Decomposition solution and method for decomposing epoxy resin

Abstract

To decompose an epoxy resin by a decomposition solution, separate fibers from a waste material, and effectively recycle and reuse the fibers.SOLUTION: A decomposition solution contains 100 pts.wt. of 30 to 50 vol.% of a hydrogen peroxide aqueous solution, 44 to 80 pts.wt. of C2 to C4 organic acid or its anhydride, 50 to 90 pts.wt. of an organic acid having a plurality of carboxylic acid groups, and 1 to 15 pts.wt. of a decomposition auxiliary agent. The decomposition solution is usable for decomposing an epoxy resin.SELECTED DRAWING: None

Description

[Technical Field] 【0001】 This technical field relates to degradation solutions used to decompose epoxy resins, and more specifically, to the recycling of fibers such as carbon fibers in waste containing epoxy resins. [Background technology] 【0002】 Lightweight, high-strength thermosetting fiber-reinforced composite materials account for the majority of the fiber composite market. Because the cross-linked structure of thermosetting resins is stable, their waste and end-of-life products are difficult to dispose of. Incineration is prohibited due to high carbon emissions and hazardous pollution. [Prior art documents] [Patent Documents] 【0003】 [Patent Document 1] Chinese Patent Application Publication No. 107849206 Specification [Patent Document 2] Chinese Patent Application Publication No. 107636054 [Overview of the project] [Problems that the invention aims to solve] 【0004】 Currently, waste can only be reduced in volume and disposed of in landfills, or crushed and used as filler, resulting in a waste of resources. Effective recycling and reuse of fibers would promote the implementation of a circular economy, reduce waste, and decrease carbon emissions. [Means for solving the problem] 【0005】 One embodiment of the present disclosure provides a decomposition solution comprising 100 parts by weight of a 30-50 vol% aqueous hydrogen peroxide solution, 44-80 parts by weight of a C2-C4 organic acid or its anhydride, 50-90 parts by weight of an organic acid having multiple carboxylic acid groups, and 1-15 parts by weight of a decomposition aid. 【0006】 One embodiment of the present disclosure provides a method for decomposing epoxy resin, comprising the step of immersing waste material containing epoxy resin in a decomposition solution at a temperature of 25°C to 100°C and atmospheric pressure for 1 to 72 hours, wherein the epoxy resin in the waste material is decomposed by the decomposition solution and a residual liquid is formed. [Effects of the Invention] 【0007】 The epoxy resin is broken down by the decomposition solution, and the fibers are separated from the waste material. 【0008】 A detailed explanation is provided in the following embodiments. [Modes for carrying out the invention] 【0009】 In the following detailed description, numerous specific details are provided for illustrative purposes to help better understand the disclosed embodiments. However, it will be apparent that one or more embodiments can be implemented without these specific details. 【0010】 One embodiment of the present disclosure provides a decomposition solution comprising 100 parts by weight of a 30-50 vol% aqueous hydrogen peroxide solution and 44-80 parts by weight of a C2-C4 organic acid or its anhydride. In the decomposition solution, the anhydride of the C2-C4 organic acid forms an organic acid. For example, acetic anhydride forms acetic acid in the decomposition solution. The action of the aqueous hydrogen peroxide solution is to oxidize the carboxyl group of the organic acid. The action of the C2-C4 organic acid or its anhydride is to swell, penetrate, and partially decompose the epoxy resin by forming a mixed system of small molecule organic acid and its peroxy acid. If the amount of the C2-C4 organic acid or its anhydride is too small, the swelling effect of the epoxy resin matrix will decrease. If the amount of the C2-C4 organic acid or its anhydride is too large, the amount of small molecule organic peroxy acid formed will be too small, thereby reducing the decomposition effect of the epoxy resin. 【0011】 In some embodiments, C2-C4 organic acids include acetic acid, propionic acid, butyric acid, or combinations thereof. If the organic acid has too few carbon atoms (e.g., formic acid), it produces a pungent odor, limiting its use in epoxy resin decomposition applications. If the organic acid has too many carbon atoms (e.g., valeric acid), it becomes difficult to achieve the desired swelling effect on small molecules in epoxy resins. 【0012】 The decomposition solution also contains 50 to 90 parts by weight of an organic acid having multiple carboxylic acid groups. The function of the organic acid having multiple carboxylic acid groups is to provide multiple oxidizable carboxyl groups, which are functional groups that can undergo a decomposition reaction with the epoxy resin by being oxidized by hydrogen peroxide. This can enhance the decomposition effect of the epoxy resin. If the amount of organic acid having multiple carboxylic acid groups is too small, the effect of accelerating the decomposition of the epoxy resin will decrease. If the amount of organic acid having multiple carboxylic acid groups is too large, the reaction rate and heating rate of the system will become too high and uncontrollable. In some embodiments, the organic acid having multiple carboxylic acid groups includes malonic acid, succinic acid, glutaric acid, maleic acid, malic acid, citric acid, or a combination thereof. 【0013】 The decomposition solution also contains 1 to 15 parts by weight of a decomposition aid. The decomposition aid is mainly a strong Lewis acid, which helps to form peroxides from C2-C4 organic acids and organic acids having multiple carboxylic acid groups. If the amount of decomposition aid is too small, the rate of peroxy acid formation will decrease. If the amount of decomposition aid is too large, the catalytic efficiency of peroxy acid formation will become difficult to control, and it may also accelerate the corrosion rate of the equipment. In some embodiments, the decomposition aid includes copper chloride, cuprous chloride, zinc chloride, potassium permanganate, sulfuric acid, phosphoric acid, or a combination thereof. 【0014】 In some embodiments, the decomposition solution further contains 5 to 34 parts by weight of water. By adjusting the concentration of the composition in the decomposition solution with additional water, it is possible to prevent the reaction from becoming excessively vigorous. Too much additional water may reduce the effectiveness of the decomposition solution. 【0015】 One embodiment of this disclosure provides a method for decomposing epoxy resin, comprising the step of immersing waste material containing epoxy resin in the above-described decomposition solution at a temperature of 25°C to 100°C and atmospheric pressure for 1 to 72 hours, wherein the epoxy resin in the waste material is decomposed by the decomposition solution and a residual liquid is formed. If the immersion time is too short, the decomposition effect will be insufficient. If the immersion time is too long, the decomposition effect will not be further enhanced, and the longer processing time will increase costs. 【0016】 The decomposition solution is primarily intended to decompose epoxy resins. If the resin in the waste material is a different resin, such as polyurethane, the polyurethane will not be effectively decomposed by the decomposition solution. If the temperature of the decomposition solution is too low, its effect on decomposing epoxy resin will be too low. If the temperature of the decomposition solution is too high, a large amount of the solution will volatilize, making it difficult to recycle and reuse the C2-C4 organic acids. 【0017】 In some embodiments, the waste material may further contain fibers, in which case the epoxy resin is decomposed by the decomposition solution, and the fibers are separated from the waste material. In some embodiments, the method for decomposing the epoxy resin further includes a step of washing and drying the fibers separated from the waste material in order to recycle and reuse the fibers. Generally, the performance (tensile strength and modulus of elasticity) of the recycled fibers is at least 95% of the performance of the original fibers. In some embodiments, the fibers include carbon fibers, glass fibers, or a combination thereof. 【0018】 In some embodiments, the method for decomposing the epoxy resin further includes a step of distilling the residual liquid or concentrating the residual liquid under reduced pressure to recycle C2-C4 organic acids. Since the C2-C4 organic acids can be recycled and reused, the cost of decomposing the epoxy resin can be further reduced. 【0019】 Hereinafter, exemplary embodiments will be described in detail so that those having ordinary knowledge in the art can easily understand. The concept of the present invention can be embodied in various forms without being limited to the exemplary embodiments shown here. 【Example】 【0020】 Production Example 1 100 g of epoxy resin DEN-438 (purchased from Dow), 87 g of epoxy resin EPON-1001 (purchased from Shell), and a curing agent DICY (purchased from Nippon Carbide Industries Co., Ltd.) were mixed. Then, 0.64 g of the mixture was applied to 1.19 g of carbon fibers (purchased from Hyosung, Republic of Korea), heated to 120°C and cured for 1 hour to obtain an epoxy resin composite material A. 【0021】 Production Example 2 80 g of epoxy resin MY-720 (purchased from Ciba-Geigy, Swiss Confederation) and a curing agent DDS (purchased from Ciba-Geigy, Swiss Confederation) were mixed, and then heated to 180°C and cured for 2 hours to obtain an epoxy resin bulk material B. 【0022】 Manufacturing Example 3 Decomposition solution I was prepared by mixing 295 g of hydrogen peroxide aqueous solution (50 vol%), 100 g of water, 266 g of citric acid, 233 g of acetic anhydride, and 33 g of phosphoric acid. 【0023】 Manufacturing Example 4 Decomposition solution II was prepared by mixing 236 g of hydrogen peroxide aqueous solution (50 vol%) and 832 g of acetic anhydride. 【0024】 Example 1 50 x 70 x 0.3 cm 3 When glass fiber composite material (containing 35 wt% epoxy resin) from scrap wind turbine blades was immersed in decomposition solution I at room temperature and maintained for 70 hours, 38% of the epoxy resin was removed (swelling and delamination). 【0025】 Comparative Example 1 5 x 5 x 0.3 cm 3 Glass fiber composite material (containing 35 wt% epoxy resin) from scrap wind turbine blades was immersed in decomposition solution II at room temperature and maintained for 70 hours. As a result, it was found that the solution could not remove the epoxy resin (only swelling occurred). 【0026】 Example 2 20 x 10 x 2 cm 3 A glass fiber composite (containing 35 wt% epoxy resin) from scrap wind turbine blades was immersed in decomposition solution I at 80°C for 1 hour, after which 99% of the epoxy resin was removed. The resulting glass fibers were extracted from the remaining solution, then washed and dried. The performance of the recycled glass fibers (tensile strength and modulus of elasticity measured according to ASTM D3379 standard) was 95% of that of the original glass fibers. 【0027】 Comparative Example 2 20 x 10 x 2 cm 3Glass fiber composite material (containing 35 wt% epoxy resin) from scrap wind turbine blades was immersed in decomposition solution II at 80°C and maintained for 2 hours, resulting in the removal of 96% of the epoxy resin. The glass fibers were extracted from the remaining solution, then washed and dried. The performance of the recycled glass fibers (tensile strength and modulus of elasticity measured according to ASTM D3379 standard) was 84% ​​of that of the original glass fibers. 【0028】 Comparative Example 3 20 x 10 x 0.2 cm 3 Carbon fiber reinforced composite waste (containing 50 wt% epoxy resin) from automotive modification parts was immersed in decomposition solution I at 5°C and maintained for 72 hours. The results showed that the solution could not remove the resin (only swelling and delamination occurred). 【0029】 Example 3 20 x 10 x 0.2 cm 3 When carbon fiber reinforced composite waste (containing 50 wt% epoxy resin) from automotive modification parts was immersed in decomposition solution I at 25°C and maintained for 70 hours, 25% of the epoxy resin was removed. 【0030】 Example 4 20 x 10 x 0.2 cm 3 Carbon fiber reinforced composite waste (containing 50 wt% epoxy resin) from automotive modification parts was immersed in decomposition solution I at 80°C and maintained for 2 hours, resulting in the removal of 99% of the epoxy resin. Carbon fibers were extracted from the remaining liquid, then washed and dried. The performance of the recycled carbon fibers (tensile strength and modulus of elasticity measured according to ASTM D3379 standard) was 97% of that of the original carbon fibers. 【0031】 Comparative Example 4 20 x 10 x 0.2 cm 3Carbon fiber reinforced composite waste (containing 50 wt% epoxy resin) from automotive modification parts was immersed in decomposition solution I at 120 °C and maintained for 1 hour. As a result, 99% of the epoxy resin was removed. The carbon fibers were taken out from the residual liquid and then washed and dried. The performance of the recycled carbon fibers (tensile strength and modulus of elasticity measured according to ASTM D3379 standard) was 97% of the performance of the original carbon fibers. Due to a large amount of the decomposition solution volatilizing, recycling and reuse could not be carried out (for example, recycling of acetic acid). 【0032】 Comparative Example 5 2×5×1 cm 3 The glass fiber composite material (containing 35 wt% epoxy resin) of the scrap of the waste windmill blade was immersed in decomposition solution I at 5 °C and maintained for 72 hours. As a result, it was found that the solution could not remove the epoxy resin (only swelling). 【0033】 Example 5 20×10×2 cm 3 The glass fiber composite material (containing 35 wt% epoxy resin) of the scrap of the waste windmill blade was immersed in decomposition solution I at 25 °C and maintained for 70 hours. As a result, 25% of the epoxy resin was removed (delamination). 【0034】 Example 6 20×10×2 cm 3 The glass fiber composite material (containing 35 wt% epoxy resin) of the scrap of the waste windmill blade was immersed in decomposition solution I at 80 °C and maintained for 1 hour. As a result, 99% of the epoxy resin was removed. The glass fibers were taken out from the residual liquid and then washed and dried. The performance of the recycled glass fibers (tensile strength and modulus of elasticity measured according to ASTM D3379 standard) was 95% of the performance of the original glass fibers. 【0035】 Comparative Example 6 20×10×2 cm 3When a glass fiber composite (containing 35 wt% epoxy resin) from scrap wind turbine blades was immersed in decomposition solution I at 120°C for less than one hour, 92% of the epoxy resin was removed. The glass fibers were extracted from the remaining solution, then washed and dried. The performance of the recycled glass fibers (tensile strength and modulus of elasticity measured according to ASTM D3379 standard) was 82% of that of the original glass fibers. Due to the large amount of decomposition solution volatilizing, recycling and reuse were not possible (e.g., recycling of acetic acid), and the performance of the recycled glass fibers was even lower. 【0036】 Example 7 When epoxy resin composite material A was immersed in decomposition solution I at 92°C and maintained for 1 hour, the epoxy resin was completely removed. 【0037】 Comparative Example 7 When epoxy resin composite material A was immersed in decomposition solution II at 108°C and maintained for 1 hour, only a portion of the epoxy resin was removed. 【0038】 Example 8 When epoxy resin bulk material B was immersed in decomposition solution I at 92°C and maintained for 3 hours, the weight of epoxy resin bulk material B decreased by 0.87 g. 【0039】 Comparative Example 8 When epoxy resin bulk material B was immersed in decomposition solution II at 108°C and maintained for 3 hours, the weight of epoxy resin bulk material B decreased by 0.4 g. 【0040】 Manufacturing Example 5 Decomposition solution III was prepared by mixing 100g of hydrogen peroxide aqueous solution (50 vol%), 50g of water, 14.3g of oxalic acid, 23g of acetic anhydride, and 7.5g of phosphoric acid. 【0041】 Comparative Example 9 Epoxy resin composite material A was immersed in decomposition solution III at 108°C and maintained for 1 hour. As a result, it was found that the solution could not remove the epoxy resin. 【0042】 Manufacturing Example 6 Decomposition solution IV was prepared by mixing 233 g of hydrogen peroxide aqueous solution (50 vol%), 100 g of water, 266 g of tartaric acid, 233 g of acetic anhydride, and 33 g of phosphoric acid. 【0043】 Comparative Example 10 Epoxy resin composite material A was immersed in decomposition solution IV at 92°C and maintained for 1 hour. As a result, it was found that the solution removed only a small amount of epoxy resin. 【0044】 Manufacturing example 7 Decomposition solution V was prepared by mixing 295 g of hydrogen peroxide aqueous solution (50 vol%), 100 g of water, 133 g of citric acid, 233 g of acetic anhydride, and 3.1 g of nickel nitrate. 【0045】 Comparative Example 11 Epoxy resin composite material A was immersed in decomposition solution V at 92°C and maintained for 1 hour. It was found that only a small amount of epoxy resin was removed from the solution. 【0046】 Manufacturing Example 8 Decomposition solution VI was prepared by mixing 295 g of hydrogen peroxide aqueous solution (50 vol%), 100 g of water, 133 g of citric acid, 233 g of acetic anhydride, and 8 g of iron(II) chloride. 【0047】 Comparative Example 12 Epoxy resin composite material A was immersed in decomposition solution VI at 92°C and maintained for 1 hour. As a result, it was found that the solution could not remove the epoxy resin. 【0048】 Comparative Example 13 Waste carbon fiber prepreg (containing 41 wt% epoxy resin) was immersed in decomposition solution II and treated with microwaves (for example, set to 700W for 1.5 minutes, followed by cooling, and this cycle was repeated three times). Although microwave treatment heated quickly, it was not possible to continuously supply heat, and temperature control was difficult. In addition, the decomposition solution disappeared quickly, and the epoxy resin could not be completely decomposed. This process was also unsuitable for mass production. 【0049】 Example 9 After the decomposition process, 552 g of the residual solution I was recovered. This residual solution was concentrated under reduced pressure to obtain 458 g of aqueous acetic acid solution. 【0050】 It will be apparent to those skilled in the art that various modifications and changes can be made to the disclosed methods and materials. Details and examples are intended to be illustrative only, and the true scope of this disclosure is indicated by the claims and their equivalents.

Claims

[Claim 1] 100 parts by weight of a 30-50 vol% aqueous solution of hydrogen peroxide, 44 to 80 parts by weight of acetic acid or its anhydride, 50 to 90 parts by weight of citric acid, 1 to 15 parts by weight of phosphoric acid, A decomposition solution containing the following: [Claim 2] The decomposition solution according to claim 1, further comprising 5 to 34 parts by weight of water. [Claim 3] A method for decomposing epoxy resin, The process includes immersing waste material containing epoxy resin in the decomposition solution described in claim 1 at a temperature of 25°C to 100°C and atmospheric pressure for 1 to 72 hours. A method comprising the decomposition of the epoxy resin in the waste material by the decomposition solution, thereby forming a residual liquid. [Claim 4] The method according to claim 3, wherein the waste material further contains fibers, and the epoxy resin is decomposed by the decomposition solution so that the fibers are separated from the waste material. [Claim 5] The method according to claim 4, wherein the fibers include carbon fibers, glass fibers, or a combination thereof.