A high volume resistivity magnesium hydroxide, its preparation method and use

Abstract

The application relates to the technical field of inorganic materials, in particular to high-volume-resistivity magnesium hydroxide as well as a preparation method and application thereof, the preparation method being that a magnesium salt solution is mixed with lye and lauric acid in proportion, heated to prepare magnesium hydroxide slurry; in the magnesium hydroxide slurry, fatty alcohol polyoxyethylene ether and polyacrylamide are added, and hydrothermal treatment is carried out; the magnesium hydroxide slurry after the hydrothermal treatment is aged after insulation, heating is turned off, a modifier is added and uniformly mixed to carry out reaction, and then high-volume-resistivity magnesium hydroxide is obtained through solid-liquid separation, washing and drying, the modifier including at least two of a titanate coupling agent, a water-soluble polymer, silicone and an unsaturated organic acid. The magnesium hydroxide prepared by the application has good insulation, good compatibility with polymers, can be added in a large amount into a polymer base material without deteriorating the mechanical properties of the material, has good water boiling aging resistance and can be applied to various environments.

Description

TECHNICAL FIELD

[0001] The present application relates to a high volume resistivity magnesium hydroxide and its preparation method and application, belonging to the technical field of inorganic materials. BACKGROUND

[0002] The main function of the cable insulation layer is to prevent current from passing through the outer skin of the wire or cable into the surrounding environment or other conductors, thereby preventing electrical accidents such as electric shock and short circuit. The insulation layer can ensure the mutual insulation between the conductors in the cable and the surrounding environment or adjacent conductors, and ensure that the current transmitted by the conductor core only propagates along the wire and does not flow to the outside.

[0003] The cable insulation layer is usually made of polyethylene as the insulation layer. Polyethylene has excellent electrical insulation performance and chemical corrosion resistance. However, polyethylene has poor flame resistance and is prone to burning under high temperature, heat, discharge and other conditions, which limits its application in some occasions with strict requirements on flame resistance.

[0004] Magnesium hydroxide is a highly efficient and environmentally friendly inorganic flame retardant and is widely used in high polymer materials. However, the surface of magnesium hydroxide has strong polarity and poor compatibility with organic polymer materials, which leads to uneven dispersion of magnesium hydroxide in the matrix and affects the mechanical properties and flame retardant properties of the composite material. In addition, magnesium hydroxide has a large specific surface area and is prone to agglomeration, which further exacerbates its dispersion problem.

[0005] The traditional method for preparing magnesium hydroxide usually uses brine as raw material to obtain magnesium hydroxide slurry by precipitation method, and then the magnesium hydroxide powder is obtained through filtration, washing, drying and other steps. The specific surface area of magnesium hydroxide prepared by this method is large, and subsequent surface modification is needed 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 improve its compatibility with high molecular materials, the surface modification method is usually used to treat magnesium hydroxide. At present, the methods for modifying magnesium hydroxide with silane coupling agent mainly include dry modification and wet modification. The dry modification process is simple, but the modification effect is uneven; although the wet modification process is relatively complex, the modification effect is better and the utilization rate of modifier is high. Patent application No. CN118852735A discloses a kind of superfine magnesium hydroxide and its preparation method and a kind of polyethylene high flame-retardant low smoke halogen-free cable material. The process includes the following steps: crushing and grinding the original ore of brucite to obtain magnesium hydroxide powder; mixing the magnesium hydroxide powder and grinding aid and then ball milling to obtain a mixture; mixing the mixture, calcium carbonate and modifier and then performing surface modification treatment to obtain superfine magnesium hydroxide. However, the addition amount of magnesium hydroxide prepared by this method in the polyethylene cable material is relatively small, and the improvement of flame retardant performance is relatively limited. SUMMARY

[0006] The present application provides a high volume resistivity magnesium hydroxide, a preparation method and application thereof, and solves the problems of strong surface polarity, large specific surface area, poor compatibility with polymer matrix and inability to be added in large amounts.

[0007] The technical scheme for solving the above technical problem is as follows: a preparation method of high volume resistivity magnesium hydroxide, the preparation method being:

[0008] S1, mixing a magnesium salt solution, lye and lauric acid, and heating to prepare magnesium hydroxide slurry;

[0009] S2, adding fatty alcohol polyoxyethylene ether and polyacrylamide into the magnesium hydroxide slurry, and performing hydrothermal treatment;

[0010] S3, performing heat preservation and aging on the magnesium hydroxide slurry after the hydrothermal treatment in step S2, closing the heating, adding a modifier, uniformly mixing and reacting, and then performing solid-liquid separation, washing, drying to obtain high volume resistivity magnesium hydroxide, the modifier including at least two of titanate coupling agent, water-soluble polymer, silicone and unsaturated organic acid.

[0011] Further, the heating temperature in step S1 is 70-80℃;

[0012] In step S2, the hydrothermal treatment temperature is 180-200℃, and the hydrothermal treatment time is 1.5-2.5h;

[0013] In step S3, the heat preservation and aging temperature is 80-90℃, and the heat preservation and aging time is 5-8h.

[0014] Further, in step S2, the total amount of the fatty alcohol polyoxyethylene ether and the polyacrylamide is 2%-5% of the mass of the magnesium hydroxide, and the mass ratio of the fatty alcohol polyoxyethylene ether to the polyacrylamide is 1: (1.5-2.5).

[0015] Further, in step S3, the amount of the modifier added is 0.5-2% of the mass of the magnesium hydroxide.

[0016] Further, the titanate coupling agent is at least one of bis (dioctyloxyphosphite) ethylene titanate, tetraisopropyl bis (dioctylphosphato) titanate, triisopropyl titanate, diisopropyl titanate, isopropyl tri (dioctylphosphato) titanate.

[0017] Further, the water-soluble polymer is at least one of polyvinyl alcohol, polymaleic acid and polyacrylic acid.

[0018] Further, the organic silicon is at least one of methyl silicone oil, dimethyl silicone oil, hydrogen-containing silicone oil and hydroxyl silicone oil.

[0019] Further, the unsaturated organic acid is at least one of methacrylic acid, itaconic acid, cinnamic acid and maleic acid.

[0020] A high volume resistivity magnesium hydroxide prepared by the preparation method according to the application.

[0021] Application of a high volume resistivity magnesium hydroxide to PE material to obtain a PE composite material, the mass content of the high volume resistivity magnesium hydroxide in the PE composite material being 40-70%.

[0022] The application has the following beneficial effects:

[0023] The high volume resistivity magnesium hydroxide according to the application controls the crystal form of magnesium hydroxide by adding lauric acid, fatty alcohol polyoxyethylene ether and polyacrylamide, so that the prepared magnesium hydroxide has less impurities, high purity, regular crystal form, thick lamella thickness, and the lauric acid, fatty alcohol polyoxyethylene ether and modifier jointly improve the surface properties of magnesium hydroxide, so that the compatibility and dispersibility of magnesium hydroxide with the polymer matrix are good, the negative influence on the mechanical properties and processing fluidity of the material is small, the flame-retardant and insulating effects of magnesium hydroxide are better, good dispersion of magnesium hydroxide in the polymer can reduce internal defects and application concentration points of the material, reduce the aggregation of charges at the defects, and the regularly shaped thick lamella magnesium hydroxide can form a physical barrier to water vapor, oxygen and conductive particles when it is arranged in parallel or overlapped in the polymer, thereby hindering the migration of conductive particles, so that the material has higher volume resistivity and better water boiling aging resistance.

[0024] The crystal growth of Mg(OH)2 has anisotropy, i.e. the growth speed in different crystal axis directions is different. In the absence of an additive, the crystal anisotropic growth tends to grow rapidly along the (100) and (010) directions (lateral direction) and slowly along the (001) direction (vertical direction) due to the lowest surface energy of the (001) crystal face, and finally forms a thin and large two-dimensional sheet or sheet aggregate.

[0025] Lauric acid is added during the reaction of the magnesium salt with the lye. The lauric acid can control the growth habit of the crystal from the nucleation stage. During the crystallization of Mg(OH)2, the laurate ion will specifically and strongly adsorb on the specific crystal face of the growing Mg(OH)2 crystal nucleus through its negatively charged carboxylate, and the long hydrophobic alkyl chain thereof extends outward to form an organic molecular barrier at the crystal-solution interface, which physically hinders the Mg2+ and OH - Ions diffuse to the crystal surface and embed into the lattice. Fatty alcohol polyoxyethylene ether is composed of a hydrophobic aliphatic long-chain alkyl group and a hydrophilic polyoxyethylene chain. During the growth of magnesium hydroxide crystals, the hydrophilic end of the fatty alcohol polyoxyethylene ether can be preferentially adsorbed on the side of the Mg(OH)2 crystal with high surface energy through hydrogen bonding and electrostatic interaction, forming a kinetic barrier and steric hindrance. This barrier will hinder the diffusion of Mg 2+ and OH - Ions diffuse to the crystal surface and embed into the lattice. Fatty alcohol polyoxyethylene ether is composed of a hydrophobic aliphatic long-chain alkyl group and a hydrophilic polyoxyethylene chain. During the growth of magnesium hydroxide crystals, the hydrophilic end of the fatty alcohol polyoxyethylene ether can be preferentially adsorbed on the side of the Mg(OH)2 crystal with high surface energy through hydrogen bonding and electrostatic interaction, forming a kinetic barrier and steric hindrance. This barrier will hinder the diffusion of Mg

[0026] Polyacrylamide is a long-chain polymer with a large number of amide groups on the molecular chain. Amide groups can be simultaneously adsorbed on the surface of multiple Mg(OH)2 microcrystals or primary particles through hydrogen bonding and dipole interaction. Through its unique steric hindrance effect and adsorption, it can effectively limit the lateral growth of magnesium hydroxide flake and promote its vertical stacking, thereby increasing the thickness of the flake to a certain extent. On the other hand, a long chain of polyacrylamide molecules can simultaneously adsorb multiple crystal nuclei, "bridging" or "crosslinking" them to form a network structure in which the free growth of crystals is severely restricted. Because the lateral expansion of the crystal is limited and the bridging effect of polyacrylamide connects many small crystal nuclei together, the system tends to orient and attach during the aging process along the direction with lower energy (vertical) for stacking and assembly. Multiple nascent thin flakes will stack together to form a thicker flake structure.

[0027] The effects of lauric acid, fatty alcohol polyoxyethylene ether, and polyacrylamide on the nucleation process of magnesium hydroxide result in thicker, more uniform, and more stable hexagonal flake-shaped magnesium hydroxide. After the magnesium hydroxide crystal nucleus is stabilized, lauric acid and fatty alcohol polyoxyethylene ether also exhibit their other functions as surfactants, cooperating with other types of modifiers to modify magnesium hydroxide, reducing the addition amount of other modifiers. The modified magnesium hydroxide has good compatibility with the matrix and a tighter interface, significantly increasing the volume resistivity of the material, and the anti-hygroscopicity of the thick flake-shaped magnesium hydroxide is better, making the material more resistant to boiling aging.

[0028] The high volume resistivity magnesium hydroxide described in the application is added into PE material, the adding amount in PE can be up to 40-70%, the vertical combustion level of the composite material reaches V-0 level, the oxygen index reaches 36, the volume resistivity can reach 6.54*10 16 Ω.cm, and the mechanical properties of the composite material are good, the strength can reach 18-30 MPa, and the elongation at break is 325-650%, the high volume resistivity magnesium hydroxide described in the application has regular crystal form, good modification effect, simple preparation process, low production cost, can be added into polymer in large amount, and will not deteriorate the mechanical properties of the material. DETAILED DESCRIPTION

[0029] In order to make the above-mentioned objectives, features and advantages of the present application more apparent and easy to understand, the specific embodiments of the present application are described in detail below. In the following description, a large number of specific details are set forth in order to fully understand the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the scope of the present application, so the present application is not limited by the specific examples disclosed below.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs. The terms used in the specification of the present application herein are only for the purpose of describing the specific embodiments and are not intended to limit the present application.

[0031] A preparation method of high volume resistivity magnesium hydroxide, the preparation method is:

[0032] S1, mix the magnesium salt solution, lye and lauric acid, heat to prepare magnesium hydroxide slurry;

[0033] S2, add fatty alcohol polyoxyethylene ether and polyacrylamide into the magnesium hydroxide slurry, and perform hydrothermal treatment;

[0034] S3, after the hydrothermal treatment of step S2, the magnesium hydroxide slurry is aged, the heating is turned off, a modifier is added and uniformly mixed to react, and then the high volume resistivity magnesium hydroxide is obtained through solid-liquid separation, washing and drying, the modifier includes at least two of titanate coupling agent, water-soluble polymer, silicone and unsaturated organic acid.

[0035] Specifically, the magnesium salt solution is one of magnesium chloride, magnesium sulfate or magnesium nitrate aqueous solution, and the lye is one of ammonia water or sodium hydroxide solution.

[0036] More specifically, in the embodiment of the present application, the magnesium salt solution is magnesium chloride aqueous solution, and the lye is sodium hydroxide solution.

[0037] The amount of lauric acid added is 1-2% of the mass of the magnesium hydroxide, and the molar ratio of the magnesium salt in the magnesium salt solution to the alkali in the alkali solution is 1: (2.1-2.2).

[0038] Specifically, in step S1, the heating temperature is 70-80℃.

[0039] In step S2, the hydrothermal treatment temperature is 180-200℃, and the hydrothermal treatment time is 1.5-2.5h.

[0040] In step S3, the temperature for heat preservation and aging is 80-90℃, and the heat preservation and aging time is 5-8h.

[0041] Specifically, in step S2, the total amount of the fatty alcohol polyoxyethylene ether and the polyacrylamide added is 2%-5% of the mass of the magnesium hydroxide, and the mass ratio of the fatty alcohol polyoxyethylene ether to the polyacrylamide is 1: (1.5-2.5).

[0042] Specifically, in step S3, the amount of the modifier added is 0.5-2% of the mass of the magnesium hydroxide.

[0043] Specifically, the titanate coupling agent is at least one of bis (dioctyloxyphosphato) ethylene titanate, tetraisopropyl di (dioctylphosphito) titanate, triisopropyl titanate, diisopropyl titanate, isopropyl tri (dioctylphosphito) titanate.

[0044] Specifically, the water-soluble polymer is at least one of polyvinyl alcohol, polymaleic acid, and polyacrylic acid.

[0045] Specifically, the organic silicon is at least one of methyl silicone oil, dimethyl silicone oil, hydrogen-containing silicone oil, and hydroxyl silicone oil.

[0046] Specifically, the unsaturated organic acid is at least one of methacrylic acid, itaconic acid, cinnamic acid, and maleic acid.

[0047] More specifically, in step S3, after the modifier is added, stirring is performed, the stirring speed is controlled at 8000-10000rpm, and the reaction time is 30-60min.

[0048] A high-volume-resistivity magnesium hydroxide prepared by the preparation method according to the present application.

[0049] The application of a high-volume-resistivity magnesium hydroxide to PE material to obtain a PE composite material, wherein the mass content of the high-volume-resistivity magnesium hydroxide in the PE composite material is 40-70%.

[0050] More specifically, the details of the raw materials used in the embodiments of the present application are as follows:

[0051] Fatty alcohol polyoxyethylene ether: model AEO-9, manufacturer Jiangsu Haian Petrochemical Factory;

[0052] Polyacrylamide: non-ionic PAM, manufacturer Shandong Fwang Chemical Co., Ltd.;

[0053] Polyvinyl alcohol: PVA-1788, manufacturer Jinan Shengda Chemical Co., Ltd.;

[0054] Polymaleic acid: high molecular weight, manufacturer Shandong Zhengtai New Material Co., Ltd.;

[0055] Polyacrylic acid: PAA-GA, manufacturer Jinan Delan Chemical Co., Ltd.;

[0056] Methyl silicone oil: low viscosity, manufacturer Dow Corning (China) Investment Co., Ltd.;

[0057] Dimethyl silicone oil: model 201-10, Dow Corning (China) Investment Co., Ltd.;

[0058] Hydrogen-containing silicone oil: high hydrogen content, manufacturer Shandong Longhui Chemical Co., Ltd.;

[0059] Hydroxyl silicone oil: model LX0203, manufacturer Shandong Longhui Chemical Co., Ltd.;

[0060] PE material: model 3518CB, manufacturer Exxon Mobil Corporation.

[0061] Example 1

[0062] A preparation method of high volume resistivity magnesium hydroxide, the preparation method comprising:

[0063] (1) Mix the magnesium salt solution with lye and lauric acid in proportion, control the reaction temperature to be 75°C, and prepare magnesium hydroxide slurry;

[0064] (2) Add the magnesium hydroxide slurry to a high-pressure reaction kettle, add fatty alcohol polyoxyethylene ether and polyacrylamide, control the reaction temperature to be 180°C, and hydrothermally treat for 2 hours;

[0065] (3) Adjust the temperature of the magnesium hydroxide slurry after hydrothermal treatment in step (2) to 90°C, then incubate and age for 5 hours, turn off the heating, add a modifier, and control the stirring rate and reaction time;

[0066] (4) After reaching the reaction time, filter, wash, and dry the slurry to obtain high volume resistivity magnesium hydroxide.

[0067] The adding amount of lauric acid is 1.5% of the mass of the magnesium hydroxide; the mass ratio of the fatty alcohol polyoxyethylene ether to the polyacrylamide is 1:2, and the total adding amount of the fatty alcohol polyoxyethylene ether and the polyacrylamide is 2% of the mass of the magnesium hydroxide; the modifier is bis (dioctyloxyphosphite) ethylene titanate and hydroxyl silicone oil; the ratio of the bis (dioctyloxyphosphite) ethylene titanate to the hydroxyl silicone oil is 1.5:1, and the amount of the modifier is 1% of the mass of the magnesium hydroxide;

[0068] In step (3), the stirring speed is controlled to be 10,000 rpm after the modifier is added, and the reaction time is 30 min.

[0069] The prepared high-volume-resistivity magnesium hydroxide is applied to PE, the powder adding amount is 60%, the PE composite material is prepared by mixing uniformly through an open mill, tabletting is performed for performance testing, and the performance test results of the composite material are shown in Table 1.

[0070] Example 2

[0071] A preparation method of high-volume-resistivity magnesium hydroxide, the preparation method comprises:

[0072] (1) A magnesium salt solution, a lye and lauric acid are mixed in proportion, the reaction temperature is controlled to be 70°C, and magnesium hydroxide slurry is prepared;

[0073] (2) The magnesium hydroxide slurry is added to a high-pressure reaction kettle, fatty alcohol polyoxyethylene ether and polyacrylamide are added, the reaction temperature is controlled to be 200°C, and hydrothermal treatment is performed for 1.5 hours;

[0074] (3) The temperature of the magnesium hydroxide slurry after the hydrothermal treatment in step (2) is adjusted to 80°C, then aging is performed for 8 hours under insulation, heating is turned off, a modifier is added, and the stirring speed and the reaction time are controlled;

[0075] (4) After the reaction time is reached, the slurry is filtered, washed and dried, and high-volume-resistivity magnesium hydroxide is prepared.

[0076] The adding amount of lauric acid is 1.5% of the mass of the magnesium hydroxide; the mass ratio of the fatty alcohol polyoxyethylene ether to the polyacrylamide is 1:2, and the total adding amount of the fatty alcohol polyoxyethylene ether and the polyacrylamide is 2% of the mass of the magnesium hydroxide; the modifier is bis (dioctyloxyphosphite) ethylene titanate and hydroxyl silicone oil; the ratio of the bis (dioctyloxyphosphite) ethylene titanate to the hydroxyl silicone oil is 1.5:1, and the amount of the modifier is 1% of the mass of the magnesium hydroxide;

[0077] In step (3), the stirring speed is controlled to be 10,000 rpm after the modifier is added, and the reaction time is 30 min.

[0078] The prepared high volume resistivity magnesium hydroxide is applied to PE, the powder addition amount is 60%, mixed uniformly by an open mill, a PE composite material is prepared, tabletting is carried out to test the performance, and the performance test results of the composite material are shown in Table 1.

[0079] Example 3

[0080] A preparation method of high volume resistivity magnesium hydroxide, the preparation method comprises:

[0081] (1) magnesium salt solution, lye and lauric acid are mixed in proportion, the reaction temperature is controlled to be 80℃, and magnesium hydroxide slurry is prepared;

[0082] (2) the magnesium hydroxide slurry is added to a high-pressure reaction kettle, fatty alcohol polyoxyethylene ether and polyacrylamide are added, the reaction temperature is controlled to be 180℃, and hydrothermal treatment is carried out for 2.5 hours;

[0083] (3) the temperature of the magnesium hydroxide slurry after hydrothermal treatment in step (2) is adjusted to 80℃, then aging is carried out for 6 hours, heating is turned off, a modifier is added, and the stirring speed and reaction time are controlled;

[0084] (4) after the reaction time is reached, the slurry is filtered, washed and dried to prepare high volume resistivity magnesium hydroxide.

[0085] The addition amount of lauric acid is 2% of the mass of the magnesium hydroxide, the mass ratio of the fatty alcohol polyoxyethylene ether to the polyacrylamide is 1:2, the total addition amount of the fatty alcohol polyoxyethylene ether and the polyacrylamide is 4% of the mass of the magnesium hydroxide, the modifier is titanium isopropyl tristearate and polyacrylic acid, the ratio of the titanium isopropyl tristearate to the polyacrylic acid is 3:1, and the amount of the modifier is 2% of the mass of the magnesium hydroxide;

[0086] In step (3), the stirring speed is controlled to be 8000 revolutions / min after the modifier is added, and the reaction time is 60 min;

[0087] The prepared high volume resistivity magnesium hydroxide is applied to PE, the powder addition amount is 50%, mixed uniformly by an open mill, a PE composite material is prepared, tabletting is carried out to test the performance, and the performance test results of the composite material are shown in Table 1.

[0088] Example 4

[0089] A preparation method of high volume resistivity magnesium hydroxide, the preparation method comprises:

[0090] (1) magnesium salt solution, lye and lauric acid are mixed in proportion, the reaction temperature is controlled to be 80℃, and magnesium hydroxide slurry is prepared;

[0091] (2) The magnesium hydroxide slurry is added to a high-pressure reaction kettle, and fatty alcohol polyoxyethylene ether and polyacrylamide are added, the reaction temperature is controlled at 190°C, and the hydrothermal treatment is performed for 2 hours;

[0092] (3) The temperature of the magnesium hydroxide slurry after the hydrothermal treatment in step (2) is adjusted to 85°C, and then the temperature is kept constant for 7 hours, the heating is turned off, the modifier is added, and the stirring speed and reaction time are controlled;

[0093] (4) After the reaction time is reached, the slurry is filtered, washed, and dried to obtain the high-volume-resistivity magnesium hydroxide.

[0094] The amount of lauric acid added is 2% of the mass of the magnesium hydroxide; the mass ratio of the fatty alcohol polyoxyethylene ether to the polyacrylamide is 1:1.5, and the total amount of the fatty alcohol polyoxyethylene ether and the polyacrylamide added is 3% of the mass of the magnesium hydroxide; the modifier is methyl silicone oil and methacrylic acid, the mass ratio of the methyl silicone oil to the methacrylic acid is 1:1, and the amount of the modifier is 1% of the mass of the magnesium hydroxide;

[0095] In step (3), the stirring speed is controlled at 9000 revolutions / min after the modifier is added, and the reaction time is 40 min;

[0096] The high-volume-resistivity magnesium hydroxide obtained is applied to PE, the powder addition amount is 60%, the mixture is uniformly mixed by an open mill, the PE composite material is prepared, the tablet is pressed for performance testing, and the performance test results of the composite material are shown in Table 1.

[0097] Example 5

[0098] A preparation method of high-volume-resistivity magnesium hydroxide, the preparation method comprising:

[0099] (1) A magnesium salt solution, a lye, and lauric acid are mixed in a proportion, and the reaction temperature is controlled at 70°C to prepare a magnesium hydroxide slurry;

[0100] (2) The magnesium hydroxide slurry is added to a high-pressure reaction kettle, and fatty alcohol polyoxyethylene ether and polyacrylamide are added, the reaction temperature is controlled at 200°C, and the hydrothermal treatment is performed for 2 hours;

[0101] (3) The temperature of the magnesium hydroxide slurry after the hydrothermal treatment in step (2) is adjusted to 80°C, and then the temperature is kept constant for 8 hours, the heating is turned off, the modifier is added, and the stirring speed and reaction time are controlled;

[0102] (4) After the reaction time is reached, the slurry is filtered, washed, and dried to obtain the high-volume-resistivity magnesium hydroxide.

[0103] The amount of lauric acid added is 1% of the mass of the magnesium hydroxide; the mass ratio of the fatty alcohol polyoxyethylene ether to the polyacrylamide is 1:2.5, the total amount of the fatty alcohol polyoxyethylene ether and the polyacrylamide added is 5% of the mass of the magnesium hydroxide, the modifier is bis (dioctyloxyphosphite) ethylene titanate, hydroxyl silicone oil and itaconic acid; the mass ratio of the bis (dioctyloxyphosphite) ethylene titanate, the hydroxyl silicone oil and the itaconic acid is 5:0.5:0.5, and the amount of the modifier is 0.5% of the mass of the magnesium hydroxide;

[0104] In step (3), the stirring speed is controlled to be 10,000 rpm after the modifier is added, and the reaction time is 60 min.

[0105] The prepared high-volume-resistivity magnesium hydroxide is applied to PE, the powder addition amount is 60%, the PE composite material is prepared by mixing uniformly through an open mill, tabletting is performed for performance testing, and the performance test results of the composite material are shown in Table 1.

[0106] Example 6

[0107] A preparation method of high-volume-resistivity magnesium hydroxide, the preparation method comprising:

[0108] (1) A magnesium salt solution, a lye and lauric acid are mixed in proportion, the reaction temperature is controlled to be 70°C, and magnesium hydroxide slurry is prepared;

[0109] (2) The magnesium hydroxide slurry is added to a high-pressure reaction kettle, fatty alcohol polyoxyethylene ether and polyacrylamide are added, the reaction temperature is controlled to be 180°C, and hydrothermal treatment is performed for 2 hours;

[0110] (3) The temperature of the magnesium hydroxide slurry after the hydrothermal treatment in step (2) is adjusted to 80°C, then aging is performed for 5-8 hours, the heating is turned off, a modifier is added, and the stirring speed and the reaction time are controlled;

[0111] (4) After the reaction time is reached, the slurry is filtered, washed and dried, and high-volume-resistivity magnesium hydroxide is prepared.

[0112] The amount of lauric acid added is 1.5% of the mass of the magnesium hydroxide; the mass ratio of the fatty alcohol polyoxyethylene ether to the polyacrylamide is 1:2, the total amount of the fatty alcohol polyoxyethylene ether and the polyacrylamide added is 5% of the mass of the magnesium hydroxide, the modifier is bis (dioctyloxyphosphite) ethylene titanate and polymaleic acid; the mass ratio of the bis (dioctyloxyphosphite) ethylene titanate to the polymaleic acid is 1:1, and the amount of the modifier is 1.5% of the mass of the magnesium hydroxide;

[0113] In step (3), the stirring speed is controlled to be 10,000 rpm after the modifier is added, and the reaction time is 60 min.

[0114] The prepared high volume resistivity magnesium hydroxide is applied to PE, the powder addition amount is 60%, mixed uniformly by an open mill, a PE composite material is prepared, tabletting is carried out for performance test, and the performance test results of the composite material are shown in Table 1.

[0115] Comparative Example 1

[0116] The magnesium hydroxide is prepared by the same method of Example 1, and the difference between Comparative Example 1 and Example 1 is that no lauric acid, fatty alcohol polyoxyethylene ether and polyacrylamide are added during the synthesis of magnesium hydroxide. The test results are shown in Table 1.

[0117] Comparative Example 2

[0118] The magnesium hydroxide is prepared by the same method of Example 1, and the difference between Comparative Example 2 and Example 1 is that the modifier used is bis (dioctyloxyphosphite) ethylene titanate. The test results are shown in Table 1.

[0119] Comparative Example 3

[0120] The magnesium hydroxide is prepared by the same method of Example 1, and the difference between Comparative Example 3 and Example 1 is that the modifier used is hydroxyl silicone oil. The test results are shown in Table 1.

[0121] Comparative Example 4

[0122] The magnesium hydroxide is prepared by the same method of Example 1, and the difference between Comparative Example 4 and Example 1 is that the stirring speed used is 5000 rpm, and the test results are shown in Table 1.

[0123] Comparative Example 5

[0124] The magnesium hydroxide is prepared by the same method of Example 1, and the difference between Comparative Example 5 and Example 1 is that the stirring speed used is 15000 rpm, and the test results are shown in Table 1.

[0125] Comparative Example 6

[0126] The magnesium hydroxide is prepared by the same method of Example 1, and the difference between Comparative Example 6 and Example 1 is that the reaction temperature in step (3) is 120℃, and the test results are shown in Table 1.

[0127] Comparative Example 7

[0128] The magnesium hydroxide is prepared by the same method of Example 1, and the difference between Comparative Example 7 and Example 1 is that the reaction temperature in step (3) is 50℃, and the test results are shown in Table 1.

[0129] Comparative Example 8

[0130] The same method as in Example 1 was used to prepare magnesium hydroxide, except that the reaction time was 20 min in this Comparative Example 8, and the test results are shown in Table 1.

[0131] Comparative Example 9

[0132] The same method as in Example 1 was used to prepare magnesium hydroxide, except that the reaction time was 90 min in this Comparative Example 9, and the test results are shown in Table 1.

[0133] Comparative Example 10

[0134] The same method as in Example 1 was used to prepare magnesium hydroxide, except that the amount of modifier was 0.2% of the mass of the magnesium hydroxide in this Comparative Example 10, and the test results are shown in Table 1.

[0135] Comparative Example 11

[0136] The same method as in Example 1 was used to prepare magnesium hydroxide, except that the amount of modifier was 3% of the mass of the magnesium hydroxide in this Comparative Example 11, and the test results are shown in Table 1.

[0137] Comparative Example 12

[0138] The same method as in Example 1 was used to prepare magnesium hydroxide, except that the amount of fatty alcohol polyoxyethylene ether and polyacrylamide added was 1% in this Comparative Example 12, and the test results are shown in Table 1.

[0139] Comparative Example 13

[0140] The same method as in Example 1 was used to prepare magnesium hydroxide, except that the amount of fatty alcohol polyoxyethylene ether and polyacrylamide added was 8% in this Comparative Example 13, and the test results are shown in Table 1.

[0141] Comparative Example 14

[0142] The same method as in Example 1 was used to prepare the PE composite material, except that the magnesium hydroxide used in this Comparative Example 14 was not modified, and the magnesium hydroxide slurry was obtained by directly reacting a magnesium salt with a lye solution, filtering, washing, and drying, and the test results are shown in Table 1.

[0143] Comparative Example 15

[0144] The same method as in Example 1 was used to prepare magnesium hydroxide, except that the mass ratio of fatty alcohol polyoxyethylene ether to polyacrylamide was 1:1 in this Comparative Example 15, and the test results are shown in Table 1.

[0145] Comparative Example 16

[0146] The same method as in Example 1 was used to prepare magnesium hydroxide, and the difference between Comparative Example 16 and Example 1 was that the mass ratio of fatty alcohol polyoxyethylene ether to polyacrylamide was 1:5, and the test results are shown in Table 1.

[0147] Comparative Example 17

[0148] The same method as in Example 1 was used to prepare magnesium hydroxide, and the difference between Comparative Example 17 and Example 1 was that no lauric acid was added in Comparative Example 17, and the test results are shown in Table 1.

[0149] The 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 detection methods involved are as follows: the volume surface resistivity detection standard is GB / T 1410-2006; the tensile test detection standard is GB / T 1040; the limiting oxygen index detection standard is GB / T 2406; and the vertical burning grade detection standard is GB / T 2408.

[0150] Table 1 Performance test results

[0151]

[0152] As can be seen from the above table data, the high volume resistivity magnesium hydroxide prepared by the preparation method of the present application in Examples 1-6 is added to the PE material, the compatibility of the magnesium hydroxide with the PE is good, a large amount of addition will not affect the mechanical properties of the PE material, the PE composite material still maintains good mechanical properties, and can significantly improve the volume resistivity of the composite material, and effectively improves the flame retardant performance of the PE material.

[0153] As can be seen from the comparison of the data of Example 1 and Comparative Example 1: not adding lauric acid, fatty alcohol polyoxyethylene ether and polyacrylamide in the preparation of magnesium hydroxide will significantly reduce the mechanical properties and volume resistivity of the composite material, because lauric acid, fatty alcohol polyoxyethylene ether and polyacrylamide will inhibit the growth of magnesium hydroxide in the horizontal direction by adsorption and steric hindrance effect during the crystal nucleus growth process of magnesium hydroxide, so that the crystal is stacked along the vertical direction, and the obtained magnesium hydroxide has thicker layer, more regular and more uniform crystal form. The regular crystal form of magnesium hydroxide limits the conduction of electrons in the crystal, and it is difficult for electrons to move quickly between layers, thereby reducing the electrical conductivity and showing good insulation.

[0154] As can be seen from the comparison of the data of Example 1 and Comparative Examples 2 and 3: the modification effect of the two modifiers defined in the present application is obviously better than that of a single modifier, because the two modifiers used in the present application can well combine the performance advantages of the two modifiers, and after being applied to the PE material, the mechanical properties and volume resistivity of the PE composite material are both good.

[0155] From the data comparison of Example 1 and Comparative Example 4, Comparative Example 5, it can be seen that: during the reaction, if the stirring speed is too slow or too fast, the modification effect of magnesium hydroxide is poor, because under the same conditions, increasing the stirring speed is beneficial to increasing the dispersion effect of the modifier, so that it is fully coated on the surface of magnesium hydroxide, but when the stirring speed is too fast, the modification effect is reduced. Because in the process of high-speed stirring, the strong friction and shear force makes the modifier coated on the surface of magnesium hydroxide desorb, thereby causing the modification effect to be poor.

[0156] From the data comparison of Example 1 and Comparative Example 6, Comparative Example 7, it can be seen that: if the heating temperature is too high or too low during the reaction, the modification effect is poor, because the reaction speed is slow at low temperature, and under the same conditions, too low reaction temperature will make the reaction of the modifier and magnesium hydroxide incomplete, and the ideal modification effect cannot be achieved, and appropriately increasing the reaction temperature can promote the strong chemical bonding reaction between the hydroxyl group on the surface of magnesium hydroxide and the hydroxyl group and carboxyl group on the surface of the modifier, thereby improving the modification effect of magnesium hydroxide. But too high temperature is easy to make the modifier decompose, volatilize or carbonize, thereby affecting the modification effect of the powder.

[0157] From the data comparison of Example 1 and Comparative Example 8, Comparative Example 9, it can be seen that: if the reaction time is too long or too short, the modification effect is poor, because too short reaction time will make the modifier and the powder not fully react, leading to uneven modification, and too long reaction time will also cause the modifier on the surface of magnesium hydroxide to desorb under the action of long-time stirring and long-time shearing, affecting the modification effect.

[0158] From the data comparison of Example 1 and Comparative Example 10, Comparative Example 11, it can be seen that: if the amount of the modifier is too small or too large, the mechanical properties of the PE composite material will be obviously affected, because the modification effect is best when the modifier reaches monolayer adsorption on the surface of the powder, when the amount of the modifier is small, the modifier cannot form a monolayer coating on the surface of the material, and when the amount of the modifier is too large, the modifier will form multiple layers of physical adsorption on the surface of the magnesium hydroxide powder, causing the interface between the magnesium hydroxide and the polymer to form a weak layer, affecting the connection of the interface, and making the mechanical properties of the composite material decrease. Therefore, using the amount of the modifier defined in the present application is more beneficial to obtain a modified magnesium hydroxide flame retardant with excellent performance.

[0159] From the data comparison of Example 1 and Comparative Example 12, Comparative Example 13, it can be seen that if the addition amount of fatty alcohol polyoxyethylene ether and polyacrylamide is too low or too high, the mechanical properties and volume resistivity of the composite material will decrease. If the addition amount is too low, the nucleation and growth of magnesium hydroxide will be affected. If the addition amount is too high, the steric hindrance effect is enhanced, the adsorption effect on the crystal surface is enhanced, and the nucleation of magnesium hydroxide is inhibited, resulting in the formation of regular crystal, thereby affecting the application effect of magnesium hydroxide in PE material.

[0160] From the data comparison of Example 1 and Comparative Example 14, it can be seen that the application effect of modified magnesium hydroxide in PE composite material is obviously better than that of unmodified magnesium hydroxide. Because the structure of the modifier contains two different chemical functional groups, one end of which can form a chemical bond with the hydroxyl group on the surface of magnesium hydroxide powder, so that the modifier is coated on the surface of magnesium hydroxide particles, and the other end can be combined with PE material, thereby improving the dispersibility of magnesium hydroxide in PE material and firmly combining the two materials with large difference in properties. Therefore, the mechanical properties of the composite material added with modified magnesium hydroxide flame retardant are obviously better than those of the composite material added with unmodified magnesium hydroxide.

[0161] From the data comparison of Example 1 and Comparative Example 15, Comparative Example 16, it can be seen that if the addition ratio of fatty alcohol polyoxyethylene ether and polyacrylamide is not appropriate, the mechanical properties and volume resistivity of the composite material will decrease seriously. If the proportion of fatty alcohol polyoxyethylene ether is high, excessive fatty alcohol polyoxyethylene ether will be adsorbed on almost all crystal nuclei and crystal surfaces, which will inhibit the growth in all directions, so that the size of the generated magnesium hydroxide is too small. These small magnesium hydroxide flakes have poor structural strength and are easy to break, and have very high surface energy, which will seriously agglomerate together, affecting the dispersion in the material and seriously affecting the performance of the composite material. If the proportion of fatty alcohol polyoxyethylene ether is small and the proportion of polyacrylamide is large, the long chain of excessive polyacrylamide will quickly wrap the small magnesium hydroxide crystals just nucleated, forming a large, amorphous flocculation, so that the fatty alcohol polyoxyethylene ether cannot effectively penetrate the polyacrylamide network to be adsorbed on the specific crystal surface, so that the final product becomes a random-shaped particle aggregate, which is difficult to disperse in the polymer, thereby seriously affecting the mechanical properties and volume resistivity.

[0162] From the comparison of the data of Example 1 and Comparative Example 17, it can be seen that if lauric acid is not added in the preparation of magnesium hydroxide, the mechanical properties and volume resistivity of the composite material will obviously decrease. Because lauric acid controls the growth habit of the crystal at the nucleation stage of magnesium hydroxide, and makes the growth of magnesium hydroxide into controllable hexagonal platelets, and in the modification stage, lauric acid participates in the surface modification of magnesium hydroxide as a fatty acid, and a layer of organic molecular layer is coated on the surface of magnesium hydroxide, so that magnesium hydroxide is more uniformly dispersed in the polymer matrix. If lauric acid is not added in the preparation of magnesium hydroxide, the dispersion of magnesium hydroxide in the polymer will be affected, the stress concentration phenomenon will be greatly increased, and thus the mechanical properties and volume resistivity of the composite material will be affected.

[0163] The technical features of the above-described embodiments can be combined arbitrarily, and for the sake of brevity, all possible combinations of the technical features in the above-described embodiments are not described, however, as long as the combinations of the technical features do not exist contradictions, they should be considered as the scope of the present disclosure.

[0164] The above-described embodiments only express several embodiments of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of the patent. It should be pointed out that for ordinary skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are all within the scope of the present application. Therefore, the scope of protection of the present application should be subject to the appended claims.

Claims

1. A method for producing high volume resistivity magnesium hydroxide, characterized by, The preparation method is: S1, the magnesium salt solution is mixed with lye and lauric acid, heated to prepare magnesium hydroxide slurry; S2, in the magnesium hydroxide slurry, fatty alcohol polyoxyethylene ether and polyacrylamide are added, and hydrothermal treatment is carried out; S3, the magnesium hydroxide slurry after hydrothermal treatment in step S2 is aged, the heating is turned off, the modifier is added and uniformly mixed to react, and then high volume resistivity magnesium hydroxide is obtained through solid-liquid separation, washing and drying, wherein the modifier comprises at least two of titanate coupling agent, water-soluble polymer, silicone and unsaturated organic acid; In step S2, the total amount of the fatty alcohol polyoxyethylene ether and the polyacrylamide is 2%-5% of the mass of the magnesium hydroxide, and the mass ratio of the fatty alcohol polyoxyethylene ether to the polyacrylamide is 1: (1.5-2.5); In step S1, the heating temperature is 70-80℃; In step S2, the hydrothermal treatment temperature is 180-200℃, and the hydrothermal treatment time is 1.5-2.5h; In step S3, the aging temperature is 80-90℃, and the aging time is 5-8h.

2. The method for preparing high volume resistivity magnesium hydroxide according to claim 1, characterized in that, In step S3, the amount of the modifier added is 0.5-2% of the mass of the magnesium hydroxide.

3. The method for preparing high volume resistivity magnesium hydroxide according to claim 1, characterized in that, The titanate coupling agent is at least one of bis (dioctyloxyphosphato) ethylene titanate, tetraisopropyl bis (dioctylphosphato) titanate, triisopropyl titanate, diisopropyl titanate, isopropyl tri (dioctylphosphato) titanate.

4. The method for preparing high volume resistivity magnesium hydroxide according to claim 1, characterized in that, The water-soluble polymer is at least one of polyvinyl alcohol, polymaleic acid and polyacrylic acid.

5. The method for preparing high volume resistivity magnesium hydroxide according to claim 1, characterized in that, The silicone is at least one of methyl silicone oil, dimethyl silicone oil, hydrogen-containing silicone oil and hydroxyl silicone oil.

6. The method for preparing high volume resistivity magnesium hydroxide according to claim 1, characterized in that, The unsaturated organic acid is at least one of methacrylic acid, itaconic acid, cinnamic acid and maleic acid.

7. A high volume resistivity magnesium hydroxide characterized in that, The high volume resistivity magnesium hydroxide is prepared by the preparation method according to any one of claims 1-6.

8. Use of the high volume resistivity magnesium hydroxide according to claim 7, characterized in that, The high volume resistivity magnesium hydroxide is applied to PE material to obtain PE composite material, and the mass content of the high volume resistivity magnesium hydroxide in the PE composite material is 40-70%.

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