TWI460331B - And a method for producing a slurry of light calcium carbonate by a causticizing step - Google Patents

Description

Method for producing a slurry of light calcium carbonate produced by a causticizing step

The present invention relates to a pulverizer, and more particularly to a blocky light calcium carbonate manufactured by a causticizing step of a pulp manufacturing step by a sulfate method or a soda method and having a calcite crystal structure. In the case of pulverization or the like, a pulverization method of a media agitating wet pulverizer having an effective L/D ratio of more than 0.6 and 1.2 or less is used.

In recent years, there has been a high demand for high-quality lightweight coated paper having high whiteness, high opacity, and high gloss. In order to comply with such requirements, in the coating pigment of high-quality lightweight coated paper, in addition to inorganic pigments such as kaolin, heavy calcium carbonate, and light calcium carbonate, expensive titanium dioxide or plastic pigments may be blended.

The calcium carbonate used for the coating pigment is very expensive to improve the blending ratio in the coating, and the whiteness or opacity of the coated paper can be improved, but the gloss of the white paper is remarkably lowered. Therefore, in order to carry out high-adjustment, in order to improve the glossiness of white paper, it is generally micronized by wet pulverization. However, in order to increase the amount of the dispersant to be added to the microparticulation system, it is necessary to pulverize for a long period of time, so that the production cost of the pigment becomes high.

In general, the pulverization method of the heavy calcium carbonate is filled with a pulverization medium (beads) inside the pulverization container, and a slurry in which the pulverized material is mixed with the liquid, and the rotating shaft of the center of the pulverizing container is rotated to make the beads and the quilt A device (grain grinder) in which the pulverized material collides and is finely pulverized. In the past, a horizontal type grain grinding machine in which a slurry processed by a bead mill was accommodated in another tank was used, but coarse particles and ultrafine particles generated by over-grinding were increased, and the particle size distribution after pulverization became no. narrow.

Therefore, it is now common to use a multi-pipe type grain grinding method in which a slurry is rotated between a grain grinder and a circulation tank. In terms of the advantages of the multi-pipe type pulverizer, it is characterized in that coarse particles are reduced and the particle size distribution is narrowed. In particular, a media agitation type wet pulverizer (Patent Document 1) having a L/D ratio of 0.5 or less is a pulverization chamber, and the filling rate of the beads can be suppressed to a very low level, so that it is characterized in that it can be large. The flow cycle runs.

Regarding the pulverization method of the above-mentioned pipe method and multi-pipe method, in order to compare the pulverization performance, after the pulverization of the heavy calcium carbonate under the same conditions by the two methods, the pulverization method of the multi-channel method is narrowed, and good results can be obtained.

In addition, the causticization step of the pulp production step by the sulphate method or the soda method is carried out by causing the quicklime to be washed with water or a weak liquid, and then causticizing the green liquor to produce a causticizing reaction (causticizing method). Light calcium carbonate produced (hereinafter referred to as caustic light calcium carbonate). This calcium carbonate is a by-product of the white liquor of the main product, so that the light calcium carbonate obtained by the method of the reaction of the conventional lime milk and carbon dioxide has a known equipment, and the investment amount of the equipment can be used. The smallest advantage. However, if the high-grade causticized light calcium carbonate is used as a coating pigment, as described above, the gloss of the white paper is remarkably lowered, so that it is necessary to perform micronization by pulverization.

From these matters, the pulverization of the causticized light calcium carbonate slurry is carried out using a media agitating wet pulverizer having a multi-channel type L/D ratio of 0.5 or less. However, the viscosity of the pulverized slurry becomes high, the use amount of the expensive dispersant increases, and the power original unit becomes higher and the cost becomes higher as compared with the pulverization of the heavy calcium carbonate.

Therefore, if a high-quality caustic light calcium carbonate slurry manufacturing technique that suppresses the use of expensive dispersant is developed, a high-quality coarcated light calcium carbonate and a white paper gloss can be highly formulated in the coating. It does not deteriorate and can produce high quality coated paper.

In the pulverization of the causticized light calcium carbonate produced by the causticizing method, even if the above pulverizer was used, good results could not be obtained. Known techniques for pulverizing light calcium carbonate include, for example, Patent Document 2, Patent Document 3, and Patent Document 4. However, in Patent Document 2, a mixture of light calcium carbonate obtained by a carbon dioxide method and heavy calcium carbonate is pulverized, and Patent Document 3 is a mixture of light calcium carbonate and kaolin, which cannot be adapted to causticized light calcium carbonate. Separate crushed and causticized light calcium carbonate mixed with heavy calcium carbonate. Further, Patent Document 4 proposes a high-efficiency pulverization method of light calcium carbonate which is a method in which the pH of the slurry is 8 to 12 when the light calcium carbonate is pulverized, and carbon dioxide is directly blown. Generally, the slurry obtained after the pulverization of causticized light calcium carbonate has a pH of 13 or more, and the slurry concentration is high. Therefore, it takes a long time to neutralize carbon dioxide to pH 12 or lower. Therefore, in the pulverization method in which the slurry is pulverized to a large amount of the target particle diameter between the slurry pulverizer and the circulation tank, carbon dioxide neutralization is insufficient or impossible, and the desired effect cannot be exhibited.

[Patent Document 1] Special Kaiping 10-230182

[Patent Document 2] JP-A-6-41463

[Patent Document 3] Special Opening 2000-110096

[Patent Document 4] Special Opening 2000-239017

In view of the above circumstances, an object of the present invention is to solve the above problems, and to provide a method for performing causticized light calcium carbonate after wet pulverization and pulverization at low cost and with high efficiency.

In order to solve the above problems, in the present invention, by using a media agitation type pulverizing apparatus, the power former unit can be reduced in the production of a causticized light calcium carbonate slurry, and the fluidity can be efficiently atomized in a state of good fluidity. The media agitating type pulverizing apparatus is characterized by comprising a pulverizing container, a cylindrical separator, a stirring member, and a supply port, wherein: the pulverizing container is formed into a cylindrical shape while being blocked at both ends; and a cylindrical separator The inside of the pulverizing container is disposed such that the axis is approximately uniform, and the inner portion is divided into two portions in the radial direction to form the inner chamber and the outer chamber, and at least a part of the circumferential surface is provided between the two chambers. a plurality of slits; a stirring member that is set to be rotatable in a state in which the pulverizing container is approximately aligned with the axis inside the inner chamber; and a supply port for supplying the treatment to the inner chamber; The double rotator has a ratio (L/D ratio) of a length (L) to a diameter (D) in the axial direction of the pulverization container of more than 0.6 and 1.2 or less. The aforementioned L/D ratio is preferably greater than 0.8 and 1.0 or less.

According to the present invention, when the high-concentration slurry of caustic light calcium carbonate is atomized, by forming a double rotor, the effect of pulverizing the medium is improved as compared with the conventional technique, and even at a low speed, the pulverization efficiency can be high. Processing, so the power original unit can be reduced. Further, regarding the physical properties of the ground causticized light calcium carbonate after the pulverization, the specific surface area is small, the viscosity is lowered, and the amount of the expensive dispersant can be reduced.

[Best form for implementing the invention]

Hereinafter, the method of the present invention will be specifically described. The light calcium carbonate of the present invention is produced by a causticizing step of a pulp production step by a sulfate method or a soda method.

[Manufacturing method of light calcium carbonate]

The production method of the light calcium carbonate is known as (1) reaction of a gas containing carbon dioxide obtained from a lime burning apparatus or the like with lime milk, and (2) ammonium carbonate and chlorination in an ammonia soda method. Calcium reaction, (3) The reaction of caustic soda to produce sodium hydroxide and sodium carbonate. Among these methods, (2) and (3) are converted into a production method in which the main product can be obtained, or calcium carbonate is a by-product, so the impurity content is large, and the utilization method is not studied. .

[CO2 method]

One (1) is a relatively simple reaction system (water, slaked lime, and carbon dioxide), and has been extensively studied for the method of producing calcium carbonate for various purposes, and some are commercially available from lime manufacturers. commodity. However, in the direct purchase from the manufacturer, there is a disadvantage that the freight cost is large and the total cost becomes high. Further, in the on-site carbon dioxide method, if the furnace is exhausted, it is possible to produce inexpensive high-quality calcium carbonate, but there is a problem that the equipment investment costs a large amount of money.

[caustic law]

Here, in the pulp production step by the sulphate method or the soda method, the calcium carbonate which is produced as a raw material for papermaking when the white liquor is produced by the causticization step of the recovery and regeneration of the retort drug is used. If this method is used, the existing equipment can be utilized, and the investment amount of the equipment can be minimized.

[causticizing step]

In the pulp production step by the sulphate method or the soda method, the cellulose is separated from wood, and the solution of sodium hydroxide and sodium sulfide is mixed and evaporated under high temperature and high pressure. Then, the cellulose is separated and purified into a solid layer to be a pulp, and the eluted components other than the cellulose of the chemical liquid and the wood are recovered as a pulp waste liquid (black liquor), and concentrated to a concentration at which the boiler can be recovered for combustion. Further, in order to replenish the sodium component and the sulfur component lost in a series of processes, sodium sulfate may be added to recover the boiler. At this time, the organic substance in the black liquor is recovered as a heat source, and the inorganic substance is mainly recovered as sodium carbonate and sodium sulfide. However, these inorganic substances are called smelt and can be taken out from the recovery boiler in a molten state. The smelting system taken out by the recovery boiler is dissolved in water or a weak liquid (a liquid of a white liquid component obtained by washing a calcium carbonate with a trace amount of water) to become a green liquid.

[causticizing reaction]

The causticization step is a step of changing the sodium carbonate in the green liquor to the sodium hydroxide of the distillate, and changing the quicklime to the elimination of the slaked lime (1), and mixing the slaked lime and the green liquor to form a hydroxide The causticization reaction of sodium and calcium carbonate (2). The liquid obtained by the causticization reaction is called white liquor, separated from calcium carbonate, clarified and sent to the distillation step. In the present invention, it is separated and recovered, and fully washed calcium carbonate is used.

CaO+H ₂ O→Ca(OH) ₂ (1): elimination reaction

Ca(OH) ₂ +Na ₂ CO ₃ →CaCO ₃ +2NaOH (2): causticization

[Characteristics of causticizing reaction]

Since the calcium carbonate is a by-product of the white liquid of the main product, the light calcium carbonate obtained by the method of reacting the conventional lime milk with carbon dioxide can be used as the existing equipment, and the equipment investment amount is The smallest advantage. In addition, calcium (lime, slaked lime, calcium carbonate) circulating in the cauterization step of the conventional closed system removes calcium carbonate to the outside of the system, and the purity of the system and the purity of the circulating lime are achieved. (2) The improvement of reactivity or the improvement of the clarification of white liquor is further reduced by waste.

[Dehydration concentration, average particle size]

The light calcium carbonate used in the present invention may be a block or residue which is dehydrated and concentrated by a dehydration device such as a press, suction or centrifugal separation method. Further, the average particle diameter of the bulk light calcium carbonate obtained in the causticization step can be concentrated to a concentration of 73% or more which can be used for the use of the pigment, but is not particularly limited, but is a laser-transmitted particle size distribution. The value of the measuring device (Mastersizer 2000, manufactured by Malvem Co., Ltd.) is preferably 10 to 30 μm, more preferably 10 to 20 μm.

[slurrying]

The method for slurrying the causticized light calcium carbonate wet powder obtained in this manner can be suitably used by a cylindrical container and a rod-shaped stirring arm, and filled with pellets of 3 to 10 mm. An attritor that is stirred while being dispersed and pulverized, or a high-concentration dispersion device equipped with a high-speed stirring blade.

[Dispersant]

Further, the dispersing agent and the dilution water are added once or in a single step, and the viscosity or concentration of the slurry can be adjusted. The dispersing agent to be used in the pigment dispersion liquid is, for example, a polyacrylate or a lignosulfonate which can be used for papermaking, and one or more of these may be used as needed. The average particle diameter of the calcined light calcium carbonate can be arbitrarily adjusted by the bead diameter, the treatment time, etc., and the average particle diameter after the coarse pulverization is a laser-transmissive particle size distribution measuring device (Mastersizer 2000, Malvem). The value of the company system should be 1~30μm, more preferably 1~10μm. The slurry concentration after coarse pulverization is preferably 65 to 80%.

Further, in addition to the causticized light calcium carbonate of an indefinite shape, for example, in the case of needle-like or columnar causticized light calcium carbonate, it is also necessary to apply the present invention to the pulverization treatment.

Further, the dispersing agent used in the pigment dispersion liquid may, for example, be a sodium polyacrylate, a sodium lignin sulfonate, a phosphate, or the like which is generally used as a papermaking material, and the like. Use one or more types and use them. The amount of the dispersing agent to be used is preferably 0.7 to 2.0 parts by weight based on 100 parts by weight of the pigment, and more preferably 0.9 to 1.8 parts by weight based on 100 parts by weight of the pigment. The causticized light calcium carbonate is highly alkaline compared with heavy calcium carbonate, and has high agglutination and hydrophobicity. Therefore, not only the viscosity of the pigment dispersion is very high, but also the load of the pulverizer during pulverization is too large, but depending on the situation, The problem of cracking or abrasion of the medium filled in the pulverizer is obvious. Further, since the viscosity of the pigment dispersion liquid rises rapidly depending on the pulverization, it is necessary to use more dispersant than the pulverization of the heavy calcium carbonate.

Further, when the content of the causticized light calcium carbonate in the mixed pigment dispersion of the ground calcium carbonate and the causticized light calcium carbonate is 50% by weight or less, the pulverization can be carried out without using the pulverizer of the present invention. In the present invention, the light calcium carbonate which is supplied to the medium agitating pulverizing apparatus as the light calcium carbonate of the pigment produced in the causticizing step of the pulp production step may contain 50% by weight of the total pigment. More than weight%.

[grinder]

The mixer 1 used in the present invention is a continuous medium agitating wet pulverizer comprising a pulverizing container 2 which is cylindrical and has both ends blocked; and agitating members 18a and 18b. Rotatingly disposed inside the pulverizing container 2, and simultaneously agitating the processing material and the pulverizing medium at the inside of the pulverizing container 2; the cylindrical separator 13 is disposed inside the pulverizing container 2 while the pulverizing container 2 is The internal treatment is separated from the comminution medium.

[Crushing container]

The pulverization container 2 has a cylindrical body 3 having one end blocked, and a disk-shaped cover 6 that closes the other end opening of the container body 3.

A cylindrical duct 4 that communicates with the inside and the outside of the container body 3 at a central portion of the container body 3 is integrally provided, and the inside of the duct 4 rotatably supports the agitating member 18a and the stirring via the bearing 8 Member 18b.

Although not shown in the inside of the container main body 3, an annular groove is provided along the inner peripheral surface, and a portion corresponding to the cover 6 corresponding to the groove is not shown, but an annular groove is provided. Then, at one end of the partition body 13 at a groove position (not shown) of the container body 3, and at the other end of the partition body 13 in the axial direction of the cover 6 (not shown), the cover 6 is not shown in the container. The main body 3 is fixed by a screw or the like to fix the separator 13 to the inside of the pulverizing container 2. Further, the container body 3 and the lid 6 are not provided with a groove, and the separator 13 is fixed in the pulverizing container 2 by another means such as a screw or the like.

The inside of the pulverizing container 2 is divided into two chambers in the radial direction by the partition body 13 to form a circular inner chamber 9 and an annular outer chamber 10. A cylindrical supply port 11 that communicates with the inside and the outside of the inside chamber 9 is integrally provided in the center portion of the cover 6, and the workpiece 11 is supplied to the inside of the inside chamber 9 by the supply port 11. A cylindrical discharge port 12 that communicates with the inside and the outside of the outer chamber 10 is integrally provided in the container body 3, and the processed material from the discharge port 12 through the separator 13 is discharged to the outside of the pulverization container 2.

When the treated material is used as a causticized light calcium carbonate, the L/D of the pulverization container 2 is selected to be greater than 0.6 and 1.2 or less. Further, the length of the L-axis direction is D, and the diameter is D. By setting the L/D ratio to 1.2 or less, 俾 tends to suppress the deflection phenomenon of the medium. Further, by more than 0.6, the range of action of the stirring member 18 can be ensured. Preferably, the L/D ratio is greater than 0.8 and 1.0 or less, and the above respective effects are more remarkable.

[separator]

The separator 13 is composed of a cylindrical inner ring 14, a cylindrical outer ring 15, and a plurality of steel bars 16, 16 provided in a wedge shape between the rings 14 and 15. The steel rod 16 has a large diameter on the inner diameter side, and is disposed at a specific interval between the outer ring 15 and the inner ring 14. Between the inner ring 14 and the outer ring 15, a plurality of steel bars 16, 16 are disposed between the adjacent steel bars 16, 16 from the inner diameter side to the outer diameter side to form wedge-shaped slits which are sequentially increased in size. 17, 17... The inner chamber 9 and the outer chamber 10 are connected to each other via the slits 17, 17 and the like. Further, a plurality of holes penetrating through the slits 17 are formed in the inner ring 14 and the outer ring 15.

Then, as described above, the inner ring 14, the outer ring 15, and the steel bar 16 are combined to form a plurality of slits 17, 17... to ensure a sufficient effective area of the processed material having a large flow rate. Further, each of the slits 17 is formed in a wedge shape in which the interval is gradually increased from the inner diameter side to the outer diameter side, so that the clogging is not caused, and the processed material can be caused to flow to the outer chamber 10 side. Further, the strength during operation can be sufficiently ensured.

In addition, the separator 13 is not limited to the above, and (1) "ensures a sufficient effective area for processing a large flow rate", (2) "no clogging", and (3) "ensures sufficient operation" The constructor of the three conditions of the "time strength" is sufficient.

[Agitating member]

The agitating member 18 has a tubular shape in which one end is blocked, and two agitating members 18a and agitating members 18b are rotatably provided in the inner chamber 9 of the pulverizing container 2 in the cylindrical portion of the agitating member 18. The outer peripheral side covers the entire circumference and covers the concave portion 19 and the convex portion 20 alternately. Each of the recesses 19 is provided with a through hole 21 through which the processed material and the pulverizing medium flow alternately in the inner and outer directions in the radial direction of the stirring member 18. One end of the agitating member 18 is blocked with a plurality of through holes 22. The through holes 22 are arranged at a specific interval in a concentric shape centering on the axis of the stirring member 18, and the workpiece and the pulverizing medium are exchanged between the inside and the outside of the stirring member 18a and the stirring member 18b through the through hole 22. The ground flows.

The inside of the agitating member 18a on the supply port 11 side is located in the dispersing member 25 screwed to the front end of the drive shaft 24, and the dispersing member 25 is also a lock nut.

The head of the dispersing member 25 covers the entire circumference, and the concave portion and the convex portion are alternately provided (not shown), and the concave portion and the convex portion are supplied from the supply port 11 to the inner chamber 9 of the pulverizing container 2, and The pulverizing medium located in the inner chamber 9 is dispersed outward in the radial direction.

Next, the role of the aforementioned ones will be explained. First, the drive shaft is actuated to rotate the drive shaft 24, and the agitating member 18a and the agitating member 18b coupled to the drive shaft 24 rotate, and the dispersing member 25 located at the center of the agitating member 18a also rotates.

Then, when the processed material is supplied from the supply port 11 to the inside of the inner chamber 9 of the pulverization container 2, the processed material is dispersed in the pulverization medium and the outer direction in the radial direction by the dispersion member 25 and the agitation member 18a, and simultaneously The mixture is stirred by the stirring member 18a and the stirring member 18b.

At this time, since the through hole 21 is formed in the cylindrical portion of the agitation member 18a and the agitation member 18b, a strong centrifugal force is applied to the treatment object and the pulverization medium by the through hole 21, and the processed material and the pulverization medium are passed through the through hole. 21 flows on the outer peripheral side of the stirring member 18a and the stirring member 18b.

Then, the processed material and the pulverizing medium which flow on the outer peripheral side of the stirring member 18a and the stirring member 18b are the outer peripheral side of the stirring member 18a and the stirring member 18b, and are the recessed part 19 and the convex part 20 of the stirring member 18a and the stirring member 18b. A strong shearing force is applied to the one end direction or the other end direction of the agitating member 18a and the agitating member 18b in the axial direction, and flows to the inside of the agitating member 18a via the gap between the cap 6 and the agitating member 18a. Further, a part of the stirring member 18b flows into the inside of the stirring member 18b from the through hole 22 through the gap between the stirring member 18b and the container body 3, and a circulating flow is generated between the stirring member 18a and the stirring member 18b along the flow of the series.

Further, the processed material and the pulverized medium are circulated inside the inner chamber 9, and both of them are completely mixed, and the treated material is finely pulverized to a specific particle size. Then, when the treatment material having reached a specific particle size flows on the outer peripheral side of the agitation member 18, it is separated from the pulverization medium by the separator 13, flows into the slits 17 of the separator, and flows to reach the inside of the outer chamber 10 The outer chamber 10 is discharged to the outside of the pulverizing container 2 via the discharge port 12.

In the pulverizer 1 of the embodiment configured as described above, the L/D ratio of the pulverizing container 2 is set to be more than 0.6 and 1.2 or less, preferably more than 0.8 and 1.0 or less, and the inner chamber 9 (pulverized region) is sufficiently ensured. Volume. Therefore, the pulverization efficiency of a conventional single rotator or more can be obtained.

Further, the separator 13 which separates the processed material from the pulverizing medium is formed into a tubular shape to form a plurality of slits 17, and the separator 13 is provided inside the pulverizing container 2 in a state where the axes are approximately coincident, so that it can be secured for processing. A large flow of treatment has a sufficient effective area. Therefore, the flow of the treatment object is not restricted by the separator 13, and it is also possible to cope with the treatment of a large-flow treatment.

Further, since the separator 13 is formed by providing a plurality of steel bars 16 between the inner ring 14 and the outer ring 15, the strength can be sufficiently ensured even when a large flow rate of the processed material is handled. Therefore, it can exert long-term stability performance.

Then, a dispersing member 25 is provided at a central portion of the agitating member 18a, and a through-hole 21 penetrating the inner and outer portions is provided in the cylindrical portion of the agitating member 18a and the agitating member 18b, respectively, and one end of the agitating member 18a and the agitating member 18b is blocked. Since the through hole 22 is penetrated through the inside and the outside, the entire inner chamber 9 can be used to circulate the processed object and the pulverizing medium. Therefore, the portion where the pulverized medium and the workpiece are not located partially inside the pulverization container 2 affects the operation, or the operation becomes difficult, and long-term excellent operation characteristics can be obtained.

[Processing System]

This media agitating wet disperser is used in a processing system as shown in FIG. That is, the processing system 140 connects the disperser 110 to the processing tank 141 and the circulation pump 142 in the circulation line 143. The processed material introduced into the supply tank 141 is circulated by the circulation pump 142, and is circulated by the dispersing machine 110. As a result, the processing is performed on the entire processed material in the system.

[Media fill rate]

Further, the filling rate of the pulverizing medium is preferably only high, but when the filling rate is too high, the effect of the medium in the pulverizing chamber is limited, so that the pulverizing efficiency may be lowered. Therefore, the filling rate of the pulverizing medium should be 70 to 90%, more preferably 75 to 85%.

[rotor rotation number]

Further, the number of rotations of the rotator (stirring member) is preferably only high, but when the number of rotations of the rotator is too high, not only the pulverizer load of the pulverizer is too large, but the medium filled in the pulverizer is used depending on the situation. Cracking or abrasion becomes obvious. Therefore, the outer diameter of the rotating sub-rotating rotor is 196 mm, preferably 700 to 1200 min ^-1 , more preferably 800 to 1000 min ^-1 .

[Manufacture of coated paper]

The causticized light calcium carbonate slurry system thus obtained can be formulated in the coating. In the coating, the pigment obtained in the present invention is added, and calcium carbonate other than the causticized light calcium carbonate obtained by the present invention, kaolin, clay, calcined kaolin, zinc oxide, aluminum hydroxide, titanium oxide and calcium carbonate are added. In addition, one or two or more kinds of inorganic pigments, which are called plastic pigments, may be used as the main component, and the inorganic pigments such as stalt and cerium oxide may be used as the main component. In order to improve the gloss of white paper, etc., it is advisable to use high territory or plastic pigments. The blending amount of the calcium carbonate having the specific physical properties of the present invention is not particularly limited, but in particular, the pigment is contained in an amount of 50 parts by weight or more per 100 parts by weight, and the white paper gloss developability and opacity can be further improved. Further, in addition to the pigment, an adhesive such as starch, polyvinyl alcohol or synthetic polymer latex can be appropriately blended. The amount of the adhesive is preferably 5 to 35 parts by weight based on 100 parts by weight of the pigment. Further, various auxiliary agents generally used, such as a dispersing agent, a thickener, a water retaining agent, an antifoaming agent, and a water resistance agent, may be suitably used as needed. The solid content concentration of the coating is about 20 to 70% by weight, more preferably 45 to 75% by weight.

The base paper used in the present invention contains a chemical pulp such as LBKP or NBKP, a mechanical pulp such as GP, PGW, RMP, TMP, CTMP, CMP, CGP, or an ancient paper pulp such as DIP, such as light calcium carbonate and heavy pulp. Various additives such as calcium carbonate, talc, clay, kaolin, etc., various additives such as a sizing agent, a fixer, a yield agent, a cationizing agent, and a paper strength enhancer are prepared by acid, neutral or alkaline. The base paper of the present invention may be a base paper or the like which is pressed by a sizing such as unsized raw paper, starch or polyvinyl alcohol.

The method of applying the coating material containing the pigment obtained by the present invention to the base paper and providing the coating layer is not particularly limited, and a coating roll layer such as a conventionally known brake roll coater or blade coater can be suitably used. You can set more than one layer.

Coating paper obtained by coating a coating material of the pigment of the present invention, if necessary, using a finishing device such as an ultra calender, a gloss calender, a soft calender, etc., can obtain a white paper gloss excellent coating Cloth paper.

[Examples]

The present invention will be specifically described below by way of examples, but the present invention is not limited thereto. In addition, the "parts" and "%" in the examples are "parts by weight" and "% by weight" unless otherwise stated.

Blocky light calcium carbonate having a solid concentration of 73% manufactured by the causticization step of the Nippon Paper Co., Ltd. plant A. Into a pigment dispersion in which 50 parts of the wet powder and 50 parts of the heavy calcium carbonate pigment dispersion or 100 parts of the bulk light calcium carbonate are mixed, the polyacrylic acid dispersant is added once to 1.6 to 3.6 parts and water. It was coarsely pulverized by a grinder (manufactured by Mitsui Mining Co., Ltd.) to have a concentration of 73% and an average particle diameter of 7 μm. The crude slurry obtained by the treatment in this manner was subjected to a double-rotor type SC grinder LSC 220 (manufactured by Mitsui Mining Co., Ltd.) having a pulverization chamber of 7.4 L, and was supplied in a predetermined amount by a metering pump, and wet-pulverized.

Using a zirconia grain (manufactured by Nikkato Co., Ltd.) having a diameter of 0.5 mm as a medium, the bead filling rate (the volume of the pulverized medium at the time of the most dense filling in the pulverization chamber) is 70 to 90%, and the number of rotations of the rotator is made. of 800 ~ 1000min ^-1, using a horizontal mill or pulverizer abrasive present invention (manufactured by Mitsui mining Co., Ltd.) and pulverized to an average particle diameter of 0.4 ~ 1.0μm. After the pulverization, the slurry concentration was 70%, and the B-type viscosity (60 rpm, manufactured by Tokyo Keiki Co., Ltd.) at 25 ° C was measured. In addition, a 50% point of the cumulative weight distribution was calculated as an average particle diameter using a Mastersizer 2000 (manufactured by Malvem Co., Ltd.), and a particle size distribution was also measured using a Sedigraph (manufactured by Micromeritics). Further, the BET specific surface area was measured using a Micromeritics Gemini 2360 (manufactured by Shimadzu Corporation).

[Paper quality assessment method]

(1) The gloss of white paper was measured at an angle of 75 degrees in accordance with JIS P-8142.

(2) Opacity is measured at an angle of 75 degrees in accordance with JIS P-8138.

(3) Surface strength, the gloss product was printed on a Roland lithographic blade printer (2 colors) using lithographic blade ink (High Unity M), and visually evaluated for surface peeling of the blue monochromatic beta portion. status.

◎: Very good, ○: Good, △: Some difference, ×: Poor

(4) The ink is dropped, and the RI-II type printing machine is used for the atomized product, and the blade process ink (trade name: TK High Echo ink MZ) manufactured by Toyo Ink Manufacturing Co., Ltd. is used in a Macbeth concentration meter using 0.50 to 0.70 cc. The measurement was carried out in such a manner that the concentration became 2.0±0.1, and after being left for a day and night, the printed sample and the white paper were rubbed three times with a load of 400 g for three times, from the low printing to the printing using a fastness tester (Suga test mechanism). The ink concentration of the white paper was visually evaluated. The less the transfer of ink, the higher the effect of preventing ink drop.

◎: No problem with ink transfer

○: There is almost no problem with ink transfer

△: Some problems with ink transfer

×: Some ink transfer problems

(5) Coverability Visually evaluate the unevenness of white paper or uneven gloss.

◎: very good, ○: good, △: slightly worse, ×: poor

[Example 1]

Adding polyacrylic acid to a pigment dispersion containing 50 parts of light calcium carbonate (hereinafter referred to as caustic light calcium) produced by causticizing step and 50 parts of heavy calcium carbonate (tri-eugen fine powder, average particle diameter 13 μm) 1.6 parts of the dispersant were coarsely slurried to an average particle diameter of 7 μm, and then wet-pulverized to a mean particle diameter of 0.4 by a double-rotor type SC grinder LSC 220 at a bead filling rate of 90% and a number of revolutions of 800 min ^{-1 .} Mm. At that time, the original unit was 165 kW‧h/t, the B-type viscosity was 3900 mPa·s, and the specific surface area was 15.7 m ² /g.

[Embodiment 2]

After adding 1.6 parts of polyacrylic dispersant to the pigment dispersion containing 100 parts of caustic light calcium, the slurry was coarsely slurried to an average particle diameter of 7 μm, and the bead filling rate was 85% with a double rotor type SC grinder LSC220. The number of rotations of the rotor was 800 min ^-1 wet-pulverized to an average particle diameter of 0.4 μm. At the time, the original unit was 171 kW ‧ h/t, the B-type viscosity was 4600 mPa ‧ and the specific surface area was 11.1 m ² /g.

[Example 3]

After adding 1.6 parts of a polyacrylic dispersant to a pigment dispersion containing 100 parts of caustic light calcium, the slurry was coarsely slurried to an average particle diameter of 7 μm, and the bead filling rate was 80% with a double rotor type SC grinder LSC220. The number of rotations of the rotor was 900 min ^-1 wet pulverization until the average particle diameter became 0.4 μm. At the time, the original unit was 171 kW ‧ h/t, the B-type viscosity was 4900 mPa ‧ and the specific surface area was 11.2 m ² /g.

[Example 4]

After adding 1.6 parts of the polyacrylic dispersant to the pigment dispersion containing 100 parts of caustic light calcium, the slurry was coarsely slurried to an average particle diameter of 7 μm, and the bead filling rate was 70% with the double rotor type SC grinder LSC220. The number of rotations of the rotor was 1000 min ^-1 wet pulverization until the average particle diameter became 0.4 μm. At the time, the original unit was 193 kW ‧ h/t, the B-type viscosity was 5000 mPa ‧ and the specific surface area was 12.4 m ² /g.

[Example 5]

After adding 1.6 parts of polyacrylic dispersant to the pigment dispersion containing 100 parts of caustic light calcium, the slurry was coarsely slurried to an average particle diameter of 7 μm, and the bead filling rate was 85% with a double rotor type SC grinder LSC220. The number of rotations of the rotor was 800 min ^-1 wet-pulverized to an average particle diameter of 1.0 μm. At that time, the original unit was 111 kW ‧ h/t, the B-type viscosity was 900 mPa ‧ and the specific surface area was 7.9 m ² /g.

[Embodiment 6]

After adding 1.6 parts of a polyacrylic dispersant to a pigment dispersion containing 100 parts of light calcium carbonate (hereinafter referred to as caustic light calcium) produced in a causticizing step, the slurry is roughly slurried to an average particle diameter of 7 μm. The double-rotor type SC grinder LSC 220 was wet-pulverized to a mean particle diameter of 0.4 μm at a bead filling rate of 85% and a number of revolutions of 800 min ^-1 . At this time, the B-type viscosity was 4,600 mPa·s, the specific surface area was 11.1 m ² /g, and the D ₉₀ /D ₃₀ was 5.8. 25 parts of kaolin clay, 75 parts of styrene/butadiene copolymerized latex as adhesive, 3.5 parts of urea phosphate esterified starch, and solid concentration of urea phosphate ester starch were prepared from 75 parts of causticized light calcium carbonate obtained in this way. 65 wt% of the coating. This coating material was coated on both sides with a doctor blade and a coating amount of 10 g/m ² per side with respect to a raw material of 45 g/m ² . After coating, an ultra calender treatment (temperature: 65 ° C, linear pressure: 100 kg/cm) was carried out to obtain coated paper.

[Embodiment 7]

After coating in the same manner as in Example 6, the coated paper was obtained without performing an ultracalender treatment.

[Comparative Example 1]

Adding 2.6 parts of a polyacrylic dispersant to a pigment dispersion containing 50 parts of caustic light calcium and 50 parts of ground calcium carbonate (tri-p-prepared powder, average particle size 13 μm), and slurried to an average particle diameter of 7 μm. The single rotor type SC grinder SC 220 was wet-pulverized to a mean particle diameter of 0.4 μm at a bead filling rate of 90% and a number of revolutions of 800 min ^-1 . At the time, the original unit was 226 kW ‧ h/t, the B-type viscosity was 7500 mPa ‧ and the specific surface area was 18.6 m ² /g.

[Comparative Example 2]

2.6 parts of a polyacrylic dispersant was added to a pigment dispersion containing 100 parts of caustic light calcium, and the slurry was coarsely slurried to an average particle diameter of 7 μm, and the bead filling rate was 85% in a single rotor type SC grinder SC220. The number of rotations of the rotor was 800 min ^-1 wet-pulverized to an average particle diameter of 0.4 μm. At that time, the original unit was 238 kW ‧ h/t, the B-type viscosity was 8700 mPa ‧ and the specific surface area was 13.1 m ² /g.

[Comparative Example 3]

2.6 parts of a polyacrylic dispersant was added to a pigment dispersion containing 100 parts of caustic light calcium, and the slurry was coarsely slurried to an average particle diameter of 7 μm, and the single-rotor type SC mill SC220 was used at a bead filling rate of 80%. The number of rotations of the rotor was 900 min ^-1 wet pulverization until the average particle diameter became 0.4 μm. At the time, the original unit was 237 kW ‧ h/t, the B-type viscosity was 8200 mPa ‧ and the specific surface area was 13.8 m ² /g.

[Comparative Example 4]

2.6 parts of a polyacrylic dispersant was added to a pigment dispersion containing 100 parts of caustic light calcium, and the average particle diameter was 7 μm. Then, the single-rotor SC mill SC220 was used at a bead filling rate of 70%. The number of rotations of the rotor was 1000 min ^-1 wet pulverization until the average particle diameter became 0.4 μm. At the time, the original unit was 285 kW ‧ h/t, the B-type viscosity was 8900 mPa ‧ and the specific surface area was 13.5 m ² /g.

[Comparative Example 5]

2.6 parts of a polyacrylic dispersant (1.6 parts) was added to a pigment dispersion containing 100 parts of caustic light calcium, and the slurry was coarsely slurried to an average particle diameter of 7 μm, and then a single rotor type SC grinder SC220 was used as a bead. The pellet filling rate was 85%, and the number of rotations of the rotor was 1000 min ^{-1 by} wet pulverization until the average particle diameter was 0.4 μm. At that time, the original unit of the power was 247 kW ‧ h / t, the viscosity of B type was 10000 mPa ‧ s or more (not measured), and the specific surface area was 13.7 m ² /g.

[Comparative Example 6]

3.6 parts of a polyacrylic dispersant was added to a pigment dispersion containing 100 parts of caustic light calcium, and the mixture was coarsely slurried to an average particle diameter of 7 μm, and then filled with beads in a horizontal type second mill (manufactured by Mitsui Mining Co., Ltd.). The rate was 90%, and the number of rotations of the rotor was 800 min ^{-1 by} wet pulverization until the average particle diameter became 0.4 μm. At the time, the original unit was 350 kW ‧ h/t, the B-type viscosity was 7100 mPa ‧ and the specific surface area was 17.1 m ² /g.

[Comparative Example 7]

2.6 parts of a polyacrylic dispersant was added to a pigment dispersion of 100 parts of causticized light calcium, and the mixture was coarsely slurried to an average particle diameter of 7 μm, and then a single rotor type SC grinder SC220 (manufactured by Mitsui Mining Co., Ltd.) was used. The bead filling rate was 85%, and the number of rotations of the rotor was 800 min ^{-1 by} wet pulverization until the average particle diameter became 0.4 μm. At this time, the B-type viscosity was 8700 mPa·s, the specific surface area was 13.1 m ² /g, and the D ₉₀ /D ₃₀ was 6.3. 25 parts of kaolin clay, 75 parts of styrene/butadiene copolymerized latex as adhesive, 3.5 parts of urea phosphate esterified starch, and solid concentration of urea phosphate ester starch were prepared from 75 parts of causticized light calcium carbonate obtained in this way. 65 wt% of the coating. This coating material was coated on both sides with a doctor blade and a coating amount of 10 g/m ² per side with respect to a raw material of 45 g/m ² . After coating, an ultra calender treatment (temperature: 65 ° C, linear pressure: 100 kg/cm) was carried out to obtain coated paper.

[Comparative Example 8]

Adding 3.6 parts of a polyacrylic dispersant to a pigment dispersion containing 100 parts of causticized light calcium to a coarse particle size to an average particle diameter of 7 μm, and then using a horizontal sand mill (manufactured by Mitsui Mining Co., Ltd.) as a bead The filling rate was 90%, and the number of rotations of the rotor was 800 min ^{-1 by} wet pulverization until the average particle diameter became 0.4 μm. At this time, the B-type viscosity was 7100 mPa·s, the specific surface area was 17.1 m ² /g, and the D ₉₀ /D ₃₀ was 6.3. 25 parts of kaolin clay, 75 parts of styrene/butadiene copolymerized latex as adhesive, 3.5 parts of urea phosphate esterified starch, and solid concentration of urea phosphate ester starch were prepared from 75 parts of causticized light calcium carbonate obtained in this way. 65 wt% of the coating. This coating material was coated on both sides with a doctor blade and a coating amount of 10 g/m ² per side with respect to a raw material of 45 g/m ² . After coating, an ultra calender treatment (temperature: 65 ° C, linear pressure: 100 kg/cm) was carried out to obtain coated paper.

[Comparative Example 9]

After coating in the same manner as in Comparative Example 7, the coated paper was obtained without performing an ultra calender treatment.

The particle size distribution of the causticized light calcium carbonate is shown in Fig. 3, and the paper on the coated paper is shown in Table 2.

[test results]

1. About B type viscosity

From Examples 1 to 4 of Table 1, according to the pulverizer of the present invention (double rotator having an L/D ratio of 0.9), the causticized light calcium is formulated in an amount of 50% by weight or more, even if the wet pulverized average particle diameter is 0.4 μm. The B-type viscosity of the slurry also becomes in the range of 3900~5000mPa‧s.

From Comparative Examples 1 to 5, in a conventional pulverizer (single rotator having an L/D ratio of 0.3), if the causticized light calcium is blended by 50% by weight or more, the wet pulverized average particle diameter is 0.4 μm, and the slurry is prepared. The B-type viscosity is in the range of 7500 to 8900 mPa‧s.

From the above, the B-type viscosity of the slurry by the pulverizer of the present invention is approximately halved and the workability is excellent as compared with those produced by the conventional pulverizer. Of course, the viscosity does not rise, so the power original unit also becomes smaller.

2. About particle size distribution

3, the solid particle size distribution of the slurry obtained by the pulverizer of the present invention of Example 2 is even if it is the same average particle diameter, and becomes narrower as compared with those of the conventional pulverizer. The particle range (in a state in which the particle diameter is uniform in the narrow particle distribution) is small in the case of fine particles or large particle diameter, and is good when used for coating a pigment.

For this reason, it is considered that in the pulverizer of the present invention of the second embodiment, the action of the impact force is easily transmitted to the particles, so that the entire particles are pulverized (so-volume pulverization), and in Comparative Example 2 or In the conventional pulverizer of the type 6, the effect of the impact force is not smoothly transmitted to the particles, and the frictional force acts to cause the pulverized particles (so-called surface pulverization).

1. . . grinder

2. . . Smash container

3. . . Container body

4. . . catheter

6. . . cover

8. . . Bearing

9. . . Medial compartment

10. . . Lateral chamber

11. . . Supply port

12. . . Discharge

13. . . Separator

14. . . Medial ring

15. . . Outer ring

16. . . Steel rod

17. . . Slit

18. . . Stirring member

18a. . . Stirring member

18b. . . Stirring member

19. . . Concave

20. . . Convex

twenty one. . . Through hole

twenty two. . . Through hole

twenty four. . . Drive shaft

25. . . Dispersing member

110. . . Media mixing type wet disperser

140. . . Processing system

141. . . Supply slot

142. . . Circulating pump

143. . . Circulation line

Fig. 1 is a schematic cross-sectional view showing an example of the embodiment of the medium agitation type wet disperser of the present invention.

Fig. 2 is a schematic explanatory view showing a processing system of the present invention.

Fig. 3 is a graph showing the relationship between the particle diameter (μm) and the existence ratio (%) of particles in Examples 2 and 6 and Comparative Examples 2, 6, 7, and 8 of the present invention.

Claims (5)

A method for producing a slurry of light calcium carbonate produced by a causticizing step, which comprises subjecting a light calcium carbonate produced in a causticizing step of a pulp production step to wet pulverization to obtain a slurry for coating pigment The manufacturing method is characterized in that a causticized calcium carbonate is slurried to obtain a coarse slurry having an average particle diameter of 1 to 10 μm, and the coarse slurry is supplied to a medium agitating type pulverizing apparatus to have a filling rate of 70. ～90%, the pulverization process is carried out in the presence of a pulverization medium, which is characterized in that it includes a pulverization container, a cylindrical separator, a stirring member, and a supply port, and is configured as the pulverization container. A double-rotator pulverizing container having a length (L) to a diameter (D) ratio (L/D ratio) in the axial direction of more than 0.6 and 1.2 or less: a tube-shaped one at the same time being blocked at both ends; a cylindrical separator: The inside of the pulverizing container is disposed in a state in which the axes are approximately uniform, and the inner portion is divided into two portions in the radial direction to form the inner chamber and the outer chamber, and at least a part of the circumferential surface is provided between the two chambers. Multiple slits; mixing member: The pulverizing container is set to be rotatable in a state in which the pulverizing container is approximately aligned with the axis inside the inner chamber; and the supply port is provided to the inside chamber. A method for producing a slurry of light calcium carbonate produced by a causticizing step according to the first aspect of the invention, wherein the calcium carbonate before the coarse slurrying has an average particle diameter of 10 to 30 μm. A method for producing a slurry of light calcium carbonate produced by a causticizing step according to the first or second aspect of the patent application, wherein 50% by weight or more of the total pigment is supplied to the medium agitating type pulverizing apparatus The aforementioned light calcium carbonate. A method for producing a slurry of light calcium carbonate produced by a causticizing step according to the first or second aspect of the invention, wherein the light calcium carbonate is in a lump shape and has a calcite crystal structure. A method for producing a slurry of light calcium carbonate produced by a causticizing step according to claim 1 or 2, wherein the L/D ratio is more than 0.8 and 1.0 or less.