Epoxy resin composition, flame-retardant epoxy resin, preparation method and application thereof

Abstract

Epoxy resin composition, flame-retardant epoxy resin, and preparation method and application thereof, relating to the technical field of epoxy resins, solve the problem that the properties of epoxy resins for existing hydrogen storage cylinders do not meet the requirements of production and application. Under a nitrogen atmosphere, dissolve 2-(4-hydroxyphenyl)ethylamine in a solvent, add hydroxybenzaldehyde, and reflux the reaction. Precipitate the crude product with deionized water, purify it with methanol and ethanol, evaporate the solvent under vacuum and then dry it under vacuum to obtain an intermediate; under a nitrogen atmosphere, dissolve the intermediate in 3-chloropropylene oxide, add tetrabutylammonium bromide and reflux the reaction. After cooling the solution, add an aqueous sodium hydroxide solution and continue the reaction. Cool the mixture to room temperature, wash it repeatedly with deionized water to remove by-products, add anhydrous magnesium sulfate to dry the reaction mixture overnight, then evaporate and dry under vacuum to remove unreacted 3-chloropropylene oxide to obtain the target product. The present invention can be applied to the preparation of the wall of a type-IV fully-wound hydrogen storage cylinder.

Description

Technical Field

[0001] The present invention relates to the technical field of epoxy resins, and particularly relates to an epoxy resin composition, a flame-retardant epoxy resin, and a preparation method and application thereof. Background Art

[0002] Epoxy resin (EP) has the advantages of high bonding strength, small curing shrinkage rate, no small molecule volatiles, good process formability, heat resistance, good chemical stability, low cost, wide source and reasonable price. Moreover, the adjustable molecular structure enables the adjustment of the applicability and functionality of monomers, and it is widely used in the fields of aerospace, mechanical manufacturing, electronic engineering, transportation, etc. However, the inherent disadvantages of the cured epoxy resin system, such as brittleness or lack of crack propagation resistance caused by high cross-linking density and strong covalent network, and the high flammability of epoxy resin itself, resulting in a high fire risk, limit its development in many fields.

[0003] However, the development of high-performance epoxy resins faces two obstacles: (1) the unsustainability of its petroleum-based raw materials in the life cycle, from production, use to waste; (2) it is difficult to further improve special properties, such as dielectric properties and flame retardant properties. At present, most epoxy resins are derived from petroleum resources, especially bisphenol A type epoxy resins, and petroleum resources are non-renewable resources. With the decreasing reserves, it will inevitably lead to the continuous increase in the cost of polymer materials derived from petroleum resources. In addition, bisphenol A is suspected of having physiological toxicity and has been restricted in many countries such as Europe. Therefore, in the current situation of the increasingly depleted petroleum resources, there is an urgent need to use raw materials from other sources to produce epoxy resins and reduce the dependence on petroleum resources. Finding sustainable, high-quality, cheap and non-toxic petroleum substitutes is the key to the existence and development of the polymer industry. It is particularly important to develop substitutes with renewable resources and comparable properties.

[0004] The development trend of hydrogen storage cylinder technology is lightweight, high pressure, high hydrogen storage density, and long life. Compared with traditional metal materials, polymer composites can reduce the wall thickness of the storage tank, increase the capacity and hydrogen storage efficiency, and reduce the energy consumption cost during long-distance transportation while maintaining the same pressure resistance level. Therefore, the performance of epoxy resin in the composite material is the key to the preparation of type IV hydrogen storage cylinders, requiring the resin to have a low curing temperature, a short curing time, a high glass transition temperature, and good rigidity of the composite material.

[0005] The viscosity of epoxy resin is also one of the most important indicators of the properties of epoxy resin. A lower viscosity is beneficial to the application of epoxy resin in the field of filament winding molding. However, DGEBA (bisphenol A epoxy resin) itself has a high viscosity, making processing challenging. In response, researchers often add diluents to DGEBA to reduce viscosity, improve fluidity and processability. Although this method improves the processing performance to a certain extent, the use of additives affects other properties, such as thermal stability, mechanical properties and glass transition temperature. Therefore, designing an epoxy resin with low viscosity and high performance according to the molecular structure not only eliminates the step of adding fillers, but also does not reduce the properties of the resin itself, which is extremely popular in industrial production.

[0006] Chinese patent document CN118755051A, "A Low-Viscosity High-Equivalent Epoxy Resin and Its Preparation Method and Application" (published on October 11, 2024), discloses a method for reducing viscosity by locally imidizing amic acid to modify epoxy resin, and proposes a solution to the problem that it is difficult to prepare a low-viscosity high-equivalent epoxy resin for waterborne epoxy resin without using active diluents. However, this resin itself cannot be flame-retardant, the raw materials cause relatively large environmental pollution, the preparation process is complex, the performance improvement is not obvious, and it is difficult to achieve large-scale production and application. Summary of the Invention

[0007] In order to solve the problem that the properties of epoxy resin for existing hydrogen storage cylinders do not meet the requirements of production and application, the present invention proposes an epoxy resin composition, a flame-retardant epoxy resin and its preparation method and application.

[0008] The technical solution of the present invention is specifically as follows:

[0009] An epoxy resin composition, the structural formula of the epoxy resin composition is one of the following structural formulas:

[0010] 。

[0011] The present invention also provides a preparation method of the above epoxy resin composition, comprising the following steps:

[0012] S1. Dissolve 2-(4-hydroxyphenyl)ethylamine in a solvent under a nitrogen atmosphere, add hydroxybenzaldehyde, and reflux and react. Precipitate the crude product with deionized water, then purify with methanol and ethanol. After vacuum evaporating the solvent, dry in vacuum to obtain the intermediate TSA;

[0013] S2. Dissolve the intermediate in 3-chloropropylene oxide under a nitrogen atmosphere, then add tetrabutylammonium bromide, and reflux the reaction. After cooling the solution to 50 °C, add an aqueous sodium hydroxide solution and continue the reaction. After the reaction is completed, cool the mixture to room temperature, wash it repeatedly with deionized water to remove by-products, add an appropriate amount of anhydrous magnesium sulfate to dry the reaction mixture overnight, then evaporate, and subsequently dry it under vacuum to remove the unreacted 3-chloropropylene oxide, obtaining the target product, flame-retardant epoxy resin TSE.

[0014] Preferably, the hydroxybenzaldehyde is o-hydroxybenzaldehyde, m-hydroxybenzaldehyde or p-hydroxybenzaldehyde.

[0015] Preferably, the solvent in step S1 is absolute ethanol; the temperature of the reflux reaction is 70 °C, and the time of the reflux reaction is 4 h to 6 h.

[0016] Preferably, the temperature of the reflux reaction in step S2 is 100 °C, and the time of the reflux reaction is 2 h to 4 h; the evaporation time is 1 h to 3 h; the time of the vacuum drying is 12 h to 14 h.

[0017] Preferably, the mass concentration of the aqueous sodium hydroxide solution is 40 wt%, and the reaction time after adding the sodium hydroxide solution is 4 h to 6 h.

[0018] The present invention also provides a flame-retardant epoxy resin cured from the above epoxy resin composition.

[0019] A preparation method of the above flame-retardant epoxy resin includes the following steps:

[0020] Mix the epoxy resin composition with a curing agent, stir evenly and place it in a vacuum oven. When there are no bubbles in the mixture under vacuum, quickly pour it into a mold preheated at 70 °C, then cure it at 75 °C for 1 h, then adjust the temperature to 110 °C and cure it for another 3 h to obtain the flame-retardant epoxy resin.

[0021] Preferably, the curing agent is 4,4'-diaminodiphenylmethane.

[0022] The present invention also provides an application of the above epoxy resin composition or flame-retardant epoxy resin, specifically as a raw material for the preparation of the wall of a type-IV fully-wrapped hydrogen storage cylinder.

[0023] Compared with the prior art, the specific beneficial effects of the present invention are:

[0024] The conjugated rigid structure formed by the Schiff base and the benzene ring in the epoxy resin composition provided by the present invention can form a denser cross-linked structure, thereby enhancing the resin strength, modulus, and glass transition temperature. At the same time, the Schiff base degrades into carbon earlier, which can hinder the further degradation of the polymer matrix and prevent combustion. The dense carbon layer forms an oxide protective film on the material surface, which can prevent the spread and propagation of the flame, reduce the combustion rate, inhibit the generation of combustible gases, and have a flame retardant effect on oxidation and thermal decomposition, thereby reducing the released heat. The reduction of the heat release is beneficial for the overall combustion environment to be suitable for personnel to escape and can also reduce the ignition of nearby non-flame-retardant materials.

[0025] The novel low-viscosity enhanced intrinsically flame-retardant epoxy resin provided by the present invention is prepared from green and renewable bio-based raw materials, which is environmentally friendly and has low viscosity, high strength, high glass transition temperature, excellent flame retardant performance, and reduces the curing temperature. It not only provides a new choice for the field of high-performance epoxy resins but also provides a more suitable resin matrix for hydrogen energy, especially for type IV fully wound hydrogen storage cylinders. The small-molecule flame-retardant epoxy resin TSE can effectively reduce the viscosity of the mixture to reach the appropriate viscosity for wet winding of type IV hydrogen storage cylinders, better infiltrate carbon fibers, and reduce the generation of bubbles. The lower curing temperature can ensure that the plastic inner liner of the type IV hydrogen storage cylinder after curing of the composite material will not fail due to high temperature, and the overall loading pressure of the cylinder will not be affected by the collapse of the inner liner. The higher glass transition temperature can improve the working temperature of the hydrogen storage cylinder and improve safety at the same time.

[0026] The reaction process of the present invention is easy to operate and the preparation method is simple, which is suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is the infrared spectrum of the reactants and products at each stage in Example 1;

[0028] Figure 2 It is the result of the viscosity change with temperature of the flame-retardant epoxy resin TSE prepared in Example 1 and the bisphenol A epoxy resin in the comparative example;

[0029] Figure 3 It is the rheological diagram of the flame-retardant epoxy resin TSE prepared in Example 1 and the bisphenol A epoxy resin in the comparative example;

[0030] Figure 4 It is the bar chart of the flexural strength and flexural modulus of the flame-retardant epoxy resin TSE prepared in Example 1 and the bisphenol A epoxy resin in the comparative example;

[0031] Figure 5 It is the stress-strain curve of the flame-retardant epoxy resin TSE prepared in Example 1 and the bisphenol A epoxy resin in the comparative example;

[0032] Figure 6Bar chart of impact strength of the flame-retardant epoxy resin TSE prepared in Example 1 and bisphenol A epoxy resin in the comparative example;

[0033] Figure 7 Comparison chart of heat release rate of the flame-retardant epoxy resin TSE prepared in Example 1 and bisphenol A epoxy resin in the comparative example;

[0034] Figure 8 Comparison chart of total heat release of the flame-retardant epoxy resin TSE prepared in Example 1 and bisphenol A epoxy resin in the comparative example;

[0035] Figure 9 Comparison chart of carbon monoxide release rate of the flame-retardant epoxy resin TSE prepared in Example 1 and bisphenol A epoxy resin in the comparative example;

[0036] Figure 10 Comparison chart of smoke generation rate of the flame-retardant epoxy resin TSE prepared in Example 1 and bisphenol A epoxy resin in the comparative example;

[0037] Figure 11 Comparison chart of total smoke production of the flame-retardant epoxy resin TSE prepared in Example 1 and bisphenol A epoxy resin in the comparative example;

[0038] Figure 12 Comparison chart of carbon dioxide release rate of the flame-retardant epoxy resin TSE prepared in Example 1 and bisphenol A epoxy resin in the comparative example;

[0039] Figure 13 Comparison chart of mass loss rate of the flame-retardant epoxy resin TSE prepared in Example 1 and bisphenol A epoxy resin in the comparative example;

[0040] Figure 14 Bar chart of limiting oxygen index of the flame-retardant epoxy resin TSE prepared in Example 1 and bisphenol A epoxy resin in the comparative example;

[0041] Figure 15 Photograph of combustion char residue in the cone calorimetry test of Example 1. Detailed implementation manners

[0042] To make the technical solutions of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the present invention. It should be noted that the following embodiments are only used to better understand the technical solutions of the present invention and should not be construed as a limitation of the present invention.

[0043] The raw materials and equipment used in the present invention are all known products and are obtained by purchasing commercially available products.

[0044] Example 1.

[0045] In a three-necked round-bottom flask, 2-(4-hydroxyphenyl)ethylamine (10 g, 0.07 mol) was dissolved in anhydrous ethanol under a nitrogen atmosphere. Subsequently, o-hydroxybenzaldehyde (8.6 g, 0.07 mol) was added to the above solution, and the mixture was refluxed at 70 °C for 5 h. The crude product was precipitated with deionized water and then purified with methanol and ethanol. After evaporating the solvent under vacuum, it was dried under vacuum at 70 °C for 12 h to obtain the desired intermediate TSA.

[0046] The reaction route is as follows:

[0047] 。

[0048] In a three-necked round-bottom flask, TSA (10 g, 0.041 mol) was dissolved in 3-chloropropylene oxide (76 g, 0.082 mol) under a nitrogen atmosphere. Subsequently, TBAB (0.86 g, 0.0026 mol) was added to the above solution, and the mixture was refluxed at 100 °C for 3 h. After the above solution was cooled to 50 °C, 40 wt% aqueous sodium hydroxide solution (8.2 g, 0.082 mol) was added and the reaction continued for 5 h. Subsequently, the mixture was cooled to room temperature, and the resulting solution was washed 7 times with deionized water to remove by-products. The reaction mixture was dried overnight by adding an appropriate amount of anhydrous magnesium sulfate. The dried reaction mixture was evaporated at 80 °C for 2 h and then placed in a vacuum oven at 80 °C for 12 h to completely remove the unreacted 3-chloropropylene oxide. The target product TSE in red-brown color was obtained.

[0049] The reaction route is as follows:

[0050] 。

[0051] One part of molten diaminodiphenylmethane (DDM) as a curing agent was added to 4 parts of TSE and mixed evenly. After stirring evenly, it was placed in a vacuum oven. When there were no bubbles in the mixture under vacuum, the mixed sample was quickly poured into a mold. The mold was preheated at 70 °C for 20 min, cured at 75 °C for 1 h, then the temperature was adjusted to 110 °C and cured for 3 h to obtain a flame-retardant epoxy resin.

[0052] In this example, the infrared spectra of the reactants and products at each stage are as Figure 1 shown. It can be seen that the disappearance of the -NH2 peak at 3334 cm -1 in the curve of 2-(4-hydroxyphenyl)ethylamine, the disappearance of the -CHO peak at 1668 cm -1 in the curve of o-hydroxybenzaldehyde, and the appearance of the Schiff base (-C=N-) bond signal peak at 1634 cm -1 in the curve of the intermediate TSA represent the successful synthesis of TSA according to the above reaction route; in the flame-retardant epoxy resin TSE, -NH2 (3334 cm -1) peak and -CHO (1668 cm -1 ) peak did not appear, and the -C=N- (1634 cm -1 ) bond signal peak remained, and at the same time, a new signal peak of the epoxy group appeared at 914 cm in the TSE curve, -1 confirming the successful synthesis of TSE.

[0053] Example 2.

[0054] In a three-necked round-bottom flask, 2-(4-hydroxyphenyl)ethylamine (12 g, 0.084 mol) was dissolved in anhydrous ethanol under a nitrogen atmosphere. Subsequently, o-hydroxybenzaldehyde (10.32 g, 0.084 mol) was added to the above solution, and the mixture was refluxed at 70 °C for 5 h. The crude product was precipitated with deionized water and then purified with methanol and ethanol. After evaporating the solvent under vacuum, it was dried in vacuo at 70 °C for 12 h to obtain the desired intermediate TSA.

[0055] In a three-necked round-bottom flask, TSA (12 g, 0.0492 mol) was dissolved in 3-chloropropylene oxide (91.2 g, 0.0984 mol) under a nitrogen atmosphere. Subsequently, TBAB (1.032 g, 0.00312 mol) was added to the above solution, and the mixture was refluxed at 100 °C for 3 h. After the above solution was cooled to 50 °C, 40 wt% aqueous sodium hydroxide solution (9.84 g, 0.0984 mol) was added and the reaction was continued for 5 h. Subsequently, the mixture was cooled to room temperature, and the resulting solution was washed 7 times with deionized water to remove by-products. The reaction mixture was dried overnight by adding an appropriate amount of anhydrous magnesium sulfate. The dried reaction mixture was evaporated at 80 °C for 1-3 h and then placed in a vacuum oven at 80 °C for 12 h to completely remove the unreacted 3-chloropropylene oxide. The target product TSE in red-brown color was obtained.

[0056] One part of molten diaminodiphenylmethane (DDM) as a curing agent was added to 4 parts of TSE and mixed evenly. After stirring evenly, it was placed in a vacuum oven. When there were no bubbles in the vacuum, the mixed sample was quickly poured into a mold. The mold was preheated at 70 °C for 20 min, cured at 70 °C for 2 h, then the temperature was adjusted to 100 °C and cured for 2 h; the temperature was adjusted to 140 °C and cured for 2 h.

[0057] Example 3.

[0058] In a three-necked round-bottom flask, 2-(4-hydroxyphenyl)ethylamine (20 g, 0.14 mol) was dissolved in anhydrous ethanol under a nitrogen atmosphere. Subsequently, o-hydroxybenzaldehyde (17.2 g, 0.14 mol) was added to the above solution, and the mixture was refluxed at 70 °C for 5 h. The crude product was precipitated with deionized water and then purified with methanol and ethanol. After evaporating the solvent in vacuo, it was dried in vacuo at 70 °C for 12 h to obtain the desired intermediate TSA.

[0059] In a three-necked round-bottom flask, TSA (20 g, 0.082 mol) was dissolved in 3-chloropropylene oxide (152 g, 0.164 mol) under a nitrogen atmosphere. Subsequently, TBAB (1.72 g, 0.0052 mol) was added to the above solution, and the mixture was refluxed at 100 °C for 3 h. After the above solution was cooled to 50 °C, an aqueous solution of 40 wt% sodium hydroxide (16.4 g, 0.164 mol) was added and the reaction was continued for 5 h. Subsequently, the mixture was cooled to room temperature, and the resulting solution was washed 7 times with deionized water to remove by-products. The reaction mixture was dried overnight by adding an appropriate amount of anhydrous magnesium sulfate. The dried reaction mixture was evaporated at 80 °C for 2 h and then placed in a vacuum oven at 80 °C for 12 h to completely remove the unreacted 3-chloropropylene oxide. The target product TSE in red-brown color was obtained.

[0060] One part of molten diaminodiphenylmethane (DDM) as a curing agent was added to 4 parts of TSE and mixed evenly. After stirring evenly, it was placed in a vacuum oven. When there were no bubbles in the mixture under vacuum, the mixed sample was quickly poured into a mold. The mold was preheated at 70 °C for 20 min, cured at 80 °C for 2 h, then the temperature was adjusted to 110 °C and cured for 2 h; the temperature was adjusted to 150 °C and cured for 2 h.

[0061] Example 4.

[0062] In a three-necked round-bottom flask, 2-(4-hydroxyphenyl)ethylamine (30 g, 0.21 mol) was dissolved in anhydrous ethanol under a nitrogen atmosphere. Subsequently, o-hydroxybenzaldehyde (25.8 g, 0.21 mol) was added to the above solution, and the mixture was refluxed at 70 °C for 5 h. The crude product was precipitated with deionized water and then purified with methanol and ethanol. After evaporating the solvent in vacuo, it was dried in vacuo at 70 °C for 12 h to obtain the desired intermediate TSA.

[0063] In a three-necked round-bottom flask, TSA (30 g, 0.123 mol) was dissolved in 3-chloro-1,2-epoxypropane (228 g, 0.246 mol) under a nitrogen atmosphere. Subsequently, TBAB (2.58 g, 0.0078 mol) was added to the above solution, and the mixture was refluxed at 100 °C for 3 h. After the above solution was cooled to 50 °C, 40 wt% aqueous sodium hydroxide solution (24.6 g, 0.246 mol) was added and the reaction continued for 5 h. Subsequently, the mixture was cooled to room temperature, and the resulting solution was washed 7 times with deionized water to remove by-products. The reaction mixture was dried overnight by adding an appropriate amount of anhydrous magnesium sulfate. The dried reaction mixture was evaporated at 80 °C for 2 h, and then placed in a vacuum oven at 80 °C for 12 h to completely remove the unreacted 3-chloro-1,2-epoxypropane. The target product TSE in red-brown color was obtained.

[0064] One part of molten diaminodiphenylmethane (DDM) as a curing agent was added to 4 parts of TSE and mixed evenly. After stirring evenly, it was placed in a vacuum oven. When there were no bubbles in the mixture under vacuum, the mixed sample was quickly poured into a mold. The mold was preheated at 70 °C for 20 min, cured at 90 °C for 2 h, then the temperature was adjusted to 120 °C and cured for 2 h; the temperature was adjusted to 160 °C and cured for 2 h.

[0065] Example 5.

[0066] In a three-necked round-bottom flask, 2-(4-hydroxyphenyl)ethylamine (40 g, 0.28 mol) was dissolved in absolute ethanol under a nitrogen atmosphere. Subsequently, o-hydroxybenzaldehyde (34.4 g, 0.28 mol) was added to the above solution, and the mixture was refluxed at 70 °C for 4 - 6 h. The crude product was precipitated with deionized water and then purified with methanol and ethanol. After evaporating the solvent in vacuo, it was dried in vacuo at 70 °C for 12 hours to obtain the desired intermediate TSA.

[0067] In a three-necked round-bottom flask, TSA (40 g, 0.164 mol) was dissolved in 3-chloro-1,2-epoxypropane (304 g, 0.328 mol) under a nitrogen atmosphere. Subsequently, TBAB (3.44 g, 0.104 mol) was added to the above solution, and the mixture was refluxed at 100 °C for 3 h. After the above solution was cooled to 50 °C, 40 wt% aqueous sodium hydroxide solution (32.8 g, 0.328 mol) was added and the reaction continued for 5 h. Subsequently, the mixture was cooled to room temperature, and the resulting solution was washed 7 times with deionized water to remove by-products. The reaction mixture was dried overnight by adding an appropriate amount of anhydrous magnesium sulfate. The dried reaction mixture was evaporated at 80 °C for 2 h, and then placed in a vacuum oven at 80 °C for 12 h to completely remove the unreacted 3-chloro-1,2-epoxypropane. The target product TSE in red-brown color was obtained.

[0068] Add 1 part of molten diaminodiphenylmethane (DDM) as a curing agent to 4 parts of TSE and mix evenly. After stirring evenly, place it in a vacuum oven. When there are no bubbles in the mixture under vacuum, quickly pour the mixed sample into a mold. The mold is preheated at 70 °C for 20 min, cured at 60 °C for 1 h, then the temperature is adjusted to 100 °C and cured for 3 h.

[0069] Example 6.

[0070] In a three-necked round-bottom flask, dissolve 2-(4-hydroxyphenyl)ethylamine (10 g, 0.07 mol) in anhydrous ethanol under a nitrogen atmosphere. Subsequently, add m-hydroxybenzaldehyde (8.6 g, 0.07 mol) to the above solution and reflux at 70 °C for 5 h. Precipitate the crude product with deionized water and then purify it with methanol and ethanol. After evaporating the solvent in vacuo, dry it in vacuo at 70 °C for 12 h to obtain the desired intermediate TH3Y.

[0071] The reaction route is as follows:

[0072]

[0073] In a three-necked round-bottom flask, dissolve TH3Y (10 g, 0.041 mol) in 3-chloropropylene oxide (76 g, 0.082 mol) under a nitrogen atmosphere. Subsequently, add TBAB (0.86 g, 0.0026 mol) to the above solution and reflux at 100 °C for 3 h. After cooling the above solution to 50 °C, add 40 wt% aqueous sodium hydroxide solution (8.2 g, 0.082 mol) and continue the reaction for 5 h. Then cool the mixture to room temperature and wash the resulting solution 7 times with deionized water to remove by-products. Dry the reaction mixture overnight by adding an appropriate amount of anhydrous magnesium sulfate. Evaporate the dry reaction mixture at 80 °C for 2 h, and then place it in a vacuum oven at 80 °C for 12 h to completely remove the unreacted 3-chloropropylene oxide. Obtain the target product TH3E in red-brown color.

[0074] The reaction route is as follows:

[0075]

[0076] Add 1 part of molten diaminodiphenylmethane (DDM) as a curing agent to 4 parts of TH3E and mix evenly. After stirring evenly, place it in a vacuum oven. When there are no bubbles in the mixture under vacuum, quickly pour the mixed sample into a mold. The mold is preheated at 70 °C for 20 min, cured at 75 °C for 1 h, then the temperature is adjusted to 110 °C and cured for 3 h to obtain a flame-retardant epoxy resin.

[0077] Example 7.

[0078] In a three-necked round-bottom flask, 2-(4-hydroxyphenyl)ethylamine (10 g, 0.07 mol) was dissolved in anhydrous ethanol under a nitrogen atmosphere. Subsequently, p-hydroxybenzaldehyde (8.6 g, 0.07 mol) was added to the above solution, and the mixture was refluxed at 70 °C for 5 h. The crude product was precipitated with deionized water and then purified with methanol and ethanol. After evaporating the solvent under vacuum, it was dried under vacuum at 70 °C for 12 h to obtain the desired intermediate TH4Y.

[0079] The reaction route is as follows:

[0080]

[0081] In a three-necked round-bottom flask, TH4Y (10 g, 0.041 mol) was dissolved in 3-chloropropylene oxide (76 g, 0.082 mol) under a nitrogen atmosphere. Subsequently, TBAB (0.86 g, 0.0026 mol) was added to the above solution, and the mixture was refluxed at 100 °C for 3 h. After the above solution was cooled to 50 °C, 40 wt% aqueous sodium hydroxide solution (8.2 g, 0.082 mol) was added and the reaction continued for 5 h. Subsequently, the mixture was cooled to room temperature, and the resulting solution was washed 7 times with deionized water to remove by-products. The reaction mixture was dried overnight by adding an appropriate amount of anhydrous magnesium sulfate. The dried reaction mixture was evaporated at 80 °C for 2 h and then placed in a vacuum oven at 80 °C for 12 h to completely remove the unreacted 3-chloropropylene oxide. The target product TH4E in red-brown color was obtained.

[0082] The reaction route is as follows:

[0083]

[0084] One part of molten diaminodiphenylmethane (DDM) was added as a curing agent to 4 parts of TH4E and mixed evenly. After stirring evenly, it was placed in a vacuum oven. When there were no bubbles in the mixture under vacuum, the mixed sample was quickly poured into a mold. The mold was preheated at 70 °C for 20 min, cured at 75 °C for 1 h, then the temperature was adjusted to 110 °C and cured for 3 h to obtain a flame-retardant epoxy resin.

[0085] Comparative example.

[0086] One part of molten diaminodiphenylmethane (DDM) was added as a curing agent to 4 parts of bisphenol A epoxy resin (E51) and mixed evenly. After stirring evenly, it was placed in a vacuum oven. When there were no bubbles in the mixture under vacuum, the mixed sample was quickly poured into a mold. The mold was preheated at 70 °C for 20 min, cured at 120 °C for 2 h, then the temperature was adjusted to 150 °C and cured for 2 h.

[0087] Effect example.

[0088] The viscosity change of the flame-retardant epoxy resin TSE prepared in Example 1 and the bisphenol A epoxy resin in the comparative example with temperature is as follows Figure 2 shown, and the rheological spectrum at 25 °C is as follows Figure 3 shown. It can be clearly seen that the viscosity of TSE is much lower than that of bisphenol A epoxy resin, only 0.539 Pa·s, far lower than the viscosity of bisphenol A epoxy resin, which is 15.107 Pa·s. It can be proved that the fluidity and processability of the epoxy resin synthesized in this example are greatly improved, making it more suitable for industrial applications.

[0089] The bar charts of the flexural strength and flexural modulus, and the stress-strain curves of the flame-retardant epoxy resin TSE prepared in Example 1 and the bisphenol A epoxy resin in the comparative example are as follows Figure 4 , Figure 5 shown. It can be seen that the flexural strength of TSE is 205 Mpa, which is about 90% higher than that of bisphenol A epoxy resin, which is 108 Mpa, and the flexural modulus also increases significantly; the tensile strength and elongation at break of TSE are almost twice that of bisphenol A epoxy resin.

[0090] The bar chart of the impact strength of the flame-retardant epoxy resin TSE prepared in Example 1 and the bisphenol A epoxy resin in the comparative example is as follows Figure 6 shown. The impact strength of the flame-retardant epoxy resin TSE is 15.934 KJ / m 2 , which is 340% higher than that of bisphenol A epoxy resin, which is 3.617 KJ / m 2 . A higher impact strength can ensure that the type-IV hydrogen storage cylinder can withstand greater external destructive forces, ensuring the safety of personnel during the operation of the type-IV hydrogen storage cylinder.

[0091] The cone calorimetry data of the flame-retardant epoxy resin TSE prepared in Example 1 and the bisphenol A epoxy resin in the comparative example are as follows Figures 7 - 14 shown. Figure 15 Figure 28 is a photo of the combustion char residue in the cone calorimetry test of Example 1. Through comparison, it can be seen that the flame-retardant epoxy resin TSE has been greatly reduced compared with the bisphenol A epoxy resin in terms of mass loss rate (MASS), smoke production rate (SPR), heat release rate (HRR), total heat release (THR), etc. The limiting oxygen index of TSE is as high as 35.5%. The above data can strongly prove that using TSE as the matrix resin can maximize the fire safety of the type-IV hydrogen storage cylinder during use.

[0092] The test results of the bending strength, bending modulus, impact strength, tensile modulus, tensile strength and other properties of the epoxy resins prepared in Examples 1 to 7 and the comparative examples are shown in Table 1. Through comparison, it can be seen that compared with the common E51 epoxy resin on the market, the epoxy resin prepared by the present invention has significantly improved flame retardant performance and various mechanical properties. When applied to type-IV hydrogen storage cylinders, it can better ensure its service performance, service life and the personal safety of relevant staff.

[0093] Table 1

[0094]

[0095] It can be understood that the present invention is described by means of some examples. As is known to those skilled in the art, without departing from the spirit and scope of the present invention, various changes or equivalent replacements can be made to these features and examples. In addition, under the teaching of the present invention, these features and examples can be modified to adapt to specific situations and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific examples disclosed herein, and all examples falling within the scope of the claims of this application belong to the scope protected by the present invention.

Claims

1. An epoxy resin, characterized in that Used for the preparation of the wall of a type IV fully wound hydrogen storage cylinder, the epoxy resin has the following structural formula: 。 2. A method for preparing an epoxy resin as claimed in claim 1, characterized in that: The steps include: S1. Dissolve 2-(4-hydroxyphenyl)ethylamine in a solvent under a nitrogen atmosphere, add o-hydroxybenzaldehyde, and reflux to react. Precipitate a crude product with deionized water, purify with methanol and ethanol, evaporate the solvent in vacuo, and then dry in vacuo to obtain an intermediate. S2. Dissolve the intermediate in 3-chloropropylene oxide under a nitrogen atmosphere, then add tetrabutylammonium bromide and reflux for reaction. After cooling the solution to 50° C., add an aqueous sodium hydroxide solution to continue the reaction. After the reaction is completed, cool the mixture to room temperature, wash repeatedly with deionized water to remove by-products, add anhydrous magnesium sulfate to dry the reaction mixture overnight, then evaporate, and then vacuum dry to remove unreacted 3-chloropropylene oxide to obtain the target product, epoxy resin.

3. The method for preparing an epoxy resin according to claim 2, characterized in that: In step S1, the solvent is anhydrous ethanol; the temperature of the reflux reaction is 70° C., and the time of the reflux reaction is 4 h to 6 h.

4. The method for preparing an epoxy resin according to claim 2, characterized in that: The temperature of the reflux reaction in step S2 is 100° C., the time of the reflux reaction is 2 h to 4 h, the evaporation time is 1 h to 3 h, and the vacuum drying time is 12 h to 14 h.

5. The method for preparing the epoxy resin according to claim 2, characterized in that: The mass concentration of the sodium hydroxide aqueous solution in step S2 is 40wt%, and the reaction time after adding the sodium hydroxide solution is 4h~6h.

6. A flame retardant epoxy resin, characterized in that: It is formed by curing the epoxy resin described in claim 1.

7. A method for preparing a flame retardant epoxy resin as claimed in claim 6, characterized in that: The steps include: The epoxy resin and curing agent are mixed, stirred evenly and placed in a vacuum oven. When the mixture has no bubbles in the vacuum, it is quickly poured into a mold preheated at 70°C, and then cured at 75°C for 1 hour, and then the temperature is adjusted to 110°C and cured for another 3 hours to obtain a flame-retardant epoxy resin.

8. The method for preparing a flame retardant epoxy resin according to claim 7, characterized in that: The curing agent is 4,4'-diaminodiphenylmethane.

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