阅读说明：本技术 一种含氮磷水滑石基阻燃剂及其制备方法 (Nitrogen-phosphorus-containing hydrotalcite-based flame retardant and preparation method thereof ) 是由 徐圣 胡杰 曾虹燕 田贤曜 吴昆� 颜文娟 钟承志 郭一卉 马嘉欣 王晗 于 2021-01-05 设计创作，主要内容包括：本发明公开了一种含氮磷水滑石基阻燃剂,包括以下原料：水滑石、含氮单体、氢氧化钠和含磷单体；制备方法：(1)称取各原料；(2)将水滑石和含氮单体超声分散于去离子水中,备用；(3)将氢氧化钠和含磷单体超声分散于去离子水中；(4)在磁力搅拌的条件下将含磷单体碱液逐滴加入水滑石悬浮液中,升温反应,过滤,真空干燥,研磨,即得。本发明将含磷单体和含氮单体引入水滑石体系中,可以将生物质和水滑石两者的优点相结合,从而得到一种有机-无机杂化的阻燃剂,并将其应用到聚合物基体中,弥补了水滑石添加量大的缺陷,对聚合物阻燃具有重要意义。(The invention discloses a nitrogen-phosphorus-containing hydrotalcite-based flame retardant which comprises the following raw materials: hydrotalcite, nitrogen-containing monomer, sodium hydroxide and phosphorus-containing monomer; the preparation method comprises the following steps: (1) weighing the raw materials; (2) ultrasonically dispersing hydrotalcite and a nitrogenous monomer into deionized water for later use; (3) ultrasonically dispersing sodium hydroxide and a phosphorus-containing monomer in deionized water; (4) dropwise adding phosphorus monomer alkali liquor into the hydrotalcite suspension under the condition of magnetic stirring, heating for reaction, filtering, drying in vacuum, and grinding to obtain the hydrotalcite. According to the invention, the phosphorus-containing monomer and the nitrogen-containing monomer are introduced into the hydrotalcite system, so that the advantages of the biomass and the hydrotalcite can be combined, and the organic-inorganic hybrid flame retardant is obtained and applied to the polymer matrix, so that the defect of large addition amount of the hydrotalcite is overcome, and the flame retardant has important significance for polymer flame retardance.)

1. The nitrogen-phosphorus-containing hydrotalcite-based flame retardant is characterized by comprising the following raw materials: hydrotalcite, nitrogen-containing monomer, sodium hydroxide and phosphorus-containing monomer;

the mass ratio of the hydrotalcite to the nitrogen-containing monomer to the sodium hydroxide to the phosphorus-containing monomer is 1 (1-3) to 2-4 to 9-14.

2. The nitrogen-phosphorus-containing hydrotalcite-based flame retardant according to claim 1, wherein the hydrotalcite is magnesium aluminum hydrotalcite comprising the following raw materials: magnesium salts, aluminum salts and urea;

mg in the magnesium salt²⁺With Al in the aluminum salt³⁺The molar ratio of (2-3) to (1);

mg in the magnesium salt²⁺And Al in the aluminum salt³⁺The ratio of the sum of the number of moles of (a) to the number of moles of the urea is 1 (3-4).

3. The nitrogen-phosphorus-containing hydrotalcite-based flame retardant according to claim 1, wherein the nitrogen-containing monomer is any one of 2-aminodiphenyl ether, melamine and p-nitro-N, N-xylidine.

4. The nitrogen-phosphorus-containing hydrotalcite-based flame retardant according to claim 1, wherein the phosphorus-containing monomer is any one of monophosphoric acid monoester, hexachlorocyclotriphosphazene and phytic acid.

5. The preparation method of the nitrogen-phosphorus-containing hydrotalcite-based flame retardant is characterized by comprising the following steps of:

(1) weighing the raw materials according to the mass ratio of the nitrogen-phosphorus-containing hydrotalcite-based flame retardant of any one of claims 1 to 4;

(2) ultrasonically dispersing hydrotalcite and a nitrogen-containing monomer in deionized water to obtain hydrotalcite suspension for later use;

(3) ultrasonically dispersing sodium hydroxide and a phosphorus-containing monomer in deionized water to obtain a phosphorus-containing monomer alkali liquor;

(4) dropwise adding phosphorus-containing monomer alkali liquor into the hydrotalcite suspension under the condition of magnetic stirring, heating for reaction, filtering, drying in vacuum, and grinding to obtain the nitrogen-phosphorus-containing hydrotalcite-based flame retardant.

6. The method for preparing nitrogen-phosphorus-containing hydrotalcite-based flame retardant according to claim 5, wherein in step (2), the hydrotalcite is prepared by the following steps:

A. dissolving magnesium salt, aluminum salt and urea in deionized water to obtain a magnesium-aluminum mixed solution;

B. heating the magnesium-aluminum mixed solution to 90-120 ℃ for reaction to obtain magnesium-aluminum reaction solution;

C. and filtering the magnesium-aluminum reaction solution, washing and drying in vacuum to obtain the hydrotalcite.

7. The method of claim 6, wherein in step A, the mass ratio of the magnesium salt to the aluminum salt to the urea to the deionized water is 1 (0.6-0.8) to (1-1.2) to (30-35);

in the step B, the reaction time is 24-32 h;

in the step C, the temperature of the vacuum drying is 60-80 ℃, and the time is 12-20 h.

8. The method for preparing nitrogen-phosphorus-containing hydrotalcite-based flame retardant according to claim 5, wherein in steps (2) and (3), the ultrasonic dispersion power is 50-200W, and the time is 10-20 min.

9. The method for preparing the nitrogen-phosphorus-containing hydrotalcite-based flame retardant according to claim 5, wherein in the step (2), the mass ratio of the nitrogen-containing monomer to the deionized water is 1: 400;

in the step (3), the mass concentration of the phosphorus-containing monomer alkali liquor is 20.9%.

10. The method as claimed in claim 5, wherein in step (4), the magnetic stirring speed is 1000-3000 r/min;

the time of dropwise addition is 0.5-1 h.

Heating to 60-90 ℃;

the reaction time is 6-12 h;

the temperature of the vacuum drying is 60-80 ℃, and the time is 12-20 h;

the grinding is carried out until the particle size is 2-5 mu m.

Technical Field

The invention relates to the technical field of flame retardants, in particular to a nitrogen-phosphorus-containing hydrotalcite-based flame retardant and a preparation method thereof.

Background

The flame retardant is a functional additive for endowing a flammable polymer with flame retardancy, is mainly designed aiming at the flame retardancy of a high polymer material, and is divided into an additive flame retardant and a reactive flame retardant according to a using method. The additive flame retardant is added into the polymer by a mechanical mixing method to enable the polymer to have flame retardance, and has a wide application range.

Hydrotalcite (LDHs) is a cationic layered compound, has no fixed chemical composition, and the type and composition proportion of metal elements of the laminate, the type and quantity of interlayer cations and the two-dimensional pore channel structure can be regulated and controlled within a certain range according to requirements, so that the material with a special structure and function is obtained. The LDHs has multiple functions due to the composition of the LDHs and the regulation and control of cations between layers, so that the LDHs becomes a novel functional material with great research potential and application prospect. In addition, the LDHs which is non-toxic, low in price and easy to prepare can absorb a large amount of heat when being heated, and the temperature of a combustion system is reduced, so that the LDHs becomes a hot spot of the flame retardant research at home and abroad.

Although LDHs have excellent flame-retardant and smoke-suppressing effects, do not contain halogen, do not generate toxic gas and corrosive gas during combustion, and have the advantages of no toxicity, low price and easy preparation, hydrotalcite is easy to agglomerate. In the flame retardant application, in order to achieve an excellent flame retardant effect, a large amount of LDHs needs to be added into a polymer, and the physical mechanical property and the processing property of the polymer are seriously influenced by the addition amount and the agglomeration phenomenon.

Therefore, how to compensate the defect of large addition amount of hydrotalcite is a problem that needs to be solved urgently by the technical personnel in the field.

Disclosure of Invention

In view of the above, the present invention aims to provide a nitrogen-phosphorus-containing hydrotalcite-based flame retardant and a preparation method thereof, so as to solve the defects in the prior art.

In order to achieve the purpose, the invention adopts the following technical scheme:

a nitrogen-phosphorus-containing hydrotalcite-based flame retardant (LDH @ PA-MEL) comprises the following raw materials: hydrotalcite (LDH), nitrogen-containing Monomer (MEL), sodium hydroxide (NaOH), and phosphorus-containing monomer (PA); wherein the mass ratio of the hydrotalcite (LDH), the nitrogen-containing Monomer (MEL), the sodium hydroxide (NaOH) and the phosphorus-containing monomer (PA) is 1 (1-3) to (2-4) to (9-14).

The invention has the beneficial effects that: according to the invention, the phosphorus-containing monomer and the nitrogen-containing monomer are introduced into the hydrotalcite system, so that the advantages of the biomass and the hydrotalcite can be combined, and the organic-inorganic hybrid flame retardant is obtained and applied to the polymer matrix, so that the defect of large addition amount of the hydrotalcite is overcome, and the flame retardant has important significance for polymer flame retardance.

Further, the hydrotalcite is magnesium-aluminum hydrotalcite, and comprises the following raw materials: magnesium salts, aluminum salts and urea; wherein Mg is contained in magnesium salt²⁺With Al in aluminium salts³⁺In a molar ratio of (2-3) to 1, Mg in the magnesium salt²⁺And Al in aluminum salt³⁺The ratio of the sum of the number of moles of (a) to the number of moles of urea is 1 (3-4).

The hydrotalcite prepared by adopting the further technical scheme has the advantages of complete grain development, small granularity, low price, no toxicity, easy preparation and the like.

Further, the nitrogen-containing monomer is any one of 2-aminodiphenyl ether, melamine and p-nitro-N, N-dimethylaniline.

The nitrogen-containing monomer selected by the invention has a triazine heterocyclic structure, can absorb heat during combustion, simultaneously releases non-combustible gas, dilutes the density of combustible gas generated by decomposition of high polymer, and has the advantages of low price, high whiteness, easy coloring and the like.

Further, the phosphorus-containing monomer is any one of monophosphoric acid monoester, hexachlorocyclotriphosphazene and phytic acid.

The phosphorus-containing monomer has the beneficial effects that the phosphorus-containing monomer contains a large amount of phosphorus elements, and can promote the high polymer matrix to form carbon during combustion, so that a heat source and oxygen are isolated, and the phosphorus-containing monomer has the advantages of reproducibility, no toxicity, low price and the like.

A preparation method of a nitrogen-phosphorus-containing hydrotalcite-based flame retardant comprises the following steps:

(1) weighing the raw materials according to the mass ratio of the nitrogen-phosphorus-containing hydrotalcite-based flame retardant;

(2) ultrasonically dispersing hydrotalcite and a nitrogen-containing monomer in deionized water to obtain hydrotalcite suspension for later use;

(3) ultrasonically dispersing sodium hydroxide and a phosphorus-containing monomer in deionized water to obtain a phosphorus-containing monomer alkali liquor;

(4) and dropwise adding phosphorus-containing monomer alkali liquor into the hydrotalcite suspension under the condition of magnetic stirring, heating for reaction, filtering, drying in vacuum, and grinding to obtain the nitrogen-phosphorus-containing hydrotalcite-based flame retardant.

The invention has the beneficial effects that: through an efficient method, a polymer (PA-MEL) containing a phosphorus monomer and a nitrogen monomer is generated on the surface of hydrotalcite, and meanwhile, anions of the phosphorus monomer are inserted into a laminate of the hydrotalcite, so that nitrogen and phosphorus elements are introduced, the thermal stability of the hydrotalcite is enhanced, the agglomeration of the hydrotalcite is reduced, the dispersibility of the hydrotalcite in a polymer matrix is improved, and the flame retardant effect of the hydrotalcite-based flame retardant is greatly enhanced.

Further, in the step (2), the preparation method of the hydrotalcite is as follows: A. dissolving magnesium salt, aluminum salt and urea in deionized water to obtain a magnesium-aluminum mixed solution; B. heating the magnesium-aluminum mixed solution to 90-120 ℃ for reaction to obtain magnesium-aluminum reaction solution; C. and filtering the magnesium-aluminum reaction solution, washing and drying in vacuum to obtain the hydrotalcite. Furthermore, in the step A, the mass ratio of the magnesium salt, the aluminum salt, the urea and the deionized water is 1 (0.6-0.8) to 1-1.2 to 30-35; in the step B, the reaction time is 24-32 h; in the step C, the temperature of vacuum drying is 60-80 ℃, and the time is 12-20 h.

The beneficial effects of the further technical scheme are that the magnesium salt and the aluminum salt respectively provide divalent cations and trivalent cations for forming the hydrotalcite laminate, urea is decomposed at high temperature to form an alkaline environment with uniformly raised pH value, and carbonate anions are provided at the same time, so that metal cations can be precipitated in the alkaline environment to form hydrotalcite; and the hydrotalcite prepared by the method has the advantages of complete grain development, small granularity and the like, is uniformly distributed, and has light particle agglomeration.

Further, in the steps (2) and (3), the power of ultrasonic dispersion is 50-200W, and the time is 10-20 min; in the step (2), the mass ratio of the nitrogen-containing monomer to the deionized water is 1: 400; in the step (3), the mass concentration of the phosphorus-containing monomer alkali liquor is 20.9%.

The further technical scheme has the beneficial effects that in the steps (2) and (3), the hydrotalcite can be prevented from agglomerating through ultrasonic dispersion, so that the nitrogen-containing monomer and the phosphorus-containing monomer can better modify the hydrotalcite in an interlayer/surface mode.

Further, in the step (4), the magnetic stirring speed is 1000-; the time for dropwise adding is 0.5-1 h; heating to 60-90 deg.C; the reaction time is 6-12 h; the temperature of vacuum drying is 60-80 ℃, and the time is 12-20 h; grinding to particle size of 2-5 μm.

The further technical scheme has the beneficial effects that the magnetic stirring can promote the full reaction of all the raw materials; dropwise adding the phosphorus-containing monomer and the nitrogen-containing monomer to control the reaction speed; heating to 60-90 ℃ to ensure the temperature required by the reaction system; vacuum drying protects the product from contamination while removing moisture from the product; grinding the product to a powder facilitates dispersion of the product in the polymeric material.

According to the technical scheme, compared with the prior art, the invention has the following beneficial effects:

1. according to the invention, the novel halogen-free flame retardant is prepared by one-step method through carrying out interlayer/surface double modification on the hydrotalcite of the nitrogen-containing substance and the phosphorus-containing substance, can be used as a novel high-molecular flame retardant additive, and has the advantages of simple and efficient process, large preparation amount and high conversion rate.

2. In practical application, the nitrogen-phosphorus-containing hydrotalcite-based flame retardant can be blended with a polymer matrix to obtain a composite material, and the modified hydrotalcite can improve the flame retardant property of the polymer matrix.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.

FIG. 1 is a schematic synthesis of LDH @ PA-MEL preparation according to examples 1-4 of the present invention;

FIG. 2 is a comparison XRD of LDH @ PA-MEL and LDH prepared in example 1 of the present invention;

FIG. 3 is a FTIR comparison of LDH @ PA-MEL, PA-MEL and LDH prepared in example 1 of the present invention;

FIG. 4 is a SEM comparison of LDH @ PA-MEL, PA-MEL and LDH prepared in example 1 of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention are clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1

The nitrogen-phosphorus-containing hydrotalcite-based flame retardant comprises the following raw materials: 0.3g of magnesium aluminum hydrotalcite, 0.5g of nitrogen-containing monomer Melamine (MEL), 0.75g of sodium hydroxide and 2mL of phosphorus-containing monomer Phytic Acid (PA); namely, the mass ratio of the hydrotalcite to the nitrogen-containing monomer to the sodium hydroxide to the phosphorus-containing monomer is 1:1.7:2.5: 9.1;

wherein, the hydrotalcite is magnesium-aluminum hydrotalcite and comprises the following raw materials: magnesium salt Mg (NO)₃)₂·6H₂O13.2313 g, aluminum salt Al (NO)₃)₃·9H₂O9.5388 g and urea 15.0859 g; i.e. Mg in magnesium salts²⁺With Al in aluminium salts³⁺In a molar ratio of 2:1, Mg in the magnesium salt²⁺And Al in aluminum salt³⁺The ratio of the sum of the number of moles of (a) to the number of moles of urea is 1: 3.3;

the preparation method of the nitrogen-phosphorus-containing hydrotalcite-based flame retardant has a synthetic schematic diagram as shown in fig. 1 (a polymer formed by PA and MEL is coated on the surface of a laminate of LDH while PA anions are inserted between LDH layers), and specifically comprises the following steps:

(1) weighing the raw materials according to the mass ratio of the nitrogen-phosphorus-containing hydrotalcite-based flame retardant;

(2) putting magnesium-aluminum hydrotalcite and melamine into a beaker, then ultrasonically dispersing in 200mL of deionized water with the ultrasonic dispersion power of 200W for 10min to obtain hydrotalcite suspension, and transferring the hydrotalcite suspension into a 500mL three-neck flask for later use;

the preparation method of the magnesium-aluminum hydrotalcite comprises the following steps: A. adding magnesium salt Mg (NO)₃)₂·6H₂O, aluminum salt Al (NO)₃)₃·9H₂Ultrasonically dispersing O and urea in 400mL of deionized water, wherein the ultrasonic dispersion power is 200W, and the ultrasonic dispersion time is 10min to obtain a magnesium-aluminum mixed solution; B. transferring the magnesium-aluminum mixed solution into a 500mL reaction kettle, screwing the reaction kettle, placing the reaction kettle in a drying oven, setting the temperature to be 110 ℃, and setting the reaction time to be 24 hours to obtain magnesium-aluminum reaction solution; C. carrying out suction filtration and washing on the magnesium-aluminum reaction solution, and carrying out vacuum drying on the obtained filter cake at 60 ℃ for 12h to obtain magnesium-aluminum hydrotalcite (LDH);

(3) ultrasonically dispersing sodium hydroxide and phytic acid in 12mL of deionized water, wherein the power of ultrasonic dispersion is 200W, the time is 10min, obtaining phosphorus-containing monomer alkali liquor with the mass concentration of 20.9%, and transferring the phosphorus-containing monomer alkali liquor into a constant-pressure burette;

(4) under the condition of magnetic stirring at 1500r/min, dropwise adding phosphorus-containing monomer alkali liquor in a constant-pressure burette into hydrotalcite suspension liquid in a three-neck flask for 0.5h, after dropwise adding, equipping a condenser tube, reacting the whole system at 80 ℃ for 6h, continuously stirring in the reaction process, after the reaction is finished, washing and filtering a product, drying in vacuum at 60 ℃ for 20h, and grinding to the particle size of 2 mu m to obtain the nitrogen-phosphorus-containing hydrotalcite-based flame retardant (LDH @ PA-MEL).

Example 2

The nitrogen-phosphorus-containing hydrotalcite-based flame retardant comprises the following raw materials: 0.3g of magnesium aluminum hydrotalcite, 0.75g of nitrogen-containing monomer Melamine (MEL), 0.75g of sodium hydroxide and 2mL of phosphorus-containing monomer Phytic Acid (PA); namely, the mass ratio of the hydrotalcite to the nitrogen-containing monomer to the sodium hydroxide to the phosphorus-containing monomer is 1:2.5:2.5: 9.1;

wherein, the hydrotalcite is magnesium-aluminum hydrotalcite and comprises the following raw materials: magnesium salt Mg (NO)₃)₂·6H₂O13.2313 g, aluminum salt Al (NO)₃)₃·9H₂O9.5388 g and urea 15.0859 g; i.e. Mg in magnesium salts²⁺With Al in aluminium salts³⁺In a molar ratio of 2:1, Mg in the magnesium salt²⁺And Al in aluminum salt³⁺The ratio of the sum of the number of moles of (a) to the number of moles of urea is 1: 3.3;

the preparation method of the nitrogen-phosphorus-containing hydrotalcite-based flame retardant has a synthetic schematic diagram as shown in fig. 1 (a polymer formed by PA and MEL is coated on the surface of a laminate of LDH while PA anions are inserted between LDH layers), and specifically comprises the following steps:

(1) weighing the raw materials according to the mass ratio of the nitrogen-phosphorus-containing hydrotalcite-based flame retardant;

(2) putting magnesium-aluminum hydrotalcite and melamine into a beaker, then ultrasonically dispersing in 200mL of deionized water with the ultrasonic dispersion power of 200W for 10min to obtain hydrotalcite suspension, and transferring the hydrotalcite suspension into a 500mL three-neck flask for later use;

the preparation method of the magnesium-aluminum hydrotalcite comprises the following steps: A. adding magnesium salt Mg (NO)₃)₂·6H₂O, aluminum salt Al (NO)₃)₃·9H₂O and urineUltrasonically dispersing the element in 400mL of deionized water, wherein the ultrasonic dispersion power is 200W, and the ultrasonic dispersion time is 10min to obtain a magnesium-aluminum mixed solution; B. transferring the magnesium-aluminum mixed solution into a 500mL reaction kettle, screwing the reaction kettle, placing the reaction kettle in a drying oven, setting the temperature to be 110 ℃, and setting the reaction time to be 24 hours to obtain magnesium-aluminum reaction solution; C. carrying out suction filtration and washing on the magnesium-aluminum reaction solution, and carrying out vacuum drying on the obtained filter cake at 60 ℃ for 12h to obtain magnesium-aluminum hydrotalcite (LDH);

(3) ultrasonically dispersing sodium hydroxide and phytic acid in 12mL of deionized water, wherein the power of ultrasonic dispersion is 200W, the time is 10min, obtaining phosphorus-containing monomer alkali liquor with the mass concentration of 20.9%, and transferring the phosphorus-containing monomer alkali liquor into a constant-pressure burette;

(4) under the condition of magnetic stirring at 1500r/min, dropwise adding phosphorus-containing monomer alkali liquor in a constant-pressure burette into hydrotalcite suspension liquid in a three-neck flask for 0.5h, after dropwise adding, equipping a condenser tube, reacting the whole system at 80 ℃ for 6h, continuously stirring in the reaction process, after the reaction is finished, washing and filtering a product, drying in vacuum at 60 ℃ for 20h, and grinding to a particle size of 3 mu m to obtain the nitrogen-phosphorus-containing hydrotalcite-based flame retardant (LDH @ PA-MEL).

Example 3

The nitrogen-phosphorus-containing hydrotalcite-based flame retardant comprises the following raw materials: 0.3g of magnesium aluminum hydrotalcite, 0.75g of nitrogen-containing monomer Melamine (MEL), 1.2g of sodium hydroxide and 2mL of phosphorus-containing monomer Phytic Acid (PA); namely, the mass ratio of the hydrotalcite to the nitrogen-containing monomer to the sodium hydroxide to the phosphorus-containing monomer is 1:2.5:4: 9.1;

wherein, the hydrotalcite is magnesium-aluminum hydrotalcite and comprises the following raw materials: magnesium salt Mg (NO)₃)₂·6H₂O13.2313 g, aluminum salt Al (NO)₃)₃·9H₂O9.5388 g and urea 15.0859 g; i.e. Mg in magnesium salts²⁺With Al in aluminium salts³⁺In a molar ratio of 2:1, Mg in the magnesium salt²⁺And Al in aluminum salt³⁺The ratio of the sum of the number of moles of (a) to the number of moles of urea is 1: 3.3;

the preparation method of the nitrogen-phosphorus-containing hydrotalcite-based flame retardant has a synthetic schematic diagram as shown in fig. 1 (a polymer formed by PA and MEL is coated on the surface of a laminate of LDH while PA anions are inserted between LDH layers), and specifically comprises the following steps:

(1) weighing the raw materials according to the mass ratio of the nitrogen-phosphorus-containing hydrotalcite-based flame retardant;

(2) putting magnesium-aluminum hydrotalcite and melamine into a beaker, then ultrasonically dispersing in 200mL of deionized water with the ultrasonic dispersion power of 200W for 10min to obtain hydrotalcite suspension, and transferring the hydrotalcite suspension into a 500mL three-neck flask for later use;

the preparation method of the magnesium-aluminum hydrotalcite comprises the following steps: A. adding magnesium salt Mg (NO)₃)₂·6H₂O, aluminum salt Al (NO)₃)₃·9H₂Ultrasonically dispersing O and urea in 400mL of deionized water, wherein the ultrasonic dispersion power is 200W, and the ultrasonic dispersion time is 10min to obtain a magnesium-aluminum mixed solution; B. transferring the magnesium-aluminum mixed solution into a 500mL reaction kettle, screwing the reaction kettle, placing the reaction kettle in a drying oven, setting the temperature to be 110 ℃, and setting the reaction time to be 24 hours to obtain magnesium-aluminum reaction solution; C. carrying out suction filtration and washing on the magnesium-aluminum reaction solution, and carrying out vacuum drying on the obtained filter cake at 60 ℃ for 12h to obtain magnesium-aluminum hydrotalcite (LDH);

(3) ultrasonically dispersing sodium hydroxide and phytic acid in 12mL of deionized water, wherein the power of ultrasonic dispersion is 200W, the time is 10min, obtaining phosphorus-containing monomer alkali liquor with the mass concentration of 20.9%, and transferring the phosphorus-containing monomer alkali liquor into a constant-pressure burette;

(4) under the condition of magnetic stirring at 1500r/min, dropwise adding phosphorus-containing monomer alkali liquor in a constant-pressure burette into hydrotalcite suspension liquid in a three-neck flask for 0.5h, after dropwise adding, equipping a condenser tube, reacting the whole system at 70 ℃ for 8h, continuously stirring in the reaction process, after the reaction is finished, washing and filtering a product, performing vacuum drying at 60 ℃ for 20h, and grinding to a particle size of 4 mu m to obtain the nitrogen-phosphorus-containing hydrotalcite-based flame retardant (LDH @ PA-MEL).

Example 4

The nitrogen-phosphorus-containing hydrotalcite-based flame retardant comprises the following raw materials: 0.3g of magnesium aluminum hydrotalcite, 0.75g of nitrogen-containing monomer Melamine (MEL), 1.2g of sodium hydroxide and 3mL of phosphorus-containing monomer Phytic Acid (PA); namely, the mass ratio of the hydrotalcite to the nitrogen-containing monomer to the sodium hydroxide to the phosphorus-containing monomer is 1:2.5:4: 13.6;

wherein, the hydrotalcite is magnesium-aluminum hydrotalcite and comprises the following raw materials: magnesium salt Mg (N)O₃)₂·6H₂O13.2313 g, aluminum salt Al (NO)₃)₃·9H₂O9.5388 g and urea 15.0859 g; i.e. Mg in magnesium salts²⁺With Al in aluminium salts³⁺In a molar ratio of 2:1, Mg in the magnesium salt²⁺And Al in aluminum salt³⁺The ratio of the sum of the number of moles of (a) to the number of moles of urea is 1: 3.3;

the preparation method of the nitrogen-phosphorus-containing hydrotalcite-based flame retardant has a synthetic schematic diagram as shown in fig. 1 (a polymer formed by PA and MEL is coated on the surface of a laminate of LDH while PA anions are inserted between LDH layers), and specifically comprises the following steps:

(1) weighing the raw materials according to the mass ratio of the nitrogen-phosphorus-containing hydrotalcite-based flame retardant;

(2) putting magnesium-aluminum hydrotalcite and melamine into a beaker, then ultrasonically dispersing in 200mL of deionized water with the ultrasonic dispersion power of 200W for 10min to obtain hydrotalcite suspension, and transferring the hydrotalcite suspension into a 500mL three-neck flask for later use;

the preparation method of the magnesium-aluminum hydrotalcite comprises the following steps: A. ultrasonically dispersing magnesium salt, aluminum salt and urea in 400mL of deionized water, wherein the ultrasonic dispersion power is 200W, and the ultrasonic dispersion time is 10min to obtain a magnesium-aluminum mixed solution; B. transferring the magnesium-aluminum mixed solution into a 500mL reaction kettle, screwing the reaction kettle, placing the reaction kettle in a drying oven, setting the temperature to be 110 ℃, and setting the reaction time to be 24 hours to obtain magnesium-aluminum reaction solution; C. carrying out suction filtration and washing on the magnesium-aluminum reaction solution, and carrying out vacuum drying on the obtained filter cake at 60 ℃ for 12h to obtain magnesium-aluminum hydrotalcite (LDH);

(3) ultrasonically dispersing sodium hydroxide and phytic acid in 12mL of deionized water, wherein the power of ultrasonic dispersion is 200W, the time is 10min, obtaining phosphorus-containing monomer alkali liquor with the mass concentration of 20.9%, and transferring the phosphorus-containing monomer alkali liquor into a constant-pressure burette;

(4) under the condition of magnetic stirring at 1500r/min, dropwise adding phosphorus-containing monomer alkali liquor in a constant-pressure burette into hydrotalcite suspension liquid in a three-neck flask for 0.5h, after dropwise adding, equipping a condenser tube, reacting the whole system at 70 ℃ for 8h, continuously stirring in the reaction process, after the reaction is finished, washing and filtering a product, drying in vacuum at 60 ℃ for 20h, and grinding to a particle size of 5 mu m to obtain the nitrogen-phosphorus-containing hydrotalcite-based flame retardant (LDH @ PA-MEL).

Performance testing

1. The LDH @ PA-MEL and LDH prepared in example 1 were taken and placed in an X-ray diffractometer, and the XRD patterns obtained are shown in FIG. 2.

As can be seen from fig. 2, the XRD peaks of LDH @ PA-MEL show that the layered structure of LDH is still retained, and the (003) peaks, the (006) peaks, and the (009) peaks are all shifted toward low 2 theta angles relative to the original LDH, indicating that PA anions successfully enter the interlayers of the LDH, while the weakened and unstable baselines of the intensities of the peaks further demonstrate that the LDH surface is coated with the polymer produced by PA-MEL.

2. The LDH @ PA-MEL, PA-MEL and LDH prepared in example 1 were put into a Fourier transform infrared absorption spectrometer, and the obtained FTIR is shown in FIG. 3.

As can be seen in FIG. 3, the newly appeared FTIR characteristic peaks of LDH @ PA-MEL indicate that LDH was successfully modified by PA and MEL and that LDH @ PA-MEL was successfully prepared.

3. The LDH @ PA-MEL, PA-MEL and LDH prepared in example 1 were taken and placed in a scanning electron microscope, and the SEM image thereof is shown in FIG. 4.

As can be seen from FIG. 4, comparing the SEM images of LDH @ PA-MEL and LDH, the LDH surface was smooth, while the surface of LDH @ PA-MEL was rough, and a layer of PA-MEL polymer was clearly observed, thus indicating successful coating of the LDH on the laminate surface by the PA-MEL polymer.