Recoverable epoxy resin adhesive system
By using a bifunctional epoxy resin and a cleavable bond curing agent, the problem of traditional epoxy resin cannot be recovered is solved, and the recycling and reuse of epoxy resin is realized. It has the characteristics of high mechanical strength and low curing shrinkage, and is suitable for bonding of large composite structures such as wind turbine blades.
Patent Information
- Application Number
- CN202380085777.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2022-12-12
- Filing Date
- 2023-12-12
- Publication Date
- 2025-07-22
AI Technical Summary
Traditional epoxy resin adhesives cannot be recycled, resulting in difficulty in recycling and disassembly of bonding nodes.
An epoxy resin binder system consisting of 60-80% bifunctional epoxy resin and 20-40% curing agent with cleavable bonds is decomposed by the crosslinking network structure under the action of heat and acid to achieve recovery.
The recycling of epoxy resin adhesive is achieved, the curing shrinkage and heat exogenous volume are reduced, while maintaining high mechanical strength and bonding strength, which is suitable for bonding of large composite structures.
Smart Images
Figure CN120359278A_ABST
Abstract
Description
Technical Field
[0001] The present disclosure relates to epoxy adhesive systems. In particular, the present disclosure relates to a recyclable epoxy adhesive system, a method for preparing the system, and applications of the system. Background Art
[0002] Epoxy adhesive systems are widely used in consumer products, industrial, and structural bonding applications due to their ease of processing, simplicity of use, and excellent mechanical properties and bonding strength. In high-demand applications such as wind turbine blades, epoxy adhesives are used to join the two halves of the blade because they are highly elastic and provide excellent fatigue resistance under static and dynamic load conditions. Traditional epoxy adhesives cannot be recycled due to the inherent properties of their epoxy thermosets. This non-recyclability poses limitations on the recycling and disassembly of bonded joints. Summary of the Invention
[0003] The present disclosure relates to a recyclable epoxy adhesive system. The recyclable epoxy adhesive system comprises: 60 - 80% (by weight) of an epoxy resin component, the epoxy resin component comprising one or more difunctional epoxy resins; and 20 - 40% (by weight) of a curing agent component, the curing agent component comprising one or more curing agents, each of the curing agents having at least one cleavable bond. Brief Description of the Drawings
[0004] Figure 1 Shows the process of debonding a bonded joint by solvent dissociation method, the bonded joint being made of the epoxy adhesive system (System 3) prepared in an embodiment of the present disclosure.
[0005] Figure 2 Shows the neutralization of the solvent dissociation solution after debonding and the recycling process of System 3.
[0006] Figure 3A and 3B Respectively show the cross-sectional views of Specimen 1 and Specimen 2 after the thermal crack resistance test.
[0007] Figure 3C and 3D Respectively show the front views of Specimen 1 and Specimen 2 after the thermal crack resistance test.
[0008] Figure 3E and 3F Respectively show the back views of Specimen 1 and Specimen 2 after the thermal crack resistance test.
[0009] Figure 4A and 4B Respectively show the photos of Panel 1 and Panel 2 after the cure shrinkage test.
[0010] Figure 5 Shows the exothermic curves of the traditional system and System 3. Detailed implementation mode
[0011] Specific embodiments of the present disclosure will be described in detail below. The terms used herein are not intended to be construed restrictively, even when used in conjunction with the detailed description of certain specific embodiments. In addition, the embodiments of the present disclosure may include several technical features, and the ideal characteristics of these features are not achieved independently by a single feature, nor are they essential for implementing the present disclosure.
[0012] Those skilled in the art will understand that the above general description and the following detailed description are intended to explain the present disclosure, rather than limit it.
[0013] The terms "a", "an", and "the" are used to refer to the grammatical object of "one or more" (i.e., at least one).
[0014] References in this specification to "one aspect", "another aspect", or similar expressions mean that a particular feature, structure, or characteristic associated with that embodiment is included in at least one embodiment of the present disclosure.
[0015] The term "comprising", "including", or any variant thereof is intended to cover non-exclusive inclusion and should not be construed as "consisting only of", that is, a process or method that includes a list of steps not only includes the steps in that list, but may also include other steps not explicitly listed or inherent in that process or method.
[0016] Similarly, the terms "having" and "including", and their grammatical variants are intended to be non-restrictive, that is, the items listed in the list do not exclude other items that can be substituted or added to the list.
[0017] Unless otherwise defined, all technical and scientific terms used herein have the general meaning commonly known to those skilled in the art. Although methods and materials similar or equivalent to those described in the present disclosure may be used in the practice or testing of the present disclosure, the preferred methods and materials are now described. All documents mentioned in the present disclosure are hereby incorporated by reference.
[0018] The present disclosure generally relates to epoxy adhesive systems. In particular, the present disclosure relates to a recyclable epoxy adhesive system.
[0019] In the context of the present disclosure, a "recyclable epoxy adhesive system" refers to a system in which, under the action of heat and acid, the cross-linked network structure can decompose, thereby enabling the recycling of the epoxy adhesive system.
[0020] The recyclable epoxy resin adhesive system of the present disclosure includes an epoxy resin component and a curing agent component, wherein the curing agent component includes one or more curing agents having at least one cleavable bond.
[0021] The recyclable epoxy resin adhesive system according to the present disclosure includes 60-80% (by weight) of an epoxy resin component, which includes one or more difunctional epoxy resins; and 20-40% (by weight) of a curing agent component, which includes one or more curing agents, and each of the curing agents includes at least one cleavable bond.
[0022] In some embodiments, the content of the one or more difunctional epoxy resins is 65-85% of the total weight of the epoxy resin component.
[0023] In some embodiments, the one or more difunctional epoxy resins are selected from bisphenol A epoxy resin, bisphenol F epoxy resin, and combinations thereof.
[0024] In some embodiments, the epoxy resin component includes a monofunctional or difunctional epoxy reactive diluent, which is selected from: aliphatic epoxy reactive diluents, aromatic epoxy reactive diluents, non-reactive diluents, and combinations thereof. In certain embodiments, the diluent is selected from 1,4-butanediol diglycidyl ether, C12-14 alkyl glycidyl ether, 1,6-hexanediol diglycidyl ether, catechol glycidyl ether, polypropylene glycol, and combinations thereof.
[0025] The cleavable bond decomposes when exposed to high temperature in an acidic medium. In some embodiments, the curing agent includes a cleavable bond selected from acetaldehyde bonds, ketone aldehyde bonds, formaldehyde bonds, orthoester bonds, orthocarbonate bonds, and siloxane bonds. In certain embodiments, the curing agent is from a curing agent platform. In some embodiments, the curing agent is selected from the adducts of 2,2'-bis(2-aminoethoxy)propane, 2,2'-(2-aminopropoxy)propane, and 2,2'-bis(2-aminobutoxy)methylsilane. In some embodiments, the content of the curing agent is 70% to 90% of the total weight of the curing agent component.
[0026] The recyclable epoxy resin adhesive system may include one or more additional components. The selection of the additional components is based on the properties or characteristics required for the epoxy resin adhesive system, as well as the end use or intended application of the epoxy resin adhesive system. Examples of such components include, but are not limited to, one or more additives, modifiers, catalysts, and combinations thereof.
[0027] The one or more additional components may be added as separate components in addition to the epoxy resin component and the curing agent component. Alternatively, the one or more additional components may be part of the epoxy resin component and / or the curing agent component. In some embodiments, the total content of the one or more additional components in the recyclable epoxy resin adhesive system is from 10% to 30% by total weight.
[0028] In some embodiments, the one or more additives are selected from: fumed silica, one or more pigments, one or more natural fibers, ground glass, carbon fiber, and combinations thereof.
[0029] In some embodiments, the one or more modifiers include one or more of the following: toughening agents, defoaming agents, coupling agents, flow additives, rheological additives, fillers, degassing additives, wetting agents, coupling agents, or combinations thereof. Examples of the modifiers include, but are not limited to, core-shell rubber toughening agents, block copolymers, activated clay, silicone defoaming agents, epoxy silanes, amino silanes, and combinations thereof.
[0030] In some embodiments, the recyclable epoxy resin adhesive system includes one or more catalysts. In certain embodiments, the catalyst is an alkyl alkanolamine or a derivative thereof.
[0031] The present disclosure also relates to a method of preparing the above-described recyclable epoxy resin adhesive system. The method includes mixing the epoxy resin component and the curing agent component. The mixing can be carried out by any known method. For example, the mixing can be carried out by a magnetic stirrer, by hand, by a static mixer, or by any other suitable device.
[0032] The present disclosure also relates to an adhesive joint prepared using the above-disclosed recyclable epoxy resin adhesive system. The adhesive joint can be recycled and debonded by a low-energy solvent decomposition process. In some embodiments, the adhesive joint includes two or more glass fiber reinforced epoxy (GRE) substrates bonded together by the above-disclosed recyclable epoxy resin adhesive system.
[0033] The present disclosure will be illustrated by the following examples. These examples are intended to illustrate various embodiments of the present disclosure and are not intended to limit the scope of the claims. Those skilled in the art will recognize that various variations and modifications can be made to the embodiments without departing from the broader scope and spirit of the present disclosure as defined by the claims.
[0034] Example
[0035] Example 1: Recyclable Epoxy Resin Adhesive Systems 1-13 Prepared According to Various Embodiments of the Present Disclosure
[0036] Preparation method: Epoxy resin adhesive systems 1-13 are prepared using the epoxy resin component formulations shown in Tables 1A and 1B, and the curing agent component formulations shown in Tables 2A and 2B. The mass ratio (parts by weight) of the epoxy resin component to the curing agent component in each system is shown in Table 3. The epoxy resin component and the curing agent component are mixed and reacted, crosslinked, and cured in a molar ratio to obtain systems 1-13.
[0037] Table 1A: Composition of epoxy resin components (Systems 1-7)
[0038]
[0039]
[0040] Table 1B: Composition of epoxy resin components (Systems 8-13)
[0041]
[0042]
[0043] Table 2A: Composition of curing agent components (Systems 1-7)
[0044]
[0045]
[0046] Table 2B: Composition of curing agent components (Systems 8-13)
[0047]
[0048]
[0049] Table 3: Mass ratio of epoxy resin component to curing agent component
[0050]
[0051]
[0052] Example 2: The bonded joints prepared using System 3 are degummed by the solvent dissociation method.
[0053] Materials:
[0054] a) System 3
[0055] b) GRE substrate with dimensions of 120 x 70 x 4 mm.
[0056] Operation steps: Coating system 3 on the GRE substrate, keeping the thickness of the adhesive line at 10 mm to form an adhesion node. Subsequently, the adhesion node is subjected to solvent dissociation degumming treatment, and then the solvent dissociation solution is neutralized, and the epoxy thermoplastic material is recovered. The specific process is as Figure 1 and Figure 2 shown. In the initial stage, the degumming of the adhesion node and the peeling of the epoxy matrix of system 3 occur after 2 hours. The recovered fiberglass cloth is removed and stirring continues at 80 - 90 °C. After 20 hours, the epoxy matrix of system 3 is completely cracked and dissolved in the dissolution solution. Subsequently, the dissolution solution is filtered to separate the coarse filler (filtration 1), and then refiltered to separate the fine filler (filtration 2). Subsequently, 50% NaOH is used to neutralize and solidify the dissolution solution, and the reaction heat is controlled by surrounding the beaker with ice. The pH value of the dissolution solution is maintained at 7 or above to ensure the complete recovery of the epoxy resin matrix of system 3 and its conversion into epoxy thermoplastic material.
[0057] Results and observations: The recovery process successfully recovered fiberglass, filler, and epoxy thermoplastic material, which can be further reused and reprocessed.
[0058] Example 3: Performance evaluation of systems 1 - 13
[0059] Procedure: For the systems 1 - 13 obtained above, evaluate their process and performance characteristics. The detailed information of the characteristics evaluated and the test methods used are shown in Tables 4A, 4B, 5A, and 5B.
[0060] Table 4A: Process characteristics of systems 1 - 7
[0061]
[0062]
[0063] Curing conditions: 60 °C / 1.5 hours + 70 °C / 7 hours
[0064] Table 4B: Process characteristics of systems 8 - 13
[0065]
[0066] Curing conditions: 60 °C / 1.5 hours + 70 °C / 7 hours
[0067] Table 5A: Performance characteristics of systems 1 - 7
[0068]
[0069] Table 5B: Performance characteristics of systems 8 - 13
[0070]
[0071]
[0072] Results and Observations: Systems 1 - 13 exhibited medium to long usage times, with high bond strength, high fracture toughness, and good toughness.
[0073] Example 4: Comparison of Crack Resistance between System 3 and Traditional Non - Recyclable Epoxy Adhesive System
[0074] Materials:
[0075] a) System 3
[0076] b) Traditional non - recyclable epoxy adhesive system ("Traditional System"), including an epoxy resin component (80 - 90% by weight), which includes: bisphenol A epoxy resin (6 - 8% by weight), hydrophobic fumed silica, methyl methacrylate - butadiene - styrene core - shell structure (3 - 7% by weight), and < 1% (by weight) of pigments, defoamers, and coupling agents; and a curing agent component, which includes: cycloaliphatic amine (5 - 10% by weight), polyetheramine (55 - 65% by weight), polyamide (15 - 255% by weight), hydrophilic fumed silica (5 - 15% by weight), and < 1% (by weight) of pigments, defoamers, and coupling agents.
[0077] c) GRE substrates 1 - 4 with a thickness of 6.5 mm.
[0078] Procedure: Heat the epoxy resin components and curing agent components of the Traditional System and System 3 to 45 °C separately with GRE substrates 1 - 4. Mix the heated epoxy resin components and curing agent components in a molar ratio to prepare the Traditional System and System 3 respectively. Lay the Traditional System and System 3 on GRE substrates 1 and 2 respectively in the specification of bead size 240 (length) × 150 (width) × 50 (thickness) mm. Coat the two systems directly on GRE substrates 1 and 2 to form triangular beads within 35 minutes. Install and position 3 thermocouples at the center of the beads on GRE substrates 1 and 2. Apply pressure to the beads on GRE substrates 1 and 2 with GRE substrates 3 and 4 respectively to obtain Specimens 1 and 2. Move the experimental device into a 45 °C oven. Raise the temperature to 95 °C at a rate of 1 °C / min. Subsequently, the specimens are held at 95 °C for 100 minutes and allowed the assembly to cure.
[0079] Results and Observations: Figure 3A and 3B respectively show the cross - sectional views of Specimen 1 (using the Traditional System) and Specimen 2 (using System 3) after the test. Figure 3C and 3D respectively show the front views of Specimen 1 and Specimen 2 after the test. Figure 3E and3F The back views of Specimen 1 and Specimen 2 after testing are shown respectively. After testing, no crack appeared in Specimen 2, while cracks were observed in the traditional system.
[0080] Example 5: Curing Shrinkage Comparison between System 3 and Traditional System
[0081] Materials:
[0082] a) System 3
[0083] b) Traditional System
[0084] c) GRE substrate with a thickness of 1.5 - 1.8 mm and dimensions of 300 x 50 x 1.5 mm
[0085] Operating Procedure: Coat the traditional system and System 3 on two different GRE substrates with a thickness of 10 mm to prepare Panels 1 and 2. Immediately take out Panels 1 and 2 after curing at 65°C for 5 hours, and place them at room temperature to cool. Measure the area (unit: mm2) under the curved surface of Panels 1 - 2 to determine the curing shrinkage rate.
[0086] Results and Observations: Figure 4A This is a post - test photo of Panel 1 processed by the traditional system. Figure 4B This is a post - test photo of Panel 2 processed by System 3. The degree of bending reflects the amount of shrinkage. After testing, significant shrinkage occurred in the traditional system, while the shrinkage amount of System 3 was extremely small.
[0087] Example 6: Exothermic Curve Comparison between System 3 and Traditional System
[0088] Operating Procedure: Compare the exothermic curves of System 3 and the traditional system. The epoxy resin component and curing agent component of System 3 and the traditional system are pre - treated in an incubator at 35°C for 4 hours. Mix each component according to the molar ratio to prepare System 3 and the traditional system respectively. Transfer 100 grams of each system to a paper cup (9 ounces). Start the temperature recorder and stopwatch after mixing evenly. Place the paper cups in an incubator at 35°C. Use a thermocouple to measure the temperature rise of System 3 and the traditional system over time.
[0089] Results and Observations: As Figure 5 shown, the traditional system shows a higher peak and a wider peak width than System 3. This indicates that the reaction rate of the traditional system is faster than that of System 3.
[0090] Industrial Applicability
[0091] The epoxy adhesive system disclosed in this disclosure is recyclable, so it can be debonded through a recycling process to recover the epoxy thermoplastic material for further reuse and reprocessing. This system has a low cure shrinkage rate, low heat release during the curing process, and high mechanical strength, bonding strength, and toughness. This system has high-performance characteristics and is particularly suitable for structural bonding applications. It is suitable for bonding large to extra-large composite structures, such as wind turbine blades, and can also be used in other bonding applications, including bonding of materials such as metal-metal, plastic-plastic, metal-plastic, wood-wood, and wood-metal.
Claims
1. A recyclable epoxy resin adhesive system, characterized in that, Comprising: a) an epoxy resin component in an amount of 60 - 80% by weight; wherein the epoxy resin component comprises one or more bifunctional epoxy resins; and b) a curing agent component in an amount of 20 - 40% by weight; wherein the curing agent component comprises one or more curing agents, and each of the curing agents comprises at least one cleavable bond.
2. The recyclable epoxy resin adhesive system according to claim 1, wherein The content of the one or more bifunctional epoxy resins is 65 - 85% of the total weight of the epoxy resin component.
3. The recyclable epoxy resin adhesive system according to claim 1 or 2, characterized in that, The one or more bifunctional epoxy resins are selected from bisphenol A epoxy resin, bisphenol F epoxy resin, and combinations thereof.
4. The recyclable epoxy resin adhesive system according to any one of claims 1 to 3, characterized in that, The epoxy resin component comprises a mono - functional or bifunctional epoxy - reactive diluent selected from: aliphatic epoxy - reactive diluents, aromatic epoxy - reactive diluents, non - reactive diluents, and combinations thereof.
5. The recyclable epoxy resin adhesive system according to claim 4, wherein, The diluent is selected from 1,4 - butanediol diglycidyl ether, C12 - 14 alkyl glycidyl ether, 1,6 - hexanediol diglycidyl ether, catechol glycidyl ether, polypropylene glycol, and combinations thereof.
6. The recyclable epoxy resin adhesive system according to any one of claims 1 to 5, characterized in that, The curing agent comprises a cleavable bond selected from acetaldehyde bond, ketone - aldehyde bond, formaldehyde bond, ortho - ester bond, ortho - carbonate bond, and siloxane bond.
7. The recyclable epoxy resin adhesive system according to any one of claims 1 to 6, characterized in that, The curing agent is selected from the adducts of 2,2’ - bis(2 - aminoethoxy)propane, 2,2’-(2 - aminopropoxy)propane, and 2,2’ - bis(2 - aminobutoxy)methylsilane.
8. The recyclable epoxy resin adhesive system according to any one of claims 1 to 7, characterized in that, The content of the curing agent is 70% to 90% of the total weight of the curing agent component.
9. The recyclable epoxy resin adhesive system according to any one of claims 1 to 8, characterized in that, Further comprising one or more components selected from: additives, modifiers, catalysts, and combinations thereof.
10. The recyclable epoxy resin adhesive system according to claim 9, wherein The total content of the one or more components is 10% to 30% of the total weight of the recyclable epoxy resin adhesive system.
11. The recyclable epoxy resin adhesive system according to claim 9 or 10, characterized in that, The one or more additives are selected from: fumed silica, one or more pigments, one or more natural fibers, ground glass, carbon fiber, and combinations thereof.
12. The recyclable epoxy resin adhesive system according to claim 9 or 10, characterized in that, The modifiers are selected from: core - shell rubber tougheners, block copolymers, activated clay, silicone defoamers, epoxy silanes, amino silanes, and combinations thereof.
13. The recyclable epoxy resin adhesive system according to claim 9 or 10, wherein, The catalyst is an alkyl alkanolamine or its derivative.
14. An adhesive node includes two or more glass fiber reinforced epoxy resin matrices; wherein, The two or more glass fiber - reinforced epoxy resin matrices are bonded together by the recyclable epoxy resin adhesive system according to any one of claims 1 to 13.
15. The bonding node according to claim 14, characterized in that, The bonding nodes can be recycled and debonded by a low - energy solvent depolymerization process.