A preparation method of double-layer coated red phosphorus flame retardant

Abstract

The invention discloses a preparation method of a double-layer coated red phosphorus flame retardant. First, magnesium hydroxide is used as an inorganic coating layer material, and magnesium hydroxide is deposited and coated on the surface of red phosphorus particles to form an inorganic coating layer, thereby obtaining an inorganic coated red phosphorus flame retardant, and then the inorganic coated red phosphorus flame retardant is subjected to surface modification treatment, and finally a resin material is coated on the inorganic coated red phosphorus flame retardant after the surface modification treatment to form an organic coating layer, thereby obtaining a double-layer coated red phosphorus flame retardant combining inorganic coating and organic coating, which has a good coating effect on red phosphorus, and can improve the flame retardant effect of red phosphorus while effectively improving the stability of red phosphorus.

Description

Technical Field

[0001] The invention relates to the field of packaging, and specifically provides a method for preparing a double-layer coated red phosphorus flame retardant. Background Art

[0002] Red phosphorus is a commonly used flame retardant with excellent thermal stability, non-volatility, no corrosive gas generation, good flame retardant effect, and good electrical insulation. However, red phosphorus has poor stability and is very easy to absorb moisture and oxidize. When added to resin as a flame retardant, it will have an adverse effect on the performance of plastic products. Therefore, it is necessary to coat the red phosphorus flame retardant to improve the stability of red phosphorus.

[0003] In Zhao Yuye's "Preparation and Application of Inorganic-Organic Double-layer Coated Red Phosphorus", a Mg(OH) 2 Preparation method of double-layer coated red phosphorus with PVC, firstly coating the surface of red phosphorus with Mg(OH) 2 , to obtain an intermediate product, and then PVC is coated on the intermediate product to obtain Mg(OH) 2 / PVC double-layer coating of red phosphorus can effectively improve the hygroscopicity, flame retardancy and mechanical properties of red phosphorus. 2 In general, due to the poor compatibility between inorganic materials and organic resins, the interface connection stability between the inorganic coating layer and the organic coating layer will be poor, thus affecting the double-layer coating effect. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides a method for preparing a double-layer coated red phosphorus flame retardant to solve the problem of poor stability of red phosphorus as a flame retardant in the prior art.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A method for preparing a double-layer coated red phosphorus flame retardant comprises the following steps:

[0007] Step 1: Preparation of inorganic coated red phosphorus flame retardant:

[0008] The method comprises adding magnesium sulfate heptahydrate to deionized water, heating and stirring until dissolved, adding red phosphorus and a dispersant, dropping a sodium hydroxide solution to adjust the pH, adding an aqueous solution of aluminum sulfate, heating for reaction, filtering, washing, and drying after the reaction to obtain an inorganic coated red phosphorus flame retardant;

[0009] Step 2: Preparation of surface-modified inorganic coated red phosphorus flame retardant:

[0010] Dimethyl (3-amino-3-acylpropyl) phosphonate is mixed with N,N-dimethylformamide, and then added to a hydrobromic acid aqueous solution for reaction. After the reaction, an inorganic coated red phosphorus flame retardant is added, and the mixture is heated for reaction. After the heating reaction, the mixture is filtered, washed, and dried to obtain a surface-modified inorganic coated red phosphorus flame retardant.

[0011] Step 3: Preparation of double-layer coated red phosphorus flame retardant:

[0012] The polyvinyl chloride resin is dissolved in an organic solvent, and a surface-modified inorganic coated red phosphorus flame retardant is added, and the reaction is heated. After the reaction, the solvent is removed by rotary evaporation, and the double-layer coated red phosphorus flame retardant is obtained by washing and drying.

[0013] Preferably, in step 1, the red phosphorus comprises refined red phosphorus;

[0014] The refined red phosphorus is prepared by the following steps:

[0015] The red phosphorus is added into an ethanol aqueous solution, ground, sieved, filtered, and filtered to obtain a filter cake, and the filter cake is dried to obtain fine red phosphorus.

[0016] Preferably, the concentration of the ethanol aqueous solution is 10%-20% (the mass percentage of ethanol in the ethanol aqueous solution is 10%-20%), the mass ratio of red phosphorus to the ethanol aqueous solution is 1:3-5, the grinding time is 30-60 minutes, the aperture of the sieve for screening is 200-300 meshes, the drying temperature is 50-60°C, and the drying time is 5-10 hours.

[0017] Preferably, in the step 1, the mass ratio of magnesium sulfate heptahydrate, deionized water, red phosphorus, dispersant, and aluminum sulfate aqueous solution is 150-200:400-600:100:5-10:0.5-1;

[0018] Wherein, the dispersant includes sodium dodecylbenzene sulfonate.

[0019] Preferably, the concentration of the aluminum sulfate aqueous solution is 3%-5% (the mass percentage of aluminum sulfate in the aluminum sulfate aqueous solution is 3%-5%).

[0020] Preferably, in step one, the heating and stirring speed is 250-350 r / min, the heating and stirring temperature is 60-70°C, the concentration of sodium hydroxide is 0.5-1.5 mol / L, the pH is adjusted to 9.5-10.5, the heating reaction temperature is 75-85°C, the heating reaction time is 1-2h, and the drying condition is drying at 100-120°C for 5-10h.

[0021] Preferably, in the step 2, the mass ratio of dimethyl (3-amino-3-acylpropyl) phosphonate, N,N-dimethylformamide, aqueous hydrobromic acid solution, and inorganic coated red phosphorus flame retardant is 180:5000-8000:150:190-200.

[0022] Preferably, the concentration of the hydrobromic acid aqueous solution is 40%-50% (the mass percentage of hydrogen bromide in the hydrobromic acid aqueous solution is 40%-50%).

[0023] Preferably, in step 2, the reaction conditions are 80-100° C. for 5 hours, the heating reaction conditions are 50-70° C. for 1-2 hours, and the drying conditions are 50-60° C. for 10-15 hours.

[0024] Preferably, in step three, the mass ratio of the polyvinyl chloride resin, the organic solvent, and the surface-modified inorganic coated red phosphorus flame retardant is 210-270:1200-2000:300.

[0025] Among them, the organic solvent includes acetone.

[0026] Preferably, in step 3, the heating reaction conditions are 60-80°C for 6-10 hours, and the drying conditions are 50-60°C for 10-15 hours.

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

[0028] 1) The red phosphorus flame retardant in the present invention is a double-layer coated red phosphorus flame retardant. First, magnesium hydroxide is deposited on the surface of red phosphorus to form an inorganic coating layer to obtain an inorganic coated red phosphorus flame retardant, and then the inorganic coated red phosphorus flame retardant is subjected to surface modification. Finally, a resin material is coated on the inorganic coated red phosphorus flame retardant after the surface modification to form an organic coating layer, thereby obtaining an inorganic and organic double-layer coated red phosphorus flame retardant. The coating effect of red phosphorus is good, and the flame retardant effect of red phosphorus can be improved while the stability of red phosphorus is effectively improved;

[0029] 2) Using magnesium hydroxide as an inorganic coating material, magnesium hydroxide is deposited and coated on the surface of red phosphorus particles to form a dense coating layer, which can improve the anti-hygroscopicity of red phosphorus. In addition, magnesium hydroxide absorbs heat and releases water when heated, has a good flame retardant effect, and can improve the flame retardant effect of red phosphorus;

[0030] 3) The inorganic coated red phosphorus flame retardant is surface modified by using dimethyl (3-amino-3-acylpropyl) phosphonate, wherein the dimethyl (3-amino-3-acylpropyl) phosphonate is hydrolyzed under the action of hydrobromic acid to obtain a phosphate group (-POOH), and the phosphate group reacts with the hydroxide of magnesium hydroxide in the surface area of ​​the inorganic coated red phosphorus flame retardant particles to convert the magnesium hydroxide into magnesium phosphate and attach it to the surface of the inorganic coated red phosphorus flame retardant particles, while not destroying the particle structure of the inorganic coating layer, introducing an active group amino group (-NH 2 ); the chlorine atoms in the polyvinyl chloride molecules can react with the amino groups on the surface of the surface-modified inorganic coated red phosphorus flame retardant to remove HCl, the surface-modified inorganic coated red phosphorus flame retardant is connected to the polyvinyl chloride molecules through the imino group (-NH), and the inorganic coating layer and the organic coating layer are tightly connected through a stable chemical bond, thereby solving the problem of poor stability of the interface connection between the inorganic coating layer and the organic coating layer caused by the poor compatibility between the inorganic material and the organic resin, the double-layer coating has a good coating effect, and the obtained double-layer coated red phosphorus flame retardant has high stability, good oxidation resistance and flame retardancy;

[0031] 4) Polyvinyl chloride is a polar polymer material, and has good compatibility with most polar polymer materials. By using polyvinyl chloride resin as an organic coating material, the compatibility between the red phosphorus flame retardant and the resin can be improved; in addition, polyvinyl chloride itself is a self-extinguishing material, and as an organic coating material of the double-coated red phosphorus flame retardant, the flame retardant effect of the double-coated red phosphorus flame retardant can be improved;

[0032] 5) Dimethyl (3-amino-3-acylpropyl) phosphonate, as a phosphate compound, has good flame retardant effect itself and can improve the flame retardant effect of the double-layer coated red phosphorus flame retardant. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The figure is a process flow chart of the preparation of the double-layer coated red phosphorus flame retardant of the present invention;

[0034] Figure 2 Schematic diagram of the hydrolysis reaction of dimethyl (3-amino-3-acylpropyl) phosphonate in the present invention;

[0035] Figure 3 Schematic diagram of the reaction between the surface-modified inorganic coated red phosphorus flame retardant and polyvinyl chloride in the present invention;

[0036] Figure 4 The figure is a test result of the hygroscopic performance of the double-layer coated red phosphorus flame retardant prepared in Examples 1-7 and Comparative Examples 1-2 of the present invention;

[0037] Figure 5The graph is a test result of the antioxidant performance of the double-layer coated red phosphorus flame retardant prepared in Examples 1-7 and Comparative Examples 1-2 of the present invention;

[0038] Figure 6 This is a flame retardant performance test result diagram of the double-layer coated red phosphorus flame retardant prepared in Examples 1-7 and Comparative Examples 1-2 of the present invention. DETAILED DESCRIPTION

[0039] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0040] Example 1

[0041] This embodiment discloses a method for preparing a double-layer coated red phosphorus flame retardant, comprising the following steps:

[0042] Step 1: Preparation of inorganic coated red phosphorus flame retardant:

[0043] Magnesium sulfate heptahydrate is added to deionized water, heated and stirred at a speed of 250 r / min and a temperature of 70°C until dissolved, red phosphorus and dispersant sodium dodecylbenzene sulfonate are added, 0.5 mol / L sodium hydroxide solution is added dropwise to adjust the pH to 9.5, and then a 5% aluminum sulfate aqueous solution is added, and the mixture is heated at a temperature of 75°C for reaction for 2 hours. After the reaction, the mixture is filtered, and the filtered residue is washed with deionized water for 3 times, and then dried at a temperature of 100°C for 10 hours to obtain the preparation of an inorganic coated red phosphorus flame retardant;

[0044] The mass ratio of magnesium sulfate heptahydrate, deionized water, red phosphorus, dispersant sodium dodecylbenzene sulfonate, and aluminum sulfate aqueous solution is 150:400:100:5:0.5;

[0045] Step 2: Preparation of surface-modified inorganic coated red phosphorus flame retardant:

[0046] After mixing dimethyl (3-amino-3-acylpropyl) phosphonate and N, N-dimethylformamide, adding the mixture to a 40% hydrobromic acid aqueous solution, reacting the mixture at 80°C for 5 hours, adding an inorganic coated red phosphorus flame retardant, heating the mixture at 50°C for 2 hours, filtering the mixture after the heating reaction, washing the filtered residue with deionized water for 3 times, and then drying the mixture at 50°C for 15 hours to obtain a surface-modified inorganic coated red phosphorus flame retardant;

[0047] The mass ratio of dimethyl (3-amino-3-acylpropyl) phosphonate, N,N-dimethylformamide, hydrobromic acid aqueous solution, and inorganic coated red phosphorus flame retardant is 180:5000:150:190;

[0048] Step 3: Preparation of double-layer coated red phosphorus flame retardant:

[0049] The polyvinyl chloride resin was dissolved in an organic solvent acetone, and a surface-modified inorganic coated red phosphorus flame retardant was added, and the reaction was carried out at 60°C for 10 hours. After the reaction, the acetone was removed by rotary evaporation at 50°C, and the mixture was washed with ethanol for 3 times and dried at 50°C for 15 hours to obtain a double-layer coated red phosphorus flame retardant.

[0050] Among them, the mass ratio of polyvinyl chloride resin, organic solvent and surface modified inorganic coated red phosphorus flame retardant is 210:1200:300.

[0051] Example 2

[0052] This embodiment discloses a method for preparing a double-layer coated red phosphorus flame retardant, comprising the following steps:

[0053] Step 1: Preparation of inorganic coated red phosphorus flame retardant:

[0054] Magnesium sulfate heptahydrate is added to deionized water, heated and stirred at a speed of 350 r / min and a temperature of 60°C until dissolved, red phosphorus and dispersant sodium dodecylbenzene sulfonate are added, 1.5 mol / L sodium hydroxide solution is added dropwise to adjust the pH to 10.5, and then a 3% aluminum sulfate aqueous solution is added, and the reaction is heated at a temperature of 85°C for 1 hour. After the reaction, the filter is filtered, and the filter retentate is washed with deionized water for 3 times, and then dried at a temperature of 120°C for 5 hours to obtain the preparation of an inorganic coated red phosphorus flame retardant;

[0055] The mass ratio of magnesium sulfate heptahydrate, deionized water, red phosphorus, dispersant sodium dodecylbenzene sulfonate, and aluminum sulfate aqueous solution is 200:600:100:10:1;

[0056] Step 2: Preparation of surface-modified inorganic coated red phosphorus flame retardant:

[0057] After mixing dimethyl (3-amino-3-acylpropyl) phosphonate and N, N-dimethylformamide, adding the mixture to a 50% hydrobromic acid aqueous solution, reacting the mixture at 100°C for 5 hours, adding an inorganic coated red phosphorus flame retardant, heating the mixture at 70°C for 1 hour, filtering the mixture after the heating reaction, washing the filtered residue with deionized water for 3 times, and then drying the mixture at 60°C for 10 hours to obtain a surface-modified inorganic coated red phosphorus flame retardant;

[0058] Wherein, the mass ratio of dimethyl (3-amino-3-acylpropyl) phosphonate, N,N-dimethylformamide, hydrobromic acid aqueous solution, and inorganic coated red phosphorus flame retardant is 180:8000:150:200;

[0059] Step 3: Preparation of double-layer coated red phosphorus flame retardant:

[0060] The polyvinyl chloride resin was dissolved in an organic solvent acetone, and a surface-modified inorganic coated red phosphorus flame retardant was added, and the reaction was carried out at 80°C for 6 hours. After the reaction, the acetone was removed by rotary evaporation at 50°C, and the mixture was washed with ethanol for 3 times and dried at 60°C for 10 hours to obtain a double-layer coated red phosphorus flame retardant.

[0061] Among them, the mass ratio of polyvinyl chloride resin, organic solvent and surface modified inorganic coated red phosphorus flame retardant is 270:2000:300.

[0062] Example 3

[0063] This embodiment discloses a method for preparing a double-layer coated red phosphorus flame retardant, comprising the following steps:

[0064] Step 1: Preparation of inorganic coated red phosphorus flame retardant:

[0065] Magnesium sulfate heptahydrate is added to deionized water, heated and stirred at a speed of 300 r / min and a temperature of 65°C until dissolved, red phosphorus and dispersant sodium dodecylbenzene sulfonate are added, 1 mol / L sodium hydroxide solution is added dropwise to adjust the pH to 10, and a 4% aluminum sulfate aqueous solution is added, and the reaction is heated at a temperature of 80°C for 1.5 hours. After the reaction, the filter is filtered, and the filter retentate is washed with deionized water for 3 times, and then dried at a temperature of 110°C for 8 hours to obtain the preparation of an inorganic coated red phosphorus flame retardant;

[0066] Among them, the mass ratio of magnesium sulfate heptahydrate, deionized water, red phosphorus, dispersant sodium dodecylbenzene sulfonate, and aluminum sulfate aqueous solution is 160:435:100:6:0.6;

[0067] Step 2: Preparation of surface-modified inorganic coated red phosphorus flame retardant:

[0068] After mixing dimethyl (3-amino-3-acylpropyl) phosphonate and N, N-dimethylformamide, adding the mixture to a 45% aqueous solution of hydrobromic acid, reacting the mixture at 90°C for 5 hours, adding an inorganic coated red phosphorus flame retardant, heating the mixture at 60°C for 1.5 hours, filtering the mixture after the heating reaction, washing the filtered residue with deionized water for 3 times, and then drying the mixture at 55°C for 12 hours to obtain a surface-modified inorganic coated red phosphorus flame retardant;

[0069] Wherein, the mass ratio of dimethyl (3-amino-3-acylpropyl) phosphonate, N,N-dimethylformamide, hydrobromic acid aqueous solution, and inorganic coated red phosphorus flame retardant is 180:5500:150:191.5; Step 3, preparation of double-layer coated red phosphorus flame retardant:

[0070] The polyvinyl chloride resin was dissolved in an organic solvent acetone, and a surface-modified inorganic coated red phosphorus flame retardant was added, and the reaction was carried out at 70°C for 8 hours. After the reaction, the acetone was removed by rotary evaporation at 50°C, and the mixture was washed with ethanol for 3 times and dried at 55°C for 12 hours to obtain a double-layer coated red phosphorus flame retardant.

[0071] Among them, the mass ratio of polyvinyl chloride resin, organic solvent acetone, and surface modified inorganic coated red phosphorus flame retardant is 220:1350:300.

[0072] Example 4

[0073] This embodiment discloses a method for preparing a double-layer coated red phosphorus flame retardant, comprising the following steps:

[0074] Step 1: Preparation of inorganic coated red phosphorus flame retardant:

[0075] Magnesium sulfate heptahydrate is added to deionized water, heated and stirred at a speed of 300 r / min and a temperature of 65°C until dissolved, red phosphorus and dispersant sodium dodecylbenzene sulfonate are added, 1 mol / L sodium hydroxide solution is added dropwise to adjust the pH to 10, and a 4% aluminum sulfate aqueous solution is added, and the reaction is heated at a temperature of 80°C for 1.5 hours. After the reaction, the filter is filtered, and the filter retentate is washed with deionized water for 3 times, and then dried at a temperature of 110°C for 8 hours to obtain the preparation of an inorganic coated red phosphorus flame retardant;

[0076] Among them, the mass ratio of magnesium sulfate heptahydrate, deionized water, red phosphorus, dispersant sodium dodecylbenzene sulfonate, and aluminum sulfate aqueous solution is 170:470:100:7:0.7;

[0077] Step 2: Preparation of surface-modified inorganic coated red phosphorus flame retardant:

[0078] After mixing dimethyl (3-amino-3-acylpropyl) phosphonate and N, N-dimethylformamide, adding the mixture to a 45% aqueous solution of hydrobromic acid, reacting the mixture at 90°C for 5 hours, adding an inorganic coated red phosphorus flame retardant, heating the mixture at 60°C for 1.5 hours, filtering the mixture after the heating reaction, washing the filtered residue with deionized water for 3 times, and then drying the mixture at 55°C for 12 hours to obtain a surface-modified inorganic coated red phosphorus flame retardant;

[0079] Wherein, the mass ratio of dimethyl (3-amino-3-acylpropyl) phosphonate, N,N-dimethylformamide, hydrobromic acid aqueous solution, and inorganic coated red phosphorus flame retardant is 180:6000:150:193; Step 3, preparation of double-layer coated red phosphorus flame retardant:

[0080] The polyvinyl chloride resin was dissolved in an organic solvent acetone, and a surface-modified inorganic coated red phosphorus flame retardant was added, and the reaction was carried out at 70°C for 8 hours. After the reaction, the acetone was removed by rotary evaporation at 50°C, and the mixture was washed with ethanol for 3 times and dried at 55°C for 12 hours to obtain a double-layer coated red phosphorus flame retardant.

[0081] Among them, the mass ratio of polyvinyl chloride resin, organic solvent acetone, and surface modified inorganic coated red phosphorus flame retardant is 230:1400:300.

[0082] Example 5

[0083] This embodiment discloses a method for preparing a double-layer coated red phosphorus flame retardant, comprising the following steps:

[0084] Step 1: Preparation of inorganic coated red phosphorus flame retardant:

[0085] Magnesium sulfate heptahydrate is added to deionized water, heated and stirred at a speed of 300 r / min and a temperature of 65°C until dissolved, red phosphorus and dispersant sodium dodecylbenzene sulfonate are added, 1 mol / L sodium hydroxide solution is added dropwise to adjust the pH to 10, and a 4% aluminum sulfate aqueous solution is added, and the reaction is heated at a temperature of 80°C for 1.5 hours. After the reaction, the filter is filtered, and the filter retentate is washed with deionized water for 3 times, and then dried at a temperature of 110°C for 8 hours to obtain the preparation of an inorganic coated red phosphorus flame retardant;

[0086] Among them, the mass ratio of magnesium sulfate heptahydrate, deionized water, red phosphorus, dispersant sodium dodecylbenzene sulfonate, and aluminum sulfate aqueous solution is 180:505:100:7:0.8;

[0087] Step 2: Preparation of surface-modified inorganic coated red phosphorus flame retardant:

[0088] After mixing dimethyl (3-amino-3-acylpropyl) phosphonate and N, N-dimethylformamide, adding the mixture to a 45% aqueous solution of hydrobromic acid, reacting the mixture at 90°C for 5 hours, adding an inorganic coated red phosphorus flame retardant, heating the mixture at 60°C for 1.5 hours, filtering the mixture after the heating reaction, washing the filtered residue with deionized water for 3 times, and then drying the mixture at 55°C for 12 hours to obtain a surface-modified inorganic coated red phosphorus flame retardant;

[0089] Wherein, the mass ratio of dimethyl (3-amino-3-acylpropyl) phosphonate, N,N-dimethylformamide, hydrobromic acid aqueous solution, and inorganic coated red phosphorus flame retardant is 180:6500:150:194.5; Step 3, preparation of double-layer coated red phosphorus flame retardant:

[0090] The polyvinyl chloride resin was dissolved in an organic solvent acetone, and a surface-modified inorganic coated red phosphorus flame retardant was added, and the reaction was carried out at 70°C for 8 hours. After the reaction, the acetone was removed by rotary evaporation at 50°C, and the mixture was washed with ethanol for 3 times and dried at 55°C for 12 hours to obtain a double-layer coated red phosphorus flame retardant.

[0091] Among them, the mass ratio of polyvinyl chloride resin, organic solvent acetone, and surface modified inorganic coated red phosphorus flame retardant is 240:1550:300.

[0092] Example 6

[0093] This embodiment discloses a method for preparing a double-layer coated red phosphorus flame retardant, comprising the following steps:

[0094] Step 1: Preparation of inorganic coated red phosphorus flame retardant:

[0095] Magnesium sulfate heptahydrate is added to deionized water, heated and stirred at a speed of 300 r / min and a temperature of 65°C until dissolved, red phosphorus and dispersant sodium dodecylbenzene sulfonate are added, 1 mol / L sodium hydroxide solution is added dropwise to adjust the pH to 10, and a 4% aluminum sulfate aqueous solution is added, and the reaction is heated at a temperature of 80°C for 1.5 hours. After the reaction, the filter is filtered, and the filter retentate is washed with deionized water for 3 times, and then dried at a temperature of 110°C for 8 hours to obtain the preparation of an inorganic coated red phosphorus flame retardant;

[0096] Among them, the mass ratio of magnesium sulfate heptahydrate, deionized water, red phosphorus, dispersant sodium dodecylbenzene sulfonate, and aluminum sulfate aqueous solution is 185:540:100:8:0.8;

[0097] Step 2: Preparation of surface-modified inorganic coated red phosphorus flame retardant:

[0098] After mixing dimethyl (3-amino-3-acylpropyl) phosphonate and N, N-dimethylformamide, adding the mixture to a 45% aqueous solution of hydrobromic acid, reacting the mixture at 90°C for 5 hours, adding an inorganic coated red phosphorus flame retardant, heating the mixture at 60°C for 1.5 hours, filtering the mixture after the heating reaction, washing the filtered residue with deionized water for 3 times, and then drying the mixture at 55°C for 12 hours to obtain a surface-modified inorganic coated red phosphorus flame retardant;

[0099] Wherein, the mass ratio of dimethyl (3-amino-3-acylpropyl) phosphonate, N,N-dimethylformamide, hydrobromic acid aqueous solution, and inorganic coated red phosphorus flame retardant is 180:7000:150:196; Step 3, preparation of double-layer coated red phosphorus flame retardant:

[0100] The polyvinyl chloride resin was dissolved in an organic solvent acetone, and a surface-modified inorganic coated red phosphorus flame retardant was added, and the reaction was carried out at 70°C for 8 hours. After the reaction, the acetone was removed by rotary evaporation at 50°C, and the mixture was washed with ethanol for 3 times and dried at 55°C for 12 hours to obtain a double-layer coated red phosphorus flame retardant.

[0101] Among them, the mass ratio of polyvinyl chloride resin, organic solvent acetone, and surface modified inorganic coated red phosphorus flame retardant is 250:1700:300.

[0102] Example 7

[0103] This embodiment discloses a method for preparing a double-layer coated red phosphorus flame retardant, comprising the following steps:

[0104] Step 1: Preparation of inorganic coated red phosphorus flame retardant:

[0105] Magnesium sulfate heptahydrate is added to deionized water, heated and stirred at a speed of 300 r / min and a temperature of 65°C until dissolved, red phosphorus and dispersant sodium dodecylbenzene sulfonate are added, 1 mol / L sodium hydroxide solution is added dropwise to adjust the pH to 10, and a 4% aluminum sulfate aqueous solution is added, and the reaction is heated at a temperature of 80°C for 1.5 hours. After the reaction, the filter is filtered, and the filter retentate is washed with deionized water for 3 times, and then dried at a temperature of 110°C for 8 hours to obtain the preparation of an inorganic coated red phosphorus flame retardant;

[0106] Among them, the mass ratio of magnesium sulfate heptahydrate, deionized water, red phosphorus, dispersant sodium dodecylbenzene sulfonate, and aluminum sulfate aqueous solution is 190:575:100:9:0.9;

[0107] Step 2: Preparation of surface-modified inorganic coated red phosphorus flame retardant:

[0108] After mixing dimethyl (3-amino-3-acylpropyl) phosphonate and N, N-dimethylformamide, adding the mixture to a 45% aqueous solution of hydrobromic acid, reacting the mixture at 90°C for 5 hours, adding an inorganic coated red phosphorus flame retardant, heating the mixture at 60°C for 1.5 hours, filtering the mixture after the heating reaction, washing the filtered residue with deionized water for 3 times, and then drying the mixture at 55°C for 12 hours to obtain a surface-modified inorganic coated red phosphorus flame retardant;

[0109] Wherein, the mass ratio of dimethyl (3-amino-3-acylpropyl) phosphonate, N,N-dimethylformamide, hydrobromic acid aqueous solution, and inorganic coated red phosphorus flame retardant is 180:7500:150:198; Step 3, preparation of double-layer coated red phosphorus flame retardant:

[0110] The polyvinyl chloride resin was dissolved in an organic solvent acetone, and a surface-modified inorganic coated red phosphorus flame retardant was added, and the reaction was carried out at 70°C for 8 hours. After the reaction, the acetone was removed by rotary evaporation at 50°C, and the mixture was washed with ethanol for 3 times and dried at 55°C for 12 hours to obtain a double-layer coated red phosphorus flame retardant.

[0111] Among them, the mass ratio of polyvinyl chloride resin, organic solvent acetone, and surface modified inorganic coated red phosphorus flame retardant is 260:1800:300.

[0112] Comparative Example 1

[0113] A method for preparing a double-layer coated red phosphorus flame retardant comprises the following steps:

[0114] Step 1: Preparation of inorganic coated red phosphorus flame retardant:

[0115] Magnesium sulfate heptahydrate is added to deionized water, heated and stirred at a speed of 250 r / min and a temperature of 70°C until dissolved, red phosphorus and dispersant sodium dodecylbenzene sulfonate are added, 0.5 mol / L sodium hydroxide solution is added dropwise to adjust the pH to 9.5, and then a 5% aluminum sulfate aqueous solution is added, and the mixture is heated at a temperature of 75°C for reaction for 2 hours. After the reaction, the mixture is filtered, and the filtered residue is washed with deionized water for 3 times, and then dried at a temperature of 100°C for 10 hours to obtain the preparation of an inorganic coated red phosphorus flame retardant;

[0116] The mass ratio of magnesium sulfate heptahydrate, deionized water, red phosphorus, dispersant sodium dodecylbenzene sulfonate, and aluminum sulfate aqueous solution is 150:400:100:5:0.5;

[0117] Step 2: Preparation of double-layer coated red phosphorus flame retardant:

[0118] The polyvinyl chloride resin was dissolved in an organic solvent acetone, and an inorganic coated red phosphorus flame retardant was added, and the reaction was carried out at 60°C for 10 hours. After the reaction, the acetone was removed by rotary evaporation at 50°C, and the mixture was washed with ethanol for 3 times and dried at 50°C for 15 hours to obtain a double-layer coated red phosphorus flame retardant.

[0119] Among them, the mass ratio of polyvinyl chloride resin, organic solvent acetone, and inorganic coated red phosphorus flame retardant is 210:1200:300.

[0120] Comparative Example 2

[0121] A method for preparing a double-layer coated red phosphorus flame retardant comprises the following steps:

[0122] Step 1: Preparation of inorganic coated red phosphorus flame retardant:

[0123] Magnesium sulfate heptahydrate is added to deionized water, heated and stirred at a speed of 250 r / min and a temperature of 70°C until dissolved, red phosphorus and dispersant sodium dodecylbenzene sulfonate are added, 0.5 mol / L sodium hydroxide solution is added dropwise to adjust the pH to 9.5, and then a 5% aluminum sulfate aqueous solution is added, and the mixture is heated at a temperature of 75°C for reaction for 2 hours. After the reaction, the mixture is filtered, and the filtered residue is washed with deionized water for 3 times, and then dried at a temperature of 100°C for 10 hours to obtain the preparation of an inorganic coated red phosphorus flame retardant;

[0124] The mass ratio of magnesium sulfate heptahydrate, deionized water, red phosphorus, dispersant sodium dodecylbenzene sulfonate, and aluminum sulfate aqueous solution is 150:400:100:5:0.5;

[0125] Step 2: Preparation of double-layer coated red phosphorus flame retardant:

[0126] The polyvinyl chloride resin was dissolved in an organic solvent acetone, and an inorganic coated red phosphorus flame retardant and dimethyl (3-amino-3-acylpropyl) phosphonate were added, and the mixture was reacted at 60°C for 10 hours. After the reaction, the acetone was removed by rotary evaporation at 50°C, and the mixture was washed with ethanol for 3 times and dried at 50°C for 15 hours to obtain a double-layer coated red phosphorus flame retardant.

[0127] Among them, the mass ratio of polyvinyl chloride resin, organic solvent acetone, inorganic coated red phosphorus flame retardant and dimethyl (3-amino-3-acylpropyl) phosphonate is 210:1200:156:144.

[0128] In Examples 1-7 and Comparative Examples 1-2:

[0129] The red phosphorus is refined red phosphorus, which is prepared by the following steps:

[0130] The red phosphorus was added into an ethanol aqueous solution with a concentration of 15%, ground for 60 minutes, passed through a 300-mesh sieve, filtered, and the filter cake was taken. The filter cake was dried at 55° C. for 8 hours to obtain fine red phosphorus.

[0131] Polyvinyl chloride resin was provided by Ningbo Aoke Polymer New Materials Co., Ltd., brand: AKW65.

[0132] Performance Testing

[0133] The performance tests were performed on the double-layer coated red phosphorus flame retardants obtained in Examples 1-7 and Comparative Examples 1-2:

[0134] (1) Hygroscopicity and antioxidant performance test: Weigh 1 g of each double-layer coated red phosphorus flame retardant sample prepared in Examples 1-7 and Comparative Examples 1-2, place them on clean surface dishes, and place them in a desiccator. A saturated sodium chloride solution is placed in the desiccator to maintain the humidity in the desiccator at above 75%. After one week, measure the mass increase ratio of the double-layer coated red phosphorus flame retardant sample, which is the moisture absorption rate of the double-layer coated red phosphorus flame retardant.

[0135] (2) Antioxidant performance test: Weigh 10 g of each double-layer coated red phosphorus flame retardant sample prepared in Examples 1-7 and Comparative Examples 1-2, add them to flasks, add 200 mL of deionized water, stir at room temperature for 1 h, filter, take 50 mL of filtrate, titrate with 0.1 mol / L sodium hydroxide solution, and calculate the antioxidant property of the double-layer coated red phosphorus flame retardant based on the volume of the consumed sodium hydroxide solution. The calculation formula is as follows:

[0136] W NaOH =(40×C×V) / (m×50 / 200×1h);

[0137] Where: C is the concentration of sodium hydroxide solution, V is the volume of the consumed sodium hydroxide solution, m is the mass of the double-layer coated red phosphorus flame retardant sample, W NaOH The unit is mg / g·h;

[0138] The test results are shown in Table 1:

[0139] Table 1

[0140] Moisture absorption rate (%) Antioxidant activity (mg / g·h) Example 1 0.81 0.52 Example 2 1.13 0.38 Example 3 0.85 0.50 Example 4 0.91 0.47 Example 5 0.96 0.45 Example 6 1.03 0.42 Example 7 1.07 0.40 Comparative Example 1 0.78 1.14 Comparative Example 2 0.79 1.13

[0141] As shown in Table 1, the double-layer coated red phosphorus flame retardant prepared by the present invention has good hygroscopicity and antioxidant properties. Compared with Example 1, in Comparative Example 1, because dimethyl (3-amino-3-acylpropyl) phosphonate is not added to perform surface modification on the inorganic coated red phosphorus flame retardant, the double-layer coated red phosphorus flame retardant formed by polyvinyl chloride resin coated on the inorganic coated red phosphorus flame retardant lacks chemical bond connection between the inorganic coating layer and the organic coating layer, and the coating effect of the organic coating layer is reduced, resulting in reduced antioxidant properties of the double-layer coated red phosphorus flame retardant. Since the moisture absorption rate of the organic polymer is higher than that of Mg(OH) 2 , therefore, the moisture absorption rate of the double-layer coated red phosphorus flame retardant is slightly increased; in Comparative Example 2, although dimethyl (3-amino-3-acylpropyl) phosphonate is added, it does not chemically react with the inorganic coating layer, and the coating effect of the organic coating layer is also reduced. Therefore, the moisture absorption rate and antioxidant properties of the double-layer coated red phosphorus flame retardant are equivalent to those of Comparative Example 1.

[0142] (3) Flame retardant performance test: The double-layer coated red phosphorus flame retardant prepared in Examples 1-7 and Comparative Examples 1-2 was added to PP (polypropylene resin) respectively, and the mass percentage ratio of the double-layer coated red phosphorus flame retardant to PP was 10%:90%. PP splines of 120 mm×75 mm×3 mm were made, which were successively recorded as spline 1, spline 2, spline 3, spline 4, spline 5, spline 6, spline 7, spline 8, and spline 9. A PP spline made of pure PP was recorded as spline 10. The LOI (limiting oxygen index) of each PP spline was tested. The test results are shown in Table 2:

[0143] Table 2

[0144]

[0145] It can be seen from Table 2 that the double-layer coated red phosphorus flame retardant prepared in the present invention has a good flame retardant effect. When the addition amount of the double-layer coated red phosphorus flame retardant is 10%, the limiting oxygen index of PP reaches 23.5%. Compared with the specimen made of pure PP, the improvement rate of the limiting oxygen index reaches 26%. Compared with Example 1, in Comparative Example 1, because dimethyl (3-amino-3-acylpropyl) phosphonate was not used to modify the inorganic coated red phosphorus flame retardant, the inorganic coating layer and the organic coating layer were not connected by chemical bonds, the coating effect of the organic coating layer was reduced, and the compatibility of the obtained double-layer coated red phosphorus flame retardant with PP was reduced, resulting in a decrease in the flame retardant properties of the double-layer coated red phosphorus flame retardant; in Comparative Example 2, although dimethyl (3-amino-3-acylpropyl) phosphonate with flame retardant effect was added, the inorganic coating layer and the organic coating layer were not connected by chemical bonds, the coating effect of the organic coating layer was reduced, the compatibility of the obtained double-layer coated red phosphorus flame retardant with PP was reduced, and the flame retardant properties were reduced.

[0146] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a double-layer coated red phosphorus flame retardant, characterized in that: The following steps are involved: Step 1: Preparation of inorganic coated red phosphorus flame retardant: The method comprises adding magnesium sulfate heptahydrate to deionized water, heating and stirring until dissolved, adding red phosphorus and a dispersant, dropping a sodium hydroxide solution to adjust the pH, adding an aqueous solution of aluminum sulfate, heating for reaction, filtering, washing, and drying after the reaction to obtain an inorganic coated red phosphorus flame retardant; Step 2: Preparation of surface modified inorganic coated red phosphorus flame retardant: Dimethyl (3-amino-3-acylpropyl) phosphonate is mixed with N,N-dimethylformamide, and then added to a hydrobromic acid aqueous solution for reaction. After the reaction, an inorganic coated red phosphorus flame retardant is added, and the mixture is heated for reaction. After the heating reaction, the mixture is filtered, washed, and dried to obtain a surface-modified inorganic coated red phosphorus flame retardant. Step 3: Preparation of double-layer coated red phosphorus flame retardant: The polyvinyl chloride resin is dissolved in an organic solvent, and a surface-modified inorganic coated red phosphorus flame retardant is added, and the reaction is heated. After the reaction, the solvent is removed by rotary evaporation, and the double-layer coated red phosphorus flame retardant is obtained by washing and drying.

2. The method for preparing a double-layer coated red phosphorus flame retardant according to claim 1, characterized in that: In the step 1, the red phosphorus comprises refined red phosphorus; The refined red phosphorus is prepared by the following steps: The red phosphorus is added into an ethanol aqueous solution, ground, sieved, filtered, and filtered to obtain a filter cake, and the filter cake is dried to obtain fine red phosphorus.

3. The method for preparing a double-layer coated red phosphorus flame retardant according to claim 2, characterized in that: The concentration of the ethanol aqueous solution is 10%-20%, the mass ratio of red phosphorus to the ethanol aqueous solution is 1:3-5, the grinding time is 30-60 minutes, the aperture of the sieve for screening is 200-300 meshes, and the drying condition is drying at a temperature of 50-60° C. for 10-15 hours.

4. The method for preparing a double-layer coated red phosphorus flame retardant according to claim 1, characterized in that: In the step 1, the mass ratio of magnesium sulfate heptahydrate, deionized water, red phosphorus, dispersant, and aluminum sulfate aqueous solution is 150-200:400-600:100:5-10:0.5-1; Wherein, the dispersant includes sodium dodecylbenzene sulfonate.

5. The method for preparing a double-layer coated red phosphorus flame retardant according to claim 1, characterized in that: In the step 1, the heating and stirring speed is 250-350 r / min, the heating and stirring temperature is 60-70°C, the concentration of sodium hydroxide is 0.5-1.5 mol / L, the pH is adjusted to 9.5-10.5, the heating reaction temperature is 75-85°C, the heating reaction time is 1-2h, and the drying condition is drying at 100-120°C for 5-10h.

6. The method for preparing a double-layer coated red phosphorus flame retardant according to claim 1, characterized in that: In the step 2, the mass ratio of dimethyl (3-amino-3-acylpropyl) phosphonate, N,N-dimethylformamide, hydrobromic acid aqueous solution, and inorganic coated red phosphorus flame retardant is 180:5000-8000:150:190-200.

7. The method for preparing a double-layer coated red phosphorus flame retardant according to claim 6, characterized in that: The concentration of the hydrobromic acid aqueous solution is 40%-50%.

8. The method for preparing a double-layer coated red phosphorus flame retardant according to claim 1, characterized in that: In the step 2, the reaction conditions are 80-100° C. for 5 hours, the heating reaction conditions are 50-70° C. for 1-2 hours, and the drying conditions are 50-60° C. for 10-15 hours.

9. The method for preparing a double-layer coated red phosphorus flame retardant according to claim 1, characterized in that: In the step 3, the mass ratio of the polyvinyl chloride resin, the organic solvent, and the surface-modified inorganic coated red phosphorus flame retardant is 210-270:1200-2000:

300. Among them, the organic solvent includes acetone.

10. The method for preparing a double-layer coated red phosphorus flame retardant according to claim 1, characterized in that: In the step 3, the heating reaction condition is 60-80°C for 6-10h, and the drying condition is 50-60°C for 10-15h.

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