Preparation method of layered magnesium-based flame-retardant smoke-suppression hybrid material

Abstract

The invention relates to a preparation method of a layered magnesium-based flame-retardant smoke-suppression hybrid material, which comprises the following steps: (1) dispersing organic anion intercalated magnesium-based LDHs into a Tris-HCl buffer solution with the pH value of about 8.5 to obtain slurry A; then adding bio-based polyphenol into the slurry A, continuously stirring, and carrying out suction filtration, washing and freeze drying to obtain organic anion intercalation magnesium-based LDHs coated with polyphenol on the surface; (2) dispersing the organic anion intercalation magnesium-based LDHs coated with polyphenol on the surface into deionized water, then adding soluble cobalt salt, soluble nickel salt and sodium citrate, and continuously stirring to obtain slurry B; and (3) adding a transition metal potassium cyanide solution into the slurry B under continuous stirring, then aging, and carrying out suction filtration, washing and freeze drying to obtain the layered magnesium-based flame-retardant and smoke-suppression hybrid material. The method is simple, low in cost and easy to implement, and the obtained material solves the problems that an anchored transition metal compound is large in particle size, uneven in distribution, lack of synergistic effect and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of flame-retardant materials, in particular to a preparation method of layered magnesium-based flame-retardant and smoke-suppression hybrid materials. BACKGROUND

[0002] Excellent electrical insulation, chemical corrosion resistance, mechanical strength, etc. make epoxy resins widely used in the fields of electronics and electrical, rail transportation, aerospace, adhesives and mechanical manufacturing, etc. However, the chemical composition mainly composed of carbon and hydrogen makes epoxy resins flammable, and a large amount of harmful gases and smoke will be generated during the combustion process, which poses a great threat to the environment and human life safety. In recent years, with the increasing number of fires caused by electronic and electrical failures worldwide, it has become very urgent to endow epoxy resins with higher flame-retardant and smoke-suppression properties to reduce their fire hazards. Magnesium-aluminum layered double hydroxide (LDH) has a unique two-dimensional layered structure, and has excellent physical barrier effect (can effectively isolate oxygen, flammable gas and heat transport), decomposition heat absorption, release of water vapor dilution and formation of protective metal oxide layer, etc. to enhance the flame-retardant properties of polymer materials. At the same time, due to its easy preparation, halogen-free, non-toxic, low price and smoke-suppression effect, it is used to enhance the fire safety of polymers. However, the poor interfacial compatibility of LDH with the organic polymer matrix, the easy agglomeration in the matrix and the high filling amount, etc. will have a great negative impact on the mechanical properties of the polymer composite.

[0003] Based on the exchangeability of LDH interlayer ions and the modifiability of the layer plate, on the one hand, specific flame-retardant functional inorganic and organic anions can be introduced into the interlayer of LDH to improve its dispersion and flame-retardant efficiency. Inorganic anion intercalation, such as silicate ions, carbonate ions, borate and phosphate, etc. is limited by the size of the molecules, and the ability to adjust the LDH interlayer spacing is limited. Organic anion intercalation can not only significantly expand the interlayer spacing of LDH, but also enhance the hydrophobicity of LDH, and promote the compatibility of LDH with the matrix. On the other hand, the dispersion of LDH in the matrix and the interaction with the matrix can be improved by functionalizing the surface of LDH. The use of coupling agents or surfactants for surface coupling or coating modification of LDH can enhance the interfacial interaction between the filler and the matrix, improve the dispersion of the filler, and thus improve the mechanical properties and flame-retardant effect of the material. In addition, transition metal elements have excellent catalytic carbonization ability at high temperatures, and anchoring transition metal compounds on the surface of LDH in a certain way can effectively suppress the release of heat and toxic smoke of the composite material.

[0004] In the prior art, it is difficult to make the composite material reach the required flame-retardant grade by modifying the LDH through the organic anion layer alone; through surface functionalization treatment, especially anchoring transition metal compounds on the surface of the LDH, the flame-retardant and smoke-suppressing performance of the composite material can be further improved, but there are problems such as large particle size and uneven distribution of the anchored transition metal compounds, single transition metal element, lack of synergistic effect, etc., resulting in unsatisfactory flame-retardant and smoke-suppressing efficiency. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a simple, low-cost and easy-to-implement preparation method of layered magnesium-based flame-retardant and smoke-suppressing hybrid material.

[0006] To solve the above problems, the preparation method of the layered magnesium-based flame-retardant and smoke-suppressing hybrid material comprises the following steps: (1) dispersing the organic anion intercalated magnesium-based LDHs into a Tris-HCl buffer solution with pH≈8.5 to obtain a slurry A with a mass concentration of 25 g / L; then adding a bio-based polyphenol into the slurry A and continuously stirring for 20-30 h, and then performing suction filtration, washing and freeze-drying to obtain the surface polyphenol-coated organic anion intercalated magnesium-based LDHs; (2) dispersing the surface polyphenol-coated organic anion intercalated magnesium-based LDHs into deionized water to make the mass concentration thereof be 30-40 g / L, and then adding a soluble cobalt salt, a soluble nickel salt and sodium citrate, and continuously stirring for 0.5-1.5 h to obtain a slurry B; (3) adding a transition metal potassium cyanide solution into the slurry B under continuous stirring, and then aging for 20-28 h, and then performing suction filtration, washing and freeze-drying to obtain the layered magnesium-based flame-retardant and smoke-suppressing hybrid material.

[0007] In the step (1), the organic anion intercalated magnesium-based LDHs are dodecylbenzenesulfonate intercalated magnesium-based LDHs.

[0008] In the step (1), the bio-based polyphenol is dopamine hydrochloride, and the mass ratio of the dopamine hydrochloride to the organic anion intercalated magnesium-based LDHs is 1-3:10-20.

[0009] In the step (2), the soluble cobalt salt is cobalt nitrate or cobalt chloride; and the soluble nickel salt is nickel nitrate or nickel chloride.

[0010] In the step (2), the ratio of the soluble cobalt salt, the soluble nickel salt and the surface polyphenol-coated organic anion intercalated magnesium-based LDHs is 1-2 mmol:1-2 mmol:3-4 g.

[0011] In the step (2), the molar ratio of the soluble cobalt salt, the soluble nickel salt and the sodium citrate is 1-2:1-2:4-5.

[0012] The transition metal potassium cyanide solution in the step ⑶ refers to a solution obtained by dissolving transition metal potassium cyanide in deionized water; the ratio of the transition metal potassium cyanide to the deionized water is 2-3 mmol: 100 mL; and the molar ratio of the transition metal potassium cyanide to the soluble cobalt salt is 2-3: 1-2.

[0013] The transition metal in the transition metal potassium cyanide is iron.

[0014] A layered magnesium-based flame-retardant and smoke-suppression hybrid material prepared by the method.

[0015] Compared with the prior art, the present application has the following advantages: 1. The natural polyphenol molecules in the present application react with transition metal ions to form a metal-phenolic coating on the surface of the organic anion intercalated magnesium-based LDHs, providing chelating sites and anchoring effects for the in-situ growth of cyan-bridged coordination polymers, and realizing the self-assembly of ultra-fine cyan-bridged coordination polymers on the surface of the LDHs.

[0016] 2. The chelation of the natural polyphenol molecules to the transition metal ions and the space-limited growth ensure that the particle size of the cyan-bridged coordination polymers assembled on the surface is small and uniform. The particle size and uniformity of the cyan-bridged coordination polymers loaded by the method of the present application are superior to those loaded by the common coprecipitation method.

[0017] 3. The three-dimensional porous framework structure assembled by the coordination of the transition metal ions and cyanide ions on the surface of the magnesium-based LDHs can ensure the uniform dispersion of the transition metal ions, more effectively exert their catalytic carbonization and catalytic oxidation effects, and trigger the synergistic effect between them, thereby efficiently improving the flame-retardant and smoke-suppression performance of the material.

[0018] 4. The method of the present application is simple, low in cost, and easy to implement. BRIEF DESCRIPTION OF DRAWINGS

[0019] The specific embodiments of the present application will be further described in detail below with reference to the accompanying drawings.

[0020] Figure 1 SEM images of cyan-bridged coordination polymers (a) prepared separately and (b) assembled on the surface of the layered magnesium-based flame-retardant and smoke-suppression hybrid material obtained in Example 1 of the present application.

[0021] Figure 2 CCT test results of (a) HRR curve, (b) SPR curve, (c) CO production rate, and (d) CO2 production rate of pure EP and EP composite material / layered magnesium-based flame-retardant and smoke-suppression hybrid material obtained in Example 1 of the present application. DETAILED DESCRIPTION

[0022] A method for preparing a layered magnesium-based flame retardant and smoke-suppressing hybrid material comprises the following steps: ⑴ The organic anion-intercalated magnesium-based LDHs were dispersed in Tris-HCl buffer with a pH of 8.5 to obtain a slurry A with a mass concentration of 25 g / L; then, bio-based polyphenols were added to the slurry A and stirred for 20 to 30 hours. After filtration, washing with anhydrous ethanol and deionized water three times each, and freeze-drying at -80 °C for 24 hours, the organic anion-intercalated magnesium-based LDHs coated with polyphenols were obtained.

[0023] Wherein: the organic anion intercalated magnesium-based LDHs is dodecylbenzenesulfonate intercalated magnesium-based LDHs.

[0024] The bio-based polyphenol is dopamine hydrochloride, and the mass ratio (g / g) of the bio-based polyphenol to the organic anion intercalated magnesium-based LDHs is 1-3:10-20.

[0025] Tris-HCl buffer consists of tris (hydroxymethyl)aminomethane (Tris) and hydrochloric acid (HCl) in water.

[0026] ⑵ Disperse the organic anion-intercalated magnesium-based LDHs coated with surface polyphenols into deionized water to a mass concentration of 30-40 g / L, then add soluble cobalt salt, soluble nickel salt and sodium citrate, and continue stirring for 0.5-1.5 h to obtain slurry B.

[0027] The soluble cobalt salt is cobalt nitrate or cobalt chloride; the soluble nickel salt is nickel nitrate or nickel chloride.

[0028] The ratio of soluble cobalt salt, soluble nickel salt and surface polyphenol-coated organic anion intercalated magnesium-based LDHs is 1-2 mmol: 1-2 mmol: 3-4 g. The molar ratio of soluble cobalt salt, soluble nickel salt and sodium citrate is 1-2: 1-2: 4-5.

[0029] ⑶ Add transition metal potassium cyanide solution to slurry B under continuous stirring, then age for 20 to 28 hours, filter, wash with anhydrous ethanol and deionized water three times each, and freeze-dry at -80°C for 24 hours to obtain a layered magnesium-based flame retardant and smoke suppression hybrid material.

[0030] The transition metal potassium cyanide solution refers to a solution obtained by dissolving transition metal potassium cyanide in deionized water; the ratio of transition metal potassium cyanide to deionized water is 2-3 mmol:100 mL; and the molar ratio of transition metal potassium cyanide to soluble cobalt salt is 2-3:1-2.

[0031] The transition metal in potassium cyanide is iron.

[0032] The design principle of this invention is to use natural polyphenol molecules as a mediator, interacting with transition metal ions to rapidly form a metal-phenolic coating on the surface of organic anion-intercalated magnesium-based LDHs. This provides chelation sites and anchoring for the in situ growth of transition metal cyano-bridged coordination polymers, achieving the successful assembly of ultrafine particle size, uniform distribution of transition metals, and synergistic effects, thereby preparing a highly effective layered magnesium-based flame-retardant and smoke-suppressing hybrid material. The reduced particle size of the coordination polymer and the uniform distribution of transition metal ions on the surface of organic anion-intercalated magnesium-based LDHs enhance the catalytic carbonization, catalytic oxidation, and synergistic effects of the transition metal ions, thereby effectively improving the flame retardancy and smoke suppression properties of the material.

[0033] Example 1: A method for preparing a layered magnesium-based flame retardant and smoke-suppressing hybrid material comprises the following steps: ⑴ Disperse 5.00 g of dodecylbenzenesulfonate-intercalated magnesium-based LDHs in 200 mL of Tris-HCl buffer at pH ≈ 8.5 to obtain slurry A with a mass concentration of 25 g / L; then add 0.50 g of dopamine hydrochloride to slurry A, continue stirring for 24 h, filter, wash with anhydrous ethanol and deionized water three times each, and freeze-dry at -80 °C for 24 h to obtain organic anion-intercalated magnesium-based LDHs coated with polyphenols on the surface.

[0034] ⑵ Disperse 3.00 g of surface polyphenol-coated organic anion-intercalated magnesium-based LDHs in 100 mL of deionized water, then add 1 mmol of cobalt nitrate, 2 mmol of nickel nitrate and 4.5 mmol of sodium citrate, and continue stirring for 1 h to obtain slurry B.

[0035] ⑶ Dissolve 2 mmol of potassium ferrocyanide in 100 mL of deionized water, then add the potassium ferrocyanide solution dropwise to slurry B under continuous stirring, then age for 24 h, filter, wash with anhydrous ethanol and deionized water three times each, and freeze-dry at -80 °C for 24 h to obtain a layered magnesium-based flame retardant and smoke suppression hybrid material.

[0036] like Figure 1 As shown in Figure 1, the particle size of the cyano-bridged coordination polymer prepared separately is around 200-300 nm. In contrast, the cyano-bridged coordination polymer on the layered magnesium-based flame-retardant and smoke-suppressing hybrid material prepared in Example 1 has a grain size range of 50-70 nm and is dispersed along the surface of the LDH layer. This reduction in the particle size of the cyano-bridged coordination polymer is attributed to the chelating anchoring sites provided by the polyphenols, which effectively increases the dispersion of the metal precursor ions (Ni²⁺ / Co²⁺), while the limited growth space induces the [Fe(CN)6] 3- This is due to the directional coordination with the previously chelated metal ions (Ni²⁺ / Co²⁺).

[0037]

Flame Retardant and Smoke Suppression Performance Test

[0038] As can be seen from Figure 2 , the heat release rate (HRR), smoke release rate (SPR) and toxic gas CO release rate (COP) of the EP composites after adding LDH-NO3 - and LDH-DBS all showed a downward trend, indicating that the flame-retardant and smoke-suppression performance of the EP composites after adding LDH-NO3 - and LDH-DBS were improved. Compared with the two, the flame-retardant and smoke-suppression performance of the EP composite after adding LDH-DBS was superior to that of the EP composite after adding LDH-NO3 - , which can be attributed to the fact that after the intercalation modification of dodecyl benzene sulfonate, the interlayer spacing of magnesium-based LDHs is increased, the compatibility of magnesium-based LDHs with the EP matrix is improved, and the dispersibility of magnesium-based LDHs in the EP matrix is also improved. Compared with the above-mentioned LDH-DBS, the addition of the layered magnesium-based flame-retardant and smoke-suppression hybrid material (LDH-DBS@PDA@PBA) obtained in Example 1 can further improve the flame-retardant and smoke-suppression efficiency of the EP composite, and the peak value of the heat release rate of the EP composite is reduced from 464.2 kW / m 2 to 312.6 kW / m 2 , which can be attributed to the high-efficiency catalytic carbonization ability of the surface-loaded fine cyan-bridged coordination polymer and the synergistic catalysis of different transition metal ions, which helps to form a dense carbon layer and prevent the matrix from burning. In addition, after adding the layered magnesium-based flame-retardant and smoke-suppression hybrid material (LDH-DBS@PDA@PBA) obtained in Example 1, the peak value of the CO release rate is reduced from 0.040 g / s of pure EP to 0.012 g / s, which benefits from the catalytic oxidation of the high-valence transition metal oxide (Fe3O4 / CoO / NiO) produced by the decomposition of the cyan-bridged coordination polymer, which converts the toxic CO gas into CO2, greatly reducing the risk of carbon monoxide poisoning in a fire scenario. It is worth noting that the carbon dioxide release rate is also significantly reduced Figure 2 d), which greatly reduces the probability of suffocation of trapped personnel in a fire.

[0039] Example 2: A method for preparing a layered magnesium-based flame retardant and smoke-suppressing hybrid material comprises the following steps: ⑴ 5.00 g of dodecylbenzenesulfonate-intercalated magnesium-based LDHs was dispersed in 200 mL of Tris-HCl buffer at pH ≈ 8.5 to obtain slurry A with a mass concentration of 25 g / L; then 0.25 g of dopamine hydrochloride was added to the slurry A and stirred for 20 h. After filtration, washing with anhydrous ethanol and deionized water three times each, and freeze-drying at -80 °C for 24 h, the surface polyphenol-coated organic anion-intercalated magnesium-based LDHs were obtained.

[0040] ⑵ Disperse 3.50 g of surface polyphenol-coated organic anion-intercalated magnesium-based LDHs in 100 mL of deionized water, then add 1.5 mmol of cobalt chloride, 1.5 mmol of nickel chloride, and 4 mmol of sodium citrate, and continue stirring for 0.5 h to obtain slurry B.

[0041] ⑶ Dissolve 2.5 mmol of potassium ferrocyanide in 100 mL of deionized water, then add the potassium ferrocyanide solution dropwise to slurry B under continuous stirring, then age for 20 h, filter, wash with anhydrous ethanol and deionized water three times each, and freeze-dry at -80 °C for 24 h to obtain a layered magnesium-based flame retardant and smoke suppression hybrid material.

[0042] Example 3: A method for preparing a layered magnesium-based flame retardant and smoke-suppressing hybrid material comprises the following steps: ⑴ Disperse 5.00 g of dodecylbenzenesulfonate-intercalated magnesium-based LDHs in 200 mL of Tris-HCl buffer at pH ≈ 8.5 to obtain slurry A with a mass concentration of 25 g / L; then add 0.75 g of dopamine hydrochloride to slurry A and continue stirring for 30 h. After filtration, washing with anhydrous ethanol and deionized water three times each, and freeze-drying at -80 °C for 24 h, the surface polyphenol-coated organic anion-intercalated magnesium-based LDHs were obtained.

[0043] ⑵ Disperse 4.00 g of surface polyphenol-coated organic anion-intercalated magnesium-based LDHs in 100 mL of deionized water, then add 2 mmol of cobalt nitrate, 1 mmol of nickel nitrate, and 5 mmol of sodium citrate, and continue stirring for 1.5 h to obtain slurry B.

[0044] ⑶ Dissolve 3 mmol of potassium ferrocyanide in 100 mL of deionized water, then add the potassium ferrocyanide solution dropwise to slurry B under continuous stirring, then age for 28 h, filter, wash with anhydrous ethanol and deionized water three times each, and freeze-dry at -80 °C for 24 h to obtain a layered magnesium-based flame retardant and smoke suppression hybrid material.

Claims

1. A method for preparing a layered magnesium-based flame retardant and smoke suppression hybrid material, comprising the following steps: (1) Dispersing organic anion-intercalated magnesium-based LDHs in a Tris-HCl buffer solution with a pH of ≈ 8.5 to obtain a slurry A with a mass concentration of 25 g / L; then adding bio-based polyphenols to the slurry A, stirring continuously for 20 to 30 hours, filtering, washing, and freeze-drying to obtain organic anion-intercalated magnesium-based LDHs coated with polyphenols; (2) dispersing the surface polyphenol-coated organic anion-intercalated magnesium-based LDHs into deionized water to a mass concentration of 30 to 40 g / L, then adding soluble cobalt salt, soluble nickel salt and sodium citrate, and continuously stirring for 0.5 to 1.5 hours to obtain slurry B; (3) Adding a transition metal potassium cyanide solution to the slurry B under continuous stirring, then aging for 20 to 28 hours, filtering, washing and freeze-drying to obtain a layered magnesium-based flame retardant and smoke suppression hybrid material.

2. The method for preparing a layered magnesium-based flame retardant and smoke suppression hybrid material according to claim 1, characterized in that: In the step (1), the organic anion intercalated magnesium-based LDHs are dodecylbenzenesulfonate intercalated magnesium-based LDHs.

3. The method for preparing a layered magnesium-based flame retardant and smoke suppression hybrid material according to claim 1, wherein: In the step (1), the bio-based polyphenol is dopamine hydrochloride, and the mass ratio of the bio-based polyphenol to the organic anion intercalated magnesium-based LDHs is 1-3:10-20.

4. The method for preparing a layered magnesium-based flame retardant and smoke suppression hybrid material according to claim 1, wherein: In the step (2), the soluble cobalt salt is cobalt nitrate or cobalt chloride; and the soluble nickel salt is nickel nitrate or nickel chloride.

5. The method for preparing a layered magnesium-based flame retardant and smoke suppression hybrid material according to claim 1, wherein: In the step (2), the ratio of the soluble cobalt salt, the soluble nickel salt and the surface polyphenol-coated organic anion intercalated magnesium-based LDHs is 1-2 mmol: 1-2 mmol: 3-4 g.

6. The method for preparing a layered magnesium-based flame retardant and smoke suppression hybrid material according to claim 1, wherein: In the step (2), the molar ratio of the soluble cobalt salt, the soluble nickel salt and the sodium citrate is 1-2:1-2:4-5.

7. The method for preparing a layered magnesium-based flame retardant and smoke suppression hybrid material according to claim 1, wherein: The transition metal potassium cyanide solution in step (3) refers to a solution obtained by dissolving transition metal potassium cyanide in deionized water; the ratio of the transition metal potassium cyanide to the deionized water is 2 to 3 mmol: 100 mL; the molar ratio of the transition metal potassium cyanide to the soluble cobalt salt is 2 to 3: 1 to 2.

8. The method for preparing a layered magnesium-based flame retardant and smoke suppression hybrid material according to claim 7, characterized in that: The transition metal in the transition metal potassium cyanide is iron.

9. A layered magnesium-based flame retardant and smoke suppression hybrid material prepared by the method according to any one of claims 1 to 8.

Images