KR101865569B1 - Method of producing a high oil absorption porous calcium carbonate - Google Patents

Abstract

There is provided a method of manufacturing a high-absorbing porous calcium carbonate.
The present invention relates to a method for producing calcium carbonate using a carbon dioxide gasification method in which an additive is mixed with a slaked slurry and carbonation is carried out as in the reaction formula 2, wherein the additive is selected from the group consisting of organic acids: 0.1 To 0.5% and polyacrylate: 0.1 to 2.0%, and the carbonation initiation temperature is in the range of 30 to 70 ° C. .

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a high-

More specifically, the present invention relates to a method for producing a highly absorbent porous calcium carbonate, which is characterized by having a large pore volume, a low apparent specific gravity and a very high absorption ratio, so that expensive silica, titanium dioxide part or complete substitution is possible, (Pore) volume of the porous layer is increased, so that the function of absorbing and retaining heat is improved, and a method of manufacturing porous calcium carbonate having a very high absorption ratio capable of replacing the calcined clay used as a pigment in a thermal layer pre-layer.

Carbon dioxide gasification method, soda carbonate method and Solvay method have been conventionally known as methods for producing precipitated calcium carbonate, and their main reaction schemes are as follows.

[Reaction Scheme 1]

_{Ca (OH) 2 + CO 2} → CaCO 3 + H 2 O ( a carbon dioxide gas method)

[Reaction Scheme 2]

_{Ca (OH) 2 + Na 2} CO 3 → CaCO 3 + 2NaOH ( sodabeop carbonate)

[Reaction Scheme 3]

Ca (OH) ₂ + 2NH ₄ Cl? CaCl ₂ + 2NH ₃ + 2H ₂ O

CaCl ₂ + Na ₂ CO ₃ → CaCO ₃ + 2 NaCl (Solvay method)

In general, carbon dioxide gasification is a process that is adopted by most companies because it is easy to manufacture and economical. However, the sodium carbonate method and the solvay method are advantageous in that they produce sodium hydroxide and sodium chloride as byproducts, but they are used economically in schools, laboratories, and the like. Therefore, the present applicant has also been manufacturing calcium carbonate using the carbon dioxide gasification method, and unlike other companies, the exhaust gas generated in the steelworks has been used for the carbonation reaction by applying the self-developed purification technology.

FIG. 1 is a manufacturing process diagram for producing calcium carbonate using a conventional carbon dioxide gas method.

The particle characteristics (shape, particle size, specific surface area value, pore volume, etc.) of the precipitated calcium carbonate can be controlled by the carbonation initiation temperature, the calcium hydroxide concentration, the additive and the like.

Here, the particle size is smaller and the specific surface area value and the pore volume become larger as the carbonation start temperature and the slurry slurry solid concentration are lower.

The carbon dioxide gasification method has the greatest effect on the particle characteristics due to the dissolution rate of carbon dioxide by the gas-liquid reaction method. Therefore, the lower the carbonation initiation temperature, the faster the carbonated water production rate in the slaked lime slurry of the carbon dioxide promotes the particle production, thereby reducing the growth. Also, the lower the solid content of the slaked slurry, the faster the carbonation reaction and the effect of inhibiting grain growth. However, considering the economical aspect for commercial production, it is difficult to control the reaction starting temperature below 20 ℃. The concentration of calcium hydroxide is not more than 5% in consideration of unit batch productivity.

On the other hand, it is a general technique to use additives to control particle characteristics. The additive is added to the slaked lime slurry before the initiation of the carbonation reaction or during the reaction. The above additives may be used alone or in combination of two or more thereof with a chelating agent such as organic acid or sugar, polyacrylic acid or polyacrylic acid salt. The amount and type of additive should be selected to produce calcium carbonate having desired quality characteristics.

The quality of the calcium carbonate product used in the paper manufacturing process and used as paper top-coating pigment is as follows: particle size of 100 nm or less, specific surface area value of 25 m 2 / g or less, pore volume of 0.05 cm 3 / g, Level. The precipitated calcium carbonate produced by such a conventional method has a problem that the absorption rate is low due to a small pore volume and therefore it is difficult to replace expensive pigments such as silica, titanium dioxide and calcined clay.

Korean Patent Publication No. 2011-0041199 (published on Jan. 21, 2011)

SUMMARY OF THE INVENTION Accordingly, the present invention has been made in order to overcome the limitations of the prior art described above, and it is an object of the present invention to provide a method for producing a calcium carbonate having a high pore volume of at least 0.05 cm 3 / g and a low oil absorption rate of 100 or more by adding an additive to a slurry The purpose is to provide.

Further, the technical problems to be solved by the present invention are not limited to the technical problems mentioned above, and other technical problems which are not mentioned can be understood from the following description in order to clearly understand those skilled in the art to which the present invention belongs .

According to an aspect of the present invention,

A method for producing calcium carbonate using a carbon dioxide gasification method in which an additive is mixed with a slaked lime slurry and then subjected to a carbonation reaction as shown in Reaction Scheme 2,

Wherein the additive is composed of 0.1 to 0.5% of organic acid and 0.1 to 2.0% of polyacrylate as weight% based on the solid content of the slaked lime,

Wherein the carbonation initiation temperature is in the range of 30 to 70 占 폚.

[Reaction Scheme 2]

Ca (OH) ₂ + additive + CO _{2 -} > CaCO ₃ + H ₂ O

It is preferable that the solid content concentration of the slaked lime slurry before the carbonation is in the range of 7.0 to 20.0 wt%.

In the present invention, the stirring speed during the carbonation reaction is preferably controlled at 30 to 50 rpm.

The additive is preferably composed of 0.3 to 0.5% of organic acid and 0.5 to 1.5% of polyacrylate as weight% based on the solid content of the slaked lime.

A step of adding 1.0 to 3.0% of dispersant (based on the total weight of calcium carbonate) to the prepared calcium carbonate to prepare a slurry state can be added.

It is preferable that the solid content concentration of the highly absorbed porous calcium carbonate slurry prepared in the above slurry state is limited to 45.0 to 55.0% by weight.

The calcium carbonate produced by the above-described invention has a pore volume of not less than 0.05 cm 3 / g, a specific surface area of not less than 30 m 2 / g, an apparent specific gravity of not more than 0.20 kg / L, It is possible to replace expensive silica and titanium dioxide, and it is possible to improve the printability when applied as a paper pigment.

In addition, the function of heat absorption preservation is improved, and it is possible to substitute plastic clay used in thermal layer pre-layer pigment, and it can be applied as additive for cable, plastic, paint etc. besides paper.

FIG. 1 is a manufacturing process diagram for producing calcium carbonate using a conventional carbon dioxide gas method.
2 is a view illustrating a manufacturing process for producing calcium carbonate using the carbonated gas method according to an embodiment of the present invention.
3 is an electron micrograph of the shape of calcium carbonate particles prepared by the method according to an embodiment of the present invention.

Hereinafter, the present invention will be described.

The present invention relates to a method for producing calcium carbonate by a carbon dioxide gasification method in which an additive is mixed with a slaked slurry and carbonation is carried out in accordance with the following reaction formula 2, wherein the additive is selected from the group consisting of 0.1% To 0.5% and polyacrylate: 0.1 to 2.0%, and the carbonation initiation temperature is in the range of 30 to 70 ° C.

[Reaction Scheme 2]

Ca (OH) ₂ + additive + CO _{2 -} > CaCO ₃ + H ₂ O

2 is a view illustrating a manufacturing process for producing calcium carbonate using the carbonated gas method according to an embodiment of the present invention.

As shown in FIG. 2, calcium oxide (CaO) is first prepared as calcium hydroxide (Ca (OH) ₂ ) through a normal hydration reaction as shown in Reaction Scheme 1 below.

[Reaction Scheme 1]

CaO + H ₂ O → Ca (OH) ₂

The quicklime used as the precipitating calcium carbonate raw material is preferably high in purity and in a proper state. In the case of a large amount of impurities, the calcium carbonate causes unevenness in particle size and causes a decrease in whiteness.

The quicklime is manufactured through a calcination process of well-known limestone, and the calcination temperature is preferably about 900 to 1100 ° C. If the calcination is less than the target value, the yield is lowered in the subsequent hydration process, and if it is too much, the reactivity is lowered, and the size of the calcium carbonate particle can not be controlled, and the aging process must be separately operated.

The hydration reaction in the above reaction formula 1 is preferably carried out at a temperature of 60 to 80 ° C. as the amount of burnt lime is increased by an exothermic reaction. The higher the hydration temperature, the faster the reaction with water to grow the size of the slaked lime particles by the heat of reaction. However, since the amount of lime added is higher at a temperature of 80 ° C or higher, the viscosity of the slaked lime slurry becomes higher, Thereby generating a trouble. Below 60 ℃, the concentration of slaked lime is low, which is disadvantageous in terms of productivity.

After the hydration reaction, sieving is performed.

Next, in the present invention, additives are mixed with the slaked slurry prepared above.

The additive may be carbonated 　 It is possible to control the shape of the calcium carbonate particles produced by charging the calcium carbonate slurry before starting the reaction. Conventionally, a suitable amount of a chelating agent such as sugar was used in the preparation of calcium carbonate having a pore volume of 0.05 cm 3 / g. However, the present invention is characterized in that an organic acid and a polyacrylate are mixed as an additive for preparing porous calcium carbonate.

The organic acid accelerates the reaction rate by controlling the calcium ion elution rate in the calcium hydroxide so that the particle size and the specific surface area value fall within the scope of the present invention. And the polyacrylate plays a role of increasing the pore volume.

In the present invention, the additive is not effective alone, and it is necessary to use the additive only in a mixed manner, so that it is possible to manufacture calcium carbonate with high oil absorption.

In the present invention, an additive comprising 0.1 to 0.5% of organic acid and 0.1 to 2.0% of polyacrylate as a weight% based on the solid content of the slaked lime solid is mixed with the slaked slurry. More preferably, the additive comprises 0.3 to 0.5% of organic acid and 0.5 to 1.5% of polyacrylate as a weight% based on the solids content of the slaked lime solid. When the amount of the additive is less than the above range, it is impossible to produce porous calcium carbonate, and if it exceeds this range, it may be economically disadvantageous to incur the additional cost of additives.

On the other hand, the subsequent solid content concentration of the slaked slurry before the initiation of the carbonation affects the particle size of calcium carbonate finally produced. In the present invention, it is preferable to limit the concentration of slaked lime to 7.0 to 20.0 wt%. The higher the concentration of hydrated lime, the longer the time required for the reaction and the larger the particle size. If the amount of hydrated lime is higher than 20.0% by weight, the irregularity of the hydrated lime is high, resulting in uneven particle size. On the other hand, when it is less than 7.0% by weight, the production capacity of the unit reaction batch is lowered, so that calcium carbonate having a desired particle size should be prepared within an appropriate range.

In the present invention, calcium carbonate is prepared by subjecting a slaked liquor mixed with additives as described above to carbonation reaction as shown in Reaction Scheme 2 below.

[Reaction Scheme 2]

Ca (OH) ₂ + additive + CO _{2 -} > CaCO ₃ + H ₂ O

The reaction initiation temperature in the reactor varies depending on the shape of the particles. Generally, Spindle Type is manufactured at 30 ℃ or more, Spindle-Cluster Type is 20 ~ 40 ℃ and Round or Cubic Type is at 30 ℃ or less.

In the present invention, it is preferable to limit the reaction initiation temperature to 30 to 70 ° C in order to prepare porous calcium carbonate. If the temperature is less than 30 ° C, porous calcium carbonate can be prepared. However, since the particle size is small and the specific surface area is high, it is difficult to control the viscosity of the slurry. On the other hand, when the temperature exceeds 70 ° C, the particle size is large, the pore volume is small, and the temperature rise process is required before the reaction, which is economically disadvantageous due to the additional energy cost.

In the present invention, the amount of CO ₂ As the gas, the exhaust gas generated in the steel process was used. When the exhaust gas is used, purification process is separately installed and operated since the quality of calcium carbonate such as whiteness is lowered due to the inflow of foreign substances. The concentration of CO _{2 in} the exhaust gas was 10 to 25%. Below 10%, the reaction time is excessive and the productivity is poor. If it exceeds 25%, the reaction effect is saturated.

However, the present invention is not limited to the use of the exhaust gas of the steel process described above, and CO ₂ Gas can be used without restriction.

The stirring rate during the carbonation reaction affects the particle size produced. Specifically, the faster the agitation speed, the larger the particle growth is by accelerating the particle collision frequency. It is therefore common to adjust the stirring speed to a level that satisfies the desired particle size value.

In the present invention, it is preferable to restrict the stirring speed to 30 to 50 rpm in the carbonation reaction. When the amount is less than 30 rpm, the particle size is too small, and the specific surface area becomes large. Therefore, it is difficult to prepare a solid content concentration of 45 wt% or more when slurries are formed for use as a paper pigment. When it exceeds 50 rpm, This is because it is difficult to prepare porous calcium carbonate for absorbing oil.

As shown in Reaction Scheme 2, CO ₂ blowing is performed in the reactor for the carbonation reaction. At this time, the pH of the initial slaked lime slurry is 12.0 to 12.5, but when the pH value falls to 8.0 or less as the reaction proceeds, the reaction is completed and dehydrated, dried or slurried in a form suitable for the intended use.

On the other hand, since the pigment for papermaking should be in a slurry state, it is convenient to use, so a dispersing process should be added to adjust the concentration of the solid. In such a dispersing step, it is required to add an appropriate amount of dispersant and the like, and the added amount is preferably in the range of 1.0 to 3.0% based on the total weight of the calcium carbonate. If the added amount of the dispersant is less than 1.0%, the viscosity is high and the workability such as transportation is lowered. If the added amount is more than 3.0%, it is not economical because the excessive charging is incurred.

Also, in the present invention, it is preferable that the solid content concentration of the highly absorbed porous calcium carbonate slurry prepared by adding the dispersant is limited to 45.0 to 55.0 wt%. If the solid content of the porous calcium carbonate slurry is less than 45.0%, it is difficult to apply it as a paper coating pigment. If it exceeds 55.0%, the viscosity is high and workability is lowered.

Hereinafter, the present invention will be described in detail by way of examples.

[Example 1]

Citric acid + Polyacrylic acid  Manufacture of calcium carbonate using a mixture of sodium

A slurry of 10% slaked lime was prepared by reacting with lime and water, and then 200 mesh sieves were sieved to remove minute and impurities. 60 L of slaked lime slurry was added to the 100 L reactor and the reaction initiation temperature was adjusted to 32 캜. As the additive, 0.5 wt% of citric acid and 1.0 wt% of sodium polyacrylate were added to the reactor as a solid content of slaked lime, after adjusting the rpm it was blown into the CO _2.

Thereafter, the carbonation reaction was stopped by the exothermic reaction as the temperature gradually increased and the pH value dropped. When the pH became constant between 7.0 and 8.0, the reaction was stopped. Then, the slurry was dispersed at a calcium carbonate solid concentration of 45.0 wt% while dispersing agent was added thereto after 325 mesh sieving and filtration. At this time, the amount of the dispersant was 2.0 wt% based on the weight of calcium carbonate.

[Comparative Example 1]

Manufacture of calcium carbonate using citric acid as an additive

Compared with Example 1, calcium carbonate was prepared in the same manner except for the additive. As an additive, 0.5 wt% of citric acid alone was used.

[Comparative Example 2]

Polyacrylic acid  Manufacture of calcium carbonate using sodium additive

Compared with Example 1, calcium carbonate was prepared in the same manner except for the additive. 1.0 wt% of sodium polyacrylate was used as an additive.

[Comparative Example 3]

Manufacture of calcium carbonate without additives

Compared with Example 1, calcium carbonate was prepared in the same manner except that the additive was not added.

The quality characteristics of the calcium carbonate produced in the above experiment are shown in Table 1 below.

division Example 1  Comparative Example 1  Comparative Example 2  Comparative Example 3 Average particle diameter (占 퐉) 2.85 2.40 3.29 3.56 Apparent Specific Gravity (kg / L) 0.16 0.21 0.23 0.27 Specific surface area value (m ² / g) 31.4 29.9 14.8 9.5 Pore volume (cm ³ / g) 0.09 0.04 0.08 0.03 Absorption rate (%) 140 120 90 60 Viscosity (45 wt%, cps) 220 180 100 80 pH (45 wt%) 9.20 9.28 9.09 9.37

As shown in Table 1, it can be seen that Example 1 in which additives are mixed and added has excellent properties. On the other hand, it can be seen that the pore volume to specific surface area value is poor in Comparative Example 1-2 in which the additive is used singly, and Comparative Example 3 in which the additive is not used shows that the results are not good in all the properties . 3 is an electron micrograph of the shape of the calcium carbonate particles of Example 1.

[Example 2]

Preparation of calcium carbonate after adjusting the reaction initiation temperature of 45 ° C

Calcium carbonate was prepared under the same conditions as in Example 1 except for the reaction initiation temperature. In Example 1, the reaction initiation temperature was adjusted to 45 캜.

[Example 3]

Reaction start temperature 60 占 폚 Calcium carbonate production

Calcium carbonate was prepared under the same conditions as in Example 1 except for the reaction initiation temperature. In Example 1, the reaction initiation temperature was adjusted to 60 캜.

[Comparative Example 4]

Lime lime Slurry  Manufacture of calcium carbonate after 5% solids concentration control

Calcium carbonate was prepared in the same manner as in Example 1 except for the solid content concentration of the slaked lime slurry. In this Comparative Example 4, the solid content concentration of the slaked slurry was adjusted to 5% by using water.

[Example 4]

Lime lime Slurry  Manufacture of calcium carbonate after 15% solids concentration control

Calcium carbonate was prepared in the same manner as in Example 1 except for the solid content concentration of the slaked lime slurry. In case of reacting with quicklime and water, the amount of quicklime was increased to prepare a 15 wt% slurry slurry, and then 200 mesh sieves were sieved to remove fine particles and impurities.

division Example 2 Example 3 Comparative Example 4  Example 4 Average particle diameter (占 퐉) 3.36 4.20 2.23 3.50 Apparent Specific Gravity (kg / L) 0.18 0.22 0.13 0.21 Specific surface area value (m ² / g) 29.2 26.9 38.6 23.4 Pore volume (cm ³ / g) 0.08 0.06 0.11 0.04 Absorption rate (%) 130 110 170 90 Viscosity (45 wt%, cps) 190 150 320 80 pH (45 wt%) 9.39 9.41 9.37 9.36

As shown in Table 2, it can be seen that all of Examples 2-4 exhibit excellent properties. On the other hand, Comparative Example 4 seems to have excellent properties at first, but the solid content of the slaked lime slurry is too low to significantly decrease the productivity.

[Example 5]

Color  Comparison of physical properties

A 40 ± 0.5 wt% coating solution was prepared using the 45 wt% calcium carbonate slurry prepared in Example 1 and the calcined clay used in the conventional Pre layer in comparison with the slurry. Table 3 shows the results.

As shown in the following Table 3, Example 5 according to the present invention shows excellent results in terms of printability, whiteness and white sensitivity as compared with the conventional fired Clay. However, the sheet gloss is as low as 50% of the plastic clay, but this is due to the difference in particle shape.

Therefore, it can be seen that all or part of the expensive silica and fired Clay of the present invention is possible.

Color Formulation  Conventional example Example 5 Plastic Clay 100 - Calcium carbonate - 100 Latex 17.5 175 PVA 1.9 1.9 Maintenance fluidizer 0.15 0.15 pH 8.80 8.78 LSV (cps, # 2, 60 rpm) 292 277 TSC (wt%) 40.0 40.0 Sheet Gloss 6.5 3.1 Whiteness 92.3 98.3 Brightness 87.9 88.6 Set off 3.7 8.0

* In Table 3, sintered clay is Ansilex® 93 from BASF Corporation of America and TSC represents Total Solid Content.

[Example 6-7]

Print Sensitivity TEST  result

The print sensitivities of the thermal paper according to the mixing ratio of the porous calcium carbonate and the calcined clay prepared in Example 1 were confirmed, and the results are shown in Table 4 below. In case of using only porous calcium carbonate, the sensitivity to the calcined clay is somewhat insufficient at 75% level, but it can be understood that satisfactory results can be obtained when 50% of the mixture is used.

division Conventional example Example 6 Example 7 Plastic Clay

Part

100 - 50 Porous calcium carbonate - 100 50 Latex 17.5 17.5 17.5 PVA 1.9 1.9 1.9 Maintenance fluidizer 0.15 0.15 0.15 Theoretical concentration wt% 40.0 40.0 40.0 pH - 7.0 7.3 7.2 LSV (cps, # 3, 60 rpm) cps 280 520 430 HSV (4,400R, Bob E) cps 13.8 14.5 14.2 Maintenance figure - 312 300 280 Solid concentration wt% 40.0 40.0 40.0 Sensitivity point 100 (standard) 75 98 Printing surface - Base Print Base Print Base Print Reliability (△)
Base / Print
Constant temperature and humidity
-
0.01 0.03 0.01 0.03 0.01 0.07 Heat resistance 0.00 0.06 0.00 0.06 -0.01 0.09 Light resistance 0.02 0.17 0.02 0.22 0.02 0.11

The test conditions in this test are as follows.

- white paper property

Base Paper & Coating Weight: 75 gsm Sheet & 4.5 gsm

· Coating Machine: Auto Coater (Japan)

· Calendering Condition: Self weight [DWR & D2-300, Dongwon Roll, Korea]

- Sensitivity evaluation

· Equipment: Atlantek 400 [Canade]

· Reliability

         → Constant temperature and humidity: 40 ° C, RH 90%, 24 hr

         → Heat resistance: 60 ° C, 24 hr

→ Light fastness: 550 W, 4 hr

As described above, the present invention provides a method for producing calcium carbonate by mixing an additive comprising an organic acid + a polyacrylate compound before the initiation of the reaction for preparing calcium carbonate, and a pore volume capable of replacing all of the conventional silica and the calcined clay It can be seen that the production of a large and highly absorbed porous calcium carbonate is possible.

While the present invention has been particularly shown and described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, Of course, this is possible. Accordingly, the scope of the present invention should not be limited to the described embodiments, but should be defined by the following claims as well as equivalents thereof

Claims (6)

A method for producing calcium carbonate using a carbon dioxide gasification method in which an additive is mixed with a slaked lime slurry and then subjected to a carbonation reaction as shown in Reaction Scheme 2,
Wherein the additive is constituted by 0.3 to 0.5% of organic acid and 0.5 to 1.5% of polyacrylate as weight% based on the weight of the slaked solids, the carbonation start temperature is in the range of 30 to 70 캜; And
Further comprising adding 1.0 to 3.0% of a dispersant (based on the total weight of calcium carbonate) to the prepared calcium carbonate to prepare a slurry state,
Wherein the solid content concentration of the highly absorbed porous calcium carbonate slurry prepared in the slurry state is limited to 45.0 to 55.0 wt%.
[Reaction Scheme 2]
Ca (OH) ₂ + additive + CO ₂ → CaCO ₃ + H ₂ O
The method of claim 1, wherein the solid content of the slaked slurry before the carbonation is in the range of 7.0 to 20.0 wt%.
The method of claim 1, wherein the stirring speed of the carbonation is controlled at 30 to 50 rpm.
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