Structured halogen-free flame-retardant heat-conducting filler and preparation method thereof

Abstract

The invention discloses a structured halogen-free flame-retardant heat-conducting filler and a preparation method thereof, and relates to a filler and a preparation method thereof. The invention aims to solve the problems that the flame-retardant and heat-conducting properties are difficult to balance under the condition of high filling amount, and the dual functions of flame retardance and heat conduction cannot be realized. The invention relates to a structured halogen-free flame-retardant heat-conducting filler which is prepared from caustic calcined magnesite, calcium oxide, a two-dimensional heat-conducting material and a flame-retardant modifier. The method comprises the following steps: 1, weighing; 2, preparing a two-dimensional heat conduction material dispersion liquid; 3, preparing a composite filler; and 4, modifying the filler. The invention relates to a structured halogen-free flame-retardant heat-conducting filler which is a low-smoke, halogen-free and nontoxic flame-retardant heat-conducting additive, is added into a polymer-based composite material and is used for flame-retardant heat-conducting polymer-based composite materials. Compared with the prior art, double functions of flame retardance and heat conduction are realized, and good comprehensive performance can be obtained.

Description

TECHNICAL FIELD

[0001] The present application relates to a filler and a preparation method thereof. BACKGROUND

[0002] With the rapid development of science and technology, electronic components are increasingly high power and high integration, resulting in significant heat accumulation during equipment operation, and the reliability of electronic equipment is exponentially related to operating temperature, temperature rise can significantly shorten the service life of the equipment, and poses a serious challenge to its stability and safety, so the heat dissipation demand is increasingly urgent. In addition, due to the temperature rise of the equipment and the aging phenomenon caused by long-term use, the fire safety hidden danger is significantly increased, and it has been proved to be one of the main causes of electrical fires. In order to meet the heat dissipation demand and fire safety at the same time, the research on materials with high efficient heat conduction and good flame retardant performance has become an important direction.

[0003] From the current development state of flame-retardant heat-conductive composite materials, adding flame-retardant and heat-conductive fillers is still the main way to obtain polymer-based flame-retardant heat-conductive composite materials. Magnesium hydroxide in metal hydroxide is one of the most common flame-retardant additives for polyethylene, polypropylene, ethylene-vinyl acetate copolymer and other polymers. The advantage of magnesium hydroxide as a flame retardant is that it decomposes into active magnesium oxide and water between 300℃ and 340℃, can absorb corrosive gases during combustion, and has flame-retardant and smoke-suppressing effects. However, due to the low flame-retardant efficiency of magnesium hydroxide, high addition amount is usually required to meet the flame-retardant requirements, and the modification of magnesium hydroxide is an important technical means in the research and application fields. However, the thermal conductivity of magnesium hydroxide is limited, and improving the thermal conductivity and flame-retardant function of magnesium hydroxide has become an important problem in its application field. SUMMARY

[0004] The purpose of the present application is to solve the problem that the flame-retardant and heat-conductive performance is difficult to balance at a high filling amount, and the flame-retardant and heat-conductive dual functions cannot be realized, and to provide a structured halogen-free flame-retardant heat-conductive filler and a preparation method thereof.

[0005] Compared with the prior art, the present application realizes the flame-retardant and heat-conductive dual functions, and can obtain good comprehensive performance.

[0006] A structured halogen-free flame-retardant heat-conductive filler is prepared from light burned magnesium, calcium oxide, two-dimensional heat-conductive material and flame-retardant modifier.

[0007] The mass ratio of the light burned magnesium, calcium oxide, two-dimensional heat-conductive material and flame-retardant modifier is 100:(5-40):(1-20):(0-10).

[0008] A preparation method of a structured halogen-free flame-retardant heat-conductive filler is completed according to the following steps:

[0009] I. Weighing:

[0010] According to the mass fraction, 100 parts of light burned magnesium, 5-40 parts of calcium oxide, 1-20 parts of two-dimensional heat-conducting material and 0-10 parts of flame-retardant modifier are taken;

[0011] II. Preparation of two-dimensional heat-conducting material dispersion liquid:

[0012] ①, under stirring, the two-dimensional heat-conducting material is mixed with the solvent, ultrasonic treatment is carried out, and dispersion liquid A is obtained;

[0013] ②, pour the dispersion liquid A into a stainless steel tank, then immerse the stainless steel tank in liquid nitrogen for freezing, and then put it into an ultrasonic cleaning machine for ultrasonic treatment until it melts into a solution, and then put the solution into an ultrasonic cell crusher for ultrasonic treatment, and obtain dispersion liquid B;

[0014] ③, repeat step two 1-5 times to obtain two-dimensional heat-conducting material dispersion liquid C;

[0015] III. Preparation of composite filler:

[0016] Deionized water and two-dimensional heat-conducting material dispersion liquid C are added to a sand mill for grinding, then light burned magnesium is added for grinding, then calcium oxide is added for grinding, and dispersion liquid D is obtained;

[0017] IV. Modification of filler:

[0018] ①, add the flame-retardant modifier to the sand mill containing the dispersion liquid D, grind, and obtain dispersion liquid E;

[0019] ②, centrifuge the dispersion liquid E, dry the solid product obtained by centrifugation, crush and sieve, and obtain the structured halogen-free flame-retardant heat-conducting filler.

[0020] A structured halogen-free flame-retardant heat-conducting filler is a low-smoke, halogen-free and non-toxic flame-retardant heat-conducting additive, which is added to a polymer-based composite material for flame-retardant polymer-based composite material.

[0021] Compared with the prior art, the present application has the following advantages:

[0022] I. The present application provides a method combining ultrasonic and freezing, which realizes efficient exfoliation and dispersion of nanosheets, and is beneficial to the formation of more regular and thinner two-dimensional heat-conducting nanosheets; the method has the advantages of green environmental protection and process controllability, and has cost and performance advantages over traditional exfoliation and dispersion methods, and is beneficial to large-scale preparation;

[0023] II. The present application provides a preparation method for structuring composite of two-dimensional heat-conducting material and inorganic flame retardant, which realizes controllable preparation of two-dimensional nanosheet layer@magnesium hydroxide@calcium hydroxide, and is more suitable for structural regulation and control of two-dimensional heat-conducting material and inorganic flame retardant composite filler compared with the prior art;

[0024] Third, the preparation method of the structured composite filler provided by the application can controllably construct a composite flame retardant on the nanosheet layer, has the advantages of strong implementability, simple process, strong applicability, and the like, and has the characteristics of pollution-free, no by-product, and green and high efficiency in the preparation process compared with the prior art.

[0025] Fourth, the application provides a method for constructing a composite inorganic flame retardant structure in situ, calcium hydroxide is grown on a magnesium hydroxide carrier to form a composite stacked inorganic flame retardant structure, which combines the decomposition characteristics of magnesium hydroxide and the carbon formation characteristics of calcium hydroxide compared with the prior art, and realizes high efficiency and low cost of the inorganic flame retardant.

[0026] Fifth, the application establishes a phosphorus-silicon composite flame retardant modification structure by means of the in-situ hydration modification method, improves the interface interaction between the two-phase systems, and enhances the flame retardant performance of the inorganic flame retardant and the two-dimensional heat-conducting filler, which is more beneficial to the flame-retardant functional modification of the filler and obtains good comprehensive performance compared with the prior art.

[0027] Sixth, the application obtains a structured halogen-free flame-retardant heat-conducting filler, the flame-retardant mechanism of which is mainly based on condensed phase physical interaction, and the heat-conducting mechanism of which is mainly based on percolation mechanism, and the filler has good thermal stability and processing performance and can be used for the preparation of various polymer composites, and meets the requirements of polymer-based composites for flame retardant and heat-conducting dual functions, and is more beneficial to obtaining green and environmentally friendly flame-retardant heat-conducting composites compared with the prior art.

[0028] The application can obtain a structured halogen-free flame-retardant heat-conducting filler. DETAILED DESCRIPTION

[0029] Specific implementation manner one: the implementation manner is a structured halogen-free flame-retardant heat-conducting filler, which is prepared from light-burned magnesium, calcium oxide, two-dimensional heat-conducting material and flame-retardant modifier.

[0030] The mass ratio of the light-burned magnesium, calcium oxide, two-dimensional heat-conducting material and flame-retardant modifier is 100:(5-40):(1-20):(0-10).

[0031] Specific implementation manner two: the difference between the implementation manner and specific implementation manner one is that the purity of the light-burned magnesium is 85-99%, and the average particle size is 0.5-50 microns; preferably, the purity of the light-burned magnesium is 90-95%, and the average particle size is 2-20 microns. The other steps are the same as those in specific implementation manner one.

[0032] Specific embodiment three: the difference between this embodiment and one or two of the specific embodiments is that the purity of the calcium oxide is 85-97%, and the average particle size is 0.5-50 μm; preferably, the purity of the calcium oxide is 90-95%, and the average particle size is 2-20 μm. The other steps are the same as those in specific embodiment one or two.

[0033] Specific embodiment four: the difference between this embodiment and one of the specific embodiments one to three is that the two-dimensional heat-conducting material is a mixture of one or several of hexagonal boron nitride, graphene nanosheet and graphene oxide nanosheet. The other steps are the same as those in specific embodiments one to three.

[0034] Specific embodiment five: the difference between this embodiment and one of the specific embodiments one to four is that the average particle size of the hexagonal boron nitride is 0.2-20 μm; the average particle size of the graphene nanosheet is 0.2-20 μm; the average particle size of the graphene oxide nanosheet is 0.2-20 μm. The other steps are the same as those in specific embodiments one to four.

[0035] Specific embodiment six: the difference between this embodiment and one of the specific embodiments one to five is that the flame-retardant modifier is one or both of hydroxyl silicone oil and 2-carboxyethyl phenyl phosphinic acid; the mass ratio of hydroxyl silicone oil and 2-carboxyethyl phenyl phosphinic acid is (0-1):(0-1). The other steps are the same as those in specific embodiments one to five.

[0036] Specific embodiment seven: this embodiment is a preparation method of a structured halogen-free flame-retardant heat-conducting filler, which is completed according to the following steps:

[0037] I. Weighing:

[0038] 100 parts of light burned magnesium, 5-40 parts of calcium oxide, 1-20 parts of two-dimensional heat-conducting material and 0-10 parts of flame-retardant modifier are weighed according to the mass fraction;

[0039] II. Preparation of two-dimensional heat-conducting material dispersion liquid:

[0040] ①, under stirring, the two-dimensional heat-conducting material is mixed with the solvent, ultrasonic treatment is carried out, and dispersion liquid A is obtained;

[0041] ②, pour dispersion liquid A into a stainless steel tank, then immerse the stainless steel tank in liquid nitrogen for freezing, then put it into an ultrasonic cleaning machine for ultrasonic treatment until it melts into a solution, and then put the solution into an ultrasonic cell crusher for ultrasonic treatment, to obtain dispersion liquid B;

[0042] ③, repeat step two 1-5 times to obtain two-dimensional heat-conducting material dispersion liquid C;

[0043] III. Preparation of composite filler:

[0044] Deionized water and two-dimensional heat conductive material dispersion liquid C were added into a sand mill for grinding, then light burned magnesium was added for grinding, then calcium oxide was added for grinding, to obtain dispersion liquid D;

[0045] Four, modification of the filler:

[0046] ① The flame-retardant modifier was added into the sand mill containing dispersion liquid D for grinding, to obtain dispersion liquid E;

[0047] ② The dispersion liquid E was centrifuged, and then the solid product obtained by centrifugation was dried, crushed, and sieved, to obtain the structured halogen-free flame-retardant heat conductive filler.

[0048] Specific embodiment eight: the difference between this embodiment and one of the specific embodiments one to seven is that the mass to volume ratio of the two-dimensional heat conductive material to the solvent in step two ① is (0.4~8g):(100~120mL); the solvent in step two ① is a mixture of deionized water and anhydrous ethanol, wherein the volume ratio of deionized water to anhydrous ethanol is 100:(1~20); the power of ultrasonic treatment in step two ① is 200~600W, and the ultrasonic treatment time is 1~10min; the power of the ultrasonic cleaning machine in step two ② is 50~250W; the power of the ultrasonic cell crusher in step two ② is 200~600W, and the ultrasonic treatment time is 1~10min. The other steps are the same as those in specific embodiments one to seven.

[0049] Specific embodiment nine: the difference between this embodiment and one of the specific embodiments one to eight is that the grinding speed in step two ① is 500~2000rpm, and the grinding time is 0.1h~8h; the mass ratio of deionized water to two-dimensional heat conductive material in dispersion liquid C in step two ① is 100mL:(0.1~2g); the grinding speed in step four ① is 500~2000rpm, and the grinding time is 0.5~5h; the centrifugation rate in step four ② is 500~4000r / min, and the centrifugation time is 5~60min; the drying temperature in step four ② is 80~120℃, and the drying time is 6~24h; the sieving in step four ② is 40~100 mesh. The other steps are the same as those in specific embodiments one to eight.

[0050] Specific embodiment ten: the structured halogen-free flame-retardant heat conductive filler is a low-smoke, halogen-free, and non-toxic flame-retardant heat conductive additive, which is added into a heat conductive polymer-based composite material for flame-retardant polymer-based composite material; specifically, the structured halogen-free flame-retardant heat conductive filler can be used for plastic modification, low-smoke halogen-free flame-retardant cable material, and flame-retardant heat conductive plastic manufacturing.

[0051] The following examples are used to verify the beneficial effects of the present application, and the following description is merely exemplary, but not intended to limit the scope of the present application and its applications. In order to clarify the effect of the examples, the following raw materials are used: the purity and average particle size of the light burned magnesium are 94% and 15 μm respectively; the purity and average particle size of the calcium oxide are 97% and 15 μm respectively; the average particle size of the hexagonal boron nitride is 0.3 μm, the average particle size of the graphene nanosheet is 5 μm, and the average particle size of the graphite oxide nanosheet is 3 μm; 2-carboxyethyl phenyl hypophosphorous acid (industrial product); hydroxyl silicone oil (solid content is 30%); ethylene-vinyl acetate copolymer (EVA) with a vinyl acetate content of 26%, a density of 0.938 g / cm 3 , and a melt index of 4.0 g / 10 min (2.16 kg@190°C).

[0052] Example 1: A structured halogen-free flame-retardant heat-conducting filler is prepared from light burned magnesium, calcium oxide, two-dimensional heat-conducting material and flame-retardant modifier;

[0053] The mass ratio of the light burned magnesium, calcium oxide, two-dimensional heat-conducting material and flame-retardant modifier is 100:25:2.5:6.25;

[0054] The two-dimensional heat-conducting material is hexagonal boron nitride;

[0055] The flame-retardant modifier is a mixture of hydroxyl silicone oil and 2-carboxyethyl phenyl hypophosphorous acid, and the mass ratio of the hydroxyl silicone oil and 2-carboxyethyl phenyl hypophosphorous acid is 4:1;

[0056] The preparation method of the structured halogen-free flame-retardant heat-conducting filler is specifically completed by the following steps:

[0057] I. Weighing:

[0058] 48 g of light burned magnesium, 12 g of calcium oxide, 1.2 g of hexagonal boron nitride and 3.0 g of flame-retardant modifier are weighed;

[0059] II. Preparation of two-dimensional heat-conducting material dispersion liquid:

[0060] ①, under stirring, 1.2 g of hexagonal boron nitride, 120 mL of deionized water and 12 mL of anhydrous ethanol are mixed, and ultrasonic treatment is carried out at a power of 520 W for 6 min to obtain dispersion liquid A;

[0061] ②, pour the dispersion liquid A into a stainless steel tank, then immerse the stainless steel tank in liquid nitrogen for freezing, and then put it into an ultrasonic cleaning machine for ultrasonic treatment at a power of 130 W until it melts into a solution, and then put the solution into an ultrasonic cell crusher and ultrasonic treat it at a power of 520 W for 6 min to obtain dispersion liquid B;

[0062] ③, repeat step two ② for 5 times to obtain dispersion liquid C containing 1.2 g of hexagonal boron nitride;

[0063] III. Preparation of the composite filler:

[0064] ①, 280 mL of deionized water and dispersion liquid C containing 1.2 g of hexagonal boron nitride were added to a sand mill, and ground at a speed of 2000 rpm for 0.5 h, then 48 g of light burned magnesium was added, and ground at a speed of 2000 rpm for 2 h, then 12 g of calcium oxide was added, and ground at a speed of 2000 rpm for 2 h, to obtain dispersion liquid D;

[0065] IV. Modification of the filler:

[0066] ①, 3.0 g of flame-retardant modifier was added to the sand mill containing dispersion liquid D, and ground at a speed of 2000 rpm for 1 h to obtain dispersion liquid E;

[0067] ②, the dispersion liquid E was centrifuged at a centrifugal speed of 4000 r / min for 30 min, and then the solid product obtained by centrifugation was dried in an oven at 120℃ for 24 h, and then crushed and sieved through a 100 mesh sieve to obtain the structured halogen-free flame-retardant thermal conductive filler.

[0068] Example 2: A structured halogen-free flame-retardant thermal conductive filler is prepared from light burned magnesium, calcium oxide and two-dimensional thermal conductive material;

[0069] The mass ratio of the light burned magnesium, calcium oxide and two-dimensional thermal conductive material is 100:25:2.5;

[0070] The two-dimensional thermal conductive material is hexagonal boron nitride;

[0071] The preparation method of the structured halogen-free flame-retardant thermal conductive filler is specifically completed by the following steps:

[0072] I. Weighing:

[0073] 48 g of light burned magnesium, 12 g of calcium oxide and 1.2 g of hexagonal boron nitride were weighed;

[0074] II. Preparation of two-dimensional thermal conductive material dispersion liquid:

[0075] ①, under stirring, 1.2 g of hexagonal boron nitride, 120 mL of deionized water and 12 mL of anhydrous ethanol were mixed, and ultrasonic treated at a power of 520 W for 6 min to obtain dispersion liquid A;

[0076] ②, the dispersion liquid A was poured into a stainless steel tank, then the stainless steel tank was immersed in liquid nitrogen for freezing, and then placed in an ultrasonic cleaner for ultrasonic treatment at a power of 130 W until melted into a solution, and the solution was placed in an ultrasonic cell crusher and ultrasonic treated at a power of 520 W for 6 min to obtain dispersion liquid B;

[0077] ③、Repeat step two ② 5 times to obtain dispersion liquid C containing 1.2g hexagonal boron nitride;

[0078] III. Preparation of the composite filler:

[0079] ①, 280mL of deionized water and dispersion liquid C containing 1.2g of hexagonal boron nitride were added to the sand mill, and ground at a speed of 2000rpm for 0.5h, then 48g of light burned magnesium was added, and ground at a speed of 2000rpm for 2h, then 12g of calcium oxide was added, and ground at a speed of 2000rpm for 2h, to obtain dispersion liquid D;

[0080] IV. Centrifuging dispersion liquid D at a centrifugal speed of 4000r / min for 30min, then putting the solid product obtained by centrifugation into an oven at 120℃ and drying for 24h, then crushing and passing through a 100 mesh sieve to obtain the structured halogen-free flame-retardant thermal conductive filler.

[0081] Example 3: A structured halogen-free flame-retardant thermal conductive filler is prepared from light burned magnesium, calcium oxide and two-dimensional thermal conductive material;

[0082] The mass ratio of the light burned magnesium, calcium oxide and two-dimensional thermal conductive material is 100:25:2.5;

[0083] The two-dimensional thermal conductive material is graphene nanosheet;

[0084] The preparation method of the structured halogen-free flame-retardant thermal conductive filler is specifically completed by the following steps:

[0085] I. Weighing:

[0086] Weighing 48g of light burned magnesium, 12g of calcium oxide and 1.2g of graphene nanosheet;

[0087] II. Preparation of two-dimensional thermal conductive material dispersion liquid:

[0088] ①, Under stirring conditions, 1.2g of graphene nanosheet, 120mL of deionized water and 12mL of anhydrous ethanol were mixed, and ultrasonic treatment was carried out at a power of 520W for 6min to obtain dispersion liquid A;

[0089] ②, Pouring dispersion liquid A into a stainless steel tank, then immersing the stainless steel tank into liquid nitrogen for freezing, then putting it into an ultrasonic cleaner for ultrasonic treatment at a power of 130W until it melts into a solution, and then putting the solution into an ultrasonic cell crusher for ultrasonic treatment at a power of 520W for 6min to obtain dispersion liquid B;

[0090] ③, Repeat step two ② 5 times to obtain dispersion liquid C containing 1.2g of hexagonal boron nitride;

[0091] III. Preparation of the composite filler:

[0092] ①, 280 mL of deionized water and dispersion liquid C containing 1.2 g of graphene nanosheet were added into a sand mill, and grinded at a speed of 2000 rpm for 0.5 h, then 48 g of light burned magnesium was added, and grinded at a speed of 2000 rpm for 2 h, then 12 g of calcium oxide was added, and grinded at a speed of 2000 rpm for 2 h, to obtain dispersion liquid D;

[0093] Four, the dispersion liquid D was centrifuged at a centrifugal speed of 4000 r / min for 30 min, and the solid product obtained by centrifugation was placed in an oven at 120℃ and dried for 24 h, then crushed and sieved through a 100 mesh sieve to obtain a structured halogen-free flame-retardant thermal conductive filler.

[0094] Example 4: A structured halogen-free flame-retardant thermal conductive filler is prepared from light burned magnesium, calcium oxide and two-dimensional thermal conductive material;

[0095] The mass ratio of the light burned magnesium, calcium oxide and two-dimensional thermal conductive material is 100:25:2.5;

[0096] The two-dimensional thermal conductive material is graphene oxide nanosheet;

[0097] The preparation method of the structured halogen-free flame-retardant thermal conductive filler is specifically completed by the following steps:

[0098] I. Weighing:

[0099] 48 g of light burned magnesium, 12 g of calcium oxide and 1.2 g of graphene oxide nanosheet were weighed;

[0100] II. Preparation of two-dimensional thermal conductive material dispersion liquid:

[0101] ①, 1.2 g of graphene oxide nanosheet, 120 mL of deionized water and 12 mL of anhydrous ethanol were mixed under stirring, and ultrasonic treated at a power of 520 W for 6 min to obtain dispersion liquid A;

[0102] ②, pour the dispersion liquid A into a stainless steel tank, then immerse the stainless steel tank in liquid nitrogen for freezing, then put it into an ultrasonic cleaner and ultrasonic treat at a power of 130 W until it melts into a solution, then place the solution in an ultrasonic cell crusher and ultrasonic treat at a power of 520 W for 6 min to obtain dispersion liquid B;

[0103] ③, repeat step two ② for 5 times to obtain dispersion liquid C containing 1.2 g of hexagonal boron nitride;

[0104] III. Preparation of composite filler:

[0105]

[0106] Four, the dispersion liquid D is centrifuged at 4000r / min for 30min, then the solid product obtained by centrifugation is placed in an oven at 120℃ for drying for 24h, then crushed and sieved through a 100 mesh sieve to obtain the structured halogen-free flame-retardant and heat-conducting filler.

[0107] Example 5: A structured halogen-free flame-retardant and heat-conducting filler is prepared from light burned magnesium, calcium oxide and flame-retardant modifier.

[0108] The mass ratio of the light burned magnesium, calcium oxide and flame-retardant modifier is 100:25:6.25.

[0109] The flame-retardant modifier is a mixture of hydroxyl silicone oil and 2-carboxyethyl phenyl hypophosphite, and the mass ratio of the hydroxyl silicone oil and 2-carboxyethyl phenyl hypophosphite is 4:1.

[0110] The preparation method of the structured halogen-free flame-retardant and heat-conducting filler is specifically completed by the following steps:

[0111] I. Weighing:

[0112] Weigh 48g of light burned magnesium, 12g of calcium oxide and 3.0g of flame-retardant modifier.

[0113] ①, 400mL of deionized water and 48g of light burned magnesium are added to a sand mill, and ground at a speed of 2000rpm for 2h, then 12g of calcium oxide is added, and ground at a speed of 2000rpm for 2h to obtain dispersion liquid A;

[0114] II. Modification of the filler:

[0115] ①, 3.0g of flame-retardant modifier is added to the sand mill containing dispersion liquid A, and ground at a speed of 2000rpm for 1h to obtain dispersion liquid B;

[0116] ②, the dispersion liquid B is centrifuged at 4000r / min for 30min, then the solid product obtained by centrifugation is placed in an oven at 120℃ for drying for 24h, then crushed and sieved through a 100 mesh sieve to obtain the structured halogen-free flame-retardant and heat-conducting filler.

[0117] Example 6: A structured halogen-free flame-retardant and heat-conducting filler is prepared from light burned magnesium and calcium oxide.

[0118] The mass ratio of the light burned magnesium and calcium oxide is 100:25.​

[0119] The preparation method of the structured halogen-free flame-retardant heat-conducting filler is specifically completed by the following steps:

[0120] I. Weighing:

[0121] Weigh 48g of light burned magnesium and 12g of calcium oxide;

[0122] ①, 400mL of deionized water and 48g of light burned magnesium were added to the sand mill and ground at a speed of 2000rpm for 2h, then 12g of calcium oxide was added and ground at a speed of 2000rpm for 2h to obtain dispersion A;

[0123] II. The dispersion A was centrifuged at a centrifugal speed of 4000r / min for 30min, and the solid product obtained by centrifugation was placed in a 120℃ oven and dried for 24h, then crushed and sieved through a 100 mesh sieve to obtain the structured halogen-free flame-retardant heat-conducting filler.

[0124] Comparative Example 1: Preparation method of magnesium hydroxide flame retardant, which is specifically completed by the following steps:

[0125] ①, 400mL of deionized water and 60g of light burned magnesium were poured into the sand mill and reacted at a speed of 2000rpm for 2h to obtain mixed liquid A; ②, the mixed liquid A was treated with a centrifuge at a centrifugal speed of 4000r / min for 30min; the solid product obtained by centrifugation was placed in a 120℃ oven and dried for 24h; the dried product was crushed and sieved through a 100 mesh sieve to obtain the magnesium hydroxide flame retardant.

[0126] Comparative Example 2: Preparation method of calcium hydroxide flame retardant, which is specifically completed by the following steps:

[0127] ①, 400mL of deionized water and 60g of calcium oxide were poured into the sand mill and reacted at a speed of 2000rpm for 2h to obtain mixed liquid A; ②, the mixed liquid A was treated with a centrifuge at a centrifugal speed of 4000r / min for 30min; the solid product obtained by centrifugation was placed in a 120℃ oven and dried for 24h; the dried product was crushed and sieved through a 100 mesh sieve to obtain the calcium hydroxide flame retardant.

[0128] Comparative Example 3:

[0129] The magnesium hydroxide prepared in Comparative Example 1 and the calcium hydroxide prepared in Comparative Example 2 were mixed in a mass ratio of 4:1, and mixed with a high-speed mixer at a speed of 28000rpm for 30s to obtain a calcium-magnesium mixed flame retardant.

[0130] To compare the effect of the designed halogen-free flame-retardant heat-conducting filler, the filler prepared in Examples 1-6 and Comparative Examples 1-3 was compounded with EVA in the proportions shown in Table 1. The specific steps were as follows: ① The EVA and the filler were mixed at a mass ratio of 9:11 using a high-speed mixer at a speed of 28000 rpm for 30 s to obtain a premixed material; ② The premixed material was mixed in a torque rheometer at 140℃ at a speed of 30-70 rpm for 20 min, and then pressed in a flat vulcanizing machine at 140℃, 5 MPa for 5 min and 10 MPa for 5 min to obtain a halogen-free flame-retardant heat-conducting composite material; the mass parts of the halogen-free flame-retardant heat-conducting composite material are shown in Table 1; the properties of each halogen-free flame-retardant heat-conducting composite material in Table 1 are shown in Table 2.

[0131] Table 1

[0132]

[0133] Table 2

[0134]

[0135] As shown in Table 2, compared with Comparative Example 1, Comparative Example 2 and Comparative Example 3, the structured halogen-free flame-retardant filler of Example 6 has better flame-retardant effect, and the UL-94 grade of the composite material F is improved to V-1 level, and the oxygen index is increased by 8.4%, 3.0% and 18.3% respectively compared with the composite materials G, H and I. Under the action of flame-retardant modification, compared with the structured halogen-free flame-retardant filler of Example 6, the addition of the structured halogen-free flame-retardant filler of Example 5 improves the UL-94 grade of the composite material E from V-1 level to V-0 level. Under the action of the two-dimensional heat-conducting material, the structured halogen-free flame-retardant heat-conducting fillers of Examples 2, 3 and 4 improve the flame-retardant performance and the thermal conductivity of the composite material, wherein the thermal conductivity of the composite materials B, C and D is increased by 12.5%, 21.9% and 2% respectively compared with the composite material F. Under the joint action of the two-dimensional heat-conducting material and the flame-retardant modifier, the structured halogen-free flame-retardant heat-conducting filler of Example 1 improves the flame-retardant performance and the thermal conductivity of the composite material, and the oxygen index and the vertical combustion grade of the composite material A are 30.3% and V-0 respectively, and the thermal conductivity is 0.74 W / (m·K).

Claims

1. A structured halogen-free flame-retardant and thermally conductive filler, characterized in that... The structured halogen-free flame-retardant thermally conductive filler is prepared from lightly calcined magnesium, calcium oxide, two-dimensional thermally conductive materials and flame-retardant modifiers; The mass ratio of the lightly calcined magnesium, calcium oxide, two-dimensional thermally conductive material and flame retardant modifier is 100:(5~40):(1~20):(0~10).

2. The structured halogen-free flame-retardant thermally conductive filler according to claim 1, characterized in that... The purity of the lightly calcined magnesium is 85-99%, and the average particle size is 0.5-50 μm.

3. The structured halogen-free flame-retardant and thermally conductive filler according to claim 1, characterized in that... The calcium oxide has a purity of 85-97% and an average particle size of 0.5-50 μm.

4. The structured halogen-free flame-retardant thermally conductive filler according to claim 1, characterized in that... The two-dimensional thermally conductive material is one or a mixture of several of hexagonal boron nitride, graphene nanosheets, and graphene oxide nanosheets.

5. A structured halogen-free flame-retardant thermally conductive filler according to claim 4, characterized in that... The average particle size of the hexagonal boron nitride is 0.2~20μm; the average particle size of the graphene nanosheets is 0.2~20μm; and the average particle size of the graphene oxide nanosheets is 0.2~20μm.

6. The structured halogen-free flame-retardant thermally conductive filler according to claim 1, characterized in that... The flame retardant modifier is one or both of hydroxyl silicone oil and 2-carboxyethylphenyl hypophosphite; the mass ratio of hydroxyl silicone oil to 2-carboxyethylphenyl hypophosphite is (0~1):(0~1).

7. The method for preparing a structured halogen-free flame-retardant thermally conductive filler as described in claim 1, characterized in that... The preparation method is specifically carried out according to the following steps: I. Weighing materials: Weigh out 100 parts of lightly calcined magnesium, 5-40 parts of calcium oxide, 1-20 parts of two-dimensional thermal conductive material and 0-10 parts of flame retardant modifier according to the following mass percentages; II. Preparation of two-dimensional thermally conductive material dispersion: ① Under stirring conditions, the two-dimensional thermally conductive material is mixed with a solvent and ultrasonically treated to obtain dispersion A; ② Pour dispersion A into a stainless steel tank, then immerse the stainless steel tank in liquid nitrogen to freeze it, and then place it in an ultrasonic cleaner to ultrasonically treat it until it melts into a solution. Place the solution in an ultrasonic cell disruptor for ultrasonic treatment to obtain dispersion B. ③ Repeat step 2.1 to 5 times to obtain a two-dimensional thermally conductive material dispersion C; III. Preparation of composite fillers: Deionized water and two-dimensional thermally conductive material dispersion C were added to a sand mill and ground. Then, lightly calcined magnesium was added and ground again. Then, calcium oxide was added and ground again to obtain dispersion D. IV. Modification of fillers: ① Add the flame retardant modifier to a sand mill containing dispersion D and grind it to obtain dispersion E; ② Centrifuge the dispersion E, then dry, pulverize, and sieve the resulting solid product to obtain the structured halogen-free flame-retardant thermally conductive filler.

8. The method for preparing a structured halogen-free flame-retardant thermally conductive filler according to claim 7, characterized in that... In step 2①, the mass ratio of the two-dimensional thermally conductive material to the volume ratio of the solvent is (0.4~8g):(100~120mL); the solvent in step 2① is a mixture of deionized water and anhydrous ethanol, wherein the volume ratio of deionized water to anhydrous ethanol is 100:(1~20); the power of the ultrasonic treatment in step 2① is 200~600W, and the ultrasonic treatment time is 1~10min; the power of the ultrasonic cleaner in step 2② is 50~250W; the power of the ultrasonic cell disruptor in step 2② is 200~600W, and the ultrasonic treatment time is 1~10min.

9. The method for preparing a structured halogen-free flame-retardant thermally conductive filler according to claim 7, characterized in that... The grinding speed in step 2① is 500~2000 rpm, and the grinding time is 0.1h~8h; the mass ratio of deionized water to the two-dimensional thermally conductive material in the two-dimensional thermally conductive material dispersion C in step 2① is 100mL:(0.1~2g); the grinding speed in step 4① is 500~2000 rpm, and the grinding time is 0.5~5h; the centrifugation rate in step 4② is 500~4000r / min, and the centrifugation time is 5~60min; the drying time in step 4② is 80~120℃, and the drying time is 6~24h; the sieving in step 4② is through a 40~100 mesh sieve.

10. The application of the structured halogen-free flame-retardant thermally conductive filler as described in claim 1, characterized in that... A structured halogen-free flame-retardant thermally conductive filler is a low-smoke, halogen-free, and non-toxic flame-retardant thermally conductive additive that is added to polymer-based composite materials for use in flame-retardant thermally conductive polymer-based composite materials.

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