Preparation method and application of magnesium aluminum hydroxide composite flame retardant

Abstract

The invention discloses a preparation method and application of a magnesium-aluminum hydroxide composite flame retardant, and relates to the technical field of flame retardancy. The preparation method comprises the following steps: mixing magnesium hydroxide and aluminum hydroxide in proportion, adding the mixture into a modified liquid for pretreatment; dispersing the mixture into DMF, dropping protocatechuic aldehyde into the mixture under stirring, introducing nitrogen, and reacting to obtain Schiff-alkalized magnesium hydroxide / aluminum hydroxide; dispersing the mixture into DMF, adding DOPO under stirring, and reacting to obtain a magnesium hydroxide / aluminum hydroxide composite flame retardant; the composite flame retardant contains three flame retardant elements, namely, N, P, and Si, and generates non-combustible gases such as N2 and NH3 to dilute the gas phase during combustion, and also generates groups such as P-O-P, Si-O-Si, and Si-C, so as to form a high-strength and dense silicon layer and carbon layer on the surface of a polymer, effectively reducing the heat conduction speed, isolating oxygen, and slowing down the escape of combustible gas, thereby reducing the decomposition rate of the resin and slowing down the combustion rate.

Description

Technical Field

[0001] The invention relates to the technical field of flame retardancy, and in particular to a preparation method and application of a magnesium aluminum hydroxide composite flame retardant. Background Art

[0002] Polypropylene (PP) is widely used in vehicles, household appliances, building materials and packaging due to its advantages such as light weight, corrosion resistance, low price and easy processing. Polypropylene resin is a synthetic resin with consumption second only to polyethylene. However, as an organic high molecular polymer, PP's pure hydrocarbon composition and carbon-carbon single bond structure lead to its poor carbon-forming performance. It is difficult to form a stable carbon layer during the combustion process, resulting in its excellent combustion performance. In addition, the combustion process will produce molten droplets and generate a large amount of heat, leading to the generation and rapid spread of fire. In addition, the combustion of PP will produce a large amount of smoke and toxic gases (mainly CO), among which smoke will reduce visibility and cause thermal burns to the human respiratory tract. The propagation speed of smoke is much greater than the propagation speed of flames, which often accelerates the spread of fire; inhalation of CO can cause suffocation and death, and death in fires is mainly caused by CO poisoning. These potential safety threats have greatly limited the application of PP.

[0003] In order to improve the safety of PP, it needs to be flame-retardant modified. The current flame retardant methods are mainly divided into reactive and additive types. Among them, the reactive type refers to the introduction of flame retardant elements such as phosphorus, nitrogen, and silicon during the polymer synthesis process to improve the flame retardancy of the polymer itself. This method has high flame retardant efficiency, but the process is complex and not easy to promote. The additive type refers to the addition of flame retardant additives during the polymer processing process. This method is simple in process and widely applicable, and is currently the most important flame retardant method. Among them, halogen flame retardants have been widely used in PP flame retardancy due to their good universality and high flame retardant efficiency. However, because a large amount of organic pollutants will be generated during its production process, it will seriously pollute the environment, especially water resources, and it will produce strong carcinogens such as dioxins during its combustion process. Harmful substances, so it is banned. Therefore, the halogen-free flame retardant has become the current research focus in the field of flame retardancy.

[0004] Currently, the commonly used halogen-free flame retardants include phosphorus-based and intumescent flame retardants, metal hydroxides, boron-based flame retardants, silicon-based flame retardants and inorganic nano flame retardants. Among them, metal hydroxide flame retardants have become the most widely used flame retardant category due to their advantages such as non-toxicity, environmental protection, smoke suppression and low price. Metal oxide flame retardants mainly include aluminum hydroxide (ATH) and magnesium hydroxide (MDH). Their flame retardant process is non-toxic, environmentally friendly and has excellent smoke suppression performance. They are currently the most widely used type of flame retardant. Its flame retardant effect is mainly achieved by reducing the thermal decomposition of the matrix through the endothermic decomposition of the flame retardant in the condensed phase to produce a corresponding oxide carbon layer. Its flame retardant mechanism is as follows: (1) The metal hydroxide decomposes to produce the corresponding oxide and water under heat. The decomposition absorbs a large amount of heat, which can effectively reduce the thermal decomposition rate of the PP matrix; (2) The water produced by the decomposition escapes into the gas phase, dilutes the concentration of the combustible gas in the combustion zone, and reduces the heat release rate in the combustion zone; (3) The oxide produced by the decomposition forms a carbon layer covering the PP surface, reducing the thermal radiation of the combustion zone to the PP matrix, reducing the thermal decomposition rate of PP. At the same time, the carbon layer can inhibit the escape of combustible gas from the condensed phase and reduce the concentration of combustible gas in the combustion zone. Therefore, metal hydroxide can effectively reduce the heat release rate of PP combustion and improve the flame retardant performance of PP. The oxide carbon layer inhibits the escape of combustible gas, resulting in an increase in the amount of smoke generated in the condensed phase of the system. The oxide carbon layer can effectively adsorb the smoke generated in the condensed phase, retain the smoke in the carbon layer, and then further thermally degrade to generate CO or CO2 and enter the gas phase, so that the hydroxide flame retardant exhibits excellent smoke suppression performance.

[0005] Chinese patent document CN201310096494.3 discloses a halogen-free flame-retardant polypropylene foam material, which is composed of the following components (in parts by weight): 40-60 parts of random copolymer polypropylene; 10-20 parts of polyethylene; 5-10 parts of red phosphorus; 3-8 parts of aluminum hydroxide; 2-5 parts of magnesium hydroxide; 5-10 parts of foaming agent; and 1-2 parts of cross-linking agent. By adding the three halogen-free flame retardants of red phosphorus, aluminum hydroxide and magnesium hydroxide, a green and environmentally friendly polypropylene foam material can be obtained.

[0006] However, the flame retardant mode of inorganic flame retardants, which releases bound water and absorbs heat to reduce temperature, is less efficient than other modes, and usually requires high filling to obtain the expected flame retardant properties. In addition, inorganic flame retardants have poor compatibility with organic polymer materials, and high inorganic flame retardant filling levels will cause the mechanical properties and processing properties of flame retardant materials to deteriorate. Summary of the invention

[0007] In order to solve the shortcomings of the prior art, the purpose of the present invention is to provide a preparation method and application of a magnesium aluminum hydroxide composite flame retardant. The prepared composite flame retardant contains three flame retardant elements, N, P, and Si. When burned, it will produce non-combustible gases such as N2 and NH3 to dilute the gas phase, and will also generate groups such as POP, Si-O-Si, and Si-C to form high-strength and dense silicon layers and carbon layers on the polymer surface, effectively reducing the heat conduction rate, isolating oxygen, and slowing down the escape of combustible gases, thereby reducing the decomposition rate of the resin and slowing down the combustion rate.

[0008] In order to achieve the above object, the present invention adopts the following technical solution:

[0009] A method for preparing a magnesium aluminum hydroxide composite flame retardant comprises the following steps:

[0010] (1) Mixing magnesium hydroxide and aluminum hydroxide in proportion, then adding them to the modified liquid, stirring for reaction, filtering and drying the product to obtain pretreated magnesium hydroxide / aluminum hydroxide;

[0011] Preferably, in step (1), the weight ratio of magnesium hydroxide to aluminum hydroxide is 1:0.5-3; the modifying liquid is obtained by mixing KH550 and anhydrous ethanol in a volume ratio of 5-10:100, and the weight ratio of magnesium hydroxide and aluminum hydroxide powder to the modifying liquid is 10:1-2.5.

[0012] Preferably, in step (1), the mixing conditions are stirring at 100-300 r / min for 10-20 min; and the stirring reaction conditions are reacting at 40-60° C. for 1.5-3 h.

[0013] (2) Dispersing the pretreated magnesium hydroxide / aluminum hydroxide in DMF, dropping protocatechuic aldehyde under stirring, continuously introducing N2, reflux reaction, filtering the product, washing with methanol, and drying to obtain Schiff-base magnesium hydroxide / aluminum hydroxide; the specific reaction process is as follows:

[0014]

[0015] In the above reaction, means magnesium hydroxide or aluminium hydroxide;

[0016] Preferably, in step (2), the weight ratio of pretreated magnesium hydroxide / aluminum hydroxide to DMF is 1:5-10; the weight ratio of pretreated magnesium hydroxide / aluminum hydroxide to protocatechuic aldehyde is 10:8.7-16.3.

[0017] Preferably, in step (2), the reflux reaction conditions are 55-85° C. for 6-12 h.

[0018] (3) Disperse Schiff-base magnesium hydroxide / aluminum hydroxide in DMF, add DOPO under stirring, continue to introduce N2, stir to react, filter the product, wash with ethanol, and dry to obtain a magnesium aluminum hydroxide composite flame retardant. The specific reaction process is as follows:

[0019]

[0020] In the above reaction, means magnesium hydroxide or aluminium hydroxide;

[0021] Preferably, in step (3), the weight ratio of Schiff alkalized magnesium hydroxide / aluminum hydroxide to DMF is 1:5-10; the weight ratio of Schiff alkalized magnesium hydroxide / aluminum hydroxide to DOPO is 10:14.5-21.2.

[0022] Preferably, in step (3), the stirring reaction condition is 50-80° C. for 8-18 h.

[0023] The present invention also claims protection for a magnesium aluminum hydroxide composite flame retardant prepared by the preparation method.

[0024] The present invention also claims to protect the application of the magnesium aluminum hydroxide composite flame retardant in polypropylene flame retardant plastic.

[0025] Preferably, the polypropylene flame retardant plastic is made of the following raw materials in parts by weight: 100 parts of polypropylene resin and 10 to 40 parts of magnesium aluminum hydroxide composite flame retardant.

[0026] Preferably, the preparation method of the polypropylene flame retardant plastic comprises the following steps: stirring and mixing the magnesium aluminum hydroxide composite flame retardant and the polypropylene resin evenly, drying at 80°C for 24 hours, adding the two raw materials into a twin-screw extruder, circulating at 200°C and 60r / min for 5 minutes, injection molding in an injection molding machine, with a mold temperature of 60°C and holding pressure for 8 seconds, to obtain the polypropylene flame retardant plastic.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1) The present invention provides a magnesium-aluminum hydroxide composite flame retardant. During the combustion process, magnesium hydroxide and aluminum hydroxide are thermally decomposed to produce MgO and Al2O3 particles, but the carbon layer structure strength is relatively low. Therefore, the present invention modifies magnesium hydroxide / aluminum hydroxide powders by KH550, protocatechuic aldehyde, and DOPO. The prepared composite flame retardant contains three flame retardant elements, N, P, and Si. During combustion, non-combustible gases such as N2 and NH3 are generated to dilute the gas phase, and groups such as POP, Si-O-Si, and Si-C are also generated to form high-strength and dense silicon layers and carbon layers on the polymer surface, which effectively reduce the heat conduction speed, isolate oxygen, and slow down the escape of combustible gases, thereby reducing the decomposition rate of the resin and slowing down the combustion rate. In addition, after the composite flame retardant is organically modified on the surface of magnesium hydroxide and aluminum hydroxide powders, its compatibility with organic polymer materials is increased, which is beneficial to improving the mechanical properties of the flame retardant material.

[0029] 2) The present invention provides a magnesium aluminum hydroxide composite flame retardant. First, magnesium hydroxide and aluminum hydroxide composite powders are modified by KH550 to obtain pretreated magnesium hydroxide / aluminum hydroxide. Then, the aldehyde group in protocatechuic aldehyde and the primary amino group in KH550 undergo a Schiff base reaction to obtain Schiff-based magnesium hydroxide / aluminum hydroxide containing a C=N double bond. Finally, the active PH bond in DOPO is reacted with it to open the C=N double bond and introduce phosphorus to obtain a magnesium aluminum hydroxide composite flame retardant. The prepared composite flame retardant is modified by KH550, protocatechuic aldehyde and DOPO, which makes up for the defect of a single flame retardant mode of inorganic flame retardants and gives the composite flame retardant excellent synergistic flame retardant effect. Results: KH550 can organically modify the surface of magnesium hydroxide / aluminum hydroxide to increase its compatibility with the system, and introduce silicon and nitrogen elements into the flame retardant, while also playing a bridging role, which is conducive to the subsequent introduction of protocatechuic aldehyde and DOPO; protocatechuic aldehyde introduces a rigid and heat-resistant benzene ring structure into the flame retardant, which can improve the rigid cohesion of organic polymer materials, and the introduction of carbon elements is also conducive to improving the carbonization effect during the combustion process; DOPO decomposition can produce phosphorus-containing substances, which can form phosphoric acid after oxidation and combination with water, thereby prompting the resin matrix macromolecular chain to participate in the solid-phase carbonization reaction, which can play a synergistic role with the water release and heat absorption of metal hydroxides, and significantly improve the flame retardant effect of the flame retardant. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solution and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with the embodiments. Of course, the specific embodiments described here are only used to explain the present invention and are not used to limit the present invention.

[0031] Unless otherwise specified, the chemical reagents and materials in the present invention are purchased from commercial sources or synthesized from raw materials purchased from commercial sources.

[0032] Polypropylene was purchased from Yanshan Petrochemical Company, model K7726H;

[0033] Magnesium hydroxide was purchased from Qinghai Aitek Salt Lake Technology Co., Ltd., with a particle size of 1 to 4 μm;

[0034] Aluminum hydroxide was purchased from Zibo Pengfeng New Material Technology Co., Ltd. with a particle size of 1 to 3 μm.

[0035] A method for preparing a magnesium aluminum hydroxide composite flame retardant comprises the following steps:

[0036] (1) 10 g of magnesium hydroxide and 5 to 30 g of aluminum hydroxide are stirred at 100 to 300 r / min for 10 to 20 min, then added into a modification liquid (prepared by mixing KH550 and anhydrous ethanol at a volume ratio of 5 to 10:100) having a weight of 1 to 2.5 times that of the powder, stirred and reacted at 40 to 60° C. for 1.5 to 3 h, and the product is filtered and dried to obtain pretreated magnesium hydroxide / aluminum hydroxide;

[0037] (2) dispersing 10 g of pretreated magnesium hydroxide / aluminum hydroxide into 50-100 g of DMF, dropping 8.7-16.3 g of protocatechuic aldehyde into the mixture under stirring, continuously introducing N2, and reflux reacting at 55-85° C. for 6-12 h. Filtering the product, washing it with methanol, and drying it to obtain Schiff-base magnesium hydroxide / aluminum hydroxide;

[0038] (3) Disperse 10 g of Schiff-base magnesium hydroxide / aluminum hydroxide in 50-100 g of DMF, add 14.5-21.2 g of DOPO under stirring, continuously introduce N2, and react at 50-80° C. with stirring for 8-18 h. Filter the product, wash with ethanol, and dry to obtain a magnesium aluminum hydroxide composite flame retardant.

[0039] A preparation method of polypropylene flame retardant plastic comprises the following steps: 10-40g of magnesium aluminum hydroxide composite flame retardant and 100g of polypropylene resin are stirred and mixed evenly, dried at 80°C for 24h, the two raw materials are added into a twin-screw extruder, circulated at 200°C and 60r / min for 5min, injection molded in an injection molding machine, with a mold temperature of 60°C and pressure holding for 8s, to obtain the polypropylene flame retardant plastic.

[0040] The present invention will be further described below through specific embodiments.

[0041] Example 1

[0042] A method for preparing a magnesium aluminum hydroxide composite flame retardant comprises the following steps:

[0043] (1) 10 g of magnesium hydroxide and 10 g of aluminum hydroxide were stirred at 200 r / min for 20 min, then added into 50 g of modified liquid (KH550 and anhydrous ethanol were mixed in a volume ratio of 10:100), stirred and reacted at 60° C. for 3 h, and the product was filtered and dried to obtain pretreated magnesium hydroxide / aluminum hydroxide;

[0044] (2) dispersing 10 g of pretreated magnesium hydroxide / aluminum hydroxide into 100 g of DMF, dropping 16.3 g of protocatechuic aldehyde into the mixture under stirring, continuously introducing N2, and reflux reacting at 85° C. for 12 h. Filtering the product, washing it with methanol, and drying it to obtain Schiff-based magnesium hydroxide / aluminum hydroxide;

[0045] (3) Disperse 10 g of Schiff-base magnesium hydroxide / aluminum hydroxide in 100 g of DMF, add 21.2 g of DOPO under stirring, continue to introduce N2, stir and react at 80° C. for 18 h, filter the product, wash with ethanol, and dry to obtain a magnesium aluminum hydroxide composite flame retardant.

[0046] A preparation method of polypropylene flame retardant plastic comprises the following steps: stirring and mixing 40g of magnesium aluminum hydroxide composite flame retardant and 100g of polypropylene resin evenly, drying at 80°C for 24h, adding the two raw materials into a twin-screw extruder, circulating at 200°C and 60r / min for 5min, injection molding in an injection molding machine, with a mold temperature of 60°C and pressure holding for 8s, to obtain the polypropylene flame retardant plastic.

[0047] Example 2

[0048] A method for preparing a magnesium aluminum hydroxide composite flame retardant comprises the following steps:

[0049] (1) 10 g of magnesium hydroxide and 10 g of aluminum hydroxide were stirred at 200 r / min for 15 min, then added into 50 g of modified liquid (KH550 and anhydrous ethanol were mixed in a volume ratio of 10:100), stirred and reacted at 55° C. for 2.5 h, and the product was filtered and dried to obtain pretreated magnesium hydroxide / aluminum hydroxide;

[0050] (2) dispersing 10 g of pretreated magnesium hydroxide / aluminum hydroxide into 100 g of DMF, dropping 13.8 g of protocatechuic aldehyde into the mixture under stirring, continuously introducing N2, and reflux reacting at 75° C. for 10 h. The product was filtered, washed with methanol, and dried to obtain Schiff-based magnesium hydroxide / aluminum hydroxide;

[0051] (3) Disperse 10 g of Schiff-base magnesium hydroxide / aluminum hydroxide in 100 g of DMF, add 18.9 g of DOPO under stirring, continue to introduce N2, stir and react at 70°C for 14 h, filter the product, wash with ethanol, and dry to obtain a magnesium aluminum hydroxide composite flame retardant.

[0052] A preparation method of polypropylene flame retardant plastic comprises the following steps: stirring and mixing 30g of magnesium aluminum hydroxide composite flame retardant and 100g of polypropylene resin evenly, drying at 80°C for 24h, adding the two raw materials into a twin-screw extruder, circulating at 200°C and 60r / min for 5min, injection molding in an injection molding machine, with a mold temperature of 60°C and pressure holding for 8s, to obtain the polypropylene flame retardant plastic.

[0053] Example 3

[0054] A method for preparing a magnesium aluminum hydroxide composite flame retardant comprises the following steps:

[0055] (1) 10 g of magnesium hydroxide and 10 g of aluminum hydroxide were stirred at 100 r / min for 10 min, then added into 50 g of modified liquid (KH550 and anhydrous ethanol were mixed at a volume ratio of 5:100), stirred and reacted at 45° C. for 2 h, and the product was filtered and dried to obtain pretreated magnesium hydroxide / aluminum hydroxide;

[0056] (2) Dispersing 10 g of pretreated magnesium hydroxide / aluminum hydroxide into 50 g of DMF, dropping 11.3 g of protocatechuic aldehyde into the mixture under stirring, continuously introducing N2, and reflux reacting at 65° C. for 8 h. Filtering the product, washing it with methanol, and drying it to obtain Schiff-based magnesium hydroxide / aluminum hydroxide;

[0057] (3) Disperse 10 g of Schiff-base magnesium hydroxide / aluminum hydroxide in 50 g of DMF, add 16.7 g of DOPO under stirring, continue to introduce N2, and stir the reaction at 60° C. for 10 h. Filter the product, wash with ethanol, and dry to obtain a magnesium aluminum hydroxide composite flame retardant.

[0058] A preparation method of polypropylene flame retardant plastic comprises the following steps: 20g of magnesium aluminum hydroxide composite flame retardant and 100g of polypropylene resin are stirred and mixed evenly, dried at 80°C for 24h, the two raw materials are added into a twin-screw extruder, circulated at 200°C and 60r / min for 5min, injection molded in an injection molding machine, the mold temperature is 60°C, and the pressure is maintained for 8s, so as to obtain the polypropylene flame retardant plastic.

[0059] Example 4

[0060] A method for preparing a magnesium aluminum hydroxide composite flame retardant comprises the following steps:

[0061] (1) 10 g of magnesium hydroxide and 10 g of aluminum hydroxide were stirred at 100 r / min for 10 min, then added into 50 g of modified liquid (KH550 and anhydrous ethanol were mixed at a volume ratio of 5:100), stirred and reacted at 40° C. for 1.5 h, and the product was filtered and dried to obtain pretreated magnesium hydroxide / aluminum hydroxide;

[0062] (2) Dispersing 10 g of pretreated magnesium hydroxide / aluminum hydroxide into 50 g of DMF, dropping 8.7 g of protocatechuic aldehyde into the mixture under stirring, continuously introducing N2, and reflux reacting at 55° C. for 6 h. Filtering the product, washing it with methanol, and drying it to obtain Schiff-based magnesium hydroxide / aluminum hydroxide;

[0063] (3) Disperse 10 g of Schiff-base magnesium hydroxide / aluminum hydroxide in 50 g of DMF, add 14.5 g of DOPO under stirring, continue to introduce N2, and stir the reaction at 50° C. for 8 h. Filter the product, wash with ethanol, and dry to obtain a magnesium aluminum hydroxide composite flame retardant.

[0064] A preparation method of polypropylene flame retardant plastic comprises the following steps: stirring and mixing 10g of magnesium aluminum hydroxide composite flame retardant and 100g of polypropylene resin evenly, drying at 80°C for 24h, adding the two raw materials into a twin-screw extruder, circulating at 200°C and 60r / min for 5min, injection molding in an injection molding machine, with a mold temperature of 60°C and pressure holding for 8s, to obtain the polypropylene flame retardant plastic.

[0065] Comparative Example 1

[0066] A method for preparing a magnesium aluminum hydroxide composite flame retardant comprises the following steps:

[0067] (1) 10 g of magnesium hydroxide and 10 g of aluminum hydroxide were stirred at 200 r / min for 20 min, then added into 50 g of modified liquid (KH550 and anhydrous ethanol were mixed in a volume ratio of 10:100), stirred and reacted at 60° C. for 3 h, and the product was filtered and dried to obtain pretreated magnesium hydroxide / aluminum hydroxide;

[0068] (2) Disperse 10 g of pretreated magnesium hydroxide / aluminum hydroxide in 100 g of DMF, add 16.3 g of protocatechuic aldehyde dropwise under stirring, continue to introduce N2, reflux at 85°C for 12 h, filter the product, wash with methanol, and dry to obtain a magnesium aluminum hydroxide composite flame retardant.

[0069] A preparation method of polypropylene flame retardant plastic comprises the following steps: stirring and mixing 40g of magnesium aluminum hydroxide composite flame retardant and 100g of polypropylene resin evenly, drying at 80°C for 24h, adding the two raw materials into a twin-screw extruder, circulating at 200°C and 60r / min for 5min, injection molding in an injection molding machine, with a mold temperature of 60°C and pressure holding for 8s, to obtain the polypropylene flame retardant plastic.

[0070] Comparative Example 2

[0071] A method for preparing a magnesium aluminum hydroxide composite flame retardant comprises the following steps:

[0072] 10g of magnesium hydroxide and 10g of aluminum hydroxide were stirred at 200r / min for 20min, then added into 50g of modified liquid (KH550 and anhydrous ethanol were mixed in a volume ratio of 10:100), stirred and reacted at 60°C for 3h, and the product was filtered and dried to obtain a magnesium aluminum hydroxide composite flame retardant.

[0073] A preparation method of polypropylene flame retardant plastic comprises the following steps: stirring and mixing 40g of magnesium aluminum hydroxide composite flame retardant and 100g of polypropylene resin evenly, drying at 80°C for 24h, adding the two raw materials into a twin-screw extruder, circulating at 200°C and 60r / min for 5min, injection molding in an injection molding machine, with a mold temperature of 60°C and pressure holding for 8s, to obtain the polypropylene flame retardant plastic.

[0074] The polypropylene flame retardant plastics prepared in Examples 1 to 4 and Comparative Examples 1 to 2 were made into specimens with a specification of 130 mm × 13 mm × 3 mm for performance testing, and the limiting oxygen index test was performed with reference to ASTM D2863-10, the vertical burning test was performed with reference to ASTM D3801-10, the tensile strength test was performed with reference to GB / T 1447-2005 "Test Method for Tensile Properties of Fiber Reinforced Plastics", the elongation at break test was performed with reference to GB / T 1040.1-2018 "Determination of Tensile Properties of Plastics Part 1: General Principles", and the notched impact strength test was performed with reference to GB / T 1843-2008 "Determination of Izod Impact Strength of Plastics". The specific data are shown in Table 1.

[0075] Table 1 Test results of polypropylene flame retardant plastic properties

[0076]

[0077] According to the data in the table, the magnesium aluminum hydroxide composite flame retardant provided by the present invention can significantly improve the flame retardant properties of polypropylene. At the same time, after modification, the compatibility of the composite flame retardant with the polypropylene system is also improved. Although the mechanical properties of the polypropylene flame retardant plastic decrease with the increase in the amount of flame retardant added, under the same addition ratio, the mechanical properties of the flame retardant material obtained by adding the modified composite flame retardant are still significantly better than those of the flame retardant material obtained by adding the unmodified flame retardant.

[0078] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for preparing a magnesium aluminum hydroxide composite flame retardant, characterized in that: The steps include: (1) Mixing magnesium hydroxide and aluminum hydroxide in proportion, adding them to the modified liquid, stirring for reaction, filtering and drying the product to obtain pretreated magnesium hydroxide / aluminum hydroxide; (2) dispersing the pretreated magnesium hydroxide / aluminum hydroxide in DMF, dropping protocatechuic aldehyde into the mixture under stirring, continuously introducing N2, reflux reaction, filtering the product, washing with methanol, and drying to obtain Schiff-base magnesium hydroxide / aluminum hydroxide; (3) Dispersing the Schiff-base magnesium hydroxide / aluminum hydroxide in DMF, adding DOPO under stirring, continuously introducing N2, stirring the reaction, filtering the product, washing with ethanol, and drying to obtain a magnesium hydroxide / aluminum hydroxide composite flame retardant; In step (1), the weight ratio of magnesium hydroxide to aluminum hydroxide is 1:0.5-3; the modifying liquid is obtained by mixing KH550 and anhydrous ethanol in a volume ratio of 5-10:100, and the weight ratio of magnesium hydroxide and aluminum hydroxide powder to the modifying liquid is 10:1-2.

5.

2. The preparation method according to claim 1, characterized in that: In step (1), the mixing condition is stirring at 100-300 r / min for 10-20 min; the stirring reaction condition is reacting at 40-60° C. for 1.5-3 h.

3. The preparation method according to claim 1, characterized in that: In step (2), the weight ratio of pretreated magnesium hydroxide / aluminum hydroxide to DMF is 1:5-10; the weight ratio of pretreated magnesium hydroxide / aluminum hydroxide to protocatechuic aldehyde is 10:8.7-16.

3.

4. The preparation method according to claim 1, characterized in that: In step (2), the reflux reaction conditions are 55-85° C. for 6-12 h.

5. The preparation method according to claim 1, characterized in that: In step (3), the weight ratio of Schiff alkalized magnesium hydroxide / aluminum hydroxide to DMF is 1:5-10; the weight ratio of Schiff alkalized magnesium hydroxide / aluminum hydroxide to DOPO is 10:14.5-21.

2.

6. The preparation method according to claim 1, characterized in that: In step (3), the stirring reaction conditions are 50-80° C. for 8-18 hours.

7. A magnesium aluminum hydroxide composite flame retardant prepared by the preparation method according to any one of claims 1 to 6.

8. Use of the magnesium aluminum hydroxide composite flame retardant as claimed in claim 7 in polypropylene flame retardant plastics.

9. The use according to claim 8, characterized in that: The polypropylene flame retardant plastic is made of the following raw materials in parts by weight: 100 parts of polypropylene resin and 10-40 parts of magnesium aluminum hydroxide composite flame retardant.

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