Methods and systems for reusing epoxy thermosetting materials, and reusable thermoplastic components obtained using this method.

Abstract

The present invention relates to a method and system for recycling epoxy thermosets containing cleavable bonds. The method involves dissolving the epoxy thermoset with an acid solution and devolatilizing the acid solution from the thermoplastic acidic mixture to produce a thermoplastic component. The method allows for recovery of a reusable thermoplastic component and optionally a reusable reinforcing matrix component. The method includes dissolving the epoxy thermoset in the acid solution under heating conditions to obtain a thermoplastic mixture, optionally filtering the thermoplastic mixture to separate the reinforcing matrix component from the thermoplastic solution, and devolatilizing the thermoplastic solution to obtain a reusable thermoplastic component.

Description

Technical Field

[0001] The present invention relates to a method and system for recycling an epoxy thermosetting material containing a cleavable bond, which removes an acid solution from a thermoplastic acidic mixture after using the acid solution. By this method, recyclable thermoplastic components and optionally recyclable reinforcing matrix components can be recovered and reused.

Background Art

[0002] Epoxy resins are an important class of thermosetting compounds. Epoxy resins are economical, low in toxicity, and provide a unique combination of heat resistance, mechanical resistance, and chemical resistance that cannot be obtained with other thermosetting resins. They have high chemical resistance, high solvent resistance, low shrinkage rate, and excellent adhesion to various substrates. Epoxy resins are also used in the manufacture of fiber reinforced polymer composites.

[0003] Epoxy thermosetting materials have a variety of applications and are widely used in automobiles, aerospace / defense equipment, wind turbines, structural adhesives, electronics, ceramic manufacturing, microelectronics packaging, etc. They also have a wide range of applications in the civil engineering and construction fields, such as structural parts, epoxy cement, floor coatings, metal coatings, ship coatings, paints, decorative artworks, lacquers, etc. Due to their excellent performance, epoxy resins are also favored for coating applications such as can coatings, powder coatings, food / packaging coatings, etc.

[0004] However, conventional epoxy resins are difficult to reuse because they become insoluble in common solvents after heat curing. In particular, epoxy resins do not melt with heat once cured, making them difficult to reuse as a resin material. As a result, the manufacture of conventional epoxy resin cured products and products to which epoxy resin cured products are attached or coated generates a large amount of waste. Furthermore, after the product lifecycle, the challenge lies in recovering and reusing beneficial components from the polymer epoxy matrix, and / or reusing the epoxy itself. Generally, all components are disposed of and lost through incineration or landfill. These disposal methods cause irreversible damage and pollution to the environment.

[0005] Reusable epoxies were developed to enable the depolymerization of epoxy resins in which thermosetting polymers have cleavable bonds. Reusable epoxies are prepared using a reusable acid-unstable curing agent and a conventional epoxy resin, or a reusable epoxy resin and a conventional curing agent. The resulting epoxy thermosetting polymer has cleavable bonds, enabling reusable depolymerization. In the case of epoxy composites, after depolymerization, the epoxy resin can be dissolved, and other materials such as metals, glass fibers, and carbon fibers can be separated, recovered, and reused.

[0006] Prior art methods for reusing reusable thermosetting resins and composite materials utilize decomposition agents such as acids and solvents. Prior art methods for reusing reusable thermosetting resins utilize a NaOH neutralization step, where the acid used to dissolve the thermoplastic component of the reusable epoxy thermosetting material is neutralized with NaOH. This step is undesirable because it generates waste such as sodium acetate, which cannot be disposed of as sewage waste. Furthermore, prior art methods are industrially unsuitable batch processes and cannot be easily scaled up. Therefore, there is a need for an industrially and commercially feasible, effective, and scalable recycling process that can recover the components of epoxy thermosetting materials and their composite materials while minimizing environmental impact.

[0007] Therefore, there remains an opportunity to develop methods for recycling epoxy polymers and their composite materials that address one or more problems associated with methods known in the art, or at least provide a viable alternative to such methods. [Overview of the project]

[0008] According to one embodiment, the present invention relates to a method for reusing an epoxy thermosetting material comprising at least one reusable component, i. To form a thermoplastic mixture, the step is to dissolve the epoxy thermosetting material in an acid solution under heating conditions of 50-110°C, ii. A step of filtering the thermoplastic mixture in order to separate the reinforcing matrix component from the thermoplastic solution, iii. A method comprising the step of defoliating the thermoplastic solution to remove the acid solution in order to obtain a reusable thermoplastic component.

[0009] According to another embodiment, the present invention relates to a system for reusing an epoxy thermosetting material comprising at least one reusable component, i. A dissolution subsystem configured to dissolve an epoxy thermosetting substance in an acid solution under heating conditions in order to form a thermoplastic mixture, ii. A filtration subsystem configured to filter the thermoplastic mixture in order to separate the reinforcing matrix components from the thermoplastic solution, iii. A system comprising a defloration subsystem configured to remove an acid solution from a thermoplastic solution in order to obtain a reusable thermoplastic component, the defloration subsystem including an extruder, a fall membrane evaporator, a distillation unit, or a combination thereof.

[0010] According to another embodiment, the present invention relates to a method for reusing an epoxy thermosetting material containing reusable components, i. To form a thermoplastic mixture, the epoxy thermosetting material is dissolved in an acid solution, and the step of dissolving the epoxy thermosetting material at least partially is performed. ii. A method comprising the step of defoliating a thermoplastic mixture to remove an acid solution in order to obtain a reusable thermoplastic component containing a reinforcing matrix component.

[0011] According to another embodiment, the present invention relates to a system for reusing epoxy thermosetting materials containing reusable components, i. A dissolution subsystem configured to dissolve an epoxy thermosetting material in an acid solution in order to form a thermoplastic mixture, ii. A system comprising a defloration subsystem configured to remove an acid solution from a thermoplastic solution in order to obtain a reusable thermoplastic component containing a reinforcing matrix component, the defloration subsystem including an extruder, a fall membrane evaporator, a distillation unit, or a combination thereof. [Brief explanation of the drawing]

[0012] Embodiments of the present invention will be described with reference, examples of which are shown in the accompanying figures. These figures are illustrative and not intended to be limiting. While the present invention will be described in general in relation to these embodiments, it should be understood that the scope of the present invention is not intended to be limited to these specific embodiments.

[0013] [Figure 1] This document describes an embodiment of the method for completely dissolving epoxy thermosetting materials and for reusing epoxy thermosetting materials (dissolution process). [Figure 2] This document describes an embodiment of the method for reusing epoxy thermosetting materials, which involves at least partially dissolving the epoxy thermosetting material (non-dissolution process). [Figure 3] This document shows one embodiment of the system for completely dissolving epoxy thermosetting materials and for reusing epoxy thermosetting materials (dissolution process apparatus). [Figure 4] This document illustrates one embodiment of a system for reusing epoxy thermosetting materials, which at least partially dissolves the epoxy thermosetting material (non-dissolution process apparatus). [Figure 5a]This graph shows the effects of different acid concentrations at 60°C on the recycling of epoxy waste over time. [Figure 5b] This graph shows the effects of different acid concentrations at 80°C on the recycling of epoxy waste over time. [Figure 5c] This graph shows the effects of different acid concentrations at 100°C on the recycling of epoxy waste over time. [Modes for carrying out the invention]

[0014] In the following detailed description, embodiments are described in sufficient detail so that those skilled in the art can carry out the invention; however, it should be understood that other embodiments may be used and modifications may be made without departing from the scope of the invention. In order to avoid details that are not necessary for those skilled in the art to carry out the embodiments described herein, certain information known to those skilled in the art may be omitted herein. Accordingly, the specification and drawings are to be considered illustrative rather than restrictive, and all such modifications are intended to be included within the scope of this teaching. It should be understood that the singular “a,” “an,” and “the” include plural references unless the context clearly indicates otherwise. It should be emphasized that, as used herein, the term “comprises / comprising” is used to identify the presence of a described feature, integer, step, or component, but does not exclude the presence or addition of one or more other features, integers, steps, components, or groups thereof.

[0015] In one embodiment, the present invention provides a method for reusing an epoxy thermosetting material comprising at least one reusable component, To form a thermoplastic mixture, the process involves dissolving an epoxy thermosetting substance in an acid solution under heating conditions of 50-110°C, To separate the reinforcing matrix component from the thermoplastic solution, the thermoplastic mixture is filtered, To obtain a recyclable thermoplastic component, a method is provided that includes the step of devolatilizing a thermoplastic solution to remove an acid solution, intending to address the drawbacks of the aforementioned prior art.

[0016] This method is an industrial dissolution process in which a thermoplastic mixture is formed by dissolving an epoxy thermosetting material. In a preferred embodiment, this process is carried out at 100 °C. In a preferred embodiment, the epoxy thermosetting material is size-reduced before being dissolved in an acid solution. The thermoplastic material is completely dissolved in the acid solution, and the resulting thermoplastic mixture contains undissolved components such as a reinforcing matrix component and non-recyclable components suspended in the thermoplastic solution. By filtration, the undissolved components can be removed from the thermoplastic solution. The thermoplastic material dissolved in the acid solution is recovered after removing the acid by devolatilizing the acid solution using distillation, wiped film evaporation, a devolatilizing extruder, etc. The recyclable thermoplastic components obtained in such a manner can be used to produce various grades of usable thermoplastic materials by compounding and reactive extrusion. In one embodiment of this method, filtration further includes the selection of undissolved components by centrifugation, manual sorting, optical sorting, or a combination thereof. The undissolved components may be sorted for recovery and reuse or discarded. The reinforcing matrix component to be removed and reused is substantially equivalent to a nearly new material. Thereby, almost all or part of the value of the reinforcing material can be recaptured. In one embodiment of this method, the reinforcing matrix component includes glass fiber, carbon fiber, aramid fiber, jute, grass, bamboo, pine, balsa, other natural fibers, and combinations thereof, and is recyclable.

[0017] In one embodiment of the dissolution process, the acid solution is acetic acid, lactic acid, propionic acid, other aliphatic acids, other organic acids, or a combination thereof, the concentration of acetic acid is 5-70%, and the concentration of lactic acid is 20-80%. According to a preferred embodiment, the acid solution is 10-15% acetic acid or 50% lactic acid. The reuse process is mild and preferably uses weak acids. In one embodiment of the method, the acid solution contains a solvent selected from water, butanol, isopropanol, propanol, ethanol, methanol, benzyl alcohol, ethylene glycol, dichloromethane, tetrahydrofuran, ethyl acetate, acetone, dimethylformamide, acetonitrile, dimethyl sulfoxide, nitromethane, propylene carbonate, pentane, hexane, cyclohexane, benzene, toluene, xylene, dioxane, glyme, polyether, diethyl ether, other non-polar solvents, other polar aprotic solvents, other polar protic solvents, and combinations thereof.

[0018] All desolvents containing acid can be reused. In one embodiment of the method, the removed acid solution, solvent, or both are reused in the process. In one embodiment, the process is continuous or batch. In a preferred embodiment, the process is continuous.

[0019] In one embodiment of the method, the epoxy thermosetting substance is prepared from a diepoxy resin and a reusable acid-labile curing agent, and the reusable acid-labile curing agent is an amine-based curing agent, a thiol-based curing agent, a polyamino compound, other acid-labile curing agents, or a combination thereof. In one embodiment, the reusable acid-labile curing agent is a compound of Formula 1 below. [Chemical formula] In the formula, m is 2, 1, or 〇, n is 2, 3, or 4, and the sum of m and n is 4. R1 is independently hydrogen, alkyl, cycloalkyl, heterocyclic, heterocycloalkyl, alkenyl, cycloalkenyl, aryl, heteroaryl, alkyloxyalkyl, or alkynyl. A is independently unsubstituted ethylene, propylene, isopropylene, butylene, isobutylene, hexylene, ethyleneoxyethylene, ethyleneaminoethylene, [ka] That is the case. Each R2 is independently -NHR3, and each R3 is independently hydrogen, alkyl, aminoalkyl, alkylaminoalkyl, cycloalkyl, heterocyclic, alkenyl, aryl, or heteroaryl. Alternatively, each pair of -OA-R2 groups independently forms a dioxanyl ring with the carbon atoms to which they are bonded, having four or more ring members, and one or more of the ring carbon atoms other than those to which the two -OA-R2 groups are bonded may be substituted with one or more independent amino groups or aminoalkyl groups. Each amino group is independently primary or secondary amino group. In one embodiment, the reusable acid-unstable curing agent is the compound of the following formula 2. [ka] In the equation, q is 4, 3, 2, or 1, t is 0, 1, 2, or 3, and the sum of q and t is 4. W is independently alkylene, cycloalkylene, heterocyclylene, alkenylene, alkylylene, cycloalkenylene, arylene, or heteroarylene, and R 5 Each of these independently consists of hydrogen, alkyl, cycloalkyl, heterocyclyl, alkenyl, alkynyl, cycloalkenyl, aryl, heteroaryl, aminoalkyl, aminoaryl, substituted amino group, or OR C That is. R CThese are alkyl (e.g., methyl, ethyl), cycloalkyl, heterocyclyl, alkenyl, alkynyl, cycloalkenyl, aryl (e.g., phenyl), or heteroaryl. In one embodiment, a reusable acid-unstable curing agent of formulas 1, 2, or combinations thereof is used with a conventional diepoxy resin selected from the group consisting of BPA diglycidyl ether, BPF diglycidyl ether, BPS diglycidyl ether, reactive diluent, diglycidylamine, aqueous epoxy resin, compound epoxy resin, and combinations thereof.

[0020] In one embodiment of this method, the epoxy thermosetting substance is prepared from a reusable epoxy resin and a curing agent, wherein the reusable epoxy resin contains an acid-degradable acetal, ketal, orthocarbonate, orthoester, orthosilicate, or silane bond. In one embodiment, the reusable epoxy resin is a compound of formula 3 or formula 4 below. Formula 3: [ka] Formula 4: [ka] In the formula, n=4 when m=0, n=3 when m=1, and n=2 when m=2. A is carbon or silicon, D is oxygen, nitrogen, or a carboxyl group, and X is oxygen or sulfur. s and t are independently 1 to 20. R1 and R2 are independently hydrogen, alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkenyl, cycloalkynyl, aryl, heterocyclyl, heterocycloalkyl, cycloalkenyl, heteroaryl, alkoxyaryl, or alkoxyalkyl.B independently comprises arylene, arylene ether, alkylene arylene, alkylene arylene alkylene, alkenylene arylene, alkenylene arylene alkenylene, alkylene arylene alkenylene, alkinylene arylene, alkinylene arylene alkinylene, heteroarylene, alkylene heteroarylene, alkylene heteroarylene alkylene, alkenylene heteroarylene, alkenylene heteroarylene alkenylene, alkylene heteroarylene alkenylene, alkinylene heteroarylene alkenylene, alkinylene he Telorirene, alkylene heteroarine alkylene, alkylene, alkylene heteroalkylene, alkenylene, alkenylene heteroalkenylene, alkylene heteroalkenylene, alkylene, neurylene Chloalkylene, alkylene heterodenodealkylene, alkylene heterodenodealkylene, alkenylene heterodenodealkylene, alkenylene heterodenodealkylene, alkylene heterodenodealkylene, alkenylene heterodenodealkylene, alkenylene heterodenodealkylene, alkenylene heterodenodealkylene, alkenylene heterodenodealkylene, alkenylene heterodenodealkylene, alkenylene, These are kenylene, alkylenedechlorokenylene, alkylenedechlorokenylene, alkylenedechlorokenylene, heterochlorokenylene, alkyleneheterochlorokenylene, alkyleneheterochlorokenylene, alkyleneheterochlorokenylene, alkyleneheterochlorokenylene, alkyleneheterochlorokenylene, alkyleneheterochlorokenylene, alkyleneheterochlorokenylene, alkyleneheterochlorokenylene, alkyleneheterochlorokenylene, alkyleneheterochlorokenylene. In one embodiment, the reusable epoxy components of formulas 3, 4, or combinations thereof are used with conventional curing agents selected from the group consisting of aliphatic amines, alicyclic polyamines, aromatic amines, polyetheramines, ketoimines, anhydrides, polyamides, imidazoles, polythiols, polyphenols, polycorvic acids, carboxylic acid polyesters, carboxylic acid polyacrylates, UV curing agents, aqueous curing agents, and combinations thereof.

[0021] In one embodiment of the dissolution process, the epoxy thermosetting material is reduced in size before being dissolved in an acid solution. This reduction in size is achieved using a shredder, crushing unit, grinder, blender, crusher, or a combination thereof.

[0022] In one embodiment, the present invention is a reusable thermoplastic component obtained using the dissolution process claimed and disclosed herein.

[0023] According to another embodiment, the present invention relates to a system for reusing an epoxy thermosetting material comprising at least one reusable component, A dissolution subsystem configured to dissolve an epoxy thermosetting material in an acid solution under heating conditions in order to form a thermoplastic mixture, A filtration subsystem configured to filter the thermoplastic mixture in order to separate the reinforcing matrix component from the thermoplastic solution, A defoliation subsystem configured to remove an acid solution from a thermoplastic solution in order to obtain a reusable thermoplastic component, comprising a defoliation subsystem including an extruder, a drop membrane evaporator, a distillation unit, or a combination thereof.

[0024] In one embodiment of the system, the defoliation subsystem is configured to remove the solvent from the thermoplastic solution. In one embodiment, the system is configured to reuse the removed acid solution, solvent, or both in the process. In one embodiment, the system is configured continuously or in batches. In a preferred embodiment, the system is continuous.

[0025] According to another embodiment, the present invention relates to a method for reusing an epoxy thermosetting material containing reusable components, To form a thermoplastic mixture, the epoxy thermosetting material is dissolved in an acid solution, and the step of dissolving the epoxy thermosetting material at least partially is performed. The method includes the step of defoliating a thermoplastic mixture to remove an acid solution in order to obtain a reusable thermoplastic component containing a reinforcing matrix component. This method is an industrial non-dissolution process in which partial dissolution of epoxy thermosetting material occurs in an acidic solution, forming a thermoplastic mixture. In the non-dissolution process, the reinforcing matrix component is not filtered from the thermoplastic solution, but the acid is removed by defoliation. This produces a reinforced, reusable thermoplastic component that can be recycled / reused as other products. The reusable thermoplastic component obtained in this way can be used to produce usable thermoplastic materials of various grades by compounding or reactive extrusion molding.

[0026] In one embodiment of the non-dissolution process, the epoxy thermosetting material is reduced in size before dissolving in the acid solution. Size reduction is achieved using a shredder, crushing unit, grinder, blender, crusher, or a combination thereof. In one embodiment of the non-dissolution process, immersion of the epoxy thermosetting material in the acid solution is carried out under heating conditions of 50°C to 110°C. This process is carried out at 100°C.

[0027] In one embodiment of the non-dissolving process, the acid solution is acetic acid, lactic acid, propionic acid, other aliphatic acids, other organic acids, sulfuric acid, phosphoric acid, other inorganic acids, or a combination thereof, with an acetic acid concentration of 5-70%, a lactic acid concentration of 20-80%, a sulfuric acid concentration of 1-10%, and a phosphoric acid concentration of 20-90%. According to a preferred embodiment, the acid solution is 10-15% acetic acid, 50% lactic acid, or 85% phosphoric acid. In one embodiment of the non-dissolving process, the acid solution contains a solvent selected from water, butanol, isopropanol, propanol, ethanol, methanol, benzyl alcohol, ethylene glycol, dichloromethane, tetrahydrofuran, ethyl acetate, acetone, dimethylformamide, acetonitrile, dimethyl sulfoxide, nitromethane, propylene carbonate, pentane, hexane, cyclohexane, benzene, toluene, xylene, dioxane, glyme, polyether, diethyl ether, other nonpolar solvents, other polar aprotic solvents, other polar protic solvents, and combinations thereof.

[0028] In one embodiment of the non-dissolving process, the removed acid solution, solvent, or both are reused in the process.

[0029] In one embodiment of the non-dissolving process, the epoxy thermosetting material is prepared from a diepoxy resin and a reusable acid-unstable curing agent, the reusable acid-unstable curing agent being an amine-based curing agent, a thiol-based curing agent, a polyamino compound, another acid-unstable curing agent, or a combination thereof, or prepared from a reusable epoxy resin and curing agent, the reusable epoxy resin containing an acid-degradable acetal, ketal, orthocarbonate, orthoester, orthosilicate, or silane bond. In one embodiment, the reusable acid-unstable curing agent is formula 1, 2, or a combination thereof. In one embodiment, the reusable epoxy resin component is formula 3, 4, or a combination thereof.

[0030] In one embodiment of the non-dissolving process, the reinforcing matrix components include glass fibers, carbon fibers, aramid fibers, jute, grass, bamboo, pine, balsa, other natural fibers, and combinations thereof.

[0031] In one embodiment, the present invention is a reusable thermoplastic component obtained using a non-dissolving process as claimed and disclosed herein.

[0032] According to another embodiment, the present invention relates to a system for reusing epoxy thermosetting materials containing reusable components, A dissolution subsystem configured to dissolve an epoxy thermosetting material in an acid solution in order to form a thermoplastic mixture, A defloration subsystem configured to remove an acid solution from a thermoplastic solution in order to obtain a reusable thermoplastic component containing a reinforcing matrix component, comprising a defloration subsystem including an extruder, a drop membrane evaporator, a distillation unit, or a combination thereof.

[0033] In one embodiment of the system, the defoliation subsystem is configured to remove the solvent from the thermoplastic solution. In one embodiment, the system is configured in a continuous or batch manner. In a preferred embodiment, the system is continuous. In one embodiment, the system is configured to reuse the removed acid solution, solvent, or both in the process.

[0034] The epoxy thermosetting material dissolved using this method includes, but is not limited to, epoxy thermosetting material, epoxy thermosetting material composites, or epoxy thermosetting material from manufacturing waste. The composite material includes a reinforcing matrix and optionally non-recyclable components. The epoxy thermosetting material may also consist of additives such as pigments, softeners, toughening agents, surface modifiers, fillers, foaming agents, curing catalysts, accelerators, and combinations thereof.

[0035] In the method disclosed herein, a neutralization step is not required because the acid solution (e.g., acetic acid) and / or solvent are evaporated from the thermoplastic solution or thermoplastic mixture in the defoliation subsystem. By defoliating the thermoplastic solution or thermoplastic mixture, the acid solution is removed, and a reusable thermoplastic component is obtained.

[0036] The aforementioned reuse method utilizes neutralization of the acid (e.g., acetic acid) in the thermoplastic solution / mixture, which is technically easier than defoliation. In this method, excess solvent and / or acid (catalyst) is removed without the need for neutralization by passing the filtered thermosetting substance solution or thermoplastic mixture through a defoliation extruder. Therefore, this method reduces the environmental impact because it does not generate sodium acetate, a byproduct of the prior art neutralization protocol. Furthermore, the reduction in the number of units of process also reduces process costs. In addition, the economic advantages of this method are further enhanced because the defoliated acid solution, solvent, or both can be reused in the process.

[0037] Figure 1 shows an embodiment of the method for reusing epoxy thermosetting materials, which completely dissolves the epoxy thermosetting material. In the embodiment of the dissolution process in Figure 1, epoxy thermosetting material is reused by immersing an epoxy thermosetting material containing at least one reusable component in an acid solution under heating conditions of 50-110°C to dissolve the epoxy thermosetting material and form a thermoplastic mixture (101). In one embodiment, the epoxy thermosetting material may be reduced to smaller fragments before dissolution in the acid solution to allow for more efficient cleavage and thus rapid dissolution. Next, the acidic thermoplastic mixture is filtered to separate the reinforcing matrix component and optionally non-reusable components from the thermoplastic solution (102). The thermoplastic solution is deflated to remove the acid solution and obtain the reusable thermoplastic component (103). The reusable thermoplastic component obtained in this way can be used to produce usable thermoplastic materials of various grades by compounding or reaction extrusion. One advantage of the method is that the acid solution from the acidic thermoplastic solution can be simply evaporated without the need for neutralization with caustic. This allows for the reuse of the acid and eliminates waste. During testing, the dissolution process allowed for the complete recovery of the carbon fiber cloth (reinforcement matrix component) in a near-new condition.

[0038] Figure 2 shows an embodiment of the method for reusing epoxy thermosetting materials, in which the epoxy thermosetting material is at least partially dissolved. The non-dissolution process involves reusing the epoxy thermosetting material by immersing the epoxy thermosetting material, which contains reusable components, in an acid solution and at least partially dissolving it to form a thermoplastic mixture (201). In one embodiment, the epoxy thermosetting material may be reduced to smaller fragments before dissolving in the acid solution to allow for more efficient cleavage and thus faster dissolution. Next, the acidic thermoplastic mixture is deflated to remove the acid solution and obtain a reusable thermoplastic component containing a reinforcing matrix component (202). The reusable thermoplastic component obtained in this manner can be used to produce usable thermoplastic materials of various grades by compounding or reaction extrusion. Although fibers cannot be recovered in the non-dissolution process, it may be a preferred option when the fibers are inexpensive (e.g., glass fibers). One advantage of the method is that the acid solution from the acidic thermoplastic solution can be simply evaporated without the need for neutralization with caustic. This allows for the reuse of the acid and generates no waste.

[0039] Figure 3 shows one embodiment of the system for reusing epoxy thermosetting materials, which completely dissolves the epoxy thermosetting material (dissolution process apparatus). The apparatus of this embodiment includes passing the epoxy waste through a shredder and then removing any metal parts using a metal detector. The remaining epoxy waste is passed through a dissolution subsystem (301) configured to dissolve the epoxy thermosetting material in an acid solution under heated conditions to form a thermoplastic mixture. The acidic thermoplastic mixture is passed through a filtration subsystem (302) configured to filter the thermoplastic mixture to separate the reinforcing matrix components and optionally non-reusable components from the thermoplastic solution. The thermoplastic solution is then passed through a defoliation subsystem (303) configured to remove the acid solution from the thermoplastic solution to obtain reusable thermoplastic components. The defoliation subsystem may include an extruder, a drop membrane evaporator such as the organic acid evaporator used in this embodiment, a distillation unit, or a combination thereof. The method is technically and economically advantageous because the organic acid (and solvent, if used) is reused in the process. The apparatus is preferably continuous. This apparatus converts epoxy resin into a thermoplastic by immersing epoxy waste in a 5-50% acetic acid solution for 1-3 days at a temperature of 20-100°C. Other acids, such as lactic acid and propionic acid, have also been tested and shown to be effective. For reuse at high temperatures such as 100°C, it was necessary to design a sealed container capable of withstanding the pressure generated by boiling (high-pressure rated reuse equipment was required). This apparatus was able to reduce the unpleasant odor generated and minimize solution loss due to rapid evaporation at high temperatures.

[0040] Figure 4 shows one embodiment of the system for reusing epoxy thermosetting materials, which at least partially dissolves the epoxy thermosetting material (non-dissolution process apparatus). The apparatus of this embodiment includes passing the epoxy waste through a shredder and then removing any metal parts using a metal detector. The remaining epoxy waste is passed through a dissolution subsystem (401) configured to partially dissolve the epoxy thermosetting material in an acid solution to form a thermoplastic mixture, and a devolatilization subsystem (402) configured to remove the acid solution from the acid thermoplastic mixture to obtain a reusable thermoplastic component containing a reinforcing matrix component. The devolatilization subsystem may include an extruder, a drop membrane evaporator, a distillation apparatus, or a combination thereof, as shown in this embodiment.

[0041] Figure 5a shows graph data illustrating the time-dependent effects of different concentrations of acetic acid on the reuse of epoxy waste at 60°C. Figure 5b shows graph data illustrating the time-dependent effects of different concentrations of acetic acid on the reuse of epoxy waste at 80°C. Figure 5c shows graph data illustrating the time-dependent effects of different concentrations of acetic acid on the reuse of epoxy waste at 100°C. Higher concentrations of acetic acid result in faster reuse at 60°C, 80°C, and 100°C. At the boiling point (100°C), there is a dramatic effect on the reuse rate. At the boiling point (100°C), 12.5% ​​acetic acid is completely reused in 2 hours. With higher concentrations of acetic acid, the reuse time decreases as the temperature rises; for 50% acetic acid, it takes about 8 hours at 60°C (not shown), but at 80°C (Figure 5b), reuse is completed in just 2 hours. In any chemical process, the rate increases as the temperature rises. On the other hand, with low concentrations of acetic acid, reuse is very slow (for example, at 60°C and 10% acetic acid, only 20% of the weight is reused in 6 hours), or it doesn't progress at all (for example, with 5% acetic acid, it doesn't progress in 3 hours). Surprisingly, however, at 100°C, 10% acetic acid is reused in just 3 hours, and 5% acetic acid is half reused. Thus, temperature and acetic acid concentration were optimized to shorten reuse time while using low concentrations of acetic acid. With concentrations of 25%, 50%, and higher, the viscosity of the solution increases during reuse. With 10-15% acetic acid, the resin solution does not become too viscous and can be used for subsequent reuse.

[0042] The epoxy industry faces sustainability concerns, particularly regarding the management of waste from spent epoxy composite materials. Furthermore, significant value loss occurs due to unrecoverable manufacturing waste. The reuse process of this invention is an industrially feasible and scalable reuse and recovery process that addresses these concerns. While various acids can be used, the use of inexpensive, weak acids such as acetic acid and lactic acid at high temperatures for this purpose constitutes an industrially suitable process.

[0043] The present invention provides an industrially viable recycling process for reusable epoxy thermosetting materials containing cleavable bonds, the process using an acid solution to dissolve the epoxy thermosetting material and defoliating the acid solution from the thermoplastic acid mixture to produce a thermoplastic component. The process is environmentally and economically advantageous, allowing for the efficient recovery of the thermoplastic component and optionally a reinforcing matrix component, both of which can be reused for further use.

[0044] Although the present invention has been described in relation to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the scope of the invention as defined in the following claims.

Claims

1. A method for reusing an epoxy thermosetting material containing at least one reusable component, i. To form a thermoplastic mixture, the step of dissolving the epoxy thermosetting substance in an acid solution under heating conditions of 50 to 110°C, ii. A step of filtering the thermoplastic mixture in order to separate the reinforcing matrix component from the thermoplastic solution, iii. In order to obtain a reusable thermoplastic component, the steps include defoliating the thermoplastic solution to remove the acid solution, Includes, The epoxy thermosetting material is Diepoxy resin, and a reusable acid-unstable curing agent which is an amine-based curing agent, a thiol-based curing agent, a polyamino compound, another acid-unstable curing agent, or a combination thereof, Prepared from a reusable epoxy resin containing acid-degradable acetal, ketal, orthocarbonate, orthoester, orthosilicate, or silane bond, and a curing agent. The acid solution is prepared by a method comprising acetic acid at a concentration of 5-70% and lactic acid at a concentration of 20-80%.

2. The method according to claim 1, wherein the filtration includes separation of components by centrifugal separation, manual sorting, optical sorting, or a combination thereof.

3. The method according to claim 1, wherein the acid solution contains a solvent selected from water, butanol, isopropanol, propanol, ethanol, methanol, benzyl alcohol, ethylene glycol, dichloromethane, tetrahydrofuran, ethyl acetate, acetone, dimethylformamide, acetonitrile, dimethyl sulfoxide, nitromethane, propylene carbonate, pentane, hexane, cyclohexane, benzene, toluene, xylene, dioxane, glyme, polyether, diethyl ether, other nonpolar solvents, other polar aprotic solvents, other polar protic solvents, and combinations thereof.

4. The method according to claim 1 or 3, wherein the removed acid solution, the solvent contained in the acid solution, or both are reused in the method.

5. The method according to claim 1, wherein the reinforcing matrix component comprises glass fiber, carbon fiber, aramid fiber, jute, grass, bamboo, pine, balsa, other natural fibers, and combinations thereof, and is reusable.

6. A system for reusing an epoxy thermosetting material comprising at least one reusable component, according to the method of claim 1, i. A dissolution subsystem configured to dissolve the epoxy thermosetting substance in an acid solution under heating conditions in order to form a thermoplastic mixture, ii. A filtration subsystem configured to filter the thermoplastic mixture in order to separate the reinforcing matrix components from the thermoplastic solution, iii. A system comprising a defoliation subsystem configured to remove the acid solution from the thermoplastic solution in order to obtain a reusable thermoplastic component, the defoliation subsystem including an extruder, a fall membrane evaporator, a distillation unit, or a combination thereof.

7. The system according to claim 6, wherein the defoliation subsystem is configured to remove the solvent from the thermoplastic solution.

8. The system according to claim 6 or 7, wherein the system is configured to be continuous or batch-based, and is configured to reuse the removed acid solution, the solvent contained in the acid solution, or both in the method.

9. A method for reusing epoxy thermosetting materials containing reusable components, i. To form a thermoplastic mixture, the epoxy thermosetting material is dissolved in an acid solution, and the epoxy thermosetting material is dissolved at least partially, ii. To obtain a reusable thermoplastic component containing a reinforcing matrix component, the steps include defoliating the thermoplastic mixture and removing the acid solution, Includes, The epoxy thermosetting material is Diepoxy resin, and a reusable acid-unstable curing agent which is an amine-based curing agent, a thiol-based curing agent, a polyamino compound, another acid-unstable curing agent, or a combination thereof, A method for preparing a reusable epoxy resin containing an acid-degradable acetal, ketal, orthocarbonate, orthoester, orthosilicate, or silane bond, and a curing agent.

10. The method according to claim 9, wherein the epoxy thermosetting substance is reduced in size before being dissolved in the acid solution.

11. The method according to claim 9, wherein the immersion of the epoxy thermosetting substance in the acid solution is carried out under heating conditions of 50°C to 110°C.

12. The method according to claim 9, wherein the acid solution is acetic acid, lactic acid, propionic acid, other aliphatic acid, other organic acid, sulfuric acid, phosphoric acid, other inorganic acid, or a combination thereof, the concentration of acetic acid is 5 to 70%, the concentration of lactic acid is 20 to 80%, the concentration of sulfuric acid is 1 to 10%, and the concentration of phosphoric acid is 20 to 90%.

13. The method according to claim 9, wherein the acid solution contains a solvent selected from water, butanol, isopropanol, propanol, ethanol, methanol, benzyl alcohol, ethylene glycol, dichloromethane, tetrahydrofuran, ethyl acetate, acetone, dimethylformamide, acetonitrile, dimethyl sulfoxide, nitromethane, propylene carbonate, pentane, hexane, cyclohexane, benzene, toluene, xylene, dioxane, glyme, polyether, diethyl ether, other nonpolar solvents, other polar aprotic solvents, other polar protic solvents, and combinations thereof.

14. The method according to claim 9 or 13, wherein the removed acid solution, the solvent contained in the acid solution, or both are reused in the method.

15. A system for reusing epoxy thermosetting material containing reusable components, according to the method of claim 9, i. A dissolution subsystem configured to dissolve the epoxy thermosetting substance in an acid solution in order to form a thermoplastic mixture, ii. A system comprising a defoliation subsystem configured to remove the acid solution from the thermoplastic mixture in order to obtain a reusable thermoplastic component containing a reinforcing matrix component, the defoliation subsystem including an extruder, a fall membrane evaporator, a distillation unit, or a combination thereof.

16. The system according to claim 15, wherein the defoliation subsystem is configured to remove the solvent from the thermoplastic mixture.

17. The system according to claim 15 or 16, wherein the system is configured to be continuous or batch-based and to reuse the removed acid solution, the solvent contained in the acid solution, or both in the process.

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