JPH04503797A - Method for producing fibrous magnesium oxide - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Method for producing fibrous magnesium oxide The present invention provides a material in the form of acicular particles containing magnesium and water of crystallization during sintering. Therefore, a method for producing fibrous magnesium oxide, which is converted into fibrous magnesium oxide. Regarding.

Magnesium oxide has a very high melting point and excellent chemical resistance to base systems. It has excellent electrical insulation properties and moderate thermal conductivity. These properties Therefore, magnesium oxide is used in different fields, especially in metallurgy. It can also be used as a material for refractory bodies and refractory bricks, as well as for the thermal conductivity of synthetic resin materials. It is widely used as a filler for synthetic resins that can improve the oxide Gnesium usually exhibits particles in granular form, i.e. approximately the same dimensions in different directions , consisting of particles resembling cubes or spheres. Similarly known is fibrous magnesium oxide. um, that is, the shape of the particles is elongated, and the ratio of the length of the particle to the maximum average lateral dimension the ratio is at least 10:1 and the cross-sectional area of one particle is less than 0.05 mm''; Magnesium oxide with a width of less than 0.25 mo+ (ASTM D3 878), such particles of fibrous magnesium oxide have moderately high strength. It is composed of magnesium oxide and is used, for example, in the formation of fire-resistant linings. body or brick, especially plastic containing magnesium oxide as filler The strength of the main body of the material is also lower than when using ordinary magnesium oxide in particle form. , can be clearly enhanced.

Known methods for producing am-like magnesium oxide have several drawbacks, such as low Efficiency, manufacturing costs are simultaneously burdened by the real cost of energy, and slow It shows a relatively complex procedure involving the formation of intermediates with a complex reaction, and furthermore, Corrosive and toxic gases are formed when the intermediates react to produce fibrous magnesium oxide. However, the processing power of this gas is difficult and increases the cost of the manufacturing process. It also has some serious drawbacks. In this known method, magnesium oxide is Oxidized mag from the vapor phase after reaction of magnesium metal vapor and oxygen to form Magnesium oxide precipitates and during this magnesium oxide precipitation from the vapor phase um fibrous particles are formed. This method is relatively inefficient and energy efficient. Requires serious expenses. In another known method, -valent to tetravalent negative ions and form acicular basic intermediate magnesium compounds containing water of crystallization Next, this intermediate product is converted into fibrous magnesium oxide by calcination. , or first produce magnesium hydroxide from such intermediate product and then Fibrous magnesium oxide is formed from the magnesium hydroxide. The basic mug The production of nesium compounds is complex and corrosive or toxic gases are released during their calcination. This makes the manufacturing process more complicated as the separation and disposal of the galis is unavoidable. Put it away.

The purpose of the present invention is to implement it from scratch as simply as possible and at the lowest possible cost. can demonstrate quantitative efficiency and reduce by-products formed during the manufacturing process. The object of the present invention is to provide a method as described above that does not cause serious problems.

r　The present invention uses acicular grains containing magnesium and water of crystallization! li child form Fibrous magnesium oxide that converts a substance into fibrous magnesium oxide by firing A method for producing MgMgC05-xH (in the formula, 1 ≦X≦5) One or more neutral magnesium carbonates, especially Using crushed magnesium carbonate trihydrate as the material to be fired? We propose a method to provide

The above-mentioned objects can be achieved by the method.

, neutral magnesium carbonate containing water of crystallization, especially magnesium carbonate/gnesium tricarbonate For example, water salt can be prepared by combining a magnesium salt solution with cyammonia, carbon dioxide, and carbonic acid. Precipitation with either ammonium or ammonium bicarbonate or by carbonating the precipitated magnesium hydroxide (by It can be obtained relatively easily. Thus, for example, carbonic acid mags in the form of needle-like crystals Nesium trihydrate can be easily and quickly precipitated from an aqueous solution; The crystal size of and f is influenced by the chosen reactor temperature. The temperature is around It is only slightly above ambient temperature and does not require special construction or energy does not require any additional costs.

Neutral magnesium carbonate containing water of crystallization is calcined using a simple method to approximately change the particle morphology. It is possible to obtain m-male magnesium oxide which maintains its strength. In this firing method, , no products with toxic or corrosive effects are formed, and a wide range of calcination temperatures. You can choose from. Good results are obtained at firing temperatures of 350-2000℃. can get. 8 (preferably using a firing temperature of 10-1600°C, Depending on the equipment used, firing periods can vary from very short firing periods, e.g. a few seconds, to as long as several hours. The period up to the firing period is used. The material to be fired is heated under vacuum for 100 minutes before firing. Drying below 0.degree. C. or partial dehydration is appropriate.

In the method of the invention, the heating of the material to be fired is performed at a temperature increase rate of less than 10° C. per minute. As a result, the firing proceeds slowly and is preferably carried out in a neutral carbonate mug. It is advantageous to convert nesium to fibrous magnesium oxide.

The fibrous magnesium oxide particles produced by the method of the present invention have high strength. In the present invention, it is produced from a basic magnesium compound by a known method. Higher strength values can be obtained than with fibrous magnesium oxide particles. . Therefore, the fibrous magnesium oxide produced by the method of the present invention If used as a filler for a resin, the strength of the plastic material receiving the filler will be Significant improvements can be made even if only a relatively small amount is used.

The invention is further illustrated by the following examples.

2nd group Pour 500ml of distilled water into a stirring container equipped with a thermostatic means, and add 200ml of MgC1t. 500 - of magnesium chloride solution containing 98 g/12 was added, and this mixture was Heated to 35°C. This solution was mixed vigorously with a stirrer and 25% of ammonia was added. % solution was added dropwise over 30 minutes to introduce COx 35I2 into this solution. After the completion of the 0 reaction in which the 9 reactor mixture was maintained at 40°C by a heat exchanger, Filter the suspension, wash the filter cake with water, and store the resulting product at a low temperature below 40°C. and dried under vacuum. This product is the same as nesquehonite MgCO5.3H20. and had the appearance of needle-like crystals.

The scanning electron micrograph shows that the needles of Nesquehonite are approximately 150 μm long and have an average straightness. It was shown that the diameter was about 5 μm.

The product thus obtained was calcined at 1100°C for 3 hours to form a fibrous magnet oxide. Obtained Sium. This synthetic #l fiber is the same as the starting material fiber of Nesquehonite used. Similarly, it had a length of about 150 μm and an average diameter of about 5 μm. X-ray diffraction This product was identified as magnesium oxide and the product was identified as magnesium oxide. The method of Example 1 was repeated. However, after the reaction is complete and the suspension is filtered, The filter cake, washed with water, was dried under vacuum at 70° C. for 2 hours. chemical content Upon analysis, neutral magnesium carbonate with the composition MgC01.2.4H,0 is formed. It turned out that it was. Scanning electron micrographs show that the obtained product has a long It was found to consist of fibers having a length of about 150 μm and an average diameter of about 5 μm.

The product thus obtained was heated to 850°C with a heating rate of 3°C per minute and After a temperature hold time of 1 hour, it was allowed to cool without any control. Approximately 150μm in length, average straightness A fibrous material having fibers with a diameter of about 5 μm was obtained. X-ray diffraction reveals that this substance It was confirmed that it was magnesium oxide.

1 blood 5yu Identified as nesquehonite MgCO5.3H20, the fruit has the appearance of needle-shaped crystals. The product of Example 1 was heated to 1.600°C with a heating rate of 5°C per minute; After a temperature maintenance period of 1 hour, it was cooled without any control. X-ray diffraction reveals that this fiber The fibrous product could be identified as magnesium oxide. Neskehonai used Similarly, the fiber length is 50 to 150 LLm, and the average fiber diameter is 2 to 150 LLm. It was 5 μm.

1 Tanen Wataru A The neutral magnesium carbonate of Example 2 having the composition MgC0*2.4H20 was The mixture was heated to 400°C at a heating rate of 10°C. 3 hours temperature maintenance time After that, fibrous magnesium oxide was obtained. This synthetic fiber is made of neutral carbonate magnet. It is not morphologically different from Si, with fiber lengths up to 150 μm and about 3-5 μm. The average fiber diameter is shown. X-ray diffraction reveals that this substance is magnesium oxide. I confirmed that.

W Improving the strength of composite materials using Mg fiber MgO obtained in Example 1 m fibers, silicon carbide whiskers and commercially available magnesium oxide in epoxy resin. The test piece was embedded in an amount of 4% by volume and the bending strength at break was tested. this The results of these tests are summarized in Table 1. As a result, MgO fibers were found to contain only a small amount. These results indicate that both significantly improve the bending strength at break of composite materials. The bending strength at break of a composite material is determined by dividing the fibers isotropically in the matrix based on the mixing standard. Compare with each other and with that of pure epoxy resin while assuming that the cloth The specific strength of the MgO fiber of the present invention is approximately 7,000 to 8,000 MPa. It is calculated as follows.

And you 4 holes % Az Base material Reinforcement material Bending strength at break Epoxy resin 44MPa Epoxy resin silicon carbide whisker 84MPa epoxy resin MgO of the present invention Fiber 64MPa Epoxy resin Commercially available Mg0 49MPa Summary of the invention Method for producing fibrous magnesium oxide, one or several medium containing crystal water Magnesium carbonate, especially magnesium carbonate trihydrate, can be extracted into acicular particles from water droplets. fibers that are precipitated in the form of Obtain fibrous magnesium oxide.

Copy and translation of amendment) submission form (Article 184-7, Paragraph 1 of the Patent Act) November 1991 B 7 days

Claims (4)

[Claims] 1. By calcination the material in the form of acicular particles containing magnesium and water of crystallization A method for producing fibrous magnesium oxide, which is converted into fibrous magnesium oxide, , containing water of crystallization and having the formula MgCO2.xH2O (wherein 1≦x≦5) seeds or some neutral magnesium carbonate, especially magnesium carbonate trihydrate , how to use it as a substance to be fired. 2. The material to be calcined is dried under vacuum at a temperature below 100°C and partially dehydrated. The method according to claim 1. 3. Calcination is carried out at a temperature of 350-2000°C, preferably 800-1600°C. The method according to claim 1 or 2. 4. During firing, heating of the material to be fired is carried out at a rate of temperature increase of less than 10 °C per minute. A method according to one of claims 1 to 3.