Preparation method of visible light induced stripping pressure-sensitive adhesive

Abstract

The invention discloses a preparation method of a visible light induced stripping pressure-sensitive adhesive, which comprises the following steps: firstly, carrying out free radical solution polymerization on a (methyl) acrylate monomer containing a p-methylbenzenesulfonylhydrazone (C = NNHTs) structure and a second monomer under the action of an ultraviolet light initiator to obtain an initial polymer solution; and then adding an organic alkali additive into the system, uniformly mixing, coating on the surface of a base material, and volatilizing the solvent to obtain the pressure-sensitive adhesive. The pressure-sensitive adhesive is suitable for surface bonding of various materials such as metal, plastic and glass, due to the addition of the organic alkali, a 4-methylbenzenesulfinic acid (HTs) structure can be removed from C = NNHTs in a polymer to generate a diazo compound (C = N2), the diazo compound can be activated under visible light to generate a free-state carbene intermediate, then a C-H bond insertion reaction is carried out in situ, and the pressure-sensitive adhesive is prepared. The crosslinking density and cohesive energy strength of the pressure-sensitive adhesive are improved, the pressure-sensitive adhesive is induced to be stripped on the surface of a base material according to needs, and the adhered base material is not damaged in the process.

Description

Technical Field

[0001] The invention belongs to the technical field of adhesives, and particularly relates to a method for preparing a pressure-sensitive adhesive capable of being peeled by visible light induction. Background Art

[0002] With the rapid development of modern industry and technology, the application scope of adhesives has continued to expand in many fields. From daily packaging and architectural decoration to high-end electronics, automobiles, aerospace and other industries, they all rely on the support of high-performance adhesives. However, when faced with complex environments and special needs, traditional adhesives often show their limitations. For example, under harsh conditions such as high temperature and humidity, low temperature, strong acids and strong alkalis, ordinary adhesives are prone to failure, resulting in a decrease in bonding strength, and even leakage, breakage and other problems. In addition, in some specific application scenarios, such as the assembly and maintenance of electronic devices, biomedical tissue repair, etc., adhesives need to have reversible adhesion properties to achieve non-destructive peeling and reuse.

[0003] In recent years, significant progress has been made in the research of stimuli-responsive materials. These materials can change their properties under the influence of external stimuli (such as light, temperature, pH, magnetic field, electric field, etc.), thereby achieving dynamic regulation of material properties. Among them, photoresponsive materials have attracted much attention due to their unique advantages. As a clean and pollution-free energy source, light has the advantages of strong penetration, concentrated energy, and easy control, which can achieve precise regulation of materials. However, most current research on photoresponsive adhesives focuses on the application of ultraviolet light or near-infrared light, while research on visible light-responsive adhesives is relatively limited. In addition, existing visible light-responsive adhesives still have shortcomings in terms of adhesion performance and response speed. For example, some adhesives have limited improvement in adhesion performance under visible light and have a slow response speed, which makes it difficult to meet the rapid response requirements in practical applications.

[0004] Therefore, developing a novel adhesive that combines high adhesion and rapid visible light responsiveness is crucial to meeting the complex demands of modern industry and technology. This adhesive must not only exhibit excellent adhesion under standard conditions but also enable rapid, non-destructive peeling under visible light irradiation without damaging the substrate. Summary of the Invention

[0005] The present invention addresses the shortcomings of the aforementioned prior art and provides a method for preparing a visible light-induced peelable pressure-sensitive adhesive. This method produces a visible light-induced peelable pressure-sensitive adhesive by reacting a (meth)acrylate monomer containing a p-toluenesulfonylhydrazone (C=NNHTs) structure with other (meth)acrylate monomers and an organic base additive. This adhesive is bonded via non-covalent bonds, enhancing its inherent strength and enabling non-destructive peeling upon exposure to visible light.

[0006] The method for preparing a pressure-sensitive adhesive capable of being released by visible light induction of the present invention comprises the following steps:

[0007] First, a first monomer and a second monomer undergo free radical polymerization in the presence of a photoinitiator to achieve initial bonding strength. An organic base additive is then added to the system and mixed thoroughly to prepare a pressure-sensitive adhesive coating. The addition of the organic base additive causes the C=NNHTs in the polymer to shed their 4-methylbenzenesulfinic acid (HTs) structure to form a diazo compound (C=N2). This diazo can be activated by visible light to form a free carbene intermediate, which then undergoes an in-situ C-H bond insertion reaction, increasing the crosslink density and cohesive strength of the pressure-sensitive adhesive. The pressure-sensitive adhesive of this invention can be peeled off from the substrate surface on demand without damaging the adhered substrate.

[0008] The first monomer is a (meth)acrylate monomer containing a p-toluenesulfonylhydrazone structure, and its general structural formula is as follows:

[0009]

[0010] Among them, R1=H or CH3, n=2 or 4, R2=OCH3, H, CF3 or NO2.

[0011] Furthermore, the first monomer is selected from one or more of the following monomers:

[0012]

[0013] Ethyl 2-(2-phenyl-2-(2-toluenesulfonylhydrazide)acetoxy)acrylate

[0014]

[0015] 2-(2-phenyl-2-(2-toluenesulfonylhydrazide)acetoxy)ethyl methacrylate

[0016]

[0017] Butyl 4-(2-phenyl-2-(2-toluenesulfonylhydrazide)acetoxy)acrylate

[0018]

[0019] 4-(2-phenyl-2-(2-toluenesulfonylhydrazide)acetoxy)butyl methacrylate

[0020]

[0021] Ethyl 2-(2-(4-nitrophenyl)-2-(2-toluenesulfonylhydrazide)acetoxy)acrylate

[0022]

[0023] 2-(2-(4-nitrophenyl)-2-(2-toluenesulfonylhydrazide)acetoxy)ethyl methacrylate

[0024]

[0025] Butyl 4-(2-(4-nitrophenyl)-2-(2-toluenesulfonylhydrazide)acetoxy)acrylate

[0026]

[0027] 4-(2-(4-nitrophenyl)-2-(2-toluenesulfonylhydrazide)acetoxy)butyl methacrylate

[0028]

[0029] Ethyl 2-(2-(2-toluenesulfonylhydrazide)-2-(4-trifluoromethylphenyl)acetoxy)acrylate

[0030]

[0031] 2-(2-(2-toluenesulfonylhydrazido)-2-(4-trifluoromethylphenyl)acetoxy)ethyl methacrylate

[0032]

[0033] Butyl 4-(2-(2-toluenesulfonylhydrazide)-2-(4-trifluoromethylphenyl)acetoxy)acrylate

[0034]

[0035] 4-(2-(2-toluenesulfonylhydrazide)-2-(4-trifluoromethylphenyl)acetoxy)butyl methacrylate

[0036]

[0037] Ethyl 2-(2-(4-methoxyphenyl)-2-(2-toluenesulfonylhydrazide)acetoxy)acrylate

[0038]

[0039] 2-(2-(4-methoxyphenyl)-2-(2-toluenesulfonylhydrazide)acetoxy)ethyl methacrylate

[0040]

[0041] Butyl 4-(2-(4-methoxyphenyl)-2-(2-toluenesulfonylhydrazide)acetoxy)acrylate

[0042]

[0043] 4-(2-(4-methoxyphenyl)-2-(2-toluenesulfonylhydrazide)acetoxy)butyl methacrylate

[0044] Furthermore, the first monomer is preferably ethyl 2-(2-phenyl-2-(2-toluenesulfonylhydrazide)acetoxy)acrylate.

[0045] The first monomer is prepared by the following method:

[0046] Benzoylformic acid monomer A with different substituents, oxalyl chloride, acrylate B containing a hydroxyl structure, triethylamine and DMF are reacted in a dichloromethane solution to produce a (meth) acrylic acid monomer C containing an aryl formyl ester structure, which is then reacted with p-toluenesulfonylhydrazine D and a small amount of catalyst in a methanol solution to obtain a (meth) acrylic acid ester monomer E containing a p-toluenesulfonylhydrazone structure. The synthetic route is as follows: Figure 1 The definitions of substituents R1 and R2 in the figure remain the same as above.

[0047] The acrylic acid ester containing a hydroxyl structure is selected from one of hydroxyethyl acrylate, hydroxyethyl methacrylate, 4-hydroxybutyl acrylate, and 2-methacrylate-4-hydroxybutyl ester.

[0048] The catalyst is acetic acid.

[0049] The equivalent ratio of the benzoylformic acid to oxalyl chloride is 1.0:1.1-2.0.

[0050] The equivalent ratio of the acrylate containing a hydroxyl structure to triethylamine is 1.0:1.1-2.0.

[0051] The second monomer is selected from one or more of acrylic acid, N-acryloylmorpholine, isooctyl acrylate, butyl acrylate, dodecyl acrylate, tetradecyl acrylate, 2-isocyanoethyl acrylate, hydroxyethyl acrylate, and 2-methoxyethyl 2-acrylate.

[0052] The specific preparation process involves mixing a first monomer, a second monomer, and an initiator. The resulting mixture is stirred under visible light irradiation to produce an initial polymer solution. An organic base additive is then added to the system, stirred in the dark, and then coated onto a plasma-treated PET substrate. After the solvent evaporates, the visible light-induced pressure-sensitive adhesive is produced. Irradiation with visible light can induce the pressure-sensitive adhesive to release on demand from the substrate surface.

[0053] The initiator is photoinitiator 1173. The addition ratio of the initiator is 0.15% of the total molar amount of the first monomer and the second monomer.

[0054] The organic base additive is selected from one of triethylamine, N,N,N',N'-tetramethylethylenediamine, pentamethyldiethylenetriamine, triethanolamine, and N,N,N',N'-tetrakis(2-hydroxyethyl)ethylenediamine, preferably N,N,N',N'-tetrakis(2-hydroxyethyl)ethylenediamine.

[0055] The molar amount of the organic base additive is 0.5-1.5 times the molar amount of the first monomer.

[0056] The visible light is violet light with a wavelength of 370 nm-390 nm and an irradiation time of 20-90 min.

[0057] The method for stripping the pressure-sensitive adhesive of the present invention is to irradiate the pressure-sensitive adhesive with visible light to achieve the stripping of the pressure-sensitive adhesive.

[0058] The visible light is blue light with a wavelength of 420 nm-460 nm and an irradiation time of 1-3 h.

[0059] The pressure-sensitive adhesive prepared by the present invention for visible light induced peeling has excellent adhesion strength and can be peeled without damage after being irradiated with visible light.

[0060] The pressure-sensitive adhesive of the present invention is suitable for surface bonding of various materials such as metal, plastic, and glass. Due to the addition of an organic base, the C=NNHTs in the polymer can remove the 4-methylbenzenesulfinic acid (HTs) structure to generate a diazo compound (C=N2). The diazo can be activated under visible light to generate a free carbene intermediate, and then a C-H bond insertion reaction occurs in situ, thereby increasing the crosslinking density and cohesive energy strength of the pressure-sensitive adhesive, inducing on-demand peeling of the pressure-sensitive adhesive on the substrate surface, and the process will not damage the adhered substrate.

[0061] Compared with the prior art, the advantages of the present invention are:

[0062] 1. The visible light induced peeling pressure-sensitive adhesive prepared by the present invention can significantly improve the adhesion strength and can be well peeled from the substrate surface under visible light irradiation, achieving non-destructive peeling.

[0063] 2. The visible light induced release pressure-sensitive adhesive provided by the present invention has a simple synthesis method, readily available raw materials, and is easy to implement industrial applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1These are (meth)acrylate monomers containing a p-toluenesulfonylhydrazone (C=NNHTs) structure. In the figure, A represents benzoylformic acid monomers with different substituents, B represents an acrylate monomer containing a hydroxyl structure, C represents a (meth)acrylate monomer containing an arylformyl structure, D represents a p-toluenesulfonylhydrazine monomer, and E represents a (meth)acrylate monomer containing a p-toluenesulfonylhydrazone structure.

[0065] Figure 2 Schematic diagram of the synthetic route for preparing the pressure-sensitive adhesive of the present invention.

[0066] Figure 3 This is the UV spectrum of ethyl (E)-2-(2-phenyl-2-(2-toluenesulfonylhydrazide)acetoxy)acrylate.

[0067] Figure 4 The adhesion strength of the pressure-sensitive adhesive prepared in Example 3.

[0068] Figure 5 The adhesion strength of the pressure-sensitive adhesive prepared in Example 4.

[0069] Figure 6 The adhesion strength of the pressure-sensitive adhesive prepared in Example 5.

[0070] Figure 7 The adhesion strength of the pressure-sensitive adhesive prepared in Example 6. DETAILED DESCRIPTION

[0071] The present invention will be described in further detail below with reference to embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0072] Example 1:

[0073] 1. Synthesis of acrylate monomers containing aromatic formyl ester structures

[0074] To a 250 mL round-bottom flask, 7.5 g of benzoylformic acid, 50 mL of dichloromethane solution, and 10 drops of DMF were added sequentially. The mixture was cooled to 0°C, and 8.5 mL of oxalyl chloride was added and stirred for 30 minutes. This was then added dropwise to a round-bottom flask containing 5.3 mL of hydroxyethyl acrylate, 9.1 mL of triethylamine, and 50 mL of dichloromethane solution. Stirring was continued until complete conversion occurred, yielding ethyl 2-(2-oxo-2-phenylethoxy)acrylate monomer.

[0075] 2. Synthesis of acrylate monomers containing aromatic p-toluenesulfonylhydrazide structures

[0076] Dissolve 4.1 g of p-toluenesulfonyl hydrazide in 10 mL of methanol solution and add it dropwise to a 100 mL methanol solution containing 5 g of ethyl 2-(2-oxo-2-phenylethoxy)acrylate monomer. Then add a few drops of acetic acid and stir until the reaction is complete to obtain ethyl (E)-2-(2-phenyl-2-(2-toluenesulfonylhydrazide)acetoxy)acrylate.

[0077] Example 2:

[0078] 1. Synthesis of methacrylate monomers containing aromatic formyl ester structures

[0079] To a 250 mL round-bottom flask, 3.0 g of benzoylformic acid, 20 mL of dichloromethane solution, and 10 drops of DMF were added sequentially. The mixture was cooled to 0°C, and 2.5 mL of oxalyl chloride was added and stirred for 30 min. This was then added dropwise to a round-bottom flask containing 3.1 mL of 4-hydroxybutyl 2-methacrylate, 6.4 mL of triethylamine, and 30 mL of dichloromethane solution. Stirring was continued until complete conversion was achieved to obtain butyl 4-(2-oxo-2-phenylacetoxy)methacrylate.

[0080] 2. Synthesis of methacrylate monomers containing aromatic p-toluenesulfonylhydrazide structures

[0081] Dissolve 4.1 g of p-toluenesulfonyl hydrazide in 10 mL of methanol solution and add the solution dropwise to a 100 mL methanol solution containing 5.8 g of butyl 4-(2-oxo-2-phenylacetoxy) methacrylate monomer. Add a few drops of acetic acid and stir until the reaction is complete to obtain butyl (E)-4-(2-phenyl-2-(2-toluenesulfonylhydrazide)acetoxy) methacrylate.

[0082] Example 3:

[0083] 35 μL of acrylic acid and 1.76 mL of dodecyl acrylate were added to 0.21 g of ethyl (E)-2-(2-phenyl-2-(2-toluenesulfonylhydrazide)acetoxy)acrylate monomer. 1.7 μL of photoinitiator 1173 and 2 mL of dichloromethane solution were then added. The mixture was stirred and irradiated under violet light for 30 minutes to obtain an initial polymer solution. 89 mg of N,N,N',N'-tetrakis(2-hydroxyethyl)ethylenediamine was then added to the mixture. Stirring was carried out in the dark for 3 hours to obtain a pressure-sensitive adhesive. This adhesive was then coated onto a plasma-treated PET film. After the solvent evaporated, another plasma-treated PET film was placed over the surface. 2 cm wide strips were cut to obtain Sample 1. A portion of Sample 1 was irradiated under blue light for 10 minutes to obtain Sample 2.

[0084] Refer to GB / T 2792-2014 standard "Test method for peel strength of adhesive tape" for peel strength test. The sample is tested for shear adhesion strength using T-type peel test. The results are as follows Figure 4 As shown in the figure, the adhesion strength of the pressure-sensitive adhesive before blue light irradiation is about 609 N / m, and the adhesion strength is about 0 after 10 min of blue light irradiation.

[0085] Example 4:

[0086] 17 μL of N-acryloylmorpholine and 1.84 mL of butyl acrylate were added to 0.21 g of ethyl (E)-2-(2-phenyl-2-(2-toluenesulfonylhydrazide)acetoxy)acrylate monomer. 1.7 μL of photoinitiator 1173 and 2 mL of dichloromethane solution were then added. The mixture was stirred and irradiated under violet light for 30 minutes to obtain an initial polymer solution. 66 μL of pentamethyldiethylenetriamine was then added to the system, and the mixture was stirred for 3 hours in the dark to obtain a pressure-sensitive adhesive. The adhesive was then coated onto a plasma-treated PET film. After the solvent evaporated, another plasma-treated PET film was placed over the surface. Sample 3 was cut into 2 cm wide strips. A portion of Sample 3 was irradiated under blue light for 10 minutes to obtain Sample 4.

[0087] The shear adhesion strength of the samples was tested using a T-glass test. The results are as follows: Figure 4 As shown in the figure, the adhesion strength of the pressure-sensitive adhesive before blue light irradiation is about 268 N / m, and the adhesion strength is about 0 after 10 min of blue light irradiation.

[0088] Example 5:

[0089] 0.13 mL of 2-isocyanatoethyl acrylate and 1.63 mL of tetradecyl acrylate were added to 0.21 g of ethyl (E)-2-(2-phenyl-2-(2-toluenesulfonylhydrazide)acetoxy)acrylate monomer. 1.7 μL of photoinitiator 1173 and 2 mL of dichloromethane solution were then added. The mixture was stirred and irradiated under violet light for 60 minutes to obtain an initial polymer solution. 104 μL of triethanolamine was then added to the system, and the mixture was stirred for 3 hours in the dark to obtain a pressure-sensitive adhesive. The adhesive was then coated onto a plasma-treated PET film. After the solvent evaporated, another plasma-treated PET film was placed over the surface. Sample 5 was cut into 2 cm wide strips. A portion of Sample 5 was irradiated under blue light for 10 minutes to obtain Sample 6.

[0090] The shear adhesion strength of the samples was tested using a T-glass test. The results are as follows: Figure 4 As shown in the figure, the adhesion strength of the pressure-sensitive adhesive before blue light irradiation is about 340 N / m, and the adhesion strength is about 0 after 10 min of blue light irradiation.

[0091] Example 6:

[0092] 0.13 mL of 2-isocyanatoethyl acrylate and 1.63 mL of tetradecyl acrylate were added to 0.21 g of ethyl (E)-2-(2-phenyl-2-(2-toluenesulfonylhydrazide)acetoxy)acrylate monomer. 1.7 μL of photoinitiator 1173 and 2 mL of dichloromethane solution were then added. The mixture was stirred and irradiated under violet light for 2 h to obtain an initial polymer solution. 104 μL of triethanolamine was then added to the system, and the mixture was stirred for 3 h in the dark to obtain a pressure-sensitive adhesive. The adhesive was then coated onto a plasma-treated PET film. After the solvent evaporated, another plasma-treated PET film was placed over the surface. Sample 7 was cut into 2 cm wide strips. A portion of Sample 7 was irradiated under blue light for 10 min to obtain Sample 8.

[0093] The shear adhesion strength of the samples was tested using a T-glass test. The results are as follows: Figure 4 As shown in the figure, the adhesion strength of the pressure-sensitive adhesive before blue light irradiation is about 417 N / m, and the adhesion strength is about 0 after 10 min of blue light irradiation.

Claims

1. A method for preparing a pressure-sensitive adhesive capable of being induced to release by visible light, characterized in that The steps include: First, the first monomer and the second monomer undergo free radical polymerization in the presence of an initiator to achieve initial bonding strength; then, an organic base additive is added to the system, mixed evenly, and then coated on the surface of the substrate. After the solvent evaporates, the pressure-sensitive adhesive is obtained; The general structural formula of the first monomer is shown below: ； Wherein, R1=H or CH3, n=2 or 4, R2=OCH3, H, CF3 or NO2; The second monomer is selected from one or more of acrylic acid, N-acryloylmorpholine, isooctyl acrylate, butyl acrylate, dodecyl acrylate, tetradecyl acrylate, 2-isocyanoethyl acrylate, hydroxyethyl acrylate, and 2-methoxyethyl 2-acrylate.

2. The preparation method according to claim 1, wherein: First, the first monomer, the second monomer and the initiator are mixed, and the obtained mixture is stirred under visible light irradiation to obtain an initial polymer solution; then, an organic base additive is added to the system, stirred in the dark, and then coated on a plasma-treated substrate. After the solvent evaporates, a visible light-induced pressure-sensitive adhesive can be obtained.

3. The preparation method according to claim 2, wherein: The initiator is photoinitiator 1173.

4. The preparation method according to claim 3, wherein: The addition ratio of the initiator is 0.15% of the total molar amount of the first monomer and the second monomer.

5. The preparation method according to claim 2, wherein: The organic base additive is selected from one of triethylamine, N,N,N',N'-tetramethylethylenediamine, pentamethyldiethylenetriamine, triethanolamine, and N,N,N',N'-tetrakis(2-hydroxyethyl)ethylenediamine.

6. The preparation method according to claim 5, characterized in that: The organic base additive is N,N,N',N'-tetrakis(2-hydroxyethyl)ethylenediamine.

7. The preparation method according to claim 5, characterized in that: The molar amount of the organic base additive is 0.5-1.5 times the molar amount of the first monomer.

8. The preparation method according to claim 2, wherein: The visible light is violet light with a wavelength of 370 nm-390 nm and an irradiation time of 20-90 min.

9. A method for peeling a pressure-sensitive adhesive prepared by the method according to any one of claims 1 to 8, characterized in that: The pressure-sensitive adhesive is irradiated with visible light to achieve peeling of the pressure-sensitive adhesive.

10. The stripping method according to claim 9, wherein: The visible light is blue light with a wavelength of 420 nm-460 nm and an irradiation time of 1-3 h.

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