Method and apparatus for decomposition and recycling of thermosetting resin composites, compositions for use therein

Abstract

A method and apparatus for decomposing and recycling thermosetting resin composite materials, as well as compositions and kits for use therein, are disclosed. The method includes: a pretreatment step of placing the thermosetting resin composite material in an aqueous formic acid solution or an aqueous hydrogen peroxide solution; and a main treatment step of placing the pretreated thermosetting resin composite material in an aqueous hydrogen peroxide solution or an aqueous formic acid solution, wherein the aqueous solutions used in the pretreatment and main treatment are different. Accordingly, unlike conventional chemical decomposition methods, the decomposition reaction time can be significantly shortened under low temperature and normal pressure conditions. This improves the difficulty of constructing mass production equipment due to chemical solution odors and material corrosion, and maintains reaction performance even when the concentration of the chemical solution is reduced, thereby significantly increasing the number of times the solution can be used. Therefore, production costs can be significantly reduced.

Description

Technical Field

[0001] This specification relates to a method and apparatus for decomposing and recycling thermosetting resin composite materials, and an aqueous solution composition therein. Specifically, it relates to a method and apparatus for decomposing and recycling thermosetting resin composite materials impregnated and cured in carbon fibers, and an aqueous solution composition therein, which can be effectively decomposed and recycled using a chemical reaction based on an environmentally friendly aqueous solution.

[0002] [National R&D projects supporting this invention]

[0003] [Project Unique Number] 1415160950

[0004] [Project Number] 20183010025470

[0005] [Department Name] Ministry of Trade, Industry and Energy

[0006] [Name of Project Management (Specialty) Organization] Korea Energy Technology Evaluation and Planning Institute

[0007] [Research Project Title] Development of Core Technologies for New Renewable Energy (R&D)

[0008] [Research Project Title] Developing Composite Blade Fibers for Wind Power Generation Using Chemical Decomposition Method Organic Materials / High Value-Added Technology Development and Waste Reuse Standards Development

[0009] [Contribution Rate] 1 / 4

[0010] [Project Implementing Institution] Korea Institute of Science and Technology

[0011] [Research Period] October 1, 2018 ~ March 31, 2019

[0012] [National R&D projects supporting this invention]

[0013] [Project Unique Number] 1415163320

[0014] [Project Number] 20183010025470

[0015] [Department Name] Ministry of Trade, Industry and Energy

[0016] [Name of Project Management (Specialty) Organization] Korea Energy Technology Evaluation and Planning Institute

[0017] [Research Project Title] Development of Core Technologies for New Renewable Energy (R&D)

[0018] [Research Project Title] Developing Composite Blade Fibers for Wind Power Generation Using Chemical Decomposition Method Organic Materials / High Value-Added Technology Development and Waste Reuse Standards Development

[0019] [Contribution Rate] 1 / 4

[0020] [Project Implementing Institution] Korea Institute of Science and Technology

[0021] [Research Period] April 1, 2019 ~ December 31, 2019

[0022] [National R&D projects supporting this invention]

[0023] [Project Unique Number] 1415166564

[0024] [Project Number] 20183010025470

[0025] [Department Name] Ministry of Trade, Industry and Energy

[0026] [Name of Project Management (Specialty) Organization] Korea Energy Technology Evaluation and Planning Institute

[0027] [Research Project Title] Development of Core Technologies for New Renewable Energy (R&D)

[0028] [Research Project Title] Developing Composite Blade Fibers for Wind Power Generation Using Chemical Decomposition Method Organic Materials / High Value-Added Technology Development and Waste Reuse Standards Development

[0029] [Contribution Rate] 1 / 4

[0030] [Project Implementing Institution] Korea Institute of Science and Technology

[0031] [Research Period] January 1, 2020 ~ December 31, 2020

[0032] [National R&D projects supporting this invention]

[0033] [Project Unique Number] 1415169648

[0034] [Project Number] 20012817

[0035] [Department Name] Ministry of Trade, Industry and Energy

[0036] [Project Management (Specialty) Organization Name] Korea Institute for Industrial Technology Evaluation

[0037] [Research Project Title] Materials and Components Technology Development (R&D)

[0038] [Research Topic Title] Development of Functional Component Manufacturing Technology to Reduce Development Costs by More Than 15% Through Upgrading and Remanufacturing Carbon Fiber and Intermediate Materials

[0039] [Contribution Rate] 1 / 4

[0040] [Name of the organization conducting the project] Envioneer Co., Ltd.

[0041] [Research Period] August 1, 2020 ~ February 28, 2021 Background Technology

[0042] Thermosetting resins are commonly used in composite materials, such as carbon fiber reinforced plastic (CFRP) and glass fiber reinforced plastic (GFRP). The use of these composite materials is gradually increasing across the entire industrial sector, including the automotive, aerospace, and new energy industries. Especially with the rapid popularization of environmentally friendly vehicles and the accompanying demand for lightweighting, their usage is expected to increase further, thus making their decomposition and recycling increasingly necessary.

[0043] However, due to their properties, thermosetting resins, once cured, are not easily soluble in solvents unless heated, making them difficult to recycle. Representative thermosetting resins include polyurethane and epoxy resins.

[0044] In the past, the main methods for processing these thermosetting resin composites were thermal decomposition and chemical decomposition.

[0045] The aforementioned thermal decomposition method has been used, or is still being used, by Japanese companies such as Toray and Teijin, or by companies such as Adherent Technology (USA), Procotex (France), and ELG Carbon Fibre (UK). However, the thermal decomposition process requires temperatures above 500°C and is not environmentally friendly, as it can produce substances harmful to human health. Therefore, the use of the thermal decomposition process is gradually decreasing.

[0046] On the one hand, chemical decomposition uses organic solvent-based methods or special processes such as supercritical or semi-critical process conditions.

[0047] However, organic solvent-based methods still have environmental problems. Furthermore, these organic solvent-based treatment solutions themselves use expensive solutions (e.g., benzyl alcohol), or their reuse is often restricted, leading to increased production costs.

[0048] In addition, under supercritical conditions and other circumstances, the process is carried out under high pressure, which presents the disadvantages of potential exposure to danger during operation and increased cost and uneconomicalness in equipping and maintaining safety equipment and devices.

[0049] In recent years, technologies have been developed that minimize the use of organic solvents and process the product under mild, water-centered conditions (Patent Document 1).

[0050] However, this chemical method has low actual decomposition efficiency and requires a long processing time, making it practically unusable in large-scale non-laboratory-level processing.

[0051] Furthermore, even under mild conditions, the chemical solutions used are difficult to handle, which has always limited their practical application. For example, the strong odor of the chemical solutions makes operation difficult, and despite the installation of dust collectors, scrubbers, and other equipment in production facilities, complaints from neighboring companies still arise. These practical problems hinder the application of this technology.

[0052] Furthermore, when constructing reactors, pumps, pipelines, valves, and other facilities or instrument control devices, there are problems such as the use of expensive materials (e.g., titanium) to prevent corrosion, or the need for frequent replacement of the equipment or instrument control devices.

[0053] To this end, the inventors conducted in-depth research on a decomposition method based on aqueous solutions excluding organic solvents. This method can decompose under mild conditions, has high decomposition efficiency, can be applied to large-scale processing facilities, and has good processability and usability due to the absence of toxic odors, corrosion problems, and minimal need to replace related equipment. This led to the completion of the present invention.

[0054] [Preliminary Technology Documents]

[0055] [Patent Literature]

[0056] (Patent Document 1) Korean Patent No. 1861095. Summary of the Invention

[0057] Technical issues

[0058] In an exemplary embodiment of the present invention, one aspect provides a method and apparatus for the decomposition and recycling of thermosetting resin composite materials, a composition therein, and a kit containing the same, which are based on an aqueous solution without the use of organic solvents, and can be decomposed under mild conditions at low temperature and normal pressure with high decomposition efficiency, and can also be applied to large-scale processing facilities.

[0059] In an exemplary embodiment of the present invention, on the other hand, a method and apparatus for the decomposition and recycling of thermosetting resin composite materials, a composition therein, and a kit containing the thereof are provided, which can significantly improve handling and corrosion problems and greatly increase the chemical reaction rate compared to the past, thereby improving productivity.

[0060] In an exemplary embodiment of the present invention, on the other hand, a method and apparatus for decomposing and recycling a thermosetting resin composite material, a composition therein, and a kit containing the same are provided. The aqueous solution used in the decomposition treatment of the thermosetting resin composite material has good reusability and is easy to process and control.

[0061] Technical solution

[0062] In an exemplary embodiment of the present invention, a method for decomposing a thermosetting resin composite material is provided. The decomposition method includes: a step of pretreating the thermosetting resin composite material in an aqueous formic acid solution or an aqueous hydrogen peroxide solution; and a step of performing a main treatment by placing the pretreated thermosetting resin composite material in an aqueous hydrogen peroxide solution or an aqueous formic acid solution, wherein the aqueous solutions used in the pretreatment and the main treatment are different.

[0063] In addition, in an exemplary embodiment of the present invention, a decomposition apparatus for a thermosetting resin composite material is provided, comprising: a pre-impregnation group for pre-impregnating the thermosetting resin composite material in a formic acid solution or a hydrogen peroxide aqueous solution; a pretreatment group connected to the pre-impregnation group for transporting the thermosetting resin composite material obtained from the pre-impregnation group and carrying the formic acid aqueous solution or the hydrogen peroxide aqueous solution; and a main treatment group connected to the pretreatment group for transporting the thermosetting resin composite material obtained from the pretreatment group and carrying the hydrogen peroxide aqueous solution or the formic acid aqueous solution, wherein the aqueous solutions carried in the pretreatment group and the main treatment group are different.

[0064] In addition, in an exemplary embodiment of the present invention, a decomposition kit for thermosetting resin composite materials is provided, comprising: a pre-impregnation composition containing a formic acid solution or a hydrogen peroxide solution; a pretreatment composition containing an aqueous formic acid solution or an aqueous hydrogen peroxide solution; and a main treatment composition containing an aqueous hydrogen peroxide solution or an aqueous formic acid solution, wherein the aqueous solutions of the pretreatment composition and the main treatment composition are different.

[0065] In addition, in an exemplary embodiment of the present invention, a decomposition composition for a thermosetting resin composite material is provided, wherein an aqueous solution of hydrogen peroxide or an aqueous solution of formic acid is preferably provided, with 0.1 to 2 wt% or less of a free radical initiator added to the aqueous solution of hydrogen peroxide.

[0066] Invention Effects

[0067] According to an exemplary embodiment of the present invention, unlike conventional chemical decomposition methods, the decomposition reaction time can be significantly shortened under mild conditions of low temperature and normal pressure. Simultaneously, it can alleviate the difficulties in constructing mass production equipment caused by chemical solution odors and material corrosion. Even with reduced chemical solution concentration, reaction performance can be maintained, thereby significantly increasing the number of times the solution can be used. Furthermore, the aqueous solution used in the decomposition treatment of thermosetting resin composites has good reusability, and the processing technology and conditions are easy to control. Accordingly, production costs can be significantly reduced. Attached Figure Description

[0068] Figure 1 A table showing the results of comparing the corrosivity of the alternative solutions used in exemplary embodiments of the present invention with that of existing solutions.

[0069] Figures 2a-2b This photo shows the results of increasing the reaction rate when using a substitute solution in Experiment 1.

[0070] Figures 3a-3g These are CFRP images before and after decomposition in Experiment 2 of this paper.

[0071] Figures 4a-4h These are CFRP images before and after decomposition in Experiment 3 of this paper.

[0072] Figure 5 This shows the results of shortening the decomposition time based on pre-impregnation in Experiment 4 of this paper.

[0073] Figure 6 This diagram shows the concentration and pH changes of the solution (D solution) used in an exemplary embodiment of the present invention with or without the addition of buffer solution, as a result of heating (90°C) time.

[0074] Figure 7 A graph showing the results of repeated decomposition (heating temperature 90°C, reaction time approximately 5 hours each time) of the solution (solution D) used in an exemplary embodiment of the present invention, with the addition of a buffer solution to adjust the concentration. Detailed Implementation

[0075] Terminology Definition

[0076] In this specification, thermosetting resin composite materials refer to various composite materials that include thermosetting resins. For example, epoxy resin composite materials may include cured epoxy resins and various filler materials such as carbon fibers.

[0077] In this specification, recycling refers to the process of chemically treating and decomposing thermosetting resin composite materials.

[0078] The term "decomposition" as used in this specification and especially in the claims means, in addition to the meaning of decomposition itself, that it may also include decomposition and the recycling (reuse) of the decomposition.

[0079] In this specification, decomposition and recycling is defined as including one or more of the decomposition and recycling processes.

[0080] In this specification, pre-impregnation refers to impregnation for a certain period of time at atmospheric pressure and at a temperature that is not considered a substantial heat treatment. The temperature that is not considered a substantial heat treatment can be any temperature without heating or a temperature below 40°C that is not considered a substantial heat treatment, but is preferably room temperature. At this temperature and atmospheric pressure, the thermosetting resin composite material is placed in an aqueous solution such as formic acid or hydrogen peroxide for a certain period of time.

[0081] In this specification, pretreatment refers to placing the thermosetting resin composite material in an aqueous solution such as formic acid or hydrogen peroxide at normal pressure and a temperature of 80°C-120°C, preferably heated to 100°C below the boiling point of water, for a certain period of time.

[0082] In this specification, the main treatment refers to placing the pretreated thermosetting resin composite material in an aqueous solution such as formic acid or hydrogen peroxide at normal pressure and a temperature of 80°C-120°C, preferably heated to 100°C below the boiling point of water, for a certain period of time.

[0083] In this instruction manual, solution A refers to an aqueous solution of acetic acid.

[0084] In this instruction manual, solution B refers to an aqueous solution of sodium hypochlorite.

[0085] In this instruction manual, solution C is an aqueous solution of formic acid.

[0086] In this instruction manual, solution D refers to an aqueous solution of hydrogen peroxide.

[0087] In this specification, a free radical initiator refers to a substance that can generate free radical species and promote free radical reactions under mild conditions, and is further added to the formic acid aqueous solution and / or hydrogen peroxide aqueous solution used in the pre-impregnation, pretreatment and / or main treatment processes in exemplary embodiments of the present invention.

[0088] In this specification, the reusability of aqueous solutions refers to the property that the aqueous solutions used in each of the pre-impregnation, pretreatment, and main treatment processes can be reused in the same process.

[0089] In this instruction manual, concentration is expressed as a percentage of the weight of the added substance in the total mass of the solution.

[0090] Exemplary examples and specific examples

[0091] The following describes in detail exemplary examples of the present invention.

[0092] The inventors recognized that existing chemical decomposition methods for thermosetting resin composites suffer from harsh process conditions, chemical solution handling issues, corrosion problems, and increased chemical solution costs. Through in-depth research and continuous improvement efforts, the inventors completed this invention.

[0093] As mentioned above, recent methods for the chemical recycling of carbon fiber composites, such as pretreatment with an aqueous acetic acid solution followed by sequential treatment with an aqueous solution containing sodium hypochlorite to decompose the thermosetting resin and then recovering the carbon fibers remaining in the solution, have significant problems in practical applications.

[0094] In other words, the above method is severely limited in terms of handling solutions and setting up reaction equipment because acetic acid (more precisely, glacial acetic acid) is highly corrosive and has a strong odor. Sodium hypochlorite is even more corrosive, and even chemically resistant alloys such as SUS316 will cause rapid corrosion, making it very difficult to set up reaction equipment.

[0095] Accordingly, in an exemplary embodiment of the present invention, in order to improve the above-mentioned problems of processability and corrosivity while obtaining high decomposition efficiency, a stepwise decomposition process of pretreatment and main treatment is performed while using alternative solutions (formic acid aqueous solution and hydrogen peroxide aqueous solution), and a pre-impregnation process is further performed before pretreatment.

[0096] For example, formic acid aqueous solution or hydrogen peroxide aqueous solution can be used instead of acetic acid for pretreatment, and hydrogen peroxide aqueous solution or formic acid aqueous solution can be used instead of sodium hypochlorite for main treatment. From the perspectives of reusability, mass production, reaction regulation, and decomposition efficiency, the compositions of the aqueous solutions used in the pretreatment and main treatment differ.

[0097] Therefore, the processability and corrosivity are significantly improved, as described below, and the chemical reaction rate is also significantly increased compared to existing methods, thereby increasing the decomposition rate and ultimately improving productivity. Furthermore, the improved reusability also enhances the capacity for large-scale production.

[0098] Figure 1 A table showing the results of comparing the corrosivity of the alternative solutions used in the exemplary embodiments of the present invention with that of the existing solutions.

[0099] like Figure 1As shown, acetic acid or sodium hypochlorite, as existing solutions, cause corrosion problems to SUS304 and SUS316 alloys with increasing number of reactions. However, formic acid and hydrogen peroxide used in the exemplary embodiments of the present invention do not cause corrosion problems and are effective. The reaction temperature can also be processed more quickly at 100°C below the boiling point of water.

[0100] The performance and cost of the pretreatment solution (solution C: aqueous formic acid) and the main treatment solution (solution D: aqueous hydrogen peroxide) in the exemplary embodiments of the present invention are compared with those of the existing pretreatment solution (solution A: aqueous acetic acid) and the main treatment solution (solution B: aqueous sodium hypochlorite), as shown in the following table of corrosion results.

[0101] Table 1

[0102] As described above, in an exemplary embodiment of the present invention, when the alternative solutions (aqueous formic acid and aqueous hydrogen peroxide) are used, the corrosivity is reduced compared to the original, the materials constituting the reaction equipment are easier to select, and as described below, the decomposition efficiency is good, even thermosetting resin composites that are difficult to decompose can be easily decomposed.

[0103] On the one hand, in an exemplary specific example, pre-impregnating the composite material in an aqueous formic acid solution or an aqueous hydrogen peroxide solution (within approximately 10 hours) before immersing it in the decomposition reaction can further shorten the pretreatment and main treatment reaction time.

[0104] Specifically, in an exemplary embodiment of the present invention, the method for recycling thermosetting resin composite materials includes: a pretreatment step of placing the thermosetting resin composite material in a formic acid solution or a hydrogen peroxide solution; and a main treatment step of placing the pretreated thermosetting resin composite material in a hydrogen peroxide solution or a formic acid solution. As mentioned above, the pretreatment solution and the main treatment solution are different solutions.

[0105] In an exemplary specific example, depending on the type of thermosetting resin composite material to be decomposed, the preimpregnation is carried out at room temperature and pressure for 17 hours or less, preferably 10 hours or less. For example, it can be carried out for more than 0 hours and less than 10 hours, 1 to 9 hours, 2 to 8 hours, 3 to 7 hours, or 4 to 6 hours. In a non-limiting example, the preimpregnation can be carried out at room temperature and pressure for less than 10 hours, less than 9 hours, less than 8 hours, less than 7 hours, less than 6 hours, less than 5 hours, less than 4 hours, less than 3 hours, less than 2 hours, or less than 1 hour. Furthermore, the preimpregnation can be carried out for more than 0 hours, more than 1 hour, more than 2 hours, more than 3 hours, more than 4 hours, more than 5 hours, more than 6 hours, more than 7 hours, more than 8 hours, or more than 9 hours.

[0106] In an exemplary embodiment, the pretreatment can be performed at atmospheric pressure and 80~120°C, preferably 80°C to less than 100°C, 85~95°C, or 90°C for 1~6 hours.

[0107] In a non-limiting example, the pretreatment temperature may be above 80°C, above 85°C, above 90°C, or above 95°C, or below 120°C, below 115°C, below 110°C, or below 105°C, preferably below 100°C, below 95°C, below 90°C, or below 85°C.

[0108] In a non-limiting example, the preprocessing time can be more than 1 hour, more than 1.5 hours, more than 2 hours, more than 2.5 hours, more than 3 hours, more than 3.5 hours, more than 4 hours, more than 4.5 hours, more than 5 hours, or more than 5.5 hours, or less than 6 hours, less than 5.5 hours, less than 5 hours, less than 4.5 hours, less than 4 hours, less than 3.5 hours, less than 3 hours, less than 2.5 hours, less than 2 hours, or less than 1.5 hours.

[0109] In an exemplary specific example, the main treatment can be carried out at atmospheric pressure and 80~120℃, preferably 80℃~less than 100℃, 85~95℃, or 90℃ for 1~3 hours.

[0110] In a non-limiting example, the main processing temperature can be above 80°C, above 85°C, above 90°C, or above 95°C, or below 120°C, below 115°C, below 110°C, or below 105°C, and preferably below 100°C, below 95°C, below 90°C, or below 85°C.

[0111] In a non-limiting example, the main processing time can be more than 1 hour, more than 1.5 hours, more than 2 hours, or more than 2.5 hours, or less than 3 hours, less than 2.5 hours, less than 2 hours, or less than 1.5 hours.

[0112] In an exemplary specific example, the concentration of formic acid in the formic acid aqueous solution can be more than 50% and less than 100%, but from an environmental point of view, it is preferred to be less than 90% or less than 85%, and from a reactivity point of view, it is preferred to use more than 50%.

[0113] In non-limiting examples, the concentration of formic acid can be, for example, 50-90%. For example, it can be less than 90%, less than 85%, less than 80%, less than 75%, less than 70%, less than 65%, less than 60%, less than 55%, and it can be more than 50%, more than 55%, more than 60%, more than 65%, more than 70%, more than 75%, more than 80%, or more than 85%.

[0114] In an exemplary specific example, the concentration of hydrogen peroxide in the aqueous solution can be above 20% and below 50%, but from an environmental perspective, it is preferable to use less than 35%, and from a reactivity perspective, it is preferable to use more than 30%. Concentrations exceeding 50% pose an explosion hazard.

[0115] In non-limiting examples, hydrogen peroxide concentrations may be below 34.5%, below 34%, below 33.5%, below 33%, below 32.5%, below 32%, below 31.5%, below 31%, and below 30.5%.

[0116] In non-limiting examples, hydrogen peroxide concentrations may be 30% or more, 30.5% or more, 31% or more, 31.5% or more, 32% or more, 32.5% or more, 33% or more, 33.5% or more, or 34% or more.

[0117] On the one hand, as can be confirmed in the experimental examples below, in aqueous solution-based decomposition, it has been established that using specific solutions in a specific sequence during pre-impregnation, pretreatment, and main treatment can lead to significant differences in actual decomposition efficiency. Although the reasons are not yet clear, it is believed that in the case of aqueous solutions, the types of chemicals used in each of the pre-impregnation, pretreatment, and main treatment processes affect the decomposition mechanism and efficiency.

[0118] Furthermore, by altering the processing sequence of the formic acid aqueous solution and hydrogen peroxide aqueous solution according to the type of thermosetting resin composite material to be decomposed and recycled, the reaction can be carried out more effectively.

[0119] For example, in cases where the decomposition of CFRP, which makes up an aircraft fuselage, is very difficult, in addition to adding the free radical initiator described below, it is preferable to use a decomposition sequence with relatively high efficiency.

[0120] On the one hand, in more than one of the aforementioned pre-impregnation, pretreatment, and main treatment processes, especially in more than one of the pretreatment and main treatment processes, the decomposition efficiency can increase dramatically, for example, by more than 10%, if used with a trace amount of free radical initiator. Considering that it is difficult to improve decomposition efficiency by simply adding a trace amount of free radical initiator in the chemical decomposition process of thermosetting resin composites while keeping other conditions constant, it is surprising that the decomposition efficiency can be improved by about 10%.

[0121] Although the mechanism has not been clearly elucidated, it is believed that during the pre-impregnation, pretreatment and / or main treatment using C solution and / or D solution, the free radical initiator participates in the free radical reaction during the decomposition of thermosetting resin composites, thereby improving the decomposition efficiency.

[0122] In one exemplary embodiment, from the perspective of improving decomposition efficiency, the free radical initiator is preferably an azo compound or an organic peroxide, etc.

[0123] As a non-limiting example, the azo compound that serves as a free radical initiator can be azobisisobutyronitrile (AIBN).

[0124] As a non-limiting example, the organic peroxide that serves as a free radical initiator can be benzoyl peroxide (BPO), dilauryl peroxide, dilauryl peroxide, etc.

[0125] In one exemplary embodiment, from the perspective of decomposition efficiency, it is preferable to add 0.01 to 2 wt% of a free radical initiator to the formic acid aqueous solution or hydrogen peroxide aqueous solution. When an excess of more than 2 wt% is used, problems may arise due to excessive reactivity, making the chemical reaction difficult to control.

[0126] In one exemplary embodiment, the decomposition process sequence of the decomposition method for the thermosetting resin composite material may include: a step of pre-impregnating the thermosetting resin composite material in an aqueous formic acid solution; a step of pre-treating the pre-impregnated thermosetting resin composite material in an aqueous hydrogen peroxide solution with added free radical initiators; and a step of pre-treating the pre-treated thermosetting resin composite material in an aqueous formic acid solution.

[0127] In one exemplary embodiment, the decomposition process sequence of the decomposition method for the thermosetting resin composite material may include: a step of pre-impregnating the thermosetting resin composite material in an aqueous formic acid solution; a step of pre-treating the pre-impregnated thermosetting resin composite material in an aqueous hydrogen peroxide solution; and a step of pre-treating the pre-treated thermosetting resin composite material in an aqueous formic acid solution with added free radical initiators.

[0128] In one exemplary embodiment, the decomposition process sequence of the decomposition method for the thermosetting resin composite material may include: a step of pre-impregnating the thermosetting resin composite material in an aqueous hydrogen peroxide solution; a step of pre-treating the pre-impregnated thermosetting resin composite material by placing it in an aqueous hydrogen peroxide solution with added free radical initiators; and a step of pre-treating the pre-treated thermosetting resin composite material by placing it in an aqueous formic acid solution.

[0129] In one exemplary embodiment, the decomposition process sequence of the decomposition method for the thermosetting resin composite material may include: a step of pre-impregnating the thermosetting resin composite material in an aqueous hydrogen peroxide solution; a step of pre-treating the pre-impregnated thermosetting resin composite material in an aqueous hydrogen peroxide solution; and a step of pre-treating the pre-treated thermosetting resin composite material in an aqueous formic acid solution with added free radical initiators.

[0130] In one exemplary embodiment, the decomposition process sequence of the decomposition method for the thermosetting resin composite material may include: pre-impregnating the thermosetting resin composite material in an aqueous hydrogen peroxide solution; pre-treating the pre-impregnated thermosetting resin composite material by placing it in an aqueous formic acid solution with added free radical initiator; and pre-treating the pre-treated thermosetting resin composite material by placing it in an aqueous hydrogen peroxide solution.

[0131] In one exemplary embodiment, the decomposition process sequence of the decomposition method for the thermosetting resin composite material may include: a step of pre-impregnating the thermosetting resin composite material in an aqueous hydrogen peroxide solution; a step of pre-treating the pre-impregnated thermosetting resin composite material in an aqueous formic acid solution; and a step of pre-treating the pre-treated thermosetting resin composite material in an aqueous hydrogen peroxide solution with added free radical initiators.

[0132] On the one hand, in an exemplary specific example, in order to maintain the continuous decomposition characteristics, the concentration and / or pH of the hydrogen peroxide aqueous solution can be adjusted to maintain it within a certain range, and a buffer solution can be used to adjust the concentration and / or pH.

[0133] In a non-limiting example, during pretreatment or main treatment, as the reaction using an aqueous hydrogen peroxide solution proceeds, the concentration and pH fluctuate with a similar correlation. To compensate for this and maintain sustained decomposition characteristics, a buffer solution can be used. In this case, the buffer solution can be one or more of citric acid, tartaric acid, and phosphoric acid.

[0134] In a non-limiting example, the concentration of the hydrogen peroxide aqueous solution before decomposition treatment is preferably less than 35% and more than 30%.

[0135] In an exemplary specific example, the decomposition rate in the decomposition method of the thermosetting resin composite material can be determined by thermogravimetric analysis (TGA), which can confirm the decomposition rate of organic matter. The decomposition rate by thermogravimetric analysis can be 90% or more, 91% or more, 92% or more, 93% or more, 94% or more, 95% or more, 96% or more, 97% or more, particularly preferably 98% or more, 99% or more, and most preferably 100%.

[0136] The decomposition rate was determined by TGA analysis of the finally recovered (dried) carbon fibers (regenerated carbon fibers). It was believed that the closer the inorganic residue was to 0%, the closer the decomposition rate was to 100%.

[0137] On one hand, the apparatus for decomposing thermosetting resin composite materials in an exemplary embodiment of the present invention may include: a pretreatment section (or pretreatment zone) for pretreatment of the thermosetting resin composite material by immersing it in a formic acid solution or a hydrogen peroxide solution; and a main treatment section (or main treatment zone) for main treatment of the pretreated thermosetting resin composite material by immersing it in a hydrogen peroxide solution or a formic acid solution. The pretreatment solution and the main treatment solution are composed of different solutions.

[0138] In one exemplary embodiment, the apparatus may further include: a pre-impregnation portion (or pre-impregnation area) in which the pre-treated thermosetting resin composite material is pre-impregnated in a formic acid solution or a hydrogen peroxide solution.

[0139] Furthermore, in one exemplary embodiment, the apparatus for decomposing thermosetting resin composite materials may include: a pre-impregnation group that pre-impregnates the thermosetting resin composite material in a formic acid solution or an aqueous hydrogen peroxide solution; a pretreatment group, for example connected to the pre-impregnation group by a conveyor belt, for transporting the thermosetting resin composite material obtained from the pre-impregnation group, carrying the aqueous formic acid solution or the aqueous hydrogen peroxide solution; and a main treatment group, for example connected to the pretreatment group by a conveyor belt, for transporting the thermosetting resin composite material obtained from the pretreatment group, carrying the aqueous hydrogen peroxide solution or the aqueous formic acid solution.

[0140] On the one hand, in an exemplary embodiment of the present invention, a kit for the decomposition of thermosetting resin composite materials can be provided.

[0141] The kit includes: a pre-impregnation composition comprising a formic acid solution or a hydrogen peroxide solution; a pretreatment composition comprising an aqueous formic acid solution or an aqueous hydrogen peroxide solution; and a main treatment composition comprising an aqueous hydrogen peroxide solution or an aqueous formic acid solution. The aqueous solutions of the pretreatment composition and the main treatment composition have different compositions.

[0142] In one exemplary embodiment, the kit may further include a free radical initiator in an aqueous hydrogen peroxide solution or an aqueous formic acid solution, particularly preferably in an aqueous hydrogen peroxide solution. Preferably, 0.01 to 2 wt% or less of the free radical initiator is added to the aqueous hydrogen peroxide solution or the aqueous formic acid solution.

[0143] The following describes specific embodiments of the present invention in more detail, based on exemplary examples. However, the present invention is not limited to the following embodiments, and various types of embodiments can be implemented within the scope of the appended claims. It should be understood that the following embodiments are only provided to fully disclose the present invention and to facilitate easy implementation of the present invention by those skilled in the art.

[0144] [Experiment 1]

[0145] In Experiment 1, we observed whether the decomposition efficiency was improved when using alternative solutions C and D compared to the existing solutions A and B.

[0146] First, the raw materials used before decomposition are aircraft-grade CFRP waste (crushed products). For reference, Figure 2b The image shows a photograph of CFRP waste before decomposition.

[0147] The solutions used for decomposition were glacial acetic acid aqueous solution (solution A - 99.9%) and sodium hypochlorite aqueous solution (solution B - 12%). Formic acid aqueous solution (solution C - 80%) and hydrogen peroxide aqueous solution (solution D - 34.5%) were also used. The volume ratio of each of solutions A, B, C, and D to CFRP was 1:20.

[0148] For reference, in the pre-impregnation, pretreatment and main treatment, the solution volume ratio of the treated composite material is 1 (composite material volume): 10 (solution volume) or higher, for example, it can be 1 (composite material volume): 10 (solution volume) to 1 (composite material volume): 30 (solution volume), but from the perspective of reducing costs, it is preferable to have a lower solution volume ratio.

[0149] Figure 2b This is a photograph showing the results of improving the reaction rate when using a substitute solution in Experiment 1. Figure 2a For existing solutions, Figure 2b This is the solution used in this embodiment.

[0150] like Figures 2a-2b As shown, for the existing solution, even if the combined reaction time of the pretreatment (Step-1) and main treatment (Step-2) exceeds 10 hours, it is difficult to remove the reaction residue (see reference). Figure 2a In an exemplary embodiment of the present invention, the reaction residue can be easily removed within a total reaction time of 4 hours for the pretreatment (Step-1) and main treatment (Step-2) (see reference). Figure 2b ).

[0151] [Experiment 2]

[0152] In Experiment 2, based on the sequences using pretreatment solution C and main treatment solution D, the changes in decomposition efficiency were determined by altering the pre-impregnation decomposition sequence, changing the pretreatment and main treatment times, and further using a free radical initiator.

[0153] First, the raw material used before decomposition is aircraft-grade CFRP sheet. Its dimensions are 30×30×5mm (1g). For reference, Figure 3a This is a photograph of the CFRP board before disassembly.

[0154] The solutions used for decomposition were an aqueous solution of formic acid (C solution - 80%) and an aqueous solution of hydrogen peroxide (D solution - 34.5%). The volume ratio of each C solution and D solution relative to CFRP was 1:20.

[0155] Pre-impregnation was carried out for 17 hours at room temperature and pressure. Both pretreatment and main treatment were carried out at room temperature and 90°C.

[0156] The free radical initiator used is AIBN, at 1 wt% per part of aqueous solution.

[0157] Decomposition efficiency was determined using thermal decomposition analysis (TGA). For reference, a SCINCOTGA N-1000 analyzer was used for TGA analysis, with a temperature range of RT to 800°C, an EGA furnace, a heating rate of 10°C, and a nitrogen atmosphere. The TGA analysis method was the same in this experiment.

[0158] The sequences, presence or absence of free radical initiators, and decomposition rates of each embodiment in Experiment 2 are as follows: In each sequence, all conditions are the same except as shown below. The decomposition photographs of Examples 1 to 6 are shown below. Figures 3b to 3g .

[0159] Table 2

[0160] As can be seen from the above, under the same conditions as Comparative Examples 1 and 2, when further pre-impregnation with solution D is performed, the decomposition efficiency can be increased by about 10%.

[0161] Furthermore, in comparison Examples 1 and 3, when both the pretreatment time and the main treatment time were increased by 1 hour, the decomposition efficiency in the D->C->D sequence reached 100%. However, without pre-impregnation with solution D, even with increases in both the pretreatment and main treatment times of 1 hour, the decomposition efficiency remained as low as 81.8%. Therefore, it can be concluded that even with increased decomposition time in the C solution pretreatment and D solution main treatment sequences, pre-impregnation with solution D is the only way to benefit from increased decomposition time. For reference, increasing the decomposition time is not ideal from the perspective of efficiency and cost in the decomposition and recycling of thermosetting resin composites; therefore, high decomposition efficiency should be achieved while minimizing the decomposition time. From these perspectives, the sequence in Example 6 below shows remarkably impressive results.

[0162] In other words, compared to Example 1, Example 5 added a free radical initiator to the pretreatment solution, which increased the decomposition efficiency by about 2%. Conversely, compared to Example 1, Example 6 added a free radical initiator to the main treatment solution, which dramatically increased the decomposition efficiency to 100%.

[0163] These results indicate that the decomposition efficiency is significantly improved when performing the D->C->D process, especially when a free radical initiator is added to the D solution. This result is consistent with the finding in Experiment 3 below that the decomposition efficiency is higher when a free radical initiator is added to the D solution.

[0164] On the one hand, in Experiment 2, the difference between the addition of an initiator (AIBN) in the pre-impregnation was observed. The results showed that the sample sheet was more ductile when pre-impregnated with solution D and free radical initiator.

[0165] [Experiment 3]

[0166] In Experiment 3, based on the sequences using pretreatment solution D and main treatment solution C, the changes in decomposition efficiency when the pre-impregnation decomposition sequence was altered and when a free radical initiator was further used were determined.

[0167] First, the raw material used before decomposition is aircraft-grade CFRP sheet. Its dimensions are 30×30×5mm (1g). For reference, Figure 4a This is a photograph of the CFRP board before disassembly.

[0168] The solutions used for decomposition were an aqueous solution of formic acid (C solution - 80%) and an aqueous solution of hydrogen peroxide (D solution - 34.5%). The volume ratio of each C solution and D solution relative to CFRP was 1:20.

[0169] Pre-impregnation was carried out at room temperature and pressure, and both pretreatment and main treatment were carried out at room pressure and 90°C.

[0170] The free radical initiator used is AIBN, at 1 wt% per part of aqueous solution.

[0171] As in Experiment 2, the decomposition efficiency was determined using thermal decomposition analysis (TGA).

[0172] The sequences, addition or absence of free radical initiators, and decomposition rates of each embodiment in Experiment 3 are as follows: In each sequence, all other conditions are the same except as shown below.

[0173] Table 3

[0174] As can be seen from the above, adding free radical initiators to the pretreatment and main treatment of the decomposition reaction significantly increases the decomposition rate (by approximately 10%). For reference, for CFRP recycling, a decomposition rate of 95% or higher is preferred, and more preferably 98% or higher.

[0175] On the one hand, when a free radical initiator is added, higher decomposition efficiency is exhibited in specific sequences during the pre-impregnation and pretreatment decomposition reactions, as well as the main treatment decomposition reaction. That is, the decomposition efficiency of Example 3 (C->D+initiator->C) is higher than that of Example 5 (C->D->C+initiator).

[0176] Furthermore, Example 4 (D->D+initiator->C) significantly improved the decomposition efficiency of Example 6 (D->D->C+initiator).

[0177] As can be seen from the above, the addition of free radical initiators will improve the decomposition efficiency. However, especially when solution D is used as the pretreatment solution and solution C is used as the main treatment solution, the addition of free radical initiators in the pretreatment will further improve the overall decomposition efficiency.

[0178] Furthermore, as mentioned above, when solution D was used for pretreatment and solution C was used for the main treatment, especially in sequences where solution C was used for pre-impregnation, the highest decomposition efficiency of 99.7% was observed under the same conditions. For reference, Figures 4b to 4h These are photographs of the regenerated carbon fibers after decomposition according to Examples 1 to 6 of Experiment 2.

[0179] On the one hand, in this experiment, the difference between adding an initiator (AIBN) during pre-impregnation was also observed. The results showed that the difference in effect was negligible when pre-impregnating with solution C and adding a free radical initiator, but the sample was more ductile when pre-impregnating with solution D and adding a free radical initiator.

[0180] In conclusion, it is believed that the addition of free radical initiators to solution D has a greater enhancing effect.

[0181] [Experiment 4]

[0182] On the one hand, by changing the decomposition sequence according to the shape of the raw material (waste CFRP), the reaction can be carried out more effectively. Before putting the raw material into the decomposition reaction, the pretreatment and main treatment reaction time can be further shortened by pre-impregnating it in C solution or D solution (at room temperature and pressure, 17 hours in Experiment 4).

[0183] In Experiment 4, the CFRP of the hydrogen tank was directly decomposed without being crushed after cutting. First, it was pre-impregnated in formic acid aqueous solution at room temperature for 17 hours. Then, it was pretreated in hydrogen peroxide aqueous solution for 4 hours.

[0184] Furthermore, after pretreatment, it is placed in a formic acid aqueous solution for 1 hour to decompose, and the treatment is completed.

[0185] The solutions used were formic acid aqueous solution (C solution - 80%) and hydrogen peroxide aqueous solution (D solution - 34.5%). The volume ratio of each C solution and D solution relative to CFRP was 1:20.

[0186] Both pretreatment and main treatment were carried out at atmospheric pressure and 90°C.

[0187] Figure 5 This is based on the results of pre-impregnation in Experiment 4 of this paper, which shortened the decomposition time. Figure 5 The upper right photo shows the pre-impregnation stage. Figure 5 The top left image shows the product before pre-impregnation. TGA analysis confirmed that no organic matter remained after pre-impregnation, while 20% organic matter remained before pre-impregnation.

[0188] [Experiment 5]

[0189] In Experiment 5, a buffer solution (pH=2.45) of 1.17% was initially added to compensate for the pH, thereby maintaining the concentration at a certain level to preserve its decomposition characteristics.

[0190] The buffer solution was prepared by dissolving 0.21g of citric acid, 0.8g of tartaric acid, and 0.5g of phosphoric acid in 100ml of water, diluting the solution to a total volume of 900ml, and stirring once more. The pH of the buffer solution was 2.45. Then, this buffer solution was mixed with solution D, and the solution was added until the pH reached 1.165.

[0191] Figure 6 This diagram shows the concentration and pH changes of the solution (D solution) used in an exemplary embodiment of the present invention with or without the addition of buffer solution, as a result of heating (90°C) time.

[0192] Figure 7The graph shows the results of repeated decomposition of the solution (solution D) used in the exemplary embodiment of the present invention, with the addition of a buffer solution to adjust the concentration and the reaction time being approximately 5 hours each time.

[0193] Depend on Figure 7 It is understood that the solution of the exemplary embodiment of the present invention can be repeatedly decomposed, and the aqueous solution has good reusability and can be repeated 7 times.

[0194] Figure 7 The residual rate is the organic matter residual rate based on TGA analysis. Figure 7 The increase in buffer concentration after the third cycle is because a buffer solution was used after the third cycle. Figure 7 It can be seen that as the number of repetitions increases, the decomposition rate will also decrease, but up to the 7th time, the residual rate of organic matter is negligible, and from the 8th time onwards, decomposition itself will not occur.

[0195] Industrial applications

[0196] This specification relates to a method and apparatus for decomposing and recycling a thermosetting resin composite material, and an aqueous solution composition therein, which enables the efficient decomposition and recycling of a composite material in which thermosetting resin is impregnated and cured in carbon fibers through a chemical reaction based on an environmentally friendly aqueous solution.

Claims

1. A method for decomposing thermosetting resin composite materials, characterized in that, The decomposition method includes: The step of pre-impregnating thermosetting resin composite materials in an aqueous formic acid solution; The step of pretreating the thermosetting resin composite material in an aqueous hydrogen peroxide solution; and The pretreated thermosetting resin composite material is placed in a formic acid aqueous solution for main treatment. In this process, a free radical initiator is added to the aqueous solution used in one or more of the pretreatment and main treatment processes. The free radical initiator is added to the aqueous solution of the pretreatment and the aqueous solution of the main treatment, or the free radical initiator is added only to the aqueous solution of the main treatment. Alternatively, the decomposition method includes: The step of pre-impregnating thermosetting resin composite materials in an aqueous hydrogen peroxide solution; The step of pretreating the thermosetting resin composite material in a formic acid aqueous solution; and The pretreated thermosetting resin composite material is placed in an aqueous hydrogen peroxide solution for main treatment. In this process, a free radical initiator is added to the aqueous solution used in one or more of the pretreatment and main treatment processes. The free radical initiator is added to both the aqueous solution of the pretreatment and the aqueous solution of the main treatment, or the free radical initiator is added only to the aqueous solution of the pretreatment.

2. The method for decomposing thermosetting resin composite materials as described in claim 1, characterized in that, The pre-impregnation is performed at room temperature and pressure for 6 to 17 hours.

3. The method for decomposing thermosetting resin composite materials as described in claim 1, characterized in that, The pretreatment is carried out at atmospheric pressure and 80-95°C for 2-6 hours.

4. The method for decomposing thermosetting resin composite materials as described in claim 1, characterized in that, The main treatment is carried out at atmospheric pressure and 80~95℃ for 1~3 hours.

5. The method for decomposing thermosetting resin composite materials as described in claim 1, characterized in that, The formic acid concentration in an aqueous solution is 50-90%, and the hydrogen peroxide concentration in an aqueous solution is 30-50%.

6. The method for decomposing thermosetting resin composite materials as described in claim 1, characterized in that, Add 0.1-2 wt% of a free radical initiator to the aqueous solution used in the pretreatment or main treatment.

7. The method for decomposing thermosetting resin composite materials as described in claim 1, characterized in that, The decomposition characteristics are adjusted by adding a buffer solution in the pretreatment or main treatment steps.

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