Preparation method of efficient magnesium-based composite flame retardant

Abstract

The invention relates to a preparation method of a high-efficiency magnesium-based composite flame retardant, which comprises the following steps: step 1, adding magnesium borate whiskers and bio-based polyphenol into an aqueous solution with the pH value of about 8.5, continuously stirring for 12-24 hours, and carrying out suction filtration, washing and freeze drying to obtain bio-based polyphenol activated magnesium borate whiskers; 2, the bio-based polyphenol activated magnesium borate whiskers, soluble nickel salt and sodium citrate are added into deionized water, a transition metal potassium cyanide solution is added under continuous stirring, then aging is conducted for 18-30 h, suction filtration, washing and freeze drying are conducted, and the magnesium-based composite flame retardant is obtained. The method is simple, low in cost and easy to implement, the density of surface active groups of the magnesium borate whiskers can be increased, and the catalytic char forming capacity can be improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of flame-retardant materials, in particular to a preparation method of high-efficiency magnesium-based composite flame retardant. BACKGROUND

[0002] Magnesium borate whisker is a high-value-added product of salt lake magnesium resources. Due to its fiber-like micro-morphology and characteristics such as light weight, high toughness, heat resistance, and wear resistance, it is mainly used as a reinforcing agent for magnesium-aluminum alloy, polymer, ceramic, and cement materials, which can effectively improve the mechanical properties of the substrate such as tensile strength, impact strength, and elastic modulus. Adding magnesium borate whisker to polymer not only improves the mechanical properties of the substrate, but also has a certain flame-retardant effect. However, the polymer composite material with excellent flame-retardant performance and mechanical properties has always been the ideal goal pursued by people. In addition, magnesium borate whisker raw materials can be obtained from salt lakes, which are abundant and inexpensive, making it show good application prospects in flame-retardant reinforced polymers. However, the surface active group density of magnesium borate whisker is small, and it is difficult to improve the compatibility with the matrix by chemical bonding with surface modifiers, resulting in unsatisfactory mechanical reinforcement effect. In addition, magnesium borate whisker flame-retardant mainly works through physical barrier effect, and has weak catalytic carbonization ability and low flame-retardant efficiency.

[0003] Studies have shown that borate-modified magnesium borate whisker has obvious advantages in reinforcing and flame-retardant properties of polyurethane compared with unmodified magnesium borate whisker. However, borate modification mainly relies on physical adsorption between the boron-oxygen skeleton of borate and magnesium borate whisker, and the material performance is not stable when the external environment changes. When other modifiers are used, it is difficult to form strong interfacial interaction due to the lack of sufficient active groups on the surface of magnesium borate whisker. By loading magnesium hydroxide on the surface of magnesium borate whisker and increasing the number of surface active hydroxyl groups, then grafting organic phosphate, this inorganic-organic modified magnesium borate whisker has good mechanical reinforcement effect. However, the magnesium hydroxide loaded by precipitation is not firmly combined with the surface of magnesium borate whisker, and is easy to fall off. Moreover, it has weak catalytic carbonization ability and limited flame-retardant efficiency improvement.

[0004] Therefore, it is urgent to seek a new surface treatment method for magnesium borate whisker to increase the density of surface active groups and composite with substances with strong catalytic carbonization ability, so as to achieve the purpose of improving the surface catalytic carbonization ability of the material, and then obtain a high-efficiency magnesium-based composite flame retardant. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a preparation method of high-efficiency magnesium-based composite flame retardant, which is simple, low in cost, and easy to implement.

[0006] To solve the above problems, the preparation method of high-efficiency magnesium-based composite flame retardant according to the present application comprises the following steps: Step 1: adding magnesium borate whiskers and bio-based polyphenol into an aqueous solution with pH≈8.5, continuously stirring for 12-24 h, and then obtaining bio-based polyphenol activated magnesium borate whiskers through suction filtration, washing and freeze-drying; Step 2: adding the bio-based polyphenol activated magnesium borate whiskers, soluble nickel salt and sodium citrate into deionized water, adding a transition metal potassium cyanide solution under continuous stirring, and then aging for 18-30 h, and then obtaining a magnesium-based composite flame retardant through suction filtration, washing and freeze-drying.

[0007] The mass ratio of the magnesium borate whiskers to the aqueous solution with pH≈8.5 in the step 1 is 1:40.

[0008] The bio-based polyphenol in the step 1 is dopamine hydrochloride, and the mass ratio of the dopamine hydrochloride to the magnesium borate whiskers is 1:20-3:20.

[0009] The mass ratio of the soluble nickel salt to the bio-based polyphenol activated magnesium borate whiskers in the step 2 is 3:20-5:20; the mass ratio of the sodium citrate to the soluble nickel salt is 9:8-9:10; and the mass ratio of the bio-based polyphenol activated magnesium borate whiskers to the deionized water is 2:35.

[0010] The soluble nickel salt is any one of nickel chloride and nickel nitrate.

[0011] The transition metal potassium cyanide solution in the step 2 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 1.50 g ~2.25 g:350 mL; and the mass ratio of the transition metal potassium cyanide to the soluble nickel salt is 9:20-9:16.

[0012] The transition metal in the transition metal potassium cyanide is iron.

[0013] A magnesium-based composite flame retardant prepared by the method.

[0014] Compared with the prior art, the present application has the following advantages: 1. The present application uses bio-based polyphenol to activate the surface of magnesium borate whiskers, and the bio-based polyphenol has strong adhesion performance and can be firmly combined with the surface of the magnesium borate whiskers, thereby avoiding the problems of poor interface combination and falling off of the modifier in the prior art. Meanwhile, the density of the active groups on the surface of the magnesium borate whiskers is improved.

[0015] 2, The application utilizes biological-based polyphenol to induce transition metal ions and cyanide ions to coordinate on the surface of magnesium borate whiskers, and in-situ grows cyan-bridged coordination polymers. The transition metal ions in the cyan-bridged coordination polymers have strong catalytic carbonization ability, and are limited to grow on the surface of magnesium borate whiskers. The particle size and uniformity of the loaded coordination polymers are superior to those of common coprecipitation methods, so that the flame retardant efficiency is higher.

[0016] 3, The method is simple, low in cost and easy to implement. BRIEF DESCRIPTION OF DRAWINGS

[0017] The specific embodiments of the application will be further described in detail below with reference to the accompanying drawings.

[0018] Figure 1 The XRD diagram of the magnesium-based composite flame retardant and magnesium borate whisker obtained in Example 1 of the application.

[0019] Figure 2 The SEM diagram of the magnesium-based composite flame retardant obtained in Example 1 of the application and the element distribution diagrams of Fe and Ni corresponding thereto. DETAILED DESCRIPTION

[0020] A preparation method of a high-efficiency magnesium-based composite flame retardant, comprising the following steps: Step 1: magnesium borate whiskers and biological-based polyphenol are added into an aqueous solution with pH≈8.5, the mass ratio (g / g) of the magnesium borate whiskers to the aqueous solution with pH≈8.5 is 1:40; the biological-based polyphenol is dopamine hydrochloride, and the mass ratio (g / g) of the dopamine hydrochloride to the magnesium borate whiskers is 1:20-3:20. After continuous stirring for 12-24 h, the mixture is filtered, washed with anhydrous ethanol and deionized water for 3 times respectively, and then freeze-dried at-80 ℃ for 12-24 h, to obtain biological-based polyphenol activated magnesium borate whiskers.

[0021] The magnesium borate whiskers are self-made in the laboratory, and the specific preparation process is shown in CN201010161693.4.

[0022] The dopamine hydrochloride is purchased from Shanghai Aladdin Reagent Co., Ltd.

[0023] Step 2: Add the bio-based polyphenol-activated magnesium borate whisker, soluble nickel salt, and sodium citrate into deionized water, and then add a transition metal potassium cyanide solution under continuous stirring. The mass ratio (g / g) of the soluble nickel salt to the bio-based polyphenol-activated magnesium borate whisker is 3:20-5:20. The mass ratio (g / g) of the sodium citrate to the soluble nickel salt is 9:8-9:10. The mass ratio (g / g) of the bio-based polyphenol-activated magnesium borate whisker to the deionized water is 2:35. The transition metal potassium cyanide solution refers to a solution obtained by dissolving a transition metal potassium cyanide in deionized water. The ratio of the transition metal potassium cyanide to the deionized water is 1.50 g-2.25 g:350 mL. The mass ratio (g / g) of the transition metal potassium cyanide to the soluble nickel salt is 9:20-9:16. Then, the mixture is aged for 18-30 h, and then filtered, washed with anhydrous ethanol and deionized water for 3 times, and then freeze-dried at-80 ℃ for 12-24 h to obtain the magnesium-based composite flame retardant.

[0024] The soluble nickel salt is any one of nickel chloride and nickel nitrate.

[0025] The transition metal in the transition metal potassium cyanide is iron.

[0026] The design principle of the present application is as follows: the bio-based polyphenol is used as an activator to perform surface activation treatment on the magnesium borate whisker to improve the density of the surface activation group and the complexing ability of the magnesium borate whisker with metal ions. Then, the soluble nickel salt, sodium citrate, and transition metal potassium cyanide are added, and the transition metal ions and cyanide ions are coordinated and complexed on the surface of the magnesium borate whisker through bio-based polyphenol induction, and an ultra-fine cyan-based bridged coordination polymer is in-situ grown to prepare a high-efficiency magnesium-based composite flame retardant. The reduction of the polymer particle size on the surface of the magnesium borate whisker and the uniform distribution of the transition metal ions can better play the catalytic carbonization ability of the transition metal ions, thereby significantly improving the flame retardant efficiency of the magnesium-based composite flame retardant.

[0027] Example 1 A preparation method of a high-efficiency magnesium-based composite flame retardant, comprising the following steps: Step 1: Add 20.00 g of magnesium borate whisker and 3.00 g of bio-based polyphenol dopamine hydrochloride into a 800 mL aqueous solution with pH≈8.5, and continuously stir for 24 h. Then, the mixture is filtered, washed with anhydrous ethanol and deionized water for 3 times, and then freeze-dried at-80 ℃ for 24 h to obtain bio-based polyphenol-activated magnesium borate whisker.

[0028] Step 2: 20.00 g of bio-based polyphenol-activated magnesium borate whiskers, 4.00 g of nickel chloride, and 4.50 g of sodium citrate were added to 350 mL of deionized water, and ultrasonic treatment was performed for 10 min to obtain slurry A; 2.25 g of potassium ferricyanide was dissolved in 350 mL of deionized water to obtain solution B. Solution B was added dropwise to slurry A under continuous stirring, and then aged for 24 h. After being filtered, washed with anhydrous ethanol and deionized water for 3 times, and then freeze-dried at -80 ℃ for 24 h, a magnesium-based composite flame retardant was obtained.

[0029] As shown in FIG. 1, compared with the XRD test results of the magnesium borate whiskers, the XRD test results of the magnesium-based composite flame retardant prepared in Example 1 showed characteristic diffraction peaks of the cyan-bridged coordination polymer. Figure 1 As shown in FIG. 2, the SEM test results of the magnesium-based composite flame retardant prepared in Example 1 showed that there were fine granular substances on the surface of the magnesium borate whiskers, and the Fe and Ni elements were distributed on the surface of the magnesium borate whiskers and were very uniform.

[0030] Figure 2 As shown in FIG. 2, the SEM test results of the magnesium-based composite flame retardant prepared in Example 1 showed that there were fine granular substances on the surface of the magnesium borate whiskers, and the Fe and Ni elements were distributed on the surface of the magnesium borate whiskers and were very uniform.

[0031]

Flame Retardant Performance Test

[0032] The results showed that the EP composites added with 2.5 wt% of the unmodified magnesium borate whiskers and the bio-based polyphenol-activated magnesium borate whiskers respectively had no grade in the UL-94 vertical burning test, and the EP composite added with the same amount of the magnesium-based composite flame retardant prepared in Example 1 reached V-1 grade in the UL-94 vertical burning test. The EP composites added with 5.0 wt% of the unmodified magnesium borate whiskers and the bio-based polyphenol-activated magnesium borate whiskers respectively still had no grade in the UL-94 vertical burning test, and the EP composite added with the same amount of the magnesium-based composite flame retardant prepared in Example 1 reached V-0 grade in the UL-94 vertical burning test.

[0033] Therefore, the flame retardant efficiency of the magnesium-based composite flame retardant prepared in the present application is significantly improved, which can be attributed to the excellent catalytic carbonization effect of the transition metal ions in the ultra-fine cyan-bridged coordination polymer on the surface of the magnesium borate whiskers and the synergistic effect of the magnesium borate whisker grid on carbon solidification.

[0034] Example 2 A method for preparing a high-efficiency magnesium-based composite flame retardant, comprising the following steps: ​Step 1: 20.00 g of magnesium borate whiskers and 2.50 g of biobased polyphenol dopamine hydrochloride were added to 800 mL of aqueous solution with pH ≈ 8.5, continuously stirred for 18 h, and then freeze-dried at -80 ℃ for 24 h after being filtered by suction and washed with anhydrous ethanol and deionized water for 3 times, to obtain biobased polyphenol-activated magnesium borate whiskers.

[0035] Step 2: 20.00 g of biobased polyphenol-activated magnesium borate whiskers, 5.00 g of nickel nitrate and 4.50 g of sodium citrate were added to 350 mL of deionized water, and ultrasonic treatment was performed for 10 min to obtain slurry A; solution B was added dropwise to slurry A under continuous stirring, and then aged for 30 h, and then freeze-dried at -80 ℃ for 24 h after being filtered by suction and washed with anhydrous ethanol and deionized water for 3 times, to obtain a magnesium-based composite flame retardant.

[0036] Solution B was prepared as in Example 1.

[0037] Example 3 A method for preparing a high-efficiency magnesium-based composite flame retardant, comprising the following steps: Step 1: 20.00 g of magnesium borate whiskers and 1.00 g of biobased polyphenol dopamine hydrochloride were added to 800 mL of aqueous solution with pH ≈ 8.5, continuously stirred for 12 h, and then freeze-dried at -80 ℃ for 24 h after being filtered by suction and washed with anhydrous ethanol and deionized water for 3 times, to obtain biobased polyphenol-activated magnesium borate whiskers.

[0038] Step 2: 20.00 g of biobased polyphenol-activated magnesium borate whiskers, 3.00 g of nickel chloride and 3.00 g of sodium citrate were added to 350 mL of deionized water, and ultrasonic treatment was performed for 10 min to obtain slurry A; 1.50 g of potassium ferricyanide was dissolved in 350 mL of deionized water to obtain solution B. Solution B was added dropwise to slurry A under continuous stirring, and then aged for 18 h, and then freeze-dried at -80 ℃ for 24 h after being filtered by suction and washed with anhydrous ethanol and deionized water for 3 times, to obtain a magnesium-based composite flame retardant.

Claims

1. A method for preparing a high-efficiency magnesium-based composite flame retardant, comprising the following steps: Step 1: Add magnesium borate whiskers and bio-based polyphenols to an aqueous solution with a pH of ≈ 8.5, and continue stirring for 12 to 24 hours. Filter, wash, and freeze-dry to obtain bio-based polyphenol-activated magnesium borate whiskers. Step 2: adding the bio-based polyphenol-activated magnesium borate whiskers, soluble nickel salt and sodium citrate to deionized water, adding a transition metal potassium cyanide solution under continuous stirring, and then aging for 18 to 30 hours, filtering, washing and freeze-drying to obtain a magnesium-based composite flame retardant.

2. The method for preparing a high-efficiency magnesium-based composite flame retardant according to claim 1, wherein: In step 1, the mass ratio of the magnesium borate whiskers to the aqueous solution with a pH value of 8.5 is 1:

40.

3. The method for preparing a high-efficiency magnesium-based composite flame retardant according to claim 1, wherein: In step 1, the bio-based polyphenol is dopamine hydrochloride, and the mass ratio of the bio-based polyphenol to the magnesium borate whisker is 1:20 to 3:

20.

4. The method for preparing a high-efficiency magnesium-based composite flame retardant according to claim 1, wherein: In step 2, the mass ratio of the soluble nickel salt to the bio-based polyphenol-activated magnesium borate whiskers is 3:20 to 5:20; the mass ratio of sodium citrate to the soluble nickel salt is 9:8 to 9:10; and the mass ratio of the bio-based polyphenol-activated magnesium borate whiskers to deionized water is 2:

35.

5. The method for preparing a high-efficiency magnesium-based composite flame retardant according to claim 4, characterized in that: The soluble nickel salt is any one of nickel chloride and nickel nitrate.

6. The method for preparing a high-efficiency magnesium-based composite flame retardant according to claim 1, wherein: The transition metal potassium cyanide solution in step 2 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 1.50 g ~ 2.25 g: 350 mL; the mass ratio of the transition metal potassium cyanide to the soluble nickel salt is 9:20 ~ 9:

16.

7. The method for preparing a high-efficiency magnesium-based composite flame retardant according to claim 6, characterized in that: The transition metal in the transition metal potassium cyanide is iron.

8. A magnesium-based composite flame retardant prepared by the method according to any one of claims 1 to 7.

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