KR100894872B1 - The method for manufacturing magnesium hydroxide having excellent dispersibility for flame retardant - Google Patents

Abstract

Provided is a method for producing highly dispersible magnesium hydroxide, which is economically effective for use as a flame retardant.

This magnesium hydroxide production method comprises the steps of grinding the magnesia prepared from seawater to have an average particle diameter of 45㎛ or less; Hydrating the pulverized magnesia in water to produce magnesium hydroxide, wherein the step of hydrating acetic acid and hydrochloric acid alone or in combination; Washing and then drying and pulverizing the magnesium hydroxide; the purity of the pulverized magnesium hydroxide is 98% or more, and the impurity content of the pulverized magnesium hydroxide metal compound is 0.05% by weight or less.

According to the present invention, it is possible to provide a magnesium hydroxide having excellent dispersibility at a low manufacturing cost, the magnesium hydroxide prepared in this way can be applied as a flame retardant to rubber and plastics.

Magnesium Hydroxide, Magnesia, Dispersibility, Flame Retardant, Acetic Acid, Impurities

Description

The method for manufacturing magnesium hydroxide having excellent dispersibility for flame retardant}

Japanese Laid-Open Patent Publication No. 2000-233924

Korean Unexamined Patent Publication No. 2001-0086246

Korean Unexamined Patent Publication No. 2006-0112624

The present invention relates to a method for producing magnesium hydroxide used for a flame retardant. More specifically, the present invention relates to a method for producing magnesium hydroxide, which is not only low in manufacturing cost but also excellent in dispersibility.

Magnesium hydroxide (Mg (OH) ₂ ) is widely known as a raw material of magnesia (MgO), which is a basic refractory material, and is used in a wide range of fields for medicine and industrial purposes. For example, medicaments include antacids, hypothalamic agents, and veterinary agents. Industrial applications include flame retardants which are incorporated into thermoplastic resins to impart flame retardancy to these resins, adsorbents for containing wastewater, flue gas desulfurization agents, drainage neutralizers, and soil improvers. .

In general, there are various methods for producing magnesium hydroxide particles, for example, a method of using magnesium salt as a magnesium salt solution using precipitated water, magnesium chloride salt solution, and the like as a alkaline solution by precipitation reaction with caustic soda, ammonia water, lime and the like; Purification of brucite or a method of calcining and hydrating the natural magnesite produced; A method produced by substitution reaction of decarbonated seawater and slaked lime; And a method of hydrating magnesium oxide with an aqueous medium for use.

However, when used as a flame retardant through the purification or pulverization of brucite ore, the dispersibility of magnesium hydroxide in the resin is lowered, and thus it is limited to be used as a flame retardant. The method of calcining and hydrating the natural magnesite produced by low purity is low There is a limit to being used as a flame retardant. In addition, it is possible to obtain magnesium hydroxide with high purity as seawater and alkali react with magnesium to produce magnesium hydroxide, but the shape of the particles produced is agglomerated into a circular shape, which makes it difficult to disperse the magnesium hydroxide. In addition, the method of using the brine or magnesium chloride of the above manufacturing method, it is possible to produce magnesium hydroxide having a high purity and hexagonal crystal form as the magnesium hydroxide is prepared by reacting magnesium chloride with alkali, the manufacturing cost is too high There is a problem that the economy is poor.

Representative prior arts for producing magnesium hydroxide include Japanese Patent Laid-Open No. 2000-233924 and Korean Patent Laid-Open No. 2001-0086246. The prior art is to prepare magnesium hydroxide particles by reacting magnesium chloride with an alkali in an aqueous medium, the reaction comprising at least one compound selected from the group consisting of organic acids, boric acid, silicic acid and their water-soluble salts as an additive It is performed by adding 0.01-150 mol% with respect to magnesium chloride.

In addition, to control the particle shape, size and distribution of the magnesium hydroxide particles by hydrothermal treatment for 30 minutes to 8 hours at a temperature of 120 ~ 200 ℃ and high pressure of 2 ~ 10kgf / ㎠ to have the characteristics of particles that can be used for flame retardant Magnesium hydroxide particles, which have undergone such a process, have excellent properties, but the manufacturing process is complicated and the reactivity is low, resulting in low productivity, and a large amount of energy for the treatment of impurities other than the magnesium hydroxide particles produced by the reaction and a large amount of energy for hydrothermal treatment. It has a disadvantage that the manufacturing cost is high.

In recent years, Korean Patent Application Publication No. 2006-0112624 is a representative conventional technique for producing magnesium hydroxide using magnesia prepared from seawater. The prior art proposes a method for producing high purity magnesium hydroxide having excellent dispersibility by hydration and acid treatment of seawater MgO. However, in order to obtain magnesium hydroxide having a MgO purity of 99% by weight or more, the manufacturing cost has a disadvantage.

The present invention is to improve the above-mentioned problems, by using magnesia prepared from seawater as a raw material, by controlling the additives and hydration reaction to properly control the purity and impurities content of magnesium hydroxide while reducing the production cost To provide a method for producing magnesium hydroxide with improved acidity, an object thereof is provided.

The present invention for achieving the above object is a step of grinding the magnesia prepared from seawater to have an average particle diameter of 45㎛ or less;

Hydrating the pulverized magnesia in water to produce magnesium hydroxide, wherein the step of hydrating acetic acid and hydrochloric acid alone or in combination;

Washing and then drying and pulverizing the magnesium hydroxide; the purity of the pulverized magnesium hydroxide is 98% or more, and the impurity content of the pulverized magnesium hydroxide metal compound is 0.05% by weight or less. It is related with the manufacturing method of magnesium hydroxide which is excellent in the dispersibility for flame retardants.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

The present inventors in the method for producing magnesium hydroxide using magnesia prepared from sea water, high impurity removal cost for high purity and the shape of magnesium hydroxide particles extracted from sea water aggregated in a circular shape to solve the difficult problem of dispersion While researching the solution, magnesia manufactured from seawater is used as a raw material, and by adding acetic acid and / or hydrochloric acid as an additive, it is hydrated with water to properly control the purity of magnesium hydroxide and the impurity content of the metal compound to lower the manufacturing cost. At the same time, it was confirmed through experiments that magnesium hydroxide having high dispersibility was obtained, and the present invention was completed based on the experimental results.

In the present invention, magnesia prepared from seawater is used as a raw material, and a conventional method of preparing magnesia from seawater is made of magnesium hydroxide by reacting decarbonated seawater with lime oil, and then washing and drying the magnesium hydroxide. It is manufactured by baking.

Hereinafter, the manufacturing method of the magnesium hydroxide particle of this invention is demonstrated.

First, in the present invention, the magnesia prepared from the sea water as described above is pulverized to have an average particle diameter of 45㎛ or less. Crushing can be applied to any method that can finely grind magnesium oxide. In the case of using particles larger than the particle size, subsequent hydration time is required for a long time, and uniform particle generation may be difficult. At the time of pulverization, degassing may be preferably performed in order to remove heavy metals such as Fe ₂ O ₃ mixed in a crushing machine or the like.

In addition, the magnesia prepared from the seawater is preferably used containing 95% by weight or more of MgO, when the MgO content is less than 95% by weight it may be difficult to secure a high-purity magnesium hydroxide targeted in the present invention.

Subsequently, the pulverized magnesia is hydrated in water to prepare magnesium hydroxide, wherein acetic acid and hydrochloric acid are added alone or in combination to perform acid treatment. The use of such additives can contribute to the improvement of dispersibility by enabling the formation of hexagonal particles. The content of acetic acid and / or hydrochloric acid to be added is preferably 0.1 to 5 M per liter of water. When added below 0.1 M, the shape of the resulting magnesium hydroxide particles may be uneven or it may be difficult for magnesium hydroxide to be completely produced. In addition, when added in excess of 5M to form a hexagonal plate-shaped particles, but the size is undifferentiated and the specific surface area is increased may inhibit the dispersibility and the use of a large amount of additives may provide a factor to deteriorate the economics.

The hydration reaction can appropriately control the time and temperature for the magnesia prepared from seawater to completely magnesium hydroxide, in particular, the hydration reaction temperature is preferably carried out at 70 ℃ or more in consideration of time and energy costs. In addition, in the present invention, an acid is added during the hydration reaction to form the target magnesium hydroxide particles, and acetic acid and hydrochloric acid may be added alone or in combination for the target reactivity, purity, and particle size.

Thereafter, the acid treated magnesium hydroxide is washed using a conventional method, and then dried and pulverized.

In addition, it is preferable that the purity of the magnesium hydroxide is 98% or more, and if the purity is less than 98%, the remaining components act as impurities, which can significantly lower the thermal stability of the final product. In addition, in the present invention, in order to reduce the high manufacturing cost for high purity, it is preferable to control the purity of the magnesium hydroxide to less than 98 ~ 99% by weight.

In addition, in the present invention, it is preferable that the impurity content composed of the metal compound of crushed magnesium hydroxide is 0.05% by weight or less, and when the impurity content exceeds 0.05% by weight, not only the flame retardancy is lowered, but also other physical properties of interest. It can be difficult to secure. The impurity metal compound may include iron, manganese, cobalt, chromium, copper, vanadium and nickel.

In addition, the magnesium hydroxide after grinding is preferably an average particle size of 0.8 ~ 3.0㎛, the specific surface area is 4 ~ 10㎡ / g or less, when the average particle size is less than 0.8㎛ or more than 10㎡ / g The dispersibility with the resin due to the small particles may be reduced, and even when the average particle size exceeds 3.0 μm or the specific surface area is less than 4 m 2 / g, the dispersibility with the resin may be reduced due to the large particles. In addition, the crystal phase of magnesium hydroxide prepared as described above is preferably in the hexagonal plate shape, because the dispersibility and other properties are the best when the crystal phase is a hexagonal plate shape.

On the other hand, the pulverized magnesium hydroxide can improve the final particle, mechanical strength and other physical properties of magnesium hydroxide by performing the pulverization and surface treatment process according to the use, it can solve the problems such as storage period due to the material easily absorbed .

Hereinafter, the present invention will be described in more detail with reference to Examples.

EXAMPLE

(Invention example)

Magnesium hydroxide produced by the reaction of decarbonated seawater with purified lime was dehydrated, dried and calcined to produce magnesia having a MgO content of 98.4 wt%, and finely ground MgO particles having an average particle diameter of 23 μm at 85 ° C. The reaction was hydrated for 7 hours. At this time, 0.25 M acetic acid was added as a particle control agent, and then MgO purity, specific gravity, and particles of magnesium hydroxide (Mg (OH) ₂ ) surface-treated with stearic acid after washing and drying in a conventional manner. Crystal phase, average particle diameter, specific surface area and manufacturing cost index were evaluated.

(Comparative Example)

Comparative Example 1 is a magnesium hydroxide which is surface-treated by refining Brucite light as a natural raw material, Comparative Example 2 is a magnesium hydroxide treated with a magnesia calcined natural magnesite using the production conditions of the invention, Comparative Example 3 Magnesium hydroxide produced by hydrothermal reaction between silver chloride and alkali ammonia water was used. The MgO purity, specific gravity, crystal phase, average particle diameter, specific surface area and manufacturing cost index of Comparative Example 1, Comparative Example 2 and Comparative Example 3 were evaluated, and the results are shown in Table 1 below.

Thereafter, 50% by weight of magnesium hydroxide of the invention examples and comparative examples prepared above was added to ethylene ethyl acetate (Ethylene Ethyl Acetate) resin, which is a wire resin, to measure dispersibility, flame retardancy (oxygen index), tensile strength, and elongation rate. The results are shown in Table 1 below.

TABLE 1

division Example Comparative Example 1 Comparative Example 2 Comparative Example 3 Magnesium hydroxide MgO Purity 98.7 96.8 97.6 99.4 importance 1.34 1.37 1.35 1.32 Crystal phase of particles Hexagonal plate shape Hexagonal plate shape Hexagonal plate shape Hexagonal plate shape Average particle size (㎛) 1.2 2.5 1.8 0.9 Specific surface area (㎡ / g) 6 4 6 5 Manufacturing Cost Index 100 90 105 187 evaluation Dispersibility ○ × △ ○ Flame Retardant (Oxygen Index) 32 29 30 33 Tensile strength (kgf / ㎠) 1.1 0.7 0.8 1.1 Elongation (%) 550 370 450 560 The manufacturing cost index is represented by the ratio of the production cost of the comparative example to 100 as the production cost of the invention example

As shown in Table 1, in the case of the invention examples satisfying the scope of the present invention, not only good dispersibility, flame retardancy and mechanical properties, but also manufacturing magnesium hydroxide can be produced at a relatively low cost.

However, in the case of Comparative Example 1 using magnesium hydroxide, which is a surface-treated magnesium hydroxide purified from a natural raw material, the manufacturing cost is low, but the purity is low, there are many impurities, as well as poor dispersibility and other physical properties. .

In addition, in Comparative Example 2 in which magnesia produced by calcining natural magnesite was treated using the method of the present invention, purity and dispersibility were very poor.

In addition, in the case of Comparative Example 3 using magnesium hydroxide produced by hydrothermal reaction of magnesium chloride and ammonia water, the purity and dispersibility were excellent, but the manufacturing cost was remarkably high, and thus it was difficult to be applied in real life.

As described above, according to the present invention, it is possible to provide magnesium hydroxide having excellent dispersibility at a low manufacturing cost, and the magnesium hydroxide thus prepared can be used as a flame retardant in rubber and plastics.

Claims (3)

Grinding magnesia prepared from seawater to have an average particle diameter of 45 μm or less; Hydrating the pulverized magnesia in water to produce magnesium hydroxide, wherein the step of hydrating acetic acid and hydrochloric acid alone or in combination; Washing and then drying and pulverizing the magnesium hydroxide; the purity of the pulverized magnesium hydroxide is 98% or more, and the impurity content of the pulverized magnesium hydroxide metal compound is 0.05% by weight or less. Method for producing magnesium hydroxide excellent in dispersibility for flame retardants. The method of claim 1, wherein the magnesia prepared from seawater has a MgO content of 95% by weight or more. According to claim 1, wherein the magnesium hydroxide has a mean particle size of 0.8 ~ 3.0㎛, specific surface area of 4 ~ 10㎡ / g or less, the crystal phase is hexagonal plate-like magnesium hydroxide excellent dispersibility for flame retardant Manufacturing method.