JPS6021813A - Preparation of fibrous basic magnesium chloride having high purity - Google Patents

Abstract

PURPOSE:To prepare fibrous basic magnesium chloride with high yield and economically by specifying the concn. of aq. MgCl2 soln., specific surface area of MgO, molar ratio of MgCl2 to MgO, and the treating temp. CONSTITUTION:MgO having >=40m<2>/g specific surface area is added to aq. soln. of MgCl2 having 20-35wt% concn., 1.18-1.38 specific gravity and 1-5pH controlling the molar ratio of MgO to MgCl2 to 0.01-0.3, and the mixture is stirred violently at 60-150 deg.C for 30min-5hr. The product is then settled or fluidized mildly to age at room temp.-80 deg.C for ca.20hr. Residual reaction liquid is separated, the residual solid is washed with water and dried to obtain fibrous basic magnesium chloride of high purity contg.>=80% fibrous acicular crystals having 10-200mum major axis, 0.5-2mum minor axis, and >=20 ratio of major axis to minor axis.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing fibrous basic magnesium chloride, and particularly to a method for economically producing high-purity a-fibrous basic magnesium chloride in a high yield. In general, basic magnesium chloride of the general formula Mg type has been reported, and these are referred to as crystalline fibrous forms, which are the object of the present invention.

When the crystals grow further and intertwine, they are called magnesia mento.

Generally, this high purity fibrous basic magnesium chloride is
Due to its shape and high purity, it is also useful as a raw material for producing magnesium oxide and magnesium salt for steel, and as a raw material for producing magnesium oxide for high-temperature refractory ceramics and socks.

Generally, basic magnesium chloride is prepared by coexisting magnesium oxide in an aqueous solution containing magnesium chloride. Various methods have been known for making A, including JournaJ o
f tJ+e American Ceramic 5
ocity.

59.51-54 (1976'): 60.504-
5071" 1977] describes a method for producing basic magnesium chloride compounds, particularly magnesia cement.

In this method, a magnesium chloride solution and magnesium oxide are mixed and left to stand at a temperature ranging from room temperature to 30°C or less to produce m-fibrous basic magnesium chloride, and finally,
This is a method of obtaining magnesia cement.

However, in this conventional method, it is clear that unreacted magnesium oxide, by-product magnesium hydroxide, and gel-like substances are co-formed, so that the needle-like C has a low purity and has the property of becoming cement over time. Therefore, it is industrially impossible to separate and recover it as a simple fibrous basic magnesium chloride product.

Next, Japanese Patent Publication No. 57-82040 describes a method for producing fibrous basic magnesium chloride as a raw material for fibrous magnesium hydroxide. ! : Chemical formula Mg
It is said that it is possible to produce the fibrous basic magnesium chloride Ramura shown in 5(OH) 50z% 4H20, but according to the results of additional tests by the present inventors, the yield of magnesium oxide is about 1/4 of the theoretical yield. , i.e. the yield is only 25%
The country is economically disadvantaged and is isolated.

Next, a conventional method for producing #41i fibrous basic magnesium chloride using n-type treatment methods at room temperature is also known. (J
ournal+ of tl+e American
Oerami.

8ociety, 54, 2872-2880 [19
821).

This method shows that the magnesium oxide yield is at most 50% at a magnesium chloride concentration of about 14%.

The present inventors have carried out various studies to produce high-yield fibrous basic magnesium chloride with high purity, which cannot be found in these conventional methods. As a result, the concentration of magnesium chloride and the specific surface area of magnesium oxide It was discovered that the object could only be achieved by specifying the characteristics, the molar ratio to magnesium chloride, and conditions such as treatment temperature, and the present invention was achieved based on this finding.

That is, the present invention provides a method for producing #I4 fibrous basic magnesium chloride from an aqueous magnesium chloride solution in the coexistence of magnesium oxide, in which the aqueous magnesium chloride solution has a concentration of about 2Qwt% to 86wj%, and the magnesium oxide has a specific surface area of 40nl/f or more. and magnesium oxide/
This is a method for producing highly pure, highly basic magnesium chloride, characterized in that the molar ratio of magnesium chloride is about 0.01 to 0.8 and the temperature is about 60 to about 150°C.

According to the present invention, a#! Basic magnesium chloride and HaM
fX(OH) 101%, needle-shaped basic magnesium chloride crystals expressed by the general formula nU20, approximately 1
000 magnification, the ratio of the major axis to the minor axis of the needle crystals is about 20 or more.

The long axis is about 10 μm to about 200 μm, the short axis is about 0.5 μm
~about 2 mm.

High purity means that the produced solid composition contains 80% or more of the above W4 fibrous needle crystals.

When the concentration of magnesium chloride is 2Qwt% to 24wt%, the chemical formula Mg10(011)18Ct2.5H20(
Basic magnesium chloride (hereinafter abbreviated as P, 9) is produced, and the concentration of 24w1% to less than 23wt% is Mg5 (0■)
%Oz, 4H20 (hereinafter abbreviated as 1; -P, 5) basic magnesium chloride at 28 wt%~! At 15 wt+%, the chemical formula Mg5(OH)s(3t, 4H20 (hereinafter P
, 3), and all of these crystals are acicular crystals with a length-to-breadth ratio of about 20 or more.

When the magnesium chloride concentration is less than 20 wt%, P and 5 are produced as fibrous needle crystals, but the amount is extremely small and the amount of magnesium hydroxide by-product is large, which is not preferable.

When the magnesium chloride concentration exceeds 85 wt%, crystal growth progresses further and crystals become entangled with each other, resulting in so-called magnesia cement, and the fibrous material of the present invention cannot be obtained.

Next, magnesium oxide, which is an acid component, must have a specific surface area of 40 d/I or more.

The larger the specific surface area, the higher the content of fibrous needles in the produced solid composition, and the greater the amount of fibrous needles produced. When magnesium oxide with a specific surface area of about 40 i/f is used, the content of the above-mentioned fibrous needles is about 90% or more, and the amount of Mtm-shaped needles produced is the yield per magnesium oxide. The percentage is 90% or more.

The specific surface area of magnesium oxide is 40. r? When it is lower than /f, plate-shaped magnesium hydroxide increases, and the specific surface Ui8
0. ? In the vicinity of /f, all magnesium hydroxide becomes plate-like.

The molar ratio of the magnesium oxide air to magnesium chloride is preferably about 0.01 to about 0.8.

The smaller the molar ratio is, the higher the content of @I4 fibrous needles in the produced solid composition is, which is preferable, but the smaller the amount produced, the lower the productivity per reaction vessel from an industrial perspective. I don't like it. Therefore, the molar ratio is at least 0. Approximately O1 is required.

The larger the molar ratio, the larger the amount produced, but when the 1 molar ratio is 0, magnesia cement is produced, gels and plate crystals are produced, and the content of fibrous needle crystals in the produced solid composition is reduced.
．． When the molar ratio is about 8, the content ratio of fibrous needle crystals is 80% or more, but when the molar ratio is 0.4, the content ratio is about 50%, which is not preferable because the quality is completely low.

The specific surface area used in the present invention is 40n? Magnesium oxide having a temperature of /I or more can be obtained by calcining basic magnesium carbonate or magnesium hydroxide at a temperature of about 600'C to 650C for 8 to 6 hours. Commercially available magnesium oxide or magnesium oxide obtained by the method described above can absorb moisture and carbon dioxide after being left for a long time.
When calcined at 60°C to 600°C for about 2 hours, the specific surface area becomes 4.
It becomes magnesium oxide with a value of 0d/I or more.

Note that the specific surface area is a value measured by the BETN2 method.

The reaction temperature of magnesium chloride and magnesium oxide in the present invention is preferably about 60°C to 150°C.

When the reaction temperature is room temperature, the reaction is slow and it takes several weeks to several months to complete the formation of fibrous needle crystals. If the temperature is low, the content of fibrous needle crystals in the solid product is also low.At 40°C, it is about 40%, and the rest is gel or plate-like crystals at 60°C.
If it is above, the content ratio of fibrous needle crystals in the solid product is 8.
0% or more and the reaction time can be completed in about 5 hours.6 The higher the temperature, the faster the reaction can be completed.

For example, the reaction can be completed in about 1 hour at 90"C and about 80 minutes at 100"C. However, if the temperature is higher, the reaction will complete faster, but more thermal energy will be consumed and the reaction pressure will be higher, so equipment Therefore, the reaction under conditions in which a concentration of about 90% or more is suitable is carried out in a suspended phase state under strong stirring.

After the reaction process is completed, ripening is performed in order to grow the vAm-shaped needles even thicker and longer.

This aging is carried out for about 20 hours by maintaining the temperature between room temperature and about 80° C. after the completion of the reaction, and allowing it to stand still or under very gentle flow. By this aging, the yield of the fibrous needle crystals to magnesium oxide can be improved to about 90% or more.

The produced fibrous needle crystals are separated from the reaction residual liquid, washed with water,
Then dry it and take it out.

The reaction residual water, which contains a large amount of magnesium chloride, is recycled as a raw material.

The new aqueous solution of magnesium chloride has a concentration of 20-8
At 5 wt%, the specific gravity is 1.18-1.38 and the pH is 4-1.
It is 5.

The reaction residual liquid and the liquid to which washing water was added had a lower specific gravity and a pH close to 7. Therefore, hydrochloric acid was added to this liquid to bring the pH to 4 to 5, and solid magnesium chloride was dissolved. By adjusting the specific gravity to 1.18 to 1.38, it can be used as a raw material magnesium chloride solution. Next, the present invention will be explained in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto. isn't it.

Example 1 Specific surface 1 in 118f of 2Qwt% magnesium chloride aqueous solution
4 'lrr? /I, and then at room temperature (around 18°C, the same applies hereinafter) about 2 Q 1sr.
sStanding generation aging treatment, followed by standing still at about 70℃, 21
+rs heat aging treatment. After cooling to room temperature, the crystals were filtered, washed with water, washed with alcohol, and dried under vacuum (room temperature). The yield of crystals was 0.9'lf. When this was observed using an electron microscope with a magnification of approximately 1000 times, it was found that it was a long-diameter needle-like crystal with a high purity content of over 90%, and was identified as P,5 by X-ray diffraction, and its counterpart magnesium oxide. The yield was as high as 91%.Example 2 A specific surface of 4
] Magnesium oxide 8.7211 with 47d/fi
(MgO/Mg0z2 = 0.8 molar ratio) was added,
Heat treatment was carried out at about 100°C under strong stirring, followed by aging treatment at room temperature for about 20 br in a still apparatus, followed by heat treatment at about 80°C for 14 hzs while standing still. After cooling to room temperature, filtration, washing with water, washing with alcohol, and vacuum drying (
The yield of crystals obtained at room temperature) was 4,481.

When this was observed using an electron microscope with a magnification of about 1000 times, the long axis of the core was 10 μm ~ 80 am, and the short axis was about 0.5 am.
2β 20 to about 40 fibrous needle-like crystals, and the content is 8
With a high purity of 0%, P. Identified as 9,
The yield of magnesium oxide was as high as 95% or more.

Example 8 Magnesium oxide (y 4 5
f (MgO/MgC3L2 = 0.08 molar ratio), intoxication treatment was carried out at about 90"C, 111r under strong stirring, followed by static aging treatment at room temperature for about 29 brs, followed by standing still. After cooling to room temperature, filtration, washing with water, washing with alcohol, and vacuum drying (room temperature) yielded 1.
It was 1g. This was observed using an electron microscope with a magnification of about 1000 times.
5/J m to 26 m long axis to short axis ratio of about 20 to about 50
It is a fibrous needle-shaped crystal with a high purity content of 90% or more, and is determined by X# diffraction to be P. 8, and its yield relative to magnesium oxide was as high as 95%.

Example 4 8 4 wt% Magnesium chloride aqueous solution 100f, specific surface M51n? Magnesium oxide with /f 0,4
5 f (MgO/Mg0z2= 0.0 4 5
molar ratio) and heated to about 100°C under strong stirring.
Heat treatment is performed, followed by aging treatment at room temperature for about 20 firs, and then left standing at about 80°C for 4 bys.
Heat-ripened. After cooling to room temperature, filtering, washing with water, alcohol washing, and direct air drying (room temperature), the yield of crystals obtained was 1.78 f. When this was observed using an electron microscope with a magnification of approximately 1000 times, the major axis was 10 tim ~ 80 μm, the minor axis was approximately 0.5 μm ~ 2 t < m, and the major axis i ratio was approximately 20 ~
It contains about 40 fibrous needle-like crystals, and its content is high purity of 90% or more, and it was determined by X-ray diffraction that P. 8, and its yield relative to magnesium oxide was as high as 95% or more.

Example 5 24 wt% magnesium chloride aqueous solution 2440f has a specific surface area of 47n? 9 g of magnesium oxide with /fl (
MgO/Mg0z2=0.04 5 molar ratio) was added,
Heat treatment was performed at about 100° C., i h , r with strong stirring, and subsequent treatments were carried out in the same manner as in Example 4, and the yield of the obtained crystals was 1'1. 'llll.

When this was observed using an electron microscope with a magnification of about 1000, it was found that the major axis was 10μff1 ~ 1-504'F.
x Minor axis of approximately 0.5gm to 2am, long axis to minor axis ratio of approximately 20
~75 fibrous needle crystals, and the content is 90%
With the above high purity, it was identified as P,5 by X-ray diffraction,
The yield of magnesium oxide was as high as 90%.

Example 6 A specific surface area of 47 n? / magnesium oxide with f 0.4
5 f (MgO/MgO1 = 0.645 molar ratio) was added and heat treated at about 60°C for 4 hours with strong stirring,
The subsequent treatment was carried out in the same manner as in Example 4, and the yield of crystals obtained was (+, 89 f/.
When observed with a multiplier electron microscope, the major axis was approximately 10 μm.
~150zsm, minor axis approximately 0.5 a m -2B rB
It is a fibrous needle-like crystal with a long axis to short axis ratio of about 20 to about 75, and its content is as high as 80%, and it is found by X-ray diffraction that P
, 5, and its yield relative to magnesium oxide was 90
%.

Comparative Example 1 115f of 17wt% magnesium chloride aqueous solution was added with a specific surface area of 4'In? Magnesium oxide with /f 0.45
f (MgO/Mg0zt = 0.0450, 55 f. When this was observed with an electron microscope at a magnification of about 1000, it was found that there were only a very small amount of needle crystals and most of the gel or plate crystals were present. This substance was identified as magnesium hydroxide by X-ray diffraction.

Comparative Example 2 An oxidized magf having a specific surface area of 4'fd/I was added to 122f of a 24 wt % magnesium chloride aqueous solution. When this was observed using an electron microscope with a magnification of approximately 1000, the major axis was 10 μm to 70 mm, and the minor axis was approximately 0.5 tt m to 8
Fibrous acicular crystals having a long axis to short axis ratio of about 20 to about 28 were observed, but their content was low purity of 40% and most of them were gels or plate crystals. It was identified as P,6 by X-ray diffraction, and its yield relative to magnesium oxide was 82%.

Comparative Example 8 20wt% magnesium chloride aqueous solution 118F D, oxide magnetic screw having a specific surface area of 82d/I') A O,4
51 (MgO/Mg0L2 = 0.045). This was observed using an electron microscope with a magnification of about too much.
No needle crystals were observed at all, only gel or plate crystals. The kernels were identified as magnesium hydroxide by X-ray diffraction.

Comparative Example 4 Magnesilla oxide A having a specific surface [4'7d/I 0.45
f (MgO/Mg0t2 = 0.068 molar ratio), and thereafter the amount was 0.6 g as in Example 1. When this was observed using a trace amount of electron M at a magnification of about 1000 times, there was only a very small amount of needle-like crystals, and most of them were gels or plate-like crystals.

This substance was identified as magnesium hydroxide by X-ray diffraction.

Comparative Example 5 24wt% magnesium chloride water/30t221 and specific surface area 61. r? Magnesium oxide with /f 0.56
1 (MgO/Mg0L2 = 0.045 molar ratio), and the temperature was about 40'05 brsl, 08f under strong stirring. When this was observed using an electron microscope with a magnification of about too much, the major axis was approximately 10 am to 80 pm, and the minor axis was approximately 0.5
s m ~2 s m long axis to short axis ratio of about 20 to about 4
0 fibrous needle crystals were observed, but the content was 40%.
The purity was low and most of it was gel or plate-like crystals.

X-ray diffraction shows that unreacted magnesium oxide and P, 5 are Ii
'tl was determined, and the yield of magnesium oxide as P, 5 was 89%.

Comparative Example 6 28 wt% magnesia chloride aqueous solution 126f Magnesium oxide having a specific surface area of 51 I/g 0.671
(MgO/MgO42 = 01045 molar ratio) was heated at about 40 degrees (!5 brs) under vigorous stirring, and the subsequent treatment was carried out in the same manner as in Example 6. The yield of the obtained precipitate was 1. When this was observed using an m-son microscope with a magnification of about 1000, it was found that the major diameter was 10 nm to 80 nm.
Fibrous needle crystals with a short axis of about 0.5 μm to 2 mm and a long axis to short axis ratio of about 20 to about 40 were observed, but the content was low purity of 50%, and most of them were It was a gel or plate-like crystal. , unreacted magnesium oxide and P by X-ray diffraction
, B and P,5 were identified, and the yield of P,5 based on magnesium oxide was 88%.

Comparative Example 7 Magnesium oxide 0.821 having a specific surface area of 4"7 d/f in 122 f of 12 wt% magnesium chloride aqueous solution
(0.05 molar ratio of MgO/MgO12) was added, and the same treatment as in Example 1 was carried out, and the yield of crystals obtained was 0.18F. When observed with a microscope, the major axis was approximately 20 μm to 50 μm.
μm1 short axis approximately 0.5 μm to 1 μm long axis to short axis ratio approximately 4
0 to about 50 fibrous needle crystals, the content of which is 60%
The purity was low, and the others were gel or plate-like crystals. Magnesium hydroxide and P,5 were identified by X-ray diffraction, and I
), the yield of magnesium oxide as 5 was as low as 25%.

Claims (1)

[Claims] In the method for producing fibrous basic magnesium chloride from an aqueous magnesium chloride solution in the coexistence of magnesium oxide, the aqueous magnesium chloride solution has a concentration of about 2Q wt% to 85%.
wt%, and magnesium oxide has a specific surface area of 40.1
/f or more, the molar ratio of magnesium oxide/magnesium chloride is about 0.01 to 0.8, and the temperature is about 0°C
A process for producing high-purity IIa fibrous cyclic basic magnesium chloride characterized by a temperature of ~150°C.