JP4802471B2 - Coated paper for printing - Google Patents

Description

  The present invention relates to a coated paper for printing, and particularly to a matte coated paper for printing having a low density and excellent printability.

  In recent years, there has been a strong demand for excellent printability that can visually convey the contents of printed matter by using a lot of photographs and designs and further colorizing them. On the other hand, there is a strong demand for weight reduction of printed matter from the viewpoint of resource saving and transportation cost. These two requests are contradictory, and in order to improve printability, the coated paper has a large amount of base paper and coating amount, and also has a density compared with the same basis weight due to smoothing by surface treatment. It is expensive and does not meet the demand for weight reduction. It is possible to select a low basis weight paper for weight reduction of the printed matter, but if the density is equal, the paper thickness decreases with the weight reduction, which is not preferable because the volume of the booklet is impaired. For this reason, a coating having a high paper thickness compared with the same basis weight, or a low basis weight compared with the same paper thickness, that is, a low density (bulk) and good printability such as ink inking property. Paper is sought.

  In general, coated paper is roughly classified into high gloss coated paper and matte coated paper. High gloss coated paper is art paper, super art paper, coated paper or the like conventionally used for high-grade printing, and the printed finish is glossy with both high gloss and white paper gloss. Matte coated paper has a dull tone and matte tone depending on the glossiness of white paper and printing gloss. The matte tone is a flat and calm print with low gloss on both the white and printed sides, and the dull tone is an intermediate between glossy and matte tone, with low gloss on the white paper but high print gloss. is there. The matte tone is easier to read after printing than the conventional glossy tone, and demand is increasing in recent years. High gloss coated paper, dull coated paper, and matt coated paper have high gloss after printing and good ink fillability, although there is a difference in the gloss of blank paper before printing. It is required to be.

  The coated paper can be divided into high-quality coated paper using 100% chemical pulp as a base paper and medium-coated paper partially using mechanical pulp. Medium-coated paper contains mechanical pulp, so it is inferior in whiteness compared to high-quality coated paper. High whiteness is also an important factor for visually appealing the contents of printed matter. It needs improvement.

  In addition, as environmental protection has increased, paper weight reduction is an unavoidable problem even in the effective use of paper pulp produced from forest resources. In the field of coated paper for printing, the weight has been reduced. Tend to be advanced.

  When trying to reduce the weight of conventional coated paper for printing, it is necessary to lower the base weight of the base paper, and as a result, the amount of coating must be reduced as the basis weight decreases. When printing paper for printing is produced based on the technology, it is inferior in opacity and rigidity, and printability such as printing gloss is also lowered.

  There is also a method of making the coated base paper bulky and improving the base paper coverage with a low coating amount.

  As a method for reducing the density of base paper, paper pulp, which is a main raw material of paper, can be considered. Generally, wood pulp is used for paper pulp. For lower density pulp, mechanical pulp produced by grinding wood with a refiner or grinder without using chemicals, rather than chemical pulp extracted with lignin, which is a reinforcing material in fibers, by chemicals. However, the fiber is rigid, which is advantageous for lowering the density. Among them, ground pulp (GP) contributes greatly to reducing the density. However, when a large amount of mechanical pulp is blended, there are problems inferior in whiteness and coating suitability. Usually, pulp for papermaking softens and fibrillates fibers by a beating process, but the beating process is a process contrary to the reduction in density, and it is desirable to reduce the density as much as possible. Paper density is also greatly affected by the choice of pulping tree species. That is, when the wood fiber itself is coarse, the density can be reduced. For example, in hardwoods, gumwood, maple, birch and the like are examples of tree species that can be relatively reduced in density. However, it is difficult to identify, collect and pulp only these tree species, especially in the current increase in environmental protection.

  In recent years, an increase in the amount of waste paper pulp has been demanded due to the increase in environmental protection and the need for resource protection. Waste paper pulp is rarely classified into pulp, such as high-quality paper, newspaper, magazine, flyer, coated paper, etc., because it is pulped in a mixed state. The density tends to be higher than that of pulp. The reason for this is that the fiber content of waste paper pulp is a mixture of chemical pulp and mechanical pulp.

  As described above, even if only the pulp is changed based on the conventional method to obtain a coated base paper for printing, the opacity and rigidity are not sufficient. It is difficult to obtain coated paper.

  As a study for reducing the density during papermaking, it is better to lower the press pressure as much as possible during the papermaking process, and not to perform a calendering process performed to impart smoothness to the paper surface.

  In addition to such a device for pulping and papermaking, a study is being made on the amount of filler that is blended in the coated base paper next to pulp. For example, a method of achieving a low density by blending a hollow synthetic organic substance capsule as a filler is known. In addition, a synthetic organic foaming filler (for example, trade name: EXPANCEL, manufactured by Nippon Philite Co., Ltd.) that achieves a reduction in density by expanding with heat in a dryer section during papermaking has also been proposed. However, with these synthetic organic foaming fillers, the drying conditions during papermaking are difficult, and even when this method is used alone to obtain a coated paper for printing, printing with low density and excellent printability is possible. It is difficult to produce coated paper.

  In addition, a method of adding fine fibrillated cellulose, although it is not a filler, has been proposed (see Patent Document 1). In the method using fine fibrillated cellulose, it is necessary to specially adjust the fine cellulose, and further, it is necessary to make the pulp freeness at the time of papermaking CSF 400 ml or more, preferably CSF 500 ml or more, which is complicated in operation and not practical. .

  Even if a bulky base paper is made by combining the above methods, the bulky base paper has a larger amount of voids than ordinary base paper, so the paint easily penetrates into the base paper, and the base paper coverage is applied to general base paper It is inferior compared with. When the base paper coverage with the paint is inferior, the printability such as the print glossiness is also inferior. Further, even when a coating liquid that is difficult to soak into the base paper is applied, it has been insufficient to obtain a low density and good stiffness, opacity, printability, and the like.

  As a technique for improving printability, a technique for imparting smoothness is conceivable, but when supercalender treatment is performed at a high linear pressure, which is a general method, the coating layer surface becomes smooth, but the coated paper density is low. Get higher. A number of methods using a high-temperature calendar have been proposed in place of the conventional super calendar, and it has been reported that printing glossiness, opacity, rigidity, etc. are relatively improved as the finishing speed increases. Even when a coated paper for printing is obtained using this technique, it is difficult to obtain a low-density paper.

  For example, offset printing containing a specific amount of delaminated clay having a volume distribution average particle size of 3.5 to 20 μm as a pigment, a blank paper glossiness of less than 30%, and a coated paper density of 0.95 g / cm3 or less. A matte coated paper is disclosed (see Patent Document 2). However, this method is not satisfactory in terms of opacity and stiffness.

  As described above, according to the conventional technology, a coated paper for printing having a low density, good opacity and rigidity, and high print glossiness despite having a low blank paper gloss is obtained. That was inadequate.

JP-A-8-13380 JP 2002-194698 A

  In view of the circumstances as described above, the object of the present invention is to provide a printing coating excellent in printability having good opacity and rigidity, low density, relatively high printing gloss despite low blank gloss. To provide craft paper.

The present invention relates to a rosetta-type light calcium carbonate particle in which spindle-shaped light calcium carbonate primary particles are aggregated in a chestnut shape on a base paper, in a coating paper for printing in which a coating layer containing a pigment and an adhesive is provided on the base paper. A coating comprising 10 to 100 parts by weight of a delaminated clay containing a light calcium carbonate-silica composite whose surface is coated with silica and having a volume distribution average particle size of 3.5 to 20 μm as a pigment. By having the working layer, it is possible to obtain an image having a low density, good opacity and rigidity suitable for practical use, and a relatively high printing glossiness with a low white paper glossiness. In the present invention, the light calcium carbonate-silica composite is preferably contained in an amount of 1 to 25% by weight as a filler in paper. In the light calcium carbonate-silica composite, the weight ratio of the solid content of light calcium carbonate and silica is preferably light calcium carbonate / silica = 30/70 to 70/30. The coated paper is preferably treated with a soft nip calender having a rigid roll temperature of 100 ° C. or higher.

  According to the present invention, low-density, practically suitable opacity and rigidity are obtained, and a coated paper for printing having excellent printability having a relatively high print gloss despite a low blank gloss is obtained. Can do.

  In the present invention, a low-density base paper containing a specific filler is provided with a coating layer mainly composed of a specific pigment and an adhesive on the base paper to obtain a coated paper for printing.

  In the present invention, it is important to blend 10 to 100 parts by weight, preferably 30 to 90 parts by weight of a delaminated clay having a volume distribution average particle size of 3.5 to 20 μm as a coating pigment. It is. In the present invention, by using as a pigment a delaminated clay obtained by peeling a normal clay layered with hexagonal plate shapes into a single layer (delamination), a plate shape having a large particle size on the surface of the coating layer Since it is easy to be oriented, even when coated on a base paper with a high porosity, with a relatively low coating amount, the base paper coverage is good, smoothness is easily achieved, and ink inking properties and printing An image having a high glossiness can be obtained. Further, since the base paper covering property is good, it can be processed under a lower pressure condition than the normal calendar process, and the opacity and rigidity can be improved at a low density.

  The delaminated clay of the present invention is characterized by a particle size distribution, and since it uses a distribution having a larger particle size than a normal one, the coverage of the base paper is improved and the same coating is applied. When compared in terms of amount, the effective coating layer thickness that contributes to printability increases, the print glossiness also increases, and even when a low coating amount and a white paper glossiness of less than 30% are low, relatively high ink coverage It is believed that meatiness and print gloss can be obtained. In order to further improve the coating suitability and the quality of the coated paper, it is preferable to blend 55 to 90 parts by weight of a delaminated clay having a volume distribution average particle diameter of 3.5 to 20 μm.

  When a delaminated clay having an average particle size smaller than 3.5 μm is used, the glossiness of the white paper is relatively high, the printing glossiness is low, and the printability is poor. When a delaminated clay having an average particle size of 20 μm or more is used, the viscosity of the coating liquid increases when the coated paper is coated with the coating liquid on the base paper, and handling during preparation is not possible. Difficult, coating defects such as streaks, scratches, and bleeding occur, resulting in operational problems. In addition, the average particle diameter prescribed | regulated by this invention uses a laser diffraction method, and is the value which measured the volume distribution average particle diameter using the Laser Diffraction particle size distribution measuring device by MALVERN Instruments.

  Further, even when a delaminated clay having a volume distribution average particle size of 3.5 to 20 μm is blended as a pigment, when the blending amount is less than 10 parts by weight with respect to 100 parts by weight, the base paper coverage is relatively high. Inferior, poor printability. When the blending amount is 90 parts by weight or more, the ink setting property during printing tends to be extremely slow. When the ink setting is extremely slow, when multicolor printing is performed, the second color is printed before the tack of the first printing ink on the coated paper rises, and the second ink has the first ink. Will occur, causing printing problems.

  As the pigment used in the present invention, other pigments can be used in combination as long as the object of the invention is not impaired. For example, kaolin, clay, engineered kaolin, heavy calcium carbonate, light calcium carbonate, talc, titanium dioxide, barium sulfate, calcium sulfate, zinc oxide, silicic acid, silicate, colloidal silica, satin white and other inorganic pigments, plastic pigments These inorganic pigments can be used alone or in combination of two or more as necessary.

As an adhesive used for the coating layer of the present invention, a plurality of adhesives can be used in combination as long as the object of the invention is not impaired. Various adhesives such as styrene / butadiene, styrene / acrylic, ethylene / vinyl acetate, butadiene / methyl methacrylate, and vinyl acetate / butyl acrylate, which have been used for coated papers. Or synthetic adhesives such as maleic anhydride copolymer, acrylic acid / methyl methacrylate copolymer; proteins such as casein, soy protein, synthetic protein; oxidized starch, positive starch, urea phosphated starch, hydroxyethyl One or more ordinary adhesives for coated paper such as etherified starch such as etherified starch are appropriately selected and used. The total amount of these adhesives is used in the range of 5 to 50 parts by weight, more preferably about 10 to 30 parts by weight per 100 parts by weight of the pigment from the viewpoint of printability and coating suitability. In addition, various commonly used auxiliaries such as a dispersant, a water retention agent, an antifoaming agent, and a water resistance agent may be used. In the present invention, when improving water retention, it is preferable to use an acrylic synthetic water retention agent and hydroxyethyl cellulose, and more preferably an association type acrylic synthetic water retention agent. The associative acrylic synthetic water retention agent functions to improve the water retention of the coating solution and to reduce the high shear viscosity of the coating solution. Therefore, it is suitable for high-speed coating, and the coating is not pushed into the coating base paper during coating, making the coating layer on the base paper bulky and improving the cushioning property of the coating layer. In addition, when using an acrylic synthetic water retention agent and / or hydroxyethyl cellulose, the blending amount is preferably 0.1 to 1.0 part by weight with respect to 100 parts by weight of the pigment.

  In the present invention, chemical pulp, semi-chemical pulp, mechanical pulp, waste paper pulp and the like can be used as the pulp constituting the base paper, but it is preferable to contain 10% by weight or more of mechanical pulp. Because mechanical pulp is more rigid than chemical pulp, the base paper blended with mechanical pulp is less crushed by various pressures applied in the paper making process, and becomes bulky as a whole, increasing the amount of voids inside the base paper, Opacity is improved and stiffness is increased at the same time. Among mechanical pulps, ground pulp can be preferably used because it contributes greatly to reducing the density. When the blending amount of the mechanical pulp is less than 10% by weight, the opacity and rigidity are relatively inferior even if the filler and calendar conditions are optimized. The mechanical pulp is preferably 60% by weight or less of the pulp for papermaking from the viewpoint of whiteness and suitability for coating. In particular, the use of waste paper pulp is preferable in terms of effective use of resources and environmental friendliness.

In the present invention, as the filler used for the base paper, the light calcium carbonate-silica composite in which the surface of the light calcium carbonate particles is coated with silica is used in whole or in part so that the coated paper density is low and sufficient rigidity is obtained. The coated paper provided with can be manufactured. The light calcium carbonate-silica composite particles are particles having the characteristics of being excellent in the effect of reducing the density of paper, having a large oil absorption, and improving the opacity. Moreover, even after performing the calendar process, it is possible to maintain the low density and exhibit contradictory properties such as high smoothness and low density. In the present invention, the light calcium carbonate-silica composite particles are preferably contained in a ratio of 1 to 25% by weight as a filler in paper, more preferably 3 to 20% by weight, and still more preferably 3 to 15%. % By weight. If the filler in the paper is less than 1% by weight, the effect of lowering the density and improving the opacity of the coated paper for printing is not sufficient, and if it exceeds 25% by weight, the interlayer strength is not sufficient, and the interlayer is not printed. A peeling phenomenon may occur, which is not preferable. In addition, the light calcium carbonate-silica composite in which the surface of the light calcium carbonate particles is coated with silica is a combination of light calcium carbonate and silica in order to achieve a better balance of density reduction, rigidity, opacity, and printability. The solid content weight ratio is preferably light calcium carbonate / silica = 30/70 to 70/30. When the weight ratio of light calcium carbonate solids is smaller than light calcium carbonate / silica = 30/70, the surface strength during printing of the coated paper tends to be inferior. When the solid weight ratio of light calcium carbonate is more than light calcium carbonate / silica = 70/30, the effect of reducing the density is not large.
In the present invention, a coating liquid containing a specific delaminated clay is applied to the low density base paper containing the light calcium-silica composite of the present invention so that the coating liquid penetrates the base paper. Since the base paper coverage is good even if the coating amount is reduced, it is excellent in printability such as ink fillability and printing gloss, whiteness, opacity and rigidity, and further density reduction It becomes possible to measure. In addition, compared with other fillers, particularly when calendering is performed, there is a feature that the coated paper is less reduced in thickness and the low density is maintained. About such an effect being obtained, it is considered that a hard pigment can be produced by covering the periphery of light calcium carbonate with silica, and it is difficult to be crushed by a calendar process.

  Since the light calcium carbonate-silica composite particles contain light calcium carbonate, the light calcium carbonate inside the particles may be decomposed or dissolved by acidity when the paper is made by acidic papermaking. Therefore, it is preferable to make paper from neutral papermaking to alkaline papermaking.

  The light calcium carbonate-silica composite production method of the present invention is a method in which silicic acid is reacted with the surface of the produced calcium carbonate. Such a light calcium carbonate-silica composite can be produced, for example, based on the description in Japanese Patent Application No. 2004-27483, and the balance of quality such as bulkiness, opacity, and rigidity can be improved. it can. This method will be described below.

First, light calcium carbonate is dispersed in water. The crystal form of the calcium carbonate may be either calcite or aragonite, and the shape may be any of acicular, columnar, spindle, spherical, cubic, and rosetta types. Among these, in particular, when rosetta type light calcium carbonate is used, a light calcium carbonate-silica composite having a particularly excellent bulkiness and high opacity improvement effect can be obtained. The Rosetta type refers to a shape in which spindle-shaped light calcium carbonate primary particles aggregate in a chestnut shape or a shape in which columnar and needle-shaped light calcium carbonate primary particles aggregate in a chestnut shape, which is higher than other light calcium carbonates. It has the characteristics of specific surface area and oil absorption. In the rosetta type, a shape in which calcite spindle-shaped light calcium carbonate primary particles are aggregated in a chestnut shape is more preferable. Light calcium carbonate may be used after being pulverized.
The concentration of the light calcium carbonate in the reaction stock solution is important for the blending ratio of light calcium carbonate and silicic acid, which will be described later. . If the concentration is less than 1%, the production amount per batch is small, and there is a problem in productivity. Further, if the concentration exceeds 20%, the dispersibility is poor, and the alkali silicate concentration used in the reaction is lower than the amount of light calcium carbonate, so the viscosity at the time of reaction increases and there is a problem in operability. .
Next, silicic acid in a form decomposed into an alkaline solution such as sodium or potassium is added to the light calcium carbonate slurry. Generally used for industrial use is sodium silicate (sodium) or potassium silicate, but any molar ratio of alkali silicate may be used. No. 3 silicic acid has a molar ratio of about SiO ₂ : Na ₂ O = 3 to 3.4: 1, but is generally easily available and used appropriately. The light calcium carbonate and alkali silicate are charged so that the weight ratio of calcium carbonate to silica in the light calcium carbonate-silica composite to be produced falls within the target range. The weight ratio of calcium carbonate to silica in the light calcium carbonate-silica composite is preferably CaCO ₃ / SiO ₂ = 30/70 to 70/30.

This slurry is stirred and dispersed with an agitator, a homomixer, a mixer, or the like. This is not a problem unless the light calcium carbonate is sufficiently dispersed in water and the light calcium carbonate particles are extremely aggregated.
Next, a neutralization reaction using an acid is performed. In this case, the acid may be any mineral acid, and further, an acid containing an acidic metal salt such as a sulfate band or magnesium sulfate in the mineral acid can be used. Industrially preferred are acids that can be purchased at relatively low cost, such as sulfuric acid and hydrochloric acid. When a high-concentration acid is used, if the stirring during neutralization with the acid is insufficient, the addition of the high-concentration acid will result in a part having a low pH, and light calcium carbonate decomposes. It is necessary to perform strong stirring using a homomixer or the like at the mouth. On the other hand, if a very dilute acid is used, the overall capacity is extremely increased by acid addition, which is not preferable. Also from this aspect, it is appropriate to use an acid having a concentration of 0.05 N or more. The mineral acid or acidic metal salt aqueous solution is added at a temperature not higher than the boiling point of the alkaline silicate metal salt aqueous solution and light calcium carbonate. By this neutralization treatment, silicate is precipitated to form amorphous silicic acid, which covers the surface of the light calcium carbonate particles.

Furthermore, this acid addition may be performed in several times. Aging may be performed after the acid addition. The aging means that the acid addition is temporarily stopped and only stirred and left. It is also possible to control the morphology of the particles by vigorous stirring and pulverization during this aging.
Next, the neutralization of the slurry by the above acid addition is performed with the target of pH = 7-9. The light calcium carbonate is covered with the precipitated silicic acid component, but when it is on the acidic side (less than pH 7), the light calcium carbonate is decomposed. On the other hand, when neutralization is completed at a high pH (over 9.0), silicic acid is not sufficiently precipitated, and unreacted silicic acid remains in the slurry, resulting in an increase in silicic acid loss. This is not preferred industrially. Therefore, the neutralization is terminated at a target pH of 7-9.

The light calcium carbonate-silicic acid composite produced in this manner is in the state of a suspension in which the surface of the light calcium carbonate particles is coated with silica. This suspension may be used in the papermaking process, but if the production scale is small, filtration equipment such as filter paper or membrane filter is used, and if it is medium or larger, a belt filter or drum filter is used. It is preferable to perform solid-liquid separation by filtration or centrifugation using a centrifuge, and to remove as much as possible salt, which is an extra by-product generated in the neutralization reaction. Furthermore, after re-dispersing the cake-like composite having a solid content concentration of 10 to 50%, which has been subjected to the solid-liquid separation, with water or ethanol, the solid-liquid separation is performed again to further remove excess silicic acid and by-product salts. It may be removed.
The obtained light calcium carbonate-silicic acid composite removes particles of 100 μm or more using a screen or the like in order to remove a composition larger than the target particle size.

As described above, the average particle size of light calcium carbonate-silicic acid can be controlled by intensive stirring or pulverization during ripening, but the neutralization reaction is completed or the reaction is completed. The solid-liquid separated later may be adjusted to the target average particle size using a wet pulverizer. Further, the average particle diameter may be adjusted by this combination.
After removing coarse particles, or after removing coarse particles, the average particle size of the light calcium carbonate-silicic acid composite that has been further stirred and pulverized is 30 μm when the use is a filler for paper. The following is preferable, More preferably, it is 20 micrometers or less, More preferably, it is 1-10 micrometers.
In the present invention, in addition to the light calcium carbonate-silica composite particles, other inorganic and organic fillers can be used as a filler as long as the effects of the present invention are not impaired. For the type, known fillers such as amorphous silica, amorphous silicate, talc, kaolin, clay, light calcium carbonate, heavy calcium carbonate, titanium oxide, synthetic resin filler, etc. can be used. Is about 1 to 25% by weight based on the pulp weight.

There are no particular restrictions on the paper making method of the base paper, and long paper machines including top wires, round net machines, machines using the two together, Yankee dryer machines, etc., acid paper making, neutral paper making, alkaline Any of the base papers made by the paper making method may be used, and medium base papers including recovered waste paper pulp obtained from used newspapers can also be used. Also, a base paper pre-coated with starch, polyvinyl alcohol or the like using a size press, a bill blade, a gate roll coater, or a pre-metering size press can be used. As the coated base paper, the basis weight used for general coated paper is 30 to 400 g / m ² , preferably about 30 to 200 g / m ² , and particularly preferably, the opacity and paper passing property of the base paper are problems. Those of 80 g / m ² or less are appropriately used. In the present invention, the density of the base paper is preferably 0.3 g / cm ³ or more and 0.8 g / cm ³ or less, and more preferably the density is 0.3 g / cm ³ or more and 0.6 g / cm ³ or less. . By using a base paper having a density of 0.3 g / cm ³ or more and 0.8 g / cm ³ or less and applying the coating liquid defined in the present invention, the base paper coverage is good even if the coating amount is reduced. Therefore, it is excellent in ink deposition property, and it is possible to further reduce the density.
As a method of coating the coating liquid adjusted on the coating base paper, using a blade coater, bar coater, roll coater, air knife coater, reverse roll coater, curtain coater, size press coater, gate roll coater, etc. Or two or more layers are coated on one or both sides of the base paper. Coating amount is determined depending on the desired properties, when approximately base paper basis weight of 60 g / ^{m 2} or less in the case of the present invention, per side ^{6~10g / m 2, 40g / m} 2 when: With a small coating amount of 5 to 8 g / m ² , sufficient coverage and printing gloss can be obtained.

  As a method for drying the wet coating layer, various methods such as a steam superheating cylinder, a heated hot air air dryer, a gas heater dryer, an electric heater dryer, and an infrared heater dryer are used alone or in combination.

  In the present invention, the coated paper obtained by applying and drying the coating liquid to the above-described coated base paper is subjected to surface finishing with a high-temperature soft nip calender composed of an elastic roll and a rigid roll heated to 100 ° C. or higher. It is preferable that the temperature of the rigid roll is more preferably 150 ° C. or higher. If the moisture content of the coated paper is appropriate, the higher the rigid roll temperature, the smoother the base paper or the coated layer can be made with a lower nip pressure or a shorter nip residence time. In order to obtain the same level of blank paper glossiness and printing glossiness obtained by using a conventional supercalender with a high-temperature soft nip calender, a low nip pressure and a short nip residence time can be obtained. And the density of the base paper is low, the opacity is high, the stiffness is low density and bulky coated paper, and the processing speed is faster than the conventional super calendar, and the rewinding frame can be omitted, so the efficiency Good production and excellent operability.

Also, in the high temperature soft nip calender, not only the temperature but also the nip residence time is important. From this point, in an actual operation, the roll equivalent diameter is 300 mm or more, and the Shore D hardness of the elastic roll is 80 to 100, preferably 85 to 95. When converted to a roll equivalent diameter of 500 mm, the paper passing speed is 400 to 3000 m / It is preferable to perform the treatment at a calender nip number of 2 or more at a minute, a linear pressure of 30 to 500 kg / cm, and a pre-calendar coating moisture of 5 to 8%. The equivalent diameter of the roll is A. V. Lyons et al. (1990 TAPPI Finishing and Converting, P5) refers to the equivalent diameter of a roll.
(Equivalent roll diameter) = (Soft roll diameter) × (Heat roll diameter) / {(Soft roll diameter) + (Heat roll diameter)}
In the present invention, the effect is particularly remarkable for coated paper for printing having a blank paper glossiness of 30% or less, a basis weight of 80 g / m ² or less, or a density of 0.95 to 0.40 g / cm ³ .

EXAMPLES The present invention will be specifically described below with reference to examples, but it is needless to say that the present invention is not limited to these examples. In addition, unless otherwise indicated, the part and% in an example show a weight part and weight%, respectively. In addition, the test was done about the coating liquid and the obtained coated paper for printing based on the evaluation method as shown below.
<Evaluation methods>
(1) Average particle diameter of internal filler: A slurry of a light calcium carbonate-silica composite was dropped into pure water to which 0.2% of a sodium hexametaphosphate dispersant was added to form a uniform dispersion, and a laser method ( The value of the 50% portion of the volume cumulative distribution measured with a Malvern particle size measuring instrument Mastersizer S type) was taken as the average particle size.
(2) Volume average particle diameter of coated pigment: Pigment slurry is dropped and mixed in pure water to which 0.2% of sodium hexametaphosphate dispersant is added to form a uniform dispersion, and laser method (Laser Diffraction manufactured by MALVERN Instruments) After measuring the volume distribution particle size distribution with a particle size distribution measuring instrument), the value of the 50% portion of the volume cumulative distribution was taken as the average particle size.
(3) Blank paper glossiness: measured based on JIS P 8142.
(4) Gloss of printing: Using a Toshiba offset rotary press (4 colors), printing was performed at a printing speed of 500 rpm using a B vertical size plate, and the surface of the obtained printed matter (4-color solid printing part) was JIS P Based on 8142.
(5) Ink inking property: Using a Toshiba offset rotary press (4 colors), printing on a B vertical size plate at a printing speed of 500 rpm, and ink inking of the resulting printed matter (indigo monochromatic solid printing part) The property was visually evaluated in four stages.
(Double-circle): Very good, (circle): Good, (triangle | delta): Somewhat inferior, X: Inferior (6) Density: It measured based on JISP8118.
(7) Smoothness: JAPAN TAPPI No. 5 Measured based on “Smoothness / air permeability test method for paper and paperboard by air micrometer type tester”.
(8) Opacity: Measured based on JIS P 8138, and evaluated according to the following criteria.
○: Good, Δ: Slightly inferior (9) Rigidity: Measured based on JIS P 8143, and evaluated according to the following criteria.
A: Extremely good, B: Good, B: Slightly inferior, X: Inferior (10) Coating suitability: The state of occurrence of stratite, story, and scratch during blade coating was visually evaluated.
A: Very good, B: Good, B: Slightly inferior, X: Inferior <Method for producing light calcium carbonate-silica composite>
(Production Example 1: Preparation of light calcium carbonate-silica composite A)
In a reaction vessel, 10 parts of commercially available Rosetta-type light calcium carbonate (trade name: Albuquer 5970 SMI Co., Ltd.) was dispersed in water, and the SiO ₂ concentration was 18.0 wt / wt% and the Na ₂ concentration was 6.1 wt / wt%. After adding 57 parts of sodium silicate solution, water was added to make the total amount 200 parts. This mixed slurry was heated with sufficient stirring with an agitator, and a 10% sulfuric acid solution was added to the slurry at 85 ° C. with stirring. The addition method is to keep the temperature constant, add sulfuric acid at a constant rate so that the final pH after addition of sulfuric acid is 8.0 and the total sulfuric acid addition time is 240 minutes, and light calcium carbonate-silica composite A slurry is added. Obtained. At this time, the average particle diameter of the light calcium carbonate-silica composite A was 3.4 μm, and the weight ratio of the solid content of the light calcium carbonate and silica was 50/50.
(Production Example 2: Preparation of light calcium carbonate-silica composite B)
28 parts of a commercially available Rosetta-type light calcium carbonate (trade name: Albuquer 5970 SMI) used for the reaction, 28 sodium silicate solution having a SiO ₂ concentration of 18.0 wt / wt% and a Na ₂ 0 concentration of 6.1 wt / wt% A light calcium carbonate-silica composite B slurry was obtained in the same manner as in Production Example 1 except that a part was added. At this time, the average particle diameter of the light calcium carbonate-silica composite A was 2.1 μm, and the weight ratio of the solid content of the light calcium carbonate and silica was 80/20.
[Example 1]
To 100 parts of pigment consisting of 70 parts of large particle delaminated clay (Nusurf manufactured by Engelhard, volume distribution average particle size 5.2 μm), 30 parts of coarse heavy calcium carbonate (FMT-75 manufactured by Phimatech), Polyacrylic acid soda was added as a dispersant (0.2 parts of inorganic pigment) and dispersed with a serie mixer to prepare a pigment slurry having a solid content of 70%. In the pigment slurry thus obtained, 13 parts of a styrene / butadiene copolymer latex (glass transition temperature 20 ° C., gel content 85%) and 8 parts of hydroxyethyl etherified starch (PG295 manufactured by Penford) were added. After the addition, water was further added to obtain a coating solution having a solid concentration of 60%.

The coated base paper contains 10% light calcium carbonate-silica composite A (light calcium carbonate / silica = 50/50, average particle size 3.4 μm) as a filler per weight of the base paper, and 25 mechanical pulp as paper pulp. %, the chemical pulp 50%, with grade paper in the basis weight of 50 g / ^{m 2} containing recycled pulp 25%.

The above-mentioned base paper is coated on both sides using a blade coater at a coating speed of 1000 m / min so that the coating amount per side of the above-mentioned coating liquid is 7 g / m ² , Was dried to 5.5%.

After drying, a soft nip calendering process was performed at a roll temperature of 150 ° C., 2 nips, a calender linear pressure of 80 kg / cm, and a paper feeding speed of 1000 m / min to obtain a coated paper for printing.
[Example 2] Printing was performed in the same manner as in Example 1, except that the soft nip calendering process was performed at a roll temperature of 70 ° C, 2 nips, a calender linear pressure of 100 kg / cm, and a paper feeding speed of 1000 m / min. Coated paper was obtained.
[Example 3] In Example 1, 70 parts of large particle size delaminated clay (Nusurf manufactured by Engelhard, volume distribution average particle size 5.2 µm), coarse heavy calcium carbonate (FMAT-75 manufactured by PMMA Tech) Instead of 30 parts, changed to 80 parts of large particle size delaminated clay (Nusurf from Engelhard, volume distribution average particle size 5.2 μm), 20 parts of coarse heavy calcium carbonate (FMT-75 from PMMA Tech) A coated paper for printing was obtained in the same manner as in Example 1 except that.
[Example 4] In Example 1, 70 parts of large particle size delaminated clay (Nusurf manufactured by Engelhard, volume distribution average particle size 5.2 µm), coarse heavy calcium carbonate (FMT-75 manufactured by PMMA Tech) Instead of 30 parts, changed to 35 parts of large particle size delaminated clay (Nusurf manufactured by Engelhard, volume distribution average particle size 5.2 μm) and 65 parts of coarse heavy calcium carbonate (FMT-75 manufactured by Phimatech). A coated paper for printing was obtained in the same manner as in Example 1 except that.
[ Reference Example 1 ] In Example 1, a coated paper for offset printing was prepared in the same manner as in Example 1 except that instead of the light calcium carbonate-silica composite A, the light calcium carbonate-silica composite B was changed. Obtained.
[Comparative Example 1] In Example 1, instead of the light calcium carbonate-silica composite A, a coating for printing was performed in the same manner as in Example 1 except that the light calcium carbonate (Albuquer 5970 manufactured by Specialty Minerals) was used. I got paper.
[Comparative Example 2] In Example 1, in place of the light calcium carbonate-silica composite A, white carbon (Tixolex 17 manufactured by Rhodia Silica Korea) was used in the same manner as in Example 1 except that the coated paper for printing was used. Got.
[Comparative Example 3] In Example 1, instead of the light calcium carbonate-silica composite A, a 50:50 mixture of white carbon (Rixia Silica Korea, Tixolex 17) and light calcium carbonate (Specialty Minerals, Albuquer 5970) A coated paper for printing was obtained in the same manner as in Example 1 except for changing to.
[Comparative Example 4] In Example 1, instead of the light calcium carbonate-silica composite A, a coated paper for offset printing was prepared in the same manner as in Example 1 except that titanium dioxide (TCA123 manufactured by Sakai Chemical Co., Ltd.) was used. Got.
Comparative Example 5 In Example 1, 70 parts of large particle size delaminated clay (Nusurf manufactured by Engelhard, volume distribution average particle size 5.2 μm), coarse heavy calcium carbonate (FMT-75 manufactured by PMMA Tech) Instead of 30 parts, changed to 5 parts large particle delaminated clay (Nusurf from Engelhard, volume distribution average particle size 5.2 μm), 95 parts coarse heavy calcium carbonate (FMT-75 from Phimatech) A coated paper for printing was obtained in the same manner as in Example 1 except that.
[Comparative Example 6] In Example 1, 70 parts of large particle size delaminated clay (Nusurf manufactured by Engelhard, volume distribution average particle size 5.2 µm), coarse heavy calcium carbonate (FMT-75 manufactured by PMMA Tech) Instead of 30 parts, 35 parts of delaminated clay (IMERIS Capim NP, volume distribution average particle size 2.5 μm) and 65 parts of coarse heavy calcium carbonate (Fimatec FMT-75) are used. Obtained a coated paper for printing in the same manner as in Example 1.
Comparative Example 7 In Example 1, 70 parts of large particle size delaminated clay (Nusurf manufactured by Engelhard, volume distribution average particle size 5.2 μm), coarse heavy calcium carbonate (FMT-75 manufactured by PMMA Tech) Example 1 except that instead of 30 parts, it was changed to 35 parts of large particle size delaminated clay B (volume distribution average particle size 22 μm) and 65 parts of coarse heavy calcium carbonate (FMT-75 manufactured by PMMA Tech). A coated paper for printing was obtained in the same manner as above.

    The above results are shown in Table 1.

Claims (3)

The surface of rosetta- type light calcium carbonate particles, in which spindle-shaped light calcium carbonate primary particles are aggregated in chestnut-like form on the base paper, is applied to a printing coated paper in which a coating layer containing a pigment and an adhesive is provided on the base paper. A light calcium carbonate-silica composite coated with a light calcium carbonate-silica composite , wherein the light calcium carbonate / silica solid content weight ratio is light calcium carbonate / silica = 30/70 to 70/30 And 10 to 100 parts by weight of a delaminated clay having a volume distribution average particle size of 3.5 to 20 μm per 100 parts by weight of the pigment. The coated paper for printing according to claim 1, wherein the light calcium carbonate-silica composite is contained in an amount of 1 to 25% by weight as a filler in the paper. The coated paper for printing according to claim 1 or 2, wherein the temperature of the rigid roll is processed by a soft nip calender having a temperature of 100 ° C or higher.