A novel bio-based epoxy resin containing a dicarbonyl structure, preparation method and application thereof

Abstract

The invention discloses a novel bio-based epoxy resin containing a dicarbonyl structure, a preparation method and an application, and belongs to the field of material science and technology. 3-(4-hydroxy-3-methoxybenzoyl) propionic acid is synthesized by a simple Friedel-Crafts acylation reaction of a bio-based compound guaiacol and succinic anhydride, and then epoxidized to prepare an epoxy resin GSA-EP. The epoxy resin prepared by the preparation method of the invention has a good carbonization effect and a high flame retardant potential. At the same time, the raw materials are based on green and environmentally friendly biomass and have high biological safety.

Description

Technical Field

[0001] The invention belongs to the technical field of material science and relates to a novel bio-based epoxy resin containing a dicarbonyl structure based on guaiacol, a preparation method and an application thereof. Background Art

[0002] Epoxy resin is a widely used polymer. It plays an irreplaceable role in the coating, electronic and electrical appliances, and composite material manufacturing industries due to its excellent bonding, corrosion resistance, insulation, mechanical properties and other comprehensive properties. It is also the most widely used and produced thermosetting resin in the world. The most common epoxy resin is bisphenol A epoxy resin. Most of the raw materials for its preparation come from petroleum fuels. The preparation process is not only harmful to the environment, but its core raw material bisphenol A also has certain biological toxicity. At the same time, the prepared epoxy resin has poor charring ability, low quality of residual char after heating, and no intrinsic flame retardancy.

[0003] Therefore, using biomass resources as raw materials to synthesize bioactive epoxy resins as a substitute for epoxy resins originally synthesized from petroleum resources is more in line with the requirements of sustainable development. At present, research mainly focuses on epoxy resins based on biomass raw materials such as vegetable oils, cardanol, tannins and their derivatives, and guaiacol. Among them, guaiacol is simple, easy to obtain and inexpensive, and has the potential to replace petroleum-based bisphenol epoxy resins. According to Ying P, Nicastro HK. Evaluation of Estrogenic Activity of Novel Bisphenol A Alternatives, Four Bio-inspired Bisguaiacol F Specimens, by in vitro Assays. [J]. Journal of agricultural and food chemistry, 2018, 66 (44): 11775-11783. and Peng Y, Nicastro HK. Methoxy groups reduced the estrogenic activity of lignin-derivable replacements relative to bisphenol A and bisphenol F as studied through two in vitro assays [J]. Food Chemistry, 2021, 338127656-127656., the ortho-methoxy group in guaiacol can significantly reduce the biological toxicity of guaiacol-based bisphenol compounds, and it has higher biosafety when used to prepare epoxy resins.

[0004] However, there is still little research on guaiacol-based epoxy resins, which mainly focuses on combining guaiacol with vanillyl alcohol and vanillin to simply prepare epoxy resins through guaiacol. Most of the methods have reduced the thermal stability, charring ability and flame retardant properties of the system due to the presence of methoxy groups. Summary of the invention

[0005] In order to solve the above existing problems, the present invention provides a preparation method and application of a novel bio-based epoxy resin containing a dicarbonyl structure.

[0006] The technical solution of the present invention:

[0007] A novel bio-based epoxy resin containing a dicarbonyl structure has the following structure:

[0008]

[0009] A method for preparing a novel bio-based epoxy resin containing a dicarbonyl structure, comprising the following steps:

[0010] (1) 3-(4-hydroxy-3-methoxybenzoyl) propionic acid (GSA), benzyltriethylammonium chloride, and epichlorohydrin are mixed in a molar ratio of 1:1:30-80, and stirred continuously for reaction at 60-100°C under N2 atmosphere for 1-4 hours; 40wt.% NaOH solution (GSA:NaOH molar ratio = 1:2-3) is added to the system and the reaction is continued for 0.5-2 hours. Wash with saturated NaCl solution three times and dry to obtain a novel bio-based epoxy resin precursor GSA-EP containing a dicarbonyl structure;

[0011] (2) 50-400 parts of the novel bio-based epoxy resin precursor GSA-EP containing a dicarbonyl structure obtained in step (1) are uniformly mixed with 1 part of an accelerator for vacuum degassing, and then the resin is poured into a mold and thermoset to obtain a novel bio-based epoxy resin containing a dicarbonyl structure.

[0012] In step (2), a curing agent in any proportion may be added to participate in the thermosetting molding.

[0013] The accelerator is a tertiary amine or imidazole, and the curing agent is a polyamine or anhydride. Under the condition of 110-200°C, the accelerator is added to the novel bio-based epoxy resin precursor GSA-EP containing a dicarbonyl structure, and after uniform mixing and vacuum degassing, the resin is poured into a mold and kept at 60-100°C for 1-4 hours, then kept at 90-140°C for 1-4 hours, then kept at 140-190°C for 1-4 hours, and finally cured at 180-230°C for 1-4 hours.

[0014] The tertiary amine is 2,4,6-tris(dimethylaminomethyl)phenol, benzyldimethylamine, 4-dimethylaminopyridine, triethylamine, triethanolamine or o-hydroxybenzyldimethylamine.

[0015] The imidazole is imidazole, 2-methylimidazole, 1-benzyl-2-ethylimidazole, 1-aminoethyl-2-methylimidazole or 2-ethyl-4-methylimidazole.

[0016] The polyamine is isophoronediamine, metaphenylenediamine, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylsulfone, 3,3'-diethyl-4,4'-diaminodicyclohexylmethane, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, diethylaminopropylamine, ethylenediamine or metaphenylenediamine, which are uniformly mixed in a molar ratio of epoxy:NH=1:1.

[0017] The acid anhydride is phthalic anhydride, methyltetrahydrophthalic anhydride, succinic anhydride, maleic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, dodecenylsuccinic anhydride, pyromellitic anhydride, benzophenone tetracarboxylic anhydride, ethylene glycol ditrimellitic anhydride, methylcyclohexenyl tetracarboxylic anhydride or trimellitic anhydride.

[0018] Beneficial effects of the present invention: The present invention uses bio-based raw materials guaiacol and succinic anhydride as raw materials, and obtains a new bio-based epoxy resin GSA-EP containing dicarbonyl groups through a simple two-step reaction, which has a high degree of greenness and biosafety. At the same time, the dicarbonyl structure can participate in the cross-linking reaction during the curing process or increase the cross-linking density of the epoxy resin after curing through an ester exchange reaction, thereby significantly increasing the residual carbon rate. The residual carbon rate of the cured product at 700°C (N2 atmosphere) can reach 43.0%, and the theoretical limiting oxygen index can reach 34.7%, which are much higher than petroleum-based bisphenol A epoxy resin. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is the TGA curve of the epoxy resin prepared by self-curing (Example 1 and Comparative Example 1).

[0020] Figure 2 It is the TGA curve of epoxy resin prepared by adding curing agent (Example 2 and Comparative Example 2). DETAILED DESCRIPTION

[0021] The specific implementation of the present invention is further described below in conjunction with the accompanying drawings and technical solutions.

[0022] Example 1

[0023] (1) Synthesis of GSA-EP epoxy precursor containing dicarbonyl structure:

[0024] 3-(4-hydroxy-3-methoxybenzoyl) propionic acid GSA (5.00 g, 0.0223 mol), benzyltriethylammonium chloride (0.51 g, 0.00223 mol), epichlorohydrin (106.51 g, 1.1150 mol) were placed in a three-necked flask, stirred and reacted for 2 hours at 80°C under N2 atmosphere; 40% mass fraction NaOH solution (3.35 mL, 4.68 g) was added to the system and the reaction was continued for 2 hours. Washed three times with saturated NaCl solution and dried to obtain a new bio-based epoxy resin precursor GSA-EP containing a dicarbonyl structure, with a yield of 85.4%.

[0025] (2) GSA-EP curing:

[0026] 1 part of 4-dimethylaminopyridine (DMAP) was mixed with 200 parts of epoxy precursor GSA-EP, heated to 110°C for melting, and then vacuum degassed until no bubbles were generated. The mixture was poured into a mold, and the curing procedure was: 70°C for 1 hour, 110°C for 2 hours, 180°C for 2 hours, and 220°C for 1 hour. The self-curing bio-based epoxy resin was named GSA-EP / DMAP, and its properties were as follows: 5% thermal weight loss temperature (T d5％ ) is 314℃, the residual carbon rate at 700℃ (C y700 ) is 32.4%, and the maximum decomposition rate temperature (T max ) is 400℃, the maximum decomposition rate (R max ) is 0.93% / min, and the theoretical limiting oxygen index (LOI) is 30.5%.

[0027] Example 2

[0028] Different from Example 1, in (2), 4,4'-diaminodiphenylmethane (DDM) and epoxy precursor GSA-EP are additionally mixed in a molar ratio of epoxy: NH = 1:1, heated to 110°C for melting, and then vacuum degassed until no bubbles are generated, and poured into a mold. The curing procedure is: 70°C for 1 hour, 110°C for 2 hours, 180°C for 2 hours, and 220°C for 1 hour. The obtained cured bio-based epoxy resin is named GSA-EP / DDM, and its properties are as follows: 5% thermal weight loss temperature (T d5％ ) is 302℃, the residual carbon rate at 700℃ (C y700 ) is 43.0%, and the maximum decomposition rate (R max ) is 0.57% / min, and the theoretical limiting oxygen index (LOI) is 34.7%.

[0029] Example 3

[0030] Different from Example 1, in (2), 4,4'-diaminodiphenyl sulfone (DDS) and epoxy precursor GSA-EP were mixed in a molar ratio of epoxy: NH = 1: 1, heated to 200°C for melting, and then vacuum degassed until no bubbles were generated, and poured into a mold. The curing procedure was: 100°C for 1 hour, 140°C for 2 hours, 190°C for 2 hours, and 230°C for 2 hours. The properties of the cured bio-based epoxy resin were as follows: 5% thermal weight loss temperature (T d5％ ) is 334℃, the residual carbon rate at 700℃ (C y700 ) was 46.7%, and the maximum decomposition rate (R max ) is 0.52% / min, and the theoretical limiting oxygen index (LOI) is 36.2%.

[0031] Example 4

[0032] Different from Example 1, in (2), isophorone diamine (IPDA) and epoxy precursor GSA-EP are mixed uniformly in a molar ratio of epoxy: NH = 1: 1, heated to 110°C for melting, and then vacuum degassed until no bubbles are generated, and poured into a mold. The curing procedure is: 60°C for 1 hour, 110°C for 2 hours, 150°C for 2 hours, and 180°C for 2 hours. The properties of the cured bio-based epoxy resin are as follows: 5% thermal weight loss temperature (T d5％ ) is 312℃, the carbon residue rate at 700℃ (C y700 ) is 38.1%, and the maximum decomposition rate (R max ) is 0.52% / min, and the theoretical limiting oxygen index (LOI) is 32.7%.

[0033] Example 5

[0034] Different from Example 1, in (2), phthalic acid (PA) and epoxy precursor GSA-EP are additionally mixed in a molar ratio of epoxy: anhydride = 1:0.75, heated to 150°C for melting, and then vacuum degassed until no bubbles are generated, and poured into a mold. The curing procedure is: 80°C for 1 hour, 120°C for 2 hours, 170°C for 2 hours, and 210°C for 2 hours. The properties of the cured bio-based epoxy resin are as follows: 5% thermal weight loss temperature (T d5％ ) is 289℃, and the residual carbon rate at 700℃ (C y700 ) is 32.3%, and the maximum decomposition rate (R max ) is 0.56% / min, and the theoretical limiting oxygen index (LOI) is 30.4%.

[0035] Example 6

[0036] Different from Example 1, in (2), methyltetrahydrophthalic anhydride (MTHPA) and epoxy precursor GSA-EP are additionally mixed in a molar ratio of epoxy: anhydride = 1:0.75, heated to 110°C for melting, and then vacuum degassed until no bubbles are generated, and poured into a mold. The curing procedure is: 60°C for 1 hour, 100°C for 1 hour, 140°C for 2 hours, and 180°C for 2 hours. The properties of the cured bio-based epoxy resin are as follows: 5% thermal weight loss temperature (T d5％ ) is 334℃, the residual carbon rate at 700℃ (C y700 ) is 20.1%, and the maximum decomposition rate (R max ) is 0.64% / min, and the theoretical limiting oxygen index (LOI) is 25.5%.

[0037] Example 7

[0038] Different from Example 1, in (2), succinic anhydride (SA) and epoxy precursor GSA-EP are additionally mixed in a molar ratio of epoxy: anhydride = 1:0.75, heated to 140°C for melting, and then vacuum degassed until no bubbles are generated, and poured into a mold. The curing procedure is: 80°C for 1 hour, 110°C for 2 hours, 140°C for 2 hours, and 180°C for 2 hours. The properties of the cured bio-based epoxy resin are as follows: 5% thermal weight loss temperature (T d5％ ) is 289℃, and the residual carbon rate at 700℃ (C y700 ) is 45.3%, and the maximum decomposition rate (R max ) is 0.35% / min, and the theoretical limiting oxygen index (LOI) is 35.6%.

[0039] Comparative Example 1

[0040] 1 part of 4-dimethylaminopyridine (DMAP) was mixed with 200 parts of epoxy precursor DGEBA, heated to 110°C for melting, and then vacuum degassed until no bubbles were generated. The mixture was poured into a mold, and the curing procedure was: 70°C for 1 hour, 110°C for 2 hours, 180°C for 2 hours, and 220°C for 1 hour. The self-curing bio-based epoxy resin obtained was named DGEBA / DMAP, and its properties were as follows: 5% thermal weight loss temperature (T d5％ ) is 256℃, the residual carbon rate at 700℃ (C y700 ) is 3.6%, the maximum decomposition rate temperature (T max ) is 316℃, the maximum decomposition rate (R max ) is 1.30% / min, and the theoretical limiting oxygen index (LOI) is 18.9%.

[0041] Comparative Example 2

[0042] Different from Comparative Example 1, 4,4'-diaminodiphenylmethane (DDM) and epoxy precursor GSA-EP were mixed uniformly in a molar ratio of epoxy: NH = 1: 1, heated to 110 ° C for melting, vacuum degassing was performed until no bubbles were generated, and poured into a mold. The curing procedure was: 70 ° C for 1 hour, 110 ° C for 2 hours, 180 ° C for 2 hours, and 220 ° C for 1 hour. The obtained cured bio-based epoxy resin was named DGEBA / DDM, and its properties were as follows: 5% thermal weight loss temperature (T d5％ ) is 373℃, the residual carbon rate at 700℃ (C y700 ) is 19.0%, and the maximum decomposition rate (R max ) is 1.96% / min, and the theoretical limiting oxygen index (LOI) is 25.1%.

[0043] Thermogravimetric test: Mettler TGA 1 thermogravimetric analyzer was used to increase the temperature from 30°C to 800°C at a heating rate of 10°C / min in a nitrogen atmosphere. Figure 1 and attached Figure 2 shown.

[0044] The above-described embodiments are only preferred embodiments for fully illustrating the present invention, and the protection scope of the present invention is not limited thereto. Equivalent substitutions and changes, or improvements and modifications made by those skilled in the art on the basis of the present invention are all within the protection scope of the present invention. The protection scope of the present invention shall be subject to the claims.

Claims

1. A method for preparing a bio-based epoxy resin containing a dicarbonyl structure, characterized in that: Here are the steps: (1) 3-(4-hydroxy-3-methoxybenzoyl)propionic acid, benzyltriethylammonium chloride and epichlorohydrin are mixed in a molar ratio of 1:1:30-80, and stirred continuously for reaction at 60-100° C. in a N2 atmosphere for 1-4 hours; 40 wt.% NaOH solution is added to the system and the reaction is continued for 0.5-2 hours, wherein the molar ratio of GSA:NaOH is 1:2-3; then washed three times with a saturated NaCl solution and dried to obtain a bio-based epoxy resin precursor GSA-EP containing a dicarbonyl structure, whose structural formula is: (2) uniformly mixing 50-400 parts of the bio-based epoxy resin precursor GSA-EP containing a dicarbonyl structure obtained in step (1) with 1 part of an accelerator, performing vacuum degassing, pouring the resin into a mold, and performing thermosetting molding to obtain a bio-based epoxy resin containing a dicarbonyl structure; In step (2), an accelerator is added to the bio-based epoxy resin precursor GSA-EP containing a dicarbonyl structure at 110-200° C., with or without a curing agent, and after uniform mixing and vacuum degassing, the resin is poured into a mold and kept at 60-100° C. for 1-4 hours, then kept at 90-140° C. for 1-4 hours, then kept at 140-190° C. for 1-4 hours, and finally cured at 180-230° C. for 1-4 hours; The accelerator is 2,4,6-tris(dimethylaminomethyl)phenol, benzyldimethylamine, 4-dimethylaminopyridine, triethylamine, triethanolamine or o-hydroxybenzyldimethylamine; and the curing agent is polyamine or acid anhydride.

2. The preparation method according to claim 1, characterized in that: The polyamine is isophoronediamine, metaphenylenediamine, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylsulfone, 3,3'-diethyl-4,4'-diaminodicyclohexylmethane, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, diethylaminopropylamine, ethylenediamine or metaphenylenediamine, which are uniformly mixed in a molar ratio of epoxy:NH=1:

1.

3. The preparation method according to claim 1, characterized in that: The acid anhydride is phthalic anhydride, methyltetrahydrophthalic anhydride, succinic anhydride, maleic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, dodecenylsuccinic anhydride, pyromellitic anhydride, benzophenone tetracarboxylic anhydride, ethylene glycol ditrimellitic anhydride, methylcyclohexenyl tetracarboxylic anhydride or trimellitic anhydride.

4. A bio-based epoxy resin containing a dicarbonyl structure prepared according to the preparation method according to any one of claims 1 to 3.

Images