Method for preparing epoxy resin composite material from phosphorus-nitrogen flame-retardant curing agent

Abstract

The invention discloses a method for preparing an epoxy resin composite material by using a phosphorus-nitrogen flame-retardant curing agent, and relates to a preparation method of the epoxy resin composite material and synthesis of the phosphorus-nitrogen flame-retardant curing agent, and the phosphorus-nitrogen flame-retardant curing agent is prepared by reacting 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide with ethanolamine. The phosphorus-nitrogen flame-retardant curing agent is further compounded with 4, 4-diaminodiphenylmethane, and the compound and an epoxy group in epoxy resin are subjected to ring-opening polymerization reaction to prepare the epoxy resin composite material. The preparation method comprises the following two steps: (1) carrying out a reaction on 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and ethanolamine to generate 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-diethylamine (MEA-DOPO), and carrying out a reaction on the MEA-DOPO and the MEA-DOPO, so as to obtain the 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide. And 2) compounding the 9, 10-dihydro-9-oxa-10-phosphaphenanthrene diethylamine and the 4, 4-diaminodiphenyl methane, and adding the mixture into the epoxy resin to prepare the flame-retardant epoxy resin composite material. And the flame-retardant curing agent is compounded with 4, 4-diaminodiphenyl methane, so that the flame-retardant property of the composite material is effectively improved.

Description

Technical Field

[0001] The present invention relates to a method for preparing an epoxy resin composite material, in particular to a method for preparing the epoxy resin composite material by using a phosphorus-nitrogen flame retardant curing agent. Background Art

[0002] With technological advancements, epoxy resin, a polymer material, has found widespread application in fields as diverse as construction and aerospace. Composed of carbon and hydrogen, it is flammable, easily igniting in fire and producing large amounts of corrosive gases. This flammability limits its application in cutting-edge scientific fields. Therefore, modifying its flame retardant properties is of great significance, both promoting the development of the chemical synthesis industry and expanding the market. Epoxy resin is a liquid at room temperature and requires a curing agent to crosslink and solidify into a macromolecular structure. Curing agents significantly affect its properties, and improving its flame retardant properties is of great significance for high-end applications in military, aviation, and other fields.

[0003] Flame retardants are categorized as halogen-based and halogen-free. While halogen-based flame retardants are inexpensive and available in limited quantities, they produce toxic gases and smoke during combustion, which harms health and the environment. With increasing environmental awareness and green demands, market demand is gradually decreasing. Additive phosphorus-containing flame retardants have poor dispersibility in epoxy resins, affecting mechanical properties. Reactive phosphorus-containing flame retardants are halogen-free, simple to react, permanently modify flame retardancy, and have minimal impact on material performance. DOPO, a new green phosphorus-containing flame retardant, is gaining attention as a novel, green phosphorus-containing flame retardant that avoids mechanical property degradation and flame retardant precipitation. It has broad applications in electronics, electrical appliances, and aerospace, and holds great promise.

[0004] Epoxy resins have advantages such as low cost, chemical resistance, and excellent mechanical stiffness and toughness, and have been widely used in aerospace, composite materials, and other fields. However, one of the main drawbacks of traditional epoxy resins is their poor flame retardancy, which greatly limits their application. Halogen-free reactive flame retardant curing agents, on the other hand, must meet the mechanical and flame retardant performance requirements of epoxy resins after curing, while also offering low-cost and high-efficiency production. Adding them as fillers to epoxy resins allows them to crosslink and cure while improving their flame retardancy, expanding the application range of epoxy resins, enabling them to play a role in more fields and promoting the development of related industries. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for preparing an epoxy resin composite material using a phosphorus-nitrogen flame retardant curing agent, a 9,10-dihydro-9-oxa-10-phosphaphenanthrene derivative and a method for preparing a cured epoxy resin composite material.

[0006] The technical solution adopted in the present invention is:

[0007] A method for preparing an epoxy resin composite material using a phosphorus-nitrogen flame retardant curing agent, the method comprising two steps:

[0008] The first step is to react 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide with ethanolamine to generate 9,10-dihydro-9-oxa-10-phosphaphenanthrene diethylamine (MEA-DOPO);

[0009] Step 2: Compounding 9,10-dihydro-9-oxa-10-phosphaphenanthrene diethylamine and 4,4'-diaminodiphenylmethane, and adding the mixture to epoxy resin to prepare a flame retardant epoxy resin composite material;

[0010] The structural formula of 9,10-dihydro-9-oxa-10-phosphaphenanthrene diethylamine prepared according to the above method is as follows:

[0011]

[0012] The method for preparing an epoxy resin composite material using a phosphorus-nitrogen flame retardant curing agent comprises the following steps: first, adding dioxane and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to a 250ml three-necked flask equipped with a mechanical stirrer and a condenser reflux device; stirring is initiated in a water bath at 50°C; and when the 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is completely dissolved, ethanolamine is slowly titrated into the reaction system and reacted for 24 hours. After the reaction is completed, the system is allowed to cool to room temperature, and filtered to obtain a white solid powder, MEA-DOPO, which is then washed with dioxane and vacuum dried at 80°C for 12 hours to obtain the final product, MEA-DOPO.

[0013] 4. The method for preparing an epoxy resin composite material using a phosphorus-nitrogen flame retardant curing agent according to claim 3, wherein the molar ratio of the 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to ethanolamine is 1:1-2.2:1.

[0014] The method for preparing an epoxy resin composite material using a phosphorus-nitrogen flame retardant curing agent comprises the following steps: in the second step, adding 9,10-dihydro-9-oxa-10-phosphaphenanthrene diethylamine and 4,4'-diaminodiphenylmethane at a molar ratio of 1:0-1:30 to an epoxy resin (E-51); and obtaining a flame retardant epoxy resin composite material after curing.

[0015] The method for preparing an epoxy resin composite material using a phosphorus-nitrogen flame retardant curing agent comprises adding 9,10-dihydro-9-oxa-10-phosphaphenanthrene diethylamine and 4,4'-diaminodiphenylmethane in a certain proportion to an epoxy resin, and obtaining the epoxy resin composite material after curing. The curing temperature of the epoxy resin composite material is 40°C-200°C.

[0016] The invention discloses a method for preparing an epoxy resin composite material using a phosphorus-nitrogen flame retardant curing agent. The composite material comprises: 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), ethanolamine (MEA), dioxane (DOX), 4,4'-diaminodiphenylmethane (DDM), and epoxy resin.

[0017] Advantages and effects of the present invention:

[0018] 1. The present invention provides a method for preparing 9,10-dihydro-9-oxa-10-phosphaphenanthrene diethylamine, which has a wide range of applications.

[0019] 2. The 9,10-dihydro-9-oxa-10-phosphaphenanthrene diethylamine prepared by the present invention has good subsequent utilization value and can be used in various aspects such as curing agents and flame retardants.

[0020] 3. The 9,10-dihydro-9-oxa-10-phosphaphenanthrene diethylamine prepared by the present invention is a white solid powder, has simple operating conditions, a high product conversion rate, and is environmentally friendly. The present invention aims to synthesize 9,10-dihydro-9-oxa-10-phosphaphenanthrene diethylamine, which has good subsequent utilization value and can be used in many aspects such as curing agents and flame retardants.

[0021] 4. 9,10-Dihydro-9-oxa-10-phosphaphenanthrene diethylamine can improve the flame retardant properties of epoxy resin composites, providing a new idea and method for fields with high fire risk requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Infrared spectra of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, ethanolamine, and 9,10-dihydro-9-oxa-10-phosphaphenanthrene diethylamine (MEA-DOPO);

[0023] Figure 2 9,10-Dihydro-9-oxa-10-phosphaphenanthrene diethylamine structure 1 HNMR spectrum;

[0024] Figure 3 Structural mass spectrum of 9,10-dihydro-9-oxa-10-phosphaphenanthrene diethylamine. DETAILED DESCRIPTION

[0025] The present invention will be described in detail below with reference to the embodiments shown in the accompanying drawings.

[0026] A phosphorus-nitrogen flame retardant curing agent is prepared by reacting 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide with ethanolamine. The phosphorus-nitrogen flame retardant curing agent is further reacted with 4,4'-diaminodiphenylmethane (DDM) to produce a flame retardant cured epoxy resin composite material.

[0027] A method for synthesizing a phosphorus-nitrogen flame retardant curing agent and preparing an epoxy resin composite material, the preparation method comprising two steps:

[0028] The first step is to react 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide with ethanolamine to generate 9,10-dihydro-9-oxa-10-phosphaphenanthrene diethylamine (MEA-DOPO);

[0029] Step 2: Compounding 9,10-dihydro-9-oxa-10-phosphaphenanthrene diethylamine and 4,4'-diaminodiphenylmethane, and adding the mixture to epoxy resin to prepare a flame-retardant epoxy resin composite material.

[0030] The synthetic route of the structure of 9,10-dihydro-9-oxa-10-phosphaphenanthrene diethylamine (MEA-DOPO) prepared according to the above method is as follows:

[0031]

[0032] A method for synthesizing a phosphorus-nitrogen flame retardant curing agent and preparing an epoxy resin composite material comprises the following steps: first, adding dioxane and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to a 250ml three-necked flask equipped with a mechanical stirrer and a condenser reflux device. The mixture is stirred in a water bath at 50°C. When the 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is completely dissolved, ethanolamine is slowly titrated into the reaction system and allowed to react for 24 hours. After the reaction is complete, the system is cooled to room temperature and filtered to obtain a white solid powder, MEA-DOPO. The powder is then washed with dioxane and vacuum dried at 80°C for 12 hours to obtain the final product, MEA-DOPO.

[0033] The molar ratio of the 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to ethanolamine is 1:1-2.2:1.

[0034] A method for synthesizing a phosphorus-nitrogen flame retardant curing agent and preparing an epoxy resin composite material. In the second step, 9,10-dihydro-9-oxa-10-phosphaphenanthrene diethylamine and 4,4'-diaminodiphenylmethane are added to an epoxy resin (E-51) at a molar ratio of 1:0-1:30, and after curing, a flame retardant epoxy resin composite material is obtained.

[0035] The epoxy resin is one of E-44, E-51, E-52, and E-55.

[0036] The curing temperature of epoxy resin composite materials is 40℃-200℃.

[0037] Example 1

[0038] Step 1: Add 150ml of dioxane and 12.96g (0.06mol) of DOPO to a 250ml three-necked flask equipped with a mechanical stirrer and reflux system. Stir in a waterbath at 50°C. Once the DOPO is completely dissolved, slowly titrate 3.66g (0.06mol) of ethanolamine into the reaction system. Allow to react for 24 hours. After the reaction is complete, allow the system to cool to room temperature and filter to obtain MEA-DOPO, a white solid powder with a yield of 85.12%.

[0039] In the second step, 30g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene diethylamine and 10.3g of DDM were added to 100g of epoxy resin (E-44), stirred and dissolved, and vacuum filtered at 40°C for 30min. The mixture was poured into a mold and cured at 55°C for 1h, 80°C for 2h, and 110°C for 1h. After curing, a flame-retardant epoxy resin composite material was obtained.

[0040] Example 2

[0041] The first step: same as in Example 1.

[0042] The second step is to add 20g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene diethylamine and 14.2g of DDM to 100g of epoxy resin (E-44), stir and dissolve each other, vacuum filter at 40°C for 30min, then pour into a mold, cure at 55°C for 1h, 80°C for 2h, and 110°C for 1h. After curing, a flame retardant epoxy resin composite material is obtained.

[0043] Example 3

[0044] The first step: same as in Example 1.

[0045] The second step is to add 10g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene diethylamine and 18g of DDM to 100g of epoxy resin (E-44), stir and dissolve each other, vacuum filter at 40°C for 30min, then pour into a mold, cure at 55°C for 1h, 80°C for 2h, and 110°C for 1h. After curing, a flame retardant epoxy resin composite material is obtained.

[0046] Comparative Example 1

[0047] Add 21.80g DDM to 100g epoxy resin, stir and dissolve, vacuum filter at 40℃ for 30min, pour into a mold, cure at 55℃ for 1h, 80℃ for 2h, and 110℃ for 1h. After curing, a flame-retardant epoxy resin composite material is obtained.

[0048] The samples of Examples 1-3 and Comparative Example 1 were subjected to performance tests, wherein the tensile strength was tested according to GB 1040-79, the flexural modulus was tested according to GB / T 9341-2008, the impact strength was tested according to GB / T 1843-2008, and the limiting oxygen index was tested according to GB / T 2406.1-2008. The test results are shown in Table 1:

[0049] Table 1 Performance test of ionic liquid modified epoxy resin composites

[0050]

[0051] Figure 1 The infrared spectra of MEA, MEA-DOPO and DOPO are shown in Figure 2. -1 The absorption peak of -CH2 is at 3197cm, and the stretching vibration of -NH2 connected to -CH2 forms a broad peak at 3197cm -1 The stretching vibration absorption peak of PC bond is located at 1675cm -1 , and 752cm -1 The peak represents the out-of-plane bending vibration of -CH2. Comparing the infrared spectrum of MEA-DOPO with that of the raw material reveals the disappearance of the PH bond in DOPO and the absorption peak of -OH in MEA, while absorption peaks of PC, -CH2, and -NH2 appear in the product, further confirming the product's molecular structure.

[0052] Figure 2 This is the H NMR spectrum of MEA-DOPO. The H chemical shift (ppm) of the -CH2 bonded to -NH2 is approximately 2.1, the H chemical shift of the -CH2 bonded to P is approximately 3.7, and the chemical shift of approximately 6.4 is attributed to the H bonded to -NH2. The chemical shift of the phosphaphenanthrene ring is around 7-8 ppm, confirming the presence of the DOPO framework. The resonance at 8 ppm originating from the pH in DOPO disappears. This H NMR spectrum is consistent with the structural formula of the target product, further confirming the successful preparation of MEA-DOPO.

[0053] Figure 3 What is shown is the mass spectrum of MEA-DOPO. By observing the figure, it can be found that after calculation, the mass spectrum test results are consistent with the theoretical values. Combined with the tests of infrared spectrum and nuclear magnetic resonance hydrogen spectrum, it is proved that MEA-DOPO has been successfully prepared.

Claims

1. A method for preparing epoxy resin composite materials using phosphorus and nitrogen flame retardant curing agents, characterized in that: The method is carried out in two steps: The first step is to react 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide with ethanolamine to generate 9,10-dihydro-9-oxa-10-phosphaphenanthrene diethylamine (MEA-DOPO); Step 2: Compounding 9,10-dihydro-9-oxa-10-phosphaphenanthrene diethylamine and 4,4'-diaminodiphenylmethane, and adding the mixture to epoxy resin to prepare a flame retardant epoxy resin composite material; The structural formula of 9,10-dihydro-9-oxa-10-phosphaphenanthrene diethylamine prepared according to the above method is as follows:

2. The method for preparing an epoxy resin composite material using a phosphorus-nitrogen flame retardant curing agent according to claim 1, characterized in that: In the first step, dioxane and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide are added to a 250 ml three-necked flask equipped with a mechanical stirrer and a condenser reflux device. The water bath temperature is 50° C. and stirring is started. When the 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is completely dissolved, ethanolamine is slowly titrated into the reaction system and reacted for 24 hours. After the reaction is completed, the system is allowed to cool to room temperature, and white solid powder MEA-DOPO is obtained by suction filtration. The powder is washed with dioxane and vacuum dried at 80° C. for 12 hours to obtain the final product MEA-DOPO.

3. The method for preparing epoxy resin composite materials using a phosphorus-nitrogen flame retardant curing agent according to claim 3, characterized in that: The molar ratio of the 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to ethanolamine is 1:1-2.2:

1.

4. The method for preparing an epoxy resin composite material using a phosphorus-nitrogen flame retardant curing agent according to claim 1, characterized in that: In the second step, 9,10-dihydro-9-oxa-10-phosphaphenanthrene diethylamine and 4,4'-diaminodiphenylmethane are added to the epoxy resin (E-51) at a molar ratio of 1:0-1:30, and after curing, a flame-retardant epoxy resin composite material is obtained.

5. The method for preparing epoxy resin composite materials using a phosphorus-nitrogen flame retardant curing agent according to claim 4, characterized in that: The method comprises adding 9,10-dihydro-9-oxa-10-phosphaphenanthrene diethylamine and 4,4'-diaminodiphenylmethane into epoxy resin in a certain proportion, and obtaining an epoxy resin composite material after curing. The curing temperature of the epoxy resin composite material is 40-200°C.

6. The method for preparing epoxy resin composite materials using a phosphorus-nitrogen flame retardant curing agent according to claim 1, characterized in that: The composite material comprises: 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), ethanolamine (MEA), dioxane (DOX), 4,4'-diaminodiphenylmethane (DDM) and epoxy resin.

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