WO2021023226A1

WO2021023226A1 - Nitrogen-rich group functionalized graphene, preparation method, and application

Info

Publication number: WO2021023226A1
Application number: PCT/CN2020/107139
Authority: WO
Inventors: 戴李宗; 吴雯倩; 许一婷; 李伟航; 罗伟昂; 陈国荣
Original assignee: 厦门大学
Priority date: 2019-08-05
Filing date: 2020-08-05
Publication date: 2021-02-11
Also published as: CN110510605B; CN110510605A

Abstract

Provided is a method for preparing a graphene oxide functionalized with a nitrogen-rich group; a simple and convenient method is used to synthesize a compound containing phosphorus and nitrogen; by means of an esterification reaction between the phenolic hydroxyl group on the compound and the carboxyl group on the graphene oxide, the introduced phosphaphenanthrene functional group is expected to improve the dispersibility of graphene in organic solvent, and the secondary amine on the compound is also involved in the epoxy resin curing process, improving the compatibility of graphene in epoxy resin. Phosphorus and nitrogen flame retardant elements are introduced into graphene oxide to synthesize a flame retardant, performing a flame retardant function on the condensed phase and the gas phase, which is likely to improve the thermal stability of epoxy resin. The reaction conditions of the method are mild, and the prepared graphene oxide functionalized with a nitrogen-rich group does not contain halogen elements and is an environmentally friendly flame retardant.

Description

Nitrogen-rich group functionalized graphene, preparation method and application

Technical field

The invention belongs to the modification field of graphene, and particularly relates to a nitrogen-rich group functionalized graphene, a preparation method and an application.

Background technique

As a typical thermosetting polymer, epoxy resin has the advantages of good chemical stability, low shrinkage, easy processing, and low cost. Therefore, it has been widely used in high-tech fields such as transportation and aerospace. However, the phenomenon of flammability, dripping and rapid flame spread during fires greatly limits the application of materials. Therefore, in order to achieve sustainable development, research on green flame-retardant epoxy resins is still in full swing.

Traditional halogen-free flame-retardant epoxy resin materials achieve flame-retardant purposes by chemically or physically adding nitrogen, phosphorus, silicon, etc. Nitrogen-containing flame retardants release inert gas, but they are often used as synergists with other types of flame retardants because they are not effective when used alone. Phosphorus-containing compounds are the most widely used flame retardants, which can play a flame retardant effect in both the gas phase and the condensed phase. However, this traditional epoxy resin material is introduced by chemical or physical methods containing phosphorus, nitrogen or silicon compounds, often requiring the addition of a large amount of flame retardants, which leads to deterioration of the thermal and mechanical properties of the material. Nanocomposite technology provides a new synthesis path for halogen-free flame-retardant epoxy resin materials, and has become one of the hot research in this field in recent decades. The appearance of graphene opened up a new chapter for it.

Many documents have revealed the excellent flame-retardant efficiency of graphene on polymers. However, due to the strong π-π interaction between each graphene sheet, its dispersion and stability in solution are affected to a certain extent. . Therefore, graphene tends to aggregate in the polymer matrix, which brings certain difficulties to subsequent processing. The emergence of graphene oxide (GO), a graphene precursor containing a large number of hydroxyl groups, epoxy groups, carbonyl groups and carboxyl groups, and other active groups, provides a feasible path for the functionalization of graphene. Studies have shown that in the process of preparing the curing agent for polyethylene diamine dendrimer (PAMAM) grafted graphene oxide (GO), when the epoxy resin is added in an amount of 3wt%, the carbon residue rate at 600℃ More than 40%. Studies have also shown that the modification of graphene oxide with phosphorus-containing small molecules with an epoxy group at one end participates in the curing of epoxy resin. The test of the micro-calorimeter shows that the E/graphene and EP/FGO composite materials are resisting Combustion performance is better than EP/GO composite material, when it contains 5wt% FGO, the peak heat release rate is reduced by 23.7%.

Summary of the invention

The purpose of the present invention is to overcome the shortcomings of the prior art, provide a nitrogen-rich group functionalized graphene, preparation method and application, and solve the above-mentioned problems in the background art. The present invention grafts phosphorus-containing small molecules with secondary amines onto graphene oxide, improves the compatibility of graphene in epoxy resins, and improves the thermal stability of epoxy resins, and has better synergistic flame retardancy Effective and low cost.

The technical solution adopted by the present invention to solve its technical problem is: a nitrogen-rich group functionalized graphene is provided, the structure is as follows:

The second technical solution adopted by the present invention to solve its technical problem is to provide a method for preparing nitrogen-rich group functionalized graphene, which includes the following steps:

1) Under inert gas protection, react 3-amino-1,2,4-triazole and p-hydroxybenzaldehyde in solvent A for 2 to 3 hours to obtain a reaction solution; add 9,10-dihydro-9- Oxa-10-phosphaphenanthrene-10-oxide (DOPO) is dissolved in solvent B, the reaction solution is added dropwise to it, and the reaction is continued for 10-12 hours, then cooled to room temperature, and the product is filtered and dried under reduced pressure. Purification is carried out to obtain a compound containing phosphorus and nitrogen, the molecular structure of which is as follows:

2) After sonicating the graphene oxide in solvent C for 30min-60min, add the phosphorus-nitrogen-containing compound, dehydrating agent and catalyst dissolved in solvent D, stir at room temperature for 32-36 hours, and purify the product by centrifugation and freeze-drying Then, graphene oxide functionalized with nitrogen-rich groups is obtained.

In a preferred embodiment of the present invention, in step 1), the solvent A is one of anhydrous ethanol, anhydrous methanol, and tetrahydrofuran, and 3-amino-1,2,4-triazole, The mass ratio of hydroxybenzaldehyde and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (total mass of each solid raw material) to solvent A is 1:5～30 The solvent B is one of anhydrous ethanol, anhydrous methanol, tetrahydrofuran, and the mass ratio of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to solvent B 1:5-30; the 3-amino-1,2,4-triazole, p-hydroxybenzaldehyde, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide The molar ratio is 1:1～2:1～2.

In a preferred embodiment of the present invention, in step 2), the solvent C is one of anhydrous ethanol, anhydrous methanol, N,N-dimethylformamide (DMF), and graphene oxide The mass ratio to solvent C is 1:500-1000; in step 2), the solvent D is one of absolute ethanol, absolute methanol, and N,N-dimethylformamide, and 9,10 The mass ratio of -dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to solvent D is 1:5-100; in step 2), the graphene oxide, phosphorus-nitrogen-containing compound, dehydration The mass ratio of agent to catalyst is 1:3～5:2～3:0.5～1; among them, the dehydrating agent is dicyclohexylcarbodiimide (DCC), N,N-diisopropylcarbodiimide, One of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC); the catalyst is 4-dimethylpyridine (DMAP), sulfuric acid, titanate One of them.

Compared with the prior art, the present invention has the following advantages:

1. The present invention uses a simple and convenient experimental method to introduce the nitrogen-rich group-triazole ring, which has high nitrogen content, and the unique five-membered heterocyclic structure endows it with excellent thermal stability and is easy to interact with the π that exists between graphene. -π bond interaction, showing great potential in the construction of efficient flame retardants and the preparation of flame retardant polymers.

2. The resin containing triazole has self-extinguishing property, ultra-low heat release and extremely high residual carbon content.

3. The present invention uses compounds containing phosphorus and nitrogen to modify graphene, which improves the dispersibility of graphene in organic solvents.

4. The compound containing phosphorus and nitrogen element synthesized in the present invention has a secondary amine, which can participate in the curing of epoxy resin and help improve the compatibility in epoxy matrix.

5. In the present invention, phosphorus and nitrogen flame-retardant elements are introduced into graphene oxide to synthesize small-molecule flame-retardants. The synergistic effect of the two helps the formation of the coke layer and improves the thermal stability of the epoxy resin.

The invention has mild reaction conditions and does not contain halogen elements, and is an environment-friendly new flame retardant.

Description of the drawings

Fig. 1 is a nuclear magnetic spectrum ( ¹ H NMR) of a compound containing phosphorus and nitrogen prepared in Example 1 of the present invention, wherein the abscissa is the chemical shift (ppm).

Figure 2 is a mass spectrum of a compound containing phosphorus and nitrogen prepared in Example 1 of the present invention.

detailed description

The present invention will be described in detail through the following examples.

Example 1

(1) Synthesis of compounds containing phosphorus and nitrogen

In a 150mL three-necked flask, add 1.83g 3-amino-1,2,4-triazole and 2.66g p-hydroxybenzaldehyde dissolved in 30mL absolute ethanol, under the protection of nitrogen, at a reaction temperature of 50 ℃ stirring reaction 2 hour. Then, 30 mL of absolute ethanol containing 4.70 g of DOPO was added dropwise with a constant pressure dropping funnel, and the reaction was continued for 12 hours. Finally, it is cooled to room temperature, and the product is purified by vacuum filtration and drying.

(2) Synthesis of functionalized graphene containing phosphorus and nitrogen

After 50 mg of graphene oxide was sonicated in DMF for 1 hour, 15 mL of DMF in which 25 mg of DMAP, 100 mg of DCC and 0.174 g of phosphorus and nitrogen-containing compounds were dissolved was added, and the mixture was stirred at room temperature for 36 hours. After the reaction, the product was washed with DMF and deionized water several times, and finally lyophilized to obtain the product.

The nitrogen-rich group-functionalized graphene prepared in this example was examined by nuclear magnetic and mass spectrometry, as shown in Figures 1 and 2, the peaks at the corresponding positions in the nuclear magnetic spectrogram, and the mass spectrum data showed a single hydrogenation ion peak ([M+ H] ⁺ ), consistent with the theoretical value.

Example 2

(1) Synthesis of compounds containing phosphorus and nitrogen

In a 150mL three-necked flask, add 1.83g 3-amino-1,2,4-triazole and 2.66g p-hydroxybenzaldehyde in 30mL anhydrous methanol, under nitrogen protection, stirring at a reaction temperature of 50℃2 hour. Then, 30 mL of anhydrous methanol containing 4.70 g DOPO was added dropwise with a constant pressure dropping funnel, and the reaction was continued for 12 hours. Finally, it is cooled to room temperature, and the product is purified by vacuum filtration and drying.

(2) Synthesis of functionalized graphene containing phosphorus and nitrogen

After 50 mg of graphene oxide was sonicated in DMF for 1 hour, 15 mL of anhydrous ethanol in which 50 mg of DMAP, 200 mg of DCC and 0.18 g of a compound containing phosphorus and nitrogen were added was added, and stirred at room temperature for 36 hours. After the reaction, the product was washed with absolute ethanol and deionized water several times, and finally lyophilized to obtain the product.

Example 3

(1) Synthesis of compounds containing phosphorus and nitrogen

In a 150mL three-necked flask, add 1.83g 3-amino-1,2,4-triazole and 3.16g p-hydroxybenzaldehyde dissolved in 30mL absolute ethanol. Under nitrogen protection, the reaction temperature is 50℃ and the reaction is stirred 2 hour. Then, 30 mL of anhydrous ethanol containing 5.21 g of DOPO was added dropwise with a constant pressure dropping funnel, and the reaction was continued for 12 hours. Finally, it is cooled to room temperature, and the product is purified by vacuum filtration and drying.

(2) Synthesis of functionalized graphene containing phosphorus and nitrogen

After 100 mg of graphene oxide was sonicated in DMF for 1 hour, 15 mL of DMF in which 50 mg of DMAP, 150 mg of EDC and 0.20 g of phosphorus-nitrogen-containing compounds were dissolved was added, and stirred at room temperature for 36 hours. After the reaction, the product was washed with DMF and deionized water several times, and finally lyophilized to obtain the product.

Example 4

The nitrogen-rich group functionalized graphene prepared in Examples 1 to 3 was used as a reactive flame retardant, and the two were combined in a covalent bond manner to avoid the migration of the flame retardant, and a flame retardant epoxy resin was obtained.

(1) Synthesis of compounds containing phosphorus and nitrogen

(2) Synthesis of functionalized graphene containing phosphorus and nitrogen

After 50 mg of graphene oxide was sonicated in DMF for 1 hour, 15 mL of anhydrous ethanol in which 50 mg of DMAP, 200 mg of DCC and 0.18 g of phosphorus-nitrogen-containing compounds were dissolved was added, and stirred at room temperature for 36 hours. After the reaction, the product was washed with absolute ethanol and deionized water several times, and finally lyophilized to obtain the product.

(3) Phosphorus-containing nitrogen functionalized graphene modified epoxy resin

Weigh the E51 bisphenol A epoxy resin prepolymer and heat it up to 90°C, add 1wt% of phosphorus-containing nitrogen functionalized graphene flame retardant, stir evenly, and then add the curing agent 4,4'-diaminodiphenyl in proportion Stir the methane (DDM) until it is completely dissolved (the mass ratio of E51 bisphenol A epoxy resin prepolymer to 4,4'-diaminodiphenylmethane is 8:2.02), then pour it into the mold and program the temperature to cure , The flame-retardant epoxy resin material is obtained; the temperature program is: curing at 120°C for 4 hours, curing at 140°C for 2 hours, and curing at 180°C for 2 hours.

Those skilled in the art can know that when the technical parameters of the present invention are changed within the following ranges, the same or similar technical effects as the foregoing embodiments can be expected:

In step 1), the inert gas is nitrogen or argon.

The above are only preferred embodiments of the present invention, so the scope of implementation of the present invention cannot be limited accordingly. That is, equivalent changes and modifications made according to the scope of the patent of the present invention and the content of the specification should still be covered by the present invention. Within range.

Industrial applicability

The invention discloses a preparation method of nitrogen-rich group functionalized graphene oxide. A simple and convenient method is used to synthesize a compound containing phosphorus and nitrogen. The phenolic hydroxyl group on the compound and the carboxyl group on the graphene oxide undergo an esterification reaction. The introduced phosphaphenanthrene functional group is expected to improve the dispersibility of graphene in organic solvents, and The secondary amine on the compound can also participate in the curing process of the epoxy resin to improve the compatibility of graphene in the epoxy resin. The invention introduces phosphorus and nitrogen flame retardant elements into graphene oxide to synthesize a flame retardant, which can play a flame retardant effect on the condensed phase and the gas phase, and is expected to improve the thermal stability of the epoxy resin. The invention has mild reaction conditions and does not contain halogen elements, is an environment-friendly new flame retardant, and has industrial applicability.

Claims

A nitrogen-rich group functionalized graphene oxide, which is characterized in that the molecular structure is as follows:
A method for preparing graphene oxide functionalized with nitrogen-rich groups is characterized in that it comprises the following steps:

1) Under inert gas protection, react 3-amino-1,2,4-triazole and p-hydroxybenzaldehyde in solvent A for 2 to 3 hours to obtain a reaction solution; add 9,10-dihydro-9- The oxa-10-phosphaphenanthrene-10-oxide is dissolved in solvent B, the reaction solution is added dropwise to it, and the reaction is continued for 10-12 hours, and then cooled to room temperature, and the product is purified by vacuum filtration and drying. Obtain a compound containing phosphorus and nitrogen;

2) After sonicating graphene oxide in solvent C for 30min-60min, add the above-mentioned phosphorus-nitrogen-containing compound, dehydrating agent and catalyst dissolved in solvent D, stir at room temperature for 32-36 hours, and purify by centrifugation and freeze-drying After the product, graphene oxide functionalized with nitrogen-rich groups is obtained.
The method for preparing graphene oxide functionalized with nitrogen-rich groups according to claim 2, wherein the molecular structural formula of the compound containing phosphorus and nitrogen in step 1) is:
The method for preparing graphene oxide functionalized with nitrogen-rich groups according to claim 2, wherein in step 1), the solvent A is one of anhydrous ethanol, anhydrous methanol, and tetrahydrofuran, In addition, the masses of 3-amino-1,2,4-triazole, p-hydroxybenzaldehyde and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide are combined with solvent A The mass ratio is 1:5～30.
The method for preparing graphene oxide functionalized with nitrogen-rich groups according to claim 2, wherein in step 1), the solvent B is one of anhydrous ethanol, anhydrous methanol, and tetrahydrofuran, And, the mass ratio of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to solvent B is 1:5-30.
The method for preparing graphene oxide functionalized with nitrogen-rich groups according to claim 2, characterized in that: in step 1), the 3-amino-1,2,4-triazole and p-hydroxybenzaldehyde The molar ratio of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is 1:1～2:1～2.
The method for preparing graphene oxide functionalized with nitrogen-rich groups according to claim 2, characterized in that: in step 2), the solvent C is anhydrous ethanol, anhydrous methanol, N,N-dimethyl One of the carbamides, and the mass ratio of graphene oxide to solvent C is 1:500-1000.
The method for preparing graphene oxide functionalized with nitrogen-rich groups according to claim 2, characterized in that: in step 2), the solvent D is anhydrous ethanol, anhydrous methanol, N,N-dimethyl One of the hydroxyformamides, and the mass ratio of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to solvent D is 1:5-100.
The method for preparing graphene oxide functionalized with nitrogen-rich groups according to claim 2, characterized in that: in step 2), the mass ratio of the graphene oxide, the phosphorus-nitrogen-containing compound, the dehydrating agent, and the catalyst is 1:3～5:2～3:0.5～1; among them, the dehydrating agent is dicyclohexylcarbodiimide, N,N-diisopropylcarbodiimide, 1-(3-dimethylaminopropyl) Yl)-3-ethylcarbodiimide hydrochloride; the catalyst is one of 4-lutidine, sulfuric acid and titanate.
The application of a nitrogen-rich group functionalized graphene oxide as a reactive flame retardant in the modification of epoxy resin materials according to claim 1.
A method for preparing nitrogen-rich group-functionalized graphene oxide, which is characterized in that it comprises the following steps: after the graphene oxide is sonicated in solvent C for 30 to 60 minutes, the phosphorus-containing nitrogen element compound dissolved in solvent D is added
The dehydrating agent and catalyst are stirred at room temperature for 32-36 hours, and the product is purified by centrifugation and freeze-drying to obtain nitrogen-rich group functionalized graphene oxide.
The method for preparing graphene oxide functionalized with nitrogen-rich groups according to claim 11, wherein the solvent C is selected from the group consisting of anhydrous ethanol, anhydrous methanol, and N,N-dimethylformamide. One; the solvent D is one of anhydrous ethanol, anhydrous methanol, and N,N-dimethylformamide.
The method for preparing graphene oxide functionalized with nitrogen-rich groups according to claim 11, wherein the mass ratio of the graphene oxide, the phosphorus-nitrogen-containing compound, the dehydrating agent, and the catalyst is 1:3~ 5: 2～3: 0.5～1; Among them, the dehydrating agent is dicyclohexylcarbodiimide, N,N-diisopropylcarbodiimide, 1-(3-dimethylaminopropyl)-3- One of ethylcarbodiimide hydrochloride; the catalyst is one of 4-lutidine, sulfuric acid, and titanate.