Coal flame retardant

Abstract

The invention discloses a coal flame retardant, and belongs to the technical field of flame retardants. The coal inhibitor is used for solving the technical problems that in the prior art, the inhibition efficiency and the safety performance of the coal inhibitor need to be further improved, and the coal inhibitor is prepared through the steps that amino-modified nano silicon dioxide and 2-hydroxy-3-(2-methyl-2-propenyl) benzaldehyde react, and modified nano silicon dioxide is obtained; in an Ar gas environment, the modified CEPPA, 5-hydroxypentyl acrylate, absolute ethyl alcohol and potassium hydroxide are mixed and react to obtain a composite flame retardant; acrylic acid, acrylamide, sodium alginate and water are mixed, an initiator, a cross-linking agent, the modified nano-silica and the composite flame retardant are added for reaction, and the carbon flame retardant with good water absorption, water retention, heat absorption and cooling performance and plugging effect is obtained. The action time of the coal flame retardant can be prolonged due to heat resistance, permeability and adsorbability, and the coal spontaneous combustion inhibition effect is further improved.

Description

Technical Field

[0001] The present invention relates to the technical field of flame retardants, in particular to a coal flame retardant. Background Art

[0002] As one of the most critical and essential basic energy sources in global economic activities, the safety of coal during its mining and storage stages has always been a focus of great concern. In the development, transportation and preservation of coal resources, it is inevitable to pile up coal. When the temperature rises to a critical value and the oxygen content is sufficient, spontaneous combustion occurs, becoming an internal factor for fire. The ignition point is generally located deep in the pile and is hidden. During the spontaneous combustion of coal, Fe 2+ 、Co 2+ 、Ni 2 + These metal ions have a strong catalytic effect. To address fire risks, liquid water spraying is commonly used due to its high specific heat capacity, cooling and dilution properties, widespread availability, and minimal environmental impact. However, this approach has certain limitations, particularly when the coal surface is dry and prone to oxidation. Currently, inhibitors are commonly used to address these situations. Inhibitors primarily slow the oxidation reaction, inhibiting the onset and progression of combustion.

[0003] Inhibitors can be categorized as physical, chemical, and composite. Physical inhibitors include halide salts, ammonium salts, and foam inhibitors. Halide salts effectively inhibit the oxidation process of coal, preventing spontaneous combustion, but they are highly corrosive. Ammonium salts have poor efficiency and emit gases that pose a health risk. Foam inhibitors also suffer from poor stability. Chemical inhibitors primarily inhibit spontaneous combustion by reacting their functional groups with active groups in the coal sample, reducing the active structures and oxidizing capacity within the coal. However, commonly used materials, such as alkaline inhibitors, are prone to precipitation, making them difficult to spray evenly and corrosive. Notably, flame retardants also have the ability to inhibit coal spontaneous combustion and, to a certain extent, reduce the burning rate, heat release, smoke, and toxic gas production. Therefore, there is a need for safe and efficient flame retardants to reduce the probability of coal combustion. Summary of the Invention

[0004] The purpose of the present invention is to provide a coal flame retardant to solve the technical problem in the prior art that the retardant efficiency and safety performance of coal inhibitors need to be further improved.

[0005] In order to achieve the above object, the present invention provides a method for preparing a coal flame retardant, comprising the following steps:

[0006] Step (1) preparing modified nano-silica;

[0007] Under a nitrogen environment, amino-modified nano-silica, 2-hydroxy-3-(2-methyl-2-propenyl)benzaldehyde and anhydrous ethanol are mixed, heated, filtered, washed and dried to obtain modified nano-silica;

[0008] Step (2) preparing a composite flame retardant;

[0009] S1: CEPPA, (2-aminophenyl)-phosphoramidic acid (4-chlorophenyl) ester, and N,N-dimethylformamide were mixed, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and 1-hydroxybenzotriazole were added, and the mixture was heated for reaction. After the reaction was completed, the mixture was distilled under reduced pressure to obtain modified CEPPA;

[0010] S2: In an Ar atmosphere, modified CEPPA, 5-hydroxypentyl acrylate, anhydrous ethanol, and potassium hydroxide are mixed, heated to react, and after the reaction is completed, vacuum distillation is performed to obtain a composite flame retardant;

[0011] Step (3) preparing a coal flame retardant;

[0012] Acrylic acid, acrylamide, sodium alginate and water are mixed, an initiator, a cross-linking agent, modified nano-silicon dioxide and a composite flame retardant are added, stirred, heated for reaction, and dried to obtain a coal flame retardant after the reaction is completed.

[0013] Preferably, the mass ratio of amino-modified nano-silica, 2-hydroxy-3-(2-methyl-2-propenyl)benzaldehyde and anhydrous ethanol is (40-60):(200-400):(800-1400); the reaction temperature is 75-95° C., and the reaction time is 10-12 h.

[0014] Preferably, the mass ratio of CEPPA, (2-aminophenyl)-phosphoramidic acid (4-chlorophenyl) ester, N,N-dimethylformamide, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and 1-hydroxybenzotriazole is (160-180):(240-280):(2000-3200):(182-206):(110-125); the reaction temperature is 30-50°C, and the reaction time is 7-9h.

[0015] Preferably, the mass ratio of modified CEPPA, 5-hydroxypentyl acrylate, anhydrous ethanol and potassium hydroxide is (300-380):(100-120):(1200-1600):(6-10); the reaction temperature is 55-75° C., and the reaction time is 35-43 h.

[0016] Preferably, the mass ratio of acrylic acid, acrylamide, sodium alginate, water, initiator, crosslinking agent, modified nano-silica and composite flame retardant is (20-40):(10-15):(4-6):(200-600):(4-8):(0.4-0.8):(5-10):(8-12); the reaction temperature is 65-75°C, and the reaction time is 4-6h.

[0017] Preferably, the initiator is potassium persulfate.

[0018] Preferably, the cross-linking agent is any one of MBA and EGDMA.

[0019] Preferably, the drying conditions in step (3) are: drying at a temperature of 85-95° C. for 8-10 hours.

[0020] Preferably, the preparation method of amino-modified nano-silica comprises the following steps:

[0021] Nano-silica, anhydrous ethanol and γ-aminoethylaminopropyltrimethoxysilane are mixed evenly, heated to react, and after the reaction is completed, centrifuged, washed and dried to obtain amino-modified nano-silica;

[0022] Wherein, the mass ratio of nano-silica, anhydrous ethanol and γ-aminoethylaminopropyltrimethoxysilane is 100:(2000-4000):(40-60);

[0023] The reaction temperature is 55-65° C., and the reaction time is 8-10 h.

[0024] A coal flame retardant is prepared by the coal flame retardant preparation method.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. The nano-silica added in the present invention is a nanostructured inorganic heat-resistant particle, the addition of which increases thermal stability and mechanical properties; it has a high specific surface area, can fill the pores of coal, and inhibit oxygen diffusion; the amino-modified nano-silica obtained after modification reacts with 2-hydroxy-3-(2-methyl-2-propenyl)benzaldehyde to obtain modified nano-silica containing a carbon-nitrogen double bond, wherein the nitrogen atom contains a lone pair of electrons, which can react with the catalytic metal ion Fe in the spontaneous combustion of coal. 2 + 、Co 2+ 、Ni 2+The phenolic hydroxyl group contained in 2-hydroxy-3-(2-methyl-2-propenyl)benzaldehyde has a certain antioxidant effect. Its addition not only effectively interrupts the chain reaction of free radicals, but also has the ability to absorb oxygen, thereby effectively preventing coal from absorbing oxygen and reducing coal spontaneous combustion.

[0027] 2. The CEPPA in this invention is an organophosphorus flame retardant. The carboxyl groups contained in it can undergo an amidation reaction with the amino groups in (2-aminophenyl)-phosphamidic acid (4-chlorophenyl) ester to produce modified CEPPA. The phosphorus oxygen groups contained in (2-aminophenyl)-phosphamidic acid (4-chlorophenyl) ester play a role in gas-phase and condensed-phase flame retardancy; during combustion, they absorb heat, lower the local temperature, and hinder combustion. The nitrogen contained in it also produces non-combustible gases during combustion, diluting the oxygen concentration and slowing combustion.

[0028] 3. The chlorine group in the modified CEPPA reacts with the hydroxyl group in 5-hydroxypentyl acrylate to obtain an ether group, further increasing the thermal stability. The modified nano-silica and the composite flame retardant in the present invention both contain unsaturated double bonds that can react with acrylic acid and acrylamide under the action of an initiator to produce free radical reactions. Under the action of a cross-linking agent, a network structure is formed, and sodium alginate is compounded to improve the adsorption to obtain a coal flame retardant, which is also a hydrogel material. The coal flame retardant prepared by the present invention has good water absorption, water retention, heat absorption and cooling properties, and blocking effects; in the process of coal heating, the evaporation of water in the hydrogel will absorb a large amount of heat, prevent heat accumulation, and slow down the coal spontaneous combustion process; at the same time, the heat resistance, permeability, and adsorption contained in the hydrogel will increase the action time of the coal flame retardant, further improving the effect of inhibiting coal spontaneous combustion. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a flow chart of the preparation process of the coal flame retardant of the present invention;

[0030] Figure 2 Schematic diagram of the reaction for preparing modified nano-silica in the present invention;

[0031] Figure 3 Schematic diagram of the reaction for preparing modified CEPPA in the present invention;

[0032] Figure 4 Schematic diagram of the reaction for preparing the composite flame retardant in the present invention. DETAILED DESCRIPTION

[0033] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0034] Example 1

[0035] This embodiment provides a method for preparing a coal flame retardant, comprising the following steps:

[0036] Step (1) preparing modified nano-silica;

[0037] Under nitrogen, amino-modified nano-silica, 2-hydroxy-3-(2-methyl-2-propenyl)benzaldehyde, and anhydrous ethanol were mixed in a mass ratio of 40:200:800, reacted at 75°C for 12 hours, filtered, washed with deionized water, and dried at 80°C for 8 hours to obtain modified nano-silica.

[0038] Step (2) preparing a composite flame retardant;

[0039] S1: CEPPA, (2-aminophenyl)-phosphoramidic acid (4-chlorophenyl) ester, and N,N-dimethylformamide were mixed, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and 1-hydroxybenzotriazole were added, and the mixture was reacted at 30°C for 9 hours. After the reaction, the mixture was distilled under reduced pressure at 15 kPa and 60°C for 2 hours to obtain modified CEPPA;

[0040] The mass ratio of CEPPA, (2-aminophenyl)-phosphoramidic acid (4-chlorophenyl) ester, N,N-dimethylformamide, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and 1-hydroxybenzotriazole is 160:240:2000:182:110;

[0041] S2: In an Ar atmosphere, modified CEPPA, 5-hydroxypentyl acrylate, anhydrous ethanol, and potassium hydroxide were mixed in a mass ratio of 300:100:1200:6, reacted at 55°C for 43 hours, and then distilled under reduced pressure at 0.08 MPa and 55°C for 100 minutes to obtain a composite flame retardant.

[0042] Step (3) preparing a coal flame retardant;

[0043] Acrylic acid, acrylamide, sodium alginate and water were mixed and stirred at a speed of 200 r / min for 6 minutes, potassium persulfate, MBA, modified nano-silica and composite flame retardant were added, and stirred at a speed of 100 r / min for 4 minutes. The mixture was reacted at a temperature of 65°C for 6 hours. After the reaction was completed, the mixture was dried at a temperature of 85°C for 10 hours to obtain a coal flame retardant.

[0044] Among them, the mass ratio of acrylic acid, acrylamide, sodium alginate, water, potassium persulfate, MBA, modified nano-silica and composite flame retardant is 20:10:4:200:4:0.4:5:8.

[0045] Example 2

[0046] This embodiment provides a method for preparing a coal flame retardant, comprising the following steps:

[0047] Step (1) preparing modified nano-silica;

[0048] Under nitrogen, amino-modified nano-silica, 2-hydroxy-3-(2-methyl-2-propenyl)benzaldehyde, and anhydrous ethanol were mixed in a mass ratio of 45:250:950, reacted at 80°C for 11.5 hours, filtered, washed with deionized water, and dried at 85°C for 7.5 hours to obtain modified nano-silica.

[0049] Step (2) preparing a composite flame retardant;

[0050] S1: CEPPA, (2-aminophenyl)-phosphoramidic acid (4-chlorophenyl) ester, and N,N-dimethylformamide were mixed, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and 1-hydroxybenzotriazole were added, and the mixture was reacted at 35°C for 8.5 hours. After the reaction, the mixture was distilled under reduced pressure at 15 kPa and 62°C for 1.8 hours to obtain modified CEPPA;

[0051] The mass ratio of CEPPA, (2-aminophenyl)-phosphoramidic acid (4-chlorophenyl) ester, N,N-dimethylformamide, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and 1-hydroxybenzotriazole is 165:250:2300:188:113;

[0052] S2: In an Ar atmosphere, modified CEPPA, 5-hydroxypentyl acrylate, anhydrous ethanol, and potassium hydroxide in a mass ratio of 320:105:1300:7 were mixed and reacted at 60°C for 41 hours. After the reaction was completed, the mixture was subjected to reduced pressure distillation at 0.08 MPa and 57°C for 90 minutes to obtain a composite flame retardant.

[0053] Step (3) preparing a coal flame retardant;

[0054] Acrylic acid, acrylamide, sodium alginate and water were mixed and stirred at a speed of 250 r / min for 5.5 min, potassium persulfate, MBA, modified nano-silica and composite flame retardant were added, and stirred at a speed of 120 r / min for 3.5 min. The mixture was reacted at a temperature of 67°C for 5.5 h. After the reaction was completed, the mixture was dried at a temperature of 87°C for 9.5 h to obtain a coal flame retardant.

[0055] Among them, the mass ratio of acrylic acid, acrylamide, sodium alginate, water, potassium persulfate, MBA, modified nano-silica and composite flame retardant is 25:11:4.5:300:5:0.5:6:9.

[0056] Example 3

[0057] This embodiment provides a method for preparing a coal flame retardant, comprising the following steps:

[0058] Step (1) preparing modified nano-silica;

[0059] Under nitrogen, amino-modified nano-silica, 2-hydroxy-3-(2-methyl-2-propenyl)benzaldehyde, and anhydrous ethanol were mixed in a mass ratio of 50:300:1100, reacted at 85°C for 11 hours, filtered, washed with deionized water, and dried at 90°C for 7 hours to obtain modified nano-silica.

[0060] Step (2) preparing a composite flame retardant;

[0061] S1: CEPPA, (2-aminophenyl)-phosphoramidic acid (4-chlorophenyl) ester, and N,N-dimethylformamide were mixed, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and 1-hydroxybenzotriazole were added, and the mixture was reacted at 40°C for 8 hours. After the reaction, the mixture was distilled under reduced pressure at 15 kPa and 65°C for 1.6 hours to obtain modified CEPPA;

[0062] The mass ratio of CEPPA, (2-aminophenyl)-phosphoramidic acid (4-chlorophenyl) ester, N,N-dimethylformamide, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and 1-hydroxybenzotriazole is 170:260:2600:194:117;

[0063] S2: In an Ar atmosphere, modified CEPPA, 5-hydroxypentyl acrylate, anhydrous ethanol, and potassium hydroxide in a mass ratio of 340:110:1400:8 were mixed and reacted at 65°C for 39 hours. After the reaction was completed, the mixture was subjected to reduced pressure distillation at 0.08 MPa and 60°C for 80 minutes to obtain a composite flame retardant.

[0064] Step (3) preparing a coal flame retardant;

[0065] Acrylic acid, acrylamide, sodium alginate and water were mixed and stirred at a speed of 300 r / min for 5 minutes, potassium persulfate, MBA, modified nano-silica and composite flame retardant were added, and stirred at a speed of 140 r / min for 3 minutes. The mixture was reacted at a temperature of 70°C for 5 hours. After the reaction was completed, the mixture was dried at a temperature of 90°C for 9 hours to obtain a coal flame retardant.

[0066] Among them, the mass ratio of acrylic acid, acrylamide, sodium alginate, water, potassium persulfate, MBA, modified nano-silica and composite flame retardant is 30:13:5:400:6:0.6:8:10.

[0067] Example 4

[0068] This embodiment provides a method for preparing a coal flame retardant, comprising the following steps:

[0069] Step (1) preparing modified nano-silica;

[0070] Under nitrogen, amino-modified nano-silica, 2-hydroxy-3-(2-methyl-2-propenyl)benzaldehyde, and anhydrous ethanol were mixed in a mass ratio of 55:350:1250, reacted at 90°C for 10.5h, filtered, washed with deionized water, and dried at 95°C for 6.5h to obtain modified nano-silica.

[0071] Step (2) preparing a composite flame retardant;

[0072] S1: CEPPA, (2-aminophenyl)-phosphoramidic acid (4-chlorophenyl) ester, and N,N-dimethylformamide were mixed, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and 1-hydroxybenzotriazole were added, and the mixture was reacted at 45°C for 7.5 hours. After the reaction, the mixture was distilled under reduced pressure at 15 kPa and 67°C for 1.4 hours to obtain modified CEPPA;

[0073] The mass ratio of CEPPA, (2-aminophenyl)-phosphoramidic acid (4-chlorophenyl) ester, N,N-dimethylformamide, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and 1-hydroxybenzotriazole is 17:270:2900:200:121;

[0074] S2: In an Ar atmosphere, modified CEPPA, 5-hydroxypentyl acrylate, anhydrous ethanol, and potassium hydroxide were mixed in a mass ratio of 360:115:1500:9, reacted at 70°C for 37 hours, and then subjected to reduced pressure distillation at 0.08 MPa and 62°C for 70 minutes to obtain a composite flame retardant.

[0075] Step (3) preparing a coal flame retardant;

[0076] Acrylic acid, acrylamide, sodium alginate and water were mixed and stirred at a speed of 350 r / min for 4.5 min, potassium persulfate, MBA, modified nano-silica and composite flame retardant were added, and stirred at a speed of 160 r / min for 2.5 min. The mixture was reacted at a temperature of 72°C for 4.5 h. After the reaction was completed, the mixture was dried at a temperature of 92°C for 8.5 h to obtain a coal flame retardant.

[0077] Among them, the mass ratio of acrylic acid, acrylamide, sodium alginate, water, potassium persulfate, MBA, modified nano-silica and composite flame retardant is 35:14:5.5:500:7:0.7:9:11.

[0078] Example 5

[0079] This embodiment provides a method for preparing a coal flame retardant, comprising the following steps:

[0080] Step (1) preparing modified nano-silica;

[0081] Under nitrogen, amino-modified nano-silica, 2-hydroxy-3-(2-methyl-2-propenyl)benzaldehyde, and anhydrous ethanol were mixed in a mass ratio of 60:400:1400, reacted at 95°C for 10 hours, filtered, washed with deionized water, and dried at 100°C for 6 hours to obtain modified nano-silica.

[0082] Step (2) preparing a composite flame retardant;

[0083] S1: CEPPA, (2-aminophenyl)-phosphoramidic acid (4-chlorophenyl) ester, and N,N-dimethylformamide were mixed, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and 1-hydroxybenzotriazole were added, and the mixture was reacted at 50°C for 7 hours. After the reaction, the mixture was distilled under reduced pressure at 15 kPa and 70°C for 1.2 hours to obtain modified CEPPA;

[0084] The mass ratio of CEPPA, (2-aminophenyl)-phosphoramidic acid (4-chlorophenyl) ester, N,N-dimethylformamide, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and 1-hydroxybenzotriazole is 180:280:3200:206:125;

[0085] S2: In an Ar atmosphere, modified CEPPA, 5-hydroxypentyl acrylate, anhydrous ethanol, and potassium hydroxide in a mass ratio of 380:120:1600:10 were mixed and reacted at 75°C for 35 hours. After the reaction was completed, the mixture was distilled under reduced pressure at 0.08 MPa and 65°C for 60 minutes to obtain a composite flame retardant.

[0086] Step (3) preparing a coal flame retardant;

[0087] Acrylic acid, acrylamide, sodium alginate and water were mixed and stirred at a speed of 400 r / min for 4 minutes, potassium persulfate, MBA, modified nano-silica and composite flame retardant were added, and stirred at a speed of 180 r / min for 2 minutes. The mixture was reacted at a temperature of 75°C for 4 hours. After the reaction was completed, the mixture was dried at a temperature of 95°C for 8 hours to obtain a coal flame retardant.

[0088] Among them, the mass ratio of acrylic acid, acrylamide, sodium alginate, water, potassium persulfate, MBA, modified nano-silica and composite flame retardant is 40:15:6:600:8:0.8:10:12.

[0089] Example 6

[0090] This embodiment provides a method for preparing amino-modified nano-silica:

[0091] Nano-silica, anhydrous ethanol, and γ-aminoethylaminopropyltrimethoxysilane were mixed uniformly in a mass ratio of 100:2000:40, heated, and reacted at 55-65°C for 8-10 hours. After the reaction, the mixture was centrifuged at 8000 r / min for 15 minutes, washed with anhydrous ethanol, and dried at 80°C for 5 hours to obtain amino-modified nano-silica.

[0092] Comparative Example 1

[0093] This comparative example provides a method for preparing a coal flame retardant, comprising the following steps:

[0094] Step (1) preparing a composite flame retardant;

[0095] S1: CEPPA, (2-aminophenyl)-phosphoramidic acid (4-chlorophenyl) ester, and N,N-dimethylformamide were mixed, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and 1-hydroxybenzotriazole were added, and the mixture was reacted at 30°C for 9 hours. After the reaction, the mixture was distilled under reduced pressure at 15 kPa and 60°C for 2 hours to obtain modified CEPPA;

[0096] The mass ratio of CEPPA, (2-aminophenyl)-phosphoramidic acid (4-chlorophenyl) ester, N,N-dimethylformamide, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and 1-hydroxybenzotriazole is 160:240:2000:182:110;

[0097] S2: In an Ar atmosphere, modified CEPPA, 5-hydroxypentyl acrylate, anhydrous ethanol, and potassium hydroxide were mixed in a mass ratio of 300:100:1200:6, reacted at 55°C for 43 hours, and then distilled under reduced pressure at 0.08 MPa and 55°C for 100 minutes to obtain a composite flame retardant.

[0098] Step (2) preparing a coal flame retardant;

[0099] Acrylic acid, acrylamide, sodium alginate and water were mixed and stirred at a speed of 200 r / min for 6 minutes, potassium persulfate, MBA, amino-modified nano-silica and composite flame retardant were added, and stirred at a speed of 100 r / min for 4 minutes. The mixture was reacted at a temperature of 65°C for 6 hours. After the reaction was completed, the mixture was dried at a temperature of 85°C for 10 hours to obtain a coal flame retardant.

[0100] Among them, the mass ratio of acrylic acid, acrylamide, sodium alginate, water, potassium persulfate, MBA, amino-modified nano-silica and composite flame retardant is 20:10:4:200:4:0.4:5:8.

[0101] Comparative Example 2

[0102] This comparative example provides a method for preparing a coal flame retardant, comprising the following steps:

[0103] Step (1) preparing modified CEPPA;

[0104] CEPPA, (2-aminophenyl)-phosphoramidic acid (4-chlorophenyl) ester, and N,N-dimethylformamide were mixed, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and 1-hydroxybenzotriazole were added, and the mixture was reacted at 30°C for 9 hours. After the reaction, the mixture was distilled under reduced pressure at 15 kPa and 60°C for 2 hours to obtain modified CEPPA;

[0105] The mass ratio of CEPPA, (2-aminophenyl)-phosphoramidic acid (4-chlorophenyl) ester, N,N-dimethylformamide, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and 1-hydroxybenzotriazole is 160:240:2000:182:110;

[0106] Step (2) preparing a coal flame retardant;

[0107] Acrylic acid, acrylamide, sodium alginate and water were mixed and stirred at a speed of 200 r / min for 6 minutes, potassium persulfate, MBA, amino-modified nano-silica and modified CEPPA were added, and the mixture was stirred at a speed of 100 r / min for 4 minutes. The mixture was reacted at a temperature of 65°C for 6 hours. After the reaction was completed, the mixture was dried at a temperature of 85°C for 10 hours to obtain a coal flame retardant.

[0108] Among them, the mass ratio of acrylic acid, acrylamide, sodium alginate, water, potassium persulfate, MBA, amino-modified nano-silica and modified CEPPA is 20:10:4:200:4:0.4:5:8.

[0109] Comparative Example 3

[0110] This comparative example provides a method for preparing a coal flame retardant, comprising the following steps:

[0111] Acrylic acid, acrylamide, sodium alginate and water were mixed and stirred at a speed of 200 r / min for 6 minutes, potassium persulfate, MBA, amino-modified nano-silica and CEPPA were added, and stirred at a speed of 100 r / min for 4 minutes. The mixture was reacted at a temperature of 65°C for 6 hours. After the reaction was completed, the mixture was dried at a temperature of 85°C for 10 hours to obtain a coal flame retardant.

[0112] Among them, the mass ratio of acrylic acid, acrylamide, sodium alginate, water, potassium persulfate, MBA, amino-modified nano-silica and CEPPA is 20:10:4:200:4:0.4:5:8.

[0113] The amino-modified nano-silica used in Examples 1-5 and Comparative Examples 1-3 of the present invention is the amino-modified nano-silica prepared in Example 6.

[0114] In the examples and comparative examples of the present invention, the nano-silicon dioxide was obtained from Shanghai Aladdin Biochemical Technology Co., Ltd., with a particle size of 7-40 nm and a surface area of about 260 m 2 / g; CEPPA was obtained from Jingmen Dongxin Biotechnology Co., Ltd., CAS No.: 14657-64-8; 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride was obtained from Shanghai Xijia Biotechnology Co., Ltd.; 1-hydroxybenzotriazole was obtained from Shanghai Covalent Chemical Technology Co., Ltd., CAS No.: 2592-95-2.

[0115] Performance testing:

[0116] The coal flame retardants prepared in Examples 1-5 and Comparative Examples 1-3 were tested as follows:

[0117] Coal sampling: Fresh coal samples were collected from Donghuantuo Mine according to the national standard GB / T482-2008 "Method for Sampling Coal Seams", wrapped in plastic wrap, and prepared according to GB474-2008 "Method for Preparing Coal Samples". The outer oxide layer of the coal sample was removed, and the middle part was reduced, crushed, and sieved to obtain a 60-mesh particle size to obtain the coal sample;

[0118] The coal flame retardants prepared in Examples 1-5 and Comparative Examples 1-3 were dissolved in deionized water to prepare a coal flame retardant solution with a concentration of 3%. The coal sample was immersed in the coal flame retardant solution for 1 hour, taken out, and naturally air-dried for 24 hours to obtain a retardant coal sample. 250 g of the retardant coal sample was placed in a coal sample tank, and a programmed temperature experimental system was started with a starting temperature of 20°C, a heating rate of 0.5°C / min, and an air flow rate of 30 mL / min. The CO gas and its content at 50°C, 70°C, 90°C, 110°C, 130°C, and 150°C were detected by gas chromatograph to calculate the retardation rate. Where W1(T) is the volume fraction of CO generated by the coal sample when the coal temperature is T, and the unit is 10 -6 ; W2(T) is the volume fraction of CO produced by the quenched coal sample at the coal temperature T, in units of 10 -6 ; The specific test results are shown in Table 1 below;

[0119] Table 1

[0120]

[0121] Data Analysis:

[0122] Comparative analysis of the data in the above table shows that the coal flame retardant prepared by the present invention has good resistance to oxidation. In Examples 1-5, as the content of modified nano-silica and composite flame retardant decreases, the resistance to oxidation gradually decreases, and the coal flame retardant prepared in Example 1 has the best resistance to oxidation. Comparative Example 1 lacks the addition of 2-hydroxy-3-(2-methyl-2-propenyl)benzaldehyde compared to Example 1, and the antioxidant effect of the phenolic hydroxyl group contained in it is reduced, which is mainly reflected in the temperature range of 50-90°C; at the same time, there is no formation of Schiff base, that is, carbon-nitrogen double bond, so it reacts with the catalytic metal ion Fe 2+ 、Co 2+ 、Ni 2+ Unable to coordinate, reduce catalytic activity ability weakened, and reduce resistance performance. The hydroxyl group in 5-hydroxypentyl acrylate in comparative example 1 reacts with the chlorine group in modified CEPPA, and the obtained composite flame retardant containing unsaturated double bonds can be reacted with free radicals in the future under the action of initiator. Once lacking, there will be the problem of composite flame retardant migration, which reduces resistance performance. Therefore, the introduction of 5-hydroxypentyl acrylate is lacking in comparative example 2, and the resistance performance is reduced compared with the coal flame retardant resistance performance in comparative example 1. Comparative example 3 lacks (2-aminophenyl)-phosphoramidic acid (4-chlorophenyl) ester compared with comparative example 2, and the phosphorus oxygen group contained therein cannot play a role, so the resistance performance is reduced.

[0123] The above contents are merely examples and explanations of the structure of the present invention. Those skilled in the art may make various modifications or additions to the described specific embodiments or replace them in a similar manner. As long as they do not deviate from the structure of the invention or exceed the scope defined by the claims, they shall fall within the scope of protection of the present invention.

[0124] Throughout this specification, references to terms such as "one embodiment," "example," or "specific example" indicate that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0125] The preferred embodiments of the present invention disclosed above are intended only to help illustrate the present invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the present invention to specific embodiments. Obviously, many modifications and variations are possible based on the contents of this specification. These embodiments are selected and described in detail in this specification to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better understand and utilize the present invention. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for preparing a coal flame retardant, characterized in that: The following steps are involved: Step (1) preparing modified nano-silica; Under a nitrogen environment, amino-modified nano-silica, 2-hydroxy-3-(2-methyl-2-propenyl)benzaldehyde and anhydrous ethanol are mixed, heated, filtered, washed and dried to obtain modified nano-silica; Step (2) preparing a composite flame retardant; S1: CEPPA, (2-aminophenyl)-phosphoramidic acid (4-chlorophenyl) ester, and N,N-dimethylformamide were mixed, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and 1-hydroxybenzotriazole were added, and the mixture was heated for reaction. After the reaction was completed, the mixture was distilled under reduced pressure to obtain modified CEPPA; S2: In an Ar atmosphere, modified CEPPA, 5-hydroxypentyl acrylate, anhydrous ethanol, and potassium hydroxide are mixed, heated to react, and after the reaction is completed, vacuum distillation is performed to obtain a composite flame retardant; Step (3) preparing a coal flame retardant; Acrylic acid, acrylamide, sodium alginate and water are mixed, an initiator, a cross-linking agent, modified nano-silicon dioxide and a composite flame retardant are added, stirred, heated for reaction, and dried to obtain a coal flame retardant after the reaction is completed.

2. The method for preparing a coal flame retardant according to claim 1, characterized in that: The mass ratio of amino-modified nano-silica, 2-hydroxy-3-(2-methyl-2-propenyl)benzaldehyde and anhydrous ethanol is (40-60):(200-400):(800-1400); the reaction temperature is 75-95° C., and the reaction time is 10-12 hours.

3. The method for preparing a coal flame retardant according to claim 1, characterized in that: The mass ratio of CEPPA, (2-aminophenyl)-phosphoramidic acid (4-chlorophenyl) ester, N,N-dimethylformamide, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and 1-hydroxybenzotriazole is (160-180):(240-280):(2000-3200):(182-206):(110-125); the reaction temperature is 30-50°C, and the reaction time is 7-9h.

4. The method for preparing a coal flame retardant according to claim 1, characterized in that: The mass ratio of modified CEPPA, 5-hydroxypentyl acrylate, anhydrous ethanol and potassium hydroxide is (300-380):(100-120):(1200-1600):(6-10); the reaction temperature is 55-75° C., and the reaction time is 35-43 hours.

5. The method for preparing a coal flame retardant according to claim 1, characterized in that: The mass ratio of acrylic acid, acrylamide, sodium alginate, water, initiator, crosslinking agent, modified nano-silica and composite flame retardant is (20-40):(10-15):(4-6):(200-600):(4-8):(0.4-0.8):(5-10):(8-12); the reaction temperature is 65-75°C, and the reaction time is 4-6h.

6. The method for preparing a coal flame retardant according to claim 1, characterized in that: The initiator is potassium persulfate.

7. The method for preparing a coal flame retardant according to claim 1, characterized in that: The cross-linking agent is either MBA or EGDMA.

8. The method for preparing a coal flame retardant according to claim 1, characterized in that: The drying conditions in step (3) are: drying at a temperature of 85-95° C. for 8-10 hours.

9. The method for preparing a coal flame retardant according to claim 1, characterized in that: The preparation method of amino-modified nano-silica comprises the following steps: Nano-silica, anhydrous ethanol and γ-aminoethylaminopropyltrimethoxysilane are mixed evenly, heated to react, and after the reaction is completed, centrifuged, washed and dried to obtain amino-modified nano-silica; Wherein, the mass ratio of nano-silica, anhydrous ethanol and γ-aminoethylaminopropyltrimethoxysilane is 100:(2000-4000):(40-60); The reaction temperature is 55-65° C., and the reaction time is 8-10 h.

10. A coal flame retardant, characterized in that: The coal flame retardant is prepared by the preparation method of the coal flame retardant according to any one of claims 1 to 9.

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