High-strength on-demand debondable UV-curable adhesive, preparation method and application thereof

Abstract

This invention relates to the field of organic materials technology, specifically to a high-strength, on-demand debonding UV-curable adhesive, its preparation method, and its applications. The adhesive is prepared using raw materials including: disulfide-bonded polyurethane acrylate oligomers, disulfide acrylic acid reactive monomers, acrylic diluents, photoinitiators, and coupling agents. This invention employs a two-step method to synthesize the disulfide-bonded polyurethane acrylate oligomers. The oligomers are mixed with photoinitiators, disulfide acrylic acid molecules, reactive diluents, and silane coupling agents in a specific ratio. After vacuum degassing in the dark, the mixture is coated onto the surface of the bonded parts and cured by UV irradiation for 1 minute. This method features mild reaction conditions, a simple preparation process, high raw material conversion rate, and high product purity, effectively solving the problem of controllable debonding in existing UV-curable adhesives. It is suitable for temporary fixation of precision devices and material recycling applications.

Description

Technical Field

[0001] This invention belongs to the field of organic materials, and particularly relates to a high-strength UV-curable adhesive that can be delaminated on demand, its preparation method, and its application. Background Technology

[0002] UV-curable adhesives, with their advantages of fast curing speed, ease of use, and environmental friendliness, are widely used in electronic device packaging, precision component micromachining, and optical component assembly, especially suitable for scenarios with high processing efficiency requirements. However, existing UV-curable adhesives form irreversible covalent cross-linked networks after curing, making it impossible to detach them on demand once bonding is complete. This poses a significant drawback in temporary fixing scenarios, not only making subsequent non-destructive disassembly of components difficult but also preventing the recycling of usable materials from scrapped parts, increasing production costs and wasting resources. Therefore, how to maintain the high-strength bonding performance of UV-curable adhesives while endowing them with controllable debonding capabilities has become a pressing technical challenge in this field. Summary of the Invention

[0003] The purpose of this invention is to provide a high-strength UV-curable adhesive that can be debonded on demand. This UV-curable adhesive can be debonded under heat stimulation, thereby solving the problem that traditional thermosetting adhesives cannot be debonded once cured, and providing a material basis for material recycling and temporary fixation of precision parts.

[0004] To achieve the above objectives, the present invention provides a high-strength UV-curable adhesive that can be delaminated on demand, the raw materials of which include: polyurethane acrylate oligomers containing disulfide bonds, disulfide acrylic reactive monomers, acrylic diluents, photoinitiators and coupling agents. The dithioacrylate active monomers include: N,N'-bis(acryloyl)cystamine; The raw materials for preparing the polyurethane acrylate oligomer containing disulfide bonds include: diisocyanate, 2-hydroxyethyl disulfide, polydiol, acrylic acid end-capping agent, catalyst and polymerization inhibitor.

[0005] To achieve the above objectives, this invention provides a high-strength, on-demand debonding UV-curable adhesive. At room temperature, disulfide-bonded polyurethane acrylate oligomers and disulfide-bonded acrylic reactive monomer N,N'-bis(acryloyl)cysteine ​​form a dense cross-linked network after UV curing, imparting excellent adhesive strength to the adhesive and meeting the mechanical requirements for temporary fixation of precision devices. Under heating conditions, the disulfide bonds in the oligomer backbone and the disulfide bonds in N,N'-bis(acryloyl)cysteine ​​undergo a dynamic exchange reaction, causing the cross-linked network to rearrange and soften, resulting in a significant decrease in adhesive strength, thereby achieving rapid and controllable debonding. Due to N... N'-bis(acryloyl)cysteine ​​is uniformly distributed and has strong chain segment mobility. This exchange reaction is sensitively triggered and responds rapidly, allowing for debonding at lower temperatures or in shorter times. Furthermore, it leaves minimal residue on the substrate surface after debonding, resulting in high cleanliness and facilitating non-destructive disassembly and material recycling. In addition, the debonding effect exhibits good controllability with heating temperature and time, allowing users to precisely control the debonding timing according to process requirements. Ultimately, this design enables the adhesive to possess both high-strength bonding and on-demand debonding functions, expanding its application scenarios from permanent fixation to temporary fixation, precision assembly, and multi-material recycling, demonstrating significant technological advancement and practical value.

[0006] According to an embodiment of the present invention, the raw materials for preparation, by weight, include: 60-70 parts of polyurethane acrylate oligomer, 5-8 parts of disulfide acrylic acid active monomer, 28-35 parts of acrylic acid diluent, 2-5 parts of photoinitiator, 1-3 parts of coupling agent, 0.01-0.05 parts of catalyst and 0.005-0.01 parts of polymerization inhibitor.

[0007] Introducing active monomers with disulfide bonds (such as N,N'-bis(acryloyl)cysteine) into UV-curable adhesive systems serves several purposes. First, this diluent participates in crosslinking as an active monomer during the curing process, enabling the adhesive to maintain high bonding strength at room temperature and meet the mechanical requirements for temporary fixation of precision devices. Second, under heating conditions, it can effectively trigger dynamic exchange reactions with disulfide bonds in the oligomer backbone, significantly improving thermal response sensitivity and allowing the adhesive to soften and debond at lower temperatures and in a shorter time.

[0008] According to an embodiment of the present invention, the raw materials for preparing the polyurethane acrylate oligomer containing disulfide bonds, by molar fraction, include: 6-10 parts of diisocyanate, 2-4 parts of 2-hydroxyethyl disulfide, 0.5-2 parts of polydiol, and 6-10 parts of acrylic acid end-capping agent.

[0009] According to embodiments of the present invention, the diisocyanate comprises at least one of aliphatic diisocyanate and alicyclic diisocyanate; The alicyclic diisocyanate includes at least one of isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, 1,4-cyclohexane diisocyanate and methylcyclohexane diisocyanate. The aliphatic diisocyanate includes at least one of 1,4-butane diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, and hexamethylene diisocyanate.

[0010] According to embodiments of the present invention, the diol comprises at least one of polytetrahydrofuran diol, polycaprolactone diol, and polycarbonate diol.

[0011] According to an embodiment of the present invention, the average molecular weight of the diol is between 500 and 1000.

[0012] According to embodiments of the present invention, the selected acrylic end-capping agent includes at least one of hydroxyethyl acrylate, hydroxyethyl methacrylate, and hydroxypropyl acrylate.

[0013] According to embodiments of the present invention, the acrylic diluent further includes at least one of hydroxyethyl acrylate, isobornyl acrylate, hydroxyethyl methacrylate, and hydroxypropyl acrylate.

[0014] According to an embodiment of the present invention, the catalyst comprises dibutyltin dilaurate.

[0015] According to an embodiment of the present invention, the polymerization inhibitor includes at least one of p-methoxyphenol, hydroquinone, p-benzoquinone, and anthraquinone.

[0016] According to embodiments of the present invention, the photoinitiator includes at least one selected from 2-hydroxy-2-methylphenylacetone, 1-hydroxycyclohexylphenyl ketone, benzophenone, 4-phenylbenzophenone, 2-isopropylthioxanthonone, 2-isopropylthioxanthonone, 2-chlorothioxanthonone, 2,4,6-trimethylbenzoyl diphenylphosphine oxide, and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide.

[0017] According to an embodiment of the present invention, the coupling agent comprises vinyltris(2-methoxyethoxy)silane.

[0018] According to a second aspect of the present invention, a method for preparing the high-strength, on-demand, UV-curable adhesive includes the following steps: S1. Diisocyanate, 2-hydroxyethyl disulfide, polydiol and catalyst are reacted in an organic solvent at 60-70°C for 2-3 hours under anhydrous and oxygen-free conditions. Then, acrylic acid end-capping agent and polymerization inhibitor are added and the reaction is continued for 6-8 hours. After post-treatment, polyurethane acrylate oligomer containing disulfide bonds is obtained. S2. The polyurethane acrylate oligomer containing disulfide bonds obtained in step S1 is mixed and reacted with acrylic diluent, photoinitiator and coupling agent. After vacuum degassing, a high-strength UV-curable adhesive that can be delaminated as needed is obtained.

[0019] According to an embodiment of the present invention, the post-processing method includes: after solvent removal, heating and drying in a vacuum environment at 50~60℃ for 10~12h to obtain polyurethane acrylate prepolymer.

[0020] According to a third aspect of the invention, the application of the high-strength, on-demand, UV-curable adhesive is proposed in device fixing.

[0021] According to an embodiment of the present invention, the adhesive is cured by ultraviolet light to form an adhesive bond to the device, and the device is disassembled by heating reaction. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0023] Figure 1 This is a diagram illustrating the curing and debonding mechanism of a high-strength, controllable debonding UV-curable adhesive according to the present invention. Figure 2 This is the stress-displacement curve of the adhesive in the tensile shear test of Example 1; Figure 3 This is the tensile shear strength change curve of the sample in Example 1 as temperature changes.

[0024] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0027] Example 1 This embodiment provides a high-strength, on-demand debonding UV-curable adhesive. Isophorone diisocyanate is used as the diisocyanate, polycaprolactone diol (Mw=530) is used as the diol, hydroxyethyl acrylate is used as the end-capping agent, and hydroquinone is used as the polymerization inhibitor to prepare a polyurethane acrylate oligomer. Hydroxyethyl acrylate is selected as the reactive diluent, and 2-hydroxy-2-methylphenylacetone is selected as the photoinitiator to prepare a high-strength, controllable debonding UV-curable adhesive. The preparation method is as follows: S1.1 Place 6g of polycaprolactone diol in a vacuum oven at 120℃ and heat for 2 hours to remove moisture, then cool to room temperature for later use. S1.2 Add 17.78g isophorone diisocyanate, 4.63g 2-hydroxyethyl disulfide, and 5.3g dehydrated polycaprolactone diol to 20ml ethyl acetate as solvent, and 2 drops of dibutyltin dilaurate catalyst. Stir at 70℃ for 2h under nitrogen protection. S1.3 After step two is completed, add 9.30g of hydroxyethyl acrylate and 0.04g of hydroquinone polymerization inhibitor, continue the reaction for 6 hours, and then stop the reaction. S1.4. The solution after the reaction in step 3 is rotary evaporated to remove the ethyl acetate solvent, and then placed in a vacuum oven at 50°C and heated for 12 hours to remove the residual ethyl acetate, so as to obtain a pure polyurethane acrylate oligomer containing disulfide bonds. Preparation of adhesives: S2. Add 15g of disulfide-bonded polyurethane acrylate oligomer, 4.28g of hydroxyethyl acrylate, 1.07g of N,N'-bis(acryloyl)cysteine, 0.64g of 2-hydroxy-2-methylphenylacetone, and 0.64g of vinyltris(2-methoxyethoxy)silane to 50ml beakers respectively, stir evenly with a stirrer, and then place in a vacuum oven and vacuum for 10min to remove bubbles, thereby obtaining a high-performance, controllable debonding UV-curable adhesive.

[0028] Adhesive performance testing: A polycarbonate (PC) sheet measuring 100 mm × 25 mm × 3 mm was selected as the bonding substrate. To ensure consistent stress direction during stretching, a fiberglass sheet measuring 37.5 × 25 × 3 mm was bonded to the clamping area of ​​the PC sheet. Before bonding, the bonding area of ​​the PC sheet was sanded and then wiped with ethanol to remove surface impurities and oil stains. The PC substrate was covered with adhesive, with a fixed coverage area of ​​25 × 12.5 mm. The bonding areas of the two substrates were then overlapped using transparent clips. The sample was irradiated in a UV oven with a main wavelength of 365 nm for 1 minute.

[0029] Tensile shear tests were conducted according to GB / T 7124-2008. Tensile tests were performed on a mechanical testing machine at a tensile rate of 3 mm / min. The tensile shear strength was calculated by dividing the maximum bond strength by the bond area. Five specimens were tested in each group, and the average value was taken.

[0030] Figure 1 This is a schematic diagram illustrating the curing and debonding mechanism of the high-strength, on-demand debonding UV-curable adhesive of the present invention. As shown in the figure, the left side illustrates the curing process of the adhesive under ultraviolet light irradiation: the disulfide-bonded polyurethane acrylate oligomer, the disulfide-bonded acrylic reactive monomer (N,N'-bis(acryloyl)cysteine), and the diluent undergo a cross-linking reaction under the action of a photoinitiator, forming a three-dimensional network structure, which endows the adhesive with high-strength adhesive properties. The right side illustrates the debonding process under heating conditions: the increase in temperature triggers a dynamic exchange reaction of disulfide bonds, causing the cross-linked network to rearrange or soften, thereby reducing the adhesive strength and achieving controllable debonding.

[0031] Figure 2 This is the stress-displacement curve of the adhesive in Example 1 under tensile shear test at room temperature. The curve shows the mechanical behavior of the adhesive in the standard tensile shear test (according to GB / T 7124-2008). The horizontal axis represents displacement (mm), and the vertical axis represents stress (MPa). The adhesive exhibits high peak stress and good ductility during the tensile process, indicating that it has excellent structural strength and adhesive properties at room temperature, meeting the strength requirements for temporary fixation of precision components. (Stress-displacement curve (e.g.)) Figure 2 The sample exhibits typical ductile fracture characteristics, with peak stress reaching the expected level. This demonstrates that the polyurethane acrylate oligomer containing disulfide bonds and the disulfide-containing diluent N,N'-bis(acryloyl)cysteine ​​form a dense cross-linked network after UV curing, giving the adhesive excellent load-bearing capacity and meeting the bonding strength requirements for temporary fixation of precision devices.

[0032] Figure 3This is a graph showing the tensile shear strength variation of the adhesive in Example 1 at different temperatures. The graph illustrates the trend of the adhesive's tensile shear strength as temperature increases. The horizontal axis represents temperature (°C), and the vertical axis represents tensile shear strength (MPa). The curves show that the adhesive strength gradually decreases with increasing temperature, especially after heating to a certain temperature (e.g., the temperature range corresponding to 105 seconds of heating with a hair dryer), where the strength significantly decreases. This result indicates that the adhesive has good thermal response debonding performance, allowing for on-demand disassembly through heating, meeting the application requirements of temporary fixation and material recycling. Heating triggers a dynamic exchange reaction of disulfide bonds in the system, causing rearrangement and softening of the crosslinked network, leading to adhesive failure. This result verifies the technical feasibility of achieving "high strength at room temperature, debonding upon heating" through a double disulfide bond design in this invention. Simultaneously, from... Figure 3 The temperature-strength curves shown indicate that the adhesive strength decreases gradually with increasing temperature, demonstrating a positive correlation between the debonding effect and the heating temperature. Users can precisely control the debonding timing by adjusting the heating temperature and time according to actual process requirements, enabling the adhesive to adapt to different usage scenarios. This allows for rapid disassembly when needed, as well as gentle debonding at lower temperatures, avoiding thermal damage to the substrate.

[0033] Example 2 This embodiment provides a high-strength, on-demand, debonding UV-curable adhesive. Isophorone diisocyanate is selected as the diisocyanate, polytetrahydrofuran diol as the diol, hydroxyethyl acrylate as the end-capping agent, and p-methoxyphenol as the polymerization inhibitor to prepare a polyurethane acrylate oligomer. Hydroxyethyl methacrylate is selected as the reactive diluent, and 2-hydroxy-2-methylphenylacetone is selected as the photoinitiator to prepare the high-strength, controllable debonding UV-curable adhesive. The preparation method is as follows: S1. Preparation of polyurethane acrylate oligomers containing disulfide bonds S1.1 Place 7g of polytetrahydrofuran diol in a vacuum oven at 120℃ and heat for 2 hours to remove moisture, then cool to room temperature for later use; S1.2 Add 17.78g isophorone diisocyanate, 4.62g 2-hydroxyethyl disulfide, and 6.5g dehydrated polytetrahydrofuran diol to 20ml ethyl acetate as solvent, add 2 drops of dibutyltin dilaurate catalyst, and stir at 70℃ for 2h under nitrogen protection. S1.3 After the reaction in S1.2 is complete, add 9.3g of hydroxyethyl acrylate and 0.04g of p-methoxyphenol polymerization inhibitor, and continue to react at 70℃ for 6h. S1.4. The reaction solution obtained in S1.3 is rotary evaporated to remove the ethyl acetate solvent, and then placed in a vacuum oven at 50°C for 12 hours to remove the residual solvent, thereby obtaining a pure polyurethane acrylate oligomer containing disulfide bonds.

[0034] S2. Preparation of adhesive: 10g of the disulfide-bonded polyurethane acrylate oligomer obtained in step S1, 3.57g of hydroxyethyl methacrylate, 1.19g of N,N'-bis(acryloyl)cysteine, 0.42g of 2-hydroxy-2-methylphenylacetone, and 0.42g of vinyltris(2-methoxyethoxy)silane were added to 50ml beakers respectively and stirred evenly with a stirrer. Then, the beakers were placed in a vacuum oven and vacuumed for 10min to remove bubbles, resulting in a high-strength UV-curable adhesive that can be delaminated as needed. Adhesive performance testing: A polycarbonate (PC) sheet measuring 100 mm × 25 mm × 3 mm was selected as the bonding substrate. To ensure consistent stress direction during stretching, a fiberglass sheet measuring 37.5 × 25 × 3 mm was bonded to the clamping area of ​​the PC sheet. Before bonding, the bonding area of ​​the PC sheet was sanded and then wiped with ethanol to remove surface impurities and oil stains. The PC substrate was covered with adhesive, with a fixed coverage area of ​​25 × 12.5 mm. The bonding areas of the two substrates were then overlapped using transparent clips. The sample was irradiated in a UV oven with a main wavelength of 365 nm for 1 minute.

[0035] Tensile shear tests were conducted according to GB / T 7124-2008. Tensile tests were performed on a mechanical testing machine at a tensile rate of 3 mm / min. The tensile shear strength was calculated by dividing the maximum bond strength by the bond area. Five specimens were tested in each group, and the average value was taken.

[0036] Comparative Example 1 This comparative example provides a UV-curable adhesive whose raw materials and preparation process differ from those in Example 1 in that the disulfide-containing diluent N,N'-bis(acryloyl)cysteine ​​is replaced with the same mass fraction of hydroxyethyl acrylate.

[0037] The performance of the comparative example was evaluated using the same test method as that of Example 1. The test results showed that under heating conditions, the strength of the comparative example 1 decreased significantly less than that of Example 1. It maintained a high bonding strength under the same heating temperature and time, but it was difficult to achieve effective debonding. Higher temperatures or longer times were required for partial softening. Moreover, a lot of residue remained on the substrate surface after debonding, requiring mechanical cleaning.

[0038] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A high-strength, on-demand, UV-curable adhesive, characterized in that, The raw materials for preparation include: polyurethane acrylate oligomers containing disulfide bonds, disulfide acrylic reactive monomers, acrylic diluents, photoinitiators, and coupling agents; The dithioacrylate active monomers include: N,N'-bis(acryloyl)cystamine; The raw materials for preparing the polyurethane acrylate oligomer containing disulfide bonds include: diisocyanate, 2-hydroxyethyl disulfide, polydiol, acrylic acid end-capping agent, catalyst and polymerization inhibitor.

2. The high-strength, on-demand, UV-curable adhesive according to claim 1, characterized in that, The raw materials for preparation, by weight, include: 60-75 parts of polyurethane acrylate oligomer, 5-8 parts of disulfide acrylic acid active monomer, 20-35 parts of acrylic acid diluent, 2-5 parts of photoinitiator, 1-3 parts of coupling agent, 0.01-0.05 parts of catalyst and 0.005-0.01 parts of polymerization inhibitor.

3. The high-strength, on-demand, UV-curable adhesive according to claim 1, characterized in that, Based on molar quantities, the raw materials for preparing polyurethane acrylate oligomers containing disulfide bonds include: 6-10 parts of diisocyanate, 2-4 parts of 2-hydroxyethyl disulfide, 0.5-2 parts of polydiol, and 6-10 parts of acrylic acid end-capping agent.

4. The high-strength, on-demand, UV-curable adhesive according to claim 1, characterized in that, The diisocyanate includes at least one of aliphatic diisocyanate and alicyclic diisocyanate; The alicyclic diisocyanate includes at least one of isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, 1,4-cyclohexane diisocyanate and methylcyclohexane diisocyanate. The aliphatic diisocyanate includes at least one of 1,4-butane diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, and hexamethylene diisocyanate.

5. The high-strength, on-demand, UV-curable adhesive according to claim 1, characterized in that, The polydiol includes at least one of polytetrahydrofuran diol, polycaprolactone diol, and polycarbonate diol.

6. The high-strength, on-demand, UV-curable adhesive according to claim 1, characterized in that, The selected acrylic end-capping agent includes at least one of hydroxyethyl acrylate, hydroxyethyl methacrylate, and hydroxypropyl acrylate.

7. The high-strength, on-demand, UV-curable adhesive according to claim 1, characterized in that, The acrylic diluent also includes at least one of hydroxyethyl acrylate, isobornyl acrylate, hydroxyethyl methacrylate, and hydroxypropyl acrylate.

8. A method for preparing a high-strength, on-demand, UV-curable adhesive as described in any one of claims 1 to 7, characterized in that, Includes the following steps: S1. Diisocyanate, 2-hydroxyethyl disulfide, polydiol and catalyst are reacted in an organic solvent at 60-70°C for 2-3 hours under anhydrous and oxygen-free conditions. Then, acrylic acid end-capping agent and polymerization inhibitor are added and the reaction is continued for 6-8 hours. After post-treatment, polyurethane acrylate oligomer containing disulfide bonds is obtained. S2. The polyurethane acrylate oligomer containing disulfide bonds obtained in step S1 is mixed and reacted with acrylic diluent, photoinitiator and coupling agent. After vacuum degassing, a high-strength UV-curable adhesive that can be delaminated as needed is obtained.

9. The application of a high-strength, on-demand, UV-curable adhesive as described in any one of claims 1 to 8 in device fixing.

10. The application according to claim 9, characterized in that, Includes the following steps: The adhesive is cured by ultraviolet light to bond the device, and the device is disassembled by heating.

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