Method for efficiently degrading and recycling waste epoxy resin and composite material thereof under catalysis of metal functionalized ionic liquid

Abstract

The invention discloses an efficient degradation and recovery method for catalyzing waste epoxy resin and a composite material thereof by using metal functionalized ionic liquid, and belongs to the technical field of waste epoxy resin degradation and recovery. The method comprises the following steps: mixing a waste epoxy resin material or a waste epoxy resin composite material with a catalytic degradation liquid according to a mass ratio of 1: (1-10), heating and refluxing under the protection of nitrogen at 60-120 DEG C, and reacting for 1-36 hours until the resin completely disappears and the degradation is completed. The structure of the waste epoxy resin material contains ester functional groups, including ester groups at cross-linking points or ester groups in the body. According to the method, central metal atoms of the metal functionalized ionic liquid are coordinated with atoms in the waste epoxy resin and the degradation liquid, so that the degradation liquid can be enriched on the surface of the resin, the erosion effect of the degradation liquid on the surface of the epoxy resin is greatly accelerated, and the degradation liquid can enter a resin system more easily; therefore, the cross-linked network is disintegrated more quickly, and the degradation efficiency is greatly improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of degradation and recycling of waste epoxy resin, and particularly relates to the technology of degrading waste epoxy resin by metal-functionalized ionic liquid catalysis. The metal-functionalized ionic liquid is used to catalyze and assist the degradation liquid to degrade waste epoxy resin and its composites. The final degradation products can be used as curing agents again for the curing of epoxy resin, realizing the full recycling and reuse of waste epoxy resin. Background Art

[0002] Epoxy resin is a common thermosetting material, which is widely used in coatings, adhesives, building materials and other engineering fields. With the use of a curing agent, small-molecular-weight epoxy monomers undergo cross-linking reactions to produce thermosetting epoxy resin with a three-dimensional (3D) network structure. It is precisely the 3D cross-linked network structure that endows epoxy resin with a series of advantages, such as excellent mechanical strength, dielectric properties, heat resistance and chemical corrosion resistance. However, it is also its irreversible 3D cross-linked network structure that makes epoxy resin an infusible and insoluble thermosetting material. Subsequently, it brings great challenges to the degradation and recycling of epoxy resin in waste power equipment and electronic equipment. The rapid development of industry has led to an increasing amount of epoxy resin used year by year, and the amount of waste epoxy resin has become larger and larger, resulting in great environmental pollution and resource waste. Therefore, realizing their effective recycling and reuse is of great significance to environmental protection and resource conservation.

[0003] Epoxy resins cured with acid anhydrides are mostly used in high-performance fields such as electronic packaging and composites due to their good heat resistance and high strength. Therefore, degrading and recycling epoxy resins cured with acid anhydrides can not only reuse the resins to create secondary value, but more importantly, recover high-value products such as rare metals or reinforcing fiber. Existing patents on degrading epoxy resins cured with acid anhydrides, such as CN119119424A, disclose a method for degrading, recycling, and reusing epoxy resin fiber-reinforced composites cured with acid anhydrides, which uses alkali-catalyzed ester hydrolysis to degrade the epoxy resin to obtain polyol products. However, polyols are difficult to further reuse subsequently and can only be used as part of the additive for epoxy resins, with little effect, and an acid solution needs to be added to generate carboxylic acid intermediates for further treatment, which is complex in operation and difficult to apply later. Another example is CN119528716A, which discloses a phase transfer separation method for the degradation products of epoxy resins cured with acid anhydrides, using a mixed solution of ethylene glycol and sodium hydroxide to degrade the ester group and separating the degradation products to obtain glycidyl ether and acid anhydride, which can be further synthesized into epoxy, but the consumption of alkali and alcohol is large in the reaction and complete degradation cannot be achieved. Another example is CN118005993B, which discloses a composition for degrading epoxy resins cured with acid anhydrides and a method for degrading and regenerating epoxy resins cured with acid anhydrides, using benzoxazine and strong alkali aqueous solution to degrade the ester group, but the degradation products need to be further reacted before they can be reused. In summary, it is of great significance to find a mild, simple degradation method and a smooth and effective post-utilization method for degrading epoxy resins cured with acid anhydrides. Summary of the Invention

[0004] To solve the above technical problems, the present invention provides a method for efficiently degrading and recycling waste epoxy resins and their composites catalyzed by metal-functionalized ionic liquids. The catalyst used in the present invention can rapidly degrade epoxy resins at a suitable temperature, and the obtained degradation products can be efficiently reused for the curing of epoxy resins. The epoxy resin cured based on this degradation product has more excellent performance and higher strength than the original epoxy resin. The content of the present invention has great environmental advantages for the recycling and reuse of thermosetting epoxy resin-based composites.

[0005] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A method for efficiently degrading and recycling waste epoxy resins and their composites catalyzed by metal-functionalized ionic liquids, the method being: mixing waste epoxy resin materials or waste epoxy resin composites with a catalytic degradation solution in a mass ratio of 1:1 - 10, heating and refluxing under nitrogen protection at 60 - 120 °C, reacting for 1 - 36 h until the resin completely disappears and the degradation is completed, and the obtained degradation products can be directly used as curing agents for epoxy resins.

[0007] Furthermore, the structure of the waste epoxy resin material contains ester functional groups, including ester groups at the crosslinking points, such as epoxy resins cured with acid anhydride curing agents; or ester groups in the main body, such as epoxy resins cured with glycidyl ester epoxy resins.

[0008] Furthermore, the waste epoxy resin composite material is prepared from epoxy resin, reinforcing body, and auxiliary materials; the epoxy resin is one with ester functional groups in its structure, including ester groups at the crosslinking points, such as epoxy resins cured with acid anhydride curing agents; or ester groups in the main body, such as epoxy resins cured with glycidyl ester epoxy resins; the reinforcing body is a fiber material or a nano material; the auxiliary materials include at least one of accelerator, diluent, plasticizer, toughening agent, thickening agent, coupling agent, defoaming agent, leveling agent, ultraviolet absorber, antioxidant, brightening agent, fluorescent reagent, pigment, and filler.

[0009] Furthermore, the fiber material is one or more of carbon fiber, glass fiber, natural fiber, chemical fiber, or fabric made of the aforementioned fiber materials; the nano material is one or more of nano carbon materials, boron nitride nano materials, metal nano particles, metal oxide nano particles, or organic nano particles.

[0010] Furthermore, the catalytic degradation liquid is composed of metal-functionalized ionic liquid and amine degradation liquid; the metal-functionalized ionic liquid is composed of a cation, an anion, and a central metal atom; the cation includes one of 1-methylimidazole, tetraethylammonium, tetrabutylammonium, ethyltriethylamine alkyltributylammonium, butyltriethylamine alkyltributylammonium, and diethylenetriamine; the anion includes one of chlorine, bromine, tetrafluoroboric acid, hexafluorophosphoric acid, trifluoroacetic acid, trifluoromethanesulfonic acid, and acetic acid; the central metal atom is one or several of Cu, Pd, Cd, Zn, Cr, Ni, Al, Mn, and Co; the amine degradation liquid is one or several of ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, 1,3-diaminocyclohexane, isophoronediamine, diaminocyclohexane, m-phenylenediamine, m-xylylenediamine, and diaminodiphenylmethane.

[0011] Furthermore, the mass ratio of the metal-functionalized ionic liquid in the catalytic degradation liquid is 1-30%; the mass ratio of the degradation liquid in the catalytic degradation liquid is 70-99%.

[0012] The beneficial effects of the present invention compared with the prior art are as follows: The present invention has successfully degraded waste epoxy resin through a method of highly efficient catalysis using metal-functionalized ionic liquids, achieving the efficient degradation of waste epoxy resin. Through the coordination of the central metal atom of the metal-functionalized ionic liquid with the atoms in the waste epoxy resin and the degradation solution, the degradation solution can be enriched on the resin surface, greatly accelerating the erosion of the degradation solution on the epoxy resin surface. The degradation solution can more easily enter the resin system, thereby more rapidly disintegrating the crosslinking network and greatly accelerating the degradation efficiency. In addition, the central metal atom of the metal-functionalized ionic liquid can also activate the ester groups contained in the waste epoxy resin, making it more easily attacked and decomposed. Further, the cations in the ionic liquid can enhance the toughness of the epoxy resin, so that when the degradation solution obtained after degradation is used to cure the epoxy resin again, the tensile strength of the obtained epoxy resin is even better than that of the original resin, thus realizing 100% recycling and 100% reuse of waste epoxy resin, which is greatly beneficial to the environment, realizes negative carbon emissions, and creates secondary value for waste epoxy resin garbage. Specific Embodiments

[0013] The technical solutions of the present invention will be further described below in conjunction with the embodiments, but are not limited thereto. Any modification or equivalent replacement of the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention shall be covered by the protection scope of the present invention.

[0014] Example 1:

[0015] Mix waste epoxy resin with the catalytic degradation solution (diethylenetriamine: [BmimCl][MnCl 2 = 90:10) at a mass ratio of 1:5 and place it in a reaction flask. Under nitrogen protection, carry out condensation reflux and heat to 80 °C for reaction for 8 h. All the solids disappear, and finally a homogeneous solution is obtained.

[0016] Directly mix the degradation product with epoxy resin E-51 and cure it at 80 °C for 2 h to make a new epoxy resin for reuse. The tensile strength of the epoxy resin prepared by degradation and reuse can reach 65 MPa, and the elongation at break can reach 4.2%.

[0017] Example 2:

[0018] Mix waste epoxy resin with the catalytic degradation solution (diethylenetriamine: [(DETA)OAc][Co(OAc) 2 = 95:5) at a mass ratio of 1:1 and place it in a reaction flask. Under nitrogen protection, carry out condensation reflux and heat to 60 °C for reaction for 10 h. All the solids disappear, and finally a homogeneous solution is obtained.

[0019] The degradation products were directly mixed with epoxy resin E-51 and cured at 80 °C for 2 h to prepare a new epoxy resin for reuse. The tensile strength of the epoxy resin prepared by degradation and reuse could reach 68 MPa, and the elongation at break could reach 4.3%.

[0020] Example 3:

[0021] The waste epoxy resin was mixed with the catalytic degradation solution (triethylenetetramine: [BmimCl][CuCl 2 = 85:15) in a mass ratio of 1:3 and placed in a reaction flask. Under nitrogen protection, it was refluxed with condensation and heated to 80 °C for reaction for 8 h. All the solids disappeared, and finally a homogeneous solution was obtained.

[0022] The degradation products were directly mixed with epoxy resin E-51 and cured at 80 °C for 2 h to prepare a new epoxy resin for reuse. The tensile strength of the epoxy resin prepared by degradation and reuse could reach 67 MPa, and the elongation at break could reach 4.3%.

[0023] Example 4:

[0024] The waste epoxy resin was mixed with the catalytic degradation solution (1,3-diaminocyclohexane: [EmimCl][NiCl 2 = 70:30) in a mass ratio of 1:3 and placed in a reaction flask. Under nitrogen protection, it was refluxed with condensation and heated to 100 °C for reaction for 10 h. All the solids disappeared, and finally a homogeneous solution was obtained.

[0025] The degradation products were directly mixed with epoxy resin E-51 and cured at 80 °C for 2 h to prepare a new epoxy resin for reuse. The tensile strength of the epoxy resin prepared by degradation and reuse could reach 72 MPa, and the elongation at break could reach 4.5%.

[0026] Example 5:

[0027] The waste epoxy resin was mixed with the catalytic degradation solution (m-phenylenediamine: [EmimCl][CoCl 2 = 75:25) in a mass ratio of 1:10 and placed in a reaction flask. Under nitrogen protection, it was refluxed with condensation and heated to 120 °C for reaction for 8 h. All the solids disappeared, and finally a homogeneous solution was obtained.

[0028] The degradation products were directly mixed with epoxy resin E-51 and cured at 80 °C for 2 h to prepare a new epoxy resin for reuse. The tensile strength of the epoxy resin prepared by degradation and reuse could reach 75 MPa, and the elongation at break could reach 4.5%.

[0029] Example 6:

[0030] The waste epoxy resin was mixed with the catalytic degradation solution (m-xylylenediamine: [PmimCl][MnCl 2= 80:20) were mixed at a mass ratio of 1:10 and placed in a reaction flask. Under nitrogen protection, it was refluxed with condensation and heated to 150 °C for reaction for 8 h. All the solids disappeared, and finally a homogeneous solution was obtained.

[0031] The degradation product was directly mixed with epoxy resin E-51 and cured at 80 °C for 2 h to make a new epoxy resin for reuse. The tensile strength of the epoxy resin prepared by degradation and reuse could reach 81 MPa, and the elongation at break could reach 5.1%.

[0032] Example 7:

[0033] Waste epoxy resin and catalytic degradation liquid (isophorone diamine: [PmimCl][CuCl 2 = 90:10) were mixed at a mass ratio of 1:10 and placed in a reaction flask. Under nitrogen protection, it was refluxed with condensation and heated to 150 °C for reaction for 12 h. All the solids disappeared, and finally a homogeneous solution was obtained.

[0034] The degradation product was directly mixed with epoxy resin E-51 and cured at 80 °C for 2 h to make a new epoxy resin for reuse. The tensile strength of the epoxy resin prepared by degradation and reuse could reach 75 MPa, and the elongation at break could reach 4.6%.

[0035] Example 8:

[0036] Waste epoxy resin and catalytic degradation liquid (diaminodiphenylmethane: [RmimCl][NiCl 2 = 90:10) were mixed at a mass ratio of 1:8 and placed in a reaction flask. Under nitrogen protection, it was refluxed with condensation and heated to 150 °C for reaction for 16 h. All the solids disappeared, and finally a homogeneous solution was obtained.

[0037] The degradation product was directly mixed with epoxy resin E-51 and cured at 80 °C for 2 h to make a new epoxy resin for reuse. The tensile strength of the epoxy resin prepared by degradation and reuse could reach 84 MPa, and the elongation at break could reach 5.3%.

[0038] Example 9:

[0039] Waste epoxy resin and catalytic degradation liquid (diethylenetriamine: [(DETA)OAc][Ni(OAc) 2 = 95:5) were mixed at a mass ratio of 1:1 and placed in a reaction flask. Under nitrogen protection, it was refluxed with condensation and heated to 60 °C for reaction for 10 h. All the solids disappeared, and finally a homogeneous solution was obtained.

[0040] The degradation product was directly mixed with epoxy resin E-51 and cured at 80 °C for 2 h to make a new epoxy resin for reuse. The tensile strength of the epoxy resin prepared by degradation and reuse could reach 66 MPa, and the elongation at break could reach 4.2%.

[0041] Example 10:

[0042] Mix the waste epoxy resin carbon fiber reinforced composite material with the catalytic degradation liquid (diethylenetriamine: [(DETA)OAc][Cu(OAc) 2 = 80:20) in a mass ratio of 1:3 and place it in a reaction flask. Under nitrogen protection, carry out condensation reflux and heat to 80 °C for reaction for 15 h. All the resin on the surface of the carbon fiber is dissolved, and all the carbon fibers are exposed. After rinsing with dichloromethane and drying, clean carbon fiber tows are obtained. Measure its single fiber tensile strength, and the strength retention rate is 92%. The degraded fiber still maintains good strength.

[0043] Mix the degradation product directly with epoxy resin E-51 and cure it at 80 °C for 2 h to make a new epoxy resin for reuse. The tensile strength of the epoxy resin prepared by degradation and reuse can reach 63 MPa, and the elongation at break can reach 4.0%.

[0044] Example 11:

[0045] Mix the waste epoxy resin glass fiber reinforced composite material with the catalytic degradation liquid (1,3-diaminocyclohexane: [PmimBr][NiBr 2 = 90:10) in a mass ratio of 1:5 and place it in a reaction flask. Under nitrogen protection, carry out condensation reflux and heat to 100 °C for reaction for 24 h. All the resin on the surface of the glass fiber is dissolved, and all the glass fibers are exposed. After rinsing with dichloromethane and drying, clean glass fiber tows are obtained. Measure its single fiber tensile strength, and the strength retention rate is 94%. The degraded fiber still maintains good strength.

[0046] Mix the degradation product directly with epoxy resin E-51 and cure it at 80 °C for 2 h to make a new epoxy resin for reuse. The tensile strength of the epoxy resin prepared by degradation and reuse can reach 66 MPa, and the elongation at break can reach 4.2%.

Claims

1. A method for efficiently degrading and recovering waste epoxy resin and its composite material catalyzed by metal functionalized ionic liquid, characterized in that: The method comprises: mixing waste epoxy resin material or waste epoxy resin composite material with catalytic degradation liquid in a mass ratio of 1:1-10, heating and refluxing at 60-120° C. under nitrogen protection, and reacting for 1-36 hours until all the resin disappears and the degradation is completed.

2. The method for efficiently degrading and recovering waste epoxy resin and its composite material catalyzed by metal functionalized ionic liquid according to claim 1, characterized in that: The waste epoxy resin material contains ester functional groups in its structure, including ester groups at the cross-linking points or in the main body.

3. The method for efficiently degrading and recovering waste epoxy resin and its composite material catalyzed by metal functionalized ionic liquid according to claim 1, characterized in that: The waste epoxy resin composite material is prepared from epoxy resin, reinforcement and auxiliary materials; the epoxy resin contains ester functional groups in its structure, including ester groups at the cross-linking points or ester groups in the body; the reinforcement is a fiber material or a nano material; the auxiliary materials include at least one of a promoter, a diluent, a plasticizer, a toughening agent, a thickener, a coupling agent, a defoamer, a leveling agent, an ultraviolet absorber, an antioxidant, a brightener, a fluorescent agent, a pigment and a filler.

4. The method for efficiently degrading and recovering waste epoxy resin and its composite material catalyzed by metal functionalized ionic liquid according to claim 3, characterized in that: The fiber material is one or more of carbon fiber, glass fiber, natural fiber, chemical fiber or fabrics made of the aforementioned fiber materials; the nanomaterial is one or more of nanocarbon material, boron nitride nanomaterial, metal nanoparticles, metal oxide nanoparticles or organic nanoparticles.

5. The method for efficiently degrading and recovering waste epoxy resin and its composite material catalyzed by metal functionalized ionic liquid according to claim 1, characterized in that: The catalytic degradation liquid is composed of a metal functionalized ionic liquid and an amine degradation liquid; the metal functionalized ionic liquid is composed of a cation, an anion and a central metal atom; the cation includes one of 1-methylimidazole, tetraethylammonium, tetrabutylammonium, ethyltriethylamine alkyltributylammonium, butyltriethylamine alkyltributylammonium and diethylenetriamine; the anion includes one of chlorine, bromine, tetrafluoroboric acid, hexafluorophosphoric acid, trifluoroacetic acid, trifluoromethanesulfonic acid and acetic acid; the central metal atom is one or more of Cu, Pd, Cd, Zn, Cr, Ni, Al, Mn and Co; the amine degradation liquid is one or more of ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, 1,3-diaminocyclohexane, isophoronediamine, diaminocyclohexane, metaphenylenediamine, metaphenylenediamine and diaminodiphenylmethane.

6. The method for efficiently degrading and recovering waste epoxy resin and its composite material catalyzed by metal functionalized ionic liquid according to claim 5, characterized in that: The mass of the metal functionalized ionic liquid accounts for 1-30% of the catalytic degradation liquid; the mass of the degradation liquid accounts for 70-99% of the catalytic degradation liquid.