Epoxy resin with low modulus and high Tg and application thereof

Abstract

The invention belongs to the technical field of high polymer materials, and particularly relates to epoxy resin with low modulus and high Tg and application thereof. The structural formula of the epoxy resin is shown as a compound I, wherein n is 0 or 1. The epoxy resin provided by the invention realizes the collaborative design of low modulus and high Tg, remarkably improves the flexibility of the material, meets the requirements of flexible electronic packaging, and is suitable for a high-temperature working environment.

Description

Technical Field

[0001] This invention belongs to the technical field of polymer materials, specifically relating to an epoxy resin with low modulus and high Tg and its applications. Background Technology

[0002] Epoxy resins are widely used in industries such as electronics, aerospace, and automotive due to their excellent mechanical properties, heat resistance, and adhesion. However, traditional epoxy resins, such as bisphenol A type epoxy resins, generally suffer from problems such as excessively high modulus and brittleness due to their highly rigid molecular chain structure, limiting their application in flexible or dynamic load environments. To improve the toughness of epoxy resins, researchers often employ methods such as introducing flexible segments and blending modification, but these methods often come at the cost of heat resistance, making it difficult to achieve a good balance between low modulus and high Tg.

[0003] Therefore, developing a novel epoxy resin system that can maintain high heat resistance while significantly reducing modulus has become a key focus of current research and development of high-performance resin materials. Summary of the Invention

[0004] Technical issues

[0005] The purpose of this invention is to provide a phenyl ether type epoxy resin with low modulus and high glass transition temperature and its preparation method. By rationally designing the molecular structure, the resin can significantly reduce the elastic modulus and improve the toughness of the material while maintaining good heat resistance.

[0006] Technical solution

[0007] A first aspect of the present invention provides an epoxy resin having low modulus and high Tg, the epoxy resin having the structural formula shown in compound I: Where n is 0 or 1.

[0008] A second aspect of the present invention provides a process for preparing an epoxy resin with high toughness and high Tg, the process being as follows:

[0009]

[0010]

[0011] Where n is 0 or 1; M is Na or K; X is Cl, Br, or I. This invention proposes a novel synthetic route: by selectively converting a phenolic hydroxyl group in a diphenol compound to sodium / potassium phenoxide, followed by a nucleophilic substitution reaction with p-dibenzylchlorobenzene / p-dichlorobenzene to generate a phenyl ether intermediate, and finally reacting it with cyclopropyl chloride to prepare a novel and high-performance phenyl ether-type epoxy resin. The phenyl ether bond (–Ph–O–Ph–) is a linkage structure that combines rigidity and flexibility. Introducing this structure into the polymer backbone helps reduce intermolecular forces and improve chain segment mobility, thereby effectively improving the toughness and modulus properties of the material without significantly reducing heat resistance.

[0012] In some embodiments, the molar ratio of compound II to MOH is 1:1 to 1.2, the molar ratio of compound III to compound IV is 2 to 2.2:1, and the molar ratio of compound V to compound VI is 1:2 to 4.

[0013] In some embodiments, the steps for preparing compound III from compound II specifically include: dissolving compound II in an ethanol / water mixed solvent, slowly adding MOH solution dropwise under stirring, then heating to 110–130°C, maintaining the temperature and stirring for 5–7 h, cooling to room temperature after the reaction is completed, separating, washing and vacuum drying the precipitated white solid to obtain compound III; wherein, M is Na or K.

[0014] In some embodiments, the volume ratio of ethanol to water in the ethanol / water mixed solvent is 1.2-1.5:1; the washing specifically involves washing with deionized water and ethanol sequentially; and the vacuum drying temperature is 55-65°C.

[0015] In some embodiments, the step of preparing compound V from compound III specifically includes: dissolving compound III and compound IV in an aprotic polar solvent, stirring the mixture at 100–130°C and a speed of 200–400 rpm for 6–10 h to obtain compound V.

[0016] In some embodiments, the aprotic polar solvent is DMF or DMSO.

[0017] In some embodiments, both compound III and compound V are prepared under an inert atmosphere.

[0018] In some embodiments, the step of preparing compound I from compound V specifically includes: dissolving compound V in a mixed solvent of epichlorohydrin and an alcohol solvent, stirring the mixture at 300-400 rpm for 1-2 hours at a temperature of 90-110°C, slowly adding a catalyst during the reaction, and continuing stirring for 1.5-2.5 hours after the catalyst addition is completed; obtaining a crude product by washing with water, separating the liquid and recovering the solvent, dissolving the crude product in a purified solvent and washing it with water 2-3 times, and finally obtaining compound I, i.e., the epoxy resin, by vacuum distillation.

[0019] In some embodiments, the alcohol solvent is n-butanol, isobutanol, or sec-butanol; the catalyst is a sodium hydroxide, potassium hydroxide, or lithium hydroxide solution; and the pH value of the reaction system in which compound V is used to prepare compound I is 9–12.

[0020] In some embodiments, the purification solvent is toluene, xylene, or ethyl acetate; the temperature at which the crude product is dissolved in the purification solvent is 50–70°C; and the conditions for vacuum distillation are 0.04–0.07 MPa and 50–60°C.

[0021] A third aspect of this invention provides the application of epoxy resins with low modulus and high Tg as described above in the fields of flexible electronic packaging, low-temperature adhesives, and composite matrix, wherein the epoxy resin has a glass transition temperature of 150–170°C, an elastic modulus of 2300–3100 MPa, an epoxy equivalent of 325–380 g / eq, and an impact strength of 20–40 KJ / m. 2 .

[0022] Technical effect

[0023] 1. Achieving a synergistic design of low modulus and high Tg, breaking through the performance limitations of traditional epoxy resins: This invention introduces a phenyl ether structure to moderately reduce the rigidity of the molecular chain, thereby improving the chain segment mobility while maintaining a high crosslinking density. Example test results show a flexural modulus of 2300–3100 MPa and a Tg of 150–170 °C, successfully resolving the technical contradiction in existing technologies where "high Tg is usually accompanied by high modulus."

[0024] 2. Significantly improves material flexibility to meet the requirements of flexible electronic packaging: The flexible linkage of ether bonds in the phenyl ether structure effectively alleviates the internal stress in the cured network, enabling the material to maintain good flexibility at high temperatures. Compared with the comparative example (modulus 2100 MPa, Tg only 118℃), the resin of this invention increases the modulus by more than 25%, significantly enhancing its applicability in flexible circuit substrates, copper-clad laminates, and other fields.

[0025] 3. Improved heat resistance, suitable for high-temperature working environments: The conjugation effect of the benzene ring and ether bond in the molecular backbone enhances thermal stability and improves the uniformity of free volume distribution, thereby significantly increasing the glass transition temperature. The Tg of this invention reaches 150–170℃, significantly better than the 110℃ of the comparative example, meeting the requirements of high-frequency high-speed communication, LED packaging, and other high-temperature applications. Simultaneously, while maintaining high heat resistance, this material also exhibits good impact strength. Compared to the brittleness and cracking issues of traditional high-Tg materials, the material of this invention has superior toughness, effectively resisting damage caused by thermal stress and mechanical impact, reducing the risk of cracks or delamination during use, and improving the structural reliability and service life of the material under complex working conditions. Attached Figure Description

[0026] Figure 1 The NMR spectrum of the final product of Example 1 is shown below.

[0027] Figure 2 The image shows the NMR spectrum of the final product of Example 2. Detailed Implementation

[0028] To facilitate the examination of the technical solutions applied for, the following is a general explanation and definition of the terms and expressions used in this application.

[0029] The terms “comprising,” “including,” or any other variations thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase “comprising one…” does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0030] In this invention, room temperature refers to 20-27°C.

[0031] The slow addition described in this invention is to control excessive fluctuations in the reaction temperature during the addition process, which could have an adverse effect on the reaction. Therefore, it is necessary to control the addition rate.

[0032] In the comparative experiments provided in this application, unless otherwise specified, all experimental conditions and materials are kept consistent to ensure comparability.

[0033] Unless otherwise specified, all reagents and instruments used in the embodiments of this invention can be purchased from the market.

[0034] The following provides a further description of an epoxy resin with low modulus and high Tg, and its applications.

[0035] Example 1: Preparation of Epoxy Resin Products

[0036] Under nitrogen protection, 320 g of bisphenol A (BPA) was added to a four-necked reactor equipped with a mechanical stirrer, followed by 800 mL of an ethanol / water mixture (volume ratio 6:4). 187–224 g of a 30 wt% sodium hydroxide aqueous solution was slowly added dropwise under stirring, controlling the dropping rate to avoid localized over-alkaliness and violent exothermic reactions. The system was heated to 120 °C and stirred for 6 hours to selectively deprotonate one of the phenolic hydroxyl groups to form sodium phenolate. After the reaction, the mixture was cooled to room temperature, and a white solid product precipitated. This product was separated by filtration using a Buchner funnel and washed sequentially with deionized water and ethanol to remove residual inorganic salts and unreacted raw materials. The resulting solid was dried in a vacuum oven at 60 °C to obtain sodium phenolate. This invention uses bisphenol A as a starting material and selectively deprotonates one of the phenolic hydroxyl groups to form a sodium phenolate group under alkaline conditions, retaining the other phenolic hydroxyl group as a nucleophile to participate in subsequent reactions, thereby obtaining a product with –OH and –O-Na groups. + A sodium phenolate compound with two functional groups. The specific reaction formula is as follows:

[0037]

[0038] Subsequently, 180.9 g of the sodium phenolate compound obtained above was added to a reaction vessel. Under nitrogen protection, 900 mL of N,N-dimethylformamide (DMF) was added as an aprotic polar solvent. After stirring and dispersing evenly, 93.9 g of p-dichlorobenzene was added, the temperature was raised to 120 °C, and the reaction was carried out at 300 rpm for 6 hours to obtain the phenyl ether intermediate. The specific reaction formula is as follows:

[0039]

[0040] Next, 200g of the above intermediate, 100g of epichlorohydrin (ECH), and 228mL of n-butanol were added to the reaction system. The temperature was raised to 90℃, and 60mL of 49% sodium hydroxide aqueous solution was slowly added dropwise over 1.5 hours with a stirring rate of 350rpm. After the addition was complete, stirring was continued for 2 hours. This invention involves reacting the obtained phenyl ether structure intermediate with epichlorohydrin in an alkaline medium to construct an epoxy group. Mild heating was used during the reaction, and the pH was maintained between 9 and 12 to improve reaction efficiency and product stability. The specific reaction formula is as follows:

[0041]

[0042] After the reaction was complete, 200 mL of water was added to the system, stirred for 10 minutes, and then allowed to stand to separate into layers. The lower aqueous phase was separated and discarded. Next, 500 mL of toluene was added to the organic phase, and the mixture was heated to 60 °C to dissolve the crude product. The product was then washed three times with 100 mL of water to remove residual inorganic salts and unreacted NaOH. Finally, toluene was removed by vacuum distillation at 0.06 MPa and 60 °C to obtain an epoxy resin product with a high glass transition temperature (Tg) and good thermal stability.

[0043] The molecular structure of the epoxy resin intermediate described in this invention was fully characterized by 1H NMR (400 MHz, CDCl3). Figure 1 As shown, a multiplet with an integral value of 8H appears in the δ 6.8–7.5 ppm range, attributed to the aromatic protons on the two benzene rings and the central benzene ring in the molecule. Due to the difference in substituent electronic effects, the ortho-hydrogen signal influenced by the electron-donating effect of the para-tert-butyl group is shifted to the high field (~6.8 ppm), while the ortho-hydrogen signal influenced by the electron-withdrawing effect of the propylene oxide group is shifted to the low field (~7.5 ppm). Due to the symmetrical diether bond structure of the central benzene ring, its aromatic hydrogens exhibit a typical para-disubstituted coupling mode, and the signal distribution is consistent with theoretical expectations. A multiplet (4H) is observed in the δ 3.0–4.0 ppm range, clearly attributed to the methylene group (–CH2–O–) directly bonded to oxygen in the two propylene oxide groups, and its low-field shift is caused by the strong electron-withdrawing effect of the propylene oxide ring. Furthermore, a singlet (18H) peak appears at δ 1.5–2.0 ppm, corresponding to the methyl protons on the two tert-butyl groups. This singlet characteristic indicates that the molecules are in completely equivalent chemical environments, and the integrated value perfectly matches the theoretical hydrogen number, fully demonstrating the high degree of structural symmetry. The above 1H NMR data are highly consistent with the symmetrical di-tert-butyl-epoxypropylene modified aryl ether skeleton of the target compound in terms of chemical shift, peak shape, and integrated area, confirming the structural clarity and synthetic controllability of the intermediate of this invention.

[0044] Example 2: Preparation of epoxy resin products

[0045] The difference from Example 1 is that 93.9g of p-dichlorobenzene was replaced with 97.1g of p-dibenzylchlorobenzene. The structural formula of the intermediate obtained from the reaction is as follows:

[0046] The structural formula of the final product obtained from the reaction is as follows:

[0047]

[0048] The structure of the epoxy resin intermediate described in this invention was characterized by 1H NMR (400MHz, CDCl3), as follows: Figure 2 As shown:

[0049] δ1.5–2.0 ppm (s, 18H) represents the methyl proton signals of the two tert-butyl groups; the singlet indicates that their chemical environments are equivalent, consistent with molecular symmetry. δ2.5–4.0 ppm (m, 6H) belongs to the protons on the rings of the two propylene oxide groups. δ4.5–5.0 ppm (m, 8H) corresponds to multiple oxygen-linked methylene (–O–CH2–) protons. The aromatic region δ6.8–7.5 ppm (m, 12H) represents the aromatic protons on the six benzene rings. The integral ratios of each signal are consistent with the hydrogen atom distribution in the target molecule, and the peak shape and chemical shift conform to the expected electronic effects, confirming that it has a centrosymmetric aromatic ether-tert-butyl-propylene oxide skeleton structure.

[0050] Example 3: Preparation of epoxy resin products

[0051] The difference from Example 1 is that n-butanol is replaced with sec-butanol.

[0052] Example 4: Preparation of epoxy resin products

[0053] The difference from Example 1 is that N,N-dimethylformamide (DMF) is replaced with DMSO (dimethyl sulfoxide).

[0054] Example 5: Preparation of Epoxy Resin Products

[0055] The difference from Example 1 is that toluene was replaced with ethyl acetate, and the mixture was heated to 50°C and then distilled under reduced pressure at 0.07 MPa and 50°C to remove ethyl acetate.

[0056] Comparative Example 1: Preparation of Epoxy Resin Products

[0057] Under nitrogen protection, 106.0 g of bisphenol A (BPA) and 463 g of epichlorohydrin (ECH) were mixed and heated to 65 °C. 100 mL of 49% sodium hydroxide (NaOH) solution was slowly added dropwise over 5 hours with a stirring rate of 300 rpm. After the addition was complete, stirring continued for 1 hour. After the reaction was complete, 200 mL of water was added to the system, and after stirring for 10 minutes, the mixture was allowed to stand and separate into layers. The lower aqueous phase was separated and discarded. Then, 500 mL of toluene was added to the organic phase, and the mixture was heated to 60 °C to dissolve the crude product. The product was washed three times with 100 mL of water to remove residual inorganic salts and unreacted NaOH. Finally, toluene was removed by vacuum distillation at 0.06 MPa and 60 °C to obtain the epoxy resin product. The main difference between Comparative Example 1 and Example 1 is that this method did not include a vinyl ether pre-reaction step, serving as a comparative experiment of the synthesis process of this invention.

[0058] Comparative Example 2: Preparation of Epoxy Resin Products

[0059] 180.9 g of the prepared sodium phenolate compound and 93.9 g of p-dichlorobenzene were added to a reaction vessel, along with 400 mL of water and 500 mL of toluene, forming a two-phase reaction system. Then, approximately 7.5 g of tetrabutylammonium bromide (TBAB) was added as a phase transfer catalyst. Under a nitrogen atmosphere, the mixture was heated and stirred at 85°C at a speed of 400 rpm for 7 hours. The main difference between Comparative Example 2 and Example 1 is that a non-protic polar solvent was not used; instead, a phase transfer catalysis was employed, resulting in a significant reduction in the coupling reaction efficiency.

[0060] Experimental Example 1: Epoxy Equivalent Test

[0061] The epoxy resins prepared in Examples 1-5 and Comparative Examples 1-2 were subjected to epoxy equivalent testing according to the standard GB / T4612-2008, and the data were recorded. The results are shown in Table 1. The epoxy equivalent range of the epoxy resin provided by the present invention is 325-380 g / eq. This range of epoxy equivalent ensures reactivity while avoiding excessive rigidity of the material.

[0062] Experimental Example 2: Elastic Modulus Test

[0063] According to standard GB / T 2567-2008, the epoxy resins prepared in Examples 1-5 and Comparative Examples 1-2 were tested for elastic modulus at 25°C. The results are shown in Table 1. The epoxy resin provided by this invention has an elastic modulus range of 2300-3100 MPa, which is relatively low.

[0064] Test Example 3: Glass Transition Temperature (Tg) Test

[0065] The epoxy resin composites prepared in Examples 1-5 and Comparative Examples 1-2 were subjected to Tg testing using DSC or DMA methods under a nitrogen atmosphere. The heating rate was 10℃ / min, and the test temperature range was 25–200℃. The glass transition temperature (Tg) was recorded and analyzed to evaluate the thermal properties of the materials. The results are shown in Table 1. The Tg range of the epoxy resin provided by this invention is 150–170℃.

[0066] Experimental Example 4 Impact Strength Test

[0067] The epoxy resin composites prepared in Examples 1-5 and Comparative Examples 1-2 were subjected to mechanical property tests using an AGS-X 10KN universal testing machine; impact resistance was determined according to GB / T 2571 (Impact Test Method for Resin Castings). The results are shown in Table 1. The impact strength range of the epoxy resin provided by this invention is 22–37 KJ / m. 2 .

[0068] Table 1 Test Results

[0069]

[0070] The above specific embodiments further illustrate the purpose, technical solution and beneficial effects of this application. It should be understood that the above are only specific embodiments of this application and are not intended to limit the scope of protection of this application. Any modifications, equivalent substitutions, improvements, etc., made on the basis of the technical solution of this application should be included within the scope of protection of this application.

Claims

1. An epoxy resin having low modulus and high Tg, characterized in that, The structural formula of the epoxy resin is shown in compound I: Where n is 0 or 1.

2. A preparation process for an epoxy resin with high toughness and high Tg, characterized in that, The preparation process is as follows: Where n is 0 or 1; M is Na or K; X is Cl, Br or I.

3. The preparation process according to claim 2, characterized in that, The molar ratio of compound II to MOH is 1:1 to 1.2, the molar ratio of compound III to compound IV is 2 to 2.2:1, and the molar ratio of compound V to compound VI is 1:2 to 4.

4. The preparation process according to claim 2, characterized in that, The specific steps for preparing compound III from compound II include: Compound II was dissolved in an ethanol / water mixture, and MOH solution was slowly added dropwise under stirring. The temperature was then raised to 110–130 °C, and the reaction was maintained at this temperature with stirring for 5–7 h. After the reaction was completed, the mixture was cooled to room temperature, and the precipitated white solid was separated, washed, and dried under vacuum to obtain compound III. M was either Na or K.

5. The preparation process according to claim 4, characterized in that, The volume ratio of ethanol to water in the ethanol / water mixed solvent is 1.2-1.5:1; the washing process specifically involves washing with deionized water and ethanol sequentially; the vacuum drying temperature is 55-65℃.

6. The preparation process according to claim 2, characterized in that, The specific steps for preparing compound V from compound III include: Compound III and compound IV were dissolved in an aprotic polar solvent and reacted at 100–130 °C with stirring at 200–400 rpm for 6–10 h to obtain compound V.

7. The preparation process according to claim 2, characterized in that, The specific steps for preparing compound I from compound V include: Compound V was dissolved in a mixed solvent of epichlorohydrin and an alcohol, and the mixture was stirred at 300-400 rpm for 1-2 hours at 90-110°C. During the reaction, a catalyst was slowly added dropwise, and stirring was continued for 1.5-2.5 hours after the catalyst addition was completed. After washing with water, separation, and solvent recovery, a crude product was obtained. The crude product was dissolved in a purified solvent and washed with water 2-3 times. Finally, compound I, i.e., the epoxy resin, was obtained by vacuum distillation.

8. The preparation process according to claim 7, characterized in that, The alcohol solvent is n-butanol, isobutanol, or sec-butanol; the catalyst is sodium hydroxide, potassium hydroxide, or lithium hydroxide solution; the pH value of the reaction system in which compound V is used to prepare compound I is 9-12.

9. The preparation process according to claim 7, characterized in that, The purification solvent is toluene, xylene, or ethyl acetate; the temperature at which the crude product is dissolved in the purification solvent is 50–70°C; and the conditions for vacuum distillation are 0.04–0.07 MPa and 50–60°C.

10. An application of an epoxy resin having low modulus and high Tg, characterized in that, This includes the application of epoxy resin with low modulus and high Tg as described in claim 1 in the fields of flexible electronic packaging, low-temperature adhesives, and composite matrix, wherein the epoxy resin has a glass transition temperature of 150-170°C, an elastic modulus of 2300-3100 MPa, and an epoxy equivalent of 325-380 g / eq.

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