Method for high-yield recovery of phenolic compounds from epoxy resin-based waste

Abstract

The invention provides a method for high-yield recovery of phenolic compounds from epoxy resin-based waste, which comprises the following steps: mixing epoxy resin with acid / acid solution and salt according to a mass ratio of 1: (5-100): (0.1-50), reacting at 30-300 DEG C for 0.5-60 hours, collecting the reaction product, and separating to obtain a liquid product, and separating, purifying and recovering the liquid product to obtain the phenolic compound. According to the method, the acid / acid solution and the salt are creatively utilized to synergistically degrade the epoxy resin material, and particularly, the yield of the phenolic compounds in the degradation product can be remarkably improved under the conditions of specific combination, specific proportion and reaction, so that a new way is provided for recovering the phenolic compounds from the epoxy resin-based waste through a chemical method; the industrial application is expected to be realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of recycling and reusing epoxy resin materials, and relates to a method for highly efficiently recovering phenolic compounds from epoxy resin-based waste. Background Art

[0002] Epoxy resin is one of the most widely used engineering plastics, and its waste includes pure epoxy resin materials such as epoxy adhesives and epoxy floor paints, and epoxy resin-based composites filled with carbon fiber, glass fiber, silica, wood, and metal. The recycling of epoxy resin-based waste is divided into energy recovery and material recovery from the recovered products. Energy recovery is to recover it as heat energy for reuse by incineration. This method not only causes air pollution but also damages the performance of fibers in resin-based composites. Material recovery is divided into mechanical recovery and chemical recovery. Mechanical recovery is to cut, crush, etc. and then use it, and the economic value of the recovered products is relatively low. For example, the Chinese patent application with the publication number CN117511125A discloses a method for grinding epoxy resin waste particles and using them as fillers to prepare composites again. This method improves the utilization rate of epoxy resin waste, but faces the problem of recycling again. Chemical recovery can modify resin-based waste into new functional materials or recover it into high-value products such as oligomers, small molecule monomers, and platform compounds and re-enter a new production cycle, which is a relatively promising recycling method. So far, the proportion of chemical recovery in the total plastic recycling is less than 1%, which means that the main technological development and market growth in the next decade may be in this field.

[0003] Modifying epoxy resin-based waste into new functional materials can improve its utilization rate, but this only delays the recycling and still faces the problem of recycling later. Recycling epoxy resin-based waste into oligomers and mixing them with new resins for use is also a good recycling method, but the degraded oligomers often have complex structures and are difficult to determine, and can only be used in a very small proportion. In contrast, degrading it into small molecule monomers or platform compounds is a more thorough recycling method, because small molecule monomers or platform compounds can enter a new production cycle as raw materials, which is more in line with the concept of circular economy.

[0004] There are many types of epoxy resins, among which bisphenol epoxy resins account for the main part. Phenolic compounds are an important chemical raw material and can be widely used in medicine, chemical industry, food and other industries. The phenolic structure can be recovered by breaking the CO bond in epoxy resin-based waste, but this often requires complex and expensive catalysts and harsh reaction conditions, with poor universality and unsatisfactory yield of phenolic products. For example, the Chinese invention patent with publication number CN115400759A discloses a method for preparing high value-added mixed chemicals such as phenol, p-isopropylphenol, bisphenol A and 2,2-diphenylpropane by degradation under the synergistic effect of a catalyst, a hydrogen-rich solvent and an acidic solution, but this method requires the use of a catalyst that is cumbersome to prepare and has high energy consumption, and the resulting mixed chemical composition is complex and the yield is very low, with a maximum of only 12.98%.

[0005] In summary, the existing epoxy resin waste recycling technology, especially chemical recycling, cannot be widely used due to problems such as complex catalysts, poor economy, poor universality, low product value and yield. Therefore, it is of great significance to seek a recycling method with a simple degradation system, low cost, easy to obtain, simple operation, high universality, and simple resin degradation products, high yield and high added value. Summary of the invention

[0006] The purpose of the present invention is to solve the problems in the above-mentioned background technology and provide a method for recovering phenolic compounds from epoxy resin-based waste with high yield. The method innovatively utilizes acid / acid solution and salt to synergistically degrade epoxy resin materials, especially under specific combinations, specific proportions and reaction conditions, the yield of phenolic compounds in the degradation products can be significantly improved, which provides a new way to recover phenolic compounds from epoxy resin-based waste by chemical methods and is expected to be realized in industrial application.

[0007] To achieve the above objectives, the present invention is implemented by adopting a technical solution consisting of the following technical measures.

[0008] A method for recovering phenolic compounds from epoxy resin-based waste with high yield mainly comprises the following steps:

[0009] (1) mixing epoxy resin, acid / acid solution and salt in a mass ratio of 1:(5-100):(0.1-50), reacting at a temperature of 30-300° C. for 0.5-60 hours, and collecting the reaction product after the time is up;

[0010] (2) The reaction product obtained in step (1) is filtered and separated to obtain a liquid product and a residual solid, and the liquid product is further separated, purified and recovered to obtain a phenolic compound.

[0011] In the step (2), different phenolic compounds are finally obtained according to different epoxy resin materials, for example, at least one of phenol, 4-isopropylphenol, 4-isopropenylphenol, 2-isopropylphenol, 4-methylphenol, 2-methylphenol, 2,4-dimethylphenol, 2,3,4-trimethylphenol, 2,6-diisopropylphenol, bisphenol A, bisphenol S, bisphenol F, tetrabromobisphenol A, 2,6-dibromophenol and 2,6-dibromo-4-isopropylphenol.

[0012] In this article, the epoxy resin described in step (1) generally refers to the product or material prepared by the epoxy resin. Generally, the method for recovering phenolic compounds in the present invention can be aimed at the scraps / waste of the epoxy resin in the production process, or it can be the discarded / wasteful epoxy resin product or material. The epoxy resin includes conventional epoxy resin types in the chemical industry, including epoxy resins with phenolic structures, such as bisphenol A type, tetrabromobisphenol A type, bisphenol F type, bisphenol S type, phenolic type, etc., with amine curing agents, anhydride curing agents or special purpose curing agents (such as phenolic resins, polyester resins, liquid polyurethanes, styrene-maleic anhydride copolymer resins and polysulfide rubbers thereof, etc.) cured epoxy resins, and also includes epoxy resin-based composite materials selected as substrates with the above-mentioned epoxy resins, such as glass fiber reinforced epoxy resins, carbon fiber reinforced epoxy resins, etc.

[0013] It should be noted that when the epoxy resin in step (1) is waste containing epoxy resin or epoxy resin-based waste, it can be selected to undergo a pretreatment including washing, which is mainly to remove impurities on the surface of the waste. If necessary, parts that are not made of epoxy resin (such as metal parts, etc.) need to be removed. Those skilled in the art can perform specific treatment based on the actual conditions of the products or materials that need to be recycled and reused according to the existing technology.

[0014] Herein, the acid / acid solution in step (1) is an acidic liquid used in the degradation process, for example, any one of inorganic acids (hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, phosphotungstic acid), organic acids (formic acid, acetic acid, propionic acid, oxalic acid, malonic acid, succinic acid, malic acid, methanesulfonic acid, toluenesulfonic acid, benzoic acid, phytic acid) and Lewis acids (aluminum chloride, zinc chloride, ferric chloride, ferrous chloride, niobium pentachloride, indium trifluoromethanesulfonate), or a solution prepared by any one of them, or a mixed solution prepared by multiple preparations.

[0015] One of the inventive points of the present invention is that, by making a horizontal comparison of different acids / acid solutions, it is found that formic acid, under the synergistic effect with iodized salt, especially under specific proportions and reaction conditions, can significantly increase the yield of phenolic compounds in degradation products, thereby providing a new way for chemically recycling phenolic compounds from epoxy resin-based waste.

[0016] Herein, the salt in step (1) is, for example, selected from at least one of salts consisting of nitrate ions, sulfate ions, sulfite ions, halogen ions (fluoride ions, chloride ions, bromide ions, iodide ions), organic acid ions (such as formate ions, acetate ions, methanesulfonate ions, etc.) and metal ions (potassium ions, sodium ions, calcium ions, copper ions, iron ions, magnesium ions, zinc ions, indium ions, etc.), and ammonium ions.

[0017] Based on the above findings, in one of the technical solutions, the salt in step (1) is a halogen ion salt. In one of the more preferred technical solutions, it is found through comparative experiments that when the salt in step (1) is an iodine salt, the yield of phenolic compounds in the degradation product can be significantly increased compared with other ion salts.

[0018] Typically, the reaction is carried out at a temperature of 30 to 300° C. for 0.5 to 60 hours in step (1). The specific reaction method and operation can be implemented by those skilled in the art according to the common knowledge of the reaction methods and operations for chemical degradation of polymer materials, such as static reaction, stirring reaction, oil bath heating reaction, water bath heating reaction, oven heating reaction, ultrasonic reaction or microwave heating reaction, any one or a combination thereof.

[0019] It should be emphasized that comparative experiments have found that when the reaction temperature and reaction time conditions are met, phenolic compounds can be degraded to obtain high yields. However, depending on the morphology (such as shape and size) of the epoxy resin to be degraded, especially the epoxy resin product, auxiliary conditions such as stirring reaction can be selected to accelerate the degradation rate.

[0020] Herein, the reaction product in step (2) is separated by filtration to obtain a liquid product and a residual solid, wherein filtration separation is a conventional chemical operation in the art, and those skilled in the art can select a suitable separation method.

[0021] In this article, the liquid product in step (2) is further separated, purified and recovered to obtain phenolic compounds, wherein the separation and purification are conventional chemical operations in the art. In one technical scheme, the separation and purification are sequentially performed by extraction, column chromatography (for example, using petroleum ether as an eluent and separating through a silica gel column), and acid-base precipitation (for example, using NaOH solution to make it alkaline to convert phenol into sodium phenolate and then using HCl solution to make it acidic to precipitate it) to separate, and then recovering the phenolic compounds by reduced pressure distillation; the residual liquid generated in the above separation and purification process contains the salt added in step (1), which can also be separated and recovered by conventional salt recovery methods in the art to reduce costs by recycling.

[0022] In one of the technical solutions, the residual solid obtained by filtration and separation in step (2) may be an epoxy resin that has not been completely degraded, depending on the epoxy resin material. It can be selected as the epoxy resin to repeat steps (1) and (2) to achieve complete degradation.

[0023] In one of the technical solutions, the liquid product in step (2) is further separated and purified. After the phenolic compound is obtained through separation and purification, a solid product may be separated during the separation process, which is mainly a resin fragment containing an undegraded phenolic structure. The solid product can be used as an epoxy resin to repeat steps (1) and (2) to recover the phenolic compound.

[0024] The method for recovering phenolic compounds from epoxy resin-based wastes with high yield can be directly applied to the technical field of epoxy resin recovery and reuse.

[0025] The present invention has the following beneficial effects:

[0026] (1) The present invention provides a method for recovering phenolic compounds from epoxy resin-based wastes with high yield. Since the epoxy resin-based wastes are degraded by combining acid and salt, the chemical bonds of CO, CN, CC and the like commonly present in epoxy resins can be effectively broken to recover high-value phenolic compounds, and thus the method has high universality.

[0027] (2) The present invention provides a method for recovering phenolic compounds from epoxy resin-based waste with high yield. On the one hand, no catalyst needs to be added, so the reaction system is simpler and the cost is low. On the other hand, since the degradation reaction temperature does not exceed 300°C, and degradation can be performed multiple times without other high-energy consumption operations, the energy consumption is relatively low.

[0028] (3) The present invention provides a method for recovering phenolic compounds from epoxy resin-based wastes with high yield. Since the acids and salts used can be purchased commercially and used directly, and can be recycled, the problem of the prior art using toxic and harmful substances such as heavy metals, precious metals and strong oxidizing acids to pollute the environment is avoided, and no secondary pollution is generated, which has a higher promotion value. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a digital photo of the phenolic compounds recovered in the examples of the present invention.

[0030] Figure 2 The gas chromatography-mass spectrometry (GCMS) detection spectrum of the phenolic product recovered in Example 24 of the present invention. From the results of the spectrum characterization, it can be seen that the degradation products are phenol and 4-isopropylphenol. DETAILED DESCRIPTION

[0031] In order to further understand the present invention, the preferred embodiments of the present invention are described below in conjunction with examples, but it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the invention. Those skilled in the art can refer to the content of this article and appropriately improve the process parameters to achieve it. It is particularly important to point out that all similar substitutions and modifications are obvious to those skilled in the art, and they are all considered to be included in the present invention. The methods and applications of the present invention have been described through preferred embodiments, and relevant personnel can obviously change or appropriately change and combine the methods and applications described herein without departing from the content, spirit and scope of the present invention to implement and apply the technology of the present invention. Although it is believed that those of ordinary skill in the art fully understand the following terms, the following definitions are still stated to help illustrate the subject matter disclosed by the present invention.

[0032] A method for recovering phenolic compounds from epoxy resin-based waste with high yield mainly comprises the following steps:

[0033] (1) mixing epoxy resin, acid / acid solution and salt in a mass ratio of 1:(5-100):(0.1-50), reacting at a temperature of 30-300° C. for 0.5-60 hours, and collecting the reaction product after the time is up;

[0034] (2) The reaction product obtained in step (1) is filtered and separated to obtain a liquid product and a residual solid, and the liquid product is further separated, purified and recovered to obtain a phenolic compound.

[0035] In the step (2), different phenolic compounds are finally obtained according to different epoxy resin materials, for example, at least one of phenol, 4-isopropylphenol, 4-isopropenylphenol, 2-isopropylphenol, 4-methylphenol, 2-methylphenol, 2,4-dimethylphenol, 2,3,4-trimethylphenol, 2,6-diisopropylphenol, bisphenol A, bisphenol S, bisphenol F, tetrabromobisphenol A, 2,6-dibromophenol and 2,6-dibromo-4-isopropylphenol.

[0036] In this article, the epoxy resin described in step (1) generally refers to the product or material prepared by the epoxy resin. Generally, the method for recovering phenolic compounds in the present invention can be aimed at the scraps / waste of the epoxy resin in the production process, or it can be the discarded / wasteful epoxy resin product or material. In one embodiment, the epoxy resin includes conventional epoxy resin types in the chemical industry, for example, including epoxy resins with phenolic structures, such as bisphenol A type, tetrabromobisphenol A type, bisphenol F type, bisphenol S type, phenolic type, etc., with amine curing agents, anhydride curing agents or special purpose curing agents (such as phenolic resins, polyester resins, liquid polyurethanes, styrene-maleic anhydride copolymer resins and polysulfide rubbers thereof), and also includes epoxy resin-based composite materials selected as substrates with the above-mentioned epoxy resins, such as glass fiber reinforced epoxy resins, carbon fiber reinforced epoxy resins, etc.

[0037] It should be noted that when the epoxy resin in step (1) is waste containing epoxy resin or epoxy resin-based waste, it can be selected to undergo a pretreatment including washing, which is mainly to remove impurities on the surface of the waste. If necessary, parts that are not made of epoxy resin (such as metal parts, etc.) need to be removed. Those skilled in the art can perform specific treatment based on the actual conditions of the products or materials that need to be recycled and reused according to the existing technology.

[0038] In one embodiment, the acid / acid solution in step (1) is an acidic liquid used in the degradation process, for example, any one of inorganic acids (hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, phosphotungstic acid), organic acids (formic acid, acetic acid, propionic acid, oxalic acid, malonic acid, succinic acid, malic acid, methanesulfonic acid, toluenesulfonic acid, benzoic acid, phytic acid) and Lewis acids (aluminum chloride, zinc chloride, ferric chloride, ferrous chloride, niobium pentachloride, indium trifluoromethanesulfonate), or a solution prepared by any one of them, or a mixed solution prepared by multiple preparations.

[0039] One of the inventive points of the present invention is that, by making a horizontal comparison of different acids / acid solutions, it is found that formic acid, under the synergistic effect with iodized salt, especially under specific proportions and reaction conditions, can significantly increase the yield of phenolic compounds in degradation products, thereby providing a new way for chemically recycling phenolic compounds from epoxy resin-based waste.

[0040] In one embodiment, the salt in step (1) is selected from at least one of nitrate ions, sulfate ions, sulfite ions, halogen ions (fluoride ions, chloride ions, bromide ions, iodide ions), organic acid ions (such as formate ions, acetate ions, methanesulfonate ions, etc.) and metal ions (potassium ions, sodium ions, calcium ions, copper ions, iron ions, magnesium ions, zinc ions, indium ions, etc.), and ammonium ions.

[0041] Based on the above findings, in one embodiment, the salt in step (1) is a halogen ion salt. In one of the more preferred technical solutions, it is found through comparative experiments that when the salt in step (1) is an iodine salt, the yield of phenolic compounds in the degradation product can be significantly increased compared with other ion salts.

[0042] Typically, the reaction is carried out at a temperature of 30 to 300° C. for 0.5 to 60 hours in step (1). The specific reaction method and operation can be implemented by those skilled in the art according to the common knowledge of the reaction methods and operations for chemical degradation of polymer materials. In one embodiment, for example, any one or a combination of static reaction, stirring reaction, oil bath heating reaction, water bath heating reaction, oven heating reaction, ultrasonic reaction or microwave heating reaction is included.

[0043] It should be emphasized that comparative experiments have found that when the reaction temperature and reaction time conditions are met, phenolic compounds can be degraded to obtain high yields. However, depending on the morphology (such as shape and size) of the epoxy resin to be degraded, especially the epoxy resin product, auxiliary conditions such as stirring reaction can be selected to accelerate the degradation rate.

[0044] In one embodiment, in step (1), the epoxy resin, the acid / acid solution and the salt are mixed in a mass ratio of 1: (5-100): (0.1-50), wherein the mass ratio of the epoxy resin to the acid / acid solution is 1: (5-100): (0.1-50).

[0045] 1:15, 1:16, 1:17, 1:18, 1:19, 1:20, 1:21, 1:22, 1:23, 1:24, 1:25, 1:26, 1:27, 1:28, 1:29, 1:30, 1:31, 1:32, 1:33, 1:34, 1:35, 1:36, 1:37, 1:38, 1:39, 1:40, 1:41, 1:42, 1:43, 1:44, 1:45, 1:46, 1:47, 1:48, 1:49, 1:50, 1:51, 1:52 2. 1:53, 1:54, 1:55, 1:56, 1:57, 1:58, 1:59, 1:60, 1:61, 1:62, 1:63, 1:64, 1:65, 1:66, 1:67, 1:68, 1:69, 1:70, 1:71, 1:72, 1:73, 1:74, 1:75, 1:76, 1:77, 1:78, 1:79, 1:80, 1:81, 1:82, 1:83, 1:84, 1:85, 1:86, 1:87, 1:88, 1:89, 1: 90, 1:91, 1:92, 1:93, 1:94, 1:95, 1:96, 1:97, 1:98, 1:99, 1:100 or any range or point value therebetween; wherein the mass ratio of epoxy resin to salt is 1:(0.1-50), for example 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15 , 1:16, 1:17, 1:18, 1:19, 1:20, 1:21, 1:22, 1:23, 1:24, 1:25, 1:26, 1:27, 1:28, 1:29, 1:30, 1:31, 1:32, 1:33, 1:34, 1:35, 1:36, 1:37, 1:38, 1:39, 1:40, 1:41, 1:42, 1:43, 1:44, 1:45, 1:46, 1:47, 1:48, 1:49, 1:50 or any range or point value therebetween.

[0046] In one embodiment, the reaction in step (1) is carried out at a temperature of 30 to 300°C, for example, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, 15 0℃、155℃、160℃、165℃、170℃、175℃、180℃、185℃、190℃、195℃、200℃、205℃、210℃、215℃、220℃、225℃、230℃、235℃、240℃、245℃、250℃、255℃、260℃、265℃、270℃、275℃、280℃、285℃、290℃、29 5°C, 300°C or any range or point value therebetween; the reaction in step (1) is 0.5 to 60h, for example 0.5h, 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, 21h, 22h, 23h, 24h, 25h, 26h, 27h, 28h, 29h, 30h, 31h, 32h, 33h, 34h, 35h, 36h, 37h, 38h, 39h, 40h, 41h, 42h, 43h, 44h, 45h, 46h, 47h, 48h, 49h, 50h, 51h, 52h, 53h, 54h, 55h, 56h, 57h, 58h, 59h, 60h or any range or point value therebetween.

[0047] Herein, the reaction product in step (2) is separated by filtration to obtain a liquid product and a residual solid, wherein filtration separation is a conventional chemical operation in the art, and those skilled in the art can select a suitable separation method.

[0048] In this article, the liquid product in step (2) is then separated, purified and recovered to obtain phenolic compounds, wherein the separation and purification are conventional chemical operations in the art. In one embodiment, the separation and purification are sequentially performed by extraction, column chromatography (for example, using petroleum ether as an eluent and separating through a silica gel column), and acid-base precipitation (for example, using NaOH solution to make it alkaline to convert phenol into sodium phenolate and then using HCl solution to make it acidic to precipitate it) to separate, and then recovering the phenolic compounds by reduced pressure distillation; the residual liquid generated in the above separation and purification process contains the salt added in step (1), which can also be separated and recovered by conventional salt recovery methods in the art to reduce costs by recycling.

[0049] In one embodiment, the residual solid obtained by filtration and separation in step (2) may be an epoxy resin that has not been completely degraded, depending on the epoxy resin material. It can be selected as the epoxy resin to repeat steps (1) and (2) to achieve complete degradation.

[0050] In one embodiment, the liquid product in step (2) is further separated and purified. After the phenolic compound is obtained through separation and purification, a solid product may be separated during the separation process, which is mainly a resin fragment containing an undegraded phenolic structure. The solid product can be used as an epoxy resin to repeat steps (1) and (2) to recover the phenolic compound.

[0051] The method for recovering phenolic compounds from epoxy resin-based wastes with high yield can be directly applied to the technical field of epoxy resin recovery and reuse.

[0052] The present invention will be further explained in detail with reference to the following examples. However, it should be understood by those skilled in the art that these examples are provided for illustrative purposes only and are not intended to limit the present invention.

[0053] Example

[0054] The embodiments of the present application will be described in detail below in conjunction with the examples, but it will be appreciated by those skilled in the art that the following examples are only used to illustrate the present application and should not be considered as limiting the scope of the present application. The specific conditions not specified in the examples are carried out according to the conditions recommended by normal conditions or manufacturers. The reagents used or the instruments not specified by the manufacturer are all conventional products that can be obtained commercially. The application should not be construed as being limited to the specific examples described.

[0055] 1. Raw materials

[0056]

[0057] 2. Test methods

[0058] In the following examples, small molecule compounds were detected by GCMS and quantified by standards;

[0059] In order to accurately calculate and verify the recovery yield that can be achieved after the epoxy resin is degraded by the method of the present invention, the calculation formula of the yield is as follows:

[0060]

[0061] Where:

[0062] C std is the concentration of the target product standard solution, mg / mL;

[0063] A 1is the chromatographic peak response area of ​​the target product in the liquid product in GCMS;

[0064] V 1 is the volume of the liquid product, mL;

[0065] A std is the chromatographic peak response area of ​​the target product in the liquid product in GCMS;

[0066] m 0 is the theoretical content of the target product in the epoxy resin, mg;

[0067] The degradation product compounds were qualitatively and quantitatively analyzed using a Shimadzu GCMS-QP2010SE system and an Rtx-5MS column (30 m × 0.25 mm × 0.25 μm). In a typical measurement, helium was used as the carrier gas at a flow rate of 1.20 mL min -1 . The temperature of the gas chromatograph oven was increased from 30°C (held for 2 minutes) to 300°C (held for 15 minutes) at a rate of 20°C / min. In split mode, the injector temperature was set to 300°C and the split ratio was 10:1. The ion source temperature was 250°C. The mass spectrometer scanning ion range was set between 29 and 650Da. Qualitative analysis was performed using GC-MS post-run analysis software. The products were identified according to the NIST21 and NIST14s libraries, and the peak areas were calculated based on the SIM chromatograms.

[0068] The surface morphology of the recycled fibers was observed using a scanning electron microscope (SEM, Phenom ProX, Phenom-World, The Netherlands) at an operating voltage of 15 kV.

[0069] 3. Preparation method

[0070] (1) mixing epoxy resin, acid / acid solution and salt in a mass ratio of 1:(5-100):(0.1-50), reacting at a temperature of 30-300° C. for 0.5-60 hours, and collecting the reaction product after the time is up;

[0071] (2) The reaction product obtained in step (1) is filtered and separated to obtain a liquid product and a residual solid, and the liquid product is further separated and purified to recover a phenolic compound.

[0072] Examples 1 to 24

[0073] In Examples 1 to 24, reference is made to the above-mentioned "3. Preparation method", wherein the epoxy resin is selected as bisphenol A epoxy resin cured with 4,4'-diaminodiphenylmethane, and the acid / acid solution selection, salt selection, mass fraction, reaction temperature and reaction time are used as variables. The specific process conditions and test results of each embodiment are shown in the following table:

[0074]

[0075]

[0076] Note: 1. In the above table, the percentages are calculated by mass, and epoxy resin is 1 part.

[0077] 2. The main products and yields in Example 24 are obtained by separating, purifying and recovering the liquid product of step (2) to obtain phenolic compounds, repeating steps (1) and (2) with the remaining solid and the solid product collected during the separation and purification process, and repeating this cycle three times to obtain the total main products and yields of the phenolic compounds.

[0078] Embodiments 25 to 31

[0079] In Examples 25 to 31, reference is made to the above-mentioned "3. Preparation method", wherein the acid / acid solution is formic acid, the salt is sodium iodide, the epoxy resin, formic acid and sodium iodide are in a mass ratio of 1:100:5, the reaction temperature is 130°C, the reaction time is 24h, and the specific selection of the epoxy resin is used as a variable. The test results of each embodiment are shown in the following table:

[0080]

[0081] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for recovering phenolic compounds from epoxy resin-based waste with high yield, characterized in that The main steps include: (1) mixing epoxy resin, acid / acid solution and salt in a mass ratio of 1:(5-100):(0.1-50), reacting at a temperature of 30-300° C. for 0.5-60 hours, and collecting the reaction product after the time is up; (2) The reaction product obtained in step (1) is filtered and separated to obtain a liquid product and a residual solid, and the liquid product is further separated and purified to recover a phenolic compound.

2. The method according to claim 1, characterized in that: The epoxy resin in step (1) includes an epoxy resin having a phenolic structure and an epoxy resin-based composite material having the epoxy resin as a substrate.

3. The method according to claim 1, characterized in that: The acid / acid solution in step (1) includes any one of an inorganic acid, an organic acid and a Lewis acid, or a solution prepared from any one of them, or a mixed solution prepared from multiple preparations thereof.

4. The method according to claim 1, characterized in that: The salt in step (1) includes at least one of salts composed of nitrate ions, sulfate ions, sulfite ions, halogen ions, organic acid ions, metal ions and ammonium ions.

5. The method according to claim 1, characterized in that: The phenolic compound described in step (2) is different according to the epoxy resin, and finally obtains different phenolic compounds, including at least one of phenol, 4-isopropylphenol, 4-isopropenylphenol, 2-isopropylphenol, 4-methylphenol, 2-methylphenol, 2,4-dimethylphenol, 2,3,4-trimethylphenol, 2,6-diisopropylphenol, bisphenol A, bisphenol S, bisphenol F, tetrabromobisphenol A, 2,6-dibromophenol, and 2,6-dibromo-4-isopropylphenol.

6. The method according to claim 1, characterized in that: Repeat steps (1) and (2) using the remaining solid obtained by filtration and separation in step (2) as epoxy resin.

7. The method according to claim 1, characterized in that: The liquid product in step (2) is separated and purified to obtain a solid product, which is used as epoxy resin to repeat steps (1) and (2).

8. The method for recovering phenolic compounds from epoxy resin-based wastes with high yield as claimed in claim 1 is applied to the field of recycling and reuse of epoxy resins.

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