Reactive phosphorus-nitrogen-containing graphene oxide flame retardant as well as preparation method and application thereof

Abstract

The invention relates to the technical field of high polymer materials, and discloses a reactive phosphorus-nitrogen-containing graphene oxide flame retardant and a preparation method and application thereof. According to the invention, the phosphorus-nitrogen flame retardant and the graphene oxide are subjected to composite modification, and a phosphorus-nitrogen compound is grafted to the surface of the graphene oxide through chemical reaction, so that not only can the dispersity and compatibility of the graphene oxide in a polypropylene matrix be improved, but also the synergistic flame-retardant effect of the phosphorus-nitrogen flame retardant and the graphene oxide can be fully exerted; and the graphene oxide can reduce the size of the polypropylene spherocrystal. In addition, the reactive flame retardant can also improve other properties such as mechanical properties, thermal stability and the like of the material to a certain extent, and has a wide application prospect.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a reactive phosphorus-containing nitrogen oxide graphene flame retardant, its preparation method, and its application. Background Technology

[0002] With the widespread application of polymer materials in various fields, the safety hazards posed by their flammability are becoming increasingly prominent, making the development of efficient flame retardants an important research direction in materials science. Polypropylene (PP), as a common crystalline plastic, has advantages such as being lightweight, non-toxic, odorless, chemically stable, and easy to process and mold, and is widely used in the automotive, electronics, construction, and packaging industries. However, PP's limiting oxygen index (LOI) is only about 18%, classifying it as a flammable material. Furthermore, the crystal morphology of polypropylene has a significant impact on its mechanical properties; large spherulites lead to low impact strength. Traditional methods often involve adding inorganic nucleating agents to reduce spherulite size, but nucleating agents often have poor compatibility with polypropylene.

[0003] Phosphorus-nitrogen flame retardants have attracted widespread attention due to their advantages such as low smoke, non-toxicity, and low or no halogen content. When heated, phosphorus-based flame retardants promote the formation of a stable char layer in materials, preventing thermal decomposition products from entering the gas phase and participating in the combustion process, thus inhibiting further decomposition and achieving a flame-retardant effect. Nitrogen-based flame retardants primarily exert their flame-retardant effect by diluting flammable gases in the gas phase and capturing free radicals. Furthermore, the presence of nitrogen can promote the formation of a more stable char layer in phosphorus-based flame retardants, demonstrating a significant synergistic flame-retardant effect between phosphorus and nitrogen.

[0004] Graphene oxide (GO) possesses excellent mechanical properties, high specific surface area, and good barrier properties. Introducing it into polymers can not only improve the mechanical properties of polymers but also form physical barriers that hinder the transfer of heat and oxygen, thereby slowing down the thermal decomposition and combustion rate of polymers.

[0005] CN105504352A discloses a phosphorus-nitrogen-containing dendritic macromolecular functionalized graphene flame retardant, which attaches phosphorus and nitrogen to the graphene surface and applies it to polyurethane flame retardancy, solving the technical problem of deterioration of material mechanical properties when small molecule flame retardants improve the flame retardancy of polymer materials.

[0006] CN105418971A discloses a method for preparing a phosphorus-nitrogen high-load graphene flame retardant. The method includes the following steps: (1) performing a surface grafting reaction between isocyanate and graphene oxide to obtain isocyanate-functionalized graphene; (2) reacting the above isocyanate-functionalized graphene with dendritic macromolecular polyamide-amine (PAMAM) to obtain dendritic macromolecular functionalized graphene; (3) reacting the above dendritic macromolecular functionalized graphene with a phosphoryl chloride compound to obtain the phosphorus-nitrogen high-load graphene flame retardant.

[0007] However, since graphene oxide is an inorganic material, it has poor compatibility when physically mixed with polymers, making it difficult to disperse uniformly in the polymers, which seriously affects its flame retardant properties and the overall performance of the material. Summary of the Invention

[0008] In order to overcome the problems of poor compatibility and uneven dispersion between graphene and phosphorus-nitrogen flame retardants, this invention provides a reactive phosphorus-nitrogen-containing graphene oxide flame retardant. The synthesized phosphorus-nitrogen flame retardant is grafted onto the surface of graphene oxide to improve the dispersibility of graphene oxide in polypropylene and give full play to the reinforcing, heat-insulating and nucleating effects of graphene oxide.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] A reactive phosphorus-containing nitrogen oxide graphene flame retardant, the structural formula of which is as follows:

[0011]

[0012] In the formula, the sheet-like carbon structure represents graphene oxide.

[0013] This invention involves the composite modification of phosphorus-nitrogen flame retardants with graphene oxide. Through a chemical reaction, phosphorus-nitrogen compounds are grafted onto the surface of graphene oxide. This not only improves the dispersibility and compatibility of graphene oxide in a polypropylene matrix but also fully leverages the synergistic flame-retardant effect of the phosphorus-nitrogen flame retardants and graphene oxide. Furthermore, this reactive flame retardant can also improve the mechanical properties, thermal stability, and other properties of the material to a certain extent, demonstrating broad application prospects.

[0014] The present invention also provides a method for preparing the aforementioned reactive phosphorus-containing nitrogen oxide graphene flame retardant, comprising the steps of:

[0015] Step 1: Reaction of pentaerythritol phosphate and phosphorus oxychloride at 80-150℃ with magnetic stirring for 4-8 hours; washing the crude product with haloalkanes and alkaline aqueous solution respectively to obtain intermediate A.

[0016] Step 2: Intermediate A, melamine and water are stirred and reacted at 70-100℃ for 10-16 hours, cooled in an ice bath, filtered, washed and dried to obtain phosphorus nitrogen flame retardant intermediate B;

[0017]

[0018] Step 3: Dissolve intermediate B and graphene oxide in a solvent, and react with ultrasonic and magnetic stirring at 60-90°C for 8-12 hours. After vacuum filtration, washing and drying, the reactive phosphorus-nitrogen-containing graphene oxide flame retardant is obtained.

[0019] In this invention, a phosphorus-nitrogen intumescent flame retardant is first synthesized and then reacted with graphene oxide. Because the surface of graphene oxide contains abundant oxygen-containing functional groups, the epoxy groups can react with a large number of amino groups on the phosphorus-nitrogen flame retardant, and the carboxyl and hydroxyl groups can form hydrogen bonds with the amino groups, thus obtaining a reactive phosphorus-nitrogen-containing graphene oxide flame retardant.

[0020] The molar ratio of pentaerythritol phosphate to phosphorus oxychloride is 1:0.8-1.2.

[0021] The molar ratio of the intermediate to melamine is 1:1.8-2.5.

[0022] The solvent in step 3 is one or more of ethanol, N,N-dimethylformamide, toluene, or water.

[0023] The halogenated hydrocarbons include one or more of dichloromethane, trichloromethane, and 1,2-dichloroethane;

[0024] The graphene oxide was prepared using the Hummers method.

[0025] In step 3, the mass ratio of intermediate B to graphene oxide is 1:0.2-1:1.

[0026] This invention provides the application of the aforementioned reactive phosphorus-containing nitrogen oxide graphene flame retardant in flame-retardant polypropylene materials.

[0027] The present invention also provides a flame-retardant PP resin material, wherein the PP resin material comprises polypropylene, the reactive phosphorus-nitrogen oxide graphene flame retardant and antioxidant 1010; the mass of the reactive phosphorus-nitrogen oxide graphene flame retardant is 10-24% of the polypropylene.

[0028] The preparation method of the PP resin material includes the following steps: melt extruding raw materials comprising polypropylene, the reactive phosphorus-containing nitrogen-oxidized graphene flame retardant, and antioxidant 1010 at 180-210℃. Melt blending is performed using a twin-screw extruder with a main extruder speed of 30-80 r / min and a feed speed of 10-30 r / min.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) Phosphorus-nitrogen-containing graphene oxide flame retardant: By loading phosphorus and nitrogen elements onto the surface of graphene oxide, the expansion flame retardant advantage of phosphorus and nitrogen compounds can be brought into play, and the sheet graphene oxide can play a heat insulation role, thus achieving a synergistic flame retardant effect.

[0031] (2) The phosphorus-nitrogen-containing graphene oxide flame retardant prepared by the present invention has a high content of graphene oxide, which breaks through the bottleneck of the difficulty of dispersing graphene oxide in polypropylene. Graphene oxide can play the role of nucleating agent and nanoparticle reinforcement, thereby improving the mechanical properties of the matrix.

[0032] (3) The flame retardant described in this invention utilizes the synergistic flame retardant effect of phosphorus and nitrogen compounds and graphene oxide to improve flame retardant efficiency and reduce the amount of flame retardant used. Attached Figure Description

[0033] Figure 1 The reaction diagram for the preparation of phosphorus-containing nitrogen oxide graphene flame retardant.

[0034] Figure 2 The infrared spectrum of the phosphorus-containing nitrogen oxide graphene flame retardant prepared in Example 1.

[0035] Figure 3 Differential scanning calorimetry curves of polypropylene composite materials in Examples 1-3 and Comparative Example 1 are shown.

[0036] Figure 4 The images show polarized light micrographs of the polypropylene composite materials in Example 2 and Comparative Example 1. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Modifications or equivalent substitutions made by those skilled in the art based on their understanding of the technical solutions of this invention, without departing from the spirit and scope of the invention, should be covered within the protection scope of this invention.

[0038] All raw materials used in the following specific implementation methods were purchased from the market.

[0039] Comparative Example 1

[0040] (1) Phosphorus oxychloride and pentaerythritol phosphate were added to a four-necked flask in a molar ratio of 1:1, heated to 120°C and magnetically stirred for 6 hours. The crude product was washed with chloroform and sodium carbonate alkaline aqueous solution to obtain intermediate A.

[0041] (2) Add intermediate A, melamine and water to a four-necked flask. The molar ratio of intermediate A to melamine is 1:2. Stir and react at 80°C for 12 hours. Cool in an ice bath, filter, wash and dry to obtain phosphorus nitrogen flame retardant intermediate B.

[0042] (3) Extrusion granulation of phosphorus-nitrogen flame retardant intermediate B, polypropylene, and antioxidant 1010, with a mass ratio of phosphorus-nitrogen flame retardant intermediate B of 18% and a melt extrusion granulation temperature of 190℃, to obtain polypropylene flame retardant composite material, and to conduct performance tests.

[0043] Example 1

[0044] (1) Phosphorus oxychloride and pentaerythritol phosphate were added to a four-necked flask in a molar ratio of 1:1, heated to 120°C and magnetically stirred for 6 hours. The crude product was washed with chloroform and sodium carbonate alkaline aqueous solution to obtain intermediate A.

[0045] (2) Add intermediate A, melamine and water to a four-necked flask. The molar ratio of intermediate A to melamine is 1:2. Stir and react at 80°C for 12 hours. Cool in an ice bath, filter, wash and dry to obtain phosphorus nitrogen flame retardant intermediate B.

[0046] (3) Intermediate B and graphene oxide were dissolved in N,N-dimethylformamide in a mass ratio of 1:1. The reaction temperature was 75℃, and the mixture was ultrasonically and magnetically stirred for 10 hours to ensure uniform dispersion and complete reaction. After vacuum filtration, washing, and drying, the reactive phosphorus-nitrogen-containing graphene oxide flame retardant was obtained. The reaction formula is as follows: Figure 1 As shown, its infrared spectrum is as follows Figure 2 As shown.

[0047] (4) Extrusion granulation was performed on phosphorus-nitrogen flame retardant intermediate B, polypropylene, and antioxidant 1010. The mass ratio of polypropylene, phosphorus-nitrogen graphene oxide flame retardant, and antioxidant 1010 was 1:0.23:0.005. The melt extrusion granulation temperature was 190℃ to obtain polypropylene flame retardant composite material, and its performance was tested.

[0048] Example 2

[0049] According to the preparation process of Example 1, in step (4), the mass ratio of polypropylene, phosphorus-nitrogen-containing graphene oxide flame retardant, and antioxidant 1010 is 1:0.23:0.005, that is, compared with polypropylene, 23% phosphorus-nitrogen flame retardant intermediate is added. The melt extrusion granulation temperature is 190℃ to obtain polypropylene flame retardant composite material, and the performance is tested.

[0050] Example 3

[0051] According to the preparation process of Example 1, in step (4), the mass ratio of polypropylene, phosphorus-nitrogen-containing graphene oxide flame retardant, and antioxidant 1010 is 1:0.28:0.005, that is, compared with polypropylene, 28% phosphorus-nitrogen flame retardant intermediate is added. The melt extrusion granulation temperature is 190℃ to obtain polypropylene flame retardant composite material, and the performance is tested.

[0052] Performance testing

[0053] Table 1. Mechanical and flame-retardant properties of polypropylene composite materials from the examples and comparative examples.

[0054]

[0055]

[0056] Take 5-8 mg of sample and place it in an aluminum crucible. Under nitrogen protection, heat to 230 °C at a heating rate of 10 °C / min, hold at that temperature for 3 min to eliminate thermal history, and then cool down at a cooling rate of 10 °C / min. Record the data during the cooling stage. The differential thermal analysis curves of Examples 1-3 and Comparative Example 1 are shown below. Figure 3 As shown, the initial crystallization temperature and maximum crystallization temperature of the composite material both increased after the addition of phosphorus-nitrogen-oxidized graphene flame retardant, indicating that the phosphorus-nitrogen-oxidized graphene flame retardant acts as a nucleating agent in the composite material, leading to earlier crystallization.

[0057] Polarizing microscope images of Example 2 and Comparative Example 1 are shown below. Figure 4 As shown. In Comparative Example 1, when 18% phosphorus-nitrogen flame retardant was added, the polypropylene spherulites were larger. In Example 2, when 23% phosphorus-nitrogen-containing graphene oxide flame retardant was added, the spherulites became smaller and denser, and surface impurities were not obvious. This indicates that the phosphorus-nitrogen-containing graphene oxide flame retardant was uniformly dispersed in the polypropylene, acting as a nucleating agent, which led to earlier crystallization and an increased crystallization temperature. Figure 3 This corresponds to the DSC data.

Claims

1. A reactive phosphorus-containing nitrogen oxide graphene flame retardant, characterized in that, Its structural formula is as follows:

2. The preparation method of the reactive phosphorus-containing nitrogen-oxidized graphene flame retardant according to claim 1, characterized in that, Including the following steps: Step 1: Pentaerythritol phosphate and phosphorus oxychloride are stirred magnetically at 80-150℃ for 4-8 hours. The crude product is washed with haloalkanes and alkaline aqueous solutions to obtain intermediate A. Step 2: Intermediate A, melamine and water are stirred and reacted at 70-100℃ for 10-16 hours, cooled in an ice bath, filtered, washed and dried to obtain phosphorus nitrogen flame retardant intermediate B; Step 3: Dissolve intermediate B and graphene oxide in a solvent, and react with ultrasonic and magnetic stirring at 60-90°C for 8-12 hours. After vacuum filtration, washing and drying, the reactive phosphorus-nitrogen-containing graphene oxide flame retardant is obtained.

3. The preparation method of the reactive phosphorus-containing nitrogen-oxidized graphene flame retardant according to claim 2, characterized in that, The molar ratio of pentaerythritol phosphate to phosphorus oxychloride is 1:0.8-1.

2.

4. The preparation method of the reactive phosphorus-containing nitrogen-oxidized graphene flame retardant according to claim 2, characterized in that, The molar ratio of the intermediate to melamine is 1:1.8-2.

5.

5. The preparation method of the reactive phosphorus-containing nitrogen-oxidized graphene flame retardant according to claim 2, characterized in that, In step 3, the solvent is one or more of ethanol, N,N-dimethylformamide, toluene, or water; the halogenated hydrocarbon includes one or more of dichloromethane, trichloromethane, and 1,2-dichloroethane.

6. The preparation method of the reactive phosphorus-containing nitrogen-oxidized graphene flame retardant according to claim 2, characterized in that, The graphene oxide was prepared using the Hummers method.

7. The preparation method of the reactive phosphorus-containing nitrogen-oxidized graphene flame retardant according to claim 2, characterized in that, In step 3, the mass ratio of intermediate B to graphene oxide is 1:0.2-1:

1.

8. The application of the reactive phosphorus-containing graphene oxide flame retardant according to claim 1 in flame-retardant polypropylene materials.

9. A flame-retardant PP resin material, characterized in that, The PP resin material includes polypropylene, the reactive phosphorus-containing graphene oxide flame retardant, and antioxidant 1010; the mass of the phosphorus-containing graphene oxide flame retardant is 10-24% of the polypropylene.

10. The method for preparing PP resin material according to claim 9, characterized in that, The process includes the following steps: obtaining the raw materials, including polypropylene, the reactive phosphorus-containing graphene oxide flame retardant, and antioxidant 1010, by melt extrusion at 180-210°C.

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