JP2013060692A - Precipitated calcium carbonate for filler and paper containing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide precipitated calcium carbonate for internal addition to paper that has a good yield of filler and is excellent in strength characteristics such as tensile strength, tear strength, folding strength and interlaminar strength, and paper containing the same.SOLUTION: There is provided precipitated calcium carbonate for internal addition. The particle of the precipitated calcium carbonate is a primary particle having a needle-like and/or columnar shape and/or an aggregate thereof. The particle diameter of 50 volume % (D) in a particle size distribution curve is 4.0-15.0 μm by a laser diffraction method and the BET specific surface area is 3-20 m/g. It is preferable that the precipitated calcium carbonate is produced through the following processes: (A) obtaining slaked lime by adding slaking water to quick lime in a range of molar ratio of 2.5 or less and mixing the slaking water and the quick lime; (B) obtaining slurry by mixing the slaked lime and water; and (C) carbonating the slaked lime slurry by spraying a gas containing carbon dioxide.

Description

  The present invention relates to light calcium carbonate, which is a filler for papermaking, and paper in which it is embedded.

  In general, paper is made of cellulosic fiber material containing inorganic material as a filler, and filler is added to improve optical properties, mainly whiteness and opacity, which are often insufficient with cellulosic fiber material alone. . However, when trying to obtain more of these optical properties by adding filler, the optical properties are improved, while strength properties such as tensile strength and tear strength are lowered. In general, chemicals such as a paper strength enhancer are added to compensate for the decreasing strength characteristics, but use of a large amount causes a problem of internal contamination.

  In recent years, neutral papermaking has progressed, and light calcium carbonate is most frequently used as a filler currently used. The reason is that the whiteness is higher than that of talc, clay, etc., and depending on the synthesis method, the particle shape, particle diameter, aggregation state, etc. can be adjusted, and the physical properties imparted to the paper can be easily controlled. For this reason, many studies have been made on the particle shape and particle size of light calcium carbonate for filler.

For example, in Patent Document 1, whisker-like light calcium carbonate having an average particle diameter of 1.3 μm, acicular light calcium carbonate having an average particle diameter of 0.5 μm, spindle-shaped light calcium carbonate having an average particle diameter of 1.0 μm, and an average It has been proposed to use columnar light calcium carbonate having a particle size of 1.5 μm. Patent Documents 2, 3, and 4 use spindle-aggregated light calcium carbonate having a particle size of 1.72 μm and a specific surface area of 11 m ² / g. Has been proposed.
Patent Document 5 proposes to use acicular calcium carbonate having an average particle diameter of 57.9 μm that does not aggregate as a filler, and Patent Document 6 discloses a secondary particle diameter of 4.5 μm, BET. There has been proposed a floc-aggregated primary particle of spindle-shaped calcium carbonate having a specific surface area of 12.1 m ² / g.

However, since the light calcium carbonate described in Patent Documents 1, 2, 3, and 4 has a small average particle size, the distribution of the filler in the paper is uniform, but since the filler yield deteriorates, It is necessary to add a large amount of chemicals, which not only increases the burden on production costs, but also causes a problem of internal contamination.
The light calcium carbonate described in Patent Document 5 is a particle that is isolated without agglomeration of primary particles. However, since the average particle size is large, the distribution of the filler at the time of papermaking is localized compared to the filler having a small particle size. There is a concern that paper strength such as interlaminar strength may be reduced.
In addition, the light calcium carbonate described in Patent Document 6 is obtained by agglomerating primary particles of spindle-shaped calcium carbonate and floc-aggregating, and when it is internally added to paper, it becomes a bulky inner paper. General decline.

JP 2005-120510 A JP 2008-274517 A JP 2008-274518 A JP 2008-274523 A JP 2003-063820 A Japanese Patent No. 4557183

  In view of the above situation, the present invention has a good filler yield, good surface smoothness, and excellent strength properties such as tensile strength, tear strength, folding strength, and interlayer strength. A light calcium carbonate and an inner paper containing the same are provided.

  As a result of intensive studies on the optical properties, strength properties, and operability of the paper with respect to the filler, the present inventors have found that the above problem can be solved by using light calcium carbonate having a desired particle form.

The present invention includes the following inventions.
(1) Light calcium carbonate for filling, wherein the light calcium carbonate particles are primary particles having an acicular and / or columnar shape and / or aggregates thereof, and the light calcium carbonate method is used for the light Incorporation characterized in that the particle diameter (D ₅₀ ) of 50% by volume of the particle size distribution curve of calcium carbonate particles is 4.0 to 15.0 μm, and the BET specific surface area is 3 to ²⁰ m ² / g. Light calcium carbonate.

(2) The light calcium carbonate for filling according to (1), wherein a particle size (D ₅₀ ) of 50% by volume of the particle size distribution curve is 5.0 to 10.0 μm.
(3) The light calcium carbonate for filling according to any one of (1) and (2), wherein the BET specific surface area is 5 to 15 m ² / g.

(4) The light calcium carbonate is a step (A) for obtaining slaked lime by adding and mixing slaked water in a molar ratio to quick lime of 2.5 or less, and mixing the slaked lime and water to obtain a slaked lime slurry. It is manufactured through a step (B) to be obtained and a step (C) in which carbon dioxide-containing gas is blown into the slaked lime slurry and carbonized, and the filling according to any one of (1) to (3) Light calcium carbonate for use.

A paper in which the light calcium carbonate according to any one of (1) to (4) is embedded.

(5) A printing paper in which a coating liquid containing starch is applied on at least one side of the paper described in the paragraph.

(7) A coated paper for printing having at least one coated layer mainly composed of a pigment and an adhesive on at least one side of the paper according to any one of (5) and (6).

  By using the light calcium carbonate of the present invention as a filler, the yield of the filler and the paper operability are good, the optical properties of the paper, especially the whiteness and opacity are not impaired, the surface smoothness is good, and the tensile strength Paper having excellent strength properties such as tear strength, folding strength, and interlayer strength can be obtained.

  The present invention relates to light calcium carbonate as a filler and an internal paper containing the same.

(Light calcium carbonate)
As a light calcium carbonate production method, for example, a “liquid-gas” method in which carbon dioxide gas is blown into a slaked lime slurry to cause a reaction and a “liquid-liquid” method using sodium carbonate or the like can be cited. The obtained light calcium carbonate has a crystal system such as a calcite type and an aragonite type, and has various shapes such as a columnar shape, a needle shape, a spindle shape, and a cubic shape.

The present inventors made various forms of light calcium carbonate obtained by various synthetic methods as fillers, mixed with pulp slurry together with cationized starch, aluminum sulfate, etc., and then made hand-sheets to obtain filler yield. Comparison of the properties and particle shape with the optical and strength properties of the paper was repeated. As a result, the light calcium carbonate particles are primary particles having an acicular and / or columnar shape and / or aggregates thereof, and the particles are 50% by volume of the particle size distribution curve of the light calcium carbonate particles by laser diffraction method. When light calcium carbonate having a diameter (D _50, hereinafter expressed as D ₅₀ ) of 4.0 to 15.0 μm and a BET specific surface area of 3 to ²⁰ m ² / g is used as a filler, the filler yield is good. Thus, it has been found that a filler-filled paper excellent in strength characteristics can be obtained without impairing whiteness and opacity. In particular, the light calcium carbonate particles preferably have a D ₅₀ of 5.0 to 10.0 μm and a BET specific surface area of 5 to 15 m ² / g.

The light calcium carbonate of the present invention must be acicular and / or columnar primary particles and / or aggregates thereof. Other shapes do not result in paper having excellent strength properties such as tensile strength and tear strength, which are the effects of the present invention, even if the particle diameter and BET specific surface area are within the scope of the present invention.
The particle size distribution of the light calcium carbonate of the present invention is measured by a laser diffraction method. A filler yield D ₅₀ is more than 15.0μm is improved, because the filler in the paper is localized, tensile strength, tear strength decreases. Further, when less than D ₅₀ of 4.0 .mu.m, filler distribution in the paper becomes uniform, while for filler yield is deteriorated, the need to Zo添chemicals such as retention aids, production The cost burden increases. Furthermore, since the amount of ash and chemicals in the white water increases, problems of internal contamination such as scale accumulation also occur. When D50 is ₅ to 10 μm, the yield as a filler is high, and the strength properties of paper are excellent, so this is the most preferable range. A particle having a particle size distribution of the above laser diffraction method and a particle size distribution curve measured by X-ray transmission method of 50 volume% (d ₅₀ ) of 4.0 to 8.0 μm is further improved in the strength properties of paper. Since it is excellent, it is especially preferable.

The BET specific surface area of the light calcium carbonate of this invention needs to be 3-20 m < ² > / g. If it is less than 3 m < ² > / g, the ink and water absorbability at the time of printing are bad, and drying property falls. On the other hand, if it exceeds 20 m ² / g, the ink and water absorbability is good, but the absorbability of papermaking chemicals is also improved, and the effect of additive chemicals such as a retention agent is lowered. Considering these absorbency and chemical effect, the BET specific surface area is particularly preferably 5 to 15 m ² / g.

  Although the present invention does not particularly limit the method for producing light calcium carbonate, a step of obtaining slaked lime by adding and mixing slaked water in a molar ratio to quick lime of 2.5 or less by the “liquid-gas” method. (A) Light calcium carbonate produced through a step (B) of obtaining a slaked lime slurry by mixing the slaked lime and water, and a step (C) of blowing a carbon dioxide-containing gas into the slaked lime slurry and carbonating it. For example, the desired particle shape, particle diameter, and BET specific surface area can be easily obtained, which is the best.

The steps (A), (B), and (C) will be described in detail.
The quick lime may be any calcined limestone. Regarding the calcining equipment, Beckenbach furnace, Melz furnace, rotary kiln, Kahdi furnace, Koma type furnace, Kalmatic furnace, fluidized firing furnace, mixed baking stand, etc. There is no particular limitation as long as it is an apparatus for converting the above. The calcining temperature and calcining time can be adjusted as appropriate, but when limestone is produced at a low temperature for a long time, quick lime is produced at a low temperature and in a short time, and light calcium carbonate with a needle shape is more easily obtained. . In addition, the lower the carbon dioxide content in quicklime, the easier it is to obtain acicular light calcium carbonate, and carbon dioxide by the barium carbonate back titration method defined in JIS R 9011: 2006 as the uncalcined portion of limestone. The content is preferably 1.5% or less. More preferably, the carbon dioxide content is 1.0% or less.
Since the light calcium carbonate is used as a filler for filling, it is preferable to use limestone having a whiteness as high as possible. In particular, since coloring components such as Fe and Mn may be a problem, it is necessary to pay attention to using limestone with as little coloring component content as possible.

  As a method for producing slaked lime, it is preferable to use dry slaked method in which quick lime, that is, calcium oxide, is added with water about twice the theoretical hydration amount to saponify. In dry soaking, the amount of soaking water added is preferably 2.5 or less in terms of a molar ratio to quick lime. When the amount of slaked water exceeds 2.5 in terms of quick lime molar ratio, water is localized when slaked water is added to quick lime, so a lot of fine slaked lime is produced, and the shape of the resulting light calcium carbonate is It becomes spindle-shaped and needle-like or columnar particles cannot be obtained.

  As described above, when the raw slaked lime particles contain a lot of fine particles, the shape of the produced light calcium carbonate tends to be a spindle shape. For this reason, the present inventors decided to measure the volume particle size distribution of slaked lime particles by a laser diffraction method. When the cumulative volume of fine slaked lime particles having a particle size of 1.0 μm or less in the volume particle size distribution exceeds 20%, spindle-shaped light calcium carbonate is likely to be produced when used as a raw material. In this product, light calcium carbonate, coarse particles are mixed and the particle diameter is non-uniform, so when used as a filler for internal addition, the filler distribution in the paper is localized. When the cumulative volume of slaked lime particles having a particle size of 1.0 μm or less is 20% or less, columnar or needle-like light calcium carbonate is likely to be generated, and the particle size of this product is relatively uniform. The cumulative volume of slaked lime particles of 1.0 μm or less is more preferably 15% or less, and further preferably 10% or less. Moreover, by sharpening the particle size distribution of the slaked lime particles, the carbonation reaction becomes uniform, and the particle diameter of the light calcium carbonate can be made more uniform.

  In addition, when coarse slaked lime particles are included in the raw material, the central part of the slaked lime particles tends to be unreacted at the end of the carbonation reaction, and when the light calcium carbonate is used as a filler, the pH becomes alkaline in the papermaking system, There is a possibility that the paper-making chemical effect will decrease.

  In order to produce uniform slaked lime with a small particle size and a small amount of fine particles, a mixer that mixes quick lime and slaked water can flow and stir the mixture or reactant three-dimensionally by the floating diffusion effect. It preferably has a structure. Specific examples include a mixer in which the mixing container itself rotates and a mixer having a small gap between the container and the stirring blade. By using these mixers, dead space does not occur during stirring, and the mixture always flows, so when adding slaked water to quicklime, water does not localize and prevent slaked lime from agglomerating. And uniform slaked lime particles with few fine particles and coarse particles can be obtained. If the floating diffusion effect in the mixer is low, water may be localized when slaked water is added to quicklime, so a lot of fine slaked lime is produced, and the resulting light calcium carbonate shape is spindle-shaped. Become.

  In order to enhance the floating diffusion effect, when the mixing in the mixer is performed by rotating the stirring blade, the peripheral speed of the stirring blade needs to be 0.5 m / s or more. The peripheral speed of the stirring blade rotation is preferably 0.8 m / s or more, and more preferably 1.5 m / s or more. Moreover, when mixing with a mixer is performed by container rotation, the peripheral speed of this container rotation needs to be 0.2 m / s or more. The peripheral speed of the container rotation is preferably 0.4 m / s or more. Further, by providing a shearing blade for dispersion and mixing, the shearing effect can be improved, and more uniform slaked lime particles with fewer fine particles and coarse particles can be obtained.

  As a mixer suitable for the continuous system, a diffusion stirring blade having a feed mechanism and a return mechanism is used to circulate the reactant in the mixer, and a special stirring blade such as a skid-shaped shovel blade or a saw-toothed shovel blade. Is more preferable because a floating diffusion effect can be obtained. By setting the stirring blade peripheral speed to 2.0 m / s or more, quick lime and water can be mixed uniformly, and aggregation of slaked lime particles can be prevented. Further, not only one mixer but two or more mixers may be used. By using two or more mixers, the stirring peripheral speed and residence time of each mixer can be changed, and there are few coarse particles, and more suitable slaked lime can be obtained.

When the average size of the quicklime is 5 mm or less, the digestion reaction proceeds rapidly when the temperature of the slaked water added to the quicklime is low, and the width of the particle size distribution of the obtained slaked lime particles becomes wide. Therefore, when the classification and pulverization process is provided, the load on the work increases, and the cost for the classification and pulverization equipment increases. Therefore, the soaking water temperature is preferably 40 ° C. or higher, more preferably 60 ° C. or higher.
When the average size of quicklime exceeds 5 mm, the temperature of the soaking water added to quicklime is not particularly limited, and a room temperature around 20 ° C. may be used.

In order to mix quicklime and slaked water uniformly, it is preferable to provide two or more sewage water addition ports instead of one. Moreover, as a method for adding deodorizing water, not only a nozzle method but also a spray method capable of spraying deodorizing water over a wide range can be used. In particular, powdered quicklime and those in the middle of the soothing reaction are preferable because the localization of the soaking water can be prevented by using a spray method.
As a preferred method of adding the soaking water in a batch system, it is preferable not to add the soaking water all at once, but to add it in portions or continuously over about 5 to 30 minutes. As a preferred method of adding the dehydrated water in the continuous system, quick lime is supplied to one end of the mixer, and a plurality of the dehydrated water is placed on the mixer until it is moved to the other end while mixing and stirring. A supply port is provided, and the supply port close to the mixer outlet is preferably a spray system.

  Although there is no restriction | limiting in particular as time to mix quicklime and slaked water, After adding a prescribed amount of slaked water, it is 1 minute or more, Preferably it is 3 minutes or more, More preferably, it is 5 minutes or more, and stirs in a mixer. It is good to do. In consideration of productivity, the mixing time is preferably about 8 to 15 minutes.

The obtained slaked lime can be used for carbonation as it is, but it is preferable to use it after removing coarse slaked lime particles, and specifically, D ₅₀ is preferably 1 mm or less.

  Examples of the method for removing coarse slaked lime particles include a centrifugal classifier, a vibrating screen, and a screen classifier. The coarse slaked lime particles sieved by a classifier or the like can be used after being pulverized by a pulverizer, but can be returned to the classification step after pulverization as a classification / pulverization closed circuit. The classification / pulverization step may be either dry or wet. The excessive pulverization of the slaked lime particles in the pulverizer needs to be prevented because the obtained light calcium carbonate becomes a spindle shape and causes deterioration of the quality.

  If the solid content concentration of the slaked lime slurry used for carbonation is less than 5% by mass, the production efficiency decreases, and if it exceeds 40% by mass, fine light calcium carbonate is generated, the viscosity increases, and the operability is improved. Inferior. Therefore, the solid content concentration of the slaked lime slurry is preferably 5 to 40% by mass. The minimum with more preferable solid content concentration of slaked lime slurry is 8 mass%, and a more preferable upper limit is 20 mass%.

  Moreover, since the slaked lime slurry temperature at the time of a carbonation start affects the crystal | crystallization shape of the light calcium carbonate which is a product, it is necessary to adjust. When the carbonation start temperature is less than 20 ° C., when carbon dioxide gas or carbon dioxide-containing gas is blown, fine amorphous crystals are aggregated. On the other hand, when the temperature exceeds 50 ° C., large acicular particles and Spindle-like particles are mixed, and light calcium carbonate particles having a uniform particle size are not formed, and there is a possibility that good strength characteristics cannot be obtained. Therefore, in order to obtain fine and uniform columnar and needle-like particles, the carbonation start temperature is desirably 20 to 50 ° C.

  The amount of carbon dioxide or carbon dioxide-containing gas to be blown in is not particularly limited, but from the viewpoint of crystal shape, 100% carbon dioxide (1 atm, converted to 20 ° C.) per kg of slaked lime before the start of reaction is 10 L / min or less. Of 5 L / min or less is more preferable. If it exceeds 10 L / min, aggregates of amorphous or spindle-like calcium carbonate are formed, and good strength characteristics may not be obtained. From the viewpoint of productivity, it is preferably 1.5 L / min or more.

  The carbonation reaction may be either a batch type or a continuous type, as long as the carbonation reaction tank can blow carbon dioxide. As a batch type reaction tank, it is preferable from the point of efficiency that carbon dioxide gas is blown from the lower part of the reaction tank using a reaction tank of a cylindrical type or a cylindrical cone type with a cylindrical shape that is conical only at the lower part. Furthermore, by making a large number of holes in the lower cone of the semi-batch reaction tank, carbon dioxide gas becomes fine bubbles, and these fine bubbles come into contact with the slaked lime slurry, allowing efficient and uniform reaction. it can.

  In addition, by providing a stirrer in the reaction tank and performing carbonation while stirring, the carbon dioxide gas becomes finer and the contact with slaked lime is improved, and the reaction is performed uniformly and efficiently. The stirring peripheral speed of the stirrer is preferably 2.0 m / s or more, and more preferably 2.5 m / s or more. As the agitator, a uniaxial or biaxial tank agitator, a coreless mixer, a high-speed agitating disperser, or the like can be used. Furthermore, the shear force of slaked lime slurry can be increased by installing a baffle plate in the reaction tank.

  You may add a seed crystal to the slaked lime slurry before carbonation reaction. For example, by adding aragonite acicular light calcium carbonate as a seed crystal in advance, similar acicular crystals are efficiently produced. The seed crystal addition rate is preferably calcium hydroxide: aragonite-based acicular light calcium carbonate = 99.7: 0.3 to 95: 5.

  Suitable examples of carbon dioxide-containing gas for carbonation reaction include mixed gas containing carbon dioxide, such as limestone calcined exhaust gas, lime calcined exhaust gas of pulp production plant, cement production kiln exhaust gas, power generation boiler exhaust gas, waste incineration exhaust gas, etc. Is mentioned. When the above exhaust gas is used as the carbon dioxide-containing gas, the exhaust gas is removed by using dust such as limestone, lime, sulfur oxide, and unburned carbon in the exhaust gas, using a bag filter, an electrostatic precipitator, a dry scrubber, a wet scrubber, or a combination thereof. It is preferable to purify.

  As a method for producing slaked lime, in addition to the dry slaked method, a wet slaked method obtained by slaked lime slurry in the state of slaked lime slurry can be used in the presence of water whose amount greatly exceeds the theoretical hydration amount. . Since the slaked lime particles produced by the wet slaked method have many fine particles of 1 μm or less and coarse particles are also mixed, in order to obtain the light calcium carbonate particles of the present invention, coarse slaked lime particles and fine slaked lime are obtained. It is preferable to remove the particles.

  Examples of the method for removing coarse slaked lime particles include a vibrating screen and a screen classifier. Fine slaked lime particles can be removed from the slaked lime slurry containing fine slaked lime particles that have passed through a vibrating screen or the like using a centrifugal separator, a cyclone classifier, or the like.

(Inside paper)
Paper using the light calcium carbonate of the present invention as a filler has good surface smoothness and excellent strength properties such as tensile strength without impairing the optical properties of the paper. The light calcium carbonate can be used without any particular limitation. In addition, the types of paper include various coating base papers, newsprint paper, high-quality and medium-quality book paper, electrophotographic paper, inkjet paper, craft paper, pressure-sensitive recording paper, PPC paper, packaging paper, paper containers, paperboard Wallpaper, fiberboard, photographic base paper, impregnating base paper, flame retardant paper, and the like.

The basis weight of the paper embedded with the light calcium carbonate of the present invention as a filler is not particularly limited, but the desired effect is exhibited in a range of about 30 to 650 g / m ² . The light calcium carbonate of the present invention can be added to thick paper such as multilayer paperboard and card exceeding this range.

  Examples of the papermaking raw material pulp include commonly used bleached chemical pulps such as LBKP and NBKP, ground pulp (GP), pressurized ground wood pulp (PGW), refined ground wood pulp (RGP), and thermomechanical pulp (TMP). Such as mechanical pulp, deinked waste paper pulp (DIP), waste paper, and the like are appropriately mixed and used. Moreover, 1 type, or 2 or more types, such as a pulp fiber obtained from non-wood fiber raw materials, such as kenaf, a synthetic pulp, an inorganic fiber, can also be mix | blended with a base paper. Mechanical pulp and DIP can be used after being bleached if necessary, and the degree of bleaching can be arbitrarily performed. For bleaching pulp, it is preferable to use a bleaching process that does not use molecular chlorine such as chlorine gas or chlorine compounds such as chlorine dioxide from the viewpoint of environmental conservation. Pulp that has undergone such bleaching process is used. Examples thereof include ECF (Elemental Chlorine Free) pulp and TCF (Totally Chlorine Free) pulp.

  The light calcium carbonate of the present invention is a commonly used filler such as heavy calcium carbonate, calcium sulfite, gypsum, talc, kaolin, clay, calcined kaolin, white carbon, amorphous silica, delaminated kaolin, Inorganic fillers such as diatomaceous earth, magnesium carbonate, titanium dioxide, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide, paper sludge, regenerated inorganic particles from deinking floss, urea formalin resin fine particles, micro hollow particles It can also be used by mixing with organic fillers such as. The mixing ratio can be adjusted according to the quality of the paper, and is not particularly limited. However, in order to obtain a good yield as a filler, good surface smoothness, and obtain the strength characteristics of the paper, It is preferable to contain 15 parts or more of light calcium carbonate in 100 parts of filler. More preferably, it contains 30 parts or more. It is particularly preferable to contain 50 parts or more. In general, the blending amount of the filler is preferably such that the paper (base paper) ash content is in the range of 1 to 30% by weight, and particularly preferably in the range of 5 to 20% by weight. If the blending amount of the filler is less than 1% by weight, the optical properties of the paper, mainly whiteness and opacity, are insufficient. If the blending amount of the filler exceeds 30% by weight, there are problems such as wire wear and dirt in the paper machine system. Prone to occur.

  In addition to pulp and filler as paper materials, various papermaking examples exemplified by internal sizing agents, anionic, nonionic, cationic or amphoteric yield improvers, drainage improvers, paper strength enhancers, etc. An internal additive can be used as needed. Specific examples of the internally added sizing agent include alkyl ketene dimer, alkenyl succinic anhydride, styrene-acrylic, higher fatty acid, petroleum resin sizing agent, rosin sizing agent and the like. Specific examples of yield improvers, drainage improvers, and paper strength enhancers include polyvalent metal compounds such as aluminum (specifically, sulfate bands, aluminum chloride, sodium aluminate, basic aluminum compounds, etc. ), Various starches, polyacrylamide, urea resin, polyamide-polyamine resin, polyethyleneimine, polyamine, polyvinyl alcohol, polyethylene oxide and the like.

  When the filler containing light calcium carbonate of the present invention is added to the pulp raw material, it is preferable to add the filler while sufficiently stirring the pulp raw material, and the addition location is preferably a machine chest inlet or a fan pump inlet. In this case, the stirring speed is preferably about 100 to 5000 rpm. Moreover, as the density | concentration of the filler for papermaking added with respect to a pulp raw material, since it manufactures after mixing a pulp raw material, if it adds in the density | concentration range which is in the range of the inlet density of a paper machine, there will be no problem.

There are no particular restrictions on the paper making conditions, and examples of paper machines include commercial-scale paper machines such as long net paper machines, twin wire paper machines, circular net paper machines, and short net paper machines. However, since the light calcium carbonate of the present invention is excellent in yield and can prevent soiling in the papermaking system, the gap former type and on-top type twins are particularly suitable. Stable operation is possible in the high speed paper machine of wire type paper machine.
As the papermaking system, any system such as acidic papermaking, neutral papermaking, weak alkaline papermaking, etc. can be used. However, since calcium carbonate dissolves in the acidic region, papermaking is performed in the neutral to weak alkaline range. It is desirable. In practice, if the pH is 5.5 or higher, calcium carbonate can be used effectively, and it is more desirable to make paper at pH 6 or higher. It is also possible to perform size treatment on paper using a natural adhesive such as starch or a synthetic adhesive such as polyvinyl alcohol with various size presses and roll coaters.

  The inner paper containing light calcium carbonate of the present invention can be used for book paper such as books and textbooks, text paper used for text flyers and instruction manuals, and copy paper. By internally adding the light calcium carbonate of the present invention, book paper, printing paper, and PPC paper excellent in feel, strength, and surface smoothness can be obtained.

  In order to impart surface strength improvement, water resistance imparting, ink ink-imparting property, etc., a surface treating agent may be applied to the inner paper obtained above. There are no particular limitations on the type of surface treatment agent, but self-modification produced by thermochemical or enzymatic modification in paper mills using raw starch, oxidized starch, esterified starch, cationized starch, and acetylated tapioca starch as raw materials. It is preferable to include starch such as starch, knitted starch such as aldehyded starch and hydroxyethylated starch. Cellulose derivatives such as carboxymethylcellulose, hydroxyethylcellulose, methylcellulose, polyacrylamide, polyvinyl alcohol, carboxyl-modified polyvinyl alcohol, modified alcohols such as acetoacetylated polyvinyl alcohol, styrene-butadiene copolymer, polyvinyl acetate, vinyl chloride-vinyl acetate Copolymers, polyvinyl chloride, polyvinylidene chloride, polyacrylic acid esters and the like can also be used in combination. In addition, surface sizing agents such as styrene sizing agents, olefin sizing agents, acrylate sizing agents, styrene-acrylic sizing agents, and cationic sizing agents may be used in combination.

As a device for applying the surface treatment coating solution, a known size press device, for example, a 2-roll type, a 3-roll type, a gate roll type, a film transfer type, or the like can be used. As the size press apparatus attached to the machine and used, a transfer type apparatus is preferable from the viewpoint of operability during high-speed operation. The film transfer type is a system in which a coating film in a wet state is formed on an applicator roll, and the coating film is transferred to the surface of the base paper. Examples thereof include a transfer roll coater and a rod metering size press coater.
After applying the surface treatment coating solution on both sides of the inner paper with these coating devices, 1.0 to 4.0 g / m ² (the coating amount per side is 0.5 to 2.0 g / m ² ), and then drying with a dryer. However, in order to improve printability, it is preferable to process with a calendar device such as a machine calendar, a soft calendar, or a shoe calendar.

  The inner paper containing light calcium carbonate of the present invention can be used as a base paper for coating, and a coated paper for printing having at least one coating layer mainly composed of a pigment and an adhesive. By internally adding the light calcium carbonate of the present invention, the interlayer strength is improved, and thus a coated paper for printing having excellent blister suitability and excellent surface smoothness can be obtained.

  Usually, a surface treatment is performed by applying a coating solution containing starch on the inner paper obtained as described above to obtain a coated base paper. By performing this surface treatment, there is an effect of improving the surface strength of the coated base paper or cleaning foreign matter on the surface of the coated base paper, and the occurrence of streaks or the like can be suppressed. However, in the case of an on-machine coater that makes a coated base paper and coats and dries a coating layer mainly composed of pigment and adhesive, surface treatment is applied to avoid the limitation of drying capacity and the risk of paper breakage. May be omitted.

In addition to starch, the surface treatment coating solution may contain a surface treatment agent such as polyvinyl alcohol or polyacrylamide, or a pigment such as heavy calcium carbonate, light calcium carbonate, or kaolin. The coating amount is not particularly limited, but is usually about 1.0 to 4.0 g / m ^{2 on} both sides. Examples of the apparatus for applying the surface treatment coating liquid include various application apparatuses such as a size press, a bar coater, a 2-roll coater, a gate roll coater, a transfer roll coater, a rod metering size press coater, and a spray coater.

  The coated base paper can be subjected to a smoothing finishing process using a machine calendar, a soft calendar, or the like.

  The pigment used in the coating layer of the present invention is not particularly limited, and pigments used in the ordinary coated paper field, such as kaolin, talc, clay, calcined kaolin, heavy calcium carbonate, light carbonate Calcium, titanium dioxide, satin white, calcium sulfite, gypsum, barium sulfate, white carbon, amorphous silica, diatomaceous earth, magnesium carbonate, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide, zinc oxide, oxidation In addition to inorganic pigments such as inorganic pigments of recycled pigments prepared from magnesium, bentonite, sericite, and paper sludge, organic pigments such as organic pigments such as solid type, hollow type, through-hole type plastic pigments, binder pigments, etc. If necessary, one or more kinds are appropriately selected and used in combination.

The light calcium carbonate has a needle-like and / or columnar shape, D ₅₀ is 0.2 to 0.7 μm, and 90% by volume particle diameter (D ₉₀ ) and 10% by volume particle diameter ( D ₁₀ ) ratio (D ₉₀ / D ₁₀ ) of 8 or less is excellent in white paper glossiness, smoothness, opacity, air permeability, ink setting, printing surface strength, ink acceptance, and printing gloss Since it has properties, it is preferably blended in the coating layer. By using light calcium carbonate having a D ₅₀ of 0.3 to 0.6 μm and a ratio of D ₉₀ to D ₁₀ (D ₉₀ / D ₁₀ ) of 6 or less, white paper glossiness and smoothness are further improved. Therefore, it is preferable. The blending amount of the light calcium carbonate is not particularly limited, but is preferably 5% by mass or more, more preferably 15% by mass or more, and more preferably 30% by mass or more based on the total pigment in the coating layer. Is most preferred. The light calcium carbonate is excellent in glossiness, and when blended in the outermost coating layer, the amount of kaolin often used in the outermost coating layer of the coated paper can be reduced for glossiness.

The light calcium carbonate can be produced by the same method as the light calcium carbonate for filler of the present invention. However, in order to make the light calcium carbonate particle size more uniform, the D ₅₀ of the slaked lime particles is 150 μm or less. Preferably, the thickness is 75 μm or less, and more preferably 50 μm or less.
In order to obtain light calcium carbonate having a desired shape, it is possible to perform dehydration, dispersion, and pulverization steps after carbonation, if necessary.

The adhesive used for the coating layer of the present invention is not particularly limited, and an adhesive used in the ordinary coated paper field, for example, a dispersion type adhesive is used. Dispersion type adhesives include conjugated diene polymer latexes such as styrene-butadiene copolymers and methyl methacrylate-butadiene copolymers, acrylic polymer latexes, and vinyl polymer latexes such as ethylene-vinyl acetate copolymers. Etc. can be exemplified.
A small amount of water-soluble adhesive can be used in combination with the above dispersion-type adhesive. Water-soluble adhesives include various starches such as oxidized starch, esterified starch, cold water soluble starch and cationized starch, proteins such as casein, soy protein, synthetic protein, cellulose derivatives such as carboxymethylcellulose and methylcellulose, polyvinyl alcohol And modified products thereof.
Although it does not specifically limit about the compounding quantity of an adhesive agent, 1-50 mass parts per 100 mass parts of pigments, Preferably 5-30 mass parts is mix | blended.

  For the coated layer of the coated paper of the present invention, a blue or purple dye or colored pigment, a fluorescent whitening dye, a thickener, a water retention agent, an antioxidant, an anti-aging agent, a conductive material, if necessary. Various auxiliaries such as an inducer, an antifoaming agent, an ultraviolet absorber, a dispersant, a pH adjuster, a mold release agent, a water-proofing agent, and a water repellent can be appropriately blended.

  The solid content concentration of the coating layer coating composition of the present invention can be selected in the range of 25 to 72% by mass. In consideration of adjustment of coating amount and operability, a range of 50 to 71% by mass is desirable.

There is no particular limitation on whether the coating layer provided on the base paper is a single layer or a multilayer of two or more layers. In the case of multiple layers, they need not all be the same, and can be appropriately adjusted according to the required quality level. Also, the coating amount of the coating layer is not particularly limited, and can be adjusted according to the blank paper quality, printing quality, etc. of the coated paper. It is about 40 g / m ² .

  As for the coating method for providing the coating layer in the present invention, various coating apparatuses used in the ordinary coated paper manufacturing field, such as air knife coaters, various blade coaters, gate roll coaters, roll coaters. A die coater, a curtain coater, or the like can be used as appropriate.

  After the coating layer coating is applied to the base paper, the coating layer is dried to obtain a coated paper. As the drying method, for example, a normal method such as a steam heater, a gas heater, an infrared heater, an electric heater, a hot air heater, a microwave, or a cylinder dryer can be arbitrarily selected and used.

  The coated paper thus obtained may be finished by passing the paper through various known and official finishing devices such as a super calender, gloss calender, soft calender, mat calender and the like.

  The inner paper containing the light calcium carbonate of the present invention can be used as newsprint by applying a surface treatment agent. By adding the light calcium carbonate of the present invention, strength characteristics such as interlayer strength are improved, so that it has sufficient strength to withstand high-speed printing by a cold offset type offset rotary press and is excellent in surface smoothness. Newspaper is obtained.

Usually, as pulp used as a papermaking material for newsprint, deinked waste paper pulp (hereinafter referred to as DIP), chemical pulp (NBKP, LBKP, etc.), mechanical pulp (GP, CGP, RGP, PGW, TMP, etc.) are optional. Can be mixed and used at a ratio of From the viewpoint of effective use of resources, it is desirable to blend 40% or more of DIP, and more desirably 60% or more. In addition to the above-mentioned pulp, various additives such as fillers other than the light calcium carbonate for filling according to the present invention, internal sizing agents, fixing agents, yield improvers, cationizing agents, paper strength enhancing agents, etc. are appropriately added. By adjusting conditions such as pH value, newsprint paper can be obtained with a normal paper machine such as a long paper machine, a twin wire paper machine, a circular paper machine, or a short paper machine. Although there is no limitation in particular as basic weight, it is the range of about 30-60 g / m < ² >.

  The addition amount of the filler is preferably 2 to 15% by weight, and more preferably 2 to 10% by weight, based on the weight of the base paper. If the amount is less than 2% by weight, the desired effect is not exhibited. If the amount exceeds 15% by weight, paper stiffness and paper dust tend to occur.

  It is also possible to apply a surface treatment agent for improving the surface strength of newspaper. The surface treatment agent is not particularly limited, and starch, starch derivatives, water-soluble resins, water-dispersible resins, etc. can be used as an adhesive. For example, starch such as corn, potato, tapioca, wheat, rice, Oxidized starch, dialdehyde starch, phosphate modified starch, starch derivatives such as cationized starch, etherified starch such as hydroxyethyl etherified starch, enzyme-modified starch, synthetic water-soluble binders such as polyacrylamide resins and polyvinyl alcohol, styrene -Copolymer latex, such as a butadiene copolymer, an acrylonitrile-butadiene copolymer, and a methyl methacrylate-butadiene copolymer. In particular, a starch or a starch derivative or a polyacrylamide resin is preferably used because it has good neppariness and is inexpensive and has good surface strength. Moreover, 1-50 weight% of surface sizing agents, such as a styrene-acrylic acid copolymer and a styrene-maleic acid copolymer, can also be added with respect to the said adhesive agent for size improvement.

  It is also possible to apply a coating solution containing a pigment and an adhesive as the surface treatment agent. The pigment used in the present invention is not particularly limited. For example, light calcium carbonate such as cubic, needle, and spindle, heavy calcium carbonate, and causticized light produced in a causticizing process. In addition to inorganic pigments such as calcium carbonate, kaolin, talc, aluminum hydroxide, titanium dioxide, satin white, inorganic pigments of recycled pigments prepared from paper sludge, solid type, hollow type, through-hole type plastic pigment, binder One or more organic pigments such as organic pigments such as pigment are appropriately selected and used in combination. The pigment in the coating layer increases the opacity after printing, but the ratio of the pigment and the adhesive should be adjusted to 0.8 to 2.5 from the viewpoint of preventing troubles due to piling and powder falling off during printing. Is preferred. When the pigment ratio is less than 0.8, the effect of improving the opacity after printing cannot be obtained sufficiently, and when it exceeds 2.5, piling and powder fall off easily occur.

  The surface treatment agent of the present invention may contain an antifoaming agent, a slime control agent, a dye and the like as appropriate in addition to the pigment and the adhesive.

The surface treatment agent of the present invention is applied on a newsprint base paper in a solid content concentration range of 2 to 15%, and the coating amount is generally 0.05 to ² g / m ² , preferably 0.1 to 0.1 g per side. It is applied in the range of 1 g / m ² . If the coating amount is less than 0.05 g / m ² is difficult to sufficient surface strength can not be obtained, more than 2 g / m ² Neppari strength is increased when, undesirably causing sticking problems to the blanket during printing.

  The coating apparatus for applying the surface treating agent composition to newsprint is not particularly limited. For example, an ink line or vertical to roll size press, a blade metalling size press, a rod metalling size press. Roll coater such as gate roll coater, trailing, flexible, roll application, fountain roll application, short dwell and other bevel type and vent type blade coater, rod blade coater, bar coater, air knife coater, curtain coater, gravure coater A publicly known apparatus such as the above is appropriately used. In addition, as a method of drying the wet coating layer after apply | coating a surface treating agent composition, various systems, such as vapor | steam drying, gas heater drying, electric heater drying, infrared heater drying, are employable, for example.

  In the production of newsprint for offset printing according to the present invention, after forming the coating layer of the surface treating agent composition, it is smoothed with various known and official finishing devices such as a super calender, gloss calender, soft calender, mat calender and the like. The treatment may be performed. It is of course possible to use a combination of a water coating device, an electrostatic humidifier, a steam humidifier, and the like for humidity control and humidification of newsprint after finishing with a calendar.

  The inner paper containing light calcium carbonate of the present invention can also be used as a kraft paper for packaging and heavy bags, and as a liner for cardboard. By using the light calcium carbonate of the present invention, a kraft paper for heavy packaging, a kraft paper for heavy bags, and a liner for cardboard having excellent strength and processability can be obtained.

As pulp used in kraft paper for packaging, softwood kraft pulp can be used, in addition, hardwood kraft pulp, stone ground pulp, pressurized stone ground pulp, refiner ground pulp, thermo ground pulp, chemical ground pulp, Mechanical pulp such as crushed wood pulp and thermomechanical pulp can be used. In addition to the above pulp, various additives such as a filler, an internal sizing agent, a fixing agent, a yield improver, a cationizing agent, and a paper strength enhancing agent are appropriately added. Kraft paper for packaging can be obtained with a normal paper machine such as a net type paper machine or a twin wire type paper machine. Although there is no limitation in particular as basic weight, it is the range of about 50-120 g / m < ² >.

Corrugated liner composed of three or more paper layers consists of soft white kraft pulp, hardwood kraft pulp, top white waste paper consisting of chemical pulp, white paper loss, etc., white loss of coated paper, etc. Waste paper pulp such as Kent waste paper, newspaper waste paper, and magazine waste paper can be blended. In addition to the above pulp, various additives such as a filler, an internal sizing agent, a fixing agent, a yield improver, a cationizing agent, and a paper strength enhancing agent are appropriately added. Paper is made by sequentially combining paper layers from a net type paper machine, a circular net type paper machine, or the like. Although there is no limitation in particular as basic weight, it is the range of about 120-400 g / m < ² >.

  About the addition amount of a filler, it can be added to such an extent that intensity | strength does not fall, and the light calcium carbonate of this invention is added so that the ash content in a base paper may be in the range of 0.5 to 10 weight%. Is more preferable, and 0.5 to 5.0% by weight is more preferable. If it is 0.5% by weight or less, the smoothness tends to be lowered and the printability tends to be lowered, and if it exceeds 10% by weight, the strength may be lowered.

If necessary, a surface treatment agent such as a water-soluble resin or a pigment can be applied to one side or both sides of the base paper. Examples of the water-soluble resin include starches such as oxidized starch, cationized starch, phosphate-modified starch, phosphate esterified starch, ester-modified starch and enzyme-modified starch, and synthetic water-soluble binders such as polyacrylamide resins and polyvinyl alcohol. , Copolymer latex such as styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, methyl methacrylate-butadiene copolymer, and the like. The pigment is not particularly limited. For example, cubic, needle-like, spindle-like light calcium carbonate, heavy calcium carbonate, causticized light calcium carbonate produced by causticizing process, kaolin, talc In addition to inorganic pigments such as inorganic pigments of recycled pigments prepared from aluminum hydroxide, titanium dioxide, satin white and paper sludge, organic pigments such as solid type, hollow type, through-hole type plastic pigments, binder pigments, etc. One kind or two or more kinds of organic pigments can be appropriately selected and used in combination. The surface treatment agent can be applied on one side using various commonly used coating apparatuses such as an air knife coater, various blade coaters, gate roll coaters, roll coaters, die coaters, curtain coaters and the like. It apply | coats so that it may become 0.5-10 g / m < ² >.

(Example)
EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. In Examples and Comparative Examples, “%” means “% by weight” unless otherwise specified.

<Preparation of light calcium carbonate>
Example 1
Using a continuous pro-shear mixer WA150 type (manufactured by Taihei Kiko Co., Ltd.) with the chopper blades removed as excavator blades as a mixer, industrial quicklime (CO ₂ content 0.3%) from one end of the mixer 4 kg / min, the residence time until slaked lime is discharged from the other end is set to 8 minutes, and shovel blade peripheral speed 3.5 m / s, 25 ° C. dehydrated water is added 2.6 kg / min. Slaked lime was obtained.
The obtained slaked lime was made 700 μm or less with a sieve and mixed with 35 ° C. water to prepare 18 kg of 8% slaked lime slurry. Next, 1.0% of aragonite columnar light calcium carbonate (trade name: TP-123CS, manufactured by Okutama Kogyo Co., Ltd.) is added as a seed crystal per slaked lime weight, and the stirring peripheral speed is 2.5 m / s, CO ₂ / air mixed gas ( Carbonation was performed until the pH reached 7 to 8 under the condition of blowing a CO ₂ gas concentration of 20 Vol%) at a flow rate of 26 L / min to obtain needle-like aggregate light calcium carbonate slurry.

(Example 2)
A light calcium carbonate slurry was obtained in the same manner as in Example 1 except that the slaked lime obtained in Example 1 was pulverized with a pulverizer.

(Example 3)
The operation was carried out in the same manner as in Example 1 except that the stirring peripheral speed during carbonation was 1.2 m / s, and a CO ₂ / air mixed gas (CO ₂ gas concentration 20 Vol%) was blown at a flow rate of 13 L / min. A calcium carbonate slurry was obtained.

Example 4
A light calcium carbonate slurry was obtained in the same manner as in Example 1 except that the slaked lime obtained in Example 1 was mixed with 30 ° C. water.

(Example 5)
2 kg of industrial quicklime (CO ₂ content 0.3%) was put into 20 L of hot water at 60 ° C. and slaked, then cooled to 35 ° C. to prepare 18 kg of 11% slaked lime slurry, using a centrifuge A light calcium carbonate slurry was obtained in the same manner as in Example 1 except that the fine particles of slaked lime were removed.
The obtained light calcium carbonate slurry was concentrated and then pulverized with a bead mill to obtain a light calcium carbonate slurry.

(Comparative Example 1)
The light calcium carbonate slurry obtained in Example 1 was concentrated by 25% and then pulverized by a bead mill to obtain a light calcium carbonate slurry.

(Comparative Example 2)
In Example 1, light calcium carbonate was obtained by operating in the same manner as in Example 1 except that the 8% slaked lime slurry temperature was 70 ° C. and the CO ₂ gas concentration was 15 Vol%.

(Comparative Example 3)
Industrial quicklime (CO ₂ content 0.3%) was added to 70 ° C. warm water and slaked to prepare 18 kg of 11% slaked lime slurry. Under conditions where the stirring peripheral speed is 1.8 m / s and a CO ₂ / air mixed gas (CO ₂ gas concentration 20 vol%) is blown at a flow rate of 30 L / min, the carbonation is performed until the pH reaches 7 to 8, and the spindle-shaped particles are condensed. A collected light calcium carbonate slurry was obtained.
The obtained light calcium carbonate slurry was concentrated and then pulverized with a bead mill to obtain a light calcium carbonate slurry.

(Comparative Example 4)
Using the slaked lime slurry obtained in Comparative Example 3, CO ₂ / air mixed gas (CO ₂ gas concentration 20 Vol%) was carbonized until pH = 7 to 8 under the condition of blowing at a flow rate of 30 L / min, and spindle shape An agglomerated light calcium carbonate slurry of particles was obtained.

(Reference example)
TP-121SA (made by Okutama Kogyo Co., Ltd.) was prepared as a spindle-shaped light calcium carbonate.

<Creation of handmade paper>
Using the light calcium carbonates of Examples 1 to 5, Comparative Examples 1 to 4 and Reference Examples as fillers, papermaking tests were performed as follows, and the paper properties of the obtained paper samples and the filler yield were evaluated. .

Cationic starch (trade name: Ace K100, manufactured by Oji Cornstarch Co., Ltd.) per 100% pulp dry weight while stirring 100% hardwood bleached kraft pulp slurry (pulp concentration 2.5%) prepared in 450 mL Canadian Standard Freeness 0.8%, aluminum sulfate 0.5%, alkyl ketene dimer (trade name: SKS-298, manufactured by Arakawa Chemical Co., Ltd.) 0.1% are sequentially added, and the ash content in the paper is 12% (according to JIS P8251). The filler was added so that the same applies hereinafter. After the pulp slurry is diluted to 0.5%, a yield improver (trade name: R-300, manufactured by Somaru) is added to 0.1% of the pulp dry weight to make a paper stock. Hand-sheeting was performed to obtain a sheet with a weight of 60 g / m ² .

  The following evaluation was performed on the light calcium carbonate of Examples 1 to 5, Comparative Examples 1 to 4, and Reference Example, the filler yield at the time of papermaking, and the sheet obtained using the same, and the results are shown in Table 1. It was.

(Particle size measurement)
The particle size distribution was measured by a laser diffraction method (Microtrack HRAX-100 manufactured by Nikkiso Co., Ltd.). The particle size cumulative volume is equivalent to 50% was determined as an average particle diameter D _50.
The particle size distribution was measured with an X-ray transmission type particle size distribution measuring device (Cedigraph 5100 manufactured by Micrometric Co., Ltd.). Cumulative mass was determined particle diameter corresponding to 50% as an average particle diameter d _50.

(BET specific surface area)
Measurement was performed according to JIS Z 8830-2001.

(Filling yield)
It calculated | required by following Formula.
Ash content in sheet (wt%) / Fraction rate of filler in paper (wt%) x 100 = Filler yield (%)

The strength characteristics were evaluated by the following test method.
(1) Tear strength: JIS P8116-2000
(2) Tensile strength: JIS P813-1998 (sample width 15 mm)
(3) Folding strength: JIS P8115-2001
(4) Interlayer strength: TAPPI T833

  From Table 1, Examples 1-5 have good yield of fillers and excellent strength properties of the obtained paper.

(Example 6)
<Creating book paper>
After adding light calcium carbonate of Example 1 as filler to 100% pulp slurry made of softwood bleached kraft pulp (LBKP) so that the ash content in the paper is 15%, aluminum sulfate is added to the total solid content of the pulp slurry. 0.5%, cationic starch (trade name: Ace K100, manufactured by Oji Cornstarch) 0.5%, alkyl ketene dimer sizing agent (trade name: Size Pine K-287, manufactured by Arakawa Chemical Industries) 0.1%, Cationic polyacrylamide (trade name: Realizer R-300, manufactured by Somar) 0.1% was sequentially added to prepare a paper stock. This paper stock was formed with a gap former at an operation speed of 1200 m / min, squeezed with two shoe presses, dried with a multi-cylinder dryer, and then 1.0 g / s solids per side of the base paper. m ² and composed as starch (trade name: Ace a, Oji cornstarch Co., Ltd.) 2% polyvinyl alcohol (trade name: PVA 105, manufactured by Kuraray Co., Ltd.) 0.5%, a surface sizing agent (trade name: Polymaron 1387S, Arakawa A surface treatment agent comprising 0.03% was applied with a rod metering size press coater and smoothed with a 1-nip machine calendar to obtain 80 g / m ² book paper.

(Example 7)
In Example 6, a book paper was obtained in the same manner as in Example 6 except that the filler was the light calcium carbonate obtained in Example 2.

(Comparative Example 5)
In Example 6, a book paper was obtained in the same manner as in Example 6 except that the filler was the light calcium carbonate obtained in Comparative Example 1.

(Comparative Example 6)
In Example 6, a book paper was obtained in the same manner as in Example 6 except that the filler was light calcium carbonate obtained in Comparative Example 2.

  The book papers of Examples 6 and 7 and Comparative Examples 5 and 6 were evaluated, and the results are shown in Table 2.

(Smoothness)
JAPAN TAPPI No. According to 5-2, it was measured with a Oken type smoothness tester.

(Stiffness)
Clark stiffness was measured according to JIS-P-8143-1996.

(Print smoothness)
Printing was performed using 0.2 cc of printing ink (FUSION-G EZ ink, manufactured by DIC Graphics Co., Ltd.) with an RI printing machine (Meiji Seisakusho), and the transfer uniformity of the ink was evaluated.
○: Excellent printing smoothness.
Δ: Print smoothness is slightly inferior.
X: Print smoothness is inferior.

(Print surface strength)
Using an RI printing tester (manufactured by Meisei Seisakusho), printing was performed using 0.6 ml of printing ink (trade name: SD50 for paper testing, manufactured by Toyo Ink Co., Ltd.), and the degree of picking on the printed surface was visually evaluated. .
○: Picking hardly occurs and is good.
Δ: A little picking occurs and slightly inferior. Practical tolerance level.
X: Many pickings occur and are inferior.

  (Filler yield) was determined by the same method as described above.

  From Table 2, the book papers of Examples 6 and 7 have a good filler yield, and are excellent in smoothness and printability.

(Example 8)
<Creation of PPC paper>
After adding the light calcium carbonate of Example 1 as a filler to 100% of the pulp slurry made of LBKP so that the ash content in the paper becomes 10%, 0.5% of aluminum sulfate with respect to the total solid content of the pulp slurry, cation Starch (trade name: Ace K100, manufactured by Oji Cornstarch Co., Ltd.) 0.5%, Alkyl ketene dimer sizing agent (trade name: Size Pine K-287, manufactured by Arakawa Chemical Industries, Ltd.) 0.1%, Cationic polyacrylamide (Product) Name: Realizer R-300, manufactured by Somar Co., Ltd.) 0.1% was sequentially added to prepare a paper stock. This paper stock was formed with a gap former at an operation speed of 1200 m / min, squeezed with two shoe presses, dried with a multi-cylinder dryer, and then 1.0 g / s solids per side of the base paper. m ² starch (trade name: Ace A, manufactured by Oji Constarch) 2%, surface sizing agent (trade name: Polymaron NP-25, manufactured by Arakawa Chemical Industries) 0.1%, bow glass 0.3 % Of the surface treatment agent was applied with a rod metering size press coater and smoothed with a 1-nip machine calendar to obtain 64 g / m ² of PPC paper.

Example 9
A PPC paper was obtained in the same manner as in Example 8 except that the light calcium carbonate obtained in Example 2 was used as the filler in Example 8.

(Comparative Example 7)
In Example 8, a PPC paper was obtained in the same manner as in Example 8 except that the light calcium carbonate obtained in Comparative Example 1 was used as the filler.

(Comparative Example 8)
In Example 8, a PPC paper was obtained in the same manner as in Example 8 except that the light calcium carbonate obtained in Comparative Example 2 was used as the filler.

  The PPC papers of Examples 8 and 9 and Comparative Examples 7 and 8 were evaluated, and the results are shown in Table 3.

(Runability)
The A4 size paper was printed on an evaluation machine (manufactured by Fuji Xerox Co., Ltd., DC750I) with the paper feed direction set to Y, and 50 sheets were continuously printed in black and white to evaluate running performance.
○: There is no paper jam and there is no problem in running performance.
Δ: Paper jam occurs once and running performance is slightly poor.
X: Paper jam occurs a plurality of times and the running performance is poor.

(Paper powder)
A4 size paper was printed on the evaluator in the Y direction as the paper feed direction, and monochrome printing was performed continuously for 1000 sheets to evaluate the amount of paper dust generated.
○: Almost no paper dust, good.
Δ: Paper dust is generated and is slightly defective.
X: A lot of paper dust is generated and defective.

  (Filler yield), (smoothness), (rigidity), and (print smoothness) were evaluated by the same methods as described above.

  From Table 3, the PPC papers of Examples 8 and 9 have good filler yield, excellent smoothness, good runnability in the copying machine, and little paper dust generation.

(Example 10)
In Example 10, base paper and paint were prepared as shown below, and coated paper was produced.
<Creation of base paper for coated paper>
After adding the light calcium carbonate of Example 1 as a filler to 100% of the pulp slurry made of LBKP so that the ash content in the paper becomes 10%, 0.5% of aluminum sulfate with respect to the total solid content of the pulp slurry, cation Starch (trade name: Ace K100, manufactured by Oji Cornstarch Co., Ltd.) 0.5%, Alkyl ketene dimer sizing agent (trade name: Size Pine K-287, manufactured by Arakawa Chemical Industries, Ltd.) 0.1%, Cationic polyacrylamide (Product) Name: Realizer R-300, manufactured by Somar Co., Ltd.) 0.1% was sequentially added to prepare a paper stock. This paper stock was formed with a gap former at an operational papermaking speed of 1200 m / min, squeezed with two shoe presses, dried with a multi-cylinder dryer, and then 0.5 g / s solids per side of the base paper. The starch was applied with a rod metalring size press coater so as to be m ^2, and smoothed with a 1-nip machine calendar to obtain 53 g / m ² of base paper.

<Preparation of light calcium carbonate for coating>
A needle-like light calcium carbonate slurry was obtained in the same manner as in Example 1 except that the slaked lime of Example 1 was reduced to 50 μm or less with a sieve. The light calcium carbonate slurry was dehydrated and manipulated by a filter press / dryer roll fit (manufactured by Unosawagumi Co., Ltd.) to obtain a cake having a solid content concentration of 73%. Subsequently, a light calcium carbonate slurry was prepared by adding and dispersing 1.0% sodium polyacrylate dispersant (trade name: Aron T-50, manufactured by Toa Gosei Co., Ltd.) to light calcium carbonate using an intensive mixer. Further, the light calcium carbonate slurry is subjected to a wet grinding process for 60 minutes with a sand grinder using glass beads having a diameter of 1.0 to 1.4 mm as a crushing medium, and a light calcium carbonate slurry for pigment having a solid content concentration of 71%. (D ₅₀ = 0.42 μm, D ₉₀ / D ₁₀ = 4.12) was prepared.

<Preparation of coating solution for coating>
80 parts Coating for precipitated calcium carbonate slurry obtained _{above, D 50} is heavy calcium carbonate 1.3 .mu.m (trade name: Hydro curve K-9, supra) to the pigment slurry comprising 20 parts to 100 parts of the pigment In contrast, oxidized starch (trade name: Ace B, supra) 4 parts, styrene-butadiene copolymer latex (trade name: T2628G, supra) 7 parts (all in terms of solid content), and defoaming as an auxiliary agent Agents and dyes were added, and finally a paint having a solid content of 62% was prepared.

<Creating coated paper for printing>
Using the blade coater that supplies the coating liquid obtained above to the base paper obtained above by the jet fountain method, the dry coating amount per side becomes 11 g / m ^2. Application and drying were performed to form a coating layer on both sides. The coated paper obtained as described above was placed on a multi-nip calender in which a metal roll and a resin roll (hardness: shear D92 °) heated to 100 ° C. were inclined, under a linear pressure of 200 kN / m, A total of 8 nips were passed so that one side was in contact with the metal roll and the resin roll 4 times each, and a coated paper for printing having a basis weight of 75 g / m ² was obtained.

(Example 11)
In Example 10, a coated paper for printing was obtained in the same manner as in Example 10, except that the light calcium carbonate obtained in Example 2 was used as the filler.

(Comparative Example 9)
In Example 10, a coated paper for printing was obtained in the same manner as in Example 10 except that the filler was the light calcium carbonate obtained in Comparative Example 1.

(Comparative Example 10)
In Example 10, a coated paper for printing was obtained in the same manner as in Example 10 except that the filler was the light calcium carbonate obtained in Comparative Example 2.

(Blank gloss)
Based on JIS P8142-1993, the glossiness of the white paper surface at 75 degrees was measured.

(PPS smoothness)
Using a Parker Print Surf (PPS) surface smoothness tester (model name: MODEL M-569, manufactured by MESSMER BUCHEL, UK), backing disk: soft rubber, clamp pressure: 0.98 MPa, 5 times smoothness measurement The average was calculated.

(Blister resistance evaluation)
With an RI printer, 1.0 cc of ink for rotary offset printing is developed and printed on both sides of the coated paper sample. The printed sample was immersed in warmed silicone oil, and the state of the generated blister was visually observed to evaluate the blister generation temperature.

  (Filler yield), (Smoothness), (Interlayer strength), and (Print smoothness) were evaluated in the same manner as described above.

  From Table 4, the coated paper for printing using Examples 10 and 11 as the base paper has good white paper gloss and smoothness, high interlayer strength, and excellent blister suitability.

(Example 12)
<Creating a newspaper for cold offset offset printing>
30 parts of unbleached kraft pulp, 30 parts of thermomechanical pulp, 40 parts of deinked waste paper pulp were mixed and disaggregated, and the pulp slurry prepared to a freeness of 120 mlC.SF (Canadian Standard Freeness) was used as a filler. Add 3.0% of the light calcium carbonate of Example 1, 0.03% of a yield improver (trade name: R-300, manufactured by Somar Co., Ltd.), and 1.5% of a sulfuric acid band. Paper making was performed with a twin-wire paper machine to obtain a newsprint base paper having a basis weight of 40 g / m ² .
Subsequently, 100 parts of oxidized starch (product surface: Oji Ace A, manufactured by Oji Cornstarch Co., Ltd.), olefin sizing agent (product name: OT-25) are coated on both sides of the above-mentioned newsprint paper as a coating solution for the surface treatment agent composition. (Manufactured by Arakawa Chemical Co., Ltd.) 10 parts of a mixed aqueous solution with a solid content concentration of 8.8% was applied with a gate roll coater so that the coating amount per side after drying was 0.39 g / m ² and dried. Thereafter, soft calender finishing comprising a resin roll / metal roll was performed to obtain a newsprint for offset printing having an actual amount of 40.7 g / m ² .

(Example 13)
Newspaper for offset printing was obtained in the same manner as in Example 12 except that the light calcium carbonate of Example 2 was used as a filler.

(Example 14)
Newsprint paper for offset printing was obtained in the same manner as in Example 12 except that 2.0% of the light calcium carbonate of Example 1 and 2.0% of white carbon (self-made) were added as fillers. .

(Comparative Example 11)
In Example 12, newsprint paper for offset printing was obtained in the same manner as in Example 12 except that the filler was the light calcium carbonate obtained in Comparative Example 1.

(Comparative Example 12)
In Example 12, newsprint paper for offset printing was obtained in the same manner as in Example 12 except that the filler was the light calcium carbonate obtained in Comparative Example 2.

  The physical properties of the newspapers of Examples 12 to 14 and Comparative Examples 11 and 12 were evaluated.

(Opacity after printing)
Printing was carried out using an offset ink for newspaper (NEWS WEBMASTER / Process Black G2, manufactured by Sataka Inks) with an RI printer (Meiji Seisakusho), and the printing opacity (Y) was determined from the following equation.
Y = {(back surface reflection ratio after printing) / (unprinted back surface reflection ratio)} × 100

(Ash in paper)
The ash content in the paper was determined according to JIS P8251-2003.

  (Interlayer strength), (Tear strength), and (Smoothness) were determined by the same method as described above.

  From Table 5, the papers obtained in Examples 12 to 14 have good smoothness and excellent interlayer strength and tear strength.

(Example 15)
<Making kraft paper for packaging>
Freeness 580 mL C.I. S. Example of F as 100% of pulp slurry made of unbleached kraft pulp, 0.2% of synthetic sizing agent, 1.0% of aluminum sulfate, 0.2% of acrylamide, and filler, based on the total solid content of pulp slurry 1% light calcium carbonate (2.0%) was added to make a paper stock, and paper was made with an on-top multi-cylinder paper machine to obtain a base paper for unbleached kraft paper for packaging having a basis weight of 84 g / m ² .
A gate roll coater is coated with a surface treatment coating solution comprising 100 parts of oxidized starch (trade name: Oji Ace A, supra) and 10 parts of sizing agent (trade name: SE2064, manufactured by Seiko PMC) on both sides of the obtained base paper. The coating amount after drying was 2.0 g / m ² to obtain kraft paper for packaging.

(Example 16)
A kraft paper for packaging was obtained in the same manner as in Example 15 except that the light calcium carbonate of Example 2 was used as a filler.

(Comparative Example 13)
A kraft paper for packaging was obtained in the same manner as in Example 15 except that the light calcium carbonate obtained in Comparative Example 1 was used as the filler.

(Comparative Example 14)
A kraft paper for packaging was obtained in the same manner as in Example 15 except that the light calcium carbonate obtained in Comparative Example 2 was used as the filler.

  The paper physical properties of the packaging kraft papers of Examples 15 and 16 and Comparative Examples 13 and 14 were evaluated.

  (Tensile strength), (tear strength), (rigidity), and (print smoothness) were evaluated by the same methods as described above.

  From Table 6, the papers obtained in Examples 15 and 16 are strong in paper and excellent in tensile strength and tear strength.

(Example 17)
<Creating a cardboard liner>
100% pulp slurry consisting of softwood unbleached kraft pulp (freeness 450 mLC.S.F) / hardwood unbleached kraft pulp (freeness 400 mLC.S.F) = 70/30, and the light calcium carbonate of Example 1 as a filler. After adding so that the middle ash content was 6%, 2.5% aluminum sulfate and 0.6% surface sizing agent were added to the total solid content of the pulp slurry to prepare a surface layer paper stock.
Light calcium carbonate of Example 1 as a filler in 100% pulp slurry comprising softwood unbleached kraft pulp (freeness 450 ml CS) / hardwood unbleached kraft pulp (freeness 400 ml CS) = 40/60 Was added so that the ash content in the paper was 10%, and then 2.5% of aluminum sulfate and 0.6% of the surface sizing agent were added to the total solid content of the pulp slurry to prepare the lower and upper layer sheet material.
Magazine waste paper pulp (freeness 350 mLC.S.F) / magazine waste paper pulp (freeness 350 mLC.S.F) = 50/50 pulp slurry 100%, aluminum sulfate 1.2% with respect to the total solid content of the pulp slurry Then, 0.2% of a surface sizing agent was added to prepare intermediate layer and back layer paper materials.
The foraminous multilayer paper machine the paper furnish at a driving machine speed 650 meters / min, the basis weight of each layer, the surface layer 40 g / ^{m 2,} Table lower 40 g / ^{m 2,} middle 50 g / ^{m 2,} the backing layer 50 g / ^{m 2} After smoothing with sheeting, pressing, drying and calendering, starch is applied on the surface layer to 1.0 g / m ² and dried, and then smoothing with calendar. And a cardboard liner having a basis weight of 180 g / m ² was obtained.

(Example 18)
A cardboard liner was obtained in the same manner as in Example 16 except that the light calcium carbonate of Example 2 was used as a filler.

(Comparative Example 15)
A cardboard liner was obtained in the same manner as in Example 16 except that the light calcium carbonate of Comparative Example 1 was used as the filler.

(Comparative Example 16)
A cardboard liner was obtained in the same manner as in Example 16 except that the light calcium carbonate of Comparative Example 2 was used as the filler.

  The paper physical properties of the cardboard liners of Examples 17 and 18 and Comparative Examples 15 and 16 were evaluated.

(Specific burst strength)
The specific burst strength was measured according to JIS P811-1995.

(Specific tensile strength)
The specific tensile strength was measured according to JIS P 8113-1998.

  (Smoothness), (interlayer strength), and (print smoothness) were evaluated in the same manner as described above.

  From Table 7, the papers obtained in Examples 17 and 18 have good smoothness and excellent interlayer strength, tensile strength, and burst strength.

Claims (7)

Light calcium carbonate for filling, wherein the light calcium carbonate particles are primary particles and / or aggregates thereof having a needle-like and / or columnar shape, and the light calcium carbonate particles obtained by laser diffraction method A light calcium carbonate for filling, wherein the particle size distribution curve of 50% by volume (D ₅₀ ) is 4.0-15.0 μm and the BET specific surface area is 3-20 m ² / g . 2. The light calcium carbonate for filling according to claim 1, wherein a particle size (D ₅₀ ) of 50% by volume of the particle size distribution curve is 5.0 to 10.0 μm. The light calcium carbonate for filling according to claim 1, wherein the BET specific surface area is 5 to 15 m ² / g.   The light calcium carbonate is a step (A) of obtaining slaked lime by adding and mixing slaked water in a molar ratio to quick lime of 2.5 or less, and a step of obtaining a slaked lime slurry by mixing the slaked lime and water ( The light calcium carbonate for filling according to any one of claims 1 to 3, wherein the light calcium carbonate is produced through B) and a step (C) in which carbon dioxide-containing gas is blown into the slaked lime slurry and carbonized. .   Paper which embedded the light calcium carbonate of any one of Claims 1-4.   A printing paper in which a coating liquid containing starch is applied to at least one side of the paper according to claim 5.   A coated paper for printing, comprising at least one coated layer mainly composed of a pigment and an adhesive on at least one side of the paper according to any one of claims 5 and 6.