A biodegradable epoxy adhesive cured by an active ester, its preparation method and application

Abstract

This invention discloses a biodegradable epoxy adhesive cured with an active ester, its preparation method, and its application. The biodegradable epoxy adhesive is obtained by curing a multifunctional epoxy resin precursor with an active ester curing agent containing a spirocyclic acetal structure. Starting from structural design, this invention combines a flexible long-chain alkyl ester-terminated active ester with a rigid aromatic ester-terminated active ester. Without introducing additional polar groups, this significantly improves the adhesive strength of the active ester curing system while maintaining good dielectric properties. Furthermore, the spirocyclic acetal structure can be rapidly hydrolyzed under mild acidic conditions, endowing the material with excellent degradation performance and enabling high-value metal recycling. This provides a green material solution for the electrical insulation and electronic packaging fields, combining high adhesion performance, low dielectric properties, and biodegradability.

Description

Technical Field

[0001] This invention relates to the field of biodegradable epoxy resin technology, specifically to a biodegradable epoxy adhesive cured by an active ester, its preparation method, and its application. Background Technology

[0002] Epoxy thermosetting resins, widely used in electronic packaging and printed circuit board (PCB) manufacturing, exhibit infusible and insoluble properties after cross-linking, making it difficult for electronic products to degrade and separate under mild conditions after disposal. Traditional incineration or landfill methods result in resource waste and environmental burden. Therefore, to address the numerous problems caused by the accumulation of large quantities of waste electronic products and improper disposal, material design for packaging and PCB substrates should utilize biomass resources as much as possible and fully consider the mild degradation and resource recycling of waste to meet the requirements of full life-cycle management in electronic manufacturing. For example, Chinese patent document CN117342976A introduces an active ester curing agent with imine bonds. The introduction of dynamic imine bond structure endows epoxy resin with secondary processing capabilities and solvent recovery capabilities, showing great potential to solve the problems of environmental pollution and resource waste caused by epoxy resin waste.

[0003] The curing characteristic of reactive ester curing agents in forming ester side chains rather than secondary hydroxyl groups during epoxy ring-opening curing gives their crosslinked networks low hygroscopicity, thus endowing them with excellent dielectric properties. For example, Chinese patent document CN117801017A discloses a naphthalene-containing main-chain phosphorus-containing reactive ester resin with excellent dielectric properties at high frequencies, which can be applied to the field of high-performance printed circuit boards.

[0004] However, the low content of free hydroxyl groups in reactive ester curing agents weakens interchain and interfacial interactions, making them prone to insufficient interfacial strength under conditions such as humid heat and thermal cycling. Simply introducing polar groups can improve adhesion, but often at the expense of dielectric properties. Therefore, it is urgent to significantly improve interfacial adhesion and humid heat stability through synergistic design at the molecular and formulation levels while maintaining low dielectric properties. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a biodegradable epoxy adhesive that is cured by an active ester, comprising an active ester curing agent containing a spirocyclic acetal structure and a multifunctional epoxy resin precursor. The design and combination of flexible alkyl ester end groups and / or rigid aromatic ester end groups in the active ester curing agent enable the epoxy adhesive to achieve a balance between interfacial strength and cohesive strength after curing. (Interfacial strength primarily corresponds to the adhesion and load-bearing capacity between the adhesive layer and the aluminum substrate, while cohesive strength primarily corresponds to the cured adhesive layer's ability to resist shear failure and dissipate stress; these two factors complement each other and jointly determine the adhesive load-bearing performance during the lap shear process, which is reflected in the aluminum lap shear strength described later.) Without introducing additional polar groups that would degrade dielectric properties, this invention significantly improves the adhesive strength of the active ester curing system of the biodegradable adhesive, further enhancing the service stability of the cured epoxy adhesive in electrical applications such as electronic packaging.

[0006] A biodegradable epoxy adhesive that is cured by an active ester includes an active ester curing agent and an epoxy resin precursor, wherein the active ester curing agent is an active ester curing agent containing flexible alkyl ester end groups and / or an active ester curing agent containing rigid aromatic ester end groups, and the structure of the active ester curing agent is R1-X-R1. Where X is or R1 is independently selected , , , , , , , , , , Any structure in the formula, where n is any integer from 0 to 16; R2, R3, R4, and R5 are all independently selected from H, methoxy, or ethoxy; "*" indicates the connection position.

[0007] From a structural design perspective, this invention proposes an improvement scheme to address the insufficient adhesive performance of reactive ester curing systems. Based on a spirocyclic acetal platform, two types of reactive ester curing agents with different end-group structures were designed—an alkyl ester-terminated reactive ester curing agent and an aromatic ester-terminated reactive ester curing agent—and co-cured with an epoxy resin precursor to construct a low-dielectric crosslinking network. The introduction of flexible alkyl ester end groups enhances the chain segment regulation capability and adhesive layer adaptability of the curing system, thereby improving the interfacial adhesion between the adhesive layer and the aluminum substrate and the cohesive energy dissipation performance of the cured adhesive layer. The introduction of rigid aromatic ester end groups enhances the rigidity and load-bearing capacity of the cured network, thereby strengthening the cohesive strength of the cured adhesive layer. By adjusting the blending ratio of flexible alkyl ester end groups and rigid aromatic ester end groups in the reactive ester curing agent, the matching relationship between interfacial strength and cohesive strength can be further adjusted. This allows the interfacial adhesion between the adhesive layer and the aluminum substrate, as well as the cohesive load-bearing capacity of the cured adhesive layer itself, to work together in the lap shear process. This improves the adhesive performance (lap shear strength) and service stability of the reactive ester-cured biodegradable epoxy adhesive in electrical applications such as electronic packaging, without introducing additional highly polar groups. Simultaneously, the spirocyclic acetal structure in the material backbone endows it with destructivability under mild acidic conditions, providing a basis for the recycling of key raw materials and packaged metal components.

[0008] Preferably, the structure of the epoxy resin precursor is as shown in formula (I): Equation (Ⅰ), Where Y is selected from , , , , ; "*" indicates a connection point.

[0009] Preferably, the molar ratio of the active ester curing agent to the epoxy resin precursor is 1:1.0~1.5.

[0010] Preferably, the active ester curing agent is an active ester curing agent containing flexible alkyl ester end groups and an active ester curing agent containing rigid aromatic ester end groups, wherein the molar ratio of the active ester curing agent containing flexible alkyl ester end groups to the active ester curing agent containing rigid aromatic ester end groups is 1~10:1~10.

[0011] Preferably, the biodegradable epoxy adhesive further includes an alkaline accelerator, wherein the alkaline accelerator is at least one selected from 4-pyrrolidinylpyridine, 4-dimethylaminopyridine, N-methylimidazolium, 2-ethyl-4-methylimidazolium, and 1,8-diazabicyclo[5.4.0]undecyl-7-ene (DBU).

[0012] More preferably, the molar ratio of the epoxy resin precursor to the alkaline accelerator is 1:0.001~0.006.

[0013] Preferably, the preparation method of the active ester curing agent includes the following steps: under the action of an acid-binding agent, acyl chloride and spiroacetal diol undergo an esterification reaction to obtain an active ester curing agent containing spiroacetal diol.

[0014] In this invention, two different types of reactive ester curing agents, one with long-chain alkyl ester end groups and the other with aromatic ester end groups, were synthesized using spiroacetal as an intermediate. These were then compounded in different proportions and cured with multifunctional epoxy precursors to prepare epoxy cured products. By changing the types of spiroacetal diol and acyl chloride, different types of reactive ester curing agents were obtained. This synthetic method is simple, the reaction conditions are controllable, it is easy to implement, and it is suitable for large-scale industrial production.

[0015] More preferably, the acyl chloride is , , , , , , , , , , At least one of the following, where n is any integer from 0 to 16.

[0016] More preferably, the spiroacetal diol is... , or .

[0017] More preferably, the acid-binding agent is at least one of triethylamine, diisopropylethylamine, pyridine, imidazole, and an inorganic base system.

[0018] More preferably, in the esterification reaction, the molar ratio of spirocyclic acetal to acyl chloride is 1:1.0~1.5, the temperature is 25~80 ℃, and the reaction time is 8~12 h.

[0019] Preferably, the method for preparing the epoxy resin precursor includes the following steps: mixing polyphenols, epichlorohydrin, a phase transfer catalyst and sodium hydroxide and then reacting them to obtain the epoxy resin precursor.

[0020] More preferably, the polyphenol is , , , , One of them.

[0021] More preferably, the phase transfer catalyst is at least one selected from tetrabutylammonium bromide, benzyltriethylammonium chloride, tetradecyltrimethylammonium chloride, tetrabutylammonium hydrogen sulfate, trioctylmethylammonium chloride, tetrabutylammonium chloride, tetrabutylammonium iodide, and benzyltriethylammonium bromide.

[0022] More preferably, the molar ratio of the polyphenol, epichlorohydrin, phase transfer catalyst and sodium hydroxide is 1:10~20:0.03~0.06:10~20.

[0023] The present invention also provides an epoxy resin cured product, which is obtained by pre-curing the above-mentioned reactive ester-cured biodegradable epoxy adhesive and then post-curing it.

[0024] Preferably, the pre-curing temperature is 80~100 ℃ and the time is 2~4 h, and the post-curing temperature is 120~160 ℃ and the time is 12~24 h.

[0025] Preferably, at a frequency of 10 MHz, the dielectric constant of the epoxy resin cured product is 3.0~3.30, and the dielectric loss is 0.009~0.018. During the curing process of the active ester, the acyl transfer reaction pathway can effectively inhibit the accumulation of free hydroxyl groups in the crosslinked network, reduce the contribution of high dipole moment sites and their orientation polarization in the network, thereby helping to reduce the dielectric constant and dielectric loss of the material.

[0026] Preferably, the moisture absorption rate of the epoxy resin cured product is 0.15%~0.30%, and the static water contact angle is >95°. Because the highly polar, strong hydrogen-bonded local environment in the active ester curing network is effectively weakened, the material exhibits weaker hydrophilic interactions and a lower tendency for water-induced polarization.

[0027] This invention also provides applications of the aforementioned epoxy resin cured material in low-dielectric, moisture- and heat-resistant bonding and electronic packaging. The aluminum lap shear strength of the epoxy resin cured material is 14~23.0 MPa; in some preferred embodiments, the aluminum lap shear strength is 20~23.0 MPa. Copper wires encapsulated using this epoxy resin cured material can achieve efficient and rapid recycling of the precious metal copper after degradation.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows: The biodegradable epoxy adhesive cured by reactive esters of this invention includes a reactive ester curing agent containing a spirocyclic acetal structure. A biodegradable reactive ester epoxy cured product is prepared by curing a multifunctional epoxy resin precursor. This invention, for the first time from a structural design perspective, proposes an improvement scheme to address the adhesive disadvantages of reactive ester curing systems: the synthesized spirocyclic acetal reactive esters are broadly classified into two categories according to the flexibility of their terminal ester groups. By adding reactive ester curing agents containing flexible alkyl ester terminal groups and / or reactive ester curing agents containing rigid aromatic ester terminal groups, the epoxy adhesive can adjust the matching relationship between interfacial adhesion and cohesive load-bearing capacity after curing. Without introducing additional polar groups that would degrade dielectric properties, the adhesive strength of the reactive ester curing system of the biodegradable adhesive is significantly improved, as evidenced by the higher aluminum lap shear strength, further enhancing the service stability of the epoxy resin cured product in electrical applications such as electronic packaging. Attached Figure Description

[0029] Figure 1 The image shows the 1H NMR spectrum of the dodecanoate-based active ester curing agent (Ⅰ) obtained in Example 1.

[0030] Figure 2 The image shows the 1H NMR spectrum of the furoate-based active ester curing agent (Ⅰ) obtained in Example 1.

[0031] Figure 3 The infrared spectra of epoxy resin cured products 1-5 obtained in Examples 1-5 are shown.

[0032] Figure 4 The DMA curves of epoxy resin cured products 1-5 obtained in Examples 1-5 are shown.

[0033] Figure 5 The graphs show the dielectric constant and dielectric loss curves of the epoxy resin cured products obtained in Examples 1-5 and Comparative Example 1.

[0034] Figure 6 The static water contact angle and 24-h water absorption rate of the epoxy resin cured products 1-5 obtained in Examples 1-5 and Comparative Example 1 are shown.

[0035] Figure 7 The epoxy resin cured products 1-5 obtained in Examples 1-5 and the aluminum sheet overlap shear strength of Comparative Example 1 are given.

[0036] Figure 8 This is a schematic diagram of the degradation of epoxy resin cured product 1 obtained in Example 1.

[0037] Figure 9 This is a diagram showing the degradation process of the epoxy resin cured product obtained in Comparative Example 1. Detailed Implementation

[0038] The present invention will be further described in detail below with reference to the embodiments, but the implementation of the present invention is not limited to the following embodiments.

[0039] All raw materials used in this invention are commercially available.

[0040] The performance test experiments of the embodiments of the present invention are as follows: (1) Glass transition temperature: The loss factor of the material was tested in tensile mode using a TA Q800 thermomechanical analyzer. The sample size was 30 mm × 10 mm × 1 mm, the heating range was -50 ℃ to 250 ℃, the heating rate was 3℃ / min, and the peak value of the loss factor was the glass transition temperature of this embodiment of the patent. (2) Overlap shear strength: The lap shear strength of the adhesive was tested using an Instron 5567 universal testing machine, according to ASTM D 5656. The application size was 12.5 mm × 25 mm, the tensile rate was 5 mm / min, the gauge length was 120 mm, and the preload was 10 N. (3) Dielectric properties: Broadband dielectric spectroscopy was performed using a Novocontrol Concept 80 analyzer in frequency domain mode. The frequency range was set to 10 Hz to 20 MHz, and the applied voltage was 5 V. Samples with a diameter of 50 mm and a thickness of approximately 1 mm were prepared for testing. (4) Degradation performance: Prepare 20 mL of degradation solution, put the sample into a sample bottle containing 20 mL of degradation solution, and then put it into a water bath for degradation experiment. Take pictures to record the degradation status until the sample is completely degraded.

[0041] Example 1 (1) One part pentaerythritol, 2.1 parts ethyl vanillin and 0.2 parts phosphoric acid were placed in a three-necked flask equipped with mechanical stirring and nitrogen purging, and reacted at 140 °C for 12 hours to obtain spiroacetal diol (I), the structure of which is shown below: (2) By molar ratio, 1 part of spiroacetal diol (I), 2.1 parts of dodecyl chloride, and 20 parts of pyridine were mixed and reacted at 60°C for 8 hours to obtain dodecyl ester active ester curing agent (I), the structure of which is shown below, and its nuclear magnetic resonance spectrum is shown below. Figure 1 As shown, By molar ratio, 1 part spiroacetal diol (I), 2.1 parts furoyl chloride, and 20 parts pyridine were mixed and reacted at 60 °C for 8 hours to obtain furoate ester-based active ester curing agent (I), the structure of which is shown below, and its nuclear magnetic resonance spectrum is shown below. Figure 2 As shown, Furfuryl ester-based active ester curing agent (I) (3) Based on molar amounts, 1 part resveratrol, 30 parts epichlorohydrin, 0.03 parts tetrabutylammonium bromide, and 20 parts sodium hydroxide were mixed and reacted at 80 °C for 24 hours to obtain a resveratrol-derived epoxy resin precursor, the structure of which is shown below: (4) The dodecanoate-based active ester curing agent (Ⅰ) obtained in step (2) is mixed with furfurylene-based active ester curing agent (Ⅰ), the resveratrol-derived epoxy resin precursor obtained in step (3), and 4-dimethylaminopyridine in a molar ratio of 5:5:3.3:0.033. The mixture is then poured into a mold at 100 °C for pre-curing for 4 h, and then cured in a vacuum oven at 160 °C for 12 h to obtain epoxy resin cured product 1. The infrared structure is as follows: Figure 3 As shown. When preparing the bonding samples, the resin was mixed in the same proportion and pre-cured for 4 hours. The resin was then applied to the overlapping metal interface and cured in a vacuum oven at 160 °C for 12 hours.

[0042] Performance testing of epoxy resin cured product 1: Glass transition temperature is 75.2 ℃ (e.g., Figure 4 As shown), the dielectric constant is 3.14 and the dielectric loss is 0.015 at 10 MHz (as shown). Figure 5 (As shown). The static water contact angle is 99.4°, and the moisture absorption rate after 24 hours at room temperature is 0.21% (e.g.). Figure 6 (As shown). The lap shear strength of aluminum materials can reach 23.0 MPa (e.g. Figure 7 (As shown). The reactive ester epoxy cured product was completely degraded in a 0.03 mol / L acetone-water (9:1) solution at 50 °C for 57 min (as shown). Figure 8 (As shown).

[0043] Example 2 The dodecanoate-based active ester curing agent (Ⅰ) obtained in step (2) of Example 1, the furoate-based active ester curing agent (Ⅰ), the resveratrol-derived epoxy resin precursor obtained in step (3) of Example 1, and 4-dimethylaminopyridine were mixed in a molar ratio of 7:3:3.3:0.033 and poured into a mold at 120 °C for pre-curing for 2 h, and then cured in a vacuum oven at 160 °C for 12 h to obtain epoxy resin cured product 2, with the structure as shown in the figure. Figure 3 As shown. When preparing the bonding samples, the resin was mixed in the same proportion and pre-cured for 4 hours. The resin was then applied to the overlapping metal interface and cured in a vacuum oven at 160 °C for 12 hours.

[0044] Performance testing of epoxy resin cured product 2: Glass transition temperature is 65.5 ℃ (e.g., Figure 4 As shown), the dielectric constant is 3.06 and the dielectric loss is 0.016 at 10 MHz (as shown). Figure 5 (As shown). The static water contact angle is 101.0°, and the moisture absorption rate after 24 hours at room temperature is 0.24% (e.g.). Figure 6 (As shown). The lap shear strength of aluminum can reach 21.2 MPa (e.g. Figure 7 (As shown). The reactive ester epoxy cured product was completely degraded in a 0.03 mol / L hydrochloric acid-acetone-water (9:1) solution at 50 °C for 55 min.

[0045] Example 3 The dodecanoate-based active ester curing agent (Ⅰ) obtained in step (2) of Example 1, the furoate-based active ester curing agent (Ⅰ), the resveratrol-derived epoxy resin precursor obtained in step (3) of Example 1, and 4-dimethylaminopyridine were mixed in a molar ratio of 3:7:3.3:0.033 and poured into a mold at 120 °C for pre-curing for 2 h, and then cured in a vacuum oven at 160 °C for 12 h to obtain epoxy resin cured product 3, with the structure as shown in the figure. Figure 3 As shown. When preparing the bonding samples, the resin was mixed in the same proportion and pre-cured for 4 hours. The resin was then applied to the overlapping metal interface and cured in a vacuum oven at 160 °C for 12 hours.

[0046] Performance testing of epoxy resin cured product 3: Glass transition temperature is 95.1 ℃ (e.g., Figure 4 As shown), the dielectric constant is 3.21 and the dielectric loss is 0.012 at 10 MHz (as shown). Figure 5 (As shown). The static water contact angle is 99.2°, and the moisture absorption rate after 24 hours at room temperature is 0.20% (e.g.). Figure 6 (As shown). The lap shear strength of aluminum can reach 20.7 MPa (e.g. Figure 7 (As shown). The reactive ester epoxy cured product was completely degraded in a 0.03 mol / L hydrochloric acid-acetone-water (9:1) solution at 50 °C for 63 min.

[0047] Example 4 The dodecanoate-based active ester curing agent (Ⅰ) obtained in step (2) of Example 1, the resveratrol-derived epoxy resin precursor obtained in step (3) of Example 1, and 4-dimethylaminopyridine were mixed in a molar ratio of 10:3.3:0.033 and poured into a mold at 120 °C for pre-curing for 2 h, and then cured in a vacuum oven at 160 °C for 12 h to obtain epoxy resin cured product 4, with the structure as shown. Figure 3 As shown. When preparing the bonding samples, the resin was mixed in the same proportion and pre-cured for 4 hours. The resin was then applied to the overlapping metal interface and cured in a vacuum oven at 160 °C for 12 hours.

[0048] Performance testing of epoxy resin cured product 4: Glass transition temperature is 55.0 ℃ (e.g., Figure 4 As shown), the dielectric constant is 3.00 and the dielectric loss is 0.018 at 10 MHz (as shown). Figure 5 (As shown). The static water contact angle is 106.2°, and the moisture absorption rate after 24 hours at room temperature is 0.22% (e.g.). Figure 6 (As shown). The lap shear strength of aluminum can reach 18.2 MPa (e.g. Figure 7 (As shown). The reactive ester epoxy cured product was completely degraded in 51 min at 50 °C in a 0.03 mol / L acetone-water (9:1) solution of hydrochloric acid.

[0049] Example 5 The furoate-based active ester curing agent (Ⅰ) obtained in step (2) of Example 1, the resveratrol-derived epoxy resin precursor obtained in step (3) of Example 1, and 4-dimethylaminopyridine were mixed in a molar ratio of 10:3.3:0.033 and poured into a mold at 120 °C for pre-curing for 2 h, and then cured in a vacuum oven at 160 °C for 12 h to obtain epoxy resin cured product 5, with the structure as shown. Figure 3 As shown. When preparing the bonding samples, the resin was mixed in the same proportion and pre-cured for 4 hours. The resin was then applied to the overlapping metal interface and cured in a vacuum oven at 160 °C for 12 hours.

[0050] Performance testing of epoxy resin cured product 5: Glass transition temperature is 120.3 ℃ (e.g., Figure 4 As shown), the dielectric constant is 3.29 and the dielectric loss is 0.009 at 10 MHz (as shown). Figure 5 (As shown). The static water contact angle is 95.2°, and the moisture absorption rate after 24 hours at room temperature is 0.27% (as shown). Figure 6 (As shown). The lap shear strength of aluminum can reach 14.2 MPa (e.g. Figure 7 (As shown). The reactive ester epoxy cured product was completely degraded in a 0.03 mol / L hydrochloric acid-acetone-water (9:1) solution at 50 °C for 63 min.

[0051] Example 6 (1) By molar ratio, 1 part of spiroacetal diol (I), 2.1 parts of hexanoyl chloride, and 20 parts of pyridine were mixed and reacted at 60 °C for 8 hours to obtain a hexanoate-based active ester curing agent, the structure of which is shown below: (2) The hexanoate-based active ester curing agent obtained in step (1), the furoate-based active ester curing agent (Ⅰ) obtained in step (2) of Example 1, the resveratrol-derived epoxy resin precursor obtained in step (3) of Example 1, and 4-dimethylaminopyridine were mixed in a molar ratio of 5:5:3.3:0.033 and poured into a mold at 120 °C for pre-curing for 2 h, and then cured in a vacuum oven at 160 °C for 12 h to obtain epoxy resin cured product 6. When preparing the bonding sample, the same proportion was mixed and pre-cured for 4 h, the resin was applied to the overlapping metal interface, and cured in a vacuum oven at 160 °C for 12 h.

[0052] Performance tests of epoxy resin cured product 6: Glass transition temperature is 88.1 ℃, dielectric constant is 3.15 at 10 MHz, and dielectric loss is 0.013. Static water contact angle is 97.6°, and moisture absorption rate is 0.21% after 24 h at room temperature. The lap shear strength of aluminum can reach 17.5 MPa. This reactive ester epoxy cured product completely degrades in 59 min at 50 ℃ in a 0.03 mol / L acetone-water (9:1) hydrochloric acid solution.

[0053] Example 7 (1) By molar amount, 1 part of spiroacetal diol (I), 2.1 parts of octadecyl chloride and 20 parts of pyridine were mixed and reacted at 60°C for 8 hours to obtain an octadecyl ester-based active ester curing agent with the structure shown below: (2) The octadecyl ester-based active ester curing agent obtained in step (1), the furfuryl ester-based active ester curing agent (Ⅰ) obtained in step (2) of Example 1, the resveratrol-derived epoxy resin precursor obtained in step (3) of Example 1, and 4-dimethylaminopyridine were mixed in a molar ratio of 5:5:3.3:0.033 and poured into a mold at 120 °C for pre-curing for 2 h, and then cured in a vacuum oven at 160 °C for 12 h to obtain epoxy resin cured product 7. When preparing the bonding sample, the same proportion was mixed and pre-cured for 4 h, the resin was applied to the overlapping metal interface, and cured in a vacuum oven at 160 °C for 12 h.

[0054] Performance tests of epoxy resin cured product 7: Glass transition temperature is 61.4 ℃, dielectric constant is 3.07 at 10 MHz, and dielectric loss is 0.016. Static water contact angle is 108.8°, and moisture absorption rate is 0.19% after 24 h at room temperature. The lap shear strength of aluminum material reaches 22.1 MPa. This reactive ester epoxy cured product is completely degraded in 52 min at 50 ℃ in a 0.03 mol / L acetone-water (9:1) hydrochloric acid solution.

[0055] Example 8 (1) By molar ratio, 1 part of spiroacetal diol (I), 2.1 parts of 2-thiophenecarboxyl chloride, and 20 parts of pyridine were mixed and reacted at 60 °C for 8 hours to obtain a thiophenecarboxyl ester-based active ester curing agent with the structure shown below: (2) The dodecanoate-based active ester curing agent (Ⅰ) obtained in step (2) of Example 1, the thiophene carbamate-based active ester curing agent obtained in step (1) of Example 8, the resveratrol-derived epoxy resin precursor obtained in step (3) of Example 1, and 4-dimethylaminopyridine were mixed in a molar ratio of 5:5:3.3:0.033 and poured into a mold at 120 °C for pre-curing for 2 h, and then cured in a vacuum oven at 160 °C for 12 h to obtain epoxy resin cured product 8. When preparing the bonding sample, the same proportion was mixed and pre-cured for 4 h, the resin was applied to the overlapping metal interface, and cured in a vacuum oven at 160 °C for 12 h.

[0056] Performance tests of epoxy resin cured product 8: Glass transition temperature is 66.5 ℃, dielectric constant is 3.13 at 10 MHz, and dielectric loss is 0.017. Static water contact angle is 99.3°, and moisture absorption rate is 0.22% after 24 h at room temperature. The lap shear strength of aluminum can reach 22.5 MPa. This reactive ester epoxy cured product is completely degraded in 55 min at 50 ℃ in a 0.03 mol / L acetone-water (9:1) hydrochloric acid solution.

[0057] Example 9 (1) One part pentaerythritol, 2.1 parts vanillin and 0.2 parts phosphoric acid were placed in a three-necked flask equipped with mechanical stirring and nitrogen purging, and reacted at 140 °C for 12 hours to obtain spiroacetal diol (II), the structure of which is shown below: (2) By molar ratio, 1 part of spiroacetal diol (II), 2.1 parts of dodecyl chloride, and 20 parts of pyridine were mixed and reacted at 60°C for 8 hours to obtain a dodecyl ester active ester curing agent. To distinguish it from the above structure, it is named dodecyl ester active ester curing agent (II) in this embodiment, and its structure is shown below. By molar proportion, 1 part spiroacetal diol (II), 2.1 parts furoyl chloride, and 20 parts pyridine were mixed and reacted at 60 °C for 8 hours to obtain a furoyl ester-based active ester curing agent. Similarly, this is named furoyl ester-based active ester curing agent (II) here, and its structure is shown below. (3) The dodecanoate-based active ester curing agent (II) obtained in step (2) of this embodiment, the furoate-based active ester curing agent (II), the resveratrol-derived epoxy resin precursor obtained in step (3) of Example 1, and 4-dimethylaminopyridine were mixed in a molar ratio of 5:5:3.3:0.033 and poured into a mold at 100 °C for pre-curing for 4 h, and then cured in a vacuum oven at 160 °C for 12 h to obtain epoxy resin cured product 9. When preparing the bonding sample, after mixing in the same proportion and pre-curing for 4 h, the resin was applied to the overlapping metal interface and cured in a vacuum oven at 160 °C for 12 h.

[0058] Performance tests of epoxy resin cured product 9: Glass transition temperature is 67.3 ℃, dielectric constant is 3.14 at 10MHz, dielectric loss is 0.014. Static water contact angle is 99.5°, and moisture absorption rate is 0.23% after 24 h at room temperature. The lap shear strength of aluminum can reach 22.9 MPa. This reactive ester epoxy cured product is completely degraded in 56 min in a 0.03 mol / L acetone-water (9:1) hydrochloric acid solution at 50 ℃.

[0059] Example 10 (1) By molar amount, 1 part erythritol, 2.1 parts ethyl vanillin and 0.2 parts phosphoric acid were placed in a three-necked flask equipped with mechanical stirring and nitrogen purging, and reacted at 140 °C for 12 hours to obtain spiroacetal diol (III), the structure of which is shown below: (2) By molar ratio, 1 part of spiroacetal diol (III), 2.1 parts of dodecyl chloride, and 20 parts of pyridine were mixed and reacted at 60°C for 8 hours to obtain a dodecyl ester active ester curing agent. To distinguish it from the above structure, it is named dodecyl ester active ester curing agent (III) in this embodiment, and its structure is shown below. By molar proportion, 1 part spiroacetal diol (III), 2.1 parts furoyl chloride, and 20 parts pyridine were mixed and reacted at 60 °C for 8 hours to obtain a furoate-based active ester curing agent. Similarly, this is named furoate-based active ester curing agent (III) here, and its structure is shown below. (3) The dodecanoate-based active ester curing agent (III) obtained in step (2) of this embodiment, the furoate-based active ester curing agent (III), the resveratrol-derived epoxy resin precursor obtained in step (3) of Example 1, and 4-dimethylaminopyridine were mixed in a molar ratio of 5:5:3.3:0.033 and poured into a mold at 100 °C for pre-curing for 4 h, and then cured in a vacuum oven at 160 °C for 12 h to obtain epoxy resin cured product 10. When preparing the bonding sample, the same proportion was mixed and pre-cured for 4 h, the resin was applied to the overlapping metal interface, and cured in a vacuum oven at 160 °C for 12 h.

[0060] Performance tests of epoxy resin cured product 10: Glass transition temperature is 94.4 ℃, dielectric constant is 3.11 at 10 MHz, and dielectric loss is 0.016. Static water contact angle is 98.9°, and moisture absorption rate is 0.22% after 24 h at room temperature. The lap shear strength of aluminum material reaches 21.43 MPa. This reactive ester epoxy cured product completely degrades in 71 min at 50 ℃ in a 0.03 mol / L acetone-water (9:1) hydrochloric acid solution.

[0061] Comparative Example 1 (1) The following active ester curing agents were synthesized using bisphenol A as an intermediate structure, and their structures are shown below: (2) By molar ratio, 1 part of bisphenol A, 2.1 parts of acetyl chloride, and 20 parts of pyridine were mixed and reacted at 60 °C for 8 hours to obtain a bisphenol A ethyl acetate active ester curing agent, the structure of which is shown below: By molar ratio, 1 part bisphenol A, 2.1 parts furoyl chloride, and 20 parts pyridine were mixed and reacted at 60 °C for 8 hours to obtain a bisphenol A-based furoate active ester curing agent, the structure of which is shown below. (3) The bisphenol A ethyl acetate active ester curing agent obtained in step (2) of this comparative example, the bisphenol A ethyl furfural active ester curing agent, the resveratrol-derived epoxy resin precursor obtained in step (3) of Example 1, and 4-dimethylaminopyridine were mixed in a molar ratio of 5:5:3.3:0.033 and poured into a mold at 100 °C for pre-curing for 4 h, and then cured in a vacuum oven at 160 °C for 12 h to obtain epoxy resin cured product 11, which is referred to here as comparative example 1. When preparing the bonding sample, after mixing in the same proportion and pre-curing for 4 h, the resin was applied to the overlapping metal interface and cured in a vacuum oven at 160 °C for 12 h.

[0062] Performance tests of Comparative Example 1: Glass transition temperature was 71.1 ℃, dielectric constant was 3.73 at 10 MHz, and dielectric loss was 0.024. Static water contact angle was 80.2°, and moisture absorption rate was 0.40% after 24 h at room temperature. The lap shear strength of the aluminum material was 9.93 MPa. This active ester epoxy cured product showed no significant mass loss after 12 h in a 0.03 mol / L acetone-water (9:1) hydrochloric acid solution at 50 ℃. Figure 9 ).

[0063] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A biodegradable epoxy adhesive that cures with an active ester, characterized in that, It includes an active ester curing agent and an epoxy resin precursor, wherein the active ester curing agent is an active ester curing agent containing flexible alkyl ester end groups and / or an active ester curing agent containing rigid aromatic ring ester end groups, and the structure of the active ester curing agent is R1-X-R1; Where X is or R1 is independently selected , , , , , , , , , , Any structure in the formula, where n is any integer from 0 to 16; R2, R3, R4, and R5 are all independently selected from H, methoxy, or ethoxy; "*" indicates a connection position.

2. The biodegradable epoxy adhesive cured with reactive ester according to claim 1, characterized in that, The structure of the epoxy resin precursor is shown in formula (Ⅰ): Equation (Ⅰ), Where Y is selected from , , , , ; "*" indicates a connection point.

3. The biodegradable epoxy adhesive cured by reactive ester according to claim 1, characterized in that, The molar ratio of the active ester curing agent to the epoxy resin precursor is 1:1.0~1.

5.

4. The biodegradable epoxy adhesive cured by reactive ester according to claim 1, characterized in that, The active ester curing agent is an active ester curing agent containing flexible alkyl ester end groups and an active ester curing agent containing rigid aromatic ester end groups, wherein the molar ratio of the active ester curing agent containing flexible alkyl ester end groups to the active ester curing agent containing rigid aromatic ester end groups is 1~10:1~10.

5. The biodegradable epoxy adhesive cured by reactive ester according to claim 1, characterized in that, The biodegradable epoxy adhesive further includes an alkaline accelerator, which is at least one of 4-pyrrolidinylpyridine, 4-dimethylaminopyridine, N-methylimidazolium, 2-ethyl-4-methylimidazolium, and 1,8-diazabicyclo[5.4.0]undecyl-7-ene (DBU).

6. The biodegradable epoxy adhesive cured by reactive ester according to claim 5, characterized in that, The molar ratio of the epoxy resin precursor to the alkaline accelerator is 1:0.001~0.

006.

7. The biodegradable epoxy adhesive cured by reactive ester according to claim 1, characterized in that, The preparation method of the active ester curing agent includes the following steps: under the action of an acid-binding agent, acyl chloride and spiroacetal diol undergo an esterification reaction to obtain an active ester curing agent containing spiroacetal diol.

8. The biodegradable epoxy adhesive cured by reactive ester according to claim 1, characterized in that, The method for preparing the epoxy resin precursor includes the following steps: mixing polyphenols, epichlorohydrin, a phase transfer catalyst and sodium hydroxide and then reacting them to obtain the epoxy resin precursor.

9. An epoxy resin cured product, characterized in that, The epoxy resin cured product is obtained by pre-curing and post-curing the biodegradable epoxy adhesive cured by the active ester as described in any one of claims 1 to 8.

10. The application of the epoxy resin cured product according to claim 9 in the fields of low dielectric, moisture-resistant bonding and electronic packaging.

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