JPS6332727B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for modifying calcium carbonate by surface fluorination, particularly an apparatus suitable for modifying calcium carbonate by reaction with hydrogen fluoride.

Calcium carbonate powder with an average particle size of 20 μm or less is currently being effectively used in large quantities for various purposes in the rubber, plastic, paper, and paint industries. In order to improve the affinity, not only fine particles with an average particle size of less than 1 μm, but also some of the minor calcium carbonate and heavy calcium carbonate with an average particle size of 1 to 20 μm, have a surface mainly composed of sodium salts such as fatty acids and resin acids. Processing is being carried out. The surface treatment method involves stirring and mixing a liquid or emulsion surface treatment agent in an aqueous suspension of calcium carbonate, so that the treatment agent is reacted and adsorbed onto the surface of each calcium carbonate, followed by dehydration, drying, and drying. Commonly used methods include pulverizing, classifying, or spraying a surface treatment agent onto powdered calcium carbonate.

However, in any of these cases, the effect of pulverizing lumps or finely pulverizing heavy calcium carbonate powder in the surface treatment step is of course undesirable.

The present invention converts calcium carbonate and hydrogen fluoride into water.
By dehumidifying it to below 0.1% or heating it above the boiling point of water to react with calcium carbonate under conditions that do not condense water, we can create particles that cannot be produced by physical methods using conventional crushing mechanisms. By adjusting the amount of hydrogen fluoride that passes through uniform fragmentation, that is, by adjusting the amount of hydrogen fluoride that passes through the process, it is possible to freely achieve the desired particle size, and it is also suitable for producing calcium fluoride on the particle surface. The present invention relates to a reforming device.

The modified calcium carbonate obtained by the present invention is extremely finely divided and has a high specific surface area, and a calcium fluoride layer is uniformly formed on the surface, so it has improved stability against acids, and is particularly useful for plastics and paints. When used as a filler for paper, rubber, etc., it brings about advantageous effects such as excellent dispersibility, mechanical properties, and optical properties, so it is expected that its use will expand dramatically in this field.

Conventionally, the contact reaction equipment for calcium carbonate and hydrogen fluoride gas has been considered to be a fixed bed type or a fluidized bed type, but the fixed bed type allows the reaction to proceed locally, while the fluidized bed type requires that the temperature is uniform. However, there were problems such as the reaction rate on the gas side being low and the powder particles flying out along with the gas.

The inventors of the present invention have repeatedly conducted various studies in order to solve the drawbacks of these conventional techniques. As a result, calcium carbonate is placed in an aluminum stirred tank type reaction vessel, and while stirring at a reaction temperature of 100°C or higher, hydrogen fluoride gas is We have discovered a reformer that can be distributed. This method is an extremely excellent reforming device, as the powder does not fly out along with the gas, and the reaction rate on the gas side is high and the reaction is uniform.

Here, as equipment materials, nickel, hydrofluoric anhydride resistant materials at temperatures of 100°C or higher in the gas-solid reaction of calcium carbonate and hydrogen fluoride gas are used.
Only expensive materials such as Monel and Hastelloy were known, and inexpensive materials such as iron were too corroded to be used.

As a result of repeated studies on equipment materials, the present inventors surprisingly discovered that aluminum material, which is thought to be unusable in high-temperature hydrogen fluoride atmospheres, is optimal for this reaction system, resulting in the present invention. This is what I did.

That is, a reactor with a lid manufactured using an aluminum material is preferably provided with an aluminum stirrer, and a top plate is provided with a nozzle for blowing hydrogen fluoride, an exhaust port for purging generated steam, and a raw material input port, If the reaction between calcium carbonate and hydrogen fluoride is carried out using a device equipped with a reaction product withdrawal valve at the bottom of the reactor and a heating device installed around the reactor, no corrosion of the device will occur and the product will not be contaminated. Calcium carbonate can be modified. As the heating device for the outer periphery of the reactor, any heating device such as a combustion furnace, an electric furnace, an external heater, etc. may be used.

That is, the present invention is a round-bottom cylindrical reaction vessel equipped with a stirrer and with a lid whose inner surface is made of aluminum material, and a hydrogen fluoride inlet and an exhaust hole for generated steam purge gas are provided on the top plate of the lid. , and an inlet for the raw material calcium carbonate, a product outlet at the bottom, and a heating device around the outer periphery of the reaction vessel to provide a temperature sufficient to promote the reaction between calcium carbonate and hydrogen fluoride. A calcium carbonate reforming device is provided. Here, at least the inner surface is made of aluminum means both cases where it is made of solid aluminum and cases where aluminum lining (cladding or colorizing processing) is applied. For example, the inner material of the cladding is made of an aluminum alloy and the outer material is made of pure aluminum, and the colorizing process infiltrates aluminum into the metal material. The same applies to the stirring device, but the stirring device may be made of other materials such as Teflon.

The calcium carbonate used as a raw material in the present invention includes all types of calcium carbonate of less than 20 μm used in plastics, paints, paper, rubber, etc., such as heavy calcium carbonate obtained by crushing and classifying crystalline limestone, and light colloidal calcium carbonate. When calcium carbonate is subjected to the modification treatment of the present invention, the above-mentioned pulverization and surface treatment effects are added, and it is possible to modify it into a highly dispersible carbon filler.

On the other hand, the hydrogen fluoride gas used in the reaction is
It is important to preheat it to 100°C or higher before introducing it into the reactor, and to carry out the reforming treatment at a reaction temperature of 100°C or higher.
The reason for preheating the hydrogen fluoride gas to 100℃ or higher is to prevent moisture from condensing when the hydrogen fluoride gas and calcium carbonate come into contact;
This is because when cold gas and hot calcium carbonate come into contact, the temperature locally drops and moisture condenses, and the reaction product acts as a binder and enlarges the particles, making it impossible to expect an increase in surface area. Also, the reaction temperature is 100
If the temperature is below ℃, the water produced by the reaction of the following formula will condense and solidify, resulting in CaCO ₃ + 2HF → CaF ₂ + CO ₂ + H ₂ O The effect of making calcium carbonate finer and the improvement of the specific surface area cannot be expected. .

The present invention will be specifically explained below.

The reaction vessel is made of aluminum and has a lid. It is a cylindrical reactor with a round bottom. The lid has an inlet for hydrogen fluoride, an outlet for the generated steam, and an inlet for charging the raw material calcium carbonate. A heating device is installed around the reactor.
For example, electric heaters, hot air jackets, etc. are installed.

The amount of calcium carbonate to be modified is fed into the reaction vessel from the raw material inlet, and heated to 100°C or higher using a heating source around the reactor while stirring at 10 to 40 rpm.
After raising the temperature, hydrogen fluoride is preheated to such an extent that the reaction temperature does not drop below 100°C, and is supplied from the introduction nozzle at the top of the reactor.

The reaction uses a flow reaction method in which only preheated hydrogen fluoride is continuously supplied, and 1.0 to 1.5 times the theoretical amount of hydrogen fluoride is passed through to conduct a gas-solid reaction, but since this reaction is an exothermic reaction, it is rapid. Since it is difficult to control the temperature in such a reaction, it is preferable to conduct the hydrogen fluoride flow rate at a moderate range of, for example, 100 to 300°C to prevent a sudden temperature rise.The hydrogen fluoride used should be diluted with an inert gas. The fluorination rate (fluorine content) of the surface can be varied and may be selected depending on the target physical properties. After the reaction is complete, introduce dehumidified air or inert gas instead of hydrogen fluoride from the hydrogen fluoride inlet to replace the residual hydrogen fluoride gas in the container, and then open the extraction valve while stirring. Therefore, modified calcium carbonate with good fluidity can be extracted. on the other hand,
The water vapor and carbon dioxide gas generated during the reaction are continuously discharged from the exhaust port provided at the top of the reactor, for example, by -2 to -5 mm.
If the system is evacuated with a negative pressure of Aq, the inside of the system will be kept dry and no material erosion will occur.

Since the inside of the reactor lid is prone to corrosion, corrosion resistance can be further improved by coating it with Teflon, if necessary. As for the stirrer used in this reactor, a paddle-type stirrer having a shape that follows the shape of the bottom plate is preferably used, and it is desirable to take measures to prevent scaling.

The gas-solid reaction of the present invention is an extremely simple reaction, and even if aluminum equipment is used, there is no corrosion of the equipment material, so high quality modified calcium carbonate can be produced efficiently and at low cost. Since the reactor is provided around the outer periphery of the reactor, internal pressure, temperature, etc. can be easily controlled without contaminating the product.

The present invention will be explained below with reference to Examples.

Example 1 Aluminum reactor 1 shown in the attached drawings
(800mmφ) and heavy calcium carbonate (average particle size 4μ)
m) 100Kg is supplied from the input port 5 (300mmφ) while being stirred at 25 rpm by the aluminum stirring blade 2 (rotated by the motor M), and the hot air 9 is heated in the heating furnace 8 so that the temperature of this raw material reaches 150°C. The reactor was heated by 10 min. After raising the temperature to the above temperature, hydrogen fluoride preheated to 100℃ was introduced into the inlet port 3 (25mmφ) for 12 hours.
The reaction was carried out at 150° C. by flowing at a rate of Kg/hour for 3 hours. After stopping the supply of hydrogen fluoride, dehumidified air was introduced from the inlet 3 to replace the remaining hydrogen fluoride in the reactor. Further, while stirring was continued, the outlet port 6 (150 mmφ) was opened using the valve 7, and the surface-modified calcium carbonate with hydrogen fluoride was extracted.
From exhaust port 4, 4.8 kg/hour of water vapor generated by the reaction,
11.7Kg/hour of CO ₂ and 0.13Kg/hour of unreacted HF were discharged. 11 is a thermocouple protection tube. No corrosion was observed in the equipment after the reaction, and the produced calcium carbonate was obtained as a product with extremely high fluidity and no impurities.

The BET specific surface area of this product was as follows.

This product 68m ² /g (F: 36.9%) Untreated product for comparison 3m ² /g Example 2 Using the same equipment as in Example 1, 100Kg of heavy calcium carbonate was heated to 250℃, and then heated to 100℃. The reaction was carried out at 250° C. by flowing HF preheated to 4 kg/hour for 1 hour. No corrosion was observed in the equipment after the reaction, and the produced calcium carbonate was obtained as a highly fluid product free of impurities.

The BET specific surface area of this product is as follows.

This product 7m ² /g (F: 3.7%) Untreated product for comparison 3m ² /g Example 3 Using the same equipment as in Example 1, 100Kg of light calcium carbonate (average particle size 5μm) was heated to 100℃. After that, HF preheated to 100°C was passed through at 8 kg/hour for 3 hours to carry out the reaction at 150°C. No corrosion was observed in the equipment after the reaction, and the produced calcium carbonate was obtained as a product with extremely high fluidity and no impurities.

The BET specific surface area of this product is as follows.

This product 28 m ² /g (F: 21.0%) Untreated product for comparison 4.5 m ² /g Example 4 Using the same equipment as in Example 1, 100 kg of colloidal calcium carbonate (average particle size 7 μm) was heated to 150°C. After heating, 10Kg/hour of HF preheated to 100℃ is 0.5
The reaction was carried out at 150°C for a certain period of time. No corrosion was observed in the equipment after the reaction, and the produced calcium carbonate was obtained as a product with extremely high fluidity and no impurities.

The BET specific surface area of this product is as follows.

This product 14 m ² /g (F: 3.9%) Untreated product for comparison 9 m ² /g Example 5 Using the same equipment as in Example 1, 100 kg of heavy calcium carbonate (average particle size 4 μm) was heated to 150°C. After heating, a mixed gas of HF and _N2 (HF6Kg/hour, _N2 8.4Kg/hour) preheated to 100℃ was passed through for 6 hours.
The reaction was carried out at 150°C. No corrosion was observed in the apparatus after the reaction, and the produced calcium carbonate was a product with extremely high fluidity and no impurities.

The BET specific surface area of this product is as follows.

This product 60m ² /g (F: 32.0%) Untreated product for comparison 3m ² /g

[Brief explanation of the drawing]

The accompanying drawing is a longitudinal cross-sectional view showing a specific proportional structure of the device of the present invention.

Claims (1)

[Claims] 1 A cylindrical reaction vessel with a round bottom and a lid, equipped with a stirrer and whose inner surface is made of aluminum, with a hydrogen fluoride inlet on the top plate of the lid, an exhaust hole for generated steam purge gas, and a raw material carbonate A calcium carbonate reforming device comprising a calcium inlet, a product outlet at the bottom, and a heating device around the outer periphery of the reaction vessel.