Double-shell microcapsule modified magnesium hydroxide flame retardant as well as preparation method and application thereof

Abstract

The invention discloses a double-shell microcapsule modified magnesium hydroxide flame retardant and a preparation method and application thereof.The flame retardant takes magnesium hydroxide as a core, and the core is sequentially coated with an inner wall formed by 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and an outer wall formed by ethyl cellulose. The preparation method comprises the following steps: dissolving and mixing 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and vinyltriethoxysilane, and adding a catalyst to carry out a reaction; adding magnesium hydroxide, reacting, and drying the product to obtain DOPO-coated modified magnesium hydroxide; dissolving ethyl cellulose, adding DOPO-coated modified magnesium hydroxide, 2, 4 toluene diisocyanate, a dispersing agent and a catalyst, reacting, and drying a product, thereby obtaining the flame retardant. Through double-layer coating modification, the compatibility with a polymer matrix is enhanced, the reduction of the tensile property of the composite material is delayed, and the flame retardant property of the material is effectively improved.

Description

Technical Field

[0001] This invention relates to a flame retardant, its preparation method and application, and more particularly to a double-shell microcapsule modified magnesium hydroxide flame retardant, its preparation method and application. Background Technology

[0002] In numerous fire scenarios, polymer materials, due to their widespread use, have become a significant source of risk. Most polymer materials are flammable; when burning, they not only spread rapidly but also release large amounts of heat and toxic fumes, significantly increasing the hazard of a fire. Therefore, flame-retardant treatment of polymer materials is of great practical importance to contemporary society.

[0003] Magnesium hydroxide (MH), a typical inorganic flame retardant, has attracted much attention due to its good smoke suppression effect, lack of toxic gas production, wide availability of raw materials, and low cost. However, MH has significant shortcomings in practical applications: its strong surface polarity and hydrophilic-oleophobic properties lead to poor dispersibility and easy aggregation in polymer matrices; simultaneously, its flame retardant efficiency is limited, requiring high addition levels to effectively improve the flame retardancy of polymer materials, while excessive addition levels can severely damage the mechanical properties of the materials, limiting their application. Therefore, modifying MH to improve its compatibility with the matrix, dispersibility, and flame retardant efficiency has become an important research direction.

[0004] In practical applications, a single flame retardant often fails to fully meet the comprehensive requirements of materials for both flame retardant and mechanical properties. Utilizing the synergistic effect of compounding flame retardants with different flame-retardant mechanisms to achieve highly efficient flame retardancy has become an important development trend.

[0005] However, magnesium hydroxide has poor dispersibility and is prone to agglomeration in polymer matrices, which leads to stress concentration points inside the material and thus reduces the mechanical properties of the material. Microcapsule coating on the surface of magnesium hydroxide reduces the relative content of magnesium hydroxide in the composite system, thereby weakening its flame retardant effect in the material.

[0006] Furthermore, most microcapsule coatings used in magnesium hydroxide coating modification lack flame-retardant properties and may even dilute the flame-retardant effect of magnesium hydroxide. Microcapsule coating on the surface of magnesium hydroxide leads to a decrease in its flame-retardant performance. Summary of the Invention

[0007] Purpose of the invention: The purpose of this invention is to provide a double-shell microcapsule modified magnesium hydroxide flame retardant that can enhance compatibility with polymer matrices, delay the decline in tensile properties of composite materials, and has high flame retardant efficiency.

[0008] The second objective of this invention is to provide a method for preparing the above-mentioned double-shell microcapsule modified magnesium hydroxide flame retardant; the third objective of this invention is to provide the application of the above-mentioned double-shell microcapsule modified magnesium hydroxide flame retardant.

[0009] Technical solution: The double-shell microcapsule modified magnesium hydroxide flame retardant of the present invention uses magnesium hydroxide as the core, and the core is sequentially coated with an inner wall formed by 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and an outer wall formed by ethyl cellulose.

[0010] The preparation method of the above-mentioned double-shell microcapsule modified magnesium hydroxide flame retardant includes the following steps:

[0011] (1) Dissolve 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and vinyltriethoxysilane separately in anhydrous ethanol, mix them, and add a catalyst to carry out the reaction;

[0012] (2) Add magnesium hydroxide to the reaction system, and after the reaction is completed, wash, filter and dry to obtain DOPO coated modified magnesium hydroxide;

[0013] (3) Ethyl cellulose was dissolved in ethyl acetate, and DOPO-coated modified magnesium hydroxide, 2,4-toluene diisocyanate, dispersant and catalyst were added. After the reaction was completed, the mixture was washed, filtered and dried to obtain double-shell microcapsule modified magnesium hydroxide flame retardant.

[0014] In step (1), the catalyst is azobisisobutyronitrile (AIBN), and the amount of AIBN is 1-2% of the system mass; the reaction temperature is 70-90℃, and the reaction time is 10-12 hours. Preferably, the amount of AIBN is 1% of the system mass, and the reaction temperature is 75℃.

[0015] In step (2), the reaction temperature is 70–90°C and the reaction time is 6–8 hours. Preferably, the reaction temperature is 75°C.

[0016] In step (3), the catalyst is dibutyltin dilaurate, and the amount of dibutyltin dilaurate is 0.1-0.2% of the system mass; the dispersant is polyoxyethylene octylphenol ether-10, and the amount of polyoxyethylene octylphenol ether-10 is 0.1-0.2% of the system mass; the reaction temperature is 70-90℃, and the reaction time is 6-8 hours. Preferably, the amount of dibutyltin dilaurate is 0.1% of the system mass, the amount of polyoxyethylene octylphenol ether-10 is 0.1% of the system mass, and the reaction temperature is 70℃.

[0017] In step (2), the drying temperature is 50℃~80℃ and the time is 36~48 hours, with the preferred drying temperature being 60℃; in step (3), the drying temperature is 50℃~80℃ and the time is 36~48 hours, with the preferred drying temperature being 60℃.

[0018] The above-mentioned double-shell microcapsule modified magnesium hydroxide flame retardant is used in flame retardant materials.

[0019] In this process, a double-shell microcapsule modified magnesium hydroxide flame retardant is added to epoxy resin, stirred, and then a curing agent is added. The mixture is stirred again, poured into a mold, and heated to cure, thus obtaining an epoxy resin flame retardant material containing the double-shell microcapsule modified magnesium hydroxide flame retardant. The curing temperature is 80~160℃, and the curing time is 2~6 hours.

[0020] In this process, a double-shell microcapsule modified magnesium hydroxide flame retardant is added to an unsaturated polyester resin, stirred, and then a curing agent is added. The mixture is stirred again, poured into a mold, and heated to cure, thereby obtaining an unsaturated polyester resin flame retardant material containing the double-shell microcapsule modified magnesium hydroxide flame retardant. The curing temperature is 80~120℃, and the curing time is 1~4 hours.

[0021] In this process, a double-shell microcapsule modified magnesium hydroxide flame retardant is added to an ethylene-vinyl acetate copolymer. The ethylene-vinyl acetate copolymer material filled with the flame retardant is then hot-pressed and sheeted to obtain an ethylene-vinyl acetate copolymer flame retardant material containing a double-shell microcapsule modified magnesium hydroxide flame retardant. The hot-pressing temperature is 100℃~120℃, and the hot-pressing time is 10~20 minutes.

[0022] Invention Principle: The core of this invention lies in simultaneously addressing the problems of poor dispersibility, low compatibility, and insufficient flame retardant efficiency of magnesium hydroxide (MH) in polymer matrices through a double-shell microcapsule structure. The principle is mainly reflected in the following two aspects: 1. Interface compatibility regulation: The outer ethyl cellulose (EC) layer is rich in hydroxyl groups, which can form hydrogen bonds with the polymer matrix, significantly reducing the surface polarity of MH, improving its dispersibility in the matrix, and reducing the loss of mechanical properties caused by agglomeration. 2. Synergistic flame retardant mechanism: The inner DOPO layer plays a dual flame retardant role during combustion—decomposing to generate phosphates to promote char formation in the matrix, while releasing PO· free radicals to capture active free radicals in the combustion chain reaction; the outer EC layer, as a carbon source, enhances the continuity and density of the char layer, and the two synergistically form a highly efficient barrier.

[0023] Beneficial effects: Compared with the prior art, the present invention achieves the following significant effects:

[0024] This invention significantly reduces the surface polarity of magnesium hydroxide through double-layer coating modification, enhancing its compatibility with the polymer matrix and reducing stress concentration caused by filler agglomeration, thereby delaying the decline in the tensile properties of the composite material. The double-shell microcapsule modified magnesium hydroxide flame retardant exhibits higher flame retardant efficiency compared to unmodified magnesium hydroxide, effectively improving the flame retardant performance of the material. Attached Figure Description

[0025] Figure 1 This is a water contact angle diagram of magnesium hydroxide and the double-shell microcapsule modified magnesium hydroxide obtained in Example 1;

[0026] Figure 2 These are SEM images of the EP materials from Example 1 and Comparative Examples 1 and 2;

[0027] Figure 3 These are SEM images of the UPR materials from Example 2 and Comparative Examples 3 and 4;

[0028] Figure 4 These are SEM images of the EVA materials from Example 3 and Comparative Examples 5 and 6;

[0029] Figure 5 These are the stress-strain curves of the EP materials in Example 1 and Comparative Examples 1 and 2;

[0030] Figure 6 These are the stress-strain curves of the UPR materials in Example 2 and Comparative Examples 3 and 4;

[0031] Figure 7 These are the stress-strain curves of the EVA materials in Example 3 and Comparative Examples 5 and 6;

[0032] Figure 8 These are digital photographs of the UL-94 vertical burning test process of the EP materials in Example 1 and Comparative Examples 1 and 2;

[0033] Figure 9 These are digital photographs of the UL-94 vertical burning test process of the UPR materials in Example 2 and Comparative Examples 3 and 4;

[0034] Figure 10 These are digital photographs of the UL-94 vertical burning test process of the EVA materials in Example 3 and Comparative Examples 5 and 6. Detailed Implementation

[0035] The present invention will now be described in further detail.

[0036] Example 1

[0037] 4.75 g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) was added to a three-necked flask, and 38 ml of anhydrous ethanol was added. The temperature was raised to 75 °C to completely dissolve the DOPO. 3.8 g of vinyltriethoxysilane was dissolved in 38 ml of anhydrous ethanol, and 1% (by weight) of azobisisobutyronitrile (AIBN) catalyst was added dropwise. The reaction was carried out at 75 °C for 12 h. 10 g of magnesium hydroxide was added, and the reaction was continued with heating and stirring for another 12 h. After the reaction was complete, the reaction solution was filtered under positive pressure to obtain the product, which was washed three times with anhydrous ethanol. The product was then dried in an oven to constant weight to obtain DOPO-coated modified magnesium hydroxide. 0.2 g of ethyl cellulose (EC) and 30 ml of ethyl acetate were added to a three-necked flask and stirred at 80 °C for 30 min to prepare an EC solution. 10 g of DOPO-coated modified magnesium hydroxide was added, followed by dropwise addition of 0.1% (by weight) of polyoxyethylene octylphenol ether-10 (OP-10) dispersant and 0.1% (by weight) of dibutyltin dilaurate catalyst (DBTDL). The reaction was carried out at 70 °C for 8 h. After the reaction was complete, the mixture was washed with ethyl acetate, filtered, and dried in a drying oven to constant weight to obtain a double-shell microcapsule modified magnesium hydroxide flame retardant.

[0038] Weigh 48g of epoxy resin (EP) into a three-necked flask, mechanically stir and heat to 70℃. After the viscosity of EP decreases upon heating, add 40g of double-shell microcapsule modified magnesium hydroxide flame retardant and mechanically stir for 30min to mix thoroughly. Then, add 12g of curing agent 4,4-diaminodiphenylmethane (DDM) and stir at 70℃ for 10min until the curing agent is completely dissolved. Place the mixture in a 70℃ vacuum drying oven and evacuate until all air bubbles are removed. Then, quickly pour the mixture into a preheated polytetrafluoroethylene mold and use a gradient curing method with the following heating program: 80℃ for 1h, 120℃ for 2h, and 160℃ for 2h. After cooling and demolding, the EP material containing double-shell microcapsule modified magnesium hydroxide flame retardant is obtained.

[0039] Depend on Figure 1 It can be seen that the water contact angle of magnesium hydroxide modified by coating with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and ethyl cellulose increased to 68.73°, indicating that its hydrophilicity decreased significantly, its hydrophobicity increased, and its anti-wetting ability improved.

[0040] Comparative Example 1

[0041] Weigh 48g of EP into a three-necked flask, mechanically stir and heat to 70℃. After the viscosity of EP decreases upon heating, add 40g of magnesium hydroxide flame retardant and mechanically stir for 30 minutes to mix thoroughly. Then, add 12g of curing agent 4,4-diaminodiphenylmethane (DDM) and stir at 70℃ for 10 minutes until the curing agent is completely dissolved. Place the mixture in a 70℃ vacuum drying oven and evacuate until all air bubbles are removed. Then, quickly pour the mixture into a preheated PTFE mold and use a gradient curing method with the following heating program: 80℃ for 1 hour, 120℃ for 2 hours, and 160℃ for 2 hours. After cooling and demolding, the EP material containing magnesium hydroxide flame retardant is obtained.

[0042] Comparative Example 2

[0043] Weigh 80g of EP into a three-necked flask, mechanically stir and heat to 70℃. Then, add 20g of curing agent 4,4-diaminodiphenylmethane (DDM), and stir at 70℃ for 10 minutes until the curing agent is completely dissolved. Place the mixture in a 70℃ vacuum drying oven and evacuate until all air bubbles are removed. Then, quickly pour the mixture into a preheated PTFE mold and use a gradient curing method with the following heating program: 80℃ for 1 hour, 120℃ for 2 hours, and 160℃ for 2 hours. After cooling and demolding, pure EP material is obtained.

[0044] Example 2

[0045] 4.75 g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) was added to a three-necked flask, and 38 ml of anhydrous ethanol was added. The temperature was raised to 75 °C to completely dissolve the DOPO. 3.8 g of vinyltriethoxysilane was dissolved in 38 ml of anhydrous ethanol, and 1% (by weight) of azobisisobutyronitrile (AIBN) catalyst was added dropwise. The reaction was carried out at 75 °C for 12 h. 10 g of magnesium hydroxide was added, and the reaction was continued with heating and stirring for another 12 h. After the reaction was complete, the reaction solution was filtered under positive pressure to obtain the product, which was washed three times with anhydrous ethanol. The product was then dried in an oven to constant weight to obtain DOPO-coated modified magnesium hydroxide. 0.2 g of ethyl cellulose (EC) and 30 ml of ethyl acetate were added to a three-necked flask and stirred at 80 °C for 30 min to prepare an EC solution. 10 g of DOPO-coated modified magnesium hydroxide was added, followed by dropwise addition of 0.1% (by weight) of polyoxyethylene octylphenol ether-10 (OP-10) dispersant and 0.1% (by weight) of dibutyltin dilaurate catalyst (DBTDL). The reaction was carried out at 70 °C for 8 h. After the reaction was complete, the mixture was washed with ethyl acetate, filtered, and dried in a drying oven to constant weight to obtain a double-shell microcapsule modified magnesium hydroxide flame retardant.

[0046] Weigh 60g of unsaturated polyester resin (UPR) into a three-necked flask, mechanically stir and heat to 40°C. Add 40g of double-shell microcapsule modified magnesium hydroxide flame retardant and mechanically stir for 30 minutes to mix thoroughly. Then, add 2g of benzoyl peroxide (BPO) and continue stirring for 20 minutes until the curing agent is completely dissolved. Place the mixture in a vacuum drying oven and evacuate until all air bubbles are removed. Then, quickly pour the mixture into a preheated polytetrafluoroethylene mold and use a gradient curing method with the heating program set as follows: cure at 80°C for 2 hours and at 100°C for 2 hours. After cooling and demolding, the UPR material containing double-shell microcapsule modified magnesium hydroxide flame retardant is obtained.

[0047] Comparative Example 3

[0048] Weigh 60g of unsaturated polyester resin (UPR) into a three-necked flask, mechanically stir and heat to 40°C. Add 40g of magnesium hydroxide flame retardant and mechanically stir for 30 minutes to mix thoroughly. Then, add 2g of benzoyl peroxide (BPO) and continue stirring for 20 minutes until the curing agent is completely dissolved. Place the mixture in a vacuum drying oven and evacuate until all air bubbles are removed. Then, quickly pour the mixture into a preheated polytetrafluoroethylene mold and use a gradient curing method, with the heating program set as follows: cure at 80°C for 2 hours, then cure at 100°C for 2 hours. After cooling and demolding, you will obtain UPR material containing only magnesium hydroxide.

[0049] Comparative Example 4

[0050] Weigh 100g of unsaturated polyester resin (UPR) into a three-necked flask, mechanically stir and heat to 40°C. Then, add 2g of benzoyl peroxide (BPO) and continue stirring for 20 minutes until the curing agent is completely dissolved. Place the mixture in a vacuum drying oven and evacuate until all air bubbles are removed. Then, quickly pour the mixture into a preheated polytetrafluoroethylene mold and use a gradient curing method, with the heating program set as follows: cure at 80°C for 2 hours, then cure at 100°C for 2 hours. After cooling and demolding, pure UPR material is obtained.

[0051] Example 3

[0052] 4.75 g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) was added to a three-necked flask, and 38 ml of anhydrous ethanol was added. The temperature was raised to 75 °C to completely dissolve the DOPO. 3.8 g of vinyltriethoxysilane was dissolved in 38 ml of anhydrous ethanol, and 1% (by weight) of azobisisobutyronitrile (AIBN) catalyst was added dropwise. The reaction was carried out at 75 °C for 12 h. 10 g of magnesium hydroxide was added, and the reaction was continued with heating and stirring for another 12 h. After the reaction was complete, the reaction solution was filtered under positive pressure to obtain the product, which was washed three times with anhydrous ethanol. The product was then dried in an oven to constant weight to obtain DOPO-coated modified magnesium hydroxide. 0.2 g of ethyl cellulose (EC) and 30 ml of ethyl acetate were added to a three-necked flask and stirred at 80 °C for 30 min to prepare an EC solution. 10 g of DOPO-coated modified magnesium hydroxide was added, followed by dropwise addition of 0.1% (by weight) of polyoxyethylene octylphenol ether-10 (OP-10) dispersant and 0.1% (by weight) of dibutyltin dilaurate catalyst (DBTDL). The reaction was carried out at 70 °C for 8 h. After the reaction was complete, the mixture was washed with ethyl acetate, filtered, and dried in a drying oven to constant weight to obtain a double-shell microcapsule modified magnesium hydroxide flame retardant.

[0053] Adjust the temperature of the front and rear rollers of the open mill to 80°C and the roller gap to the minimum. Place 60g of ethylene-vinyl acetate copolymer (EVA) between the two rollers and start open milling until the EVA is completely melted and wraps around the rollers. Then slightly increase the roller gap and add 40g of double-shell microcapsule modified magnesium hydroxide flame retardant. Continue open milling until the flame retardant is completely and uniformly incorporated into the EVA matrix. Heat the flame retardant-filled EVA material at 120°C for 10 minutes using a flat vulcanizing machine to obtain EVA material containing double-shell microcapsule modified magnesium hydroxide flame retardant.

[0054] Comparative Example 5

[0055] Adjust the temperature of the front and rear rollers of the open mill to 80°C and the roller gap to the minimum. Place 60g of ethylene-vinyl acetate copolymer (EVA) between the two rollers and start open milling until the EVA is completely melted and wraps around the rollers. Then slightly increase the roller gap and add 40g of magnesium hydroxide flame retardant. Continue open milling until the flame retardant is completely and uniformly incorporated into the EVA matrix. Heat the EVA material filled with flame retardant at 120°C for 10 minutes using a flat vulcanizing machine to obtain EVA material containing only magnesium hydroxide.

[0056] Comparative Example 6

[0057] Adjust the temperature of the front and rear rollers of the open mill to 80°C and the roller gap to the minimum. Place 100g of ethylene-vinyl acetate copolymer (EVA) between the two rollers and start open milling until the EVA is completely melted and wraps around the rollers. Then heat the uniformly molten pure EVA material through a flat vulcanizing machine at 120°C for 10 minutes to obtain pure EVA material.

[0058] Mechanical performance tests, LOI value tests, and UL-94 vertical burning tests were conducted on each of the above embodiments and comparative examples.

[0059] Tensile property testing: The tensile strength and elongation at break of the samples were tested using an INSTRON 3367 twin-column benchtop universal testing machine from INSTRON Corporation, USA, according to the national standard GB / T1040.2-2022. The tensile speed was 10 mm / min, and the test temperature was room temperature. Five specimens were tested for each group of samples, and the average value and standard deviation were calculated.

[0060] Limiting Oxygen Index (LOI) Test: The oxygen index of the sample was determined using a JF-3 limiting oxygen index instrument manufactured by Nanjing Jiangning District Analytical Instrument Factory. The test standard was GB / T 2406.2-2009, and the size of the cuboid sample was 130mm×6.5mm×3mm.

[0061] Vertical flammability test (UL-94): The vertical flammability rating of the sample was determined using a Phoenix Contact PX-3002A automatic horizontal and vertical flammability tester, according to the national standard GB / T 2408-2008. The dimensions of the cuboid sample were 130mm × 13mm × 3mm.

[0062] The mechanical properties of the EP materials of Example 1 and Comparative Examples 1 and 2 are shown in Table 1; the mechanical properties of the UPR materials of Example 2 and Comparative Examples 3 and 4 are shown in Table 2; the mechanical properties of the EVA materials of Example 3 and Comparative Examples 5 and 6 are shown in Table 3; the LOI values ​​and UL-94 vertical burning test results of the EP materials of Example 1 and Comparative Examples 1 and 2 are shown in Table 4; the LOI values ​​and UL-94 vertical burning test results of the UPR materials of Example 2 and Comparative Examples 3 and 4 are shown in Table 5; and the LOI values ​​and UL-94 vertical burning test results of the EVA materials of Example 3 and Comparative Examples 5 and 6 are shown in Table 6.

[0063] Table 1. Mechanical property values ​​of EP materials in Example 1 and Comparative Examples 1 and 2

[0064]

[0065] Table 2. Mechanical properties of UPR materials in Example 2 and Comparative Examples 3 and 4

[0066]

[0067] Table 3. Mechanical properties of EVA materials from Example 3 and Comparative Examples 5 and 6

[0068]

[0069] Table 4. LOI values ​​and UL-94 vertical burning test results of the EP materials in Example 1 and Comparative Examples 1 and 2

[0070]

[0071] Note: NR indicates no flame retardant rating.

[0072] Table 5. LOI values ​​and UL-94 vertical burning test results of UPR materials in Example 2 and Comparative Examples 3 and 4

[0073]

[0074] Note: NR indicates no flame retardant rating.

[0075] Table 6. LOI values ​​and UL-94 vertical burning test results of EVA materials in Example 3 and Comparative Examples 5 and 6

[0076]

[0077] Note: NR indicates no flame retardant rating.

[0078] Figure 2-4 As can be seen, magnesium hydroxide in Comparative Examples 1, 3, and 5 exhibits obvious agglomeration and uneven dispersion; while in Examples 1, 2, and 3, which contain the same amount of flame-retardant filler, the double-shell microcapsule modified magnesium hydroxide is more uniformly dispersed in the polymer matrix and has better compatibility.

[0079] Depend on Figure 5 As can be seen from the data in Table 1, compared with Comparative Example 1 which added the same mass of magnesium hydroxide flame retardant, Example 1 with added double-shell microcapsule modified magnesium hydroxide flame retardant has a tensile strength of 31.89 MPa and an elongation at break of 5.03%, both of which are better than Comparative Example 1's 13.76 MPa and 1.38%, respectively.

[0080] Figure 6 , Figure 7 Tables 2 and 3 further demonstrate that the tensile properties of Examples 2 and 3 are also superior to those of Comparative Examples 3 and 5. This indicates that the double-shell microcapsule modified magnesium hydroxide flame retardant prepared in this invention can effectively mitigate the decline in mechanical properties caused by the addition of flame-retardant fillers in different polymer matrices.

[0081] Figure 8-10The results in Tables 4-6 show that, at the same addition amount, the flame retardant performance of Examples 1-3 is superior to that of Comparative Examples 1, 3, and 5. Examples 1-3 all achieved a V-0 rating in the vertical burning test, while Comparative Examples 1, 3, and 5 showed no rating. This indicates that the double-shell microcapsule modified magnesium hydroxide flame retardant prepared in this invention can effectively improve the flame retardant performance of different polymer matrices.

Claims

1. A double-shell microcapsule modified magnesium hydroxide flame retardant, characterized in that, The core is made of magnesium hydroxide, and the core is covered by an inner wall formed of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and an outer wall formed of ethyl cellulose.

2. A method for preparing the double-shell microcapsule modified magnesium hydroxide flame retardant according to claim 1, characterized in that, Includes the following steps: (1) Dissolve 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and vinyltriethoxysilane separately in anhydrous ethanol, mix them, and add a catalyst to carry out the reaction; (2) Add magnesium hydroxide to the reaction system, and after the reaction is completed, wash, filter and dry to obtain DOPO coated modified magnesium hydroxide; (3) Ethyl cellulose was dissolved in ethyl acetate, and DOPO-coated modified magnesium hydroxide, 2,4-toluene diisocyanate, dispersant and catalyst were added. After the reaction was completed, the mixture was washed, filtered and dried to obtain double-shell microcapsule modified magnesium hydroxide flame retardant.

3. The preparation method of the double-shell microcapsule modified magnesium hydroxide flame retardant according to claim 2, characterized in that, In step (1), the catalyst is azobisisobutyronitrile, and the amount of azobisisobutyronitrile is 1 to 2% of the mass of the system; the reaction temperature is 70 to 90°C, and the reaction time is 10 to 12 hours.

4. The preparation method of the double-shell microcapsule modified magnesium hydroxide flame retardant according to claim 2, characterized in that, In step (2), the reaction temperature is 70-90°C and the reaction time is 6-8 hours.

5. The preparation method of the double-shell microcapsule modified magnesium hydroxide flame retardant according to claim 2, characterized in that, In step (3), the catalyst is dibutyltin dilaurate, and the amount of dibutyltin dilaurate is 0.1-0.2% of the system mass; the dispersant is polyoxyethylene octylphenol ether-10, and the amount of polyoxyethylene octylphenol ether-10 is 0.1-0.2% of the system mass; the reaction temperature is 70-90℃, and the reaction time is 6-8 hours.

6. The preparation method of the double-shell microcapsule modified magnesium hydroxide flame retardant according to claim 2, characterized in that, The drying temperature in step (2) is 50℃~80℃ and the time is 36~48 hours; the drying temperature in step (3) is 50℃~80℃ and the time is 36~48 hours.

7. The application of the double-shell microcapsule modified magnesium hydroxide flame retardant as described in claim 1 in flame retardant materials.

8. The application according to claim 7, characterized in that, A double-shell microcapsule modified magnesium hydroxide flame retardant is added to epoxy resin, stirred, and then a curing agent is added. The mixture is stirred again, poured into a mold, and heated to cure, thus obtaining an epoxy resin flame retardant material containing the double-shell microcapsule modified magnesium hydroxide flame retardant. The curing temperature is 80~160℃, and the curing time is 2~6 hours.

9. The application according to claim 7, characterized in that, The double-shell microcapsule modified magnesium hydroxide flame retardant is added to the unsaturated polyester resin, stirred, and then a curing agent is added. The mixture is stirred again, poured into a mold, and heated to cure, thus obtaining an unsaturated polyester resin flame retardant material containing the double-shell microcapsule modified magnesium hydroxide flame retardant. The curing temperature is 80~120℃, and the curing time is 1~4 hours.

10. The application according to claim 7, characterized in that, A double-shell microcapsule modified magnesium hydroxide flame retardant is added to an ethylene-vinyl acetate copolymer. The ethylene-vinyl acetate copolymer material filled with the flame retardant is then hot-pressed and sheeted to obtain an ethylene-vinyl acetate copolymer flame retardant material containing a double-shell microcapsule modified magnesium hydroxide flame retardant. The hot-pressing temperature is 100℃~120℃, and the hot-pressing time is 10~20 minutes.

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