Flame-retardant magnesium hydroxide for polypropylene film material

Abstract

The invention relates to flame-retardant magnesium hydroxide for a polypropylene film material. A preparation method of the flame-retardant magnesium hydroxide comprises the following steps: step 1, preparing ethylene magnesium hydroxide; step 2, preparing activated magnesium hydroxide; and step 3, preparing flame-retardant magnesium hydroxide. According to the flame-retardant material suitable for the polypropylene film material, the flame-retardant material is prepared by taking magnesium hydroxide as a base material and carrying out modification treatment, and the flame-retardant efficiency of the prepared magnesium hydroxide flame-retardant material is greatly improved; and the polypropylene film material has a good enhancement effect on the aspects of mechanical strength, impact resistance and the like of the polypropylene film material.

Description

Technical Field

[0001] The invention relates to the field of flame retardant materials, and in particular to flame retardant magnesium hydroxide for polypropylene film materials. Background Art

[0002] At present, most of the high-performance composite materials used in the fields of aerospace, automobile manufacturing, construction and building materials are prepared by pre-impregnating fibers with thermosetting resins and then curing them through multi-layer composites. However, due to the unidirectional irreversibility of thermosetting materials, the prepared composite materials cannot be reprocessed and reused after being discarded, resulting in material waste and environmental pollution. In addition, most thermosetting composite materials have a long curing time, many preparation steps, and low production efficiency. The use of thermoplastic film or plate materials to replace traditional thermosetting resins has become the development trend of high-performance composite materials in the future. Polypropylene is widely used in many fields such as automobile manufacturing, construction and building materials, aerospace, food and drug packaging, etc. due to its excellent mechanical properties, thermal stability, corrosion resistance, and easy processing.

[0003] In recent years, polypropylene co-extruded film composite materials have gradually attracted people's attention. For composite materials used in aerospace, automobile manufacturing and other fields, waterproof, oxygen-barrier and flame-retardant properties are crucial, which directly affects the application range of the material. However, polypropylene material itself has weak oxygen barrier properties and is a low-barrier polymer material. At the same time, polypropylene is also a non-self-supporting, flammable polymer with a fast flame propagation speed and a low oxygen index, which seriously affects its safety during use. Therefore, a large amount of flame retardant needs to be added to it.

[0004] As the whole society is more and more aware of the necessity of environmental protection, people's requirements for the environmental protection of flame retardants are also getting higher and higher. However, although the existing antimony bromine flame retardants have the advantages of high flame retardant efficiency and small addition amount, they are extremely harmful to people and the environment because they produce a lot of smoke and toxic and corrosive gases when burning; while inorganic flame retardants are the direction of flame retardant technology development because they are non-toxic, smoke-free, and the toxicity of combustion products is low, and they do not pollute the environment. Among them, magnesium hydroxide is an excellent environmentally friendly inorganic flame retardant with the advantages of non-toxicity, environmental protection, and high decomposition temperature, but its flame retardant efficiency is low, the addition amount is large, and the mechanical properties of the substrate are greatly affected, which limits its application. Summary of the invention

[0005] In view of the problems existing in the prior art, the object of the present invention is to provide a flame retardant magnesium hydroxide for polypropylene film material.

[0006] The purpose of the present invention is achieved by the following technical solutions:

[0007] In a first aspect, the present invention provides a method for preparing a flame retardant magnesium hydroxide for a polypropylene film material, comprising the following steps:

[0008] Step 1, preparation of ethylene magnesium hydroxide:

[0009] Weigh magnesium hydroxide powder and mix it in a mixture of ethanol and deionized water, stir until uniform, then drop silane coupling agent A-172, heat to react, then centrifuge, wash and dry to obtain ethylene magnesium hydroxide;

[0010] Step 2, preparing activated magnesium hydroxide:

[0011] Weighing ethylene magnesium hydroxide and dispersing it in toluene, adding 4-amino-2-mercaptopyrimidine, and evenly dispersing it again, then introducing nitrogen as a protective gas, adding a photoinitiator, stirring and reacting under ultraviolet light, and after the reaction is completed, centrifuging, washing and drying to obtain activated magnesium hydroxide;

[0012] Step 3, preparing flame retardant magnesium hydroxide:

[0013] Weigh o-phenylenediamine phosphoryl chloride and add it to tetrahydrofuran. After stirring evenly, add activated magnesium hydroxide, drop triethylamine, introduce nitrogen as a protective gas, reflux and stir to react. After the reaction is completed, centrifuge, wash and dry to obtain flame-retardant magnesium hydroxide.

[0014] Preferably, in step 1, the particle size of the magnesium hydroxide (MH) powder is 10-20 μm.

[0015] Preferably, in step 1, the mass volume ratio of magnesium hydroxide powder, ethanol and deionized water is 1 g: (5-10) mL: (2-6) mL.

[0016] Preferably, in step 1, the amount of silane coupling agent A-172 added is 5%-15% of the mass of the magnesium hydroxide powder.

[0017] Preferably, in step 1, the reaction temperature is 50-60° C. and the reaction time is 5-10 h.

[0018] Preferably, in step 2, the mass volume ratio of activated magnesium hydroxide, 4-amino-2-mercaptopyrimidine and toluene is 1 g:(0.16-0.32) g:(10-20) mL.

[0019] Preferably, in step 2, the photoinitiator is any one of benzoin dimethyl ether, benzoin diethyl ether, and 2,2-diethoxyacetophenone; and the amount of the photoinitiator added is 1%-6% of the mass of 4-amino-2-mercaptopyrimidine.

[0020] Preferably, in step 2, the irradiation intensity of the ultraviolet light is 10-50 mw / cm 2 , wavelength is 365nm, and reaction time is 1-3h.

[0021] Preferably, in step 3, o-phenylenediamine phosphoryl chloride is obtained by reacting o-phenylenediamine and phosphorus oxychloride in an organic solvent, the reaction temperature is 60° C., the reaction time is 8 h, and the mass ratio of o-phenylenediamine to phosphorus oxychloride is 0.15:0.16.

[0022] Preferably, in step 3, the mass volume ratio of activated magnesium hydroxide, o-phenylenediamine phosphoryl chloride and tetrahydrofuran is 1 g: (0.16-0.32) g: (10-20) mL.

[0023] Preferably, in step 3, the amount of triethylamine added is 3%-10% of the mass of o-phenylenediamine phosphoryl chloride.

[0024] Preferably, in step 3, the reaction temperature is 60-80° C. and the reaction time is 10-20 h.

[0025] In a second aspect, the present invention provides a flame retardant magnesium hydroxide for polypropylene film material, which is prepared by the above-mentioned preparation method.

[0026] The beneficial effects of the present invention are:

[0027] 1. The present invention prepares a flame retardant material suitable for polypropylene film materials. The flame retardant material is prepared by using magnesium hydroxide as a base material after modification. The prepared magnesium hydroxide flame retardant material not only greatly improves the flame retardant efficiency, but also has a good enhancement effect on the mechanical strength and impact resistance of the polypropylene film material.

[0028] 2. The flame retardant of the present invention is an organic-inorganic coated core-shell material, and the preparation process includes: first, treating magnesium hydroxide with a vinyl silane coupling agent to obtain vinyl magnesium hydroxide; then using a pyrimidine compound 4-amino-2-mercaptopyrimidine to react with vinyl magnesium hydroxide, and combining through a thiol-double bond click reaction to obtain activated magnesium hydroxide containing a thioether group; then using the amino group in the activated magnesium hydroxide to combine with o-phenylenediamine phosphoryl chloride, and generating a phosphoramide group through the combination of phosphoryl chloride-amino group, and finally obtaining a flame retardant containing thioether groups, phosphoramide groups, pyrimidine groups and the like on the surface.

[0029] 3. After applying the flame retardant prepared by the present invention to polypropylene film materials, it was found that compared with the traditional magnesium hydroxide flame retardant, the usage can be greatly reduced while maintaining the same flame retardant efficiency, and a lower smoke density can be maintained. In addition, the strength and impact resistance of the polypropylene film material are improved to a certain extent. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The present invention is further described using the accompanying drawings, but the embodiments in the accompanying drawings do not constitute any limitation to the present invention. A person skilled in the art can obtain other drawings based on the following drawings without creative work.

[0031] Figure 1 It is a scanning electron microscope schematic diagram of the flame retardant magnesium hydroxide for the polypropylene film material prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0032] The technical solution of the present invention is described below through specific examples. It should be understood that the one or more method steps mentioned in the present invention do not exclude the existence of other method steps before and after the combination step or the insertion of other method steps between these explicitly mentioned steps; it should also be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. Moreover, unless otherwise specified, the numbering of each method step is only a convenient tool for identifying each method step, and is not intended to limit the order of arrangement of each method step or to limit the scope of the present invention. The change or adjustment of the relative relationship thereof shall also be regarded as the scope of the present invention without substantially changing the technical content.

[0033] The present invention will be further described below in conjunction with the following examples.

[0034] Example 1

[0035] A method for preparing flame-retardant magnesium hydroxide for polypropylene film material comprises the following steps:

[0036] Step 1, preparation of ethylene magnesium hydroxide:

[0037] Weigh magnesium hydroxide powder (MH) with a particle size of 10-20 μm and mix it in a mixed solution of ethanol and deionized water, the mass volume ratio of magnesium hydroxide powder, ethanol and deionized water is 1g:8mL:4mL, stir until uniform, add silane coupling agent A-172 dropwise, the addition amount is 10% of the mass of magnesium hydroxide powder, heat to 55°C, stir for 6h, and then centrifuge, wash and dry to obtain ethylene magnesium hydroxide;

[0038] Step 2, preparing activated magnesium hydroxide:

[0039] Weigh ethylene magnesium hydroxide and disperse it in toluene, add 4-amino-2-mercaptopyrimidine, and the mass volume ratio of activated magnesium hydroxide, 4-amino-2-mercaptopyrimidine and toluene is 1g:0.24g:15mL. Disperse evenly again, then introduce nitrogen as protective gas, add photoinitiator benzoin dimethyl ether, and irradiate at an intensity of 25mw / cm 2 , stirred for 2 hours under ultraviolet light with a wavelength of 365 nm, and after the reaction was completed, centrifuged, washed and dried to obtain activated magnesium hydroxide;

[0040] Step 3, preparing flame retardant magnesium hydroxide:

[0041] Weigh o-phenylenediamine and phosphorus oxychloride and mix them in dichloroethane, heat them for reaction, the reaction temperature is 60° C., the reaction time is 8 hours, the mass ratio of o-phenylenediamine to phosphorus oxychloride is 0.15:0.16, after the reaction is completed, reduce pressure, wash and dry to obtain o-phenylenediamine phosphoryl chloride;

[0042] Weigh o-phenylenediamine phosphoryl chloride and add it to tetrahydrofuran. After stirring evenly, add activated magnesium hydroxide, the mass volume ratio of activated magnesium hydroxide, o-phenylenediamine phosphoryl chloride and tetrahydrofuran is 1g:0.24g:15mL, add triethylamine dropwise, the addition amount is 8% of the mass of o-phenylenediamine phosphoryl chloride, introduce nitrogen as protective gas, reflux and stir at 70°C for 15h, after the reaction is completed, centrifuge, wash and dry to obtain flame-retardant magnesium hydroxide.

[0043] Example 2

[0044] A method for preparing flame-retardant magnesium hydroxide for polypropylene film material comprises the following steps:

[0045] Step 1, preparation of ethylene magnesium hydroxide:

[0046] Weigh magnesium hydroxide powder (MH) with a particle size of 10-20 μm and mix it in a mixed solution of ethanol and deionized water, the mass volume ratio of magnesium hydroxide powder, ethanol and deionized water is 1g:5mL:2mL, stir until uniform, add silane coupling agent A-172 dropwise, the addition amount is 5% of the mass of magnesium hydroxide powder, heat to 50°C, stir for 5h, and then centrifuge, wash and dry to obtain ethylene magnesium hydroxide;

[0047] Step 2, preparing activated magnesium hydroxide:

[0048] Weigh ethylene magnesium hydroxide and disperse it in toluene, add 4-amino-2-mercaptopyrimidine, and the mass volume ratio of activated magnesium hydroxide, 4-amino-2-mercaptopyrimidine and toluene is 1g:0.16g:10mL. Disperse evenly again, then introduce nitrogen as protective gas, add photoinitiator benzoin dimethyl ether, and irradiate at an intensity of 10mw / cm 2 , stirred for 1 hour under ultraviolet light with a wavelength of 365 nm, and after the reaction was completed, centrifuged, washed and dried to obtain activated magnesium hydroxide;

[0049] Step 3, preparing flame retardant magnesium hydroxide:

[0050] Weigh o-phenylenediamine and phosphorus oxychloride and mix them in dichloroethane, heat them for reaction, the reaction temperature is 60° C., the reaction time is 8 hours, the mass ratio of o-phenylenediamine to phosphorus oxychloride is 0.15:0.16, after the reaction is completed, reduce pressure, wash and dry to obtain o-phenylenediamine phosphoryl chloride;

[0051] Weigh o-phenylenediamine phosphoryl chloride and add it to tetrahydrofuran. After stirring evenly, add activated magnesium hydroxide, the mass volume ratio of activated magnesium hydroxide, o-phenylenediamine phosphoryl chloride and tetrahydrofuran is 1g:0.16g:10mL, add triethylamine dropwise, the addition amount is 3% of the mass of o-phenylenediamine phosphoryl chloride, introduce nitrogen as protective gas, reflux and stir at 60°C for 10h, after the reaction is completed, centrifuge, wash and dry to obtain flame-retardant magnesium hydroxide.

[0052] Example 3

[0053] A method for preparing flame-retardant magnesium hydroxide for polypropylene film material comprises the following steps:

[0054] Step 1, preparation of ethylene magnesium hydroxide:

[0055] Weigh magnesium hydroxide powder (MH) with a particle size of 10-20 μm and mix it in a mixed solution of ethanol and deionized water, the mass volume ratio of magnesium hydroxide powder, ethanol and deionized water is 1g:10mL:6mL, stir until uniform, add silane coupling agent A-172 dropwise, the addition amount is 15% of the mass of magnesium hydroxide powder, heat to 60°C, stir for 10 hours, and then centrifuge, wash and dry to obtain ethylene magnesium hydroxide;

[0056] Step 2, preparing activated magnesium hydroxide:

[0057] Weigh ethylene magnesium hydroxide and disperse it in toluene, add 4-amino-2-mercaptopyrimidine, and the mass volume ratio of activated magnesium hydroxide, 4-amino-2-mercaptopyrimidine and toluene is 1g:0.32g:20mL. Disperse evenly again, then introduce nitrogen as protective gas, add photoinitiator benzoin diethyl ether, and irradiate at an intensity of 50mw / cm 2 , stirred for 3 hours under ultraviolet light with a wavelength of 365 nm, and after the reaction was completed, centrifuged, washed and dried to obtain activated magnesium hydroxide;

[0058] Step 3, preparing flame retardant magnesium hydroxide:

[0059] Weigh o-phenylenediamine and phosphorus oxychloride and mix them in dichloroethane, heat them for reaction, the reaction temperature is 60° C., the reaction time is 8 hours, the mass ratio of o-phenylenediamine to phosphorus oxychloride is 0.15:0.16, after the reaction is completed, reduce pressure, wash and dry to obtain o-phenylenediamine phosphoryl chloride;

[0060] Weigh o-phenylenediamine phosphoryl chloride and add it to tetrahydrofuran. After stirring evenly, add activated magnesium hydroxide, the mass volume ratio of activated magnesium hydroxide, o-phenylenediamine phosphoryl chloride and tetrahydrofuran is 1g:0.32g:20mL, add triethylamine dropwise, the addition amount is 10% of the mass of o-phenylenediamine phosphoryl chloride, introduce nitrogen as protective gas, reflux and stir at 80°C for 20h, after the reaction is completed, centrifuge, wash and dry to obtain flame-retardant magnesium hydroxide.

[0061] Example 4

[0062] A method for preparing flame-retardant magnesium hydroxide for polypropylene film material comprises the following steps:

[0063] Step 1, preparation of ethylene magnesium hydroxide:

[0064] Weigh magnesium hydroxide powder (MH) with a particle size of 10-20 μm and mix it in a mixed solution of ethanol and deionized water, the mass volume ratio of magnesium hydroxide powder, ethanol and deionized water is 1g:6mL:5mL, stir until uniform, add silane coupling agent A-172 dropwise, the addition amount is 12% of the mass of magnesium hydroxide powder, heat to 60°C, stir for 5h, and then centrifuge, wash and dry to obtain ethylene magnesium hydroxide;

[0065] Step 2, preparing activated magnesium hydroxide:

[0066] Weigh ethylene magnesium hydroxide and disperse it in toluene, add 4-amino-2-mercaptopyrimidine, and the mass volume ratio of activated magnesium hydroxide, 4-amino-2-mercaptopyrimidine and toluene is 1g:0.24g:15mL. Disperse evenly again, then introduce nitrogen as protective gas, add photoinitiator benzoin diethyl ether, and irradiate at an intensity of 30mw / cm 2 , stirred for 2 hours under ultraviolet light with a wavelength of 365 nm, and after the reaction was completed, centrifuged, washed and dried to obtain activated magnesium hydroxide;

[0067] Step 3, preparing flame retardant magnesium hydroxide:

[0068] Weigh o-phenylenediamine and phosphorus oxychloride and mix them in dichloroethane, heat them for reaction, the reaction temperature is 60° C., the reaction time is 8 hours, the mass ratio of o-phenylenediamine to phosphorus oxychloride is 0.15:0.16, after the reaction is completed, reduce pressure, wash and dry to obtain o-phenylenediamine phosphoryl chloride;

[0069] Weigh o-phenylenediamine phosphoryl chloride and add it to tetrahydrofuran. After stirring evenly, add activated magnesium hydroxide, the mass volume ratio of activated magnesium hydroxide, o-phenylenediamine phosphoryl chloride and tetrahydrofuran is 1g:0.24g:15mL, add triethylamine dropwise, the addition amount is 5% of the mass of o-phenylenediamine phosphoryl chloride, introduce nitrogen as protective gas, reflux and stir at 80°C for 18h, after the reaction is completed, centrifuge, wash and dry to obtain flame-retardant magnesium hydroxide.

[0070] Comparative Example 1

[0071] A method for preparing flame-retardant magnesium hydroxide for polypropylene film material, using the ethylene magnesium hydroxide in Example 1 as the flame-retardant magnesium hydroxide, comprises the following steps:

[0072] Weigh magnesium hydroxide powder (MH) with a particle size of 10-20 μm and mix it in a mixed solution of ethanol and deionized water, the mass volume ratio of magnesium hydroxide powder, ethanol and deionized water is 1g:8mL:4mL, stir until uniform, add silane coupling agent A-172 dropwise, the addition amount is 10% of the mass of the magnesium hydroxide powder, heat to 55°C, stir for 6 hours, and then centrifuge, wash and dry to obtain ethylene magnesium hydroxide, i.e. flame retardant magnesium hydroxide.

[0073] Comparative Example 2

[0074] A method for preparing flame-retardant magnesium hydroxide for polypropylene film material, using the activated magnesium hydroxide in Example 1 as the flame-retardant magnesium hydroxide, comprises the following steps:

[0075] Step 1, preparation of ethylene magnesium hydroxide:

[0076] Weigh magnesium hydroxide powder (MH) with a particle size of 10-20 μm and mix it in a mixed solution of ethanol and deionized water, the mass volume ratio of magnesium hydroxide powder, ethanol and deionized water is 1g:8mL:4mL, stir until uniform, add silane coupling agent A-172 dropwise, the addition amount is 10% of the mass of magnesium hydroxide powder, heat to 55°C, stir for 6h, and then centrifuge, wash and dry to obtain ethylene magnesium hydroxide;

[0077] Step 2, preparing activated magnesium hydroxide:

[0078] Weigh ethylene magnesium hydroxide and disperse it in toluene, add 4-amino-2-mercaptopyrimidine, and the mass volume ratio of activated magnesium hydroxide, 4-amino-2-mercaptopyrimidine and toluene is 1g:0.24g:15mL. Disperse evenly again, then introduce nitrogen as protective gas, add photoinitiator benzoin dimethyl ether, and irradiate at an intensity of 25mw / cm 2 , stirred for 2 hours under ultraviolet light with a wavelength of 365nm. After the reaction is completed, activated magnesium hydroxide, i.e. flame retardant magnesium hydroxide, is obtained through centrifugation, washing and drying.

[0079] Comparative Example 3

[0080] A method for preparing flame-retardant magnesium hydroxide for polypropylene film material, using a mixture of a reaction product of o-phenylenediamine phosphoryl chloride and 4-amino-2-mercaptopyrimidine and magnesium hydroxide as the flame-retardant magnesium hydroxide, comprising the following steps:

[0081] Weigh o-phenylenediamine phosphoryl chloride and add it to tetrahydrofuran. After stirring evenly, add magnesium hydroxide and 4-amino-2-mercaptopyrimidine. The mass volume ratio of magnesium hydroxide, 4-amino-2-mercaptopyrimidine, o-phenylenediamine phosphoryl chloride and tetrahydrofuran is 1g:0.24g:0.24g:15mL. Add triethylamine dropwise in an amount of 5% of the mass of o-phenylenediamine phosphoryl chloride. Pass nitrogen as a protective gas. Reflux and stir at 80°C for 18h. After the reaction is completed, reduce pressure, wash and dry to obtain flame-retardant magnesium hydroxide.

[0082] Experimental testing

[0083] The flame-retardant magnesium hydroxide prepared in Example 1 and Comparative Examples 1-3 was applied to a polypropylene film material, and then the mechanical properties, flame-retardant properties and anti-aging properties of the polypropylene film material were tested.

[0084] The flame-retardant magnesium hydroxide and polypropylene resin (melt index 10 g / 10 min) prepared in Example 1 and Comparative Examples 1-3 were mixed in a mass ratio of 1:5, melt-mixed evenly in a stirrer, extruded through a twin-screw extruder in a temperature range of 180-210° C., and formed on a cooling roller to prepare a flame-retardant polypropylene film material.

[0085] The prepared flame-retardant polypropylene film materials were numbered and then tested for performance. The test results are shown in the following table. Among them, the tensile strength and elongation at break test reference standard GB / T 1040.1-2018, the impact brittle temperature test reference standard GB / T 5470-2008, the smoke density test reference standard GB / T 8627-2007, and the flame retardant grade (UL-94) test reference standard ANSI / UL-94-2009 vertical combustion method.

[0086] Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Tensile strength(MPa) 32.1 23.5 27.3 28.9 Elongation at break (%) 227 158 201 186 Impact brittle temperature (℃) -37 -26 -29 -32 Smoke Density Rating (SDR) 48.3 67.5 59.7 53.1 UL-94(3.2mm) V-0 V-1 V-1 V-0

[0087] From the test results in the above table, it can be seen that the flame-retardant polypropylene film material prepared using the flame-retardant magnesium hydroxide in Example 1 obviously has stronger mechanical properties and impact resistance, and the UL-94 flame retardant grade can reach V-0, and the smoke density grade SDR is only 48.3, indicating that it has good flame retardant properties while maintaining a low smoke density.

[0088] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms should not be understood as necessarily being directed to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine different embodiments or examples described in this specification.

[0089] 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 method for preparing flame-retardant magnesium hydroxide for polypropylene film material, characterized in that: The following steps are involved: Step 1, preparation of vinyl magnesium hydroxide: Weigh magnesium hydroxide powder and mix it in a mixture of ethanol and deionized water, stir until uniform, then drop silane coupling agent A-172, heat to react, then centrifuge, wash and dry to obtain ethylene magnesium hydroxide; Step 2, preparing activated magnesium hydroxide: Weighing ethylene magnesium hydroxide and dispersing it in toluene, adding 4-amino-2-mercaptopyrimidine, and evenly dispersing it again, then introducing nitrogen as a protective gas, adding a photoinitiator, stirring and reacting under ultraviolet light, and after the reaction is completed, centrifuging, washing and drying to obtain activated magnesium hydroxide; Step 3, preparing flame retardant magnesium hydroxide: Weigh o-phenylenediamine phosphoryl chloride and add it to tetrahydrofuran. After stirring evenly, add activated magnesium hydroxide, drop triethylamine, introduce nitrogen as a protective gas, reflux and stir to react. After the reaction is completed, centrifuge, wash and dry to obtain flame-retardant magnesium hydroxide.

2. The method for preparing a flame retardant magnesium hydroxide for polypropylene film material according to claim 1, characterized in that: In the step 1, the mass volume ratio of magnesium hydroxide powder, ethanol and deionized water is 1g:(5-10)mL:(2-6)mL; and the added amount of silane coupling agent A-172 is 5%-15% of the mass of magnesium hydroxide powder.

3. The method for preparing a flame retardant magnesium hydroxide for polypropylene film material according to claim 1, characterized in that: In the step 1, the reaction temperature is 50-60° C. and the reaction time is 5-10 h.

4. The method for preparing a flame retardant magnesium hydroxide for polypropylene film material according to claim 1, characterized in that: In the step 2, the mass volume ratio of activated magnesium hydroxide, 4-amino-2-mercaptopyrimidine and toluene is 1 g: (0.16-0.32) g: (10-20) mL.

5. The method for preparing a flame retardant magnesium hydroxide for polypropylene film material according to claim 1, characterized in that: In the step 2, the photoinitiator is any one of benzoin dimethyl ether, benzoin diethyl ether, and 2,2-diethoxyacetophenone; and the amount of the photoinitiator added is 1%-6% of the mass of 4-amino-2-mercaptopyrimidine.

6. The method for preparing a flame retardant magnesium hydroxide for polypropylene film material according to claim 1, characterized in that: In step 2, the irradiation intensity of the ultraviolet light is 10-50mw / cm 2 , wavelength is 365nm, and reaction time is 1-3h.

7. The method for preparing a flame retardant magnesium hydroxide for polypropylene film material according to claim 1, characterized in that: In the step 3, o-phenylenediamine phosphoryl chloride is obtained by reacting o-phenylenediamine and phosphorus oxychloride in an organic solvent, the reaction temperature is 60° C., the reaction time is 8 hours, and the mass ratio of o-phenylenediamine to phosphorus oxychloride is 0.15:0.

16.

8. The method for preparing a flame retardant magnesium hydroxide for polypropylene film material according to claim 1, characterized in that: In the step 3, the mass volume ratio of activated magnesium hydroxide, o-phenylenediamine phosphoryl chloride and tetrahydrofuran is 1 g: (0.16-0.32) g: (10-20) mL.

9. The method for preparing a flame retardant magnesium hydroxide for polypropylene film material according to claim 1, characterized in that: In the step 3, the reaction temperature is 60-80° C. and the reaction time is 10-20 h.

10. A flame retardant magnesium hydroxide for polypropylene film material, characterized in that: The preparation method according to claim 1 is used for preparation.

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