KR790001084B1 - Method for manufacturing of wollastonite crystals - Google Patents

Abstract

Hydrous wollastonite slurry was prepd. dispersing wollastonite crystal into water forming a rectangular shaped lump with a crust radius<150μ and internal spaces. The curst had a three dimensional cross-linked structure and contained at least 50% β-wollastonite. Useful products were prepd. by shaping the slurry into desired shape and drying.

Description

Process for the preparation of the desired form of wollastonite crystals

1 is a black background micrograph showing the diameter of an agglomerate 120 times.

FIG. 2 is an electron micrograph showing the diameter of an agglomerate 13,000 times larger.

3 is an electron scanning micrograph showing an enlarged diameter 600 times.

4 is an electron scanning micrograph of a broken agglomerate with a diameter of 1,000 times larger.

The present invention relates to a method for producing a desired form of wollastonite crystals. As is known, certain types of products composed of wollastonite crystals have excellent properties without deterioration in quality even at high temperatures of 1,000 ° C or higher.

Therefore, this product would be useful as a thermal insulation material such as refractory bricks, but no effective way to combine them has yet been proposed. In conventional methods, the desired form product of wollastonite crystals has been produced by shaping a mixture of natural or artificial wollastonite crystals and mud as a solid and then calcining the resulting desired form.

However, the above method does not yield a light and desired form product useful for thermal insulation materials, and further complicates the calcination process that must be performed after the shaping step to obtain a product with sufficient mechanical strength, thereby impairing the stability of the final product. Let it be.

The present inventors have proposed a method for producing a light predetermined product of wollastonite crystals, characterized by firing a predetermined lump of light sonorite crystals to convert xonotlite crystals to wollastonite crystals. .

However, this method requires that the firing step, which is necessary for the preparation of the desired form agglomerate of sonolite crystals, is disadvantageous in terms of heat saving and places a limitation on the size of the desired form product, especially its thickness, so that the sonolite crystals are of considerable size or thickness. The difficulty remains in converting the entire interior of the desired form of product into wollastonite crystals uniformly.

It is an object of the present invention to provide one method for producing the desired form product of wollastonite crystals which overcomes the above drawbacks.

A second object is to provide a method in which wollastonite crystals are uniformly formed all over the inside of the product to produce a desired product having light weight and good mechanical strength.

A third object is to provide a method of making a product in the form of wollastonite having good mechanical strength and a high level of stability.

It is a fourth object to provide a method for producing the desired form product of wollastonite crystals with any desired shape and exact dimensions.

It is a fifth object to provide a method for producing a desired form of wollastonite crystals which can be improved in its properties using various additives.

These and other purposes are as follows.

The process for producing the desired form product of wollastonite crystals is the result of dispersing the aggregate of wollastonite crystals in water to produce the aqueous dispersion of the wollastonite crystals as a result to produce the desired form product of wollastonite crystals. The resulting aqueous dispersion is shaped and dried (the agglomerate of the wollastonite crystals described above has a spherical shell structure with a diameter of up to 150 µm and one shell and the internal space defined by it). Wollastonite crystals having a weight ratio of 50% are made of wollastonite crystals three-dimensionally bonded to each other.

According to the research of the present inventors, the wollastonite crystal agglomerates are easily and uniformly dispersed in an aqueous medium to make its aqueous acid, and the resulting aqueous acid is simply used without any binder or without the following firing procedure. It has been found that by shaping and drying it can be made into a desired product with good mechanical strength. The resulting desired product consists of a number of aggregates bound together.

Since each agglomerate constituting the predetermined form product has a low volume density, according to the present invention, it is possible to produce a predetermined form product of light wollastonite crystals having a wide range of bulk density, including a bulk density of 0.45 g / cm 3 or less. Some, but not more than 0.3 g / cm 3, are useful as thermal insulation materials.

Moreover, certain form products of wollastonite crystals of various shapes and dimensions have a high degree of stability in the dimension because the firing procedure is unnecessary after the shaping step.

Furthermore, various additives can be added to the aqueous acid of wollastonite crystal agglomerate, so that the properties of the final desired form product obtained therefrom can be improved depending on the type of additive used.

The agglomeration of the wollastonite crystals in the present invention forms a substantially spherical shell structure with a diameter of up to 150 µ. If the diameter of the agglomerate exceeds 150 microns, the mechanical strength of the desired product obtained therefrom will be reduced. Rather, the diameter of the agglomerate is suitable 3-150μ, the most suitable 30-90μ.

The diameters of the agglomerates given in this specification and claims were measured by inspection with an optical microscope.

The shell structure of this mass is virtually spherical in shape.

This was shown through a microscopic image, for example, from a black background micrograph of an agglomerate taken at 120 magnification and an electron scanning micrograph of an agglomerate taken at 600 magnification.

The shell structure consists of one shell and one interior space defined by it. The shell is composed of wollastonite crystals closely bonded to each other, but the specificity is good. The shell is hollow inside or has a coarse distribution of one wollastonite crystal.

This particular structure can be observed through electron scanning micrographs of broken masses. Electron micrographs also show that the agglomerate has a large number of crystals protruding from its surface.

The crystals constituting the present agglomerate are whey crystals containing at least 50% of β- wollastonite crystals by weight relative to the total weight of the wollastonite crystals. However, agglomerates may be composed only of β- wollastonite crystals, but other types of wollastonite crystals, such as α- wollastonite crystals, may be made up to 50% by weight of the total weight of wollastonite crystals. Agglomeration of wollastonite crystals can be readily prepared from a particular aqueous slurry of sonorite crystals.

Such a slush is shown in this US Pat.

For example, the agglomerate is prepared by drying, and then the slurry is calcined at 780-1,200 ° C. The sonorite crystal constituting the agglomerate is preferably calcined at 1,000-1,100 ° C to reduce the wollastonite crystal.

The aqueous sonorite crystal slurry is characterized by the fact that the needle-shaped sonorite crystals are dispersed in water in the form of numerous aggregates.

The agglomerate has a substantially spherical shell structure composed of one shell and the interior space defined by it. The shell consists of sonolite crystals that are stericly bound to each other. An aqueous slurry of sonolite crystals is prepared by heating with stirring the starting aqueous slurry of siliceous material and lime under steam pressure. The amount of lime to be proportional to the siliceous material is suitably a mass ratio of 0.8: 1 and 1.3: 1 of CaO: SiO ₂ .

The amount of water used in the starting slurry is proportional to yield an aqueous slurry of sonolite crystals having a weight ratio of solids to water of 1: 1.0 and 1: 2.5.

The steam pressure applied is suitably in the range 8-15 kg / cm ² and the reaction temperature is the saturation temperature under such steam pressure.

Agglomerates composed of sonorite crystals are prepared by drying the aqueous slurry of sonorite crystals. When the dried agglomerates are fired at 780-1,200 ° C and 1,000-1,100 ° C, the sonolite crystals constituting the agglomerate are converted into wollastonite crystals to make agglomerates of wollastonite crystals.

It was found that virtually no change occurred in the structure of the agglomerates during the firing step.

The shape of the wollastonite crystals changes depending on the firing temperature and firing time. Β- wollastonite crystals are formed at a firing temperature of about 780-1,100 ° C. and α- wollastonite crystals at 1,200 ° C. or higher. It varies in proportion to the firing time of the mixture of β- wollastonite crystals and α- wollastonite crystals at temperatures between 1,100 ° C and 1,200 ° C. Therefore, the firing temperature and firing time are appropriately determined in the present invention. Agglomerates of wollastonite crystals are easily dispersed in aqueous media to create an aqueous dispersion in which a number of agglomerates are dispersed therein.

The aqueous medium to be used is usually water, and a mixture of water-soluble organic solvents such as methanol may be used. The agglomerates originally exhibit no activity, but when dispersed in aqueous media, they are filled with aqueous media that penetrate through the permeable shells of the agglomerates in their interior space, resulting in special activity. In other words, the desired form product of wollastonite crystals having excellent mechanical strength can be obtained only by shaping and drying the resulting aqueous acid.

This means that when the resulting aqueous acid is shaped under pressure, the agglomerates are physically bound together in a form of mass and then dried when the aqueous media fills their internal space without collapsing. This is because the lumps of form combine with the agglomerate to produce one desired form product that exhibits a high degree of mechanical strength.

As the pressure increases in the shaping step, the aqueous medium is gradually removed from the agglomerate to form a compacted lump. The volume density of a given form product thus depends on the pressure applied to the shaping. The amount of door to be used should be at least as large as necessary to fill the interior space of the agglomerate.

Generally, the amount of water is 3-25 times the total solid weight and about 10-15 times is appropriate.

By simply forming and drying, the aqueous acid can be made into the desired product of wollastonite crystals with low bulk density and high mechanical strength.

The aqueous acid does not necessarily form aggregates of all wollastonite crystals up to 150 µm in diameter, and the small amount of aggregates may contain 150 µm or more.

The study of the present invention also found that if more than 150 micron of agglomerate were considered to be about 40% by weight of all wollastonite crystals in dispersion, the dispersion would give a light and mechanically strong desired form product only when shaped and dried.

The inventors also found that particularly good results were obtained if agglomerates of diameter up to 150 μ in dispersion were considered to be 90-100% of all of the wollastonite crystals by weight.

Furthermore, if the wollastonite crystals forming the agglomerate are 50% β- wollastonite crystals by weight, only by forming and drying can obtain a mechanically strong predetermined form product having a low bulk density.

Various reinforcing materials can be added to the aqueous acid of the present invention to improve the properties of the resulting desired product.

In order to improve mechanical strength, inorganic or organic fibers may be used. Inorganic fibers include asbestos, rock wool, glass fibers, and the like.

Examples of organic fibers include pulp, wood flour, polyamide fibers, polyester fibers, and the like.

These fibers are preferably used in an amount of about 2-25% by weight, in particular 2-15% by weight, relative to the total weight of the solids in the dispersion. Muds such as bentonite, kaolin, lobite, refractory clay, etc. can be used to deliver further improved thermal resistance to the desired form product.

As a rule, these muds use 5-100% or 8-30% of the total solid weight in dispersion.

Cement can also increase the surface strength and density of the desired desired product by using 3-20%, in particular 5-15%, of the total solid weight in the dispersion of the present invention.

Only one or at least two of these reinforcements are used.

In preparing one desired form product from the aqueous acid of the present invention, the dispersion is first shaped into a desired form such as a block, pipe, plate, column or the like, and then substantially dried to remove the separated water. Various shaping methods may be used for shaping, but filter molding is preferred.

Filtering molding places the current dispersion in a female mold with the desired shape and a number of small holes and compresses the dispersion into a male mold to form a self-supporting mass of excess water. Remove until

In the case of a dispersion containing pulp, the dispersion is formed as a piece of paper and then pressed by a paper machine into a paper-shaped product of the desired shape and dried to obtain the final finished product.

Drying may be carried out under atmospheric pressure and temperature but reduced pressure may be applied to facilitate drying. The desired shaped products thus obtained are characterized by having one particular structure which consists of agglomerates bonded together and pressed in a pressured direction for shaping.

In other words, in the present product of the predetermined form, the agglomerate is somewhat compressed in at least one direction because of the pressure applied in the shaping step. The agglomerates themselves have considerable strength so that they do not fully crush unless subjected to very high orthopedic pressures.

In general, the bulk density of a given type of product is mainly due to the pressure exerted for shaping, ie low shaping pressure has a low volume density, and high shaping pressure has a high volume density.

Therefore, certain shaped products with low densities consist of compacted but not crushed agglomerates.

When the fractured surfaces of certain shaped products having virtually low volume densities are magnified and observed through light microscopy or electron scanning microscopy, the agglomerates find that they combine to form the desired shaped products.

This can also be confirmed by examining a transmission photograph showing a thin cross section of a given product taken at the right angle in the pressure direction during shaping.

Certain types of products with low bulk densities up to 0.45 g / cm 3 are useful as thermal insulation materials because they have sufficient mechanical strength and good thermal insulation properties.

According to the present invention, it may be difficult to identify agglomerates in enlarged photographs or transmission photographs as a predetermined form product having a high bulk density, but when it is diffracted by X-ray, such a predetermined form product exhibits a unique orientation. Shows that the agglomerates forming the squeezer were strongly pressed against the pressure direction applied in the shaping step.

Features of the invention will become more apparent from the examples given below, where all ratios are by weight.

Example 1

49 parts of quicklime was added to 1,200 parts of water to make it slaking, and the resulting solution of quenched lime was stirred with 51 parts of siliceous sand containing 97% by weight and passed through a 325 mesh. This resulted in starting aqueous slurs containing sparked lime and siliceous sand.

The slurry was placed in an autoclave and stirred for 4 hours at a temperature of 191-198 ° C. under a steam pressure of 12-14 kg / cm ² to obtain an aqueous slurry containing a large number of agglomerates composed of sonolite crystals. The crystals were identified as sonolite crystals by X-ray recrystallization. Black background micrographs of the slurries obtained at a magnification of 120 times diameter and electron micrographs obtained at a magnification of 13,000 times contain a large number of agglomerates in which the resulting slurries are dispersed in water and are substantially spherical in shape. It was shown that it was made of needle-shaped sonolite crystals that were -150μ and connected three-dimensionally to each other. The resulting slurries were dried to obtain dry sonolite crystal agglomerates.

The dried agglomerates were baked in an electric furnace at 1,000 ± 10 ° C. for three hours, so that the sonolite crystals were converted to β- wollastonite crystals to yield agglomerate of β- wollastonite crystals.

During the firing step it was observed that the agglomerates did not collapse or shrink. The resulting agglomerates by X-ray gray matter were confirmed to be composed of β- wollastonite crystals.

Figures 1-4 are micrographs of the agglomerates, in which Figure 1 shows a black background micrograph obtained by enlarging the diameter 120 times, and Figure 2 shows an electron micrograph obtained by enlarging the diameter 13,000 times. Is an electron scanning microscope photograph obtained by enlarging the magnification to 600 times, and FIG. 4 shows an electron scanning micrograph of a broken agglomerate with a diameter magnified 1,000 times.

It was evident that the agglomerates obtained from the above micrographs had a substantially spherical shell structure with a diameter of 10-150 microns.

In particular, Figures 3-4 show that each agglomerate has a substantially spherical shell structure resembling a nearly chestnut shell consisting of one shell and a defined inner space.

The shell consists of acicular β- wollastonite crystals that are closely linked to each other in three dimensions.

The agglomerates of the β- wollastonite crystals thus obtained were dispersed in water together with the additives shown in the first table below to yield an aqueous acid containing a plurality of agglomerates dispersed therein.

The amount of water used was 10 times the total weight of the solids contained in it.

TABLE 1

The dispersion thus obtained is put into a female mold having a plurality of holes and pressed by a male mold to form a desired mass. The desired mass is removed from the mold and dried in an air cooker at 190 ° C.

Scanning electron micrographs of the broken surface of the dried product showed that the product was formed of a number of aggregates bound together. The mechanical strength and thermal resistance of the product is shown in the second table below.

TABLE 2

Example 2

The dried sonorite crystal agglomerates obtained in the same manner as in Example 1 were calcined at 1,150 ± 10 ° C. for three hours.

It was found that the resulting agglomerates by X-ray gray matter consisted of a predominant amount of β- wollastonite and a small amount of α- wollastonite.

The same results as in FIGS. 1-4 were observed with black background micrographs and electron scanning micrographs of the masses. The agglomerates thus obtained were dispersed in water and the additives shown in Table 3 below were added. The resulting dispersion was shaped and dried in the same manner as in Example 1 to produce the desired product having the physical properties shown in the third table below.

TABLE 3

Example 3

47 parts of quicklime were added for ignition to 560 parts of water, and 53 parts of siliceous material dispersed in 320 parts of water were added to the resulting liquefied lime solution.

The siliceous material used was a by-product obtained during the production of metal silicon containing amorphous silica soil containing 92% of SiO ₂ as the main component and its average particle size was 0.2 mu.

The mixture was diluted in 1,520 parts of water and the resulting aqueous slurry was placed in an autoclave and heated with stirring at 191 ° C. under steam pressure of 12 kg / cm 2 for 8 hours.

This provided an aqueous slurry consisting of sonolite crystals that contained a number of aggregates measuring 3-30 μm in diameter and bonded three-dimensionally to each other.

This slurry was dried to obtain dried agglomerates. The dried agglomerates were again heated at 1,000 ° C. for 3 hours, whereby B- wollastonite crystal agglomerates were obtained.

The same results as in Example 1 were observed through black background micrographs, electron micrographs, and electron scanning micrographs of the agglomerates. The agglomerates thus obtained were dispersed in water and added with the additives shown in Table 4 below.

The resulting dispersion was shaped and dried in the same manner as in Example 1 to yield the desired form product having the physical properties shown in Table 4 below.

TABLE 4

Claims (1)

Dispersing the wollastonite crystal agglomerate in water to produce an aqueous acid solution of the wollastonite crystal agglomerate, the agglomerate is a shell having a diameter of 150 μ or less and a substantially spherical shell structure made from the inner space, the shell having at least 50% A method of producing a predetermined form product of wollastonite crystals in which β- wollastonite crystals are formed by fusion of three-dimensionally to each other and formed by shaping the aqueous acid solution into a desired form and then drying.

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