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 a degradation solution used to decompose epoxy resins, and more particularly to the recycling of fibers such as carbon fibers in waste containing epoxy resins.

Background Art

[0002] Lightweight, high-strength thermosetting fiber-reinforced composite materials occupy most of the fiber composite market. Due to the stable cross-linked structure of thermosetting resins, their waste and end-of-life products are difficult to process. Incineration is prohibited because of high carbon emissions and the generation of harmful pollution.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] Currently, waste can only be volume-reduced, stacked and landfilled, or crushed and used as a filler, resulting in a waste of resources. If fibers can be effectively recycled and reused, the implementation of a circular economy, waste reduction, and a decrease in carbon emissions will be promoted.

Means for Solving the Problems

[0005] One embodiment of the present disclosure provides a decomposition solution comprising 100 parts by weight of an aqueous hydrogen peroxide solution containing 30 to 50 vol% hydrogen peroxide, 44 to 80 parts by weight of a C2 - C4 organic acid or its anhydride, 50 to 90 parts by weight of an organic acid having a plurality of carboxylic acid groups, and 1 to 15 parts by weight of a decomposition aid.

[0006] One embodiment of the present disclosure is a method for decomposing an epoxy resin, which includes a step of immersing waste material containing the epoxy resin in a decomposition solution at a temperature of 25°C to 100°C and normal pressure for 1 to 72 hours, wherein the epoxy resin in the waste material is decomposed by the decomposition solution to form a residual liquid, and provides a method for decomposing an epoxy resin.

Advantages of the Invention

[0007] The epoxy resin is decomposed by the decomposition solution, and the fibers are separated from the waste material.

[0008] Detailed descriptions will be given in the following embodiments.

Modes for Carrying Out the Invention

[0009] In the following detailed description, for the purpose of explanation, numerous specific details are set forth in order to provide a more thorough understanding of the disclosed embodiments. However, it will be apparent that one or more embodiments can be practiced without these specific details.

[0010] One embodiment of the present disclosure provides a decomposition solution comprising 100 parts by weight of an aqueous hydrogen peroxide solution containing 30 to 50 vol% of hydrogen peroxide, and 44 to 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 form a mixed system of small - molecule organic acids and their peroxyacids, thereby swelling, penetrating, and partially decomposing the epoxy resin. 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 the small - molecule organic peroxyacid formed will be too small, resulting in a decrease in the decomposition effect of the epoxy resin.

[0011] In some embodiments, the C2 - C4 organic acids include acetic acid, propionic acid, butyric acid, or a combination thereof. If the number of carbon atoms of the organic acid is too small (e.g., formic acid), a pungent odor will occur, restricting its use in epoxy resin decomposition applications. If the number of carbon atoms of the organic acid is too large (e.g., valeric acid), it will be difficult to achieve the swelling effect of small molecules in the epoxy resin.

[0012] The decomposition solution also includes 50 to 90 parts by weight of an organic acid having a plurality of carboxylic acid groups. The action of the organic acid having a plurality of carboxylic acid groups is to provide a plurality of oxidizable carboxyl groups, and by being oxidized by hydrogen peroxide, to provide a plurality of functional groups capable of causing a decomposition reaction with the epoxy resin. Thereby, the decomposition effect of the epoxy resin can be enhanced. If the amount of the organic acid having a plurality of carboxylic acid groups is too small, the effect of accelerating the decomposition of the epoxy resin will decrease. If the amount of the organic acid having a plurality of carboxylic acid groups is too large, the reaction rate and heating rate of the system will be too high to be controllable. In some embodiments, the organic acid having a plurality of 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 and helps to form peroxides from C2-C4 organic acids and organic acids having a plurality of carboxylic acid groups. If the amount of the decomposition aid is too small, the formation rate of peroxyacids will decrease. If the amount of the decomposition aid is too large, it will be difficult to control the catalytic efficiency of peroxyacid formation, 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 using additional water, it is possible to prevent the reaction from becoming overly intense. If the amount of additional water is too large, the effect of the decomposition solution may decrease.

[0015] One embodiment of the present disclosure is a method for decomposing an epoxy resin, which includes the step of immersing waste material containing the epoxy resin in the above-described decomposition solution at a temperature of 25°C to 100°C and normal pressure for 1 to 72 hours, wherein the epoxy resin in the waste material is decomposed by the decomposition solution to form a residual liquid, and a method for decomposing an epoxy resin is provided. 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 increase further, and the cost will increase due to the longer treatment time.

[0016] The decomposition solution is mainly intended to decompose the epoxy resin. If the resin in the waste material is another 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, the effect of decomposing the epoxy resin will be too low. If the temperature of the decomposition solution is too high, a large amount of the decomposition 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 of 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 of decomposing the epoxy resin further includes a step of distilling the residual liquid or concentrating the residual liquid under reduced pressure to recycle the C2-C4 organic acid. Since the C2-C4 organic acid 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 skilled in the art can easily understand them. The inventive concept can be embodied in various forms without being limited to the exemplary embodiments shown herein.

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, then heated to 180°C and cured for 2 hours to obtain an epoxy resin bulk material B.

[0022] Production Example 3 295 g of an aqueous hydrogen peroxide solution (50 vol%), 100 g of water, 266 g of citric acid, 233 g of acetic anhydride, and 33 g of phosphoric acid were mixed to prepare a decomposition solution I.

[0023] Production Example 4 236 g of an aqueous hydrogen peroxide solution (50 vol%) and 832 g of acetic anhydride were mixed to prepare a decomposition solution II.

[0024] Example 1 50×70×0.3 cm 3 The glass fiber composite material (containing 35 wt% of epoxy resin) of the scrap blade of the discarded windmill of was immersed in the decomposition solution I at room temperature and maintained for 70 hours. As a result, 38% of the epoxy resin was removed (swelling and delamination).

[0025] Comparative Example 1 5×5×0.3 cm 3 The glass fiber composite material (containing 35 wt% of epoxy resin) of the scrap blade of the discarded windmill of was immersed in the 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).

[0026] Example 2 20×10×2 cm 3 The glass fiber composite material (containing 35 wt% of epoxy resin) of the scrap blade of the discarded windmill of was immersed in the decomposition solution I at 80 °C and maintained for 1 hour. As a result, 99% of the epoxy resin was removed. The glass fiber obtained was taken out from the residual liquid, then washed and dried. The performance (tensile strength and modulus of elasticity measured according to ASTM D3379 standard) of the recycled glass fiber was 95% of the performance of the original glass fiber.

[0027] Comparative Example 2 20×10×2 cm 3The glass fiber composite material (containing 35 wt% of epoxy resin) of the scrap blades of the discarded windmill was immersed in the decomposition solution II at 80 °C and maintained for 2 hours. As a result, 96% of the epoxy resin was removed. The glass fibers were taken out from the remaining 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 84% of the performance of the original glass fibers.

[0028] Comparative Example 3 20×10×0.2 cm 3 The carbon fiber reinforced composite waste (containing 50 wt% of epoxy resin) from the parts for automobile modification of 3 was immersed in the decomposition solution I at 5 °C and maintained for 72 hours. As a result, it was found that the solution could not remove the resin (only swelling and peeling).

[0029] Example 3 20×10×0.2 cm 3 The carbon fiber reinforced composite waste (containing 50 wt% of epoxy resin) from the parts for automobile modification of 3 was immersed in the decomposition solution I at 25 °C and maintained for 70 hours. As a result, 25% of the epoxy resin was removed.

[0030] Example 4 20×10×0.2 cm 3 The carbon fiber reinforced composite waste (containing 50 wt% of epoxy resin) from the parts for automobile modification of 3 was immersed in the decomposition solution I at 80 °C and maintained for 2 hours. As a result, 99% of the epoxy resin was removed. The carbon fibers were taken out from the remaining 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.

[0031] Comparative Example 4 20×10×0.2 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 remaining solution 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. Since a large amount of the decomposition solution evaporated, recycling and reuse were not possible (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 blade of a discarded windmill 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 blade of a discarded windmill 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 blade of a discarded windmill 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 remaining solution 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 3The glass fiber composite material (containing 35 wt% of epoxy resin) of the scrap blades of the discarded windmill was immersed in the decomposition solution I at 120 °C and maintained for less than 1 hour. As a result, 92% of the epoxy resin was removed. The glass fibers were taken out from the remaining solution and then washed and dried. The performance of the recycled glass fibers (tensile strength and elastic modulus measured according to ASTM D3379 standard) was 82% of that of the original glass fibers. Since a large amount of the decomposition solution volatilized, recycling and reuse were not possible (for example, recycling of acetic acid), and the performance of the recycled glass fibers was lower.

[0036] Example 7 The epoxy resin composite material A was immersed in the decomposition solution I at 92 °C and maintained for 1 hour. As a result, the epoxy resin was completely removed.

[0037] Comparative Example 7 The epoxy resin composite material A was immersed in the decomposition solution II at 108 °C and maintained for 1 hour. As a result, only part of the epoxy resin was removed.

[0038] Example 8 The epoxy resin bulk material B was immersed in the decomposition solution I at 92 °C and maintained for 3 hours. As a result, the weight of the epoxy resin bulk material B decreased by 0.87 g.

[0039] Comparative Example 8 The epoxy resin bulk material B was immersed in the decomposition solution II at 108 °C and maintained for 3 hours. As a result, the weight of the epoxy resin bulk material B decreased by 0.4 g.

[0040] Production Example 5 100 g of an aqueous hydrogen peroxide solution (50 vol%), 50 g of water, 14.3 g of oxalic acid, 23 g of acetic anhydride, and 7.5 g of phosphoric acid were mixed to prepare a decomposition solution III.

[0041] Comparative Example 9 The epoxy resin composite material A was immersed in the 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] Production Example 6 233 g of an aqueous hydrogen peroxide solution (50 vol%), 100 g of water, 266 g of tartaric acid, 233 g of acetic anhydride, and 33 g of phosphoric acid were mixed to prepare a decomposition solution IV.

[0043] Comparative Example 10 The epoxy resin composite material A was immersed in the 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 the epoxy resin.

[0044] Production Example 7 295 g of an aqueous hydrogen peroxide solution (50 vol%), 100 g of water, 133 g of citric acid, 233 g of acetic anhydride, and 3.1 g of nickel nitrate were mixed to prepare a decomposition solution V.

[0045] Comparative Example 11 The epoxy resin composite material A was immersed in the decomposition solution V at 92°C and maintained for 1 hour. It was found that the solution removed only a small amount of the epoxy resin.

[0046] Production Example 8 295 g of an aqueous hydrogen peroxide solution (50 vol%), 100 g of water, 133 g of citric acid, 233 g of acetic anhydride, and 8 g of iron(II) chloride were mixed to prepare a decomposition solution VI.

[0047] Comparative Example 12 The epoxy resin composite material A was immersed in the 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 A waste carbon fiber fabric prepreg (containing 41 wt% of epoxy resin) was immersed in the decomposition solution II and treated with microwaves (for example, set at 700 W for 1.5 minutes, then cooled, and this cycle was repeated 3 times). The microwave treatment had a fast heating rate, but it could not continue to supply heat, and it was difficult to control the temperature. In addition, the decomposition solution disappeared quickly, and the epoxy resin could not be completely decomposed. This process was also disadvantageous for mass production.

[0049] Example 9 After the decomposition process, 552 g of the residual liquid of decomposition solution I was recovered. The residual liquid was concentrated under reduced pressure to obtain 458 g of an aqueous acetic acid solution.

[0050] It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed methods and materials. The details and examples are intended to be regarded merely as illustrative, and the true scope of the present disclosure is indicated by the claims and their equivalents.

Claims

1. 100 parts by weight of a 30 to 50 vol% aqueous hydrogen peroxide solution; C 2 ~C 4 44 to 80 parts by weight of an organic acid or anhydride thereof; 50 to 90 parts by weight of an organic acid having a plurality of carboxylic acid groups; 1 to 15 parts by weight of a decomposition assistant; A digestion solution comprising:

2. 2. The degradation solution of claim 1, wherein the organic acid having multiple carboxylic acid groups comprises malonic acid, succinic acid, glutaric acid, maleic acid, malic acid, citric acid, or combinations thereof.

3. 10. The decomposition solution of claim 1, wherein the decomposition aid comprises copper chloride, cuprous chloride, zinc chloride, potassium permanganate, sulfuric acid, phosphoric acid, or a combination thereof.

4. 2. The decomposition solution of claim 1, further comprising 5 to 34 parts by weight of water.

5. A method for decomposing an epoxy resin, comprising the steps of: The method includes the step of immersing waste material containing epoxy resin in the decomposition solution according to claim 1 at a temperature of 25° C. to 100° C. and at normal pressure for 1 to 72 hours, The method, wherein the epoxy resin in the waste material is decomposed by the decomposition solution to form a residual liquid.

6. The method of claim 5 , wherein the waste material further comprises fibers, and the epoxy resin is decomposed by the decomposition solution to separate the fibers from the waste material.

7. The method of claim 6 , wherein the fibers include carbon fibers, glass fibers, or a combination thereof.