Degradable acetal amine structure-containing glycidyl amine epoxy resin and preparation method thereof

Abstract

The invention discloses a degradable glycidyl amine epoxy resin containing an aminal structure and a preparation method thereof, the degradable glycidyl amine epoxy resin containing the aminal structure has the following molecular structure general formula: # imgabs0 #, in the formula, R1 and R2 are one of alkyl, cycloalkyl, heterocyclic radical, heterocycloalkyl, aryl and heteroaryl. According to the invention, an aminal structure is introduced into an epoxy resin cross-linked structure through a cross-linking curing reaction, aminal synthesis is simple and green, and the azacyclo-hexahydropyrimidine structure of the epoxy resin enables the epoxy resin to have relatively high mechanical properties and thermal stability, and the epoxy resin can be degraded under an acidic condition; and the catalyst still has certain stability under normal temperature and low-concentration acidic conditions, and has huge economic and environmental advantages for recycling of thermosetting resin.

Description

Technical Field

[0001] The invention relates to a degradable epoxy resin and a preparation method thereof, and in particular to a degradable glycidylamine epoxy resin containing an aminal structure and a preparation method thereof. Background Art

[0002] my country has become the country with the largest demand for epoxy resin in the world, accounting for two-thirds of the global consumption. As my country's industrialization scale continues to grow, the demand for epoxy resin is also expected to show an upward trend. However, the three-dimensional cross-linked network formed after epoxy resin is cured is relatively stable, making it difficult to effectively degrade and recycle. Only 1% of composite materials are recycled and reused each year.

[0003] Common energy recovery methods, physical crushing recovery methods, chemical recovery methods, etc. all have problems such as high energy consumption, environmental pollution, and low added value of recycled products. Among them, energy recovery methods are difficult to achieve the recycling of fibers and resins, physical crushing can only achieve low-value recovery, and chemical methods often destroy the stable chemical bonds in the resin cross-linking network through high temperature and high pressure, catalysts or harsh chemical treatments, which can achieve the recycling of carbon fibers. However, due to harsh degradation conditions, the chemical structure of recycled carbon fibers is usually damaged to a certain extent, resulting in a certain decline in mechanical properties and thermal stability. At the same time, harsh degradation conditions bring a lot of energy consumption, and it is impossible to achieve the recycling of resins. At present, a series of degradable epoxy resins have been developed, including epoxy resin systems containing imine bonds, disulfide bonds, acetal bonds, and hexahydrotriazine structures. The degradation and recovery of resins can be achieved through stimulation methods such as acid, alkali, heat, and solvation. However, the above chemical bonds also have problems such as low bond energy, poor stability, and harsh synthesis conditions, which are difficult to commercialize. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a degradable glycidylamine epoxy resin containing an aminal structure and a degradation method thereof. The present invention introduces the aminal structure into the cross-linked structure of the epoxy resin through a cross-linking curing reaction. The aminal synthesis is simple and green, and the nitrogen heterocyclic hexahydropyrimidine structure of the epoxy resin gives it high mechanical properties and thermal stability, and it can be degraded under acidic conditions, and still has a certain stability under normal temperature and low-concentration acidic conditions, which has huge economic and environmental advantages for the recycling and reuse of thermosetting resins.

[0005] The objective of the present invention is achieved through the following technical solutions:

[0006] A degradable glycidylamine epoxy resin containing an aminal structure has the following general molecular structure formula:

[0007]

[0008] In the formula, R1 and R 2 It is one of an alkyl group, a cycloalkyl group, a heterocyclic group, a heterocycloalkyl group, an aromatic group, and a heteroaromatic group.

[0009] A method for preparing the above-mentioned degradable glycidylamine epoxy resin containing an aminal structure is prepared according to the following reaction process:

[0010]

[0011] The specific preparation steps are as follows:

[0012] Step 1: Compound I and Compound II are subjected to an amine-aldehyde condensation reaction in a solvent, and after the reaction is completed, the solvent is evaporated to dryness to obtain an aminal compound, wherein:

[0013] The structural formula of the compound I is The structural formula of compound II is The equivalent ratio of the two is 1:2~2.1;

[0014] The solvent is at least one of toluene, xylene, dichloromethane, methanol, ethanol, ethylene glycol, propanol, isopropanol, ethyl acetate, ether, tetrahydrofuran, chloroform, acetone and acetonitrile;

[0015] The temperature of the amine-aldehyde condensation reaction is 0 to 80° C. and the time is 4 to 12 hours;

[0016] Step 2: mixing the aminal compound with epichlorohydrin to react, wherein:

[0017] The molar ratio of the aminal compound to epichlorohydrin is 1:3-10;

[0018] The reaction temperature is 50-80°C and the reaction time is 3-8 hours;

[0019] Step 3: After the reaction is completed, an alkali metal hydroxide is added dropwise to carry out a desalting ring-closing reaction, wherein:

[0020] The alkali metal hydroxide is sodium hydroxide or potassium hydroxide, and the molar ratio of the aminal compound to the alkali metal hydroxide is 1:2.1-2.5;

[0021] The desalting ring-closing reaction is carried out at a temperature of 20 to 40°C and for a time of 2 to 4 hours;

[0022] Step 4: After the desalting ring-closing reaction is completed, the degradable glycidylamine epoxy resin containing an aminal structure is obtained through extraction, water washing, liquid separation and vacuum removal of the solvent.

[0023] A method for preparing a degradable thermosetting epoxy resin comprises the following steps:

[0024] The above-mentioned degradable glycidylamine epoxy resin containing an aminal structure is subjected to a heat curing cross-linking reaction with a curing agent to generate a degradable thermosetting epoxy resin, wherein:

[0025] The weight ratio of the degradable glycidylamine epoxy resin containing an aminal structure to the curing agent is 0.1 to 10:1;

[0026] The curing agent is one of an amine curing agent, an acid anhydride curing agent, an anionic polymerization curing agent, a cationic polymerization curing agent, and the like;

[0027] The temperature of the heat curing cross-linking reaction is 30 to 200°C;

[0028] The degradable thermosetting epoxy resin contains the following breakable cross-linking structure:

[0029]

[0030] The degradable glycidylamine epoxy resin containing an aminal structure can be used as a matrix to prepare a degradable epoxy resin composite material.

[0031] A method for degrading the above-mentioned degradable glycidylamine epoxy resin containing an aminal structure and a degradable epoxy resin composite material includes the following two technical solutions:

[0032] Technical Solution 1: Under heating conditions, amines and solvents are used as degradation liquids, and degradation of degradable glycidylamine epoxy resins containing aminal structures and degradable epoxy resin composites is achieved under mechanical stirring, wherein:

[0033] The heating temperature is 40 to 200° C. and the heating time is 1 to 12 hours;

[0034] The mass concentration of the amine in the solvent is 20 to 100%;

[0035] The amine is at least one of aliphatic amines (such as ethylenediamine, propylenediamine, 3-methylaminopropylamine, etc.), alicyclic amines (such as isophoronediamine, 1,3-cyclohexanedimethylamine, etc.), aromatic amines (such as m-phenylenediamine, 4,4-diaminodiphenylmethane, etc.), etc.;

[0036] The solvent is at least one of water, isopentane, n-pentane, petroleum ether, hexane, cyclohexane, cyclopentane, heptane, carbon tetrachloride, benzene, toluene, xylene, chlorobenzene, o-dichlorobenzene, dichloromethane, carbon tetrachloride, methanol, ethanol, ethylene glycol, propanol, isopropanol, butanol, isobutanol, tert-butanol, amyl alcohol, benzyl alcohol, ethyl acetate, ether, petroleum ether, isopropyl ether, tetrahydrofuran, chloroform, dioxane, pyridine, acetone, acetonitrile, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, and dimethyl sulfoxide;

[0037] Technical Solution 2: Under heating conditions, acid and solvent are used as degradation liquids, and degradation of degradable glycidylamine epoxy resins containing aminal structures and degradable epoxy resin composites is achieved under mechanical stirring, wherein:

[0038] The heating temperature is 40 to 200° C. and the heating time is 1 to 12 hours;

[0039] The mass concentration of the acid in the solvent is 20 to 40%;

[0040] The acid is at least one of hydrochloric acid, sulfuric acid, acetic acid, p-toluenesulfonic acid, phosphotungstic acid, nitric acid, etc.;

[0041] The solvent is at least one of water, isopentane, n-pentane, petroleum ether, hexane, cyclohexane, cyclopentane, heptane, carbon tetrachloride, benzene, toluene, xylene, chlorobenzene, o-dichlorobenzene, dichloromethane, carbon tetrachloride, methanol, ethanol, ethylene glycol, propanol, isopropanol, butanol, isobutanol, tert-butanol, amyl alcohol, benzyl alcohol, ethyl acetate, ethyl ether, petroleum ether, isopropyl ether, tetrahydrofuran, chloroform, dioxane, pyridine, acetone, acetonitrile, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, and dimethyl sulfoxide.

[0042] Compared with the prior art, the present invention has the following advantages:

[0043] 1. The present invention prepares a degradable epoxy resin through an amine-aldehyde condensation reaction, and introduces an aminal structure into the epoxy resin cross-linking structure through a cross-linking curing reaction. Under the conditions of an acid or amine and a solvent, the aminal structure can undergo a reverse reaction of the amine-aldehyde condensation or an exchange reaction, and degrade to obtain an aldehyde compound and an amino-terminated epoxy resin prepolymer, thereby achieving the purpose of degrading a thermosetting epoxy resin, and the epoxy resin has excellent mechanical and heat resistance properties.

[0044] 2. The degradable thermosetting epoxy resin of the present invention is used in a fiber-reinforced composite material. Under the degradation conditions provided by the present invention, the thermosetting epoxy resin matrix in the fiber-reinforced composite material is degraded into a polymer with a smaller molecular weight, which can be dissolved in an organic solvent. After a simple separation, the epoxy resin matrix and the fiber can be separated, thereby achieving the purpose of recycling and reusing the fiber reinforcement. At the same time, the degradation and recovery method under amine conditions provided by the present invention can recycle the curing agent, epoxy resin prepolymer, and solvent, and will not generate a secondary pollution source to the environment. It is an economically feasible industrial production route. DETAILED DESCRIPTION

[0045] The technical solution of the present invention is further described below in conjunction with the embodiments, but is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention should be included in the protection scope of the present invention.

[0046] Example 1: Preparation of Epoxy Resin I

[0047] 35.40 g of terephthalaldehyde and 17.60 g of 3-methylaminopropylamine were dissolved in 250 mL of anhydrous ethanol respectively. After complete dissolution, they were transferred to a 1000 mL round-bottom flask and heated under reflux for 4 h. The solvent was removed in vacuo, washed with cold water, and dried to obtain an acetal amine compound with a yield of up to 93%.

[0048] Take 27.4 g of the above aminal compound, dissolve it in 250 mL of anhydrous methanol, slowly drop it into 92.5 g of epichlorohydrin, react at 50 ° C, continue to react for 6 hours after the addition is completed, then cool to 40 ° C, add 14 g of 30 wt% sodium hydroxide solution, continue to react for 2 hours after the addition is completed, add 500 mL of dichloromethane, take the organic phase, wash it with saturated brine until it is neutral, and remove the solvent in vacuo to obtain an amber viscous liquid, which is epoxy resin I, with the following structural formula:

[0049]

[0050] Example 2: Preparation of Epoxy Resin II

[0051] 17.60 g of 3-methylaminopropylamine and 0.35 g of p-toluenesulfonic acid were dissolved in 300 mL of toluene, and 20.00 g of a 50 wt% aqueous solution of glutaraldehyde was added dropwise to the above solution. The mixture was heated to 85°C and refluxed for 8 h. The solvent was then removed in vacuo, the mixture was washed with cold water, and the acetal amine compound was obtained after drying with a yield of up to 90%.

[0052] Take 26.8g of the above aminal compound, dissolve it in 250mL of anhydrous methanol, slowly drop it into 46.25g of epichlorohydrin, react at 60°C, continue to react for 5h after the addition is completed, then cool to 30°C, add 14g of 30wt% sodium hydroxide solution, continue to react for 2h after the addition is completed, add 500mL of dichloromethane, take the organic phase, wash it with saturated brine until it is neutral, remove the solvent in vacuo to obtain an amber viscous liquid, which is epoxy resin II, and the structural formula is as follows:

[0053]

[0054] Example 3: Preparation of Degradable Thermosetting Resin I from Epoxy Resin I

[0055] At room temperature, 38.6 g of the epoxy resin I prepared in Example 1 and 11.5 g of polyetheramine D230 were mixed, stirred evenly and then degassed, and then transferred to a stainless steel mold pre-coated with a release agent, heated at 60°C for 1 hour to form a gel, and heated at 100°C for 4 hours to completely cure. After cooling to room temperature, a degradable epoxy resin I was obtained, and its thermodynamic properties are shown in Table 1.

[0056] Table 1 Thermodynamic properties of degradable epoxy resin I

[0057] project performance Tensile strength(MPa) 73.2±3.2 Tensile modulus(GPa) 2.7±0.5 Tensile strain (%) 4.5±0.5 Bending strength(MPa) 127.6±5.2 Flexural modulus(GPa) 3.3±0.5 Tg(℃) 78-86

[0058] Example 4: Preparation of Degradable Thermosetting Resin II from Epoxy Resin II

[0059] At room temperature, 38.0 g of the epoxy resin II prepared in Example 2 and 20 g of polyetheramine D400 were mixed, stirred evenly and then degassed, and then transferred to a stainless steel mold pre-coated with a release agent, heated at 60°C for 1 hour to form a gel, and heated at 100°C for 4 hours to completely cure. After cooling to room temperature, a degradable epoxy resin II was obtained, and its thermodynamic properties are shown in Table 2.

[0060] Table 2 Thermodynamic properties of degradable epoxy resin II

[0061] project performance Tensile strength(MPa) 67.2±2.7 Tensile modulus(GPa) 2.3±0.8 Tensile strain (%) 4.8±0.5 Bending strength(MPa) 117.3±4.3 Flexural modulus(GPa) 2.8±0.6 Tg(℃) 73-80

[0062] Example 5: Degradation and recovery of degradable thermosetting resin 1

[0063] In a 50 mL glass bottle, 20 mg of the degradable thermosetting resin 1 prepared in Example 3, 3 mL of 1,3-propylenediamine and 12 mL of DMSO were added and stirred at 60° C. for 2 h. The degradable resin was completely degraded to obtain a clear and transparent yellow solution with a recovery rate of up to 92%.

[0064] Example 6: Degradation and recovery of degradable thermosetting resin II

[0065] 20 mg of the degradable thermosetting resin II prepared in Example 4 and 20 mL of 3-methylaminopropylamine were added to a 50 mL glass bottle and stirred at 60° C. for 1 h. The degradable resin was completely degraded to obtain a clear and transparent yellow solution with a recovery rate of up to 100%.

[0066] Example 7: Degradation and recovery of degradable thermosetting resin II

[0067] 20 mg of the degradable thermosetting resin II prepared in Example 4, 10 mL of hydrochloric acid and 12 mL of THF were added to a 50 mL glass bottle and stirred at 60° C. for 1 hour to completely degrade the resin to obtain a clear and transparent yellow solution. The solution was neutralized with a saturated potassium carbonate solution to recover the degradation product, with a recovery rate of up to 75%.

[0068] Example 8: Preparation and degradation recovery of thermosetting resin II-carbon fiber composite material

[0069] The T300-grade carbon fiber was impregnated with the degradable thermosetting resin II prepared in Example 4 and then laid out in 5 layers. The carbon fiber was placed in a metal mold and pressurized and cured using a hot press. After heating at 60°C for 1 hour to gel, a pressure of 1 MPa was applied and the carbon fiber composite material was completely cured by heating at 100°C for 4 hours to obtain a carbon fiber composite material.

[0070] The composite material was immersed in a mixed solution of hydrochloric acid / THF and stirred at 60°C for 3 hours, and then it was completely degraded to obtain a yellow solution and recycled carbon fiber with a clean surface.

Claims

1. A degradable glycidylamine epoxy resin containing an aminal structure, characterized in that The epoxy resin has the following molecular structure formula: In the formula, R1 and R2 are one of an alkyl group, a cycloalkyl group, a heterocyclic group, a heterocycloalkyl group, an aromatic group, and a heteroaromatic group.

2. A method for preparing the degradable glycidylamine epoxy resin containing an aminal structure according to claim 1, characterized in that The method comprises the following steps: Step 1: Compound I and Compound II are subjected to an amine-aldehyde condensation reaction in a solvent, and after the reaction is completed, the solvent is evaporated to dryness to obtain an aminal compound, wherein: The structural formula of the compound I is The structural formula of compound II is The equivalent ratio of the two is 1:2~2.1; The temperature of the amine-aldehyde condensation reaction is 0 to 80° C. and the time is 4 to 12 hours; Step 2: mixing the aminal compound with epichlorohydrin to react, wherein: The molar ratio of the aminal compound to epichlorohydrin is 1:3-10; The reaction temperature is 50-80°C and the reaction time is 3-8 hours; Step 3: After the reaction is completed, an alkali metal hydroxide is added dropwise to carry out a desalting ring-closing reaction, wherein: The molar ratio of the aminal compound to the alkali metal hydroxide is 1:2.1-2.5; The desalting ring-closing reaction is carried out at a temperature of 20 to 40°C and for a time of 2 to 4 hours; Step 4: After the desalting ring-closing reaction is completed, the degradable glycidylamine epoxy resin containing an aminal structure is obtained through extraction, water washing, liquid separation and vacuum removal of the solvent.

3. The method for preparing the degradable glycidylamine epoxy resin containing an aminal structure according to claim 2, characterized in that The solvent is at least one of toluene, xylene, dichloromethane, methanol, ethanol, ethylene glycol, propanol, isopropanol, ethyl acetate, ether, tetrahydrofuran, chloroform, acetone and acetonitrile; and the alkali metal hydroxide is sodium hydroxide or potassium hydroxide.

4. A method for preparing a degradable thermosetting epoxy resin, characterized in that The method comprises the following steps: subjecting the degradable glycidylamine epoxy resin containing an aminal structure as claimed in claim 1 to a heat-curing cross-linking reaction with a curing agent to generate a degradable thermosetting epoxy resin, wherein: The weight ratio of the degradable glycidylamine epoxy resin containing an aminal structure to the curing agent is 0.1 to 10:1; The temperature of the heat curing cross-linking reaction is 30 to 200°C; The degradable thermosetting epoxy resin contains the following breakable cross-linking structure:

5. The method for preparing a degradable thermosetting epoxy resin according to claim 4, characterized in that The curing agent is one of curing agents such as amine curing agents, acid anhydride curing agents, anionic polymerization curing agents, and cationic polymerization curing agents.

6. A method for degrading a degradable glycidylamine epoxy resin containing an aminal structure prepared by the method according to any one of claims 4 to 5, characterized in that The method comprises the following steps: under heating conditions, using amine and solvent as degradation liquid, and achieving degradation of degradable glycidylamine epoxy resin containing aminal structure and degradable epoxy resin composite material under mechanical stirring, wherein: The heating temperature is 40 to 200° C. and the heating time is 1 to 12 hours; The mass concentration of the amine in the solvent is 20-100%.

7. The method for degrading the degradable glycidylamine epoxy resin containing an aminal structure according to claim 6, characterized in that The amine is at least one of aliphatic amines, alicyclic amines, and aromatic amines; the solvent is at least one of water, isopentane, n-pentane, petroleum ether, hexane, cyclohexane, cyclopentane, heptane, carbon tetrachloride, benzene, toluene, xylene, chlorobenzene, o-dichlorobenzene, dichloromethane, carbon tetrachloride, methanol, ethanol, ethylene glycol, propanol, isopropanol, butanol, isobutanol, tert-butanol, amyl alcohol, benzyl alcohol, ethyl acetate, ether, petroleum ether, isopropyl ether, tetrahydrofuran, chloroform, dioxane, pyridine, acetone, acetonitrile, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, and dimethyl sulfoxide.

8. A method for degrading a degradable glycidylamine epoxy resin containing an aminal structure prepared by the method according to any one of claims 4 to 5, characterized in that The method comprises the following steps: under heating conditions, using acid and solvent as degradation liquid, and achieving degradation of the degradable glycidylamine epoxy resin containing an aminal structure and the degradable epoxy resin composite material under mechanical stirring, wherein: The heating temperature is 40 to 200° C. and the heating time is 1 to 12 hours; The mass concentration of the acid in the solvent is 20-40%.

9. The method for degrading the degradable glycidylamine epoxy resin containing an aminal structure according to claim 8, characterized in that The acid is at least one of hydrochloric acid, sulfuric acid, acetic acid, p-toluenesulfonic acid, phosphotungstic acid, and nitric acid; the solvent is at least one of water, isopentane, n-pentane, petroleum ether, hexane, cyclohexane, cyclopentane, heptane, carbon tetrachloride, benzene, toluene, xylene, chlorobenzene, o-dichlorobenzene, dichloromethane, carbon tetrachloride, methanol, ethanol, ethylene glycol, propanol, isopropanol, butanol, isobutanol, tert-butanol, amyl alcohol, benzyl alcohol, ethyl acetate, ether, petroleum ether, isopropyl ether, tetrahydrofuran, chloroform, dioxane, pyridine, acetone, acetonitrile, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, and dimethyl sulfoxide.

10. Use of the degradable thermosetting epoxy resin prepared by the method of claim 5 as a matrix in a degradable epoxy resin composite material.

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