JPH03122012A - Production of fibrous basic magnesium sulfate - Google Patents

Abstract

PURPOSE:To obtain high-quality fibrous magnesium sulfate by heating and reacting slurry having specific magnesium oxide powder dispersed in an aqueous solution containing soluble sulfate and opening this cocoon-like reaction product. CONSTITUTION:Magnesium oxide powder having >=0.7 apparent specific gravity is dispersed into an aqueous solution containing a soluble sulfate to prepare slurry having <=15 wt.% MgO. Then the prepared slurry is reacted under heating to form cocoon-like basic magesium sulfate. High-strength shear stress is applied to the reaction product, which is opened to give the objective fibrous basic magnesium sulfate. When magnesium oxide powder having < 0.7 apparent specific gravity is used as the magnesium oxide, reaction to the aqueous solution containing a soluble sulfate is extremely insufficient and high-quality cocoon-like basic magnesium sulfate is not obtained. The reaction under heating is prefer ably carried out under normal pressure at >= 60 deg.C and the <= the boiling point of the reaction system.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing fibrous basic magnesium sulfate.

[Conventional technology] Recently, the development of various composite materials and shallow products using new materials has been actively carried out. In particular, plain short fibers are often used as reinforcement materials for plastics and metals. Basic magnesium sulfate is one of the R-free short fibers that has attracted attention because of its a-ability and because it can be obtained industrially at low cost.

Conventionally, as a method for producing fibrous basic magnesium sulfate, magnesium hydroxide or magnesium oxide is dispersed in an aqueous magnesium sulfate solution.
A method of conducting a hydrothermal reaction at a temperature of °C is known.
Publication No.). These methods require a hydrothermal reaction,
In order to carry out the reaction, it is necessary to reduce the pressure volume by 2 liters and then suddenly heat it at 170 to 270°C under pressure for 1 to 30 hours. This method has the disadvantage that it is inefficient and that expanding the scale of production is a national disaster and increases costs.

[Problem to be Solved by the Invention 1] The present inventors have conducted various studies on an efficient method for producing fibrous basic magnesium sulfate that does not require the use of a pressurized reaction vessel, and have found that magnesium oxide with specific properties has been developed. It has been discovered that high quality fibrous basic magnesium sulfate can be obtained by using cocoon-like basic magnesium sulfate obtained by the reaction of powder and an aqueous solution containing soluble sulfate as an intermediate raw material and subjecting it to fibrillation treatment, and has developed the present invention. completed.

``Means for Solving the Problems'' That is, the present invention disperses magnesium oxide powder with an apparent specific gravity of 0.7 or more in an aqueous solution containing soluble sulfate.
A slurry containing 15% by weight or less as gO is prepared, the slurry is then reacted by heating to produce cocoon-like basic magnesium sulfate, and then a strong shearing force is applied to the cocoon-like product to defibrate it. The present invention relates to a method for producing fibrous basic magnesium sulfate.

The present invention will be explained in detail below.

The magnesium oxide powder used in the method of the present invention has a particle size of 25
It is suitable to have a diameter of 0 μm or less, preferably 100 μm or less, and it may be produced from any compound, but
Its appearance requires that the specific gravity be 0.7 or more.

If magnesium hydroxide or magnesium oxide with an apparent specific gravity of less than 0.7 is used, not only will the reaction with the soluble sulfate-containing aqueous solution be extremely insufficient, but also good quality monobasic magnesium sulfate, Therefore, high quality fibrous basic magnesium sulfate cannot be obtained.

The apparent specific gravity value of the magnesium oxide powder in the method of the present invention is determined by the following method. That is, 50 g of a sample of magnesium oxide powder with an average particle size of 100 μM or less was collected, and the inner diameter was 26+.
After transferring it to a measuring cylinder of ntn and dropping the graduated cylinder 300 times from a height of 3 cIn, the volume Rt V (ml) of the magnesium oxide powder is read on the scale, and the apparent specific gravity TD is calculated using the following formula.

(2) Also, since impurity components in the acid (magnesium powder) inhibit the crystal growth of basic magnesium sulfate, it is preferable that the purity of MgO is as high as possible, at least 95%.

Many of the high-purity magnesia clinkers currently used in large quantities as refractories in steelmaking meet the above requirements and are suitable as raw stones for the method of the present invention.

On the other hand, examples of the soluble sulfate include magnesium sulfate and ammonium sulfate, and red sea bream sium sulfate is particularly preferred.

In the reaction, the above magnesium oxide powder is added to an aqueous solution containing soluble sulfate in an amount of 15% by weight or less, preferably 10% by weight as MgO.
Disperse the slurry to a concentration of 5% by weight or less, more preferably 5% by weight or less, and heat at 60°C under good stirring.
This is done by heating to a temperature above.

If the concentration of the slurry exceeds 15% by weight, the viscosity of the slurry will increase significantly as the reaction progresses, making it difficult to stir h' and making it impossible to obtain a uniform cocoon-like product.

A heating temperature of 60 to 100°C is sufficient in most cases, but
It is also possible to carry out the reaction by heating to 100° C. or higher in a pressurized reactor, if desired. Also, the reaction time often requires at least 0.5 hours, and often 0.5 hours.
It ranges from 5 to 40 hours, preferably from 3 to 24 hours.

The soluble sulfate-containing aqueous solution used in the method of the present invention suitably contains soluble sulfate in a ratio of at least 0.2 mol, preferably 0.3 to 2 mol, per 1 mol of magnesium oxide powder MgO component. . If it is less than 0.2 mol, the reaction will be insufficient, while if it exceeds 2 mol, the effect will not be particularly different.

Some amount of other salts may be present in the soluble sulfate-containing aqueous solution, and various additives, surfactants, etc. may be present as necessary.

Note that as a means of dispersing magnesium oxide powder in an aqueous solution containing soluble sulfate, sulfuric acid is added to an aqueous slurry of magnesium oxide, a portion of magnesium oxide is dissolved in the sulfuric acid, and a predetermined quantitative relationship is obtained. It goes without saying that a method for preparing a slurry is also included.

By the above heating operation, the magnesium oxide powder is converted into cocoon-like basic magnesium sulfate by reaction with soluble sulfate.

That is, a large number of fibrous crystals of basic magnesium sulfate aggregate and intertwine with each other to form uniform individual or several agglomerated aggregates with a size of 30 to 500 μm, which can be observed under an electron microscope. Then, it can be confirmed that it looks like the mask of a silkworm.

The apparent specific gravity as a powder is often 0.1 to 0.
5, and the specific surface area is in the range of about 5 to 30 fn2/2.

The cocoon-shaped basic mago-sium sulfate slurry produced by such a reaction may be used as it is, or after all or part of the mother liquor has been replaced with water, the cocoon-shaped product is disintegrated by applying strong shearing force, and the cocoon-shaped product is individually separated. is defibrated into fibrous crystals of basic magnesium sulfate.

Examples of crushing devices that apply strong shearing force include high-speed stirrers, colloid mills, ultrasonic devices, homogenizers, impact crushers, and ball mills.

After disintegration (11i), undisintegrated parts and coarse particles are subjected to repeated sedimentation and classification as necessary, and then solid-liquid separation (5) washing with water and (02) drying are carried out using conventional methods to obtain fibrous basic sulfuric acid. Finished as a magnesium product.

The present invention provides that the fibrous basic magnesium sulfate is 5Mg0
・Mg5O, ・8 I+ Has a chemical composition close to 20,
Often 0.1-5μm in diameter and 10-300μm in length
m, short fibrous crystal particles with an aspect ratio of 10 to 250, which are useful as various auxiliary fillers.

[Function] According to the production method of the present invention, magnesium oxide powder having an apparent specific gravity of 0.7 or more is heated in an aqueous solution containing a soluble sulfate, thereby converting it into basic magnesila sulfate 11 under normal pressure. do. In the method according to the present invention, the basic magnesium sulfate initially obtained has a spherical structure like the so-called silkworm face, in which fine fibers X-1 single crystals of basic magnesium sulfate are intertwined with each other. The details of the mechanism of such a formation reaction are unknown, but it is presumed that a type of wet whisker is formed due to the pressure associated with crystal transformation in an aqueous solution of soluble sulfate 3 with magnesium oxide particles as the nucleus. be done.

Next, the cocoon-like basic magnesium sulfate can be disintegrated by applying a strong shearing force to form fine fibrous basic magnesium sulfate.

[Example of implementation] The present invention will be further explained with reference to Examples below.

Example 1 Water 1.0 OR magnesium sulfate heptahydrate 12.1k
Then, 2.0 ky of magnesia clinker powder having an apparent specific gravity of 1.75 was dispersed to obtain a slurry. This slurry contained magnesium oxide powder with a weight number of 9≦1.8 as M g O. Next, the slurry was reacted at about 100°C for 24 hours.

After the reaction was completed, the solid content was separated from the mother liquor and washed with water to obtain primary basic magnesium sulfate consisting of uniform particles of about 200 μm, which are aggregates of fine fibers.

1:) An electron micrograph of a cocoon-like basic magnesium sulfate is shown in FIG.

This product was mixed with 60 I of water! After applying strong shearing treatment for 5 minutes with a homogenizer, undisintegrated cocoon-like particles and unreacted 111 fi particles were classified and removed by sedimentation separation, and the disintegrated fibrous basic magnesium sulfate was obtained. It was collected by filtration, dried and ground in a conventional manner.

The obtained fibrous basic magnesium sulfate has a diameter of 0.2~
It is a bulky powder consisting of fibrous particles with a length of 0.5 μm, a length of 10 to 30) l+n, and an aspect ratio of 20 to 150.
The apparent specific gravity is 0.1, and the specific surface area is 12.0 by the BIET method.
It was 112/g.

An electron micrograph of the obtained fibrous basic magnesylanosulfate is shown in FIG.

Example 2 Instead of magnesia clinker, a magnesium oxide powder with an apparent specific gravity of 138 obtained by calcining hydroxide (magnesium) was used. Cocoon-shaped particles consisting of basic magnesium sulfate and tIY.

Disperse this product in water 801 and use a homogenizer to
After applying strong shearing treatment for 0 minutes, undisintegrated cocoon-like particles and unreacted coarse particles are classified and removed by sedimentation separation, and the disintegrated fibrous basic magnesium sulfate is recovered by filtration.
It was dried and ground by a conventional method.

The obtained fibrous basic magnesium sulfate has a diameter of 0.2~
03μm, length 10~30μm, aspect ratio 33~
It is a bulky powder consisting of fibrous particles with an apparent specific gravity of 0.09 and a specific surface area measured by the BET method], 4.0 m2.
/y was there.

Example 3 22.2 ky of ammonium sulfate was dissolved in 100 a of water, and then 13.7 kg of magnesia clinker powder having an apparent specific gravity of 175 was dispersed to obtain a slurry. This slurry contained 10.1% by weight of magnesium oxide powder as MgO.

Next, the slurry was reacted at 100°C for 24 hours.

After the reaction is completed, the solid content is separated from the mother liquor, washed with water, and
A cocoon-like basic magnesium sulfate fraction consisting of uniform particles of approximately 200 ) t + n, which is an aggregate of II fibers, was obtained.

Disperse this product in 1002 and use a homogenizer to
After applying strong shearing treatment for 0 minutes, undisintegrated cocoon-like particles and unreacted coarse particles are classified and removed by sedimentation separation, and the disintegrated fibrous basic magnesium sulfate is collected by filtration, and then processed by a conventional method. Dried and ground.

The obtained fibrous basic sulfate maqui, sia, has a diameter of 0.2
~0.3t, tm, length 5~20μm, aspect 1~
It is a bulky powder consisting of fibrous particles with a ratio of 17 to 100, an apparent specific gravity of 0.14, and a specific surface area of 1 by the BET method.
It was 4.0 m2/g.

Example 4 Magnesium clinker with an apparent specific gravity of 1.75 was prepared by dissolving 2.1 kg of magnesium sulfate heptahydrate in 50 ml of water.
Powder 2. A slurry was obtained by dispersing Okg. This slurry contained 3.1% by weight of magnesium oxide powder as MgO. Next, the slurry was placed in a pressure vessel.
The reaction was carried out at 80°C for 5 hours. After the reaction is complete, the solid content is
Separate from the L liquid, wash with water, and collect about 4
A cocoon-shaped basic red sea bream sium sulfate consisting of uniform particles of 00 μm in size was obtained. An electron micrograph of the obtained cocoon-like basic magnesium sulfate is shown in FIG.

Disperse this product in water 601 and use a homogenizer to
After applying strong shearing treatment for 1 minute, undisintegrated cocoon-like particles and unreacted coarse particles are classified and removed by sedimentation separation, and the disintegrated fibrous basic magnesium sulfate is recovered by filtration.
It was dried and ground by a conventional method.

The obtained fibrous basic magnesium sulfate has a diameter of 0.2~
0.4μm, length 10-40μm, aspect ratio 1-25
It is a bulky powder made of ~200 fiber T and Ti-like particles, with an apparent specific gravity of 0.09 and a specific surface area of 8 by the BET method.
It was 0 m2/g. An electrophotograph of the obtained fibrous basic magnesium sulfate is shown in FIG.

[Effects of the Invention] According to the method of the present invention, it is possible to provide an efficient method for producing fibrous basic magnesium sulfate without using a pressurized reaction vessel.

1 series fibrous basic magnesium sulfate is an additive for resins,
It can be used as a filler, a flame retardant, a heat insulating material, a raw material for producing other fibrous magnesium salts, and other uses.

[Brief explanation of drawings]

FIG. 1 is an electron micrograph of the cocoon-like basic magnesium sulfate obtained in Example 1, FIG. 2 is an electron micrograph of the fibrous basic magnesium sulfate obtained in Example 1, and FIG. The figure is a single electron micrograph of the cocoon-like basic magnesium sulfate obtained in Example 4. FIG. 4 is an electron micrograph of the fibrous basic magnesium sulfate obtained in Example 4.

Claims (1)

[Claims] 1. Magnesium oxide powder with an apparent specific gravity of 0.7 or more is dispersed in an aqueous solution containing soluble sulfate to produce 15% MgO.
A fiber characterized in that a slurry of % by weight or less is prepared, the slurry is then heated and reacted to produce cocoon-like basic magnesium sulfate, and then a strong shearing force is applied to the cocoon-like product to defibrate it. A method for producing basic magnesium sulfate. 2. The method for producing fibrous basic magnesium sulfate according to claim 1, wherein the heating reaction is carried out at a temperature of 60° C. or higher and lower than the boiling point of the reaction system under normal pressure.