High-temperature-resistant edge sealing adhesive for flexible electronic paper and preparation method thereof

Abstract

The application relates to the technical field of electronic packaging materials, and discloses a high-temperature-resistant edge sealing glue for flexible electronic paper and a preparation method thereof, which is made of polysiloxane modified epoxy resin, tetra-functional epoxy resin, hydroxyl-terminated hyperbranched polyester, titanate coupling agent, active diluent, modified alicyclic amine curing agent, accelerator and fumed silica. Through a high-temperature vacuum pre-reaction process, the titanate coupling agent is in-situ reacted with hydroxyl groups in the resin system to form a coordination structure with kinetic latent characteristics. The structure significantly prolongs the pot life of the glue solution by using the steric hindrance effect, and migrates to form a hydrophobic long-chain coating layer in the curing process. The obtained edge sealing glue has excellent high-temperature resistance, toughness and moisture and heat aging resistance, and can meet the strict packaging requirements of the flexible electronic paper.

Description

Technical Field

[0001] This invention relates to the field of electronic packaging materials technology, and in particular to a high-temperature resistant edge-sealing adhesive for flexible electronic paper and its preparation method. Background Technology

[0002] Flexible electronic paper displays are widely used in electronic tags, wearable devices, and smart education terminals due to their paper-like display characteristics and bendability. As a key material for ensuring the sealing and structural integrity of the display module, the edge-sealing adhesive not only needs to withstand the mechanical stress generated by module bending, but also needs to maintain excellent barrier properties and adhesive strength over a long period in harsh environments such as high temperature and high humidity.

[0003] Traditional epoxy resin edge banding adhesives struggle to simultaneously meet the aforementioned comprehensive performance requirements. While using high-functionality epoxy resins can improve the system's heat resistance and modulus, the resulting high crosslinking density leads to increased internal stress in the cured product, causing the adhesive layer to become brittle and prone to brittle fracture or interfacial delamination during repeated bending of flexible substrates. Introducing long-chain flexible segments to improve toughness is a common approach, but this typically sacrifices the material's glass transition temperature and resistance to humid heat, creating a trade-off between heat resistance and toughening.

[0004] Furthermore, to improve adhesion and water resistance, existing technologies often add coupling agents to the formulation. However, direct physical addition has significant limitations. On the one hand, free coupling agents are prone to self-polymerization or hydrolysis failure during long-term storage, resulting in poor batch stability of the product. On the other hand, highly reactive coupling agents often react rapidly upon contact with curing agents, leading to a significant shortening of the pot life of the two-component adhesive mixture and excessively rapid viscosity increase, which cannot meet the time requirements for fine coating in electronic paper packaging processes. Therefore, developing an edge-sealing adhesive system that can balance high temperature resistance, high toughness, resistance to damp heat aging, and a good pot life is a pressing technical problem that the industry urgently needs to solve. Summary of the Invention

[0005] The technical problem solved by this invention is that existing flexible electronic paper sealing adhesives are difficult to balance high temperature resistance, damp heat resistance and construction applicability. Usually, increasing the crosslinking density to resist high temperature will lead to increased brittleness of the adhesive layer, and conventional physical addition of coupling agents will easily lead to poor storage stability of the adhesive and decreased damp heat aging performance after curing.

[0006] To address the above problems, the present invention provides the following technical solution:

[0007] In a first aspect, the present invention provides a high-temperature resistant sealing adhesive for flexible electronic paper, which is made from raw materials comprising the following parts by weight:

[0008] 55-65 parts of polysiloxane-modified epoxy resin; 15-25 parts of tetrafunctional epoxy resin; 8-12 parts of hydroxyl-terminated hyperbranched polyester; 0.5-1.5 parts of titanate coupling agent; 8-12 parts of reactive diluent; 42-48 parts of modified alicyclic amine curing agent; 0.8-1.2 parts of accelerator; 2-4 parts of fumed silica;

[0009] The titanate coupling agent reacts in situ with the hydroxyl groups in the polysiloxane-modified epoxy resin and the hydroxyl-terminated hyperbranched polyester to form a coordination structure with kinetic latency characteristics, and the network structure after the sealing adhesive is cured has a hydrophobic long-chain titanate coating layer.

[0010] By employing the above technical solution, this invention utilizes the high bond energy characteristics of polysiloxane segments and the high crosslinking density characteristics of tetrafunctional epoxy resins to construct a polymer matrix that combines heat resistance and toughness. Based on this, the spherical topology of the hydroxyl-terminated hyperbranched polyester is used to reduce the system viscosity and absorb curing stress, while its abundant terminal hydroxyl groups serve as anchor points for chemical reactions.

[0011] In particular, the titanate coupling agent does not exist in a physically mixed state in the system, but rather modifies the resin network through an in-situ chemical reaction. The specific mechanism is as follows:

[0012] During the preparation process, the alkoxy groups in the titanate coupling agent molecule undergo alcoholysis exchange reaction with the hydroxyl groups on the polysiloxane-modified epoxy resin and the hydroxyl-terminated hyperbranched polyester, so that the titanium atoms and the resin skeleton form a stable coordination structure through Ti-OC bonds.

[0013] This coordination structure utilizes the large organic ligand groups on the titanate molecule to spatially encapsulate the titanium center and adjacent active sites. The resulting steric hindrance effect inhibits the reaction rate of the active groups at room temperature, thereby endowing the adhesive system with kinetic latency characteristics and extending its pot life.

[0014] During the high-temperature curing stage, as the thermal motion of the molecular chains intensifies, steric hindrance is overcome, and the system undergoes a cross-linking reaction. At the same time, the hydrophobic long-chain organic groups attached to the titanium atoms migrate to the interface or surface of the polymer network and orient themselves, eventually forming a dense hydrophobic coating layer in the cured network, which blocks moisture penetration.

[0015] Preferably, the raw materials are in the following proportions by weight: 60 parts of polysiloxane-modified epoxy resin; 20 parts of tetrafunctional epoxy resin; 10 parts of hydroxyl-terminated hyperbranched polyester; 1.0 part of titanate coupling agent; 10 parts of reactive diluent; 45 parts of modified alicyclic amine curing agent; 1.0 part of accelerator; and 3 parts of fumed silica.

[0016] By adopting the above technical solution, the crosslinking density and flexibility can be balanced, preventing the adhesive layer from becoming brittle due to excessive tetrafunctional epoxy resin content, while ensuring sufficient hydroxyl groups to coordinate with titanate esters to achieve the expected hydrophobic modification effect.

[0017] Preferably, the sealing adhesive is a two-component system, comprising component A and component B; component A comprises: all of the polysiloxane-modified epoxy resin, the tetrafunctional epoxy resin, the hydroxyl-terminated hyperbranched polyester, the titanate coupling agent, the reactive diluent, and a portion of the fumed silica; component B comprises: all of the modified alicyclic amine curing agent, the accelerator, and the remaining amount of the fumed silica.

[0018] By adopting the above technical solution, the resin and titanate involved in the coordination reaction are placed in component A, and the amine curing agent is placed in component B. This isolates the latent coordination structure from direct contact with the curing agent, preventing the disruption of coordination equilibrium due to amine attack during storage, thereby ensuring the storage stability of component A.

[0019] Preferably, the polysiloxane-modified epoxy resin is prepared by reacting bisphenol A type liquid epoxy resin with hydroxyl-terminated polydimethylsiloxane under the action of a catalyst, wherein the content of organosilicon is 20wt% to 30wt%, and the epoxy equivalent of the polysiloxane-modified epoxy resin is 240 to 295 g / eq.

[0020] By adopting the above technical solution, the content of organosilicon is controlled between 20wt% and 30wt%, which reduces the internal stress of epoxy resin through organosilicon segments and avoids phase separation problems caused by excessive organosilicon content, thus ensuring that the modified resin remains in a homogeneous and transparent state.

[0021] Preferably, the hydroxyl-terminated hyperbranched polyester is prepared by esterification polycondensation of trimethylolpropane and 2,2-dimethylolpropionic acid, and has a hydroxyl value of 465-515 mgKOH / g; the tetrafunctional epoxy resin is N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenylmethane; and the titanate coupling agent is isopropyltris(dioctylpyrophosphate)titanate.

[0022] By adopting the above technical solutions, the high hydroxyl value hyperbranched polyester increases the grafting density with titanate; N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenylmethane improves the heat distortion temperature by introducing a rigid benzene ring and high-density crosslinking points; isopropyltris(dioctylpyrophosphate)titanate has a longer pyrophosphate side chain, which provides a stronger steric hindrance effect compared to short-chain titanates, and the hydrophobic layer formed has a higher barrier efficiency for water molecules.

[0023] Preferably, the active diluent is a C12-14 alkyl glycidyl ether; and the accelerator is 2-ethyl-4-methylimidazole.

[0024] By adopting the above technical solution, C12-14 alkyl glycidyl ether utilizes its long-chain alkyl structure to assist in toughening and viscosity adjustment; 2-ethyl-4-methylimidazolium, as a latent promoter, matches the latent effect induced by titanate, so that the system reacts slowly at room temperature but cures rapidly at high temperature.

[0025] Secondly, the present invention provides a method for preparing a high-temperature resistant sealing adhesive for flexible electronic paper, comprising the following steps:

[0026] S1. Preparation of component A: Polysiloxane modified epoxy resin, tetrafunctional epoxy resin, hydroxyl-terminated hyperbranched polyester and titanate coupling agent are mixed, heated to 100-115℃, and subjected to constant temperature reaction and degassing under vacuum conditions. During the reaction, nitrogen gas is introduced to remove small molecule volatiles generated in the reaction. After the reaction is completed, the temperature is lowered, and an active diluent and part of fumed silica are added and dispersed evenly to obtain component A.

[0027] S2. Preparation of component B: The modified alicyclic amine curing agent, accelerator and residual fumed silica are mixed and dispersed evenly under vacuum conditions to obtain component B;

[0028] S3. Mixing: When using, mix component A and component B evenly in proportion.

[0029] By adopting the above technical solution, this preparation method differs from the traditional physical blending process, and instead introduces a high-temperature vacuum pre-reaction stage.

[0030] In step S1, by controlling the temperature conditions of 100–115°C and the vacuum environment, the titanate coupling agent is driven to undergo a de-alcoholization reaction with the hydroxyl groups in the resin system. Since this reaction is a reversible equilibrium reaction, if the small molecule alcohols generated during the reaction remain in the system, they will inhibit the forward reaction and may form bubbles during the subsequent curing process.

[0031] This method utilizes high temperature combined with vacuum and nitrogen stripping to remove the volatile small molecules generated in the reaction in a timely manner, disrupting the chemical equilibrium and promoting the reaction towards the formation of coordination structures. This ensures that the titanate ester is firmly grafted onto the resin skeleton in the form of chemical bonds, thus constructing a stable latent system.

[0032] Preferably, in step S1, the preparation method of the polysiloxane-modified epoxy resin includes: heating the bisphenol A type liquid epoxy resin to 120°C to remove water, adding the catalyst triphenylphosphine, adding terminal hydroxyl polydimethylsiloxane dropwise, and after the dropwise addition is complete, heating to 160°C for constant temperature reaction until the system becomes a clear, transparent, homogeneous liquid.

[0033] By employing the above technical solution, a grafting reaction is carried out between hydroxyl-terminated polydimethylsiloxane and epoxy groups or hydroxyl groups in epoxy resin. The system changes from an initial milky white and turbid state to a clear, transparent, homogeneous liquid, indicating that the hydrophobic polysiloxane segments have been successfully chemically bonded to the epoxy resin molecular chain. This solves the problem of poor compatibility between organosilicon and epoxy resin, achieves homogeneous modification at the molecular level, and avoids the decline in mechanical properties caused by macroscopic phase separation.

[0034] Preferably, the preparation method of the hydroxyl-terminated hyperbranched polyester includes: mixing and melting trimethylolpropane, 2,2-dimethylolpropionic acid and the catalyst p-toluenesulfonic acid, carrying out an esterification polycondensation reaction at 170-175°C and continuously removing the generated water until the acid value of the reaction system drops below 5 mg KOH / g.

[0035] By employing the above technical solution and using a one-step melt polycondensation method, water generated during the esterification reaction is continuously removed via a water separator, thus driving the polycondensation reaction. By controlling the acid value to below 5 mg KOH / g, the polymer ends are predominantly hydroxyl groups, reducing the presence of free carboxyl groups and preventing uncontrollable side reactions between residual carboxyl groups and subsequently added epoxy resin. This ensures the integrity of the hyperbranched structure and its chemical stability as a reaction intermediate.

[0036] Preferably, in step S1, the isothermal reaction and degassing time is 50-90 minutes, and the vacuum condition is a vacuum degree below -0.098 MPa; the small molecule volatiles include isopropanol generated by the coordination reaction of titanate coupling agent.

[0037] By employing the above technical solution and controlling the reaction time and high vacuum, the conversion rate of the alcohol removal reaction is ensured. The removed small-molecule volatiles are mainly isopropanol produced by the hydrolysis or alcoholysis of titanate esters. If isopropanol remains, it will lower the flash point of the adhesive, affecting safety; furthermore, as a proton donor, isopropanol may accelerate the initiation of the epoxy-amine reaction, shorten the pot life, and even vaporize during high-temperature curing, leading to pinholes or voids in the adhesive layer. A thorough gas-lift removal process eliminates these potential defects, ensuring the density and insulation reliability of the sealing adhesive.

[0038] In summary, the present invention has at least one of the following beneficial technical effects:

[0039] 1. This invention improves the heat resistance of the cured product by introducing high bond energy Si-O segments into the polysiloxane-modified epoxy resin and providing high density crosslinking nodes with tetrafunctional epoxy resin; in combination with the spherical cavity structure of the hydroxyl-terminated hyperbranched polyester to absorb curing shrinkage stress, it alleviates the internal stress and brittleness problems caused by high crosslinking density, so that the sealing adhesive can maintain mechanical strength and bonding stability in high temperature environment.

[0040] 2. This invention utilizes a titanate coupling agent to undergo an in-situ chemical reaction with the hydroxyl groups in the resin system, grafting hydrophobic long-chain organic groups into the polymer network; during the high-temperature curing process, the hydrophobic groups migrate to the interface or surface and orient themselves, forming a dense hydrophobic coating layer, which blocks the penetration path of water molecules and improves the aging resistance of the sealing adhesive in high-temperature and high-humidity environments.

[0041] 3. This invention uses a high-temperature vacuum pre-reaction process to enable the titanate coupling agent to form a coordination structure with kinetic latency characteristics with the matrix resin; by utilizing the steric hindrance effect generated by the long-chain titanate ligands, the reaction rate of the active groups at room temperature is suppressed, and the pot life of the two-component adhesive solution is extended without reducing the high-temperature curing speed, thus meeting the operational requirements of flexible electronic paper packaging process. Attached Figure Description

[0042] Figure 1 This is a comparison of the Fourier Transmission Spectra (FT-IR) of the components in Example 1 and Comparative Example A; where (a) is the spectrum from 4000 to 400 cm⁻¹. -1 (a) Full spectrum of the range; (b) 3000–3700 cm⁻¹ -1 A magnified view of the area;

[0043] Figure 2 The graphs show the DSC curing kinetics analysis of the adhesive systems in Example 2 and the comparative example; where (a) is the dynamic curing heat flow curve and (b) is the bar chart comparing the curing characteristic temperatures. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0045] The main raw materials and reagents used in the following examples and comparative examples have the following sources and specifications. Reagents not specifically mentioned are all commercially available analytical grade or higher grade products.

[0046] Bisphenol A type liquid epoxy resin, brand name E-51, CAS number 25068-38-6, epoxy equivalent 182~192g / eq.

[0047] Tetrafunctional epoxy resin, grade AG-80, chemical name N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenylmethane, CAS number 28768-32-3, epoxy equivalent 110~130g / eq.

[0048] Titanate coupling agent, brand name NDZ-201, chemical name isopropyl tris(dioctylpyrophosphoryloxy)titanate, CAS number 65345-34-8.

[0049] Silane coupling agent, brand name KH-560, chemical name γ-glycidyl etheroxypropyltrimethoxysilane, CAS number 2530-83-8.

[0050] Fumed silica, grade R972, CAS number 68611-44-9, specific surface area 110±20 m² 2 / g.

[0051] Modified alicyclic amine curing agent, active hydrogen equivalent 95 g / eq, viscosity 200~400 mPa·s at 25℃.

[0052] Reactive diluent, chemical name C12-14 alkyl glycidyl ether, CAS number 68609-97-2, epoxy equivalent 275~300g / eq.

[0053] Accelerator, chemical name 2-ethyl-4-methylimidazole, CAS number 931-36-2.

[0054] Raw materials for synthesis: hydroxyl-terminated polydimethylsiloxane (CAS No. 70131-67-8, molecular weight Mn≈2500); trimethylolpropane (CAS No. 77-99-6); 2,2-dimethylolpropionic acid (CAS No. 4767-03-7); triphenylphosphine (CAS No. 603-35-0); p-toluenesulfonic acid (CAS No. 104-15-4).

[0055] Preparation Example 1:

[0056] This preparation example provides a method for preparing a polysiloxane-modified epoxy resin, wherein the organosilicon content is 25%, comprising the following steps:

[0057] (1) In a reactor equipped with an anchor stirrer, a reflux condenser, a thermometer and a nitrogen protection device, add 750g of bisphenol A type liquid epoxy resin E-51, heat to 120°C, turn on the stirrer and pass nitrogen gas to remove water for 30 minutes.

[0058] (2) Add 1.5g of triphenylphosphine as a catalyst, stir evenly, and then add 250g of hydroxyl-terminated polydimethylsiloxane at a uniform rate over 60 minutes.

[0059] (3) After the addition is complete, heat to 160℃ and react at a constant temperature for 3.5 hours. During this period, closely observe the appearance of the reaction system until the system changes from the initial milky white and turbid state to a clear and transparent homogeneous liquid, and there is no layering phenomenon after stirring is stopped.

[0060] (4) Cool down to 80°C and discharge to obtain a light yellow transparent liquid polysiloxane modified epoxy resin. The epoxy equivalent is 265 g / eq and the viscosity at 25°C is 28000 mPa·s.

[0061] Preparation Example 2:

[0062] This preparation example provides a method for preparing a polysiloxane-modified epoxy resin, wherein the organosilicon content is 20%, comprising the following steps:

[0063] (1) In a reactor equipped with an anchor stirrer, a reflux condenser, a thermometer and a nitrogen protection device, add 800g of bisphenol A type liquid epoxy resin E-51, heat to 120°C, turn on the stirrer and pass nitrogen gas to remove water for 30 minutes.

[0064] (2) Add 1.2g of triphenylphosphine as a catalyst, stir evenly, and then add 200g of hydroxyl-terminated polydimethylsiloxane at a uniform rate over 60 minutes.

[0065] (3) After the addition is complete, heat to 160°C and react at a constant temperature for 3 hours until the system becomes a clear and transparent homogeneous liquid;

[0066] (4) Cool down to 80°C and discharge to obtain a light yellow transparent liquid polysiloxane modified epoxy resin. The epoxy equivalent is 242 g / eq and the viscosity at 25°C is 22000 mPa·s.

[0067] Preparation Example 3:

[0068] This preparation example provides a method for preparing a polysiloxane-modified epoxy resin, wherein the organosilicon content is 30%, comprising the following steps:

[0069] (1) In a reactor equipped with an anchor stirrer, a reflux condenser, a thermometer and a nitrogen protection device, add 700g of bisphenol A type liquid epoxy resin E-51, heat to 120°C, turn on the stirrer and pass nitrogen gas to remove water for 30 minutes.

[0070] (2) Add 1.8g of triphenylphosphine as a catalyst, stir evenly, and then add 300g of hydroxyl-terminated polydimethylsiloxane at a uniform rate over 60 minutes.

[0071] (3) After the addition is complete, heat to 160°C and react at a constant temperature for 4 hours until the system becomes a clear and transparent homogeneous liquid;

[0072] (4) Cool down to 80°C and discharge to obtain a light yellow transparent liquid polysiloxane modified epoxy resin. The epoxy equivalent is 295 g / eq and the viscosity at 25°C is 35000 mPa·s.

[0073] Preparation Example 4:

[0074] This preparation example provides a method for preparing a hydroxyl-terminated hyperbranched polyester, comprising the following steps:

[0075] (1) Add 13.4 g (0.1 mol) of trimethylolpropane and 241.2 g (1.8 mol) of 2,2-dimethylolpropionic acid to a four-necked flask equipped with a water separator, condenser, thermometer and mechanical stirrer;

[0076] (2) Add 1.2g of p-toluenesulfonic acid as a catalyst, purge with nitrogen for protection, and heat to 140℃ to completely melt the material;

[0077] (3) Turn on the stirrer (200 rpm) and slowly heat to 175°C to carry out the esterification polycondensation reaction. During the reaction, the generated water is continuously removed through the water separator. The reaction time is about 5 hours.

[0078] (4) Take a sample every 30 minutes to test the acid value. When the acid value drops below 5 mg KOH / g, stop heating and cool down to 100°C to discharge the material. The hydroxyl-terminated hyperbranched polyester is a viscous semi-solid at room temperature. Its hydroxyl value is 485 mg KOH / g.

[0079] Preparation Example 5:

[0080] This preparation example provides a method for preparing a hydroxyl-terminated hyperbranched polyester, comprising the following steps:

[0081] (1) Add 13.4 g (0.1 mol) of trimethylolpropane and 402.0 g (3.0 mol) of 2,2-dimethylolpropionic acid to a four-necked flask equipped with a water separator, condenser, thermometer and mechanical stirrer;

[0082] (2) Add 2.0g of p-toluenesulfonic acid as a catalyst, purge with nitrogen for protection, and heat to 140℃ to completely melt the material;

[0083] (3) Turn on the stirrer (250 rpm) and slowly heat to 175°C to carry out the esterification polycondensation reaction. During the reaction, the generated water is continuously removed through the water separator. The reaction time is about 6.5 hours.

[0084] (4) When the acid value drops to below 5 mg KOH / g, stop heating, cool down and discharge the material to obtain end-hydroxyl hyperbranched polyester, whose hydroxyl value is 465 mg KOH / g.

[0085] Preparation Example 6:

[0086] This preparation example provides a method for preparing a hydroxyl-terminated hyperbranched polyester, comprising the following steps:

[0087] (1) Add 13.4 g (0.1 mol) of trimethylolpropane and 120.6 g (0.9 mol) of 2,2-dimethylolpropionic acid to a four-necked flask equipped with a water separator, condenser, thermometer and mechanical stirrer;

[0088] (2) Add 0.8g of p-toluenesulfonic acid as a catalyst, purge with nitrogen for protection, and heat to 140℃ to completely melt the material;

[0089] (3) Turn on the stirrer (200 rpm) and slowly heat to 170°C to carry out the esterification polycondensation reaction. During the reaction, the generated water is continuously removed through the water separator. The reaction time is about 4 hours.

[0090] (4) When the acid value drops to below 5 mg KOH / g, stop heating, cool down and discharge the material to obtain end-hydroxyl hyperbranched polyester, whose hydroxyl value is 515 mg KOH / g.

[0091] Example 1:

[0092] This embodiment provides a method for preparing a high-temperature resistant edge-sealing adhesive for flexible electronic paper, including the following steps:

[0093] (1) Preparation of component A:

[0094] Add 60 parts of the polysiloxane-modified epoxy resin prepared in Preparation Example 1, 20 parts of the tetrafunctional epoxy resin AG-80, 10 parts of the hydroxyl-terminated hyperbranched polyester prepared in Preparation Example 4, and 1.0 part of the titanate coupling agent NDZ-201 to a planetary mixer; start stirring and heat to 110°C, react at a constant temperature under a vacuum of -0.098 MPa and degas for 60 minutes, then introduce nitrogen gas for stripping, using the high temperature and vacuum environment to promote the in-situ coordination pre-reaction of the titanate with the hydroxyl groups of the resin and hyperbranched polyester, while removing small molecule volatiles; then cool to 60°C, add 10 parts of the reactive diluent C12-14 alkyl glycidyl ether and 2 parts of fumed silica R972, disperse at high speed for 30 minutes, and discharge to obtain component A.

[0095] (2) Preparation of component B:

[0096] Add 45 parts of modified alicyclic amine curing agent, 1.0 part of accelerator 2-ethyl-4-methylimidazole and 1 part of fumed silica R972 to a stirred tank and stir and disperse under vacuum for 30 minutes until the mixture is uniform and free of bubbles to obtain component B.

[0097] (3) Mixed use:

[0098] Mix component A and component B at a weight ratio of 100:45, stir well, and then apply the adhesive.

[0099] Example 2:

[0100] This embodiment provides a method for preparing a high-temperature resistant edge-sealing adhesive for flexible electronic paper, including the following steps:

[0101] (1) Preparation of component A:

[0102] Add 60 parts of the polysiloxane-modified epoxy resin prepared in Preparation Example 1, 20 parts of the tetrafunctional epoxy resin AG-80, 10 parts of the hydroxyl-terminated hyperbranched polyester prepared in Preparation Example 4, and 0.5 parts of the titanate coupling agent NDZ-201 to a planetary mixer; start stirring and heat to 110°C, react at a constant temperature under a vacuum of -0.098 MPa and degas for 60 minutes, then introduce nitrogen for stripping, using the high temperature and vacuum environment to promote in-situ coordination pre-reaction of the titanate with the hydroxyl groups of the resin and hyperbranched polyester, while removing small molecule volatiles; then cool to 60°C, add 10 parts of the reactive diluent C12-14 alkyl glycidyl ether and 2 parts of fumed silica R972, disperse at high speed for 30 minutes, and discharge to obtain component A.

[0103] (2) Preparation of component B:

[0104] 45 parts of modified alicyclic amine curing agent, 1.0 part of accelerator 2-ethyl-4-methylimidazole and 1 part of fumed silica R972 were added to a stirred tank and stirred and dispersed under vacuum for 30 minutes to obtain component B.

[0105] (3) Mixed use:

[0106] Mix component A and component B at a weight ratio of 100:45, stir well, and then apply the adhesive.

[0107] Example 3:

[0108] This embodiment provides a method for preparing a high-temperature resistant edge-sealing adhesive for flexible electronic paper, including the following steps:

[0109] (1) Preparation of component A:

[0110] Add 60 parts of the polysiloxane-modified epoxy resin prepared in Preparation Example 1, 20 parts of the tetrafunctional epoxy resin AG-80, 10 parts of the hydroxyl-terminated hyperbranched polyester prepared in Preparation Example 4, and 1.5 parts of the titanate coupling agent NDZ-201 to a planetary mixer; start stirring and heat to 110°C, react at a constant temperature under a vacuum of -0.098 MPa and degas for 60 minutes, then introduce nitrogen gas for stripping, using the high temperature and vacuum environment to promote the in-situ coordination pre-reaction of the titanate with the hydroxyl groups of the resin and hyperbranched polyester, while removing small molecule volatiles; then cool to 60°C, add 10 parts of the reactive diluent C12-14 alkyl glycidyl ether and 2 parts of fumed silica R972, disperse at high speed for 30 minutes, and discharge to obtain component A.

[0111] (2) Preparation of component B:

[0112] 45 parts of modified alicyclic amine curing agent, 1.0 part of accelerator 2-ethyl-4-methylimidazole and 1 part of fumed silica R972 were added to a stirred tank and stirred and dispersed under vacuum for 30 minutes to obtain component B.

[0113] (3) Mixed use:

[0114] Mix component A and component B at a weight ratio of 100:45, stir well, and then apply the adhesive.

[0115] Example 4:

[0116] This embodiment provides a method for preparing a high-temperature resistant edge-sealing adhesive for flexible electronic paper, including the following steps:

[0117] (1) Preparation of component A:

[0118] 55 parts of the polysiloxane-modified epoxy resin (20% organosilicon content) prepared in Preparation Example 2, 25 parts of tetrafunctional epoxy resin AG-80, 12 parts of the hydroxyl-terminated hyperbranched polyester prepared in Preparation Example 5, and 1.0 part of titanate coupling agent NDZ-201 were added to a planetary mixer. The mixer was started and the temperature was raised to 115°C. The mixture was kept at a constant temperature under a vacuum of -0.098 MPa and degassed for 50 minutes. Nitrogen gas was introduced for stripping. The high temperature and vacuum environment promoted the in-situ coordination pre-reaction of titanate with the hydroxyl groups of the resin and hyperbranched polyester, while removing small molecule volatiles. The temperature was then lowered to 60°C, and 8 parts of reactive diluent C12-14 alkyl glycidyl ether and 2.5 parts of fumed silica R972 were added. The mixture was dispersed at high speed for 30 minutes, and component A was discharged.

[0119] (2) Preparation of component B:

[0120] 48 parts of modified alicyclic amine curing agent, 1.2 parts of accelerator 2-ethyl-4-methylimidazole and 1 part of fumed silica R972 were added to a stirred tank and mixed evenly to obtain component B.

[0121] (3) Mixed use:

[0122] Mix component A and component B at a weight ratio of 100:48, stir well, and then apply the adhesive.

[0123] Example 5:

[0124] This embodiment provides a method for preparing a high-temperature resistant edge-sealing adhesive for flexible electronic paper, including the following steps:

[0125] (1) Preparation of component A:

[0126] Add 65 parts of the polysiloxane-modified epoxy resin (organosilicon content 30%) prepared in Preparation Example 3, 15 parts of the tetrafunctional epoxy resin AG-80, 8 parts of the hydroxyl-terminated hyperbranched polyester prepared in Preparation Example 6, and 1.0 part of the titanate coupling agent NDZ-201 to a planetary mixer; start stirring and heat to 105°C, react at a constant temperature under a vacuum of -0.098 MPa and degas for 70 minutes, then introduce nitrogen gas for stripping, using the high temperature and vacuum environment to promote the in-situ coordination pre-reaction of the titanate with the hydroxyl groups of the resin and hyperbranched polyester, while removing small molecule volatiles; then cool to 60°C, add 12 parts of the reactive diluent C12-14 alkyl glycidyl ether and 1.5 parts of fumed silica R972, disperse at high speed for 30 minutes, and discharge to obtain component A.

[0127] (2) Preparation of component B:

[0128] 42 parts of modified alicyclic amine curing agent, 0.8 parts of accelerator 2-ethyl-4-methylimidazole and 1 part of fumed silica R972 were added to a stirred tank and mixed evenly to obtain component B.

[0129] (3) Mixed use:

[0130] Mix component A and component B at a weight ratio of 100:42, stir well, and then apply the adhesive.

[0131] Example 6:

[0132] This embodiment provides a method for preparing a high-temperature resistant edge-sealing adhesive for flexible electronic paper, including the following steps:

[0133] (1) Preparation of component A:

[0134] Add 60 parts of the polysiloxane-modified epoxy resin prepared in Preparation Example 1, 20 parts of the tetrafunctional epoxy resin AG-80, 10 parts of the hydroxyl-terminated hyperbranched polyester prepared in Preparation Example 4, and 1.0 part of the titanate coupling agent NDZ-201 to a planetary mixer; start stirring and heat to 100°C, and extend the isothermal reaction time to 90 minutes under a vacuum of -0.098 MPa to ensure sufficient coordination reaction; introduce nitrogen gas stripping to promote in-situ coordination pre-reaction of titanate with the hydroxyl groups of resin and hyperbranched polyester using high temperature and vacuum environment, while removing small molecule volatiles; then cool to 60°C, add 10 parts of reactive diluent C12-14 alkyl glycidyl ether and 2 parts of fumed silica R972, disperse at high speed for 30 minutes, and discharge to obtain component A.

[0135] (2) Preparation of component B:

[0136] 45 parts of modified alicyclic amine curing agent, 1.0 part of accelerator 2-ethyl-4-methylimidazole and 1 part of fumed silica R972 were added to a stirred tank and mixed evenly to obtain component B.

[0137] (3) Mixed use:

[0138] Mix component A and component B at a weight ratio of 100:45, stir well, and then apply the adhesive.

[0139] Comparative Example 1:

[0140] Compared with Example 1, the difference is that the titanate coupling agent NDZ-201 was not added, while the other raw materials and preparation process are the same.

[0141] Comparative Example 2:

[0142] Compared with Example 1, the difference is that the 110°C vacuum isothermal reaction process in the preparation step of component A was not carried out. Instead, all the raw materials of component A were directly physically mixed and dispersed at room temperature. All other aspects are the same.

[0143] Comparative Example 3:

[0144] The difference from Example 1 is that an equal mass of linear polyether polyol (molecular weight 1000) was used to replace the hydroxyl-terminated hyperbranched polyester, while all other aspects remained the same.

[0145] Comparative Example 4:

[0146] Compared with Example 1, the difference is that an equal mass of ordinary bisphenol A type epoxy resin E-51 is used instead of polysiloxane modified epoxy resin, and all other aspects are the same.

[0147] Comparative Example 5:

[0148] Compared with Example 1, the difference is that silane coupling agent KH-560 is used instead of titanate coupling agent NDZ-201, and the same pre-reaction process is used, while the rest are the same.

[0149] Comparative Example 6:

[0150] The difference from Example 1 is that nitrogen was not introduced for stripping during the preparation of component A; the reaction was carried out only under vacuum conditions. All other aspects are the same.

[0151] Test Example 1:

[0152] This test uses infrared spectroscopy analysis to verify whether the high-temperature vacuum pre-reaction process in the example promotes the chemical bonding between the titanate coupling agent and the hydroxyl groups in the hydroxyl-terminated hyperbranched polyester and epoxy resin, thus providing evidence for the kinetic latency mechanism.

[0153] The experiment used a Fourier transform infrared spectrometer equipped with an ATR (attenuated total reflectance) accessory. Component A prepared in Example 1 (reacted at 110°C), Component A prepared in Example 2 (low titanate content), Component A prepared in Example 3 (high titanate content), and Component A prepared in Comparative Example 2 (physically mixed at room temperature, unreacted) were selected as test samples. Additionally, pure hydroxyl-terminated hyperbranched polyester was used as a reference.

[0154] The specific steps are as follows:

[0155] (1) Turn on the infrared spectrometer and preheat for 30 minutes. Clean the surface of the diamond ATR crystal with anhydrous ethanol. After the solvent evaporates, collect the air background spectrum.

[0156] (2) Take a small amount of the sample to be tested and coat it evenly on the surface of the ATR crystal to ensure complete coverage and no bubbles.

[0157] (3) Set the scanning range to 4000cm -1 Up to 400cm -1 The resolution is 4cm. -1 The number of scans was 32.

[0158] (4) Collect the infrared absorption spectra of each sample and perform baseline correction.

[0159] (5) Select the benzene ring skeleton vibration peak (approximately 1509 cm⁻¹). -1 The reference peak (derived from bisphenol A type epoxy resin and AG-80, with a basically constant concentration before and after the reaction) was used as an internal standard.

[0160] (6) Select the hydroxyl stretching vibration peak (approximately 3300–3500 cm⁻¹). -1 The broad peak is used as a characteristic variation peak.

[0161] (7) Calculate the absorbance of the hydroxyl peak (A). OH ) and internal standard peak absorbance (A ref The ratio of I to A OH / A ref The residual level of active hydroxyl groups in the system is characterized by relative absorbance intensity.

[0162] The test results are shown in Table 1, and the corresponding comparison chart is shown below. Figure 1 As shown.

[0163] Table 1. Record of relative absorbance data of characteristic infrared peaks of sample A for each component:

[0164]

[0165] Note: The formula for calculating hydroxyl conversion rate is (I对比例2 I 样品 ) / I 对比例2 ×100%.

[0166] According to Table 1 and Figure 1 Data analysis showed that the relative intensity of hydroxyl groups in Comparative Example 2 (physical mixture) was 0.934, reflecting the total amount of hydroxyl groups originally contained in the terminal hydroxyl hyperbranched polyester and epoxy resin in the system. After introducing a high-temperature vacuum pre-reaction process and a titanate coupling agent, the intensity of the characteristic peak of hydroxyl groups in the example samples decreased to varying degrees.

[0167] The relative strength of the hydroxyl group in Example 1 decreased to 0.382, and the hydroxyl conversion rate was approximately 59.1% compared to Comparative Example 2. This data indicates that, under 110°C and vacuum conditions, the isopropoxy or pyrophosphate oxy groups of the titanate coupling agent underwent a significant chemical reaction with the active hydroxyl groups in the system. The reaction consumed a large amount of highly reactive primary hydroxyl groups, converting them into thermally unstable Ti-OC coordination bonds.

[0168] Comparing Example 2 (conversion rate 25.4%) and Example 3 (conversion rate 64.0%), it can be seen that the degree of hydroxyl group capping increases with the increase of titanate content. However, although the titanate content increased by 50% compared to Example 1, the conversion rate only increased by about 5% in Example 3, indicating that at 1.0 part, the reaction against the highly active terminal hydroxyl groups in the system is close to saturation, and the remaining hydroxyl groups may mainly be secondary hydroxyl groups of epoxy resin with large steric hindrance, which are difficult to be completely reacted by titanate.

[0169] In summary, infrared spectroscopy data confirmed that the pre-reaction process successfully achieved chemical modification of the terminal hydroxyl groups of the hyperbranched polyester. This modification, on the one hand, reduced the concentration of free hydroxyl groups in the system, thereby inhibiting their low-temperature catalytic activity against amine curing agents and verifying the material basis of the kinetic latent mechanism; on the other hand, the consumption of hydroxyl groups means that hydrophilic groups are replaced by hydrophobic titanate long chains, providing chemical structural support for improving the hydrophobicity and interfacial compatibility of the system.

[0170] Test Example 2:

[0171] This test uses differential scanning calorimetry (DSC) to examine the heat flow changes of the adhesive system during dynamic heating. By comparing the onset temperature and peak temperature of the curing reaction, the kinetic latent effect of the introduction of titanate coupling agent on the epoxy-amine curing system is verified.

[0172] The test subjects were the mixed adhesive solutions of Example 1, Example 2, Example 3 and Comparative Example 1.

[0173] The specific steps are as follows:

[0174] (1) Weigh component A and component B according to the proportions set in each embodiment and comparative example, and mix them quickly and evenly at 25°C to obtain the gel sample to be tested.

[0175] (2) Immediately take about 5 to 8 mg of the mixed gel sample and place it in an aluminum liquid crucible, seal it with a pressure cap, and at the same time prepare an empty aluminum crucible as a reference sample.

[0176] (3) Place the sample crucible and the reference crucible into the DSC furnace, equilibrate to 30°C under a nitrogen atmosphere (flow rate 50 mL / min) and hold for 2 minutes.

[0177] (4) Perform dynamic scanning at a heating rate of 10℃ / min, with the temperature range set from 30℃ to 250℃.

[0178] (5) Record the curve of heat flow with temperature, and use the instrument’s built-in analysis software to integrate the exothermic peak and extract the extrapolated initial curing temperature, peak temperature and curing reaction enthalpy.

[0179] The test results are shown in Table 2, and the corresponding comparison chart is shown below. Figure 2 As shown.

[0180] Table 2. DSC dynamic curing characteristic parameter data records for each adhesive system:

[0181]

[0182] Note: Latent temperature difference = initial curing temperature of sample - initial curing temperature of comparative example 1.

[0183] According to Table 2 and Figure 2 The data shows that, in Comparative Example 1, without the addition of titanate coupling agent, the initial curing temperature was 68.4℃. This indicates that the ordinary epoxy-modified amine system can be catalyzed and initiated by the hydroxyl groups present in the system (derived from the hyperbranched polyester and epoxy resin itself) at relatively low temperatures, resulting in a short pot life and poor room temperature storage stability.

[0184] In Example 1, after introducing 1.0 part of titanate and undergoing pre-reaction treatment, the initial curing temperature significantly increased to 94.7℃, a delay of 26.3℃ compared to Comparative Example 1; the peak temperature also shifted from 105.2℃ to 128.5℃. This significant temperature hysteresis confirms that the system has formed an effective kinetic latency mechanism. The coordination structure formed by titanate and hydroxyl groups is relatively stable at low temperatures, shielding the promoting effect of hydroxyl groups on epoxy ring-opening through steric hindrance. At the same time, the long-chain structure of titanate hinders the diffusion of curing agent to epoxy groups.

[0185] Comparing the data from Examples 2 and 3, it can be seen that the latency effect is positively correlated with the amount of titanate grafted. When the temperature rises to a specific threshold (approximately 90°C or higher in this system), the heat energy is sufficient to disrupt the coordination balance of the titanate or accelerate molecular chain movement, causing the blocked active sites to be rapidly released, triggering a concentrated and rapid curing reaction. This thermal behavior characteristic of "stable at low temperatures and fast curing at high temperatures" ensures both the operating window (potential life) of the sealing adhesive during the application process and meets the requirements of rapid curing in flexible electronic paper packaging technology. In addition, the slight decrease in reaction enthalpy (from 342.5 J / g to 328.4 J / g) is within the normal range, mainly attributed to the fine adjustment of crosslinking density caused by the introduction of macromolecular side chains and the increase in the mass proportion of some non-reactive groups, which does not affect the overall degree of curing.

[0186] Test Example 3:

[0187] This test uses Soxhlet extraction to determine the gel content of the cured product, thereby characterizing the perfection of the cross-linking network and the chemical resistance of the adhesive system. A higher gel content indicates fewer unreacted small molecules or linear oligomers remaining in the system, and a higher cross-linking density.

[0188] The experiment was modified according to ASTM D2765 standard, using acetone as the extraction solvent. The test subjects were the cured samples from Examples 1, 2, 3, and Comparative Example 3.

[0189] The specific steps are as follows:

[0190] (1) After degassing the components according to the formula ratio, inject them into the polytetrafluoroethylene mold and prepare a 1mm thick curing film according to the curing procedures of 80℃ / 30min and 120℃ / 60min. After cooling to room temperature, cut it into particles of about 2mm×2mm.

[0191] (2) Take a clean 120-mesh stainless steel wire mesh bag, dry it in an oven at 105℃ for 1 hour, and weigh it after cooling. Record the weight as m0. Weigh about 1.0g of sample particles, put them into the mesh bag, seal it, and weigh it. Record the weight as m1 (sample mass M=m1). m0).

[0192] (3) Place the mesh bag containing the sample into the extraction tube of the Soxhlet extractor, add 200 mL of analytical grade acetone and zeolite to the round-bottom flask, and assemble the reflux condenser.

[0193] (4) Continuous reflux extraction was carried out for 24 hours under water bath heating at 80℃, ensuring that the number of solvent siphons was not less than 6 times / hour, so as to fully dissolve the uncrosslinked sol portion.

[0194] (5) After extraction, remove the mesh bag and let the solvent evaporate naturally in the fume hood for 2 hours. Then place it in a vacuum oven at 100°C and dry for 4 hours until constant weight. After cooling, weigh it and record it as m2.

[0195] (6) According to the formula Gel%=(m2) m0) / (m1 The gel content was calculated by multiplying m0 by 100%, and the average value was taken for each sample in three parallel tests.

[0196] The test results are shown in Table 3.

[0197] Table 3. Raw data of Soxhlet extraction test and calculation of gel content of cured products of various adhesives:

[0198]

[0199] According to the data in Table 3, the average gel content of Comparative Example 3 (linear polyether system) was only 86.85%, and the data fluctuated relatively greatly (standard deviation 0.42). This indicates that in the network constructed by linear molecular chains, approximately 13% of the components were not effectively chemically bonded. These soluble components mainly consist of unreacted linear polyether segments or low molecular weight epoxy oligomers. Linear molecules only have active hydroxyl groups at both ends. Once one end remains unreacted or undergoes intramolecular ring formation, free segments are easily formed, making it impossible to form an infinite network structure.

[0200] In contrast, Example 1 exhibited an average gel content as high as 98.45% and a very low standard deviation (0.08), demonstrating extremely high curing integrity and uniformity. This result confirms that the hydroxyl-terminated hyperbranched polyester acts as a highly functional crosslinking center in the system. The spherical structure of the hyperbranched molecules and the dense hydroxyl sites on their surface ensure that, even when some hydroxyl groups are capped by titanate, the remaining active sites and the coupling effect of the titanate itself (Ti-OC bonds) still ensure that the molecular chains form a dense network structure in three-dimensional space.

[0201] The gel content of Examples 2 (97.12%) and 3 (97.92%) was slightly lower than that of Example 1, but still remained at a high level of over 97%. The decrease in Example 2 may be due to the smaller amount of titanate used, resulting in some hydrophilic segments not fully participating in the coupling reaction; while the slight decrease in Example 3 may be attributed to the large steric hindrance introduced by the excessive long titanate chains, leading to an increase in the spacing between local crosslinking points or the encapsulation of a few unreacted ends.

[0202] In summary, the synergistic effect of the hyperbranched topology and titanate coupling agent not only achieves kinetic latency but also constructs a rigid network with almost no sol residue after curing. This high gel content characteristic is crucial for electronic packaging materials, meaning that under subsequent high-temperature and high-humidity conditions, very few small molecules will precipitate or migrate, thus ensuring the long-term reliability of electronic components and the stability of interfacial adhesion.

[0203] Test Example 4:

[0204] This test evaluates the performance of adhesive systems from application process to post-curing service performance, including rheological property testing of mixed adhesives, thermomechanical property (DMA / TMA) analysis of cured products, and characterization of static mechanical properties (tensile, shear).

[0205] The specific steps are as follows:

[0206] (1) Process performance test: Take each group of prepared adhesive solutions and test them using a rotational rheometer under constant temperature conditions of 25℃. First, at a low shear rate (2s 1 ) and high shear rate (20s) 1 Viscosity values ​​were recorded at different rates, and the thixotropic index (TI) was calculated. Subsequently, the viscosity was continuously monitored over time at a constant low shear rate, and the time required for the viscosity to increase to twice the initial value was recorded to define the pot life.

[0207] (2) Thermomechanical property testing: The cured adhesive film was cut into strips of specified size. Using a dynamic thermomechanical analyzer (DMA), in tensile mode, at a frequency of 1 Hz and a heating rate of 3 °C / min, the temperature was scanned from 30 °C to 200 °C, and the storage modulus (E') and loss factor (tanδ) were recorded. The peak temperature of tanδ was taken as the glass transition temperature (Tg). Another sample was used with a thermomechanical analyzer (TMA) using an expansion probe, heated at 5 °C / min in a nitrogen atmosphere, and the coefficient of linear thermal expansion (CTE) in the range below Tg was calculated.

[0208] (3) Mechanical property testing: Dumbbell-shaped tensile specimens were prepared according to ASTM D638 standard and tested using a universal testing machine at a tensile rate of 5 mm / min. The stress-strain curves were recorded, and the tensile strength, elongation at break, and Young's modulus were calculated. At the same time, lap shear specimens were prepared with polyimide (PI) film and glass sheet as substrates, with an overlap area of ​​12.5 mm × 25 mm. The shear strength was tested to evaluate the interfacial adhesion.

[0209] The test results are shown in Tables 4 to 6.

[0210] Table 4. Test data on the processing performance of the mixed adhesive (viscosity and pot life):

[0211]

[0212] Table 5. Test data of thermomechanical properties of cured products (DMA / TMA):

[0213]

[0214] Table 6. Static mechanical property test data of cured products:

[0215]

[0216] According to the process performance data in Table 4, the pot life of Comparative Example 1 (without titanate) was only 42 minutes, indicating that the conventional epoxy-amine system has excessively high reactivity at room temperature, making it difficult to meet the long-term application window requirements in industrial production. Comparative Example 5, which used a silane coupling agent instead of titanate, only slightly increased the pot life to 55 minutes, indicating that the silane coupling agent mainly functions as an interfacial thickener and does not possess the coordination latency mechanism unique to titanate. In contrast, the pot life of Example 1 was extended to 255 minutes (>4 hours), and the thixotropic index reached 2.8. This confirms that the coordination structure formed by titanate and the terminal hydroxyl groups of the hyperbranched polyester effectively inhibits the reactivity at low temperatures, while simultaneously imparting good thixotropic properties to the adhesive, facilitating shape retention after dispensing and preventing adhesive overflow.

[0217] Based on the thermomechanical data in Table 5, the Tg of Example 1 reached 136.2℃, significantly higher than the 108.5℃ of Comparative Example 3 (linear polyether system). This indicates that despite the introduction of flexible segments, the high functionality of the hyperbranched polyester constructed a high-density cross-linked network, effectively limiting the movement of segments at high temperatures and maintaining the heat resistance of the material. Meanwhile, the CTE of Example 1 (42.1ppm / ℃) was much lower than that of Comparative Example 3 (68.4ppm / ℃), indicating that the dense spherical network structure effectively suppressed the thermal expansion of the polymer chains, which is crucial for ensuring the dimensional stability of electronic paper during thermal cycling.

[0218] Analyzing the mechanical property data in Table 6 reveals the differences in the contribution of each component to the material's strength and toughness. Comparative Example 4 (without silicone) exhibits typical high strength (58.4 MPa) but also high brittleness (elongation 2.8%) and high modulus (3.25 GPa). This high-rigidity material is unsuitable for the bending requirements of flexible electronic paper and is prone to brittle cracking. Comparative Example 3 (linear polyether), although having a relatively high elongation (12.5%), suffers from a significant drop in tensile strength to 28.6 MPa and an excessively low modulus, making it difficult to provide sufficient structural support. Example 1, through its molecular structure design of "flexible silicone segments and a hyperbranched rigid core," achieves a balance of performance: tensile strength remains at a relatively high level of 46.2 MPa, elongation at break increases to 8.4%, while Young's modulus decreases to 1.15 GPa. This low modulus, high strength, and moderate elongation characteristic can both buffer bending stress and provide reliable mechanical protection. Furthermore, Example 1 achieved a shear strength of 18.6 MPa on a PI film / glass substrate, which was superior to all comparative examples, demonstrating that the abundant polar groups in the titanate coupling agent and hyperbranched structure significantly enhanced the interfacial wetting and chemical bonding ability to heterogeneous substrates.

[0219] Test Example 5:

[0220] This test aims to simulate the high humidity, high voltage, and dynamic bending environments that flexible electronic paper may face during actual service, and to comprehensively evaluate the hydrophobic protection capability, electrical insulation integrity, and fatigue aging resistance of the adhesive system. Examples 1, 2, and 3, and Comparative Examples 2 (unreacted), 3 (linear polyether), 4 (without organosilicon), 5 (silane coupling agent), and 6 (without nitrogen stripping) were selected for comparative testing.

[0221] The specific steps are as follows:

[0222] (1) Prepare circular cured samples with a diameter of 50 mm and a thickness of 2 mm according to GB / T 1034 standard, and weigh the initial mass m0. Immerse the sample completely in deionized water at 25℃ for 24 hours, remove it, wipe off the surface moisture, and weigh it m1. Then, place the sample in a high-pressure accelerated aging test chamber (PCT) and set the conditions to 121℃, 100%RH, and 2 atm. After 48 hours of treatment, remove it and weigh it m2. Calculate the water absorption rate at room temperature and the water absorption rate under PCT conditions.

[0223] (2) Prepare PI film / glass overlap shear test specimens (same as test example 4) and determine the initial shear strength. Take another set of specimens of the same specifications and boil them in boiling water at 100℃ for 24 hours. After cooling, test the shear strength and calculate the strength retention rate after wet heat aging.

[0224] (3) According to ASTM D149 standard, the breakdown voltage of a 1 mm thick cured film was tested in transformer oil using a voltage breakdown tester at a voltage rise rate of 500 V / s. The voltage value at the moment of breakdown was recorded and the dielectric strength was calculated. At the same time, the volume resistivity was tested using a high resistance meter.

[0225] (4) Apply the adhesive evenly between two flexible PI films (adhesive layer thickness 50μm), and cut it into strips of 10mm×100mm after curing. Perform dynamic fatigue testing using a flexible plate bending tester with a bending radius R=3mm and a frequency of 60 cycles / min for 100,000 cycles. After the experiment, observe the cross-section of the adhesive layer for cracks, delamination, or whitening using an optical microscope.

[0226] The test results are shown in Tables 7-9.

[0227] Table 7. Test data on hygroscopicity and resistance to boiling water aging:

[0228]

[0229] Table 8 Electrical insulation performance test data:

[0230]

[0231] Table 9. Results of flexible bending aging test (R=3mm, 100,000 cycles):

[0232]

[0233] According to the data in Table 7, Example 1 showed a water absorption rate of only 0.84% ​​after 48 hours of high-pressure cooking with PCT, and a shear strength retention rate of 91.9% after boiling. In contrast, Comparative Example 2 (without pre-reaction) showed a PCT water absorption rate as high as 2.15%, and a strength retention rate of only 70.9%. This significant difference confirms the key role of the "pre-reaction" process: by pre-grafting titanate to the ends of the hyperbranched polyester, a stable hydrophobic shell is formed, effectively shielding the internal hydrophilic ester and ether bonds and blocking the penetration path of water molecules. Without pre-reaction (Comparative Example 2), the titanate is unevenly dispersed in the system and is prone to self-hydrolysis before curing, failing to form an effective coating structure. Furthermore, although Comparative Example 5 (silane coupling agent) performed better than the blank group, its strength retention rate (81.2%) was still lower than that of Example 1, indicating that the steric hindrance effect of long-chain titanate is superior to that of short-chain silane in terms of water-blocking performance.

[0234] Table 8 shows the impact of the stripping process on electrical insulation performance. The breakdown voltage of Comparative Example 6 (without nitrogen stripping) was only 14.2 kV / mm, significantly lower than the 26.5 kV / mm of Example 1. This is because the reaction of titanate with hydroxyl groups releases isopropanol, a byproduct. If this is not removed by nitrogen stripping, the isopropanol remains in the adhesive. During high-temperature curing, the residual isopropanol volatilizes, forming micron-sized bubbles or pores. These defects become weak points in electrical breakdown, leading to a significant decrease in dielectric strength. Example 1 removed small-molecule byproducts through the stripping process, ensuring the compactness of the adhesive layer and thus achieving excellent insulation withstand voltage performance.

[0235] Table 9 shows the bending test results, verifying the decisive role of the material's microstructure in its macroscopic mechanical life. Comparative Example 4 (without silicone) developed brittle cracks after 50,000 bends due to the lack of flexible segments; Comparative Example 3 (linear polyether), although flexible, experienced interface fatigue peeling under repeated stress due to low crosslinking density and modulus mismatch. Examples 1-3 all successfully passed the 100,000-bending test, with the adhesive layer remaining intact. This is attributed to the organic combination of the flexibility provided by the silicone segments and the strong anchoring effect provided by the hyperbranched rigid core. This "soft-hard synergy" structure can dissipate bending stress while maintaining strong interfacial adhesion, fully meeting the requirements of repeated bending of flexible electronic paper.

[0236] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A high-temperature resistant edge-sealing adhesive for flexible electronic paper, characterized in that, Including the following parts by weight of raw materials: 55-65 parts of polysiloxane-modified epoxy resin; the polysiloxane-modified epoxy resin is prepared by reacting bisphenol A type liquid epoxy resin with hydroxyl-terminated polydimethylsiloxane under the action of a catalyst, wherein the content of organosilicon is 20wt%-30wt%, and the epoxy equivalent of the polysiloxane-modified epoxy resin is 240-295g / eq. 15-25 parts of a tetrafunctional epoxy resin; wherein the tetrafunctional epoxy resin is N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenylmethane. 8-12 parts of hydroxyl-terminated hyperbranched polyester; 0.5 to 1.5 parts of titanate coupling agent; wherein the titanate coupling agent is isopropyl tris(dioctyl pyrophosphate) titanate; 8-12 parts of reactive diluent; 42-48 parts of modified alicyclic amine curing agent; Accelerator 0.8–1.2 parts; 2-4 parts of fumed silica; The titanate coupling agent reacts in situ with the hydroxyl groups in the polysiloxane-modified epoxy resin and the hydroxyl-terminated hyperbranched polyester to form a coordination structure with kinetic latency characteristics, and the network structure of the edge sealant after curing has a hydrophobic long-chain titanate coating layer. The edge sealing adhesive is a two-component system, comprising component A and component B; Component A is prepared by the following steps: mixing all amounts of the polysiloxane-modified epoxy resin, the tetrafunctional epoxy resin, the hydroxyl-terminated hyperbranched polyester, and the titanate coupling agent, heating to 100-115°C, and carrying out a constant-temperature reaction and degassing under vacuum conditions, during which nitrogen gas is introduced to remove small molecule volatiles generated in the reaction, cooling after the reaction is completed, adding all amounts of the reactive diluent and a portion of the fumed silica, and dispersing evenly to obtain component A; Component B comprises: the entire amount of the modified alicyclic amine curing agent, the accelerator, and the remaining amount of the fumed silica.

2. The high-temperature resistant sealing adhesive for flexible electronic paper according to claim 1, characterized in that, The weight parts of the raw materials are: 60 parts of polysiloxane-modified epoxy resin; 20 parts of a four-functional epoxy resin; 10 parts of hydroxyl-terminated hyperbranched polyester; 1.0 part of titanate coupling agent; 10 parts reactive diluent; 45 parts of modified alicyclic amine curing agent; Accelerator 1.0 part; 3 parts of fumed silica.

3. The high-temperature resistant sealing adhesive for flexible electronic paper according to claim 1, characterized in that, The hydroxyl-terminated hyperbranched polyester is prepared by esterification polycondensation reaction of trimethylolpropane and 2,2-dimethylolpropionic acid, and its hydroxyl value is 465-515 mgKOH / g.

4. The high-temperature resistant sealing adhesive for flexible electronic paper according to claim 1, characterized in that, The active diluent is a C12-14 alkyl glycidyl ether; the accelerator is 2-ethyl-4-methylimidazole.

5. A method for preparing a high-temperature resistant sealing adhesive for flexible electronic paper as described in any one of claims 1-4, characterized in that, Includes the following steps: S1. Preparation of component A: Polysiloxane modified epoxy resin, tetrafunctional epoxy resin, hydroxyl-terminated hyperbranched polyester and titanate coupling agent are mixed, heated to 100-115℃, and subjected to constant temperature reaction and degassing under vacuum conditions. During the reaction, nitrogen gas is introduced to remove small molecule volatiles generated in the reaction. After the reaction is completed, the temperature is lowered, and an active diluent and part of fumed silica are added and dispersed evenly to obtain component A. S2. Preparation of component B: The modified alicyclic amine curing agent, accelerator and residual fumed silica are mixed and dispersed evenly under vacuum conditions to obtain component B; S3. Mixing: When using, mix component A and component B evenly in proportion.

6. The preparation method according to claim 5, characterized in that, In step S1, the preparation method of the polysiloxane-modified epoxy resin includes: Bisphenol A type liquid epoxy resin was heated to 120℃ to remove water, and triphenylphosphine catalyst was added. Hydroxyl-terminated polydimethylsiloxane was then added dropwise. After the addition was complete, the temperature was raised to 160℃ and the reaction was carried out at a constant temperature until the system became a clear, transparent, and homogeneous liquid.

7. The preparation method according to claim 5, characterized in that, The method for preparing the hydroxyl-terminated hyperbranched polyester includes: Trimethylolpropane, 2,2-dimethylolpropionic acid and the catalyst p-toluenesulfonic acid were mixed and melted, and an esterification polycondensation reaction was carried out at 170-175°C while continuously removing the generated water until the acid value of the reaction system dropped below 5 mg KOH / g.

8. The preparation method according to claim 5, characterized in that, In step S1, the isothermal reaction and degassing time is 50-90 minutes, and the vacuum condition is a vacuum degree below -0.098 MPa; the small molecule volatiles include isopropanol generated by the coordination reaction of titanate coupling agent.

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