A modified magnesium hydroxide flame retardant and its preparation method and application

Abstract

The present invention relates to the technical field of inorganic materials, and in particular to a modified magnesium hydroxide flame retardant and a preparation method and application thereof. The preparation method of the modified magnesium hydroxide flame retardant is as follows: (1) adding a modifier to an alcohol solution with a certain pH value in proportion for hydrolysis; (2) preparing a magnesium hydroxide slurry with a certain solid content; (3) adding the magnesium hydroxide slurry to a reaction container, stirring and heating, and adding a completely hydrolyzed modifier in proportion after the temperature reaches a set value; (4) taking out the slurry after the reaction is completed, filtering, and drying to obtain modified magnesium hydroxide. The modified magnesium hydroxide of the present invention is lipophilic and hydrophobic, has good compatibility with polymers, can be added in large quantities when applied to EVA / PE, thereby effectively improving the flame retardant properties of EVA / PE, will not deteriorate the mechanical properties of EVA / PE materials, and can reduce material costs.

Description

Technical Field

[0001] The invention relates to a modified magnesium hydroxide flame retardant and a preparation method and application thereof, belonging to the technical field of inorganic materials. Background Art

[0002] Magnesium hydroxide is a white or off-white crystalline powder. As an environmentally friendly flame retardant, it has good flame retardancy and smoke suppression properties. It is low in price and has a higher decomposition temperature. It has a wider range of uses than aluminum hydroxide and will occupy an extremely important position in the future flame retardant market.

[0003] Magnesium hydroxide flame retardant has outstanding flame retardant properties of non-toxicity, smoke suppression and environmental protection, but the amount of magnesium hydroxide required for use is large. However, the surface of magnesium hydroxide is hydrophilic and oleophobic, the polarity is large, and it is easy to agglomerate, which makes its compatibility and dispersibility in polymer materials poor, directly leading to serious deterioration of the mechanical properties of the material, which greatly limits the scope of use of magnesium hydroxide flame retardant. In order to improve the compatibility and dispersibility of magnesium hydroxide with polymers and change its "hydrophilic and oleophobic" surface properties, magnesium hydroxide must be surface modified.

[0004] Chinese patent application CN113429631A discloses a method for preparing a modified magnesium hydroxide flame retardant, wherein the method is as follows: dry and oil-free compressed air forms a high-speed jet to drive the original magnesium hydroxide powder to move at a high speed, so that the original powder collides, rubs and crushes, and the crushed magnesium hydroxide material arrives at the classification area with the airflow, and the collector collects the magnesium hydroxide fine powder with a particle size D50 of 3.5μm-4.5μm; then the crushed magnesium hydroxide fine powder is put into a high-speed stirring machine preheated to 90-110℃ for stirring, and silane coupling agent is sprayed for modification; then the semi-finished magnesium hydroxide flame retardant after modification is transferred into a continuous modifier, and the preheated modifier is sprayed for coating; then the magnesium hydroxide flame retardant after secondary coating is transferred into a rotary screen for screening and bagging. The addition amount of the modified magnesium hydroxide flame retardant when applied to halogen-free cable material is about 50%, the addition ratio is relatively small, and the preparation process is relatively cumbersome.

[0005] At present, these conventional methods for modifying magnesium hydroxide often cannot take into account both the flame retardant properties of the application materials and the performance requirements of the products themselves. That is to say, when magnesium hydroxide is used in a polymer matrix, if the amount added is too much, it will affect the mechanical and other performance requirements of the polymer matrix itself. If the amount added is too little, the flame retardant requirements cannot be met. Summary of the invention

[0006] The present invention aims at the deficiencies in the prior art and provides a modified magnesium hydroxide flame retardant and a preparation method and application thereof, so as to solve the problems that the surface polarity of magnesium hydroxide is strong, the compatibility with a polymer substrate is poor, and a large amount of addition is not possible. By means of the technical means of the present invention, the surface of magnesium hydroxide is made oleophilic and hydrophobic, and the magnesium hydroxide has good compatibility with the polymer, and can be added to the polymer in large quantities without deteriorating the mechanical properties of the material and reducing the material cost.

[0007] The technical solution of the present invention to solve the above technical problems is as follows: a method for preparing a modified magnesium hydroxide flame retardant, the preparation method comprising:

[0008] S1. Adding a modifier into an alcohol solution for hydrolysis to obtain a completely hydrolyzed modifier; the modifier includes an organosilicon modifier and an unsaturated organic acid modifier, and the mass ratio of the organosilicon modifier to the unsaturated organic acid modifier is (1.5-2.5):1;

[0009] Mixing magnesium hydroxide and water to prepare magnesium hydroxide slurry;

[0010] S2, stirring and heating the magnesium hydroxide slurry, and after the temperature reaches the set value, adding a completely hydrolyzed modifier to react;

[0011] S3. After the reaction is completed, the modified magnesium hydroxide flame retardant is obtained by solid-liquid separation and drying.

[0012] Furthermore, the organosilicon modifier is at least one of dimethyl silicone oil, methyl silicone oil, hydrogenated silicone oil and hydroxy silicone oil.

[0013] Furthermore, the unsaturated organic acid modifier is at least one of acrylic acid, sorbic acid and itaconic acid.

[0014] Furthermore, the solid content of the magnesium hydroxide slurry is 30-50%, and the mass ratio of the modifier to the alcohol is 1:(1-4).

[0015] Furthermore, the pH of the alcohol solution is 3-5 or 10-11, and glacial acetic acid or ammonia water is used to adjust the pH.

[0016] Furthermore, the amount of the modifier used is 0.5-2% of the mass of magnesium hydroxide.

[0017] Furthermore, in step S2, the stirring speed is controlled at 1000-1500 rpm, the heating temperature is 70-90° C., and the reaction time is 20-40 min.

[0018] The invention also discloses a modified magnesium hydroxide flame retardant, and the modified magnesium hydroxide flame retardant is prepared by adopting the preparation method of the invention.

[0019] The invention also discloses an application of a modified magnesium hydroxide flame retardant, wherein the modified magnesium hydroxide flame retardant is applied to EVA / PE material.

[0020] Furthermore, the modified magnesium hydroxide flame retardant is applied to EVA / PE material to obtain an EVA / PE composite material, and the mass content of the modified magnesium hydroxide flame retardant in the EVA / PE composite material is 65-73%.

[0021] The beneficial effects of the present invention are:

[0022] The modified magnesium hydroxide flame retardant of the present invention adopts a wet modification technology and has a simple process flow. By using modifiers based on different principles and reasonably matching the modifiers, the modified magnesium hydroxide has good hydrophobicity. The modified magnesium hydroxide flame retardant is added to a polymer substrate and has good compatibility with the polymer. A large amount of addition will not affect the mechanical properties of the material and can reduce the cost of the composite material.

[0023] The modified magnesium hydroxide flame retardant of the present invention is added to the EVA / PE material, and the addition amount can be as high as 70%, so that the oxygen index of the composite material is as high as 48-52%, the vertical combustion grade reaches V-0 level, and the mechanical properties of the composite material are good, the strength can reach 15-17MPa, and the elongation at break is 120-200%. The modified magnesium hydroxide flame retardant of the present invention has good modification effect, simple process flow, low production cost, can be added to polymers in large quantities, will not deteriorate the mechanical properties of the material, and can also improve the thermal stability of the composite material. DETAILED DESCRIPTION

[0024] The specific implementation of the present invention is described in detail below. The present invention can be implemented in many other ways than those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific embodiments disclosed.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used are only for describing specific embodiments and are not intended to limit the present invention.

[0026] A method for preparing a modified magnesium hydroxide flame retardant, the preparation method comprising:

[0027] S1. Adding a modifier into an alcohol solution for hydrolysis to obtain a completely hydrolyzed modifier; the modifier includes an organosilicon modifier and an unsaturated organic acid modifier, and the mass ratio of the organosilicon modifier to the unsaturated organic acid modifier is (1.5-2.5):1;

[0028] Mixing magnesium hydroxide and water to prepare magnesium hydroxide slurry;

[0029] S2, stirring and heating the magnesium hydroxide slurry, and after the temperature reaches the set value, adding a completely hydrolyzed modifier to react;

[0030] S3. After the reaction is completed, the modified magnesium hydroxide flame retardant is obtained by solid-liquid separation and drying.

[0031] Specifically, the silicone oil modifier is at least one of dimethyl silicone oil, methyl silicone oil, hydrogenated silicone oil and hydroxy silicone oil.

[0032] Specifically, the acid modifier is at least one of acrylic acid, sorbic acid and itaconic acid.

[0033] Specifically, the solid content of the magnesium hydroxide slurry is 30-50%, and the mass ratio of the modifier to the alcohol is 1:(1-4).

[0034] More specifically, the alcohol used in the embodiment of the present invention is anhydrous ethanol, wherein the alcohol solution includes water and anhydrous ethanol, and the mass ratio of water to alcohol is 1:1.

[0035] Specifically, the pH of the alcohol solution is 3-5 or 10-11, and glacial acetic acid or ammonia water is used to adjust the pH.

[0036] Specifically, the amount of the modifier used is 0.5-2% of the mass of magnesium hydroxide.

[0037] More specifically, the magnesium hydroxide used in the embodiment of the present invention is chemical magnesium hydroxide produced by our company, with a model of MH01 and a particle size of 2-5 μm.

[0038] Specifically, in step S2, the stirring speed is controlled at 1000-1500 rpm, the heating temperature is 70-90° C., and the reaction time is 20-40 min.

[0039] A modified magnesium hydroxide flame retardant is prepared by the preparation method of the invention.

[0040] An application of a modified magnesium hydroxide flame retardant, wherein the modified magnesium hydroxide flame retardant is applied to EVA / PE materials.

[0041] Specifically, the modified magnesium hydroxide flame retardant is applied to EVA / PE material to obtain an EVA / PE composite material, and the mass content of the modified magnesium hydroxide flame retardant in the EVA / PE composite material is 65-73%.

[0042] More specifically, the EVA / PE material used in the embodiment of the present invention is commercially available, wherein EVA is EA28025 from LG of South Korea, and PE is DGDK-3364 from Dow of the United States, wherein the mass ratio of EVA to PE in the EVA / PE material is 5:3.

[0043] More specifically, in an embodiment of the present invention, the specific operation method of applying the modified magnesium hydroxide flame retardant to the EVA / PE material is as follows: first, EVA and PE materials are added to two rollers of an open mill, the open mill is started to mix EVA and PE evenly, and then the modified magnesium hydroxide flame retardant is added to the EVA / PE material and mixed evenly to obtain an EVA / PE composite material, and then the mixed composite material is pressed into a sheet using a flat vulcanizer. The temperature of the open mill is controlled at 140°C, the temperature of the flat vulcanizer is 160°C, the pressure is 10MPa, and the hot pressing is performed for 5 minutes and then the cold pressing is performed for 5 minutes.

[0044] Example 1

[0045] A preparation and application of a modified magnesium hydroxide flame retardant, the preparation method comprising:

[0046] (1) Add the modifier in proportion to an alcohol solution with a certain pH value for hydrolysis; the hydrolysis time is 0.5 h;

[0047] (2) preparing magnesium hydroxide slurry with a certain solid content;

[0048] (3) adding magnesium hydroxide slurry into a reaction vessel, stirring and heating, and after the temperature reaches a set value, adding a completely hydrolyzed modifier in proportion;

[0049] (4) After the reaction is completed, the slurry is taken out, filtered, and dried to obtain modified magnesium hydroxide.

[0050] The modifier is hydroxy silicone oil and acrylic acid; the mass ratio of hydroxy silicone oil to acrylic acid is 2:1, the solid content of magnesium hydroxide slurry is 30%, the pH value of the alcohol solution is adjusted to 3-5 with glacial acetic acid, the mass ratio of the modifier to the alcohol is 1:2, and the amount of the modifier is 1% of the mass of magnesium hydroxide;

[0051] In step (3), the stirring speed is controlled to 1500 rpm, the temperature is 70°C, and the reaction time is 40 min;

[0052] The prepared modified magnesium hydroxide was applied to EVA / PE, with the addition amount of modified magnesium hydroxide being 65%. The mixture was evenly mixed in an open mixer to obtain an EVA / PE composite material, which was then pressed into sheets for performance testing. The performance test results are shown in Table 1.

[0053] Example 2

[0054] A preparation and application of a modified magnesium hydroxide flame retardant, the preparation method comprising:

[0055] (1) Add the modifier in proportion to an alcohol solution with a certain pH value for hydrolysis; the hydrolysis time is 0.5 h;

[0056] (2) preparing magnesium hydroxide slurry with a certain solid content;

[0057] (3) adding magnesium hydroxide slurry into a reaction vessel, stirring and heating, and after the temperature reaches a set value, adding a completely hydrolyzed modifier in proportion;

[0058] (4) After the reaction is completed, the slurry is taken out, filtered, and dried to obtain modified magnesium hydroxide.

[0059] The modifiers are hydroxy silicone oil and acrylic acid; the ratio of hydroxy silicone oil to acrylic acid is 2:1, and the ratio of the modifier to alcohol is 1:3; the pH value of the alcohol solution is adjusted to 3-5 with glacial acetic acid, the solid content of the magnesium hydroxide slurry is 40%, and the amount of the modifier is 1% of the mass of the magnesium hydroxide;

[0060] In step (3), the stirring speed is controlled to be 1200 rpm, the temperature is 80°C, and the reaction time is 40 min;

[0061] The prepared modified magnesium hydroxide was applied to EVA / PE, with the addition amount of modified magnesium hydroxide being 70%. The mixture was mixed evenly on an open mixer to obtain an EVA / PE composite material, which was then pressed into sheets for performance testing. The performance test results are shown in Table 1.

[0062] Example 3

[0063] A preparation and application of a modified magnesium hydroxide flame retardant, the preparation method comprising:

[0064] (1) Add the modifier in proportion to an alcohol solution with a certain pH value for hydrolysis; the hydrolysis time is 0.5 h;

[0065] (2) preparing magnesium hydroxide slurry with a certain solid content;

[0066] (3) adding magnesium hydroxide slurry into a reaction vessel, stirring and heating, and after the temperature reaches a set value, adding a completely hydrolyzed modifier in proportion;

[0067] (4) After the reaction is completed, the slurry is taken out, filtered, and dried to obtain modified magnesium hydroxide.

[0068] The modifiers are hydroxy silicone oil and acrylic acid; the mass ratio of hydroxy silicone oil to acrylic acid is 2:1, the mass ratio of the modifier to alcohol is 1:1, the pH value of the alcohol solution is adjusted to 10-11 with ammonia water, the solid content of the magnesium hydroxide slurry is 50%, and the amount of the modifier is 1% of the mass of the magnesium hydroxide;

[0069] In step (3), the stirring speed is controlled to 1200 rpm, the temperature is 90°C, and the reaction time is 30 min;

[0070] The prepared modified magnesium hydroxide was applied to EVA / PE, with the addition amount of modified magnesium hydroxide being 73%. The mixture was mixed evenly on an open mixer to obtain an EVA / PE composite material, which was then pressed into sheets for performance testing. The performance test results are shown in Table 1.

[0071] Example 4

[0072] A preparation and application of a modified magnesium hydroxide flame retardant, the preparation method comprising:

[0073] (1) Add the modifier in proportion to an alcohol solution with a certain pH value for hydrolysis; the hydrolysis time is 0.5 h;

[0074] (2) preparing magnesium hydroxide slurry with a certain solid content;

[0075] (3) adding magnesium hydroxide slurry into a reaction vessel, stirring and heating, and after the temperature reaches a set value, adding a completely hydrolyzed modifier in proportion;

[0076] (4) After the reaction is completed, the slurry is taken out, filtered, and dried to obtain modified magnesium hydroxide.

[0077] The modifiers are methyl silicone oil and itaconic acid; the mass ratio of methyl silicone oil to itaconic acid is 2.5:1, the solid content of magnesium hydroxide slurry is 35%, the pH value of the alcohol solution is adjusted to 3-5 with glacial acetic acid, the mass ratio of the modifier to the alcohol is 1:4, and the amount of the modifier is 0.5% of the mass of magnesium hydroxide;

[0078] In step (3), the stirring speed is controlled to be 1500 rpm, the temperature is 90°C, and the reaction time is 20 min;

[0079] The prepared modified magnesium hydroxide was applied to EVA / PE, with the addition amount of modified magnesium hydroxide being 70%. The mixture was mixed evenly on an open mixer to obtain an EVA / PE composite material, which was then pressed into sheets for performance testing. The performance test results are shown in Table 1.

[0080] Example 5

[0081] A preparation and application of a modified magnesium hydroxide flame retardant, the preparation method comprising:

[0082] (1) Add the modifier in proportion to an alcohol solution with a certain pH value for hydrolysis; the hydrolysis time is 0.5 h;

[0083] (2) preparing magnesium hydroxide slurry with a certain solid content;

[0084] (3) adding magnesium hydroxide slurry into a reaction vessel, stirring and heating, and after the temperature reaches a set value, adding a completely hydrolyzed modifier in proportion;

[0085] (4) After the reaction is completed, the slurry is taken out, filtered, and dried to obtain modified magnesium hydroxide.

[0086] The modifiers are dimethyl silicone oil and sorbic acid; the mass ratio of dimethyl silicone oil to sorbic acid is 1.5:1, the solid content of magnesium hydroxide slurry is 40%, the pH value of the alcohol solution is adjusted to 3-5 with glacial acetic acid, the mass ratio of the modifier to the alcohol is 1:3, and the amount of the modifier is 2% of the mass of magnesium hydroxide;

[0087] In step (3), the stirring speed is controlled to 1500 rpm, the temperature is 70°C, and the reaction time is 30 min;

[0088] The prepared modified magnesium hydroxide was applied to EVA / PE, with the addition amount of modified magnesium hydroxide being 68%. The mixture was evenly mixed in an open mixer to obtain an EVA / PE composite material, which was then pressed into sheets for performance testing. The performance test results are shown in Table 1.

[0089] Example 6

[0090] A preparation and application of a modified magnesium hydroxide flame retardant, the preparation method comprising:

[0091] (1) Add the modifier in proportion to an alcohol solution with a certain pH value for hydrolysis; the hydrolysis time is 0.5 h;

[0092] (2) preparing magnesium hydroxide slurry with a certain solid content;

[0093] (3) adding magnesium hydroxide slurry into a reaction vessel, stirring and heating, and after the temperature reaches a set value, adding a completely hydrolyzed modifier in proportion;

[0094] (4) After the reaction is completed, the slurry is taken out, filtered, and dried to obtain modified magnesium hydroxide.

[0095] The modifier is dimethyl silicone oil, acrylic acid and itaconic acid; the mass ratio of dimethyl silicone oil, acrylic acid and itaconic acid is 2:0.5:0.5, the solid content of magnesium hydroxide slurry is 40%, the pH value of the alcohol solution is adjusted to 3-5 with glacial acetic acid, the mass ratio of the modifier to the alcohol is 1:3, and the amount of the modifier is 1.5% of the mass of magnesium hydroxide;

[0096] In step (3), the stirring speed is controlled to 1300 rpm, the temperature is 70°C, and the reaction time is 40 min;

[0097] The prepared modified magnesium hydroxide was applied to EVA / PE, with the addition amount of modified magnesium hydroxide being 70%. The mixture was mixed evenly on an open mixer to obtain an EVA / PE composite material, which was then pressed into sheets for performance testing. The performance test results are shown in Table 1.

[0098] Comparative Example 1

[0099] The modified magnesium hydroxide flame retardant was prepared by the same method as in Example 1, and the difference between this comparative example 1 and Example 1 is that the modifier used is silane coupling agent A172. The test results are shown in Table 1.

[0100] Comparative Example 2

[0101] The modified magnesium hydroxide flame retardant was prepared by the same method as in Example 1, and the difference between Comparative Example 2 and Example 1 was that the ratio of hydroxy silicone oil to acrylic acid was 1:1. The test results are shown in Table 1.

[0102] Comparative Example 3

[0103] The modified magnesium hydroxide flame retardant was prepared by the same method as in Example 1. The difference between Comparative Example 3 and Example 1 is that no acid was added to adjust the pH value of the solution when the modifier was hydrolyzed. 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 Comparative Example 4 and Example 1 is that the stirring speed used is 500 rpm. 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 Comparative Example 5 and Example 1 is that the stirring speed used is 2000 rpm. 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 is that the heating temperature in step (3) is 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 Comparative Example 7 and Example 1 is that the modifier is hydroxy silicone oil. 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 is that the modifier is acrylic acid. 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 is that the amount of the modifier is 0.4% of the mass of the magnesium hydroxide. 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 is that the amount of the modifier is 3% of the mass of the magnesium hydroxide. 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 is that the magnesium hydroxide was not modified. The test results are shown in Table 1.

[0120] The EVA / PE composite materials prepared in the above examples and comparative examples were tested for performance, and the specific results are shown in Table 1. The testing methods involved are: tensile test test standard is GB / T 1040; heat deformation temperature test standard is GB / T1634; limiting oxygen index test standard is GB / T 2406; vertical burning grade test standard is GB / T 2408.

[0121] Table 1 Test results of composite material properties of examples and comparative examples

[0122]

[0123] It can be seen from the above table data that the modified magnesium hydroxide prepared by the preparation method of the present invention in Examples 1-6 has good hydrophobicity, and the modified magnesium hydroxide flame retardant is added to the EVA / PE material, and has good compatibility with the EVA / PE material. A large amount of addition will not affect the mechanical properties of the EVA / PE material. The EVA / PE composite material still maintains good mechanical properties and effectively improves the flame retardant properties of the EVA / PE material.

[0124] From the data comparison of Example 1 and Comparative Example 1, it can be seen that the use of the modifier defined in the present invention is significantly better than the application effect of the conventional modifier silane coupling agent A172, because the two modifiers used in the present invention can well combine the performance advantages of the two. After being applied to the EVA / PE material, the tensile strength and elongation at break of the EVA / PE composite material can be made better.

[0125] From the data comparison of Example 1 and Comparative Example 2, it can be seen that the inappropriate usage ratio of the organosilicon modifier and the unsaturated organic acid modifier will lead to the poor application effect of the modified magnesium hydroxide flame retardant, because the organosilicon modifier is coated on the surface of the magnesium hydroxide to form a flexible interface layer, which increases 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 toughness fracture, thereby having a higher elongation at break; and the unsaturated organic acid modifier has two functional groups, an unsaturated double bond and a carboxyl group. The carboxyl group can chemically bond with magnesium hydroxide, and the unsaturated double bond can undergo a series of chemical reactions such as grafting and cross-linking with the matrix resin, so that the magnesium hydroxide and the polymer substrate are better combined together, which can improve the tensile strength of the composite material. Controlling the addition ratio of the two modifiers can make the tensile strength and elongation at break of the composite material higher. Therefore, the usage ratio defined in the present invention is more conducive to obtaining a modified magnesium hydroxide flame retardant with excellent performance.

[0126] From the comparison of the data of Example 1 and Comparative Example 3, it can be seen that if no acid is added to adjust the pH value of the solution when the modifier is hydrolyzed, the hydrolysis of the modifier will be incomplete, and part of the modifier will not be hydrolyzed. During the modification reaction, it will float on the water surface and cannot fully contact with the magnesium hydroxide, affecting the modification effect of the magnesium hydroxide, thereby affecting the application effect of the modified magnesium hydroxide flame retardant in the EVA / PE material.

[0127] From the data comparison of Example 1 and Comparative Examples 4 and 5, it can be seen that if the stirring speed is too slow or too fast during the reaction, the modification effect of magnesium hydroxide is poor. This is because under the same other conditions, increasing the stirring speed is conducive to improving the dispersion effect of the modifier, so that it is fully coated on the surface of magnesium hydroxide and improving the modification effect. However, when the stirring speed reaches 2000r / min, the modification effect is reduced. It is due to excessive stirring speed, strong friction and shearing force that the modifier coated on the surface of magnesium hydroxide is desorbed, resulting in poor modification effect.

[0128] From the comparison of the data of Example 1 and Comparative Example 6, it can be seen that if the heating temperature is too high during the reaction, the modification effect will be poor, because the appropriate increase in the modification temperature can promote the hydroxyl groups on the surface of magnesium hydroxide to react with the hydroxyl groups and carboxyl groups on the surface of the modifier to form a strong chemical bonding reaction, thereby improving the modification effect of magnesium hydroxide. However, if the temperature is too high, the modifier will easily decompose, volatilize or carbonize, thereby affecting the modification effect of the powder.

[0129] From the data comparison of Example 1 and Comparative Examples 7 and 8, it can be seen that if only silicone modifiers or unsaturated organic acid modifiers are used as modifiers, the application effect of the modified magnesium hydroxide flame retardant in EVA / PE materials will be poor. In the system using silicone modifiers alone, the tensile strength of the composite material is low and the elongation at break is high. This is because the hydroxy silicone oil is coated on the surface of the magnesium hydroxide to form a flexible interface layer, which improves the adhesion state and dispersibility of the interface and increases the toughness of the system. When the material is subjected to external force and breaks, the gap between the modified filler and the resin is The interface layer can withstand high external forces and show a certain toughness fracture, thus having a high elongation at break; while the system modified by unsaturated organic acid alone has a high tensile strength of the composite material, but a low elongation at break, because this type of modifier has two functional groups, unsaturated double bonds and carboxyl groups. The carboxyl group can chemically bond with magnesium hydroxide, and the unsaturated double bonds contained in it, when compounded with the matrix resin, partially open the double bonds, and undergo a series of chemical reactions such as grafting and cross-linking with the matrix resin, so that the magnesium hydroxide and the polymer substrate are better combined together, thereby improving the tensile strength of the composite material. Therefore, the appropriate amount of organosilicon modifiers and unsaturated organic acid modifiers are used in combination with each other, which is more conducive to obtaining modified magnesium hydroxide flame retardants with excellent performance.

[0130] From the data comparison of Example 1 and Comparative Examples 9 and 10, it can be seen that if the amount 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 of the modifier is best when the modifier reaches a monomolecular layer adsorption on the powder surface. When the amount of the modifier is small, the modifier cannot form a monomolecular layer coating on the material surface, and when the amount of the modifier is too large, the modifier will form a multi-layer physical adsorption on the surface of the magnesium hydroxide powder, resulting in a weak layer at the interface between the magnesium hydroxide and the polymer, affecting the connection of the interface and reducing the mechanical properties of the composite material. Therefore, the use of the modifier amount defined in the present invention is more conducive to obtaining a modified magnesium hydroxide flame retardant with excellent performance.

[0131] From the data comparison of Example 1 and Comparative Example 11, 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 group on the surface of the magnesium hydroxide powder, so that the modifier is coated on the surface of the magnesium hydroxide particles, and the other end can be combined with the EVA / PE material, thereby improving the dispersibility of magnesium hydroxide in the EVA / PE material and firmly combining the two materials with large differences in properties. Therefore, the mechanical properties of the composite material added with the modified magnesium hydroxide flame retardant are significantly better than those of the unmodified magnesium hydroxide.

[0132] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are exhaustively listed. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0133] For those skilled in the art, several modifications and improvements may be made without departing from the concept of the present invention, all of which belong to the protection scope of the present invention. The protection scope of the present invention shall be based on the attached claims.

Claims

1. A method for preparing a modified magnesium hydroxide flame retardant, characterized in that: The preparation method is: S1. Adding a modifier into an alcohol solution for hydrolysis to obtain a completely hydrolyzed modifier; the modifier includes an organosilicon modifier and an unsaturated organic acid modifier, and the mass ratio of the organosilicon modifier to the unsaturated organic acid modifier is (1.5-2.5):1; the pH of the alcohol solution is 3-5 or 10-11, and glacial acetic acid or ammonia water is used to adjust the pH; the amount of the modifier is 0.5-2% of the mass of magnesium hydroxide; Mixing magnesium hydroxide and water to prepare magnesium hydroxide slurry; S2, stirring and heating the magnesium hydroxide slurry, and after the temperature reaches the set value, adding a completely hydrolyzed modifier to react; S3, after the reaction is completed, solid-liquid separation and drying are performed to obtain a modified magnesium hydroxide flame retardant; In step S2, the stirring speed is controlled at 1000-1500 rpm, the heating temperature is 70-90° C., and the reaction time is 20-40 min.

2. A method for preparing a modified magnesium hydroxide flame retardant according to claim 1, characterized in that: The organosilicon modifier is at least one of dimethyl silicone oil, methyl silicone oil and hydrogen-containing silicone oil.

3. A method for preparing a modified magnesium hydroxide flame retardant according to claim 1, characterized in that: The unsaturated organic acid modifier is at least one of acrylic acid, sorbic acid and itaconic acid.

4. A method for preparing a modified magnesium hydroxide flame retardant according to claim 1, characterized in that: The solid content of the magnesium hydroxide slurry is 30-50%, and the mass ratio of the modifier to the alcohol is 1:(1-4).

5. A modified magnesium hydroxide flame retardant, characterized in that: The modified magnesium hydroxide flame retardant is prepared by any one of the preparation methods of claims 1-4.

6. An application of a modified magnesium hydroxide flame retardant according to claim 5, characterized in that: The modified magnesium hydroxide flame retardant is applied to EVA / PE materials.

7. The use of a modified magnesium hydroxide flame retardant according to claim 6, characterized in that: The modified magnesium hydroxide flame retardant is applied to EVA / PE material to obtain an EVA / PE composite material, and the mass content of the modified magnesium hydroxide flame retardant in the EVA / PE composite material is 65-73%.

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