CN1341694A - Preparation process of magnesium hydroxide fire-retarding nanomaterial - Google Patents

Abstract

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

A new preparation process of nano-magnesium hydroxide flame retardant material

field of invention

The invention belongs to the technical field of chemical industry, and in particular relates to a new preparation process of nano magnesium hydroxide material.

Background technique

Magnesium hydroxide powder material is an inorganic, smoke-suppressing, non-toxic flame retardant, widely used in the field of high polymer flame retardant, suitable for polypropylene, polyethylene, polyvinyl chloride, EPDM rubber and unsaturated polyethylene Flame retardant and smoke suppression of polymer materials such as esters. As an inorganic flame retardant, magnesium hydroxide has the characteristics of good thermal stability, non-toxic, non-volatile, no corrosive gas, less smoke, no secondary pollution, etc. It is a low-halogen, halogen-free flame retardant The main types of the system.

With the rapid development of the industrial application of polymer materials, the market demand for inorganic flame retardants is increasing. The largest sales volume is aluminum hydroxide, but compared with it, magnesium hydroxide has high thermal stability, high efficiency, It can promote the carbonization of substrates, strong acid removal ability, lower cost, better whiteness and other advantages. Therefore, it has a tendency to replace aluminum hydroxide in the flame retardant market, and the market prospect is very promising.

However, when ordinary magnesium hydroxide reaches the flame retardant ratio, because of its large particle size, the mechanical properties of polymer materials are too reduced. Therefore, when the amount of magnesium hydroxide is increased, in order to better exert its flame retardant effect, and To minimize the impact on the mechanical properties of polymer materials, the ultra-fine magnesium hydroxide powder is the development direction.

Magnesium hydroxide is synthesized by gas phase method, metal alkoxide method and direct precipitation method. The gas phase method has high requirements on equipment and technology and low output; the metal alkoxide method has high raw material cost and complicated process; the direct precipitation method is easy to operate, easy to obtain raw materials, low production cost, and high product purity. It is a synthetic method that is easy to industrialize.

The traditional direct precipitation method is to add a precipitant to a soluble salt solution containing one or more ions, and under certain conditions, a precipitate is formed and precipitated from the mother liquor. Therefore, the general magnesium hydroxide preparation process is to first add a certain concentration of magnesium salt The solution is placed in a stirred tank reactor, and an appropriate amount of precipitant NH ₃ ·H ₂ O is added dropwise at a certain temperature and under sufficient stirring conditions. After the reaction is complete, it is filtered and washed until there is no chloride ion, and the magnesium hydroxide precipitate is dried and removed. After removing the adsorbed water, sieve to finally obtain the powder of magnesium hydroxide.

However, the general magnesium hydroxide preparation process also has many disadvantages: in the process flow, the production process is long, the heat treatment time is long, the production output is small, the reaction temperature condition is high, the energy consumption is large, and the investment is large; Large and uneven distribution, difficult to control the shape and other shortcomings in the preparation, so the magnesium hydroxide powder produced by the traditional process often cannot meet the requirements of the modern polymer material industry for inorganic flame retardants.

The purpose of the present invention is to solve the shortcomings of the traditional process of direct precipitation, such as complex process, high energy consumption, large particle size, uneven particle size distribution, and difficult to control the shape, and proposes a new method that can greatly strengthen the conventional process. A new production process based on a rotating packed bed (high gravity) reactor with high quality and enhanced micro-mixing.

Contents of the invention

Main content of the present invention:

Reaction principle:

This process uses refined magnesium salt solution and industrial ammonia water or ammonia gas as raw materials to react in a rotary packed bed. It has two reaction modes: liquid-liquid phase mixed reaction mode and gas-liquid phase contact reaction mode. The former is that under certain temperature conditions, magnesium salt solution and industrial ammonia water are mixed and reacted in a rotating packed bed to obtain a magnesium hydroxide emulsion, and then heat-preserved and matured for half an hour to 4 hours, preferably about 1-2 hours, to obtain Nano-scale flake magnesium hydroxide; the latter is to circulate the magnesium salt solution between the rotating packed bed and the liquid storage tank under certain temperature and pressure conditions, and pass ammonia gas into the precipitation reaction according to a certain gas-liquid ratio, and the pH at the end of the reaction is value is 8-9, and then heat-preserved and matured for half an hour to 4 hours, preferably about 1-2 hours, to obtain nano-sized magnesium hydroxide. In this way, different shapes of nano-sized magnesium hydroxide can be obtained under conditions such as controlling different temperatures and different pressures. For example, at normal pressure and temperature of 60-110°C, it is mainly flake, and at high pressure and temperature of 110-160°C, it is mainly needle-like and fibrous nano-sized magnesium hydroxide. Filtration, washing, drying and surface treatment of the suspension obtained from the reaction can produce a flame retardant-grade nano-magnesium hydroxide product.

According to a solution of the present invention, the processing steps of the present invention are as follows:

(A) at first prepare magnesium salt solution;

(B) Pour the magnesium salt solution and ammonia water into the liquid storage tank respectively, and heat up, the magnesium salt solution is controlled at 10-100°C, and the ammonia water temperature is controlled at 10-60°C;

(C) start the rotary packed bed, adjust the rotor speed according to the required particle size of the product, continuously feed the magnesium salt solution and ammonia into the rotary packed bed for reaction, and obtain a suspension of magnesium hydroxide precipitation and ammonium salt;

(D) then the magnesium hydroxide suspension is processed by stirring tank insulation aging;

(E) Suction filtration of the magnesium hydroxide emulsion product of gained is washed 2-3 times with deionized water;

(F) magnesium hydroxide is dried, obtains nanometer magnesium hydroxide powder product;

(G) Magnesium hydroxide is carried out wet method or dry method modification with coupling agent, can obtain modified nano-magnesium hydroxide flame-retardant material;

(H) Optionally calcining at 330-350° C. for 2-5 hours, preferably 3-4 hours, to obtain ultrafine spherical magnesium hydroxide.

Wherein the magnesium salt can be refined magnesium chloride solution or magnesium sulfate solution or other magnesium salt solutions obtained by utilizing old brine or magnesite, and the prepared magnesium salt concentration is 10-60%, preferably 25-45%, in step (B) The concentration of ammonia water 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 speed of the nozzle of the magnesium salt solution flowing into the rotating packed bed is 2-7m/s, and the ammonia water is 4-10m/s.

The heat preservation curing treatment is carried out at 80-110° C. for half an hour to 4 hours.

The rotor speed of the rotary packed bed is 300-2900rpm, the reaction temperature is 40-160°C, the reaction pressure is 0-0.6Mpa, and the rotor speed is adjusted by a frequency-adjustable speed changer. The rotor speed should be selected according to the required particle size of the product. The smaller the particle size required, the faster the speed, and the smaller the particle size, the slower the speed.

In step (F), the magnesium hydroxide filter cake is preferably dried at 100-140°C for 4-10 hours, preferably about 6 hours.

The coupling agent is a common silane coupling agent.

According to second scheme of the present invention, technique of the present invention comprises the following steps:

(A) at first prepare the magnesium salt solution of certain concentration;

(B) Pour the magnesium salt solution and ammonia water into the liquid storage tank respectively, and heat up, the magnesium salt solution is controlled to circulate at 60-160 ° C, and ammonia gas is introduced;

(C) Start the rotary packed bed, adjust the rotor speed according to the required particle size of the product, circulate the ammonia gas and magnesium salt solution in the rotary packed bed according to a certain gas-liquid ratio for precipitation reaction, and obtain magnesium hydroxide precipitate and ammonium salt the suspension;

(D) then the magnesium hydroxide suspension is processed by stirring tank insulation aging;

(E) Suction filtration of the magnesium hydroxide emulsion product of gained is washed with deionized water;

(F) magnesium hydroxide is dried at last, obtains nanometer magnesium hydroxide powder product;

(G) Magnesium hydroxide is carried out wet method or dry method modification with coupling agent, can obtain modified nano-magnesium hydroxide flame-retardant material;

(H) Optionally calcining at 330-350° C. for 2-5 hours, preferably 3-4 hours, to obtain ultrafine spherical magnesium hydroxide.

Among them, the magnesium salt can be refined magnesium chloride solution or magnesium sulfate solution and other magnesium salts obtained by using old brine or magnesite, and the prepared magnesium salt concentration is 10-60%, and the gas-liquid ratio of ammonia gas and magnesium salt is 3-15%. .

The rotor speed of the rotary packed bed is 300-2900rpm, the reaction temperature is 40-160°C, the reaction pressure is 0-0.6Mpa, and the rotor speed is adjusted by a frequency-adjustable speed changer. The rotor speed is selected according to the desired particle size of the product.

The heat preservation curing treatment is preferably carried out at 80-110° C. for half an hour to 4 hours, preferably 1 hour to 2 hours.

In step (F), the magnesium hydroxide filter cake is preferably dried at 100-140°C for 4-10 hours, preferably about 6 hours.

The coupling agent is a common silane coupling agent.

The process steps developed by the invention are simple, the required equipment occupies less land, the investment is small, the cost is low, the pollution is small, the heat treatment time is short, and the yield is high. Moreover, the magnesium hydroxide prepared by the invention has good quality, stable performance and uniform particle size, and can be used as a high-grade inorganic flame retardant. The particle size of the nano-sized magnesium hydroxide particles prepared by the invention is generally 20-100nm, the particle size distribution is uniform, and the purity is greater than 96%, which meets the requirements of flame retardants. It can also be calcined at 330-350°C for 2-5 hours, preferably 3-4 hours to obtain ultrafine spherical magnesium oxide.

Nano-scale magnesium hydroxide solves the contradiction that the mechanical properties of polymer materials decrease too much when the flame retardant ratio is reached, and has a good application prospect. Moreover, the particle size and shape of the magnesium hydroxide product can be adjusted by changing the process conditions such as the rotor speed of the rotating packed bed, the material flow rate, the reaction temperature, the reaction time, and the pH value, and different particle sizes and shapes can be produced according to different requirements. Shaped nano-magnesium hydroxide products.

Brief description of the drawings

Fig. 1 is a schematic diagram of the preparation process of nano-magnesium hydroxide flame retardant.

Figure 2 is a schematic structural diagram of a rotating packed bed, where 1: liquid inlet pipe; 2: shell; 3: gas inlet pipe; 4: rotor; 5: packing; 6: sealing ring; 7: shaft; 8: liquid outlet; 9: Gas outlet. The rotating speed of the rotor is adjusted by driving the shaft through a frequency modulation speed changer (not shown in the figure). The raw materials react within the packing to form products.

Example

Example 1:

In the liquid-liquid production mode, pour 30% magnesium salt solution and 20% industrial ammonia water into the liquid storage tank respectively, and heat up. The magnesium salt solution is controlled at 95°C, and the temperature of industrial ammonia is controlled at 35°C. Start the rotating packed bed and adjust the rotor speed to 700rpm. The magnesium salt solution and ammonia water are sent into the rotating packed bed according to the molar ratio of 1:2.5. Control the linear speed of the magnesium salt solution nozzle to 4m/s, and the industrial ammonia water nozzle speed to 7m/s to continuously feed into the rotating packed bed for reaction, with a pH value of 8.5, to obtain a suspension of magnesium hydroxide precipitate and ammonium salt. Then the magnesium hydroxide suspension was kept at 90°C by stirring the kettle, and the time was controlled at 120min. The resulting magnesium hydroxide suspension was filtered and washed 3 times with deionized water. Finally, the magnesium hydroxide filter cake was dried at 120° C. for 6 hours to obtain a flake-shaped nano-magnesium hydroxide powder with an average particle size of 90 nm, and then surface-treated to form a nano-magnesium hydroxide flame retardant.

Example 2

In the liquid-liquid production mode, pour 30% magnesium salt solution and 20% industrial ammonia water into the liquid storage tank respectively, and heat up. The magnesium salt solution is controlled at 20°C, and the temperature of industrial ammonia is controlled at 20°C. Start the rotating packed bed and adjust the rotor speed to 1200rpm. The magnesium salt solution and ammonia water are sent into the rotating packed bed according to the molar ratio of 1:2.2. Control the linear speed of the magnesium salt solution nozzle to 4m/s, and the industrial ammonia water nozzle speed to 7m/s to continuously feed into the rotating packed bed for reaction, with a pH value of 8.5, to obtain a suspension of magnesium hydroxide precipitate and ammonium salt. Then the magnesium hydroxide suspension was kept at 90°C by stirring the kettle, and the time was controlled at 120min. The resulting magnesium hydroxide suspension was filtered and washed 3 times with deionized water. Finally, dry the magnesium hydroxide filter cake at 100-140°C for 4-6 hours to obtain flake nano-magnesium hydroxide powder with an average particle size of 40nm, and then surface-treated it into a nano-magnesium hydroxide flame retardant .

Example 3

In the liquid-liquid production mode, pour 30% magnesium salt solution and 20% industrial ammonia water into the liquid storage tank respectively, and heat up. The magnesium salt solution is controlled at 95°C, and the temperature of industrial ammonia is controlled at 30°C. Start the rotating packed bed and adjust the rotor speed to 1000rpm. The magnesium salt solution and ammonia water are sent into the rotating packed bed according to the molar ratio of 1:2.2. The linear speed of magnesium salt solution nozzle is controlled to be 6m/s, and the nozzle speed of industrial ammonia water is 10m/s to continuously feed into the rotating packed bed for reaction, the pH value is 8, and a suspension of magnesium hydroxide precipitate and ammonium salt is obtained. Then the magnesium hydroxide suspension was kept at 90°C by stirring the kettle, and the time was controlled at 120min. The resulting magnesium hydroxide suspension was filtered and washed 3 times with deionized water. Finally, dry the magnesium hydroxide filter cake at 100-140°C for 4-6 hours to obtain flake nano-magnesium hydroxide powder with an average particle size of 60nm, and then surface-treated it into a nano-magnesium hydroxide flame retardant .

Example 4

Under the gas-liquid production mode, the 30% magnesium salt solution is controlled at 90 ° C and circulated in the rotating packed bed, and ammonia gas is introduced, and the precipitation reaction is carried out according to the gas-liquid ratio of 15:1 ammonia gas, and the pH of the reaction end point is 8. A suspension of magnesium hydroxide precipitate and ammonium salt was obtained. Then the magnesium hydroxide suspension was kept warm by the stirring tank, and the time was controlled at 100min. The resulting magnesium hydroxide suspension was filtered and washed 2-3 times with deionized water. Finally, dry the magnesium hydroxide filter cake at 100-140°C for 4 to 6 hours to obtain a sheet-shaped nano-magnesium hydroxide powder with an average particle size of 80nm, and then surface-treated it into a nano-magnesium hydroxide flame retardant .

Example 5:

Under the gas-liquid production mode, the 25% magnesium salt solution is controlled at a temperature of 120° C., and the pressure is 0.2 MPa to circulate in the rotating packed bed, and ammonia gas is introduced, and the ammonia gas is precipitated according to the gas-liquid ratio of 10:1. The reaction The end point pH was 8, and a suspension of magnesium hydroxide precipitate and ammonium salt was obtained. Then the magnesium hydroxide suspension was kept warm by the stirring tank, and the time was controlled at 60min. The resulting magnesium hydroxide suspension was filtered and washed 2-3 times with deionized water. Finally, dry the magnesium hydroxide filter cake at 100-140°C for 4-6 hours to obtain a needle-shaped nano-magnesium hydroxide powder with an average particle size of 50nm, and then surface-treated it into a nano-magnesium hydroxide flame retardant .

Example 6

In the gas-liquid production mode, the 25% magnesium salt solution is controlled at a temperature of 155°C and circulated in a rotating packed bed under a pressure of 0.5 MPa, and pressurized ammonia gas is introduced, and the precipitation reaction is carried out according to the gas-liquid ratio of 10:1 ammonia gas , the pH at the end of the reaction was 8, and a suspension of magnesium hydroxide precipitate and ammonium salt was obtained. Then the magnesium hydroxide suspension was kept warm by the stirring tank, and the time was controlled at 60min. The resulting magnesium hydroxide suspension was filtered and washed 3 times with deionized water. Finally, the magnesium hydroxide filter cake was dried at 120° C. for 6 hours to obtain a fiber-shaped nano-magnesium hydroxide powder with an average particle size of 35 nm, and then surface treated to form a nano-magnesium hydroxide flame retardant.

Claims (12)

1, the preparation technology of nanometer magnesium hydroxide is characterized in that this technology comprises the following steps successively: (A) at first prepare magnesium salt solution; (B) Pour the magnesium salt solution and ammonia water into the liquid storage tank respectively, and heat up, the magnesium salt solution is controlled at 10-100°C, and the ammonia water temperature is controlled at 10-60°C; (C) start the rotary packed bed, adjust the rotor speed according to the required particle size of the product, continuously feed the magnesium salt solution and ammonia into the rotary packed bed for reaction, and obtain a suspension of magnesium hydroxide precipitation and ammonium salt; (D) then the magnesium hydroxide suspension is processed by stirring tank insulation aging; (E) Suction filtration of the magnesium hydroxide emulsion product of gained is washed with deionized water; (F) magnesium hydroxide is dried, obtains nanometer magnesium hydroxide powder product; (G) Magnesium hydroxide is carried out wet method or dry method modification with coupling agent, can obtain modified nano-magnesium hydroxide flame-retardant material; (H) Optionally calcining at 330-350° C. for 2-5 hours to obtain ultrafine spherical magnesium hydroxide. 2. The preparation process of ultra-fine magnesium hydroxide according to claim 1, characterized in that the magnesium salt is refined magnesium chloride solution or magnesium sulfate solution obtained by utilizing old brine or magnesite, and the prepared magnesium salt concentration is 10- 60%, the concentration of ammoniacal liquor is 20-30% in the step (B). 3. The preparation process of ultrafine magnesium hydroxide according to claim 1, characterized in that in step (C), the molar flow rate ratio of the magnesium salt solution to ammonia water is 1: 2.0-3.5, and the magnesium salt solution is fed into the rotary filling The linear velocity of the spout of the bed is 2-7m/s, and the ammonia water is 4-10m/s. 4. The preparation process of ultrafine magnesium hydroxide according to claim 1, characterized in that the heat preservation and aging treatment is carried out at 80-110°C for half an hour to 4 hours. 5. The preparation process of ultra-fine magnesium hydroxide according to claim 1, characterized in that the rotor speed of the rotating packed bed is 300-2900rpm, the reaction temperature is 40-160°C, the reaction pressure is 0-0.6Mpa, and the frequency modulation speed changer is used Adjust the rotor speed. 6. The preparation process of ultrafine magnesium hydroxide according to claim 1, characterized in that the coupling agent is a silane coupling agent. 7, the preparation technology of nano-magnesium hydroxide, it is characterized in that this technology comprises the following steps successively: (A) at first prepare the magnesium salt solution of certain concentration; (B) Pour the magnesium salt solution and ammonia water into the liquid storage tank respectively, and heat up, the magnesium salt solution is controlled to circulate at 60-160 ° C, and ammonia gas is introduced; (C) Start the rotary packed bed, adjust the rotor speed according to the required particle size of the product, circulate the ammonia gas and magnesium salt solution in the rotary packed bed according to a certain gas-liquid ratio for precipitation reaction, and obtain magnesium hydroxide precipitate and ammonium salt the suspension; (D) then the magnesium hydroxide suspension is processed by stirring tank insulation aging; (E) Suction filtration of the magnesium hydroxide emulsion product of gained is washed with deionized water; (F) magnesium hydroxide is dried at last, obtains nanometer magnesium hydroxide powder product; (G) Magnesium hydroxide is carried out wet method or dry method modification with coupling agent, can obtain modified nano-magnesium hydroxide flame-retardant material; (H) Optionally calcining at 330-350° C. for 2-5 hours to obtain ultrafine spherical magnesium hydroxide. 8. The preparation process of ultra-fine magnesium hydroxide according to claim 7, characterized in that the magnesium salt is refined magnesium chloride solution or magnesium sulfate solution obtained from old brine or magnesite, and the prepared magnesium salt concentration is 10- 60%. 9. The preparation process of ultra-fine magnesium hydroxide according to claim 7, characterized in that the gas-liquid ratio of ammonia gas and magnesium salt is 3-15. 10. The preparation process of ultra-fine magnesium hydroxide according to claim 7, characterized in that the rotor speed of the rotating packed bed is 300-2900rpm, the reaction temperature is 40-160°C, the reaction pressure is 0-0.6Mpa, and the frequency modulation speed changer is used Adjust the rotor speed. 11. The preparation process of ultrafine magnesium hydroxide according to claim 7, characterized in that the heat preservation and aging treatment is carried out at 80-110°C for half an hour to 4 hours. 12. The preparation process of ultrafine magnesium hydroxide according to claim 7, characterized in that the coupling agent is a silane coupling agent.

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