An n-phenyl-p-phenylenediamine epoxy resin, its preparation method and application

Abstract

The application provides an N-phenyl-p-phenylenediamine epoxy resin and a preparation method and application thereof, and relates to the technical field of resin materials.The N-phenyl-p-phenylenediamine epoxy resin (ADPTGA) provided by the application contains a rigid benzene ring structure in the structure, and can improve the rigid strength of the epoxy system; in addition, since the ADPTGA has multiple epoxy groups and is similar to the structure of E-51, the ADPTGA can be uniformly dispersed in the system, the brittleness of pure E-51 can be reduced, and the mechanical properties of the epoxy resin cured product can be improved. Moreover, the N-phenyl-p-phenylenediamine epoxy resin provided by the application has a high epoxy value and low viscosity, can enhance the rigidity, toughness, high-temperature resistance and processing performance of the E-51 epoxy resin cured product, and has excellent product performance. The application is prepared by using a two-step method (ring-opening reaction and ring-closing reaction), the epoxy degree of raw materials is ensured, the raw materials are widely sourced, the operation is simple, and the application is suitable for industrial production.

Description

Technical Field

[0001] This invention relates to the field of resin materials technology, specifically to an N-phenyl-p-phenylenediamine epoxy resin, its preparation method, and its applications. Background Technology

[0002] Bisphenol A type epoxy resins (EP) possess advantages such as high storage stability, good processability, flexible formulation design, and low volume shrinkage during curing. Furthermore, cured EP products exhibit excellent mechanical properties, chemical resistance, electrical properties, and adhesive properties, making them widely used as thermosetting resins in machinery, electronics, aerospace, transportation, and construction. However, the rapid development of high-tech fields such as aerospace and electronics presents new challenges to thermosetting polymers. Thermosetting polymers must possess sufficient heat resistance and high-modulus composite material properties to meet the requirements of high-performance engineering. Based on the general correlation between resin structure and properties, it has been found that higher crosslinking density can effectively improve resin performance. Therefore, developing multifunctional multifunctional (trifunctional or tetrafunctional) epoxides is one of the most effective methods to achieve this requirement. Among them, multifunctional glycidylamine epoxy resins have attracted widespread attention due to their excellent high-temperature resistance and mechanical properties. Because these epoxy resins contain aromatic rings, ether bonds, and methylene bonds, they can form a highly cross-linked three-dimensional network structure when cured with an appropriate amount of curing agent. This significantly improves their heat resistance compared to general-purpose epoxy resins, making them widely used in high-temperature adhesives, high-temperature coatings, and high-temperature advanced composite materials.

[0003] N,N,N′,N′-Tetraglycidylamine-4,4′-diaminodiphenylmethane (TGDDM), a typical representative of multifunctional amine epoxides, has demonstrated superior performance as a matrix for aerospace fiber-reinforced composites since the 1970s. However, it still has some shortcomings, such as high viscosity, hard and brittle cured products, and reduced processability in common organic solvents, which greatly limits its applications. Therefore, the development of multifunctional glycidylamine epoxy resins with excellent thermal stability and processability is of great significance. Summary of the Invention

[0004] In view of this, the object of the present invention is to provide an N-phenyl-p-phenylenediamine epoxy resin, its preparation method, and its application. The N-phenyl-p-phenylenediamine epoxy resin provided by the present invention can significantly improve the rigidity, toughness, high temperature resistance, and processability of bisphenol A type E-51 epoxy resin cured products.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] This invention provides an N-phenyl-p-phenylenediamine epoxy resin having the structure shown in Formula I:

[0007]

[0008] The N-phenyl-p-phenylenediamine epoxy resin has an epoxy value ≥ 0.58 eq / 100g and a viscosity ≤ 7000 mPa·s.

[0009] Preferably, the N-phenyl-p-phenylenediamine epoxy resin has an epoxy value of 0.58–0.68 eq / 100g and a viscosity of 5000–7000 mPa·s.

[0010] This invention provides a method for preparing the N-phenyl-p-phenylenediamine epoxy resin described in the above technical solution, comprising the following steps:

[0011] N-phenyl-p-phenylenediamine, epichlorohydrin, a phase transfer catalyst, and an organic solvent are mixed to carry out a ring-opening reaction. Then, an inorganic alkaline solution is added to carry out a ring-closing reaction to obtain N-phenyl-p-phenylenediamine epoxy resin.

[0012] Preferably, the molar ratio of N-phenyl-p-phenylenediamine to epichlorohydrin is 1:3 to 10.

[0013] Preferably, the molar ratio of the N-phenyl-p-phenylenediamine to the inorganic base in the inorganic base solution is 1:3 to 3.6.

[0014] Preferably, the organic solvent includes one or more of diethoxymethane, dipropoxymethane, dibutoxymethane, toluene, and xylene.

[0015] Preferably, the phase transfer catalyst comprises one or more of benzyltriethylammonium chloride, benzyltrimethylammonium chloride, tetrabutylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium hydrogen sulfate, trioctylmethylammonium chloride, dodecyltrimethylammonium chloride, and tetradecyltrimethylammonium chloride;

[0016] The mass of the phase transfer catalyst is 0.05% to 0.5% of the total mass of N-phenyl-p-phenylenediamine, epichlorohydrin, and inorganic base.

[0017] Preferably, the ring-opening reaction is carried out at a temperature of 30–130°C for 2–8 hours.

[0018] Preferably, the closed-loop reaction is carried out at a temperature of 30–100°C for a time of 0.5–5 hours.

[0019] This invention provides the application of the N-phenyl-p-phenylenediamine epoxy resin described in the above-described technical solution or the N-phenyl-p-phenylenediamine epoxy resin prepared by the above-described technical solution as a reinforcing material in epoxy resin modification.

[0020] The N-phenyl-p-phenylenediamine epoxy resin (ADPTGA) provided by this invention contains a rigid benzene ring structure, which can improve the rigidity and strength of the epoxy system. Furthermore, because ADPTGA has polyepoxy groups, similar to the E-51 structure, it can be uniformly dispersed in the system. Adding it to the E-51 epoxy resin system can improve the mechanical properties of the cured E-51 epoxy resin. Moreover, the N-phenyl-p-phenylenediamine epoxy resin provided by this invention has a high epoxy value and low viscosity, which can enhance the rigidity, toughness, high-temperature resistance, and processability of the cured E-51 epoxy resin, resulting in excellent product performance.

[0021] This invention also provides a method for preparing the epoxy resin described in the above-mentioned technical solution. This invention uses N-phenyl-p-phenylenediamine as a raw material for modification, employing a two-step method (ring-opening reaction and ring-closing reaction) to ensure the degree of epoxidation of the raw material, resulting in a novel liquid epoxy resin with low viscosity and high epoxy value. This resin is used to modify bisphenol A type epoxy resin, effectively enhancing the rigidity and toughness of E-51 epoxy resin cured products, as well as effectively improving their high-temperature resistance and processing performance, exhibiting excellent overall performance. Furthermore, the preparation method provided by this invention utilizes widely available raw materials, is simple to operate, and is suitable for industrial production.

[0022] Furthermore, by controlling the proportions of each raw material and the temperature, time, and pressure of the ring-opening and ring-closing reactions, this invention ensures the degree of epoxidation of the raw materials, thereby obtaining an N-phenyl-p-phenylenediamine epoxy resin with an epoxy value of 0.58–0.68 eq / 100g and a viscosity of 5000–7000 mPa·s. This epoxy resin has a high epoxy value and low viscosity, which can improve the high-temperature resistance, rigidity, toughness, and processing performance of the cured epoxy resin. Attached Figure Description

[0023] Figure 1 Infrared spectra of N-phenyl-p-phenylenediamine (ADPA) and the N-phenyl-p-phenylenediamine epoxy resin (ADPTGA) prepared in Example 1;

[0024] Figure 2 The 1H NMR spectrum of N-phenyl-p-phenylenediamine;

[0025] Figure 3 The NMR spectrum of the N-phenyl-p-phenylenediamine epoxy resin prepared in Example 1 is shown in the figure.

[0026] Figure 4 Scanning electron microscope (SEM) images of the impact fracture surfaces of pure E-51 epoxy resin cured product (a) and N-phenyl-p-phenylenediamine epoxy resin curing product (b) with an N-phenyl-p-phenylenediamine content of 10 wt%.

[0027] Figure 5Thermogravimetric analysis (TGA) curves of pure E-51 epoxy resin cured product and N-phenyl-p-phenylenediamine epoxy resin incorporated at 10 wt%. Detailed Implementation

[0028] This invention provides an N-phenyl-p-phenylenediamine epoxy resin having the structure shown in Formula I:

[0029]

[0030] The N-phenyl-p-phenylenediamine epoxy resin has an epoxy value ≥ 0.58 eq / 100g and a viscosity ≤ 7000 mPa·s.

[0031] In this invention, the epoxy value of the N-phenyl-p-phenylenediamine epoxy resin is preferably 0.58–0.68 eq / 100g, more preferably 0.6–0.65 eq / 100g, and specifically preferably 0.60 eq / 100g, 0.61 eq / 100g, 0.62 eq / 100g, or 0.64 eq / 100g; the viscosity of the N-phenyl-p-phenylenediamine epoxy resin is preferably 5000–7000 mPa·s, more preferably 5400–6500 mPa·s, and specifically preferably 5400 mPa·s, 5800 mPa·s, 6000 mPa·s, or 6300 mPa·s. The N-phenyl-p-phenylenediamine epoxy resin provided by this invention has a high epoxy value and a low viscosity, and can be used to enhance the toughness, rigidity, and high-temperature resistance of epoxy resins.

[0032] The present invention provides a method for preparing the N-phenyl-p-phenylenediamine epoxy resin described in the above technical solution, comprising the following steps: mixing N-phenyl-p-phenylenediamine, epichlorohydrin, a phase transfer catalyst and an organic solvent to carry out a ring-opening reaction, and then adding an inorganic alkaline solution to carry out a ring-closing reaction to obtain the N-phenyl-p-phenylenediamine epoxy resin.

[0033] Unless otherwise specified, all materials and equipment used in this invention are commercially available products in the field.

[0034] In this invention, the molar ratio of N-phenyl-p-phenylenediamine to epichlorohydrin is preferably 1:3 to 10, more preferably 1:3 to 5, and specifically preferably 1:3, 1:4 or 1:5.

[0035] In this invention, the organic solvent preferably includes one or more of diethoxymethane, dipropoxymethane, dibutoxymethane, toluene, and xylene. In this invention, the mass ratio of N-phenyl-p-phenylenediamine to the organic solvent is preferably 1:2 to 3.6, more preferably 1:2 to 3.

[0036] In this invention, the phase transfer catalyst preferably comprises one or more of benzyltriethylammonium chloride (BTEAC), benzyltrimethylammonium chloride (BTMAC), tetrabutylammonium bromide (TBAB), tetrabutylammonium chloride (TBAC), tetrabutylammonium bisulfate, trioctylmethylammonium chloride, dodecyltrimethylammonium chloride, and tetradecyltrimethylammonium chloride, more preferably benzyltriethylammonium chloride (BTEAC), tetrabutylammonium bromide (TBAB), or tetrabutylammonium chloride; the mass of the phase transfer catalyst is preferably 0.05-0.5% of the total mass of N-phenyl-p-phenylenediamine, epichlorohydrin, and inorganic base, more preferably 0.1-0.2%.

[0037] In this invention, the mixing of N-phenyl-p-phenylenediamine, epichlorohydrin, phase transfer catalyst, and organic solvent is preferably carried out by mixing N-phenyl-p-phenylenediamine, epichlorohydrin, and organic solvent until N-phenyl-p-phenylenediamine is completely dissolved, followed by dropwise addition of epichlorohydrin. In this invention, the dropwise addition time of epichlorohydrin is preferably 0.5–6 h, more preferably 1–2 h. The dropwise addition method used in this invention has the advantage of stable reaction, preventing a sudden temperature rise caused by a vigorous ring-opening reaction, which could affect product quality and create hazards.

[0038] In this invention, the temperature of the ring-opening reaction is 30–130°C, more preferably 30–100°C, and even more preferably 40–90°C; the time of the ring-opening reaction is preferably 2–8 h, more preferably 2–5 h, and even more preferably 3–4 h; the pressure of the ring-opening reaction is preferably atmospheric pressure.

[0039] In this invention, the mass concentration of the inorganic alkali solution is preferably 20-40%, more preferably 25-40%, and the inorganic alkali in the inorganic alkali solution preferably includes NaOH and / or KOH. In this invention, the molar ratio of the N-phenyl-p-phenylenediamine to the inorganic alkali is preferably 1:3-3.6, more preferably 1:3.1-3.5, and even more preferably 1:3.1-3.2. In this invention, the inorganic alkali solution is preferably added dropwise, and the dropwise addition time is preferably 0.5-6 hours, more preferably 1-2 hours.

[0040] In this invention, the temperature of the closed-loop reaction is 30–100°C, more preferably 30–70°C, and even more preferably 30–60°C; the time of the closed-loop reaction is preferably 0.5–5 h, more preferably 0.5–2 h, and even more preferably 1–2 h; and the pressure of the closed-loop reaction is preferably atmospheric pressure.

[0041] This invention employs a two-step ring-opening and ring-closing reaction, and controls the temperature, time, and pressure of the ring-opening and ring-closing reactions to ensure the degree of glycidyl amination of the raw materials, so that the final N-phenyl-p-phenylenediamine epoxy resin has an epoxy value of 0.58-0.68 eq / 100g and a viscosity of 5000-7000 mPa·s.

[0042] Following the ring-closure reaction, the present invention preferably further includes purification, which includes: solid-liquid separation of the ring-closure reaction liquid obtained from the ring-closure reaction, separation of the resulting liquid components into layers, and sequential washing, neutralization, and distillation of the resulting organic phase to obtain N-phenyl-p-phenylenediamine epoxy resin. The present invention does not have specific limitations on the solid-liquid separation; any solid-liquid separation method well known to those skilled in the art can be used, such as filtration, vacuum filtration, or centrifugation. In the present invention, the purpose of the layering is to remove the brine. In the present invention, the neutralizing agent preferably includes one or more of sodium dihydrogen phosphate, potassium dihydrogen phosphate, and acetic acid; the present invention does not have specific limitations on the amount of the neutralizing agent, and the pH value after neutralization should be controlled at 7-8 (more preferably 7-7.5). The present invention does not have specific limitations on the distillation conditions, as long as the organic solvent and unreacted epichlorohydrin are completely recovered.

[0043] The present invention does not impose any particular limitation on the apparatus used for the preparation of N-phenyl-p-phenylenediamine epoxy resin; any reaction apparatus well known to those skilled in the art can be used. Specifically, the two-step ring-opening and ring-closing reactions are carried out in a four-necked flask. N-phenyl-p-phenylenediamine, an organic solvent, and a phase transfer catalyst are added to a four-necked flask equipped with a mechanically sealed stirrer, a reflux condenser, and a thermometer. The temperature is raised to the ring-opening reaction temperature of the two-step method, and epichlorohydrin is added dropwise to carry out the two-step ring-opening reaction. After the reaction is completed, the temperature is lowered to the ring-closing reaction temperature of the two-step method, and an inorganic alkaline solution is added to carry out the ring-closing reaction of the two-step method.

[0044] This invention provides the application of the N-phenyl-p-phenylenediamine epoxy resin described in the above-described technical solution or the N-phenyl-p-phenylenediamine epoxy resin prepared by the above-described technical solution as a reinforcing material in epoxy resin modification.

[0045] In this invention, the application method preferably includes the following steps: mixing the N-phenyl-p-phenylenediamine epoxy resin, bisphenol A type epoxy resin, and a curing agent, and then curing to obtain a cured epoxy resin product. In this invention, the N-phenyl-p-phenylenediamine epoxy resin preferably accounts for 5-20% of the mass of the bisphenol A type epoxy resin, more preferably 10-15%. In this invention, the bisphenol A type epoxy resin preferably includes E-51 bisphenol A type epoxy resin. In this invention, the curing agent preferably includes a 4,4'-diaminodiphenylmethane curing agent. In this invention, the curing is preferably staged curing, which preferably includes sequentially curing at 100-120°C (more preferably 100-110°C) for 1-3 hours (more preferably 2 hours), at 130-140°C (more preferably 130-135°C) for 1-3 hours (more preferably 2 hours), at 150-160°C (more preferably 155-160°C) for 1-3 hours (more preferably 2 hours), and then aging at room temperature for 5-10 days (more preferably 6-7 days). The N-phenyl-p-phenylenediamine epoxy resin provided by this invention can significantly improve the rigidity, toughness, and high-temperature resistance of bisphenol A type E-51 epoxy resin cured products.

[0046] To further illustrate the present invention, the N-phenyl-p-phenylenediamine epoxy resin, its preparation method, and its application are described in detail below with reference to the accompanying drawings and embodiments, but these descriptions should not be construed as limiting the scope of protection of the present invention.

[0047] Raw materials used in the examples: N-phenyl-p-phenylenediamine (ADPA), tetrabutylammonium bromide, tetrabutylammonium chloride, benzyltriethylammonium chloride, sodium hydroxide, potassium hydroxide, epichlorohydrin (ECH), E-51 bisphenol A epoxy resin, and 4,4'-diaminodiphenylmethane were industrial grade and provided by Anhui Xinyuan Technology Co., Ltd.; hydrochloric acid, acetone, xylene, and toluene were all analytical grade and produced by Nanjing Chemical Reagent Co., Ltd.

[0048] The epoxy value of N-phenyl-p-phenylenediamine epoxy resin was determined by the hydrochloric acid-acetone method.

[0049] FTIR measurements were performed using a Nicolet FTIR-360 Fourier transform infrared spectrometer (USA): the potassium bromide coating method was employed, and the measurement range was 400–4000 cm⁻¹. -1 .

[0050] The structure of the polymer was characterized using a Burker Fourier Transform 600 spectrometer with deuterated chloroform as the solvent.

[0051] Scanning electron microscopy test: After the fracture surface of the impact sample was plated with gold, the morphology of the bubbles was observed using a Quanta 200 environmental scanning electron microscope.

[0052] The thermal stability of the cured material was tested and analyzed using a TGA / DSCl / 1100SF thermogravimetric analyzer. The test parameters of the thermogravimetric analyzer were set as follows: heating range 30~700℃, heating rate 10℃ / min, carrier gas nitrogen, and its flow rate 40mL / min.

[0053] 4,4'-Diaminodiphenylmethane is a curing agent for epoxy resin curing products, and its dosage is calculated as shown in Formula 1:

[0054] G = (M × E) / Hn (Equation 1);

[0055] In Formula 1: G—the number of grams of curing agent required for 100g of epoxy resin, g; M—the molecular weight of the curing agent, g / mol; E—the epoxy value of the epoxy resin, eq / 100g; Hn—the total number of active hydrogens in the curing agent molecule.

[0056] Example 1

[0057] 46g of N-phenyl-p-phenylenediamine, 120g of toluene, and 1.2g of benzyltriethylammonium chloride were added to a four-necked flask equipped with a reflux condenser, thermometer, and constant-pressure dropping funnel. The temperature was raised to 70℃, and after the solid N-phenyl-p-phenylenediamine was completely dissolved, 69.4g of ECH was added dropwise over 1 hour. The reaction was maintained at 70℃ for 4 hours, then cooled to 40℃, and 93.7g of a 32% NaOH aqueous solution was added dropwise over 1 hour. The reaction was then maintained at this temperature for 1 hour. After the reaction was completed, the mixture was filtered, and the filtrate was separated into layers. The brine phase was removed, and sodium dihydrogen phosphate was added to the organic phase for neutralization. The mixture was washed with water, and the vacuum degree was controlled at -0.09MPa and the reactor temperature ≤130℃. The solvent toluene was recovered by distillation to obtain N-phenyl-p-phenylenediamine epoxy resin with an epoxy value of 0.61 eq / 100g and a viscosity of 5400 mPa·s.

[0058] Figure 1 The infrared spectra of N-phenyl-p-phenylenediamine (ADPA) and N-phenyl-p-phenylenediamine epoxy resin (ADPTGA) are shown; it can be seen that 2919 cm⁻¹ -1 The peak at 1598 cm⁻¹ is the absorption peak of the CH stretching vibration on the alkyl chain. -1 and 1515cm -1 The peak at 827 cm⁻¹ is the absorption peak of the C=C skeleton vibration on the benzene ring. -1 The peak at 1373 cm⁻¹ was identified as a position indicator peak for the benzene ring, and no other indicator peaks were found on the benzene ring. Therefore, it can be confirmed that no other groups were attached to the benzene ring after the reaction. -1 The peak at this location is the CN peak, 1234 cm. -1The peak at 906 cm⁻¹ represents the absorption peak of the asymmetric stretching vibration of the COC structure, while the characteristic absorption peak of the epoxy group appears at 906 cm⁻¹. -1 Place.

[0059] Figure 2 This is the 1H NMR spectrum of N-phenyl-p-phenylenediamine.

[0060] Figure 3 The image shows the 1H NMR spectrum of N-phenyl-p-phenylenediamine epoxy resin. From the image, we can see that δ = 3.78 × 10⁻⁶. -6 and δ = 3.57 × 10 -6 The peak at δ = 2.87 × 10⁻⁶ belongs to the hydrogen in the methylene group bonded to the epoxy group. -6 The peak belongs to the hydrogen atom of the methine group in the epoxy group, at δ = 3.26 × 10⁻⁶. -6 and δ=2.6×10 -6 The peaks on the left and right belong to the methylene peaks on the epoxy group.

[0061] Analysis of both infrared spectroscopy and nuclear magnetic resonance (NMR) data reveals that the main component structure of N-phenyl-p-phenylenediamine epoxy resin is shown in Formula I.

[0062] Example 2

[0063] 46g of N-phenyl-p-phenylenediamine, 100g of xylene, and 0.8g of tetrabutylammonium bromide were added to a four-necked flask equipped with a reflux condenser, thermometer, and constant-pressure dropping funnel. The temperature was raised to 70℃, and after all the solid N-phenyl-p-phenylenediamine was dissolved, 74g of ECH was added dropwise over 1 hour. The reaction was maintained at 80℃ for 5 hours, then cooled to 30℃, and 124g of a 25% NaOH aqueous solution was added dropwise over 1 hour. The reaction was then maintained at this temperature for 1 hour. After the reaction was completed, the mixture was filtered, and the filtrate was separated into layers. The brine phase was removed, and sodium dihydrogen phosphate was added to the organic phase for neutralization. The mixture was washed with water, and the vacuum was controlled at -0.095MPa and the reactor temperature ≤130℃. The solvent xylene was recovered by distillation to obtain N-phenyl-p-phenylenediamine epoxy resin with an epoxy value of 0.60 eq / 100g and a viscosity of 5800 mPa·s.

[0064] Example 3

[0065] 46g of N-phenyl-p-phenylenediamine, 100g of xylene, and 1.4g of benzyltetrabutylammonium chloride were added to a four-necked flask equipped with a reflux condenser, thermometer, and constant-pressure dropping funnel. The temperature was raised to 90℃, and after the solid N-phenyl-p-phenylenediamine was completely dissolved, 115.6g of ECH was added dropwise over 2 hours. The reaction was maintained at 70℃ for 6 hours, then cooled to 50℃, and 80g of 40% KOH aqueous solution was added dropwise over 1 hour. The reaction was then maintained at this temperature for 1 hour. After the reaction was completed, the mixture was filtered, and the filtrate was separated into layers. The brine phase was removed, and sodium dihydrogen phosphate was added to the organic phase for neutralization. The mixture was washed with water, and the vacuum was controlled at -0.095MPa and the reactor temperature ≤130℃. The solvent xylene was recovered by distillation to obtain N-phenyl-p-phenylenediamine epoxy resin with an epoxy value of 0.64 eq / 100g and a viscosity of 6000 mPa·s.

[0066] Example 4

[0067] 46g of N-phenyl-p-phenylenediamine, 120g of diethoxymethane, and 0.6g of benzyltriethylammonium chloride were added to a four-necked flask equipped with a reflux condenser, a thermometer, and a constant-pressure dropping funnel. The temperature was raised to 70°C, and after all the solid N-phenyl-p-phenylenediamine had dissolved, 138.8g of ECH was added dropwise over 2 hours. The reaction was then carried out at 90°C for 3 hours. The temperature was lowered to 50°C, and 144.6g of 32% KOH aqueous solution was added dropwise over 1 hour. The reaction was then maintained at this temperature for 1 hour. After the reaction was completed, the mixture was filtered, and the resulting filtrate was separated into layers. The brine phase was removed, and sodium dihydrogen phosphate was added to the organic phase for neutralization. The mixture was washed with water, and the reaction was carried out under normal pressure and then under reduced pressure (vacuum degree controlled at -0.05MPa) with a reactor temperature ≤130℃. The solvent diethoxymethane was recovered by distillation to obtain N-phenyl-p-phenylenediamine epoxy resin with an epoxy value of 0.62 eq / 100g and a viscosity of 6300 mPa·s.

[0068] Application Example 1

[0069] The N-phenyl-p-phenylenediamine epoxy resin prepared in Example 1 was incorporated into 65g of E-51 bisphenol A epoxy resin, followed by the addition of 3.25g of 4,4'-diaminodiphenylmethane for curing. The curing conditions were as follows: temperature was increased from room temperature to 100℃ and held for 2h, then increased to 130℃ and held for 2h, and then increased to 160℃ and held for 2h (recorded as 100℃ / 2h + 130℃ / 2h + 160℃ / 2h). The resin was then aged at room temperature for 7 days. The curing performance data are shown in Table 1. The amount of N-phenyl-p-phenylenediamine epoxy resin incorporated was calculated as the mass fraction of N-phenyl-p-phenylenediamine epoxy resin in the bisphenol A epoxy resin.

[0070] Table 1. Performance results of N-phenyl-p-phenylenediamine epoxy resin after incorporation.

[0071]

[0072] Table 1 shows that the incorporation of N-phenyl-p-phenylenediamine epoxy resin significantly improves the tensile strength (52.2–62.84 MPa), flexural strength (104.35–115.39 MPa), elongation at break (3.44–5.15%), and impact strength (24.2–25.28 kJ / m) of E-51 epoxy resin cured products. 2 Among them, the epoxy resin with 15% N-phenyl-p-phenylenediamine admixture has the best tensile strength and elongation at break of the cured product, as well as high flexural strength and impact strength, and its comprehensive mechanical properties are the best.

[0073] When the N-phenyl-p-phenylenediamine epoxy resin content was 10 wt%, the impact fracture surface of the cured product was tested. Figure 4 Scanning electron microscopy (SEM) images of the impact fracture surfaces of pure E-51 epoxy resin cured product (a) and N-phenyl-p-phenylenediamine epoxy resin curing product (b) with an N-phenyl-p-phenylenediamine content of 10 wt%. Figure 4 It can be seen that the surface of the pure E-51 cured product is rough, while when 10wt% ADPTGA is added, the fracture surface of the cured product becomes smooth, the crack direction is unidirectional and regular, exhibiting typical rigid fracture characteristics. This is because adding a small amount of ADPTGA to replace E-51 increases the crosslinking density of the composite resin. Therefore, compared with pure E-51 resin, the rigidity of the composite resin is enhanced, and both its tensile strength and flexural strength are greater than those of E-51 resin.

[0074] The thermogravimetric analysis (TGA) curves of cured N-phenyl-p-phenylenediamine epoxy resin with a dopant content of 10 wt% and cured E-51 epoxy resin were obtained using a Shimadzu DTG-60 thermogravimetric analyzer (Japan). The results are shown in the figure. Figure 5 As shown, from Figure 5 It can be seen that the initial decomposition temperature of the cured product with 10wt% N-phenyl-p-phenylenediamine epoxy resin is slightly lower than that of the cured product with pure E-51 epoxy resin. Therefore, it can be seen that the thermal properties of the cured product did not decrease significantly after the addition of ADPTGA.

[0075] As can be seen from the above embodiments, the N-phenyl-p-phenylenediamine epoxy resin provided by the present invention has a high epoxy value. When incorporated into E-51 resin, it can improve the toughness, rigidity and high temperature resistance of the cured product.

[0076] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, not all embodiments. People can obtain other embodiments based on the present invention without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. An N-phenyl-p-phenylenediamine epoxy resin, characterized in that, It has the structure shown in Equation I: The N-phenyl-p-phenylenediamine epoxy resin has an epoxy value ≥0.58 eq / 100g and a viscosity ≤7000 mPa·s.

2. The N-phenyl-p-phenylenediamine epoxy resin according to claim 1, characterized in that, The N-phenyl-p-phenylenediamine epoxy resin has an epoxy value of 0.58–0.68 eq / 100g and a viscosity of 5000–7000 mPa·s.

3. The method for preparing the N-phenyl-p-phenylenediamine epoxy resin according to claim 1 or 2, characterized in that, Includes the following steps: N-phenyl-p-phenylenediamine, epichlorohydrin, a phase transfer catalyst, and an organic solvent are mixed to carry out a ring-opening reaction. Then, an inorganic alkaline solution is added to carry out a ring-closing reaction to obtain N-phenyl-p-phenylenediamine epoxy resin.

4. The preparation method according to claim 3, characterized in that, The molar ratio of N-phenyl-p-phenylenediamine to epichlorohydrin is 1:3 to 10.

5. The preparation method according to claim 3, characterized in that, The molar ratio of the N-phenyl-p-phenylenediamine to the inorganic base in the inorganic base solution is 1:3 to 3.

6.

6. The preparation method according to claim 3, characterized in that, The organic solvent includes one or more of diethoxymethane, dipropoxymethane, dibutoxymethane, toluene, and xylene.

7. The preparation method according to claim 3, characterized in that, The phase transfer catalyst includes one or more of benzyltriethylammonium chloride, benzyltrimethylammonium chloride, tetrabutylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium hydrogen sulfate, trioctylmethylammonium chloride, dodecyltrimethylammonium chloride, and tetradecyltrimethylammonium chloride; The mass of the phase transfer catalyst is 0.05% to 0.5% of the total mass of N-phenyl-p-phenylenediamine, epichlorohydrin, and inorganic base.

8. The preparation method according to claim 3, characterized in that, The ring-opening reaction is carried out at a temperature of 30–130°C for 2–8 hours.

9. The preparation method according to claim 3, characterized in that, The closed-loop reaction is carried out at a temperature of 30–100°C for a time of 0.5–5 hours.

10. The use of the N-phenyl-p-phenylenediamine epoxy resin according to any one of claims 1 to 2 or the N-phenyl-p-phenylenediamine epoxy resin prepared by the preparation method according to any one of claims 3 to 9 as a reinforcing material in epoxy resin modification.

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