Epoxidation method of anhydride cured epoxy resin degradation product

Abstract

The invention relates to an epoxidation method of an anhydride cured epoxy resin degradation product, which comprises the following steps of: degrading epoxy resin by using degradation liquid to obtain a degradation mixture, and separating the degradation mixture to obtain polyhydric alcohol; the preparation method comprises the following steps: mixing polyol with epoxy chloropropane, adding tetrabutylammonium bromide, and heating to obtain a reactant solution after reaction; cooling the reactant solution to room temperature, adding a NaOH solution, and stirring and reacting at low temperature to obtain an epoxy monomer and a mixture solution; adding ethyl acetate to extract the obtained mixture solution, and repeatedly washing the ethyl acetate phase with a sodium chloride aqueous solution for multiple times; ethyl acetate is removed through evaporation, and the epoxy monomer is obtained. According to the method, the epoxy resin can be degraded and recycled through a simple and efficient alkali / alcohol system, a hydroxyl-containing degradation product is further converted into the epoxy monomer, the regenerated epoxy monomer can be used for preparing a new epoxy resin insulating material, closed-loop recycling is achieved, resources are effectively saved, and the production cost is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of epoxy resin material recycling, in particular to an epoxidation method for anhydride-cured epoxy resin degradation products. Background Art

[0002] Epoxy resin is widely used in the fields of power equipment insulation materials and electronic component packaging materials due to its excellent insulation performance, good physical and chemical properties, etc. However, the existing anhydride curing system of epoxy resin has a dense three-dimensional cross-linked structure, and due to the particularity of the structure of electrical equipment, epoxy solid insulation is often recycled by chemical degradation.

[0003] At present, the recycling method of anhydride-cured epoxy resin degradation products is basically to add new epoxy monomers and curing agents for re-curing. Due to the low reactivity of the degradation products, it is difficult to directly prepare new epoxy thermosetting plastics. A high proportion of epoxy monomers and curing agents still need to be added. The direct utilization rate of the degradation products is extremely low, and the economic benefits are poor. At present, there is almost no method for targeted functional group repair of the main component polyol in the alcoholysis product and efficient recycling. However, the traditional epoxy monomer production method has the problems of expensive catalysts, low reaction efficiency, and harsh reaction conditions such as temperature and pressure. Summary of the invention

[0004] In order to solve the above problems, the present invention proposes an epoxidation method for anhydride-cured epoxy resin degradation products, and the specific technical scheme is as follows: A method for epoxidation of anhydride-cured epoxy resin degradation products comprises the following steps: Step 1: Degrading the epoxy resin with a degradation solution to obtain a degradation mixture, and separating the degradation mixture to obtain a polyol; Step 2: mixing polyol and epichlorohydrin, then adding tetrabutylammonium bromide, and heating to obtain a reactant solution; Step 3: Cool the above reactant solution to room temperature, add NaOH solution, and stir to react at low temperature to obtain epoxy monomer and mixture solution; Step 4: adding ethyl acetate to extract the obtained mixture solution, and repeatedly washing the ethyl acetate phase with sodium chloride aqueous solution for several times; Step 5: Remove the ethyl acetate by evaporation to obtain the epoxy monomer.

[0005] Furthermore, the molar ratio of the polyol, epichlorohydrin and tetrabutylammonium bromide is 1:5 to 15:0.2.

[0006] Furthermore, in step 2, the temperature of the heating reaction is 120-160° C., and the reaction time is 6-10 hours.

[0007] Furthermore, the mass fraction of the NaOH solution is 50wt%.

[0008] Furthermore, the reaction temperature in step 3 is 0-5°C, and the reaction time is 2-4h.

[0009] Furthermore, the mass fraction of the sodium chloride solution is 5 to 10 wt %.

[0010] Furthermore, the degradation liquid is prepared by mixing ethylene glycol and sodium hydroxide in a mass ratio of 15 to 30:1.

[0011] Furthermore, the epoxy resin in step 1 is degraded in a sealed container at a degradation temperature of 150°C.

[0012] Furthermore, the polyol is obtained by separating the degradation mixture through extraction.

[0013] Furthermore, the epoxy resin is prepared with a bisphenol A epoxy resin matrix, methyltetrahydrophthalic anhydride as a curing agent and 2,4,6-tris(dimethylaminomethyl)phenol as a catalyst.

[0014] Beneficial effects: The anhydride-cured epoxy resin prepared by the present invention can be degraded and recycled through a simple and efficient alkali / alcohol system, and a degradation product containing multiple hydroxyl groups or carboxyl groups is obtained through alkali-catalyzed degradation of epoxy thermosetting plastics. The hydroxyl-containing degradation product is further converted into an epoxy monomer, and the regenerated epoxy monomer can be used to prepare new epoxy resin insulating materials, thereby realizing closed-loop recycling, effectively saving resources, and reducing production costs. A solution is provided for the problems of low effective utilization rate and poor economic benefits of degradation and recycling products of epoxy materials under a traditional anhydride curing system, and resources can be effectively saved. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a mechanism diagram of the epoxidation of polyols, which are degradation products of the epoxy resin of the present invention.

[0016] Figure 2 The hydrogen nuclear magnetic resonance spectra of the epoxidation of polyols in Examples 1, 2 and 3 of the present invention are shown.

[0017] Figure 3 It is the hydrogen nuclear magnetic resonance spectrum of the epoxidation of polyols in Examples 4, 5 and 6 of the present invention. DETAILED DESCRIPTION

[0018] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. For the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0019] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0020] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0021] like Figure 1 As shown, a method for epoxidation of anhydride-cured epoxy resin degradation products comprises the following steps: Step 1: Degrading the epoxy resin with a degradation liquid to obtain a degradation mixture, and separating the degradation mixture to obtain a polyol.

[0022] The epoxy resin is prepared with a bisphenol A epoxy resin matrix, methyltetrahydrophthalic anhydride (MTHPA) as a curing agent and 2,4,6-tris(dimethylaminomethyl)phenol (DMP-30) as a catalyst. The epoxy resin is degraded in a sealed container at a degradation temperature of 150°C. The degradation liquid is prepared by mixing ethylene glycol and sodium hydroxide in a mass ratio of 15 to 30:1.

[0023] Step 2: The polyol is mixed with epichlorohydrin (EHC), and then tetrabutylammonium bromide (TBAB) is added and heated to obtain a reactant solution.

[0024] The molar ratio of the polyol, epichlorohydrin and tetrabutylammonium bromide is 1:5-15:0.2; the heating reaction temperature is 120-160°C, and the reaction time is 6-10 hours.

[0025] Step 3: Cool the above reactant solution to room temperature, add NaOH solution, and stir the mixture at low temperature to obtain epoxy monomer and mixture solution.

[0026] The mass fraction of the NaOH solution is 50 wt %, the reaction temperature is 0-5° C., and the reaction time is 2-4 h.

[0027] Step 4: Ethyl acetate (EA) was added to extract the resulting mixture solution, and the ethyl acetate phase was repeatedly washed with aqueous sodium chloride solution several times.

[0028] Wherein, the mass fraction of the sodium chloride solution is 5-10wt%.

[0029] Step 5: Remove the ethyl acetate by evaporation to obtain the epoxy monomer.

[0030] like Figure 1 As shown, the mechanism of epoxidation of polyols, the degradation products of epoxy resins, is: (1) Ring-opening reaction: Under the catalytic action of tetrabutylammonium bromide, the hydroxyl group of the polyol reacts with the epoxy group of epichlorohydrin to generate a chlorohydrin with a chlorinated hydroxyl terminal group.

[0031] (2) Ring-closing reaction: The chlorinated hydroxyl group of chlorohydrin reacts with sodium hydroxide, removes HCl and re-forms the epoxy group to obtain the epoxy monomer.

[0032] In one embodiment, the polyol is obtained by separating the degradation mixture through extraction.

[0033] Specifically, ethanol is added to the degradation mixture to generate precipitation, and the precipitate is filtered; the ethanol in the filtered solution is removed, and water is added thereto, and the mixture is allowed to stand for stratification, and the oil phase in the lower layer is taken out, which is the polyol.

[0034] The specific embodiments are as follows: Embodiment 1: (1) Preparation of epoxy resin 23g of E-51 resin was weighed and added to a container containing a magnet, and 16.2g of curing agent methyltetrahydrophthalic anhydride was weighed and added to the container, and MTHPA and E-51 resin were mixed and stirred at 80°C for 20 minutes to make them evenly mixed, wherein the stirring speed was 200rpm. The mixed solution was vacuum degassed in a vacuum drying oven at a temperature of 80°C for 30 minutes; after the vacuum degassed, 0.24g of catalyst 2,4,6-tris(dimethylaminomethyl)phenol was added to the mixed solution, and stirred again at a constant temperature of 60°C for 20 minutes to make them evenly mixed, and a resin prepolymer glue was obtained. Subsequently, vacuum degassing was carried out in a vacuum drying oven at 80°C for 30 min, and the degassed resin prepolymer glue was poured into a stainless steel mold preheated at 120°C and coated with a release agent. It was first cured at 120°C for 2 h and then at 150°C for 4 h. After natural cooling and demolding, the epoxy resin was prepared.

[0035] (2) Epoxy resin degradation 3 g of the epoxy resin prepared above was weighed and placed in a degradation container, and 20 mL of degradation solution was added to the container, wherein the degradation solution was prepared by ethylene glycol and sodium hydroxide at a mass ratio of 25:1, and the mass ratio of epoxy resin to ethylene glycol and sodium hydroxide was 3:25:1. The container was then sealed and placed in a 150°C constant temperature drying oven, and allowed to stand for degradation for 6 hours to finally obtain a degradation mixture, which was extracted and separated to obtain polyols.

[0036] (3) Epoxy monomer production 3.76 g (0.01 mol) of polyol was weighed and added to a container containing a magnet, and then 4.63 g (0.05 mol) of raw epichlorohydrin was weighed and mixed with the polyol, and then 0.64 g (0.002 mol) of tetrabutylammonium bromide (TBAB) was added, and the container was placed in a 140°C oil bath pot, heated and stirred for 8 hours. After the reaction was completed, the solution was cooled to room temperature, 3.28 g (0.04 mol) of 50 wt.% NaOH solution was added dropwise within 15 minutes, and stirred for 2 hours in an ice bath at 0°C to obtain an epoxy monomer and a mixture solution; then ethyl acetate (EA) was added to the container to extract the obtained mixture solution, and after the extraction was completed, the EA phase was separated using a separatory funnel, and the EA phase was repeatedly washed several times with a 5 wt.% sodium chloride aqueous solution; finally, EA was removed by rotary evaporation to obtain an epoxy monomer.

[0037] Embodiment 2: Based on step (3) of Example 1, 9.26 g (0.1 mol) of epichlorohydrin was weighed, and the epoxy monomer was generated according to the above steps.

[0038] Embodiment 3: Based on step (3) of Example 1, 13.89 g (0.15 mol) of epichlorohydrin was weighed, and the epoxy monomer was generated according to the above steps.

[0039] Embodiment 4: Based on step (3) of Example 1, 9.26 g (0.1 mol) of epichlorohydrin was weighed, the temperature of the oil bath was adjusted to 120° C., and the epoxy monomer was generated according to the above steps.

[0040] Embodiment 5: Based on Example 4, the temperature of the oil bath was adjusted to 140° C., and the epoxy monomer was generated according to the above steps.

[0041] Embodiment 6: Based on Example 4, the temperature of the oil bath was adjusted to 160° C., and the epoxy monomer was generated according to the above steps.

[0042] The data of each embodiment are shown in the following table:

[0043] like Figure 2 As shown in Figure 1, when the reaction temperature is 140°C, the NMR hydrogen spectrum of the epoxidation product obtained by changing the ratio of polyol to ECH is shown. As can be seen from the figure, the polyol is successfully epoxidized, and when the ratio of polyol to ECH is 1:10, the impurity peak on the NMR hydrogen spectrum of the epoxidation product is the smallest, which is the optimal ratio.

[0044] like Figure 3 As shown in Figure 1, when the ratio of polyol to ECH is 1:10, the H NMR spectrum of the epoxidation product obtained by changing the reaction temperature is shown in Figure 2. As can be seen from the figure, when the reaction temperature is 140°C, the impurity peak on the H NMR spectrum of the epoxidation product is the smallest, which is the optimal reaction temperature.

[0045] Therefore, through many experimental explorations, it was found that when the ratio of polyol to raw material is 1:10 and the reaction temperature is 140°C, the yield and quality of epoxy monomer are optimal, achieving full and high-quality utilization of waste epoxy thermosetting plastic degradation products and effectively solving the problem of resource waste.

[0046] It should be noted that all raw materials used in the examples of the present invention were purchased from commercial sources, and the instruments used were conventional laboratory equipment.

[0047] Reagents used in the present invention:

[0048] Instruments used in the present invention:

[0049] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the present invention.

Claims

1. A method for epoxidation of anhydride-cured epoxy resin degradation products, characterized in that: The following steps are involved: Step 1: Degrading the epoxy resin with a degradation solution to obtain a degradation mixture, and separating the degradation mixture to obtain a polyol; Step 2: mixing polyol and epichlorohydrin, then adding tetrabutylammonium bromide, and heating to obtain a reactant solution; Step 3: Cool the above reactant solution to room temperature, add NaOH solution, and stir to react at low temperature to obtain epoxy monomer and mixture solution; Step 4: adding ethyl acetate to extract the obtained mixture solution, and repeatedly washing the ethyl acetate phase with sodium chloride aqueous solution for several times; Step 5: Remove the ethyl acetate by evaporation to obtain the epoxy monomer.

2. The method according to claim 1, characterized in that The molar ratio of the polyol, epichlorohydrin and tetrabutylammonium bromide is 1:5 to 15:0.

2.

3. The method according to claim 1, characterized in that The temperature of the heating reaction in step 2 is 120-160° C., and the reaction time is 6-10 hours.

4. The method according to claim 1, characterized in that: The mass fraction of NaOH solution is 50wt%.

5. The method according to claim 4, characterized in that The reaction temperature in step 3 is 0-5°C, and the reaction time is 2-4h.

6. The method according to claim 1, characterized in that The mass fraction of the sodium chloride solution is 5-10wt%.

7. The method according to claim 1, characterized in that The degradation liquid is prepared by mixing ethylene glycol and sodium hydroxide in a mass ratio of 15 to 30:

1.

8. The method according to claim 7, characterized in that The epoxy resin in step 1 is degraded in a sealed container at a degradation temperature of 150°C.

9. The method according to claim 1, characterized in that: The polyol is obtained by separating the degradation mixture through extraction.

10. The method according to claim 1, characterized in that The epoxy resin is prepared with bisphenol A epoxy resin as a matrix, methyltetrahydrophthalic anhydride as a curing agent and 2,4,6-tris(dimethylaminomethyl)phenol as a catalyst.

Images