Epoxy degradable resin and application thereof

Abstract

The invention provides an epoxy degradable resin and an application thereof. The invention also provides an anhydride cured epoxy resin composition. According to the invention, the waste cured epoxy resin or a composite material thereof is degraded and recycled to obtain the hydroxyl-rich degradable resin, and the degradable resin can be subjected to secondary crosslinking with the epoxy resin at high temperature, so that the performance of the obtained cured product can be improved; the epoxy degradable resin provided by the invention can replace part of fresh epoxy resin raw materials for cross-linking and curing, so that the dosage of the epoxy resin raw materials can be greatly reduced, the manufacturing cost is reduced, the waste epoxy resin cured material can be effectively reused, and the treatment pressure is relieved.

Description

Technical Field

[0001] The present invention relates to the field of polymer materials, in particular to an epoxy degradable resin and applications thereof, and also to an anhydride-cured epoxy resin composition and a cured product prepared therefrom. Background Art

[0002] Anhydride-cured epoxy resins are a type of curing system that forms a cross-linked network structure through the reaction of an anhydride curing agent with an epoxy resin. These resins feature low shrinkage, no byproducts, excellent heat resistance, excellent sealing properties, good insulation, and a wide selection of additives. They are used in a variety of applications, including electronic potting, electrical casting, and pultrusion. They can also be used as prepreg resins. Improving the performance of anhydride-cured epoxy resins and reducing their cost through effective means has long been a key research topic.

[0003] Chinese patent application CN 118878787A discloses a high-degradability, low-carbon, and environmentally friendly insulating resin system comprising a base material, an anhydride curing agent, and a curing accelerator. The base material comprises an epoxy resin oligomer and an epoxy resin, the epoxy resin oligomer being formed by degradation of a cured epoxy resin, and the curing accelerator comprising a salt of a tertiary amine compound. Compared to existing technologies, this patent application utilizes a dynamic bond exchange reaction between epoxy resin and an alcohol solvent to degrade high-performance epoxy resins commonly used in industry into oligomers. These oligomers are then used as reactants to prepare new epoxy resins, termed remanufactured epoxy resins. This completes the entire manufacturing, recycling, and remanufacturing process for industrial epoxy resins and their composites, creating a closed-loop recycling and remanufacturing process. However, this patent application only examines the degradation and remanufacturing of E51 epoxy resin, without further in-depth research. Moreover, in this patent application, the maximum amount of recycled epoxy resin oligomers used is 3% of the mass of the base epoxy resin material. When the amount of oligomers continues to increase, the tensile strength, elastic modulus and thermal stability of the remanufactured epoxy resin begin to decline, which limits the reuse of oligomers. Summary of the Invention

[0004] To overcome the shortcomings of the prior art in the reuse and development of waste epoxy resin cured products, the present invention aims to provide an epoxy degradable resin. The epoxy degradable resin is obtained from waste epoxy resin cured products and can be used as a partial raw material for preparing new epoxy resin cured products. The resulting cured products have excellent properties and can also reduce manufacturing costs. At the same time, they can also reduce waste disposal costs and alleviate environmental pressures.

[0005] A first aspect of the present invention provides an epoxy degradable resin, which is prepared by degrading an epoxy resin cured product formed by cross-linking an epoxy resin and an amine curing agent, or a composite material with an epoxy resin cured product formed by cross-linking an epoxy resin and an amine curing agent as a resin matrix; wherein the epoxy degradable resin has a weight-average molecular weight of 1000 to 5000 and a hydroxyl value of 80 to 500 mg KOH / g.

[0006] In some embodiments of the present invention, the weight average molecular weight of the epoxy degradable resin may be further 1000 to 4500, and the hydroxyl value may be further 100 to 400 mg KOH / g.

[0007] In some embodiments of the present invention, the composite material can be selected from composite materials commonly used in the art with epoxy resin cured material as the resin matrix, such as resin-fiber composite reinforced materials. In this case, the composite material can also include toughening fibers, such as carbon fibers, glass fibers, etc.

[0008] In some embodiments of the present invention, the epoxy resin cured material or the composite material thereof used to prepare the epoxy degradable resin may be a recycled epoxy resin cured material or the composite material thereof.

[0009] In some embodiments according to the present invention, the epoxy resin can be selected from the glycidyl ether epoxy resins commonly used in the art for forming epoxy resin cured products. In some preferred embodiments, the viscosity of the glycidyl ether epoxy resin at 25°C can be 1000 to 10000 mPa.s, for example, 2000 to 4000 mPa.s, and the epoxy equivalent weight of the glycidyl ether epoxy resin can be 150 to 200 g / eq, for example, 170 to 190 g / eq. In some more preferred embodiments, the epoxy resin can be selected from one or more of bisphenol A epoxy resin, bisphenol F epoxy resin, and novolac epoxy resin.

[0010] In some embodiments according to the present invention, the amine curing agent can be selected from the amine curing agents commonly used in the art for forming epoxy resin cured products. In some preferred embodiments, the amine curing agent can be selected from one or more of aliphatic amine curing agents, polyamide curing agents, and ester ring amine curing agents, for example, one or more of diethylenetriamine, polyamide 650, and isophorone diamine. In some more preferred embodiments, the amine value of the amine curing agent can be 200 to 800 mg KOH / g, for example, 400 to 600 mg KOH / g.

[0011] In some embodiments of the present invention, the epoxy degradable resin can be prepared by degrading the epoxy resin cured product or the composite material in a degradation system comprising a polar solvent, a hydrogen-donating solvent, and a degradation catalyst.

[0012] In some embodiments of the present invention, the polar solvent can be selected from the common polar solvents in the art with a solubility parameter of 20 to 30 MPa. 1 / 2 The invention also provides a polar solvent such as one or more of N,N-dimethylformamide, N,N-diethylformamide, and N-methylpyrrolidone; the hydrogen-donating solvent can be selected from one or more of formic acid, acetic acid, and phenol; and the degradation catalyst can be selected from a common non-oxidizing strong acid with a boiling point ≥100°C and a pKa ≤2 in the art, such as one or more of p-toluenesulfonic acid and benzenesulfonic acid. In some preferred embodiments, the polar solvent can be selected from N-methylpyrrolidone, the hydrogen-donating solvent can be selected from formic acid or acetic acid, and the degradation catalyst can be selected from p-toluenesulfonic acid.

[0013] In some embodiments of the present invention, in the degradation system, the weight ratio of the cured epoxy resin material or the cured epoxy resin material in the composite material, the polar solvent, the hydrogen donating solvent, and the degradation catalyst may be 1:5-50:0.05-1:0.1-1. In some preferred embodiments, the weight ratio of the cured epoxy resin material or the cured epoxy resin material in the composite material, the polar solvent, the hydrogen donating solvent, and the degradation catalyst may be 1:10-30:0.1-0.8:0.1-0.8. In some more preferred embodiments, the weight ratio of the cured epoxy resin material or the cured epoxy resin material in the composite material, the polar solvent, the hydrogen donating solvent, and the degradation catalyst may be 1:15-25:0.1-0.6:0.2-0.8.

[0014] In some embodiments of the present invention, the preparation process of the epoxy degradable resin may include the following steps:

[0015] S1: degrading the epoxy resin cured material or the composite material in the degradation system at a temperature of 150-250° C. (e.g., 200-250° C.) until the epoxy resin cured material or the epoxy resin cured material in the composite material is dissolved in the degradation system, thereby obtaining a degradation solution;

[0016] S2: filtering the degradation solution, and concentrating the filtrate to 10-20% (eg, 14-16%) of the initial total solvent weight to obtain a concentrate; and

[0017] S3: dissolving the concentrate in 1 to 3 times (for example, 1 to 1.5 times) the weight of a low-boiling-point solvent and adjusting the pH value of the resulting solution to 7 to 7.5, separating the resulting precipitate, washing it, and drying it to obtain the epoxy degradable resin.

[0018] In some preferred embodiments, the low boiling point solvent can be selected from one or more of dichloromethane and chloroform.

[0019] In some preferred embodiments, the drying temperature may be 50-120°C, for example, 60-100°C.

[0020] A second aspect of the present invention provides use of the epoxy degradable resin described in any one of the above technical solutions for preparing a cured epoxy resin or a composite material having the cured epoxy resin as a resin matrix.

[0021] In some embodiments of the present invention, the epoxy resin cured material may be selected from epoxy resin cured materials prepared by curing with an acid anhydride curing agent.

[0022] In some embodiments of the present invention, the composite material with epoxy resin cured material as the resin matrix can be selected from resin-fiber composite reinforcement materials. In this case, the composite material can also include toughening fibers such as carbon fibers, glass fibers, etc.

[0023] A third aspect of the present invention provides an anhydride-cured epoxy resin composition, which comprises an epoxy resin mixed material (i.e., an epoxy resin raw material for curing) and an anhydride curing agent, wherein, by weight percentage, the epoxy resin mixed material contains greater than 0 and no more than 50% of the epoxy degradable resin described in any one of the above technical solutions.

[0024] In some embodiments of the present invention, the amount of the epoxy degradable resin provided herein in the epoxy resin mixed material can be adjusted based on actual performance requirements, cost requirements, etc., as long as the performance of the resulting cured product is not inferior to that of a cured product without the epoxy degradable resin. In some preferred embodiments, the amount of the epoxy degradable resin provided herein in the epoxy resin mixed material can be 5-30% by weight, and further can be 10-20% by weight.

[0025] In some embodiments of the present invention, the anhydride-cured epoxy resin composition may comprise, by weight, 100 parts of an epoxy resin mixed material, 70-100 parts of an anhydride curing agent, 0.1-0.3 parts of a defoaming agent, and 0.5-3 parts of a curing accelerator, wherein, by weight percentage, the epoxy resin mixed material comprises greater than 0 and no more than 30% of the epoxy degradable resin described in any one of the above technical solutions, and the balance is a liquid epoxy resin. In some preferred embodiments, by weight percentage, the epoxy resin mixed material comprises 5-30% of the epoxy degradable resin described in any one of the above technical solutions, and the balance is a liquid epoxy resin.

[0026] In some embodiments of the present invention, the liquid epoxy resin may be a common type in the art, having a viscosity lower than 20,000 mPa.s at 25° C., for example, one or more selected from bisphenol A epoxy resin and bisphenol F epoxy resin.

[0027] In some embodiments of the present invention, the acid anhydride curing agent can be a common type in the art, for example, it can be selected from one or more of methyl nadic anhydride, methyltetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, and phthalic anhydride.

[0028] In some embodiments of the present invention, the curing accelerator may be a common type in the art, for example, one or more selected from triethanolamine, 2,4,6-tris(dimethylaminomethyl)phenol, benzyldimethylamine, and triethylamine.

[0029] In some embodiments of the present invention, the defoaming agent may be a common type in the art, for example, may be selected from BYK066.

[0030] The fourth aspect of the present invention provides an anhydride-cured epoxy resin cured material, or a composite material with an anhydride-cured epoxy resin cured material as a resin matrix, wherein the anhydride-cured epoxy resin cured material is obtained by curing the anhydride-cured epoxy resin composition described in any one of the above technical solutions.

[0031] In some embodiments of the present invention, the composite material with the epoxy resin cured product obtained by curing with an anhydride-type curing agent as the resin matrix can be selected from resin-fiber composite reinforcement materials. In this case, the composite material can also include toughening fibers, such as carbon fibers, glass fibers, etc.

[0032] In some embodiments of the present invention, the curing process may include curing at 80-120° C. for 1-5 hours, and then curing at 140-180° C. for 2-10 hours. In some preferred embodiments, the curing process may include curing at 90-110° C. for 1-3 hours, and then curing at 140-160° C. for 4-6 hours.

[0033] In some embodiments of the present invention, the desired material (e.g., separated precipitate) can be obtained through a separation step, and the separation equipment or method can be a common equipment or method in the art, including but not limited to natural sedimentation, (normal pressure or vacuum) filtration, centrifugation, etc. and their common equipment.

[0034] In some embodiments of the present invention, the washing step refers to washing the material with distilled water or deionized water. The number of washing times can be adjusted according to actual conditions, for example, 2 to 5 times, usually 3 times.

[0035] The technical solution provided by the present invention has the following advantages:

[0036] (1) The present invention utilizes discarded epoxy resin cured products or their composite materials, and recovers a hydroxyl-rich degraded resin after degradation treatment. The degraded resin can undergo secondary cross-linking with the epoxy resin raw material at high temperature, and because it contains more hydroxyl groups, it can promote further curing of the epoxy resin, thereby improving the performance of the obtained cured product. Therefore, the epoxy degradable resin provided by the present invention has great application prospects in the field of manufacturing epoxy resin cured products or their composite materials.

[0037] (2) The epoxy degradable resin provided by the present invention can replace part of the fresh epoxy resin raw materials for curing, thereby greatly reducing the amount of epoxy resin raw materials used and lowering the manufacturing cost. Moreover, the waste epoxy resin cured product or its composite material can also be effectively reused, reducing the processing pressure, and thus has the advantages of environmental protection, high efficiency, and green recycling.

[0038] (3) The epoxy degradable resin provided by the present invention has a simple preparation process, strong operability and easy control, and a wide range of raw material sources, thus having good industrial applicability. DETAILED DESCRIPTION

[0039] The technical solution of the present invention is further described in detail below with reference to specific embodiments.

[0040] The epoxy resin cured product to be degraded used in the examples and comparative examples of the present invention is:

[0041] (1) Epoxy resin curing block: a glycidyl ether epoxy resin (viscosity of 2200-3200 mPa.s (25°C), epoxy equivalent of 172-185 g / eq) and a mixed ester ring amine curing agent (amine value of 450-550 mg KOH / g) with the trade name 5089A produced by Huibai New Materials Technology (Shanghai) Co., Ltd. were uniformly mixed in a mass ratio of 100:30 and then cured at 25°C for 24 h and 70°C for 6 h to form a curing block.

[0042] (2) Composite material blocks: glycidyl ether epoxy resin (trade name 5089A) and mixed ester cyclic amine curing agent (trade name 5089B) of Huibai New Material Technology (Shanghai) Co., Ltd. were uniformly mixed in a mass ratio of 100:30 as the infusion resin, and the composite material blocks were prepared by vacuum infusion process with glass fiber fabric S-EWF800 (Changzhou Tianma Group Co., Ltd.). The blocks were cured at 25°C for 24 hours and 70°C for 6 hours. The mass content of glass fiber was about 74.0%.

[0043] Other raw materials or reagents were commercially available unless otherwise specified.

[0044] Unless otherwise specified, the percentages used in the examples and comparative examples of the present invention are all percentages by mass.

[0045] In the examples and comparative examples of the present invention, room temperature refers to 25±5°C.

[0046] Example 1 Preparation of epoxy degradable resin Z-1

[0047] 1.7 g of a cured epoxy resin block (15 mm × 10 mm × 10 mm) was placed in a mixture consisting of 40.0 g of N-methylpyrrolidone, 1.0 g of acetic acid, and 1.2 g of p-toluenesulfonic acid, and the p-toluenesulfonic acid was completely dissolved. The mixture was reacted in an autoclave at 230°C for 2 hours until the cured epoxy resin block was completely dissolved. The resulting degradation solution was filtered and the filtrate was recovered. The filtrate was vacuum evaporated until the residual solvent in the filtrate was approximately 12% of the initial total solvent weight. The evaporated product was dissolved in dichloromethane at a weight ratio of 1:1, and then a saturated aqueous sodium bicarbonate solution was added to adjust the pH to 7-7.5. The mixture was then precipitated and washed with water until the washing liquid was colorless. The clean precipitate was dried in an 80°C oven to constant weight to obtain epoxy degradation resin Z-1. GPC analysis revealed a weight-average molecular weight of approximately 1100 and a titrated hydroxyl number of 342 mg KOH / g.

[0048] Example 2 Preparation of epoxy degradable resin Z-2

[0049] Five composite material blocks (each measuring 20 mm × 20 mm × 2 mm), totaling 8.5 g, were placed in a mixture of 40.0 g N-methylpyrrolidone, 0.4 g formic acid, and 0.8 g p-toluenesulfonic acid, and the p-toluenesulfonic acid was completely dissolved. The mixture was reacted in an autoclave at 220° C. for 2 hours until the epoxy resin cured material in the composite material blocks was completely dissolved, leaving only glass fiber in the autoclave. The resulting degradation liquid was filtered and the filtrate was recovered. The filtrate was vacuum evaporated until the residual solvent in the filtrate was 15% of the initial total solvent weight. The rotary evaporation product was dissolved in dichloromethane solvent at a weight ratio of 1:1, and then a saturated sodium bicarbonate aqueous solution was added to adjust the pH to 7-7.5. The mixture was then precipitated and washed with water until the washing liquid was colorless. The clean precipitate was placed in an 80° C. oven and dried to constant weight to obtain epoxy degradation resin Z-2. GPC testing showed that its weight-average molecular weight was approximately 4100 and the titrated hydroxyl value was 100 mgKOH / g.

[0050] Example 3 Application of epoxy degradable resin

[0051] The epoxy resin mixture was prepared by using the epoxy degradable resin Z-1 prepared in Example 1 as a recycled raw material, and the preparation steps were as follows:

[0052] (1) Heat 90.0 g of liquid epoxy resin (trade name: Nan Ya 128 bisphenol A epoxy resin) to 130°C, add 10.0 g of epoxy degradation resin Z-1, and stir to dissolve until the solution is free of particles and has a uniform color.

[0053] (2) Cool the product obtained in step (1) to 50°C, add 0.2 g of defoamer (trade name: BYK066), and stir evenly;

[0054] (3) The product obtained in step (2) was temperature-controlled to 50° C., 0.8 g of an accelerator (2,4,6-tris(dimethylaminomethyl)phenol) and 80.0 g of an anhydride curing agent (methyltetrahydrophthalic anhydride) were added, and the mixture was stirred evenly. Degassing was continued for 40 min under a vacuum condition of -0.090 MPa to form an epoxy resin mixture.

[0055] Example 4 Application of epoxy degradable resin

[0056] The epoxy resin mixture was prepared by using the epoxy degradable resin Z-1 prepared in Example 1 as a recycled raw material, and the steps were as follows:

[0057] (1) Heat 80.0 g of liquid epoxy resin (trade name: Nan Ya 170 bisphenol F epoxy resin) to 120°C, add 20.0 g of epoxy degradation resin Z-1, and stir to dissolve until there are no particles and the color is uniform;

[0058] (2) Cool the product obtained in step (1) to 50°C, add 0.1 g of defoamer (trade name: BYK066), and stir evenly;

[0059] (3) The product obtained in step (2) was temperature-controlled to 50° C., 1.35 g of an accelerator (2,4,6-tris(dimethylaminomethyl)phenol) and 90.0 g of an anhydride curing agent (methyltetrahydrophthalic anhydride) were added, stirred evenly, and degassed continuously for 40 min under a vacuum of -0.090 MPa to form an epoxy resin mixture.

[0060] Example 5 Application of epoxy degradable resin

[0061] The raw material ratio and preparation process of Example 3 were followed, except that the epoxy degradable resin was replaced by the epoxy degradable resin Z-2 prepared in Example 2 as the recycled raw material, and other changes were not made.

[0062] Example 6 Application of epoxy degradable resin

[0063] The raw material ratio and preparation process of Example 4 were followed, except that the epoxy degradable resin was replaced by the epoxy degradable resin Z-2 prepared in Example 2 as the recycled raw material, and other changes were not made.

[0064] Comparative Example 1 Preparation of epoxy degradable resin

[0065] The epoxy resin cured block was degraded according to the preparation method of Example 1, except that p-toluenesulfonic acid was not added and was replaced with an equal weight of acetic acid (i.e., the total amount of acetic acid was 2.2 g and the amount of p-toluenesulfonic acid was 0 g). After the degradation system was evenly mixed, it was reacted in an autoclave at 230°C for 2 hours. The epoxy resin cured block was broken and not degraded, and the desired epoxy degradable resin could not be obtained.

[0066] Comparative Example 2 Preparation of epoxy degradable resin

[0067] 1.7 g (15 mm × 10 mm × 10 mm) of the epoxy resin cured block used in Example 1 was placed in a mixture of 40.0 g of N-methylpyrrolidone, 1.0 g of acetic acid, and 2.0 g of p-toluenesulfonic acid, and the p-toluenesulfonic acid was completely dissolved; the mixture was reacted in an autoclave at 250° C. for 2 hours until the epoxy resin cured block was completely dissolved; the resulting degradation liquid was filtered and the filtrate was recovered, and the filtrate was vacuum evaporated until the residual solvent in the filtrate was approximately 15% of the initial total solvent weight; the rotary evaporation product was dissolved in dichloromethane solvent at a weight ratio of 1:1, and then a saturated sodium bicarbonate aqueous solution was added to adjust the pH to 7-7.5, followed by precipitation, and the precipitate was washed with water until the washing liquid was colorless; the clean precipitate was placed in an 80° C. oven and dried to constant weight to obtain epoxy degradable resin Z-3. GPC testing showed that the weight average molecular weight was about 550 and the titrated hydroxyl value was 542 mg KOH / g, indicating that excessive use of the catalyst p-toluenesulfonic acid would lead to a higher degree of degradation, resulting in a smaller molecular weight of the degraded resin and an increased hydroxyl content.

[0068] Comparative Example 3 Preparation of epoxy degradable resin

[0069] 1.7 g (15 mm × 10 mm × 10 mm) of the epoxy resin cured block used in Example 1 was placed in a mixture of 40.0 g of N-methylpyrrolidone, 1.0 g of acetic acid, and 0.1 g of p-toluenesulfonic acid, and the p-toluenesulfonic acid was completely dissolved; the mixture was reacted in an autoclave at 250° C. for 5 hours until the epoxy resin cured block was completely dissolved; the resulting degradation liquid was filtered and the filtrate was recovered, and the filtrate was vacuum evaporated until the residual solvent in the filtrate was approximately 15% of the initial total solvent weight; the rotary evaporation product was dissolved in dichloromethane solvent at a weight ratio of 1:1, and then a saturated sodium bicarbonate aqueous solution was added to adjust the pH to 7-7.5, followed by precipitation, and the precipitate was washed with water until the washing liquid was colorless; the clean precipitate was placed in an 80° C. oven and dried to constant weight to obtain epoxy degradable resin Z-4. GPC testing showed that the weight average molecular weight was about 6500 and the titrated hydroxyl value was 72 mg KOH / g, indicating that when the amount of the catalyst p-toluenesulfonic acid was too small, the degree of degradation would be insufficient, and the molecular weight of the degraded resin would increase and the hydroxyl content would decrease.

[0070] Comparative Example 4

[0071] An epoxy resin mixture was prepared according to the preparation process of Example 3, except that no epoxy degradation resin was added as a recycled raw material. Other changes were not made, that is, 100.0 g of liquid epoxy resin (trade name: Nan Ya 128 bisphenol A epoxy resin) was used.

[0072] Comparative Example 5

[0073] An epoxy resin mixture was prepared according to the preparation process of Example 4, except that no epoxy degradation resin was added as a recycled raw material. That is, 100.0 g of liquid epoxy resin (trade name: Nan Ya 170 bisphenol F epoxy resin) was used.

[0074] Comparative Example 6

[0075] An epoxy resin mixture was prepared according to the preparation process of Example 3, except that epoxy degradation resin Z-3 was used instead of Z-1 as the recycled raw material. All other changes were made. That is, 90.0 g of liquid epoxy resin (trade name: Nan Ya 128 bisphenol A epoxy resin) and 10.0 g of epoxy degradation resin Z-3 were used, for a total of 100.0 g.

[0076] Comparative Example 7

[0077] An epoxy resin mixture was prepared according to the preparation process of Example 3, except that epoxy degradation resin Z-4 was used instead of Z-1 as the recycled raw material. The other steps were unchanged, that is, 90.0 g of liquid epoxy resin (trade name: Nan Ya 128 bisphenol A epoxy resin) and 10.0 g of epoxy degradation resin Z-4 were used, for a total of 100.0 g.

[0078] The epoxy resin mixtures prepared in Examples 3-6 and Comparative Examples 4-7 were cured according to the following process: each epoxy resin mixture was poured into a tetrafluoroethylene mold, placed in an oven, cured at 100°C for 2 hours, then heated to 150°C for 5 hours, then cooled to room temperature, allowed to stand for 24 hours, and then demolded to obtain test specimens. The test specimens were then subjected to relevant performance tests as follows:

[0079] ① Take 10 mg of the cured test sample and use a Q2000 differential scanning calorimeter (DSC) to measure the glass transition temperature (Tg) of the sample;

[0080] ② Make dumbbell-shaped specimens according to GB / T1040 and test the tensile and bending strength;

[0081] ③ Prepare a 15mm×10mm×10mm sample and use a precision electronic balance to weigh the sample to be tested as W1. Then soak it in deionized water (60℃) and take it out after 48 hours. Wipe the surface moisture with filter paper and weigh it as W2. Calculate the water absorption rate = (W2-W1) / W1×100%.

[0082] The test results are shown in Table 1:

[0083] Table 1 Performance test results of epoxy resin cured products

[0084]

[0085]

[0086] It can be seen from the above examples and comparative examples that:

[0087] (1) By comparing Examples 1-2 and Comparative Example 1, it can be seen that the degradation catalyst is the key to preparing the epoxy degradable resin. The system with only polar solvents and hydrogen-donating solvents cannot successfully obtain the degradable resin.

[0088] (2) Comparative Examples 2 and 3 illustrate that the amount of degradation catalyst used is crucial to the degree of degradation of epoxy resin cured products. Excessive or insufficient degradation will lead to drastic changes in the molecular weight and hydroxyl value of the degraded resin, thereby affecting its reuse.

[0089] (3) By comparing Examples 3-4 and Comparative Examples 4-5, it can be seen that the epoxy degradable resin provided by the present invention can replace part of the fresh epoxy resin raw materials, and the obtained cured product has good performance, and is even significantly better than the cured product prepared from all fresh raw materials. This shows that the epoxy degradable resin with a suitable molecular weight and hydroxyl value can participate in the curing reaction and promote cross-linking at high temperature, thereby improving the temperature resistance and mechanical properties of the cured resin, and reducing the water absorption of the cured product at high temperature; moreover, the epoxy degradable resin provided by the present invention can replace a considerable part of the fresh epoxy resin raw materials (based on Examples 3-4, if the performance standard of the cured product is maintained without adding recycled resin, the amount of recycled resin used can be further increased), thereby significantly reducing the amount of epoxy resin raw materials used, and then significantly reducing the manufacturing cost. At the same time, it also effectively reduces the processing pressure of waste cured products or their composite materials, is environmentally friendly, and can form a green cycle.

[0090] (4) By comparing Example 3 with Comparative Examples 6-7, it can be seen that the molecular weight and hydroxyl value of the epoxy degradable resin provided by the present invention are very important for replacing part of the fresh epoxy resin raw material to form a cured product. When the molecular weight and hydroxyl value change significantly, it will lead to unsatisfactory curing and cross-linking, and the performance of the cured product will be significantly reduced. At this time, the recovered epoxy degradable resin cannot be effectively reused or can only be reused in a very small amount.

[0091] Unless otherwise defined, the terms used in the present invention have the same meanings as those commonly understood by those skilled in the art.

[0092] The embodiments described in the present invention are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. Those skilled in the art may make various other substitutions, changes and improvements within the scope of the present invention. Therefore, the present invention is not limited to the above-mentioned embodiments, but is only limited by the claims.

Claims

1. An epoxy degradable resin, characterized in that The epoxy degradable resin is prepared by degrading an epoxy resin cured product formed by cross-linking an epoxy resin and an amine curing agent, or a composite material with an epoxy resin cured product formed by cross-linking an epoxy resin and an amine curing agent as a resin matrix; wherein the epoxy degradable resin has a weight average molecular weight of 1000 to 5000 and a hydroxyl value of 80 to 500 mg KOH / g.

2. The epoxy degradable resin according to claim 1, wherein The epoxy degradable resin has a weight average molecular weight of 1000 to 4500 and a hydroxyl value of 100 to 400 mg KOH / g; and / or The composite material further comprises toughening fibers, preferably selected from carbon fibers and / or glass fibers; Preferably, the epoxy resin cured material or the composite material is selected from recycled epoxy resin cured material or composite material.

3. The epoxy degradable resin according to claim 1 or 2, wherein The epoxy resin is selected from glycidyl ether epoxy resins; Preferably, the glycidyl ether epoxy resin has a viscosity of 1000 to 10000 mPa.s at 25° C. and an epoxy equivalent weight of 150 to 200 g / eq; and / or The amine curing agent is selected from one or more of aliphatic amine curing agents, polyamide curing agents, and ester ring amine curing agents; Preferably, the amine value of the amine curing agent is 200 to 800 mg KOH / g.

4. The epoxy-degradable resin according to any one of claims 1 to 3, characterized in that The epoxy degradable resin is prepared by degrading the epoxy resin cured product or the composite material in a degradation system comprising a polar solvent, a hydrogen-donating solvent, and a degradation catalyst; Preferably, the polar solvent is selected from the group consisting of solvents with a solubility parameter of 20 to 30 MPa. 1 / 2 A polar solvent, preferably one or more selected from N,N-dimethylformamide, N,N-diethylformamide, N-methylpyrrolidone; and / or The hydrogen-donating solvent is selected from one or more of formic acid, acetic acid, and phenol; and / or The degradation catalyst is selected from a non-oxidizing strong acid with a boiling point ≥100°C and a pKa ≤2, preferably selected from one or more of p-toluenesulfonic acid and benzenesulfonic acid; More preferably, the weight ratio of the epoxy resin cured material or the epoxy resin cured material in the composite material, the polar solvent, the hydrogen donating solvent and the degradation catalyst is 1:5-50:0.05-1:0.1-1.

5. The epoxy degradable resin according to claim 4, characterized in that The preparation process of the epoxy degradable resin comprises: S1: degrading the epoxy resin cured material or the composite material in the degradation system at a temperature of 150 to 250° C. until the epoxy resin cured material or the epoxy resin cured material in the composite material is dissolved in the degradation system, thereby obtaining a degradation liquid; S2: filtering the degradation solution, and concentrating the filtrate to 10-20% of the initial total solvent weight to obtain a concentrate; and S3: dissolving the concentrate in 1 to 3 times its weight of a low-boiling-point solvent and adjusting the pH value of the resulting solution to 7 to 7.5, separating the resulting precipitate, washing it, and drying it to obtain the epoxy degradable resin; Preferably, the low boiling point solvent is selected from one or more of dichloromethane and chloroform.

6. Use of the epoxy degradable resin according to any one of claims 1 to 5 for preparing a cured epoxy resin or a composite material having the cured epoxy resin as a resin matrix; Preferably, the epoxy resin cured material is selected from epoxy resin cured materials obtained by curing with an acid anhydride curing agent; More preferably, the composite material further comprises toughening fibers, preferably selected from carbon fibers and / or glass fibers.

7. An anhydride-cured epoxy resin composition comprising an epoxy resin mixed material and an anhydride curing agent, characterized in that: Calculated by weight percentage, the epoxy resin mixed material contains more than 0 and no more than 50% of the epoxy degradable resin according to any one of claims 1 to 5.

8. The anhydride-cured epoxy resin composition according to claim 7, wherein The anhydride-cured epoxy resin composition comprises, by weight, 100 parts of an epoxy resin mixed material, 70-100 parts of an anhydride curing agent, 0.1-0.3 parts of a defoaming agent, and 0.5-3 parts of a curing accelerator, wherein, by weight percentage, the epoxy resin mixed material comprises greater than 0 and no more than 30% of the epoxy degradable resin according to any one of claims 1 to 5 and the balance is a liquid epoxy resin; Preferably, the epoxy resin mixed material comprises, by weight percentage, 5 to 30% of the epoxy degradable resin according to any one of claims 1 to 5 and the balance being liquid epoxy resin.

9. The anhydride-cured epoxy resin composition according to claim 8, wherein The liquid epoxy resin has a viscosity of less than 20,000 mPa.s at 25° C. and is preferably selected from one or more of bisphenol A epoxy resin and bisphenol F epoxy resin; and / or The anhydride curing agent is selected from one or more of methyl nadic anhydride, methyltetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, and phthalic anhydride; and / or The curing accelerator is selected from one or more of triethanolamine, 2,4,6-tris(dimethylaminomethyl)phenol, benzyldimethylamine, and triethylamine.

10. An acid anhydride-cured epoxy resin cured product, or a composite material using an acid anhydride-cured epoxy resin cured product as a resin matrix, characterized in that: The anhydride-cured epoxy resin cured product is obtained by curing the anhydride-cured epoxy resin composition according to any one of claims 7 to 9; Preferably, the composite material further comprises toughening fibers, preferably selected from carbon fibers and / or glass fibers; More preferably, the curing process comprises: curing at 80-120° C. for 1-5 hours, and then curing at 140-180° C. for 2-10 hours.

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