Silane modified magnesium hydroxide as well as preparation method and application thereof

Abstract

The invention relates to the technical field of inorganic materials, in particular to silane modified magnesium hydroxide and a preparation method and application thereof.The preparation method comprises the steps that brine and excessive alkali liquor are mixed and react to prepare magnesium hydroxide slurry; a modifying agent is added into an alcoholic solution with a certain pH value for hydrolysis to obtain a hydrolysis modifying agent, the modifying agent comprises a silane coupling agent and an organic silicon modifying agent, and the mass ratio of the silane coupling agent to the organic silicon modifying agent is (3-5): 1; adding the hydrolysis modifier into the magnesium hydroxide slurry for reaction; and after the reaction is finished, filtering, washing and drying to obtain the silane modified magnesium hydroxide. The prepared magnesium hydroxide is small in specific surface area, uniform in particle size and good in compatibility with polymers, can be added into a polymer base material in a large scale without deteriorating the mechanical property of the material, can be applied to EVA / PE or LLDPE / POE / EVA, can realize high filling of filler, and can effectively improve the flame retardant property of the material.

Description

Technical Field

[0001] The present invention relates to a silane-modified magnesium hydroxide, its preparation method and application, belonging to the technical field of inorganic materials. Background Art

[0002] As an efficient and environmentally friendly inorganic flame retardant, magnesium hydroxide is widely used in polymer materials. However, magnesium hydroxide has a strong surface polarity and poor compatibility with organic polymer materials, resulting in uneven dispersion in the matrix and affecting the mechanical properties and flame retardancy of the composite material. In addition, magnesium hydroxide has a large specific surface area and is prone to agglomeration, further exacerbating its dispersion problem.

[0003] Traditional methods for preparing magnesium hydroxide usually use brine as raw material, obtain magnesium hydroxide slurry through precipitation method, and then obtain magnesium hydroxide powder through steps such as filtration, washing, and drying. The magnesium hydroxide prepared by this method has a large specific surface area, and subsequent surface modification is required to improve its compatibility with polymers. The process is complex and the cost is high. In order to improve the surface properties of magnesium hydroxide and enhance its compatibility with polymer materials, surface modification methods are usually used to treat magnesium hydroxide. At present, there are mainly two methods for modifying magnesium hydroxide with silane coupling agent: dry method modification and wet method modification. The dry method modification process is simple, but the modification effect is uneven; although the wet method modification process is relatively complex, the modification effect is better and the utilization rate of the modifier is high. The patent application with publication number CN118852735A discloses an ultrafine magnesium hydroxide, its preparation method and a polyethylene high-flame-retardant low-smoke halogen-free cable material. The magnesite ore is sequentially crushed and ground to obtain magnesium hydroxide powder; the magnesium hydroxide powder and a grinding aid are mixed and then ball-milled to obtain a mixture; the mixture, calcium carbonate and a modifier are mixed and then subjected to surface modification treatment to obtain ultrafine magnesium hydroxide. However, the addition amount of the magnesium hydroxide prepared by this method in the polyethylene cable material is relatively small, and the improvement of the flame retardancy is relatively limited. Summary of the Invention

[0004] Aiming at the deficiencies of the existing technology, the present invention provides a silane-modified magnesium hydroxide, its preparation method and application, to solve the problems that magnesium hydroxide has strong surface polarity, large specific surface area, poor compatibility with polymer substrates, and cannot be added in large amounts. Through the technical means of the present invention, the obtained magnesium hydroxide has a small specific surface area, is not easy to agglomerate, has good compatibility with polymers, can be added to polymers in large amounts, and will not deteriorate the mechanical properties of the material.

[0005] The technical solution for the present invention to solve the above technical problems is as follows: A preparation method of a silane-modified magnesium hydroxide, the preparation method is:

[0006] S1. Mix brine and an excessive amount of alkali solution in proportion and react to prepare a magnesium hydroxide slurry;

[0007] S2. Add the modifier into an alcohol solution with a certain pH value in proportion for hydrolysis to obtain a hydrolyzed modifier. The modifier includes a silane coupling agent and an organosilicon modifier, and the mass ratio of the silane coupling agent to the organosilicon modifier is (3 - 5):1;

[0008] S3. Add the hydrolyzed modifier into the magnesium hydroxide slurry for reaction, and control the reaction time, temperature, and stirring rate;

[0009] S4. After the reaction is completed, filter, wash, and dry to obtain silane-modified magnesium hydroxide.

[0010] Further, the silane coupling agent is at least one of vinyl-tris(2-methoxyethoxy)silane, vinyltrimethoxysilane, vinylmethyldimethoxysilane, methyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane.

[0011] Further, the organosilicon modifier is at least one of dimethyl silicone oil, hydrogen-containing silicone oil, amino silicone oil, epoxy silicone oil, and hydroxy silicone oil.

[0012] Further, the mass ratio of the modifier to the alcohol is 1:(3 - 5).

[0013] Further, the hydrolysis time is 0.5 - 1 h; the pH of the alcohol solution is 11 - 13.

[0014] Further, the dosage of the modifier is 0.3 - 0.5% of the mass of magnesium hydroxide.

[0015] Further, in step S3, the stirring speed is controlled at 150 - 500 rpm, the reaction temperature is 50 - 80 °C, and the reaction time is 60 - 120 min.

[0016] The present invention also discloses a silane-modified magnesium hydroxide, which is prepared by the preparation method described in the present invention.

[0017] The present invention also discloses an application of the silane-modified magnesium hydroxide, and the silane-modified magnesium hydroxide is applied to EVA / PE or LLDPE / POE / EVA materials.

[0018] Further, the silane-modified magnesium hydroxide is applied to EVA / PE and LLDPE / POE / EVA materials to obtain EVA / PE and LLDPE / POE / EVA composite materials. The mass content of the silane-modified magnesium hydroxide in the EVA / PE composite material is 60 - 75%, and the mass content of the silane-modified magnesium hydroxide in the LLDPE / POE / EVA composite material is 65 - 78%.

[0019] The beneficial effects of the present invention are as follows:

[0020] The silane-modified magnesium hydroxide of the present invention adopts a direct wet modification technical means, with a simple process flow. The filtrate can be recycled, the production cost is low, and it is easy to be industrially produced. By directly performing wet modification on the magnesium hydroxide slurry at the back end of production, the modifier is more uniformly coated on the surface of magnesium hydroxide, avoiding the agglomeration of magnesium hydroxide particles. The obtained magnesium hydroxide has a small specific surface area, uniform particle size, good dispersibility, and good compatibility with polymers. It can be added in large amounts, which is beneficial to improving the mechanical properties and flame retardancy of the composite material. The preparation method of the silane-modified magnesium hydroxide has a simple process, high utilization rate of the modifier, and good modification effect. The silane-modified magnesium hydroxide has a small specific surface area and can be more applied to EVA / PE, LLDPE / POE / EVA materials, with more excellent flame retardancy.

[0021] The present invention uses brine and alkali solution as raw materials to prepare magnesium hydroxide, and directly performs wet modification on the magnesium hydroxide slurry. By controlling the reaction conditions, the modifier is fully hydrolyzed and chemically reacts with the surface of magnesium hydroxide to form an organic film on the surface of magnesium hydroxide, thereby improving the surface properties of magnesium hydroxide and enhancing its compatibility with polymer materials. This method omits the steps of filtering, washing, drying the magnesium hydroxide slurry and re-modifying the magnesium hydroxide powder in the traditional method. It is completed in one step from production to modification, simplifies the process flow, and reduces the production cost. Directly performing wet modification in the magnesium hydroxide slurry can make the silane coupling agent more uniformly coated on the surface of magnesium hydroxide, improving the modification effect. Since the intermediate drying step is omitted, the agglomeration of magnesium hydroxide particles is avoided, and the obtained modified magnesium hydroxide has a small specific surface area and good dispersibility. The introduction of the modifier improves the surface properties of magnesium hydroxide and enhances its compatibility with polymers, which is beneficial to improving the mechanical properties and flame retardancy of the composite material. This method is easy to operate, does not require additional equipment, has a low addition amount of the modifier, high utilization rate, the filtrate can be recycled, the production cost is low, and it is easy to be industrially produced.

[0022] The magnesium hydroxide modified by silane according to the present invention is added to EVA / PE and LLDPE / POE / EVA materials. The addition amount in EVA / PE can be as high as 60-75%, making the oxygen index of the composite material as high as 53-65%, the vertical burning grade reaching V-0, and the mechanical properties of the composite material being good, with the strength reaching 16-18 MPa and the elongation at break being 124-253%. When applied to LLDPE / POE / EVA materials, the addition amount can be as high as 65-78%, the oxygen index of the composite material is as high as 50-68%, the vertical burning grade reaches V-0, the strength can reach 17-20 MPa, and the elongation at break is 150-280%. The modified magnesium hydroxide of the present invention has good modification effect, high utilization rate of the modifier, small specific surface area, simple process flow, low production cost, can be added to polymers in large amounts, and will not deteriorate the mechanical properties of the materials. Detailed Description of the Invention

[0023] The following makes a detailed description of the specific embodiments of the present invention. The present invention can be implemented in many other ways different from those described herein. Those skilled in the art can make similar improvements without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used are only for describing specific embodiments and do not limit the present invention.

[0025] A preparation method of magnesium hydroxide modified by silane, the preparation method is as follows:

[0026] S1. Mix brine and excessive alkali solution in proportion for reaction to prepare a magnesium hydroxide slurry;

[0027] S2. Add the modifier to an alcohol solution with a certain pH value in proportion for hydrolysis to obtain a hydrolyzed modifier. The modifier includes a silane coupling agent and an organosilicon modifier, and the mass ratio of the silane coupling agent to the organosilicon modifier is (3-5):1;

[0028] S3. Add the hydrolyzed modifier to the magnesium hydroxide slurry for reaction, and control the reaction time, temperature and stirring rate;

[0029] S4. After the reaction is completed, filter, wash and dry to obtain magnesium hydroxide modified by silane.

[0030] More specifically, the brine is sea brine, the main substances are sodium chloride, magnesium chloride, magnesium sulfate, etc., and the content of magnesium salt is 18-25%. The alkali solution is an aqueous solution of sodium hydroxide or ammonia water.

[0031] More specifically, the preparation method of the magnesium hydroxide slurry in the embodiments of the present invention is as follows: First, the brine is decolorized and purified, and then a sodium hydroxide solution is added. The concentration of sodium hydroxide is 25%, and the mass ratio of the brine to the sodium hydroxide solution is 1:1.2. The reaction temperature is controlled at 120 °C, and the reaction is carried out for 2 h to obtain the magnesium hydroxide slurry.

[0032] Preferably, the mass ratio of the silane coupling agent to the organosilicon modifier is (3.5-5):1.

[0033] Specifically, the silane coupling agent is at least one of vinyl-tris(2-methoxyethoxy)silane, vinyltrimethoxysilane, vinylmethyldimethoxysilane, methyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane.

[0034] Specifically, the organosilicon modifier is at least one of dimethyl silicone oil, hydrogen-containing silicone oil, amino silicone oil, epoxy silicone oil, hydroxy silicone oil; among them, the dimethyl silicone oil adopts the 201-500 type, the hydrogen-containing silicone oil adopts the HMS-1501 type, the amino silicone oil adopts the AS-700 type, the epoxy silicone oil adopts the ES-500 type, and the hydroxy silicone oil adopts the HS-800 type.

[0035] Specifically, the mass ratio of the modifier to the alcohol is 1:(3-5).

[0036] More specifically, the alcohol in the embodiments of the present invention is anhydrous ethanol.

[0037] Specifically, the hydrolysis time is 0.5-1 h; the pH of the alcohol solution is 11-13.

[0038] More specifically, the filtrate after filtration in step S4 can be used to adjust the pH of the alcohol solution, so as to realize the recycling of the filtrate.

[0039] Specifically, the dosage of the modifier is 0.3-0.5% of the mass of magnesium hydroxide.

[0040] Specifically, in step S3, the stirring speed is controlled at 150-500 revolutions per minute, the reaction temperature is 50-80 °C, and the reaction time is 60-120 min.

[0041] The present invention also discloses a silane-modified magnesium hydroxide, which is prepared by using the preparation method described in the present invention.

[0042] The present invention also discloses an application of the silane-modified magnesium hydroxide, and the silane-modified magnesium hydroxide is applied to EVA / PE or LLDPE / POE / EVA materials.

[0043] Specifically, the silane-modified magnesium hydroxide is applied to EVA / PE and LLDPE / POE / EVA materials to obtain EVA / PE and LLDPE / POE / EVA composite materials. The mass content of the silane-modified magnesium hydroxide in the EVA / PE composite material is 60-75%, and the mass content of the silane-modified magnesium hydroxide in the LLDPE / POE / EVA composite material is 65-78%.

[0044] Example 1

[0045] A preparation method of silane-modified magnesium hydroxide, the preparation method includes:

[0046] (1) Mix brine and excessive alkali solution in proportion for reaction to prepare magnesium hydroxide slurry;

[0047] (2) Add the modifier to the alcohol solution with a certain pH value in proportion for hydrolysis;

[0048] (3) Add the hydrolyzed modifier to the magnesium hydroxide slurry for reaction, and control the reaction time, temperature and stirring rate;

[0049] (4) After the reaction is completed, filter, wash and dry to obtain silane-modified magnesium hydroxide.

[0050] Among them, the modifier is vinyltrimethoxysilane and dimethyl silicone oil; the mass ratio of vinyltrimethoxysilane to dimethyl silicone oil is 5:1, the pH value of the alcohol solution is adjusted to 12-13 with the filtrate, the mass ratio of the modifier to the alcohol is 1:4.5, hydrolyze for 0.5 h, and the dosage of the modifier is 0.5% of the mass of magnesium hydroxide;

[0051] In step (3), the stirring speed is controlled at 150 rpm, the temperature is 70 °C, and the reaction time is 80 min;

[0052] Apply the prepared silane-modified magnesium hydroxide to EVA / PE, the addition amount of the modified magnesium hydroxide is 70%, mix evenly by an open mill, prepare an EVA / PE composite material, press into tablets for performance testing, and the specific surface area of magnesium hydroxide and the performance test results of the composite material are shown in Table 1.

[0053] Example 2

[0054] A preparation method of silane-modified magnesium hydroxide, the preparation method includes:

[0055] (1) Mix brine and excessive alkali solution in proportion for reaction to prepare magnesium hydroxide slurry;

[0056] (2) Add the modifier to the alcohol solution with a certain PH value in proportion for hydrolysis;

[0057] (3) Add a hydrolysis modifier to the magnesium hydroxide slurry for reaction, controlling the reaction time, temperature, and stirring rate;

[0058] (4) After the reaction is completed, filter, wash, and dry to obtain silane-modified magnesium hydroxide.

[0059] Among them, the modifier is vinyltrimethoxysilane and hydroxyl silicone oil; the mass ratio of vinyltrimethoxysilane to hydroxyl silicone oil is 3.5:1. Adjust the pH value of the alcohol solution to 12 - 13 with the filtrate. The mass ratio of the modifier to the alcohol is 1:4, hydrolyze for 0.5 h, and the dosage of the modifier is 0.5% of the mass of magnesium hydroxide;

[0060] In step (3), the stirring speed is controlled at 300 r / min, the temperature is 70 °C, and the reaction time is 80 min;

[0061] Apply the prepared silane-modified magnesium hydroxide to EVA / PE. The addition amount of the modified magnesium hydroxide is 68%. Mix evenly by an open mill to obtain an EVA / PE composite material. Press into tablets for performance testing. The specific surface area of magnesium hydroxide and the performance test results of the composite material are shown in Table 1.

[0062] Example 3

[0063] A preparation method of silane-modified magnesium hydroxide, the preparation method comprising:

[0064] (1) Mix and react brine with an excessive amount of alkali solution in proportion to prepare a magnesium hydroxide slurry;

[0065] (2) Add the modifier to an alcohol solution with a certain pH value in proportion for hydrolysis;

[0066] (3) Add the hydrolyzed modifier to the magnesium hydroxide slurry for reaction, controlling the reaction time, temperature, and stirring rate;

[0067] (4) After the reaction is completed, filter, wash, and dry to obtain silane-modified magnesium hydroxide.

[0068] Among them, the modifier is methyltrimethoxysilane and hydrogen-containing silicone oil; the mass ratio of methyltrimethoxysilane to hydrogen-containing silicone oil is 3:1. Adjust the pH value of the alcohol solution to 11 - 12 with the filtrate. The mass ratio of the modifier to the alcohol is 1:3, hydrolyze for 1 h, and the dosage of the modifier is 0.3% of the mass of magnesium hydroxide;

[0069] In step (3), the stirring speed is controlled at 500 r / min, the temperature is 50 °C, and the reaction time is 120 min;

[0070] The prepared silane-modified magnesium hydroxide was applied to EVA / PE. The addition amount of the modified magnesium hydroxide was 60%. After being uniformly mixed by an open mill, an EVA / PE composite material was prepared. Tablets were made for performance testing. The specific surface area of the magnesium hydroxide and the performance test results of the composite material are shown in Table 1.

[0071] Example 4

[0072] A preparation method of silane-modified magnesium hydroxide, the preparation method comprising:

[0073] (1) Mixing brine and excessive alkali solution in proportion for reaction to prepare a magnesium hydroxide slurry;

[0074] (2) Adding a modifier into an alcohol solution with a certain pH value in proportion for hydrolysis;

[0075] (3) Adding the hydrolyzed modifier into the magnesium hydroxide slurry for reaction, controlling the reaction time, temperature and stirring rate;

[0076] (4) After the reaction, through filtration, washing and drying, silane-modified magnesium hydroxide was obtained.

[0077] Among them, the modifier is vinyltrimethoxysilane, vinylmethyldimethoxysilane and dimethyl silicone oil; the mass ratio of vinyltrimethoxysilane, vinylmethyldimethoxysilane and dimethyl silicone oil is 3:2:1. The pH value of the alcohol solution was adjusted to 12 - 13 with the filtrate. The mass ratio of the modifier to the alcohol is 1:5, hydrolyzed for 0.8 h, and the dosage of the modifier is 0.4% of the mass of magnesium hydroxide;

[0078] In step (3), the stirring speed was controlled at 350 rpm, the temperature was 80 °C, and the reaction time was 60 min;

[0079] The prepared silane-modified magnesium hydroxide was applied to EVA / PE. The addition amount of the modified magnesium hydroxide was 75%. After being uniformly mixed by an open mill, an EVA / PE composite material was prepared. Tablets were made for performance testing. The specific surface area of the magnesium hydroxide and the performance test results of the composite material are shown in Table 1.

[0080] Example 5

[0081] A preparation method of silane-modified magnesium hydroxide, the preparation method comprising:

[0082] (1) Mixing brine and excessive alkali solution in proportion for reaction to prepare a magnesium hydroxide slurry;

[0083] (2) Adding a modifier into an alcohol solution with a certain pH value in proportion for hydrolysis;

[0084] (3) Add the hydrolysis modifier to the magnesium hydroxide slurry for reaction, and control the reaction time, temperature and stirring rate;

[0085] (4) After the reaction, filter, wash and dry to obtain silane-modified magnesium hydroxide.

[0086] Among them, the modifier is vinyltrimethoxysilane, hydroxy silicone oil and hydrogen-containing silicone oil; the mass ratio of vinyltrimethoxysilane, hydroxy silicone oil and hydrogen-containing silicone oil is 4:0.5:0.5. Use the filtrate to adjust the pH value of the alcohol solution to 11 - 12, the mass ratio of the modifier to the alcohol is 1:3, hydrolyze for 1 h, and the dosage of the modifier is 0.5% of the mass of magnesium hydroxide;

[0087] In step (3), the stirring speed is controlled at 200 rpm, the temperature is 60 °C, and the reaction time is 100 min;

[0088] Apply the prepared silane-modified magnesium hydroxide to EVA / PE, with the addition amount of the modified magnesium hydroxide being 72%. Mix evenly by an open mill to obtain an EVA / PE composite material. Press into tablets for performance testing. The specific surface area of magnesium hydroxide and the performance test results of the composite material are shown in Table 1.

[0089] Example 6

[0090] A preparation method of silane-modified magnesium hydroxide, the preparation method comprising:

[0091] (1) Mix and react brine with an excessive amount of alkali solution in proportion to prepare a magnesium hydroxide slurry;

[0092] (2) Add the modifier to an alcohol solution with a certain pH value in proportion for hydrolysis;

[0093] (3) Add the hydrolysis modifier to the magnesium hydroxide slurry for reaction, and control the reaction time, temperature and stirring rate;

[0094] (4) After the reaction, filter, wash and dry to obtain silane-modified magnesium hydroxide.

[0095] Among them, the modifier is vinyltrimethoxysilane and dimethyl silicone oil; the mass ratio of vinyltrimethoxysilane and dimethyl silicone oil is 5:1. Use the filtrate to adjust the pH value of the alcohol solution to 12 - 13, the mass ratio of the modifier to the alcohol is 1:4.5, hydrolyze for 0.5 h, and the dosage of the modifier is 0.5% of the mass of magnesium hydroxide;

[0096] In step (3), the stirring speed is controlled at 150 rpm, the temperature is 70 °C, and the reaction time is 80 min;

[0097] The prepared silane-modified magnesium hydroxide was applied to LLDPE / POE / EVA. The addition amount of the modified magnesium hydroxide was 75%. After being uniformly mixed by an open mill, an LLDPE / POE / EVA composite material was prepared. It was pressed into tablets for performance testing. The specific surface area of magnesium hydroxide and the performance test results of the composite material are shown in Table 1.

[0098] Comparative Example 1

[0099] Silane-modified magnesium hydroxide was prepared by the same method as in Example 1. The difference between this Comparative Example 1 and Example 1 was that the modifier used was vinyltrimethoxysilane. The test results are shown in Table 1.

[0100] Comparative Example 2

[0101] Silane-modified magnesium hydroxide was prepared by the same method as in Example 1. The difference between this Comparative Example 2 and Example 1 was that the modifier used was dimethyl silicone oil. The test results are shown in Table 1.

[0102] Comparative Example 3

[0103] Silane-modified magnesium hydroxide was prepared by the same method as in Example 1. The difference between this Comparative Example 3 and Example 1 was that the ratio of the modifier vinyltrimethoxysilane to dimethyl silicone oil was 1:1. The test results are shown in Table 1.

[0104] Comparative Example 4

[0105] The modified magnesium hydroxide flame retardant was prepared by the same method as in Example 1. The difference between this Comparative Example 4 and Example 1 was that the stirring speed used was 100 revolutions per minute. The test results are shown in Table 1.

[0106] Comparative Example 5

[0107] The modified magnesium hydroxide flame retardant was prepared by the same method as in Example 1. The difference between this Comparative Example 5 and Example 1 was that the stirring speed used was 1000 revolutions per minute. The test results are shown in Table 1.

[0108] Comparative Example 6

[0109] The modified magnesium hydroxide flame retardant was prepared by the same method as in Example 1. The difference between this Comparative Example 6 and Example 1 was that the heating temperature in step (3) was 100 °C. The test results are shown in Table 1.

[0110] Comparative Example 7

[0111] The modified magnesium hydroxide flame retardant was prepared by the same method as in Example 1. The difference between this Comparative Example 7 and Example 1 was that the heating temperature in step (3) was 40 °C. The test results are shown in Table 1.

[0112] Comparative Example 8

[0113] The modified magnesium hydroxide flame retardant was prepared by the same method as in Example 1. The difference between Comparative Example 8 and Example 1 was that the hydrolysis time of the modifier was 0.3 h, and the test results are shown in Table 1.

[0114] Comparative Example 9

[0115] The modified magnesium hydroxide flame retardant was prepared by the same method as in Example 1. The difference between Comparative Example 9 and Example 1 was that the hydrolysis time of the modifier was 1.5 h, and the test results are shown in Table 1.

[0116] Comparative Example 10

[0117] The modified magnesium hydroxide flame retardant was prepared by the same method as in Example 1. The difference between Comparative Example 10 and Example 1 was that the dosage of the modifier was 0.2% of the mass of magnesium hydroxide, and the test results are shown in Table 1.

[0118] Comparative Example 11

[0119] The EVA / PE composite material was prepared by the same method as in Example 1. The difference between Comparative Example 11 and Example 1 was that the dosage of the modifier was 1% of the mass of magnesium hydroxide, and the test results are shown in Table 1.

[0120] Comparative Example 12

[0121] The EVA / PE composite material was prepared by the same method as in Example 1. The difference between Comparative Example 12 and Example 1 was that the pH value of the solution was not adjusted with the filtrate when hydrolyzing the modifier, and the test results are shown in Table 1.

[0122] Comparative Example 13

[0123] The EVA / PE composite material was prepared by the same method as in Example 1. The difference between Comparative Example 13 and Example 1 was that the magnesium hydroxide used was unmodified and directly obtained by filtering, washing and drying the magnesium hydroxide slurry prepared by reacting brine with lye, and the test results are shown in Table 1.

[0124] The EVA / PE composite materials prepared in the above examples and comparative examples were subjected to performance tests, and the specific results are shown in Table 1 below. The detection methods involved were as follows: the specific surface area detection standard was GB / T 19587-2017; the tensile test detection standard was GB / T 1040; the limiting oxygen index detection standard was GB / T 2406; and the vertical burning grade detection standard was GB / T 2408.

[0125] Table 1 Performance test results of examples and comparative examples

[0126]

[0127] As can be seen from the above table data, the silane-modified magnesium hydroxide prepared by the preparation method described in the present invention in Examples 1-6 is added to EVA / PE and LLDPE / POE / EVA materials. The silane-modified magnesium hydroxide has good compatibility with EVA / PE and LLDPE / POE / EVA materials. Adding a large amount will not affect the mechanical properties of EVA / PE and LLDPE / POE / EVA materials. The EVA / PE and LLDPE / POE / EVA composites still maintain good mechanical properties and effectively improve the flame retardancy of EVA / PE and LLDPE / POE / EVA materials.

[0128] As can be seen from the data comparison between Example 1 and Comparative Example 1 and Comparative Example 2: The modification effect of using the two modifiers defined in the present invention is significantly better than that of a single modifier. Because the two modifiers used in the present invention can combine the performance advantages of the two well. After being applied to EVA / PE materials, the tensile strength and elongation at break of the EVA / PE composite material are both better.

[0129] As can be seen from the data comparison between Example 1 and Comparative Example 3: If the dosage ratio of the silane coupling agent and the organosilicon modifier is inappropriate, the application effect of the modified magnesium hydroxide flame retardant will become worse. The silane coupling agent can produce chemical reactions or physical adsorption with inorganic fillers and organic polymer matrices through its unique molecular structure to achieve effective combination of the two. In a high-filler system, the silane coupling agent modifies the surface of the filler, making the filler more evenly dispersed in the polymer, reducing local stress concentration in the composite material, thereby improving the tensile strength of the material. The organosilicon modifier is coated on the surface of magnesium hydroxide to form a flexible interface layer, increasing the toughness of the system. When the material is subjected to external force and breaks, the interface layer between the modified filler and the resin can withstand a higher external force, showing a certain ductile fracture, thus having a higher elongation at break. Controlling the addition ratio of the two modifiers can better combine the tensile strength and elongation at break of the composite material. Therefore, using the dosage ratio defined in the present invention is more conducive to obtaining modified magnesium hydroxide with excellent comprehensive performance.

[0130] As can be seen from the data comparison between Example 1 and Comparative Example 4 and Comparative Example 5: During the reaction process, if the stirring speed is too slow or too fast, the modification effect of magnesium hydroxide is poor. Because when other conditions are the same, increasing the stirring speed is beneficial to improving the dispersion effect of the modifier and enabling it to fully coat the surface of magnesium hydroxide. However, when the stirring speed is too fast, the modification effect decreases instead. This is because during high-speed stirring, strong frictional and shear forces cause the modifier coated on the surface of magnesium hydroxide to desorb, resulting in a poor modification effect.

[0131] From the data comparison of Example 1 and Comparative Example 6 and Comparative Example 7, it can be seen that: if the heating temperature is too high or too low during the reaction process, the modification effect will deteriorate. Because at a low temperature, the reaction rate is slow. Under the condition that other conditions are the same, too low reaction temperature will cause the reaction between the modifier and magnesium hydroxide to be incomplete, and the ideal modification effect cannot be achieved. Appropriately increasing the modification temperature can promote the strong chemical bonding reaction between the hydroxyl groups on the surface of magnesium hydroxide and the hydroxyl groups and carboxyl groups on the surface of the modifier, thereby improving the modification effect of magnesium hydroxide. However, too high a temperature is likely to cause the decomposition, volatilization or carbonization of the modifier, thus affecting the powder modification effect.

[0132] From the data comparison of Example 1 and Comparative Example 8 and Comparative Example 9, it can be seen that: too long or too short hydrolysis time of the modifier is not conducive to the modification of magnesium hydroxide. Because too short hydrolysis time will cause incomplete hydrolysis of the modifier, and when participating in the reaction, part of the modifier will float on the liquid surface in the form of oil droplets, thus not participating in the reaction. While too long hydrolysis time will lead to the polycondensation reaction of the hydrolyzed modifier, resulting in insufficient amount of the modifier actually participating in the reaction and affecting the modification effect.

[0133] From the data comparison of Example 1 and Comparative Example 10 and Comparative Example 11, it can be seen that: if the dosage of the modifier is too little or too much, the mechanical properties of the EVA / PE composite material will be significantly affected. Because the modification effect is the best when the modifier reaches monolayer adsorption on the powder surface. When the dosage of the modifier is small, the modifier cannot form a monolayer coating on the material surface, and when the dosage of the modifier is too large, the modifier will form multi-layer physical adsorption on the surface of magnesium hydroxide powder, resulting in the formation of a weak layer at the interface between magnesium hydroxide and the polymer, affecting the connection effect of the interface and reducing the mechanical properties of the composite material. Therefore, using the dosage of the modifier defined in the present invention is more conducive to obtaining a modified magnesium hydroxide flame retardant with excellent properties.

[0134] From the data comparison of Example 1 and Comparative Example 12, it can be seen that: if the pH value of the solution is not adjusted with filtrate when hydrolyzing the modifier, it will lead to incomplete hydrolysis of the modifier, and part of the modifier is not hydrolyzed and will float on the water surface during the modification reaction and cannot fully contact with magnesium hydroxide, affecting the modification effect of magnesium hydroxide, and thus affecting the application effect of the modified magnesium hydroxide flame retardant in the EVA / PE material.

[0135] From the data comparison between Example 1 and Comparative Example 13, it can be seen that in the EVA / PE composite material, the application effect of the modified magnesium hydroxide is significantly better than that of the unmodified magnesium hydroxide. Because there are two different chemical functional groups in the structure of the modifier. One end of it can form a chemical bond with the hydroxyl groups on the surface of the magnesium hydroxide powder, so that the modifier is coated on the surface of the magnesium hydroxide particles. The other end can combine with the EVA / PE material, improve the dispersion of magnesium hydroxide in the EVA / PE material, and firmly combine the two materials with large property differences together. Therefore, the mechanical properties of the composite material added with the modified magnesium hydroxide flame retardant are significantly better than those using the unmodified magnesium hydroxide.

[0136] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, all possible combinations of the technical features in the above embodiments are not exhaustively listed. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0137] For those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. The protection scope of the present invention shall be subject to the appended claims.

Claims

1. A method for preparing silane-modified magnesium hydroxide, characterized in that: The preparation method is: S1, mixing brine and excess alkali solution in proportion to react and prepare magnesium hydroxide slurry; S2, adding a modifier in proportion to an alcohol solution having a certain pH value for hydrolysis to obtain a hydrolysis modifier, wherein the modifier comprises a silane coupling agent and an organosilicon modifier, and the mass ratio of the silane coupling agent to the organosilicon modifier is (3-5):1; S3, adding the hydrolysis modifier to the magnesium hydroxide slurry for reaction, controlling the reaction time, temperature and stirring rate; S4. After the reaction is completed, the silane-modified magnesium hydroxide is obtained by filtering, washing and drying.

2. A method for preparing a silane-modified magnesium hydroxide according to claim 1, characterized in that: The silane coupling agent is at least one of vinyl-tri(2-methoxyethoxy)silane, vinyl trimethoxysilane, vinyl methyl dimethoxysilane, methyl trimethoxysilane, and γ-methacryloxypropyl trimethoxysilane.

3. A method for preparing a silane-modified magnesium hydroxide according to claim 1, characterized in that: The organosilicon modifier is at least one of dimethyl silicone oil, hydrogen silicone oil, amino silicone oil, epoxy silicone oil and hydroxy silicone oil.

4. A method for preparing a silane-modified magnesium hydroxide according to claim 1, characterized in that: The mass ratio of the modifier to the alcohol is 1:(3-5).

5. A method for preparing a silane-modified magnesium hydroxide according to claim 1, characterized in that: The hydrolysis time is 0.5-1h; the pH of the alcohol solution is 11-13.

6. A method for preparing a silane-modified magnesium hydroxide according to claim 1, characterized in that: The dosage of the modifier is 0.3-0.5% of the mass of magnesium hydroxide.

7. A method for preparing a silane-modified magnesium hydroxide according to claim 1, characterized in that: In step S3, the stirring speed is controlled at 150-500 rpm, the reaction temperature is 50-80° C., and the reaction time is 60-120 min.

8. A silane-modified magnesium hydroxide, characterized in that: The silane-modified magnesium hydroxide is prepared by any one of the preparation methods of claims 1-7.

9. An application of a silane-modified magnesium hydroxide according to claim 8, characterized in that: The silane-modified magnesium hydroxide is applied to EVA / PE or LLDPE / POE / EVA materials.

10. The use of a silane-modified magnesium hydroxide according to claim 9, characterized in that: The silane-modified magnesium hydroxide is applied to EVA / PE and LLDPE / POE / EVA materials to obtain EVA / PE and LLDPE / POE / EVA composite materials, wherein the mass content of the silane-modified magnesium hydroxide in the EVA / PE composite material is 60-75%, and the mass content of the silane-modified magnesium hydroxide in the EVA / PE composite material is 65-78%.

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