JP2007063737A - Coated paper for printing and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide coated paper for printing, produced by coating a coated layer contacted with base paper by a film transfer system and forming at least one or more coated layers thereon, and having excellent surface smoothness and printability, and to provide a method for producing the same. <P>SOLUTION: This coated paper for printing has two or more layers of the coated layers containing pigments and an adhesive as main components on at least one surface of the base paper, wherein the coated layer contacted with the base paper is coated by the film transfer system and the coated layer contacted with the base paper contains tricalcium sulfoaluminate in an amount of 5-35 mass% and another pigment in an amount of 65-95 mass% as pigment components and further contains a water-soluble adhesive in an amount of 1-60 pts.wt. based on 100 pts.wt. of the pigment components as an adhesive component. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a coated paper for printing containing calcium trisulfoaluminate (hereinafter referred to as “satin white”) in a coating layer in contact with the base paper, and in particular, has excellent surface smoothness and white paper gloss, The present invention also relates to a coated paper for printing excellent in printing suitability such as ink fillability and printing smoothness, and a method for producing the same.

  In general, coated paper for printing is manufactured by applying and drying a coating liquid mainly composed of pigment and adhesive on a base paper, and depending on the coating amount of the coating liquid and the finishing method of the coated paper, , Art paper, coated paper, finely coated paper, etc. These coated papers are subjected to multicolor printing or single color printing, and are widely used as commercial printed materials such as flyers, brochures, and posters, or as publications such as books and magazines.

In recent years, the visualization and colorization of printed materials has progressed, and the demand for higher quality of coated paper for printing has increased. White paper quality such as white paper glossiness, smoothness, whiteness, and print gloss, print smoothness, Quality such as appearance in printing finish such as ink fillability is regarded as important.
In addition, flyers and brochures, especially among commercial printed materials, are demanding low-cost, high-quality prints for the purpose of advertising media, and the paper used is becoming thinner and lighter. .

  There are two methods for producing coated paper: the off-machine method, in which papermaking and coating are performed in separate steps, and the on-machine method, in which papermaking and coating are performed continuously on a single machine. More efficient production is possible. Therefore, an on-machine method is generally used as an equipment for producing lightweight coated paper. After paper making, the pigment coating solution is applied to a gate roll coater, rod or blade metering size press coater, fountain, which is a film transfer method. It is produced by the short dwell blade coater that is a method.

On the other hand, in order to obtain coated paper with higher quality, a multi-layer coating is applied in which an undercoat coating solution containing an inexpensive pigment is applied, and then an overcoat coating solution is applied in consideration of white paper quality and printing quality. Is generally done.
Conventionally, the base paper surface to which the pigment coating liquid is applied has a surface size mainly composed of starch so that the pigment coating liquid does not soak into the base paper. However, when multi-layer coating is performed by the on-machine method, since the coating of the undercoat pigment coating liquid also serves as the starch surface size, the undercoat pigment coating liquid penetrates into the base paper, and after coating In order to obtain sufficient smoothness on the surface of the undercoat layer, it was necessary to increase the coating amount of the undercoat pigment coating solution.

Moreover, when both the undercoat coating layer and the topcoat coating layer are applied by a blade method, a coated paper having high surface smoothness and quality can be obtained. However, when manufacturing lightweight coated paper, considering the operability at the time of coating, it is not possible to reduce the base paper rice tsubo unlimitedly, and a certain amount of base paper rice tsubo is required, so the amount that can be coated is that much. Limited. However, when applying by the blade method, it is difficult to apply at a coating amount of less than 6 g / m ² while maintaining sufficient surface smoothness.

  Conventionally, various methods for applying an undercoat coating layer by a film transfer method have been proposed (see Patent Documents 1, 2, 3, 4, and 5). These mainly disclose means for solving mist and paint gum-up occurring at a coating speed of 1100 m / min or more. In addition, the coating composition is composed of a low-viscosity starch with a specific viscosity and a pigment with a small aspect ratio, and by using a coating material for film transfer roll coating that defines the concentration and viscosity of the coating material, it is comparable to blade coating. A method for obtaining coated paper having high gloss and smoothness has also been proposed (see Patent Document 6). However, this method uses a low-viscosity starch adhesive and is characterized by a high concentration of the pigment coating solution of 58% or more. However, the starch adhesive used has a low viscosity. For this reason, after coating by the film transfer method, the starch-based adhesive may migrate in the coating layer, which may cause uneven printing.

The use of satin white as a pigment for coated paper for printing is conventionally known. For example, there has been proposed a method (see Patent Document 7) for improving absorption absorption property, ink drying property, etc. by blending satin white in the top coating layer and maintaining a certain void volume in the coating layer. Yes.
In addition, a method of using satin white in combination with pigments such as kaolin and plastic pigment to impart high surface smoothness and high white paper gloss to coated paper is also introduced (see Patent Documents 8, 9, and 10). However, these are all composed mainly of the outermost coating layer, and do not disclose optimization when using satin white for the undercoat layer.

Further, an undercoat layer having a tension of 0.7 g / cm ³ or less is formed on the base paper, and on the undercoat layer having an air permeability of 8 to 80 seconds after providing the undercoat layer, precipitated calcium carbonate and A bulky matte coated paper provided with an overcoat layer in combination with heavy calcium carbonate has been proposed (see Patent Document 11). In the same document, satin white is also exemplified as a pigment for the undercoat layer, but it is only described as an example of a pigment suitable for obtaining a specific air permeability.
In addition, a coating liquid containing 50 parts by weight or more of an inorganic pigment having a pigment particle diameter ratio (laser method / precipitation method) measured by a laser method and a precipitation method in the range of 3.0 to 10 parts by weight, There has been proposed a coated paper for offset printing (see Patent Document 12) coated on a base paper by a film transfer method. However, nothing is disclosed as to what kind of average particle size or particle size distribution is optimal when used in combination with a coating layer that contacts the base paper in multilayer coated paper, especially satin white. .

Japanese Patent No. 3143899 Japanese Patent No. 2967723 Japanese Patent No. 2910030 Japanese Patent No. 3328554 Japanese Patent No. 3328922 Japanese Patent No. 2737897 JP-A-11-247097 JP 09-256295 A JP 09-67794 A Japanese Patent Laid-Open No. 02-14098 JP 07-238495 A JP 2005-89868 A

  In the present invention, a coating liquid containing satin white is coated on a base paper by a film transfer method, and at least one pigment coating layer is provided thereon, which is excellent in surface smoothness and white paper gloss, and ink. The present invention provides a coated paper for printing excellent in printability such as inking property and printing smoothness, and a method for producing the same.

The printing coated paper according to the present invention is a printing coated paper having at least one coating layer mainly composed of a pigment and an adhesive on at least one side of the base paper, wherein the coating layer in contact with the base paper is a film transfer. The coating layer in contact with the base paper contains 5-35% by mass of satin white and 65-95% by mass of other pigments as pigment components, and pigment component 100 as an adhesive component. It contains 1 to 60 parts by mass of a water-soluble adhesive per part by mass.
Other pigments, at least 50 wt% of a pigment component, there preferably 50 to 80 mass%, average particle diameter d50 ₁ as measured by light scattering method in the range of 2.0～5.0Myuemu, by sedimentation method The measured average particle diameter d50 ₂ is in the range of 0.35 to 0.55 μm, and the ratio (d50 ₁ / d50 ₂ ) of the average particle diameter d50 ₁ to the average particle diameter d50 ₂ is 4 or more, and In the particle size distribution curve by the sedimentation method, the delaminated kaolin in which the mass distribution of particles of 2 μm or less is in the range of 80 to 95% and the mass distribution of particles of 0.3 μm or less is in the range of 30 to 45% It is preferable to comprise.
Moreover, it is preferable to mix | blend 10-60 mass parts with respect to 100 mass parts of pigment components at least 1 sort (s) of starch as a water-soluble adhesive.
Furthermore, it is preferable to use a satin white having a pH of 12 or less.
Further, the coating layer in contact with the base paper preferably further contains 1 to 20 parts by mass of a copolymer latex having a particle diameter of 40 to 150 nm as an adhesive component per 100 parts by mass of the pigment component.
The outermost coating layer has, as a pigment, an average particle diameter d50 ₂ measured by a precipitation method in the range of 0.2 to 1.6 μm, and a particle diameter d90 corresponding to 90 cumulative mass% of the particle size distribution curve by the precipitation method. And the ratio of the average particle diameter d50 ₂ (d90 / d50 ₂ ) is in the range of 1 to 4.0, and the mass proportion of the kaolin in the pigment is 55 to 100% by mass. The surface smoothness, the ink inking property, and the printing smoothness are preferable because excellent effects are obtained.

Further, the method for producing a coated paper for printing according to the present invention is a method for producing a coated paper for printing having two or more coating layers mainly composed of a pigment and an adhesive on at least one side of the base paper. The coating layer to be contacted is coated by a film transfer method using the following coating solution.
Coating liquid: 5 to 35% by mass of satin white as pigment component and 65 to 95% by mass of other pigments, and 1 to 60 parts by mass of water-soluble adhesive as an adhesive component per 100 parts by mass of pigment component Coating liquid to be used.
Other pigments, at least 50 wt% of a pigment component, there preferably 50 to 80 mass%, average particle diameter d50 ₁ as measured by light scattering method in the range of 2.0～5.0Myuemu, by sedimentation method The measured average particle diameter d50 ₂ is in the range of 0.35 to 0.55 μm, and the ratio (d50 ₁ / d50 ₂ ) of the average particle diameter d50 ₁ to the average particle diameter d50 ₂ is 4 or more, and In the particle size distribution curve by the sedimentation method, the delaminated kaolin in which the mass distribution of particles of 2 μm or less is in the range of 80 to 95% and the mass distribution of particles of 0.3 μm or less is in the range of 30 to 45% It is preferable to comprise.
Further, as the water-soluble adhesive, it is preferable to form a coating layer in contact with the base paper by using a coating solution containing 10 to 60 parts by mass of at least one kind of starch per 100 parts by mass of the pigment component. .
The coating liquid for forming the coating layer in contact with the base paper preferably contains at least one thickener or water retention agent, and the content thereof is 0.01 to 1 per 100 parts by mass of the pigment component. A range of 0.0 part by mass is preferred.
In the method of the present invention, the outermost coating layer is, as a pigment, an average particle diameter d50 ₂ as measured by sedimentation method is in the range of 0.2～1.6Myuemu, 90 of the particle size distribution curve by sedimentation method The ratio of the particle diameter d90 corresponding to the cumulative mass% and the ratio (d90 / d50 ₂ ) of the average particle diameter d50 ₂ is kaolin in the range of 1 to 4.0, and the mass ratio of the kaolin in the pigment Is preferably 55 to 100% by mass and includes a step of preparing a dispersion containing an adhesive and a step of applying the coating solution by a blade method.

  The coated paper for printing according to the present invention has the advantages of having excellent surface smoothness and white paper gloss, and excellent printing suitability such as ink fillability and printing smoothness.

  In the present invention, two or more pigment coating layers are provided on the base paper, and the pigment coating layer in contact with the base paper is formed by a film transfer system using a pigment coating liquid containing a specific amount of satin white as a pigment component. By forming it, surface smoothness can be expressed, and performance excellent in printability such as printing smoothness and ink deposition after the pigment coating layer serving as the outermost coating layer can be imparted.

Satin white (official name: calcium trisulfoaluminate) is an inorganic complex compound obtained by the reaction of calcium hydroxide and aluminum sulfate, and is a pigment having a needle-like particle shape.
In the present invention, among the pigment components constituting the coating layer in contact with the base paper, 5 to 35% by mass is satin white, the coating liquid containing this is applied by a film transfer method, and the coating layer in contact with the base paper It is characterized by increased surface smoothness. Incidentally, when the blending ratio of satin white is less than 5% by mass, the improvement in smoothness is insufficient. On the other hand, when it exceeds 35% by mass, the smoothness is improved, but the printing coating is improved. This is not preferable because the amount of adhesive required for developing the strength required for the paper is increased, which is uneconomical.
The particle size of satin white is not particularly limited, but when the average particle size measured by the precipitation method is in the range of 0.1 to 1.3 μm, the smoothness is further improved and the printing strength is maintained. This is preferable because the amount of the adhesive necessary for this is not excessive.
In addition, the average particle diameter by the sedimentation method prescribed | regulated here is the value measured by Cedygraph 5100 (made by Micromeritics).

  The pH of the satin white dispersion is usually around 12.5, and satin white having such a dispersion pH can also be used in the present invention. However, if satin white having a high dispersion pH is used, there is a risk of promoting color reversion due to drying by a dryer or heat treatment such as a heat supercalender, or a decrease in whiteness when the coated paper is stored for a long period of time. Therefore, it is desirable to use satin white whose pH of the dispersion is 12.0 or less, more preferably 8.5 to 11.0.

An example of a method for producing a satin white having a dispersion pH of 12.0 or less that hardly causes such a color return phenomenon is described below.
That is, in the method for producing satin white by reacting a calcium hydroxide suspension and an aqueous aluminum sulfate solution, the aqueous aluminum sulfate solution is added in multiple stages to the calcium hydroxide suspension, Production in which at least one of a plurality of stages of addition of an aqueous aluminum sulfate solution to a calcium hydroxide suspension is performed by continuous addition in which an aqueous aluminum sulfate solution is continuously added to a continuously transferred calcium hydroxide suspension Is the method.
Here, the calcium hydroxide suspension to which the aluminum sulfate aqueous solution is added is pure water in the first stage addition (before the addition of the aluminum sulfate aqueous solution) of the multi-stage addition. Although it is a calcium oxide suspension, it means a mixture of calcium hydroxide and aluminum sulfate (after the addition of the aqueous aluminum sulfate solution) in the second and subsequent stages of the multistage addition. .
In this method, the addition of the aqueous aluminum sulfate solution divided into a plurality of stages is carried out by a so-called “batch” method in which the aqueous aluminum sulfate solution is gradually added to a predetermined amount of calcium hydroxide suspension over a long period of time. However, in order to finely and uniformly control the particle size of the produced satin white, the aqueous solution of aluminum sulfate is continuously applied to the calcium hydroxide suspension that is continuously transferred rather than the “batch” method. Since the “continuous addition” method to be added is superior, the addition by the “continuous addition” method is performed at least once in any addition of the aqueous aluminum sulfate solution divided into a plurality of stages. Is.

  Also, in this method, the addition of the aqueous aluminum sulfate solution by the “continuous addition” method may be changed to the “continuous addition” method in the first step of the addition of the aqueous aluminum sulfate solution divided into a plurality of stages. Further, among the addition of the aqueous aluminum sulfate solution divided into a plurality of stages, all the additions except the final addition can be made a “continuous addition” method. It should be noted that all additions including the final addition may be a “continuous addition” method.

Further, in this method, of the addition of the aqueous aluminum sulfate solution divided into a plurality of stages, the subsequent addition which is the second and subsequent stages is added, and the pH of the composition to which the aqueous aluminum sulfate solution is added in the subsequent addition. Is preferably 11.0 or more, more preferably 12.0 or more, and most preferably 12.5 to 13.0.
“Subsequent addition” as used herein refers to each aqueous solution of aluminum sulfate, which is performed in the second stage to the final stage when the aqueous solution of aluminum sulfate is added in multiple stages to the calcium hydroxide suspension. Addition.
The “composition to which an aluminum sulfate aqueous solution is added in the subsequent addition” referred to here is a mixture of a calcium hydroxide suspension and an aluminum sulfate aqueous solution, and a predetermined amount (total amount) of the aluminum sulfate aqueous solution is still present. A composition that is not mixed (that is, the final stage is not added) and immediately before the aqueous aluminum sulfate solution is added by the subsequent addition, specifically, the produced satin white and unreacted hydroxylation. This indicates a composition in which calcium coexists.
Incidentally, if the pH of the mixed composition before adding aluminum sulfate is less than 11.0, there is a high possibility that the reactivity recovery of calcium hydroxide in the mixed composition is insufficient, and the mixed composition in this state If an aqueous solution of aluminum sulfate is added to the product, it is difficult to carry out the satin white reaction properly and stably, and a large amount of reaction by-products such as aluminum oxide and calcium sulfate may be generated. .

The ratio (a / b) between the number of moles a of the calcium hydroxide suspension and the number of moles b of the total added amount of the aqueous aluminum sulfate solution added in multiple stages is theoretically a / b. = 6.0, indicating that 6 moles of calcium hydroxide and 1 mole of aluminum sulfate are required to produce 1 mole of satin white.
In this production method, the ratio of the number of moles a of the calcium hydroxide suspension when the satin white is produced to the number of moles b of the total amount of the aluminum sulfate aqueous solution added in multiple stages (a / B) is preferably from 5.5 to 7.0, particularly preferably from 5.8 to 7.0.
By the way, when the reaction molar ratio (a / b) between calcium hydroxide and aluminum sulfate is less than 5.5, the ratio of aluminum sulfate to calcium hydroxide becomes excessive, and reaction by-products such as aluminum oxide and calcium sulfate are produced. Since a large amount of product is generated, it is not preferable, and a reaction molar ratio exceeding 7.0 is not preferable because it becomes difficult to obtain satin white having a pH of 12.0 or less.

According to this production method, the aqueous aluminum sulfate solution is added to the reaction end point by adding a predetermined amount of the aqueous aluminum sulfate solution to the poorly reactive calcium hydroxide suspension in a plurality of stages. Since the residual of unreacted calcium hydroxide in the satin white suspension can be suppressed, high-quality satin white having low alkalinity can be stably produced.
For this reason, the ratio (a / b) of the total number of moles a of the calcium hydroxide suspension to the number of moles b of the aluminum sulfate aqueous solution added in multiple stages is in the range of 5.5 to 7.0. By adjusting, it becomes possible to adjust the pH of the composition containing satin white to be produced to 12.0 or less, and by optimizing the addition amount of the aluminum sulfate aqueous solution, a preferred value of 11.0 or less A more preferable value of 10.5 or less can be obtained. In addition, as a minimum of pH, it is preferable that pH shall be 8.5 or more.

In the present invention, among the pigment components constituting the coating layer in contact with the base paper, 5-35% by mass is satin white, and 65-95% by mass is composed of other pigments.
Although it does not specifically limit about the kind of pigment used as this other pigment, When 50 mass% or more of all the pigment components, More preferably, 50-80 mass% is delaminated kaolin which satisfy | fills the following prescription | regulation. It is preferable because a coated paper for printing having excellent printability such as print smoothness and ink fillability, surface smoothness, and blank paper gloss can be obtained.
Delaminated kaolin: the average particle diameter d50 ₁ measured by the light scattering method is in the range of 2.0 to 5.0 μm, and the average particle diameter d50 ₂ measured by the sedimentation method is in the range of 0.35 to 0.55 μm. The ratio of the average particle diameter d50 ₁ to the average particle diameter d50 ₂ (d50 ₁ / d50 ₂ ) is 4 or more, and in the particle size distribution curve by the precipitation method, the mass distribution of particles of 2 μm or less is Delaminated kaolin in the range of 80 to 95% and the mass distribution of particles of 0.3 μm or less in the range of 30 to 45%.

Delaminated kaolin is a clay mineral obtained by peeling a layered bulk kaolin into a single layer, and has a large aspect ratio.
In general, the individual shape characteristics of tabular grains such as delaminated kaolin can be defined by the ratio (aspect ratio d / t) to the major axis d thickness t. In the present invention, the delaminated kaolin The granular characteristics are defined by the average particle diameter d50 ₁ by the light scattering method and the average particle diameter d50 ₂ by the sedimentation method.
In the light scattering method average particle size d50 ₁ measurement by the contrast its diameter is regarded all individual particles to spherical particles are measured, the average particle size d50 ₂ measured by sedimentation method, particle shape sedimentation In order to affect the property, particles having a flat plate shape and slower sedimentation are measured as particles having a smaller apparent diameter. Therefore, it is considered that the ratio of the average particle diameter d50 ₁ by the light scattering method and the average particle diameter d50 ₂ by the precipitation method, d50 ₁ / d50 ₂ , increases as the above-described aspect ratio increases. In the present invention, a laser diffraction particle size distribution measuring device SALD-2000 (manufactured by Shimadzu Corporation) is used as a method for measuring the average particle size by the light scattering method, and Cedy is used as a method for measuring the particle size distribution and the average particle size by the precipitation method. Graph 5100 (manufactured by Micromeritics) was used.

In the particle size distribution of delaminated kaolin measured by the sedimentation method, when the mass distribution of particles of 2 μm or less is less than 80% and the mass distribution of particles of 0.3 μm or less is less than 30%, a component having a large particle size is present. Therefore, the effect of improving the smoothness of the coating layer is difficult to obtain, and when the mass distribution of particles of 2 μm or less exceeds 95% and the mass distribution of particles of 0.3 μm or less exceeds 45%, a component having a small particle size is present. Therefore, it is difficult to obtain an effect of improving the smoothness of the coating layer because the aqueous coating solution using this pigment easily penetrates into the base paper.
In addition, when the average particle diameter d50 ₁ and the average particle diameter d50 ₂ are less than 2.0 μm and less than 0.35 μm, respectively, the delaminated kaolin in the coating liquid easily penetrates into the base paper. It is difficult to obtain an effect of improving smoothness. In addition, when the average particle diameter d50 ₁ and the average particle diameter d50 ₂ exceed 5.0 μm and 0.55 μm, respectively, it becomes difficult to obtain a coated paper having a sufficient white gloss.
For this reason, when using the said delaminated kaolin together, it is necessary to use the delaminated kaolin which satisfy | fills all these regulations.
Furthermore, even when d50 ₁ / d50 ₂ is less than 4, the effect of using the delaminated kaolin in combination cannot be obtained. In the present invention, the value of d50 ₁ / d50 ₂ is preferably 4 to 12, and more preferably 5 to 11.

  In the present invention, among the pigment components constituting the coating layer in contact with the base paper, as other pigments occupying 65 to 95% by mass, pigments other than the specific delaminated kaolin, specifically, calcium carbonate, calcination Inorganic pigments such as kaolin, talc, calcium sulfate, barium sulfate, aluminum hydroxide, titanium dioxide, zinc oxide, alumina, magnesium carbonate, magnesium oxide, silica, magnesium aluminosilicate, calcium silicate, bentonite, zeolite, sericite, smectite Alternatively, it may be composed of only one or two or more pigments selected from organic pigments such as plastic pigments such as solid type, hollow type and through-hole type, and binder pigments. In the present invention, as described above, the specific delaminated kaolin is preferably used as the other pigment in an amount of 50% by mass or more, more preferably 50 to 85% by mass of the pigment component. In such a case, it may be used in combination so that the sum of satin white, delaminated kaolin and the other pigments is 100% by mass.

In order to develop the surface strength of the coated paper of the present invention, a water-soluble adhesive or a water-dispersible adhesive is used for the coating layer in contact with the base paper. Examples of water-soluble adhesives include starches such as oxidized starch, esterified starch, etherified starch, dextrin and cold water soluble starch, proteins such as casein, soy protein, synthetic protein, cellulose derivatives such as hydroxyethyl cellulose, polyvinyl alcohol, Such modified products can be used.
In this invention, it is necessary to use a water-soluble adhesive in the ratio of 1-60 mass parts per 100 mass parts of pigments. Especially, it is preferable to mix | blend 10-60 mass parts with respect to 100 mass parts of pigments at least 1 sort (s) of starch or a starch derivative. Incidentally, if the blending amount of the water-soluble adhesive is less than 1 part by mass, the surface strength of the coated paper is not sufficiently developed, and the coating layer is peeled off during printing. On the other hand, when the amount exceeds 60 parts by mass, the viscosity of the coating solution increases excessively, and the paper separation at the application nip exit is not stable when coating by the film transfer method, and unevenness having a certain pattern on the paper surface. Occurs.

Examples of the water-dispersible adhesive used in the present invention include conjugated diene copolymer latexes such as styrene-butadiene copolymer latex, methyl methacrylate-butadiene copolymer latex, and styrene-methyl methacrylate-butadiene copolymer latex. Acrylic polymer latex such as acrylic acid ester and / or methacrylic acid ester polymer or copolymer latex, vinyl polymer latex such as ethylene-vinyl acetate polymer latex, or carboxyl of these various polymer latexes Examples thereof include a polymer or copolymer latex modified with a functional group-containing monomer such as a group, and among these, those having an average particle diameter of 40 to 150 nm are preferable. With the same content, the smaller the average particle diameter of the latex, the larger the contact area with the pigment in the coating layer, and the strength of the coating layer can be effectively expressed. By the way, if the particle size of the water-dispersible adhesive is smaller than 40 nm, wetting surface strength due to dampening water during offset printing, even with a pigment coating solution in contact with the base paper, due to the effect of the emulsifier compounded at the time of latex production Is not preferable. Furthermore, when the particle diameter of the latex exceeds 150 nm, the contact strength with the pigment in the coating layer is reduced at the same content, so that the surface strength may be insufficient.
In the present invention, only a water-soluble adhesive can be used as the adhesive component, but from the viewpoint of printing strength, it is preferable to use a copolymer latex as described above, in which case the pigment component 100 It is preferable to use the copolymer latex at a ratio of 1 to 20 parts by mass per part by mass.

The satin white essential for the present invention tends to lower the water retention of the coating liquid, and if the water retention of the coating liquid is low, the water of the coating liquid is quickly absorbed by the base paper at the time of coating. The upper coating liquid is solidified and is difficult to peel off from the roll, and roll contamination may occur. In order to prevent this, it is preferable to contain at least one thickener or water retention agent in the coating solution of the coating layer in contact with the base paper.
Examples of such thickeners or water retention agents include polycarboxylic acids, alkali thickening types such as acrylic copolymers, and associations in which lipophilic groups are arranged at both ends of hydrophilic base polymers such as acrylic polymers and polyethylene oxide. Examples thereof include naturally derived types such as type, carboxymethylcellulose, and sodium alginate, and acrylic copolymer emulsions are particularly preferably used from the viewpoint of workability and cost. As a compounding quantity of a thickener or a water retention agent, the range of 0.01-1.0 mass part is preferable with respect to 100 mass parts of pigments, More preferably, it is the range of 0.05-0.8 mass part.

  In addition to thickeners and water-retaining agents, the coating solution used to form the coating layer in contact with the base paper contains blue or purple dyes, colored pigments, fluorescent dyes, and antioxidants as necessary. Various auxiliaries such as an agent, an anti-aging agent, a conductive inducer, an antifoaming agent, an ultraviolet absorber, a dispersant, a pH adjuster, a mold release agent, a water-resistant agent, and a water repellent can be appropriately blended.

  In the present invention, the solid content concentration of the coating solution containing satin white, other pigments, adhesives such as water-soluble adhesives, and various auxiliary agents used as necessary is in the range of 25 to 65% by mass. Can be selected. In consideration of adjustment of coating amount and operability, it is desirable to be in the range of 30 to 55% by mass.

The dry coating amount of the coating layer in contact with the base paper of the present invention is preferably 0.5 to 10.0 g / m ² per side. Incidentally, when the coating amount is less than 0.5 g / m ² , the surface coverage of the paint is inferior and it is difficult to obtain the desired quality. On the other hand, if it exceeds 10.0 g / m ² , the surface coverage is improved, but when a coating layer containing a pigment and an adhesive is applied onto the blade, a streak defect called streak occurs. The quality of the coated paper may be significantly impaired.

The base paper used in the present invention is not particularly limited, and the base paper used in conventional coated paper for printing can be used.
Examples of the pulp component constituting the base paper include bleached chemical pulp such as commonly used bleached hardwood pulp (LBKP) and bleached softwood pulp (NBKP), groundwood pulp (GP), pressurized groundwood pulp (PGW), and refiner. Mechanical pulp such as groundwood pulp (RGP) and thermomechanical pulp (TMP), deinked waste paper pulp (DIP), waste paper, and the like are appropriately mixed and used. The amount of mechanical pulp preferably does not exceed 70% by mass of the total pulp constituting the base paper. If it exceeds 70% by mass, printability such as print smoothness and surface strength of the finally obtained coated paper may be impaired. 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 deinked waste paper pulp can be bleached and used as 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 pulp and TCF pulp.

Examples of fillers added to the base paper include heavy calcium carbonate, light calcium carbonate, calcium sulfite, gypsum, talc, clay, calcined kaolin, white carbon, amorphous silica, delaminated kaolin, diatomaceous earth, and magnesium carbonate. Examples include inorganic pigments such as titanium dioxide, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, and zinc hydroxide, and organic pigments such as urea / formalin resin fine particles and fine hollow particles, and are included in waste paper and waste paper. The filler can also be reused. Two or more fillers can be used in combination.
The blending amount of the filler is generally added so that the paper (base paper) ash content is in the range of 3 to 20% by mass.

  In addition to pulp and filler in the base paper, internal additives for papermaking such as internal sizing agent, anionic, nonionic, cationic or amphoteric yield improver, drainage improver, paper strength enhancer, etc. Can be added as needed. Specific examples of the internal sizing agent include sizing agents such as alkyl ketene dimer, alkenyl succinic anhydride, styrene-acrylic, higher fatty acid, petroleum resin, and rosin. Specific examples of yield improvers, drainage improvers, and paper strength enhancers include, for example, 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, polyamiin, polyvinyl alcohol, polyethylene oxide and the like. Moreover, it is also possible to use a bulking agent and a softening agent having a function of inhibiting the binding between pulp fibers as long as the desired effect of the present invention is not hindered. Specific examples of bulking agents and softeners include, for example, ester compounds of polyhydric alcohols and fatty acids, polyoxyalkylene compounds of polyhydric alcohols and fatty acid ester compounds, fatty acid polyamidoamines, polyhydric alcohol surfactants, An ionic surfactant etc. can be illustrated. The amount of the bulking agent and softening agent is generally about 0.05 to 2.0% by mass with respect to the pulp.

There are no particular limitations on the paper making conditions of the base paper, and for example, commercial scale paper machines such as long net paper machines, gap former paper machines, round net paper machines, short net paper machines, etc. It can be appropriately selected and used. The papermaking method may be any method such as acidic papermaking, neutral papermaking, or weak alkali papermaking. However, in recent years, since paper preservation is required, base paper made by neutral papermaking is preferred. The base paper can be subjected to normal size press treatment or pigment size press treatment, and starch derivative, polyvinyl alcohol, polyacrylamide or the like is appropriately used as an adhesive for such size press treatment. The basis weight of the base paper made under these paper making conditions is preferably 30 to 70 g / m ² .

  In the production method of the present invention, the coating liquid for forming the coating layer in contact with the base paper is applied by a film transfer type coating apparatus. As a film transfer type coating apparatus, a gate roll coater, a blade metering size press coater, a rod metering size press coater, or the like can be used.

  In the coated paper of the present invention, one or more coating layers mainly composed of a pigment and an adhesive are applied on the coating layer in contact with the base paper. Examples of such pigments include, but are not limited to, calcium carbonate, calcined kaolin, structural kaolin, delaminated kaolin, talc, calcium sulfate, barium sulfate, aluminum hydroxide, titanium dioxide, zinc oxide, alumina, carbonic acid. Inorganic pigments such as magnesium, magnesium oxide, silica, magnesium aluminosilicate, calcium silicate, bentonite, zeolite, sericite, and smectite; plastic pigments such as solid, hollow, and through-hole types; organic pigments such as binder pigments, etc. It is possible to use pigments used in the ordinary coated paper field. Among these pigments, one or more types are appropriately selected and used according to the level of white paper gloss required for the target coated paper.

Among the coating layers formed on the coating layer in contact with the base paper, the following pigments are preferably used for the outermost coating layer. That is, the average particle diameter d50 ₂ measured by the precipitation method is in the range of 0.2 to 1.6 μm, and the particle diameter d90 corresponding to 90 cumulative mass% of the particle size distribution curve by the precipitation method and the average particle diameter d50 ₂ It is preferable to use kaolin having a ratio (d90 / d50 ₂ ) of 1 to 4.0. So long as the average particle diameter d50 ₂ is 0.2～1.6Myuemu, excellent effects by the surface smoothness and sheet gloss is obtained, more preferably 0.2～1.4Myuemu.

Further, d90 / d50 _2, which is the ratio of the 90% particle size d90 to the average particle size d50 ₂ , is an index value indicating the breadth of the particle size distribution of the pigment, and the value is substantially 1 or more. The closer the value is, the closer to monodispersion and the narrower the particle size distribution, and the larger the value, the wider the particle size distribution. In the present invention, the closer the d90 / d50 ₂ value is to 1, the more the orientation of kaolin in the outermost coating layer is promoted and the surface smoothness of the coated paper is improved, while the d90 / d50 ₂ value is 4 If it exceeds 0.0, the orientation effect of kaolin is small, and the effect of improving the surface smoothness of the coated paper may be small. Moreover, More preferably, it is 1-3.5.

  In the present invention, the kaolin content in the pigment of the outermost coating layer is preferably in the range of 55 to 100 parts by mass, and more preferably in the range of 60 to 100 parts by mass. When the kaolin content is 55 parts by mass or more, the smoothness improving effect by the kaolin is increased.

  Generally, in a coated paper for printing in which two or more coating layers are provided on at least one side of a base paper, from the viewpoint of cost effectiveness, the coating layer is composed of a coating layer in contact with the base paper and a single layer formed thereon. In many cases, it has a two-layer structure composed of coating layers. When the coating layer has a two-layer structure as described above, the outermost coating layer is directly formed on the coating layer in contact with the base paper, and therefore the specific kaolin described above is used for the outermost coating layer. The effect of improving the smoothness of the ink is remarkable, and more excellent effects can be exhibited in the surface smoothness, the ink inking property and the printing smoothness.

  In addition, in the coated paper for printing having three or more layers on at least one side of the base paper, the pigment and the adhesive used for the intermediate layer between the coating layer in contact with the base paper and the outermost coating layer are particularly limited. In general, raw materials used in the field of coated paper can be used, and the amounts of pigments, adhesives and auxiliaries are not particularly limited, and are within the range of amounts normally used in the field of coated paper. Can be used in

The adhesive of the outermost coating layer is not particularly limited, and is an adhesive used in the ordinary coated paper field, for example, various starches such as oxidized starch, esterified starch, cold water soluble starch, and casein. , Proteins such as soybean protein and synthetic protein, cellulose derivatives such as carboxymethylcellulose and methylcellulose, water-soluble adhesives such as polyvinyl alcohol and its modified products, styrene-butadiene copolymer, methylmethacrylate-butadiene copolymer It is possible to use vinyl polymer latex such as conjugated diene polymer latex, acrylic polymer latex, ethylene-vinyl acetate copolymer, etc. Two or more types can be appropriately selected and used.
Further, the amount of the adhesive is not particularly limited, but is 5 to 20 parts by mass, preferably 8 to 15 parts by mass per 100 parts by mass of the pigment.

  In the present invention, the coating solution for the outermost coating layer includes, as necessary, a blue or purple dye or a colored pigment, a fluorescent dye, a thickening water retention agent, an antioxidant, an anti-aging agent, Various auxiliary agents such as a conductivity-inducing agent, an antifoaming agent, an ultraviolet absorber, a dispersant, a pH adjuster, a mold release agent, a water-resistant agent, and a water-repellent agent can be appropriately blended.

  Moreover, although the solid content concentration of the coating liquid containing the above-mentioned pigment, adhesive, and various auxiliary agents used as necessary can be selected in the range of 40 to 75% by mass, in consideration of operability. It is preferable that it is the range of 45-70 mass%.

  In coating the coating liquid on the coating layer in contact with the base paper, for example, a blade coater, an air knife coater, a roll coater, a reverse roll coater, a bar coater, a curtain coater, a die slot coater, a gravure coater, a Chanplex A blade that provides excellent surface smoothness, although coating devices commonly used in the production of coated paper such as coaters, two-roll size press coaters, gate roll size press coaters, and film metering size press coaters can be used. The use of a coater is most preferably used.

The dry coating amount of the coating layer applied on the coating layer in contact with the base paper is adjusted in the range of 5.0 to 20.0 g / m ² per side. Even when two or more coating layers are overcoated, the dry coating amount per layer may be adjusted within this range.

  The coated paper thus obtained is passed through various publicly known finishing devices such as a super calender, gloss calender, soft calender, etc., and finished with a product.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. In addition, unless otherwise indicated, the part and% in an example show a mass part and the mass%, respectively. Moreover, the addition amount of the used chemical | medical agent shows the mass part of solid content conversion.

The average particle size by the precipitation method of satin white used in Examples and Comparative Examples, and the particle size distribution and average particle size by the precipitation method of kaolin used together were measured by the following methods. Moreover, the average particle diameter by the light scattering system of the kaolin used together was measured by the following method.
(Pigment particle size distribution and average particle size measurement by sedimentation method)
The particle size distribution of the pigment was measured using a Sedigraph 5100 manufactured by US Micromeritics, and the average particle size (d50 ₂ ) corresponding to 50 cumulative mass% and the particle size corresponding to 90 cumulative mass% (d90 ) Was measured. Further, from the particle size distribution curve, the mass distribution of particles of 2 μm or less and the mass distribution of particles of 0.3 μm or less were obtained. The pigment dispersion used for the measurement was prepared by adding a pigment slurry having a solid content concentration of 5% by mass prepared by adding 0.05% of a dispersant (sodium polyacrylate) to a pigment, solubilizing pyrophosphate salt (trade name: Nankaline). It was obtained by diluting with a 0.1% aqueous solution (S1, manufactured by Rin Chemical Co., Ltd.) so that the pigment solid content concentration was about 1%, and subjected to ultrasonic dispersion treatment (30 W, 45 kHz, 60 minutes).
(Measurement of average particle diameter of pigments by light scattering method)
The particle size distribution of the pigment was measured using a laser diffraction particle size distribution analyzer SALD-2000 manufactured by Shimadzu Corporation, and the average particle size (d50 ₁ ) corresponding to 50 cumulative mass% was measured. The pigment dispersion used for the measurement is a region where a pigment slurry having a solid content concentration of 5% by mass prepared by adding 0.05% of a dispersant (sodium polyacrylate) to the pigment can be measured with the measuring device. Obtained by diluting up to

The pH of the satin white slurry was measured by the following method. The pH in the process of preparing satin white was also measured in the same manner.
(PH measurement method)
Using a Lacom Tester pH meter (pHScanWPBN type, manufactured by ASONE), the pH electrode was directly immersed in various dispersions to measure the pH of the pigment dispersion. In addition, about the pH meter used for the pH measurement, NIST standard calibration solution (pH 6.86 and pH 9.18)
The pH was measured after calibrating the pH using.

The coated papers for printing obtained in Examples and Comparative Examples were evaluated by the following methods, and the results are shown in Tables 1 and 2. The following evaluation test was performed in an environment of 23 ° C. and a relative humidity of 50%.
(White paper gloss)
It measured using the 75 degree glossiness meter according to ISO 8254-1 (1999), and calculated | required the average.

(PPS smoothness of coated paper)
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.

(Printability (ink fillability and print smoothness))
Using an RI printer, printing was performed using 0.1 cc of printing ink (Values-G type, manufactured by Dainippon Ink & Chemicals, Inc.), transferred ink density (ink fillability), and ink transfer uniformity. (Print smoothness) was visually observed and comprehensively evaluated.
A: Printability is particularly excellent.
○: Printability is excellent.
Δ: Printability is slightly inferior (practical minimum level).
X: Printability is inferior.

(Surface printing strength)
With a RI printer (Meiji Seisakusho), 0.4 cc of printing ink (paper test SD50 red BT = 13, manufactured by T & K TOKA) is spread on the roll, and the transfer speed is slowed down on the coated paper to be evaluated. After transferring the ink and printing, knead the ink without wiping off the ink on the roll, overprint it on the coated paper once printed, then knead the ink again without wiping off the ink on the roll. Overprinting was performed on the coated paper that had been printed once, and overprinted three times for convenience. Thereafter, the peeled state of the paper surface present in the ink remaining on the roll was transferred to another paper, and the color loss state of the transferred ink was visually evaluated.
A: No color loss.
'': Color loss is slightly observed, but it is a good level as coated paper.
○: Slight color loss is recognized, but it is a practical level as coated paper.
Δ: Color loss is observed.
X: The color is remarkably lost.

(Evaluation test for thermal fading)
After performing heat treatment for 24 hours under conditions of 70 ° C. and RH 90% using a thermo-hygrostat, the whiteness difference and color difference before and after the treatment were measured by the following methods to evaluate the thermal fading.
-Measurement of whiteness difference According to JIS-P8148, the whiteness before and after heat treatment was measured, and the difference in whiteness (ΔW) was determined by the following formula. The smaller the value, the better the thermal fading.
ΔW = (Whiteness before heat treatment) − (Whiteness after heat treatment)
-Measurement of color difference The hue before and after heat treatment was measured according to JIS-Z8722. The color difference (ΔE) was determined from the color difference formula based on the L ^* a ^* b ^* color system based on JIS-Z8730. The smaller the value, the better the thermal fading.

Example 1
(Preparation of coating solution for coating layer in contact with base paper)
In an aqueous solution in which 0.1 part of kaolin in which sodium polyacrylate is dispersed as a dispersant is added, the average particle diameter d50 ₁ measured by the light scattering method is 2.25 μm, and the average particle diameter d50 ₂ measured by the sedimentation method is 0.61 μm, d50 ₁ / d50 ₂ is 3.7, the mass distribution of particles of 2 μm or less in the particle size distribution curve by the sedimentation method is 88.3%, and the mass distribution of particles of 0.3 μm or less is 22.2%. kaolin is (trade name: Capim DG, manufactured by Imerys, Inc.) 90 parts of satin white (trade name mean particle size d50 ₂ as measured by sedimentation method is 1.0 .mu.m: satin white B, slurry pH: 12.5, 10 parts) (manufactured by Shiroishi Kogyo Co., Ltd.) were sequentially added and dispersed with a Coreless disperser to prepare a pigment slurry. To this slurry, 40 parts of oxidized starch (trade name: Ace B, manufactured by Oji Cornstarch Co., Ltd.), styrene-butadiene copolymer latex (trade name: SN-113I, particle size: 190 nm) as an adhesive with respect to 100 parts of pigment. (Manufactured by Nippon A & L Co., Ltd.) was sequentially added to finally prepare a coating solution having a solid concentration of 40%.

(Preparation of coating solution for outermost coating layer)
As the pigment component, an average particle diameter d50 ₂ is 0.40μm as measured by sedimentation method, 90% particle size d90 is 1.75 [mu] m, kaolin (trade name d90 / d50 ₂ is 4.4: Kaogurosu 90, seal Co. ) In a pigment slurry consisting of 70 parts and 30 parts of heavy calcium carbonate having an average particle size of 0.8 μm (trade name: Hydrocurve 90, manufactured by Bihoku Flour Chemical Co., Ltd.) Name: Oji Ace B, manufactured by Oji Cornstarch Co., Ltd.) 2 parts, styrene-butadiene copolymer latex (trade name: Smartex PA2323, particle size: 89 nm, manufactured by Nippon A & L Co., Ltd.), and antifoaming agent, dye, etc. An auxiliary agent was added to finally prepare a coating solution having a solid content of 59%.

(Create coated paper for printing)
Using a rod metalling size press coater, apply a coating solution for the coating layer in contact with the base paper obtained above to a high-quality base paper (rice basis 45 g / m ² ) having an intensity of 0.77 g / cm ^3. An undercoat layer was formed by applying to both sides so that the dry coating amount per unit was 4 g / m ² and drying. Next, on each of the undercoat layers, the coating liquid for the outermost coating layer obtained above was applied and dried using a blade coater so that the dry coating amount per side was 8 g / m ² . The outermost coating layer was provided on both sides. The coated paper thus obtained was passed through a super calender under conditions of a temperature of 70 ° C. and a linear pressure of 200 kN / m to obtain a coated paper for printing.

Example 2
In the preparation of the coating solution for the coating layer in contact with the base paper of Example 1, the average particle size d50 ₁ measured by the light scattering method is 2.25 μm, the average particle size d50 ₂ measured by the sedimentation method is 0.61 μm, A kaolin having a d50 ₁ / d50 ₂ of 3.7, a mass distribution of particles of 2 μm or less in a particle size distribution curve by a sedimentation method is 88.3%, and a mass distribution of particles of 0.3 μm or less is 22.2% ( (Trade name: Capim DG), the average particle diameter d50 ₁ measured by the light scattering method is 3.25 μm, the average particle diameter d50 ₂ measured by the sedimentation method is 0.38 μm, and d50 ₁ / d50 ₂ is 8.6. The amount of oxidized starch (trade name: Oji Ace B) using Ted Kaolin (trade name: Conzer 1160, manufactured by Imeris Co., Ltd.) with a particle size of 2 μm or less in the particle size distribution curve by the sedimentation method. Reduced to 25 parts, instead of styrene-butadiene copolymer latex (trade name: SN-113I), styrene-butadiene copolymer latex (trade name: SMARTEX PA2323, particle size: 89 nm, manufactured by A & L Japan) is used. A coated paper for printing was obtained in the same manner as in Example 1 except that.

Example 3
In the preparation of the coating solution for the coating layer in contact with the base paper of Example 2, styrene-butadiene copolymer latex (trade name: SN) was used instead of styrene-butadiene copolymer latex (trade name: SMARTEX PA2323). A coated paper for printing was obtained in the same manner as in Example 2 except that -113I) was used.

Example 4
In the preparation of the coating solution for the coating layer in contact with the base paper of Example 2, the average particle size d50 ₁ measured by the light scattering method is 3.25 μm, the average particle size d50 ₂ measured by the sedimentation method is 0.38 μm, d50 ₁ / d50 ₂ is 8.6, and 2 μm in the particle size distribution curve by the sedimentation method
The average particle diameter measured by a light scattering method instead of delaminated kaolin (trade name: Conzer 1160) having a mass distribution of 91.3% and a particle distribution of 0.3 μm or less of 42.0%. d50 ₁ is 3.64 μm, the average particle diameter d50 ₂ measured by the sedimentation method is 0.47 μm, d50 ₁ / d50 ₂ is 7.7, and the mass distribution of particles of 2 μm or less in the particle size distribution curve by the sedimentation method is 90 .1%, using delaminated kaolin (trade name: Konzer 2000, manufactured by Imeris Co., Ltd.) having a mass distribution of particles of 35.4% or less, and using oxidized starch (trade name: Oji Ace B) Except for reducing the amount used to 10 parts and using 3 parts of polyvinyl alcohol (trade name: PVA-105, manufactured by Kuraray Co., Ltd.) in addition to the styrene-butadiene copolymer latex, A coated paper for printing was obtained in the same manner as in Example 2.

Example 5
In the preparation of the coating solution for the coating layer in contact with the base paper of Example 2, Example 2 was used except that Satin White prepared by the following method was used instead of Sachin White (trade name: Sachin White B). In the same manner, a coated paper for printing was obtained.
Preparation of Satin White Addition of first stage aluminum sulfate aqueous solution to calcium hydroxide suspension 6% calcium hydroxide suspension was 300 g / min and 6% sulfuric acid against an in-line mixer rotated at 9000 rpm An aqueous aluminum solution was simultaneously and continuously injected at 185 g / min (80% of the reference mole number. The calculation method of the reference mole number and the like will be described later), and the injection was continuously performed for 14 minutes. The mixed composition (composition discharged from the in-line mixer) obtained at that time was continuously received in a pH restoration tank and allowed to stand for 30 minutes to recover the pH. The pH of the mixed composition after the pH recovery (hereinafter referred to as “first composition”) was 12.8.

Here, a method for calculating the reference number of moles will be briefly described.
The molecular weights of calcium hydroxide and aluminum sulfate are 74.1 and 342.16, respectively, and 300 g / min of 6% calcium hydroxide suspension has a solid content of 18 g / min. The number of moles charged) is 18 / 74.1 = 0.243. Therefore, the reference number of moles which is 1/6 of the number of moles of the calcium hydroxide suspension is 0.243 × 1/6 = 0.0405 mol / min.
On the other hand, 185 g / min of 6% aluminum sulfate aqueous solution contains 185 g × 6% = 11.1 g / min of aluminum sulfate, which is 11.1 g / min × 1 / 342.16 in terms of moles. = 0.0324 mol / min.
Therefore, the calculation of the ratio of the aqueous aluminum sulfate solution added to the first stage to the reference mole number is calculated as (0.0324 mol / min) / (0.0405 mol / min) = 80%.

(2) Addition of second-stage aluminum sulfate aqueous solution In the same manner as in (1) above, 485 g / min of the mixed composition (first composition) was applied to the in-line mixer rotated at 9000 rpm, and 6 % Aluminum sulfate aqueous solution was injected simultaneously and continuously at 35 g / min (15% of the reference mole number), and the injection was continuously performed for 12 minutes. The mixed composition (composition discharged from the in-line mixer) obtained at that time was continuously received in a pH restoration tank and allowed to stand for 30 minutes to recover the pH. The pH of the mixed composition after the pH recovery (hereinafter referred to as “second composition”) was 12.4.

(3) Addition of third-stage aluminum sulfate aqueous solution (end of reaction)
In the same manner as (2) above, 520 g / min of the mixed composition (second composition) and 11 g / min of a 6% aqueous solution of aluminum sulfate (based on the reference number of moles) with respect to the in-line mixer rotated at 9000 rpm. 5%) at the same time and continuously, and the injection was continued for 10 minutes (reaction completed). The mixed composition (composition discharged from the in-line mixer) obtained at that time was continuously received in a cushion tank to obtain a composition after completion of the reaction (hereinafter referred to as “reaction completed composition”). The pH of the reaction finished composition was 10.6.

A method for calculating the ratio (a / b) of the total number of moles a of the calcium hydroxide suspension to the number of moles b of the aluminum sulfate aqueous solution added in a plurality of stages will be briefly described.
First, 6% calcium hydroxide finally used is 300 g / min × 10 min = 3000 g, the solid content contained in the 6% calcium hydroxide is 180 g, and the molar number a of calcium hydroxide is 2.43 mol. . The total amount of 6% aluminum sulfate added in multiple stages was 231 g / min × 10 minutes = 2310 g, the solid content contained in it was 138.6 g, and the molar number b of aluminum sulfate was 0.405. Is a mole. Accordingly, the molar ratio (calcium hydroxide / aluminum sulfate = a / b) is 6.0. Moreover, the total addition rate of aluminum sulfate was 100% (= 80% + 15% + 5%) of the reference mole number.

  The reaction completion composition obtained above is dehydrated with a filter press to obtain a composition having a solid content of about 32 to 34%, and then the dehydrated composition is redispersed 56 in water so that the solid content becomes 27%. It was. At the time of the redispersion, a polyacrylic acid dispersant (trade name: Aron T-50, manufactured by Toa Gosei Chemical Co., Ltd.) is added to water in advance in an amount of 0.5 part relative to the solid content of the dehydrated composition. Further, the amount of the dispersant added was adjusted so that the concentration of the redispersed composition dispersion was 27%. The average particle size was 0.49 μm.

Example 6
(Preparation of coating solution for coating layer in contact with base paper)
In an aqueous solution in which 0.1 part of kaolin in which sodium polyacrylate is dispersed as a dispersant is added, the average particle diameter d50 ₁ measured by the light scattering method is 3.64 μm, and the average particle diameter d50 ₂ measured by the sedimentation method is 0.47 μm, d50 ₁ / d50 ₂ is 7.7, the mass distribution of particles of 2 μm or less in the particle size distribution curve by the sedimentation method is 90.1%, and the mass distribution of particles of 0.3 μm or less is 35.4%. 65 parts of delaminated kaolin (trade name: Conzer 2000, manufactured by Imeris), 5 parts of self-made satin white used in Example 5 (average particle calcium (trade name: Hydrocurve 60, manufactured by Bihoku Flour Industries)) Were added in order and dispersed with a Coreless disperser to prepare a pigment slurry, which was oxidized starch (trade name) as an adhesive with respect to 100 parts of pigment. Ace B (manufactured by Oji Cornstarch Co., Ltd.) 30 parts, styrene-butadiene copolymer latex (trade name: Smartex PA2323) 10 parts were sequentially added, and water retention agent (trade name: S-350, manufactured by Somar Co.) 0.1 Finally, a coating solution having a solid content concentration of 38% was prepared.
(Create coated paper for printing)
A coated paper for printing was obtained in the same manner as in Example 1 except that the coating liquid for the coating layer in contact with the base paper obtained above was used.

Example 7
In the preparation of the coated liquid for the outermost coating layer of Example 1, kaolin (trade name: Kaogurosu 90) instead of the average particle diameter d50 ₂ is 1.14μm as measured by sedimentation method, 90% particle size d90 There 1.90μm, d90 / d50 ₂ is kaolin is 1.7 (trade name: Astra plus, manufactured by Imerys, Inc.) was used instead got coated paper for printing in the same manner as in example 1.

Example 8
In the preparation of the coated liquid for the outermost coating layer of Example 1, kaolin (trade name: Kaogurosu 90) instead of the average particle diameter d50 ₂ is 0.48μm as measured by sedimentation method, 90% particle size d90 There 1.34 .mu.m, d90 / d50 ₂ kaolin 2.8 (trade name: para printed, manufactured PPSA Ltd.) was used instead got coated paper for printing in the same manner as in example 1.

Example 9
In the preparation of the coated liquid for the outermost coating layer of Example 1, kaolin (trade name: Kaogurosu 90) instead of the average particle diameter d50 ₂ is 0.24μm as measured by sedimentation method, 90% particle size d90 Was used in the same manner as in Example 1 except that kaolin (trade name: Hydra Gloss 90, manufactured by Huber) having a d90 / d50 ₂ of 3.1 was used.

Example 10
In the preparation of the coated liquid for the outermost coating layer of Example 1, kaolin (trade name: Kaogurosu 90) instead of the average particle diameter d50 ₂ is 0.95μm as measured by sedimentation method, 90% particle size d90 There 3.21μm, d90 / d50 ₂ is kaolin is 3.4 (trade name: Capim NP, manufactured by Imerys, Inc.) was used instead got coated paper for printing in the same manner as in example 1.

Example 11
In the preparation of the coated liquid for the outermost coating layer of Example 1, kaolin (trade name: Kaogurosu 90) instead of the average particle diameter d50 ₂ is 0.53μm as measured by sedimentation method, 90% particle size d90 Was used in the same manner as in Example 1 except that kaolin (trade name: Contrast 300, manufactured by Engelhard) having a d90 / d50 ₂ of 4.0 was used.

Example 12
In the preparation of the coated liquid for the outermost coating layer of Example 1, kaolin (trade name: Kaogurosu 90) instead of the average particle diameter d50 ₂ is 1.69μm as measured by sedimentation method, 90% particle size d90 Was used in the same manner as in Example 1 except that kaolin (trade name: Mirrorana 950, manufactured by Engelhard) having a d90 / d50 ₂ of 3.2 was used.

Example 13
In the preparation of the coated liquid for the outermost coating layer of Example 1, kaolin (trade name: Kaogurosu 90) instead of the average particle diameter d50 ₂ is 0.18μm as measured by sedimentation method, 90% particle size d90 There 0.46 .mu.m, d90 / d50 ₂ kaolin 2.5 (trade name: Japan gloss, manufactured by Huber Corporation) was used instead got coated paper for printing in the same manner as in example 1.

Example 14
In the preparation of the coated liquid for the outermost coating layer of Example 7, the pigment component, an average particle diameter d50 ₂ as measured by sedimentation method 1.14 .mu.m, 90% particle size d90 1.9μm, d90 / d50 _A coated paper for printing was obtained in the same manner as in Example 7 except that 100 parts of kaolin (trade name: Astraplus) ₂ was 1.7.

Example 15
In the preparation of the coated liquid for the outermost coating layer of Example 7, the pigment component, an average particle diameter d50 ₂ as measured by sedimentation method 1.14 .mu.m, 90% particle size d90 1.9μm, d90 / d50 Same as Example 7 except that 60 parts kaolin (trade name: Astraplus) ₂ is 1.7 and 40 parts light calcium carbonate (Brilliant S-15, manufactured by Shiraishi Kogyo Co., Ltd.) with an average particle size of 0.39 μm. In this way, a coated paper for printing was obtained.

Comparative Example 1
(Preparation of coating solution for coating layer in contact with base paper)
In an aqueous solution in which 0.1 part of kaolin in which sodium polyacrylate is dispersed as a dispersant is added, the average particle diameter d50 ₁ measured by the light scattering method is 1.95 μm, and the average particle diameter d50 ₂ measured by the sedimentation method is 0.28 μm, d50 ₁ / d50 ₂ is 7.0, the mass distribution of particles of 2 μm or less in the particle size distribution curve by the sedimentation method is 94.9%, and the mass distribution of particles of 0.3 μm or less is 52.6%. 20 parts of kaolin (trade name: Milagros J, manufactured by Engelhard) and 80 parts of heavy calcium carbonate (trade name: Hydrocurve 60) having an average particle size (according to the precipitation method) of 1.3 μm are sequentially added. Then, the mixture was dispersed with a Coreless disperser to prepare a pigment slurry. To this slurry, 20 parts of styrene-butadiene copolymer latex (trade name: SN-113I) is added as an adhesive with respect to 100 parts of pigment, and a water retention agent (trade name: S-350, manufactured by Somar Co.) 0 .1 part was added, and finally a coating solution having a solid content concentration of 45% was prepared.
(Create coated paper for printing)
A coated paper for printing was obtained in the same manner as in Example 1 except that the coating liquid for the coating layer in contact with the base paper obtained above was used.

Comparative Example 2
In the preparation of a coating solution for a coating layer in contact with the base paper of Comparative Example 1, heavy calcium carbonate (trade name: Hydrocurve 90, Bihoku) having an average particle diameter (according to a sedimentation method) of 0.8 μm as a pigment component. A coated paper for printing was obtained by the same method as in Comparative Example 1 except that only (Made by Flour Industries) was used.

Comparative Example 3
In the preparation of the coating solution for the coating layer in contact with the base paper of Comparative Example 1, as a pigment component, 45 parts of satin white (trade name: Sachin White B) and an average particle diameter (according to a sedimentation method) of 0.8 μm Using 55 parts of certain heavy calcium carbonate (trade name: Hydrocurve 90), as an adhesive component, 0.5 part of oxidized starch (trade name: Ace B) and styrene-butadiene copolymer latex (trade name: SN-113I) using 20 parts, further using 0.12 part of water retention agent (trade name: S-350), preparing a coating solution with a solid content concentration of 40%, and using this coating solution A coated paper for printing was obtained in the same manner as in Comparative Example 1 except that.

Comparative Example 4
In the preparation of the coating solution for the coating layer in contact with the base paper of Comparative Example 1, as the pigment component, the average particle size d50 ₁ measured by the light scattering method is 3.64 μm, and the average particle size d50 ₂ measured by the sedimentation method is 0.47 μm, d50 ₁ / d50 ₂ is 7.7, the mass distribution of particles of 2 μm or less in the particle size distribution curve by the sedimentation method is 90.1%, and the mass distribution of particles of 0.3 μm or less is 35.4%. Only delaminated kaolin (trade name: Conzer 2000), 70 parts of oxidized starch (trade name: Ace B) and styrene-butadiene copolymer latex (trade name: SN-113I) as adhesive components ) Using 5 parts, a coating liquid having a solid content of 40% was prepared without adding a water retention agent, and a coated paper for printing was obtained in the same manner as in Comparative Example 1 except that this coating liquid was used. It was.

  The coating layer in contact with the base paper contains 5-35% by mass of satin white and 65-95% by mass of other pigments as pigment components, and 1-60 masses of water-soluble adhesive as an adhesive per 100 parts by mass of pigment. Coated paper for printing obtained by coating a coating solution containing part by a film transfer method and forming a coating layer mainly composed of a pigment and an adhesive on the coating liquid has surface smoothness. Excellent printability such as ink fillability and printing smoothness, and can be applied as a light-weight coated paper.

Claims (14)

  In a printing coated paper having two or more coating layers mainly composed of a pigment and an adhesive on at least one side of the base paper, the coating layer in contact with the base paper is coated by a film transfer method and touches the base paper. The coating layer contains 5 to 35% by weight of calcium trisulfoaluminate and 65 to 95% by weight of other pigments as the pigment component, and 1 to 60 parts by weight per 100 parts by weight of the pigment component as the adhesive component. A coated paper for printing, comprising a water-soluble adhesive. The printing coating according to claim 1, wherein the other pigment contains delaminated kaolin that satisfies the following conditions, and a mass ratio of the delaminated kaolin in the pigment component is 50% by mass or more. paper.
Delaminated kaolin: the average particle diameter d50 ₁ measured by the light scattering method is in the range of 2.0 to 5.0 μm, and the average particle diameter d50 ₂ measured by the sedimentation method is in the range of 0.35 to 0.55 μm. The ratio of the average particle diameter d50 ₁ to the average particle diameter d50 ₂ (d50 ₁ / d50 ₂ ) is 4 or more, and in the particle size distribution curve by the precipitation method, the mass distribution of particles of 2 μm or less is Delaminated kaolin in the range of 80 to 95% and the mass distribution of particles of 0.3 μm or less in the range of 30 to 45%.   The coated paper for printing according to claim 2, wherein a mass ratio of the delaminated kaolin to the pigment component is 50 to 80 mass%.   The coated paper for printing according to any one of claims 1 to 3, comprising 10 to 60 parts by mass of at least one starch as the water-soluble adhesive per 100 parts by mass of the pigment component.   The coated paper for printing according to any one of claims 1 to 4, wherein the calcium trisulfoamylate has a pH of 12 or less.   The coating layer in contact with the base paper further contains, as an adhesive component, 1 to 20 parts by mass of a copolymer latex having a particle diameter of 40 to 150 nm per 100 parts by mass of the pigment component. Coated paper for printing as described in 1. In the coated paper for printing, the outermost coating layer is, as a pigment, an average particle diameter d50 ₂ as measured by sedimentation method is in the range of 0.2～1.6Myuemu, 90 cumulative particle size distribution curve by sedimentation method The ratio of the particle diameter d90 corresponding to mass% and the average particle diameter d50 ₂ (d90 / d50 ₂ ) includes kaolin in the range of 1 to 4.0, and the mass ratio of the kaolin in the pigment is It is 55-100 mass%, The coated paper for printing as described in any one of Claims 1-6 characterized by the above-mentioned. In a method for producing a coated paper for printing having two or more coating layers mainly composed of a pigment and an adhesive on at least one side of a base paper, the coating layer in contact with the base paper is formed using the following coating liquid. A method for producing a coated paper for printing, which is coated by a transfer method.
Coating liquid: 5 to 35% by mass of calcium trisulfoaluminate as a pigment component and 65 to 95% by mass of other pigments, and 1 to 60 parts of water-soluble adhesive as an adhesive component per 100 parts by mass of pigment component Coating solution containing part by mass. The coating for printing according to claim 7, wherein the other pigment contains a delaminated kaolin that satisfies the following conditions, and a mass ratio of the delaminated kaolin in the pigment component is 50% by mass or more. Paper manufacturing method.
Delaminated kaolin: the average particle diameter d50 ₁ measured by the light scattering method is in the range of 2.0 to 5.0 μm, and the average particle diameter d50 ₂ measured by the sedimentation method is in the range of 0.35 to 0.55 μm. The ratio of the average particle diameter d50 ₁ to the average particle diameter d50 ₂ (d50 ₁ / d50 ₂ ) is 4 or more, and in the particle size distribution curve by the precipitation method, the mass distribution of particles of 2 μm or less is Delaminated kaolin in the range of 80 to 95% and the mass distribution of particles of 0.3 μm or less in the range of 30 to 45%.   The manufacturing method of the coated paper for printing of Claim 8 whose mass ratio of the said delaminated kaolin occupied to the said pigment component is 50-80 mass%.   The printing coating according to any one of claims 7 to 9, wherein a coating liquid containing 10 to 60 parts by mass of at least one kind of starch per 100 parts by mass of the pigment component is used as the water-soluble adhesive. A method for producing paper.   The method for producing a coated paper for printing according to any one of claims 7 to 10, wherein the coating liquid is a coating liquid further containing at least one of a thickener or a water retention agent.   The manufacturing method of the coated paper for printing of Claim 11 which contains 0.01-1.0 mass part of at least 1 sort (s) of a thickener or a water retention agent per 100 mass parts of pigment components. In the method for producing the coated paper for printing, the coating liquid for forming the outermost coating layer has an average particle diameter d50 ₂ measured by a sedimentation method in the range of 0.2 to 1.6 μm. And a kaolin having a ratio (d90 / d50 ₂ ) of the particle diameter d90 corresponding to 90 cumulative mass% of the particle size distribution curve by the sedimentation method to the average particle diameter d50 _{2 in} the range of 1 to 4.0, and And a step of preparing a dispersion containing an adhesive having a mass ratio of the kaolin in the pigment of 55 to 100% by mass and applying the coating solution by a blade method. The manufacturing method of the coated paper for printing as described in any one of Claims 7-12 characterized by these.