL-1 was 25 parts, resulting in tensile strengths of 3.2 MPa and 3.7 MPa on PVC and Al substrates, respectively. However, with further increases in the amount of SIL-1, there was no significant improvement in bonding performance.

[0054] The overlap shear properties of the samples in Example 2 and Comparative Example 2 were compared and tested. Figure 5 The figure shows the lap shear test curves of PVB-0 without ionic liquid reinforcement in Comparative Example 2. It can be seen that the adhesive without ionic liquid reinforcement (Comparative Example 2) exhibits low strength and high brittleness. Its strength on the three substrates is ranked as aluminum > PMMA > PVC. All curves show a brittle fracture characteristic with a sharp drop after the peak, indicating poor impact resistance. Figure 6 The image shows the overlap shear test curve of PVB-SIL reinforced with SIL-1 prepared in Example 2. It can be seen that the adhesive reinforced with ionic liquid (Example 2) exhibits high strength, with the highest adhesion force on the aluminum substrate reaching nearly 600N. This indicates that ionic liquids integrating multiple strong action mechanisms can greatly improve the performance of PVB adhesives and achieve high-strength adhesion.

[0055] While specific embodiments of the present invention have been described above, those skilled in the art should understand that these are merely illustrative examples, and various changes or modifications can be made to these embodiments without departing from the principles and essence of the present invention. The scope of protection of the present invention is defined only by the appended claims.

Claims

1. An imidazole-based ionic liquid, characterized in that, Its general chemical structure is shown in formula (1): (1)。 2. A method for preparing the imidazole ionic liquid according to claim 1, comprising the following steps: (1) Dissolve 1-(methoxymethyl)imidazolium in acetonitrile solvent, add ω-bromool under an inert atmosphere to react, wash with methyl tert-butyl ether after the reaction is completed, and dry to obtain the ionic liquid precursor. (2) The ionic liquid precursor obtained above was dissolved in acetonitrile, and 4-trifluoromethylbenzene isocyanate was added under an inert atmosphere to carry out the reaction. After the reaction was completed, the product was washed with methyl tert-butyl ether and dried to obtain the target imidazole ionic liquid.

3. The application of the imidazole ionic liquid of claim 1 as an additive in PVB resin adhesives.

4. A PVB resin adhesive composition, characterized in that, By weight, including: 80-120 parts of polyvinyl butyral; 10-25 parts of ethyl cellulose; 220-400 parts of anhydrous ethanol; 90-150 parts of isopropanol; 5-30 parts of imidazole ionic liquid of formula (1).

5. The PVB resin adhesive composition according to claim 4, characterized in that, It also includes 10-25 parts of plasticizer, wherein the plasticizer is one or more of the following: dioctyl phthalate, dibutyl phthalate, diisononyl phthalate, diisodecyl phthalate, dioctyl terephthalate, tributyl citrate, trioctyl triphthalate, epoxidized soybean oil, and epoxidized oleate.

6. A PVB resin adhesive, characterized in that, The PVB resin adhesive is prepared by the PVB resin adhesive composition according to claim 4 or 5.

7. A method for preparing the PVB resin adhesive according to claim 6, characterized in that, include: Polyvinyl butyral and ethyl cellulose were added to a mixed solvent of anhydrous ethanol and isopropanol and stirred to dissolve. Then, an imidazole ionic liquid was added and mixed thoroughly to obtain a PVB resin adhesive.

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