Curing, chemical degradation and physical remodeling method of o-vanillin-based epoxy resin

Abstract

The invention relates to a curing, chemical degradation and physical remodeling method of o-vanillin-based epoxy resin. An o-vanillin-based epoxy monomer containing a Schiff base bond is used as a raw material and is subjected to cross-linking curing with an amine curing agent to obtain the high-performance degradable bio-based epoxy resin. Compared with the traditional commercial bisphenol A epoxy resin, the curing system has the advantages of low curing temperature and short curing time, the energy consumption can be effectively reduced, and the prepared epoxy resin has the degradation characteristic of reversible dynamic bonds and can be physically recycled in a hot pressing manner.

Description

Technical Field

[0001] The invention relates to the field of bio-based epoxy resins, and in particular to a method for curing, chemical degradation and physical remodeling of an o-vanillin-based epoxy resin. Background Art

[0002] With the increasing attention to sustainability and environmental responsibility, the recycling or reuse of epoxy resins after their effective service life has become a very important and necessary topic. The traditional epoxy resin matrix is ​​mainly composed of petroleum-based bisphenol A diglycidyl ether (DGEBA), which is produced by the reaction of epichlorohydrin and bisphenol A. Due to the introduction of anhydride, amine and carboxylic acid curing agents, the strong three-dimensional network structure formed by the cross-linking curing reaction of epoxy resin has an insoluble nature and cannot be processed again after molding. Therefore, waste, aging and damaged epoxy resins are difficult to recycle and reuse, resulting in waste of resources and solid waste pollution.

[0003] In view of the problems of traditional epoxy resins such as being harmful to the environment, non-degradable and difficult to recycle, biomass materials that can be extracted from nature are often used to replace traditional bisphenol A, which is then cured after reaction with epichlorohydrin to obtain a new type of bio-based epoxy resin. At the same time, by introducing a certain number of degradable covalent bonds such as acetal bonds, disulfide bonds and Schiff base bonds into the covalent cross-linking network, epoxy resins that can be degraded into small molecular monomers or oligomers under mild conditions can be prepared. Summary of the invention

[0004] In view of the above problems existing in the prior art, the present invention provides a method for curing, chemical degradation and physical remodeling of o-vanillin-based epoxy resin. The obtained bio-based epoxy resin can be degraded and remodeled, achieving green recycling and reducing pollution and damage to the environment.

[0005] In order to achieve the above object, the present invention adopts the following technical scheme: a method for curing, chemical degradation and physical remodeling of o-vanillin-based epoxy resin, comprising the following steps:

[0006] S1: Mix the o-vanillin epoxy monomer and the amine curing agent, and stir at 60°C-100°C for 10min-60min until the amine curing agent and the vanillin epoxy monomer are fully mixed, wherein the molar ratio of the epoxy group in the o-vanillin epoxy monomer to the amino group in the amine curing agent is 1:(1-2).

[0007] S2: The mixture is transferred to a mold sprayed with a release agent and preheated, and vacuumed in a vacuum drying oven at 40°C-70°C for 1h-2h to remove excess bubbles, and then cured and heated at 70°C-180°C for 3h-9h to finally obtain a cured o-vanillin-based epoxy resin.

[0008] S3: Take the cured o-vanillin-based epoxy resin, soak it in 10ml-50ml hydrochloric acid solution at 25℃-35℃ for 12-24h, and then place it in a degradation solution to carry out degradation reaction at a temperature of 25℃-100℃ for 6h-24h, wherein the mass ratio of o-vanillin-based epoxy resin to hydrochloric acid solution is 1:(5-15), and the concentration of hydrochloric acid solution is 0.1-1mol / L.

[0009] S4: Take the cured o-vanillin-based epoxy resin, grind it into powder, dry it for 12h-24h, and then heat and pressurize it in a hot press for reshaping at a temperature of 100℃-180℃, a pressure of 1MPa-10MPa, and a time of 0.5h-3h.

[0010] Furthermore, the chemical structure of the o-vanillin epoxy monomer is:

[0011]

[0012] Furthermore, the amine curing agent in step S1 is 4,4'-diaminodiphenylmethane (DDM), 4,4'-diaminodiphenyl sulfone (DDS), diethylenetriamine (DETA) or triethylenetetramine (TETA).

[0013] Furthermore, the curing in step S2 is divided into three stages, and the curing temperature and time of each curing stage are respectively: 70-100°C, 1-3h; 110-140°C, 1-3h; 150-180°C, 1-3h.

[0014] Furthermore, the degradation liquid in step S3 is obtained by mixing methanol, ethanol, dimethyl sulfoxide or dimethyl sulfoxide with deionized water in a molar ratio of 4:6.

[0015] Compared with the prior art, the present invention has at least the following advantages:

[0016] (1) The present invention uses an o-vanillin-based epoxy monomer containing a Schiff base bond, whose internal reversible dynamic chemical bonds make the epoxy resin have higher reactivity during the re-curing process.

[0017] (2) The o-vanillin-based epoxy resin prepared by the present invention can be completely degraded in an acidic degradation solution, and has better degradation performance under high temperature environment.

[0018] (3) Compared with traditional commercial bisphenol A epoxy resin, the curing system has higher curing reaction activity, low curing temperature and short curing time, which can effectively reduce energy consumption. In addition, the prepared epoxy resin has a Schiff base chemical bond. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1This is the infrared spectrum of Example 1 before and after curing.

[0020] Figure 2a and Figure 2b They are infrared spectra of Example 1 before and after hot pressing.

[0021] Figure 3 This is a comparison chart of the degradation of Example 2 in organic solutions at different temperatures.

[0022] Figure 4 is the degradation rate of Example 2 in different solutions.

[0023] Figure 5 The thermogravimetric analysis spectra of Example 3 and Comparative Example 1 are shown. DETAILED DESCRIPTION

[0024] In order to further clearly and completely describe the implementation scheme of the present invention, the present invention is described in detail below in conjunction with the accompanying drawings and examples. These examples are purely illustrative and are only used to specifically describe the present invention rather than to limit the present invention.

[0025] Example 1 A method for curing, chemical degradation and physical remodeling of an o-vanillin-based epoxy resin comprises the following steps:

[0026] (1) 4.1125 g (0.01 mol) of o-vanillin epoxy monomer and 0.9913 g (0.005 mol) of 4,4'-diaminodiphenylmethane (DDM) were mixed and stirred at 60° C. for 10 min until the curing agent and the o-vanillin epoxy monomer were fully mixed.

[0027] (2) The mixture was transferred into a mold sprayed with a release agent and preheated, and vacuumed in a vacuum drying oven at 70° C. for 1 h to remove excess bubbles, and then cured at 70° C., 110° C., and 150° C. for 2 h, respectively, to finally obtain a cured o-vanillin-based epoxy resin.

[0028] (3) The cured o-vanillin-based epoxy resin was soaked in 10 ml of 0.1 M hydrochloric acid solution at 25° C. for 12 h, and then placed in methanol, ethanol and DMF solutions for degradation reaction at 60° C. for 12 h.

[0029] (4) The cured o-vanillin-based epoxy resin was ground into powder, dried for 12 h, and then heated and pressurized in a hot press at a temperature of 100° C. and a pressure of 1 MPa for 3 h.

[0030] The infrared spectrum of the o-vanillin based epoxy resin prepared in this embodiment is as follows: Figure 1Compared with the o-vanillin epoxy monomer, the characteristic peak of the epoxy group of the epoxy resin disappears after curing, indicating that the epoxy group is completely consumed at the end of the curing process. The infrared spectrum of the epoxy resin after hot pressing in step (4) is shown in Figure 2b As shown, it can be seen that the characteristic peaks before and after reprocessing are basically the same, especially the characteristic peak of C=N at 1632cm-1 and the ortho-substitution of the benzene ring at 1510cm-1, indicating that the chemical structure of the epoxy resin cross-linking network after reprocessing has no significant change, which also shows that the o-vanillin epoxy resin of the present invention has physical remodeling properties.

[0031] Example 2 A method for curing, chemical degradation and physical remodeling of an o-vanillin-based epoxy resin comprises the following steps:

[0032] (1) 8.225 g (0.02 mol) of o-vanillin epoxy monomer and 3.972 g (0.016 mol) of diaminodiphenyl sulfone (DDS) were mixed and stirred at 80° C. for 30 min until the curing agent and the o-vanillin epoxy monomer were fully mixed.

[0033] (2) The mixture was transferred to a mold sprayed with a release agent and preheated, and vacuumed in a vacuum drying oven at 60° C. for 1.5 h to remove excess bubbles, and then cured at 80° C., 130° C., and 160° C. for 1.5 h, respectively, to finally obtain a cured o-vanillin-based epoxy resin.

[0034] (3) The cured o-vanillin-based epoxy resin was soaked in 20 ml of 0.1 M hydrochloric acid solution at 30° C. for 24 h, and then placed in methanol, ethanol and DMF solutions for degradation reaction at 25° C. and 65° C. for 6 h.

[0035] (4) The cured o-vanillin-based epoxy resin was ground into powder, dried for 18 h, and then heated and pressurized in a hot press at a temperature of 150° C. and a pressure of 5 MPa for 1 h.

[0036] The degradation test results of the o-vanillin epoxy resin prepared in this example are as follows: Figure 3 and Figure 4 It can be seen that at room temperature, the epoxy resin only swells in the four degradation solutions, and at 65°C, it degrades in the four solutions, among which the degradation rate in the DMF solution is the highest.

[0037] Example 3 A method for curing, chemical degradation and physical remodeling of an o-vanillin-based epoxy resin comprises the following steps:

[0038] (1) 6.169 g (0.015 mol) of o-vanillin epoxy monomer and 5.948 g (0.015 mol) of 4,4'-diaminodiphenylmethane (DDM) were mixed and stirred at 90° C. for 10 min until the curing agent and the o-vanillin epoxy monomer were fully mixed.

[0039] (2) The mixture was transferred into a mold sprayed with a release agent and preheated, and vacuumed in a vacuum drying oven at 40° C. for 2 h to remove excess bubbles, and then cured at 90° C., 150° C., and 180° C. for 1 h, respectively, to finally obtain a cured o-vanillin-based epoxy resin.

[0040] (3) The cured o-vanillin-based epoxy resin was soaked in 10 ml of 0.2 M hydrochloric acid solution at 35° C. for 24 h, and then placed in methanol, ethanol and DMF solutions for degradation reaction at 80° C. for 24 h.

[0041] (4) The cured o-vanillin-based epoxy resin was ground into powder, dried for 24 hours, and then heated and pressurized in a hot press at a temperature of 180° C. and a pressure of 3 MPa for 1.5 hours.

[0042] The o-vanillin epoxy prepared in this example was heated from 40°C to 800°C at a heating rate of 10°C / min in a nitrogen atmosphere, and its initial decomposition temperature and the residual carbon content at 800°C were tested. The test results are as follows: Figure 4 The initial decomposition temperature is 210.27℃ and the residual carbon content is 29.61%.

[0043] Example 4 A method for curing, chemical degradation and physical remodeling of an o-vanillin-based epoxy resin comprises the following steps:

[0044] (1) 4.1125 g (0.01 mol) of o-vanillin epoxy monomer and 0.413 g (0.005 mol) of diethylenetriamine (DETA) were mixed and stirred at 60° C. for 60 min until the curing agent and the o-vanillin epoxy monomer were fully mixed.

[0045] (2) The mixture was transferred to a mold sprayed with a release agent and preheated, and vacuumed in a vacuum drying oven at 50° C. for 1 h to remove excess bubbles, and then cured at 90° C., 130° C., and 150° C. for 1.5 h, respectively, to finally obtain a cured o-vanillin-based epoxy resin.

[0046] (3) The cured o-vanillin-based epoxy resin was soaked in 25 ml of 0.2 M hydrochloric acid solution at 30° C. for 16 h, and then placed in methanol, ethanol, DMF and DMSO solutions for degradation reaction at 80° C. for 12 h.

[0047] (4) The cured o-vanillin-based epoxy resin was ground into powder, dried for 24 hours, and then heated and pressurized in a hot press at a temperature of 120° C. and a pressure of 2 MPa for 1 hour.

[0048] The present invention provides a method for curing, chemical degradation and physical remodeling of o-vanillin-based epoxy resin. There are many methods and ways to implement the technical solution. The above is only a preferred embodiment of the present invention, and does not limit the present invention in any form. Although the present invention has been disclosed as above with a preferred embodiment, it is not used to limit the present invention. Any technical personnel in this field can make some changes or modify the technical content disclosed above to an equivalent embodiment of equivalent changes without departing from the scope of the technical solution of the present invention. However, any brief introduction modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still belongs to the scope of the technical solution of the present invention.

Claims

1. A method for curing, chemical degradation and physical remodeling of an o-vanillin-based epoxy resin, comprising the following steps: S1: mixing the o-vanillin epoxy monomer and the amine curing agent, stirring at 60° C.-100° C. for 10 min-60 min until the amine curing agent and the vanillin epoxy monomer are fully mixed, wherein the molar ratio of the epoxy group in the o-vanillin epoxy monomer to the amino group in the amine curing agent is 1:(1-2); S2: The mixture is transferred into a mold sprayed with a release agent and preheated, and vacuumed in a vacuum drying oven at 40°C-70°C for 1h-2h to remove excess bubbles, and then cured and heated at 70°C-180°C for 3h-9h to finally obtain a cured o-vanillin-based epoxy resin; S3: Take the cured o-vanillin epoxy resin, soak it in 10ml-50ml hydrochloric acid solution at 25℃-35℃ for 12-24h, and then place it in a degradation solution to carry out degradation reaction at a temperature of 25℃-100℃ for 6h-24h, wherein the mass ratio of the o-vanillin epoxy resin to the hydrochloric acid solution is 1:(5-15), and the concentration of the hydrochloric acid solution is 0.1-1mol / L; S4: Take the cured o-vanillin-based epoxy resin, grind it into powder, dry it for 12h-24h, and then heat and pressurize it in a hot press for reshaping at a temperature of 100℃-180℃, a pressure of 1MPa-10MPa, and a time of 0.5h-3h.

2. A curing method for o-vanillin based epoxy resin according to claim 1, characterized in that: The chemical structure of the o-vanillin epoxy monomer is:

3. A method for curing an o-vanillin based epoxy resin according to claim 1, characterized in that: The amine curing agent in step S1 is 4,4'-diaminodiphenylmethane (DDM), 4,4'-diaminodiphenyl sulfone (DDS), diethylenetriamine (DETA) or triethylenetetramine (TETA).

4. A method for curing o-vanillin based epoxy resin according to claim 1, characterized in that: The curing in step S2 is divided into three stages, and the curing temperature and time of each curing stage are respectively: 70-100° C., 1-3 h; 110-140° C., 1-3 h; 150-180° C., 1-3 h.

5. The method for degrading o-vanillin based epoxy resin according to claim 1, characterized in that: The degradation solution in step S3 is obtained by mixing methanol, ethanol, dimethyl sulfoxide or dimethyl sulfoxide with deionized water in a molar ratio of 4:6.

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