Flame-retardant and smoke-suppressing coating as well as preparation method and application thereof

Abstract

The invention discloses a flame-retardant and smoke-suppressing coating and a preparation method and application thereof, and the raw materials of the coating comprise the following components in percentage by weight: 2-30% of gelatin, 1-5% of metal oxide functionalized black phosphorus, 5-25% of Kosmotropic salt, 0.1-2% of a bacteriostatic agent and the balance of water, the metal oxide functionalized black phosphorus is prepared by taking black phosphorus nanosheets, cobalt salt, ferrous salt and sodium acetate as raw materials and taking an organic solvent as a solvent to perform solvothermal reaction, and the mass ratio of the black phosphorus nanosheets to the cobalt salt to the ferrous salt is 2: (2.5-5): (2.5-3.75). Under the interaction of the components with the content, the coating has excellent flame retardant property. The limit oxygen index of the polyurethane foam after coating modification is increased from 17.5% to 32.0%; the peak heat release rate is reduced from 485kW / m < 2 > to 200kW / m < 2 >; the peak smoke release rate is reduced from 0.30 m < 2 > / s to 0.15 m < 2 > / s; and the tensile strength is improved from 0.8 MPa to 1.8 MPa.

Description

Technical Field

[0001] The invention relates to the technical field of flame retardancy, and in particular to a flame retardant and smoke suppressing coating, a preparation method and 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 flame retardancy of black phosphorus can capture OH· and H· 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 are still highly challenging.

[0003] To date, many protection strategies have been used to prevent the degradation of black phosphorus, including heteroatom doping, chemical passivation, physical coating or chemical functionalization of polymers, to improve the environmental stability of black phosphorus nanosheet flame retardants. However, these functionalized black phosphorus nanosheets usually have high performance in single flame retardant applications but cannot effectively inhibit 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, wherein the raw materials thereof include the following components in percentage by weight: 2-30% gelatin, 1-5% metal oxide functionalized black phosphorus, 5-25% kosmotropic salt, 0.1-2% antibacterial agent, and the balance water; wherein the metal oxide functionalized black phosphorus is prepared by solvothermal reaction with black phosphorus nanosheets, cobalt salt, ferrous salt and sodium acetate as raw materials and with an organic solvent as 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 suppressing 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 is carried out at a temperature of 100-190° C. and for a time of 1 h.

[0012] Preferably, the mass ratio of the black phosphorus nanosheets, the cobalt salt and the 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, which 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 suppression coating provided by the present invention comprises 5-25% of kosmotropic salt, preferably a mixture of one or more of sodium sulfate, ammonium sulfate and sodium phosphate. The kosmotropic salt is used to enhance the hydrophobic interaction within the gelatin chain and improve the loading rate and mechanical properties of the coating.

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

[0018] The flame retardant and smoke suppression coating provided by the present invention comprises 0.1-2% of an antibacterial agent. The function of the antibacterial agent is to inhibit the growth of microorganisms in the material and prolong the effective storage period. The antibacterial agent is preferably selected from one or more of O-phenylphenol, potassium 2,4-hexadienoate and sodium diacetate. The antibacterial agent preferably has a weight percentage of 0.2% or 0.1%.

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

[0020] Preferably, the preparation method of the metal oxide functionalized black phosphorus is as follows: black phosphorus nanosheets are mixed 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 with ethanol 2-7 times, 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 method for preparing black phosphorus nanosheets is as follows: a mixed solvent consisting of anhydrous ethanol and distilled water (the volume ratio of anhydrous ethanol to distilled water is 1:1) and black phosphorus are added to a stirrer to make the mass concentration of black phosphorus 5wt%, sheared at a high speed of 12000rpm for 5 minutes, and then the suspension is allowed to stand for 3-6 minutes, circulated for 10-36 hours, and the components with a speed between 12000 and 3000 rpm are collected by differential centrifugation, and the deposited large particles are recovered and used for cyclic mechanical shearing. The centrifugal precipitate is collected and freeze-dried for 12-24 hours to obtain black phosphorus nanosheets.

[0022] Preferably, the method for preparing black phosphorus is as follows: first, the 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 cooled to 500°C at a rate of 0.6°C per minute and maintained for 2 hours. The temperature is then reduced to 200°C at a cooling rate of 0.6-1°C per minute, and the black phosphorus is taken out after the quartz tube is naturally cooled to room temperature.

[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 min and then dried in an oven at 80-100° C. for 6-12 h.

[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, and the kosmotropic salt can increase the loading amount of the coating on the polymer material, which can induce the enhancement of the hydrophobic interaction of the gelatin chain 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 of 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. 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 down 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 nanosheet synthesized in Example 1 of the present invention;

[0031] Figure 3 TEM image and EDS-mapping image 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] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described in combination with the embodiments of the present invention. Obviously, the described embodiments are 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 creative work are 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 art 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 for 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, take out the black phosphorus, and its SEM image 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] Add a mixed solvent consisting of 200 mL of anhydrous ethanol and 200 mL of distilled water and black phosphorus into a stirrer to make the mass concentration of black phosphorus 5wt%; shear at 12000 rpm for 5 minutes to obtain a suspension, then let the suspension stand for 3 minutes, and cycle the shear-stand process for 24 hours. Collect the components with a speed between 12000 and 3000 rpm by differential centrifugation, recover the deposited large particles and use them for cyclic mechanical shearing. Collect the centrifugal precipitate and freeze-dry it for 12 hours to obtain black phosphorus nanosheets, whose STEM image is shown in the figure below. 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 image are shown in Figure 1. Figure 3 As shown, the EDS spectrum is Figure 4 As shown by Figure 3 and Figure 4It can be seen that the uniform distribution of phosphorus, iron, cobalt and oxygen elements can be seen 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 into water and stirred at 50° C. to form a gelatin solution. Then, sodium sulfate and metal oxide functionalized black phosphorus are added into 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, which is different from Example 1 only in that the synthesis process of metal oxide functionalized black phosphorus in step (3) is not carried out, 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 for flame retardant surface treatment of polyurethane foam. In 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 oven at 80°C for 6 hours to obtain a polyurethane foam modified with a flame retardant coating. The polyurethane foam modified with the flame retardant coating was self-tested for limiting oxygen index and heat release rate according to international standards ISO 4589-22017 and ISO5660. The specific test results are shown in Table 1 below:

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

[0052] Inspection items Unmodified polyurethane foam Example 1 Polyurethane foam after coating modification 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] It can be seen from the above 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 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 down to 0.15m 2 / s.

[0054] Comparative Example 2

[0055] The coating prepared in Comparative Example 1 was used for flame retardant surface treatment of polyurethane foam. In 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 polyurethane foam modified with a flame retardant coating. The polyurethane foam modified with a flame retardant coating was self-tested for limiting oxygen index and heat release rate according to international standards ISO 4589-22017 and ISO5660. The specific test results are shown in Table 2 below:

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

[0057]

[0058] It can be seen from the above embodiments 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, which 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, and the remaining steps are the same as in Example 1.

[0061] The coatings prepared in Comparative Examples 3-5 and Example 3 were used for flame retardant surface treatment 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 oven at 80°C for 6 hours to obtain polyurethane foam modified with a flame retardant coating. The peak CO release rate and peak smoke release rate of the polyurethane foam were measured using a cone calorimeter. The polyurethane foam modified with a flame retardant coating was self-tested for limiting oxygen index and heat release rate according to international standards ISO4589-22017 and ISO5660. 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 will significantly affect the smoke release of the material. The smoke suppression effect is best when the mass ratio of Co salt:Fe salt is 2:1 and the mass ratio of Co salt:Fe salt is 1:1. It is proved that the material in the embodiment 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, which is different from Example 1 only in that: the amount of black phosphorus nanosheets used in Comparative Examples 6-8 is 50 mg, 100 mg and 500 mg respectively. The mass of black scale nanosheets used in Comparative Examples 9-11 is 200 mg, wherein the ratios of cobalt salt and ferrous salt are 4:1, 1:2.5 and 1:1 respectively. According to the method of Example 2, the coatings in Comparative Examples 6-11 are used to perform flame retardant surface treatment on polyurethane foam, and the specific results are as follows:

[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] From the above comparative examples 6-8, it can be seen that although significantly reducing the content of black phosphorus nanosheets will lead to a reduction in smoke release, it will cause a significant decrease in the limiting oxygen index and the material will lose its flame retardant ability. Significantly increasing the content of black phosphorus nanosheets will lead to increased smoke release. Adding a large amount of black phosphorus nanosheets does not achieve a significantly superior limiting oxygen index than Example 1, but will instead cause more smoke release. It is proved that the material in Example 1 has a better smoke suppression effect than comparative examples 6-8.

[0072] From the above comparative examples 9-11, it can be seen that increasing the quality of a certain metal salt will lead to a decrease in the limiting oxygen index, which may be because the change in the ion environment causes the structure of black phosphorus to be destroyed, and the smoke release rate is also higher. It is proved 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 the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. 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 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; wherein the metal oxide functionalized black phosphorus is prepared by solvothermal reaction with black phosphorus nanosheets, cobalt salt, ferrous salt and sodium acetate as raw materials and with an organic solvent as solvent, and 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, the cobalt salt and the 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 suppression coating according to any one of claims 1 to 8 in flame retardant treatment of polyurethane foam.

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