Melamine ammonium polyphosphate flame retardant containing metal catalytic function and preparation method thereof

Abstract

The present invention adds ammonium polyphosphate and cobalt nitrate hexahydrate to an organic solvent, adds 2-methylimidazole organic solution after stirring and continues to react; after the reaction is completed, the reaction solution is vacuum filtered, washed and dried in sequence to obtain a powdered precursor; melamine, bisphenol A and paraformaldehyde are mixed and added to an organic solvent, and the reaction is refluxed and stirred under heating conditions to generate a coating body; after a period of reaction, the above-mentioned precursor is added and the reaction is continued; the temperature is then raised for reflux reaction; after the reaction is completed, the reaction product is poured out, dried, and crushed to obtain a melamine / ammonium polyphosphate flame retardant containing a metal catalytic function. The melamine / ammonium polyphosphate flame retardant monomer containing a metal catalytic function prepared by the present invention can be completely volatilized by heating in the reaction stage, and only needs to be dried and crushed to be used later, and the simplified synthesis and purification process will greatly reduce the waste of the product and improve the preparation and synthesis efficiency.

Description

Technical Field

[0001] The invention relates to the technical field of flame retardant polymer materials, in particular to a modified ammonium polyphosphate flame retardant, in particular to a melamine / ammonium polyphosphate flame retardant containing a metal catalytic function, a preparation method thereof and application thereof in epoxy resin. Background Art

[0002] Epoxy resin has the characteristics of good processing performance, high bonding strength, high mechanical strength, excellent electrical insulation performance and good chemical stability. It plays an irreplaceable role in various fields such as biomedicine, coatings, industrial tools, electronic devices, aerospace, etc.

[0003] However, like other commonly used engineering plastics, flammability is one of its main disadvantages. In the event of a fire, it can continue to burn even if it leaves the fire source, and with a large amount of thick smoke and molten dripping, it is very easy to cause secondary combustion. Therefore, improving the flame retardant properties of epoxy resins is of great practical significance. Research on the flame retardant technology of epoxy resins can improve the fire safety of epoxy resins. The flame retardant modification of epoxy resins requires that the epoxy resin structure has flexible designability, and additive flame retardants have therefore become one of the important means to enhance the flame retardancy of the epoxy resin matrix. Currently commonly used flame retardants include halogen flame retardants, phosphorus flame retardants, nitrogen flame retardants, and inorganic flame retardants. Halogen flame retardants are widely used for flame retardant epoxy resins due to their good flame retardant properties and low cost, but they produce a large amount of toxic and harmful smoke during the flame retardant process. Therefore, efficient and environmentally friendly halogen-free flame retardants, especially phosphorus and nitrogen flame retardants, have become the main focus of the current flame retardant field.

[0004] Ammonium polyphosphate (APP) is a common phosphorus-based intumescent flame retardant. Its flame retardant system has both a gas source for the foaming agent and an acid source for producing an acid catalyst. Other flame retardant sources can be added to form a highly efficient phosphorus / nitrogen synergistic flame retardant material. Introducing a melamine-based triazine carbonizing agent to coat ammonium polyphosphate can supplement the missing carbon source in the flame retardant system, increase the carbonizing function of the flame retardant, and improve its flame retardant effect. At the same time, introducing metal ions for catalysis can further improve the flame retardant efficiency of the flame retardant.

[0005] Therefore, how to provide a melamine / ammonium polyphosphate flame retardant containing a metal catalytic function and use it to improve the flame retardant properties of epoxy resin is a technical problem that those skilled in the art need to solve urgently. Summary of the invention

[0006] In view of this, the present invention provides a melamine / ammonium polyphosphate flame retardant containing a metal catalytic function which is simple and convenient to operate and has an excellent flame retardant effect, and a preparation method thereof.

[0007] In order to achieve the above object, the present invention adopts the following technical solution:

[0008] A melamine ammonium polyphosphate flame retardant containing a metal catalytic function, wherein the melamine / ammonium polyphosphate flame retardant containing a metal catalytic function has a structure of formula I:

[0009] The present invention also provides the above-mentioned melamine / ammonium polyphosphate flame retardant containing metal catalytic function, wherein the melamine / ammonium polyphosphate flame retardant containing metal catalytic function is a flame retardant with a three-layer flame retardant structure, wherein the inner layer is ammonium polyphosphate, the middle layer is a metal organic framework catalyst layer ZIF-67, and the outermost layer is a triazine carbon former.

[0010] The preparation method of a melamine ammonium polyphosphate flame retardant containing a metal catalytic function comprises the following steps:

[0011] (1) adding ammonium polyphosphate and cobalt nitrate hexahydrate to an organic solvent, stirring, adding 2-methylimidazole organic solution and continuing to stir for reaction;

[0012] (2) After the reaction is completed, the reaction solution is vacuum filtered, washed, and dried in sequence to obtain a powdery precursor;

[0013] (3) adding melamine, bisphenol A and paraformaldehyde to an organic solvent, and reacting them under reflux and stirring under heating conditions to form a coating body;

[0014] (4) After a period of reaction, the precursor is added to continue the reaction;

[0015] (5) After a period of reaction, the temperature is raised to perform a reflux reaction;

[0016] (6) After the reaction is completed, the reaction product is poured out, dried, and crushed to obtain a melamine / ammonium polyphosphate flame retardant containing a metal catalytic function.

[0017] The molar ratio of the ammonium polyphosphate, cobalt nitrate hexahydrate and 2-methylimidazole in step (1) is (5.5-5.65):(1-1.5):(13-13.33);

[0018] The organic solvent is ethanol;

[0019] The weight ratio of the 2-methylimidazole organic solution is (1.0-1.2):(2.39-2.42);

[0020] The reaction temperature of the reaction is room temperature;

[0021] The continuous stirring reaction speed of the reaction is 130-150r / min.

[0022] The washing solvent in step (2) is ethanol, the drying temperature is 70-80° C., and the drying time is 24-48 hours.

[0023] The molar ratio of melamine, bisphenol A and paraformaldehyde in step (3) is (1-1.15):(1.5-1.52):(6-6.05);

[0024] The organic solvents are toluene and ethanol;

[0025] The heating is to raise the temperature to 90-95°C;

[0026] The reflux reaction time is 2-3h.

[0027] In step (4), the weight ratio of the coating body to the precursor is (1.0-1.2):(0.9-1.1); and the reaction time is 1-2h.

[0028] The heating in step (5) is to raise the temperature to 140-145° C., and the reflux reaction time is 1-2 h.

[0029] The drying temperature in step (6) is 100-110° C. and the drying time is 20-24 hours.

[0030] The beneficial effects of the present invention are embodied in:

[0031] 1. The melamine / ammonium polyphosphate flame retardant containing metal catalytic function proposed in the present invention has excellent flame retardant performance as a polymer material. Compared with the ordinary ammonium polyphosphate flame retardant, the melamine-based triazine carbonizing agent coating is added to supplement the missing carbon source in the flame retardant system and enhance the flame retardant effect of the flame retardant.

[0032] 2. The melamine / ammonium polyphosphate flame retardant containing metal catalytic function proposed in the present invention also introduces a metal catalytic layer, so that the flame retardant has a catalytic function and endows the flame retardant with more efficient flame retardant properties.

[0033] 3. The flame retardant structure of the present invention is highly efficient and has a simple preparation process, and takes advantage of the flexible structure of the additive flame retardant.

[0034] The present invention also provides the use of the melamine / ammonium polyphosphate flame retardant containing metal catalytic function in improving the flame retardancy of epoxy resin. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 ] is the infrared spectra of APP, TR, and TR@ZIFAPP in Example 1 of the present invention.

[0036] Figure 2 1 is the X-ray diffraction pattern of APP, TR and TR@ZIFAPP in Example 1 of the present invention.

[0037] Figure 3This is a scanning electron microscope elemental mapping image of TR@ZIFAPP prepared in Example 1 of the present invention.

[0038] Figure 4 This is the structural diagram of triazine carbon former.

[0039] Figure 5 This is the synthetic route of triazine carbon former. DETAILED DESCRIPTION

[0040] Example 1

[0041] The melamine / ammonium polyphosphate flame retardant containing metal catalytic function of the present invention has a synthesis route as follows:

[0042] Ammonium polyphosphate is used as the inner core to construct a three-layer flame retardant structure, the middle layer is a metal organic framework catalyst layer ZIF-67, and the outermost layer is a triazine carbon former TR. The structure of the triazine carbon former TR is as follows Figure 4 As shown, the synthesis route of triazine carbon forming agent is as follows Figure 5 As shown:

[0043] Its preparation method is:

[0044] (1) 25.2 g of APP and 8.85 g of cobalt nitrate hexahydrate were mixed and added to 300 mL of ethanol, and stirred at room temperature for 2 hours; 32.9 g of 2-methylimidazole was dissolved in 100 mL of ethanol and slowly added to the flask, and the reaction was continued by stirring for 12 hours;

[0045] (2) filtration, washing with ethanol until the filtrate is transparent, and drying to obtain the precursor (ZIFAPP);

[0046] (3) 5.046 g of melamine (0.04 mol), 13.6968 g of bisphenol A (0.04 mol), and 7.2 g of paraformaldehyde (0.24 mol) were mixed and added to 6 g of toluene and 12 g of ethanol, heated to 95° C., and refluxed for 2 hours;

[0047] (4) After 2 h, add 25 g of precursor and continue the reaction for 1 h;

[0048] (5) The reaction temperature was raised to 145°C and the reflux reaction was continued;

[0049] (6) After the reaction is completed, the reaction product is poured out, dried at 80° C. for 24 h, and crushed to obtain a melamine / ammonium polyphosphate flame retardant containing a metal catalytic function (TR@ZIFAPP).

[0050] Example 2

[0051] (1) 75.6 g of APP and 26.55 g of cobalt nitrate hexahydrate were mixed and added to 700 mL of ethanol, and stirred at room temperature for 2 hours; 98.7 g of 2-methylimidazole was dissolved in 300 mL of ethanol and slowly added to the flask, and the reaction was continued by stirring for 12 hours;

[0052] (2) filtration, washing with ethanol until the filtrate is transparent, and drying to obtain the precursor (ZIFAPP);

[0053] (3) 16.4 g melamine (0.13 mol), 44.515 g bisphenol A (0.195 mol), and 23.4 g paraformaldehyde (0.78 mol) were mixed and added to 19 g toluene and 38 g ethanol, heated to 95° C., and refluxed for 2 hours;

[0054] (4) After 2 h, 84 g of precursor was added and the reaction continued for 1 h;

[0055] (5) The reaction temperature was raised to 145°C and the reflux reaction was continued;

[0056] (6) After the reaction is completed, the reaction product is poured out, dried at 80° C. for 24 h, and crushed to obtain a melamine / ammonium polyphosphate flame retardant containing a metal catalytic function (TR@ZIFAPP).

[0057] Example 3

[0058] (1) 16.8 g of APP and 5.9 g of cobalt nitrate hexahydrate were mixed and added to 500 mL of ethanol, and stirred at room temperature for 2 hours; 32.9 g of 2-methylimidazole was dissolved in 200 mL of ethanol and slowly added to the flask, and the reaction was continued by stirring for 12 hours;

[0059] (2) filtration, washing with ethanol until the filtrate is transparent, and drying to obtain the precursor (ZIFAPP);

[0060] (3) 15.138 g of melamine (0.12 mol), 41.09 g of bisphenol A (0.18 mol), and 21.6 g of paraformaldehyde (0.72 mol) were mixed and added to 18 g of toluene and 36 g of ethanol, heated to 95° C., and refluxed for 2 hours;

[0061] (4) After 2 h, 77.83 g of precursor was added and the reaction was continued for 1 h;

[0062] (5) The reaction temperature was raised to 145°C and the reflux reaction was continued;

[0063] (6) After the reaction is completed, the reaction product is poured out, dried at 80° C. for 24 h, and crushed to obtain a melamine / ammonium polyphosphate flame retardant containing a metal catalytic function (TR@ZIFAPP).

[0064] Experimental Example 1 Characterization of TR@ZIFAPP

[0065] Fourier transform infrared spectra of APP, TR and TR@ZIFAPP are shown in Figure 2. Figure 1 As shown. Ammonium polyphosphate shows some characteristic absorption peaks at 798cm-1 (POP), 880cm-1 (PO), 1244cm-1 (P=O), 1681cm-1 (P-OH) and 3173cm-1 (NH), and accordingly, these peaks also appear in the spectrum of TR@ZIFAPP. In contrast, some new absorbance peaks appear in the spectrum of TR@ZIFAPP. The peak at 1058cm-1 originates from the stretching vibration of CO, the peak at 2968cm-1 is attributed to CH in TR, and the peak at 1541cm-1 belongs to C=N in the triazine ring. This shows that the expected flame retardant monomer has been successfully synthesized.

[0066] like Figure 2 As shown in the figure, the crystal structure of TR@ZIFAPP was characterized by X-ray diffraction. TR triazine carbonization intermediate has a broad peak at 19°, showing the amorphous structure of the coating. In TR@ZIFAPP, no other new peaks appeared except the signal of pure ammonium polyphosphate, indicating that the modification reaction did not affect the crystal structure of ammonium polyphosphate, but because the surface of ammonium polyphosphate particles was coated with amorphous assemblies, the intensity of the peak was significantly reduced. This shows that TR@ZIFAPP conforms to the expected design structure.

[0067] like Figure 3 As shown in Figure 2, the scanning electron microscope elemental mapping of TR@ZIFAPP shows the existence and uniform distribution of various elements. The surface elements such as phosphorus and cobalt can prove its successful coating, further proving the successful synthesis of TR@ZIFAPP.

[0068] Preparation of basic flame retardant composite materials

[0069] Bisphenol A type E51 epoxy resin is selected as the material matrix, and diaminodiphenylmethane (DDM) is used as the only epoxy resin curing agent, with a ratio of E51:DDM=4:1. After the epoxy resin is stirred at 120°C to a fluid state, the melamine / ammonium polyphosphate containing metal catalytic function prepared by the present invention is added according to the weight ratio of 1%, 3% and 5% of the previous mixture; after the flame retardant powder is completely dissolved, the solution temperature is lowered to 75°C, and DDM is added and continued to be stirred until fully dispersed. Finally, the fully stirred mixture is quickly poured into a polytetrafluoroethylene mold coated with a release agent, and the epoxy resin composite material is completely cured according to the heat treatment procedure of 120°C / 2h; 140°C / 2h; 180°C / 2h.

[0070] Comparative Example 1: Pure Epoxy Resin

[0071] Bisphenol A type E51 epoxy resin was used to prepare pure epoxy resin as a comparative example.

[0072] Comparative test of flame retardancy between Example 1 and Comparative Example 1:

[0073] In the present invention, the UL-94 vertical combustion test adopts the GB / T2408-2008 standard; the limiting oxygen index test adopts the GB / T2406-93 standard, and the basic flame retardant composite material prepared in Example 1 of the present invention and pure epoxy resin are tested and compared, and the results are shown in the following table.

[0074] Table 1 Performance test results

[0075]

[0076] In the table, NR stands for No Grade, which is a flammable material.

[0077] As can be seen from the table, the flame retardant prepared by the present invention can obtain efficient flame retardant effect at a relatively low addition amount, so that the epoxy resin composite material has more excellent flame retardant properties. When the addition amount is only 3%, a V-0 grade can be obtained in the vertical combustion test, and a limiting oxygen index value of 28.5% can be obtained. The flame retardant structure synthesized by the present invention has a sandwich structure, which not only has a metal ion catalytic functional layer, but also has a triazine carbon-forming functional layer on the second layer, so that the ammonium polyphosphate flame retardant has multiple flame retardant effects, which is reflected in the fact that the obtained sample has a significant improvement in limiting oxygen index and vertical combustion grade compared with other ammonium polyphosphate flame retardant technologies, and the flame retardant has an extremely efficient flame retardant effect.

[0078] The invention discloses a prepared product as a melamine / ammonium polyphosphate flame retardant containing a metal catalytic function, which can be used for flame retardancy of high molecular polymers. The invention first uses melamine, bisphenol A, and polyformaldehyde to prepare a triazine carbon-forming agent coating, and the synthesis conditions are mild, the reaction time is short, and it is conducive to efficient actual production; then, the ammonium polyphosphate is coated with a sandwich structure, so that the ammonium polyphosphate flame retardant has metal catalysis and triazine carbon-forming functions, and the preparation of a high-efficiency flame retardant is completed. At the same time, the synthesis step of the invention does not require a complicated coating step, and only a layer of coated ammonium polyphosphate flame retardant needs to be added after the synthesis of the triazine carbon-forming agent coating to complete the preparation of the flame retardant, and the solvent can be completely distilled by heating in the reaction container, and only drying and crushing are needed to use it later. The simplified synthesis and purification process will greatly reduce the waste of the product, improve the yield, and improve the preparation and synthesis efficiency, which has great economic benefits.

[0079] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A melamine ammonium polyphosphate flame retardant containing a metal catalytic function, characterized in that: The melamine / ammonium polyphosphate flame retardant containing metal catalytic function is a flame retardant with a three-layer flame retardant structure, wherein the inner layer is ammonium polyphosphate, the middle layer is a metal organic framework catalytic layer zeolite imidazole framework-67 (ZIF-67), and the outermost layer is a triazine carbon former having a structure of formula I: Formula Ⅰ.

2. The method for preparing a melamine / ammonium polyphosphate flame retardant containing a metal catalytic function according to claim 1, characterized in that: The following steps are involved: (1) adding ammonium polyphosphate and cobalt nitrate hexahydrate to an organic solvent, stirring, adding 2-methylimidazole organic solution and continuing to stir for reaction; (2) After the reaction is completed, the reaction solution is vacuum filtered, washed, and dried in sequence to obtain a powdered precursor; (3) Mixing melamine, bisphenol A and paraformaldehyde into an organic solvent, and stirring and refluxing the mixture under heating conditions to form a coating; (4) After a period of reaction, the precursor is added to continue reacting with the coating; (5) After a period of reaction, the temperature is raised to perform a reflux reaction; (6) After the reaction is completed, the reaction product is poured out, dried, and crushed to obtain a melamine / ammonium polyphosphate flame retardant containing a metal catalytic function.

3. The method for preparing a melamine / ammonium polyphosphate flame retardant containing a metal catalytic function according to claim 2, characterized in that: The molar ratio of the ammonium polyphosphate, cobalt nitrate hexahydrate and 2-methylimidazole organic solution in step (1) is (5.5-5.65):(1-1.5):(13-13.33); The organic solvent is ethanol; The weight ratio of the 2-methylimidazole organic solution is (1.0-1.2):(2.39-2.42); The reaction temperature of the reaction is room temperature; The continuous stirring reaction speed is 130-150 r / min.

4. The method for preparing a melamine / ammonium polyphosphate flame retardant containing a metal catalytic function according to claim 2, characterized in that: The washing solvent in step (2) is ethanol, the drying temperature is 70-80°C, and the drying time is 24-48h.

5. The method for preparing a melamine / ammonium polyphosphate flame retardant containing a metal catalytic function according to claim 2, characterized in that: The molar ratio of melamine, bisphenol A and paraformaldehyde in step (3) is (1-1.15):(1.5-1.52):(6-6.05); The organic solvents are toluene and ethanol; The heating condition is that the reaction temperature is 90-95°C; The reflux reaction time is 2-3h.

6. The method for preparing a melamine / ammonium polyphosphate flame retardant containing a metal catalytic function according to claim 2, characterized in that: In step (4), the weight ratio of the coating body to the precursor is (1.0-1.2):(0.9-1.1); and the reaction time is 1-2h.

7. The method for preparing a melamine / ammonium polyphosphate flame retardant containing a metal catalytic function according to claim 6, characterized in that: The heating in step (5) is to raise the temperature to 140-145° C., and the reflux reaction time is 1-2 h.

8. The method for preparing a melamine / ammonium polyphosphate flame retardant containing a metal catalytic function according to claim 2, characterized in that: The drying temperature in step (6) is 100-110°C and the drying time is 20-24h.

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