阅读说明：本技术 一种高性能可回收、易修复环氧树脂及制备方法 (High-performance recyclable and easily-repaired epoxy resin and preparation method thereof ) 是由 汪东 李丽英 尹先鹏 李娜 许晓洲 王国勇 赵英民 于 2020-11-24 设计创作，主要内容包括：本发明涉及一种高性能可回收、易修复环氧树脂及制备方法。该可回收、易修复环氧树脂由环氧树脂、固化剂及促进剂经固化反应制得,所述固化剂为动态硼酸酯键桥联的改性多胺固化剂,其每一个重复单元中至少含有如下片段：所述固化剂由一端带有苯硼酸基团的有机胺分子A1与多元二醇分子B1反应制得,或由一端带有单二醇基团的有机胺分子A2与多元苯硼酸分子B2反应制得。本发明制备的环氧树脂兼具优异的力学性能、热氧稳定性及抗水解性能,对于推进该类树脂材料在工程中的实际应用具有重要意义。(The invention relates to a high-performance recyclable and easily-repairable epoxy resin and a preparation method thereof. The recyclable and easily-repaired epoxy resin is prepared by carrying out curing reaction on epoxy resin, a curing agent and an accelerator, wherein the curing agent is a modified polyamine curing agent bridged by a dynamic borate bond, and each repeating unit at least comprises the following segments:)

1. The recyclable and easily-repaired epoxy resin is characterized by being prepared by carrying out curing reaction on epoxy resin, a curing agent and an accelerator, wherein the curing agent is a modified polyamine curing agent bridged by a dynamic borate bond, and each repeating unit at least comprises the following segments:

2. the recyclable, easy-repair epoxy resin of claim 1 wherein the curing agent is characterized by the following structural formula:

wherein R is₁Is any one ofFunctional group, R₂Is composed ofn≥2。

3. The recyclable, easily repairable epoxy resin according to claim 2, wherein the curing agent is prepared by reacting an organic amine molecule A1 having a phenylboronic acid group at one end with a polyhydric diol molecule B1, or an organic amine molecule A2 having a monodiol group at one end with a polyhydric phenylboronic acid molecule B2.

4. The recyclable, easy-repair epoxy resin of claim 3 wherein the organic amine molecule having a phenylboronic acid group at one end A1 has the following structural formula:

wherein R is₁Is any functional group.

5. The recyclable, easy-repair epoxy resin of claim 3 wherein the polyglycol molecule B1 is characterized by the following structural formula:

wherein R is₁Is any functional group.

6. The recyclable, easy-repair epoxy resin of claim 3 wherein the organic amine molecule having a single diol group at one end A2 is characterized by the following structural formula:

wherein R is₁Is any functional group.

7. The recyclable, easy-repair epoxy resin of claim 3 wherein the polyphenylboronic acid molecule B2 is characterized by the following structural formula:

wherein R is₁Is any functional group, and n is more than or equal to 2.

8. A method for preparing the recyclable, easily repairable epoxy resin of claim 1, wherein the curing agent is prepared by reacting an organic amine molecule a1 having a phenylboronic acid group at one end with a polyhydric diol molecule B1, or an organic amine molecule a2 having a mono-diol group at one end with a polyhydric phenylboronic acid molecule B2, the method comprising the steps of:

1) mixing and dissolving organic molecules A1 and B1 or A2 and B2 in a certain proportion in an organic solvent, adding a molecular sieve or a drying agent, fully reacting at room temperature, filtering, and concentrating in vacuum to obtain a dynamic borate bond bridged modified polyamine curing agent;

2) uniformly mixing the epoxy resin with the curing agent and the accelerator prepared in the step 1), and obtaining the epoxy resin material after complete curing reaction.

9. The method of claim 8, wherein the ratio of a1 to B1 or a2 to B2 is in molar ratio f: 1, wherein f is the number of functional groups of the polybasic phenylboronic acid or the polybasic diol monomer, and f is not less than 2.

10. The method of claim 8, wherein the promoter is a secondary or tertiary amine small molecule containing a N atom; the epoxy resin is any one or a mixture of more of glycidyl ether type epoxy resin, glycidyl ester type epoxy resin and glycidyl ammonia type epoxy resin; the organic solvent is one or a mixture of more of tetrahydrofuran, ethyl acetate, dichloromethane and toluene.

Technical Field

The invention particularly relates to a high-performance recyclable and easily-repaired epoxy resin and a preparation method thereof, belonging to the field of high-performance resins.

Background

Epoxy resin is widely applied in various fields due to excellent performance, and a large amount of epoxy waste is urgently required to be recycled every year. However, due to the irreversible chemical crosslinking structure of the thermosetting epoxy resin, on one hand, when the material is damaged in the using process, the in-situ body repair is difficult to carry out, and the maintenance cost is greatly increased; on the other hand, once cured and molded, thermosetting resins are insoluble and infusible, and a large amount of waste resins and composite materials cannot be effectively reprocessed and recycled, so that environmental pollution and energy waste caused by the waste resins and the waste materials become prominent problems which hinder the application and development of resin-based composite materials.

In 2011, Leibler et al reported a dynamic ester exchange reaction-based epoxy resin material in Science, and found that the epoxy resin material can be melt-processed at high temperature like glass, thereby realizing real recycling. After this work has been published, the introduction of reversibly crosslinked networks based on dynamic covalent bonds in polymer networks has received much attention as one of the important approaches to solving the problem of recycling and reprocessing thermoset polymers. At present, most dynamic covalent bond systems studied include transesterification, disulfide bond exchange, olefin metathesis, etc., but these reactions all have the problems of instability in a thermal oxygen environment or side cross-linking reaction at high temperature, etc., and the utilization efficiency and performance of the resin after repair or recovery are seriously affected.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a recyclable and easily-repaired epoxy resin which has excellent recyclable and easily-repaired performances, and is resistant to thermal oxygen and hydrolysis.

The technical solution of the invention is as follows:

the recoverable easily-repaired epoxy resin is prepared by carrying out curing reaction on epoxy resin, a curing agent and an accelerator, wherein the curing agent is a modified polyamine molecule bridged by a dynamic borate bond, and each repeating unit at least comprises the following fragments:

the curing agent is a polyamine curing agent bridged by a dynamic boric acid ester bond, the boric acid ester bond is obtained by esterification dehydration condensation reaction of a phenylboronic acid group and a dihydric alcohol group, and the curing agent has the following structural formula characteristics:

wherein R is₁Is an arbitrary functional group, R₂Is composed ofn≥2。

The curing agent can be prepared by reacting an organic amine molecule A1 with a phenylboronic acid group at one end with a polyhydric diol molecule B1, or an organic amine molecule A2 with a single diol group at one end with a polyhydric phenylboronic acid molecule B2.

The organic amine molecule A1 having a phenylboronic acid group at one end has the following structural formula:

wherein R is₁And may be any functional group such as a meta or para functional group.

The organic amine molecule a1 may preferably be, but is not limited to, one of the following structural formulas:

the polyglycol molecule B1 is characterized by the following structural formula:

wherein R is₁And may be any functional group.

The polyhydric diol molecule B1 may preferably be, but is not limited to, one of the following structural formulae:

the organic amine molecule a2 having a single diol group at one end has the following structural formula:

wherein R is₁And may be any functional group.

The organic amine molecule a2 may preferably be, but is not limited to, one of the following structural formulas:

the poly phenylboronic acid molecule B2 has the following structural formula:

wherein, the connecting functional group can be meta or para, and n is more than or equal to 2. R₁And may be any functional group.

The poly (phenylboronic acid) molecule B2 may preferably be, but is not limited to, one of the following structural formulas:

the invention also provides a method for preparing the high-performance recyclable and easily-repaired epoxy resin, which is realized by the following steps:

1) mixing and dissolving organic molecules A1 and molecules B1 or A2 and B2 in a certain proportion in an organic solvent, adding a molecular sieve or a drying agent, fully reacting at room temperature, filtering, and concentrating in vacuum to obtain a dynamic borate bond bridged modified polyamine curing agent; the conditions are selected to ensure that the dehydration condensation reaction is fully carried out;

2) uniformly mixing the epoxy resin with the curing agent and the accelerator prepared in the step 1), and obtaining the epoxy resin material after the curing reaction is completed.

The organic amine molecules and the poly-phenylboronic acid or the poly-glycol molecules are mixed according to a molar ratio f: 1 (i.e., the ratio of a1 to B1, or the ratio of a2 to B2), wherein f is the number of functional groups of the polybasic phenylboronic acid or the polybasic diol monomer, and f ≧ 2.

The accelerator is a secondary or tertiary amine small molecule containing a N atom, and can be preferably tertiary amine or pyridine.

The epoxy resin is preferably a glycidyl epoxy resin system, and can be any one or a mixture of more of glycidyl ether type epoxy resin, glycidyl ester type epoxy resin and glycidyl ammonia type epoxy resin, and is more preferably bisphenol A type epoxy resin or bisphenol F type epoxy resin.

The organic solvent can be any common organic solvent, and preferably any one or a mixture of several of tetrahydrofuran, ethyl acetate, dichloromethane and toluene.

In the step 2), the curing reaction conditions may adopt conventional epoxy resin curing conditions, and may be: and (3) placing the uniformly mixed mixture of the epoxy resin and the curing agent into a vacuum oven, vacuumizing and defoaming for 30-50min, pouring the defoamed solution into a preheated stainless steel mold, heating and curing, cooling and demolding.

The design principle of the invention is as follows:

according to the invention, the modified polyamine curing agent with borate bridging groups is synthesized, and borate cross-linking points containing N → B coordination bonds are constructed by introducing the amine curing agent and the accelerator, so that the epoxy resin based on borate double decomposition reaction is prepared. Under certain conditions, epoxy resin fragments or damaged interfaces can be fused by inducing macromolecular chain movement and rearrangement through a borate metathesis reaction, so that the re-molding of the resin and the repair of the damaged interfaces are realized. The boric acid ester crosslinking point constructed by the invention has higher bond energy and good thermo-oxidative stability, and the introduction of the N → B coordination bond greatly improves the problem of non-hydrolysis resistance of the traditional boric acid ester bond and overcomes the defects of unstable thermo-oxidative stability, non-hydrolysis resistance, poor mechanical property and the like of the traditional dynamic bond crosslinking polymer.

The invention has the beneficial effects that:

according to the invention, the epoxy resin with recoverable and easily repairable performance is obtained by constructing dynamic borate crosslinking points containing N → B coordination bonds in a resin curing crosslinking network. The curing agent prepared by the invention has universality for different epoxy resins, high universality, mild reaction conditions and simple preparation process, does not need other catalysts during recovery or repair, and can realize better recovery and repair performance under certain heating conditions based on double decomposition reaction of boric acid ester. In addition, compared with other dynamic bond system cross-linked polymers, the epoxy resin prepared by the invention has excellent mechanical property, thermal-oxidative stability and hydrolysis resistance, and has important significance for promoting the practical application of the resin material in engineering.

Detailed Description

The present invention will be described in further detail with reference to examples, but the present invention is not limited thereto.

The epoxy resin recovery method provided by the invention comprises the steps of breaking and finely crushing the epoxy resin prepared by the method, and carrying out die pressing for 6-12 h at 100-160 ℃ and 5-10 MPa in an air atmosphere.

Example 1: the curing agent of this example was prepared by reacting an organic amine molecule A2 having a single diol group at one end with a polyphenylboronic acid molecule B2, wherein 3-amino-1, 2-propanediol was used for A2 and 1, 4-benzenediboronic acid was used for B2.

Step 1: under the protection of nitrogen, dissolving 1, 4-phenyl diboronic acid (16.5g) in 150mL tetrahydrofuran, performing ultrasonic treatment, stirring until the mixture is completely dissolved, then adding 3-amino-1.2-propylene glycol (18.2g) and 20mL deionized water for full dissolution, stirring for 2h, then adding magnesium sulfate (20g), heating and refluxing for 2h, filtering after the reaction is finished, and performing rotary evaporation and concentration on the filtrate to obtain a white solid, so as to obtain a curing agent containing a borate bridging group, wherein the structural formula is as follows:

step 2: and (2) uniformly mixing 50g of bisphenol A epoxy resin solution E51, 17.5g of the prepared curing agent and 0.6g (1 wt% of mass ratio) of tertiary amine accelerator, putting the mixture into a vacuum oven, vacuumizing and defoaming for 30-50min, pouring the defoamed solution into a preheated stainless steel mold, curing at room temperature for 8h, cooling and demolding to obtain the epoxy resin.

The prepared epoxy resin is broken and finely crushed, the resin fragments are molded for 6 hours at the temperature of 110 ℃ and under the pressure of 8MPa, the recovered sample is tested for tensile property, and the recovery efficiency of the recovered epoxy resin is shown in table 1.

Example 2: the curing agent of this example was prepared by reacting an organic amine molecule A1 having a phenylboronic acid group at one end with a polyhydric diol molecule B1, wherein A1 used was 3-aminophenylboronic acid and B1 used was pentaerythritol.

Step 1: pentaerythritol (13.6g) and 3-aminophenylboronic acid (27.4g) were weighed out and dissolved in 150ml of tetrahydrofuran, and the mixture was stirred with ultrasound until it was completely dissolved. Adding 15g of magnesium sulfate, fully reacting at room temperature for 24 hours, filtering after the reaction is finished, and performing rotary evaporation and concentration on filtrate to obtain a white solid to obtain the curing agent containing the borate bridging group, wherein the structural formula is as follows:

step 2: uniformly mixing 50g of bisphenol A epoxy resin solution E51, 21.5g of the prepared curing agent and 0.7g (1 wt% of mass ratio) of pyridine accelerator, putting the mixture into a vacuum oven, vacuumizing and defoaming for 30-50min, pouring the defoamed solution into a preheated stainless steel mold, curing at 90 ℃ for 1h, curing at 130 ℃ for 6h, cooling and demolding to obtain the epoxy resin.

The prepared epoxy resin is broken and finely crushed, the resin fragments are molded for 6 hours at 140 ℃ under the pressure of 10MPa, the recovered sample is tested for tensile property, and the recovery efficiency of the recovered epoxy resin is shown in table 1.

Example 3: the curing agent of this example was prepared by reacting an organic amine molecule A2 having a single diol group at one end with a polyphenylboronic acid molecule B2, wherein A2 used 4-amino-1.2-butanediol and B2 used 1,3, 5-benzenetriboric acid.

Step 1: under the protection of nitrogen, dissolving 1,3, 5-benzene tricarbonic acid (20.9g) in 300mL of toluene, performing ultrasonic stirring until the solution is completely dissolved, then adding 4-amino-1.2-butanediol (31.5g), stirring for 2h to fully dissolve and mix, then adding 4A molecular sieve (20g), heating and refluxing for 2h, filtering after the reaction is finished, and performing rotary evaporation and concentration on the filtrate to obtain a white solid to obtain a curing agent containing a boric acid ester bridging group, wherein the structural formula is as follows:

step 2: uniformly mixing 51g of bisphenol F epoxy resin CYDF-170, 20.8g of the prepared curing agent and 0.7g (1 wt% of mass ratio) of tertiary amine accelerator, placing the mixture into a vacuum oven, vacuumizing and defoaming for 30-50min, pouring the defoamed solution into a preheated stainless steel mold, curing for 3h at 60 ℃, curing for 1h after 130 ℃, cooling and demolding to obtain the epoxy resin, and cooling and demolding to obtain the epoxy resin.

The prepared epoxy resin is broken and finely crushed, the resin fragments are molded for 6 hours at the temperature of 130 ℃ and under the pressure of 8MPa, the recovered sample is subjected to tensile property test, and the recovery efficiency of the recovered epoxy resin is shown in Table 1.

Comparative example 1:

step 1: uniformly mixing 100g of bisphenol A epoxy resin solution E51 with a curing agent diaminodiphenylmethane (DDM), placing the mixture into a vacuum oven, vacuumizing and defoaming for 30-50min, pouring the defoamed solution into a preheated stainless steel mold, curing for 4h at 60 ℃, curing for 4h after 100 ℃, cooling and demolding to obtain the epoxy resin.

Step 2: the prepared epoxy resin is broken and finely crushed, the resin fragments are molded for 6 hours at 140 ℃ under the pressure of 10MPa, the recovered sample is tested for tensile property, and the recovery efficiency of the recovered epoxy resin is shown in table 1.

TABLE 1 comparison of the Performance and recovery efficiency of epoxy resins of the invention and comparative materials

Sample examples	Tensile Strength (MPa)	Glass transition temperature (. degree. C.)	Recovery efficiency
				Example 1	78±5	68	86％
Example 2	85±7	120	75％
				Example 3	92±6	92	79％
Comparative example 1	82±4	132	Can not be formed after recovery

The invention has not been described in detail and is in part known to those of skill in the art.

The particular embodiments of the present invention disclosed above are illustrative only and are not intended to be limiting, since various alternatives, modifications, and variations will be apparent to those skilled in the art without departing from the spirit and scope of the invention. The invention should not be limited to the disclosure of the embodiments in the present specification, but the scope of the invention is defined by the appended claims.