Bimetal organic framework complex / polycarbonate composite flame-retardant material and preparation method thereof

Abstract

The invention provides a bimetallic organic framework complex / polycarbonate composite flame-retardant material and a preparation method thereof, and belongs to the technical field of flame-retardant materials. The material is prepared from the following components in percentage by weight: 1 to 10 weight percent of bimetal organic framework complex and 90 to 99 weight percent of polycarbonate, the bimetal organic framework complex is prepared by taking Zn < 2 + > or Co < 2 + > as nodes and imidazole and benzimidazole as ligands. The bimetal organic framework complex in the composite material contains Zn < 2 + > or Co < 2 + >, and the two metals can generate catalytic action in the polymer combustion process at high temperature, so that combustion heat release and smoke release are reduced, and the flame retardant property of the composite material is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of flame-retardant materials, and particularly relates to a bimetallic organic framework complex / polycarbonate composite flame-retardant material and a preparation method thereof. BACKGROUND

[0002] Polycarbonate (PC) is a kind of thermoplastic engineering plastic with excellent performance, which has high strength and high toughness and can withstand a large external force impact without being easily broken. It is widely used in electronic, electrical, aerospace, mechanical, automotive textile, light industry and construction industries. However, the potential flammability of PC greatly limits its application range, and the fire safety problems it brings also seriously threaten human property and life safety.

[0003] In recent years, catalyzing the carbonization of polymers to improve their flame-retardant performance has gradually become a hot spot in the international flame-retardant field. Metal-organic frameworks (MOFs) are inorganic-organic hybrid materials formed by coordination bonds between metal nodes and organic linkers, which have been widely used in the design of flame-retardant polymer nanocomposites. On the one hand, MOFs have high specific surface area and porous structure, which can form a physical barrier layer in PC composites, slow down heat transfer, and inhibit the diffusion of flammable gas and oxygen, thereby preventing combustion. On the other hand, the metal ions in some MOFs can catalyze the dehydration and carbonization of PC at high temperatures, forming a carbon layer that further prevents heat and oxygen from transferring to the interior. In addition, the non-combustible gases released by MOFs during thermal decomposition, such as carbon dioxide and water vapor, can dilute the oxygen and flammable gas concentration in the combustion area, interrupting the combustion chain reaction. However, the flame-retardant and smoke-suppressing efficiency of a single metal ion is often not high enough, so how to improve the catalytic efficiency and flame-retardant effect of metal-organic framework complexes has become one of the important problems in the flame-retardant field. Among them, the synergistic flame-retardant effect of multiple metal ions is one of the effective methods to improve the flame-retardant efficiency. At the same time, changing the types of ions and the ratio of different ions can also effectively control the structure of metal-organic framework complexes, thereby changing the physical changes and chemical reactions that occur during combustion, and further improving the flame-retardant efficiency.

[0004] Metal-organic framework glass (MOF glass) has macroscopic solid-liquid phase change behavior (i.e. melting behavior), which is one of the typical characteristics of the fourth generation of MOFs materials. Composite materials based on MOF glass have also developed into a class of functional materials with dynamic properties and hierarchical structure control. In fact, solid flame retardants can form self-supporting ceramic bodies through melting, flowing, sintering and other physical and chemical changes, thereby preventing the spread of flames to the interior of the material and achieving a significant improvement in flame-retardant performance. Therefore, MOF glass with melting behavior can act as both a catalyst and a flux, possessing both the functions of catalyzing polymer carbonization and optimizing carbon layer structure. SUMMARY

[0005] The application aims to provide a bimetallic organic framework complex / polycarbonate composite flame-retardant material and a preparation method thereof. 2+ or Co 2+ two metals, which can not only synergistically regulate the melting characteristics of the complex, but also trigger a catalytic effect in a high-temperature environment of polymer combustion, reduce the heat release and smoke release during combustion, and improve the flame-retardant performance of the composite material.

[0006] To achieve the above-mentioned purpose, the application adopts the following technical solutions. The application first provides a bimetallic organic framework complex / polycarbonate composite flame-retardant material, which comprises 1-10wt% of the bimetallic organic framework complex and 90-99wt% of polycarbonate according to the weight percentage. The bimetallic organic framework complex is prepared by taking Zn 2+ or Co 2+ two metals as nodes and imidazole and benzimidazole as ligands.

[0007] Preferably, the composite flame-retardant material comprises 4wt% of the bimetallic organic framework complex and 96wt% of polycarbonate according to the weight percentage.

[0008] The application further provides a preparation method of the bimetallic organic framework complex / polycarbonate composite flame-retardant material, which comprises the following steps. Step one: zinc oxide, imidazole, benzimidazole, cobalt acetate and a solvent are put into a ball mill to obtain a bimetallic organic framework complex. Step two: the bimetallic organic framework complex obtained in step one and polycarbonate are pre-mixed and then put into a torque rheometer to perform melt blending, so as to obtain a composite flame-retardant material.

[0009] Preferably, the molar ratio of the total amount of zinc oxide and cobalt acetate, imidazole and benzimidazole in step one is 4:7:1.

[0010] Preferably, the molar ratio of zinc oxide and cobalt acetate in step one is (4-19):1.

[0011] Preferably, the molar ratio of zinc oxide and cobalt acetate in step one is 4:1.

[0012] Preferably, the solvent in step one is N,N-dimethylformamide.

[0013] Preferably, the rotation speed of the ball mill in step one is 400-800 revolutions per minute, and the time is 0.5-2h.

[0014] Preferably, the rotation speed of the ball mill in step one is 500 revolutions per minute, and the time is 1h.

[0015] Preferably, the melt blending temperature in step two is 220-250℃, the rotation speed is 40-80 rpm, and the time is 5-10 minutes.

[0016] Beneficial effects of the present invention This invention provides a bimetallic organic framework / polycarbonate composite flame retardant material and its preparation method. The material, by weight percentage, comprises 1-10 wt% bimetallic organic framework complex and 90-99 wt% polycarbonate. This invention selects Zif-62, a zeolite imidazole ester framework Zif series, as the metal-organic complex flame retardant; it is a typical MOF glass with melting behavior. Zn... 2+ or Co 2+ Bimetallic MoFs (Zn80-Co20-MOF-4) were synthesized using two metals as nodes and imidazole and benzimidazole as ligands. This organometallic complex synthesis method employs a mechanochemical approach, avoiding the use of large amounts of organic melts and the harsh conditions of high temperature and pressure, thus offering advantages such as environmental friendliness and energy conservation.

[0017] The two metals in the bimetallic organic framework complex of this invention can catalyze the polymer combustion process at high temperatures, reducing the release of combustion heat and smoke, and improving the flame retardant properties of the composite material. In addition, by adjusting the type and content of the metals, the melting behavior of the complex can be controlled, promoting the formation of a dense carbon layer, thereby improving the flame retardant efficiency. Attached Figure Description

[0018] Figure 1 X-ray diffraction patterns of zinc oxide, the raw material, for Example 1 and Comparative Example 2; Figure 2 Thermogravimetric curves of the organometallic complexes prepared in Example 1 and Comparative Example 2 in a nitrogen atmosphere; Figure 3 The heat flow curves of the organometallic complexes prepared in Example 1 and Comparative Example 2 in a nitrogen atmosphere are shown. Detailed Implementation

[0019] This invention first provides a bimetallic organic framework complex / polycarbonate composite flame retardant material, which, by weight percentage, comprises 1-10 wt% bimetallic organic framework complex, preferably 4 wt%, and 90-99 wt% polycarbonate, preferably 96 wt%. The bimetallic organic framework complex is based on Zn 2+ or Co 2+ The method uses two metals as nodes and imidazole and benzimidazole as ligands to prepare the solution.

[0020] This invention also provides a method for preparing a bimetallic organic framework / polycarbonate composite flame retardant material, comprising: Step 1: Place zinc oxide, imidazole, benzimidazole, cobalt acetate, and solvent into a ball mill and ball mill. The ball milling speed is preferably 400-800 rpm, more preferably 500 rpm, and the time is 0.5-2 h, more preferably 1 h, to obtain a bimetallic organic framework complex. The molar ratio of the total amount of zinc oxide and cobalt acetate, imidazole, and benzimidazole is preferably 4:7:1, and the molar ratio of zinc oxide to cobalt acetate is preferably (4~19):1, more preferably 4:1. The solvent is preferably N,N-dimethylformamide.

[0021] Step 2: The bimetallic organic framework complex and polycarbonate prepared in Step 1 are premixed and placed in a torque rheometer for melt blending. The melt blending temperature is preferably 220-250℃, more preferably 230℃, the rotation speed is 40-80 rpm, more preferably 60 rpm, and the time is 5-10 minutes, more preferably 6 minutes, to obtain a composite flame retardant material.

[0022] The bimetallic organic framework complex of this invention is synthesized using a planetary ball mill via a mechanochemical synthesis method. ZnO is selected as the metal source to provide the metal center, and cobalt acetate is added to introduce a second metal component. Imidazole (Im) and benzimidazole (bIm) are also added as organic ligands to coordinate with zinc ions and form the framework structure. A small amount of solvent is added to ensure thorough mixing and contact of the reactants, which is beneficial for the reaction. The preferred solvent in this invention is dimethylformamide (DMF).

[0023] The present invention will be further described in detail below with reference to specific embodiments. All raw materials involved in the embodiments are commercially available.

[0024] Example 1 This embodiment provides a bimetallic organic framework / polycarbonate composite flame retardant material, the preparation of which includes the following steps: Weigh out 16 mmol zinc oxide, 35 mmol imidazole, 5 mmol benzimidazole, 4 mmol cobalt acetate, and 0.5 mL N,N-dimethylformamide, and add them to a 100 mL ball mill jar of a planetary ball mill. After reacting at 500 rpm for 1 h, the mixture was filtered under reduced pressure, washed three times with deionized water, and dried in a vacuum oven at 80 °C to obtain Zn80-Co20-MOF, in which the molar percentage of Co was 20%. Weigh Zn80-Co20-MOF and polycarbonate at a weight ratio of 4:96, premix them, and place them in a torque rheometer. Melt-blend them at 230℃ and 60 rpm for 6 minutes to obtain the flame-retardant composite material (PC / Zn80-Co20-MOF-4).

[0025] Example 2 The only difference between the flame-retardant composite material in this embodiment and that in Example 1 is that the weight ratio of Zn80-Co20-MOF to polycarbonate is 10:90.

[0026] Example 3 The only difference between the flame-retardant composite material in this embodiment and that in Example 1 is that the weight ratio of Zn80-Co20-MOF to polycarbonate is 1:99.

[0027] Example 4 This embodiment provides a bimetallic organic framework / polycarbonate composite flame retardant material, the preparation of which includes the following steps: Weigh out 19 mmol zinc oxide, 35 mmol imidazole, 5 mmol benzimidazole, 1 mmol cobalt acetate, and 0.5 mL N,N-dimethylformamide, and add them to a 100 mL ball mill jar of a planetary ball mill. After reacting at 500 rpm for 1 h, the mixture was filtered under reduced pressure, washed three times with deionized water, and dried in a vacuum oven at 80 °C to obtain Zn95-Co5-MOF, in which the molar percentage of Co was 5%. Weigh Zn95-Co5-MOF and polycarbonate at a weight ratio of 4:96, premix them, and place them in a torque rheometer. Melt-blend them at 230℃ and 60 rpm for 6 minutes to obtain the flame-retardant composite material (PC / Zn95-Co5-MOF-4).

[0028] Comparative Example 1 Comparative Example 1 provides a polycarbonate material without metal-organic framework complexes, the preparation of which includes the following steps: Polycarbonate was placed in a torque rheometer and melt-blended for 6 minutes at 230°C and 60 rpm to obtain polycarbonate material (PC) without metal-organic framework complexes.

[0029] Comparative Example 2 Comparative Example 2 provides a cobalt-free metal-organic framework / polycarbonate composite flame retardant material, the preparation of which includes the following steps: Weigh out 19 mmol zinc oxide, 35 mmol imidazole, 5 mmol benzimidazole, 1 mmol zinc acetate, and 0.5 mL N,N-dimethylformamide, and add them to a 100 mL ball mill jar of a planetary ball mill. After reacting at 500 rpm for 1 h, the mixture was filtered under reduced pressure, washed three times with deionized water, and dried in a vacuum oven at 80 °C to obtain Zn100-MOF, in which the molar percentage of Co was 0%. Weigh Zn100-MOF and polycarbonate at a weight ratio of 4:96, premix them, and place them in a torque rheometer. Melt-blend them at 230℃ and 60 rpm for 6 minutes to obtain the flame-retardant composite material (PC / Zn100-MOF-4).

[0030] Figure 1 X-ray diffraction patterns of zinc oxide, the raw material, for Example 1 and Comparative Example 2; Figure 1 The XRD patterns show that the peaks of the raw material zinc oxide have basically disappeared, and the crystallization peaks of MOF appear in both Example 1 and Comparative Example 2, confirming that the material preparation was successful.

[0031] Figure 2 Thermogravimetric curves of the organometallic complexes prepared in Example 1 and Comparative Example 2 in a nitrogen atmosphere; Figure 2 The metal-organic framework complexes of Examples 1 and 2 showed a residue of over 65% at 750°C, indicating that the flame retardant forms a stable solid substance during high-temperature combustion, catalyzing the char formation of the polymer matrix and promoting the formation of an effective heat-insulating char layer.

[0032] Figure 3 The heat flow curves of the organometallic complexes prepared in Example 1 and Comparative Example 2 in a nitrogen atmosphere are shown. Figure 3 The comparative example showed an endothermic peak at 375°C, while Example 1 showed an endothermic peak at 354°C. This indicates that the introduction of cobalt metal can regulate the melting behavior of the metal-organic framework complex. Pre-melting helps to form a complete and dense heat-insulating carbon layer, thereby improving the flame retardant efficiency.

[0033] The materials prepared in Examples 1-4 and Comparative Examples 1-2 were tested, and the specific implementation process is as follows: (1) Limiting oxygen index test: conducted according to ISO-4589 standard, with sample size of 130×6.5×3mm. 3 The test results are shown in Table 1.

[0034] (2) Cone calorimetry test: The test was conducted according to ISO-5660 standard, with an irradiance of 35 kW / m². 2 The sample size is 100×100×3mm. 3 The test results are shown in Table 1.

[0035] Table 1. Flame retardant properties of the flame retardant composite materials in Examples 1-4 and Comparative Examples 2-5

[0036] As shown in Table 1, the bimetallic organic complex Zn-Co-MOF, as a halogen-free and environmentally friendly flame retardant, exhibits high flame retardant efficiency in polycarbonate materials. Compared to Comparative Example 2 (4 wt% Zn-MOF), the flame-retardant composite material with the addition of 4 wt% Zn80-Co20-MOF has a higher oxygen index and lower heat release and smoke release.

[0037] The above description is merely a preferred embodiment of the present invention, and should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A bimetallic organic framework / polycarbonate composite flame retardant material, characterized in that, The material, by weight percentage, comprises 1-10 wt% bimetallic organic framework complex and 90-99 wt% polycarbonate; The bimetallic organic framework complex is based on Zn 2+ or Co 2+ The method uses two metals as nodes and imidazole and benzimidazole as ligands to prepare the solution.

2. The bimetallic organic framework / polycarbonate composite flame retardant material according to claim 1, characterized in that, The composite flame retardant material comprises, by weight percentage, 4 wt% bimetallic organic framework complex and 96 wt% polycarbonate.

3. The method for preparing a bimetallic organic framework / polycarbonate composite flame retardant material according to claim 1 or 2, characterized in that, include: Step 1: Place zinc oxide, imidazole, benzimidazole, cobalt acetate and solvent into a ball mill and ball mill to obtain a bimetallic organic framework complex; Step 2: The bimetallic organic framework complex and polycarbonate prepared in Step 1 are premixed and placed in a torque rheometer for melt blending to obtain a composite flame retardant material.

4. The method for preparing a bimetallic organic framework / polycarbonate composite flame retardant material according to claim 3, characterized in that, The total amount of zinc oxide and cobalt acetate, imidazole, and benzimidazole mentioned in step one are in a molar ratio of 4:7:

1.

5. The method for preparing a bimetallic organic framework / polycarbonate composite flame retardant material according to claim 3, characterized in that, The molar ratio of zinc oxide to cobalt acetate in step one is (4~19):

1.

6. The method for preparing a bimetallic organic framework / polycarbonate composite flame retardant material according to claim 5, characterized in that, The molar ratio of zinc oxide to cobalt acetate in step one is 4:

1.

7. The method for preparing a bimetallic organic framework / polycarbonate composite flame retardant material according to claim 3, characterized in that, The solvent mentioned in step one is N,N-dimethylformamide.

8. The method for preparing a bimetallic organic framework / polycarbonate composite flame retardant material according to claim 3, characterized in that, The ball milling speed in step one is 400-800 rpm, and the time is 0.5-2 hours.

9. The method for preparing a bimetallic organic framework / polycarbonate composite flame retardant material according to claim 8, characterized in that, The ball milling speed in step one is 500 rpm, and the time is 1 hour.

10. The method for preparing a bimetallic organic framework / polycarbonate composite flame retardant material according to claim 3, characterized in that, The melting and blending temperature in step two is 220-250℃, the rotation speed is 40-80 rpm, and the time is 5-10 minutes.

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