JP2008037664A - Method for producing calcium aluminate monocarbonate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method rapidly producing calcium aluminate monocarbonate excellent in grain size controllability by using inexpensive raw materials and an inexpensive device. <P>SOLUTION: Aluminum hydroxide as one of raw materials is subjected to grinding treatment, and is mechanochemically activated, thus mutual reaction between slaked lime and calcium carbonate progresses, and calcium aluminate monocarbonate is synthesized in water at ordinary temperature under ordinary pressure. In this case, when high speed shear mixing treatment is performed at the start of the reaction, the fining and satisfactory dispersion of primary particles can be attained together with the acceleration of reaction time. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

In the present invention, calcium aluminate monocarbonate (hereinafter referred to as monocarbonate) 3CaO · Al ₂ O ₃ · CaCO ₃ · 11H ₂ O with good productivity and form controllability is obtained by applying mechanochemical treatment to aluminum hydroxide and activating it. It is related with the method of manufacturing.

  Monocarbonate is a crystalline substance having a layered structure and is in the form of a fine hexagonal plate. Similarly, kaolinite, which is a fine hexagonal plate-like crystal, is widely used as a coating pigment for papermaking because it helps to improve printing suitability. Inorganic powders such as kaolinite are used in many industrial products such as papermaking, plastics, rubber, cosmetics, etc., which give the product functions such as surface gloss, weight gain, reinforcement and flame retardancy.

Furthermore, monocarbonate is known as a substance produced in a hardened cement together with ettringite 3CaO.Al ₂ O ₃ .3CaSO ₄ .32H ₂ O, and both are anionic compounds of calcium aluminate. There are many common characteristics. However, as a simple substance, Ettlingite has established a long history of more than 100 years as a high gloss and high whiteness coating pigment called “satin white” in the paper industry, whereas monocarbonate is industrial Was never manufactured.

  The high glossiness of satin white is derived from the shape of the particles and the thermal behavior of crystal water. Since satin white particles are needle-shaped, they are easily oriented flat on the paper surface, and a large amount of crystal water is easily released by heat of several tens of degrees, so that the water vapor softens the coating layer. The calendar effect is easy to achieve. Such behavior of crystal water is a property common to monocarbonate, and is a characteristic part not found in other paper coating pigments.

  Although it is a monocarbonate having such excellent features, most of the synthesis is one of the researches of alumina cement, and industrial production has never been attempted.

For example, Gypsum & Lime / No. 207 (1987), Sango and Miyagawa et al. Reacted with carbon dioxide in the air or in water while synthesizing calcium aluminate hexahydrate (hydrogarnet) 3CaO.Al ₂ O ₃ .6H ₂ O by the atmospheric pressure aqueous solution method. It was reported that monocarbonate was produced as a by-product.

In Inorganic Materials, Vol. 4, May (1997), Itai and Daimon et al. Obtained anhydrous calcium aluminate 3CaO · Al ₂ O ₃ obtained by dry mixing calcium carbonate and aluminum oxide at 1350 ° C. at room temperature. Is reacted with calcium carbonate in water to synthesize monocarbonate having a particle size of about 1 to 2 μm.

  In order to industrially produce monocarbonate as a pigment for paper coatings and plastic fillers, it must be a manufacturing method that does not contain impurities and is low in cost and excellent in form controllability. So it is difficult to achieve these.

The method of synthesizing monocarbonate by actively blowing carbon dioxide gas by applying the atmospheric pressure aqueous solution method must be carried out without generating hydrogarnet that does not easily react with carbon dioxide gas. Control of the gas introduction speed is required. Even if this is carried out strictly, hydrogarnet into the product, hemicarbonate 3CaO · Al ₂ O ₃ · 1 / 2Ca (OH) ₂ · 1 / 2CaCO ₃ · 12H ₂ O, calcite CaCO ₃ , gibbsite Al Some contamination such as (OH) ₃ is inevitable. Further, when the reaction site is heated to promote the reaction of aluminum hydroxide, monocarbonate having a large particle diameter exceeding 5 μm is mixed due to the change in solubility.

  The reaction of anhydrous calcium aluminate and calcium carbonate in water proceeds relatively quickly at room temperature of 20 to 30 ° C., and a monocarbonate having a thin thickness of about 1 to 5 μm is obtained. Although the particle size controllability can be expected because it reacts even at a low temperature, an ultra-high temperature of 1350 ° C. and fine pulverization of the obtained sintered body are necessary to produce anhydrous calcium aluminate. Further, when the raw material concentration is increased in the synthesis in water, the water temperature rises due to the hydration heat of anhydrous calcium aluminate, and when it exceeds 35 ° C., hydrogarnet is generated. Furthermore, anhydrous calcium aluminate is accompanied by rapid cement-like agglomeration with hydration and must be reacted in a strong stirrer or wet grinder to obtain a product with good dispersibility. As described above, it is difficult to increase the productivity of the method via anhydrous calcium aluminate, and the cost is not completely met.

  In light of these circumstances, the present inventors have intensively studied a method for producing monocarbonate capable of achieving both productivity and particle size controllability. As a result, the object of the present invention is to mechanochemically activate aluminum hydroxide by grinding treatment or the like. Has been found to be achieved, and it has been found that a relatively fine grinding process is sufficient, and the present invention has been completed.

  Mechanochemical activation is a technique that uses the disorder of the crystal structure (= lattice disorder) that occurs when a solid material is subjected to mechanical actions such as compression, shearing, friction, tension, bending, etc., to promote chemical reactions. It is. Since such a method changes the chemical potential of the substance itself, depending on how it is used, it may have an excellent effect that cannot be achieved by general reaction operations such as heating, miniaturization, pressurization, and stirring. .

  That is, the present invention reacts slaked lime, aluminum hydroxide and calcium carbonate in the presence of water to produce monocarbonate, in which aluminum hydroxide is mechanochemically activated particularly by grinding treatment, The first feature of the aluminum hydroxide is that the 10 minute value-1 minute value = 0.3% or more in the method of measuring the heating loss at 110 ° C. It is an object of the present invention to provide a method for producing monocarbonate characterized by the following.

Hereinafter, the present invention will be described in detail. The monocarbonate which is the target substance of the present invention is specifically represented by the formula 2 {[Ca ₂ Al (OH) ₆ ⁺ ] (CO ₃ ²⁻ ) _0.5 (H ₂ O) _2.5 }, and [Ca ₂ Al (OH) ₆ ⁺ ] forms a layer structure and is laminated with carbonate ions and water molecules sandwiched therebetween.

  The number of water molecules sandwiched between the layers can be easily reduced by operations such as heating and drying, and at the same time the layer spacing can be changed, but the entry and exit of some water molecules does not significantly affect the essence of monocarbonate. In the invention, the number of water molecules is not particularly limited.

  In the method for producing monocarbonate of the present invention, mechanochemically activated aluminum hydroxide, slaked lime and calcium carbonate are reacted in water. Therefore, it is possible to use quick lime instead of slaked lime, but the substantial reaction is a reaction with slaked lime, and it is preferable to use slaked lime because the controllability of reaction temperature and the quality are stable.

  Calcium carbonate is classified according to crystal form, and includes calcite, aragonite, and vaterite. However, in the present invention, calcium carbonate reacts after dissolution, so that any crystal form can be used without any problem. For the same reason, it is not affected by the types of light calcium carbonate and heavy calcium carbonate. Furthermore, for the same reason, there is no problem using intentionally or naturally partially carbonated slaked lime. What is important is that the particles are small in order to promote dissolution. However, since such calcium carbonate is sufficiently compatible with commercially available general grades, the particle size of calcium carbonate is not particularly specified in the present invention.

  As described in claim 1, in the present invention, it is essential to use mechanochemically activated aluminum hydroxide as a raw material by a grinding treatment or the like, and the degree of mechanochemical activation is determined by a heating loss rate measurement method at 110 ° C. 10 minute value-1 minute value = 0.3% or more. If the content is less than 0.3%, the activity is low, so that the reaction takes time and a monocarbonate having a uniform particle size cannot be obtained.

The 110 ° C. heat loss rate measurement method is a method of measuring the weight loss rate when heating aluminum hydroxide at 110 ° C. (= weight loss before heating / weight before overheating) after 1 minute so as to measure the water content of ordinary powder. This is a method of measuring after 10 minutes and evaluating by subtracting 1 minute value from 10 minute value. Here, the weight loss rate is used as an absolute value.

Commercially available general aluminum hydroxide does not dehydrate unless heated to 220 ° C. or higher, but mechanochemically activated aluminum hydroxide has a disordered crystal structure and weakens the bond between Al and OH. In Fig. 1, dehydration is already started as in Chemical Formula 1, and the stronger the activation, the higher the dehydration rate.

[Chemical 1]
Al (OH) ₃ → AlOOH + H ₂ O ↑

The reason why the evaluation method subtracts the 1-minute value from the 10-minute value is to remove the influence of moisture adsorbed from the atmosphere. With heating at 110 ° C., dehydration derived from mechanochemicals is random in which the bond is disturbed, so that it lasts for a relatively long time, whereas the evaporation of adsorbed water is almost completed within one minute. Paying attention to such a difference in behavior, the numerical value as shown in claim 1 has been reached.

The heat source for heating can be anything as long as the product temperature can reach 110 ° C as quickly as possible. However, an electronic balance type moisture meter equipped with a halogen lamp has a rapid rise in heating, and the rate of weight loss is monitored. It is preferable because it is possible. In addition, in the measurement with a general electronic balance type moisture meter, if the weighing is extremely different, the reliability of the numerical value is affected. If the number of samples is too small, the value will fly greatly in reading of the minimum unit of measurement, and if there are too many samples, uniform heating cannot be performed and the value may be small. In the said evaluation method in the case of using an electronic balance type moisture meter, 1.5 to 1.6 g is an appropriate amount.

Aluminum hydroxide activated mechanochemically by grinding or the like reacts with slaked lime in water in a short time even at a room temperature of about 20-30 ° C., and calcium aluminate hydrate as shown in the chemical formula 2 is obtained. Generate. Moreover, since the calcium aluminate hydrate produced in this way is also amorphous and has high activity, it reacts easily with calcium carbonate to produce monocarbonate as shown in Chemical Formula 3.

[Chemical 2]
3Ca (OH) ₂ + 2Al (OH) ₃ → 3CaO · Al ₂ O ₃ · 6H ₂ O

[Chemical formula 3]
3CaO · Al ₂ O ₃ · 6H ₂ O + CaCO ₃ + 5H ₂ O → 3CaO · Al ₂ O ₃ · CaCO ₃ · 11H ₂ O

  Although it does not restrict | limit especially about the raw material aluminum hydroxide which performs a grinding process etc., the aluminum hydroxide with an average particle diameter of 1-100 micrometers manufactured industrially can be used.

  By the way, not limited to aluminum hydroxide, it is generally said that inorganic compounds are irregular in crystal structure and mechanochemically activated by grinding treatment, and metal hydroxides are particularly prone to irregularities. It is introduced in various literatures and known that aluminum hydroxide is likely to cause crystal structure irregularity by grinding treatment. However, such treatment requires several times to several tens of times the energy cost as compared with ordinary pulverization, and has not been industrially utilized because of many problems such as contamination.

  The apparatus used for the milling treatment is not particularly limited as long as it can mechanochemically activate aluminum hydroxide. For example, in addition to a vibration mill such as a vibration ball mill and a vibration rod mill, a conical mill, a pot mill, a tube mill, a centrifugal mill, a planetary planet Examples thereof include a ball mill, a stirring mill, a pin mill, a shaking mill, a stamp mill, a disk mill, a grinder, and a jet mill.

  The high-speed shear mixing treatment described in claim 2 exhibits the maximum effect by being performed at the start of the reaction. The seed crystal of monocarbonate is atomized and dispersed by the high-speed shear mixing treatment, and the reaction time can be greatly shortened. When high-speed shear mixing treatment is not performed, a monocarbonate having a non-uniform particle size is formed, but it can be used without any trouble if it is used only for a chemical composition such as an anion scavenger.

  The apparatus used for the high-speed shear mixing treatment is preferably a wet-type apparatus that generates a high shearing force, such as an open impeller type high-speed stirrer, a generator-type homogenizer, a high-pressure homogenizer, or a media mill.

  The time for performing the high-speed shear mixing treatment is not particularly specified because the shearing force varies depending on the raw material concentration and the mixing device, but it is instantaneous if it is a device such as a continuous homogenizer, and is usually used for a batch homogenizer. The objective is achieved in about 1 to 10 minutes.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to the following Example.

As the raw material aluminum hydroxide, Sumitomo Chemical Co., Ltd. C-31 was used. A batch type vibration mill manufactured by Chuo Kakoki Co., Ltd. was used for the aluminum hydroxide grinding apparatus. The apparatus was equipped with two 15-liter grinding cylinders, and stainless steel rods were used as the grinding media. The operation conditions of the mill were 1150 revolutions / minute, the amplitude was 9 mm, and the input amount of aluminum hydroxide was 1 kg for each cylinder. A mechanochemically activated aluminum hydroxide was produced by grinding for 60 minutes under these conditions. When the weight loss rate at 110 ° C. of the obtained powder was measured with a halogen moisture meter HR73 manufactured by METTLER TOLEDO, the 10 minute value-1 minute value was 1.74%. Next, 21 g of aluminum hydroxide subjected to the treatment, 29 g of slaked lime (made in-house), 44 g of calcium carbonate (light / reagent), and 900 g of water are placed in a 1 liter glass container with a lid, and immediately heated to 80 ° C., When the electrical conductivity of the slurry was traced while stirring, the completion of the reaction was confirmed after about 110 minutes. The product is recognized as a single phase of monocarbonate by XRD (powder X-ray diffractometer), and as a result of SEM (scanning electron microscope) observation, thin hexagonal plate-like particles having a width of 1 to 5 μm and a thickness of 0.05 μm or less Was slightly agglomerated.

Insert high speed shear mixing for 3 minutes with a batch-type juicer mixer, 1.75 liters in pot capacity, stirring at 16000 rpm before milling aluminum hydroxide, slaked lime, calcium carbonate at 80 ° C. The reaction was performed in the same manner as in Example 1 except that the completion of the reaction was confirmed after about 40 minutes. The product was a single phase of monocarbonate, in which thin hexagonal plate-like particles having a width of 1 to 2 μm and a thickness of 0.05 μm or less were well dispersed and oriented.

The reaction was performed in the same manner as in Example 2 except that the grinding time of aluminum hydroxide was changed to 30 minutes, and the completion of the reaction was confirmed after about 100 minutes. The 10-minute value minus 1-minute value obtained from the 110 ° C. heating loss rate of the aluminum hydroxide was 1.10%. The product was a single phase of monocarbonate, in which thin hexagonal plate-like particles having a width of 0.5 to 1.5 μm and a thickness of 0.05 μm or less were well dispersed and oriented.

When the same procedure as in Example 2 was performed except that the grinding time of aluminum hydroxide was changed to 12 minutes, the completion of the reaction was confirmed after about 6 hours. The 10-minute value minus 1-minute value determined from the heating loss rate of the aluminum hydroxide at 110 ° C. was 0.51%. The product was a single phase of monocarbonate, in which thin hexagonal plate-like particles having a width of 1 to 2 μm and a thickness of 0.05 μm or less were well dispersed and oriented.

When the same procedure as in Example 4 was performed except that the heating and stirring temperature was changed to 95 ° C., the completion of the reaction was confirmed after about 110 minutes. The product was a single phase of monocarbonate, in which thin hexagonal plate-like particles having a width of 1 to 2 μm and a thickness of 0.05 μm or less were well dispersed and oriented.
(Comparative Example 1)

The same operation as in Example 2 was performed except that C-31 was used as it was without grinding the aluminum hydroxide. Incidentally, the 10-minute value minus 1-minute value determined from the heating loss rate of the aluminum hydroxide at 110 ° C. was 0.00%. This mixed slurry does not complete the reaction even after 24 hours of stirring, and the powder collected at the time of 24 hours contains a large amount of hydrogarnet and calcium carbonate (calcite) in addition to 10-30 μm of huge monocarbonate. It was.
(Comparative Example 2)

When the same procedure as in Example 2 was performed except that the grinding time of aluminum hydroxide was changed to 5 minutes, the completion of the reaction was confirmed after about 10 hours. The 10-minute value minus 1-minute value determined from the heating loss rate of the aluminum hydroxide at 110 ° C. was 0.27%. The product was a single phase of monocarbonate, but the particles were non-uniform in width, thickness and shape, and formed strongly aggregated secondary particles.

  As described above, according to the present invention, monocarbonate can be easily produced at room temperature from inexpensive raw materials such as slaked lime, aluminum hydroxide, and calcium carbonate. Since monocarbonate selectively forms hexagonal plate-like particles, it is expected to exhibit the same function in applications where plate-like particles are conventionally used. In particular, pigments for papermaking paints are preferably used because they are excellent in covering property, whiteness of color and lightness.

Electron micrograph of monocarbonate according to Example 2 (× 10000)

Claims (2)

In a method for producing calcium aluminate monocarbonate by reacting slaked lime, aluminum hydroxide and calcium carbonate in the presence of water, the aluminum hydroxide is aluminum hydroxide that has been mechanochemically activated, particularly by grinding treatment, and the like. A method for producing calcium aluminate monocarbonate characterized in that the mechanochemically activated aluminum hydroxide obtained by crushing treatment has a value of 10 minutes-1 minutes = 0. . In a method of producing calcium aluminate monocarbonate by reacting mechanochemically activated aluminum hydroxide and calcium carbonate by slaked lime and grinding treatment in the presence of water, particularly high-speed shear mixing treatment is performed at the start of the reaction. The method for producing a calcium aluminate monocarbonate according to claim 1.

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