JPH1179736A - Production of slurry of magnesium hydroxide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease viscosity of the system and to obtain a slurry of high density by hydrating magnesium oxide under the presence of a copolymer salt of α, β-unsatd. dicarboxylic acid monomer and/or its anhydride and an ethylenically unsatd. monomer, thereby suppressing rapid heat generation by the hydration. SOLUTION: A salt of a copolymer described below is added by 0.01 to 5 pts.wt. to 100 pts.wt. of magnesium oxide, and magnesium oxide is mixed with water to carry out hydration to obtain a magnesium hydroxide slurry. The copolymer salt consists of a copolymer of 20 to 80 mol.% α,β-unsatd. dicarboxylic acid monomer and/or its anhydride and an ethylenically unsatd. monomer, preferably monoolefin monomer having 2 to 10 carbon atoms. The copolymer has 500 to 5000 number average mol.wt. and >=50 mol.% of the carboxyl groups in the molecule form alkali (earth) metal salts. The hydration is carried out at 5 to 90 deg.C with 30 to 60 wt.% magnesium oxide and 70 to 40 wt.% water (total 100 wt.%).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a slurry of magnesium hydroxide.

[0002]

2. Description of the Related Art Magnesium hydroxide is widely used as an absorbent for sulfur dioxide gas and nitric oxide gas in flue gas desulfurization or as a component of magnesium ferrite. In any application, it is often used as an aqueous dispersion of magnesium hydroxide (hereinafter, sometimes referred to as a slurry), for example, to improve the processing capacity as an absorber for flue gas desulfurization, In production, it is used to reduce the drying energy in the firing / granulation process. As a method for producing a slurry of magnesium hydroxide, a method is known in which water is added to magnesium oxide to form a slurry of magnesium hydroxide by a hydration reaction. In this production method, a sodium salt of naphthalenesulfonic acid or the like is added as a dispersant for the purpose of controlling heat generation due to a rapid hydration reaction and suppressing a significant increase in viscosity of the entire system. Attempted. However, with the conventional dispersants, it is difficult to sufficiently suppress rapid heat generation, and improvement is required.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a magnesium hydroxide slurry capable of suppressing rapid heat generation due to a hydration reaction of magnesium oxide, lowering the viscosity of the system, and increasing the slurry concentration. To provide.
Therefore, the present inventors have conducted intensive studies and as a result, when replacing the sodium salt of naphthalenesulfonic acid known as a conventional dispersant with a water-soluble salt of a maleic anhydride copolymer, the hydration reaction proceeds slowly, In addition, they found that the slurry viscosity of the system was significantly reduced, and based on this finding, completed the present invention.

[0004]

Thus, according to the present invention, there is provided an α, β-unsaturated dicarboxylic acid monomer and / or an anhydride thereof and a copolymer salt of an ethylenically unsaturated monomer. Thus, there is provided a method for producing a slurry of magnesium hydroxide, comprising performing a hydration reaction of magnesium oxide.

[0005]

Embodiments of the present invention will be described below in detail. The copolymer salt used in the present invention comprises α, β
-At least a part of the carboxyl groups present in the molecule of the copolymer of the unsaturated dicarboxylic acid monomer and / or the anhydride thereof and the ethylenically unsaturated monomer, preferably 50
More than mol% forms a salt. The molecular weight of the copolymer is usually 500 to 50 as a number average molecular weight,
000, preferably 1,000 to 25,000, and more preferably 3,000 to 10,000. If the number average molecular weight of the copolymer is excessively large, dispersibility decreases, and the magnesium hydroxide slurry is undesirably thickened and aggregated.

Specific examples of such salts include, for example, salts of metals of Group 1 or 2 of the periodic table such as sodium, potassium, magnesium, calcium, barium and the like, and furthermore, ammonium salts, amine salts and the like. Sodium salts are preferred in terms of economy.

An α, β-unsaturated dicarboxylic acid monomer and / or
Or the anhydride thereof is an unsaturated dicarboxylic acid having a carboxyl group or an acid anhydride group or an anhydride thereof, and specific examples thereof include maleic acid, fumaric acid, itaconic acid, maleic anhydride, itaconic anhydride, Those having 4 to 10 carbon atoms, such as citraconic anhydride, are exemplified. Of these, maleic anhydride is awarded from the viewpoints of reactivity, quality, economy and the like.

[0008] The ethylenically unsaturated monomer is the α, β-
It is not particularly limited as long as it can be copolymerized with an unsaturated dicarboxylic acid monomer and / or an anhydride thereof. Specific examples thereof include, for example, ethylene, propylene, butene, 2-methyl-butene-1, 2-methyl -Monoolefin monomers such as butene-2, hexene, octene, isoamylene, diisobutylene, decene, cyclopentene and cyclohexene; aromatic vinyl monomers such as styrene, vinyltoluene, α-methylstyrene, cumarone and indene; methoxy Polyoxyalkylene allyl ether monomers such as polyoxyethylene monoallyl ether, ethoxypolyoxyethylene monoallyl ether, methoxypolyoxypropylene monoallyl ether, and ethoxypolyoxyethylene-polyoxypropylene monoallyl ether;
Vinyl ether monomers such as methyl vinyl ether; alkyl acrylate monomers such as ethyl acrylate and methyl methacrylate; and vinyl acetate. Above all, monoolefin monomers having 2 to 10 carbon atoms, especially monoolefin monomers having 4 to 6 carbon atoms, are awarded. These monomers can be used in combination of two or more if necessary.

The ratio of the α, β-unsaturated dicarboxylic acid monomer and / or its anhydride in the copolymer can be appropriately selected, but is usually from 20 mol% to 80 mol%, preferably 40 mol%. % To 60 mol%, more preferably 50 mol%.

The method for producing a copolymer of an α, β-unsaturated dicarboxylic acid monomer and / or an anhydride thereof and an ethylenically unsaturated monomer used in the present invention is not particularly limited. Usually, it is produced by radical polymerization according to a conventional method. The method for producing the salt of the copolymer is not particularly limited and may be a method of polymerizing after neutralizing a monomer, or a method of synthesizing a polymer or a copolymer in the presence of a base according to a conventional method. Any of the summing methods may be adopted.

The salt form of the copolymer of the α, β-unsaturated dicarboxylic acid monomer and / or its anhydride and the ethylenically unsaturated monomer used in the present invention may be solid or aqueous. Although it may be present, it is usually used in an aqueous solution having a solid concentration of 10 to 50% by weight in consideration of easy handling. At this time, additives such as a water reducing agent, a dispersant, an air entrainer, an antifoaming agent, and other compounding agents can be appropriately mixed as long as the effects of the present invention are not essentially impaired.

The amount of the salt of the copolymer of the α, β-unsaturated dicarboxylic acid monomer and / or its anhydride and the ethylenically unsaturated monomer used in the present invention depends on the concentration of magnesium oxide, It can be appropriately selected depending on the particle size,
Usually 100 parts by weight of magnesium oxide, 0.0
It is 1 to 5 parts by weight, preferably 0.05 to 2 parts by weight.
If the amount is too small, the effect of suppressing the hydration reaction of magnesium oxide cannot be obtained, and the effect of lowering the viscosity of the magnesium hydroxide slurry is insufficient. On the other hand, if the amount is too large, the effect of lowering the viscosity may be reduced, which is not preferable.

According to the present invention, by performing a hydration reaction of magnesium oxide in the presence of the above-mentioned dispersant, rapid heat generation due to the hydration reaction is suppressed, and a high concentration is obtained without increasing the viscosity of the system. Can be obtained. The hydration reaction involves mixing magnesium oxide and water in the presence of a salt of a copolymer of an α, β-unsaturated dicarboxylic acid monomer and / or an anhydride thereof and an ethylenically unsaturated monomer. It is performed by The temperature of the hydration reaction is not particularly limited, but is usually 5 to 90 ° C, preferably 30 to 90 ° C.
80 ° C. range. The form of magnesium oxide is not particularly limited, but is usually used in the form of powder. The mixing method of magnesium oxide and water is not particularly limited, but usually,
Water containing a salt of a copolymer of an α, β-unsaturated dicarboxylic acid monomer and / or an anhydride thereof and an ethylenically unsaturated monomer is stirred, and magnesium oxide powder is continuously added to the water. Alternatively, a method of intermittent addition, a method of continuously mixing water containing the salt of the copolymer and magnesium oxide powder, and a method of collectively mixing the salt of the copolymer with water and the magnesium oxide powder, followed by stirring. The method is adopted. The mixing ratio of magnesium oxide and water is not particularly limited, but is usually 30 to 60% by weight of magnesium oxide and 70 to 40% of water.
Wt% (total is 100 wt%).

[0014]

The present invention will be described more specifically below with reference to examples and comparative examples. Synthesis Example 1 (Synthesis of Maleic Anhydride-C5 Monoolefin Monomer Copolymer) In an autoclave, 98 parts of maleic anhydride and 5 carbon atoms obtained by extractive distillation from a C5 fraction obtained by purifying naphtha were added. Monoolefin monomer fraction (pentene-1 = 5.
3%, pentene-2 = 5.5%, 2-methyl-1-butene =
8.0%, 2-methyl-2-butene = 4.0%, n-pentane = 43.4%, i-pentane = 28.7%, etc.)
380 parts (monoolefin monomer 87 having 5 carbon atoms)
Parts), 4 parts of benzoyl peroxide, and 20 to 20 carbon atoms
28 parts of a copolymer of α-olefin and maleic anhydride (“PA-208”, manufactured by Mitsubishi Chemical Corporation)
The mixture was stirred at 75 ° C. for 3 hours and reacted to synthesize a maleic anhydride-monocarbon monomer copolymer having 5 carbon atoms (composition ratio, maleic anhydride: monoolefin monomer having 5 carbon atoms =). 60:40 (unit mol%)).

Synthesis Example 2 (Synthesis of Maleic Anhydride-C5 Monoolefin Monomer Sodium Salt) The maleic anhydride-C5 monoolefin monomer obtained in Synthesis Example 1 was synthesized. To 100 parts of the polymer, 64 parts of sodium hydroxide and 300 parts of water were charged and neutralized at 70 ° C., followed by unreacted monoolefin monomer having 5 carbon atoms and 5 carbon atoms.
Of maleic anhydride with PH = 8
Sodium salt aqueous solution of monoolefin monomer copolymer having 5 carbon atoms (active ingredient concentration = 40%, average molecular weight = 5.7
00).

Synthesis Example 3 (Synthesis of Maleic Anhydride-C5 Monoolefin Monomer Monomer Copolymer) The maleic anhydride-C5 monoolefin monomer obtained in Synthesis Example 1 was synthesized. To 100 parts of the polymer, 44 parts of magnesium hydroxide and 500 parts of water were charged, and after a neutralization reaction at 70 ° C., unreacted monoolefin monomer having 5 carbon atoms and paraffin having 5 carbon atoms were distilled off. An aqueous solution of a magnesium salt of a maleic anhydride-pH 5 monoolefin monomer copolymer having a pH of 6 (active ingredient concentration = 30%, average molecular weight =
6,800).

Example 1 (Preparation of Magnesium Hydroxide Slurry and Measurement of Viscosity) Using the aqueous solution obtained in Synthesis Example 2, a magnesium hydroxide slurry (charged magnesium oxide concentration 35%, magnesium oxide The hydration reaction resulted in a magnesium hydroxide concentration of 50%). Formulation Magnesium oxide ("AM-2" manufactured by Ako Kasei) 245 parts Aqueous solution obtained in Synthesis Example 2 1.84 parts (active ingredient = 0.3% magnesium oxide) Water 355 parts Predetermined amount of magnesium oxide in container , Water and the aqueous solution obtained in Synthesis Example 2 were weighed, and the mixture was stirred with a homomixer (auto homomixer M, manufactured by Tokushu Kika Kogyo Co., Ltd.) (about 500 rpm).
pm), the container was placed in a 70 ° C. water bath. The slurry temperature reached 80 ° C. due to the hydration reaction of magnesium oxide, but the fluidity was maintained. After 3 hours, the slurry concentration was 50%, and the magnesium oxide had completely reacted with the magnesium hydroxide. The concentration of the obtained magnesium hydroxide slurry is 50%, and the viscosity is 150 mPa · s.
Met.

Example 2 2.45 parts of the aqueous solution obtained in Synthesis Example 2 (active ingredient = 0.
A slurry of magnesium hydroxide was prepared in the same manner as in Example 1 except that 3% of magnesium oxide was used. The concentration of the obtained slurry of magnesium hydroxide is 50%,
The viscosity was 270 mPa · s.

Comparative Example 1 A slurry of magnesium hydroxide was prepared in the same manner as in Example 1 except that the aqueous solution obtained in Synthesis Example 2 was not used. The slurry temperature became 95 ° C. due to the hydration reaction of magnesium oxide. The fluidity decreases with time, 3
After 0 minute, the fluidity of the slurry was lost, and stirring was no longer possible. To obtain a stirrable slurry, the magnesium oxide concentration had to be reduced to 20% (the magnesium hydroxide concentration was 29% due to the hydration reaction).

Comparative Example 2 Example 1 was repeated except that 1.84 parts (active ingredient = 0.3% of magnesium oxide) of formalin condensate of sodium naphthalene sulfonate (“Mighty 150” manufactured by Kao Corporation) was used. Similarly, a slurry of magnesium hydroxide was prepared. The slurry temperature became 95 ° C. due to the hydration reaction of magnesium oxide. The fluidity decreased with time, and after one hour, the fluidity of the slurry was lost, and the slurry could not be stirred. To obtain a stirrable slurry, the magnesium oxide concentration had to be reduced to 22% (the hydration reaction resulted in a magnesium hydroxide concentration of 32%).

Example 3 (Preparation of magnesium hydroxide slurry and measurement of viscosity) Using the aqueous solution obtained in Synthesis Example 3, a magnesium hydroxide slurry (magnesium oxide concentration = 42%, magnesium oxide (The concentration of magnesium hydroxide becomes 60% by hydration). Formulation Magnesium oxide ("AM-2" manufactured by Ako Kasei) 245 parts Aqueous solution obtained in Synthesis Example 3 1.84 parts (active ingredient = 0.3% of magnesium oxide) Water 338 parts Predetermined amount of magnesium oxide in container , Water and the aqueous solution obtained in Synthesis Example 2 were weighed, and the mixture was stirred with a homomixer (auto homomixer M, manufactured by Tokushu Kika Kogyo Co., Ltd.) (about 500 rpm).
pm), the container was placed in a 70 ° C. water bath. The slurry temperature reached 85 ° C. due to the hydration reaction of magnesium oxide, but the fluidity was maintained. After 2 hours, the slurry concentration was 60%, and the magnesium oxide had completely reacted with the magnesium hydroxide. The resulting magnesium hydroxide slurry had a concentration of 60% and a viscosity of 440 mPa ·
s.

Example 4 2.45 parts of the aqueous solution obtained in Synthesis Example 2 (active ingredient = 0.45 parts)
A slurry of magnesium hydroxide was prepared in the same manner as in Example 3 except that 3% of magnesium oxide was used. The viscosity of the obtained slurry of magnesium hydroxide having a concentration of 60% was 570 mPa · s.

Comparative Example 3 A magnesium hydroxide slurry was prepared in the same manner as in Example 3 except that the aqueous solution obtained in Synthesis Example 2 was not used. The slurry temperature reached 105 ° C. due to the hydration reaction of magnesium oxide, and the slurry was brought into a boiling state. The fluidity decreased over time, and after 30 minutes, the fluidity of the slurry was lost, and stirring became impossible.

Comparative Example 4 Example 3 was repeated except that 1.84 parts (active ingredient = 0.3% of magnesium oxide) of formalin condensate of sodium naphthalenesulfonate (“Mighty 150” manufactured by Kao Corporation) was used. Similarly, a slurry of magnesium hydroxide was prepared. The slurry temperature reached 105 ° C. due to the hydration reaction of magnesium oxide, and the slurry was brought into a boiling state. The fluidity decreased over time, and after 30 minutes, the fluidity of the slurry was lost, and stirring became impossible.

From Examples 1 to 4, the hydration reaction of magnesium oxide was carried out in the presence of a sodium or magnesium salt of a copolymer of maleic anhydride and a monoolefin monomer having 5 carbon atoms, It can be seen that the hydration reaction proceeds gently and the viscosity of the slurry of the system is significantly reduced. On the other hand, when a sodium salt of a copolymer of maleic anhydride and a monoolefin monomer having 5 carbon atoms is not used (Comparative Examples 1 and 3) and in the presence of a formalin condensate of sodium naphthalene sulfonate It can be seen that when the hydration reaction is carried out (Comparative Examples 2 and 4), the hydration reaction progresses rapidly, and the viscosity of the system increases rapidly and the fluidity is lost.

[0026]

As described above, according to the present invention, it is possible to obtain a method for producing a magnesium hydroxide slurry capable of suppressing rapid heat generation due to a hydration reaction of magnesium oxide, lowering the viscosity of the system, and increasing the slurry concentration. it can.

The specific embodiments of the present invention are as follows. (1) The α, β-unsaturated dicarboxylic acid monomer and / or anhydride thereof is maleic acid, fumaric acid, itaconic acid, citraconic acid, maleic anhydride, itaconic anhydride, or citraconic anhydride. (2) Ethylenically unsaturated monomers such as ethylene, propylene, butene, 2-methyl-butene-1, 2-methyl-butene-2, hexene, octene, isoamylene, diisobutylene, decene, cyclopentene, cyclohexene, etc. Monoolefin monomer; styrene, vinyl toluene,
aromatic vinyl monomers such as α-methylstyrene, coumarone and indene; vinyl ether monomers such as methyl vinyl ether; alkyl acrylate monomers such as ethyl acrylate and methyl methacrylate; and vinyl acetate. (3) a copolymer of an α, β-unsaturated dicarboxylic acid monomer and / or an anhydride thereof and an ethylenically unsaturated monomer,
Α, β-unsaturated dicarboxylic acid monomer in the copolymer and / or
Or, the ratio of the anhydride is 20 mol% or more and 80 mol%.
The content is preferably from 40 mol% to 60 mol%, more preferably 50 mol%. (4) The number average molecular weight of the copolymer of the α, β-unsaturated carboxylic acid monomer and / or its anhydride and the ethylenically unsaturated monomer is usually 500 to 50,000, preferably 1 to 50,000. 2,000 to 25,000. (5) A copolymer salt of an α, β-unsaturated dicarboxylic acid monomer and / or an anhydride thereof and an ethylenically unsaturated monomer may be a carboxyl group or an acid present in a molecule of the copolymer. At least a portion of the anhydride groups, preferably 50 mol%
The above is what forms a salt. (6) The copolymer salt of an α, β-unsaturated dicarboxylic acid monomer and / or an anhydride thereof and an ethylenically unsaturated monomer is an alkali metal such as sodium, potassium, magnesium, calcium, barium, etc. Or salts of alkaline earth metals, ammonium salts and amine salts. (7) The amount of the salt of the copolymer of the α, β-unsaturated dicarboxylic acid monomer and / or its anhydride and the ethylenically unsaturated monomer is based on 100 parts by weight of magnesium oxide.
Usually, it is 0.01 to 5 parts by weight, preferably 0.05 to 2 parts by weight.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08L 35/00 C08L 35/00

Claims (1)

[Claims] 1. A hydration reaction of magnesium oxide in the presence of a salt of a copolymer of an α, β-unsaturated dicarboxylic acid monomer and / or an anhydride thereof and an ethylenically unsaturated monomer. A method for producing a slurry of magnesium hydroxide, comprising: