Modified adenine and high water-resistant pressure-sensitive adhesive, preparation method and application thereof

Abstract

This invention provides a modified adenine, a high water-resistant pressure-sensitive adhesive, its preparation method, and its application, belonging to the field of adhesive technology. The invention involves mixing adenine, 2,6-di-tert-butyl-p-cresol, an alkaline reagent, and a polar aprotic solvent. The resulting mixture is then reacted with 1,4-bis(acryloyloxy)butane to obtain the modified adenine. The mass ratio of adenine to 2,6-di-tert-butyl-p-cresol is 2:0.112~0.130; the mass ratio of adenine to 1,4-bis(acryloyloxy)butane is 2:4~9. This invention modifies adenine with 1,4-bis(acryloyloxy)butane in the presence of 2,6-di-tert-butyl-p-cresol. Using the resulting modified adenine as an additive, a high water-resistant pressure-sensitive adhesive can be prepared, which enables TPU car wraps to maintain high adhesion strength to the paint surface.

Description

Technical Field

[0001] This invention relates to the field of adhesive technology, and more particularly to a modified adenine and highly water-resistant pressure-sensitive adhesive, its preparation method, and its application. Background Technology

[0002] Thermoplastic polyurethane (TPU) car wraps are protective films for automotive paint, characterized by structural stability, water resistance, flexibility, self-healing properties, and high elongation. Although TPU car wraps have a hydrophobic coating that provides waterproofing, over time, this coating ages or hydrolyzes, leading to a decrease in waterproofing capabilities and resulting in seepage or leakage. This, in turn, causes the pressure-sensitive adhesive bonding the car wrap to the paint to absorb water, swell, and lose viscosity, reducing the lifespan of the car wrap. Therefore, developing a pressure-sensitive adhesive with high water resistance that maintains high adhesion strength between the TPU car wrap and the paint is crucial. Summary of the Invention

[0003] The purpose of this invention is to provide a modified adenine and a high water-resistant pressure-sensitive adhesive, as well as a preparation method and application. The modified adenine provided by this invention can be used to prepare a high water-resistant pressure-sensitive adhesive, which can maintain high adhesion strength between TPU car wrap and paint surface.

[0004] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing modified adenine, comprising the following steps: Adenine, 2,6-di-tert-butyl-p-cresol, a basic reagent, and a polar aprotic solvent were mixed, and the resulting mixture was mixed with 1,4-bis(acryloyloxy)butane and reacted to obtain the modified adenine. The mass ratio of adenine to 2,6-di-tert-butyl-p-cresol is 2:0.112~0.130; The mass ratio of adenine to 1,4-bis(acryloyloxy)butane is 2:4~9.

[0005] Preferably, the alkaline reagent includes one or more of K2CO3, Na2CO3 and NaHCO3; the mass ratio of adenine to the alkaline reagent is 2:0.04~0.08.

[0006] Preferably, the polar aprotic solvent includes one or more of dimethyl sulfoxide, acetonitrile, and acetone; the ratio of adenine to polar aprotic solvent is 2g:20~40mL.

[0007] Preferably, the temperature of the first stage reaction is 50~60℃ and the time is 0.5~1.5h; the temperature of the reaction is 50~60℃ and the time is 3~5h; the reaction is carried out under stirring conditions.

[0008] The present invention provides modified adenine prepared by the preparation method described in the above technical solution.

[0009] This invention provides a highly water-resistant pressure-sensitive adhesive, comprising the following raw materials by weight: The mixture comprises 60-80 parts of soft monomer, 55-65 parts of hard monomer, 7-9 parts of functional monomer, 0.2-0.7 parts of modified adenine as described in the above technical solution, 0.1-0.35 parts of initiator, 1-5 parts of curing agent, 8-12 parts of polymerization inhibitor, and 180-220 parts of organic solvent.

[0010] Preferably, the soft monomer includes one or more of isooctyl acrylate, ethyl acrylate, and n-butyl acrylate; the hard monomer includes one or more of methyl acrylate, methyl methacrylate, and vinyl acetate; and the functional monomer includes acrylic acid and / or methacrylic acid. The initiator includes an azo radical initiator; the curing agent includes aluminum acetylacetonate; the polymerization inhibitor includes acetylacetonate; and the organic solvent includes one or more of ethyl acetate, toluene, acetone, and isopropanol.

[0011] This invention provides a method for preparing the high water-resistant pressure-sensitive adhesive described in the above technical solution, comprising the following steps: Modified adenine was mixed with an organic solvent to obtain component A; soft monomers, hard monomers, functional monomers, and part of the initiator were mixed with an organic solvent to obtain component B; the remaining initiator was mixed with an organic solvent to obtain component C; and curing agent and polymerization inhibitor were mixed with an organic solvent to obtain component D. Component A is heated to 75-80°C, then component A is mixed with component B, and after a first heat preservation treatment, a first mixed liquid is obtained; The first mixture is mixed with component C, and then subjected to a second heat preservation treatment to obtain the second mixture. The second mixture is cooled to below 35°C, and then mixed with component D to obtain the high water resistance pressure-sensitive adhesive.

[0012] Preferably, the mixing of component A and component B includes: adding component B dropwise to component A; the first heat preservation treatment time is 40~60 min; The mixing of the first mixture with component C includes: adding component C dropwise to the first mixture; the second heat preservation treatment time is 100~130 min; The mixing of the second mixture with component D includes: adding component D dropwise to the second mixture; after the addition of component D is complete, the mixture is stirred for 30 to 50 minutes.

[0013] This invention provides the application of the high water-resistant pressure-sensitive adhesive described in the above technical solution or the high water-resistant pressure-sensitive adhesive prepared by the preparation method described in the above technical solution in bonding automotive paint and TPU car wrap.

[0014] Beneficial Effects: This invention provides a method for preparing modified adenine, comprising the following steps: mixing adenine, 2,6-di-tert-butyl-p-cresol, an alkaline reagent, and a polar aprotic solvent; mixing the resulting mixture with 1,4-bis(acryloyloxy)butane; and reacting to obtain the modified adenine; wherein the mass ratio of adenine to 2,6-di-tert-butyl-p-cresol is 2:0.112~0.130; and the mass ratio of adenine to 1,4-bis(acryloyloxy)butane is 2:4~9. This invention modifies adenine with 1,4-bis(acryloyloxy)butane in the presence of 2,6-di-tert-butyl-p-cresol. Using the obtained modified adenine as an additive, a highly water-resistant pressure-sensitive adhesive can be prepared, which enables TPU car wraps to maintain high adhesion strength to the paint surface. Specifically, the modified adenine can form strong hydrogen bond interactions between polymer chains to improve the cohesive force of the pressure-sensitive adhesive, and can also act as a dynamic adhesion factor to form non-covalent interactions with the substrate to improve interfacial adhesion. When the pressure-sensitive adhesive is coated on the car paint surface and then bonded with TPU car wrap, it can maintain high adhesion strength in a water environment. Detailed Implementation

[0015] This invention provides a method for preparing modified adenine, comprising the following steps: Adenine, 2,6-di-tert-butyl-p-cresol, a basic reagent, and a polar aprotic solvent were mixed, and the resulting mixture was mixed with 1,4-bis(acryloyloxy)butane and reacted to obtain the modified adenine. The mass ratio of adenine to 2,6-di-tert-butyl-p-cresol is 2:0.112~0.130; The mass ratio of adenine to 1,4-bis(acryloyloxy)butane is 2:4~9.

[0016] In this invention, unless otherwise specified, all raw materials used are commercially available products well known to those skilled in the art or prepared using methods well known to those skilled in the art.

[0017] This invention involves mixing adenine, 2,6-di-tert-butyl-p-cresol, an alkaline reagent, and a polar aprotic solvent to obtain a mixed solution. In this invention, the mass ratio of adenine to 2,6-di-tert-butyl-p-cresol is 2:0.112~0.130, specifically 2:0.112, 2:0.115, 2:0.120, 2:0.125, or 2:0.130. Controlling the ratio within this range prevents oxidative degradation of the base and helps maintain the stability of the modified adenine. Insufficient 2,6-di-tert-butyl-p-cresol results in poor structural stability of the modified adenine, affecting the water resistance of the pressure-sensitive adhesive. Furthermore, the use of 2,6-di-tert-butyl-p-cresol as a protective agent, compared to other types of 2,6-di-tert-butyl-p-cresol such as 4,6-di-tert-butyl-p-cresol, is more conducive to ensuring the superior water resistance of the final pressure-sensitive adhesive.

[0018] In one embodiment of the present invention, the alkaline reagent includes K2CO3, Na2CO3, and Na H One or more of CO3, K2CO3 is used in the examples; the mass ratio of adenine to the basic reagent is 2:0.04~0.08, specifically 2:0.04, 2:0.05, 2:0.06, 2:0.07 or 2:0.08. As one embodiment of the invention, the polar aprotic solvent includes one or more of dimethyl sulfoxide, acetonitrile and acetone, dimethyl sulfoxide is used in the examples; the volume ratio of adenine to the polar aprotic solvent is 2g:20~40mL, specifically 2g:30mL.

[0019] In one embodiment of the present invention, the mixing temperature of adenine, 2,6-di-tert-butyl-p-cresol, the basic reagent, and the polar aprotic solvent is 50-60°C, specifically 50°C, 53°C, 55°C, 57°C, or 60°C; the mixing time is 0.5-1.5 hours, specifically 0.5 hours, 1 hour, or 1.5 hours; the mixing is preferably carried out under stirring conditions; the 2,6-di-tert-butyl-p-cresol used in the present invention acts as a protective agent to prevent adenine from being oxidized, which is beneficial to ensuring the stability of modified adenine.

[0020] After obtaining the mixed solution, the present invention mixes the mixed solution with 1,4-bis(acryloyloxy)butane and reacts it to obtain the modified adenine. In the present invention, the mass ratio of adenine to 1,4-bis(acryloyloxy)butane is 2:4~9, specifically 2:4, 2:5, 2:6, 2:7, 2:8 or 2:9; the present invention controls the amount ratio of the two within the above range, which is beneficial to the synthesis of modified adenine with long alkyl chains; if the amount of 1,4-bis(acryloyloxy)butane is too small, the modified adenine properties are unstable, which affects the water resistance of the pressure-sensitive adhesive.

[0021] In one embodiment of the present invention, the reaction temperature is 50~60℃, specifically 50℃, 53℃, 55℃, 57℃ or 60℃; the time is 3~5h, specifically 3h, 3.5h, 4h, 4.5h or 5h; the reaction is preferably carried out under stirring conditions. In the present invention, during the reaction, 1,4-bis(acryloyloxy)butane and adenine undergo an addition reaction to generate modified adenine with a long alkyl chain; if other types of 1,4-bisbutane such as 1,4-bis(dicyclohexylphosphine)butane, 1,4-bis(chloromethoxy)butane or other similar compounds such as 1,4-dithionylcyclopentene-2,5-dimethylthiol are used, the adhesion performance of the pressure-sensitive adhesive will be reduced.

[0022] In one embodiment of the present invention, the reaction preferably further includes: mixing the product liquid obtained after the reaction with water, performing precipitation treatment, followed by solid-liquid separation, collecting the solid material, washing it with a non-polar solvent, and drying it to obtain the modified adenine. In one embodiment of the present invention, the water can be deionized water; the volume ratio of the polar aprotic solvent to water can be 30:450~550, specifically 30:500; the precipitation treatment temperature is 20~30℃, specifically room temperature (25℃), and the time is 10~15h, specifically 12h; the solid-liquid separation method can be filtration; the non-polar solvent includes one or more of n-hexane, cyclohexane, and heptane, with n-hexane used in the examples; the washing can be performed 2~3 times.

[0023] The present invention provides modified adenine prepared by the preparation method described in the above technical solution.

[0024] This invention provides a highly water-resistant pressure-sensitive adhesive, comprising the following raw materials by weight: The mixture comprises 60-80 parts of soft monomer, 55-65 parts of hard monomer, 7-9 parts of functional monomer, 0.2-0.7 parts of modified adenine as described in the above technical solution, 0.1-0.35 parts of initiator, 1-5 parts of curing agent, 8-12 parts of polymerization inhibitor, and 180-220 parts of organic solvent.

[0025] The raw materials for preparing the high water-resistant pressure-sensitive adhesive of the present invention, by weight, include 60-80 parts of soft monomers, specifically 60 parts, 63 parts, 65 parts, 68 parts, 70 parts, 73 parts, 75 parts, 78 parts, or 80 parts. As one embodiment of the present invention, the soft monomers include one or more of isooctyl acrylate, ethyl acrylate, and n-butyl acrylate; isooctyl acrylate is used in the examples.

[0026] Based on the mass fraction of the soft monomer, the raw materials for preparing the high water-resistant pressure-sensitive adhesive of the present invention include 55-65 parts of hard monomer, specifically 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, or 65 parts. As one embodiment of the present invention, the hard monomer includes one or more of methyl acrylate, methyl methacrylate, and vinyl acetate; methyl acrylate is used in the examples.

[0027] Based on the mass fraction of the soft monomer, the raw materials for preparing the high water-resistant pressure-sensitive adhesive of the present invention include 7 to 9 parts of functional monomer, specifically 7 parts, 7.5 parts, 8 parts, 8.5 parts, or 9 parts. As one embodiment of the present invention, the functional monomer includes acrylic acid and / or methacrylic acid; acrylic acid is used in the examples.

[0028] Based on the mass fraction of the soft monomer, the raw materials for preparing the high water-resistant pressure-sensitive adhesive of the present invention include 0.2 to 0.7 parts of modified adenine as described in the above technical solution, specifically 0.2, 0.3, 0.4, 0.5, 0.6, or 0.7 parts. By controlling the amount of modified adenine within the above range, the present invention can form strong hydrogen bond interactions between polymer chains to improve the cohesive force of the pressure-sensitive adhesive. It can also act as a dynamic adhesion factor, forming non-covalent interactions with the substrate to improve interfacial adhesion, which is beneficial for ensuring that the pressure-sensitive adhesive maintains high underwater adhesion strength during use.

[0029] Based on the mass fraction of the soft monomer, the raw materials for preparing the high water-resistant pressure-sensitive adhesive of the present invention include 0.1 to 0.35 parts of initiator, specifically 0.1, 0.2, 0.3, or 0.35 parts. As one embodiment of the present invention, the initiator includes an azo radical initiator, which may include one or more of azobisisobutyronitrile, azobisisoheptanenitrile, and dimethyl azobisisobutyrate; in the examples, azobisisobutyronitrile is used.

[0030] Based on the mass fraction of the soft monomer, the raw materials for preparing the high water-resistant pressure-sensitive adhesive of the present invention include 1 to 5 parts of curing agent, specifically 1 part, 2 parts, 3 parts, 3.2 parts, 3.5 parts, 4 parts, or 5 parts. In one embodiment of the present invention, the curing agent may be aluminum acetylacetonate.

[0031] Based on the mass fraction of the soft monomer, the raw materials for preparing the high water-resistant pressure-sensitive adhesive of the present invention include 8 to 12 parts of a polymerization inhibitor, specifically 8, 9, 10, 11, or 12 parts. In one embodiment of the present invention, the polymerization inhibitor may be acetylacetone.

[0032] Based on the mass fraction of the soft monomer, the raw materials for preparing the high water-resistant pressure-sensitive adhesive of the present invention include 180-220 parts of organic solvent, specifically 180 parts, 185 parts, 190 parts, 195 parts, 200 parts, 205 parts, 210 parts, 215 parts, or 220 parts. As one embodiment of the present invention, the organic solvent includes one or more of ethyl acetate, toluene, acetone, and isopropanol.

[0033] This invention provides a method for preparing the high water-resistant pressure-sensitive adhesive described in the above technical solution, comprising the following steps: Modified adenine was mixed with an organic solvent to obtain component A; soft monomers, hard monomers, functional monomers, and part of the initiator were mixed with an organic solvent to obtain component B; the remaining initiator was mixed with an organic solvent to obtain component C; and curing agent and polymerization inhibitor were mixed with an organic solvent to obtain component D. Component A is heated to 75-80°C, then component A is mixed with component B, and after a first heat preservation treatment, a first mixed liquid is obtained; The first mixture is mixed with component C, and then subjected to a second heat preservation treatment to obtain the second mixture. The second mixture is cooled to below 35°C, and then mixed with component D to obtain the high water resistance pressure-sensitive adhesive.

[0034] This invention involves mixing modified adenine with an organic solvent to obtain component A; mixing a soft monomer, a hard monomer, a functional monomer, and part of an initiator with an organic solvent to obtain component B; mixing the remaining initiator with an organic solvent to obtain component C; and mixing a curing agent, a polymerization inhibitor, and an organic solvent to obtain component D. In one embodiment of this invention, the organic solvent in component A can be ethyl acetate; the organic solvent in component B can be ethyl acetate; the organic solvent in component C can be toluene and ethyl acetate, with a mass ratio of toluene to ethyl acetate of 8:25~35, specifically 8:30; the organic solvent in component D can be toluene and isopropanol, with a mass ratio of toluene to isopropanol of 25:10~11, specifically 25:10.5; and the mass ratio of the organic solvents in component A, component B, component C, and component D can be 70~75:53~58:35~40:30~40, specifically 72:55.5:38:35.5. In one embodiment of the present invention, the mass ratio of the partial initiator to the remaining initiator can be 0.2~0.3:0.1, specifically 0.25:0.1.

[0035] After obtaining component A and component B, the present invention heats component A to 75-80°C, then mixes component A and component B, and performs a first heat preservation treatment to obtain a first mixed liquid. In one embodiment of the present invention, the mixing of component A and component B includes: adding component B dropwise to component A; preferably, component B is added dropwise at a uniform rate; in this embodiment, the dropwise addition time of component B is 120-150 min, specifically 120 min, 130 min, 140 min, or 150 min; the first heat preservation treatment time is 40-60 min, specifically 40 min, 45 min, 50 min, 55 min, or 60 min, and the first heat preservation treatment time begins from the completion of component B dropwise addition.

[0036] After obtaining the first mixture and component C, the present invention mixes the first mixture and component C, and then performs a second heat preservation treatment to obtain a second mixture. In one embodiment of the present invention, mixing the first mixture and component C includes: adding component C dropwise to the first mixture; preferably, component C is added dropwise at a uniform rate; in this embodiment, the dropwise addition time of component C is 10-15 minutes, specifically 10 minutes, 12 minutes, or 15 minutes; the second heat preservation treatment time is 100-130 minutes, specifically 100 minutes, 110 minutes, 120 minutes, or 130 minutes, and the second heat preservation treatment time is counted from the completion of component C dropwise addition.

[0037] After obtaining the second mixture and component D, the present invention cools the second mixture to below 35°C, and then mixes the second mixture with component D to obtain the high water-resistant pressure-sensitive adhesive. As one embodiment of the present invention, the mixing of the second mixture and component D includes: adding component D dropwise to the second mixture; preferably, component D is added dropwise at a uniform rate; in this embodiment, the dropwise addition time of component D is 30-40 minutes, specifically 30 minutes, 35 minutes, or 40 minutes; after the addition of component D is complete, stirring is further included for 30-50 minutes, specifically 30 minutes, 40 minutes, or 50 minutes.

[0038] This invention provides the application of the high water-resistant pressure-sensitive adhesive described in the above technical solution or the high water-resistant pressure-sensitive adhesive prepared by the preparation method described in the above technical solution in bonding automotive paint and TPU car wrap.

[0039] The high water-resistant pressure-sensitive adhesive provided by this invention can be used as a pressure-sensitive adhesive for TPU car wraps. Specifically, the high water-resistant pressure-sensitive adhesive can be coated on the surface of the car paint, and then the TPU car wrap can be bonded, maintaining high adhesion strength in a water environment. As one embodiment of this invention, the high water-resistant pressure-sensitive adhesive can form a pressure-sensitive adhesive layer between the car paint surface and the TPU car wrap, and the thickness of the pressure-sensitive adhesive layer can be 25~27μm.

[0040] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0041] Example 1 2g of adenine, 60mg of K2CO3, and 115mg of 2,6-di-tert-butyl-p-cresol were added to 30mL of dimethyl sulfoxide (DMSO) and stirred at 55°C for 1h to obtain a mixed solution. 5g of 1,4-bis(acryloyloxy)butane was added to the mixed solution, and the mixture was stirred at 55°C for 4h. After the reaction was complete, the resulting solution was poured into 500mL of deionized water and precipitated at room temperature (25°C) for 12h. The precipitate was then filtered, and the collected solid was washed three times with n-hexane. The washed solid was dried in an oven to obtain modified adenine (a white solid). By mass fraction, 0.3 parts of the modified adenine were mixed with 72 parts of ethyl acetate to obtain component A; 70 parts of isooctyl acrylate, 60 parts of methyl acrylate, 8 parts of acrylic acid, 0.25 parts of azobisisobutyronitrile (AIBN) were mixed with 55.5 parts of ethyl acetate to obtain component B; 0.1 parts of AIBN, 8 parts of toluene, and 30 parts of ethyl acetate were mixed to obtain component C; and 3.2 parts of aluminum acetylacetonate, 10 parts of acetylacetonate, 25 parts of toluene, and 10.5 parts of isopropanol were mixed to obtain component D. Component A is heated to reflux (75~80℃), and then component B is added dropwise to component A at a uniform rate over a period of 130 min. After the addition is complete, the mixture is kept at this temperature for 50 min to obtain a first mixture. Component C is added dropwise to the first mixture at a uniform rate over a period of 10 min. After the addition is complete, the mixture is kept at this temperature for 120 min to obtain a second mixture. Heating is stopped and the second mixture is cooled to 35℃. Then, component D is added dropwise to the second mixture at a uniform rate over a period of 35 min. After the addition is complete, the mixture is stirred for 40 min to obtain a high water-resistant pressure-sensitive adhesive.

[0042] Example 2 The preparation method is basically the same as Example 1, except that the amount of 2,6-di-tert-butyl-p-cresol used in the preparation of modified adenine is adjusted to 120 mg.

[0043] Example 3 The preparation method is basically the same as Example 1, except that the amount of 1,4-bis(acryloyloxy)butane used in the preparation of modified adenine is adjusted to 7g.

[0044] Example 4 It is basically the same as Example 1, except that the amount of modified adenine is adjusted to 0.5 parts.

[0045] Comparative Example 1 The method is basically the same as in Example 1, except that the amount of modified adenine is adjusted to 0 parts, that is, no modified adenine is added when preparing the high water resistance pressure-sensitive adhesive.

[0046] Comparative Example 2 It is basically the same as Example 1, except that the amount of modified adenine is adjusted to 0.1 parts.

[0047] Comparative Example 3 The process is basically the same as in Example 1, except that the modified adenine is replaced with adenine, that is, 0.3 parts of adenine are used directly when preparing the high water resistance pressure-sensitive adhesive.

[0048] Comparative Example 4 It is basically the same as Example 1, except that 2,6-di-tert-butyl-p-cresol is replaced with 4,6-di-tert-butyl-p-cresol.

[0049] Comparative Example 5 It is basically the same as Example 1, except that 1,4-bis(acryloyloxy)butane is replaced with 1,4-bis(dicyclohexylphosphine)butane.

[0050] Comparative Example 6 It is basically the same as Example 1, except that 1,4-bis(acryloyloxy)butane is replaced with 1,4-bis(chloromethoxy)butane.

[0051] Comparative Example 7 It is basically the same as Example 1, except that 1,4-bis(acryloyloxy)butane is replaced with 1,4-dithionyl-2,5-dimethyl mercaptan.

[0052] Comparative Example 8 The preparation method is basically the same as Example 1, except that the amount of 2,6-di-tert-butyl-p-cresol used in the preparation of modified adenine is adjusted to 105 mg.

[0053] Comparative Example 9 The preparation method is basically the same as Example 1, except that the amount of 2,6-di-tert-butyl-p-cresol used in the preparation of modified adenine is adjusted to 110 mg.

[0054] Comparative Example 10 The preparation method is basically the same as Example 1, except that the amount of 1,4-bis(acryloyloxy)butane used in the preparation of modified adenine is adjusted to 3g.

[0055] Test Example 1 1. The viscosity of the pressure-sensitive adhesive in each embodiment and comparative example was tested. Specifically, the pressure-sensitive adhesive was placed in a constant temperature water bath at 25°C. After the temperature of the pressure-sensitive adhesive reached 25°C, the viscosity of the pressure-sensitive adhesive was measured using a viscometer.

[0056] 2. TPU films were prepared using the pressure-sensitive adhesives in the various examples and comparative examples, and peel strength tests were performed, as detailed below: The structure of the TPU film, from bottom to top, consists of a self-healing coating, a TPU base film, a pressure-sensitive adhesive layer, and a release film. The thickness of the self-healing coating is 7 μm, the thickness of the TPU base film is 130 μm, the thickness of the pressure-sensitive adhesive layer is 26 ± 1 μm, and the thickness of the release film is 75 μm. The preparation method of the TPU film includes the following steps: coating a pressure-sensitive adhesive onto a release film and drying it at 110°C for 140 seconds to obtain a pressure-sensitive adhesive layer; transferring the pressure-sensitive adhesive layer loaded on the release film to the surface of the TPU base film; then coating a self-healing coating onto the other surface of the TPU film (i.e., the surface that is not in contact with the pressure-sensitive adhesive layer) and drying it at 110°C for 90 seconds to obtain a self-healing coating; and then curing it at 50°C for 72 hours to obtain the TPU film.

[0057] The TPU film was subjected to a peel strength test, as detailed below: 24h 180℃ peel strength: Peel strength was tested according to the method in PSTC-101; Peel strength at 180°C after 3 months of soaking: The newly prepared TPU film was soaked in tap water (neutral pH) and simulated rainwater (pH 5.6) for 3 months, and then the peel strength was tested according to the method in PSTC-101.

[0058] 3. PET films were prepared using the pressure-sensitive adhesives in the various examples and comparative examples, and their tack resistance was tested, as follows: The PET film has a structure from bottom to top consisting of a PET base film, a pressure-sensitive adhesive layer, and a release film, wherein the thickness of the PET base film is 50 μm, the thickness of the pressure-sensitive adhesive layer is 26 ± 1 μm, and the thickness of the release film is 75 μm. The method for preparing the PET film includes the following steps: coating a pressure-sensitive adhesive onto a PET base film and drying it at 120°C for 180 seconds to obtain a pressure-sensitive adhesive layer; covering the pressure-sensitive adhesive layer with a release film and curing it at 65°C for 24 hours to obtain the PET film.

[0059] The newly prepared PET film was soaked in tap water (pH neutral) and simulated rainwater (pH 5.6) for 6 months. Then the PET film was attached to a steel plate and the tackiness test was performed according to the PSTC-107 method.

[0060] Table 1 shows the performance test results of the pressure-sensitive adhesives in each embodiment and comparative example. As can be seen from Table 1, the present invention introduces modified adenine into the pressure-sensitive adhesive. The modified adenine can form strong hydrogen bond interactions between polymer chains to improve the cohesive force of the pressure-sensitive adhesive. It can also act as a dynamic adhesion factor, forming non-covalent interactions with the substrate to improve interfacial adhesion. After coating the pressure-sensitive adhesive on the car paint surface and then bonding the TPU car wrap, it can maintain high adhesion strength in various harsh water environments. Furthermore, Table 1 shows that the raw materials and dosage of modified adenine, as well as the amount of modified adenine used in the preparation of the pressure-sensitive adhesive, all affect the performance of the pressure-sensitive adhesive. In particular, if the amount of modified adenine is too small, the water resistance decreases, and in severe cases, bubbling may occur.

[0061] Table 1 Performance test results of pressure-sensitive adhesives in each embodiment and comparative example

[0062] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing modified adenine, comprising the following steps: Adenine, 2,6-di-tert-butyl-p-cresol, a basic reagent, and a polar aprotic solvent were mixed, and the resulting mixture was mixed with 1,4-bis(acryloyloxy)butane and reacted to obtain the modified adenine. The mass ratio of adenine to 2,6-di-tert-butyl-p-cresol is 2:0.112~0.130; The mass ratio of adenine to 1,4-bis(acryloyloxy)butane is 2:4~9.

2. The preparation method according to claim 1, characterized in that, The alkaline reagent includes one or more of K2CO3, Na2CO3 and NaHCO3; the mass ratio of adenine to the alkaline reagent is 2:0.04~0.

08.

3. The preparation method according to claim 1, characterized in that, The polar aprotic solvent includes one or more of dimethyl sulfoxide, acetonitrile, and acetone; the ratio of adenine to polar aprotic solvent is 2g:20~40mL.

4. The preparation method according to any one of claims 1 to 3, characterized in that, The reaction is carried out at a temperature of 50-60°C for 3-5 hours, and under stirring conditions.

5. Modified adenine prepared by the preparation method according to any one of claims 1 to 4.

6. A highly water-resistant pressure-sensitive adhesive, comprising the following raw materials by weight: The mixture comprises 60-80 parts of soft monomer, 55-65 parts of hard monomer, 7-9 parts of functional monomer, 0.2-0.7 parts of modified adenine as described in claim 5, 0.1-0.35 parts of initiator, 1-5 parts of curing agent, 8-12 parts of polymerization inhibitor, and 180-220 parts of organic solvent.

7. The high water resistance pressure-sensitive adhesive according to claim 6, characterized in that, The soft monomer includes one or more of isooctyl acrylate, ethyl acrylate, and n-butyl acrylate; the hard monomer includes one or more of methyl acrylate, methyl methacrylate, and vinyl acetate; the functional monomer includes acrylic acid and / or methacrylic acid. The initiator includes an azo radical initiator; the curing agent includes aluminum acetylacetonate; the polymerization inhibitor includes acetylacetonate; and the organic solvent includes one or more of ethyl acetate, toluene, acetone, and isopropanol.

8. A method for preparing the high water-resistant pressure-sensitive adhesive according to claim 6 or 7, comprising the following steps: Modified adenine was mixed with an organic solvent to obtain component A; soft monomers, hard monomers, functional monomers, and part of the initiator were mixed with an organic solvent to obtain component B; the remaining initiator was mixed with an organic solvent to obtain component C; and curing agent and polymerization inhibitor were mixed with an organic solvent to obtain component D. Component A is heated to 75-80°C, then component A is mixed with component B, and after a first heat preservation treatment, a first mixed liquid is obtained; The first mixture is mixed with component C, and then subjected to a second heat preservation treatment to obtain the second mixture. The second mixture is cooled to below 35°C, and then mixed with component D to obtain the high water resistance pressure-sensitive adhesive.

9. The preparation method according to claim 8, characterized in that, The mixing of component A and component B includes: adding component B dropwise to component A; the first heat preservation treatment time is 40~60 min; The mixing of the first mixture with component C includes: adding component C dropwise to the first mixture; the second heat preservation treatment time is 100~130 min; The mixing of the second mixture with component D includes: adding component D dropwise to the second mixture; after the addition of component D is complete, the mixture is stirred for 30 to 50 minutes.

10. The application of the high water-resistant pressure-sensitive adhesive of claim 6 or 7 or the high water-resistant pressure-sensitive adhesive prepared by the preparation method of claim 8 or 9 in bonding automotive paint to TPU car wrap.

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