KR20090099928A - Process for incombustible magnesium hydroxide - Google Patents

Abstract

PURPOSE: A method for manufacturing flame-retardant magnesium hydroxide is provided to show high dispersibility even when the highly concentrated magnesium hydroxide is added to synthetic resin as a flame-retardant agent. CONSTITUTION: A method for manufacturing flame-retardant magnesium hydroxide comprises the following steps of: putting 20-60wt% of 15-30% magnesium salt solution among its total amount in a reactor at 30~60°C; slowly adding 15-50wt% of 40-60% alkaline solution among its total amount and powerfully agitating them; agitating them at 30~80°C and normal pressure for 1-3 hours in order to induce gelation; raising the temperature up to 100~120°C at normal pressure after the gelation, and making progress of crystallization for 3-7 hours; slowly adding the rest of the 15-30% magnesium salt solution to it after the crystallization; making progress of second crystallization at 90~120°C and normal pressure for 3-7 hours; and washing the obtained flame-retardant magnesium hydroxide with distilled water after the second crystallization and drying it at 120~180°C for 1-3 hours.

Description

Process for producing flame retardant magnesium hydroxide {Process for Incombustible Magnesium Hydroxide}

The present invention relates to a method for producing flame retardant magnesium hydroxide, and more particularly, to manufacturing a flame retardant magnesium hydroxide capable of producing magnesium hydroxide fine particles in a plate-shaped shape to be suitable as a flame retardant material requiring uniformity and high dispersibility under normal pressure conditions. It is about a method.

Magnesium hydroxide is a Mg (OH) ₂ chemical formula, and it is a hydroxide of magnesium, which is a raw material for metal magnesium, adsorbent for containing wastewater, flue gas desulfurizer, drainage neutralizer, heavy oil boiler corrosion inhibitor, etc. It is widely used in medicine, such as antacids and animal medicines.

In addition, halogen compounds, antimony trioxide, phosphorus compounds, and the like are frequently used as flame retardants. Since these flame retardants generate a large amount of smoke and organic gas in a fire, their use has recently been reduced.

In recent years, magnesium hydroxide has a small amount of smoke during combustion, which prevents suffocation due to smoke, and is a non-toxic environmentally friendly substance, and exhibits flame retardant characteristics (fire and suppression of fire) by releasing water vapor (water) during combustion. As a new flame retardant, it is in the limelight.

A method using conventional ionized water, seawater or magnesia for producing magnesium hydroxide, using lime or caustic soda as alkali source, a method by hydrating magnesium oxide, crystallizing magnesium hydroxide crystals by reacting magnesium salt with ammonia It is a method to make it. These manufacturing methods differ in that the shape of the magnesium hydroxide particles is specific, making it difficult to obtain magnesium hydroxide having a plate-like shape and a uniform particle size distribution for uniformity and high dispersibility required as a flame retardant.

Therefore, various methods have been proposed and utilized under high temperature and high pressure to obtain magnesium hydroxide having a plate-like shape and a uniform particle size distribution.

By the way, the conventional method of reacting at high temperature and high pressure conditions is expensive manufacturing equipment, there is a limit to the size of the reactor equipment is difficult to mass production, high energy consumption, there is a problem that there is a risk of industrial safety.

An object of the present invention is to solve the above problems, to provide a flame-retardant magnesium hydroxide manufacturing method capable of producing a plate-shaped magnesium hydroxide having a uniformity and high dispersibility by reacting a magnesium salt and an alkaline solution under normal pressure conditions will be.

Flame retardant magnesium hydroxide production method proposed in the present invention is to put a 20 to 60% by weight of 15-30% magnesium salt solution in the total amount of 100% by weight in a reactor to maintain a 40 to 60% alkaline solution at 30 to 60 ℃ A gelation step in which 15 to 50% by weight of the magnesium salt solution is slowly added while stirring slowly over 0.5 to 2 hours, followed by stirring for 1 to 3 hours while maintaining the temperature at 30 to 80 ° C. When the gelation is completed, the first crystallization step of increasing the temperature to 100 to 120 ° C. and performing crystallization for 3 to 7 hours, and when the first crystallization is completed, the remaining 40 to 80 of the 15 to 30% magnesium salt solution A second crystallization step of slowly adding the weight% and maintaining the temperature at 90 to 120 ° C. for 3 to 7 hours, and washing with distilled water after completion of the second crystallization, drying at 120 to 180 ° C. for 1 to 3 hours. Washing to dry It comprise the system.

As the magnesium salt, magnesium sulfate (MgSO ₄ ), magnesium chloride (MgCl ₂ ), magnesium nitride (MgNO ₃ ), magnesium acetate (Mg (CH ₃ COO) ₂ ), and the like may be used.

As the alkaline solution, sodium hydroxide (NaOH), ammonia (NH ₄ OH), calcium hydroxide (Ca (OH) ₂ ), or the like can be used.

In the above, the reaction molar ratio of magnesium and alkali is preferably maintained at 1: 1.8 to 3.0, more preferably 1: 2 to 2.3. When the reaction molar ratio of magnesium and alkali is small, the reactivity is insufficient, and even if the molar ratio is larger, the reactivity does not change and is not practical.

In the method for preparing flame-retardant magnesium hydroxide of the present invention, 20 to 60 wt% of the total amount of 15 to 30% magnesium salt solution is added in the second crystallization step, and 15 to 30% magnesium is again provided after the second crystallization is completed. The remaining 20 to 60% by weight of the salt solution is slowly added, and the third crystallization step of proceeding the crystallization for 3 to 7 hours while maintaining the temperature 90 to 120 ℃ it is also possible to proceed to the washing and drying step.

In the secondary crystallization step and the tertiary crystallization step, the addition rate of the magnesium salt solution is preferably maintained in the range of 3 to 20 g / min. In the above, if the feed rate is too low, productivity is bad, and if the feed rate is too fast, particles are irregularly formed and excessively small particles are produced.

When magnesium hydroxide is produced through the above process, slightly circular plate-shaped fine particles having a primary average particle size of 0.3 to 1 m and a secondary average particle size of 1.1 to 2.0 m are obtained.

In the method for producing flame-retardant magnesium hydroxide of the present invention, it is preferable to maintain the pH of the reactants at each step, and more preferably maintain the pH of 12-14. In the above pH value is closer to alkali, the crystallization is promoted, if it is close to neutral productivity is low, if too strong alkali, in the gelation step or primary crystallization step is excessive aggregation of particles and secondary crystallization step or tertiary crystallization There is not enough growth of the particles in the step.

And the flame-retardant magnesium hydroxide production method of the present invention is carried out each step under normal pressure (condition of normal pressure).

According to the flame-retardant magnesium hydroxide manufacturing method according to the present invention, it is possible to obtain the plate-shaped magnesium hydroxide particles under the conditions of normal pressure, even when the magnesium hydroxide is added to the synthetic resin as a flame retardant, it has a high dispersibility, and the composition of the synthetic resin composition It does not deteriorate characteristics.

In addition, according to the method for producing flame-retardant magnesium hydroxide according to the present invention, since the particles are grown through the gelation step and the first crystallization step and then the secondary crystallization step and the tertiary crystallization step, the primary average particle diameter is 0.3 to 1 μm. It is possible to obtain uniform high quality magnesium hydroxide having a constant particle size distribution having a secondary average particle diameter of 1.1 to 2.0 mu m.

The flame retardant magnesium hydroxide manufacturing method according to the present invention makes it possible to manufacture a suitable magnesium hydroxide as a flame retardant having uniformity and high dispersibility under normal pressure conditions, thereby reducing production costs, mass production, and safety in the manufacturing process. The risk of an accident is reduced.

Next, a preferred embodiment of the method for producing a flame retardant magnesium hydroxide according to the present invention will be described in detail, but it is apparent that the present invention is illustrative, and the scope of the present invention is not limited thereto.

The following examples and comparative examples were all performed under normal pressure.

Example 1

985 g of 21% magnesium sulfate (MgSO ₄ ) solution was added to a 3 liter reactor, while 579 g of 50% sodium hydroxide (NaOH) solution was slowly added while maintaining the temperature at 50 ° C, and then stirred vigorously for 2 hours while maintaining the temperature at 70 ° C. Agitation proceeded to gelation. In the solution added, the reaction molar ratio of magnesium and alkali was 1: 2.1. At this time, the pH of the reactant was maintained at 10-14. After gelation was completed, the temperature was raised to 110 ° C. and crystallization proceeded for 5 hours. After completion of the first crystallization, 985 g of 21% magnesium sulfate (MgSO ₄ ) solution was slowly added over 1 hour, and crystallization was performed for 5 hours while maintaining the temperature at 105 ° C. After the completion of the second crystallization, washed with distilled water and dried for 2 hours at 150 ℃ to the primary average particle size of 0.3 ~ 1㎛, secondary average particle diameter of 1.3㎛, slightly spherical plate-shaped particles of flame-retardant magnesium hydroxide according to the present invention Example 1 of the particles was obtained.

1 shows an electron microscope photograph (magnification 40,000 times) of the first embodiment.

Example 2

657 g of 21% magnesium sulfate (MgSO ₄ ) solution was added to a 3 L reactor, while 579 g of 50% sodium hydroxide (NaOH) solution was slowly added while maintaining the temperature at 50 ° C, and then stirred vigorously for 2 hours while maintaining the temperature at 70 ° C. Agitation proceeded to gelation. In the solution added, the reaction molar ratio of magnesium and alkali was 1: 2.1. At this time, the pH of the reactant was maintained at 10-14. After gelation was completed, the temperature was raised to 110 ° C. and crystallization proceeded for 5 hours. After completion of the first crystallization, 657 g of 21% magnesium sulfate (MgSO ₄ ) solution was slowly added over 1 hour, and crystallization was performed for 5 hours while maintaining the temperature at 105 ° C. After completion of the second crystallization, 657 g of 21% magnesium sulfate (MgSO ₄ ) solution was slowly added over 1 hour, and crystallization was performed for 5 hours while maintaining the temperature at 105 ° C. After completion of tertiary crystallization, the mixture was washed with distilled water and dried at 150 ° C. for 2 hours. Example 2 of the particles was obtained.

2 shows an electron microscope photograph of Example 2 at 20,000 times magnification, and FIG. 3 shows an electron microscope photograph at 40,000 times magnification.

Example 3

657 g of 21% magnesium sulfate (MgSO ₄ ) solution was added to the 3L reactor, and 579 g of 50% sodium hydroxide (NaOH) solution was slowly added while maintaining 50 ° C, followed by vigorous stirring, and then the temperature was maintained at 70 ° C. The gelation was performed by stirring for a time. In the solution added, the reaction molar ratio of magnesium and alkali was 1: 2.1. At this time, the pH of the reactant was maintained at 10-14. After gelation was completed, the temperature was raised to 110 ° C., and then crystallization was performed for 5 hours. After completion of the first crystallization, 1314 g of 21% magnesium sulfate (MgSO ₄ ) solution was slowly added over 5 hours, and crystallization was performed for 5 hours while maintaining the temperature at 105 ° C. After completion of the second crystallization, washed with distilled water and dried for 2 hours at 150 ℃ to the primary average particle size of 0.5 ~ 1㎛, secondary average particle diameter of 1.7㎛, plate-shaped flame retardant magnesium hydroxide particles according to the present invention Got 3.

4 shows an electron microscope photograph of Example 3 at 20,000 times magnification.

[Comparative Example]

After putting 1970g of 21% magnesium sulfate (MgSO ₄ ) solution in a 3L reactor, 579g of 50% sodium hydroxide (NaOH) solution was slowly added while maintaining the temperature at 50 ° C, and then stirred vigorously for 2 hours while maintaining the temperature at 70 ° C. Agitation proceeded to gelation. In the solution added, the reaction molar ratio of magnesium and alkali was 1: 2.1. At this time, the pH of the reactant was maintained at 10 to 14, and the magnesium hydroxide (Mg (OH) ₂ ) solid was about 7.8%. After gelation was completed, the temperature was raised to 105 ° C. and crystallization was performed for 7 hours. After crystallization was completed, washed with distilled water and dried at 150 ℃ 2 hours.

The magnesium hydroxide particles obtained through the above process had a primary average particle diameter of 0.1 to 0.5 µm and a secondary average particle diameter of 1.2 µm.

5 shows an electron microscope photograph of a comparative example obtained as described above at a magnification of 40,000 times.

When comparing Examples 1 to 3 and Comparative Example according to the present invention obtained as described above with reference to Figs. 1 to 5, the embodiment according to the present invention in the primary particle size and the secondary particle size is more than the comparative example It was confirmed that the growth was large, it was confirmed that the plate-like form was wider than the comparative example.

In addition, when the tertiary crystallization step is carried out after the secondary crystallization step, the second average particle diameter is increased, and in the second crystallization step, the crystallization is performed by adding 200% by weight of the magnesium salt solution longer than the initial 100% by weight. In the case of proceeding, it was confirmed that the first and second average particle diameters grow larger.

Therefore, in the case of the comparative example, it can be estimated that sufficient crystal growth has not been achieved by performing crystallization in one step.

According to the flame-retardant magnesium hydroxide manufacturing method according to the present invention, the crystallization is divided into two or three stages, or by adding more magnesium salt in two stages than in the first stage, even growth of magnesium hydroxide particles and effective plate-like growth It is possible to derive

In the above description of the preferred embodiment of the method for producing a flame retardant magnesium hydroxide according to the present invention, the present invention is not limited thereto, and the invention can be modified in various ways within the scope of the claims and the detailed description of the invention and the accompanying drawings. This also belongs to the scope of the present invention.

1 is an electron micrograph (magnification 40,000 times) of the magnesium hydroxide particles prepared by Example 1 of the method for preparing a flame-retardant magnesium hydroxide according to the present invention.

Figure 2 is an electron micrograph (magnification of 20,000 times) of the magnesium hydroxide particles prepared by Example 2 of the method for producing a flame-retardant magnesium hydroxide according to the present invention.

Figure 3 is an electron micrograph (magnification 40,000 times) of the magnesium hydroxide particles prepared by Example 2 of the method for producing a flame-retardant magnesium hydroxide according to the present invention.

Figure 4 is an electron micrograph (magnification of 40,000 times) of the magnesium hydroxide particles prepared by Example 3 of the method for producing a flame-retardant magnesium hydroxide according to the present invention.

Figure 5 is an electron micrograph (magnification 40,000 times) of the magnesium hydroxide particles prepared by the present invention and another magnesium hydroxide manufacturing method for comparison.

Claims (7)

20 to 60% by weight of 15-30% magnesium salt solution is added to 100% by weight of the reactor and 40 to 60% alkaline solution is added to the total amount of magnesium salt solution while maintaining 30 to 60 ° C. A gelling step of stirring by vigorously while slowly adding the weight% and then stirring the gel at 1 to 3 hours while maintaining the temperature at 30 to 80 ° C. under normal pressure; After the gelation is completed, the first crystallization step of increasing the temperature to 100 ~ 120 ℃ under normal pressure and then undergoing crystallization for 3 to 7 hours, After the first crystallization is completed, the second crystallization step of slowly adding the remaining 40 to 80% by weight of the 15-30% magnesium salt solution and performing the crystallization for 3 to 7 hours while maintaining the temperature at 90 to 120 ℃ under normal pressure; , When the second crystallization is completed, a flame-retardant magnesium hydroxide manufacturing method comprising a washing and drying step of washing with distilled water for 1 to 3 hours at 120 to 180 ℃. The method according to claim 1, Magnesium salt (MgSO ₄ ) or magnesium chloride (MgCl ₂ ) is used as the magnesium salt, sodium hydroxide (NaOH) is used as the alkaline solution, flame retardant magnesium hydroxide manufacturing method. The method according to claim 1, Reaction molar ratio of magnesium and alkali in the gelling step is 1: 1.8 to 3.0 range of flame retardant magnesium hydroxide production method. The method according to claim 1, Method of preparing a flame retardant magnesium hydroxide to maintain the input rate of the magnesium salt solution in the secondary crystallization step in the range of 3 to 20g / min. The method according to claim 1, In the secondary crystallization step, 20 to 60% by weight of the total amount of magnesium salt solution is added slowly, After the completion of the second crystallization, the remaining 20 to 60% by weight of the 15-30% magnesium salt solution was slowly added again, and the crystallization was performed for 3 to 7 hours while maintaining the temperature at 90 to 120 ° C under normal pressure, and then the washing and drying step. Flame retardant magnesium hydroxide manufacturing method further comprising a third crystallization step to proceed to. The method according to claim 5, Flame retardant magnesium hydroxide manufacturing method in which the input rate of the magnesium salt solution in the third crystallization step maintains the range of 3 to 20g / min. The method according to any one of claims 1 to 6, Flame retardant magnesium hydroxide production method for maintaining the pH of the reactants at 8 to 14 in each step.

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