Degradable epoxy resin and preparation method thereof

Abstract

The invention belongs to the technical field of resin, and particularly relates to degradable epoxy resin, degradable thermosetting resin and a preparation method and application of the degradable epoxy resin and the degradable thermosetting resin. The degradable epoxy resin provided by the invention has a structure as shown in a formula 1: # imgabs0 #. By introducing disulfide bonds and Schiff base, the epoxy resin is endowed with degradability. The degradable epoxy resin provided by the invention can be completely degraded at room temperature (20-35 DEG C), normal pressure (0.1 MPa) and acid solution (0.4-0.6 mol / L of tetrahydrofuran solution of hydrochloric acid).

Description

Technical Field

[0001] The invention belongs to the technical field of resins, and in particular relates to a degradable epoxy resin, a degradable thermosetting resin, and a preparation method and application thereof. Background Art

[0002] Epoxy resin is an epoxy oligomer containing two or more epoxy groups, which forms a three-dimensional network of thermosetting plastics through the reaction of epoxy groups and curing agents. Epoxy resin has excellent adhesion, corrosion resistance, mechanical properties, thermal stability and formability. Due to these advantages, it can be used as a coating, adhesive and molding material, and has been widely used in the fields of electrical, electronic, optical machinery, engineering technology, civil engineering and construction, and cultural and sports goods manufacturing.

[0003] Since traditional thermosetting epoxy resins form a highly cross-linked three-dimensional network structure through irreversible covalent cross-linking, epoxy resins are difficult to degrade and cannot be reprocessed, resulting in waste of resources and environmental pollution. Summary of the invention

[0004] In view of this, the present invention provides a degradable epoxy resin, a degradable thermosetting resin, and a preparation method and application thereof. The epoxy resin and thermosetting resin provided by the present invention have good degradability and can be reused, thereby realizing resource utilization.

[0005] In order to solve the above technical problems, the present invention provides a degradable epoxy resin having a structure as shown in Formula 1:

[0006]

[0007] The present invention also provides a method for preparing the degradable epoxy resin described in the above technical solution, comprising the following steps:

[0008] Dissolving vanillin and 4,4-diaminodiphenyl disulfide in an organic solvent for an aldehyde-amine condensation reaction to obtain an intermediate having a structure shown in Formula 2;

[0009] The intermediate, epichlorohydrin and the catalyst are first mixed for addition reaction and then mixed with sodium hydroxide aqueous solution for ring closing reaction to obtain the degradable epoxy resin;

[0010]

[0011] Preferably, the molar ratio of 4,4-diaminodiphenyl disulfide to vanillin is 1:1 to 3;

[0012] The organic solvent includes anhydrous ethanol;

[0013] The temperature of the aldehyde-amine condensation reaction is 0 to 100° C., and the time is 3 to 24 hours.

[0014] Preferably, the catalyst comprises tetrabutylammonium bromide;

[0015] The mass of the intermediate and the volume ratio of epichlorohydrin are 15-17 g:33-37 mL;

[0016] The temperature of the addition reaction is 30-100° C., and the time is 2-6 hours.

[0017] Preferably, the mass concentration of the sodium hydroxide aqueous solution is 18-22%;

[0018] The molar ratio of sodium hydroxide to the intermediate in the sodium hydroxide aqueous solution is 1.8 to 2.2:1;

[0019] The temperature of the ring-closing reaction is 30-60° C., and the time is 2-6 hours.

[0020] The invention also provides a degradable thermosetting resin, which is obtained by mixing a degradable epoxy resin and a curing agent and then curing the mixture.

[0021] Preferably, the curing agent is methylhexahydrophthalic anhydride.

[0022] Preferably, the mass ratio of the degradable epoxy resin to the curing agent is 1 to 3:1.

[0023] Preferably, the curing comprises low temperature curing, medium temperature curing and high temperature curing performed sequentially;

[0024] The temperature of the low temperature curing is 88-92°C, and the insulation time of the low temperature curing is 1.8-2.2h;

[0025] The medium temperature curing temperature is 115-125°C, and the medium temperature curing holding time is 1.5-2.5h;

[0026] The temperature of the high temperature curing is 145-155° C., and the heat preservation time of the high temperature curing is 1.5-2.5 hours.

[0027] The present invention also provides the use of the degradable epoxy resin described in the above technical solution or the degradable thermosetting resin described in the above technical solution in the recycling of carbon fiber composite materials or electronic chips.

[0028] The present invention provides a degradable epoxy resin having a structure as shown in Formula 1: The invention endows the epoxy resin with degradable properties by introducing disulfide bonds and Schiff bases; the epoxy resin containing the Schiff base structure undergoes an imine hydrolysis reaction, an amine-imine exchange reaction and an imine metathesis-decomposition reaction under acidic conditions, thereby endowing the epoxy resin with reprocessability and degradability; under the conditions of heating, ultraviolet irradiation or a catalyst, the disulfide bonds can undergo a thiol-disulfide bond exchange reaction or a disulfide bond metathesis reaction, and the disulfide bonds can also be broken by a reduction reaction; the degradable epoxy resin provided by the invention is endowed with degradable properties due to the introduction of disulfide bonds, and the disulfide bonds undergo a disulfide bond exchange reaction at high temperatures, so that the degradable epoxy resin has self-repairing and shape memory functions; the broken fragments can be reshaped under hot pressing, thereby realizing the recycling and reuse of the resin. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The infrared spectra of vanillin, 4,4-diaminodiphenyl disulfide, intermediate and degradable epoxy resin in Example 1;

[0030] Figure 2 This is the H NMR spectrum of the intermediate in Example 1;

[0031] Figure 3 is the H NMR spectrum of the degradable epoxy resin in Example 1;

[0032] Figure 4 This is a columnar comparison chart of the mechanical properties of the cured resins prepared in Example 1 and Comparative Example 1;

[0033] Figure 5 This is a comparison diagram of the degradable thermosetting resin prepared in Example 1 before and after being immersed in a tetrahydrofuran solution of hydrochloric acid. DETAILED DESCRIPTION

[0034] The present invention provides a degradable epoxy resin having a structure as shown in Formula 1:

[0035]

[0036] The degradable epoxy resin provided by the present invention contains Schiff base and disulfide bond double dynamic covalent bonds, so that it has degradable properties. The degradable epoxy resin provided by the present invention can be completely degraded at room temperature (20-35°C), normal pressure (0.1MPa), and acidic solution (0.4-0.6mol / L hydrochloric acid tetrahydrofuran solution).

[0037] The present invention also provides a method for preparing the degradable epoxy resin described in the above technical solution, comprising the following steps:

[0038] Dissolving vanillin and 4,4-diaminodiphenyl disulfide in an organic solvent for an aldehyde-amine condensation reaction to obtain an intermediate having a structure shown in Formula 2;

[0039] The intermediate, epichlorohydrin and the catalyst are first mixed for addition reaction and then mixed with sodium hydroxide aqueous solution for ring closing reaction to obtain the degradable epoxy resin;

[0040]

[0041] The present invention dissolves vanillin and 4,4-diaminodiphenyl disulfide in an organic solvent to carry out an aldehyde-amine condensation reaction to obtain an intermediate. As a specific embodiment of the present invention, the organic solvent includes anhydrous ethanol; the molar ratio of the 4,4-diaminodiphenyl disulfide to vanillin can be 1:1-3, or 1:1.5-2. The present invention has no special limitation on the amount of the organic solvent as long as the reaction materials can be completely dissolved.

[0042] As a specific embodiment of the present invention, the temperature of the aldehyde-amine condensation reaction can be 0-100°C, or 75-80°C; the time of the aldehyde-amine condensation reaction can be 3-24h, or 5-20h, or further 10-12h. As a specific embodiment of the present invention, the aldehyde-amine condensation reaction can be accompanied by stirring, and the present invention has no special requirements on the stirring speed, as long as the reaction can be completed.

[0043] As a specific embodiment of the present invention, the aldehyde-amine condensation reaction may further include: adding the system after the aldehyde-amine condensation reaction to water to precipitate solids, and then separating the solids and liquids, and washing and drying the solids obtained by the solid-liquid separation in sequence to obtain the intermediate. As a specific embodiment of the present invention, the water may be deionized water; the present invention has no special restrictions on the rate of the dripping as long as it can be added dropwise; the temperature of the water may be 20-25°C. As a specific embodiment of the present invention, the solid-liquid separation may be suction filtration; the washing may be water washing, the water used for the water washing may be deionized water, and the temperature of the water used for the water washing may be 20-25°C. As a specific embodiment of the present invention, the drying temperature may be 55-65°C, and may also be 60°C; the drying time may be 10-14h, and may also be 12-13h. In the present invention, the intermediate is orange-yellow.

[0044] After obtaining the intermediate, the present invention first mixes the intermediate, epichlorohydrin and the catalyst for addition reaction, and then mixes with sodium hydroxide aqueous solution for ring closure reaction to obtain the degradable epoxy resin. As a specific embodiment of the present invention, the catalyst may include tetrabutylammonium bromide, and the molar ratio of the catalyst to the intermediate may be 0.8 to 1.2:1, and may be specifically 1:1; the mass ratio of the intermediate to the volume ratio of epichlorohydrin may be 15 to 17 g:33 to 37 mL, and may be specifically 16.81 g:35 mL.

[0045] The present invention has no special limitation on the first mixing, as long as it can be mixed evenly. As a specific embodiment of the present invention, the temperature of the addition reaction can be 30-100°C, or 50-90°C, or 80-85°C; the time of the addition reaction can be 2-6h, or 3-5h. As a specific embodiment of the present invention, the addition reaction can be accompanied by stirring, and the present invention has no special requirements on the stirring speed, as long as the reaction can be completed.

[0046] In the present invention, the product obtained by the addition reaction is

[0047]

[0048] In order to simplify the preparation steps, the present invention can directly cool the system after the addition reaction to the temperature required for the closed-loop reaction. As a specific embodiment of the present invention, the mass concentration of the sodium hydroxide aqueous solution can be 18-22%, specifically 20%; the molar ratio of the sodium hydroxide to the intermediate can be 1.8-2.2:1, specifically 2:1. The present invention can drop the sodium hydroxide aqueous solution into the system after the addition reaction. The present invention has no special requirements for the rate of the drop addition as long as it can be completed in 0.5-2h.

[0049] The present invention has no special limitation on the second mixing, as long as it can be mixed evenly. As a specific embodiment of the present invention, the temperature of the ring-closing reaction can be 30-60°C, or 40-50°C; the time of the ring-closing reaction can be 2-6h, or 3-5h. As a specific embodiment of the present invention, the ring-closing reaction can be accompanied by stirring, and the present invention has no special requirements on the stirring speed, as long as the reaction can be completed.

[0050] In the present invention, the ring-closure reaction may further include:

[0051] Cooling the system after the ring-closing reaction to room temperature, separating the solid from the liquid, and taking the liquid phase;

[0052] The liquid phase and dichloromethane are mixed and then washed with water to obtain an organic phase;

[0053] The organic phase and anhydrous magnesium sulfate are mixed, dehydrated, and then filtered. The filtrate obtained by filtration is rotary evaporated to obtain the degradable epoxy resin.

[0054] As a specific implementation of the present invention, the room temperature may be 20-35° C., or 25-30° C.; the solid-liquid separation may be suction filtration.

[0055] As a specific embodiment of the present invention, the volume ratio of the dichloromethane to the liquid phase is 1.8-2.2:1, specifically 2:1; the water can be deionized water, and the volume ratio of the water used for washing to the liquid phase is 3.8-4.2:1, specifically 4:1. As a specific embodiment of the present invention, the number of times of washing can be 5-7 times.

[0056] The present invention has no special limitation on the amount of magnesium sulfate used in the sewage, as long as the water in the organic phase can be removed. The present invention has no special limitation on the filtration, and a conventional method in the art can be adopted. The present invention can remove dichloromethane and unreacted epichlorohydrin in the organic phase through the rotary evaporation.

[0057] The present invention also provides a degradable thermosetting resin, which is obtained by curing a mixture of a degradable epoxy resin and a curing agent. As a specific embodiment of the present invention, a degassing treatment can be performed before curing, and the degassing treatment can be performed by placing the mixture in a vacuum oven.

[0058] As a specific embodiment of the present invention, the curing agent may be methylhexahydrophthalic anhydride; the mass ratio of the degradable epoxy resin to the curing agent may be 1 to 3:1, or may be 1.5 to 2.5:1.

[0059] As a specific embodiment of the present invention, the curing can be carried out in a mold; the curing may include low-temperature curing, medium-temperature curing and high-temperature curing carried out in sequence; the temperature of the low-temperature curing may be 88-92°C, specifically 90°C; the insulation time of the low-temperature curing may be 1.8-2.2h, specifically 2h; the temperature of the medium-temperature curing may be 115-125°C, specifically 120°C; the insulation time of the medium-temperature curing may be 1.5-2.5h, specifically 2h; the temperature of the high-temperature curing may be 145-155°C, specifically 150°C; the insulation time of the high-temperature curing may be 1.5-2.5h, specifically 2h.

[0060] The degradable thermosetting resin provided by the invention has not only good mechanical properties but also degradability.

[0061] The present invention also provides the use of the degradable epoxy resin described in the above technical solution or the degradable thermosetting resin described in the above technical solution in the recycling of carbon fiber composite materials or electronic chips.

[0062] In order to further illustrate the present invention, the technical solutions provided by the present invention are described in detail below in conjunction with embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0063] Example 1

[0064] 11.41 g (0.075 mol) of vanillin and 9.314 g (0.043 mol) of 4,4-diaminodiphenyl disulfide were dissolved in 150 mL of anhydrous ethanol and subjected to an aldehyde-amine condensation reaction at 75°C in an oil bath with magnetic stirring for 12 h; the system after the aldehyde-amine condensation reaction was added dropwise to 25°C deionized water, and a yellow solid precipitated. After filtration, the solid was washed twice with 25°C deionized water and dried in an oven at 60°C for 12 h to obtain an orange-yellow intermediate;

[0065] 16.81 g of the intermediate and 1.096 g of tetrabutylammonium bromide were dissolved in 35 mL of epichlorohydrin, stirred at 80° C. for addition for 5 h, then cooled to 60° C., 3.56 g of a 20% sodium hydroxide aqueous solution was added dropwise to the cooled system within 1 h, and a closed-loop reaction was carried out at 60° C. for 3 h; the system after the reaction was cooled to 30° C., and then filtered to remove the white solid, and dichloromethane (the volume ratio of dichloromethane to the filtrate was 2:1) was added to the filtrate obtained by filtration, and then deionized water was added for washing 6 times (the total volume of the washing water was 4 times the volume of the filtrate), and the organic phase was taken; anhydrous magnesium sulfate powder was added to the organic phase, and the anhydrous magnesium sulfate was removed by filtration after standing for 24 h, and the filtrate obtained by filtration was rotary evaporated to obtain a degradable epoxy resin;

[0066] The degradable epoxy resin and methylhexahydrophthalic anhydride (MeH-HPA) are evenly mixed in a mass ratio of 5:3, the mixture is degassed in a vacuum oven and poured into a mold for curing, and the mixture is demolded after cooling to 30°C to obtain a degradable thermosetting epoxy resin; the curing conditions are: keeping warm at 90°C for 2h, then keeping warm at 120°C for 2h, and finally keeping warm at 150°C for 2h.

[0067] Example 2

[0068] The degradable epoxy resin was prepared according to the method of Example 1, except that the temperature of the aldehyde-amine condensation reaction was 80°C and the time was 10 h; the temperature of the addition reaction was 85°C and the time was 4 h; and the temperature of the ring-closing reaction was 50°C and the time was 2 h.

[0069] Comparative Example 1

[0070] E51 epoxy resin and methylhexahydrophthalic anhydride (MeH-HPA) were fully mixed in a mass ratio of 25:22, the mixture was degassed in a vacuum oven and poured into a mold for curing, and the mixture was demolded after cooling to 30°C. The cured epoxy resin was recorded as E51 / MeH-HPA; the curing conditions were: keeping warm at 90°C for 2h, then keeping warm at 120°C for 2h, and finally keeping warm at 150°C for 2h.

[0071] Infrared detection was performed on the vanillin, 4,4-diaminodiphenyl disulfide, intermediate and degradable epoxy resin in Example 1 to obtain an infrared spectrum, such as Figure 1 shown. Figure 1 In the infrared spectrum of degradable epoxy resin, at 530cm -1 and 1668cm -1 The infrared absorption peak is attributed to the characteristic absorption of disulfide bonds and Schiff bases, indicating that disulfide bonds and Schiff bases are introduced into the degradable epoxy resin.

[0072] The intermediate in Example 1 was subjected to H NMR spectrum detection to obtain a H NMR spectrum. Figure 2 As shown. Figure 2 It can be seen that the intermediate has the structure shown in Formula 2.

[0073] The degradable epoxy resin in Example 1 was subjected to nuclear magnetic resonance hydrogen spectrum detection to obtain a nuclear magnetic resonance hydrogen spectrum. Figure 3 As shown. Figure 3 It can be seen that the degradable epoxy resin has a structure shown in Formula 1.

[0074] The mechanical properties of the cured resins prepared in Examples 1 to 2 and Comparative Example 1 were measured according to GB / T 1040.2-2006 and GB / T9341-2008. The results are listed in Table 1.

[0075] Table 1 Mechanical properties of cured resins prepared in Examples 1 to 2 and Comparative Example 1

[0076]

[0077] A bar chart is drawn based on the test results of Example 1 and Comparative Example 1 in Table 1, as shown in FIG. Figure 4 Combining Table 1 and Figure 4 It can be seen that the cured resin provided by the present invention has good mechanical properties.

[0078] The cured resin (degradable thermosetting resin) prepared in Example 1 was cut into strips with a size of 0.5 mm in length and 0.5 mm in width. The strips were then immersed in a 0.5 mol / L hydrochloric acid tetrahydrofuran solution at 25° C. for 2 h. The strips were completely dissolved. The comparison diagram before and after immersion is shown in FIG. Figure 5As shown, the left side is the actual picture before immersion, and the right side is the actual picture after immersion. Figure 5 It can be seen that the degradable thermosetting resin can be completely degraded in an acidic solution.

[0079] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A degradable epoxy resin, characterized in that: It has the structure shown in Formula 1:

2. The method for preparing the degradable epoxy resin according to claim 1, characterized in that: The following steps are involved: Dissolving vanillin and 4,4-diaminodiphenyl disulfide in an organic solvent for an aldehyde-amine condensation reaction to obtain an intermediate having a structure shown in Formula 2; The intermediate, epichlorohydrin and the catalyst are first mixed for addition reaction and then mixed with sodium hydroxide aqueous solution for ring closing reaction to obtain the degradable epoxy resin; 3. The preparation method according to claim 2, characterized in that: The molar ratio of 4,4-diaminodiphenyl disulfide to vanillin is 1:1-3; The organic solvent includes anhydrous ethanol; The temperature of the aldehyde-amine condensation reaction is 0-100° C., and the time is 3-24 hours.

4. The preparation method according to claim 2, characterized in that: The catalyst includes tetrabutylammonium bromide; The mass of the intermediate and the volume ratio of epichlorohydrin are 15-17 g:33-37 mL; The temperature of the addition reaction is 30-100° C., and the time is 2-6 hours.

5. The preparation method according to claim 2, characterized in that: The mass concentration of the sodium hydroxide aqueous solution is 18-22%; The molar ratio of sodium hydroxide to the intermediate in the sodium hydroxide aqueous solution is 1.8 to 2.2:1; The temperature of the ring-closing reaction is 30-60° C., and the time is 2-6 hours.

6. A degradable thermosetting resin, characterized in that: The degradable epoxy resin is mixed with a curing agent and then cured.

7. The degradable thermosetting resin according to claim 6, characterized in that: The curing agent is methylhexahydrophthalic anhydride.

8. The degradable thermosetting resin according to claim 6 or 7, characterized in that: The mass ratio of the degradable epoxy resin to the curing agent is 1 to 3:

1.

9. The degradable thermosetting resin according to claim 8, characterized in that: The curing includes low temperature curing, medium temperature curing and high temperature curing performed sequentially; The temperature of the low temperature curing is 88-92°C, and the insulation time of the low temperature curing is 1.8-2.2h; The medium temperature curing temperature is 115-125°C, and the medium temperature curing holding time is 1.5-2.5h; The temperature of the high temperature curing is 145-155° C., and the heat preservation time of the high temperature curing is 1.5-2.5 hours.

10. Use of the degradable epoxy resin according to claim 1 or the degradable thermosetting resin according to any one of claims 6 to 9 in the recycling of carbon fiber composite materials or electronic chips.

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