JPH05311150A - Thixotropic agent - Google Patents

Abstract

PURPOSE:To provide the thixotropic agent composed of a fibrous or acicular magnesium oxysulfate surface-treated with sodium silicate and exhibiting excellent dispersibility, etc., and stable thixotropy when mixed to a hydrophilic polymer or a mixture of the polymer and water. CONSTITUTION:The thixotropic agent is produced by surface-treating fibrous or acicular magnesium oxysulfate having a length of 0.5-50mum, a diameter of 0.05-1mum and an aspect ratio (length/diameter) of 10-300 with sodium silicate. The magnesium oxysulfate is preferably produced by dispersing magnesium hydroxide or magnesium oxide having a BET specific surface area of <=20m<2>/g in an aqueous solution of magnesium sulfate at a concentration of <=25wt.% and subjecting to hydrothermal reaction at 100-300 deg.C. The surface-treatment with sodium silicate is preferably carried out e.g. by adding sodium silicate to an aqueous solution obtained by the hydrothermal reaction.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a thixotropic agent comprising fibrous or acicular magnesium oxysulfate surface-treated with sodium silicate.

[0002]

2. Description of the Related Art Rheology modifiers that adjust the flow characteristics of thickening and thixotropy are used in a wide variety of fields such as various paints, coating agents, adhesives and sealants. Such rheology modifiers include modified castor oil derivatives that impart structural viscosity, polyolefin waxes, organic amides, urea compounds, finely divided silica, basic calcium sulfonate gels, organic microgels, non-aqueous dispersion resin particles, amine-treated clays. Etc.

Asbestos has excellent properties of imparting thickening and thixotropic properties, but is said to be harmful to health. Further, Japanese Patent Laid-Open No. 63-314250 discloses a thixotropic agent containing acicular calcium silicate crystals having a particle size of 10 to 150 μm.

Regarding the thickening property of fibrous or acicular magnesium oxysulfate, gypsum and lime, No. 6 Two
16, 337 to 339 (1988), it has been shown that the viscosity increases when added to water, a polyol, which is a raw material of an epoxy resin, a polyurethane resin, and asphalt, as in asbestos. However, thixotropy is not mentioned.

Fibrous or acicular magnesium oxysulfate is disclosed in Japanese Patent Application Laid-Open No. 4-20585 (Japanese Patent Application No. 2-205585).
123076) and shows excellent thixotropy.

JP-A-4-20585 discloses that a mixture of fibrous or needle-shaped magnesium oxysulfate and a liquid polymer exhibits thixotropic properties.
Further, in a mixture of fibrous or acicular magnesium oxysulfate, a liquid polymer and an organic solvent, the thixotropic property is remarkably improved when the organic solvent is a polar solvent which is a compound having at least one alcoholic hydroxyl group or sulfur in the molecule. However, the mixing ratio of the polar solvent and the fibrous or acicular magnesium oxysulfate in this case is 1 to 100 parts by weight, preferably 5 to 50 parts by weight, of the fibrous or acicular magnesium oxysulfate per 100 parts by weight of the polar solvent. Has been shown.

Further, in Japanese Patent Application No. 3-242895, when fibrous or acicular magnesium oxysulfate is surface-treated with a compound having at least one alcoholic hydroxyl group in the molecule, further thickening and thixotropic properties are obtained. It has been shown to improve.

[0008]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
In the publication, fibrous or acicular magnesium oxysulfate has a chemically active magnesium ion, an alkaline hydroxyl group and a sulfate ion. Therefore, when mixed with a liquid polymer or in the liquid polymer and in the molecule, an alcoholic hydroxyl group or a sulfur It has been shown that when it is mixed with a mixture of polar solvents which is a compound having at least one of the above, thixotropic properties are imparted to the composition obtained by the mixing. However, since fibrous or acicular magnesium oxysulfate has high cohesiveness and poor dispersibility, it is particularly preferable to mix without using the polar solvent as described above, or to mix with water as the polar solvent. There was a problem in that a fibrous or acicular magnesium oxysulfate aggregate was present in the solution.

Further, Japanese Patent Application No. 3-242895 discloses that when a fibrous or acicular magnesium oxysulfate surface-treated with a compound having at least one alcoholic hydroxyl group in the molecule is mixed with a liquid polymer, the viscosity is increased. It has been shown that thixotropy is improved, but when such fibrous or acicular magnesium oxysulfate is mixed with water, cohesiveness and dispersibility are considerably solved, but the problem is still insufficient. was there.

The object of the present invention is to obtain good cohesiveness and dispersibility when fibrous or acicular magnesium oxysulfate is mixed with a water-affinitive polymer or a water-affinitive polymer and water. It is to provide a thixotropic agent that exhibits denaturation.

[0011]

The above objects of the present invention are as follows.
Surface treated with sodium silicate 0.5 ~ 50μm in length
m, a diameter of 0.05 to 1 μm, and an aspect ratio (length / diameter) of 10 to 300, which is a thixotropic agent comprising fibrous or acicular magnesium oxysulfate.

The fibrous or acicular magnesium oxysulfate is prepared by the method described in JP-A-1-126218, that is, magnesium hydroxide or magnesium oxide having a BET specific surface area of 20 m ² / g or less is added to an aqueous solution of magnesium sulfate. It can be suitably produced by a method in which the content is dispersed to 25% by weight or less and then hydrothermal reaction is performed at a temperature of 100 to 300 ° C.

The method described in JP-A-1-41544, that is, after dispersing magnesium sulfate and magnesium hydroxide or magnesium oxide so that the concentration thereof is 25% by weight or less, the temperature is 100 to 300 ° C. When a fibrous or acicular magnesium oxysulfate is produced by hydrothermally reacting with, it can be suitably produced by the method of incorporating a surfactant in the hydrothermal reaction system in the same manner as the above method.

The powdery X-ray diffraction spectrum of the obtained fibrous or acicular magnesium oxysulfate is ASTM No. It matches well with that of 7-415,
Typically, the ASTM No. It is considered that it can be represented by MgSO ₄ .5Mg (OH) ₂ .3H ₂ O, which is the rational formula described in 7-415.

The fibrous or acicular magnesium oxysulfate generally has a specific gravity of 2.0 to 2.5, a length (fiber length) of several microns to 1000 μm, and an apparent specific gravity of 0.05 to 0.3. It is a bulky fibrous or needle-shaped substance, and the product name is Mosheiji (Ube Industries, Ltd.)
It is distributed in the market as

Since fibrous or acicular magnesium oxysulfate has a chemically active magnesium ion, an alkaline hydroxyl group and a sulfate ion, it is mixed with a water-affinitive polymer or a water-affinitive polymer and water. When mixed with a mixture with, the composition obtained by mixing imparts thixotropy. However, since the fibrous or acicular magnesium oxysulfate has high cohesiveness and poor dispersibility, when mixed without using such a polar solvent as described above, the fibrous or acicular magnesium oxysulfate is mixed in the composition. There is a problem in that the presence of aggregates makes the viscosity unstable and thixotropic properties decrease.

Therefore, various studies were conducted on a method in which thixotropy was not reduced even when a fibrous or acicular magnesium oxysulfate was mixed with a polymer having affinity for water or a mixture thereof with water. As a result, fibrous or acicular magnesium was obtained. The inventors have found that the above problems can be solved by treating the surface of oxysulfate with sodium silicate, and have reached the present invention.

Fibrous or acicular magnesium oxysulfate is usually produced by hydrothermally reacting magnesium hydroxide and sulfuric acid as raw materials and then filtering, washing and drying. The following three methods are suitable for treating the surface of oxysulfate with sodium silicate.

That is, after hydrothermal treatment, a method of adding sodium silicate or an aqueous solution containing sodium silicate to an aqueous solution obtained, and a dehydrated cake of fibrous or acicular magnesium oxysulfate obtained after washing Add water to make a slurry again, and add sodium silicate or an aqueous solution containing sodium silicate to this slurry, and sodium silicate or silicic acid on the dehydrated cake of fibrous or acicular magnesium oxysulfate obtained after washing. This is a method of adding an aqueous solution containing sodium.

The surface of the fibrous or acicular magnesium oxysulfate is treated by such a method, then filtered if necessary, and dried to obtain the thixotropic agent of the present invention.

The amount of sodium silicate added to the fibrous or acicular magnesium oxysulfate is 0.1 to 20 parts by weight, preferably 0.3 to 8 parts by weight per 100 parts by weight of the fibrous or acicular magnesium oxysulfate.
Parts by weight.

The water-affinitive polymer to which the thixotropic agent of the present invention imparts thixotropy is, for example, a maleated oil-modified resin, a maleated fatty acid-modified polyester, a special phenol resin-modified resin, or acrylic acid as a monomer component. Acrylic resin, trimellitic acid modified alkyd resin, styrene-butadiene copolymer system or acrylic polymer system emulsion.

Fibrous or acicular magnesium oxysulfate suitable as a thixotropic agent has a length of 0.5 to 50.
μm, diameter 0.05 to 1 μm, aspect ratio (length / diameter) 10 to 300. Length 5
When it exceeds 0 μm or the aspect ratio exceeds 300, the fibrous or acicular magnesium oxysulfate is entangled with each other and the sufficient effect is not exhibited.

The mixing ratio of the thixotropic agent fibrous or acicular magnesium oxysulfate as the thixotropic agent of the present invention and the water-affinitive polymer or a mixture of the water and the polymer is a target and a target. It depends on the degree of thixotropy and it is difficult to express it in a simple manner, but it is usually 0.5 to 20 per 100 parts by weight of the polymer or its mixture with water.
Parts by weight, preferably 1 to 10 parts by weight.

[0025]

[Operation] When the fibrous or acicular magnesium oxysulfate is mixed with a water-affinitive polymer or a mixture of water and the fibrous or acicular magnesium oxysulfate, the fibrous or acicular magnesium oxysulfate has a thixotropic effect. It is thought to occur in order to generate a mesh structure. Since sodium silicate is easily dissolved in a polymer having an affinity for water, when the surface of fibrous or acicular magnesium oxysulfate is treated with sodium silicate,
Prevents agglomeration of fibrous or acicular magnesium oxysulfate, improves dispersibility when mixed with a polymer having affinity for water or its mixture with water, and the surface of fibrous or acicular magnesium oxysulfate is active. It is considered that the state returns to the state, the formation of a network structure showing thixotropy is facilitated, and thixotropy is increased.

[0026]

EXAMPLES The main properties of sodium silicate used in the examples of this specification are as follows. Sodium No.1 silicon dioxide silicic acid _(SiO 2)% 35 to 38 sodium oxide _(Na 2 O)% _17~19 iron (Fe)% 0.03 or less water-insoluble matter% 0.2

Sodium silicate No. 2 Specific gravity (15 ° C. Be) 54 or more Silicon dioxide (SiO ₂ )% 34-36 Sodium oxide (Na ₂ O)% 14-15 Iron (Fe)% 0.03 or less Water insoluble matter % 0.2 or less

Sodium silicate No. 3 Specific gravity (15 ° C Be) 40 or more Silicon dioxide (SiO ₂ )% 28-30 Sodium oxide (Na ₂ O)% 9-10 Iron (Fe)% 0.02 or less Water insoluble matter % 0.2 or less

Example 1 A fibrous or acicular magnesium oxysulfate seed crystal and a magnesium hydroxide slurry were added to an aqueous magnesium sulfate solution and well dispersed, and then the dispersion was placed in an autoclave at a temperature of 180 ° C. and a pressure of 10 kg / cm ₂
・ G was hydrothermally reacted for 2 hours.

After the reaction, the product was filtered and washed with water to obtain a dehydrated cake of fibrous or acicular magnesium oxysulfate having a water content of 77.6%. This dehydrated cake 46.
9 g and 553.1 g of water were placed in a 1000 ml beaker and subjected to dispersion treatment for 5 minutes with a homomixer (4C type manufactured by Tokushu Kika Kogyo Co., Ltd., the same hereinafter). Next, an aqueous solution prepared by adding 0.105 g of sodium silicate (water glass No. 1) to 100 g of water was added while dispersing with a homomixer, and then mixed with an ordinary stirrer for 30 minutes for surface treatment. A mixture of fibrous or acicular magnesium oxysulfate surface-treated with sodium silicate having a length of 5 to 20 μm and a diameter of 0.3 to 0.7 μm and water was obtained.
The mixture was dispersed for another 10 minutes. Then 2
The mixture was placed in a decompression device heated to 5 ° C., decompressed to remove air bubbles, and then the viscosity was measured under heating at 25 ° C. with a B-type viscometer (B8H type manufactured by Tokyo Keiki Co., Ltd., hereinafter the same). The results are shown in Table 1.

[0031]

[Table 1]

Examples 2 and 3 In Example 1, sodium silicate was replaced with water glass No. 2 (Example 2) and water glass No. 3 (Example 3) to carry out a surface treatment to form fibers or needles. A mixture of magnesium oxysulfate and water was prepared, and the viscosity was measured as in Example 1. The results are shown in Table 1.

Comparative Example 1 Seed crystal fibrous or acicular magnesium oxysulfate and magnesium hydroxide slurry were added to an aqueous solution of magnesium sulfate and well dispersed, and the dispersion was put in an autoclave at a temperature of 180 ° C. and a pressure of 10 kg /. cm ₂
・ G was hydrothermally reacted for 2 hours.

After the reaction, the product was filtered and washed with water to obtain a dehydrated cake of fibrous or acicular magnesium oxysulfate having a water content of 77.6%. This dehydrated cake 46.
9 g and 553.1 g of water were put into a beaker of 1000 ml and subjected to dispersion treatment for 5 minutes with a homomixer. Then 10
After adding 0 g of water while dispersing with a homomixer, mix with an ordinary stirrer for 30 minutes to obtain a length of 5 to 20 μm.
m, a diameter of 0.3 to 0.7 μm, and a mixture of fibrous or acicular magnesium oxysulfate and water were obtained, and the mixture was subjected to dispersion treatment for further 10 minutes. After that, 25 ℃
After removing the air bubbles by putting in a decompression device heated to
The viscosity was measured with a B-type viscometer under heating at 25 ° C. The results are shown in Table 1.

Comparative Example 2 A fibrous or acicular magnesium oxysulfate seed crystal and magnesium hydroxide slurry were added to an aqueous magnesium sulfate solution and well dispersed, and the dispersion was put in an autoclave at a temperature of 180 ° C. and a pressure of 10 kg /. cm ₂
・ G was hydrothermally reacted for 2 hours.

After the reaction, the product was filtered and washed with water to obtain a dehydrated cake of fibrous or acicular magnesium oxysulfate having a water content of 77.6%. This dehydrated cake 112
g and 1500 g of water were placed in a 3000 ml beaker and dispersed for 5 minutes with a homomixer. Next, an aqueous solution prepared by adding 12 g of polyethylene glycol (200) to 500 g of water was added while dispersing with a homomixer, followed by mixing with an ordinary stirrer for 30 minutes for surface treatment, and a length of 5 to 20 μm. A mixture of fibrous or acicular magnesium oxysulfate surface-treated with polyethylene glycol (200) having a diameter of 0.3 to 0.7 μm and water was obtained. The mixture was filtered and the water content obtained was 7
The 7.7% dehydrated cake was dried at a temperature of 125 ° C. for 5 hours. 10.5 g of fibrous or acicular magnesium oxysulfate thus obtained and 689.5 g of water
And were placed in a beaker of 1000 ml and dispersed for 10 minutes. Then, after putting in a decompression device heated to 25 ° C. to reduce the pressure to remove bubbles, the viscosity was measured with a B-type viscometer under heating at 25 ° C. The results are shown in Table 1.

Example 4 A seed crystal fibrous or acicular magnesium oxysulfate and magnesium hydroxide slurry were added to an aqueous magnesium sulfate solution and well dispersed, and then the dispersion was put into an autoclave at a temperature of 180 ° C. and a pressure of 10 kg / cm ₂
・ G was hydrothermally reacted for 2 hours.

After the reaction, the product was filtered and washed with water to obtain a dehydrated cake of fibrous or acicular magnesium oxysulfate having a water content of 77.6%. This dehydrated cake 46.
9 g and 553.1 g of water were put into a beaker of 1000 ml and subjected to dispersion treatment for 5 minutes with a homomixer. Then 10
0.1 g of sodium silicate (water glass No. 2) in 0 g of water
An aqueous solution prepared by adding 05 g was added while being dispersed by a homomixer, and then mixed for 30 minutes with an ordinary stirrer to perform surface treatment, and the length was 5 to 20 μm and the diameter was 0.3 to 0.
A mixture of fibrous or acicular magnesium oxysulfate surface-treated with 7 μm sodium silicate and water was obtained. This mixture was dispersed for 10 minutes and then filtered to obtain a dehydrated cake. 100 of the obtained dehydrated cake
Place in a 0 ml beaker and add 700 pieces of dehydrated cake and water.
After water was added to reach g, dispersion treatment was performed with a homomixer for 10 minutes. Then, after putting in a decompression device heated to 25 ° C to decompress and remove air bubbles, B was heated at 25 ° C.
The viscosity was measured with a Viscometer. The results are shown in Table 1.

Example 5 A fibrous or acicular magnesium oxysulfate seed crystal and a magnesium hydroxide slurry were added to an aqueous magnesium sulfate solution and well dispersed, and then the dispersion was placed in an autoclave at a temperature of 180 ° C. and a pressure of 10 kg / cm ₂
・ G was hydrothermally reacted for 2 hours.

After the reaction, the product was filtered and washed with water to obtain a dehydrated cake of fibrous or acicular magnesium oxysulfate having a water content of 77.6%. This dehydrated cake 46.
9 g and 553.1 g of water were put into a beaker of 1000 ml and subjected to dispersion treatment for 5 minutes with a homomixer. Then 10
0.2 g of sodium silicate (water glass No. 2) in 0 g of water
An aqueous solution prepared by adding 63 g was added while being dispersed in a homomixer, and then mixed for 30 minutes with an ordinary stirrer to perform surface treatment, and the length was 5 to 20 μm and the diameter was 0.3 to 0.
A mixture of fibrous or acicular magnesium oxysulfate surface-treated with 7 μm sodium silicate and water was obtained. This mixture was dispersed for 10 minutes and then filtered to obtain a dehydrated cake. The dehydrated cake obtained is 160
Dry at 5 ° C for 5 hours. The thus-obtained sodium silicate surface-treated fibrous or acicular magnesium oxysulfate (10.5 g) and water (689.5 g) were placed in a 1000 ml beaker and dispersed for 10 minutes with a homomixer. Then, after putting in a decompression device heated to 25 ° C. to reduce the pressure to remove bubbles, the viscosity was measured with a B-type viscometer under heating at 25 ° C. The results are shown in Table 1.

[0041]

INDUSTRIAL APPLICABILITY The present invention provides a thixotropic mixture of fibrous or acicular magnesium oxysulfate with a water-affinitive polymer by surface-treating fibrous or acicular magnesium oxysulfate with sodium silicate. Alternatively, the inventors have succeeded in solving the problem that when used as a thixotropic mixture of a water-affinitive polymer and water, the dispersibility is poor and the viscosity is unstable, resulting in unstable thixotropy.

Claims (1)

[Claims] 1. A fibrous or acicular magnesium oxysulfate having a length of 0.5 to 50 μm, a diameter of 0.05 to 1 μm, and an aspect ratio (length / diameter) of 10 to 300, which is surface-treated with sodium silicate. Thixotropic agent.