Bio-based epoxy resin and preparation method thereof

Abstract

The invention discloses bio-based epoxy resin and a preparation method thereof, and belongs to the field of chemical engineering. According to the invention, dimethyl succinylsuccinate and epichlorohydrin which are derived from organisms are used as raw materials to prepare an epoxy resin monomer, and the monomer is cured. According to the invention, the bio-based epoxy resin monomer containing the dimethyl succinylsuccinate structure is obtained, and the monomer is cured. The bio-based epoxy resin is novel in structure, excellent in performance, less in influence on the environment, green and environment-friendly, conforms to the concept of sustainable development, and contributes to reduction of dependence on limited fossil resources.

Description

Technical Field

[0001] The invention belongs to the field of chemical industry and materials, and relates to a method for synthesizing an epoxy resin monomer containing a dimethyl succinylsuccinate structure. Technical Background

[0002] Epoxy resin (EP) is one of the most widely used thermosetting materials. Due to its excellent adhesion, mechanical and electrical properties, and chemical resistance, it is widely used in adhesives, coatings, structural components, and electronic materials. The molecular structure of epoxy resin monomers contains active epoxy groups. These groups can undergo cross-linking reactions with a variety of curing agents, and the resulting thermosetting materials are insoluble in common organic reagents such as ethyl acetate, methanol, ethanol, and acetone. However, epoxy resin thermosetting materials with high cross-linking density are generally brittle and often exhibit poor crack resistance, which limits their application in certain structural components. Therefore, it is necessary to improve the toughness of epoxy resins.

[0003] Bisphenol A diglycidyl ether (DGEBA) is the most commonly used epoxy monomer (its preparation route is as follows), accounting for about 80% of the market share. Studies have comprehensively studied the metabolic transformation of DGEBA in vitro and in vivo. The results showed that 12 metabolites and 7 metabolites were identified in vitro and in vivo, respectively (Food Chem. Toxicol, 2022; 166, 113252), indicating that it poses a potential threat to the human body. In addition, the raw material bisphenol A (BPA) has been shown to have an impact on human health and the environment (Biotechnol Adv. 2018; 36(1): 311-327).

[0004]

[0005] Research on bio-based epoxy resins has become a hot topic in recent years, driven by the demand of global chemical and materials giants for new, environmentally friendly materials. New bio-based epoxy resin monomers are synthesized primarily from renewable biomass resources through various methods. Common green alternatives to DGEBA include vegetable oils such as soybean, linseed, and castor oils; polysaccharides such as cellulose and starch; epoxidized natural rubber; and lignin. Researchers are committed to developing bio-based epoxy resins with superior properties to meet the demands of environmental protection and sustainable development. For example, the introduction of functional groups containing elements such as nitrogen and phosphorus can further enhance the flame retardancy and drip resistance of epoxy resins.

[0006] In addition, bio-based epoxy resins have also made significant progress in heat resistance, mechanical properties and flame retardancy. Chinese patent CN106243324A introduces a flame-retardant epoxy resin and its preparation method. It uses common lignin as raw material for processing, and the yield of the prepared epoxy resin can reach more than 99%. The epoxy value and viscosity of the product are both high, its glass transition temperature is high, and its flame retardant properties are good. Chinese patent CN118580202A introduces a new bio-based epoxy resin containing a dicarbonyl structure. It is synthesized by a simple Friedel-Crafts acylation reaction of the bio-based compound guaiacol and succinic anhydride. The prepared epoxy resin has a good carbonization effect and a high flame retardant potential. At the same time, the raw material is based on green and environmentally friendly biomass and has high biosafety. Its structure is as follows:

[0007]

[0008] Chinese patent CN119351022A uses chelidonic acid to prepare a bio-based epoxy resin monomer, which is then blended with bisphenol A epoxy resin to successfully prepare an epoxy adhesive with excellent antioxidant and mechanical properties. The structure of the bio-based epoxy resin monomer is as follows:

[0009]

[0010] Itaconic acid (IA) is produced by fermentation of carbohydrates (e.g., glucose) in the presence of Aspergillus terreus. It has attracted considerable attention as a starting material for the preparation of bio-based epoxy resins. Studies have shown that a more environmentally friendly epoxy resin can be synthesized from itaconic acid (IA), bisphenol A (BPA), and epichlorohydrin (ECH) without the use of a catalyst. Compared to a commercial epoxy resin (ER-SIKA), its thermal properties are superior to ER-SIKA (Polymer, 2021, 235, 124285). The structure of the itaconic acid-based epoxy resin is as follows:

[0011]

[0012] Chinese patent CN118772736A introduces an anti-corrosion bio-based epoxy coating with good acid resistance, alkali resistance, salt water resistance, and salt spray resistance. It can provide excellent protection in environments with anti-corrosion requirements, especially marine environments. CN118638067A introduces a new bio-based epoxy resin containing a triazole structure and its curing agent. The epoxy resin curing agent prepared by this method has a high degree of greenness. Due to the nitrogen heterocyclic structure of triazole, the cured epoxy resin has a higher charring ability and lower flammability than the use of common aromatic amine epoxy curing agents, effectively improving the intrinsic flame retardant properties of the cured epoxy resin. The structure of the bio-based epoxy curing agent is as follows:

[0013]

[0014] Chinese patent CN118580201A describes an acid-degradable sulfite-based bio-based epoxy resin that, after curing, rapidly degrades at low temperatures under acidic conditions. The degradation products of the epoxy resin can be used to prepare high-value-added photothermal conversion materials through simple coordination reactions with iron and titanium ions, enabling the recycling of epoxy resin. Its structure is as follows:

[0015]

[0016] World Patent WO2016172353A, U.S. Patent US2024301125A, and U.S. Patent US2009275674A all describe bio-based epoxy resins for coatings. Japanese Patent JP2002265562A describes a phosphorus-containing epoxy resin that imparts excellent flame retardancy to the cured product without compromising heat and moisture resistance.

[0017] Dimethyl succinylsuccinate (DMSS) is an important intermediate for the synthesis of quinacridone pigments, 1,4-cyclohexanedione, and photosensitive polymers. Dimethyl succinate can be obtained from succinic acid by esterification, and then by Diekmann condensation (Tian Huarong. Improvement of dimethyl succinylsuccinate (DMSS), a high-grade pigment intermediate [D]. Jiangsu: Soochow University, 2005.). Among them, succinic acid, also known as succinic acid (SA), has been identified by the U.S. National Renewable Energy Laboratory and the U.S. Department of Energy as one of the top value-added platform chemicals obtained from biomass (Bozell JJ, Petersen GR. Technology development for the production of biobased products from biorefinery carbohydrates - the US Department of Energy's "top 10" revisited [J]. Green Chemistry, 2010, 12 (4): 539-554.).

[0018] The widespread application of DMSS is closely related to the reactivity and stability of its diester structure. In the field of photosensitive materials, it is widely used as a charge regulator in laser printing toners, significantly improving image quality. In the polymer industry, it serves as a crosslinker or plasticizer for polyesters and polyurethanes, enhancing their mechanical properties. The pharmaceutical industry leverages its lipid solubility to develop sustained-release drug carriers, showing particular potential in targeted anti-tumor delivery systems. Furthermore, in the dye industry, DMSS is used as a dispersing aid, effectively improving dyeing uniformity and color fastness.

[0019] In 2024, China's production of dimethyl succinylsuccinate reached 150,000 tons, and is expected to reach 180,000 tons by 2026, accounting for over 90% of quinacridone pigments. Chinese patent CN118724736A describes a method for preparing 2,5-diarylamino-terephthalic acid, a quinacridone pigment intermediate. This method features a simple process, low operational complexity, and high synthesis efficiency. Chinese patent CN117720824A describes an improved method for producing quinacridone solid solution pigments, which offer advantages over traditional quinacridone pigments. Summary of the Invention

[0020] The purpose of the present invention is to provide a new type of bio-based epoxy resin monomer method containing a succinylsuccinate dimethyl ester structure. The raw material can be started from succinylsuccinate dimethyl ester, which has the advantages of being cheap, easily available and having low potential toxicity.

[0021] The present invention provides a bio-based epoxy resin monomer containing dimethyl succinylsuccinate (DMSS-ECH), as shown in formula (I):

[0022]

[0023] The specific preparation method of the bio-based epoxy resin monomer of formula (I) prepared by the present invention is prepared by the following three steps:

[0024] S1. reacting dimethyl succinylsuccinate with epichlorohydrin in the presence of a catalyst;

[0025] S2. The reaction solution was cooled in an ice bath and an alkaline aqueous solution was added dropwise;

[0026] S3. Use organic solvent for extraction, and finally make sand and pass it through a column to separate the bio-based epoxy resin monomer (DMSS-ECH).

[0027] The reaction equation is as follows:

[0028]

[0029] In the S1, the molar ratio of dimethyl succinylsuccinate to epichlorohydrin is 1:8-1:12, preferably 1:10.

[0030] In the S1, the catalyst can be tetrabutylammonium bromide (TBAB), Na2CO3, K2CO3, preferably Na2CO3, the molar ratio of dimethyl succinylsuccinate to the catalyst is 1:0.1-1:0.8, preferably 1:0.5, and the reaction temperature is 70-85°C, preferably 80°C.

[0031] In the S2, the alkaline solution can be a NaOH aqueous solution, a Na2CO3 aqueous solution, or a K2CO3 aqueous solution, preferably a NaOH aqueous solution, with a concentration of 40-60wt%, preferably 40wt%.

[0032] The extraction organic solvent in S3 can be dichloromethane or ethyl acetate, preferably dichloromethane.

[0033] The bio-based epoxy resin of formula (II) prepared in the present invention is prepared by weighing (I) in a sample bottle, stirring, and heating to melt. After (I) is melted, a curing agent is added. After the two are uniformly mixed, the mixture is poured into a mold and placed in a high-temperature oven for curing.

[0034]

[0035] Wherein, R is an alkyl group, a polyether segment, an aromatic group, or an alicyclic group, and m and n are natural numbers.

[0036] The curing agent is diamine 1074, polyetheramine (D400, D230, D2000, ED600), and pentamethylenediamine.

[0037] The molar ratio of (I) to the curing agent is 1.8:1-2.2:1, preferably 2:1.

[0038] The curing temperature is 100°C-160°C, preferably 120°C.

[0039] Helpful Notes

[0040] (1) The raw material used in the present invention is dimethyl succinylsuccinate of biological origin, which has the advantages of being cheap, readily available, green and non-toxic, and the resin synthesis steps are simple.

[0041] (2) Dimethyl succinylsuccinate contains only one unsaturated six-membered ring structure, which can significantly improve the toughness of epoxy resin compared to bisphenol A which contains two benzene rings.

[0042] (2) By curing a bio-based epoxy resin monomer having a structure of formula (I) with a curing agent such as diamine 1074, pentamethylenediamine, polyetheramine D400, isophoronediamine, and 4,4'-diaminobenzylmethane, a bio-based epoxy resin having a structure of formula (II) can be prepared. The synthesis steps of the resin are simple and the resin has potential application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Embodiments of the present invention are described in detail with reference to the accompanying drawings, in which:

[0044] Figure 1 : Example 1 Bio-based epoxy resin monomer (DMSS-ECH) 1 H NMR spectrum.

[0045] Figure 2 : IR spectrum of bio-based epoxy resin in Example 11 (diamine 1074 as curing agent). Specific implementation methods

[0046] The experimental methods described in the following examples are conventional methods unless otherwise specified; the reagents and materials are commercially available unless otherwise specified.

[0047] The hydrogen nuclear magnetic resonance spectra involved in the examples were measured using a Bruker Ascend TM-400 hydrogen nuclear magnetic resonance spectrometer from Bruker, the deuterated reagent used was deuterated chloroform (Chloroform-d), and the infrared spectra involved were measured using a Nicoletis 10 Fourier transform infrared spectrometer from Thermo Fisher Scientific.

[0048] The tensile and flexural strength tests involved in the examples were conducted using a CMT6013 electronic universal testing machine, and the glass transition temperature Tg involved was measured using a NETZSCH differential scanning calorimeter.

[0049] Example 1

[0050] Preparation of bio-based epoxy resin monomer (DMSS-ECH): Dimethyl succinylsuccinate (DMSS) (2.28 g, 0.01 mol, 1 eq.), epichlorohydrin (9.25 g, 0.1 mol, 10 eq.), and Na₂CO₃ (0.53 g, 0.005 mol, 0.5 eq.) were added to a 250 mL eggplant-shaped flask. The mixture was stirred and refluxed at 80°C for 3 h. After the reaction, the reaction solution was cooled to room temperature in an ice bath. Sodium hydroxide (8 g, 0.2 mol, 20 eq.) was dissolved in 20 mL of water and slowly added to the flask. Extraction was performed using a dichloromethane / water system. The organic phase was collected and dried over anhydrous sodium sulfate. The dichloromethane was removed by rotary evaporation and the mixture was filtered through a column. The resulting white solid was the bio-based epoxy resin monomer with a yield of 72.5%. 1 H NMR (400MHz, Chloroform-d) δ4.32 (dd, J=11.1, 2.8Hz, 1H), 4.04 (dd, J=11.1, 5.1Hz, 1H ), 3.91 (s, 3H), 3.75-3.68 (m, 1H), 3.37 (ddd, J=6.9, 5.2, 2.8Hz, 1H), 2.94-2.82 (m, 2H).

[0051] Example 2-10

[0052] The preparation of the bio-based epoxy resin monomer (DMSS-ECH) of Examples 2-10 is shown in Table 1.

[0053]

[0054] Example 11

[0055] Preparation of bio-based epoxy resin (diamine 1074 as curing agent (Croda Company)): The bio-based epoxy resin monomer (DMSS-ECH) (1.424 g, 0.004 mol, 2.0 eq.) prepared in Example 1 was added to a 20 mL sample bottle and heated to 110°C under vacuum conditions. After it melted, diamine 1074 (0.54 g, 0.002 mol, 1 eq.) was added to the sample bottle. After mixing evenly, it was poured into a mold and cured in an oven at 120°C.

[0056] Examples 12-21

[0057] The curing agent diamine 1074 in Example 12 was replaced with the same molar amounts of polyetheramine (D400, D230, D2000, ED600) and pentamethylenediamine to obtain Examples 12-21, as shown in Table 2.

[0058] Table 2 Formulations of Examples 12-21

[0059]

[0060] Comparative Example 1

[0061] Commercially available bisphenol A epoxy resin E54 (manufacturer) (epoxy equivalent weight 184 g / mol) was added to a 20 mL sample bottle and heated to 110°C under vacuum. After it melted, diamine 1074 (0.54 g, 0.002 mol, 1 eq.) was added to the sample bottle. After mixing evenly, it was poured into a mold and cured in an oven at 120°C.

[0062] Comparative Example 2

[0063] Commercially available bisphenol A epoxy resin E54 (epoxy equivalent of 184 g / mol) was added to a 20 mL sample bottle and heated to 110°C under vacuum. After it melted, diamine 1074 (0.54 g, 0.002 mol, 1 eq.) was added to the sample bottle. After mixing evenly, it was poured into a mold and cured in an oven at 160°C.

[0064] Comparative Example 3

[0065] Commercially available bisphenol A epoxy resin E54 (epoxy equivalent of 184 g / mol) was added to a 20 mL sample bottle and heated to 110°C under vacuum. After it melted, polyetheramine (D230) (0.46 g, 0.002 mol, 1 eq.) was added to the sample bottle. After mixing evenly, it was poured into a mold and cured in an oven at 120°C.

[0066] Comparative Example 4

[0067] Commercially available bisphenol A epoxy resin E54 (epoxy equivalent of 184 g / mol) was added to a 20 mL sample bottle and heated to 110°C under vacuum. After it melted, polyetheramine (D400) (0.8 g, 0.002 mol, 1 eq.) was added to the sample bottle. After mixing evenly, it was poured into a mold and cured in an oven at 160°C.

[0068] Performance Testing

[0069] Table 3 shows mechanical property tests and thermogravimetric analysis of the properties of the cured resins obtained in Examples 11-21 and Comparative Examples 1-4.

[0070] Table 3 Performance comparison of Examples 11-21 and Comparative Examples 1-4

[0071]

[0072] As can be seen from the table, the bio-based epoxy resin synthesized in this invention has high mechanical properties. Compared with Comparative Examples 1 and 3, the glass transition temperature of Example 11 is increased by 12°C and 5°C, respectively, and the tensile and flexural strengths are also improved to a certain extent, showing potential application value.

Claims

1. A bio-based epoxy resin monomer (DMSS-ECH), characterized in that Having the structure shown in formula (I):

2. The bio-based epoxy resin monomer (DMSS-ECH) of formula (I) as claimed in claim 1 is prepared by: S1. reacting dimethyl succinylsuccinate with epichlorohydrin in the presence of a catalyst, S2. Cool the reaction solution in an ice bath and add alkaline aqueous solution dropwise. S3. Use organic solvent for extraction, and finally make sand and pass it through a column to separate the bio-based epoxy resin monomer (DMSS-ECH).

3. The molar ratio of dimethyl succinylsuccinate to epichlorohydrin in S1 as claimed in claim 2 is 1:8-1:

12.

4. As claimed in claim 2, the catalyst of S1 is Na2CO3, the molar ratio of dimethyl succinylsuccinate to Na2CO3 is 1:0.1-1:0.8, and the reaction temperature is 70-85°C.

5. The alkaline aqueous solution in S2 as claimed in claim 2 is a NaOH aqueous solution with a concentration of 40-60 wt%.

6. The organic solvent in S3 as claimed in claim 2 is dichloromethane.

7. A bio-based epoxy resin, characterized in that It has a structure as shown in formula (II): Wherein, R is an alkyl group, a polyether segment, an aromatic group, an alicyclic group, and m and n are natural numbers.

8. The bio-based epoxy resin of formula (II) as claimed in claim 7 is prepared by heating and melting the bio-based epoxy resin monomer of formula (I), adding a curing agent, mixing well, and pouring into a mold for molding.

9. The molar ratio of the bio-based epoxy resin monomer (DMSS-ECH) to the curing agent as claimed in claim 8 is 1.8:1-2.2:

1.

10. The curing agent as claimed in claim 8 and claim 9 is dimeramine 1074, polyetheramine (D400, D230, D2000, ED600), or pentamethylenediamine.

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