Naphthalic acid type epoxy resin as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of high polymer materials, and particularly relates to naphthalic acid type epoxy resin as well as a preparation method and application thereof. The structural formula of the naphthalic acid type epoxy resin is shown as a compound I, wherein R is-(CH2) 2-,-(CH2) 3-,-(CH2) 4,-(CH2) 5-or-(CH2) 6-. By embedding the specific flexible spacer into the molecular rigid skeleton, the contradiction of high rigidity, heat resistance and low toughness of the traditional product is solved, the rigidity and flexibility balance is realized, the defects of the existing toughening method are avoided, the application of the material in occasions needing to bear impact loads is expanded, the preparation process is stable, and the product characteristics are good.

Description

Technical Field

[0001] This invention belongs to the technical field of polymer materials, specifically relating to a naphthalene dicarboxylic acid type epoxy resin, its preparation method, and its application. Background Technology

[0002] Epoxy resins are widely used in aerospace, electronics, and composite materials industries due to their excellent adhesion, mechanical properties, electrical insulation, and chemical stability. With increasing application demands, the comprehensive performance requirements for epoxy resins, especially those combining high rigidity and high toughness, are becoming increasingly urgent.

[0003] The naphthalene ring structure possesses advantages such as high rigidity, high thermal stability, and good chemical resistance. Epoxy resins synthesized from naphthalenedicarboxylic acid (e.g., 2,6-naphthalenedicarboxylic acid) can acquire extremely high glass transition temperature (Tg), modulus, and dimensional stability due to the rigid backbone of the naphthalene ring, meeting the requirements for high rigidity. However, this highly rigid molecular structure also leads to high brittleness and low impact strength, limiting its application in applications requiring impact loads.

[0004] Existing technologies for improving the toughness of epoxy resins mainly include adding rubber elastomers, thermoplastics, nanofillers, or using flexible curing agents. However, these methods often suffer from drawbacks such as poor compatibility, complex processes, high costs, or significant reductions in rigidity and heat resistance while improving toughness. Summary of the Invention

[0005] Technical issues

[0006] The present invention aims to develop a novel naphthalene dicarboxylic acid type epoxy resin that starts with molecular structure design and introduces toughness components during the synthesis stage to achieve synergistic optimization of rigidity and toughness.

[0007] Technical solution

[0008] The first aspect of this invention provides a naphthalene dicarboxylic acid type epoxy resin, the structural formula of which is shown in Compound I: Where R is -(CH2)2-, -(CH2)3-, -(CH2)4-, -(CH2)5- or -(CH2)6-.

[0009] A second aspect of this invention provides a method for preparing a naphthalene-based epoxy resin, the preparation process of which is as follows:

[0010]

[0011] Where R is -(CH2)2-, -(CH2)3-, -(CH2)4-, -(CH2)5- or -(CH2)6-.

[0012] In some embodiments, the molar ratio of compound II to compound III is 1:2-2.4; the molar ratio of compound IV to compound V is 1:2.2-2.8; the catalyst is tetrabutyl titanate or dibutyltin dilaurate; and the alkaline aqueous solution is a sodium hydroxide aqueous solution or a potassium hydroxide aqueous solution with a mass fraction of 25-35%.

[0013] In some embodiments, the step of preparing compound IV from compound II specifically includes: adding compound II, compound III and catalyst to the reaction system, heating to 150-180°C, maintaining the temperature for 4-6 hours, and obtaining a solution of compound IV after the reaction is completed.

[0014] In some embodiments, the heat preservation reaction is carried out under a nitrogen atmosphere.

[0015] In some embodiments, the step of preparing compound I from compound IV specifically includes: dissolving compound IV in an organic solvent, cooling to 45-55°C, slowly adding compound V and an alkaline aqueous solution, and then keeping the mixture at 55-65°C for 2-3 hours after the addition is complete, and then post-processing to obtain compound I, i.e., naphthalene dicarboxylic acid type epoxy resin.

[0016] In some embodiments, the organic solvent is toluene or ethyl acetate.

[0017] In some embodiments, the post-processing steps are sequentially liquid-liquid separation, washing of the organic phase, and vacuum distillation, followed by collection of the target fraction to obtain the purified product.

[0018] The third aspect of the present invention provides an application of naphthalene dicarboxylic acid type epoxy resin, including the application of the above-mentioned naphthalene dicarboxylic acid type epoxy resin in the fields of flexible electronic packaging, low-temperature adhesives, and composite material matrices.

[0019] In some embodiments, the glass transition temperature of the naphthalene dicarboxylic acid type epoxy resin is 200-215℃; the epoxy equivalent is 215-225 g / eq; the elastic modulus is 3500-4000 MPa; and the impact strength is 10-25 KJ / m. 2 .

[0020] Technical effect

[0021] 1. This invention creatively solves the inherent contradiction of traditional naphthalene-based epoxy resins—characterized by "high rigidity and high heat resistance, but low toughness." By embedding flexible spacer groups of specific lengths (ethylene glycol, butanediol, and hexanediol) into the rigid framework, a "balance of rigidity and flexibility" is achieved at the molecular level, resulting in an excellent balance between rigidity and toughness in macroscopic properties. This is the fundamental difference between this and direct epoxidation or physical blending for toughening.

[0022] 2. Compared with the unmodified 2,6-naphthalenedicarboxylic acid type epoxy resin in the comparative example, the toughened epoxy resin in the examples significantly improved toughness-related properties while maintaining the advantages of high glass transition temperature (Tg), modulus, dimensional stability and chemical resistance brought about by the naphthalene ring structure.

[0023] 3. Unlike existing toughening methods that involve adding rubber elastomers, thermoplastics, nanofillers, or using flexible curing agents, this technology starts with molecular structure design and introduces toughening components during the synthesis stage. It does not require the addition of other substances and avoids the disadvantages of existing methods, such as poor compatibility, complex processes, high costs, or reduced rigidity and heat resistance when improving toughness. Detailed Implementation

[0024] 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.

[0025] 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.

[0026] In the comparative experiments provided in this application, unless otherwise specified, all experimental conditions and materials are kept consistent to ensure comparability.

[0027] 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.

[0028] Unless otherwise specified, all reagents and instruments used in the embodiments of this invention can be purchased from the market.

[0029] The following provides a further description of a naphthalene dicarboxylic acid type epoxy resin, its preparation method, and its application.

[0030] Example 1: Preparation of toughened epoxy resin based on 2,6-naphthalenedicarboxylic acid and 1,6-hexanediol

[0031] (1) In a three-necked flask equipped with a stirrer, thermometer, water separator, and nitrogen inlet tube, add 2,6-naphthalenedicarboxylic acid (40.4 g, 0.19 mol), 1,6-hexanediol (47.2 g, 0.4 mol), and tetrabutyl titanate (0.30 g); purge with nitrogen, heat to 160°C, and react for 5 hours until the water output reaches the theoretical value (7.2 g), thus obtaining the polyester prepolymer. The specific steps are as follows:

[0032]

[0033] (2) Transfer the prepolymer to another three-necked flask, add toluene (240 mL) to dissolve it, and cool to 50°C. While stirring, slowly add epichlorohydrin (88.9 g, 0.96 mol) and 30% NaOH aqueous solution (120.0 g, containing 0.90 mol NaOH) dropwise over 1.5 hours, controlling the temperature at 60°C. After the addition is complete, maintain the reaction at 60°C for 2.5 hours. The specific steps are as follows:

[0034]

[0035] (3) The organic phase was removed by vacuum distillation at 60°C to remove toluene and excess epichlorohydrin, and finally 86.8g of pale yellow viscous liquid was obtained.

[0036] In CDCl3, at 400MHz 1 ¹H NMR revealed the following characteristic peaks: δ = 8.55–8.50 ppm (m, 4H), corresponding to aromatic hydrogens on the naphthalene ring; δ = 8.10–8.05 ppm (m, 2H), corresponding to aromatic hydrogens at the ortho position on the naphthalene ring. Furthermore, δ = 4.25 ppm (t, 4H) represents the methylene proton in the ester bond (-COOCH²⁻); δ = 1.75 ppm (m, 4H), δ = 1.35 ppm (m, 4H), and δ = 1.28 ppm (m, 4H) correspond to methylene protons in the 1,6-hexanediol unit, respectively. The integral ratios of each signal conform to the expected alternating copolymer structure, indicating the successful synthesis of the target prepolymer.

[0037] Example 2: Preparation of toughened epoxy resin based on 2,6-naphthalenedicarboxylic acid and 1,4-butanediol

[0038] (1) Following step (1) of Example 1, 1,6-hexanediol was replaced with 1,4-butanediol (36.1 g, 0.4 mol), and other conditions remained unchanged to obtain a polyester prepolymer.

[0039] (2) The subsequent epoxidation and post-treatment steps were the same as in Example 1, yielding 83.6 g of a light yellow viscous liquid. The structural formula of the final product is:

[0040] Similarly, in CDCl3, at 400MHz 1 ¹H NMR revealed the following signals: δ = 8.54–8.49 ppm (m, 4H) and δ = 8.09–8.04 ppm (m, 2H) correspond to protons on the naphthalene ring. δ = 4.23 ppm (t, 4H) belongs to methylene protons in the ester bond, while δ = 1.72 ppm and δ = 1.68 ppm (both m, total 8H) represent methylene protons in the 1,4-butanediol unit. The splitting modes and integration ratios of all signals are consistent with the expected alternating copolymer structure.

[0041] Example 3: Preparation of toughened epoxy resin based on 2,6-naphthalenedicarboxylic acid and ethylene glycol

[0042] (1) Following step (1) of Example 1, 1,6-hexanediol was replaced with ethylene glycol (24.8 g, 0.4 mol), and other conditions remained unchanged to obtain a polyester prepolymer.

[0043] (2) The subsequent epoxidation and post-treatment steps were the same as in Example 1, yielding 80.5 g of a yellow viscous liquid. The structural formula of the final product is:

[0044] In CDCl3, at 400MHz 1 H NMR revealed proton signals in the naphthalene ring at δ = 8.53–8.48 ppm (m, 4H) and δ = 8.08–8.03 ppm (m, 2H). The signal at δ = 4.21 ppm (s, 4H) points to the methylene proton in the ethylene glycol unit, and its singlet characteristic indicates a highly symmetrical chemical environment. No obvious terminal hydroxyl signals were observed (e.g., no broad peak was observed at δ ≈ 2.5 ppm), indicating that the condensation reaction proceeded relatively completely.

[0045] Comparative Example 1: Preparation of unmodified 2,6-naphthalenedicarboxylic acid type epoxy resin (direct epoxidation)

[0046] (1) In a three-necked flask equipped with a stirrer, thermometer, water separator and nitrogen inlet tube, add 2,6-naphthalenedicarboxylic acid (40.4 g, 0.2 mol) and toluene (300 mL); introduce nitrogen gas, heat to reflux (110 °C), and azeotropically remove water for 2 hours.

[0047] (2) Cool the reaction solution to 50°C, and slowly add epichlorohydrin (43.7g, 0.47mol) and 30% NaOH aqueous solution (62.7g, containing 0.47mol NaOH) dropwise over 1.5 hours with stirring, maintaining the reaction temperature at 60-65°C; after the addition is complete, keep the reaction at 65°C for 4 hours. The specific steps are as follows:

[0048]

[0049] (3) After the reaction is complete, transfer the reaction solution to a separatory funnel, let it stand to separate into layers, and discard the aqueous phase; wash the organic phase three times with deionized water until neutral.

[0050] (4) The organic phase was removed by vacuum distillation at 60°C to remove toluene and excess epichlorohydrin, yielding 73.5 g of a light red viscous liquid.

[0051] Experimental Example 1: Epoxy Equivalent Test

[0052] The epoxy resins prepared in Examples 1-3 and Comparative Example 1 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 this invention is 215-225 g / eq.

[0053] Experimental Example 2: Elastic Modulus Test

[0054] According to standard GB / T 2567-2008, the epoxy resins prepared in Examples 1-3 and Comparative Example 1 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 3500-4000 MPa, which is relatively low.

[0055] Test Example 3: Glass Transition Temperature (Tg) Test

[0056] The glass transition temperatures (Tg) of the epoxy resin composites prepared in Examples 1-3 and Comparative Example 1 were tested using DSC or DMA under a nitrogen atmosphere. The heating rate was 10 °C / min, and the test temperature range was 25–200 °C. The glass transition temperatures (Tg) were recorded and analyzed to evaluate the thermal properties of the materials. The results are shown in Table 1. The glass transition temperature of the epoxy resin provided by this invention is 200–215 °C.

[0057] Experimental Example 4 Impact Strength Test

[0058] The epoxy resin composites prepared in Examples 1-3 and Comparative Example 1 were subjected to mechanical property tests using an AGS-X10 KN 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 10-25 KJ / m. 2 .

[0059] Table 1. Performance Test Results of Epoxy Resin Products

[0060]

[0061] 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. A naphthalene dicarboxylic acid type epoxy resin, characterized in that, The structural formula of the naphthalene dicarboxylic acid type epoxy resin is shown in compound I: Where R is -(CH2)2-, -(CH2)3-, -(CH2)4-, -(CH2)5- or -(CH2)6-.

2. A method for preparing a naphthalene-dicarboxylic acid type epoxy resin, characterized in that, The preparation process is as follows: Where R is -(CH2)2-, -(CH2)3-, -(CH2)4-, -(CH2)5- or -(CH2)6-.

3. The preparation method according to claim 2, characterized in that, The molar ratio of compound II to compound III is 1:2-2.4; the molar ratio of compound IV to compound V is 1:2.2-2.8; the catalyst is tetrabutyl titanate or dibutyltin dilaurate; the alkaline aqueous solution is a sodium hydroxide aqueous solution or potassium hydroxide aqueous solution with a mass fraction of 25-35%.

4. The preparation method according to claim 3, characterized in that, The specific steps for preparing compound IV from compound II include: adding compound II, compound III, and catalyst to the reaction system, heating to 150-180℃, maintaining the temperature for 4-6 hours, and obtaining a solution of compound IV after the reaction is complete.

5. The preparation method according to claim 4, characterized in that, The heat preservation reaction was carried out under a nitrogen atmosphere.

6. The preparation method according to claim 3, characterized in that, The specific steps for preparing compound I from compound IV include: dissolving compound IV in an organic solvent, cooling the temperature to 45-55℃, slowly adding compound V and an alkaline aqueous solution, and then keeping the temperature at 55-65℃ for 2-3 hours after the addition is complete. After post-treatment, compound I, i.e., naphthalene dicarboxylic acid type epoxy resin, is obtained.

7. The preparation method according to claim 6, characterized in that, The organic solvent is toluene or ethyl acetate.

8. The preparation method according to claim 6, characterized in that, The post-processing steps are, in sequence, separation, washing of the organic phase and vacuum distillation, followed by collection of the target fraction to obtain the purified product.

9. An application of a naphthalene dicarboxylic acid type epoxy resin, characterized in that, This includes the application of the naphthalene dicarboxylic acid type epoxy resin as described in claim 1 in the fields of flexible electronic packaging, low-temperature adhesives, and composite matrix.

10. The application according to claim 9, characterized in that, The glass transition temperature of the naphthalene dicarboxylic acid type epoxy resin is 200-215℃; the epoxy equivalent is 215-225 g / eq; the elastic modulus is 3500-4000 MPa; and the impact strength is 10-25 KJ / m. 2 .

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