CN1128199C - Preparation process of magnesium hydroxide fire-retarding nanomaterial - Google Patents
Preparation process of magnesium hydroxide fire-retarding nanomaterial Download PDFInfo
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- CN1128199C CN1128199C CN 01141787 CN01141787A CN1128199C CN 1128199 C CN1128199 C CN 1128199C CN 01141787 CN01141787 CN 01141787 CN 01141787 A CN01141787 A CN 01141787A CN 1128199 C CN1128199 C CN 1128199C
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Abstract
本发明属于化工技术领域，它的主要内容是利用老卤水或菱镁矿得到的精制氯化镁溶液和工业氨水或氨气为原料，或者利用硫酸镁溶液和工业氨水或氨气为原料，采用超重力(旋转填充床)技术，利用液-液相反应或气-液相反应方式，制备纳米氢氧化镁阻燃材料。本工艺解决了传统工艺存在的工艺复杂、成本高、且颗粒粒径不均匀和不易控制等缺点。
The invention belongs to the technical field of chemical industry, and its main content is to use refined magnesium chloride solution obtained from old brine or magnesite and industrial ammonia water or ammonia gas as raw materials, or use magnesium sulfate solution and industrial ammonia water or ammonia gas as raw materials, and adopt supergravity (Rotating packed bed) technology, using liquid-liquid phase reaction or gas-liquid phase reaction mode, to prepare nano-magnesium hydroxide flame retardant materials. This process solves the shortcomings of the traditional process such as complicated process, high cost, uneven particle size and difficult control.
Description
Technical Field
The invention belongs to the technical field of chemical industry, and particularly relates to a novel preparation process of a nano magnesium hydroxide material.
Background
The magnesium hydroxide powder material is an inorganic, smoke-inhibiting and non-toxic flame retardant, is widely applied to the field of high polymer flame retardance, and is suitable for flame retardance and smoke abatement of high polymer materials such as polypropylene, polyethylene, polyvinyl chloride, ethylene propylene diene monomer, unsaturated polyester and the like. The magnesium hydroxide is used as an inorganic flame retardant, has the characteristics of good thermal stability, no toxicity, no volatilization, no generation of corrosive gas, small smoke generation amount, no secondary pollution and the like, and is a main variety of a low-halogen-free flame retardant system.
With the rapid development of the industrial application of high molecular materials, the market demands more and more inorganic flame retardants, and the largest sale amount of magnesium hydroxide is aluminum hydroxide, but compared with magnesium hydroxide, magnesium hydroxide has the advantages of high thermal stability, high efficiency, capability of promoting base materials to form carbon, strong acid removal capability, lower cost, better whiteness and the like, so the magnesium hydroxide has the tendency of replacing aluminum hydroxide in the flame retardant market, and has very considerable market prospect.
However, when the common magnesium hydroxide reaches the flame retardant portion, the mechanical properties of the polymer material are greatly reduced due to the larger particle size of the common magnesium hydroxide, so that when the addition amount of the magnesium hydroxide is increased, the superfine magnesium hydroxide powder is developed in order to better exert the flame retardant effect and reduce the influence on the mechanical properties of the polymer material as much as possible.
The magnesium hydroxide is synthesized by a gas phase method, a metal alkoxide method and a direct precipitation method. The gas phase method has high requirements on equipment and technology and low yield; the metal alkoxide method has high raw material cost and complex process; the direct precipitation method has the advantages of simple and convenient operation, easily obtained raw materials, low production cost and high product purity, and is a synthetic method which is easy to industrialize.
The traditional direct precipitation method is to add a precipitant into a soluble salt solution containing one or more ions to generate a precipitate under a certain condition to be separated out from a mother liquor, so that the general magnesium hydroxide preparation process is to firstly put a magnesium salt solution with a certain concentration into a stirring tank reactor, and dropwise add a proper amount of precipitant NH under a certain temperature and under a full stirring condition3·H2And O, filtering and washing the reaction product until no chloride ion exists after the reaction is completed, drying the magnesium hydroxide precipitate to remove the adsorbed water, and sieving the magnesium hydroxide precipitate to finally obtain the magnesium hydroxide powder.
However, the general magnesium hydroxide preparation process also has many disadvantages: the process flow has the advantages of longer production flow, long heat treatment time, smallproduction yield, higher reaction temperature condition, high energy consumption and large investment; the product quality has the defects of large particle size, uneven distribution, difficult shape control in preparation and the like, so the magnesium hydroxide powder produced by the traditional process can not meet the requirements of modern high polymer material industry on inorganic flame retardant machines.
The invention aims to solve the defects of complex process flow, high energy consumption, large particle size, uneven particle size distribution and difficult shape control of the traditional direct precipitation method, and provides a novel production process method based on a brand-new rotary packed bed (hypergravity) reactor capable of greatly strengthening mass transfer and micro mixing.
Disclosure of Invention
The invention mainly comprises the following contents:
the reaction principle is as follows:
the process uses refined magnesium salt solution and industrial ammonia water or ammonia gas as raw materials to react in a rotary packed bed, and has two reaction modes: a liquid-liquid phase mixed reaction mode and a gas-liquid phase contact reaction mode. The former is that under a certain temperature condition, magnesium salt solution and industrial ammonia water are mixed and reacted with each other in a rotating packed bed to obtain magnesium hydroxide emulsion, and then the magnesium hydroxide emulsion is aged for half an hour to 4 hours, preferably about 1 to 2 hours, to obtain nanoscale flaky magnesium hydroxide; the latter is to circulate magnesium salt solution between a rotary packed bed and a liquid storage tank under the condition of certain temperature and pressure, introduce ammonia gas according to a certain gas-liquid ratio for precipitation reaction, the pH value at the end of the reaction is 8-9, and then keep the temperature and age for half an hour to 4 hours, preferably about 1-2 hours, to obtain the nano-scale magnesium hydroxide. The method can obtain the nano-scale magnesium hydroxide with different shapes under the conditions of controlling different temperatures, different pressures and the like. For example, the magnesium hydroxide is mainly flaky at the normal pressure and the temperature of 60-110 ℃, and is mainly needle-shaped and fibrous nano-scale magnesium hydroxide at the high pressure and the temperature of 110-160 ℃. And filtering, washing, drying and surface treating the suspension obtained by the reaction to obtain the flame retardant grade nano magnesium hydroxide product.
According to one aspect of the invention, the process steps of the invention are as follows:
(A) firstly, preparing a magnesium salt solution;
(B) respectively pouring the magnesium salt solution and ammonia water into a liquid storage tank, heating and raising the temperature, wherein the magnesium salt solution is controlled at 10-100 ℃, and the temperature of the ammonia water is controlled at 10-60 ℃;
(C) starting the rotary packed bed, adjusting the rotating speed of the rotor according to the required granularity of the product, and continuously introducing the magnesium salt solution and ammonia water into the rotary packed bed for reaction to obtain a suspension of magnesium hydroxide precipitate and ammonium salt;
(D) then preserving heat and curing the magnesium hydroxide suspension by a stirring kettle;
(E) carrying out suction filtration on the obtained magnesium hydroxide emulsion product, and washing for 2-3 times by using deionized water;
(F) drying magnesium hydroxide to obtain a nano magnesium hydroxide powder product;
(G) carrying out wet or dry modification on magnesium hydroxide by using a coupling agent to obtain a modified nano magnesium hydroxide flame-retardant material;
(H) optionally calcining at 330-350 ℃ for 2-5 hours, preferably 3-4 hours to obtain the superfine spherical magnesium hydroxide.
Wherein the magnesium salt can be refined magnesium chloride solution or magnesium sulfate solution or other magnesium salt solution obtained from old brine or magnesite, the concentration of the prepared magnesium salt is 10-60%, preferably 25-45%, and the concentration of the ammonia water in the step (B) is preferably 20-30%.
In the step (C), the molar flow rate ratio of the magnesium salt solution to the ammonia water is 1: 2.0-3.5, the linear velocity of a nozzle for introducing the magnesium salt solution into the rotating packed bed is 2-7m/s, and the ammonia water is 4-10 m/s.
The heat preservation curing treatment is carried out for half an hour to 4 hours at the temperature of 80-110 ℃.
The rotating speed of the rotor of the rotating packed bed is 300-2900rpm, the reaction temperature is 40-160 ℃, the reaction pressure is 0-0.6 Mpa, and the rotating speed of the rotor is adjusted by adopting a frequency modulation speed changer. The rotor speed should be selected according to the desired particle size of the product. The smaller the required particle size, the faster the rotation speed, and the smaller the required particle size, the slower the rotation speed.
In the step (F), the magnesium hydroxide filter cake is preferably dried at 140 ℃ for 4-10 hours, preferably about 6 hours.
The coupling agent is a commonsilane coupling agent.
According to a second aspect of the invention, the process of the invention comprises the following steps:
(A) firstly, preparing a magnesium salt solution with a certain concentration;
(B) respectively pouring the magnesium salt solution and ammonia water into a liquid storage tank, heating and raising the temperature, controlling the magnesium salt solution to circulate at 60-160 ℃, and introducing ammonia gas;
(C) starting the rotary packed bed, adjusting the rotating speed of a rotor according to the granularity required by a product, and circulating ammonia gas and a magnesium salt solution in the rotary packed bed according to a certain gas-liquid ratio for precipitation reaction to obtain a suspension of magnesium hydroxide precipitate and ammonium salt;
(D) then preserving heat and curing the magnesium hydroxide suspension by a stirring kettle;
(E) carrying out suction filtration on the obtained magnesium hydroxide emulsion product, and washing with deionized water;
(F) finally, drying the magnesium hydroxide to obtain a nano magnesium hydroxide powder product;
(G) carrying out wet or dry modification on magnesium hydroxide by using a coupling agent to obtain a modified nano magnesium hydroxide flame-retardant material;
(H) optionally calcining at 330-350 ℃ for 2-5 hours, preferably 3-4 hours to obtain the superfine spherical magnesium hydroxide.
Wherein the magnesium salt can be refined magnesium chloride solution or magnesium sulfate solution obtained from old brine or magnesite, and other magnesium salts, the concentration of the prepared magnesium salt is 10-60%, and the gas-liquid ratio of ammonia gas and magnesium salt is 3-15.
The rotating speed of the rotor of the rotating packed bed is 300-2900rpm, the reaction temperature is 40-160 ℃, the reaction pressure is 0-0.6 Mpa, and the rotating speed of the rotor is adjusted by adopting a frequency modulation speed changer. The rotor speed is selected according to the desired particle size of the product.
The heat-insulating aging treatment is preferably carried out at 80 to 110 ℃ for half an hour to 4 hours, preferably 1 hour to 2 hours.
In the step (F), the magnesium hydroxide filter cake is preferably dried at 140 ℃ for 4-10 hours, preferably about 6 hours.
The coupling agent is a common silane coupling agent.
The invention has the advantages of simple development process, small occupied area of required equipment, small investment, low cost, small pollution, short heat treatment time and high yield. Moreover, the magnesium hydroxide product prepared by the method has the advantages of excellent quality, stable performance and uniform particle size, and can be used as a high-grade inorganic flame retardant. The nano-scale magnesium hydroxide particles prepared by the method have the particle size of 20-100nm generally, uniform particle size distribution and purity of more than 96 percent, and meet the requirements of flame retardants. It can also be calcined at 330-350 ℃ for 2-5 hours, preferably 3-4 hours to obtain the ultrafine spherical magnesium oxide.
The nanoscale magnesium hydroxide solves the problem that the mechanical property of the high polymer material is greatly reduced when the flame retardant share is achieved, and has good application prospect. And the particle size and the shape of the magnesium hydroxide product can be adjusted by changing the process conditions of the rotor rotation speed, the material flow rate, the reaction temperature, the reaction time, the pH value and the like of the rotating packed bed, and the nano magnesium hydroxide products with different particle sizes and shapes can be prepared according to different requirements.
Brief Description of Drawings
FIG. 1 is a schematic diagram of a process flow for preparing a nano magnesium hydroxide flame retardant.
Fig. 2 is a schematic structural view of a rotating packed bed, in which 1: a liquid inlet pipe; 2: a housing; 3: a gas inlet pipe; 4: a rotor; 5: a filler; 6: a seal ring; 7: a shaft; 8: a liquid outlet; 9: and a gas outlet. Wherein the rotor speed is regulated by driving a shaft by means of a frequency-modulated variator (not shown in the figure). The raw materials react in the packing to form the product.
Examples
Example 1:
in the liquid-liquid production mode, 30% magnesium salt solution and 20% industrial ammonia water are respectively poured into a liquid storage tank and heated to raise the temperature. The magnesium salt solution is controlled at 95 ℃, and the temperature of the industrial ammonia water is controlled at 35 ℃. The rotating packed bed was started and the rotor speed was adjusted to 700 rpm. The magnesium salt solution and ammonia water are fed into a rotating packed bed according to the molar ratio of 1: 2.5. And controlling the linear velocity of a magnesium salt solution nozzle to be 4m/s and the nozzle velocity of industrial ammonia water to be 7m/s, continuously introducing the solution into the rotating packed bed for reaction, wherein the pH value is 8.5, and obtaining a suspension of magnesium hydroxide precipitate and ammonium salt. Then keeping the temperature of the magnesium hydroxide suspension at 90 ℃ for 120min by using a stirring kettle. The resulting suspension of magnesium hydroxide was filtered and washed 3 times with deionized water. Finally, drying the magnesium hydroxide filter cake for 6 hours at 120 ℃ to obtain flaky nano magnesium hydroxide powder with the average particle size of 90nm, and then carrying out surface treatment to obtain the nano magnesium hydroxide flame retardant.
Example 2
In the liquid-liquid production mode, 30% magnesium salt solution and 20% industrial ammonia water are respectively poured into a liquid storage tank and heated to raise the temperature. The magnesium salt solution is controlled at 20 ℃, and the temperature of the industrial ammonia water is controlled at 20 ℃. The rotating packed bed was started and the rotor speed was adjusted to 1200 rpm. The magnesium salt solution and ammonia water are fed into a rotating packed bed according to the molar ratio of 1: 2.2. And controlling the linear velocity of a magnesium salt solution nozzle to be 4m/s and the nozzle velocity of industrial ammonia water to be 7m/s, continuously introducing the solution into the rotating packed bed for reaction, wherein the pH value is 8.5, and obtaining a suspension of magnesium hydroxide precipitate and ammonium salt. Then keeping the temperature of the magnesium hydroxide suspension at 90 ℃ for 120min by using a stirring kettle. The resulting suspension of magnesium hydroxide was filtered and washed 3 times with deionized water. And finally, drying the magnesium hydroxide filter cake at the temperature of 100-140 ℃ for 4-6 hours to obtain flaky nano magnesium hydroxide powder with the average particle size of 40nm, and performing surface treatment to obtain the nano magnesium hydroxide flame retardant.
Example 3
In the liquid-liquid production mode, 30% magnesium salt solution and 20% industrial ammonia water are respectively poured into a liquid storage tank and heated to raise the temperature. The magnesium salt solution is controlled at 95 ℃, and the temperature of the industrial ammonia water is controlled at 30 ℃. The rotating packed bed was started and the rotor speed was adjusted to 1000 rpm. The magnesium salt solution and ammonia water are fed into a rotating packed bed according to the molar ratio of 1: 2.2. And controlling the linear velocity of a magnesium salt solution nozzle to be 6m/s and the nozzle velocity of industrial ammonia water to be 10m/s, continuously introducing the industrial ammonia water into the rotary packed bed for reaction, and controlling the pH value to be 8 to obtain a suspension of magnesium hydroxide precipitate and ammonium salt. Then keeping the temperature of the magnesium hydroxide suspension at 90 ℃ for 120min by using a stirring kettle. The resulting suspension of magnesium hydroxide was filtered and washed 3 times with deionized water. Finally, drying the magnesium hydroxide filter cake at the temperature of 100-140 ℃ for 4-6 hours; the obtained powder particles are flaky nano magnesium hydroxide powder with the average particle size of 60nm, and then the nano magnesium hydroxide flame retardant is obtained through surface treatment.
Example 4
In the gas-liquid production mode, 30% magnesium salt solution is controlled to circulate in a rotating packed bed at 90 ℃, ammonia gas is introduced, the ammonia gas is subjected to precipitation reaction according to the gas-liquid ratio of 15: 1, the pH value at the end of the reaction is 8, and suspension of magnesium hydroxide precipitate and ammonium salt is obtained. And then keeping the temperature of the magnesium hydroxide suspension liquid in the stirring kettle for 100 min. The resulting suspension of magnesium hydroxide is filtered and washed 2-3 times with deionized water. And finally, drying the magnesium hydroxide filter cake at the temperature of 100-140 ℃ for 4-6 hours to obtain the flake-shaped nano magnesium hydroxide powder with the average particle size of 80 nm, and carrying out surface treatment to obtain the nano magnesium hydroxide flame retardant.
Example 5:
in the gas-liquid production mode, 25% magnesium salt solution is controlled at 120 ℃, the pressure is 0.2MPa, the solution circulates in a rotating packed bed, ammonia gas is introduced, the ammonia gas is subjected to precipitation reaction according to the gas-liquid ratio of 10: 1, the pH value at the reaction end point is 8, and suspension of magnesium hydroxide precipitate and ammonium salt is obtained. And then keeping the temperature of the magnesium hydroxide suspension liquid in the stirring kettle for 60 min. The resulting suspension of magnesium hydroxide is filtered and washed 2-3 times with deionized water. And finally, drying the magnesium hydroxide filter cake at the temperature of 100-140 ℃ for 4-6 hours to obtain needle-shaped nano magnesium hydroxide powder with the average particle size of 50nm, and carrying out surface treatment to obtain the nano magnesium hydroxide flame retardant.
Example 6
In the gas-liquid production mode, 25% magnesium salt solution is circulated in a rotating packed bed at the temperature of 155 ℃ and the pressure of 0.5MPa, pressurized ammonia gas is introduced, the ammonia gas is subjected to precipitation reaction according to the gas-liquid ratio of 10: 1, and the pH at the end of the reaction is 8, so that suspension of magnesium hydroxide precipitate and ammonium salt is obtained. And then keeping the temperature of the magnesium hydroxide suspension liquid in the stirring kettle for 60 min. The resulting suspension of magnesium hydroxide was filtered and washed 3 times with deionized water. And finally, drying the magnesium hydroxide filter cake for 6 hours at 120 ℃ to obtain fiber-shaped nano magnesium hydroxide powder with the powder particles of 35nm average particle size, and carrying out surface treatment to obtain the nano magnesium hydroxide flame retardant.
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| CN 01141787 CN1128199C (en) | 2001-09-19 | 2001-09-19 | Preparation process of magnesium hydroxide fire-retarding nanomaterial |
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| CN100372771C (en) * | 2004-07-09 | 2008-03-05 | 华东理工大学 | Preparation method of high-purity nano-magnesium hydroxide |
| CN100350015C (en) * | 2005-01-18 | 2007-11-21 | 西北师范大学 | Palygorskite compound flame retardant |
| CN1295270C (en) * | 2005-02-23 | 2007-01-17 | 杨第伦 | Process for preparing magnesium hydroxide loose nano blocked flame retardant and products therefrom |
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| CN1331984C (en) * | 2006-02-23 | 2007-08-15 | 山东大学 | Prepn of magnesium hydroxide for fire retardant |
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| CN113277534A (en) * | 2021-05-07 | 2021-08-20 | 李治涛 | Synthesis method of nano-scale magnesium hydroxide |
| GR1010709B (en) | 2023-05-12 | 2024-06-19 | Εθνικο Κεντρο Ερευνας Και Τεχνολογικης Αναπτυξης (Ε.Κ.Ε.Τ.Α.), | One-step hydromagnesite nanoparticles production method performed in an intensified rotating bed arrangement furnished with filler |
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