JP2002003219A - Highly concentrated calcium carbonate slurry and method for manufacturing it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide highly concentrated and low viscous calcium carbonate slurry whose viscosity dose not increase with the passage of time without unnecessarily increasing the amount of added anion surfactant when it is used as filler for papermaking and painting and the process is simplified and high productivity and its cost is low-priced and a producing method for it. SOLUTION: Highly concentrated low anionic calcium carbonate slurry with time-stable viscosity is produced by a method in which the dehydrated cake 17 is obtained by mechanical dehydration of calcium carbonate slurry 16 obtained by reacting carbonic acid gas 12 with milk of lime 15, and moreover, the crushed dehydrated cake 17 put into the dispersing device 9 is added with an anion surfactant such as disperse material 20 and water-soluble natural polymer such as sub additive 21, mixed, dispersed and modulated desirable solid concentration with water in the concentration adjustment bath 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-concentration calcium carbonate slurry which can be used as an inner filler for papermaking and a material for coating, has a high concentration and good flow properties, has a low viscosity and has stability over time. The present invention relates to the manufacturing method.

[0002]

2. Description of the Related Art In a conventional papermaking process for neutral paper, there has been known a method of using calcium carbonate as an inner filler in order to improve paper quality. This calcium carbonate is roughly classified into a means of mechanically pulverizing natural white limestone by a dry method or a wet method, and a means of chemically synthesizing it. Have been. Among them, synthetic calcium carbonate is also called light calcium carbonate, and is produced by a carbon dioxide gasification method in which carbon dioxide is blown into lime milk to cause a reaction.

[0003] Calcium carbonate as a papermaking filler manufactured by a maker is supplied to a user as a dried fine powder, a dehydrated cake or a slurry. Is used by dispersing it by adding water to give the required concentration and applying mechanical energy, and in the case of a slurry, it is diluted to the required concentration and mixed with pulp and other necessary components. It is used as a papermaking raw material.

In the case of supplying to a user as a slurry, it is advantageous to reduce the volume by increasing the concentration as much as possible from the viewpoint of transportation and storage. However, when the slurry of synthetic calcium carbonate is concentrated, the viscosity sharply increases. As a result, there is a problem in that transfer and handling are inconvenient when used as a filler in papermaking, and the concentration and viscosity of the slurry are mutually contradictory technical problems.

[0005] In the papermaking industry, the advantage of neutral papermaking using calcium carbonate as compared with conventional talc and sulfuric acid band-based acid papermaking, namely, pulp paper strength retention by alkalization of the system, reduction of machine corrosivity, closeness of white water. , Water saving,
The transition to neutral papermaking is progressing from various viewpoints of quality and user needs, such as reduction of drainage cost, improvement of weather resistance, strength, opacity, bulk, whiteness, printability by neutralization of paper, etc. Calcium is consumed in large quantities in the paper industry as a pigment and filler to meet its requirements.

On the other hand, from the viewpoint of how to manufacture and handle calcium carbonate at low cost, a product in the form of a dry fine powder or a dehydrated cake is packed in a bag, and the bag is unpacked before use to obtain an aqueous dispersion slurry having an appropriate concentration. From a handling state in which the slurry is transported in the form of a slurry having a solid content of about 30% without adding an anionic surfactant, and then diluted with water to obtain a proper concentration for use. Means for rationalizing the transport mode and reducing costs on the user side by handling calcium in a high-concentration slurry have been proposed.

[0007] In order to form a high concentration slurry of calcium carbonate, an anionic polyelectrolyte is added to calcium carbonate, and the anionic polyelectrolyte is adsorbed on the surface of calcium carbonate, and the ionic surfactant is reduced to a static concentration. A steric repulsion occurs due to the superposition of the electrorepulsion and the polymer adsorption layer, resulting in a high-concentration calcium carbonate slurry. The high-concentration calcium carbonate slurry is required to have fluid characteristics satisfying handling and use characteristics without impairing the basic physical properties of calcium carbonate.

[0008]

However, the conventional technology for making a high-concentration calcium carbonate slurry has a solid content of 9 to 9%.
Since the 21% by weight calcium carbonate slurry reaction solution is subjected to low-load solid-liquid separation and concentration by a filter press, belt press, or the like, the productivity is low, the process is complicated, and the amount of anionic surfactant added is large. There is a problem that the cost rises, and there is a problem that the viscosity of the obtained high-concentration calcium carbonate slurry increases to 200 centipoise (cps) or more over time.

Specifically, the solid content is 9 to 21% by weight.
Mechanically solid-liquid separation and concentration of the calcium carbonate slurry of
The addition of 0.3 to 0.1% by weight of the anionic electrolyte based on the solid content, including the solid content of 50% by weight or more and the viscosity at that time of 200 centipoise or less, It is difficult to secure the viscosity stability over time over a period of time. The degree of this is that the viscosity of a slurry obtained by slurrying a cake treated with a normal centrifugal effect of 700 or more in a centrifuge is 200 centipoise or more at 60% by weight. It has a high viscosity and is difficult to use as a filler for papermaking.

With respect to the solid content of calcium carbonate, if the anionic electrolyte is set in the high-addition region, the viscosity of a high-concentration slurry becomes higher with the lapse of time even if the viscosity of 200 centipoise or less is satisfied. Can not be obtained. In addition, since it contains a large amount of anionic electrolyte, when it is used as a filler for neutral papermaking, the potential of the papermaking system shifts significantly to the negative side, deviating greatly from the appropriate potential for papermaking, causing the pigment to be removed from the pulp. As a result, the papermaking system circulating raw material increases, resulting in uneven distribution of the raw material and an increase in the difference between the front and back sides, poor dewatering, adverse effects of pitch slime, and poor quality per unit cost of added chemicals. There is a problem that it does.

Japanese Patent Publication No. 7-107239 discloses that a spindle-shaped calcium carbonate-containing aqueous suspension having a maximum solid content of 33% by weight is dehydrated in two stages by a specific means, and then dispersed by adding a low viscosity agent. There is disclosed a method for preparing an aqueous slurry having a high concentration of 50% by weight or more and a viscosity at 20 ° C. of 1000 centipoise or less and having good fluidity by treating to form a slurry. However, before a high-concentration slurry containing 50% by weight or more of calcium carbonate was used, a centrifugal separator could not be used as a solid-liquid separation / concentration operation to reduce the viscosity. In this method, solid-liquid separation and concentration are performed in two steps, and there is a problem that the process becomes complicated and the cost is increased. In addition, even when the amount of the anionic polymer surfactant is low, for example, 0.2 to 0.3% by weight, the viscosity becomes 400 centipoise or more, and there is a problem in stability with time.

Anionic surfactant is added to the centrifugally dehydrated cake in an amount of 0.5 to 0.25% by weight based on the solid content of the cake to reduce the viscosity of the slurry of 60% by weight high-concentration calcium carbonate to 200 centipoise or less. And there is a problem that a thickening phenomenon occurs over time. Further, anionic surfactant is added in an amount of 0.15 to
In the low addition region where 0.25% by weight is added, there is a problem that low viscosity stability cannot be ensured.

The slurry immediately after the calcium carbonate reaction is treated with 0.3 to 1.0% by weight of an anionic surfactant as a surface treatment agent, and then 0.5% of the anionic surfactant is added as a post-treatment of the dehydrated cake. There is a method of adding ス ラ リ ー 1.5% by weight to form a slurry (see Japanese Patent Application No. 51-100068). However, this method has a disadvantage in that the amount of anion added is too large and cost is low. The anion potential becomes high as a filler, and is not suitable for practical use.

A method is also known in which two kinds of calcium carbonates having different particle size distributions are blended, and an anionic polymer dispersant and an inorganic electrolyte are blended and added thereto (Japanese Patent Application No. 56-69140). ), The dispersant addition amount is high, the strong anion potential is high, the operation is complicated, and it cannot be said that it is advantageous from the viewpoint of cost, and there is a problem in the retention when used as an inner filler.

On the other hand, in an aqueous dispersion of precipitated calcium carbonate comprising precipitated calcium carbonate, water, a polymeric carboxylic acid, or an alkali salt thereof, an Sr salt, a Ba salt, or both of them are added and mixed with vigorous stirring. To obtain a high concentration calcium carbonate slurry. The particle size distribution (Dp) is in the colloid range of 0.2 to 0.44 μm, and means for use in paper and coating are known (see Japanese Patent Application No. 57-176796). Has a large amount of dispersant added and cannot be used as a filler for papermaking.

Further, the particle size distribution (Dp) is 0.05 to 1 μm
After adjusting the pH of the precipitated calcium carbonate of 45 to 60% by weight to 10 or more, adding sodium hexametaphosphate to the mixture, kneading, heating and ripening, lowering the pH to 9.8 or less, and adding 0.2% water. Magnesium oxide Mg (OH) ₂
There is a method of obtaining a paste of low-concentration high-concentration calcium carbonate by adding the same (see Japanese Patent Publication No. 55-51851).
This method has complicated processes such as aging and heating, and has disadvantages in productivity and cost. When this calcium carbonate paste is used as a filler for papermaking, in addition to the high cation equivalent weight value of sodium hexametaphosphate, the number of added parts is high, and it is also used for retention as a filler for papermaking. There's a problem.

Therefore, the present invention solves the above problems,
As a filler and coating material for papermaking, the process is simplified, the productivity is high, the cost is reduced without unnecessary increase in the amount of anionic surfactant added, and high concentration calcium carbonate is used. An object of the present invention is to provide a high-concentration and low-viscosity calcium carbonate slurry in which the viscosity of the slurry does not increase with time and a method for producing the same.

[0018]

According to the present invention, in order to achieve the above object, a calcium carbonate slurry is dehydrated by a mechanical dehydrating means into a dehydrated cake, and an anionic surfactant is added to the dehydrated cake as a dispersant, and Add one or more selected from water-soluble natural polymers, natural polymer compound derivatives, water-soluble anion polymers, synthetic low anion polymers, and synthetic water-soluble polymers as additives.
Disclosed is a high-concentration calcium carbonate slurry having a solid content concentration of 50% by weight or more and a viscosity of 200 centipoise or less and low anionicity and low viscosity stability over time, and a method for producing the same.

Specifically, a polymer type polymer system, a polycondensation type,
Anionic surfactants such as copolymerized high molecular weight polymers are added in an amount of 0.
001% by weight polydiallyldimethylammonium chloride 2 to 10 ml / g · DryS
The present invention provides a configuration in which an equivalent amount of olidCaCO ₃ is added, and a configuration in which the cation equivalent of the auxiliary additive has an anionic strength of 70% or less of the anionic surfactant as a dispersant.

Further, a structure in which the dewatered cake is crushed and then put into a disperser, and as a mechanical dewatering means, a centrifuge, a filter press, a belt press, a leaf filter, a centrifugal sedimenter,
Provided is a structure using mechanical solid-liquid separation means such as a continuous Oliver filter.

According to the high-concentration calcium carbonate slurry and the method for producing the same, the production process is simplified, the productivity is high, and the unnecessary amount of the anionic surfactant is prevented from increasing unnecessarily, thereby reducing the cost. And a high-concentration, low-viscosity calcium carbonate slurry that is optimal as a filler for papermaking and a material for coating by preventing viscosity from increasing over time is provided.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Specific embodiments of a high-concentration calcium carbonate slurry and a method for producing the same according to the present invention will be described below. The present inventor can obtain a high-concentration calcium carbonate slurry even when the amount of the anionic surfactant as a dispersant for the calcium carbonate slurry is reduced, and is stable in quality and satisfactory in productivity and cost. As a result of elaborate research to obtain a product, a conventional anionic high-molecular-weight polymer was added to a high-load solid-liquid dewatering treatment cake having a centrifugal effect of 700 to 1000 in a centrifugal separator of 0.3 to 0.1.
The water-soluble natural polymer substance (plant-based, animal-based, microbial-based, polysaccharide derivative, protein derivative) or low-anion synthetic polymer-based substance is added at
It has been found that a method for producing high-concentration calcium carbonate which can satisfy long-term stability of productivity, flow characteristics and viscosity can be established by adding mechanical energy by adding 0.1 to 0.1% by weight. . Therefore, the present invention is applicable to high-load solid-liquid separation and low-load solid-liquid separation.

More specifically, the calcium carbonate slurry is dehydrated by mechanical dehydration means to form a dewatered cake, and the dewatered cake has an anionic surfactant as a dispersant, and a water-soluble natural polymer or natural polymer as a secondary additive. A solid concentration of 5 obtained by adding, mixing, and dispersing one or more compounds selected from a compound derivative, a water-soluble anion polymer, a synthetic low anion polymer, and a synthetic water-soluble polymer.
It is characterized in that a high-concentration calcium carbonate slurry having a concentration of 0% by weight or more and a viscosity of 200 centipoise or less and having low anionicity and low viscosity stability over time is obtained.

The method for producing a high-concentration calcium carbonate slurry according to the present invention will be described with reference to the flowchart of FIG. First, as main components, 1 is limestone as a raw material, 2 is coke, 3 is a pyrolysis furnace, 4 is a hydroxylation reactor, 5
Is a reaction tower, 6 is a centrifuge, 7 is a crusher, 9 is a disperser,
Reference numeral 10 denotes a concentration adjusting tank, and 11 denotes a product tank.

According to such a configuration, first, limestone 1 and coke 2 as raw materials are charged into the pyrolysis furnace 3 and coke 2
By the heat of combustion, quicklime 13 (CaO: 95% or more) is obtained. The quicklime 13 is put into the hydroxylation reactor 4 and water 14 is added to obtain lime milk 15 (calcium hydroxide, Ca (OH) ₂ ).

The lime milk 15 is put into the reaction tower 5 and reacted with the carbon dioxide gas 12 generated from the pyrolysis furnace, and subjected to a carbonation reaction to form a calcium carbonate slurry 16 (CaCO 2).
₃ ) is obtained. The calcium carbonate slurry 16 is put into the centrifugal separator 6 and centrifuged to be separated into a dehydrated cake 17 and a filtrate 18. The filtrate 18 is concentrated by a concentration tank 18a to concentrate solids, the supernatant and clear water are treated by a discharge 19, and the concentrated slurry is a calcium carbonate slurry 1
Return to 6.

Next, the dewatered cake 17 is put into the disintegrator 7 and sufficiently disintegrated. In the disperser 9, a dispersant 20 of an anionic surfactant and a water-soluble natural polymer, a natural polymer compound derivative, a water-soluble anion polymer, a synthetic low anion polymer, and a synthetic water-soluble polymer were selected. One or a plurality of sub-additives 21 are added using the metering pumps P ₁ and P ₂ , respectively, and the crushed dehydrated cake 1 is added.
7 and sufficiently mixed and dispersed. Transferred to a concentration adjusting tank 10 then dispersed slurried slurry using pump P _3,
Water 14 was added to adjust the concentration, as high concentration calcium carbonate slurries, comprising a ship 22 and stored in the product tank 11 by means of a pump P _4. In addition, water 14
When adding a preservative, the quality can be stabilized by adding a preservative.

Limestone 1 (CaCO ₃ ) is converted to quicklime 13 (C
aO) and carbon dioxide 12 (CO ₂ ).
3 (CaO) reacted with water to make lime milk 15 (Ca (OH)
₂ ), the reaction formula up to the calcium carbonate slurry 16 (CaCO ₃ ) by adding and reacting the carbon dioxide gas (CO ₂ ) 12 is as follows. CaCO ₃ → CaO + CO ₂ ↑ CaO + H ₂ O → Ca (OH) ₂ Ca (OH) ₂ + CO ₂ → CaCO ₃ + H ₂ O

In the above-mentioned production process, one of the features of the production method is to carry out a step of dewatering the calcium carbonate slurry 16 by the centrifugal separator 6, and then crushing and dispersing.
The obtained high-concentration calcium carbonate slurry has a solid content concentration of 50% by weight or more, a low viscosity of 200 centipoise or less, and is characterized by low anionicity and stability over time.

[0030] Here, described with respect to the characteristics of the calcium carbonate slurry 16, the particle size distribution or particle size particle size distribution of less than D ₅₀ median diameter 2μm by sedimentation according sedimentation synthetic calcium carbonate synthesized under certain conditions And a dewatered cake 17 obtained by dewatering with a centrifugal separator 6. In addition, centrifuge 6
Alternatively, mechanical solid-liquid separation means such as a filter press, a belt press, a leaf filter, a centrifugal sedimenter, and a continuous Oliver filter may be used.

The size of the dewatered cake 17 to be crushed by the crusher 7 is not particularly limited, but the dewatered cake 17 is prevented from being clogged at the inlet of the disperser 9 and the residence time in the disperser 9 is shortened. It is required to enhance the productivity and the energy saving effect, and to reduce the concentration standard deviation value by eliminating the dispersion of the concentration in the concentration adjusting tank 10.

The solid content of the dewatered cake 17 in the dispersing machine 9 is set to 65% by weight to 70% by weight.
7. Dispersant 2 comprising anionic surfactant as dispersant
0 and a secondary additive 21 such as a water-soluble polymer are added, mechanical energy is applied by mixing to form a dispersion slurry, and then the slurry is transferred to the concentration adjusting tank 10, and water 14 is added to the target concentration and stirred. As a result, a high-concentration calcium carbonate slurry is obtained. The reason for adjusting the slurry concentration by adding the water 14 has a meaning in conforming to the delivery standard required by the user, and is a factor for improving the running concentration stability.
In terms of cost, the higher the concentration of the slurry, the more advantageous.

As a means for applying mechanical energy to a high-concentration slurry, a straight cylinder type turbine specification disper, a homomixer, a sand turbo, a flow jet mixer, a speed mixer and the like can be used.

As the dispersant 20, an anionic surfactant such as a polymerizable polymer, a polycondensation polymer, or a copolymer polymer is used in an amount of 2 to 10 ml in terms of 0.001% by weight of a polydiallyldimethylammonium chloride cation. / GD
rySolidCaCO ₃ equivalent amount is added, and a water-soluble natural polymer or a water-soluble low anionic polymer polymer or the like is further added as an auxiliary additive 21 in an amount of 0.001 to 0.1% by weight based on the solid content of calcium carbonate. By applying mechanical energy, a high-concentration calcium carbonate slurry of 50% by weight or more can be obtained.

In the high-concentration calcium carbonate slurry system, calcium ions ionized from calcium carbonate are present. When a chelating reaction occurs between the anion of the dispersant and the calcium ions, the function as a dispersant is lost and the viscosity increases. Phenomenon occurs. Therefore, it is necessary to evaluate the viscosity stability by measuring the viscosity of the high-concentration calcium carbonate slurry over time.

The function as a dispersant is exhibited by a three-dimensional structure based on electrostatic repulsion and a molecular structure, a loop, a tail, a train, and a particle crosslinking effect. As a result, a high-concentration calcium carbonate slurry is obtained by containing and fluidizing water between the particles in the system. However, the electrostatic repulsive force of the dispersant decreases due to the chelation reaction with the lapse of time, and the initial viscosity cannot be maintained only by the particle crosslinking effect, and the viscosity gradually increases with the lapse of time. The effect of temporarily lowering the viscosity can be obtained by putting a chelating agent in the system,
When the chelating agent is saturated with cations, a thickening phenomenon occurs again.

Thus, the cation equivalent value of the water-soluble natural polymer, natural polymer derivative water-soluble anionic polymer (CMC-Na), synthetic water-soluble polymer (PVC), and synthetic low anion polymer is mainly dispersed. By adding one or more of the compounds having an anionic strength of 70% or less of the anionic surfactant as the auxiliary agent as a secondary additive, water is retained between the particles and the stability of the slurry is improved. .

As described above, when a synthetic low anionic high molecular weight polymer is added as a secondary additive, or when a natural high molecular weight compound derivative water-soluble anionic high molecular weight compound is added, its cation equivalent weight is 0.001% by weight. % Polydiallyldimethylammonium chloride An additive having a cation equivalent weight value of 70% or less of the main anionic surfactant value is used.

Next, various examples and comparative examples of the present invention will be described in detail.

[0040]

EXAMPLES Example 1 A solid content of 16% by weight and a particle size distribution of 1 μm were obtained by synthesis using a conventional carbon dioxide gasification method.
m> 46.2%, 2 μm> 70.9%, 5 μm <0,5
The calcium carbonate slurry 16 having a 0% diameter of 1.07 μm is centrifuged at a peripheral speed of 73 m / sec and a centrifugal separator 6 having a centrifugal effect of 900.
A sodium polyacrylate anionic surfactant (weight average number of molecules: 6 × 10 ³ ) as a dispersant was added to a cake having a solid content of 65% by weight centrifuged and dehydrated for 0 minute at 0.21% by weight based on the solid content of calcium carbonate. At the same time, a natural polymer polysaccharide-derived cellulose-based sodium carboxymethylcellulose (CMC-Na) as a secondary additive is added in an amount of 0.05% by weight to 0.01% by weight based on calcium carbonate, and a high-speed disperser 9 is used. 26m / sec at 10
For a minute, mechanical energy was applied, and water 14 was added to the obtained calcium carbonate solids concentration of 62.7% to 64.4% by weight to prepare a 60.3% by weight calcium carbonate slurry. Table 1 shows the change over time in the viscosity.

[0041]

[Table 1]

According to Table 1, CMC- as an auxiliary additive
In the case where Na is not added, the initial viscosity (0 hour) is 4
When the viscosity is 800 centipoise and the viscosity after 800 hours, that is, after about 33 days, is 1000 centipoise, when CMC-Na is added as an auxiliary additive by 0.05% by weight based on calcium carbonate, the initial viscosity is increased. Is 76 centipoise, and the viscosity after 800 hours is 48 centipoise. Similar results are obtained in cases where other CMC-Na is added at 0.025% by weight and 0.01% by weight.

Example 2 16% by weight used in Example 1
The calcium carbonate slurry is centrifugally dehydrated for 10 minutes by a centrifuge 6 having a centrifugal effect of 900 at a peripheral speed of 73 m / sec and a sodium polyacrylate polymer anionic surfactant is used as a dispersant in the obtained cake having a solid content of 65% by weight. (Weight-average molecular number 6 × 10 ³ ) per calcium carbonate solid content of 0.
22 and 0.23 and 0.25% by weight, respectively, and in addition to each of the sodium polyacrylate polymer anionic surfactant-added samples, 0% of the plant-based natural polymer dextrin was added as an auxiliary additive. .05, 0.10
% By weight, and a peripheral speed of 26 m / sec with a high-speed dispersing machine 9.
Mechanical energy was applied for 10 minutes, and water 14 was added to the obtained calcium carbonate slurry to prepare a 60.3% by weight high-concentration calcium carbonate slurry. Table 2 shows the change over time in the viscosity.

[0044]

[Table 2]

According to Table 2, in the case where the plant-based natural polymer dextrin was not added as an auxiliary additive for each sample, the initial viscosities (0 hours) were 270 centipoise, 180 centipoise, and 170 centipoise, respectively. Viscosity after 180 hours is 600 centipoise, 4
In contrast to 70 centipoise and 340 centipoise, when 0.05 or 0.10% by weight of a plant-based natural polymer dextrin as an auxiliary additive was added, the viscosity after a lapse of a predetermined period of time was low. It can be seen that the stability is good.

Example 3 A sodium polyacrylate polymer anion was used as a dispersant for a dehydrated cake having a solid content of 65% by weight by solid-liquid separation of the same calcium carbonate slurry as in Example 1 under the same conditions as in Example 1. The surfactant (weight average molecular number: 6 × 10 ³ ) is added in an amount of 0.1% per solid calcium carbonate.
21% by weight, and polyvinyl alcohol (PVA) as an auxiliary additive in an amount of 0.01, 0.05, 0.10
% By weight, and a peripheral speed of 26 m / sec with a high-speed dispersing machine 9.
Mechanical energy was applied for 10 minutes, and water 14 was added to the obtained calcium carbonate slurry to prepare a 60.2% by weight high concentration calcium carbonate slurry. Table 3 shows the change over time in the viscosity.

[0047]

[Table 3]

According to Table 3, by adding 0.01, 0.05, and 0.10% by weight of PVA as an auxiliary additive, the viscosity after a lapse of a predetermined time was increased in the same manner as in Examples 1 and 2. Low and good stability over time.

[Example 4] A sodium polyacrylate polymer anion was used as a dispersant for a dehydrated cake having a solid content of 65% by weight by solid-liquid separation of the same calcium carbonate slurry as in Example 1 under the same conditions as in Example 1. The surfactant (weight average molecular number: 6 × 10 ³ ) is added in an amount of 0.1% per solid calcium carbonate.
21% by weight, together with 0.01% by weight of a plant-based natural high molecular weight pectin (made of apple or citrus) as an auxiliary additive per solid calcium carbonate for each sample
Then, mechanical energy was applied for 10 minutes at a peripheral speed of 26 m / sec by a high-speed dispersing machine 9, and water 14 was added to the obtained calcium carbonate slurry to prepare a 60.3% by weight high-concentration calcium carbonate slurry. Table 4 shows the change over time in the viscosity.

[0050]

[Table 4]

According to Table 4, it was found that the viscosity after a lapse of a predetermined time was low and the stability with time was good by adding a plant-based natural polymer pectin as an auxiliary additive.

Example 5 A sodium polyacrylate polymer anion interface was used as a dispersant for a 65% by weight solids dehydrated cake obtained by solid-liquid separation of the same calcium carbonate slurry as in Example 1 under the same conditions as in Example 1. The activator (weight average molecular number 6 × 10 ³ ) is added in an amount of 0.2 per solid calcium carbonate.
1% by weight, together with a cation equivalent of 0.3 and 0.5 with respect to the cation equivalent of the sodium polyacrylate anionic surfactant as a dispersant. A polycarboxylic acid type anionic surfactant and a polysulfonate type anionic surfactant as additives were added in an amount of 0.01% by weight and 0.05% by weight, respectively, based on the solid content of calcium carbonate. Peripheral speed 2
6 m / sec, mechanical energy was applied for 10 minutes, and water 14 was added to the obtained calcium carbonate slurry to obtain 60.1
High-concentration calcium carbonate slurry diluted to 60.2% by weight was prepared. Table 5 shows the change over time in the viscosity.

[0053]

[Table 5]

According to Table 5, the viscosity after a lapse of a predetermined time was low, regardless of whether a polycarboxylic acid type anionic surfactant or a polysulfonate type anionic surfactant was used as a secondary additive. Is good.

Example 6 The calcium carbonate slurry having a solid content of 16% by weight obtained in Example 1 was vacuumed to 310 t.
orr Nutsche suction-solid-liquid separation, and the obtained solid content of 40% by weight cake is further subjected to an electric dryer at 65% by weight of solid content.
The resulting cake was added with a sodium polyacrylate anionic surfactant having a weight-average molecular weight of 6 × 10 ³ as a dispersant, 0.21% by weight based on the solid content of calcium carbonate, and a peripheral speed of 13 m / sec. A dispersion treatment of 10 minutes was performed to obtain a high-concentration calcium carbonate slurry having a solid content concentration of 64.6% by weight, and water 14 was further added to prepare a high-concentration calcium carbonate slurry having a solids concentration of 60.3% by weight. did. As shown in Table 6, the viscosity was 303 centipoise.

[0056]

[Table 6]

Similarly, when slurrying with a disper, 0.01% by weight of natural polymer polysaccharide cellulose-based sodium carboxymethylcellulose is added to calcium carbonate as an auxiliary additive to form a slurry, and water 14 is further added. The solid content concentration was adjusted to a high concentration calcium carbonate slurry of 60.4%. At that time, the viscosity was 50 centipoise. On the other hand, centrifugal effect 900, peripheral speed 73m
/ Sec by centrifugal dehydration with a centrifugal separator 6 for 10 minutes. The resulting dehydrated cake having a calcium carbonate solid content of 65% by weight is used as a dispersant as a dispersant and has a sodium polyacrylate polymer anion interface having a weight average molecular weight of 6 × 10 ^3. An activator was added in an amount of 0.23% by weight based on the solid content of calcium carbonate, and a peripheral speed of 13% was added.
Water 14 was added to a 64.8% by weight solids calcium carbonate slurry obtained by dispersing at m / sec for 10 minutes to obtain a high-concentration calcium carbonate slurry having a solids concentration of 60.1% by weight. The viscosity at that time was 1090 centipoise as shown in Table 6.

Comparative Example 1 The calcium carbonate slurry having a reaction solid content of 16% by weight obtained in Example 1 was rotated at a peripheral speed of 73 m.
/ Sec, centrifugal dewatering with a centrifuge having a centrifugal effect of 900 for 10 minutes, and dispersing a sodium polyacrylate polymer anionic surfactant having a weight average molecular weight of 6 × 10 ³ as a dispersant into a cake having a solid content of 65% by weight. 0.21, 0.22, 0.23, 0.24, 0.
25 wt% and the number of added parts were varied, and the peripheral speed was 2
6 m / sec, mechanical energy is applied for 10 minutes, and water 14 is added to the obtained calcium carbonate slurry to obtain a high-concentration calcium carbonate slurry having a solid content of 60.1% by weight to 60.3% by weight. Was measured over time. Table 7 shows the results.

[0059]

[Table 7]

According to Table 7, when the sodium polyacrylate polymer anionic surfactant was added in an amount of 0.21% by weight based on the solid content of calcium carbonate, the initial viscosity was 4%.
It is a considerably high value of 06 centipoise. It can be seen that in the other variation examples, although the viscosity is low, the stability over time is not good.

Comparative Example 2 The calcium carbonate slurry having a reaction solid content of 16% by weight obtained in Example 1 was rotated at a peripheral speed of 73 m.
/ Sec, centrifugal dewatering with a centrifuge having a centrifugal effect of 900 for 10 minutes and a sodium polyacrylate anionic surfactant having a weight-average molecular weight of 6 × 10 ³ added to a 65% by weight solid content cake obtained by solidification of calcium carbonate 0.2 for
2% by weight and 0.23% by weight were added.
Mold, sodium polydithiocarbamate, sodium tripolyphosphate, and sodium hexametaphosphate alone were added in an amount of 0.05% by weight and 0.10% by weight based on the solid content of calcium carbonate, followed by a dispersing treatment at a peripheral speed of 26 m / sec for 10 minutes. Water 14 was added to the obtained calcium carbonate slurry to obtain a high-concentration calcium carbonate slurry having a solid content concentration of 60% to 60.3% by weight, and a change in viscosity over time was measured. Table 8 shows the results.
Shown in

[0062]

[Table 8]

According to Table 8, it can be seen that even if Na zeolite type, sodium polydithiocarbamate, sodium tripolyphosphate, and sodium hexametaphosphate are added, the viscosity varies and the stability over time of the viscosity is not good.

[0064]

As described in detail above, according to the present invention, the process is simplified, the productivity is high, and the cost can be reduced without unnecessarily increasing the amount of anionic surfactant added. A high-concentration, low-viscosity calcium carbonate slurry and a method for producing the same, which prevent the viscosity of the high-concentration calcium carbonate slurry from increasing with time and are optimal as a filler for papermaking and a coating material Can be provided.

In particular, as in the conventional high-concentration calcium carbonate slurry technology, the solid content of calcium carbonate is mechanically solid-liquid separated and concentrated so that the solid content is 50% by weight or more and the viscosity is 20%.
It is difficult to maintain viscosity stability over time for a slurry with a density of 0 centipoise or less, and a high-concentration slurry obtained by a centrifugal separator high-load dewatering method is used for low-load filtration such as a filter press. Compared to the system, in the anion electrolyte low addition region has a much higher viscosity and is difficult to use as a papermaking filler,
The method for producing a high-concentration calcium carbonate slurry according to the present invention has a viscosity of 200
In addition to satisfying centipoise or less, the viscosity does not increase over time, and the potential of the papermaking system is prevented from greatly shifting to the negative side even when used as a filler. Taste is enhanced. In addition, factors that adversely affect quality and cost, such as uneven distribution of raw materials, increase in front-back differences, poor dewatering, pitch slime, and poor basic unit consumption of added chemicals due to an increase in circulating raw materials for papermaking are eliminated.

From the viewpoint of the production method, according to the conventional technique, when the synthetic calcium carbonate synthesized by the carbon dioxide gasification method is converted into a high-concentration slurry, it is subjected to a solid-liquid dehydration treatment under the effect of a high centrifugal effect to carry out polymerization and heavy polymerization. By adding a condensation type or copolymerization type polymer anionic surfactant and applying mechanical energy, even if a high-concentration slurry can be obtained, the viscosity becomes excessively high, and the viscosity increases with time and the pump is transferred. There is a problem that handling operation such as liquid storage cannot be performed,
The present invention easily and efficiently dehydrates calcium carbonate obtained by a carbon dioxide gasification method or the like, and adds a low number of polymerization type, copolymerization type, polycondensation type polymer anionic surfactants and water solubility. A cationic equivalent weight of 70 compared to a natural polymer and a natural polymer compound derivative, a water-soluble anionic polymer, or an anionic surfactant as a dispersant.
% Of a high-concentration calcium carbonate slurry having high concentration, low viscosity, and excellent stability over time by adding a small amount of an anionic polymer compound having a% value or less and applying mechanical energy. .

[Brief description of the drawings]

FIG. 1 is a flowchart showing a method for producing a high-concentration calcium carbonate slurry according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Limestone 2 ... Coke 3 ... Pyrolysis furnace 4 ... Hydroxidation reactor 5 ... Reaction tower 6 ... Centrifuge 7 ... Crusher 8 ... Measuring device 9 ... Disperser 10 ... Concentration adjustment tank 11 ... Product tank 12 ... Carbon dioxide Gas 13: Quicklime 14: Water 15: Lime milk 16: Calcium carbonate slurry 17: Dehydrated cake 18: Filtrate 18a: Concentrating tank 20: Dispersant 21: Secondary additive Reference number P3074

Claims (7)

[Claims] 1. A calcium carbonate slurry is dehydrated by mechanical dehydration means to form a dewatered cake, and an anionic surfactant is used as a dispersant and a water-soluble natural polymer or natural polymer compound derivative is used as a secondary additive. One or more selected from a conductive anionic polymer compound, a synthetic low anionic polymer polymer, and a synthetic water-soluble polymer are added and mixed and dispersed to obtain a solid content concentration of 50% by weight or more and a viscosity of 200%. A high-concentration calcium carbonate slurry characterized by being not more than centipoise. 2. The high-concentration calcium carbonate slurry according to claim 1, which has low anionicity and low viscosity stability over time. 3. An anionic surfactant, such as a polymerizable polymer, a polycondensation polymer, or a copolymer polymer, is used in an amount of 0.001% by weight of a polydiallyldimethylammonium chloride cation equivalent of 2 to 10 ml / g. DrySolidC
ACO ₃ added in an amount corresponding to claim 1 or 2 high-concentration calcium carbonate slurry according. 4. The high-concentration calcium carbonate slurry according to claim 1, wherein the secondary additive has an anionic strength of not more than 70% of that of the anionic surfactant which is a dispersant. 5. A calcium carbonate slurry is dehydrated by a mechanical dehydration means to obtain a dehydrated cake, and the dehydrated cake is charged into a dispersing machine, and an anionic surfactant is used as a dispersant, and a water-soluble natural The solid content concentration is 5 by adding and mixing and dispersing one or more selected from a molecule, a natural polymer compound derivative, a water-soluble anion polymer, a synthetic low anion polymer, and a synthetic water-soluble polymer.
A method for producing a high-concentration calcium carbonate slurry, characterized by obtaining a high-concentration calcium carbonate slurry having 0% by weight or more and a viscosity of 200 centipoise or less and having low anionicity and stability over time. 6. The method for producing a high-concentration calcium carbonate slurry according to claim 5, wherein the dehydrated cake is put into a disperser after being crushed. 7. The mechanical dewatering means according to claim 5, wherein a mechanical solid-liquid separating means such as a centrifuge, a filter press, a belt press, a leaf filter, a centrifugal sedimenter, a continuous Oliver filter or the like is used. A method for producing the high-concentration calcium carbonate slurry described above.