WO2018213317A1 - Degradable cyclic amine curing agents with high glass temperature and applications thereof - Google Patents

Abstract

The present invention provides, among others, compounds of the following formula which can be used as degradable curing agents, methods for preparing the compounds, degradable polymers and reinforced composites, methods for degrading and recycling the polymers and composites. (I)

Description

DEGRADABLE CYCLIC AMINE CURING AGENTS WITH HIGH GLASS

TEMPERATURE AND APPLICATIONS THEREOF

Cross-Reference to Related Application

[01] This application claim priority to US Application No. 62/506,201, filed on May 15, 2017, the contents of which are incorporate herein by reference in their entirety.

Background of the Invention

[02] Epoxy resin as binder and coating has a large global market as an industry standard plastic matrix of the manufacture of fiber-reinforced plastics (FRP). FRPs are composite materials composed by a polymer matrix and fibers such as carbon fibers, glass fibers, aramid fibers, natural fibers or other fibers. Fiber helps to enhance the strength, elasticity and other aspects of performance of plastics. FRPs are also commonly referred to as "plastic composite material," or simply as "composite material." "Plastic composite material" also includes non-fibrous materials such as metal or nanomaterials. Plastic composite material can be used as lightweight alternatives for other structural materials (such as steel or aluminum), which are widely used in automotive, aerospace, marine craft, wind energy, PCB and sporting goods industries. Lightweight composite material help to improve energy efficiency, which has significant environmental benefits, however, the persistence and limits of recycling of thermoset plastic composite material in the

environment offset its positive impact. On the growing wind power can be predicted to cause accumulation of garbage of industrial waste materials will be a typical example.

[03] The most common epoxy formulations consist of a diepoxide ("resin") and a polyamine ("hardener") to form a polymeric network of essentially infinite molecular weight. The combination of "resin and hardener" is sometimes referred to as "cured epoxy," "cured resin," or simply "resin" or "epoxy." The widespread utility of such epoxy formulations is due to their excellent processability prior to curing and their excellent post-cure adhesion, mechanical strength, thermal profile, electronic properties, chemical resistance, etc.

Furthermore, the high-density, infusible three-dimensional network of epoxies makes it an extremely robust material, resulting in it being the material of choice for many long-term applications. For instance, epoxy resin, due to its excellent physical and mechanical properties, electrical insulation, and adhesive performance, is widely used in composite materials, casting parts, electronics, coating, etc. At the same time, this durability makes its removal, recycling and reworking notoriously difficult, raising concerns about the longevity of epoxy-based materials in the environment. The cross-linking reactions that occur with two convertibly used component epoxies are essentially irreversible. Therefore, the material cannot be melted and reshaped without decomposition of the material. Thus, there exists a need for new epoxy formulations that retain the remarkable physical properties of classical epoxies, but can be disassembled in a controlled and mild manner when desired, without damaging the underlying structure.

[04] As epoxy adhesives are used for the assembly of a variety of common items and epoxies serve as the matrix materials for a variety of structural materials and composites, the development of such a "reworkable" material would have implications in recycling, recovery, and waste disposal. Furthermore, an easily removable epoxy could expand the use of epoxies to new consumer markets. For example, joints could be bonded with epoxy glue and any spill-over could be easily removed, even post-curing, while the joint remains bonded. As another example, epoxy based paints and varnishes could be more easily removed.

[05] The intractability of a cured resin stems, in part, from its highly cross-linked network. If the links in the three-dimensional network can be cleaved under controlled conditions, the network can be disassembled or degraded into smaller, soluble molecules and/or polymer, therefore removing the cured resin stem. In principal, this can be accomplished through use of either a dissolvable resin or a curing agent that contains a bond capable of cleavage under a specific set of conditions. In the limited amount of prior art on this topic, the majority has focused on cleavable groups in the resin component. Epoxy formulations that possess cleavable linkages in the hardener, are particularly attractive, as those skilled in the art realize that a great deal of more flexibility exists with regard to the constituents in a hardener component, due to the resin components in most epoxies are based on bisphenol digylcidyl ether (BPADGE).

[06] Global composites production capacity significantly increased in recent years to exceed 10 million tons per year. However, how to deal with and recycle the waste of fiber composites is now a worldwide problem and has prevented the fiber composite industry's growth, thereby constraining the sustainable development of fiber composites. [07] In literature, the recovery process of fiber composites has been reported roughly in the following ways: 1. High temperature thermal degradation (see, e.g., Thermochimica Acta, 2007(454):109-115), which can recycle composite material to obtain clean filler and fiber, but requires high temperature processing and high standard equipment; 2. Fluidized bed (see, .e.g, Applied Surface Science, 2008(254): 2588-2593), which requires high temperature processing to obtain the clean fiber; 3. Supercritical fluid: water (see, e.g., Materials and Design, 2010(31):999-1002), alcohol (see, e.g., Ind. Eng. Chem. Res.,

2010(49):4535-4541), or carbon dioxide (see, e.g., CN 102181071), for degrading epoxy resin system, which is still in the laboratory stage and far from practical industrialization; 4. Use of nitric acid (see, e.g., J. Applied Polymer Sci., 2004 (95): 1912-1916) to degrade the epoxy resin and obtain fiber with clean surface, which has strong corrosion resistance of acid like nitric acid, requires high standard equipment, and results in low operating security, high recycle cost, and difficult post-processing. Chinese researchers in Chinese Academy Ningbo Institute reported their findings using various methods recycling carbon fiber composites: 1. Using solid super-strong acid S04/MxOyas catalysts and hydrogen peroxide oxidation degradation to recycle gram scale composites (see CN 101928406 A), 2. The cut small pieces(less than 5 cm3) of CFRP composites were pre-treated with acids under heat, then washed and dried, and were treated with strong oxidation agents and solvents in sealed reactors to recover fiber and degrade resin (see CN 102391543 A). However, these recycling methods are either in need of high temperature or high pressure, and recycling process is rather tedious. Moreover, these research is at laboratory stage and hard to perform at industrial scale. In general, these methods have their limitations in varying degrees, existing disadvantages of fiber shortening, performance degradation, environmental pollution, and high recycling cost and so on, therefore, effective and feasible method for the recycling of waste composite materials is still an issue to be addressed in composites field.

Brief Summary of the Invention

[08] Aiming at the problems of the existing technology, this application provides novel curing agents, methods for synthesizing these curing agents, synthetic polymer and reinforced composite materials comprising these curing agent and epoxy resin, and methods for degrading the polymer and reinforced composite materials. The prepared degradable reinforced composite materials provided by this invention have good mechanical properties and are suitable for different composite application fields; under certain conditions, the composites are degraded, and the matrix degradation products of reinforcing material and epoxy resin can be separated and recovered. Furthermore, the degradation and recovery method of reinforced composite material is economic, easy to control and can proceed in relatively mild reaction conditions.

[09] Accordingly, in one aspect, this invention provides a curing agent for curing epoxy resin, having Formula I:

I

wherein:

each of Ri, R₂, R3, R4, R5, R6, R7, Rs_, R9 and Ri₀, independently, is hydrogen, alkyl, cycloalkyl, heterocyclic, heterocycloalkyl, alkenyl, cycloalkenyl, alkynyl, aryl, heteroaryl, alkylene-oxy-alkyl, alkylene-oxy-cycloalkyl, alkylene-oxy-hetero-cyclic, alkylene-oxy-hetero- cycloalkyl, alkylene-oxy-alkenyl, alkylene-oxy-cycloalkenyl, alkylene-oxy-aryl, alkylene-oxy- heteroaryl, cycloalkylene-oxy-alkyl, cycloalkylene-oxy-cycloalkyl, cycloalkylene-oxy- heterocyclic, cycloalkylene-oxy-heterocycloalkyl, cycloalkylene-oxy-alkenyl, cycloalkylene- oxy-cycloalkenyl, cycloalkylene-oxy-aryl, cycloalkylene-oxy-heteroaryl, heterocycloalkylene- oxy-alkyl, heterocycloalkylene-oxy-cycloalkyl, heterocycloalkylene-oxy-heterocyclic, heterocycloalkylene-oxy-heterocycloalkyl, heterocycloalkylene-oxy-alkenyl,

heterocycloalkylene-oxy-cycloalkenyl, heterocycloalkylene-oxy-aryl, heterocycloalkylene- oxy-heteroaryl, arylene-oxy-alkyl, arylene-oxy-cycloalkyl, arylene-oxy-heterocyclic, arylene- oxy-heterocycloalkyl, arylene-oxy-alkenyl, arylene-oxy-cycloalkenyl, arylene-oxy-aryl, or arylene-oxy-heteroaryl;

each of Ra , Rb and Rc, independently, is alkylene, alkylene-hetero-alkylene, alkenylene, alkenylene-hetero-alkenylene, alkylene-hetero-alkenylene, alkynylene, cycloalkylene, alkylene-cycloalkylene, alkylene-cycloalkylene-alkylene, alkenylene- cycloalkylene, alkenylene-cycloalkylene-alkenylene, alkylene-cycloalkylene-alkenylene, alkynylene-cycloalkylene, alkynylene-cycloalkylene-alkynylene, heterocycloalkylene, alkylene-heterocycloalkylene, alkylene-heterocycloalkylene-alkylene, alkenylene- heterocycloalkylene, alkenylene-heterocycloalkylene-alkenylene, alkylene- heterocycloalkylene-alkenylene, alkynylene-heterocycloalkylene, alkynylene- heterocycloalkylene-alkynylene, cycloalkenylene, alkylene-cycloalkenylene, alkylene- cycloalkenylene-alkylene, alkenylene-cycloalkenylene, alkenylene-cycloalkenylene- alkenylene, alkylene-cycloalkenylene-alkenylene, alkynylene-cycloalkenylene, alkynylene- cycloalkenylene-alkynylene, heterocycloalkenylene, alkylene-heterocycloalkenylene, alkylene-heterocycloalkenylene-alkylene, alkenylene-heterocycloalkenylene, alkenylene- heterocycloalkenylene-alkenylene, alkylene-heterocycloalkenylene-alkenylene, alkynylene- heterocycloalkenylene, alkynylene-heterocycloalkenylene-alkynylene, arylene, alkylene- arylene, alkylene-arylene-alkylene, alkenylene-arylene, alkenylene-arylene-alkenylene, alkylene-arylene-alkenylene, alkynylene-arylene, alkynylene-arylene-alkynylene,

Heteroarylene, alkylene-heteroarylene, alkylene-heteroarylene-alkylene, alkenylene- heteroarylene, alkenylene-heteroarylene-alkenylene, alkylene-heteroarylene-alkenylene, alkynylene-heteroarylene, alkynylene-heteroarylene-alkynylene, carbonyl, or thiocarbonyl; or

Ri, R₂ and Ra together with the two carbon atoms between Ri and Ra, and between R₂ and Ra form a spiro-ring structure; and

each of mi, m₂, ni and n_2/ independently, is 1, 2, 3, or 4.

[010] As used herein, the phrase "carbon atom(s) between [two moieties]" can refer to the carbon atom to which the two moieties both attached, or the carbon atoms that link the two moieties. For example, when ni or n₂ is 1, the "carbon atom(s) between [R₄ and Rc]" is the carbon atom to which both R₄ and Rc attached, the "carbon atom(s) between [R₉ and Rb]" is the carbon atom to which both R₉ and Rb attached; when ni or n₂ is 2, the "carbon atom(s) between [R₄ and Rc]"are the two carbon atoms attached to R₄ and Rc respectively OR the "carbon atom(s) between [R₄ and Rc]"are the same carbon atom to which R₄ and Rc attached, the "carbon atom(s) between [R₉ and Rb]"are the two carbon atoms attached to R₉ and Rb respectively OR the "carbon atom(s) between [R₉ and Rb]"are the same carbon atom to which R₉ and Rb attached; when ni or n₂ is 3, the "carbon atom(s) between [R₄ and Rc]"are the three carbon atoms that link R₄ and Rc, two of which are attached to R₄ and Rc, respectively OR the "carbon atom(s) between [R₄ and Rc]"are the same carbon atom to which R₄ and B attached, the "carbon atom(s) between [R₉ and Rb]"are the three carbon atoms that link Rg and Rb, two of which are attached to Rg and Rb, respectively OR the "carbon atom(s) between [Rg and Rb]"are the same carbon atom to which both Rg and Rb attached; when ni or n₂ is 4, the "carbon atom(s) between [R₄ and Rc]"are the four carbon atoms that link R₄ and Rc, two of which are attached to R₄ and Rc, respectively OR the "carbon atom(s) between [R₄ and Rc]"are the same carbon atom to which R₄ and B attached, the "carbon atom(s) between [Rg and Rb]"are the four carbon atoms that link Rg and Rb, two of which are attached to Rg and Rb, respectively OR the "carbon atom(s) between [Rg and Rb]"are the same carbon atom to which both Rg and Rb attached.

[Oil] In some embodiments, each of Ri, R₂, R3, R₄, R5, R6, R7, Rs, R9 and Ri₀ may be the same as or different from the other; each of Ra, Rb and Rc may be the same as or different from the other; and each of mi, m₂, ni and n₂ may be the same as or different from the other.

[012] In some embodiments, mi, m₂, ni and n₂ is 1.

[013] In some embodiments, each of Ri, R_2j R_3j R_4j R₅, R₆, R₇, R₈, Rgand Ri₀, independently, is hydrogen or lower alkyl.

[014] In some embodiments, each of Ra, Rb and Rc independently is alkylene,

cycloalkylene, arylene, or heteroarylene.

[015] In some embodiments, the curing agent is:

[016] Another aspect of this invention provides methods for preparing the curing agent as described above. Set forth below are some exemplary schemes of methods that have been used or can be used for synthesizing the curing agents of this invention.

Scheme A

[017] In Scheme A, each of Xi and X₂ independently is chlorine, bromine, iodine, methanesulfonic acid ester, trifluoromethanesulfonate, or p-toluenesulfonic ester group.

[018] Scheme A depicts the following step: compound 1 undergoes an amination reaction to give a curing agent of Formula 2. Formula 2 is defined above. [019] In some embodiments, Compound 1 undergoes an amination reaction to form a curing agent of Formula 2. For instance, the amination reaction refers to a procedure, in which the compound 1, R₃NH₂ and RioNH₂ dissolve in an organic solvent or in a mixed system combined by water and organic solvent, with or without a catalyst at a certain reaction temperature, to give cyclic acetal, cyclic ketal mixing polyamine reaction liquid, and after neutralization, solvent extraction and vacuum distillation, to give a curing agent of Formula 2.

[020] In some embodiments, the mole ratio of the compound 1 and the sum of R₃NH₂ and RioNH₂ is 1:2 ~ 500. For example, when the amount of compounds 1 is 1 mole, the amount of R3NH2 and R10NH2 may be from 2 to 100 mole.

[021] In some embodiments, each of R₃NH₂ and RioNH₂ independently is liquid ammonia, ammonia, or organic amines.

[022] In some embodiments, the organic solvent is at least one selected from the group consisting of benzene, toluene, xylene, pentane, hexane, heptane, octane, nonane, cyclopentane, cyclohexane, cycloheptane, cyclooctane, tetrahydrofuran, and dioxane;

[023] In some embodiments, the catalyst can be ammonium carbonate, ammonium bicarbonate, ammonium acetate, hexamine, ammonium chloride, ammonium bromide, ammonium iodide, ammonium hydroxide, ammonium sulfate, ammonium bisulfate, ammonium sulfite, ammonium bisulfite , ammonium nitrate, ammonium phosphate, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, ammonium formate, ammonium propionate, ammonium trifluoroacetate or ammonium benzoate.

[024] In some embodiments, the reaction temperature is 10 ~ 200 °C; the reaction time can be 2 ~ 240 hours at reaction temperature.

[025] In some embodiments, the neutralization reaction refers to a procedure to adjust the pH > 7 of the reaction liquid by using aqueous alkaline solution. Examples of the alkali used in such neutralization step include, but are not limited to, lithium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, and ammonia. The mass concentration of the said aqueous alkaline solution can be 0.1 ~ 100%.

[026] In some embodiments, the solvent extraction refers to a procedure using an organic solvent to extract the cyclic acetal, cyclic ketal mixing polyamineis from the neutralized reaction solution. In some further embodiments, the organic solvent used in the solvent extraction step is chloroform, dichloromethane, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, t-butanol, ethyl acetate, or ethyl ether.

[027] In some embodiments, the vacuum fractionation refers to a procedure separating the degradable cyclic acetal, cyclic ketal diamines from the cyclic acetal, cyclic ketal mixing polyamine extract under a reduced pressure condition.

[028] A further aspect of this invention provides a cross-linked polymer formed by a curing agent of this invention (e.g., a curing agent of Formula I) and an epoxy resin, wherein the cross-linked polymer comprises a cross-linking group of Formula II:

II

In this Formula II,

each of Ri, R₂, 4, R5, R6, R7, Rs and R₉,independently, is hydrogen, alkyl, cycloalkyl, heterocyclic, heterocycloalkyl, alkenyl, cycloalkenyl, alkynyl, aryl, heteroaryl, alkylene-oxy- alkyl, alkylene-oxy-cycloalkyl, alkylene-oxy-hetero-cyclic, alkylene-oxy-hetero-cycloalkyl, alkylene-oxy-alkenyl, alkylene-oxy-cycloalkenyl, alkylene-oxy-aryl, alkylene-oxy-heteroaryl, cycloalkylene-oxy-alkyl, cycloalkylene-oxy-cycloalkyl, cycloalkylene-oxy-heterocyclic, cycloalkylene-oxy-heterocycloalkyl, cycloalkylene-oxy-alkenyl, cycloalkylene-oxy- cycloalkenyl, cycloalkylene-oxy-aryl, cycloalkylene-oxy-heteroaryl, heterocycloalkylene-oxy- alkyl, heterocycloalkylene-oxy-cycloalkyl, heterocycloalkylene-oxy-heterocyclic, heterocycloalkylene-oxy-heterocycloalkyl, heterocycloalkylene-oxy-alkenyl,

heterocycloalkylene-oxy-cycloalkenyl, heterocycloalkylene-oxy-aryl, heterocycloalkylene- oxy-heteroaryl, arylene-oxy-alkyl, arylene-oxy-cycloalkyl, arylene-oxy-heterocyclic, arylene- oxy-heterocycloalkyl, arylene-oxy-alkenyl, arylene-oxy-cycloalkenyl, arylene-oxy-aryl, or arylene-oxy-heteroaryl; and optionally Ri, R₂ and Ra together with the two carbon atoms between Ri and Ra, and between R₂ and Ra form a spiro-ring structure; each of Ra, Rb and Rc independently is alkylene, alkylene-hetero-alkylene, alkenylene, alkenylene-hetero-alkenylene, alkylene-hetero-alkenylene, alkynylene, cycloalkylene, alkylene-cycloalkylene, alkylene-cycloalkylene-alkylene, alkenylene- cycloalkylene, alkenylene-cycloalkylene-alkenylene, alkylene-cycloalkylene-alkenylene, alkynylene-cycloalkylene, alkynylene-cycloalkylene-alkynylene, heterocycloalkylene, alkylene-heterocycloalkylene, alkylene-heterocycloalkylene-alkylene, alkenylene- heterocycloalkylene, alkenylene-heterocycloalkylene-alkenylene, alkylene- heterocycloalkylene-alkenylene, alkynylene-heterocycloalkylene, alkynylene- heterocycloalkylene-alkynylene, cycloalkenylene, alkylene-cycloalkenylene, alkylene- cycloalkenylene-alkylene, alkenylene-cycloalkenylene, alkenylene-cycloalkenylene- alkenylene, alkylene-cycloalkenylene-alkenylene, alkynylene-cycloalkenylene, alkynylene- cycloalkenylene-alkynylene, heterocycloalkenylene, alkylene-heterocycloalkenylene, alkylene-heterocycloalkenylene-alkylene, alkenylene-heterocycloalkenylene, alkenylene- heterocycloalkenylene-alkenylene, alkylene-heterocycloalkenylene-alkenylene, alkynylene- heterocycloalkenylene, alkynylene-heterocycloalkenylene-alkynylene, arylene, alkylene- arylene, alkylene-arylene-alkylene, alkenylene-arylene, alkenylene-arylene-alkenylene, alkylene-arylene-alkenylene, alkynylene-arylene, alkynylene-arylene-alkynylene, heteroarylene, alkylene-heteroarylene, alkylene-heteroarylene-alkylene, alkenylene- heteroarylene, alkenylene-heteroarylene-alkenylene, alkylene-heteroarylene-alkenylene, alkynylene-heteroarylene, or alkynylene-heteroarylene-alkynylene;

each of mi, m₂, ni and n_2/ independently, is 1, 2, 3, or 4.

[029] In some embodiments, each of Ri, R_2, R4, R5, R6, R7, Rs and R₉ may be the same as or different from the other; each of Ra, Rb and Rc may be the same as or different from the other; each of mi, m₂, ni and n₂ may be the same as or different from the other.

[030] In some embodiments, mi, m₂, ni and n₂ is 1.

[031] In some embodiments, each of Ri, R_2j R_4j R_5j R_6j R_7j R₈ and R₉, independently, is hydrogen or lower alkyl.

[032] In some embodiments, each of Ra, Rb and Rc independently is alkylene, cycloalkylene, arylene, or heteroarylene.

[033] In some embodiments, the epoxy resin comprises a glycidyl ether epoxy resin, glycidyl ester epoxy resin, glycidyl amine epoxy resin, novolac epoxy resin, aliphatic epoxy resin. [034] In some embodiments, the cross-linked polymer as described above is biodegradable.

[035] Accordingly, another aspect of this invention provides a method for degrading the cross-linked polymer as described above.

[036] In some embodiments, the method includes a step of degrading the cross-linked polymer as described above using a solvent and an acid (e.g., under a heating condition), and a step of neutralization using an alkali solution.

[037] More specifically, the method may include the following steps:

(1) U nder the heating and stirring conditions, the degradable cross-linked polymer is immersed in a mixed acid and solvent system for the degradation, and the degradation solution is obtained. In some embodiments, the heating temperature is 15 ~ 400 °C, heating time is 1 ~ 600 hours, the mass concentration of acid in the solvent is 0.1 ~ 100%.

(2) Neutralization: using an alkaline solution at a certain temperature to control the pH of the degradation solution. In some embodiments, the temperature is 0 ~ 200 °C, the final pH is more than 6, and the mass concentration of alkali solution is 0.1 ~ 100 %.

[038] In some embodiments, the acid is hydrochloric acid, hydrobromic acid, hydrofluoric acid, acetic acid, trifluoroacetic acid, lactic acid, formic acid, propionic acid, citric acid, methanesulfonic acid, p-toluenesulfonic acid, nitric acid, sulfuric acid, sulfurous acid, phosphoric acid, perchloric acid, benzoic acid, salicylic acid, or phthalic acid.

[039] In some embodiments, the solvent is methanol, ethanol, ethylene glycol, propanol, isopropanol, butanol, isobutanol, t-butanol, pentanol, hexanol, heptanol, octanol, nonanol, benzyl alcohol, phenethyl falcohol, p-hydroxymethyl benzene, m-hydroxymethyl benzene, o-hydroxy benzene, p-hydroxyethyl benzene, m-hydroxyethyl benzene, o-hydroxyethyl benzene, water, N,N-dimethylformamide, Ν,Ν-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, tetrahydrofuran, methyl tetrahydrofuran, glycerol, or dioxane.

[040] In some embodiments, the alkali is lithium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, or ammonia.

[041] In some embodiments, the alkali solvent is methanol, ethanol, ethylene glycol, propanol, isopropanol, butanol, isobutanol, t-butanol, pentanol, hexanol, heptanol, octanol, nonanol, water, N,N-dimethylformamide, Ν,Ν-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, tetrahydrofuran, methyl tetrahydrofuran, glycerol, or dioxane. [042] In some embodiments, in the first step, the heating temperature is 80 ~ 150 °C; heating period is 4 ~ 8 hours, the mass concentration of acid in the solvent is 0.5 ~ 20%; in the second step, the temperature is 5 ~ 50 °C, the final pH is 6 ~ 12, and the concentration of alkali solution is 5 ~ 30%.

[043] Still another aspect of this invention provides a prepreg or a reinforced composite material prepared by the curing agent of this invention. In some embodiments, the prepreg or the reinforced composite comprises a curing agent of Formula I as described above, an epoxy resin, an auxiliary material, and a reinforcing material.

[044] In some embodiments, the epoxy resin is glycidyl ether epoxy resin, glycidyl ester epoxy resins, glycidyl epoxy amine epoxy resins, trifunctional epoxy resins, tetrafunctional epoxy resins, novolac epoxy resin, o-cresol formaldehyde epoxy resin, aliphatic epoxy resin, alicyclic epoxy resin, or nitrogen-containing epoxy resin.

[045] In some embodiments, the reinforcing material comprises at least one of carbon nanotubes, boron nitride nanotubes, carbon black, metal nano-particles, metal oxide nanoparticles, organic nanoparticles, iron oxide, glass fibers, carbon fibers, natural fibers, synthetic fibers and the fabric made up by fiber material.

[046] In some embodiments, the auxiliary material comprises at least one of accelerators, diluents, plasticizers, toughening agents, thickening agents, coupling agents, defoamers, flatting agent, ultraviolet absorbers, antioxidants, brighteners, fluorescent agents, pigments, and filler.

[047] In some embodiments, the reinforced composite is degradable and recyclable.

[048] Yet still another aspect of this invention provides a method for recycling or degrading the reinforced composite as described above.

[049] In some embodiments, the method includes a step of degrading the reinforced composite using a solvent and an acid (e.g., under a heating condition), a step of neutralization using an alkali solution, and a step of separation (e.g., physical separation).

[050] More specifically, the method may include the following steps:

(1) Under conditions of heating and stirring, immerse reinforced composite material in a degradation system mixed with acid and solvent, and the degradation solution is obtained. In some embodiments, the mass concentration of acid in the solvent is 0.1 ~ 100%; the heating temperature is 15 ~ 400 °C, heating time is 1 ~ 600 hours. (2) Neutralization: using an alkaline solution to adjust the pH of the degradation solution in step (1). In some embodiments, the concentration of alkali solution is 0.1 ~ 100%, the range of the temperature should be kept to adjust the pH of the degradation solution is

0 ~ 200 °C, the final pH of the degradation solution is more than 6, and a precipitate was produced.

(3) Physical separation, washing and drying of the precipitate and degradation solution after pH adjusting in step (2).

[051] In some embodiments, the acid is hydrochloric acid, hydrobromic acid, hydrofluoric acid, acetic acid, trifluoroacetic acid, lactic acid, formic acid, propionic acid, citric acid, methanesulfonic acid, p-toluenesulfonic acid, nitric acid, sulfuric acid, sulfurous acid, phosphoric acid, perchloric acid, benzoic acid, salicylic acid, or phthalic acid.

[052] In some embodiments, the solvent is at least one of methanol, ethanol, ethylene glycol, propanol, isopropanol, butanol, isobutanol, t-butanol, pentanol, hexanol, heptanol, octanol, nonanol, benzyl alcohol, phenethyl alcohol, p-hydroxymethyl benzene, m- hydroxymethyl benzene, o-hydroxy benzene, p-hydroxyethyl benzene, m-hydroxyethyl benzene, o-hydroxyethyl benzene, water, Ν,Ν-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, tetrahydrofuran, methyl tetrahydrofuran, glycerol, and dioxane.

[053] In some embodiments, the alkali is at least one of lithium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, and ammonia.

[054] In some embodiments, the alkali solvent is at least one of methanol, ethanol, ethylene glycol, propanol, isopropanol, butanol, isobutanol, t-butanol, pentanol, hexanol, heptanol, octanol, nonanol, water, N,N-dimethylformamide, Ν,Ν-dimethylacetamide, N- methylpyrrolidone, dimethyl sulfoxide, tetrahydrofuran, methyl tetrahydrofuran, glycerol, and dioxane.

[055] In some embodiments, in Step (1), the mass concentration of acid in the solvent is 0. 5~ 20%; the heating temperature is 80 ~ 200 °C; and heating time is 2~ 12 hours.

[056] In some embodiments, in Step (2), the mass concentration of alkali solution is 5 ~ 30%; and the temperature is 5 ~ 60 °C.

[057] This invention provides at least the following technical advantages: (1) This invention provides composites formed by degradable epoxy resin curing agent, epoxy resin, auxiliary material and reinforcing material. Such composites can degrade under relatively mild temperature, with more than 95% of reinforcing materials can be recycled (such as carbon fiber, glass fiber, synthetic fiber and natural fiber), and can maintain most of the original texture and mechanical properties, so that they can be reused in new composites. The recycled epoxy resin polymer degradation products can be used in plastic products after processing. The epoxy resin reinforced composite with degradable property, which is generated by degradable epoxy resin curing agent, introduced by this invention has not been reported. Thus, this invention provides novel, highly efficient, feasible, and economic methods for recovering epoxy resin and reinforcing materials.

(2) According to this invention, during the degradation procedure of the epoxy resin composite, the cross-linked structure of epoxy resin matrix will have the specific chemical bonds fracture under the action of acid, resulting in the degradation of the epoxy resin matrix. Then the cross-linked structure transfers to the non-cross-linked epoxy resin polymer (like thermoplastic epoxy resin) which can dissolve in the organic solvent. When the epoxy resin matrix fully dissolves in an organic solvent, fiber reinforcing materials can be separated from the solvent. After alkali neutralization, sedimentation, and solid-liquid separation, degraded products of epoxy resin matrix are recycled. Both recycled reinforcing materials and non-cross-linked polymer can be separated, recycled and reused. By far, the reinforcing material of the thermosetting composite can only be recycled after burning out the plastic parts of the composite. Thus, this invention provides novel biodegradable epoxy resin adhesives composite, and the plastic part and reinforcing material of such composite can be recycled with high efficiency. In particular,

(a) Cross-linked epoxy resin curing products can be degraded to form thermoplastic epoxy resin polymer. The degradation procedure only has limited loss of shrinkage group, and the resulted thermoplastic epoxy resin polymer has high recycling quality. Such polymer can be processed for industrial uses.

(b) The recycling quality ratio of epoxy resin curing products or reinforcing materials is more than 96%, and the recycled reinforcing materials is very stable under the acid condition. The surface of the recycled reinforcing material is clean and basically has no defect. (c) The methods for recycling and degrading epoxy resin composites also have the following advantages: mild reaction conditions, economic, and easy to control.

[058] As used herein, the term "alkyl," when used alone or as part of a larger moiety (e.g., as in "cycloalkenyla/Zcy/"), refers to a saturated aliphatic hydrocarbon group. It can contain 1 to 12 (e.g., 1 to 8, 1 to 6, or 1 to 4) carbon atoms. As a moiety, it can be denoted as -C_nH2n+i- An alkyl group can be straight or branched. Examples of alkyl groups include, but are not limited to, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, n- heptyl, and 2-ethylhexyl. An alkyl group can be substituted (i.e., optionally substituted) with one or more substituents. When an alkyl is preceded by a carbon-number modifier, e.g., Ci_ 8, its means the alkyl group contains 1 to 8 carbon atoms. A lower alkyl is an alkyl group with 1-6 carbon atoms.

[059] As used herein, the term "alkylene," when used alone or as part of a larger moiety (e.g., as in "arylaa/Zcy/eneoxy"), refers to a saturated aliphatic hydrocarbon group with two radical points for forming two covalent bonds with two other moieties. It can contain 1 to 12 (e.g., 1 to 8, 1 to 6, or 1 to 4) carbon atoms. As a moiety, it can be denoted as -C_nH2n~- Examples of an alkylene group include, but are not limited to, methylene (-CH₂-), ethylene (- CH₂CH₂-), and propylene (-CH 2CH 2CH2-). When an alkylene is preceded by a carbon-number modifier, e.g., C₂-s, its means the alkylene group contains 2 to 8 carbon atoms. A lower alkylene is an alkylene group with 1-6 carbon atoms.

[060] As used herein, the term "alkynyl," when used alone or as part of a larger moiety (e.g., as in "a//cyny/alkyl"), refers to an aliphatic hydrocarbon group with at least one triple bond. It can contain 2 to 12 (e.g., 2 to 8, 2 to 6, or 2 to 4) carbon atoms. An alkynyl group can be straight or branched. Examples of an alkynyl group include, but are not limited to, propargyl and butynyl. When an alkynyl is preceded by a carbon-number modifier, e.g., C₂-s, its means the alkynyl group contains 2 to 8 carbon atoms. A lower alkynyl has 1-6 carbon atoms.

[061] As used herein, the term "alkenyl," when used alone or as part of a larger moiety (e.g., as in "o/teny/alkyl"), refers to an aliphatic hydrocarbon group with at least one double bond. It can contain 2 to 12 (e.g., 2 to 8, 2 to 6, or 2 to 4) carbon atoms. An alkenyl group with one double bond can be denoted as -C_nH2n-i, or -C_n H2n-3 with two double bonds. Like an alkyl group, an alkenyl group can be straight or branched. Examples of an alkenyl group include, but are not limited to, allyl, isoprenyl, 2-butenyl, and 2-hexenyl. When an alkylene is preceded by a carbon-number modifier, e.g., C₃-₈, its means the alkylene group contains 3 to 8 carbon atoms. A lower alkenyl has 1-6 carbon atoms.

[062] As used herein, the term "cycloalkyi," when used alone or as part of a larger moiety (e.g., as in "cyc/oa//cy/a I kyl"), refers to a saturated carbocyclic mono-, bi-, ortri-cyclic (fused or bridged or spiral) ring system. It can contain 3 to 12 (e.g., 3 to 10, or 5 to 10) carbon atoms. Examples of cycloalkyi groups include, but are not limited to, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, adamantyl, norbornyl, cubyl, octahydro- indenyl, decahydro-naphthyl, bicyclo[3.2.1]octyl, bicyclo[2.2.2]octyl, bicyclo[3.3.1]nonyl, bicyclo[3.3.2.]decyl, bicyclo[2.2.2]octyl, adamantyl, azacycloalkyl, or

((aminocarbonyl)cycloalkyl)cycloalkyl. When a cycloalkyi is preceded by a carbon-number modifier, e.g., C₃-₈, its means the alkyl group contains 3 to 8 carbon atoms.

[063] As used herein, the term "cycloalkenyl," when used alone or as part of a larger moiety (e.g., as in "cycloalkenylalkyl"), refers to a non-aromatic carbocyclic ring system having one or more double bonds. It can contain 3 to 12 (e.g., 3 to 10, or 5 to 10) carbon atoms. Examples of cycloalkenyl groups include, but are not limited to, cyclopentenyl, 1,4- cyclohexa-di-enyl, cycloheptenyl, cyclooctenyl, hexahydro-indenyl, octahydro-naphthyl, cyclohexenyl, cyclopentenyl, bicyclo[2.2.2]octenyl, orbicyclo[3.3.1]nonenyl.

[064] As used herein, the term "heterocycloalkyi," when used alone or as part of a larger moiety (e.g., as in "heterocycloalkyla\Vy\"), refers to a 3- to 16- membered mono-, bi-, or tricyclic (fused or bridged or spiral)) saturated ring structure, in which one or more of the ring atoms is a heteroatom (e.g., N, O, S, or combinations thereof). In addition to the heteroatom(s), the heterocycloalkyi can contain 3 to 15 carbon atoms (e.g., 3 to 12 or 5 to 10). Examples of a heterocycloalkyi group include, but are not limited to, piperidyl, piperazyl, tetrahydropyranyl, tetrahydrofuryl, 1,4-dioxolanyl, 1 ,4-dithianyl, 1 ,3-dioxolanyl, oxazolidyl, isoxazolidyl, morpholinyl, thiomorpholyl, octahydrobenzofuryl,

octahydrochromenyl, octahydrothiochromenyl, octahydroindolyl, octahydropyrindinyl, decahydroquinolinyl, octahydrobenzo[b]thiopheneyl, 2-oxa-bicyclo[2.2.2]octyl, l-aza- bicyclo[2.2.2]octyl, 3-aza- bicyclo[3.2.1]octyl, and 2,6-dioxa-tricyclo[3.3.1.03,7]nonyl. A monocyclic heterocycloalkyi group can be fused with a phenyl moiety such as

tetrahydroisoquinoline. When a heterocycloalkyi is preceded by a carbon-number modifier, e.g., C₄-8, its means the heterocycloalkyi group contains 4 to 8 carbon atoms. [065] As used herein, the term "hetero," when used alone or as part of a larger moiety (e.g., as in "heterocyclo," "heterocycloalkyl," "heterocycloalkylene" or "heteroaryl"), refers to a hetero atom or group that is -0-, -S-, -N H-, or -C(=0)-.

[066] As used herein, the term "aryl," when used alone or as part of a larger moiety (e.g., as in "ary/kyl," or "ary/koxy"), refers to a monocyclic (e.g., phenyl), bicyclic (e.g., indenyl, naphthalenyl, or tetrahydronaphthyl), and tricyclic (e.g., fluorenyl, tetrahydrofluorenyl, tetrahydroanthracenyl, or anthracenyl) ring system in which the monocyclic ring system is aromatic (e.g., phenyl) or at least one of the rings in a bicyclic or tricyclic ring system is aromatic (e.g., phenyl). The bicyclic and tricyclic groups include, but are not limited to, benzo-fused 2- or 3-membered carbocyclic rings. For instance, a benzo-fused group includes phenyl fused with two or more C₄-₈ carbocyclic moieties.

[067] As used herein, the term "heteroaryl" refers to a monocyclic, bicyclic, or tricyclic ring system having 5 to 15 ring atoms wherein at least one of the ring atoms is a heteroatom (e.g., N, O, S, or combinations thereof) and when the monocyclic ring system is aromatic or at least one of the rings in the bicyclic or tricyclic ring systems is aromatic. It can contain 5 to 12 or 8 to 10 ring atoms. A heteroaryl group includes, but is not limited to, a benzo-fused ring system having 2 to 3 rings. For example, a benzo-fused group includes benzo fused with one or two 4- to 8- membered heterocycloalkyl moieties (e.g., indolizyl, indolyl, isoindolyl, 3H-indolyl, indolinyl, benzo[b]furyl, benzo[b]thiophenyl, quinolinyl, or isoquinolinyl). Some examples of heteroaryl are pyridyl, IH-indazolyl, furyl, pyrrolyl, thienyl, thiazolyl, oxazolyl, imidazolyl, tetrazolyl, benzofuryl, isoquinolinyl, benzithiazolyl, xanthenyl, thioxanthenyl, phenothiazinyl, dihydroindolyl, benzo[l,3]dioxolyl, benzo [b] furyl, benzo [bjthiophenyl, indazolyl, benzimidazolyl, benzthiazolyl, puryl, quinolinyl, quinazolinyl, phthalazyl, quinazolyl, quinoxalyl, isoquinolinyl, 4H-quinolizyl, benzo- 1,2,5-thiadiazolyl, and 1 ,8-naphthyridyl.

[068] As used herein, the suffix "-ene" is used to describe a bivalent group with two radical points for forming two covalent bonds with two other moieties. In other words, any of the terms as defined above can be modified with the suffix "-ene" to describe a bivalent version of that moiety. For example, a bivalent aryl ring structure is "arylene," a bivalent benzene ring structure is "phenylene," a bivalent heteroaryl ring structure is "heteroarylene," a bivalent cycloalkyl ring structure is a "cycloalkylene," a bivalent heterocycloalkyl ring structure is "heterocycloalkylene," a bivalent cycloalkenyl ring structure is "cycloalkenylene," a bivalent alkenyl chain is "alkenylene," and a bivalent alkynyl chain is "alkynylene." [069] As used herein, the term "optionally" (e.g., as in "optionally substituted with") means that the moiety at issue is either substituted or not substituted, and that the substitution occurs only when chemically feasible. For instance, H cannot be substituted with a substituent and a covalent bond or -C(=0)- group cannot be substituted with a substituent.

[070] As used herein, an "oxo" group refers to =0.

[071] As used herein, a "carbonyl" group refers to -C(O)- or -C(=0)-.

[072] As used herein, the term "substituted," whether preceded by the term "optionally" or not, refers to the replacement of hydrogen radicals in a given structure with the radical of a specified substituent. Specific substituents are described above in the definitions and below in the description of compounds and examples thereof. Unless otherwise indicated, an optionally substituted group can have a substituent at each substitutable position of the group, and when more than one position in any given structure can be substituted with more than one substituent selected from a specified group, the substituent can be either the same or different in every position. A ring substituent, such as a heterocycloalkyl, can be bound to another ring, such as a cycloalkyl, to form a spiro-bicyclic ring system, e.g., both rings share one common atom. As one of ordinary skill in the art will recognize,

combinations of substituents envisioned by this invention are those combinations that result in the formation of stable or chemically feasible compounds.

[073] For convenience and as commonly understood, the term "optionally substituted" only applies to the chemical entities that can be substituted with suitable substituents, not to those that cannot be substituted chemically.

[074] As used herein, the term "or" can mean "or" or "and."

Brief Descriptions of the Drawings

[075] Fig. 1 shows the relationship between viscosity and temperature of the cured resin of Example 39.

[076] Fig. 2 shows the relationship between viscosity and time at different temperatures of the cured resin of Example 39.. Detailed Description of the Invention

[077] The following examples are provided for illustration only, and not intended to be limiting in any aspect.

[078] At room temperature, 68g 2,5-hexanedione, 200g 3-chloro glycerol, 1.5g p- toluenesulfonic acid and 450gtoluene were mixed and slowly heated to reflux with DEAN- STARK apparatus to distill the evolved water. When no water separated, the reaction time extended 0.5 to 1 hour. After the reaction completed, cooled to 40°C , 500g water was added and stirred for 5 minutes, stood to give the toluene layer. The toluene layer was concentrated under reduced pressure to give 150gintermediate 1.

[079] 36g intermediate 1, 55g phthalimide potassium and 180g DMF were mixed and stirred, heated to 148 ~ 152°C for 8 hours. After the reaction completed, cooled to 100°C, filtered while hot, the filter cake was washed by DM F for one time. The filtrate was frozen to cool and the solid was precipitated, filtered, the filter cake was washed by water once, and dried to give 50g intermediate 2.

[080] 50g intermediate 2 and 200g 25% sodium hydroxide solution were mixed and reacted for 6 ~ 8 hours at 95 ~ 100°C. After the reaction completed, cooled to 15°C, extracted by 120mL chloroform/ethyl alcohol (V/V=3/l) for 3 times, the organic phase was combined and dried with anhydrous sodium sulfate, filtered, the filtrate was concentrated under reduced pressure to give 20g curing agent I. ¹H-NMR (CDCI₃, 400 MHz): 1.36 (m, 6H),1.76(t, 4H), 2.81 (m, 4H), 3.61(m, 1H), 3.69(m, 1H), 4.13(m, 2H), 4.13(m, 4H) Example 2:

[081] At room temperature, 829g 3-chloro glycerol, 144g 1,4-cyclohexanedione, 600g toluene and 5.7g p-toluenesulfonic acid were mixed and stirred, heated to reflux with DEAN-STARK apparatus to distill the evolved water. After the reaction completed, cooled to room temperature , the reaction solution was washed by 200mL water for one time, stood to give the organic phase. The organic phase concentrated under reduced pressure to give 875g intermediate 1.

[082] 828g intermediate 1, 1300g phthalimide potassium salt and 2800g DM F were mixed and stirred, heated to reflux for 8-10 hours. After the reaction completed, cooled to 100°C, filtered while hot, the filter cake was washed by DM F for one time. The filtrate was frozen overnight and the solid was precipitated, filtered, the filter cake was washed by water once, and dried to give 748g intermediate 2.

[083] 7000g ethyl alcohol, 231g intermediate 2 and 1017g 80% hydrazine hydrate were mixed and heated to reflux overnight. After the reaction completed, cooled to room temperature, filtered, the filtrate was concentrated to dry. 3000g dichloromethane was added into the residue, stirred for 2 to 3 hours at room temperature, filtered, the filtrate was concentrated under reduced pressure to give 305g curing agent II. ¹H-N MR (DMSO, 400 MHz): 1.88 (m, 8H), 2.83(m, 4H), 3.65 (m, 2H), 4.03 (m, 2H), 3.60(m, 1H), 4.13(m, 2H)

[084] 276g 3-chloro glycerol, 112g 1,3-cyclohexanedione, 200g toluene and 1.9g p- toluenesulfonic acid were mixed and stirred, heated to reflux with DEAN-STARK apparatus to distill the evolved water. After the reaction completed, cooled to room temperature , the reaction solution was washed by lOOmL water for one time. The organic phase concentrated under reduced pressure to give 270g intermediate 1.

[085] 207g intermediate 1, 324g phthalimide potassium salt and 700g DMF were mixed and stirred, heated to reflux overnight. After the reaction completed, cooled to 100°C, filtered while hot, the filter cake was washed by DM F for one time. The filtrate was frozen overnight and the solid was precipitated, filtered, the filter cake was washed by water once, and dried to give 14g intermediate 2.

[086] 14g intermediate 2, 140g ethyl alcohol and 20.8g 80% hydrazine hydrate were mixed and heated to reflux overnight. After the reaction completed, cooled to room temperature, filtered, the filtrate was concentrated to dry. 20g dichloromethane was added into the residue, stirred at room temperature, filtered, the filtrate was concentrated under reduced pressure to give 4g curing agent III. ¹H-N MR (DMSO, 400 MHz): 1.75 (m, 8H), 2.75(m, 4H), 3.70 (m, 2H), 4.10(m, 4H)

Example 4:

[087] 276g 3-chloro glycerol, 112g 1,3-cyclohexanedione, 200g toluene and 1.9g p- toluenesulfonic acid were mixed and stirred, heated to reflux with DEAN-STARK apparatus to distill the evolved water. After the reaction completed, cooled to room temperature , the reaction solution was washed by lOOmL water for one time. The organic phase concentrated under reduced pressure to give 270g intermediate 1.

[088] 150g intermediate 1, 800g liquid ammonia added to a 2 liter pressure reactor. Mixed for 20 hours at 110°C. Recovered the liquid ammonia, dissolved the product mixture in 200g water, extracted the mixture with 200ml TH F for three times. Evaporated water. Dissolved the product in 200ml THF. Separated the organic solution from the salt by vacuum filtration. Recovered the final product 90g by removing the THF using vacuum distillation. ¹H-N MR (DMSO, 400 MHz): Example 5:

[089] At room temperature, 67g 1,4-phthalaldehyde, 121g 3-chloro glycerol, 0.8g p- toluenesulfonic acid and 300g toluene were mixed and slowly heated to reflux with DEAN- STARK apparatus to distill the evolved water. When no water separated, the reaction time extended 0.5 to 1 hour. After the reaction completed, cooled to 40°C , 0.5L water was added and stirred for 5 minutes, stood to give the toluene layer. The toluene layer was concentrated under reduced pressure to give 140g intermediate 1.

[090] 140g intermediate 1, 215g phthalimide potassium and 600g DMF were mixed and stirred, heated to reflux for 8 hours. After the reaction completed, cooled to 100°C, filtered while hot, the filter cake was washed by DMF for one time. The filtrate was frozen to cool and the solid was precipitated, filtered, the filter cake was washed by water once, and dried to give 178g intermediate 2.

[091] 178g intermediate 2, 2000g ethyl alcohol and 320g 80% hydrazine hydrate were mixed and heated to reflux overnight. After the reaction completed, cooled to room temperature, filtered, filtrate was concentrated to dry. 300g dichloromethane was added into the residue, stirred for 2 hours at room temperature, filtered, the filtrate was concentrated under reduced pressure to give 54g curing agent IV. ¹H NM R (CDCI₃, 400 MHz) 2.95 (m, 4H), 3.72(m, 2H), 3.85 (m,lH), 4.09(m, 1H), 4.22(m, 3H), 5.82(d, 1H), 5.95(d, 1H), 5.85(d, 1H), 7.49(m, 4H)

[092] At room temperature, 67g 1,4-phthalaldehyde, 121g 3-chloro glycerol, 0.8g p- toluenesulfonic acid and 300g toluene were mixed and slowly heated to reflux with DEAN- STARK apparatus to distill the evolved water. When no water separated, the reaction time extended 0.5 to 1 hour. After the reaction completed, cooled to 40°C , 0.5L water was added and stirred for 5 minutes, stood to give the toluene layer. The toluene layer was concentrated under reduced pressure to give 140g intermediate 1.

[093] 150g intermediate 1, 700g liquid ammonia added to a 2 liter pressure reactor. Mixed for 20 hours at llOoC. Recovered the liquid ammonia, dissolved the product mixture in 200g water, extracted the mixture with 200ml TH F/Toluene (1:1) for three times. Evaporated water. Dissolved the product in 200ml THF. Separated the organic solution from the salt by vacuum filtration. Recovered the final product lOOg by removing the TH F using vacuum distillation.

Example 7:

[094] lOOg liquid bisphenol A epoxy resin N PEL-128 (EEW 0.52~0.55eq./100g) and 35g curing agent I (AEW 1.54 N-H eq./ΙΟΟ g) were mixed and stirred evenly at room

temperature, cured at 125°C for 2 hours to give the sample 1.

Example 8:

[095] 100 g liquid bisphenol A epoxy resin NPEL-128 (EEW 0.52~0.55eq./100g) and 34.8g curing agent II (AEW 1.55 N-H eq./ΙΟΟ g) were mixed and stirred evenly at room

temperature, cured at 125°C for 2 hours to give the sample 2. Example 9:

[096] 100 g liquid bisphenol A epoxy resin NPEL-128 (EEW 0.52~0.55eq./100g) and 34.8g curing agent III (AEW 1.55 N-H eq./ΙΟΟ g) were mixed and stirred evenly at room temperature, cured at 125^°C for 2 hours to give the sample 3.

Example 10:

[097] lOOg liquid bisphenol A epoxy resin N PEL-128 (EEW 0.52~0.55eq./100g) and 37.7g curing agent IV (AEW 1.43 N-H eq./ΙΟΟ g) were mixed and stirred evenly at room temperature, cured at 125^°C for 2 hours to give the sample 4.

Example 11:

[098] 18g liquid bisphenol A epoxy resin NPEL-127 (EEW 0.54~0.56eq./100g), triglycidyl- p-aminophenol epoxy resin AFG-90 (EEW 0.82~0.83eq./100g), 3.3g curing agent I (AEW 1.54 N-H eq./lOOg) and 2.2g degradable curing agent 2,2'-(methylenebis(oxy))bis(ethan-l- amine) (AEW 2.99 N-H eq./lOOg) were mixed and stirred evenly, cured at 80 °C for 2 hours to give the sample 5.

Example 12:

[099] 18g liquid bisphenol A epoxy resin NPEL-127 (EEW 0.54~0.56eq./100g), 2g three- functional active diluent XY636 (EEW 0.69~0.71eq./100g), 3.3g curing agent II (AEW 1.55 N- H eq./lOOg) and 2.08g degradable curing agent 2,2'-(methylenebis(oxy))bis(ethan-l-amine) (AEW 2.99 N-H eq./lOOg) were mixed and stirred evenly, cured at 120^°C for 1 hour to give the sample 6.

Example 13:

[0100] 18g liquid bisphenol A epoxy resin NPEL-127 (EEW 0.54~0.56eq./100g), 2g three- functional active diluent XY636 (EEW 0.69~0.71eq./100g), 3.12g curing agentIII(AEW 1.55 N-H eq./lOOg) and 2.08g degradable curing agent 2,2'-(methylenebis(oxy))bis(ethan-l- amine) (AEW 2.99 N-H eq./lOOg) were mixed and stirred evenly, cured at 120^°C for 1 hour to give the sample 7. Example 14:

[0101] 18g liquid bisphenol A epoxy resin NPEL-127 (EEW 0.54~0.56eq./100g), 3.12g curing agent I (AEW 1.54 N-H eq./lOOg) and 2.08g degradable curing agent 2,2'- (methylenebis(oxy))bis(ethan-l-amine) (AEW 2.99 N-H eq./lOOg) were mixed and stirred evenly, cured at 80 ^°C for 2 hours to give the sample 8.

Example 15:

[0102] lg sample in example 7, 20mL 30% hydrogen peroxide, and 80mLacetic acid were mixed and stirred at 108^°C until degraded completely to get brown solution. The time was 3 hours.

Example 16:

[0103] lg sample in example 8, 20mL 30% hydrogen peroxide, and 80mL acetic acid were mixed and stirred at 108^°C until degraded completely to get brown solution. The time was 2 hours.

Example 17:

[0104] lg sample in example 9, 20mL 30% hydrogen peroxide, and 80mL acetic acid were mixed and stirred at 108^°C until degraded completely to get brown solution. The time was 2 hours.

Example 18:

[0105] lg sample in example 10, 20mL 30% hydrogen peroxide, and 80mL acetic acid were mixed and stirred at 108^°C until degraded completely to get brown solution. The time was 4 hours.

Example 19:

[0106] lg sample in example 11, 20mL 30% hydrogen peroxide, and 80mL acetic acid were mixed and stirred at 108^°C until degraded completely to get brown solution. The time was 4 hours. Example 20:

[0107] lg sample in example 12, 20mL 30% hydrogen peroxide, and 80mL acetic acid were mixed and stirred at 108°C until degraded completely to get brown solution. The time was 3 hours.

Example 21:

[0108] lg sample in example 13, 20mL 30% hydrogen peroxide, and 80mL acetic acid were mixed and stirred at 108°C until degraded completely to get brown solution. The time was 3 hours.

Example 22:

[0109] lg sample in example 14, 20mL 30% hydrogen peroxide, and 80mL acetic acid were mixed and stirred at 108°C until degraded completely to get brown solution. The time was 3 hours.

Example 23:

[0110] lg sample in example 7, lOmL 30% concentrated hydrochloric acid, and 90mL ethylene glycol were mixed and stirred at 138°C until degraded completely to get yellow solution. The time was 16 hours.

Example 24:

[0111] lg sample in example 8, lOmL 30% concentrated hydrochloric acid, and 90mL ethylene glycol were mixed and stirred at 138°C until degraded completely to get yellow solution. The time was 12 hours.

Example 25:

[0112] lg sample in example 9, lOmL 30% concentrated hydrochloric acid, and 90mL ethylene glycol were mixed and stirred at 138°C until degraded completely to get yellow solution. The time was 13 hours. Example 26:

[0113] lg sample in example 10₇ lOmL 30% concentrated hydrochloric acid, and 90mL ethylene glycol were mixed and stirred at 138°C until degraded completely to get yellow solution. The time was 16 hours.

Example 27:

[0114] lg sample in example 11, 10 mL 30% concentrated hydrochloric acid, and 90mL ethylene glycol were mixed and stirred at 138°C until degraded completely to get yellow solution. The time was 16 hours.

Example 28:

[0115] lg sample in example 12, lOmL 30% concentrated hydrochloric acid, and 90mL ethylene glycol were mixed and stirred at 138°C until degraded completely to get yellow solution. The time was 12 hours.

Example 29:

[0116] lg sample in example 13, lOmL 30% concentrated hydrochloric acid, and 90mL ethylene glycol were mixed and stirred at 138°C until degraded completely to get yellow solution. The time was 16 hours.

Example 30:

[0117] lg sample in example 14, lOmL 30% concentrated hydrochloric acid, and 90mL ethylene glycol were mixed and stirred at 138°C until degraded completely to get yellow solution. The time was 16 hours.

Example 31:

[0118] lg sample in example 7, 5mL 30% concentrated hydrochloric acid, and 95mL ethylene glycol were mixed and stirred at 146°C until degraded completely to get yellow solution. The time was 12 hours. Example 32:

[0119] lg sample in example 8, 5mL 30% concentrated hydrochloric acid, and 95mL ethylene glycol were mixed and stirred at 146°C until degraded completely to get yellow solution. The time was 9 hours.

Example 33:

[0120] lg sample in example 9, 5mL 30% concentrated hydrochloric acid, and 95mL ethylene glycol were mixed and stirred at 146°C until degraded completely to get yellow solution. The time was 9 hours.

Example 34:

[0121] lg sample in example 10₇ 5mL 30% concentrated hydrochloric acid, and 95mL ethylene glycol were mixed and stirred at 146°C until degraded completely to get yellow solution. The time was 9 hours.

Example 35:

[0122] lg sample in example 11, 5mL 30% concentrated hydrochloric acid, and 95mL ethylene glycol were mixed and stirred at 146°C until degraded completely to get yellow solution. The time was 11 hours.

Example 36:

[0123] lg sample in example 12, 5mL 30% concentrated hydrochloric acid, and 95mL ethylene glycol were mixed and stirred at 146°C until degraded completely to get yellow solution. The time was 9 hours.

Example 37:

[0124] lg sample in example 13, 5mL 30% concentrated hydrochloric acid, and 95mL ethylene glycol were mixed and stirred at 146°C until degraded completely to get yellow solution. The time was 12 hours. Example 38:

[0125] lg sample in example 14, 5mL 30% concentrated hydrochloric acid, and 95mL ethylene glycol were mixed and stirred at 146°C until degraded completely to get yellow solution. The time was 12 hours.

Example 39: Preparation of carbon fiber composite laminate sample based on degradable fast curing epoxy formulation used in the field of automotive

(1) Preparation of recyclable fast curing epoxy resin formulation:

[0126] Bisphenol A epoxy resin and glycidyl amine epoxy resin and catalyst were mixed and stirred at 65 °C for 30 minutes, then cooled to room temperature to give resin mix A component. Two degradable curing agents were mixed and stirred at the room

temperature to give hardener B component.

(2) Typical properties of fast curing epoxy formulation

[0127] Comparison

Flexural modulus (GPa) 2.5 ~ 2.7 3.00±0.1

(3) Preparation of recyclable carbon fiber composite laminate sample

[0128] Component A and B of the fast curing formulation prepared above were mixed at room temperature to give epoxy resin matrix. Carbon fiber laminate was made using 3K carbon fiber cloth and epoxy resin matrix by wet lay-up method, then pressed on the tablet pressing machine at 120 °C for 5 minutes to give carbon fiber composite laminate sample.

Example 40:

[0129] 8 g of the samples of the carbon fiber composite laminate in Example 39, 20 mL concentrated hydrochloric acid and 90 mL ethylene glycol were placed in a one-neck round flask, stirred and heated to 150-155 °C, epoxy resin matrix was completely degraded after 17 hours, cool down to 100 °C, filtered, the carbon fiber and the degradation solution were separated, the solution was neutralized with 10% sodium hydroxide solution and precipitated solid was filtered and the solid was washed with water and dried to give 2.5 g degradation products of thermoset epoxy resin and 5.1 g carbon fiber. The surface of recycled fiber was clean and basically has no defect.

[0130] 138g 3-chloro glycerol, 58 g 1,3-cyclohexanedione, 300 g toluene and lg p- toluenesulfonic acid were mixed and stirred, heated to reflux with DEAN-STARK apparatus to distill the evolved water. After the reaction completed, cooled to room temperature, the reaction solution was washed by 200 g water for one time. The organic phase was concentrated and solved removed under reduced pressure to give 137 g intermediate 1.

[0131] 34 g intermediate 1, 196 g liquid ammonia added to a 0.6 liter pressure reactor. Mixed for 10 hours at 120 °C. Recovered the liquid ammonia, dissolved the product mixture in 100 g water, neutralized with sodium hydroxide till the pH=13, extracted the mixture with 100 mL TH F for three times. Evaporated water. Dissolved the product in 100 mL TH F.

Separated the organic solution from the salt by vacuum filtration. Recovered the final product 35 g by removing the THF using vacuum distillation.

Example 42:

[0132] At the room temperature, 69 g 1,4-phthalaldehyde, 138 g 3-chloro glycerol, lg p- toluenesulfonic acid and 300 g toluene were mixed and slowly heated to reflux with DEAN- STARK apparatus to distill the evolved water for 20 hrs. When no water separated, the reaction time extended 0.5 to 1 hour. After the reaction completed, cooled to the room temperaturue, 0.5 L water was added and stirred for 5 minutes. The toluene layer was concentrated under reduced pressure to give 140 g intermediatel.

[0133] 50g intermediate 1, 267g liquid ammonia added to a 0.6 liter pressure reactor, mixed for 20 hours at 120 °C, recovered the liquid ammonia, dissolved the product mixture in 100 g water, neutralized with sodium hydroxide till the pH=13, extracted the mixture with 100ml TH F for three times. Water was evaporated and the product was dissolved in 200 mL THF. Separated the organic solution from the salt by vacuum filtration. Recovered the final product 33g by removing the THF using vacuum distillation.

Claims

What Is Claimed Is:

1. A curing agent for curing epoxy resin, having Formula I:

I

wherein:

each of Ri, R₂, R3, R4, Rs, Re, R7, Rs, R9, and Ri₀, independently, is hydrogen, alkyl, cycloalkyl, heterocyclic, heterocycloalkyl, alkenyl, cycloalkenyl, alkynyl, aryl, heteroaryl, alkylene-oxy-alkyl, alkylene-oxy-cycloalkyl, alkylene-oxy-hetero-cyclic, alkylene-oxy-hetero-cycloalkyl, alkylene-oxy-alkenyl, alkylene-oxy-cycloalkenyl, alkylene-oxy-aryl, alkylene-oxy-heteroaryl, cycloalkylene-oxy-alkyl, cycloalkylene- oxy-cycloalkyl, cycloalkylene-oxy-heterocyclic, cycloalkylene-oxy-heterocycloalkyl, cycloalkylene-oxy-alkenyl, cycloalkylene-oxy-cycloalkenyl, cycloalkylene-oxy-aryl, cycloalkylene-oxy-heteroaryl, heterocycloalkylene-oxy-alkyl, heterocycloalkylene- oxy-cycloalkyl, heterocycloalkylene-oxy-heterocyclic, heterocycloalkylene-oxy- heterocycloalkyl, heterocycloalkylene-oxy-alkenyl, heterocycloalkylene-oxy- cycloalkenyl, heterocycloalkylene-oxy-aryl, heterocycloalkylene-oxy-heteroaryl, arylene-oxy-alkyl, arylene-oxy-cycloalkyl, arylene-oxy-heterocyclic, arylene-oxy- heterocycloalkyl, arylene-oxy-alkenyl, arylene-oxy-cycloalkenyl, arylene-oxy-aryl, or arylene-oxy-heteroaryl;

each of Ra, Rb, and Rc, independently, is alkylene, alkylene-hetero-alkylene, alkenylene, alkenylene-hetero-alkenylene, alkylene-hetero-alkenylene, alkynylene, cycloalkylene, alkylene-cycloalkylene, alkylene-cycloalkylene-alkylene, alkenylene- cycloalkylene, alkenylene-cycloalkylene-alkenylene, alkylene-cycloalkylene- alkenylene, alkynylene-cycloalkylene, alkynylene-cycloalkylene-alkynylene, heterocycloalkylene, alkylene-heterocycloalkylene, alkylene-heterocycloalkylene- alkylene, alkenylene-heterocycloalkylene, alkenylene-heterocycloalkylene- alkenylene, alkylene-heterocycloalkylene-alkenylene, alkynylene- heterocycloalkylene, alkynylene-heterocycloalkylene-alkynylene, cycloalkenylene, alkylene-cycloalkenylene, alkylene-cycloalkenylene-alkylene, alkenylene- cycloalkenylene, alkenylene-cycloalkenylene-alkenylene, alkylene-cycloalkenylene- alkenylene, alkynylene-cycloalkenylene, alkynylene-cycloalkenylene-alkynylene, heterocycloalkenylene, alkylene-heterocycloalkenylene, alkylene- heterocycloalkenylene-alkylene, alkenylene-heterocycloalkenylene, alkenylene- heterocycloalkenylene-alkenylene, alkylene-heterocycloalkenylene-alkenylene, alkynylene-heterocycloalkenylene, alkynylene-heterocycloalkenylene-alkynylene, arylene, alkylene-arylene, alkylene-arylene-alkylene, alkenylene-arylene, alkenylene- arylene-alkenylene, alkylene-arylene-alkenylene, alkynylene-arylene, alkynylene- arylene-alkynylene, heteroarylene, alkylene-heteroarylene, alkylene-heteroarylene- alkylene, alkenylene-heteroarylene, alkenylene-heteroarylene-alkenylene, alkylene- heteroarylene-alkenylene, alkynylene-heteroarylene, alkynylene-heteroarylene- alkynylene, carbonyl, or thiocarbonyl;

or, Ri, R₂, and Ra, together with the carbon atom between Ri and Ra and the carbon atom between R₂ and Ra, form a ring structure; and

each of mi, m₂, ru and n₂, independently, is 1, 2, 3, or 4.

2. The curing agent of claim 1, wherein each of mi, m₂, ni, and n₂ is 1.

3. The curing agent of claim 1 or 2, wherein each of Ri, R₂, R₃, R₄, R₅, R₆, R₇, R₈, Rg and Rio, independently, is hydrogen or lower alkyl.

4. The curing agent of any of claims 1 to 3, wherein each of Ra, Rb and Rc, independently, is alkylene, cycloalkylene, arylene, or heteroarylene.

5. The curing agent of any of claims 1 to 4, wherein the curing agent is

A method for preparing a curing agent of claim 1, comprising a step as depicted the following scheme:

wherein each of Xi and X2 independently is chlorine, bromine, iodine, methanesulfonic acid ester, trifluoromethanesulfonate, or p-toluenesulfonic ester group; and Ri, R₂, R3, R4, R5, R6, R7, Rs, R9, Rio, Ra, Rb, Rc, mi, m₂, ni, and n₂ are as defined in claim 1.

7. A cross-linked polymer formed by a curing agent of any of claims 1 to 5 and an epoxy resin, wherein the cross-linked polymer comprises a cross-linking group of Formula II:

II

wherein:

each of Ri, R₂, R4, R5, Re, R7, Rs and R₉,independently, is hydrogen, alkyl, cycloalkyl, heterocyclic, heterocycloalkyl, alkenyl, cycloalkenyl, alkynyl, aryl, heteroaryl, alkylene-oxy-alkyl, alkylene-oxy-cycloalkyl, alkylene-oxy-hetero-cyclic, alkylene-oxy-hetero-cycloalkyl, alkylene-oxy-alkenyl, alkylene-oxy-cycloalkenyl, alkylene-oxy-aryl, alkylene-oxy-heteroaryl, cycloalkylene-oxy-alkyl, cycloalkylene- oxy-cycloalkyl, cycloalkylene-oxy-heterocyclic, cycloalkylene-oxy-heterocycloalkyl, cycloalkylene-oxy-alkenyl, cycloalkylene-oxy-cycloalkenyl, cycloalkylene-oxy-aryl, cycloalkylene-oxy-heteroaryl, heterocycloalkylene-oxy-alkyl, heterocycloalkylene- oxy-cycloalkyl, heterocycloalkylene-oxy-heterocyclic, heterocycloalkylene-oxy- heterocycloalkyl, heterocycloalkylene-oxy-alkenyl, heterocycloalkylene-oxy- cycloalkenyl, heterocycloalkylene-oxy-aryl, heterocycloalkylene-oxy-heteroaryl, arylene-oxy-alkyl, arylene-oxy-cycloalkyl, arylene-oxy-heterocyclic, arylene-oxy- heterocycloalkyl, arylene-oxy-alkenyl, arylene-oxy-cycloalkenyl, arylene-oxy-aryl, or arylene-oxy-heteroaryl;

each of Ra, Rb and Rc independently is alkylene, alkylene-hetero-alkylene, alkenylene, alkenylene-hetero-alkenylene, alkylene-hetero-alkenylene, alkynylene, cycloalkylene, alkylene-cycloalkylene, alkylene-cycloalkylene-alkylene, alkenylene- cycloalkylene, alkenylene-cycloalkylene-alkenylene, alkylene-cycloalkylene- alkenylene, alkynylene-cycloalkylene, alkynylene-cycloalkylene-alkynylene, heterocycloalkylene, alkylene-heterocycloalkylene, alkylene-heterocycloalkylene- alkylene, alkenylene-heterocycloalkylene, alkenylene-heterocycloalkylene- alkenylene, alkylene-heterocycloalkylene-alkenylene, alkynylene- heterocycloalkylene, alkynylene-heterocycloalkylene-alkynylene, cycloalkenylene, alkylene-cycloalkenylene, alkylene-cycloalkenylene-alkylene, alkenylene- cycloalkenylene, alkenylene-cycloalkenylene-alkenylene, alkylene-cycloalkenylene- alkenylene, alkynylene-cycloalkenylene, alkynylene-cycloalkenylene-alkynylene, heterocycloalkenylene, alkylene-heterocycloalkenylene, alkylene- heterocycloalkenylene-alkylene, alkenylene-heterocycloalkenylene, alkenylene- heterocycloalkenylene-alkenylene, alkylene-heterocycloalkenylene-alkenylene, alkynylene-heterocycloalkenylene, alkynylene-heterocycloalkenylene-alkynylene, arylene, alkylene-arylene, alkylene-arylene-alkylene, alkenylene-arylene, alkenylene- arylene-alkenylene, alkylene-arylene-alkenylene, alkynylene-arylene, alkynylene- arylene-alkynylene, heteroarylene, alkylene-heteroarylene, alkylene-heteroarylene- alkylene, alkenylene-heteroarylene, alkenylene-heteroarylene-alkenylene, alkylene- heteroarylene-alkenylene, alkynylene-heteroarylene, or alkynylene-heteroarylene- alkynylene;

or, Ri, R_2/ and Ra, together with the carbon atom between Ri and Ra and the carbon atom between R₂ and Ra, form a ring structure; and

each of mi, m₂, ni and n₂, independently, is 1, 2, 3, or 4.

8. The cross-linked polymer of claim 7, wherein each of mi, m₂, ni and n₂ is 1.

9. The cross-linked polymer of claim 7 or 8, wherein each of Ri, R₂, R4, R5, R6, R7, Rs and R₉, independently, is hydrogen or lower alkyl.

10. The cross-linked polymer of any of claims 7 to 9, wherein each of Ra, Rb and Rc independently is alkylene, cycloalkylene, arylene, or heteroarylene.

11. The cross-linked polymer of any of claims 7 to 10, wherein the epoxy resin comprises a glycidyl ether epoxy resin, glycidyl ester epoxy resin, glycidyl amine epoxy resin, novolac epoxy resin, or aliphatic epoxy resin.

12. A method for degrading a cross-linked polymer of any of claims 7 to 11, comprising a step of degrading the cross-linked polymer using a solvent and an acid.

13. The method of claim 12 , wherein the acid comprises a hydrochloric acid,

hydrobromic acid, hydrofluoric acid, acetic acid, trifluoroacetic acid, lactic acid, formic acid, propionic acid, citric acid, methanesulfonic acid, p-toluenesulfonic acid, nitric acid, sulfuric acid, sulfurous acid, phosphoric acid, perchloric acid, benzoic acid, salicylic acid, or phthalic acid.

14. The method of claim 12 or 13, wherein the solvent comprises methanol, ethanol, ethylene glycol, propanol, isopropanol, butanol, isobutanol, t-butanol, pentanol, hexanol, heptanol, octanol, nonanol, benzyl alcohol, phenethyl alcohol, p- hydroxymethyl benzene, m-hydroxymethyl benzene, o-hydroxy benzene, p- hydroxyethyl benzene, m-hydroxyethyl benzene, o-hydroxyethyl benzene, water, N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, tetrahydrofuran, methyl tetrahydrofuran, glycerol, or dioxane.

15. The method of claim 12, further comprising a step of neutralization using an alkali solution.

16. The method of claim 15, wherein the alkali comprises lithium hydroxide, sodium

hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, or ammonia.

17. A reinforced composite comprising a curing agent of any of claims 1 to 5, an epoxy resin, auxiliary materials, and a reinforcing material.

18. The reinforced composite of claim 17, wherein the epoxy resin comprises a glycidyl ether epoxy resin, glycidyl ester epoxy resin, glycidyl epoxy amine epoxy resin, or aliphatic epoxy resin;

the reinforcing material comprises a carbon nanotube, boron nitride nanotube, carbon black, metal nano-particles, metal oxide nanoparticle, organic nanoparticle, iron oxide, glass fiber, carbon fiber, natural fiber, synthetic fiber, or fabric made by fiber materials;

the auxiliary material comprises accelerator, diluent, plasticizer, toughening agent, thickening agent, coupling agent, defoamer, flatting agent, ultraviolet absorber, antioxidant, brightener, fluorescent agent, pigment, or filler.

19. The reinforced composite of claim 17 or 18, wherein the reinforced composite is degradable and recyclable.

20. A method for recycling or degrading a reinforced composite of any of claims 17 to 19, comprising a step of degrading the reinforced composite using a solvent and an acid.

21. The method of claim 20, wherein the acid comprises hydrochloric acid, hydrobromic acid, hydrofluoric acid, acetic acid, trifluoroacetic acid, lactic acid, formic acid, propionic acid, citric acid, methanesulfonic acid, p-toluenesulfonic acid, nitric acid, sulfuric acid, sulfurous acid, phosphoric acid, perchloric acid, benzoic acid, salicylic acid, or phthalic acid; and the solvent comprises methanol, ethanol, ethylene glycol, propanol, isopropanol, butanol, isobutanol, t-butanol, pentanol, hexanol, heptanol, octanol, nonanol, benzyl alcohol, phenethyl alcohol, p-hydroxymethyl benzene, m- hydroxymethyl benzene, o-hydroxy benzene, p-hydroxyethyl benzene, m- hydroxyethyl benzene, o-hydroxyethyl benzene, water, N,N-dimethylformamide, Ν,Ν-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, tetrahydrofuran, methyl tetrahydrofuran, glycerol, or dioxane.

22. The method of claim 20 or 21, further comprising a step of neutralization using an alkali solution and a step of degraded resins separation.

23. The method of claim 22, wherein the alkali comprises lithium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, or ammonia.