JP2812420B2 - Fibrous magnesium oxysulfate and its production method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel fibrous magnesium oxysulfate and a method for producing the same. More specifically, the present invention relates to a novel fibrous magnesium oxysulfate having an excellent effect of improving mechanical properties when filled in a composite material, and a method for producing the same.

[0002]

2. Description of the Related Art Magnesium oxysulfate (Mg)
SO ₄ .5MgO.nH ₂ O, where n is an integer of 6 to 9, is widely used as a filler in order to improve the mechanical properties of composite materials such as synthetic resins, paints, and rubbers.

[0003] Since fibrous magnesium oxysulfate has a fibrous particle shape, it is easy to form an aggregate in which fibers are entangled. Fibrous magnesium oxysulfate usually contains 150,000 or more such aggregates per gram. About one-tenth of these aggregates are solid agglomerates (hereinafter referred to as strong agglomerates) having a particle size of 30 to 100 μm formed in the stage of synthesizing fibrous magnesium oxysulfate. Particle size 1 generated in processes such as dehydration, washing, granulation, and drying after synthesis
It is a relatively weak aggregate having a size of 00 μm or more (hereinafter referred to as a weak aggregate). When the particle shape such as fibrous magnesium oxysulfate is filled with fibrous particles in a composite material, if such agglomerates are present in the fibrous particles, the dispersibility of the fibers is deteriorated, and the mechanical properties of the composite material are reduced. Inhibits improvement of physical properties. Further, when such aggregates are present in the composite material, specific physical properties such as impact strength are reduced. At present, kneading is performed under conditions where strong shearing force can be obtained in order to dissolve aggregates when filling fibrous magnesium oxysulfate into a composite material. But,
Since the strong aggregate remains without being dispersed, the impact strength is reduced. Further, since the length of the fibers is reduced to a fraction of that before kneading by vigorous kneading, the mechanical properties of the composite material are not sufficiently improved.

The present applicant has already disclosed in Japanese Patent Application No. 4-168148, fibrous particles such as fibrous magnesium oxysulfate in an aqueous solution containing magnesium ions, and then added a sodium stearate solution. Thus, a method has been proposed in which magnesium stearate excellent in lubricity is coated to improve dispersibility in a composite material.

However, in this surface treatment method, it is impossible to perform a surface treatment on the inside of the strong aggregate formed in the synthesis stage. For this reason, when weak kneading is performed to such an extent that the fibers are not broken, even if the weak aggregates are dispersed, the aggregates that have not been surface-treated to the inside are not dispersed, and a sufficient dispersibility improving effect on the composite material is obtained. It is not currently done.

[0006]

When kneading fibrous magnesium oxysulfate into a composite material, kneading is carried out under conditions where a strong shearing force can be obtained in order to break up aggregates. However, even under such kneading conditions, since the strong aggregate remains without being dispersed, the impact strength decreases. In addition, since the fiber breaks, the physical properties of the composite material are not sufficiently improved.

[0007] Even when kneading a fibrous magnesium oxysulfate coated with magnesium stearate and a composite material by the method described in Japanese Patent Application No. 4-168148, strong aggregates that have not been surface-treated to the inside can still be used. At present, mechanical properties of composite materials are not sufficiently improved because they do not disperse.

[0008] The present invention relates to a particle size of 30 to
An object of the present invention is to provide a fibrous magnesium oxysulfate capable of obtaining a good dispersion state of not more than 3,000 firm aggregates of 100 μm and a production method thereof.

[0009]

The gist of the present invention is: (1) a fiber length of 1 to 100 μm, a fiber diameter of 0.1 to 5 μm,
Fibrous magnesium having a bulk specific gravity of 0.03 to 0.3 g / cm ³ , a BET specific surface area of 20 cm ² / g or less, and an aggregate having a particle size of 30 to 100 μm contained in 1 g of 3,000 or less. Oxysulfate,

(2) The fiber according to claim 1, wherein a slurry is prepared by dispersing the fibrous magnesium oxysulfate, and aggregates having a size of 30 μm or more in the slurry are removed by using a liquid cyclone. Manufacturing method of magnesium oxysulfate,

(3) A fibrous magnesium oxysulfate coated with magnesium stearate obtained by coating the particle surface of the fibrous magnesium oxysulfate according to claim 1 with magnesium stearate.

Next, the method for producing the fibrous magnesium oxysulfate of the present invention will be described in detail. The outline of the method for producing magnesium oxysulfate will be described. First, magnesium hydroxide or magnesium oxide is dispersed in an aqueous solution of magnesium sulfate so that the concentration becomes 25% by weight or less. Magnesium sulfate is required to be 0.2 mol or more per 1 mol of magnesium hydroxide or magnesium oxide. If this is hydrothermally synthesized at a temperature of 100 to 300 ° C. for 0.1 to 20 hours, a magnesium oxysulfate slurry can be obtained. This slurry is dewatered, granulated, dried,
Magnesium oxysulfate is separated and obtained by operations such as crushing.

Since the particle shape of magnesium oxysulfate is selectively fibrous, the specific surface area by the BET method is 2%.
Use up to 0 cm ² / g of magnesium hydroxide or magnesium oxide or add a surfactant before hydrothermal synthesis.

Since magnesium sulfate and magnesium oxide only need to coexist in the reaction system, sulfuric acid can be used instead of magnesium sulfate. Many aggregates are contained in the fibrous magnesium oxysulfate thus produced.

Next, aggregates having a particle size of 30 μm or more are removed from the fibrous magnesium oxysulfate to obtain the fibrous magnesium oxysulfate of the present invention. First, fibrous magnesium oxysulfate containing 150,000 or more agglomerates having a particle size of 30 μm or more is dispersed in water, and is preferably dispersed in a concentration of 0.5 to 5% by weight, more preferably 1 to 3% by weight. Prepare a uniform slurry.

If the amount of fibrous magnesium oxysulfate in the slurry is less than 0.5% by weight, the yield per unit time decreases, and if it is more than 5% by weight, the slurry viscosity becomes high and it is difficult to remove aggregates. become.

The fibrous magnesium oxysulfate slurry may have a concentration of 0.5 to 5% by weight, and may be used after adjusting the concentration of the slurry after hydrothermal synthesis. Aggregates having a particle size of 30 μm or more contained in the slurry are removed from the fibrous magnesium oxysulfate slurry thus prepared using a liquid cyclone. FIG. 1 shows a hydrocyclone used for removing aggregates of fibrous magnesium oxysulfate.

As shown in FIG. 1, the dimensions of the hydrocyclone are as follows: the length of the cylindrical portion is 25 to 165 mm, and the diameter of the cylindrical portion is 20 to 1 mm.
The range of 50 mm and the length of the conical portion of 65 to 465 mm is preferable. If the range is larger than this range, a sufficient effect of removing aggregates cannot be obtained. In addition, when the size is reduced, it is necessary to reduce the slurry flow rate at the inlet of the hydrocyclone, which is not preferable because the yield per unit time decreases.

The fibrous magnesium oxysulfate slurry flows in from the hydrocyclone inlet, the agglomerates are separated in the hydrocyclone and flow out as an underflow slurry. On the other hand, the fibrous particles flow out as overflow slurry.

If the flow rate of the slurry at the inlet of the hydrocyclone is too large or too small, a good effect of removing aggregates cannot be obtained. Suitable hydrocyclone inlet slurry flow rates depend on the size of the hydrocyclone. For example, the diameter of the cylindrical portion is 50 mm, the length of the cylindrical portion is 55 mm, and the length of the conical portion is 115 mm.
, The slurry flow rate at the liquid cyclone inlet is 1.0 ~
5.0 m ³ / hour is preferred.

The underflow slurry flow rate is preferably 5 to 30% with respect to the hydrocyclone inlet slurry flow rate,
More preferably, by adjusting the content to 10 to 20%, a good aggregate removing effect can be obtained. When the underflow slurry flow rate is less than 5% or more than 30% with respect to the hydrocyclone inlet slurry flow rate, aggregates are mixed in the overflow slurry, and the aggregate removal effect is reduced.

When a multistage hydrocyclone is used, a better aggregate removing effect can be obtained. Usually more dehydration
Through the steps of washing, granulation, drying, crushing, etc., the fibrous magnesium oxysulfate of the present invention having a good dispersibility of 3000 or less strong aggregates having a particle size of 30 to 100 μm contained in 1 g is obtained. can get.

In the production of magnesium stearate-coated fibrous magnesium oxysulfate, a fibrous magnesium oxysulfate slurry obtained by performing the above-mentioned aggregate separation operation is used, and is disclosed in Japanese Patent Application No. 4-16814.
No. 8, a magnesium stearate coating layer is formed on the surface of the fibrous magnesium oxysulfate particles. Further, magnesium stearate-coated fibrous magnesium oxysulfate is produced through steps such as dehydration, washing, granulation, drying, and crushing.

The fibrous magnesium oxysulfate of the present invention is improved in dispersibility by surface treatment using a coupling agent such as silane, titanate or chromium, in addition to magnesium stearate, thereby improving the dispersibility. , The effect of improving the mechanical properties can be improved.

In the method for measuring the aggregates, first, water or alcohol is added to fibrous magnesium oxysulfate and dispersed to prepare a slurry, and the slurry concentration is measured.
The slurry is dropped into a glass plate coated with a surfactant on one side by a predetermined weight, and a colorant is further dropped and mixed well. A glass plate is placed from above, and the number of aggregates in the glass plate is counted by a microscope. By substituting the slurry concentration, the weight of the slurry dropped on the glass plate, and the number of aggregates into Equation 1, the number of aggregates in 1 g of fibrous magnesium oxysulfate is obtained.

[0026]

A = (D × 100) / (B × C) where A is 1 g of fibrous magnesium oxysulfate
Number of aggregates in the medium (pieces), B is the slurry concentration (% by weight), C
Is the weight (g) of the slurry dropped on the glass plate, and D is the measured number of aggregates (pieces).

The fibrous magnesium oxysulfate of the present invention obtained as described above has a particle size of 30 to 100.
Since the number of agglomerates having a size of less than 3,000 that is difficult to disperse is 3,000 or less, the mechanical properties of the composite material are more efficiently improved. Further, the fibrous magnesium oxysulfate of the present invention and talc,
By mixing with a reinforcing material such as an elastomer and filling the composite material, the mechanical properties of the composite material can be further improved. In addition, antioxidants, flame retardants, anti-coloring agents,
You may mix | blend so that the mechanical property of a composite material is not affected.

[0028]

【Example】

Example-1 Fibrous magnesium oxysulfate containing 18,000 agglomerates having a particle size of 30 × 100 μm per 1 g (manufactured by Ube Industries, Ltd., trade name: Mos Heidi (long fiber product); the same applies hereinafter) 5 kg was dispersed in 98.5 kg of water to prepare a uniform slurry. This slurry is transferred to a cylindrical part having a diameter of 50 m.
m Using a liquid cyclone having a cylindrical portion length of 55 mm and a conical portion length of 155 mm, a slurry flow rate of 2.5 m ³ / hour at the inlet of the liquid cyclone and an underflow slurry flow rate of 0.2
The mixture was treated under an operating condition of 5 m ³ / hour to remove aggregates.
Furthermore, after performing dehydration and washing, it was granulated into granules having a diameter of 2.5 mm and dried at 170 ° C. to produce the fibrous magnesium oxysulfate of the present invention.

This product has a fiber length of 10 to 30 μm.
m, fiber diameter 0.5-5 μm, bulk specific gravity 0.21 g / cm
^3. BET method Specific surface area: 15 m ³ / g, 1 g of product contained 11100 aggregates having a particle size of 30 to 100 μm.

Next, this fibrous magnesium oxysulfate was blended with 20% by weight based on the polypropylene, and an antioxidant (BHT reagent) was blended at 0.25% by weight based on the total of the fibrous magnesium oxysulfate and the polypropylene, and mixed well. . This was strongly kneaded with a twin-screw kneading extruder (manufactured by Ikegai Iron Works Co., Ltd.) to produce pellets, which were dried at 80 ° C. for 12 hours.

This polypropylene pellet is rolled for a mastication test of rubber, plastic, etc. (Nissin Kagaku Co., Ltd.)
0.25 mm thick, area 8 cm × 10
cm polypropylene sheet was molded. The number of aggregates was determined using a microscope at three places of 2 cm × 2 cm in the polypropylene sheet, and the dispersibility was evaluated.

Table 1 shows the results of the dispersibility evaluation. 100 μm
The following aggregates were small and showed good dispersibility. Further, test pieces are molded from the polypropylene pellets, and the tensile properties, bending properties, and Izod impact strength are measured by AST.
M-D638, ASTM-D790, ASTM-D25
8 and measured.

[0033]

[Table 1]

Table 2 shows the measurement results of the physical properties. Polypropylene to which fibrous magnesium oxysulfate is added, because there are few strong aggregates having a particle size of 100 μm or less,
Improved Izod impact strength is seen. As mentioned above,
Polypropylene to which fibrous magnesium oxysulfate was added exhibited good physical properties.

[0035]

[Table 2]

Example 2 After dissolving 3936 g of magnesium sulfate heptahydrate in 98 liters of water, 640 g of magnesium oxide having a specific surface area of 16 m ³ / g by the BET method was dispersed, and the dispersion was heated at 170 ° C. in a pressure vessel at 170 ° C.
After stirring for an hour, fibrous magnesium oxysulfate was obtained. The concentration of the fibrous magnesium oxysulfate in this slurry was 1.46% by weight. A fibrous magnesium oxysulfate was produced in the same manner as in Example 1, except that the obtained slurry was used instead of the fibrous magnesium oxysulfate slurry manufactured by Ube Industries, Ltd.

This product has a fiber length of 10 to 30 μm.
m, fiber diameter 0.5-5 μm, bulk specific gravity 0.20 g / cm
^{3. It} has a characteristic of a BET specific surface area of 15 m ³ / g, and the number of particles having a particle size of 30 to 100 μm contained in 1 g of a product is 9
One hundred.

Next, polypropylene pellets were formed from this product in the same manner as in Example 1, and then a polypropylene sheet was molded and evaluated for dispersibility. Table 1 shows the results of the dispersibility evaluation. The number of aggregates was small and good dispersibility was exhibited. Furthermore, a polypropylene test piece was molded in the same manner as in Example 1, and the physical properties were measured. Table 2 shows the measurement results of the physical properties. The polypropylene to which fibrous magnesium oxysulfate was added in the same manner as in Example 1 showed good physical properties.

Comparative Example 1 A fibrous magnesium oxysulfate (17,000 aggregates having a particle size of 30 to 100 μm in 1 g of the product) not subjected to the aggregate separation operation was obtained in the same manner as in Example 1. After preparing the polypropylene pellets, a polypropylene sheet was prepared, and the dispersibility was evaluated. Table 1 shows the results
Shown in The dispersibility of the fibrous magnesium oxysulfate was poor as compared with the fibrous magnesium oxysulfate subjected to the aggregate separation operation.

Next, a polypropylene test piece was molded in the same manner as in Example 1, and the physical properties were measured. Table 2 shows the measurement results of the physical properties. Polypropylene to which fibrous magnesium oxysulfate, which has not been subjected to an aggregate separation operation, was kneaded strongly during the preparation of the polypropylene pellets, so that the physical properties such as flexural modulus were not sufficiently improved, and a large number of aggregates were present. Izod impact strength was also reduced. As described above, the physical properties of the polypropylene to which the fibrous magnesium oxysulfate to which the separation operation was not performed were poorer than the polypropylene to which the fibrous magnesium oxysulfate to which the separation operation was performed was added.

Example 3 A fibrous magnesium oxysulfate containing 17,000 particles per gram of aggregates having a particle size of 30 to 100 μm was separated from the aggregates in the same manner as in Example 1. 985 g of magnesium sulfate was added to the obtained slurry and dissolved. Separately, 23 g of sodium stearate was added to 31 liters of water and heated to 80 ° C. to prepare a sodium stearate solution. This sodium stearate solution was added to the slurry prepared above over 10 minutes, and after a coating treatment with magnesium stearate was performed, dehydration, washing, granulation, and drying were performed to obtain magnesium stearate-coated fibrous magnesium oxysulfate. Obtained. When the number of aggregates having a particle size of 30 to 100 μm was measured, it was 1,000 per gram.

Next, this product was added to polypropylene for 20
By weight, an antioxidant (BHT reagent) was mixed with fibrous magnesium oxysulfate coated with magnesium stearate in an amount of 0.25% by weight based on the total amount of polypropylene, and mixed well. The mixture is weakly kneaded with a twin-screw kneader (made by Ikegai Iron Works Co., Ltd.) to form pellets.
Dry at 0 ° C. for 12 hours. A polypropylene sheet was formed using the obtained polypropylene pellets, and the dispersibility was evaluated. Table 1 shows the results of the dispersibility evaluation. The number of agglomerates was very low, indicating very good dispersibility.

Further, a polypropylene test piece was molded in the same manner as in Example 1, and the physical properties were measured. Table 2 shows the measurement results of the physical properties. Polypropylene to which magnesium stearate-coated fibrous magnesium oxysulfate is added has a small number of strong aggregates of 100 μm or less,
Since the fiber breakage due to kneading is small, physical properties such as Izod impact strength and flexural modulus are improved. As described above, the polypropylene to which the magnesium stearate-coated fibrous magnesium oxysulfate was added exhibited extremely good physical properties.

Comparative Example 2 Example of fibrous magnesium oxysulfate coated with magnesium stearate (16.7 million aggregates having a particle diameter of 30 to 100 μm per gram of product) without performing the aggregate separation operation. After preparing polypropylene pellets in the same manner as in No. 3, a polypropylene sheet was molded, and the dispersibility was evaluated.

Table 1 shows the results of the dispersibility evaluation. The dispersibility of magnesium stearate-coated fibrous magnesium oxysulfate was poorer than that of magnesium stearate-coated fibrous magnesium oxysulfate which had been subjected to an aggregate separation operation.

Further, a polypropylene test piece was molded in the same manner as in Example 1, and physical properties were measured. Table 2 shows the measurement results of the physical properties. Polypropylene to which magnesium stearate-coated fibrous magnesium oxysulfate has been added is improved in physical properties such as flexural modulus due to less breakage of fibers due to kneading.
m or less, the Izod impact strength is reduced due to the presence of many strong aggregates. As described above, the physical properties of the polypropylene to which the magnesium stearate-coated fibrous magnesium oxysulfate was added were inferior to those of the magnesium stearate-coated fibrous magnesium oxysulfate subjected to the aggregate separation operation.

[0047]

As described above, the fibrous magnesium oxysulfate of the present invention has less than 3,000 hardly dispersible agglomerates having a particle size of 30 to 100 μm. Thus, the mechanical properties can be more efficiently improved, and a decrease in impact strength and the like can be prevented.

[Brief description of the drawings]

FIG. 1 is a view schematically showing a hydrocyclone used in one embodiment of the production method of the present invention.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) C01F 5/40 C08K 3/30 C08K 7/08

Claims (3)

(57) [Claims] 1. A fiber having a fiber length of 1 to 100 μm and a fiber diameter of 0.1 μm.
1-5 μm, bulk specific gravity 0.03-0.3 g / cm ³ , BE
A fibrous magnesium oxysulfate having a characteristic of T specific surface area of 20 cm ² / g or less and containing 3,000 or less aggregates having a particle size of 30 to 100 μm contained in 1 g. 2. The fiber according to claim 1, wherein the slurry is prepared by dispersing fibrous magnesium oxysulfate in water, and agglomerates of 30 μm or more in the slurry are removed using a liquid cyclone. Of magnesium oxide sulphate. 3. A fibrous magnesium oxysulfate coated with magnesium stearate obtained by coating the surface of the particles of the fibrous magnesium oxysulfate according to claim 1 with magnesium stearate.