Process for the preparation of low smoke halogen-free flame retardant insulating powder

Abstract

The application discloses a preparation method of low-smoke halogen-free flame-retardant insulating powder. The preparation method of the low-smoke halogen-free flame-retardant insulating powder comprises the following steps: step (1), preparing an intermediate mixed solution; step (2), adding modified layered double hydroxide into an ethanol aqueous solution, ultrasonic treating to obtain a mixed solution, dropping the mixed solution into the intermediate mixed solution prepared in step (1), reacting, filtering, removing impurities, and drying to obtain the low-smoke halogen-free flame-retardant insulating powder. The application prepares organic-inorganic composite low-smoke halogen-free flame-retardant insulating powder with multiple elements P / N / Si / B, realizes synergistic effects of multiple elements, and achieves the flame-retardant insulating powder with excellent flame-retardant and insulating effects by using a low addition amount.

Description

Technical Field

[0001] This invention belongs to the field of functional powder technology, specifically relating to a method for preparing low-smoke halogen-free flame-retardant insulating powder. Background Technology

[0002] Epoxy resin (EP) is widely used in construction, automotive, electronics, and aerospace industries due to its high mechanical strength, chemical resistance, corrosion resistance, and good electrical insulation properties. However, EP is highly flammable. Once ignited, it burns rapidly and tends to release large amounts of smoke and toxic gases. Simultaneously, the dripping of numerous flame-laden droplets can cause large-scale and deadly fires. This flammability defect makes EP a significant fire threat to human life and property during everyday use. With the development of technology, many industries such as automotive and electronics have increased their requirements for the flame-retardant properties of EP. Therefore, the development of high-efficiency flame retardants has become a focus of attention.

[0003] Patent CN 108997714B discloses a reactive flame retardant for epoxy resin and the flame-retardant epoxy resin thereof. The reactive flame retardant for epoxy resin includes at least one of DOPO-AM, DOPO-Urea, and DOPO-THU. DOPO is reacted with acrylamide, urea, and thiourea to obtain DOPO-AM, DOPO-Urea, and DOPO-THU, which are reactive organophosphorus flame retardants, all containing amine groups. When these reactive flame retardants are added to epoxy resin, their amine groups can react with the epoxy resin, grafting the flame retardant onto the epoxy resin backbone. However, the introduction of a large number of amine groups affects the hydrophobicity and insulation properties of the material, and can further improve its flame retardancy. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing low-smoke halogen-free flame-retardant insulating powder, which solves the technical problems of poor insulation, flame retardancy, and compatibility with resin in existing flame-retardant powders.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] This invention provides a method for preparing low-smoke halogen-free flame-retardant insulating powder, comprising the following steps:

[0007] Step (1) Mix 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 3-phenyl-2-propenal and 3-aminopropyltrimethoxysilane, stir under nitrogen atmosphere, add anhydrous ethanol, heat and stir until the solid is completely dissolved, then heat up and add formic acid, react for 3-5 h to obtain intermediate mixture;

[0008] Step (2) The modified layered double hydroxide is added to an ethanol aqueous solution and ultrasonically treated to obtain a mixture. The mixture is then dropped into the intermediate mixture prepared in step (1), reacted, filtered, impurities removed, and dried to obtain a low-smoke halogen-free flame-retardant insulating powder.

[0009] In the above process, the pH of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, the amino group of 3-aminopropyltrimethoxysilane, and the aldehyde group of 3-phenyl-2-propenal are grafted together. Then, the Si-OH obtained by hydrolysis of 3-aminopropyltrimethoxysilane reacts with the hydroxyl groups on the surface of the modified layered double hydroxide to generate a low-smoke halogen-free flame-retardant insulating powder.

[0010] The synthesis reaction formula for low-smoke halogen-free flame-retardant insulating powder is as follows:

[0011]

[0012] Preferably, the method for preparing the modified layered double hydroxide includes the following steps:

[0013] S1: Slowly add 800-1600 mL of 0.5 mol / L Zn(NO3)2·6H2O to 800-1600 mL of 0.25 mol / L sodium dodecyl sulfate solution. Under nitrogen atmosphere, stir for 10-20 min, then add 1.0 mol / L NaOH solution to adjust the pH to 6-7. After complete precipitation, continue stirring for 20-40 min, then transfer to a high-pressure reactor and store at 70-90℃ for 110-130 min. Centrifuge at 5000-6000 r / min for 5-10 min, and vacuum dry the centrifuged solid product at 70-90℃ for 10-16 h to obtain layered double hydroxides.

[0014] In the above process, Zn(NO3)2·6H2O reacts with NaOH to generate a layered double hydroxide, and then the anion of sodium dodecyl sulfate replaces the intercalating anion of the layered double hydroxide.

[0015] S2: Mix 20-40g of layered double hydroxide, 20-40g of borax, and 1000-2000mL of deionized water, react at 30-40℃ in a nitrogen atmosphere for 10-14h, then stir at room temperature for 36-54h, filter, wash with deionized water 3-5 times, and vacuum dry at 70-90℃ for 10-16h to obtain the modified layered double hydroxide.

[0016] In the above process, the anions of borax replace the anions of sodium dodecyl sulfate as the guest ions.

[0017] Preferably, in step (1), the ratio of the amounts of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 3-phenyl-2-propenal, 3-aminopropyltrimethoxysilane, ethanol, and formic acid is (16-32.4)g:(10-19.8)g:(15-33.2)g:(225-450)mL:(10-20)mL.

[0018] Preferably, in step (1), the stirring treatment is performed under the following conditions: stirring time is 10-20 min, stirring speed is 200-400 r / min; heating temperature is 60-80℃; temperature rise is 80-100℃; and reaction time is 3-5 h.

[0019] Preferably, in step (2), the ratio of the modified layered double hydroxide to the ethanol aqueous solution is (10-20) g: (100-120) mL.

[0020] Preferably, in step (2), the mass fraction of the ethanol aqueous solution is 70-80 wt%; the ultrasonic treatment conditions are: ultrasonic treatment time is 0.5-1.5 h, ultrasonic treatment frequency is 50-60 kHz; the reaction time is 4-6 h; the impurity removal method is: the filter residue is washed with ethanol 3-5 times; the drying conditions are: drying temperature is 70-90 ℃, and drying time is 12-36 h.

[0021] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0022] 1. This invention successfully synthesizes an organic-inorganic composite low-smoke halogen-free flame-retardant insulating powder with multiple elements (P / N / Si / B) through an aldehyde-amine condensation reaction. This flame-retardant insulating powder utilizes the synergistic effect of multiple elements, simultaneously exerting the flame-retardant function of each element. Excellent flame-retardant effects can be achieved by using low addition amounts. Simultaneously, the double bonds in the flame-retardant insulating powder readily react with the epoxy groups of epoxy resin to generate macromolecules in situ, forming a barrier layer in the resin. This prevents radial diffusion of molecules, reduces molecular migration, improves thermal stability, and increases the tightness with the resin matrix and the cross-linking density between molecular chains, resulting in a strong binding effect. During combustion, the flame retardant, due to its alkaline nature and porous structure, can absorb smoke during combustion, leading to a stronger smoke suppression effect and effectively inhibiting the emission of toxic gases and smoke from persistent organic pollutants.

[0023] 2. In the modified layered double hydroxide prepared by this invention, the metal cations and borate anions increase the interlayer space of the layered double hydroxide, which helps the epoxy resin to cure quickly. During the thermal degradation process of the modified layered double hydroxide, it absorbs a large amount of heat and lowers the temperature. During the decomposition process, the generated water vapor reduces the content of oxygen and flammable gases. Zinc and borate ions synergistically enhance the flame retardancy. Furthermore, the modified double hydroxide is grafted with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 3-phenyl-2-propenal, and 3-aminopropyltrimethoxysilane. The P / N / Si / B multi-element synergistic effect improves the flame retardancy. Then, 3-aminopropyltrimethoxysilane is used to improve the hydrophobicity of the flame retardant powder and its compatibility with the resin. A flame retardant powder with multiple elements is prepared with strong insulation properties. The resin with added flame retardant and insulating powder has good mechanical properties. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a process flow diagram for preparing the low-smoke halogen-free flame-retardant insulating powder of the present invention. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Example 1

[0028] This embodiment discloses a method for preparing a modified layered double hydroxide, comprising the following steps:

[0029] S1: 1200 mL of 0.5 mol / L Zn(NO3)2·6H2O was slowly added to 1200 mL of 0.25 mol / L sodium dodecyl sulfate solution. After stirring for 15 min under nitrogen atmosphere, 1.0 mol / L NaOH solution was added to adjust the pH to 6.5. After complete precipitation, stirring was continued for 30 min. Then, the mixture was transferred to a high-pressure reactor and stored at 80 °C for 120 min. The mixture was then centrifuged at 5500 r / min for 7 min. The centrifuged solid product was vacuum dried at 80 °C for 13 h to obtain layered double hydroxides.

[0030] S2: Mix 30g of layered double hydroxide, 30g of borax, and 1500mL of deionized water, react at 35℃ in a nitrogen atmosphere for 12h, stir at room temperature for 48h, filter, wash with deionized water 4 times, and vacuum dry at 80℃ for 13h to obtain the modified layered double hydroxide.

[0031] Example 2

[0032] See Figure 1 As shown in the figure, this embodiment discloses a method for preparing low-smoke halogen-free flame-retardant insulating powder, including the following steps:

[0033] Step (1) Mix 24g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 15g of 3-phenyl-2-propenal and 16.5g of 3-aminopropyltrimethoxysilane, stir at 300r / min for 15min under nitrogen atmosphere, add 300mL of anhydrous ethanol, heat to 70℃, stir until the solid is completely dissolved, raise the temperature to 90℃, add 15mL of formic acid, react for 4h to obtain intermediate mixture;

[0034] Step (2) 15g of the modified layered double hydroxide prepared in Example 1 was added to 110mL of 75wt% ethanol aqueous solution and ultrasonically treated at a frequency of 55KHz for 1h. Then, it was added dropwise into the intermediate mixture and reacted for 5h. After filtration, the filter residue was washed with ethanol 4 times and dried at 80℃ for 24h to obtain low smoke halogen-free flame retardant insulating powder.

[0035] Example 3

[0036] See Figure 1 As shown in the figure, this embodiment discloses a method for preparing low-smoke halogen-free flame-retardant insulating powder, including the following steps:

[0037] Step (1) Mix 16g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 19.8g of 3-phenyl-2-propenal and 15g of 3-aminopropyltrimethoxysilane, stir at 400r / min for 10min under nitrogen atmosphere, add 450mL of anhydrous ethanol, heat to 60℃, stir until the solid is completely dissolved, raise the temperature to 100℃, add 10mL of formic acid, react for 5h to obtain intermediate mixture;

[0038] Step (2) 20g of the modified layered double hydroxide prepared in Example 1 was added to 120mL of 70wt% ethanol aqueous solution and ultrasonically treated at a frequency of 60KHz for 0.5h. Then, it was added dropwise into the intermediate mixture and reacted for 6h. After filtration, the filter residue was washed with ethanol 3 times and dried at 90℃ for 12h to obtain low smoke halogen-free flame retardant insulating powder.

[0039] Example 4

[0040] See Figure 1 As shown in the figure, this embodiment discloses a method for preparing low-smoke halogen-free flame-retardant insulating powder, including the following steps:

[0041] Step (1) Mix 32.4g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 10g of 3-phenyl-2-propenal and 33.2g of 3-aminopropyltrimethoxysilane, stir at 200r / min for 20min under nitrogen atmosphere, add 225mL of anhydrous ethanol, heat to 80℃, stir until the solid is completely dissolved, raise the temperature to 80℃, add 20mL of formic acid, react for 3h to obtain intermediate mixture;

[0042] Step (2) 10g of the modified layered double hydroxide prepared in Example 1 was added to 100mL of 80wt% ethanol aqueous solution and ultrasonically treated at a frequency of 50KHz for 1.5h. Then, it was added dropwise into the intermediate mixture and reacted for 4h. After filtration, the filter residue was washed with ethanol 5 times and dried at 70℃ for 36h to obtain low smoke halogen-free flame retardant insulating powder.

[0043] Example 5

[0044] See Figure 1 As shown in the figure, this embodiment discloses a method for preparing low-smoke halogen-free flame-retardant insulating powder, including the following steps:

[0045] Step (1) Mix 20g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 18g of 3-phenyl-2-propenal and 30g of 3-aminopropyltrimethoxysilane, stir at 250r / min for 12min under nitrogen atmosphere, add 420mL of anhydrous ethanol, heat to 65℃, stir until the solid is completely dissolved, raise the temperature to 85℃, add 18mL of formic acid, react for 3.5h to obtain intermediate mixture;

[0046] Step (2) 12g of the modified layered double hydroxide prepared in Example 1 was added to 105mL of 72wt% ethanol aqueous solution and ultrasonically treated at a frequency of 52KHz for 0.6h. Then, it was added dropwise into the intermediate mixture and reacted for 4.5h. After filtration, the filter residue was washed with ethanol 3 times and dried at 88℃ for 20h to obtain low smoke halogen-free flame retardant insulating powder.

[0047] Example 6

[0048] See Figure 1 As shown in the figure, this embodiment discloses a method for preparing low-smoke halogen-free flame-retardant insulating powder, including the following steps:

[0049] Step (1) Mix 17g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 12g of 3-phenyl-2-propenal and 20g of 3-aminopropyltrimethoxysilane, stir at 220r / min for 13min under nitrogen atmosphere, add 400mL of anhydrous ethanol, heat to 68℃, stir until the solid is completely dissolved, raise the temperature to 92℃, add 17mL of formic acid, react for 4.5h to obtain intermediate mixture;

[0050] Step (2) 16g of the modified layered double hydroxide prepared in Example 1 was added to 115mL of 72wt% ethanol aqueous solution and ultrasonically treated at a frequency of 56KHz for 1.2h. Then, it was added dropwise into the intermediate mixture and reacted for 4-6h. After filtration, the filter residue was washed with ethanol 5 times and dried at 74℃ for 15h to obtain low smoke halogen-free flame retardant insulating powder.

[0051] Comparative Example 1

[0052] Compared with Example 2, Comparative Example 1 did not add 3-aminopropyltrimethoxysilane in step (1), and all other conditions remained unchanged.

[0053] Comparative Example 2

[0054] Compared with Example 2, Comparative Example 2 did not add 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide in step (1), and all other conditions remained unchanged.

[0055] Comparative Example 3

[0056] Compared with Example 2, in Comparative Example 3, the modified layered double hydroxide in step (2) was replaced with the unmodified layered double hydroxide, while all other conditions remained unchanged.

[0057] Experimental Example

[0058] The performance of the low-smoke halogen-free flame-retardant insulating powders prepared in Examples 2-6 and Comparative Examples 1-3 was tested.

[0059] Low-smoke halogen-free flame-retardant insulating powder was dispersed in acetone for 2 hours using ultrasound. Then, 77.6 wt% epoxy resin was rotated and heated to 80°C in a frying pan. Under magnetic stirring, 3 wt% of low-smoke halogen-free flame-retardant insulating powder was added in proportion and stirred for 6 hours to completely disperse the flame-retardant insulating powder in the epoxy resin. Then, 19.4 wt% of 4,4'-diaminodiphenylmethane was added and stirred until completely dissolved. The mixture was then placed in a vacuum oven at 45°C to eliminate air bubbles. Under magnetic stirring, the temperature was reduced to about 60°C, and 1 wt% of double bond initiator styrene peroxide was added and stirred until completely mixed. The resulting mixture was then quickly poured into a preheated Teflon mold and heat-cured at 120°C for 2 hours to obtain an epoxy resin composite material.

[0060] I. Flame retardancy test:

[0061] (1) Vertical flammability test: The vertical flammability test was performed using a UL94 instrument in accordance with the standard test method ASTM D 3801(2021).

[0062] (2) Oxygen Index Test: The oxygen index was measured using an oxygen index meter according to the standard test method ISO 4589-2:(2017). The test results are shown in Table 1:

[0063] Table 1

[0064] Vertical flammability rating Limiting oxygen index / % Example 2 V0 34.5 Example 3 V0 33.2 Example 4 V0 33.4 Example 5 V0 32.7 Example 6 V0 33.3 Comparative Example 1 V1 25.1 Comparative Example 2 V2 22.8 Comparative Example 3 V2 21.5

[0065] As shown in Table 1, the low-smoke halogen-free flame-retardant insulating powders prepared in Examples 2-6 of this invention exhibit excellent flame retardancy. A comparison between Comparative Example 1 and Examples 2-6 shows that the addition of 3-aminopropyltrimethoxysilane enhances the flame retardancy of the low-smoke halogen-free flame-retardant insulating powder. A comparison between Comparative Example 2 and Examples 2-6 shows that the addition of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide enhances the flame retardancy of the low-smoke halogen-free flame-retardant insulating powder. A comparison between Comparative Example 3 and Examples 2-6 shows that the modified layered double hydroxide enhances the flame retardancy of the low-smoke halogen-free flame-retardant insulating powder more effectively than the unmodified layered double hydroxide.

[0066] II. Mechanical Performance Testing

[0067] The mechanical properties of Examples 2-6 and Comparative Examples 1-3 were tested. The mechanical property testing methods were performed according to GB / T 2568-1995. The test results are shown in Table 2.

[0068] Table 2

[0069] Tensile strength (MPa) Bending strength (MPa) Example 2 109 142 Example 3 101 136 Example 4 101 135 Example 5 98 131 Example 6 103 133 Comparative Example 1 80 92 Comparative Example 2 75 86 Comparative Example 3 71 83

[0070] As shown in Table 1, the low-smoke halogen-free flame-retardant insulating powders prepared in Examples 2-6 of this invention exhibit excellent flame retardancy. A comparison between Comparative Example 1 and Examples 2-6 shows that the addition of 3-aminopropyltrimethoxysilane enhances the flame retardancy of the epoxy resin with added low-smoke halogen-free flame-retardant insulating powder. A comparison between Comparative Example 2 and Examples 2-6 shows that the addition of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide enhances the flame retardancy of the epoxy resin with added low-smoke halogen-free flame-retardant insulating powder. A comparison between Comparative Example 3 and Examples 2-6 shows that the modified layered double hydroxide enhances the flame retardancy of the epoxy resin with added low-smoke halogen-free flame-retardant insulating powder more effectively than the unmodified layered double hydroxide.

[0071] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

[0072] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. Process for the production of low-smoke halogen-free flame-retardant insulating powders, characterized in that, The method comprises the following steps: Step (1): mixing 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 3-phenyl-2-propenal and 3-aminopropyltrimethoxysilane, stirring under nitrogen atmosphere, adding anhydrous ethanol, heating, stirring until the solid is completely dissolved, then increasing the temperature, adding formic acid, and reacting for 3-5 hours to obtain an intermediate mixture; Step (2): adding the modified layered double hydroxide into an ethanol aqueous solution, ultrasonic treatment to obtain a mixture, dropping the mixture into the intermediate mixture prepared in step (1), reacting, filtering, removing impurities, and drying to obtain a low-smoke halogen-free flame-retardant insulating powder; The preparation method of the modified layered double hydroxide comprises the following steps: S1: slowly adding 800-1600 mL of 0.5 mol / L Zn(NO3)2·6H2O into 800-1600 mL of 0.25 mol / L sodium dodecyl sulfate solution, stirring under nitrogen atmosphere for 10-20 min, then adding 1.0 mol / L NaOH solution to adjust the pH to 6-7, continuing to stir for 20-40 min, then moving to a high-pressure reaction kettle, storing at 70-90°C for 110-130 min, centrifuging at a speed of 5000-6000 r / min for 5-10 min, vacuum drying the centrifuged solid product at 70-90°C for 10-16 h to obtain the layered double hydroxide; S2: mixing 20-40 g of the layered double hydroxide, 20-40 g of borax and 1000-2000 mL of deionized water, reacting at 30-40°C under nitrogen atmosphere for 10-14 h, then stirring at room temperature for 36-54 h, filtering, washing with deionized water for 3-5 times, and vacuum drying at 70-90°C for 10-16 h to obtain the modified layered double hydroxide.

2. A process for the preparation of low smoke zero halogen flame retardant insulating powder according to claim 1, characterized in that, In step (1), the amount ratio of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 3-phenyl-2-propenal, 3-aminopropyltrimethoxysilane, ethanol and formic acid is (16-32.4) g:(10-19.8) g:(15-33.2) g:(225-450) mL:(10-20) mL.

3. A process for the preparation of low smoke zero halogen flame retardant insulating powder according to claim 1, characterized in that, In step (1), the stirring treatment: stirring treatment condition: stirring treatment time is 10-20 min, stirring treatment speed is 200-400 r / min; heating temperature is 60-80°C; temperature increasing temperature is 80-100°C; reaction time is 3-5 h.

4. The process for the preparation of low smoke zero halogen flame retardant insulating powder as claimed in claim 1, wherein, In step (2), the amount ratio of the modified layered double hydroxide and the ethanol aqueous solution is (10-20) g:(100-120) mL.

5. The process for the preparation of low smoke zero halogen flame retardant insulating powder according to claim 1, characterized in that, In step (2), the mass fraction of the ethanol aqueous solution is 70-80 wt%.

6. A process for the preparation of low smoke zero halogen flame retardant insulating powder according to claim 1, characterized in that, In step (2), the ultrasonic treatment condition: ultrasonic treatment time is 0.5-1.5 h, ultrasonic treatment frequency is 50-60 KHz.

7. The process for the preparation of low smoke zero halogen flame retardant insulating powder according to claim 1, characterized in that, The reaction time in the step (2) is 4-6h; the impurity removing method is that the residue is washed with ethanol for 3-5 times; the drying condition is that the drying temperature is 70-90℃ and the drying time is 12-36h.

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