CN115181079A - A kind of preparation method and application of epoxy resin which is both recyclable and degradable and thermoplastic processable - Google Patents

Abstract

The invention relates to an epoxy resin with thermoplasticity processing and cyclic degradation and a preparation method thereof, belonging to the technical field of new material synthesis. The invention comprises the following steps: mixing an epoxy monomer with an aromatic ketone structure with the existing commercial amine curing agent according to the mass part ratio of 1.4-0.7, pouring the mixture into a mold after stirring, heating the mixture step by step, and demolding after complete curing to obtain the thermoplastic processing and cyclic degradation epoxy resin. The cured epoxy resin chips were hot pressed (10 MPa,10 min) at 150-200 ℃ to give a complete sheet. The epoxy resin can be completely degraded circularly in 24 hours at a temperature below 80 ℃ in a mixed solution of an acidic aqueous solution and an organic solvent after being cured, and the degraded product can be recycled for re-curing of the epoxy resin after being recovered. The tensile strength, young modulus and elongation at break of the epoxy resin after the resolidification of the degradation product and repeated hot pressing are equivalent to those of the original epoxy resin. The invention has simple process, and the product has the functions of cyclic degradation and thermoplastic processing, and is expected to be used in the fields of the recovery of reinforced fibers in epoxy composite materials, cyclic degradation or self-repair epoxy coatings, cyclic degradation epoxy adhesives and the like.

Description

A kind of preparation method of epoxy resin with both recyclable degradation and thermoplastic processability and application

technical field

The invention relates to an epoxy resin which can be thermoplastically processed and cyclically degraded and a preparation method thereof, and belongs to the technical field of new material synthesis.

Background technique

Epoxy resin is widely used in transportation, aerospace, electronic appliances, paint anticorrosion and other fields, and is currently the most widely used thermosetting resin. Since the epoxy resin forms a three-dimensional cross-linked network after curing, the cured epoxy resin is insoluble and insoluble and difficult to degrade. The increasing speed of replacement of electronic devices has led to the generation of a large amount of electronic waste, and the environmental protection problem has become increasingly serious; the amount of carbon fiber/epoxy composite materials is huge, but the recycling of high-performance and high-value-added carbon fibers in composite material waste is difficult. The research and development of recyclable degradable epoxy has very important economic and social value.

The cleavable covalent bonds in the existing cyclically degradable epoxy resins are mainly esters with different substituents, such as sulfonates), sulfites, carbonates, phosphates; acetal structures, etc., and the degradation temperature is generally Above 140℃, so the energy consumption of carbon fiber recycling is high. Since the above-mentioned covalent bonds do not have reversible properties, the prepared epoxy thermosetting resin is also not thermoplastically processable. The dynamic covalent bond is a reversible covalent bond, which is introduced into the polymer network to construct covalent adaptive networks (CANs), which can make the material not only have the molecular structure stability of traditional covalent polymers, but also under certain conditions. It also possesses the dynamic reversibility of supramolecular polymers, which endows the material with rich responsiveness to external stimuli, and can realize the degradation of thermosetting resins induced by heat, acid, ultrasound and external small molecules. Recently, epoxy monomers and amine curing agents with dynamic covalent bonds such as Diels–Alder dynamic covalent bonds, disulfide bonds, and imines have been reported to realize the thermoplastic processing and degradation of thermosetting resins.

I prepared an epoxy resin with imine (Schiff base) dynamic covalent bond in the early stage, and found that the resin can be thermoplastically processed and degraded by acid, but the uncontrollable cross-linked network structure leads to complex degradation products, so the degradation products cannot be recycled. In order to realize the recycling and reuse of epoxy resin degradation products, this patent reports for the first time the synthetic route and preparation method of epoxy monomer with aromatic ketone structure, and the preparation process of epoxy resin obtained by curing with amine curing agent, etc. By controlling the curing conditions, the acid degradation products of the epoxy resin can be recycled and reused. The thermoplastic processing properties of epoxy resins facilitate the molding of composite materials. Therefore, the preparation of both recyclable and thermoplastically processable epoxy resins undoubtedly has important application value for the recycling of reinforcing fillers in epoxy composites, the reuse of epoxy thermosetting resins, degradable epoxy adhesives, and environmental protection.

SUMMARY OF THE INVENTION

The purpose of the present invention is to solve the above technical problems, to provide a method for preparing a cyclically degradable and thermoplastically processable epoxy resin, and to provide a new idea for the preparation of cyclically degradable epoxy resin and the recycling of thermosetting resin reinforced fibers.

To achieve the above purpose of the invention, the present invention provides an epoxy monomer and a preparation method thereof.

An epoxy monomer, the epoxy monomer is synthesized by reacting p-hydroxyacetophenone, epichlorohydrin and a phase transfer catalyst at 60-85° C. for 1-3 hours; adding water to the obtained synthetic product mixed solution and organic phase extractant, collect by liquid separation and dry the organic phase solution with anhydrous sodium sulfate to obtain pure epoxy resin monomer; the schematic diagram of the synthesis is shown in Figure 1, and the nuclear magnetic spectrum of the monomer is shown in Figure 2.

1. a preparation method of epoxy resin monomer, described preparation method is carried out according to the following steps:

S1. After mixing 1 part of p-hydroxyacetophenone, 3-7 parts of epoxidation monomer and 0.1-0.3 part of phase transfer catalyst uniformly, react at 60-85° C. for 1-3 hours to obtain mixed solution a.

S2. Add 0.1-0.3 parts of a phase transfer catalyst and 1-2 parts of sodium hydroxide aqueous solution to the mixed solution a obtained in S1, and react at room temperature for 0.5-3 h to obtain a mixed solution b.

S3. 50 parts of water and an organic phase extractant are added to the mixed solution b obtained in S2, and the organic phase solution is obtained by liquid separation and collection after shaking.

S4. add 30 parts by mass of anhydrous sodium sulfate dry organic phase solution 200r/min to the organic phase solution obtained in S3

S5. Rotary evaporation of the dried organic phase solution obtained in S4 at 80° C. to obtain an epoxy resin monomer.

The epoxidized monomer is epichlorohydrin; the phase transfer catalyst includes but is not limited to the existing organic quaternary ammonium salt system, such as benzyl triethyl ammonium chloride, etc.; the organic phase extraction agent is ethyl acetate or diethyl ether. Chloromethane.

2. a curing method of epoxy resin monomer, described curing method is carried out according to the following steps:

S1. Mix 1 part of epoxy resin monomer and 0.4-0.7 part of curing agent uniformly to obtain a mixed solution, pour the mixed solution into a mold, and heat and react at 80° C. for 10 minutes to obtain an epoxy resin precursor.

S2. The epoxy resin precursor obtained from S1 is heated to 180° C. for curing for 6 hours, and the cured epoxy resin sheet can be cyclically degraded and thermoplastically processed.

3. A method for degradation and recycling of a cured epoxy resin polymer, the method is carried out according to the following steps:

S1. Immerse the cured epoxy resin in a mixed solution of an acidic aqueous solution and an organic solvent I mixed solution at room temperature to 80 °C, degrade after 24 hours of reaction, and dissolve the degradation product in the mixed solution.

S2. Add an equivalent amount of NaOH to neutralize the acid in the mixed solution obtained from S1, adjust the pH of the degradation solution to neutrality, volatilize the solvent at room temperature, then add an equal volume of water and organic solvent II to extract the degradation product, separate the organic phase solution, spin Degradation products are obtained after evaporation.

Wherein, the acidic aqueous solution is a 1 mol/L hydrochloric acid aqueous solution or a 1 mol/L sulfuric acid aqueous solution; an acidic aqueous solution and an organic solvent

The mass fraction ratio is 8:2-2:8; the organic solvent I is methanol or ethanol or tetrahydrofuran; the organic solvent II is dichloromethane or ethyl acetate

ethyl acetate.

The recovered degradation products are reacted at 180 degrees for 6 hours, and the cured epoxy resin with the same structure as the initial epoxy resin can be obtained again, realizing the recycling of the degradation products.

4. a thermoplastic processing method of epoxy resin monomer, the thermoplastic processing method is carried out according to the following steps:

The cured epoxy resin is crushed and placed in a mold, and the mold is placed in a high-temperature flat vulcanizer for hot pressing for 10 minutes to obtain a complete epoxy resin sheet.

Among them, the temperature of the flat vulcanizer is 150-200 ° C, and the pressure is 10 MPa.

The present invention adopts the above technical scheme, and compared with the prior art, the present invention has the following technical effects:

1. The epoxy resin obtained by curing the epoxy monomer and amine curing agent provided by the present invention can be cyclically degraded in 24 hours in an acidic solution mixed with an acidic aqueous solution and an organic solution at 80°C.

2. The epoxy resin obtained after curing the epoxy monomer and the amine curing agent provided by the present invention can realize the thermoplastic processing of the thermosetting resin by hot pressing.

3. After the epoxy resin is damaged, it can be repaired by hot pressing (10MPa, 10min) at 130-180℃. The repaired epoxy resin has the same tensile strength, modulus and elongation at break as the original resin.

Description of drawings

Figure 1. The preparation route of cyclically degradable and thermoplastically processable epoxy resin monomers;

Figure 2 1H-NMR spectrum of aromatic ketone-based epoxy monomers.

Detailed ways

The present invention will be further described in detail below through specific embodiments, but it should not be understood that the scope of the present invention is limited to the following examples. Without departing from the above-mentioned method idea of the present invention, various substitutions or changes made according to common technical knowledge in the art and conventional means should all be included within the scope of the present invention.

It is worth noting that: 1) The parts of the materials used in the following examples are all parts by weight.

Example 1

(1) Synthesis of epoxy resin monomer

S1. After mixing 1 part of p-hydroxyacetophenone, 3.4 parts of epoxidation monomer and 0.17 part of catalyst benzyltriethylammonium chloride, react at 80°C for 2 hours to obtain mixed solution a.

S2. Add 0.17 parts of benzyltriethylammonium chloride and 1.18 parts of sodium hydroxide aqueous solution to the mixed solution a obtained in S1, and react at room temperature for 0.5 h to obtain a mixed solution b.

S3. Add 50 parts of water and a dichloromethane extractant to the mixed solution b obtained in S2, and after shaking, liquid-separate and collect to obtain a dichloromethane phase solution.

S4. To the dichloromethane phase solution obtained in S3, add 30 parts by mass of anhydrous sodium sulfate, stir at 200 r/min for 30 min, leave it to stand for 3 h, and recover by suction filtration to obtain a dry dichloromethane phase solution.

S5. Rotary evaporation of the dried dichloromethane phase solution obtained in S4 at 80° C. to obtain an epoxy resin monomer.

(2) Curing of epoxy resin

S1. Mix 1 part of epoxy resin monomer and 0.45 part of hexanediamine evenly to obtain a mixed solution, pour the mixed solution into a mold and place it in an oven, and pre-cured at 70° C. for 2 hours to obtain an epoxy resin precursor.

S2. The epoxy resin precursor obtained from S1 is heated up to be cured at 180° C. for 6 hours, and the cured epoxy resin sheet can be cyclically degraded and thermoplastically processed.

(3) Degradation and recycling of cured epoxy resin polymers

S1. Immerse the cured epoxy resin in a mixed solution of 8 parts of hydrochloric acid aqueous solution (1mol/L)/2 parts of methanol at room temperature to 80 ℃, and degrade after 24 hours of reaction, and the degradation products are dissolved in the mixed solution.

S2. Add 8 parts of NaOH to neutralize the acid in the mixed solution obtained from S1, adjust the pH of the degradation solution to neutrality, volatilize the solvent at room temperature, then add 5 parts of water and 5 parts of ethyl acetate to extract the degradation product, and collect the organic phase solution by liquid separation , and the degradation products were obtained after rotary evaporation.

The recovered degradation products are reacted at 180 degrees for 6 hours, and the cured epoxy resin with the same structure as the initial epoxy resin can be obtained again, realizing the recycling of the degradation products.

(4) Thermoplastic processing of epoxy resin monomer The broken epoxy resin is placed in a mold, and the mold is placed in a high-temperature flat vulcanizer for hot pressing for 10 minutes to obtain a complete epoxy resin sheet.

Among them, the temperature of the flat vulcanizer is 150°C and the pressure is 10MPa.

The sheets obtained in the step "(2) curing of epoxy resin", step "(3) degradation and recycling of cured epoxy resin polymer" and step "(4) thermoplastic processing of epoxy resin monomer" are as follows: The national standard GB/T2567-2008 was cut and tested, and the step "(2) curing of epoxy resin" was obtained, that is, the Young's modulus, tensile strength and elongation at break of the initial resin were 1.4GP, 61MPa and 4.0% respectively; step "(3) Degradation and recycling of cured epoxy resin polymers", that is, the Young's modulus, tensile strength and elongation at break of the re-cured resin after degradation were 1.4GP, 60MPa and 3.8%, respectively; step "( 4) "Thermoplastic processing of epoxy resin monomer", that is, the Young's modulus, tensile strength and elongation at break of the self-healing resin were 1.3GP, 60MPa and 4.2%, respectively.

Claims (2)

1. A thermoplastically processable epoxy resin capable of being cyclically degraded has a structural formula as shown in formula 1:

formula 1 preparation route of epoxy resin monomer capable of cyclic degradation and thermoplastic processing

Commercial amine curing agents, including but not limited to, existing commercial aliphatic and cycloaliphatic amine curing agents.

2. A process for preparing a cyclically degradable and thermoplastically processable epoxy thermosetting resin as claimed in claim 1

The method is characterized by comprising the following steps:

(1) Synthesis of epoxy resin monomer

S1, uniformly mixing 1 part of p-hydroxyacetophenone, 3-7 parts of epoxy monomer and 0.1-0.3 part of phase transfer catalyst, and reacting at 60-85 ℃ for 1-3h to obtain a mixed solution a;

s2, adding 0.1-0.3 part of phase transfer catalyst and 1-2 parts of sodium hydroxide aqueous solution into the mixed solution a obtained in the S1, and reacting for 0.5-3h at room temperature to obtain a mixed solution b;

s3, adding 50 parts of water and an organic phase extracting agent into the mixed solution b obtained in the S2, and separating and collecting liquid after shaking to obtain an organic phase solution;

s4, adding 30 parts by mass of anhydrous sodium sulfate into the organic phase solution obtained in the S3, drying the organic phase solution at a speed of 200r/min, stirring for 30min, standing for 3h, and performing suction filtration and recovery to obtain a dried organic phase solution;

s5, rotationally evaporating the dried organic phase solution obtained in the step S4 at 80 ℃ to obtain an epoxy resin monomer;

the epoxidation monomer is epichlorohydrin; phase transfer catalysts include, but are not limited to, existing organic quaternary ammonium salt systems, such as benzyltriethylammonium chloride, and the like; the organic phase extractant is ethyl acetate or dichloromethane;

(2) Curing of epoxy resin monomers

S1, uniformly mixing 1 part of epoxy resin monomer and 0.4-0.7 part of curing agent to obtain a mixed solution, pouring the mixed solution into a mold, and heating and reacting at 80 ℃ for 10min to obtain an epoxy resin precursor;

s2, heating the epoxy resin precursor obtained in the step S1 to 180 ℃ for curing for 6h, and obtaining the cured epoxy resin sheet which can be degraded circularly and can be processed by thermoplasticity;

(3) Degradation and recycling of cured epoxy resin polymers

S1, soaking the cured epoxy resin into an acidic aqueous solution/organic solvent I mixed solution, reacting for 24 hours at the temperature of between room temperature and 80 ℃, and degrading, wherein degradation products are dissolved in the mixed solution;

s2, adding equivalent NaOH into the mixed solution obtained in the step S1 to neutralize acid, regulating the pH of the degradation solution to be neutral, volatilizing the solvent at room temperature, sequentially adding equivalent water and an organic solvent II to extract degradation products, separating liquid, collecting organic phase solution, and performing rotary evaporation to obtain the product

Degradation products;

wherein the acidic aqueous solution is 1mol/L hydrochloric acid aqueous solution or 1mol/L sulfuric acid aqueous solution; acidic aqueous solution and organic solvent

The mass fraction ratio is 8; the organic solvent I is methanol or ethanol or tetrahydrofuran; the organic solvent II is dichloromethane or ethyl

Ethyl ester acid;

the recycled degradation product reacts for 6 hours at 180 ℃, and the cured epoxy resin with the same structure as the initial epoxy resin can be obtained again, so that the cyclic utilization of the degradation product is realized;

(4) Thermoplastic processing of epoxy monomers

Placing the crushed epoxy resin into a mold, and placing the mold into a high-temperature flat vulcanizing machine for hot pressing for 10min to obtain a complete epoxy resin sheet;

wherein the temperature of the plate vulcanizing machine is 150-200 ℃, and the pressure is 10MPa.

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