Flame retardant smoke suppression coating and its preparation method and application

Abstract

The present invention discloses a flame retardant and smoke suppressing coating, and a preparation method and application thereof. The raw materials of the coating include the following components in terms of weight percentage: 2-30% gelatin, 1-5% metal oxide functionalized black phosphorus, 5-25% kosmotropic salt, 0.1-2% antibacterial agent, and the balance water; the metal oxide functionalized black phosphorus is prepared by solvent thermal reaction using black phosphorus nanosheets, cobalt salts, ferrous salts and sodium acetate as raw materials and an organic solvent as solvent, and the mass ratio of black phosphorus nanosheets, cobalt salts and ferrous salts is 2:2.5-5:2.5-3.75. The present invention enables the coating to have excellent flame retardant properties through the interaction of the components in the above contents. The limiting oxygen index of the polyurethane foam after coating modification increases from 17.5% to 32.0%; the peak heat release rate increases from 485kW / m 2 Down to 200kW / m 2 ; Peak smoke release rate from 0.30m 2 / s dropped to 0.15m 2 / s; tensile strength increased from 0.8MPa to 1.8MPa.

Description

Technical Field

[0001] The present invention relates to the field of flame retardant technology, and in particular to a flame retardant and smoke suppressing coating, a preparation method thereof, and an application thereof. Background Art

[0002] Black phosphorus is the most stable allotrope of phosphorus. When bulk black phosphorus is exfoliated into nanosheets, its dispersibility, compatibility and thermal stability are significantly improved, and it has great application potential in flame-retardant surface treatment. However, recent studies have shown that the free radicals (P·, PO· and HPO·) released during the black phosphorus flame retardancy process can capture OH· and H· free radicals in the combustion environment, terminate the combustion chain reaction, and lead to increased release of smoke and carbon monoxide (CO), which is harmful to human health. On the other hand, black phosphorus nanosheets will irreversibly degrade into phosphate compounds under water, oxygen and light. This environmental instability limits the use of black phosphorus in flame-retardant materials. The design and preparation of functionalized two-dimensional black phosphorus materials with flame retardancy, smoke suppression and environmental stability remain highly challenging.

[0003] To date, researchers have employed a variety of strategies to protect black phosphorus from degradation, including heteroatom doping, chemical passivation, physical coating, or chemical functionalization with polymers, to improve the environmental stability of black phosphorus nanosheet flame retardants. However, these functionalized black phosphorus nanosheets typically exhibit high performance in single flame retardant applications but fail to effectively suppress the release of harmful combustion products. Summary of the Invention

[0004] The technical problem to be solved by the present invention is how to improve the flame retardant and smoke suppression performance of the coating.

[0005] The present invention solves the above technical problems through the following technical means:

[0006] A flame retardant and smoke suppressing coating comprises the following raw materials, measured by weight percentage: 2-30% gelatin, 1-5% metal oxide functionalized black phosphorus, 5-25% kosmotropic salt, 0.1-2% antibacterial agent, and the balance water. The metal oxide functionalized black phosphorus is prepared by a solvothermal reaction using black phosphorus nanosheets, cobalt salt, ferrous salt, and sodium acetate as raw materials in an organic solvent, and the mass ratio of the black phosphorus nanosheets, cobalt salt, and ferrous salt is 2:2.5-5:2.5-3.75.

[0007] Preferably, the raw materials of the flame retardant and smoke suppression coating include the following components by weight percentage: 15% gelatin, 5% metal oxide functionalized black phosphorus, 10% kosmotropic salt, 0.1% antibacterial agent, and the balance water.

[0008] Preferably, the kosmotropic salt is a mixture of one or more of sodium sulfate, ammonium sulfate and sodium phosphate.

[0009] Preferably, the antibacterial agent is a mixture of one or more of O-phenylphenol, potassium 2,4-hexadienoate and sodium diacetate.

[0010] Preferably, the cobalt salt is cobalt acetate; the ferrous salt is ferrous chloride; and the organic solvent is ethylene glycol.

[0011] Preferably, the solvothermal reaction temperature is 100-190° C. and the time is 1 hour.

[0012] Preferably, the mass ratio of the black phosphorus nanosheets, cobalt salt and ferrous salt is 2:5:2.5.

[0013] Preferably, the mass ratio of the sodium acetate to the black phosphorus nanosheets is 25:2.

[0014] The flame retardant and smoke suppression coating provided by the present invention comprises 2-30% gelatin, preferably 5-15%, more preferably 10% or 15%. The gelatin serves to provide a carbon source for the formation of a heat-insulating carbonized layer.

[0015] The flame retardant and smoke suppression coating provided by the present invention comprises 1-5%, preferably 5%, of metal oxide functionalized black phosphorus. The metal oxide functionalized black phosphorus can catalyze the formation of a carbon layer, accelerate the conversion of carbon monoxide to carbon dioxide, and reduce fire smoke.

[0016] The flame-retardant and smoke-suppressing coating provided by the present invention includes 5-25% of a kosmotropic salt, preferably a mixture of one or more of sodium sulfate, ammonium sulfate, and sodium phosphate. The kosmotropic salt acts to enhance hydrophobic interactions within gelatin chains, improving the coating's loading rate and mechanical properties.

[0017] Preferably, the water is deionized water or industrial soft water.

[0018] The flame-retardant and smoke-suppressing coating provided herein includes 0.1-2% of a bacteriostatic agent. The bacteriostatic agent inhibits microbial growth in the material, thereby extending its shelf life. The bacteriostatic agent is preferably selected from one or more of O-phenylphenol, potassium 2,4-hexadienoate, and sodium diacetate. The bacteriostatic agent preferably has a weight percentage of 0.2% or 0.1%.

[0019] The present invention also provides a method for preparing the flame retardant and smoke suppressing coating, comprising the following steps: adding gelatin and an antibacterial agent to water, heating and stirring to form a gelatin solution, and then adding kosmotropic salt and metal oxide functionalized black phosphorus to the gelatin solution to obtain the flame retardant and smoke suppressing coating.

[0020] Preferably, the metal oxide-functionalized black phosphorus is prepared by mixing black phosphorus nanosheets with cobalt acetate, ferrous chloride, and sodium acetate in ethylene glycol. The mixture is then sealed in an autoclave and stored at 100-190°C for 1 hour. The product is then collected, centrifuged at 10,000 rpm for 10 minutes, washed 2-7 times with ethanol, and dried in a vacuum oven at 60-100°C for 12-24 hours to obtain the metal oxide-functionalized black phosphorus.

[0021] Preferably, the black phosphorus nanosheet preparation method is as follows: a mixed solvent consisting of anhydrous ethanol and distilled water (anhydrous ethanol and distilled water volume ratio of 1:1) and black phosphorus are added to a blender to a black phosphorus concentration of 5 wt%. The mixture is sheared at a high speed of 12,000 rpm for 5 minutes, and then the suspension is allowed to stand for 3-6 minutes. The cycle is repeated for 10-36 hours. The fractions with speeds between 12,000 and 3,000 rpm are collected by differential centrifugation, and the deposited large particles are recovered and used for repeated mechanical shearing. The centrifuged precipitate is collected and freeze-dried for 12-24 hours to obtain the black phosphorus nanosheets.

[0022] Preferably, the black phosphorus preparation method is as follows: first, red phosphorus is placed in a vacuum oven to dry, and then the red phosphorus: tin iodide: tin powder is put into a mortar and ground evenly according to a mass ratio of 50:12:3, and the mixture is vacuum-sealed into a quartz tube. The temperature is raised from room temperature to 650-800°C within 4-10 hours and maintained for two hours. Then, the temperature is lowered to 500°C at a rate of 0.6°C per minute and maintained for 2 hours. The temperature is then lowered to 200°C at a cooling rate of 0.6-1°C per minute. After the quartz tube naturally cools to room temperature, the black phosphorus is taken out.

[0023] The present invention also proposes an application of the flame retardant and smoke suppressing coating in flame retardant treatment of polyurethane foam.

[0024] Preferably, in a specific application process, the polyurethane foam is immersed in the coating and then dried to obtain the flame-retardant treated polyurethane foam.

[0025] Preferably, the polyurethane foam is immersed in the coating for 10-70 minutes and then dried in an oven at 80-100° C. for 6-12 hours.

[0026] The metal oxide-functionalized black phosphorus in the coating of the present invention can promote the formation of a flame-retardant and heat-insulating carbonized layer. The metal oxide inserted into the surface of the black phosphorus can catalyze the oxidation of carbon monoxide and eliminate fire smoke. The kosmotropic salt can increase the loading capacity of the coating on the polymer material, which can induce enhanced hydrophobic interactions between gelatin chains and improve the tensile strength of the base material.

[0027] The advantages of the present invention are:

[0028] The present invention utilizes the synergistic effect of two-dimensional black phosphorus and metal oxides to achieve flame retardancy and smoke suppression. The metal oxides exhibit excellent CO catalytic activity and selectivity, and can inhibit the release of smoke. At the same time, the metal oxides covered on the surface of black phosphorus can fix the lone pair electrons of black phosphorus, prevent black phosphorus from reacting with oxygen molecules, inhibit the spontaneous degradation of black phosphorus when exposed to the environment, and enhance the environmental stability of black phosphorus. Through the interaction of the components in the above content, the combustible material has excellent flame retardant properties. The raw materials used in the flame retardant coating will not cause pollution to the environment. It has strong flame retardant ability. The experimental results show that the limiting oxygen index of the polyurethane foam after coating modification increased from 17.5% to 32.0%; the peak heat release rate increased from 485kW / m 2 Down to 200kW / m 2 ; Peak smoke release rate from 0.30m 2 / s dropped to 0.15m 2 / s; tensile strength increased from 0.8MPa to 1.8MPa. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a SEM image of black phosphorus synthesized in Example 1 of the present invention;

[0030] Figure 2 This is a STEM image of the black phosphorus nanosheets synthesized in Example 1 of the present invention;

[0031] Figure 3 TEM images and EDS-mapping images of the metal oxide functionalized black phosphorus synthesized in Example 1 of the present invention;

[0032] Figure 4 This is the EDS spectrum of the metal oxide functionalized black phosphorus synthesized in Example 1 of the present invention. DETAILED DESCRIPTION

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, 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, not 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 efforts shall fall within the scope of protection of the present invention.

[0034] Unless otherwise specified, the test materials and reagents used in the following examples can be obtained from commercial sources.

[0035] If no specific techniques or conditions are specified in the examples, they can be carried out according to the techniques or conditions described in the literature in the field or according to the product instructions.

[0036] Example 1

[0037] A method for preparing a flame retardant and smoke suppressing coating comprises the following steps:

[0038] (1) Synthesis of black phosphorus

[0039] Place the red phosphorus in a vacuum oven at 60°C and dry it for 12 hours. Then, grind it into a mortar in a mass ratio of 50:12:3 of red phosphorus: tin iodide: tin powder to obtain a mixture. Take 0.5g of the mixture and vacuum seal it into a quartz tube. The quartz tube containing the material is then placed in a tube furnace, with the end with the material as the hot end. The heating procedure is as follows: first, raise the temperature from room temperature to 650°C in 4 hours and maintain it for two hours. Then, cool it down to 500°C at a rate of 0.6°C per minute and maintain it for 2 hours. Reduce the temperature to 200°C at a cooling rate of 0.6°C per minute. After the quartz tube naturally cools to room temperature, the black phosphorus is taken out, and its SEM picture is as shown below. Figure 1 As shown by Figure 1 It can be seen that the obtained bulk black phosphorus has a layered structure, and the lateral size of the bulk black phosphorus is observed to be greater than 1 micron.

[0040] (2) Synthesis of black phosphorus nanosheets

[0041] A mixed solvent consisting of 200 mL of anhydrous ethanol and 200 mL of distilled water and black phosphorus were added to a blender to a concentration of 5 wt% black phosphorus. The suspension was sheared at 12,000 rpm for 5 minutes, and then allowed to rest for 3 minutes. The shear-rest cycle was repeated for 24 hours. Components with speeds between 12,000 and 3,000 rpm were collected by differential centrifugation, and the deposited large particles were recovered and used for cyclic mechanical shearing. The centrifuged precipitate was collected and freeze-dried for 12 hours to obtain black phosphorus nanosheets, as shown in the STEM image. Figure 2 As shown by Figure 2 It can be seen that the layered structure of black phosphorus is destroyed to form black phosphorus nanosheets, and the lateral size of the nanosheets is observed to be less than 500nm.

[0042] (3) Synthesis of metal oxide functionalized black phosphorus

[0043] 200 mg of black phosphorus nanosheets were mixed with 500 mg of cobalt acetate, 250 mg of ferrous chloride, and 2500 mg of sodium acetate in 300 g of ethylene glycol. The mixture was then sealed in an autoclave and stored at 190 ° C for 1 hour. The product was then collected, centrifuged at 10,000 rpm for 10 minutes, washed three times with ethanol, and dried in a vacuum oven at 60 ° C for 12 hours. Its TEM image and EDS-mapping map are shown as follows: Figure 3 As shown, the EDS spectrum is Figure 4 As shown by Figure 3 and Figure 4It can be seen that phosphorus, iron, cobalt and oxygen elements are evenly distributed on the black phosphorus nanosheets, indicating that iron-cobalt metal oxides are formed on the surface of the black phosphorus nanosheets. Figure 4 The red and green colors in the middle represent the element distribution in different regions, indicating that the element distribution in different regions is similar, indicating that the metal oxides are evenly loaded on the black phosphorus nanosheets.

[0044] (4) Preparation of flame retardant and smoke suppression coatings

[0045] The raw materials include the following components in terms of weight percentage: 15% gelatin, 5% metal oxide functionalized black phosphorus, 10% sodium sulfate, 0.1% O-phenylphenol, and the balance water;

[0046] Gelatin and O-phenylphenol are added to water and stirred at 50° C. to form a gelatin solution. Then, sodium sulfate and metal oxide functionalized black phosphorus are added to the gelatin solution to obtain the flame retardant and smoke suppression coating.

[0047] Comparative Example 1

[0048] A method for preparing a flame retardant and smoke suppressing coating is different from Example 1 only in that the synthesis process of metal oxide functionalized black phosphorus in step (3) is not performed, and the black phosphorus nanosheets prepared in step (2) are directly used in step (4) to replace the metal oxide functionalized black phosphorus.

[0049] Example 2

[0050] The coating prepared in Example 1 was used to treat the flame-retardant surface of polyurethane foam. During the flame-retardant surface treatment process, the polyurethane foam was immersed in the coating described in Example 1 for 20 minutes and then dried in an 80°C oven for 6 hours to obtain a polyurethane foam modified with a flame-retardant coating. The polyurethane foam modified with the flame-retardant coating was subjected to self-tests for limiting oxygen index and heat release rate according to international standards ISO 4589-22017 and ISO 5660. The specific test results are shown in Table 1 below:

[0051] Table 1 Test results of flame retardant smoke suppression coating on polyurethane foam prepared in Example 1 of the present invention

[0052] Inspection items Unmodified polyurethane foam Example 1 Coating-modified polyurethane foam Limiting oxygen index 17.5％ 32.0％ Peak heat release rate <![CDATA[485kW / m 2 ]]> <![CDATA[200kW / m 2 ]]> Peak CO release rate 17mg / s 8.8mg / s Peak smoke release rate <![CDATA[0.30m 2 / s]]> <![CDATA[0.15m 2 / s]]> tensile strength 0.8MPa 1.8MPa

[0053] From the above, it can be seen that the coating provided by the present invention has excellent flame retardant properties through the interaction of the components in the above contents. The experimental results show that the limiting oxygen index of the polyurethane foam modified by the coating increased from 17.5% to 32.0%; the peak heat release rate increased from 485kW / m 2 Down to 200kW / m 2 ; Peak smoke release rate from 0.30m 2 / s dropped to 0.15m 2 / s.

[0054] Comparative Example 2

[0055] The coating prepared in Comparative Example 1 was used to perform flame-retardant surface treatment on polyurethane foam. During the flame-retardant surface treatment process, the polyurethane foam was immersed in the coating in Comparative Example 1 for 20 minutes and then dried in an oven at 80°C for 6 hours to obtain a flame-retardant coating-modified polyurethane foam. The flame-retardant coating-modified polyurethane foam was subjected to self-tests for limiting oxygen index and heat release rate according to international standards ISO 4589-22017 and ISO 5660. The specific test results are shown in Table 2 below:

[0056] Table 2 Test results of the flame retardancy of polyurethane foam by the coatings prepared in Example 1 of the present invention and Comparative Example 1

[0057]

[0058] It can be seen from the above examples and comparative examples that when unmodified black phosphorus nanosheets are added (Comparative Example 1), the peak CO release rate and the peak smoke release rate are both improved compared with Example 1, proving that the material in Example 1 has a better smoke suppression effect.

[0059] Comparative Examples 3-5 and Example 3

[0060] A method for preparing a flame retardant and smoke suppressing coating is different from Example 1 only in that: in the synthesis of metal oxide functionalized black phosphorus, the masses of cobalt acetate and ferrous chloride used are different, ferrous chloride is not used in Comparative Example 3, the amount of cobalt acetate used in Example 3 is 375 mg, the amount of cobalt acetate used in Comparative Example 4 is 250 mg, and cobalt acetate is not used in Comparative Example 5. The remaining steps are the same as in Example 1.

[0061] The coatings prepared in Comparative Examples 3-5 and Example 3 were used to treat the flame retardant surface of polyurethane foam. In the flame retardant surface treatment process, the polyurethane foam was immersed in the coatings prepared in Comparative Examples 3-5 and Example 3 for 20 minutes and then dried in an 80°C oven for 6 hours to obtain a flame retardant coating-modified polyurethane foam. The peak CO release rate and peak smoke release rate of the polyurethane foam were measured using a cone calorimeter. The flame retardant coating-modified polyurethane foam was self-tested for limiting oxygen index and heat release rate according to international standards ISO 4589-22017 and ISO 5660. The specific test results are shown in Table 3 below:

[0062] Table 3 Test results of the flame retardancy of polyurethane foam by the coatings prepared in Comparative Examples 3-5 and Example 3 of the present invention

[0063]

[0064]

[0065] From the above, it can be seen that when the black phosphorus content and the total mass of the metal salt remain unchanged, changing the mass ratio of cobalt acetate and ferrous chloride has little effect on the flame retardant properties, but it will significantly affect the smoke release of the material. The smoke suppression effect is best when the Co salt:Fe salt mass ratio = 2:1 and the Co salt:Fe salt mass ratio = 1:1. This proves that the material in the example has a better smoke suppression effect than the comparative example.

[0066] Comparative Examples 6-11

[0067] A method for preparing a flame-retardant and smoke-suppressing coating differs from Example 1 only in that the amounts of black phosphorus nanosheets used in Comparative Examples 6-8 are 50 mg, 100 mg, and 500 mg, respectively. The mass of black scale nanosheets used in Comparative Examples 9-11 is 200 mg, and the ratios of cobalt salt to ferrous salt are 4:1, 1:2.5, and 1:1, respectively. Polyurethane foam was flame-retarded using the coatings in Comparative Examples 6-11, as in Example 2. The specific results are shown below:

[0068] Table 3 Test results of the flame retardancy of polyurethane foam by the coatings prepared in Comparative Examples 6-11 of the present invention

[0069]

[0070]

[0071] As shown in Comparative Examples 6-8, while significantly reducing the black phosphorus nanosheet content leads to reduced smoke emission, it also significantly reduces the limiting oxygen index, causing the material to lose its flame retardant properties. Significantly increasing the black phosphorus nanosheet content leads to increased smoke emission. Adding a large amount of black phosphorus nanosheets does not achieve a significantly superior limiting oxygen index compared to Example 1, but instead results in increased smoke emission. This demonstrates that the material in Example 1 has a better smoke suppression effect than Comparative Examples 6-8.

[0072] As shown in Comparative Examples 9-11, increasing the mass of a metal salt can lead to a decrease in the limiting oxygen index, likely due to the structural destruction of black phosphorus caused by the altered ionic environment. Furthermore, the smoke release rate is also higher, demonstrating that the material in Example 1 has a better smoke suppression effect than Comparative Examples 9-11.

[0073] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A flame retardant and smoke suppressing coating, characterized in that: The raw materials include the following components in terms of weight percentage: 2-30% gelatin, 1-5% metal oxide functionalized black phosphorus, 5-25% kosmotropic salt, 0.1-2% antibacterial agent, and the balance water. The metal oxide functionalized black phosphorus is prepared by solvothermal reaction using black phosphorus nanosheets, cobalt salt, ferrous salt, and sodium acetate as raw materials using an organic solvent. The mass ratio of the black phosphorus nanosheets, cobalt salt, and ferrous salt is 2:2.5-5:2.5-3.

75.

2. The flame retardant and smoke suppressing coating according to claim 1, characterized in that: The raw materials include the following components in terms of weight percentage: 15% gelatin, 5% metal oxide functionalized black phosphorus, 10% kosmotropic salt, 0.1% antibacterial agent and the balance water.

3. The flame retardant and smoke suppressing coating according to claim 1, characterized in that: The kosmotropic salt is a mixture of one or more of sodium sulfate, ammonium sulfate, and sodium phosphate.

4. The flame retardant and smoke suppressing coating according to claim 1, characterized in that: The antibacterial agent is a mixture of one or more of O-phenylphenol, potassium 2,4-hexadienoate and sodium diacetate.

5. The flame retardant and smoke suppressing coating according to claim 1, characterized in that: The cobalt salt is cobalt acetate; the ferrous salt is ferrous chloride; and the organic solvent is ethylene glycol.

6. The flame retardant and smoke suppressing coating according to claim 1, characterized in that: The temperature of the solvent thermal reaction is 100-190° C. and the time is 1 hour.

7. The flame retardant and smoke suppressing coating according to claim 1, characterized in that: The mass ratio of the black phosphorus nanosheets, cobalt salt and ferrous salt is 2:5:2.

5.

8. The flame retardant and smoke suppressing coating according to any one of claims 1 to 7, characterized in that: The mass ratio of the sodium acetate to the black phosphorus nanosheets is 25:

2.

9. A method for preparing a flame retardant and smoke suppressing coating according to any one of claims 1 to 8, characterized in that: The following steps are involved: Gelatin and an antibacterial agent are added into water, heated and stirred to form a gelatin solution, and then Kosmotropic salt and metal oxide functionalized black phosphorus are added into the gelatin solution to obtain the flame retardant and smoke suppression coating.

10. Use of the flame retardant and smoke suppressant coating according to any one of claims 1 to 8 in flame retardant treatment of polyurethane foam.

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