Reversible acrylate adhesive with excellent secondary bond strength and method of making, using and applying same

Abstract

The application discloses a reversible acrylate adhesive with excellent secondary bonding strength and a preparation method, a use method and an application thereof. The adhesive is a new reversible acrylate adhesive formed by combining the reversible anthracene group with the good double bond environment and pressure-sensitive characteristics of the acrylate system. Through the steps of photocuring, thermal depolymerization and photocuring, the problem of reduced strength after secondary bonding of the existing reversible adhesive is overcome, and the shear strength after secondary bonding is increased by 42% compared with that after primary bonding. In addition, the debonding rates of the adhesive in the present application in two debonding processes are 91% and 82% respectively, and the adhesive has good debonding performance. Therefore, the reversible acrylate adhesive can be effectively applied in the electronic field and solve the problem of poor mechanical properties after secondary bonding in the existing reversible electronic adhesive field.

Description

Technical Field

[0001] This invention belongs to the field of adhesives, and in particular relates to a reversible acrylate adhesive with excellent secondary bonding strength and its preparation method. Background Technology

[0002] In this era of rapid scientific and technological development, the pace of electronic product updates is accelerating. This not only demands more precise manufacturing of components but also places higher requirements on electronic adhesives, a fundamental and crucial component in the electronics field. For example, during the manufacturing process, components may require temporary positioning, or they may need to be recycled and reused. This necessitates that adhesives, while fulfilling their bonding function, can also debond under specific conditions. Therefore, research on reusable adhesives is of great significance to the development of the electronics industry.

[0003] Existing technologies have conducted extensive research on the reversibility of adhesives. For example, CN113621340A discloses a method for preparing a photoreversible adhesive containing anthracene groups. This method involves preparing an anthracene-containing allyl product through an allylation reaction, followed by reaction with a thiol and a photosensitizer to produce the photoreversible adhesive. While existing reversible adhesives can achieve secondary bonding (i.e., "reversible"), the secondary bond strength of the adhesive is always reduced. This reduced secondary bond strength is detrimental to the re-fixation of electronic components, affecting their application in the electronics field. Therefore, to meet the needs of adhesives in the electronics industry, there is an urgent need to develop a reversible adhesive with excellent debonding properties and superior secondary bond strength. Summary of the Invention

[0004] To address the problem of reduced secondary bonding strength in existing reversible adhesives, this invention provides a reversible acrylic adhesive with excellent secondary bonding strength, along with its preparation and application methods. This adhesive is a novel reversible acrylic adhesive formed by combining the favorable double-bond environment and pressure-sensitive properties of the acrylic system with the reversibility of anthracene groups. Through photocuring, thermal depolymerization, and photocuring steps, it overcomes the problem of reduced strength after secondary bonding found in existing reversible adhesives, increasing the shear strength after secondary bonding by 42% compared to the initial bonding. Furthermore, the adhesive of this invention exhibits debonding rates of 91% and 82% after the two debonding processes, demonstrating excellent debonding performance. Therefore, the reversible acrylic adhesive of this invention can be effectively applied in the electronics field to solve the problem of poor mechanical properties after rebonding in existing reversible electronic adhesives.

[0005] This invention provides a reversible acrylate adhesive with excellent secondary bonding strength. The adhesive is composed of a mercapto-anthracene small molecule functional monomer, difunctional and trifunctional acrylates, and a photoinitiator. The molar ratio of mercapto groups to double bonds is 1:1. The photoinitiator is 1173, and its amount is 1%-7% of the total mass of the monomers, preferably 4%. The difunctional and trifunctional acrylate monomers in the adhesive are tripropylene glycol diacrylate and trimethylolpropane triacrylate, respectively. The molar ratio of the difunctional and trifunctional acrylate monomers is (10-5):(0-5), preferably 9:1.

[0006] The present invention also provides a method for preparing a reversible acrylate adhesive with excellent secondary bonding strength, wherein the method comprises fully mixing a mercapto-anthracene small molecule functional monomer with difunctional and trifunctional acrylates and a photoinitiator in a certain ratio.

[0007] In the method for preparing the reversible acrylate adhesive, the thiol-anthracene small molecule functional monomer is prepared according to the following method:

[0008]

[0009] The specific steps include:

[0010] (1) Anthraquinol (An-OH), dithiodipropionic acid (DTDP), catalyst, and tetrahydrofuran were dissolved completely under stirring, and then placed in an ice-water bath under argon protection. A tetrahydrofuran solution of coupling agent was then added dropwise to the system over a period of about 2 hours. After the addition was complete, the system was moved to room temperature and reacted for 24 hours. After the reaction was completed, the reactants were frozen overnight, centrifuged, washed with anhydrous ethanol, filtered, and then dried under vacuum at 60°C for 6 hours to obtain a light yellow solid powder (anthraquinone dithiodipropionic acid). The product was stored at room temperature in a sealed container away from light.

[0011] (2) The anthracene dithiodipropionic acid methanol ester, reducing agent, catalyst, and tetrahydrofuran / water solution prepared in step (1) were fully dissolved under stirring. Argon gas was introduced, and the reaction was carried out at 30°C in the dark for 24 hours. After the reaction was completed, the product was rotary evaporated, dissolved in dichloromethane, washed with deionized water, washed with saturated NaCl solution, filtered, and finally rotary evaporated again. The product was then vacuum dried at 60°C for 6 hours to obtain a brownish-yellow oily viscous liquid. The product was stored at room temperature in a sealed container in the dark.

[0012] Preferably, the catalyst in step (1) above is 4-dimethylaminopyridine (DMAP);

[0013] Preferably, the coupling agent in step (1) above is N,N′-dicyclohexylcarbodiimide (DCC);

[0014] Preferably, the molar ratio of DTDP, An-OH, DCC, and DMAP in step (1) above is 1:0.77:1.15:0.077;

[0015] Preferably, the reducing agent mentioned in step (2) above is 1,4-dithiothreitol (DTT);

[0016] Preferably, the catalyst mentioned in step (2) above is triethylamine (Et3N);

[0017] Preferably, the volume ratio of tetrahydrofuran / water in step (2) above is 3:1;

[0018] Preferably, the molar ratio of anthracene dithiodipropionate methanol ester, DCC, and Et3N in step (2) above is 1:1.5:1.5.

[0019] The present invention also provides a method for using the reversible acrylic adhesive with excellent secondary bonding strength, comprising the following steps:

[0020] (1) Sample preparation: After the acrylic adhesive is mixed evenly, it is applied to a quartz glass plate (100mm*25mm*2mm) with an area of ​​12.5mm*25mm. Then, another quartz glass plate is used to overlap it.

[0021] (2) One-time UV curing: The adhesive is cross-linked and cured by irradiation with 365nm UV for 5 minutes;

[0022] (3) Thermal depolymerization: Heat at 100℃ for 5 minutes to destroy the integrity of the cross-linked network and cause it to depolymerize;

[0023] (4) Secondary UV curing: Irradiate with 365nm UV for 5 minutes to rebuild the cross-linked network in the adhesive and perform secondary bonding.

[0024] The reversible acrylic adhesive with excellent secondary bonding strength provided by this invention can be applied in the electronics field.

[0025] The reversible acrylate adhesive and its preparation method provided by this invention have the following beneficial effects:

[0026] The reversible acrylate adhesive provided by this invention has a specific molar ratio of difunctional to trifunctional acrylate monomers within the range of (10⁻⁵):(0⁻⁵). Experiments have shown that the optimal performance, with the highest shear strength (1.6681 MPa), is achieved when the molar ratio of difunctional to trifunctional acrylate monomers is 9:1. This is because when there is no trifunctional acrylate in the system, there is no cross-linking network after curing, only entanglement between long chain segments, resulting in low shear strength. Increasing the amount of trifunctional acrylate increases the cross-linking density after curing, enhancing the mechanical properties of the material and increasing the shear strength. However, excessive trifunctional acrylate leads to an excessively high cross-linking density, increasing the brittleness of the material and causing a decrease in strength.

[0027] The reversible acrylic adhesive provided by this invention exhibits excellent secondary bond strength and superior debonding properties. Experiments have shown that the adhesive of this invention can increase the shear strength after secondary bonding by 42% compared to the initial bonding. Furthermore, the debonding rates for the two separations are 91% and 82%, respectively, demonstrating good debonding performance.

[0028] The mechanism by which the reversible acrylic adhesive provided by this invention improves the secondary bonding strength is as follows: A reversible acrylic adhesive is prepared by utilizing the favorable double-bond environment and pressure-sensitive properties of the acrylic system combined with the reversibility of anthracene groups. The adhesive undergoes bonding, debonding, and secondary bonding through photocuring, thermal depolymerization, and photocuring steps. Under light irradiation, anthracene groups form anthracene photodimers to construct a cross-linked network, and some double bonds copolymerize to form branched macromolecules. Under thermal stimulation, the covalent bonds in the anthracene photodimers break, disrupting the integrity of some cross-linked networks. However, the acrylate copolymers formed by the double bond copolymerization still exist in the system. At this point, the adhesive is in a viscoelastic state, tending towards the properties of a pressure-sensitive adhesive, exhibiting a certain degree of pressure sensitivity. Furthermore, under heating conditions, the adhesive can achieve sufficient fluidity to fully wet and smooth the substrate surface. When exposed to light again, the formed anthracene photodimers and the pressure sensitivity synergistically result in higher shear strength in the adhesive, thus achieving a better secondary bonding effect.

[0029] The reversible acrylic adhesive of the present invention can be effectively applied in the electronics field and solves the problem of poor mechanical properties after re-bonding in the field of existing reversible electronic adhesives. Attached Figure Description

[0030] Figure 1 This is a schematic diagram illustrating the bonding and debonding of the adhesive prepared in this invention onto a substrate. Detailed Implementation

[0031] The present invention will be further illustrated below through specific embodiments and application examples. Obviously, the described embodiments are only a part of the embodiments of the present invention and are not intended to limit the scope of the present invention.

[0032] Preparation of thiol-anthracene small molecule functional monomers:

[0033] Anthraquinone (An-OH, 27.42 g, 0.13 mol), dithiodipropionic acid (DTDP, 18 g, 0.086 mol), 4-dimethylaminopyridine (DMAP, 1.61 g, 0.013 mol), and tetrahydrofuran (THF, 400 g) were dissolved completely under stirring, and then placed in an ice-water bath under argon protection. A tetrahydrofuran solution of N,N′-dicyclohexylcarbodiimide (DCC) (40.76 g, 0.33 mol, 200 g THF) was then added dropwise over approximately 2 hours. After the addition was complete, the system was allowed to react at room temperature for 24 hours. After the reaction was complete, the reactants were frozen overnight, centrifuged, washed with anhydrous ethanol, filtered, and then dried under vacuum at 60 °C for 6 hours to obtain a light yellow solid powder (anthraquinone dithiodipropionic acid ester). The product was stored at room temperature in a sealed container protected from light.

[0034] Anthracene dithiodipropionate methanol (3 g, 0.005 mol), 1,4-dithiothreitol (DTT, 1.1750 g, 0.0076 mol), triethylamine (Et3N, 0.7708 g, 0.0076 mol), and tetrahydrofuran / water (V THF V 水 The product was dissolved in a mixture of 3:1 (ratio of 2:1) under stirring, and argon gas was introduced. The reaction was carried out at 30°C in the dark for 24 hours. After the reaction was completed, the product was rotary evaporated, dissolved in dichloromethane, washed with deionized water, washed with saturated NaCl solution, filtered, and finally rotary evaporated again. The product was then vacuum dried at 60°C for 6 hours to obtain a brownish-yellow oily viscous liquid. The product was stored at room temperature in a sealed container in the dark.

[0035] Example 1

[0036] An adhesive was prepared by mixing mercapto-anthracene small molecule functional monomer (2.3 g), difunctional acrylate monomer (1.2949 g), and 1173 photoinitiator (0.1438 g, 4% of the total monomer mass).

[0037] The prepared adhesive was evenly applied to a quartz glass plate (100mm*25mm*2mm), with an application area of ​​12.5mm*25mm. Another quartz glass plate was then used to overlap the adhesive, and finally, the plate was cured by irradiation with 365nm UV for 5 minutes.

[0038] Example 2

[0039] An adhesive was prepared by mixing mercapto-anthracene small molecule functional monomer (2.3 g), difunctional (1.0618 g) and trifunctional acrylate monomer (0.0726 g) and 1173 photoinitiator (0.1374 g, 4% of the total monomer mass).

[0040] The prepared adhesive was evenly applied to a quartz glass plate (100mm*25mm*2mm), with an application area of ​​12.5mm*25mm. Another quartz glass plate was then used to overlap the adhesive, and finally, the plate was cured by irradiation with 365nm UV for 5 minutes.

[0041] Example 3

[0042] An adhesive was prepared by mixing mercapto-anthracene small molecule functional monomer (2.3 g), difunctional (1.0410 g) and trifunctional acrylate monomer (0.1622 g) and 1173 photoinitiator (0.1410 g, 4% of the total monomer mass).

[0043] The prepared adhesive was evenly applied to a quartz glass plate (100mm*25mm*2mm), with an application area of ​​12.5mm*25mm. Another quartz glass plate was then used to overlap the adhesive, and finally, the plate was cured by irradiation with 365nm UV for 5 minutes.

[0044] Example 4

[0045] An adhesive was prepared by mixing mercapto-anthracene small molecule functional monomer (2.3 g), difunctional (0.9064 g) and trifunctional acrylate monomer (0.2421 g) with 1173 photoinitiator (0.1380 g, 4% of the total monomer mass).

[0046] The prepared adhesive was evenly applied to a quartz glass plate (100mm*25mm*2mm), with an application area of ​​12.5mm*25mm. Another quartz glass plate was then used to overlap the adhesive, and finally, the plate was cured by irradiation with 365nm UV for 5 minutes.

[0047] Example 5

[0048] An adhesive was prepared by mixing mercapto-anthracene small molecule functional monomer (2.3 g), difunctional (0.6474 g) and trifunctional acrylate monomer (0.4115 g) with 1173 photoinitiator (0.1343 g, 4% of the total monomer mass).

[0049] The prepared adhesive was evenly applied to a quartz glass plate (100mm*25mm*2mm), with an application area of ​​12.5mm*25mm. Another quartz glass plate was then used to overlap the adhesive, and finally, the plate was cured by irradiation with 365nm UV for 5 minutes.

[0050] Application Example 1

[0051] The acrylate adhesives prepared in Examples 1-5 were subjected to shear strength tests.

[0052] Testing instruments and conditions: Sansi CMT 6000 universal testing machine. Shear strength was tested according to GB / T 7124-86. Results are shown in Table 1.

[0053] Table 1 Shear strength test results

[0054]

[0055] As shown in Table 1, the shear strength first increases and then decreases with the increase of trifunctional acrylate content. The shear strength is the highest when the molar ratio of difunctional to trifunctional acrylate is 9:1, reaching 1.6681 MPa.

[0056] Application Example 2

[0057] The repeatability bonding performance of the acrylic adhesive prepared in Example 2 was tested.

[0058] Experimental procedure: After the first photocuring, the thermopolymer was heated at 100℃ for 5 minutes to perform thermal depolymerization, and then irradiated with 365nm UV for 5 minutes for a second photocuring.

[0059] Testing instruments and conditions: Sansi CMT 6000 universal testing machine. Shear strength was tested according to GB / T 7124-86. Results are shown in Table 2.

[0060] Table 2 Results of Repeatable Adhesion Shear Strength Test

[0061]

[0062] As shown in Table 2, the prepared reversible acrylic adhesive underwent two bonding and debonding tests. The shear strength of the second bond was 42% higher than that of the first bond. The debonding rate was 91% in the first bond and 82% in the second bond. Although the debonding rate decreased in the second bond, it was still within the ideal range.

[0063] As can be seen from the comprehensive application examples 1-2, the reversible acrylic adhesive with excellent secondary bonding strength provided by this invention overcomes the problem of reduced strength after secondary bonding of existing reversible adhesives through photocuring, thermal depolymerization, and photocuring steps, increasing the shear strength after secondary bonding by 42% compared to the initial bonding. Furthermore, the adhesive of this invention exhibits good debonding performance with debonding rates of 91% and 82% after the two debonding processes. Therefore, the reversible acrylic adhesive of this invention can be effectively applied in the electronics field and solves the problem of poor mechanical properties after rebonding in existing reversible electronic adhesives.

[0064] The above description is merely a preferred embodiment of the present invention, intended to help readers better understand the invention. However, the embodiments of the present invention are not limited to the above examples. Any other specific changes, combinations, or modifications made by those skilled in the art based on the technical solution and inventive concept of the present invention are included within the protection scope of the present invention.

Claims

1. A reversible acrylic adhesive with excellent secondary bonding strength, characterized in that: The adhesive is composed of a thiol-anthracene small molecule functional monomer, difunctional and trifunctional acrylates, and a photoinitiator. The structure of the thiol-anthracene small molecule functional monomer is as follows. The molar ratio of thiol groups to double bonds is 1:1; the photoinitiator is 1173, and its amount is 1%-7% of the total mass of monomers; the difunctional and trifunctional acrylate monomers in the adhesive are tripropylene glycol diacrylate and trimethylolpropane triacrylate, respectively; the molar ratio of the difunctional and trifunctional acrylate monomers is (10-5):(0-5).

2. The method for preparing the reversible acrylic adhesive with excellent secondary bonding strength according to claim 1, characterized in that: A reversible acrylate adhesive with excellent secondary bonding strength was prepared by thoroughly mixing mercapto-anthracene small molecule functional monomers with difunctional and trifunctional acrylates and photoinitiators in a certain ratio.

3. The method for preparing the reversible acrylic adhesive with excellent secondary bonding strength according to claim 2, characterized in that: The specific steps of the preparation method of the thiol-anthracene small molecule include: (1) Using anthraquinol and dithiodipropionic acid as raw materials, anthraquinol dithiodipropionic acid is synthesized by Steglich esterification under the action of catalyst and coupling agent. (2) The anthracene dithiodipropionate methanol ester obtained in step (1) is synthesized into mercaptopropionate anthracene methanol ester under the action of a reducing agent. In step (1), the preparation method of anthracene dithiodipropionate methanol ester includes the following steps: (11) Dissolve anthraquinol An-OH, dithiodipropionic acid DTDP, catalyst and tetrahydrofuran under stirring, and then place them in an ice-water bath and protect them with argon gas. (12) Add a tetrahydrofuran solution of coupling agent dropwise to the system over a period of about 2 hours. After the addition is complete, move the system to room temperature and react for 24 hours. (13) After the reaction is complete, the reactants are frozen overnight, centrifuged, washed with anhydrous ethanol, filtered, and then dried under vacuum at 60°C for 6 hours to obtain a light yellow solid powder. The product is stored at room temperature in a sealed container away from light. In step (2), the preparation method of anthracene mercaptopropionic acid methanol ester includes the following steps: (21) Dissolve anthracene dithiodipropionate methanol ester, reducing agent, catalyst and tetrahydrofuran / water solution under stirring, introduce argon gas, and react in the dark at 30°C for 24 hours. (22) After the reaction is complete, the product is rotary evaporated and dissolved in dichloromethane, washed with deionized water, washed with saturated NaCl solution, filtered, and then rotary evaporated again. It is then vacuum dried at 60°C for 6 hours to obtain a brownish-yellow oily viscous liquid. The product is stored at room temperature in a sealed container away from light. Wherein, the catalyst mentioned in step (11) is 4-dimethylaminopyridine DMAP; the coupling agent mentioned in step (12) is N,N′-dicyclohexylcarbodiimide DCC; the reducing agent mentioned in step (21) is 1,4-dithiothreitol DTT; the catalyst mentioned in step (21) is triethylamine Et3N; the volume ratio of tetrahydrofuran / water mentioned in step (21) is (3-5):1; the molar ratio of anthracene dithiodipropionate methanol ester, DTT, and Et3N mentioned in step (21) is 1:1.5:1.

5.

4. The method of using the reversible acrylic adhesive with excellent secondary bonding strength according to claim 1, characterized in that: The method of use includes the following steps. (1) Sample preparation: After the acrylic adhesive is mixed evenly, it is applied to a 100mm*25mm*2mm quartz glass plate with an area of ​​12.5mm*25mm. Then, another quartz glass plate is used to overlap it. (2) One-time UV curing: The adhesive is cross-linked and cured by irradiation with 365nm UV for 5 minutes; (3) Thermal depolymerization: Heat at 100℃ for 5 minutes to destroy the integrity of the cross-linked network and cause it to depolymerize; (4) Secondary UV curing: Irradiate with 365nm UV for 5 minutes to rebuild the cross-linked network in the adhesive and perform secondary bonding.

5. The reversible acrylic adhesive with excellent secondary bonding strength according to claim 1, characterized in that, The adhesive is used in the electronics field.

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